• Bulletin of the Korean Chemical Society
• /
• v.31 no.8
• /
• pp.2304-2308
• /
• 2010

A $LiNi_{0.8}Co_{0.15}Al_{0.05}O_2$ (LNCAO/C) active material composite cathode was coated with carbon. The conductive carbon coating was obtained by addition of surfactant during synthesis. The addition of surfactant led to the formation of an amorphous carbon coating layer on the pristine LNCAO surface. The layer of carbon coating was clearly detected by FE-TEM analysis. In electrochemical performance, although the LNCAO/C showed similar capacity at low C-rate conditions, the rate capability was improved by the form of the carbon coating at high current discharge state. After 40 cycles of charge-discharge processes, the capacity retention of LNCAO/C was better than that of LNCAO. The carbon coating is effectively protected the surface structure of the pristine LNCAO during Li insertion-extraction.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.9
• /
• pp.1737-1741
• /
• 2008

The electrochemical and thermal stability of $LiNi_{0.8}Co_{0.16}Al_{0.04}O_2$ were studied before and after $Co_3(PO_4)_2$ coating. Different to conventional coating material such as $ZrO_2$ or AlPO4, the coating layer was not detected clearly by TEM analysis, indicating that the $Co_3(PO_4)_2$ nanoparticles effectively reacted with surface impurities such as $Li_2CO_3$. The coated sample showed similar capacity at a low C rate condition. However, the rate capability was significantly improved by the coating effect. It is associated with a decrease of impedance after coating because impedance can act as a major barrier for overall cell performances in high C rate cycling. In the DSC profile of the charged sample, exothermic peaks were shifted to high temperatures and heat generation was reduced after coating, indicating the thermal reaction between electrode and electrolyte was sucessfully suppressed by $Co_3(PO_4)_2$ nanoparticle coating.

• The Journal of Korean Academy of Prosthodontics
• /
• v.35 no.1
• /
• pp.103-117
• /
• 1997

The purpose of this experiment was to determind whether the gold electrodeposit on Pd-Ag and Ni-Cr alloys influences on the shear bond strength between veneering resin and silicoated metal surface. All the metal specimens were sandblasted with $250{\mu}m$ aluminum oxide and followed by silicoating and resin veneering. According to the metal surfaces to be veneered, experimental groups were divided into five. Group Prec : Gold alloy without gold coating Group Semi : Pd-Ag alloy without gold coating Group Base : Ni-Cr alloy without gold coating Group Semi-G : Pd-Ag alloy with gold coating Group Base-G : Ni-Cr alloy with gold coating All specimens were thermocycled 1,000 times at temperature of $5^{\circ}C$ to $55^{\circ}C$. The effects of gold electrodeposit on the shear bond strength between resin and metal interface were measured and fractured surface of the resin veneered metal was examined under the scaning electron microscope. The following results were obtained 1. The shear bond strength between resin and metal was $64.51{\pm}11.11Kg/cm^2$ in Prec group, $62.77{\pm}11.23Kg/cm^2$ in Base group and $58.97{\pm}9.20Kg/cm^2$ in Semi Group. There was no significant difference among the groups. 2. The bond strength in groups Semi-G and Base-G decreased about 17%, compared to the nongold-electrodeposit groups(Semi, Base). 3. In groups of non electrodeposit(Prec, Semi, Base), fracture occurred at the interface between alloy and resin, while fracture interface was observed between gold coating and resin in group Semi-G, and between metal substrate and gold coating in group Base-G respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2011.05a
• /
• pp.58-58
• /
• 2011

Nickel-ceramics nanocomposite coatings can be applied as the wear resistance coating, corrosion protection of underlying materials, and decorative coatings. Hence, Nickel based nanocomposite coatings, especially Ni-SiC, have been extensively studied in recent years. However, more often agglomeration problem of the nanoparticles in the nickel matrix can cause deterioration of the mechanical properties rather than improvement. The homogeneous distribution of the nanoparticles in the matrix coating is still being challenging. In this experiment, electrochemical deposition of Ni-SiC composite coating was done in presence of ultrasound. The effects of different ultrasonic powers and frequencies on the nanoparticle dispersion were studied. The electrodeposition was carried out in nickel sulfamate bath by applying pulse current technique. Compared to the conventional mechanical stirring technique to prevent nanoparticles agglomeration and sedimentation during composite electrodeposition, the aid of ultrasonic dispersion along with mechanical stirring has been found to be more effective not only for the nanoparticles dispersion, but also for the mechanical properties of the electrodeposited coatings. Nanoparticles were found to be distributed homogeneously with reduced agglomeration. The microstructure of the composite coating has also been changed, allowing some random orientations of the nickel crystallite grain growths, smooth surface, and finer grains. As a consequence, better mechanical properties of the composites were observed.

