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        검색결과 3

        1.
        2020.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The co-doping effect of aliovalent metal ions such as Mg2+, Ca2+, Sr2+, Ba2+, and Zn2+ on the photoluminescence of the Y2O3:Eu3+ red phosphor, prepared by spray pyrolysis, is analyzed. Mg2+ metal doping is found to be helpful for enhancing the luminescence of Y2O3:Eu3+. When comparing the luminescence intensity at the optimum doping level of each Mg2+ ion, the emission enhancement shows the order of Zn2+ Ba2+ > Ca2+ > Sr3+> Mg2+. The highest emission occurs when doping approximately 1.3% Zn2+, which is approximately 127% of the luminescence intensity of pure Y2O3:Eu3+. The highest emission was about 127% of the luminescence intensity of pure Y2O3:Eu3+ when doping about 1.3% Zn2+. It is determined that the reason (Y, M)2O3:Eu3+ has improved luminescence compared to that of Y2O3:Eu3+ is because the crystallinity of the matrix is improved and the non-luminous defects are reduced, even though local lattice strain is formed by the doping of aliovalent metal. Further improvement of the luminescence is achieved while reducing the particle size by using Li2CO3 as a flux with organic additives.
        4,000원
        2.
        2006.05 KCI 등재 서비스 종료(열람 제한)
        In the aqueous solutions the dephosphorylations of isopropyl phenyl-4-nitrophenyl phosphinate(IPNPIN) mediated by hydroxide(OH⊖) and o-iodosobenzoate(IB⊖) ions are relatively slow, because of hydrophobicity of the substrate, and however it appears that OH⊖ is inherently better nucleophile than IB⊖, which is more soft ion. On the other hand, in cetyltrimetylammonium bromide(CTABr) solutions which contain cationic micelles, the dephosphorylations of IPNPIN mediated by OH⊖ or IB⊖ are very accelerated to 120 or 100,000 times as compared with those in the aqueous solutions. The values of pseudo first order rate constants reach a maximum with increasing. Such rate maxima are typical of micellar catalysed bimolecular reactions and the rise in rate constant followed by a gradual decrese is characteristic of reactions of hydrophobic substrates. In the cationic micellar solutions of CTABr, IB⊖ accelerates the reactions much more than that OH⊖ does. The reason seems that IB⊖ which is more hydrophobic and soft ion than OH⊖ is more easily moved into the Stern layer of the CTABr micelles than OH⊖. In the anionic micellar solutions of sodium dodecyl sulfate(SDS), the dephosphorylations of IPNPIN are slower than those in aqeous solutions. It means that OH⊖ or IB⊖ cannot easily move and approach to the Stern layer of the micelle in which almost all the hydrophobic substrate are located and which has a negative circumstance.
        3.
        2004.06 KCI 등재 서비스 종료(열람 제한)
        두 양이온 유기폴리머(Hexadecyltrimethylammonium (HDTMA)과 Cetylpyridinium (CP))를 합성한 유기벤토나이트에 대해 음이온의 흡착특성을 조사하였다. 이들 유기벤토나이트는 상온에서 저면간격이 약 42.0 a으로 현저한 층간팽창을 나타냈다 유기벤토나이트 시료 0.2 g을 음이온인 질산염, 황산염, 인산염의 각 여러 농도별 용액 40 mL와 반응시킨 흡착실험을 행하였다. 그 결과, 무처리 벤토나이트는 모든 음이온에 대해서 거의 흡착능력을 보이지 않는데 비하여. 유기벤토나이트는 아주 높은 흡착성을 나타냈다. HDTMA-bentonite의 경우, 인산이온과 질산이온의 흡착률이 100 mg/L의 농도에서 약 90% 정도로 높게 나타나고, CP-bentonite의 경우, 질산이온의 흡착률이 100 mg/L의 농도에서 97%로 높게 나타났다. 음이온 및 유기벤토나이트의 종류에 따라 흡착거동이 약간차이를 나타냈다. 두 유기벤토나이트에 있어서 질산이온과 인산이온의 흡착률은 황산이온에 비해 모두 상대적으로 높게 나타났다. 이러한 유기벤토나이트의 높은 음이은 흡착성은 유해성 음이온의 제거와 같은 환경오염처리에 활용될 수 있을 것으로 생각된다.