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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Simulation Model of Microsphere Distribution for Selective Internal Radiation Therapy Agrees With Observations

Purpose: To perform a detailed analysis of microsphere distribution in biopsy material from a patient treated with {sup 90}Y-labeled resin spheres and characterize microsphere distribution in the hepatic artery tree, and to construct a novel dichotomous bifurcation model for microsphere deposits and evaluate its accuracy in simulating the observed microsphere deposits. Methods and Materials: Our virtual model consisted of arteries that successively branched into 2 new generations of arteries at 20 nodes. The artery diameter exponentially decreased from the lowest generation to the highest generation. Three variable parameters were optimized to obtain concordance between simulations and measure microsphere distributions: an artery coefficient of variation (ACV) for the diameter of all artery generations and the microsphere flow distribution at the nodes; a hepatic tree distribution volume (HDV) for the artery tree; and an artery diameter reduction (ADR) parameter. The model was tested against previously measured activity concentrations in 84 biopsies from the liver of 1 patient. In 16 of 84 biopsies, the microsphere distribution regarding cluster size and localization in the artery tree was determined via light microscopy of 30-μm sections (mean concentration, 14 microspheres/mg; distributions divided into 3 groups with mean microsphere concentrations of 4.6, 14, and 28 microspheres/mg). Results: Single spheres and small clusters were observed in terminal arterioles, whereas large clusters, up to 450 microspheres, were observed in larger arterioles. For 14 microspheres/mg, the optimized parameter values were ACV=0.35, HDV = 50 cm{sup 3}, and ADR=6 μm. For 4.6 microspheres/mg, ACV and ADR decreased to 0.26 and 0 μm, respectively, whereas HDV increased to 130 cm{sup 3}. The opposite trend was observed for 28 microspheres/mg: ACV = 0.49, HDV = 20 cm{sup 3}, and ADR = 8 μm. Conclusion: Simulations and measurements reveal that microsphere clusters are larger and more common in volumes with high microsphere concentrations and indicate that the spatial distribution of the artery tree must be considered in estimates of microsphere distributions.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

In situ growth of copper nanocrystals from carbonaceous microspheres with electrochemical glucose sensing properties

Graphical abstract: In situ growth of copper nanoparticles from hydrothermal copper-containing carbonaceous microspheres was induced by annealing or electron beam irradiation. Obtained micro-nano carbon/copper composite microspheres show electrochemical glucose sensing properties. - Highlights: • We synthesized carbonaceous microspheres containing non-nanoparicle copper species through a hydrothermal route. • By annealing or electron beam irradiation, copper nanoparticles would form from the carbonaceous microspheres in situ. • By controlling the annealing temperature, particle size of copper could be controlled in the range of 50–500 nm. • The annealed carbon/copper hierarchical composite microspheres were used to fabricate an electrochemical glucose sensor. - Abstract: In situ growth of copper nanocrystals from carbon/copper microspheres was observed in a well-controlled annealing or an electron beam irradiation process. Carbonaceous microspheres containing copper species with a smooth appearance were yielded by a hydrothermal synthesis using copper nitrate and ascorbic acid as reactants. When annealing the carbonaceous microspheres under inert atmosphere, copper nanoparticles were formed on carbon microspheres and the copper particle sizes can be increased to a range of 50–500 nm by altering the heating temperature. Similarly, in situ formation of copper nanocrystals from these carbonaceous microspheres was observed on the hydrothermal product carbonaceous microspheres with electron beam irradiation in a vacuum transmission electron microscopy chamber. The carbon/copper composite microspheres obtained through annealing were used to modify a glassy carbon electrode and tested as an electrochemical glucose sensor.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Use of a Pressurized Water Treatment to Prevent Cracking of Internal Gelation Sol-Gel Microspheres

