Papers by Author: J. Ding

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Authors: J.B. Yi, J. Ding
Abstract: Co/CoO hybrid films are prepared by annealing Co films with various ratio of oxygen of O2/Ar mixture. The nanocomposite film shows a relatively large exchange bias (5.32 kOe) and coercivity (HC-: 6.17 kOe) taken at 80 K when formed by post annealing at 473 K under 3% O2 for 1h. Both are much larger than that of Co/CoO nanocomposite by reactive sputtering with an oxygen partial pressure. Investigation shows that the formation of interface by post annealing is of importance for the large exchange bias and enhanced coercivity. The surface CoO, grain size of CoO and composition may also contribute to magnetic properties of the post annealing film.
Authors: H. Pan, J.B. Yi, B.H. Liu, S. Thongmee, J. Ding, Yuan Ping Feng, Jian Yi Lin
Abstract: We have fabricated metal/alumina hybrid materials by electrodepositon of metal nanowires into nanopores of anodic aluminum oxide templates. Single crystalline Ni and Co nanowires have been successfully fabricated. Structural characterization (XRD and HRTEM) shows that the single crystalline Ni nanowire has a preferred orientation along (220) direction. The preferred orientation of Co nanowire is along (100). These single crystalline Ni and Co nanowires have exhibited excellent magnetic properties. Their alloy nanowires have exhibited a large shift in hysteresis, probably due to the surface oxidation and exchange bias effect.
Authors: J. Ding, Yuan Yuan Li, X.Z. Wang
Authors: B.H. Liu, J. Ding, Z.L. Dong, Zeng Yong Zhong, Jian Yi Lin, T. White
Abstract: Mechanochemical process was employed to prepare Fe/MgO and Fe/NaCl nanocomposites. The carbon nanostructures (nanotubes and carbon-encapsulated Fe nanoparticles) were successfully synthesized using two nanocomposites as the catalyst. Our wok revealed that the morphology of Fe nanoparticles in the Fe/MgO nanocomposites depended on the distribution and particle size of iron oxides in the precursors. The size of Fe nanoparticles greatly affected their catalytic properties and the morphologies of carbon nanotubes. The successful carbon encapsulation of Fe nanoparticles was achieved by using the mechanochemically derived Fe/NaCl catalyst.
Authors: A.V. Nurmikko, J. Ding, R.L. Gunshor, J. Han
Authors: L.H. Van, M.H. Hong, J. Ding
Abstract: Nano-hybrid CoO/ZnO and CoO/TiO2 thin films are interesting magnetic semiconductors, which may be the potential candidates in spintronic devices. We report a study of the morphology and properties of highly crystalline and textured CoO/ZnO and CoO/TiO2 nanohybrid thin films grown on Al2O3 (006) substrates by pulse laser deposition (PLD). The structural and magnetic properties of the deposited films were analyzed by AFM, SEM, XRD and AGM. Highly crystalline CoO/ZnO and CoO/TiO2 films were formed on single crystal Al2O3 substrates at 1x10-4 Torr oxygen partial pressure. It has been found that with a fine tune of the deposition conditions and heat treatment, the films can have highly crystalline ZnO zincite hexagonal and TiO2 rutile structure. The XRD rocking curves showed that the thin films grown are highly textured with FWHM of 0.251o for ZnO zincite and 0.065o for TiO2 rutile respectively. Both zincite and rutile exhibited properties of ferromagnetics above room temperature. The AGM results show that the saturation magnetization (Ms) is strongly dependent on substrate temperature.
Authors: L. Si, J. Ding, Yuan Yuan Li, X.Z. Wang
Authors: B.H. Liu, J. Ding, Z.L. Dong, Zeng Yong Zhong, Jian Yi Lin, T.J. White
Abstract: Mechanical milling was employed to prepare the nanocomposite precursors for the catalytic growth of carbon nanostructures. For alumina substrates, our study showed that mechanical-millingderived catalyst precursors possessed high hydrogen reduction efficiency that in turn enabled the high yield of CNTs. The alloying effects presented by the mechanical milling could accelerate the substitutional reactions between the parent oxides and thus the quality of CNTs was apparently improved. In addition, by using water-soluble substrates such as NaCl, we realized large-scale formation of carbon-encapsulated metal nanoparticles (CEMNs) that can be completely separated by a simple washing process. It was found that the morphologies of as-obtained carbon nanostructures were strongly dependent on the substrate effects. By selecting different salt substrates, we can strategically change the morphologies of the as-obtained nanostructures, from CNTs to CEMNs and the intermediate state between CNTs and CEMNs, such as quasi-nanocages.
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