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Materials, Volume 15, Issue 7 (April-1 2022) – 365 articles

Cover Story (view full-size image): As microbial infections caused by various drug-resistant microorganisms become more common and the number of newly approved antimicrobials for systemic administration capable of acting against these resistant pathogens is limited, formulation innovations of existing drugs are gaining prominence, and the applications of nanoformulations have become a useful alternative for improving/enhancing the effect of existing antimicrobial drugs. This work summarizes the most recent results of nanoformulations of antibiotics and antibacterial active nanomaterials. Nanoformulations of antimicrobial peptides and synergistic combinations of antimicrobial active agents with polymers, metals, metal oxides, and metalloids are also described. The mechanisms of action of selected nanoformulations, including systems with magnetic, photothermal, and photodynamic effects, are discussed. View this paper
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Article
Experimental and Molecular Dynamics Simulation Study on Sol–Gel Conversion Process of Aluminum Carboxylate System
Materials 2022, 15(7), 2704; https://doi.org/10.3390/ma15072704 - 06 Apr 2022
Viewed by 580
Abstract
Due to the lack of relevant in situ characterization techniques, the investigation of aluminum sol–gel progress is lacking. In this study, combined with molecular dynamics simulation and conventional experimental methods, the microstructures, rheological properties, and gelation process of the carboxylic aluminum sol system [...] Read more.
Due to the lack of relevant in situ characterization techniques, the investigation of aluminum sol–gel progress is lacking. In this study, combined with molecular dynamics simulation and conventional experimental methods, the microstructures, rheological properties, and gelation process of the carboxylic aluminum sol system were studied. The experimental results showed that, with the increase in solid content, the microstructure of the colloid developed from a loose and porous framework to a homogeneous and compact structure. The viscosity of aluminum sol decreased significantly with the increase in temperature, and a temperature above 318 k was more conducive to improving the fluidity. The simulation results show that the increase in free volume and the connectivity of pores in colloidal framework structure were the key factors to improve fluidity. In addition, free water molecules had a higher migration rate, which could assist the rotation and rearrangement of macromolecular chains and also played an essential role in improving fluidity. The Molecular dynamics simulation (MD) results were consistent with experimental results and broaden the scope of experimental research, providing necessary theoretical guidance for enhancing the spinning properties of aluminum sol. Full article
(This article belongs to the Section Advanced and Functional Ceramics and Glasses)
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Communication
Milling Parameter Optimization of Continuous-Glass-Fiber-Reinforced-Polypropylene Laminate
Materials 2022, 15(7), 2703; https://doi.org/10.3390/ma15072703 - 06 Apr 2022
Viewed by 667
Abstract
The composite-material laminate structure will inevitably encounter connection problems in use. Among them, mechanical connections are widely used in aerospace, automotive and other fields because of their high connection efficiency and reliable connection performance. Milling parameters are important for the opening quality. In [...] Read more.
The composite-material laminate structure will inevitably encounter connection problems in use. Among them, mechanical connections are widely used in aerospace, automotive and other fields because of their high connection efficiency and reliable connection performance. Milling parameters are important for the opening quality. In this paper, continuous-glass-fiber-reinforced-polypropylene (GFRPP) laminates were chosen to investigate the effects of different cutters and process parameters on the hole quality. The delamination factor and burr area were taken as the index to characterize the opening quality. After determining the optimal milling tool, the process window was obtained according to the appearance of the milling hole. In the selected process parameter, the maximum temperature did not reach the PP melting temperature. The best hole quality was achieved when the spindle speed was 18,000 r/min and the feed speed was 1500 mm/min with the corn milling cutter. Full article
(This article belongs to the Special Issue Advances in Polymer Blends and Composites)
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Article
Microstructure and Texture Evolution in Low Carbon and Low Alloy Steel during Warm Deformation
Materials 2022, 15(7), 2702; https://doi.org/10.3390/ma15072702 - 06 Apr 2022
Viewed by 570
Abstract
Warm compression tests were carried out on low carbon and low alloy steel at temperatures of 600–850 °C and stain rates of 0.01–10 s−1. The evolution of microstructure and texture was studied using a scanning electron microscope and electron backscattered diffraction. [...] Read more.
Warm compression tests were carried out on low carbon and low alloy steel at temperatures of 600–850 °C and stain rates of 0.01–10 s−1. The evolution of microstructure and texture was studied using a scanning electron microscope and electron backscattered diffraction. The results indicated that cementite spheroidization occurred and greatly reduced at 750 °C due to a phase transformation. Dynamic recrystallization led to a transition from {112}<110> texture to {111}<112> texture. Below 800 °C, the intensity and variation of texture with deformation temperature is more significant than that above 800 °C. The contents of the {111}<110> texture and {111}<112> texture were equivalent above 800 °C, resulting in the better uniformity of γ-fiber texture. Nucleation of <110>//ND-oriented grains increased, leading to the strengthening of <110>//ND texture. Microstructure analysis revealed that the uniform and refined grains can be obtained after deformation at 800 °C and 850 °C. The texture variation reflected the fact that 800 °C was the critical value for temperature sensitivity of warm deformation. At a large strain rate, the lowest dislocation density appeared after deformation at 800 °C. Therefore, 800 °C is a suitable temperature for the warm forming application, where the investigated material is easy to deform and evolves into a uniform and refined microstructure. Full article
(This article belongs to the Special Issue Hot Deformation and Microstructure Evolution of Metallic Materials)
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Article
Influence of Freeze–Thaw Cycles on the Mechanical Properties of Highly Rubberised Asphalt Mixtures Made with Warm and Cold Asphalt Binders
Materials 2022, 15(7), 2701; https://doi.org/10.3390/ma15072701 - 06 Apr 2022
Viewed by 645
Abstract
The present study has been developed to investigate the effect of freeze and thaw (F–T) cycles on the characteristics of highly rubberised asphalt materials to be used as impact-absorbing pavement (IAP) in urban road infrastructures. The tested samples were produced in the laboratory [...] Read more.