Pressurized water treatments were investigated as a means to prevent cracking of internal gelation sol-gel microspheres upon drying and heating. A batch of gelled cerium oxide microspheres was prepared, split into two samples that were processed with and without a pressurized water treatment, and dried in air at room temperature. Thermal gravimetric analysis was used to compare the mass loss profiles between the two samples and to understand volatile emissions from cerium oxide microspheres during heat treatments up to 600 °C. Microspheres that were processed without a pressurized water treatment lost approximately 4.6 times more mass upon heating than microspheres that were subjected to a pressurized water treatment. Comparison of the cracking behavior of microspheres prepared with and without a pressurized water treatment indicated that microspheres subjected to a pressurized water treatment were virtually crack-free after heat treatments. Conversely, microspheres processed without a pressurized water treatment, which is typical of traditional washing processes, exhibited extensive cracking. Analysis of residues dried from pressurized water treatment effluents indicated that hexamethylenetetramine and urea, which are excess reactants from the internal gelation process, were removed from gelled microspheres during the pressurized water treatment step. Traditional processing methods for preparing internal gelation microspheres use specific feed solution and gelation parameters to reduce subsequent cracking upon drying and heating. Results from this study indicate that more aggressive gel-forming conditions may be used to produce crack-free microspheres, if a pressurized water treatment step is included after washing and before air-drying.

cerium oxide, internal gelation, microsphere, TRIS↗
DOE OSTI2013

Thermal oxidation synthesis hollow MoO{sub 3} microspheres and their applications in lithium storage and gas-sensing

Graphical abstract: MoO{sub 3} hollow microspheres were synthesized via a facile and template-free solvothermal route and subsequent heat treatment in air. The MoO{sub 3} hollow microspheres exhibit an improved lithium storage and gas-sensing performance. Highlights: ► Hollow MoO{sub 3} microspheres were synthesized by thermal oxidation of hollow MoO{sub 2}. ► The MoO{sub 3} hollow microspheres have a relatively high specific surface area. ► The MoO{sub 3} hollow microspheres exhibit improved lithium storage performance. ► The MoO{sub 3} hollow microspheres show good responses to ammonia gas. - Abstract: In this paper, MoO{sub 3} hollow microspheres were synthesized via a facile and template-free solvothermal route and subsequent heat treatment in air. The MoO{sub 3} hollow microspheres have a relatively high specific surface area, and with such a feature, the as-synthesized MoO{sub 3} hollow microspheres have potential applications in Li-ion battery and gas-sensor. When tested as a Li-storage anode material, the MoO{sub 3} hollow microspheres show a higher discharge capacity of 1377.1 mA h g{sup −1} in the first discharge and a high reversible capacity of 780 mA h g{sup −1} after 100 cycles at a rate of 1 C. Furthermore, as a gas sensing material, the MoO{sub 3} hollow microspheres exhibit an improved sensitivity and short response/recovery time to trace levels of ammonia gas.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effects of a Pressurized Water Treatment on Internal Gelation Sol-Gel Microspheres

Based on previous observations that a pressurized water treatment (PWT) prevented cracking of sol-gel microspheres, we investigated the effects of a PWT on microsphere crystallinity, density, and specific surface area (SSA). Results were used to determine how a PWT alters the properties of microspheres upon drying and heating. Microspheres with diameters near 100-200 µm were prepared with and without a PWT and measured using x-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption (BET), and pycnometry. Properties of air-dried microspheres processed with and without a PWT are compared. Additionally, the properties of microspheres processed using a PWT are reported after heating to 150 °C, 450 °C, 750 °C, 1050 °C, and 1350 °C. X-ray diffraction measurements indicate that the PWT step improves the crystallinity of air-dried microspheres. XRD data was also used to calculate crystallite size, which increases with higher heat treatment temperatures. TEM images support crystallite size calculations from XRD data and provide an indication of the range of crystallite sizes, particularly for samples processed at higher temperatures where crystallite sizes are too large for estimation using the Scherrer formula. Density and SSA measurements performed as a function of heat treatment temperature indicate that a PWT increases the density of air-dried microspheres, creates a pore network, and that significant densification occurs between 450 - 750 °C. These results may be used to inform decisions on internal gelation flowsheet parameters to optimize the microsphere formation and gelation step, prevent microsphere cracking, and produce microspheres suitable for subsequent coating operations or pressing into pellets.

