• Resources Recycling
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• v.16 no.6
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• pp.3-9
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• 2007

Although the ferrous material was separated by the magnetic separation before the incineration process, the municipal solid waste incineration bottom ash generated during incinerator in metropolitan area consists of many iron products which account for about $3{\sim}11%$ as well as ceramics and glasses. The formation of $NiFe_2O_4$ and $FeCr_2O_4$ with a $Fe_3O_4-Fe_2O_3$ (similar to pure Fe) on the surface of iron product was found during air-annealing in the incinerator at $1000^{\circ}C$, because Ni and Cr has a chemical attraction about iron is using to coat with Ni and Cr metals for poish or to prevent corrosion. Therefore, Fe-Ni Cr oxide can be formed on durface of the iron product and it can be separated from bottom ash through the magnetic separation. So, in this study, the separation ratio of heavy metals as magnetic separation and mineralogical formation of Fe-ion(heavy metal) in ferrous metals corroded were investigated. As the result, the separation ratio of Ni and Cr based on particle sizes accounted for about $45{\sim}50%$, and Cu and Pb accounted for below 20%. Also, the leaching concentration of Ni and Cr in bottom ash separated by magnetic separation was lower than that in fresh bottom ash.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.213-213
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• 2016

현재 반도체 산업에서는 디바이스의 고 집적화, 고 수율을 목적으로 패턴의 미세화 및 웨이퍼의 대면적화와 같은 이슈가 크게 부각되고 있다. 다중 패터닝(multiple patterning) 기술을 통하여 고 집적 패턴을 구현이 가능해졌으며, 이와 같은 상황에서 각 패턴의 임계치수(critical dimension) 변화는 패턴의 위치 및 품질에 큰 영향을 끼치기 때문에 포토마스크의 임계치수 균일도(critical dimension uniformity, CDU)가 제작 공정에서 주요 파라미터로 인식되고 있다. 반도체 광 리소그래피 공정에서 크롬(Cr) 박막은 사용되는 포토 마스크의 재료로 널리 사용되고 있으며, 이러한 포토마스크는 fused silica, chrome, PR의 박막 층으로 이루어져 있다. 포토마스크의 패턴은 플라즈마 식각 장비를 이용하여 형성하게 되므로, 식각 공정의 플라즈마 균일도를 계측하고 관리 하는 것은 공정 결과물 관리에 필수적이며 전체 반도체 공정 수율에도 큰 영향을 미친다. 흔히, 포토마스크 임계치수는 플라즈마 공정에서의 라디칼 농도 및 식각 선택비에 의해 크게 영향을 받는 것으로 알려져 왔다. 본 연구에서는 Cr 포토마스크 에칭 공정에서의 Cl2/O2 공정 플라즈마에 대해 O2 가스 주입량에 따른 식각 선택비(etch selectivity) 변화를 계측하여 선택비 제어를 통한 Cr 포토마스크 임계치수 균일도 향상을 실험적으로 입증하였다. 연구에서 사용한 플라즈마 계측 방법인 발광분광법(OES)과 optical actinometry의 적합성을 확인하기 위해서 Cl2 가스 주입량에 따른 actinometer 기체(Ar)에 대한 atomic Cl 농도비를 계측하였고, actinometry 이론에 근거하여 linear regression error 1.9%을 보였다. 다음으로, O2 가스 주입비에 따른 Cr 및 PR의 식각률(etch rate)을 계측함으로써 식각 선택비(etch selectivity)의 변화율이 적은 O2 가스 농도 범위(8-14%)를 확인하였고, 이 구간에서 임계치수 균일도가 가장 좋을 것으로 예상할 수 있었다. (그림 1) 또한, spatially resolvable optical emission spectrometer(SROES)를 사용하여 플라즈마 챔버 내부의 O atom 및 Cl radical의 공간 농도 분포를 확인하였다. 포토마스크의 임계치수 균일도(CDU)는 챔버 내부의 식각 선택비의 변화율에 강하게 영향을 받을 것으로 예상하였고, 이를 입증하기 위해 각각 다른 O2 농도 환경에서 포토마스크 임계치수 값을 확인하였다. (표1) O2 11%에서 측정된 임계치수 균일도는 1.3nm, 그 외의 O2 가스 주입량에 대해서는 임계치수 균일도 ~1.7nm의 범위를 보이며, 이는 25% 임계치수 균일도 향상을 의미함을 보인다.

