Effects of firing temperature on the microstructures and properties of porous mullite ceramics prepared by foam-gelcasting

Abstract

Porous mullite ceramics were prepared at 1300-1600°C for 2 h via a foam-gelcasting route using industrial-grade mullite powders as the main raw material, Isobam 104 as the dispersing and gelling agent, triethanolamine lauryl sulphate as the foaming agent and sodium carboxymethyl cellulose as the foam stabilising agent. The effects of firing temperature on the sintering behaviour of green samples as well as microstructures and properties of final porous mullite products were investigated. With increasing the temperature from 1300 to 1600°C, linear shrinkage and bulk density values of fired samples increased, whereas their porosity decreased. Mechanical strength and thermal conductivity values of fired samples decreased with increasing their porosities. Even at a porosity level as high as 79.4%, compressive and flexural strengths of fired samples (with average pore size of 314 μm) remained as high as 9.0 and 3.7 MPa, respectively, and their thermal conductivity (at 200°C) remained as low as 0.21 W (m −1 K −1 ).

Freeze-drying preparation of porous diatomite ceramics with high porosity and low thermal conductivity

“…as a catalyst support, an adsorbent, an industrial filter and a supercapacitor [3,4]. Several methods, including replica route [5], sacrificial template technology [6], direct foaming method [7], gelcasting [8], foam-gelcasting [9][10][11] and freeze-drying technology [12], are commonly employed to fabricate porous ceramics. Compared to the freeze-drying technique, the other techniques suffer from more disadvantages.…”

Fundamental Influences of Crosslinking Structure on the Cell Morphology, Creep Property, Thermal Property, and Recycling Behavior of Microcellular EPDM Foams Blown with Compressed CO2

“…Shrinkage was evaluated by marking off 10 cm on the surface of the foam samples and then placed into an oven at 60 °C for 6 h, after which time the sample was taken out and cooled at 20 °C for 2 h, and the length of the line was measured. The shrinkage is calculated by the following equation: where S is the percentage of shrinkage, L m is the length of the original sample, and L c is the length of the final sample after heating and cooling.…”

Fabrication and characterisation of ZrO2-reinforced porous mullite ceramics

“…Crystalline phases in the fabricated porous materials were examined by powder X-ray diffraction (XRD, Bruker D8 Advance, Germany) under Cu Ka radiation. Phase identification of mullite, m-ZrO 2 , t-ZrO 2 , α-Al 2 O 3 and ZrSiO 4 was -reinforced porous mullite ceramics was evaluated using the following equation [16,33]:…”