• Title/Summary/Keyword: yttrium

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Yttrium Doping Effect on Varistor Properties of Zinc-Vanadium-Based Ceramics

  • Nahm, Choon-W.
    • Journal of the Korean Ceramic Society
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    • v.55 no.5
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    • pp.504-509
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    • 2018
  • The influence of yttrium doping on varistor properties of zinc-vanadium-based ceramics was comprehensively investigated. The average grain size varied slightly between 5.2 and $5.5{\mu}m$ as the yttrium content increased; and similarly, the sintered density varied slightly between 5.47 and $5.51g/cm^3$. The threshold field exhibited a maximum value (5387 V/cm) when the yttrium content was 0.1 mol%. The highest nonlinear exponent (67) was obtained when the yttrium content was 0.05 mol%. The donor concentration increased in the range of $(2.46-5.56){\times}10^{17}cm^{-3}$ as the yttrium content increased, and the maximum barrier height was obtained (1.24 eV) when the yttrium content reached 0.05 mol%.

Studies on Carrier-Free Yttrium-90 with Membrane Filters (막여과지에 의한 무단체 이트륨-90에 관한 연구)

  • Jae, Won-Mok
    • Journal of the Korean Chemical Society
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    • v.14 no.4
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    • pp.347-355
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    • 1970
  • The state of carrier-free yttrium-90 has been studied by filtration method with membrane filters. The studies include the adsorption ratio of carrier-free yttrium-90 on membrane filters by the change of PH, concentration of yttrium-90, and the pore size of member filters. The adsorption followed to Freundlich adsorption isotherm. The adsorption mechanism was proposed by the adsorption of transient state as an ionic form of $Y^{3+}$, and the experimental results were explained satisfactorily by the proposal. The adsorbed state of yttrium was present in the forms of yttrium such as $Y^{3+},\;Y(OH)^{3+},\;Y(OH)^{2+},\;Y(OH)^+_3,\;and\;Y(OH)_3$,and the existing ratios of the forms of yttrium were sharply changed by PH. It seems to be valid tha the carrier-free yttrium-90 exists mostly in $Y^{3+}$ state.

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Preparation of Monodispersed Colloidal Particles of Yttrium Compound by Homogeneous Precipitation. I.Effect of $Y(NO_3)_3$ Concentration (균일침전법에 의한 균일입도 초미분 이트륨화합물의 제조에 관한 연구 I. $Y(NO_3)_3$ 농도의 영향)

  • 권영식;김연식
    • Journal of the Korean Ceramic Society
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    • v.33 no.5
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    • pp.495-506
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    • 1996
  • Monodispersed colloidaly yttria(Y2O3) can be used in a variety of applications such as phosphors. IR transparent materials and fine ceramics. For preparing monodispersed yttria homogeneous precipitation has been regarded as a fovorable method that is monodispersed yttria can be obtained through calcining monodispersed colloidal compound of yttrium (eg:Y(OH)CO3.nH2O)which can be prepared by homogeneous precipitation with urea. It is however still required to find out the quantitative effects of important variables of precipitation such as concentration of yttrium and urea reaction temperature and initial pH of reactant even though homogeneous precipitation of Y3+ with urea has been studied extensively. Among the effects of these variables we investiga-ted 1) the effect of yttrium concentration on the shape and size of precipitate and the reation rate 2) range of yttrium concentration required to make monodispersed colloidal particles 3) the reason for limited concentra-tion range of yttrium and 4) the effect of ultrasonic radiation on the limited concentration.

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Hydrogen Trapping Using Yttrium to Manage Hydrogen in HSLA Steel Welds (고장력강의 용접부에서 Yttrium을 이용한 수소의 트랩에 관한 연구)

  • Park, Yeong-Do
    • Proceedings of the KWS Conference
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    • 2005.06a
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    • pp.141-143
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    • 2005
  • Yttrium has been investigated as hydrogen trapping site in pure iron and HSLA steel welds. Assessment of hydrogen trapping parameters for yttrium oxide has also shown the high potential of yttrium addition to improve hydrogen management in high strength steel welding. The purpose of this study was to reduce and control the diffusible hydrogen content in the weld deposit.

