• Title/Summary/Keyword: $Nb_2_O3$

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The Charge/Discharge for Metal Oxides Substitution and Doping of $Li_4Ti_5O_{12}$ ($Li_4Ti_5O_{12}$에서 금속 산화물 치환에 따른 충방전 효과)

  • Kang, Mi-Ra;Jee, Mi-Jung;Bae, Hyeon;Choi, Byung-Hyun;Kim, Sei-Ki;Lee, Mi-Jea
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.06a
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    • pp.44-45
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    • 2006
  • 초고용량 캐패시터(Supercapacitor)는 이차전지와 더불어 차세대 전지로 분류되는 신형에너지 장치로서 충 방전 속도가 다르고 순간 전력공급이 가능하며 충 방전 수명이 반영구적으로 길고 고출력을 내기 때문에 이차전지가 갖지 못하는 영역에서 동력에너지원으로 사용된다. 본 연구에서는 초고용랑 캐패시터의 전극소재인 탄소계 재료를 대신하여 비탄소계 전극소재인 $Li_4Ti_5O_{12}$의 고상법 제조를 위한 Li/Ti의 최적 조성과 혼합 방법으로 Li-Ti 계에 $Fe_2O_3$, NiO, $Nb_2O_5$, $Sb_2O_3$ 그리고 ZnO와 같은 금속산화물로 치환시켜 합성된 Li -Ti계 금속산화물의 특성 및 충 방전 효과에 미치는 영향을 관찰하고자 하였다.

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Modulator of surface plasmon polariton based cycle branch graphene waveguide

  • Zhu, Jun;Xu, Zhengjie;Xu, Wenju;Wei, Duqu
    • Carbon letters
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    • v.25
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    • pp.84-88
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    • 2018
  • At present, an important research area is the search for materials that are compatible with CMOS technology and achieve a satisfactory response rate and modulation efficiency. A strong local field of graphene surface plasmon polariton (SPP) can increase the interaction between light and graphene, reduce device size, and facilitate the integration of materials with CMOS. In this study, we design a new modulator of SPP-based cycle branch graphene waveguide. The structure comprises a primary waveguide of graphene-$LiNbO_3$-graphene, and a secondary cycle branch waveguide is etched on the surface of $LiNbO_3$. Part of the incident light in the primary waveguide enters the secondary waveguide, thus leading to a phase difference with the primary waveguide as reflected at the end of the branch and interaction coupling to enhance output light intensity. Through feature analysis, we discover that the area of the secondary waveguide shows significant localized fields and SPPs. Moreover, the cycle branch graphene waveguide can realize gain compensation, reduce transmission loss, and increase transmission distance. Numerical simulations show that the minimum effective mode field area is about $0.0130{\lambda}^2$, the gain coefficient is about $700cm^{-1}$, and the quality factor can reach 150. The structure can realize the mode field limits of deep subwavelength and achieve a good comprehensive performance.

Electrochemical Characteristics of Nanotubular Ti-25Nb-xZr Ternary Alloys for Dental Implant Materials

  • Byeon, In-Seop;Park, Seon-Young;Choe, Han-Cheol
    • Journal of Korean Dental Science
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    • v.10 no.1
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    • pp.10-21
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    • 2017
  • Purpose: The purpose of this study was to investigate the electrochemical characteristics of nanotubular Ti-25Nb-xZr ternary alloys for dental implant materials. Materials and Methods: Ti-25Nb-xZr alloys with different Zr contents (0, 3, 7, and 15 wt.%) were manufactured using commercially pure titanium (CP-Ti), niobium (Nb), and zirconium (Zr) (99.95 wt.% purity). The alloys were prepared by arc melting in argon (Ar) atmosphere. The Ti-25Nb-xZr alloys were homogenized in Ar atmosphere at $1,000^{\circ}C$ for 12 hours followed by quenching into ice water. The microstructure of the Ti-25Nb-xZr alloys was examined by a field emission scanning electron microscope. The phases in the alloys were identified by an X-ray diffractometer. The chemical composition of the nanotube-formed surfaces was determined by energy-dispersive X-ray spectroscopy. Self-organized $TiO_2$ was prepared by electrochemical oxidation of the samples in a $1.0M\;H_3PO_4+0.8wt.%$ NaF electrolyte. The anodization potential was 30 V and time was 1 hour by DC supplier. Surface wettability was evaluated for both the metallographically polished and nanotube-formed surfaces using a contact-angle goniometer. The corrosion properties of the specimens were investigated using a 0.9 wt.% aqueous solution of NaCl at $36^{\circ}C{\pm}5^{\circ}C$ using a potentiodynamic polarization test. Result: Needle-like structure of Ti-25Nb-xZr alloys was transform to equiaxed structure as Zr content increased. Nanotube formed on Ti-25Nb-xZr alloys show two sizes of nanotube structure. The diameters of the large tubes decreased and small tubes increased as Zr content increased. The lower contact angles for nanotube formed Ti-25NbxZr alloys surfaces showed compare to non-nanotube formed surface. The corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface showed longer the passive regions compared to non-treatment surface. Conclusion: It is confirmed that corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface has longer passive region compared to without treatment surface.

