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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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56 pages, 7034 KiB  
Review
Color Conversion Light-Emitting Diodes Based on Carbon Dots: A Review
by Danilo Trapani, Roberto Macaluso, Isodiana Crupi and Mauro Mosca
Materials 2022, 15(15), 5450; https://doi.org/10.3390/ma15155450 - 8 Aug 2022
Cited by 21 | Viewed by 4418
Abstract
This paper reviews the state-of-the-art technologies, characterizations, materials (precursors and encapsulants), and challenges concerning multicolor and white light-emitting diodes (LEDs) based on carbon dots (CDs) as color converters. Herein, CDs are exploited to achieve emission in LEDs at wavelengths longer than the pump [...] Read more.
This paper reviews the state-of-the-art technologies, characterizations, materials (precursors and encapsulants), and challenges concerning multicolor and white light-emitting diodes (LEDs) based on carbon dots (CDs) as color converters. Herein, CDs are exploited to achieve emission in LEDs at wavelengths longer than the pump wavelength. White LEDs are typically obtained by pumping broad band visible-emitting CDs by an UV LED, or yellow–green-emitting CDs by a blue LED. The most important methods used to produce CDs, top-down and bottom-up, are described in detail, together with the process that allows one to embed the synthetized CDs on the surface of the pumping LEDs. Experimental results show that CDs are very promising ecofriendly candidates with the potential to replace phosphors in traditional color conversion LEDs. The future for these devices is bright, but several goals must still be achieved to reach full maturity. Full article
(This article belongs to the Special Issue Organic Materials for Electronic and Optoelectronic Applications)
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18 pages, 15322 KiB  
Article
A High Temporal-Spatial Resolution Temperature Sensor for Simultaneous Measurement of Anisotropic Heat Flow
by Xuwen Luo and Haidong Wang
Materials 2022, 15(15), 5385; https://doi.org/10.3390/ma15155385 - 5 Aug 2022
Cited by 5 | Viewed by 2716
Abstract
The thermal measurement sensor applied to hypersonic vehicles requires characteristic size in the order of micrometers and characteristic time in the order of microseconds. The measurement criteria of localized detection, high temporal-spatial precision, and long-term stability cannot all be reached by current thermal [...] Read more.
The thermal measurement sensor applied to hypersonic vehicles requires characteristic size in the order of micrometers and characteristic time in the order of microseconds. The measurement criteria of localized detection, high temporal-spatial precision, and long-term stability cannot all be reached by current thermal measuring techniques. This work presents a temperature sensor with excellent temporal-spatial resolution that can measure both in-plane and out-of-plane heat flow. The sensor was made of thin platinum nano-film and an aluminum nitride ceramic sheet. The sensor was calibrated using a thermostatic vacuum chamber and used for in-plane and out-of-plane heat flow measurements. The temperature measurement accuracy of the sensor was estimated to be 0.01 K. The sensor’s resolution for measuring heat flow density is more than 500 W/m2 and its measurement uncertainty is roughly 3%. To ensure the structural stability of the device, the aluminum nitride ceramic sheet was chosen as the substrate of the thermal sensing unit, and the response time became longer due to the high thermal conductivity of aluminum nitride. The suspension platinum nano-film sensor can reach a sub-microsecond response time according to the theoretical derivation. Experimental results of pneumatic thermal effects of high-temperature flames using the sensor prove that the designed sensor has good sensitivity and accuracy. Full article
(This article belongs to the Special Issue Advances in Heat Transfer and Property Characterization of Nano Materials)
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15 pages, 6046 KiB  
Article
Effect of Ultrafine Fly Ash and Water Glass Content on the Performance of Phosphorus Slag-Based Geopolymer
by Jin Yang, Xiaolei Yu, Xingyang He, Ying Su, Jingyi Zeng, Fei Dai and Shiyu Guan
Materials 2022, 15(15), 5395; https://doi.org/10.3390/ma15155395 - 5 Aug 2022
Cited by 12 | Viewed by 2291
Abstract
Phosphorus slag (PS), an industrial waste slag, has been used in geopolymers because it is rich in silicon and calcium. The poor performance of phosphorus slag-based geopolymer is due to its aluminum deficiency. In this work, low-calcium fly ash, treated by a wet-grinding [...] Read more.
