• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.4
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• pp.157-160
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• 2007

The van der Pauw technique is one of the popular methods for determining the conductivity of flat metal samples. Traceability of the national standard for the conductivity has been achieved by direct current measurement techniques in national measurement institutes of many countries. But recently, alternative current measurement techniques for determining the conductivity of flat metal samples is also interested. In this study, we measured the conductivity of non-ferrous and ferrous flat metals at alternative current using van der Pauw technique. As measurement results, the conductivities of the samples were decreased according to increasing the test frequency even though the decreasing ratio was different.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.63-66
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• 1992

Using an aromatic system, we made a ultra thin insulator through LB-method. We measured and wrote down afternating currant characteristics of ultraviolet rays extincting-spectrum and I.R extincting-spectrum. We surveyed the thickness of a film through X-ray diffracting method and certified about $4{\AA}$ by the layer. Measuring the characteristics of direct current voltage and electric current with this sample, we produced its conductivity and discovered that this sample had a god insulating performance. Addition to this, we measured the characteristics of voltage and electric current, and the temperature dependency of conductivity in a high voltage system and with these results tried to interpret a mechanism of conduction.

• Electrical & Electronic Materials
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• v.9 no.6
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• pp.572-577
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• 1996

Alternating current and direct current of pure, ball milled, and $Al_{2}$O$_{3}$ added ZnO were investigated by means of complex impedance measurement and voltage-current source measurement unit. The electrical conductivity of A1$_{2}$O$_{3}$ added ZnO samples increases when the content of A1$_{2}$O$_{3}$ is used within 1 at% and decreases when it's used more than that. The increase and decrease of electrical conductivity seem to be the donor effect of $Al_{2}$O$_{3}$ and the increase of the number of ZnO grains, respectively. Impedance spectrum seems to be one semircicle. The size of semicircle increase with increasing the A1$_{2}$O$_{3}$ contents. The calculated dielectric constant(at 50.deg. C) were about 70-140 at the peak of the semicircle. The semicircles seem not to be the resistance of ZnO grain as compared to that of 10 for pure ZnO.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.4
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• pp.75-82
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• 1990

To study on the behavior of the early stage of the spark kernel at constant pressure condition, the expressions of the thermal properties such as compressibility factor, thermal conductivity, and electrical conductivity of the high temperature air were newly suggested. The newly suggested simple expressions of the thermal properties of the high temperature air showed good results. Under the assumption of constant pressure, one dimensional numerical analysis was executed by varying surrounding conditions and discharging current of electrical spark. Numerical results show tat high surrounding pressure suppresses the growth of the spark kernel but supplies much electrical energy into the air, on the other hand high surrounding temperature increases the growth of the spark kernel but supplies less electrical energy. Also the result shows that , in case of direct current discharge, deposited electrical energy is able to be expressed in linear function of time approximately.

• Carbon letters
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• v.22
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• pp.25-35
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• 2017

The aim of the work was to investigate the thermo-electrical properties of low cost and rapidly produced randomly oriented carbon/carbon (C/C) composite. The composite body was fabricated by combining the high-pressure hot-pressing (HP) method with the low-pressure impregnation thermosetting carbonization (ITC) method. After the ITC method step selected samples were graphitized at $3000^{\circ}C$. Detailed characterization of the samples' physical properties and thermal properties, including thermal diffusivity, thermal conductivity, specific heat and coefficient of thermal expansion, was carried out. Additionally, direct current (DC) electrical conductivity in both the in-plane and through-plane directions was evaluated. The results indicated that after graphitization the specimens had excellent carbon purity (99.9 %) as compared to that after carbonization (98.1). The results further showed an increasing trend in thermal conductivity with temperature for the carbonized samples and a decreasing trend in thermal conductivity with temperature for graphitized samples. The influence of the thickness of the test specimen on the thermal conductivity was found to be negligible. Further, all of the specimens after graphitization displayed an enormous increase in electrical conductivity (from 190 to 565 and 595 to 1180 S/cm in the through-plane and in-plane directions, respectively).

• Transactions on Electrical and Electronic Materials
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• v.1 no.2
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• pp.32-37
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• 2000

Effect of alloying element additions to Ag on thermal conductivity and electrical conductivity of sheath materials for Bi-Pb-Sr-Ca-Cu-O(BSCCO) tapes has been characterized. The thermal conductivity at low temperature range (10~300K) of Ag and Ag alloys were evaluated by both direct and indirect measurement techniqueas and compared with each other, It was observed that the thermal conductivity decreases with increasing the content of alloying element such as Au, Pd and Mg. Thermal conductivity of pure Ag at 3 0K was measured to be 994.0 W(m.K) on the other hand, the corresponding values of $Ag_{0.9995}Mg_{0.0005}$, $Ag_{0.974}$, $Au_{0.025}$, $Mg_{0.001}$, $Ab_{0.973}$, $Au_{0.025}$, $Mg_{0.002}$ and $Ag_{0.92}$, $Pb_{0.06}$, $Mg_{0.02}$ were 342.6, 62.1, 59.2 and 28.9 W(m.K), respectively, indicating 3 to 30 times lower than that of pure Ag. In addition, the thermal conductivity of pure Ag measured by direct and indirect measurement techniques was 303.2 and 363.8 W(m.K) The difference in this study is considered to be within an acceptable error range compared to the reference data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.8
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• pp.711-717
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• 2000

