• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 춘계학술발표대회 논문집
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• pp.214-219
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• 2009

In high-efficiency crystalline silicon solar cells, If high-efficiency solar cells are to be commercialized. It is need to develop superior contact formation method and material that can be inexpensive and simple without degradation of the solar cells ability. For reason of plated metallic contact is not only high metallic purity but also inexpensive manufacture. It is available to apply mass production. Especially, Nickel, Copper and Silver are applied widely in various electronic manufactures as easily formation is available by plating. The metallic contact system of silicon solar cell must have several properties, such as low contact resistance, easy application and good adhesion. Ni is shown to be a suitable barrier to Cu diffusion as well as desirable contact metal to silicon. Nickel monosilicide(NiSi) has been suggested as a suitable silicide due to its lower resistivity, lower sintering temperature and lower layer stress than $TiSi_2$. Copper and Silver can be plated by electro & light-induced plating method. Light-induced plating makes use the photovoltaic effect of solar cell to deposite the metal on the front contact. The cell is immersed into the electrolytic plating bath and irradiated at the front side by light source, which leads to a current density in the front side grid. Electroless plated Ni/ Electro&light-induced plated Cu/ Light-induced plated Ag contact solar cells result in an energy conversion efficiency of 14.68 % on $0.2{\sim}0.6{\Omega}{\cdot}cm,\;20{\times}20mm^2$, CZ(Czochralski) wafer.

• 한국분말재료학회지
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• 제13권1호
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• pp.18-24
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• 2006

The brazing adhesion properties of Ag coated W-Ag electric contact on the Cu substrate have been investigated in therms of microstructure, phase equilibrium and adhesion strength. Precoating of Ag layer ($3{\mu}m$ in thickness) on the $W-40\%Ag$ contact material was done by electro-plating method. Subsequently the brazing treatment was conducted by inserting BCuP-5 filler metal (Ag-Cu-P alloy) layer between Ag coated W-Ag and Cu substrate and annealing at $710^{\circ}C$ in $H_2$ atmosphere. The optimum brazing temperature of $710^{\circ}C$ was semi-empirically calculated on the basis of the Cu atomic diffusion profile in Ag layer of commercial electric contact produced by the same brazing process. As a mechanical test of the electric contact after brazing treatment the adhesion strength between the electric contact and Cu substrate was measured using Instron. The microstructure and phase equilibrium study revealed that the sound interlayer structure was formed by relatively low brazing treatment at $710^{\circ}C$. Thin Ag electro-plated layer precoated on the electric contact ($3{\mu}m$ in thickness) is thought to be enough for high adhesion strength arid sound microstructure in interface layer.

• 한국자동차공학회논문집
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• 제22권4호
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• pp.65-71
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• 2014

As an important component of a fuel cell, the bipolar plate comprises a large proportion in the fuel cell's volume, weight and price. The bipolar plate is the most widely used; however, graphite bipolar plate is large in volume, brittle and therefore easily broken during assembling. In addition, due to its poor machinability, production costs a lot, unless mass production. Compared with the graphite bipolar plate, the metal bipolar plate has good machinability, high electric conductivity and strong mechanical strength; however, it corrodes easily and has a high contact resistance, so in order to prevent corrosion and reduce the contact resistance, the basic metal needs to be processed by use of electro polishing and coating. The water which is produced by electrochemical reactions in the fuel cell must be discharged smoothly. In this study, in order to prevent corrosion the processes of electro polishing and CrN coating were used. According to the presence or absence of these processes, the contact angles can be measured and different metal bipolar plates can be made, these plates can be used for comparing and analyzing the performance of the fuel cell.

• 소성∙가공
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• 제8권1호
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• pp.22-28
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• 1999

The explicit and implicit time integration methods are applied effectively to analyze sheet metal stamping processes, which include the forming stage and the springback stage consecutively. The explicit time integration method has better merits in the forming stage including highly complicated three-dimensional contact conditions. By contrary, the implicit time integration method is better for analyzing springback since the complicated contact conditions are removed and the computing time to get the final static state is short. In this work, brief descriptions of the formulation and the factor study for springack simulations are presented. Further, the simulated results for the S-rail and the roof panel stamping processes are shown and discussed.

