Materials

20 pages, 17038 KiB

Open AccessEditor’s ChoiceArticle

Microstructural Understanding of Flow Accelerated Corrosion of SA106B Carbon Steel in High-Temperature Water with Different Flow Velocities

by Ying Hu, Long Xin, Chang Hong, Yongming Han and Yonghao Lu

Materials 2023, 16(11), 3981; https://doi.org/10.3390/ma16113981 - 26 May 2023

Cited by 4 | Viewed by 1256

Abstract

All light or heavy water reactors fabricated with carbon steels suffer from flow-accelerated corrosion (FAC). The FAC degradation of SA106B with different flow velocities was investigated in terms of microstructure. As flow velocity increased, the major corrosion type changed from general corrosion to [...] Read more.

All light or heavy water reactors fabricated with carbon steels suffer from flow-accelerated corrosion (FAC). The FAC degradation of SA106B with different flow velocities was investigated in terms of microstructure. As flow velocity increased, the major corrosion type changed from general corrosion to localized corrosion. Severe localized corrosion occurred in the pearlite zone, which can be the prior location for generating pits. After normalizing, the improvement in microstructure homogeneity reduced the oxidation kinetics and lowered cracking sensitivity, causing a decrease in FAC rates of 33.28%, 22.47%, 22.15%, and 17.53% at flow velocity of 0 m/s, 1.63 m/s, 2.99 m/s, and 4.34 m/s, respectively. Additionally, localized corrosion tendency was decreased by reducing the micro-galvanic effect and tensile stresses in oxide film. The maximum localized corrosion rate decreased by 21.7%, 13.5%, 13.8%, and 25.4% at flow velocity of 0 m/s, 1.63 m/s, 2.99 m/s, and 4.34 m/s, respectively. Full article

(This article belongs to the Special Issue Corrosion Mechanism and Protection Technology of Metallic Materials)

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23 pages, 4413 KiB

Open AccessEditor’s ChoiceReview

Copper-Based Electrocatalysts for Nitrate Reduction to Ammonia

by Jia-Yi Fang, Jin-Long Fan, Sheng-Bo Liu, Sheng-Peng Sun and Yao-Yin Lou

Materials 2023, 16(11), 4000; https://doi.org/10.3390/ma16114000 - 26 May 2023

Cited by 7 | Viewed by 2935

Abstract

Ammonia (NH₃) is a highly important industrial chemical used as fuel and fertilizer. The industrial synthesis of NH₃ relies heavily on the Haber–Bosch route, which accounts for roughly 1.2% of global annual CO₂ emissions. As an alternative route, the [...] Read more.

Ammonia (NH₃) is a highly important industrial chemical used as fuel and fertilizer. The industrial synthesis of NH₃ relies heavily on the Haber–Bosch route, which accounts for roughly 1.2% of global annual CO₂ emissions. As an alternative route, the electrosynthesis of NH₃ from nitrate anion (NO₃⁻) reduction (NO₃⁻RR) has drawn increasing attention, since NO₃⁻RR from wastewater to produce NH₃ can not only recycle waste into treasure but also alleviate the adverse effects of excessive NO₃⁻ contamination in the environment. This review presents contemporary views on the state of the art in electrocatalytic NO₃⁻ reduction over Cu-based nanostructured materials, discusses the merits of electrocatalytic performance, and summarizes current advances in the exploration of this technology using different strategies for nanostructured-material modification. The electrocatalytic mechanism of nitrate reduction is also reviewed here, especially with regard to copper-based catalysts. Full article

(This article belongs to the Special Issue Electrochemical Materials and Devices for Energy Conversion and Storage)

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23 pages, 2594 KiB

Open AccessEditor’s ChoiceReview

Advancement of Nonwoven Fabrics in Personal Protective Equipment

by Dhanya Venkataraman, Elnaz Shabani and Jay H. Park

Materials 2023, 16(11), 3964; https://doi.org/10.3390/ma16113964 - 25 May 2023

Cited by 6 | Viewed by 3039

Abstract

While nonwoven fabrics have existed for several decades, their usage in personal protective equipment (PPE) has been met with a rapid surge of demands, in part due to the recent COVID-19 pandemic. This review aims to critically examine the current state of nonwoven [...] Read more.

While nonwoven fabrics have existed for several decades, their usage in personal protective equipment (PPE) has been met with a rapid surge of demands, in part due to the recent COVID-19 pandemic. This review aims to critically examine the current state of nonwoven PPE fabrics by exploring (i) the material constituents and processing steps to produce fibers and bond them, and (ii) how each fabric layer is integrated into a textile, and how the assembled textiles are used as PPE. Firstly, filament fibers are manufactured via dry, wet, and polymer-laid fiber spinning methods. Then the fibers are bonded via chemical, thermal, and mechanical means. Emergent nonwoven processes such as electrospinning and centrifugal spinning to produce unique ultrafine nanofibers are discussed. Nonwoven PPE applications are categorized as filters, medical usage, and protective garments. The role of each nonwoven layer, its role, and textile integration are discussed. Finally, the challenges stemming from the single-use nature of nonwoven PPEs are discussed, especially in the context of growing concerns over sustainability. Then, emerging solutions to address sustainability issues with material and processing innovations are explored. Full article

(This article belongs to the Special Issue Advances in High-Performance Functional Nonwovens)

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13 pages, 4713 KiB

Open AccessEditor’s ChoiceArticle

Alloy Disordering Effects on the Thermal Conductivity and Energy Gap Temperature Dependence of Cd_1−xZn_xSe Ternary Crystals Grown by the Bridgman Method

by Karol Strzałkowski, Ali Abouais, Amine Alaoui-Belghiti, Diksha Singh and Abdelowahed Hajjaji

Materials 2023, 16(11), 3945; https://doi.org/10.3390/ma16113945 - 25 May 2023

Cited by 4 | Viewed by 900

Abstract

Investigated in this work, Cd_1−xZn_xSe-mixed ternary compounds were grown by the Bridgman method. Several compounds with zinc content varying in the range 0 < x < 1 were produced between two binary parents, CdSe and ZnSe crystals. Using the [...] Read more.

Investigated in this work, Cd_1−xZn_xSe-mixed ternary compounds were grown by the Bridgman method. Several compounds with zinc content varying in the range 0 < x < 1 were produced between two binary parents, CdSe and ZnSe crystals. Using the SEM/EDS technique, the accurate composition of formed crystals was determined along the growth axis. Thanks to that, the grown crystals’ axial and radial uniformity were determined. Characterization of the optical and thermal properties was undertaken. The energy gap was measured using photoluminescence spectroscopy for different compositions and temperatures. The bowing parameter describing the behavior of the fundamental gap with composition for this compound was found to be 0.416 ± 0.06. The thermal characteristics of grown Cd_1−xZn_xSe alloys were systematically studied. The thermal diffusivity and effusivity of the crystals under investigation were experimentally determined, allowing the calculation of the thermal conductivity. We applied the semi-empirical model that Sadao Adachi developed to analyze the results. Thanks to that, it was possible to estimate the contribution arising from chemical disorder to the crystal’s total resistivity. Full article

(This article belongs to the Special Issue Crystallographic Design of Material Thermal Properties)

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18 pages, 5017 KiB

Open AccessEditor’s ChoiceArticle

Core–Shell Spheroid Structure TiO₂/CdS Composites with Enhanced Photocathodic Protection Performance

by Tingting Chen, Bo Li, Xiaolong Zhang, Xiang Ke and Rengui Xiao

Materials 2023, 16(11), 3927; https://doi.org/10.3390/ma16113927 - 24 May 2023

Cited by 1 | Viewed by 1071

Abstract

In order to improve the conversion and transmission efficiency of the photoelectron, core–shell spheroid structure titanium dioxide/cadmium sulfide (TiO₂/CdS) composites were synthesized as epoxy-based coating fillers using a simple hydrothermal method. The electrochemical performance of photocathodic protection for the epoxy-based composite [...] Read more.

In order to improve the conversion and transmission efficiency of the photoelectron, core–shell spheroid structure titanium dioxide/cadmium sulfide (TiO₂/CdS) composites were synthesized as epoxy-based coating fillers using a simple hydrothermal method. The electrochemical performance of photocathodic protection for the epoxy-based composite coating was analyzed by coating it on the Q235 carbon steel surface. The results show that the epoxy-based composite coating possesses a significant photoelectrochemical property with a photocurrent density of 0.0421 A/cm² and corrosion potential of −0.724 V. Importantly, the modified composite coating can extend absorption in the visible region and effectively separate photoelectron hole pairs to improve the photoelectrochemical performance synergistically, because CdS can be regarded as a sensitizer to be introduced into TiO₂ to form a heterojunction system. The mechanism of photocathodic protection is attributed to the potential energy difference between Fermi energy and excitation level, which leads to the system obtaining higher electric field strength at the heterostructure interface, thus driving electrons directly into the surface of Q235 carbon steel (Q235 CS). Moreover, the photocathodic protection mechanism of the epoxy-based composite coating for Q235 CS is investigated in this paper. Full article

(This article belongs to the Special Issue Functional Nanomaterials for a Better Life (Volume II))

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22 pages, 3849 KiB

Open AccessEditor’s ChoiceReview

A Review on Sustainable Inks for Printed Electronics: Materials for Conductive, Dielectric and Piezoelectric Sustainable Inks

by Leire Sanchez-Duenas, Estibaliz Gomez, Mikel Larrañaga, Miren Blanco, Amaia M. Goitandia, Estibaliz Aranzabe and José Luis Vilas-Vilela

Materials 2023, 16(11), 3940; https://doi.org/10.3390/ma16113940 - 24 May 2023

Cited by 6 | Viewed by 3053

Abstract

In the last decades, the demand for electronics and, therefore, electronic waste, has increased. To reduce this electronic waste and the impact of this sector on the environment, it is necessary to develop biodegradable systems using naturally produced materials with low impact on [...] Read more.

In the last decades, the demand for electronics and, therefore, electronic waste, has increased. To reduce this electronic waste and the impact of this sector on the environment, it is necessary to develop biodegradable systems using naturally produced materials with low impact on the environment or systems that can degrade in a certain period. One way to manufacture these types of systems is by using printed electronics because the inks and the substrates used are sustainable. Printed electronics involve different methods of deposition, such as screen printing or inkjet printing. Depending on the method of deposition selected, the developed inks should have different properties, such as viscosity or solid content. To produce sustainable inks, it is necessary to ensure that most of the materials used in the formulation are biobased, biodegradable, or not considered critical raw materials. In this review, different inks for inkjet printing or screen printing that are considered sustainable, and the materials that can be used to formulate them, are collected. Printed electronics need inks with different functionalities, which can be mainly classified into three groups: conductive, dielectric, or piezoelectric inks. Materials need to be selected depending on the ink’s final purpose. For example, functional materials such as carbon or biobased silver should be used to secure the conductivity of an ink, a material with dielectric properties could be used to develop a dielectric ink, or materials that present piezoelectric properties could be mixed with different binders to develop a piezoelectric ink. A good combination of all the components selected must be achieved to ensure the proper features of each ink. Full article

(This article belongs to the Special Issue Advanced and Multifunctional Flexible Electronic Materials and Devices)

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20 pages, 9327 KiB

Open AccessEditor’s ChoiceArticle

Numerical Study of Ti6Al4V Alloy Tube Heated by Super-Frequency Induction Heating

by Cheng Liu, Jingtao Han, Ruilong Lu, Jiawei Liu and Xiaoyan Ma

Materials 2023, 16(11), 3938; https://doi.org/10.3390/ma16113938 - 24 May 2023

Cited by 1 | Viewed by 953

Abstract

Ti6Al4V alloys have a narrow processing window, which complicates temperature control, especially during large-scale production. Therefore, a numerical simulation and experimental study on the ultrasonic induction heating process of a Ti6Al4V titanium alloy tube were conducted to obtain stable heating. The electromagnetic and [...] Read more.

