기상응축법으로 제조한 나노 WC 및 WC-Co 분말의 후속 열처리에 의한 상 및 형상 변화

Abstract

Nanosized WC and WC-Co powders were synthesised by chemical vapor condensation(CVC) process using the pyrolysis of tungsten hexacarbonyl(W(CO)6) and cobalt octacarbonyl(Co2(CO)8). The microstructural changes and phase evolution of the CVC powders during post heat-treatment were studied using the XRD, FE-SEM, TEM, and ICP-MS. CVC powders were consisted of the loosely agglomerated sub-stoichimetric WC1-x and the long-chain Co nanopowders. The sub-stochiometric CVC WC and WC-Co powders were carburized using the mixture gas of CH4-H2 in the temperature range of 750-850℃. Carbon content of CVC powder controlled by the gas phase carburization at 850℃ was well matched with the theoretical carbon stoichiometry of WC, 6.13 wt%. During the gas phase carburization, the particle size of WC increased from 20 nm to 40 nm and the long chain structure of Co powders disappeared.