共查询到20条相似文献,搜索用时 46 毫秒
1.
Chuen-Jinn Tsai Guan-Yu Lin Chun-Nan Liu Chi-En He Chun-Wan Chen 《Journal of nanoparticle research》2012,14(4):777
A standard rotating drum with a modified sampling train (RD), a vortex shaker (VS), and a SSPD (small-scale powder disperser)
were used to investigate the emission characteristics of nano-powders, including nano-titanium dioxide (nano-TiO2, primary diameter: 21 nm), nano-zinc oxide (nano-ZnO, primary diameter: 30–50 nm), and nano-silicon dioxide (nano-SiO2, primary diameter: 10–30 nm). A TSI SMPS (scanning mobility particle sizer), a TSI APS (aerodynamic particle sizer), and
a MSP MOUDI (micro-orifice uniform deposit impactor) were used to measure the number and mass distributions of generated particles.
Significant differences in specific number and mass concentration or distributions were found among different methods and
nano-powders with the most specific number and mass concentration and the smallest particles being generated by the most energetic
SSPD, followed by VS and RD. Near uni-modal number or mass distributions were observed for the SSPD while bi-modal number
or mass distributions existed for nano-powders except nano-SiO2 which also exhibited bimodal mass distributions. The 30-min average results showed that the mass median aerodynamic diameter
(MMAD) and number median diameter (NMD) of the SSPD ranged 1.1–2.1 μm and 166–261 nm, respectively, for all three nano-powders,
which were smaller than those of the VS (MMAD: 3.3–6.0 μm and NMD: 156–462 nm), and the RD (MMAD: 5.2–11.2 μm and NMD: 198–479 nm).
For nano-particles (electric mobility diameter < 100 nm), specific mass concentrations were nearly negligible for all three
nano-powders and test methods. Specific number concentrations of nano-particles were low for the RD tester but were elevated
when more energetic VS and SSPD testers were used. The quantitative size and concentration data obtained in this study is
useful to elucidate the field emission and personal exposure data in the future provided that particle loss in the generation
system is carefully assessed. 相似文献
2.
Manuj Nahar Ignacio F. Gallardo Kristofer L. Gleason Michael F. Becker John W. Keto Desiderio Kovar 《Journal of nanoparticle research》2011,13(8):3455-3464
A continuous aerosol process has been studied for producing nanoparticles of oxides that were decorated with smaller metallic
nanoparticles and are free of organic stabilizers. To produce the oxide carrier nanoparticles, an aerosol of 3–6 μm oxide
particles was ablated using a pulsed excimer laser. The resulting oxide nanoparticle aerosol was then mixed with 1.5–2.0 μm
metallic particles and this mixed aerosol was exposed to the laser for a second time. The metallic micron-sized particles
were ablated during this second exposure, and the resulting nanoparticles deposited on the surface of the oxide nanoparticles
producing an aerosol of 10–60 nm oxide nanoparticles that were decorated with smaller 1–5 nm metallic nanoparticles. The metal
and oxide nanoparticle sizes were varied by changing the laser fluence and gas type in the aerosol. The flexibility of this
approach was demonstrated by producing metal-decorated oxide nanoparticles using two oxides, SiO2 and TiO2, and two metals, Au and Ag. 相似文献
3.
F. Kokai K. Uchiyama T. Shimazu A. Koshio 《Applied Physics A: Materials Science & Processing》2010,101(3):497-502
Two types of one-dimensional (1D) nanostructures—amorphous silicon carbide (SiC) nanowires, 5–30 nm thick and 0.5–2 μm long,
and carbon nanotubes (CNTs) filled completely with crystalline SiC nanowires, 10–60 nm thick and 2–20 μm long—were synthesized
by the laser ablation of carbon-silicon targets in the presence of high-pressure Ar gas up to 0.9 MPa. All the CNTs checked
by transmission electron microscopy contained SiC, and no unfilled CNTs were produced. We discuss the growth of the two nanostructures
based on the formation of molten Si–C composite particles and their instabilities leading to the precipitation of Si and C. 相似文献
4.
