Bulletin of Materials Science最新文献

Water contamination by hazardous heavy metal ions and organic compounds causes environmental damage towards aquatic species and human health. Thus the evolution of highly selective, affordable, rapid and effective analytical tools for the removal and detection of toxic heavy metal ions and organic compounds in aqueous environments is a challenging objective. Electrochemical detection of metal ions and organic compounds is a very useful and effective method, where modified electrodes with metal nanocomposite particles are used. Materials with high porosity, low-charge transfer resistance and large electroactive area are desirable for electrode modification in order to act as an efficient electrochemical sensor. It has been established that natural polysaccharide-based graft copolymers with acrylic monomers can be efficiently used as ‘bio-template’ for preparing mono and bimetallic/metal oxide composite nanoparticles for sensing and catalytic applications. This is because of the fact that polysaccharide-based graft copolymers are eco-friendly in nature and have the potential to act as reducing and stabilizing agents. The bio-template-based metal/metal oxide nanocomposites are successfully used for the electrochemical sensing of some heavy metal ions, like Hg²⁺, Cd²⁺, Th⁴⁺, Zn²⁺, Pb²⁺, etc., and toxic phenolic compounds, and also show efficient catalytic application in azo dye degradation and p-nitrophenol reduction. The developed electrochemical sensors are selective, sensitive and effective for the detection of toxic heavy metal ions in real water samples. Here we summarize the various investigations carried out using metal/metal oxide nanocomposite particles (mono and bimetallic) in electrochemical sensing of toxic heavy metal ions and catalytic applications.

This study investigates the current–voltage (I–V) characteristics of a Schottky Metal-Insulator-Semiconductor (MIS) structure, specifically featuring a titanium nitride (TiN) electrode interfaced with p-type silicon (p-Si) and a high-k aluminum oxide (Al₂O₃) layer with a thickness of 17 nm, enabling a detailed analysis of its influence on device performance. Conducted over a temperature range of 270 to 450 K, the research employs thermionic emission (TE) theory to extract critical electrical parameters, including reverse saturation current (I₀), ideality factor (n), zero bias barrier height ((Phi_{B0})), series resistance (Rs) and rectification rate (RR). The analysis reveals a mean barrier height (BH) of 0.274 eV and a Richardson constant (A*) of 42.19 A (cm K)⁻¹, both of which closely align with theoretical predictions for p-type silicon, suggesting that the thermionic emission mechanism, characterised by a Gaussian distribution of barrier heights, effectively describes the I–V–T behaviour of the fabricated Schottky structure. These findings elucidate the complex interplay between temperature and diode performance, offering significant insights for the optimisation and design of thermally-sensitive electronic devices leveraging this advanced Schottky MIS configuration.

The electrocatalytic behaviour of bulk eutectic high entropy alloys (EHEAs) has rarely been explored despite possessing large electrocatalytic active sites. In this work, bulk EHEA has been investigated as an electrocatalyst considering hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The results depict good kinetic behaviour, evidenced by a low Tafel slope of 251 mV dec⁻¹ and an overpotential of −0.415 V to achieve −0.01 A cm⁻² for HER. Similarly, for OER, a low Tafel slope of 115 mV dec⁻¹ and overpotential of 1.5879 V to achieve 0.01 A cm⁻², with good long-term electrolysis stability for 24 h are achieved. The electrochemically active surface area of EHEA catalyst for both HER and OER is 0.033 and 0.0727 cm², respectively.

This study involves the synthesis of nanocrystalline Fe₉₀Nb₁₀ (wt%) binary powders through the use of a high-energy planetary ball mill within an inert argon environment. The milling process was used to investigate changes in structure, morphology and magnetic properties. This was accomplished through the utilization of techniques such as X-ray diffraction (XRD) using the MAUD program, which is based on the Rietveld method, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and vibrating sample magnetometry. From the XRD analysis, it was observed that a disordered solid solution of αFe(Nb) with a body-centred cubic (bcc) crystal structure formed after 12 h of milling. Interestingly, the analysis also indicated that the average crystallite size 〈D〉 within this αFe(Nb) solid solution was remarkably small, measuring a mere 13.15 nm. Furthermore, the ultimate lattice strain 〈σ²〉^1/2 was quantified at 1.08%. It is worth noting that the lattice parameter underwent a rapid and substantial increase, peaking at 0.2879 nm after 36 h of milling. The SEM analyses revealed the development of diverse morphologies at different milling stages. The elemental maps of Fe and Nb done with EDX experiments confirmed the results found by XRD about the evolution of the alloy formation. The changes in saturation magnetization (M_s), coercive field (H_c), remanent magnetization (M_r) and squareness ratio (M_r/M_s) were investigated in relation to microstructural modifications during the milling process. Annealing Fe₉₀Nb₁₀ (wt%) samples promotes the formation of a homogeneous solid solution and increases coercivity.

