【作者】 姜淼；

【导师】 侯峰；

【作者基本信息】 天津大学 ， 材料学， 2005， 硕士

【摘要】 本论文以氮化硅在天线罩材料上的应用为背景,研究了堇青石和锂辉石作为烧结助剂在氮化硅材料烧结过程的作用,探讨了烧结机理。通过材料力学性能和介电性能的表征,证明复合烧结助剂更有利于促进材料低温烧结。分别通过Sol-gel法和固相法,在1250°C烧结制备得到堇青石粉体。将按照3:7的比例混合的堇青石和氮化硅复合粉体成型、烧结。在1350°C到1515°C的烧结温度范围获得结构富含大量微孔的复相陶瓷材料。材料主晶相为Si₂N₂O,经研究认为是Si₃N₄、SiO₂、Si₂N₂O在高温综合作用的结果。Sol-gel法堇青石作为烧结助剂的样品在烧成过程中以蒸发-凝聚传质为主,抗弯强度很低。而固相法堇青石作为烧结助剂的样品以溶解-沉淀为主要传质机理,在1490°C烧成后保持了一定的强度（147.09MPa）,同时可以获得较好的介电性能(ε=5.174,tgδ=1.340×10^-2)。在研究堇青石的基础上,通过Sol-gel法和固相法,在1200°C煅烧,制备得到锂辉石粉体。按照不同的比例混合堇青石和锂辉石为复合烧结助剂,与氮化硅复合粉体混合、成型、烧结。Sol-gel法锂辉石作为烧结助剂没有对材料介电性能产生明显改善,烧结后的样品抗弯强度很低。固相法锂辉石与堇青石作为复合助剂的材料经烧结后比堇青石单一助剂更加明显的降低了材料烧结温度,烧结后强度明显提高。但是烧结温度继续升高会引起强度的下降,证明锂辉石一方面可以降低烧结温度,实现较致密的烧结;另一方面随着温度的继续升高,锂辉石的玻璃相大量析出,会导致材料力学性能降低。经过比较,认为堇青石与锂辉石比例为2:1的复合烧结助剂,在1390°C烧结后ε=4.103,tgδ=2.641×10^-2,抗弯强度为129.77MPa,基本满足了材料的应用。更多还原

【Abstract】 The fundamental goal of the study was to develop a sintering additive system for silicon nitride based ceramics in radome application use. Cordierite and spodumene were fabricated and mixed with silicon nitride powders. The reactions in sintering process were discussed, and the dielectric properties and mechanical properties indicated that a composite sintering additive had a great effect in decreasing sintering temperature.The cordierite powders that were prepared by both sol-gel method and solid-state reaction method were used as sintering additives. The main phase was identified as Si₂N₂O in high sintering temperatures, which was believed as a resultant of complex reaction of Si₃N₄, SiO₂ and Si₂N₂O. Evaporating-condensation transferring took place in the sintering process for the samples using sol-gel method cordierite, but high strength couldn’t be achieved in this way. The samples using solid-state reaction cordierite sintered at 1490°C achieved low dielectric properties (ε=5.174, tgδ=1.340×10^-2) with an appropriate strength （147.09MPa）, which could be explained by solution-precipitation transferring.The spodumene powders were fabricated at 1200°C by both sol-gel method and solid-state reaction method. Spodumene and cordierite mixed as composite additive were used in sintering silicon nitride material. The samples using sol-gel method spodumene could decrease the sintering temperature, but didn’t improve the dielectric properties and strength. The samples added solid-state reaction spodumene showed lower sintering temperature than using cordierite as additive only, as the lower forming temperature of liquid phase. Composite material sintered at 1390°C using cordierite and spodumene with the ratio of 2:1 showed the most appropriate properties (ε=4.103, tgδ=2.641×10^-2, 129.77MPa), which could fulfill the application use.更多还原