Phase retarders normally show strong wavelength dependence. Achromatic retarders which exhibit nearly identical characteristics
over a wide wavelength spectrum is used in polychromatic light. The present investigation deals with a technique to design
and study the characteristics of an achromatic combination of birefringent plates in 800–2000 nm range. The retarder has been
designed using calcite, crystalline quartz and ADP. The thicknesses of the plates are 19.38 μm, 446.14 μm and 12.57 μm respectively. The new arrangement of three birefringent plates proposed has the promise of producing a zero-order quarter
wave achromatic combination with fairly good accuracy. 相似文献
5.
Transmission electron microscopy (TEM) and electron diffraction (ED) are used to investigate the nanostructures of two ensembles
of Co:CoO core–shell particles. TEM images show that particles of size about 12 nm are almost fully oxidized, while particles
with size about 18 nm have a core–shell structure where a Co core is surrounded by a shell of CoO. ED simulation confirms
that the larger particles have an fcc-structured Co core and a rock-salt CoO shell structure, while the smaller particles
mostly have the rock-salt CoO structure. The core–shell structure is responsible for the unusual magnetic properties of the
Co:CoO nanoclusters, especially the occurrence of inverted hysteresis loops (proteresis), but previous research has been indirect,
largely based on magnetic measurements and on a cross-comparison with granular materials. Our measurements show that the structures
have ferromagnetic fcc Co cores of varying sizes down to 1 nm which are surrounded by antiferromagnetic rock-salt CoO shells.
The core radii obtained from the TEM pictures are used to estimate the exchange interactions responsible for proteresis and
to pinpoint the core-size window in which proteresis occurs. 相似文献
6.
J. A. González J. P. Andrés J. A. De Toro P. Mu?iz T. Mu?oz O. Crisan C. Binns J. M. Riveiro 《Journal of nanoparticle research》2009,11(8):2105-2111
The technique of gas-phase aggregation has been used to prepare partially oxidized Co nanoparticles films by allowing a controlled
flow of oxygen gas into the aggregation zone. This method differs from those previously reported, that is, the passivation
of a beam of preformed particles in a secondary chamber and the conventional (low Ar pressure) reactive sputtering of Co to
produce Co–CoO composite films. Transmission electron microscopy shows that the mean size of the particles is about 6 nm.
For sufficiently high oxygen pressures, the nanoparticles films become super-paramagnetic at room temperature. X-ray diffraction
patterns display reflections corresponding to fcc Co and fcc CoO phases, with an increasing dominance of the latter upon increasing
the oxygen pressure in the aggregation zone, which is consistent with the observed reduction in saturation magnetization.
The cluster films assembled with particles grown under oxygen in the condensation zone exhibit exchange-bias fields (about
8 kOe at 20 K) systematically higher than those measured for Co–CoO core-shell nanoparticles prepared by oxidizing preformed
particles in the deposition chamber, which we attribute, in the light of results from annealing experiments, to a higher ferromagnetic–antiferromagnetic
(Co–CoO) interface density. 相似文献
7.
C. Y. Li Q. J. Peng B. S. Wang Y. Bo D. F. Cui Z. Y. Xu X. Q. Feng Y. B. Pan 《Applied physics. B, Lasers and optics》2011,103(2):285-289
We demonstrate for the first time a diode-side-pumped quasi-continuous-wave (QCW) operation of a 1123 nm Nd:YAG ceramic laser.
The single 1123 nm wavelength is acquired through precise coating. With a pump power of 1000 W, an output power of 247 W is
obtained, corresponding to an optical–optical conversion efficiency of 24.7%. At the maximal output power, the pulse repetition
rate and pulse width are measured to be 1.1 kHz and 180 μs, respectively. The numerical simulations for wavelength selectivity
from 1112, 1116 and 1123 nm are discussed in detail. 相似文献
8.
Domínguez-García P Pastor JM Rubio MA 《The European physical journal. E, Soft matter》2011,34(4):36-7
This article presents results on the aggregation and disaggregation kinetics on a 1μm diameter charged superparamagnetic particles
dispersed in water under a constant uniaxial magnetic field in experiments with salt (KCl) added to the suspension in order
to observe the behaviour of the system when the electrical properties of the particles have been screened. These particles
have an electric charge and are confined between two separated 100μm thick quartz windows, and sediment near the charged bottom
wall. The electrostatic interactions that take place in this experimental setup may affect the micro-structure and colloidal
stability of the suspension and thus, the dynamics of aggregation and disaggregation. 相似文献
9.
