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전기방사법에 의한 $SiO_2$-$TiO_2$계 복합무기섬유의 제조 및 광촉매 활성 평가
현동호,김상범,이승구,정원양,김진호,이성욱,Hyun, Dong-Ho,Kim, Sang-Beom,Lee, Seung-Goo,Chung, Won-Yang,Kim, Jin-Ho,Lee, Sung-Wook 한국섬유공학회 2009 한국섬유공학회지 Vol.46 No.5
A series of $SiO_2$-$TiO_2$ composite sols have been prepared by the hydrolysis of tetraethyl orthosilicate (TEOS) and titanium (IV) isopropoxide dissolved in isopropanol which was controlled by HCl addition. The maximum amount of $TiO_2$ for suitable fiber formation was about 50 mol% in $SiO_2$-$TiO_2$ composite inorganic fibers. The SEM, TEM, and FT-IR results showed that the surface morphology and crystalline phase of the electro spun composite micro/nanoscale $SiO_2$-$TiO_2$ fibers were strongly affected by the content of $TiO_2$ and calcination temperature. The SEM and TEM images reveal that the fibers had diameters varying from hundreds of nanometer to 2 micrometer. The photocatalytic activity of composite inorganic fibers was evaluated by decomposition of methylene blue, acetaldehyde, and formaldehyde in waste water which are recognized as volatile organic compounds (VOCs).
SiO<sub>2</sub>-TiO<sub>2</sub>계 복합 나노섬유의 제조 및 광활성 연구
현동호,임태호,이성욱,Hyun, Dong Ho,Lim, Tae-Ho,Lee, Sung Wook 한국공업화학회 2008 공업화학 Vol.19 No.5
전구체로서 알콕사이드[Tetraethyl orthosilicate (TEOS), Titanium (IV) isopropoxide (TiP)]를 사용하여 졸-겔 방법으로 전기방사에 적합한 졸을 제조한 후, $(1-x)SiO_2-(x)TiO_2$계 복합 나노섬유를 제조하였다. 제조된 광활성 무기나노섬유의 표면 및 구조적 특성은 X-선회절분석(XRD), 주사전자현미경(SEM), 투과전자현미경(TEM), 열중량분석 및 미분주사칼로리미터분석 (TGA-DSC), 적외선분광분석((FT-IR)을 통하여 확인하였다. $(1-x)SiO_2-(x)TiO_2$계에서 $TiO_2$ 양이 증가하면 전기방사된 복합섬유직경은 증가하였으며, 저온에서 안정한 아나타제 $TiO_2$ 결정에서 루타일로의 상전이는 $1000^{\circ}C$에서의 열처리 후에도 고루 분산되어 있는 $SiO_2$로 인해 $0.6SiO_2-0.4TiO_2$계까지는 아나타제상으로 존재하였다. $SiO_2-TiO_2$계 복합체 나노섬유의 광활성은 메틸렌블루 광분해 실험 및 UV-vis/DRS 분석을 통해 자외선 영역에서 나타남을 확인하였다. $(1-x)SiO_2-(x)TiO_2$ composite fibers with various compositions of $TiO_2$ were prepared by electrospinning their sol-gel precursors of titanium (IV) iso-propoxide (TiP), and tetraethyl orthosilicate (TEOS). The surface morphology and structure of sintered composite fibers were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), simultaneous thermogravimetric analysis-differential scanning calorimetry (TGA-DSC) and Fourier transform infrared spectroscopy (FT-IR). As the content of $TiO_2$ in $(1-x)SiO_2-(x)TiO_2$ system was increased the average diameter of composite fibers was proportionally increased. Also, the transformation of $TiO_2$ from anatase to rutile form was inhibited by the highly dispersed $TiO_2$ around $SiO_2$ particles up to $0.6SiO_2-0.4TiO_2$ composite fibers even after calcination at $1000^{\circ}C$. The photocatalytic activity of $SiO_2-TiO_2$ composite fibers was examined for the methylene blue (MB) decomposition which was confirmed using UV-vis/DRS spectra. The experiments demonstrated that the MB in aqueous solution was successfully photodegraded using $SiO_2-TiO_2$ composite nanofibers under UV-visible light irradiation.
계절변화를 설명하는 초등학교 6학년 학생들의 대안개념 연구
현동호 ( Hyun Dong-ho ),양경은 ( Kyonng-eun Yang ) 한국교원대학교 과학교육연구소 2016 청람과학교육연구논총 Vol.22 No.2
This study has the premise that Lakatos research program having concepts of the core that scientists strongly maintain in the science theory development and the protection area that protects the core is similar to student`s structure of alternative concept. Therefore, the study is conducted under the assumption that the core of Lakatos research program and the core of alternative concept of students are similar. And to research the structure of alternative concept, the center theory, the firm core, the additional theory, the guard protecting the core and the basic theory of Lakatos research program known as a natural phenomenon are used and the experimentation to change the alternative concept by proposing discording circumstances is imported. The following conclusion is made based on results of the research. The reason for students having difficulties in the optics area that performs the decisive roles for students to understand the astronomical phenomenon is their insufficiencies for understanding on the relation among celestial bodies in large scale rather than their insufficient specific knowledge. Students see the Sun that transmits lights spread to all directions and hit the Earth as a lamp, not as a celestial body. Also, on the item suggested to check the background knowledge on the seasonal change, students select the oval orbit more than any others. This is because students support the lamp theory and the distance theory mostly as the cause of seasonal change. Such knowledge is the recognition formed by experiences in younger years of students. Such firm cores interfere formations of scientific concepts leanrned in classes. Also, the tendency explaining the seasonal change with changes of the length of daytime and the meridian transit altitude by the tilted axis of the Earth without weakening the distance theory after a class through textbook. Such transition concept connected to scientific concept is confirmed also in the phase having suspicion gradually on the own belief. It shows that one concept is not completely disappeared and replaced by other concept and remains in any formation.