cerium oxide, TRISO, internal gelation, nuclear fu↗
DOE OSTI2014

Photoluminescence and photocatalytic activity of flowerlike hierarchical TiO{sub 2}:Sm{sup 3+} microspheres

Graphical abstract: Flowerlike hierarchical TiO{sub 2}:Sm{sup 3+} microspheres were successfully prepared via a solvothermal method. The crystalline size decreased with increasing Sm{sup 3+} concentration. Each TiO{sub 2}:Sm{sup 3+} microsphere consists of several dozen nanopetals, which are composed of several aggregated nanothorns. Under 290, 360, 362, and 368 nm excitation, the {sup 4}G{sub 5/2} → {sup 6}H{sub 5/2}, {sup 4}G{sub 5/2} → {sup 6}H{sub 7/2}, and {sup 4}G{sub 5/2} → {sup 6}H{sub 9/2} transitions were observed. The luminescence intensity increased with increasing Sm{sup 3+} concentration, up to about 1.5 mol%, and then decreased abruptly. In addition to the aforementioned photoluminescence properties, TiO{sub 2}:Sm{sup 3+} microspheres can present photocatalytic activity for the degradation of RhB. - Highlights: • Flowerlike hierarchical TiO{sub 2}:Sm{sup 3+} microspheres were synthesized by a solvothermal method. • TiO{sub 2}:Sm{sup 3+} microspheres can present photocatalytic activity for the degradation of RhB. • The optical properties of TiO{sub 2}:Sm{sup 3+} microspheres with different Sm{sup 3+} concentration were studied in detail. - Abstract: Flowerlike hierarchical TiO{sub 2}:Sm{sup 3+} microspheres were successfully prepared via a solvothermal method. The results of the X-ray diffraction measurements revealed that the TiO{sub 2}:Sm{sup 3+} microspheres were anatase phase. The crystalline size of microspheres decreased with increasing Sm{sup 3+} concentrations. Each TiO{sub 2}:Sm{sup 3+} microsphere consists of several dozen nanopetals, which are composed of several aggregated nanothorns. Under 290, 360, 362, and 368 nm excitation, the {sup 4}G{sub 5/2} → {sup 6}H{sub 5/2}, {sup 4}G{sub 5/2} → {sup 6}H{sub 7/2}, and {sup 4}G{sub 5/2} → {sup 6}H{sub 9/2} transitions were observed. The luminescence intensity increased with increasing Sm{sup 3+} concentration, up to about 1.5 mol%, and then decreased abruptly. The peak positions and the shape of emissions were independent of Sm{sup 3+} concentrations. In addition to the aforementioned photoluminescence properties, TiO{sub 2}:Sm{sup 3+} microspheres can possess superior photocatalytic activity for the degradation of RhB. In addition, the BET surface areas increased with increasing Sm{sup 3+} concentrations, which should be benefit for RhB adsorption.

36 MATERIALS SCIENCE↗
DOE OSTI2011

A facile method to fabricate porous Co{sub 3}O{sub 4} hierarchical microspheres

Flower-like Co{sub 3}O{sub 4} hierarchical microspheres composed of self-assembled porous nanoplates have been prepared by a two-step method without employing templates. The first step involves the synthesis of flower-like Co(OH){sub 2} microspheres by a solution route at low temperatures. The second step includes the calcination of the as-prepared Co(OH){sub 2} microspheres at 200 deg. C for 1 h, causing their decomposition to form porous Co{sub 3}O{sub 4} microspheres without destruction of their original morphology. The samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffractormeter and Fourier transform infrared spectroscope. Some experimental factors including solution temperature and surfactant on the morphologies of the final products have been investigated. The magnetic properties of Co{sub 3}O{sub 4} microspheres were also investigated. - Graphical Abstract: Flower-like Co{sub 3}O{sub 4} microspheres are composed of self-assembled nanoplates and these nanoplates appear to be closely packed in the microspheres. These nanoplates consist of a large number of nanocrystallites less than 5 nm in size with a porous structure, in which the connection between nanocrystallites is random. Research Highlights: {yields} Flower-like Co{sub 3}O{sub 4} hierarchical microspheres composed of self-assembled porous nanoplates have been prepared by a two-step method without employing templates. {yields} Layered Co(OH){sub 2} microspheres were prepared with an appropriate approach under low temperatures for 1 h reaction. {yields} Calcination caused Co(OH){sub 2} decomposition to form porous Co{sub 3}O{sub 4} microspheres without destruction of their original morphology.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Urchin-like m-LaVO{sub 4} and m-LaVO{sub 4}/Ag microspheres: Synthesis and characterization

