• Journal of Welding and Joining
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• v.18 no.2
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• pp.86-94
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• 2000

This study was performed to investigate types and formation mechanism of cracks in two Al alloy welds, A5083 and A7N01 spot-welded by pulse Nd : YAG laser, using SEM, EPMA and Micro-XRD. In the weld zone, three types of crack were observed : center line crack({TEX}$C_{C}${/TEX}), diagonal crack({TEX}$C_{D}${/TEX}), and U shape crack({TEX}$C_{U}${/TEX}). Also, HAZ crack({TEX}$C_{H}${/TEX}) was observed in the HAZ region, furthermore, mixing crack({TEX}$C_{M}${/TEX}) consisting of diagonal crack and HAZ crack was observed. White film was formed at th hot crack region in the fractured surface after it was immersed to 10% NaOH water. In the case of A5083 alloy, white films in {TEX}$C_{C}${/TEX} crack and {TEX}$C_{D}${/TEX} crack region were composed of low melting phases, {TEX}$Fe_{2}SiAl_{8}${/TEX} and eutectic phases, $Mg_2$Al$_3$ and $Mg_2$Si. Such films observed $CuAl_2$, {TEX}$Mg_{32}(Al,Zn)_{3}${/TEX}, MgZn$_2$, $Al_2$CuMg and $Mg_2$Si were observed in the whitely etched films near {TEX}$C_{C}${/TEX} crack and {TEX}$C_{D}${/TEX} crack regions. The formation of liquid films was due to the segregation of Mg, Si, Fe in the case of A5083 alloy and Zn, Mg, Cu, Sim in the case of A7N01 alloy, respectively. The {TEX}$C_{C}${/TEX} and {TEX}$C_{D}${/TEX} cracks were regarded as a result of the occurrence of tensile strain during the welding process. The formation of {TEX}$C_{M}${/TEX} crack is likely to be due to the presence of liquid film at the grain boundary near the fusion line in the base metal as well as in the weld fusion zone during solidification. The {TEX}$C_{U}${/TEX} crack is considered a result of the collapsed keyhole through incomplete closure during rapid solidification.

• Journal of Powder Materials
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• v.29 no.3
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• pp.240-246
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• 2022

Novel Ni- and Fe-based alloys are developed to impart improved mechanical properties and corrosion resistance. The designed alloys are manufactured as a powder and deposited on a steel substrate using a high-velocity oxygen-fuel process. The coating layer demonstrates good corrosion resistance, and the thus-formed passive film is beneficial because of the Cr contained in the alloy system. Furthermore, during low-temperature heat treatment, factors that deteriorate the properties and which may arise during high-temperature heat treatment, are avoided. For the heattreated coating layers, the hardness increases by up to 32% and the corrosion resistance improves. The influence of the heat treatment is investigated through various methods and is considered to enhance the mechanical properties and corrosion resistance of the coating layer.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.11a
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• pp.42-42
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• 2011

To evaluate the Hwangsu spring as natural mordants effect on dyeing. The natural mordants effect of Hwangsu spring were analyzed by pH, temperature, trace elements, organic matter and color fastness. Hwangsu spring having pH 2.42 and $14.4^{\circ}C$ was harvested at the end of September, in Yeongcheon (Gyeongbuk Province, Korea) and left on a $0^{\circ}C$ and $25^{\circ}C$ before use. Hwangsu spring during storage at $25^{\circ}C$ turned brown by photochemical reaction. The Result of ICP analysis, it contained Fe(414.9 ppm), Al(88.9 ppm), Mn(4.9 ppm) and observed character by water analysis. Dyeing and post-mordant procedure; Cotton(KS K 0905) were dyed with clove powder for 30 min at $70^{\circ}C$. Hwangsu spring, Aluminium Sulfate $14-18H_20(Al_2(SO_4)_3{\cdot}14-18H_2O)$, Iron Sulfate Heptahydrate($FeSO_4{\cdot}7H_2O$) were used by post mordant at the same ratio. The dyed fabrics were treated with 20% each mordant solution at $25^{\circ}C$ for 10min. Comparison with a reproduced chemical mordant, the K/S values of cotton fabrics dyed with Hwangsu sping were increased.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.5
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• pp.719-725
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• 2003

