Effect of the Dosage of Tourmaline on Far Infrared Emission Properties of Tourmaline/Glass Composite Materials

Tourmaline/glass composite materials were prepared by sintering at 600 °C using micron-size tourmaline mineral and glass powders as raw materials. The glass has lower melting point than the transition temperature of tourmaline. The Fourier transform infrared spectroscopy showed that the far infrared emissivity of composite was significantly higher than that of either tourmaline or glass powders. A highest far infrared emissivity of 0.925 was obtained when the dosage of tourmaline was 10 wt%. The effects of the amount of tourmaline on the far infrared emission properties of composite was also systematically studied by field emission scanning electron microscope and X-ray diffraction. The tourmaline phase was observed in the composite, showing a particle size of about 70 nm. This meant that the tourmaline particles showed nanocrystallization. They distributed homogenous in the glass matrix when the dosage of tourmaline was not more than 20 wt%. Two reasons were attributed to the improved far infrared emission properties of composite: the particle size of tourmaline-doped was nanocrystallized and the oxidation of Fe 2+ (0.076 nm in radius) to Fe 3+ (0.064 nm in radius) took place inside the tourmaline-doped. This resulted in the shrinkage of unit cell of the tourmaline in the composite.