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과 액상 형성에 의한 비납계 압전 (Na,K)NbO<sub>3</sub>-Ba(Cu,Nb)O<sub>3</sub> 결정립의 비정상 성장 거동 및 전기적 특성
임지호,이주승,이승희,정한보,박춘길,안철우,유일열,조경훈,정대용,Lim, Ji-Ho,Lee, Ju-Seung,Lee, SeungHee,Jung, Han-Bo,Park, Chun-kil,Ahn, Cheol-Woo,Yoo, Il-Ryeol,Cho, Kyung-Hoon,Jeong, Dae-Yong 한국재료학회 2019 한국재료학회지 Vol.29 No.4
$Pb(Zr,Ti)O_3$ (PZT) is used for the various piezoelectric devices owing to its high piezoelectric properties. However, lead (Pb), which is contained in PZT, causes various environment contaminations. $(K,Na)NbO_3$ (NKN) is the most well-known candidate for a lead-free composition to replace PZT. A single crystal has excellent piezoelectric-properties and its properties can be changed by changing the orientation direction. It is hard to fabricate a NKN single crystal due to the sodium and potassium. Thus, $(Na,K)NbO_3-Ba(Cu,Nb)O_3$ (NKN-BCuN) is chosen to fabricate the single crystal with relative ease. NKN-BCuN pellets consist of two parts, yellow single crystals and gray poly-crystals that contain copper. The area that has a large amount of copper particles may melt at low temperature but not the other areas. The liquid phase may be responsible for the abnormal grain growth in NKN-BCuN ceramics. The dielectric constant and tan ${\delta}$ are measured to be 684 and 0.036 at 1 kHz in NKN-BCuN, respectively. The coercive field and remnant polarization are 14 kV/cm and $20{\mu}C/cm^2$.
상온분말분사공정을 이용한 고밀도 폴리머-세라믹 혼합 코팅층 제조 및 에너지 저장 특성 향상
임지호,김진우,이승희,박춘길,류정호,최두현,정대용,Lim, Ji-Ho,Kim, Jin-Woo,Lee, Seung Hee,Park, Chun-kil,Ryu, Jungho,Choi, Doo hyun,Jeong, Dae-Yong 한국재료학회 2019 한국재료학회지 Vol.29 No.3
This study examines paraelectric $Bi_{1.5}Zn_{1.0}Nb_{1.5}O_7$ (BZN), which has no hysteresis and high dielectric strength, for energy density capacitor applications. To increase the breakdown dielectric strength of the BZN film further, poly(vinylidene fluoride) BZN-PVDF composite film is fabricated by aerosol deposition. The volume ratio of each composition is calculated using dielectric constant of each composition, and we find that it was 12:88 vol% (BZN:PVDF). To modulate the structure and dielectric properties of the ferroelectric polymer PVDF, the composite film is heat-treated at $200^{\circ}C$ for 5 and 30 minutes following quenching. The amount of ${\alpha}-phase$ in the PVDF increases with an increasing annealing time, which in turn decreases the dielectric constant and dielectric loss. The breakdown dielectric strength of the BZN film increases by mixing PVDF. However, the breakdown field decreases with an increasing annealing time. The BZN-PVDF composite film has the energy density of $4.9J/cm^3$, which is larger than that of the pure BZN film of $3.6J/cm^3$.
동적 물성치를 고려한 진공 인터럽터 충격특성의 영향인자 분석
임지호,송정한,허훈,박우진,오일성,안길영,최종웅,Lim, Ji-Ho,Song, Jeong-Han,Huh, Hoon,Park, Woo-Jin,Oh, Il-Seong,Ahn, Gil-Young,Choe, Jong-Woong 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.5
Vacuum interrupters in order to be used in various switch-gear components such as circuit breakers, distribution switches, contactors, etc. spread the arc uniformly over the surface of the contacts. The electrodes of vacuum interrupters are made of sinter-forged Cu-Cr materials for good electrical and mechanical characteristics. Since the closing velocity is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain rate is obtained from the split Hopkinson pressure bar test using disc-type specimens. Experimental results from both quasi-static and dynamic compressive tests are Interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the value of five parameters such as the initial velocity of a movable electrode, the added mass of a movable electrode, the wipe spring constant, initial offset of a wipe spring and the virtual fixed spring constant.
