Vapor properties of gold at extreme temperatures by pulsedhyphen;electronhyphen;beam measurement

摘要

Currently, only limited vaporhyphen;pressure information exists for materials at temperatures above 3000 K. To provide additional information in this range, a new transient method has been developed for measuring the pressurendash;internalhyphen;energy states of the liquidhyphen;vapor phase boundary at highhyphen;vaporhyphen;pressure levels (above 1 MPa). To study these vapor states, samples are rapidly heated and the vapor is inertially confined by a dynamic graphite crucible for 2 to 20 mgr;s. A thermomechanical model of the mixedhyphen;phase material is described which relates the observed crucible expansion to total vapor pressure. The internal energy state of the vapor sample, which is heated by a pulsed electron beam, is determined from electron absorption diagnostics. Application of the method to gold has given new total vaporhyphen;pressure information between 3 and 600 MPa (30 and 6000 bar) which is consistent with extrapolation of static vapor data. Temperatures associated with these pressures range in excess of 10thinsp;000 K. Preliminary evidence for independent flow of the mixed phases is also obtained from analysis of these highhyphen;temperature expansion measurements.