Materials

14 pages, 5129 KiB

Open AccessArticle

Estimating Compressive Strength of Concrete Using Neural Electromagnetic Field Optimization

by Mohammad Reza Akbarzadeh, Hossein Ghafourian, Arsalan Anvari, Ramin Pourhanasa and Moncef L. Nehdi

Materials 2023, 16(11), 4200; https://doi.org/10.3390/ma16114200 - 05 Jun 2023

Cited by 23 | Viewed by 1245

Abstract

Concrete compressive strength (CCS) is among the most important mechanical characteristics of this widely used material. This study develops a novel integrative method for efficient prediction of CCS. The suggested method is an artificial neural network (ANN) favorably tuned by electromagnetic field optimization [...] Read more.

Concrete compressive strength (CCS) is among the most important mechanical characteristics of this widely used material. This study develops a novel integrative method for efficient prediction of CCS. The suggested method is an artificial neural network (ANN) favorably tuned by electromagnetic field optimization (EFO). The EFO simulates a physics-based strategy, which in this work is employed to find the best contribution of the concrete parameters (i.e., cement (C), blast furnace slag (

S_{B F}

), fly ash (

{F A}_{1}

), water (W), superplasticizer (SP), coarse aggregate (

A_{C}

), fine aggregate (

{F A}_{2}

), and the age of testing (

A_{T}

)) to the CCS. The same effort is carried out by three benchmark optimizers, namely the water cycle algorithm (WCA), sine cosine algorithm (SCA), and cuttlefish optimization algorithm (CFOA) to be compared with the EFO. The results show that hybridizing the ANN using the mentioned algorithms led to reliable approaches for predicting the CCS. However, comparative analysis indicates that there are appreciable distinctions between the prediction capacity of the ANNs created by the EFO and WCA vs. the SCA and CFOA. For example, the mean absolute error calculated for the testing phase of the ANN-WCA, ANN-SCA, ANN-CFOA, and ANN-EFO was 5.8363, 7.8248, 7.6538, and 5.6236, respectively. Moreover, the EFO was considerably faster than the other strategies. In short, the ANN-EFO is a highly efficient hybrid model, and can be recommended for the early prediction of the CCS. A user-friendly explainable and explicit predictive formula is also derived for the convenient estimation of the CCS. Full article

(This article belongs to the Special Issue Development of High-Durability, Sustainable, and Carbon-Neutral Concrete Composites)

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13 pages, 2596 KiB

Open AccessArticle

Bactericidal Activity of Graphene Oxide Tests for Selected Microorganisms

by Katarzyna Olczak, Witold Jakubowski and Witold Szymański

Materials 2023, 16(11), 4199; https://doi.org/10.3390/ma16114199 - 05 Jun 2023

Cited by 1 | Viewed by 1314

Abstract

The aim of this study was to determine the bactericidal potential of graphene oxide (GO) in contact with four species of bacteria: E. coli, S. mutans, S. aureus and E. faecalis. Bacterial cell suspensions of each species were incubated in [...] Read more.

The aim of this study was to determine the bactericidal potential of graphene oxide (GO) in contact with four species of bacteria: E. coli, S. mutans, S. aureus and E. faecalis. Bacterial cell suspensions of each species were incubated in a medium containing GO, with incubation times of 5, 10, 30 and 60 min, at final concentrations of 50, 100, 200, 300 and 500 μg/mL. The cytotoxicity of GO was evaluated using live/dead staining. The results were recorded using a BD Accuri C6 flow cytofluorimeter. Obtained data were analyzed using BD CSampler software. A significant bacteria viability reduction was noted in all GO-containing samples. The antibacterial properties of GO were strongly influenced by GO concentration and incubation time. The highest bactericidal activity was observed at concentrations of 300 and 500 μg/mL for all incubation times (5, 10, 30 and 60 min). The highest antimicrobial potential was observed for E. coli: after 60 min, the mortality rate was 94% at 300 µg/mL GO and 96% at 500 µg/mL GO; the lowest was found for S. aureus—49% (300 µg/mL) and 55% (500 µg/mL). Full article

(This article belongs to the Special Issue Biomaterials and Mechanics in Dentistry)

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20 pages, 4545 KiB

Open AccessArticle

Enhancing Mechanical and Corrosion Properties of AISI 420 with Titanium-Nitride Reinforcement through High-Power-Density Selective Laser Melting Using Two-Stage Mixed TiN/AISI 420 Powder

by Duc Tran, Chih-Kuang Lin, Pi-Cheng Tung, Jeng-Rong Ho, Jason Shian-Ching Jang, Jing-Chie Lin, I-Yu Tsao and Thanh-Long Le

Materials 2023, 16(11), 4198; https://doi.org/10.3390/ma16114198 - 05 Jun 2023

Cited by 2 | Viewed by 1335

Abstract

This study investigates the effect of laser volume energy density (VED) on the properties of AISI 420 stainless steel and TiN/AISI 420 composite manufactured by selective laser melting (SLM). The composite contained 1 wt.% TiN and the average diameters of AISI 420 and [...] Read more.

This study investigates the effect of laser volume energy density (VED) on the properties of AISI 420 stainless steel and TiN/AISI 420 composite manufactured by selective laser melting (SLM). The composite contained 1 wt.% TiN and the average diameters of AISI 420 and TiN powders were 45 µm and 1 µm, respectively. The powder for SLMing the TiN/AISI 420 composite was prepared using a novel two-stage mixing scheme. The morphology, mechanical, and corrosion properties of the specimens were analyzed, and their correlations with microstructures were investigated. The results showed that the surface roughness of both SLM samples decreases with increasing VED, while relative densities greater than 99% were achieved at VEDs higher than 160 J/mm³. The SLM AISI 420 specimen fabricated at a VED of 205 J/mm³ exhibited the highest density of 7.7 g/cm³, tensile strength (UTS) of 1270 MPa, and elongation of 3.86%. The SLM TiN/AISI 420 specimen at a VED of 285 J/mm³ had a density of 7.67 g/cm³, UTS of 1482 MPa, and elongation of 2.72%. The microstructure of the SLM TiN/AISI 420 composite displayed a ring-like micro-grain structure consisting of retained austenite on the grain boundary and martensite in the grain. The TiN particles strengthened the mechanical properties of the composite by accumulating along the grain boundary. The mean hardnesses of the SLM AISI 420 and TiN/AISI 420 specimens were 635 and 735 HV, respectively, which exceeded previously reported results. The SLM TiN/AISI 420 composite exhibited excellent corrosion resistance in both 3.5 wt.% NaCl and 6 wt.% FeCl₃ solutions, with a resulting corrosion rate as low as 11 µm/year. Full article

(This article belongs to the Section Advanced Composites)

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12 pages, 2046 KiB

Open AccessArticle

Determination of the Oxygen Content in the LiF–NaF–KF Melt

by Anna A. Maslennikova, Peter N. Mushnikov, Alexey V. Dub, Olga Yu. Tkacheva, Yury P. Zaikov, Ya-Lan Liu and Wei-Qun Shi

Materials 2023, 16(11), 4197; https://doi.org/10.3390/ma16114197 - 05 Jun 2023

Cited by 3 | Viewed by 1181

Abstract

The present paper is dedicated to the quantitative determination of oxygen-containing impurities in the LiF–NaF–KF eutectic using electrochemical (cyclic and square-wave voltammetry) and reduction melting methods. The LiF–NaF–KF melt was analyzed before and after purifying electrolysis. The amount of oxygen-containing impurities removed from [...] Read more.

