Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
5.8
3.1
Journals
Materials
Editor’s Choice
materials-logo

Journal Menu

► Journal Menu

Journal Browser

► Journal Browser
share announcement

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.

Order results
Result details
Results per page
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
13 pages, 1684 KiB  
Article
Facile Synthesis of Platinum Nanoparticle-Embedded Reduced Graphene Oxide for the Detection of Carbendazim
by Suthira Pushparajah, Shinichi Hasegawa, Tien Song Hiep Pham, Mahnaz Shafiei and Aimin Yu
Materials 2023, 16(24), 7622; https://doi.org/10.3390/ma16247622 - 13 Dec 2023
Cited by 1 | Viewed by 1175
Abstract
In recent years, there has been a significant interest in the advancement of electrochemical sensing platforms to detect pesticides with high sensitivity and selectivity. Current research presents a novel approach utilising platinum nanoparticles (NPs) and reduced graphene oxide deposited on a glassy carbon [...] Read more.
In recent years, there has been a significant interest in the advancement of electrochemical sensing platforms to detect pesticides with high sensitivity and selectivity. Current research presents a novel approach utilising platinum nanoparticles (NPs) and reduced graphene oxide deposited on a glassy carbon electrode (Pt-rGO/GCE) for direct electrochemical measurement of carbendazim (CBZ). A straightforward one-step electrodeposition process was applied to prepare the Pt-rGO sensing platform. The incorporation of conductive rGO nanosheets along with distinctive structured Pt NPs significantly enhanced the effective electrode surface area and electron transfer of CBZ. Additionally, when exposed to 50 µM CBZ, Pt-rGO/GCE exhibited a higher current response compared to the bare electrode. Further investigations were performed to analyse and optimise the experimental parameters that could influence pesticide detection. Under the optimised conditions of pH 7 and 5 min of accumulation time, the Pt-rGO/GCE sensor showed a linear concentration detection range from 0.1 µM to 50 µM, with a detection limit of 3.46 nM. The fabricated sensor was successfully employed for CBZ detection in milk and tap water with 98.88% and 98.57% recovery, respectively. The fabricated sensor showed higher sensitivity and reproducibility, thus indicating the potential of this technology in the development of reliable sensors for the detection of CBZ or similar pesticides in forthcoming applications. Full article
(This article belongs to the Special Issue Applications of Advanced Nanomaterials in Sensor Devices)
►▼ Show Figures

Figure 1

19 pages, 2026 KiB  
Article
Metal Organic Frameworks: Current State and Analysis of Their Use as Modifiers of the Vulcanization Process and Properties of Rubber
by Katarzyna Klajn, Tomasz Gozdek and Dariusz M. Bieliński
Materials 2023, 16(24), 7631; https://doi.org/10.3390/ma16247631 - 13 Dec 2023
Cited by 3 | Viewed by 1438
Abstract
The interest in and application of metal organic frameworks (MOF) is increasing every year. These substances are widely used in many places, including the separation and storage of gases and energy, catalysis, electrochemistry, optoelectronics, and medicine. Their use in polymer technology is also [...] Read more.
The interest in and application of metal organic frameworks (MOF) is increasing every year. These substances are widely used in many places, including the separation and storage of gases and energy, catalysis, electrochemistry, optoelectronics, and medicine. Their use in polymer technology is also increasing, focusing mainly on the synthesis of MOF-polymer hybrid compounds. Due to the presence of metal ions in their structure, they can also serve as a component of the crosslinking system used for curing elastomers. This article presents the possibility of using zeolitic imidazolate framework ZIF-8 or MOF-5 as activators for sulfur vulcanization of styrene-butadiene rubber (SBR), replacing zinc oxide in conventional (CV) or effective (EF) curing systems to different extents. Their participation in the curing process and influence on the crosslinking density and structure, as well as the mechanical and thermal properties of the rubber vulcanizates, were examined. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
►▼ Show Figures

Figure 1

18 pages, 12761 KiB  
Article
Preparation and Characterization of Modified ZrO2/SiO2/Silicone-Modified Acrylic Emulsion Superhydrophobic Coating
by Jiaxin Ben, Peipei Wu, Yancheng Wang, Jie Liu and Yali Luo
Materials 2023, 16(24), 7621; https://doi.org/10.3390/ma16247621 - 13 Dec 2023
Cited by 2 | Viewed by 1794
Abstract
Superhydrophobic coatings have increasingly become the focal point of research due to their distinctive properties like water resistance, wear resistance, and acid-base resilience. In pursuit of maximizing their efficiency, research has primarily revolved around refining the fabrication process and the composition of emulsion/nanoparticle [...] Read more.
Superhydrophobic coatings have increasingly become the focal point of research due to their distinctive properties like water resistance, wear resistance, and acid-base resilience. In pursuit of maximizing their efficiency, research has primarily revolved around refining the fabrication process and the composition of emulsion/nanoparticle coatings. We innovatively devised a superhydrophobic coating by employing a spraying technique. This involved integrating a γ-Methacryloyloxypropyltrimethoxysilane (KH570)-modified ZrO2/SiO2/silicone-modified acrylic emulsion. A comprehensive evaluation of this coating was undertaken using analytical instruments such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and confocal laser scanning microscopy (CLSM). The coating demonstrated exceptional performance across a range of tests, including wear, immersion, and anti-icing cleaning, showcasing notable wear resistance, sodium chloride corrosion resistance, self-cleaning efficiency, and thermal stability. In particular, one coating exhibited super-hydrophobic properties, with a high contact angle of 158.5 degrees and an impressively low rolling angle of 1.85 degrees. This remarkable combination of properties is attributed to the judicious selection of components, which significantly reinforced the mechanical strength of the coating. These enhancements make it highly suitable for industrial applications where self-cleaning, anti-icing, and anti-contamination capabilities are critical. Full article
(This article belongs to the Section Thin Films and Interfaces)
►▼ Show Figures

Figure 1

15 pages, 5584 KiB  
Article
Multi-Order Asymmetric Acoustic Metamaterials with Broad Bandgaps at Subwavelength Scales
by Xiaopeng Wang, Wenjiong Chen and Sheng Li
Materials 2023, 16(24), 7587; https://doi.org/10.3390/ma16247587 - 10 Dec 2023
Viewed by 1129
Abstract
Noise manipulation at the subwavelength scale remains a challenging problem. To obtain better broadband sound isolation within the subwavelength range, a class of asymmetric acoustic metamaterials (AAMs) based on rotation is proposed, and this class of AAMs can further improve subwavelength sound isolation [...] Read more.
Noise manipulation at the subwavelength scale remains a challenging problem. To obtain better broadband sound isolation within the subwavelength range, a class of asymmetric acoustic metamaterials (AAMs) based on rotation is proposed, and this class of AAMs can further improve subwavelength sound isolation performance by introducing multi-orders. The influences of changing the alternate propagation length of the coiled channel and the square cavity in the unit cell on the band frequency distribution and the omnidirectional band structure were investigated. The effective parameters are calculated with the S-parameter retrieval method, and the generation and change mechanisms of the bandgaps were elucidated. The calculation of sound transmission characteristics showed that, in the asymmetric mode, the overall sound isolation performance of the structure was greatly improved, and the relative bandwidth expanded as the alternate propagation length of the coiled channel and square cavity increased. The omnidirectional bandgaps from the first-order to the third-order AAMs occupied 63.6%, 75.96%, and 76.84% of the subwavelength range, respectively. In particular, the first bandgap moves to the low frequency and becomes wider. Both the experimental results and numerical analyses consistently showed that disrupting structural symmetry enhances acoustic metamaterials for superior broadband sound isolation, inspiring broader applications for asymmetry in this field. Full article
(This article belongs to the Section Materials Simulation and Design)
►▼ Show Figures

Figure 1

29 pages, 26002 KiB  
Article
Effective Mechanical Properties of Periodic Cellular Solids with Generic Bravais Lattice Symmetry via Asymptotic Homogenization
by Padmassun Rajakareyar, Mostafa S. A. ElSayed, Hamza Abo El Ella and Edgar Matida
Materials 2023, 16(24), 7562; https://doi.org/10.3390/ma16247562 - 8 Dec 2023
Cited by 1 | Viewed by 1176
Abstract
In this paper, the scope of discrete asymptotic homogenization employing voxel (cartesian) mesh discretization is expanded to estimate high fidelity effective properties of any periodic heterogeneous media with arbitrary Bravais’s lattice symmetry, including those with non-orthogonal periodic bases. A framework was developed in [...] Read more.
In this paper, the scope of discrete asymptotic homogenization employing voxel (cartesian) mesh discretization is expanded to estimate high fidelity effective properties of any periodic heterogeneous media with arbitrary Bravais’s lattice symmetry, including those with non-orthogonal periodic bases. A framework was developed in Python with a proposed fast–nearest neighbour algorithm to accurately estimate the periodic boundary conditions of the discretized representative volume element of the lattice unit cell. Convergence studies are performed, and numerical errors caused by both voxel meshing and periodic boundary condition approximation processes are discussed in detail. It is found that the numerical error in periodicity approximation is cyclically dependent on the number of divisions performed during the meshing process and, thus, is minimized with a refined voxel mesh. Validation studies are performed by comparing the elastic properties of 2D hexagon lattices with orthogonal and non-orthogonal bases. The developed methodology was also applied to derive the effective properties of several lattice topologies, and variation of their anisotropic macroscopic properties with relative densities is presented as material selection charts. Full article
(This article belongs to the Special Issue Characterizations, Mechanical Properties and Constitutive Modeling of Advanced Materials)
►▼ Show Figures

Figure 1

22 pages, 3811 KiB  
Article
Photocatalyst Based on Nanostructured TiO2 with Improved Photocatalytic and Antibacterial Properties
by Roberta Irodia, Camelia Ungureanu, Veronica Sătulu and Vasilica Mihaela Mîndroiu
Materials 2023, 16(24), 7509; https://doi.org/10.3390/ma16247509 - 5 Dec 2023
Cited by 1 | Viewed by 1198
Abstract
This study shows an easy way to use electrochemistry and plasma layering to make Cobalt-Blue-TiO2 nanotubes that are better at catalysing reactions. Once a titanium plate has been anodized, certain steps are taken to make oxygen vacancies appear inside the TiO2 [...] Read more.
This study shows an easy way to use electrochemistry and plasma layering to make Cobalt-Blue-TiO2 nanotubes that are better at catalysing reactions. Once a titanium plate has been anodized, certain steps are taken to make oxygen vacancies appear inside the TiO2 nanostructures. To find out how the Co deposition method changed the final catalyst’s properties, it was put through electrochemical tests (to find the charge transfer resistance and flat band potential) and optical tests (to find the band gap and Urbach energy). The catalysts were also described in terms of their shape, ability to stick to surfaces, and ability to inhibit bacteria. When Cobalt was electrochemically deposited to Blue-TiO2 nanotubes, a film with star-shaped structures was made that was hydrophilic and antibacterial. The band gap energy went down from 3.04 eV to 2.88 eV and the Urbach energy went up from 1.171 eV to 3.836 eV using this electrochemical deposition method. Also, photodegradation tests with artificial doxycycline (DOX) water were carried out to see how useful the study results would be in real life. These extra experiments were meant to show how the research results could be used in real life and what benefits they might have. For the bacterial tests, both gram-positive and gram-negative bacteria were used, and BT/Co-E showed the best response. Additionally, photodegradation and photoelectrodegradation experiments using artificial doxycycline (DOX) water were conducted to determine the practical relevance of the research findings. The synergistic combination of light and applied potential leads to 70% DOX degradation after 60 min of BT/Co-E irradiation. Full article
(This article belongs to the Special Issue Novel Green Nanotechnologies Applied in Environmental Protection and Health)
►▼ Show Figures

