Variation Of Critical Temperature Research Articles

Upper and lower critical solution temperatures in the cosolvent system acetone(1)+ diethyl ether(2)+ polystyrene(3)

Phase diagrams for different molecular weight fractions of polystyrene in the mixed solvent system acetone + diethyl ether have been obtained. The system shows a variation of upper and lower critical solution temperatures with solvent composition which indicates the cosolvent nature of the mixed solvent. No solvent composition is found which can dissolve high molecular weight poly-styrene (M106). The separation of critical solution temperatures can be predicted by the Prigogine theory of polymer solution thermodynamics, but not the absolute values.

Buckling of thin cylindrical shells heated along an axial strip

The results of buckling tests on circular cylinders heated uniformly along axial strips are presented and discussed. Calculations of critical temperature based upon the small-deflection theory for thin circular cylindrical shells are included and a comparison is made between theoretical and experimental results. Cylinders heated along axial strips of given widths have a theoretically predicted behaivor which corresponds reasonably well to the behavior obtained by experiment. Curves are included showing the variation of critical temperature with respect to heated axial-strip width.

The critical temperature of superconducting alloys

An analytic expression involving two arbitrary constants is fitted to the variation of critical temperature with alloy concentration in primary solid solutions. The fit is good over both the low concentration region where T c decreases rapidly with concentration, and at higher concentration where often T c increases well above the value for the pure solvent. The fit continues up to the limit of solid solution (in some cases up to 15 at. % solute). Both constants correlate qualitatively with the square of the difference in valence between solute and solvent and quantitatively with the change in reciprocal free path with solute concentration. The correlation is apparent for fifteen different solid solutions with solvents In, Sn and Al. As a result we have predicted and found Al-Mg and Al-Zn rich solid solutions to be superconducting at temperature above the critical temperature for pure Al. The effect for gallium in indium, previously an anomaly, fits into this empiricism.