Acta Phys. -Chim. Sin. ›› 2003, Vol. 19 ›› Issue (08): 705-708.doi: 10.3866/PKU.WHXB20030806

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

Niu Zhen-Jiang;Wu Ting-Hua;Li Ze-Lin   

  1. Institute of Physical Chemistry, College of Life and Environmental Science, Zhejiang Normal University, Jinhua 321004
  • Received:2003-01-09 Revised:2003-03-18 Published:2003-08-15
  • Contact: Niu Zhen-Jiang E-mail:zjniu@mail.zjnu.net.cn

Abstract: 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.

Key words: Electroless deposition, Ni-P alloy, Crystallization, In situ XRD