Figure 1

14 pages, 8347 KiB  
Article
Wire Electrochemical Etching of Superhydrophobic Nickel Surfaces with Enhanced Corrosion Protection
by Binghan Wu, Defeng Yan, Junyi Lin and Jinlong Song
Materials 2023, 16(23), 7472; https://doi.org/10.3390/ma16237472 - 1 Dec 2023
Cited by 9 | Viewed by 1295
Abstract
Superhydrophobic nickel surfaces have significant advantages in the field of corrosion protection compared with traditional nickel corrosion protection methods which need a toxic chemical corrosion inhibitor. Electrochemical etching, an ideal method for fabricating superhydrophobic nickel surfaces, was also limited by low current density, [...] Read more.
Superhydrophobic nickel surfaces have significant advantages in the field of corrosion protection compared with traditional nickel corrosion protection methods which need a toxic chemical corrosion inhibitor. Electrochemical etching, an ideal method for fabricating superhydrophobic nickel surfaces, was also limited by low current density, resulting in low processing efficiency. To overcome this limitation, we proposed a new method to fabricate a superhydrophobic nickel surface using a wire electrochemical etching method. The wire electrochemical etching method accomplished the etching process by sweeping a controlled wire cathode across the surface of the anode nickel plate in an environmentally friendly neutral electrolyte, NaCl. The superhydrophobic nickel sample with a contact angle of 153° and a rolling angle of 10° could be fabricated by wire electrochemical etching and modification. Additionally, the optimal parameters of the wire electrochemical etching and the principle of superhydrophobic surface formation had also been systematically investigated, respectively. Moreover, the superhydrophobic nickel surface had self-cleaning performance, antifouling performance, corrosion protection, and abrasion resistance. Wire electrochemical etching improves the current density of processing, which means that this method improves the processing efficiency for fabricating a superhydrophobic nickel surface. This work is expected to enrich the theory and technology for fabricating superhydrophobic nickel surfaces to improve the corrosion protection of nickel. Full article
(This article belongs to the Special Issue Recent Progress in Corrosion Protection and Electrochemical Characterization of New and Advanced Materials)
►▼ Show Figures

Figure 1

18 pages, 19065 KiB  
Article
Optical and Structural Properties of Aluminum Nitride Epi-Films at Room and High Temperature
by Yanlian Yang, Yao Liu, Lianshan Wang, Shuping Zhang, Haixia Lu, Yi Peng, Wenwang Wei, Jia Yang, Zhe Chuan Feng, Lingyu Wan, Benjamin Klein, Ian T. Ferguson and Wenhong Sun
Materials 2023, 16(23), 7442; https://doi.org/10.3390/ma16237442 - 30 Nov 2023
Cited by 3 | Viewed by 1530
Abstract
The high-quality aluminum nitride (AlN) epilayer is the key factor that directly affects the performance of semiconductor deep-ultraviolet (DUV) photoelectronic devices. In this work, to investigate the influence of thickness on the quality of the AlN epilayer, two AlN-thick epi-film samples were grown [...] Read more.
The high-quality aluminum nitride (AlN) epilayer is the key factor that directly affects the performance of semiconductor deep-ultraviolet (DUV) photoelectronic devices. In this work, to investigate the influence of thickness on the quality of the AlN epilayer, two AlN-thick epi-film samples were grown on c-plane sapphire substrates. The optical and structural characteristics of AlN films are meticulously examined by using high-resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), a dual-beam ultraviolet-visible spectrophotometer, and spectroscopic ellipsometry (SE). It has been found that the quality of AlN can be controlled by adjusting the AlN film thickness. The phenomenon, in which the thicker AlNn film exhibits lower dislocations than the thinner one, demonstrates that thick AlN epitaxial samples can work as a strain relief layer and, in the meantime, help significantly bend the dislocations and decrease total dislocation density with the thicker epi-film. The Urbach’s binding energy and optical bandgap (Eg) derived by optical transmission (OT) and SE depend on crystallite size, crystalline alignment, and film thickness, which are in good agreement with XRD and SEM results. It is concluded that under the treatment of thickening film, the essence of crystal quality is improved. The bandgap energies of AlN samples obtained from SE possess larger values and higher accuracy than those extracted from OT. The Bose–Einstein relation is used to demonstrate the bandgap variation with temperature, and it is indicated that the thermal stability of bandgap energy can be improved with an increase in film thickness. It is revealed that when the thickness increases to micrometer order, the thickness has little effect on the change of Eg with temperature. Full article
(This article belongs to the Special Issue Chemical Vapor Deposition (CVD) Techniques in Materials Science for Electronic Devices Applications)
►▼ Show Figures

Figure 1

23 pages, 8459 KiB  
Review
Structural Relaxation, Rejuvenation and Plasticity of Metallic Glasses: Microscopic Details from Anelastic Relaxation Spectra
by Michael Atzmon, Jong Doo Ju and Tianjiao Lei
Materials 2023, 16(23), 7444; https://doi.org/10.3390/ma16237444 - 30 Nov 2023
Cited by 4 | Viewed by 1401
Abstract
The lack of periodicity and long-range order poses significant challenges in explaining and modeling the properties of metallic glasses. Conventional modeling of nonexponential relaxation with stretched exponents leads to inconsistencies and rarely offers information on microscopic properties. Instead, using quasi-static anelastic relaxation, we [...] Read more.
The lack of periodicity and long-range order poses significant challenges in explaining and modeling the properties of metallic glasses. Conventional modeling of nonexponential relaxation with stretched exponents leads to inconsistencies and rarely offers information on microscopic properties. Instead, using quasi-static anelastic relaxation, we have obtained relaxation-time spectra over >10 orders of magnitude of time for several metallic glasses. The spectra enable us to examine in microscopic detail the distribution of shear transformation zones and their properties. They reveal an atomically-quantized hierarchy of shear transformation zones, providing insights into the effect of structural relaxation and rejuvenation, the origin of plasticity and the mechanisms of the alpha and beta relaxation. Full article
(This article belongs to the Special Issue Advances in Glass and Glass-Ceramic Materials)
►▼ Show Figures

Figure 1

21 pages, 4542 KiB  
Review
Poly(ethylene glycol)-Engrafted Graphene Oxide for Gene Delivery and Nucleic Acid Amplification
by Khushbu Chauhan, Jin Woo, Woong Jung and Dong-Eun Kim
Materials 2023, 16(23), 7434; https://doi.org/10.3390/ma16237434 - 29 Nov 2023
Cited by 1 | Viewed by 1578
Abstract
Graphene oxide (GO) is an oxidized form of graphene accommodating various oxygen-containing functional groups such as hydroxyl, epoxy, and carboxyl groups on its surface. GO has been extensively utilized in various biomedical applications including the delivery of biomolecules and the development of biosensors [...] Read more.
Graphene oxide (GO) is an oxidized form of graphene accommodating various oxygen-containing functional groups such as hydroxyl, epoxy, and carboxyl groups on its surface. GO has been extensively utilized in various biomedical applications including the delivery of biomolecules and the development of biosensors owing to its beneficial properties such as high surface area, nucleic acid adsorption, and fluorescence quenching through fluorescence resonance energy transfer (FRET). However, despite these favorable properties, the direct utilization of GO in these applications is often limited by low dispersibility in a physiological medium, cytotoxicity, low biocompatibility, and a strong binding affinity of nucleic acids to GO surface. The large surface area of GO and the presence of various functional groups on its surface make it highly amenable to facile surface modifications, offering scope for GO surface functionalization to overcome these limitations. When polyethylene glycol (PEG), which is a biocompatible polymer, is conjugated to GO, the PEGylated GO enhances the biocompatibility and dispersibility, reduces cytotoxicity, and allows controlled drug delivery with controllable binding affinity towards nucleic acid. PEG-engrafted GO retains the beneficial properties of GO while effectively addressing its limitations, rendering it suitable for various biomedical applications. In this review, we present the recent advancements of PEGylated GO in gene/drug delivery and the facilitation of nucleic acid amplification techniques, which aid in the development of therapeutic and diagnostic tools, respectively. Full article
(This article belongs to the Special Issue Preparation and Application of High-Performance Multifunctional Graphene Macroscopic Assemblies and Composites)
►▼ Show Figures

Figure 1

14 pages, 10632 KiB  
Article
On Impact Damage and Repair of Composite Honeycomb Sandwich Structures
by Hang Zhang, Xiaopei Wang, Zhenhan Guo, Yuan Qian, Yan Shang and Deng’an Cai
Materials 2023, 16(23), 7374; https://doi.org/10.3390/ma16237374 - 27 Nov 2023
Viewed by 1867
Abstract
This study is conducted on glass fiber-reinforced composite honeycomb sandwich structures by introducing delamination damage through low-velocity impact tests, establishing a three-dimensional progressive damage analysis model, and evaluating the delamination damage characteristics and laws of honeycomb sandwich structures under different impact energies through [...] Read more.
This study is conducted on glass fiber-reinforced composite honeycomb sandwich structures by introducing delamination damage through low-velocity impact tests, establishing a three-dimensional progressive damage analysis model, and evaluating the delamination damage characteristics and laws of honeycomb sandwich structures under different impact energies through experiments. Repair techniques and process parameters for delamination damage are explored. It is found that as the impact energy increases, the damage area of honeycomb sandwich panels also increases, and the delamination damage extends from the impact center to the surrounding areas, accompanied by damage such as fiber fracture and matrix cracking. The strength recovery rates of sandwich panels at impact energies of 5 J, 15 J, and 25 J after repair are 71.90%, 65.89%, and 67.10%, respectively, which has a considerable repair effect. In addition, a progressive damage model for low-velocity impact on the composite honeycomb sandwich structure is established, and its accuracy and reliability are verified. Full article
(This article belongs to the Special Issue Advanced Fiber-Reinforced Composites: Design, Properties and Applications)
►▼ Show Figures

Figure 1

13 pages, 4908 KiB  
Article
Fabrication of Yttrium Oxide Hollow Films for Efficient Passive Radiative Cooling
by Heegyeom Jeon, Sohyeon Sung, Jeehoon Yu, Hyun Kim, Yong Seok Kim and Youngjae Yoo
Materials 2023, 16(23), 7373; https://doi.org/10.3390/ma16237373 - 27 Nov 2023
Cited by 1 | Viewed by 1169
Abstract
In recent years, many parts of the world have researched the transition to renewable energy, reducing energy consumption and moving away from fossil fuels. Among the studies to reduce energy consumption, passive radiative cooling can reduce the energy used for building cooling, and [...] Read more.
In recent years, many parts of the world have researched the transition to renewable energy, reducing energy consumption and moving away from fossil fuels. Among the studies to reduce energy consumption, passive radiative cooling can reduce the energy used for building cooling, and to improve this, the optical properties of atmospheric window emissivity and solar reflectance must be increased. In this study, hollow yttrium oxide (H-Y2O3) was fabricated using melamine formaldehyde (MF) as a sacrificial template to improve the optical properties of passive radiative cooling. We then used finite-difference time-domain (FDTD) simulations to predict the optical properties of the fabricated particles. This study compares the properties of MF@Y(OH)CO3 and H-Y2O3 particles derived from the same process. H-Y2O3 was found to have a solar reflectance of 70.73% and an atmospheric window emissivity of 86.24%, and the field tests revealed that the temperature of MF@Y(OH)CO3 was relatively low during the daytime. At night, the temperature of the H-Y2O3 film was found to be 2.6 °C lower than the ambient temperature of 28.8 °C. The optical properties and actual cooling capabilities of the particles at each stage of manufacturing the hollow particles were confirmed and the cooling capabilities were quantified. Full article
(This article belongs to the Special Issue Advanced Electronic Devices for Biomedical Applications)
►▼ Show Figures

