Journal of the Australian Ceramic Society最新文献

To explore the effect of sintering temperature on the mechanical properties and clarify the relationship between their microstructure and properties of porcelain insulators, the green body of porcelain insulators were prepared by dry moulding and sintered at different temperatures. The effect of sintering temperature on bulk density, apparent porosity, water absorption, linear shrinkage, compressive strength and bending strength of the insulators were investigated. The phase composition and microstructure of the sintered specimens were obtained to explain the essential reasons for changes in mechanical properties. The results showed that the apparent porosity and water absorption decrease first and then increase with the increase of sintering temperature, and the compressive strength and bending strength increase first and then decrease with the increase of sintering temperature. The sample sintered at 1280 °C exhibited the optimum overall properties, with the lowest apparent porosity and water absorption of 0.43% and 0.15%, the highest compressive strength and bending strength of 434.1 MPa and 110.8 MPa, respectively. The reinforcing effect caused by the interlocking bonding network formed by the in-situ generated rod-shaped mullite are the key factors in improving the mechanical properties.

Β-tricalcium phosphate (β-TCP) is preferred among of the calcium phosphate family member owing to its resorbility for bone related implant materials. In addition to this feature, antibacterial and low cytotoxicity attributes are necessary to mitigate the risk of infection caused by bacteria and minimize the rejection rate from the body. Silver (Ag) and Copper (Cu) are two metals that have been extensively utilized since ancient times to suppress microbial growth. β-TCP powders with dopant of the Ag, Cu and Ag/Cu co-doped were prepared with spray pyrolysis (SP). A series of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) were employed to analyze the crystalline phase, morphology, and elemental composition of un-doped, Ag-doped, Cu-doped and Ag/Cu co-doped β-TCP samples. From the results showed, all prepared powders have a spherical shape with metals distributed homogenously on the β-TCP. This confirms the effective synthesis of dopant Ag and Cu to β-TCP by the SP method. Furthermore, at lower concentrations, the antibacterial efficacy of 2.9 mol% Ag/2.9 mol% Cu co-doped β-TC is equal to 5.8% mol Ag-doped and demonstrated higher cell viability, indicating a favorable influence of the co-doping technique on improving the bioactivity of β-TCP.

This study investigates the synthesis and characterization of hydroxyapatite (HAp) ceramic biomaterials doped with silver (Ag) and pyrocatechol. HAp, commonly utilized in the treatment of hard tissues including teeth and bones, was produced and analyzed to assess the structural, morphological, elemental, and thermal properties of the materials. The phase and crystal structures of the synthesized HAp biomaterials were examined using X-ray diffraction (XRD), revealing that the incorporation of Ag and pyrocatechol influenced the crystallinity and lattice parameters. Fourier transform infrared (FT-IR) spectroscopy verified the presence of the characteristic OH- and PO₄³⁻ groups of HAp, while scanning electron microscopy (SEM) displayed consistent morphologies across all samples, free of residues or impurities. Elemental compositions were determined by energy dispersive X-ray (EDX) spectroscopy, and thermal stability was assessed through differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Additionally, computational studies using density functional theory (DFT) were conducted to further investigate the electronic and structural properties of 0.44% Ag-doped HAp. The DFT calculations revealed that Ag atoms replace calcium (Ca1 and Ca2) positions in the lattice, leading to slight distortions in the lattice structure and changes in the electronic density distribution. Minor changes were observed in the band structure and electronic properties, indicating the stability and tunability of the doped system. A small amount of β-tricalcium phosphate (β-TCP) phase was also detected alongside the main HAp phase. These results underscore the importance of incorporating pyrocatechol and silver doping into HAp for biomedical applications. The resulting biomaterials exhibit enhanced structural, thermal, and electronic properties, with improved biocompatibility and antimicrobial activity.

Cordierite-mullite kiln furniture for lepidolite calcination was prepared from cordierite, M45 mullite, and clay with the addition of potassium feldspar fines. The effects of potassium feldspar content and firing temperature on phase composition, microstructure, mechanical properties, and thermal shock resistance were investigated. The findings indicate that the incorporation of potassium feldspar enhances the liquid phase content in the samples without significantly altering the phase compositions, thereby facilitating the densification of the materials. In combination with the thermodynamic calculations and the results of the finite element simulation, it is evident that the stresses within the cordierite-mullite system result in less damage to the samples and exhibit a lower degree of stress concentration in the aggregate compared to the mullite-cordierite system. The porous structure of the cordierite aggregate, combined with stress concentration, leads to the formation of microscopic cracks that redirect crack propagation and consume additional fracture energy as the cracks extend. Consequently, cordierite-mullite kiln furniture exhibits a fracture strength of 16.5 MPa and a retention rate of 92.7% following thermal shock.