The present study has been developed to investigate the effect of freeze and thaw (F–T) cycles on the characteristics of highly rubberised asphalt materials to be used as impact-absorbing pavement (IAP) in urban road infrastructures. The tested samples were produced in the laboratory following the dry process incorporation. Two main types of crumb rubber particles in the range of 0–4 mm were used. Moreover, two types of binders, one warm and one cold, were utilised to prove the feasibility of cold-produced admixtures. The temperature range of the F–T procedure was comprised between −18 ± 2 °C (dry freezing), and 4 ± 2 °C (in water), and the cycles were repeated, on the samples, 10 times. At 0, 1, 5, and 10 cycles, the samples were tested with non-destructive and destructive testing methods, including air voids content, ITSM, ITS, and Cantabro loss. The waters of the thawing period were collected, and the pH, electric conductivity, and particle loss were measured. A consequent change in mechanical behaviour has been recorded between warm and cold produced samples. However, the tests found that the F–T cycles had limited influence on the deterioration of the highly rubberised samples. The loss of particles in the thaw waters were identified as being potentially caused by the temperature stresses. The research suggested various ways to optimise the material to enhance the cold-produced layer mechanical performances, aiming at a fume and smell-free industrialised solution and reducing the potential leaching and particle losses. Full article
(This article belongs to the Special Issue Advances in Sustainable Asphalt Pavements)
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Article
Designing Carbon-Enriched Alumina Films Possessing Visible Light Absorption
Materials 2022, 15(7), 2700; https://doi.org/10.3390/ma15072700 - 06 Apr 2022
Viewed by 494
Abstract
Aluminum anodization in an aqueous solution of formic acid and sodium vanadate leads to the formation of alumina/carbon composite films. This process was optimized by varying the concentrations of formic acid and sodium vanadate, the pH, and the processing time in constant-voltage (60–100 [...] Read more.
Aluminum anodization in an aqueous solution of formic acid and sodium vanadate leads to the formation of alumina/carbon composite films. This process was optimized by varying the concentrations of formic acid and sodium vanadate, the pH, and the processing time in constant-voltage (60–100 V) or constant-current mode. As estimated, in this electrolyte, the anodizing conditions played a critical role in forming thick, nanoporous anodic films with surprisingly high carbon content up to 17 at.%. The morphology and composition of these films were examined by scanning electron microscopy, ellipsometry, EDS mapping, and thermogravimetry coupled with mass spectrometry. For the analysis of incorporated carbon species, X-ray photoelectron and Auger spectroscopies were applied, indicating the presence of carbon in both the sp2 and the sp3 states. For these films, the Tauc plots derived from the experimental diffuse reflectance spectra revealed an unprecedentedly low bandgap (Eg) of 1.78 eV compared with the characteristic Eg values of alumina films formed in solutions of other carboxylic acids under conventional anodization conditions and visible-light absorption. Full article
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Article
Effectiveness of Curing Compounds for Concrete
Materials 2022, 15(7), 2699; https://doi.org/10.3390/ma15072699 - 06 Apr 2022
Viewed by 604
Abstract
Curing compounds are widely used materials that are used in place of other methods of curing fresh concrete. The article presents an overview of the effectiveness of the concrete curing compounds widely used in Europe. Eleven different products have been tested. FTIR spectroscopy [...] Read more.
Curing compounds are widely used materials that are used in place of other methods of curing fresh concrete. The article presents an overview of the effectiveness of the concrete curing compounds widely used in Europe. Eleven different products have been tested. FTIR spectroscopy identification tests showed that all tested products might be divided into two main groups, depending on the type of their active substance. The water retention efficiency of each curing compound was examined, and the tensile strength of the cured samples was tested using the pull-off method. The dry mass content of the tested products was examined to check for a correlation between their effectiveness and active substance content. The microstructure of mortars treated with the most effective compounds and the reference mortar were examined using SEM techniques. Significant differences in microstructure were found between cured samples with different curing compounds, and also with uncured samples. Full article
(This article belongs to the Special Issue Advanced Cement and Concrete Composites)
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Communication
Intrinsic Effect of Pulsed Current on the Recrystallization of Deformed AZ31 Alloy
Materials 2022, 15(7), 2698; https://doi.org/10.3390/ma15072698 - 06 Apr 2022
Viewed by 444
Abstract
Two ensemble configurations were designed to investigate the intrinsic effect of a pulsed current on the recrystallization of rolled AZ31 alloy. The samples with a total reduction of about 60% were crystallized at 473K for 5 min when treated with the pulsed current. [...] Read more.
Two ensemble configurations were designed to investigate the intrinsic effect of a pulsed current on the recrystallization of rolled AZ31 alloy. The samples with a total reduction of about 60% were crystallized at 473K for 5 min when treated with the pulsed current. By forcing the pulsed current flow only through the graphite die, and the sample was heated by Joule effect, a microstructure with a grain size of ~5 μm was formed and the recrystallized fraction achieved 60% reduction. Moreover, a fully recrystallized microstructure with a grain size of ~9 μm was obtained when heated with Joule and athermal effects by forcing the pulsed current flow through the sample only. Based on the experimental results, the recrystallization behavior of deformed AZ31 under a pulsed current should be governed by the high Joule heating effect, which could generate transient high stress in the sample due to the nonsynchronous change in temperature and thermal expansion. The athermal effect of the pulsed current could enhance the dislocation mobility and thus accelerate coarsening of the recrystallization grains, but it should not be the key factor governing the recrystallization behavior of rolled AZ31B. This led to the p erroneous conclusion that the athermal effect of pulsed current played a crucial role in the recrystallization of deformed alloys. Full article
(This article belongs to the Topic Advanced Forming Technology of Metallic Materials)
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Article
Influence of Modification on Flow Stress Behavior and Corrosive Properties of a Hypoeutectic Al-Si Alloy
Materials 2022, 15(7), 2697; https://doi.org/10.3390/ma15072697 - 06 Apr 2022
Viewed by 565
Abstract
The flow stress behavior and corrosive properties of Al-7Si alloy were studied by thermal compression test, electrochemical test, and electron probe microanalysis. The influences of temperatures, strain rates, strains, and morphology of Si particles on stress-strain curves of Al-7Si alloy were analyzed. The [...] Read more.
