Materials

21 pages, 4927 KiB

Open AccessEditor’s ChoiceArticle

A Novel Nickel-Plated Carbon Fiber Insert in Aluminum Joints with Thermoplastic ABS Polymer or Stainless Steel

by Yoshitake Nishi, Kouhei Sagawa, Michael C. Faudree, Helmut Takahiro Uchida, Masae Kanda, Satoru Kaneko, Michelle Salvia, Yoshihito Matsumura and Hideki Kimura

Materials 2023, 16(17), 5777; https://doi.org/10.3390/ma16175777 - 23 Aug 2023

Viewed by 1064

Abstract

New types of hybrid aluminum joints: Al-acrylonitrile butadiene styrene (ABS) carbon fiber reinforced thermoplastic polymer (CFRTP) designated Al/Ni-CFP/ABS, and Al-18-8 Stainless steel, Al/Ni-CFP/18-8, by Ni-plated carbon fiber plug (Ni-CFP) insert not before seen in the literature have been fabricated. [...] Read more.

New types of hybrid aluminum joints: Al-acrylonitrile butadiene styrene (ABS) carbon fiber reinforced thermoplastic polymer (CFRTP) designated Al/Ni-CFP/ABS, and Al-18-8 Stainless steel, Al/Ni-CFP/18-8, by Ni-plated carbon fiber plug (Ni-CFP) insert not before seen in the literature have been fabricated. The goal is to take advantage of extremely high ~6 mm CF surface area for high adhesion, to enhance the safety level of aircraft and other parts. This is without fasteners, chemical treatment, or glue. First, the CFP is plated with Ni. Second, the higher melting point half-length is spot welded to the CFP; and third, the remaining half-length is fabricated. The ultimate tensile strength (UTS) of Al/Ni-CFP/ABS was raised 15 times over that of Al/ABS. Normalized ^cUTS according to CFP cross-section by Rule of Mixtures for ^cAl/Ni-CFP/18-8 was raised over that of ^cAl/Ni-CFP/18-8 from 140 to 360 MPa. Resistance energy to tensile deformation, U_T, was raised 12 times from Al/ABS to Al/Ni-CFP/ABS, and 6 times from Al/CFP/18-8 to Al/Ni-CFP/18-8. Spot welding allows rapid melting followed by rapid solidification for amorphous metal structures minimizing grain boundaries. The Ni-coating lowers or counters the effects of brittle Al₄C₃ and Fe_xC formation at the interface and prevents damage by impingement to CFs, allowing joints to take on more of the load. Full article

(This article belongs to the Special Issue New Advances in Aluminum Alloys and Composites for Lightweight Applications)

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14 pages, 6636 KiB

Open AccessEditor’s ChoiceArticle

Properties of PBZTS Ferroelectric Ceramics Obtained Using Spark Plasma Sintering

by Dagmara Brzezińska, Dariusz Bochenek, Przemysław Niemiec and Grzegorz Dercz

Materials 2023, 16(17), 5756; https://doi.org/10.3390/ma16175756 - 23 Aug 2023

Viewed by 744

Abstract

In this paper, spark plasma sintering was used to obtain and investigate (Pb_0.97Ba_0.03)(Zr_0.98Ti_0.02)_1−xSn_xO₃ (PBZTS) ceramic materials for x = 0, 0.02, 0.04, 0.06, and 0.08. Crystal structure, microstructure, dielectric [...] Read more.

In this paper, spark plasma sintering was used to obtain and investigate (Pb_0.97Ba_0.03)(Zr_0.98Ti_0.02)_1−xSn_xO₃ (PBZTS) ceramic materials for x = 0, 0.02, 0.04, 0.06, and 0.08. Crystal structure, microstructure, dielectric and ferroelectric properties, and electrical conductivity tests of a series of samples were carried out. The SPS sintering method ensures favorable dielectric and ferroelectric properties of PBZTS ceramic materials. X-ray studies have shown that the material has a perovskite structure. The samples have a densely packed material structure with properly crystallized grains. The fine-grained microstructure of the PZBZTS material with high grain homogeneity allows the application of higher electric fields. Ceramic samples obtained by the SPS method have higher density values than samples obtained by the classical method (FS). The permittivity at room temperature is in the range of 245–282, while at the phase transition temperature is in the range of 10,259–12,221. At room temperature, dielectric loss factor values range from 0.006 to 0.036. The hysteresis loops of PBZTS ceramics have a shape typical for ferroelectric hard materials, and the remnant polarization values range from 0.32 to 0.39 µC/cm². The activation energy E_a values of the PBZTS samples result mainly from the presence of oxygen vacancies. The PZT material doped with Ba and Sn and sintered via the SPS method has favorable physical parameters for applications in modern devices such as actuators or pulse capacitors. Full article

(This article belongs to the Special Issue Advances in Dielectric Ceramics)

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25 pages, 8948 KiB

Open AccessEditor’s ChoiceArticle

Dynamic Characteristics and Effective Stiffness Properties of Sandwich Panels with Hierarchical Hexagonal Honeycomb

by Zixuan Bai, Cheng Chen, Xinlong Yang, Yifeng Zhong and Rong Liu

Materials 2023, 16(17), 5741; https://doi.org/10.3390/ma16175741 - 22 Aug 2023

Cited by 2 | Viewed by 926

Abstract

The dynamic characteristics of sandwich panels with a hierarchical hexagonal honeycomb (SP-HHHs) show significant improvements due to their distinct hierarchy configurations. However, this also increases the complexity of structural analysis. To address this issue, the variational asymptotic method was utilized to homogenize the [...] Read more.

The dynamic characteristics of sandwich panels with a hierarchical hexagonal honeycomb (SP-HHHs) show significant improvements due to their distinct hierarchy configurations. However, this also increases the complexity of structural analysis. To address this issue, the variational asymptotic method was utilized to homogenize the unit cell of the SP-HHH and obtain the equivalent stiffness, establishing a two-dimensional equivalent plate model (2D-EPM). The accuracy and effectiveness of the 2D-EPM were then verified through comparisons with the results from a detailed 3D FE model in terms of the free vibration and frequency- and time-domain forced vibration, as well as through local field recovery analysis at peak and trough times. Furthermore, the tailorability of the typical unit cell was utilized to perform a parametric analysis of the effects of the length and thickness ratios of the first-order hierarchy on the dynamic characteristics of the SP-HHH under periodic loading. The results reveal that the vertices serve as weak points in the SP-HHH, while the vertex cell pattern significantly influences the specific stiffness and stiffness characteristics of the panel. The SP-HHH with hexagonal vertex cells has superior specific stiffness compared to panels with circular and rectangular vertex cells, resulting in a more lightweight design and enhanced stiffness. Full article

(This article belongs to the Special Issue Lightweight and High-Strength Sandwich Panel)

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18 pages, 3901 KiB

Open AccessEditor’s ChoiceArticle

Study on the Dye Removal from Aqueous Solutions by Graphene-Based Adsorbents

by Paunka Vassileva, Vencislav Tumbalev, Diana Kichukova, Dimitrinka Voykova, Daniela Kovacheva and Ivanka Spassova

Materials 2023, 16(17), 5754; https://doi.org/10.3390/ma16175754 - 22 Aug 2023

Cited by 1 | Viewed by 881

Abstract

In the current investigation, the removal efficiency regarding a cationic dye, methylene blue (MB), from three graphene-based materials was investigated. The materials’ characterization process involved instrumental methods such as XRD, XPS, SEM, TEM, FTIR, and nitrogen adsorption at 77 K. The survey examined [...] Read more.

In the current investigation, the removal efficiency regarding a cationic dye, methylene blue (MB), from three graphene-based materials was investigated. The materials’ characterization process involved instrumental methods such as XRD, XPS, SEM, TEM, FTIR, and nitrogen adsorption at 77 K. The survey examined how various process factors influenced the ability of the studied materials to adsorb cationic dyes. These parameters encompassed contact time, initial dye concentrations, solution pH, and temperature. The adsorption procedure was effectively explained through the application of pseudo-second-order and Langmuir models. The maximum adsorption capacity for the best adsorbent at 293 K was found to be 49.4 mg g⁻¹. In addition, the study also determined the entropy, enthalpy, and Gibbs free energy values associated with the removal of MB and showed that the adsorption of MB is endothermic, feasible, and spontaneous. The results also revealed that the studied materials are suitable adsorbents for the removal of cationic dyes. Full article

(This article belongs to the Special Issue Size-Dependent Effects in Materials for Environmental Protection and Energy Application)

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37 pages, 21017 KiB

Open AccessEditor’s ChoiceArticle

Milling Mechanism and Chattering Stability of Nickel-Based Superalloy Inconel 718

by Jin Zheng, Yaoman Zhang and Hanying Qiao

Materials 2023, 16(17), 5748; https://doi.org/10.3390/ma16175748 - 22 Aug 2023

Cited by 3 | Viewed by 964

Abstract

Nickel-based superalloy Inconel 718 is widely used in the aerospace industry for its excellent high-temperature strength and thermal stability. However, milling Inconel 718 presents challenges because of the significantly increased cutting force and vibration, since Inconel 718 is a typical difficult-to-machine material. This [...] Read more.

Nickel-based superalloy Inconel 718 is widely used in the aerospace industry for its excellent high-temperature strength and thermal stability. However, milling Inconel 718 presents challenges because of the significantly increased cutting force and vibration, since Inconel 718 is a typical difficult-to-machine material. This paper takes the milling process of Inconel 718 as the research object, initially, and a milling force model of Inconel 718 is established. Subsequently, the finite element analysis method is used to analyze the stress field, temperature field, and milling force in the milling process of Inconel 718. Building upon this, a dynamic equation of the milling of Inconel 718 is established, and based on the modal experiment, stability lobe diagrams are drawn. Furthermore, milling experiments on Inconel 718 are designed, and the results calculated using the milling force model and finite element analysis are verified through comparison to the experimental results; then, the fmincon optimization algorithm is used to optimize the processing parameters of Inconel 718. Eventually, the results of the multi-objective optimization illustrate that the best processing parameters are a spindle speed of 3199.2 rpm and a feed speed of 80 mm/min with an axial depth of cut of 0.25 mm. Based on this, the best machining parameters are determined, which point towards an improvement of the machining efficiency and quality of Inconel 718. Full article

(This article belongs to the Section Metals and Alloys)

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13 pages, 8068 KiB

Open AccessEditor’s ChoiceArticle

Effect of Tempering Temperature on Hydrogen Embrittlement of SCM440 Tempered Martensitic Steel

by Sang-Gyu Kim, Jae-Yun Kim and Byoungchul Hwang

Materials 2023, 16(16), 5709; https://doi.org/10.3390/ma16165709 - 21 Aug 2023

Viewed by 1200

Abstract

The effect of tempering temperature on the hydrogen embrittlement characteristics of SCM440 tempered martensitic steels was investigated in terms of their microstructure and hydrogen desorption behavior. The microstructures were characterized using scanning and transmission electron microscopy, as well as X-ray diffraction and electron [...] Read more.

The effect of tempering temperature on the hydrogen embrittlement characteristics of SCM440 tempered martensitic steels was investigated in terms of their microstructure and hydrogen desorption behavior. The microstructures were characterized using scanning and transmission electron microscopy, as well as X-ray diffraction and electron backscattered diffraction analysis. Thermal desorption analysis (TDA) was performed to examine the amount and trapping behavior of hydrogen. The cementite morphology of the SCM440 tempered martensitic steels gradually changed from a long lamellar shape to a segmented short-rod shape with an increasing tempering temperature. A slow strain rate tensile test was conducted after electrochemical hydrogen charging to evaluate the hydrogen embrittlement resistance. The hydrogen embrittlement resistance of the SCM440 tempered martensitic steels increased with an increasing tempering temperature because of the decrease in the fraction of the low-angle grain boundaries and dislocation density. The low-angle grain boundaries and dislocations, which acted as reversible hydrogen trap sites, were critical factors in determining the hydrogen embrittlement resistance, and this was supported by the decreased diffusible hydrogen content as measured by TDA. Fine carbides formed in the steel tempered at a relatively higher temperature acted as irreversible hydrogen trap sites and contributed to improving the hydrogen embrittlement resistance. Our findings can suggest that the tempering temperature of SCM440 tempered martensitic steel plays an important role in determining its hydrogen embrittlement resistance. Full article

(This article belongs to the Section Metals and Alloys)

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18 pages, 3483 KiB

Open AccessEditor’s ChoiceArticle

Application of Anodic Titanium Oxide Modified with Silver Nanoparticles as a Substrate for Surface-Enhanced Raman Spectroscopy

by Mateusz Czerwiński, Ruben del Olmo Martinez and Marta Michalska-Domańska

Materials 2023, 16(16), 5696; https://doi.org/10.3390/ma16165696 - 19 Aug 2023

Viewed by 804

Abstract

The formation of nanostructured anodic titanium oxide (ATO) layers was explored on pure titanium by conventional anodizing under two different operating conditions to form nanotube and nanopore morphologies. The ATO layers were successfully developed and showed optimal structural integrity after the annealing process [...] Read more.

