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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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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Interfacial reaction induced phase separation in La{sub x}Hf{sub y}O films

Amorphous La{sub x}Hf{sub y}O films containing La at concentrations (x) of 50 and 20% were prepared by atomic layer deposition on ultrathin SiO{sub 2} films (1 nm). We examined the electronic structures and microstructures of the La{sub x}Hf{sub y}O films by x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD). Phase separation into La{sub 2}O{sub 3} and HfO{sub 2} was observed in the La{sub x}Hf{sub y}O films subjected to annealing temperatures over 900 deg. C, although the mixture of La{sub 2}O{sub 3} and HfO{sub 2} is thermodynamically stable. The structural changes that occurred as the result of phase separation were dependent on the concentrations of La and Hf in the films. During the annealing treatment, silicate was produced due to interfacial reactions and the interfacial reactions were found to be dependent on the La{sub 2}O{sub 3} content in the La{sub x}Hf{sub y}O films, which has a significant influence on the phase separation process and resulting film structure.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Biomimetic synthesis of aragonite superstructures using hexamethylenetetramine

In this paper, biomimetic synthesis of aragonite superstructures using a low molecular weight organic-hexamethylenetetramine (HMT) as an additive in the presence of CO{sub 2} supplied by an ammonium carbonate ((NH{sub 4}){sub 2}CO{sub 3}) diffusion method at room temperature was studied. The products were characterized by scanning or transmission electron microscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray powder diffractometry, and selected area electron diffraction. The results showed the aragonite superstructures especially dumbbell-flower-like ones were obtained. The formation process of calcium carbonate (CaCO{sub 3}) in HMT aqueous solution was investigated, suggesting that the products transformed from calcite to vaterite primarily, and then changed into a mixture of aragonite and calcite with an increase of reaction time. The formation mechanism of CaCO{sub 3} in HMT solution was also discussed, revealing that aragonite might be controlled by HMT molecules and NH{sub 4}{sup +} ions together. - Graphical abstract: The well-defined aragonite hierarchical superstructures are formed using hexamethylenetetramine in aqueous solution. Highlights: > Aragonite superstructures are formed with hexamethylenetetramine at about 25 deg. C. > Dumbbell-flower-like aragonite produces when hexamethylenetetramine/Ca{sup 2+}=10:1. > CaCO{sub 3} formation in hexamethylenetetramine solution violates the Ostwald ripening. > Hexamethylenetetramine and NH{sub 4}{sup +} might control the growth of aragonite together.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Alteration of municipal solid waste incineration bottom ash focusing on the evolution of iron-rich constituents

Municipal solid waste incineration (MSWI) bottom ash contains a considerable amount of Fe-rich constituents. The behaviors of these constituents, such as dissolution and precipitation, are quite important as they regulate the distribution of a series of ions between the liquid (percolated fluid) and solid (ash deposit) phases. This paper studied both fresh and weathered MSWI bottom ash from the mineralogical and geochemical viewpoint by utilizing optical microscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), and powder X-ray diffraction. The analysis results revealed that for the fresh bottom ash, iron preferentially existed in the chemical forms of spinel group (mainly Fe{sub 3}O{sub 4}, and a series of Al- or Ti- substituted varieties), metallic inclusions (including Fe-P, Fe-S, Fe-Cu-Pb), hematite (Fe{sub 2}O{sub 3}) and unburned iron pieces. In the 1-20 years weathered bottom ash collected from a landfill site, interconversions among these Fe-rich constituents were identified. Consequently, numerous secondary products were developed, including goethite ({alpha}-FeOOH), lepidocrocite ({gamma}-FeOOH), hematite, magnetite, wustite (FeO), Fe-Si-rich gel phase. Of all these transformation products, hydrous iron oxides were the most common secondary minerals. Quantitative chemical analysis of these secondary products by SEM/EDX disclosed a strong association between the newly formed hydrous iron oxides and heavy metals (e.g. Pb, Zn, Ni, and Cu). The results of this study suggest that the processes of natural weathering and secondary mineralization contribute to reduction of the potential risks of heavy metals to the surrounding environments.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2011

