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Silicon nitride (SiN) coating optimization on carbon fiber surfaces by wet-thermal methods
김현혜,한웅,이해성,김병주 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
In this work, the silicon nitride on carbon fiber surfaces were synthesized directly from the wet-thermal reaction via an 3-aminopropyltriethoxysilane (APS) without additives under N<sub>2</sub>/NH<sub>3</sub> mix gas at high temperature (1400℃). Silicon nitride synthesis was investigated in terms of heating temperature, time, and content of APS. It was found that most combined silanol group (Si-OH) in carbon fiber surfaces has changed to silicon nitride at 1400℃ in an atmosphere of N<sub>2</sub>/NH<sub>3</sub> mix gas during thermal treatment steps of silane-treated carbon fibers. As a result, the morphology of the resulting silicon nitride appeared as a whisker shape. Synthesis of silicon nitride was conjectured that the transformation occurs via the gas phase and is affected by reaction time.
김현혜,김병주 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
This study was conducted to develop novel antimicrobial nano-composites, with the aim of fully utilizing the antitoxic properties of multi-walled carbon nanotubes (MWCNTs), copper (Cu) and zinc oxide (ZnO). Cu doped-MWCNTs with ZnO addition were prepared and evaluated for their potential application as an antimicrobial material for synchronous concentrating and inactivating pathogenic bacteria. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray energy dispersive spectroscopy (EDS) were used to characterize the ZnO/CuO-MWCNTs. Escherichia coli (E.coil) was employed as the target bacterium. Comparing with the raw and the purified MWCNTs (p-MWCNTs), which have been reported to possess antibacterial activity towards E.coil, ZnO/CuO-MWCNTs exhibited stronger antibacterial ability. The deposited ZnO was suggested to play an important role in the bactericidal action of ZnO/CuO-MWCNTs.
제1급 부정교합 환자에서 치료전후 PAR 지수와 두부방사선 계측치의 변화
김현혜,김종철 전남대학교 치과대학 1998 전남치대논문집 Vol.10 No.1
The purpose of this study was to evaluate the relation between the treatment duration and cephalometric measurements and the PAR index in Class Ⅰ malocclusion patients. In 100 Class Ⅰ malocclusion patients, PAR score and cephalometric measurements were taken and analyzed from study model and cephalometric radiographs. The results of this study were obtained as follows; 1. Excellent correlation was exhibited within and between examiners in measuring the PAR score. 2. Treatment duration was correlated with extraction and pre PAR index. 3. ANB, FMA, FMIA and IMPA exhibited positive correlation between pre PAR index and pretreatment cephalometric measurements. 4. 1_ to FP exhibited positive correlation between post PAR index and posttreatment cephalometric measurements, and 1 ̄ to FP exhibited negative correlation. 5. 1_ to SN, IIA and 1 ̄ to exhibited positive correlation between % PAR reduction and the change of cephalometric measurements and FMA, FMIA, WITS and UL exhibited negative correlation.
金賢惠,郭炳華 한국화훼연구회 1995 화훼연구 Vol.4 No.1
The present experiments were carried out to reveal the polarity responses and probable mechanisms involved in the polarity of Hibiscus syriacus and some other ornamental plant cuttings. In the normal position, hibiscus cut stems looked fleshy even after 6 days, however, when inverted position, they became wilted gradually. In the normal position, Coleus blumei cut stems looked fleshy ever after 44 days, and all were even rooted. In the inverted position, the cut stems became rotten particularly in the portion of water contact. When cuttings were done in the normal position, they were rooted, while the inverted cuttings did not root in the absence of NAA for hibiscus and forsythia. In coleus cuttings buried deep in the sand without application of NAA, the normally positioned cutting were rooted at the lower part of stem, and the inverted cuttings rooted at only the upper part of stem. For the inverted cuttings with NAA treated, produced roots on hibiscus and forsythia. It was therefore assumed that rooting of the inverted cuttings was induced by NAA. In coleus cuttings buried deep in the sand, NAA application to the base of inverted cuttings caused rooting at the whole part of stem, indicating that auxin plays an important role in the expression of the stem polarity.
Thermal properties of Si-N/Si-C coated carbon fiber/polypropylene matrix composites
김현혜,이해성,한웅,김병주 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1
In this work, thermal properties of silicon nitride coated carbon fibers (CFs) reinforced polypropylene(PP) composites were investigated. The CFs was treated by silane. After that, the CFs was exposed under NH<sub>3</sub> / N<sub>2</sub> mixed atmosphere at 1400°C - 1600°C. The surface properties of CFs were analyzed using SEM, EDX, XRD and FT-IR. The thermal properties of composites and Si-N or Si-C coated CFs were measured by thermal conductivity meter and TGA. As the result, the thermal properties of Si-N or Si-C coated CFs/PP composites improved better than uncoated CFs/PP composites. The Si-N or Si-C provided high thermal conductivity and stability to carbon fibers or composites.
The effect of synthesis parameters on aluminum nitride whiskers synthesis by direct nitridation
김현혜,한웅,김병주 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
In this work, the syntheses of aluminum nitride (AlN) whiskers on carbon fiber surfaces were prepared by directly nitridation of Al-NH3 mixtures. The nitridation experiments were carried out in a horizontal tube furnace at 1500°C for 1 h under N2/NH3 mix gas. Aluminum chloride hexahydrate (AlCl3·6H2O) was used as raw materials of Al source. The effects of synthesis parameters on the nitridation rate were investigated. The morphology and structure of the nanowires were characterized by SEM, EDS, XRD, Raman and TEM. The results revealed that the morphology and the crystal structure of AlN whiskers could be grown through reaction mechanism in the nitridation between Al and N.
Synthesis and charaterization of silicon carbide coated carbon fibers
김현혜,김병주 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
In this study, the synthesized silicon carbide (SiC) coated carbon fibers (SiCF) were prepared via heat treatment of silicon dioxide (SiO<sub>2</sub>) coating layer onto carbon fibers. SiO<sub>2</sub> sol was prepared with tetraethylorthosilicate (TEOS). Carbon fibers were impregnated with SiO<sub>2</sub> sol by dip coating method and heat treatment at above 1400°C in a furnace under argon (Ar) atmosphere. The results of the characterization by X-ray diffractometer (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) indicated that the SiC cover with a thin layer of amorphous SiO<sub>2</sub>. The structural and crystalline observations revealed the existence of SiC and SiO<sub>2</sub> phase, which noticeably confirmed the formation of SiC on the carbon fiber surface.