• Journal of the Korean institute of surface engineering
• /
• v.32 no.6
• /
• pp.686-694
• /
• 1999

Insoluble anodes of the Ta/Ir mixed metal oxide for electrodeposition of Ni-W alloy in ammoniacal citrate bath were prepared by thermal decomposition method. Ti plate was etched in boiling oxalic acid solution and coated with ethanol solution of $TaCl_{5}$ and $IrCl_4$ mixed in a fixed ratio, followed by drying and treating at various temperatures. The coating layer of these insoluble anode was characterized by SEM, EDX, XRD and DSC. The decomposition rate of citric acid in plating bath was determined by measuring the $CO_2$ gas evolved at the anodes with Gas Chromatography. Evolution of $CO_2$ gas from Ta/Ir oxide anodes decreased about 5% compared with that of Pt. The $CO_2$ gas evolution was increased with the amount of Ir-oxide in the coatings. The coatings which have more than 40% ratio of Ta content and heat-treated at the temperature higher than $400^{\circ}C$ showed better efficiency

• Progress in Superconductivity and Cryogenics
• /
• v.8 no.4
• /
• pp.19-21
• /
• 2006

Biaxially textured Ni was fabricated by electrodeposition process and delaminated from the biaxially textured cathode surface for further buffer layer deposition process. Those electrode posited Ni substrates showed well-developed biaxial texture and smooth surface. In order to improve the thermal stability of Ni substrates, Mn was alloyed by adding Mn precursor into the electrodeposition bath. Subsequently, $CeO_2$ buffer layers are deposited by MOD process to prevent interfacial reaction between superconductor and substrates. In particular, Bismuth oxide was added to $CeO_2$ to realize lower temperature processing of buffer layers. The microstructure and texture development of each layers have been investigated. Preliminary results shows that all electro/chemical process can be a candidate for cost effective route to YBCO coated conductor.

• Korean Journal of Materials Research
• /
• v.21 no.5
• /
• pp.288-294
• /
• 2011

Simultaneous Ni and C codeposition by electrolysis was investigated with the aim of obtaining better corrosion resistivity and surface conductivity of a metallic bipolar plate for application in fuel cells and redox flow batteries. The carbon content in the Ni-C composite plate fell in a range of 9.2~26.2 at.% as the amount of carbon in the Ni Watt bath and the roughness of the composite were increased. The Ni-C composite with more than 21.6 at.% C content did not show uniformly dispersed carbon. It also displayed micro-sized defects such as cracks and crevices, which result in pitting or crevice corrosion. The corrosion resistance of the Ni-C composite in sulfuric acid is similar with that of pure Ni. Electrochemical test results such as passivation were not satisfactory; however, the Ni-C composite still displayed less than $10^{-4}$ $A/cm^2$ passivation current density. Passivation by an anodizing technique could yield better corrosion resistance in the Ni-C composite, approaching that of pure Ni plating. Surface resistivity of pure Ni after passivation was increased by about 8% compared to pure Ni. On the other hand, the surface resistivity of the Ni-C composite with 13 at.% C content was increased by only 1%. It can be confirmed that the metal plate electrodeposited Ni-C composite can be applied as a bipolar plate for fuel cells and redox flow batteries.

• Corrosion Science and Technology
• /
• v.11 no.6
• /
• pp.275-279
• /
• 2012

Ni-W alloy deposits have lately attracted the interest as an alternative surface treatment method for hard chromium electrodeposits because of higher wear resistance, hardness at high temperature, and corrosion resistance. This study deals with influences of process variables, such as electodeposition current density, plating temperature and pH, on the internal stress of Ni-W nanocrystalline deposits. The internal stress was increased with increasing the applied current density. With increasing applied current density, the grain size of the deposit decreases and concentration of hydrogen in the deposit increases. The subsequent release of the hydrogen results in shrinkage of the deposit and the introduction of tensile stress in the deposit. Consequently, for layers deposited at high current density, cracking occurs readily owing to high tensile stress value. By increasing the temperature of the electrodeposition from $60^{\circ}C$ to $80^{\circ}C$, the internal stress was decreased. It seems that an increase in the number of active ions overcoming the activation energy at elevated temperature caused a decline in the concentration polarization and surface diffusion. It decreased the level of hydrogen absorption due to the lessened hydrogen evolution reaction. Therefore, the lower level of hydrogen absorption degenerated the hydride on the surface of the electrode, resulting in the reduction of the internal stress of the deposits. By increasing the pH of the electrodeposition from 5.6 to 6.8, the internal stress in the deposits were slightly decreased. It is considered that the decrease in internal stess of deposits was due to supply of W complex compound in cathode surface, and hydrogen ion resulted from decrease of activity.

