• Journal of Welding and Joining
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• 제26권6호
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• pp.74-80
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• 2008

A finite element modeling approach has been described for the simulation and analysis of the micron-scaled solid particle impact behavior in kinetic spraying process, using an explicit code (ABAQUS 6.7-2). High-strain-rate plastic deformation and interface bonding features of the copper, nickel, aluminum, and titanium were investigated via FEM in conjunction with the Johnson-Cook plasticity model. Different aspects of adiabatic shear instabilities of the materials were characterized as a concept of thermal boost-up zone (TBZ), and also discussed based upon energy balance concept with respect to relative recovery energy (RRE) for the purpose of optimizing the bonding process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 G
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• pp.2541-2543
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• 1998

This paper describes the fabrication process to fabricate metallic structure of high aspect ratio using LlGA-like process. SU-8 is used as an electroplating mold. SU-8 is an epoxy-based photoresist, designed for ultrathick PR structure with single layer coating [1,2]. We can get more than $100{\mu}m$ thick layer by single coating with conventional spin coater, and applying multiple coating can make thicker layers. In the experiments, we used different kinds of SU-8, having different viscosity. To optimize the conditions for mold fabrication process, experiments are performed varying spinning time and speed, soft-bake, develop and PEB (Post Expose Bake) condition. With the optimized condition, minimum line and space of $3{\mu}m$ pattern with a thickness of $40{\mu}m$ and $4{\mu}m$ pattern with a thickness of $130{\mu}m$ were obtained. Using the patterned PR as a plating mold, metallic structure was fabricated by electroplating. We have fabricated a electroplated nickel comb actuator using SU-8 as plating mold. The thickness of PR mold is $45{\mu}m$ and that of plated nickel is$40{\mu}m$. Minimum line of the mold is $5{\mu}m$. Patterned metallic layer or polymer layer, which has selectivity with the structural plated metallic layer, can be used as sacrificial layer for fabrication of free-standing structure.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.215-216
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• 2013

The silicide is a compound of Si with an electropositive component. Silicides are commonly used in silicon-based microelectronics to reduce resistivity of gate and local interconnect metallization. The popular silicide candidates, CoSi2 and TiSi2, have some limitations. TiSi2 showed line width dependent sheet resistance and has difficulty in transformation of the C49 phase to the low resistive C54. CoSi2 consumes more Si than TiSi2. Nickel silicide is a promising material to substitute for those silicide materials providing several advantages; low resistivity, lower Si consumption and lower formation temperature. Nickel silicide (NiSi) nanowire (NW) has features of a geometrically tiny size in terms of diameter and significantly long directional length, with an excellent electrical conductivity. According to these advantages, NiSi NWs have been applied to various nanoscale applications, such as interconnects [1,2], field emitters [3], and functional microscopy tips [4]. Beside its tiny geometric feature, NW can provide a large surface area at a fixed volume. This makes the material viable for photovoltaic architecture, allowing it to be used to enhance the light-active region [5]. Additionally, a recent report has suggested that an effective antireflection coating-layer can be made with by NiSi NW arrays [6]. A unique growth mechanism of nickel silicide (NiSi) nanowires (NWs) was thermodynamically investigated. The reaction between Ni and Si primarily determines NiSi phases according to the deposition condition. Optimum growth conditions were found at $375^{\circ}C$ leading long and high-density NiSi NWs. The ignition of NiSi NWs is determined by the grain size due to the nucleation limited silicide reaction. A successive Ni diffusion through a silicide layer was traced from a NW grown sample. Otherwise Ni-rich or Si-rich phase induces a film type growth. This work demonstrates specific existence of NiSi NW growth [7].

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권6호
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• pp.367-374
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• 2000

This paper presents a method to fabricate freestanding structures by (100) silicon anisotropic etching and nickel electroless plating. The electroless plating process is simpler than the electroplating, and provides good coating uniformity and improved mechanical properties. Furthermore, the (100) silicon anisotropic etching in KOH solution with being aligned to <100> direction provides vertical (100) sidewalls on etched (100) surface. In this paper, the effects of the nickel electroless plating condition on the properties of electroless plated metal structures are investigated to apply fabrication of micro structures and then various micro structures are fabricated by nickel electroless plating. And then, the structures are released by silicon anisotropic etching in KOH solution with a large gap between the structure and the substrate. The fabricated cantilever structures are $210\mum$. wide, $5\mum$. thick and $15\mum$. over the silicon substrate, and the comb structure has the comb electrodes which are $4\mum$. wide and $4.3\mum$. thick separated by$1\mum$. It is released by silicon anisotropic etching in KOH solution. The gap between the structure and the substrate is $2.5\mum$.

