I have prepared amorphous silica powder using sol-gel method, now i want to convert into the crystalline phase of silica, How can i do it.
Hi
Do slow cooling rate while obtaining sample from solgel method .prefer furnace cooling
Pure amorphous SiO2 begins to crystallize into cristobalite from approx. 1150°C (in powder form from approx. 950°C). In the presence of catalysts (crystallization accelerators), this temperature the beginning of crystallization can be reduced below 900°C. Crystallization accelerators for SiO2 are, for example, traces of CaO, MgO, FeO and others. Temperatures above 1250°C are necessary for complete crystallization of the amorphous SiO2 into cristobalite.
Hi Vadim sir i just wanted to ask for how much time the heat treatment should be given in order to convert amorphous silica into crystalline one.
Hi Akhilesh, It depends on the temperature. When several hours can be necessary at 1100°C, only a few minutes is sufficient at 1400°C.
I have a furnace which go upto 1150 and the silica which i have prepared doesn't have any nucleating agent like CaO or MgO etc
Without any nucleating agent, it will take a long time at 1150°C and crystallization will not be complete. Try to keep it at 1150°C for 24 hours. Perhaps it is enough to get cristobalite peaks with X-ray diffraction analysis.
Ok sir i have put my sample at 1150 for 24 hrs. Let's see what happens next.
I have done the xrd of the as prepared sample i.e. heating at 1150 for 24 hrs but no change is observed from previous data.
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