Journal of the Australian Ceramic Society最新文献

SiO_2f/SiO₂ composites were prepared by compression molding and sintering using short-cut quartz fibers as reinforcement. The effects of fiber volume fraction (15%∼35%) on bulk density, apparent porosity, and mechanical and thermal properties of the composites were investigated. The results indicated that the samples with 25% fiber volume fraction had the best comprehensive performance, with an apparent porosity and compressive strength of 36% and 46.3 MPa, respectively. The flexural strength of the samples was 13.9 MPa, which represented a 90% increase compared to the samples without fibers. It was attributed to the occurrence of fiber debonding and fiber pull-out in the porous matrix. Meanwhile, the residual strength ratio of the samples after 20 thermal shocks was 74.8%. In addition, the average coefficient of thermal expansion was 0.95 × 10^− 6/℃ at 300 ℃∼700 ℃ and the thermal conductivity was 0.388 W·m^− 1·K^− 1 at 800 °C. This approach can satisfy the requirements of low cost, fast preparation of SiO_2f/SiO₂ composites, which offers the prospect of its application in the integration of load-bearing and thermal insulation.

In this study, a series of aluminum borate ceramics (ABCs) with needle-like whiskers were obtained using a low-cost, solid-state, pressureless sintering ceramic route, without any additives during the preparation process. The effects of different alumina/boric acid molar ratios and sintering temperatures on the phase composition, microstructure, mechanical properties, specific surface area, pore size distribution, and sub-cadmium neutron shielding properties of ABCs were studied using orthogonal experiments. It was observed that pure phase aluminum borate (Al₁₈B₄O₃₃) ceramics could be obtained at 1100 ℃, forming a mass of needle-like whiskers. The whiskers’ aspect ratio, fracture work, specific surface area, and pore size distribution of ABCs are maximized when ABCs are sintered at 1100 ℃ with 9:6 alumina/boric acid molar ratio. In this condition, ABCs (0.5 cm) can shield 70% of sub-cadmium neutrons (E<0.4 eV). These findings demonstrate the great potential of aluminum borate ceramics for neutron shielding applications.

High early-strength concrete and geopolymer offer advantages of faster construction and require less curing time than traditional concrete. Bagasse ash (BA), an inert pozzolan with low reactivity in alkaline media, was activated with 10M NaOH to enhance its porosity and surface area. It was then incorporated into an 80:20 wt% mixture of metakaolin (MK) and BA to improve the early-strength properties of geopolymers. This study investigates the effects of varying amounts of activated bagasse ash (ABA) on the physical and mechanical properties of a binary MK-BA-based geopolymer. The pozzolan-to-alkali ratio was maintained at 1:1, with a difference of 10M NaOH-to-Na₂SiO₃. The results indicated that the compressive strength of formulation with 50 wt% ABA increased by approximately 33% compared with formulation without ABA. XRD analysis showed a sodium aluminum silicate peak at 3 days, which decreased after 28 days, confirmed by SEM/EDS. The transformation of sodium aluminosilicate gel into a dense geopolymer matrix was observed, with IR spectra demonstrating the presence of Si–O-(Si/Al) bonds contributing to high compressive strength formulations. Overall, the ABA led to the early formation of the geopolymer 3D network with high compressive strength values.

This study presents a comprehensive investigation into the electronic properties of Hydroxyapatite (HAp) doped with Zinc (Zn) and Cobalt (Co). Five distinct compositions, denoted as 0.15Zn-HAp, 0.15Co-0.15Zn-HAp, 0.30Co-0.15Zn-HAp, 0.45Co-0.15Zn-HAp, and 0.6Co-0.15Zn-HAp (at%,) have been systematically studied employing Density of States (DOS) and band structure calculations. The computed band gap values for these compositions were determined to be 4.6663, 4.6888, 4.7049, 4.7159, and 4.7082 eV, respectively. These results illuminate the profound influence of Zn and Co doping on the electronic structure of Hydroxyapatite. These findings hold significant implications for the potential applications of these materials in diverse technological and biomedical domains. The systematic approach and precise electronic property characterizations presented in this study provide a robust foundation for further advancements in the realm of advanced materials, with particular relevance to the development of innovative materials for use in cutting-edge technologies and medical applications.

