State Key Laboratory of New Ceramics and Fine Processing

Beijing, China

State Key Laboratory of New Ceramics and Fine Processing

Beijing, China

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Cao T.,Tsinghua University | Shi Y.,Tsinghua University | Jiang Y.,State Key Laboratory of New Ceramics and Fine Processing | Cai N.,Tsinghua University | Gong Q.,State Key Laboratory of New Ceramics and Fine Processing
Energy | Year: 2017

Liquid Sb anode has been intensively studied for its capability to convert various solid carbon fuels into electricity. Performance of anode is one of the most important issues. In present research, performance of liquid Sb anode SOFC is promoted by an “assisted oxidation process”: fuel cell achieved larger current by electrochemically introducing extra amount of Sb2O3 into the anode region. By revealing the interfacial structure between anode and electrolyte, the mechanism of performance promotion is then explained by numerical model from a microstructural point of view: the oxidation process built ionic transporting pathways and extended the electrochemical reactive sites in liquid Sb anode. With the help of extended electrochemical reactive sites, the fuel cell reaches a better performance. The “assisted oxidation process” can be taken as an in-situ method to refine the structure of liquid Sb anode. © 2017 Elsevier Ltd

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.

Sun P.,State Key Laboratory of New Ceramics and Fine Processing | Zheng F.,State Key Laboratory of New Ceramics and Fine Processing | Zhu M.,State Key Laboratory of New Ceramics and Fine Processing | Zhu M.,Tsinghua University | And 8 more authors.
ACS Nano | Year: 2014

Graphene and graphene oxide (G-O) have been demonstrated to be excellent filters for various gases and liquids, showing potential applications in areas such as molecular sieving and water desalination. In this paper, the selective trans-membrane transport properties of alkali and alkaline earth cations through a membrane composed of stacked and overlapped G-O sheets ("G-O membrane") are investigated. The thermodynamics of the ion transport process reveal that the competition between the generated thermal motions and the interactions of cations with the G-O sheets results in the different penetration behaviors to temperature variations for the considered cations (K+, Mg2+, Ca2+, and Ba2+). The interactions between the studied metal atoms and graphene are quantified by first-principles calculations based on the plane-wave-basis-set density functional theory (DFT) approach. The mechanism of the selective ion trans-membrane transportation is discussed further and found to be consistent with the concept of cation-π interactions involved in biological systems. The balance between cation-π interactions of the cations considered with the sp2 clusters of G-O membranes and the desolvation effect of the ions is responsible for the selectivity of G-O membranes toward the penetration of different ions. These results help us better understand the ion transport process through G-O membranes, from which the possibility of modeling the ion transport behavior of cellular membrane using G-O can be discussed further. The selectivity toward different ions also makes G-O membrane a promising candidate in areas of membrane separations. © 2014 American Chemical Society.

Li J.,Tsinghua University | Wang L.,Tsinghua University | Wang L.,State Key Laboratory of New Ceramics and Fine Processing | He X.,Tsinghua University | Wang J.,Tsinghua University
ACS Sustainable Chemistry and Engineering | Year: 2016

Phosphorus@carbon composites are alternative anode materials for lithium-ion batteries due to their high specific capacity. Serving as a conductive and buffer matrix, the carbon substrate is important to the performance of the composite. Our results exhibit that the electrochemical performances of phosphorus@carbon composites could be significantly enhanced by pore size distributions of the carbon matrix. The initial Coulombic efficiency of phosphorus@YP-50F reaches 80% and the capacity remains stable at 1370 mAh g-1 after 100 cycles at 300 mA g-1. The work may provide a general strategy for designing or selecting the optimal carbon matrix for phosphorus@carbon performance, and pave the way to practical application in lithium-ion batteries. © 2016 American Chemical Society.

