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최은영,이윤복,신동우,김광호,Choi, Eun-Young,Lee, Yoon-Bok,Shin, Dong-Woo,Kim, Kang-Ho 한국재료학회 2002 한국재료학회지 Vol.12 No.11
Silica powders were prepared from $SiCl_4$-$H_2$O system by chemical vapor deposition process, and investigated on size control of the products with reaction conditions. The products were amorphous and nearly spherical particles with 130nm~50nm in size. The size distribution became narrow with the increase of [$H_2$O]/[SiCl$_4$] concentration ratio. The particle size decreased with the increase of reaction temperature, [$H_2$O]/[SiCl$_4$] concentration ratio and total flow rate. The specific surface area measured by BET method was about three times larger than that of electron microscope method.
산화물 분산강화 표면처리에 따른 지르코늄 피복관의 기계적 강도
정양일,김일현,김현길,장훈,이승재,Jung, Yang-Il,Kim, Il-Hyun,Kim, Hyun-Gil,Jang, Hun,Lee, Seung-Jae 한국재료학회 2019 한국재료학회지 Vol.29 No.4
Oxide-dispersion-strengthened (ODS) alloy has been developed to increase the mechanical strength of metallic materials; such an improvement can be realized by distributing fine oxide particles within the material matrix. In this study, the ODS layer was formed in the surface region of Zr-based alloy tubes by laser beam treatment. Two kinds of Zr-based alloys with different alloying elements and microstructures were used: KNF-M (recrystallized) and HANA-6 (partial recrystallized). To form the ODS layer, $Y_2O_3$-coated tubes were scanned by a laser beam, which induced penetration of $Y_2O_3$ particles into the substrates. The thickness of the ODS layer varied from 20 to $55{\mu}m$ depending on the laser beam conditions. A heat affected zone developed below the ODS layer; its thickness was larger in the KNF-M alloy than in the HANA-6 alloy. The ring tensile strengths of the KNF-M and HANA-6 alloy samples increased more than two times and 20-50%, respectively. This procedure was effective to increase the strength while maintaining the ductility in the case of the HANA-6 alloy samples; however, an abrupt brittle facture was observed in the KNF-M alloy samples. It is considered that the initial microstructure of the materials affects the formation of ODS and the mechanical behavior.
50μm급 이트리아 안정화 지르코니아 비드의 미세구조 및 마모 조건에 따른 마모율 분석
김정환,윤세중,한병동,안철우,윤운하,최종진,Kim, Jung-Hwan,Yoon, Sae-Jung,Hahn, Byung-Dong,Ahn, Cheol-Woo,Yoon, Woon-Ha,Choi, Jong-Jin 한국재료학회 2019 한국재료학회지 Vol.29 No.4
This study analyzes the mechanical properties, including the attrition rate, of $50{\mu}m$ size yttria-stabilized zirconia (YSZ) beads with different microstructures and high-energy milling conditions. The yttria distribution in the grain and grain-boundary of the fully sintered beads relates closely to Vickers hardness and the attrition rate of the YSZ beads. Grain size, fractured surfaces, and yttrium distribution are analyzed by electronic microscopes. For standardization and a reliable comparison of the attrition rate of zirconia beads with different conditions, Zr content in milled ceramic powder is analyzed and calculated by X-ray Fluorescence Spectrometer(XRF) instead of directly measuring the weight change of milled YSZ beads. The beads with small grain sizes sintered at lower temperature exhibit a higher Vickers hardness and lower attrition rate. The attrition rate of $50{\mu}m$ YSZ beads is measured and compared with the various materials properties of ceramic powders used for high-energy milling. The attrition rate of beads appears to be closely related to the Vickers hardness of ceramic materials used for milling, and demonstrates more than a 10 times higher attrition rate with Alumina(Hv ~1650) powder than $BaTiO_3$ powder (Hv ~315).
실리콘 태양전지 투명전극용 스크린 프린팅을 이용한 구리 도금 전극 패터닝 형성
김경민,조영준,장효식,Kim, Gyeong Min,Cho, Young Joon,Chang, Hyo Sik 한국재료학회 2019 한국재료학회지 Vol.29 No.4
Copper electroplating and electrode patterning using a screen printer are applied instead of lithography for heterostructure with intrinsic thin layer(HIT) silicon solar cells. Samples are patterned on an indium tin oxide(ITO) layer using polymer resist printing. After polymer resist patterning, a Ni seed layer is deposited by sputtering. A Cu electrode is electroplated in a Cu bath consisting of $Cu_2SO_4$ and $H_2SO_4$ at a current density of $10mA/cm^2$. Copper electroplating electrodes using a screen printer are successfully implemented to a line width of about $80{\mu}m$. The contact resistance of the copper electrode is $0.89m{\Omega}{\cdot}cm^2$, measured using the transmission line method(TLM), and the sheet resistance of the copper electrode and ITO are $1{\Omega}/{\square}$ and $40{\Omega}/{\square}$, respectively. In this paper, a screen printer is used to form a solar cell electrode pattern, and a copper electrode is formed by electroplating instead of using a silver electrode to fabricate an efficient solar cell electrode at low cost.
