Si粉氮化法合成Si3N4-SiC材料

以SiC、Si粉和Al2O3微粉为主要原料,羧甲基纤维素(CMC)为临时结合剂,采用氮化反应烧结法合成了Si3N4-SiC材料,主要研究了Si粉的粒度(≤0.074、≤0.044 mm)和加入量(质量分数分别为15%、17%、19%、21%)、烧成温度(分别为1 380、1 400、1 420、1 430、1 440、1 460和1 480℃)、Al2O3微粉添加量(质量分数分别为0、1%、2%、3%、4%,取代相应量的SiC粉)对Si3N4-SiC材料的显气孔率、体积密度、常温耐压强度、常温抗折强度、高温抗折强度及Si3N4含量的影响。结果表明:1)采用粒度较细Si粉的试样具有较高的致密度、常温强度、高温抗折强度和Si3N4含量;随着Si粉加入量的增加,试样的致密度略有增大但变化不大,常温强度和Si3N4含量逐渐增大,而高温抗折强度先增大后减小;2)适当提高烧成温度会明显改善Si3N4-SiC材料的高温抗折强度,但当温度超过1 440℃反而略有下降;3)添加Al2O3微粉对烧后试样的致密度、常温强度和高温抗折强度有益。综合来看,Si粉的适宜添加量(质量分数)为17%,较适宜的烧成温度为1 420～1 440℃,Al2O3微粉的适宜添加质量分数为2%。

Si3N4-SiC materials synthesized with nitridation of Si powder

Si3N4-SiC materials were prepared by nitride reaction sintering process,using SiC,Si powder and Al2O3 micropowder as main starting materials,and carboxymethyl cellulose as binder.The effects of grain size(≤0.074 and ≤0.044 mm) and additions(15%,17%,19% and 21% in mass) of Si powder,synthesizing temperatures(1380,1 400,1420,1430,1440,1460 and 1480 ℃) and Al2O3 micropowder additions(0,1%,2%,3% and 4% in mass,replacing equivalent SiC powder) on apparent porosity,bulk density,CCS,MOR,HMOR and Si3N4 content of Si3N4-SiC materials were studied.The results show that:(1)the Si3N4-SiC materials with higher density,cold strength,HMOR and Si3N4 content can be achieved using finer Si powder;with the increase of Si powder addition,the density of the materials increases slightly,the cold strength and Si3N4 content increase gradually,but the HMOR increases firstly and then decreases;(2)higher synthesizing temperature can improve the HMOR,but it will decrease slightly when the temperature exceeds 1440 ℃;(3)adding Al2O3 micropowder is beneficial to the density,cold strength and HMOR of the fired specimens.So the proper conditions are 17 mass% of Si powder,1420-1440 ℃ of synthesizing temperature and 2 mass% of Al2O3 micropowder.