JOURNAL OF THE ELECTROCHEMICAL SOCIETY
·
2018
·Vol. 165
·期 11
·E616
·
IF 3.662
Junfeng Li,Mingyong Wang,Jiguo Tu,Shuqiang Jiao
The direct preparation of metallic Sm or alloys from raw oxide Sm2O3 is an attracting but challenging process. The stable electrochemical behavior and low solubility of Sm2O3 limit the extraction of Sm element in molten salts. Here, it is found that metallic Sm is hardly obtained by electro-deoxidation and aluminothermic reduction of solid Sm2O3 pellet according to experiment and calculation. Through the novel electrochemical reduction of solid Sm2O3-Al pellet, Al3Sm alloy with ∼0.4 Sm/Al molar ratio is successfully prepared in calcium chloride melt at 1173 K. The reduction potential of Sm2O3-Al pellet to Al-Sm alloy is more positive than that of calcium. Al plays an indispensable role in the reduction of Sm2O3. The preparation process of alloy can be well identified as two steps: Sm(III) → Sm(II) and Sm(II) → Sm(0). Sm2O3 is firstly converted to Sm(II) based on the combination of electrochemical and aluminothermic reduction. Then, Al3Sm is formed by electrochemical reduction and alloying with Al.
研究领域:
材料科学
·
电化学
·
冶金学
✓ 已验证
产品关联
DOI
高影响因子
ELECTROCHIMICA ACTA
·
2021
·
IF 6.901
Na Li,Yaru Peng,Zeng Chen,Wenjuan Xiong,Jiaqi Sun,Yiming Chen,Putao Zhang,Meiyue Liu,Shengjun Li
The electro-deoxidation of MgO does not proceed efficiently due to the electrical insulation properties of MgO and large molar volume of metallic magnesium. In this experiment, an attempt was done to prepare Mg-Zr alloy from their oxides using the method of electro-deoxidation. The electrochemical mechanism of the deoxidation process of MgO, ZrO 2 and MgO-ZrO 2 composite was studied through cyclic voltammetry using metallic cavity electrode (MCE). There was an intermediate phase (Zr 3 O) in the reduction process of ZrO 2 . The electro-deoxidation of MgO occurred for MgO-ZrO 2 composite in CaCl 2 -NaCl molten salt. Moreover, the electro-deoxidation of MgO was promoted by the addition of polyvinyl butyral (PVB). The formation of metal phase Mg was confirmed by XRD, EDS, Raman spectroscopy, and inductively-coupled plasma spectroscopy. The electro-deoxidation products showed significant differences with the concentration of PVB and the ratio between MgO and ZrO 2 . The electro-deoxidation of MgO and ZrO 2 was favorable when the PVB concentration was 5.0% (wt.%). Pure metal phase of Mg-Zr alloys was formed when the molar ratio of MgO and ZrO 2 was 1:2. The atomic fraction of Mg in the electrolytic product was ca. 28.0 mol.%. This work shows that MgO could be directly electro-deoxidized to Mg without the formation of intermediate phase oxide.
研究领域:
材料科学
·
冶金工程
·
无机化学
·
电化学
·
金属合金制备
✓ 已验证
DOI
高影响因子
ELECTROCHIMICA ACTA
·
2025
·
IF 5.6
Longdi Ma,Yinxiang Han,Xiwen Chen,Yuran Chen,Liqiang Wang,Yangyang Fan,Xuemin Liang,Yapeng Kong
The molten salts electro-deoxidation process, also known as the FFC-Cambridge process, offers substantial potential for the environmentally friendly synthesis of niobium powder in a relatively short process. However, this process suffers from uncontrolled intermediate particle coarsening and the resultant sluggish oxygen-ion diffusion kinetics. To address this, we engineered a novel hierarchically porous Nb 2 O 5 (HPS-Nb 2 O 5 ) cathode with interconnected macropores (∼10 2 μm), mesopores (∼10 1 μm), and micropores (submicron). Electrochemical analyses coupled with potentiostatic electrolysis reveal a four-step reduction pathway of Nb 2 O 5 in molten Na 3 AlF 6 -K 3 AlF 6 -AlF 3 salts: Nb 2 O 5 →Na 2 Nb 8 O 21 /NbO 2 →NbO→Nb, where solid-state oxygen diffusion remains rate-limiting. The novel cathode pore architecture optimizes the solid-liquid interfaces between the cathode and the electrolyte, facilitating uniform insertion of Na⁺/F⁻ ions into cathode particles to generate intermediate particles. Consequently, rhombohedral Na 2 Nb 8 O 21 intermediate with uniform size and morphology was formed, thereby effectively preventing the excessive coarsening of intermediate particles and associated oxygen diffusion path elongation that occurs in the conventional electro-deoxidation processes. Remarkably, complete reduction of 1 g Nb 2 O 5 to Nb powder was achieved in only 1.5 h at 2.5 V. This represents an 8-13-fold efficiency enhancement over the reported processes. The resultant niobium powder exhibits uniform submicron particles (200–500 nm) with near-spherical morphology. This pore-structure-regulated strategy overcomes fundamental bottlenecks in the FFC process and offers broad applicability for the efficient preparation of diverse refractory metals and alloys.
