【摘要】 以硼化锆(ZrB2)为代表的硼化物陶瓷以其优异的综合性能成为超高温陶瓷(UHTCs)家族中的重要成员并引起了广泛的关注,有望作为热防护结构部件应用于高超声速飞行器的鼻锥和机翼前缘等关键部位.本文从物质循环的角度,提出了硼化锆陶瓷生命周期的概念,其主要包括硼化锆陶瓷的制备和应用2个过程.硼化锆陶瓷的制备过程通常可以分为粉体的合成制备和陶瓷的烧结致密化2个主要步骤.前者的固相法制备主要涉及从原料Zr4+(O2–)2到Zr2+(B–)2的还原反应,后者则涉及第二相除氧的局部化学反应过程.此外,制备过程还包括将上述2个步骤有机结合而实现一步完成的反应烧结过程.生命周期的应用过程则发生ZrB2向ZrO2转变的氧化过程.鉴于化学反应在硼化锆陶瓷的整个生命周期中的重要作用,本文对上述生命周期各过程中涉及的化学反应分别进行了阐述.更多还原

【Abstract】 Zirconium diboride(ZrB2), a typical boride-based ceramic, is an important member of the ultra-high temperature ceramics(UHTCs) family, and has attracted much attention in recent years. Because of its combination of excellent properties, ZrB2 is considered to be a suitable candidate for use in the thermal protection components of the sharp noses and leading edges of hypersonic vehicles. In this review, the concept of the life cycle of ZrB2 ceramics, based on material flow, is proposed. The life cycle consists of two main processes: fabrication and applications. The reduction reactions that occur during fabrication and the oxidation reactions that occur during applications form the material flow in the life cycle, and can be summarized as ZrO2→(fabrication, reduction reaction) →ZrB2→(application, oxidation reaction) →ZrO2. The fabrication process usually involves powder synthesis and ceramic sintering. Powder synthesis, which here only refers to solid reduction synthesis, mainly involves the reduction of Zr4+(O2–)2 to Zr2+(B–)2, and ceramic sintering usually involves a local oxygen-removing reaction, when ZrB2 is used as the starting material. The fabrication process involves another method namely reactive sintering, which combines powder synthesis and ceramic sintering, and produces the final products in one step. However, during the life cycle, in a rich oxygen environment at high temperature, ZrB2 is oxidized under oxidation and ablation conditions, to give ZrO2. In some respects, it can therefore be said that the oxidation reactions during the application process are the opposite of the reduction reactions during fabrication. In view of the important roles of chemical reactions in the life cycle of ZrB2 ceramics, the chemical reactions in all the life-cycle processes were reviewed, and the relationships between the chemical reactions and microstructural properties were studied. The properties of UHTCs in applications are dependent on the powder properties, densification processes, and microstructures, so optimization of the reaction processes is important for the fabrication of high-performance UHTCs. Also, the study of oxidation processes is helpful in investigating the behaviors of ZrB2 ceramics during applications. It can be concluded that chemical thermodynamic and kinetic processes have significant effects on the microstructures and properties of ZrB2 ceramics, in their synthesis, fabrication, and applications.更多还原