A comparative study of TiN and TiC: Oxidation resistance and retention of xenon at high temperature and under degraded vacuum

Dense TiN and TiC samples were prepared by hot pressing using micrometric powders. Xenon species (simulating rare gas fission products) were then implanted into the ceramics. The samples were annealed for 1 h at 1500 deg. C under several degraded vacuums with P{sub O{sub 2}} varying from 10{sup -6} to 2x10{sup -4} mbars. The oxidation resistance of the samples and their retention properties with respect to preimplanted xenon species were analyzed using scanning electron microscopy, grazing incidence x-ray diffraction, Rutherford backscattering spectrometry, and nuclear backscattering spectrometry. Results indicate that TiC is resistant to oxidation and does not release xenon for P{sub O{sub 2{<=}}}6x10{sup -6} mbars. When P{sub O{sub 2}} increases, geometric oxide crystallites appear at the surface depending on the orientation and size of TiC grains. These oxide phases are Ti{sub 2}O{sub 3}, Ti{sub 3}O{sub 5}, and TiO{sub 2}. Apparition of oxide crystallites is associated with the beginning of xenon release. TiC surface is completely covered by the oxide phases at P{sub O{sub 2}}=2x10{sup -4} mbars up to a depth of 3 {mu}m and the xenon is then completely released. For TiN samples, the results show a progressive apparition of oxide crystallites (Ti{sub 3}O{sub 5} mainly) at the surface when P{sub O{sub 2}} increases. The presence of the oxide crystallites is also directly correlated with xenon release, the more oxide crystallites are growing the more xenon is released. TiN surface is completely covered by an oxide layer at P{sub O{sub 2}}=2x10{sup -4} mbars up to 1 {mu}m. A correlation between the initial fine microstructure of TiN and the properties of the growing layer is suggested.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Synthesis of AlN/Al Polycrystals along with Al Nanoparticles Using Thermal Plasma Route

This paper for the first time reports the (200) oriented growth of hexagonal Aluminum nitride crystals during synthesis of aluminum nanoparticles in dc transferred arc thermal plasma reactor by gas phase condensation in nitrogen plasma. The structural and morphological study of as synthesized AlN crystal and aluminium nanoparticles was done by using the x-ray diffraction method, scanning electron microscopy and transmission electron microscopy.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Seed-mediated synthesis, properties and application of {gamma}-Fe{sub 2}O{sub 3}-CdSe magnetic quantum dots

Seed-mediated growth of fluorescent CdSe quantum dots (QDs) around {gamma}-Fe{sub 2}O{sub 3} magnetic cores was performed at high temperature (300 deg. C) in the presence of organic surfactants. Bi-functional magnetic quantum dots (MQDs) with tunable emission properties were successfully prepared. The as-synthesized MQDs were characterized by high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS), which confirmed the assembly of heterodimers. When a longer growth period was employed, a homogeneous dispersion of QDs around a magnetic nanoparticle was obtained. The magnetic properties of these nanocomposites were examined. The MQDs were superparamagnetic with a saturation magnetization of 0.40 emu/g and a coercivity of 138 Oe at 5 K. To demonstrate their potential application in bio-labeling, these MQDs were coated with a thin silica shell, and functionalized with a polyethylene glycol (PEG) derivative. The functionalized MQDs were effectively used for the labeling of live cell membranes of 4T1 mouse breast cancer cells and HepG2 human liver cancer cells. - Graphical abstract: (a) HRTEM image of oleic acid capped MPs. The size of MPs ranges from 8 to 10 nm. (b) XRD pattern of {gamma}-Fe{sub 2}O{sub 3} MPs. Highlights: > The fabrication of MQDs through a seed-mediated approach has been demonstrated. > The formation and assembly of these bi-functional nanocomposites have been elucidated. > The MQDs exhibit superparamagnetism and tunable emissions characteristic of the components. > MQDs with thin silica coating were successfully employed in the labeling of cancer cell membranes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