An experiment was conducted to study the requirement of calcium (Ca) and non-phytin phosphorus (NPP) in commercial broilers during starter phase. Seven hundred and twenty day-old Vencob male broiler chicks were randomly distributed into 144 stainless steel battery brooders, 5 birds in each. Four levels each of Ca (6, 7, 8, and 9 g/kg) and NPP (3, 3.5, 4, and 4.5 g/kg diet) were fed in a factorial design in a corn-soya basal diet. Levels of dicalcium phosphate and oyster shell grit were adjusted to obtain the desired levels of Ca and NPP. Each diet was fed ad libidum to chicks in 9 battery brooders from one d to 21 d of age. Body weight gain and feed intake were depressed (p<0.01) by increasing the dietary Ca level (8 and 9 g/kg) at lower levels of NPP (3 and 3.5 g/kg diet). The growth depression observed at lower NPP level was alleviated by reducing the Ca content to 6 g/kg diet. The tibia ash content and tibia breaking strength increased with increase in both Ca (>6 g/kg) and NPP (>3 g/kg) levels. The leg abnormality score decreased (p<0.01) with increase in NPP content in the diet at all levels of Ca tested. The serum Ca and inorganic P levels were increased with increase in the level of the respective mineral in the diet, but the serum concentration of Ca and P were inversely related to the level of NPP and Ca, respectively /kg diet. In general, the excretion of macro minerals (Ca, and P), and micro minerals {zinc (Zn), manganese (Mn), iron (Fe), and copper (Cu)} was significantly lower at lower levels of Ca and NPP tested (6 and 3 g/kg diet, respectively). The mineral excretion increased with increase in dietary Ca and NPP levels, more conspicuously at the disproportionate ratio of these minerals (>2:1, Ca and NPP). Similarly, the retention of Zn, Mn, and Fe in liver was significantly higher (p<0.01) at lower levels of Ca and NPP tested. Results from this study indicate that the commercial broilers do not require more than 3 g NPP and 6g Ca/kg diet during starter phase (up to 21 d of age) for optimum weight gain, feed efficiency and utilization of Ca, P, Zn, Mn, Fe and Cu. However, the requirements of these minerals for optimum bone mineralization were higher than the levels suggested above.

• Journal of the Korean Chemical Society
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• v.53 no.4
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• pp.407-414
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• 2009

The solid complexes of Cu(II), Ni(II), Co(II), Mn(II) and Fe(III) with 4-hydroxy-3-(1-{2-(2-hydroxybenzylidene)- amino phenylimino}-ethyl)-6-methy-pyran-2-one (H2L) derived from o-phenylenediamine, 3-acetyl- 6-methyl-(2H) pyran, 2,4 (3H)-dione (dehydroacetic acid or DHA) and salicylic aldehyde have been synthesized and characterized by elemental analysis, conductometry, magnetic susceptibility, UV-visible, IR, $^1H$-NMR spectra, X-ray diffraction, thermal analysis, and screened for antimicrobial activity. The IR spectral data suggest that the ligand behaves as a dibasic tetradentate ligand with ONNO donor atoms sequence towards central metal ion. From the microanalytical data, the stoichiometry of the complexes has been found to be 1:1 (metal: ligand). The physico-chemical data suggests square planar geometry for Cu(II) and Ni(II) complexes and octahedral geometry for Co(II), Mn(II) and Fe(III) complexes. The x-ray differaction data suggests orthorhombic crystal system for Cu(II) complex, monoclinic crystal system for Ni(II), Co(II) and Fe(III) and tetragonal crystal system for Mn(II) complex. Thermal behaviour (TG/DTA) of the complexes was studied and kinetic parameters were determined by Coats-Redfern method. The ligand and their metal complexes were screened for antibacterial activity against Staphylococcus aureus and Escherichia coli and fungicidal activity against Aspergillus Niger and Trichoderma.

• Journal of the Korean Ceramic Society
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• v.15 no.3
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• pp.135-139
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• 1978

Sintering oxide which was prepared by sintering at $1200^{\circ}C$ the mixture of ${\gamma}$-$Fe_2O_3$ and $Sb_2O_3$ in 2 : 1 mol ratio, showed 1st electrical switching and stable 2nd switching when D.C. voltage was applied. This electrical switching mechanism was known to be thermal mechanism from dependence of environmental temperature of threshold Voltage(Vm), Current(Im) and the conductivity of the current filament of the sintering oxide.

