Preparation Technology And Microstructure Of Bauxite Ceramic Materials

China’s bauxite resource reserves are among the highest in the world,but they are also facing problems such as insufficient supply,declining quality,and uneven distribution.Bauxite-based ceramic materials have important applications in industry,such as oil fracturing proppant.Improving the physicochemical properties of bauxite-based ceramic materials by changing the microstructure and increasing the possibility of their being used in practical applications broadens the range of materials,enabling bauxite-based ceramic materials to be useful in their applications and improving productivity.At the same time,the improvement of mechanical properties can also reduce the use of related raw material resources and contribute to the protection of the natural environment.Therefore,it is important to investigate the influence of the microstructure of bauxite-based ceramic materials on flexural strength,so as to prepare ceramic materials with high flexural strength.(1)The physicochemical changes during the calcination of the secondary bauxite ore used in this experiment were investigated by physical and thermal analyses and based on this,bauxite-based ceramic materials with a maximum flexural strength of 147.58 MPa were prepared with a combination of two sintering aids "manganese ore powder-feldspar" as additives.The effect of feldspar addition in the binary additive system on the sintering of the bauxite-based ceramic materials was investigated.Using four combinations of "feldspar-dolomite-iron ore powder-manganese ore powder’ as auxiliary raw materials,the effect of the addition of feldspar to the four-level additive system on the microstructure and properties of bauxite ceramic materials was investigated by controlling the sintering temperature and other process parameters.The bending strength of the bauxite-based ceramic materials was high at 1360℃ for 30 min,and the bending strength was up to 183.83 MPa.With feldspar:dolomite:iron ore powder:manganese ore powder=3:1:1:3,the ceramic proppant was completely sintered at 1390℃ with a minimum crushing rate of 8.2%and acid solubility of 7.6%at a closing pressure of 69 MPa.The acid solubility was 7.6%,which met the requirements for use.(2)The effect of iron ore powder content on the microstructure and properties of bauxite-based ceramics was investigated by controlling the addition of iron ore powder.The addition of iron ore powder successfully promoted the secondary mullite reaction process,so that the vast majority of pores could be discharged during the sintering process.By controlling the morphology and number of mullite whiskers,a high-strength bauxite mineral-based ceramic material with a maximum flexural strength of 195.87 MPa was successfully prepared.at iron ore powder:manganese ore powder=3:6,the ceramic pellets could complete the secondary mullitization reaction and sintered at 1390℃ with a minimum fracture rate of 5.5%and an acid solubility of 5.2%at a confining pressure of 69 MPa.The very low content of alkaline components in the formula is favorable to reduce the fracture rate and acid solubility of ceramic pellets.The performance meets the requirements of use.(3)The effect of cooling rate on the phase composition,microstructure and properties of ceramics were investigated on the basis of the high-strength ceramic materials prepared from secondary bauxite ore as the main raw material and manganese ore powder and iron ore powder as additives.The following conclusions were drawn from XRD and SEM analysis.The decrease in cooling rate led to the decrease in the content of Fe3+solidly dissolved in the mullite lattice and the low eutectic formed by Fe3+entering the liquid phase with other alkaline oxides and quartz,resulting in the decrease in the mullite phase content.The mullite grains are needle-like when the cooling rate is the fastest,and the grains grow excessively into rods when the cooling rate is the slowest.When the cooling rate is the fastest,the mullite grains are needle shaped,while when the cooling rate is the slowest,the grains excessively grow into rod-shaped grains.The faster cooling rate during the cooling process can maintain the toughening effect of mullite whiskers in the sample,while keeping the closed pores continuously closed and maintaining high bending strength.The faster the cooling rate,the better the material performance.