The flow stress behavior and corrosive properties of Al-7Si alloy were studied by thermal compression test, electrochemical test, and electron probe microanalysis. The influences of temperatures, strain rates, strains, and morphology of Si particles on stress-strain curves of Al-7Si alloy were analyzed. The peak stress of unmodified-Al-7Si alloy is higher than that of Sr-modified-Al-7Si alloy at the same deformation conditions, and the phenomenon is obviously relevant to the distribution and morphology of Si particles. The morphology of Si particles of unmodified-undeformed-Al-7Si alloy is a typical thick layer, and that of unmodified-deformed-Al-7Si alloy is broken into relatively small particles and the distribution is relatively even in homogeneous deformation zone II. The distribution of Si particles in Sr-modified-deformed-Al-7Si alloy is obviously more even than undeformed alloy. The effect of a small deformation of 20% on the distribution and morphology of Si particles is obviously smaller than that of a large deformation of 50%. The electrochemical self-corrosion potential of Sr-modified-Al-7Si alloy is higher than that of unmodified-Al-7Si alloy, and it proves that the distribution and morphology of Si particles have a certain influence on the corrosive properties of Al-7Si alloy. That is, the even fine Si particles are more conducive to improving the corrosive properties of Al-7Si alloy. Full article
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Article
Amino Surface Modification and Fluorescent Labelling of Porous Hollow Organosilica Particles: Optimization and Characterization
Materials 2022, 15(7), 2696; https://doi.org/10.3390/ma15072696 - 06 Apr 2022
Viewed by 567
Abstract
Surface modification of silica nanoparticles with organic functional groups while maintaining colloidal stability remains a synthetic challenge. This work aimed to prepare highly dispersed porous hollow organosilica particles (pHOPs) with amino surface modification. The amino-surface modification of pHOPs was carried out with 3-aminopropyl(diethoxy)methylsilane [...] Read more.
Surface modification of silica nanoparticles with organic functional groups while maintaining colloidal stability remains a synthetic challenge. This work aimed to prepare highly dispersed porous hollow organosilica particles (pHOPs) with amino surface modification. The amino-surface modification of pHOPs was carried out with 3-aminopropyl(diethoxy)methylsilane (APDEMS) under various reaction parameters, and the optimal pHOP-NH2 sample was selected and labelled with fluorescein isothiocyanate (FITC) to achieve fluorescent pHOPs (F-HOPs). The prepared pHOPs were thoroughly characterized by transmission electron microscopy, dynamic light scattering, FT-IR, UV-Vis and fluorescence spectroscopies, and microfluidic resistive pulse sensing. The optimal amino surface modification of pHOPs with APDEMS was at pH 10.2, at 60 °C temperature with 10 min reaction time. The positive Zeta potential of pHOP-NH2 in an acidic environment and the appearance of vibrations characteristic to the surface amino groups on the FT-IR spectra prove the successful surface modification. A red-shift in the absorbance spectrum and the appearance of bands characteristic to secondary amines in the FTIR spectrum of F-HOP confirmed the covalent attachment of FITC to pHOP-NH2. This study provides a step-by-step synthetic optimization and characterization of fluorescently labelled organosilica particles to enhance their optical properties and extend their applications. Full article
(This article belongs to the Special Issue Functionalized Silica Materials: Preparation and Applications)
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Article
Oxygen Vacancy Formation and Migration within the Antiphase Boundaries in Lanthanum Scandate-Based Oxides: Computational Study
Materials 2022, 15(7), 2695; https://doi.org/10.3390/ma15072695 - 06 Apr 2022
Viewed by 711
Abstract
The atomic structure of antiphase boundaries in Sr-doped lanthanum scandate (La1−xSrxScO3−δ) perovskite, promising as the proton conductor, was modelled by means of DFT method. Two structural types of interfaces formed by structural octahedral coupling were [...] Read more.
The atomic structure of antiphase boundaries in Sr-doped lanthanum scandate (La1−xSrxScO3−δ) perovskite, promising as the proton conductor, was modelled by means of DFT method. Two structural types of interfaces formed by structural octahedral coupling were constructed: edge- and face-shared. The energetic stability of these two interfaces was investigated. The mechanisms of oxygen vacancy formation and migration in both types of interfaces were modelled. It was shown that both interfaces are structurally stable and facilitate oxygen ionic migration. Oxygen vacancy formation energy in interfaces is lower than that in the regular structure, which favours the oxygen vacancy segregation within such interfaces. The calculated energy profile suggests that both types of interfaces are advantageous for oxygen ion migration in the material. Full article
(This article belongs to the Special Issue Advances in Lanthanide Complexes)
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Article
Influence of the Grain Size Distribution of the Limestone Additives on the Color Properties and Phase Composition of Sintered Ceramic Materials Based on Cream-Firing Clays
Materials 2022, 15(7), 2694; https://doi.org/10.3390/ma15072694 - 06 Apr 2022
Viewed by 563
Abstract
The study focused on determining color changes in materials made of cream-firing clays from the Opoczno region (Poland) due to the addition of calcium carbonate in the form of limestone. Moreover, the influence of the grain size distribution of this additive on the [...] Read more.
