• Journal of the Korean Society of Industry Convergence
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• v.6 no.3
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• pp.165-169
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• 2003

To extract alkali metal ions and heavy metal ions, search for crown ether model compounds (4a-b, 5a-b, 6a-b) bearing side arm has led to achieve in 5~6 steps starting from 2,6-dimethylaniline. The determination of structure in their compound derivatives were on the basis of melting point and nuclear magnetic resonance spectroscopy. In the solvent extraction of metal ions from the synthesized derivatives, we observed that silver ion has only high selectivity for synergistic ligation of crown ether.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.9
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• pp.729-735
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• 1991

To form shallow $p^+$ -n junctions, Ge and As ions were employed for preamorphization, and B or BF2 was implanted for doping. Same B and BF$_2$ implantations were performed into single crystalline silicon to compare the material and electrical characteristics with the preamorphized samples. SIMS measurements for 10KeV B implanted samples revealed the somilar boron distribution for two preamophized cases, but the ASR profiles indicated that the shallower junctions could be formed by Ge preamorphzation. Sheet resostance of Ge preamorphized sample was lower than the As preamorphized sample, and the diode leakage current characteristics were similar for the preamorphized and non-preamorphized samples. Among the samples implanted with BF ions into the substrates preamorphized with 25keV Ge or As ions, high sheet resistance and leaky diode characteristics were observed for the As preamorphized samples. It was found that Ge preamorphization is more useful than As preamorphization for the purpose of forming shallow $p^+$ -n junctions using low energy BF$_2$ implantation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.9
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• pp.700-704
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• 1998

In this paper, the optical properties of boron ion implanted GaAs were investigated by photoluminescence(PL) measurements. The implantations were preformed at room temperature with the energy of 150 eV. The range of implanted dose was $10^{12}~10^{15} ions/cm^2$. The boron implanted samples were annealed between $450^{\circ}C$ and $800^{\circ}C$ for 20 minutes. The crystallinity of low dosed samples were increased with increasing annealing temperature up to $700^{\circ}C$ while that of the high dosed($10^{15} ions/cm^2$) was almost same. From the samples with dose of $10^{14}~10^{15} ions/cm^2$, two emission bands were observed at 1.438 eV (B1) and 1.459 eV (B2) after the thermal treatment. These emission bands seems to be attributed to the $B_{Ga}$-defect complex.

• Korean Journal of Materials Research
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• v.13 no.1
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• pp.48-52
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• 2003

The substituted yttrium iron garnet systems $Y_{ 3-x}$/Gd$_{x}$X$0.2_{0.2}$ $Fe_{4.8}$ $O _{12}$ (x = 0.2, 0.4, 0.6) have been investigated by means of X-ray diffraction, Mossbauer spectroscopy and SQUID. The X-ray diffraction patterns at room temperature confirm the samples to have a single phase of the garnet structure over the whole composition range. The lattice constants of all the samples linearly change with increasing x due to the size of substituted ions in the dodecahedral sites. $Y_{3-x}$ $Gd_{x}$ X$Fe_{4.8}$ $In_{0.2}$ $O_{12}$ system which $Y_{3-x}$ ions are substituted with Gd$^{ 3＋}$ ions, the Mossbauer spectrum consists of three Zeeman sextets at room temperature, one due to the $Fe^{3＋}$ ions on the octahedral(a-) sites and the others due to the $Fe^{3＋}$ ions on the tetrahedral(d-, d'-) sites, respectively. From the hysteresis loop measured by means of SQUID over the whole composition range, the saturation magnetization $M_{s}$ and magnetic moments $\mu_{ B}$ per unit cell have been obtained. The increment of Gd-ion content causes $M_{s}$ and $\mu_{B}$ decrease while the increment of In-ion content does not.

• Journal of Life Science
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• v.8 no.3
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• pp.339-347
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• 1998

As a part of a study on the development of microbiological methods for petroleum exploration, the distribution of the avarafe survival rate for heterotrophs to various heavy metal ions and hydrocarbons were surveyed and compared by the use of plate count method. In consequence of the avarage survival rate to heavy metal ions(2 hours treatment) and hydrocarbons(1 hour treatment) for heterotrophs isolatinf from soil samples(50cm depth) which located in Doum mountain(A, B and D site) and Aedowon(C site) at Pohang area, the survival rate of heterotrophs for nickel(600ppm), cobalt(500ppm), cadmiun(100ppm), mercury(20ppm), zinc(400 ppm) and lead(500ppm) were 73.7%, 82.6%, 76.8%, 9.5%, 77.8% and 73.6% at A site and 67.9%, 82.5%, 86.0%, 5.8%, 82.5% and 91.7% at B site, 87.8%, 79.8%, 87.5%, 7.0%, 84.2% AND 47.7% AT c SITE, AND 71.8%, 76%, 85.9%, 1,2%, 79.6% AND 88.3% AT D site, respectively. Also the survival rate of heterotrophs from A,B,C and D site to pentane and hexane(each concentration is 20%) were 26.7% and 42.5%, 11.8% and 8.1%, 44.3% and 36.2%, and 12% and 3.5%, respectively. therefore, heterotrophs from B and D site that alternated gravelstone, muddy sandstone and sandstone were higher survival rate to the heavy metal ions than heterotrophs from A site which mainly composed gravelstone. Also, heterotrophs from C site which mainly composed muddy sandstone and once produced natural gas were showed relatively higher survival rate to the heavy metal ions and hydrocarbons than the other sites. Consequently, we confirmed that the distributions of tolerant heterotrophs to heavy metal ions and hydrocarbons were differ from the lithological compositon.

