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2012年11月15日

【期刊论文】Flower-Like Nickel Nanocrystals: Facile Synthesis, Shape Evolution, and Their Magnetic Properties

王荣明, Pengwei Li, Ning Wang, and Rongming Wang

Eur. J. Inorg. Chem. 2010, 2261–2265,-0001,():

-1年11月30日

摘要

In this paper, flower-, star-, and chain-like hierarchically nanostructured nickel crystals as well as [Ni(N2H4)2]Cl2 nanorods were first synthesized by a simple reduction method. This method is template-free, environmentally benign, and can be carried out at low temperature (60 °C) with high efficiency on a large scale. Investigation of the growth kinetics has proved that the crystal sizes are sensitive to the reaction temperature and reaction time. Various nickel nanostructures can be achieved by the oriented growth of preferred nickel crystal planes. The magnetic properties of the flower-like nickel nanocrystals were also characterized with the results of much enhanced coercivity (Hc) and decreased saturation magnetization (Ms).

Nickel /, Nanostructures /, Solution synthesis /, Magnetic properties

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2009年03月24日

【期刊论文】FePt Icosahedra with Magnetic Cores and Catalytic Shells

王荣明, Rongming Wang, *, †, ‡ Olga Dmitrieva, § Michael Farle, § Gunter Dumpich, § Mehmet Acet, § Sergio Mejia-Rosales, ‖Eduardo Perez-Tijerina, ‖ Miguel Jose Yacaman, and Christian Kisielowski‡

J. Phys. Chem. C 2009, 113, 4395-4400,-0001,():

-1年11月30日

摘要

Surprisingly oxidation resistant icosahedral FePt nanoparticles showing hard-magnetic properties have beenfabricated by an inert-gas condensation method with in-flight annealing. High-resolution transmission electronmicroscopy (HRTEM) images with sub-Angstrom resolution of the nanoparticle have been obtained withfocal series reconstruction, revealing noncrystalline nature of the nanoparticle. Digital dark-field methodcombined with structure reconstruction as well as HRTEM simulations reveal that these nanoparticles haveicosahedral structure with shell periodicity. Localized lattice relaxations have been studied by extracting theposition of individual atomic columns with a precision of about (0.002 nm. The lattice spacings of (111)planes from the surface region to the center of the icosahedra are found to decrease exponentially with shellnumbers. Computational studies and energy-filtered transmission electron microscopy analyses suggest thata Pt-enriched surface layer is energetically favored and that site-specific vacancies are formed at the edges offacettes, which was experimentally observed. The presence of the Pt-enriched shell around an Fe/Pt coreexplains the environmental stability of the magnetic icosahedra and strongly reduces the exchange couplingbetween neighboring particles, thereby possibly providing the highest packing density for future magneticstorage media based on FePt nanoparticles.

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2012年11月15日

【期刊论文】Co2P nanostructures by thermal decomposition: phase formation and magnetic properties

王荣明, Nan Zhang, Aixian Shan, Rongming Wang* and Chinping Chen

CrystEngComm, 2012, 14, 1197–1200,-0001,():

-1年11月30日

摘要

We have synthesized firework-like Co2P nanostructures using a simple and reliable thermal decomposition route with the precursors, triphenyl phosphine and cobalt acetylacetonate, in oleylamine. The optimized reaction temperature is within a narrow window around 280 _C. The nanostructures have a firework-like morphology with nanoneedles growing out of a center core. The nanoneedles are single crystals with clean surfaces, about 200 nm in length, and a tapering tip less than 10 nm in diameter. These nanostructures exhibit Curie–Weiss PM behavior with the effective moment determined as 2.46 mB per FU. Based on the synthesis designs with detailed characterizations on the intermediates at different stages of the phase formation, the growth mechanism of the firework-like Co2P nanostructures is proposed. It is feasible to apply this method of synthesis for some of the other transition-metal phosphide nanostructures.

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2009年11月28日

【期刊论文】Structural stability of icosahedral FePt nanoparticles

王荣明, Rongming Wang, *, a, b Hongzhou Zhang, c Michael Farled and Christian Kisielowskib

Nanoscale, 2009, 1, 276-279,-0001,():

-1年11月30日

摘要

The structural stability of FePt nanoparticles of about 5-6nm diameter was investigated by dynamic high resolution transmission electron microscopy. The FePt icosahedra were very stable under an electron beam flux of~20 A/cm2 at 300 kV. Surface sputtering was suppressed due to the large sputtering threshold energy of a Pt-rich shell. Under a flux of~50 A/cm2, the trapping potential well of the FePt particle on the supporting carbon film was lowered by the magnetic interaction between the electron beam and the particle, which leads to rotational and translational motions of the particle. A large dose of electrons (of~200 A/cm2) initiated melting and recrystallization of the FePt particle. The structure of the FePt nanoparticle, a Pt enriched shell around an Fe/Pt magnetic core, is believed to be responsible for its dynamic behaviour under different beam conditions.

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2011年03月11日

【期刊论文】From ZnS nanobelts to ZnO/ZnS heterostructures: Microscopy analysis and their tunable optical property

王荣明, Wei Liu, Rongming Wang, , a and Ning Wang, a

APPLIED PHYSICS LETTERS 97, 041916 (2010),-0001,():

-1年11月30日

摘要

Ultrathin ZnS nanobelts were assembled by ultrasmall nanocrystals with oriented self assembly, which were then transformed into their single-crystal counterparts by thermal treatment in N2. ZnO/ZnS heterostructures were also obtained at elevated temperature in open air, where well aligned ZnO nanocones were grown along the ZnS nanobelts with a definite rientation relationship described as 0001 ZnS 0001 ZnO and 101¯0 ZnS 101¯0 ZnO. Mixed transition and tuned band gaps of the heterostructure were experimentally observed, which was in good agreement with the theoretical predications and can be interpreted based on the model of a strained staggered type-II band structure. © 2010 American Institute of Physics.

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    北京科技大学,北京

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