2，2，3-三甲基丁烷(C7H16)晶体的成核动力学

Kinetics of Crystal Nucleation in 2,2,3-trimethylbutane C_7H_(16)

High temperature solid phase I of 2,2,3-trimethylbutane(C7H16)(TMB) was investigated by X-ray powder diffraction. The electron diffraction technique for observing the kinetics of phase transitions in the condensed matter has been applied to study the freezing of TMB clusters with diameter of~13nm. Cluster beams were generated from the supersonically expanded TMB vapor with mole fraction of 0.01 in neon carrier gas. The freezing evolution was monitored by electron diffraction in interval of 7-9 μs. Clusters with an average size of ~5,500 molecules were observed to freeze into the solid phase I at a nucleation rate of 3.5 × 1028 m-3•s- 1 at the freezing temperature of clusters, ～170K. The estimated growth rate of postcritical nuclei indicates that the observed nucleation in the present experiment corresponds to mononuclear freezing of the clusters into single crystals of solid phase I.