抄録
The ultrasonic velocity in molten bismuth, aluminum, silver and copper has been measured by using a pulse-echo method at 10 MHz in the temperature range from their melting points to the temperatures about 250 K higher than the melting point. The relation between the velocity and the temperature can be represented by a straight line having a negative temperature coefficient for molten Al, Ag and Cu. But the temperature dependence of molten Bi is different from the others, i.e., it remains almost constant over the range of 100 K above the melting point and then becomes negative with increasing temperature.
The adiabatic and isothermal compressibilities were calculated at the melting points from the experimental results combining with the other thermodynamic data and compared with theoretical values calculated by simple models. It was found that the values calculated by Ascarelli’s model agreed well with the experimental values except Ag and Cu, while the hard sphere model did not yield satisfactory results. From this fact, it may be concluded that the contribution of free electron gas can not be neglected for the explanation of the compressibility of these molten metals.
