目的 针对磨料在机械耐用性和化学抛光效率两个方面的高需求制备出一种应用于KDP晶体等脆性材料抛光的新型双壳层复合磨料。方法 采用沸腾体系无皂乳液聚合法合成了3-(甲基丙烯酰氧)丙基三甲氧基硅烷（MPS）修饰的P(MMA-MPS)微球作为内核,使用溶胶-凝胶法在微球表面包覆SiO2内壳层,通过均匀沉淀法沉积CeO2外壳层,制备了P(MMA-MPS)/SiO2/CeO2双壳层核壳复合磨料用于KDP晶体抛光。用扫描电镜、透射电镜、XRD、FT-IR、X射线衍射等手段分析样品的结构和性质。结果 P(MMA-MPS)微球粒径在280~320 nm之间,Si—O—Si键和Ce—O键的XPS吸收峰的出现验证了SiO2壳层和CeO2壳层都均匀地依次包覆在P(MMA-MPS)微球上,P(MMA-MPS)/SiO2/CeO2磨料的单分散性良好。SiO2层的引入增加了CeO2层中氧空位的浓度,Ce3+含量增多,抛光时的氧化还原反应活性增强;同时增强了核壳间的结合强度。相比PMMA/CeO2磨料,抛光后在5 μm×5 μm范围内的KDP晶体表面粗糙度RMS值由(1.03±0.05) nm降至(0.51±0.03) nm。材料去除率由(268.84 ±7) nm/min提升至(302.26±6.6) nm/min。结论 成功制备出一种克服界面结合弱和单一CeO2壳活性受限,可以应用于KDP晶体等脆性材料抛光的新型双壳层复合磨料。
Abstract
To address the issue of low material removal efficiency observed in traditional polymethyl methacrylate (PMMA)/cerium oxide (CeO2) composite abrasives during chemical and mechanical polishing (CMP), a novel P(MMA-MPS)/ SiO2/CeO2 double-shell composite abrasive system was designed. Through a hierarchical structural design, this system achieved synergistic optimization of the mechanical properties and surface activity of the abrasive, providing a new material solution for the high-performance polishing process.
In terms of material preparation, a stepwise synthesis strategy was employed: Firstly, monodisperse P(MMA-MPS) core microspheres were prepared via soap-free emulsion polymerization under reflux conditions. By systematically adjusting key parameters such as reaction temperature, MPS dosage, and monomer concentration, the morphology and size of the microspheres were successfully controlled. Characterization results confirmed the successful grafting of MPS onto the PMMA chains, as evidenced by the presence of the Si—O—Si crosslinked network and the C==C bonds from the methacryloxy groups. When the MPS dosage was 2 mL, spherical microspheres with a uniform diameter of approximately 300 nm and narrow size distribution were obtained.
Subsequently, with the synthesized P(MMA-MPS) microspheres as cores, a SiO2 inner shell layer was constructed via the sol-gel method. Under alkaline conditions and with a tetraethyl orthosilicate (TEOS) dosage of 5 mL, monodisperse P(MMA-MPS)/SiO2 composite microspheres with a uniform, dense, strawberry-like morphology were successfully prepared. This intermediate layer not only enhanced the overall structural rigidity but also provided active sites on its surface via silanol groups for the subsequent anchoring of CeO2.
Finally, an in-situ chemical precipitation method under alkaline conditions was used to uniformly deposit a shell of CeO2 nanoparticles onto the surface of the SiO2 interlayer, resulting in the formation of core-double-shell structured P(MMA-MPS)/ SiO2/CeO2 composite abrasives. The thickness of the active polishing layer (CeO2) was precisely controlled by varying the concentration of cerium nitrate. X-ray diffraction (XRD) analysis confirmed that the CeO2 exhibited a typical cubic fluorite structure. X-ray photoelectron spectroscopy (XPS) analysis further revealed the formation of Si—O—Si chemical bonds between the silanol groups of MPS and the SiO2 layer, ensuring the stability of the interlayer bonding. Particularly noteworthy was that the Ce³+ percentage in the double-shell structure reached 25.6%, indicating an abundance of oxygen vacancy defects on the material surface, which provided ample active centers for surface reactions during the subsequent synergistic polishing process.
To evaluate the practical polishing performance, CMP experiments were conducted on potassium dihydrogen phosphate (KDP) crystals. The results demonstrated that after polishing with the P(MMA-MPS)/SiO2/CeO2 composite abrasive, the workpiece surface roughness (RMS) decreased to 0.51 nm and the material removal rate (MRR) reached 302.26 nm/min. Two-dimensional atomic force microscopy (AFM) topography analysis revealed that compared with traditional PMMA/CeO2 abrasives (which yielded RMS=1.03 nm and MRR=268.8 nm/min), the double-shell abrasive not only achieved a higher polishing rate but also produced a KDP crystal surface with superior quality. This performance enhancement was primarily attributed to the synergistic effect of the double-shell structure: the rigid SiO2 intermediate layer provided necessary mechanical support, while the CeO2 outer shell rich in oxygen vacancies enhanced the surface chemical reactivity, thereby achieving highly efficient synergy between chemical action and mechanical removal.
关键词
双壳层 /
核壳结构 /
P(MMA-MPS)/SiO2/CeO2磨料 /
制备 /
抛光性能
Key words
double shell /
core-shell structure /
P(MMA-MPS)/SiO2/CeO2 abrasive /
preparation /
polishing performance
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基金
国家自然科学基金（52465053,51965053）; 内蒙古自然科学基金（2022MS05038）; 自治区直属高校基本科研业务费（2024XKJX007）
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