Electrodeposition Of Pd-Ni-P Amorphous Alloys And Their Performance

The amorphous alloys have been widely studying due to their excellent mechanical properties and well corrosion resistance.It is very easy to obtain amorphous Pd-Ni-P alloy within a wide composition range.The Pd-Ni-P alloy has unique physical-chemical performance and is a promising material in both engineering and electrocatalytic processes. Although many studies have been carried out on the Pd-Ni-P alloy prepared by physical methods,relatively little done by electrochemical method.Therefore,it is worthwhile to study Pd-Ni-P alloy prepared by simple electrodeposition method and their chemical performance.In this thesis,Pd-Ni-P alloy deposits with various morphology and composition have been prepared by electrodeposition.X-ray diffraction (XRD),scanning electron microscope(SEM),and energy dispersive X-ray(EDX)were employed to characterize phase structure,morphology and composition of the deposits.The thermal stability,corrosion resistance and performance of electroreduction nitrate of amorphous Pd-Ni-P deposits were investigated.And the influence of ultrasound on electrodeposition of the Pd-Ni-P alloys was also studied.The main results are as follows: 1.In the solutions containing PdCl₂ 1.8～5.3 g/L,NiSO₄·6H₂O 10 100 g/L,H₃PO₃ 10～40 g/L,H₃BO₃ 20 g/L,ethylene diamine 3 16 g/L,pH 4.0,50℃,Pd-Ni-P alloy films were electrodeposited at 25～100 mA/cm².The results show that the Pd-Ni-P alloys with different composition and morphologies can obtained by controlling the concentration of PdCl₂,NiSO₄·6H₂O or current density.The structures of Pd-Ni-P alloys as-prepared under our experiment conditions are amorphous or microcrystalline structure.2.The amorphous Pd-Ni-P alloy films still keep amorphous state under 300℃heated for 1 h,but they transfer to crystalline state when thermal treated to 350℃for 1 h and form mainly Ni₃P,Ni₂Pd₂P phases.Based on the Tafel curves,the corrosion behaviors of the Pd-Ni-P alloys in 3%NaCl are better than Ni-P alloys.The cyclic voltammetric(CV)results indicated that the activity of electrocatalytic reduction of nitrate on an amorphous Pd₃₃Ni₆₀P₇ alloy deposit is much higher than that of crystal Pd₄₁Ni₅₉alloy in a neutral 0.1 mol/L KClO₄ solution.3.In the solution containing PdCl₂ 3.5 g/L,NiSO₄·6H₂O 10 g/L, H₃PO₃ 20 g/L,H₃BO₃ 20g/L,ethylene diamine 4.6 g/L,pH4.0,50℃,Pd-Ni-P films were prepared by ultrasonic electrodeposition. The results indicated:Pd-Ni-P alloys electrodeposited under ultrasonic condition are also amorphous structure,and the surface morphology become more compact and homogenous and the content of Pd increase.Ultrasound frequency is found to have a significant effect on the morphologies of deposits.The cyclic voltammogram showed that the ultrasonic speed the electrodeposition of Pd-Ni-P alloys,especially that of Pd²⁺ electroreduction.The Tafel curves of the Pd-Ni-P ultrasonic-electrodeposited showed that the corrosion resistance of the alloys is improved in 1.0 mol/L NaOH solution.