化学镀镍-高磷合金晶化行为的现场XRD研究

从柠檬酸-酒石酸-乳酸-EDTA混合体系中得到含P 12％(质量比)的化学镀高磷Ni-P合金，其差热曲线显示，在350和420 ℃出现两个放热过程.现场XRD分析结果显示，镀层在300 ℃以下保持非晶态结构，在320 ℃之后开始晶化，首先析出介稳的Ni5P2和Ni12P5相，在360 ℃后开始有稳定的Ni3P和Ni相的衍射峰出现， 400 ℃以上只有Ni3P和Ni相. 325 ℃恒温时，镀层在4 min内保持非晶态的衍射特征，随即析出Ni5P2和Ni12P5相, 并在2 h内基本保持不变. 350 ℃恒温时，析出的Ni5P2和Ni12P5介稳相只存在40 min.实验结果表明, DTA曲线上350 ℃的放热峰不仅有非晶相转变为介稳相的过程，也包含部分介稳相转化为稳定相的过程.

In situ XRD Investigation on the Crystallization Behaviors of Electroless High-Phosphorous Ni-P Alloys

Crystallization behaviors of electroless Ni-P deposits with 12％(w) P were studied by differential thermal analysis (DTA), thermogravimetry (TG) and in situ X-ray diffraction (XRD). The Ni-P alloys were prepared from a bath containing NiSO4 28 g•L－1, NaH2PO2•3H2O 32 g•L－1, C6H8O7•H2O 16 g•L－1,EDTA[CH2N(CH2COOH)2]2 7 g•L－1, C4H4O6 6 g•L－1, NaAc 18 g•L－1, C3H6O3 6 g•L－1, KIO3 0.001 g•L－1, with pH 4.5～5.0， at 90 ℃. The DTA curves of the alloys indicate that there were two exothermic processes at 350 and 420 ℃, respectively, which could be related to the processes of phases change of the alloys as the mass change is less than ±1％ as revealed by the TG curves. The results of in situ XRD show that the structure of the alloy is amorphous when the temperature bellows 300 ℃. The XRD pattern of metastable Ni5P2 and Ni12P phases initially appeared at the temperature over 320 ℃, and disappeared completely at 400 ℃. The XRD peaks belonging to Ni3P and Ni stable phases emerged at 360 ℃. The metastable Ni5P2 and Ni12P5 remained during the testing period of 2 h at 325 ℃, and lasted just for 40 min at 350 ℃ before transferring into the stable phases of Ni3P and Ni. According to the results, the exothermic peak of the DTA curves for the deposits at 350 ℃ should result from the two processes, i.e., the amorphous Ni-P alloys crystallized into metastable Ni5P2 and Ni12P5 phases, and then the metastable phases partially turned into the stable phases of Ni3P and Ni.