Synthesis of Low Temperature Cristobalite Na1.55Al1.55Si0.45O4/Mullite Ceramic Fibers Using a Nanocellulose Fiber Aerogel Template

Abstract

The most common form of crystalline silica found in rice straw is quartz. On the other hand, cristobalite considered as one form of crystalline silica. Mullite (3Al2O3·2SiO2) is a well-known, stable compound in the alumina-silica system. Due to its structural advantage, it is the most desirable phase in alumina ceramics. The mineral cristobalite (silicon dioxide) is a high-temperature polymorph of silica, but a distinct crystal structure. The purpose of the present study was the preparation of nanofibrillated cellulose aerogel fibers (NFCA) from bagasse pulp as a template for in situ preparation of cristobalite/mullite nanorods. This study analyzes the use of biomass combustion ash waste as secondary raw materials in the fabrication of ceramic fibers. High-quality silica nanoparticles (SNPs) can be won from rice straw as one of agricultural waste. Rice husk (RH) was used as a possible starting material in order to extract silica via an environmentally friendly technique. The extracted amorphous silica was reprocessed in order to synthesize nanocrystalline cristobalite/mullite nanorods and/or fibers. Samples were determined by XRD, EDX, SEM, and TEM. The energy dispersive X-ray spectrum (EDX), depicts the Al, O, Si, and Na peaks. Contrary, the X-ray diffraction (XRD) pattern conceals the diffraction peaks of both the cristobalite and the mullite. TEM exposed the mullite inside the alumina grains. The obtained composite of nanofibers are composed of mullite and cristobalite nanocrystals. The composite fibers exhibited a coarse surface, due to the precipitation of mullite and cristobalite nanocrystals.