W{sub 18}O{sub 49} nanorods decorated with Ag/AgCl nanoparticles as highly-sensitive gas-sensing material and visible-light-driven photocatalyst

A novel gas-sensing material and photocatalyst was successfully obtained by decorating Ag/AgCl nanoparticles on the W{sub 18}O{sub 49} nanorods through a clean photochemical route. The as-prepared samples were characterized using combined techniques of X-ray diffractometry, electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Gas-sensing measurements indicate that the Ag/AgCl/W{sub 18}O{sub 49} NRs sensors exhibit superior reducing gas-sensing properties to those of bare W{sub 18}O{sub 49} NRs, and they are highly selective and sensitive to NH{sub 3}, acetone, and H{sub 2}S with short response and recovery times. The Ag/AgCl/W{sub 18}O{sub 49} NRs photocatlysts also possess higher photocatalytic performance than bare W{sub 18}O{sub 49} NRs for degradation of methyl orange under simulated sunlight irradiation. Possible mechanisms concerning the enhancement of gas-sensing and photocatalytic activities of the Ag/AgCl/W{sub 18}O{sub 49} NRs composite were proposed. - Graphical Abstract: The Ag/AgCl nanoparticles adhered well to the W{sub 18}O{sub 49} nanorod. The Ag could act as transfer center of the photoexcited carriers, prohibiting their recombinations in both W{sub 18}O{sub 49} and AgCl. Highlights: > Ag/AgCl/W{sub 18}O{sub 49} NRs were successfully obtained via a clean photochemical route. > The Ag/AgCl nanoparticles decorated on the W{sub 18}O{sub 49} NRs possessed cladding structure. > The Ag/AgCl/W{sub 18}O{sub 49} NRs exhibited excellent gas-sensing and photocatalytic properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Periodic mesoporous organosilicas with co-existence of diurea and sulfanilamide as an effective drug delivery carrier

In this article we report the synthesis of new periodic mesoporous organosilicas (PMOs) with the co-existence of diurea and sulfanilamide-bridged organosilica that are potentially useful for controlled drug release system. The materials possess hexagonal pores with a high degree of uniformity and show long-range order as confirmed by the measurements of small-angle X-ray scattering (SAXS), N{sub 2} adsorption isotherms, and transmission electron microscopy(TEM). FT-IR and solid state {sup 29}Si MAS and {sup 13}C CP MAS NMR spectroscopic analyses proved that the bridging groups in the framework are not cleaved and covalently attached in the walls of the PMOs. It was found that the organic functionality could be introduced in a maximum of 10 mol% with respect to the total silicon content and be thermally stable up to 230 {sup o}C. The synthesized materials were shown to be particularly suitable for adsorption and desorption of hydrophilic/hydrophobic drugs from a phosphate buffer solution at pH 7.4. -- Graphical Abstract: We report the synthesis of new periodic mesoporous organosilicas (PMOs) with the co-existence of diurea and sulfanilamide-bridged organosilica that are potentially useful for controlled drug release system. Display Omitted Highlights: {yields} Synthesis of new periodic mesoporous organosilicas (PMOs) with the co-existence of diurea and sulfanilamide-bridged organosilica that are potentially useful for controlled drug release system. {yields} The organic functionality could be introduced in a maximum of 10 mol% with respect to the total silicon content and be thermally stable up to 230 {sup o}C. {yields} The synthesized materials were shown to be particularly suitable for adsorption and desorption of hydrophilic/hydrophobic drugs from a phosphate buffer solution at pH 7.4.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Dislocation structures, interfacing, and magnetism in the L1 0 - MnGa on η ⊥ - Mn 3 N 2 bilayer

