• Title/Summary/Keyword: Nb addition

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Growth and upconversion properties of erbium doped $LiNbO_{3}$ single crystal fibers

  • Yang, Woo-Seok;Suh, Su-Jeong;Lee, Jong-Ho;Fukuda, Tsuguo;Yoon, Dae-Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.9 no.4
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    • pp.377-380
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    • 1999
  • Erbium (Er) doped $LiNbO_{3}(Er:LiNbO_{3})$ single crystal fibers were grown free of creacks along the c-axis by micro-pulling down method. The $Er^{3+}$ concentration was distributed homogeneously along the growth axis. The samples for optical characterization were cut from as-grown single crystal fibers and polished. When the 980nm light was incident on the sample, upconversion phenomena were observed at the green range of wavelength 510~570nm. In addition, the intensity of upconversion was remarkably increased by increasing the concentration of $Er_{2}O_{3}$ dopant in as-grown $Er:LiNbO_{3}$ crystals.

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Effect of additives on the microstructure of $PbNb_2{O_6}$ ceramics ($PbNb_2{O_6}$ 세라믹스에서 미세구조에 미치는 첨가제의 영향)

  • 김영상;안형식;오영우
    • Electrical & Electronic Materials
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    • v.7 no.5
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    • pp.417-424
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    • 1994
  • PbNb$_{2}$O$_{6}$ piezoelectric ceramics have good properties, but the applications of them have been limited due to the problems of microstructures. In the present study, effects of additives on the phase stability, microstructure, and electrical proper-ties of ferroetectric phase were investigated. La$_{2}$O$_{3}$, Nd$_{2}$O$_{3}$ and Sm$_{2}$O$_{3}$ were added with the amounts of 1, 3, 5 mol% respectively. The results showed that single orthorhombic(ferroelectric phase) phase compared with the mixed phase of pure PbNb2O6 was obtained. In the case of 5 mol% Nd$_{2}$O$_{3}$ addition, relative density of >95% and dense microstructure with -2.mu.m grain size were obtained.d.

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Cavitation-erosion Resistance of Stabilized Stainless Steel with Niobium Addition in Sea Water Environment (해수 내 캐비테이션-침식 저항성에 미치는 스테인리스강의 Nb 첨가의 영향)

  • Choi, Yong-Won;Han, Min-Su;Kim, Seong-Jong
    • Journal of the Korean institute of surface engineering
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    • v.49 no.3
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    • pp.274-279
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    • 2016
  • Stainless steel is widely used in various industries due to its excellent anti-corrosion characteristics. However, if the stainless steel is exposed to high speed fluid flow and chloride ion in the marine environment, corrosion and cavitation damage occurred on the surface easily. Therefore, to prevent these problems, stabilzed stainless steel is applied to offshore and shipbuilding industries. In this study, stabilized stainless steel specimen was made by 19%Cr-9%Ni with different Nb contents (0.29%, 0.46% and 0.71%). And then, their cavitation characteristics were investigated. As a result, the characteristics of cavitation resistance of stainless steel could be improved by increasing Nb contents.

Effect of Niobium and Tin on Mechanical Properties of Zirconium Alloys (Zr 합금의 기계적 특성에 미치는 Nb와 Sn의 영향)

  • Kim, Gyeong-Ho;Choe, Byeong-Gwon;Baek, Jong-Hyeok;Kim, Seon-Jae;Jeong, Yong-Hwan
    • Korean Journal of Materials Research
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    • v.9 no.2
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    • pp.188-194
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    • 1999
  • To investigate the effect of niobium and tin on the mechanical properties of zirconium alloys, the tensile test and the microstructural analysis were performed on the Zr-based binary(Zr-xNb, Zr-xSn) and ternary(Zr-0.8Sn-xNb, Zr-0.4Nb-xSn) alloys. As the content of Nb or Sn element increased, the strengths of the Zr-based alloys tended to gradually increase. The increase of mechanical strength was remarkable strength was remarkable in the range more than the solubility of Nb and Sn. The strengthening effects were discussed on the basis of the solid solution hardening, the precipitate hardening, the grain size effect, and the texture effect. The mechanical strength is mainly controlled by the solid solution hardening and additionally by the precipitate hardening in the content more than solubility limit of Nb and Sn. The grain refinement also has a slight effect on the strength of the zirconium alloys with the addition of Nb and Sn. However, the texture effect can be excluded due to the same Kearns number regardless of the content of alloying elements.

