Thermoelectric properties of porous SiC/C composites

• Published in: Renewable energy Vol. 33; no. 2; pp. 309 - 313
• Main Authors: Fujisawa, Masashi, Hata, Toshimitsu, Kitagawa, Hiroyuki, Bronsveld, Paul, Suzuki, Youki, Hasezaki, Kazuhiro, Noda, Yasutoshi, Imamura, Yuji
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2008; Elsevier Science
• Subjects: Applied sciences; Carbon; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Mhd generators; SiC; Thermoelectric properties; Germany, Niedersachsen, Seebeck; SiC; Carbon; Thermoelectric properties; Thermoelectric conversion; Scanning electron microscopy; Temperature; Wood; Porous material; Composite material; Silicon carbide; Thermal conductivity; Raman spectrometry; Microstructure
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2007.07.010

We developed a porous SiC/C composite by oxidizing a SiC/C composite made from a mixed powder of wood charcoal and SiO 2 (32–45 μm) by pulse current sintering at 1600 and 1800 °C under a N 2 atmosphere. The microstructures of the porous SiC/C composites with oxidation and the SiC/C composites without oxidation were analyzed by Raman spectroscopy and scanning electron microscopy (SEM). Raman spectra revealed the disappearance of excess carbon and the presence of β-SiC. The porous microstructure was monitored by SEM observation as a function of the heat treatment temperature. The thermoelectric properties of porous SiC/C composites with oxidation and SiC/C composites without oxidation were investigated by measuring the Seebeck coefficient, the electrical conductivity and thermal conductivity. The Seebeck coefficient of all samples revealed n-type conduction, and the absolute value of the Seebeck coefficient for the porous SiC/C samples with oxidation was much larger than that for the SiC/C samples without oxidation. For the electrical conductivity the reverse is true. Only the thermal conductivity of the SiC/C sample heated to 1800 °C without oxidation was high initially and stayed rather high. In general, the thermoelectric properties improved at higher measurement temperatures indicating their suitability for high-temperature thermoelectric conversion. A maximum figure of merit of 2.01×10 −5 K −1 was obtained at 700 °C in porous SiC/C samples sintered at 1800 °C with oxidation.