• Korean Journal of Materials Research
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• v.20 no.2
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• pp.60-64
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• 2010

This study looked at high performance copper-based alloys as LED lead frame materials with higher electrical-conductivity and the maintenance of superior tensile strength. This study investigated the effects on the tensile strength, electrical conductivity, thermal softening, size and distribution of the precipitation phases when Cr was added in Cu-Fe alloy in order to satisfy characteristics for LED Lead Frame material. Strips of the alloys were produced by casting and then properly treated to achieve a thickness of 0.25 mm by hot-rolling, scalping, and cold-rolling; mechanical properties such as tensile strength, hardness and electrical-conductivity were determined and compared. To determine precipitates in alloy that affect hardness and electrical-conductivity, electron microscope testing was also performed. Cr showed the effect of precipitation hardened with a $Cr_3Si$ precipitation phase. As a result of this experiment, appropriate aging temperature and time have been determined and we have developed a copper-based alloy with high tensile strength and electrical-conductivity. This alloy has the possibility for use as a substitution material for the LED Lead Frame of Cu alloy.

• Journal of the Korean institute of surface engineering
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• v.52 no.5
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• pp.246-250
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• 2019

Nano-multilayered $Cr_{25.2}Al_{19.5}Si_{4.7}N_{50.5}$ films were deposited on the steel substrate by cathodic arc plasma deposition. They were corroded at $900^{\circ}C$ in $Ar/1%SO_2$ gas in order to study their corrosion behavior in sulfidizing/oxidizing environments. Despite the presence of sulfur in the gaseous environment, the corrosion was governed by oxidation, leading to formation of protective oxides such as $Cr_2O_3$ and ${\alpha}-Al_2O_3$, where Si was dissolved. Iron diffused outward from the substrate to the film surface, and oxidized to $Fe_2O_3$ and $Fe_3O_4$. The films were corrosion-resistant up to 150 h owing to the formation of thin ($Cr_2O_3$ and/or ${\alpha}-Al_2O_3$)-rich oxide layers. However, they failed when corroded at $900^{\circ}C$ for 300 h, resulting in the formation of layered oxide scales due to not only outward diffusion of Cr, Al, Si, Fe and N, but also inward movement of sulfur and oxygen.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.3
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• pp.195-214
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• 2020

The Samgwang Au-Ag deposit has been one of the largest deposits in Korea. The deposit consists of eight lens-shaped quartz veins which filled fractures along fault zones in Precambrian metasedimentary rock, which feature suggest that it is an orogenic-type deposit. The Ti-bearing minerals occur in wallrock (titanite, ilmenite and rutile) and laminated quartz vein (rutile). They occur minerals including biotite, muscovite, chlorite, white mica, monazite, zircon, apatite in wallrock and white mica, chlorite, arsenopyrite in laminated quartz vein. Chemical composition of titanite has maximum vaules of 3.94 wt.% (Al₂O₃), 0.49 wt.% (FeO), 0.52 wt.% (Nb₂O₅), 0.46 wt.% (Y₂O₃) and 0.43 wt.% (V₂O₅). Titanite with 0.06~0.14 (Fe/Al ratio) and 0.06~0.15 (X_Al (=Al/Al+Fe³⁺+Ti)) corresponds with metamorphic origin and low-Al variety. Chemical composition of ilmenite has maximum values of 0.07 wt.% (ZrO₂), 0.12 wt.% (HfO₂), 0.26 wt.% (Nb₂O₅), 0.04 wt.% (Sb₂O₅), 0.13 wt.% (Ta₂O₅), 2.62 wt.% (As₂O₅), 0.29 wt.% (V₂O₅), 0.12 wt.% (Al₂O₃) and 1.59 wt.% (ZnO). Chemical composition of rutile in wallrock and laminated quartz vein has maximum values of 0.35 wt.%, 0.65 wt.% (HfO₂), 2.52 wt.%, 0.19 wt.% (WO₃), 1.28 wt.%, 1.71 wt.% (Nb₂O₃), 0.03 wt.%, 0.07 wt.% (Sb₂O₃), 0.28 wt.%, 0.21 wt.% (As₂O₅), 0.68 wt.%, 0.70 wt.% (V₂O₃), 0.48 wt.%, 0.59 wt.% (Cr₂O₃), 0.70 wt.%, 1.90 wt.% (Al₂O₃) and 4.76 wt.%, 3.17 wt.% (FeO), respectively. Rutile in laminated quartz vein is higher contents (HfO₂, Nb₂O₃, As₂O₅, Cr₂O₃, Al₂O₃ and FeO) and lower content (WO₃) than rutile in wallrock. The substitutions of rutile in wallrock and laminated quatz vein are as followed : rutile in wallrock [(Fe³⁺, Al³⁺, Cr³⁺) + Hf⁴⁺ + (W⁵⁺, As⁵⁺, Nb⁵⁺) ⟵⟶ 2Ti⁴⁺ + V⁴⁺, 2Fe²⁺ + (Al³⁺, Cr³⁺) + Hf⁴⁺ + (W⁵⁺, As⁵⁺, Nb⁵⁺) ⟵⟶ 2Ti⁴⁺ + 2V⁴⁺], rutile in laminated quartz vein [(Fe³⁺, Al³⁺) + As⁵⁺ ⟵⟶ Ti⁴⁺ + V⁴⁺, (Fe³⁺, Al³⁺) + As⁵⁺ ⟵⟶ Ti⁴⁺ + Hf⁴⁺, 4(Fe³⁺, Al³⁺) ⟵⟶ Ti⁴⁺ + (W⁵⁺, Nb⁵⁺) + Cr³⁺], respectively. Based on these data, titanite, ilmenite and rutile in wallrock were formed by resolution and reconcentration of cations (W⁵⁺, Nb⁵⁺, As⁵⁺, Hf⁴⁺, V⁴⁺, Cr³⁺, Al³⁺, Fe³⁺, Fe²⁺) in minerals of wallrock during regional metamorphism. And then rutile in laminated quartz vein was formed by reconcentration of cations (Nb⁵⁺, As⁵⁺, Hf⁴⁺, Cr³⁺, Al³⁺, Fe³⁺, Fe²⁺) in alteration minerals (white mica, chlorite) and Ti-bearing minerals reaction between hydrothermal fluid originated during ductile shear and Ti-bearing minerals (titanite, ilmenite and rutile) in wallrock.

