• Journal of the Korean Chemical Society
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• v.26 no.3
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• pp.128-134
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• 1982

The electrical conductivity of n-type polycrystalline MnOx-Ti$O_2$ system containing 0.40, 0.80, and 1.60 mol % of manganese oxide has been measured from 100 to 400$^{\circ}$C and 1100 to 1300$^{\circ}$C under oxygen partial pressures of$10^{-8}\;to\;10^{-1}$ atm. Plots of log conductivity vs. reciprocals of absolute temperature at constant $Po_2$'s are found to be linear with an inflection, and the activation energies obtained from the slopes appear to be an enough average 0.18eV for the extrinsic and 3.70eV for the intrinsic. The log $\sigma$ vs. log $Po_2$ are found to be linear at $Po_2$'s of $10^{-8}\;to\;10^{-1}$atm. The conductivity dependences on $Po_2$at the two temperature regions are closely approximated by $\sigma{\propto}$Po_2$-1}6$ for the extrinsic and $${\sigma}{\propto}Po_2^{-1}4}$$ for the intrinsic, respectively. The predominant defects are believed to be Vo-2e' and $Ti^3$${\cdot}$interstitial at the extrinsic and intrinsic. From the interpretations of conductivity dependences on temperature and$Po_2$ , the conduction mechanisms and possible band models are proposed.

• Korean Journal of Materials Research
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• v.32 no.11
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• pp.489-495
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• 2022

This research investigated how adding Sb (0.75, 1.0, 2.0 and 5.0 wt%) to as-extruded aluminum alloys affected their microstructure, mechanical properties, electric and thermal conductivity. The addition of Sb resulted in the formation of AlSb intermetallic compounds. It was observed that intermetallic compounds in the alloys were distributed homogenously in the Al matrix. As the content of Sb increased, the area fraction of intermetallic compounds increased. It can be clearly seen that the intermetallic compounds were crushed into fine particles and homogenously arrayed during the extrusion process. As the Sb content increased, the average grain size decreased remarkably from 282.6 ㎛ (0.75 wt%) to 109.2 ㎛ (5.0 wt%) due to dynamic recrystallization by the dispersed intermetallic compounds in the aluminum matrix during the hot extrusion. As the Sb content increased from 0.75 to 2.0 wt%, the electrical conductivity decreased from 61.0 to 59.8 % of the International Annealed Copper Standard. Also, as the Sb content increased from 0.75 to 2.0 wt%, the ultimate tensile strength did not significantly change, from 67.3 to 67.8 MPa.

• Journal of Korean Society of Forest Science
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• v.88 no.1
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• pp.101-110
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• 1999

This research was investigated to check characteristics of stream water quality at four points to analyze the characteristics of stream water in the northeastern part of Puk'ansan National Park during a period of July to November, 1998. The results are as follows. The level of average pH(6.56) and dissolved oxygen($10.22mg/{\ell}$) in the stream water quality on northeastern area in Puk'ansan National Park were at the level of the first class in the quality of river water quality standard. Also, the water in these streams was soft and equilibrated the ration and anion. Electrical conductivity in the stream water was correlated with total amount of ion and number of visitors, but conversely correlated with pH. And the number of visitors influenced stream water quality pollution. The multiple regression equations for electrical conductivity were well explained by pH, Zn and $Mg^{2+}$ statistically.

• Journal of the Korean Chemical Society
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• v.33 no.1
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• pp.25-30
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• 1989

The nonstoichiometry and electrical conductivities of Tm$_2O_3$ were studied in the oxygen pressure $2\;{\times}\;10^{-1}\;-1\;{\tiems}\;10^{-4}$ atm under the temperature ranges from 700 to 1100$^{\circ}$C. The x values of $TmO_{1.5+X}$ were varied in the ranges of 0.1004∼0.0110. The enthalpies of formation of the nonstoichiometric compounds were found to be 5.40-4.71 kcal/mole, and the average activation energy obtained from the plots of log conductivity vs. 1000/T was 1.65 eV. The Po$_2$ dependencies of the electrical conductivity were found to be linear and closely approaximated to ${\sigma}{\alpha} PO{\frac{1}{2}^{/5.3}$ in the temperature range 700∼1100$^{\circ}$C. The nonstoichiometry and the electrical conductivity are due to trivalent metal vacancies.

• Journal of the Korean Ceramic Society
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• v.29 no.4
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• pp.319-327
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• 1992

Sb-doped SnO2 films were formed on Corning glass 7059 substrate by chemical vapor deposition using simulataneous hydrolysis of SnCl4 and SbCl5. Fairly good transparent conducting film with a low resistivity of ~6$\times$10-4{{{{ OMEGA }}cm and high average optical transparency above ~85% in the range of visible light was obtained at the deposition condition of 50$0^{\circ}C$ and input-gas ratio, [Psbcl5/Psncl4] of 0.05. Film conductivity was improved without loosing optical transparency at light doping of Sb and found to be due to the increase of electron concentration. However, high doping of Sb into SnO2 film largely deteriorated conductivity, optical transparency and crystallinity of the film.

