Vapor properties of gold at extreme temperatures by pulsed‐electron‐beam measurement

摘要

Currently, only limited vapor‐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 pressure–internal‐energy states of the liquid‐vapor phase boundary at high‐vapor‐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 μs. A thermomechanical model of the mixed‐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 vapor‐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 10 000 K. Preliminary evidence for independent flow of the mixed phases is also obtained from analysis of these high‐temperature expansion measurements.