共查询到20条相似文献,搜索用时 171 毫秒
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Synthesis and characterization of CdS nanoparticles embedded in a polymethylmethacrylate matrix 总被引:3,自引:0,他引:3
Pedone L Caponetti E Leone M Militello V Pantò V Polizzi S Saladino ML 《Journal of colloid and interface science》2005,284(2):495-500
CdS nanopowder capped with sodium bis(2-ethylhexyl)sulfosuccinate was synthesized by using water-in-oil microemulsions. The CdS nanoparticles of about 5 nm obtained were embedded in polymethylmethacrylate matrix by a photocuring process. The transparent yellow solid compound was characterized by optical absorption and emission spectroscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The properties of this compound were compared with those of the nanopowder dispersed in heptane and in methylmethacrylate. The results obtained indicate that the nanoparticles are homogeneously dispersed in the matrix and do not change in size during the embedding process. Even if the surface slightly changes its luminescence properties, as a consequence of the different new chemical environment, the final product seems to be suitable for practical applications. 相似文献
12.
M. I. Alymov N. M. Rubtsov B. S. Seplyarskii V. A. Zelenskii A. B. Ankudinov I. D. Kovalev R. A. Kochetkov A. S. Shchukin 《Doklady Chemistry》2017,477(1):261-264
It was experimentally shown that, at a temperature below–25°C, an iron nanopowder produced by a chemical metallurgical method does not ignite spontaneously in dry air. At this temperature, the nanopowder is passivated by atmospheric oxygen so that it neither is oxidized, nor self-ignites in air at room temperature. Thus, the proposed nanopowder production method ensures an acceptable safety level of handling nanopowders while preserving their unique properties. 相似文献
13.
14.
Effects of monomer (AM) concentration, monomer/crosslinker (AM/MBAM) ratio and salt concentration on the thermal behavior
of precursor gel and the properties of BeO nanopowder synthesized by polyacrylamide gel method were investigated. The decomposition
process of precursor gel was also studied. The decomposition process of precursor gel is that, first, the extraction of free
and crystallized water, and then the thermal degradation of polymeric network under temperature higher than 600 °C, final,
the decomposition of nanoscale beryllium sulfate to BeO nanopowder. As the monomer concentration increases, the calcination
temperature of precursor gel decreases due to more compact network structure of gel and thus smaller size of salt in nanocaves
in gel. The average particle size of nanopowder reduces correspondingly. The AM/MBAM ratio also has significant effect on
the thermal behavior of precursor gel and the average particle size of product. When the ratio of AM to MBAM is 6, the calcination
temperature of precursor gel is the lowest, the average particle size of powders is the smallest, because the network structures
of gel is the tightest and thus the sizes of salts in precursor gels are the smallest. As the AM/MBAM ratio deviates from
this value, the network structures of gel becomes looser and thus the size of salt in precursor gel becomes larger, so the
calcination temperature increases and the average particle size of powders becomes larger certainly. For the same reason,
both the calcination temperature and the average particle size of powders increases with increasing the salt concentration.
The synthesis conditions have no effect on the particle size distribution of the final product due to the natural random distribution
of porosity in gel. 相似文献
15.
Nanostructured silver sulfide powder with an average particle size of about 45 nm, an acanthite α-Ag2S monoclinic structure (space group P21/c), and nonstoichiometric composition Ag1.93S has been synthesized by the chemical deposition method. The silver sulfide nanopowder has been studied by Raman spectroscopy. According to the Raman scattering data, heating the nanopowder with high-power laser radiation in air leads to photoinduced decomposition of the Ag1.93S nanopowder to give silver metal. The Raman spectrum of the silver sulfide nanopowder shows a series of bands in the low-frequency range from 90 to 260 cm–1 associated with vibrations of silver atoms, Ag–S bonds, and symmetric Ag–S–Ag longitudinal modes. Raman spectroscopy confirmed an acanthite monoclinic structure of synthesized silver sulfide nanopowder. 相似文献
16.
Rondinone AJ Pawel M Travaglini D Mahurin S Dai S 《Journal of colloid and interface science》2007,306(2):281-284
CdWO4 has only previously been reported in the monoclinic, or wolframite, phase. Here we report the first metastable, tetragonal or scheelite, CdWO4 nanopowder. The tetragonal CdWO4 was synthesized by a propylene glycol solvothermal method. The scheelite phase is stabilized by a combination of high surface area and surface complexation by the propylene glycol. The CdWO4 is stable at 1 bar to 300 degrees C, and converts back to the monoclinic wolframite phase between 300 and 500 degrees C. The nanopowder exhibits cubic morphology and the average particle size of the nanopowder is around 50 nm. 相似文献
17.