The formation of nanostructured anodic titanium oxide (ATO) layers was explored on pure titanium by conventional anodizing under two different operating conditions to form nanotube and nanopore morphologies. The ATO layers were successfully developed and showed optimal structural integrity after the annealing process conducted in the air atmosphere at 450 °C. The ATO nanopore film was thinner (1.2 +/− 0.3 μm) than the ATO nanotube layer (3.3 +/− 0.6 μm). Differences in internal pore diameter were also noticeable, i.e., 88 +/− 9 nm and 64 +/− 7 nm for ATO nanopore and nanotube morphology, respectively. The silver deposition on ATO was successfully carried out on both ATO morphologies by silver electrodeposition and Ag colloid deposition. The most homogeneous silver deposit was prepared by Ag electrodeposition on the ATO nanopores. Therefore, these samples were selected as potential surface-enhanced Raman spectroscopy (SERS) substrate, and evaluation using pyridine (aq.) as a testing analyte was conducted. The results revealed that the most intense SERS signal was registered for nanopore ATO/Ag substrate obtained by electrodeposition of silver on ATO by 2.5 min at 1 V from 0.05M AgNO₃ (aq.) (analytical enhancement factor, AEF ~5.3 × 10⁴) and 0.025 M AgNO₃ (aq.) (AEF ~2.7 × 10²). The current findings reveal a low-complexity and inexpensive synthesis of efficient SERS substrates, which allows modification of the substrate morphology by selecting the parameters of the synthesis process. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

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27 pages, 7456 KiB

Open AccessEditor’s ChoiceArticle

New Experimental Evidence for Drying Shrinkage of Alkali-Activated Slag with Sodium Hydroxide

by Marco Sirotti, Brice Delsaute and Stéphanie Staquet

Materials 2023, 16(16), 5659; https://doi.org/10.3390/ma16165659 - 17 Aug 2023

Cited by 1 | Viewed by 711

Abstract

Alkali-activated slag (AAS) is emerging as a possible and more sustainable alternative to Ordinary Portland Cement (OPC) in the construction industry, thanks to its good mechanical and chemical properties. Conversely, the effects of its high drying shrinkage are still a concern for its [...] Read more.

Alkali-activated slag (AAS) is emerging as a possible and more sustainable alternative to Ordinary Portland Cement (OPC) in the construction industry, thanks to its good mechanical and chemical properties. Conversely, the effects of its high drying shrinkage are still a concern for its long-term durability. This study aims to investigate the drying shrinkage behaviour of six AAS/sodium hydroxide mortar compositions and the main phenomena affecting their drying shrinkage behaviour. Specifically, the molarity, solution-to-binder ratio (s/b), autogenous shrinkage, creep compliance, microcracking, and carbonation are considered as possible causes of the differences between AAS and OPC. The results show that it is not possible to correlate the shrinkage magnitude with the molarity of the activating solution, while an increase in the s/b increases the drying shrinkage. Concerning the other factors, autogenous deformation remains significant even after a period of 112 days, while the creep compliance is definitely affected by the drying process but does not seem to affect the shrinkage magnitude. Furthermore, the presence of microcracks caused by the drying process definitely influences the drying shrinkage. Finally, carbonation depends on the molarity of the activating solution, even though its effects on the material are still unclear. Full article

(This article belongs to the Special Issue Research on Alkali-Activated Materials)

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10 pages, 2282 KiB

Open AccessEditor’s ChoiceArticle

Al₂O₃ Layers Grown by Atomic Layer Deposition as Gate Insulator in 3C-SiC MOS Devices

by Emanuela Schilirò, Patrick Fiorenza, Raffaella Lo Nigro, Bruno Galizia, Giuseppe Greco, Salvatore Di Franco, Corrado Bongiorno, Francesco La Via, Filippo Giannazzo and Fabrizio Roccaforte

Materials 2023, 16(16), 5638; https://doi.org/10.3390/ma16165638 - 15 Aug 2023

Cited by 2 | Viewed by 1118

Abstract

Metal-oxide-semiconductor (MOS) capacitors with Al₂O₃ as a gate insulator are fabricated on cubic silicon carbide (3C-SiC). Al₂O₃ is deposited both by thermal and plasma-enhanced Atomic Layer Deposition (ALD) on a thermally grown 5 nm SiO₂ interlayer [...] Read more.

Metal-oxide-semiconductor (MOS) capacitors with Al₂O₃ as a gate insulator are fabricated on cubic silicon carbide (3C-SiC). Al₂O₃ is deposited both by thermal and plasma-enhanced Atomic Layer Deposition (ALD) on a thermally grown 5 nm SiO₂ interlayer to improve the ALD nucleation and guarantee a better band offset with the SiC. The deposited Al₂O₃/SiO₂ stacks show lower negative shifts of the flat band voltage V_FB (in the range of about −3 V) compared with the conventional single SiO₂ layer (in the range of −9 V). This lower negative shift is due to the combined effect of the Al₂O₃ higher permittivity (ε = 8) and to the reduced amount of carbon defects generated during the short thermal oxidation process for the thin SiO₂. Moreover, the comparison between thermal and plasma-enhanced ALD suggests that this latter approach produces Al₂O₃ layers possessing better insulating behavior in terms of distribution of the leakage current breakdown. In fact, despite both possessing a breakdown voltage of 26 V, the T-ALD Al₂O₃ sample is characterised by a higher current density starting from 15 V. This can be attributable to the slightly inferior quality (in terms of density and defects) of Al₂O₃ obtained by the thermal approach and, which also explains its non-uniform dC/dV distribution arising by SCM maps. Full article

(This article belongs to the Special Issue Silicon Carbide: Material Growth, Device Processing and Applications)

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13 pages, 5163 KiB

Open AccessEditor’s ChoiceArticle

Controlling the Cooling Rate of Hydrothermal Synthesis to Enhance the Supercapacitive Properties of β-Nickel Hydroxide Electrode Materials

by Yang-Ming Lu and Sheng-Huai Hong

Materials 2023, 16(16), 5576; https://doi.org/10.3390/ma16165576 - 11 Aug 2023

Cited by 1 | Viewed by 836

Abstract

The demand for power storage devices with good quality, fast charging and high energy density is becoming more and more urgent in today’s electronic technology. For batteries and traditional capacitors, it is an insurmountable challenge to combine fast charging and discharging, large capacitance [...] Read more.

The demand for power storage devices with good quality, fast charging and high energy density is becoming more and more urgent in today’s electronic technology. For batteries and traditional capacitors, it is an insurmountable challenge to combine fast charging and discharging, large capacitance and long-life properties. The characteristics of supercapacitors can meet all the above requirements at the same time. In this study, a simple one-step hydrothermal method was successfully used to grow β-nickel hydroxide nanocone particles directly on the 3D foamed nickel substrate as a working electrode material for supercapacitors. After growing β-nickel hydroxide crystals on 3D foamed nickel substrate, by controlling the cooling rate, a well-crystalized β-nickel hydroxide with good capacitance characteristics can be obtained. Cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) were used to analyze the capacitance characteristics of the β-nickel hydroxide electrode. The research results show that the specific capacitance value of the β-Ni(OH)₂/3D nickel foam electrode material prepared at the cooling rate of 10 °C/h can reach 539 F/g with the charge–discharge test at a current density of 3 A/g. After 1000 continuous charge and discharge cycles, the material still retains 94.1% of the specific capacitance value. Full article

(This article belongs to the Special Issue Electrochemical Material Science and Electrode Processes)

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14 pages, 5451 KiB

Open AccessEditor’s ChoiceArticle

Effect of High-Speed Sintering on the Optical Properties, Microstructure, and Phase Distribution of Multilayered Zirconia Stabilized with 5 mol% Yttria

by Mi-Hyang Cho and Hyo-Joung Seol

Materials 2023, 16(16), 5570; https://doi.org/10.3390/ma16165570 - 10 Aug 2023

Cited by 1 | Viewed by 883

Abstract

As dental 5 mol% yttria-stabilized (5Y-) zirconia demand high esthetics, it is necessary to clarify how the optical properties are affected by high-speed sintering, which is not yet fully understood. Our study aimed to investigate the effect of high-speed sintering on the translucency [...] Read more.

As dental 5 mol% yttria-stabilized (5Y-) zirconia demand high esthetics, it is necessary to clarify how the optical properties are affected by high-speed sintering, which is not yet fully understood. Our study aimed to investigate the effect of high-speed sintering on the translucency and opalescence parameters (TP and OP, respectively), as well as their related microstructure and phase distribution, using two types of multilayered 5Y-zirconia. Multilayered 5Y-zirconia (Cercon xt ML, Lava Esthetic) were cut layer-by-layer, followed by conventional and high-speed sintering. The TP and OP values were subsequently obtained using a spectrophotometer, and field emission scanning electron microscopy images were used to analyze the average grain size. The phase fractions were analyzed using X-ray diffraction. Regardless of the zirconia type, the TP was slightly lowered by high-speed sintering in all the layers except the dentin layer (DL) for Lava Esthetic (p < 0.05). The OP decreased by high-speed sintering in the DL for Cercon xt ML and in all the layers for Lava Esthetic (p < 0.05). The decrease in translucency after high-speed sintering was attributed to a decrease in the yttria-rich t’-phase with low tetragonality, along with an increase in the yttria-lean t-phase with high tetragonality. Full article

(This article belongs to the Special Issue Advanced Materials for Dental Prosthesis: Current Advances and Future Trends)

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17 pages, 3590 KiB

Open AccessEditor’s ChoiceReview

Optimization of Spark Plasma Sintering Technology by Taguchi Method in the Production of a Wide Range of Materials: Review

by Robert Kruzel, Tomasz Dembiczak and Joanna Wachowicz

Materials 2023, 16(16), 5539; https://doi.org/10.3390/ma16165539 - 09 Aug 2023

Cited by 1 | Viewed by 996

Abstract

This paper reviews the production of sinters using the spark plasma sintering method. SPS (spark plasma sintering) technology has been used for several decades, mainly in laboratories, to consolidate a huge number of both new and traditional materials. However, it is now more [...] Read more.

This paper reviews the production of sinters using the spark plasma sintering method. SPS (spark plasma sintering) technology has been used for several decades, mainly in laboratories, to consolidate a huge number of both new and traditional materials. However, it is now more often introduced into practical industrial use, with equipment as early as the fifth generation capable of producing larger-size components at competitive costs. Although the mechanism of sintering with the use of this method is not yet understood, the effectiveness of the SPS process for the rapid and efficient consolidation of a wide range of materials with novel micro-structures remains indisputable. With a relatively wide variation in chemical composition, the structure allows the selection of appropriate consolidation parameters for these materials. The influence on the values of apparent density and mechanical properties depends on the parameters of the spark plasma sintering process. In order to achieve a density close to the theoretical density of sinters, optimization of the sintering parameters, i.e., sintering temperature, heating rate, sintering time, pressing pressure and protective atmosphere, should be carried out. In this paper, the optimization of spark plasma sintering of Si₃N₄–Al₂O₃–ZrO₂ composite was carried out using the Taguchi method. The effects of four sintering factors, namely heating rate, sintering time, sintering temperature and sintering pressure, on the final density were investigated. Optimal sintering conditions were proposed and a confirmation experiment was conducted. The optimal combination of sintering conditions for spark plasma sintering (SPS) of Si₃N₄–Al₂O₃–ZrO₂ composite for high apparent density was determined as A3-B3-C3-D2. Based on ANOVA analysis, it was found that the apparent density of sintering was significantly influenced by sintering temperature, followed by pressing pressure, sintering time and heating rate. Validation of the developed mathematical model predicting the apparent density of sinters showed close agreement between the predicted response results and experimental results. Full article

(This article belongs to the Special Issue Advanced Powder Metallurgy Materials and Technology)

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25 pages, 7104 KiB

Open AccessEditor’s ChoiceReview

Cyclodextrins for Lithium Batteries Applications

by Mohamed M. H. Desoky, Fabrizio Caldera, Valentina Brunella, Riccardo Ferrero, Gjylije Hoti and Francesco Trotta

Materials 2023, 16(16), 5540; https://doi.org/10.3390/ma16165540 - 09 Aug 2023

Cited by 4 | Viewed by 1856

Abstract

Due to their high energy and power density, lithium-ion batteries (LIBs) have gained popularity in response to the demand for effective energy storage solutions. The importance of the electrode architecture in determining battery performance highlights the demand for optimization. By developing useful organic [...] Read more.