Figure 1

20 pages, 1209 KiB  
Article
Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3
by Francesco Cordero, Floriana Craciun, Patrizia Imperatori, Venanzio Raglione, Gloria Zanotti, Antoniu Moldovan and Maria Dinescu
Materials 2023, 16(23), 7323; https://doi.org/10.3390/ma16237323 - 24 Nov 2023
Viewed by 946
Abstract
We measured the anelastic, dielectric and structural properties of the metal-free molecular perovskite (ABX3) (MDABCO)(NH4)I3, which has already been demonstrated to become ferroelectric below TC= 448 K. Both the dielectric permittivity measured in air on [...] Read more.
We measured the anelastic, dielectric and structural properties of the metal-free molecular perovskite (ABX3) (MDABCO)(NH4)I3, which has already been demonstrated to become ferroelectric below TC= 448 K. Both the dielectric permittivity measured in air on discs pressed from powder and the complex Young’s modulus measured on resonating bars in a vacuum show that the material starts to deteriorate with a loss of mass just above TC, introducing defects and markedly lowering TC. The elastic modulus softens by 50% when heating through the initial TC, contrary to usual ferroelectrics, which are stiffer in the paraelectric phase. This is indicative of improper ferroelectricity, in which the primary order parameter of the transition is not the electric polarization, but the orientational order of the MDABCO molecules. The degraded material presents thermally activated relaxation peaks in the elastic energy loss, whose intensities increase together with the decrease in TC. The peaks are much broader than pure Debye due to the general loss of crystallinity. This is also apparent from X-ray diffraction, but their relaxation times have parameters typical of point defects. It is argued that the major defects should be of the Schottky type, mainly due to the loss of (MDABCO)2+ and I−, leaving charge neutrality, and possibly (NH4)+ vacancies. The focus is on an anelastic relaxation process peaked around 200 K at ∼1 kHz, whose relaxation time follows the Arrhenius law with τ0 ∼ 10−13 s and E≃0.4 eV. This peak is attributed to I vacancies (VX) hopping around MDABCO vacancies (VA), and its intensity presents a peculiar dependence on the temperature and content of defects. The phenomenology is thoroughly discussed in terms of lattice disorder introduced by defects and partition of VX among sites that are far from and close to the cation vacancies. A method is proposed for calculating the relative concentrations of VX, that are untrapped, paired with VA or forming VX–VA–VX complexes. Full article
(This article belongs to the Special Issue Piezoelectric, Ferroelectric and Dielectric Properties of Materials and Related Applications)
►▼ Show Figures

Figure 1

39 pages, 8010 KiB  
Review
Advances in Structural and Morphological Characterization of Thin Magnetic Films: A Review
by Payel Aich, Carlo Meneghini and Luca Tortora
Materials 2023, 16(23), 7331; https://doi.org/10.3390/ma16237331 - 24 Nov 2023
Cited by 1 | Viewed by 2289
Abstract
The present review places emphasis on a comprehensive survey of experimental techniques to probe the structural and morphological features at the nanoscale range in thin magnetic films, incorporating those available at in-house laboratories as well as those at state-of-the-art synchrotron radiation facilities. This [...] Read more.
The present review places emphasis on a comprehensive survey of experimental techniques to probe the structural and morphological features at the nanoscale range in thin magnetic films, incorporating those available at in-house laboratories as well as those at state-of-the-art synchrotron radiation facilities. This elucidating the range of available techniques, and the information they can yield represents a step for advancing the understanding of and for unlocking new possibilities in the design and optimization of thin magnetic films across a wide range of applications. Full article
(This article belongs to the Special Issue Growth and Applications of Oxide Thin Films and Heterostructures)
►▼ Show Figures

Figure 1

16 pages, 3301 KiB  
Article
Lignin-Based Mesoporous Hollow Carbon@MnO2 Nanosphere Composite as an Anodic Material for Lithium-Ion Batteries
by Shun Li, Jianguo Huang and Guijin He
Materials 2023, 16(23), 7283; https://doi.org/10.3390/ma16237283 - 23 Nov 2023
Cited by 2 | Viewed by 1405
Abstract
The lignin-based mesoporous hollow carbon@MnO2 nanosphere composites (L-C-NSs@MnO2) were fabricated by using lignosulfonate as the carbon source. The nanostructured MnO2 particles with a diameter of 10~20 nm were uniformly coated onto the surfaces of the [...] Read more.
The lignin-based mesoporous hollow carbon@MnO2 nanosphere composites (L-C-NSs@MnO2) were fabricated by using lignosulfonate as the carbon source. The nanostructured MnO2 particles with a diameter of 10~20 nm were uniformly coated onto the surfaces of the hollow carbon nanospheres. The obtained L-C-NSs@MnO2 nanosphere composite showed a prolonged cycling lifespan and excellent rate performance when utilized as an anode for LIBs. The L-C-NSs@MnO2 nanocomposite (24.6 wt% of MnO2) showed a specific discharge capacity of 478 mAh g−1 after 500 discharge/charge cycles, and the capacity contribution of MnO2 in the L-C-NSs@MnO2 nanocomposite was estimated ca. 1268.8 mAh g−1, corresponding to 103.2% of the theoretical capacity of MnO2 (1230 mAh g−1). Moreover, the capacity degradation rate was ca. 0.026% per cycle after long-term and high-rate Li+ insertion/extraction processes. The three-dimensional lignin-based carbon nanospheres played a crucial part in buffering the volumetric expansion and agglomeration of MnO2 nanoparticles during the discharge/charge processes. Furthermore, the large specific surface areas and mesoporous structure properties of the hollow carbon nanospheres significantly facilitate the fast transport of the lithium-ion and electrons, improving the electrochemical activities of the L-C-NSs@MnO2 electrodes. The presented work shows that the combination of specific structured lignin-based carbon nanoarchitecture with MnO2 provides a brand-new thought for the designation and synthesis of high-performance materials for energy-related applications. Full article
(This article belongs to the Section Materials Chemistry)
►▼ Show Figures

Graphical abstract

15 pages, 20857 KiB  
Article
The Effect of Sliding Speed on the Tribological Properties of Ceramic Materials
by Giovanni Paolo Alparone, David Penney, Eifion Jewell, James Sullivan and Christopher Mills
Materials 2023, 16(23), 7252; https://doi.org/10.3390/ma16237252 - 21 Nov 2023
Cited by 1 | Viewed by 1538
Abstract
Ceramics are considered to be candidate materials for galvanising pot bearing materials due to their excellent corrosion resistance in many molten metals. Galvanising pot roll bearings must have excellent wear resistance, and, therefore, it is important to understand the wear behaviour of prospective [...] Read more.
Ceramics are considered to be candidate materials for galvanising pot bearing materials due to their excellent corrosion resistance in many molten metals. Galvanising pot roll bearings must have excellent wear resistance, and, therefore, it is important to understand the wear behaviour of prospective bearing materials. This study investigates the friction- and wear-resistant properties of select ceramics, namely, pure hBN, BN M26, AlN-BN, Macor, 3YSZ, Al2O3 and Si3N4. The ceramics were tested at different sliding speeds using a pin-on-disc device equipped with SiC pins. The lowest coefficient of friction (COF) achieved was below 0.1, and it was measured for pure hBN at a 3.14 m/min sliding speed. However, a wear scar analysis showed that the BN grades suffered from severe wear. The highest wear rate was obtained for BN M26 at a 9.42 m/min sliding speed and was equal to 17.1 × 10−6 mm3 N−1 m−1. It was shown that the wear coefficient of the tested ceramics varied exponentially with hardness. The lowest wear was observed on the 3YSZ, Al2O3 and Si3N4 ceramics, which showed no volume loss, and, for this reason, they can be potentially used as bearing materials in continuous galvanising lines. Full article
(This article belongs to the Section Advanced and Functional Ceramics and Glasses)
►▼ Show Figures

Figure 1

16 pages, 7242 KiB  
Article
Graphene-Based Composites for Thermoelectric Applications at Room Temperature
by Sonya Harizanova, Vassil Vulchev and Radostina Stoyanova
Materials 2023, 16(23), 7262; https://doi.org/10.3390/ma16237262 - 21 Nov 2023
Cited by 1 | Viewed by 1406
Abstract
The thermoelectric materials that operate at room temperature represent a scientific challenge in finding chemical compositions with three optimized, independent parameters, namely electrical and thermal conductivity and the Seebeck coefficient. Here, we explore the concept of the formation of hybrid composites between carbon-based [...] Read more.
The thermoelectric materials that operate at room temperature represent a scientific challenge in finding chemical compositions with three optimized, independent parameters, namely electrical and thermal conductivity and the Seebeck coefficient. Here, we explore the concept of the formation of hybrid composites between carbon-based materials and oxides, with the aim of modifying their thermoelectric performance at room temperature. Two types of commercially available graphene-based materials are selected: N-containing reduced graphene oxide (NrGO) and expanded graphite (ExGr). Although the NrGO displays the lowest thermal conductivity at room temperature, the ExGr is characterized by the lowest electrical resistivity and a negative Seebeck coefficient. As oxides, we choose two perspective thermoelectric materials: p-type Ca3Co4O9 and n-type Zn0.995Al0.005O. The hybrid composites were prepared by mechanical milling, followed by a pelleting. The thermoelectric efficiency was evaluated on the basis of its measured electrical resistivity, Seebeck coefficient and thermal conductivity at room temperature. It was found that that 2 wt.% of ExGr or NrGO leads to an enhancement of the thermoelectric activity of Ca3Co4O9, while, for Zn0.995Al0.005O, the amount of ExGr varies between 5 and 20 wt.%. The effect of the composites’ morphology on the thermoelectric properties is discussed on the basis of SEM/EDS experiments. Full article
(This article belongs to the Special Issue Size-Dependent Effects in Materials for Environmental Protection and Energy Application)
►▼ Show Figures

Figure 1

15 pages, 4525 KiB  
Article
Synthesis and Characterization of Flame Retarded Rigid Polyurethane Foams with Different Types of Blowing Agents
by Marcin Zemła, Sławomir Michałowski and Aleksander Prociak
Materials 2023, 16(22), 7217; https://doi.org/10.3390/ma16227217 - 17 Nov 2023
Cited by 2 | Viewed by 1282
Abstract
In this study, rigid polyurethane foams modified with non-halogenated flame retardant were obtained. The foams were synthesized using two systems containing different blowing agents. In the first one, cyclopentane and water were used as a mixture of blowing agents, and in the second [...] Read more.
In this study, rigid polyurethane foams modified with non-halogenated flame retardant were obtained. The foams were synthesized using two systems containing different blowing agents. In the first one, cyclopentane and water were used as a mixture of blowing agents, and in the second one, only water was used as a chemical blowing agent. The systems were modified with the additive phosphorus flame retardant Roflam F5. The obtained modified foams were tested for their flammability and basic properties, such as apparent density, closed-cell contents and analyses of the cell structures, thermal conductivity, mechanical properties, and water absorption. Increasing the content of Roflam F5 caused a decrease in temperature during the combustion of the material and extended the burning time. The addition of 1.0 wt.% phosphorus derived from Roflam F5 caused the modified rigid polyurethane foam to become a self-extinguishing material. The increase in the content of Roflam F5 caused a decrease in the total heat release and the maximum heat release rate during the pyrolysis combustion flow calorimetry. The foams with the highest content of flame retardant and foamed with a chemical-physical and chemical blowing agent had a lower total heat release by 19% and 11%, respectively, compared to reference foams. Full article
(This article belongs to the Special Issue Advances in Development and Characterization of Polyurethane Foams)
►▼ Show Figures