상온분사분말공정에 의해 SrTiO<sub>3</sub> (100), (110) Seed에 코팅된 BaTiO<sub>3</sub>의 고온 성장 거동 분석
임지호,이승희,김기현,지성엽,정승운,박춘길,정한보,정대용,Lim, Ji-Ho,Lee, Seung Hee,Kim, Ki Hyun,Ji, Sung-Yub,Jung, Suengwoon,Park, Chun-kil,Jung, Han-Bo,Jeong, Dae-Yong 한국재료학회 2019 한국재료학회지 Vol.29 No.11
Single crystals, which have complexed composition, are fabricated by solid state grain growth. However, it is hard to achieve stable properties in a single crystal due to trapped pores. Aerosol deposition (AD) is suitable for fabrication of single crystals with stable properties because this process can make a high density coating layer. Because of their unique features (nano sized grains, stress inner site), it is hard to fabricate single crystals, and so studies of grain growth behavior of AD film are essential. In this study, a $BaTiO_3$ coating layer with ${\sim}9{\mu}m$ thickness is fabricated using an aerosol deposition method on (100) and (110) cut $SrTiO_3$ single crystal substrates, which are adopted as seeds for grain growth. Each specimen is heat-treated at various conditions (900, 1,100, and $1,300^{\circ}C$ for 5 h). $BaTiO_3$ layer shows different growth behavior and X-ray diffraction depending on cutting direction of $SrTiO_3$ seed. Rectangular pillars at $SrTiO_3$ (100) and laminating thin plates at $SrTiO_3$ (110), respectively, are observed.
Hyperledger Fabric 기반 스마트자동차 기술자료 임치 시스템에 관한 연구
임지호(Ji-Ho Lim),이민형(Min-Hyung Rhie),김기형(Ki-Hyung Kim) 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
스마트자동차 개발은 완성차업체와 협력업체의 공동 작업으로 이루어지는데, 상호 의사소통하는 과정 가운데 신기술자료 교환이 일어날 수밖에 없는 구조이다 보니 산업기술 유출에 더 취약할 수 있다. 기술자료 임치제도는 앞선 기술 유출 방지를 위한 제도이다. 하지만 서비스 확대를 위해선 보안성 검토가 필요하다. 본 논문은 Hyperledger Fabric 기반으로 기술자료 임치제도 시스템의 보안성을 높이는 플랫폼을 연구한다.
LCA기법을 활용한 태양광 시스템의 자원효율성 및 자원요구량 예측
임지호(Ji Ho Lim),황용우(Yong Woo Hwang),김준범(Jun Beum Kim),문진영(Jin Young Moon) 大韓環境工學會 2013 대한환경공학회지 Vol.35 No.7
본 연구에서는 LCA 기법으로 태양광 시스템 생산 시 소비되는 원료, 부원료, 에너지 등의 물질수지 자료를 분석하여 금속자원의 자원효율성 산정 및 필요금속자원량을 예측하였다. 태양광 시스템 생산 시 투입되는 금속자원의 자원효율성 분석결과 철·비철금속은 4가지 기술(SC-Si, MC-Si, CI(G)S, CdTe)에 대해 동일하게 납, 주석 순으로, 희유금속은 결정질 실리콘시스템의 경우 갈륨, 레늄 순으로, 박막형 시스템의 경우 레늄, 로듐 순으로, 희토류는 4가지 기술에 대해 동일하게 가돌리늄, 사마리움 순으로 자원효율성이 높은 것으로 나타났다. 2030년까지 우리나라의 태양광 시스템의 증설에 필요한 금속자원량을 예측한 결과 자원순환에 의한 자체 수급량을 제외하고 알루미늄 2,545,670 ton, 구리 22,044 ton, 니켈 31 ton, 주석 1,695 ton 및 아연 92,069 ton이 필요한 것으로 나타났다. In this study, the resource efficiency and future metal resource requirement in photovoltaic (PV) production system were evaluated by using material balance data and life cycle assesment (LCA) method. As a result, in the resource efficiency of ferrous and non-ferrous metal, lead and tin had higher resource efficiency than other materials in all PV systems (SC-Si, MC-Si, CI(G)S, CdTe). In the resource efficiency of rare metals, gallium and rhenium in silicon system and rhenium and rhodium in thin-film system ranked as the first and second high resource efficiency. In case of rare earth metal, gadolinium and samarium took higher resource efficiency. The results of the future metal resource requirement in PV systems showed that 2,545,670 ton of aluminium, 92,069 ton of zinc, 22,044 ton of copper, 1,695 ton of tin and 31 ton of nickel will be needed by 2030 in South Korea, except resource recycling supplement.
상온분말분사법에 의해 Yttria Stabilized Zirconia 코팅된 STS304 표면 경도 특성
임지호 ( Ji-ho Lim ),박춘길 ( Chun-kil Park ),이용석 ( Yong-seok Lee ),공영민 ( Young-min Kong ),강권호 ( Kweon Ho Kang ),김형순 ( Hyung Sun Kim ),정대용 ( Dea-yong Jeong ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.3
To improve the surface harndess of the STS304, Yttria stabilized zirconia (YSZ) films with nano-sized grain were deposited by an aerosol-deposition (AD) method. Coating layers showed dense structure and had ~5μm thickness. When 3 mol% YSZ powders with tetragonal phase were deposited on STS304 substrate, tetragonal structure was transformed to cubic structure due to the high impact energy during the AD process. At the same time, strong impact by YSZ particles allowed the austenite phase in STS304 to be transformed into martensite phase. Surface hardness measured with nano indentor showed that YSZ coated film had 11.5 GPa, which is larger value than 7 GPa of STS304.