Bulletin of Materials Science最新文献

Silicon dioxide (SiO₂) is considered to be a promising material for thermal insulation. However, the application scenarios of insulation materials are limited, and how to enhance their practical application value has been an attractive research topic. In this work, SiO₂ nanofibres were prepared by the electrospinning technology. Effects of different heat-treatment parameters on SiO₂ crystal transformation, nanofibres’ diameter and thermal conductivity were investigated, and the thermal-insulation mechanism of SiO₂ nanofibres was further studied. Results of the study show that the heat-treatment process has a significant effect on nanofibre diameter, which affects thermal conductivity. When the heat-treatment temperature is 900°C, the heating rate is 8°C min⁻¹ and holding time is 2 h, the diameter of SiO₂ nanofibres is the finest, and thermal conductivity is the lowest (0.039 W mK⁻¹). In addition, nanofibres is demonstrated as functional fillers of thermal-insulation coating, which exhibit excellent thermal insulation and mechanical properties. This study can provide a certain reference value for the development of new lightweight and functional thermal-insulation fillers.

In this work, the structural, mechanical, and electronic properties of LiCu₂O₂ compound under different pressures were studied using the density functional theory. The spin-polarized generalized-gradient approximation has been used for modelling the exchange-correlation effects. In particular, the electronic structure under zero pressure was analysed using both conventional GGA-PBE and meta-GGA (mBJLDA) functional. The structural optimization was performed by using VASP-code, and the lattice parameters and magnetic moments were calculated. Bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, anisotropy factors, sound velocities, and Debye temperature were obtained from the calculated elastic constants for LiCu₂O₂ compound. While the electronic band structures obtained from both functionals for spin up under zero pressure are semiconductor in nature, the electronic band structures obtained from PBE and mBJLDA functionals for spin down are narrow semiconductor and semiconductor, respectively. For the spin-up state, the E_g value decreases linearly after 5 GPa, while the E_g value increases linearly for the spin-down state. The real and imaginary parts of the dielectric function along the x, y, and z axes and the optical constants, such as the energy loss function, refractive index, reflectivity coefficient, and extinction coefficient are also calculated and presented.

Comprehensive structural and electronic properties of zircon-type ternary-metal oxide, dysprosium orthovanadate, doped with varying concentrations of Er have been investigated using first-principles density functional theory (DFT). Furthermore, the significance of substitutional site doping has been elucidated, revealing that Er incorporation can profoundly alter the structural and electronic characteristics of DyVO₄. Replacing Er atoms with Dy atoms through substitutional doping reduces the band gap to 2.79 eV compared to the pure zircon-type dysprosium vanadate oxide’s band gap value of 2.87 eV. Cohesive energy of Er-doped DyVO₄ oxide has also been computed at the ab initio level of calculation. Partial density of states’ (PDOS) calculations of all configurations, suggest that the doping element Er exhibits favourable chemical interactions with the host metal oxide, DyVO₄. Electronic bands near the zero-energy or Fermi level strongly originate from the molecular orbitals of O, V and Dy atoms. Still, we have found that cation substitution at Dy ions’ site largely influences these electronic states and decreases band gap energy value. Consequently, by adjusting concentration of the dopant, the band gap of DyVO₄ oxide can be finely tuned to achieve specific desired levels, which is suitable for electronic applications.

At the realm of luminescence in the present period, phosphates are the fresh and developing candidates. In the suggested study work, citric acid is used as a fuel to create Sm³⁺- and Eu³⁺-activated/co-activated KSrPO₄ phosphor by a simple combustion process. Through the use of XRD and Rietveld refinement, the phase identity and crystal structure of produced phosphor are examined. SEM is used to examine the morphological study, elemental analysis and elemental analysis of the sample together with the planned phosphor. The suggested phosphors’ vibrational properties were confirmed through the use of FTIR. The suggested phosphor’s charge compensation effect and photochromic qualities demonstrate three instantaneous emission peaks in the visible range, which results in the emission of white light. The produced phosphor is a viable option for white light-emitting diodes and display applications, as confirmed by all these findings.

