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1996-12-31
Considering integrated hull and piping design in shipbuilding industry as a good example for concurrent engineering (CE), discussions were given on a computer aided method to perform integrated hull and piping design smoothly. When CE aiding by means of a computer is considered, it is important to discuss a method for information management not only for `utilization of product models`, but also for `maintaining consistency between items of product information` and `concurrent utilization and production of product information` in concurrent designs. For the CE aided information management, utilization and production of the product information is effective if restrictive relationship between items of product information, and design functions are made clear. Definitions were given on the restrictive relationship between items of product information and `restrictive relationship information` that has `decision/provisional decision`, `date and time`, `designer` and `design functions`. Furthermore, `comprehensive relationship between items of product information` that can be produced from the restrictive relationship information was defined as a `restrictive network`. Utilizing the restrictive relationship between items of product information for CE aiding is effective. 9 refs., 14 figs.
1994-12-21
When a structure is constructed on the soft ground, a design taking a sufficient countermeasure against a settlement is necessary. Conventionally, a foundation settlement was suppressed to the utmost, it was a general trend that a design was so performed that an influence of settlement did not affect on the super-structure. When by this kind of design, a foundation with a large scale is constructed, a structure constructed on it can be independently designed apart from the foundation. However, when a design to suppress a settlement in the soft ground with a large layer thickness is applied, a foundation scale becomes large and a construction cost will increase. In addition, a difference in level between a foundation and the surrounding ground is generated, and such a problem and others occur. Accordingly in recent years, a design, a foundation settles together with the ground, by using a friction pile even in case of a direct foundation and pile foundation, has become to be used. The authors proposed an optimum technique of the monolithic system considering a settlement making bridge as an object, and its effectiveness was demonstrated. Along with it, in this paper furthermore, a monolithic system taking into account of a deformation in the soft and weak layer below a foundation was proposed. 13 refs., 20 figs., 4 tabs.
Secondary liquefaction of starch in ethanol production : WO 0238787
Theoretical investigation of the luminescence centres in PbWO{sub 4} and CdWO{sub 4} crystals
2005-01-21
Electronic structures of possible centres of luminescence in the perfect lead (PbWO{sub 4}) and cadmium tungstate (CdWO{sub 4}) crystals are calculated using cluster approach. Electronic states of Pb{sup 2+}, and Cd{sup 2+} cations, WO42- and WO66- are obtained on the basis of partial densities of electronic states calculated for several clusters containing from 72 to 104 atoms of the crystals. Calculated energies of one-electron transitions in these centers are compared with experimental data on luminescence and luminescence excitation. Obtained results evidence in favor of a tungstate nature of intrinsic luminescence in the PbWO{sub 4} and CdWO{sub 4} crystals . I ntrinsic luminescence probably originates from the tungstate groups WO42- in scheelite-type, and from the WO66- groups in the raspite-type PbWO{sub 4} crystals. Tungstate groups WO66- are assumed to be the centres of excitation of blue-green and yellow luminescence bands in CdWO{sub 4} crystals.
2007-01-01
For the first time ever it is demonstrated that, in spontaneous conditions and following the imposition of an electric field, mutual penetration of components of WO3 and Me2(WO4)3 occurs at heterophase interfaces WO3| Me2(WO4)3 where Me = In, Eu, or Sc. Tungsten oxide, WO3, is pulled onto the inner surface of ceramic Me2(WO4)3 and, in turn, components of Me2(WO4)3 penetrate onto the surface of grains of ceramic WO3, which is confirmed by X-ray fluorescence analysis. Data concerning the conductivity and transport numbers of Eu2(WO4)3 and a composite on its basis, which was manufactured as a result the electro surface transport of ... >>
Heat capacity of hexagonal tungsten bronzes. [1 to 55K]
Measurements in the temperature range 1 to 55K are reported for K/sub x/WO/sub 3/, Rb/sub x/WO/sub 3/, Cs/sub x/WO/sub 3/, Tl/sub x/WO/sub 3/, WO/sub 3/ and Na/sub x/WO/sub 3/ and the excess heat capacity due to an Einstein mode is found in K/sub x/WO/sub 3/, CsWO/sub 3/ and Tl/sub x/WO/sub 3/. A value of x equals 0.33 is determined. The general results are discussed and related to the superconducting properties of the four hexagonal bronzes. 25 references.
Heat capacity of hexagonal tungsten bronzes. [1 to 55K]
1974-04-15
Measurements in the temperature range 1 to 55K are reported for K/sub x/WO/sub 3/, Rb/sub x/WO/sub 3/, Cs/sub x/WO/sub 3/, Tl/sub x/WO/sub 3/, WO/sub 3/ and Na/sub x/WO/sub 3/ and the excess heat capacity due to an Einstein mode is found in K/sub x/WO/sub 3/, CsWO/sub 3/ and Tl/sub x/WO/sub 3/. A value of x equals 0.33 is determined. The general results are discussed and related to the superconducting properties of the four hexagonal bronzes. 25 references.
Facile Preparation of Strontium Tungstate and Tungsten Trioxide Hollow Spheres
2006-01-01
A simple and low-cost technique was developed to produce unique SrWO4 and WO3 hollow spheres. The SrWO4 hollow spheres were prepared via a precipitation reaction between SrCl2 and Na2WO4 in the presence of polymethacrylic acid, and the synthesis of WO3 spheres used the as-prepared SrWO4 hollow spheres as both precursors and templates. After soaking in HNO3 and calcinations, the SrWO4 were completely transformed into WO3 while the hollow structures were perfectly retained. The "polymer-cation template" model was proposed to describe the formation of the SrWO4 hollow spheres. This technique is feasible in fabricating other inorganic hollow-structured materials.
Application of PbWO4 crystal scintillators in experiment to search for double beta decay of 116Cd
2004-12-10
PbWO4 crystal scintillators are discussed as an active shield and light-guides in 116Cd double beta decay experiment with CdWO4 scintillators. Scintillation properties and radioactive contamination of PbWO4 scintillators were investigated. Energy resolution of CdWO4 detector, coupled to PbWO4 crystal as a light-guide, was tested. Efficiency of PbWO4-based active shield to suppress background from the internal contamination of PbWO4 crystals was calculated. Using of lead tungstate crystal scintillators as high efficiency 4-pi active shield could allow to build sensitive double beta experiment with 116CdWO4 crystal scintillators.
1995-03-30
In connection with hybrid structures in civil engineering construction, classification and application of composite types of steel and concrete are discussed. H steel embedded beam is a composite beam in which the H shape steel of the main beam is connected to rolled or welded H shape steel using cross beams. Composite structure columns are grouped into the composite column and the steel pipe concrete column. SRC piers are often adopted from the viewpoints of constraints for execution of works and vibration proof. Steel and concrete hybrid structure is a kind of structural system in which various kinds of materials such as steel, RC, or PC members are connected. The cable stayed bridge utilizes characteristics of steel and concrete effectively. For the piers of municipal expressway viaducts, there are executed cases of mixed structures which have RC, SRC columns for T shape piers and S structure for the bridges. SRC structure and composite columns are adopted often for structures of subway stations. 7 refs., 7 figs.
Electric conductivity of the melts in the systems Na/sub 2/WO/sub 4/-WO/sub 3/, K/sub 2/WO/sub 4/-WO/sub 3/ and Na/sub 2/WO/sub 4/-K/sub 2/WO/sub 4/ and chemical interaction in the systems above have been studied. Electric caductivity has been measured using capillary quartz cell and alternating current bridge R-568 at alternating current frequency 16000 Hz. The hardened melt samples are subjected to X-ray phase analysis using ''Dron-1'' diffractometer (copper radiation, Ni filter). It is shown that bends on electric conductivity isotherms mainly correspond to characteristic points on state diagrams. The presence of chemical interaction in the systems is confirmed by X-ray phase analysis.
