• Transactions of Materials Processing
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• v.28 no.1
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• pp.43-48
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• 2019

Aluminum nitride (AlN) is used by the semiconductor industry, and is a compound that is required when manufacturing high thermal conductivity. The AlN films with c-axis orientation and thermal conductivity characteristic were deposited by using the Pulsed Laser Deposition (PLD). The AlN thin films were characterized by changing the deposition conditions. In particular, we have researched the AlN thin film deposited under optimal conditions for growth atmosphere. The epitaxial AlN films were grown on sapphire ($c-Al_2O_3$) single crystals by PLD with AlN target. The AlN films were deposited at a fixed temperature of $650^{\circ}C$, while conditions of nitrogen ($N_2$) pressure were varied between 0.1 mTorr and 10 mTorr. The quality of the AlN films was found to depend strongly on the $N_2$ partial pressure that was exerted during deposition. The X-ray diffraction studies revealed that the integrated intensity of the AlN (002) peak increases as a function the corresponding Full width at half maximum (FWHM) values decreases with lowering of the nitrogen partial pressure. We found that highly c-axis orientated AlN films can be deposited at a substrate temperature of $650^{\circ}C$ and a base pressure of $2{\times}10^{-7}Torr$ in the $N_2$ partial pressure of 0.1 mTorr. Also, it is noted that as the $N_2$ partial pressure decreased, the thermal conductivity increased.

• Resources Recycling
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• v.28 no.4
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• pp.3-14
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• 2019

Lead is one of the common non-ferrous metals used in modern industry. The usage of lead continues to increase and has risen from 5 million tonnes per year worldwide in the 1970s to 11 million tonnes in the 2010s. In principle lead is virtually 100 % recyclable as an element without loss of quality. The recycling of lead scrap reduces the energy consumption and environmental burden, comparing to the primary metal production. Therefore production of secondary lead from scrap has been steadily growing and at present it meets approximately 60 % of usage worldwide. Lead scrap (mainly lead-acid battery) is smelted in primary and secondary smelter. Most secondary lead smelting were performed in a shaft-type furnace (blast furnace), rotary furnace and reverberatory furnace. The lead bullion is either cast into ingots and re-melted in refining kettles or refining is performed on the hot lead bullion immediately after production. This work provides an overview of the primary lead production and recycling process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.68-74
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• 2019

In the case of a partition panel for a vehicle, it is used as a vehicle chassis component that serves to distinguish the indoor and outdoor spaces of a vehicle and is mounted on a backrest portion of the vehicle's back seat to ensure the convenience of passengers by connecting the floor and the side of the vehicle. Because it is a relatively large-sized plate material among automobile chassis parts except the moving parts and non-ferrous materials can be applied, it is considered as a part having a large light-weight effect. However, the partition panel is one of the vehicle parts that must satisfy the light-weight effect as well as various structural reliability, such as torsional rigidity, vibration, and impact characteristics, for securing the running stability of the vehicle when driving at the same time. So, In this study, the possibility of replacing the aluminum partition panel as CFRP(Carbon Fiber Reinforced Plastic) partition panel is evaluated through comparing the two partition panels by using the structural reliability(stiffness/strength analysis), vibration analysis, impact analysis.

• Animal Bioscience
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• v.34 no.2
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• pp.265-275
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• 2021

Objective: The study developed mushroom stalk residues as feed additives in the broiler diet for improving the growth performance and immunity of broilers as well as to increase the value of mushroom stalk residues. Methods: In total, 300 ROSS 308 broilers were randomly allocated into fifteen pens with five dietary treatments: i) control, basal diet; ii) CMWM, supplemented with 1% Cordyceps militaris waster medium (CM); iii) CMPE, supplemented with 0.5% CM+0.5% Pleurotus eryngii stalk residue (PE); iv) CMPS, supplemented with 0.5% CM+0.5% Pleurotus sajorcaju stalk residue (PS); v) CMFV, supplemented with 0.5% CM+0.5% Fammulina velutipes stalk residue (FV). Results: The chemical analysis results showed that CM extracts, PE extracts, PS extracts, and FV extracts contain functional components such as polysaccharides and phenols and have both 2, 2-diphenyl-1-picryl-hydrazyl-hydrate scavenging and Ferrous scavenging capacities. The group CMWM saw increased body weight gain and feed conversion rate and the promotion of jejunum villus growth, but there is no significant difference in the intestinal bacteria phase. Antioxidant genes in the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)- antioxidant responsive element pathway among the groups are significantly higher than that of the control group, especially in group CMWM. Conclusion: The mushroom stalk residues have antioxidant functional components, can improve the intestinal health and body weight gain of chickens, and can activate the antioxidant pathway of Nrf2 to increase the heme oxygenase-1 expression. The treatment with 1% CM was the most promising as a feed additive.

