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Due to excellent chemical stability, high rigidity, superior corrosion and wear resistance, aluminum oxynitride (AlON) has been considered as one of most promising candidate ceramic materials in high-performance structural, advanced abrasives and refractory fields. However, it usually exhibited relatively low flexural strength and poor fracture toughness. The study is aimed to develop silicon carbide (SiC) and zirconium nitride (ZrN) nano-particulate reinforced AlON composites with improved mechanical properties and fracture resistance via a hot-press sintering process. It was found that the addition of ZrO 2 nanoparticles would be transformed into ZrN during sintering. Due to the pinning effect of SiC and ZrN nano-particles positioned at grain boundaries of micro-sized AlON particles, the presence of SiC and ZrN nano-particles resulted in the reduction of both porosity and grain size, and a change of fracture mode from intergranular cracking in AlON to intragranular cracking in composites. With presence of 8 wt% SiC and 5.2 wt% ZrN nano-particles, the relative density, microhardness, Young’s modulus, flexural strength and fracture toughness increased. Different toughening mechanisms including crack bridging, crack branching and crack deflection were observed, thus effectively increasing the crack propagation resistance and leading to a considerable improvement in flexural strength and fracture toughness. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum oxynitride (AlON) exhibits excellent stability, chemical and mechanical properties. Corrosion resistance to molten steel is an important performance index of ceramic refractories. While silicon carbide (SiC) particles have been proven to improve the mechanical properties and thermal shock resistance of AlON ceramic, the corrosion of AlON and SiC–AlON composites by molten steel were unknown. The aim of this investigation was to evaluate the corrosion resistance to molten steel and identify the underlying mechanisms of AlON ceramic and 8wt% SiC–AlON composites at the temperature of 1550°C for 30min. Due to the reaction between AlON and molten steel, a solid product of Al2O3 is detected in the corrosion region. Besides, some round shaped pores form and increase toward the sample surface in the corrosion region. The thickness of corrosion region of AlON ceramic is about 150μm, indicating that the AlON ceramic has an excellent corrosion resistance to molten steel. However, the corrosion resistance of 8wt% SiC–AlON composites to molten steel can be characterized with a penetrated depth of approximately 250μm. This is mainly attributed to the thermal dissociation of SiC and the reaction between SiC and molten steel. [Copyright &y& Elsevier]

Abstract: Aluminum oxynitride (AlON) has been considered as a potential ceramic material for high-performance structural and advanced refractory applications owing to its excellent stability and mechanical properties such as high rigidity and good chemical stability. Thermal shock resistance is a major concern and an important performance index of refractories and high-temperature ceramics. While zirconium nitride (ZrN) particles have been proven to improve mechanical properties of AlON ceramic, the thermal shock behavior has not been evaluated yet. The aim of this investigation was to identify the thermal shock resistance and underlying mechanisms of hot-pressed 2.7% ZrN–AlON composites by a water-quenching technique over a temperature range between 225°C and 275°C. The residual strength and Young''s modulus after thermal shock decreased with increasing temperature range and thermal shock times due to large temperature gradients and thermal stresses caused by abrupt water-quenching. The presence of nano-sized ZrN particles exhibited a positive effect on the improvement of both residual strength and critical temperature difference of AlON ceramic due to the toughening effects, the higher thermal conductivity of ZrN, the refined grain size and the reduction of porosity. Different toughening mechanisms including crack deflection, crack bridging and crack branching were observed during thermal shock experiments, thus effectively enhancing the crack initiation and propagation resistance and leading to a considerable improvement in thermal shock resistance in the ZrN–AlON composites. [Copyright &y& Elsevier]

