THERMOPHYSICAL PROPERTIES OF LIQUID PLATINUM

Material properties of liquid metals are inherently difficult to measure. Static measurements are difficult to make on most metals because of the typically high values of critical temperature and pressure, problems with sample-container contamination, and physical strength limits of high-pressure vessels. Data on thermophysical properties of metals are needed for a variety of applications, and measurements on most liquid metals are performed using dynamic techniques. Dynamic pulse heating experiments are typically performed on nanosecond to millisecond timescales, providing data that would not otherwise be obtainable. We use a resistive pulse heating method to reach high-temperature expanded liquid-metal states at a constant pressure. This technique can be used for a variety of metals and allows accurate data to be obtained over a wide range of temperature. Metallic wire-shaped samples (1 x 25 mm) are resistively heated in an inert gas atmosphere for a period of about 10(-4) s by an almost-square current pulse (approximately 15 x 10(3) A). Samples expand along an isobaric path, with remote diagnostics providing data on current, voltage. temperature, volume, and sound speed. These basic quantities are then used to calculate several derivative quantities. We report measurements of enthalpy, temperature. volume, electrical resistivity, and sound velocity of liquid platinum for temperatures from the melting point up to approximately 5100 K.