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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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27 pages, 14051 KiB  
Article
Modified Micro-Mechanics Based Multiscale Model for Damage Analysis of Open-Hole Composite Laminates under Compression
by Meng Wang and Xiaochen Hang
Materials 2022, 15(15), 5105; https://doi.org/10.3390/ma15155105 - 22 Jul 2022
Cited by 4 | Viewed by 2321
Abstract
The multiscale model based on micro-mechanics failure theory is modified to consider complex internal structures, including a fiber random arrangement pattern and interface with the clustering method. Then, a feed-forward-neural-network (FFNN)-based damage evolution method is developed to evaluate the macroscale property degradation. The [...] Read more.
The multiscale model based on micro-mechanics failure theory is modified to consider complex internal structures, including a fiber random arrangement pattern and interface with the clustering method. Then, a feed-forward-neural-network (FFNN)-based damage evolution method is developed to evaluate the macroscale property degradation. The progressive damage analysis of open-hole laminates under compression is conducted to validate the modified multiscale method. The predicted results reveal that the interface results in the premature initiation of damage, and the fiber random arrangement pattern contributes to the decrease in the predicted compression responses. The developed FFNN-based method aimed at degradation results in an increase in the predicted compression strength. For the fiber random distribution pattern, the increase in percentage of predicted compressive strength is 6.0%, which is much larger than the value for the fiber diamond distribution pattern. Full article
(This article belongs to the Special Issue Analytical and Computational Methods in Material and Mechanical Engineering)
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15 pages, 1194 KiB  
Article
Clinical and Microbiological Evaluation of a Chlorhexidine-Modified Glass Ionomer Cement (GIC-CHX) Restoration Placed Using the Atraumatic Restorative Treatment (ART) Technique
by Jithendra Ratnayake, Arthi Veerasamy, Hassan Ahmed, David Coburn, Carolina Loch, Andrew R. Gray, Karl M. Lyons, Nicholas C. K. Heng, Richard D. Cannon, Marcus Leung and Paul A. Brunton
Materials 2022, 15(14), 5044; https://doi.org/10.3390/ma15145044 - 20 Jul 2022
Cited by 7 | Viewed by 2680
Abstract
The aims of this study were to investigate the clinical effectiveness and patient acceptability of a modified glass ionomer cement placed using the atraumatic restorative treatment (ART) technique to treat root caries, and to carry out microbiological analysis of the restored sites. Two [...] Read more.
The aims of this study were to investigate the clinical effectiveness and patient acceptability of a modified glass ionomer cement placed using the atraumatic restorative treatment (ART) technique to treat root caries, and to carry out microbiological analysis of the restored sites. Two clinically visible root surface carious lesions per participant were restored using ART. One was restored with commercial glass ionomer cement (GIC) (ChemFil® Superior, DENTSPLY, Konstonz, Germany) which acted as the control. The other carious root lesion was restored with the same GIC modified with 5% chlorhexidine digluconate (GIC-CHX; test). Patient acceptability and restoration survival rate were evaluated at baseline and after 6 months. Plaque and saliva samples around the test and control restorations were collected, and microbiological analysis for selected bacterial and fungal viability were completed at baseline, and after 1, 3, and 6 months. In total, 52 restorations were placed using GIC and GIC-CHX in 26 participants; 1 patient was lost to follow-up. After reviewing the restorations during their baseline appointments, participants indicated that they were satisfied with the appearance of the restorations (n = 25, 96%) and did not feel anxious during the procedure (n = 24, 92%). Forty-eight percent (n = 12) of the GIC-CHX restorations were continuous with the existing anatomic form as opposed to six for the GIC restorations (24%), a difference which was statistically significant (p = 0.036). There was no statistically significant reduction in the mean count of the tested microorganisms in plaque samples for either type of restorations after 1, 3, or 6 months. Restoration of carious root surfaces with GIC-CHX resulted in higher survival rates than the control GIC. ART using GIC-CHX may therefore be a viable approach for use in outreach dental services to restore root surface carious lesions where dental services are not readily available, and for older people and special needs groups. Full article
(This article belongs to the Special Issue Bioinspired Materials for Dentistry)
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8 pages, 1581 KiB  
Article
Stretchable and Conductive Cellulose/Conductive Polymer Composite Films for On-Skin Strain Sensors
by Joo Won Han, Jihyun Park, Jung Ha Kim, Siti Aisyah Nurmaulia Entifar, Ajeng Prameswati, Anky Fitrian Wibowo, Soyeon Kim, Dong Chan Lim, Jonghee Lee, Myoung-Woon Moon, Min-Seok Kim and Yong Hyun Kim
Materials 2022, 15(14), 5009; https://doi.org/10.3390/ma15145009 - 19 Jul 2022
Cited by 11 | Viewed by 2793
Abstract
Conductive composite materials have attracted considerable interest of researchers for application in stretchable sensors for wearable health monitoring. In this study, highly stretchable and conductive composite films based on carboxymethyl cellulose (CMC)-poly (3,4-ethylenedioxythiopehe):poly (styrenesulfonate) (PEDOT:PSS) (CMC-PEDOT:PSS) were fabricated. The composite films achieved excellent [...] Read more.
Conductive composite materials have attracted considerable interest of researchers for application in stretchable sensors for wearable health monitoring. In this study, highly stretchable and conductive composite films based on carboxymethyl cellulose (CMC)-poly (3,4-ethylenedioxythiopehe):poly (styrenesulfonate) (PEDOT:PSS) (CMC-PEDOT:PSS) were fabricated. The composite films achieved excellent electrical and mechanical properties by optimizing the lab-synthesized PEDOT:PSS, dimethyl sulfoxide, and glycerol content in the CMC matrix. The optimized composite film exhibited a small increase of only 1.25-fold in relative resistance under 100% strain. The CMC-PEDOT:PSS composite film exhibited outstanding mechanical properties under cyclic tape attachment/detachment, bending, and stretching/releasing tests. The small changes in the relative resistance of the films under mechanical deformation indicated excellent electrical contacts between the conductive PEDOT:PSS in the CMC matrix, and strong bonding strength between CMC and PEDOT:PSS. We fabricated highly stretchable and conformable on-skin sensors based on conductive and stretchable CMC-PEDOT:PSS composite films, which can sensitively monitor subtle bio-signals and human motions such as respiratory humidity, drinking water, speaking, skin touching, skin wrinkling, and finger bending. Because of the outstanding electrical properties of the films, the on-skin sensors can operate with a low power consumption of only a few microwatts. Our approach paves the way for the realization of low-power-consumption stretchable electronics using highly stretchable CMC-PEDOT:PSS composite films. Full article
(This article belongs to the Special Issue Advanced Materials and Systems for Biomedical Application)
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10 pages, 1784 KiB  
Article
Application of Genetically Encoded Photoconvertible Protein SAASoti for the Study of Enzyme Activity in a Single Live Cell by Fluorescence Correlation Microscopy
by Ilya D. Solovyev, Liliya G. Maloshenok and Alexander P. Savitsky
Materials 2022, 15(14), 4962; https://doi.org/10.3390/ma15144962 - 16 Jul 2022
Cited by 6 | Viewed by 1937
Abstract
Fluorescent Correlation Spectroscopy (FCS) allows us to determine interactions of labeled proteins or changes in the oligomeric state. The FCS method needs a low amount of fluorescent dye, near nanomolar concentrations. To control the amount of fluorescent dye, we used new photoconvertible FP [...] Read more.
Fluorescent Correlation Spectroscopy (FCS) allows us to determine interactions of labeled proteins or changes in the oligomeric state. The FCS method needs a low amount of fluorescent dye, near nanomolar concentrations. To control the amount of fluorescent dye, we used new photoconvertible FP SAASoti. This work is devoted to the proof of principle of using photoconvertible proteins to measure caspase enzymatic activity in a single live cell. The advantage of this approach is that partial photoconversion of the FP makes FCS measurements possible when studying enzymatic reactions. To investigate the process, in vivo we used HeLa cell line expressing the engineered FRET sensor, SAASoti-23-KFP. This FRET sensor has a cleavable (DEVD) sequence in the linker between two FPs for the detection of one of the key enzymes of apoptosis, caspase-3. Caspase-3 activity was detected by registering the increase in the fluorescent lifetimes of the sensor, whereas the diffusion coefficient of SAASoti decreased. This can be explained by an increase in the total cell viscosity during apoptosis. We can suppose that in the moment of detectible caspase-3 activity, cell structure already has crucial changes in viscosity. Full article
(This article belongs to the Special Issue Feature Paper in Optical and Photonic Materials)
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24 pages, 14705 KiB  
Article
Vibration-Based Fatigue Analysis of Octet-Truss Lattice Infill Blades for Utilization in Turbine Rotors
by Sajjad Hussain, Wan Aizon W. Ghopa, S. S. K. Singh, Abdul Hadi Azman, Shahrum Abdullah, Zambri Harun and Hawa Hishamuddin
Materials 2022, 15(14), 4888; https://doi.org/10.3390/ma15144888 - 14 Jul 2022
Cited by 7 | Viewed by 2568
Abstract
Vibration fatigue characteristics are critical for rotating machinery components such as turbine rotor blades. Lattice structures are gaining popularity in engineering applications due to their unique ability to reduce weight and improve the mechanical properties. This study is an experimental investigation of octet-truss [...] Read more.
Vibration fatigue characteristics are critical for rotating machinery components such as turbine rotor blades. Lattice structures are gaining popularity in engineering applications due to their unique ability to reduce weight and improve the mechanical properties. This study is an experimental investigation of octet-truss lattice structure utilization in turbine rotor blades for weight reduction and to improve vibration fatigue characteristics. One completely solid and three lattice infilled blades with variable strut thickness were manufactured via additive manufacturing. Both free and forced experimental vibration analyses were performed on the blades to investigate their modal and vibration fatigue characteristics. The blades were subjected to random vibration using a vibration shaker. The response was measured using a triaxial accelerometer in terms of vibration acceleration time histories in the X, Y, and Z directions. Results indicate a weight reduction of up to 24.91% and enhancement in the first natural frequency of up to 5.29% were achieved using lattice infilled blades. The fatigue life of the blades was investigated using three frequency domain approaches, namely, Lalanne, Dirlik and narrow band. The fatigue life results indicate that the 0.25 mm lattice blade exhibits the highest fatigue life, while the solid blade exhibits the lowest fatigue life of all four blades. The fatigue life of the 0.25 mm lattice blade was 1822-, 1802-, and 1819- fold higher compared to that of the solid blade, using the Lalanne, Dirlik, and narrow-band approaches, respectively. These results can serve as the first step towards the utilization of lattice structures in turbine blades, with thermal analysis as the next step. Therefore, apart from being light weight, the octet-truss lattice infilled blades exhibited superior vibration fatigue characteristics to vibration loads, thereby making them a potential replacement for solid blades in turbine rotors. Full article
(This article belongs to the Section Mechanics of Materials)
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14 pages, 2924 KiB  
Article
Synthesis and Processing Parameter Optimization of Nano-Belite via One-Step Combustion Method
by Hongfang Sun, Weixing Lian, Xiaogang Zhang, Wei Liu, Feng Xing and Jie Ren
Materials 2022, 15(14), 4913; https://doi.org/10.3390/ma15144913 - 14 Jul 2022
Cited by 6 | Viewed by 1925
Abstract
This paper proposes a new chemical combustion method for the synthesis of nano-low-carbon belite cement via a simple one-step process without using any oxidizers, and related mechanisms are briefly introduced. The starting materials used, including micro-silica (silica fume) as a byproduct of the [...] Read more.