The development of iron-containing Aurivillius-phase bismuth layer-structured ferroelectrics (BLSFs) has garnered considerable attention due to their unique multiferroic properties, characterized by the coexistence of ferroelectric and magnetic ordering. Among these materials, bismuth titanate-ferrite (Bi₅Ti₃FeO₁₅) stands out as a prominent candidate for high-temperature piezoelectric applications, given its elevated Curie temperature (T_C) of 760 °C. Despite its potential, the practical utilization of Bi₅Ti₃FeO₁₅ in high-temperature piezoelectric devices is limited by low resistance at elevated temperatures and poor piezoelectric performance. To address these issues, we explored a composition optimization strategy involving the partial substitution of bismuth ions with rare-earth dysprosium (Dy) ions to enhance piezoelectric performance and direct-current (DC) electrical resistivity of Bi₅Ti₃FeO₁₅. This substitution aims to mitigate the volatility of bismuth ions and stabilize the (Bi₂O₂)²⁺ layer, thereby reducing oxygen vacancy concentration. We successfully synthesized Bi_5-xDy_xTi₃FeO₁₅ (BTF-100xDy) oxide compounds using a solid-state reaction method. Our experimental results demonstrate that dysprosium-substituted Bi₅Ti₃FeO₁₅ exhibits markedly enhanced piezoelectric performance compared to the unmodified Bi₅Ti₃FeO₁₅. Specifically, the BTF-5Dy composition achieved a significant increase in the piezoelectric constant (d₃₃) to 23.1 pC/N, which is approximately three times higher than that of the unmodified Bi₅Ti₃FeO₁₅ (7.1 pC/N). The temperature-dependent measurements of DC electrical resistivity revealed that dysprosium substitution substantially improves the material’s electrical resistivity at elevated temperatures. Additionally, BTF-5Dy exhibited a high T_C of 787 °C, a low dielectric loss tanδ (~ 0.38% at 1 MHz), and good thermal stability of electromechanical properties up to 300 °C. These improvements are attributed to lattice distortion and reduced oxygen vacancies. Collectively, these findings suggest that dysprosium-substituted Bi₅Ti₃FeO₁₅ ceramics hold great promise as high-performance materials for high-temperature piezoelectric applications.

This study examines the effects of sand type on the properties of the calcined zeolite-based geopolymer mortars. The geopolymer mortars were prepared using different sand types, standard and crushed, in different ratios. The zeolite calcined at 600 ^oC was used for the alumina silicate resource. The sodium hydroxide at 4 M, 8 M, and 12 M and sodium silicate solutions with 2Ms and 3Ms were used for the alkaline activation process. Using a vibrating table, the prepared geopolymer mortar samples were placed in a 40 × 40 × 160 mm metallic mold. The samples were then cured in the oven at 90 ^oC for 6 h. According to the results, the geopolymer mortars’ apparent porosity and water absorption values varied depending on the NaOH molarity and the sand used in the mixtures. The apparent porosity and water absorption rates varied in between 11.85 − 25.54% and 7.02 − 16.51%, respectively. Considering the data obtained from the geopolymer mortars activated with different NaOH molarities and SS solutions, the flexural strengths are between 0.93 MPa − 4.0 MPa, and compressive strength values are 3.39 MPa − 12.54 MPa. The highest flexural (4 MPa) and compressive strength (12.54 MPa) were obtained in the CS40 samples. As a result, the increased amount of crushed sand content increases the strength values.

The combustion in open-air of complex aluminothermic TiO₂-Al-C mixtures, followed by sintering was used to produce TiC-Al₂O₃ based ceramics. For this purpose, powders mixtures containing [TiO₂-Al-C], [TiO₂ + Al + (90%C + 10%B)], [TiO₂ + (90%Al + 10%Mg) + C] and [(90%TiO₂ + 10%SiO₂) + Al + C], were prepared via the conventional powder metallurgy route. The combustion product was crushed and sieved in order to recover the fractions less than 40 µm. The different mixtures of ceramic powders first underwent cold uniaxial compression followed by a sintering at 2023 K, under a cyclic load of 50 MPa applied for 2.4 ks. X-ray diffraction analysis of the samples revealed the presence of TiC, Al₂O₃ and Al₂TiO₅ spinel. The combustion in open-air is accompanied by an evaporation of aluminum, the presence of unreduced TiO₂ and the formation of new oxides such as Ti₃O₅ and Ti₄O₇ which generate Al₂TiO₅ spinel during the sintering. Microstructural analyses using a scanning electron microscope combined with semi-quantitative evaluation revealed the basic ceramic structure composed of TiC, Al₂O₃ and Al₂TiO₅. The additions of boron, magnesium or silica generate new phases such as TiB₂, MgAl₂O₄ and Ti₃SiC₂ modifying the structure and the ceramic composition. Finally, the aluminothermic mixtures composition therefore has a significant impact on the structure, hardness, micro-indentation results and tribological behavior of the ceramics studied. Thus, the lowest wear rate and friction coefficient were recorded on the ceramic containing 33.81wt.% TiC—51.73wt.% Al₂O₃—3.42wt.% Al₂TiO₅—11.04wt.% Ti₃SiC₂.

