Crystallization of forsterite xerogel under carbon dioxide: A new crystalline material synthesized by homogeneous distribution of carbonaceous component into forsterite xerogel

Abstract

By heating the magnesiumsilicate (Mg2SiO4: forsterite) xerogel in carbon dioxide, carbonaceous component was intentionally introduced into the amorphous solid precursor. Carbon was introduced homogeneously as unidentate carbonate. Upon being heated at 800 degrees C in carbon dioxide, the xerogel which had homogeneously distributed carbonaceous component in it crystallized into a single phase product of a new crystalline material, which had approximate composition of Mg8Si4O18C The powder X-ray diffraction pattern of the new crystalline material did not match with any known crystalline compound registered in the powder diffraction file. Crystallization from amorphous xerogel to the new crystalline phase occurred in a very narrow range of temperature, from 750 degrees C to 850 degrees C in carbon dioxide, or in dry oxygen. Upon being heated above 850 degrees C, carbonaceous component was expelled from the product, accompanied by irreversible transition from the new crystalline material to forsterite.