• Korean Journal of Crystallography
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• v.3 no.1
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• pp.53-66
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• 1992

Extensive research has been perform성 on the property-microstructure-process condition relations of thin films. The various proposed models are mainly based on physical vapor deposition processes. Especially the study on the surface condition of substrates in Zone 1 with low surface mobility has not been sufficient. In this study, therefore, we discussed the mochological changes of TiN films deposited by plusma enhanced chemical vapor deposition process with substrates of different composition and micro-rorghness, and compared it with the Structure Zone Model. We could find out that the growth rate of films increased and micro-grain size decreased with the increase in micro-roughness, but it does not improve the mechanical properties because of many imperfections like voids, micro-cracks, stacking faults, etc. This means that, in these deposition conditions, the increase in shadowing diffect is more effective than the increase in nucleation sites on the growth of films due to the increase in substrate roughness.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2002.05a
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• pp.35-35
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• 2002

Atomic force microscopy was applied to study the formation and growth mechanism of thin chrome layers prepared under various pulse plating conditions. The chrome was electro-deposited from an electrolyte bath containing 250 gl-l of chromic acid, 25 gl-l of sulfuric acid using direct current density of $1.6{\;}mA.$\textrm{mm}^{-2} and pulse currents with on-off time from 5 to 900 ms. The higher current density enhanced nucleation rate which resulted in refining grain size. The chrome growth kinetics determining nodule size and shape significantly depends on the duration of on-time rather than duration of off-time and on/off time ratio.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.350.2-350.2
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• 2014

We investigated the structural and optical evolution of Ga2O3 thin films on glass substrates deposited using radio frequency magnetron sputtering. Initially, amorphous Ga2O3 thin film is grown, and then, surface humps and nanowire (NW) bundles are gradually formed as the film thickness increases. The surface humps are Ga-rich and provide nucleation sites for NWs through a self-catalytic vapor-liquid-solid mechanism with self-assembled Ga droplets. Both the surface humps and the NWs induce variation of the optical properties such as the optical bandgap and refractive index by absorbing light in the ultraviolet region.

• Macromolecular Research
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• v.17 no.6
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• pp.397-402
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• 2009

In emulsifier-free, emulsion polymerization with ionizable comonomer, the ionization of the comonomer is critical in determining the size of the final polymerie particles at sub-micrometer scale. In this study, polystyrene latex beads with carboxylates on the surface were synthesized using acrylic acid as a comonomer. Specifically, ammonium hydroxide was added to the emulsifier-free polymerization system to promote the ionization of acrylic acid by increasing pH. Smaller polystyrene latex particles were produced by increasing the ammonium hydroxide concentration in the reaction system, due to the enhanced stability promoted by the ionization of acrylic acid during the nucleation step. In addition, the surface morphology of the polystyrene latex particles was controlled by the concentration of acrylic acid, the dissociation of which was influenced by the ammonium hydroxide concentration.

• International Journal of Air-Conditioning and Refrigeration
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• v.14 no.2
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• pp.66-75
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• 2006

The effect of antifreeze solution liquid film on the frost prevention is experimentally investigated. It is desirable that the antifreeze solution spreads widely on the heat exchanger surface forming thin liquid film to prevent frost nucleation while having small thermal resistance across the film. A porous layer coating technique is adopted to improve the wettability of the antifreeze solution on a parallel plate heat exchanger. The antifreeze solution spreads widely on the heat exchanger surface with $100{\mu}m$ thickness by the capillary force resulted from the porous structure. It is observed that the antifreeze solution liquid film prevents a parallel plate heat exchanger from frosting. The reductions of heat and mass transfer rate caused by the thin liquid film are only $1{\sim}2%$ compared with those for non-liquid film surface.

• Applied Science and Convergence Technology
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• v.25 no.6
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• pp.149-153
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• 2016

Thermal oxidation has significant potential for use in synthesizing metal-oxide nanostructures from metallic materials. However, this method has limited applicability to the synthesis of multi-morphology NiO from Ni foil. Techniques consisting of mechanical and chemical approaches were used to pre-treat the Ni foil (prior to oxidation) to promote the formation of nanowires and nanoplates on the NiO layer. These morphologies were realized on the Ni foils scratched by sand paper and a knife, respectively, and subsequently heat-treated at $500^{\circ}C$ for 24 h. Small nanowires (diameter: <10 nm) formed on the Ni foil treated by absolute $HNO_3$ and then oxidized at $500^{\circ}C$ for 24 h. The formation of various morphologies (on the pre-treated Ni foil), which differ from that formed in the case of pristine Ni foil after oxidation, may be attributed to the surface melting phenomenon that occurs during the nucleation process.

