• Corrosion Science and Technology
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• 제16권6호
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• pp.317-327
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• 2017

The change in the oxidation behavior of three types of B-added ultrahigh strength martensitic steels containing Ti and Nb induced by applying constant cathodic current was investigated. In a 3% NaCl+0.3% $NH_4SCN$ solution, the overall polarization behavior of the three alloys was similar, and degradation of the oxide film was observed in the three alloys after applying constant cathodic current. A significant increase in the anodic current density was observed in the Nb-added alloy, while it was diminished in the Ti-added alloy. Both Ti and Nb alloying decreased the hydrogen overpotential by forming NbC and TiC particles. In addition, the thickest oxide film was formed on the Ti-added alloy, but the addition of Nb decreased the film thickness. Therefore, it was concluded that the remarkable increase in the anodic current density of Nb-added alloy induced by applying constant cathodic current density was attributed to the formation of the thinnest oxide film less protective to hydrogen absorption, and the addition of Ti effectively blocked the hydrogen absorption by forming TiC particles and a relatively thick oxide film.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.543-546
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• 2000

Ferroeleclric 0.05PZN-xPZT(90/10)-(0.95-x)PZT(10/90) (x=0.65, 0.85) specimens were fabricated by the mixed-oxide method and cold-pressing method using sol-gel derived PZT(90/10) and PZT(10/90) powders. All specimens show a uniform ferroelectric grain without the presence of the pyrocholre phase. Average grain size increased with an increase in sintering temperature, the value for the x=0.65 specimen sintered at 125$0^{\circ}C$ was 14.4$\mu$m. The dielectric constant and dielectric loss of the x=0.65 specimen sintered at 125$0^{\circ}C$ were 1247, 2.06%, respectively. All specimens showed fairly good temperature and frequency stability of dielectric constant with the range from -2$0^{\circ}C$ to 6$0^{\circ}C$ and 100Hz to 10MHz. The coercive field and the remanent polarization of x = 0.65 specimen sintered at 125$0^{\circ}C$ were 8.5 kV/cm and 13 $\mu$C/cm$^2$, respectively. The pyroelectric coefficient of the x=0.65 specimen sintered at 125$0^{\circ}C$ was 5.64$\times$10$^{-8}$ C/cm$^2$K, respectively.

• 한국콘텐츠학회논문지
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• 제7권11호
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• pp.76-83
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• 2007

순차 회전 배열 안테나에서, 순차 배열 정수(배열소자 수, 회전정수)의 변화에 따른 안테나 이득, 축비 및 교차편파 특성을 각각 비교 분석하였다. 여기서 안테나 기본소자로는 중심주파수 11.85GHz인 좌원편파(LHCP), 프로브급전 트렁케이티드 마이크로스트립 안테나를 사용하였다. M=2, 3, 4, 6, 8인 경우에 대하여 P값을 $1{\sim}M$으로 변화시킨 순차 회전 배열 안테나 총 23개에 대한 시뮬레이션을 수행한 결과, 축비 대역폭은 배열소자 수 M에 상관없이 P=2인 경우가 가장 넓으며, 이득은 순차배열 정수(M, P)가 (2, 1), (3, 2), (4, 1), (6, 3), (8, 1)일 때 가장 크게 나타나고 있다. 특히 M=P인 경우 모든 안테나 특성이 나빠진다. 따라서 순차 회전 배열 안테나를 설계할 때, 많은 시뮬레이션 데이터들 중에서 최적의 순차배열 정수를 찾아 다음 설계하여야 한다.

• 한국표면공학회지
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• 제32권2호
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• pp.172-181
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• 1999

The effect of the DMAB concentration, temperature, deposition time, and stabilizer concentration on the precipitation reaction of the electroless nickel plating using dimethylamine borane (DMAB) as reducing agent was investigated to by the weight gain and electrochemical method. The deposition rate was dependent with DMAB concentration. The polarization resistance of the precipitation reaction was reduced with DMAB concentration. The precipitation reaction rate of Ni-B deposits was controlled by the oxidation rate of DMAB as the source of electron. The boron content of the deposit was constant at about 5.5wt%, even when DMAB concentration in the solution was increased. The effect of temperature and stabilizer ($Pb(NO_3)_2$) concentration on deposition rate was shown to have co-dependent behaviors.

• Bulletin of the Korean Chemical Society
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• 제20권9호
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• pp.1049-1055
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• 1999

Electrochemical oxidation of silicon (p-type Si(100)) at room temperature in ethylene glycol and in aqueous solutions has been performed by applying constant low current densities for the preparation of thin SiO2 layers. In-situ ac impedance spectroscopic methods have been employed to characterize the interfaces of electrolyte/oxide/semiconductor and to estimate the thickness of the oxide layer. The thicknesses of SiO2 layers calculated from the capacitive impedance were in the range of 25-100Å depending on the experimental conditions. The anodic polarization resistance parallel with the oxide layer capacitance increased continuously to a very large value in ethylene glycol solution. However, it decreased above 4 V in aqueous solutions, where oxygen evolved through the oxidation of water. Interstitially dissolved oxygen molecules in SiO2 layer at above the oxygen evolution potential were expected to facilitate the formation of SiO2 at the interfaces. Thin SiO2 films grew efficiently at a controlled rate during the application of low anodization currents in aqueous solutions.