Ti6Al4V alloys have a narrow processing window, which complicates temperature control, especially during large-scale production. Therefore, a numerical simulation and experimental study on the ultrasonic induction heating process of a Ti6Al4V titanium alloy tube were conducted to obtain stable heating. The electromagnetic and thermal fields in the process of ultrasonic frequency induction heating were calculated. The effects of the current frequency and current value on the thermal and current fields were numerically analyzed. The increase in current frequency enhances the skin and edge effects, but heat permeability was achieved in the super audio frequency range, and the temperature difference between the interior and exterior of the tube was less than 1%. An increase in the applied current value and current frequency caused an increase in the tube’s temperature, but the influence of current was more prominent. Therefore, the influence of stepwise feeding, reciprocating motion, and stepwise feeding superimposed motion on the heating temperature field of the tube blank was evaluated. The coil reciprocating with the roll can maintain the temperature of the tube within the target temperature range during the deformation stage. The simulation results were validated experimentally, which demonstrated good agreement between the results. The numerical simulation method can be used to monitor the temperature distribution of Ti6Al4V alloy tubes during the super-frequency induction heating process. This is an economical and effective tool for predicting the induction heating process of Ti6Al4V alloy tubes. Moreover, online induction heating in the form of reciprocating motion is a feasible strategy for processing Ti6Al4V alloy tubes. Full article

(This article belongs to the Special Issue Analytical and Computational Methods in Material and Mechanical Engineering)

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61 pages, 18764 KiB

Open AccessEditor’s ChoiceReview

Polymer-Matrix Composites: Characterising the Impact of Environmental Factors on Their Lifetime

by Rui Barreira-Pinto, Rodrigo Carneiro, Mário Miranda and Rui Miranda Guedes

Materials 2023, 16(11), 3913; https://doi.org/10.3390/ma16113913 - 23 May 2023

Cited by 9 | Viewed by 2769

Abstract

Polymer-matrix composites are widely used in engineering applications. Yet, environmental factors impact their macroscale fatigue and creep performances significantly, owing to several mechanisms acting at the microstructure level. Herein, we analyse the effects of water uptake that are responsible for swelling and, over [...] Read more.

Polymer-matrix composites are widely used in engineering applications. Yet, environmental factors impact their macroscale fatigue and creep performances significantly, owing to several mechanisms acting at the microstructure level. Herein, we analyse the effects of water uptake that are responsible for swelling and, over time and in enough quantity, for hydrolysis. Seawater, due to a combination of high salinity and pressures, low temperature and biotic media present, also contributes to the acceleration of fatigue and creep damage. Similarly, other liquid corrosive agents penetrate into cracks induced by cyclic loading and cause dissolution of the resin and breakage of interfacial bonds. UV radiation either increases the crosslinking density or scissions chains, embrittling the surface layer of a given matrix. Temperature cycles close to the glass transition damage the fibre–matrix interface, promoting microcracking and hindering fatigue and creep performance. The microbial and enzymatic degradation of biopolymers is also studied, with the former responsible for metabolising specific matrices and changing their microstructure and/or chemical composition. The impact of these environmental factors is detailed for epoxy, vinyl ester and polyester (thermoset); polypropylene, polyamide and poly etheretherketone (thermoplastic); and for poly lactic acid, thermoplastic starch and polyhydroxyalkanoates (biopolymers). Overall, the environmental factors mentioned hamper the fatigue and creep performances, altering the mechanical properties of the composite or causing stress concentrations through microcracks, promoting earlier failure. Future studies should focus on other matrices beyond epoxy as well as on the development of standardised testing methods. Full article

(This article belongs to the Section Advanced Composites)

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14 pages, 2420 KiB

Open AccessEditor’s ChoiceArticle

Construction of Bio-TiO₂/Algae Complex and Synergetic Mechanism of the Acceleration of Phenol Biodegradation

by Jinxin Guo, Xiaoman Guo, Haiyan Yang, Daohong Zhang and Xiaogeng Jiang

Materials 2023, 16(10), 3882; https://doi.org/10.3390/ma16103882 - 22 May 2023

Cited by 1 | Viewed by 1152

Abstract

Microalgae have been widely employed in water pollution treatment since they are eco-friendly and economical. However, the relatively slow treatment rate and low toxic tolerance have seriously limited their utilization in numerous conditions. In light of the problems above, a novel biosynthetic titanium [...] Read more.

Microalgae have been widely employed in water pollution treatment since they are eco-friendly and economical. However, the relatively slow treatment rate and low toxic tolerance have seriously limited their utilization in numerous conditions. In light of the problems above, a novel biosynthetic titanium dioxide (bio-TiO₂ NPs)—microalgae synergetic system (Bio-TiO₂/Algae complex) has been established and adopted for phenol degradation in the study. The great biocompatibility of bio-TiO₂ NPs ensured the collaboration with microalgae, improving the phenol degradation rate by 2.27 times compared to that with single microalgae. Remarkably, this system increased the toxicity tolerance of microalgae, represented as promoted extracellular polymeric substances EPS secretion (5.79 times than single algae), and significantly reduced the levels of malondialdehyde and superoxide dismutase. The boosted phenol biodegradation with Bio-TiO₂/Algae complex may be attributed to the synergetic interaction of bio-TiO₂ NPs and microalgae, which led to the decreased bandgap, suppressed recombination rate, and accelerated electron transfer (showed as low electron transfer resistance, larger capacitance, and higher exchange current density), resulting in increased light energy utilization rate and photocatalytic rate. The results of the work provide a new understanding of the low-carbon treatment of toxic organic wastewater and lay a foundation for further remediation application. Full article

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

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12 pages, 5403 KiB

Open AccessEditor’s ChoiceArticle

Effects of Steel Slag Powder Content and Curing Condition on the Performance of Alkali-Activated Materials Based UHPC Matrix

by Kangyi Shi, Hongyang Deng, Jinxuan Hu, Junqi Zhou, Xinhua Cai and Zhiwei Liu

Materials 2023, 16(10), 3875; https://doi.org/10.3390/ma16103875 - 21 May 2023

Cited by 3 | Viewed by 1565

Abstract

The accumulation of steel slag and other industrial solid wastes has caused serious environmental pollution and resource waste, and the resource utilization of steel slag is imminent. In this paper, alkali-activated ultra-high-performance concrete (AAM-UHPC) was prepared by replacing ground granulated blast furnace slag [...] Read more.

The accumulation of steel slag and other industrial solid wastes has caused serious environmental pollution and resource waste, and the resource utilization of steel slag is imminent. In this paper, alkali-activated ultra-high-performance concrete (AAM-UHPC) was prepared by replacing ground granulated blast furnace slag (GGBFS) powder with different proportions of steel slag powder, and its workability, mechanical properties, curing condition, microstructure, and pore structure were investigated. The results illustrate that the incorporation of steel slag powder can significantly delay the setting time and improve the flowability of AAM-UHPC, making it possible for engineering applications. The mechanical properties of AAM-UHPC showed a tendency to increase and then decrease with the increase in steel slag dosing and reached their best performance at a 30% dosage of steel slag. The maximum compressive strength and flexural strength are 157.1 MPa and 16.32 Mpa, respectively. High-temperature steam or hot water curing at an early age was beneficial to the strength development of AAM-UHPC, but continuous high-temperature, hot, and humid curing would lead to strength inversion. When the dosage of steel slag is 30%, the average pore diameter of the matrix is only 8.43 nm, and the appropriate steel slag dosage can reduce the heat of hydration and refine the pore size distribution, making the matrix denser. Full article

(This article belongs to the Collection Alkali‐Activated Materials for Sustainable Construction)

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12 pages, 2849 KiB

Open AccessEditor’s ChoiceArticle

Validating the Use of Gaussian Process Regression for Adaptive Mapping of Residual Stress Fields

by Chris M. Fancher, Singanallur Venkatakrishnan, Thomas Feldhausen, Kyle Saleeby and Alex Plotkowski

Materials 2023, 16(10), 3854; https://doi.org/10.3390/ma16103854 - 20 May 2023

Viewed by 1085

Abstract

Probing the stress state using a high density of measurement points is time intensive and presents a limitation for what is experimentally feasible. Alternatively, individual strain fields used for determining stresses can be reconstructed from a subset of points using a Gaussian process [...] Read more.

Probing the stress state using a high density of measurement points is time intensive and presents a limitation for what is experimentally feasible. Alternatively, individual strain fields used for determining stresses can be reconstructed from a subset of points using a Gaussian process regression (GPR). Results presented in this paper evidence that determining stresses from reconstructed strain fields is a viable approach for reducing the number of measurements needed to fully sample a component’s stress state. The approach was demonstrated by reconstructing the stress fields in wire-arc additively manufactured walls fabricated using either a mild steel or low-temperature transition feedstock. Effects of errors in individual GP reconstructed strain maps and how these errors propagate to the final stress maps were assessed. Implications of the initial sampling approach and how localized strains affect convergence are explored to give guidance on how best to implement a dynamic sampling experiment. Full article

(This article belongs to the Special Issue Neutron Scattering Studies in Materials Science)

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38 pages, 9986 KiB

Open AccessEditor’s ChoiceReview

Advances in Cellulose-Based Composites for Energy Applications

by Choon Peng Teng, Ming Yan Tan, Jessica Pei Wen Toh, Qi Feng Lim, Xiaobai Wang, Daniel Ponsford, Esther Marie JieRong Lin, Warintorn Thitsartarn and Si Yin Tee

Materials 2023, 16(10), 3856; https://doi.org/10.3390/ma16103856 - 20 May 2023

Cited by 10 | Viewed by 4054

Abstract

The various forms of cellulose-based materials possess high mechanical and thermal stabilities, as well as three-dimensional open network structures with high aspect ratios capable of incorporating other materials to produce composites for a wide range of applications. Being the most prevalent natural biopolymer [...] Read more.

The various forms of cellulose-based materials possess high mechanical and thermal stabilities, as well as three-dimensional open network structures with high aspect ratios capable of incorporating other materials to produce composites for a wide range of applications. Being the most prevalent natural biopolymer on the Earth, cellulose has been used as a renewable replacement for many plastic and metal substrates, in order to diminish pollutant residues in the environment. As a result, the design and development of green technological applications of cellulose and its derivatives has become a key principle of ecological sustainability. Recently, cellulose-based mesoporous structures, flexible thin films, fibers, and three-dimensional networks have been developed for use as substrates in which conductive materials can be loaded for a wide range of energy conversion and energy conservation applications. The present article provides an overview of the recent advancements in the preparation of cellulose-based composites synthesized by combining metal/semiconductor nanoparticles, organic polymers, and metal-organic frameworks with cellulose. To begin, a brief review of cellulosic materials is given, with emphasis on their properties and processing methods. Further sections focus on the integration of cellulose-based flexible substrates or three-dimensional structures into energy conversion devices, such as photovoltaic solar cells, triboelectric generators, piezoelectric generators, thermoelectric generators, as well as sensors. The review also highlights the uses of cellulose-based composites in the separators, electrolytes, binders, and electrodes of energy conservation devices such as lithium-ion batteries. Moreover, the use of cellulose-based electrodes in water splitting for hydrogen generation is discussed. In the final section, we propose the underlying challenges and outlook for the field of cellulose-based composite materials. Full article

(This article belongs to the Special Issue Functional Cellulosic Materials)

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17 pages, 20289 KiB

Open AccessEditor’s ChoiceArticle

WO₃ Thin-Film Optical Gas Sensors Based on Gasochromic Effect towards Low Hydrogen Concentrations

by Michał Mazur, Paulina Kapuścik, Wiktoria Weichbrodt, Jarosław Domaradzki, Piotr Mazur, Małgorzata Kot and Jan Ingo Flege

Materials 2023, 16(10), 3831; https://doi.org/10.3390/ma16103831 - 19 May 2023

Cited by 2 | Viewed by 1749

Abstract

Hydrogen gas sensors have recently attracted increased interest due to the explosive nature of H₂ and its strategic importance in the sustainable global energy system. In this paper, the tungsten oxide thin films deposited by innovative gas impulse magnetron sputtering have been [...] Read more.

