Abstract:
Nonpyrophoric tungsten powders with an average particle size of about 30 nm were obtained by pyrolysis of tungsten hexacarbonyl in a flow of microwave discharge nitrogen plasma. It is found that these powders are stable in air up to 300$^\circ$C. The reason for such stability is that the structure of powder particles is of the core-double shell type, in which the metal core is covered with an oxide film approximately 1 nm in thickness, coated in turn with roentgenoamorphous layer consisting of carbon, oxygen, and nitrogen atoms. It is also established that the powders under investigation mainly release carbon oxides (CO and CO$_2$) and water into the gas phase upon heating in vacuum. Among the molecules present in the gas phase in small concentrations, nitrogen monoxide (NO) and formaldehyde (H$_2$CO) are worth mentioning apart from C1–C3 hydrocarbons.
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