Journal of the Australian Ceramic Society最新文献

The widespread use of alternative fuels in cement kilns requires improvement of the alkali attack resistance of mullite raw materials for the kiln linings. In this study, a novel mullite raw material with excellent alkali resistance was prepared by introducing kyanite tailings into low-grade raw bauxite. The effects of the microstructure, glass phase composition and phase distribution on the alkali attack resistance of such raw material were investigated. As the amount of kyanite tailings introduced increased, the glass-phase content of the specimens had little change, while the silica content in the glass phase increased obviously. Additionally, with increasing kyanite tailings content, the mullite phase gradually transformed from fine needle-like structures into columnar or tabular structures, allowing mullite to be better enclosed within the glass phase. The alkali attack test indicated that adding kyanite tailings significantly improved the alkali attack resistance of the specimens. This was explained as follows. (i) The silica-rich glass would be transformed into liquid phase during alkali attack, changing the corrosion process from the direct gas–solid reactions to dissolution–precipitation process. The formed liquid phase also densified the corrosion layer, effectively preventing further penetration of the alkali vapor. (ii) The mullite phase was wrapped in the silica-rich glass phase, preventing its direct reaction with alkali vapor and the resulting volume expansion. Besides, alkali attack resistance of the mullite phase was enhanced due to its particle coarsening.

The present study successfully synthesized hexagonal boron nitride (h-BN) with different morphologies, including flake, dendritic, and spherical shapes, using a one-step combustion synthesis method in a short period of time. A simple and innovative strategy was employed to control the preferred growth direction of h-BN crystals by adding a small amount of Ni(NO₃)₂·6H₂O. By adjusting the addition of Ni(NO₃)₂·6H₂O, morphology of h-BN was manipulated from flake to spherical, and the formation mechanism was investigated. Two mechanisms were proposed to explain the different morphologies of as-grown h-BN in vapor-solid (VS) and vapor-liquid-solid (VLS) processes. This study provides valuable insights into the preparation of h-BN with diverse morphologies through combustion synthesis methods, which would guide future research in this field.

In this study, the effect of Co-Cr(0) and Co-Cr-B nanocatalysts on sodium borohydride hydrolysis was investigated. The extract obtained from the pods of the bean plant was produced using the environmentally friendly green synthesis method, along with the chemical reduction method as the production procedure for the catalysts. The analyses used to study the structure and surface morphology of catalysts are SEM, TEM, EDX, XRD, FTIR, and XPS. From the SEM and TEM pictures, the shape of the catalysts comprises of tiny spheres and has a porous nanostructure, and the particle size is 35–40 nm. The XRD investigation revealed that the catalysts had an amorphous structure. The catalysts’ structure has been confirmed to include the components Co, Cr, and B using EDX and XPS analyses. It was examined how different amounts of catalyst, different NaBH₄/NaOH concentrations, and different solution temperatures affected the hydrolysis of sodium borohydride. The n-th order kinetic model was utilized to determine the activation energies of Co-Cr(0) and Co-Cr-B nanocatalysts, which were found to be 24.39 kJ/mol and 43.09 kJ/mol, respectively. Also, the turnover frequency (TOF) values of synthesized nanocatalysts Co-Cr(0) and Co-Cr-B at 60 °C were calculated as 19,210 mLmin^− 1g^− 1 and 12,410 mLmin^− 1g^− 1, respectively. The repeatability of catalysts in NaBH₄ hydrolysis showed high activity even after the fifth use.

Graphical Abstract

The production scheme of Co-Cr(0) and Co-Cr-B nanocatalysts

In this study, we explored the gamma-ray shielding properties of As₂O₃ glass ceramics, which were doped with varying concentrations of Ag₂O within chalcogenide oxides (SeO₂ and TeO₂). Utilizing the Monte Carlo N-Particle (MCNP) code for simulations, alongside the Phy-X/PSD software for theoretical validation, we aimed to understand the influence of Ag₂O integration on the attenuation characteristics of these glass systems. Among the five glass compositions analyzed, ATSAg0.50, containing 0.50 mol% Ag₂O, stood out due to its superior density and attenuation coefficients, suggesting enhanced shielding capabilities. Our methodology encompassed detailed assessments of linear and mass attenuation coefficients, alongside parameters like the half-value layer (HVL), mean free path (MFP), and transmission factors (TFs), across a wide photon energy spectrum. Notably, ATSAg0.50 exhibited the lowest TFs and shortest MFP, indicating its potential as an efficient shield against gamma radiation. Furthermore, its high linear attenuation coefficients across all energies emphasize the pivotal role of material composition and density in effective radiation protection. It can be concluded that ATSAg0.50 emerges as a promising candidate for gamma-ray shielding applications, balancing material efficiency with performance.

Calcite is one of the significant components used in the wall tile application at a rate of 10–12% as its content contributes to the formation of pores. This study investigates the usability of snail shell waste with high calcium oxide content as an alternative to calcite raw material. Thus, depletion of calcite reserves will be prevented and value-added commercial products will be obtained by using waste. In addition, proper waste management will prevent environmental pollution and damage caused by waste accumulation. The chemical analysis of snail shell waste revealed a CaO content of 55%, while the CaO content in calcite was measured at 58%. Considering their similar chemical properties, different amounts of snail shell waste (%6, %9, %12) were added to the wall tile recipe instead of calcite. The addition of snail shell waste to the recipe resulted in an increase in sludge density and viscosity. Physical and mechanical tests were conducted on wall tiles made with the addition of snail shell waste and compared to standard wall tiles according to TSE EN ISO standards. When the waste material was used in a 50–50 ratio with calcite, the strength of the recipe was calculated to be 279.41 kg/cm². Water absorption values were within standard limits and recorded at 15%. The phases that occur in the structure of wall tiles with the increase of waste addition were examined by X-ray Diffraction Analysis. The microstructures of the samples were compared with SEM–EDX analysis. Sustainable and low-cost wall tiles were obtained through the use of snail shell waste, with environmentally friendly solutions.

