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Sol-Gel 법으로 제작한 Zn<sub>1-x</sub>Co<sub>x</sub>O 박박의 미세조직 및 자기적 특성
고윤덕,태원필,김응권,김기출,최춘기,김종민,송준태,박태석,서수정,김용성,Ko, Yoon-Duk,Tai, Weon-Pil,Kim, Eung-Kwon,Kim, Ki-Chul,Choi, Choon-Gi,Kim, Jong-Min,Song, Joon-Tae,Park, Tae-Seok,Suh, Su-Jeung,Kim, Young-Sung 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.7
Zn$_{l-x}$Co$_{x}$O (x = 0.05 - 0.20) films were grown on Coming 7059 glass by sol-gel process. A homogeneous and stable Zn$_{l-x}$Co$_{x}$O sol was prepared by dissolving zinc acetate dihydrate (Zn(CH$_{3}$COO)$_{2}$$\cdot$2H$_{2}$O), cobalt acetate tetrahydrate ((CH$_{3}$)$_{2}$$\cdot$CHOH) and aluminium chloride hexahydrate (AlCl$_{3}$ $\cdot$ 6H$_{2}$O) as solute in solution of isopropanol ((CH$_{3}$)$_{2}$$\cdot$CHOH) and monoethanolamine (MEA:H$_{2}$NCH$_{2}$CH$_{2}$OH). The films grown by spin coating method were postheated in air at 650°C for 1 h and annealed in the condition of vacuum (5 $\times$ 10$^{-6}$ Torr) at 300$^{\circ}C$ for 30 min and investigated the nature of c-axis preferred orientation and physical properties with different Co concentrations. Znl_xCOxO thin films with different Co concentrations were well oriented along the c-axis, but especially a highly c-axis oriented Zn$_{l-x}$Co$_{x}$O thin film was grown at 10 at$\%$ Co concentration. The transmittance spectra showed that Zn$_{l-x}$Co$_{x}$O thin films occur typical d-d transitions and sp-d exchange interaction became activated with increasing Co concentration. The electrical resistivity of the films at 10 at$\%$ Co had the lowest value due to the highest c-axis orientation. X-ray photoelectron spectroscopy and alternating gradient magnetometer analyses indicated that no Co metal cluster was formed, and the ferromagnetic properties appeared, respectively. The characteristics of the electrical resistivity and room temperature ferromagnetism of Zn$_{l-x}$Co$_{x}$O thin films suggested the possibility for the application to dilute magnetic semiconductors.
증착온도를 달리하여 제조한 Zn<sub>0.8</sub>Co<sub>0.2</sub>O 박막의 미세조직 및 자기 특성
강영훈,김봉석,태원필,김기출,서수정,박태석,김용성,Kang, Young-Hun,Kim, Bong-Seok,Tai, Weon-Pil,Kim, Ki-Chul,Suh, Su-Jeung,Park, Tae-Seok,Kim, Young-Sung 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.2
We studied the microstructure and magnetic property of the pulsed DC magnetron sputtered $Zn_{\0.8}Co_{0.2}O$ film as a function of substrate temperatures. The X-ray patterns of the $Zn_{\0.8}Co_{0.2}O$ film showed a strong (002) preferential orientation at $500^{\circ}C$. The films with a crystallite size of 23-35 nm were grown in the form of nano-sized structure and this tendency was remarkable with increasing substrate temperature. The UV-visible result showed that the $Zn_{\0.8}Co_{0.2}O$ film prepared above $300^{\circ}C$ has a high optical transmittance of over $80\%$ in the visible region. The absorption bands were observed due to sp-d interchange action by $Co^{2+}$ complex ion and dd transition in the region from 500 to 700nm. The resistivity of the film was below $10^{-1}\;\Omega-cm\;above\;300^{\circ}C$. The AGM analysis results for the all films showed the magnetic hysteresis curves of ferromagnetic nature. The low electrical resistivity and room temperature ferromagnetism of ZnCoO thin films 'deposited above $300^{\circ}C$ suggested the possibility for the application to Diluted Magnetic Semiconductors (DMSs).
