配碳量对锆英石和氧化铝碳热还原氮化合成ZrN-SiAlON的影响

为了降低合成成本,以低能耗、低成本的天然锆英石、工业氧化铝和焦炭为原料,采用碳热还原氮化法合成了ZrN-SiAlON复相材料。根据反应方程式3Al2O3+6ZrSiO4+27C+8N 26ZrN+2Si3Al3O3N5+27CO设计锆英石和工业氧化铝的原料配比,改变还原剂焦炭的配入质量分数(分别为理论用量、过量5%、过量10%、过量20%),经球磨混合、成型、干燥后,在流动氮气中分别于1 500、1 550、1 600℃保温4 h合成,自然冷却后分析合成产物的相组成和显微结构。结果表明:1)在合成温度为1 500℃时,配碳量的增加有助于ZrN的生成;2)在合成温度为1 550℃时,配炭量过量20%的试样中有15R型的多型体SiAlON(即SiAl4O2N4)生成;3)在合成温度为1 600℃时,配碳量为理论量和过量5%的试样中的多型体SiAlON为15R型,而配碳过量10%和20%的试样中的多型体SiAlON则主要为12H型(即SiAl5O2N5)。

Effects of carbon coke additions on synthesis of ZrN-SiAlON from zircon and alumina by carbothermal reduction nitridation process

Natural zircon,alumina and carbon coke were used as starting materials for the preparation of ZrN-SiAlON composite by carbonthermal reduction nitridation.The mass ratio of zircon and industrial alumina was designed according to equation 3Al2O3+6ZrSiO4+27C+8N2 6ZrN+2Si3Al3O3N5+27CO.The additions of carbon coke were stoichiometric amount,excess 5 mass%,excess 10 mass% and excess 20 mass%,respectively.After ball-milling,molding,drying and firing at 1 500,1 550 and 1 600 ℃ for 4 h under flowing nitrogen followed by natural cooling down to room temperature,respectively,the phase compositions and microstructure of the synthetic products were investigated.The results show that:(1)increasing coke content is beneficial to the formation of ZrN at 1 500 ℃;(2)when the firing temperature is 1 550 ℃,there is 15R-SiAl4O2N4(SiAl4O2N4) in the products with excess 20 mass% carbon coke addition;(3)when the firing temperature is 1 600 ℃,there is 15R-SiAl4O2N4 in the products with stoichiometric or excess 5 mass% carbon coke addition and there is 12H-SiAl4O2N4(SiAl5O2N5) in the products with excess 10 mass% or excess 20 mass% carbon coke addition.