纳米晶内气孔和原位TiCN相协同强韧化Al2O3基陶瓷机制研究

The performance of bulletproof armor materials has significant effects on the fighting capability of military equipment, hence, designing a high-performance lightweight bulletproof armor has great significance for the national defense. Alumina ceramic is the most commonly used bulletproof armor material in our country. However, the application range of alumina ceramic is restricted by its low fracture toughness. In order to develop low-cost alumina-based bulletproof ceramic with high mechanical properties and low density, high-titania special-grade bauxite was selected as raw material in this project. On the one hand, nano-sized particles with high-temperature superplasticity was added to increase the grain boundary migration during the sintering process. By investigating the pore structure and properties evolution behaviors of samples fabricated under different conditions, the formation mechanism of nano-sized intracrystalline pores was revealed. Alumina-based ceramic containing nano-sized intracrystalline pores was obtained to enhance the toughness and reduce the density. On the other hand, by adopting carbothermal-reduction and nitridation method, the TiO2 in raw materials would transform into in-situ TiCN phase, which could further improve the toughness of ceramic. Finally, the toughening theoretical formulas were corrected according to the experimental results, based on single factor variance analysis, the fracture behaviors of Al2O3-TiCN composite ceramic containing nano-sized intracrystalline pores under the action of multiple factors were investigated. The combined-toughness mechanism of nano-sized intracrystalline pores and in-situ TiCN phase was revealed to obtain the fabrication theory of lightweight bulletproof armor materials with outstanding performances and low cost.

防弹装甲材料直接制约着军事装备的作战能力，其高性能和轻量化对于国防建设意义重大。Al2O3陶瓷是我国主流防弹装甲材料，然而，Al2O3陶瓷韧性差的缺陷限制了其应用范围。为开发具有高力学性能和低密度、低成本的Al2O3基防弹陶瓷，本项目以高钛特级铝矾土为原料，一方面从材料显微结构着手，引入具有高温超塑性的纳米粒子以加快烧结过程中晶界迁移速率，研究不同条件下材料孔结构及其性能演变规律，探明纳米晶内气孔形成机理，在材料内部形成大量纳米晶内气孔，实现强韧化及轻量化；另一方面，从材料组分着手，利用原料中的TiO2成分，采用碳热还原氮化法原位形成TiCN，实现进一步增强。最后，依据实验结果，修正增韧理论公式，结合单因素方差分析，揭示多因素作用下Al2O3-TiCN纳米晶内气孔复相陶瓷的断裂规律，探明纳米晶内气孔及原位TiCN相的协同强韧化机制，掌握高性能、低成本的轻量化防弹陶瓷装甲材料的制备基础理论。

Al2O3陶瓷是我国主流防弹装甲材料，然而，Al2O3陶瓷韧性差和体积密度偏大的缺陷限制了其应用范围，实现Al2O3陶瓷的强韧化和轻量化对于国防建设意义重大。本项目提出利用晶内微-纳米气孔和原位Ti(C,N)相实现Al2O3基陶瓷的强韧化和轻量化。以高钛特级铝矾土为原料，首先，研究高钛特级铝矾土在不同热处理温度下的组成、结构和性能演变规律；一方面，研究锆溶胶引入对Al2O3基陶瓷显微结构及性能的影响，揭示晶内微-纳米尺度气孔的形成原理；另一方面，采用碳热还原氮化法利用原料中的TiO2组分原位形成Ti(C,N)相，研究不同氮化温度及C/TiO2对Ti(C,N)形成及Al2O3基陶瓷性能的影响，阐明原位Ti(C,N)相的形成条件。最后，揭示多因素作用下复相陶瓷的断裂规律，探明晶内气孔及原位Ti(C,N)相的强韧化机制。. 主要结论如下：（1）随着热处理温度提升，试样烧结程度变优，致密度增加，力学性能改善。但是，温度过高会导致钛酸铝发生分解，液相中Al2O3和TiO2含量增加，材料中出现各向异性的刚玉和莫来石晶粒，致密度和力学性能降低。（2）在高钛铝矾土中引入锆溶胶，部分氧化锆会固溶进入钛酸铝相中，形成“薄晶界非晶相”晶界，且TiO2的存在能够提升ZrO2的高温超塑性，促进材料的烧结过程中晶界移动，形成晶内微-纳米尺度气孔。随着锆溶胶的引入，体积密度降低，由于晶内微-纳米气孔和第二相的钉扎、裂纹偏转及微裂纹作用，导致材料的断裂韧性和抗弯强度增大。但是，当锆溶胶引入量过多时，此时颗粒之间存在大量的ZrO2，氧化铝颗粒的晶界扩散及表面扩散被延缓，反而会阻碍烧结，导致孔径变大，力学性能降低。（3）采用碳热还原氮化法可将高钛特级铝矾土中的TiO2组分转化为Ti(C,N)相。在氮化温度为1700 °C、C/TiO2比为2.2时，可获得综合性能较好的Al2O3-Ti(C0.7N0.3)复相材料。Ti(C,N)颗粒具有高硬度、高弹性模量，形成的残余应力场可以使得裂纹偏转并产生钉扎作用，提升材料力学性能。. 项目研究成果对于掌握高性能、低成本的轻量化防弹陶瓷装甲材料的制备基础理论和关键核心技术具有重要意义。