研究领域:
材料科学
·
电化学
·
冶金学
·
纳米技术
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS
·
2025
·
IF 4.6
Yapeng Kong,Xiwen Chen,Longdi Ma,Yinxiang Han,Yuran Chen,Liqiang Wang,Yangyang Fan,Xuemin Liang
The molten salt electro-deoxidation, i.e. the FFC (Fray-Farthing-Chen) process, demonstrates considerable potential for the synthesis of tantalum powder. However, its practical application is hindered by the long electrolysis duration. This study proposes an accelerated electro-deoxidation process in molten Na 3 AlF 6 -AlF 3 salts for preparing ultrafine Ta powder, which achieves a sequential cathode phase transformation from Ta 2 O 5 through intermediate NaTaO 3 to Ta. NaTaO 3 is formed through in situ interfacial reactions between Ta 2 O 5 and the electrolyte. We demonstrate for the first time that the growth of the FFC-type intermediate is driven by nanoparticle assembly and oriented attachment mechanism. This growth mechanism is influenced by the structure of the electrolyte/particle interface. By constructing a novel hierarchical pore structure Ta 2 O 5 cathode with optimized interfaces, we facilitated a microstructurally controllable transformation of Ta 2 O 5 to fine NaTaO 3 , thereby effectively mitigating the elongation of oxygen ions solid diffusion pathway induced by intermediate coarsening. In the case of self-assembled NaTaO 3 , the weak bonding between the nanoparticles also favors the kinetics of their subsequent decomposition into Ta. This approach has been shown to enable the complete reduction of 1 g of Ta 2 O 5 within only 1 h, demonstrating a significant enhancement in process efficiency. The resulting Ta powder exhibits uniform monodisperse morphology and good capacitive behavior in Na 2 SO 4 electrolyte solution. The present study may now guide the way towards establishing the electrochemical route for the efficient preparation of many other refractory powders materials.
研究领域:
材料科学
·
电化学
·
粉末冶金
·
纳米技术
·
无机化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
·
2020
·Vol. 167
·期 8
·082501
·
IF 3.721
Kejia Liu,Yaowu Wang,Yuezhong Di,Jianping Peng,Jing You,Naixiang Feng,Yi Zhang
Diagrams of the equilibrium potential E (relative to the standard chlorine electrode) against the activity of oxide ion ( expressed as its logarithm, pO2−) in systems of Ti-O-Cl-M (M=Li, Na, Mg, Ca, Sr and Ba) were plotted to investigate the electro-deoxidation of porous TiO2 pellets in different chloride molten salts, including LiCl, NaCl, MgCl2, CaCl2, SrCl2 and BaCl2. From the diagrams, the reduction pathways of TiO2 in different molten salts are similar; and the applied potential (vs Cl−/Cl2) on the cathode and O2− ion activity influence greatly on the reduction pathway of TiO2 and the deoxidation limit. To test and verify the results of the thermodynamic analysis, electro-deoxidation experiments in different molten salts were done to determine the actual pathways in the electrochemical reduction of TiO2 and the possible deoxidation limits in the molten salts. The results indicated that the thermodynamic analysis is helpful in predicting and understanding the electrochemical reduction process of titanium oxides though the experimental results differ slightly from the thermodynamic analysis in some systems. Low-oxygen Ti can be obtained only in molten CaCl2.
研究领域:
材料科学
·
电化学
·
冶金学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）