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Variations of ferroelectric properties with the addition of Yttrium acetate in the $Pb(Zr_{0.65}Ti_{0.35})O_3$ thin films prepared by Sol-Gel processing (Sol-Ge법에 의한 $Pb(Zr_{0.65}Ti_{0.35})O_3$박막의 Yttrium acetate 첨가에 따른 강유전 특성의 변화)

  • 김준한;이규선;이두희;박창엽
    • Electrical & Electronic Materials
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    • v.8 no.3
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    • pp.261-266
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    • 1995
  • In this study, PZT solutions added impurities of Yttrium acetate were prepared by sol-gel processing and were deposited on Pt/ $SiO_{2}$/Si substrates at 5000 rpm for 20 sec. using spin-coating method. Coated films were annealed at 700-750.deg. C for 30 min. using conventional furnace method. Variations of the crystallographic structure and microstructure of PZT thin films with adding impurities were observed using XRD and SEM, and the electrical properties, such as relative permittivity, tan .delta., hysteresis curves and leakage currents, were measured. As the yttrium contents were increased, the remanent polarization and coercive field were decreased. Variations of remanent polarizations and coercive fields of pure and yttrium doped specimens according to polarization reversal cycles were observed using hysteresis measurement. PZT thin films added $Y^{3+}$ ions were completely crystallized at 750.deg. C. $Y^{3+}$ ions, as donor impurity, substituted Pb.sup 2+/ ions located at A-site of perovskite structure. By substitution of $Y^{3+}$ ions, leakage currents became less by decreasing the space charges. Degradation of remanent polarizations of Yttrium added specimens after fatigue was not observed and coercive fields increased more than those of pure PZT thin films.

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Effects of Excess Yttrium Addition on YBCO Thin Films Prepared by TFA-MOD Process (MOD-TFA 공정에 의한 YBCO박막제조시 과잉 yttrium첨가 효과에 관한 연구)

  • Lee Seung-Yi;Song Seul-A;Kim Byeong-Joo;Park Jin-A;Kim Ho-Jin;Lee Hee-Gyoun;Hong Gye-Won;Jang Seog Heon;Joo Jinho;Yoo Jai-Moo;Pradeep Halder
    • Progress in Superconductivity
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    • v.7 no.1
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    • pp.87-91
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    • 2005
  • [ $YBa_{2}Cu_{3}O_{7-x}$ ] thin films were fabricated on $LaAlO_3$(100) substrate by TFA-MOD process. Yttrium-excess (0, 2.5, 5, 10, 15, 20 $at\%$) coating solution was prepared by adding extra amount of yttrium into a stoichiometric(Y:Ba:Cu=1:2:3) TFA precursor solution. Results are presented concerning the influence of excess yttrium additions on the microstructure development and superconducting properties of $YBa_{2}Cu_{3}O_{7-x}$ film. Large sized CuO particles was observed by SEM EDS investigation. The addition of excess yttrium affected little on $T_c$ of $YBa_{2}Cu_{3}O_{7-x}$ film. $J_c$ of YBCO film was enhanced with excess yttrium addition. Jc maximum of $2.21\;MA/cm^2$ (77 K, self field) appeared with the $15\;at\%$ addition of excess yttrium. With further yttrium addition up to $20\;at\%$, Jc decreased down to $0.9\;MA/cm^2$.

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Recovery of Yttrium from the Sludge Generated in Recycling Process of the Obsolete CRT (폐CRT의 재활용 공정에서 발생한 슬러지로부터 Y의 회수)

  • 전준미;이재천;정진기;김남철
    • Resources Recycling
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    • v.10 no.6
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    • pp.22-28
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    • 2001
  • A study on the recovery of yttrium was conducted using the phosphor sludges generated in the recycling process of obsolete CRTs. Yttrium was leached by HCl and $HNO _3$. The leaching efficiency of yttrium was extensively investigated in terms of acid concentration, leaching temperature and time, and pulp density. Yttrium and lead was recovered from leaching solutions also by precipitation method. The leaching behavior of yttrium was similar in both acids. The leaching efficiency of yttrium for both acids increased with time at the conditions of 3.0M, $90^{\circ}C$, and 280 g/L of pulp density. After 40 minutes, it was saturated to 93% and 90% for HCl and HNO$_3$respectively. Yttrium was recovered from leaching acid solution by the addition of $H_2$$C_2$$O_4$while lead was removed as $PbSO_4$by $Na_2$ $SO_4$.