Nickel–tungsten (Ni–W) coatings reinforced with silicon carbide (SiC) were successfully produced on a steel substrate using the pulse electrodeposition method (PED). Influence of SiC addition on phases, crystallite size, dislocation density, residual stress, mechanical properties and corrosion resistance of the coating were investigated. Field emission scanning electron microscopy (FESEM) images revealed a refinement in the coating’s surface morphology and distribution of SiC particles. Higher residual stress observed in the as-deposited Ni–W coating was attributed to hydrogen dissolution into the coating, leading to lattice expansion, with the subsequent release of hydrogen, contributing to this stress. Addition of SiC to the Ni–W coating resulted in improvements in hardness and bonding strength by ~23% and ~184%, respectively. Moreover, the addition of SiC to Ni–W coating led to a reduction in the coefficient of friction by about ~34% compared to Ni–W coating. Corrosion properties were evaluated using an immersion test in a 3.5 wt.% NaCl solution. The Ni–W–SiC composite coating exhibited significantly higher corrosion resistance, with ~67% decrease in corrosion rate compared to Ni–W coating. This enhanced corrosion resistance was linked to the grain refinement induced by SiC, which restricted the penetration of corrosive ions onto the substrate. Furthermore, the formation of a continuous barrier layer composed of SiO₂, contributed to the improved corrosion resistance.

A novel and straightforward ion-catalysed magnesite solid-phase conversion method was used to prepare nesquehonite powder. Magnesite and slaked lime were used as raw materials and MgCl₂ was used as the catalyst. Magnesite could be directly converted to magnesium hydroxide by the solid-phase conversion method, and nesquehonite crystals were prepared by carbonisation and pyrolysis. The physical composition and microscopic morphology of the products were characterised by XRD and SEM, and the solid-phase conversion mechanism was analysed. The effect of catalyst type, solid-to-liquid ratio, hydration temperature, MgCl₂ addition and magnesite ore powder to slake lime mass ratio on the magnesium conversion rate was investigated. The rod-like nesquehonite crystals with good crystalline structures were obtained when the hydration temperature was 85°C, the solid-liquid ratio was 1:40, addition of MgCl₂ was 5%, magnesite ore powder to calcium hydroxide ratio was 1:2 and magnesium conversion rate reached 20.98%. The catalyst MgCl₂ could react with Ca(OH)₂ rapidly to form CaCl₂, which improves the ionic strength in the bulk solution as an intermediate product. Consequently, the solubility of magnesite was improved due to the salt effect and the conversion rate of magnesium was further increased.

The structural, elastic, electronic and optical properties of Ruddlesden–Popper-layered (Sr,Ca)₃Ti₂O₇ compounds in the paraelectric phase have been studied in detail using a first-principles method based on density functional theory. The results obtained from structural optimization demonstrate that they are consistent with existing experimental and theoretical results in the literature. To investigate the mechanical properties of the Sr₃Ti₂O₇ and Ca₃Ti₂O₇ compounds, second-order elastic constants were calculated. The obtained results confirm that the Sr₃Ti₂O₇ and Ca₃Ti₂O₇ compounds are mechanically stable. The polycrystalline elastic modulus, including bulk modulus (B), shear modulus (G), Young’s modulus (E) and Poisson’s ratio (ν), for both compounds was calculated using the obtained elastic constants. It was estimated from the calculated ({H}_{text{macro}}) and ({H}_{text{micro}}) hardness values that these compounds are medium-hard materials. Furthermore, both compounds were found to be elastically anisotropic and brittle materials. The electronic structure analysis indicates that the Sr₃Ti₂O₇ and Ca₃Ti₂O₇ compounds are semiconductor materials with indirect bandgaps of 2.92 and 2.89 eV, respectively. To determine their potential application areas in optoelectronic devices, the frequency-dependent complex dielectric function of the Sr₃Ti₂O₇ and Ca₃Ti₂O₇ compounds was calculated.

Recovery of lithium (Li) compounds from various Li resources is attracting attention due to the increased demand in Li-ion battery industry. Current work presents an innovative route for selective recovery of lithium content in the form of lithium hydroxide monohydrate (LiOH·H₂O) from discarded LIBs. Lithium carbonate (Li₂CO₃) with purity > 99% is recovered from black mass. The recovered Li₂CO₃ is then crystallised to LiOH·H₂O by using calcium hydroxide (Ca(OH)₂) as the base. The method comprises of: (i) pre-treatment of LIB black mass powder; (ii) selective extraction of Li content from black mass; (iii) crystallisation and solid–liquid separation to recover LiOH·H₂O as final recovered product. A total of 0.1933 wt.% impurities comprising of Ca, Al, Cu and Fe were detected in the recovered product. Elemental analysis at each processing step was carried out using inductively coupled plasma-optical emission spectroscopy. Structural properties of the recovered materials are analysed by using X-ray diffraction, field emission scanning electron microscopy. Fourier-transform infrared spectroscopy spectrum of recovered product was found consistent with the formation of LiOH·H₂O. The LiOH·H₂O is successfully recovered from discarded LIBs with purity of 99.8%, which finds its potential use as secondary raw material in battery manufacturing, Li-based high temperature grease manufacturing, carbon dioxide scrubbing in space craft and submarines, etc.