Phosphorus slag (PS), an industrial waste slag, has been used in geopolymers because it is rich in silicon and calcium. The poor performance of phosphorus slag-based geopolymer is due to its aluminum deficiency. In this work, low-calcium fly ash, treated by a wet-grinding process, named wet-grinding ultrafine fly ash (WUFA) was used as an Al supplement to replace some of the phosphorus slag, and the wet-grinding, ultrafine fly ash-phosphorus slag (WUFA-PS)-based geopolymer was prepared. The effects of the substitution amount of WUFA and the activator dosage on the hydration properties, mechanical properties, pore structure and SEM of the WUFA-PS geopolymer were discussed in detail. The results indicate that WUFA and more activators contribute to the Al and high alkalinity environment, which positively induces the production of more geopolymer gels, thus releasing more heat and optimizing the pore structure of the matrix. The compressive strength increased by up to 28.1%. The enhanced performance of the WUFA-PS-based geopolymer may also arise from the filling effect and activity improvement of WUFA. This study has proved the feasibility of preparing a geopolymer by blending wet-grinding ultrafine fly ash and phosphorus slag and has provided references for the ratio and performance evaluation of WUFA-PS-based geopolymer concrete. Full article
(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)
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21 pages, 4521 KiB  
Article
Superhydrophobic Anticorrosive Phosphonate–Siloxane Films Formed on Zinc with Different Surface Morphology
by Galina V. Redkina, Alexandra S. Sergienko, Yurii I. Kuznetsov and Oleg Yu. Grafov
Materials 2022, 15(15), 5360; https://doi.org/10.3390/ma15155360 - 4 Aug 2022
Cited by 9 | Viewed by 1950
Abstract
The composition, structure, and protective and hydrophobic properties of nanoscale films formed layer-by-layer in solutions of sodium dodecylphosphonate (SDDP) and vinyltrimethoxysilane or n-octyltriethoxysilane (OTES) on the zinc surface with different morphologies were studied by SEM, XPS, water contact angle measurements, and electrochemical [...] Read more.
The composition, structure, and protective and hydrophobic properties of nanoscale films formed layer-by-layer in solutions of sodium dodecylphosphonate (SDDP) and vinyltrimethoxysilane or n-octyltriethoxysilane (OTES) on the zinc surface with different morphologies were studied by SEM, XPS, water contact angle measurements, and electrochemical and corrosion tests. The protective, hydrophobic properties of phosphonate–siloxane films on zinc and their stability in a corrosive media are determined both by the initial surface morphology and composition of the surface oxide layer, and by the nature of inhibitors. It was shown that preliminary laser texturing of the zinc surface is preferable than chemical etching to enhance the anticorrosive properties of the resulting thin films. The most stable films with excellent superhydrophobic and protective properties in atmospheres of high humidity and salt spray are formed on the zinc surface with fractal morphology during layer-by-layer passivation with SDDP and OTES. Full article
(This article belongs to the Special Issue Corrosion Prediction and Corrosion Protection)
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14 pages, 4993 KiB  
Article
An Overview of Some Nonpiezoelectric Properties of BaTiO3 Ceramics Doped by Eu Ions
by Magdalena Krupska-Klimczak, Przemyslaw Gwizd, Irena Jankowska-Sumara, Dorota Sitko and Piotr Jeleń
Materials 2022, 15(15), 5363; https://doi.org/10.3390/ma15155363 - 4 Aug 2022
Cited by 7 | Viewed by 2376
Abstract
Ferroelectric ceramics BaTiO3:x%Eu (x = 0, 0.1, 1, 2, 3) were synthesized by a conventional method. Structural investigation confirmed that all ceramics possessed tetragonal (P4mm) symmetries at room temperature for the undoped ceramics as well as for the [...] Read more.