The semiconductor nanostructures decorated with noble metals have attracted increasing attention due to their interesting physical and chemical properties. In this work, urchin-like monoclinic (m-) LaVO{sub 4} microspheres were prepared by a hydrothermal method and used as a template to fabricate Ag nanoparticle-decorated m-LaVO{sub 4} composites. The morphology and structure were characterized by transmission electron microscope, high-resolution transmission electron microscope, scanning electron microscope, and energy-dispersive X-ray. It was found that Ag nanoparticles with narrow size distribution were uniformly loaded on urchin-like m-LaVO{sub 4} microspheres, and the resulted composite microspheres showed distinct surface plasmon absorption band compared to pure m-LaVO{sub 4} microspheres. Photocatalytic activities of as-prepared samples were examined by studying the degradation of methyl orange solutions under visible-light irradiation (> 400 nm). Results clearly showed that urchin-like m-LaVO{sub 4}/Ag microspheres possess much higher photocatalytic activity than pure m-LaVO{sub 4} microspheres and P25. - Highlights: • m-LaVO{sub 4}/Ag composites microspheres were fabricated by a hydrothermal method. • m-LaVO{sub 4} microspheres show higher photocatalytic activity than m-LaVO{sub 4} microspheres. • m-LaVO{sub 4}/Ag microspheres exhibit a good stability.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Photocatalytic hydrogen generation over porous ZnIn{sub 2}S{sub 4} microspheres synthesized via a CPBr-assisted hydrothermal method

Graphical abstract: ZnIn{sub 2}S{sub 4} porous microspheres were synthesized via a cetylpyridinium bromide (CPBr)-assisted hydrothermal method. It could be seen from the SEM image that the flowerlike microspheres were composed of numerous nanosheets. Many slit-like pores were formed among the curved nanosheets. The porous structure benefited the adsorption of reactants, the diffuseness of products, the charge separation on surface, the transfer of the interfacial charge carriers and the charge carrier trapping. And porous ZnIn{sub 2}S{sub 4} photocatalyst exhibited higher photocatalytic activity than nonporous ZnIn{sub 2}S{sub 4} material. Highlights: {yields} A series of unique flower-like porous ZnIn{sub 2}S{sub 4} microspheres of hexagonal crystal phase as efficient visible-light photocatalysts have been synthesized through CPBr-assisted hydrothermal method. {yields} The CPBr addition would visibly influence the self-assemble growing and the crystal structure including the position and intensity of some peaks. {yields} We also found that the pH value plays a crucial role in the formation of ZnIn{sub 2}S{sub 4} porous microspheres and the influence of the pH on the structure of product has been first reported in our paper. {yields} The results showed that our as-synthesized porous ZnIn{sub 2}S{sub 4} microspheres possessed a specific surface area of 165.4 m{sup 2} g{sup -1} and performed higher visible-light photocatalytic activity than bulk ZnIn{sub 2}S{sub 4} for hydrogen evolution. The maximum H{sub 2} evolution rate of ZnIn{sub 2}S{sub 4} reaches 1544.8 {mu}mol/(h g). -- Abstract: Hexagonal ZnIn{sub 2}S{sub 4} porous microspheres were synthesized via a cetylpyridinium bromide (CPBr)-assisted hydrothermal method. The structure, morphology and optical property of these prepared products were characterized by wide angle X-ray diffraction (WAXRD), small angle X-ray diffraction (SAXRD), UV-Vis diffusive reflectance spectroscopy (DRS), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analyzer (EDX) and nitrogen sorption analysis. The effects of CPBr and pH on the crystal structure, morphology and photocatalytic activity of ZnIn{sub 2}S{sub 4} products were studied. The results demonstrated that the flowerlike ZnIn{sub 2}S{sub 4} microspheres, which were composed of numerous nanosheets, performed higher visible-light photocatalytic activity than bulk ZnIn{sub 2}S{sub 4} for hydrogen evolution. The CPBr addition influenced the crystal structure including the position and intensity of some peaks. Furthermore, the pH played a crucial role in the formation of ZnIn{sub 2}S{sub 4} porous microspheres. The as-synthesized porous ZnIn{sub 2}S{sub 4} microspheres possessed the specific surface area of 165.4 m{sup 2} g{sup -1} and the slit-like porous configuration, which was beneficial to photocatalytic reaction.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Controllable growth and photocatalytic activity of Cu{sub 2}O solid microspheres

