Thermal Conductive Networks Constructed by Sialon Fibers in-Situ Synthesized in Barium Aluminosilicate Glass-Ceramic

The application of ceramic materials is limited due to the complicated preparation process and intrinsic brittleness. In this work, a pressureless manufacturing route that enables the formation of barium aluminosilicate (BAS) glass-ceramic consisting of internal β-Sialon fibers with enhanced thermal conductivity is developed. By adjusting the carbon source content, composites with different Sialon contents can be easily fabricated. The thermal conductivity of the sample with 3.5 wt.% is improved to 5.845 W/m ∙ K with the Sialon content of 26 wt.% in the composite, which is 112.64 % higher than that of the pure BAS matrix. The theoretical models suggest that the enhanced thermal conductivity is mainly ascribed to the thermal conduction network constructed by Sialon fibers. This work provides a method with industrial application prosperity to fabricate the high temperature ceramic matrix composite of different sizes and complex shapes.

BaO-Al2O3-SiO2-B2O3 Glass-Ceramic SOFCs Sealant: Effect of ZnO Additive

The crystallization of planar solid oxide fuel cells (SOFCs) sealant glasses in the systems BaO-Al2O3-SiO2-B2O3 (BaBS) and BaO-Al2O3-SiO2-B2O3-ZnO (BaBS-Zn) was investigated via both X-ray diffractometer and scanning electron microscopy with energy dispersive spectroscopy. The effect of nucleation heat-treatment of the BaBS glass at different temperature for 5 hours, i.e. 550 and 590 °C, on the crystallization behavior was also studied. Thermal expansion profiles of the glasses indicate that both glasses have a low sealing temperature. XRD patterns of all BaBS glass-ceramics, devitrified at 800 °C for 30 hours, show that Ba2Si3O8, BaAl2Si2O8, Ba3B2O6 and some unknown crystalline phases were found. It was also found that crystalline size of unknown barium aluminosilicate with low silicon content depends on the nucleation heat-treatment temperature. For the ZnO-containing glass, ZnO reduces the coefficient of thermal expansion value of glass and causes the devitrification of large needle-like barium zinc silicate phases. The crack at the YSZ/BaBS-Zn glass-ceramic interface was also observed. Two barium silicate phases, which are BaZnSiO4 and BaZn2Si2O7 were devitrified in ZnO-containing glass-ceramic.