Hydrogen gas sensors have recently attracted increased interest due to the explosive nature of H₂ and its strategic importance in the sustainable global energy system. In this paper, the tungsten oxide thin films deposited by innovative gas impulse magnetron sputtering have been investigated in terms of their response to H₂. It was found that the most favourable annealing temperature in terms of sensor response value, as well as response and recovery times, was achieved at 673 K. This annealing process caused a change in the WO₃ cross-section morphology from a featureless and homogenous form to a rather columnar one, but still maintaining the same surface homogeneity. In addition to that, the full-phase transition from an amorphous to nanocrystalline form occurred with a crystallite size of 23 nm. It was found that the sensor response to only 25 ppm of H₂ was equal to 6.3, which is one of the best results presented in the literature so far of WO₃ optical gas sensors based on a gasochromic effect. Moreover, the results of the gasochromic effect were correlated with the changes in the extinction coefficient and the concentration of the free charge carriers, which is also a novel approach to the understanding of the gasochromic phenomenon. Full article

(This article belongs to the Special Issue Application of Emerging Materials for Advanced Imaging and Sensing)

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16 pages, 6986 KiB

Open AccessEditor’s ChoiceArticle

Polysiloxanes and Silanes with Various Functional Groups—New Compounds for Flax Fibers’ Modification

by Weronika Gieparda, Marcin Przybylak, Szymon Rojewski and Beata Doczekalska

Materials 2023, 16(10), 3839; https://doi.org/10.3390/ma16103839 - 19 May 2023

Cited by 2 | Viewed by 1137

Abstract

There is an increasing desire to use natural products that will be both effective and biodegradable. The aim of this work is to investigate the effect of modifying flax fibers with silicon compounds (silanes and polysiloxanes), as well as examining the effect of [...] Read more.

There is an increasing desire to use natural products that will be both effective and biodegradable. The aim of this work is to investigate the effect of modifying flax fibers with silicon compounds (silanes and polysiloxanes), as well as examining the effect of the mercerization process on their properties. Two types of polysiloxanes have been synthesized and confirmed by infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). Scanning electron microscopy (SEM), FTIR, thermogravimetry analysis (TGA) and pyrolysis-combustion flow calorimetry (PCFC) tests of the fibers were performed. On the SEM pictures, flax fibers purified and covered with silanes were visible after treatment. FTIR analysis showed stable bonds between the fibers and the silicon compounds. Promising results of thermal stability were obtained. It was also found that modification had a positive effect on the flammability. The conducted research showed that the use of such modifications, in the context of using flax fibers for composites, can yield very good results. Full article

(This article belongs to the Section Biomaterials)

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15 pages, 5859 KiB

Open AccessEditor’s ChoiceArticle

Influence of Alumina Grade on Sintering Properties and Possible Application in Binder Jetting Additive Technology

by Maciej Kwiatkowski, Joanna Marczyk, Piotr Putyra, Michał Kwiatkowski, Szymon Przybyła and Marek Hebda

Materials 2023, 16(10), 3853; https://doi.org/10.3390/ma16103853 - 19 May 2023

Cited by 3 | Viewed by 1707

Abstract

Alumina is one of the most popular ceramic materials widely used in both tooling and construction applications due to its low production cost, and high properties. However, the final properties of the product depend not only on the purity of the powder, but [...] Read more.

Alumina is one of the most popular ceramic materials widely used in both tooling and construction applications due to its low production cost, and high properties. However, the final properties of the product depend not only on the purity of the powder, but also, e.g., on its particle size, specific surface area, and the production technology used. These parameters are particularly important in the case of choosing additive techniques for the production of details. Therefore, the article presents the results of comparing five grades of Al₂O₃ ceramic powder. Their specific surface area (via Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods), particle size distribution, and phase composition by X-ray diffraction (XRD) were determined. Moreover, the surface morphology was characterized by the scanning electron microscopy (SEM) technique. The discrepancy between generally available data and the results obtained from measurements has been indicated. Moreover, the method of spark plasma sintering (SPS), equipped with the registration system of the position of the pressing punch during the process, was used to determine the sinterability curves of each of the tested grades of Al₂O₃ powder. Based on the obtained results, a significant influence of the specific surface area, particle size, and the width of their distribution at the beginning of the Al₂O₃ powder sintering process was confirmed. Furthermore, the possibility of using the analyzed variants of powders for binder jetting technology was assessed. The dependence of the particle size of the powder used on the quality of the printed parts was demonstrated. The procedure presented in this paper, which involves analyzing the properties of alumina varieties, was used to optimize the Al₂O₃ powder material for binder jetting printing. The selection of the best powder in terms of technological properties and good sinterability makes it possible to reduce the number of 3D printing processes, which makes it more economical and less time-consuming. Full article

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

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25 pages, 8623 KiB

Open AccessEditor’s ChoiceArticle

Potential of Fe-Mn-Al-Ni Shape Memory Alloys for Internal Prestressing of Ultra-High Performance Concrete

by Maximilian Schleiting, Alexander Wetzel, André Bauer, Johanna-Maria Frenck, Thomas Niendorf and Bernhard Middendorf

Materials 2023, 16(10), 3816; https://doi.org/10.3390/ma16103816 - 18 May 2023

Cited by 4 | Viewed by 1180

Abstract

Prestressing of concrete is a commonly used technique in civil engineering to achieve long spans, reduced structural thicknesses, and resource savings. However, in terms of application, complex tensioning devices are necessary, and prestress losses due to shrinkage and creep of the concrete are [...] Read more.

Prestressing of concrete is a commonly used technique in civil engineering to achieve long spans, reduced structural thicknesses, and resource savings. However, in terms of application, complex tensioning devices are necessary, and prestress losses due to shrinkage and creep of the concrete are unfavourable in terms of sustainability. In this work, a prestressing method using novel Fe-Mn-Al-Ni shape memory alloy rebars as a tensioning system in UHPC is investigated. A generated stress of about 130 MPa was measured for the shape memory alloy rebars. For the application in UHPC, the rebars are prestrained prior to the manufacturing process of the concrete samples. After sufficient hardening of the concrete, the specimens are heated inside an oven to activate the shape memory effect and, thus, to introduce the prestress into the surrounding UHPC. It is clearly shown that an improvement in maximum flexural strength and rigidity is achieved due to the thermal activation of the shape memory alloy rebars compared to non-activated rebars. Future research will have to focus on the design of the shape memory alloy rebars in relation to construction applications and the investigation of the long-term performance of the prestressing system. Full article

(This article belongs to the Section Construction and Building Materials)

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35 pages, 11056 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Magnetic Polymer Composites for BioMEMS: A Review

by Zhengwei Liao, Oualid Zoumhani and Clementine M. Boutry

Materials 2023, 16(10), 3802; https://doi.org/10.3390/ma16103802 - 17 May 2023

Cited by 12 | Viewed by 3188

Abstract

The objective of this review is to investigate the potential of functionalized magnetic polymer composites for use in electromagnetic micro-electro-mechanical systems (MEMS) for biomedical applications. The properties that make magnetic polymer composites particularly interesting for application in the biomedical field are their biocompatibility, [...] Read more.

The objective of this review is to investigate the potential of functionalized magnetic polymer composites for use in electromagnetic micro-electro-mechanical systems (MEMS) for biomedical applications. The properties that make magnetic polymer composites particularly interesting for application in the biomedical field are their biocompatibility, their adjustable mechanical, chemical, and magnetic properties, as well as their manufacturing versatility, e.g., by 3D printing or by integration in cleanroom microfabrication processes, which makes them accessible for large-scale production to reach the general public. The review first examines recent advancements in magnetic polymer composites that possess unique features such as self-healing capabilities, shape-memory, and biodegradability. This analysis includes an exploration of the materials and fabrication processes involved in the production of these composites, as well as their potential applications. Subsequently, the review focuses on electromagnetic MEMS for biomedical applications (bioMEMS), including microactuators, micropumps, miniaturized drug delivery systems, microvalves, micromixers, and sensors. The analysis encompasses an examination of the materials and manufacturing processes involved and the specific fields of application for each of these biomedical MEMS devices. Finally, the review discusses missed opportunities and possible synergies in the development of next-generation composite materials and bioMEMS sensors and actuators based on magnetic polymer composites. Full article

(This article belongs to the Special Issue Design, Fabrication, and Characterization of Magnetoresponsive Materials and Devices)

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17 pages, 20268 KiB

Open AccessEditor’s ChoiceArticle

Fabrication of Mechanically Strong Silica Aerogels with the Thermally Induced Phase Separation (TIPS) Method of Poly(methyl methacrylate)

by Hainan Ma, Baomin Wang, Jiarui Qi, Yiheng Pan and Chao Chen

Materials 2023, 16(10), 3778; https://doi.org/10.3390/ma16103778 - 17 May 2023

Viewed by 1141

Abstract

Constructing and maintaining a three-dimensional network structure with high porosity is critical to the preparation of silica aerogel materials because this structure provides excellent properties. However, due to the pearl-necklace-like structure and narrow interparticle necks, aerogels have poor mechanical strength and a brittle [...] Read more.

Constructing and maintaining a three-dimensional network structure with high porosity is critical to the preparation of silica aerogel materials because this structure provides excellent properties. However, due to the pearl-necklace-like structure and narrow interparticle necks, aerogels have poor mechanical strength and a brittle nature. Developing and designing lightweight silica aerogels with distinct mechanical properties is significant to extend their practical applications. In this work, thermally induced phase separation (TIPS) of poly(methyl methacrylate) (PMMA) from a mixture of ethanol and water was used to strengthen the skeletal network of aerogels. Strong and lightweight PMMA-modified silica aerogels were synthesized via the TIPS method and supercritically dried with carbon dioxide. The cloud point temperature of PMMA solutions, physical characteristics, morphological properties, microstructure, thermal conductivities, and mechanical properties were investigated. The resultant composited aerogels not only exhibit a homogenous mesoporous structure but also achieve a significant improvement in mechanical properties. The addition of PMMA increased the flexural strength and compressive strength by as much as 120% and 1400%, respectively, with the greatest amount of PMMA (M_w = 35,000 g/mole), while the density just increased by 28%. Overall, this research suggests that the TIPS method has great efficiency in reinforcing silica aerogels with less sacrifice of low density and large porosity. Full article

(This article belongs to the Section Porous Materials)

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16 pages, 3861 KiB

Open AccessEditor’s ChoiceArticle

Tungsten and Copper (II) Oxide Mixtures as Gasless Time Delay Compositions for Mining Detonators

by Marcin Gerlich, Marcin Hara and Waldemar A. Trzciński

Materials 2023, 16(10), 3797; https://doi.org/10.3390/ma16103797 - 17 May 2023

Cited by 1 | Viewed by 1116

Abstract

The widespread use of pyrotechnic compositions in time delay detonators is the reason for research aimed at expanding knowledge of the combustion properties of new pyrotechnic mixtures, whose components react with each other in the solid or liquid state. Such a method of [...] Read more.

