Mechanical Strength and Thermal Conductivity of Modified Expanded Vermiculite/Forsterite Composite Materials

Abstract

The mechanical and thermal insulation properties of expanded vermiculite (EV)/forsterite composite materials before and after the modification of EV by in situ alumina gel were characterized by three-point bending test, compressive strength test, and the flat-plate method for the determination of the thermal conductivity. The estimation method for the determination of the thermal conductivity of modified EV/forsterite composite materials was put forward, and the thermal conductivity in case of a high content of modified EV (the substitution rate of modified EV is more than 50 wt.%) is forecasted in this paper. The results show that, the mechanical properties and thermal insulation properties of the composite materials were significantly improved by increasing the modified EV content. When the substitution rate of modified EV was 50 wt.%, the flexural and compressive strength were 11.55 and 22.80 MPa, improved by 23.8 and 44.9%, respectively, compared with the unmodified sample; and the thermal conductivity was 0.169 W/m/K (at 1073 K), improved by 30.5%. The estimated thermal conductivities of modified EV/forsterite composite materials show good agreement with that of experiments, and the thermal conductivity of modified EV/forsterite composite materials was 0.157 W/m/K (at 1073 K) in case the substitution rate of modified EV was 100 wt.% through estimation.