김영혁,허대영,태원필,이재신,Kim, Young-Hyeok,Heo, Dae-Young,Tai, Weon-Pil,Lee, Jae-Shin 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.6
Lead-free $(K_{0.44}Na_{0.52})(Nb_{0.86}Ta_{0.10})-0.04LiSbO_3$ piezoelectric ceramics have been synthesized by conventional sintering process and then investigated on the sintering and piezoelectric properties by high energy ball milling (HEBM) treatment. The powders milled for different time are characterized by XRD, FE-SEM. The powders are pressed into a pellet and sintered. It is found that the piezoelectric properties of sintered specimens are strongly dependent on the milling time. The piezoelectric properties are enhanced by high energy ball milling treatment. The planer electromechanical coupling factor ($k_p$) and piezoelectric constant ($d_{33}$) of a specimen sintered at $1050^{\circ}C$ are 0.44 and 267 pC/N, respectively.
펄스 DC 마그네트론 스퍼터링법에 의한 Zn<sub>1-x</sub>Co<sub>x</sub>O 박막의 미세조직 및 자기적 특성
고윤덕,고석배,최문순,태원필,김기출,김종민,서수정,김용성,Ko, Yoon-Duk,Ko, Seok-Bae,Choi, Moon-Soon,Tai, Weon-Pil,Kim, Ki-Chul,Kim, Jong-Min,Soh, Su-Jeung,Kim, Young-Sung 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.3
펄스 마그네트론 스퍼터링법을 이용하여 Co농도 변화에 따라 유리 기판 위에 ZnJ-xcoxo 박막을 제조하였다. Co 농도의 증가에 따라 $Zn_{1-x}Co_{x}O$ 박막의 c축 결정 배향성은 향상되었다. 표면 형상 분석을 통하여 매우 치밀한 박막이 성장되었음을 찰 수 있었다. 박막의 UV-visible투과율 측정 결과, $Co^{2+}$ 이온에 의한 sp-d상호교환 작용과 d-d 천이를 확인할 수 있었다. $Zn_{1-x}Co_{x}O$ 박막의 비저항은 $10^{-2}\~10^{-3}\;\Omega{\cdot}cm$의 값을 가지며 Co농도의 증가에 따라 박막의 비저항은 증가하였고, 특히 $30\;at\%$ Co에서는 박막의 결정성 저하로 인하여 급격한 비저항 증가가 발생하였다. X-ray photoelecoon specooscopy분석을 통해 Co와 O 간의 결합 상태를 확인하였으며, alternating gradient magnetometer측정 결과 $Zn_{1-x}Co_{x}O$ 박막의 상온 강자성 치력 현상을 관찰할 수 있었다. 낮은 비저항 및 상온 강자성 이력 특성을 갖는 $Zn_{1-x}Co_{x}O$ 박막은 자성 반도체 소자로의 응용 가능성을 나타내었다 . [ $Zn_{1-x}Co_{x}O$ (x=0-0.3) films were grown on Corning 7059 glasses by asymmetrical bipolar pulsed dc magnetron sputtering. The c-axis orientation along (002) plane was enhanced with increasing Co concentration. The $Zn_{1-x}Co_{x}O$ films are grown with fibrous grains of tight dome shape. The transmittance spectra measured from UV-visible showed that sp-d exchange interactions and typical d-d transitions become activated with increasing Co concentration. The electrical resistivity of $Zn_{1-x}Co_{x}O$ films increased with increasing Co concentration, especially it increased greatly at $30at\% Co. X-ray photoelectron spectroscopy and alternating gradient magnetometer analyses indicated that no Co metal cluster is formed and the ferromagnetic properties are exhibited. The low electrical resistivity and room temperature ferromagnetism of $Zn_{1-x}Co_{x}O$ thin films suggested the possibility of the application to Diluted Magnetic Semiconductors (DMSs).
