关键词: 阻燃;钙矾石;水热法;二氧化硅;包覆

Abstract: Ettringite(AFt,3CaO· Al2O3· 3CaSO4· 32H2O)possessed the potential to be used as flame retardant material because of its plenty crystal water .Al2(SO4)3· 18H2O and Ca(OH)2 was used as raw materials and reacted in a hydrothermal condition of 200 ℃ to implement the experiment of synthesising ettringite .The influences of the concentration of raw material , reaction time and pH value on the product were researched.An improved St?ber method was used to coat a shell of SiO 2 on the surface of ettringite crystal in order to prepare AFt/SiO2 core/shell structure .The products were characterized by XRD , SEM, FT-IR, and TG.The results show that hydrothermal method can be used to synthesize ettringite crystal with high purity and excellent crystallinity , pH=10 is a suitable circumstance of the growth of ettringite crystals .The coating of SiO 2 can control the dehydration speed of AFt and decrease the moisture content of AFt .

Key words: flame retardant;ettringite;hydrothermal method;silica;coat