Efficient Preparation And Characterization Of Several Kinds Of Functional Materials

Microwave heating is a kind of heating technology which converts the microwave energy to thermal energy, from which to increase the temperature of the heated materials. Microwave heating technique has the advantages, including: integral heating, selective heating, high ramping speed and high thermal efficiency. Therefore, it is important to explore the application of microwave heating in synthesis of various functional materials.Based on the microwave heating technique combined with typical hot pressing, the preparations of Silicon-base thermoelectric materials Mg₂Si_0.5875Sn_0.4Sb_0.0125 and MnSi_1.74 compounds as well as nanomaterial MoS2 were improved with much higher efficiency in this paper. The main results are presented as below:（1） Efficient preparation and performance characterization of Mg2Si0.5875Sn0.4 Sb0.0125Mg₂Si_0.5875Sn_0.4Sb_0.0125 was fabricated by one step hot-pressing reaction method and microwave heating technology. The phase and thermoelectric performance of the sample were characterized. The results show that the product obtained by one step hot-pressing reaction has high purity and satisfactory crystalline, reaching the highest ZT value 0.53 at 800 K. Microwave heating synthesized single phase Mg₂Si_0.5875Sn_0.4Sb_0.0125 with the preparation time greatly shortened, with the absolute value of Seebeck coefficient up to 240μV/K and the power factor up to 1.78×10-4 W/mK2.（2） Efficient preparation and performance characterization of MnSi_1.74Higher manganese silicide compounds have high thermal stability, excellent high temperature antioxidant capacity and friendliness to environment. Moreover, they have the best thermoelectric properties as p-type semiconductor materials in the Silicon-base thermoelectric materials because of the high Seebeck coefficient and low resistivity. MnSi_1.74 bulks have been prepared by solid state hybrid microwave heating and subsequent hot pressing. The X-ray powder diffraction analysis shows that the microwave heating helps to eliminating the MnSi phase from the final products. The maximum value of Seebeck coefficient 210 μV/K appears at 450 K, where the largest power factor P = 7.3×10-4 W/m K2.（3） Synthesis of nanoflakes MoS2 using solid state hybrid microwave heatingBeing widely used in solid lubricant, super capacitor and lithium battery, MoS2 has received much attention. Typical preparation for MoS2 needs long duration time and high energy consumption. MoS2 powders with high purity were fabricated by solid state hybrid microwave heating from the mixture of Mo and S powders. The characterizations using powder X-ray diffraction, scanning electron microscopy, energy dispersive and high resolution transmission electron microscopy show that as-synthesized products are of single-phase hexagonal structure with the final compositions close to those of the starting materials. The results indicate that increasing the reacting temperature can optimize the product crystallization, decrease the particle size and promote the layered growth.