This paper proposes a new chemical combustion method for the synthesis of nano-low-carbon belite cement via a simple one-step process without using any oxidizers, and related mechanisms are briefly introduced. The starting materials used, including micro-silica (silica fume) as a byproduct of the metallurgic industry and CaCO3 powders, are of great abundance, and the processing parameters involved were optimized using a series of systematic experiments based on X-ray diffraction (XRD) and the Rietveld fitting method. Besides, the properties of the synthesized belite cement were characterized by the Brunauer–Emmett–Teller (BET) technique and scanning electron microscopy (SEM). Experimental results revealed that the optimized fuel agent was urea with a dosage of 4.902 times that of the starting materials by mass, and the corresponding holding temperature and time were 1150 °C and 2 h, respectively. In addition, the CaO/(SiO2 + CaO) for the starting materials should be set at 62.5% by mass ratio. BET and SEM results showed that the obtained belite cement had a specific surface area of 11.17 m2/g and a size of around 500 nm or even smaller in spherical shapes, suggesting that this method was successfully implemented. Thus, it can be a promising approach for the synthesis of nano-belite particles as a low-carbon construction material, which could be used more in the near future, such as for low-carbon concrete productions. Full article
(This article belongs to the Section Construction and Building Materials)
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17 pages, 5833 KiB  
Article
Evaluation of Solidified Wastewater Treatment Sludge as a Potential SCM in Pervious Concrete Pavements
by Ognjen Govedarica, Marina Aškrabić, Milica Hadnađev-Kostić, Tatjana Vulić, Branislava Lekić, Vladana Rajaković-Ognjanović and Dimitrije Zakić
Materials 2022, 15(14), 4919; https://doi.org/10.3390/ma15144919 - 14 Jul 2022
Cited by 12 | Viewed by 2711
Abstract
Waste and recycled materials have recently been used in the construction industry to comply with the principles of circular economy and sustainable development. The aim of this paper is to examine the potentials of solidified wastewater treatment sludge (SWWTS) as a supplementary cementitious [...] Read more.
Waste and recycled materials have recently been used in the construction industry to comply with the principles of circular economy and sustainable development. The aim of this paper is to examine the potentials of solidified wastewater treatment sludge (SWWTS) as a supplementary cementitious material (SCM) in the production of lightweight pervious concrete pavers (LWPCP) suitable for pedestrian trails and rooftops (green) that comply with EU standards. Detailed characterization of SWWTS was performed, in order to understand its properties related to application as SCM, which led to the conclusion that it may be applied only as a filler, having 89.5% of Ca(OH)2. After thorough characterization, LWPCP samples were prepared and testing of physical and mechanical properties was conducted. The research showed that partial replacement of cement with SWWTS led to the decrease of all mechanical properties, ranging between 3.91 and 5.81 MPa for compressive strength and 0.97 to 1.23 MPa for flexural strength. However, all of the investigated mixtures showed a value higher than 3.5 MPa, which was defined as the lowest compressive strength in the range of pervious concrete properties. The addition of SWWTS led to a slight decrease in bulk density of the mixtures and an increase in water absorption. This could be explained by the reduction in hydration products that would fill in the micropores of the matrix, since SWWTS showed no pozzolanic reactivity. Pore sizes that prevail in the tested binder matrices are in accordance with the results measured on ordinary pervious concrete (the largest fraction of pores had a diameter between 0.02 and 0.2 μm). Low thermal conductivity nominates produced pavers as potential rooftop elements. Full article
(This article belongs to the Special Issue Industrial Symbiosis and Development of New Materials or Products in Building Sector)
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15 pages, 3530 KiB  
Article
Promotion Effect of Carboxymethyl Chitosan on Dental Caries via Intrafibrillar Mineralization of Collagen and Dentin Remineralization
by Qi Zhang, Jiaxin Guo, Zihua Huang and Sui Mai
Materials 2022, 15(14), 4835; https://doi.org/10.3390/ma15144835 - 12 Jul 2022
Cited by 15 | Viewed by 3262
Abstract
Objective: To observe ultrastructural changes during the process of carboxymethyl chitosan (CMC)-mediated intrafibrillar mineralization, we evaluated the biomimetic remineralization potential of CMC in type-I collagen fibrils and membranes, and further explored the bond strength as well as the bond interfacial integrity of the [...] Read more.
Objective: To observe ultrastructural changes during the process of carboxymethyl chitosan (CMC)-mediated intrafibrillar mineralization, we evaluated the biomimetic remineralization potential of CMC in type-I collagen fibrils and membranes, and further explored the bond strength as well as the bond interfacial integrity of the biomimetic remineralized artificial caries-affected dentin (ACAD). Methods: A mineralized solution containing 200 μg/mL CMC was used to induce type-I collagen biomimetic remineralization in ACAD, while traditional mineralization without CMC was used as a control. The process and pattern of mineralization were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) as well as structured illumination microscopy (SIM). The Vickers hardness test was used to quantify the dentin hardness, while the microtensile bond strength (µTBS) test was used to assess the bond strength and durability. The bond interfacial integrity was evaluated by a confocal laser scanning microscope (CLSM). Results: TEM, SEM, and SIM images showed that CMC had a positive effect on stabilizing amorphous calcium phosphate (ACP) and promoting intrafibrillar mineralization, while extrafibrillar mineralization was formed without CMC. Furthermore, hardness evaluation and µTBS proved that CMC significantly increased dentin hardness and bond strength. CLSM indicated that CMC could create a significantly better bond interfacial integrity with less of a micro-gap in ACAD. Significance: CMC possessed the ability to promote intrafibrillar mineralization and remineralization in demineralized caries dentin lesions, as well as improve bond performance, which implied its potential in carious dentin demineralization or dentin hypersensitivity and possibly even as a possible material for indirect pulp-capping, to deal with deep caries. Highlights: CMC possessed the ability to induce intrafibrillar mineralization effectively; the bond strength and bond durability of demineralized caries dentin were improved via CMC-induced remineralization; the CMC-induced remineralization complex is a potential material for indirect pulp-capping, to deal with deep caries. Full article
(This article belongs to the Special Issue New Materials and Their Applications: Perspectives in Restorative Dentistry and Endodontics)
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23 pages, 2784 KiB  
Review
Comparison between Piezoelectric and Piezoresistive Wearable Gait Monitoring Techniques
by Zhiyuan Zhang, Zhenyu Xu, Wenbin Chen and Shuo Gao
Materials 2022, 15(14), 4837; https://doi.org/10.3390/ma15144837 - 12 Jul 2022
Cited by 9 | Viewed by 3567
Abstract
Insole plantar stress detection (PSD) techniques play an important role in gait monitoring. Among the various insole PSD methods, piezoelectric- and piezoresistive-based architectures are broadly used in medical scenes. Each year, a growing number of new research outcomes are reported. Hence, a deep [...] Read more.
Insole plantar stress detection (PSD) techniques play an important role in gait monitoring. Among the various insole PSD methods, piezoelectric- and piezoresistive-based architectures are broadly used in medical scenes. Each year, a growing number of new research outcomes are reported. Hence, a deep understanding of these two kinds of insole PSD sensors and state-of-the-art work would strongly benefit the researchers in this highly interdisciplinary field. In this context, this review article is composed of the following aspects. First, the mechanisms of the two techniques and corresponding comparisons are explained and discussed. Second, advanced materials which could enhance the performance of current piezoelectric and piezoresistive insole prototypes are introduced. Third, suggestions for designing insole PSD prototypes/products for different diseases are offered. Last, the current challenge and potential future trends are provided. Full article
(This article belongs to the Special Issue Functional Materials Based Human-Machine Interactivities)
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13 pages, 3586 KiB  
Article
New Insight into the Gas Phase Reaction Dynamics in Pulsed Laser Deposition of Multi-Elemental Oxides
by Xiang Yao, Christof W. Schneider, Alexander Wokaun and Thomas Lippert
Materials 2022, 15(14), 4862; https://doi.org/10.3390/ma15144862 - 12 Jul 2022
Cited by 1 | Viewed by 1705
Abstract
The gas-phase reaction dynamics and kinetics in a laser induced plasma are very much dependent on the interactions of the evaporated target material and the background gas. For metal (M) and metal–oxygen (MO) species ablated in an Ar and O2 background, the [...] Read more.
The gas-phase reaction dynamics and kinetics in a laser induced plasma are very much dependent on the interactions of the evaporated target material and the background gas. For metal (M) and metal–oxygen (MO) species ablated in an Ar and O2 background, the expansion dynamics in O2 are similar to the expansion dynamics in Ar for M+ ions with an MO+ dissociation energy smaller than O2. This is different for metal ions with an MO+ dissociation energy larger than for O2. This study shows that the plume expansion in O2 differentiates itself from the expansion in Ar due to the formation of MO+ species. It also shows that at a high oxygen background pressure, the preferred kinetic energy range to form MO species as a result of chemical reactions in an expanding plasma, is up to 5 eV. Full article
(This article belongs to the Special Issue Preparation and Properties of Thin Films)
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16 pages, 8499 KiB  
Article
Corrosion Behavior of the AlCoCrFeNi2.1 Eutectic High-Entropy Alloy in Chloride-Containing Sulfuric Acid Solutions at Different Temperatures
by Longfei Song, Wenbin Hu, Xiaowen Zhang, Bokai Liao, Shan Wan, Lei Kang and Xingpeng Guo
Materials 2022, 15(14), 4822; https://doi.org/10.3390/ma15144822 - 11 Jul 2022
Cited by 19 | Viewed by 2438
Abstract
In this work, the influence of temperature on the corrosion behavior of AlCoCrFeNi2.1 eutectic high-entropy alloy in a chloride-containing sulfuric acid solution was investigated using electrochemical measurement, X-ray photoelectron spectroscopy, and scanning electron microscopy. Results show that the passive film of AlCoCrFeN [...] Read more.
In this work, the influence of temperature on the corrosion behavior of AlCoCrFeNi2.1 eutectic high-entropy alloy in a chloride-containing sulfuric acid solution was investigated using electrochemical measurement, X-ray photoelectron spectroscopy, and scanning electron microscopy. Results show that the passive film of AlCoCrFeNi2.1 is stable in chloride-containing sulfuric acid solutions at low temperatures, while an unstable film forms on the alloy at high temperatures. Furthermore, temperature changes the proportion of hydroxide and oxide in Fe and Cr, but it has no noticeable effect on Al and Ni, which is a significant factor on the passive behavior. L12 phase exhibits good corrosion resistance at different temperatures. Pitting occurred on B2 phase in the chloride-containing sulfuric acid solution at a low temperature of 5 °C, while pitting and dissolution take place on AlCoCrFeNi2.1 in the acid solution at room temperature and above. Full article
(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)
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14 pages, 29106 KiB  
Article
Graphene Reinforced Anticorrosion Transparent Conductive Composite Film Based on Ultra-Thin Ag Nanofilm
by Xiaowei Fan, Zenghua Zhao, Xiaoping Liang, Xuguo Huai, Chan Wang, Juncheng Liu and Chunyang Duan
Materials 2022, 15(14), 4802; https://doi.org/10.3390/ma15144802 - 9 Jul 2022
Cited by 3 | Viewed by 1985
Abstract
Transparent conductive films are widely used in electronic products and industrial fields. Ultra-thin Ag conductive nanofilm (ACF) was prepared on a soda lime silica glass (ordinary architectural glass) substrate with industrial magnetron sputtering equipment with AZO (Al2O3 doped ZnO) as [...] Read more.
