Research on preparation and related properties of macro–micro porous mullite ceramic skeletons via twice pore-forming technology

Abstract

A lot of solid waste coal gangue is produced every year in the process of coal mining and coal washing, which poses a great threat to human health. How to deal with coal gangue properly is still a serious problem. In this study the macro–micro composite porous mullite ceramic skeletons were successfully prepared using solid waste coal gangue and α-Al₂O₃ as main raw materials via twice pore-forming technology. The main phase composition of the porous ceramic skeletons was mullite tested by X-ray Diffractometer (XRD). The morphology and microstructure of the porous ceramic skeletons were analyzed by Scanning Electron Microscope (SEM). The results show that the microstructure of porous ceramic skeletons was mainly composed of mullite whiskers. With the increase of sintering temperature from 1200 °C to 1350 °C, the maximum length of mullite whiskers grew up from 2.68 μm to 8.10 μm and their average length grew up from 0.78 μm to 2.98 μm. The maximum compressive strength of the porous ceramic skeletons with 30 PPI and 45 PPI were 1.25 MPa and 1.54 MPa tested by Universal Testing Machine (UTM) at the sintering temperature of 1250 °C, respectively. The linear shrinkage, bulk density and pore stem density of the porous ceramic skeletons became larger with the rising of sintering temperatures from 1150 °C to 1350 °C. However, the corresponding performance values of 45 PPI porous ceramic skeletons were greater than that of 30 PPI at the same sintering temperature. The prepared porous ceramic skeletons will be used in ceramic–metal wear-resistant composites for the later research and the study provides a new idea for coal gangue on the comprehensive utilization with high added value and brings both good environmental and economic benefits.