The present paper is dedicated to the quantitative determination of oxygen-containing impurities in the LiF–NaF–KF eutectic using electrochemical (cyclic and square-wave voltammetry) and reduction melting methods. The LiF–NaF–KF melt was analyzed before and after purifying electrolysis. The amount of oxygen-containing impurities removed from the salt during purification was determined. It was found that after electrolysis, the concentration of oxygen-containing impurities decreased by 7 times. The results obtained via electrochemical techniques and reduction melting were well-correlated, which made it possible to evaluate the quality of the LiF–NaF–KF F melt. To verify the analysis conditions, mechanical mixtures of LiF–NaF–KF containing Li₂O were analyzed using the reduction melting method. The oxygen concentration in the mixtures varied from 0.672 to 2.554 wt. %. Based on the analysis results, the dependence approximated by the straight line was obtained. These data may be used to draw calibration curves and to further develop the procedure of oxygen analysis of fluoride melts. Full article

(This article belongs to the Special Issue Electrochemical Processes, Materials and Devices)

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15 pages, 4473 KiB

Open AccessArticle

Crashworthiness Analysis of Thin-Walled Square Columns with a Hole Trigger

by Michał Rogala and Jakub Gajewski

Materials 2023, 16(11), 4196; https://doi.org/10.3390/ma16114196 - 05 Jun 2023

Cited by 5 | Viewed by 983

Abstract

Thin-walled structures dynamically loaded with an axial force are the subject of this study. The structures work as passive energy absorbers by progressive harmonic crushing. The absorbers were made of AA-6063-T6 aluminum alloy and subjected to both numerical and experimental tests. Experimental tests [...] Read more.

Thin-walled structures dynamically loaded with an axial force are the subject of this study. The structures work as passive energy absorbers by progressive harmonic crushing. The absorbers were made of AA-6063-T6 aluminum alloy and subjected to both numerical and experimental tests. Experimental tests were performed on an INSTRON 9350 HES bench, while numerical analyses were performed using Abaqus software. The energy absorbers tested had crush initiators in the form of drilled holes. The variable parameters were the number of holes and their diameter. The holes were located in a line 30 mm away from the base. This study shows a significant effect of the hole diameter on the values of the stroke efficiency indicator and mean crushing force. Full article

(This article belongs to the Special Issue Compressive Behavior of Materials and Structures)

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11 pages, 6236 KiB

Open AccessArticle

The Impact of Commercially Available Dry Mouth Products on the Corrosion Resistance of Common Dental Alloys

by Anna Yu. Turkina, Irina M. Makeeva, Oleg N. Dubinin, Julia V. Bondareva, Daniil A. Chernodoubov, Anastasia A. Shibalova, Alina V. Arzukanyan, Artem A. Antoshin, Peter S. Timashev and Stanislav A. Evlashin

Materials 2023, 16(11), 4195; https://doi.org/10.3390/ma16114195 - 05 Jun 2023

Viewed by 1082

Abstract

Dental implants are thought to be implanted for life, but throughout their lifespan, they function in aggressive oral environment, resulting in corrosion of the material itself as well as possible inflammation of adjacent tissues. Therefore, materials and oral products for people with metallic [...] Read more.

Dental implants are thought to be implanted for life, but throughout their lifespan, they function in aggressive oral environment, resulting in corrosion of the material itself as well as possible inflammation of adjacent tissues. Therefore, materials and oral products for people with metallic intraoral appliances must be chosen carefully. The purpose of this study was to investigate the corrosion behavior of common titanium and cobalt–chromium alloys in interaction with various dry mouth products using electrochemical impedance spectroscopy (EIS). The study showed that different dry mouth products lead to different open circuit potentials, corrosion voltages, and currents. The corrosion potentials of Ti64 and CoCr ranged from −0.3 to 0 V and −0.67 to 0.7 V, respectively. In contrast to titanium, pitting corrosion was observed for the cobalt–chromium alloy, leading to the release of Co and Cr ions. Based on the results, it can be argued that the commercially available dry mouth remedies are more favorable for dental alloys in terms of corrosion compared to Fusayama Meyer’s artificial saliva. Thus, to prevent undesirable interactions, the individual characteristics of not only the composition of each patient’s tooth and jaw structure, but also the materials already used in their oral cavity and oral hygiene products, must be taken into account. Full article

(This article belongs to the Section Corrosion)

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13 pages, 4058 KiB

Open AccessReview

Effects of Bioactive Glasses (BGs) on Exosome Production and Secretion: A Critical Review

by Sara Gorgani, Seyede Atefe Hosseini, Andrew Z. Wang, Francesco Baino and Saeid Kargozar

Materials 2023, 16(11), 4194; https://doi.org/10.3390/ma16114194 - 05 Jun 2023

Viewed by 1885

Abstract

There is an increasing trend toward the application of bioactive glasses in different areas of biomedicine, including tissue engineering and oncology. The reason for this increase is mostly attributed to the inherent properties of BGs, such as excellent biocompatibility, and the ease of [...] Read more.

There is an increasing trend toward the application of bioactive glasses in different areas of biomedicine, including tissue engineering and oncology. The reason for this increase is mostly attributed to the inherent properties of BGs, such as excellent biocompatibility, and the ease of tailoring their properties by changing, for example, the chemical composition. Previous experiments have demonstrated that the interactions between BGs and their ionic dissolution products, and mammalian cells, can affect and change cellular behaviors, and thereby govern the performance of living tissues. However, limited research exists on their critical role in the production and secretion of extracellular vesicles (EVs) such as exosomes. Exosomes are nanosized membrane vesicles that carry various therapeutic cargoes such as DNA, RNA, proteins, and lipids, and thereby can govern cell–cell communication and subsequent tissue responses. The use of exosomes is currently considered a cell-free approach in tissue engineering strategies, due to their positive roles in accelerating wound healing. On the other hand, exosomes are known as key players in cancer biology (e.g., progression and metastasis), due to their capability to carry bioactive molecules between tumor cells and normal cells. Recent studies have demonstrated that the biological performance of BGs, including their proangiogenic activity, is accomplished with the help of exosomes. Indeed, therapeutic cargos (e.g., proteins) produced in BG-treated cells are transferred by a specific subset of exosomes toward target cells and tissues, and lead to a biological phenomenon. On the other hand, BGs are suitable delivery vehicles that can be utilized for the targeted delivery of exosomes to cells and tissues of interest. Therefore, it seems necessary to have a deeper understanding of the potential effects of BGs in the production of exosomes in cells that are involved in tissue repair and regeneration (mostly mesenchymal stem cells), as well as in those that play roles in cancer progression (e.g., cancer stem cells). This review aims to present an updated report on this critical issue, to provide a roadmap for future research in the fields of tissue engineering and regenerative medicine. Full article

(This article belongs to the Special Issue Biomaterials and Scaffolds for Enhanced Production of Exosomes and Accelerated Tissue Repair and Regeneration)

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10 pages, 4105 KiB

Open AccessArticle

Preparation and Characterization of Carbazole-Based Luminogen with Efficient Emission in Solid and Solution States

by Beibei Zhang, Lingzhong Wei, Xuansi Tang, Zizhan Jiang, Song Guo, Linmin Zou, Huihong Xie, Yongyang Gong and Yuanli Liu

Materials 2023, 16(11), 4193; https://doi.org/10.3390/ma16114193 - 05 Jun 2023

Cited by 1 | Viewed by 1109

Abstract

Organic luminescent materials with high luminescence efficiency in both solution and solid states, namely dual-state emission (DSE), have attracted considerable attention due to their promising applications in various fields. In order to enrich the variety of DSE materials, carbazole, similar to triphenylamine (TPA), [...] Read more.