Evaluation of Bioactivity of Ti-6Al-7Nb Alloys with Various Hydrothermal Treatment Times (열수처리 시간에 따른 Ti-6Al-7Nh 합금의 생체활성 평가)

  • Kwon O. S.;Choi S. K.;Park K. B.;Lee M. H.;Bae T. S.;Lee O. Y.
    • Korean Journal of Materials Research
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    • v.14 no.12
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    • pp.876-884
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    • 2004
  • This study was to investigate whether the bioactivity of the anodized and hydrothermally treated Ti-6Al-7Nb alloy were affected by the time of hydrothermal treatment. Anodizing was performed at current density 30 $mA/cm^2$ up to 300 V in electrolyte solutions containing $DL-{\alpha}-glycerophosphate$ disodium salt hydrate $(DL-{\alpha}-GP)$ and calcium acetate (CA). Hydrothermal treatment was done at $300^{\circ}C$ for 30 min, 1 hr, 2 hrs, and 4 hrs to produce a thin film layer of hydroxyapatite (HA). The bioactivity was evaluated from HA formation on the surfaces in a Hanks' solution with pH 7.4 at $36.5^{\circ}C$ for 10, 20, and 30 days. Anodic oxide films were porous with pore size of $1\sim4{\mu}m\;and\;3\sim4{\mu}m$ thickness. The anodic oxide films composed with strong anatase peak with presence of rutile peak, and showed the increase in intensity of anatase peak after hydrothermal treatment. It was shown that the intensity of anatase peak increased with increasing the time of hydrothermal treatment but was no difference in rutile peak. The corrosion voltage was the highest in the group of hydrothermal treatment for 2 hrs (Ecorr: -338.6 mV). The bioactivity in Hank's solution was accelerated with increasing the time of hydrothermal treatment.

Geochemical Characteristics of Stream Sediments Based on Bed Rocks in the Cheongpung Area (기반암에 따른 청풍지역 하상퇴적물의 지구화학적 특성)

  • Park, Young-Seog;Park, Dae-Woo;Kim, Jong-Kyun;Song, Yeung-Sang;Lee, Jang-Jon
    • Economic and Environmental Geology
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    • v.39 no.6 s.181
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    • pp.675-687
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    • 2006
  • The purpose of this study is to determine the geochemical characteristics of the stream sediments in the Cheongpung area. So that we can understand the natural background and predict the prospects of geochemical disaster, if any. We collected the stream sediments samples by wet sieving along the primary channels and slow dried the collected samples in the laboratory and ground them to pass a 200 mesh using an alumina mortar and pestle for chemical analysis. Miner-alogical characteristics, major, trace and rare earth elements were determined by XRD, XRF, ICP-AES and NAA analysis methods. For geochemical characteristics on the geological group of stream sediments, the studied area was grouped into granitic gneiss area, metatectic gneiss area, Dado tuff area, Yuchi conglomerate area, and Neungju flow area in the Cheongpung area. Contents of major elements for the stream sediments in the Cheongpung area were $SiO_2\;47.31{\sim}72.81\;wt.%,\;A1_2O_3 \;11.26{\sim}21.88\;wt.%,\;Fe_2O_3\;2.83{\sim}8.39\;wt.%,\;CaO\;0.34{\sim}7.54\;wt.%,\;MgO\; 0.55{\sim}3.59\;wt.%,\;K_2O\;1.71{\sim}4.31\;wt.%,\;Na_2O\;0.56{\sim}2.28\;wt.%,\;TiO_2\;0.46{\sim}1.24\;wt.%,\;MnO\;0.04{\sim}0.27\;wt.%,\;P_2O_5\;0.02{\sim}0.45\;wt.%$. The con-tents of trace and rare earth elements for the stream sediments were $Ba\;700ppm{\sim}8990ppm,\;Be\;1.0{\sim}3.50ppm,\;Cu\;6.20{\sim}60ppm,\;Nb\;12{\sim}28ppm,\;Ni\;4.4{\sim}61ppm,\;Pb\;13{\sim}34ppm,\;Sr\;65{\sim}787ppm,\;V\;4{\sim}98ppm,\;Zr\;32{\sim}164ppm,\;Li\;21{\sim}827ppm,\;Co\;3.68{\sim}65ppm,\;Cr\;16.7{\sim}409ppm,\;Cs\;2.72{\sim}37.1ppm,\;Hf\;4.99{\sim}49.2ppm,\;Rb\;71.9{\sim}649ppm,\;Sb\;0.16{\sim}5.03ppm,\;Sc\;4.97{\sim}52ppm,\;Zn\;26.3{\sim}375ppm,\;Ce\;60.6{\sim}373ppm,\;Eu\;0.82{\sim}6ppm,\;Yb\;0.71{\sim}10ppm$.