• Korean Journal of Metals and Materials
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• v.48 no.5
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• pp.377-386
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• 2010

An investigation was conducted into the effects of $\kappa$-carbides on the cracking phenomenon, which often occurred in cold-rolled light-weight steel plates. Three kinds of steels were fabricated by varying the C content, and their microstructures and tensile properties were investigated. In the two steels that contained a high carbon content, the band structures of ferrites and $\kappa$-carbides that were severely elongated along the rolling direction were well developed, whereas continuous arrays of $\kappa$-carbides were formed in the steel that contained a low carbon content. Detailed microstructural analyses of the deformed region beneath the tensile fracture surface showed that the cracks initiated at arrays of $\kappa$-carbides or $\kappa$-carbides formed interfaces between the band structures, which initiated cleavage fractures in the ferrite bands, while the bands populated with a number of $\kappa$-carbides did not play an important role in propagating the cracks. Thus, the minimization of interfacial $\kappa$-carbides or $\kappa$-carbide arrays by increasing the carbon content was essential for preventing cracking from occurring during cold rolling.

• Korean Journal of Environmental Agriculture
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• v.40 no.1
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• pp.67-72
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• 2021

BACKGROUND: Biological iron redox transformation alters iron minerals, which may act as effective adsorbents for arsenate [As(V)] in the environments. In the viewpoint of alleviating arsenate, microbial Fe(III) reduction was sought under high concentration of As(V). In this study, Fe(III)-reducing bacteria were isolated from the wild plant rhizosphere soils collected at abandoned mine areas, which showed tolerance to high concentration of As(V), in pursuit of potential agents for As(V) bioremediation. METHODS AND RESULTS: Bacterial isolation was performed by a series of enrichment, transfer, and dilutions. Among the isolated strains, two strains (JSAR-1 and JSAR-3) with abilities of tolerance to 10 mM As(V) and Fe(III) reduction were selected. Phylogenetic analysis using 16S rRNA genesequences indicated the closest members of Pseudomonas stutzeri DSM 5190 and Paenibacillus selenii W126, respectively for JSAR-1 and JSAR-3. Ferric and ferrous iron concentrations were measured by ferrozine assay, and arsenic concentration was analyzed by ICP-AES, suggesting inability of As(V) reduction whereas ability of Fe(III) reduction. CONCLUSION: Fe(III)-reducing bacteria isolated from the enrichments with arsenate and ferric iron were found to be resistant to a high concentration of As(III) at 10 mM. We suppose that those kinds of microorganisms may suggest good application potentials for As(V) bioremediation, since the bacteria can transform Fe while surviving under As-contaminated environments. The isolated Fe(III)-reducing bacterial strains could contribute to transformations of iron minerals which may act as effective adsorbents for arsenate, and therefore contribute to As(V) immobilization

• Journal of Soil and Groundwater Environment
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• v.26 no.1
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• pp.45-53
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• 2021

The removal of 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution by coupled electro-oxidation and Fe(II) activated persulfate oxidation process was investigated. The electrochemical oxidation was performed using carbon sheet electrode and persulfate using Fe(II) ion as an activator. The oxidation efficiency was investigated by varying current density (2 - 10 mA/㎠), electrolyte (Na2SO4) concentration (10 - 100 mM), persulfate concentration (5 - 20 mM), and Fe(II) concentration (10 - 20 mM). The 2,4-D removal efficiency was in the order of Fe(II) activated persulfate-assisted electrochemical oxidation (Fe(II)/PS/ECO, 91%) > persulfate-electrochemical oxidation (PS/ECO, 51%) > electro-oxidation (EO, 36%). The persulfate can be activated by electron transfer in PS/ECO system, however, the addition of Fe(II) as an activator enhanced 2,4-D degradation in the Fe(II)/PS/ECO system. The 2,4-D removal efficiency was not affected by the initial pHs (3 - 9). The presence of anions (Cl- and HCO3-) inhibited the 2,4-D removal in Fe(II)/PS/ECO system due to scavenging of sulfate radical. Scavenger experiment using tert-butyl alcohol (TBA) and methanol (MeOH) confirmed that although both sulfate (SO4•-) and hydroxyl (•OH) radicals existed in Fe(II)/PS/ECO system, hydroxyl radical (SO4•-) was the predominant radical.