Transparent conductive films are widely used in electronic products and industrial fields. Ultra-thin Ag conductive nanofilm (ACF) was prepared on a soda lime silica glass (ordinary architectural glass) substrate with industrial magnetron sputtering equipment with AZO (Al2O3 doped ZnO) as the crystal bed and wetting layer. In order to improve the corrosion resistance and conductivity of the ACF, graphene nanosheets were modified on the surface of the ACF by electrospraying for the first time. The results show that this graphene modification could be carried out continuously on a meter scale. With the modification of the graphene layer, the corrosion rate of graphene-decorated ACF (G/ACF) can be reduced by 74.56%, and after 72 h of salt spray test, the conductivity of ACF samples without modification of graphene can be reduced by 34.1%, while the conductivity of G/ACF samples with modification of graphene can be reduced by only 6.5%. This work proves the potential of graphene modified ACF to prepare robust large-area transparent conductive film. Full article
(This article belongs to the Special Issue Sputter Deposition/Physical Vapor Deposition (PVD) Materials and Processes)
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13 pages, 6225 KiB  
Article
Numerical Investigation of the Defects Effect in Additive Manufactured Ti-6Al-4V Struts on Deformation Behavior Based on Microtomographic Images
by Michał Doroszko
Materials 2022, 15(14), 4807; https://doi.org/10.3390/ma15144807 - 9 Jul 2022
Cited by 4 | Viewed by 1988
Abstract
This paper describes the influence of defects occurring in struts under tension, obtained using the additive method of laser powder bed fusion (LPBF), on the stress and strain distributions. The study used struts of different thicknesses separated from Ti-6Al-4V diamond lattice structures. For [...] Read more.
This paper describes the influence of defects occurring in struts under tension, obtained using the additive method of laser powder bed fusion (LPBF), on the stress and strain distributions. The study used struts of different thicknesses separated from Ti-6Al-4V diamond lattice structures. For numerical modeling of stress and strain fields, models that reflect the realistic shape of the tested struts with their imperfections were used. The shape of the diamond structure struts was obtained based on microtomographic measurements. Based on the results obtained, the influence of defects in the material structure on the stress and strain distribution was analyzed. It was observed that the main factor influencing the stress and strain distribution in the struts are micronotches on their external surface. These imperfections have a significantly greater impact on the stress and strain concentration than the micropores inside. Furthermore, the interactions of the imperfections are also important, which in turn affects the stress distributions and the formation of bands of high-stress values inside the material. The relationship between the presence of micropores, the stress–strain curves, and the mechanical properties of the material was also assessed. Full article
(This article belongs to the Special Issue Experimental Research and Numerical Simulations of Metal Additive Manufacturing)
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20 pages, 8725 KiB  
Article
Study on the Influence of Defects on Fracture Mechanical Behavior of Cu/SAC305/Cu Solder Joint
by Sinan Zhang, Zhen Wang, Jie Wang, Guihua Duan and Haixia Li
Materials 2022, 15(14), 4756; https://doi.org/10.3390/ma15144756 - 7 Jul 2022
Cited by 6 | Viewed by 2357
Abstract
The fracture behavior of the Cu/Sn-3.0Ag-0.5Sn (SAC305)/Cu solder joint was investigated by conducting tensile tests with in situ X-ray micro-computed tomography (μ-CT) observation, and finite element (FE) simulation. The tensile fracture process of solder joints with a real internal defect structure was simulated [...] Read more.
The fracture behavior of the Cu/Sn-3.0Ag-0.5Sn (SAC305)/Cu solder joint was investigated by conducting tensile tests with in situ X-ray micro-computed tomography (μ-CT) observation, and finite element (FE) simulation. The tensile fracture process of solder joints with a real internal defect structure was simulated and compared with the experimental results in terms of defect distribution and fracture path. Additionally, the stress distribution around the defects during the tensile process was calculated. The experimental results revealed that the pores near the intermetallic compound (IMC) layers and the flaky cracks inside the solder significantly affected the crack path. The aggregation degree of the spherical pores and the angle between the crack surface and the loading direction controlled the initiation position and propagation path of the cracks. The fracture morphology indicated that the fracture of the IMC layer was brittle, while the solder fracture exhibited ductile tearing. There were significant differences in the fracture morphology under tensile and shear loading. Full article
(This article belongs to the Special Issue Mechanical Properties and Deformation Mechanisms of Advanced Metals and Alloys)
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15 pages, 4796 KiB  
Article
The Effect of Bi2O3 and Fe2O3 Impurity Phases in BiFeO3 Perovskite Materials on Some Electrical Properties in the Low-Frequency Field
by Cristian Casut, Iosif Malaescu, Catalin Nicolae Marin and Marinela Miclau
Materials 2022, 15(14), 4764; https://doi.org/10.3390/ma15144764 - 7 Jul 2022
Cited by 5 | Viewed by 2691
Abstract
Pure bismuth ferrite (BFO) and BFO with impurity phases (Bi2O3 or Fe2O3) were synthesized by the hydrothermal method. Complex dielectric permittivity (ε) and electrical conductivity (σ) were determined by complex impedance measurements at different frequencies (200 [...] Read more.
Pure bismuth ferrite (BFO) and BFO with impurity phases (Bi2O3 or Fe2O3) were synthesized by the hydrothermal method. Complex dielectric permittivity (ε) and electrical conductivity (σ) were determined by complex impedance measurements at different frequencies (200 Hz–2 MHz) and temperatures (25–290) °C. The conductivity spectrum of samples, σ(f), complies with Jonscher’s universal law and the presence of impurity phases leads to a decrease in the static conductivity (σDC); this result is correlated with the increased thermal activation energy of the conduction in impure samples compared to the pure BFO sample. The conduction mechanism in BFO and the effect of impurity phases on σ and ε were analyzed considering the variable range hopping model (VRH). Based on the VRH model, the hopping length (Rh), hopping energy (Wh) and the density of states at the Fermi level (N(EF)) were determined for the first time, for these samples. In addition, from ε(T) dependence, a transition in the electronic structure of samples from a semiconductor-like to a conductor-like behavior was highlighted around 465–490 K for all samples. The results obtained are useful to explain the conduction mechanisms from samples of BFO type, offering the possibility to develop a great variety of electrical devices with novel functions. Full article
(This article belongs to the Special Issue Advances in Electromagnetic Properties of Magnetic Materials)
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24 pages, 4319 KiB  
Review
A Comparative Mini-Review on Transition Metal Oxides Applied for the Selective Catalytic Ammonia Oxidation (NH3-SCO)
by Magdalena Jabłońska and Alejandro Mollá Robles
Materials 2022, 15(14), 4770; https://doi.org/10.3390/ma15144770 - 7 Jul 2022
Cited by 17 | Viewed by 3932
Abstract
The selective catalytic oxidation of NH3 (NH3-SCO) into N2 and H2O is an efficient technology for NH3 abatement in diesel vehicles. However, the catalysts dedicated to NH3-SCO are still under development. One of the [...] Read more.
The selective catalytic oxidation of NH3 (NH3-SCO) into N2 and H2O is an efficient technology for NH3 abatement in diesel vehicles. However, the catalysts dedicated to NH3-SCO are still under development. One of the groups of such catalysts constituted transition metal-based catalysts, including hydrotalcite-derived mixed metal oxides. This class of materials is characterized by tailored composition, homogenously dispersed mixed metal oxides, exhibiting high specific surface area and thermal stability. Thus, firstly, we give a short introduction to the structure and composition of hydrotalcite-like materials and their applications in NH3-SCO. Secondly, an overview of other transition metal-based catalysts reported in the literature is given, following a comparison of both groups. The challenges in NH3-SCO applications are provided, while the reaction mechanisms are discussed for particular systems. Full article
(This article belongs to the Section Catalytic Materials)
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13 pages, 4525 KiB  
Article
Fabrication of Mn-Doped SrTiO3/Carbon Fiber with Oxygen Vacancy for Enhanced Photocatalytic Hydrogen Evolution
by Qi Hu, Jiantao Niu, Ke-Qin Zhang and Mu Yao
Materials 2022, 15(13), 4723; https://doi.org/10.3390/ma15134723 - 5 Jul 2022
Cited by 20 | Viewed by 2915
Abstract
With carbon fiber, it is difficult to load semiconductor photocatalysts and easy to shed off thanks to its smooth surface and few active groups, which has always been a problem in the synthesis of photocatalysts. In the study, SrTiO3 nanoparticles were loaded [...] Read more.
With carbon fiber, it is difficult to load semiconductor photocatalysts and easy to shed off thanks to its smooth surface and few active groups, which has always been a problem in the synthesis of photocatalysts. In the study, SrTiO3 nanoparticles were loaded onto the Tencel fibers using the solvothermal method, and then the Tencel fibers were carbonized at a high temperature under the condition of inert gas to form carbon fibers, thus SrTiO3@CF photocatalytic composite materials with solid core shell structure were prepared. Meanwhile, Mn ions were added into the SrTiO3 precursor reagent in the solvothermal experiment to prepare Mn-doped Mn-SrTiO3@CF photocatalytic composite material. XPS and EPR tests showed that the prepared Mn-SrTiO3@CF photocatalytic composite was rich in oxygen vacancies. The existence of these oxygen vacancies formed oxygen defect states (VOs) below the conduction band, which constituted the capture center of photogenerated electrons and significantly improved the photocatalytic activity. The photocatalytic hydrogen experimental results showed that the photocatalytic hydrogen production capacity of Mn-SrTiO3@CF composite material with 5% Mn-doped was six times that of the SrTiO3@CF material, and the doping of Mn ions not only promoted the red shift of the light absorption boundary and the extension to visible light, but also improved the separation and migration efficiency of photocarriers. In the paper, the preparation method solves the difficulty of loading photocatalysts on CF and provides a new design method for the recycling of catalysts, and we improve the hydrogen production performance of photocatalysts by Mn-doped modification and the introduction of oxygen vacancies, which provides a theoretical method for the practical application of hydrogen energy. Full article
(This article belongs to the Section Mechanics of Materials)
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14 pages, 2099 KiB  
Article
Concrete/Glass Construction and Demolition Waste (CDW) Synergies in Ternary Eco-Cement-Paste Mineralogy
by Raquel Vigil de la Villa Mencía, Moises Frías, Sagrario Martínez Ramírez, Lucía Fernandez Carrasco and Rosario García Giménez
Materials 2022, 15(13), 4661; https://doi.org/10.3390/ma15134661 - 2 Jul 2022
Cited by 15 | Viewed by 3153
Abstract
The study described sought further understanding of the synergies in a mix of CDW pozzolans, containing (calcareous and siliceous) concrete and glass waste, used to prepare ternary eco-cement paste bearing 7% of the binary blend at concrete/glass ratios of 2:1 and 1:2. The [...] Read more.
The study described sought further understanding of the synergies in a mix of CDW pozzolans, containing (calcareous and siliceous) concrete and glass waste, used to prepare ternary eco-cement paste bearing 7% of the binary blend at concrete/glass ratios of 2:1 and 1:2. The mineralogical phases in the 2-day, 28-day, and 90-day cement matrices were identified and monitored using XRF, XRD-Rietveld, SEM-EDX, FT-IR, and NMR. The findings showed that changes in the reaction kinetics in the ternary blended pastes relative to OPC pastes depended on the nature of the recycled concrete and the glass content. Adding the binary mix bearing calcareous concrete (at a ratio of 2:1) favoured ettringite, portlandite, and amorphous phase formation, whilst the blends with siliceous concrete favoured C-S-H gel formation. Monocarboaluminate was detected in the 90-day siliceous concrete and glass pastes in amounts similar to those found in the reference OPC paste. Full article
(This article belongs to the Section Construction and Building Materials)
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25 pages, 4132 KiB  
Review
Magnetic Metal Oxide-Based Photocatalysts with Integrated Silver for Water Treatment
by George V. Belessiotis, Pinelopi P. Falara, Islam Ibrahim and Athanassios G. Kontos
Materials 2022, 15(13), 4629; https://doi.org/10.3390/ma15134629 - 1 Jul 2022
Cited by 38 | Viewed by 4335
Abstract
In this review, the most recent advances in the field of magnetic composite photocatalysts with integrated plasmonic silver (Ag) is presented, with an overview of their synthesis techniques, properties and photocatalytic pollutant removal applications. Magnetic attributes combined with plasmonic properties in these composites [...] Read more.