Ferroelectric ceramics BaTiO3:x%Eu (x = 0, 0.1, 1, 2, 3) were synthesized by a conventional method. Structural investigation confirmed that all ceramics possessed tetragonal (P4mm) symmetries at room temperature for the undoped ceramics as well as for the doped ceramics. Furthermore, a slight downshifting of the Curie temperature (TC) with an increasing Eu3+ doping amount has been noted. The Raman spectra unveiled the existence of new modes for higher-doped BaTiO3:x%Eu (BTEx) which are related to local disorders and defects. The ferroelectric properties were found to depend on both doping and the microstructure. The electrocaloric effect was also studied for those ceramics. It was observed that ΔT decreases with doping; however, the temperature range of its occurrence widens considerably. Full article
(This article belongs to the Special Issue Emerging Dielectric, Piezoelectric and Ferroelectric Ceramic and Crystalline Materials and Their Applications)
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16 pages, 1798 KiB  
Article
Effect of Biochar Modification by Vitamin C, Hydrogen Peroxide or Silver Nanoparticles on Its Physicochemistry and Tetracycline Removal
by Agnieszka Tomczyk and Katarzyna Szewczuk-Karpisz
Materials 2022, 15(15), 5379; https://doi.org/10.3390/ma15155379 - 4 Aug 2022
Cited by 19 | Viewed by 3123
Abstract
Chemical modification of biochars can improve their adsorption capacity relative to antibiotics, posing a serious threat to the environment. Therefore, this research is aimed at the treatment of sunflower husk biochar (BC) by vitamin C, hydrogen peroxide or silver nanoparticles and the impact [...] Read more.
Chemical modification of biochars can improve their adsorption capacity relative to antibiotics, posing a serious threat to the environment. Therefore, this research is aimed at the treatment of sunflower husk biochar (BC) by vitamin C, hydrogen peroxide or silver nanoparticles and the impact of this procedure on the biochar porosity, surface chemistry, and ability to remove tetracycline (TC). During the study, BC was produced by pyrolysis of sunflower husks at 650 °C. All solids were characterized using potentiometric titration, nitrogen adsorption/desorption, Fourier transform infrared spectroscopy, etc. The experimental adsorption data was described by kinetics equations: pseudo-first order, pseudo-second order, and particle internal diffusion (IPD) models as well as by isotherms of Langmuir, Langmuir-Freundlich, and Redlich-Peterson. The obtained results indicated that the biochar upgraded by vitamin C (BCV) had the highest ability to attract antibiotic molecules and, as a result, the TC adsorption on its surface was the largest. Furthermore, the TC desorption from this material was minimal. The measured TC adsorbed amounts for the modified BCs were as follows: 47.75% (7.47 mg/g) for BCV, 37.35% (8.41 mg/g)-for biochar treated by hydrogen peroxide (BCH), and 42.04% (9.55 mg/g) for biochar modified by silver nanoparticles (BCA). The lowest adsorption level was noted for non-modified biochar, i.e., 34.17% (6.83 mg/g). Based on the presented results it can be stated that the upgraded biochars had a good potential to improve the tetracycline removal from aqueous media, e.g., groundwater. Full article
(This article belongs to the Special Issue Advances in Eco-Friendly Adsorbent Materials for Removal of Inorganic and Organic Pollutants (Volume II))
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17 pages, 6822 KiB  
Article
Influence of the Additive of Ceramic and Intermetallic Powders on the Friction Properties and Temperature of the Wet Clutch Disc
by Aleksander Yevtushenko, Michal Kuciej, Piotr Grzes, Aleksander Ilyushchanka and Andrey Liashok
Materials 2022, 15(15), 5384; https://doi.org/10.3390/ma15155384 - 4 Aug 2022
Cited by 2 | Viewed by 1996
Abstract
The basic function of friction clutches is to transfer the torque in the conditions of its smooth engagement without vibrations. Hard working conditions under high thermal and mechanical loads, leading to high temperature in the contact area, intense wear, and instability of the [...] Read more.
The basic function of friction clutches is to transfer the torque in the conditions of its smooth engagement without vibrations. Hard working conditions under high thermal and mechanical loads, leading to high temperature in the contact area, intense wear, and instability of the coefficient of friction impose restrictive criteria in the design of friction materials. In this paper, the results of experimental research of the effect of ceramic and intermetallic additives to the copper-based material of the friction disc of the clutch on the thermophysical and frictional properties were presented. Next, these properties were incorporated in the proposed contact 3D numerical model of the clutch to carry out computer simulations of the heating process and subsequent cooling. Based on the obtained experimental data and transient temperature changes of the friction and steel discs, the relations between the powder additives, thermophysical properties of the five friction materials, and coefficients of friction, wear, and temperature reached were discussed. Among these, it was found that when working with the lubrication, the largest values of the coefficient of friction 0.068 and wear 13.5  μm  km−1 were reached when using the 3 wt.% SiC additive. Full article
(This article belongs to the Special Issue Use of Modern Materials in Technological Processes Accompanied by Frictional Heating)
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16 pages, 9579 KiB  
Article
Effect of Silver Doping on the Superconducting and Structural Properties of YBCO Films Grown by PLD on Different Templates
by Ilya A. Shipulin, Aleena Anna Thomas, Sigrid Holleis, Michael Eisterer, Kornelius Nielsch and Ruben Hühne
Materials 2022, 15(15), 5354; https://doi.org/10.3390/ma15155354 - 3 Aug 2022
Cited by 5 | Viewed by 2971
Abstract
We report the local structural and superconducting properties of undoped and Ag-doped YBa2Cu3O6+x (YBCO) films with a thickness of up to 1 µm prepared by pulsed laser deposition on SrTiO3 (STO) single crystals and on ion-beam-assisted deposition [...] Read more.
