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Liu H.,Wuhan University | Lu Z.,Wuhan University of Science and Technology | Yue L.,Wuhan University | Liu J.,Wuhan University of Science and Technology | And 7 more authors.
Applied Surface Science | Year: 2011

A series of Ti1-xMoxO2-yNy samples were prepared by using sol-gel method and characterized by X-ray diffraction, transmission electron microscopy and UV-vis absorption spectroscopy. All Ti1-xMoxO2-yNy samples are anatase phase. It is found that Mo, N mono-doping can increase visible light absorption, while (Mo + N) co-doping can greatly enhance absorption in whole visible region. Results of our first-principles band structure calculations reveal that (Mo + N)-doping, especially passivated co-doping can increase the up-limit of dopant concentration and create more impurity bands in the band gap of TiO2, which leads to a greatly increase of its visible-light absorption without a decrease of its redox potential. It reveals that (Mo + N) co-doped TiO2 is promising for a photocatalyst with high photocalystic activity under visible light. © 2011 Elsevier B.V. All rights reserved.


Zhang Y.,Wuhan University | Dong F.,Wuhan University | Liu Y.,Wuhan University | Fei C.,Wuhan University | And 7 more authors.
Materials Chemistry and Physics | Year: 2010

Composite ceramics composed of the ferrimagnetic (FM) CoFe 2O4 and the antiferromagnetic (AFM) CoO were synthesized by using the chemical combustion method. The characterization measurements including X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis show that CoFe2O4 nano-particles are embedded in CoO matrix. The magnetic measurements show that the hysteresis loops display a small negative exchange bias field (He) of 106 Oe as the ceramic is cooled to 10 K in an applied field of 10,000 Oe. Furthermore, the magnetic parameters including coercivity, remanence, and He show clear dependence on temperature and the applied magnetic field in the cooling procedures. This exchange bias effect is ascribed to the exchange coupling at the FM/AFM interfaces. © 2010 Elsevier B.V. All rights reserved.


Zhang Y.,Wuhan University | Zhang Y.,Hubei Key Laboratory on Organic and Polymeric Opto electronic Materials | Yang Z.,Wuhan University | Yin D.,Wuhan University | And 7 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2010

Cobalt ferrite nano-particles were prepared using the co-precipitation method followed by annealing treatment. The formation of nano-particles with different composition, microstructure and sizes were confirmed by X-ray diffraction, Raman, thermogravimetric-differential thermal analysis and transmission electron microscope. The magnetic hysteresis loops measured at room temperature revealed smaller effective magnetic anisotropy constant, coercivity and remanence ratio for the samples prepared by adding the NaOH solutions into the mixed solutions of Co2 and Fe3 ions due to the formation of Co3 ions. A small saturation magnetization and an enhanced coercivity were observed for the nano-particles prepared by adding the mixed solutions of Co2 and Fe3 ions into the NaOH solutions, which was related to the formation of outer layers with poor crystallization on the surfaces of the cobalt ferrite nano-crystals. Furthermore, the existence of these outer layers induced the oxidation of Co2 ions in cobalt ferrite nano-crystals at 200 and 300 °C, and led to a large change on the composition and magnetic properties. © 2010 Elsevier B.V. All rights reserved.


Li C.,Wuhan University | Li C.,Hubei Key Laboratory on Organic and Polymeric Opto electronic Materials | Yue L.,Wuhan University | Yue L.,Hubei Key Laboratory on Organic and Polymeric Opto electronic Materials | And 4 more authors.
Materials Science Forum | Year: 2011

Ti1-xFexO2 nanocrystals with x = 0.01, 0.02, 0.03 were prepared via a nonaqueous synthesis route. X-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy characterization confirmed the formation of anatase-phase nanocrystals with the average crystallite sizes of around 10 nm. The lattice constants alternate with the increase of the Fe content and no iron clusters were generated. X-ray photoelectron spectroscopy measurements showed that the substitutional Fe ions present mainly the valence of +3. The magnetic hysteresis loops measured at room temperature (RT) 300K showed that all the doped samples are atypically ferromagnetic, and the coercivity (Hc) of all the Fe-doping samples is around 0.1 T. An interpretation for the intrinsic RT ferromagnetism is put up based on the free carriers and defects induced interaction between Fe 3+ ions. © (2011) Trans Tech Publications.


Liu Y.,Wuhan University | Liu Y.,Hubei Key Laboratory on Organic and Polymeric Opto electronic Materials | Ruan X.,Wuhan University | Zhu B.,Huazhong University of Science and Technology | And 6 more authors.
Journal of the American Ceramic Society | Year: 2011

Magnetoelectric (ME) ceramic composites of CoFe2O4 (CFO) and BaTiO3 (BTO) were prepared by spark plasma sintering. The CFO/BTO ceramic composites with fine microstructures exhibited a significant improvement in the ME voltage coefficient reaching up to 0.18 V/cm Oe. A perfect ME anisotropy was also observed in the CFO/BTO ceramic composites which consisted well with the fitted curve. The enhanced ME voltage coefficient alone with the perfect ME anisotropy in these ceramic composites provides a possibility of developing a magnetic field sensor capable of probing the strength as well as the direction of an unknown magnetic vector. © 2011 The American Ceramic Society.

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