Effect of Cations on Crystallization of Amorphous Silica(Part3)

In this study amorphous silica was used as a starting material for various experimental analysis, and the effects of cations on its crystallization were investigated.The amorphous SiO2 was heated at 800 ℃ and 600 ℃ in the presence of Na2S04, K2S04, NaOH and KOH, each treated separately, and the original amorphous silica was also subjected to heat at 600 ℃ with NaOH and KOH.When a small amount of Na2SO4 was added to original amorphous silica, cristobalite was formed after heating at 800 ℃ for 17 days, but when a large amount of Na2SO4 was added, cristobalite was formed only after heating at 800 ℃ for 23 days.When a small amount of K2SO4 was added to amorphous silica, cristobalite was formed after heating at 800 ℃ for 10 days, and with a large amount of K2SO4 added, cristobalite was produced after heating for 23 days.At 800 ℃, when a small amount of NaOH was added, silica minerals such as quartz, tridymite, cristobalite and sodium-silicate were formed, but when the amount of NaOH was increased, quartz, tridymite and sodium-silicate were the only minerals produced.With the application of a small amount of KOH at 800 ℃, quartz, tridymite and cristobalite were formed, however, if a large amount of KOH was added, tridymite, cristobalite and potassium-silicate were produced.At 600 ℃, when a small amount of NaOH was added, only cristobalite was formed after heating for 10 days, and when a small amount of KOH was applied, no products were formed.In this experiment, the results indicate that the process of amorphous silica transformation in the presence of various cations are different from each other and the inclusion of impurities has a great effect on the formation of silica minerals from the original amorphous silica.