Figure 1

18 pages, 2522 KiB  
Article
Cell-Laden 3D Printed GelMA/HAp and THA Hydrogel Bioinks: Development of Osteochondral Tissue-like Bioinks
by Shahrbanoo Jahangir, Jana Vecstaudza, Adriana Augurio, Elena Canciani, Liga Stipniece, Janis Locs, Mauro Alini and Tiziano Serra
Materials 2023, 16(22), 7214; https://doi.org/10.3390/ma16227214 - 17 Nov 2023
Cited by 5 | Viewed by 2335
Abstract
Osteochondral (OC) disorders such as osteoarthritis (OA) damage joint cartilage and subchondral bone tissue. To understand the disease, facilitate drug screening, and advance therapeutic development, in vitro models of OC tissue are essential. This study aims to create a bioprinted OC miniature construct [...] Read more.
Osteochondral (OC) disorders such as osteoarthritis (OA) damage joint cartilage and subchondral bone tissue. To understand the disease, facilitate drug screening, and advance therapeutic development, in vitro models of OC tissue are essential. This study aims to create a bioprinted OC miniature construct that replicates the cartilage and bone compartments. For this purpose, two hydrogels were selected: one composed of gelatin methacrylate (GelMA) blended with nanosized hydroxyapatite (nHAp) and the other consisting of tyramine-modified hyaluronic acid (THA) to mimic bone and cartilage tissue, respectively. We characterized these hydrogels using rheological testing and assessed their cytotoxicity with live-dead assays. Subsequently, human osteoblasts (hOBs) were encapsulated in GelMA-nHAp, while micropellet chondrocytes were incorporated into THA hydrogels for bioprinting the osteochondral construct. After one week of culture, successful OC tissue generation was confirmed through RT-PCR and histology. Notably, GelMA/nHAp hydrogels exhibited a significantly higher storage modulus (G′) compared to GelMA alone. Rheological temperature sweeps and printing tests determined an optimal printing temperature of 20 °C, which remained unaffected by the addition of nHAp. Cell encapsulation did not alter the storage modulus, as demonstrated by amplitude sweep tests, in either GelMA/nHAp or THA hydrogels. Cell viability assays using Ca-AM and EthD-1 staining revealed high cell viability in both GelMA/nHAp and THA hydrogels. Furthermore, RT-PCR and histological analysis confirmed the maintenance of osteogenic and chondrogenic properties in GelMA/nHAp and THA hydrogels, respectively. In conclusion, we have developed GelMA-nHAp and THA hydrogels to simulate bone and cartilage components, optimized 3D printing parameters, and ensured cell viability for bioprinting OC constructs. Full article
(This article belongs to the Section Biomaterials)
►▼ Show Figures

Figure 1

15 pages, 2984 KiB  
Article
Turning Waste into Treasure: The Full Technological Process and Product Performance Characterization of Flushable Wet Wipes Prepared from Corn Stalk
by Lulu Liu, Yeying Wang, Ziying He, Yang Cai, Kai Meng, Ke-Qin Zhang and Huijing Zhao
Materials 2023, 16(22), 7189; https://doi.org/10.3390/ma16227189 - 16 Nov 2023
Cited by 1 | Viewed by 1531
Abstract
As a daily consumable, wet wipes are mostly synthetic fibers, which are incinerated or landfilled after use. The nanoplastics generated during this process will lead to environmental pollution. The application of flushable wet wipes, which are dispersible and fully degradable, is of great [...] Read more.
As a daily consumable, wet wipes are mostly synthetic fibers, which are incinerated or landfilled after use. The nanoplastics generated during this process will lead to environmental pollution. The application of flushable wet wipes, which are dispersible and fully degradable, is of great significance. The main raw material for flushable wipes is wood pulp, which has a long growth cycle and high cost. Corn is widely planted and has a short growth cycle. Currently most corn stalk is treated by incineration, which produces a lot of smoke that pollutes the environment. Therefore, using corn stalk as the raw material for flushable wet wipes, replacing wood pulp, is both cost-effective and environmentally friendly. In this study, aiming at industrial production, we explored the full process of producing flushable wet wipes from corn stalk to pulp board, then to the final wipes. The corn stalk was treated using alkali and a bleaching agent to obtain corn stalk pulp, which was then made into pulp board through the nonwoven wet-laid process. The optimal parameters for the alkali treatment and bleaching were obtained. The properties of the corn stalk pulp board were compared with the commercial wood pulp board. Further, we mixed the corn stalk pulp with Lyocell fiber to prepare wet-laid webs, which were then bonded using a chemical binder poloxamer. Then, the evenness of the web, mechanical properties, absorption, and dispersibility of the flushable wipes were characterized. Results showed that the pulp obtained using the optimal treatment process has a high yield and better whiteness. The properties of the corn stalk pulp board are comparable with the commercial wood pulp board, which can therefore potentially be replaced by the corn stalk board prepared in our study. The prepared flushable wet wipes had good evenness and their water absorption rate was more than 600%. The mechanical strength in dry and wet states achieved 595.94 N/m and 179.00 N/m, respectively. Most importantly, the wet wipes can completely disperse under the standardized testing method. A good balance of dispersibility and wet strength of the wet wipes was achieved. Full article
(This article belongs to the Special Issue Advances in High-Performance Functional Nonwovens)
►▼ Show Figures

Graphical abstract

16 pages, 4193 KiB  
Article
A Yield Stress and Work Hardening Model of Al-Mg-Si Alloy Considering the Strengthening Effect of β” and β’ Precipitates
by Xiaoyu Zheng, Qi Huang, Hong Mao, Kai Li, Namin Xiao, Xingwu Li, Yong Du, Yuling Liu and Yi Kong
Materials 2023, 16(22), 7183; https://doi.org/10.3390/ma16227183 - 16 Nov 2023
Cited by 1 | Viewed by 1570
Abstract
Precipitates are the primary source of strength for the Al-Mg-Si alloy. Aluminum alloy in the peak-aged state mainly contains β” and β’ precipitates. Most of the literature has only considered the strengthening effect of β”. Here, we develop a single-crystal intensity model including [...] Read more.
Precipitates are the primary source of strength for the Al-Mg-Si alloy. Aluminum alloy in the peak-aged state mainly contains β” and β’ precipitates. Most of the literature has only considered the strengthening effect of β”. Here, we develop a single-crystal intensity model including both precipitate enhancement effects for the first time. This model was subsequently implemented into a crystal plastic finite-element method to model the uniaxial tensile process of a polycrystalline aggregate model of Al-Mg-Si alloy. The simulation results for uniaxial stretching are in good agreement with the experimental results, confirming that the constitutive parameters used for the single-crystal strength model with two precipitates are based on realistic physical implications. Furthermore, by comparing the uniaxial tensile simulation results of a peak-aged alloy considering the actual precipitated phase composition of the alloy with those assuming that the precipitated phase is only the β” phase, the predicted tensile strength of the former is around 5.65% lower than that of the latter, suggesting that the two kinds of precipitation should be separately considered when simulating the mechanical response of Al-Mg-Si alloy. It is highly expected that the present simulation strategy is not limited to Al-Mg-Si alloys, and it can be equally applied to the other age-enhanced alloys. Full article
(This article belongs to the Special Issue Metallic Materials: Microstructure, Phase Equilibria and Thermodynamics)
►▼ Show Figures

Figure 1

18 pages, 5364 KiB  
Article
Study of the Chemical Vapor Deposition of Nano-Sized Carbon Phases on {001} Silicon
by Teodor Milenov, Dimitar Trifonov, Dobromir A. Kalchevski, Stefan Kolev, Ivalina Avramova, Stoyan Russev, Kaloyan Genkov, Georgi Avdeev, Dimitar Dimov, Desislava M. Karaivanova and Evgenia Valcheva
Materials 2023, 16(22), 7190; https://doi.org/10.3390/ma16227190 - 16 Nov 2023
Cited by 1 | Viewed by 1512
Abstract
Different nano-sized phases were synthesized using chemical vapor deposition (CVD) processes. The deposition took place on {001} Si substrates at about 1150–1160 °C. The carbon source was thermally decomposed acetone (CH3)2CO in a main gas flow of argon. We [...] Read more.
Different nano-sized phases were synthesized using chemical vapor deposition (CVD) processes. The deposition took place on {001} Si substrates at about 1150–1160 °C. The carbon source was thermally decomposed acetone (CH3)2CO in a main gas flow of argon. We performed experiments at two ((CH3)2CO + Ar)/Ar) ratios and observed that two visually distinct types of layers were deposited after a one-hour deposition process. The first layer type, which appears more inhomogeneous, has areas of SiO2 (about 5% of the surface area substrates) beside shiny bright and rough paths, and its Raman spectrum corresponds to diamond-like carbon, was deposited at a (CH3)2CO+Ar)/Ar = 1/5 ratio. The second layer type, deposited at (CH3)2CO + Ar)/Ar = a 1/0 ratio, appears homogeneous and is very dark brown or black in color and its Raman spectrum pointed to defect-rich multilayered graphene. The performed structural studies reveal the presence of diamond and diamond polytypes and seldom SiC nanocrystals, as well as some non-continuously mixed SiC and graphene-like films. The performed molecular dynamics simulations show that there is no possibility of deposition of sp3-hybridized on sp2-hybridized carbon, but there are completely realistic possibilities of deposition of sp2- on sp2- and sp3- on sp3-hybridized carbon under different scenarios. Full article
(This article belongs to the Special Issue Silicon Carbide Materials: Crystal Growth, Device Processing and Functional Applications)
►▼ Show Figures

Figure 1

14 pages, 2807 KiB  
Article
Influence of NF3 Plasma-Treated HfO2 Gate Insulator Surface on Tin Oxide Thin-Film Transistors
by Christophe Avis and Jin Jang
Materials 2023, 16(22), 7172; https://doi.org/10.3390/ma16227172 - 15 Nov 2023
Viewed by 1355
Abstract
We studied the impact of NF3 plasma treatment on the HfO2 gate insulator of amorphous tin oxide (a-SnOx) thin-film transistors (TFTs). The plasma treatment was for 0, 10, or 30 s. The HfO2 insulator demonstrated a slightly higher [...] Read more.
We studied the impact of NF3 plasma treatment on the HfO2 gate insulator of amorphous tin oxide (a-SnOx) thin-film transistors (TFTs). The plasma treatment was for 0, 10, or 30 s. The HfO2 insulator demonstrated a slightly higher breakdown voltage, whereas the capacitance value remained almost constant (~150 nF/cm2). The linear mobility slightly increased from ~30 to ~35 cm2/Vs when the treatment time increased from 0 to 10 s, whereas a 30 s-treated TFT demonstrated a decreased mobility of ~15 cm2/Vs. The subthreshold swing and the threshold voltage remained in the 100–120 mV/dec. range and near 0 V, respectively. The hysteresis dramatically decreased from ~0.5 V to 0 V when a 10 s treatment was applied, and the 10 s-treated TFT demonstrated the best stability under high current stress (HCS) of 100 μA. The analysis of the tin oxide thin film crystallinity and oxygen environment demonstrated that the a-SnOx remained amorphous, whereas more metal–oxygen bonds were formed with a 10 s NF3 plasma treatment. We also demonstrate that the density of states (DOS) significantly decreased in the 10 s-treated TFT compared to the other conditions. The stability under HCS was attributed to the HfO2/a-SnOx interface quality. Full article
(This article belongs to the Special Issue High-Performance Materials for Thin-Film Transistors and Other Electronic Device Applications)
►▼ Show Figures

Figure 1

19 pages, 6987 KiB  
Article
Research on the Mechanical Model and Hysteresis Performance of a New Mild Steel-Rotational Friction Hybrid Self-Centering Damper
by Debin Wang, Ran Pang, Gang Wang and Guoxi Fan
Materials 2023, 16(22), 7168; https://doi.org/10.3390/ma16227168 - 15 Nov 2023
Cited by 2 | Viewed by 1193
Abstract
A mild steel-friction self-centering damper with a hybrid energy-dissipation mechanism (MS-SCFD) was proposed, which consisted of a mild steel, frictional, dual-energy-dissipation system and a disc spring resetting system. The structure and principle of the MS-SCFD were explained in detail while the restoring force [...] Read more.
A mild steel-friction self-centering damper with a hybrid energy-dissipation mechanism (MS-SCFD) was proposed, which consisted of a mild steel, frictional, dual-energy-dissipation system and a disc spring resetting system. The structure and principle of the MS-SCFD were explained in detail while the restoring force model was established. The hysteretic behavior of the MS-SCFD under low-cycle reciprocating loading was modeled. Then, the influence of parameters such as the disc spring preload, the friction coefficient, and the soft-steel thickness on the mechanical properties of the MS-SCFD was investigated. The results indicate that the simulation results are basically consistent with the theoretical prediction results, with a maximum error of only 9.46% for the key points of bearing capacity. Since the MS-SCFD is provided with a hysteretic curve in the typical flag type, it will obtain the capacity of excellent self-centering performance. It can effectively enhance the stiffness, bearing capacity, and self-centering capability of the damper after the pre-pressure of the disc spring is increased. The energy-dissipation capacity of the MS-SCFD increases with the increase in the friction coefficient. However, it also increases the residual deformation of the MS-SCFD. The energy dissipation of the MS-SCFD is particularly sensitive to the thickness of mild steel. After being loaded, all components of the MS-SCFD are not damaged except for the plastic deformation caused by the yielding of the mild steel. The normal function of the MS-SCFD can be restored simply by replacing the mild steel plates after the earthquake. Therefore, it can significantly enhance the economy and applicability of the damper. Full article
(This article belongs to the Special Issue Structure and Mechanical Properties of Alloys, Volume III)
►▼ Show Figures