Organic luminescent materials with high luminescence efficiency in both solution and solid states, namely dual-state emission (DSE), have attracted considerable attention due to their promising applications in various fields. In order to enrich the variety of DSE materials, carbazole, similar to triphenylamine (TPA), was utilized to construct a novel DSE luminogen named 2-(4-(9H-carbazol-9-yl)phenyl)benzo[d]thiazole (CZ-BT). CZ-BT exhibited DSE characteristics with fluorescence quantum yields of 70, 38 and 75% in solution, amorphous and crystalline states, respectively. CZ-BT shows thermochromic and mechanochromic properties in solution and solids, respectively. Theoretical calculations show that there is a small conformational difference between the ground state and the lowest singly excited state of CZ-BT and that it exhibits a low non-radiative transition characteristic. The oscillator strength during the transition from the single excited state to the ground state reaches 1.0442. CZ-BT adopts a distorted molecular conformation with intramolecular hindrance effects. The excellent DSE properties of CZ-BT can be explained well using theoretical calculations and experimental results. In terms of application, the CZ-BT has a detection limit for the hazardous substance picric acid of 2.81 × 10⁻⁷ mol/L. Full article

(This article belongs to the Section Electronic Materials)

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13 pages, 2831 KiB

Open AccessArticle

RAFT Synthesis and Characterization of Poly(Butyl-co-2-(N,N-Dimethylamino)Ethyl Acrylates)-block-Poly(Polyethylene Glycol Monomethyl Ether Acrylate) as a Photosensitizer Carrier for Photodynamic Therapy

by Makoto Obata and Shiho Hirohara

Materials 2023, 16(11), 4192; https://doi.org/10.3390/ma16114192 - 05 Jun 2023

Viewed by 987

Abstract

Polymer micelles are promising drug delivery systems for highly hydrophobic photosensitizers in photodynamic therapy (PDT) applications. We previously developed pH-responsive polymer micelles consisting of poly(styrene-co-2-(N,N-dimethylamino)ethyl acrylate)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(St-co-DMAEA)-b-PPEGA) [...] Read more.

Polymer micelles are promising drug delivery systems for highly hydrophobic photosensitizers in photodynamic therapy (PDT) applications. We previously developed pH-responsive polymer micelles consisting of poly(styrene-co-2-(N,N-dimethylamino)ethyl acrylate)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(St-co-DMAEA)-b-PPEGA) for zinc phthalocyanine (ZnPc) delivery. In this study, poly(butyl-co-2-(N,N-dimethylamino)ethyl acrylates)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(BA-co-DMAEA)-b-PPEGA) was synthesized via reversible addition and fragmentation chain transfer (RAFT) polymerization to explore the role of neutral hydrophobic units in photosensitizer delivery. The composition of DMAEA units in P(BA-co-DMAEA) was adjusted to 0.46, which is comparable to that of P(St-co-DMAEA)-b-PPEGA. The size distribution of the P(BA-co-DMAEA)-b-PPEGA micelles changed when the pH decreased from 7.4 to 5.0, indicating their pH-responsive ability. The photosensitizers, 5,10,15,20-tetrakis(pentafluorophenyl)chlorin (TFPC), 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TFPP), protoporphyrin IX (PPIX), and ZnPc were examined as payloads for the P(BA-co-DMAEA)-b-PPEGA micelles. The encapsulation efficiency depended on the nature of the photosensitizer. TFPC-loaded P(BA-co-DMAEA)-b-PPEGA micelles exhibited higher photocytotoxicity than free TFPC in the MNNG-induced mutant of the rat murine RGM-1 gastric epithelial cell line (RGK-1), indicating their superiority for photosensitizer delivery. ZnPc-loaded P(BA-co-DMAEA)-b-PPEGA micelles also exhibited superior photocytotoxicity compared to free ZnPc. However, their photocytotoxicity was lower than that of P(St-co-DMAEA)-b-PPEGA. Therefore, neutral hydrophobic units, as well as pH-responsive units, must be designed for the encapsulation of photosensitizers. Full article

(This article belongs to the Special Issue Science and Technology of Advanced Materials Applied to Society: Including Collections from the Latest Papers of KRIS 2023)

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12 pages, 6405 KiB

Open AccessArticle

A Facile and Eco-Friendly Hydrothermal Synthesis of High Tetragonal Barium Titanate with Uniform and Controllable Particle Size

by Tingting Wang, Xiaoxiao Pang, Bin Liu, Jie Liu, Jing Shen and Cheng Zhong

Materials 2023, 16(11), 4191; https://doi.org/10.3390/ma16114191 - 05 Jun 2023

Cited by 1 | Viewed by 1552

Abstract

The preparation of tetragonal barium titanate (BT) powders with uniform and suitable particle sizes is a significant prerequisite for ultra-thin and highly integrated multilayer ceramic capacitors (MLCCs). However, the balance of high tetragonality and controllable particle size remains a challenge, which limits the [...] Read more.

The preparation of tetragonal barium titanate (BT) powders with uniform and suitable particle sizes is a significant prerequisite for ultra-thin and highly integrated multilayer ceramic capacitors (MLCCs). However, the balance of high tetragonality and controllable particle size remains a challenge, which limits the practical application of BT powders. Herein, the effects of different proportions of hydrothermal medium composition on the hydroxylation process are explored to obtain high tetragonality. The high tetragonality of BT powders under the optimal solvent condition of water:ethanol:ammonia solution of 2:2:1 is around 1.009 and increases with the particle size. Meanwhile, the good uniformity and dispersion of BT powders with particle sizes of 160, 190, 220, and 250 nm benefit from the inhibition of ethanol on the interfacial activity of BT particles (BTPs). The core–shell structure of BTPs is revealed by different lattice fringe spacings of the core and edge and the crystal structure by reconstructed atomic arrangement, which reasonably explains the trend between tetragonality and average particle size. These findings are instructive for the related research on the hydrothermal process of BT powders. Full article

(This article belongs to the Special Issue Advances in Hydrothermal/Solvothermal Processing)

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18 pages, 8073 KiB

Open AccessArticle

Manganese-Titanium Mixed Ion Sieves for the Selective Adsorption of Lithium Ions from an Artificial Salt Lake Brine

by Yaxuan Ding, Nguyen Thi Hong Nhung, Jiahao An, Hao Chen, Lianying Liao, Chunlin He, Xinpeng Wang and Toyohisa Fujita

Materials 2023, 16(11), 4190; https://doi.org/10.3390/ma16114190 - 05 Jun 2023

Cited by 4 | Viewed by 1647

Abstract

Lithium recovery is imperative to accommodate the increase in lithium demand. Salt lake brine contains a large amount of lithium and is one of the most important sources of lithium metal. In this study, Li₂CO₃, MnO₂, and [...] Read more.

