堇青石蜂窝陶瓷的低温烧成试验

Low-temperature firing of cordierite honeycomb ceramics

以高岭土、滑石和氧化铝粉为主要原料,以面粉和活性炭为成孔剂,按堇青石理论化学组成配料,经球磨、压滤、练泥、陈腐后,挤压成型为孔密度为每平方英寸100个孔,孔壁厚0.3 mm的坯体,干燥后,做不同温度(1 280、1 300、1 340和1 380℃)保温3 h和1 300℃保温不同时间(3、4、5、6 h)的烧成试验,然后检测烧后试样的显气孔率和热膨胀系数,并进行XRD和SEM分析。结果表明:(1)在1 340℃保温5 h烧成可制备出显气孔率约为60%,平均热膨胀系数(室温～800℃)为1.67×10-6℃-1的纯堇青石相蜂窝陶瓷。(2)在1 280～1 380℃保温5 h烧成的堇青石蜂窝陶瓷的显气孔率及吸水率均没有显著差异。在1 300℃的烧成温度下,当保温时间由3 h增加到4 h时,试样的显气孔率和吸水率略有下降;继续延长保温时间,试样的显气孔率和吸水率变化不大。(3)在保温5 h的条件下,当烧成温度从1 280℃升至1 340℃时,试样的热膨胀系数逐渐降低;当烧成温度从1 340℃升至1 380℃时,试样的热膨胀系数升高。在烧成温度为1 300℃的条件下,当保温时间从3 h增加到5 h时,试样的热膨胀系数逐渐降低;从5 h增加到6 h时,试样的热膨胀系数升高。(4)与1 300℃烧成的试样相比,1 340℃烧成的试样中有较多呈短柱状的堇青石晶粒,且气孔平均孔径较大。

Honeycomb cordierite ceramics were prepared using kaolin,talc and Al2O3 powders as starting materials based on the theoretical cordierite composition, adding activated carbon and flour as pore formers, ball-milling, pressure filtrating, pugging and aging. Honeycomb bodies with the pore density of 100 cells per square inch and the wall thickness of 0.3 mm were extruded. After dried, specimens were fired at 1280, 1300,1340 and 1380℃ for 5 h,respectively,or were fired at 1300℃ for 3,4,5 and 6 h,respectively. Thermal expansion coefficient and apparent porosity of the specimens were determined. The phase composition and microstructure of specimens were examined by XRD and SEM, respectively. The results showed. （1） Pure cordierite honeycomb ceramics could be prepared after being fired at 1340℃ for 5 h with the apparent porosity of 60% and average thermal expansion coefficient of 1.67×10^-6℃^-1（ RT-800℃）. （2）There was no appreciable difference in the apparent porosity and water absorption of the specimens fired at 1280-1380℃ for 5 h. For the specimens fired at 1300℃, apparent porosity and water absorption decreased appreciably when soaked time prolonged from 3 h to 4 h, but unchanged during the further prolonging. （3）Thermal expansion coefficient of the specimens soaked for 5 h decreased when the firing temperature rised from 1280℃ to 1340℃, but increased from 1340℃ to 1380℃. For the specimens fired at 1300℃,thermal expansion coefficient fell gradually when the soaked time prolonged from 3h to 5h, but increased from 5 h to 6h. （4）Compared with the specimens fired at 1300℃ for 5h, more columnar crystal particles and pores with an larger average size were observed in the specimens fired at 1340 ℃.