Good bioactivity and tunable mechanical properties of akermanite (Ca₂MgSi₂O₇), as compared to calcium phosphate materials, have garnered increasing attention as a potential bone substitute material. Typically, these Ca-Mg-Si bioceramics are synthesised using commercially available chemicals. In this study, we aimed to transform clinical dental mould waste (DMW) into an alternative calcium source used in synthesising akermanite ceramics. The DMW were initially refined involving alkaline roasting and caustic leaching, resulting in high purity Ca(OH)₂ powder. This Ca(OH)₂ powder was then mixed with MgO and SiO₂ in stoichiometric proportion and subsequently subjected to planetary ball milling, pressed into pellets and sintered at 1200–1250 °C, forming the desired akermanite ceramics. Two calcium sources were investigated: Ca(OH)₂ refined from DMW and chemically available CaO. Comparative analyses between Akr-Ca(OH)₂ and Akr-CaO confirmed that both types of akermanite ceramics exhibited akermanite as the major phase with a minor phase of diopside. Regardless of the calcium source used, the physical and mechanical properties of the akermanite produced improved with increasing sintering temperature. However, Akr-Ca(OH)₂ possess relatively lower mechanical properties than Akr-CaO. These intriguing findings underscored the potential for utilising calcium derived from DMW in producing akermanite ceramics with acceptable mechanical properties. Utilising this sustainable approach to create akermanite ceramics for bone substitutes may indirectly alleviate environmental pollution. This is because dental mould waste (DMW), which contains small amounts of chromium that can leach out and harm soil quality when discarded into landfills, is minimised. Furthermore, this innovative method shows potential for providing an affordable bone substitute option for patients in need.

Mesoporous calcium phosphate based-bioceramics with ionic substitution have attracted attention for treatment of bone diseases and bone regeneration. Carbonate apatite (CO₃Ap) is a promising candidate for bone replacement through bone remodelling, similar to that of autologous bone, owing to the chemical composition of the bone mineral. In this work, we present a dual approach to synthesize mesoporous carbonate apatite (CO₃Ap) and strontium-substituted CO₃Ap (Sr-CO₃Ap) artificial bone nanocrystals, aiming to assess the impact of strontium on CO₃Ap characteristics and biological performance. Mesoporous CO₃Ap was created by transforming hard templates composed of CaCO₃, while Sr-substituted CaCO₃ (Sr-CaCO₃) microspheres were formed using an organic complexing agent to induce pore formation. The resulting CO₃Ap and Sr-CO₃Ap granules exhibited an irregular shape, with rod-like nanocrystals composing their particles. Adsorption/desorption isotherms confirmed the mesoporous nature of the structures, featuring pore sizes ranging from 10 to 50 nm. Specifically, mesoporous CO₃Ap displayed slit-like pores, while Sr-CO₃Ap showed cylinder-like ones. High-resolution transmission electron microscopy images of Sr-CO₃Ap powder revealed mesopores within the particles, with Sr-CO₃Ap exhibiting larger pore volume and specific surface area compared to CO₃Ap. When osteoblast-like MC3T3-E1 cells were cultured on both CO₃Ap and Sr-CO₃Ap samples, they demonstrated good cell attachment, proliferation rates, and increased ALP activity, particularly evident at higher strontium concentrations. These findings suggest promising potential for further exploration of mesoporous apatite nanocrystals in bone replacement and drug delivery applications.

This study investigates the mechanical and wear properties of AA6061 composites reinforced with monosynthesized Al₂TiO₅ particles. Bottom pouring and stir casting were employed to achieve uniform dispersion of Al₂TiO₅. Five composite samples were fabricated with varying Al₂TiO₅ weight percentages (wt%) (0, 1, 2, 3, and 3.5) while maintaining a constant stirring speed of 400 rpm. Tensile strength, impact energy, and microhardness were evaluated according to ASTM standards. Wear rate and coefficient of friction (CoF) were measured using a Pin-on-Disc apparatus on samples prepared through ASTM G99. Composites reinforced with 2 wt% and 3.5 wt% Al₂TiO₅ exhibited the highest tensile strength (215.96 MPa) and impact strength (12.6 J), respectively. Microhardness increased significantly in samples 6R1 (75.37 HV), 6R2 (83.75 HV), and 6R3 (91.6 HV) compared to 6R0 (71.52 HV) and 6R3.5 (72.26 HV). Based on the finding that 1, 2, and 3 wt% Al₂TiO₅ reinforcement improved hardness, RSM optimization was applied to these compositions to further adapt the wear rate and CoF. Field emission scanning electron microscopy (FESEM) was used to examine the worn surface morphology of the composites and understand how Al₂TiO₅ particles influence wear mechanisms. The 3 wt% Al₂TiO₅ reinforced composite demonstrated an 83.5% increase in wear resistance compared to other samples under a 10 N load and 1600 m sliding distance.