Due to their high energy and power density, lithium-ion batteries (LIBs) have gained popularity in response to the demand for effective energy storage solutions. The importance of the electrode architecture in determining battery performance highlights the demand for optimization. By developing useful organic polymers, cyclodextrin architectures have been investigated to improve the performance of Li-based batteries. The macrocyclic oligosaccharides known as cyclodextrins (CDs) have relatively hydrophobic cavities that can enclose other molecules. There are many industries where this “host–guest” relationship has been found useful. The hydrogen bonding and suitable inner cavity diameter of CD have led to its selection as a lithium-ion diffusion channel. CDs have also been used as solid electrolytes for solid-state batteries and as separators and binders to ensure adhesion between electrode components. This review gives a general overview of CD-based materials and how they are used in battery components, highlighting their advantages. Full article

(This article belongs to the Special Issue Cyclodextrins: Aged Materials for New Applications)

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12 pages, 3093 KiB

Open AccessEditor’s ChoiceArticle

Mono- and Co-Doped Mn-Doped CsPbCl₃ Perovskites with Enhanced Doping Efficiency and Photoluminescent Performance

by Hao Jiang, Yiting Zhao, Fangchao Liu, Yongqi Yan, Yinuo Ma, Hexin Bao, Zhongchen Wu, Wei-Yan Cong and Ying-Bo Lu

Materials 2023, 16(16), 5545; https://doi.org/10.3390/ma16165545 - 09 Aug 2023

Viewed by 1382

Abstract

To investigate the effect of Mn and other metal dopants on the photoelectronic performance of CsPbCl₃ perovskites, we conducted a series of theoretical analyses. Our findings showed that after Mn mono-doping, the CsPbCl₃ lattice contracted and the bonding strength increased, resulting [...] Read more.

To investigate the effect of Mn and other metal dopants on the photoelectronic performance of CsPbCl₃ perovskites, we conducted a series of theoretical analyses. Our findings showed that after Mn mono-doping, the CsPbCl₃ lattice contracted and the bonding strength increased, resulting in a more compact structure of the metal octahedral cage. The relaxation of the metal octahedral cage, along with the Jahn–Teller effect, results in a decrease in lattice strain between the octahedra and a reduction in the energy of the entire lattice due to the deformation of the metal octahedron. These three factors work together to reduce intrinsic defects and enhance the stability and electronic properties of CsPbCl₃ perovskites. The solubility of the Mn dopant is significantly increased when co-doped with Ni, Fe, and Co dopants, as it compensates for the lattice strain induced by Mn. Doping CsPbCl₃ perovskites reduces the band gap due to the decreased contributions of 3d orbitals from the dopants. Our analyses have revealed that strengthening the CsPbCl₃ lattice and reducing intrinsic defects can result in improved stability and PL properties. Moreover, increasing Mn solubility and decreasing the bandgap can enhance the PLQY of orange luminescence in CsPbCl₃ perovskites. These findings offer valuable insights for the development of effective strategies to enhance the photoelectronic properties of these materials. Full article

(This article belongs to the Section Materials Physics)

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13 pages, 4252 KiB

Open AccessEditor’s ChoiceArticle

Microstructure of TiAl Capsules Processed by Electron Beam Powder Bed Fusion Followed by Post-Hot Isostatic Pressing

by Hanieh Bakhshi Farkoush, Giulio Marchese, Emilio Bassini, Alberta Aversa and Sara Biamino

Materials 2023, 16(16), 5510; https://doi.org/10.3390/ma16165510 - 08 Aug 2023

Viewed by 935

Abstract

The microstructures of intermetallic γ-titanium aluminide (TiAl) alloys are subjected to a certain degree of Al evaporation when processed by electron beam powder bed fusion (EB-PBF). The magnitude of the Al-loss is mainly correlated with the process parameters, and highly energetic parameters produce [...] Read more.

The microstructures of intermetallic γ-titanium aluminide (TiAl) alloys are subjected to a certain degree of Al evaporation when processed by electron beam powder bed fusion (EB-PBF). The magnitude of the Al-loss is mainly correlated with the process parameters, and highly energetic parameters produce significant Al evaporation. The Al-loss leads to different microstructures, including the formation of inhomogeneous banded structures, thus negatively affecting its mechanical performance. For this reason, the current work deals with creating EB-PBFed TiAl capsules with the inner part produced using only the pre-heating step and melting parameters with low energetic parameters applying high beam speed from 5000 to 3000 mm/s. This approach is investigated to reduce the Al-loss and microstructure inhomogeneity after hot isostatic pressing (HIP). The results showed that the HIP treatment effectively densified the capsules obtaining a relative density of around 100%. After HIP, the capsules produced with the inner part melted at 3000 mm/s presented a lower area shrinkage (around 6.6%) compared to the capsules produced using only the pre-heating step in the core part (around 20.7%). The different magnitudes of shrinkage derived from different levels of residual porosity consolidated during the HIP process. The HIPed capsules exhibited the presence of previous particle boundaries (PPBs), covered by α₂ phases. Notably, applying low energetic parameters to melt the core partially eliminates the particles’ surface, thus reducing the PPBs formation. In this case, the capsules melted with low energetic parameters (3000 mm/s) exhibited α₂ concentration of 3.5% and an average size of 13 µm compared to the capsules produced with the pre-heating step in the inner part with an α₂ around 5.7% and an average size around 23 µm. Moreover, the Al-loss of the capsules was drastically limited, as determined by X-ray fluorescence (XRF) analysis. More in detail, the capsules produced with the pre-heating step reported an atomic percentage of Al of 48.75, while using low energetic melting parameters led to 48.36. This result was interesting, considering that the massive samples produced with standard parameters (so more energetic ones) revealed atomic Al percentage from 48.04 to 47.70. Finally, the recycled small particles showed a higher fraction of α₂ phases with respect to the coarse particles, as determined by X-ray diffraction (XRD). Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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28 pages, 6109 KiB

Open AccessEditor’s ChoiceArticle

Properties of Self-Compacting Concrete Produced with Optimized Volumes of Calcined Clay and Rice Husk Ash—Emphasis on Rheology, Flowability Retention and Durability

by Abubakar Muhammad and Karl-Christian Thienel

Materials 2023, 16(16), 5513; https://doi.org/10.3390/ma16165513 - 08 Aug 2023

Cited by 1 | Viewed by 1142

Abstract

The durability of concrete requires a dense microstructure which can be achieved by using self-compacting concrete (SCC). Both calcined clay (CC) and rice husk ash (RHA) are promising supplementary cementitious materials (SCMs) that can partially replace cement, but their use in SCC is [...] Read more.

The durability of concrete requires a dense microstructure which can be achieved by using self-compacting concrete (SCC). Both calcined clay (CC) and rice husk ash (RHA) are promising supplementary cementitious materials (SCMs) that can partially replace cement, but their use in SCC is critical due to their higher water demand (WD) and specific surface area (SSA) compared to cement. The effect of partial substitution of cement at 20 vol-% with binary and ternary blends of CC and RHA on flowability retention and durability of SCC was investigated. The empirical method of SCC design was adopted considering the physical properties of both CC and RHA. The deformability of the SCC was evaluated using the slump flow and J-ring tests. The T₅₀₀ time and the V-funnel test were used to assess the viscosity of the SCC. The flowability retention was monitored by the plunger method, and flow resistance was determined based on the rheological measurements of SCC. The evolution of the hydrate phases of the binder in SCC was determined by thermogravimetric analysis, while the durability was evaluated by a rapid chloride migration test. Cement partial replacement with 20 vol-% CC has no significant effect on fresh SCC, flowability retention, compressive strength and durability properties. On the other hand, 20 vol-% RHA requires a higher dosage of SP to achieve self-compactability and increase the viscosity of SCC. Its flowability retention is only up to 30 min after mixing and exhibited higher flow resistance. It consumes more calcium hydroxide (CH) and improves the compressive strength and chloride resistance of SCC. The ternary blending with CC and RHA yielded better fresh SCC properties compared to the binary blend with RHA, while an improved chloride penetration resistance could be achieved compared to the binary CC blend. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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18 pages, 16569 KiB

Open AccessEditor’s ChoiceArticle

Origin and Evolution of Cracks in the Glaze Surface of a Ceramic during the Cooling Process

by Tiantian Chen, Bin Gong and Chun’an Tang

Materials 2023, 16(16), 5508; https://doi.org/10.3390/ma16165508 - 08 Aug 2023

Cited by 1 | Viewed by 927

Abstract

Because of the significant difference between the thermal expansion coefficients of ceramic blank and glaze, the glaze typically undergoes more pronounced shrinkage than the blank during ceramic cooling, which results in high stress concentrations and cracking. In this study, the mechanical mechanism of [...] Read more.

Because of the significant difference between the thermal expansion coefficients of ceramic blank and glaze, the glaze typically undergoes more pronounced shrinkage than the blank during ceramic cooling, which results in high stress concentrations and cracking. In this study, the mechanical mechanism of glaze cracking is studied, based on the statistical strength theory, damage mechanics, and continuum mechanics. Furthermore, the influence of the glaze layer thickness, heat transfer coefficient, expansion coefficient, and temperature difference on the creation and propagation of inner microcracks is systematically investigated, and the final discrete fracture network of ceramics is discussed at the specific crack saturation state. The results show that (1) a higher heat transfer coefficient will lead to a more uniform distribution of the surface temperature and a faster cooling process of the ceramics, reducing the number of microcracks when the ambient temperature is reached; (2) the thinner glaze layer is less prone to cracking when its thickness is smaller than that of the blank. However, when the thickness of the glaze layer is similar to that of the blank, the increased thickness of the glaze layer will increase the number of cracks on its surface; and (3) when the expansion coefficient of the glaze layer is smaller than that of the blank, cracks will not occur inside the glaze layer. However, as the coefficient of the thermal expansion of the glaze layer continuously rises, the number of cracks on its surface will first increase and then decrease. Full article

(This article belongs to the Special Issue Damage, Fracture and Fatigue of Ceramic Matrix Composites (CMCs))

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18 pages, 4641 KiB

Open AccessEditor’s ChoiceArticle

Cetuximab-Conjugated Magnetic Poly(Lactic-co-Glycolic Acid) Nanoparticles for Dual-Targeted Delivery of Irinotecan in Glioma Treatment

by Banendu Sunder Dash, Yu-Jen Lu, Shu-Hui Luo and Jyh-Ping Chen

Materials 2023, 16(16), 5526; https://doi.org/10.3390/ma16165526 - 08 Aug 2023

Cited by 2 | Viewed by 1286

Abstract

A glioma is the most common malignant primary brain tumor in adults and is categorized according to its growth potential and aggressiveness. Within gliomas, grade 4 glioblastoma remains one of the most lethal malignant solid tumors, with a median survival time less than [...] Read more.

A glioma is the most common malignant primary brain tumor in adults and is categorized according to its growth potential and aggressiveness. Within gliomas, grade 4 glioblastoma remains one of the most lethal malignant solid tumors, with a median survival time less than 18 months. By encapsulating CPT-11 and oleic acid-coated magnetic nanoparticles (OMNPs) in poly(lactic-co-glycolic acid) (PLGA) nanoparticles, we first prepared PLGA@OMNP@CPT-11 nanoparticles in this study. After conjugating cetuximab (CET) with PLGA@OMNP@CPT-11, spherical PLGA@OMNP@CPT-11-CET nanoparticles with 250 nm diameter, 33% drug encapsulation efficiency, and 22% drug loading efficiency were prepared in a single emulsion/evaporation step. The nanoparticles were used for dual-targeted delivery of CPT-11 to U87 primary glioblastoma cells by actively targeting the overexpressed epidermal growth factor receptor on the surface of U87 cells, as well as by magnetic targeting. The physicochemical properties of nanoparticles were characterized in detail. CET-mediated targeting promotes intracellular uptake of nanoparticles by U87 cells, which can release four times more drug at pH 5 than at pH 7.4 to facilitate drug release in endosomes after intracellular uptake. The nanovehicle PLGA@OMNP-CET is cytocompatible and hemocompatible. After loading CPT-11, PLGA@OMNP@CPT-11-CET shows the highest cytotoxicity toward U87 compared with free CPT-11 and PLGA@OMNP@CPT-11 by providing the lowest drug concentration for half-maximal cell death (IC₅₀) and the highest rate of cell apoptosis. In orthotopic brain tumor-bearing nude mice with U87 xenografts, intravenous injection of PLGA@OMNP@ CPT-11-CET followed by guidance with a magnetic field provided the best treatment efficacy with the lowest tumor-associated signal intensity from bioluminescence imaging. Full article

(This article belongs to the Special Issue Advances in Functional Magnetic Nanomaterials)

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14 pages, 6093 KiB

Open AccessEditor’s ChoiceArticle

Study of the Mineralogical Composition of an Alumina–Silica Binder System Formed by the Sol–Gel Method

by Lenka Nevřivová and David Zemánek

Materials 2023, 16(15), 5466; https://doi.org/10.3390/ma16155466 - 04 Aug 2023

Cited by 1 | Viewed by 829

Abstract

Colloidal bonds are realized by sol–gel technology. The binder system of the refractory castable belongs to the Al₂O₃–SiO₂ binary diagram. Mullite is the most thermally stable mineral in this system. This work was motivated by an attempt to [...] Read more.

