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      • KCI등재

        Fabrication and properties of reaction-bonded SiC prepared by gelcasting

        Lifang Nie,Hongyu Gong,Tao Zhang,Yujun Zhang 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.1

        The properties of green and reaction-bonded SiC (RBSC) samples prepared by a gelcasting technique are investigated in this paper. The results show that solid loading and monomer content of the suspension in the gelcasting process are the main factors that effect the density and shrinkage of the green bodies. A slurry with a solid loading of 58 vol% was solidified in situ to a green body with a linear shrinkage of 1.1% and flexural strength of 27 ± 2 MPa. SEM micrographs show that the SiC and C particles in the green body were closely compact by a connection of the polymer network. The maximum density and flexural strength of samples reaction sintered at 1700℃ in vacuum were 2.97 g/㎤ and 378 ± 12 MPa respectively. The properties of green and reaction-bonded SiC (RBSC) samples prepared by a gelcasting technique are investigated in this paper. The results show that solid loading and monomer content of the suspension in the gelcasting process are the main factors that effect the density and shrinkage of the green bodies. A slurry with a solid loading of 58 vol% was solidified in situ to a green body with a linear shrinkage of 1.1% and flexural strength of 27 ± 2 MPa. SEM micrographs show that the SiC and C particles in the green body were closely compact by a connection of the polymer network. The maximum density and flexural strength of samples reaction sintered at 1700℃ in vacuum were 2.97 g/㎤ and 378 ± 12 MPa respectively.

      • SCIESCOPUS

        Enhanced Performance of La<sub>0.6</sub>Sr<sub>0.4</sub>Co<sub>0.2</sub>Fe<sub>0.8</sub>O<sub>3-\delta</sub> (LSCF) Cathodes with Graded Microstructure Fabricated by Tape Casting

        Nie, Lifang,Liu, Ze,Liu, Mingfei,Yang, Lei,Zhang, Yujun,Liu, Meilin The Korean Electrochemical Society 2010 Journal of electrochemical science and technology Vol.1 No.1

        $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ (LSCF) powders with different particle sizes, synthesized through a citrate complexation method and a gel-casting technique, are used to fabricate porous LSCF cathodes with graded microstructures via tape casting. To create porous electrodes with desired porosity and pore structures, graphite and starch are used as pore former for different layers of the graded cathode. Examination of the microstructures of the as-prepared LSCF cathode using an SEM revealed that both grain size and porosity changed gradually from the catalytically active layer (near the electrodeelectrolyte interface) to the current collection layer (near the electrode-interconnect interface). Impedance analysis showed that a 3-layer LSCF cathode with graded microstructures exhibited much-improved performance compared to that of a single-layer LSCF cathode, corresponding to interfacial resistance of 0.053, 0.11, and 0.27 $\Omega{\cdot}cm^2$ at 800, 750, and $700^{\circ}C$ respectively.

      • KCI등재

        Microwave hydrothermal synthesis and temperature sensing behavior of Lu2Ti2O7:Yb3þ/Er3þ nanophosphors

        Jinsheng Liao,Qi Wang,Lifang Lan,Jiangfei Guo,Liling Nie,Suijun Liu,He-Rui Wen 한국물리학회 2017 Current Applied Physics Vol.17 No.3

        Lu2Ti2O7:Yb3þ/Er3þ (LTO:Yb3þ/Er3þ) nanophosphors codoped with Yb3þ (8e20 at%) and Er3þ ions (0.5 e4 at%) were synthesized by a microwave hydrothermal process. Under the 980 nm excitation, the sample gives a set of upconversion light: very strong red emissions near 661 nm (4F9/2 / 4I15/2), weak green around 523 nm and 545 nm (2H11/2/4I15/2 and 4S3/2/4I15/2, respectively). The optimum doping concentrations of Er3þ and Yb3þ for the highest emission intensity were determined by photoluminescence (PL) analyses. Concentration dependent studies revealed that the optimal composition was realized for the 12 at% Yb3þ and 2.0 at% Er3þ-doping concentration with a strong emission. A possible UC mechanism for LTO:Yb3þ/Er3þ is discussed via the change of the pump power. The temperature dependence of the fluorescence intensity ratios (FIR) for the two green UC emission bands peaked at 523 and 545 nm was studied in the range of 298e573 K under excitation by a 980 nm diode laser and the maximum sensitivity was approximately 0.00313 K『1 at 536 K. This indicates that LTO:Yb3þ/Er3þ nanophosphors are potential candidates for optical temperature sensors with high sensitivity.

      • Orthorhombic carbon oC24: A novel topological nodal line semimetal

        Li, Zhen-Zhen,Chen, Jia,Nie, Simin,Xu, Lifang,Mizuseki, Hiroshi,Weng, Hongming,Wang, Jian-Tao Elsevier 2018 Carbon Vol.133 No.-

        <P><B>Abstract</B></P> <P>We identify by <I>ab initio</I> calculations a stable three-dimensional carbon allotrope that constructed by inserting benzene rings into the carbon-carbon bonds in a previously reported oC8 carbon. This new carbon phase has a 24-atom orthorhombic unit cell in C m m m ( D 2 H 19 ) symmetry and thus termed oC24. Phonon mode analysis confirms its dynamical stable. Total-energy calculations show that it is energetically stable comparable with (5,5) carbon nanotube. Detailed electronic band calculations reveal that oC24 is a topological node-line semimetal with two mirror-inversion symmetric nodal lines that go through the whole Brillouin zone in bulk and a projected surface flat band around the Fermi level. The present results establish a new type of carbon phases and offer insights into their outstanding structural and electronic properties.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

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