PZT-PMN Ceramics for Large Displacement Piezoelectric Devices

  • Lim, Kee-Joe;Park, Jae-Yeol;Lee, Jong-Sub;Kang, Seong-Hwa;Kim, Hyun-Hoo
    • Transactions on Electrical and Electronic Materials
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    • v.5 no.2
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    • pp.76-80
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    • 2004
  • Piezoelectric and dielectric properties as functions of x and y mole ratio in yPb(ZrxTil-x)O$_3$(1-y)Pb(Mn$\_$1/3/Nb/2/3/)O$_3$, ceramics, PZT-PMN, are investigated for large displacement piezoelectric devices. From the experimental results, when y is 0.95 and x is 0.505, the piezoelectric and dielectric properties are maximum, that is, electromechanical coupling coefficient(kp), piezoelectric strain constant(d$\_$33/), permittivity($\varepsilon$$\_$33/$\^$T//$\varepsilon$$\_$0/), and Curie temperature are 58 %, 272 pC/N, 1520 and about 350$^{\circ}C$, respectively. Also, when y is 0.90 and x is 0.50, their properties are 56 %, 242 pC/N, 1220, and 290$^{\circ}C$, respectively. As MgO dopant is added from 0 wt% to 1 wt%, kp increases to 63 % and Qm decreases to 500 at the MgO dopant of 0.1 wt%, and then kp decreases to 57 % as MgO is added.

The effect of PCN substitution on dielectric and piezoelectric properties of PMN-PZT Ceramics (PCN 치환이 PMN-PZT 세라믹스에 유전 및 압전특성에 미치는 영향)

  • Nam, Seung-Hyon;Yoo, Ju-Hyun;Lee, Su-Ho;Jeong, Yeong-Ho;Park, Chang-Yub
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.04b
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    • pp.161-164
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    • 2004
  • In this study, to develop the composition ceramics for the Ultrasonic vibrator, $Pb(Mn_{1/3}Nb_{2/3})O_3Pb(Zr.Ti)O_3$ system ceramics were manufactured as a function of PCN substitution. Its dielectric and piezoelectric characteristics were investigated. With increasing the amount of PCN substitution, electromechanical coupling factor(kp) were increased until 3mol% PCN and that after decreased. mechanical quality factor(Qm) showed the maxinum value at 2mol% PCN. Eletromechanical coupling factor, mechanical quality factor and dielectric constant were showed optimum value at PCN 2mol% as 0.58, 1630 and 1407, respectively for ultrasonic vibrator applications.

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A Study on the Piezoelectric Sounder Using the PMN-PT-PZ with Sr Sustitutions (Sr이 치환된 PMN-PT-PZ 계 세라믹스를 이용한 압전 발음체에 관한 연구)

  • You, H.S.;Paek, D.S.;Kang, J.K.;Park, C.Y.
    • Proceedings of the KIEE Conference
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    • 1991.11a
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    • pp.293-295
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    • 1991
  • In this study, we investigated the possibilty that $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3-PbZrO_3$ ceramics with strontium substitutions could be used for piezoelectric sounders. Piezoelectric buzzer is one of them. By partially substituting Sr for Ph, dielectric constants had values greater than 2000, the value proper piezoelectric buzzer, piezoelectric constant($d_{31}$) had a maximum value, 298 $[10^{-12}C/N]$, at the Sr 5 mol % substitution. Sound level of piezoelectric buzzer had the highest value of 91 dB at the Sr 5 mol % substitution.

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Effect of Pyrochlore Phase on Electric Properties for PNN-PT-PZ Piezoelectric Ceramics (PNN-PT-PZ계 압전세라믹스의 전기적 특성에 미치는 Pyrochlore 상의 영향)

  • 이기태;남효덕
    • Journal of the Korean Ceramic Society
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    • v.31 no.9
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    • pp.1030-1036
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    • 1994
  • The ceramics in the system 0.5[Pb(Ni1/3Nb2/3)O3]-0.5[0.65PbTiO3-0.35PbZrO3] were prepared by conventional solid state reaction method, double calcined method (columbite precursor method) and flux method using NaCl-KCl. Amount of pyrochlore phase for the calcined powders, sintering charateristrics, dielectric and piezoelectric properties were then investigated. Sintering temperature was 1000~120$0^{\circ}C$ and in case of flux method, the amount of flux to oxide was 1 : 1 mole ratio. The dielectric and piezoelectric properties of ceramics prepared by double calcined method and flux method were found to be better than those by conventional method. It was also possible to lower sintering temperature and reduce the amount of pyrochlore phase either by double calcined method or flux method. But with increasing sintering temperature, the difference in characteristrics due to diffrent fabrication method gradually.

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