Research on Thermoelectric System Utilizing C/C Composites

研究了碳纤维增强碳基复合材料（UD C/C）的热电性能。当SiC含量为10wt%时，UD C/C复合材料在垂直于纤维方向上的热电性能是普通UD C/C复合材料的10倍左右。UD C/C复合材料在垂直于纤维方向上的导热系数是平行于纤维方向上的1/30。采用无机盐和有机配体溶胶-凝胶法合成了热电半导体NaCo_2O_4。在比烧结温度低的温度下得到结晶良好的NaCo_2O_4粉末。通过溶胶-凝胶起始溶液的组成来优化NaCo_2O_4的微观结构，可以得到高效的热电材料B，并研究了FeSi_2热电器件的传热和电性能与其形状的关系。以提高发电功率为目的，将实验结果与数值计算结果进行了比较，并计算了不同切口尺寸的热电器件的冷热端温差和发电功率。结果表明，通过优化切口尺寸，发电功率提高了23%左右。

Thermoelectric properties of UD C/C composites(Carbon fiber-reinforced carbon matrix composites)have been investigated. The thermoelectric performance of UD C/C composites, including 10 w% Sic in the carbon matrix, in perpendicular direction to the fiber direction was about 10 times larger than that of normal UD C/C composites. Thermal conductivity of UD C/C composites in perpendicular direction to fiber direction was a one thirtieth of that in parallel direction to fiber direction. It is suggested that increases in amount of SiC and density of carbon fiber in UD C/C composites lead to the high power factor and the small thermal conductivity in perpendicular direction to fiber direction.Thermoelectric semiconductor NaCo_2O_4 has been synthesized by the sol-gel method using inorganic salts and organic ligands. Well-crystallized powder of NaCo_2O_4 was obtained at lower temperatture t han s intering t emperature. Efficient t hermoelectric materials c an b e o ptimized a s microscopic structure of NaCo_2O_4 is controlled by constitution of sol-gel starting solution.The dependence of heat transfer and electric performances in a FeSi_2 thermoelectric device on its shape was investigated. For the purpose of the increase of generated electric power, we made a comparison between experimental and numerical result, and calculated the difference of temperature from hot to cold junction and electric power in the thermoelectric device with various sizes of incision. The result showed that generated electric power increased to about 23% by optimization of incision size.