Study On The Mullitization Behavior And Mineralogical Characteristics Of Andalusite From Yangnaigou In Xixia,Henan Province

The mineralogical characteristics and mullitization behavior of andalusite fromYangnaigou in Xixia Country, Henan Province were entirely studied through usingmodern testing techniques such as the observation under microscope, analysis ofEPMA, XRD, IR, UVLS, TG-DSC, grain size testing, high-temperature roasting andobservation under SEM.The results show that the chemical compositions of andalusite were Al2O3andSiO2, Fe was the main impurity element, containing a small amount of Na, K, Ca,Mn, Cr, Ti etc. The distribution of Fe in andalusite is not even, increased from centerto periphery. The compositions of black cross inclusions were from wall rocks ofandalusite, including quartz, mica, carbon and small amount of garnet, kaolinite. Thelattice parameters of andalusite was a0=7.817, b0=7.906, c0=5.590, byanalyzing XRD data of samples. Foreign ions got into the lattice of andalusite,causing the value of lattice parameter c0increased and the vibration of IR shifted.The energy level transition of Fe3+made andalusite appeared red. The maintransition types of Fe3+were6A1gâ†'4A1g,6A1gâ†'A2g,6A1gâ†'2T1g.Andalusite micro powder (d50=3.841μm, d90=37.362μm) started transformedinto mullite at1150℃, made the mullitization temperature of andalusite reduced250℃. The fast decomposed temperature of Andalusite micro powder was between1250℃to1300℃, made the sintering temperature of refractory products reduced150℃.The andalusite whose black cross is clear and even can be used to make jewel.The refractory which is made by andalusite micro powder has obviousenvironmental and economic significance. Andalusite micro powder has broadprospects of application.