• Journal of the Korea Organic Resources Recycling Association
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• v.13 no.4
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• pp.107-117
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• 2005

The objective of this study was to investigate the proper operation conditions of fenton oxidation such as initial pH, $H_2O_2/Fe^{2+}$ ratio, $H_2O_2/Fe^{2+}$ dosage amount, and neutralizing agent for pretreatment of the livestock wastewater. Fenton oxidation reagents were reacted with the livestock wastewater for 2 hours at 120 rpm and the settling was performed for 2 hours using jar-tester apparatus under the different experimental conditions. And then the supernatant was sampled and measured for the residual $H_2O_2$, $COD_{Cr}$, and SS. The results are as follows; optimum initial pH=4, optimum $H_2O_2/Fe^{2+}$ ratio=10:1, optimum $H_2O_2/Fe^{2+}$ dosage amount=5,000/500 mg/L and $Ca(OH)_2$ as proper neutralizing agent. The removal efficiency of $COD_{Cr}$ and SS were 43% and 84% under those optimal fenton oxidation conditions.

• Korean Journal of Environmental Agriculture
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• v.39 no.4
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• pp.289-296
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• 2020

BACKGROUND: There is a need for a revolutionary method to overcome the problem of biochar, which has relatively low adsorption capacity for existing anion pollutants, along with collectively recycling fallen leaves, a kind of forest by-product. Therefore, the objective of this study was to prepare iron-decorated biochar derived from fallen leaves (Fe-FLB), and to evaluate their adsorption properties to Congo red (CR) as anionic dye. METHODS AND RESULTS: The adsorption properties of CR by fallen leaves biochar (FLB) and Fe-FLB were performed under various conditions such as initial CR concentration, reaction time, pH and dosage with isotherm and kinetic models. In this study, Fe-FLB prepared through iron impregnation and pyrolysis of fallen leaves contained 56.9% carbon and 6.3% iron. Congo red adsorption by FLB and Fe-FLB was well described by Langmuir model and pseudo second order model and the maximum adsorption capacities of FLB and Fe-FLB were 1.1 mg/g and 25.6 mg/g, respectively. In particular, it was found that the adsorption of CR was occurred by chemical adsorption process by the outer boundary layer of Fe-FLB. CONCLUSION: Overall, the production of Fe-FLB using fallen leaves and using it as an anion adsorbent is considered to be a way to overcome the problem of biochar with relatively low anion adsorption in addition to the reduction effect of waste.

• Journal of the Korean institute of surface engineering
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• v.33 no.1
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• pp.10-16
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• 2000

Characteristics of cavitation erosion resistance of Fe-20Cr-1Si-1C-xMn(x=0, 5, 15) alloys were investigated by SEM and XRD analysis. The effects on strain-induced transformations were considerably reduced with increasing the amounts of Mn due to twining that occurred at 5, 15Mn alloys, activating cavitation erosion rates(mg/$\textrm{cm}^2$) which varied as 0.055, 0.114 and 0.160mg/$\textrm{cm}^2$ for 0, 5, 15Mn. From the results, it was found that the addition of Mn element in Fe-base alloy provides more cracking sites at twins rather than absorbing strain energies, so accelerates cavitation erosion rates.