We report the local structural and superconducting properties of undoped and Ag-doped YBa2Cu3O6+x (YBCO) films with a thickness of up to 1 µm prepared by pulsed laser deposition on SrTiO3 (STO) single crystals and on ion-beam-assisted deposition (IBAD) and rolling-assisted biaxially textured substrate (RABiTS)-based metal templates. X-ray diffraction demonstrates the high crystalline quality of the films on both single crystalline substrates and metal-based templates, respectively. Although there was only a slight decrease in Tc of up to 1.5 K for the Ag-doped YBCO films on all substrates, we found significant changes in their transport characteristics. The effect of the silver doping mainly depended on the concentration of silver, the type of substrate, and the temperature and magnetic field. In general, the greatest improvement in Jc over a wide range of magnetic fields and temperatures was observed for the 5%Ag-doped YBCO films on STO substrates, showing a significant increase compared to undoped films. Furthermore, a slight Jc improvement was observed for the 2%Ag-doped YBCO films on the RABiTS templates at temperatures below 65 K, whereas Jc decreased for the Ag-doped films on IBAD-MgO-based templates compared to undoped YBCO films. Using detailed electron microscopy studies, small changes in the local microstructure of the Ag-doped YBCO films were revealed; however, no clear correlation was found with the transport properties of the films. Full article
(This article belongs to the Special Issue Advances in Superconducting Materials: Characterization, Properties and Applications)
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19 pages, 4137 KiB  
Article
Archaeometric Characterization of the Industrial Production of Porcelains in the Vieillard & Co. Manufactory (Bordeaux, France, 19th Century)
by Emmie Beauvoit, Nadia Cantin, Quentin Lemasson, Rémy Chapoulie and Ayed Ben Amara
Materials 2022, 15(15), 5311; https://doi.org/10.3390/ma15155311 - 2 Aug 2022
Cited by 2 | Viewed by 1906
Abstract
In this paper, we focus on the industrial production of porcelain in the Bordeaux area (France) in the 19th century. Our main objective is to assess the evolution of production technology of the same manufactory over a period of more than 40 years. [...] Read more.
In this paper, we focus on the industrial production of porcelain in the Bordeaux area (France) in the 19th century. Our main objective is to assess the evolution of production technology of the same manufactory over a period of more than 40 years. A multi-analytical approach was used to investigate glazes and bodies of thirty-four sherds of biscuit and porcelain found in an archaeological context. The microstructural, chemical, and mineralogical characterization was performed using a combination of scanning electron microscopy, coupled with energy dispersive spectroscopy (SEM-EDS), particles induced X-ray and gamma emission (PIXE-PIGE), and X-ray diffraction (XRD). Results obtained on the characterization of the ceramic production technologies and on the chemical modification over time contributes to investigate this industrial production, which is not well documented by the written archives. The examination of the biscuits, rare artifacts, showed that the porcelain bodies were produced by mixing kaolinitic clays, quartz, and potassium feldspars. The mineralogical analysis of the ceramic supports allowed hypotheses to be put forward on the temperatures of the biscuit firing (around 950 °C) and the second firing (over 1200 °C). Furthermore, the treatment of the compositional data, including both glazes and bodies, using multivariate statistical analysis, revealed different types of production corresponding to the different chronological periods of production at Bordeaux throughout the 19th century. These results will enable us to consider the possibility of authenticating non-stamped and undecorated pieces. Full article
(This article belongs to the Special Issue Science and Technology of Porcelain: History, Processing, Structure and Properties)
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24 pages, 9840 KiB  
Article
Effect of Polycarboxylate-Silane Modified Graphene Oxide Composite on the Properties of Cement Pastes
by Shuang Liu, Shiyu Li, Qin Wang, Ruifeng Zhang and Xiao Liu
Materials 2022, 15(15), 5313; https://doi.org/10.3390/ma15155313 - 2 Aug 2022
Cited by 5 | Viewed by 2069
Abstract
As a nano-carbon material with excellent properties, Graphene oxide (GO) has been widely used in cement-based materials, and the negative effect of paste workability caused by GO agglomeration has also been widely concerning. In this study, a polycarboxylate-silane modified graphene oxide composite (PSG) [...] Read more.