The widespread use of pyrotechnic compositions in time delay detonators is the reason for research aimed at expanding knowledge of the combustion properties of new pyrotechnic mixtures, whose components react with each other in the solid or liquid state. Such a method of combustion would make the rate of combustion independent of the pressure inside the detonator. This paper presents the effect of the parameters of W/CuO mixtures on their properties of combustion. As this composition has not been the subject of previous research and is not described in the literature, the basic parameters, such as the burning rate and the heat of combustion, were determined. In order to determine the reaction mechanism, a thermal analysis was performed, and the combustion products were determined using the XRD technique. Depending on the quantitative composition and density of the mixture, the burning rates were between 4.1–6.0 mm/s and the heat of combustion in the range of 475–835 J/g was measured. The gas-free combustion mode of the chosen mixture was proved using DTA and XRD. Determination of the qualitative composition of the combustion products and the heat of combustion allowed estimation of the adiabatic combustion temperature. Full article

(This article belongs to the Special Issue Newer Paradigms in Advanced Materials Characterisation)

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14 pages, 491 KiB

Open AccessEditor’s ChoiceArticle

Anharmonicity of Plasmons in Metallic Nanostructures Useful for Metallization of Solar Cells

by Zofia Krzemińska and Witold A. Jacak

Materials 2023, 16(10), 3762; https://doi.org/10.3390/ma16103762 - 16 May 2023

Viewed by 944

Abstract

Metallic nanoparticles are frequently applied to enhance the efficiency of photovoltaic cells via the plasmonic effect, and they play this role due to the unusual ability of plasmons to transmit energy. The absorption and emission of plasmons, dual in the sense of quantum [...] Read more.

Metallic nanoparticles are frequently applied to enhance the efficiency of photovoltaic cells via the plasmonic effect, and they play this role due to the unusual ability of plasmons to transmit energy. The absorption and emission of plasmons, dual in the sense of quantum transitions, in metallic nanoparticles are especially high at the nanoscale of metal confinement, so these particles are almost perfect transmitters of incident photon energy. We show that these unusual properties of plasmons at the nanoscale are linked to the extreme deviation of plasmon oscillations from the conventional harmonic oscillations. In particular, the large damping of plasmons does not terminate their oscillations, even if, for a harmonic oscillator, they result in an overdamped regime. Full article

(This article belongs to the Special Issue Design, Performance, and Application of Lithium-Ion Batteries)

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14 pages, 5703 KiB

Open AccessEditor’s ChoiceArticle

Comparative Study of Iron-Tailings-Based Cementitious Mortars with Incorporated Graphite Ore and Graphite Tailings: Strength Properties and Microstructure

by Jiale Zhang, Qi Wei, Na Zhang, Shuai Zhang and Yihe Zhang

Materials 2023, 16(10), 3743; https://doi.org/10.3390/ma16103743 - 15 May 2023

Cited by 1 | Viewed by 1154

Abstract

Graphite ore and graphite tailings were blended into iron-tailings-based cementitious mortars, and their mechanical properties and microstructure were experimentally investigated. The flexural and compressive strengths of the resulting material were tested to compare the effects of graphite ore and graphite tailings as supplementary [...] Read more.

Graphite ore and graphite tailings were blended into iron-tailings-based cementitious mortars, and their mechanical properties and microstructure were experimentally investigated. The flexural and compressive strengths of the resulting material were tested to compare the effects of graphite ore and graphite tailings as supplementary cementitious materials and fine aggregates on the mechanical properties of iron-tailings-based cementitious mortars. Additionally, their microstructure and hydration products were mainly analyzed using scanning electronic microscope and X-ray powder diffraction techniques. The experimental results showed that the mechanical properties of the mortar material incorporating graphite ore were reduced due to the lubricating properties of graphite ore. As a result, the unhydrated particles and aggregates were not tightly bound to the gel phase, making the direct application of graphite ore in construction materials unfeasible. In the iron-tailings-based cementitious mortars prepared in this work, the optimal incorporation rate of graphite ore as a supplementary cementitious material was 4 wt%. The compressive strength of the optimal mortar test block after 28 days of hydration was 23.21 MPa, and the flexural strength was 7.76 MPa. The mechanical properties of the mortar block were found to be optimal with a graphite-tailings content of 40 wt% and an iron-tailings content of 10 wt%, resulting in a 28-day compressive strength of 48.8 MPa and a flexural strength of 11.7 MPa. By observing the microstructure and XRD pattern of the 28-day hydrated mortar block, it was determined that the hydration products of the mortar with graphite tailings as an aggregate included ettringite, Ca(OH)₂, and C-A-S-H gel. Full article

(This article belongs to the Special Issue Industrial Solid Wastes for Construction and Building Materials)

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18 pages, 4982 KiB

Open AccessEditor’s ChoiceReview

Varnish Formation and Removal in Lubrication Systems: A Review

by Sung-Ho Hong and Eun Kyung Jang

Materials 2023, 16(10), 3737; https://doi.org/10.3390/ma16103737 - 15 May 2023

Cited by 1 | Viewed by 2079

Abstract

This study presents the current literature regarding the investigation of varnish contamination among the various types of lubricant contaminations. As the duration of use of lubricants increases, the lubricant deteriorates and may become contaminated. Varnish has been known to cause filter plugging, sticking [...] Read more.

This study presents the current literature regarding the investigation of varnish contamination among the various types of lubricant contaminations. As the duration of use of lubricants increases, the lubricant deteriorates and may become contaminated. Varnish has been known to cause filter plugging, sticking of the hydraulic valves and fuel injection pumps, flow obstruction, clearance reduction, poor heating and cooling performance, and increased friction and wear in various lubrication systems. These problems may also result in mechanical system failures, performance degradation, and increased maintenance and repair costs. To improve the problems caused by varnish contamination, an adequate understanding of varnish is required. Therefore, in this review, the definitions and characteristics, generating machinery, generating mechanisms, causes, measurement methods, and prevention or removal methods of varnish are summarized. Most of the data presented herein are reports from manufacturers related to lubricants and machine maintenance that are included in published works. We expect that this summary will be helpful to those who are engaged in reducing or preventing varnish-related problems. Full article

(This article belongs to the Special Issue Mechanical and Tribological Properties of Advanced Materials and Coatings)

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11 pages, 2642 KiB

Open AccessEditor’s ChoiceArticle

Transparent Conducting Amorphous IZO Thin Films: An Approach to Improve the Transparent Electrode Quality

by Akhmed K. Akhmedov, Aslan Kh. Abduev, Eldar K. Murliev, Victor V. Belyaev and Abil Sh. Asvarov

Materials 2023, 16(10), 3740; https://doi.org/10.3390/ma16103740 - 15 May 2023

Cited by 3 | Viewed by 1475

Abstract

It is common knowledge that using different oxygen contents in the working gas during sputtering deposition results in fabrication of indium zinc oxide (IZO) films with a wide range of optoelectronic properties. It is also important that high deposition temperature is not required [...] Read more.

It is common knowledge that using different oxygen contents in the working gas during sputtering deposition results in fabrication of indium zinc oxide (IZO) films with a wide range of optoelectronic properties. It is also important that high deposition temperature is not required to achieve excellent transparent electrode quality in the IZO films. Modulation of the oxygen content in the working gas during RF sputtering of IZO ceramic targets was used to deposit IZO-based multilayers in which the ultrathin IZO unit layers with high electron mobility (μ-IZO) alternate with ones characterized by high concentration of free electrons (n-IZO). As a result of optimizing the thicknesses of each type of unit layer, low-temperature 400 nm thick IZO multilayers with excellent transparent electrode quality, indicated by the low sheet resistance (R ≤ 8 Ω/sq.) with high transmittance in the visible range (

\bar{T}

> 83%) and a very flat multilayer surface, were obtained. Full article

(This article belongs to the Special Issue Sputter Deposition/Physical Vapor Deposition (PVD) Materials and Processes)

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23 pages, 4718 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Usability of Sorbents in Restoring Enzymatic Activity in Soils Polluted with Petroleum-Derived Products

by Jadwiga Wyszkowska, Agata Borowik, Magdalena Zaborowska and Jan Kucharski

Materials 2023, 16(10), 3738; https://doi.org/10.3390/ma16103738 - 15 May 2023

Cited by 9 | Viewed by 1288

Abstract

Due to their ability to adsorb or absorb chemical pollutants, including organic compounds, sorbents are increasingly used in the reclamation of soils subjected to their pressure, which results from their high potential in eliminating xenobiotics. The precise optimization of the reclamation process is [...] Read more.

Due to their ability to adsorb or absorb chemical pollutants, including organic compounds, sorbents are increasingly used in the reclamation of soils subjected to their pressure, which results from their high potential in eliminating xenobiotics. The precise optimization of the reclamation process is required, focused primarily on restoring the condition of the soil. This research are essential for seeking materials sufficiently potent to accelerate the remediation process and for expanding knowledge related to biochemical transformations that lead to the neutralization of these pollutants. The goal of this study was to determine and compare the sensitivity of soil enzymes to petroleum-derived products in soil sown with Zea mays, remediated using four sorbents. The study was conducted in a pot experiment, with loamy sand (LS) and sandy loam (SL) polluted with VERVA diesel oil (DO) and VERVA 98 petrol (P). Soil samples were collected from arable lands, and the effects of the tested pollutants were compared with those used as control uncontaminated soil samples in terms of Zea mays biomass and the activity of seven enzymes in the soil. The following sorbents were applied to mitigate DO and P effects on the test plants and enzymatic activity: molecular sieve (M), expanded clay (E), sepiolite (S), and Ikasorb (I). Both DO and P exerted a toxic effect on Zea mays, with DO more strongly disturbing its growth and development and the activities of soil enzymes than P. In sandy clay (SL), P was found to be a significant inhibitor of dehydrogenases (Deh), catalase (Cat), urease (Ure), alkaline phosphatase (Pal), and arylsulfatase (Aryl) activities, while DO stimulated the activity of all enzymes in this soil. The study results suggest that the sorbents tested, mainlya molecular sieve, may be useful in remediating DO-polluted soils, especially when alleviating the effects of these pollutants in soils of lower agronomic value. Full article

(This article belongs to the Special Issue Advances in Eco-Friendly Adsorbent Materials for Removal of Inorganic and Organic Pollutants (Volume II))

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24 pages, 4826 KiB

Open AccessEditor’s ChoiceReview

The Integration of Triboelectric Nanogenerators and Supercapacitors: The Key Role of Cellular Materials

by Jiajing Meng, Zequan Zhao, Xia Cao and Ning Wang

Materials 2023, 16(10), 3751; https://doi.org/10.3390/ma16103751 - 15 May 2023

Cited by 4 | Viewed by 1614

Abstract

The growing demand for sustainable and efficient energy harvesting and storage technologies has spurred interest in the integration of triboelectric nanogenerators (TENGs) with supercapacitors (SCs). This combination offers a promising solution for powering Internet of Things (IoT) devices and other low−power applications by [...] Read more.

The growing demand for sustainable and efficient energy harvesting and storage technologies has spurred interest in the integration of triboelectric nanogenerators (TENGs) with supercapacitors (SCs). This combination offers a promising solution for powering Internet of Things (IoT) devices and other low−power applications by utilizing ambient mechanical energy. Cellular materials, featuring unique structural characteristics such as high surface−to−volume ratios, mechanical compliance, and customizable properties, have emerged as essential components in this integration, enabling the improved performance and efficiency of TENG−SC systems. In this paper, we discuss the key role of cellular materials in enhancing TENG−SC systems’ performance through their influence on contact area, mechanical compliance, weight, and energy absorption. We highlight the benefits of cellular materials, including increased charge generation, optimized energy conversion efficiency, and adaptability to various mechanical sources. Furthermore, we explore the potential for lightweight, low−cost, and customizable cellular materials to expand the applicability of TENG−SC systems in wearable and portable devices. Finally, we examine the dual effect of cellular materials’ damping and energy absorption properties, emphasizing their potential to protect TENGs from damage and increase overall system efficiency. This comprehensive overview of the role of cellular materials in the integration of TENG−SC aims to provide insights into the development of next−generation sustainable energy harvesting and storage solutions for IoT and other low−power applications. Full article

(This article belongs to the Special Issue New Advances in Characterization of Cellular Materials)

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20 pages, 12745 KiB

Open AccessEditor’s ChoiceArticle

Durability and Additional Properties of Anodized Aluminum-Based Coatings with Different Wettability under Natural Conditions

by Klaudia Olkowicz, Kamil Kowalczyk, Zofia Buczko, Joanna Czwartos and Barbara Nasiłowska

Materials 2023, 16(10), 3729; https://doi.org/10.3390/ma16103729 - 14 May 2023

Cited by 1 | Viewed by 2024

Abstract

The study aimed to test the durability of coatings under natural conditions. The present study focused on the changes in wettability and additional properties of the coatings under natural conditions. The specimens were subjected to outdoor exposure and additionally immersed in the pond. [...] Read more.

