Al_2O_3/SiO_2比和煅烧温度对煤系高岭土物理性能与显微结构的影响

Influence of Al_2O_3/SiO_2 Ratio on the Physical Properties and Microstructure of Calcined Coal-based Kaolin

以内蒙产的煤系高岭土为原料,通过添加α-Al2O3和SiO2细粉,以羧甲基纤维素为结合剂,在1450℃、1500℃、1550℃、1600℃的煅烧温度下制备了不同Al2O3/SiO2(Al/Si)比的试样。对试样的体积密度、显气孔率、耐压强度、线变化率等物理性能进行了检测。采用SEM与EDS分析,研究了试样的显微结构。研究表明:随着煤系高岭土中Al2O3/SiO2比从0.856增加到4.5,试样的体积密度从2.55下降到2.14 g/cm3,气孔率从5%增加到30%,耐压强度从20 MPa增加到50 MPa,体积变化从-17%增加到7%。当Al2O3/SiO2比为2.6时,试样经过1500℃×3 h后,可以生成大量的柱状莫来石,具有良好的物理性能,可以作为一种有用的Al2O3-SiO2系低蠕变耐火材料。

Samples with different Al2O3/SiO2 ratio were made from coal-based kaolin （Inner Mongolia） by adding α-Al2O3 and SiO2 fine powder and using carboxymethyl cellulose as binder at calcining temperature such as 1450 ℃, 1500 ℃, 1550 ℃ , 1600 ℃ respectively. Physical properties of sintered samples involving bulk density,apparent porosity,compressive strength and linear change rate were tested Using Scanning Electron Microscope （SEM） and energy dispersive spectrometer （EDS） were used to investigate microstructure of specimen. Experimental results indicated that the bulk density of sample decreases from 2.55 to 2.14 g/cm^3 with Al2O3/SiO2 ratio increase from 0. 856 to 4.5, and meanwhile, apparent porosity rate increases from 5% to 30% ,the compressive strength increases from 20 MPa to 50 MPa ,volume change rate increases from -17% to 7%. Sample with excellent physical properties can be get because of massive mullite phase generating under the condition of Al2O3/SiO2 2.6 and sintering at 1500 ℃ with 3 hours, which has potential use in series low creep refractories.