A thermodynamic approach to the study of phase equilibria in the sodium-potassium alloy system I. The phase diagram for NaK at atmospheric pressure ; II. High pressure phase studies

• Main Author: Anderson, Donald Ray
• Format: Others
• Published: BYU ScholarsArchive 1969
• Subjects: High pressure (Science); Research; Sodium; Potassium compounds; Phase rule and equilibrium
• Online Access: https://scholarsarchive.byu.edu/etd/8153; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=9153&context=etd

Ultra-pure reagents, platinum resistance thermometry and modern inert atmosphere glove box facilities have made possible a detailed examination of the NaK system at atmospheric pressure. A thermoanalytical study of solid-liquid phase equilibria in the NaK alloy system was conducted in the tetrahedral press to 55 kbars to investigate possible intermediate compound formation and shifting of the invariant points at various pressures. An expected shift in the eutectic composition to lower potassium content with an increase in the halt temperature on increasing pressure was confirmed. A merging of the meritectic and eutectic points at 343 ±2°K and 37 ±3 kbars occurred at 0.40 mole fraction K. Above 35 kbars the original meritectic halt behaves much like elemental cesium, suggesting new structural modifications. The possibility of a eutectoid with increased solid solubility limits is suggested for the invariant point which decreases with increasing pressure. The formation of NaK2 under pressure is suggested but not confirmed.