As a nano-carbon material with excellent properties, Graphene oxide (GO) has been widely used in cement-based materials, and the negative effect of paste workability caused by GO agglomeration has also been widely concerning. In this study, a polycarboxylate-silane modified graphene oxide composite (PSG) was prepared by coupling polycarboxylate molecules to the surface of graphene oxide (GO) via a reaction with vinyl triethoxysilane. The effects of GO and PSG on the cement paste and the mechanisms underpinning these effects were investigated using fluidity and rheological parameter measurements, and ion concentration and zeta potential analyses. It was found that, in the aqueous phase of the paste, the polycarboxylate molecular chains on the surface of the PSG complexed with calcium ions (Ca2+), thereby preventing Ca2+ from bridging the GO sheets, and thus stabilizing the surface potential and the electrostatic repulsion. This prevented the PSG from forming an agglomerate structure such as that formed by GO under the same conditions, thereby substantially enhancing workability of paste with nano-carbon material. This study provides some new foundations and ideas for the further application of graphene oxide materials in cement-based materials. Full article
(This article belongs to the Special Issue Development and Characterization of Novel Cement Materials)
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16 pages, 5950 KiB  
Article
Zirconia versus Titanium Implants: 8-Year Follow-Up in a Patient Cohort Contrasted with Histological Evidence from a Preclinical Animal Model
by Warwick J. Duncan, Sunyoung Ma, Allauddin Siddiqi and Reham B. Osman
Materials 2022, 15(15), 5322; https://doi.org/10.3390/ma15155322 - 2 Aug 2022
Cited by 4 | Viewed by 3304
Abstract
Zirconia ceramic (ZC) implants are becoming more common, but comparisons between preclinical histology and long-term clinical trials are rare. This investigation comprised (1) 8-year clinical follow-up of one-piece ZC or titanium (Ti) implants supporting full overdentures and (2) histomorphometric analysis of the same [...] Read more.
Zirconia ceramic (ZC) implants are becoming more common, but comparisons between preclinical histology and long-term clinical trials are rare. This investigation comprised (1) 8-year clinical follow-up of one-piece ZC or titanium (Ti) implants supporting full overdentures and (2) histomorphometric analysis of the same implants in an animal model, comparing implants with various surface treatments. Methods: (1) Clinical trial: 24 completely edentulous participants (2 groups of N = 12) received 7 implants (one-piece ball-abutment ZC or Ti; maxilla N = 4, mandible N = 3) restored with implant overdentures. Outcomes after 8-years included survival, peri-implant bone levels, soft-tissue responses, and prosthodontic issues. (2) Preclinical trial: 10 New Zealand sheep received 4 implants bilaterally in the femoral condyle: Southern Implants ZC or Ti one-piece implants, identical to the clinical trial, and controls: Southern ITC® two-piece implants with the same surface or Nobel (NBC) anodised (TiUnite™) surface. %Bone-implant contact (%BIC) was measured after 12 weeks of unloaded healing. Results: 8 of 24 participants (33%) of an average age of 75 ± 8 years were recalled; 21% of original participants had died, and 46% could not be contacted. 80.4% of implants survived; excluding palatal sites, 87.5% of Ti and 79% of ZC implants survived. All failed implants were in the maxilla. Three ZC implants had fractured. Bone loss was similar for Ti vs. ZC; pocket depths (p = 0.04) and attachment levels (p = 0.02) were greater for Ti than ZC implants. (1.7 ± 1.6 mm vs. 1.6 ± 1.3 mm). All implants in sheep femurs survived. %BIC was not statistically different for one-piece blasted surface Ti (80 ± 19%) versus ZC (76 ± 20%) or ITC® (75 ± 16 mm); NBC had significantly higher %BIC than ITC (84 ± 17%, p = 0.4). Conclusion: Short-term preclinical results for ZC and Ti one-piece implants showed excellent bone-implant contact in unloaded femoral sites. This differed from the long-term clinical results in older-aged, edentulous participants. While ZC and Ti implants showed equivalent performance, the risks of peri-implantitis and implant loss in older, completely edentulous patients remain a significant factor. Full article
(This article belongs to the Special Issue Zirconia Implants: Current Status and Future Prospects)
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10 pages, 1250 KiB  
Article
Injectable Click Fibroin Bioadhesive Derived from Spider Silk for Accelerating Wound Closure and Healing Bone Fracture
by Woong-Jin Lee, Kyoungjoo Cho, Aaron-Youngjae Kim and Gyung-Whan Kim
Materials 2022, 15(15), 5269; https://doi.org/10.3390/ma15155269 - 30 Jul 2022
Cited by 5 | Viewed by 2831
Abstract
Wound closure is a critical step in postoperative wound recovery. Substantial advancements have been made in many different means of facilitating wound closure, including the use of tissue adhesives. Compared to conventional methods, such as suturing, tissue bioadhesives better accelerate wound closure. However, [...] Read more.
