Thermal Conductivity of Partially Graphitized Biocarbon Obtained by Carbonization of Medium-Density Fiberboard in the Presence of a Ni-Based Catalyst

摘要

The thermal conductivity k and resistivity ρ of biocarbon matrices, prepared by carbonizing\udmedium-density fiberboard at Tcarb = 850 and 1500°C in the presence of a Ni-based catalyst (samples MDFC(\udNi)) and without a catalyst (samples MDF-C), have been measured for the first time in the temperature\udrange of 5–300 K. X-ray diffraction analysis has revealed that the bulk graphite phase arises only at Tcarb =\ud1500°C. It has been shown that the temperature dependences of the thermal conductivity of samples MDFC-\ud850 and MDF-C-850(Ni) in the range of 80–300 K are to each other and follow the law of k(T) ~ T1.65,\udbut the use of the Ni-catalyst leads to an increase in the thermal conductivity by a factor of approximately 1.5,\uddue to the formation of a greater fraction of the nanocrystalline phase in the presence of the Ni-catalyst at\udTcarb = 850°C. In biocarbon MDF-C-1500 prepared without a catalyst, the dependence is k(T) ~ T1.65, and\udit is controlled by the nanocrystalline phase. In MDF-C-1500(Ni), the bulk graphite phase formed increases\udthe thermal conductivity by a factor of 1.5–2 compared to the thermal conductivity of MDF-C-1500 in the\udentire temperature range of 5–300 K; k(T = 300 K) reaches the values of ~10 W m–1 K–1, characteristic of\udbiocarbon obtained without a catalyst only at high temperatures of Tcarb = 2400°C. It has been shown that\udMDF-C-1500(Ni) in the temperature range of 40‒300 K is characterized by the dependence, k(T) ~ T1.3,\udwhich can be described in terms of the model of partially graphitized biocarbon as a composite of an amorphous\udmatrix with spherical inclusions of the graphite phase