EFFECT OF HIGH ENERGY MILLING ON THE PHASES AND MICROSTRUCTURE OF CaAl4O7/CaZrO3 COMPOSITES

L.B. GARRIDO; F.N.BOOTH; Y. L. BRUNI; E.F.AGLIETTI

CERAMICS-SILIKáTY

INST CHEMICAL TECHNOLOGY

Año: 2019

0862-5468

ABSTRACTComposites based on CA2 (CaAl4O7) / CaZrO3 are widely used as insulatingmaterials, structural components, filters at high temperatures and corrosiveenvironments due to their interesting thermomechanical properties. In this work, CA2 /CaZrO3-based composites were prepared from commercial powder mixtures of highalumina cement (HAC) and pure ZrO2 with some adittion of α-Al2O3 and CaCO3.Themixture was processed by high energy milling at 500 and 800 rpm. Differentcomposites were obtained using mixtures with and without milling by solid statesintering at 1400 °C. The reaction was followed by thermal analysis techniques (TGDTA)and the cristallynes phases were analyzed by Ritvield method and X-raydiffraction (XRD). The composites were characterized by density measurements andvolume and pore size distribution determined by mercury porosimetry. Themicrostructure was analyzed by SEM-EDS.CA2 and CaZrO3 were the main phases present in the ceramics with c-ZrO2 assecondary phase and scarce CaAl2O4 (CA) were also found. Due to effect of milling adecrease in c-ZrO2 content was observed. In addition an increase in the density of thecomposite and a decrease in volume and pore size distribution, related to the decreaseof particle size, were determined. The composite obtained by milling at 800 rpm andsintered at 1400 °C presented an homogeneus microestructure (porosity of 22%,average pore size near to 0.5 μm) and a low linear thermal of expansion coefficientnear to the corresponding to mullite.