【作者】 李秋菊；

【导师】 刘中华；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2003， 硕士

【摘要】 简要介绍了化学复合镀层的应用，详细地分析了化学镀镍磷溶液的组成及其在化学镀中所起的作用和镀液组成及工艺对化学镀镀速和镀层性能的影响，着重研究了化学镀Ni-P合金和化学复合镀Ni-P-纳米Al2O3合金镀层的结构和性能。本实验采用正交实验法优选化学镀工艺参数，得到最佳工艺参数：NiSO4·6H2O 25g／l，NaH2PO2·H2O 25g／l， C3H6O3 20ml／l，CH3COONa 10g／l，CH3COOH 10ml／l，PH为4～5，温度为80～85℃。PH对化学镀镀液、工艺及镀层性能的影响很大，在酸性镀液中，沉积速度随PH值增加而增大，在PH值为4． 5时，镀速达到最大值。继续升高PH，镀液易分解。温度是影响反应动力学的重要参数。温度不仅影响镀速，而且也影响镀层的性能。在镀液温度超过60℃后，镀速随温度上升而迅速增加，当温度超过90℃后，镀液容易分解。在镀液加入乳酸后，与主盐形成稳定的络合离子，防止镀液析出沉淀，增加镀液的稳定性。同时，络合剂的加入，可提高工件的表面活性，从而增强了反应速度。次亚磷酸钠是本实验所选用的还原剂。镀液中次亚磷酸根离子浓度增加，增强了次亚磷酸根的还原能力，因而沉积速度加快。当Ni2+／H2PO2-的摩尔比达到0． 4左右时，镀速达到最大值。本实验选用次亚磷酸根离子浓度为25g／l。继续提高次亚磷酸根离子的浓度，镀速不会加快，相反，会使镀件表面的镀液浓度与镀液内部的浓度不同，形成浓差极化，导致镀液分解。次亚磷酸钠对镀层性能影响，表现在镀层中的磷含量上。显而易见，镀层中磷含量随次亚磷酸根离子的增大而上升。镀层的结构分析采用了X-射线衍射仪和原子能谱仪。结果表明，镍磷镀层在镀态下是一种介稳定的过饱和合金。通过XRD分析，在磷含量低于3％时，镀层主要为微晶结构，随磷含量的增加，镀层结构为微晶与非晶的混合，当含磷量超过12％后，镀层变为非晶结构。随着磷含量增加，镀层结构变化规律为：微晶→微晶+非晶→非晶。昆l归理下人学寸吹_卜学位论文摘要 镍磷镀层是介稳态，对镀层进行加热处理后，介稳态就会向平衡态转变。渡层加热后处理，最终转变为Ni3P和Ni平衡相。镀层由非晶或混晶结构转变为晶体结构。而且加热处理后，可消除镀层的氢脆，提高镀层与基体的结合力。由于热处理后Ni一P合金会析出Ni3P硬质相，镀层的显微硬度由镀态的HV300提高到HV900，而复合镀层由于硬质纳米粒子A1203的存在显微硬度显著提高，由镀态的Hv600提高到HV1050。 镀层在酸性、中性、碱性介质中强化腐蚀。结果表明，两种镀层在碱性介质中的耐蚀性最好，中性次之，在酸性溶液中的耐蚀性最差。研究还表明，高磷的耐蚀性能比低磷的好，这与高磷的非晶组织有关，高磷的非晶结构原子顺序无周期性，结构组织中不存在晶界等缺陷，是单一结构，因此，高磷镀层的耐蚀性好。 化学复合镀由于其优异的耐磨性能和耐高温性能，广泛地应用在各个工业领域。随着材料技术的发展和新材料的出现，不断地丰富化学镀液的种类，为化学镀的进一步发展提供广阔的前景。更多还原

【Abstract】 The functions of electroless composite deposits were introduced in this paper.The solution constitutes and its functions of electroless nickel phosphorus were introduced ,as well as their influence on the rate and properties of the coatings were studied in this paper. The configuration and properties of electroless nickel-phosphorus and electroless nickel-phosphorus composite Al2O3 deposits were investigated.Orthogonal experimentation was used to choose the technical parameter. The bath contained the main constituents: nickel sulfate (25g/l),sodium hypophosphite(25g/l),lactic acid (20ml/l),sodium acetate (10g/l),acetum(10m/l), the bath temperature was kept at 85 ℃ with the PH in range of 4~5.PH had great influence to the solution, technology of electroless nickel-phosphorus and deposits characteristics. In acid solution, the deposit rate increased with the PH rising up and reached maximum when the PH was adjusted to 4.5 .The temperature of the bath was an important dynamic parameter. Temperature affected not only the deposit rate but also the characteristics of the coatings. The rate increased quickly with the temperature exceeding 60℃. When temperature was higher than 90℃, the solution of electroless nickel-phosphorus was easily decomposed.In the bath, lactic acid and nickel ion were created complex compound that made the solution more stable, and the surface of workpiece could be actively increased .The deoxidate capability of sodium hypophosphite could be increased with its concentration going up .The deposits rate reached maximum when Ni2+/H2PO2- reached 0.4, the concentration of hypophosphite was continued going up ,there would be different concentration between the workpiece surface and inner of the bath ,which could induce the bath to decompose .The structure of the deposits was studied using X-ray diffraction technique. The deposits was a metastable supersataration as deposits condition ,whichcould be microcrystalline as the P content below wt3% ,while those in the Higher range were mixture of microcrystalline and amorphous phase, when the P content exceeded 12%,the deposits could be as amorphous. With the P content rising up ,the structure of the deposits was described as :microcrystalline-mixture of microcrystalline and amorphous -amorphous phases.The structure of the deposits was converted from amorphous phase and mixture of microcrystalline and amorphous into crystallization after heat treatment. Through heat treatment,the deposits hydrogen brittleness could be eliminated and the binding energy could be improved. The deposits microhardness was increased from HV300 as deposits condition to HV900 after heat treatment because of horniness precipitate Ni3P , while eletroless nickel-phosphorus composite Al2O3 deposits microhardness was increased from HV600 to HV1050.Deposits were dipped in acidic ,litmusless and alkalescent medium, its corrosion resistance was better in alkalescent medium than in the acidic, and the high P content was better than the low. The result was related to the amorphous phase. The deposits structure of high P content was amorphous which was single-structure ,the deposits was a definite indication of the lattice disorder .With good wear and resistance high temperature ,the composite deposits had been used in many industrial areas. Owing to new materials ,the electroless technology had a triumph prospects.更多还原