http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Electro-Optical Properties of Holographic PDLC Containing Polyhedral Oligomeric Silsesquioxane
김은희,명상원,Woo-Ram Lee,정연길 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.3
Holographic polymer dispersed liquid crystal (HPDLC) was fabricated with different contents of polyhedral oligomeric silsesquioxane (POSS) at a specific polymer composition to optimize the electro-optical performance of the HPDLC film. The off-state diffraction efficiency increased gradually with the addition of POSS owing to the presumably increased elasticity of the polymer matrix and the immiscibility between the polymer matrix and the liquid crystal (LC). Phase separation of the polymer and the LC was augmented by effectively squeezing the LC molecules out of the polymer matrix. The effect of POSS on the diffraction efficiency was enhanced by increasing the added amounts of POSS. However, the diffraction efficiency decreased in the HPDLC film until above 5 % POSS because of fast polymerization and poor phase separation between the LC and the polymer. The HPDLC film containing POSS obtained a low driving voltage and a fast rising time due to a lowering of the anchoring energy at the polymer-LC interface, indicating that the POSS was preferentially exposed at the interfaces between the LC and the polymer due to the low surface energy of the silicon (Si) atom. A HPDLC film showing a low driving voltage «50 V), a fast response time «10 ms) and a high diffraction efficiency (>70 %) could be obtained with 3 wt% POSS at 40 wt% LC.
Jeong-Pyo Kim,Hyun-Min Cha,명상원,Pyung-Ho Lee,Jae-Hyun Lee,정연길 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.3
Silicon carbide (SiC) nanofibers have been synthesized by a solid-vapor reaction (SVR) between carbon nanofibers (CNFs) and SiO vapor, the CNFs being grown using alloys of Ni-Fe, Fe-Al, and Ni-Fe-Al as catalysts by thermal decomposition of C2H4 in the temperature range of 550-650℃. After removal of the catalysts in the as-synthesized CNFs with 2 mol/l HNO3, the SVR process occurred between the CNFs and the SiO vapor in the temperature range of 1200-1450 ℃ for a fixed dwell time of 5 h, with a heating rate of 5℃·minute−1 under an Ar/H2 (160 : 40) flow of 200 ㎠ (ml/minute). The SiC nanofibers consisted of β-SiC and α-SiC and have a thicker diameter than that of the mother CNFs. The effects of catalyst composition and synthesis temperature on the microstructural evolution of the SiC nanofibers are discussed based on the quantitative and qualitative results obtained.