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Structure-tunable synthesis of titanate nanotube thin films via a simple hydrothermal process
Guo, Yupeng,Lee, Nam-Hee,Oh, Hyo-Jin,Yoon, Cho-Rong,Park, Kyeong-Soon,Lee, Hee-Gyoun,Lee, Kyung-Sub,Kim, Sun-Jae IOP Pub 2007 Nanotechnology Vol.18 No.29
<P>In this study, titanium metal acts as the titanium source to prepare oriented titanate nanotube thin film. The effects of preparation parameters, such as reaction temperature, duration and post-treatment conditions, on the film morphology and stability have been examined. A general formation mechanism for oriented titanate nanotube thin film is proposed on the basis of detailed observations of the products using two-dimensional surface SEM studies and TEM images. The overall formation of titanate nanotubes can be summarized as a sequence of four steps: (a)?titanium dissolution and alkali titanate hydrogel formation; (b)?alkali titanate hydrogel dissolution, increased TiO<SUB>3</SUB><SUP>2−</SUP>, TiO<SUB>2</SUB>(OH)<SUB>2</SUB><SUP>2−</SUP> or Ti<SUB><I>n</I></SUB>O<SUB>2<I>n</I>+<I>m</I></SUB><SUP>2<I>m</I>−</SUP> concentration and layered Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> formation; (c)?layered Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> growth; (d)?nanotube formation via Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> splitting and the multilayer scrolling process. The Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> lamellar structures split between the (010) planes into nanosheets. </P>
Formation of 1-D nanostructures of titanate thin films and thermal stability study.
Guo, Yupeng,Lee, Nam-Hee,Oh, Hyo-Jin,Park, Kyeong-Soon,Jung, Sang-Chul,Kim, Sun-Jae American Scientific Publishers 2008 Journal of Nanoscience and Nanotechnology Vol.8 No.10
<P>One-dimensional (1-D) layered titanate nanotubes and nanoribbon thin films were prepared via the hydrothermal reaction of Ti metal flakes with concentrated NaOH solution. TEM, SEM, and XRD studies of the reaction products revealed that 20-nm-wide and about 1-microm-long nanoribbons formed in 5 M NaOH aqueous solution at 140 degrees C for 12 h, while 6 aproximately 8-nm-wide and several hundred-nanometer-long nanotubes formed with 10 M NaOH. The effect of post treatments on the thermal stablity, phase structure and morphology of the as-prepared nanotubes films was investigated. Different morphologies and crystallinity changes of the as-prepared nanotubes films during heat treatment process are attributed to the sodium impurity.</P>
Transformation of TiO₂ Film to Titanate Nanotube Thin Film Using Hydrothermal Method
Yupeng Guo,Nam-Hee Lee,Hyo-Jin Oh,Cho-Rong Yoon,Sun-Jae Kim 한국표면공학회 2007 한국표면공학회 학술발표회 초록집 Vol.2007 No.-
In this study, the technology to grow oriented nanotube thin film from dip-coated TiO₂using hydrothermal method has been successfully developed. The effects of preparation parameters, such as reaction temperature, duration and post treatment conditions on the film morphologies and the adherence to the substrate, have been examined. A general formation mechanism of oriented titanate nanotube thin film is proposed in terms of the detailed observation of the products via two dimensional surface FESEM studies and HRTEM images. The overall formation of TiO₂-based nanotube thin film can be summarized with three successive steps: (1) TiO₂dissolving and amorphous Na₂TiO₃deposition process; (2) layered Na₂Ti₃O?, formation via spontaneous crystallization and rapid growth process; (3) formation of nanotube thin film via Na₂Ti₃O? splitting and multilayer scrolling process of (l00) planes around the c axis of NazTi:I07.
Sun, Shikai,Guo, Hui,Zhang, Yimeng,Jia, Yupeng,Lv, Hongliang,Song, Qingwen,Tang, Xiaoyan,Zhang, Yuming The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.3
In this paper, a novel modulation method is proposed for the torque ripple suppression of a brushless DC motor (BLDCM) during both the commutation period and the speed regulation period. The main sources of torque ripple are the imbalance current during commutation and the PWM during speed regulation. A single-inductor multiple-output (SIMO) Buck DC-DC converter is adopted to generate input voltage for the inverter driver of a BLDCM. During the commutation period, the input voltage of an inverter can be adjusted to four times the back electromotive force (EMF), which suppresses the torque ripple caused by imbalance commutation current. Meanwhile, by changing the output voltage of a SIMO DC-DC, the speed of a BLDCM can be regulated without PWM on the inverter switches, which also suppresses the torque ripple. A control algorithm is applied on a Field Programmable Gate Array (FPGA), and the proposed BLDCM drive prototype is fabricated and tested. Measurement results show that with the proposed speed regulation strategy, the torque ripple is suppressed from 33.3% to 20.1%, and that with the proposed suppression strategy in commutation, the torque ripple is suppressed further to 5.3%.
