Synthesis And Application Of Al₄O₄C Ternary Carbide

The ternary carbide Al₄O₄C is as a promising ceramic material or carbon containing refractories because of its low density,high melting point and oxidation resistance and hydration resistances.In this paper,based on the stability of Al₄O₄C ternary carbides in different atmospheres?Ar and N₂?,the Al₄O₄C-CNT composites were fabricated by Al₄SiC₄,and Al₂O₃ nanowires and AlN?Particles,whiskers?were synthesized Al₄O₄C.Based on the previous research,effects of heating temperature and keeping time on composition and microstructures were investigated.?1?The effect of Ar-CO atmosphere on the synthesis of Al₄O₄C nanorod/CNT composites was studied.Al₄O₄C nanorod/CNT composites were fabricated by heat-treating an Al₄SiC₄ solid solution in a high-temperature furnace equipped with a carbon heater.Low P_COO value and appropriate temperature are two important factors for the growth of such composites.The amount,and morphology,of the resulting Al₄O₄C nanorods were influenced by the heating temperature which controls the amount of Al vapour supplied to the system.The formation of carbon nanotubes can be described by a vapour-liquid-solid process,and the mechanism for the formation of Al₄O₄C nanorods could be a vapour-vapour-solid reaction.Al vapour was first produced from Al₄SiC₄ at a high temperature and this vapour then reacted with CO to form the Al₄O₄C nuclei.Subsequently,it grew to form Al₄O₄C nanorods as the Al vapour was continuously deposited on Al₄O₄C nuclei.?2?A novel route was developed for the synthesis of Al₂O₃ nanowires by heat-treating Al₄O₄C via Si atom doping in a furnace with a carbon heater.The nanowires had dimensions of 20⁶0 nm in diameter and a few hundred microns in length,and were tunable by adjusting the heating temperature.Al₂O₃ nanowires exhibited a curved,or twisted,structure and the interface of the bending part had a defective microstructure.The study of their growth mechanism indicates that the Al₂O₃nanowires grew by a vapour-liquid-solid?VLS?growth process.?3?A novel route has been developed to synthesise AlN whiskers by heat-treating Al₄O₄C via Si atom doping under Nitrogen atmosphere.The obtained AlN whiskers have dimensions of greater than 200 nm in diameter and several hundred micrometers in length,and the whiskers with zigzag shaped and noodle-like morphology were formed by adjusting the heat-treating conditions.The mechanism responsible for AlN whiskers formation was established to be a vapour-liquid-solid reaction?nucleation reaction?in the initial stage,and a vapour-solid reaction thereafter?growth reaction?.In addition,N₂can accelerate the decomposition of Al₄O₄C,which provides meaningful information for the application of Al₄O₄C under nitrogen atmosphere at high temperatures.?4?A novel route has been developed to synthesise AlN particles by heat-treating Al₄O₄C under Nitrogen atmosphere.The initial formation of Al N particles was controlled by the vapour-solid reaction.Al vapor phase partial pressure of Al₄O₄C was low,most of the Al vapor phase flowed out of the furnace together with the flowing N₂atmosphere.A small part of the Al vapor phase reacted with nitrogen,and the growth rate of AlN particles was low.upon increasing the temperature,the Al₂O₃ and C began to react with the N₂ to form AlN via carbothermal reduction-nitridation?CRN?,and the AlN particle growth stage is mainly promoted by the solid-solid reaction.