Journal of the Australian Ceramic Society最新文献

MnZn ferrites synthesized from the pickling by-product powder (Fe₂O₃) of the steel industry by varying Zn and Mn stoichiometry. A single step solid-state synthesis process in argon atmosphere with rapid atmospheric cooling was followed to achieve structurally modified MnZn ferrite with low coercivity. Among the stoichiometric variations, Mn-rich variant exhibited a highly strained body centered tetragonal (BCT) mixed spinel structure Mn_0.75Zn_0.75Fe_1.5O₄ with Fe(Mn) octahedra distortion stabilized through the synthesis parameters. It demonstrates extremely low coercivity of 10.34 A/m i.e., 0.13 Oe, shallow hysteresis loss of 0.456 J/m³, along with high permeability and high saturation magnetization. Phase evolution studies of all the synthesized powders were done through DTA-TG and Raman spectroscopy. The crystal structures were determined and verified through XRD and TEM respectively, while the morphologies were studied using SEM. Effect of Mn incorporation was studied through first-order electronic structure calculations capturing Bohr magneton, energy per unit cell and corresponding saturation magnetization which was experimentally verified through VSM. This work outlines a critically designed single step solid state synthesis process which can stabilize a highly strained BCT structured MnZn ferrite with a particular stoichiometry making it suitable for advanced soft magnetic core application.

In the present study, a peanut shell biochar iron-oxide (Fe₃O₄) magnetic nanoparticle composite was used for the removal of pendimethalin. The adsorption of pendimethalin was studied in batches at different experimental conditions like pH, contact time, adsorbent dosage, herbicide concentration and temperature. The adsorption was found to be pH-dependent, and maximum adsorption was found at pH 2. In aqueous solution at room temperature, the adsorption data could be fitted by the Freundlich isotherm model with adsorption intensity of n = 2.0387. Time studies showed that pendimethalin uptake was 100% with shaking for 70 min. The kinetic data were analyzed using four kinetic equations; pseudo-first-order, pseudo-second-order, intraparticle diffusion. The rates of adsorption confirmed the pseudo-first-order kinetics with good correlation value (R² = 0.8733). Thermodynamic parameters like standard enthalpy (∆H˚=10.61525 KJ/mol), Gibbs free energy (∆G˚) and standard entropy (∆S˚= 9.63593 J/mol) were calculated which indicate that the adsorption of pendimethalin is a spontaneous and endothermic process. The adsorbent could be easily regenerated with methanol. The results indicated that biochar magnetic composite could be effectively used for the removal of pendimethalin.

This study investigated the influence of target composition, reactive gas concentration, and annealing temperature on the formation of the MAX phase in coatings deposited by reactive D.C. magnetron sputtering and subsequent annealing. For this aim, Ti-Al-C coatings were deposited using two different Ti-Al alloy targets with atomic ratios of (1:1) and (1:2) in a CH₄/Ar mixture atmosphere with various ratios (1/20, 1/10) at room temperature. The coatings were then annealed in a vacuum furnace at 800 °C and 1000 °C. XRD analysis showed that the MAX phase could not form in the coating produced by the 1Ti-1Al target due to insufficient aluminum content, resulting in the Ti₃AlC phase with a perovskite cubic crystal structure. Conversely, the 1Ti-2Al target produced coatings containing the gamma TiAl phase with a tetragonal structure and the Ti₂AlC MAX phase with a hexagonal layered structure. Increasing the concentration of CH₄ gas led to the formation of more MAX phase as a result of the transformation of the gamma TiAl phase into the Ti₂AlC MAX phase. Microstructure characterization showed that the coating was compact, dense, and without cracks or porosity. Nano-indentation and Nano-scratch analysis determined the elastic modulus of 73–77 GPa, hardness of 6.5–7.5 GPa, and friction coefficient of 0.2–0.3 for the coating with the highest amount of Ti₂AlC MAX phase produced by sputtering of the 1Ti-2Al target in a CH₄/Ar atmosphere with a 1/10 ratio and annealing at 800 °C.