1983-01-01
Electric conductivity of the melts in the systems Na/sub 2/WO/sub 4/-WO/sub 3/, K/sub 2/WO/sub 4/-WO/sub 3/ and Na/sub 2/WO/sub 4/-K/sub 2/WO/sub 4/ and chemical interaction in the systems above have been studied. Electric caductivity has been measured using capillary quartz cell and alternating current bridge R-568 at alternating current frequency 16000 Hz. The hardened melt samples are subjected to X-ray phase analysis using ''Dron-1'' diffractometer (copper radiation, Ni filter). It is shown that bends on electric conductivity isotherms mainly correspond to characteristic points on state diagrams. The presence of chemical interaction in the systems is confirmed by X-ray phase analysis.
2000-01-01
A quaternary system of alkali and alkaline earth metal tungstates has been studied by a complex of physical-chemical methods: visual-polythermal, differential thermal, projective-thermographic analyses. A crystallization tree was drawn up by prognosis of the phase complex. Two nonvariant points of eutectic and peritectic nature of the melting T=473 and 483 Deg C respectively were found in the system
Optical and luminescence properties of CdWO4 and CdWO4:Mo single crystals
2008-01-01
Luminescence properties of a pure CdWO4 crystal and a CdWO4:Mo crystal doped with molybdenum in different concentrations have been investigated. The effect of molybdenum impurity on the intrinsic luminescence of CdWO4 has been found, and the role of the impurity in the formation of new luminescence centers has been investigated. The features of the formation of the intrinsic and impurity luminescence excitation spectra of CdWO4 and CdWO4:Mo crystals in the fundamental-absorption region have been considered. The reflection spectra of the CdWO4 crystal have been investigated taking into account the crystal structure anisotropy.
Liquidus relations in the Na2WO4-LiPO3-WO3 system Poverkhnost' likvidusa sistemy Na2WO4-LiPO3-WO3
2001-01-01
System Na2WO4-LiPO3-WO3, which is a diagonal cross section of quaternary mutual system Li, Na//PO3, WO4, WO3, was studied. For detecting low-fusible mixtures thermal analysis was conducted. It was ascertained that in the concentration range studied the liquids surface of the given ternary system consists of crystallization fields of sodium tungstate, lithium metaphosphate, congruently melting compounds of the relevant binary systems. Characteristics of boundary points and intersection points in the system cross sections studied are presented. It is shown that the character of fusibility curve is predetermined by interaction of components in double combinations
Dielectric properties of PbSrWO4 and PbBaWO4 compounds
2009-01-01
PbSrWO4 and PbBaWO4 have been synthesized by the solid state reaction technique XRD patterns show them to be tetragonal. Dielectric constant (K) and dielectric loss (K') of PbSrWO4 and PbBaWO4 have been measured at 1 kHz in the temperature range of 300 to 1050 K. The log K vs T as well as log K' vs T plot of PbSrWO4 and PbBaWO4 shows rapid increase of dielectric constant above 590 K and 640 K, respectively. (author)
Crystal structure and electrical properties of new tungsten bronzes: B xWO3 (0.01
2007-01-01
Boron tungsten bronzes B xWO3 (0.01 >
Radioactive contamination of CaWO4, ZnWO4, CdWO4, and Gd2SiO5:Ce crystal scintillators
Radioactive contaminations of CaWO4, ZnWO4, CdWO4, and Gd2SiO5:Ce crystal scintillators were measured in the Solotvina Underground Laboratory. The Monte Carlo simulation of contributing radioactive sources, the time-amplitude and pulse-shape analyses of the experimental data were applied. CaWO4 and GSO scintillators are considerably polluted by uranium and thorium, while the total {alpha} activity in ZnWO4 and CdWO4 scintillators does not exceed the level of a few mBq/kg. Particular radioactivity was observed in CaWO4 ({alpha} active 180W), CdWO4 ({beta} active 113Cd, 2v2{beta} decay of 116Cd, 180W), and GSO ({alpha} active 152Gd) detectors. The radioactive contamination of the studied scintillation crystals is compared with that of commonly used detectors.
Radioactive contamination of CaWO4, ZnWO4, CdWO4, and Gd2SiO5:Ce crystal scintillators
2005-01-01
Radioactive contaminations of CaWO4, ZnWO4, CdWO4, and Gd2SiO5:Ce crystal scintillators were measured in the Solotvina Underground Laboratory. The Monte Carlo simulation of contributing radioactive sources, the time-amplitude and pulse-shape analyses of the experimental data were applied. CaWO4 and GSO scintillators are considerably polluted by uranium and thorium, while the total alpha activity in ZnWO4 and CdWO4 scintillators does not exceed the level of a few mBq/kg. Particular radioactivity was observed in CaWO4 (alpha active 180W), CdWO4 (beta active 113Cd, 2v2beta decay of 116Cd, 180W), and GSO (alpha active 152Gd) detectors. The radioactive contamination of the studied scintillation crystals is compared with that of commonly used detectors
Preparation of Pt supported on WO3 C with enhanced catalytic activity by microwave-pyrolysis method
2010-01-01
The WO3-C hybrid materials are prepared by intermittently microwave-pyrolysis using ammonium tungstate as the precursor, and then Pt nano-particles are deposited by microwave-assited polyol process on WO3-C. The TEM images show the dispersion of ~10nm WO3 particles size supported on carbon and ~3nm Pt metal crystallites supported on WO3-C. XRD results illustrate that WO3 presented as monoclinic phase and the content of WO3 in WO3/C and Pt/WO3-C catalysts is further characterized by EDAX. Furthermore, XPS characterizations indicate that the interaction between Pt and WO3 is dramatically enhanced after heat treatment at 200^oC. The activities of Pt/WO3-C for the electrochemical oxidation of methanol are compared with Pt/C in acid solution by cyclic voltammetry, CO-stripping and chronoaperome...
2009-01-01
The electronic and IR spectra of molten systems NaCl-CsCl-NaF-Na2WO4, KBr-NaF-Na2WO4, NaCl-CsCl-NaF-Na n WO3F3, and KBr-NaF-Na n WO3F3(n = 3, 4) were measured. It was found that, depending on oxidation/reduction conditions, penta- and hexavalent tungsten oxyfluoride complexes—WO3F−, WO3F 2 2− , WO3F 2 3− , WO3F 3 3− and WO3F 2 4− —are formed in all molten mixtures. The coordination number and composition of the coordination sphere of these complexes depend on the molar ratio δ = F/W.
1980-01-01
Measurements of the resistivity rho, Hall voltage V/sub H/, Seebeck coefficient S, superconducting transition temperature T/sub c/, and the superconducting upper critial field H/sub c2/ were obtained for single crystals of K/sub x/ WO3(0.18 >
Study of photoactivity of tungsten trioxide (WO3) for water splitting
2007-01-01
The paper presents the properties of WO3 films considering the possibility to build a photoelectrochemical cell (PECC) for hydrogen production. The photocurrent response of the PECC containing WO3/TCO as photoanode and Pt as cathode was analysed. The morphology, crystalline structure and electrical aspects were investigated. Tungsten trioxide (WO3) thin film with porous morphology and high crystallinity was obtained using the spray pyrolysis deposition technique
Morphology-controlled synthesis of CdWO4 nanorods and nanoparticles via a molten salt method
2006-01-01
Cadmium tungstate (CdWO4) nanoparticles and nanorods have been successfully synthesized by a molten salt method at 270 deg. C, and the morphology of the nanocrystals can be controlled by adjusting such reaction conditions as the calcined time and the weight ratio of the salt to the CdWO4 precursor. The resultant sample is a pure phase of CdWO4 without any other impurities
Mechanical control of electrical nerve stimulation system for the treatment of pelvic disorders : WO2009080786 (A2)
Mechanical control of electrical nerve stimulation system for the treatment of pelvic disorders : WO2009080786 (A2)
Inductive control of electrical nerve stimulation system for the treatment of pelvic disorders : WO2009080784 (A1)
Inductive control of electrical nerve stimulation system for the treatment of pelvic disorders : WO2009080784 (A1)
DNA Microarray Analysis of Gene Expression in Chronic Rhinosinusitis
Chronic Rhinosinusitis w/o Nasal Polyps
Contributions of phosphorylation to regulation of OCTN2 uptake of carnitine are minimal in BeWo cells
2008-01-01
Ultraviolet photoconductance of a single hexagonal WO3 nanowire
2010-01-01
The ultraviolet (UV) photoconductance properties of a single hexagonal WO3 nanowire have been studied systematically. The conductance of WO3 nanowires is very sensitive to ultraviolet B light and a field-effect transistor (FET) nanodevice incorporating a single WO3 nanowire exhibits excellent sensitivity, reversibility, and wavelength selectivity. A high photoconductivity gain suggests that WO3 nanowires can be used as the sensing element for UV photodetectors. Measurements under UV light in vacuum show that the adsorption and desorption of oxygen molecules on the surface of the WO3 nanowire can significantly influence its photoelectrical properties. The WO3 nanowires have potential applications in biological sensors, optoelectronic devices, optical memory, and other areas.
