Preparation Of Al₄SiC₄ Powders By SHS And The Influence Of Al₄SiC₄ Additive On The Properties Of Al₂O₃-C Refractories

Al₄SiC₄ has well application prospect in functional refractory materials due to its high melting-point (about 2037℃),high thermal conductivity and higher corrosion resistance to high-temperature melt and slag. It has been of great interesting to add Al₄SiC₄ into carbon containing refractory as an additive to improve the properties of the materials.This experiment systematically studies the preparation of self-propagating high temperature synthesis of Al₄SiC₄ powders, and the influence on the properties of alumina-graphite material added to Al₄SiC₄ powders as an additive. Conclusions are drawn as following:1. Preparation(1) Al₄SiC₄ powders can be obtained by C.O.SHS(chemical oven SHS) with C and Ti mixture powders ,but it can't be synthesized by common SHS.(2) The synthesis of Al₄SiC₄ powders includes two steps: first of all, SiC and Al₄C₃ are reacted from simple substance of Al,Si and C, then Al₄SiC₄ is synthesized by SiC and Al₄C₃.(3) Powders with 80wt% of Al₄SiC₄ powders but without Al₄C₃ phrase are obtained from the composition with 30% of carbon.(4) To minish the crystal gravesize of metal Al powders is in favor of the growth of Al₄SiC₄.2. The effect on properties(1) The addition of composition Al₄SiC₄. can decrease the apparent porosity, increase the density of structure, improve the cold modulus of rupture (CMOR) of the alumina-graphite materials to a certain extent and markedly increase the hot modulus of rupture (HMOR).(2) Because Al₄SiC₄ is oxidized before the graphite, the created solid matter deposits into the pore or at the surface of solid and then forms a dense protective layer of mullite, and C can serves as a barriev for the diffusion of oxygen from the exterior into the interior, which provides the self-repair and remarkable effect on the oxidation resistance of the carbon containing refractory with Al₄SiC₄.(3) Al₄SiC₄ has excellent hydration resistance, and is helpful to advided the bad effect of the metal Al on the carbon containing refractory, and can replace the additives metal Al, therefore, it has a better application prospect. 4)At the contact face of melt steel, Al₄SiC₄ forms a dense layer of mullite by oxidation, which makes the oxidizing dissolving of graphite and the penetration of the melt steel to slower, so as to markedly improve the corrosion resistance to the melt steel of the materials.In conclusion, Self-propagating high temperature synthesis is an effective preparation way of Al₄SiC₄ powders, which is quick and simple, with lower energy consumption. The obtained powder has excellent properties which meet the demands of the additive of carbon containing refractory, is remarkably improve the properties in room and high temperature of the alumina-graphite materials, especially, in resistance to oxidation, hydration and erosion of melt steel. Therefore, it may remedy the defect of the common Al containing additive, and can be used better than additive to carbon containing refractory.