Search Results (86)

The chemical and structural similarity of calcium orthophosphates to hard tissues in the human body makes them suitable as biomaterials for bone implants, cements, injection systems, etc., for bone regeneration and reconstruction. Tetracalcium phosphate (Ca₄(PO₄)₂O, TTCP) is a promising component for such biomaterials due to its high calcium content and alkaline nature. The former makes it suitable for promoting mineralization, while the latter supports neutralization of the acidic environment, helping to prevent inflammation and improve the biocompatibility of the materials. However, it is the least used calcium orthophosphate due to the difficulties in its synthesis. This study examines the effect of high-energy mechanochemical activation on the phase evolution, particle morphology, and thermal behaviour of equimolar mixtures of Ca(OH)₂ and CaHPO₄, with the aim of optimizing precursor conditions for the synthesis of (TTCP)-rich ceramic materials. The results demonstrate that mechanochemical activation effectively induces structural disorder, promotes the formation of amorphous and nanocrystalline phases, and facilitates subsequent phase transitions upon calcination. The combined use of solid-state NMR, XRD, TEM, and thermal analysis provides a comprehensive understanding of the transformation pathways. Ultimately, 24 h of activation under the experimental conditions was identified as optimal for producing a precursor with a favorable phase composition for obtaining TTCP-rich ceramic materials after calcination at 1350 °C. Full article

The (AlFeCoNi)C high-entropy alloy carbide films (HECFs) with tunable carbon contents were fabricated by magnetron sputtering to investigate the carbon-driven structural evolution and its coupling effects on mechanical and chemical properties. With increasing carbon incorporation (0–47.6 at.%), the HECFs formed a composite structure of amorphous phase and BCC nanocrystalline phase, as evidenced by XRD and TEM. Atom probe tomography (APT) reveals Al segregation in the film. Remarkably, the wear rate decreases exponentially from 4.8 × 10⁻⁵ to 6.7 × 10⁻⁶ mm³/N·m, attributed to the amorphous carbon phase acting as solid lubricant. Simultaneously, the corrosion current density reduces by two orders of magnitude (7.2 × 10⁻⁸ A/cm² in 3.5% NaCl), benefiting from the amorphous network inhibiting ion diffusion pathways. This work establishes a carbon-content–property correlation paradigm for designing multifunctional HEA films in extreme environments. Full article

Multilayer thin films composed of cobalt (Co), carbon (C), and chromium (Cr) possess promising electromagnetic properties, yet the combined Co–C–Cr system remains underexplored, particularly regarding its performance as a microwave absorber. Existing research has primarily focused on binary Co–C or Co–Cr compositions, leaving a critical knowledge gap in understanding how ternary multilayer architectures influence electromagnetic behavior. This study addresses this gap by investigating the structure, phase composition, and microwave absorption performance of Co–C–Cr multilayer coatings fabricated via magnetron sputtering onto porous silicon substrates. This study compares four-layer and eight-layer configurations to assess how multilayer architecture affects impedance matching, reflection coefficients, and absorption characteristics within the 8.2–12.4 GHz frequency range. Structural analyses using X-ray diffraction and transmission electron microscopy confirm the coexistence of amorphous and nanocrystalline phases, which enhance absorption through dielectric and magnetic loss mechanisms. Both experimental and simulated results show that increasing the number of layers improves impedance gradients and broadens the operational bandwidth. The eight-layer coatings demonstrate a more uniform absorption response, while four-layer structures exhibit sharper resonant minima. These findings advance the understanding of ternary multilayer systems and contribute to the development of frequency-selective surfaces and broadband microwave shielding materials. Full article