Microstructural analysis and electrical conductivity of hexagonal WO3 thin films during annealing
2008-01-01
WO3 thin films have been deposited by thermal evaporation on (0001) surfaces of alpha-Al2O3 single crystal and annealed between 423 K and 623 K in air with a mean humidity of 50%. The structural and morphological properties of the films have been characterized by transmission electron microscopy and compatible selected area electron diffraction. During annealing, important changes in grain size and structure occur. As the annealing temperature increases slightly, the WO3.1/3H2O structure successively transforms to hexagonal WO3 and Magneli WO3-x phases. During these structural transformations, the grains are constructed of twinned microdomains in different directions with largest lattice parameters of WO3. The conductivity of the WO3 ... >>
Microstructural analysis and electrical conductivity of hexagonal WO3 thin films during annealing
2008-01-01
WO3 thin films have been deposited by thermal evaporation on (0001) surfaces of a-Al2O3 single crystal and annealed between 423 K and 623 K in air with a mean humidity of 50%. The structural and morphological properties of the films have been characterized by transmission electron microscopy and compatible selected area electron diffraction. During annealing, important changes in grain size and structure occur. As the annealing temperature increases slightly, the WO31/3H2O structure successively transforms to hexagonal WO3 and Magneli WO3-x phases. During these structural transformations, the grains are constructed of twinned microdomains in different directions with largest lattice parameters of WO3. The conductivity of the WO3 thin films has been investigated as a function of annealing t...
Growth and sintering effects of hydrated polycrystalline Li2WO4
2010-01-01
Polycrystalline Li2WO4 was sintered at temperatures, 400, 450, 500, 550, 600, 650, and 700 °C. After sintering at each particular temperature, the Li2WO4 was cooled to room temperature. The X-ray diffraction pattern of Li2WO4 exhibits dominant peaks attributable to 7Li2WO4.4H2O (cubic) and Li2WO4 (hexagonal) and thus reveals the extent of hydration of the material. The composition varies on heating at several temperatures as shown by the presence of new peaks in the diffractogram. Thermogravimetric analysis is used to correlate respective structural and thermal properties in variation. The impedance spectra show the presence of a semicircle in the higher frequency regions and straight line behaviors at lower frequencies. SEM micrographs depict the image of sintered Li2WO4. Grain growth ...
2007-01-01
We report high-resolution angle-resolved photoemission spectroscopy on sodium tungsten bronzes, NaxWO3, which exhibit a metal-insulator transition as a function of x. We found that the near-EF states are localized in NaxWO3 (x=+ ions in the WO3 lattice, which makes the system insulating. In the metallic regime we found that the rigid shift of band structure can explain the metallic NaxWO3 band structure with respect to Na doping
Gamma-ray absorption studies in some scheelites
1982-07-01
We present here gamma-ray absorption data obtained for CaWO/sub 4/, CaMoO/sub 4/ and PbWO/sub 4/ crystals. CaWO/sub 4/ and CaMoO/sub 4/ crystals were grown using a slow-cooling flux technique employing a LiCl melt, while in the case of PbWO/sub 4/, Na/sub 2/WO/sub 4/ was found to be a better flux. The method is described. The results are compared and discussed.
A study of electron excitations in CaWO sub 4 and PbWO sub 4 single crystals
The excitation spectra of photo- and thermo-luminescence were compared in the VUV-UV spectral region in CaWO sub 4 and PbWO sub 4 scheelite tungstates. Temperature dependences of emission intensities and decay times were measured for PbWO sub 4 in the 80-300 K range and approximated by a simple phenomenological model. The energy level structure of the emission centre excited state and related kinetic processes are discussed for both tungstates. (author)
2007-01-01
Transport numbers of oxygen ions, tO2-, in metacomposites (left braceMeWO4 centre dot centre dot xWO3right brace, where Me = Sr and Ba and x=0-0.55, are determined in the temperature interval 600 to 900 deg C by the emf method with an oxygen-air galvanic cell. It is demonstrated that the region of small contents of the WO3 additive (x 0.35. It is confirmed once again that sub-eutectic compositions left braceMeWO4 centre dot xWO3right brace, where Me = Sr and Ba and x = 0-0.2 belong to the class of ion-conducting ... >>
2009-01-01
The Li,K,Ca,BaâF,WO4 quinary reciprocal system was differentiated on the basis of graph theory with account for already known inner secants. Possible exchange and complex-formation chemical reactions that occur throughout the composition polyhedron of the system were revealed. The results of the differentiation and thermal analysis of several samples in each Phase unit block (PUB) were used to build crystallization tree of the title system. It is for the first time that the set of physicochemical methods (differential thermal analysis, visual polythermal analysis, and X-ray powder diffraction in tandem with projective thermal analysis) was used to study the LiF-LiKWO4-Li2WO4-CaWO4-BaWO4 five-component system; this system is the stable pentatope of the Li,K,Ca,BaâF,WO4 quinary reciproca...
Spectral properties and thermoluminescence of codoped PbWO4:(Mo,Y) and PbWO4:(F,Y) crystals
2009-01-01
Lead tungstate, PbWO4 single crystals codoped with Mo6+/F- and Y3+ ions were grown using the modified Bridgman method. Optical transmission, X-ray excited luminescence, photoluminescence, ultrashort pulsed X-ray excited fluorescent lifetime and thermoluminescence have been investigated. Compared to pure PbWO4, the codoped PbWO4:(Mo,Y) and PbWO4:(F,Y) crystals exhibit improved transmittance in the short-wavelength region. Luminescence and light-yield measurements demonstrated that Mo6+/F- and Y3+ codoping could enhance the luminescence of PbWO4 and reduce slow decay components. Doped Mo6+ and F- ions in PbWO4 were tentatively considered to occupy W and O sites, while Y3+ ions codoped in PbWO4:Mo/F mostly occupy Pb sublattice sites. The second excitation peak at 335 nm, which is the second e...
Phase relations in the WO/sub 2/--V/sub 2/WO/sub 6/ system
1977-12-01
Crystalline solubility and structural changes brought about by the replacement of V/sup 4 +/ by W/sup 4 +/ in the system VO/sub 2/-V/sub 2/WO/sub 6/ are reported. Three structurally related phases were identified between the monoclinic WO/sub 2/ and the trirutile V/sub 2/WO/sub 6/ phases. The crystalline solubility of V/sub 2/WO/sub 6/ in MO/sub 2/ or MO/sub 2/ in V/sub 2/WO/sub 6/ was found to be entirely different depending upon whether M=V or W. This difference in crystalline solubility is explained on the basis of differences in the ionic radii of the two ions. Unit cell parameters at room temperature are tabulated, and it is reported that the parameter decreases while the c parameter increases with increasing amounts of V/sub 2/WO/sub 6/ in WO/sub 2/. (BLM)
Investigation of Bi/sub 6/Ti/sub 3/WO/sub 18/ and Bi/sub 2/WO/sub 6/ formation process
The process of Bi/sub 6/Ti/sub 3/WO/sub 18/ and Bi/sub 2/WO/sub 6/ synthesis has been studied by methods of differential thermal analysis and x-ray phase analysis. The ternary compound Bi/sub 6/Ti/sub 3/WO/sub 18/ is formed as a result of interaction between intermediate binary compounds Bi/sub 4/Ti/sub 3/O/sub 12/ and B+/sub 2/WO/sub 6/; Bi/sub 2/WO/sub 6/ is the product of interaction of Bi/sub 2/O/sub 3/-WO/sub 3/ cubic solid solution with WO/sub 3/.