Graphical abstract: - Highlights: • 3 μm uniform Cu{sub 2}O solid microspheres with abundant nanopores are achieved. • NH{sub 2}OH·HCl and SDS are main factors that manipulate morphologies of Cu{sub 2}O particles. • Surface features of microspheres influenced the photocatalytic activity of Cu{sub 2}O. • Microspheres are transforming to polyhedrons with extended holding time. - Abstract: A series of Cu{sub 2}O solid microspheres with different surface features were prepared and their photocatalytic activities were studied. The experiment conditions were investigated and the formation mechanism was explored systematically. It was found that varying the amounts of NH{sub 2}OH·HCl reductant in alkaline solutions changed the reaction process and thus altered the surface features of Cu{sub 2}O microspheres. Sodium dodecyl sulfate (SDS) surfactant, introduced as a morphology directing agent, caused the nuclei aggregation and growth process of Cu{sub 2}O solid microspheres by precisely realizing the opposite charges’ directional attraction. This SDS-mediated method can be readily extended to synthesizing solid microspheres of other metal oxides. Meanwhile, it was found that Cu{sub 2}O solid microspheres with abundant nanopores on the surface showed much higher efficient catalytic activity for decoloring methyl orange (MO) aqueous solution than with other surface features under visible light irradiation. Furthermore, we found that prolonging the holding time made Cu{sub 2}O microspheres transform to polyhedrons.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Uniform Cu{sub 2}Cl(OH){sub 3} hierarchical microspheres: A novel adsorbent for methylene blue adsorptive removal from aqueous solution

Using the solution phase method without any surfactants or templates, the hierarchical of Cu{sub 2}Cl(OH){sub 3} microspheres were synthesized by freeze drying. The size and surface area of the microspheres are ca. 1–2 µm and 76.61 m{sup 2} g{sup −1}, respectively. A possible formation mechanism is presented based on the experimental results. Methylene blue was chosen to investigate the adsorption capacity of the as-prepared adsorbent. The effects of various experimental parameters, such as pH, initial dye concentration, and contact time were investigated. The results showed that the dye removal increased with the increasing in the initial concentration of the dye and also increased in the amount of microspheres used and initial pH. Adsorption data fitted well with the Freundlich adsorption isotherm. The thermodynamic analysis presented the exothermic, spontaneous and more ordered arrangement process. The microspheres could be employed effective for removal of dyes from aqueous solution. - Graphical abstract: The single-crystalline hierarchical Cu{sub 2}Cl(OH){sub 3} spheres can be prepared for the first time by using a template-free process through freeze-drying. Meanwhile, the hierarchical spheres exhibited high adsorption capacity to methylene blue. Display Omitted - Highlights: • Cu{sub 2}Cl(OH){sub 3} microspheres were successfully synthesized through a freeze drying process. • A possible formation mechanism of hierarchical microspheres was presented. • The Cu{sub 2}Cl(OH){sub 3} microspheres have high methylene blue adsorption capacity. • Methylene blue adsorption is a spontaneous and exothermic process. • The adsorption mechanism of microspheres onto dye was proposed in detail.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Hydrothermal synthesis of iron phosphate microspheres constructed by mesoporous polyhedral nanocrystals

