• Transactions of Materials Processing
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• v.18 no.4
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• pp.310-316
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• 2009

Micro lens array(MLA) is widely used in information technology(IT) industry fields for various applications such as a projection display, an optical power regulator, a micro mass spectrometer and for medical appliances. Recently, MLA have been fabricated and developed by using a reflow method having the processes of micro etching, electroplating, micro machining and laser local heating. Laser thermal relaxation method is introduced in marking of microdots on the surface of densified glass. In this paper, we have proposed a new direct fabrication process using UV laser local thermal-expansion(UV-LLTE) and investigated the optimal processing conditions of MLA on the surface of negative photo-resist material. We have also studied the 3D shape of the micro lens obtained by UV laser irradiation and the optimal process conditions. And then, we made chrome mold by electroplating. After that, we made MLA using chrome mold by hot embossing processing. Finally, we have measured the opto-physical properties of micro lens and then have also tested the possibility of MLA applications.

• Solar Energy
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• v.9 no.2
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• pp.69-77
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• 1989

The thermal degradation of electroplated black chrome coating on Ni substrates has been investigated by using Auger electron spectroscopy technique. The sample was prepared by electroplating at $20^{\circ}C$ for 20 seconds with the current density at $0.4A/cm^2$. Its surface oxidation process was investigated with 1 hour annealed sample for a temperature range of $300-550^{\circ}C$. While its optical solar absorption was dominated by fine metallic Cr particles, thermal degradation was occurred primarily by oxidation of metallic Cr particles as increasing the annealing temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.113-116
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• 2011

A total of 9 coating specimens were fabricated through 3 different processes to evaluate the availability and performance of a nickel/chrome coating for the protection of the inner wall of a thrust chamber operating on a condition of high temperature and pressure. Thickness and thermal conductivity of the specimens were measured and thermal shock test was conducted.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.111-118
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• 2016

A method to quantitatively analyze the defects formed by the hydrogen evolution during electroplating was suggested based on the theoretical approach of the small angle neutron scattering technique. In case of trivalent chrome layers, an isolated defect size due to the hydrogen evolution was about 40 nm. Direct and pulse plating conditions gave the average defect size of about 4.9 and $4.5{\mu}m$ with rod or calabash shape, respectively. Current density change of the pulse plating from $1.5A/dm^2$ to $2.0A/dm^2$ enlarged the average defect size from 3.3 to $7.8{\mu}m$. The defect morphology like rod or calabash was originated by inter-connecting the isolated defects. Small angle neutron scattering was useful to quantitatively evaluate defect morphology of the deposit.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1794-1798
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• 2004

We present a fabrication method of high aspect ratio 100nm-scale nickel stamper using e-beam writing for the injection molding of optical grating patterns. Conventional nickel stamper is fabricated by nickel electroplating process which is followed by seed layer deposition. In this paper, we have used chrome coated blank mask without anti-reflection layer of CrON in order to simplified electroplating process. In experimental study, we have optimized electron-beam dosage for 100nm-scale optical grating patterns with 2.5-aspect ratio, and fabricated nickel stamper using above grating patterns as PR mold. Fabricated nickel stamper have showed height of 240$\pm$20nm and width of 116$\pm$6nm.

• Journal of the Korean institute of surface engineering
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• v.25 no.4
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• pp.181-186
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• 1992

To investigate how to produce the crack free and chromium deposits, bath compositions, additives, electrolysis conditions and other electroplating parameters, such as cathodic current efficiency, surface hard-ness, crack density and corrosion rate of deposits were examined carefully. The crack free chrome deposits were well obtained using both wetting agents and two kind of additives. At 60 A/d$\m^2$, $60^{\circ}C$ electrolysis condition, crack free bright hard chromium deposits were well obtained to a thickness $300\mu\textrm{m}$ in Additive-I and Additive-II added solution.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.89-94
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• 2015

