• Journal of the Korean Society of Industry Convergence
• /
• v.23 no.6_2
• /
• pp.927-934
• /
• 2020

Magnesium powder has been widely used in various industries because it is light weight and extremely high mechanical strength including aeronautics and chemicals. However, magnesium, as a combustible metal, poses serious safety issues such as fires and explosions if it is not managed properly. Especially, magnesium's max adiabatic flame temperature is 3,340℃ and it is impossible to extinguish it by using water, CO2 and Halonagents. The aim of this study is to identify the combustion characteristics of magnesium powder. We carried out a combustion experiment, using 1 kg of magnesium (purity > 99 %, particle < 150 ㎛). The features of the magnesium burning process were scrutinized using infrared thermal image analysis. Also, a field-emission scanning electron microscope (FE-SEM) were used employed to analyze particulate composites and properties. It concludes the significant tendency of magnesium fire and light, combustion carbide's particle characteristics. This study contributes to make better prevention and response manners to magnesium fires, as well as fire investigation measures.

• Korean Journal of Materials Research
• /
• v.25 no.8
• /
• pp.386-390
• /
• 2015

Fe-base superalloy powders with $Y_2O_3$ dispersion were prepared by high energy ball milling, followed by spark plasma sintering for consolidation. High-purity elemental powders with different Fe powder sizes of 24 and 50 mm were used for the preparation of $Fe-20Cr-4.5Al-0.5Ti-O.5Y_2O_3$ powder mixtures (wt%). The milling process of the powders was carried out in a horizontal rotary ball mill using a stainless steel vial and balls. The milling times of 1 to 5 h by constant operation (350 rpm, ball-to-powder ratio of 30:1 in weight) or cycle operation (1300 rpm for 4 min and 900 rpm for 1 min, 15:1) were applied. Microstructural observation revealed that the crystalline size of Fe decreased with an increase in milling time by cyclic operation and was about 15 nm after 3 h, forming a FeCr alloy phase. The cyclic operation had an advantage over constant milling in that a smaller-agglomerated structure was obtained. The milled powders were sintered at $1100^{\circ}C$ for 30 min in vacuum. With an increase in milling time, the sintered specimen showed a more homogeneous microstructure. In addition, a homogenous distribution of Y-compound particles in the grain boundary was confirmed by EDX analysis.

• Journal of the Korean Chemical Society
• /
• v.53 no.4
• /
• pp.407-414
• /
• 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 Environmental Health Sciences
• /
• v.20 no.2
• /
• pp.73-79
• /
• 1994

The effects of packing materials in the anaerobic reactor and inorganic chemicals in the synthetic wastewater on the anaerobic treatment during the start up period were investigated using anaeroic filter process. The Ringlace and Honeycomb tube as packing materials were used in the anaerobic reactors. The Ca$^{2+}$ and Fe$^{2+}$ ion concentration as inorganic chemicals contained higher 40 times and 100 times as compared to the control synthetic wastewater, respectively. A start up period 104 and 150 days were necessary to achieve loading rate of 0.37 and 0.74 kg-Toc/m$^3$.d in the anaerobic filter process packed by Ringlace and Honeycomb tube, respectively. The loading rates of the reactor using the synthetic wastewater containing Ca$^{2+}$ (40 times) could be increased faster than in the reactors using the synthetic wastewater containing Fe$^{2+}$ ion (100 times) and control synthetic wastewater. The results of XMA analysis that a lot of the Ca$^{2+}$ ion on the surface of the anaerobic sludge in the anaerobic reactor packed by Ringlace which were fed supplied with synthetic wastewater containing Ca$^{2+}$ ion (40 times) observed as compared to the reactors supplied with control synthetic wastewater and containing Fe$^{2+}$ ion (100 times).

• Journal of the Korean Magnetics Society
• /
• v.13 no.4
• /
• pp.171-175
• /
• 2003

Electron paramagnetic resonance (EPR) of Fe$^{3+}$ in LiTaO$_3$ single crystal, grown by Czochralski method, has been studied by employing an X-band spectrometer. Resonance spectra of Fe$^{3+}$ ion on the crystallographic principal axes were obtained with 9.447 ㎓ at room temperature. The spectroscopic splitting parameter g and zero-field splitting (ZFS) parameter D (= 3 B$_{2}$sup 0/) are calculated with effective spin Hamiltonian. Fe$^{3+}$ center in stoichometric single crystal turns out to be different with that in congruent single crystal reported previously. From the analysis of temperature dependence of resonance fields for Fe$^{3+}$ ion, there is no any phase transition at the temperature range (from -160 $^{\circ}C$ to 20 $^{\circ}C$).