Novel monodispersed Fe{sub 5}(PO{sub 4}){sub 4}(OH){sub 3}·2H{sub 2}O microspheres with the diameters of several micrometers were prepared by a facile one-step hydrothermal method without using any templates, only employing FeCl{sub 3}·6H{sub 2}O and NaNH{sub 4}HPO{sub 4} as the initial materials. The obtained samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM), respectively. The characterizations revealed that the as-prepared microspheres are constructed by the polyhedral nanoparticles with an average diameter of 100 nm. The corresponding FePO{sub 4} microspheres assembled by mesoporous polyhedral nanocrystals can be easily obtained by calcining a sphere-like Fe{sub 5}(PO{sub 4}){sub 4}(OH){sub 3}·2H{sub 2}O precursor. - Graphical abstract: Novel monodispersed Fe{sub 5}(PO{sub 4}){sub 4}(OH){sub 3}·H{sub 2}O microspheres with a diameter of several micrometers were successfully obtained by a simple, template-free hydrothermal route. FePO{sub 4} microspheres constructed by mesoporous polyhedral FePO{sub 4} nanocrystals could be easily prepared by calcining an Fe{sub 5}(PO{sub 4}){sub 4}(OH){sub 3}·2H{sub 2}O precursor. Display Omitted - Highlights: • Monodispersed Fe{sub 5}(PO{sub 4}){sub 4}(OH){sub 3}·2H{sub 2}O microspheres were prepared by a facile hydrothermal method without using any templates • Fe{sub 5}(PO{sub 4}){sub 4}(OH){sub 3}·2H{sub 2}O microspheres present a novel morphology, which was constructed by closely polyhedral nanoparticles. • The FePO{sub 4} microspheres assembled by mesoporous polyhedral nanocrystals obtained by calcining Fe{sub 5}(PO{sub 4}){sub 4}(OH){sub 3}·2H{sub 2}O precursor.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Preparation of porous nitrogen-doped titanium dioxide microspheres and a study of their photocatalytic, antibacterial and electrochemical activities

Graphical abstract: Porous N-doped TiO{sub 2} microspheres were prepared for the first time via plasma technique. The sample exhibited better photocatalytic activity, photoinduced inactivation activity and better electrochemical activity than those of TiO{sub 2} microspheres and P25. Display Omitted Highlights: ► Porous N-doped TiO{sub 2} microspheres were prepared via nitrogen plasma technique. ► Plasma treatment did not affect the porous structure of the TiO{sub 2} microspheres. ► With the plasma treatment, the N contents in the samples increased. ► Their photocatalytic, antibacterial and electrochemical activities were studied. -- Abstract: Nitrogen-doped titanium dioxide (N-doped TiO{sub 2}) microspheres with porous structure were prepared via the nitrogen-assisted glow discharge plasma technique at room temperature for the first time. The samples were characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption–desorption measurement, UV–Vis diffuse reflectance spectra, photoluminescence spectroscopy and X-ray photoelectron spectroscopy. The results indicated that the plasma treatment did not affect the porous structure of the TiO{sub 2} microspheres. With the plasma treatment, the N contents in the samples increased. During the photocatalytic degradation of methylene blue under simulative sunlight irradiation, the sample after plasma treatment for 60 min (N-TiO{sub 2}-60) exhibited higher photocatalytic activity than those of the TiO{sub 2} microspheres, P25 and other N-doped TiO{sub 2} microspheres. Furthermore, the N-TiO{sub 2}-60 showed excellent antibacterial activities towards Escherichia coli under visible irradiation. These should be attributed to the enhancement of the visible light region absorption for TiO{sub 2} after N-doping. Electrochemical data demonstrated that the N-doping not only enhanced the electrochemical activity of TiO{sub 2}, but also improved the reversibility of Li insertion/extraction reactions and the rate behavior of TiO{sub 2} during charge–discharge cycles.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Solar photocatalytic activities of porous Nb-doped TiO{sub 2} microspheres by coupling with tungsten oxide

