中文摘要：

以平均粒径40 nm的W粉为原料,采用“预碳化＋二段碳化”的阶段碳化工艺制备出平均粒径为82 nm的近球形WC粉。利用X射线衍射（XRD）、场发射扫描电镜（FE-SEM）、BET比表面积分析仪等测试方法,分别对碳化产物的物相组成、形貌和粒径大小进行表征。研究了不同预碳化温度和二段碳化温度对WC粉粒径和形貌的影响,并对阶段碳化的机制进行了讨论。结果表明,在800~1000℃范围内,WC粉的平均粒径随预碳化温度升高呈先减小后增大的变化趋势,在900℃达到最小值。WC粉的平均粒径随二段碳化温度升高而增大,当二段碳化温度高于1250℃时,WC粉的平均粒径显著增大。碳化过程中WC颗粒的长大主要是由碳化初期纳米W颗粒的烧结合并引起的。低温预碳化能够在W粉颗粒表面形成一定厚度的WC层,阻碍W粉颗粒发生烧结合并,从而有效抑制WC粉的长大。阶段碳化制备纳米WC粉的最佳工艺为：预碳化温度900℃,二段碳化温度1150~1200℃。

英文摘要：

Tungsten carbide nano-powders were prepared from tungsten nano-powders with the average particle size of 40 nm by two- stage carbonization method, which included pre-carbonization and second-stage carbonization process. The phase composition, mor- phology and particle size of carbonization products were investigated by X-ray diffraction （XRD） , field emission scanning electronic microscope （FE-SEM） and BET surface area measurement, respectively. The effects of pre-carbonization and second-stage carboniza- tion temperatures on the size and morphology of WC particles were studied. The mechanism of two-stage carbonization was discussed. The results showed that the mean size of WC particles first decreased and then increased with the pre-carbonization temperature （ 800 1000 ℃ ） rising. The WC particles had the smallest size when pre-carbonization temperature was 900 ℃. The mean size of WC parti- cles increased with the second-stage carbonization temperature rising, whereas it showed the average particle size increased when the carbonization temperature was above 1250 ℃. The increase of WC particles size was caused by sintering conlbination of W nano-pow- ders in the initial stage of carbonization process. There would be formed thin WC layers on the surface of W particles during the low temperature pre-carbonization process, which could hinder the sintering combination of W, therefore, the growth of WC nano-powders was inhibited. The optimum two-stage carbonization process was the pre-carbonization temperature of 900 ℃ and second-stage carboni- zation temperature of 1150- 1200 ℃.