Study On Preparation And Performance Of Rare Earth Composite Coating By Electroless Plating In Absolute Ethanol

In recent years,electroless plating has become the protagonist of surface modification technology,and its application prospects are very broad.There are two types of electroless plating baths,one is an aqueous system and the other is a non-aqueous system(DMF and absolute ethanol etc.).In this paper,Eu-Ni-B rare earth composite coatings and Eu-Co-Ni-B rare earth composite coatings(Eu-Ni-B coatings and Eu-Co-Ni-B coatings)are successfully prepared on copper substrates by using non-aqueous system(absolute ethanol as solvent)through low-temperature electroless plating technology.The bath composition is improved by single factor experiment,gradient experiment and orthogonal experiment with the deposition rate as the index.The coatings is analyzed by modern instruments(SEM,EDS and XRD,etc.).Discuss the anti-corrosion ability of the coating at different heat treatment temperatures.The Eu-Ni-B coating and Eu-Co-Ni-B coating are used as working electrodes to prepare Na BH₄ by electrochemical technology.The results show that:(1)Bath composition and electroless plating temperature are improved through single factor experiment,orthogonal experiment and gradient experiment.Bath composition and electroless plating temperature of the Eu-Ni-B coating:anhydrous nickel chloride 10 g/L,DMAB 8 g/L,citric acid 1.3 g/L,sodium hydroxide 1.0 g/L,europium nitrate 3.2 g/L,malic acid 1.5 g/L and adipic acid 1.5g/L,the electroless plating temperature is 37±1°C.Bath composition and electroless plating temperature of Eu-Co-Ni-B coating:anhydrous nickel chloride 10 g/L,anhydrous cobalt chloride 0.6 g/L,DMAB 9 g/L,citric acid 1.5 g/L,sodium hydroxide 0.8 g/L,europium nitrate 3.4 g/L,malic acid 1.5 g/L and adipic acid 1.5g/L,electroless plating temperature is 40±1°C.(2)A variety of characterization techniques proved that Eu-Ni-B and Eu-Co-Ni-B coatings are successfully prepared.(3)The EC model of Eu-Ni-B coating and Eu-Co-Ni-B coating is researched by EIS technology using 3%Na Cl solution as the corrosive medium.Both equivalent circuit belong to the R(C)R model,and the Nyquist diagrams of the two are consistent,which indicates that the two have the same or similar corrosion mechanism.(4)The Eu-Ni-B coating is an amorphous nanocrystalline multiphase structure,and the Eu-Co-Ni-B coating is an amorphous structure.The anti-corrosion ability of the coating can be improved by heat treatment.The anti-corrosion ability of the coating was discussed in Na Cl and Na OH solutions.The Eu-Ni-B-600 coating has excellent anti-corrosion ability,while the Eu-Co-Ni-B-400 coating has excellent anti-corrosion ability.(5)LSV technique is used to determine the peak current values at different concentrations of sodium borohydride,and the linear regression equation is established(y=0.00525x+0.00445,R²=0.98).(6)Sodium borohydride is prepared by electrochemical reduction using 1 mol/L Na OH+0.5 mol/L Na BO₂ and 1 mol/L Na OH systems.Eu-Ni-B coating as the working electrode:Sodium borohydride has the largest output,its value is 1.63×10^-4 mol/L,when the forward pulse voltage is-1.2V,the reverse pulse voltage is+0.5 V,the forward pulse during is 2 s and the reverse pulse during is 2 s.Eu-Co-Ni-B coating as the working electrode:Sodium borohydride has the largest output,its value is 1.25×10^-4 mol/L,when the forward pulse voltage is-1.5V,the reverse pulse voltage is+0.5 V,the forward pulse during is 1 s and the reverse pulse during is 2 s.(7)The successful preparation of sodium borohydride is once again proved by comparing the cyclic voltammetry curve of the electrolyte after electrochemical reduction and that of the electrolyte containing sodium borohydride.