Figure 1

27 pages, 17279 KiB  
Article
Support Structures Optimisation for High-Quality Metal Additive Manufacturing with Laser Powder Bed Fusion: A Numerical Simulation Study
by Antonios Dimopoulos, Mohamad Salimi, Tat-Hean Gan and Panagiotis Chatzakos
Materials 2023, 16(22), 7164; https://doi.org/10.3390/ma16227164 - 14 Nov 2023
Cited by 5 | Viewed by 2331
Abstract
This study focuses on Metal Additive Manufacturing (AM), an emerging method known for its ability to create lightweight components and intricate designs. However, Laser Powder Bed Fusion (LPBF), a prominent AM technique, faces a major challenge due to the development of high residual [...] Read more.
This study focuses on Metal Additive Manufacturing (AM), an emerging method known for its ability to create lightweight components and intricate designs. However, Laser Powder Bed Fusion (LPBF), a prominent AM technique, faces a major challenge due to the development of high residual stress, resulting in flawed parts and printing failures. The study’s goal was to assess the thermal behaviour of different support structures and optimised designs to reduce the support volume and residual stress while ensuring high-quality prints. To explore this, L-shaped specimens were printed using block-type support structures through an LPBF machine. This process was subsequently validated through numerical simulations, which were in alignment with experimental observations. In addition to block-type support structures, line, contour, and cone supports were examined numerically to identify the optimal solutions that minimise the support volume and residual stress while maintaining high-quality prints. The optimisation approach was based on the Design of Experiments (DOE) methodology and multi-objective optimisation. The findings revealed that block supports exhibited excellent thermal behaviour. High-density supports outperformed low-density alternatives in temperature distribution, while cone-type supports were more susceptible to warping. These insights provide valuable guidance for improving the metal AM and LPBF processes, enabling their broader use in industries like aerospace, medical, defence, and automotive. Full article
(This article belongs to the Section Materials Simulation and Design)
►▼ Show Figures

Figure 1

15 pages, 4127 KiB  
Article
Analysis of the Effect of Skew Rolling Parameters on the Surface Roughness of C60 Steel Products Using ML Methods
by Konrad Lis
Materials 2023, 16(22), 7136; https://doi.org/10.3390/ma16227136 - 12 Nov 2023
Viewed by 1231
Abstract
This paper presents results from experimental and numerical studies of the skew rolling process used to shape axisymmetric products made of C60-grade steel. An experimental study was carried out to investigate the effect of process parameters described by the forming angle α, [...] Read more.
This paper presents results from experimental and numerical studies of the skew rolling process used to shape axisymmetric products made of C60-grade steel. An experimental study was carried out to investigate the effect of process parameters described by the forming angle α, the skew angle θ, the reduction ratio δ, and the jaw chuck velocity Vu on the surface roughness Ra of the forgings. Stepped forgings made of C60-grade steel were rolled. Based on numerical calculations, a machine learning regression model was developed that uses process parameters to predict the surface roughness of produced parts. The random forest model was found to be the most effective based on the determined metrics (MAE, RMSE, R2). A more detailed analysis of this model was performed using the SHAP library. The application of ML methods will enable optimization of skew rolling through appropriate selection of process parameters affecting improvement in product quality. Full article
(This article belongs to the Special Issue Advanced Manufacturing Processes of Metal Forming)
►▼ Show Figures

Figure 1

11 pages, 2303 KiB  
Article
Tailoring the Structure and Properties of Epitaxial Europium Tellurides on Si(100) through Substrate Temperature Control
by Fan Yu, Xiaodong Qiu, Jinming Zhou, Lin Huang, Bin Yang, Junming Liu, Di Wu, Gan Wang and Yi Zhang
Materials 2023, 16(22), 7093; https://doi.org/10.3390/ma16227093 - 9 Nov 2023
Viewed by 1251
Abstract
In this study, we improved the growth procedure of EuTe and realized the epitaxial growth of EuTe4. Our research demonstrated a selective growth of both EuTe and EuTe4 on Si(100) substrates using the molecular beam epitaxy (MBE) technique and reveals [...] Read more.
In this study, we improved the growth procedure of EuTe and realized the epitaxial growth of EuTe4. Our research demonstrated a selective growth of both EuTe and EuTe4 on Si(100) substrates using the molecular beam epitaxy (MBE) technique and reveals that the substrate temperature plays a crucial role in determining the structural phase of the grown films: EuTe can be obtained at a substrate temperature of 220 °C while lowering down the temperature to 205 °C leads to the formation of EuTe4. A comparative analysis of the transmittance spectra of these two films manifested that EuTe is a semiconductor, whereas EuTe4 exhibits charge density wave (CDW) behavior at room temperature. The magnetic measurements displayed the antiferromagnetic nature in EuTe and EuTe4, with Néel temperatures of 10.5 and 7.1 K, respectively. Our findings highlight the potential for controllable growth of EuTe and EuTe4 thin films, providing a platform for further exploration of magnetism and CDW phenomena in rare earth tellurides. Full article
(This article belongs to the Special Issue Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application)
►▼ Show Figures

Figure 1

39 pages, 5360 KiB  
Review
The Alphabet of Nanostructured Polypyrrole
by Sylwia Golba and Jan Loskot
Materials 2023, 16(22), 7069; https://doi.org/10.3390/ma16227069 - 7 Nov 2023
Viewed by 1479
Abstract
This review is devoted to polypyrrole and its morphology, which governs the electroactivity of the material. The macroscopic properties of the material are strictly relevant to microscopic ordering observed at the local level. During the synthesis, various (nano)morphologies can be produced. The formation [...] Read more.
This review is devoted to polypyrrole and its morphology, which governs the electroactivity of the material. The macroscopic properties of the material are strictly relevant to microscopic ordering observed at the local level. During the synthesis, various (nano)morphologies can be produced. The formation of the ordered structure is dictated by the ability of the local forces and effects to induce restraints that help shape the structure. This review covers the aspects of morphology and roughness and their impact on the final properties of the modified electrode activity in selected applications. Full article
(This article belongs to the Special Issue Conducting Polymers: Structure Characterization, Conductivity, and Application)
►▼ Show Figures

Graphical abstract

16 pages, 10763 KiB  
Article
Influence of Long-Term Storage and UV Light Exposure on Characteristics of Polyurethane Foams for Cryogenic Insulation
by Beatrise Sture, Vladimir Yakushin, Laima Vevere and Ugis Cabulis
Materials 2023, 16(22), 7071; https://doi.org/10.3390/ma16227071 - 7 Nov 2023
Cited by 2 | Viewed by 1354
Abstract
Rigid polyurethane (PUR) foams have been the most effective insulation material used in space launchers since the beginning of cryogenic fuel use, due to their outstanding thermal and mechanical properties. In this study, spray-applied PUR foams using different ratios of amine-based catalysts were [...] Read more.
Rigid polyurethane (PUR) foams have been the most effective insulation material used in space launchers since the beginning of cryogenic fuel use, due to their outstanding thermal and mechanical properties. In this study, spray-applied PUR foams using different ratios of amine-based catalysts were produced. Due to climate change, several restrictions have been made regarding the usage of blowing agents used for PUR foam production. Lately, hydrofluoroolefins (HFOs) have been suggested as an alternative for PUR foam production due to their low global warming potential (GWP) and ozone depletion potential (ODP), replacing the hydrofluorocarbons (HFCs) so far used. This change in blowing agents naturally altered the usage of catalysts. Reactive amine-based catalysts are less hazardous because of their low volatility and ability to react successfully with isocyanate or polyols. Spray-applied PUR foams with a potential application for cryogenic insulation were produced and tested for long-term storage, analyzing parameters such as the pH value of polyol composition, foaming kinetics (trise, tcream), etc. Athermal analysis (TG, DSC) was also applied to developed materials, as well as artificial ageing by exposing samples to UV light. It was discovered that PUR foams obtained using reactive amine-based catalysts, such as Polycat 203 and 218, have a higher integral heat capacity, but polyol mixtures containing these catalysts cannot exceed a storage time of more than 4 months. It was also observed from artificial ageing tests of PUR cryogenic insulation by exposure to UV light that the thickness of the degraded layer reached 0.8 mm (after 1000 h), but no significant destruction of cellular structure deeper in the material was observed. Full article
(This article belongs to the Special Issue Advances in Development and Characterization of Polyurethane Foams)
►▼ Show Figures

Figure 1

20 pages, 8002 KiB  
Review
Recent Progress in Resonant Acoustic Metasurfaces
by Dongan Liu, Limei Hao, Weiren Zhu, Xiao Yang, Xiaole Yan, Chen Guan, You Xie, Shaofang Pang and Zhi Chen
Materials 2023, 16(21), 7044; https://doi.org/10.3390/ma16217044 - 5 Nov 2023
Cited by 4 | Viewed by 2635
Abstract
Acoustic metasurfaces, as two-dimensional acoustic metamaterials, are a current research topic for their sub-wavelength thickness and excellent acoustic wave manipulation. They hold significant promise in noise reduction and isolation, cloaking, camouflage, acoustic imaging, and focusing. Resonant structural units are utilized to construct acoustic [...] Read more.
Acoustic metasurfaces, as two-dimensional acoustic metamaterials, are a current research topic for their sub-wavelength thickness and excellent acoustic wave manipulation. They hold significant promise in noise reduction and isolation, cloaking, camouflage, acoustic imaging, and focusing. Resonant structural units are utilized to construct acoustic metasurfaces with the unique advantage of controlling large wavelengths within a small size. In this paper, the recent research progresses of the resonant metasurfaces are reviewed, covering the design mechanisms and advances of structural units, the classification and application of the resonant metasurfaces, and the tunable metasurfaces. Finally, research interest in this field is predicted in future. Full article
(This article belongs to the Special Issue Metamaterials and Metasurfaces: Fundamentals and Applications)
►▼ Show Figures

Figure 1

13 pages, 3240 KiB  
Article
Effect of the Solid Solution and Aging Treatment on the Mechanical Properties and Microstructure of a Novel Al-Mg-Si Alloy
by Yan Chen, Wu Wei, Yu Zhao, Wei Shi, Xiaorong Zhou, Li Rong, Shengping Wen, Xiaolan Wu, Kunyuan Gao, Hui Huang and Zuoren Nie
Materials 2023, 16(21), 7036; https://doi.org/10.3390/ma16217036 - 4 Nov 2023
Cited by 4 | Viewed by 1808
Abstract
A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and [...] Read more.
A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and strengthening mechanism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques are employed to examine the changes in the microstructure resulting from various solid solution treatments and aging treatments. The best strengthening effect can be achieved when the solubility of the MgSi phase and precipitate β″ (Mg2Si phase) is at their maximum. The addition of Er and Zr elements promotes the precipitation of the β″ phase and makes the b″ phase more finely dispersed. The aging strengthening of alloys is a comprehensive effect of the dislocation cutting mechanism and bypass mechanism, the joint effect of diffusion strengthening of Al3(Er,Zr) particles and the addition of Er and Zr elements promoting the precipitation strengthening of β″ phases. In this paper, by adding Er and Zr elements and exploring the optimal heat treatment system, the yield strength of the alloy reaches 437 MPa and the tensile strength reaches 453 MPa after solid solution treatment at 565 °C/30 min and aging at 175 °C/10 h. Full article
(This article belongs to the Special Issue Metallic Materials: Structure Transition, Processing, Characterization and Applications)
►▼ Show Figures

