Time filter

Source Type

Chen S.,Tianjin University | Feng Y.,Tianjin University | Feng Y.,Key Laboratory of Advanced Ceramics and Machining Technology | Feng Y.,Tianjin Key Laboratory of Composite and Functional Materials | And 5 more authors.
Carbon | Year: 2017

Combining heat transfer and high-temperature heat resistance is very important for realising thermal management in harsh environments. Achieving high heat conduction in the through-thickness direction (k⊥) is challenging for carbon fibre (CF) reinforced SiC matrix composite (CF/SiC) based heat resistant materials due to their anisotropic structures and weak bonding between the CF and the matrix. We present a three-dimensional (3-D) hierarchical vertically aligned carbon nanotubes (VACNTs)-CF hybrid by growing VACNTs on the surface of CF fabric. The SiO2 coating enables the strong deposition of the catalyst, facilitating high-density growth of VACNT. The VACNT-CF reinforced SiC composite is prepared by stacking VACNT-CF following by precursor infiltration and pyrolysis process. The VACNT forest not only enables strong interfacial bonding between the CF and the matrix but also greatly improve the k⊥ due to the good interfacial compatibility. The VACNT-CF/SiC composite exhibits k⊥ of 16.80 W/(m K), which is higher than that of the CF/SiC (7.94 W/(m K)), due to highly thermally conductive pathways in the dense structure. The VACNT-CF/SiC composite also conducts heat rapidly in the through-thickness direction. The VACNT-CF/SiC composite with high thermal conductivity, high strength and high oxidation resistance can be used for heat dissipation and resistance by optimising the microstructure. © 2017 Elsevier Ltd


Feng W.,Tianjin University | Feng W.,Key Laboratory of Advanced Ceramics and Machining Technology | Feng W.,Tianjin Key Laboratory of Composite and Functional Materials | Qin M.,Tianjin University | And 3 more authors.
Carbon | Year: 2016

All-carbon composites are ideal heat-dissipating materials because they possess a high thermal conductivity (K), excellent mechanical properties, high temperature resistance, low coefficient of thermal expansion, outstanding chemical stability, and so on. The rapid development of science and technology has put forward the need for a higher K of all-carbon composites. Different from individual carbon materials, all-carbon composites have assembled structures, including the interface, orientation, and pores, which provide challenges and opportunities to improve the thermal and mechanical properties. Until now, a number of studies have reported on how to adjust the K of various all-carbon composites by controlling their microstructures and mesostructures. This review compiles recent research progress on highly thermally conductive all-carbon composites, including flexible carbon papers (carbon nanotube paper, graphene paper, exfoliated graphite paper), stiff carbon blocks (graphite block, carbon fiber block), and porous carbon foams (pitch-based carbon foam, graphene-based carbon foam, three dimensional graphene-carbon nanotube-based carbon foam). The key structures and their control methods related to their high K are outlined. Finally, the strategies and challenges in the development of highly thermally conductive all-carbon composites are presented. © 2016 Elsevier Ltd


Han J.,Tianjin University | Shen Y.,Tianjin University | Shen Y.,Key Laboratory of Advanced Ceramics and Machining Technology | Shen Y.,Tianjin Key Laboratory of Composite and Functional Materials | And 3 more authors.
Nanoscale | Year: 2016

Three-dimensional (3D) graphene materials have attracted a lot of attention for efficiently utilizing inherent properties of graphene sheets. However, 3D graphene materials reported in the previous literature are constructed through covalent or weak non-covalent interactions, causing permanent structure/property changes. In this paper, a novel 3D graphene material of dynamic interactions between lamellas with 2-ureido-4[1H]-pyrimidinone as a supra-molecular motif has been synthesized. This 3D graphene material shows enhanced sheet interactions while the cross-linking takes place. With proper solvent stimulation, the integrated 3D graphene material can disassemble as isolated sheets. The driving force for the 3D structure assembly or disassembly is considered to be the forming or breaking of the multiple hydrogen bonding pairs. Furthermore, the 3D material is used as an intelligent dye adsorber to adsorb methylene blue and release it. The controllable and reversible characteristic of this 3D graphene material may open an avenue to the synthesis and application of novel intelligent materials. © 2016 The Royal Society of Chemistry.