The study aimed to test the durability of coatings under natural conditions. The present study focused on the changes in wettability and additional properties of the coatings under natural conditions. The specimens were subjected to outdoor exposure and additionally immersed in the pond. Impregnating porous anodized aluminum is a popular production method for hydrophobic and superhydrophobic surfaces. However, prolonged exposure of such coatings to natural conditions causes leaching of the impregnate and, thus, the loss of hydrophobic properties. After the loss of hydrophobic properties, all kinds of impurities and fouling adhere better to the porous structure. Additionally, deterioration of anti-icing and anti-corrosion properties was observed. Finally, the self-cleaning, anti-fouling, anti-icing and anti-corrosion properties were comparable or even worse to those of the hydrophilic coating. In the case of superhydrophobic specimens, during outdoor exposure there was no loss of superhydrophobicity, self-cleaning and anti-corrosion properties. Still, despite this, the icing delay time dropped. During outdoor exposure, the structure, which initially had anti-icing properties, may degrade. Nevertheless, the hierarchical structure responsible for the superhydrophobic effect can still be preserved. The superhydrophobic coating initially had the best anti-fouling properties. However, the coating was also gradually losing its superhydrophobic properties during water immersion. Full article

(This article belongs to the Special Issue New Insights in Wettability and Surface Repellency of Advanced Materials)

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15 pages, 4711 KiB

Open AccessEditor’s ChoiceArticle

In Situ Reactive Formation of Mixed Oxides in Additively Manufactured Cobalt Alloy

by Jack Lopez, Rok Cerne, David Ho, Devin Madigan, Qing Shen, Bo Yang, Joseph Corpus, William Jarosinski, Haiyan Wang and Xinghang Zhang

Materials 2023, 16(10), 3707; https://doi.org/10.3390/ma16103707 - 13 May 2023

Cited by 2 | Viewed by 1380

Abstract

Oxide-dispersion-strengthened (ODS) alloys have long been considered for high temperature turbine, spacecraft, and nuclear reactor components due to their high temperature strength and radiation resistance. Conventional synthesis approaches of ODS alloys involve ball milling of powders and consolidation. In this work, a process-synergistic [...] Read more.

Oxide-dispersion-strengthened (ODS) alloys have long been considered for high temperature turbine, spacecraft, and nuclear reactor components due to their high temperature strength and radiation resistance. Conventional synthesis approaches of ODS alloys involve ball milling of powders and consolidation. In this work, a process-synergistic approach is used to introduce oxide particles during laser powder bed fusion (LPBF). Chromium (III) oxide (Cr₂O₃) powders are blended with a cobalt-based alloy, Mar-M 509, and exposed to laser irradiation, resulting in reduction–oxidation reactions involving metal (Ta, Ti, Zr) ions from the metal matrix to form mixed oxides of increased thermodynamic stability. A microstructure analysis indicates the formation of nanoscale spherical mixed oxide particles as well as large agglomerates with internal cracks. Chemical analyses confirm the presence of Ta, Ti, and Zr in agglomerated oxides, but primarily Zr in the nanoscale oxides. Mechanical testing reveals that agglomerate particle cracking is detrimental to tensile ductility compared to the base alloy, suggesting the need for improved processing methods to break up oxide particle clusters and promote their uniform dispersion during laser exposure. Full article

(This article belongs to the Special Issue Advances in Materials Processing Engineering)

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19 pages, 2602 KiB

Open AccessEditor’s ChoiceArticle

Plasmonic Nanodomains Decorated on Two-Dimensional Oxide Semiconductors for Photonic-Assisted CO₂ Conversion

by Mohammad Karbalaei Akbari, Nasrin Siraj Lopa, Jihae Park and Serge Zhuiykov

Materials 2023, 16(10), 3675; https://doi.org/10.3390/ma16103675 - 11 May 2023

Cited by 1 | Viewed by 1514

Abstract

Plasmonic nanostructures ensure the reception and harvesting of visible lights for novel photonic applications. In this area, plasmonic crystalline nanodomains decorated on the surface of two-dimensional (2D) semiconductor materials represent a new class of hybrid nanostructures. These plasmonic nanodomains activate supplementary mechanisms at [...] Read more.

Plasmonic nanostructures ensure the reception and harvesting of visible lights for novel photonic applications. In this area, plasmonic crystalline nanodomains decorated on the surface of two-dimensional (2D) semiconductor materials represent a new class of hybrid nanostructures. These plasmonic nanodomains activate supplementary mechanisms at material heterointerfaces, enabling the transfer of photogenerated charge carriers from plasmonic antennae into adjacent 2D semiconductors and therefore activate a wide range of visible-light assisted applications. Here, the controlled growth of crystalline plasmonic nanodomains on 2D Ga₂O₃ nanosheets was achieved by sonochemical-assisted synthesis. In this technique, Ag and Se nanodomains grew on 2D surface oxide films of gallium-based alloy. The multiple contribution of plasmonic nanodomains enabled the visible-light-assisted hot-electron generation at 2D plasmonic hybrid interfaces, and therefore considerably altered the photonic properties of the 2D Ga₂O₃ nanosheets. Specifically, the multiple contribution of semiconductor–plasmonic hybrid 2D heterointerfaces enabled efficient CO₂ conversion through combined photocatalysis and triboelectric-activated catalysis. The solar-powered acoustic-activated conversion approach of the present study enabled us to achieve the CO₂ conversion efficiency of more than 94% in the reaction chambers containing 2D Ga₂O₃-Ag nanosheets. Full article

(This article belongs to the Special Issue Novel Nanostructured Materials for Optoelectronic Applications)

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29 pages, 4902 KiB

Open AccessEditor’s ChoiceReview

Review of Potential Drug-Eluting Contact Lens Technologies

by Tina Lovrec-Krstič, Kristjan Orthaber, Uroš Maver and Tomislav Sarenac

Materials 2023, 16(10), 3653; https://doi.org/10.3390/ma16103653 - 11 May 2023

Cited by 3 | Viewed by 3510

Abstract

The field of ophthalmology is expanding exponentially, both in terms of diagnostic and therapeutic capabilities, as well as the worldwide increasing incidence of eye-related diseases. Due to an ageing population and climate change, the number of ophthalmic patients will continue to increase, overwhelming [...] Read more.

The field of ophthalmology is expanding exponentially, both in terms of diagnostic and therapeutic capabilities, as well as the worldwide increasing incidence of eye-related diseases. Due to an ageing population and climate change, the number of ophthalmic patients will continue to increase, overwhelming healthcare systems and likely leading to under-treatment of chronic eye diseases. Since drops are the mainstay of therapy, clinicians have long emphasised the unmet need for ocular drug delivery. Alternative methods, i.e., with better compliance, stability and longevity of drug delivery, would be preferred. Several approaches and materials are being studied and used to overcome these drawbacks. We believe that drug-loaded contact lenses are among the most promising and are a real step toward dropless ocular therapy, potentially leading to a transformation in clinical ophthalmic practice. In this review, we outline the current role of contact lenses in ocular drug delivery, focusing on materials, drug binding and preparation, concluding with a look at future developments. Full article

(This article belongs to the Special Issue Advanced Bio-Based Polymers: Synthesis, Characterization and Applications (Second Volume))

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15 pages, 4464 KiB

Open AccessEditor’s ChoiceArticle

Thermal Programming of Commercially Available Orthodontic NiTi Archwires

by Andrea Wichelhaus, Amelie Mehnert, Thomas Stocker, Uwe Baumert, Matthias Mertmann, Hisham Sabbagh and Corinna L. Seidel

Materials 2023, 16(10), 3683; https://doi.org/10.3390/ma16103683 - 11 May 2023

Cited by 2 | Viewed by 1441

Abstract

The shape of superelastic Nickel-Titanium (NiTi) archwires can be adjusted with thermal treatments using devices such as the Memory-Maker^TM (Forestadent), which potentially affects their mechanical properties. The effect of such treatments on these mechanical properties was simulated by means of a laboratory [...] Read more.

The shape of superelastic Nickel-Titanium (NiTi) archwires can be adjusted with thermal treatments using devices such as the Memory-Maker^TM (Forestadent), which potentially affects their mechanical properties. The effect of such treatments on these mechanical properties was simulated by means of a laboratory furnace. Fourteen commercially available NiTi wires (0.018″ × 0.025″) were selected from the manufacturers American Orthodontics, Dentaurum, Forestadent, GAC, Ormco, Rocky Mountain Orthodontics and 3M Unitek. Specimens were heat treated using different combinations of annealing duration (1/5/10 min) and annealing temperature (250–800 °C) and investigated using angle measurements and three-point bending tests. Complete shape adaptation was found at distinct annealing durations/temperatures for each wire ranging between ~650–750 °C (1 min), ~550–700 °C (5 min) and ~450–650 °C (10 min), followed by a loss of superelastic properties shortly afterwards at ~750 °C (1 min), ~600–650 °C (5 min) and ~550–600 °C (10 min). Wire-specific working ranges (complete shaping without loss of superelasticity) were defined and a numerical score (e.g., stable forces) was developed for the three-point bending test. Overall, the wires Titanol Superelastic (Forestadent), Tensic (Dentaurum), FLI CuNiTi²⁷ (Rocky Mountain Orthodontics) and Nitinol Classic (3M Unitek) proved to be the most user-friendly. Thermal shape adjustment requires wire-specific working ranges to allow complete shape acceptance and high scores in bending test performance to ensure permanence of the superelastic behaviour. Full article

(This article belongs to the Special Issue Characterization of Shape Memory Alloy Materials)

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19 pages, 8541 KiB

Open AccessEditor’s ChoiceReview

3D Textiles Based on Warp Knitted Fabrics: A Review

by Lars Hahn, Konrad Zierold, Anke Golla, Danny Friese and Steffen Rittner

Materials 2023, 16(10), 3680; https://doi.org/10.3390/ma16103680 - 11 May 2023

Cited by 5 | Viewed by 4458

Abstract

Fibre-reinforced composites (FRCs) are already well established in several industrial sectors such as aerospace, automotive, plant engineering, shipbuilding and construction. The technical advantages of FRCs over metallic materials are well researched and proven. The key factors for an even wider industrial application of [...] Read more.