• Journal of the Korean institute of surface engineering
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• v.32 no.1
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• pp.43-48
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• 1999

Oxidation behavior of 304 and 316 stainless steels was studied. After solution heat treatment, specimens were polished up to 1$mu \textrm{m}$ using $Al_2O_3$ powder and then subjected to oxidation between $300^{\circ}C$ and 50$0^{\circ}C$ in dry air. TEM and EDS were used for analyzing the components and structure of oxide film. TEM analysis of oxide film revealed that thin amorphous Fe oxide ($Fe_2O_3$) was formed on the top of surface while polycrystalline (Cr, $Fe_2O_3$ was formed below the amorphous Fe oxide layer. The specimens oxidized at $500^{\circ}C$ showed that 316 stainless steel had higher oxidation resistance than 304 stainless steel. These results suggest that Mo component of 316 stainless steel suppresses the formation of Cr carbide which may result in a local Cr depleted area.

• Journal of the Korean institute of surface engineering
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• v.51 no.4
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• pp.214-217
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• 2018

Stainless steel grade 430 with a composition of Fe-17%Cr was corroded in $Na_2SO_4$ and ($Na_2SO_4+NaCl$) salts at 800 and at $900^{\circ}C$ for up to 20 h. It corroded mainly to $Cr_2O_3$, along with a small amount of $Fe_2O_3$ and $Fe_3O_4$. The formed oxide scales were neither dense nor compact enough owing to their ensuing dissolution into the salt during corrosion, which facilitated internal corrosion. Corrosion occurred faster at $900^{\circ}C$ than $800^{\circ}C$. NaCl in $Na_2SO_4$ aggravated the scale adherence.

• Transactions of Materials Processing
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• v.26 no.6
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• pp.356-364
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• 2017

In this study, submerged arc cladded Fe-Cr-Ni-Mo-CuWNbV-C stainless steels containing various Cr contents between 11.2 wt.% and 16.7 wt.% were prepared with fixed C content at about 0.14 wt.%. Using these alloys, changes in microstructure, tensile property, and thermal fatigue property were investigated. Phase fraction of delta-ferrite was increased gradually with increasing Cr content. However, tensile strength, hardness, and thermal fatigue resistance appeared to be decreased. When the microstructure of delta-ferrite was observed, it was revealed that the mesh structure retained up to about 15% Cr content. Although thermal fatigue resistance was almost the same for Cr contents between 11.0 and 14.5 wt.%, it was significantly decreased at higher Cr contents. This was evident from mean value of crack lengths of 10 largest ones. Evaluation of thermal fatigue resistance on alloys with various Cr contents revealed the following important results. First, the reproducibility of ranking test was excellent regardless of the number of cycles. Second, thermal fatigue resistance was increased in proportion to true tensile fracture strength values of overlay materials. Finally, the number of thermal fatigue cracks per unit length was increased with increasing true tensile fracture strength.

• Korean Journal of Materials Research
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• v.6 no.6
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• pp.585-588
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• 1996

여러 가지 Zr합금에서 생성되는 석출물의 특성을 규명하기 위하여 시편을 $600^{\circ}C$에서 1시간 동안 열처리 한후 EDX가 부착된 TEM을 이용하여 석출물에 관한 연구를 수행하였다. Zr1.4Sn0.2Fe0.1Cr 합금에서는 두 종류의 석출물이 생성되는데 하나는 석출물의 대부분을 차지하는 HCP 구조으 Zr(Cr, Fe)2 석출물로서 이는 둥근 형태를 유지하며 결정립내나 결정립계에 관계없이 널리 분산되어 분포된다. 다른 하나의 석출물은 극히 일부에서만 관찰되는 Zr2(Fe, Si)성분의 석출물로서 이는 tetragonal 구조를 갖는다. Zr0.5Nb0.6Fe0.3V 합금에서는 tetragonal (Zr, Nb)2(Fe, V) 석출물이 형성되며, Nb이 1.0 wt.% 첨가된 Zr1.0Nb0.6Fe0.3V 합금에서는 HCP 구조의 (Zr, Nb)(Fe, V)2 석출물과 BCC 구조인 $\beta$-Zr이 생성된다. Zr1.0Nb0.6Fe0.3V합금을 제외하고는 대부분의 합금에서 석출물은 약 1.0$\mu\textrm{m}$의 크기를 나타냈다. 합금 조성이 다를 경우에 석출물 크기와 35$0^{\circ}C$ 부식 특성과는 부식 특성과는 연관성이 없는 것로 나타났다.