Based on in situ high pressure x-ray diffraction with diamond anvil cell by using synchrotron radiation and pressure-quench x-ray measurement,phase transition of C_(60)under high pressured is studied.The maximum press...Based on in situ high pressure x-ray diffraction with diamond anvil cell by using synchrotron radiation and pressure-quench x-ray measurement,phase transition of C_(60)under high pressured is studied.The maximum pressure used is 30GPa in quasi-hydrostatic case but 44GPa in nonhydrostatic case.At ambient pressure,C_(60)crystal is a fcc phase with lattice parameter a=14.2086Å.It transforms from fcc to a lower symmetry phase at pressure of 13.7GPa,and then transforms to an amorphous state under pressure up to 25-30 GPa.This amorphous state is metastable at normal condition.Finally,the experimental results are discussed.展开更多
The elastic modulus and attenuation coefficient of polycrystalline NdFeB magnet have been measured at different temperatures by ultrasonic method.At room temperature,the elastic modulus shows small but apparent anisot...The elastic modulus and attenuation coefficient of polycrystalline NdFeB magnet have been measured at different temperatures by ultrasonic method.At room temperature,the elastic modulus shows small but apparent anisotropy,while at low temperatures the ultrasonic velocity and attenuation coefficient are both changed anomalously.We suppose that this phenomenon is caused by the abrupt change of the direction of magnetization.展开更多
基金C_(60)sample is provided by LI Yuliang and YAO Youxin,Institute of Chemistry,Academia Sinica.This research is supported by the Beijing Synchrotron Radiation Laboratory,Institute of High Energy Physics,Academia Sinica,and the National Natural Science Foundation of China.
文摘Based on in situ high pressure x-ray diffraction with diamond anvil cell by using synchrotron radiation and pressure-quench x-ray measurement,phase transition of C_(60)under high pressured is studied.The maximum pressure used is 30GPa in quasi-hydrostatic case but 44GPa in nonhydrostatic case.At ambient pressure,C_(60)crystal is a fcc phase with lattice parameter a=14.2086Å.It transforms from fcc to a lower symmetry phase at pressure of 13.7GPa,and then transforms to an amorphous state under pressure up to 25-30 GPa.This amorphous state is metastable at normal condition.Finally,the experimental results are discussed.
文摘The elastic modulus and attenuation coefficient of polycrystalline NdFeB magnet have been measured at different temperatures by ultrasonic method.At room temperature,the elastic modulus shows small but apparent anisotropy,while at low temperatures the ultrasonic velocity and attenuation coefficient are both changed anomalously.We suppose that this phenomenon is caused by the abrupt change of the direction of magnetization.