• The Korean Journal of Mycology
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• v.19 no.4
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• pp.282-284
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• 1991

The yeast, Hansenula anomala B-7, isolated from the $Cd^{2+}$ rich soils and determined to be tolerant in the high concentration of $Cd^{2+}$ were employed in this work. Its intact cells grown in high concentration of $Cd^{2+}$ were observed to be Iysed at the early stage when transferred to a cadmium deficient broth. Its intact cells found to be not Iysed and grow well under the high concentration of $Cd^{2+}$. The Iysis of the intact cells grown at the high concentration of $Cd^{2+}$ ion was not found when the metal ions were replaced with $Cd^{2+}$ ion in the same concentration. This result indicated that Iysis of yeast cells, at least in this isolate, would be related to cell osmosis with the mineral ions added.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.1
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• pp.27-31
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• 2017

In this study, the effect of Tb inward diffusion on the magnetic properties of the Nd-Fe-B sintered magnets was studied. After sintering of the magnets, $TbF_3$ slurries were dip-coated on the surface of the samples, then heat-treatment was followed for $TbF_3$ diffusion. The element distribution in the magnets and the diffusion profiles of Tb ions were analyzed by an EPMA (electron probe micro-analyzer). Prolonged heat treatment resulted in a deeper diffusion length of Tb ions. Coercivity of the $1^{st}$ heat-treated sample showed 21.86 kOe, while that of the $1^{st}$, $2^{nd}$ heat-treated and annealed sample revealed 34 kOe.

• Bulletin of the Korean Chemical Society
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• v.25 no.6
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• pp.847-851
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• 2004

The complexation characteristics of tetramethyl (1) and tetraethyl esters (2) of p-tert-butylcalix[4]arene with alkali metal cations have been investigated by ab initio calculation. The structures of endo- or exocomplexation of the hosts in cone conformation with alkali metal ions have been optimized using HF/6-31G method followed by B3LYP/6-31G(d) single point calculation. B3LYP/6-31G(d) calculations suggest that exo-complexation efficiencies of sodium ion to the cavity of lower rim of hosts 1 and 2 are 27.1 and 25.8 kcal/mol better than that of potassium ion, respectively. The exo-complexation efficiencies of potassium ion to the cavity of lower rim of hosts 1 and 2 are 33.3 and 31.5 kcal/mol better than the endo-complexation inside the upper rim (four aromatic rings) as expected from the experimental results. B3LYP/6-31G(d) calculation of the ethyl ester 2 shows 29.5 and 30.8 kcal/mol better exo-complexation efficiency for both sodium and potassium ions than the methyl ester 1.

• Journal of the Korean Ceramic Society
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• v.48 no.3
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• pp.222-227
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• 2011

The hexavalent chromium ions in wastewater are highly toxic chemicals even at low concentrations. It causes serious diseases, such as cancer, skin disease, digestive trouble et. al. In this study, $Cr^{6+}$ ions were removed by using borosilicate glasses. Various glasses system with different compositions were prepared and then reacted in a solution contaning $Cr^{6+}$ ions. After the reaction, the concentration of the $Cr^{6+}$ ions remained in the solution was measured by ICP-OES. The reacted surface of the glasses was also analyzed by using a XRD, SEM, and EDS. When $Na_2O-RO-SiO_2-B_2O_3$ (RO=MgO, CaO, SrO, BaO) glasses were reacted with a solution containing $Cr^{6+}$ ions, the optimum removal efficiency of $Cr^{6+}$ ions was observed in the BaO glass. $Ba^{2+}$ ions leached out of these glasses combine with $Cr^{6+}$ ions in a solution to form $BaCrO_4$ crystals on the glass surface. In this manner, the $Cr^{6+}$ ions can be removed from the solution. It is conceivable that $Ba^{2+}$ ions are reacted with $Cr^{6+}$ ions in a solution immedeately after leaching out of the glasses. The pH of the solution for optimum removal of $Cr^{6+}$ ions were 3.0~5.0.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.12 s.243
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• pp.1329-1334
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• 2005

Synthesis of silver nanoparticles by the supersonic nozzle expansion method with corona discharge ions was investigated. Corona discharge ions functioned as seeds for heterogeneous nucleation in the silver nanoparticles formation process and provided silver nanoparticles with electronic repulsive force that prevents aggregation of the particles. For ion ejecting, we used sonic-jet corona discharger. Upon application of the corona discharge ions, the mean diameter of the produced particles was decreased from 12.54 to 6.22nm and the standard deviation was decreased from 5.02 to 3.34nm. In addition, the agglomeration of silver nanoparticles was reduced.