Materials Chemistry and Physics最新文献

This work presents a method for fabricating metallic nanostructures and metal oxides using a closed, low-temperature growth system. The technique uses vacuum thermal evaporation, enabling nanostructure formation under controlled conditions. The growth system features a double-crucible arrangement within a vacuum chamber, allowing precise control of deposition parameters such as temperature, time, and pressure. This innovative approach has successfully produced a variety of nanostructures, including nanoparticles, nanowires, and nanotowers, with materials such as Au, Ge, and Al and oxides such as SnO₂, ZnO, and Al₂O₃. The results emphasize the critical role of substrate temperature in determining the morphology and size of nanostructures, with particular attention paid to the ratio of substrate temperature to the melting point of the fabricated nanomaterial. The work finds that this ratio significantly influences whether the resulting nanostructures form nanoparticles, nanowires, or more complex shapes. Characterization techniques, including field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD), confirm the successful fabrication and crystallization of the nanostructures. The ability of the method to control the formation of nanostructures through simple modifications of experimental parameters makes it a promising approach for producing tailor-made nanomaterials for various technological applications.

Electrochemical water splitting and CO₂ reduction are important processes to produce hydrogen and low–carbon fuels as renewable energy sources. Here, nanostructured MnMoO₄, prepared by the reflux precipitation method, was investigated as a trifunctional electrocatalyst for overall water splitting and CO₂ reduction reactions. Using a combination of diffuse reflectance spectroscopy and electrochemical impedance spectroscopy results, a direct band gap of 3.05 eV was obtained experimentally for the prepared MnMoO₄. An overpotential of 0.36 V at a current density of 5 mA cm⁻² and a Tafel slope of 58 mV dec⁻¹ were obtained for the oxygen evolution reaction. At a current density of 3 mA cm⁻², overpotentials of 0.39 V and 0.58 V were achieved in the absence and presence of CO₂ bubbling into a 0.1 M KOH solution, respectively, emphasizing the poisoning effect of CO₂ reduction intermediates for the hydrogen evolution reaction. Based on the obtained results, MnMoO₄ could be a promising electrocatalyst for water splitting and CO₂ reduction reactions.

The effects of cold rolling routes followed by annealing on the mechanical properties of AISI 316L stainless steel were characterized. Both unidirectional and cross rolling methods were applied and the evolutions of shear mechanical properties by shear punch testing (SPT) and hardness during reversion/recrystallization annealing were systematically investigated. It was revealed that cross rolling promotes strain-induced martensitic transformation during rolling and also enhances grain refinement during annealing, leading to improved hardness and ultimate shear strength (USS). The variation of USS with annealing time was similar to that of Vickers hardness (H_V), so that the simple and useful equation of USS = 0.196H_V was derived. Moreover, by relating the USS to the ultimate tensile strength (UTS) via von Mises criterion, the finalized equation of H_V = 2.95UTS was obtained, confirming the empirical formula of H_V = 3UTS for steels. Accordingly, this work can shed light on the application of SPT for investigating the mechanical properties of austenitic stainless steels.

The most important task of flexible and stretchable electronics is to modify the structure in nanoheterogeneous metal-dielectric media to control the properties of materials and create new small-sized devices based on them. In this paper, we present the results of experimental studies of the structure and microwave reflective properties in the frequency range of 8–12 GHz of amorphous nanogranulated composites ${\left(CoTaNb\right)}_x{\left(MgO\right)}_{1-x}$, 21.73 ≤ x ≤ 73.27 at.% with a thickness of 311–1040 nm. Niobium and tantalum, which are part of the metal alloy, are the most promising metals used in aircraft and rocket engineering, as well as in radio electronics and microprocessor technology, for example, as capacitors. The AFM method revealed a granular structure with a granule size from 70 to 200 nm at a metal alloy content of up to 51.70 at.%. The spectra of the microwave reflectivity as a function of frequency, the dependence of the reflectivity on the metallic phase content and the effective thickness of the composite layer are obtained. It is shown that a significant increase in the microwave reflectivity and its saturation are determined to a greater extent by the metallic phase content than by the effective layer thickness. The results of the experimental effect of magnetic fields with induction up to 0.3 T on the microwave reflectivity of composite films are presented. It is shown that magnetic fields can most effectively change the reflective properties of composites (from 8 % to 29 %) at the extremes of the microwave reflectivity of films with the lowest metallic phase content of 22.61–21.73 at.%. With an increase in the metallic phase content, the maximum change in the microwave reflectivity decreases exponentially.

