高密度反应烧结SiC的耐化学腐蚀性能

Resistance to Chemical Corrosion of High Density Reaction-bonded SiC

考察了以SiC和碳粉为主要原料制备的不同密度和游离硅含量的反应烧结SiC陶瓷的耐酸碱腐蚀性能,结果表明:游离硅含量及其分布状况是决定SiC陶瓷耐化学腐蚀性能的主要因素。密度为3.16 g/cm3的反应烧结SiC耐化学腐蚀性能显著优于密度为3.07 g/cm3的材料。同等密度但含少量游离碳的高密度材料耐腐蚀性能更好,在98℃5%HF/5%HNO3(质量分数)中腐蚀30 h后失重量仅为中等密度材料的1/17.4。混酸腐蚀时反应烧结SiC初始1 h腐蚀量与材料中游离硅的体积含量呈线性关系,其后,高、低密度材料的腐蚀失重量的比值减小。

The resistance to acid and alkali corrosion of reaction-bonded SiC ceramic was studied, which is prepared by principal raw material SiC and powdered carbon with a variety of densities and contents of free silicon. It is found that the contents of free silicon and its distribution are the major factors to determining the resistance of chemical corrosion of SiC ceramic. The reaction bonding SiC ceramic whose density is 3. 16 g/cm^3 apparently has advantage over the one whose density is 3.07 g/cm^3. The one who has less free carbon shows stronger resistance to chemical corrosion then Others when they are of the same density. For example, when corrodeci by deposited in 5% HF/5% HNO3 （ mass fraction ） solution for 30 hours at high temperature （98 ℃ ） ,the lost weight of SiC ceramic is only 1/17. 4 of SiC ceramic of medium density, When corroded by mix acid, the lost weight of reaction-bonded SiC ceramic in the beginning 1 hour is linear with its volume content of free silicon. When the corroding time is beyond 1 hour, the ratio of high density sample＇ s lost weight to low density sample＇s lost weight begins to reduce.