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Estimation of critical point parameters for liquid-vapor phase transition of molybdenum from shock-wave experiments
Andrey N. Emelyanov, Dmitriy N. Nikolaev and Vladimir Ya. Ternovoi

Results of experiments with expansion of shock-compressed porous molybdenum samples into helium and with quasi-isobaric heating of a molybdenum foil during launching in the helium atmosphere are presented. The brightness temperature of molybdenum samples and shock wave velocity in helium were measured by optical pyrometer, while other parameters (pressure, particle velocity, helium temperature) were calculated. To increase the entropy of shock compression up to a near critical value, the compression of porous (m = 3.1) samples was carried out. The expansion adiabate was studied from shocked state of 146 GPa and final states below 2 GPa, determined by initial helium pressures. Isobaric heating of molybdenum foil by hot multiple-shocked helium during acceleration allowed us to obtain near critical point states. Molybdenum critical point pressure and temperature have been estimated as Pc = 0.96 ± 0.10 GPa, Tc = 13300 ± 700K from the first type experiments and Pc = 1.0 ± 0.1 GPa, Tc = 12500 ± 1000K from the second type.

Keywords: Critical point, liquid-vapor, phase transition, molybdenum, shock wave.