Two simple, accurate and highly sensitive spectrofluorometric methods were developed for the determination of ethamsylate
(ETM). Method I is based on measuring the native fluorescence of ethamsylate in water at 354 nm after excitation at 302 nm.
The calibration plot was rectilinear over the range of 0.05–1 μg/mL for ETM with limits of detection and quantitation of 7.9
and 26 ng/mL, respectively. Method II involved synchronous and first derivative synchronous fluorometric methods for the simultaneous
determination of ethamsylate (ETM) and hydroquinone (HQ) which is considered as an impurity and/or acidic degradation product.
The synchronous fluorescence of both the drug and its impurity were measured in methanol at Δ λ of 40 nm. The peak amplitudes
(1D) were estimated at 293.85 or 334.17 nm for ETM and at 309.05 nm for HQ. Good linearity was obtained for ETM over the ranges
0.1–1.4 μg/mL and 0.1–1.0 μg/mL at 293.85 and 334.17 nm, respectively. For HQ, the calibration plot was rectilinear over the
range of 0.01–0.14 μg/mL at 309.05 nm. Limits of detection were 20, 2.01 ng/mL and limits of quantitation were 60, 6.7 ng/mL
for ETM and HQ by method II, respectively. Both methods were successfully applied to commercial ampoules and tablets. The
results were in good agreement with those obtained by the reference method. Method I was utilized to study the stability of
ETM and its degradation kinetics using peroxide. The apparent first-order rate constant, half-life times and activation energy
of the degradation process were calculated. Method I was further extended to the in-vitro and in-vivo determination of ETM
in spiked and real plasma samples. The mean% recoveries were 99.57 ± 3.85 and 89.39 ± 5.93 for spiked and real human plasma,
respectively. 相似文献
10.
F. Kokai T. Shimazu K. Adachi A. Koshio Y. Takahashi 《Applied Physics A: Materials Science & Processing》2009,97(1):55-62
Carbon nanotubes (CNTs) filled completely with polycrystalline Cu nanowires were synthesized by laser vaporization of Cu and
graphite under high-pressure Ar gas atmosphere. Depending on the Ar gas pressure (0.1–0.9 MPa) and the Cu content (1–40 at.%)
in graphite targets for laser vaporization, various products with different morphologies were observed by scanning and transmission
electron microscopy. The ratios of the Cu-filled CNTs and carbon nanocapsules particularly increased as Ar gas pressure was
increased. The maximum ∼60% fraction of Cu-filled CNTs with outer diameter of 10–50 nm and length of 0.3–3 μm was achieved
at 0.9 MPa from graphite containing 20 at.% Cu. Most of the encapsulated Cu-nanowires were surrounded by single, double, or
triple graphitic layers. Although the yield of the Cu-filled CNTs was also dependent on the Cu content in the graphite targets,
no unfilled CNTs were produced even for low Cu content. The growth of Cu-filled CNTs is explained by the formation of molten
Cu–C composite particles with an unusually C-rich composition in a space confined by high-pressure Ar gas, followed by precipitating
Cu and C from the particles and subjecting them to phase separation. 相似文献
11.
V. Martina M. F. De Riccardis D. Carbone P. Rotolo B. Bozzini C. Mele 《Journal of nanoparticle research》2011,13(11):6035-6047
Composite films of polyaniline (PANI) and carbon nanotubes (CNTs) were prepared by electrochemical co-deposition from solutions
of the corresponding monomer containing two different kinds of CNTs. The first type was commercial (diameter = 110–170 nm,
length = 5–9 μm) and the second one was home-made (diameter = 30 nm, length = 5–20 μm). The electrochemical behaviour of PANI–CNTs
composite films was investigated with Cyclic Voltammetry and the surface morphology was analysed by Scanning Electron Microscopy
(SEM). Subtractively Normalised Interfacial FT-IR procedure was used to investigate the presence of corrosion products when
the films were deposited on stainless steel substrates and exposed to acid environment. The spectral investigations were utilised
to understand the role of composite films in the corrosion protection and to discriminate the best performance CNTs. 相似文献
12.