• Journal of Powder Materials
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• v.20 no.5
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• pp.345-349
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• 2013

Carbon nanotube-dispersed bismuth telluride matrix (CNT/$Bi_2Te_3$) nanopowders were synthesized by chemical routes followed by a ball-milling process. The microstructures of the synthesized CNT/$Bi_2Te_3$ nanopowders showed the characteristic microstructure of CNTs dispersed among disc-shaped $Bi_2Te_3$ nanopowders with as an average size of 500 nm in-plane and a few tens of nm in thickness. The prepared nanopowders were sintered into composites with a homogeneous dispersion of CNTs in a $Bi_2Te_3$ matrix. The dimensionless figure-of-merit of the composite showed an enhanced value compared to that of pure $Bi_2Te_3$ at the room temperature due to the reduced thermal conductivity and increased electrical conductivity with the addition of CNTs.

• Tribology and Lubricants
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• v.15 no.3
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• pp.240-247
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• 1999

The electrorheological (ER) behavior of suspensions in silicone oil of phosphoric ester cellulose particles (average particle size : 18$\pm$1${\mu}{\textrm}{m}$) coated with octadecylamine ( $C_{18}$ $H_{37}$ N $H_2$) as surfactant was investigated at room temperature. For development of anhydrous ER suspension using at real application, it should be researched how can reduce deposition of ER particles in ER suspension. Anhydrous ER suspensions mixing with phosphoric ester cellulose particles coated with octadecylamine were measured. As increasing the coating concentration of octadecylamine, not only analysis of electrical properties such as dielectric constant, current density and electrical conductivity but also rheological properties of ER suspensions were studied. From the experimental results, coating concentration of surfactant had large influence to ER properties of anhydrous ER suspension. Current density, conductivity and electrorheological effect ($\tau$/$\tau$$_{0}$) of ER suspension were linearly reduced with increasing the coating concentration of octadecylamine. But ER suspensions dispersed the phosphoric ester cellulose particles coated with octadecylamine showed reducing deposition of ER particles and could be redispersed easily.

• Tribology and Lubricants
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• v.14 no.3
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• pp.7-16
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• 1998

The electrorheological (ER) behavior of suspensions in silicone oil of phosphoric ester cellulose powder (average particle size: 17.77 $\mu$m) was investigated at room temperature with electric fields up to 2.5 KV/mm. For development of anhydrous ER suspensions using at wide temperature range, we aimed to know the effect of activation of phosphoric ester cellulose particles on the ER activities. As a first step, the anhydrous ER suspensions mixing with the phosphoric ester cellulose particles which were treated with 2M phosporic acid and 4M urea were measured. After activating the anhydrous ER suspensions at 12$0^{\circ}C$, not only the analysis of dispersing cellulose particles which were reacted by phosphoric ester but also the electrorheological characteristics of ER suspensions such as dielectric constant, current density, electrical conductivity and rheological properties were studied. From the experimental results, the activation of phosphoric ester cellulose particles had an influence on the ER properties of anhydrous ER suspensions. As the activation time went by, the size and number of dispersing particles, the electrical properties and the initial apparent viscosity $(η_0)$ of ER suspensions were increased till the activation time passed 5 hours. Also, it was possible, the electrorheological effect $($\tau$/$\tau$_0)$ of ER fluids was grown by the activation of phosphoric ester cellulose particles.

• Tribology and Lubricants
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• v.15 no.1
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• pp.8-16
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• 1999

The electrorheological (ER) behavior of suspensions in silicone oil of phosphoric ester cellulose powder (average particle size : 18$\pm$1 ${\mu}{\textrm}{m}$) was investigated on the elevated temperature up to 10$0^{\circ}C$. For development of anhydrous ER fluids using at wide temperature range, it should be researched to how the effect of temperature on the ER activities. As a first step, the anhydrous ER suspensions mixing with the phosphoric ester cellulose particles which were made from the phosphoric ester reaction of cellulose were measured. As increasing the temperature, not only the analysis of electrical properties such as dielectric constant current density and electrical conductivity but also the rheological properties of ER fluids were studied. From the experimental results, the temperature had a large influence to the ER properties of anhydrous ER fluids. The current density, conductivity and elecoorheological effect ($\tau$$_{A}$$\tau$$_{0}$) of phosphoric ester cellulose ER fluids were proportional to the temperature with power law. And the shear stress of them was closely related with the square of dielectric constant mismatch parameter ($\beta$$^2$) under constant shear rate and electric field.d.

• Journal of the Korean Ceramic Society
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• v.33 no.7
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• pp.735-742
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• 1996

Antimony-doped Tin oxide (ATO) thin films were deposited on soda-lime glass substrates by DC magnetron sputtering technique. Effects of DC power film thickness and post heat-treatment on electrical conductivity of ATO film were investigated. Other properties of ATO film such as optical anti-chemical and wear properties were also reported in this work. The obtained ATO films showed electrical resistivities ranging from 5$\times$10-3 $\Omega$cm to 3$\times$10-3 $\Omega$cm with the average optical transparency above 80% in visible wavelength range and excel-lent anti-chemical properties where the electrical resistivity was not changed even after soaking the films in 1M HCl or 1M NaOH solution for 10 days. These properties were found to be related to the crystallinity of ATO film and the films having higher crystallinity showed better properties.