The effects of adding Oryza sativa straw ash to ceramic crystalline glaze

Abstract

Oryza sativa (Rice straw) is a natural resource that has the potential as a raw material in the ceramic field. Rice straw ash (RSA) contains high silica (SiO2) after it goes through the calcination process. This paper presents the investigation on the effects of crystalline glaze using RSA as an alternative substance for silica in the glaze formulation. Silica is significant material was used in the crystalline glaze to react with zinc oxide to seeding crystals as willemite (Zn2SiO4) in the form of spherulites during the firing process. This study is performed to identify SiO2 content from RSA because this residue is still not fully utilized in Malaysia. The aims of the present study are to identify the effects of adding RSA to ceramic crystalline glaze and the potential of conventional silica replaced with RSA, as well as identifying the optimum calcination temperature of rice straw. Rice straws were fired at different firing calcination temperatures of 700 ºC, 800 ºC, 900 ºC, and 1000 ºC. Crystalline glaze samples were then fired at 1200 ºC for four hours of gloss temperature and hold for five hours at crystallization temperature. After firing, the morphology of the crystalline structure on the ceramic substrate body identified using visual observation. In summary, amorphous silica derived from RSA brings high silica content. It provides a potential alternative material for silica used in crystalline glaze, SiO2 content in rice straw ash combined with zinc oxide to encourage the nucleus crystal seed. From XRF test, 89.7% silica content was determined in RSA and the results also show apparent growth of crystals on the ceramic substrate samples with different effects.