Ti6Al4V-xYH₂ (x = 0, 0.1, 0.2, and 0.3 wt%) was produced in this research employing conventional powder metallurgy methods (cold pressing and sintering). The densification behavior, microstructure and mechanical properties of Ti6Al4V alloy caused by the addition of YH₂ were systematically studied. The outcomes indicated that the Ti6Al4V containing 0.1 wt% YH₂ has received a synergistic increase in ductility and strength (Ultimate tensile strength: 976.4 MPa; Elongation: 9.3 %), which is mainly attributable to the combined effect of grain refinement and purification of impurity oxygen. The study provides an economical approach for employing low-cost, high-oxygen HDH Ti powder to produce high-performance Ti material.

In this research, the high entropy alloy (HEA) of Al_0.5CoCrFeNiNb_0.5-Si_0.1 was successfully synthesized through mechanical alloying utilizing a high-energy planetary ball mill. The synthesized HEA powder was subsequently pressed and sintered at 1400 °C with varying holding times. The phase evolution was investigated using X-Ray Diffraction (XRD) technique. Furthermore, the microstructural, morphological, and compositional characteristics of the powders were examined using Transmission Electron Microscopy (TEM) with Selected Area Electron Diffraction (SAED), as well as Scanning Electron Microscopy (SEM) in conjunction with Energy Dispersive Spectroscopy (EDS). The nano-mechanical properties of the HEA compact were evaluated through nanoindentation to determine nano-hardness and elastic modulus.

The mechanical alloying process was conducted for a duration of 30 h, resulting in the formation of a single-phase BCC solid solution, as confirmed by XRD and SAED analyses. The study investigated the criteria for phase stability based on the minimum Gibbs free energy and Hume-Rothery rules, which were consistent with the observed microstructural characteristics. Furthermore, the sintering process resulted in porosity levels of 6.01 % and 4.71 %, with corresponding densities of 6.96 g/cm³ and 7.12 g/cm³ for holding times of 3 and 4 h, respectively. It was noted that extended holding times improved the mechanical properties, with the alloy achieving a maximum hardness of 546 HV, nano-hardness of 5.57 GPa, elastic modulus of 265.47 GPa, and yield stress of 1.89 GPa after a holding time of 4 h.

A new simple preparation method for water-in-salt-type cellulose hydrogels filled with ZnBr₂ is reported. The ZnBr₂ hydrogel electrolyte can be applied to zinc-ion hybrid supercapacitors and Zn–Br interfacial batteries. The water-in-salt ZnBr₂ hydrogel serves as a stable electrolyte for good electrochemical performance in zinc-ion hybrid supercapacitors without redox reactions and can participate in the charging/discharging process of the Zn–Br interfacial battery through the redox reaction of halogen anions. The assembled zinc-ion hybrid supercapacitor exhibits a specific capacitance of 241.8 F g⁻¹ at 0.5 A g⁻¹. Furthermore, after a 10,000-cycle-long charging/discharging test at 5 A g⁻¹, the coulombic efficiency is found at nearly 100 %. The interfacial battery reaches the highest energy efficiency of 66 % at a current density of 3 mA cm⁻² at 0–1.8 V and displays a good cycle life with an 88 % average coulombic efficiency at 3 mA cm⁻². This work expands the application of hydrogels and provides new possibilities for optimizing the high performance of electrolytes.

Graphene Oxide (GO) was associated to Fe-doped SnO₂ nanoparticles (NPs) through a simple elaboration method to obtain Fe-doped SnO₂/reduced graphene oxide (rGO) nanostructure. The effect of GO content on the structural, morphology, transport and dielectric properties of the SnO₂/rGO nanocomposite was deeply investigated. X-ray diffraction (XRD) patterns depict the obtention of SnO₂ rutile structure and revealed an effect of the NPs size the rGO layer to layer distance. However, transmission electron microscopy (TEM) exploration shows the formation of rGO nanospheres co-present with Fe-doped SnO₂ NPs. The electrical properties of the obtained structure were examined through impedance analysis. The conductivity of the SnO₂:Fe/rGO nanocomposite obviously increases with the GO amount. The analysis of the relaxation phenomenon shows an abrupt decrease of the relaxation time upon GO addition. A charge carriers transfer is suggested to occur between Fe-doped SnO₂ NPs and rGO for high graphene oxide concentrations. Hydrogen bonds are suggested to be established between these NPs and rGO. The functional groups at the NPs/rGO interface were found to considerably contribute to the dielectric response of the heterostructure. Dielectric losses were also evaluated and are suggested to be particularly affected by the rGO functional groups. The explored electric and dielectric properties present the SnO₂:Fe/rGO heterostructure as a potential candidate for supercapacitor and electrical battery electrodes.

