自结合碳化硅材料高温氧化行为研究

High Temperature Oxidation Behavior of Self Bonded Silicon Carbide

研究了气孔率为１１ ．５ ％ 的自结合碳化硅材料在１ ３００ ℃空气中的高温氧化行为．研究结果表明：氧化初期形成的非晶态ＳｉＯ２ 对材料中孔隙与裂纹尖端起钝化作用，造成材料室温强度随氧化时间的增加而增加．当氧化２２ ．５ ｈ 时，材料强度最高，达２９３ ＭＰａ；随着氧化时间的增加，非晶态ＳｉＯ２ 晶化形成方石英，以及冷却过程中引发的表面裂纹，造成材料室温强度的降低．表面裂纹的出现。

High temperature oxidation behavior of self bonded silicon carbide in air at 1 300 ℃ is investigated. Experimental result shows that the room temperature flexural strength of specimens experienced oxidation increases first with time and reaches a maximum of 293 MPa at the oxidation time of 22.5 h, due to the blunting of amorphous silica scale. Subsequently, the flexural strength decreases with time because of the crystallizing of the amorphous silica and cracking of the oxide scale. It is also oxide cracking that makes the oxidation kinetics curve of the material obey logarithmic equation.