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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Chemical pressure effects on structural, dielectric and magnetic properties of solid solutions Mn{sub 3−x}Co{sub x}TeO{sub 6}

Highlights: • Mn{sub 3}TeO{sub 6} and Co{sub 3}TeO{sub 6} are antiferromagnets with corundum related structures. • The structural and magnetic properties of Mn{sub 3−x}Co{sub x}TeO{sub 6} ceramics were investigated. • All compounds adopt the trigonal structure of Mn{sub 3}TeO{sub 6} up to at least x = 2.4. • The antiferromagnetic transition temperature monotonously increases with x. • NPD data evidences the magnetic structure of the Mn{sub 3−x}Co{sub x}TeO{sub 6} ceramics. - Abstract: The effects of Co{sup 2+} doping on the structural, magnetic and dielectric properties of the multiferroic frustrated antiferromagnet Mn{sub 3}TeO{sub 6} have been investigated. Ceramic samples of the solid solution series Mn{sub 3−x}Co{sub x}TeO{sub 6} were prepared by a solid-state reaction route. X-ray and neutron powder diffraction and electron microscopy techniques were combined with calorimetric, dielectric and magnetic measurements to investigate the dependence of the crystal structure and physical properties on temperature and composition. It is shown that the compounds with x ≤ 2.4 adopt the trigonal corundum-related structure of pure Mn{sub 3}TeO{sub 6} (space group R3{sup ¯}) in the temperature range 5–295 K and that the lattice parameters a and c and the unit-cell volume V decrease linearly with increasing Co{sup 2+} concentration. The low-temperature magnetic susceptibility and heat capacity data evidence the antiferromagnetic ordering of all samples. The Neel temperature linearly increases with Co{sup 2+} concentration x. Curie–Weiss fits of the high temperature susceptibility indicate that the magnetic frustration decreases with x. The derived magnetic structure of Mn{sub 3}TeO{sub 6} can be described as an incommensurately modulated magnetic spin state with k = [0, 0, k{sub z}] and an elliptical spin-spiral order of spins within the chains of MnO{sub 6} octahedra. With increasing Co{sup 2+} concentration the propagation vector k{sub z} changes from 0.453 (x = 0) to 0.516 (x = 2.4). The magnetic anisotropy changes as well, leading to a reorientation of the spiral-basal plane. A possible coexistence of long-range order of electrical dipoles and magnetic moments in Mn{sub 3−x}Co{sub x}TeO{sub 6} is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2014

In situ synthesis of TiH{sub 2} layer on metallic titanium foil through gaseous hydrogen free acid-hydrothermal method

Graphical abstract: The reaction mechanism for in situ synthesizing TiH{sub 2} layer on titanium foil by a gaseous hydrogen free acid-hydrothermal methodology. - Highlights: • A dense TiH{sub 2} layer is synthesized by a hydrogen free acid-hydrothermal method. • Hydrogen in a TiH{sub 2} layer synthesized can release at low temperature. • During the dehydrogenation process, there is no any intermediate phase forming. • We report a method of low-cost, low-risk and convenience toward productive TiH{sub 2}. - Abstract: A novel strategy for synthesis of TiH{sub 2} layer on surface of metallic titanium by using an acid-hydrothermal method was proposed. During the synthesis process, no any elemental hydrogen was involved. X-ray powder diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy results confirmed that a TiH{sub 2} layer of 20 μm thickness on a Ti foil surface can be formed in situ by an interface reaction of metallic titanium with sulfuric acid solution, hydrochloric acid, or phosphoric acid, which is a hydrogen self-storage process. By tuning reaction parameters, for example, concentration of acid, composition and morphology of TiH{sub 2}-Ti hybrid materials can be adjusted. The TiH{sub 2} layer on a metallic titanium surface can be decompounded completely heated below 400 °C. This convenient, safe and low-cost method is a promising gaseous hydrogen free approach for the synthesis of hydride-based hydrogen storage materials.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Synthesis of g-C{sub 3}N{sub 4}/Ag{sub 3}PO{sub 4} heterojunction with enhanced photocatalytic performance

