Symmetrical and Unsymmetrical Frictions in Pyrophyllite Medium on High-Temperature Measurement in Piston-Cylinder Type High-Pressure Chamber

Frictions in pyrophyllite medium at elevated temperature in piston-cylinder type apparatus are examined by measuring the melting curve of lead. The obtained results show evident unsymmetrical frictions grown out during pressure calibration at higher temperatures. As a result, the widely used fixed points calibration method becomes inapplicable. As temperature differs greatly at the central and outside parts of the assembly, this unsymmetrical friction is assumed to be originated from the corresponding evident disparity in mechanical properties of the medium, showing a large differential loading. We conclude that as the pyrophyllite is very cheap and easy in machining, it should get wide application as a qualified medium in high-temperature high-pressure measurement of physical properties, if the unsymmetrical friction is understand in its nature and if it could be well controlled.