The study focused on determining color changes in materials made of cream-firing clays from the Opoczno region (Poland) due to the addition of calcium carbonate in the form of limestone. Moreover, the influence of the grain size distribution of this additive on the color properties of the materials and their phase composition was determined. Test samples were prepared using theplastic method and fired at four different temperatures: 1120, 1140, 1160 and 1180 °C. The color properties of the surface of ceramic materials were determined in CIE-Lab color space using a colorimeter. Quantitative phase analysis was performed using the Rietveld method. The research showed that the addition of calcium carbonate causes an increase in the yellow color factor and a decrease in the red color factor and the brightness of the material. Moreover, it was proven that the grain size distribution of the additive used significantly influences the phase composition of the materials, thus determining the values of physical properties and the color of the materials. Full article
(This article belongs to the Section Advanced and Functional Ceramics and Glasses)
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Article
Wettability, Corrosion Resistance, and Osteoblast Response to Reduced Graphene Oxide on CoCr Functionalized with Hyaluronic Acid
Materials 2022, 15(7), 2693; https://doi.org/10.3390/ma15072693 - 06 Apr 2022
Cited by 2 | Viewed by 544
Abstract
The durability of metal–metal prostheses depends on achieving a higher degree of lubrication. The beneficial effect of hyaluronic acid (HA) on the friction and wear of both natural and artificial joints has been reported. For this purpose, graphene oxide layers have been electrochemically [...] Read more.
The durability of metal–metal prostheses depends on achieving a higher degree of lubrication. The beneficial effect of hyaluronic acid (HA) on the friction and wear of both natural and artificial joints has been reported. For this purpose, graphene oxide layers have been electrochemically reduced on CoCr surfaces (CoCrErGO) and subsequently functionalized with HA (CoCrErGOHA). These layers have been evaluated from the point of view of wettability and corrosion resistance in a physiological medium containing HA. The wettability was analyzed by contact angle measurements in phosphate buffer saline-hyaluronic acid (PBS-HA) solution. The corrosion behavior of functionalized CoCr surfaces was studied with electrochemical measurements. Biocompatibility, cytotoxicity, and expression of proteins related to wound healing and repair were studied in osteoblast-like MC3T3-E1 cell cultures. All of the reported results suggest that HA-functionalized CoCr surfaces, through ErGO layers in HA-containing media, exhibit higher hydrophilicity and better corrosion resistance. Related to this increase in wettability was the increase in the expressions of vimentin and ICAM-1, which favored the growth and adhesion of osteoblasts. Therefore, it is a promising material for consideration in trauma applications, with improved properties in terms of wettability for promoting the adhesion and growth of osteoblasts, which is desirable in implanted materials used for bone repair. Full article
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Article
Organo-Nanocups Assist the Formation of Ultra-Small Palladium Nanoparticle Catalysts for Hydrogen Evolution Reaction
Materials 2022, 15(7), 2692; https://doi.org/10.3390/ma15072692 - 06 Apr 2022
Cited by 1 | Viewed by 634
Abstract
Ultra-small palladium nanoparticles were synthesized and applied as catalysts for a hydrogen evolution reaction. The palladium metal precursor was produced via beta-cyclodextrin as organo-nanocup (ONC) capping agent to produce ultra-small nanoparticles used in this study. The produced ~3 nm nanoparticle catalyst was then [...] Read more.
Ultra-small palladium nanoparticles were synthesized and applied as catalysts for a hydrogen evolution reaction. The palladium metal precursor was produced via beta-cyclodextrin as organo-nanocup (ONC) capping agent to produce ultra-small nanoparticles used in this study. The produced ~3 nm nanoparticle catalyst was then characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), and Fourier transform infrared spectroscopy (FTIR) to confirm the successful synthesis of ~3 nm palladium nanoparticles. The nanoparticles’ catalytic ability was explored via the hydrolysis reaction of sodium borohydride. The palladium nanoparticle catalyst performed best at 303 K at a pH of 7 with 925 μmol of sodium borohydride having an H2 generation rate of 1.431 mL min−1 mLcat−1. The activation energy of the palladium catalyst was calculated to be 58.9 kJ/mol. Full article
(This article belongs to the Special Issue Feature Paper in Section Catalytic Materials)
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Article
Preparation of CSHW with Flue Gas Desulfurization Gypsum
Materials 2022, 15(7), 2691; https://doi.org/10.3390/ma15072691 - 06 Apr 2022
Viewed by 550
Abstract
Calcium sulfate hemihydrate whiskers (CSHW), a multi-functional and high value-added building material, were prepared with flue gas desulfurization (FGD) gypsum by hydrothermal method, which could be a reasonable disposal of FGD gypsum. In order to obtain CSHW of a high aspect ratio, a [...] Read more.
Calcium sulfate hemihydrate whiskers (CSHW), a multi-functional and high value-added building material, were prepared with flue gas desulfurization (FGD) gypsum by hydrothermal method, which could be a reasonable disposal of FGD gypsum. In order to obtain CSHW of a high aspect ratio, a series of manufacturing parameters such as reaction temperature, stirring speed, material–water ratio, and reaction time were investigated. The effect of stabilizing treatment and glycerol concentration on CSHW morphology were also studied by environmental scanning electron microscopy (ESEM) and statistical analysis. The results showed that the optimum preparing conditions of reaction temperature, stirring speed, water–material ratio, and reaction time were 160 °C, 200~300 rpm, 11:1 and 1 h, respectively. Furthermore, stabilizing treatment with octodecyl betaine was necessary for the preparation of CSHW. The final prepared whiskers had smooth surface, uniform morphology, a diameter of 260 nm, and a corresponding aspect ratio of 208.2. Moreover, the addition of glycerol reduced the activity of water, contributing to a lower reaction temperature and much smaller diameter. Full article
(This article belongs to the Topic Fiber-Reinforced Cementitious Composites)
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Article
In Situ Testing of Polymers Immersed in Aging Fluids at Elevated Temperature and Pressure
Materials 2022, 15(7), 2690; https://doi.org/10.3390/ma15072690 - 06 Apr 2022
Viewed by 537
Abstract
A novel elevated-temperature and high-pressure in situ punch-shear-test cell was developed to qualify materials for reliable service in harsh environments representative of those typically encountered in oil and gas operations. The proposed modular and compact test device is an extension of the ASTM [...] Read more.