Lithium recovery is imperative to accommodate the increase in lithium demand. Salt lake brine contains a large amount of lithium and is one of the most important sources of lithium metal. In this study, Li₂CO₃, MnO₂, and TiO₂ particles were mixed, and the precursor of a manganese–titanium mixed ion sieve (M-T-LIS) was prepared by a high-temperature solid-phase method. M-T-LISs were obtained by DL-malic acid pickling. The adsorption experiment results noted single-layer chemical adsorption and maximum lithium adsorption of 32.32 mg/g. From the Brunauer–Emmett–Teller and scanning electron microscopy results, the M-T-LIS provided adsorption sites after DL-malic acid pickling. In addition, X-ray photoelectron spectroscopy and Fourier transform infrared results showed the ion exchange mechanism of the M-T-LIS adsorption. From the results of the Li⁺ desorption experiment and recoverability experiment, DL-malic acid was used to desorb Li⁺ from the M-T-LIS with a desorption rate of more than 90%. During the fifth cycle, the Li⁺ adsorption capacity of the M-T-LIS was more than 20 mg/g (25.90 mg/g), and the recovery efficiency was higher than 80% (81.42%). According to the selectivity experiment, the M-T-LIS had good selectivity for Li⁺ (adsorption capacity of 25.85 mg/g in the artificial salt lake brine), which indicates its good application potential. Full article

(This article belongs to the Special Issue Advanced Materials for Water Remediation)

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14 pages, 716 KiB

Open AccessArticle

Evaluation of Physical–Chemical Properties of Contemporary CAD/CAM Materials with Chromatic Transition “Multicolor”

by Monika Lukomska-Szymanska, Mateusz Radwanski, Naji Kharouf, Davide Mancino, Herve Tassery, Corrado Caporossi, Francesco Inchingolo, Aline de Almeida Neves, Yu Fu Chou and Salvatore Sauro

Materials 2023, 16(11), 4189; https://doi.org/10.3390/ma16114189 - 05 Jun 2023

Viewed by 1262

Abstract

The use of materials for computer-aided design/computer-aided manufacturing (CAD/CAM) has been rapidly increasing in daily practice. However, one of the main issues regarding modern CAD/CAM materials is their aging in the oral environment, which may lead to significant changes in their overall properties. [...] Read more.

The use of materials for computer-aided design/computer-aided manufacturing (CAD/CAM) has been rapidly increasing in daily practice. However, one of the main issues regarding modern CAD/CAM materials is their aging in the oral environment, which may lead to significant changes in their overall properties. The aim of this study was to compare the flexural strength, water sorption, cross-link density (softening ratio%), surface roughness, and SEM analysis of three modern CAD/CAM “multicolor” composites. Grandio (Grandio disc multicolor—VOCO GmbH, Cuxhaven, Germany), Shofu (Shofu Block HC—Shofu Inc., Kyoto, Japan), and Vita (Vita Enamic multiColor—Vita Zahnfabrik, Bad Sackingen, Germany) were tested in this study. They were prepared in stick-shaped specimens and submitted to different tests after several aging protocols, such as thermocycling and mechanical cycle loading challenge. Further disc-shaped specimens were also created and tested for water sorption, cross-link density, surface roughness, and SEM ultramorphology, before and after storage in an ethanol-based solution. For flexural strength and ultimate tensile strength, Grandio showed the greatest values both at baseline and after aging (p < 0.05). Grandio and Vita Enamic presented the highest modulus of elasticity and the lowest water sorption (p < 0.05). A significant reduction (p < 0.05) in microhardness after ethanol storage (softening ratio%) was observed especially in Shofu. Grandio had the lowest roughness parameters compared to the other tested CAD/CAM materials, while ethanol storage significantly increased the Ra and RSm values in Shofu (p < 0.05). Despite the comparable modulus of elasticity of Vita and Grandio, this latter showed greater flexural strength and ultimate tensile strength both at baseline and after aging. Hence, Grandio and Vita Enamic may be employed for the anterior teeth and for those restorations requiring load-bearing capacity. Conversely, aging seems to affect several properties of Shofu, so its use for permanent restorations should be well-pondered based on the clinical situation. Full article

(This article belongs to the Special Issue Prospects for Dental Materials in Prosthodontics)

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13 pages, 4305 KiB

Open AccessArticle

Three-Layered Thin Films for Simultaneous Infrared Camouflage and Radiative Cooling

by Luyu Zhang, Wenjie Zhang, Yuanbin Liu and Linhua Liu

Materials 2023, 16(11), 4188; https://doi.org/10.3390/ma16114188 - 05 Jun 2023

Cited by 1 | Viewed by 1705

Abstract

With the rapid advancements in aerospace technology and infrared detection technology, there are increasing needs for materials with simultaneous infrared camouflage and radiative cooling capabilities. In this study, a three-layered Ge/Ag/Si thin film structure on a titanium alloy TC4 substrate (a widely used [...] Read more.

With the rapid advancements in aerospace technology and infrared detection technology, there are increasing needs for materials with simultaneous infrared camouflage and radiative cooling capabilities. In this study, a three-layered Ge/Ag/Si thin film structure on a titanium alloy TC4 substrate (a widely used skin material for spacecraft) is designed and optimized to achieve such spectral compatibility by combining the transfer matrix method and the genetic algorithm. The structure exhibits a low average emissivity of 0.11 in the atmospheric windows of 3–5 μm and 8–14 μm for infrared camouflage and a high average emissivity of 0.69 in 5–8 μm for radiative cooling. Furthermore, the designed metasurface shows a high degree of robustness regarding the polarization and incidence angle of the incoming electromagnetic wave. The underlying mechanisms allowing for the spectral compatibility of the metasurface can be elucidated as follows: the top Ge layer selectively transmits electromagnetic waves ranging from 5–8 μm while it reflects those in the ranges of 3–5 μm and 8–14 μm. The transmitted electromagnetic waves from the Ge layer are first absorbed by the Ag layer and then localized in the Fabry-Perot resonance cavity formed by Ag layer, Si layer and TC4 substrate. Ag and TC4 make further intrinsic absorptions during the multiple reflections of the localized electromagnetic waves. Full article

(This article belongs to the Section Thin Films and Interfaces)

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14 pages, 2427 KiB

Open AccessArticle

Evaluation of the Mechanical, Thermal and Rheological Properties of Hop, Hemp and Wood Fiber Plastic Composites

by Sierra Talcott, Benjamin Uptmor and Armando G. McDonald

Materials 2023, 16(11), 4187; https://doi.org/10.3390/ma16114187 - 05 Jun 2023

Cited by 2 | Viewed by 1086

Abstract

The aim of this study was to evaluate the use of waste natural fibers from milled hop bines and hemp stalks, without chemical treatment, and compare them to a commercial wood fiber for use in wood–plastic composite (WPC) materials. The fibers were characterized [...] Read more.

The aim of this study was to evaluate the use of waste natural fibers from milled hop bines and hemp stalks, without chemical treatment, and compare them to a commercial wood fiber for use in wood–plastic composite (WPC) materials. The fibers were characterized (density, fiber size and chemical composition). WPCs were produced by the extrusion of a blend of fibers (50%), high-density polyethylene (HDPE) and coupling agent (2%). The WPCs were characterized for their mechanical, rheological, thermal, viscoelastic and water resistance properties. Pine fiber was about half the size of hemp and hop fibers and thus had a higher surface area. The pine WPC melts had a higher viscosity than the other two WPCs. Additionally, the tensile and flexural strengths of the pine WPC were higher than those of hop and hemp WPCs. The pine WPC was also shown to have the least water absorption followed by hop and hemp WPCs. This study highlights that different lignocellulosic fibers influence their WPC properties. The properties of the hop- and hemp-based WPCs were comparable to commercial WPCs and can be improved by further milling/screening the fibers to a smaller particle size (volumetric mean of ~88 μm) to increase their surface area, fiber–matrix interactions and improve stress-transfer. Full article

(This article belongs to the Special Issue Advances in the Circularity of Polymeric and Composite Materials)