Worldwide industries are drawing their attention to the usage of bio-based substances for their operational purposes. Herein, the bimetallic nanoparticles (Bi-MNPs) were synthesised using a unique combination of Zn–Cr in bio-based mustard oil by green route utilizing wet chemical approach. Synthesised Bi-MNPs (0.12–0.15 wt%) were employed in the synthesis of bimetallic bio-based nanolubricant (Bi-BNL), and the impact was also evaluated on low carbon steel (grade SAE1006). The reduction of Bi-MNPs was carried out by green reducing agents and their stabilisation was confirmed by Fourier transform infrared spectroscopy (FTIR). Whereas, the synthesis of Bi-MNPs was followed by Surface plasma resonance (SPR), average size of Bi-MNPs which was about 60 nm and morphology was established using Scanning electron microscopy (SEM). The efficiency of Bi-BNL and impact of Bi-MNPs on the stability of Bi-BNL was investigated by Dynamic light scattering (DLS), Zeta potential (ZP) and comparative study was carried out with reference lubricant. Interestingly, the kinematic viscosity (KV) values of the lubricants are quite compatible, and have linear relationsip with coefficient of friction which is very suitable to conclude the anti-friction and anti-wearing properties. The KV of bio-based oil was monitored under the criteria of standard test method ASTM D445, and the resultant value was compared with the reference oil. The stability of Bi-BNL and its interaction with low carbon metal sheet was also studied; the outcomes were very impressive due to no rust patches, oil spots and surface deterioration on the metal sheet. The paramount creativity of this research work is the modification of bio-based oil via Bi-MNPs for the synthesis of Bi-BNL that offers the best surface quality of low-carbon steel. Cumulatively, these findings of Bi-BNL could be open up new possibilities to explore the bio-based synthesis of lubricants on a comprehensive scale.

Investigating the magnetic nanoparticle size and the effective magnetic interactions that form the magnetic domain can lead us to nanoparticles with targeted applications, such as targeted drug delivery and higher resolution MRI imaging. In this study magnetic susceptibility and coercive field properties, and the structure size range of single-domain magnetic capsules with high magnetization were obtained by structural analysis of volumetric DLS properties. In this regard, the role of exchange, anisotropy, and magnetostatic interaction was investigated in the structure of a magnetic capsule containing Fe₃O₄ nanoparticles (MCap-NPs). The stable capsules were synthesized in an emulsion solution with magnetic surfactants M(AOT)₂ (M = Co, Ni). Vibrating Sample Magnetometer (VSM) and capsule relative volume (CRV) of Dynamic Light Scattering (DLS) were used to determine the magnetic properties of the single-domain (SD) structure. The produced emulsion samples were found to have superparamagnetic properties property with saturation magnetization in the range of 2–6 × 10⁻³emu/g for NiCap-NPs, and 5-13 × 10⁻³emu/g for CoCap-NPs. The results show that nanoparticles have the most significant effect on magnetization. The coercive field, the anisotropy energy values, and the SD of M(AOT)₂ were determined using magnetic susceptibility distribution. The outcome results show that the surface of the magnetic capsule plays an essential role in forming a single-domain structure. It was also found that the saturation magnetization of the samples in the emulsion solution is proportional to the nanoparticle density and not to the mass of nanoparticles. All produced samples have distinct peaks in CRV versus capsule size, and each peak follows a log-normal distribution. For both samples, except for the samples with molar ratios ω of 23 (Co3 and Ni4 samples), the positions of the second and third relative volume peaks were constant at 269 ± 3 nm and 424±6 nm, respectively. The behavior of the CRV function normalized to the peak size showed a proportionality between the coercive field and the CRV.