Zinc oxide (ZnO) and Cu-doped ZnO (CZO) thin films were prepared on borosilicate glass substrates by spray pyrolysis technique.
The X-ray diffraction study revealed that Cu doping caused a reduction in crystallite size. AFM study showed an increase in
roughness with doping. This is attributed to the aggregation of particles to form clusters. From transmission electron microscopy
analysis, the particle size is measured to be in the range 30–65 nm (average particle size 48 nm) for undoped ZnO, whereas
it is in the range 24–56 nm (average particle size 40 nm) for CZO film. The electrical resistivity of the thin films was investigated
in the presence of air as well as N2 mixed air at different temperatures in the range 30–270 °C. The change in resistivity properties was explained on the basis
of conduction phenomena within the grain along with the grain boundaries as well as Cu- and N2-induced defect states. The thermal activation energy of ZnO was found to be in the range 0.04–0.7 eV and dependent on Cu
doping and N2 level in air. 相似文献
13.
A simple ultrasound assisted precipitation method with addition of glycosaminoglycans (GAGs) is proposed to prepare stable
hydroxyapatite (HAP) nanoparticles suspension from the mixture of Ca(H2PO4)2 solution and Ca(OH)2 solution. The product was characterized by XRD, FT-IR, TEM, HRTEM and particle size, and zeta potential analyzer. TEM observation
shows that the suspension is composed of 10–20 nm × 20–50 nm short rod-like and 10–30 nm similar spherical HAP nanoparticles.
The number-averaged particle size of stable suspension is about 30 nm between 11.6 and 110.5 nm and the zeta potential is
−60.9 mV. The increase of stability of HAP nanoparticles suspension mainly depends on the electrostatic effect and steric
effect of GAGs. The HAP nanoparticles can be easily transported into the cancer cells and exhibit good potential as gene or
drug carrier system. 相似文献
14.
Controlled plasmon coupling is observed in nanoparticle assemblies composed of 20 nm silver ‘satellite’ nanoparticles tethered
by reconfigurable duplex DNA linkers to a 50 nm gold ‘core’ particle. The assemblies incorporate silver nanoparticle–oligonucleotide
conjugates prepared using a new conjugation method in which the recognition strand is anchored by a 10 base pair, double strand
spacer that presents adjacent 3’- and 5’-thiols to the silver surface. Reconfiguration of the DNA linkers from a compact to
an extended state results in decreased core–satellite coupling and a blue-shift in the gold core plasmon resonance. The structural
basis for the observed resonance modulation is investigated through simulation of the scattering spectra of binary assemblies
with various core–satellite separations. Additional simulations of core–satellite assemblies composed of gold satellite particles
bound to silver cores and of assemblies composed entirely of silver particles are used to clarify the dependence of the coupling
response on the composition of the components and their distribution within the assembly.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
15.
Optical properties of spherical gold particles with diameters of 150–650 nm (mesoparticles) are studied by reflectance spectroscopy.
Particles are fabricated by laser-induced transfer of metallic droplets onto metal and dielectric substrates. Contributions
of higher multipoles (beyond the quadrupole) in the scattering spectra of individual spherical particles are experimentally
observed. These observations are performed for particles in a homogeneous environment and for particles located in air on
a metal surface. Good agreement between calculations on the basis of Mie theory and experimental results obtained in homogeneous
environment is demonstrated. Multipole resonance features in the experimental reflection spectra of particles located on a
gold substrate, in the wavelength range of 500–1000 nm, are discussed and theoretically analyzed on the basis of finite-difference
time-domain simulations. High-resolution Raman images of mesoparticle pairs at different polarizations of light are also presented. 相似文献
16.
The double perovskite Sr2NiMoO6 powders and ceramics were prepared by two different (conventional and precursor) solid-state reaction methods. The phase
structure was characterized by XRD and TEM techniques. It has been indicated that single-phase perovskite powders were obtained
when calcined in air at 1300°C. However, nano-particles of the size 30–60 nm have been found in powders prepared with the
precursor method, while those from the conventional route exhibit large irregular shaped particles with aggregation. The dielectric
properties (ε
r
and tanδ) were also examined in the sintered ceramics. The results showed the transition point at 280°C for conventional route, while
no clear phase change was observed in ceramics from the precursor route. These observations clearly indicate that the different
starting processes affected the phase formation behavior and the electrical properties of Sr2NiMoO6 ceramics. 相似文献
17.
