Journal of the Australian Ceramic Society最新文献

Boron suboxide (B₆O), offering a good balance between abundance of its constituents and promising tribological performance, is intriguing. Applications such as cutting tools, high-wear resistant coatings, and ballistics would benefit from such properties, however a feasible synthesis method is yet to be realized. The synthesis of B₆O under atmospheric pressure is a challenging pursuit, and there is insufficient thermodynamic data for the formation of boron suboxide in the literature. In this study, boron suboxide powder was synthesized by reducing B₂O₃ by amorphous boron. Phase analysis of the formation of boron suboxide was demonstrated within the temperature range of 1200–1350 °C. The amorphous phase beside boron suboxide is present for all temperature treatments, but the best fitting crystalline phase was observed of the powder synthesized at 1300 °C. The powder was also heat treated at 1300 °C for various hours (2–6 h), and the crystalline phase was only observed for the powder heat treated for 4 h. The morphology of synthesized powder exhibited a star-like morphology. The production of B₆O-TiB₂ composite powder by reduction of TiO₂ by amorphous boron with the excess addition of boron is also reported in this study.

In order to verify the formation of gaseous phase fluoride and its influence on the morphological evolution and the growth mechanism of α-Al₂O₃, the α-phase transformation temperature and morphology of α-Al₂O₃ powders from the calcination of commercial γ-Al₂O₃ and Al(OH)₃ precursor with the addition of AlF₃·3H₂O additive have been studied through the incorporation of mixed placement experiments, layered placement experiments and separated placement experiments. The formation of gaseous phase fluoride has been experimentally confirmed by means of layered placement experiments and separated placement experiments, especially by the enhancement of the α-phase transformation occurred outside the small crucible in separated placement experiments. AlF₃·3H₂O additive significantly enhances shape anisotropy of α-Al₂O₃ precursor and lowers the total α-transformation temperature (900 °C for Al(OH)₃ precursor and 1100 °C for γ-Al₂O₃ precursor ), even though the commercial precursor and AlF₃·3H₂O additive has been completely isolated by small crucible with cover.

This study evaluates copper/vanadate co-doped hydroxyapatite (Cu-V-HAP) composites synthesized with varying vanadate concentrations to assess their crystallinity, hardness, antibacterial activity, and cell viability. The Cu-0.0V-HAP exhibited an average particle diameter of approximately 50 nm, while the Cu-0.8V-HAP showed a reduced size of around 30 nm, indicating significant disruption of the crystalline structure. Hardness measurements revealed values of 1.8 ± 0.1 GPa for Cu-0.0V-HAP, peaking at 4.5 ± 0.14 GPa for Cu-0.6V-HAP, with a decrease observed in Cu-0.8V-HAP. Antibacterial activity against E. coli ranged from 0 mm for Cu-0.0V-HAP to 8.1 ± 0.6 mm for Cu-0.8V-HAP. Furthermore, cell viability results indicated that Cu-0.6V-HAP achieved a high rate of 98.2 ± 4%, compared to 88.4 ± 4% for Cu-0.0V-HAP. These results suggest that optimal vanadate concentrations enhance the mechanical stability, antibacterial properties, and biocompatibility of co-doped HAP composites, indicating their potential for biomedical applications.

The rubidium yttrium diphosphate compoundwas synthesized by solid route. The characteristics of this compound have been determined using X-ray powder diffraction, morphological, Raman and complex impedance spectroscopy. While X-ray powder diffraction revealed that RbYP₂O₇ compound crystallizes in the monoclinic system (P2₁/c space group), the SEM mapping demonstrated that the particles have the shape of squares of different sizes and demonstrate that the mean crystalline size of the specimen is 1.75 μm. The complex impedance spectra analysis indicated that the electrical features of the compound are largely dependent on temperature and frequency. Two semi circles are detectable in the Nyquist plots of the complex impedance spectra, suggesting the contribution of the effects of the grain and grain boundary. Non-Debye type relaxation mechanism coupled with negative temperature coefficient of resistance (NTCR) behaviour was indicated by temperature dependent impedance spectroscopy. Additionally, the AC conductivity frequency dependence was interpreted in terms of Jonscher’s law, whereas DC conductivity promotes the polaron assisted hopping in RbYP₂O₇ composition having activation energies of the grain σ_g and grain boundary are Ea_g= 0.81 eV and Ea_gb = 1.21 eV, respectively. The power law exponent (s) yielded that the correlated barrier hopping (CBH) model corresponds to the dominant transport process in this material. Furthermore, the multiple relaxation process was revealed by the modulus spectroscopy dominated by the mixed Rb⁺ cation motion within the investigated material structure.

Replacing calcium aluminate cement as hydraulic binder by silica sol as sol-gel binder for refractory castables is known to reduce drawbacks of hydraulic binders but still comprehensive information regarding the effect of various raw materials and additives are required. In this research bauxite, andalusite and argellite were chosen as aluminosilicate aggregates and silica sol as binder and the effect of citric acid, micro silica and cement as setting agent were investigated for different compositions. Mechanical strength of the obtained castables at different temperatures of 110, 1000 and 1400°C were probed for various compositions. Finally based on the maximum mechanical strength of 342.5 and 241 Kg/cm² at 110°C, workability and flowability of the castables, optimum compositions were selected. The used amounts of citric acid, micro silica and cement for bauxite optimized composition were 0.04%, 2% and 1% while there were 0.02%, 0% and 1%, respectively for andalusite based one. The effect of sol-gel binder on the corrosion resistance of the optimized compositions was investigated in contact with molten sodium silicate using static cup test. Bauxite based castables showed mechanical strength higher than andalusite ones, while the later exhibited better corrosion resistance which related to the intrinsic characteristics of the used aggregates.

