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Feng J.-J.,Wuhan University of Technology | Feng J.-J.,Dongfeng Commercial Vehicle Technology Center | Pan C.-X.,Wuhan University of Technology | Lu L.-L.,Dongfeng Commercial Vehicle Technology Center | And 2 more authors.
Journal of Iron and Steel Research International | Year: 2016

A Cr-Ni-Mo overlayer was deposited on the surface of compacted graphite iron (CGI) by the plasma transferred arc (PTA) alloying technique. The microstructure of Cr-Ni-Mo overlayer was characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), and X-ray diffractometer (XRD). Results show that the cross-section consists of four regions: alloying zone (AZ), molten zone (MZ), heat affected zone (HAZ), and the substrate (SUB). The microstructure of AZ mainly consists of cellular γ-(Fe, Ni) solid solution, residual austenite and a network of eutectic Cr7C3 carbide while the MZ area has a typical feature of white cast iron (M3C-type cementite). The martensite/ledeburite double shells are observed in the HAZ. With decreasing the concentration of Cr-Ni-Mo alloys, the fracture mode changes from ductile in the AZ to brittle in the MZ. The maximum hardness of the AZ (450 HV0.2) is lower than that of the MZ (800 HV0.2). The eutectic M3C and M7C3 carbides increase the microhardness, while the austenite decreases that of the AZ. © 2016 Central Iron and Steel Research Institute.


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).


Zheng W.,Wuhan Institute of Technology | Zheng W.,Wuhan University | Yang D.,Wuhan University of Technology | Bi P.,Wuhan University | And 7 more authors.
Journal of Electronic Materials | Year: 2016

Atomic scale point defects play important roles in tuning the carrier concentration and ultimately influencing electrical and thermal properties. Herein, we fabricated the ternary Sb2Te3−xSex alloys to study the intimate relationship of internal point defects and thermoelectric performance. The Se substitution of Te atoms in the Sb2Te3 lattice decreased the electrical conductivity from 2.2 × 105 S/m to 6.4 × 104 S/m owing to the reduced holes concentration. The declined point defects, including antisite defects and vacancies in materials, gave rise to the decrease in carrier concentration. The Seebeck coefficient of the ternary Sb2Te3−xSex exhibited an increase with doping of Se atoms. Simultaneously, the thermal conductivity behaved a fallihg trend as well as increasing Se content. As a result, the ZT value reached the maximum from the corresponding Sb2Te2.9Se0.1 pellet. Positron annihilation measurement revealed that the average positron lifetime showed a monotonic decrease with Se addition, demonstrating the reduced point defects, which was in agreement with the thermoelectric performance. © 2016 The Minerals, Metals & Materials Society


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.


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.


Yang Y.,Wuhan University | Wang Z.,Wuhan University | Wang Z.,Dongfeng Commercial Vehicle Technology Center | Ding Y.,Wuhan University | And 8 more authors.
APL Materials | Year: 2013

This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz-1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67) is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials. © 2013 Author(s).


Zheng W.,Wuhan University | Yang D.,Wuhan University of Technology | Wei W.,Hubei Cancer Hospital | Liu F.,Wuhan University of Science and Technology | And 5 more authors.
Applied Physics Letters | Year: 2015

In this work, Sb2Te3/Poly(3,4-ethylenedioxythiophene)/Sb2Te3 sandwich structure was artificially fabricated. This leads to a simultaneous increase of electrical conductivity and decrease of thermal conductivity by tailoring electric flow along the more-electrically conductive parallel path and thermal flow blocked across the less-thermally conductive perpendicular direction. The maximum of thermoelectric figure of merit was increased by 116%, reaching 1.3 at 523 K. © 2015 AIP Publishing LLC.


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.


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.

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