Highlights: • Nb-TiO{sub 2}/WO{sub 3} was prepared by USP method combined impregnation method. • Nb-doping extend the spectral absorption of TiO{sub 2} into visible spectrum. • Nb-TiO{sub 2}/WO{sub 3} has a similar optical band gap as Nb-TiO{sub 2}. • PL spectra indicate WO{sub 3} can accept the photoexcited electrons from Nb-TiO{sub 2}. • Nb-TiO{sub 2}/WO{sub 3} shows higher activity than TiO{sub 2} and Nb-TiO{sub 2} under solar light. - Abstract: Nb doped TiO{sub 2} microspheres modified with WO{sub 3} (Nb-TiO{sub 2}/WO{sub 3}) was prepared by ultrasonic spray pyrolysis method combined with impregnation method. The microspheres were characterized with SEM, TEM, XRD, BET, photoluminescence and UV–vis absorption spectra. The Nb-doping was observed to extend the spectral absorption of TiO{sub 2} into visible spectrum, and the absorption onset was red-shifted for about 88 nm compared to pristine TiO{sub 2} microspheres. Nb-TiO{sub 2}/WO{sub 3} microspheres do not display a red-shifted absorption edge compared with Nb doped TiO{sub 2} microspheres. Under solar irradiation, Nb-TiO{sub 2}/WO{sub 3} microspheres showed higher photocatalytic activity for methylene blue degradation compared with that of pure TiO{sub 2} microspheres and Nb doped TiO{sub 2} microspheres, which could be ascribed to the extended light absorption range and the suppression of electron-hole pair recombination.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Preparation with a facile template-free method of uniform-sized mesoporous microspheres of rare earth (La, Ce, Pr, Nd) oxides

Highlights: {yields} Mesoporous microspheres of light rare earth hydroxycarbonates and oxides were fabricated. {yields} The supersaturated urea has important effect on formation of mesoporous microspheres. {yields} The influences of [cation]/[urea] ratio and amount of water on the formation of spherical crystallites were discussed. -- Abstract: Mesoporous microspheres of light rare earth (La, Ce, Pr, Nd) hydroxycarbonates and oxides were successfully fabricated by a facile surfactant free hydrothermal method in supersaturated aqueous urea solution. The techniques of XRD, TEM, SEM, TG/DTA and N{sub 2} adsorption-desorption were employed to investigate the structure and formation process of mesoporous microspheres. It was revealed that supersaturated urea not only serve as a reactant and pH modifier in the reaction system but also guide the oriented assembly of hydroxycarbonate crystallites into microspheres by acting as a structure-directing agent. The microspheres of rare earth oxides could easily be obtained by simple calcination of corresponding hydroxycarbonates precursors without undergoing morphology changes. In addition, the influences of rare earth precursor and urea concentrations on the formation of microspheres were also investigated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Pt-TiO{sub 2} microspheres with exposed {001} facets for degradation of formaldehyde in air: Formation mechanism and enhanced visible light photocatalytic activity

