化学镀法制备Ni/TiH2复合粉末的显微组织及其Ni镀层的生长和作用机理

Microstructure characterization and mechanism of Ni-coated TiH2composite powders prepared by electroless plating

采用化学镀法对TiH2粉末表面镀Ni,制备Ni/TiH2复合粉末。通过X射线衍射（XRD）、扫描电镜（SEM）、能谱分析（EDS）及差热分析（DSC/TG）对Ni/TiH2复合粉末进行表征,探索Ni镀层的生长及作用机理,建立镀层在粉末表面的生长模型。结果表明：施镀温度为85℃时Ni/TiH2复合粉末表面Ni层包覆完整,镀层均匀致密,Ni层厚度约为1.0~2.0μm;施镀温度低于65℃时施镀几乎无法进行,而施镀温度高于95℃时,镀层很不均匀,且容易脱落;镀层的生长机制遵循奥斯特瓦尔德（Ostwald ripening）机制;与包覆前TiH2粉末相比,Ni/TiH2复合粉末的释氢反应开始温度由450℃上升至540℃。包覆层可降低TiH2粉末和熔融铝的温度梯度,从而推迟开始释氢的时间。

The Ni-coated TiH2 composite powder was prepared by electroless plating.The morphology,composition and hydrogen releasing performance were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,energy dispersion spectroscopy（EDS） and differential thermal analysis（DSC＋TG）.The plated Ni layer growth and action mechanism were explored preliminary,the growth model of the synthesis path on the powder surface was established.The results show that Ni coating layer with a average thickness of about 1.0～2.0 μm can be successfully prepared by electroless plating.When the plating temperature is 85 ℃,the coating is dense and uniform;while the temperature is over 95 ℃ or below 65 ℃,the plating is ineffective and the coating will be nonuniform and falling off easily.The growth mechanism of the coating follows the Ostwald ripening mechanism.Compared with the particles of TiH2uncoated with Ni layers,the hydrogen releasing reaction temperature of Ni-coated TiH2composite powder increases from 450 ℃ to 540 ℃.The coating can reduce the temperature gradient between TiH2 powder and molten aluminum and delays the hydrogen releasing time.