Bulletin of Materials Science最新文献

This study investigates the electronic, transport and optical properties of selenium-doped zinc telluride (ZnSe_xTe_1−x) ternary alloys in the hexagonal wurtzite (B4) phase at varying selenium concentrations using DFT-based FP-LAPW methods at (x = 0.0, 0.25, 0.50, 0.75, 1.0). Structural properties were calculated using the WC-GGA functional, while electronic, transport and optical properties were computed using the mBJ-GGA functional. All the specimen exhibits direct bandgaps with a Γ–Γ transition. The lattice constants (a and c) decrease nonlinearly with more selenium, while the bulk modulus (B) and bandgap (E_g) increase. The electronic transport properties were evaluated through the Seebeck coefficient, electrical conductivity, electronic thermal conductivity and electronic power factor. Additionally, the optical properties due to scattering were computed, and the results reveal the optically anisotropic nature of all the studied alloys, with birefringence clearly observed. The optical energy gap (E_opt) of each ternary alloy lies in the UV region, promising for UV optoelectronic device applications.

This study synthesised zeolite from bentonite clay, utilizing an ultrasound-assisted technique and response surface methodology (RSM) to optimize the process. Bentonite clay was dehydrated by calcining at 800°C for 1 h. Thereafter, dehydrated bentonite clay was subjected to alkali dissolution using ultrasonication and hydrothermal treatment. In the alkali dissolution stage, optimum conditions of 2.5 M of NaOH at 2 h of sonication were determined using the RSM tool, showcasing a SiO₂ and Al₂O₃ composition of 26.93 and 4.64%, respectively. After alkali dissolution, the obtained residues from the remaining dehydrated bentonite clay were characterized using X-ray fluorescence (XRF) to observe the remaining silica and alumina composition. In hydrothermal treatment, the synthesized zeolites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and fourier-transform infrared spectroscopy (FTIR). The RSM analysis indicated optimum hydrothermal treatment conditions of 105°C for temperature treated at 1 h 30 min. Furthermore, the RSM plots for hydrothermal treatment showed that the crystallinity of the obtained zeolite samples increased with hydrothermal temperature and time. Moreover, the characterisation results showed that lower hydrothermal temperatures and crystallization times exhibited zeolite NaP phases with uniform spherical morphology, whilst higher temperatures and times exhibited hydroxy sodalite phases and large irregular particles. This methodology offers a promising approach for efficient and controlled zeolite synthesis from bentonite clay with the assistance of RSM.

This study investigates γ-ray shielding properties of Ni–Ti–Hf shape memory alloys under uniaxial tension, correlating their mechanical properties with linear attenuation coefficients (LAC). We evaluated LAC (cm^–1) values across various photon energies (E (MeV)), Ti:Hf ratio and APF, revealing an increase in LAC as (E, Ti:Hf, APF, LAC): (0.1, 2:3, 0.70, 32.5) to (0.1, 0:5, 0.74, 49.8) for samples subject to maximum deformation. The mechanical properties were also found to correlate very well with the γ-rays attenuation under optimal conditions. Notably, the plastic deformation of the alloys was found to enhance radiation shielding performance, with a significant reduction in γ-ray transmission (e.g., LAC = 1520 cm^–1) observed in samples with higher mass recovery (e.g., 120%) rates post-deformation. These findings underscore the importance of maintaining alloy density and optimizing mechanical properties for effective radiation shielding in practical applications.

In this study, a novel aligned hierarchical Zn(OH)₂/GaN heterostructure was fabricated at low temperature through a solution-based approach, offering a promising strategy for anisotropic ultraviolet (UV) photodetection. The structure consists of vertically aligned two-dimensional Zn(OH)₂ nanosheets grown epitaxially on a lateral epitaxial overgrowth uncoalesced GaN film. Photoresponse measurements reveal an excellent photoresponse performance with anisotropic photoresponse properties. This anisotropy stems from the directional charge transport pathways facilitated by the aligned Zn(OH)₂ nanosheet/uncoalesced GaN structure. These findings provide a new method to design high-performance UV detection sensors based on GaN grown using lateral epitaxy.

Lightweight and mechanically strong sandwich panels are extensively used in the aerospace, defence and energy sectors. In this context, the present study aims to develop high-strength lightweight multifunctional composites using epoxy and reticulated vitreous carbon (RVC) foam. For this, epoxy-infiltrated RVC foams were prepared by the scalable vacuum-assisted resin transfer moulding (VARTM) technique. The complex porous structure of RVC foam, owing to its local variations in the density as well as open-cell content, entails variations in the compressive strength of the composite, making it a function of density and porosity. To rationalize the statistical variations in composites, the Weibull distribution was used to predict compressive properties, measured on a large number of specimens. The Weibull analysis revealed a regression coefficient of 0.98 and a characteristic strength of ~75.1 MPa. The average compressive strength and modulus of the epoxy–RVC foam composite were found to be 68.52 ± 16.03 and 1303.7 ± 141.63 MPa, respectively. Moreover, the flexural strength and modulus of these composites were found to be 33.6 ± 6.6 and 4.73 ± 2.6 GPa, respectively. In addition, the composites showed electromagnetic interference shielding effectiveness of >20 dB with absorption domination in X-band frequency. On account of its lightweight, promising microwave absorption and mechanical properties, epoxy–RVC foam composites are potential candidates as multifunctional core materials in sandwich panels.