Graphical abstract: g-C{sub 3}N{sub 4}/Ag{sub 3}PO{sub 4} heterojunction photocatalyst with visible-light response was prepared by a facile coprecipitation method. The results show that g-C{sub 3}N{sub 4}/Ag{sub 3}PO{sub 4} possesses a much higher activity for the decomposition of RhB than that of the pure Ag{sub 3}PO{sub 4} particles. The most mechanism is that g-C{sub 3}N{sub 4}/Ag{sub 3}PO{sub 4} heterojunction photocatalyst can efficiently separate the photogenerated electron–hole pairs, enhancing the photocatalytic activity of g-C{sub 3}N{sub 4}/Ag{sub 3}PO{sub 4} composites. - Highlights: • g-C{sub 3}N{sub 4}/Ag{sub 3}PO{sub 4} heterojunction showed much higher activity than that of Ag{sub 3}PO{sub 4}. • The high activity could be attributed to g-C{sub 3}N{sub 4} for modifying Ag{sub 3}PO{sub 4}. • More ·OH radicals may be significant reason to improve Ag{sub 3}PO{sub 4} activity. - Abstract: g-C{sub 3}N{sub 4}/Ag{sub 3}PO{sub 4} heterojunction photocatalyst with visible-light response was prepared by a facile coprecipitation method. The photocatalysts were characterized by X-ray powder diffraction, transmission electron microscopy, UV–vis absorption spectroscopy and Fourier transform infrared spectroscopy. The photocatalytic activities of the obtained samples were tested by using Rhodamine B (RhB) as the degradation target under visible light irradiation. g-C{sub 3}N{sub 4}/Ag{sub 3}PO{sub 4} decomposed RhB more effectively than the pure Ag{sub 3}PO{sub 4} particles did, and 2 wt.% g-C{sub 3}N{sub 4} had the highest activity. Furthermore, 2 wt.% g-C{sub 3}N{sub 4}/Ag{sub 3}PO{sub 4} degraded high-concentration RhB more potently than unmodified Ag{sub 3}PO{sub 4} did, probably because g-C{sub 3}N{sub 4}/Ag{sub 3}PO{sub 4} heterojunction photocatalyst enhanced the photocatalytic activity by efficiently separating the photogenerated electron–hole pairs.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Enhancement of photocatalytic performance of TiO{sub 2} produced by an alcohothermal approach through inclusion of water

Graphical abstract: - Highlights: • High crystallinity of TiO{sub 2} with exposed (0 0 1) facets was prepared by an alcohothermal approach through inclusion of water. • Water played an important role in conducting the size, shape, crystallinity, microstructure and photocatalytic activity of TiO{sub 2}. • High crystallinity of TiO{sub 2} could retard the recombination and promote the separation of electron–hole pairs. - Abstract: High crystallinity of TiO{sub 2} nanoparticles (NPs) with exposed (0 0 1) facets was prepared by an alcohothermal method without the addition of any specific organic reagents, in which titanium isopropoxide was used as the titania precursor, water and ethanol (0.6/90–5/90, v/v) as the reaction medium. The X-ray powder diffraction (XRD) and transmission electron microscope (TEM) measurements showed that water played an important role in conducting the size, shape, crystallinity and microstructure of TiO{sub 2} NPs. The photoluminescence spectroscopy and photocurrent measurements indicated that enhanced crystallinity could hinder effectively the recombination and promote significantly the separation of electron–hole pairs in TiO{sub 2} NPs. These will contribute to the enhancement of photocatalytic performance. Methyl orange photodegradation under UV light confirmed that high crystallinity of TiO{sub 2} NPs did exhibit a high photocatalytic activity due to the effective separation of photoinduced charges and exposure of highly reactive (0 0 1) facets.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Surface phase of TiO{sub 2} modified with La{sub 2}O{sub 3} and its effect on the photocatalytic H{sub 2} evolution