Ferromagnetic L1 0 -MnGa was grown by molecular beam epitaxy under ultrahigh vacuum conditions to a 73 ± 5 nm thickness atop of 50 ± 5 nm thick molecular beam epitaxy grown antiferromagnetic η ⊥ -Mn 3 N 2 on a MgO(001) substrate. The MnGa grew along the c-axis with an out-of-plane spacing of c = 3.71 ± 0.01 Å and a relaxed in-plane spacing of a = 4.00 ± 0.05 °A measured with X-ray diffraction and reflection high-energy electron diffraction respectively. Williamson-Hall analysis revealed 67 ± 17 nm tall columnar grains with a residual stress of 2.40 ± 0.26 (×10 -3 ). A radial distribution plot of screw dislocations observed in scanning tunneling microscopy images found an in-plane coherence length of 15 ± 5 nm. Reflection high-energy electron diffraction analysis of the in-plane lattice spacing during growth reveals a critical thickness of 1.05 ± 0.65 nm for the MnGa, by which the MnGa film relaxes by incorporating dislocations of both edge and screw type. Vibrating sample magnetometry was employed to obtain the magnetic properties of the bilayer system. It is found that the dislocation density plays a significant role in understanding the measured moment per unit cell, where a large dislocation density lowers the moment per unit cell significantly due to chemical layering disorder. Finally, this finding is important for materials development of large saturation magnetization.

36 MATERIALS SCIENCE↗
DOE OSTI2014

High-dynamic-range coherent diffractive imaging: ptychography using the mixed-mode pixel array detector

Coherent (X-ray) diffractive imaging (CDI) is an increasingly popular form of X-ray microscopy, mainly due to its potential to produce high-resolution images and the lack of an objective lens between the sample and its corresponding imaging detector. One challenge, however, is that very high dynamic range diffraction data must be collected to produce both quantitative and high-resolution images. In this work, hard X-ray ptychographic coherent diffractive imaging has been performed at the P10 beamline of the PETRA III synchrotron to demonstrate the potential of a very wide dynamic range imaging X-ray detector (the Mixed-Mode Pixel Array Detector, or MM-PAD). The detector is capable of single photon detection, detecting fluxes exceeding 1 × 10 8 8-keV photons pixel -1 s -1 , and framing at 1 kHz. A ptychographic reconstruction was performed using a peak focal intensity on the order of 1 × 10 10 photons µm -2 s -1 within an area of approximately 325 nm × 603 nm. This was done without need of a beam stop and with a very modest attenuation, while `still' images of the empty beam far-field intensity were recorded without any attenuation. The treatment of the detector frames and CDI methodology for reconstruction of non-sensitive detector regions, partially also extending the active detector area, are described.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Dielectric Properties of PVDF/PZT

Poly(vinylidene fluoride)/ lead zirconate titanate nanocomposite (PVDF/PZT-NPs) were successfully prepared by mixing fine Pb(Zr{sub 0.52}, Ti{sub 0.48})O{sub 3} nanoparticles (PZT-NPs) into a PVDF solution under ultrasonication. The mixture was spin coated onto glass substrate and then annealed at 80 deg. C. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used to characterize the structure and properties of the obtained thin-film nanocomposites. The nanocomposites exhibited good dielectric stability over a wide frequency range.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

Reactive magnetron sputtering of Cu{sub 2}O: Dependence on oxygen pressure and interface formation with indium tin oxide

Thin films of copper oxides were prepared by reactive magnetron sputtering and structural, morphological, chemical, and electronic properties were analyzed using x-ray diffraction, atomic force microscopy, in situ photoelectron spectroscopy, and electrical resistance measurements. The deposition conditions for preparation of Cu(I)-oxide (Cu{sub 2}O) are identified. In addition, the interface formation between Cu{sub 2}O and Sn-doped In{sub 2}O{sub 3} (ITO) was studied by stepwise deposition of Cu{sub 2}O onto ITO and vice versa. A type II (staggered) band alignment with a valence band offset {Delta}E{sub VB} 2.1-2.6 eV depending on interface preparation is observed. The band alignment explains the nonrectifying behavior of p-Cu{sub 2}O/n-ITO junctions, which have been investigated for thin film solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2019

A Coherently Strained Monoclinic [111]PbTiO 3 Film Exhibiting Zero Poisson's Ratio State