• Corrosion Science and Technology
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• 제2권1호
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• pp.53-57
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• 2003

The MarM247 based superalloy (8wt.%Cr- 9wt.%Co- 3wt.%Ta- 1.5wt.%Hf- 5.6%wt.Al- 9.5wt.%W- Bal. Ni) specimens were diffusion aluminized by for types of pack cementation methods, and their coating structure and their high temperature oxidation resistance were investigated. The coated specimens treated at 973K in high aluminum concentration pack had a coating layer containing large hafunium rich precipitates, which were originally included in substrate alloy. After the high temperature oxidation test in air containing 30 vol.% $H_2O$ at 1273K ~ 323K, the deep localized corrosion which reached to the substrate were observed along with these hafnium rich precipitates. On the other hand, the coated specimens treated at 1323K using low aluminum concentration pack showed the coating layer without the large hafunium rich precipitates, and after the high temperature oxidation test at 1273K for 1800 ksec, it did not show the deep localized corrosion. The nickel electroplating before the aluminizing forms thick hafnium free area, and its high temperature oxidation resistance were comparable to platinum modified aluminizing coatings at 1273K.

• 한국표면공학회지
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• 제40권2호
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• pp.70-76
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• 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.

• 한국재료학회지
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• 제32권5호
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• pp.249-257
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• 2022

Transparent thin films of pure and nickel-doped ZrO₂ are grown successfully by sol-gel dip-coating technique. The structural and optical properties according to the different annealing temperatures (300 ℃, 400 ℃ and 500 ℃) are investigated. Analysis of crystallographic properties through X-ray diffraction pattern reveals an increase in crystallite size due to increase in crystallinity with temperature. All fabricated thin films are highly-oriented along (101) planes, which enhances the increase in nickel doping. Scanning electron microscopy and energy dispersive spectroscopy are employed to confirm the homogeneity in surface morphology as well as the doping configuration of films. The extinction coefficient is found to be on the order of 10^-2, showing the surface smoothness of deposited thin films. UV-visible spectroscopy reveals a decrease in the optical band gap with the increase in annealing temperature due to the increase in crystallite size. The variation in Urbach energy and defect density with doping and the change in annealing temperature are also studied.

• Current Photovoltaic Research
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• 제11권4호
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• pp.103-107
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• 2023

A Nickel oxide (NiO_x) thin films were prepared via sol-gel process on a transparent conductive oxide glass substrate. The NiO_x thin films were spin-coated in ambient air and subsequently annealed for 30 minutes at temperatures ranging from 150℃ to 450℃. The structural and optical characteristics of the NiO_x thin films annealed at various temperatures were measured using X-ray diffraction, field emission scanning electron microscopy, and ultraviolet-visible spectroscopy. After optimizing the NiO_x coating conditions, perovskite solar cells were fabricated with p-i-n inverted structure, and its photovoltaic performance was evaluated. NiO_x thin films annealed at 350℃ exhibited the most favorable characteristics as a hole transport layer, resulting in the highest power conversion efficiency of 17.88 % when fabricating inverted perovskite solar cells using this film.

• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 The 4th Korea-Italy Workshop
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• pp.25-28
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• 2003

Low cost composite metallic membranes for the hydrogen separation and production have been prepared by using thin Pd-Ag foils reinforced by metallic (stainless steel and nickel) structures. Especially, “supported membranes” have been obtained by a diffusion welding procedure in which Pd-Ag thin foils have been joined with perforated metals (nickel) and expanded metals (stainless steel): in these membranes the thin palladium foil assures both the high hydrogen permeability and the perm-selectivity while the metallic support provides the mechanical strength. A second studied method of producing "laminated membranes" consists of coating non-noble metal sheets with very thin palladium layers by diffusion welding and cold-rolling. Palladium thin coatings over these metals reduce the activation energy of the hydrogen adsorption process and make them permeable to the hydrogen. In this case, the dense non-noble metal has been used as a support structure of the thin Pd-Ag layers coated over its surfaces: a proper thickness of the metal assures the mechanical strength, the absence of defects (cracks, micro-holes) and the complete hydrogen selectivity of the membrane. membrane.

• 한국분말재료학회지
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• 제17권6호
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• pp.489-493
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• 2010

Nickel-based and iron-based alloys have been developed and commercialized for a wide range of high performance applications at severely corrosive and high temperature environment. This alloy foam has an outstanding performance which is predestinated for diesel particulate filters, heat exchangers, and catalyst support, noise absorbers, battery, fuel cell, and flame distributers in burners in chemical and automotive industry. Production of alloy foam starts from high-tech coating technology and heat treatment of transient liquid-phase sintering in the high temperature. These technology allow for preparation of a wide variety of foam compositions such as Ni, Cr, Al, Fe on various pore size of pure nickel foam or iron foam in order for tailoring material properties to a specific application.