Investigation of Bi/sub 6/Ti/sub 3/WO/sub 18/ and Bi/sub 2/WO/sub 6/ formation process
1981-01-01
The process of Bi/sub 6/Ti/sub 3/WO/sub 18/ and Bi/sub 2/WO/sub 6/ synthesis has been studied by methods of differential thermal analysis and x-ray phase analysis. The ternary compound Bi/sub 6/Ti/sub 3/WO/sub 18/ is formed as a result of interaction between intermediate binary compounds Bi/sub 4/Ti/sub 3/O/sub 12/ and B+/sub 2/WO/sub 6/; Bi/sub 2/WO/sub 6/ is the product of interaction of Bi/sub 2/O/sub 3/-WO/sub 3/ cubic solid solution with WO/sub 3/.
Influence of the thermal treatment in the crystallization of NiWO4 and ZnWO4
2009-01-01
NiWO4 and ZnWO4 were synthesized by the polymeric precursor method at low temperatures with zinc or nickel carbonate as secondary phase. The materials were characterized by thermal analysis (TG/DTA), infrared spectroscopy, UVâVis spectroscopy and X-ray diffraction. NiWO4 was crystalline after calcination at 350 °C/12 h while ZnWO4 only crystallized after calcination at 400 °C for 2 h. Thermal decomposition of the powder precursor of NiWO4 heat treated for 12 h had one exothermic transition, while the precursor heat treated for 24 h had one more step between 600 and 800 °C with a small mass gain. Powder precursor of ZnWO4 presented three exothermic transitions, with peak temperatures and mass losses higher than NiWO4 has indicating that nickel made carbon elimination easier.
Hydrothermal synthesis and electronic properties of FeWO4 and CoWO4 nanostructures
2010-01-01
Iron tungstate (FeWO4) and cobalt tungstate (CoWO4) nanostructures were prepared by the hydrothermal method using sodium tungstate (Na2WO4.2H2O), ferrous ammonium sulfate [(NH4)2Fe(SO4)2.6H2O] and cobalt chloride (CoCl2.6H2O) solutions as precursors. The crystal structure and morphology of the as-prepared tungstates were characterized by X-ray diffraction analysis and transmission electron microscopy. The above characterizations render that the products obtained belong to the monoclinic crystal system and P2/a space group, with average sizes of nanoparticles of about 150nm and 70nm in the case of FeWO4 and CoWO4, respectively. Electronic properties of the FeWO4 and CoWO4 tungstates were studied using several X-ray spectroscopy methods, mainly X-ray photoelectron spectroscopy (XPS), X-ray e...
Electrical Properties of Sol-Gel Derived PZT/WO3 Ceramics
2009-01-01
PZT/xWO3 powders were prepared from the powders synthesized by a modified triol sol-gel method. XRD and TEM results suggested that fully crystallized powders were obtained at the calcination temperature of 600°C for 4 h. A reaction between PZT and WO3 powders seemed more pronounced with increasing WO3 content. To prepare PZT/xWO3 ceramics, the powders were pressed and sintered at 1100°C for 6 h. Phase characterization by XRD indicated that the concentration of WO3 affected lattice parameters and reduced c/a ratios, especially for high content of WO3. SEM images showed that an addition of only 0.5 wt% WO3 significantly decreased grain size of the ceramics. Density of the ceramics, however, did not significantly depend on WO3 concentration below 1 wt%. Addition of suitable amount o...
Cu/sub 3/Sm(WO/sub 4/)/sub 3/-Sm/sub 2/(WO/sub 4/)/sub 3/ system
Vast regions (up to 25 mol%) of the existence of limited solid solutions with Dalton compositions Cu/sub 3/Sm(WO/sub 4/)/sub 3/, Cu/sub 13/Sm/sub 7/x(WO/sub 4/)/sub 17/, Cu/sub 9/Sm/sub 11/(WO/sub 4/)/sub 21/ and Cu/sub 3/Sm/sub 17/(WO/sub 4/)/sub 27/ possessing the structures related to scheelite distorted monoclinic structure of Eu/sub 2/(WO/sub 4/)/sub 3/ A-phase were revealed in the Cu/sub 3/Sm(WO/sub 4/)/sub 3/-Sm/sub 2/(WO/sub 4/)/sub 3/ system at 500-1100 deg C temperatures and oxygen partial pressure of 0.9-1.3 Pa (total pressure of the noble gas - 102.1+-0.6 kPa).
Cu/sub 3/Sm(WO/sub 4/)/sub 3/-Sm/sub 2/(WO/sub 4/)/sub 3/ system
1982-11-01
Vast regions (up to 25 mol%) of the existence of limited solid solutions with Dalton compositions Cu/sub 3/Sm(WO/sub 4/)/sub 3/, Cu/sub 13/Sm/sub 7/x(WO/sub 4/)/sub 17/, Cu/sub 9/Sm/sub 11/(WO/sub 4/)/sub 21/ and Cu/sub 3/Sm/sub 17/(WO/sub 4/)/sub 27/ possessing the structures related to scheelite distorted monoclinic structure of Eu/sub 2/(WO/sub 4/)/sub 3/ A-phase were revealed in the Cu/sub 3/Sm(WO/sub 4/)/sub 3/-Sm/sub 2/(WO/sub 4/)/sub 3/ system at 500-1100 deg C temperatures and oxygen partial pressure of 0.9-1.3 Pa (total pressure of the noble gas - 102.1+-0.6 kPa).
1993-01-01
The state of tungsten oxide on the surface of dispersed silica in the course of thermal treatment was studied by the method of X-ray phase analysis and derivatography. It is shown that the structure of applied tungsten oxide phase can vary from the one similar to WO3 x 2H2O or WO3 x H2O to the structure of crystalline WO3. A higher degree of WO3/SiO2 samples surface hydration as compared with SiO2 is related to the presence of H2O molecules included into the composition of the applied phase on the surface of the carrier
2009-02-20
The WO{sub 3} nanoparticles are synthesized on titanate nanotubes (TNTs) by a facile hydrothermal method. The prepared WO{sub 3}/TNTs nanocomposites are characterized by XPS, TEM, XRD and UV-vis spectra. The result shows that the WO{sub 3} nanoparticles with the diameter of a few nanometers are evenly distributed on internal cavity and external surfaces of TNTs. As is expected, the WO{sub 3}/TNTs nanocomposite exhibit enhanced photocatalytic activity toward Rhodamine B (RhB) degradation compared with both of pure TNTs and P25, and the optimum percentage of WO{sub 3} decorated on TNTs for the improvement of photocatalytic properties is 5 wt.%. The enhanced photocatalytic activity may be attributed to the reduction of electron-hole recombination and the enlargement of light absorption scope for photoexcitation.
2009-01-01
The WO3 nanoparticles are synthesized on titanate nanotubes (TNTs) by a facile hydrothermal method. The prepared WO3/TNTs nanocomposites are characterized by XPS, TEM, XRD and UV-vis spectra. The result shows that the WO3 nanoparticles with the diameter of a few nanometers are evenly distributed on internal cavity and external surfaces of TNTs. As is expected, the WO3/TNTs nanocomposite exhibit enhanced photocatalytic activity toward Rhodamine B (RhB) degradation compared with both of pure TNTs and P25, and the optimum percentage of WO3 decorated on TNTs for the improvement of photocatalytic properties is 5 wt.%. The enhanced photocatalytic activity may be attributed to the reduction of electron-hole recombination and the enlargement of light absorption scope for photoexcitation
Spectroscopic properties of Pr sup 3+ doped LaWO sub 4 Cl and La sub 3 WO sub 6 Cl sub 3
1992-01-01
The spectroscopic properties of Pr{sup 3+} doping two lanthanum chlorotungstate hosts: the orthorhombic LaWO4Cl (1-1) and the hexagonal La3WO4Cl6 (3-1), as well as those of PrWO4Cl and Pr3wO613 have been investigated. The simulations of the energy level schemes are carried out within the crystal field theory frame. Each simulation involves 7 free ion parameters and 14 non-zero crystal field parameters (cfps), corresponding to the C{sub s} point symmetry of the site occupied by the rare earth, in both structures.