In this review, the most recent advances in the field of magnetic composite photocatalysts with integrated plasmonic silver (Ag) is presented, with an overview of their synthesis techniques, properties and photocatalytic pollutant removal applications. Magnetic attributes combined with plasmonic properties in these composites result in enhancements for light absorption, charge-pair generation-separation-transfer and photocatalytic efficiency with the additional advantage of their facile magnetic separation from water solutions after treatment, neutralizing the issue of silver’s inherent toxicity. A detailed overview of the currently utilized synthesis methods and techniques for the preparation of magnetic silver-integrated composites is presented. Furthermore, an extended critical review of the most recent pollutant removal applications of these composites via green photocatalysis technology is presented. From this survey, the potential of magnetic composites integrated with plasmonic metals is highlighted for light-induced water treatment and purification. Highlights: (1) Perspective of magnetic properties combined with plasmon metal attributes; (2) Overview of recent methods for magnetic silver-integrated composite synthesis; (3) Critical view of recent applications for photocatalytic pollutant removal. Full article
(This article belongs to the Section Materials Physics)
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19 pages, 12565 KiB  
Article
Determination of CCT Diagram by Dilatometry Analysis of High-Strength Low-Alloy S960MC Steel
by Jaromír Moravec, Miloš Mičian, Miloslav Málek and Martin Švec
Materials 2022, 15(13), 4637; https://doi.org/10.3390/ma15134637 - 1 Jul 2022
Cited by 12 | Viewed by 5187
Abstract
High-strength steels are used more than general structural steel due to their combination of properties such as high strength, good toughness and weldability. They are mainly used in the manufacture of heavy vehicles for the mining industry, cranes, transportation, etc. However, welding these [...] Read more.
High-strength steels are used more than general structural steel due to their combination of properties such as high strength, good toughness and weldability. They are mainly used in the manufacture of heavy vehicles for the mining industry, cranes, transportation, etc. However, welding these grades of steel brings new challenges. Also, a simulation for welding high-strength steel is required more often. To insert a material database into the simulation program, it is necessary to conduct investigations using CCT (Continuous Cooling Transformation) diagrams, welded joints research, and more. To investigate the behavior of S960MC steel during heating and cooling, we used dilatometry analysis supported by EBSD (Electron Backscatter Diffraction) analysis. A CCT diagram was constructed. The transformation temperatures of Ac1 and Ac3 increase with increasing heating rate. The Ac1 temperature increased by 54 °C and the Ac3 temperatures by 24 °C as the heating rate increased from 0.1 °C/s to 250 °C/s. The austenite decomposition temperatures have a decreasing trend in the cooling phase with increasing cooling rate. As the cooling rate changes from 0.03 °C/s to 100 °C/s, the initial transformation temperature drops from 813 °C to 465 °C. An increase in the cooling rate means a higher proportion of bainite and martensite. At the same time, the hardness increases from 119 HV10 to 362 HV10. Full article
(This article belongs to the Special Issue Technologies for Joining and Forming Thin-Walled Structures in the Construction of Transportation Vehicles)
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10 pages, 2026 KiB  
Article
Pressure-Induced Superconductivity of the Quasi-One-Dimensional Organic Conductor (TMTTF)2TaF6
by Miho Itoi, Toshikazu Nakamura and Yoshiya Uwatoko
Materials 2022, 15(13), 4638; https://doi.org/10.3390/ma15134638 - 1 Jul 2022
Cited by 3 | Viewed by 2339
Abstract
We investigated the superconductivity of (TMTTF)2TaF6 (TMTTF: tetramethyl-tetrathiafulvalene) by conducting resistivity measurements under high pressure up to 8 GPa. A cubic anvil cell (CAC) pressure generator, which can produce hydrostatic high-pressure, was used for this study. Since the generalized temperature-pressure [...] Read more.
We investigated the superconductivity of (TMTTF)2TaF6 (TMTTF: tetramethyl-tetrathiafulvalene) by conducting resistivity measurements under high pressure up to 8 GPa. A cubic anvil cell (CAC) pressure generator, which can produce hydrostatic high-pressure, was used for this study. Since the generalized temperature-pressure (T-P) diagram of (TMTCF)2X (C = Se, S, X: monovalent anion) based on (TMTTF)2PF6 (TCO = 70 K and spin-Peierls: SP, TSP = 15 K) was proposed by Jérome, exploring superconductivity states using high-pressure measurement beyond 4 GPa has been required to confirm the universality of the electron-correlation variation under pressure in (TMTTF)2X (TMTTF)2TaF6, which has the largest octahedral-symmetry counter anion TaF6 in the (TMTTF)2X series, possesses the highest charge-ordering (CO) transition temperature (TCO = 175 K) in (TMTTF)2X and demonstrates an anti-ferromagnetic transition (TAF = 9 K) at ambient pressure. A superconducting state in (TMTTF)2TaF6 emerged after a metal-insulator transition was suppressed with increasing external pressure. We discovered a superconducting state in 5 ≤ P ≤ 6 GPa from Tc = 2.1 K to 2.8 K, whose pressure range is one-third narrower than that of X = SbF6 (5.4 ≤ P ≤ 9 GPa). In addition, when the pressures with maximum SC temperatures are compared between the PF6 and the TaF6 salts, we found that (TMTTF)2TaF6 has a 0.75 GPa on the negative pressure side in the T-P phase diagram of (TMTTF)2PF6. Full article
(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)
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18 pages, 4408 KiB  
Article
Electrospun Nisin-Loaded Poly(ε-caprolactone)-Based Active Food Packaging
by Alena Opálková Šišková, Katarína Mosnáčková, Marta Musioł, Andrej Opálek, Mária Bučková, Piotr Rychter and Anita Eckstein Andicsová
Materials 2022, 15(13), 4540; https://doi.org/10.3390/ma15134540 - 28 Jun 2022
Cited by 8 | Viewed by 3208
Abstract
Packaging for fresh fruits and vegetables with additional properties such as inhibition of pathogens grown can reduce food waste. With its biodegradability, poly(ε-caprolactone) (PCL) is a good candidate for packaging material, especially in the form of an electrospun membrane. The preparation of nonwoven [...] Read more.
Packaging for fresh fruits and vegetables with additional properties such as inhibition of pathogens grown can reduce food waste. With its biodegradability, poly(ε-caprolactone) (PCL) is a good candidate for packaging material, especially in the form of an electrospun membrane. The preparation of nonwoven fabric of PCL loaded with food additive, antimicrobial nisin makes them an active packaging with antispoilage properties. During the investigation of the nonwoven fabric mats, different concentrations of nisin were obtained from the solution of PCL via the electrospinning technique. The obtained active porous PCL loaded with varying concentrations of nisin inhibited the growth of Staphylococcus aureus and Escherichia coli. Packages made of PCL and PCL/nisin fibrous mats demonstrated a prolongation of the fruits’ freshness, improving their shelf life and, consequently, their safety. Full article
(This article belongs to the Special Issue Frontiers in Advanced Smart Textiles)
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13 pages, 1971 KiB  
Article
TiO2/Karaya Composite for Photoinactivation of Bacteria
by Anderson C. B. Lopes, Francisca P. Araújo, Alan I. S. Morais, Idglan S. de Lima, Luzia M. Castro Honório, Luciano C. Almeida, Ramón Peña Garcia, Edson C. Silva-Filho, Marcelo B. Furtini and Josy A. Osajima
Materials 2022, 15(13), 4559; https://doi.org/10.3390/ma15134559 - 28 Jun 2022
Cited by 12 | Viewed by 2305
Abstract
TiO2/Karaya composite was synthesized by the sol-gel method for the photoinactivation of pathogens. This is the first time that we have reported this composite for an antimicrobial approach. The structure, morphology, and optical properties were characterized by X-ray diffraction (XRD), scanning [...] Read more.
TiO2/Karaya composite was synthesized by the sol-gel method for the photoinactivation of pathogens. This is the first time that we have reported this composite for an antimicrobial approach. The structure, morphology, and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-rays (EDS), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance, and the surface area was characterized by the BET method. The XRD and EDS results showed that the TiO2/Karaya composite was successfully stabilized by the crystal structure and pore diameter distribution, indicating a composite of mesoporous nature. Furthermore, antibacterial experiments showed that the TiO2/Karaya composite under light was able to photoinactivate bacteria. Therefore, the composite is a promising candidate for inhibiting the growth of bacteria. Full article
(This article belongs to the Special Issue Photocatalytic Properties and Kinetics of Materials)
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20 pages, 2386 KiB  
Perspective
From Quantum Materials to Microsystems
by Riccardo Bertacco, Giancarlo Panaccione and Silvia Picozzi
Materials 2022, 15(13), 4478; https://doi.org/10.3390/ma15134478 - 25 Jun 2022
Cited by 3 | Viewed by 2616
Abstract
The expression “quantum materials” identifies materials whose properties “cannot be described in terms of semiclassical particles and low-level quantum mechanics”, i.e., where lattice, charge, spin and orbital degrees of freedom are strongly intertwined. Despite their intriguing and exotic properties, overall, they appear far [...] Read more.
The expression “quantum materials” identifies materials whose properties “cannot be described in terms of semiclassical particles and low-level quantum mechanics”, i.e., where lattice, charge, spin and orbital degrees of freedom are strongly intertwined. Despite their intriguing and exotic properties, overall, they appear far away from the world of microsystems, i.e., micro-nano integrated devices, including electronic, optical, mechanical and biological components. With reference to ferroics, i.e., functional materials with ferromagnetic and/or ferroelectric order, possibly coupled to other degrees of freedom (such as lattice deformations and atomic distortions), here we address a fundamental question: “how can we bridge the gap between fundamental academic research focused on quantum materials and microsystems?”. Starting from the successful story of semiconductors, the aim of this paper is to design a roadmap towards the development of a novel technology platform for unconventional computing based on ferroic quantum materials. By describing the paradigmatic case of GeTe, the father compound of a new class of materials (ferroelectric Rashba semiconductors), we outline how an efficient integration among academic sectors and with industry, through a research pipeline going from microscopic modeling to device applications, can bring curiosity-driven discoveries to the level of CMOS compatible technology. Full article
(This article belongs to the Section Quantum Materials)
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19 pages, 4588 KiB  
Article
Using Machine Learning Algorithms to Estimate the Compressive Property of High Strength Fiber Reinforced Concrete
by Li Dai, Xu Wu, Meirong Zhou, Waqas Ahmad, Mujahid Ali, Mohanad Muayad Sabri Sabri, Abdelatif Salmi and Dina Yehia Zakaria Ewais
Materials 2022, 15(13), 4450; https://doi.org/10.3390/ma15134450 - 24 Jun 2022
Cited by 20 | Viewed by 2759
Abstract
The low tensile strain capacity and brittle nature of high-strength concrete (HSC) can be improved by incorporating steel fibers into it. Steel fibers’ addition in HSC results in bridging behavior which improves its post-cracking behavior, provides cracks arresting and stresses transfer in concrete. [...] Read more.