Wound closure is a critical step in postoperative wound recovery. Substantial advancements have been made in many different means of facilitating wound closure, including the use of tissue adhesives. Compared to conventional methods, such as suturing, tissue bioadhesives better accelerate wound closure. However, several existing tissue adhesives suffer from cytotoxicity, inadequate tissue adhesive strength, and high costs. In this study, a series of bioadhesives was produced using non-swellable spider silk-derived silk fibroin protein and an outer layer of swellable polyethylene glycol and tannic acid. The gelation time of the spider silk-derived silk fibroin protein bioadhesive is less than three minutes and thus can be used during rapid surgical wound closure. By adding polyethylene glycol (PEG) 2000 and tannic acid as co-crosslinking agents to the N-Hydroxysuccinimide (NHS), and 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) reaction, the adhesive strength of the bioadhesive became 2.5 times greater than that of conventional fibrin glue adhesives. Silk fibroin bioadhesives do not show significant cytotoxicity in vitro compared with other bioadhesives. In conclusion, silk fibroin bioadhesive is promising as a new medical tool for more effective and efficient surgical wound closure, particularly in bone fractures. Full article
(This article belongs to the Special Issue Development and Application of Silk-Proteins Based Biomaterials)
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28 pages, 7705 KiB  
Article
Topology Optimization and Multiobjective Optimization for Drive Axle Housing of a Rear Axle Drive Truck
by Bin Zheng, Shengyan Fu and Jilin Lei
Materials 2022, 15(15), 5268; https://doi.org/10.3390/ma15155268 - 30 Jul 2022
Cited by 10 | Viewed by 4644
Abstract
As one of the important load-bearing components of a truck, the drive axle housing must meet the requirements of stiffness and strength. The traditional design method uses redundancy design to meet the performance requirements. The joint design between the three-dimensional mathematical model and [...] Read more.
As one of the important load-bearing components of a truck, the drive axle housing must meet the requirements of stiffness and strength. The traditional design method uses redundancy design to meet the performance requirements. The joint design between the three-dimensional mathematical model and finite element model is adopted, and the optimal design of the drive axle housing is realized based on topology optimization and multiobjective optimization. Firstly, the static analysis of the drive axle housing of a rear axle drive truck was carried out with four typical working conditions. It was concluded that the four working conditions all operate under the yield limit of the material, and it was found that the maximum equivalent stress of the four working conditions occurs at the step of the half-shaft casing. Among the four working conditions, the most critical one is the maximum vertical force working condition. Then, based on the maximum vertical force working condition, the fatigue life analysis is conducted, and the minimum fatigue life appears at the transition position of the half-shaft sleeve and the arc transition position of the main reducer chamber. The remaining parts can meet the design requirements. The overall safety factor of the drive axle housing is mainly between 1 and 5 when operating under this working condition. Then, through modal analysis, the first to sixth natural frequency and vibration modes of the drive axle housing are extracted. Based on the modal analysis, the dynamic characteristics of the drive axle housing are further studied by harmonic response analysis and random vibration analysis. Finally, two kinds of lightweight optimization schemes for the drive axle housing are given. Topology optimization reduces the mass of the drive axle housing by 17.4%, but the overall performance slightly decreases. Then, the five dimensional parameters of the drive axle housing are selected as design variables. The mass, maximum deformation, equivalent stress, service life, and the first-, second- and third-order natural frequencies are defined as objective functions. Through the optimal space-filling design method, the experimental designs are performed and the sample points are obtained. Based on the results of experiment design, the multiobjective genetic algorithm and response surface method are combined to optimize the objective functions. The analysis results show that the mass is reduced by 4.35%, the equivalent stress is reduced by 21.05%, the minimum life is increased by 72.28%, and the first-, second-, and third-order natural frequency are also increased to varying degrees. Two different optimization strategies are provided for the design of the drive axle housing. 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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12 pages, 6330 KiB  
