PDA CCFL 구동을 위한 압전트랜스포머 용 PNW-PMN-PZT 세라믹스의 Nb₂O₅ 첨가에 따른 미세구조 및 압전특성

류주현,황락훈,김철희,오동언,장은성,정영호,홍재일 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.3

PNW-PMN-PZT ceramics were fabricated with the variations of Nb$_2$O$_{5}$ addition and their microstructural and piezoelectric characteristics were investigated. When the amount of Nb$_2$O$_{5}$ increased, grain size decreased gradually. At 0.3wt% Nb$_2$O$_{5}$ which is the same weight percent with Fe$_2$O$_3$, maximum tetragonality(c/a) and density were shown due to the complexed doping effects. Also, this composition that showed Qm of 2,041, kp of 0.55, grain size of 2.5${\mu}{\textrm}{m}$ and $\varepsilon$r of 1704 were proper for high power application. Using this composition, Rosen-type piezoelectric transformer was fabricated as the size of 1 ${\times}$ 16 ${\times}$ 5㎣ and its electrical characteristics were investigated with the variations of load resistance and driving frequency. At the resistance of 200㏀, maximum step-up ratio of 13.68 was shown. After driving PDA CCFL for 25 min using the inverter circuit, at driving frequency of 214.4KHz, input voltage of 31.78 V and input current of 21.1mA were measured at the input part of piezoelectric transformer. And then, output voltage of 293.2 V and output current of 2.2mA were shown at the output part of piezoelectric transformer. At the same time, efficiency of 96.2% and temperature rise of 3.5$^{\circ}C$ were appeared at the piezoelectric transformer.ormer.

무연계 (Na0.53K0.47)0.96Li0.04(Nb1−xTax)O3 세라믹스의 온도에 따른 압전 및 유전 특성

김민수,김진수,류경현,임상윤,김명호,박태곤,박종규,송재성 한국물리학회 2013 새물리 Vol.63 No.8

High performance lead-free materials are required for piezoelectric applications. Among leadfree candidate materials, (Na0.5K0.5)NbO3 (NKN) is considered the most promising. However, pure NKN has a poor piezoelectirc coefficient and poor sinterability. To improve the piezoelectric properties of NKN ceramics, we have studied the effect of Ta substitution on the dielectric and the piezoelectric properties of (Na0.53K0.47)0.96Li0.04(Nb1−xTax)O3 (NKLNT, x = 0.0, 0.13, 0.15, 0.17, 0.19, and 0.21) ceramics. Phase transition temperatures such as the TO−T (orthorhombictetragonal) and the TC (tetragonal-cubic) decreased with increasing Ta substitution. In addition, the piezoelectric properties of NKLNT were enhanced by Ta substitution. Especially, a high piezoelectric coefficient, d33 = 233 pC/N, was obtained at x = 0.19 - 0.21. We found that NKLNT ceramics with proper Ta-ion substitution had improved piezoelectric properties. Futhermore, we showed that the enhanced piezoelectric properties were related to the phase formation and to the polymorphic phase transition (PPT). 무연계(Na0.53K0.47)0.96Li0.04(Nb1−xTax)O3 세라믹 (x = 0.0, 0.13, 0.15, 0.17, 0.19, 0.21)을 제조하여 온도에따른 유전 및 압전 특성을 조사하였다. X-선 회절 분석을 통해 잘 성장된페로브스카이트 구조를 확인하였다. Ta의 양이 증가함에 따라 큐리 온도(TC)와 orthorhombic - tetragonal 상전이 온도 (TO-T)가감소하였고, 압전 계수 (d33)는 증가하였다. TO-T가 실온가까이 존재하는 x = 0.17 ~ 0.21 조성에서 압전 특성이향상되었다. 특히 $x$ = 0.19 ~ 0.21 조성에서 233 pC/N의 향상된압전 계수값을 가졌고, 온도가 증가함에 따라 압전 계수는 서서히감소하였다.

