The unique emission properties of trivalent rare earth (RE) ions originate from the intra-4f transitions which are shielded by outer shells. However, as the transition within the partially filled 4f electrons is in principle spin-forbidden, the absorption coefficients of RE ions are low. In order to overcome this problem, RE complexes using organic ligands such as β-diketones were investigated. In a RE complex system, organic ligands can serve as an energy absorption antenna, then via an efficient intramolecular energy transfer, the RE ions obtain energy and exhibit intense characteristic emissions. For organic doping in mesophase thin films, during the film formation by evaporation-induced self-assembly (EISA), silica/surfactant/organic additive could be co-assembled by inorganic/organic interaction. The components can be combined at the nanoscopic level into a single thin film to prepare organic doped mesophase material.
This work is concerned on the fabrication and characterization of mesophase silica thin films doped with rare earth metal comples. Transparent silica mesophase silica thin films doped with rare earth metal comples. Transparent silica mesophase thin film doped with highly luminescent rare earth (europium (Eu) or terbium (Tb)), organic ligands (dibenzoylmethane (DBM), 1,10-phenanthroline (phen) or salicylic acid(SA)) complexes was synthesized by an in-situ synthesis method. For this, Pluronic P123 triblock copolymer was used as a template. The block copolymer can enhance the solubility of organic ligands and separate the ligands in hydrophobic regions uniformly. The rare earth complexes $(Eu(DBM)_3$phen or $Tb(SA)_3)$ were combined at the nanoscopic level in the hydrophobic core of micelles and a homogenous mesophase thin film was formed. XRD and TEM analysis confirmed that the homogenous thin films had typical 2d-hexagonal mesostructure. Under UV excitation, the mesophase silica thin films exhibited the strong characteristic emissions of $Eu^{3+}$ (612 nm) or $Tb^{3+}$ (544 nm) ions. The emission and excitation spectra for the mesophase thin films suggested that, in fact, a rare earth complexes were formed in-situ during the synthesis of the composite films. The decay process indicated that only one luminescence center was contained in the mesophase thin films, and that the mesophase silica thin films were homogeneous. The quantum yields of the pure $Eu(DBM)_3$ phen complex and the mesophase silica thin film doped with $Eu(DBM)_3$ phen were calculated, and the results show that the mesophase silica thin film possess higher quantum yields. Additionally, the mesophase silica thin film doped with Eu-Tb-excess ligands showed various emission color with excitation wavelength and Eu-Tb-ligands ratio.
스테인리스강과 같이 내식성이 우수한 합금을 이용한 금속 분리판의 경우 가공성이 매우 좋아 제작이 용이하여 분리판 재료로 유망하지만, 합금 표면에 생성된 부동태 피막에 의해 전기저항이 높아져 연료전지의 성능을 감소시키는 문제점이 있다. 이러한 문제점을 해결하기 위해 스테인리스강 표면에 TiN 및 Gold 등 전도성 및 내식성이 우수한 재료를 코팅하여 사용하기도 하지만, 모재와 코팅 재료의 열팽창 계수 차이에 의해 모재와 코팅 층에 미세한 틈이나 공극이 생겨 모재와의 접착력이 약해지고 파괴되기 싶다. 또한 까다로운 코팅공정에 의한 추가 비용이 필요하기 때문에 경제성 및 실효성 측면에서 궁극적인 대안으로 부적합하다 본 연구에서는 316 스테인리스강의 표면에 내식성 및 전기전도성이 우수한 탄화물을 석출시킴으로써, 부동태피막으로 인해 전기전도성이 저하되는 문제점을 해결하고자 한다. TiC, NbC 등과 같은 탄화물을 석출시키기 위해 C와 친화력이 높은 Ti, Nb 등의 합금 원소를 첨가하여 900-1000℃에서 열처리를 수행하였다. 또한 blasting 및 산세 등과 같은 표면처리를 수행하여, 열처리를 통해 석출된 TiC, NbC 등의 탄화물을 합금 표면에 돌출시키고자 하였다. 최종적으로 Davies법을 이용하여 각 시편의 접촉저항을 측정함으로써 TiC, NbC의 탄화물형성에 의한 316 스테인리스강의 전기전도성 개선효과를 조사하였다.
