纳米晶WC-6Co复合粉合成及特性研究（英文）

Synthesis and Characterization of WC-6Co Nanocrystalline Composite Powder

使用喷雾转化、煅烧和原位还原碳化技术制备了纳米晶WC-6Co复合粉末。通过XRD研究相组成发现,经过喷雾转化处理后粉末为无定形相、经煅烧后的粉末为WO_3与Co_3O_4相、经还原碳化工艺后的物相是WC与Co相;由于Co对碳化过程的催化作用,将煅烧后的粉末置于氢气气氛中加热至900℃还原碳化1 h,即可将粉末碳化完全,制备出WC与Co相共存的纯净复合粉。研究了还原碳化温度(700～900℃)对粉末相组成的影响,并通过SEM和HRTEM观察粉末形貌与微观组织。结果表明:制备的粉末具有球形结构,WC晶粒约0.36μm,亚晶尺寸约为56 nm,说明WC晶粒是多晶体。同时发现粉末中的WC单颗粒被Co相互粘结在一起,且在WC与WC颗粒的接触部位发现存在烧结颈。还讨论了复合粉球形结构的形成过程和机理。

WC-6 Co nanocrystalline composite powders without excess C and decarburization phases were synthesized via a facile route including spraying conversion, calcination and in situ reduction-carbonization processes. The phase constituents obtained by XRD show that the as-prepared powders after each step of the preparation are amorphous, WO_3 and Co_3 O_4 phases, WC and Co phases, respectively. Pure WC-Co composite powders could be obtained by a reduction-carbonization process heat treated at 900 ℃for 1 h under a hydrogen atmosphere due to the catalytic effect of Co on the carbonation reaction. The effects of heat treatment temperature on phase constituents of powders were investigated in a range of 700～900 ℃. Morphology and microstructure of powders were observed by SEM and HRTEM. The results indicate that the morphology of powder is spherical. The grain size of WC is about 0.36 μm, and the crystalline size of WC is about 56 nm, which indicates that the WC grain is polycrystalline and composed of many crystallites. It is also found that the individual particles of WC are bonded together under the action of Co. Furthermore, a few sintering necks could be observed in the composite powders due to the contacts between WC particles. The stoichiometry of WC-Co composite powders could be adjusted easily. Moreover, the formation process and mechanism of the sphere structure were also discussed in this paper.