Study On Surface Modification Of SiC And The Rheology Of SiC Slurry

SiC is used widely in material field, especially in ceramic materials aspects, because SiC materials are nonoxide materials which have high performance.The essential prerequisite of getting fine quality SiC ceramic materials is that preparing suspension which are high solids and low viscosity. With the development of the science and technology, the SiC powder get Super-refinement, so brings some difficulty to get suspension of ultrafine SiC powder.In this paper, surface modification on silicon carbide and the preparation of SiC suspension which are low viscosity, high solids, good fluidity, high stability after surface modification are researched.Two different schemes are adopted for surface modification on silicon carbide in this research, the one is that SiC powders are modified with tetraethoxysilane, then modify SiC powders using polyethylene glycol and glycol separately; The another is that surface modification of SiC powders with silane coupling agent, then modify SiC powders with acrylicamide.The investigation indicates that the dispersion of SiC powders modified by polyethylene glycol is the best in the first scheme, and the solid content of only ultrafine SiC powders modified can reach 45vol%, also, the content of polyethylene glycol is 2wt%, the viscosity of SiC suspension is lowest, when the shear rate is 49.81s-1, the viscosity is about 233.352mPa·s; Despite that the solid content of only fine SiC powders modified by glycol can reach 45vol%, the content of glycol is 3wt%, and the shear rate is 49.81s-1 too, the viscosity is about 300.024mPa·s. Different modifiers have different modifying mechanism, on this account, modification effect is not the same.In the second scheme, the dispersion and the stability of the SiC powders modified with acrylamide are worse than the SiC powders modified in the first scheme, the solid content of only fine SiC powders modified can only reach 40vol%.In this paper, Surface structure, colloidal properties and the dispersion stability of SiC powders are researched by means of FT-IR infrared spectrometer, TG-DSC thermal analyser, X-ray analyzer, Zeta potentiometric analyzer.Research indicates shows that electrification property on surface of SiC powders varied obviously before and after modification.The isoelectric points move a little to the alkaline direction in the first scheme, and the maximum absolute value of potential of SiC powders modified, by glycol reach up to 22.69mv from 16.22mv. Polyethylene glycol is nonionic polymerm, so have little effect on potential. The maximum potential of the SiC powders modified with acrylamide reach up to 22.13 mv.The relationships between solid content and viscosity, shearing rate and shearing stress, shearing rate and viscosity and so on were studied in the process which research on the theology of SiC powders. In the first scheme, adding some amount of coarse powder to fine SiC powders modified by polyethylene glycol, when making the weight ratio of fine powder to coarse powder was 1:1, the rheology of composite powder is researched, and the solid content can reach 50vol%.