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Wu Z.-H.,Shanghai Second Polytechnic University | Xie H.-Q.,Shanghai Second Polytechnic University | Zhai Y.-B.,Shanghai Yueda New Materials Science and Technology Ltd.
Journal of Nanoscience and Nanotechnology | Year: 2015

Zinc oxide (ZnO) has attracted increasing attention as one of the most promising n -type thermoelectric materials, but its practice use was limited by high thermal conductivity and low electrical conductivity. Therefore, we herein prepared Co-doped ZnO nanoparticles by sol-gel method and then compressed nanoparticles into bulk materials through spark plasma sintering. The thermoelectric properties, including electrical conductivity, Seebeck coefficient, thermal conductivity, and ZT value, have been investigated. We found that the substitution of Co2+ causes the decrease of bandgap and the increase of carrier concentration, thus the improvement of electrical conductivity. At the same time, the Co-induced lattice distortion and nanoparticles reduce the thermal conductivity by shortening the mean free path (MFP) of the phonons. The resultant ZT is 0.037 for Zn0.-9 Co0-.1 O, which is more than 23-fold higher than that of the pure ZnO samples. Copyright © 2015 American Scientific Publishers All rights reserved. Source


Yu W.,Shanghai Second Polytechnic University | Xie H.-Q.,Shanghai Second Polytechnic University | Chen L.-F.,Shanghai Second Polytechnic University | Chen L.-F.,Shanghai Yueda New Materials Science and Technology Ltd. | Zhou X.-F.,Nanjing Southeast University
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics | Year: 2013

Graphene is a new kind of carbon materials with high thermal conductivity, attracting extensive attention. This paper adopts the mechanical mixing method to prepare the nylon 6 composite containing graphene nanoplatelets. Research results indicate that graphene can greatly improve the thermal conductivity of the polymer matrix material. The thermal conductivity enhanced ratio is 42.6% for 1.0 vol.% graphene additive, and the enhanced ratio is more than 15 times when the graphene volume fraction is 20%, illustrating the strong application potential in the heat management field. Source


Yu W.,Shanghai Second Polytechnic University | Zhao J.,Shanghai Yueda New Materials Science and Technology Ltd. | Wang M.,Shanghai Second Polytechnic University | Hu Y.,Shanghai Second Polytechnic University | And 2 more authors.
Nanoscale Research Letters | Year: 2015

Different cupric oxide (CuO) structures have attracted intensive interest because of their promising applications in various fields. In this study, three kinds of CuO structures, namely, CuO microdisks, CuO nanoblocks, and CuO microspheres, are synthesized by solution-based synthetic methods. The morphologies and crystal structures of these CuO structures are characterized by field-emission scanning electron microscope and X-ray diffractometer, respectively. They are used as thermal conductive fillers to prepare silicone-based thermal greases, giving rise to great enhancement in thermal conductivity. Compared with pure silicone base, the thermal conductivities of thermal greases with CuO microdisks, CuO nanoblocks, and CuO microspheres are 0.283, 0256, and 0.239 W/mK, respectively, at filler loading of 9 vol.%, which increases 139%, 116%, and 99%, respectively. These thermal greases present a slight descendent tendency in thermal conductivity at elevated temperatures. These experimental data are compared with Nan's model prediction, indicating that the shape factor has a great influence on thermal conductivity improvement of thermal greases with different CuO structures. Meanwhile, due to large aspect ratio of CuO microdisks, they can form thermal networks more effectively than the other two structures, resulting in higher thermal conductivity enhancement. © 2015, Yu et al.; licensee Springer. Source


Wu Z.-H.,Shanghai Second Polytechnic University | Xie H.-Q.,Shanghai Second Polytechnic University | Zhai Y.-B.,Shanghai Yueda New Materials Science and Technology Ltd.
Applied Physics Letters | Year: 2013

We report in this letter the synthesis and thermoelectric properties of Zn1-xNixO/polyparaphenylene (Zn1-xNi xO/PPP) organic-inorganic hybrid materials. Compared to the inorganic ZnO-based materials, hybrid materials exhibit dual effects of increased power factor consistent with the molecular junction effect and a reduction in thermal conductivity by the incorporation of conductive PPP. As a result, the greatest ZT = 0.54 of hybrid materials was obtained at 1173 K, which corresponds to a 6-fold enhancement compared to that of the best inorganic Zn 0.97Ni0.03O sample (ZT = 0.09) at 1000 K. © 2013 AIP Publishing LLC. Source


Wu Z.-H.,Shanghai Second Polytechnic University | Xie H.-Q.,Shanghai Second Polytechnic University | Zhai Y.-B.,Shanghai Yueda New Materials Science and Technology Ltd. | Gan L.-H.,Shanghai Second Polytechnic University | Liu J.,Shanghai Second Polytechnic University
Chinese Physics B | Year: 2015

In order to study the thermoelectric properties of TiO2-based hybrid materials, TiO2/polyparaphenylene (PPP) nanocomposites are fabricated by spark plasma sintering (SPS). The results show that the electrical conductivity follow percolation theory is enhanced due to the electron transfer highway provided by the conducting PPP phase. Furthermore, the thermal conductivity is reduced due to the drastic difference of vibrational spectra between organic and inorganic components. As a result, the greatest ZT = 0.24 is obtained for TiO2/0.75 wt% PPP sample, which is 15-fold higher than pure TiO2 (ZT = 0.016). © 2015 Chinese Physical Society and IOP Publishing Ltd. Source

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