• EDISON SW 활용 경진대회 논문집
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• 제3회(2014년)
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• pp.478-482
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• 2014

Graphene have renewed considerable interest in inorganic, two-dimensional materials for future electronics. However, graphene does not have a bandgap, it is limited to apply directly to transistors and logic devices. Hence, other layered materials such as molybdenum disulphide ($MoS_2$) have been investigated to address this challenge. Here, we find that the nature of contacts plays a more important role than the semiconductor itself. In order to understand the nature of $MoS_2$/metal contacts, we perform density functional theory electronic structure calculations based on linear combination of atomic for the geometry, bonding, binding energy, PDOS, LDOS and electronic structure. We choose Au as a contact metal because it is the most common contact metal. In this paper, we demonstrate $MoS_2$/Au contacts have a more promising potential in flexible nanoelectronics than $MoS_2$ itself.

• 한국기계가공학회지
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• 제11권6호
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• pp.145-151
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• 2012

In this study, finite element analysis is carried out to estimate horizontal forces needed for the required power calculation and vertical forces applied on the structural analysis model for the development of automatic serrated surface at metal gasket core machining system. By considering of elasto-plastic material characteristics, nonlinear contact analysis was conducted to compute these loads according to the change of roll reduction, frictional coefficient and core thickness. As the result, horizontal and vertical reaction force variations are found according to parameters and maximum reaction force is also confirmed to be most affected by roll reduction.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.140.1-140.1
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• 2013

The native silicon-oxide (SiOx) layer at the metal/Silicon interface acts as an electrical resistance to the metal contact of devices. Various methods are proposed for removing this layer, such as sputtering before metal contact formation or high temperature annealing. We studied the chemical evolution of the Au/SiOx/Si system during the annealing at $500^{\circ}C$ using a spatially resolved photoelectron emission method. Scanning photoelectron emission microscopy (SPEM) and core level spectra from local area of the sample show the inhomogeneous oxidation and formation of silicide of Au, as well as valence band spectra reveals the role of Au atoms during the dissociation process of SiOx.

• Steel and Composite Structures
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• 제49권3호
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• pp.281-291
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• 2023

Due to the fact that the nonlinear low-velocity impact response of graphene platelets reinforced metal foams (GPLRMF) doubly curved shells have not been investigated in the existing works, this paper aims to solve this issue. Using Reddy's high-order shear deformation theory (HSDT), the nonlinear governing equations of GPLRMF doubly curved shells are obtained by Euler-Lagrange method, discretized by Galerkin principle, and solved by the fourth-order Runge-Kutta method to obtain the impact force and central deflection. The nonlinear Hertz contact law is applied to determine the contact force. Finally, the impacts of graphene platelets (GPLs) distribution pattern, porosity distribution form, porosity coefficient, damping coefficient, impact parameters (radius and initial velocity), GPLs weight fraction, pre-stressing force and different shell types on the low-velocity impact curves are analyzed. It can be found that, among the four shell structures, the impact resistance of spherical shell is the best, while that of cylindrical shell is the worst.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1569-1572
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• 2003

Meshfree approximations exhibit significant potential to solve partial differential equations. Meshfree methods have been successfully applied to various problems which the traditional finite element methods have difficulties to handle, including the quasi-static and dynamic fracture. large deformation problems, contact problems, and strain localization problems. A meshfree method based on the reproducing kernel particle approximation(RKPM) is applied to sheet metal forming analysis in this research. Metal forming examples, such as stretch forming and flanging operation, are analyzed to demonstrate the performance of the proposed meshfree method for largely deformed elasto-plastic material.

