Abstract: Mullite samples were in-situ synthesized by solid state reaction using coal gangue , fly ash, yellow sand, Suzhou clay as a silicon-source, industrial aluminum hydroxide as aluminum-source and AlF3 with V2 O5 as additives.The phase structure and microstructure of the samples were analyzed by X-ray diffraction and scanning electron microscopy .The characteristics of the samples prepared under different silicon-source and their structural changes were studied .The results show that mullite crystal phase with acicular morphology is synthesized by using Suzhou clay as a silicon-source , and a columnar morphology of mullite and flaky morphology of alumina crystal phase can be obtained by using coal gangue and yellow sand as a silicon-source respectively , and the main crystal phase with fly ash as the silicon-source was columnar mullite .The bulk density , porosity and flexural strength of the samples prepared from different silicon-source were studied respectively , and the formation mechanism of mullite was discussed .

Key words: Mullite samples were in-situ synthesized by solid state reaction using coal gangue , fly ash, yellow sand, Suzhou clay as a silicon-source, industrial aluminum hydroxide as aluminum-source and AlF3 with V2 O5 as additives.The phase structure and microstructure of the samples were analyzed by X-ray diffraction and scanning electron microscopy .The characteristics of the samples prepared under different silicon-source and their structural changes were studied .The results show that mullite crystal phase with acicular morphology is synthesized by using Suzhou clay as a silicon-source , and a columnar morphology of mullite and flaky morphology of alumina crystal phase can be obtained by using coal gangue and yellow sand as a silicon-source respectively , and the main crystal phase with fly ash as the silicon-source was columnar mullite .The bulk density , porosity and flexural strength of the samples prepared from different silicon-source were studied respectively , and the formation mechanism of mullite was discussed .