Graphical abstract: The La{sub 2}O{sub 3}/TiO{sub 2}-900 °C (or La{sub 2}O{sub 3}/Ti(OH){sub 4}-900 °C), with surface anatase phase, show the similar photocatalytic activity. The presence of the surface anatase phase is important for high photocatalytic activity of TiO{sub 2} modified with La{sub 2}O{sub 3} (La{sub 2}O{sub 3}/Ti(OH){sub 4}-900 °C or La{sub 2}O{sub 3}/Ti(OH){sub 4}-900 °C){sub .} - Highlights: • Loading La{sub 2}O{sub 3} on anatase TiO{sub 2} is an effective method for stabilizing the anatase phases both in the surface and in the bulk region. • The high crystallinity of the surface anatase phase is important for high photocatalytic activity of TiO{sub 2} modified with La{sub 2}O{sub 3.} - Abstract: TiO{sub 2} nanoparticles modified with La{sub 2}O{sub 3} were prepared by an impregnation method using anatase TiO{sub 2} support (La{sub 2}O{sub 3}/TiO{sub 2}) or amorphous Ti(OH){sub 4} support (La{sub 2}O{sub 3}/Ti(OH){sub 4}). The bulk and surface crystalline phases of La{sub 2}O{sub 3}/TiO{sub 2} (or La{sub 2}O{sub 3}/Ti(OH){sub 4}) have been characterized by X-ray powder diffraction (XRD) and UV Raman spectroscopy. Besides, morphology and particle size of La{sub 2}O{sub 3}/TiO{sub 2} and La{sub 2}O{sub 3}/Ti(OH){sub 4} samples have been determined by TEM (transmission electron microscope) and Brunauer–Emmett–Teller (BET), respectively. It is found that the phase transformation and increase of the particle size of TiO{sub 2} can be more effectively inhibited in the La{sub 2}O{sub 3}/TiO{sub 2} than in the La{sub 2}O{sub 3}/Ti(OH){sub 4}. Photocatalytic experiments indicated that the La{sub 2}O{sub 3}/TiO{sub 2} (or La{sub 2}O{sub 3}/Ti(OH){sub 4}) samples with surface anatase phase have the similar overall photocatalytic activities. Moreover, it is found that the high crystallinity of surface anatase phase is benefit for the high photocatalytic activity of TiO{sub 2} modified with La{sub 2}O{sub 3}.

36 MATERIALS SCIENCE↗
DOE OSTI2014

A self-activated silicate phosphor of Na{sub 5}YZrSi{sub 6}O{sub 18}

Graphical abstract: Self-activated Na{sub 5}YZrSi{sub 6}O{sub 18} shows a bright green luminescence. It presents obvious LLP afterglow with duration time >3 h after the removal of excitation. The substitution of Y{sup 3+} by rare earth ions except Yb{sup 3+} cannot prolong the afterglow. It is proposed that the disorder in the lattices can result in different trap centers attributing to the long last phosphorescence. - Highlights: • Na{sub 5}YZrSi{sub 6}O{sub 18} was firstly developed to be a new bluish green-emitting silicate. • Na{sub 5}YZrSi{sub 6}O{sub 18} presents unusual properties: efficient excitation and longer emission wavelength. • Na{sub 5}YZrSi{sub 6}O{sub 18} shows long-lasting phosphorescence with duration time above 3 h. - Abstract: A new self-activated silicate phosphor of Na{sub 5}YZrSi{sub 6}O{sub 18} was prepared by a solid-state reaction method. The phase formation was confirmed by X-ray powder diffraction measurement. The photoluminescence excitation and emission spectra, X-ray-excited luminescence, decay curves, quantum efficiencies and the color coordinates were investigated. It can be efficiently excited by UV light and X-ray and presents unusual green emission (centered at 475 nm) from Zr{sup 4+} to O{sup 2−} charge transfer transition. Meanwhile, the phosphor shows long-lasting phosphorescence with duration time above 3 h after the removal of excitation. The afterglow curves and thermo-luminescence were measured for pure and rare earth ions (RE = Yb, Er, Ho, Dy, Tb, Sm, Nd) doped Na{sub 5}YZrSi{sub 6}O{sub 18}. The possible defects and the mechanism of long-lasting phosphorescence were suggested on the base of the strong disorder of the multiply cation sites in the lattices.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Hydrothermal synthesis of hydroxyapatite nanorods using pyridoxal-5′-phosphate as a phosphorus source

