Sialon多型体对Si3N4和CBN界面结合修饰机理的研究

Vitrified bond with good properties and its good interfical bonding to CBN are essential for strengthening and toughening of ceramic binding PCBN superhard materials. It is known that Si3N4 has excellent mechanical and physicochemical properties, and Sialon polytype system has the characteristic of gradient variation of structure and thermo-physical properties with composition. Si4N3/CBN interificial bonding can be modified by controlled formation of Sialon polytypes. In this proposed project, the interfacial bonding of Si3N4 and CBN will be studied in details.The composition of Sialon polytype with structure and thermo-physical properties compatible with CBN, is designed on the basis of the first principle/molecular dynamics. The mechanism of modification of Sialon polytype will be investigated through the study of the effects of composition and sintering kinetics on the gradient variation of Sialon polytype composition, the interfacial phases, structures and thermo-physical properties. The intrinsic relationship between the interfacial composition and process parameters and the elastic modulus, strength, toughness and hardness of Si3N4 binding CBN material will be explored. A model to reveal the relationship between the distribution and structure of Sialon polytypes and the mechanical properties of bulk material will be established, and strengthening and toughening of Si3N4 binding PCBN superhard materials can be realized.

陶瓷结合剂性能优异和与CBN界面结合良好是陶瓷结合PCBN超硬材料强韧化的基础，Si3N4综合力学性能和理化性能优异，Sialon多型体系列存在结构和热物理性能随成分同步梯度变化的特点，在Si3N4和CBN结合界面控制形成Sialon多型体，可以修饰两相的界面结合。本课题拟对Si3N4结合PCBN界面结合问题进行研究：以第一性原理分子动力学理论指导设计Sialon多型体的成分，使其结构及热物理性能与CBN相容，建立Si3N4和CBN功能结合的基础；研究成分设计及烧结动力学条件对多型体成分梯度变化的影响，以及结合界面物相、结构和热物理性能的影响规律，揭示Sialon多型体修饰界面结合的机理；探讨界面成分设计和制备工艺因素与Si3N4结合CBN材料的弹性模量、强度、韧性及硬度关系的内在联系，建立Sialon多型体分布及结构与材料力学性能关系的模型，实现Si3N4结合PCBN超硬材料的强韧化。

陶瓷结合剂性能优异和与CBN界面结合良好是陶瓷结合PCBN超硬材料强韧化的基础，Si3N4综合力学性能和理化性能优异，Sialon多型体系列存在结构和热物理性能随成分同步梯度变化的特点，在Si3N4和CBN结合界面控制形成Sialon多型体，可以修饰两相的界面结合。本课题对Sialon多型体（Si6-ZAlZN8-ZOZ 0≤Z≤4.2）对Si3N4结合PCBN界面结合问题进行了研究：以第一性原理分子动力学理论指导设计Sialon多型体的成分， Z=1-2对应的Sialon多型体结构及热物理性能与Si3N4及CBN相容，适当的玻璃相形成量，利于Sialon多型体的生成及形成棒晶增韧PCBN，建立了与CBN功能结合的基础；研究成分设计及烧结动力学条件对多型体成分梯度变化的影响，以及结合界面物相、结构和热物理性能的影响规律，随着Sialon多型体Z值的提高，体系中的玻璃相增多，利于Sialon多型体的现成，但热学性能的失配和高温玻璃相的软化，不利于PCBN界面结合；实验证明：Z=1-1.5的Sialon多型体和高温超高压（1700℃/5.5GPa）制备利于与Si3N4结合PCBN材料的强度、韧性及硬度的提高，实现Si3N4结合PCBN超硬材料的强韧化。