Metal-based halide perovskite materials are very promising for high-performance optoelectronic devices due to their extraordinary photoelectric properties. Bismuth-based perovskites are believed to replace the toxic Pb-based perovskites in optoelectronics due to their remarkable stability, and nontoxic properties. Here, we report self-powered Cs₃Bi₂Br₉/SnO₂ heterojunction ultraviolet (UV) photodetectors with excellent photoelectric detectivity. The optimized device exhibits an excellent ON/OFF ratio of 5.5 (times) 10³, a large responsivity of 25 mA/W, and a detectivity of 6.9 (times) 10¹¹ Jones at 0 V bias, which is much better than other bismuth halide perovskites with the same structure. In addition, our photodetector performance of the optimized device exhibits almost no change even after 30 days of exposure under an ambient environment, indicating excellent stability. Sulphur is introduced to Cs₃Bi₂Br₉ via bismuth ethyl-xanthogenate (Bi(Xt)₃) to further improve the device performance. Detectivity of 9.2 × 10¹¹ Jones and responsivity of 37 mAW^–1 are achieved, which shows the best performance for bismuth-perovskite photodetector in this work. This work provides a method for fabricating high-performance and stable bismuth-based perovskite photodetectors with perovskite/inorganic heterojunctions.

Amount of waste heat exergy generated globally (~69.058 EJ) can be divided into low temperature <373 K, 30.496 EJ; medium temperature 373–573 K, 14.431 EJ; and high temperature >573 K, 24.131 EJ. The minimum number of thermoelectric pn-junctions required to convert this high-temperature exergy into electrical power using currently known best materials is found to increase from 8.22 × 10¹¹ to 24.66 × 10¹¹ when the aspect ratio of the legs increases from 0.5 to 1.5 cm⁻¹. To convert the low-temperature exergy, 81.76 × 10¹¹ to 245.25 × 10¹¹ junctions will be required. The amount of alloys required to synthesize these is of the order of ‘millions of tons’, which means the elements Bi, Te, Pb, Sb, Sn and Se required are also of similar magnitude. The current production of these elements, however, falls far short of this requirement by several orders of magnitude, indicating significant materials supply chain risk. The production of these elements and devices, even if resources are available, will emit millions of tons of CO₂ showing that current alloys are non-sustainable. It therefore becomes clear that alternate materials with low embodied energy, emissions and toxicity footprint, as well as minimal supply chain risk, need to be pursued.

To increase the active surface area of copper collectors in Li-ion batteries, electrochemical deposition of porous copper films was carried out using a solution of 0.15 M CuSO₄·5H₂O in 0.5 M H₂SO₄. Square-wave pulsating overpotential deposition was performed at overpotential amplitudes of −1100, −1250 and −1400 mV vs. Ag/AgCl on copper foil, rated for Li batteries. Energy-dispersive method analysis and a scanning electron microscope were used to characterize film morphology. X-ray diffraction method was used to analyse structural properties of the deposits. Electroactive and real surfaces of the samples were measured using cyclic voltammetry (CV) in a 0.1 M KOH solution. The results showed that by increasing the applied negative overpotential, the electroactive and real surface area of the samples were increased. As a result, the sample values of 47.13, 58.50 and 62.63 cm² were obtained at the respective deposition overpotential amplitudes of −1100, −1250 and −1400 mV. For untreated film, however, the value was around 9.35 cm². Ultimately, it was discovered that CV is a highly effective technique for determining the real surface area of porous copper foils.

