轻质层状硼化物复合陶瓷结构设计及双尺度理论研究

Urgent demand has been raised to new armor protection materials with the development in weapon, space technology and shipbuilding industry. Boride ceramics are considered as the best choice of armor materials for their lightweight, high strength and resistance to high temperature. In order to solve the brittleness problem of Boride ceramic materials and realize utility, it is suggested in the present proposal that new lightweight laminated composite ceramics be constructed by using boride materials with different physical and chemical properties as soft and hard layers, and that the microscopic structure of composite ceramics be modulated and designed by layer thickness ratio, chemical constituents,laminated patterns of the soft and hard layers, and also by lattice injection and other means as well. With the hot pressing and pressureless sintering technologies, boride composite ceramic materials with different structures will be prepared, and their mechanical properties will be further testified systematically. Physics models and computational methods will be established and then theoretical calculations will be applied to study the interface binding energies, electronic structures, and thermal expansion coefficient of laminated composite materials,based on which the interface behavior of laminated composite materials will be elaborated. After the origin of brittleness of composite materials is elucidated according to the change in fracture energy and bonding structure along specific directions of the materials, a strengthening protocol will be proposed. By combining theoretical calculations and experimental characterization, the inherent relationship between the microscopic structure and macroscopic mechanical properties of boride laminated ceramic materials will be elaborated, which provides an important foundation for the performance optimization of composite materials and the development of new armor materials.

兵器、航空及船舶工业的发展对新型装甲防护材料提出了迫切的需求。硼化物陶瓷以其轻质、高强和耐高温等特性，成为最佳的装甲候选材料。为解决硼化物陶瓷的脆性问题并使之实用化，本项目拟用一些具有不同物理化学特性的硼化物分别作为软、硬质层构筑轻质层状复合陶瓷，通过改变软硬质层的层厚比、化学组成和叠层方式，以及采用点阵注入等方法调控和设计复合陶瓷的微观结构；采用热压和无压烧结工艺制备出结构不同的硼化物复合陶瓷材料，并对其力学性能展开系统的测试；建立相关的物理模型和计算方法，并通过理论计算研究研究层状复合材料的界面结合能、电子结构及热膨胀系数，阐明复合材料的界面行为；研究层状陶瓷复合材料在特定方向上的断裂功及成键结构的变化，揭示复合材料脆性的本源，并提出韧化方案；理论计算和实验表征相结合，揭示硼化物层状陶瓷复合材料的微观结构和宏观力学性能的内在联系，为复合材料的性能优化及新型装甲材料的研发奠定重要的基础。

硼化物陶瓷以其轻质、高强和耐高温等特性，成为最佳的装甲候选材料。为解决硼化物陶瓷的脆性问题并使之实用化，本项目拟用B4C为主要层，BN和SiC分别作为软、硬质层构筑轻质层状复合陶瓷，通过改变软硬质层的层厚比、化学组成和叠层方式，以及采用点阵注入等方法调控和设计复合陶瓷的微观结构。课题采用热压烧结工艺制备出结构不同的硼化物复合陶瓷材料，并对其力学性能展开系统的测试，发现层状硼化物陶瓷的抗弯强度随着软质层、硬质层的加入有所降低，其中B4C/BN的抗弯强度为345 Mpa，B4C/ SiC的抗弯强度为321 Mpa；但层状硼化物陶瓷的断裂韧性提升很多，层状B4C/BN的断裂韧性高达9.32 Mpa·m1/2，是传统碳化硼的2到3倍，对缺陷更不敏感；而层状B4C/SiC的断裂韧性为8.47 Mpa·m1/2，但其综合硬度更高，抗侵彻能力更强。.通过实验观察测试和有限元模拟分析发现，异质层的存在使得裂纹横向扩展将会削弱前一B4C层的裂纹情况，进而提高了材料的损伤容限能力。裂纹的多次偏转，横裂纹对纵裂纹的多次阻滞，使得材料在开裂以后仍具有一定的承载力，同时起到了增韧的作用。通过Materials studio建立了硼化物陶瓷的晶体模型，并用第一性原理对其电子结构进行了计算，研究层状陶瓷复合材料在特定方向上的断裂功及成键结构的变化，计算了不同硼化物陶瓷的理论硬度。发现层状硼化物陶瓷的硬度主要由B4C层提供，并且最弱的B-B键先断裂后，B4C晶体并没有完全失效，其它的B-B键也起到了决定性作用，这是其晶体结构决定的。 .课题组还成功开发出具有良好流变性能的高固含量陶瓷流延浆料，流延膜的固含量达到76wt%以上，制备出来的流延膜最小厚度在50μm以下，达到国际先进水平。并且发明了陶瓷非水基流延水浴成膜方法，属于国内外首创，为流延膜的大规模生产提供了另一个解决方案。项目资助了19篇学术论文和一篇专利，培养了4名博士研究生和6名硕士研究生。

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