Study On The Effects Of Surface Modification On The Character Of SiC Powder Surface And Its Suspension

In order to get SiC slurry with high solid volume loading, low viscosity and defoaming easily, in this paper SiC powders were coated by various modifying agents such as sulfanilic acid, succinic acid, ethylene glycol and PEG400, which had different structures. The impacts of structures of modifying agents on the surface characteristic of SiC powders and the rheological peculiarity of SiC slurry and the relation between rheological peculiarity and density of body were analyzed. The cooperation of defoaming agents and modifying agents was studied. The foam's stability of coated SiC slurry and the factor of influencing defoaming effect on coated SiC slurry were briefly discussed.The compose and surface structure of SiC powders were analyzed by XRD and FTIR and the surface characteristic and suspension characteristic of SiC powders were tested. The rheological peculiarity of SiC slurry was tested by NDJ-1 viscosity apparatus. The configuration of SiC slip casting bodys were observed by SEM, and by which to see about the defoaming effect of slurry.The results showed that the stability mechanisms of the SiC powders coated by sulfanilic acid, succinic acid and ethylene glycol were static electricity stabilization, and solid volume loadings of powder were not high and viscosities of suspensions were big because of the big molecule polarity and thick water film. The stability mechanisms of the SiC powders coated by PEG400 was space distance stabilization, and molecule polarity was small and water film was thin, so solid volume loadings of powder were high up to 58.3vol% and viscosities of slurries were lowest, less than 1Pa-s.The effect of defoaming agents on stability of suspension were not great and it lied on modifying agents. The three defoaming agents had different influences on rheological behavior of slurry: the viscosities of slurry could debased by using NXZ, BYK-020 had a small impact on it, and 470 made it increased. The influence of rheological behavior of slurry on density of green body was very distinct, and the key of getting high density of green body was that slurry had low viscosity at low shear rate.The structure of modifying agents had great influence on foam's stability of SiC slurry. SiC slurry modified with PEG400 had strongest stability on foam. The defoaming effect of slurry was not only related to defoaming agent, and also to viscosity of slurry. The type of defoaming agent and the viscosity of slurry were important factors of defoaming, and the lower viscosity was, the more advantageous foam eliminated. In this experiment, the defoaming effect of NXZ with 0.1 wt% on SiC slurry modified with PEG400 was best.