Bulletin of Materials Science最新文献

This study investigates the effects of sintering parameters on the mechanical properties and microstructure of spark plasma sintered aluminium hybrid composites reinforced with 10 wt% SiC and 4 wt% kaolin. Using Taguchi–grey relational analysis (TGRA), the sintering temperature, compaction time, and compaction pressure were optimized based on their influence on density, ultimate tensile strength (UTS), and compression strength. Experiments were designed using an L₉ orthogonal array, and ANOVA analysis was performed to determine the percentage contribution of each parameter. The optimal sintering conditions were found to be at a temperature of 570°C, a compaction time of 5 min, and a pressure of 20 MPa, resulting in a maximum density of 2.72 g/cc, UTS of 313 MPa, and compression strength of 379 MPa. Microstructural analysis through SEM revealed a homogeneous distribution of reinforcements at the optimal conditions, while the presence of Al₂Cu intermetallic compounds was detected near the grain boundaries at non-optimal conditions. These results confirm that optimized sintering parameters significantly enhance the mechanical properties of the composite.

The Na-P1 type zeolites were synthesized using coal fly ash (FA-Na-P1) and also using chemical reagents (CA-Na-P1) for comparison. Both Na-P1 type zeolites showed a superior adsorption ability for the non-radioactive metal ions of Cs, Sr, Mn, Zn, Co, or Fe, assuming radioisotopes with relatively long half-lives. These zeolites were heat-treated for the immobilization of the adsorbed metal ions in the decomposed zeolite. The elution ratio of the metal ions in the deionized water and seawater for 14 days showed a low elution when the sample was heated at 1000°C and higher temperature for both zeolites. In particular, the elution of the 1100°C heated sample for the zeolite from fly ash significantly decreased compared with that from the chemical reagents. The reaction between the adsorbed cation and zeolite was confirmed to form polymetallic oxide. The formation of the reacted oxide phase suppressed the elution ratio for the FA-Na-P1 zeolite.

In this work, a comprehensive analysis was performed on the perovskite solar cells (PSCs) considering MoS₂ as the electron transport layer. For the initial calculations, numerical simulations obtained through SCAPS-1D were matched with experimental results. Further, multi-faceted exploration of material parameters was performed to obtain better performing PSC device. Electron affinity values of MoS₂ layer were varied to obtain an optimum value to quantify its n-type behaviour. Furthermore, the impact of charge density and thickness of MoS₂, Spiro-OMeTAD, thickness of perovskite layer, interface engineering of perovskite/charge transport layers and temperature were investigated in detail. Incorporation of optimized parameters has resulted in an improved device with J_sc, V_oc, FF and η values as 23.7 mA cm⁻², 1.15 V, 83.04 and 22.76%, respectively. To ensure higher stability, MoTe₂ and WSe₂ as hole transport layers were also investigated in this work. The obtained results point to the applicability of these HTLs as an optimum replacement for the commonly employed transport layers. Analysis conducted in this work provides a pathway to explore prospective options for improving the efficiency and sustainability of PSCs for commercial applications.

In this study, EuCrO₃ (ECO) and Eu_0.9Dy_0.10CrO₃ (EDCO) rare-earth orthochromite compositions were synthesized through the traditional solid-state reaction technique. A comprehensive investigation was conducted to analyse the effect of the substitution of 10 wt% Dy³⁺ ions on the structural, optical and magnetic properties of EuCrO₃. The X-ray diffraction results along with Rietveld refinement confirm the monophasic nature with an orthorhombic distorted perovskite structure for both compositions. Field emission scanning electron microscopy reveals polycrystalline microstructures with average grain sizes ranging from 269 to 327 nm for both compounds. The optical bandgap is evaluated by Tauc’s relation and is observed to slightly increase from 2.24 to 2.33 eV with Dy³⁺ ions substitution. Optical parameters, including skin depth, extinction coefficient, refractive index and optical conductivity are determined and their variations with Dy substitution are analysed. Temperature-dependent magnetic analysis reveals a Néel temperature (T_N) of 177 K in EDCO composition, lower than that of pristine EuCrO₃ (T_N ~181 K). The magnetocaloric effect of the EDCO compound demonstrates a magnetic entropy change (ΔS) and relative cooling power of –0.27 J kg⁻¹ K and 4.4 J kg⁻¹, respectively, near T_N under the application of 7 Tesla field. This study highlights the tunability of EuCrO₃ properties through Dy ion substitution for customized applications.

The effect of the grain size on the dielectric properties and electrical conductivity was studied for single-phase solid solution of the ZrO₂–CeO₂ system with 75% CeO₂. The bi-ceramic composition of ZrO₂–CeO₂ as Ce_0.75Zr_0.25O₂ was prepared through a solid-state reaction to synthesize single-phasic material followed by high-energy ball milling to make finer particle size. Structural properties were confirmed through advanced analytical techniques such as XRD and Raman spectroscopy. SEM confirmed large porosity with a grain size of 204 ± 3 nm, which is larger than the crystallite size of 22.64 ± 8.6 nm calculated from the XRD analysis for Ce_0.75Zr_0.25O₂. The dielectric measurements were performed as a function of temperature by impedance spectroscopy. The relative dielectric constant decreases on increasing frequency for all temperatures, which validates the polar nature of nanocrystalline Ce_0.75Zr_0.25O₂ ceramic. In addition, temperature-dependent enhancement in ({varepsilon }_{text{r}}) is more pronounced in low-frequency regions due to low-frequency dielectric dispersion phenomena. The dielectric loss also increases with increasing temperature over the frequency region from 100 Hz to 2 MHz. The electrical conductivity of nanocrystalline Ce_0.75Zr_0.25O₂ was found to be smaller than the micron-sized sample of Ce_0.75Zr_0.25O₂. The present study revealed the crucial role of grain size in tuning the dielectric properties of Ce_0.75Zr_0.25O₂ along with ac conductivity.

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.