A novel elevated-temperature and high-pressure in situ punch-shear-test cell was developed to qualify materials for reliable service in harsh environments representative of those typically encountered in oil and gas operations. The proposed modular and compact test device is an extension of the ASTM D 732 punch-shear method. Conventionally, materials are first exposed to harsh environments, then removed from the aging environment for mechanical testing. This practice can lead to the generation of unrealistic (often optimistic) mechanical properties. This is especially true in the case of materials for which fluid ingress is reversible. The present contribution elaborates on the developed in situ punch-shear device that has been successfully used to realistically assess the tensile yield strength and modulus properties of in-service polymer materials based on experimentally established correlations between shear and tensile tests. Full article
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Article
Stress–Strain Field in an Innovative Metallic Dam Gate Used to Control the Water Flow
Materials 2022, 15(7), 2689; https://doi.org/10.3390/ma15072689 - 06 Apr 2022
Viewed by 409
Abstract
The paper aims to determine the stress and strain field in metallic dam gates to identify an optimal constructive solution for their design, from the point of view of strength in service. The study is of a dam with a central, oscillating pivot, [...] Read more.
The paper aims to determine the stress and strain field in metallic dam gates to identify an optimal constructive solution for their design, from the point of view of strength in service. The study is of a dam with a central, oscillating pivot, which has the role of closing the gates when the downstream water level becomes too high and can thus flood the upstream portion of the river. It starts from a constructive solution initially proposed by the designers, which is then modified in several steps, until a better solution is reached in terms of strength to mechanical stress. This solution is obtained after analyzing several structural scenarios. The final results ensure an excellent behavior of the mechanical stresses, and represent a constructive solution that is easy to achieve and is economically convenient. Full article
(This article belongs to the Special Issue Analysis and Design of Structures and Materials)
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Article
Reliability Analysis of Reinforced Concrete Structure with Shock Absorber Damper under Pseudo-Dynamic Loads
Materials 2022, 15(7), 2688; https://doi.org/10.3390/ma15072688 - 06 Apr 2022
Cited by 3 | Viewed by 511
Abstract
Past historical earthquake events from neighbouring countries have been proven to be disastrous. Building in the aftermath of an earthquake may reduce structural reliability, posing risk upon re-occupation of the building. Shock absorber viscous dampers were installed on a specific structure storey that [...] Read more.
Past historical earthquake events from neighbouring countries have been proven to be disastrous. Building in the aftermath of an earthquake may reduce structural reliability, posing risk upon re-occupation of the building. Shock absorber viscous dampers were installed on a specific structure storey that could reduce the spectral acceleration and storey-drift caused by an earthquake. The research object is a low-rise, three-storey, reinforced concrete (RC) structure. This study aims to identify the dynamic response of the scaled RC structure with and without attached dampers and performs structural reliability of the tested model under the excitation of Peak Ground Acceleration (PGA) of 0.1 g to 1.0 g with a unidirectional shaking table. APIDO viscous dampers were installed parallel to the movement direction of the dynamic load test. The findings show the scaled model with attached viscous dampers reduces spectral acceleration and storey drift by 9.66% and 4.85%, respectively. Findings also show the change of the structural behaviour from single curvature to double curvature due to the increase in seismic structural resistance by viscous dampers. The breakthrough of this research shows that structural reliability analysis performed by the Weibull distribution function has a base shear capacity increment of 1.29% and 6.90% in seismic performance level Life Safety (LS) and Collapse Prevention (CP), respectively. The novelty of this case study building with dampers managed to increase the building’s base shear and roof shear capacity by 6.90% and 16% compared to the building without dampers under dynamic load excitation. Full article
(This article belongs to the Special Issue Recyclable Materials for Ecofriendly Technology)
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Review
Analysis of the Usability of Iron Ore Ultra-Fines for Hydrogen-Based Fluidized Bed Direct Reduction—A Review
Materials 2022, 15(7), 2687; https://doi.org/10.3390/ma15072687 - 06 Apr 2022
Viewed by 640
Abstract
This review focuses on the usability of iron ore ultra-fines for hydrogen-based direct reduction. Such technology is driven by the need to lower CO2 emissions and energy consumption for the iron and steel industry. In addition, low operational and capital expenditures and [...] Read more.
This review focuses on the usability of iron ore ultra-fines for hydrogen-based direct reduction. Such technology is driven by the need to lower CO2 emissions and energy consumption for the iron and steel industry. In addition, low operational and capital expenditures and a high oxide yield because of the direct use of ultra-fines can be highlighted. The classification of powders for a fluidized bed are reviewed. Fluid dynamics, such as minimum fluidization velocity, entrainment velocity and fluidized state diagrams are summarized and discussed regarding the processing of iron ore ultra-fines in a fluidized bed. The influence of the reduction process, especially the agglomeration phenomenon sticking, is evaluated. Thus, the sticking determining factors and the solutions to avoid sticking are reviewed and discussed. The essential theoretical considerations and process-relevant issues are provided for the usability of iron ore ultra-fines for hydrogen-based fluidized bed direct reduction. Full article
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Article
Microstructures and Mechanical Properties of H13 Tool Steel Fabricated by Selective Laser Melting
Materials 2022, 15(7), 2686; https://doi.org/10.3390/ma15072686 - 06 Apr 2022
Viewed by 594
Abstract
H13 stool steel processed by selective laser melting (SLM) suffered from severe brittleness and scatter distribution of mechanical properties. We optimized the mechanical response of as-SLMed H13 by tailoring the optimisation of process parameters and established the correlation between microstructure and mechanical properties [...] Read more.
