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1.
Jong Dae Lee Dong-Hwal Lee No-Kuk Park Si Ok Ryu Tae Jin Lee 《Current Applied Physics》2006,6(6):1040
The reduction–carburization of tungsten trioxide (WO3) under carbon monoxide flow was studied in the temperature range of 300–750 °C. The reduction–carburization of WO3 was improved by mechanically mixing with zeolite-HX, -NaX and -KX. The interaction between cation in zeolite-X and oxygen in WO3 affected the improvement of the reduction–carburization of WO3 to WC. Moreover, the improved reduction–carburization of WO3 could lead to the decrease of reaction temperature. Because the particle size of WC is in contact with a reaction temperature, the nanophase WC can be prepared at low temperature. In particular, the particle size of WC was controlled by reaction temperature. The particle sizes of produced WC at 550, 650 and 700 °C were 25, 50 and 100 nm respectively. 相似文献
2.
Andrew P. Purdy Rebecca Sorber Albert Epshteyn Katherine A. Pettigrew Joel B. Miller 《Journal of nanoparticle research》2011,13(10):5435-5448
Hafnium tetrachloride was reduced in organic solvents with lithium powder, sodium–potassium alloy, or lithium hydride/Et3B. All reductions required sonochemical agitation to proceed at an appreciable rate, with the notable exception of the reaction
of HfCl4 with Li in diethyl ether. Activation of C–H bonds occurred in all reactions, which resulted in carbon-containing products.
HfCl4 was reduced on a 50-g scale with LiH/Et3B, and a 10-g scale with Li powder in pentane. All the solid products from the reductions were converted to nanomaterials
by annealing under vacuum from 500 to 1,000 °C, which also resulted in the sublimation of the alkali metal salts. The nanomaterials
contain a mixture of products with the α-Hf (hexagonal) structure (crystallite size 8–250 nm) and the HfC (FCC) structure
(crystallite size 3–80 nm), with the amount of hafnium in the bulk annealed product varying from 88 to 99 wt%. When toluene,
pentane, or triethylamine solvents were used, the presence of amorphous graphitic or carbonaceous material was also detected
by solid state 13C NMR. Thermally annealed products were additionally characterized by electron microscopy and thermal analysis under Ar/O2, and have BET surface areas ranging from 2.7 to 155 m2/g. 相似文献
3.
We report on the effect of oxygen partial pressure and vacuum annealing on structural and optical properties of pulsed laser-deposited
nanocrystalline WO3 thin films. XRD results show the hexagonal phase of deposited WO3 thin films. The crystallite size was observed to increase with increase in oxygen partial pressure. Vacuum annealing changed
the transparent as-deposited WO3 thin film to deep shade of blue color which increases the optical absorption of the film. The origin of this blue color could
be due to the presence of oxygen vacancies associated with tungsten ions in lower oxidation states. In addition, the effects
of VO2 content on structural, electrochemical, and optical properties of (WO3)1−x
(VO2)
x
nanocomposite thin films have also been systematically investigated. Cyclic voltammogram exhibits a modification with the
appearance of an extra cathodic peak for VO2–WO3 thin film electrode with higher VO2 content (x ≥ 0.2). Increase of VO2 content in (WO3)1−x
(VO2)
x
films leads to red shift in optical band gap. 相似文献
4.
M. Miettinen M. Johansson S. Suvanto J. Riikonen U. Tapper T. T. Pakkanen V.-P. Lehto J. Jokiniemi A. Lähde 《Journal of nanoparticle research》2011,13(10):4631-4645
Silicon–carbon nanoceramics have been synthesised from hexamethyldisilane (HMDS) by the atmospheric pressure chemical vapour
synthesis (APCVS). Direct aerosol phase synthesis enables continuous production of high purity materials in one-stage process.
The particle formation is based on the decomposition of the precursor in a high temperature reactor. Reaction of the gas phase
species leads to homogeneous nucleation and formation of the nanoparticles with a narrow size distribution (geometric mean
diameter range of particle number size distribution 160–200 nm with 1.5–1.6 geometric standard deviation at reaction temperatures
800–1200 °C). A systematic investigation of the influence of the process temperature on the powder characteristics, including
the particle size, crystallinity, chemical structure, surface and bulk composition and surface morphology, was carried out.
