• Proceedings of the Korean Magnestics Society Conference
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• 2009.12a
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• pp.72-73
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• 2009

First-principles calculations were carried out to investigate the effects of Al impurities on bcc Fe magnetism by considering SOC. No significant solid solution hardening effect was found. Albeit the effects of the SOC by Al on spin magnetic moments were minor, there are sizeable orbital magnetic effects. It is concluded that the orbital magnetism due to the Al impurity is strongly related with the impurity screening of the system as seen in Si impurity case [3], but the effects of Al impurity is stronger than those of Si impurity in terms of orbital magnetism.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.195-196
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• 2007

In this paper, we investigated impurity content of carbon nanotube reinforced semiconductive shield materials and conventional semiconductive shield materials in power cables. To reduce impurity content, we used solution compounding method that an adding process of extra additives neglected. Impurity content measured through ICP-AES(Inductively Coupled Plasma Atomic Emission Spectroscopy). Also, impurity measured Ca, Cu, Fe, Al, Mg, Na, K, Si in eight. As a result, carbon nanotube reinforced semiconductive shield materials is lower than conventional semiconductive shield materials in impurity content by ICP-AES.

• Journal of Magnetics
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• v.16 no.1
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• pp.1-5
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• 2011

The magnetism and electronic structure of bcc $Al_1Fe_{26}$ was investigated by means of first-principles calculations with and without spin-orbit coupling (SOC). From the calculated total energy, the SOC corrected system is shown to be approximately 5 meV per atom lower than the SOC uncorrected system. The induced spin magnetic moment at the Al site was -0.125 ${\mu}_B$ without SOC and -0.124 ${\mu}_B$ with SOC. The orbital magnetic moments were calculated to be 0.002 ${\mu}_B$ in [$\overline{1}$00] direction for Al. The electronic structures showed the nearest neighbor antiferromagnetic interaction between Fe and Al to be essential for determining the magnetism of the $Al_1Fe_{26}$ system.

• Journal of Korea Foundry Society
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• v.24 no.3
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• pp.145-152
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• 2004

The eutectic Si in Al-8.5wt.%Si alloy was changed from large flake to fine lemellar(or fibrous) shape when the Sc amount in the Al-Si alloy reaches 0.2wt.%. The optimum amount of Sc for the best modification effect was 0.8wt.% and slight decrease of modification effect occurred over this value. The study on the distribution of the modifiers(Sr, Na, and Sc) and the measurement of the surface tension of the Al-8.5wt.%Si alloy melt added with Sr, Na, and Sc modifier, respectively, reveals that Sc modifies the eutectic Si by the decrease of surface tension, while Sr and Na modify the eutectic Si mainly by impurity induced twinning mechanism.

• Proceedings of the Materials Research Society of Korea Conference
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• 1994.11a
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• pp.99-99
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• 1994

• Korean Journal of Materials Research
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• v.2 no.2
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• pp.157-160
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• 1992

Unusual surface impurity levels of PREPed Ti-51at%Al powders were analyzed using Auger spectroscopy and they were compared with these obtained from bulk starting electrode. Oxygen and carbon contents were varied very much with particle size. Powder surfaces were believed to be mainly covered by a complex compound containing Ti, Al, O, and C. The decrease in contents of oxygen and carbon of powders were attributed to the certain refining reaction of transfer type DC Ar plasma during the powder production.

• Progress in Superconductivity
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• v.10 no.1
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• pp.35-39
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• 2008

By using the hybrid physical-chemical vapor deposition (HPCVD) technique, we have fabricated $MgB_2$ thick films on $Al_{2}O_3$ substrates with various impurity layers of Ni, Ti, and SiC. We have found a significant enhancement of the critical current density ($J_c$) for $MgB_2$ films grown on impurity layered substrates, indicating that additional impurity layers were provided as possible pinning sites by chemical doping in $MgB_2$ films. All samples doped by Ni, Ti, and SiC were observed to have high superconducting transition temperatures of 39 - 41 K. The $J_c$ of $MgB_2$ films grown on SiC impurity layered substrates showed three times higher than that of undoped films at high magnetic fields above 1 T.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.88-93
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• 2002

$Zn_{0.5}Cd_{0.5}Al_{2}Se_{4}$ and $Zn_{0.5}Cd_{0.5}Al_{2}Se_{4}:Co^{2+}$ + single crystals were grown by CTR method. The grown single crystals have defect chalcopyrite structure with lattice constant a= 5.5966A. c= 10.8042${{\AA}}$ for the pure. a= 5.6543${{\AA}}$. c= 10.8205${{\AA}}$ for the Co-doped single crystal. respectively. The optical energy band gap was given as indirect band gap. The optical energy band gap was decreased according to add of Co-impurity. Temperature dependence of optical energy band gap was fitted well to the Varshni equation. From this relation. we can deduced the entropy. enthalpy and heat capacity. Also. we can observed the Co-impurity optical absorption peaks assigned to the $Co^{2+}$ ion sited at the $T_d$ symmetry lattice and we consider that they were attributed to the electron transitions between energy levels of ions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1148-1151
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• 2002

Dielectric ceramics with nominal composition of $(Ba_{0.93}Sr_{0.07}O)-0.5Sm_2O_3-4.5TiO_2$ was prepared using the conventional mixed oxide process-derived powder. Effect of $SiO_2$, $MnO_2$ and $Al_2O_3$ impurity addition on the microwave properties was examined in some detail. Measured relative permittivity $(\varepsilon_r)$ values were in the range of 53 to 59 and showed little dependence on impurity addition. In contrast, quality factor $(Q{\cdot}f)$ and temperature coefficient of resonant frequency $(\tau_f)$ values were greatly influenced by the type and the amount of impurities. It was found that 0.1~0.2wt% addition of $Al_2O_3$ was most effective for improving the properties, where ${\varepsilon}_r$, $Q{\cdot}f$ and $\tau_f$ values were 57.7, 10000, and +7ppm/$^{\circ}C$, respectively.

• Electrical & Electronic Materials
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• v.10 no.5
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• pp.447-452
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• 1997

Effects of metal impurities in insulation of distribution cables on electrical conduction of distribution cables was investigated. Samples of Al, Cu, Fe are fabricated as metallic impurities, and measured electrical conductivity in the voltage range of 0~10 KV. Temperature dependent effect of hysteresis curves and the relationship between forward and reverse current due to impurity content are discussed.