Removal of Rhodamine 6G induced by laser and catalyzed by Pt/WO3 nanocomposite
2010-01-01
The present study deals with the surface modification of nano-structured tungsten oxide (WO3) with nanoparticles of platinum (Pt) by applying a novel laser-based photocatalytic process. Microscopic studies revealed that Pt particles were homogeneously dispersed with narrow size distribution (2-4nm) onto the surface of WO3 within a short time of laser irradiation while XPS studies indicated that the deposited Pt nanoparticles were in the metallic form. Nano-structured bimetallic assemblies that consisted of WO3 and Pt particles showed enhanced photocatalytic removal of Rhodamine 6G as compared to pure WO3. Influence of laser irradiation time and platinum content has been studied. The Pt/WO3 nanocomposites were also prepared using conventional setup and the resulting photocatalytic activity ...
2010-01-01
Tungsten oxide (WO3) nanorods were grown on W substrates by thermal evaporation of WO3 powder at high temperature without using any catalyst and then by subsequent air annealing. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations revealed that the synthesized WO3 nanorods were highly dense and single crystalline. Optical absorption measurements showed that WO3 nanorods can absorb light up to 480-500nm. WO3 nanorods showed good photocurrent response with maximum current density of 1.5mAcm^-^2. The photocatalytic degradation of methylene blue revealed that WO3 nanorods have enhanced photocatalytic efficiency.
PbWO/sub 4/-SrWO/sub 4/ system
1983-12-01
The phase diagram of the PbWO/sub 4/-SrWO/sub 4/ system is studied by the methods of X-ray phase and visual polythermal analyses. A continuous series of solid substitution solutions in shown to be formed in this system. Substitution of strontium cations by lead cations leads to reduction of the melting point of samples from 1535 deg C (SrWO/sub 4/) to 1123 deg C (PbWO/sub 4/). The dependences of a and c crystal lattice parameter variation on the Pbsub(1-x)Srsub(x)WOsub(4) sample composition (where 0
Effect of gold on the properties of nitrogen dioxide sensors based on thin WO3 films
2010-01-01
The microstructure and properties of gold-doped WO3 (WO3:Au) thin films before and after deposition of dispersed Au layers have been studied. It is shown that the γ-WO2.72 phase arises in WO3:Au layers, which leads to a significant increase in the film conductivity. Deposition of a dispersed gold layer results in an increase in the sensor response to NO2 by several times. The concentration dependences and the dynamics of sensor responses to nitrogen dioxide are described by the analytical expressions derived under the assumption that WO3 films contain grains connected by conducting bridges. An analysis of the experimental data using these expressions made it possible to determine the activation energies of NO2 adsorption and desorption and the adsorption heat.
Crystal structure of monoclinic Y/sub 2/WO/sub 6/ and Yb/sub 2/WO/sub 6/
The crystal structure of TR/sub 2/WO/sub 6/ oxytungstates was determined for TR--Ho-Lu and Y taking Y/sub 2/WO/sub 6/ and Yb/sub 2/WO/sub 6/ as examples (sp. gr. P2/c, Z=4, R=4.5 and 2.9%, respectively). Three-dimensional skeleton is formed of polyhedrons WO/sub 6/(octahedrons), TR1O/sub 8/ and TR2O/sub 8/ (antiprisms) and TR3O/sub 7/ (single-cap trigonal prisms). The presence of rather perfect fluorite-like cation frame is typical.
Crystal structure of monoclinic Y/sub 2/WO/sub 6/ and Yb/sub 2/WO/sub 6/
The crystal structure of TR/sub 2/WO/sub 6/ oxytungstates was determined for TR--Ho-Lu and Y taking Y/sub 2/WO/sub 6/ and Yb/sub 2/WO/sub 6/ as examples (sp. gr. P2/c, Z=4, R=4.5 and 2.9%, respectively). Three-dimensional skeleton is formed of polyhedrons WO/sub 6/(octahedrons), TR1O/sub 8/ and TR2O/sub 8/ (antiprisms) and TR3O/sub 7/ (single-cap trigonal prisms). The presence of rather perfect fluorite-like cation frame is typical.
Carbothermic reduction of cobalt and nickel tungstates
2006-01-01
Data are presented on the formation sequence of metallic, carbide, and intermediate oxide phases in the carbon reduction of CoWO4 and NiWO4. The surface reaction between CoWO4 particles and solid carbon yields the mixed carbide Co6W6C, while the reaction with the CO originating from carbon vaporization yields the intermetallic phase Co7W6. The initial stage of the solid-state and gas-phase reduction of NiWO4 yields a solid solution of tungsten in nickel (∼10 at % W), Ni4W, and, presumably, the NiWO4-WO3 eutectic. The solid solution reacts with carbon to form Ni2W4C and with CO to form filamentary tungsten crystals.
Mechanochemical synthesis of nanoparticulate ZnOâZnWO4 powders and their photocatalytic activity
2009-01-01
In this study, mechanochemical reaction systems with H2WO4 as a precursor were investigated for the synthesis of nanoparticulate powders of WO3, ZnWO4, and dual-phase (ZnWO4)x(ZnO)1–x. The objective was to establish whether mechanochemical processing can be used to manufacture high activity photocatalysts in the ZnO–WO3 system. Milling and heat treatment of H2WO4 + 12NaCl was found to result in the formation of irregularly shaped platelets of a sodium tungstate rather than nanoparticles of WO3. Powders of single-phase ZnWO4 and dual-phase (ZnWO4)x(ZnO)1–x were successfully synthesised by incorporating H2WO4 into the ZnCl2 + Na2CO3 + 4NaCl reactant mixture. The photocatalytic activity of these powders was evaluated using the spin-trapping technique with electron paramagnetic resonance spectroscopy. It was found that the photocatalytic activity decreased with the ZnWO4 content. This decrease in activity was attributed to the larger average particle size of the ZnWO4 component compared to the ZnO, which reduced the surface area available for interfacial transfer of the photogenerated charge carriers.
Lifetime of electrochromism of amorphous WO sub 3 -TiO sub 2 thin films
In this paper, the degradation of the electrochromism of amorphous WO{sub 3} and WO{sub 3}-TiO{sub 2} films prepared by electron-beam deposition are studied. The lifetime of the WO{sub 3}-TiO{sub 2} films is five times longer than that of the WO{sub 3} films. SIMS and XPS analyses have revealed that lithium accumulates as OLi in the WO{sub 3} films, but that it cannot accumulate in the WO{sub 3}-TiO{sub 2} film. Ols electron energy loss spectroscopy (EELS) spectra have indicated that the change of the electronic structure for the WO{sub 3}-TiO{sub 2} film by coloration is smaller than that for the WO{sub 3} film. The increase of plasmon energy has been obtained in low loss EELS spectrum and the increase of the bond length in the WO{sub 3}-TiO{sub 2} film has been measured by Raman spectrum. From these results, the number of the defect bonds as a trapping site of lithium is reduced and the bond length of W-O decreases in the WO{sub 3}-TiO{sub 2} films. The authors conclude that lithium cannot accumulate in the structure of the WO{sub 3}-TiO{sub 2} film and that the structure gives a prolonged lifetime to the electrochromism.
The rate of convergence of the Walk on Spheres Algorithm
2008-10-21
In this paper we examine the rate of convergence of one of the standard algorithms for emulating exit probabilities of Brownian motion, the Walk on Spheres (WoS) algorithm. We obtain the complete characterization of the rate of convergence of WoS in terms of the local geomnetry of a domain.
