• 전자공학회논문지D
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• 제35D권1호
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• pp.72-78
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• 1998

Polarization mode converters have been produced by utilizing Ti:LiNbO$_{3}$ channel waveguide and strain-optic effect. Shear strain for periodic perturbations of optical channel waveguides and phase matching can be obtained by an evaporated periodic SiO$_{2}$ thin film at 300.deg. C. The electrodes located on the either side of waveguide provide a means to electro-optically tune the wavelength for maximum polarization conversion via the electrooptic effect. The maximum conversion effeciency was observed at 21.deg. C for V=0 and 46.deg. C for V=30V aro the device having 7 .mu.m waveguide wiith and 350 periodic pads. The dependence of the number of pads on conversion efficiency was observed experimentally.fficiency was observed experimentally.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 정기총회 및 추계학술대회 논문집 학회본부
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• pp.237-239
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• 1993

$MnO_2$ added $(Pb_{0.45}Ca_{0.55})(Fe_{0.5}Nb_{0.5})O_3$ was calcined at $850^{\circ}C$ for two hours and sintered at $1100^{\circ}C$ for two hours. The microstructure was examined using XRD and SEM. The dielectric constant, the quality factor, and the temperature stability was measured using Hakki and Coleman method. Dielectric constant was improved to 94 from 0.5wt% $MnO_2$ added sample with $Q{\cdot}f=4260GHz$ and acceptable ${\tau}_f$ (< $20ppm/^{\circ}C$).

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.1041-1043
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• 1999

In this work, a possible new PD detection technique, based on the electro-optic effect, has been proposed. A proto-type probe sensor for detection partial discharge is made by $LiNbO_3$ Pockels cell, diachroic sheet polarizer and right-angle prism. The Mach-Zehnder interferometer system is proposed by using this sensor and this system is applied to detecting high electric field. we show the characteristic of the proto-type probe sensor and the design of a proposed probe type sensor.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1232-1233
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• 2006

To co-fire with commercial LTCC (Low Temperature Co-fired Ceramic) materials at $850^{\circ}C{\sim}880^{\circ}C$, different contents of $B_2O_3$ were added to the $Bi_2O_3-ZnO-Nb_2O_5$ (BZN) ceramics. According to the test results, the cubic phase of BZN was transformed into orthorhombic in all the test materials. $BiNbO_4$ phase was formed in test materials with $2{\sim}5wt%$ of $B_2O_3$ addition. The phase transformation of cubic BZN was controlled during the synthesis process with excess ZnO content. The Cubic and orthorhombic phases of BZN could coexist and be sintered densely at $850^{\circ}C/2hr$.

• 한국전기전자재료학회논문지
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• 제12권1호
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• pp.62-68
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• 1999

Ferroelectric $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$(x=0, 0.1, 0.2, 0.3) thin films were deposited on $Pt/SiO_2/Si$ substrate by MOD(Metalorganic Decomposition) process. Metal carboxylate and metal alkoxide were used as precursors, and 2-methoxyethanol, xylene as solvents. After spin coating, thin films were pre-annealed at $400^{\circ}C$, followed by RTA(Rapid Thermal Annealing) and final annealing at $800^{\circ}C$ in oxygen atmosphere. These procedures were repeated three times to obtain thin films with the thickness of $2000{\AA}$. To enhance the nucleation and growth of layered-perovskite phase, thin films were rapid-thermally annealed above $720^{\circ}C$ in oxygen atmosphere. As RTA temperature increased, fluorite phase was transformed to layered-perovskite phase. And the change of Nb contents affected dielectric / electrical properties and microstructure. The ferroelectric characteristics of $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$ thin film were Pr=8.67 $\mu{C}/cm^2$, Ec=62.4kV/cm and $I_{L}=1.4\times10^{-7}A/cm^2$ at the applied voltage of 5V, respectively.

• 대한금속재료학회지
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• 제49권2호
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• pp.121-127
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• 2011

The mechanical properties of the various heat treatment conditions on Ti-15Mo-3Nb-3Al-0.2Si alloy plates were examined. XRD patterns from the surface of Ti-15Mo-3Nb-3Al-0.2Si were analyzed as a solution-treated Ti alloy has the single-phase ${\beta}$ structure whereas the aged Ti alloys have the ${\beta}$ matrix embedded with ${\alpha}$ needles. High strength (~1500 MPa) with decent ductility (7%) was obtained by the Ti alloy double aged at $300^{\circ}C$ and $520^{\circ}C$ for 8 hours each. The double-aged alloy exhibits the finer structure than the single-aged alloy at $300^{\circ}C$ for 8 hours because of the higher nucleation rate of ${\alpha}$ needles at an initial low aging temperature ($320^{\circ}C$). TEM observation revealed that the fine nanostructure with ${\alpha}$ needles in the ${\beta}$ matrix ensured the excellent mechanical properties in the double aged Ti-15Mo-3Nb-3Al-0.2Si alloy. In the solution treated alloy, the yield drop, stress-serrations and the ductility minimum typically associated with dynamic strain aging can be attributed to the dynamic interaction between dislocations and oxygen atoms. The yield drop and the stress serration were not observed in aged samples because the geometrically introduced dislocations due to phase precipitates suppressed the dynamic strain aging.

