Figure 4

Analysis of time-dependent driving force. (a) X-ray projection images collected at 1272.5 K (40 sec, top image) and 1247.8 K (1520 sec, bottom image) during continuous cooling, respectively. The region contained in the first white box (“1”) was used to calibrate the average intensity from the liquid, \( < {{\rm{x}}}_{{\rm{Co}},{\rm{Ni}}}^{{\rm{L}}} > ({\rm{t}})\), and the second white box (“2”) was used to calibrate the average intensity from the QC. The wrinkles in the bottom image are due to the thin oxide skin. Scale bars measure 100 µm. (b) Average facet velocity of the ten quasicrystalline facets of the decagonal QC (red) and kinetic driving force (blue), during the growth process. The driving force of supersaturation was calculated by subtracting the equilibrium liquid composition from the instantaneous liquid composition, see text and equation (2) for details. Errors in the measurement of average facet velocity are due to small errors in segmentation while those in the calculation of driving force are attributed to errors in the calibration of the phase compositions at equilibrium. (c) Average facet velocity vs. driving force. The slope gives the kinetic coefficient β _s associated with the growth process.