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Zheng W.,Wuhan University | Bi P.,Wuhan University | Kang H.,Huazhong University of Science and Technology | Wei W.,Hubei Cancer Hospital | And 6 more authors.
Applied Physics Letters | Year: 2014

p-type Sb2Te3/poly(3,4-ethylenedioxythiophene) (PEDOT) thermoelectric composites are fabricated by embedding PEDOT into Sb 2Te3 matrix. The grains of Sb2Te3 in the composites are found to be in micron degree and keep plate-like shapes. The measurements of thermoelectric properties show that the thermal conductivity κ of the composites is about 0.14 W m-1 K-1 in the temperature range of 300-523 K, much lower than that of Sb2Te 3 compounds. The maximum of dimensionless figure of merit of the composites reaches to 1.18 at 523 K, which is the highest value for the reported Sb2Te3/organic composites. It is suggested that the plate-like Sb2Te3 grains and the embedded PEDOTs may play a significant role in decreasing the thermal conductivity. Furthermore, results of the thermal cycling between the room temperature and 523 K for 50 cycles show that the composites are stable with κ remaining a low value. © 2014 AIP Publishing LLC. Source

Yang Y.,Wuhan University | Zhu B.,Wuhan University | Zhu B.,Huazhong University of Science and Technology | Yin D.,Wuhan University | And 7 more authors.
Nano Energy | Year: 2015

The recoverable motion sensor with high sensitivity was made based on flexible self-healing nanocomposites. The preparation of these nanocomposites involved incorporating surface-modified CaCu3Ti4O12 (S-CCTO) nanoparticles in self-healing polymer matrix based on dynamic Diels-Alder (DA) adducts. The dependences of electric and dielectric properties of the resultant composites on volume fractions of filler and frequency were investigated. It is found that composites present a high dielectric permittivity of 93 at 100Hz with 17vol% filler, approximately 36 times higher than that of pure film. These results agree well with the percolation theory. Furthermore, the hybrid film recovers its capacitance well following a cut and the self-healing process based on DA and retro-DA (r-DA) reaction. We herein show that a polymer matrix based on dynamic DA adducts can be used to make self-healing high-K polymer nanocomposites and recoverable motion sensors. This work may lead to new opportunities for the design and fabrication of various next-generation wearable sensor devices. © 2015 Elsevier Ltd. Source

Seyfried P.,Hamburg University of Applied Sciences | Taiss E.J.M.,CBMM Co. | Calijorne A.C.,Caltra Projetos & Consultoria | Li F.-P.,Dongfeng Commercial Vehicle Technology Center | Song Q.-F.,China First Automobile Works Group Corporation
Advances in Manufacturing | Year: 2015

This paper focuses on an estimation of light weighting opportunities for the frame structure of commercial road vehicles. This estimation is based on simplified static load cases which play a predominant role for the dimensioning of a frame structure and therefore these simplifications are not putting the general validity of the conclusions into question. A comparison of different materials under this scenario shows that light metals do not show any weight reduction advantage in comparison to steel while a material-independent topology optimization has more weight reduction potential for the frame structure than a simple change of materials. Considering the constraints of part complexity which is directly linked with production and assembly cost, the ladder frame structure has become the current state of the art design. Thus the paper also puts a spotlight on basic rules of node design and vertical load induction in order to keep the weight of such a design as low as possible. Practical examples from manufacturers show that the weight of a commercial vehicle could be reduced by 10% and main parts of the frame structure could be reduced by 30% using high strength steel in combination with innovative production methods like roll forming. © 2015, The Author(s). Source

Yang Y.,Wuhan University | Zhu B.-P.,Huazhong University of Science and Technology | Lu Z.-H.,Wuhan University of Science and Technology | Wang Z.-Y.,Wuhan University | And 7 more authors.
Applied Physics Letters | Year: 2013

This work reports the high dielectric permittivity of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanoparticles. The dielectric behavior has been investigated over a frequency of 100 Hz-1 MHz. High dielectric permittivity (ε = 171) and low dielectric loss (tan δ = 0.45) at 100 Hz have been observed near the percolation threshold. The experimental results fit well with the Percolation theory. We suggest that the high dielectric permittivity originates from the large interface area and the remarkable Maxwell-Wagner-Sillars effect at percolation in which nomadic charge carriers are blocked at internal interfaces between CCTO nanoparticles and the polyimide matrix. © 2013 American Institute of Physics. Source

Yang Y.,Wuhan University | Sun H.,Wuhan University | Yin D.,Wuhan University | Lu Z.,Wuhan University of Science and Technology | And 8 more authors.
Journal of Materials Chemistry A | Year: 2015

This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu3Ti4O12(CCTO)/Ag nanoparticles (CCTO@Ag). By functionalizing the surface of CCTO nanoparticles with Ag coating, the dielectric permittivity of PI/CCTO@Ag composites is significantly increased to 103 (100 Hz) at 3 vol% filler loading. The enhancement of dielectric permittivity is attributed to the increment of conductivity of the interlayer between CCTO and PI by Ag, which enhances the space charge polarization and Maxwell-Wagner-Sillars (MWS) effect. The experimental results fit well with percolation theory. Moreover, the low loss (0.018 at 100 Hz) achieved is attributed to the blockage of charge transfer by insulating polyimide chains. It is shown that the electrical field distortion is significantly improved by decorating the surface of CCTO nanoparticles with Ag using Comsol Multiphysics. This plays an important role in the enhancement of the dielectric properties. © 2015 The Royal Society of Chemistry. Source

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