The Size-Strain Plot (SSP) method has been modified and optimized for improved X-ray diffraction (XRD) analysis, particularly focusing on its application in probing the structural properties of pure and Ca-doped zinc oxide nanoparticles (Zn_1 − xCa_xO, x = 0.0: ZnO, x = 0.01: ZCa1, x = 0.03: ZCa3, x = 0.05: ZCa5). Zn_1 − xCa_xO nanoparticles were synthesized by a gelatin-based sol-gel method. Through rigorous experimentation and analysis, the optimized SSP method demonstrates enhanced accuracy and reliability in determining crystallite size and lattice strain. The structural properties of Zn_1 − xCa_xO, including crystallite size distribution and lattice strain effects, are thoroughly investigated, shedding light on the underlying mechanisms influencing ZnO’s structural behavior. This refined SSP method offers valuable insights into the nanostructural characteristics of Zn_1 − xCa_xO, contributing to advancements in material science and nanotechnology. Also, the optical properties of the prepared samples were investigated in the UV-vis range. The results showed that adding calcium to zinc oxide with the mentioned amounts does not cause significant changes in its structure and optical properties.

In this work, highly ordered ZrO₂ nanotube arrays were fabricated on commercial pure Zr substrates through anodic oxidation in the water-based electrolyte at various voltages (30 V, 40 V and 50 V) for 1 h. The monoclinic- and tetragonal-ZrO₂ phases were obtained on ZrO₂ nanotubes through anodic oxidation. 13 vibration modes have been observed for the samples grown at low voltages (30 V and 40 V), which are assigned to monoclinic symmetry (7Ag + 6Bg), while—with the increasing growth voltage, the dominant phonon peak intensities associated with the monoclinic symmetry 6 times are decreased, and Eg (268 and 645 cm − 1) mode corresponding to tetragonal symmetry is observed. The nanotube array surfaces exhibited hydrophilic and super-hydrophilic behavior compared to the bare Zr surface. The elastic modulus values of ZrO₂ nanotube surfaces (14.41 GPa) were highly similar to those of bone structure (10–30 GPa) compared to bare Zr substrate (120.5 GPa). Moreover, hardness values of ZrO₂ nanotube surfaces were measured between ∼76.1 MPa and ∼ 283.0 MPa. The critical load values required to separate the nanotubes from the metal surface were measured between ∼1.6 N and ∼26.3 N. The wear resistance of the ZrO₂ nanotube arrays was improved compared to that of plain Zr substrate.

Doping of Hydroxyapatite (HA) with foreign ions is known as a chemical approach to improve its physicochemical characteristics and expand its biomedical applications. In the current paper, Pt-doped HA (Pt-HA) was synthesized by the co-precipitation method, and the product was characterized using conventional techniques. The XRD analysis results show that the as-synthesized Pt-HA powder exhibits apatite characteristics with lower degrees of crystallinity compared to pure hydroxyapatite, and no new phase or impurity is found. The SEM observations suggest the plate-shaped particles with homogeneous surfaces in which doping of hydroxyapatite with Pt ions led to a decrease in the length of HA particles. The EDS analysis highlighted the purity of the samples and confirmed the presence of Ca, P, O, and Pt elements in the Pt-HA sample. FTIR spectroscopy revealed the presence of the various vibrational modes corresponding to PO₄³⁻, OH⁻ and CO₃²⁻ functional groups. The mean particle size measurement of the as-prepared HA and Pt-HA samples, using the dynamic Light Scattering (DLS) analysis confirmed a decrease in particle size in the Pt-doped HA sample compared to pure HA. TGA results indicated that the prepared Pt-doped HA sample has good thermal stability.