저탄소 미량합금강의 미세조직에 미치는 고온변형의 효과

김새암 ( Sea Arm Kim ),이상우 ( Sang Woo Lee ) 한국열처리공학회 2003 熱處理工學會誌 Vol.16 No.2

N/A As a research for developing fine-grained high strength low carbon steels, the effects of austenitization temperature and hot deformation on microstructure was investigated in 0.15 wt% carbon steels with microalloying elements such as Nb and Ti. When the steels were reheated at 1250℃, Nb containing steel showed very coarse austenite grain size of 200㎛ whereas Nb-Ti steel did fine one of 70㎛ because Ti carbonitrides could suppress the austenite grain growth. In case of 50% reduction at 850℃, the austenite grains in the Nb steel partially recrystallized while those in the Nb-Ti steel fully recrystallized probably due to finer prior austenite grains. For the Nb-Ti steel, ferrite grain size was not sensitively changed with austenitization temperature and compression strain and, severe deformation of 80% reduction was not essentially necessary to refine ferrite grains to about 3㎛ which could be obtained through lighter deformation of 40% reduction.

Nb 첨가 Zr 합금의 미세조직과 Creep 특성에 미치는 마지막 열처리 온도의 영향

박용권,윤영권,위명용,김택수,정용환,Park, Yong-Gwon,Yun, Yeong-Gwon,Wi, Myeong-Yong,Kim, Taek-Su,Jeong, Yong-Hwan 한국재료학회 2001 한국재료학회지 Vol.11 No.10

The effects of final annealing temperature on the microstructure and creep characteristics were investigated for the Zr-lNb-0.2X (X=0, Mo, Cu) and Zr-lNb- 1Sn-0.3Fe-0.1X (X=0, Mo, Cu) alloys. The microstructures were observed by using TEM/EDS, and grain size and distributions of precipitates were analyzed using a image analyzer. The creep test was performed at $400^{\circ}C$ under applied stress of 150 MPa for 10 days. The $\beta$-Zr was observed at annealing temperature above $600^{\circ}C$. In the temperature above$ 600^{\circ}C$, the grain sizes of both alloy systems appeared to be increased with increasing the final annealing temperature. The creep strengths of Zr-1Nb-1Sn-0.3Fe-0.1X alloys were higher than those of Zr-1Nb-0.2X ones due to the effect of solid solution hardening by Sn in Zr-lNb-lSn-0.3Fe-0.1X alloy system. Also, Mo addition showed the strong effect of precipitate hardening in both alloy systems. The creep strength rapidly decreased with increasing the annealing temperature up to $600^{\circ}C$. However, a superior creep resistance was obtained in the sample that annealed to have a second phase of $\beta$-Zr. It was considered that the appearance of $\beta$-Zr would play an important role in the strengthening mechanism of creep deformation.

Carbide Formation and Matrix Strengthening by Nb Addition in Austenitic Stainless Cast Steels Used for Turbo-Charger-Housing Materials

Jisung Yoo,Won‑Mi Choi,Byeong‑Joo Lee,Gi‑Yong Kim,Hyungjun Kim,Won‑Doo Choi,Yong‑Jun Oh,Sunghak Lee 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.10

In order to increase the exhaust-gas temperature of austenitic stainless cast steels used for turbo-charger-housings up to1050 °C, the more excellent high-temperature strength should be obtained because it works for keeping a sustainability ofthe housing shape. Three austenitic stainless cast steels were fabricated in this study by adding Nb into the Ni/Mn-replacedconventional ASTM HK40 steel, and their high-temperature strength was investigated in relation with the carbide formationand matrix strengthening. The 1-wt%-Nb-added steel showed the enhancement in high-temperature strength over thenon-Nb-added steel. This indicated that the Nb addition was effective on the strength improvement because it raised boththe fraction of thermally-stable hard MC-type carbides and the austenite-matrix hardness. However, the 1.5-wt%-Nb-addedsteel showed the lower high-temperature strength than the 1-wt%-Nb-added steel, although it contained the more MC carbides. The more MC carbides reduced the matrix hardness, enlarged the hardness difference between carbides and matrix,and deteriorated the high-temperature strength. Our results demonstrate that the strengthened matrix as well as populatedcarbides due to the Nb addition are desirable for further improving the high-temperature strength.

