Effects of polysiloxane on thermal conductivity and compressive strength of porous silica ceramics

In this paper, we propose a novel processing technique to prepare lightweight porous silica thermal insulators by considering both structural integrity and thermal conductivity. Porous silica ceramics with high thermal insulation performances (0.044-0.085 Wm(-1)K(-1)) and excellent compressive strengths (3.9-14.5 MPa) were fabricated by adding polysiloxane into fumed silica. Fumed silica was selected as the matrix material and further reinforced with polysiloxane-derived silica to enhance the mechanical strength. The addition of 10 wt% of polysiloxane increased the compressive strength (6.8 MPa) of the porous silica ceramic to almost 74% more than that (3.9 MPa) of porous silica without polysiloxane sintered at 600 degrees C, with a minimal increase in thermal conductivity from 0.044 to 0.049 Wm(-1)K(-1). The specific compressive strengths (16.4-21.1 MPa (g/cm(3))(-1)) of the porous silica ceramics fabricated with 20 wt% polysiloxane were remarkably high compared to those (1.0-14.7 MPa (g/cm(3))(-1)) calculated in previous studies.