Highlights: • TiO{sub 2} microspheres with exposed {001} facets were successfully synthesized. • Pt-TiO{sub 2} catalyst combined the properties of Pt nanoparticles and TiO{sub 2} {001} facet. • The catalyst exhibited an enhanced visible-light photocatalytic activity. • The formation mechanism of TiO{sub 2} microspheres with exposed {001} facets was studied. - Abstract: In this study, TiO{sub 2} microspheres with exposed {001} facets were successfully synthesized by a low-temperature hydrothermal method without using any organic solvents as morphology controlling agent. Furthermore, an active Pt-TiO{sub 2} catalyst was prepared by impregnation and deposition-precipitation methods with reduction processes. The photocatalytic activity of the samples was evaluated by degradation of formaldehyde in air under visible light irradiation at room temperature. After modification with Pt, the optical absorption property of the Pt-TiO{sub 2} microspheres was extended to visible light range. More importantly, the Pt-TiO{sub 2} microspheres exhibited excellent photocatalytic performance for formaldehyde degradation under visible light irradiation, being superior to pure TiO{sub 2} microspheres and even Pt-P25. The formation mechanism of the TiO{sub 2} microspheres with exposed {001} facets was studied. Moreover, the proper photocatalytic mechanism was also proposed. This work provided new insight into the improvement of photocatalytic activity by special high-energy facet exposing and noble metal depositing.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Nanoparticle-assembled LiMn{sub 2}O{sub 4} hollow microspheres as high-performance lithium-ion battery cathode

Highlights: • The LiMn{sub 2}O{sub 4} hollow microspheres are assembled by LiMn{sub 2}O{sub 4} octahedral nanoparticles. • The LiMn{sub 2}O{sub 4} hollow microspheres exhibit larger diffusion coefficient and better rate performance. • The LiMn{sub 2}O{sub 4} hollow microspheres display longer cycling stability. - Abstract: Spinel LiMn{sub 2}O{sub 4} is an attractive cathode material for rechargeable lithium-ion batteries. However, its cycling and rate performance need further improvement. Herein, we present a novel LiMn{sub 2}O{sub 4} hollow microsphere cathode fabricated via a simple solid-state reaction utilizing MnO{sub 2} hollow microspheres and LiOH·H{sub 2}O as the reactants. Interestingly, the as-prepared LiMn{sub 2}O{sub 4} hollow microspheres are assembled by LiMn{sub 2}O{sub 4} octahedral nanoparticles with exposed {111} planes, exhibiting abundant void spaces for the stress buffering and larger diffusion coefficient (1.570 × 10{sup −7} cm{sup 2} s{sup −1}) for fast lithium ion transfer as compared to the simply aggregated LiMn{sub 2}O{sub 4} nanoparticles. As a result, the LiMn{sub 2}O{sub 4} hollow microspheres exhibit much improved cycling stability and deliver a specific discharge capacity of 86.3 mAh g{sup −1} at a high rate of 10C, higher than that of the aggregated LiMn{sub 2}O{sub 4} (73.9 mAh g{sup −1}). Our work suggests that the electrochemical performance of LiMn{sub 2}O{sub 4} cathode can be manipulated by the design of unique hollow sphere structure.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Raspberry—like monodispersity ZnO microspheres for photodegradation of rhodamine B

Highlights: • Rasberry-like ZnO microspheres were successfully prepared through a F108-assisted one-pot hydrothermal route. • The resulting ZnO microspheres are composed of many small nanoparticles, generating a unique rough surface. • The surface rough and the diameter of the microspheres can be easily tuned only by changing the composition of the precursor. • The Au decorated-ZnO composite demonstrates better photocatalytic activities for degradation of RhB than the pristine ZnO micropheres. - Abstract: In the article, we propose a simple and effective one-pot hydrothermal approach for synthesis of raspberry-like ZnO microspheres, where triblockpoly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide), triethanolamine, ethylene glycol acts as the structure-directing agent (SDA), co-template, and solvent, respectively. They are together responsible for the growth of ZnO products with uniform morphology, high crystallinity, and good monodispersity. The resulting ZnO microspheres possess rough surface, which are composed of many small nanoparticles. Moreover, the surface roughness and the diameter of the microspheres can be easily tuned only by changing the composition of the precursor. Meanwhile, the photodegradation behavior of the products is also tested by selecting the rhodamine B (RhB) as the model pollutant. The photocatalytic results indicate that the raspberry-like ZnO products exhibit excellent photocatalytic activity. In particular, the Au decorated-ZnO composite demonstrates an enhanced photocatalytic activity towards degradation of RhB under UV irradiation compared with the pristine ZnO microspheres.

77 NANOSCIENCE AND NANOTECHNOLOGY↗