• Journal of Magnetics
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• v.18 no.4
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• pp.400-404
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• 2013

Grain boundary diffusion technique with $DyH_3$ nanoparticles was applied to fabricate Dy-less sintered Nd-Fe-B permanent magnets with high coercivity. The magnetic properties and microstructure of magnets were systematically studied. The coercivity and remanence of grain boundary diffusion magnet were improved by 60% and reduced by 7% compared with those of the original magnet, respectively. Meanwhile, both the remanence temperature coefficient (${\alpha}$) and the coercivity temperature coefficient (${\beta}$) of the magnets were improved after diffusion treatment. Investigation shows that Dy is preferentially enriched as (Nd, Dy)$_2Fe_{14}B$ phase in the surface region of the $Nd_2Fe_{14}B$ matrix grains indicated by the remarkable enhancement of the magneto-crystalline anisotropy field of the magnet. As a result, the magnet diffused with a small amount of Dy nanoparticles possesses enhanced coercivity without remarkably sacrificing its magnetization.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.149-152
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• 1997

High-power piezoelectric materials are being developed for applications such as actuators and ultrasonic motors. In this paper, ferroelectric property of iron-doped 0.57 (Sc$_{1}$2//Nb$_{1}$2/)O$_3$-0.43 PbTiO$_3$. which is the morphotropic phase boundary composition for the PSN-PT system, was investigated. The maximum dielectric constant ( $\varepsilon$$_{33}$/$\varepsilon$$_{0}$ = 2551) and the minimum dielectric loss(tan $\delta$ = 0.51 %) at room temperature were obtained at 01. wt% and 0.3 wt% of iron additions. With additions of the Fe$_2$O$_3$ the electromechanical coupling factor of radial mode k$_{p}$ and the piezoelectric coefficient d$_{33}$ were slightly decreased, on the other hand the mechanical quality factor was increased significantly. The highest mechanical quality factor (Qm= 297) was obtained at 0.3 wt% Fe$_2$O$_3$, which is 4.4 times larger than that of pure 0.57 PSN-0.43PT ceramics. The temperature dependence of the dielectric constant and dielectic loss was observed between 2$0^{\circ}C$ and 35$0^{\circ}C$ .X> .X> .

• Economic and Environmental Geology
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• v.11 no.3
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• pp.89-98
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• 1978

Mineralogy, beneficiation, and processes of titanium ores are reviewed from petrographic viewpoints. The most important titanium minerals are ilmenite ($FeTiO_3$) and rutile ($TiO_2$). Ilmenite will play major role :for raw material, because rutile are rapidly diminishing. Thus, there is a need to develope a successful process for producing high grade Ti02 from ilmenite. Commercial, as well as R and D processes to treat more abundant ilmenite ores fall in three general classess: 1. Iron in ilmenite is partially or completely reduced and separated either physically or chemically. 2. Iron is reduced to ferrous state and chemically leached away from the titanium. 3. Ore is treated to make chlorides either selectively or with subsequent separation and purification of $TiC_4$. Routes and efficiencies of these process technologies are primarily influenced by the particular ore deposit to be mined and secondly by environmental considerations. One deposit parameters which influence ilmenite process technologies are: 1. Complexity of microtextures of ilmenite intergrown with Fe-oxide minerals. 2. Composition of concentrates; ilmenites contain minor amounts of substituted Mg, Mn, and V. These elements plus iron and gangue minerals can cause difficulties to complete reactions, substantial acid consumption, difficulties of removing waste solids, and waste disposal problems. Major contributions to be made by petrologists for process optimization are: characterization and interpretation of compositional and physical changes of raw materials and solids derived from process streams. These informations can play significant role in selecting and improving process steps for titania production.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.1
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• pp.37-43
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• 2015

This paper presents a detailed procedure for a nonlinear soil-structure interaction of a seismically isolated NPP(Nuclear Power Plant) structure using the boundary reaction method (BRM). The BRM offers a two-step method as follows: (1) the calculation of boundary reaction forces in the frequency domain on an interface of linear and nonlinear regions, (2) solving the wave radiation problem subjected to the boundary reaction forces in the time domain. For the purpose of calculating the boundary reaction forces at the base of the isolator, the KIESSI-3D program is employed in this study to solve soil-foundation interaction problem subjected to vertically incident seismic waves. Wave radiation analysis is also employed, in which the nonlinear structure and the linear soil region are modeled by finite elements and energy absorbing elements on the outer model boundary using a general purpose nonlinear FE program. In this study, the MIDAS/Civil program is employed for modeling the wave radiation problem. In order to absorb the outgoing elastic waves to the unbounded soil region, spring and viscous-damper elements are used at the outer FE boundary. The BRM technique utilizing KIESSI-3D and MIDAS/Civil programs is verified using a linear soil-structure analysis problem. Finally the method is applied to nonlinear seismic analysis of a base-isolated NPP structure. The results show that BRM can effectively be applied to nonlinear soil-structure interaction problems.