聚碳硅烷对低碳铝碳材料结构与性能的影响

Effect of polycarbosilane on structure and properties of low-carbon Al_2O_3-C refractories

为了提高低碳铝碳耐火材料的高温性能,以板状刚玉、电熔白刚玉、α-Al_2O_3微粉、鳞片石墨为主要原料,环保沥青、液态热塑性酚醛树脂、固态树脂粉、固态聚碳硅烷和正己烷为外加剂,研究了聚碳硅烷外加量(加入质量分数分别为0、0. 3%和0. 6%)和热处理温度(950、1 100、1 250、1 400和1 550℃)对低碳铝碳材料显微结构、强度及抗热震性的影响。结果表明:经950℃热处理后,聚碳硅烷热解破坏酚醛树脂热解碳结构; 1 100～1 250℃时,聚碳硅烷生成网状结构,弥补材料强度;当聚碳硅烷外加量为0. 6%(w),于1 550℃热处理后,聚碳硅烷高温裂解生成含Si纤维,材料强度提高。但含Si纤维的生成,会引起材料热膨胀失配,从而导致试样热震后的强度保持率下降。

In order to improve the high temperature properties of low-carbon Al2O3-refractories,tabular corundum,white fused corundum,α-Al2O3 micropowder,and flake graphite were used as raw materials,and environment-friendly pitch,thermal plastic phenolic resin liquid,solid resin powder,solid polycarbosilane (PCS) and n-hexane as additives.Effects of PCS extra-additions (0,0.3% and 0.6%,by mass) and heat-treatment temperatures (950,1100,1250,1400 and 1550 ℃) on microstructure,strength and thermal shock resistance of low-carbon Al2O3-C refractories were studied.The results show that:PCS pyrolyzes and destroys the pyrolytic carbon structure of phenolic resin at 950 ℃.The reticulate structure forms by PCS pyrolysis from 1100 ℃ to 1250 ℃,thus the material strength increases.When the extra-addition of PCS is 0.6% and the heat-treatment temperature is 1550 ℃,Si-containing whiskers form,which enhance the strength greatly.But the formed Si-containing whiskers will result in the mismatch of thermal expansion of the material,thus the retention ratio of the strength after thermal shock declines.