Bulletin of Materials Science最新文献

The structure, electronic, magnetic and optical properties of pyrite CrO₂ at 46 GPa are extensively investigated for the first time using first-principles electronic structure calculations. Structural distortion is observed in the present material due to distortion in the CrO₆ octahedra. The system is found to be half-metallic and ferromagnetic. The two available electrons are found to be distributed among all five Cr-3d orbitals. The three Cr-t_2g (Cr-d_xy, d_yz, d_xz) as well as the two Cr-e_g (Cr-3d_3z²_{- r}², Cr-3d_x²_{- y}²) orbitals are observed to be degenerate. The partial filling and delocalization of electrons in all five Cr-3d orbitals for the majority spin channel are responsible for the half-metallic behaviour of pyrite CrO₂. The simultaneous effect of p-d hybridization and Cr–O antiferromagnetic coupling is responsible for ferromagnetism in the present material. The system remains half-metallic upon the application of U = 3 eV. The strength of ferromagnetism is enhanced at U = 3 eV. The Curie temperature T_c of pyrite CrO₂ is significantly reduced to 146 K (~156 K for U = 3 eV) at 46 GPa. The metallicity and anisotropy in the structure are observed in the investigation of the real [({upvarepsilon }_{1}left(upomega right))] and imaginary [({upvarepsilon }_{2}left(upomega right))] parts of the dielectric function. In the study of the energy loss function [(text{L}left(upomega right))], a significant electron energy loss is observed at a high pressure of 46 GPa. The system exhibits low dissipation or transparency up to 30 eV. The plasmon frequencies observed for ({text{L}}_{text{xx}}left(upomega right)), ({text{L}}_{text{yy}}left(upomega right)) and ({text{L}}_{text{zz}}left(upomega right)) (x-, y- and z-components of [(text{L}left(upomega right))]) are 26.72, 26.65 and 26.34 eV, respectively, below which the system remains metallic. It is observed that the optical properties do not change substantially upon applying U=3 eV.

This research explores the fabrication of tungsten trioxide (WO₃) nanocomposite thin films as an electron transport layer for photovoltaic solar cells. WO₃ was deposited on fluorine-doped tin oxide (FTO) glass using spin coating and aerosol-assisted chemical vapour deposition (AACVD) method to study the differences in structural, morphological, optical and electrical properties of the thin films. WO₃ nanocomposite thin films were characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), ultraviolet–visible (UV–Vis) spectroscopy and linear sweep voltammetry (LSV). From XRD analysis, WO₃ thin films obtained from both methods showed a tetragonal anatase crystal phase with a h k l index of (2 2 1). FESEM images found that the particles in WO₃ thin films by the spin coating method were more even and uniformly distributed, while the film by the AACVD method had some agglomerations. From AFM, the surface of the WO₃ thin film prepared by the spin coating method was found to be smoother, whereas the thin film prepared by the AACVD method was rougher. UV–Vis spectroscopy analysis found that the bandgap energy of the thin film by the spin coating method is lower (2.40 eV) than which by the AACVD method (2.57 eV). From J–V characteristic analysis, it was found that the spin-coated WO₃ thin film has lower current density but higher power conversion efficiency (PCE; η = 0.278%), compared to the thin film by AACVD method, which has higher current density and lower PCE (η = 0.235%). This finding demonstrates the occurrence of a more efficient rate of charge movement between WO₃ layers through the spin coating method. Although it produces a lower photocurrent value, it enhances the efficiency of polymer solar cells.

The study of half-Heusler alloys has captured significant attention in materials science due to their unique electronic and mechanical properties. In this paper, we conducted an in-depth density functional theory (DFT) analysis to explore the half-metallic characteristics of the novel PdFeGa alloy, with particular focus on its band structure and elastic constants. As ternary compounds, half-Heusler alloys have attracted interest due to their versatile properties, which make them suitable for applications in thermoelectrics, spintronics and optoelectronics. Our theoretical investigation into the structural, mechanical, electronic, and magnetic properties of PdFeGa aims to identify stable half-metallic ferromagnets with Curie temperatures exceeding room temperature. PdFeGa exhibits half-metallic ferromagnetism, featuring a high magnetic moment localized at the Fe atom. The compound demonstrates a high Curie temperature and significant spin polarization. To ensure accuracy and convergence, calculations were conducted using the generalized gradient approximation (GGA) for the exchange-correlation potential, along with a dense k-point grid and high-energy cutoff. This DFT study confirms the half-metallic nature of PdFeGa, highlighting its promise for various technological applications.