This study investigates the development and characterization of glass–ceramic tiles (GC tiles) produced from a mixture of raw materials such as rice husk ash (RHA), waste glass powder (WGP), potassium-feldspar (K-feldspar) and several fluxes in trace amounts. The raw materials were melted at 1170 °C to form a glass frit, which was subjected to ground into fine powder. The powder was moistened with 7–8% water and sodium silicate to prepare the green tiles. The tiles were sintered at temperatures between 810 °C and 1110 °C. This one-hour heating process allowed the glass to densify and form the desired crystal phases. The physical, chemical, and mechanical properties of GC tiles were observed using WD-XRF, XRD, SEM and UTM analyses. Linear shrinkage (13.84% at 810 °C to 11% at 1110 °C) and water absorption (2.2% to 0.02%) decreased with increasing temperature. Bulk density peaked at 950 °C, while modulus of rupture peaked at 925 °C. Glossiness reached a maximum of 55% at 950 °C. Crystalline phases of wollastonite and mullite were identified from XRD data, and a uniform microstructure with dispersed crystals in a glassy matrix was observed at 925 °C.

The structural, electrical, and magnetic properties of (1-x) ZnFe₂O₄ - (x) BaTiO₃ (x = 0, 0.05, 0.10, 1) were systematically studied. Samples were synthesized using the sol-gel auto-combustion method for x = 0 and the conventional ceramic route for x = 0.05, 0.10, and 1. Phase formation was confirmed via X-ray diffraction (XRD), while Raman spectroscopy provided insights into vibrational and rotational modes. Field-emission scanning electron microscopy (FESEM) was used to analyze morphology. X-ray photoelectron spectroscopy (XPS) verified the oxidation states of Ti, Fe, and O, confirming the presence of Ti and Fe in multivalent states. Electrical studies revealed negative permittivity in Zinc ferrite-containing samples, well-explained by Drude-Lorentz theory. Magnetic properties were investigated through temperature-dependent magnetization measurements in ZFCW, FCC, and FCW modes, while M-H loops provided insights into saturation magnetization (M_s), remanence (M_r), and coercivity (H_c), all of which increased with decreasing temperature. These findings highlight the potential of these metamaterials for electromagnetic interference (EMI) shielding and coil-less inductor applications.

Carassius gibelio (Cg), an omnivorous invasive species in European and Turkish waters, originated in Asia and spread to Europe in the 17th century. In contrast, the carnivorous Esox lucius (El) (northern pike) inhabits rivers, lakes, and brackish waters across the Northern Hemisphere. Utilizing these species as biomaterials can supports waste management and biocompatible material synthesis. In this study, the morphological and chemical characteristics of calcined fish bone powders from different anatomical parts, including head bone (HEB), otolith bone (OTB), operculum bone (OPB), and spine bone (SPB), were systematically investigated. The particle size distribution analysis revealed that Cg-HEB exhibited the smallest particle size (53.91 μm), whereas El-OTB had the largest (431.54 μm). Morphological analysis confirmed a predominant rod-shaped structure for both Cg and El samples, except for El-OTB, which exhibited a distinct morphology. X-ray diffraction (XRD) analysis confirmed hydroxyapatite (HA) as the primary crystalline phase in all samples, accompanied by the presence of β-tricalcium phosphate (β-TCP). Fourier transform infrared (FTIR) spectroscopy further validated the presence of phosphate (PO₄³⁻) bands at 1030–1100 cm⁻¹ and 560–600 cm⁻¹, reinforcing HA as the dominant phase. The Ca/P ratio analysis indicated that Cg-SPB had a slightly lower ratio (0.07 less) than the stoichiometric Ca/P ratio of human bone, suggesting an increased β-TCP content. Conversely, El samples generally exhibited lower Ca/P ratios compared to Cg samples. These findings emphasis the potential of fish bone-derived materials for biomedical, particularly in bone tissue engineering.