Zhu X.,Tianjin University | Zhu X.,Tianjin University of Technology and Education | Lin B.,Tianjin University | Lin B.,Key Laboratory of Advanced Ceramics and Machining Technology | And 3 more authors.
IEEE Transactions on Industrial Electronics | Year: 2016

In rotary ultrasonic grinding (RUG), a rotating transformer can be used to replace the established slip ring technology and provide a contactless power supply to the revolving transducer. Such contactless energy transfer (CET) is safe, and high rotation speeds are possible. Compared with a closely coupled transformer, the transfer efficiency of the rotating transformer is lower. Compensation of the windings is necessary to improve efficiency. In addition, the cutting force in RUG is not constant; this will influence the power transfer performance, which in turn affects the vibration amplitude of the tool. In this paper, by considering the distinct capacitive and mechanical behavior of the transducer and the equivalent series resistances (ESRs) of the compensation elements, mathematical models are developed to identify the transfer efficiency and the output power of the rotating transformer. A general mathematical compensation model is developed for maximum transfer efficiency. The effects of the cutting force on the transfer efficiency, the output power, and the power factor are also researched. The experimental results basically agree with the calculated results. A CET system that can produce high efficiency, a high power factor and adaptive output power that adapts to the variations of cutting force in the RUG is therefore possible. © 2016 IEEE.


Wu S.,Tianjin University | Feng J.-M.,Key Laboratory of Advanced Ceramics and Machining Technology | Fu X.,Tianjin University | Hu X.-D.,Tianjin University | And 3 more authors.
Nanotechnology | Year: 2011

Controlled placement of carbon nanotubes is important for carbon-based nanodevice assembly. However, it is difficult to manipulate individual nanotubes because of their extremely small dimensions. Ultra-fine tubes are often in the form of bundles and are hard to efficiently move on a surface due to the strong adhesion among themselves and between the tubes and the substrate. This paper presents a novel manipulation approach of individual double-walled carbon nanotubes encased in a thick amorphous carbon shell. With an atomic force microscope, we are able to freely displace the nanotubes within a casing shell, and unpack it from the shell on a silicon surface. The theoretical analysis demonstrates that the unpacking process is determined by the difference of the static friction between the shell and the substrate and the resistance force between the shell and the embedded nanotube. © 2011 IOP Publishing Ltd.


Liu E.,Tianjin University | Liu E.,Tianjin Key Laboratory of Composite and Functional Materials | Wang J.,Tianjin University | Wang J.,Tianjin Key Laboratory of Composite and Functional Materials | And 11 more authors.
International Journal of Hydrogen Energy | Year: 2011

Electrochemical hydrogen storage of multi-walled carbon nanotubes (MWCNTs) decorated by TiO2 nanoparticles (NPs) has been studied by the galvanostatic charge and discharge method. The TiO2 NPs are deposited on the surface of MWCNTs by sol-gel method. Structural and morphological characterizations have been carried out using XRD, SEM and TEM, respectively. TiO2 NPs can significantly enhance the discharge capacity of MWCNTs. The cyclic voltammograms analysis indicates that the electrical double layer contributes little to the discharge capacity of TiO2-decorated MWCNTs. The MWCNTs modified with a certain amount of TiO2 NPs have a discharge capacity of 540 mAh/g, corresponding to an electrochemical hydrogen storage capacity of about 2.02 wt%, which is quite interesting for the battery applications. The enhancement effect of TiO2 NPs on the discharge capacity of MWCNTs could be related to the increased effective area for the adsorption of hydrogen atoms in the presence of TiO2 NPs on MWCNTs and the preferable redox ability of TiO2 NPs. Copyright © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Feng J.-M.,Key Laboratory of Advanced Ceramics and Machining Technology | Wang R.,Key Laboratory of Advanced Ceramics and Machining Technology | Li Y.-L.,Key Laboratory of Advanced Ceramics and Machining Technology | Zhong X.-H.,Key Laboratory of Advanced Ceramics and Machining Technology | And 3 more authors.
Carbon | Year: 2010

High-quality double-walled carbon nanotubes (DWCNTs) thin-films have been fabricated in one-step by the catalytic chemical vapor deposition gas-flow reaction process with acetone as a carbon source in an argon flow. The DWCNTs film is formed through the self-assembly of the DWCNTs in the gas flow, which is achieved by controlling the gas rates in the synthesis reaction. The DWCNT film is self-supported and consists of preferentially aligned high-quality DWCNT bundles. Raman spectral analysis shows a low intensity ratio of the D band and the G band with ID/IG being 0.025 indicating a high-quality of DWCNTs at a macroscopic scale. Property measurements show that the DWCNT film is mechanically robust and highly electrically conductive. The formation of high-quality DWCNTs can be attributed to the reaction in the argon environment that is inert and does not attack the DWCNTs at the high synthesis temperature (1170 °C). This one-step fabrication process is feasible for large-scale productions of high-quality DWCNTs films with promising structural and functional applications. © 2010 Elsevier Ltd. All rights reserved.


