Thermophysical and mechanical property assessment of UB2 and UB4 sintered via spark plasma sintering

Influence of boron isotope ratio on the thermal conductivity of uranium diboride (UB2) and zirconium diboride (ZrB2)

“…[35] but a different code was used to obtain the results. The moduli obtained in this work agrees fairly well with the experimental measurement of Dancausse et al [13] but differs to Kardoulaki et al [55] where the authors suggest potential internal cracking in their sample. There is variation in the values of θ D due to the different methods and samples e.g.…”

“…In both calculated heat ca-215 pacities the electronic contribution, γT (where γ = 9.40 mJ / K 2 • mol [58]) is included. It can be seen that the calculation reproduces the experimental result well, particularly at low temperatures, and therefore the large discrepancy between the calculated and experimental κ l [55] is likely due to either ν or τ. The discrepancy between the results obtained through DFT and Phono3py calculations and the available experimental data [55] could be due to an overestimated calculated phonon relaxation time.…”

“…It can be seen that the calculation reproduces the experimental result well, particularly at low temperatures, and therefore the large discrepancy between the calculated and experimental κ l [55] is likely due to either ν or τ. The discrepancy between the results obtained through DFT and Phono3py calculations and the available experimental data [55] could be due to an overestimated calculated phonon relaxation time. The scattering rate, which is the inverse of the phonon relaxation time, is a sum of individual scattering rates 225 due to interactions between phonons and other phonons, defects/impurities, surfaces, magnetic entropy and electrons [23,53] i.e.…”

“…The accumulated lattice thermal conductivity at 300 K is displayed in Figure 5(a) in both x and z directions. The κ l produced by Phono3py, which calculates phonon-phonon and phonon-isotope scattering only, was found to be 2 to 3 times larger than the experimental result [55]. The associated phonon density of states are shown in Figure 5 Other phonon properties are related to κ l via [53]:…”

“…Following the fit, U and b were found to be 11419 K −3 s −1 and 4.39 respectively. The parameter B responsible for phonon-boundary scattering was estimated from ν and assumes a typical grain size of 7.5 µm [55], which produces a value of 6.0 ×10 8 s −1 . The addition of the phonon-boundary term has an insignificant impact on the total lattice thermal conductivity values.…”