| In this paper,Pb-based alloys were prepared by molten salt electrolysis,and the electrochemical behavior of Pb???co-deposition with Pr,Sm,Gd and Ca to prepare Pb-Pr,Pb-Sm and Pb-Gd-Ca alloys were investigated.The electrochemical measurement methods such as cyclic voltammetry,square wave voltammetry and open circuit chronopotentiometry have been used to study the redox mechanism of molten salt system of LiCl-KCl-PbCl2-PrCl3,LiCl-KCl-PbCl2-SmCl3 and LiCl-KCl-PbCl2-GdCl3-CaCl2.The test results show that Pb???could co-deposited with Pr???,Sm???,Gd???and Ca???ions to form Pb-based compounds in molten salt system.The Pb–Pr,Pb–Sm,Pb–Gd–Ca alloys were prepared by potentiometric electrolysis,and the alloy samples were characterized and analyzed by XRD,SEM and EDS.The electrochemical behavior of Pb???was studied by cyclic voltammetry and square wave voltammetry in LiCl–KCl molten salt system on Mo electrode at 823 K.Then cyclic voltammogram,square wave voltammogram,open circuit transient curve,chronopotentiometry were used to study the deposition mechanism of Pr???and Sm???in the LiCl–KCl–PrCl3 and LiCl-KCl-SmCl3 molten salt system on Pb cathode.On Mo electrode,by calculating the number of transfer electrons of Pr???and Sm???,it is known that Pr???ions were reduced to metal Pris a reversible reaction by one-step three-electron transfer,and the process is diffusion control.The diffusion coefficient of Pr???was 1.11×10-5cm2·s-1.On Mo electrode,when the electrode potentials were–1.29 V,-1.37 V and–1.42 V,the precipitation of the three Pb–Pr alloys corresponded.The data of the Sm???/Sm???process are calculated.The results show that Sm???is reduced to metal Sm after two-step electron transfer,Sm???to Sm???is reversible,and is controlled by diffusion.The diffusion coefficient of Sm???is 1.53×10-5 cm2·s-1.On the Mo electrode,when the electrode potentials were-1.68 V,-1.89 V,and-2.01 V,the precipitation of the three Pb–Sm alloys corresponded.The Pb–Pr alloy and Pb–Sm alloy were obtained by constant voltage electrolysis for 3 h,respectively.The morphology and composition of the alloys were analyzed by XRD,SEM and EDS.In this experiment,the Pb–Gd–Ca alloy was formed by co-depositing Pb,Gd and Ca on the Mo electrode in LiCl–KCl–PbCl2–GdCl3–CaCl2 molten salt system at 900 K.The cyclic voltammograms show that the starting potential of Pb,Gd,and Ca eutectic in the LiCl–KCl–PbCl2–GdCl3–CaCl2 molten salt system is-2.30 V.When the applied potential is greater than-2.30 V,Pb,Ca,and Gd will co-deposition.The Pb–Gd–Ca alloy was obtained by constant voltage electrolysis for 3 h,and the morphology and composition of the alloy were analyzed by XRD,SEM,and EDS.Use the electrochemical methods of cyclic voltammetry,square wave voltammetry and open chronopotentiometry in the LiCl–KCl–PbCl2–LnCl3 molten salt system,the electroanalysis of 823 K lanthanoid elements on the Pb cathode was studied.From the open chronopotential curve,the precipitation potentials of seven kinds of rare earth-forming lead alloys were obtained.These deposition potential data were plotted against the atomic number of rare earths and found to be similar to the curve of rare earth atomic radius,with peaks appearing at Eu and Yb.It shows that the evolution law of the precipitation potential of lanthanide elements on the lead cathode shows a Bimodal effect.Based on this,we found a mathematical equation for the relationship between the precipitation potential of a rare earth lead alloy and the radius of a rare earth through mathematical simulations:1/E×?r2/r1?3=0.0049?x1Inx1+x2Inx2?-0.69Among them,the formula E is the precipitation potential?unit:V?of the lanthanoid element on the lead cathode,r1,r2 are the atomic radius of Pb and the atomic radius of the lanthanoid element?unit:nm?.The significance of this equation is that if we know the radius of a certain element,we can calculate the precipitation potential of alloying with lead,which will increase the theoretical basis for the preparation of new intermetallic compounds. |
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