Sun P.,State Key Laboratory of New Ceramics and Fine Processing | Liu H.,Tsinghua University | Wang K.,State Key Laboratory of New Ceramics and Fine Processing | Zhong M.,State Key Laboratory of New Ceramics and Fine Processing | And 3 more authors.
Journal of Physical Chemistry C | Year: 2014

Recently, graphene oxide (GO) membranes have been reported with the ability to separate different solutes in aqueous suspensions by a molecular sieving effect. On the other hand, we propose that the chemical interactions between ions and GO membranes might also take effect in selective ion transmembrane transportation. In this paper, on the basis of the permeation of Cu2+ and Mg2+ sources through hydroxyl-, carboxyl-, and amino-functionalized graphene membranes, the delicate ion-graphene interactions which might be responsible for the selective ion permeation are investigated. We demonstrate experimentally that the coordination between transition-metal cations and carboxyl functionalities and the cation-π interactions between main-group cations and sp2 regions are responsible for the selective transport of small ions through graphene-based membranes, which is beyond the scope of molecular sieving effect proposed previously. Notably, by grafting amino groups onto the graphene basal planes, the permeations of Cu2+ and Mg2+ cations are both weakened. These results not only throw light upon the mechanism for the selective ion permeation through graphene-based membranes but also lay a foundation for the separation of target ions by grafting specific functionalities. © 2014 American Chemical Society.

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.

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.

Liu J.,Tsinghua University | Liu J.,Key Laboratory for Advanced Materials Processing Technology | Liu J.,State Key Laboratory of New Ceramics and Fine Processing | Gong Q.,Tsinghua University | And 10 more authors.
Applied Surface Science | Year: 2014

MoSi2/SiC-Mo2C gradient coating on molybdenum was in situ prepared with pack cementation process by two steps: (1) carburizing with graphite powder to obtain a Mo2C layer on Mo substrate, and (2) siliconizing with Si powder to get a composite MoSi2/SiC layer on the upper part of Mo2C layer. The microstructure and elemental distribution in the coating were investigated with scanning electron microscopy (SEM), back scattered electron (BSE), energy dispersive spectroscopy (EDS), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Cyclic oxidation tests (at 500 °C, 1200 °C, 1400 °C and 1600 °C) demonstrated excellent oxidation resistance for the gradient composite coating and the mass loss was only 0.23% in 60 min at 1600 °C. XRD, EPMA, thermal dynamic and phase diagram analyses indicated that the Mo2C barrier layer played the key role in slowing down the diffusion of C and Si toward inner Mo substrate at high temperature and principally this contributed to the excellent anti-oxidation for Mo besides the outer MoSi2/SiC composite layer. © 2014 Elsevier B.V.

Yang D.,Tsinghua University | Yang D.,State Key Laboratory of New Ceramics and Fine Processing | Lu N.,Tsinghua University | Lu N.,State Key Laboratory of New Ceramics and Fine Processing | And 2 more authors.
Proceedings - Electronic Components and Technology Conference | Year: 2013

The wettability of the molten lead-free solder on the substrate is an important property for the lead-free solder joints in electronic products. In this paper, we investigated the wettability of lead-free solder pastes on electroplated Co-P films. We measured the contact angles of one kind of Sn-Bi and two kinds of Sn-Ag-Cu (SAC305 and SAC387) solder pastes on the Co-P films with nanocrystalline, amorphous and mixed structures and studied the dependence of the contact angles of the molten solders on the microstructure of the Co-P film. The experimental data showed that in general the amorphous Co-P film with a large phosphorous content was favorable for all three solder pastes in terms of wettability. SAC305 had a contact angle less than 10° on the amorphous Co-P film and Sn-Bi had a contact angle of about 20° on it. Although SAC387 spread out completely on the amorphous and mixed Co-P films, Sn in SAC387 diffused quickly into the Co-P films and even penetrated the films. In addition, we observed the cross-sections of the solder joints, studied the interfacial reaction between the solders and the Co-P films by scanning electron microscopy and explained the variation of the contact angles of the solders on different Co-P films. © 2013 IEEE.

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.

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