Spectral properties and thermoluminescence of codoped PbWO4:(Mo,Y) and PbWO4:(F,Y) crystals
2009-01-01
Lead tungstate, PbWO4 single crystals codoped with Mo6+/F- and Y3+ ions were grown using the modified Bridgman method. Optical transmission, X-ray excited luminescence, photoluminescence, ultrashort pulsed X-ray excited fluorescent lifetime and thermoluminescence have been investigated. Compared to pure PbWO4, the codoped PbWO4:(Mo,Y) and PbWO4:(F,Y) crystals exhibit improved transmittance in the short-wavelength region. Luminescence and light-yield measurements demonstrated that Mo6+/F- and Y3+ codoping could enhance the luminescence of PbWO4 and reduce slow decay components. Doped Mo6+ and F- ions in PbWO4 were tentatively considered to occupy W and O sites, while ... >>
2009-01-01
A ZnWO4 nanocrystal catalyst with rod-like structure was first synthesized by powerful ultrasonic irradiation method at room temperature. Then, Ag was introduced to ZnWO4 nanorods by a photodeposited method. The as-synthesized Ag/ZnWO4 catalysts have been investigated by photocatalytic reaction tests and some physicochemical characterizations like XRD, BET, IR, TEM, EDX, XPS, PL, and UV-vis DRS. The results show that the prepared samples have good crystallinity and Ag addition can improve the photocatalytic performance of ZnWO4 in degradation of rhodamine-B (RhB) under UV light irradiation. The deposition of 1 wt% Ag over ZnWO4 leads to about a one-time increase in the photocatalytic performance with the reference of ZnWO4. The high performance of Ag/ZnWO4 could be attributed ... >>
Sol-gel deposition and luminescence properties of lanthanide ion-doped Y2(1-x)Gd2xSiWO8 (0
2005-01-01
Y2(1-x)Gd2xSiWO8:A (0>
Preparation and evaluation of thin-film sodium tungsten bronzes
Thin films of sodium tungsten bronze (NaxWO3) were investigated as reversible sodium ion electrodes for solid electrolytes. The films were made by electron beam evaporation of the three phases, W metal, Na2WO4, and ...
Preparation and evaluation of thin-film sodium tungsten bronzes
Thin films of sodium tungsten bronze (NaxWO3) were investigated as reversible sodium ion electrodes for solid electrolytes. The films were made by electron beam evaporation of the three phases, W metal, Na2WO4, ...
Photoinduced doping of thin amorphous WO3 films
During exposure of thin amorphous WO3 films to UV light, both the optical absorptivity and the electrical conductivity increase. Using optically excited surface plasmons, we were able to measure even ... Full Text Available
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Photocatalytic energy storage ability of TiO2-WO3 composite prepared by wet-chemical technique
2010-01-01
TiO2-WO3 hybrid photocatalysts were prepared using wet-chemical technique, and their energy storage performance was characterized by electrochemical galvanostatic method. TiO2 powder was coupled with WO3 powder, which was used as electron pool and the reductive energy could be stored in. As a result, the prepared TiO2-WO3 had good energy storage ability while pure TiO2 showed no capacity and pure WO3 showed quite low performance. The energy storage ability was affected by the crystal structure of WO3 and calcination temperature. The photocatalyst had better capacity when WO3 had low degree of crystallinity, since its loose structure made it easier for electrons and cations to pass through. The photocatalytic energy storage performance was also affected by the molar ratio of TiO2 to WO3. En...
Luminescence of CdWO{sub 4} single crystals doped with molybdenum
1994-06-01
Luminescence properties of emission centers formed in molybdenum-doped CdWO{sub 4} single crystals are studied. 3 refs., 4 figs.
Enthalpies of formation of WO/sub 2/Br/sub 2/ and WO/sub 2/I/sub 2/
1982-07-01
The enthalpies of formation for WO/sub 2/Br/sub 2/ and WO/sub 2/I/sub 2/ were derived from the enthalpies of solution in NaOH and KOH respectively. The determination based on the enthalpy of formation for Na/sub 2/WO/sub 4/, K/sub 2/WO/sub 4/, MeOH, MeX and their enthalpies of solution in NaOH and KOH respectively. The solution enthalpies of the compounds have been measured in the precision calorimeter LKB 8700 at 298 K. The dependence of the enthalpy of solution on concentration have been obtained for NaCl, NaBr, NaI, Na/sub 2/WO/sub 4/, KCl, KBr, KI, and K/sub 2/WO/sub 4/.
2010-01-01
Total and partial densities of states of the constituent atoms of iron tungstate, FeWO4, and cobalt tungstate, CoWO4, have been calculated using the first-principles self-consistent full potential linearized augmented plane wave (FP-LAPW) method. The results obtained reveal that the O 2p-like states are the dominant contributors into the valence band of the tungstates under consideration, whilst the bottom of the conduction band of FeWO4 and CoWO4 is dominated by contributions of the empty Fe 3d- and Co 3d-like states, respectively. The FP-LAPW data indicate that the O 2p-like states contribute mainly into the top of the valence band, with also significant contributions throughout the whole valence-band region, of FeWO4 and CoWO4 compounds. Other significant contributors into the valence-b...
1978-09-01
The domain and surface structures of metallic sodium tungsten bronzes, Na/sub x/WO/sub 3/, 0.4
Densities of calcium nuclei as deduced by analyses of WO scattering
1985-01-03
Densities of UCa, USCa, UUCa and UYCa nuclei are derived by analyses of the scattering processes initiated by a WO beam. The procedure is based on the use of real potentials that specifically involve the densities of the interacting nuclei. The results are compared with densities deduced from alpha-particle scattering. (orig.).
Conduction properties of the hexagonal tungsten bronze, Rb/sub x/WO/sub 3/
1979-09-01
Studies of the electrical transport properties: resistivity, Hall effect, and Seebeck coefficient: of the hexagonal tungsten bronze Rb/sub x/WO/sub 3/ for 0.16
Conditions and mechanism of solid-phase synthesis of strontium tungstates
The kinetics and mechanism of solid-phase synthesis of strontium tungstates were studied in the temperature range of 1103-1573 K. Temperatures of the beginning of interactions and phase transformation sequences in the SrO-WO/sub 3/ system were determined. The interrelation between the constants of SrWO/sub 4/ and Sr/sub 3/WO/sub 6/ synthesis rates, their electrophysical properties and conditions of the experiment was established. It was shown that tungstates formation was proceeding in the diffusional regime at the expense of primary mobility of tungsten (6) ions during SrWO/sub 3/ synthesis and primary mobility of strontium (2) during Sr/sub 3/WO/sub 6/ synthesis. Temperature dependences of W(6) effective diffusion coefficients in SrWO/sub 4/ structure and those of Sr(2) in Sr/sub 3/WO/sub 6/ were calculated. An attempt was made to regulate the mobility of cations in the SrWO/sub 4/ lattice by introducing donor-type heterovalent admixtures.
Conditions and mechanism of solid-phase synthesis of strontium tungstates
1982-11-01
The kinetics and mechanism of solid-phase synthesis of strontium tungstates were studied in the temperature range of 1103-1573 K. Temperatures of the beginning of interactions and phase transformation sequences in the SrO-WO/sub 3/ system were determined. The interrelation between the constants of SrWO/sub 4/ and Sr/sub 3/WO/sub 6/ synthesis rates, their electrophysical properties and conditions of the experiment was established. It was shown that tungstates formation was proceeding in the diffusional regime at the expense of primary mobility of tungsten (6) ions during SrWO/sub 3/ synthesis and primary mobility of strontium (2) during Sr/sub 3/WO/sub 6/ synthesis. Temperature dependences of W(6) effective diffusion coefficients in SrWO/sub 4/ structure and those of Sr(2) in Sr/sub 3/WO/sub 6/ were calculated. An attempt was made to regulate the mobility of cations in the SrWO/sub 4/ lattice by introducing donor-type heterovalent admixtures.
2006-01-01
Lead tungstate (PbWO4) crystal scintillators are discussed as an active shield and light guides in 116Cd double-beta decay experiment with Cadmium tungstate (CdWO4) scintillators. Scintillation properties and radioactive contamination of PbWO4 scintillators were investigated. Energy resolution of CdWO4 detector, coupled to PbWO4 light guide, was tested. Efficiency of PbWO4-based active shield to suppress background from the internal contamination of PbWO4 crystals, as well as possible contribution from radioactivity of copper shield and phototubes were calculated. Using of lead tungstate crystal scintillators as high-efficiency Formula Not Shown active shield could allow to build sensitive Formula Not Shown experiment Formula Not Shown to search for Formula Not Shown decay of 116Cd with 11...
