• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권8호
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• pp.598-604
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• 1999

This paper describes the research to minimize the film stress and maximize the aspect ratio of photoresist structure, especially about SU-8 for electroplating mold. UV LIGA process using SU-8 allows fabricating high aspect ratio polymer structures. However, it is hard to get fine patterns in the high aspect ratio structures because of high internal stress and difficulty of removing SU-8. The purpose of this paper is to setup the process condition for the obtainment of both low film stress and high aspect ratio and to find design rules that make the pattern be less dependent on stress problem. Firstly, the process of heat treatment and exposure of SU-8 are proposed. These two conditions control the amount of cross-linkage in polymer structure, which is the most important parameter of both pattern generation and remaining stress. Heat treatment is dealed with soft bake and post-exposure-bake. Temperature and time duration of each step are varied with heat treatment condition. Some test patterns are fabricated to evaluate the proposed process. Nickel electroplating is performed with the mold fabricated through the proposed process to confirm the SU-8 as a good electroplating mold.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.143-144
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• 2006

In this paper, we proposed XP KMPR-1050 negative tone resist to replace SU-8 resist for multi-layer micro-structures and thick plating mold fabrication using UV-LIGA process. XP KMPR resist proposed in this paper can be easily striped using a common stripping solution such as NMP without damage of micro-structure. The conditions for the fabrication of XP KMPR micro-structure were optimized by adjustment of exposure and post-exposure bake(PEB). The $140{\mu}m$ -thick and an aspect ratio at least 10 micro-structure and multi-layer structures were successfully fabricated through the process conditions. Through-mold electroplating and PR striping of XP KMPR has been successfully demonstrated.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.188-203
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• 2021

The specific benefits of the modified films formed on preliminary anodized aluminum, including the versatility of their potential applications impose the need for evaluation of the exploitation reliability of these films. In this aspect, the durability of Cu and Ni modified anodized aluminum oxide (AAO) films on the low-doped AA1050 alloy was assessed through extended exposure to a 3.5% NaCl model corrosive medium. The electrochemical measurements by means of electrochemical impedance spectroscopy (EIS) and potentiodynamic scanning (PDS) after 24 and 720 hours of exposure have revealed that the obtained films do not change their obvious barrier properties. In addition, supplemental analyses of the coatings were performed, in order to elucidate the impact of the AC-deposition of Cu and Ni inside the pores. The scanning electron microscopy (SEM) images have shown that the surface topology is not affected and resembles the typical surface of an etched metal. The subsequent energy dispersive X-ray spectroscopy (EDX) tests have revealed a predominance of Cu in the combined AAO-Cu/Ni layers, whereas additional X-ray photoelectron (XPS) analyses showed that both metals form oxides with different oxidation states due to alterations in the deposition conditions, promoted by the application of AC-polarization of the samples.

• 대한치과기공학회지
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• 제32권3호
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• pp.195-207
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• 2010

Purpose: The purpose of this study was to observe the microstructural changes of surface in the specimens, performing the shear bond strength testing. The currently most used non-precious alloys are nickel-chromium based alloys with or without beryllium. However, their biocompatibility has been questioned concerning possible damages to the health of the patient and professionals involved in the fabrication of prosthesis caused by long exposure to Ni and Be. An option to nickel-chromium alloys is the cobalt-chromium alloy, an alternative that does not sacrifice the physical properties of the metal porcelain systems. Studies in the animals substantially show that the cobalt-chromium alloys are relatively well tolerated, being therefore more biocompatible than the nickel-chromium alloys. Methods: Non-addition Be to nickel-chromium based alloy(Bellabond plus) and cobalt-chromium alloy which has been widely used(Wirobond C) fused with ZEO light porcelain classified control group and cobalt-chromium alloy which is developing alloy of Alphadent company in Korea(Alphadent alloy) fused with ZEO light porcelain classified experimental group. The specimens of $4mm{\times}4mm{\times}0.5mm$ were prepared as-cast and as-opaque to cast body to analyze the mechanical characteristic change, the microstructure of alloy surface. The phase change was used to observe through XRD analysis and OM/SEM was used to observe the surface of specimens as-cast and as-opaque to cast body. Chemical formation of their elements was measured with EDS. Then hardness was measured with Micro Vicker's hardness tester. Shear bond strength test thirty specimens of $10mm{\times}10mm{\times}2mm$ was prepared, veneered, 3mm high and 3mm in diameter, over the alloy specimens. The shear bond strength test was performed in a universal testing machine(UTM) with a cross head speed of 0.5mm/min. Ultimate shear bond strength data were analyzed with one-way ANOVA and the Scheffe's test (P<0.05). Within the limits of this study, the following conclusions were drawn: The X-ray diffraction analysis results for the as-cast and as-opaque specimens showed that the major relative intensity of Bellabond plus alloy were changed smaller than Wirobond C and Alphadent Co-Cr based alloys. Results: Microstructural analysis results for the opaque specimens showed all the alloys increased carbides and precipitation(PPT). Alphadent Co-Cr based alloy showed the carbides of lamellar type. The Vickers hardness results for the opaque specimens showed Wirobond C and Alphadent Co-Cr based alloys were increaser than before ascast, but Bellabond plus alloy relatively decreased. The mean shear bond strengths (MPa) were: 33.11 for Wirobond C/ZEO light; 25.00 for Alphadent Co-Cr alloy/ZEO light; 18.02 for Bellabond plus/ZEO light. Conclusion: The mean shear bond strengths for Co-Cr and Ni-Cr based alloy were significantly different. But the all groups showed metal-metal oxide modes in shear bond strengths test at the interface.