• Journal of the Korean Ceramic Society
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• v.12 no.1
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• pp.29-36
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• 1975

This study was conducted to research the formation, color development and application for colored glazes of the spinel solid solutions of the green pigment. On specimens prepared by calcining the oxide and basic carbonate mixture at 1250℃ for 1.5 hour, the x-ray analysis, measurement of reflectance and the test of their stabiality as a glaze pigment were carried out. The results are summarized as follows 1) Each sample is composed of single spinel and not of mixture of spinel. 2) Formation of continuous soild solution, except for a few instances, pertaining to Vegard's law was confirmed by means of the x-ray analysis. 3) The more difference between absorption and reflectance lies, the lighter colors are. When the absorption occurs at the high-reflectance, the excitation purity becomes low. On the contrary when the absorption takes place at the low-reflectance, the excitation purity becomes low. On the contrary when the absorption takes place at the low-reflectance, the excitation purity is higher. 4) Colors obtained in the CdO-MgO-Cr2O3-Al2O3 system, as the amounts of Al3+ increased, change from green through brown to pink, and the absorption peak shifts towards violet region. 5) An increase in Co2+ in the CoO-MgO-Cr2O3-Al2O3 system, changes the color from blue green to dark blue. The excitation purity is higher, and the absorption peak shifts toward regions. 6) Colors are green in the NiO-MgO-Cr2O3 and CdO-MgO-Cr2O3 systems in general, but in the ZnO-MgO-Cr2O3 system brillant hue is not obtained. 70 According to the results of the colored glaze test, the spinels turn outto be stable as brilliant glaze pigment in the calcium-magnesia glaze.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.2
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• pp.235-242
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• 2007

Road runoff water includes various heavy metals (zinc, Zn; lead, Pb; copper, Cu; chrome, Cr; cadmium, Cd; etc.) and pathogens (E-coli and coliform). Since these pollutants are significantly harmful to human beings and have negative impact on water streams, numerous studies have been conducted to determine the characterization of these non-point pollutants from road runoff water. However, since these non-point pollutant concentrations vary depending on road traffic, road construction, and road maintenance, measurement of pollutant loadings in different site is necessary to estimate the effect of road runoff water on drinking water source. The objective of this study was to examine the quality of road runoff water from a city bridge in Seoul, Korea. This study was conducted for two years to assess annual discharge pollution loads. In this study, five key heavy metals (Zn, Pb, Cu, Cr, and Cd) and two pathogens (E-coli and coliform) were measured at 18 different events. The pollutant load mass transported was always higher than the corresponding runoff volume for Zn, Cu, and Cd, while Pb and Cr showed similar values between the load mass transported and the corresponding runoff volume. The event mean concentrations were Zn (0.908 mg/L), Pb (0.092 mg/L), Cu (0.141 mg/L), Cr (0.023 mg/L), and Cd (0.006 mg/L). Like Zn, Cu, and Cd, E-coli and coliform values (relatively high in Summer and Fall) are higher at the beginning of each event and decrease afterwards.

• Journal of Soil and Groundwater Environment
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• v.8 no.2
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• pp.19-35
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• 2003

In order 새 investigate the spatial and seasonal variations of heavy metal pollution in heavily industrialized urban area, urban roadside sediments were collected for five years from gully pots in Seoul City. A series of studies have been carried out concerning the physicochemical characteristics of the sediments in order to evaluate the contamination of heavy metals such as Cd, Co, Cr, Cu, Ni, Pb and Zn. Roadside sediments and uncontaminated stream sediments were analyzed for total metal concentrations using acid extraction. The roadside sediments are characterized by very high concentrations of Zn (2,665.0$\pm$1,815.0 $\mu\textrm{g}$/g), Cu (445.6$\pm$708.0 $\mu\textrm{g}$/g), Pb (214.3$\pm$147.9 $\mu\textrm{g}$/g) and Cr (182.1$\pm$268.8 $\mu\textrm{g}$/g), indicating an artificial accumulation of these metals to the sediment chemistry. Comparing with average contents of uncontaminated stream sediments, roadside sediments were shown zinc 14 times (up to 64.4), copper 9 times (up to 181.7), lead 6 times (up to 63.7), cobalt 6 times (up to 168.7), nickel 4 times (up to 98.4), cadmium 2 times (up to 12.8) and chrome 2 times (up to 40.2) high content. The relative degree of heavy metal pollution for roadside sediments collected from each district in Seoul City is evaluated using the “geoaccumulation index”. As a result, heavy-metal contamination is highest centering the oldest residential district and industry area, and contamination level decreases as go to outer block of the city. The factor analysis results indicate that the levels of Cu, Ni, Fe and Cr are strongly related to numbers of factories, whereas the concentrations of Cr, Zn and Cd dependant on pollution index, indicating artificial contamination due to site-specific traffic density.

