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Dive into the research topics where Haile Lei is active.

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Featured researches published by Haile Lei.


Applied Physics Letters | 2006

In situ organic coating of metal nanoparticles

Haile Lei; Yongjian Tang; Jun Li; Jiangshan Luo; Xibo Li

A physical approach has been developed to in situ coat metal nanoparticles with a nanolayer of organic hydrocarbon film. Copper nanoparticles produced by the flow-levitation method were in situ coated with hydrocarbon films via a dielectric barrier discharge. The hydrocarbon-coated Cu nanoparticles have been analyzed by transmission electron microscopy and infrared absorption to determine the size distribution and dispersion of nanoparticles as well as the chemical components and thickness of the coatings.


Applied Physics Letters | 2007

In situ encapsulation of copper nanoparticles by the dielectric barrier discharge

Haile Lei; Yongjian Tang; Jun Li; Jiangshan Luo; Jingmin Zhang

An experimental investigation is reported on in situ encapsulating copper nanoparticles with a nanolayer of hydrocarbon coating. Copper nanoparticles produced by the flow-levitation method are in situ encapsulated by the dielectric barrier discharge, which generates carbon and hydrogen plasmas for forming a polymerized nanolayer of hydrocarbon at the surface of Cu nanoparticles. The structural, chemical components and optical properties of the encapsulated Cu nanoparticles are characterized by transmission electron microscopy, energy dispersive x-ray spectra, x-ray diffraction, x-ray photoelectron spectra, and UV-visible absorption.


EPL | 2013

Structure-dependent vibrational properties of metallic nanoclusters

Haile Lei; Jun Li; Yuanqiong Liu; Xue Liu

The thermally vibrational properties of icosahedral (ICH) and face-center-cubic (FCC) copper nanoclusters have been compared by carrying out molecular dynamics simulations with a local-environment-dependent tight-binding potential. Although both ICH and FCC copper nanoclusters exhibit a low- and high-energy enhancement of vibrational density of states (VDOS) in comparison with the bulk copper, the vibrational properties of nanoclusters show a strong structure-dependent feature. The different structure is revealed to result in the different atom package, the different lattice shrinkage, the different local pressure, and thus the different VDOS. The different atom package at the surfaces of clusters is responsible for the different low-energy VDOS in a different power-law behavior between the FCC and ICH clusters. The lattice contraction and the internal pressure in the sense of the bulk are unified to explain the enhanced high-energy tail in the VDOS of FCC clusters, but not in the case of ICH clusters.


Applied Physics Letters | 2016

Anomalous specific heats of metallic nanocrystals induced by surface oxidation

Haile Lei; Jiangshan Luo; Jun Li; Fei Dai; Mengsheng Yang; Jicheng Zhang; Jingmin Zhang

Although the low-temperature specific heat in metallic nanocrystals has been extensively demonstrated to be always enhanced due to the surface phonon softening, it is revealed here to be anomalously depressed by the surface oxidation so that the excess specific heat can be either positive or negative as a function of temperature with respect to the counterparts of the bulk crystals. The background mechanism has been theoretically deduced to well explain these experimental phenomena by calculating and comparing the vibrational densities of states (VDOS) of face-centered-cubic-aluminum (fcc-Al) and amorphous-alumina (a-Al2O3) nanoparticles. Different from fcc-Al nanocrystals, both the surface and volume VDOSs g(ω) of a-Al2O3 nanoparticles are scaled as g(ω) ∼ ω1.5 at the low-frequency limit (ω). The effective spatial dimension for the a-Al2O3 surfaces and volume as well as the fcc-Al surfaces is thus assumed to be between 2D and 3D while it is 3D for the fcc-Al volume. The specific heat of a-Al2O3@Al nanopa...


