Electrochemical formation of holmium-cobalt alloys

The electrochemical formation processes of holmium-cobalt alloys on cobaltcathode in molten HoCl_3-KCl were investigated by cyclic voltammetry and open current potential-timecurve alter potentiostatic electrolysis. The structure of Ho-Co alloys' films deposited on cobaltelectrode by potentiostatic electrolysis was characterized by X-ray diffraction. The standard Gibbsfree energies of formation for the intermetallic compounds of Ho and Co were determined. Thediffusion coefficient and diffusion activation energy of Ho atom in the alloy phase were calculatedto be 10^(-10) -10^(-11) cm^2/s and 96.0 kJ/mol, respectively, from the current-time curve atpotential step.

Electrochemical formation of Mg-La-Mn alloys by coreduction of Mg(Ⅱ),La(Ⅲ)and Mn(Ⅱ)in LiCl+KCl molten salts

In the present work,cyclic voltammetry(CV),square wave voltammetry(SWV)and chronopotentiometry(CP)were used to investigate the electrochemical coreduction behaviors of La(Ⅲ)and Mg(Ⅱ)as well as La(Ⅲ),Mg(Ⅱ)and Mn(Ⅱ)on Mo electrode in LiCl+KCl molten salts.CV and SWV results exhibit that the coreduction mechanism of La(Ⅲ)and Mg(Ⅱ)on Mo electrode is that La(Ⅲ)is reduced and Mg-La intermetallic compound is formed,leading to the deposition potential of La(Ⅲ)shifting to more positive one.The electrochemical signals pertaining to the formation of metallic La,Mg and Mn as well as Mg-La intermetallic compound are also observed by coreduction of La(Ⅲ),Mg(Ⅱ),and Mn(Ⅱ)in LiCl+KCl molten salt on the inert Mo electrode.However,the electrochemical signals associated with the formation of La-Mn and Mg-Mn alloys are not observed,which means that the depolarization effect of La(Ⅲ)and Mg(Ⅱ)does not occur on pre-deposited Mn electrode.The Mg-La-Mn alloys were formed by co-deposition of La(Ⅲ),Mg(Ⅱ),and Mn(Ⅱ)on Mo electrode at various concentration ratios of La(Ⅲ)and Mg(Ⅱ).The results of scanning electron microscopy equipped with energy dispersive spectroscopy and X-ray diffraction displays that the Mg-La-Mn alloys are comprised of La-Mg compound Mg_(17)La_(2),Mg and Mn phases.The concentration ratio of La(Ⅲ)and Mn(Ⅱ)has few effects on the alloy composition.

A new electrochemical preparation method for formation Sm-Al alloys on inert Mo electrode from Sm_2O_3 in LiCl-KCl-MgCl_2 -KF molten salts

This work presents a new method for preparation of samarium alloy. Using A1 rod as anode, electrochemical formation of Sm-A1 alloy on Mo electrode from Sm203 in LiC1- KC1-MgC12-KF molten salts was investigated. Samarium mainly exists in the form of A12Sm in Li-Mg matrix, and the concentration of Sm in this alloy runs up to be as high as 34.7%. The reaction of samarium preparation appears like a replacement reaction. The new preparation method makes possible a high samarium content in electrochemical deposition of Sm-A1 alloy. Using A1 rod as anode consumedly decreased, the electrolytic cell voltage, and facilitated Sm deposition from Sm203. This preparation method uses 8m203 as raw materials to gain samarium alloy directly, which could revolutionize the industrial production of samarium alloys.

Electrochemical behavior of Y(Ⅲ) and preparation of Y-Ni intermetallic compounds in molten LiCl-KCl salts

The work concerned the electrochemical behaviors of Y（Ⅲ） on W and Ni electrodes in molten LiCl-KCl salts by a series of electrochemical techniques. The electrochemical reaction of Y（Ⅲ） to Y（0） proceeded in a one-step reduction process with the exchange of three electrons, Y（Ⅲ）＋3e^–→Y（0）. Compared with the cyclic voltammogram and square wave voltammogram obtained on W electrode, the reduction potential of Y（Ⅲ） on Ni electrode was observed at less negative potential than the one of Y（Ⅲ） to give pure Y metal on W electrode, which revealed the occurrence of underpotential deposition of Y（Ⅲ） on Ni electrode. Electromotive force（emf） measurements were performed to calculate the relative partial molar Gibbs energies and activities of Y in Y-Ni alloys. The standard Gibbs energies of formation for different Y-Ni intermetallic compounds were also estimated. The different Y-Ni alloys were formed by potentiostatic electrolysis at different potentials and characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and energy dispersive spectrometry（EDS）. It was found that four intermetallic compounds, YNi5, Y2Ni7, YNi3 and YNi2, were selectively produced by controlling applied potential.