• 대한치과보철학회지
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• 제33권3호
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• pp.584-609
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• 1995

The purpose of this study was to evaluate the difference of the galvanic corrosion behaviour of the titanium in contact with gold alloy, silva-palladium alloy, and nickel-chromium alloy using the immersion and electrochemical method. And the effects of galvallit couples between titanium and the dental alloys were assessed for their usefulness as materials for superstructure. The immersion method was performed by measuring the amount of metal elementsreleased by Inductivey coupled plasma emission spectroscopy(ICPES) The specimen of fifteen titanium plates, the five gold alloy, five silver-palladium, five nickel-chromium plates, and twenty acrylic resin plates ware fabricated, and also the specimen of sixty titanium plugs, the thirty gold alloy, thirty silver-palladium, and nickelc-hromium plugs were made. Thereafter, each plug of gold alloy, silver-palladium, and nickel-chromium inserted into the the titanium and acrylic resin plate, and also titanium plug inserted into the acrylic resin plate. The combination specimens uf galvanic couples immersed in 70m1 artificial saliva solution, and also specimens of four type alloy(that is, titanium, gold, silver-palladium and nickel-chromium alloy) plugs were immersed solely in 70m1 artificial sativa solution. The amount of metal elements released was observed during 21 weeks in the interval of each seven week. The electrochemical method was performed using computer-controlled potentiosta(Autostat 251. Sycopel Sicentific Ltd., U.K). The wax patterns(diameter 11.0mm, thickness,in 1.5mm) of four dental casting alloys were casted by centrifugal method and embedded in self-curing acrylic resin to be about $1.0cm^2$ of exposed surface area. Embedded specimens were polished with silicone carbide paper to #2,000, and ultrasonically cleaned. The working electrode is the specimen of four dental casting alloys, the reference electrode is a saturated calmel electrode(SCE) and the ounter electrode is made of platinum plate. In the artificial saliva solution, the potential scanning was carried out starting from-700mV(SCE) TO +1,000mV(SCE) and the scan rate was 75mV/min. Each polarization curve of alloy was recorded automatically on a logrithmic graphic paper by XY recorder. From the polarization curves of each galvanic couple, corrosion potential and corrosion rates, that is, corrosion density were compared and order of corrosion tendency was determined. From the experiments, the following results were obtained : 1. In the case of immersing titanium, gold alloy, silver-palladium alloy, and nickel-chromium alloysolely in the artificial saliva solution(group 1, 2, 3, and 4), the total amount of metal elements released was that group 4 was greater about 2, 3 times than group 3, and about 7.8 times than group 2. In the case of group 1, the amount of titanium released was not found after 8 week(p<0.001). 2. In the case of galvanic couples of titanium in contact with alloy(group 5, 6), the total amount of metal elements released of group 5 and 6 was less than that of group 7, 8, 9, and 10(p<0.05). 3. In the case of galvanic couples of titanium in contact with silver-palladium alloy(group 7, 8), the total amount of metal elements released of group 7 was greater about twice than that of group 5, and that of group 8 was about 14 times than that of group 6(p<0.05). 4. In the case of galvanic couples of titanium in contact with nickel-chromium alloy(group 9, 10), the total amount of metal elements released of group 9 and 10 was greater about 1.8-3.2 times than that of group 7 and 8, and was greater about 4.3~25 times than that of group 5 and 6(p<0.05). 5. In the effect of galvanic corrosion according to the difference of the area ratio of cathode and anode, the total amount of metal elements released was that group 5 was greater about 4 times than group 6, group 8 was greater about twice than group 7, and group 10 was greater about 1.5 times than group 9(p<0.05). 6. In the effect of galvanic corrosion according to the elasped time during 21 week in the interval of each 7 week, the amount of metal elements released was decreased markedly in the case of galvanic couples of the titanium in contact with gold alloy and silver-palladium alloy but the total amount of nickel and beryllium released was not decreased markedly in the case of galvanic couples of the titanium in contact with nickel-chromium alloy(p<0.05). 7. In the case of galvanic couples of titanium in contact with gold alloy, galvanic current was lower than any other galvanic couple. 8. In the case of galvanic couples of titanium in contact with nickel-chromium alloy, galvanic current was highest among other galvanic couples.