XAFS Study of Active Tungsten Species on WO3/TiO2 as a Catalyst for Photo-SCR
2007-01-01
The activity of the photo-assisted selective catalytic reduction of NO with NH3 (photo-SCR) was enhanced by the addition of WO3 to TiO2. From the result of XAFS analysis, the W species on TiO2 had a WO4 tetrahedral structure and agglutination took place as the addition of WO3 was increased. We conclude that the isolated W species enhances the surface acidity and photo-SCR activity whereas the agglutinated W species is an inactive species
Superconductivity in the tungsten bronze RbxWO3 (0.20
2007-01-01
We have measured the magnetic susceptibility of the RbxWO3 compound (0.20rubidium content, i.e., of the conduction electron density [what we shall name the ''Tc (x) paradox''], and (ii) the destabilizing effect of the ordering of the Rb ions. We also performed density-functional calculations of the phonon dispersion in the ''stoichiometric'' Rb0.33WO3 and Cs0.33WO3 to identify the main features of the phonon spectra. These calculations give a very satisfactory ... >>
Study of the tungsten bronze Ag{sub 0.01}WO{sub 3} using positron annihilation method
1992-12-31
Short communication.
2008-01-01
Density-functional calculations of the electronic structure and atomic positions are reported for Li2WO4. This compound is found to be very different from the tungstate scintillators such as PbWO4 in that both the valence and conduction bands are much less dispersive. This leads to a substantially larger band gap. The difference is understood in terms of the crystal structure, in particular, the longer O-O distances connecting the WO4 tetrahedra
Paramagnetic resonance of erbium in CaWO sub 4.
Paramagnetic resonance of Er ion in calcium tungstate single crystal, determining spin- Hamiltonian parameters
Paramagnetic resonance of erbium in CaWO sub 4.
Paramagnetic resonance of Er ion in calcium tungstate single crystal, determining spin- Hamiltonian parameters
O papel dos modificadores de rede na produção da fotoluminescência no CaWO4
2004-03-01
Full Text Available
Growth of PbWO4:MeF2(MeF2 = PbF2, BaF2) single crystals and their properties
2008-01-01
PbF2-and BaF2-doped PbWO4 crystals have been grown by the Czochralski method. The scintillation characteristics of the grown crystals have been determined. It is shown that introduction of BaF2 leads to an increase in the light yield of PbWO4 crystals by 20%, while PbWO4:PbF2 crystals demonstrate a significant increase in radiation hardness.
Evidence of hexagonal WO3 structure stabilization on mica substrate
2009-01-01
WO3 nanorods are grown by a simple vapor deposition method on a mica substrate and characterized by Selected Area Electron Diffraction and Energy Dispersive X-rays Spectroscopy. Experimental results show the clear evidence of an unexpected WO3 hexagonal structure as well as an epitaxial growth on the mica substrate. Besides, potassium is evidenced inside the nanorods. It is thus deduced that a metastable WO3 hexagonal phase is stabilized by epitaxy through a tungsten bronze interlayer having same hexagonal structure.
2009-01-01
This work reports on the development of the first phonon detectors based on CaMoO4 and ZnWO4 scintillating crystals for the CRESST-II experiment. In particular, a novel technique for the production of the ZnWO4 phonon detector with a separate thermometer carrier was investigated. The influence of the thermal and mechanical treatment on the scintillation light output of CaMoO4 and ZnWO4 crystals at room temperature is discussed.
2008-11-13
This work reports on the development of the first phonon detectors based on CaMoO4 and ZnWO4 scintillating crystals for the CRESST-II experiment. In particular, a novel technique for the production of the ZnWO4 phonon detector with a separate thermometer carrier was investigated. The influence of the thermal and mechanical treatment on the scintillation light output of CaMoO4 and ZnWO4 crystals at room temperature is discussed.
Acetone vapor sensing properties of screen printed WO3 thick films
2007-01-01
This paper presents acetone vapor sensing properties of WO3 thick films. In this work, the WO3 thick films were prepared by standard screen-printing method. These films were characterized by X-ray diffraction (XRD) measurements, and scanning electron microscopy (SEM). The acetone vapor sensing properties of these thick films were investigated at different operating temperature and acetone vapor concentrations. The WO3 thick films exhibit excellent acetone vapor sensing properties with the maximum sensitivity 456% at 300degreeC in air atmosphere with fast response and recovery time.
This work investigates the development of a proton-conducting ceramic between room temperature and at least 300{degree}C for use in galvanic-cell gas sensors. This paper examines the proton-conducting materials NH{sub 4}NbWO{sub 6} and NH{sub 4}TaWO{sub 6}.
1987-10-01
This work investigates the development of a proton-conducting ceramic between room temperature and at least 300{degree}C for use in galvanic-cell gas sensors. This paper examines the proton-conducting materials NH{sub 4}NbWO{sub 6} and NH{sub 4}TaWO{sub 6}.
A new proton-conducting ceramic: Part I. Preparation of RbTaWO sub 6 and RbNbWO sub 6
A new proton-conducting ceramic for use in galvanic gas sensors between room temperature and 300{degree}C has been developed. Special emphasis was placed on the optimization of sintering methods and sintering aids to obtain a dense, pressureless-sintered precursor ceramic. Starting with the preparation of RbTaWO{sub 6} and RbNbWO{sub 6} powders, part I presents a detailed description of the ceramic processing procedure.
A new proton-conducting ceramic: Part I. Preparation of RbTaWO sub 6 and RbNbWO sub 6
1987-10-01
A new proton-conducting ceramic for use in galvanic gas sensors between room temperature and 300{degree}C has been developed. Special emphasis was placed on the optimization of sintering methods and sintering aids to obtain a dense, pressureless-sintered precursor ceramic. Starting with the preparation of RbTaWO{sub 6} and RbNbWO{sub 6} powders, part I presents a detailed description of the ceramic processing procedure.
Thermal analysis of Na, Rb//Cl, WO4 system Termicheskij analiz sistemy Na, Rb//Cl, WO4
2004-01-01
By the methods of visual polythermal and differential thermal analysis ternary mutual system Na, Rb//Cl, WO4 is investigated for the first time. It is determined that liquidus of the system consists of crystallization fields of initial components and two compounds. Lines of mutual formation of phases crystallizing in the system comes together in four nonvariant points: three eutectic and one peritectic
The coloration of tungsten-oxide film by oxygen deficiency and its mechanism
2008-01-01
The transmissivity and the optical absorption of a WO3 film with oxygen deficiencies introduced were characterized and compared with those of an electrochromically colored WO3 upon injecting a proton (H+). The WO3 film with oxygen deficiencies introduced was clearly colored blue. It was shown that the wavelength regions of optical absorption of both films almost overlapped each other
Study of thermal disordering of the KSc(WO4)2 crystal structure by Raman spectroscopy
2002-01-01
Raman spectra of KSc(WO4)2, exhibiting three reversible phase transitions from the trigonal phase to monoclinic and triclinic structures, have been studied in the temperature region of 100-294 K. The measurements have revealed the presence of significant broadening of vibrational and translational modes of the WO42- ions with increasing temperature. This broadening was explained as a result of anisotropic activation of the complex ion reorientation. (author)
Structure of tungstic acids and amorphous and crystalline WO/sub 3/ thin films
1982-11-16
The structure of tungstic acids and amorphous and crystalline WO/sub 3/ thin films was investigated by thermal analysis methods and Raman spectroscopy. It could be concluded that the structure of A-WO/sub 3/ films consists of a layered type structure of tungsten hydrates and of a framework structure of tungsten anhydride.
Solid-state synthesis in the system Na0.8NbyW1-yO3 with 0
2008-01-01
Series of compounds in the system NaxNbyW1-yO3 were prepared according to the appropriate molar ratio of Na2WO4, WO3, WO2 and Nb2O5 with x=0.80 and 0.0>
1992-11-01
Some characteristics including radiation resistance of PbWO[sub 4], NaBi(WO[sub 4])[sub 2] and KYb(WO[sub 4])[sub 2] crystals, which are promising for application in detectors at new accelerators and colliders, are described. (orig.).
The optical damage induced by UV light in PbWO4 crystals is found to be similar to that induced by g radiation. Due to the peculiarities of optical absorption in PbWO4, the damage induced by UV light is a bulk process. This fact has important consequences for the approach to be adopted both for the use of the crystal as scintillator and for the qualification methods foreseen in the Regional Centres of the ECAL CMS Collaboration.