The low tensile strain capacity and brittle nature of high-strength concrete (HSC) can be improved by incorporating steel fibers into it. Steel fibers’ addition in HSC results in bridging behavior which improves its post-cracking behavior, provides cracks arresting and stresses transfer in concrete. Using machine learning (ML) techniques, concrete properties prediction is an effective solution to conserve construction time and cost. Therefore, sophisticated ML approaches are applied in this study to predict the compressive strength of steel fiber reinforced HSC (SFRHSC). To fulfil this purpose, a standalone ML model called Multiple-Layer Perceptron Neural Network (MLPNN) and ensembled ML algorithms named Bagging and Adaptive Boosting (AdaBoost) were employed in this study. The considered parameters were cement content, fly ash content, slag content, silica fume content, nano-silica content, limestone powder content, sand content, coarse aggregate content, maximum aggregate size, water content, super-plasticizer content, steel fiber content, steel fiber diameter, steel fiber length, and curing time. The application of statistical checks, i.e., root mean square error (RMSE), determination coefficient (R2), and mean absolute error (MAE), was also performed for the assessment of algorithms’ performance. The study demonstrated the suitability of the Bagging technique in the prediction of SFRHSC compressive strength. Compared to other models, the Bagging approach was more accurate as it produced higher, i.e., 0.94, R2, and lower error values. It was revealed from the SHAP analysis that curing time and super-plasticizer content have the most significant influence on the compressive strength of SFRHSC. The outcomes of this study will be beneficial for researchers in civil engineering for the timely and effective evaluation of SFRHSC compressive strength. Full article
(This article belongs to the Special Issue Importance of Machine Intelligence for Construction Material and Structural Engineering Applications)
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14 pages, 45836 KiB  
Article
Effect of Zn and Cu Addition on Mechanical Properties of As-Extruded Mg-3Sn-1Ca Alloy
by Zheng Jia, Bing Yu and Li Fu
Materials 2022, 15(13), 4438; https://doi.org/10.3390/ma15134438 - 23 Jun 2022
Cited by 2 | Viewed by 1750
Abstract
The effects of Zn and Cu addition on the microstructure and mechanical properties of the extruded Mg-3Sn-1Ca alloy were systematically studied. The effects of the grain size, texture, type and distribution of the second phase on the mechanical properties of the alloy were [...] Read more.
The effects of Zn and Cu addition on the microstructure and mechanical properties of the extruded Mg-3Sn-1Ca alloy were systematically studied. The effects of the grain size, texture, type and distribution of the second phase on the mechanical properties of the alloy were analyzed. The mechanical test results show that the addition of Zn and Cu elements can significantly improve the mechanical properties of the alloy. The as-extruded Mg-3Sn-1Ca-1Zn-1Cu alloy has the best comprehensive mechanical properties, and the UTS, YS and EL are 244 MPa, 159 MPa and 13.4%, respectively. Compared with the Mg-3Sn-1Ca alloy, the UTS and EL of the Mg-3Sn-1Ca-1Zn alloy are increased by 50 MPa and 132%, respectively. However, the UTS of the TXC311 alloy is increased by 55 MPa, but the ductility of the Mg-3Sn-1Ca-1Cu alloy is far less than that of the Mg-3Sn-1Ca-1Zn alloy, which is mainly attributed to the presence of a large amount of hard and brittle Mg2Cu phase in the alloy. Interestingly, the addition of Zn to Mg-3Sn-1Ca-1Cu alloy can improve the elongation of the alloy, which is due to the solid solution strengthening caused by the Zn element and the formation of small MgZnCu phase with Zn element and the consumption of Mg2Cu phase. Full article
(This article belongs to the Section Mechanics of Materials)
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24 pages, 8434 KiB  
Article
Design and Control of Magnetic Shape Memory Alloy Actuators
by Bartosz Minorowicz and Andrzej Milecki
Materials 2022, 15(13), 4400; https://doi.org/10.3390/ma15134400 - 22 Jun 2022
Cited by 10 | Viewed by 4207
Abstract
This paper presents research on the application of magnetic shape memory alloys (MSMAs) in actuator design. MSMAs are a relatively new group of so-called smart materials that are distinguished by repeatable strains up to 6% and dynamics much better than that of thermally [...] Read more.
This paper presents research on the application of magnetic shape memory alloys (MSMAs) in actuator design. MSMAs are a relatively new group of so-called smart materials that are distinguished by repeatable strains up to 6% and dynamics much better than that of thermally activated shape memory alloys (SMAs). The shape change mechanism in MSMAs is based on the rearrangement of martensite cells in the presence of an external magnetic field. In the first part of the article a review of the current state of MSMA actuator design is presented, followed by a description of the design, modelling and control of a newly proposed actuator. The developed actuator works with MSMA samples of 3 × 10 × 32 mm3, guaranteeing an available operating range of up to 1 mm, despite its great deformation range and dynamics. In the paper its dynamics model is proposed and its transfer function is derived. Moreover, the generalised Prandtl-Ishlinskii model of MSMA-actuator hysteresis is proposed. This model is then inverted and used in the control system for hysteresis compensation. A special test stand was designed and built to test the MSMA actuator with compensation. The step responses are recorded, showing that the compensated MSMA actuator exhibits the positioning accuracy as ±2 µm. As a result, the authors decided to apply a control system based on an inverse hysteresis model. The paper concludes with a summary of the research results, with theoretical analysis compared with the registered actuator characteristics. Full article
(This article belongs to the Section Smart Materials)
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15 pages, 12925 KiB  
Article
Topology Optimization of Piezoelectric Energy Harvesters for Enhanced Open-Circuit Voltage Subjected to Harmonic Excitations
by Meng He, Mu He, Xiaopeng Zhang and Liang Xia
Materials 2022, 15(13), 4423; https://doi.org/10.3390/ma15134423 - 22 Jun 2022
Cited by 4 | Viewed by 2827
Abstract
Energy harvesting devices made of piezoelectric material are highly anticipated energy sources for power wireless sensors. Tremendous efforts have been made to improve the performance of piezoelectric energy harvesters (PEHs). Noticeably, topology optimization has shown an attractive potential to design PEHs with enhanced [...] Read more.
Energy harvesting devices made of piezoelectric material are highly anticipated energy sources for power wireless sensors. Tremendous efforts have been made to improve the performance of piezoelectric energy harvesters (PEHs). Noticeably, topology optimization has shown an attractive potential to design PEHs with enhanced energy conversion efficiency. In this work, an alternative yet more practical design objective was considered, where the open-circuit voltage of PEHs is enhanced by topologically optimizing the through-thickness piezoelectric material distribution of plate-type PEHs subjected to harmonic excitations. Compared to the conventional efficiency-enhanced designs, the open-circuit voltage of PEHs can be evidently enhanced by the proposed method while with negligible sacrifice on the energy conversion efficiency. Numerical investigations show that the voltage cancellation effect due to inconsistent voltage phases can be effectively ameliorated by optimally distributed piezoelectric materials. Full article
(This article belongs to the Special Issue Mechanical Metamaterials: Optimization and New Design Ideas)
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18 pages, 8774 KiB  
Article
Corrosion–Resistance Mechanism of TC4 Titanium Alloy under Different Stress-Loading Conditions
by Xin-Yu Wang, Shi-Dong Zhu, Zhi-Gang Yang, Cheng-Da Wang, Ning Wang, Yong-Qiang Zhang and Feng-Ling Yu
Materials 2022, 15(13), 4381; https://doi.org/10.3390/ma15134381 - 21 Jun 2022
Cited by 11 | Viewed by 3012
Abstract
Titanium alloys have now become the first choice of tubing material used in the harsh oil- and gas-exploitation environment, while the interaction of force and medium is a serious threat to the safety and reliability of titanium alloy in service. In this paper, [...] Read more.
Titanium alloys have now become the first choice of tubing material used in the harsh oil- and gas-exploitation environment, while the interaction of force and medium is a serious threat to the safety and reliability of titanium alloy in service. In this paper, different stresses were applied to TC4 titanium alloy by four-point bending stress fixture, and the corrosion behavior of TC4 titanium alloy was studied by high-temperature and high-pressure simulation experiments and electrochemical techniques, and the microscopic morphologies and chemical composition of the surface film layer on the specimen were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), to reveal the corrosion-resistance mechanism of TC4 titanium alloy under different stress-loading conditions. The results showed that the pits appeared on the specimens loaded with elastic stress, but the degree of pitting corrosion was still lighter, and the surface film layer showed n-type semiconductor properties with cation selective permeability. While the pits on the specimens loaded with plastic stress were deeper and wider in size, and the semiconductor type of the surface film layer changed to p-type, it was easier for anions such as Cl− and CO32− to adsorb on, destroy, and pass through the protective film and then to contact with the matrix, resulting in a decrease in corrosion resistance of TC4 titanium alloy. Full article
(This article belongs to the Special Issue Advance in Corrosion and Protection of Metals)
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14 pages, 4727 KiB  
Article
Preparation and Properties of Bulk and Porous Ti-Ta-Ag Biomedical Alloys
by Grzegorz Adamek, Mikolaj Kozlowski, Adam Junka, Piotr Siwak and Jaroslaw Jakubowicz
Materials 2022, 15(12), 4332; https://doi.org/10.3390/ma15124332 - 18 Jun 2022
Cited by 6 | Viewed by 2252
Abstract
The paper presents the results of the preparation of bulk and porous Ti-Ta-Ag alloys. The first step of this study was the preparation of the powder alloys using mechanical alloying (MA). The second was hot-pressing consolidation and sintering with a space holder, which [...] Read more.
The paper presents the results of the preparation of bulk and porous Ti-Ta-Ag alloys. The first step of this study was the preparation of the powder alloys using mechanical alloying (MA). The second was hot-pressing consolidation and sintering with a space holder, which resulted in high-density and high-porosity (approximately 70%) samples, respectively. Porosity, morphology, mechanical properties, biocompatibility, and antibacterial behavior were investigated and related to the preparation procedures. The authors found that Ta and Ag heavily influence the microstructure and determine other biomaterial-related properties. These new materials showed positive behavior in the MTT assay, and antibacterial properties. Such materials could find applications in the production of hard tissue implants. Full article
(This article belongs to the Special Issue Advanced Porous Biomaterials)
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14 pages, 4626 KiB  
Article
Mesitylene Tribenzoic Acid as a Linker for Novel Zn/Cd Metal-Organic Frameworks
by Dana Bejan, Ioan-Andrei Dascalu, Sergiu Shova, Alexandru F. Trandabat and Lucian G. Bahrin
Materials 2022, 15(12), 4247; https://doi.org/10.3390/ma15124247 - 15 Jun 2022
Cited by 1 | Viewed by 2237
Abstract
Three new Metal-Organic Frameworks, containing mesitylene tribenzoic acid as a linker and zinc (1) or cadmium as metals (2,3), were synthesized through solvothermal reactions, using DMF/ethanol/water as solvents, at temperatures of 80 °C (structures 1 and 3 [...] Read more.
