Optical Spectra of Nickel‐Bearing Silicate Gels Prepared by the Geopolymer Technique, with Special Reference to the Low‐Temperature Formation of Liebenbergite (Ni ₂ SiO ₄ )

Abstract

A nickel‐bearing silicate gel was prepared from sodium disilicate and nickel nitrate solutions at room temperature. Then, the gel was heat‐treated in air up to 800°C at intervals of 200°C. The products were completely amorphous after heating at ≤600°C. However, liebenbergite and cristobalite were identified as products of the crystallization of the gel after heating at 800°C. The polycondensation process of the gel was discussed based on X‐ray diffractometry, thermogravimetry‐differential thermal analysis, and optical spectroscopy, to clarify the easy crystallization of the gel to liebenbergite and cristobalite. The present technique is very useful for the low‐temperature preparation of liebenbergite, which has potential application in the decomposition catalysis of chlorofluorocarbons, in connection with the problem with the ozone layer.