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3 pages, 170 KiB

Open AccessEditorial

Experimental Testing and Constitutive Modelling of Pavement Materials

by Xueyan Liu, Yuqing Zhang, Zhanping You, Linbing Wang and Changhong Zhou

Materials 2023, 16(11), 4186; https://doi.org/10.3390/ma16114186 - 05 Jun 2023

Viewed by 1279

Abstract

Pavement materials such as asphalt mixtures, granular aggregates and soils exhibit complex material properties and engineering performance under external loading and environmental conditions [...] Full article

(This article belongs to the Special Issue Experimental Testing and Constitutive Modelling of Pavement Materials)

17 pages, 10492 KiB

Open AccessArticle

Flexural Strength Characteristics of Fiber-Reinforced Cemented Soil

by Gabriel Orquizas Mattielo Pedroso, Ricardo Domingos dos Santos Junior, Jefferson Lins da Silva, Mariana Ferreira Benessiuti Motta and Emerson Felipe Félix

Materials 2023, 16(11), 4185; https://doi.org/10.3390/ma16114185 - 04 Jun 2023

Cited by 3 | Viewed by 1406

Abstract

This work deals with the flexural performance of a soil-cement for pavement reinforced by polypropylene and steel fibers, and the main purpose is to evaluate the effect of different curing times. In this sense, three different curing times were employed to investigate the [...] Read more.

This work deals with the flexural performance of a soil-cement for pavement reinforced by polypropylene and steel fibers, and the main purpose is to evaluate the effect of different curing times. In this sense, three different curing times were employed to investigate the influence of fibers on the material’s behavior at varying levels of strength and stiffness as the matrix became increasingly rigid. An experimental program was developed to analyze the effects of incorporating different fibers in a cemented matrix for pavement applications. Polypropylene and steel fibers were used at 0.5/1.0/1.5% fractions by volume for three different curing times (3/7/28 days) to assess the fiber effect in the cemented soil (CS) matrices throughout time. An evaluation of the material performance was carried out using the 4-Point Flexural Test. The results show that steel fibers with 1.0% content improved by approximately 20% in terms of initial strength and peak strength at small deflections without interfering the flexural static modulus of the material. The polypropylene fiber mixtures had better performance in terms of ductility index reaching values varying from 50 to 120, an increase of approximately 40% in residual strength, and improved cracking control at large deflections. The current study shows that fibers significantly affect the mechanical performance of CSF. Thus, the overall performance presented in this study is useful for selecting the most suitable fiber type corresponding to the different mechanisms as a function of curing time. Full article

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

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14 pages, 6552 KiB

Open AccessArticle

Study on the Performance and Mechanism of Cement Solidified Desulfurization Manganese Residue

by Shicheng Wang, Fang Wang, Jialing Che and Lihua Ma

Materials 2023, 16(11), 4184; https://doi.org/10.3390/ma16114184 - 04 Jun 2023

Cited by 3 | Viewed by 1327

Abstract

Desulfurized manganese residue (DMR) is an industrial solid residue produced by high-temperature and high-pressure desulfurization calcination of electrolytic manganese residue (EMR). DMR not only occupies land resources but also easily causes heavy metal pollution in soil, surface water, and groundwater. Therefore, it is [...] Read more.

Desulfurized manganese residue (DMR) is an industrial solid residue produced by high-temperature and high-pressure desulfurization calcination of electrolytic manganese residue (EMR). DMR not only occupies land resources but also easily causes heavy metal pollution in soil, surface water, and groundwater. Therefore, it is necessary to treat the DMR safely and effectively so that it can be used as a resource. In this paper, Ordinary Portland cement (P.O 42.5) was used as a curing agent to treat DMR harmlessly. The effects of cement content and DMR particle size on flexural strength, compressive strength, and leaching toxicity of a cement-DMR solidified body were studied. The phase composition and microscopic morphology of the solidified body were analyzed by XRD, SEM, and EDS, and the mechanism of cement-DMR solidification was discussed. The results show that the flexural strength and compressive strength of a cement-DMR solidified body can be significantly improved by increasing the cement content to 80 mesh particle size. When the cement content is 30%, the DMR particle size has a great influence on the strength of the solidified body. When the DMR particle size is 4 mesh, the DMR particles will form stress concentration points in the solidified body and reduce its strength. In the DMR leaching solution, the leaching concentration of Mn is 2.8 mg/L, and the solidification rate of Mn in the cement-DMR solidified body with 10% cement content can reach 99.8%. The results of XRD, SEM, and EDS showed that quartz (SiO₂) and gypsum dihydrate (CaSO₄·2H₂O) were the main phases in the raw slag. Quartz and gypsum dihydrate could form ettringite (AFt) in the alkaline environment provided by cement. Mn was finally solidified by MnO₂, and Mn could be solidified in C-S-H gel by isomorphic replacement. Full article

(This article belongs to the Special Issue Microstructures and Mechanical Properties of Cement-Based Composites)

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19 pages, 5631 KiB

Open AccessArticle

Control of Tooth Form Deformation in Heat Treatment of Spiral Bevel Gears Based on Reverse Adjustment of Cutting Parameters

by Ganhua Liu, Xiaodong Huo and Shiyi Deng

Materials 2023, 16(11), 4183; https://doi.org/10.3390/ma16114183 - 04 Jun 2023

Viewed by 1158

Abstract

The tooth surface structure of spiral bevel gear is complex and requires high machining accuracy. In order to reduce the tooth form deformation of heat treatment, this paper proposes a reverse adjustment correction model of tooth cutting for heat treatment tooth form deformation [...] Read more.

The tooth surface structure of spiral bevel gear is complex and requires high machining accuracy. In order to reduce the tooth form deformation of heat treatment, this paper proposes a reverse adjustment correction model of tooth cutting for heat treatment tooth form deformation of spiral bevel gear. Based on the Levenberg–Marquardat method, a stable and accurate numerical solution for the reverse adjustment amount of the cutting parameters is solved. Firstly, a mathematical model of the tooth surface of spiral bevel gears was established based on the cutting parameters. Secondly, the effect law of each cutting parameter on tooth form was studied by using the method of small variable perturbation. Finally, based on the tooth form error sensitivity coefficient matrix, a reverse adjustment correction model of tooth cutting is established to compensate the heat treatment tooth form deformation by reserving the tooth cutting allowance in the tooth cutting stage. The effectiveness of the reverse adjustment correction model of tooth cutting was verified through experiments on reverse adjustment of tooth cutting processing. The experimental results show that the accumulative tooth form error of the spiral bevel gear after heat treatment is 199.8 μm, which is reduced by 67.71%, and the maximum tooth form error is 8.7 μm, which is reduced by 74.75%, after reverse adjustment of cutting parameters. This research can provide technical support and a theoretical reference for heat treatment tooth form deformation control and high-precision tooth cutting processing of spiral bevel gears. Full article

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18 pages, 6667 KiB

Open AccessArticle

Effect of the Surface Chemical Composition on the Corrosion Resistance in the Mixture of FeCrMoNbB (140MXC) and FeCMnSi (530AS) Coatings Produced with the Electric Wire Arc Spraying Technique: Part I

by Héctor F. Rojas-Molano, Jhon J. Olaya-Flórez, María A. Guzmán-Pardo, José E. Alfonso-Orjuela and Néstor E. Mendieta-Reyes

Materials 2023, 16(11), 4182; https://doi.org/10.3390/ma16114182 - 04 Jun 2023

Cited by 2 | Viewed by 1310

Abstract

In this study, FeCrMoNbB (140MXC) and FeCMnSi (530AS) coatings were simultaneously projected on the substrate AISI-SAE 4340 using the electric wire arc spraying technique. The projection parameters, such as current (I), voltage (V), primary air pressure (1st), and secondary air pressure (2nd), were [...] Read more.