• 환경위생공학
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• 제16권2호
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• pp.38-46
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• 2001

In this work, the heterogeneous ion exchange membrane was used in a electrodialysis apparatus to treat a Ni planting rinse water because the heterogeneous ion exchange membrane was excellent efficiency as compared with low manufacturing cost, was easy to make, and had a good mechanical properties. For a regeneration of membrane and to obtain the optimal condition for a scale-up of apparatus after treating Ni plating rinse water, we would find about the limiting current density and the concentration polarization. When the Ni plating rinse water 150mg/L was treated with the electrodialysis apparatus using the heterogeneous ion exchange membrane, the limiting current density was about $1.49{\;}mA/\textrm{cm}^2$. And the limiting current density increased with the flow rate and concentration of Ni plating rinse water. We recognized that the used membrane could be reused by periodic backwashing because efficiency was constant when the membrane was backwashed after treating wastewater.

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권2호
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• pp.43-47
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• 2003

Lead zirconate titanate (PZT) thin films were fabricated by the pulsed laser ablation deposition (PLAD) method onto Pt/Ti/SiO$_2$/Si substrates. Crystalline phases as well as preferred orientations in PZT films were investigated by X-ray diffraction analysis (XRD). The well-crystallized perovskite phase and the (101) preferred orientation were obtained by two-step annealing at the conditions of $650^{\circ}C$, 1 hour. It was found that the temperature for the pulsed laser ablated PZT films annealed via a two-step annealing process can be reduced 20$0^{\circ}C$ compared to that of the conventional three-step annealing temperature profile for enhancing the transformation of the perovskite phase. The remanent polarization and the coercive field of this film were about 20 $\mu$C/$\textrm{cm}^2$ and 46 kV/cm, while the dielectric constant and loss values measured at 1 KHz were approximately 860 and 0.04, respectively. The interesting phenomena of this film, such as vertical shift in hysteresis curve, are also discussed.

• Journal of Advanced Marine Engineering and Technology
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• 제27권7호
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• pp.872-878
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• 2003

As the results of recent industrial development, many industrial plants and marine structures are exposed to severe corrosion environment than before. Especially, under the wet environment, crevice corrosion damage problems necessarily occur and encourage many interests to prevent them. In this study, the electrochemical polarization test was carried out to study characteristics of crevice corrosion for AISI 304 stainless steel in various solution temperatures. The results are as follows ; 1) as the solution temperature increased in IN $\textrm{H}_2\textrm{SO}_4$, the passive current density and critical current density were increased, whereas corrosion potential and break down potential were nearly constant, 2) as the solution temperature increased. the induced time for initiation of crevice corrosion was shortened. 3) The potential range in the crevice was -220mV/SCE to -380mV/SCE according to the distance from the crevice opening, which is lower than that of external surface of -200mV/SCE.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.213-215
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• 1987

In this paper, influences or grain size on the electro-optic properties were studied on the penferroelectric PLZT ceramics. The specimens were fabricated by the two stage sintering method. Relative permittivity was a little increased with the increment or grain size in 9,9.5/65/35 (La/Zr/Ti) PLZT specimens, and Curie temperature was decreased in the 9.5/65/35 specimens but constant in the 9.5/65/35 specimens. As the grain size was increased, field induced polarization and dP/dE were increased. Because domain walls can be easily moved by electric field. Light transmittance was increased in the 9/65/35 PLZT specimens but there was little effect on the grain size in the 9.5/65/35 PLZT specimens.

• Transactions on Electrical and Electronic Materials
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• 제7권2호
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• pp.72-75
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• 2006

Ferroelectric PZT heterolayered thick films were fabricated by the alkoxide-based sol-gel method. PZT(Zr/Ti=60/40) paste was made and alternately screen-printed on the $Al_2O_3$ substrates. We have introduced a press-treatment to obtain a good densification of screen printed films. The porosity of the thick films was decreased with increasing the applied pressure and the thick films pressed at $0.6ton/cm^2$ showed the dense microstructure and thickness of about $76{\mu}m$. The relative dielectric constant increased with increasing the applied pressure. The remanent polarization and coercive field increased with increasing applied pressure and the values for the PZT thick films pressed at $0.6ton/cm^2$ were $16.6{\mu}C/cm^2$, 76.9 kV/cm, respectively.