• Journal of the Korean institute of surface engineering
• /
• v.40 no.2
• /
• pp.70-76
• /
• 2007

Ni-P-SiC composite coating layers were prepared by electroless plating method and their deposition rate, codeposition of SiC, morphology, surface roughness, hardness, wear and friction properties were investigated. The deposition rate was kept almost constant independent of the concentration of SiC in the plating solution and the codeposition of SiC in the composite coating layer increased with increased concentration of SiC in the plating solution except the early stage. Vickers microhardness increased with respect to the increased codeposition of SiC and the heat treatment at $300^{\circ}C$ in air for 1 hour. It was found that the wear volume decreased with increased up to 50 wt.% of SiC codeposition, and that friction coefficient increased gradually with increased codeposition of SiC. Considering the wear and the friction behaviors, the composite coating layer obtained by using 50 wt.% of SiC codeposition is desirable for the practical application for anti-wear and anti-friction coatings.

• Journal of Electrochemical Science and Technology
• /
• v.12 no.2
• /
• pp.272-278
• /
• 2021

In this study, high nickel layered LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials for lithium-ion batteries were modified by yttrium doping and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) coating. The effects of yttrium doping and PEDOT:PSS coating on the structural and electrochemical properties of the LiNi_0.8Co_0.1Mn_0.1O₂ cathode material were investigated and compared. The substitution of nickel with an electrochemically inert yttrium was confirmed to be successful in stabilizing the layered structure framework. Moreover, coating the surfaces of the LiNi_0.8Co_0.1Mn_0.1O₂ particles with a conductive polymer, PEDOT:PSS, improved the capacity retention, thermal stability, and impedance of the cathode material by increasing its ionic and electric conductivities.

• Applied Chemistry for Engineering
• /
• v.33 no.5
• /
• pp.459-465
• /
• 2022

A pitch coating method was proposed for the purpose of improving the electrochemical properties of natural graphite. The synthesis conditions of pitch coating were optimized via measuring electrochemical properties of pitch-coated graphite anodes. As the synthesis temperature increased, the thermal stability was improved in addition to an increase in the softening point and residual carbon weight. However, the synthesis temperature of 430 ℃ resulted in the synthesis of a large amount of NI (NMP Insoluble) due to excessive condensation reaction. As the surface uniformity and coating thickness increased due to high thermal stability, the initial coulombic efficiency and rate capability of the pitch-coated graphite were improved. However, the graphite coated with the pitch containing excessive NI showed lower electrochemical properties than the uncoated graphite. NI had low dispersibility and formed spheres after heat treatment, so it formed the heterogeneous and thicker SEI layer. The optimum conditions for forming a uniform surface and an appropriate coating layer were investigated.

• Carbon letters
• /
• v.26
• /
• pp.51-60
• /
• 2018

An electroless deposition method was used to modify the surface properties of rice husk ceramic particles (RHC) by depositing nano-nickel on the surface of the RHC (Ni-RHC). The dry tribological performances of aluminum matrix composite adobes containing different contents of RHC and Ni-RHC particles have been investigated using a micro-tribometer. Results showed that the Ni-RHC particles substantially improved both the friction and wear properties of the Ni-RHC/aluminum matrix adobes. The optimal concentration was determined to be 15 wt% for both the RHC and Ni-RHC particles. The improvements in the tribological properties of aluminum adobes including the Ni-RHC were ascribed to friction-induced peeling off of Ni coating and formation of protection layer on the wear zone, both of which led to low friction and wear volume.

• Journal of Korea Foundry Society
• /
• v.31 no.2
• /
• pp.83-86
• /
• 2011

Ni-Al based intermetallic compounds of self-propagating high-temperature synthesis (SHS) by the heat of molten aluminum and been coated on the aluminum casting alloy. The effects of the pouring temperature in casting and the thickness of casting substrate on SHS of the coating layer have been investigated. The experimental result showed that the reaction of the coating layer was activated with increasing the pouring temperature in casting and the thickness of casting substrate. However, the aluminum substrate was re-melted by the heat of formation for intermetallic compounds. Then, it was considered that some mechanical or thermal treatments for elemental powder mixtures were required to control the heat of formation for intermetallic compounds in advance.

• Journal of Power System Engineering
• /
• v.18 no.6
• /
• pp.40-44
• /
• 2014

The purpose of this paper is to investigate polarization characteristics of WC-based alloy coatings in alkaline solution. The coatings were fabricated with WC-CrC-Ni, WC-Co-Cr and WC-Co composite powders by HVOF process. Corrosion tests of coatings and substrate were carried out using potentiostat/galvanostat at solution with pH 8 and pH 13. Corrosion potential(Ecorr) and corrosion current density(Icorr) could be studied from polarization curve, and corrosion behavior was analyzed by SEM and EDS. WC-Co-Cr coating and WC-CrC-Ni coating showed more favorable anti-corrosion characteristics than WC-Co coating and substrate at solution with pH 8 and pH 13.