This work presents the synthesis of near-infrared absorbing materials based on copper phosphate by wet chemical precipitation with calcined temperatures of 250–750°C. At lower temperatures, it resulted in libethenite. From 450°C, copper oxy bisphosphate was formed and then transformed to copper dioxide bis(phosphate) and copper orthophosphate at 550–650°C. Sequently, copper dioxide bis(phosphate) decomposition was at 750°C. These thermal products showed significant changes in crystalline phase, morphology, and vibration characteristics, as well as the optical properties of obtained samples. While the samples treated at 250, 350, and 450°C gave pale colours, the ones calcined at 550, 650, and 750°C exhibited darker colours but stronger near-infrared absorbing ability.

The electrochemical corrosion behaviour of Sn-0.7Cu-xTi (x = 0, 1, 2, and 3 wt.%) lead-free solder alloys was investigated using Potentiodynamic polarisation analysis in a 3.5 wt.% sodium chloride solution at room temperature. This study aims to determine the impact of titanium (Ti) variation on the corrosion properties of Sn-0.7Cu-xTi alloys and to provide insights into the optimal composition of Sn-0.7Cu solders based on their corrosion resistance. According to electrochemical impedance spectroscopy (EIS) data, the addition of Ti influenced the corrosion product surface, altering the electrochemical behaviour from charge transfer control to diffusion control. Notably, the inclusion of a trace amount of Ti (1 wt.%) significantly enhanced the corrosion resistance and microstructure of Sn-0.7Cu solder, as evidenced by a markedly higher total resistance (R_t) and a substantially lower corrosion current density (I_corr). However, the excessive addition of Ti (Ti > 1 wt.%) led to the formation of Ti₂Sn₃ intermetallic compounds (IMCs), which diminished the corrosion resistance of Sn-0.7Cu-xTi solders. The primary corrosion products identified were Sn₃O(OH)₂Cl₂ with minor amount of TiO₂, SnO₂ and SnCl₂ complexes. This study concludes that an optimal Ti content of 1 wt.% in Sn-0.7Cu solder significantly improves corrosion resistance, while higher Ti levels adversely affect the alloy's performance.

Combining exceptional crushing strength of hollow glass microspheres (HGM) with reinforcing properties of carbon nanotubes as well as carbon fibres with epoxy resins results in a design poised to meet the demand for advanced, lightweight and high strength materials required in a variety of industries, such as aerospace and automotive, particularly, in the manufacture of composite rocket motor casings. In this study, unidirectional laminates of HGM/multi-walled CNTs (MWCNTs)/carbon-epoxy (CE) composites (samples nomenclature A–F) of varying wt.% of HGM and constant 0.1 wt.% of MWCNTs by filament winding technique were fabricated and subsequently cured. The HGM (iM16K) was varied as 0.2, 0.4, 0.6, 0.8, 1.0 wt.% by maintaining a constant concentration of 0.1 wt.% of MWCNTs. The hardener, fine hard (FH5200) was utilized in combination with epoxy resin (Epofine 1555). The epoxy resin was heated to 60°C after the fillers were added. Thermogravimetric analysis, differential mechanical analyzer and thermal mechanical analyzer were used to estimate the thermal stability, glass transition temperature and coefficient of thermal expansion (CTE), respectively. HGM and MWCNTs dispersion in the fracture samples caused by transverse tensile loading was examined using scanning electron microscopy. The effect of variation of HGM and 0.1 wt.% constant MWCNTs on tensile and compressive properties in transverse fibre directions of these composites has been investigated. Transverse tensile strength and tensile modulus were improved by 29.07 and 12.33%, respectively, up on the addition of 0.2 wt.% of HGM and 0.1 wt.% of MWCNTs in CE composite. The other findings indicated that > 0.2 wt.% HGM along with constant concentration of MWCNTs had decreasing effect on transverse tensile strength, modulus and compressive strength. The MWCNTs agglomeration was identified as the cause of these mechanical property degradations. The addition of HGM and MWCNTs decreased the CTE of the composite and increased the glass transition temperature as HGM limits the thermal motions of the epoxy polymer chain’s molecular segments. The HGM/MWCNTs/CE composite was shown to be thermally stable up to 310°C.