High Pressure Synthesis of Tungsten Disulfide

As an efficient preparation method of tungsten disulfide (WS2), high pressure synthesis has attracted more and more attention. The preparation process is simple, low-cost and environmentally friendly. And the prepared tungsten disulfide usually has high density, crystallinity and good symmetry.

High pressure synthesis is a process to transform substances or combine different substances, by applying high pressure. New phases, compounds or new materials can be obtained by such a process.

Usually, the prepared material has special structure and properties that can keep its state under constant temperature and pressure as that under high temperature and pressure.

The high pressure synthesis of tungsten disulfide involves the following steps:

1. Tungsten disulfide synthesis is carried out on the high pressure device YJ-3000T press. Chemical reagents are used as raw materials in this experiment. And the sample room is made of iron tube that is 16mm high and has an outer diameter of 10 mm. Next, tungsten disulfide is placed in the sample chamber and pyrophyllite whose volume is 32x32x32 mm³ is used as pressure transfer medium. There is a hole with a diameter of 13mm in the center of pyrophyllite. A metal tubular heater is placed in the straight hole while an insulated oxide ceramic tube is placed between the heater and the sample tube. Then the upper and lower ends are sealed with pyrophyllite.

2. The assembled sample is placed in the high pressure chamber and the press (the rated pressure is 4x10⁸ Pa) is turned on to heat. Thermoelectric power is used in the heating. The synthesis temperature is 1025°C and the holding time is about 15 minutes. Then, the sample is quenched and released.

Tungsten disulfide synthesized at high pressure and high temperature is black, and its crystal structure is basically the same as that of hexagonal tungsten disulfide at normal pressure. Two layers of sulfur atoms and a middle layer of tungsten atoms constitute the sandwich structure of tungsten disulfide. Among them, the sulfur layer has a superimposed 2H structure while tungsten atoms interlace along the C axis.

High pressure synthesis of tungsten disulfide is short-term and simple. And the prepared tungsten disulfide has high crystallinity, density and symmetry.

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