Ferrosilicon nitride (Fe-Si₃N₄) is a promising additive for enhancing the performance of carbon (C)-containing refractories due to the exceptional high-temperature properties of Si₃N₄ and the enhanced sintering characteristics of the iron (Fe) phase. This study examined the effects of the atmosphere and Fe phase on the Si₃N₄-C system to elucidate the reaction behavior and mechanisms of Fe-Si₃N₄ in C-containing materials at elevated temperatures. Phase composition, microstructure, and elemental distribution were analyzed, alongside theoretical thermodynamic calculations. The results indicated that the presence of the Fe phase reduced the complete conversion temperature of Si₃N₄ to silicon carbide (SiC) from 1600 °C to 1500 °C. This suggested that the Fe phase significantly accelerated the conversion rate and lowered the conversion temperature. This effect was attributable to the formation of an Fe-Si–C melt, wherein [Fe] decomposed Si₃N₄, absorbing [Si] to form a high-Si mesophase. Subsequently, [Si] reacted with C to form SiC. Additionally, in a reducing atmosphere, the final stable products of the Fe- Si₃N₄-C system were SiC and FeSi₃. However, the presence of CO led to slight oxidization of Si₃N₄ compared with its behavior in an argon atmosphere.

Structure and mechanical properties of α-Al₂O₃ ceramics modified with different amounts of Y₂O₃ (0, 0.5, 1, 1.5, 2, 3, 4 and 5 wt.%) were investigated. The samples were obtained by reverse chemical co-precipitation from AlCl₃ × 6H₂O and Y(NO₃)₃ aqueous solutions. Calcination of the obtained powder mixtures was carried out in air at 800 and 900 °C for 2 h. Afterwards, θ-Al₂O₃ with a small addition of γ-Al₂O₃ phase was formed. The calcined powders were further compacted at high hydrostatic pressure (HHP) of 300 or 700 MPa and sintered at 1550 °C for 2 h. A mutual inhibition of crystallization processes in the Al₂O₃–Y₂O₃ powders was observed. Several characteristics were determined using X-ray diffraction (XRD) analysis: the formation of the yttrium aluminium garnet (Y₃Al₅O₁₂, YAG) phase was detected, tensile stresses of the first kind (positive macrostresses of the 1 st kind) and textured structure of the α-Al₂O₃ matrix characterise some of the sintered samples. The study clarified the mechanical properties of the obtained ceramics in dependence of the quantity and particle size of the YAG phase, the calcination temperature and HHP magnitude.

This study investigates the machinability of hybrid polymer ceramic composites (PCCs) using abrasive jet machining (AJM). Composite samples were fabricated by incorporating barium titanate (BT: BaTiO₃) and calcium copper titanate (CCT: CaCu₃Ti₄O₁₂) in varying ratios (BT: CCT = 100:0, 60:40, 50:50, 40:60, 0:100) within an epoxy resin matrix (20:80). As BT was substituted with CCT, density decreased and porosity by 11.66% and 28.85%, respectively. A 60:40 BT-CCT blend improved tensile strength, flexural strength, impact resistance, and microhardness by 12.26%, 46.72%, 21.74%, and 27.41%, respectively. Machinability evaluation was conducted using 150-micron SiC abrasives in an AJM system by following Taguchi’s method. The rate of material removal (RMR) and surface roughness (Ra) were analyzed across five PCC compositions, varying pressure (2–6 bar) and standoff distance (2–6 mm). ANOVA determined the significance of control factors, and optimal machining settings were identified that improved RMR and Ra through 3.7998% and 0.8651%. The desirability approach in Response Surface Methodology (RSM) was employed for individual and combined optimization of machining parameters, with confirmatory tests validating performance enhancements. A high degree of accuracy is observed with 1.187% and 1.079% deviation between predicted and actual values for RMR for Ra.