Influence of LaCl3 addition on microstructure and properties of nickel-electroplating coating

The influence of rare earth chloride LaCl3 ·7H2O addition on the microstructural features, phase structure, corrosion resistance and microhardness of nickel-electroplating was investigated. The Watts-type with different additive amounts of LaCl3·7H2O(0-1.2g/L) were used in the experiment. Surface morphologies of coatings were examined by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) was used to measure the coatings’ grain size and the microstructure of coatings was detected by X-ray diffraction (XRD). Corrosive investigation was carried out in 3.5 wt.% NaCl solution. The microhardness values of the coatings with different amounts of LaCl 3·7H2O were measured, and the mechanism of the variation in microhardness was studied. Results showed that the addition of rare earth lanthanum refined the grain size and improved the surface consistency of the coatings, meanwhile the microhardness and corrosion property of coatings were improved and achieved a maximum with arround 1.0g/L LaCl 3·7H2O addition in electrolyte. The preferred growth orientation of lanthanum doped coating was crystal face (200), meanwhile the La2 Ni7 phase was detected in the nickel coating by XRD and this was due to the induced co-deposition of elements La and Ni. The reason maybe was that the special out-layer electronic structure of element La raised the polarization of Ni cathode deposition, accelerated the nucleation of Ni and reduced hydrogen evolution from cathode surface.     

溅射镍钇涂层1000℃高温氧化机理研究

研究了纯镍表面磁控溅射Ni-0.5Y微晶涂层在1000℃空气中的恒温氧化和循环氧化行为。通过扫描电镜(SEM)和透射电镜(TEM)对涂层以及表面NiO氧化膜的形貌和结构进行了研究。结果表明,Ni-0.5Y微晶涂层与基体镍相比有更低的氧化增重速率,表面NiO氧化膜的晶粒尺寸明显减小,膜的高温塑性得以改善。同时,氧化膜内的压应力水平也有所降低,因而改善了NiO氧化膜的粘附性和保护性。磁控溅射涂层的微晶结构以及稀土元素钇的存在均有助于提高涂层的抗高温氧化性能。     

6063铝合金多种阳极氧化封孔膜性能比较

本文针对6063铝合金阳极氧化膜分别进行沸水封孔、高浓度K2Cr2O7封孔、低浓度K2Cr2O7封孔、Ni2+封孔、Ni2+-Co2+封孔、CeCl3封孔。采用场发射扫描电子显微镜(FESEM)观察封孔膜的表面形貌,测试封孔膜的磷-铬酸失重并采用动电位法测氧化膜在NaCl腐蚀介质中Tafel腐蚀极化曲线,结果表明CeCl3封孔膜失重最小,具有良好的耐蚀性,对铝基体具有较好的保护作用。