Phase Composition And Expansion Property Of The Vermiculite From Yuli,Xinjiang Province

Vermiculite can be expanded by several times in volume when heated rapidly due to the sudden release of interlayer water.The expanded vermiculite is a kind of new lightweight building material with good noise insulation,thermal insulation,shock resistance and fire resistance property,so it is widely used.Expansion ratio is an important criterion to the quality of vermiculite mineral.At present,the vermiculite expansion property can not be effectively improved and conclusion about phase composition of the vermiculite from Yuli,Xinjiang province is not consistent in view of research results of many scholars,so the studies of phase composition of vermiculite from Yuli,Xinjiang province and vermiculite expansion influencing factors and then to prepare high expansion ratio vermiculite have important scientific significance and application prospect.The main contents of this paper can be divided into three parts.The first part is obout the qualitative and quantitative analysis of Xinjiang Yuli vermiculite.The second part mainly studies the effect of phase compositions,calcination temperature and particle size on the expansion property of the vermiculite.The third part focus on the influence of vermiculite modification on its expansion ratio,including salt modification(NaCl,CaCl2 and MgCl2 solution modification),thermal modification(heat treatment under different temperature),acid modification(treatment with different concentration hydrochloric acid)and composite modification(acid-salt modification).For the first part,phase compositions of vermiculite were investigated by X-ray diffraction,thermogravimetric-differential thermal analysis,infrared spectroscopy,and chemical analysis.Results indicate that vermiculite sample is the mixture of vermiculite,mica,calcite and two kinds of vermiculite-mica mixed-layer minerals Hy-a(vermiculite/mica mole ratio of 6:4),Hy-b(vermiculite/mica ratio of 4:6).Phlogopite is identified as the main type of mica and mica layer in mixed-layer minerals,and the two types of vermiculite are Mg-vermiculite and Na-vermiculite.For the second part,Results show that vermiculite expansion capacity is mainly affected by the mixed layer minerals(Hy-a and Hy-b),while Hy-a plays greater role compared to Hy-b in this regard.The expansion ratio of vermiculite mixture increases rapidly with the increase of the calcining temperature at 700 ?,and then it becomes stable.The expansion ratio of the vermiculite mixture is proportional to its particle size when it is less than 2mm and is inversely proportional to the particle size when it is larger than 2mm.For the third part,vermiculites modified by NaCl solution can lower the beginning expansion temperature,while the vermiculites modified by CaCl2 and MgCl2 solutions can show high expansion ratio.Neither thermal modification nor acid modification improves the vermiculite expansion ratio.For composite modification,both acid-NaCl and acid-CaCl2 modification vermiculite have lower expansion ratio compared to raw vermiculite.Although acid-MgCl2 modification vermiculite shows better expansion than that of raw vermiculite,it is also not as good as MgCl2 solution modification vermiculite in terms of expansion property.