Electrochemical preparation of the Fe-Ni36 Invar alloy from a mixed oxides precursor in molten carbonates

Abstract

The Fe-Ni36 alloy was prepared via the one-step electrolysis of a mixed oxides precursor in a molten Na₂CO₃-K₂CO₃ eutectic melt at 750°C, where porous Fe₂O₃-NiO pellets served as the cathode and the Ni10Cu11Fe alloy was an inert anode. During the electrolysis, NiO was preferentially electro-reduced to Ni, then Fe₂O₃ was reduced and simultaneously alloyed with nickel to form the Fe-Ni36 alloy. Different cell voltages were applied to optimize the electrolytic conditions, and a relatively low energy consumption of 2.48 kWhkg⁻¹ for production of FeNi36 alloy was achieved under 1.9 V with a high current efficiency of 94.6%. The particle size of the alloy was found to be much smaller than that of the individual metal. This process provides a low-carbon technology for preparing the Fe-Ni36 alloy via molten carbonates electrolysis.

Keywords

molten carbonates / cyclic voltammetry / electro-reduction / inert anode / Invar36 alloy

References

[1] Callister WD. Materials Science and Engineering: An Introduction, 2007, 7th ed., Hoboken, NJ, John Wiley & Sons, Inc., 1.

[2] Nagayama T, Yamamoto T, Nakamura T, Fujiwara Y. Properties of electrodeposited invar Fe-Ni alloy/SiC composite film. Surf. Coat. Technol., 2017, 322, 70.

[3] Nagayama T, Yamamoto T, Nakamura T. Thermal expansions and mechanical properties of electrodeposited Fe-Ni alloys in the Invar composition range. Electrochim. Acta, 2016, 205, 178.

[4] Sharma SK, Vastola FJ, Walker PL Jr. Reduction of nickel oxide by carbon: III. Kinetic studies of the interaction between nickel oxide and natural graphite. Carbon, 1997, 35(4): 535.

[5] Chen GZ, Fray DJ, Farthing TW. Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride. Nature, 2000, 407(6802): 361.

[6] Abdelkader AM, Kilby KT, Cox A, Fray DJ. DC voltammetry of electro-dexoidation of solid oxides. Chem. Rev., 2013, 113(5): 2863.

[7] Xiao W, Wang DH. The electrochemical reduction processes of solid compounds in high temperature molten salts. Chem. Soc. Rev., 2014, 43(10): 3215.

[8] Ma M, Wang DH, Hu XH, Jin XB, Chen GZ. A direct electrochemical route from ilmenite to hydrogen-storage ferrotitanium alloys. Chem. Eur. J., 2006, 12(19): 5075.

[9] Jiao SQ, Zhang LL, Zhu HM, Fray DJ. Production of NiTi shape memory alloys via electro-deoxidation utilizing an inert anode. Electrochim. Acta, 2010, 55(23): 7016.

[10] Zhu Y, Ma M, Wang DH, Jiang K, Hu XH, Jin XB, Chen GZ. Electrolytic reduction of mixed solid oxides in molten salts for energy efficient production of the TiNi alloy. Chin. Sci. Bull., 2006, 51(20): 2535.

[11] Qiu GH, Wang DH, Jin XB, Chen GZ. Preparation of Tb₂Fe₁₇ by direct electrochemical reduction of Tb₄O₇-Fe₂O₃ pellet in molten calcium chloride. Acta Metall. Sinica, 2008, 44(7): 859.

[12] Zhu Y, Wang DH, Ma M, Hu XH, Jin XB, Chen GZ. More affordable electrolytic LaNi₅-type hydrogen storage powders. Chem. Commun., 2007 2515.

[13] Qiu GH, Wang DH, Jin XB, Chen GZ. A direct electrochemical route from oxide precursors to the terbium-nickel intermetallic compound TbNi₅. Electrochim. Acta, 2006, 51(26): 5785.

[14] Yin HY, Yu T, Tang DY, Ruan XF, Zhu H, Wang DH. Electrochemical preparation of NiAl intermetallic compound from solid oxides in molten CaCl₂ and its corrosion behaviors in NaCl aqueous solution. Mater. Chem. Phys., 2012, 133(1): 465.

[15] Cox A, Fray DJ. Electrolytic formation of iron from haematite in molten sodium hydroxide. Ironmaking Steelmaking, 2008, 35(8): 561.

[16] Yin HY, Tang DY, Zhu H, Zhang Y, Wang DH. Production of iron and oxygen in molten K₂CO₃-Na₂CO₃ by electrochemically splitting Fe₂O₃ using a cost affordable inert anode. Electrochem. Commun., 2011, 13(12): 1521.

[17] Cheng XH, Tang DY, Tang DD, Zhu H, Wang DH. Cobalt powder production by elecro-reduction of Co₃O₄ granules in molten carbonates using an inert anode. J. Electrochem. Soc., 2015, 162(6): E68.

[18] Tang DY, Yin HY, Cheng XH, Xiao W, Wang DH. Green production of nickel powder by electro-reduction of NiO in molten Na₂CO₃-K₂CO₃. Int. J. Hydrogen Energy, 2016, 41(41): 18699.

[19] Cox A, Fray DJ. Mechanistic investigation into the electrolytic formation of iron from iron(III) oxide in molten sodium hydroxide. J. Appl. Electrochem., 2008, 38(10): 1401.

[20] Yin HY, Mao XH, Tang DY, Xiao W, Xing LR, Zhu H, Wang DH, Sadoway DR. Capture and electrochemical conversion of CO₂ to value-added carbon and oxygen by molten salt electrolysis. Energy Environ. Sci., 2013, 6(5): 1538.

[21] Cheng XH, Yin HY, Wang DH. Rearrangement of oxide scale on Ni-11Fe-10Cu alloy under anodic polarization in molten Na₂CO₃-K₂CO₃. Corros. Sci., 2018, 141, 168.

[22] Tang DY, Zheng KY, Yin HY, Mao XH, Sadoway DR, Wang DH. Electrochemical growth of a corrosion-resistant multi-layer scale to enable an oxygen-evolution inert anode in molten carbonate. Electrochim. Acta, 2018, 279, 250.

[23] Tang DY, Yin HY, Xiao W, Zhu H, Mao XH, Wang DH. Reduction mechanism and carbon content investigation for electrolytic production of iron from solid Fe₂O₃ in molten K₂CO₃-Na₂CO₃ using an inert anode. J. Electroanal. Chem., 2013, 689, 109.

[24] Zheng KY, Du KF, Chen XH, Jiang R, Deng BW, Zhu H, Wang DH. Nickel-iron-copper alloy as inert anode for ternary molten carbonate electrolysis at 650°C. J. Electrochem. Soc., 2018, 165(11): E572.