Bulletin of Materials Science最新文献

Porous transport layers (PTL) are used in the proton exchange membrane water electrolyzers to facilitate the gas/water transport and the electric charge transfer. As a result, the PTL is critical in ensuring the efficiency of the electrolyzing process. This work aims to produce titanium PTLs through the spark plasma sintering process. The sintering temperature was varied from 500 to 650°C to investigate the characteristics of the titanium PTL samples while maintaining the sintering pressure and holding time at 10 MPa and 10 min, respectively. The phase structure and morphology of the samples were investigated by X-ray diffraction and scanning electron microscopy analyses. The compressive strength and the corrosion behaviour of the samples were investigated by the compressive testing and the electrochemical corrosion testing, respectively. The experimental results showed that there were no new phases formed when the Ti PTLs were sintered at different temperatures. With an increase in the sintering temperature, the porosity of the samples considerably decreased, while their compressive strength, electrical conductivity and corrosion resistance increased. It is suggested that selecting the optimum sintering temperature for sintered samples can improve the mass transport behaviour in PEM electrolyzers and produce superior PTLs.

Carbon-derived materials are suitable for use as anodes in lithium-ion batteries due to low production cost and abundance. However, there is a need to improve the electrochemical performance with various modifications due to the limited capacity. In this study, a porous carbon is modified with anionic sodium dodecyl sulphate (SDS) and cationic cetyl trimethyl ammonium bromide (CTAB) surfactants and prepared as an anode for use in lithium-ion batteries. Morphological and structural properties change with the addition of surfactants, and the use of only one or two of them together has different effects. The morphology formed by adding only SDS is homogeneous and only CTAB is heterogeneous. When both surfactants are used SDS also provides homogeneous dispersion of CTAB. The changes in I_2D/I_G and I_D/I_G ratios obtained from Raman analyses show that the layer arrangement and the ratio of defects in the structure have changed. Electrochemical performances with different surfactant amounts are compared by using charge/discharge tests, cyclic voltammetric tests and differential capacity analysis (dQ/dV). The combined use of SDS and CTAB creates a synergetic effect (catanionic) and increases the capacity nearly 1.5 times by improving wetting, amount of lithium-ion storage areas and reducing the irreversible loss of capacity caused by solid electrolyte interface.

ZnFe₂O₄ was thermally synthesised through the mediation of different polymers such as Poly(vinyl alcohol), Poly(vinyl pyrrolidone) and Poly(ethylene glycol) to prevent the unwanted agglomeration. The Rietveld refinement of the XRD spectra confirmed the sample to be fcc, while the FESEM/TEM micrographs exhibited the formation of spherical nanoparticles. The TGA/DSC analysis confirmed that the sample is stable up to 500°C. The dielectric, impedance and modulus spectroscopy as a function of temperature up to 200°C and within the frequency range of 20 Hz to 2 MHz confirm a single non-Debye type relaxation behaviour at different temperatures (well fitted by the KWW (Kohlrausch–Williams–Watts) function) attributed to the grain boundary/MWS polarisation present in the samples. The modulus and impedance master curve confirmed the distribution of relaxation times being independent of temperature. The AC conductivity phenomenon is explained using the CBH (correlated barrier hopping) model, satisfying Jonscher's universal power law with exponents in the range of [0,1] with an activation energy in the range of 0.4–0.8 eV. The obtained optical spectra of the samples with the help of UV-visible/PL spectra evaluate the direct energy band gap to be from 1.7 eV to 2.8 eV and these ferrites may be suitable for high-frequency as well as for optoelectronic applications.

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.