Article
Self-Powered Photodetector Based on FTO/n-TiO2/p-CuMnO2 Transparent Thin Films
by Carmen Lazau, Mircea Nicolaescu, Corina Orha, Viorel Şerban and Cornelia Bandas
Materials 2022, 15(15), 5229; https://doi.org/10.3390/ma15155229 - 28 Jul 2022
Cited by 5 | Viewed by 2619
Abstract
A self-powered photodetector with the FTO/n-TiO2/p-CuMnO2 configuration, representing the novelty of the work, was successfully achieved for the first time and presumes two steps: deposition of the n-type semiconductor (TiO2) by the doctor [...] Read more.
A self-powered photodetector with the FTO/n-TiO2/p-CuMnO2 configuration, representing the novelty of the work, was successfully achieved for the first time and presumes two steps: deposition of the n-type semiconductor (TiO2) by the doctor blade method and of the p-type semiconductor (CuMnO2) by the spin coating technique, respectively. Investigation techniques of the structural and morphological characteristics of the as-synthesized heterostructures, such as XRD, UV-VIS analysis, and SEM/EDX and AFM morphologies, were used. The I-t measurements of the photodetector showed that the responsivity in the self-powered mode was 2.84 × 107 A W−1 cm2 and in the 1 V bias mode it was 1.82 × 106 A W−1 cm2. Additionally, a self-powered current of 14.2 nA was generated under UV illumination with an intensity of 0.1 mW/cm2. Furthermore, under illumination conditions, the response time (tres) and the recovery time (trec) of the sensor exhibited a good response; thus, tres = 7.30 s and trec = 0.4 s for the self-powered mode, and in the 1 V bias mode, these were tres = 15.16 s and trec = 2.18 s. The above results show that the transparent heterojunction device of n-TiO2/p-CuMnO2 exhibited a self-powered ultraviolet photodetector with high sensitivity. Full article
(This article belongs to the Special Issue Nano-Engineering of Functional Oxides: Synthesis, Functional Properties and Applications)
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19 pages, 14590 KiB  
Article
Performance of 3D-Printed Bionic Conch-Like Composite Plate under Low-Velocity Impact
by Mincen Wan, Dayong Hu and Baoqing Pei
Materials 2022, 15(15), 5201; https://doi.org/10.3390/ma15155201 - 27 Jul 2022
Cited by 12 | Viewed by 2906
Abstract
Biological armors can provide an effective protection against predators. In this study, inspired by conch shell, beetle exoskeleton, and nacre, three different types of bionic composites plates were fabricated: Bio-S, Bio-B, and Bio-N, as well as an equivalent monolithic plate formed from the [...] Read more.
Biological armors can provide an effective protection against predators. In this study, inspired by conch shell, beetle exoskeleton, and nacre, three different types of bionic composites plates were fabricated: Bio-S, Bio-B, and Bio-N, as well as an equivalent monolithic plate formed from the same stiff material designed and manufactured by additive manufacturing, respectively. Low velocity impact tests using drop tower were conducted to study their impact resistance. Experimental findings indicated that the Bio-S composite had superior impact resistance compared with the other bionic composites and the monolithic plate. Furthermore, the influence of the ply angle on the impact resistance of the Bio-S composite plate was investigated. The (0°/30°/0°/30°) arrangement was able to provide the highest impact resistance. Finally, the crack propagation mode in Bio-S composites plates was analyzed, enhancing our understanding of the underlying mechanisms during impact. Such findings may lead to the development of superior lightweight protective structures with improved anti-impact performance. Full article
(This article belongs to the Special Issue Advanced Composite Material Design and Manufacturing Technology for Aerospace Engineering)
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16 pages, 4627 KiB  
Article
Compression Deformation Prediction of Chiral Metamaterials: A Compression–Shear Coupling Model
by Xin Zhou, Xi Liang, Zeliang Liu, Chenglin Tao and Huijian Li
Materials 2022, 15(15), 5180; https://doi.org/10.3390/ma15155180 - 26 Jul 2022
Cited by 4 | Viewed by 1990
Abstract
A category of metamaterials consisting of chiral cytosolic elements assembled periodically, in which the introduction of a rotatable annular structure gives metamaterials the ability to deform in compression–shear, has been a focus of research in recent years. In this paper, a compression–shear coupling [...] Read more.
