Piston-cylinder apparatus
The piston-cylinder apparatus is a solid media device, used in Geosciences and Material Sciences, for generating simultaneously high pressure (up to 6 GPa) and temperature (up to 1700 °C).
The pressure vessel is a cylinder that is closed at one end by a rigid plate with a small hole for the thermocouple to pass through.
Nowadays both the piston and the cylinder are constructed of cemented tungsten carbide and electrical insulation is provided in a different manner than in the device of Coes.
In particular, the basis for the modern piston-cylinder apparatus is given by the design described by Boyd and England in 1960,[4] which has been the first machine that allowed experiments under upper mantle conditions to be routinely carried out in a laboratory.
Geologist Bernard Wood has made multiple important contributions to science using piston-cylinder experiments and has consequently become a prominent figure in experimental petrology.
Along with Fred Wheeler, a workshop worker at the University of Bristol, he has designed a model of piston-cylinder that is known for its simplicity and blue features.
[5] The piston-cylinder apparatus is based on the same simple relationship of other high-pressure devices (e.g. Multi-anvil press and Diamond Anvil Cell):
During the experiment, water circulates around the pressure vessel, the bridge and the upper plates to cool the system.
To locate the sample exactly in the centre of the furnace and to grip the thermocouple, a support rod usually made of crushable ceramics is used.
Thus, it must be adjusted taking into account the friction: Peffective = Pnominal + Pcorrection In order to determine the effective pressure, calibration experiments can be done using either static or dynamic methods, and usually make use of known phase transitions or reactions, melting curves or measured water solubility in melts.
Since frictional effects also depend on whether the press is in compression or in decompression, it is good practice to perform the experiments in the same way as the calibration runs.
The main advantages of the piston-cylinder press are the relatively large volume of the assembly, fast heating and quenching rates, and the stability of the equipment over long run durations.
These aspects, together with the ease and safety of procedure make this device suitable for geochemical studies and in-situ measurements of the physical properties of materials.
Some applications, especially in Geosciences, are: synthesis of high-pressure and temperature materials, hot pressing and investigation of partial melting of rocks.