Three new Metal-Organic Frameworks, containing mesitylene tribenzoic acid as a linker and zinc (1) or cadmium as metals (2,3), were synthesized through solvothermal reactions, using DMF/ethanol/water as solvents, at temperatures of 80 °C (structures 1 and 3) and 120 °C (structure 2). Following single-crystal X-ray diffraction, it was found that 1 and 3 crystallize in the P21/c and C2/c space groups and form 2D networks, while 2 crystallizes in the Fdd2 space group, forming a 3D network. All three frameworks, upon heating, were found to be stable up to 350 °C. N2 sorption isotherms revealed that 1 displays a BET area of 906 m2/g. Moreover, the porosity of this framework is still present after five cycles of sorption/desorption, with a reduction of 14% of the BET area, down to 784 m2/g, after the fifth cycle. The CO2 loading capacity of 1 was found to be 2.9 mmol/g at 0 °C. Full article
(This article belongs to the Special Issue Metal Organic Frameworks: Chemistry and Applications)
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11 pages, 4460 KiB  
Article
Microstructure Evolution in Plastic Deformed Bismuth Telluride for the Enhancement of Thermoelectric Properties
by Haishan Shen, In-Yea Kim, Jea-Hong Lim, Hong-Baek Cho and Yong-Ho Choa
Materials 2022, 15(12), 4204; https://doi.org/10.3390/ma15124204 - 14 Jun 2022
Cited by 3 | Viewed by 2382
Abstract
Thermoelectric generators are solid-state energy-converting devices that are promising alternative energy sources. However, during the fabrication of these devices, many waste scraps that are not eco-friendly and with high material cost are produced. In this work, a simple powder processing technology is applied [...] Read more.
Thermoelectric generators are solid-state energy-converting devices that are promising alternative energy sources. However, during the fabrication of these devices, many waste scraps that are not eco-friendly and with high material cost are produced. In this work, a simple powder processing technology is applied to prepare n-type Bi2Te3 pellets by cold pressing (high pressure at room temperature) and annealing the treatment with a canning package to recycle waste scraps. High-pressure cold pressing causes the plastic deformation of densely packed pellets. Then, the thermoelectric properties of pellets are improved through high-temperature annealing (500 ∘C) without phase separation. This enhancement occurs because tellurium cannot escape from the canning package. In addition, high-temperature annealing induces rapid grain growth and rearrangement, resulting in a porous structure. Electrical conductivity is increased by abnormal grain growth, whereas thermal conductivity is decreased by the porous structure with phonon scattering. Owing to the low thermal conductivity and satisfactory electrical conductivity, the highest ZT value (i.e., 1.0) is obtained by the samples annealed at 500 ∘C. Hence, the proposed method is suitable for a cost-effective and environmentally friendly way. Full article
(This article belongs to the Special Issue Materials Physics in Thermoelectric Materials)
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11 pages, 3144 KiB  
Article
The Preforming of an Interlaminar Toughened Carbon Fiber/Bismaleimide Resin Composite by a Benzoxazine-Based Tackifier
by Yaxian Zi, Yulian Zhang, Weidong Li, Gang Liu, Yujing Zhou, Hua Bai and Xiaolan Hu
Materials 2022, 15(12), 4196; https://doi.org/10.3390/ma15124196 - 13 Jun 2022
Cited by 3 | Viewed by 2741
Abstract
When thermoplastic resin-toughened carbon fiber (CF) composites are formed by liquid resin transfer molding (RTM), the conventional methods cannot be used to set the fabric preform, which affects the overall mechanical properties of the composites. To address this challenge, the benzoxazine-based tackifier BT5501A [...] Read more.
When thermoplastic resin-toughened carbon fiber (CF) composites are formed by liquid resin transfer molding (RTM), the conventional methods cannot be used to set the fabric preform, which affects the overall mechanical properties of the composites. To address this challenge, the benzoxazine-based tackifier BT5501A was designed, a preforming–toughening bifunctional CF fabric was fabricated by employing thermoplastic polyaryletherketone (PEK-C), and an aviation RTM-grade bismaleimide (BMI) resin was used as the matrix to study the effect of the benzoxazine-based tackifier on the thermal curing property and heat resistance of the resin matrix. Furthermore, the preforming and toughening effects on the bifunctional CF fabric reinforced the BMI resin composites. The tackifier BT5501A has good process operability. The application of this tackifier can advance the thermal curing temperature of the BMI resin matrix and decrease the glass transition temperature of the resin, compared to that of the pure BMI resin. Furthermore, when the tackifier was added into the CF/PEK-C/BMI composites, the obtained CF/BT5501A/PEK-C/BMI composites had comparable compression strength after impact, pit depth, and damage area, compared to the CF/PEK-C/BMI composites, while the tackifier endowed the fabric preform with an excellent preforming effect. Full article
(This article belongs to the Special Issue Advanced Composite Material Design and Manufacturing Technology for Aerospace Engineering)
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9 pages, 1966 KiB  
Article
Achieving Good Temperature Stability of Dielectric Constant by Constructing Composition Gradient in (Pb1−x,Lax)(Zr0.65,Ti0.35)O3 Multilayer Thin Films
by Ming Wu, Yanan Xiao, Yu Yan, Yongbin Liu, Huaqiang Li, Jinghui Gao, Lisheng Zhong and Xiaojie Lou
Materials 2022, 15(12), 4123; https://doi.org/10.3390/ma15124123 - 10 Jun 2022
Cited by 8 | Viewed by 1973
Abstract
Ferroelectrics with a high dielectric constant are ideal materials for the fabrication of miniaturized and integrated electronic devices. However, the dielectric constant of ferroelectrics varies significantly with the change of temperature, which is detrimental to the working stability of electronic devices. This work [...] Read more.
Ferroelectrics with a high dielectric constant are ideal materials for the fabrication of miniaturized and integrated electronic devices. However, the dielectric constant of ferroelectrics varies significantly with the change of temperature, which is detrimental to the working stability of electronic devices. This work demonstrates a new strategy to design a ferroelectric dielectric with a high temperature stability, that is, the design of a multilayer relaxor ferroelectric thin film with a composition gradient. As a result, the fabricated up-graded (Pb,La)(Zr0.65,Ti0.35)O3 multilayer thin film showed a superior temperature stability of the dielectric constant, with variation less than 7% in the temperature range from 30 °C to 200 °C, and more importantly, the variation was less than 2.5% in the temperature range from 75 °C to 200 °C. This work not only develops a dielectric material with superior temperature stability, but also demonstrates a promising method to enhance the temperature stability of ferroelectrics. Full article
(This article belongs to the Special Issue The Electronics Applications of Multifunctional Materials)
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16 pages, 10531 KiB  
Article
The Application of a Hybrid Method for the Identification of Elastic–Plastic Material Parameters
by Beata Potrzeszcz-Sut and Agnieszka Dudzik
Materials 2022, 15(12), 4139; https://doi.org/10.3390/ma15124139 - 10 Jun 2022
Cited by 4 | Viewed by 1806
Abstract
The indentation test is a popular method for the investigation of the mechanical properties of materials. The technique, which combines traditional indentation tests with mapping the shape of the imprint, provides more data describing the material parameters. In this paper, such methodology is [...] Read more.
The indentation test is a popular method for the investigation of the mechanical properties of materials. The technique, which combines traditional indentation tests with mapping the shape of the imprint, provides more data describing the material parameters. In this paper, such methodology is employed for estimating the selected material parameters described by Ramberg–Osgood’s law, i.e., Young’s modulus, the yield point, and the material hardening exponent. Two combined identification methods were used: the P-A procedure, in which the material parameters are identified on the basis of the coordinates of the indentation curves, and the P-C procedure, which uses the coordinates describing the imprint profile. The inverse problem was solved by neural networks. The results of numerical indentation tests—pairs of coordinates describing the indentation curves and imprint profiles—were used as input data for the networks. In order to reduce the size of the input vector, a simple and effective method of approximating the branches of the curves was proposed. In the Results Section, we show the performance of the approximation as a data reduction mechanism on a synthetic dataset. The sparse model generated by the presented approach is also shown to efficiently reconstruct the data while minimizing error in the prediction of the mentioned material parameters. Our approach appeared to consistently provide better performance on the testing datasets with considerably easier computation than the principal component analysis compression results available in the literature. Full article
(This article belongs to the Special Issue Finite Element Analysis of Mechanical Behaviors and Properties of Engineering Materials and Structures)
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14 pages, 7052 KiB  
Article
Preparation and Properties of Modified Phenylethynyl Terminated Polyimide with Neodymium Oxide
by Peng Zhang, Hansong Liu, Yilun Yao, Tao Yang, Jinsong Sun, Xiangyu Zhong, Jianwen Bao, Yan Zhao and Xiangbao Chen
Materials 2022, 15(12), 4148; https://doi.org/10.3390/ma15124148 - 10 Jun 2022
Cited by 6 | Viewed by 2580
Abstract
Modified phenylethynyl terminated polyimides (PIs) were successfully prepared by using neodymium oxide (Nd2O3) via high-speed stirring and ultrasonic dispersion methods. In addition, the structure and properties of the Nd2O3-modified imide oligomers as well as the [...] Read more.
Modified phenylethynyl terminated polyimides (PIs) were successfully prepared by using neodymium oxide (Nd2O3) via high-speed stirring and ultrasonic dispersion methods. In addition, the structure and properties of the Nd2O3-modified imide oligomers as well as the thermo-oxidative stability of the modified polyimides (PI/Nd2O3 hybrid) and its modification mechanism were investigated in detail. The thermogravimetric analysis (TGA) results indicated that the 5% decomposition temperature (Td5%) of the PI/Nd2O3 hybrids improved from 557 °C to 575 °C, which was also verified by the TGA-IR tests. Meanwhile, the weight loss rate of the PI/Nd2O3 hybrids significantly decreased by 28% to 31% compared to that of pure PI under isothermal aging at 350 °C for 450 h when the added content of Nd2O3 was between 0.4 wt% and 1 wt%, showing outstanding thermo-oxidative stability. Moreover, the mechanism of the enhanced thermo-oxidative stability for the modified PIs was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Full article
(This article belongs to the Special Issue Advanced Composite Material Design and Manufacturing Technology for Aerospace Engineering)
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33 pages, 2000 KiB  
Article
Lightweight Design of Variable-Stiffness Cylinders with Reduced Imperfection Sensitivity Enabled by Continuous Tow Shearing and Machine Learning
by Rogério R. dos Santos and Saullo G. P. Castro
Materials 2022, 15(12), 4117; https://doi.org/10.3390/ma15124117 - 9 Jun 2022
Cited by 9 | Viewed by 2602
Abstract
The present study investigates how to apply continuous tow shearing (CTS) in a manufacturable design parameterization to obtain reduced imperfection sensitivity in lightweight, cylindrical shell designs. The asymptotic nonlinear method developed by Koiter is applied to predict the post-buckled stiffness, whose index is [...] Read more.
The present study investigates how to apply continuous tow shearing (CTS) in a manufacturable design parameterization to obtain reduced imperfection sensitivity in lightweight, cylindrical shell designs. The asymptotic nonlinear method developed by Koiter is applied to predict the post-buckled stiffness, whose index is constrained to be positive in the optimal design, together with a minimum design load. The performance of three machine learning methods, namely, Support Vector Machine, Kriging, and Random Forest, are compared as drivers to the optimization towards lightweight designs. The new methodology consists of contributions in the areas of problem modeling, the selection of machine learning strategies, and an optimization formulation that results in optimal designs around the compromise frontier between mass and stiffness. The proposed ML-based framework proved to be able to solve the inverse problem for which a target design load is given as input, returning as output lightweight designs with reduced imperfection sensitivity. The results obtained are compatible with the existing literature where hoop-oriented reinforcements were added to obtain reduced imperfection sensitivity in composite cylinders. Full article
(This article belongs to the Special Issue Variable Stiffness Composite Materials and Structures)
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14 pages, 2749 KiB  
Article
Innovative Calcium Carbonate-Based Products to Repair Cracked Cement Mortars
by Martina Zuena, Andreja Pondelak, Enrico Garbin, Matteo Panizza, Luca Nodari, Andrijana Sever Škapin, Luka Škrlep, Gilberto Artioli and Patrizia Tomasin
Materials 2022, 15(12), 4044; https://doi.org/10.3390/ma15124044 - 7 Jun 2022
Viewed by 2662
Abstract
The durability of Portland cement mortars is often affected by environmental factors, which can cause physicochemical and mechanical degradation processes. In this study, the performance of three products, calcium acetoacetate and calcium tetrahydrofurfuryloxide dissolved in two different solvents developed and tested as stone [...] Read more.
