SEMINAR
　　The State Key Lab of
　　High Performance Ceramics and Superfine Microstructure
　　Shanghai Institute of Ceramics, Chinese Academy of Sciences
　　中 国 科 学 院 上 海 硅 酸 盐 研 究 所 高 性 能 陶 瓷 和 超 微 结 构 国 家 重 点 实 验 室

　　1、Tribological Behavior of Graphene

　　2、Intense Infrared-to-Visible Upconversion Emission in Ho³⁺ /Er³⁺ and Tm³⁺/ Er³⁺ Doped α-Silaon Ceramics Under 980 nm Laser Excitation

　　Prof. Soo Wohn Lee

　　Research Center for Eco-Multifunctional Nano Materials, Sun Moon University

　　时间：2015年07月13日（星期一）下午 3:00

　　地点： 2号楼607会议室 （国家重点实验室）

　　欢迎广大科研人员和研究生参与讨论！

　　联系人：孙静（4301）、曾毅（1020）

　　Abstract:

　　Tribological Behavior of Graphene

　　Khagendra Tripathi^a, Soo Wohn Lee^b*
a Department of Advanced Materials Engineering, Sun Moon University, Korea.
^b* Department of Environmental and Bio-Chemical Engineering, Sun Moon University, Korea

　　Single too few layers graphene was synthesized on metallic substrates (Ni/Cu) by using chemical vapor deposition (CVD). Nano-scale AFM friction tests were carried out with stepwise increase in load in ambient environment using Si-tip. Graphene synthesized this way was characterized by using optical microscope (OM), AFM and Raman spectroscopy. Single to bilayer graphene was confirmed on Cu-plate whereas single-few layers of graphene were confirmed for Ni-plate. The reduction in friction coefficient is reported on graphene coated substrates in ambient environment. Approximately 80 % reduction of friction coefficient was achieved for graphene coated substrates in comparison to uncoated substrates. It was obtained the significance of graphene layers on sliding contact surfaces to minimize friction and wear of materials. So, graphene can be considered as two-dimensional thinnest lubricious coating on sliding pairs in micro- and macro-scale friction coefficient and wear reduction.

　　Intense Infrared-to-Visible Upconversion Emission in Ho³⁺ /Er³⁺ and

　　Tm³⁺/ Er³⁺ Doped α-Silaon Ceramics Under 980 nm Laser Excitation

　　Yuwaraj K. Kshetri, Bhupendra Joshi, Soo Wohn Lee^*
Research Center for Eco-Multifunctional Nano Materials, Sun Moon University, Asan, Korea

　　Ho³⁺ and Tm³⁺ doped α-Sialon ceramics sensitized by Er³⁺ have been prepared by hot press sintering technique. The Sialon ceramics were characterized by X-ray diffraction(XRD), Fourier Transform Infrared Spectroscopy(FTIR), Transmission Electron Microscopy(TEM), Raman Spectroscopy and Up-conversion(UC) emission Spectroscopy. Very intense red and green frequency upconversion luminescence has been demonstrated, for the first time in α-Sialon ceramics, under 980 nm laser excitation. Observed red and green emission bands are the result of very effective energy transfer from Er³⁺ to Ho³⁺ and Tm³⁺ ions with two photonic phonon-assisted excited-state absorption processes. Bands of low phonon energy centered at 546 cm^-1 and 765 cm^-1 observed under Raman investigation makes the material potential candidate for various photonic applications in addition to the well-known structural engineering application of the α-Sialon ceramics.