Thermal conductivity at the amorphous-nanocrystalline phase transition in beech wood biocarbon

• Published in: Physics of the solid state Vol. 56; no. 5; pp. 1071 - 1080
• Main Authors: Parfen’eva, L. S., Orlova, T. S., Smirnov, B. I., Smirnov, I. A., Misiorek, H., Jezowski, A., Ramirez-Rico, J.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.05.2014; Springer
• Subjects: Analysis; Diffraction; Physics; Physics and Astronomy; Pyrolysis; Solid State Physics; Thermal Properties; X-rays; Carb; Electrical Resistivity; Thermal Conductivity; Carbonization Temperature; Amorphous Carbon
• ISSN: 1063-7834; 1090-6460
• DOI: 10.1134/S1063783414050229

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.