静电作用调控下反应烧结SiC同步改性抛光研究

Reaction-bonded SiC is a two-phase material consisting of SiC and Si. It has a wide prospect for application in the field of advanced optics. The material removal rates when polishing SiC and Si are different because of their hardness difference. Therefore, when polishing reaction-bonded SiC, it is unable to obtain a super smooth surface because the surface has large amount of micro craters in the depth of nanometer-order. In order to resolve this problem, a conception of synchronous modification of SiC and Si through chemical reaction is proposed in this project. Modification mechanism including the oxidation and hydrolysis of reaction-bonded SiC are to be studied. Removal mechanism of the modified surface layer by the action of colloidal nanoparticles is to be clarify. In order to improve polishing removal rate, electrostatic interaction between the modified surface layer and colloidal abrasive is to be further studied. It is expected that this work can reveal the relationship between the ionic strength of polishing slurry and the material removal rate of modified surface layer. Moreover, a supplying system for polishing slurry is to be developed to keep the chemical stability of polishing slurry. This system is to be equipped on a former-developed polishing machine tool. Shape corrective polishing of reaction-bonded SiC optical surface is to be performed. Finally, polishing mechanism and key technology for ultra-smooth and ultra-precision synchronous polishing of reaction-bonded SiC are expected to be obtained. The implementation of this project has important significance for improving the manufacture level of high-quality SiC optical elements.

反应烧结SiC是由SiC和Si构成的两相材料，具有广泛应用前景。由于SiC相和Si相的硬度差异较大，采用游离磨粒抛光时的材料去除速率不等，导致抛光表面遍布纳米深度离散微观凹陷区域，无法获得超光滑表面。针对上述问题，本项目提出两相材料同步改性等速率去除的抛光思想，研究反应烧结SiC表面的氧化/水解改性机理，阐明改性层在纳米胶体磨粒作用下的抛光去除机制。为提高改性层抛光去除速率，进一步开展胶体磨粒与改性层表面间的静电作用调控研究，揭示抛光液离子强度对改性层去除速率的影响机制。在基础工艺方面，研制能够提高抛光液化学稳定性的在线调配内供给系统，并将该系统搭载于已开发的多自由度抛光机床，开展反应烧结SiC光学元件面形误差的同步改性修正抛光研究。基于上述研究，凝练出反应烧结SiC超光滑曲面的超精密同步改性修正抛光理论及关键技术。本项目的实施对提升我国高品质SiC光学元件的制造水平具有重要意义。

本项目针对反应烧结碳化硅（RB-SiC）材料中SiC相和Si相不等速率去除导致反应烧结SiC表面无法获得超光滑表面的问题，开展了静电作用调控下反应烧结SiC的同步改性抛光研究。揭示了RB-SiC表面改性层的生长机制，研究了催化剂种类、H2O2浓度、PH值、温度等参数对反应烧结SiC中两相组织同步氧化过程的影响，获得了有利于反应烧结SiC同步氧化的环境参数。从微观层面探讨了RB-SiC抛光的静电作用调控过程，研究了静电作用调控对改性层材料去除速率的影响规律，通过实验获得了提高材料去除速率的静电作用调控方法。开发了抛光液在线调配内供给抛光工具系统。建立了材料去除模型，从单磨粒去除角度分析了压力、转速、表面摩擦系数和磨粒性质等抛光工艺参数对加工表面塑性变形、残余应力及工件表面形貌的影响。在此基础上开展了反应烧结SiC电化学机械抛光(ECMP)材料去除机理的研究。通过正交实验分析了激励电压、抛光液配比对抛光结果的影响程度，确定了抛光RB-SiC的最优抛光液配比；通过回归分析法建立了基于幂函数的表面粗糙度预测模型；根据试件与抛光垫的相对运动规律，建立了速度模型和轨迹模型，分析了影响速度分布和磨粒分布的因素，获得了高材料去除率和高表面质量的工艺方案。为高品质SiC光学元件的高效、超光滑、超精密抛光加工提供了新工艺原理和关键技术。