| Due to excellent mechanical properties,especially the high temperature mechanical properties,mullite whiskers are often used to toughen high temperature ceramic materials.In-situ growth of mullite whiskers matrix material in a way has incomparable superiority.Due to dry pressing process conditions for matrix,it requires mullite precursor to mold on dry pressing conditions.However,to our knowledge,preparation of the mullite whiskers have not been reported on the dry pressing process conditions.In the topic,based on the low costs and waste utilization,mullite whiskers were in-situ prepared by using the waste coal gangue and different aluminum on the dry pressing process conditions.The effects of mullite whisker morphology and aspect ratio were studied,and the optimum conditions were determined.In our paper,it was innovatively proposed that gas-solid reactions,pure solid-phase reactions and solid-liquid phase reactions involved in a three-stage reaction model which was applyed to explain the relationship between properties and microstructure of the samples.Compared to calcined alumina and bauxite,coal gangue was more helpful for the growth of mullite whisker with larger aspect ratio of 17.6 and the densification.When different mineralizing agents were added as sintering aids,the aspect ratio of whiskers becomes small.When the firing temperature was from 1400℃ to 1500℃,needle-like mullite whiskers with cross network structure will transform to the accumulation structure of columnar mullite.The sample with internal AlF3 form an uniform and a lot of mullite whiskers,which is superior to the sample with external AlF3 that only locally formed mullite whiskers,and granular and scaly mullite.With the increase of AlF3 contents,aspect ratio of mullite whiskers increased.When AlF3 content was 10wt%,the aspect ratio of mullite whisker was 38.5.The related experimental results for in-situ growth of the mullite whiskers provide an experimental basis. |
PDF Full Text Request