In this study, FeCrMoNbB (140MXC) and FeCMnSi (530AS) coatings were simultaneously projected on the substrate AISI-SAE 4340 using the electric wire arc spraying technique. The projection parameters, such as current (I), voltage (V), primary air pressure (1st), and secondary air pressure (2nd), were determined using the experimental model Taguchi L9 (3⁴⁻²). Its main purpose is to produce dissimilar coatings and to evaluate the effect of the surface chemical composition on the corrosion resistance in the mixture of 140MXC-530AS as commercial coatings. Three phases were considered to obtain and characterize the coatings: Phase 1: Preparation of materials and projection equipment; Phase 2: Coatings production; and Phase 3: Coatings characterization. The characterization of the dissimilar coatings was carried out using the techniques of Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), Auger Electronic Spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The results of this characterization corroborated the electrochemical behavior of the coatings. The presence of B was determined with the XPS characterization technique in the mixtures of the coatings in the form of Iron Boride. Moreover, the XRD technique showed Nb in the form of FeNb as a precursor compound for the 140MXC wire powder. The most relevant contributions are the pressures, provided that the quantity of oxides in the coatings decreases with respect to the reaction time between the molten particles and the atmosphere of the projection hood; moreover, for the corrosion potential, the operating voltage of the equipment does not exert any effect since these tend to remain constant. Full article

(This article belongs to the Section Corrosion)

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15 pages, 2121 KiB

Open AccessArticle

Radionuclides’ Recovery from Seawater Using FIC and FIC A Sorbents

by Nikolay A. Bezhin, Vitaliy V. Milyutin, Natalia V. Kuzmenkova, Iuliia G. Shibetskaia, Ol’ga N. Kozlovskaia, Evgeniy V. Slizchenko, Victoria A. Razina and Ivan G. Tananaev

Materials 2023, 16(11), 4181; https://doi.org/10.3390/ma16114181 - 04 Jun 2023

Viewed by 1067

Abstract

To solve radioecological and oceanological problems (estimate the vertical transport, flows of particulate organic carbon, phosphorus biodynamics, submarine groundwater discharge, etc.), it is necessary to determine the natural values of the radionuclides’ activity in seawater and particulate matter. For the first time, the [...] Read more.

To solve radioecological and oceanological problems (estimate the vertical transport, flows of particulate organic carbon, phosphorus biodynamics, submarine groundwater discharge, etc.), it is necessary to determine the natural values of the radionuclides’ activity in seawater and particulate matter. For the first time, the radionuclides’ sorption from seawater was studied using sorbents based on activated carbon modified with iron(III) ferrocyanide (FIC) and based on activated carbon modified with iron(III) hydroxide (FIC A—activated FIC) obtained by FIC sorbent treatment with sodium hydroxide solution. The possibility of trace amounts of phosphorus, beryllium, and cesium recovery in laboratory conditions has been investigated. Distribution coefficients, dynamic, and total dynamic exchange capacities were determined. The physicochemical regularities (isotherm and kinetics) of sorption have been studied. The results obtained are characterized via Langmuir, Freindlich, and Dubinin–Radushkevich isotherm equations, as well as pseudo-first and pseudo-second-order kinetic models, intraparticle diffusion, and the Elovich model. Under expeditionary conditions, the sorption efficiency of ¹³⁷Cs using FIC sorbent, ⁷Be, ³²P, and ³³P—using FIC A sorbent with a single-column method by adding a stable tracer, as well as the sorption efficiency of radionuclides ²¹⁰Pb and ²³⁴Th with their natural content by FIC A sorbent in a two-column mode from large volumes of seawater was assessed. High values of efficiency of their recovery by the studied sorbents were achieved. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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22 pages, 8320 KiB

Open AccessArticle

Failure Mechanism and Control Countermeasures for Argillaceous Surrounding Rock of Horsehead Roadway under High Stress

by Deyu Qian, Qi Cui, Hexi Jiao, Guanghui Zhu, Zhiyi Zhang, Linyou Jiang, Qingbin Meng, Jiale Liu, Xing Gao and Fujia Xing

Materials 2023, 16(11), 4180; https://doi.org/10.3390/ma16114180 - 04 Jun 2023

Viewed by 909

Abstract

The argillaceous surrounding rock of a horsehead roadway under high stress conditions is prone to deformation and failure, and the control of its long-term stability is difficult. Based on the engineering practices that control the argillaceous surrounding rock of a horsehead roadway in [...] Read more.

The argillaceous surrounding rock of a horsehead roadway under high stress conditions is prone to deformation and failure, and the control of its long-term stability is difficult. Based on the engineering practices that control the argillaceous surrounding rock of a horsehead roadway in the return air shaft in the Libi Coal Mine in Shanxi Province, field measurements, laboratory experimentation, numerical simulation, and industrial tests are used to analyze the main influencing factors and mechanism of the deformation and failure of the surrounding rock of the horsehead roadway. We propose principles and countermeasures to control the stability of the horsehead roadway. The main factors of the surrounding rock failure of the horsehead roadway include the poor lithology of argillaceous surrounding rocks, horizontal tectonic stress, the superimposed influence of additional stress from the shaft and construction disturbance, the small thickness of the anchorage layer in the roof, and the insufficient depth of floor reinforcement. The results show that the shaft’s presence increases the horizontal stress peak and stress concentration range in the roof, and the plastic zone range. The stress concentration and plastic zones and deformations of the surrounding rock increase significantly with the increase in horizontal tectonic stress. The control principles for the argillaceous surrounding rock of the horsehead roadway include increasing the thickness of the anchorage ring, the floor reinforcement exceeding the minimum depth, and reinforced support in key positions. The key control countermeasures include an innovative prestressed full-length anchorage for the mudstone roof, active and passive reinforcement technology with cables, and a reverse arch for floor reinforcement. The field measurements show that the control of the surrounding rock using the prestressed full-length anchorage of the innovative anchor-grouting device is remarkable. Full article

(This article belongs to the Special Issue The Composite Materials of Today and Tomorrow)

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16 pages, 2292 KiB

Open AccessArticle

Engineering of Silica Mesoporous Materials for CO₂ Adsorption

by Oyundari Tumurbaatar, Margarita Popova, Violeta Mitova, Pavletta Shestakova and Neli Koseva

Materials 2023, 16(11), 4179; https://doi.org/10.3390/ma16114179 - 04 Jun 2023

Cited by 1 | Viewed by 1242

Abstract

Adsorption methods for CO₂ capture are characterized by high selectivity and low energy consumption. Therefore, the engineering of solid supports for efficient CO₂ adsorption attracts research attention. Modification of mesoporous silica materials with tailor-made organic molecules can greatly improve silica’s performance [...] Read more.

