Non-isothermal oxide bond phase formation kinetics of SiC powder coated with yttrium aluminum garnet (YAG) sol

SiC powders (d50 = 6.25 μm) were coated with YAG by co-precipitation method and the coated powders were characterized by surface area, surface potential measurement, FTIR spectroscopy, XRD and thermal analysis. Non-isothermal kinetic data of two exothermic peaks in the temperature range 1200-1450 °C were evaluated by isoconversional methods using Netzsch Thermokinetics software module. The best fitting was obtained with second order reaction (F2) model for the peak I (1207-1359 °C) and Avrami-Erofeev (An) nucleation model for the peak-II (1324-1450 °C). The activation energy was determined as 605.57 kJ/mol and 1041 kJ/mol for peaks I and II respectively. Oxide bonded porous SiC ceramics fabricated at 1450 °C using YAG coated SiC powders exhibited flexural strength of ∼26.1 MPa at porosity level of ∼38.6 vol %. The corrosion results of ceramic sample after 10 days in strong acid solution revealed 6.5 wt % mass loss and 80% reduction of flexural strength.