Objectives: The objective of this study was to determine characteristics of workers' exposures to airborne total and hexavalent chromium by job title in electroplating processes. Methods: Total Cr was determined through a modified method based on NIOSH Method 7024. Airborne hexavalent Cr, Cr(VI), was sampled and extracted according to NIOSH Method 7600 and analyzed at 520 nm using an ion chromatograph/visible detector. Results: The geometric mean(GM) of total Cr concentrations from all factories was $11.2{\mu}g/m^3$(GSD=4.9). The GM of Cr(VI) concentrations from all factories was $2.84{\mu}g/m$ (GSD=5.2), and the concentrations among factories were significantly different (p<0.05). The Cr(VI) levels were lower than total Cr levels. Total Cr exposure levels were highest among buffing workers ($21.6{\mu}g/m^3$), but Cr(VI) levels were highest among plating workers($4.15{\mu}g/m^3$). The concentrations of Cr(VI) and total Cr from plating tasks was highly correlated(r=0.91). Conclusions: In the electroplating industry, plating workers were mainly exposed to Cr(VI), but others were not. Oxidation-reduction states of Cr and job titles should be considered in the exposure or risk assessments of chrome electroplating factories.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.7 no.2
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• pp.223-232
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• 1997

The accuracy and precision of a modified method of NIOSH Method 7600 and EPA method 218.6 was determined for analyzing hexavalent chromium, Cr(VI), collected on PVC filter from workplace air. The method was designed to extract from Cr(VI) on PVC filter with a alkali solution, 2% NaOH/3% $Na_2CO_3$, and to analyze it using ion chromatography/visible absorbance detection(IC/VAD). The results and conclusion are as the following. 1. The peak of Cr(VI) was separated sharply on chromatogram and was linearly related with Cr(VI) concentration in sloution. The correlation coefficient was 0.9999 in a calibration curve. The limit of detection was 0.25 $0.25{\mu}g/sample$. 2. The accuracy(% recovery) was 93.3% in a set of sample($9-50{\mu}g$) stored for a day, and 100.1%($10-60{\mu}g$) in another set of samples stored for 2 hours. It is assumed that the difference in recovery by storage time was due to reduction of Cr(VI) to Cr(III). 3. The precision(coefficient of variation, CV) of the method was 0.015 in spiked samples with Cr(VI) standard solution, and 0.010 in spiked samples with plating solution from a chrome electroplating factory. The overall CV in all types of samples was 0.0013. 4. The Cr(VI) was stable in 2% NaOH/3% $Na_2CO_3$ at least for 10 hours. In conclusion, the IC/VAD method is appropriate for determining low-level Cr(VI) in workplace air containing various interferences.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.805-806
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• 2011

Thermal conductivities of a Ni-Cr coating applied for the protection of a thrust chamber operating under the condition of high pressure and high temperature were measured. Results showed that the data used in heat transfer calculation has a 20~25% margin compared with data measured.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.1 no.2
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• pp.117-127
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• 1991

The exposure level of chromium and nickel for chrome and nickel plating workers were evaluated. Chromium and nickel concentrations in serum from 82 exposed workers and 66 controls, who were not exposed occupationally to metals, were analyzed by flameless atomic absorption spectrophotometry. The results were as follows : 1. The recovery percent of chromium and nickel concentrations in personal air samples were 95-108.2%, 88.0-107.7%, precisions (C.V., %) were 2.7-3.1%, 2.1-4.4%. respectively. 2. The recovery percent of chromium and nickel concentrations in serum were 93.6-106.4%, 91.3-107.9% and precisions (C.V. %) were 1.1-7.6%, 2.4-5.4% respectively. 3. The exposure level of chromium and nickel concentrations in the place of preparation process were $2.0{\pm}2.00{\mu}g/m^3$, chromplating were $35.7{\pm}53.07{\mu}g/m^3$, $2.8{\pm}3.42{\mu}g/m^3$, nickelplating were $4.6.0{\pm}5.8{\mu}g/m^3$, $18.62{\pm}4.41{\mu}g/m^3$, and covering were $2.9{\pm}2.02{\mu}g/m^3$, $1.1{\pm}0.47{\mu}g/m^3$ respectively. There were significant difference of concentrations for chromium and nickel in workplaces by groups statistically. 4. Chromium concentrations in serum of exposed group and control were $0.68{\pm}0.399{\mu}g/l$, $1.41{\pm}0.748{\mu}g/l$, respectively. There were significant difference of concentrations for chromium and nickel in serum by groups statistically. 5. Chromium and nickel concentrations in serum of exposed group were not significant by workplaces.