Colloidal bonds are realized by sol–gel technology. The binder system of the refractory castable belongs to the Al₂O₃–SiO₂ binary diagram. Mullite is the most thermally stable mineral in this system. This work was motivated by an attempt to maximize the mullite content in the NCC binder system, because a high content of mullite is a guarantee of the long service life of refractories. Initially, the mineralogical composition of the pure gel was tested after drying and firing at temperatures between 1000 °C and 1600 °C. The behavior of the gel during drying was described. Subsequently, a method of minimizing gel shrinkage during drying was sought. To this aim, fine fillers (microfillers) of alumina and silica were tested. In particular, the reactivity of the microfillers, the ability of the microfillers to react with the sol to form mullite, and the drying shrinkage of the microfiller-doped gel were evaluated. The study showed that the least suitable source of Al₂O₃ in terms of its reactivity is tabular corundum, which produces the lowest amount of mullite. The internal structure of the prepared binder system when using different microfillers was described. Based on the results from the second stage of the work, several complete matrixes of the binder system were designed and the degree of their mullitization at different firing temperatures was studied. During this stage, it was shown that the degree of mullitization of the binder system depends mainly on the microsilica content. In the binder system, the maximum mullite content recorded was 76%. The effect of amorphous SiO₂ on the bulk density and internal structure of the binder system was also described. Full article

(This article belongs to the Special Issue Advanced Ceramics Composites and Its Applications)

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14 pages, 5161 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Photoelectrochemical Water Oxidation Using TiO₂-Co₃O₄ p–n Heterostructures Derived from in Situ-Loaded ZIF-67

by Chau Thi Thanh Thu, Hyo Jeong Jo, Ganesh Koyyada, Dae-Hwan Kim and Jae Hong Kim

Materials 2023, 16(15), 5461; https://doi.org/10.3390/ma16155461 - 04 Aug 2023

Viewed by 1139

Abstract

Exposing catalytically active metal sites in metal–organic frameworks (MOFs) while maintaining porosity is beneficial for increasing electron transport to achieve better electrochemical energy conversion performance. Herein, we propose an in situ method for MOF formation and loading onto TiO₂ nanorods (NR) using [...] Read more.

Exposing catalytically active metal sites in metal–organic frameworks (MOFs) while maintaining porosity is beneficial for increasing electron transport to achieve better electrochemical energy conversion performance. Herein, we propose an in situ method for MOF formation and loading onto TiO₂ nanorods (NR) using a simple solution-processable method followed by annealing to obtain TiO₂-Co₃O₄. The as-prepared TiO₂-ZIF-67 based photoanodes were annealed at 350, 450, and 550 °C to study the effect of carbonization on photo-electrochemical water oxidation. The successful loading of ZIF-67 on TiO₂ and the formation of TiO₂-Co₃O₄ heterojunction were confirmed by XRD, XPS, FE-SEM, and HRTEM analyses. TiO₂-Co₃O₄-450 (the sample annealed at 450 °C) showed an enhanced photocurrent of 2.4 mA/cm², which was 2.6 times larger than that of pristine TiO₂. The improved photocurrent might be ascribed to the prepared p–n heterostructures (Co₃O₄ and TiO₂), which promote electron–hole separation and charge transfer within the system and improve the photoelectrochemical performance. Moreover, the preparation of Co₃O₄ from the MOF carbonization process improved the electrical conductivity and significantly increased the number of exposed active sites and enhanced the photoresponse performance. The as-prepared ZIF-67 derived TiO₂-Co₃O₄ based photoanodes demonstrate high PEC water oxidation, and the controlled carbonization method paves the way toward the synthesis of low-cost and efficient electrocatalysts. Full article

(This article belongs to the Special Issue Novel Approaches to Photoelectrochemical and Electrochemical Nanomaterials)

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16 pages, 16702 KiB

Open AccessEditor’s ChoiceArticle

Effect of Cu as a Minority Alloying Element on the Corrosion Behaviour of Amorphous and Crystalline Al-Ni-Si Alloy

by Vanya Dyakova, Yoanna Kostova, Boriana Tzaneva, Hristina Spasova and Daniela Kovacheva

Materials 2023, 16(15), 5446; https://doi.org/10.3390/ma16155446 - 03 Aug 2023

Viewed by 815

Abstract

The effect of copper as a minority alloying element on the corrosion behaviour of amorphous and crystalline Al₇₄Ni₁₆Si₁₀ and Al₇₄Ni₁₅Si₉Cu₂ alloys was investigated in this study. Amorphous alloys were produced as [...] Read more.

The effect of copper as a minority alloying element on the corrosion behaviour of amorphous and crystalline Al₇₄Ni₁₆Si₁₀ and Al₇₄Ni₁₅Si₉Cu₂ alloys was investigated in this study. Amorphous alloys were produced as rapidly solidified ribbons using the Chill Block Melt Spinning (CBMS) method and subsequently annealed to complete crystallisation. The corrosion rate of alloys was obtained through continuous immersion tests in 3.5% NaCl at 25 °C and 50 °C for 360 h. The electrochemical parameters corrosion current density (J_corr) and corrosion potential (E_corr) were determined via the potentiodynamic polarisation test. The results showed better corrosion characteristics of amorphous alloys. The addition of 2 at.% copper to the Al₇₄Ni₁₆Si₁₀ alloy improved pitting corrosion resistance without significant effect on the corrosion current and potential. In immersion tests at 25 °C, the presence of copper resulted in an increase in the corrosion rate of about 300% for both amorphous and crystalline alloys. At a temperature of 50 °C, this increase is on average 130%. The apparent difference between the results of the two test methods is discussed in terms of the imperfections on the surface of rapidly solidified ribbons. The results of this study will contribute to a more complex understanding of the nature of amorphous alloys and their application. Full article

(This article belongs to the Special Issue Size-Dependent Effects in Materials for Environmental Protection and Energy Application)

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13 pages, 4429 KiB

Open AccessEditor’s ChoiceArticle

Nonlinear Optical Properties of Zn(II) Porphyrin, Graphene Nanoplates, and Ferrocene Hybrid Materials

by Francesca Limosani, Francesca Tessore, Alessandra Forni, Angelo Lembo, Gabriele Di Carlo, Cecilia Albanese, Stefano Bellucci and Pietro Tagliatesta

Materials 2023, 16(15), 5427; https://doi.org/10.3390/ma16155427 - 02 Aug 2023

Viewed by 863

Abstract

Following some previous work by some of us on the second order nonlinear optical (NLO) properties of Zn(II) meso-tetraphenylporphyrin (ZnP), fullerene, and ferrocene (Fc) diads and triads, in the present research, we explore the NLO response of some new hybrids with two-dimensional [...] Read more.

Following some previous work by some of us on the second order nonlinear optical (NLO) properties of Zn(II) meso-tetraphenylporphyrin (ZnP), fullerene, and ferrocene (Fc) diads and triads, in the present research, we explore the NLO response of some new hybrids with two-dimensional graphene nanoplates (GNP) instead of a zero-dimensional fullerene moiety as the acceptor unit. The experimental data, collected by Electric Field Induced Second Harmonic generation (EFISH) technique in CH₂Cl₂ solution with a 1907 nm incident wavelength, combined with Coupled-Perturbed (CP) and Finite Field (FF) Density Functional Theory (DFT) calculations, show a strongly enhanced contribution of the cubic electronic term γ(−2ω; ω, ω, 0), due to the extended π-conjugation of the carbonaceous acceptor moiety. Full article

(This article belongs to the Special Issue Feature Paper in Optical and Photonic Materials)

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15 pages, 5092 KiB

Open AccessEditor’s ChoiceArticle

SiC Doping Impact during Conducting AFM under Ambient Atmosphere

by Christina Villeneuve-Faure, Abdelhaq Boumaarouf, Vishal Shah, Peter M. Gammon, Ulrike Lüders and Rosine Coq Germanicus

Materials 2023, 16(15), 5401; https://doi.org/10.3390/ma16155401 - 01 Aug 2023

Viewed by 895

Abstract

The characterization of silicon carbide (SiC) by specific electrical atomic force microscopy (AFM) modes is highly appreciated for revealing its structure and properties at a nanoscale. However, during the conductive AFM (C-AFM) measurements, the strong electric field that builds up around and below [...] Read more.

The characterization of silicon carbide (SiC) by specific electrical atomic force microscopy (AFM) modes is highly appreciated for revealing its structure and properties at a nanoscale. However, during the conductive AFM (C-AFM) measurements, the strong electric field that builds up around and below the AFM conductive tip in ambient atmosphere may lead to a direct anodic oxidation of the SiC surface due to the formation of a water nanomeniscus. In this paper, the underlying effects of the anodization are experimentally investigated for SiC multilayers with different doping levels by studying gradual SiC epitaxial-doped layers with nitrogen (N) from 5 × 10¹⁷ to 10¹⁹ at/cm³. The presence of the water nanomeniscus is probed by the AFM and analyzed with the force–distance curve when a negative bias is applied to the AFM tip. From the water meniscus breakup distance measured without and with polarization, the water meniscus volume is increased by a factor of three under polarization. AFM experimental results are supported by electrostatic modeling to study oxide growth. By taking into account the presence of the water nanomeniscus, the surface oxide layer and the SiC doping level, a 2D-axisymmetric finite element model is developed to calculate the electric field distribution nearby the tip contact and the current distributions at the nanocontact. The results demonstrate that the anodization occurred for the conductive regime in which the current depends strongly to the doping; its threshold value is 7 × 10¹⁸ at/cm³ for anodization. Finally, the characterization of a classical planar SiC-MOSFET by C-AFM is examined. Results reveal the local oxidation mechanism of the SiC material at the surface of the MOSFET structure. AFM topographies after successive C-AFM measurements show that the local oxide created by anodization is located on both sides of the MOS channel; these areas are the locations of the highly n-type-doped zones. A selective wet chemical etching confirms that the oxide induced by local anodic oxidation is a SiOCH layer. Full article

(This article belongs to the Special Issue Silicon Carbide: Material Growth, Device Processing and Applications)

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15 pages, 6437 KiB

Open AccessEditor’s ChoiceArticle

Electrochemical Response of 3D-Printed Free-Standing Reduced Graphene Oxide Electrode for Sodium Ion Batteries Using a Three-Electrode Glass Cell

by Cristina Ramírez, María Isabel Osendi, Juan José Moyano, Jadra Mosa and Mario Aparicio

Materials 2023, 16(15), 5386; https://doi.org/10.3390/ma16155386 - 31 Jul 2023

Cited by 3 | Viewed by 903

Abstract

Graphene and its derivatives have been widely used to develop novel materials with applications in energy storage. Among them, reduced graphene oxide has shown great potential for more efficient storage of Na ions and is a current target in the design of electrodes [...] Read more.