A category of metamaterials consisting of chiral cytosolic elements assembled periodically, in which the introduction of a rotatable annular structure gives metamaterials the ability to deform in compression–shear, has been a focus of research in recent years. In this paper, a compression–shear coupling model is developed to predict the compressive deformation behaviour of chiral metamaterials. This behaviour will be analysed by coupling the rotation of the annular node and the bending characteristics of ligament beam, which are obtained as a function of the length of ligament beam and the angle of rotation at the end of the beam. The shape function of the ligament beam under large deformation is obtained based on the elliptic integral theory; the function characterises the potential relationship between key parameters such as displacement and rotation angle at any point on the ligament beam. By simulating the deformation of cells under uniaxial compression, the reasonableness of the large deformation model of the ligament beam is verified. On this basis, a chiral cell-compression mechanical model considering the ductile deformation of the annular node is established. The compression–shear deformation of two-dimensional planar chiral metamaterials and three-dimensional cylindrical-shell chiral metamaterials was predicted; the offset displacements and torsion angles agreed with the experimental and finite element simulation results with an error of less than 10%. The developed compression–shear coupling model provides a theoretical basis for the design of chiral metamaterials, which meet the need for the precise control of shapes and properties. Full article
(This article belongs to the Section Mechanics of Materials)
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9 pages, 1962 KiB  
Communication
Energy-Resolved Ultrafast Spectroscopic Investigation on the Spin-Coupled Electronic States in Multiferroic Hexagonal HoMnO3
by Wei-Hong Huang, Hao-Keng Wei, Nguyen Nhat Quyen, Pei-Tsung Yang, Yi-Cheng Cheng, Yu-Ting Wang, Ying-Kuan Ko, Chien-Ming Tu, Atsushi Yabushita and Chih-Wei Luo
Materials 2022, 15(15), 5188; https://doi.org/10.3390/ma15155188 - 26 Jul 2022
Cited by 1 | Viewed by 1902
Abstract
A complete temperature-dependent scheme of the Mn3+ on-site d-d transitions in multiferroic hexagonal HoMnO3 (h-HoMnO3) thin films was unveiled by energy-resolved ultrafast spectroscopy. The results unambiguously revealed that the ultrafast responses of the e1g and e [...] Read more.
A complete temperature-dependent scheme of the Mn3+ on-site d-d transitions in multiferroic hexagonal HoMnO3 (h-HoMnO3) thin films was unveiled by energy-resolved ultrafast spectroscopy. The results unambiguously revealed that the ultrafast responses of the e1g and e2g states differed significantly in the hexagonal HoMnO3. We demonstrated that the short-range antiferromagnetic and ferroelectric orderings are more relevant to the e2g state, whereas the long-range antiferromagnetic ordering is intimately coupled to both the e2g and e1g states. Moreover, the primary thermalization times of the e2g and e1g states were 0.34 ± 0.08 ps and 0.38 ± 0.08 ps, respectively. Full article
(This article belongs to the Special Issue Application of Emerging Materials for Advanced Imaging and Sensing)
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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 2387
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 8 | Viewed by 2778
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 2895
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 1995
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 8 | Viewed by 2678
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 1993
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 14 | Viewed by 2818
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 17 | Viewed by 3392
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 3733
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 1757
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 2531
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 2061
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 2045
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 2464
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 7 | Viewed by 2836
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 4071
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 3015
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 3330
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 39 | Viewed by 4459
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 15 | Viewed by 5677
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 4 | Viewed by 2423
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 10 | Viewed by 3316
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 2358
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 2701
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 25 | Viewed by 2883
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 3 | Viewed by 1838
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 4434
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 2980
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 15 | Viewed by 3146
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 2339
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 2286
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 2450
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 2837
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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