Figure 1

12 pages, 7966 KiB  
Article
MOF-808 as an Efficient Catalyst for Valorization of Biodiesel Waste Production: Glycerol Acetalization
by Fátima Mirante, Pedro Leo, Catarina N. Dias, Luís Cunha-Silva and Salete S. Balula
Materials 2023, 16(21), 7023; https://doi.org/10.3390/ma16217023 - 3 Nov 2023
Cited by 4 | Viewed by 1974
Abstract
Glycerol is the main residue in the biodiesel production industry; therefore, their valorization is crucial. The acetalization of glycerol toward fuel additives such as solketal (2,2-dimethyl-1,3-dioxolan-4-methanol) is of high interest, promoting circular economy since it can be added to biodiesel or even fossil [...] Read more.
Glycerol is the main residue in the biodiesel production industry; therefore, their valorization is crucial. The acetalization of glycerol toward fuel additives such as solketal (2,2-dimethyl-1,3-dioxolan-4-methanol) is of high interest, promoting circular economy since it can be added to biodiesel or even fossil diesel to improve their quality and efficiency. Straightforward-prepared metal–organic framework (MOF) materials of the MOF-808 family were applied to the valorization of glycerol for the first time. In particular, MOF-808(Hf) was revealed to be an effective heterogeneous catalyst to produce solketal under moderate conditions: a small amount of the MOF material (only 4 wt% of glycerol), a 1:6 ratio of glycerol/acetone, and a temperature of 333 K. The high efficiency of MOF-808(Hf) was associated with the high amount of acid centers present in its structure. Furthermore, its structural characteristics, such as window opening cavity size and pore diameters, were shown to be ideal for reusing this material for at least ten consecutive reaction cycles without losing activity (conversion > 90% and selectivity > 98%). Remarkably, it was not necessary to wash or activate the MOF-808(Hf) catalyst between cycles (no pore blockage occurred), and it maintained structural integrity after ten cycles, confirming its ability to be a sustainable heterogeneous catalyst for glycerol valorization. Full article
(This article belongs to the Special Issue Heterogeneous Catalysts for Biomass Conversion and Environmental Remediation)
►▼ Show Figures

Figure 1

18 pages, 11760 KiB  
Article
Sintered Brake Pads Failure in High-Energy Dissipation Braking Tests: A Post-Mortem Mechanical and Microstructural Analysis
by Alexandre Mege-Revil, Jessie Rapontchombo-Omanda, Itziar Serrano-Munoz, Anne-Lise Cristol, Vincent Magnier and Philippe Dufrenoy
Materials 2023, 16(21), 7006; https://doi.org/10.3390/ma16217006 - 1 Nov 2023
Cited by 3 | Viewed by 1400
Abstract
The industrial sintering process used to produce metallic matrix pads has been altered to diminish the amount of copper used. Unfortunately, replacing a large part of the copper with iron seems to have reached a limit. In the high-energy, emergency-type rail braking used [...] Read more.
The industrial sintering process used to produce metallic matrix pads has been altered to diminish the amount of copper used. Unfortunately, replacing a large part of the copper with iron seems to have reached a limit. In the high-energy, emergency-type rail braking used in this study, the materials are put to the very limit of their usage capacity, allowing us to observe the evolution of the microstructure and mechanical properties of sintered, metallic matrix pads. After the braking test, their compressive behaviour was assessed using digital image correlation (DIC), and their microstructure with scanning electron microscopy (SEM). The worn material has three flat layers with different microstructures and compressive behaviours. The bottom layer seems unmodified. Macroscopic and microscopic cracks run through the intermediate layer (2–15 mm depth). The top layer has stiffened thanks to resolidification of copper. The temperature reaches 1000 °C during the braking test, which also explains the carbon diffusion into iron that result in the weakening of iron –graphite interfaces in the pad. Finally, submicronic particles are detected at many open interfaces of the worn and compressed pad. Associated with the predominant role of graphite particles, this explains the weak compressive behaviour of the pads. Full article
(This article belongs to the Special Issue Microstructure, Mechanical Properties and Wear Performance of High-Strength Steels)
►▼ Show Figures

Figure 1

17 pages, 8119 KiB  
Article
Unsupervised Deep Learning for Advanced Forming Limit Analysis in Sheet Metal: A Tensile Test-Based Approach
by Aleksandra Thamm, Florian Thamm, Annette Sawodny, Sally Zeitler, Marion Merklein and Andreas Maier
Materials 2023, 16(21), 7001; https://doi.org/10.3390/ma16217001 - 1 Nov 2023
Cited by 1 | Viewed by 1586
Abstract
An accurate description of the formability and failure behavior of sheet metal materials is essential for an optimal forming process design. In this respect, the forming limit curve (FLC) based on the Nakajima test, which is determined in accordance with DIN EN ISO [...] Read more.
An accurate description of the formability and failure behavior of sheet metal materials is essential for an optimal forming process design. In this respect, the forming limit curve (FLC) based on the Nakajima test, which is determined in accordance with DIN EN ISO 12004-2, is a wide-spread procedure for evaluating the formability of sheet metal materials. Thereby the FLC is affected by influences originating from intrinsic factors of the Nakajima test-setup, such as friction, which leads to deviations from the linear strain path, biaxial prestress and bending superposition. These disadvantages can be circumvented by an alternative test combination of uniaxial tensile test and hydraulic bulge test. In addition, the forming limit capacity of many lightweight materials is underestimated using the cross-section method according to DIN EN ISO 12004-2, due to the material-dependent occurrence of multiple strain maxima during forming or sudden cracking without prior necking. In this regard, machine learning approaches have a high potential for a more accurate determination of the forming limit curve due to the inclusion of other parameters influencing formability. This work presents a machine learning approach focused on uniaxial tensile tests to define the forming limit of lightweight materials and high-strength steels. The transferability of an existing weakly supervised convolutional neural network (CNN) approach was examined, originally designed for Nakajima tests, to uniaxial tensile tests. Additionally, a stereo camera-based method for this purpose was developed. In our evaluation, we train and test materials, including AA6016, DX54D, and DP800, through iterative data composition, using cross-validation. In the context of our stereo camera-based approach, strains for different materials and thicknesses were predicted. In this cases, our method successfully predicted the major strains with close agreement to ISO standards. For DX54D, with a thickness of 0.8 mm, the prediction was 0.659 (compared to ISO’s 0.664). Similarly, for DX54D, 2.0 mm thickness, the predicted major strain was 0.780 (compared to ISO 0.705), and for AA6016, at 1.0 mm thickness, a major strain of 0.314 (in line with ISO 0.309) was estimated. However, for DP800 with a thickness of 1.0 mm, the prediction yielded a major strain of 0.478 (as compared to ISO 0.289), indicating a divergence from the ISO standard in this particular case. These results in general, generated with the CNN stereo camera-based approach, underline the quantitative alignment of the approach with the cross-section method. Full article
(This article belongs to the Special Issue Forming Process and Mechanical Behavior Analysis of Light Metals and Alloys)
►▼ Show Figures

Figure 1

14 pages, 3685 KiB  
Article
Collagen-Coated Hyperelastic Bone Promotes Osteoblast Adhesion and Proliferation
by Andrei Gresita, Iman Raja, Eugen Petcu and Michael Hadjiargyrou
Materials 2023, 16(21), 6996; https://doi.org/10.3390/ma16216996 - 1 Nov 2023
Cited by 1 | Viewed by 1348
Abstract
Successfully reconstructing bone and restoring its dynamic function represents a significant challenge for medicine. Critical size defects (CSDs), resulting from trauma, tumor removal, or degenerative conditions, do not naturally heal and often require complex bone grafting. However, these grafts carry risks, such as [...] Read more.
Successfully reconstructing bone and restoring its dynamic function represents a significant challenge for medicine. Critical size defects (CSDs), resulting from trauma, tumor removal, or degenerative conditions, do not naturally heal and often require complex bone grafting. However, these grafts carry risks, such as tissue rejection, infections, and surgical site damage, necessitating the development of alternative treatments. Three-dimensional and four-dimensional printed synthetic biomaterials represent a viable alternative, as they carry low production costs and are highly reproducible. Hyperelastic bone (HB), a biocompatible synthetic polymer consisting of 90% hydroxyapatite and 10% poly(lactic-co-glycolic acid, PLGA), was examined for its potential to support cell adhesion, migration, and proliferation. Specifically, we seeded collagen-coated HB with MG-63 human osteosarcoma cells. Our analysis revealed robust cell adhesion and proliferation over 7 days in vitro, with cells forming uniform monolayers on the external surface of the scaffold. However, no cells were present on the core of the fibers. The cells expressed bone differentiation markers on days 3 and 5. By day 7, the scaffold began to degrade, developing microscopic fissures and fragmentation. In summary, collagen-coated HB scaffolds support cell adhesion and proliferation but exhibit reduced structural support after 7 days in culture. Nevertheless, the intricate 3D architecture holds promise for cellular migration, vascularization, and early osteogenesis. Full article
(This article belongs to the Special Issue Bio-Inspired and Biomimetic Materials for Healthcare: From Nature to Clinics)
►▼ Show Figures

Figure 1

17 pages, 7395 KiB  
Article
Influence of Surface Preparation on the Microstructure and Mechanical Properties of Cold-Sprayed Nickel Coatings on Al 7075 Alloy
by Wojciech Żórawski, Anna Góral, Medard Makrenek, Lidia Lityńska-Dobrzyńska and Paweł Czaja
Materials 2023, 16(21), 7002; https://doi.org/10.3390/ma16217002 - 1 Nov 2023
Viewed by 1088
Abstract
This work presents the effect of surface roughness (Al 7075) on the microstructure and mechanical properties of cold-sprayed nickel coatings. Coating analysis included substrate surfaces and coating geometry, microstructure characterization, microhardness, nanohardness, elastic modulus, and adhesion. The results show that the surface preparation [...] Read more.
This work presents the effect of surface roughness (Al 7075) on the microstructure and mechanical properties of cold-sprayed nickel coatings. Coating analysis included substrate surfaces and coating geometry, microstructure characterization, microhardness, nanohardness, elastic modulus, and adhesion. The results show that the surface preparation had a significant effect on coating adhesion and microstructure. The coating deposited at the highest gas temperature revealed a dense microstructure, showing very good adhesion of the impacting powder particles to the substrate and good bonding between deposited layers. The Ni grains with different shapes (elongated, equiaxed) and sizes of a few dozen to several hundred nanometres were present in the splats. An increase in temperature caused significant growth in coating thickness as a result of the powder grains’ higher velocity. Moreover, higher gas temperature resulted in the enhancement of micro- and nanohardness, elastic modulus, and adhesion. The adhesive bond strength of Ni coatings in the tested temperature ranges from 500 °C to 800 °C increased with the increase in the surface roughness of the substrate. For the Al 7075 coarse grit-blasted (CG) substrate with the highest roughness, the adhesion reached the highest value of 44.6 MPa when the working gas was at a temperature of 800 °C. There were no distinct dependencies of surface roughness and thickness on the mechanical properties of the cold-sprayed nickel coating. Full article
(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))
►▼ Show Figures