Fibre-reinforced composites (FRCs) are already well established in several industrial sectors such as aerospace, automotive, plant engineering, shipbuilding and construction. The technical advantages of FRCs over metallic materials are well researched and proven. The key factors for an even wider industrial application of FRCs are the maximisation of resource and cost efficiency in the production and processing of the textile reinforcement materials. Due to its technology, warp knitting is the most productive and therefore cost-effective textile manufacturing process. In order to produce resource-efficient textile structures with these technologies, a high degree of prefabrication is required. This reduces costs by reducing the number of ply stacks, and by reducing the number of extra operations through final path and geometric yarn orientation of the preforms. It also reduces waste in post-processing. Furthermore, a high degree of prefabrication through functionalisation offers the potential to extend the application range of textile structures as purely mechanical reinforcements by integrating additional functions. So far, there is a gap in terms of an overview of the current state-of-the-art of relevant textile processes and products, which this work aims to fill. The focus of this work is therefore to provide an overview of warp knitted 3D structures. Full article

(This article belongs to the Collection Advanced Composite Materials and Structures for Aerospace, Automotive and Civil Engineering Applications)

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16 pages, 12362 KiB

Open AccessEditor’s ChoiceArticle

Full-Scale Fatigue Test and Finite Element Analysis on External Inclined Strut Welded Joints of a Wide-Flanged Composite Box Girder Bridge

by Bin Wang, Laijun Liu, Yuqing Liu, Xudong Jia, Xiaoqing Xu, Kaixiang Miao and Jiandong Ji

Materials 2023, 16(10), 3637; https://doi.org/10.3390/ma16103637 - 10 May 2023

Cited by 1 | Viewed by 1532

Abstract

For a wide-flanged composite box girder bridge, the risk of fatigue cracking in the external inclined strut welded joint under the fatigue vehicle load is a problem. The main purposes of this research are to verify the safety of the main bridge of [...] Read more.

For a wide-flanged composite box girder bridge, the risk of fatigue cracking in the external inclined strut welded joint under the fatigue vehicle load is a problem. The main purposes of this research are to verify the safety of the main bridge of the Linyi Yellow River Bridge, a continuous composite box girder bridge, and to propose suggestions for optimization. In this research, a finite element model of one segment of the bridge was established to investigate the influence surface of the external inclined strut, and, using the nominal stress method, it was confirmed that the fatigue cracking of the welded details of the external inclined strut was risky. Subsequently, a full-scale fatigue test of the external inclined strut welded joint was carried out, and the crack propagation law and S-N curve of the welded details were obtained. Finally, a parametric analysis was conducted with the three-dimensional refined finite element models. The results showed that the welded joint in the real bridge has a fatigue life larger than that of the design life, and methods such as increasing the flange thickness of the external inclined strut and the diameter of the welding hole are beneficial to improve its fatigue performance. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials)

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19 pages, 4852 KiB

Open AccessEditor’s ChoiceArticle

Combined DFT-D3 Computational and Experimental Studies on g-C₃N₄: New Insight into Structure, Optical, and Vibrational Properties

by Paolo Negro, Federico Cesano, Silvia Casassa and Domenica Scarano

Materials 2023, 16(10), 3644; https://doi.org/10.3390/ma16103644 - 10 May 2023

Cited by 4 | Viewed by 2011

Abstract

Graphitic carbon nitride (g-C₃N₄) has emerged as one of the most promising solar-light-activated polymeric metal-free semiconductor photocatalysts due to its thermal physicochemical stability but also its characteristics of environmentally friendly and sustainable material. Despite the challenging properties of g-C [...] Read more.

Graphitic carbon nitride (g-C₃N₄) has emerged as one of the most promising solar-light-activated polymeric metal-free semiconductor photocatalysts due to its thermal physicochemical stability but also its characteristics of environmentally friendly and sustainable material. Despite the challenging properties of g-C₃N₄, its photocatalytic performance is still limited by the low surface area, together with the fast charge recombination phenomena. Hence, many efforts have been focused on overcoming these drawbacks by controlling and improving the synthesis methods. With regard to this, many structures including strands of linearly condensed melamine monomers, which are interconnected by hydrogen bonds, or highly condensed systems, have been proposed. Nevertheless, complete and consistent knowledge of the pristine material has not yet been achieved. Thus, to shed light on the nature of polymerised carbon nitride structures, which are obtained from the well-known direct heating of melamine under mild conditions, we combined the results obtained from XRD analysis, SEM and AFM microscopies, and UV-visible and FTIR spectroscopies with the data from the Density Functional Theory method (DFT). An indirect band gap and the vibrational peaks have been calculated without uncertainty, thus highlighting a mixture of highly condensed g-C₃N₄ domains embedded in a less condensed “melon-like” framework. Full article

(This article belongs to the Special Issue Graphene and Other 2D Layered Nanomaterials and Hybrid Structures: Synthesis, Properties and Applications (Volume II))

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15 pages, 9508 KiB

Open AccessEditor’s ChoiceArticle

Evolution of Toughening Mechanisms in PH13-8Mo Stainless Steel during Aging Treatment

by Honglin Zhang, Peng Mi, Luhan Hao, Haichong Zhou, Wei Yan, Kuan Zhao, Bin Xu and Mingyue Sun

Materials 2023, 16(10), 3630; https://doi.org/10.3390/ma16103630 - 10 May 2023

Cited by 2 | Viewed by 1349

Abstract

PH13-8Mo stainless steel has been widely used in aerospace, petroleum and marine construction, obtaining continuous investigation attention in recent years. Based on the response of a hierarchical martensite matrix and possible reversed austenite, a systematic investigation of the evolution of the toughening mechanisms [...] Read more.

PH13-8Mo stainless steel has been widely used in aerospace, petroleum and marine construction, obtaining continuous investigation attention in recent years. Based on the response of a hierarchical martensite matrix and possible reversed austenite, a systematic investigation of the evolution of the toughening mechanisms in PH13-8Mo stainless steel as a function of aging temperature was carried out. It showed there was a desirable combination of high yield strength (~1.3 GPa) and V-notched impact toughness (~220 J) after aging between 540 and 550 °C. With the increase of aging temperature, the martensite matrix was recovered in terms of the refined sub-grains and higher ratio of high-angle grain boundaries (HAGBs). It should be noted there was a reversion of martensite to form austenite films subjected to aging above 540 °C; meanwhile, the NiAl precipitates maintained a well-coherent orientation with the matrix. Based on the post mortem analysis, there were three stages of the changing main toughening mechanisms: Stage I: low-temperature aging at around 510 °C, where the HAGBs contributed to the toughness by retarding the advance of cracks; Stage II: intermediate-temperature aging at around 540 °C, where the recovered laths embedded by soft austenite facilitated the improvement of toughness by synergistically increasing the advance path and blunting the crack tips; and Stage III: without the coarsening of NiAl precipitates around 560 °C, more inter-lath reversed austenite led to the optimum toughness, relying on “soft barrier” and transformation-induced plasticity (TRIP) effects. Full article

(This article belongs to the Special Issue Advanced Special and High-Strength Steels)

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18 pages, 4636 KiB

Open AccessEditor’s ChoiceArticle

Experimental and Numerical Investigation into the Effect of Water Uptake on the Capacitance of an Organic Coating

by Steven A. Policastro, Rachel M. Anderson, Carlos M. Hangarter, Attilio Arcari and Erick B. Iezzi

Materials 2023, 16(10), 3623; https://doi.org/10.3390/ma16103623 - 9 May 2023

Cited by 4 | Viewed by 1191

Abstract

Water uptake by organic coating systems used for corrosion prevention on airframes is one of the principal contributors to the loss of barrier properties of the coating. We used equivalent circuit analyses of electrochemical impedance spectroscopy (EIS) data to track changes in coating [...] Read more.

Water uptake by organic coating systems used for corrosion prevention on airframes is one of the principal contributors to the loss of barrier properties of the coating. We used equivalent circuit analyses of electrochemical impedance spectroscopy (EIS) data to track changes in coating layer capacitance for a two-layer coating system consisting of an epoxy primer and polyurethane topcoat immersed in NaCl solutions with different concentrations and temperatures. The capacitance curve exhibited two different response regions, consistent with the “two-stage kinetics” mechanisms for water uptake by the polymers. We tested several numerical diffusion models of water sorption and found the most successful to be one that varied the diffusion coefficient as a function of polymer type and immersion time and accounted for physical aging processes in the polymer. We employed the Brasher mixing law along with the water sorption model to estimate the coating capacitance as a function of water uptake. The predicted capacitance of the coating was found to be consistent with the capacitance obtained from the EIS data, which is consistent with theories that water uptake occurs via initial rapid transport followed by a much slower aging process. Thus, both these water uptake processes need to be considered when making EIS measurements to assess the state of a coating system. Full article

(This article belongs to the Special Issue Advanced Polymer-Coated Materials: Fabrication, Characterization and Applications)

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22 pages, 13507 KiB

Open AccessEditor’s ChoiceArticle

Signal-Decay Based Approach for Visualization of Buried Defects in 3-D Printed Ceramic Components Imaged with Help of Optical Coherence Tomography

by Malgorzata Kopycinska-Müller, Luise Schreiber, Eric Schwarzer-Fischer, Anne Günther, Conner Phillips, Tassilo Moritz, Jörg Opitz, Yeong-Jin Choi and Hui-suk Yun

Materials 2023, 16(10), 3607; https://doi.org/10.3390/ma16103607 - 9 May 2023

Viewed by 1534

Abstract

We propose the use of Optical Coherence Tomography (OCT) as a tool for the quality control of 3-D-printed ceramics. Test samples with premeditated defects, namely single- and two-component samples of zirconia, titania, and titanium suboxides, were printed by stereolithography-based DLP (Digital Light Processing) [...] Read more.

We propose the use of Optical Coherence Tomography (OCT) as a tool for the quality control of 3-D-printed ceramics. Test samples with premeditated defects, namely single- and two-component samples of zirconia, titania, and titanium suboxides, were printed by stereolithography-based DLP (Digital Light Processing) processes. The OCT tomograms obtained on the green samples showed the capability of the method to visualize variations in the layered structure of the samples as well as the presence of cracks and inclusions at depths up to 130 µm, as validated by SEM images. The structural information was visible in cross-sectional images as well as in plan-view images. The optical signal measured from the printed zirconia oxide and titanium oxide samples showed strong attenuation with depth and could be fit with an exponential decay curve. The variations of the decay parameter correlated very well with the presence of defects and material variation. When used as an imaging quantity, the decay parameter projects the position of the defects into 2-D (X,Y) coordinates. This procedure can be used in real time, it reduces the data volume up to 1000 times, and allows for faster subsequent data analysis and transfer. Tomograms were also obtained on sintered samples. The results showed that the method can detect changes in the optical properties of the green ceramics caused by sintering. Specifically, the zirconium oxide samples became more transparent to the light used, whereas the titanium suboxide samples became entirely opaque. In addition, the optical response of the sintered zirconium oxide showed variations within the imaged volume, indicating material density variations. The results presented in this study show that OCT provides sufficient structural information on 3-D-printed ceramics and can be used as an in-line tool for quality control. Full article

(This article belongs to the Special Issue Recent Advances in Ceramic Manufacturing)

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15 pages, 5624 KiB

Open AccessEditor’s ChoiceArticle

The Application of Additive Composites Technologies for Clamping and Manipulation Devices in the Production Process

by Richard Joch, Michal Šajgalík, Mário Drbúl, Jozef Holubják, Andrej Czán, Vladimír Bechný and Miroslav Matúš

Materials 2023, 16(10), 3624; https://doi.org/10.3390/ma16103624 - 9 May 2023

Cited by 1 | Viewed by 1469

Abstract

Additive technologies have been widely adopted in various industries. The choice of additive technology and material directly affects the functionality of the manufactured components. The development of materials with better mechanical properties has led to a growing interest in replacing traditional metal components [...] Read more.