1960-11-02
The objective of this production test is to evaluate the behavior of brazed fuel element end closures prepared with a 12 w/o Iron, 4 w/o Beryllium, 84 w/o Zirconium braze alloy during high temperature irradiation in the KER Loops.
Oxidative coupling of methane over Mn/Na{sub 2}WO{sub 4}/MgO and related catalysts
1996-10-01
The oxidative coupling of methane over Mn/Na{sub 2}WO{sub 4}/MgO, Mn/Na{sub 2}WO{sub 4}/silica, and NaMnO{sub 4}/MgO catalysts was studied. Results are described.
Lead tungstate (PbWO sub 4) scintillators for LHC EM-calorimeter
A characterization of the radiation hardness of PbWO sub 4 scintillators by means of transmission measurements will be described. The gamma radiation induced changes in the absorption spectra of PbWO sub 4 crystals undoped as well as doped with trivalent ions will be illustrated. The characteristics of the room temperature recovery of the radiation induced colour centres in these crystals will be reported.
Temperature dependences of combination light scattering (CLS) spectra of CaWO/sub 4/ crystal were studied to improve the technique of non-destructive control of crystal structure transformations (upto 1900 K). CLS changes during melting were investigated. It was found that the dissociation of WO/sub 4//sup 2 -/ complexes did not occur in CaWO/sub 4/ melt near fusing temperature.
Electrochromic and photoelectrochemical behavior of electrodeposited tungsten trioxide films
1999-06-10
Electrodeposited WO{sub 3} films exhibit reversible photochromic and electrochromic behavior (blue coloration with absorption in the near-IR region). The W-4f core level of WO{sub 3} film at different levels of coloration has been investigated using XPS. The W-4f peaks become broader after coloration. Photoelectrochemical measurements have shown a low photoelectric conversion, efficiency of WO{sub 3} film
Band structure of cubic Na/sub x/WO/sub 3/
1977-01-01
The band structures of cubic WO/sub 3/ and NaWO/sub 3/ have been calculated, and they are shown to be nearly identical, demonstrating the validity of the rigid band model for different sodium concentrations. To elucidate the nature of the bonding, the density of states is decomposed into its s, p, and d contributions from each atomic site.
A new multiferroic material: MnWO4
2006-01-01
We report the multiferroic behaviour of MnWO4, a magnetic oxide with monoclinic crystal structure and spiral long-range magnetic order. Based upon recent theoretical predictions, MnWO4 should exhibit ferroelectric polarization coexisting with the spiral magnetic structure. We have confirmed the multiferroic state below 13 K by observing a finite electrical polarization in the magnetically ordered state via pyroelectric current measurements. (letter to the editor)
A New Multiferroic Material: MnWO4
2006-08-23
We report the multiferroic behaviour of MnWO$_4$, a magnetic oxide with monoclinic crystal structure and spiral long-range magnetic order. Based upon recent theoretical predictions MnWO$_4$ should exhibit ferroelectric polarization coexisting with the proper magnetic structure. We have confirmed the multiferroic state below 13 K by observing a finite electrical polarization in the magnetically ordered state via pyroelectric current measurements.
Production test IP-694-A: Depleted uranium irradiation, K reactors
1964-08-17
The AEC has indicated a need for plutonium with a high concentration of the Pu-240 isotope. Concentrations up to 25 W/o Pu-240 have been requested with a firm commitment given for 25 kilograms of plutonium with at least 18 W/o Pu-240. To meet this production demand, irradiation of depleted uranium, 0.22 W/o U-235, will be undertaken. This test authorizes half of the irradiation in a Hanford K reactor, outlines the general plans, and presents the details of the irradiation. The objective of this test is to authorize irradiation of approximately 12 tons of depleted uranium, 0.22 W/o U-235, in a Hanford K reactor. The depleted uranium will be irradiated to exposures which will yield plutonium with at least 18 W/o Pu-240, an average exposure of approximately 1600 MWD/T.
Optical characteristics of WO/sub 3/ electrochromic cells under heavy Li ion injection
1982-11-01
This paper reports on conspicuous coloration phenomena in amorphous WO3 films under heavy Li ion injection levels. After heavy coloration, blue WO3 films turn into highly reflective golden-yellow films. An Li2 WO4 mixture with glycerine is tested for the effect of residual water on coloration. It is also shown that lithium ion dissolved in glycerine is not responsible for the coloration. Optical absorption spectra and electrical conductivity during coloration are measured. Optical property measurements show that the blue WO3 film changes irreversibly and reproducibly into golden yellow films as a consequence of Li injection.
Nanostructured WO3 films using high temperature anodization
2009-01-01
We have investigated the formation of highly porous nanostructured tungsten trioxide (WO3) films of several microns thickness using elevated temperature anodization in nitric acid. Plate-like crystals with thicknesses in the range of 20.60nm and lengths in the order of 50.1000nm were obtained after anodization of tungsten foil in 1.5MHNO3 at 50 .C. High intensity {200}WO3 crystallographic signatures from platelets revealed the presence of predominantly orthorhombicWO3 nanoplatelets in annealed (up to 550 .C) samples. Photocurrent measurements revealed that 4 h anodized sample at 20V produced the largest photocurrent density. High photocurrent response from the nanoplateleted films show the possibility of developing efficient WO3/electrolyte sandwiched photosensors.
Nanostructured WO3 films using high temperature anodization
2009-01-01
We have investigated the formation of highly porous nanostructured tungsten trioxide (WO3) films of several microns thickness using elevated temperature anodization in nitric acid. Plate-like crystals with thicknesses in the range of 20-60nm and lengths in the order of 50-1000nm were obtained after anodization of tungsten foil in 1.5M HNO3 at 50^oC. High intensity {200} WO3 crystallographic signatures from platelets revealed the presence of predominantly orthorhombic WO3 nanoplatelets in annealed (up to 550^oC) samples. Photocurrent measurements revealed that 4h anodized sample at 20V produced the largest photocurrent density. High photocurrent response from the nanoplateleted films show the possibility of developing efficient WO3/electrolyte sandwiched photosensors.
The electrochromism of phosphomolybdic acid (PM) in solution and in a series of solid WO{sub 3}-PM composites is investigated. PM in solution changes color from light yellow to dark blue upon reduction whereas the composites show a change from light yellow to bluish brown under identical conditions. PM could not be deposited as a thin film by itself, and electrochemical codeposition was used to incorporate it into the WO{sub 3} matrix. The basic electrochromatic properties of WO{sub 3} are changed upon the incorporation of PM even in small quantities. The composites have a more intense color, a different cold spectrum, and a slower electrochromic response speed than that of WO{sub 3}. The composites, like WO{sub 3}, are also degraded by slow and continuous potential cycling.
2009-01-01
CaWO4 and SrWO4 nanostructures have been synthesized via a simple microemulsion-mediated route. With careful control of the fundamental experimental parameters including the concentration of reactants, the reaction time and the temperature, the products with different morphologies of dumbbell, coral, rod and dendrite have been obtained, respectively. The possible formation mechanism of these unique morphologies has been proposed based on surfactant self-assembly under different experimental conditions. The as-synthesized CaWO4 samples with various morphologies exhibit different photoluminescence properties. X-ray powder diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and luminescence spectroscopy were used to characterize these products
Application of WO3 thin films for enhancement of photolysis in AgCl
2009-01-01
A double-layer AgCl-WO3 structure was employed to produce photochemical hydrogen for doping of an AgCl film. Atomic photochemical hydrogen, detached under the action of light from hydrogen donor molecules, previously adsorbed on the WO3 surface, migrated through the WO3 film into the AgCl film, which provided doping of the AgCl surface and yielded hydrogen sensitization simultaneous to illumination and yielded the enhancement of photochromism in the AgCl films. The atomic hydrogen played the role of a reducing agent and triggered the formation of sensitization centers on the halide surface, which in turn facilitated the growth of silver clusters and colloids under the action of light. The double-layer AgCl-WO3 structure realizes the idea of two-stage catalysis: first the oxide surface cata...
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