Graphene and its derivatives have been widely used to develop novel materials with applications in energy storage. Among them, reduced graphene oxide has shown great potential for more efficient storage of Na ions and is a current target in the design of electrodes for environmentally friendly Na ion batteries. The search for more sustainable and versatile manufacturing processes also motivates research into additive manufacturing electrodes. Here, the electrochemical responses of porous 3D-printed free-standing log-type structures fabricated using direct ink writing (DIW) with a graphene oxide (GO) gel ink are investigated after thermal reduction in a three-electrode cell configuration. The structures delivered capacities in the range of 50–80 mAh g⁻¹ and showed high stability for more than 100 cycles. The reaction with the electrolyte/solvent system, which caused an initial capacity drop, was evidenced by the nucleation of various Na carbonates and Na₂O. The incorporation of Na into the filaments of the structure was verified with transmission electron microscopy and Raman spectroscopy. This work is a proof of concept that structured reduced GO electrodes for Na ion batteries can be achieved from a simple, aqueous GO ink through DIW and that there is scope for improving their performance and capacity. Full article

(This article belongs to the Section Carbon Materials)

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18 pages, 4139 KiB

Open AccessEditor’s ChoiceArticle

Hierarchical Zeolites Containing Vanadium or Tantalum and Their Application in Cyclohexene Epoxidation Reaction

by Paulina Szczyglewska, Agnieszka Feliczak-Guzik, Sylwia Chałupniczak and Izabela Nowak

Materials 2023, 16(15), 5383; https://doi.org/10.3390/ma16155383 - 31 Jul 2023

Viewed by 718

Abstract

The aim of this study was the synthesis, characterization, and catalytic application of new hierarchical materials modified with tantalum and vanadium ions. These materials exhibit secondary porosity, thus allowing the reactant molecules to access the active sites of the material while maintaining the [...] Read more.

The aim of this study was the synthesis, characterization, and catalytic application of new hierarchical materials modified with tantalum and vanadium ions. These materials exhibit secondary porosity, thus allowing the reactant molecules to access the active sites of the material while maintaining the acidity and crystallinity of the zeolites. Based on the results, these systems were found to be highly active and selective in the oxidation of cyclohexene. The performance of the catalysts was compared in oxidation processes carried out by conventional and microwave-assisted methods. Microwave-assisted experiments showed that in the presence of a hierarchical FAU zeolite containing Ta, long reaction times could be shortened with increased activity and selectivity under the same residual experimental conditions. Full article

(This article belongs to the Special Issue Advanced Materials in Catalysis and Adsorption (Volume II))

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23 pages, 5145 KiB

Open AccessEditor’s ChoiceArticle

High-Pressure Synthesis and the Enhancement of the Superconducting Properties of FeSe_0.5Te_0.5

by Mohammad Azam, Manasa Manasa, Tatiana Zajarniuk, Ryszard Diduszko, Tomasz Cetner, Andrzej Morawski, Jarosław Więckowski, Andrzej Wiśniewski and Shiv J. Singh

Materials 2023, 16(15), 5358; https://doi.org/10.3390/ma16155358 - 30 Jul 2023

Cited by 5 | Viewed by 1696

Abstract

A series of FeSe_0.5Te_0.5 bulk samples have been prepared using the high gas pressure and high-temperature synthesis (HP-HTS) method to optimize the growth conditions for the first time and investigated for their superconducting properties using structural, microstructure, transport, and magnetic [...] Read more.

A series of FeSe_0.5Te_0.5 bulk samples have been prepared using the high gas pressure and high-temperature synthesis (HP-HTS) method to optimize the growth conditions for the first time and investigated for their superconducting properties using structural, microstructure, transport, and magnetic measurements to reach the final conclusions. Ex situ and in situ processes are used to prepare bulk samples under a range of growth pressures using Ta-tube and without Ta-tube. The parent compound synthesized by convenient synthesis method at ambient pressure (CSP) exhibits a superconducting transition temperature of 14.8 K. Our data demonstrate that the prepared FeSe_0.5Te_0.5 sealed in a Ta-tube is of better quality than the samples without a Ta-tube, and the optimum growth conditions (500 MPa, 600 °C for 1 h) are favorable for the development of the tetragonal FeSe_0.5Te_0.5 phase. The optimum bulk FeSe_0.5Te_0.5 depicts a higher transition temperature of 17.3 K and a high critical current density of the order of >10⁴ A/cm² at 0 T, which is improved over the entire magnetic field range and almost twice higher than the parent compound prepared using CSP. Our studies confirm that the high-pressure synthesis method is a highly efficient way to improve the superconducting transition, grain connectivity, sample density, and pinning properties of a superconductor. Full article

(This article belongs to the Special Issue Characterization and Application of Superconducting Materials)

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24 pages, 3248 KiB

Open AccessEditor’s ChoiceReview

Nanoparticles in Cancer Diagnosis and Treatment

by Jaya Baranwal, Brajesh Barse, Amalia Di Petrillo, Gianluca Gatto, Luca Pilia and Amit Kumar

Materials 2023, 16(15), 5354; https://doi.org/10.3390/ma16155354 - 30 Jul 2023

Cited by 8 | Viewed by 2664

Abstract

The use of tailored medication delivery in cancer treatment has the potential to increase efficacy while decreasing unfavourable side effects. For researchers looking to improve clinical outcomes, chemotherapy for cancer continues to be the most challenging topic. Cancer is one of the worst [...] Read more.

The use of tailored medication delivery in cancer treatment has the potential to increase efficacy while decreasing unfavourable side effects. For researchers looking to improve clinical outcomes, chemotherapy for cancer continues to be the most challenging topic. Cancer is one of the worst illnesses despite the limits of current cancer therapies. New anticancer medications are therefore required to treat cancer. Nanotechnology has revolutionized medical research with new and improved materials for biomedical applications, with a particular focus on therapy and diagnostics. In cancer research, the application of metal nanoparticles as substitute chemotherapy drugs is growing. Metals exhibit inherent or surface-induced anticancer properties, making metallic nanoparticles extremely useful. The development of metal nanoparticles is proceeding rapidly and in many directions, offering alternative therapeutic strategies and improving outcomes for many cancer treatments. This review aimed to present the most commonly used nanoparticles for cancer applications. Full article

(This article belongs to the Special Issue Nanomaterials for Medical Application (Second Volume))

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21 pages, 18129 KiB

Open AccessEditor’s ChoiceArticle

The Effects of Partial Replacement of Ground Granulated Blast Furnace Slag by Ground Wood Ash on Alkali-Activated Binder Systems

by Ece Ezgi Teker Ercan, Andrzej Cwirzen and Karin Habermehl-Cwirzen

Materials 2023, 16(15), 5347; https://doi.org/10.3390/ma16155347 - 29 Jul 2023

Viewed by 1252

Abstract

Cement production contributes significantly to carbon dioxide emissions. Alkali-activated materials offer an environmentally friendly alternative due to their comparable strength, durability and low-carbon emissions while utilizing wastes and industrial by-products. Wood ash is a waste material that shows promising results as a partial [...] Read more.

Cement production contributes significantly to carbon dioxide emissions. Alkali-activated materials offer an environmentally friendly alternative due to their comparable strength, durability and low-carbon emissions while utilizing wastes and industrial by-products. Wood ash is a waste material that shows promising results as a partial replacement for Portland cement and precursors in alkali-activated systems. The aim of this study was to examine the effect of ground wood ash on the mechanical properties of alkali-activated mortars. Wood ash was incorporated as a 0 wt%, 10 wt% and 20 wt% partial replacement for ground granulated blast furnace slag (GGBFS). The wood ashes were ground in a planetary ball mill for 10 and 20 min. Sodium silicate (Na₂SiO₃), sodium carbonate (Na₂CO₃), and sodium hydroxide (NaOH) were used as alkali activators. The results demonstrated that ground wood ash improved the mechanical properties of alkali-activated systems compared to untreated wood ash. However, the incorporation of wood ash increased the porosity of the binder matrix. Full article

(This article belongs to the Special Issue Advances in Sustainable Construction and Building Materials)

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16 pages, 4423 KiB

Open AccessEditor’s ChoiceArticle

Influence of Pre-Tension on Free-End Torsion Behavior and Mechanical Properties of an Extruded Magnesium Alloy

by Hongbing Chen, Zhikang Shen, Bo Song and Jia She

Materials 2023, 16(15), 5343; https://doi.org/10.3390/ma16155343 - 29 Jul 2023

Viewed by 692

Abstract

In this study, the influence of pre-tension on free-end torsion behavior and compression mechanical properties and micro-hardness of an extruded AZ31 Mg alloy was investigated using electron backscatter diffraction (EBSD), compression testing and micro-hardness testing. The result indicates that pre-tension can cause significant [...] Read more.

In this study, the influence of pre-tension on free-end torsion behavior and compression mechanical properties and micro-hardness of an extruded AZ31 Mg alloy was investigated using electron backscatter diffraction (EBSD), compression testing and micro-hardness testing. The result indicates that pre-tension can cause significant dislocation strengthening, which can increase the torsion yield strength and make the shear stress–shear strain curve of the pre-tension sample almost parallel to that of the as-extruded sample during plastic deformation stage. Texture in edge position on the cross-section of both the pre-tension and as-extruded samples can be rotated towards the extrusion direction by about ~30° by free-end torsion. The Swift effect is mainly responsible for the occurrence of massive extension twins in the central region. In contrast, normal stress is the main cause of extension twins occurring in the edge region. However, the effect of extension twins on micro-hardness is less than that of dislocations. The micro-hardness of both free-end torsion specimens increases almost linearly with increasing distance from center to edge on the cross-section. Nevertheless, the increase in micro-hardness of the pre-tension and then torsion sample is inconspicuous because pre-tension leads to dislocation proliferation and dislocation accumulation saturation. The result also indicates that both pre-tension and free-end torsion can lead to dislocation strengthening, which can obviously increase the micro-hardness and compressive yield stress. The underlying mechanisms were explored and discussed in detail. Full article

(This article belongs to the Special Issue Research on Forming and Serving Performance of Advanced Alloys)

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2 pages, 157 KiB

Open AccessEditor’s ChoiceEditorial

Finite Element Modeling of Microstructures in Composite Materials: A Special Issue in Materials

by Yunhua Luo

Materials 2023, 16(15), 5332; https://doi.org/10.3390/ma16155332 - 29 Jul 2023

Viewed by 618

Abstract

This Special Issue of the journal Materials aims to gather recent advancements and novel developments in the field of finite element modeling of microstructures in composite materials [...] Full article

(This article belongs to the Special Issue Finite Element Modeling of Microstructures in Composite Materials)

19 pages, 848 KiB

Open AccessEditor’s ChoiceReview

The Intraoperative Use of Defensive Antibacterial Coating (DAC^®) in the Form of a Gel to Prevent Peri-Implant Infections in Orthopaedic Surgery: A Clinical Narrative Review

by Daniele Pressato, Angela Battista, Marco Govoni, Leonardo Vivarelli, Dante Dallari and Antonio Pellegrini

Materials 2023, 16(15), 5304; https://doi.org/10.3390/ma16155304 - 28 Jul 2023

Viewed by 1380

Abstract

Periprosthetic joint infections (PJIs) in arthroplasty and osteosynthesis-associated infections (OAIs) in reconstructive surgery still represent a challenging complication in orthopaedics and traumatology causing a burden worsening the patient’s quality of life, for caregiver and treating physicians, and for healthcare systems. PJIs and OAIs [...] Read more.

Periprosthetic joint infections (PJIs) in arthroplasty and osteosynthesis-associated infections (OAIs) in reconstructive surgery still represent a challenging complication in orthopaedics and traumatology causing a burden worsening the patient’s quality of life, for caregiver and treating physicians, and for healthcare systems. PJIs and OAIs are the result of bacterial adhesion over an implant surface with subsequent biofilm formation. Therefore, the clinical pathological outcome is a difficult-to-eradicate persistent infection. Strategies to treat PJIs and OAIs involve debridement, the replacement of internal fixators or articular prostheses, and intravenous antibiotics. However, long treatments and surgical revision cause discomfort for patients; hence, the prevention of PJIs and OAIs represents a higher priority than treatment. Local antibiotic treatments through coating-release systems are becoming a smart approach to prevent this complication. Hydrophilic coatings, loaded with antibiotics, simultaneously provide a barrier effect against bacterial adhesion and allow for the local delivery of an antibiotic. The intraoperative use of a hyaluronan (HY)-derivative coating in the form of a gel, loaded with antibiotics to prevent PJI, has recently raised interest in orthopaedics. Current evidence supports the use of this coating in the prophylaxis of PJI and IRIs in terms of clinical outcomes and infection reduction. Thus, the purpose of this narrative review is to assess the use of a commercially available HY derivative in the form of a gel, highlighting the characteristics of this biomaterial, which makes it attractive for the management of PJIs and IRIs in orthopaedics and traumatology. Full article

(This article belongs to the Special Issue Synthetic and Biologic Materials for Prosthetic and Reconstructive Applications for Musculoskeletal Tissue)

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12 pages, 7291 KiB

Open AccessEditor’s ChoiceArticle

Strengthening Mechanisms and Retention Properties of Sintered Iron-Based Matrix Material for Metallic-Diamond Tools

by Elżbieta Cygan-Bączek and Andrzej Romański

Materials 2023, 16(15), 5307; https://doi.org/10.3390/ma16155307 - 28 Jul 2023

Viewed by 856

Abstract

This work presents the analysis of mechanisms controlling the deformation strengthening of the surface during abrasion and their impact on structural changes and mechanical properties of Fe-Mn-Cu-Sn-C matrix material, which was prepared by means of powder metallurgy (PM). The powder mixture was ball-milled [...] Read more.