High-energy ball milling for different durations was used to synthesize nanocrystalline Mg₆₀Ni₂₅Cu₁₀Ce₅ powders. The morphology and microstructure of the milled powders were investigated by scanning electron microscopy and X-ray diffraction, respectively. It was found that different milling times result in considerably different phase composition. The powder milled for 1 h is characterized by elemental Mg, Ni, Cu and Ce with some minor content of intermetallics. In total, 3 h milling promotes the intensive formation of intermetallic compounds, while 10 h of powder processing results in a partially amorphous state coupled with compound phases. Isothermal hydrogenation and dehydrogenation experiments were conducted in a Sieverts’-type apparatus. It was found that all powders absorb H₂ reversibly, while the shortest milling time provides the best overall capacity. Excellent kinetics without any activation cycle were obtained for the 3 h milled composite, releasing and absorbing 50% of the total hydrogen content within 120 s. Each kinetic measurement has satisfactorily been fitted by the Johnson–Mehl–Avrami function. X-ray diffraction analysis on the dehydrided powders confirmed the complete desorption. Full article

Tungsten–diamond metal matrix composites (MMCs) fabricated via L-PBF show potential for applications in nuclear facility shielding, heat sinks, precision cutting/grinding tools, and aerospace hot-end components. In this paper, tungsten (W), diamond (D), and diamond with Ni coating (D-Ni) powders are used to fabricate W+D and W+(D-Ni) composites by L-PBF technology. The results show that at the interface of the W+D sample, the W powder melts while the D powder remains in a solid state during L-PBF processing, and W and C elements gradually diffuse into each other. Due to the high cooling rate of L-PBF processing, the C phase forms a diamond-like carbon (DLC) phase with an amorphous structure, and the W phase becomes a supersaturated solid solution of the C element. At the interface of the W+(D-Ni) sample, the diffusion capacity of Ni and W elements in the solid state is weaker than in the molten state. C and W elements diffuse into the Ni melt, forming a rich Ni area of the DLC phase, while Ni and W elements diffuse into the solid D powder, forming a lean Ni area of the DLC phase. In the rich Ni area of the DLC phase, Ni segregation leads to the precipitation of nanocrystals (several hundred nanometers), whereas in the lean Ni area of the DLC phase, the diffusion capacity of Ni and W elements in the solid D powder is limited, resulting in nanocrystalline sizes of only about tens of nanometers. During W dendrite growth, the addition of the Ni coating and the expelling of the C phenomenon leads to W grain refinement at the interface, which reduces the number and length of cracks in the W+(D-Ni) sample. This paper contributes to the theoretical development and engineering applications of tungsten–diamond MMCs fabricated by L-PBF. Full article

Three alloys differing in their nominal chemical composition (Ni₅₀Ti₅₀, Ni₅₁Ti₄₉, and Ni₅₂Ti₄₈) were produced in the form of powders using high-energy ball milling. Their microstructure, morphology, structure, and phase composition were studied using the X-ray diffraction technique, scanning, and transmission electron microscopy. For the detailed structural analysis, the Rietveld method was used. The results show that each of the alloys consists of three fractions: fine, medium, and thick. The fractions varied in particle/agglomerate size from 200 nm to 800 μm. Additionally, they varied in phase composition. The fine fraction comprised a mixture of amorphous and nanocrystalline phases. Additionally, the medium and coarse phases showed crystalline solid solutions formed on the bases of nickel or titanium, as well as a crystalline bcc phase—a precursor of the parent phase (B2). The largest contribution in the alloy powders, over 80%, comes from the amorphous–nanocrystalline mixture (ANM). The increase in the nickel content resulted in an increase in ANM quantity of 3 wt.%. Similarly, the weight content of the titanium-based solid solution increased to about 7 wt.%. In contrast, the quantity of the nickel-based solid solution decreased from 3 wt.% to approximately 1 wt.% in the Ni₅₀Ti₅₀ and Ni₅₂Ti₄₈ alloys. Full article