H13 stool steel processed by selective laser melting (SLM) suffered from severe brittleness and scatter distribution of mechanical properties. We optimized the mechanical response of as-SLMed H13 by tailoring the optimisation of process parameters and established the correlation between microstructure and mechanical properties in this work. Microstructures were examined using XRD, SEM, EBSD and TEM. The results showed that the microstructures were predominantly featured by cellular structures and columnar grains, which consisted of lath martensite and retained austenite with numerous nanoscale carbides being distributed at and within sub-grain boundaries. The average size of cellular structure was ~500 nm and Cr and Mo element were enriched toward the cell wall of each cellular structure. The as-SLMed H13 offered the yield strength (YS) of 1468 MPa, the ultimate tensile strength (UTS) of 1837 MPa and the fracture strain of 8.48%. The excellent strength-ductility synergy can be attributed to the refined hierarchical microstructures with fine grains, the unique cellular structures and the presence of dislocations. In addition, the enrichment of solute elements along cellular walls and carbides at sub-grain boundaries improve the grain boundary strengthening. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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Article
Study on Dissolution and Modification of Cotton Fiber in Different Growth Stages
Materials 2022, 15(7), 2685; https://doi.org/10.3390/ma15072685 - 06 Apr 2022
Viewed by 494
Abstract
Cotton fibers with ultra-high purity cellulose are ideal raw materials for producing nanocellulose. However, the strong hydrogen bond and high crystallinity of cotton fibers affect the dissociation of cotton fibers to prepare nanocellulose. The structures of two kinds of cotton fibers (CM and [...] Read more.
Cotton fibers with ultra-high purity cellulose are ideal raw materials for producing nanocellulose. However, the strong hydrogen bond and high crystallinity of cotton fibers affect the dissociation of cotton fibers to prepare nanocellulose. The structures of two kinds of cotton fibers (CM and XM) in different growth stages from 10 to 50 days post-anthesis (dpa) were studied by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). In the process of cotton fiber growth, the deposition rate of cellulose macromolecules firstly increased and then stabilized. Then, the surface morphology, the chemical composition, and the crystal structure of the nanocellulose prepared from cotton fibers with different growth stages by deep eutectic solvent, a green solvent, were characterized by Transmission Electron Microscope (TEM), scanning electron microscopy (SEM) analysis, XRD, and Thermo Gravimetry (TG). The growth time of cotton fibers affected the properties of prepared nanocellulose, and nanocellulose obtained from cotton fibers at about 30 dpa had less energy consumption, higher yield, and milder reaction conditions. Full article
(This article belongs to the Special Issue Preparation and Application of Biomass-Based Nanocellulose)
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Article
Mineralogical and Technological Characterization of Zeolites from Basin and Range as Pozzolanic Addition of Cement
Materials 2022, 15(7), 2684; https://doi.org/10.3390/ma15072684 - 06 Apr 2022
Cited by 2 | Viewed by 507
Abstract
The present paper assesses petrographic, mineralogical, chemical, and technological features of different zeolitic tuff samples from various western USA districts of the Basin and Range Province containing mainly erionite, mordenite, clinoptilolite/heulandite and phillipsite. The aim of this characterization is to evaluate the pozzolanic [...] Read more.
The present paper assesses petrographic, mineralogical, chemical, and technological features of different zeolitic tuff samples from various western USA districts of the Basin and Range Province containing mainly erionite, mordenite, clinoptilolite/heulandite and phillipsite. The aim of this characterization is to evaluate the pozzolanic activity of these samples according to European normative UNI-EN 196/5 (Fratini test) to program a possible use as addition for blended cements. Petrographic and mineralogical results show that the two phillipsite-bearing tuffs have a higher theoretical Cation Exchange Capacity (CEC) than the other samples; technological characterization shows a pozzolanic behavior for all the samples but higher for the tuff samples containing phillipsite, which shows a higher reactivity with CaO. All the samples could be thus advantageously employed for the preparation of blended cements, potentially reducing CO2 emissions by 70–90%. Full article
(This article belongs to the Special Issue Zeolitic Materials: Structure, Properties, and Applications)
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Review
Microplastics in Wastewater by Washing Polyester Fabrics
Materials 2022, 15(7), 2683; https://doi.org/10.3390/ma15072683 - 06 Apr 2022
Cited by 2 | Viewed by 1267
Abstract
Microplastics have become one of the most serious environmental hazards today, raising fears that concentrations will continue to rise even further in the near future. Micro/nanoparticles are formed when plastic breaks down into tiny fragments due to mechanical or photochemical processes. Microplastics are [...] Read more.
Microplastics have become one of the most serious environmental hazards today, raising fears that concentrations will continue to rise even further in the near future. Micro/nanoparticles are formed when plastic breaks down into tiny fragments due to mechanical or photochemical processes. Microplastics are everywhere, and they have a strong tendency to interact with the ecosystem, putting biogenic fauna and flora at risk. Polyester (PET) and polyamide (PA) are two of the most important synthetic fibres, accounting for about 60% of the total world fibre production. Synthetic fabrics are now widely used for clothing, carpets, and a variety of other products. During the manufacturing or cleaning process, synthetic textiles have the potential to release microplastics into the environment. The focus of this paper is to explore the main potential sources of microplastic pollution in the environment, providing an overview of washable polyester materials. Full article
(This article belongs to the Special Issue Advanced Materials for Clothing and Textile Engineering)
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Article
Influence of Multiple Factors on the Workability and Early Strength Development of Alkali-Activated Fly Ash and Slag-Based Geopolymer-Stabilized Soil
Materials 2022, 15(7), 2682; https://doi.org/10.3390/ma15072682 - 06 Apr 2022
Viewed by 555
Abstract
The complexity of composite geopolymer materials results in instability in the setting and hardening of geopolymer-stabilized soil. In order to determine the appropriate mix proportion scheme for composite geopolymer-stabilized soil, this study investigated the effects of two preparation methods, fly ash/slag ratio and [...] Read more.
