Studying the thermal resistance of superhydrophobic carbon soot coatings for heat transfer management in cryogenic facilities

Except in microelectronics, food industry and power generation, the accurate temperature control is a fundamental precondition for the sustainable development of cryobiology too, where the partial cryodamage of frozen/thawed biospecies is still unavoidable. Setting favorable cooling and warming rates during cryopreservation helps to mitigate the detrimental intracellular icing and recrystallization, which is accomplishable using superhydrophobic carbon soot, whose thermal resistance however, has not been examined so far. This research introduces the first attempts of quantifying the thermal behavior of three basic categories soot distinguished by morphology, porosity, chemical composition and film thickness. The gradual cooling of six pairs of non-wettable soot coatings reveals that the diffusive thermal transport in their bulk is accompanied by phonon scattering governed predominantly by the pore arrangements, particle size, chemical bonding and interlayer spacing in the material. In turn, the soot incorporating similar to 50-120 nm-sized nanoparticles, mesopores, moderate surface oxidation and thickness exceeding 50 mu m exhibits the greatest capacity to delay the bulk heat conduction, opposite to the empirically established solid-liquid interfacial heat transfer mechanisms of the soot. Thus, merging specific physicochemical features within a single coating, via controlled flame synthesis and alcoholfluorocarbon functionalization, would facilitate the fabrication of custom cryovials alleviating the two-factor freezing injury.