随形自适应复合磨料的结构设计及其对非均质多相硬脆材料的超精密抛光机理

A “step effect” is easily generated in the polishing process of inhomogeneous and multiphase hard-brittle materials, resulting from their property differences among constituent phases. It is difficult to achieve high-quality finishing surfaces, and the effective solution is still ambiguous. The structural design of abrasive provides a helpful solution for this common problem. This project proposes to design and synthesis the structurally functionalized composite abrasives with self-regulated and shape-adaptive functions. The approach to accomplish the functionalized dual-controls of integral mechanical properties and surface tribo-chemical activities will be explored. The effects of processing parameters and structural characteristics of the as-synthesized composite abrasives on the polishing performances will be investigated systematically. The approaches of gentle and controlled removal for constituent phases will be explored. And the effective solution will be proposed for eliminating “step effect” and achieving high-quality polished surfaces. We will dedicate to exploration of the contact behavior, interfacial friction and wear, and adhesion mechanism between abrasive particles and constituent phases, and reveal the deformation and removal mechanism at atomic and molecular scale. Consequently, we will devote to exploring the relation between macroscopic tribological phenomenon and microscopic surface/interfacial interaction; clarifying self-regulated and shape-adaptive actions in the process of controlled material removal and further the ultra-precision polishing mechanism of composite abrasives. Furthermore, this project will contribute to enriching the fundamental theory of tribology, and is beneficial to improving the quality of ultra-smooth finish for inhomogeneous and multiphase hard-brittle materials.

非均质多相硬脆材料各组成相之间存在性质差异，在加工过程中易出现“台阶效应”，导致难以获得高质量抛光表面，尚未给出有效对策。磨料的结构设计则为解决这一共性问题提供了有益思路。本项目提出设计合成具有“自我调节”和“随形自适应”效用的结构功能化复合磨料，探寻对磨料整体力学特性与表面摩擦化学活性双调控的手段。系统考察磨料结构特征和加工过程变量对抛光效果的影响规律，探索实现各组成相可控剥离、柔性去除的途径，寻求消除“台阶效应”、获得高质量抛光表面的有效方法。查明磨料与工件之间的接触行为、界面摩擦磨损与粘着机制，深入探索材料在原子/分子尺度的变形与剥离方式，重点揭示“宏观摩擦学现象”与“微观尺度表/界面作用”之间的本质关系。阐明结构功能化复合磨料在可控剥离过程中的自我调节与自适应机制，及其对非均质多相硬脆材料的超精密抛光机理。这些研究对于丰富摩擦学基础理论，提升我国超光滑表面加工水平具有重要参考价值。

在国家自然科学基金项目(51875052)的资助下，本项目以实现非均质多相硬脆材料高效超精抛光加工为技术背景和研究目标，开展了随形自适应氧化铈基非刚性核/壳复合磨料的结构设计、可控制备、性能调控，及其在CMP过程中的摩擦磨损行为与机理研究。借助经典Stöber法，调控介孔导向模板剂与硅酸盐低聚物之间的协同自组装过程，制备出具有蠕虫状、平行状、树枝状开放孔道的介孔氧化硅(mSiO2)。利用液相体系原位包覆手段，诱导(过渡族或镧系元素掺杂)CeO2纳米晶在mSiO2内核表面形核生长，得到了一系列具有均匀包覆结构的mSiO2/CeO2核/壳磨料，建立了复合磨料的可控制备体系。系统考察了孔道结构、内核尺寸(50-500 nm)、平均孔径(2-10 nm)、壳层厚度(5-20 nm)、掺杂元素种类及用量(x=0-100%)、表层Ce3+/Ce4+混合价态与分布等因素，对mSiO2/CeO2磨料加工表面形貌、粗糙度、截面轮廓、抛光效率和表层/亚表层损伤等宏观摩擦学现象的基本影响规律。探索了磨料的结构特征－物化性质－抛光效果－摩擦磨损与粘着行为之间的联系，探寻出磨料整体力学特性与表面摩擦化学活性的双调控方法。证实利用低模量mSiO2内核与活性CeO2壳层在抛光过程中的协同作用，可兼顾对抛光表面质量(RMS粗糙度小于0.15 nm，轮廓波动范围在±0.26 nm)和加工效率(大于200 nm/min)的实际需求。借助于磨料结构与组分设计，调控并优化磨料与工件在接触微区内的物理接触状态与应力分布、界面摩擦磨损行为和材料去除方式，初步摸索出实现原子及近原子尺度表面抛光加工的可行途径和控制手段，着力从接触摩擦磨损与粘着和界面摩擦化学反应两个方面探索了mSiO2/CeO2磨料在抛光材料剥离过程中的协同作用机制。面向光化学增强机械抛光体系，设计合成了兼备优秀光化学氧化活性和摩擦化学去除活性的聚苯乙烯/聚苯胺/氧化铈三元复合磨料和碳基氧化铈磨料体系，有望在实现碳化硅、氮化镓、金刚石薄膜等材料的清洁、高质、高效抛光中发挥积极作用。本项目实施丰富了超精密抛光加工和纳米摩擦学等基础理论，为高性能氧化铈基磨料的组分与结构设计、性能调控及其在CMP、PCMP、ECMP、PECMP中的应用提供了技术支持和理论依据。