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Liu J.,University Of Science And Technology Liaoning | Xie Z.,State Key Laboratory of New Ceramics and Fine Processing | Li Z.,University Of Science And Technology Liaoning
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2016

The high-performance silicon nitride ceramics were prepared via spark plasma sintering (SPS) with submicron-sized powder of silicon nitride as a raw material and Al2O3-Y2O3 as a sintering aid. The phase constitution and microstructure of specimens were analyzed by X-ray diffraction and scanning electronic microscopy. The effect of sintering temperature on the microstructure and mechanical properties of silicon nitride ceramics were investigated. The results show that β-phase silicon nitride ceramic with a high density and good mechanical properties can be obtained at a lower sintering temperature by SPS. The density, flexural strength and fracture toughness of the samples improve with the increase of the sintering temperature. The flexural strength and fracture toughness of the samples sintered at 1 500 ℃ are 973.74 MPa and 8.23 MPa·m1/2, respectively. According to the phase composition and microstructure analysis, the β-phase content of silicon nitride ceramics is 98%. The elongated columnar silicon nitride grains are uniform and well-developed. The compact connection between the grains results in the less pores of grain boundaries. The abnormal growth of some grains produces the more microscopic pores, leading to that the flexural strength decreases as sintering temperature further incerases. © 2016, Chinese Ceramic Society. All right reserved. Source

Bai A.,Tsinghua University | Wang L.,Tsinghua University | Wang L.,State Key Laboratory of New Ceramics and Fine Processing | Li J.,Tsinghua University | And 3 more authors.
Journal of Power Sources | Year: 2015

Graphite/Phosphorus composite anodes are prepared by mixing graphite and the phosphorus/carbon material, which prepared by heating the mixture of red phosphorus and porous carbon. Their electrochemical performances are evaluated as anodes for Li-ion batteries. A graphite/Phosphorus composite|LiFePO4 full-cell is also attempted. When the phosphorus/carbon content in the composite anode is 28.6 wt.%, the composite anode presents high reversible capacity of 500 mAh g-1 and considerable cycleability comparable to that of graphite anode, showing promising performance. © 2015 Elsevier B.V. All rights reserved. Source

Meng L.-R.,State Key Laboratory of New Ceramics and Fine Processing | Peng Q.,State Key Laboratory of New Ceramics and Fine Processing | Peng Q.,Tsinghua University | Zhou H.-P.,State Key Laboratory of New Ceramics and Fine Processing | And 2 more authors.
Gaodeng Xuexiao Huaxue Xuebao/Chemical Journal of Chinese Universities | Year: 2011

The assembly of nanocrystals into various ordered structures is key to their future applications. In this article, we describe the recent progresses in the assembly routes and mechanisms of the three-dimensional superlattices of nanocrystals. This review focuses on the techniques of nanocrystal assembly based on solvent evaporation of colloidal solutions, non-solvent diffusion, micelle-induced aggregation, hydrogen bonding linkage, electrostatic interactions, DNA base-pairing, external field-assistance, and oil-water interface templating. The existing challenges and future development of nanocrystals assembly are also discussed. Source

Ding J.,Tsinghua University | Xu B.,Tsinghua University | Xu B.,Key Laboratory of Advanced Materials of Ministry of Education of China | Lin Y.,Tsinghua University | And 5 more authors.
New Journal of Physics | Year: 2015

BiCuSeO has recently been shown to be one of the best oxide-based thermoelectric materials. The electrical properties of this material have been widely studied; however, the reasons for its intrinsically low thermal conductivity have only been briefly discussed. In this paper, we calculated the band structure and the electrical properties of BiCuSeO. The phonon spectrum, mode Grüneisen parameters and the thermal properties were also investigated. Additionally, we proposed a new method for illustrating the interlayer interactions in this material. For the first time, using first principles calculations, we provide direct evidence of the structural in-layer and interlayer off-phase vibration modes, which contribute to the anharmonic vibrations and structural scattering of phonons and result in an intrinsic low lattice thermal conductivity for BiCuSeO. © 2015 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. Source

Yao S.,Tsinghua University | Yao S.,State Key Laboratory of New Ceramics and Fine Processing | Lin X.,Tsinghua University | Lin X.,State Key Laboratory of New Ceramics and Fine Processing | And 6 more authors.
Key Engineering Materials | Year: 2012

A high molecular weight block copolymer dispersant with pigment affinic groups - DISPERBYK163 (BYK163) was chosen to disperse submicron-sized Si 3N 4 in tert-butylalcohol (TBA) solvent. The stability of Si 3N 4 powders in TBA with dispersant BYK163 was studied by sedimentation. To achieve good casting behavior, rheological measurement was employed to find a reasonable dispersant content in the slurry. The adsorption isotherm of BYK163 on Si 3N 4 particles surface was obtained by thermogravimetric analysis (TGA). Based on the surface chemical properties of Si 3N 4 particles, the dispersing phenomena and mechanism of BYK163 in TBA were summarized. BYK163 could form a steric layer on the surface of Si 3N 4 particles, and effectively prevent particles agglomeration. Therefore, porous Si 3N 4 samples with porosity of 40% to 80% could be prepared from Si 3N 4 slurries with low and high solid loadings due to well dispersion with BYK163 addition. © (2012) Trans Tech Publications. Source

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