Precursor synthesis and properties of nanodispersed tungsten carbide and nanocomposites WC:nC

• Published in: Ceramics international 2017-04, Vol.43 (5), p.4131-4138
• Main Authors: Krasil’nikov, Vladimir N., Polyakov, Еvgenii V., Khlebnikov, Nikolai А., Tarakina, Nadezda V., Kuznetsov, Мikhail V.
• Format: Article
• Language: English
• Subjects: Carbon; Composites; Tungsten carbides
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2016.12.026

Nanoscale tungsten carbide (WC) and WC:nC nanocomposites have been synthesized by the precursor method. The precursor, obtained in the form of a glassy mass by thermal treatment of a mixture of (NH4)10W12O41∙7H2O and glycerol, was heated in inert gaseous atmosphere up to 1050–1100°C. The concentration of chemically active carbon in the precursor and nanocomposites depends on the W/C ratio in the initial mixture. At W/C=1/3 pure tungsten carbide is formed; at W/C>1/3 composites of WC and free carbon (WC:nC) are formed. Heating of the precursor with W/C=1/6 up to 1100°C in helium atmosphere results in the formation of carbon-encapsulated tungsten carbide nanoparticles. An increase in the precursor-heating rate leads to the formation of chain-like structures. Each chain consists of hexagonal WC grains with unit cell parameters a=2.93Å and c=2.83Å. Free carbon in WC:nC composites forms agglomerates of carbon “nano-onions” of spherical or multi-layered tubular shapes.