The durability of Portland cement mortars is often affected by environmental factors, which can cause physicochemical and mechanical degradation processes. In this study, the performance of three products, calcium acetoacetate and calcium tetrahydrofurfuryloxide dissolved in two different solvents developed and tested as stone consolidants, was evaluated in terms of crack filling or sealing and consolidation. Realistic cracks were induced in quasibrittle cement mortar prisms using a custom-designed test rig. The effectiveness and the performance of the considered treatments, investigated on specimens, were evaluated by optical and scanning electron microscopy, colourimetry, water absorption rate, ultrasonic pulse velocity, and surface hardness measurements. Results revealed that, in the examined conditions, the products were more suitable as surface consolidants than as crack fillers. Full article
(This article belongs to the Special Issue Advances in Research and Materials in Cultural Heritage)
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18 pages, 7820 KiB  
Article
An Accuracy Comparison of Micromechanics Models of Particulate Composites against Microstructure-Free Finite Element Modeling
by Yunhua Luo
Materials 2022, 15(11), 4021; https://doi.org/10.3390/ma15114021 - 6 Jun 2022
Cited by 9 | Viewed by 2337
Abstract
Micromechanics models of composite materials are preferred in the analysis and design of composites for their high computational efficiency. However, the accuracy of the micromechanics models varies widely, depending on the volume fraction of inclusions and the contrast of phase properties, which have [...] Read more.
Micromechanics models of composite materials are preferred in the analysis and design of composites for their high computational efficiency. However, the accuracy of the micromechanics models varies widely, depending on the volume fraction of inclusions and the contrast of phase properties, which have not been thoroughly studied, primarily due to the lack of complete and representative experimental data. The recently developed microstructure-free finite element modeling (MF-FEM) is based on the fact that, for a particulate-reinforced composite, if the characteristic size of the inclusions is much smaller than the composite representative volume element (RVE), the elastic properties of the RVE are independent of inclusion shape and size. MF-FEM has a number of advantages over the conventional microstructure-based finite element modeling. MF-FEM predictions have good to excellent agreement with the reported experiment results. In this study, predictions produced by MF-FEM are used in replace of experimental data to compare the accuracy of selected micromechanics models of particulate composites. The results indicate that, only if both the contrasts in phase Young’s moduli and phase Poisson’s ratios are small, the micromechanics models are able to produce accurate predictions. In other cases, they are more or less inaccurate. This study may serve as a guide for the appropriate use of the micromechanics models. Full article
(This article belongs to the Special Issue Experimental and Numerical Investigation of Composite Materials)
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10 pages, 4520 KiB  
Article
Unraveling the Phase Stability and Physical Property of Modulated Martensite in Ni2Mn1.5In0.5 Alloys by First-Principles Calculations
by Xin-Zeng Liang, Jing Bai, Zi-Qi Guan, Yu Zhang, Jiang-Long Gu, Yu-Dong Zhang, Claude Esling, Xiang Zhao and Liang Zuo
Materials 2022, 15(11), 4032; https://doi.org/10.3390/ma15114032 - 6 Jun 2022
Cited by 2 | Viewed by 2622
Abstract
Large magnetic field-induced strains can be achieved in modulated martensite for Ni-Mn-In alloys; however, the metastability of the modulated martensite imposes serious constraints on the ability of these alloys to serve as promising sensor and actuator materials. The phase stability, magnetic properties, and [...] Read more.
Large magnetic field-induced strains can be achieved in modulated martensite for Ni-Mn-In alloys; however, the metastability of the modulated martensite imposes serious constraints on the ability of these alloys to serve as promising sensor and actuator materials. The phase stability, magnetic properties, and electronic structure of the modulated martensite in the Ni2Mn1.5In0.5 alloy are systematically investigated. Results show that the 6M and 5M martensites are metastable and will eventually transform to the NM martensite with the lowest total energy in the Ni2Mn1.5In0.5 alloy. The physical properties of the incommensurate 7M modulated martensite (7M–IC) and nanotwinned 7M martensite (7M−(52¯)2) are also calculated. The austenite (A) and 7M−(52¯)2 phases are ferromagnetic (FM), whereas the 5M, 6M, and NM martensites are ferrimagnetic (FIM), and the FM coexists with the FIM state in the 7M–IC martensite. The calculated electronic structure demonstrates that the splitting of Jahn–Teller effect and the strong Ni–Mn bonding interaction lead to the enhancement of structural stability. Full article
(This article belongs to the Special Issue Magnetic Functional Materials: Synthesis, Characterization and Application)
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14 pages, 4407 KiB  
Article
Comparative Analysis of the Thermal Conductivity of Handmade and Mechanical Bricks Used in the Cultural Heritage
by Alejandro Cabeza-Prieto, María Soledad Camino-Olea, María Paz Sáez-Pérez, Alfredo Llorente-Álvarez, Ana Belén Ramos Gavilán and María Ascensión Rodríguez-Esteban
Materials 2022, 15(11), 4001; https://doi.org/10.3390/ma15114001 - 4 Jun 2022
Cited by 6 | Viewed by 2078
Abstract
During interventions to improve the energy efficiency of cultural heritage, it is common to use methodologies that are used for current buildings with different thermal behaviour. For this reason, research has been carried out on the thermal behaviour of old brick walls by [...] Read more.
During interventions to improve the energy efficiency of cultural heritage, it is common to use methodologies that are used for current buildings with different thermal behaviour. For this reason, research has been carried out on the thermal behaviour of old brick walls by carrying out thermal flow tests in the laboratory on brickwork specimens, in order to compare the behaviour of handmade bricks and mechanical bricks from more than a century ago, and to analyse the relationship between the values of thermal conductivity, humidity, density and porosity, as well as to compare these results with those obtained by applying the procedure of the EN-1745 standard. It was concluded that bricks behave thermally differently, depending on the manufacturing process: handmade or mechanical, in both types of brick it was found that the higher the moisture content and density were, the higher the brick’s thermal conductivity value. It has also been concluded that old bricks have thermal conductivity values different from those indicated in EN-1745 as a function of density, and that the ratio detected in these specimens in the dry state and in the wet state does not conform to the processes indicated in the standard. With regard to porosity, it is important to note that the greater the closed porosity, the lower the conductivity. It has been concluded that in order to intervene in cultural heritage buildings, it is necessary to carry out a specific study of the behaviour of the systems with which they were constructed. Full article
(This article belongs to the Section Construction and Building Materials)
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9 pages, 6718 KiB  
Article
Molecular Dynamics Investigation of Spreading Performance of Physiological Saline on Surface
by Jianhua Pan and Xiao Wang
Materials 2022, 15(11), 3925; https://doi.org/10.3390/ma15113925 - 31 May 2022
Cited by 1 | Viewed by 1741
Abstract
Physiological saline is an indispensable element for maintaining the functions of life. The spreading performance of physiological saline droplets on the surface of graphene under different NaCl concentrations and electric field intensities was studied in the present work. The results show that the [...] Read more.
Physiological saline is an indispensable element for maintaining the functions of life. The spreading performance of physiological saline droplets on the surface of graphene under different NaCl concentrations and electric field intensities was studied in the present work. The results show that the increase in NaCl concentration reduces the displacement vector value of molecules in droplets. In addition, NaCl is easy to aggregate on the surface of graphene. The increase in NaCl concentration makes it more difficult for droplets to penetrate the surface of graphene, and the penetration angle of droplets increases with the rise in NaCl concentration. With the increase in electric field intensity, the wetting effect of droplets is more obvious. The greater the electric field intensity is, the smaller the penetration angle is, which is mainly due to the polarity of water molecules. This study has reference significance for the study of body fluid volatilization on the human surface. Full article
(This article belongs to the Special Issue Modelling Materials and Devices at Atomistic Level)
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25 pages, 1420 KiB  
Review
Strongly Correlated Quantum Spin Liquids versus Heavy Fermion Metals: A Review
by Vasily R. Shaginyan, Alfred Z. Msezane, George S. Japaridze, Stanislav A. Artamonov and Yulya S. Leevik
Materials 2022, 15(11), 3901; https://doi.org/10.3390/ma15113901 - 30 May 2022
Cited by 2 | Viewed by 2639
Abstract
This review considers the topological fermion condensation quantum phase transition (FCQPT) that explains the complex behavior of strongly correlated Fermi systems, such as frustrated insulators with quantum spin liquid and heavy fermion metals. The review contrasts theoretical consideration with recent experimental data collected [...] Read more.
This review considers the topological fermion condensation quantum phase transition (FCQPT) that explains the complex behavior of strongly correlated Fermi systems, such as frustrated insulators with quantum spin liquid and heavy fermion metals. The review contrasts theoretical consideration with recent experimental data collected on both heavy fermion metals (HF) and frustrated insulators. Such a method allows to understand experimental data. We also consider experimental data collected on quantum spin liquid in Lu3Cu2Sb3O14 and quasi-one dimensional (1D) quantum spin liquid in both YbAlO3 and Cu(C4H4N2)(NO3)2 with the aim to establish a sound theoretical explanation for the observed scaling laws, Landau Fermi liquid (LFL) and non-Fermi-liquid (NFL) behavior exhibited by these frustrated insulators. The recent experimental data on the heavy-fermion metal α−YbAl1−xFexB4, with x=0.014, and on its sister compounds β−YbAlB4 and YbCo2Ge4, carried out under the application of magnetic field as a control parameter are analyzed. We show that the thermodynamic and transport properties as well as the empirical scaling laws follow from the fermion condensation theory. We explain how both the similarity and the difference in the thermodynamic and transport properties of α−YbAl1−xFexB4 and in its sister compounds β−YbAlB4 and YbCo2Ge4 emerge, as well as establish connection of these (HF) metals with insulators Lu3Cu2Sb3O14, Cu(C4H4N2)(NO3)2 and YbAlO3. We demonstrate that the universal LFL and NFL behavior emerge because the HF compounds and the frustrated insulators are located near the topological FCQPT or are driven by the application of magnetic fields. Full article
(This article belongs to the Special Issue Exploration of Novel Quantum Spin Liquid Materials)
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9 pages, 3006 KiB  
Article
Electrical and Thermal Characteristics of AlGaN/GaN HEMT Devices with Dual Metal Gate Structure: A Theoretical Investigation
by Yongfeng Qu, Ningkang Deng, Yuan Yuan, Wenbo Hu, Hongxia Liu, Shengli Wu and Hongxing Wang
Materials 2022, 15(11), 3818; https://doi.org/10.3390/ma15113818 - 27 May 2022
Cited by 12 | Viewed by 2939
Abstract
The electrical and thermal characteristics of AlGaN/GaN high-electron mobility transistor (HEMT) devices with a dual-metal gate (DMG) structure are investigated by electrothermal simulation and compared with those of conventional single-metal gate (SMG) structure devices. The simulations reveal that the DMG structure devices have [...] Read more.