In this study, metal nitrates were used as precursors and citric acid as a chelating and combustion agent to synthesize lithium-substituted zinc ferrite Li_xZn_1−xFe₂O₄ (0.00 ≤ x ≤ 0.12) for gas sensing applications that aim to detect small traces of NH₃ molecules. The effects of Li-doping on the structural and morphological properties of Li_xZn_1−xFe₂O₄ nano-ferrite were investigated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). XRD findings indicated that the synthesized samples formed a pure phase with crystallite sizes ranging from ∼17–28 nm. The preparation process produced spherical particles with high porosity, as confirmed by FESEM images. The grain size of the samples was calculated using the Image J software. The gas response of ZnFe₂O₄ nano-ferrite with different Li doping at different operating temperatures and a constant NH₃ gas concentration was studied. Sensing measurements revealed that Li doping increases the ZnFe₂O₄-based sensor’s response to NH₃ gas. At 200°C, the 0.12 Li–ZnFe₂O₄ nano-ferrite showed the highest sensitivity. Li_xZn_1−xFe₂O₄ is a promising candidate to fabricate an ammonia sensor with high performance.

Choline halide can effectively passivate defects by binding with charged point defects of perovskite. Experimental results at room temperature demonstrated that the reaction of ChI with CsPbI₃ resulted in the formation of a new one-dimensional (1D) crystal phase of ChPbI₃, characterized by synchrotron high-resolution single-crystal X-ray diffraction. Due to the new 1D crystalline phase, the designed structures witnessed considerable photovoltaic improvement. The SCAPS-1D simulation software was used to model a perovskite solar cell featuring a 1D ChPbI₃ absorber. We studied the performance of perovskite solar cells based on a 1D ChPbI₃ absorber layer with different electron/hole transport layers (ETL/HTL). Parameters such as power conversion efficiency (PCE), open-circuit voltage (V_OC), short-circuit current density (J_SC), fill factor (FF), external quantum efficiency (EQE), ideality factor (n_id), photocurrent (J_Ph), Mott–Schottky (M–S) plot, built-in potential (V_bi) and recombination resistance (R_rec) were calculated. The analysis of interface recombination currents indicates that the solar cell with CuSCN as the HTL and TiO₂-MXene as the ETL exhibits the highest performance. By optimizing this type of cell, it is possible to achieve an efficiency of 25.50%.

Electrospinning is the most cost-effective technique for fabricating non-woven mats of fibre ranging in size from nano to submicron. Several polymers have been effectively electrospun in ultrafine fibre form by the electrospinning technique, either in melt or solution form. This study analysed the effect of various electrospinning parameters, such as solution concentration, applied voltage, flow rate, conductivity and solvent types, on the morphology of ultra-high molecular-weight polyethylene (UHMWPE) fibres. Different solvents, such as decalin, p-xylene, p-cymene and cyclohexanone, have been used in various combinations to study the effects of solvent types. It has been observed that the concentration of the solution is critical for producing fibres instead of beads during the electrospinning process. A higher ratio of decalin in a mixture with cyclohexanone leads to the merging of fibres due to insufficient solvent evaporation, which results in solvent entrapment. Conversely, increasing the proportion of cyclohexanone enhances the solution conductivity, reducing the fibre diameter. At a 2 wt% solution concentration of UHMWPE, a smooth and uniform fibre can be produced using a 70:30 ratio of decalin to cyclohexanone, with a flow rate of 1 µl s^–1 and an applied voltage of 15 kV. This combination of electrospinning parameters represents the optimal conditions for generating defect-free fibres.

In this work, several types of deformations (extrusion, one- and two-directional hot pressing) were applied to estimate the influence of regimes of deformations and annealing on characteristics of low-alloying Ru-bearing molybdenum (content of Ru is about 0.3 wt%). This study shows that a combination of extrusion and two-directional hot pressing leads to the formation of a more equiaxial microstructure of the material after annealing. The temperatures of full recrystallization of the studied alloy lie in the range of around 1300–1400°C, depending on the regime of deformation. The median values of grain size in fully recrystallized samples vary from 45 to 75 µm.

In this study we present the synthesis and characterization of graphene oxide (GO) with distinct oxidation degrees, designated as ‘GO-1’ (less oxidized) and ‘GO-2’ (more oxidized), and their impact on water absorption and mechanical properties in cementitious composites. XRD analysis confirmed the complete oxidation phase in GO-2. Thermal analysis quantified oxygenated groups at 12% (m/m) for GO-1 and 35% (m/m) for GO-2. FTIR and Raman spectroscopy revealed heightened oxygenated group presence and increased structural disorder in GO-2, with a D/G intensity ratio of 1.12 for GO-2 compared to 0.98 for GO-1. SEM analysis confirmed large lamellar structures in GO-2. Incorporating GO-1 and GO-2 into cementitious composites resulted in significant changes in water absorption and mechanical properties. The composite with GO-1 reduced water absorption by 14%, while GO-2 increased it by 10%. Compressive strength for GO-1 reached 28 MPa, a 17% increase over GO-2 (24 MPa) and 3.7% higher than the control (27 MPa). Tensile strength for GO-1 was 3.0 MPa (7.1% higher than the control at 2.8 MPa), while GO-2 achieved 3.1 MPa, a 10.7% improvement over the control. Contact angle measurements further supported these trends, with GO-1 showing ~22% increase (indicating hydrophobicity) and GO-2 ~4% decrease (indicating hydrophilicity). These findings highlight the critical role of GO oxidation degree in tailoring cementitious composites for enhanced durability (reduced water absorption) or improved tensile strength, providing a pathway for optimizing material performance.