The complexity of composite geopolymer materials results in instability in the setting and hardening of geopolymer-stabilized soil. In order to determine the appropriate mix proportion scheme for composite geopolymer-stabilized soil, this study investigated the effects of two preparation methods, fly ash/slag ratio and alkali activator modulus, on workability and strength development trends in alkali-excited fly ash and slag-based geopolymer-stabilized soil. The results showed that the high ambient temperatures created by the one-step method were more conducive to the setting and hardening of the geopolymer-stabilized soil; its 3 d/28 d UCS (unconfined compression strength) ratio was 62.43–78.60%, and its 7 d/28 d UCS ratio was 70.37–83.63%. With increases of the alkali activator modulus or the proportion of fly ash, the setting time of stabilized soil was gradually prolonged, and its fluidity increased. Meanwhile, the strength development of stabilized soil was significantly affected by the proportion of fly ash and the alkali activator modulus; the maximum UCS value was obtained at II-2-O, prepared by the one-step method, with an alkali activator modulus of 1.2 and a fly ash/slag ratio of 20/80. Specifically, the 3, 7, and 28 d UCS values of II-2-O were 1.65, 1.89, and 2.26 MPa, respectively, and its 3 d/28 d UCS ratio and 7 d/28 d UCS ratio were 73.01% and 83.63%, respectively. These results will be of great importance in further research on (and construction guidance of) composite geopolymer-stabilized soil. Full article
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Article
Combining the Finite Element Analysis and Kriging Model for Study on Laser Surface Hardening Parameters of Pitch Bearing Raceway
Materials 2022, 15(7), 2681; https://doi.org/10.3390/ma15072681 - 06 Apr 2022
Viewed by 495
Abstract
Laser surface hardening is used to improve the fatigue performance of the large diameter pitch bearing. Determination of the process parameters by a trial and error method, depending on the experience of the technician, by changing the parameters repeatedly for each laser surface [...] Read more.
Laser surface hardening is used to improve the fatigue performance of the large diameter pitch bearing. Determination of the process parameters by a trial and error method, depending on the experience of the technician, by changing the parameters repeatedly for each laser surface hardening process is time-consuming and costly. In this paper, a method of analyzing the maximum temperature and depth of a hardened layer during the laser surface hardening process for a pitch bearing raceway of a wind turbine is proposed, which combines finite element simulation and the Kriging model. A three-dimensional finite element model of a pitch bearing ring was established using ABAQUS. The temperature field analysis was performed. The effects of process parameters including laser power, scanning speed, and laser spot radius on the depth of the hardening layer were investigated. Then, taking into account the interactional effects of different process parameters, Kriging models were constructed to reflect the relationship between input process parameters and output responses. The results show that the Kriging approximation model has a small relative error compared with the simulated results and can be used to predict the hardened layer depth. Full article
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Article
The Influences of Soluble Phosphorus on Hydration Process and Mechanical Properties of Hemihydrate Gypsum under Deep Retarding Condition
Materials 2022, 15(7), 2680; https://doi.org/10.3390/ma15072680 - 05 Apr 2022
Cited by 1 | Viewed by 634
Abstract
Phospho-gypsum is an industrial solid waste discharged from the phosphate production process. The waste includes complex impurities such as phosphoric acid and its salts, fluoride, and organics. Usually, retarders are mixed in gypsum-based building materials to extend setting time. Although the effects of [...] Read more.
Phospho-gypsum is an industrial solid waste discharged from the phosphate production process. The waste includes complex impurities such as phosphoric acid and its salts, fluoride, and organics. Usually, retarders are mixed in gypsum-based building materials to extend setting time. Although the effects of the impurities on hydration properties and the mechanical strength of calcined gypsum have been analyzed, the impact and mechanism of soluble phosphorus on the phospho-gypsum under retardation is yet to be defined. In this study, we employed thermogravimetry (TG), X-ray diffraction (XRD) and scanning electron microscopy (SEM) to evaluate the hydration kinetics, phase transformation, structure, and morphology of the calcined gypsum. The data showed that the retarder or soluble phosphorus prolonged the setting time. A single retarder considerably shortened the initial setting time from 95 min to 60 min, even at the lowest dosage of 0.1 wt.% soluble phosphorus. In addition, drying flexural and compressive strengths were markedly decreased. On the other hand, the induction period was advanced with extension of acceleration and deceleration stage. SEM results indicated that the crystal morphology of the gypsum changed from a long to short column or block. An EDS analysis showed that phosphates were concentrated on the surface of gypsum crystals. Full article
(This article belongs to the Section Construction and Building Materials)
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Article
Potential of Commercial Wood-Based Materials as PCB Substrate
Materials 2022, 15(7), 2679; https://doi.org/10.3390/ma15072679 - 05 Apr 2022
Cited by 2 | Viewed by 757
Abstract
In our research on sustainable solutions for printed electronics, we are moving towards renewable materials in applications, which can be very challenging from the performance perspective, such as printed circuit boards (PCB). In this article, we examine the potential suitability of wood-based materials, [...] Read more.
In our research on sustainable solutions for printed electronics, we are moving towards renewable materials in applications, which can be very challenging from the performance perspective, such as printed circuit boards (PCB). In this article, we examine the potential suitability of wood-based materials, such as cardboard and veneer, as substrate materials for biodegradable solutions instead of the commonly used glass-fiber reinforced epoxy. Our substrate materials were coated with fire retardant materials for improved fire resistance and screen printed with conductive silver ink. The print quality, electrical conductivity, fire performance and biodegradation were evaluated. It was concluded that if the PCB application allows manufacturing using screen printing instead of an etching process, there is the potential for these materials to act as substrates in, e.g., environmental analytics applications. Full article
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Article
Matrix Metamaterial Shielding Design for Wireless Power Transfer to Control the Magnetic Field
Materials 2022, 15(7), 2678; https://doi.org/10.3390/ma15072678 - 05 Apr 2022
Viewed by 550
Abstract
A wireless power transfer (WPT) system can bring convenience to human life, while a leakage magnetic field around the system can be harmful to humans or the environment. Due to application limitations of aluminum and ferrite materials, it is urgent to find a [...] Read more.
