纳米钨粉的制备及其表征

以钨酸和氨水为原料，采用液氮预冻-冷冻干燥-两段还原方法制备获得了30nm的纳米W粉末。并对粉末制备过程中的各阶段产物进行了表征：采用XRD、SEM、FESEM对冻干粉、一次还原粉和二次还原粉的物相组成和形貌进行了分析。结果表明，冻干粉是呈现非晶态的，粉末呈絮状团聚在一起，没有明显的颗粒形貌，表面平滑。一次还原粉末也是呈现非晶态，疏松的海绵体结构。最终产物是晶态的W粉，粒度分布均匀。红外光谱分析结果表明，冻干粉末仍保持Keggin结构；热分析表明，冻干粉分三个阶段失去其吸附水、结晶水、结构水。

Preparation and characterization of tungsten nanopowder

The synthesis of tungsten nanopowder plays a key role in the preparation of the relevant alloys. In this paper, the nanopowder tungsten were prepared by liquid N2 freezing, freeze drying, and two-stage reduction. The particle size of the powder produced is about 30nm. The transformation in phase composition during the producing process of nanopowder was studied by XRD. The appearance of freeze-dried powder, first-reduced powder, and nanopowder was analyzed by SEM and FESEM. It is proven that most of the powder exist in the non-hygroscopic and non-crystalline state. And the final product of the experiments is the tungsten powder, which exists in the form of crystalline state. The result of IR analysis indicates that the freeze-dried powder remains Keggin structure. In addition, through TG and DTA thermal analysis, it is shown that the loss process of water contained in the powder could be divided into three stages.