不同粒度特征的SiO_2微粉浆体流变性能研究

Rheological properties of SiO_2 micropowder slurry with various granulometric characteristics

采用流变学的方法研究了固相体积分数为35%的4类Si O2微粉悬浮液的流变性能,从粒度特征的角度,探讨了在不添加减水剂、添加六偏磷酸钠、三聚磷酸钠及高效减水剂FS20的条件下,悬浮液表现出不同的流变行为机制。结果表明:在不添加减水剂时,粉体中含有中位径小的细颗粒比例越高,悬浮液黏度越大,而含有较多粗颗粒的Si O2微粉悬浮液出现了剪切稠化行为;添加减水剂后,悬浮液流变行为与Si O2微粉的比表面积大小及粒度分布密切相关,均表现为假塑性流体特征。FS20对Si O2微粉的分散效果明显优于六偏磷酸钠和三聚磷酸钠的,这主要是由于后者的分散机制为静电排斥作用,而FS20除了上述分散稳定机制外,还可产生很强的空间位阻效应。

The rheological properties of four silica fume slurries with 35% solid volume fraction were investi-gated by rheological method.The silica fume slurries without and with the dispersants of sodium hexameta-phosphate,sodium tripolyphosphate or FS20 were prepared,and the mechanism of different rheological behaviors was analyzed from the view of granulometric characteristics.The results show that,as the fraction of fine particles charactered by small middle particle size in the silica fume increases,the viscosity of slurry without dispersants becomes higher,and the slurries made from more coarse particles exhibit shear-thick-ening behavior.When further adding the dispersants,the rheological behavior of the slurries is closely relat-ed to the specific surface area and particle size distribution of silica fume,and all the slurries behave as pseudoplastic liquid.Compared with the dispersants of sodium hexametaphosphate and sodium tri-polyphosphate,FS20 has better dispersion effect upon silica fume.The reason is mainly FS20 has a strong space steric hindrance besides the electrostatic repulsion effect possessed by sodium hexametaphoshpate and sodium tripolyphosphate.