The present work discusses novel alumina composites with single crystalline α-alumina platelets as reinforcement, fabricated by integrating gelcasting with rapid prototyping technique. Commonly used alumina fibre reinforced composites, though exhibit high fracture toughness, show limitation for use at high temperatures, due to structural transformation and recrystallization of the fibres, and for net-shaping into intricate geometries. Present work addresses these constraints by choosing α-alumina platelets of approximately 150 ± 25 nm thickness as reinforcement, and gelcasting process for shape-forming the composites. A free-flowing ceramic slurry having uniform distribution of monazite (LaPO₄)-coated platelets was cast and gelled in disposable expanded polystyrene (EPS) molds that are machined as per the computer aided design (CAD). The green bodies are dried, debindered and sintered to obtain compacts of alumina composites with different amounts of platelet alumina (0 to 25 wt%) and are characterized. Compared to monolithic alumina, a notable enhancement (by 80%) to 5.4 MPa(:surd:m) in fracture toughness was observed, while maintaining a flexural strength of 310 MPa, in the composite with 4 wt% platelet content. Microstructural studies reveal deflection, bridging, and branching of the cracks caused by the coated platelets and provide evidence for their contribution to improved fracture toughness. The optimized composites have the potential for use in biomedical sector. They are particularly suitable for high-temperature applications, furthermore, α-alumina platelets possess superior thermal stability at elevated temperatures compared to alumina fibres and exhibit excellent oxidation resistance, unlike carbon fibres. These attributes ensure their structural integrity under extreme conditions, making them highly effective as reinforcements for high-temperature applications where both mechanical performance and environmental durability are critical. The present process is inexpensive and enables manufacturing of complex geometries, making it attractive for adoption by industries.

In this study (Zr1-2 × Hfx Tix) B2 ultra-high temperature ceramic (UHTCs) matrix composites were fabricated and reinforced with various additives (SiC, Si-Gr, Si-CNT) through spark plasma sintering (SPS) at 2000 °C, 40 MPa, for 10 min. The research investigates the impact of different reinforcement types on densification behavior, microstructure, and solid solution formation. Relative density measurements were conducted using the Archimedes method, while microstructural analysis and phase identification were performed using FE-SEM and XRD respectively. The findings revealed that the highest level of densification was achieved in (Zr1-2 × Hfx Tix) B2 samples reinforced with Si–C and Si-CNT, with relative densities of 98.2% and 95.8%, respectively, while the lowest densification was observed in the SiC-reinforced sample, denoted as HZTSiC. XRD analysis indicated the formation of new peaks distinct from the initial powders, corresponding to B₄Si, HfSiO4, TiB₂ and solid solution phases. It was observed that Ti and Hf diffused and dissolved into the ZrB2 lattices, resulting in the formation of (Zr1-2 × Hfx Tix) B2 solid solutions. The lowest level of oxide impurity (3.7 wt%) and the highest proportion of solid solution phases (88.7 wt%) were observed in (Zr1-2 × Hfx Tix) B2 containing Si-Gr.

Graphical Abstract

Predicting phase structures is crucial for the discovery and design of high-performance High Entropy Carbide Ceramics (HECCs). Data-driven approaches are increasingly popular in materials science. However, these methods heavily rely on dataset size. To tackle this, we propose a two-step data enhancement method using Auxiliary Enhanced-Least Squares Generative Adversarial Networks—Tree-structured Parzen Estimator—Multilayer Perceptron (AE-LSGAN-TPE-MLP). The method improves model stability and data quality by adding auxiliary generator and discriminator networks that operate alongside the primary ones in the LSGAN framework. Additionally, data enhancement occurs in two steps to further ensure data quality. In the first step, feature enhancement is performed using a label-guided feature separation strategy. Features corresponding to different label categories are separated, and the AE-LSGAN model is trained independently for each category to generate realistic feature data. In the second step, pseudo-labels for augmented features are predicted. An MLP model is pre-trained on 50% of the dataset, and the generated features are used as input to predict pseudo-labels. Finally, the augmented dataset is merged with the training set, and a TPE-MLP model is built for prediction. Comparative results show that the proposed method significantly improves model performance, achieving 0.9629 accuracy on a test set comprising 50% of the dataset. Moreover, three HECCs were synthesized through experiments, further validating the model's accuracy. Finally, an interpretability analysis of the model was performed, with the shapley additive explanations (SHAP) summary plot revealing that σχ and σV were the paramount influencers of HECCs' phase structures. Notably, when σχ and σV were below 0.079 and 0.125, single-phase HECCs were more likely to be formed. This work is expected to facilitate the discovery and design of HECCs with bespoke phase structures and properties.