Adsorption methods for CO₂ capture are characterized by high selectivity and low energy consumption. Therefore, the engineering of solid supports for efficient CO₂ adsorption attracts research attention. Modification of mesoporous silica materials with tailor-made organic molecules can greatly improve silica’s performance in CO₂ capture and separation. In that context, a new derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, possessing an electron-rich condensed aromatic structure and also known for its anti-oxidative properties, was synthesized and applied as a modifying agent of 2D SBA-15, 3D SBA-16, and KIT-6 silicates. The physicochemical properties of the initial and modified materials were studied using nitrogen physisorption and temperature-gravimetric analysis. The adsorption capacity of CO₂ was measured in a dynamic CO₂ adsorption regime. The three modified materials displayed a higher capacity for CO₂ adsorption than the initial ones. Among the studied sorbents, the modified mesoporous SBA-15 silica showed the highest adsorption capacity for CO₂ (3.9 mmol/g). In the presence of 1 vol.% water vapor, the adsorption capacities of the modified materials were enhanced. Total CO₂ desorption from the modified materials was achieved at 80 °C. The obtained silica materials displayed stable performance in five CO₂ adsorption/desorption cycles. The experimental data can be appropriately described by the Yoon–Nelson kinetic model. Full article

(This article belongs to the Special Issue Low-Dimensional Structures for Smart Materials and Composites: Preparation, Properties and Applications)

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13 pages, 5708 KiB

Open AccessArticle

A Quad-Band and Polarization-Insensitive Metamaterial Absorber with a Low Profile Based on Graphene-Assembled Film

by Shiyi Jin, Haoran Zu, Wei Qian, Kaolin Luo, Yang Xiao, Rongguo Song and Bo Xiong

Materials 2023, 16(11), 4178; https://doi.org/10.3390/ma16114178 - 04 Jun 2023

Cited by 4 | Viewed by 987

Abstract

A quad-band metamaterial absorber using a periodically arranged surface structure placed on an ultra-thin substrate is demonstrated in this paper. Its surface structure consists of a rectangular patch and four L-shaped structures distributed symmetrically. The surface structure is able to have strong electromagnetic [...] Read more.

A quad-band metamaterial absorber using a periodically arranged surface structure placed on an ultra-thin substrate is demonstrated in this paper. Its surface structure consists of a rectangular patch and four L-shaped structures distributed symmetrically. The surface structure is able to have strong electromagnetic interactions with incident microwaves, thereby generating four absorption peaks at different frequencies. With the aid of the near-field distributions and impedance matching analysis of the four absorption peaks, the physical mechanism of the quad-band absorption is revealed. The usage of graphene-assembled film (GAF) provides further optimization to increase the four absorption peaks and promotes the low-profile characteristic. In addition, the proposed design has good tolerance to the incident angle in vertical polarization. The proposed absorber in this paper has the potential for filtering, detection, imaging, and other communication applications. Full article

(This article belongs to the Special Issue Application of Graphene-Based Materials in Sensors and RF Electronics)

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22 pages, 7400 KiB

Open AccessArticle

Experimental Study on Shear Behavior of Non-Stirrup Ultra-High Performance Concrete Beams

by Pingjie Li, Quan Cheng, Nanxun Chen, Yueqiang Tian, Junfa Fang and Haibo Jiang

Materials 2023, 16(11), 4177; https://doi.org/10.3390/ma16114177 - 04 Jun 2023

Cited by 1 | Viewed by 1289

Abstract

Due to the high tensile strength of ultra-high performance concrete (UHPC), the shear stirrups in UHPC beams could potentially be removed. The aim of this study is to assess the shear performance of non-stirrup UHPC beams. Six UHPC beams were tested and compared [...] Read more.

Due to the high tensile strength of ultra-high performance concrete (UHPC), the shear stirrups in UHPC beams could potentially be removed. The aim of this study is to assess the shear performance of non-stirrup UHPC beams. Six UHPC beams were tested and compared with three stirrup-reinforced normal concrete (NC) beams, taking into consideration the testing parameters of steel fiber volume content and shear span-to-depth ratio. The findings demonstrated that incorporating steel fibers can efficiently strengthen the ductility, cracking strength, and shear strength of non-stirrup UHPC beams and alter their failure mode. Additionally, the shear span-to-depth ratio had a significant impact on the shear strength of beams, as it was negatively related to it. This study revealed that the French Standard and PCI-2021 formulae were suitable for designing UHPC beams with 2% steel fibers and no stirrups. When applying Xu’s formulae for non-stirrup UHPC beams, taking into account a reduction factor was necessary. Full article

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11 pages, 6155 KiB

Open AccessArticle

Conventional and Digital Impressions for Fabrication of Complete Implant-Supported Bars: A Comparative In Vitro Study

by Samanta N. V. Vieira, Matheus F. Lourenço, Rodrigo C. Pereira, Esdras C. França, Ênio L. Vilaça, Rodrigo R. Silveira and Guilherme C. Silva

Materials 2023, 16(11), 4176; https://doi.org/10.3390/ma16114176 - 04 Jun 2023

Cited by 2 | Viewed by 988

Abstract

Obtaining accurate models and well-fitting prostheses during the fabrication of complete implant-supported prostheses has been a significant challenge. Conventional impression methods involve multiple clinical and laboratory steps that can lead to distortions, potentially resulting in inaccurate prostheses. In contrast, digital impressions may eliminate [...] Read more.

Obtaining accurate models and well-fitting prostheses during the fabrication of complete implant-supported prostheses has been a significant challenge. Conventional impression methods involve multiple clinical and laboratory steps that can lead to distortions, potentially resulting in inaccurate prostheses. In contrast, digital impressions may eliminate some of these steps, leading to better-fitting prostheses. Therefore, it is important to compare conventional and digital impressions for producing implant-supported prostheses. This study aimed to compare the quality of digital intraoral and conventional impressions by measuring the vertical misfit of implant-supported complete bars obtained using both types of techniques. Five digital impressions using an intraoral scanner and five impressions using elastomer were made in a four-implant master model. The plaster models produced with conventional impressions were scanned in a laboratory scanner to obtain virtual models. Screw-retained bars (n = five) were designed on the models and milled in zirconia. The bars fabricated using digital (DI) and conventional (CI) impressions were screwed to the master model, initially with one screw (DI1 and CI1) and later with four screws (DI4 and CI4), and were analyzed under a SEM to measure the misfit. ANOVA was used to compare the results (p < 0.05). There were no statistically significant differences in the misfit between the bars fabricated using digital and conventional impressions when screwed with one (DI1 = 94.45 µm vs. CI1 = 101.90 µm: F = 0.096; p = 0.761) or four screws (DI4 = 59.43 µm vs. CI4 = 75.62 µm: F = 2.655; p = 0.139). Further, there were no differences when the bars were compared within the same group screwed with one or four screws (DI1 = 94.45 µm vs. DI4 = 59.43 µm: F = 2.926; p = 0.123; CI1 = 101.90 µm vs. CI4 = 75.62 µm: F = 0.013; p = 0.907). It was concluded that both impression techniques produced bars with a satisfactory fit, regardless of whether they were screwed with one or four screws. Full article

(This article belongs to the Special Issue Material, Design and Biological Studies of Bones & Implants)

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21 pages, 5985 KiB

Open AccessReview

Recent Experimental Advances in Characterizing the Self-Assembly and Phase Behavior of Polypeptoids

by Liying Kang, Qi Wang, Lei Zhang, Hang Zou, Jun Gao, Kangmin Niu and Naisheng Jiang

Materials 2023, 16(11), 4175; https://doi.org/10.3390/ma16114175 - 03 Jun 2023

Cited by 1 | Viewed by 1525

Abstract

Polypeptoids are a family of synthetic peptidomimetic polymers featuring N-substituted polyglycine backbones with large chemical and structural diversity. Their synthetic accessibility, tunable property/functionality, and biological relevance make polypeptoids a promising platform for molecular biomimicry and various biotechnological applications. To gain insight into the [...] Read more.