Effect of alloying element additions to Ag on thermal conductivity electrical conductivity and mechanical properties of sheath materials for BSCCO tapes has been characterized. The thermal conductivity at low temperature range(10~300K) of Ag alloys were evaluated by both direct and indirect measurement techniques and compared with each other. It was observed that thermal conductivity decreased with increasing the content of alloying elements such as Au, Pd and Mg. Thermal conductivity of pure Ag at 30 K was measured to be 994.0 W/m.K on the other hand the corresponding values of A $g_{0.9995}$/M $g_{0.0005}$, A $g_{0.974}$/A $u_{0.025}$/M $g_{0.001}$, A $g_{0.973}$/Au.0.025//M $g_{0.002}$, and A $g_{0.92}$/P $d_{0.06}$/M $g_{0.02}$ were 342.6, 62.1, 59.2, 28.9 W/m.K respectively indicating 3 to 30 times lower than that of pure Ag. In addition alloying element additions to Ag improved mechanical strength while reduced elongation probably due to the strengthening mechanisms by the presence of additive atoms.s.

• Journal of Powder Materials
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• v.28 no.3
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• pp.253-258
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• 2021

There is increasing demand for the development of a new material with high strength, high stiffness, and good electrical conductivity that can be used for high-voltage direct current cables. In this study, we develop aluminum-based composites containing C₆₀ fullerenes, carbon nanotubes, or graphene using a powder metallurgical route and evaluate their strength, stiffness, coefficient of thermal expansion, and electrical conductivity. By optimizing the process conditions, a material with a tensile strength of 800 MPa, an elastic modulus of 90 GPa, and an electrical conductivity of 40% IACS is obtained, which may replace iron-core cables. Furthermore, by designing the type and volume fraction of the reinforcement, a material with a tensile strength of 380 MPa, elastic modulus of 80 GPa, and electrical conductivity of 54% IACS is obtained, which may compete with AA 6201 aluminum alloys for use in all-aluminum conductor cables.

• Korean Journal of Materials Research
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• v.34 no.6
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• pp.267-274
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• 2024

In this study, four different samples of Se₆₀Ge_40-xBi_x chalcogenides glasses were synthesized by heating the melt for 18 h in vacuum Pyrex ampoules (under a 10^-4 Torre vacuum), each with a different concentration (x = 0, 10, 15, and 20) of high purity starting materials. The results of direct current (DC) electrical conductivity measurements against a 1,000/T plot for all chalcogenide samples revealed two linear areas at medium and high temperatures, each with a different slope and with different activation energies (E₁ and E₂). In other words, these samples contain two electrical conduction mechanisms: a localized conduction at middle temperatures and extended conduction at high temperatures. The results showed the local and extended state parameters changed due to the effective partial substitution of germanium by bismuth. The density of extended states N(E_ext) and localized states N(E_loc) as a function of bismuth concentration was used to gauge this effect. While the density of the localized states decreased from 1.6 × 10¹⁴ to 4.2 × 10¹² (ev^-1 cm^-3) as the bismuth concentration increased from 0 to 15, the density of the extended states generally increased from 3.552 × 10²¹ to 5.86 × 10²¹ (ev^-1 cm^-3), indicating a reduction in the mullet's randomness. This makes these alloys more widely useful in electronic applications due to the decrease in the cost of manufacturing.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.99-106
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• 2013

Polyaniline-yttrium trioxide (PAni-$Y_2O_3$) composites were synthesized by the in-situ polymerization of aniline in the presence of $Y_2O_3$ The composite formation and structural changes in these composites were investigated by X-ray diffraction (XRD), Fourier transform infra red spectroscopy (FTIR), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The direct current (DC) electrical conductivity of the order of $0.51{\times}10^{-2}\;S\;cm^{-1}-0.283\;S\;cm^{-1}$ in the temperature range 300 K-473 K indicates semiconducting behavior of the composites. Room temperature AC conductivity and dielectric response of the composites were studied in the frequency range of 10 Hz to 1 MHz. The variation of AC conductivity with frequency obeyed the power law, which decreased with increasing weight percentage (wt %) of $Y_2O_3$. Studies on dielectric properties shows the relaxation contribution coupled by electrode polarization effect. The dielectric constant and dielectric loss in these composites depend on the content of $Y_2O_3$ with a percolation threshold at 20 wt % of $Y_2O_3$ in PAni. Electromagnetic interference shielding effectiveness (EMI SE) of the composites in the frequency range 100 Hz to 2 GHz was in the practically useful range of -12.2 dB to -17.2 dB. The observed electrical and shielding properties were attributed to the interaction of $Y_2O_3$ particles with the PAni molecular chains.