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Niu W.,Zhejiang University | Xu H.,Zhejiang University | Guo Y.,State Key Laboratory of Silicon Materials | Li Y.,Zhejiang University | And 2 more authors.
Physical Chemistry Chemical Physics | Year: 2015

P-type sulphur-nitrogen (S-N) co-doped ZnO thin films are deposited and the effect of sulphur on the electrical properties is discussed. First-principles calculations indicate that the structure is most stable when the S atom is close to the N atom in the (0002) plane, implying that dual-doped ZnO is relatively feasible to approach. The partial density of states of S-N co-doped ZnO shows that the S impurity plays a vital role in forming the p-type conductivity. This journal is © the Owner Societies.

Wang L.,Beijing University of Technology | Zhang Z.,Beijing University of Technology | Zhang Z.,State Key Laboratory of Silicon Materials | Han X.,Beijing University of Technology
NPG Asia Materials | Year: 2013

Sub-micron and nanostructured materials exhibit high strength, ultra-large elasticity and unusual plastic deformation behaviors. These properties are important for their applications as building blocks for the fabrication of nano- and micro-devices as well as for their use as components for composite materials, high-strength structural and novel functional materials. These nano-related deformation and mechanical behaviors, which are derived from possible size and dimensional effects and the low density of defects, are considerably different from their conventional bulk counterparts. The atomic-scale understanding of the microstructural evolution process of nanomaterials when they are subjected to external stress is crucial for understanding these 'unusual' phenomena and is important for designing new materials, novel structures and applications. This review presents the recent developments in the methods, techniques, instrumentation and scientific progress for atomic-scale in situ deformation dynamics on nanomaterials, including nanowires, nanotubes, nanocrystals, nanofilms and polycrystalline nanomaterials. The unusual dislocation initiation, partial-full dislocation transition, crystalline-amorphous transitions and fracture phenomena related to the experimental mechanics of the nanomaterials are reviewed. Current limitations and future aspects using in situ high-resolution transmission electron microscopy of nanomaterials are also discussed. A new research field of in situ experimental mechanics at the atomic scale is thus expected. © 2013 Nature Japan K.K. All rights reserved.

Liu H.,State Key Laboratory of Silicon Materials | Wang X.,State Key Laboratory of Silicon Materials | Wang X.,Zhejiang University | Liu Y.,State Key Laboratory of Silicon Materials | And 4 more authors.
Journal of Physical Chemistry C | Year: 2014

Niobium fluoride (NbF5) is introduced into the MgH2 + 1/4AlH3 hydride composite by ball milling to improve the hydrogen desorption properties of the Mg-Al-H system. It is found that after being ball milled with 1 mol % of NbF5, AlH3 in the composite has almost fully decomposed and forms metallic Al, which indicates that NbF 5 can significantly destabilize AlH3. DSC results show that NbF5 addition also helps reduce the peak desorption temperature of MgH2 in the composite from 324 to 280 °C. Isothermal desorption measurements demonstrate that MgH2 in the doped composite can rapidly release 98% of its hydrogen after desorption at 300 °C for 1 h, while the valued is only 46% for the undoped composite. The activation energy for hydrogen desorption of MgH2 in the doped composite is calculated to be 104.5 kJ/mol, much lower than that in the undoped composite (127.4 kJ/mol). These results suggest that NbF5 addition dramatically improves the hydrogen desorption kinetics of the MgH2 + 1/4AlH 3 composite. Dehydrogenation-hydrogenation measurements reveal that the hydrogen desorption kinetics of the undoped composite declines with cycle number, whereas the NbF5-doped composite maintains good cycling stability. Microstructure studies indicate that the decline of the kinetics is attributed to the grain growth and particle agglomeration of MgH2 during hydrogen sorption cycling. However, NbF5 addition can suppress this grain growth through the formation of Nb/NbH layers surrounding the particles of MgH2 and acting both as the impediment to grain growth of Mg/MgH2 and as the gateway for hydrogen diffusion. Finally, the role that AlH3 plays in the hydrogen desorption process of the Mg-Al-H composites is discussed. © 2014 American Chemical Society.

Huang H.,State Key Laboratory of Silicon Materials | Zhang L.,State Key Laboratory of Silicon Materials | Wu K.,State Key Laboratory of Silicon Materials | Yu Q.,State Key Laboratory of Silicon Materials | And 6 more authors.
Nanoscale | Year: 2012

A controllable synthesis of various morphologies of CuO nanostructures with tuning by hetero-metal cations has been developed in aqueous solution at room temperature. The morphologies of CuO can be engineered from nanosheets to nanoparticles with different length ratios of the long axis to the short axis. The formation of many metal-ion complexes plays an important role in slowing the release rate of OH- and affects the reaction kinetics further. We found that the effect of hetero-metal cations on the final morphology of the CuO nanostructures was the same as that of the cooling temperature. A series of temperature-controlled experiments demonstrated this. Furthermore, among all the synthesized CuO nanostructures, the fascinating colloidal mesoporous CuO quasi-monocrystalline nanosheets prepared at 25°C with a thickness of ca. 10 nm and large specific surface area of 80.32 m2 g-1 is investigated intensively. These CuO nanosheets demonstrate a superior catalytic activity for CO oxidation, with features of high CO conversion efficiency (47.77 mmolCO g-1 CuO h-1 at 200°C), which is close to that reported for previously investigated supported-CuO catalysts, and a low apparent activation energy Ea (53.3 kJ mol -1). This journal is © 2012 The Royal Society of Chemistry.

Ying P.,State Key Laboratory of Silicon Materials | Liu X.,State Key Laboratory of Silicon Materials | Fu C.,State Key Laboratory of Silicon Materials | Yue X.,State Key Laboratory of Silicon Materials | And 6 more authors.
Chemistry of Materials | Year: 2015

Bi2Te3 based alloys have long been the best and most unique thermoelectric materials for power generation below 550 K. Their substitutes with abundantly available elements are highly desirable due to the scarcity of Te element. In this work the band structure calculation of the α-MgAgSb compound shows a narrow gap characteristic. Highly pure α-MgAgSb is obtained by carefully controlled processing. The samples exhibit an intrinsically low thermal conductivity due to the unique crystal structure. A high zT of ∼1.1 at 525 K is achieved in the In doped α-MgAgSb with the optimal carrier concentration of 8-9 × 1019 cm-3, comparable to that of Bi2Te3 based alloys. Considering the abundantly available constituent elements, the present results demonstrate that α-MgAgSb is a promising candidate for low-temperature (RT-550 K) power generation. © 2015 American Chemical Society.

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