The electrochemical behavior of Fe3+/Fe2+system and ferricyanide ion were investigated by cyclic voltammetry,linear sweep voltammetry,and chronoamperometry in the super gravity field.The results show that diffusion coefficient of ferricyanide ion increased in the super gravity field,and diffusion coefficient under gravity coefficient 125 is almost two times of that in the natural gravity field.The peaks of oxidation and the reduction of Fe3+/Fe2+ disappeared gradually with the increase of the gravity coefficients,and the limiting current densities appeared at 0.10 and 0.80 V(vs.SCE),with increasing super gravity coefficients.When G=30,the limiting current density is 0.100 A/cm2 at 0.10 V,while it is up to 0.196 A/cm2 under G=280.
The effect of super-gravity on electrochemical deposition of nickel from aqueous solution was studied. The SEM pictures show that the microstructure of nickel film deposited under the super-gravity condition is finer and more uniform compared with that obtained in normal gravity condition, and the crystal grains diminish with the increase of super-gravity coefficient. The XRD patterns indicate that the arrangement of crystalline grains of nickel film deposited under the super-gravity field is more regular, and the crystalline grain sizes decrease with the increase of super-gravity coefficient. Toughness, tensile stress and hardness of the nickel film are markedly raised with the increase of super-gravity coefficient, and hydrogen content in the nickel film decreases with the increase of super-gravity coefficient. From the polarization curves of hydrogen evolution reaction under the super-gravity condition, a significant reduction of over-potential on electrode was found when current density increased. The process of hydrogen evolution reaction was enhanced under the super-gravity condition. The electro-deposition rate, the microstructure and properties of deposited nickel film under super-gravity condition were still affected by the relative orientation between inertia force and depositing surface. It is favorable to gain the nickel film with better mechanic properties when inertia force orientates vertically towards depositing surface. Keywords super-gravity - electrochemistry - electro-deposition - nickel film Supported by the Notional Natural Science Foundation of China (Grant No. 50674011)
GUO ZhanCheng1,2, GONG YingPeng2 & LU WeiChang2 1 Metallurgical & Ecological School, University of Science and Technology, Beijing 100083, China
The effects of gravity on nickel electrodeposition,the morphology and mechanical properties of deposits were studied in a super gravity field.Predictions in a microgravity field were also presented based on the obtained experimental tendency.Linear sweep voltammetry reveals that the nickel electrodeposition process is enhanced by increasing the gravity coefficient（G）.The limiting current density changes from 10.2 to 293.0 mA·cm-2 with the increase of the G value from 10-4 to 354.The morphology of deposits was analyzed by scanning electron microscopy（SEM） and atomic force microscopy（AFM）.The images show that the morphology deposited in the super gravity field has finer grain sizes and denser and smoother surfaces.The roughness reduces from 48.3 to 4.9 nm with the increase of the G value from 10-4 to 354.Meanwhile,mechanical tests indicate that the mechanical properties of nickel foils are greatly improved due to introducing a super gravity field during electrodeposition.
Super gravity field was employed to enhance electrolytic reaction for the preparation of copper powders.The morphology, microstructure and size of copper powders were characterized by scanning electron microscopy,X-ray diffractometry and laser particle analysis.The results indicated that current efficiencies of electrolytic copper powders under super gravity field increased by more than 20% compared with that under normal gravity condition.Cell voltage under super gravity field was also much lower.The size of copper powders decreased with the increase of gravity coefficient(G).The increase of current efficiency can be contributed to the disturbance of electrode/electrolyte interface and enhanced mass transfer of Cu2+ in super gravity field.Meanwhile,the huge gravity acceleration would promote the detachment of copper powders from electrode surface during electrolytic process,which can prevent the growth of copper powders.