Additive technologies have been widely adopted in various industries. The choice of additive technology and material directly affects the functionality of the manufactured components. The development of materials with better mechanical properties has led to a growing interest in replacing traditional metal components with those manufactured using additive technologies. The application of Onyx as a material comes into consideration, which contains short carbon fibers to increase the mechanical properties. This study aims to experimentally verify the viability of substituting metal gripping elements with nylon and composite materials. The design of the jaws was customized to meet the requirements of a three-jaw chuck of a CNC machining center. The evaluation process involved monitoring the functionality and deformation effects on the clamped PTFE polymer material. When the metal jaws were applied, significant deformation of the clamped material occurred, which varied with the clamping pressure. This deformation was evidenced by the formation of spreading cracks on the clamped material and permanent shape changes in the tested material. Conversely, nylon and composite jaws manufactured using additive technology demonstrated functionality across all tested clamping pressures, without causing permanent deformation of the clamped material, unlike the traditional metal jaws. The results of this study confirm the applicability of the Onyx material and provide practical evidence of the potential for reducing deformation caused by clamping mechanisms. Full article

(This article belongs to the Special Issue 3D & 4D Printing in Engineering Applications)

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15 pages, 2304 KiB

Open AccessEditor’s ChoiceArticle

Fabrication and Arc Erosion Behavior of Ag-SnO₂-ZnO Electrical Contact Materials

by Danny Guzmán, Felipe González, Diego Muranda, Claudio Aguilar, Alexis Guzmán, Álvaro Soliz, Lorena Lozada, Iñigo Iturriza and Felipe Castro

Materials 2023, 16(10), 3618; https://doi.org/10.3390/ma16103618 - 9 May 2023

Cited by 4 | Viewed by 1842

Abstract

This study investigated the synthesis of Ag-SnO₂-ZnO by powder metallurgy methods and their subsequent electrical contact behavior. The pieces of Ag-SnO₂-ZnO were prepared by ball milling and hot pressing. The arc erosion behavior of the material was evaluated using [...] Read more.

This study investigated the synthesis of Ag-SnO₂-ZnO by powder metallurgy methods and their subsequent electrical contact behavior. The pieces of Ag-SnO₂-ZnO were prepared by ball milling and hot pressing. The arc erosion behavior of the material was evaluated using homemade equipment. The microstructure and phase evolution of the materials were investigated through X-ray diffraction, energy-dispersive spectroscopy and scanning electron microscopy. The results showed that, although the mass loss of the Ag-SnO₂-ZnO composite (9.08 mg) during the electrical contact test was higher than that of the commercial Ag-CdO (1.42 mg), its electrical conductivity remained constant (26.9 ± 1.5% IACS). This fact would be related to the reaction of Zn₂SnO₄’s formation on the material’s surface via electric arc. This reaction would play an important role in controlling the surface segregation and subsequent loss of electrical conductivity of this type of composite, thus enabling the development of a new electrical contact material to replace the non-environmentally friendly Ag-CdO composite. Full article

(This article belongs to the Special Issue Powder Metallurgy: Materials and Processing)

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12 pages, 7301 KiB

Open AccessEditor’s ChoiceArticle

Structure and Wear Performance of a Titanium Alloy by Using Low-Temperature Plasma Oxy-Nitriding

by Haidong Li, Haifeng Wang, Shijie Wang, Yange Yang, Yunsong Niu, Shenglong Zhu and Fuhui Wang

Materials 2023, 16(10), 3609; https://doi.org/10.3390/ma16103609 - 9 May 2023

Cited by 1 | Viewed by 1264

Abstract

To solve the problems of high nitriding temperature and long nitriding time with conventional plasma nitriding technologies, a kind of low-temperature plasma oxy-nitriding technology containing two-stage processes with different ratios of N to O was developed on a TC4 alloy in this paper. [...] Read more.

To solve the problems of high nitriding temperature and long nitriding time with conventional plasma nitriding technologies, a kind of low-temperature plasma oxy-nitriding technology containing two-stage processes with different ratios of N to O was developed on a TC4 alloy in this paper. A thicker permeation coating can be obtained with this new technology compared to conventional plasma nitriding technology. The reason for this is that the oxygen introduction in the first two-hour oxy-nitriding step can break the continuous TiN layer, which facilitates the quick and deep diffusion of the solution-strengthening elements of O and N into the titanium alloy. Moreover, an inter-connected porous structure was formed under a compact compound layer, which acts as a buffer layer to absorb the external wear force. Therefore, the resultant coating showed the lowest COF values during the initial wear state, and almost no debris and cracks were detected after the wear test. For the treated samples with low hardness and no porous structure, fatigue cracks can easily form on the surface, and bulk peeling-offcan occur during the wear course. Full article

(This article belongs to the Special Issue Advances in Coating Materials Research: From Preparation to Application)

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16 pages, 9623 KiB

Open AccessEditor’s ChoiceArticle

Synergistic Effects of 2-Butyne-1,4-Diol and Chloride Ions on the Microstructure and Residual Stress of Electrodeposited Nickel

by Ming Sun, Chao Zhang, Ruhan Ya, Hongyu He, Zhipeng Li and Wenhuai Tian

Materials 2023, 16(9), 3598; https://doi.org/10.3390/ma16093598 - 8 May 2023

Viewed by 1206

Abstract

To assess the individual and synergistic effects of 2-butyne-1,4-diol (BD) and chloride ions on the microstructure and residual stress of electrodeposited nickel, various nickel layers were prepared from sulfamate baths comprising varying concentrations of BD and chloride ions by applying direct-current electrodeposition. And [...] Read more.

To assess the individual and synergistic effects of 2-butyne-1,4-diol (BD) and chloride ions on the microstructure and residual stress of electrodeposited nickel, various nickel layers were prepared from sulfamate baths comprising varying concentrations of BD and chloride ions by applying direct-current electrodeposition. And their surface morphologies, microstructure, and residual stress were tested using SEM, XRD, EBSD, TEM, and AFM. While the nickel layers composed of pyramid morphology were prepared from additive-free baths, the surface flattened gradually as the BD concentration of the baths was increased, and the acicular grains in the deposits were replaced with <100> oriented columnar grains or <111> oriented nanograins; additionally, the residual tensile stress of the deposits increased. The addition of chloride ions to the baths containing BD significantly increased the residual stress in the nickel layers, although it only slightly promoted surface flattening and columnar grain coarsening. The effects of BD and chloride ions on the growth mode and residual stress of nickel deposits were explained via analysis of surface morphologies and microstructure. And the results indicate that the reduction of chloride ion concentration is a feasible way to reduce the residual stress of the nickel deposits when BD is included in the baths. Full article

(This article belongs to the Special Issue Advances in Coatings Prepared by Deposition: Microstructure, Properties and Applications)

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23 pages, 11793 KiB

Open AccessEditor’s ChoiceReview

Plasmonic Functionality of Optical Fiber Tips: Mechanisms, Fabrications, and Applications

by Bobo Du, Yunfan Xu, Lei Zhang and Yanpeng Zhang

Materials 2023, 16(9), 3596; https://doi.org/10.3390/ma16093596 - 8 May 2023

Cited by 1 | Viewed by 1591

Abstract

Optical fiber tips with the flat end-facets functionalized take the special advantages of easy fabrication, compactness, and ready-integration among the community of optical fiber devices. Combined with plasmonic structures, the fiber tips draw a significant growth of interest addressing diverse functions. This review [...] Read more.

Optical fiber tips with the flat end-facets functionalized take the special advantages of easy fabrication, compactness, and ready-integration among the community of optical fiber devices. Combined with plasmonic structures, the fiber tips draw a significant growth of interest addressing diverse functions. This review aims to present and summarize the plasmonic functionality of optical fiber tips with the current state of the art. Firstly, the mechanisms of plasmonic phenomena are introduced in order to illustrate the tip-compatible plasmonic nanostructures. Then, the strategies of plasmonic functionalities on fiber tips are analyzed and compared. Moreover, the classical applications of plasmonic fiber tips are reviewed. Finally, the challenges and prospects for future opportunities are discussed. Full article

(This article belongs to the Special Issue Advances in Multimaterial Fibers and Devices)

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18 pages, 6570 KiB

Open AccessEditor’s ChoiceArticle

Fracture Response of X80 Pipe Girth Welds under Combined Internal Pressure and Bending Moment

by Li Zhu, Naixian Li, Bin Jia and Yu Zhang

Materials 2023, 16(9), 3588; https://doi.org/10.3390/ma16093588 - 7 May 2023

Cited by 2 | Viewed by 1510

Abstract

In order to determine the effect of defect size on the pipeline fracture performance of girth welds in oil and gas pipelines, ABAQUS was used to simulate the fracture responses of X80 pipelines with girth weld defects under internal pressure and bending moment [...] Read more.

In order to determine the effect of defect size on the pipeline fracture performance of girth welds in oil and gas pipelines, ABAQUS was used to simulate the fracture responses of X80 pipelines with girth weld defects under internal pressure and bending moment conditions based on damage mechanics. In particular, the length and depth of defects were parametrically studied; the defect depth range was 20–80% of the wall thickness, and the circumferential length range of the defects was 5–20% of the pipeline circumference. The results show that, under the combined action of internal pressure and bending moment, the defect depth was more associated with adverse effects than the circumferential length of the defect. The failure load did not linearly decrease as the size of the defect increased, but when the depth of the defect reached a certain value, the failure load suddenly decreased. Full article

(This article belongs to the Special Issue Mechanics Behavior, Fatigue Damage, and Microstructure Evolution of Metallic Material)

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14 pages, 22598 KiB

Open AccessEditor’s ChoiceArticle

Microstructure Evolution and Mechanical Response of a Direct Quenched and Partitioned Steel at Different Finishing Rolling Temperatures

by Yajun Liu, Xiaolong Gan, Wen Liang, Guang Xu, Jianghua Qi and Man Liu

Materials 2023, 16(9), 3575; https://doi.org/10.3390/ma16093575 - 6 May 2023

Cited by 2 | Viewed by 1320

Abstract

The effects of finishing rolling temperature on the microstructure and mechanical properties of a direct quenched and partitioned (DQ&P) steel were investigated by a thermal simulation machine, a field emission scanning electron microscope (FE-SEM), electron backscattering diffraction (EBSD), and a transmission electron microscope [...] Read more.

The effects of finishing rolling temperature on the microstructure and mechanical properties of a direct quenched and partitioned (DQ&P) steel were investigated by a thermal simulation machine, a field emission scanning electron microscope (FE-SEM), electron backscattering diffraction (EBSD), and a transmission electron microscope (TEM). The results show that the original austenite grain size was refined by 31% as the finishing rolling temperature decreased from 920 °C to 840 °C, leading to the formation of the finest martensite lath at 840 °C. At the same time, the lower finishing rolling temperature resulted in a higher dislocation density, and consequently improved the stability of the retained austenite. Moreover, compared to the conventional Q&P process, the comprehensive mechanical properties of a steel with similar chemical composition can be enhanced by DQ&P processing. With the decrease of finishing rolling temperature from 920 °C to 840 °C, the strength and total elongation increases. The yield strength, tensile strength, and total elongation reach the maximum values of 1121 MPa, 1134 MPa, and 11.7%, respectively, at 840 °C. Full article

(This article belongs to the Special Issue Microstructure, Mechanical Properties and Wear Performance of High-Strength Steels)

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30 pages, 16400 KiB

Open AccessEditor’s ChoiceReview

Recent Progress for Single-Molecule Magnets Based on Rare Earth Elements

by Xiang Yin, Li Deng, Liuxia Ruan, Yanzhao Wu, Feifei Luo, Gaowu Qin, Xiaoli Han and Xianmin Zhang

Materials 2023, 16(9), 3568; https://doi.org/10.3390/ma16093568 - 6 May 2023

Cited by 3 | Viewed by 1898

Abstract

Single-molecule magnets (SMMs) have attracted much attention due to their potential applications in molecular spintronic devices. Rare earth SMMs are considered to be the most promising for application owing to their large magnetic moment and strong magnetic anisotropy. In this review, the recent [...] Read more.

