Thermal conductivity at the amorphous-nanocrystalline phase transition in beech wood biocarbon
High-porosity samples of beech wood biocarbon (BE-C) were prepared by pyrolysis at carbonization temperatures T carb = 650, 1300, and 1600°C, and their resistivity ρ and thermal conductivity κ were studied in the 5–300 and 80–300 K temperature intervals. The experimental results obtained were evaluated by invoking X-ray diffraction data and information on the temperature dependences ρ(T) and κ(T) for BE-C samples prepared at T carb = 800, 1000, and 2400°C, which were collected by the authors earlier. An analysis of the κ(T carb) behavior led to the conclusion that the samples under study undergo an amorphous-nanocrystalline phase transition in the interval 800°C < T carb < 1000°C. Evaluation of the electronic component of the thermal conductivity revealed that the Lorentz number of the sample prepared at T carb = 2400°C exceeds by far the classical Sommerfeld value, which is characteristic of metals and highly degenerate semiconductors.
KeywordsThermal Conductivity Electrical Resistivity Carb Amorphous Carbon Carbonization Temperature
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- 15.V. F. Gantmakher, Electrons and Disorder in Solids (Fizmatgiz, Moscow, 2003; Clarendon, Oxford, 2005).Google Scholar
- 25.E. A. Bel’skaya and A. S. Tarabanov, in Thermophysical Properties of Solids: Collection of Papers (Naukova Dumka, Kiev, 1971), p. 111 [in Russian].Google Scholar
- 26.E. Ya. Litovskii, Izv. Akad. Nauk SSSR, Neorg. Mater. 16, 559 (1980).Google Scholar
- 28.Handbook of Physical Quantities, Ed. by I. S. Grigoriev and E. S. Meilikhov (Energoatomizdat, Moscow, 1991; CRC Press, Boca Raton, Florida, United States, 1997).Google Scholar
- 32.N. V. Kolomoets, Sov. Phys. Solid State 8(4), 799 (1966).Google Scholar