유방촬영용장치 부가필터에 따른 선량변화 및 화질개선

조우일,김영근,이길동 대한방사선방어학회 2013 방사선방어학회지 Vol.38 No.2

최근 방사선 피폭에 대한 관심이 높아지고 있다. 유방촬영용장치의 방사선 피폭은 일반 X선 촬영에 비해 비교적 흡수선량이 높기 때문에 화질은 개선하되 불필요한 피폭을 줄여야 노력을 할 필요가 있다. 최근 국제방사선방어위원회(ICRP)나 우리나라의 한국의료영상품질관리원(KIAMI)에서 권고하는 평균유선선량은 3 mGy이하이지만 이는 유방의 두께에 따라 다르므로 모든 경우에 권고수치가 넘지 않는다고 해서 적다고 말할 수는 없다. 일반적으로 방사선 촬영에 사용되는 선질은 영상의 화질과 피폭선량을 결정하는 중요한 인자로 촬영 관전압과 부가필터에 영향을 받는다. 일반적으로 유방촬영용장치에서 방출되는 X선 에너지는 연속 스펙트럼(spectrum)으로서 영상의 화질에 미치는 영향이 적은 저 에너지부터 이미지상의 대조도(contrast)를 저해하는 고 에너지 성분까지 포함하고 있다[1,3]. 현재 유방촬영용장치에 많이 사용되고 있는 부가필터는 몰리브덴(molybdenum, Mo), 로듐(rhodium, Rh)등이 있으며, 이는 사용되어지는 X선질의 에너지 영역에 따라 구분하여 사용되고 있다. 현재 유방촬영용장치에 가장 많이 사용되어지고 있는 부가필터의 물질인 몰리브덴(Molybdenum, Mo), 로듐(rhodium, Rh)외에 원자번호와 K-흡수단 영역이 비슷한 니오븀(niobium,Nb)이나 지르코늄(zirconium, Zr)재질의 부가여과판을 사용 하였을때 화질과 선량의 개선된 변화를 알아보고, X선의 저에너지를 흡수할 수 있는 알루미늄(aluminum, Al)재질을 복합으로 사용하였을 때 유방촬영용장치의 화질에 손실없이 알루미늄(aluminum, Al)두께에 따른 조사선량의 경감 정도를 확인하려 한다. 본 실험에서는 몰리브덴(molybdenum, Mo), 니오븀(niobium, Nb), 지르코늄(zirconium, Zr)등의 부가필터를 종류별로 단일필터로 사용할 경우와 이들 단일필터에 알루미늄(aluminum, Al)필터를 복합으로 사용한다. 이 경우 상기 부가필터의 종류에 따른 화질의 개선이 될 것으로 판단되고, 알루미늄(aluminum, Al)필터를 복합으로 사용함으로 인해 저 에너지의 불필요한 X선이 흡수되므로 동일한 농도가 되었을 때 화질에 큰 영향없이 선량이 감소될 것으로 기대된다.

불소 이온이 함유된 인공타액 내 적층제조 Ti-13Nb-13Zr 합금의 열처리에 따른 부식 거동

안경빈,강창민,장희진 한국표면공학회 2022 한국표면공학회 학술발표회 초록집 Vol.2022 No.6

니오븀함량에 따른 치과용 Ti - xNb 합금의 물리적 성질

박일송(Il-Song Park),박정은(Jung-Eun Park),지정희(Jeong-Hui Ji),Jin Guang-Chun,윤동주(Dong-Joo Yoon),박주미(Ju-Mi Park) 대한치과재료학회 2011 대한치과재료학회지 Vol.38 No.1

The materials currently used for surgical implants include 316L stainless steel (316LSS), cobalt chromium (Co-Cr) alloys and titanium and its alloys. Elements such as Ni, Cr and Co are found to be released from the stainless steel and cobalt chromium alloys due to the corrosion in the body environment. The materials currently used for surgical implants include 316L stainless steel (316LSS), cobalt chromium (Co-Cr) alloys and titanium and its alloys. Elements such as Ni, Cr and Co are found to be released from the stainless steel and cobalt chromium alloys due to the corrosion in the body environment. The relative intensity o f β phase increased according to t he increase of niobium contents. Also the dendrite structures were changed to globular structures with increasing niobium contents. The microhardness values and corrosion resistance of all the Ti-xNb alloys were significantly higher than that of pure Ti and the Ti-37Nb alloy showed the best corrosion resistance among the other groups.