• Journal of dental hygiene science
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• v.14 no.3
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• pp.405-410
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• 2014

The purpose of this study in vitro investigation was to compare the marginal and internal fit of Ni-Cr alloy metal ceramic crown before and after porcelain veneering. Furthermore, this study evaluated whether the influence of the porcelain firing on the precision of fit of dental prostheses. The maxillary right incisor was selected as an abutment for experiments. Ten working models were prepared. Ni-Cr alloy cores appropriate for each abutment were prepared by lost wax technique. The marginal area and four internal areas of the crowns were measured at two stages: before veneering process and after upper porcelain firing. Silicone replica techniques were used. The data were statistically analyzed with the paired t-test (${\alpha}=0.05$). $Mean{\pm}SD$ marginal and internal gap were $67.1{\pm}23.3{\mu}m$ for the nickle chrome alloy core group and $74.4{\pm}21.9{\mu}m$ for the metal ceramic crown group. There were statistically significant differences in all investigated areas (p<0.05). Within the limitations of this study, none of the Ni-Cr alloy metal crown values measured after porcelain firing process exceeded $120{\mu}m$, which is the clinically acceptable threshold.

• Journal of Welding and Joining
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• v.32 no.6
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• pp.41-46
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• 2014

In this study, cracking susceptibility of laser cladding was investigated according to the processing parameters such as laser power, scan speed and feeding rate with blended powders of stellite#6 and technolase40s (WC+NiCr). The solidification microstructure of clad was composed of Co-based dendrite structures with ${\gamma}+Cr7C3$ eutectic phases at the dendritic boundaries. The crack propagation showed transgranular fracture along dendritic boundaries due to brittle chrome carbide at the eutectic phases. From results of fractography experiments, the fracture surface was typical cleavage brittle fracture in the clad and substrate. The number of clad cracks, caused by a tensile stress after the solidification, increased with increase of laser power, scan speed and feeding rate. Increase of the laser power caused large pores by facilitating WC decarburizing reaction. And the pores affected increase of crack susceptibility. High scan speed caused increment of clad cracks due to thermal stress and WC particle fractures. Also, increase of the feeding rate accompanied an amount of WC particles causing crack initiation and decarburizing reaction.

• Journal of Nutrition and Health
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• v.8 no.1
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• pp.39-46
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• 1975

This studies were designed to know the contents of trace element and magnesium in cereals. Twenty two kinds of cereal, 104'samples, were analyzed by atomic absorption spectrophotometer for the determination of Manganese, Iron, Magnesium, Chrome, Cupper, Nickel, Zinc, Stannous, Lead and Cadmium. The results are as follows: 1) The contents of Mn and Fe in the sesame group show highest value and next is bean group. In the rice group its content shows lowest value than other cereals. 2) In the Cr content its value is lower than other elements in cereals respectively. Cr content of sesame and bean group show higher than rice and barley group. 3) The contents of Cu and Ni in the sesame and bean group show higher value than the value of rice and barley group. Its contents of rice and barley group is almost equal in Cu and Ni. 4) For the Zn content the value of sesame group is higher than other cereals and next is bean group. In the Sn content the value of bean group shows higher one than other cereals. The contents of Zn and Sn in rice and barley group are lower than other cereals. 5) The value of Pb is almost equal to each cereal. The content of Cd in bear group and barley group show higher than other cereals and its value of rice group is equal to the value of barley group.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.2
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• pp.98-102
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• 2000

The effect of vacuum heat treatment in the thermal sprayed ceramics coating on a capstan by either high velocity oxygen fuel(HVOF) or plasma thermal spray process was investigated. The coating materials applied on the capstan were tungsten and chrome carbides. In order to characterize the interface between coating layer and bare materials, hardness, adhesion strength, X-ray diffraction(XRD) and microstructural analysis are conducted. The adhesion strength of the carbide coated materials by HVOF process is over 500MPa compared to those of plasma coating process is 230MPa. In case of the carbide coated materials by HVOF process, the adhesion strength is increased to 15MPa and the porosity is reduced under 5% by vacuum heat treatment for 5 hrs at $1000^{\circ}C$. The XRD results reveal that the increasement is believed due to the phase stabilization of metastable $Cr_3C_2$ phase to stable $Cr_{23}C_6$ phase.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.956-961
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• 2003

Recently, environmental pollution has become a significant problem in industry and many researches have been investigated in order to preserve the environment. Environmentally conscious machining and technology have more and more important position in machining process. In the milling process, the cutting fluid has greatly bad influence on the environment. In this study, the machining of blade parts(12Cr steel) using the cutting fluid, compressed cold air and oil mist etc., also, the productivity and the surface topography was improved by using new end-mil tool considering tool material and shape.