Schematic diagram of the ocatahedron-shaped high-pressure cell with thermocouple (graphic: C. Schimpf)Two hydraulic presses with 1000 t and 750 t pressing force are used for static high-pressure, high-temperature tests at the Freiberg High-Pressure Research Centre. With the help of Walker-type modules from Max Voggenreiter GmbH, the uniaxial load of the press can be distributed to eight carbide cubes (WC-Co) via six press plungers (wedges). These have ground cube corners (truncations) and thus enclose an octahedron-shaped pressure cell in the centre of which the sample is located. A quasi-hydrostatic compression of the sample can be achieved through the multi-stage distribution of the load. The maximum achievable sample pressures depend primarily on the size of the high-pressure cell (with sample) and the applied load.

Established standard sizes (octahedron edge length/cube truncation in mm) at the Freiberg High Pressure Research Centre are:

18/12 18/11 14/8 10/5 10/4.5

The maximum achievable sample pressures are 18 GPa. The sample volumes are in the range of 0.001-0.2 cm³. By installing a suitable furnace material (e.g. graphite or metal foil furnaces) in the high-pressure cell, it is also possible to heat treat the sample under high pressure (or even during compression/decompression). An electric heater (DC or AC) can be used to set temperature conditions >2000 °C and, if necessary, keep them stable for several hours. To protect the sample from reactions with the atmosphere or the furnace material, the sample can also be encapsulated. As the high-pressure cells and the consumables required for the experiments are manufactured in the laboratory itself, customisation to the desired experimental conditions is easily possible.
 

Typical objectives of these high-pressure, high-temperature experiments, which are investigated as part of research activities and for teaching purposes, are:

• ex-situ investigations of phase transformations and phase stabilities(e.g. DOI: (e.g. DOI: ).e.g. DOI: 10.1080/08957959.2013.857020)
• Synthesis of new materials (e.g. DOI: 10.1103/PhysRevB.100.054403)
• Setting specific phases and/or microstructures (e.g. DOI: 10.1039/C2CS15351C)
• Manufacture of semi-finished products, e.g. for tool manufacture (e.g. DOI: 10.1088/1757-899X/564/1/012004)
• Investigation of sintering behaviour under high-pressure conditions
• Methodological developments(e.g.
  DOI: 10.1088/1742-6596/215/1/012193)