Capabilities of pulse current heating to study the properties of graphite at elevated pressures and at high temperatures (up to 5000 K)

Intrinsic Planar Defects in Germanium and Their Contribution to the Excess Specific Heat at High Temperatures

“…In one study, [19] the dependence of the resulting specific heat on the AC frequency was mentioned, which would also corroborate the influence of quenching effects on the measurement results. On the other hand, experiments on graphite [34,35] are performed in one-shot regime by the pulse heating method. In this type of experiments, only inserted heat is taken into account and the quenching effect is not possible.…”

“…We believe, that it is connected to possible separation of the sample into domains, with planar defects aligned along a single crystallographic direction. This also implies, that extended defects in 3D case (like in germanium) behave qualitatively different from 2D materials (like graphite), where observed high temperature contribution to the specific heat was [34,35] much greater. This indicates, that orientation of extended defects in graphite is purely random and configurational multiplier reaches its maximum theoretical value (i.e., 3).…”

The Stone–Wales transformation: from fullerenes to graphite, from radiation damage to heat capacity

“…It is the basis of commercial heat storage systems operating up to 1000 • C and, remarkably, above 2000 • C graphite's heat capacity has been reported to grow strongly [49][50][51]. In the third reference, the measurement is ultrafast, so the divergence temperature is much enhanced (around 3200 • C).…”

“…Finally, we shall consider the role of the SW transformation in thermal energy storage: graphite has a very high heat capacity, which was first modelled in DFT in 2005 [48]. It is the basis of commercial heat storage systems operating up to 1000 • C and, remarkably, above 2000 • C graphite's heat capacity has been reported to grow strongly [49][50][51]. In the third reference, the measurement is ultrafast, so the divergence temperature is much enhanced (around 3200 • C).…”

“…In the third reference, the measurement is ultrafast, so the divergence temperature is much enhanced (around 3200 • C). Speculations to date are that this is due to the reversible formation of lattice vacancies [51,52], but it has been suggested [52] that this is not compatible with the direct measurement of vacancy concentrations by etching, which gives below 10 −10 per atomic site [53]. In addition, unless surfaces are involved, increasing the vacancy concentration must be achieved by thermal generation of Frenkel pairs, which have an activation energy greater than the Frenkel pair energy of 14 eV [43,44].…”