Thermal Behavior Of Tourmaline At High Tempreature

Physicochemical changes, microstructure and evolution of tourmaline powders at25-1200°C were detected online under heating and cooling processes using HT-PSP,TG-DSC, HT-XRD, HT-MM and HT-RAM. On the basis, the tourmaline/glass composite was prepared. The parameters of the composite such as phase composition, microstructure,infrared properties and microhardness were investigated by means of XRD, TEM, SEM,FTIR and microhardness tester.The evolution of tourmaline in heating process and cooling process was systematically studied. In heating process, at the first stage 25-890°C, schorl phase structure showed no change, whose grain size decreased appreciably; at the second stage 890-1050°C, schorl decomposed into cordierite, whose grain size decreased quickly; at the third stage1050-1200°C, schorl had melted and its grain size increased. In cooling process, at the first stage 1200-890°C, schorl re-precipitated surprisingly, whose grain size reached the maximum at 890°C; at the second stage 890-25°C, the grain size decreased gradually. It is deduced that the pinning effect of the second phase cordierite was responsible for the schorl grain refinement.Tourmaline/glass composite was prepared by sintering at 600°C for 1h using micron-size tourmaline mineral and glass powders as raw materials. The tourmaline phase was observed in the composite, showing a particle size of about 70 nm. This meant that the tourmaline particles were refinement. The Fourier transform infrared spectroscopy showed that the far infrared emissivity of composite was significantly higher than tourmaline or glass powders. A higher far infrared emissivity up to 0.925 was obtained when the dosage of tourmaline was 10wt%. As the increasing of the tourmaline dosage, the value of the microhardness of the composite increased, however, the most dosage should not exceed30%.