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71.
Cooling rate effects on structure and thermodynamics of amorphous nanoparticles were studied in a spherical model using Molecular Dynamics (MD) method. The good equilibrium melts are cooling down by three different cooling rates in order to observe the cooling rate effects. We find that cooling rate effects on thermodynamic quantities such as potential energy and surface energy are more pronounced than those for static quantities. Microstructure of amorphous nanoparticles is analyzed via radial distribution function (RDF) and coordination number distributions. Relatively weak cooling rate effects on such quantities are found. Microstructure of surface and core of amorphous nanoparticles are analyzed. 相似文献
72.
In this study, we investigated the surface properties of diamond-like carbon (DLC) films for biomedical applications through plasma etching treatment using oxygen (O2) and hydrogen (H2) gas. The synthesis and post-plasma etching treatment of DLC films were carried out by 13.56 MHz RF plasma enhanced chemical vapor deposition (PECVD) system. In order to characterize the surface of DLC films, they were etched to a thickness of approximately 100 nm and were compared with an as-deposited DLC film. We obtained the optimum condition through power variation, at which the etching rate by H2 and O2 was 30 and 80 nm/min, respectively. The structural and chemical properties of these thin films after the plasma etching treatment were evaluated by Raman and Fourier transform infrared (FT-IR) spectroscopy. In the case of as-deposited and H2 plasma etching-treated DLC film, the contact angle was 86.4° and 83.7°, respectively, whereas it was reduced to 35.5° in the etching-treated DLC film in O2 plasma. The surface roughness of plasma etching-treated DLC with H2 or O2 was maintained smooth at 0.1 nm. These results indicated that the surface of the etching-treated DLC film in O2 plasma was hydrophilic as well as smooth. 相似文献
73.
A new class of lattice Bhatnagar-Gross-Krook (BGK) models is proposed, based on the Lie symmetry preservation ansatz for the local equilibria. This class extends the range of stability of previous models, especially for thermohydrodynamic lattice BGK schemes. 相似文献
74.
Stable colloidal systems composed of a double surfactant water-based magnetic fluid mixed with a cationic isotropic micellar solution of cetyletrymethyleammonium bromide (CTABr) are prepared for different concentrations of magnetic fluid. The structural integrity between nanomagnetic particles of magnetic fluids and soft micelles is investigated using the magneto-optical techniques like magnetic birefringence, transmission and relaxation measurements. Magneto-optically induced retardation and relaxation measurement indicates the existence of magnetically induced interactions in this mixed system. Similar behaviour is also observed in small angle neutron scattering experiments. 相似文献
75.
V. V. Hoang H. Zung N. H.B. Trong 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):515-524
Structural properties of amorphous TiO2 spherical nanoparticles have
been studied in models with different sizes of 2 nm, 3 nm, 4 nm and 5 nm under
non-periodic boundary conditions. We use the pairwise interatomic potentials
proposed by Matsui and Akaogi. Models have been obtained by cooling from the
melt via molecular dynamics (MD) simulation. Structural properties of an
amorphous nanoparticle obtained at 350 K have been analyzed in detail
through the partial radial distribution functions (PRDFs), coordination
number distributions, bond-angle distributions and interatomic distances.
Moreover, we show the radial density profile in a nanoparticle. Calculations
show that size effects on structure of a model are significant and that if
the size is larger than 3 nm, amorphous TiO2 nanoparticles have a
distorted octahedral network structure with the mean coordination number
ZTi-O ≈6.0 and ZO-Ti ≈3.0 like those observed in the
bulk. Surface structure and surface energy of nanoparticles have been
obtained and presented. 相似文献
76.
Upconversion luminescence has been studied for Er3+ in a germanate-oxyfluoride and a tellurium-germanate-oxyfluoride transparent glass-ceramic using 800 nm excitation. Significantly increased upconversion luminescence was observed from transparent glass-ceramics compared with that from their corresponding as-prepared glasses. In addition to a strong green emission centered at 545 nm from 4S3/2 state and a weaker red emission centered at 662 nm from 4F9/2 state generally seen from Er3+-doped glasses, a violet emission centered at 410 nm from 2H9/2 state and a near-ultra-violet emission centered at 379 nm from 4G11/2 state were also observed from transparent glass-ceramics. The upconversion luminescence of Er3+ ions in transparent glass-ceramics revealed sharp Stark-splitting peaks generally seen in a crystal host. The increased upconversion efficiency is attributed to the decreased effective phonon energy and the increased energy transfer between excited ions when Er3+ ions were incorporated into the precipitated β-PbF2 nanocrystals. 相似文献
77.
Ordered 20 nm Fe-Pd nanowire arrays with different compositions have been fabricated by alternating current electrodeposition into nanoporous anodic alumina. The structural and magnetic properties of the arrays were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). When Fe content is lower than 46 at.%, Fe-Pd alloy phase with fcc structure forms for the as-deposited. After annealing the alloy structure remains unchanged, but the coercivity (HC) and squareness (Mr/Ms) increase. When Fe content is up to 60 at.%, α-Fe and Fe-Pd phases with fcc structure coexist for the as-deposited. After annealing the nanowires consist of a uniform Fe-Pd phase with fcc structure and the coercivity and squareness decrease. The change of the structure and magnetic properties with the alloy composition and annealing are explained reasonably. 相似文献
78.
Er3+ doped multicomponent fluoride based glass was prepared. These precursor fluoride glass samples were then heated using different schedules. Crystalline phase particles were successfully precipitated in the multicomponent fluoride glass samples after heat treatment. The influence of heat treatment on the spectroscopic properties of Er3+ in multicomponent fluoride based glass samples were discussed. Small changes of the Judd-Ofelt parameters Ωi (i = 2, 4, 6) were found in multicomponent fluoride glass samples before and after heat treatment compared to oxyfluoride telluride glass. Preparation conditions used to produce transparent multicomponent fluoride glass ceramics doped with rare-earth ions are discussed. 相似文献
79.
The relationship between the luminescence at 1.9 eV and the absorption bands at 2.0 eV and at 4.8 eV were investigated in a wide variety of synthetic silica samples exposed to different γ- and β-ray irradiation doses. We found that the intensities of these optical bands are linearly correlated in agreement with a model in which they are assigned to a single defect. This finding allows the determination of spectroscopic parameters related to the optical transitions efficiencies. In this case the absorption oscillator strength at 4.8 eV is ∼200 times higher than that at 2.0 eV; while the 1.9 eV luminescence quantum yield under 4.8 eV excitation is lower (by a factor ∼3) than that under 2.0 eV excitation. These results are consistent with the energetic level scheme proposed in the literature for the non-bridging oxygen hole center. Moreover, they account for the excitation → luminescence pathways occurring after UV and visible absorption. 相似文献
80.
Ordered Co-Pb nanowire arrays embedded in anodic alumina template were successfully fabricated by electrodeposition. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) observations revealed that the Co-Pb nanowires were polycrystalline with uniform diameters around 20 nm and lengths up to several micrometers. Magnetic measurements showed that the coercivity and remanence of the as-deposited Co-Pb nanowires decreased with the increase of the Pb content. After annealing the Co-Pb nanowires present higher coercivities (2.4-2.5 kOe) than that of pure Co nanowires (2.1 kOe) and the dependence of coercivity and remanence on the Pb content is inconspicuous. A phase separation of Co and Pb occurred after annealing. The familiar pinning model was employed to explain the above experimental results. 相似文献