Figure 11.

Variation of grain sizes for nano Ni as a function of temperature at atmospheric pressure (neutron data) and 7.4 GPa (X-ray data). All values are derived from Eq.2and represent the average grain sizes for the Ni nanocrystals. For neutron data, the grain sizes derived with the (E_hkl/E₁₁₁)² and (E_hkl/E₂₀₀)² corrections are shown, respectively, by solid red and blue circles. The solid green diamonds denote the grain sizes derived from the high-P X-ray data using the (E_hkl/E₂₀₀)² correction. The insert plots the grain size variation on a larger/logarithm scale as well as over a wider temperature range, showing the rapid growth of Ni nanocrystals approaching or entering the micrometer region. The plots clearly show that the grain growth is kinetically suppressed at high pressures