Yu Y.,Tianjin University | Yu Y.,Tianjin Key Laboratory of Composite and Functional Materials | Zhao N.,Tianjin University | Zhao N.,Tianjin Key Laboratory of Composite and Functional Materials | And 9 more authors.
International Journal of Hydrogen Energy | Year: 2012

The electrochemical hydrogen storage of expanded graphite (EG) decorated with TiO2 nanoparticles (NPs) calcined at different temperatures has been investigated with the galvanostatic charge and discharge method. The TiO2 NPs are deposited on and between the graphene-like nanosheets of EG by a sol-gel method. The morphology, structure, composition, and specific surface area of the samples were characterized. The electrochemical measurement reveals that the EG decorated with TiO2 NPs calcined at 500 °C has a discharge capacity of 373.5 mAh/g which is 20 times higher than that of pure EG and quite appealing for the battery applications. The mechanism of enhancement of the electrochemical activity for the TiO2-decorated EG could be attributed to the preferable redox ability and photocatalytic property of TiO2 NPs. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.


Wang P.F.,Key Laboratory of Advanced Ceramics and Machining Technology | Li Zh.H.,Key Laboratory of Advanced Ceramics and Machining Technology | Zhu Y.M.,Key Laboratory of Advanced Ceramics and Machining Technology | Gao K.,Key Laboratory of Advanced Ceramics and Machining Technology | Wang K.Y.,Key Laboratory of Advanced Ceramics and Machining Technology
Journal of Alloys and Compounds | Year: 2010

Cubic boron nitride (cBN) ceramics were prepared by sintering cBN micro-powder with magnesium at high temperature and high-pressure conditions (HTHP). Following the sintering, the ceramics were annealed in nitrogen atmosphere. Surface microstructure, phase compositions and photoluminescence of the ceramics were examined comprehensively using scanning electronic microscopy, energy-dispersive spectrometer, X-ray diffraction, and fluorescence spectrophotometer. Experimental results indicated that flower-like MgO crystals clustered in the annealed surface of the ceramics after annealing at 1100 °C for 2 h. Oxygen vacancies in MgO crystals increased the emission peak near 400 nm. The emission peak near 317 nm was attributed to oxygen vacancies in cBN crystals due to scavenging of O from cBN by Mg. The optical vibrational eigenmodes of hBN resulted in phonon replicas in photoluminescence spectra due to the interactions between LO phonon of the hBN and LO phonon of the MgO crystal lattice, or with the nitrogen vacancies in cBN grains. © 2009 Elsevier B.V. All rights reserved.


Su D.,Key Laboratory of Advanced Ceramics and Machining Technology | Duan H.-Z.,Key Laboratory of Advanced Ceramics and Machining Technology
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2015

Polyzirconosiloxane (PZSO) fibers were obtained from silicon alkoxide solution consisting of tetraethoxylsilane (TEOS) and dimethyldiethoxylsilane (DMDES) using ZrOCl2 as zirconium source by sol-gel process, and the spinnability of the solution were optimized by varying the amount of ZrOCl2 and H2O. Subsequent drying and pyrolysis treatment of the PZSO gel fibers yields SiZrOC fibers with high ceramic yield of 84.7wt% at 1000℃. Scanning electron microscopy shows that SiZrOC fibers are smooth and dense, and maintain the initial round shape of PZSO fibers. FTIR analysis shows Zr is incorporated into Si-O tetrahedron suggesting the formation of =Zr-O-Si≡ bridge through co-condensation of ZrOCl2, TEOS and DMDES. SiZrOC fibers exhibit less than 5wt% weight loss under heat-treating up to 1500℃ in flowing argon indicating their good thermal stability in high temperature. ©, 2015, Chinese Ceramic Society. All right reserved.

Loading Key Laboratory of Advanced Ceramics and Machining Technology collaborators
Loading Key Laboratory of Advanced Ceramics and Machining Technology collaborators