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Visible Light Photoelectrocatalytic Properties of Novel Yttrium Treated Carbon Nanotube/Titania Composite Electrodes

  • Zhang, Feng-Jun;Chen, Ming-Liang;Zhang, Kan;Oh, Won-Chun
    • Bulletin of the Korean Chemical Society
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    • v.31 no.1
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    • pp.133-139
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    • 2010
  • Photoelectrocatalytic decolorization of methlene blue (MB) in the presence of two types of carbon nanotube/titania and yttrium-treated carbon nanotube/titania electrodes in aqueous solutions were studied under visible light. The prepared composite electrodes were characterized by X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray analysis, and photoelectrocatalytic activity. The photoelectrocatalytic performances of the supported catalysts were evaluated for the decolorization of MB solution under visible light irradiation. The results showed that yttrium incorporation enhanced the decolorization rate of MB. It was found that the photoelectrocatalytic degradation of a MB solution could be attributed to the combined effects caused by the photo-degradation of titania, the electron assistance of carbon nanotube network, the enhancement of yttrium and a function of the applied potential. The repeatability of photocatalytic activity was also tested. The presence of yttrium enhanced the hydrophillicity of yttrium-carbon nanotubes/titania electrode because more OH groups can be adsorbed on the surface.

Simultaneous Extraction of Yttrium and Neodymium from Fly Ash by Two-Step Leaching Process with Aid of Ultrasonic Wave (2단계 침출 과정에서 발생되는 비산회로부터 초음파 활용하여 이트륨과 네오디뮴의 동시 추출)

  • Kim, Jae-Kwan;Park, Seok-Un
    • KEPCO Journal on Electric Power and Energy
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    • v.7 no.1
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    • pp.153-159
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    • 2021
  • A two-step process for increasing the leaching efficiency of yttrium and neodymium from coal fly ash were investigated at solid loadings of 5.0 g ash ~1,000 g ash/l of 1.0 N~10.0 N H2SO4, temperature ranging from 30℃ to 90℃, ultrasonic leaching time of 1~10 hours, and ultrasonic power of 25~200 W. The yttrium and neodymium from coal fly ash were effectively leached into ion phases by step change of the first conventional dissolution at room temperature and then the second heating process with the aid of ultrasonic wave, and maximum leaching efficiency of yttrium and neodymium obtained were 66 % and 63 %, respectively. The activation energies for the leaching reaction of yttrium and neodymium at second heating process dependent on leaching time and temperature were derived to be 41.540 kJmol-1 and 507.92 kJmol-1, respectively. The optimum conditions for the maximum leaching of yttrium and neodymium were found to be the solid loading of 250 g ash/l of H2SO4, solvent concentration of 2.0 N H2SO4, and second step process of temperatures of 30℃ for 3 hours and then 90℃ for 4 hours with ultrasonic intensity of 100 W.

The Effect of Yttrium on Corrosion Behavior of NiAl Intermetallic Compound in the Molten Carbonate Salt (용융탄산염내에서의 NiAl합금의 내식성에 미치는 Yttrium의 첨가 영향)

  • Hwang, Eung-Rim;Lee, Dae-Hui;Kim, Seon-Jin;Kang, Seong-Gun
    • Korean Journal of Materials Research
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    • v.8 no.8
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    • pp.685-692
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    • 1998
  • Since a wet-seal area of Molten Carbonate Fuel Cell (MCFC) operated at $650^{\circ}C$ is exposed to severe environment, a life-time of MCFC is influenced by the corrosion resistance of separator. In order to improve corrosion resistance of 316L stainless steel used as separator material, AI- base alloy such as NiAI has been widely used as coat¬ing material on the wet-seal area. The purpose of this work is to develope a more protective coating material by adding yttrium on NiAI alloy. An immersion test and a polarization test were performed in molten carbonate salt at $650^{\circ}C$ to estimate corrosion resistance of the NiAI alloy and the NiAl/Y alloys with up to L5at% yttrium. NiAl/Y alloys showed better corrosion resistance than NiAI alloy. We found that more than 0.7 at% yttrium was required to improve the corrosion resistance of NiAI alloy in molten carbonate salt at $650^{\circ}C$.

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