Polypeptoids are a family of synthetic peptidomimetic polymers featuring N-substituted polyglycine backbones with large chemical and structural diversity. Their synthetic accessibility, tunable property/functionality, and biological relevance make polypeptoids a promising platform for molecular biomimicry and various biotechnological applications. To gain insight into the relationship between the chemical structure, self-assembly behavior, and physicochemical properties of polypeptoids, many efforts have been made using thermal analysis, microscopy, scattering, and spectroscopic techniques. In this review, we summarize recent experimental investigations that have focused on the hierarchical self-assembly and phase behavior of polypeptoids in bulk, thin film, and solution states, highlighting the use of advanced characterization tools such as in situ microscopy and scattering techniques. These methods enable researchers to unravel multiscale structural features and assembly processes of polypeptoids over a wide range of length and time scales, thereby providing new insights into the structure–property relationship of these protein-mimetic materials. Full article

(This article belongs to the Special Issue Synthetic Protein Mimics: Advances in Architectures and Applications)

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22 pages, 9006 KiB

Open AccessEditor’s ChoiceArticle

Modelling of Fatigue Microfracture in Porous Sintered Steel Using a Phase-Field Method

by Zoran Tomić, Tomislav Jarak, Tomislav Lesičar, Nenad Gubeljak and Zdenko Tonković

Materials 2023, 16(11), 4174; https://doi.org/10.3390/ma16114174 - 03 Jun 2023

Cited by 2 | Viewed by 1285

Abstract

Porosity in sintered materials negatively affects its fatigue properties. In investigating its influence, the application of numerical simulations reduces experimental testing, but they are computationally very expensive. In this work, the application of a relatively simple numerical phase-field (PF) model for fatigue fracture [...] Read more.

Porosity in sintered materials negatively affects its fatigue properties. In investigating its influence, the application of numerical simulations reduces experimental testing, but they are computationally very expensive. In this work, the application of a relatively simple numerical phase-field (PF) model for fatigue fracture is proposed for estimation of the fatigue life of sintered steels by analysis of microcrack evolution. A model for brittle fracture and a new cycle skipping algorithm are used to reduce computational costs. A multiphase sintered steel, consisting of bainite and ferrite, is examined. Detailed finite element models of the microstructure are generated from high-resolution metallography images. Microstructural elastic material parameters are obtained using instrumented indentation, while fracture model parameters are estimated from experimental S–N curves. Numerical results obtained for monotonous and fatigue fracture are compared with data from experimental measurements. The proposed methodology is able to capture some important fracture phenomena in the considered material, such as the initiation of the first damage in the microstructure, the forming of larger cracks at the macroscopic level, and the total life in a high cycle fatigue regime. However, due to the adopted simplifications, the model is not suitable for predicting accurate and realistic crack patterns of microcracks. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study (2nd Volume))

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18 pages, 6395 KiB

Open AccessArticle

Plate Load Tests of Soft Foundations Reinforced by Soilbags with Solid Wastes for Wind Farms

by Chenchen Zhang, Jie Liao, Yuchi Zhang and Liujiang Wang

Materials 2023, 16(11), 4173; https://doi.org/10.3390/ma16114173 - 03 Jun 2023

Cited by 1 | Viewed by 1130

Abstract

Soilbags are expandable three-dimensional geosynthetic bags made from high-density polyethylene or polypropylene. This study conducted a series of plate load tests to explore the bearing capacity of soft foundations reinforced by soilbags filled with solid wastes based on an onshore wind farm project [...] Read more.

Soilbags are expandable three-dimensional geosynthetic bags made from high-density polyethylene or polypropylene. This study conducted a series of plate load tests to explore the bearing capacity of soft foundations reinforced by soilbags filled with solid wastes based on an onshore wind farm project in China. The effect of contained material on the bearing capacity of the soilbag-reinforced foundation was investigated during the field tests. The experimental studies indicated that soilbag reinforcement with reused solid wastes could substantially improve the bearing capacity of soft foundations under vertical loading conditions. Solid wastes like excavated soil or brick slag residues were found to be suitable as contained material, and the soilbags with plain soil mixed with brick slag had higher bearing capacity than those with pure plain soil. The earth pressure analysis indicated that stress diffusion occurred through the soilbag layers to reduce the load transferred to the underlying soft soil. The stress diffusion angle of soilbag reinforcement obtained from the tests was approximately 38°. In addition, combining soilbag reinforcement with bottom sludge permeable treatment was an effective foundation reinforcement method, which required fewer soilbag layers due to its relatively high permeability. Furthermore, soilbags are considered sustainable construction materials with advantages such as high construction efficiency, low cost, easy reclamation and environmental friendliness while making full use of local solid wastes. Full article

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

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15 pages, 6503 KiB

Open AccessEditor’s ChoiceArticle

Structural Evolution of Polyaluminocarbosilane during the Polymer–Ceramic Conversion Process

by Fucheng Xie, Yangpeng Duan, Gaoming Mo, Qing Huang and Zhengren Huang

Materials 2023, 16(11), 4172; https://doi.org/10.3390/ma16114172 - 03 Jun 2023

Cited by 1 | Viewed by 1059

Abstract

Polyaluminocarbosilane (PACS) is an important precursor for silicon carbide (SiC) fibers and ceramics. The structure of PACS and the oxidative curing, thermal pyrolysis, and sintering effect of Al have already been substantially studied. However, the structural evolution of polyaluminocarbosilane itself during the polymer–ceramic [...] Read more.

Polyaluminocarbosilane (PACS) is an important precursor for silicon carbide (SiC) fibers and ceramics. The structure of PACS and the oxidative curing, thermal pyrolysis, and sintering effect of Al have already been substantially studied. However, the structural evolution of polyaluminocarbosilane itself during the polymer–ceramic conversion process, especially the changes in the structure forms of Al, are still pending questions. In this study, PACS with a higher Al content is synthesized and the above questions are elaborately investigated by FTIR, NMR, Raman, XPS, XRD, and TEM analyses. It is found that up to 800–900 °C the amorphous SiO_xC_y, AlO_xSi_y, and free carbon phases are initially formed. With increasing temperature, the SiO_xC_y phase partially separates into SiO₂ then reacts with free carbon. The AlO_xSi_y phase changes into Al₃C₄ and Al₂O₃ by reaction with free carbon at around 1100 °C. The complicated reactions between Al₃C₄, Al₂O₃, and free carbon occur, leading to the formation of the Al₄O₄C and Al₂OC phases at around 1600 °C, which then react with the SiC and free carbon, resulting in the formation of the Al₄SiC₄ phase at 1800 °C. The amorphous carbon phase grows with the increasing temperature, which then turns into a crystalline graphitic structure at around 1600 °C. The growth of β-SiC is inhibited by the existence of the Al₄O₄C, Al₂OC, and Al₄SiC₄ phases, which also favor the formation of α-SiC at 1600–1800 °C. Full article

(This article belongs to the Section Advanced and Functional Ceramics and Glasses)

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4 pages, 198 KiB

Open AccessEditorial

Special Issue “Fracture Mechanics and Fatigue Damage of Materials and Structures”

by Grzegorz Lesiuk and Dariusz Rozumek

Materials 2023, 16(11), 4171; https://doi.org/10.3390/ma16114171 - 03 Jun 2023

Viewed by 932

Abstract

One of the most important aspects of engineering assessment of the technical condition of structures and materials is the ability to assess the fatigue behavior of materials and structures [...] Full article

(This article belongs to the Special Issue Fracture Mechanics and Fatigue Damage of Materials and Structures)

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