Preparation and properties of ZrO2-strengthened porous mullite insulation materials using Y2O3 additive

ZrO 2 -strengthened porous mullite insulation materials were prepared by foaming technology utilizing ZrSiO 4 and Al 2 O 3 as primary materials and Y 2 O 3 as an additive. The effects of Y 2 O 3 contents on the phase composition, microstructure, mechanical properties, and heat conductivity of the porous mullite insulation materials were investigated. A suitable Y 2 O 3 content could promote phase transition of monoclinic ZrO 2 (m-ZrO 2 ) to tetragonal ZrO 2 (t-ZrO 2 ), reduce pore size, and improve the strengths of as-prepared specimens. The cold crushing strength and bending strength of as-prepared specimens with a 119 µm spherical pore size using 6 wt.% Y 2 O 3 were 35.2 and 13.0 MPa, respectively, with a heat conductivity being only 0.248 W/(m K).