The thermodynamic calculation was used in the Cd–Nd phase diagram according to the thermodynamic rule. Based on the newly reported phase relations, the thermodynamic expression of the four solution phases (liquid, bcc, dhcp and hcp_A3) was described with the Redlich–Kister form. Four species (Cd₁₁Nd, Cd₆Nd, Cd₅₈Nd₁₃ and Cd₃Nd) were treated as stoichiometric compounds. Three intallic compounds (α-Cd₂Nd, β-Cd₂Nd, CdNd and Cd₄₅Nd₁₁), which exhibited a little homogeneity range, were treated as a two-sublattice model (Model I). Three compounds (α-Cd₂Nd, β-Cd₂Nd, CdNd and Cd₄₅Nd₁₁), with low solubility, were used as a two-sublattice thermodynamic model (Model I). The compound CdNd was simultaneously optimized with another model to cope with disorderly transitions from bcc-A2 to bcc-B2 (Model II). The prescription of (Cd, Nd)_0.5(Cd, Nd)_0.5(Va)₃ was given expression to the order structure of the CdNd phase. Fourteen different types of phase transition were raised in the Cd–Nd system.

The slow hydrogen absorption kinetics, primarily caused by significant exothermic effects and resulting temperature variations, restrict the practical application of metal hydride. This study presents both experimental and numerical investigations of the Ti₂₄Zr₁₃Cr₂₅Mn₃₂Fe₆-based bed. The necessary kinetics and thermodynamic parameters for the simulation model were determined, showing a high degree of agreement between the experimental measurements and the fitted results. A cylindrical test reactor was also developed to evaluate the hydrogenation behaviours of the metal hydride bed under various operational conditions, using 9 Kg of powder in the larger reactor. The absorption and desorption processes of the AB₂-type metal hydride were simulated within this reactor. In order to improve heat dissipation and decrease experimental duration, internal square fins and heat exchange tubes (1/4′′, SS 316) were integrated into the reactor (outer diameter 76 mm, SS 316). The temperature evolution curves obtained experimentally were found to align closely with the simulation results, validating the numerical model’s accuracy and supporting the optimization of future metal hydride tank designs. This study offers valuable insights into the application of numerical simulations in advanced hydrogen storage systems.

Blue phase liquid crystals (BPLCs) possess remarkable optical properties, including selective visible light reflection, sub-millisecond response times and wide viewing angles without the need for alignment layers. These attributes make them highly promising for advanced display technologies. However, the narrow temperature range and high operating fields required for blue phase liquid crystal (BPLC) devices present significant challenges. Consequently, the integration of liquid crystals (LCs) with nanoparticles (NPs) to form BPLC composites has garnered considerable attention. This review summarizes experimental and synthetic methodologies, compares design strategies, and discusses both current cum potential applications of these composite materials.

The indium-free transparent conductive SnO₂:Mo/Ag/SnO₂:Mo tri-layer films were prepared by magnetron sputtering at room temperature for the first time, and the mechanism of the effect of Ag layer thickness on the properties of tri-layer films was systematically investigated. The results showed that the change of the morphology of Ag layer caused by the Ag layer thickness is the main factor for determining the optical and electrical properties of the SnO₂:Mo/Ag/SnO₂:Mo film. Moreover, the optical properties of the tri-layer film can be significantly optimized by adjusting the SnO₂:Mo layer thickness. The tri-layer films with the Ag layer thickness of 7 nm and SnO₂:Mo layer thickness of 40 nm exhibited optimum properties, with a maximum figure of merit of 2.5 × 10⁻² Ω⁻¹, a high visible light transparency of 84% and a low sheet resistance of 7 Ω/sq, and excellent mechanical flexibility. In addition, the application potential of the SnO₂:Mo/Ag/SnO₂:Mo electrodes were also demonstrated in the thin film transistor device.