In this study, α-cellulose was extracted from lignocellulosic simpor leaf residue as a sustainable alternative to conventional cellulose sources. The extraction process involved the removal of hemicellulose, lignin, and other phytocompounds using alkali (NaOH) treatment and bleaching with hydrogen peroxide (H₂O₂). The nanocrystalline cellulose (NCC) was isolated from α-cellulose using sulfuric acid hydrolysis treatment followed by ultrasonication. The extracted α-cellulose and isolated NCC were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and dynamic light scattering (DLS). The obtained results confirmed that the extracted NCC exhibited characteristic cellulose functional groups and a crystallinity index of 64.7%, indicating the effective removal of amorphous regions through sulfuric acid hydrolysis. The thermal stability of the extracted cellulose increased to 332 °C due to the elimination of extractives. DLS analysis showed that the extracted NCC exhibited high colloidal stability in polar solvents, characterized by a zeta potential of −70.8 mV and an average particle size of 251.7 nm. This study highlights an environmentally friendly approach for converting low-value biomass waste into high-value cellulose materials with potential applications in sustainable packaging, biomedical applications and composite reinforcement. Full article

Nanocrystalline powders, characterized by a biphasic amorphous nanocrystalline structure, demonstrate outstanding soft magnetic characteristics, including reduced coercivity (H_c), enhanced effective permeability (μ_e), and increased resistivity. However, their high hardness, poor formability, and significant core loss (P_cv) restrict their use in high-performance molded inductors. In this study, FeSiBCuNb/FeSiAl nanocrystalline soft magnetic composites (NSMCs) were fabricated, and the influence of varying the FeSiAl concentration on the microstructure, density, and soft magnetic characteristics of NSMCs was investigated. Then, the underlying mechanisms of these effects were explained. The results demonstrate that FeSiAl exhibits apparent deformation following compression, effectively filling the air gap between the FeSiBCuNb powder particles, thereby enhancing coupling among the magnetic particles. Consequently, the density of the NSMCs was enhanced, leading to a significant improvement in their overall soft magnetic properties. When 50 wt.% FeSiAl is added, the NSMCs display outstanding magnetic properties, including a low H_c of 4.36 Oe, a high μ_e of 48.7, a low P_cv of 119.35 kW/m³ at 50 mT and 100 kHz, and a high DC-bias performance of 73.29% at 100 Oe. Compared to NSMCs without FeSiAl, μ_e increased by 59.4% and P_cv decreased by 66.1%. Meanwhile, the incorporation of ultrafine FeSiAl powder was found to significantly improve the material properties, as the deformable FeSiAl particles effectively fill interparticle gaps during compaction, enhancing density and magnetic coupling. The 50 wt.% FeSiAl composition demonstrated exceptional properties. These advances address critical challenges in high-frequency power electronic applications and provide a practical material solution for next-generation power electronics. Full article

Fe-based amorphous and nanocrystalline alloys, such as FINEMET and its improved variants, are highly valued as green energy-saving materials due to their unique magnetic properties, including high permeability, low coercivity, and near-zero saturation magnetostriction. These characteristics have enabled their extensive use in power electronics and information technology. However, the full potential of these alloys remains unfulfilled due to insufficient understanding of their stress sensitivity. This study focuses on the development history, heat treatment, annealing processes, chemical composition, and underlying mechanisms of Fe-based amorphous and nanocrystalline alloys, aiming to provide insights into stress-induced magnetic anisotropy and guide the development of greener and more efficient soft magnetic materials. Full article

