BN-SiC纳米复相陶瓷非晶活化烧结与强韧化机理研究

Nanocomposite ceramics of BN-SiC has widely application prospect in some high-tech fields of aerospace, metallurgy, machinery and electronics industry due to its excellent physical and chemical properties. Because of the low self-diffusion coefficient of BN and SiC and the layer structure of BN,forming of card bridge structure supported each other, however, however, it is difficult for BN and SiC to sintered density.This project prepared amorphous powders successfully by the wet chemical method combining Polymer three dimensional network technology with sol-gel technology. Then, through the structure design and control of three dimensional network gel precursor, some influencing factors of Si-B-C-N amorphous powders fabricated by three dimensional network wet chemical method were investigated, , such as the formation mechanism of Si-B-C-N amorphous powders, the microscopic mechanism of restraining the formation of the card bridge structure of BN and the strengthening and toughening mechanism.Based on the In-situ dispersion precipitation of nanometer SiC phase, the excellent BN-SiC nanocomposite ceramics without BN card bridge structure were synthetized. This project will provide a new approach for the preparation of nanocomposite ceramics, and establish the theoretical foundation for the generalization and application of nanocomposite ceramics.

BN-SiC纳米复相陶瓷具有优良的物理性能和化学性能、重量轻、可机加工等特点，在航空航天、冶金、机械和电子等高科技领域具有广泛应用前景。然而BN和SiC的自扩散系数低，且BN呈片层状，形成相互支撑的卡片搭桥结构，很难烧结致密。本项目通过高分子三维网络技术与溶胶凝胶技术相结合的湿化学法制备具有晶格原子排列混乱、烧结活性较高的Si-B-C-N非晶态粉体，通过三维网络凝胶前躯体的结构设计与控制，研究三维网络湿化学法制备Si-B-C-N非晶态粉体的影响因素、Si-B-C-N非晶态粉体的合成机理、抑制BN卡片搭桥结构形成的微观机理和材料强韧化机理等主要内容，基于Si-B-C-N非晶态粉体原位弥散析出纳米SiC第二相的方法，制备无BN卡片搭桥结构、性能优良的BN-SiC纳米复相陶瓷。项目完成将为BN-SiC纳米复相陶瓷材料的制备和推广应用奠定理论基础。

BN-SiC纳米复相陶瓷具有优良的物理性能和化学性能、重量轻、可机加工等特点，在航空、航天、冶金、机械和电子等高科技领域具有广泛应用前景。然而BN和SiC的自扩散系数低，且BN呈片层状，形成相互支撑的卡片搭桥结构，很难烧结致密。本项目通过高分子三维网络技术与溶胶凝胶技术相结合的湿化学法制备具有晶格原子排列混乱、烧结活性较高的BN-SiC非晶态粉体，通过三维网络凝胶前躯体的结构设计与控制，研究三维网络湿化学法制备BN-SiC非晶态粉体的影响因素和BN-SiC非晶态粉体的合成机理，研究非晶活化烧结机理和强韧化机理。研究结果表明：在水含量为120ml，陈化时间为48h，网络剂含量范围为14.119.3%时，采用高分子凝胶三维网络方法可以制备出非晶态BN-SiC复合陶瓷粉体。此非晶态陶瓷粉体具有活化烧结的特性，可以使烧结致密化温度明显降低，该方法也为多种粉体达到原子级别的均匀混合提供了一个崭新途径。以该方法制备的非晶态BN-SiC复合粉体为原料，在烧结温度为1750℃，保温时间为120min时，采用传统热压烧结方法可以实现非晶活化烧结的目的。明确了BN-SiC纳米复相陶瓷的强韧化机制是细晶强化和纳米SiC第二相的弥散强化。项目完成为BN-SiC纳米复相陶瓷材料的非晶态活化烧结及应用奠定了理论基础。