• Journal of Korea Foundry Society
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• v.41 no.4
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• pp.342-348
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• 2021

Almost all ferrous foundries use press scrap as the main charge material. In this study, we tried to reduce the melting energy by optimizing the shape and size of press scrap. The experiment was conducted using 3t/h medium frequency induction melting furnaces at two foundries. In the case of the improved condition, customized press scrap was used for initial charging, and small press scrap was used for additional charging. The energy reduction effect of the improved condition was enhanced by reinforcing the cleaning process of the return scrap surface. The reduction ratios of the melting energy basic unit by the improved condition at the two foundries were almost the same (23.3 and 23.9%). The improved condition was very effective in both foundries with different basic unit levels. The reasons for energy reduction and the economic effects of the improved condition were described.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.533-537
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• 2003

Compared to sintered polycrystalline diamond (PCD), the deposited thin film diamond has a great advantage on the fabrication of cutting tools with complex geometries such as drills. Because of high performance in high speed machining non-ferrous difficult-to-cut materials in the field of automobiles industry, aeronautics and astronautics industry, diamond-coated drills find large potentialities in commercial applications. However, the poor adhesion of the diamond film on the substrate and high surface roughness of the drill flute adversely affect the tool lift and machining quality and they become the main technical barriers for the successful development and commercialization of diamond-coated drills. In this paper, diamond thin films were deposited on the commercial WC-Co based drills by the electron aided hot filament chemical vapor deposition (EACVD). A new multiple coating technology based on changing gas pressure in different process stages was developed. The large triangular faceted diamond grains may have great contribution to the adhesive strength between the film and the substrate, and the overlapping ball like blocks consisted of nanometer sized diamond crystals may contribute much to the very low roughness of diamond film. Adhesive strength and quality of diamond film were evaluated by scanning electron microscope (SEM), atomic force microscope (AFM), Raman spectrum and drilling experiments. The ring-block tribological experiments were also conducted and the results revealed that the friction coefficient increased with the surface roughness of the diamond film. From a practical viewpoint, the cutting performances of diamond-coated drills were studied by drilling the SiC particles reinforced aluminum-matrix composite. The good adhesive strength and low surface roughness of flute were proved to be beneficial to the good chip evacuation and the decrease of thrust and consequently led to a prolonged tool lift and an improved machining quality. The wear mechanism of diamond-coated drills is the abrasive mechanical attrition.

• Corrosion Science and Technology
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• v.23 no.4
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• pp.283-288
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• 2024

Hot-dip Zn-Mg-Al coatings have a complex microstructure consisting of Zn, Al, and MgZn₂ phases. Its crystal structure depends on alloy content and cooling rates. Microstructure and corrosion resistance of these coatings might be affected by heat treatment. To investigate effect of heat treatment on microstructure and corrosion resistance of Zn-Mg-Al coatings, Zn-1.5%Mg-1.5%Al coated steel was heated up to 550 ℃ at a heating rate of 80 ℃/s and cooled down to room temperature. At above 500 ℃, the ternary phase of Zn-MgZn₂-Al was melted down. Only Zn and MgZn₂ phases remained in the coating. Heat- and non-heat-treated specimens showed similar corrosion resistance in Salt Spray Test (SST). When a Zn-3.0%Mg-2.5%Al coated steel was subjected to heat treatment at 100 ℃ or 300 ℃ for 200 h and compared with GA and GI coated steels, the microstructure of coatings was not significantly changed at 100 ℃. However, at 300 ℃, most Al in the coating reacted with Fe in the substrate, forming a Fe-Al compound layer in the lower part of the coating. MgZn₂ was preferentially formed in the upper part of the coating. As a result of SST, Zn-Mg-Al coated steels showed excellent corrosion resistance, better than GA and GI.