In order to address the weaknesses of poor corrosion resistance of hydraulic cylinder piston rods, we have developed a surface protection strategy for titanium aluminum nitride coatings by filter cathode vacuum arc (FCVA) technology. The optimization and regulatory mechanism of N₂ flow rate on the microstructure, mechanical, and electrochemical oxidation behaviors have been emphasized. The results indicated that all coatings revealed a nanocrystalline amorphous composite structure dominated by an fcc TiAlN phase. However, the solid solution content, growth orientation, and grain size could be controlled by the nitrogen flow rate, thereby achieving optimized hardness, adhesion strength, corrosion, and oxidation resistance. Specifically, with the increase in the N₂ flow rate, the solid solution content continued to rise, while the crystal orientation transformed from the (111) to the (200) plane, and the grain size initially increased and then decreased. As a result, mechanical properties, including hardness, toughness, resistance to plastic deformation, and adhesion strength, displayed a trend of initially increasing and then decreasing. The corrosion failure of coatings was linked to surface defects controlled by the N₂ flow rate, rather than the composition and phase structure. The coating displayed superior corrosion resistance at low N₂ flow rates due to fewer macroscopic particles and pore defects. This study provides valuable insights into the corrosion behavior of an aluminum titanium nitrogen coating, providing crucial guidance for coating design in harsh environments. Full article

The incorporation of a homogeneously distributed nanocrystalline phase in Fe-based amorphous coatings is widely acknowledged to enhance wear resistance across various applications. In this study, FeCrMoWBRE amorphous/nanocrystalline composite coatings were fabricated on 45# steel substrates using high-velocity arc spraying (HVAS). The coatings were produced under varying spraying voltages, currents, and distances, following the Taguchi experimental design methodology. The microstructure, mechanical properties, and wear resistance of the coatings were systematically analyzed, with a particular focus on the relationship between nanocrystalline/amorphous phase content and key performance metrics, including microhardness, adhesive strength, and wear rate. A positive correlation was observed between the nanocrystalline phase content and both mechanical properties and wear resistance. The coating with optimized nanocrystalline phase content of 21.4% exhibits the lowest wear rate of 1.39 × 10⁻⁷ mm³·N⁻¹·m⁻¹ under a 100 N load and oil lubrication. These findings underscore the critical role of controlling the nanocrystalline phase content in Fe-based amorphous/nanocrystalline composite coatings to maximize wear resistance under oil-lubricated conditions. Full article

The TiB₂ film exhibits exceptional hardness and chemical stability due to its unique crystal structure and robust covalent bonds, but it also demonstrates high brittleness and poor toughness, which restricts its practical applications in engineering. By appropriately incorporating metal dopants, the toughness of the ceramic matrix can be enhanced without compromising its inherent hardness. In this study, TiB₂ films with different nickel contents (0–32.22 at.%) were fabricated through radio frequency magnetron sputtering. The microstructure, chemical composition, phase structure, and mechanical properties were analyzed using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and nanoindentation tester. The pure TiB₂ film exhibited (0001) and (0002) peaks; however, the addition of nickel resulted in broadening of the (0001) peak and disappearance of the (0002) peak, and no crystalline nickel or other nickel-containing phases could be identified. It was found that the incorporation of nickel refines the grain structure of titanium diboride, with nickel present in an amorphous form at the boundaries of titanium diboride, thereby forming a wrapped structure. The enrichment of nickel at the grain boundary becomes more pronounced as the nickel content is further increased, which hinders the growth of TiB₂ grains, resulting in the thinning of columnar crystals and formation of nanocrystalline in the film, and the coating hardness remains above 20 GPa, when the nickel content is less than 10.83 at.%. With the increase in nickel content, titanium diboride exhibited a tendency to form an amorphous structure, while nickel became increasingly enriched at the boundaries, and the coating hardness and elastic modulus decreased. The wrapped microstructure could absorb the energy generated by compressive shear stress through plastic deformation, which should be beneficial to improve the toughness of the coatings. The addition of nickel enhanced the adhesion between the film and substrate while reducing the friction coefficient of the film. Specifically, when the nickel content reached 4.26 at.%, a notable enhancement in both nanohardness and toughness was observed for nanocomposite films. Full article