Figure 1

13 pages, 4111 KiB  
Article
Synergetic Effect and Phase Engineering by Formation of Ti3C2Tx Modified 2H/1T-MoSe2 Composites for Enhanced HER
by Lei Xiao, Qichao Yang, Xiangyang Zhu, Yang Wei and Jing Wang
Materials 2023, 16(21), 6991; https://doi.org/10.3390/ma16216991 - 31 Oct 2023
Cited by 1 | Viewed by 1385
Abstract
The typical semi conductivity and few active sites of hydrogen evolution of 2H MoSe2 severely restrict its electrocatalytic hydrogen evolution performance. At the same time, the 1T MoSe2 has metal conductivity and plentiful hydrogen evolution sites, making it feasible to optimize [...] Read more.
The typical semi conductivity and few active sites of hydrogen evolution of 2H MoSe2 severely restrict its electrocatalytic hydrogen evolution performance. At the same time, the 1T MoSe2 has metal conductivity and plentiful hydrogen evolution sites, making it feasible to optimize the electrocatalytic hydrogen evolution behavior of MoSe2 using phase engineering. In this study, we, through a simple one-step hydrothermal method, composed 1T/2H MoSe2, and then used newly emerging transition metal carbides with several atomic-layer thicknesses Ti3C2Tx to improve the conductivity of a MoSe2-based electrocatalyst. Finally, MoSe2@Ti3C2Tx was successfully synthesized, according to the control of the additional amount of Ti3C2Tx, to form a proper MoSe2/ Ti3C2Tx heterostructure with a better electrochemical HER performance. As obtained MoSe2@4 mg-Ti3C2Tx achieved a low overpotential, a small Tafel slope and this work offers additional insight into broadened MoSe2 and MXenes-based catalyst’s electrochemical application. Full article
(This article belongs to the Special Issue Electrochemical Material Science and Electrode Processes)
►▼ Show Figures

Figure 1

11 pages, 4019 KiB  
Article
Study on the Stability of Cu-Ni Cluster Components and the Effect of Strain on Its Structure
by Xiaochuan Zeng, Cuizhu He, Xuejun Li and Qiaodan Hu
Materials 2023, 16(21), 6952; https://doi.org/10.3390/ma16216952 - 30 Oct 2023
Viewed by 1054
Abstract
Solute clusters are one of the important mechanisms of irradiation embrittlement of ferritic steels. It is of great significance to study the stability of solute clusters in ferritic steels and their effects on the mechanical properties of the materials. Molecular dynamics was used [...] Read more.
Solute clusters are one of the important mechanisms of irradiation embrittlement of ferritic steels. It is of great significance to study the stability of solute clusters in ferritic steels and their effects on the mechanical properties of the materials. Molecular dynamics was used to study the binding energy, defect energy, and interaction energy of 2 nm-diameter Cu-Ni clusters in the ferritic lattice, which have six categories of Cu-Ni clusters, such as the pure Cu cluster, the core–shell structural cluster with one layer to four layers of Ni atoms and the pure Ni cluster. It was found that Cu-Ni clusters have lower energy advantages than pure Ni clusters. Through shear strain simulation of the three clusters, the structure of 2 nm diameter clusters does not undergo phase transformation. The number of slip systems and the length of dislocation lines in the cluster system are positively correlated with the magnitude of the critical stress of material plastic deformation. Full article
(This article belongs to the Special Issue Key Materials in Nuclear Reactors)
►▼ Show Figures

Figure 1

13 pages, 4155 KiB  
Article
Cyclic Voltammetry of C.I. Disperse Orange 62 in an Aqueous Electrolyte
by Thomas Bechtold, Noemí Aguiló-Aguayo and Tung Pham
Materials 2023, 16(21), 6901; https://doi.org/10.3390/ma16216901 - 27 Oct 2023
Viewed by 1129
Abstract
Disperse dyes are an important group of colorants for dyeing polyester fibers. Approximately 30.000 tons of disperse dyes are released into the waste water annually from spent dyebaths. Therefore, methods for decolorizing such dyes are of general interest. The reductive after-treatment of disperse [...] Read more.
Disperse dyes are an important group of colorants for dyeing polyester fibers. Approximately 30.000 tons of disperse dyes are released into the waste water annually from spent dyebaths. Therefore, methods for decolorizing such dyes are of general interest. The reductive after-treatment of disperse dyes using reducing agents, such as Na2S2O4, is a widely used process to improve rub fastness through dye reduction. Electrochemical dye reduction could be an alternative process for reductive dye treatment. In this work C.I. Disperse Orange 62 was used as a representative dye to study the direct cathodic reduction of a disperse dye with cyclic voltammetry. As anticipated for dispersed organic matter, relatively low current densities were observed, which strongly depend on the state of dispersion of the dye. The current density was increased by using dispersions prepared through dye precipitation from DMF solution and by the use of N-cetyl-N,N,N,-trimethyl-ammonium bromide as a cationic surfactant. The results demonstrate the successful cathodic reduction of a dispersed organic dye; however, the low solubility of the reaction products in the aqueous electrolyte hinders an efficient cathodic dye reduction. Full article
(This article belongs to the Special Issue Electrochemistry of Organic Compounds and Their Applications)
►▼ Show Figures

Graphical abstract

22 pages, 4675 KiB  
Article
Screening Ba0.9A0.1MnO3 and Ba0.9A0.1Mn0.7Cu0.3O3 (A = Mg, Ca, Sr, Ce, La) Sol-Gel Synthesised Perovskites as GPF Catalysts
by Nawel Ghezali, Álvaro Díaz Verde and María José Illán Gómez
Materials 2023, 16(21), 6899; https://doi.org/10.3390/ma16216899 - 27 Oct 2023
Cited by 4 | Viewed by 1210
Abstract
Ba0.9A0.1MnO3 (BM-A) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) (A = Mg, Ca, Sr, Ce, La) perovskite-type mixed oxides were synthesised, characterised, and used for soot oxidation in simulated Gasoline Direct Injection (GDI) [...] Read more.
Ba0.9A0.1MnO3 (BM-A) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) (A = Mg, Ca, Sr, Ce, La) perovskite-type mixed oxides were synthesised, characterised, and used for soot oxidation in simulated Gasoline Direct Injection (GDI) engine exhaust conditions. The samples have been obtained by the sol-gel method in an aqueous medium and deeply characterised. The characterization results indicate that the partial substitution of Ba by A metal in BaMnO3 (BM) and BaMn0.7Cu0.3O3 (BMC) perovskites: (i) favours the hexagonal structure of perovskite; (ii) improves the reducibility and the oxygen desorption during Temperature-Programmed Desorption (O2-TPD) tests and, consequently, the oxygen mobility; (iii) mantains the amount of oxygen vacancies and of Mn(IV) and Mn(III) oxidation states, being Mn(IV) the main one; and (iv) for Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) series, copper is partially incorporated into the structure. The soot conversion data reveal that Ba0.9La0.1Mn0.7Cu0.3O3 (BMC-La) is the most active catalyst in an inert (100% He) reaction atmosphere, as it presents the highest amount of copper on the surface, and that Ba0.9Ce0.1MnO3 (BM-Ce) is the best one if a low amount of O2 (1% O2 in He) is present, as it combines the highest emission of oxygen with the good redox properties of Ce(IV)/Ce(III) and Mn(IV)/Mn(III) pairs. Full article
(This article belongs to the Special Issue Sol-Gel Technology Applied to Materials Science: Synthesis, Characterization and Applications)
►▼ Show Figures

Figure 1

17 pages, 5028 KiB  
Article
Synthesis and Characterization of Bioactive Glass and Zinc Oxide Nanoparticles with Enamel Remineralization and Antimicrobial Capabilities
by Ryota Nagasaki, Keiji Nagano, Takashi Nezu and Masahiro Iijima
Materials 2023, 16(21), 6878; https://doi.org/10.3390/ma16216878 - 26 Oct 2023
Viewed by 1399
Abstract
Background: We investigated the effect of bioactive glass and zinc oxide nanoparticles on enamel remineralization, as well as their antimicrobial effect on cariogenic microbes. This is the first study that investigated the properties of bioactive glass and zinc oxide nanoparticles with mixed materials. [...] Read more.
Background: We investigated the effect of bioactive glass and zinc oxide nanoparticles on enamel remineralization, as well as their antimicrobial effect on cariogenic microbes. This is the first study that investigated the properties of bioactive glass and zinc oxide nanoparticles with mixed materials. Methods: Fluoride gel (F), bioactive glass microparticles (µB), bioactive glass nanoparticles (nB), zinc oxide nanoparticles (Z), and a mixed suspension of nB and Z (nBZ) were prepared and characterized by scanning and transmission electron microscopy, zeta potential measurement, X-ray diffraction, and acid buffering capacity testing. Further, we performed a remineralization cycle test of 28 days, and nanoindentation testing was carried out during the immersion period, and then the enamel surfaces were examined using scanning electron microscopy. Additionally, the antimicrobial effects of the sample suspensions were evaluated by measuring their minimum microbicidal concentrations against various cariogenic microbes. Results: Our results revealed that nB had a near-circular shape with an amorphous structure and a considerably large specific surface area due to nanoparticulation. Additionally, nB possessed a rapid acid buffering capacity that was comparable to that of μB. In the remineralization test, faster recovery of mechanical properties was observed on the enamel surface immersed in samples containing bioactive glass nanoparticles (nB and nBZ). After remineralization, demineralized enamel immersed in any of the samples showed a rough and porous surface structure covered with mineralized structures. Furthermore, nBZ exhibited a broad antimicrobial spectrum. Conclusions: These results demonstrated that bioactive glass and zinc oxide nanoparticles have superior demineralization-suppressing and remineralization-promoting effects. Full article
(This article belongs to the Special Issue The Search for Real Biologically Active Dental Materials of the Future)
►▼ Show Figures

Figure 1

11 pages, 627 KiB  
Article
Analysis of Stress Concentration in Functionally Graded Plates with Linearly Increasing Young’s Modulus
by Hassan Mohamed Abdelalim Abdalla, Daniele Casagrande and Francesco De Bona
Materials 2023, 16(21), 6882; https://doi.org/10.3390/ma16216882 - 26 Oct 2023
Cited by 5 | Viewed by 1356
Abstract
In this article, the strain and stress analyses of functionally graded plates with circular holes that are subject to a uniaxial far-field traction load are analytically considered. The Young’s modulus is assumed to vary linearly along the radial direction around the hole. The [...] Read more.
In this article, the strain and stress analyses of functionally graded plates with circular holes that are subject to a uniaxial far-field traction load are analytically considered. The Young’s modulus is assumed to vary linearly along the radial direction around the hole. The adoption of such a type of inhomogeneity variation can be justified as follows. Firstly, and among all the possible variations of stiffness, the linear one is indeed the simplest inhomogeneity distribution. Surprisingly however, according to our knowledge extent, the associated elastic fields were not yet addressed in the literature. Secondly, a linearly varying stiffness could reasonably imply a remarkable advantage from a technological point of view. In fact, unlike nonlinearly varying stiffness plates, manufacturing routes are only required to handle constant variations throughout the radial domain. After recalling the basic equations for plane stress elasticity, the displacement, strain, and stress fields around the hole were numerically tackled and discussed for different stiffness ratios. A comparison was also carried out with other Young’s modulus distributions that have been commonly employed in the literature. Full article
(This article belongs to the Section Advanced Composites)
►▼ Show Figures

Figure 1

14 pages, 3835 KiB  
Article
Martensitic Phase-Transforming Metamaterial: Concept and Model
by Sosuke Kanegae, Masayuki Okugawa and Yuichiro Koizumi
Materials 2023, 16(21), 6854; https://doi.org/10.3390/ma16216854 - 25 Oct 2023
Viewed by 1287
Abstract
We successfully developed a mechanical metamaterial that displays martensitic transformation for the first time. This metamaterial has a bistable structure capable of transitioning between two stable configurations through shear deformation. The outer shape of the unit cell of this structure is a parallelogram, [...] Read more.
We successfully developed a mechanical metamaterial that displays martensitic transformation for the first time. This metamaterial has a bistable structure capable of transitioning between two stable configurations through shear deformation. The outer shape of the unit cell of this structure is a parallelogram, with its upper and lower sides forming the bases of two solid triangles. The vertices from these triangles within the parallelogram are linked by short beams, while the remaining vertices are linked by long beams. The elastic energy of the essential model of the metamaterial was formulated analytically. The energy barrier between these two stable configurations consists of the elastic strain energy due to the tensile deformation of the short beams, the compressive deformation of the long beams, and the bending deformation of the connecting hinges. One example of a novel metamaterial was additively manufactured via the materials extrusion (MEX) process of thermoplastic polyurethane. The metamaterial exhibited deformation behaviors characteristic of martensitic transformations. This mechanical metamaterial has the potential to obtain properties caused by martensitic transformation in actual materials, such as the shape memory effect and superelasticity. Full article
(This article belongs to the Special Issue Acoustic and Mechanical Metamaterials: Recent Advances)
►▼ Show Figures

