表面氧化物含量对SiC浆料黏度影响的研究

研究了表面杂质对SiC浆料黏度和固相含量的影响,利用HF酸洗可有效降低SiC微粉表面SiO2和金属氧化物含量,从而提高SiC微粉的表面Zeta电位.试样SiC1的Zeta电位由酸洗前的60.71mV升高至酸洗后的72.49mV,试样SiC2的Zeta电位由酸洗前的55.728mV升高至酸洗后的63.546mV.HF酸洗还可破坏SiC微粉表面羟基结构,并以F-取代OH-的位置,使SiC表面由亲水性变为疏水性.Zeta电位的提高可使SiC微粉充分分散并保持稳定;表面疏水可大量释放出因氢键作用而与SiC表面牢固结合的吸附水,使之可自由流动.二者综合作用,可大大降低SiC浆料的黏度并提高固相含量.通过HF酸洗,试样SiC-1和SiC-2的浆料在黏度小于1Pa·s时,φ(SiC-1)、φ(SiC2)可分别达到61%和51%,基本满足胶态成型的需要.

Study of SiC Slurry Viscosity Affected by Surface Oxide Content

The influences of surface oxide content on SiC slurry viscosity are investigated. To avoid the disadvantage of SiC slurry stable dispersion affected by surface SiO_2 layer and micro-content of metal oxide, it is necessary for SiC powder to be leached by acid. With the decrease of contents of SiO_2 and metal oxide adsorbed on SiC powders surface by acid treatment, Zeta potentials of SiC-1 and SiC-2 powders increase from 60.71 mV to 72.49 mV and from 55.728 mV to 63.546 mV respectively, and OH-group adsorbed on SiC powders surface is destroyed and replaced by F-. With the breakdown of OH-group, hydrogen bond adsorbed on OH-group is removed. Therefore the surface state of SiC powders is changed from hydrophilic to hydrophobic. The change of SiC powders surface state can be proved by XPS and FT-IR analysis. The repulsion force between SiC powders that dispersed in slurry is enhanced due to the increase of Zeta potential, thus the SiC powders can be dispersed fully in slurry. H_2O that adsorbed on SiC powders surface is released and flows freely as hydrogen bond is removed. These two changes of SiC surface state result in the viscosity of SiC slurry being decreased and the solid volume fractions of SiC-1 and SiC-2 powders in slurry being increased to 62% and 51% respectively.