나노 및 마이크로 입자 비율에 따른 광조형 3D 프린팅용 ZrO<sub>2</sub>/High-temp 복합 수지의 분산 안정성 및 기계적 특성
송세연,박민수,윤지선,Song, Se Yeon,Park, Min Soo,Yun, Ji Sun 한국재료학회 2019 한국재료학회지 Vol.29 No.4
This study examines the role of the nano- and micro-particle ratio in dispersion stability and mechanical properties of composite resins for SLA(stereolithography) 3D printing technology. VTES(vinyltriethoxysilane)-coated $ZrO_2$ ceramic particles with different nano- and micro-particle ratios are prepared by a hydrolysis and condensation reaction and then dispersed in commercial photopolymer (High-temp) based on interpenetrating networks(IPNs). The coating characteristics of VTES-coated $ZrO_2$ particles are observed by FE-TEM and FT-IR. The rheological properties of VTES-coated $ZrO_2/High-temp$ composite solution with different particle ratios are investigated by rheometer, and the dispersion properties of the composite solution are confirmed by relaxation NMR and Turbiscan. The mechanical properties of 3D-printed objects are measured by a tensile test and nanoindenter. To investigate the aggregation and dispersion properties of VTES-coated $ZrO_2$ ceramic particles with different particle ratios, we observe the cross-sectional images of 3D printed objects using FE-SEM. The 3D printed objects of the composite solution with nano-particles of 80 % demonstrate improved mechanical characteristics.
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 $20{\mu}C/cm^2$.
복합주조용 Al-Si-Mg 합금의 인장성질, 부식특성 및 주철과의 접합계면 화합물에 미치는 Cu 및 Zr 첨가의 영향
민경민,정기채,신제식,김정민 한국재료학회 2023 한국재료학회지 Vol.33 No.1
In order to broaden the range of application of light weight aluminum alloys, it is necessary to enhance the mechanical properties of the alloys and combine them with other materials, such as cast iron. In this study, the effects of adding small amounts of Cu and Zr to the Al-Si-Mg based alloy on tensile properties and corrosion characteristics were investigated, and the effect of the addition on the interfacial compounds layer with the cast iron was also analyzed. Although the tensile strength of the Al-Si-Mg alloy was not significantly affected by the additions of Cu and Zr, the corrosion resistance in 3.5 %NaCl solution was found to be somewhat lowered in this research. The influence of Cu and Zr addition on the type and thickness of the interfacial compounds layer formed during compound casting with cast iron was not significant, and the main interfacial compounds were identified to be Al5FeSi and Al8Fe2Si phases, as in the case of the Al-Si-Mg alloys.
RF reactive magnetron sputtering으로 제조한 TiO<sub>2</sub> 박막의 구조 및 광학적 특성
강계원,이영훈,곽재천,이동구,정봉교,박성호,최병호,Gang, Gye-Won,Lee, Yeong-Hun,Gwak, Jae-Cheon,Lee, Dong-Gu,Jeong, Bong-Gyo,Park, Seong-Ho,Choe, Byeong-Ho 한국재료학회 2002 한국재료학회지 Vol.12 No.6
Titanium oxide films were prepared by RF reactive magnetron sputtering. The effect of sputtering conditions on structural and optical properties was investigated systemically as a function of sputtering pressure(5~20 mTorr) and $O_2/Ar$ flow ratio(0.08~0.4). The results of the X-ray diffraction showed that all films had only the anatase $TiO_2$ phase. At low sputtering pressure and $O_2/Ar$ flow ratio, the films had preferred orientations along [101] and [200] directions. As the sputtering pressure and $O_2/Ar$ flow ratio increased, the intensity of the 101 and 200 diffraction peaks decreased gradually. The microstructure of the sputtered films showed the fine grain size (20nm~50nm) and columnar microcrystals perpendicular to the substrate. With increasing the sputtering pressure and decreasing $O_2/Ar$ flow ratio, the sputtered films showed the more porous columnar structure. XPS analysis showed that stoichiometric $TiO_2$ films were deposited at 7 mTorr sputtering pressure and 0.2 $O_2/Ar$ flow ratio. The results of the X-ray diffraction showed that all films had only the anatase $TiO_2$ phase. Ellipsometeric analysis showed that the refractive index increased from 2.32 to 2.46 as the sputtering pressure decreased. The packing density calculated using the refractive index varied from 0.923 to 0.976, indicating that $TiO_2$films became denser as the sputtering pressure decreased.