This work presents the analysis of mechanisms controlling the deformation strengthening of the surface during abrasion and their impact on structural changes and mechanical properties of Fe-Mn-Cu-Sn-C matrix material, which was prepared by means of powder metallurgy (PM). The powder mixture was ball-milled for 8 h and densified to <1% porosity using hot pressing at 900 °C and 35 MPa. Phases and structural transformations taking place in austenite during plastic deformation were identified. The participation, distribution, and morphology of the phases, as well as the physicomechanical properties of the matrix material, were tested. It has been shown that during grinding, deformation twins are generated in areas where an austenitic microstructure is present. To test the ability of the matrix to keep diamond crystals firmly cylindrical (Ø11.3 mm× 5 mm), diamond-impregnated specimens containing diamond grits of 30/40 mesh in size and at a concentration of 20 (5% vol.) were prepared. It was finally determined by the diamond-retention index, which is the number of retained diamond particles compared to the total number of diamond particles and the pullouts on the working surface of the segment. This research shows that materials containing Ti- and Si-coated diamond particles, deposited by the CVD method, have the highest abrasion resistance and, therefore, have the best retention properties. In order to determine the bonding mechanism at the matrix–diamond interface, specimens were also analyzed by SEM and TEM. Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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11 pages, 4517 KiB

Open AccessEditor’s ChoiceArticle

Effect of Nano Ni Particles on the Microstructure and Thermophysical Properties of Sn–Bi–Zn Heat Transfer and Heat Storage Alloys

by Qingmeng Wang, Xiaomin Cheng, Xiuli Wang, Tao Yang, Qianju Cheng, Zhi Liu and Zean Lv

Materials 2023, 16(15), 5325; https://doi.org/10.3390/ma16155325 - 28 Jul 2023

Viewed by 733

Abstract

The specific heat capacity plays a crucial role in influencing the heat transfer efficiency of materials. Considering the relatively low specific heat capacity of metals, this study focuses on investigating the impact of second-phase nano Ni particles on the microstructure and thermophysical properties [...] Read more.

The specific heat capacity plays a crucial role in influencing the heat transfer efficiency of materials. Considering the relatively low specific heat capacity of metals, this study focuses on investigating the impact of second-phase nano Ni particles on the microstructure and thermophysical properties of the alloy matrix. The alloys’ phase compositions and microstructures were examined using X-ray diffraction phase analysis (XRD), electron probe micromorphology analysis (EPMA), and X-ray fluorescence spectroscopy (XRF). Furthermore, the thermophysical properties of the alloys were comprehensively analyzed through the employment of a differential scanning calorimeter (DSC) and the laser flash method (LFA). The addition of second-phase nanoparticles significantly increased the specific heat capacity of the alloy in the liquid state; however, the phenomenon of nanoparticle agglomeration diminishes this improvement. The analysis of the specific heat enhancement mechanism indicates that ordered states are formed between the second-phase solid nanoparticles and the melted metal in the liquid state. With the increase in temperature, the destruction of these ordered states requires additional heat, resulting in the increase of specific heat capacity. Full article

(This article belongs to the Section Metals and Alloys)

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10 pages, 2921 KiB

Open AccessEditor’s ChoiceArticle

Iron Selenide Particles for High-Performance Supercapacitors

by Davide Scarpa, Claudia Cirillo, Eleonora Ponticorvo, Carla Cirillo, Carmine Attanasio, Mariagrazia Iuliano and Maria Sarno

Materials 2023, 16(15), 5309; https://doi.org/10.3390/ma16155309 - 28 Jul 2023

Cited by 4 | Viewed by 861

Abstract

Nowadays, iron (II) selenide (FeSe), which has been widely studied for years to unveil the high-temperature superconductivity in iron-based superconductors, is drawing increasing attention in the electrical energy storage (EES) field as a supercapacitor electrode because of its many advantages. In this study, [...] Read more.

Nowadays, iron (II) selenide (FeSe), which has been widely studied for years to unveil the high-temperature superconductivity in iron-based superconductors, is drawing increasing attention in the electrical energy storage (EES) field as a supercapacitor electrode because of its many advantages. In this study, very small FeSe particles were synthesized via a simple, low-cost, easily scalable, and reproducible solvothermal method. The FeSe particles were characterized using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) measurements, and electrochemical impedance spectroscopy (EIS), revealing enhanced electrochemical properties: a high capacitance of 280 F/g at 0.5 A/g, a rather high energy density of 39 Wh/kg and a corresponding power density of 306 W/kg at 0.5 A/g, an extremely high cycling stability (capacitance retention of 92% after 30,000 cycles at 1 A/g), and a rather low equivalent series resistance (R_ESR) of ~2 Ω. Full article

(This article belongs to the Special Issue Physics and Application of Superconductivity)

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25 pages, 3730 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in the Synthesis and Application of Vacancy-Ordered Halide Double Perovskite Materials for Solar Cells: A Promising Alternative to Lead-Based Perovskites

by Santhosh Murugan and Eun-Cheol Lee

Materials 2023, 16(15), 5275; https://doi.org/10.3390/ma16155275 - 27 Jul 2023

Cited by 9 | Viewed by 1925

Abstract

Lead-based halide perovskite materials are being developed as efficient light-absorbing materials for use in perovskite solar cells (PSCs). PSCs have shown remarkable progress in power conversion efficiency, increasing from 3.80% to more than 25% within a decade, showcasing their potential as a promising [...] Read more.

Lead-based halide perovskite materials are being developed as efficient light-absorbing materials for use in perovskite solar cells (PSCs). PSCs have shown remarkable progress in power conversion efficiency, increasing from 3.80% to more than 25% within a decade, showcasing their potential as a promising renewable energy technology. Although PSCs have many benefits, including a high light absorption coefficient, the ability to tune band gap, and a long charge diffusion length, the poor stability and the toxicity of lead represent a significant disadvantage for commercialization. To address this issue, research has focused on developing stable and nontoxic halide perovskites for use in solar cells. A potential substitute is halide double perovskites (HDPs), particularly vacancy-ordered HDPs, as they offer greater promise because they can be processed using a solution-based method. This review provides a structural analysis of HDPs, the various synthesis methods for vacancy-ordered HDPs, and their impact on material properties. Recent advances in vacancy-ordered HDPs are also discussed, including their role in active and transport layers of solar cells. Furthermore, valuable insights for developing high-performance vacancy-ordered HDP solar cells are reported from the detailed information presented in recent simulation studies. Finally, the potential of vacancy-ordered HDPs as a substitute for lead-based perovskites is outlined. Overall, the ability to tune optical and electronic properties and the high stability and nontoxicity of HDPs have positioned them as a promising candidate for use in photovoltaic applications. Full article

(This article belongs to the Special Issue Advanced Nanostructured Materials for Solar Energy Conversion)

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18 pages, 17877 KiB

Open AccessEditor’s ChoiceArticle

Experimental Investigations of Ni–Ti–Ru System: Liquidus Surface Projection and 1150 °C Isothermal Section

by Dupei Ma, Zhi Li, Yan Liu, Manxiu Zhao and Jingxian Hu

Materials 2023, 16(15), 5299; https://doi.org/10.3390/ma16155299 - 27 Jul 2023

Viewed by 786

Abstract

Ruthenium addition inhibits the formation of the topologically close-packed phases in Ni-based superalloys and improves the solid solution strength of Ni–Ti shape memory alloys. Therefore, the Ni–Ti–Ru phase stability is a very valuable indicator of the effects of Ru in Ni-based superalloys and [...] Read more.

Ruthenium addition inhibits the formation of the topologically close-packed phases in Ni-based superalloys and improves the solid solution strength of Ni–Ti shape memory alloys. Therefore, the Ni–Ti–Ru phase stability is a very valuable indicator of the effects of Ru in Ni-based superalloys and Ni–Ti shape memory alloys. In this study, the isothermal section at 1150 °C and liquidus surface projection of the Ni–Ti–Ru ternary system were determined experimentally using the equilibrated alloy method and diffusion couple method, respectively. Alloys were prepared through the arc-melting of Ni, Ti, and Ru (all 99.99% purity), and then vacuum encapsulation in quartz tubes, followed by annealing at 1150 °C for 36 to 1080 h depending on the alloy composition. Diffusion couples were fabricated by joining one single-phase block (τ1) with one two-phase block (Ni₃Ti + γ(Ni)), and the couples were annealed under vacuum at 1150 °C for 168 h. Reaction temperatures of as-cast alloys were determined by differential scanning calorimetry performed with heating and cooling rates of 10 °C/min. Scanning electron microscopy and X-ray diffraction were used to analyze the microstructure. Seven three-phase regions were found at the 1150 °C isothermal section. Seven primary solidification regions and five ternary invariant reactions were deduced in the liquidus surface projection. A new ternary compound τ1 was discovered in both the isothermal section at 1150 °C and liquidus surface projection. The results aid in thermodynamic modeling of the system and provide guidance for designing Ni-based superalloys and Ni–Ti shape memory alloys. Full article

(This article belongs to the Special Issue Metallic Materials: Microstructure, Phase Equilibria and Thermodynamics)

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15 pages, 4888 KiB

Open AccessEditor’s ChoiceArticle

Influence of Multiple Used Implant Drills on Their Cutting Performance and Fracture Resistance

by Vasilios Alevizakos, Richard Mosch and Constantin von See

Materials 2023, 16(15), 5271; https://doi.org/10.3390/ma16155271 - 27 Jul 2023

Cited by 1 | Viewed by 830

Abstract

This study aimed to analyze the influence of multiple uses of zirconia implant drills on their cutting performance and bending strength. The hypothesis was that drill usage and sterilization cycles would not affect drilling time or flexural strength. Sixty zirconia twist drills from [...] Read more.

This study aimed to analyze the influence of multiple uses of zirconia implant drills on their cutting performance and bending strength. The hypothesis was that drill usage and sterilization cycles would not affect drilling time or flexural strength. Sixty zirconia twist drills from Z-Systems were used to drill in the angulus mandibulae region of fresh porcine jaws. The drills were divided into four groups based on the cycle count, and the drilling time was measured. Bending strength tests were conducted using a universal testing machine, and statistical analysis was performed using ANOVA tests. The results showed that drilling times followed a normal distribution, and significant differences were observed in drilling times between group 1 and the other groups for the pilot drill. However, no significant differences were found for ø3.75 mm and ø4.25 mm drills, and drilling times also varied significantly among different drill diameters, regardless of the cycle count. Flexural strength did not significantly differ among drill diameters or sterilization cycles. Overall, using and sterilizing zirconia implant drills had no significant impact on drilling time or flexural strength. Nevertheless, drilling times did vary depending on the diameter of the drill. These findings provide valuable insights into the performance and durability of zirconia implant drills, contributing to the optimization of dental implant procedures. Full article

(This article belongs to the Special Issue Dental Implants and Materials (Second Volume))

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13 pages, 1594 KiB

Open AccessEditor’s ChoiceArticle

Catalysis of a Diels–Alder Reaction between Azachalcones and Cyclopentadiene by a Recyclable Copper(II)-PEIP Metal-Organic Framework

by Eleni Hadjikyprianou, Sotiris Petrides, Andreas Kourtellaris, Anastasios J. Tasiopoulos and Savvas N. Georgiades

Materials 2023, 16(15), 5298; https://doi.org/10.3390/ma16155298 - 27 Jul 2023

Viewed by 860

Abstract

Metal-organic frameworks (MOFs) have attracted considerable interest as emerging heterogeneous catalysts for organic transformations of synthetic utility. Herein, a Lewis-acidic MOF, {[Cu₃(PEIP)₂(5-NH₂-mBDC)(DMF)]·7DMF}∞, denoted as Cu(ΙΙ)-PEIP, has been synthesized via a one-pot process and deployed as [...] Read more.