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Electrical properties of lead free (Na,K,Li)(Nb,Sb,Ta)$O_3$ ceramics with $MnO_2$ addition ($MnO_2$ 첨가량에 따른 비납계 (Na,K,Li)(Nb,Sb,Ta)$O_3$ 세라믹스의 전기적특성)

  • Lee, Seung-Hwan;Nam, Sung-Pill;Lee, Sung-Gap;Shin, Dong-Jin;Lee, Young-Hie
    • Proceedings of the KIEE Conference
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    • 2011.07a
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    • pp.1487-1488
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    • 2011
  • Electrical properties and microstructure were investigated on the effects of $MnO_2$ and the lead-free $(Na_{0.44}K_{0.52}Li_{0.04})(Nb_{0.83}Sb_{0.07}Ta_{0.1})O_3$ ceramics with the addition of $MnO_2$ were fabricated by a conventional mixed oxide method. A gradual change in the crystal and microstructure was observed with the increase of $MnO_2$ addition. For the NKN-LST-xmol%$MnO_2$ sintered at $1100^{\circ}C$, bulk density increased with the addition of $MnO_2$ and showed maximum value at addition 1.0mol% of $MnO_2$. Curie temperature of the NKN-LST ceramics slightly decreased with adding $MnO_2$. The dielectric constant, piezoelectric constant ($d_{33}$) and electromechanical coupling factor ($k_p$) increased below 0.25mol% of $MnO_2$ addition, which might be due to the increase in density. The high piezoelectric properties = 145 pC/N, electromechanical coupling factor = 0.421 and dielectric constant = 2883 were obtained for the NKN-LST-0.25mol%$MnO_2$ sintered at $1100^{\circ}C$ for 4h.

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Electrical Properties of lead free (Na,K,Li)(Nb,Sb,Ta)O3 Ceramics with MnO2 Addition (MnO2 첨가량에 따른 비납계 (Na,K,Li)(Nb,Sb,Ta)O3 세라믹스의 전기적특성)

  • Lee, Seung-Hwan;Nam, Sung-Pill;Lee, Dong-Hyun;Lee, Sung-Gap;Lee, Sang-Chul;Lee, Young-Hie
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.4
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    • pp.801-804
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    • 2011
  • Electrical properties and microstructure were investigated on the effects of $MnO_2$ and the lead-free $(Na_{0.44}K_{0.52}Li_{0.04})(Nb_{0.83}Sb_{0.07}Ta_{0.1})O_3$ ceramics with the addition of $MnO_2$ were fabricated by a conventional mixed oxide method. A gradual change in the crystal and microstructure was observed with the increase of $MnO_2$ addition. For the NKN-LST-xmol%$MnO_2$ sintered at $1100^{\circ}C$, bulk density increased with the addition of $MnO_2$ and showed maximum value at addition 1.0mol% of $MnO_2$. Curie temperature of the NKN-LST ceramics slightly decreased with adding $MnO_2$. The dielectric constant, piezoelectric constant ($d_{33}$) and electromechanical coupling factor ($k_p$) increased below 0.25mol% of $MnO_2$ addition, which might be due to the increase in density. The high piezoelectric properties = 145 pC/N, electromechanical coupling factor = 0.421 and dielectric constant = 2883 were obtained for the NKN-LST-0.25mol%$MnO_2$ sintered at $1100^{\circ}C$ for 4h.

$(Na,Li)NbO_3-BaTiO_3$세라믹스의 유전 및 압전 특성

  • Seong, Geum-Hyeon;Lee, Yu-Hyeong;Ryu, Ju-Hyeon;Jeong, Yeong-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.11a
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    • pp.77-77
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    • 2009
  • $Pb(Zr,Ti_O_3$계 세라믹스는 우수한 압전 특성으로 인하여 압전변압기 및 액츄에이터, 센서 등 많은 분야에 응용이 되어져 왔다. 그러나, 최근 들어 $1000^{\circ}C$에서 급속도로 많은 휘발을 하는 PbO는 환경 및 인체에 나쁜 영향을 미칠 뿐 아니라 사용 후의 처리도 어려워 선진국에서는 사용을 제한하거나 줄이고 있는 추세에 있다. 따라서, PbO를 포함하지 않은 무연 (Lead-free)계 압전 세라믹스에 대한 연구가 많은 관심을 끌고 있으며 앞으로는E 장래성 있는 하나의 이슈 분야가 될 것이다. 이러한 Pb-based System 세라믹스를 대체 할 재료로서 $(Bi_{1/2}Na_{1/2})TiO_3$나 Tungsten-Bronze type, $(K_{1/2}Na_{1/2})NbO_3$ 등이 주로 연구가 되고 있다. 특히, alkali niobate를 기초로 한 $(K_{1/2}Na_{1/2})NbO_3(NKN)$은 무연 압전 물질로서 많은 주목을 받고 있다. 그러나, NKN의 주요 성분인 K 의 높은 조해성 때문에 일반적인 고상방법으로는 고 밀도의 세라믹을 얻기 힘들뿐더러 낮은 상전이 온도 때문에 많은 응용에는 제약이 되고 있다. 이러한 세라믹의 단점을 보완하고자 Hot forging, RTGG, SPS 등 과 같이 특수한 소결방법을 사용하여 고밀도의 세라믹을 제작하지만 이 방법들은 제품 대량 생산에 있어 경제적으로나 복잡한 제조과정을 고려할 때 매우 비효율적이라고 판단된다. 그러므로 $BaTiO_3$, $LiTaO_3$, Mg, Ca등을 첨가 시켜 소결을 향상시키고 고밀도를 얻기 위해 많은 연구가 진행 중이다. 따라서 본 연구에서는 Pb-based계의 세라믹스를 대체할 우수한 특성의 세라믹스를 제작하고자 기존의 $(K_{1/2}Na_{1/2})NbO_3(NKN)$세라믹스에서 낮은 용융온도 때문에 소결하기 어려운 $KNbO_3$를 제거한 $NaNbO_3$$LiNbO_3$$BaTiO_3$를 추가한 $NaLiNbO_3-BaTiO_3$세라믹스에 $K_4CuNb_8O_{23}$(KCN)을 첨가함으로서 이에 따른 압전 및 유전 특성을 조사하였다.

