THERMOPHYSICAL PROPERTIES OF LIQUID PLATINUM

Material properties of liquid metals are inherently difficult to measu re. Static measurements are difficult to make on most metals because o f the typically high values of critical temperature and pressure, prob lems 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 li quid metals are performed using dynamic techniques. Dynamic pulse heat ing experiments are typically performed on nanosecond to millisecond t imescales, providing data that would not otherwise be obtainable. We u se a resistive pulse heating method to reach high-temperature expanded liquid-metal states at a constant pressure. This technique can be use d 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 abo ut 10(-4) s by an almost-square current pulse (approximately 15 x 10(3 ) A). Samples expand along an isobaric path, with remote diagnostics p roviding data on current, voltage. temperature, volume, and sound spee d. These basic quantities are then used to calculate several derivativ e quantities. We report measurements of enthalpy, temperature. volume, electrical resistivity, and sound velocity of liquid platinum for tem peratures from the melting point up to approximately 5100 K.