Graphical abstract: Hydroxyapatite nanorods are synthesized using biocompatible biomolecule pyridoxal-5′-phosphate as a new organic phosphorus source by the hydrothermal method. - Highlights: • Hydrothermal synthesis of hydroxyapatite nanorods is reported. • Biocompatible pyridoxal-5′-phosphate is used as an organic phosphorus source. • This method is simple, surfactant-free and environmentally friendly. - Abstract: Hydroxyapatite nanorods are synthesized by the hydrothermal method using biocompatible biomolecule pyridoxal-5′-phosphate (PLP) as a new organic phosphorus source. In this method, PLP biomolecules are hydrolyzed to produce phosphate ions under hydrothermal conditions, and these phosphate ions react with pre-existing calcium ions to form hydroxyapatite nanorods. The effects of experimental conditions including hydrothermal temperature and time on the morphology and crystal phase of the products are investigated. This method is simple, surfactant-free and environmentally friendly. The products are characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric (TG) analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Facile fabrication of p-BiOI/n-Zn{sub 2}SnO{sub 4} heterostructures with highly enhanced visible light photocatalytic performances

Highlights: • The BiOI/Zn{sub 2}SnO{sub 4} photocatalysts were prepared by a mild wet chemical method. • The ZB-1/2 (Zn to Bi molar ratio = 1/2) exhibits the best photocatalytic activity. • The enhanced performance results from high separation of photogenerated carriers. - Abstract: New BiOI/Zn{sub 2}SnO{sub 4} p–n heterojunction photocatalysts were prepared by anchoring n-type Zn{sub 2}SnO{sub 4} nanoparticles on p-type BiOI plates. The physicochemical characteristics of the catalysts were studied by X-ray powder diffraction pattern (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Ultraviolet visible (UV–vis) diffuse reflectance spectroscopy (DRS), nitrogen adsorption–desorption, and photoelectrochemistry measurement. The as-prepared catalysts exhibited excellent photocatalytic activity for the decomposition of methyl orange (MO) under visible light irradiation. The enhanced photocatalytic performance of BiOI/Zn{sub 2}SnO{sub 4} was not only attributed to the matched band potentials but also the interconnected heterojunction of BiOI and Zn{sub 2}SnO{sub 4} nanoparticles.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Luminescence properties of Eu-activated alkaline and alkaline-earth silicate Na{sub 2}Ca{sub 3}Si{sub 6}O{sub 16}

Highlights: • A novel yellow-emitting alkaline and alkaline-earth silicate Na{sub 2}Ca{sub 3}Si{sub 6}O{sub 16}:Eu{sup 2+} was first developed. • Under excitation with UV or near UV light the silicate presents broad emission band centered at 580 nm. - Abstract: Yellow-emitting phosphors of Na{sub 2}Ca{sub 3}Si{sub 6}O{sub 16}:Eu{sup 2+} was prepared by wet chemistry sol–gel method. X-ray powder diffraction and SEM measurements were applied to characterize the structure and morphology, respectively. The luminescence properties were investigated by the photoluminescence excitation and emission spectra, decay curve (lifetimes), CIE coordinates and the internal quantum efficiencies. The excitation spectra can match well with the emission light of near UV-LED chips (360–400 nm). Na{sub 2}Ca{sub 3}Si{sub 6}O{sub 16}:Eu{sup 2+} presents a symmetric emission band from 4f{sup 6}5d{sup 1} ⟶ 4f{sup 7}({sup 8}S{sub 7/2}) transitions of Eu{sup 2+} ions on doping below 3.0 mol%. On increasing Eu-doping levels, the sample contains two kinds of emission centers, i.e., Eu{sup 2+} and Eu{sup 3+} ions, which present the characteristic broad band (5d ⟶ 4f) and narrower (4f ⟶ 4f) luminescence lines, respectively. The energy transfer, the luminescence thermal stability (activation energy ΔE for thermal quenching) and luminescence mechanism of Na{sub 2}Ca{sub 3}Si{sub 6}O{sub 16}:Eu{sup 2+} phosphors were discussed by analyzing the relationship between the luminescence characteristics and the crystal structure.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Low-temperature solvothermal synthesis of EuS hollow microspheres