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The Magnetic Properties of Ultrathin Fe-Al-Nb-B-Cu Nanocrystalline Alloys (극박형 Fe-Al-Nb-B-Cu계 초미세결정합금의 자기적 특성)

  • 박진영;서수정;김광윤;노태환
    • Journal of the Korean Magnetics Society
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    • v.6 no.4
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    • pp.211-217
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    • 1996
  • The effects of Al addition to Fe-B-Nb-Cu alloy for improving the high-frequency magnetic properties and the magnetic properties of ultrathin $Fe_{78}Al_{4}Nb_{5}B_{12}Cu_{1}$ nanocrystalline alloy ribbons with the thickness less than $10\;\mu\textrm{m}$ were investigated. It was found that the effective permeability at frequencies over- 100 kHz was very high and the core loss was very low for the composition $Fe_{78}Al_{4}Nb_{5}B_{12}Cu_{1}$ alloy. Moreover, the reduction of the ribbon thickness below $10\;\mu\textrm{m}$ was very effective in improving their permeability and the core loss characteristics up to the MHz frequency range. The values of effective permeability at 1 MHz and core loss at 0.2 T, 1 MHz were 5,000 and 1.4 kW/kg, respectively. It was considered that these results were due to far refined $\alpha-Fe$ phase structure with grain size less than 10 nm and domain structure modification.

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A Study on the Viability of Human Dermal Fibroblast Cell by Media for Ni-Cr alloy elution (치과용 Ni-Cr합금 용출배지에 의한 인간 피부 섬유아세포 성장도 관찰 연구)

  • Kim, Kap-Jin;Choi, Sung-Min;Kim, Chi-Young
    • Journal of Technologic Dentistry
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    • v.31 no.3
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    • pp.21-26
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    • 2009
  • Purpose: Standards of alloy for porcelain fused to metal crown be classified by metallic factor and biological factor. Metallic factors consist of stability of alloy composition and mechanical strength and surface characteristics for chemical bond. Biological factors be considered properties of metallic elements and problems originated by toxicity and hypersensitive reaction. Alloys considered such controversial points are the most suitable alloy for dental instrument. Method: Alloys added Be and Nb using Ni-Cr alloy which has been widely used for dental instrument be selected and classified experimental group. Non-addition Be and Nb to Ni-Cr alloy classify control group and addition Be alloy is Be-experimental group, addition Nb alloy is Nb-experimental group. Specimens for cytotoxicity analysis gave effect to washing and sterilization. and then made an experiment on elution with cell medium after disinfection. It conducted specimens within cell medium with 24hours, 48hours, 72hours, respectively. It cultured human dermal fibroblast(HDF) using cell medium for cytotoxicity test and then investigated elution rate through spectroscopic analysis by MTT-assay. Result: As results of cytotoxicity test by MTT-assay, cultured cell rate of VII measured more low numerical value within elution medium for 24hours focused on control group. Also, cultured cell rate of K3 alloys observed low value for 48hours, 72hours than value of control group. Conclusion: According to final result that synthesize above results, Ni-Cr alloy added Be and Ni has little difference in Cytotoxicity by MTT-assay.

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Crystal Growth and Photoluminescence Property of Stoichiometric LiNbO3 Single Crystal Fiber by Addition of Nd2O3 (Nd\2O3 첨가에 따른 화학양론조성 LiNbO3 단결정의 성장 및 형광특성)

  • Shur, Joong-Won;Yoon, Seok-Gyu;Lee, Sung-Mun;Yoon, Dae-Ho
    • Journal of the Korean Ceramic Society
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    • v.39 no.10
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    • pp.977-980
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    • 2002
  • Using the micro-pulling down method, $Nd_2O_3$ doped crack-free stoichiometric $LiNbO_3$ single crystals were grown in 1 mm diameter and 30∼35 mm length. The homogeneous distributions of $Nd_2O_3$ concentration were confirmed by the electron probe micro analysis. The absorption and photoluminescence spectra were measured with respect to the $Nd_2O_3$ doping.