The electrical and thermal characteristics of AlGaN/GaN high-electron mobility transistor (HEMT) devices with a dual-metal gate (DMG) structure are investigated by electrothermal simulation and compared with those of conventional single-metal gate (SMG) structure devices. The simulations reveal that the DMG structure devices have a 10-percent higher transconductance than the SMG structure devices when the self-heating effect is considered. In the meantime, employing the DMG structure, a decrease of more than 11% in the maximum temperature rise of the devices can be achieved at the power density of 6 W/mm. Furthermore, the peak in heat generation distribution at the gate edge of the devices is reduced using this structure. These results could be attributed to the change in the electric field distribution at the gate region and the suppression of the self-heating effect. Therefore, the electrical and thermal performances of AlGaN/GaN HEMT devices are improved by adopting the DMG structure. Full article
(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)
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20 pages, 7329 KiB  
Article
Hinged Adaptive Fiber-Rubber Composites Driven by Shape Memory Alloys—Development and Simulation
by Felix Lohse, Achyuth Ram Annadata, Eric Häntzsche, Thomas Gereke, Wolfgang Trümper and Chokri Cherif
Materials 2022, 15(11), 3830; https://doi.org/10.3390/ma15113830 - 27 May 2022
Cited by 3 | Viewed by 2200
Abstract
Adaptive structures based on fiber-rubber composites with integrated Shape Memory Alloys are promising candidates for active deformation tasks in the fields of soft robotics and human-machine interactions. Solid-body hinges improve the deformation behavior of such composite structures. Textile technology enables the user to [...] Read more.
Adaptive structures based on fiber-rubber composites with integrated Shape Memory Alloys are promising candidates for active deformation tasks in the fields of soft robotics and human-machine interactions. Solid-body hinges improve the deformation behavior of such composite structures. Textile technology enables the user to develop reinforcement fabrics with tailored properties suited for hinged actuation mechanisms. In this work, flat knitting technology is used to create biaxially reinforced, multilayer knitted fabrics with hinge areas and integrated Shape Memory Alloy wires. The hinge areas are achieved by dividing the structures into sections and varying the configuration and number of reinforcement fibers from section to section. The fabrics are then infused with silicone, producing a fiber-rubber composite specimen. An existing simulation model is enhanced to account for the hinges present within the specimen. The active deformation behavior of the resulting structures is then tested experimentally, showing large deformations of the hinged specimens. Finally, the simulation results are compared to the experimental results, showing deformations deviating from the experiments due to the developmental stage of the specimens. Future work will benefit from the findings by improving the deformation behavior of the specimens and enabling further development for first applications. Full article
(This article belongs to the Section Smart Materials)
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10 pages, 3497 KiB  
Article
Optimizing Evanescent Efficiency of Chalcogenide Tapered Fiber
by Xudong Zhao, Ni Yao, Xianghua Zhang, Lei Zhang, Guangming Tao, Zijian Li, Quan Liu, Xiujian Zhao and Yinsheng Xu
Materials 2022, 15(11), 3834; https://doi.org/10.3390/ma15113834 - 27 May 2022
Cited by 3 | Viewed by 2142
Abstract
Evanescent wave absorption-based mid-infrared chalcogenide fiber sensors have prominent advantages in multicomponent liquid and gas detection. In this work, a new approach of tapered-fiber geometry optimization was proposed, and the evanescent efficiency was also theoretically calculated to evaluate sensing performance. The influence of [...] Read more.
Evanescent wave absorption-based mid-infrared chalcogenide fiber sensors have prominent advantages in multicomponent liquid and gas detection. In this work, a new approach of tapered-fiber geometry optimization was proposed, and the evanescent efficiency was also theoretically calculated to evaluate sensing performance. The influence of fiber geometry (waist radius (Rw), taper length (Lt), waist deformation) on the mode distribution, light transmittance (T), evanescent proportion (TO) and evanescent efficiency (τ) is discussed. Remarkably, the calculated results show that the evanescent efficiency can be over 10% via optimizing the waist radius and taper length. Generally, a better sensing performance based on tapered fiber can be achieved if the proportion of the LP11-like mode becomes higher or Rw becomes smaller. Furthermore, the radius of the waist boundary (RL) was introduced to analyze the waist deformation. Mode proportion is almost unchanged as the RL increases, while τ is halved. In addition, the larger the micro taper is, the easier the taper process is. Herein, a longer waist can be obtained, resulting in larger sensing area which increases sensitivity greatly. Full article
(This article belongs to the Special Issue Advanced Functional Glass: Preparation, Properties, and Applications)
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25 pages, 4384 KiB  
Article
Effect of Biochar on Metal Distribution and Microbiome Dynamic of a Phytostabilized Metalloid-Contaminated Soil Following Freeze–Thaw Cycles
by Maja Radziemska, Mariusz Z. Gusiatin, Agnieszka Cydzik-Kwiatkowska, Aurelia Blazejczyk, Vinod Kumar, Antonin Kintl and Martin Brtnicky
Materials 2022, 15(11), 3801; https://doi.org/10.3390/ma15113801 - 26 May 2022
Cited by 10 | Viewed by 2829
Abstract
In the present paper the effectiveness of biochar-aided phytostabilization of metal/metalloid-contaminated soil under freezing–thawing conditions and using the metal tolerating test plant Lolium perenne L. is comprehensively studied. The vegetative experiment consisted of plants cultivated for over 52 days with no exposure to [...] Read more.
In the present paper the effectiveness of biochar-aided phytostabilization of metal/metalloid-contaminated soil under freezing–thawing conditions and using the metal tolerating test plant Lolium perenne L. is comprehensively studied. The vegetative experiment consisted of plants cultivated for over 52 days with no exposure to freezing–thawing in a glass greenhouse, followed by 64 days under freezing–thawing in a temperature-controlled apparatus and was carried out in initial soil derived from a post-industrial urban area, characterized by the higher total content of Zn, Pb, Cu, Cr, As and Hg than the limit values included in the classification provided by the Regulation of the Polish Ministry of Environment. According to the substance priority list published by the Toxic Substances and Disease Registry Agency, As, Pb, and Hg are also indicated as being among the top three most hazardous substances. The initial soil was modified by biochar obtained from willow chips. The freeze–thaw effect on the total content of metals/metalloids (metal(-loid)s) in plant materials (roots and above-ground parts) and in phytostabilized soils (non- and biochar-amended) as well as on metal(-loid) concentration distribution/redistribution between four BCR (community bureau of reference) fractions extracted from phytostabilized soils was determined. Based on metal(-loid)s redistribution in phytostabilized soils, their stability was evaluated using the reduced partition index (Ir). Special attention was paid to investigating soil microbial composition. In both cases, before and after freezing–thawing, biochar increased plant biomass, soil pH value, and metal(-loid)s accumulation in roots, and decreased metal(-loid)s accumulation in stems and total content in the soil, respectively, as compared to the corresponding non-amended series (before and after freezing–thawing, respectively). In particular, in the phytostabilized biochar-amended series after freezing–thawing, the recorded total content of Zn, Cu, Pb, and As in roots substantially increased as well as the Hg, Cu, Cr, and Zn in the soil was significantly reduced as compared to the corresponding non-amended series after freezing–thawing. Moreover, exposure to freezing–thawing itself caused redistribution of examined metal(-loid)s from mobile and/or potentially mobile into the most stable fraction, but this transformation was favored by biochar presence, especially for Cu, Pb, Cr, and Hg. While freezing–thawing greatly affected soil microbiome composition, biochar reduced the freeze–thaw adverse effect on bacterial diversity and helped preserve bacterial groups important for efficient soil nutrient conversion. In biochar-amended soil exposed to freezing–thawing, psychrotolerant and trace element-resistant genera such as Rhodococcus sp. or Williamsia sp. were most abundant. Full article
(This article belongs to the Special Issue Recent Progress of Biochar and Biomass Pyrolysis)
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20 pages, 9421 KiB  
Article
A Modified Three-Dimensional Negative-Poisson-Ratio Metal Metamaterial Lattice Structure
by Fangyi Li, Qiang Zhang, Huimin Shi and Zheng Liu
Materials 2022, 15(11), 3752; https://doi.org/10.3390/ma15113752 - 24 May 2022
Cited by 14 | Viewed by 3415
Abstract
Mechanical metamaterials are of interest to researchers because of their unique mechanical properties, including a negative Poisson structure. Here, we study a three-dimensional (3D) negative-Poisson-ratio (NPR) metal metamaterial lattice structure by adding a star structure to the traditional 3D concave structure, thus designing [...] Read more.
Mechanical metamaterials are of interest to researchers because of their unique mechanical properties, including a negative Poisson structure. Here, we study a three-dimensional (3D) negative-Poisson-ratio (NPR) metal metamaterial lattice structure by adding a star structure to the traditional 3D concave structure, thus designing three different angles with a modified NPR structure and control structure. We further study the mechanical properties via finite element numerical simulations and show that the stability and stiffness of the modified structures are improved relative to the control structure; the stability decreases with increasing star body angle. The star angle has the best relative energy absorption effect at 70.9°. The experimental model is made by selective laser melting (SLM) technology (3D printing), and the compression experiment verification used an MTS universal compressor. The experimental results are consistent with the changing trend in finite element simulation. Full article
(This article belongs to the Special Issue Mechanical Metamaterials: Optimization and New Design Ideas)
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9 pages, 13590 KiB  
Article
Direct Wafer-Scale CVD Graphene Growth under Platinum Thin-Films
by Yelena Hagendoorn, Gregory Pandraud, Sten Vollebregt, Bruno Morana, Pasqualina M. Sarro and Peter G. Steeneken
Materials 2022, 15(10), 3723; https://doi.org/10.3390/ma15103723 - 23 May 2022
Cited by 6 | Viewed by 3459
Abstract
Since the transfer process of graphene from a dedicated growth substrate to another substrate is prone to induce defects and contamination and can increase costs, there is a large interest in methods for growing graphene directly on silicon wafers. Here, we demonstrate the [...] Read more.
Since the transfer process of graphene from a dedicated growth substrate to another substrate is prone to induce defects and contamination and can increase costs, there is a large interest in methods for growing graphene directly on silicon wafers. Here, we demonstrate the direct CVD growth of graphene on a SiO2 layer on a silicon wafer by employing a Pt thin film as catalyst. We pattern the platinum film, after which a CVD graphene layer is grown at the interface between the SiO2 and the Pt. After removing the Pt, Raman spectroscopy demonstrates the local growth of monolayer graphene on SiO2. By tuning the CVD process, we were able to fully cover 4-inch oxidized silicon wafers with transfer-free monolayer graphene, a result that is not easily obtained using other methods. By adding Ta structures, local graphene growth on SiO2 is selectively blocked, allowing the controlled graphene growth on areas selected by mask design. Full article
(This article belongs to the Special Issue Carbon-Based Electronic Materials)
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10 pages, 2710 KiB  
Article
Application of Laser-Induced Breakdown Spectroscopy in the Quantitative Analysis of Elements—K, Na, Ca, and Mg in Liquid Solutions
by Wojciech Skrzeczanowski and Maria Długaszek
Materials 2022, 15(10), 3736; https://doi.org/10.3390/ma15103736 - 23 May 2022
Cited by 5 | Viewed by 1818
Abstract
Results of laser-induced breakdown spectroscopy measurements of K, Na, Ca, and Mg content in liquid media are discussed in the paper. Calibration results show correct parameters—linearity and R2 coefficients of determination at the levels of 0.94–0.99. Obtained regression equations have been used [...] Read more.
Results of laser-induced breakdown spectroscopy measurements of K, Na, Ca, and Mg content in liquid media are discussed in the paper. Calibration results show correct parameters—linearity and R2 coefficients of determination at the levels of 0.94–0.99. Obtained regression equations have been used to determine K, Na, Ca, and Mg concentrations in biological samples with known element content. Measurement results showed acceptable, within the expanded standard uncertainty, conformity with their content in the certified materials. Results have been supported by multivariate factorial analysis, which was especially effective for Ca and Mg samples. For these elements, factorial analysis allows the application of the whole spectra to obtain quantitative data on the tested samples, in contrast to a common method based on the selection of a particular spectral line for the calibration. Full article
(This article belongs to the Section Optical and Photonic Materials)
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