Graphical abstract: Synthesis of EuS hollow microspheres at low-temperature via solvothermal method for the first time. - Highlights: • We adopt an improved method to synthesise the (Phen)Eu(Et{sub 2}CNS{sub 2}){sub 3} in deionized water. • We have successfully synthesised the EuS hollow microsphere at 230 °C in acetonitrile. • The price of acetonitrile is more inexpensive, so the price of preparation was reduced. - Abstract: EuS crystals are synthesized by low-temperature solvothermal decomposition of the single source precursor complex (Phen)Eu(Et{sub 2}CNS{sub 2}){sub 3} in acetonitrile. X-ray powder diffraction, scanning electron microscopy, granulocyte diameter statistical analysis, surface energy-dispersive X-ray spectroscopy analysis, and UV–vis absorption spectroscopy are used to characterize the structure and properties of the obtained EuS crystals. The results show that the formed EuS crystals are uniform hollow microspheres with a typical cubic phase structure of rock salt and the average particle size of 2.01 μm. The mechanisms for the thermal decomposition of the precursor complex and the formation of the EuS hollow microspheres are postulated based on the experimental observations and previous reports.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Electrodeposition synthesis of MnO{sub 2}/TiO{sub 2} nanotube arrays nanocomposites and their visible light photocatalytic activity

Highlights: • MnO{sub 2}/TiO{sub 2} nanotube arrays nanocomposites are prepared by electrodeposition. • MnO{sub 2}/TiO{sub 2} exhibits high visible light photocatalytic activity. • The results of XRD show the depositions are attributed to α-MnO{sub 2}. • A photocatalytic mechanism is discussed under visible light irradiation. - Abstract: MnO{sub 2}/TiO{sub 2} nanotube arrays nanocomposite photocatalysts have been synthesized through an electrodeposition method. X-ray powder diffraction analysis and X-ray photoelectron spectroscopy measurements reveal that the products of electrodeposition method are MnO{sub 2}. Scanning electron microscopy measurements suggest that the depositions are deposited on the surface or internal of the nanotube. UV–vis light absorbance spectra demonstrate the excellent adsorption properties of MnO{sub 2}/TiO{sub 2} over the whole region of visible light, which enables this novel photocatalytic material to possess remarkable activity in the photocatalytic degradation of acid Orange II under visible light radiation. Moreover, a possible photocatalytic mechanism is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Sol–gel synthesis of silver nanocrystals embedded in sodium borosilicate monolithic transparent glass with giant third-order optical nonlinearities

Highlights: • We prepared Ag-doped sodium borosilicate monolithic glass. • The influence of temperature on the SPR absorption peak intensity was studied. • Nonlinear optical properties of the glass were investigated. • A mechanism for the formation of Ag quantum dots glass was proposed. - Abstract: We report the preparation of uniform spherical shape silver nanocrystals doped sodium borosilicate monolithic transparent glass by sol–gel method. The characterization of the resulting Ag nanocrystals was accomplished by using X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectrum. Surface plasma resonance absorption peaks of the silver nanocrystals glass at about 406 nm have been obtained from ultraviolet–visible absorption spectrometer and their intensity is changed with different heat treatment temperatures. We have investigated the nonlinear optical properties of silver quantum dots doped glass using Z-scan technique. Third-order nonlinear optical susceptibility χ{sup (3)} of the glass was estimated to be 1.01 × 10{sup −11} esu. In particular, a mechanism for the formation of Ag quantum dots glass is proposed. This work will significantly promote the obtained material applications in optical devices.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Successive ionic layer adsorption and reaction deposited kesterite Cu{sub 2}ZnSnS{sub 4} nanoflakes counter electrodes for efficient dye-sensitized solar cells