A wireless power transfer (WPT) system can bring convenience to human life, while a leakage magnetic field around the system can be harmful to humans or the environment. Due to application limitations of aluminum and ferrite materials, it is urgent to find a new type of shielding material. This paper first proposes a detailed model and analysis method of the matrix shielding metamaterial (MSM), which is applied to the low-frequency WPT system in an electric vehicle (EV). The MSM is placed on the top and side of the EV system to shield the magnetic field from all positions. To explore its function, a theoretical analysis of the MSM is proposed to prove the shielding performance. The simulation modeling and the design procedure of the MSM are introduced. Moreover, the prototype model of the WPT system with the MSM is established. The experimental results indicate that the magnetic field is controlled when the MSM is applied on the top or side of the EV-WPT system. The proposed MSM has been successfully proven to effectively shield the leakage magnetic field in the WPT system, which is suitable for the kHz range frequency. Full article
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Article
Dual Electrorheological and Magnetorheological Behaviors of Poly(N-methyl aniline) Coated ZnFe2O4 Composite Particles
Materials 2022, 15(7), 2677; https://doi.org/10.3390/ma15072677 - 05 Apr 2022
Viewed by 585
Abstract
Magnetic/conducting polymeric hybrid core-shell typed zinc ferrite (ZnFe2O4)/poly(N-methyl aniline) (PMA) particles were fabricated and adopted as electrorheological (ER) and magnetorheological (MR) fluids, and their rheological properties were examined. Solvo-thermally synthesized ZnFe2O4 was coated with a conducting [...] Read more.
Magnetic/conducting polymeric hybrid core-shell typed zinc ferrite (ZnFe2O4)/poly(N-methyl aniline) (PMA) particles were fabricated and adopted as electrorheological (ER) and magnetorheological (MR) fluids, and their rheological properties were examined. Solvo-thermally synthesized ZnFe2O4 was coated with a conducting PMA through chemical oxidation polymerization. The size, shape, and chemical composition of the final core-shell shaped particles were scrutinized by scanning electron microscopy, transmission electron microscopy, and Fourier transform-infrared spectroscopy. The crystal faces of the particles before and after coating with PMA were analyzed by X-ray diffraction. The ZnFe2O4/PMA products were suspended in silicone oil to investigate the rheological response to electro- or magnetic stimuli using a rotating rheometer. The shear stresses were analyzed using the CCJ equation. The dynamic yield stress curve was suitable for the conductivity mechanism with a slope of 1.5. When magnetic fields of various intensities were applied, the flow curve was analyzed using the Hershel–Bulkley equation, and the yield stresses had a slope of 1.5. Optical microscopy further showed that the particles dispersed in insulating medium form chain structures under electric and magnetic fields. Via this core-shell fabrication process, not only spherical conducting particles were obtained but also their dual ER and MR responses were demonstrated for their wide potential applications. Full article
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Article
Residual Stresses Measurements in Laser Powder Bed Fusion Using Barkhausen Noise Analysis
Materials 2022, 15(7), 2676; https://doi.org/10.3390/ma15072676 - 05 Apr 2022
Viewed by 698
Abstract
In recent years, the advancement of technology brought the laser powder bed fusion process to its industrialisation step. Despite all the advancements in process repeatability and general quality control, many challenges remain unsolved due to the intrinsic difficulties of the process, notably the [...] Read more.
In recent years, the advancement of technology brought the laser powder bed fusion process to its industrialisation step. Despite all the advancements in process repeatability and general quality control, many challenges remain unsolved due to the intrinsic difficulties of the process, notably the residual stresses issue. This work aimed to assess the usability of Barkhausen noise analysis (BNA) for the residual stress in situ monitoring of laser powder bed fusion on Maraging steel 300 (18Ni-300/1.2709). After measuring the evolution of grain size distribution over process parameter changes, two series of experiments were designed. First, a setup with an external force allows to validate the working principle of BNA on the chosen material processed using LPBF. The second experiment uses on-plates samples with different residual stress states. The results show a good stability in microstructure, a prerequisite for BNA. In addition, the external load setup acknowledges that signal variation correlates with the induced stress state. Finally, the on-plate measurement shows a similar signal variation to what has been observed in the literature for residual stress variation. It is shown that BNA is a suitable method for qualitative residual stresses variation monitoring developed during the LPBF process and underlines that BNA is a promising candidate as an in situ measurement method. Full article
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Article
Evaluating the Effect of Rail Fastener Failure on Dynamic Responses of Train-Ballasted Track-Subgrade Coupling System for Smart Track Condition Assessment
Materials 2022, 15(7), 2675; https://doi.org/10.3390/ma15072675 - 05 Apr 2022
Viewed by 617
Abstract
Rail fasteners are among the key components of ballasted track of high-speed railway due to their functionality of fixing rails to sleepers. The failure of rail fastening system hinders the transmission of train loads to underlying track substructure and therefore endangers the operation [...] Read more.
Rail fasteners are among the key components of ballasted track of high-speed railway due to their functionality of fixing rails to sleepers. The failure of rail fastening system hinders the transmission of train loads to underlying track substructure and therefore endangers the operation safety and longevity of ballasted track. This paper first established a three-dimensional (3D) numerical model of the train-ballasted track-subgrade coupling system by integrating multibody dynamics (MBD) and finite element method (FEM). Numerical simulations were then performed to investigate the effects of different patterns of rail fastener failure (i.e., consecutive single-side, alternate single-side, and consecutive double-side) on critical dynamic responses of track structures, train running stability, and operation safety. The results show that the resulting influences of different patterns of rail fastener failure descend in the order of consecutive double-side failure, consecutive single-side failure, and alternate single-side failure. As the number of failed fasteners increases, the range where dynamic responses of track structures are influenced extends, and the failure of two consecutive single-side fasteners exerts a similar influence as that of four alternate single-side fasteners. The failure of single-side fasteners affects dynamic responses of the intact side of track structures relatively insignificantly. The influence of rail fastener failure on track structures exhibits hysteresis, thus indicating that special attention needs to be paid to locations behind failed fasteners during track inspection and maintenance. The occurrence of the failure of two or more consecutive fasteners demands timely maintenance work in order to prevent aggravated deterioration of track structures. The findings of this study could provide useful reference and guidance to smart track condition assessment and condition-based track maintenance. Full article
(This article belongs to the Special Issue Smart Materials: Next Generation in Science and Technology)
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