Encapsulation of carbides of chromium, molybdenum and tungsten in carbon nanocapsules by arc discharge

Encapsulation of Cr, Mo and W in multilayered graphitic cages by are evaporation of metal/carbon composites under different pressures of helium gas (100, 600 and 1500 Torr) has been studied. Electron microscopy and X-ray diffraction of carbonaceous products revealed that encapsulated crystallites were carbides, i.e. Cr7C3 and Cr3C2 for Cr; Mo2C, delta-MoC1-x (NaCl type) and gamma'-MoC (AsTi type) for Mo; W2C and beta-WC1-x (NaCl type) for W. Effect of the pressure of helium gas on the formation of filled nanocapsules was markedly found for tungsten: Encapsulated tungsten carbides were formed at the highest pressure, but not in the lower pressures.