A series of Na(La_1 − xEu_x)(WO₄)₂ (NLW) phosphors were directly generated without calcination and organic additive via reaction of the (La_1 − xEu_x)(OH)SO₄ template with Na₂WO₄ by hydrothermal reaction. The XRD results show that pure Na(La_1 − xEu_x)(WO₄)₂ can be obtained by the reaction at 150 °C for 24 h or at 200 °C for 2 h under the molar ratio of WO₄²⁻/ Ln³⁺ = 5. The NaLa(WO₄)₂ has a tetragonal structure in I4₁/a space group, and has lattice parameters of a = b = 5.332 Å, c = 11.731 Å. The FT-IR results show that the SO₄²⁻ and hydroxyl vibrations of the template were hardly observed in the product and confirmed that phase conversion is complete. The UV-vis analysis yield bandgap values of 4.07 and 3.94 eV for NaLa(WO₄)₂ and Na(La_0.95Eu_0.05)(WO₄)₂ respectively. Photoluminescence excitation (PLE) studies found two distinct strong excitation peaks at ~ 395 nm and ~ 465 nm, with the former slightly stronger and both significantly stronger than other excitation peaks/bands. Under 395 nm excitation, the phosphors exhibited the strongest red emission at 614 nm (⁵D₀→⁷F₂ transition of Eu³⁺). The optimal Eu³⁺ concentration was found to be as high as 25% due to the layered structure of NLW phosphor and well isolated Eu³⁺ activator by [WO₄] polyhedron. An evaluation and comparison with other phosphors were conducted to assess the performance of optical temperature sensing. It was discovered that the NLW phosphor cannot be employed as a probe for optical thermometry via fluorescence intensity ratio (FIR) mode due to similar intensity loss rates with increasing temperatures for different emission peaks. The NLW was demonstrated to be well capable of temperature sensing via fluorescence lifetime (FL) mode. Fluorescence decay analysis found that higher measurement temperature shortened the lifetime of the 614 nm main emission, and the lifetime decreased in liner mode. The maximum absolute sensitivity (S_A) and relative sensitivity (S_R) are 43.0 × 10^− 4 K^− 1 (298–498 K) and 144 × 10^− 4 K^− 1(498 K), respectively.

Al₂O₃-13wt. %TiO₂ is a widely used coating material for the protection of metallic surfaces. The reduced graphene oxide (rGO) added alumina-titania composite coatings deposited using Air Plasma Spraying (APS) are used for enhancing the wear resistance of engineering components. In this work, the addition of rGO at varying weight percentages of 0.5, 1, and 1.5% to the Al₂O₃-13wt.%TiO₂ powder resulted in composite coatings with improved microstructural characteristics, mechanical properties, and tribological performance. The use of SEM and XRD analyses revealed the presence of rGO between the coating splats, offering protection from crack initiation. Furthermore, there were noticeable changes in the microhardness and surface roughness of the coatings. Coatings reinforced with higher weight percentages of rGO had extremely low wear rates and offered a low coefficient of friction, with unpulled rGO acting as protective layers. However, it was also observed that the wear of coatings with 0.5 wt% and 1.0 wt% rGO addition was mainly due to the delimitation and subsequent pulverization at 1.5 kgf load and 0.17 m/s sliding speed. Overall, this work provides valuable insights into the use of composite coatings for enhancing the wear resistance of surfaces of components.

For this study, Zr-substituted BaTi₂O₅ particles were synthesized using an aqueous solution method with peroxidized polytitanic acid as the starting material. After Zr/Ti heteropolyacids were synthesized by complexing Zr with polytitanic acid (Ti-IPA) in aqueous solution using ZrOCl₂, the obtained Zr/Ti heteropolyacids were mixed with barium hydroxide. Subsequently, the precipitate was dried and heat-treated at 1100 °C for 10 h. Thereby, we obtained single-phase Ba(Zr,Ti)₂O₅ powder. Using this method, BaTi₂O₅ was synthesized with up to 6 mol% Zr solid solution on Ti sites. These results were evaluated using XRD and XRF. The crystal structure and structural transition of the resulting Ba(Zr,Ti)₂O₅ were evaluated using Raman measurements. All Ba(Zr,Ti)₂O₅ samples showed a structural transition. The Curie temperatures T_c of BaTi₂O₅, BaZr_0.034Ti_0.966O₅, and BaZr_0.059Ti_0.941O₅ were, respectively, 480, 450, and 430 °C.