Abstract: Aluminum oxynitride (AlON) has been considered as a potential ceramic material for high-performance structural and advanced refractory applications. Thermal shock resistance is a major concern and an important performance index of high-temperature ceramics. While silicon carbide (SiC) particles have been proven to improve mechanical properties of AlON ceramic, the high-temperature thermal shock behavior was unknown. The aim of this investigation was to identify the thermal shock resistance and underlying mechanisms of AlON ceramic and 8wt% SiC–AlON composites over a temperature range between 175°C and 275°C. The residual strength and Young''s modulus after thermal shock decreased with increasing quenching temperature and thermal shock times due to large temperature gradients and thermal stresses caused by abrupt water-quenching. A linear relationship between the residual strength and thermal shock times was observed in both pure AlON and SiC–AlON composites. The addition of nano-sized SiC particles increased both residual strength and critical temperature from 200°C in the monolithic AlON to 225°C in the SiC–AlON composites due to the toughening effect, the lower coefficient of thermal expansion and higher thermal conductivity of SiC. The enhancement of the thermal shock resistance in the SiC–AlON composites was directly related to the change of fracture mode from intergranular cracking along with cleavage-type fracture in the AlON to a rougher fracture surface with ridge-like characteristics, crack deflection, and crack branching in the SiC–AlON composites. [Copyright &y& Elsevier]

Abstract: Aluminum oxynitride (Alon) has been considered as a potential ceramic material due to excellent stability, chemical and mechanical properties such as high rigidity and good chemical stability, but it has relatively low strength and poor fracture toughness. The aim of this study was to investigate a type of silicon carbide (SiC) nano-particulate reinforced Alon composites with improved mechanical properties and fracture resistance via hot-press sintering. The addition of SiC nano-particles resulted in a reduction of both porosity and grain size, and a change of fracture mode from intergranular cracking in the monolithic Alon to intragranular cracking in the composites due to the pinning effect of SiC nano-particles positioned at grain boundaries or triple junctions of micro-sized Alon particles. With 8wt% SiC nano-particles addition, the relative density, microhardness, Young''s modulus, flexural strength, and fracture toughness all increased. Different toughening mechanisms including crack bridging, crack branching and crack deflection were observed, thus effectively increasing the crack propagation resistance and leading to a considerable improvement in the flexural strength and fracture toughness of the composites. [Copyright &y& Elsevier]

Abstract: Silicon carbide (SiC)–aluminium oxynitride (Alon) ceramic composites exhibited improved mechanical properties, but the high temperature oxidation behaviour was unknown. The aim of this investigation was to identify oxidation characteristics and kinetics of 8wt% SiC–Alon composites over a temperature range between 700°C and 1200°C in air. The Alon matrix and SiC particles near the surface were oxidized to form Al2O3 and SiO2, respectively. The starting oxidation temperature of Alon was observed to be about 1000°C. While the addition of nano-sized SiC particles resulted in a reduced starting oxidation temperature due to the large cumulative surface area and high total surface energy, the oxidation resistance at higher temperatures of 1100°C and 1200°C was remarkably enhanced. The oxidation kinetics changed from a linear weight gain for pure Alon into a logarithmic weight gain for the composites due to the formation of a dense protective oxidation layer arising from the presence of SiO2. [Copyright &y& Elsevier]

Abstract: Aluminium oxynitride (Alon) exhibits excellent stability, high rigidity and good thermal shock resistance, but it has relatively low strength and poor fracture toughness. The aim of this investigation was to develop a new type of zirconium nitride (ZrN) nano-particulate reinforced Alon composites via a change of ZrO2 nano-particles during sintering. A reduction of porosity and grain size was observed in the composite. With increasing amount of ZrN nano-particles up to 2.7%, the relative density, hardness, Young''s modulus, flexural strength, and fracture toughness all increased. When the ZrN nano-particles exceeded 2.7%, while the flexural strength and fracture toughness decreased slightly, the density, hardness and Young''s modulus continued to increase. Different toughening mechanisms including crack bridging, crack branching and crack deflection were observed, thus effectively increasing the crack propagation resistance and leading to a considerable improvement in the flexural strength and fracture toughness of the composites. [Copyright &y& Elsevier]