Metal-organic frameworks (MOFs) have attracted considerable interest as emerging heterogeneous catalysts for organic transformations of synthetic utility. Herein, a Lewis-acidic MOF, {[Cu₃(PEIP)₂(5-NH₂-mBDC)(DMF)]·7DMF}∞, denoted as Cu(ΙΙ)-PEIP, has been synthesized via a one-pot process and deployed as an efficient heterogeneous catalyst for a Diels–Alder cycloaddition. Specifically, the [4 + 2] cycloaddition of 13 substituted azachalcone dienophiles with cyclopentadiene has been investigated. MOF-catalyzed reaction conditions were optimized, leading to the selection of water as the solvent, in the presence of 10% mol sodium dodecyl sulfate (SDS) to address substrate solubility. The Cu(II)-PEIP catalyst showed excellent activity under these green and mild conditions, exhibiting comparable or, in some cases, superior efficiency to a homogeneous catalyst often employed in Diels–Alder reactions, namely, Cu(OTf)₂. The nature of the azachalcone substituent played a significant role in the reactivity of the dienophiles, with electron-withdrawing (EW) substituents enhancing conversion and electron-donating (ED) ones exhibiting the opposite effect. Coordinating substituents appeared to enhance the endo selectivity. Importantly, the Cu(II)-PEIP catalyst can be readily isolated from the reaction mixture and recycled up to four times without any significant reduction in conversion or selectivity. Full article

(This article belongs to the Special Issue Chemistry and Applications of Metal-Organic Frameworks)

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18 pages, 10869 KiB

Open AccessEditor’s ChoiceArticle

The Superiority of TiO₂ Supported on Nickel Foam over Ni-Doped TiO₂ in the Photothermal Decomposition of Acetaldehyde

by Beata Tryba, Piotr Miądlicki, Piotr Rychtowski, Maciej Trzeciak and Rafał Jan Wróbel

Materials 2023, 16(15), 5241; https://doi.org/10.3390/ma16155241 - 26 Jul 2023

Cited by 2 | Viewed by 1019

Abstract

Acetaldehyde decomposition was performed under heating at a temperature range of 25–125 °C and UV irradiation on TiO₂ doped by metallic Ni powder and TiO₂ supported on nickel foam. The process was carried out in a high-temperature reaction chamber, “The Praying [...] Read more.

Acetaldehyde decomposition was performed under heating at a temperature range of 25–125 °C and UV irradiation on TiO₂ doped by metallic Ni powder and TiO₂ supported on nickel foam. The process was carried out in a high-temperature reaction chamber, “The Praying Mantis^TM”, with simultaneous in situ FTIR measurements and UV irradiation. Ni powder was added to TiO₂ in the quantity of 0.5 to 5.0 wt%. The photothermal measurements of acetaldehyde decomposition indicated that the highest yield of acetaldehyde conversion on TiO₂ and UV irradiation was obtained at 75 °C. The doping of nickel to TiO₂ did not increase its photocatalytic activity. Contrary to that, the application of nickel foam as a support for TiO₂ appeared to be highly advantageous because it increased the decomposition of acetaldehyde from 31 to 52% at 25 °C, and then to 85% at 100 °C in comparison with TiO₂ itself. At the same time, the mineralization of acetaldehyde to CO₂ doubled in the presence of nickel foam. However, oxidized nickel foam used as support for TiO₂ was detrimental. Most likely, different mechanisms of electron transfer between Ni–TiO₂ and NiO-TiO₂ occurred. The application of nickel foam greatly enhanced the separation of free carriers in TiO₂. As a consequence, high yields from the photocatalytic reactions were obtained. Full article

(This article belongs to the Special Issue Advanced Photocatalytic Materials for Environmental and Energy Applications)

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20 pages, 5922 KiB

Open AccessEditor’s ChoiceReview

Asymmetric Extrusion Technology of Mg Alloy: A Review

by Qingshan Yang, Dan Zhang, Peng Peng, Guobing Wei, Jianyue Zhang, Bin Jiang and Fusheng Pan

Materials 2023, 16(15), 5255; https://doi.org/10.3390/ma16155255 - 26 Jul 2023

Cited by 1 | Viewed by 1099

Abstract

Magnesium (Mg) alloy is a widely used lightweight metal structural material due to its high specific strength and stiffness, excellent damping performance, and recyclability. Wrought Mg alloys are particularly favored in fields such as aerospace, transportation, and biomedical stents. However, most wrought Mg [...] Read more.

Magnesium (Mg) alloy is a widely used lightweight metal structural material due to its high specific strength and stiffness, excellent damping performance, and recyclability. Wrought Mg alloys are particularly favored in fields such as aerospace, transportation, and biomedical stents. However, most wrought Mg alloys with a hexagonal close-packed (HCP) crystal structure lack sufficient independent slip systems to meet the von Mises criterion for uniform plastic deformation at room temperature. This can result in the formation of a strong basal texture during plastic deformation and poor room temperature plastic formability. Enhancing the room temperature forming performance is therefore a crucial challenge that needs to be addressed in order to expand the application of Mg alloy sheets. Our research group has comprehensively summarized significant work and the latest research progress in improving the room temperature forming of Mg alloy sheets via extrusion technology in recent years. Specifically, we have developed a new type of asymmetric extrusion technology that combines material structure evolution, mechanical properties, and forming behavior analysis. We have elucidated the extrusion process characteristics, texture control mechanism, and forming properties of Mg alloy sheets through plastic deformation mechanisms, mold design, and finite element numerical simulation. The findings of our study present an innovative extrusion technology for the fabrication of highly formable Mg alloy sheets, which can be utilized in various applications. Full article

(This article belongs to the Special Issue Microstructure, Mechanical Properties, and Deformation Characteristics of Metals and Alloys)

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18 pages, 25099 KiB

Open AccessEditor’s ChoiceArticle

Corrosion and Erosion Wear Behaviors of HVOF-Sprayed Fe-Based Amorphous Coatings on Dissolvable Mg-RE Alloy Substrates

by Jun Yang, Yijiao Sun, Minwen Su, Xueming Yin, Hongxiang Li and Jishan Zhang

Materials 2023, 16(14), 5170; https://doi.org/10.3390/ma16145170 - 22 Jul 2023

Viewed by 599

Abstract

To suppress the corrosion and erosion wear of dissolvable magnesium alloy ball seats in wellbores, Fe-based amorphous coatings were deposited on dissolvable Mg-RE alloy substrates, and their microstructure, corrosion behavior, and erosion wear behavior were studied. The thickness of Fe-based amorphous coatings on [...] Read more.

To suppress the corrosion and erosion wear of dissolvable magnesium alloy ball seats in wellbores, Fe-based amorphous coatings were deposited on dissolvable Mg-RE alloy substrates, and their microstructure, corrosion behavior, and erosion wear behavior were studied. The thickness of Fe-based amorphous coatings on dissolvable Mg-RE alloy substrates can reach 1000 μm without any cracks, and their porosity and amorphous contents are 0.79% and 86.8%, respectively. Although chloride ions will damage the compactness and protective efficacy of passive films, Fe-based amorphous coatings still maintain low corrosion current density (3.31 μA/cm²) and high pitting potential (1 V_SCE) in 20 wt% KCl solution. Due to their higher hardness, the erosion wear resistance of Fe-based amorphous coatings is about 4.16 times higher than that of dissolvable Mg-RE alloy substrates when the impact angle is 30°. Moreover, the erosion rates of Fe-based amorphous coatings exhibit a nonlinear relationship with the impact angle, and the erosion rate reaches the highest value when the impact angle is 60°. The erosion wear mechanisms of Fe-based AMCs vary with the impact angles, including cutting, delamination, splat fracture, and deformation wear. This work can provide effective guidance for the corrosion and wear protection of plugging tools made from dissolvable magnesium alloy. Full article

(This article belongs to the Special Issue Coatings on Light Alloys Substrate—2nd Volume)

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35 pages, 33012 KiB

Open AccessEditor’s ChoiceReview

Dynamic Hydrogels with Viscoelasticity and Tunable Stiffness for the Regulation of Cell Behavior and Fate

by Yuhang Zhang, Zhuofan Wang, Qingqing Sun, Qian Li, Shaohui Li and Xiaomeng Li

Materials 2023, 16(14), 5161; https://doi.org/10.3390/ma16145161 - 21 Jul 2023

Cited by 6 | Viewed by 2260

Abstract

The extracellular matrix (ECM) of natural cells typically exhibits dynamic mechanical properties (viscoelasticity and dynamic stiffness). The viscoelasticity and dynamic stiffness of the ECM play a crucial role in biological processes, such as tissue growth, development, physiology, and disease. Hydrogels with viscoelasticity and [...] Read more.

The extracellular matrix (ECM) of natural cells typically exhibits dynamic mechanical properties (viscoelasticity and dynamic stiffness). The viscoelasticity and dynamic stiffness of the ECM play a crucial role in biological processes, such as tissue growth, development, physiology, and disease. Hydrogels with viscoelasticity and dynamic stiffness have recently been used to investigate the regulation of cell behavior and fate. This article first emphasizes the importance of tissue viscoelasticity and dynamic stiffness and provides an overview of characterization techniques at both macro- and microscale. Then, the viscoelastic hydrogels (crosslinked via ion bonding, hydrogen bonding, hydrophobic interactions, and supramolecular interactions) and dynamic stiffness hydrogels (softening, stiffening, and reversible stiffness) with different crosslinking strategies are summarized, along with the significant impact of viscoelasticity and dynamic stiffness on cell spreading, proliferation, migration, and differentiation in two-dimensional (2D) and three-dimensional (3D) cell cultures. Finally, the emerging trends in the development of dynamic mechanical hydrogels are discussed. Full article

(This article belongs to the Special Issue Feature Paper in the Section 'Polymeric Materials' (2nd Edition))

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32 pages, 5170 KiB

Open AccessEditor’s ChoiceArticle

Characterization of PLA Sheets Prepared by Stretching under Different Conditions: Influence of Reprocessing and Establishing Optimal Conditions

by Zaida Ortega, Paula Douglas, Paul R. Hanna, Graham Garrett, Alan Clarke, Eoin Cunningham and Luis Suárez

Materials 2023, 16(14), 5114; https://doi.org/10.3390/ma16145114 - 20 Jul 2023

Viewed by 912

Abstract

Polylactide (PLA) is one of the most commonly used biomaterials nowadays, with many recognized benefits, particularly in the packaging and single-use products industries. However, little research has been conducted on its stretching behavior. This work investigates the optimal conditions of biaxial stretching of [...] Read more.

Polylactide (PLA) is one of the most commonly used biomaterials nowadays, with many recognized benefits, particularly in the packaging and single-use products industries. However, little research has been conducted on its stretching behavior. This work investigates the optimal conditions of biaxial stretching of injection-molded PLA samples produced under different processing conditions (pressure, drying, and pre-processing by extrusion, to simulate a recycling step). The injection-molded samples were characterized to determine their mechanical, thermal and thermo-mechanical behavior, water absorption, thermal behavior, and crystallization kinetics. The extruded samples showed reduced thermal stability, lower viscosity, decreased mechanical properties, and higher crystallization rates due to thermal degradation. However, the stretched samples provided similar properties regardless of the materials pre-processing. Regarding the assessment of the biaxial stretching process, processing at lower temperatures provides the films with a higher yield and breaking strength, while the time and strain rates have little influence on such properties. It was then determined that 82 °C is the optimal temperature for stretching the PLA samples. An increase in the stretch ratio provided a higher elastic modulus and higher values of opacity due to an increased crystallinity induced by stress during the process. Films as thin as 50 μm can be obtained by biaxially stretching injection-molded preforms, producing a deformation over 150% and acquiring good mechanical properties: about 90 MPa for the yield and a breaking strength and elastic modulus of 4000 MPa. Full article

(This article belongs to the Special Issue Advanced Polymeric Materials: Synthesis, Properties, and Applications)

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21 pages, 5849 KiB

Open AccessEditor’s ChoiceArticle

Interesterification of Glyceryl Trioctanoate Catalyzed by Sulfonic Silica-Based Materials: Insight into the Role of Catalysts on the Reaction Mechanism

by Maria Luisa Testa, Maria Laura Tummino, Anna Maria Venezia and Marco Russo

Materials 2023, 16(14), 5121; https://doi.org/10.3390/ma16145121 - 20 Jul 2023

Cited by 1 | Viewed by 943

Abstract

In the present work, the acid-catalyzed interesterification of glyceryl trioctanoate (GTO) with ethyl acetate was investigated as a model reaction for the one-step production of biofuel and its additives. The activity of heterogeneous acid catalysts, such as silica-based propyl-sulfonic ones, was evaluated. Propyl-sulfonic [...] Read more.