• 한국전기전자재료학회논문지
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• 제22권11호
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• pp.925-929
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• 2009

In this study, $0.95(K_{0.5}Na_{0.5})NbO_3-0.05Li(Sb_{0.8}Nb_{0.2})O_3$ ceramics were investigated as a function of the amount of $Ag_2O$ addition in order to improve dielectric and piezoelectric properties of lead-free piezoelectric ceramics. With increasing the amount of $Ag_2O$ addition, density and electromechanical coupling factor ($k_p$) increased up to 0.2 wt.% $Ag_2O$ and decreased above 0.2 wt.% $Ag_2O$. At the sintering temperature of $1020^{\circ}C$, electromechanical coupling factor ($k_p$), density, dielectric constant (${\varepsilon}r$) and curie temperature (Tc) of ceramics with 0.2 wt% $Ag_2O$ showed the optimal values of 0.42, $4.33\;g/cm^3$, 738 and $393^{\circ}C$, respectively.

• Nuclear Engineering and Technology
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• 제35권6호
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• pp.529-536
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• 2003

The objective of this study is to investigate the reorientation of hydrides with applied stress intensity factor, the peak temperature and the time when to apply the stress intensity factor in a Zr-2.5Nb pressure tube during its thermal cycle treatment. Cantilever beam (CB) specimens with a notch of 0.5 mm in depth made from the Zr-2.5Nb tube were subjected to electrolytic hydrogen charging to contain 60 ppm H and then to a thermal cycle involving heating to the peak temperature of either 310 or $380^{\circ}C$, holding there for 50 h and then cooling to the test temperature of $250^{\circ}C$. The stress intensity factor of either 6.13 or $18.4\;MPa\sqrt{m}$ was applied at the beginning of the thermal cycle, at the end of the hold at the peak temperatures and after cooling to the test temperature, respectively. The reorientation of hydrides in the Zr-2.5Nb tube was enhanced with the increased peak temperature and applied stress intensity factor. Furthermore, when the CB specimens were subjected to $18.4\;MPa\sqrt{m}$ from the beginning of the thermal cycle, the reoriented hydrides occurred almost all over the Zr-2.5Nb tube, surprisingly suppressing the growth of a DHC crack. In contrast, when the CB specimens were subjected to the stress intensity factor at the test temperature, little reorientation of hydrides was observed except the notch region, leading the Zr-2.5Nb to grow a large DHC crack. Based on the correlation between the reorientation of hydrides and the DHC crack growth, a governing factor for DHC is discussed along with the feasibility of the Kim's DHC model.

• 폴리머
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• 제27권5호
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• pp.429-435
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• 2003

양이온η$^3$-알릴 팔라듐 촉매를 사용하여 환상형 올레핀 단량체인 노보넨 (NB)과 5-비닐-2-노보넨(VNB)을 조성별로 비닐 부가 공중합하였다. 공중합체는 고수율과 고분자량 (M$_{w}$ > 760000)으로 얻을 수 있었다. VNB 함량이 많아질수록 공중합체의 분자량과 수득율은 감소하였으며, 첨가한 공단량체의 양과 공중합한 후 함유된 단량체의 양이 비례함을 FT-IR 분광분석으로 확인하였다. $^1$H-NMR 분석 결과 VNB는 exo, endo 이성체 모두 중합에 참여하는 것을 알 수 있었다. NB-VNB 공중합체의 분해 개시 온도는 약 300 $^{\circ}C$이었고, 열안정성은 VNB 함량과 관계없이 유사한 거동을 나타내었다. 합성된 NB-VNB 공중합체의 곁사슬 비닐기는 m-CPBA를 이용하여 에폭시화 하였고, 또한 9-BBN을 이용하여 수산화기를 도입하였다. 조성별 공중합체에 각각의 치환기가 도입된 것은 FT-IR, $^1$H-NMR 분석으로 확인하였다..

• 한국세라믹학회지
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• 제41권7호
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• pp.508-512
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• 2004

치과 임프란트의 상부구조물로 응용하기 위해 Zr $O_2$, $Y_2$ $O_3$, Nb$_2$ $O_{5}$를 각각 90.24, 5.31, 4.45mo1%씩 혼합한 정방정 지르코니아 고용체에 알루미나를 부피비로 10-90%를 10vo1%간격으로 첨가하여 (Y, Nb)-TZP/알루미나 복합체를 제조하였다. 최적의 기계적 물성은 알루미나를 10vo1% 첨가했을 때 이축 곡강도는 900MPa이었으며 파괴인성은 8.9MPam$^{1}$2/이었고 20$0^{\circ}C$ 오토크레이브하에서 10시간 열처리했을 때 저온열화가 관찰되지 않았다. 복합체를 임프란트 상부구조물로 제작하여 40명의 환자에게 총 65개를 시술한 후 2년 동안 관찰한 결과 부작용이나 나사의 풀림 또는 파절이 전혀 일어나지 않아 우수한 임상결과를 보였다.