Single-molecule magnets (SMMs) have attracted much attention due to their potential applications in molecular spintronic devices. Rare earth SMMs are considered to be the most promising for application owing to their large magnetic moment and strong magnetic anisotropy. In this review, the recent progress in rare earth SMMs represented by mononuclear and dinuclear complexes is highlighted, especially for the modulation of magnetic anisotropy, effective energy barrier (U_eff) and blocking temperature (T_B). The terbium- and dysprosium-based SMMs have a U_eff of 1541 cm⁻¹ and an increased T_B of 80 K. They break the boiling point temperature of liquid nitrogen. The development of the preparation technology of rare earth element SMMs is also summarized in an overview. This review has important implications and insights for the design and research of Ln-SMMs. Full article

(This article belongs to the Special Issue Theory and Simulations of Magnetic Materials)

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18 pages, 5619 KiB

Open AccessEditor’s ChoiceReview

A Review of Numerical Simulation of Laser–Arc Hybrid Welding

by Zhaoyang Wang, Mengcheng Gong, Longzao Zhou and Ming Gao

Materials 2023, 16(9), 3561; https://doi.org/10.3390/ma16093561 - 6 May 2023

Cited by 3 | Viewed by 1911

Abstract

Laser–arc hybrid welding (LAHW) is known to achieve more stable processes, better mechanical properties, and greater adaptability through the synergy of a laser and an arc. Numerical simulations play a crucial role in deepening our understanding of this interaction mechanism. In this paper, [...] Read more.

Laser–arc hybrid welding (LAHW) is known to achieve more stable processes, better mechanical properties, and greater adaptability through the synergy of a laser and an arc. Numerical simulations play a crucial role in deepening our understanding of this interaction mechanism. In this paper, we review the current work on numerical simulations of LAHW, including heat source selection laws, temperature field, flow field, and stress field results. We also discuss the influence of laser–arc interaction on weld defects and mechanical properties and provide suggestions for the development of numerical simulations of LAHW. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes)

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18 pages, 2294 KiB

Open AccessEditor’s ChoiceArticle

Mechanistic Study of Fast Performance Decay of PtCu Alloy-based Catalyst Layers for Polymer Electrolyte Fuel Cells through Electrochemical Impedance Spectroscopy

by Maximilian Grandi, Matija Gatalo, Ana Rebeka Kamšek, Gregor Kapun, Kurt Mayer, Francisco Ruiz-Zepeda, Martin Šala, Bernhard Marius, Marjan Bele, Nejc Hodnik, Merit Bodner, Miran Gaberšček and Viktor Hacker

Materials 2023, 16(9), 3544; https://doi.org/10.3390/ma16093544 - 5 May 2023

Viewed by 1522

Abstract

In the past, platinum–copper catalysts have proven to be highly active for the oxygen reduction reaction (ORR), but transferring the high activities measured in thin-film rotating disk electrodes (TF-RDEs) to high-performing membrane electrode assemblies (MEAs) has proven difficult due to stability issues during [...] Read more.

In the past, platinum–copper catalysts have proven to be highly active for the oxygen reduction reaction (ORR), but transferring the high activities measured in thin-film rotating disk electrodes (TF-RDEs) to high-performing membrane electrode assemblies (MEAs) has proven difficult due to stability issues during operation. High initial performance can be achieved. However, fast performance decay on a timescale of 24 h is induced by repeated voltage load steps with H₂/air supplied. This performance decay is accelerated if high relative humidity (>60% RH) is set for a prolonged time and low voltages are applied during polarization. The reasons and possible solutions for this issue have been investigated by means of electrochemical impedance spectroscopy and distribution of relaxation time analysis (EIS–DRT). The affected electrochemical sub-processes have been identified by comparing the PtCu electrocatalyst with commercial Pt/C benchmark materials in homemade catalyst-coated membranes (CCMs). The proton transport resistance (R_pt) increased by a factor of ~2 compared to the benchmark materials. These results provide important insight into the challenges encountered with the de-alloyed PtCu/KB electrocatalyst during cell break-in and operation. This provides a basis for improvements in the catalysts’ design and break-in procedures for the highly attractive PtCu/KB catalyst system. Full article

(This article belongs to the Special Issue Novel Materials for Green Hydrogen Production, Energy Conversion, and Fuel Cell Applications)

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17 pages, 4713 KiB

Open AccessEditor’s ChoiceArticle

Novel Graphene-Based Materials as a Tool for Improving Long-Term Storage of Cultural Heritage

by George Gorgolis, Steffen Ziemann, Maria Kotsidi, George Paterakis, Nikos Koutroumanis, Christos Tsakonas, Manfred Anders and Costas Galiotis

Materials 2023, 16(9), 3528; https://doi.org/10.3390/ma16093528 - 4 May 2023

Cited by 1 | Viewed by 1570

Abstract

The very serious problem of temperature and humidity regulation, especially for small and medium-sized museums, galleries, and private collections, can be mitigated by the introduction of novel materials that are easily applicable and of low cost. Within this study, archive boxes with innovative [...] Read more.

The very serious problem of temperature and humidity regulation, especially for small and medium-sized museums, galleries, and private collections, can be mitigated by the introduction of novel materials that are easily applicable and of low cost. Within this study, archive boxes with innovative technology are proposed as “smart” boxes that can be used for storage and transportation, in combination with a nanocomposite material consisting of polyvinyl alcohol (PVA) and graphene oxide (GO). The synthesis and characterization of the PVA/GO structure with SEM, Raman, AFM, XRD, Optical Microscopy, and profilometry are fully discussed. It is shown that the composite material can be integrated into the archive box either as a stand-alone film or attached onto fitting carriers, for example, those made of corrugated board. By applying the PVA/GO membrane this way, even with strong daily temperature fluctuations of ΔT = ±24.1 °C, strong external humidity fluctuations can be reduced by −87% inside the box. Furthermore, these humidity regulators were examined as Volatile Organic Compounds (VOCs) adsorbers since gas pollutants like formic acid, formaldehyde, acetic acid, and acetaldehyde are known to exist in museums and induce damages in the displayed or stored items. High rates of VOC adsorption have been measured, with the highest ones corresponding to formic acid (521% weight increase) and formaldehyde (223% weight increase). Full article

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

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25 pages, 63751 KiB

Open AccessEditor’s ChoiceReview

Copper-Based Diamond-like Thermoelectric Compounds: Looking Back and Stepping Forward

by Wenying Wang, Lin Bo, Junliang Zhu and Degang Zhao

Materials 2023, 16(9), 3512; https://doi.org/10.3390/ma16093512 - 3 May 2023

Cited by 2 | Viewed by 1990

Abstract

The research on thermoelectric (TE) materials has a long history. Holding the advantages of high elemental abundance, lead-free and easily tunable transport properties, copper-based diamond-like (CBDL) thermoelectric compounds have attracted extensive attention from the thermoelectric community. The CBDL compounds contain a large number [...] Read more.

The research on thermoelectric (TE) materials has a long history. Holding the advantages of high elemental abundance, lead-free and easily tunable transport properties, copper-based diamond-like (CBDL) thermoelectric compounds have attracted extensive attention from the thermoelectric community. The CBDL compounds contain a large number of representative candidates for thermoelectric applications, such as CuInGa₂, Cu₂GeSe₃, Cu₃SbSe₄, Cu₁₂SbSe₁₃, etc. In this study, the structure characteristics and TE performances of typical CBDLs were briefly summarized. Several common synthesis technologies and effective strategies to improve the thermoelectric performances of CBDL compounds were introduced. In addition, the latest developments in thermoelectric devices based on CBDL compounds were discussed. Further developments and prospects for exploring high-performance copper-based diamond-like thermoelectric materials and devices were also presented at the end. Full article

(This article belongs to the Special Issue Materials Physics in Thermoelectric Materials)

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16 pages, 3316 KiB

Open AccessEditor’s ChoiceArticle

Insights into the Contribution of Oxidation-Reduction Pretreatment for Mn_0.2Zr_0.8O_2−δ Catalyst of CO Oxidation Reaction

by Denis D. Mishchenko, Zakhar S. Vinokurov, Tatyana N. Afonasenko, Andrey A. Saraev, Mikhail N. Simonov, Evgeny Yu. Gerasimov and Olga A. Bulavchenko

Materials 2023, 16(9), 3508; https://doi.org/10.3390/ma16093508 - 2 May 2023

Cited by 1 | Viewed by 1477

Abstract

A Mn_0.2Zr_0.8O_2−δ mixed oxide catalyst was synthesized via the co-precipitation method and studied in a CO oxidation reaction after different redox pretreatments. The surface and structural properties of the catalyst were studied before and after the pretreatment using [...] Read more.

A Mn_0.2Zr_0.8O_2−δ mixed oxide catalyst was synthesized via the co-precipitation method and studied in a CO oxidation reaction after different redox pretreatments. The surface and structural properties of the catalyst were studied before and after the pretreatment using XRD, XANES, XPS, and TEM techniques. Operando XRD was used to monitor the changes in the crystal structure under pretreatment and reaction conditions. The catalytic properties were found to depend on the activation procedure: reducing the CO atmosphere at 400–600 °C and the reaction mixture (O₂ excess) or oxidative O₂ atmosphere at 250–400 °C. A maximum catalytic effect characterized by decreasing T₅₀ from 193 to 171 °C was observed after a reduction at 400 °C and further oxidation in the CO/O₂ reaction mixture was observed at 250 °C. Operando XRD showed a reversible reduction-oxidation of Mn cations in the volume of Mn_0.2Zr_0.8O_2−δ solid solution. XPS and TEM detected the segregation of manganese cations on the surface of the mixed oxide. TEM showed that Mn-rich regions have a structure of MnO₂. The pretreatment caused the partial decomposition of the Mn_0.2Zr_0.8O_2−δ solid solution and the formation of surface Mn-rich areas that are active in catalytic CO oxidation. In this work it was shown that the introduction of oxidation-reduction pretreatment cycles leads to an increase in catalytic activity due to changes in the origin of active states. Full article

(This article belongs to the Section Catalytic Materials)

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17 pages, 5358 KiB

Open AccessEditor’s ChoiceArticle

Production of AC from Bamboo, Orange, and Paulownia Waste—Influence of Activation Gas and Biomass Maturation

by Carlos Grima-Olmedo, Laura M. Valle-Falcones, Dulce Gómez-Limón Galindo and Ramón Rodríguez-Pons Esparver

Materials 2023, 16(9), 3498; https://doi.org/10.3390/ma16093498 - 1 May 2023

Cited by 2 | Viewed by 1698

Abstract

The production of agricultural waste is associated with environmental problems and risks to public health. The general interest demands, as an ecological alternative, the proper management of waste generated by industrial activity through its transformation into value-added products. Carbonization/activation (2 h/2 h) at [...] Read more.

The production of agricultural waste is associated with environmental problems and risks to public health. The general interest demands, as an ecological alternative, the proper management of waste generated by industrial activity through its transformation into value-added products. Carbonization/activation (2 h/2 h) at 700 °C in a vertical furnace (20 K/min), to produce biochar and activated carbon (AC) from bamboo, orange, and paulownia residue, was carried out in a laboratory facility with physical activation by CO₂ and steam. The characterization of the carbonaceous material obtained was based on the determination of the N₂ adsorption–desorption isotherms at 77 K, the specific surface area with the BET procedure, and its internal structure by means of SEM images. The BET surface area values obtained as a function of the CO₂/steam agent used were 911/1182 m²/g, 248/388 m²/g, and 800/1166 m²/g for bamboo, orange, and paulownia, respectively. The range of variation of porosity in paulownia residue generated after steam activation was 485–1166 m²/g, varying depending on the degree of maturity of the biomass used. Research has shown that both the type of activation agent used to produce AC and the degree of plant maturation of the precursor residue affect the quality and characteristics of the final product. Full article

(This article belongs to the Section Carbon Materials)

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