Figure 1

16 pages, 4388 KiB  
Article
Durability Analysis of CFRP Adhesive Joints: A Study Based on Entropy Damage Modeling Using FEM
by Yutong Li, Huachao Deng, Maruri Takamura and Jun Koyanagi
Materials 2023, 16(20), 6821; https://doi.org/10.3390/ma16206821 - 23 Oct 2023
Cited by 2 | Viewed by 1334
Abstract
Experimental methodologies for fatigue lifetime prediction are time-intensive and susceptible to environmental variables. Although the cohesive zone model is popular for predicting adhesive fatigue lifetime, entropy-based methods have also displayed potential. This study aims to (1) provide an understanding of the durability characteristics [...] Read more.
Experimental methodologies for fatigue lifetime prediction are time-intensive and susceptible to environmental variables. Although the cohesive zone model is popular for predicting adhesive fatigue lifetime, entropy-based methods have also displayed potential. This study aims to (1) provide an understanding of the durability characteristics of carbon fiber-reinforced plastic (CFRP) adhesive joints by incorporating an entropy damage model within the context of the finite element method and (2) examine the effects of different adhesive layer thicknesses on single-lap shear models. As the thickness of the adhesive layer increases, damage variables initially increase and then decrease. These peak at 0.3 mm. This observation provides a crucial understanding of the stress behavior at the resin–CFRP interface and the fatigue mechanisms of the resin. Full article
(This article belongs to the Special Issue Advanced Composite Material Design and Manufacturing Technology for Aerospace Engineering (2nd Edition))
►▼ Show Figures

Figure 1

30 pages, 5370 KiB  
Article
A Method for Predicting the Creep Rupture Life of Small-Sample Materials Based on Parametric Models and Machine Learning Models
by Xu Zhang, Jianyao Yao, Yulin Wu, Xuyang Liu, Changyin Wang and Hao Liu
Materials 2023, 16(20), 6804; https://doi.org/10.3390/ma16206804 - 22 Oct 2023
Cited by 4 | Viewed by 1989
Abstract
In view of the differences in the applicability and prediction ability of different creep rupture life prediction models, we propose a creep rupture life prediction method in this paper. Various time–temperature parametric models, machine learning models, and a new method combining time–temperature parametric [...] Read more.
In view of the differences in the applicability and prediction ability of different creep rupture life prediction models, we propose a creep rupture life prediction method in this paper. Various time–temperature parametric models, machine learning models, and a new method combining time–temperature parametric models with machine learning models are used to predict the creep rupture life of a small-sample material. The prediction accuracy of each model is quantitatively compared using model evaluation indicators (RMSE, MAPE, R2), and the output values of the most accurate model are used as the output values of the prediction method. The prediction method not only improves the applicability and accuracy of creep rupture life predictions but also quantifies the influence of each input variable on creep rupture life through the machine learning model. A new method is proposed in order to effectively take advantage of both advanced machine learning models and classical time–temperature parametric models. Parametric equations of creep rupture life, stress, and temperature are obtained using different time–temperature parametric models; then, creep rupture life data, obtained via equations under other temperature and stress conditions, are used to expand the training set data of different machine learning models. By expanding the data of different intervals, the problem of the low accuracy of the machine learning model for the small-sample material is solved. Full article
(This article belongs to the Special Issue Analytical and Computational Methods in Material and Mechanical Engineering)
►▼ Show Figures

Figure 1

13 pages, 11044 KiB  
Article
Tellurium Corrosion of Type 304/304L Stainless Steel, Iron, Chromium, and Nickel in High-Temperature Liquid Sodium
by Yi Xie
Materials 2023, 16(20), 6798; https://doi.org/10.3390/ma16206798 - 21 Oct 2023
Cited by 3 | Viewed by 1175
Abstract
Investigating tellurium (Te) corrosion on structural materials is crucial for sodium-cooled fast reactors (SFRs) due to radionuclide presence and knowledge gaps. In this study, Type 304/304L stainless steel (SS304), chromium (Cr), iron (Fe), and nickel (Ni) samples were immersed in low-oxygen environments with [...] Read more.
Investigating tellurium (Te) corrosion on structural materials is crucial for sodium-cooled fast reactors (SFRs) due to radionuclide presence and knowledge gaps. In this study, Type 304/304L stainless steel (SS304), chromium (Cr), iron (Fe), and nickel (Ni) samples were immersed in low-oxygen environments with Te in liquid sodium at 773 K for 30 days. At 10 ppm oxygen, SS304 showed multiple oxide layers, including a compact NaCrO2 interlayer and porous Na-Fe-Ni-O outer layers. Tellurium penetrated through the porous layers but was hindered by the NaCrO2 interlayer. At 0.01 ppm oxygen, Cr had no oxide layer, while Fe and Ni had unstable ones. Tellurium-induced pitting was deeper in Fe and Ni compared to Cr. Oxygen levels and Cr composition are critical factors affecting stable oxide compound layer formation and mitigating Te-induced pitting. Full article
(This article belongs to the Section Corrosion)
►▼ Show Figures

Figure 1

16 pages, 7283 KiB  
Article
Network Structure and Luminescent Properties of ZnO–B2O3–Bi2O3–WO3:Eu3+ Glasses
by Aneliya Yordanova, Margarita Milanova, Reni Iordanova, Margit Fabian, Lyubomir Aleksandrov and Petia Petrova
Materials 2023, 16(20), 6779; https://doi.org/10.3390/ma16206779 - 20 Oct 2023
Cited by 2 | Viewed by 1418
Abstract
In this study, we investigated the influence of Bi2O3 and WO3 on both structure and optical properties of 50ZnO:(49 − x)B2O3:1Bi2O3:xWO3; x = 1, 5, 10 glasses doped with [...] Read more.
In this study, we investigated the influence of Bi2O3 and WO3 on both structure and optical properties of 50ZnO:(49 − x)B2O3:1Bi2O3:xWO3; x = 1, 5, 10 glasses doped with 0.5 mol% Eu2O3. IR spectroscopy revealed the presence of trigonal BØ3 units connecting superstructural groups, [BØ2O]− metaborate groups, tetrahedral BØ4− units in superstructural groupings (Ø = bridging oxygen atom), borate triangles with nonbridging oxygen atoms, [WO4]2− tetrahedral, and octahedral WO6 species. Neutron diffraction experimental data were simulated by reverse Monte Carlo modeling. The atomic distances and coordination numbers were established, confirming the short-range order found by IR spectra. The synthesized glasses were characterized by red emission at 612 nm. All findings suggest that Eu3+ doped zinc borate glasses containing both WO3 and Bi2O3 have the potential to serve as a substitute for red phosphor with high color purity. Full article
(This article belongs to the Special Issue Size-Dependent Effects in Materials for Environmental Protection and Energy Application)
►▼ Show Figures

Figure 1

14 pages, 2178 KiB  
Article
Dual-Emissive Monoruthenium Complexes of N(CH3)-Bridged Ligand: Synthesis, Characterization, and Substituent Effect
by Si-Hai Wu, Zhe Zhang, Ren-Hui Zheng, Rong Yang, Lianhui Wang, Jiang-Yang Shao, Zhong-Liang Gong and Yu-Wu Zhong
Materials 2023, 16(20), 6792; https://doi.org/10.3390/ma16206792 - 20 Oct 2023
Cited by 1 | Viewed by 1151
Abstract
Three monoruthenium complexes 1(PF6)2–3(PF6)2 bearing an N(CH3)-bridged ligand have been synthesized and characterized. These complexes have a general formula of [Ru(bpy)2(L)](PF6)2, where L [...] Read more.
Three monoruthenium complexes 1(PF6)2–3(PF6)2 bearing an N(CH3)-bridged ligand have been synthesized and characterized. These complexes have a general formula of [Ru(bpy)2(L)](PF6)2, where L is a 2,5-di(N-methyl-N’-(pyrid-2-yl)amino)pyrazine (dapz) derivative with various substituents, and bpy is 2,2′-bipyridine. The photophysical and electrochemical properties of these compounds have been examined. The solid-state structure of complex 3(PF6)2 is studied by single-crystal X-ray analysis. These complexes show two well-separated emission bands centered at 451 and 646 nm (Δλmax = 195 nm) for 1(PF6)2, 465 and 627 nm (Δλmax = 162 nm) for 2(PF6)2, and 455 and 608 nm (Δλmax = 153 nm) for 3(PF6)2 in dilute acetonitrile solution, respectively. The emission maxima of the higher-energy emission bands of these complexes are similar, while the lower-energy emission bands are dependent on the electronic nature of substituents. These complexes display two consecutive redox couples owing to the stepwise oxidation of the N(CH3)-bridged ligand and ruthenium component. Moreover, these experimental observations are analyzed by computational investigation. Full article
(This article belongs to the Special Issue Advanced Materials for Luminescent Applications)
►▼ Show Figures

Figure 1

24 pages, 8416 KiB  
Article
Comparison of Grain-Growth Mean-Field Models Regarding Predicted Grain Size Distributions
by Marion Roth, Baptiste Flipon, Nathalie Bozzolo and Marc Bernacki
Materials 2023, 16(20), 6761; https://doi.org/10.3390/ma16206761 - 19 Oct 2023
Cited by 2 | Viewed by 1103
Abstract
Mean-field models have the ability to predict the evolution of grain size distribution that occurs through thermomechanical solicitations. This article focuses on a comparison of mean-field models under grain-growth conditions. Different microstructure representations are considered and discussed, especially regarding the consideration of topology [...] Read more.
Mean-field models have the ability to predict the evolution of grain size distribution that occurs through thermomechanical solicitations. This article focuses on a comparison of mean-field models under grain-growth conditions. Different microstructure representations are considered and discussed, especially regarding the consideration of topology in the neighborhood construction. Experimental data obtained with a heat treatment campaign on 316L austenitic stainless steel are used for the identification of material parameters and as a reference for model comparisons. Mean-field models are also applied to both mono- and bimodal initial grain size distributions to investigate the potential benefits of introducing neighborhood topology in microstructure prediction models. This article demonstrates that improvements in the predictions can be obtained in monomodal cases for topological models. In the bimodal test, no comparison with experimental data was performed as no data were available. But relative comparisons between models indicated few differences in the predictions. Although of interest, the consideration of neighborhood topology in grain-growth mean-field models generally results in only small improvements compared to classical mean-field models, especially in terms of implementation complexity. Full article
(This article belongs to the Special Issue Modeling and Simulation of Solid State Phenomena in Metals and Alloys)
►▼ Show Figures

Figure 1

14 pages, 10278 KiB  
Article
The Characteristic of {101¯2}<101¯1¯> Twin of Ti-10V-2Fe-3Al under Planar Wave Detonation
by Tong Wang, Ping Yang, Jin Zhang and Xin-Fu Gu
Materials 2023, 16(20), 6739; https://doi.org/10.3390/ma16206739 - 18 Oct 2023
Viewed by 1068
Abstract
The microstructure evolution of the twin of TB6 (Ti-10V-2Fe-3Al) under planar wave detonation was studied. The initial microstructure of the alloy consists of an α and β phase. It is found that twin deformation is operated in only the α phase due to [...] Read more.
The microstructure evolution of the twin of TB6 (Ti-10V-2Fe-3Al) under planar wave detonation was studied. The initial microstructure of the alloy consists of an α and β phase. It is found that twin deformation is operated in only the α phase due to the limited slip system in this phase. α grains are mainly rotated from {101¯0} to {0002} during the deformation due to the {101¯2}<101¯1¯> twin. Twin variant selection is found in this study, and the orientation of all {101¯2} twins is oriented at {0002} in different α grains with different deformation degrees. The twin variant selection is well explained based on the strain relaxation along the loading axis and the Schmid factor for twinning shear. Full article
(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))
►▼ Show Figures

Figure 1

Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying article 151-200 on page 4 of 36.

Go to page    first_page chevron_left 2 3 4 5 6 chevron_right last_page
Back to TopTop