Development of structural ceramic products from rice husk ash

Abstract

In this research, mullite based products are developed from rice husk ash (RHA) which is the silica source and waste sediment (WS) from the aluminum industry which give alumina. Effectiveness of WS on mullitization is studied in comparison with a commercial grade alumina powder (SRM30). WS and SRM30 are mixed with RHA by weight ratios of RHA:WS/SRM30 are 80:20, 60:40, 40:60 and 20:80. The mixtures are wet milled with additions of 0.2 wt% deflocculant and 60 wt% water. Samples are formed by slip casting and fired at 1300, 1400 and 1500 °C for 2 hours. Mullite formation is observed in RHA/WS and RHA/SRM30 at 1300 and 1500 °C, respectively. WS, therefore, is selected as the alumina source for fabrication. To determine amount of the deflocculant suitable for the fabrication, wt% of the deflocculant is varied stepping up from 0.1, 0.2, 0.3, 0.4 and 0.5. The ratios of RHA: WS_H (WS has been heated) for this study are 40:60, 30:70 and 20:80. Each composition is Wet milled for 24 hours with 60 wt% water added. The appropriate amount of deflocculant for RHA: WS_H = 40:60, 30:70 and 20:80 slips is 0.3, 0.3 and 0.4 wt%, respectively. The influence of particle size of the solids in the slips on the properties of products is investigated. The slips of RHA: WS_H = 40:60, 30:70 and 20:80 with additions of the deflocculant by 0.3, 0.3 and 0.4wt%, respectively and 60 wt% water are prepared. The milling time is set at 10 and 24 hours. The samples are slip casted and fired at 1400 °C for 2 hours and subsequently at 1700 “C for 1 hour. The properties of the fired samples, i.e. the composition, phases, microstructure, physical mechanical and thermal properties are characterized. RHA: WS_H = 30:70 sample with milling time 24 hours has the best properties.