At the reactor temperature of 800 °C, the synthesised nanoparticles were amorphous preceramics containing mostly SiC4, Si–CH2–Si and Si–H units. The composition of the powder turned towards nanocrystalline 3C–SiC (crystal size under 2 nm) when the
reaction temperature was increased to 1200 °C. The reaction temperature appeared to be a key parameter controlling the structure
and properties of the synthesised powders. 相似文献
5.
Nobumitsu Sakai Masato Takakura Harutoshi Imamura Miki Sugimoto Yasuto Matsui Hirokazu Miyoshi Aki Nakayama Minoru Yoneda 《Journal of nanoparticle research》2012,14(5):849
We analyzed the whole-body distribution of 14C–ADP-labeled silica nanoparticles (14C–ADP–SiO2 nanoparticles) and submicron particles (14C–ADP–SiO2 submicron particles) after intravenous injection into ICR mice. The 14C–ADP–SiO2 nanoparticles and submicron particles were synthesized before the injection and the particle size was 19.6 and 130 nm, respectively.
Similarly, the shape was spherical and the crystallinity was amorphous. After the synthesis, we injected mice with the 14C–ADP–SiO2 nanoparticles or the 14C–ADP–SiO2 submicron particles and dissected tissues after 1, 2, 4, 8 and 24 h. The radioactivity in the tissues was measured with a
liquid scintillation counter. As a result, the retention percentage in bone, skin, lymph nodes, and the digestive mixture
was at least twofold higher in the 14C–ADP–SiO2 nanoparticles-exposed mice, whereas the retention percentage in the kidney was statistically higher in the 14C–ADP–SiO2 submicron particles-exposed mice. Both types of 14C–ADP–SiO2 particles mainly translocated to the muscle, bone, skin, and liver, but hardly translocated to the brain and olfactory bulb.
Furthermore, the 14C–ADP–SiO2 nanoparticles had a higher retention percentage (62.4 %) in the entire body at 24-h post-injection than did the 14C–ADP–SiO2 submicron particles (50.7 %). Therefore, we suggested that the 14C–ADP–SiO2 nanoparticles might be more likely than the 14C–ADP–SiO2 submicron particles to be retained in the body, and consequently they might be gradually accumulated by chronic exposure. 相似文献
6.
The optimisation of the morphology of WO3 thin films allowed a more efficient electrochromic colouring using Na+ ions than H+ ones. Therefore, sodium superionic conductor (Na3Zr2Si2PO12, NASICON) films may be used as electrolyte in inorganic electrochromic devices. In this paper, the structure, chemical composition,
morphology and electrochromic properties of WO3, ZnO:Al and Na3Zr2Si2PO12 thin films were studied to develop a novel type of electrochromic device. WO3, ZnO:Al and Na3Zr2Si2PO12 thin films were deposited using reactive magnetron sputtering of tungsten, zinc and aluminium and Zr–Si and Na3PO4 targets, respectively. For transparent conductive oxide coatings, a correlation was established between the deposition parametres
and the film’s structure, transmittance and electrical resistivity. Classical sputtering methods were not suitable for the
deposition of NASICON films on large surface with homogenous composition. On the other hand, the use of high-frequency pulsed
direct current generators allowed the deposition of amorphous films that crystallised after thermal annealing upon 700 °C
in the Na3Zr2Si2PO12 structure. Amorphous films exhibited ionic conductivity close to 2 × 10−3 S cm−1. Finally, preliminary results related to the electrochromic performance of NASICON, WO3 and indium tin oxide devices were given.
Paper presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, France, Sept. 9–15, 2007. 相似文献
7.
Cherng-Yuh Su Hsuan-Ching Lin Tsung-Kun Yang Chung-Kwei Lin 《Journal of nanoparticle research》2010,12(5):1755-1763
With the use of a modified plasma arc gas condensation technique and control of the processing parameters, namely, plasma
current and chamber pressure, we synthesized tungsten oxide nanomaterials with aspect ratios ranging from 1.1 (for equiaxed
particles with the length and width of 48 nm and 44 nm, respectively) to 12.7 (for rods with the length and width of 266 nm
and 21 nm, respectively). The plasma current and chamber pressure, respectively, ranged from 70 to 90 A and from 200 to 600 Torr.