In the present work, the acid-catalyzed interesterification of glyceryl trioctanoate (GTO) with ethyl acetate was investigated as a model reaction for the one-step production of biofuel and its additives. The activity of heterogeneous acid catalysts, such as silica-based propyl-sulfonic ones, was evaluated. Propyl-sulfonic groups were grafted on both amorphous and mesoporous silica oxide (SBA-15, KIT-6) using different functionalization processes and characterized by N₂ adsorpion–desorption isotherm (BET), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy, and potentiometric titration. During the optimization of the reaction conditions with the most active catalyst (Am-Pr-SO₃H), it was shown that the addition of ethanol allowed a total conversion of GTO together with 89% and 56% yield of ethyl octanoate and triacetin, respectively. The catalytic performance is strictly correlated to the catalyst features, in terms of both the acid capacity and the porous structure. Moreover, the catalytic performance is also affected by a synergistic mechanism between silanols and Pr-SO₃H groups towards the ‘silanolysis’ of ethyl acetate. The overall results show that the presence of ethanol, the reaction time, and the amount of catalyst shifts the reaction towards the formation of the biofuel mixture composed by ethyl octanoate and triacetin. Full article

(This article belongs to the Special Issue Heterogeneous Catalysts for Biomass Conversion and Environmental Remediation)

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13 pages, 4051 KiB

Open AccessEditor’s ChoiceArticle

Nondestructive Evaluation of Residual Stress in Shot Peened Inconel Using Ultrasonic Minimum Reflection Measurement

by Yeong-Won Choi, Taek-Gyu Lee, Yun-Taek Yeom, Sung-Duk Kwon, Hun-Hee Kim, Kee-Young Lee, Hak-Joon Kim and Sung-Jin Song

Materials 2023, 16(14), 5075; https://doi.org/10.3390/ma16145075 - 18 Jul 2023

Cited by 1 | Viewed by 799

Abstract

Shot peening is a process wherein the surface of a material is impacted by small, spherical metal shots at high velocity to create residual stresses. Nickel-based superalloy is a material with high strength and hardness along with excellent corrosion and fatigue resistance, and [...] Read more.

Shot peening is a process wherein the surface of a material is impacted by small, spherical metal shots at high velocity to create residual stresses. Nickel-based superalloy is a material with high strength and hardness along with excellent corrosion and fatigue resistance, and it is therefore used in nuclear power plants and aerospace applications. The application of shot peening to INCONEL, a nickel-based superalloy, has been actively researched, and the measurement of residual stresses has been studied as well. Previous studies have used methods such as perforation strain gauge analysis and X-ray diffraction (XRD) to measure residual stress, which can be evaluated with high accuracy, but doing so damages the specimen and involves critical risks to operator safety due to radiation. On the other hand, ultrasonic testing (UT), which utilizes ultrasonic wave, has the advantage of relatively low unit cost and short test time. One UT method, minimum reflection measurement, uses Rayleigh waves to evaluate the properties of material surfaces. Therefore, the present study utilized ultrasonic minimum reflectivity measurements to evaluate the residual stresses in INCONEL specimens. Specifically, this study utilized ultrasonic minimum reflection measurements to evaluate the residual stress in INCONEL 718 specimens. Moreover, an estimation equation was assumed using exponential functions to estimate the residual stress with depth using the obtained data, and an optimization problem was solved to determine it. Finally, to evaluate the estimated residual stress graph, the residual stress of the specimen was measured and compared using the XRD method. Full article

(This article belongs to the Special Issue Advances in Nondestructive Evaluation of Materials and Structures)

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13 pages, 5300 KiB

Open AccessEditor’s ChoiceArticle

Porous Rod-like NiTiO₃-BiOBr Heterojunctions with Highly Improved Visible-Light Photocatalytic Performance

by Kaiyue Sun, Mengchao Li, Hualei Zhou, Xiaohui Ma and Wenjun Li

Materials 2023, 16(14), 5033; https://doi.org/10.3390/ma16145033 - 17 Jul 2023

Viewed by 928

Abstract

NiTiO₃-BiOBr heterostructured photocatalysts were constructed via precipitation, calcination and hydrothermal treatments. Various characterizations demonstrated that BiOBr nanosheets were decorated on NiTiO₃ nanoparticals, forming porous rod-like heterojunctions. Compared with independent NiTiO₃ and BiOBr, the composites with optimal BiOBr content presented [...] Read more.

NiTiO₃-BiOBr heterostructured photocatalysts were constructed via precipitation, calcination and hydrothermal treatments. Various characterizations demonstrated that BiOBr nanosheets were decorated on NiTiO₃ nanoparticals, forming porous rod-like heterojunctions. Compared with independent NiTiO₃ and BiOBr, the composites with optimal BiOBr content presented highly improved visible-light photocatalytic efficiency. The degradation rates of Rhodamine B (RhB) and tetracycline (TC) reached 96.6% in 1.5 h (100% in 2 h) and 73.5% in 3 h, which are 6.61 and 1.53 times those of NiTiO₃, respectively. The result is an improved photocatalytic behavior from the formation of heterojunctions with a large interface area, which significantly promoted the separation of photogenerated carriers and strengthened the visible-light absorption. Based on the free radical capture experiments and band position analysis, the photodegradation mechanism of type-II heterojunction was deduced. This study provides a new way to fabricate highly efficient NiTiO₃-based photocatalysts for degrading certain organics. Full article

(This article belongs to the Special Issue Research on Electrocatalytic Materials for Hydrogen Evolution and Oxygen Evolution)

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26 pages, 4639 KiB

Open AccessEditor’s ChoiceReview

A Review on Multiple I-III-VI Quantum Dots: Preparation and Enhanced Luminescence Properties

by Ting Chen, Yuanhong Chen, Youpeng Li, Mengbiao Liang, Wenkui Wu and Yude Wang

Materials 2023, 16(14), 5039; https://doi.org/10.3390/ma16145039 - 17 Jul 2023

Cited by 3 | Viewed by 1879

Abstract

I-III-VI type QDs have unique optoelectronic properties such as low toxicity, tunable bandgaps, large Stokes shifts and a long photoluminescence lifetime, and their emission range can be continuously tuned in the visible to near-infrared light region by changing their chemical composition. Moreover, they [...] Read more.

I-III-VI type QDs have unique optoelectronic properties such as low toxicity, tunable bandgaps, large Stokes shifts and a long photoluminescence lifetime, and their emission range can be continuously tuned in the visible to near-infrared light region by changing their chemical composition. Moreover, they can avoid the use of heavy metal elements such as Cd, Hg and Pb and highly toxic anions, i.e., Se, Te, P and As. These advantages make them promising candidates to replace traditional binary QDs in applications such as light-emitting diodes, solar cells, photodetectors, bioimaging fields, etc. Compared with binary QDs, multiple QDs contain many different types of metal ions. Therefore, the problem of different reaction rates between the metal ions arises, causing more defects inside the crystal and poor fluorescence properties of QDs, which can be effectively improved by doping metal ions (Zn²⁺, Mn²⁺ and Cu⁺) or surface coating. In this review, the luminous mechanism of I-III-VI type QDs based on their structure and composition is introduced. Meanwhile, we focus on the various synthesis methods and improvement strategies like metal ion doping and surface coating from recent years. The primary applications in the field of optoelectronics are also summarized. Finally, a perspective on the challenges and future perspectives of I-III-VI type QDs is proposed as well. Full article

(This article belongs to the Special Issue Advances of Photoelectric Functional Materials and Devices)

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18 pages, 6897 KiB

Open AccessEditor’s ChoiceArticle

Estimation of Cyclic Stress–Strain Curves of Steels Based on Monotonic Properties Using Artificial Neural Networks

by Tea Marohnić, Robert Basan and Ela Marković

Materials 2023, 16(14), 5010; https://doi.org/10.3390/ma16145010 - 15 Jul 2023

Viewed by 1178

Abstract

This paper introduces a novel method for estimating the cyclic stress–strain curves of steels based on their monotonic properties and plastic strain amplitudes, utilizing artificial neural networks (ANNs). ANNs were trained on a substantial number of experimental data for steels, collected from relevant [...] Read more.

This paper introduces a novel method for estimating the cyclic stress–strain curves of steels based on their monotonic properties and plastic strain amplitudes, utilizing artificial neural networks (ANNs). ANNs were trained on a substantial number of experimental data for steels, collected from relevant literature, and divided into subgroups according to alloying elements content (unalloyed, low-alloy, and high-alloy steels). Only monotonic properties that were proven to be relevant for the estimation of points on the stress–strain curve were used. The performance of the developed ANNs was assessed using an independent set of data, and the results were compared to experimental values, values obtained by existing empirical estimation methods, and by previously developed ANNs. The results showed that the new approach which combines relevant monotonic properties and plastic strain amplitudes as inputs to ANNs for cyclic stress–strain curve estimation is better than the previously used approach where ANNs estimate the parameters of the Ramberg–Osgood material model separately. This shows that a more favorable approach to the estimation of cyclic stress–strain behavior would be to directly estimate corresponding material curves using monotonic properties. Additionally, this may also reduce inaccuracies resulting from simplified representations of the actual material behavior inherent in the material model. Full article

(This article belongs to the Special Issue Machine Learning Techniques in Materials Science and Engineering)

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16 pages, 5269 KiB

Open AccessEditor’s ChoiceArticle

Design and Synthesis of NTU-9/C₃N₄ Photocatalysts: Effects of NTU-9 Content and Composite Preparation Method

by Damian Makowski, Wojciech Lisowski, Mateusz A. Baluk, Tomasz Klimczuk and Beata Bajorowicz

Materials 2023, 16(14), 5007; https://doi.org/10.3390/ma16145007 - 14 Jul 2023

Cited by 1 | Viewed by 1004

Abstract

Hybrid materials based on graphitic carbon nitride (g-C₃N₄) and NTU-9 metal–organic frameworks (MOF) were designed and prepared via solvothermal synthesis and calcination in air. The as-prepared photocatalysts were subsequently characterized using Brunauer–Emmett–Teller (BET) analysis, UV-Vis diffuse reflectance spectroscopy (DRS), [...] Read more.

Hybrid materials based on graphitic carbon nitride (g-C₃N₄) and NTU-9 metal–organic frameworks (MOF) were designed and prepared via solvothermal synthesis and calcination in air. The as-prepared photocatalysts were subsequently characterized using Brunauer–Emmett–Teller (BET) analysis, UV-Vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) emission spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The obtained NTU-9/C₃N₄ composites showed a greatly improved photocatalytic performance for the degradation of toluene in the gas phase under LED visible-light irradiation (λ_max = 415 nm). The physicochemical properties and photocatalytic activities of the obtained NTU-9/C₃N₄ materials were tuned by varying the NTU-9 content (5–15 wt%) and preparation method of the composite materials. For composites prepared by calcination, the photocatalytic activity increased with decreasing NTU-9 content as a result of the formation of TiO₂ from the MOFs. The best photocatalytic performance (65% of toluene was photodegraded after 60 min) was achieved by the NTU-9/C₃N₄ sample prepared via the solvothermal method and containing 15 wt% MOF, which can be attributed to the appropriate amount and stable combination of composite components, efficient charge separation, and enhanced visible-light absorption ability. The photocatalytic mechanisms of the prepared hybrid materials depending on the preparation method are also discussed. Full article

(This article belongs to the Section Materials Chemistry)

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19 pages, 2788 KiB

Open AccessEditor’s ChoiceReview

Computational Materials Design for Ceramic Nuclear Waste Forms Using Machine Learning, First-Principles Calculations, and Kinetics Rate Theory

by Jianwei Wang, Dipta B. Ghosh and Zelong Zhang

Materials 2023, 16(14), 4985; https://doi.org/10.3390/ma16144985 - 13 Jul 2023

Cited by 2 | Viewed by 1160

Abstract

Ceramic waste forms are designed to immobilize radionuclides for permanent disposal in geological repositories. One of the principal criteria for the effective incorporation of waste elements is their compatibility with the host material. In terms of performance under environmental conditions, the resistance of [...] Read more.

Ceramic waste forms are designed to immobilize radionuclides for permanent disposal in geological repositories. One of the principal criteria for the effective incorporation of waste elements is their compatibility with the host material. In terms of performance under environmental conditions, the resistance of the waste forms to degradation over long periods of time is a critical concern when they are exposed to natural environments. Due to their unique crystallographic features and behavior in nature environment as exemplified by their natural analogues, ceramic waste forms are capable of incorporating problematic nuclear waste elements while showing promising chemical durability in aqueous environments. Recent studies of apatite- and hollandite-structured waste forms demonstrated an approach that can predict the compositions of ceramic waste forms and their long-term dissolution rate by a combination of computational techniques including machine learning, first-principles thermodynamics calculations, and modeling using kinetic rate equations based on critical laboratory experiments. By integrating the predictions of elemental incorporation and degradation kinetics in a holistic framework, the approach could be promising for the design of advanced ceramic waste forms with optimized incorporation capacity and environmental degradation performance. Such an approach could provide a path for accelerated ceramic waste form development and performance prediction for problematic nuclear waste elements. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Materials Chemistry)

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