Nuclear Fusion | 2015

Solidification of an atomic fluid inside a spherical shell

Haile Lei; Peng Bi; Yong Yi; Kai Wang; Wei Lin

Extensive molecular dynamics simulations have been applied to investigate the solidification process of atomic fluid confined in a hollow spherical shell for the inertial-confinement-fusion cryotarget. Supercooling is demonstrated to be induced by an ultrarapid cooling due to the formation of the critical nucleus with delays in temperature. Solidification out of the liquid phase is revealed to start at the core/shell interface in the local hexagonal close-packed form. Slow cooling is favourable to improve the inner surface shape, structure, and roughness of the resultant solid inside the shell.


Review of Scientific Instruments | 2009

Preparation and characterization of planar deuterium cryotargets

Haile Lei; Jun Li; Yongjian Tang; Yuanqiong Liu

Using a planar-cryotarget system with the cooling power provided by a Gifford-McMahon cryocooler, the deuterium vapor is condensed to form liquid in a cylinder target cell. The liquefaction processes of deuterium are examined by the Mach-Zehnder interference and infrared spectra. The infrared-absorption spectra of deuterium show a strong absorption peak around 3040 nm at 19 K. The thickness distribution of the condensed deuterium in the target cell is determined from Mach-Zehnder interference images by developing a new mathematical treatment method in combination with the digital-image processing technique.


Review of Scientific Instruments | 2018

The optical lens coupled X-ray in-line phase contrast imaging system for the characterization of low Z materials

Kai Wang; Wei Lin; Fei Dai; Jun Li; Xiaobo Qi; Haile Lei; Yuanqiong Liu

Due to the high spatial resolution and contrast, the optical lens coupled X-ray in-line phase contrast imaging system with the secondary optical magnification is more suitable for the characterization of the low Z materials. The influence of the source to object distance and the object to scintillator distance on the image resolution and contrast is studied experimentally. A phase correlation algorithm is used for the image mosaic of a serial of X-ray phase contrast images acquired with high resolution, the resulting resolution is less than 1.0 μm, and the whole field of view is larger than 1.4 mm. Finally, the geometric morphology and the inner structure of various weakly absorbing samples and the evaporation of water in the plastic micro-shell are in situ characterized by the optical lens coupled X-ray in-line phase contrast imaging system.


Applied Physics Letters | 2018

Surface-initiated phase transition in solid hydrogen under the high-pressure compression

Haile Lei; Wei Lin; Kai Wang; Xibo Li

The large-scale molecular dynamics simulations have been performed to understand the microscopic mechanism governing the phase transition of solid hydrogen under the high-pressure compression. These results demonstrate that the face-centered-cubic-to-hexagonal close-packed phase transition is initiated first at the surfaces at a much lower pressure than in the volume and then extends gradually from the surface to volume in the solid hydrogen. The infrared spectra from the surface are revealed to exhibit a different pressure-dependent feature from those of the volume during the high-pressure compression. It is thus deduced that the weakening intramolecular H-H bonds are always accompanied by hardening surface phonons through strengthening the intermolecular H2-H2 coupling at the surfaces with respect to the counterparts in the volume at high pressures. This is just opposite to the conventional atomic crystals, in which the surface phonons are softening. The high-pressure compression has further been predic...


Ultrasonics Sonochemistry | 2007

Synthesis of tungsten nanoparticles by sonoelectrochemistry

Haile Lei; Yongjian Tang; J.-J. Wei; Jun Li; Xibo Li; H.-L. Shi


Nanoscale | 2015

Surface specific heats of metal nanocrystals at low temperatures

Haile Lei; Jun Li; Jiangshan Luo

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Jun Li

China Academy of Engineering Physics

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Jiangshan Luo

China Academy of Engineering Physics

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Kai Wang

China Academy of Engineering Physics

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Wei Lin

China Academy of Engineering Physics

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Yongjian Tang

China Academy of Engineering Physics

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Kai Du

China Academy of Engineering Physics

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Yuanqiong Liu

China Academy of Engineering Physics

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Fei Dai

China Academy of Engineering Physics

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Jicheng Zhang

China Academy of Engineering Physics

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Xiaobo Qi

China Academy of Engineering Physics

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