Electrochemical behavior of Dy(Ⅲ) on bismuth film electrode in eutectic LiCl-KCl melts

An electrochemical study of dysprosium（III） on Bi film electrode was carried out in eutectic LiCl-KCI melts by transient and steady state electrochemical techniques.The results of transient electrochemical techniques showed that the reduction of Dy（III） appears at a more positive value than the one detected on W electrode owing to the formation of Bi-Dy intermetallic compounds through electrochemical deposition of Dy on bismuth film electrode.The thermodynamic properties of the formation for Dy-Bi intermetallics were estimated by a steady state electrochemical method in a temperature range of 713-803 K.Furthermore,the electrochemical preparation of Bi-Dy alloys was conducted by galvanostatic electrolysis at different current intensities.The Bi-Dy alloys,characterized by scanning electron microscopy equipped with energy dispersive spectrometry and X-ray diffraction,are comprised of DyBi3/5 and DyBi phases

Electrochemical Behaviour of Magnesium（Ⅱ） on Ni Electrode in LiCl-KCl Eutectic

The electrochemical behaviour of magnesium（Ⅱ） and the formation mechanism of Mg-Ni alloys on Ni electrode were studied in LiCl-KCl eutectic using various electrochemical techniques. Cyclic voltammogram and square-wave voltammogram revealed that under-potential deposition of magnesium occurred on Ni electrode because Mg-Ni alloy compounds were formed. The thermodynamic properties of the Mg-Ni intermetaUics, Mg2Ni and MgNi2, were determined using open circuit chronopotentiometry in the temperature range of 8186893 K. Moreover, the Mg-Ni alloys were produced by potentiostatic and galvanostatic electrolysis under different conditions and characterized by means of scanning electron microscopy（SEM） equipped with energy dispersive spectrometry（EDS） and X-ray diffraction（XRD）. The experimental results indicate that Mg-Ni intermetaUic compounds can be selectively produced by potentiostatic electrolysis.

Electrochemical co-reduction of holmium and magnesium ions in eutectic LiCl-KCl salts

The electrochemical co-reduction of Ho(Ⅲ)and Mg(Ⅱ)ions was investigated on Mo electrode in eutectic LiCl–KCl salts at temperature of 773 K using various electrochemical techniques.Cyclic voltammogram(CV)and square wave voltammogram exhibit three reduction peaks corresponding to the reduction of Ho(Ⅲ)on pre-deposited Mg electrode,whose potentials are more positive than that of Ho on Mo electrode because of the formation of Mg-Ho intermetallic compounds by co-reduction of Ho(Ⅲ)and Mg(Ⅱ)ions.Meanwhile,chronopotentiometry and open-circuit chronopotentiometry were used to explore the electrochemical formation of Mg–Ho intermetallics.Mg–Ho alloys were produced by galvanostatic electrolysis at the current of 1.5 A for different electrolysis durations.Ho_(5)Mg_(24),HoMg_(2) and HoMg intermetallic compounds were acquired and characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM)coupled with energy-dispersive spectroscopy(EDS).The results indicate that Mg–Ho intermetallic compounds,Ho_(5)Mg_(24),HoMg_(2) and HoMg,could be prepared by molten salts electrolysis.

Fluorination reaction of UO_(3)and electrochemical preparation of UO_(2)

In this work,a technique was proposed to prepare UO_(2)from UO_(3)by the two processes of fluorination reaction of UO_(3)with NH_(4)HF_(2)and electrochemical reduction of UO_(2)^(2+)for the recycle uranium.The feasibility of fluorination reaction was firstly confirmed using thermodynamic calculation;then,the products were analyzed using XRD,Raman and fluorescence to be UO_(2)F_(2).The fluorination mechanism was inferred to be UO_(3)(s)+NH_(4)HF_(2)→(NH_(4))_(3)UO_(2)F_(5)→NH_(4)(UO_(2))_(2)F_(5)→UO_(2)F_(2).The redox behavior of UO_(2)^(2+)on W electrode was investigated by cyclic voltammetry and square wave voltammetry,which indicated that UO_(2)^(2+) was reduced to UO_(2)via a two-step single electron transfer with diffusion-controlled.The diffusion coefficient of UO_(2)^(2+) was calculated to be 6.22×10^(-5)cm/s.The disproportionation reaction of UO_(2)^(+) was observed,and the relationship between the disproportionation reaction and scan rate was discussed.Moreover,the electrochemical fabrication of UO_(2) was conducted by electrolysis at-0.8 V,and the product was analyzed by XRD,SEM and EDS to be UO_(2).ICP-AES results showed that the extraction efficiency of UO_(2) could reach 98.53%.

Progress in preparation of rare earth metals and alloys by electrodeposition in molten salts

Rare earth（RE） metals and their alloys have attracted considerable practical interests due to their functional properties. Because of their negative deposition potentials, RE metals cannot be electrochemically deposited from aqueous media. Using molten salt as medium provides a unique opportunity for the electrowinning and electrorefining of high-purity RE metals, as well as for the electrochemical formation of their alloys and intermetallic compounds. Certainly, the electrochemical behaviors of RE metals and their alloys have been investigated in a number of different molten salts comprising all-fiuorides,all-chlorides and mixed chloride-fiuoride media. Based on the results, RE and their alloys were produced by molten salt electrolysis. In this paper, the developments of preparation of RE metals and their alloys by electrolysis in molten salts in recent years were systematically summarized on both the local and international levels. Attention was paid mainly to the electrodeposition of RE metals and their alloys, including RE-Mg, RE-Al, RE-Ni, RE-Co,RE-Cu, RE-Fe and RE-Zn alloys.