Mullite (3Al2O3?2SiO2) ceramics obtained by reaction sintering of rice husk ash and alumina, phase evolution, sintering and microstructure

M.F. SERRA; G. SUAREZ; M. S. CONCONI; E. AGLIETTI; M.R. GAUNA; N.M. RENDTORFF

Journal of Asian Ceramic Societies

ELSEVIER

Año: 2016 vol. 4 p. 61 - 67

2187-0764

The use of industrial waste (by-products) as raw materials in the ceramicindustry has been under study for decades due to the economical, energy, taxand environmental advantages. The specificity of the waste requires a basiccharacterization and technology thereof.The applicability of rice husk ash (RHA), as silica (SiO2) source, in refractory andporous materials with potential structural, insulating and/or filteringapplications was carried out by characterizing the ceramic behavior ofstoichiometric mixtures of calcined alumina (Al2O3) and RHA. A reactionsinteringframework can be defined in the (Al2O3-SiO2) system. The sinterabilityand conversion during the reaction sintering processes were studied in order toobtain mullite (3Al2O3.2SiO2) ceramics. Also some microstructural features ofthe developed materials were studied in the 1100°-1600°C range. Themullitization was studied quantitatively.Partial densification was achieved (30%) and highly converted materials wereobtained. The developed microstructure consisted in a dense ceramic matrixwith homogenous interconnected porosity, with a narrow pore size distributionbelow 20 μm. The developed material gives enough information for designingmullite ceramics materials with either porous or dense microstructures withstructural, insulating or filtering applications employing RHA as silica sourceand calcined alumina as the only other raw material.