L. Cabaret 《Applied physics. B, Lasers and optics》2009,94(1):71-79
An efficient pumping scheme for a quasi-continuous-wave diode-pumped Yb:YAG laser is presented. Single-mode operation and
fine wavelength tuning are assured by the use of a rubidium titanyl phosphate (RTP) Fabry–Perot étalon. When frequency doubled,
the 200–420 μs duration pulses reach a peak power of 70 W at a wavelength of 515 nm. The TEM00 beam is nearly diffraction limited with an M
2 factor of 1.06 at full power. The tuning range spans from 512 to 520 nm and the pulse to pulse frequency stability is on
the order of ±10 MHz.
Laboratoire Aimé Cotton is associated with Université Paris Sud 11. 相似文献
18.
Albert?Mihranyan Mortadha?Muhel Maria?Str?mme 《Applied Physics A: Materials Science & Processing》2009,94(2):299-305
The dissolution process of sparingly soluble CaCO3 microparticles and how the fractal surface dimension of the particles changes during dissolution is analyzed. The particles
and the dissolution process are studied using scanning electron microscopy, X-ray diffraction, nitrogen adsorption, laser
diffraction and conductance measurements. Ball milling of the particles is shown to maintain the particle crystallinity, and
to introduce an increased fractal surface dimension in the 1–10 μm size range. Dissolution is found to increase the surface
dimension of initially smooth particles and to maintain the fractal surface roughness of milled particles. The dissolution
process increases the relative number of small particles (50 nm–1 μm) whereas the larger ones decrease in size. The solubility
of the milled fractal particles was ∼1.8 times higher than that for the initially smooth ones. The presented findings show
that developing methods for increasing the fractal surface roughness of particles should be of interest for improving the
solubility of poorly soluble drug candidates. 相似文献
19.
A. Eremin E. Gurentsov E. Popova K. Priemchenko 《Applied physics. B, Lasers and optics》2011,104(2):285-295
The evidence of the change of the complex refractive index function E(m) of carbon and iron nanoparticles as a function of their size was found from two-color time-resolved laser-induced incandescence
(TiRe-LII) measurements. Growing carbon particles were observed from acetylene pyrolysis behind a shock wave and iron particles
were synthesized by pulse Kr–F excimer laser photo-dissociation of Fe(CO)5. The magnitudes of refractive index function were found through the fitting of two independently measured values of particle
heat up temperature, determined by two-color pyrometry and from the known energy of the laser pulse and the E(m) variation. Small carbon particles of about 1–14 nm in diameter had a low value of E(m)∼0.05–0.07, which tends to increase up to a value of 0.2–0.25 during particle growth up to 20 nm. Similar behavior for iron
particles resulted in E(m) rise from ∼0.1 for particles 1–3 nm in diameter up to ∼0.2 for particles >12 nm in diameter. 相似文献
20.
Dung T. Tran Ian P. Jones Jon A. Preece Roy L. Johnston Coenraad R. van den Brom 《Journal of nanoparticle research》2011,13(9):4229-4237
Dodecanethiol-capped Cu–Au nanoparticles, synthesized via a successive two-phase (water/toluene) and galvanic-exchange procedure,
were characterized using transmission electron microscopy (TEM). The size range of the particles is around 1–7 nm. Electron-induced
morphological evolution was observed under high resolution (HR) TEM. Cuboctahedral morphology was found to be thermodynamically
stable. Electron-induced aggregation of two particles was also observed. Chemical ordering of cuboctahedral particles was
studied by atomic-resolution high angle annular dark field (HAADF) imaging in scanning TEM (STEM) mode and energy dispersive
X-ray (EDX) element mapping using a silicon drift detector (SDD). The particles were found to be Cu–Au mixed, and to be stable
in air. Surface plasmon resonance (SPR), which is dependent on local structure and morphology, was investigated by electron
energy loss spectroscopy (EELS). 相似文献