Thermal Conductivity of Bulk Attapulgite Prepared by Pressureless Sintering

Abstract

To explore the potential of attapulgite as thermal barrier materials, bulk attapulgite samples were prepared by pressureless sintering. The effects of sintering temperature on the phase composition, porosity, microstructure, and thermal conductivity of bulk attapulgite were investigated. With increasing sintering temperature, bulk attapulgite transforms from predominant quartz phase (700 ℃) to coexistence of quartz and enstatite phases (800—900 ℃), and to coexistence of quartz, enstatite and cristobalite phases (1000—1200 ℃). Meanwhile, the microstructure of the bulk attapulgite changes from random, loose packed fiber-like porous morphology, to dense structure with a random distribution of MgO·SiO2 grains inside the SiO2 matrix to result in a significant decrease in porosity. The thermal conductivity of bulk attapulgite increases with increasing temperature. When sintered at 700 ℃, bulk attapulgite presents a temperature-independent thermal conductivity with an ultra-low value of 0.16 W/(m·K) at room temperature. Attapulgite, with its natural abundance and low cost, along with the ultra-low thermal conductivity, has a great potential as thermal barrier materials.

Keywords

• attapulgite
• pressureless sintering
• thermal conductivity
• thermal barrier materials