We then characterized the tungsten oxide nanomaterials by means of X-ray diffraction, high-resolution transmission electron
microscope, UV–visible spectroscope, and photoluminescence (PL) spectroscope. Experimental results show that equiaxed tungsten
oxide nanoparticles were produced at a relatively low plasma current of 70 A, whereas nanorods were produced when plasma currents
or chamber pressures were increased. All of the as-prepared tungsten oxide nanomaterials exhibited a WO2.8 phase. Compared to the nanoparticles, the nanorods exhibited unique properties, such as a redshift in the UV–visible spectrum,
a blue emission in PL spectrum, and a good performance in field emission. With respect to the field emission, the turn-on
voltage for WO2.8 nanorods was found to be as low as 1.7 V/μm. 相似文献
8.
A novel technique based on the excimer laser induced crystallization and modification of TiO2 thin films is being reported. W+6 ions loaded TiO2 (WTO) precursor films were prepared by a modified sol–gel method and spin-coated onto microscopic glass slides. Pulsed KrF
(248 nm, 13 ns) excimer laser was used to irradiate the WTO amorphous films at various laser parameters. Mesoporous and nanostructured
films consisting of anatase and rutile were obtained after laser irradiation at room temperature. The effect of varying W+6 ions concentrations on structural and optical properties the WTO films was analyzed by X-ray diffraction, field-emission
scanning electron microscope, UV-Vis spectrophotometer and transmission electron microscope before and after laser treatment.
Films irradiated for 10 pulses at 65–75 mJ/cm2 laser fluence, exhibited anatase whereas higher parameters promoted the formation of rutile. XPS results revealed WO3 along with minor proportion of WO2 compounds after laser irradiation. Photo-absorbance of the WTO films was increased with increase in W+6 ions concentration in the film. TEM results exhibited a crystallite size of 15 nm which was confirmed from SEM results as
well. 相似文献
9.
《Current Applied Physics》2014,14(3):389-395
Vanadium pentoxide (V2O5) mixed tungsten trioxide (WO3) thin films have been synthesized by a novel pulsed spray pyrolysis technique (PSPT) on glass and fluorine doped tin oxide (FTO) coated glass substrates at 400 °C. Aqueous solutions of equimolar vanadium chloride and ammonium tungstate were mixed in volume proportions (5%, 10% and 15%) for the deposition of V2O5–WO3 thin films. The structural, morphological, optical and electrochemical properties of V2O5–WO3 thin films were investigated by FT-IR, XRD, SEM, cyclic voltammetry, chronoamperometry and chronocoulometry techniques. The results showed that the electrochemical properties of V2O5 were altered by mixing WO3. All the films exhibited cathodic electrochromism in lithium containing electrolyte (0.5 M LiClO4 + propylene carbonate (PC)). Maximum coloration efficiency (CE) of about 49 cm2 C−1 was observed for the V2O5 film mixed with 15% WO3. The electrochemical stability of the sample was examined and it was found to be stable up to 1000 cycles. 相似文献
10.
Yuki Yamaguchi Yukari Emoto Tohru Kineri Masakatsu Fujimoto Hideo Mae Atsuo Yasumori Keishi Nishio 《Ionics》2012,18(5):449-453
A well-known gasochromic material is Pt particle-dispersed tungsten trioxide (Pt/WO3). Its optical properties could make it effective as a hydrogen gas sensor. In this study, Pt nanoparticle-dispersed WO3 thin films were prepared using the sol–gel process, and their optical and electrical properties dependent on the working
environment (i.e., temperature, hydrogen gas concentration, oxygen partial pressure, etc.) were investigated. The Pt/WO3 thin films prepared at 400 °C showed the largest change in optical transmittance and electrical conductivity when exposed
to hydrogen gas compared with the films prepared at other temperatures. The optical absorbance and electrical conductivity
were found to be dependent on the hydrogen and oxygen gas concentration in the atmosphere because generation and disappearance
of W5+ in the thin films depend on the equilibrium reaction between injection and rejection of H+ into and from the thin films. In addition, the equilibrium reaction depends on the hydrogen and oxygen gas concentrations. 相似文献
11.