Aluminium-bronze alloys are widely used in engineering applications due to their strength, wear resistance and corrosion behaviour. This study investigates the production of Cu-10 wt% Al alloys using the electric current-assisted sintering (ECAS) method, with sintering times of 10, 15 and 20 min, under a current range of 850 ± 50 A. The structural properties, phase composition, hardness, wear resistance and corrosion behaviour of the alloys were thoroughly examined. Scanning electron microscopy and energy-dispersive spectroscopy analyses revealed that the reactions continued with increasing sintering time. The hardness of the alloys increased with sintering duration, with values of 138 HV_0.1, 145 HV_0.1 and 176 HV_0.1 for the 10, 15 and 20-min sintering times, respectively. After 20 min of sintering, the hardness of the alloy was 2.5 times higher than that of pure Cu and pure Al. The Cu-10 wt% Al alloy sintered for 20 min exhibited superior friction and wear properties, suggesting that prolonged sintering led to the formation of intermetallic phases. Additionally, the corrosion resistance improved with longer sintering times, with the sample sintered for 20 min showing the best protective surface characteristics, attributed to the formation of intermetallic compounds, such as CuAl₂. All findings were supported by regression analysis and surface response graphics. These results demonstrate that optimized ECAS parameters can significantly enhance the mechanical and corrosion properties of Cu-Al alloys.

This study investigates the impact of Ti substitution on the microstructural features, mechanical hardness, martensitic transformation behaviour and magnetic hyperfine interactions of FeNiSi-based alloys. FeNiSi and FeNiSiTi alloys were synthesized via arc melting and subsequently characterized using scanning electron microscopy, Vickers microhardness testing, differential scanning calorimetry (DSC) and Mössbauer spectroscopy. Microstructural analysis revealed that the Fe-34.5%Ni-4.2%Si alloy exhibits an austenitic matrix with lenticular martensitic structures, while Fe-28.5%Ni-4.1%Si-0.6%Ti alloy showed microstructural changes attributed to lower nickel content and titanium addition. Mechanical hardness measurements showed that the Fe-28.5%Ni-4.1%Si-0.6%Ti alloy exhibited lower microhardness compared to the Fe-34.5%Ni-4.2%Si alloy, which is potentially due to reduced nickel content, coarser grain size or processing variations. DSC analysis indicated nearly identical martensitic transformation temperatures for both alloys, but the Fe-28.5%Ni-4.1%Si-0.6%Ti alloy exhibited a significantly more distinct exothermic peak, releasing approximately 65 times more energy during transformation, suggesting a more extensive or complete phase transformation in the titanium-containing alloy. Mössbauer spectroscopy confirmed the presence of both magnetic (martensite) and non-magnetic (austenite) phases in both alloys. The Ti-containing alloy showed a slight increase in the volumetric percentage of the austenite phase and a weakening of magnetic interactions within the ferromagnetic phases, along with changes in isomer shift and quadrupole splitting values. This indicates the influence of titanium on the electronic environment and local symmetry around iron nuclei. These results highlight the significant role of titanium in influencing the microstructural evolution, mechanical properties and phase transformation characteristics of FeNiSi-based alloys.

Under the virtual crystal approximation (VCA), the pseudopotential approach (EPM) has been applied to our calculations. The lattice vibrational, electronic, and optical properties of GaAs_1-xP_x alloy for fixed values of temperature are calculated and their dependence on the GaP concentration is examined. The used technique represents the first theoretical predictions for compositions x in the range 0–1, whereas our results for GaAs (x=0) and GaP (x=1) are generally in reasonable accord with the known data in the literature. Our findings showed the transition from direct to indirect energy band gap at various temperatures for the GaAs_1-xP_x alloy and the results may help us understand the heat dissipation in computer chips and thermoelectric devices.