Highlights: • Cu{sub 2}ZnSnS{sub 4} nanoflakes by SILAR technique. • Hydrothermal synthesis of TiO{sub 2}. • Counter electrode for DSSC application. • 4.48% conversion efficiency. - Abstract: In this investigation, we have successfully synthesized Cu{sub 2}ZnSnS{sub 4} (CZTS) nanoflakes by successive ionic layer adsorption and reaction (SILAR) method and used as a counter electrode in the hydrothermally grown TiO{sub 2} based dye sensitized solar cells (DSSCs). The prepared CZTS nanoflakes were characterized using X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), micro Raman spectroscopy and energy dispersive analysis. Our DSSCs results revealed that, compared with conventional Pt/FTO counter electrode DSSCs, nanoflakes of p-type CZTS as the photocathode and n-type TiO{sub 2} thin films as the photoanode shows an increased short circuit current (13.35 mA/cm{sup 2}) with 4.84% power conversion efficiency. The detailed interface properties of were analyzed by electrochemical impedance spectroscopy (EIS) measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Uniform hollow magnetite spheres: Facile synthesis, growth mechanism, and their magnetic properties

Highlights: • Uniform Fe{sub 3}O{sub 4} hollow spheres with high saturation magnetization were synthesized through a simple solvothermal process. • Without using any hard templates or external magnetic field. • The as-prepared magnetite hollow spheres exhibit a ferromagnetic behavior with high Ms of ca. 85.9 emu/g at room temperature. • The morphology of Fe{sub 3}O{sub 4} with nanoparticles, hollow, and irregular structures could be adjusted by changing the reactive conditions. - Abstract: Hierarchical porous Fe{sub 3}O{sub 4} hollow spheres with high saturation magnetization were synthesized through a simple solvothermal process in ethylene glycol (EG) in the presence of Tetrabutylammonium chloride (TBAC) and urea. By investigating the effect of reaction temperature, time, the amount of urea, and concentration of iron ion on the formation of hollow spheres, it was proposed that the main formation mechanism of hollow spheres is Ostwald ripening process combined with assembly-then-inside-out evacuation process. Additionally, it is found that the morphology of Fe{sub 3}O{sub 4} with nanoparticles, hollow, and irregular structures could be adjusted by changing the above factors. The resulting products were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometer (VSM). The hierarchical porous Fe{sub 3}O{sub 4} hollow spheres exhibited enhanced saturation magnetization as compared with Fe{sub 3}O{sub 4} nanoparticles.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Sodium citrate (Na{sub 3}Cit)-assisted hydrothermal synthesis of uniform spindle-like SrMoO{sub 4}:Eu{sup 3+} phosphors

Graphical abstract: A facile hydrothermal method for the synthesis of uniform spindle-like SrMoO{sub 4}:Eu{sup 3+} phosphors with the assistance of sodium citrate (Na{sub 3}Cit). - Highlights: • Well-crystallized spindle-like SrMoO{sub 4}:Eu{sup 3+} phosphors have been synthesized. • The influence of the reaction temperature and reaction time were clearly shown. • The dosage of Na{sub 3}Cit has a strong effect on the spindle-like SrMoO{sub 4}:Eu{sup 3+} phosphors. • The growth mechanism for the formation of final samples was proposed. - Abstract: Highly uniform spindle-like SrMoO{sub 4}:Eu{sup 3+} phosphors have been prepared by a facile hydrothermal method using sodium citrate (Na{sub 3}Cit) as the chelating reagent. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform-infrared spectroscopy (FT-IR) and photoluminescence spectra (PL) were used to characterize the resulting samples. The dosage of sodium citrate, reaction temperature and reaction time play key roles in the formation of the final samples. The possible formation mechanism for SrMoO{sub 4}:Eu{sup 3+} phosphors has been proposed. Upon excitation by ultraviolet radiation, the as-synthesized SrMoO{sub 4}:Eu{sup 3+} phosphors show the characteristic {sup 5}D{sub 0}–{sup 7}F{sub J} (J = 1, 2, 3, 4) emission lines with red emission {sup 5}D{sub 0}–{sup 7}F{sub 2} (613 nm) as the most prominent group.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Interfacial hydrothermal synthesis of SnO{sub 2} nanorods towards photocatalytic degradation of methyl orange