T. Li Q. Lou J. Dong Y. Wei J. Liu 《Applied Physics A: Materials Science & Processing》2001,73(3):391-397
Surface ablation of cobalt-cemented tungsten carbide hard metal has been carried out in this work using a 308 nm, 20 ns XeCl
excimer laser. Surface microphotography and XRD, as well as an electron probe have been used to investigate the transformation
of phase and microstructure as a function of the pulse-number of laser shots at a laser fluence of 2.5 J/cm2. The experimental results show that the microstructure of cemented tungsten carbide is transformed from the original polygonal
grains of size 3 μm to interlaced large, long grains with an increase in the number of laser shots up to 300, and finally
to gross grains of size 10 μm with clear grain boundaries after 700 shots of laser irradiation. The crystalline structure
of the irradiated area is partly transformed from the original WC to βWC1-x, then to αW2C and CW3, and finally to W crystal. It is suggested that the undulating ‘hill–valley’ morphology may be the result of selective removal
of cobalt binder from the surface layer of the hard metal. The formation of non-stoichiometric tungsten carbide may result
from the escape of elemental carbon due to accumulated heating of the surface by pulsed laser irradiation.
Received: 13 July 2000 / Accepted: 27 October 2000 / Published online: 10 January 2001 相似文献
12.
The relationship between structural transformations and colour centres creation is discussed for deeply coloured hydrogen
tungsten bronzes and for pure WO3 powders, acquiring less intense colour after mechanical treatments of variable duration. A comparative study on coloration
is made also for mixed compounds (1−x)WO3−y·xReO2, where an evidence of a resonance effect for a particular Raman band at 970 cm−1, attributed to the color centres, is observed. Besides, it is found that even moderate milling treatments result in a quite
different structural evolution of tungsten trioxide upon cooling.
Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999. 相似文献
13.
WO3 is believed to be the most stable electrochromic material, particularly in organic solvents. This paper deals with the effects
of prolonged cycling around and below 2 V vs Li/Li+ in propylene carbonate/lithium triflate electrolyte. A dramatic loss of charge capacity was observed when the sample was
cycled between 4.5 V and 1.6 V vs Li/Li+. This was not the case when the lower limit was set to 2.0 V vs Li/Li+. Spectrophotometric analysis showed that the charge capacity loss was not accompanied by presence of tungsten in the electrolyte
or the counter electrode. SEM pictures show some electrode damage and precipitation at the electrode surface. A corrosion
mechanism is suggested.
Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997. 相似文献
14.
Fourier transform infrared spectroscopy studies have been conducted to investigate the interaction among components in a system
of high molecular weight polyvinylchloride (PVC)–lithium trifluoromethanesulfonate (LiCF3SO3) incorporated with different type of plasticizers, namely, ethylene carbonate (EC), propylene carbonate (PC), and dibutylphthalate
(DBP). Interaction between PVC and LiCF3SO3 was confirmed by C–H rocking mode at 1,255 cm−1 for PVC shift to 1,252 cm−1 in PVC–LiCF3SO3. The plasticizers’ carbonyl (C=O) oxygen atom which carries lone pair electrons interact with Li+ of LiCF3SO3 and methine hydrogen of PVC in LiCF3SO3–plasticizer system and PVC–plasticizer system, respectively. Changes in peaks assigned to 1,264 cm−1 (ν
as(SO3)), 1,033 cm−1 (ν
s(SO3)), 1,181 cm−1 (ν
as(CF3)), 1,230 cm−1 (ν
s(CF3)), 765 cm−1 (δ
s(CF3)), 644 cm−1 (δ
s(SO3)), 578 cm−1 (δ
as(CF3)), and 519 cm−1 (δ
as(SO3)) indicate the occurrence of complexation in the PVC–LiCF3SO3 system, LiCF3SO3–plasticizer system, and PVC–LiCF3SO3–plasticizer system. 相似文献
15.
Tungsten oxides are known to exhibit interesting electrochemical properties. Ion insertion (Li+, H+) within the oxide network is highly reversible. It leads to a blue coloration and WO3 thin films can be used as electrochromic layers in display devices or smart windows.
Tungsten oxide thin films can be conveniently deposited from aqueous solutions of tungstic acid. However polytungstic acids
are not stable and tend to precipitate into hydrated tungsten oxide WO3⋅2H2O. The condensation of polytungstic species can be chemically controlled by adding foreign ions in the solution. Precipitation
is no more observed in the presence of H2O2. Peroxopolytungstic acids are formed in which chelating [O2]2− ligands prevent the formation of an oxide network. Such solutions are specially convenient for the deposition of optically
transparent thin films. Mixed oxides WO3-MoO3 are obtained when condensation is performed in the presence of Mo6+ cations.
