粒度分级对TiB2惰性阴极涂层导电性能影响研究

Influence of size classification on conductivity of TiB_2 inert cathode coating

采用等离子喷涂法制备不同粒度的TiB_2惰性阴极涂层,利用双电测四探针法测量粒度分级下TiB_2涂层的电阻率,研究粒度分级对涂层电阻率的影响。结果表明:涂层的电阻率与喷涂的粒度有很大的关系,当喷涂TiB_2粉末粒度在-325^+400目范围内导电性最好,电阻率最小,低至19.66 mΩ·cm。并对粒度分级下TiB_2涂层进行微观形貌、XRD分析,探究粒度分级下微观组织形貌与电阻率的关系,结果显示:粒度在-325^+400目范围涂层内部结构最致密,行核率最高,造成组织弥散强化,颗粒熔化较好,孔隙率减小,从而使电阻率减小,导电性提高;同时喷涂过程中氧化产物引起的润湿角差异影响熔滴的铺展、扁平化导致孔隙的再现,使涂层孔隙率增加,致密度下降,电导率降低。

In this paper the influence of size classification on conductivity of TiB2 inert cathode coating is researched by Dual -configuration four- point probe method, which the TiB2 inert cathode coating of different size is prepared by the plasma spraying. The result shows there is relationship between the resistivity of the coating and spaying particle size, the resistivity of the coating from - 325 mesh to ＋ 400 mesh is the lowest of 19.66mΩ·cm. The relationship between the micro - morphology and resistivity under different particle size is investigated by micro - morphology and XRD. The result shows that the internal structure of the coating from -325mesh to ＋ 400mesh is feature with the most dense, the highest nucleation rate, the structure of dispersion strengthening, better melted particles and decreased porosity rate, so the resistivity of coating is reduced and conductivity is increased. Which the wetting angle difference caused by oxidation product during spaying process has influence on droplet spread, flat leads to porosity reproduction and the density decrease, so that the conductivity of coating decreases.