졸-겔법에 의해 제조된 Al-Doped ZnO 박막의 후열처리 온도에 따른 전기 및 광학적 특성
고석배,최문순,고형덕,이충선,태원필,서수정,김용성,Ko, Seok-Bae,Choi, Moon-Sun,Ko, Hyungduk,Lee, Chung-Sun,Tai, Weon-Pil,Suh, Su-Jeong,Kim, Young-Sung 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.10
비등점이 낮은 용매인 isopropanol에 용질농도 0.7mol/$\iota$ Zn acetate를 용해시키고 dopant로 Al chloride를 첨가하여 균일하고 안정한 sol을 합성하였다. 졸-겔법에 의한 Al-doped ZnO(AZO) 박막의 제조시 $500\~700^{\circ}C$의 범위에서 후열처리 온도를 제어하여 박막의 전기 및 광학적 특성을 조사하였다. 후열처리 온도가 증가할수록 (002) 면으로의 c-축 결정배향성은 증가하였고, 박막 표면은 균일한 나노입자의 미세구조를 형성하였다. 광 투과도는 $650^{\circ}C$ 이하의 후열처리 온도에서 $86\%$이상이었으나, $700^{\circ}C$에서는 감소하였다. 박막의 전기 비저항 값은 $650^{\circ}C$ 이하에서 열처리 온도가 증가함에 따라 73에서 22$\Omega$-cm로 감소하였으나 $700^{\circ}C$에서 580$\Omega$-cm로 급격히 증가하였다. 후열처리 온도 $700^{\circ}C$에서 AZO 박막의 전기 및 광학적 특성의 열화는 XPS 분석결과, 박막 표면에 석출된 $Al_2O_3$ 상에 기인하였다. AZO 박막의 전기 및 광학적 특성 향상을 위한 최적의 후열처리 온도는 $600^{\circ}C$였다. Isopropanol of low boiling point was used as a solvent to prepare Al-doped ZnO(AZO) thin films. A homogeneous and stable sol was made from Zn acetate a solute whose mole concentration was 0.7mol/$\iota$ and Al chloride as a dopant. Al-doped ZnO thin films were prepared by sol-gel method as a function of post-heating temperature from 500 to $700^{\circ}C$ and the optical and electrical properties were investigated. The c-axis orientation along (002) plane was enhanced with the increasing of post-heating temperature and the surface morphology of the films showed a homogeneous and nano-sized microstructure. The optical transmittance of the films post-heated below $650^{\circ}C$ was over $86\%$, but decreased at $700^{\circ}C$. The electrical resistivity of the thin films decreased from 73 to 22 $\Omega$-cm as the post-heating temperature increased up to $650^{\circ}C$, but increased greatly to 580 $\Omega$-cm at $700^{\circ}C$. XPS analysis indicated that the deterioration of electrical and optical properties was attributed to the precipitation of $Al_2O_3$ phase on the surface of AZO thin film. This result suggests that the optimum post-heating temperature to improve electrical and optical properties is $600^{\circ}C$.
수열합Ethosome에 캡슐화된 Palmitoyl Tripeptide의 항균효과성법으로 제조된 지르코니아의 나노분말 특성
조치욱 ( Chi Wook Cho ),태원필 ( Weon Pil Tai ),이학성 ( Hak Sung Lee ) 한국공업화학회 2014 공업화학 Vol.25 No.6
Zirconia nanoparticles were synthesized by hydrothermal process, and experimental parameters such as reaction temperature, reaction time, kind and concentration of precipitator, kind of precursor were varied. Particle sizes and crystalline phases of each synthesized nanoparticles were analyzed with X-ray diffraction and FE-scanning electron microscope (SEM). The particle size and crystallization of zirconia increased with increasing concentration of precipitator. The growth rate of particle sizes when NaOH as a precipitator was used also increased more than that of KOH. Therefore, the use of KOH rather than NaOH was more effective in the control of particle sizes. An amorphous zirconia nanoparticle was found in 4 h of hydrothermal reaction, but the monoclinic zirconia nanoparticle was found in 8 h and over of hydrothermal reaction, and the width of nanoparticles was slightly slimmed and the length of nanoparticles was slightly extended with increasing reaction time. The smallest particle size was produced at the same synthesis condition when zirconium chloride among the precursors such as zirconium (Ⅳ) acetate, zirconium nitrate and zirconium chloride was used.
과하중 및 휴식기간이 AISI 4340 강의 피로균열 성장거동에 미치는 영향
태원필,김송희 대한금속재료학회(대한금속학회) 1987 대한금속·재료학회지 Vol.25 No.9
Effects of intermittent rest period at 300℃, overload in tension and overload followed by rest period on fatigue crack growth in 4340 steel were investigated. The intermittent lest period stopped the growth of fatigue cracks completely near the threshold level of △K. The alleviation effect of rest period on the rate of crack growth was more distinct at the lower level of △K. The higher overload ratio was (i.e., OLR = 3), the more the alleviation effect. It is suggested that compressive residual stress at the ahead of crack tip was produced during overloading period, and it is enhanced roughness of the crack surface due to crack deflection after the overloading, which, in turn, ceased or retarded crack propagation during the subsequent cycling. The most retardation of fatigue crack growth was observed when overload and subsequent rest period were combined. The mechanisms are discussed.