Luo Guoqiang, Zhang Zhuang, Hu Jianian, Zhang Jian, Sun Yi, Shen Qiang, Zhang Lianmeng
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.
Materials (Basel). 2020 Mar 25;13(7):1496. doi: 10.3390/ma13071496.
A colloidal stability study of a nonaqueous silicon carbide suspension is of great significance for preparing special silicon carbide ceramics by colloidal processing. In this paper, three different chemical dispersants, which are amphiphilic, acidophilic, and alkaliphilic, are selected to compare their ability to stabilize nonaqueous slurries of silicon carbide. The analysis of the flow index factor is first used to estimate the colloidal stability of the suspensions. The results show that the addition of only 5 wt.% polyvinylpyrrolidone (PVP) forms a silicon carbide slurry with a low viscosity value of 17 mPas at 25 s. In addition, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS)measurements indicate that the PVP molecule is successfully adsorbed on the surface of silicon carbide. The different adsorption models are fitted, and the adsorption of PVP molecules on the surface of silicon carbide belongs to the Langmuir single-layer adsorption model. At the optimal PVP amount, the volume content of the suspension is as high as 22.27 vol.%, a Newtonian-like fluid still appears, and no agglomerate structure is formed in the system. After the volume content exceeds 22.27 vol.%, the flow index factor of the slurry begins to plummet, indicating that the slurry begins to transform from a Newtonian-like fluid to a shear-thinning fluid. The particles undergo inevitable agglomeration accompanied by the emergence of yield stress. Finally, a maximum solid loading of the system is predicted to be 46 vol.%, using the Krieger-Dougherty model.
对非水碳化硅悬浮液进行胶体稳定性研究，对于通过胶体加工制备特殊碳化硅陶瓷具有重要意义。本文选择了三种不同的化学分散剂，分别为两亲性、亲酸性和亲碱性，比较它们稳定碳化硅非水浆料的能力。首先使用流动指数因子分析来评估悬浮液的胶体稳定性。结果表明，仅添加5 wt.%的聚乙烯吡咯烷酮（PVP）就能形成在25 s时粘度值低至17 mPas的碳化硅浆料。此外，傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）测量表明，PVP分子成功吸附在碳化硅表面。对不同的吸附模型进行拟合，PVP分子在碳化硅表面的吸附属于朗缪尔单层吸附模型。在最佳PVP用量下，悬浮液的体积含量高达22.27 vol.%，仍呈现类牛顿流体，体系中未形成团聚结构。当体积含量超过22.27 vol.%后，浆料的流动指数因子开始急剧下降，表明浆料开始从类牛顿流体转变为剪切变稀流体。颗粒发生不可避免的团聚，并伴随着屈服应力的出现。最后，使用Krieger-Dougherty模型预测该体系的最大固体装载量为46 vol.%。
