论文标题:聚氨酯海绵基体低磷化学镀镍工艺及机理研究
A Theoretical and Experimental Study on Keyhole Effects in Laser Deep Penetration Welding
论文作者 曾建皇
论文导师 陈范才,论文学位 硕士,论文专业 材料学
论文单位 湖南大学,点击次数 121,论文页数 75页File Size2071k
2002-03-01论文网 http://www.lw23.com/lunwen_152159092/ 化学镀镍;低磷;聚氨酯海绵;机理
electroless nickel;low phosphorus content;polyurethane foam substrate;mechanism
本文采用聚氨酯海绵为基体材料，以次磷酸钠为还原剂，在碱性化学镀镍溶液中对低磷化学镀镍磷合金工艺进行了详细的研究。同时，本文还采取线性电位扫描研究方法，对化学镀镍沉积过程中磷析出的可能机理进行了初步的探讨。 在制备泡沫镍材料的过程中，首先要求在聚氨酯海绵基体上低磷化学镀镍制备导电层。本文针对聚氨酯海绵基体的特殊性，研究并确定了合适的前处理工艺和镀层成分镍和磷分析的分光光度法。 降低化学镀镍镀层磷含量的主要方法是选择合适的络合剂。对于以聚氨酯海绵为基体的化学镀镍，研究认为，三乙醇胺是较好的选择。本研究采用正交试验方法，筛选并确定了镀层磷含量为1.5％的最佳低磷化学镀镍配方，并研究了硫酸镍浓度、次磷酸钠浓度、三乙醇胺浓度和温度对镀层磷含量的影响。 运用线性电位扫描法，研究了含有不同络合剂的化学镀镍溶液中镍离子阴极还原行为和次磷酸盐阳极氧化行为。研究认为，化学镀镍阴、阳极各分步反应之间存在强烈的影响。对于阴极过程，镍离子放电和氢气析出过程存在耦合，氢气的析出可能掩盖了线性电位扫描曲线上镍还原的电流峰。络合剂对镍离子的络合能力越强，镍阴极还原的起始电位越负。本论文还提出了化学镀镍的可能机理。
An electroless nickel process with sodium hypophosphite as reducing agents in alkaline bath, which is applied on polyurethane foam substrate, was studied in detail in this paper. Least sweep voltammetry was employed to investigate preliminarily into probable mechanism on phosphorus incorporation into deposits.As an initial stage on the process of foamed nickel preparation, a layer with low phosphorus content nickel deposit is applied on polyurethane foam substrate as a conducting layer. In view of particular characteristics of polyurethane foam substrate, the paper designed a suitable pre-treatment process and feasible spectrophotometric determining phosphorus and nickel content in deposits.An effective way to reduce phosphorus content in electroless nickel deposits is to use appropriate complexing agents. Triethanolamine was considered as a desirable complexing agent to reduce phosphorus content in electroless nickel deposits applied on polyurethane foam substrate. Othogonal testing method was employed to screen electroless nickel bath composition producing deposits with phosphorus content of wtl.5%. The paper also discussed the effects of Ni2+ concentration, H2PO2- concentration, triethanolamine concentration and bath temperature on phosphorus content of electroless nickel deposits respectively.Least sweep voltammetry method was employed to study H2PO2- anodic oxidation and Ni2+ cathodic reduction in electroless nickel plating solutions containing different complexing agents. Experimental results showed that strong interactions existed between partial reduction and oxidation reactions. For the cathodic process it is likely that there exists a coupling between Ni2+ discharge and hydrogen evolution. Hydrogen evolution on working electrode should have masked the nickel ion reduction peak in LSV curve. The stronger the complexing agent, the more negative the initial potential on which nickel ion discharges. Probable mechanism on electroless plating is proposed in this paper.
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