Highlights: • Efficient interfacial hydrothermal strategy was developed. • 1D SnO{sub 2} nanorods as an advanced photocatalyst. • SnO{sub 2} nanorods exhibit photocatalytic degradation of the MO. - Abstract: One-dimensional (1D) SnO{sub 2} nanorods (NRs) have been successfully synthesized by means of an efficient interfacial hydrothermal strategy. The resulting product was physically characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscope, etc. The as-fabricated SnO{sub 2} NRs exhibited excellent photocatalytic degradation of the methyl orange with high degradation efficiency of 99.3% with only 60 min ultra violet light irradiation. Meanwhile, the 1D SnO{sub 2} NRs exhibited intriguing photostability after four recycles.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Structure, sintering behavior, and microwave dielectric properties of (1 − x) CaWO{sub 4}–xYLiF{sub 4} (0.02 ≤ x ≤ 0.10) ceramics

Highlights: • Structure, sinterability, and dielectric properties of CaWO{sub 4}–YLiF{sub 4} were studied. • CaWO{sub 4} can be densified (TD 97%) at 750 °C/2 h by YLiF{sub 4} doping. • Excellent microwave dielectric properties could be obtained. - Abstract: Structures and sintering behaviors of (1 − x) CaWO{sub 4}–xYLiF{sub 4} (0.02 ≤ x ≤ 0.10) ceramic have been investigated by X-ray powder diffraction (XRD), dilatometry, scanning electron microscopy (SEM) in this work. The microwave dielectric properties were measured with a network analyzer at the frequency of about 8–15 GHz. Limited solid solution could be formed within the compositional range of x < 0.1. The sintering temperature of CaWO{sub 4} could successfully be reduced to ∼750 °C/2 h by doping with small amount of YLiF{sub 4}. An optimized microwave dielectric properties with ϵ{sub r} = 10.5, Q × f = 73 000 GHz and τ{sub f} = −37.7 ppm/°C could be obtained after sintered at the 750 °C for 2 h for x = 0.04 compositions. XRD and back scattering SEM analysis indicated that the (1 − x) CaWO{sub 4}–xYLiF{sub 4} (x = 0.04) ceramic could be chemically compatible with Ag after sintering at 750 °C/2 h.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Chemical degradation of trimethyl phosphate as surrogate for organo-phosporus pesticides on nanostructured metal oxides

Nanostructured TiO{sub 2} and mixed oxides of Ti and Fe, Hf, In, Mn or Zr -were prepared by homogeneous hydrolysis of aqueous solution of metal sulphates with urea. The oxides were characterised by X-ray powder diffraction (XRD), scanning electron microscopy, particle size distribution, surface area and porosity. The oxide materials consists of a few nanometre primary crystals (mainly anatase) arranged in a few micrometre regular spherical agglomerates with specific surface area 133–511 m{sup 2} g{sup −1}. The FTIR diffuse spectroscopy was used for monitoring chemical degradation of trimethylphosphate (TMP) as a surrogate for organo-phosphorus pesticides under ambient and higher temperatures. Undoped TiO{sub 2} and Ti,Mn-mixed oxide were most active in cleavage (hydrolysis) of CH{sub 3}O from TMP at room temperature and 100 °C. Cleavage of CH{sub 3}O in the other studied mixed oxides was not complete until temperature exceeds the boiling point of TMP.

36 MATERIALS SCIENCE↗