研究論文
コロイダル・シリカ中の水分の蒸発及びシリカ粒子の凝集過程の考察
1977 年 49 巻 3 号 p. 144-149
詳細
1977 年 49 巻 3 号 p. 144-149
Colloidal silica which is widely using as a binder to make ceramic shell mold, goes through the stages of drying (after slurry coating on wax pattern) and heating (for dewax and mold firing) during mold making. Then, water evaporation from colloidal silica and consequent aggregation of dispersed silica particles were studied by drying and heating below 500°C.
Below 500°C, water as disperse medium is evaporated. From the total grammetric analysis curve gained at the heating speed of 2.5°C/min, colloidal silica lost 65-66% of water at 100°C though the water content in the sample was about 70%. The water which evaporated is considered to be the liberated water. The residual moisture was evaporated by keeping the sample at 100°C for several hours. Amorphous silica was produced when colloidal silica was thoroughly dehydrated. By the following process, solid amorphous silica is considered to be produced from colloidal silica. In the original colloid, it is considered that the silica particles are dispersed in water with many silanol bonds (Si-OH). When water evaporates from colloidal silica, such particles colloide in succession with each other. And as the following bridging reaction occurs, silica particles aggregate together into amorphous silica.
[Written in non-displayable characters.]
and
[Written in non-displayable characters.]