This study investigated the effects of fine particles with high surface area synthesized by Self-propagating High-Temperature Synthesis (SHS) on the SPS process and the properties of the resulting products. Correlations were established between particle size, SHS product addition, sinterability, and mechanical properties. The products were characterized by measuring shrinkage percentages, relative density, microhardness, elastic modulus, and fracture toughness, which were further correlated with SEM–EDS results. The results revealed that SHS nanoparticles significantly increased fracture toughness, especially with additions above 60%, by reducing average particle size, increasing powder porosity, and adding composite powder. The product exhibited high relative density (99.03%), elastic modulus (464 GPa), and fracture toughness (4.65 MPa.m^1/2) when SPS was used on B₄C-TiB₂ powders containing 80% SHS product at a low temperature of 1550 °C. By adding 80% SHS product, hardness increased by 62% (19.5 GPa) and fracture toughness by 24%, even at low sintering temperatures, thus reducing energy consumption.

This study explores the synthesis and characterization of superparamagnetic iron oxide nanoparticles (SPIONs) coated with zinc (Zn) and/or europium (Eu) doped bioactive glass. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) confirmed spherical agglomerated morphology and core@shell structure, respectively. High-Resolution TEM (HR-TEM) revealed lattice fringe values consistent with the cubic magnetite phase. Magnetic property assessment showed stable superparamagnetic behavior with slight reductions in saturation magnetization (σ_s) after immersion in simulated body fluid (SBF) solution. Photoluminescence (PL) spectra of Eu-doped samples exhibited red emission, confirming Eu rare earth element incorporation and maintaining luminescence post-immersion in SBF. Upon the interaction with SBF, hydroxyapatite (HA) formation occurred on the nanoparticle surfaces, suggesting the bioactive nature of the nanoparticles. These findings suggest that the synthesized nanoparticles exhibit promising potential for biomedical applications, including imaging, and orthopedics, due to their bioactive, magnetic, and luminescent properties.

There are two primary methods for creating superhydrophilic surfaces: applying photochemically active chemicals as coatings or creating a textured surface. Texture-induced superhydrophilic surfaces have a further advantage of being stable and without requiring radiation. The creation of texture on the surface mostly depends on the chemical composition and firing conditions. Therefore, this study aims to assess the influence of alterations in glaze composition and firing cycle on crystal phase development, microstructure, contact angle, surface roughness, and specific surface energy in nano ZnO/ZnO-Cu included glazes. In this sense, glaze formulations comprising 7.8% nano zinc oxide / 7.8% nano zinc oxide, and 0.780% nano copper, with industrial glaze, were developed. Glazed samples were sintered at 1210 °C and underwent heat treatment at 965 °C for periods of 8 and 32 h. The surfaces of the samples were examined utilizing scanning electron microscopy, X-ray diffraction, surface profilometry, and wetting angle goniometry. As a result, superhydrophilic surfaces was obtained with the formation of multi-layer structures consisting of micro-sized willemite islands at the bottom and on top of well crystalized smaller (around 1 micron in size) willemite grains and at the top nano spherical shape plagioclase granular structures. After 8 h of heat treatment, the surface achieves its maximum superhydrophilic state with a contact angle of 5◦. The superhydrophilicity was caused by the nano crystalline plagioclase granules’ surface architecture, not its chemical composition.

A commercial SiO₂-Al₂O₃-CaO-based commercial glass, Al₂O₃, and nano-TiO₂ were used as initial materials. Glass/Al₂O₃/TiO₂ samples were fabricated using the uniaxial dry pressing method, using C55 with 15 wt% TiO₂, 23 wt% TiO₂ and 36 wt% TiO₂. The optimum bulk density temperature for the C55 was 800 ˚C, for the C55-15 T was 900 ˚C, for the C55-23 T was 900 ˚C, for the C55-36 T was 1000 ˚C. TiO₂ neither chemically reacted with the other phases nor decomposed with temperature which was critical to increasing the dielectric constant. The C55-36 T sample was highlighted for its low sintering temperature of 1000 °C, high dielectric constant values (18.92 at 5 MHz, 17.40 at 1 GHz, and 17.03 at 10 GHz), low dielectric loss (0.0058 at 5 MHz, 0.0063 at 1 GHz, and 0.0075 at 10 GHz), as well as a near-zero temperature coefficient (1.7 ppm/°C) along with high mechanical properties.

Experimentation plays an important role in ceramic science and engineering, which involves the design of new products, development of new manufacturing processes, and also the optimization of processing. In this work, a cautionary note on the inadvertent use of split-plot designs was presented to understand the processing of mullite-based ceramics from kaolin waste. Samples were obtained by solid-state reactive sintering of kaolin waste following a 2² × 2 full factorial split-plot design. The influence of firing temperature, time and applied pressing pressure on the physical properties was evaluated. The structural and microstructural analyses of fired samples were evaluated by X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM). Kaolin waste processed ceramics at 1400 ºC consist of elongated mullite crystals uniformly embedded into a glassy phase and minor amounts of quartz. Statistical models were constructed for open porosity and density at 1% level of significance. The estimated P-values indicate that the coefficients associated with the applied pressing pressure and its interaction with firing temperature and time ((:gamma:) and (:{delta:}_{1})) were statistically significant for open porosity and density. The higher applied pressing pressure leads to lower open porosity. The densification process was influenced by different sintering mechanisms depending on temperature (solid phase sintering vs. liquid phase sintering). The lack of harmony between the planning and the execution of the experiment does not allow the testing of the main effects of firing temperature, time and the interaction between them (β₁, β₂ and β₃). Understanding the proper way to plan, execute and analyze experiments are of urgent interest in the field of ceramic processing, and that is the key message of this paper.