Amorphous and nanocrystalline alloys, as novel soft magnetic materials, can enable high efficiency in a wide range of power conversion techniques. Their wide application requires a thorough understanding of the fundamental material mechanisms, typical characteristics, device design, and applications. The first part of this review briefly overviews the development of amorphous and nanocrystalline alloys, including the structures of soft magnetic composites (SMCs), the key performance, and the underlying property-structure correction mechanisms. The second part discusses three kinds of high-power conversion applications of amorphous and nanocrystalline alloys, such as power electronics transformers (PETs), high-power inductors, and high-power electric motors. Further detailed analysis of these materials and applications are reviewed. Finally, some critical issues and future challenges for material tailoring, device design, and power conversion application are also highlighted. Full article

Nowadays, the application of protective multicomponent coatings based on hard metal nitrides is increasingly used to increase the resistance of structures and tools to wear, corrosion, and oxidation. In the present work, the multicomponent system Ti-Al-Ta-Si-N is studied, which has high hardness and crack resistance combined with thermal stability and oxidation resistance. The process of formation of the nanocrystalline structure of the coating during its deposition on materials plays a key role in the optimization of these properties. The nanocrystalline structure of the coating is formed due to Si impurity, which is poorly soluble in the Ti_1−x−yAl_xTa_yN system based on B1-TiN and segregates mainly along grain boundaries, forming grain boundary amorphous phases of Si_zN type. In order to find the optimal composition of multicomponent coatings with improved physical and mechanical properties, it is necessary to understand the peculiarities of interaction of Si impurity with the surface of B1-TiN phase in the presence of Al and Ta substitutional impurities. In the present work, with the help of first-principles calculations of electronic and atomic structure of (001) and (111) surfaces of the Ti_1−x−yAl_xTa_yN system with adsorbed Si atom and the interatomic bond study apparatus based on the calculation of a crystal orbital Hamilton population and a crystal orbital bond index, the nature of the bonds between adsorbed Si and the N, Ti, Al, and Ta atoms of the Ti_1−x−yAl_xTa_yN surface system has been studied. It was found that the binding energy of Si with the Ti_1−x−yAl_xTa_yN surface system can be both higher and lower than the binding energy of its bonding with the surface of the binary TiN compound depending on the position of the Al and Ta substitution atoms in the surface layers. The Si bonding with the atoms of the Ti_1−x−yAl_xTa_yN surface is ionic–covalent in nature. It is shown that the Si-Ta interaction has the highest degree of covalency and strength, and the Si-Al interaction is predominantly ionic in most cases considered and is weaker than the Si-Ti and Si-N bonds. Impurity atoms of Al or Ta have very little effect on the Si-Ti and Si-N bonds due to the local nature of the bonds in the Ti_1−x−yAl_xTa_yN surface system with adsorbed silicon atoms. Full article

In the realm of photoelectrocatalytic (PEC) water splitting, the BiVO₄/WO₃ photoanode exhibits high electron–hole pair separation and transport capacity, rendering it a promising avenue for development. However, the charge transport and reaction kinetics at the heterojunction interface are suboptimal. This study uses the hydrothermal–electrodeposition–dip coating–calcination method to prepare a microcrystalline WO₃ photoanode thin film as the substrate material and combines it with nanocrystalline BiVO₄ to form a micro–nano-structured heterojunction photoanode to enhance the intrinsic and surface/interface charge transport properties of the photoanode. Under the condition of 1.23 V vs. RHE, the photoelectric current density reaches 1.09 mA cm⁻², which is twice that of WO₃. Furthermore, by using a simple impregnation–mineralization method to load the amorphous FeOOH catalyst, a noncrystalline–crystalline composite structure is formed to increase the number of active sites on the surface and reduce the overpotential of water oxidation, lowering the onset potential from 0.8 V to 0.6 V (vs. RHE). The photoelectric current density is further increased to 2.04 mA cm⁻² (at 1.23 V vs. RHE). The micro–nano-structure and noncrystalline–crystalline composite structure proposed in this study will provide valuable insights for the design and synthesis of high-efficiency photoelectrocatalysts. Full article