《Electrochemistry communications》2007,9(10):2514-2518
In the present work, a more sensitive and conveniently usable electrode sensor for a trace analysis of heavy metal was developed by using Bi nanopowder synthesized by levitational gas condensation (LGC) method. It was observed from the TEM image that the Bi nanopowder is spherical in shape with a size of nearly 50 nm. The XRD pattern revealed intense peaks which can be indexed as a rhombohedral structure of Bi without any other diffraction peaks corresponding to an oxide or an impurity. This indicates that the resulting nanopowder synthesized by the LGC method is a highly crystallized Bi with a high purity. The square wave anodic stripping voltammograms (SWASV), experimentally measured for the Bi nanopowder electrode, showed well-defined and highly reproducible electrochemical responses relating to the stripping of Cd and Pb. The detection limit of the electrode was estimated to be 0.15 μg/l and 0.07 μg/l for Cd and Zn, respectively, on the basis of the signal-to-noise characteristics (S/N = 3) of the response for the 1.0 μg/l solution under a 10 min accumulation. 相似文献
18.
The main objective of this research is to prepare nickel nanoparticles with more porous structure by the pulsed current electrochemical
method. A nickel optimized nanopowder was synthesized by using nickel chloride (0.005 M) as precursor, silver nitrate as a
nucleation agent (at 0.5% mole of nickel salt in the starting solution), polyvinyl pyrrolidone (PVP) as structure director
(with PVP/Ni = 1.7 g/g), ammonia (2 M), and hydrazine as reduction agent (with Hydrazine/Ni = 16 g/g) by pulsed current of
58 mA cm−2 with a frequency of 12 Hz. The morphology and particle size of each synthesized sample was studied by scanning electron microscopy
(SEM). The obtained results showed that temperature has no considerable effect on the morphology and particle size of nickel
nanopowder. The nickel nanopowder synthesized in optimum conditions has excellent uniform and a more porous structure including
nanoclusters with a particle size of approximately 10–20 nm. The obtained results indicate that the pulsed current electrochemical
method can be used as a confident and controllable method for the preparation of nickel nanoparticles. Optimized nickel nanoclusters
were used as catalyst for hydrogen and oxygen revolutions. Cyclic Voltammetry results showed that the synthesized nanoclusters
can facilitate hydrogen reduction and increase hydrogen and oxygen revolution rates. 相似文献
19.
SmAlO3 nanopowder synthesized by a citrate precursor method using citric acid as a chelating agent and ethylene glycol as an esterifying
agent was reported in this paper. The phase purity of the as-prepared powder was examined using thermogravimetry (TG) analysis
and differential scanning calorimetry (DSC) analysis, Fourier transform infrared spectroscopy (FTIR). The X-ray diffraction
(XRD) studies showed that pure SmAlO3 phase with orthorhombic perovskite structure could be synthesized at 800 °C for 2 h without any detectable intermediate phase.
The average particle size calculated from transmission electron microscopy (TEM) investigation for the powder synthesized
at 900 °C was as low as 45 nm. The nanopowder was sintered to a density of 97% of the theoretical density at 1,550 °C for
2 h and the bulk ceramics exhibited excellent microwave dielectric properties as follows: a dielectric constant of 20.54,
a quality factor of 75,380 GHz and a temperature coefficient of resonate frequency of −69.2 ppm/K. 相似文献
20.
Effect of particle size distribution on sensor characteristics of nano‐Bi fixed electrode has been investigated using square wave anodic stripping voltammetry. Bi nanopowders with various particle size distributions were synthesized by gas condensation (GC) method with the change of chamber pressure. As the chamber pressure decreased, the size of Bi nanopowder became smaller with narrower distribution due to a shorter residence time of Bi vapor. The square wave anodic stripping voltammograms (SWASV) showed well‐defined and highly reproducible peaks at ?1.2 V, ?0.8 V and ?0.6 V (vs. SCE), which are closely related to the oxidation of Zn, Cd and Pb, respectively. The sensitivity and detection limit of the nano‐Bi fixed electrode were quantitatively estimated from the analyses of SWASV. From the results, it is concluded that as the size of Bi nanopowder becomes smaller with narrower particle size distribution, the sensitivity and detection limit of sensor electrode for Zn, Cd and Pb are improved, which is ascribed to the increase in electrochemical‐active surface area. 相似文献