• Journal of the Microelectronics and Packaging Society
• /
• v.29 no.4
• /
• pp.71-75
• /
• 2022

In this research, Fe-Ni alloy films were electrodeposited on stainless steel (SS304 and SS430) and Ti plates to investigate the effects of surface conditions of cathode on deposits. The Ti plates were electropolished in 3 M H₂SO₄-methanol electrolytes at various conditions before electrodeposition, and unpolished Ti and the optimized specimen, polished at 10 V for 8 min, were used as cathode. The anomalous codeposition, the phenomenon which more active Fe is reduced preferentially, occurred on all substrate, however, there were differences in composition of all deposits. As the results of potential monitoring during electrodeposition, it was confirmed that the larger overpotential was applied to the deposition cell when using Ti cathode, leading to high Fe content of deposits from unpolished Ti due to increase in nucleation of Fe. Also, it was founded that the polished Ti can reduced deposition overpotential.

• Journal of the Korean institute of surface engineering
• /
• v.30 no.5
• /
• pp.347-354
• /
• 1997

Composite plating is a method of co-depositing fine particles of metallic, non-metallic compound or polymers in the plated layer to improve material properties such as were-resistance, lubrication, or corrosion resistance. Graded Ni-Sic composite coating were produced in this research. Prior to produce Graded Ni-SiC composite coatings, effects of particle size, particle content, pH of electrolyte, temperature, current density, stirring rate on the amount of SiC deposited in the Ni layer were investigated. By manipulating current density and plating time properties of these coating were evaluated by micro-indentation hardness test.

• Journal of the Korean Magnetics Society
• /
• v.15 no.4
• /
• pp.241-245
• /
• 2005

CoFeNi alloys are some of the most studied soft magnetic materials because of their applications as write-head core materials in HDD and MEMS. Ternary CoFeNi films with high saturation magnetic flux density, Bs and low coercivity, He were successfully grown by electrodeposition. The optimal composition was $Co_{30}\;Fe_{34}\;Ni_{36}(at\%)$, and Bs and Hc were 1.9 T and 0.16 A/m, respectively. The XRD and TEM results show that the low Hc of the CoFeNi films was due to very fine crystal particles and mixed fcc and bcc phases.

• Journal of the Korean institute of surface engineering
• /
• v.51 no.1
• /
• pp.62-70
• /
• 2018

Sulfamate plating solution containing a small amount of chloride bath was fabricated to study the properties of the electrodeposited Ni thin films. Effects of the changes of current density and additive concentration on current efficiency, residual stress, surface morphology and microstructure of Ni thin films electrodeposited from Ni sulfamate-chloride baths were investigated. The current efficiency was measured to be more than about 95%, independent of the changes of current density and saccharin concentration in the baths. Residual stress of Ni thin film was appeared to be the compressive stress modes in the range of $5{\sim}30mA/cm^2$ current density. Maximum compressive stress was observed at the current density of $10mA/cm^2$. Compressive stress values of Ni thin/thick films were increased to be about -85~-100 MPa with increasing saccharin concentration from 0 to 0.0195 M(4 g/L). Surface morphology was changed from smooth to nodule surface appearance with increasing the current density. Smooth surface morphology of Ni thin films electrodeposited from the baths containing saccharin was observed, independent of the saccharin concentration. Ni thin/thick films consist of FCC(111), FCC(200), FCC(220), FCC(311) and FCC(222) peaks. It was revealed that the FCC(200) peak of Ni thin films is the preferred orientation in the range of $5{\sim}30mA/cm^2$ current density. The intensity of FCC(200) peak was gradually decreased and the intensity of FCC(111) peak was increased with increasing saccharin concentration in the baths.

• Korean Journal of Materials Research
• /
• v.8 no.10
• /
• pp.898-904
• /
• 1998

Ni-W alloys containing 10 to 50wt% W were prepared by electrodeposition. Tungsten content in the alloy increased with current density. X-ray diffraction analysis revealed that the alloy was crystalline phase when deposited at current densities lower than 50mA/${cm}^2$. Their crystal structure transformed to amorphous at higher current densities. In terms of tungsten content, the crystal -+ amorphous transition occurred at 40-46wt% which was identified by the 3 fold increase in the width of a diffraction peak. The lattice parameter of crystalline phase increased with W upto 40wt% which is higher than the solubility limit of W (about 30wt%) in Ni. Therefore, the alloys are considered to be Ni solid solution supersaturated with W. The amorphous Ni-W alloys were recrystallized by annealing them at temperatures over $400^{\circ}C$. This was evidenced by the appearance a strong [ 11 11 annealing texture. The supersaturated W was precipitated during the annealing at over $800^{\circ}C$. The current-density dependence of W content and crystallinity was utilized to produce alternating layers of crystalline (30wt% W) and amorphous (50wt%) phases which may exhibit unique mechanical and corrosion properties.

• Journal of the Korean Magnetics Society
• /
• v.23 no.1
• /
• pp.12-17
• /
• 2013

Nanocrystalline nickel (Ni) tick films were synthesized by direct current electrodeposition at current density from 1 to $30mA/cm^2$ and pH = 4. The basic composition of the bath, which was prepared by dissolving Ni metal particles in HCl, was 0.2M Ni ions. The effects of the current density on the average grain size of Ni deposits were investigated by XRD and SEM techniques. The results showed that the surface roughness was decreased as the saccharin addition was increased up to 2 g/l. The experimental results showed that the increase in the current density had a considerable effect on the average grain size of the Ni deposits. The perpendicular magnetization was raised as the thickness of coating layer was increased.