• Korean Journal of Materials Research
• /
• v.24 no.10
• /
• pp.515-519
• /
• 2014

The aim of this paper is to consider the effect of annealing on the coefficient of thermal expansion (CTE) of electroplated Invar Fe-Ni alloy. The CTE of the as-electroplated alloy is lower than those of alloys annealed at $400^{\circ}C$ and $800^{\circ}C$. XRD peaks become sharper as the as-electroplated alloy is annealed, which means the grain growth. The average grain sizes of as-electroplated and as-annealed alloys at $400^{\circ}C$ and $800^{\circ}C$ are 10 nm, 70 nm, and $2{\mu}m$, respectively, as determined by TEM and EBSD analyses. The CTE variation for the various grain sizes after annealing may come from the magnetostriction effect, which generates strain due to changes in the magnetization state of the alloys. The thermal expansion coefficient is considered to be affected by nano grain size in electroplated Fe-Ni Invar alloys. As grain size decreases, ferromagnetic forces might change to paramagnetic forces. The effect of lattice vibration damping of nano grain boundaries could lead to the decrease of CTE.

• Proceedings of the KIEE Conference
• /
• 2005.10c
• /
• pp.129-131
• /
• 2005

This paper deals with an electromagnetic analysis and control parameter estimation of a moving-coil linear oscillatory actuator (MCLOA). Analytical solutions for electromagnetic characteristics of the MCLOA are obtained from transfer relations derived in terms of a magnetic vector potential and two-dimensional (2-d) rectangular coordinate systems. And then, on the basis of 2-d analytical solutions, control parameters such as the thrust constant, the back-emf constant and winding inductances are estimated. Finally, analytical results for both electromagnetic characteristics and control parameters of the MCLOA are validated extensively by finite element (FE) analyses. In particular, test results such as static thrust, resistance and inductance measurements are given to confirm the analyses.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.5
• /
• pp.29-37
• /
• 1993

The extension of the weighted integral method in the area of stochastic finite element analysis is presented. The use of weighted integral method in numerical analysis was extended to CST(constant strain triangle) element by Deodatis to calculate the response variability of 2D stochastic systems. In this paper, the extension of the weighted integral method for general plane-elements is represented. It has been shown that the same mesh used in the deterministic FE analysis can be used in the stochastic FE analysis. Furthermore, because the CST element is a special case which has constant strain-displacement matrix the mingling of CST elements with the other quadrilateral elements in the analysis may also be possible.

• Journal of Powder Materials
• /
• v.18 no.1
• /
• pp.29-34
• /
• 2011

In order to increase the coercivity of (Nd, Dy)-Fe-B sintered magnets without much reduction of remanence, small amount of Dy compounds such as $Dy_2O_3$ and $DyF_3$ was mixed with (Nd, Dy)-Fe-B powder. After mixing, the coercivity of (Nd, Dy)-Fe-B sintered magnets apparently increased with the increase of Dy compound in the mixture. Addition of $DyF_3$ was more effective than $Dy_2O_3$ for the improvement of coercivity. Reduction of the remanence by the addition of Dy compound, however, was larger than expected mostly due to unresolved coarse Dy compound in the magnet. EPMA analysis revealed that Dy was diffused throughout the grains in the magnet mixed with $DyF_3$ whereas Dy was rather concentrated around grain boundaries in the magnet mixed with $Dy_2O_3$.

• The Journal of Engineering Geology
• /
• v.27 no.4
• /
• pp.439-449
• /
• 2017

The cause of yield reduction in a collector well, which is located in Anseong-cheon watershed in Kyunggi province, is studied by using aquifer sediments' composition and hydraulic conductivity near four horizontal wells, no. 1, no. 4, no. 6, and no. 7 wells. During test-pumping periods, groundwater yield is reduced with a trend of $12.4m^3/d/d$ at no. 1, $2.3m^3/d/d$ at no. 4, $24.4m^3/d/d$ at no. 6, and $187.3m^3/d/d$ at no. 7 and no. 7 well shows the biggest reduction. The sediments along no. 7 horizontal well have low hydraulic conductivity and high coefficient of uniformity ($C_u$), and a deviation of $C_u$ along the well is also large. This characteristics can bring the fine particles' movement and make the openings filled. Additionally, high iron ($Fe^{2+}$) content results in a precipitation of iron hydroxides during pumping or injection and they can produce a clogging in sediments. In the future study, the analysis of physical and hydrochemical changes through a long-term pumping procedure will give a more exact interpretation for the cause of yield reduction.