4H-SiC has been widely exploited in semiconductor industry. Nevertheless, the scratch-free surface with less oxide layer (required for its high-performance) is difficult to realize at high efficiency. Hence, to address this issue, an electrochemical mechanical polishing (ECMP) test was conducted based on the electrochemical-mechanical balance between the SiC corrosion rate and the SiO2 layer removal rate. Firstly, we synthesized polystyrene (PS)/CeO2 core/shell abrasives, which have the potential to obtain the high-quality surface due to its elastic effect. These as-synthesized abrasives were then characterized by FESEM and XRD. Results showed the CeO2 shells were coated on the PS cores successfully. Next, equations of the SiO2 layer removal rate and the SiC corrosion rate were experimentally obtained based on the modified Preston's equation and the Faraday's law of electrolysis, respectively. Finally, a verified test for 4H-SiC-ECMP was conducted in a 0.2 M NaOH electrolyte solution containing 5.0 wt% PS/CeO2 abrasives. After ECMP, these samples were characterized by microscope, AFM, Raman spectrometer and profile-meter, respectively; and the scratch-reduction mechanisms were deduced based on these characterization results. Results showed under balanced conditions, the scratch-free surface (Ra: 0.449 nm) with less oxide layer was obtained at high efficiency (∼2.3 μm/h).

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In this study, Ce-rich coating is investigated as corrosion inhibitor of carbon fibers reinforcement aluminum matrix (Cf/Al) composites. The coatings are obtained by immersion in aqueous solution containing Ce(NO 3 ) 3 onto composite surface, whereas the Ce-rich coating process produces a coating with highly heterogeneous nature of the surface, but micro-cracked layer with ''dry-mud'' morphology. The coatings were composed of Ce-rich nano-particles, Ce-rich particles with a sphere-like morphology, which are agglomerated particles with diameter 4 $ 8 nm and piled up for this coating. TEM observation for Ce conversion coating of the corresponding ring-like SAED patterns could not be matched to any of the previously reported structures of cerium compounds. Results of high-resolution XPS spectra of Ce3d obtained for Ce conversion coating show that the Ce3d spectra has several components with binding energies characteristic of Ce 3þ and Ce 4þ . The Ce-rich coating process produces effective corrosion protecting of Cf/Al composites, which is verified by electrochemical measurement results. The R t values of coated sample are higher than those of uncoated sample, this confirms the better corrosion resistance of coating obtained after immersion treatment for Cf/Al composites.