잉크젯 프린팅을 이용한 자외선 차단용 TiO₂ 박막제조
윤초롱,오효진,이남희,Guo Yupeng,김선재 한국표면공학회 2007 한국표면공학회 학술발표회 초록집 Vol.2007 No.-
자외선 차단용 TiO₂박막을 제조하기 위해 수열합성법 중 외부로부터 N₂가스를 인가하는 방법으로 200 bar의 압력을 유지하여 브룩카이트상의 TiO₂졸을 합성하였다. 제조된, TiO₂졸을 잉크젯 프린터로 FTO glass에 프린팅하여 TiO₂박막을 제조하였고 합성된 졸과 박막의 특성 평가를 실시하였다. 합성된 졸의 크기는 30nm 이하로 비교적 균질하였으며 잉크젯 프린팅 후에도 입자 형상 및 크기의 변화는 나타나지 않았다. 또한, 코팅 횟수가 증가함에 따라 자외선 영역에서의 흡수도가 증가함을 알 수 있었다.
Assessment of the Cytotoxic and Apoptotic Effects of Chaetominine in a Human Leukemia Cell Line
Jing-Yun Yao,Ruihua Jiao,Changqing Liu,Yupeng Zhang,Wan-Guo Yu,Yan-Hua Lu,Renxiang Tan 한국응용약물학회 2016 Biomolecules & Therapeutics(구 응용약물학회지) Vol.24 No.2
Chaetominine is a quinazoline alkaloid originating from the endophytic fungus Aspergillus fumigatus CY018. In this study, we showed evidence that chaetominine has cytotoxic and apoptotic effects on human leukemia K562 cells and investigated the pathway involved in chaetominine-induced apoptosis in detail. Chaetominine inhibited K562 cell growth, with an IC50 value of 35 nM, but showed little inhibitory effect on the growth of human peripheral blood mononuclear cells. The high apoptosis rates, morphological apoptotic features, and DNA fragmentation caused by chaetominine indicated that the cytotoxicity was partially caused by its pro-apoptotic effect. Under chaetominine treatment, the Bax/Bcl-2 ratio was upregulated (from 0.3 to 8), which was followed by a decrease in mitochondrial membrane potential, release of cytochrome c from mitochondria into the cytosol, and stimulation of Apaf-1. Furthermore, activation of caspase-9 and caspase-3, which are the main executers of the apoptotic process, was observed. These results demonstrated that chaetominine induced cell apoptosis via the mitochondrial pathway. Chaetominine inhibited K562 cell growth and induced apoptotic cell death through the intrinsic pathway, which suggests that chaetominine might be a promising therapeutic for leukemia.
잉크젯 프린팅을 이용한 초박막 투명 TiO₂ 코팅층 제조
윤초롱(Cho-Rong Yoon),오효진(Hyo-Jin Oh),이남희(Nam-Hee Lee),Guo Yupeng,이원재(Won-Jae Lee),박경순(Kyeong-Soon Park),김선재(Sun-Jae Kim) 한국표면공학회 2007 한국표면공학회지 Vol.40 No.4
Dye sensitized solar cells(DSSC) are the most promising future energy resource due to their high energy efficiency, low production cost, and simple manufacturing process. But one problem in DSSC is short life time compared to silicon solar cells. This problem occurred from photocatalytic degradation of dye material by nanometer sized TiO₂ particles. To prevent dye degradation as well as to increase its life time, the transparent coating film is needed for UV blocking. In this study, we synthesized nanometer sized TiO₂ particles in sols by increasing its internal pressure up to 200 bar in autoclave at l20℃ for 10 hrs. The synthesized TiO₂ sols were all formed with brookite phase and their particle size was several ㎚ to 30 ㎚. Synthesized TiO₂ sols were coated on the backside of fluorine doped tin oxide(FTO) glass by ink jet printing method. With increasing coating thickness by repeated ink jet coating, the absorbance of UV region (under 400 ㎚) also increases reasonably. Decomposition test of titania powders dispersed in 0.1 mM amaranth solution covered with TiO₂ coating glass shows more stable dye properties under UV irradiation, compared to that with as-received FTO glass.