This paper shows how the condensation of tungstic acid can be chemically controlled and describes the electrochemical properties
of the films deposited from such solutions.
Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997 相似文献
16.
WO3 nanoparticles were prepared by evaporating tungsten filament under a low pressure of oxygen gas, namely, by a gas evaporation method. The crystal structure, morphology, and NO2 gas sensing properties of WO3 nanoparticles deposited under various oxygen pressures and annealed at different temperatures were investigated. The particles obtained were identified as monoclinic WO3. The particle size increased with increasing oxygen pressure and with increasing annealing temperature. The sensitivity increased with decreasing particle size, irrespective of the oxygen pressure during deposition and annealing temperature. The highest sensitivity of 4700 to NO2 at 1 ppm observed in this study was measured at a relatively low operating temperature of 50 °C; this sensitivity was observed for a sensor made of particles as small as 36 nm. 相似文献
17.
Soumya Kanti Biswas Jin-Ook Baeg Sang-Jin Moon Ki-jeong Kong Won-Wook So 《Journal of nanoparticle research》2012,14(1):667-12
Different morphologies of WO3 nanocrystals such as nanorods and nanoplates have been obtained under hydrothermal conditions using ammonium metatungstate
as the precursor in presence of different organic acids such as citric, oxalic, and tartaric acid in the reaction medium.
Detailed characterization of the crystal structure, particle morphology, and optical band gap of the synthesized powders have
been done by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and solid-state UV–visible
spectroscopy study. The as-synthesized materials are WO3 hydrates with orthorhombic phase which transform to the hexagonal WO3 through dehydration upon heating at 350 °C. The resultant products are crystalline with nanoscale dimensions. Finally, the
photoactivity of the synthesized materials annealed at 500 °C has been compared employing in photoelectrochemical water oxidation
under the illumination of AM 1.5G simulated solar light (100 mWcm−2). The photocurrent measurements upon irradiation of light exhibit obvious photocatalytic activity with a photocurrent of
about 0.77, 0.61, and 0.65 mAcm−2 for the WO3 film derived with the oxalic acid, tartaric, and citric acid assisting agents, respectively, at 1.8 V versus Ag/AgCl electrode. 相似文献
18.
N. V. Alov D. M. Kutsko 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(2):225-228
The surface reduction of higher oxide WO3 under irradiation by He+ ions with the energies 1 and 3 keV in a high vacuum is investigated by X-ray photoelectron spectroscopy. It is found that
lower WO2 and intermediate WO
x
(2 < x < 3) oxides form first in WO3 surface layers under He+ ion bombardment, and with an increase in the irradiation dose metallic tungsten forms. It is shown that the degree of irradiated
oxide surface metallization increases with an increase in the energy of the bombarding He+ ions. A comparison of WO3 oxide surface composition modification under He+ and Ar+ ion irradiation is presented. 相似文献
19.
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
20.
Cubic-stabilized ((DyO1.5)
x
–(WO3)
y
–(BiO1.5)1 − x − y
) electrolytes (DWSB) with much higher conductivity than (ErO1.5)0.2(BiO1.5)0.8, 20ESB, were developed through a double-doping strategy. (DyO1.5)0.08–(WO3)0.04–(BiO1.5)0.88, 8D4WSB, is the highest conductivity composition but underwent the greatest conductivity degradation at 500 °C due to its
low total dopant concentration. The effect of dopant composition on conductivity behavior with time at 500 °C demonstrates
that there is a trade-off between initial conductivity and long-term stability at this temperature. Therefore, it is necessary
to find an optimal total and relative concentration of dopants to provide the enhanced long-term stability needed to make
this DWSB electrolyte system feasible for 500 °C operation. To this end, it was found that (DyO1.5)0.25–(WO3)0.05–(BiO1.5)0.70, 25D5WSB, maintained a conductivity of 0.0068 S/cm without appreciable degradation after annealing at 500 °C for 500 h. Moreover,
since bismuth oxide-based electrolytes do not exhibit any grain boundary impedance, the total conductivity of 25D5WSB is significantly
higher than that of alternate electrolytes (e.g., GDC: Gd0.1Ce0.9O1.95) at this temperature. 相似文献