氮化硼/二氧化硅复相陶瓷的强化机理研究

项目名称： 氮化硼/二氧化硅复相陶瓷的强化机理研究

项目编号： No.50802099

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 陈继新

作者单位： 中国科学院金属研究所

项目金额： 20万元

中文摘要： 氮化硼/二氧化硅复相陶瓷是一种适用于超高速飞行器的候选透波材料。该复相陶瓷的抗弯强度最高可达六方氮化硼（h-BN）或石英玻璃（SiO2）的4～7倍，出现了所谓的共增强效应。本项目针对其强化机理开展研究工作。首先制备出了多组分氮化硼/二氧化硅复相陶瓷。抗弯强度测试表明，该复合材料在二氧化硅含量约为30wt.%时达到最大值。根据成分、化学键合、显微结构的分析，可以确定其强化机理主要为：（a）细晶强化。主要是氮化硼晶粒的细化，与此同时，分布于氮化硼晶粒间的非晶二氧化硅也必须保持较小的尺寸，一旦发生团聚将使材料强度下降。（b）界面强化。氮化硼中氮和硼可以扩散至二氧化硅中，而二氧化硅中的氧也向氮化硼中扩散，并且形成了B-O-Si键。这就使得氮化硼与二氧化硅间的界面变成一部分化学结合，而非纯机械结合，有利于材料强度的提高。（c）残余压应力强化。非晶二氧化硅具有比氮化硼低的热膨胀系数，所以在二氧化硅中形成的是压应力，使其因加入氮化硼而得到增强。最后，成功合成了新型Y4Si2O7N2-BN复合材料，同样在其中观察到了共增强效应，验证了以上强化机理。

中文关键词： 氮化硼/二氧化硅复相陶瓷；透波材料；成分分析；显微结构；强化机理

英文摘要： Boron nitride/silica composite is one of potential materials for radome and antena windows of hypersonic aircraft. The flexual strength of h-BN/SiO2 composite can be 4-7 times of h-BN or SiO2. An evident co-operative enhancement was observed.In this item, the strengthening mechanisms were systematiclly studied.A series of h-BN/SiO2 composites were firstly fabricated.The flexual strength reached the highest value when the content of silca is about 30wt.%. Based on the results of composition analysis, chemical analysis,and microstucture observation, the strengthening mechanisms are as follows: (a) (a) Grain refinement strengthening. It includes grain refinement of boron nitride as well as small-sized fused silica. (b) Strengthening of interface. Nitrogen and boron in boron nitride can diffuse into silica, meanwhile, oxygen in silica can also diffuse into boron nitride. As a result, new B-O-Si bond comes into being. This means that the phase interface is a partially chemical combination instead of pure mechanical one, which is of benefit to the strength. (c) Residual stress strengthening. Fused silica suffers from a compressive stress due to its lower coefficient of thermal expansion, so it was strengthened by the addition of boron nitride. At last, novel Y4Si2O7N2/BN composites were produced to confirm above proposed strengthening mechanisms. Fortunately, co-enhanced effect was also found in this material.

英文关键词： Boron nitride/silica composite; Microwave-transparent materials; Element analysis; Microstructure; Strengthening mechanisms