• Journal of the Korean institute of surface engineering
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• v.24 no.4
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• pp.187-195
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• 1991

Adhesion strength of electroless-plated Ni, Ni-P and Cu deposites on alumina substrate has been studied. Grain boundary spaces produced on the substrate surface by etching treatment provided anchoring sites for enhancing the adhesion strength. Adhesion strengths of Ni-P and Ni deposit were higher than that of Cu deposit, because of higher initial nucleation rates than the latter. The electroless-plated Ni-P and Ni underlayer improved the adhesion strength of the Cu deposit. In could be attributed to the enhanced adhesion between the substrate and those underlayers as well as the satisfactory adhesion between Cu deposits and those underlayers. Heat treatment was also conducted in order to enhance the adhesion strength of Cu layer. The strength was enhanced by about 19% when the treatment was conducted at $150^{\circ}C$ for 2 hours. The enhancement was attributed to relief of internal stress and release of hydrogen.

• Journal of the Korean Ceramic Society
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• v.31 no.1
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• pp.17-24
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• 1994

Al2O3-ZrO2(ZTA) composites were fabricated by a surface-induced coating of the precursor for the ZrO2 phase on the kinetically stable colloid particles of Al2O3. The fabricated composites were characterized by a uniform spatial distribution of the dispersed ZrO2 phase and by the absence of large ZrO2 grains throughout the Al2O3 matrix. The fracture toughness (KIC) and the bending strength of ZTA composites sintered at 1$600^{\circ}C$, respectively, were 5.6 MPa.m1/2 (for 20 wt% ZrO2) and 600 MPa (for 15wt% ZrO2). The fraction of tetragonal ZrO2 phase decreases as the total content of ZrO2, suggesting that both the stress-induced tlongrightarrowm transformation and the microcrack nucleation contribute to the toughening of the ZTA composites fabricated by the surface-induced coating.

• Journal of the Korean institute of surface engineering
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• v.35 no.2
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• pp.122-128
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• 2002

This study was conducted to synthesize the diamond like carbon films by plasma enhanced chemical vapor deposition (PECVD). The effects of gas composition on growth and mechanical properties of the films were investigated. A little amount of hydrogen or oxygen were added to base gas mixture of methane and argon. Methane dissociation and diamond like carbon nucleation were enhanced by installing negatively bias grid near substrate. The deposited films were indentified as hard diamond like carbon films by micro-Raman spectroscopy. The surface and fractured cross section of the films which were observed by scanning electron microscopy showed that film growth is very slow as about 0.3$\mu\textrm{m}$/hour, and relatively uniform with hydrogen addition. Vickers hardness of tungsten carbide (WC) cutting tool increased from about 1000 to 1600~1800 by deposition of DLC film, that of commercial TiN coated tool was about 1270. In cutting test of aluminum 6061 alloy, DLC coated cutting tool showed 1/3 or lower crater and flank wear than TiN coated or non-coated WC cutting tools.

• Journal of the Korean institute of surface engineering
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• v.49 no.5
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• pp.401-407
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• 2016

In this work, effect of zincate treatment of AZ91 Mg alloy on the following electrodeposition of copper was examined in a non-cyanide bath containing pyrophosphate ions in view of surface morphology and adhesion of the electrodeposited copper layer. Without zincate treatment, the electrodeposited copper layer showed very porous structure and poor adhesion. On the other hand, the copper layer electrodeposited on the zincate-treated surface showed dense structure and good adhesion. The dissolution rate of AZ91 Mg alloy after the zincate treatment appeared to decrease about 40 times in the copper pyrophosphate bath, as compared to that of the surface without zincate treatment. The porous morphology and poor adhesion of a copper layer on the AZ91 Mg alloy surface without zincate treatment were attributed to small number of nucleation sites of copper because of rapid dissolution of the magnesium substrate in the pyrophosphate bath. Based on the experimental results, it is concluded that the zincate treatment to form a conducting and protecting layer on the AZ91 Mg alloy surface is essential for successful electrodeposition of a copper layer on AZ91 Mg alloy with good adhesion and dense structure in the copper pyrophosphate bath.