• 한국산업보건학회지
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• 제10권1호
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• pp.45-57
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• 2000

Results of environmental monitoring for 35 steel industry welders exposed to manganese and chromium fume were evaluated. Efficiency of respiratory protectors, welding face shields and local exhaust ventilation were also evaluated to establish more efficient preventive measures that can protect welders from occupational disease as related to welding fume. The results are as follows; 1. Total fume from $CO_2$ arc welding with mild steel occurred 1.5 to 2.2 times more than that from shielded metal arc welding. Chromium and nickel fume from welding with stainless steel occurred 27 to 59 times and 18 to 30 times, respectively, than those with mild steel. 2. Proportions of water-soluble chromium(VI) and insoluble chromium(VI) Compare to total chromium occurring from $CO_2$ arc welding with stainless steel were 10.5% and 8.7%, respectively, while those with mild steel were 57.1 to 63.2% and 31.6 to 38.1%, respectively. 3. The efficiencies of 4 types of respiratory protectors to reduce welding fume exposure were evaluated as 54.4 to 64.4%. 4. The reducing effect of head type welding face shield was 67.6%, and that of hand type welding face shield was 58.5%. The highest reducing effect was shown in air supply welding face shield as 99.2%, although it is not convenient to wear. 5. When welding face shield and respiratory protectors were worn together, the reducing efficiency increased to 79.0 to 87.5%. 6. When local exhaust ventilation was installed in workplace, the reducing efficiencies varied from 31.5 to 73.1% according to the types of welding.

• Safety and Health at Work
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• 제14권1호
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• pp.17-30
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• 2023

The human reproductive system can be affected by occupational exposure to many physical and chemical risk factors. This study was carried out to review the studies conducted on the issue of the pathophysiological effects of occupational physical and chemical risk factors on the reproductive system of females and males. In this systematic review, the databases such as "Google Scholar," "Pub-Med," "Scopus," and "Web of Science" were used. Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA 2020), the studies included in our study were published between 2000 and 2021. In order to extract the required data, all sections of the articles were reviewed. Out of 57 articles we reviewed, 34 articles were related to field studies and 23 articles to clinical studies. Among them, 43 studies dealt with the pathophysiological effects of chemical agents, six studies dealt with the pathophysiological effects of physical factors, and 8 studies dealt with the pathophysiological effects of physicochemical factors on the human reproductive system. Physical (noise, heat, and radiofrequency radiation) and chemical (such as carbamate and organophosphate pesticides, benzene, toluene, xylene, formaldehyde, NO2, CS2, manganese, lead, nickel, and n-hexane) risk factors had pathophysiological effects on the human reproductive system. The presence of these risk factors in the workplace caused damage to the human reproductive system. The rate of these negative pathophysiological effects can be reduced by performing appropriate managerial, technical, and engineering measures in work environments.

• 한국세라믹학회지
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• 제54권4호
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• pp.314-322
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• 2017

This study investigates changes in the mechanical behavior, such as changes in indentation load-displacement curve, wear resistance and contact fatigue resistance of thermal barrier coatings (TBCs) by thermal cycling test and thermal shock test. Relatively dense and porous TBCs on nickel-based bondcoat/superalloy are prepared; the highest temperature applied during thermal durability test is $1350^{\circ}C$. The results indicate that the porous TBCs have relatively longer lifetime during thermal cycling and thermal shock tests, while denser TBCs have relatively higher wear and contact fatigue resistance. The mechanical behavior is influenced by sintering of the TBCs by exposure to high temperature during tests.

• Environmental Analysis Health and Toxicology
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• 제13권1_2호
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• pp.27-31
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• 1998

Motor vehicle exhaust is the major cause to the air contamination in Seoul. It includes many toxic chemicals to human health such as aidehyde, PAHs, benzene, xylene, toluene, benzo[a]pyrene, nickel, arsenic and cadmium in gasoline exhaust and formaldehyde, PAHs, 1,3-butadiene, benzene and particulate matter in diesel exhaust. Some chemicals out of them are classified as a human carcinogen. Many large diesel vehicles such as buses and trucks are drivened frequently in Seoul so that the air in Seoul is seriously contaminated by diesel exhaust, especially particulate matter. The amounts of particulate matter from large diesel vehicles may be estimated to be more than 50% of small dust in Seoul. The particles of particulate matter are coated with many toxic chemicals and some of these are considered as a human carcinogen. The cancer risk has to be throughly managed because the population density of Seoul is very high. Government should list hazardous air pollutants in Seoul, assess the exposure of people to toxic pollutants, especially carcinogens and manage human health risk.

• 한국세라믹학회지
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• 제55권5호
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• pp.452-460
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• 2018

This study investigate changes in mechanical behaviors such as indentation load-displacement and hardness of thermal barrier coatings (TBCs) using cycling of thermal shock test. Relatively dense and porous TBCs on nickel-based bondcoat/super alloy are prepared using different starting granules, 204C-NS and 204NS commercial powers, and the effect of double layers of 204C-NS on 204NS and 204NS on 204C-NS are investigated. The highest temperature applied during thermal shock test is $1100^{\circ}C$ and the maximum number of cycles is 1,200. The results indicate that bilayered TBC showed a relatively mechanically resistant property during thermal shock cycles and that the mechanical behavior is influenced by the microstructure of TBCs by exposure to high temperature during tests or different starting granules.

• Advances in Energy Research
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• 제3권1호
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• pp.45-57
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• 2015

This article is addressed to define a new composite electrode constituted by porous nickel and an array of highly ordered $TiO_2$ nanotubes obtained by a previous galvanostatic anodization treatment in an ethylene glycol solution. The electrochemical performances of the composite anode were evaluated in a photo-electrolyser, which showed good solar conversion efficiency with respect to the UV irradiance together with a reduction of energy consumption. Such a combination of materials makes our system simple and able to work both in dark and under solar light exposure, thus opening new perspectives for industrial-scale applications.