Abstract [111]‐Oriented perovskite oxide films exhibit unique interfacial and symmetry breaking effects, which are promising for novel quantum materials as topological insulators and polar metals. However, due to strong polar mismatch and complex structural reconstructions on (111) surfaces/interfaces, it is still challenging to grow high quality [111] perovskite heterostructures, let alone explore the as‐resultant physical properties. Here, the fabrication of ultrathin PbTiO 3 films grown on a SrTiO 3 (111) substrate with atomically defined surfaces, by pulsed laser deposition, is reported. High‐resolution scanning transmission electron microscopy and X‐ray diffraction reveal that the as‐grown [111]PbTiO 3 films are coherent with the substrate and compressively strained along all in‐plane directions. In contrast, the out‐of‐plane lattices are almost unchanged compared with that of bulk PbTiO 3 , resulting in a 4% contraction in unit cell volume and a nearly zero Poisson's ratio. Ferroelectric displacement mapping reveals a monoclinic distortion within the compressed [111]PbTiO 3 , with a polarization larger than 50 µC cm −2 . The present findings, as further corroborated by phase field simulations and first principle calculations, differ significantly from the common [001]‐oriented films. Fabricating oxide films through [111] epitaxy may facilitate the formation of new phase components and exploration of novel physical properties for future electronic nanodevices.

Tang, Yunlong↗
DOE OSTI2011

Effects of mixing energy on technological properties and hydration kinetics of grouting mortars

During slurry preparation, effects of certain phenomena on fluidity and hardening characteristics of cement-based grouts have been reported. Deterioration of fluidity and hardening will affect the slurry performance, quality of workmanship and result in subsequent structural defects. There has been little research conducted on the effects of mixing energy during slurry preparation which has focused on the reasons or mechanisms for changes in characteristic properties. This work describes and measures the effects of several mixing parameters on properties of grouting materials, such as fluidity, hardening characteristics, shrinkage, heat of hydration, ion elution and crystallographic structure using X-ray diffraction and SEM. The results indicate that long mixing processes cause deterioration in fluidity and setting properties. These observations can be explained by acceleration in hydration kinetics and changes in microstructures and subsequent changes in dispersion states due to different mixing durations.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Structure distortion and magnetism in double perovskites Ca{sub 2-x}La{sub x}FeReO{sub 6} (0{<=}x{<=}0.8)

The crystal structure and magnetism of Ca{sub 2-x}La{sub x}FeReO{sub 6} (0{<=}x{<=}0.8) double perovskites have been investigated. The samples with low doping (x{<=}0.4) are found to crystallize with the monoclinic P2{sub 1}/n superstructure, while those in the high doping ones (x{>=}0.6) have orthorhombic Pbnm superstructure. With the increase of an La doping, the anti-site defects increases, giving rise to highly disordered samples at the Fe and Re positions. At the low doping region (x{<=}0.4), the compounds undergo a simultaneous structural and magnetic transition accompanying a slight increase of the Curie temperature. The increase of Curie temperature is discussed in terms of the structural change with doping. -- Graphical abstract: The crystal structures of Ca{sub 2-x}La{sub x}FeReO{sub 6} transform from monoclinic to orthorhombic; meanwhile, high degree of anti-site disorder was present at B/B' position, which promotes AFM correlations as an La increases. Display Omitted

36 MATERIALS SCIENCE↗
DOE OSTI2011

Effect of amine functionalization of spherical MCM-41 and SBA-15 on controlled drug release

MCM-41 and SBA-15 silica materials with spherical morphology and different particle sizes were synthesized and modified by post-synthesis method with 3-aminopropyltriethoxysilane (APTES). A comparative study of the adsorption and release of a model drug, ibuprofen, were carried out. The modified and drug loaded mesoporous materials were characterized by XRD, TEM, N{sub 2} physisorption, thermal analysis, elemental analysis and FT-IR spectroscopy. Surface modification with amino groups resulted in high degree of ibuprofen loading and slow rate of release for MCM-41, whereas it was the opposite for SBA-15. The adsorbed drug content and the delivery rate can be predetermined by the choice of mesoporous material with the appropriate structural characteristics and surface functionality. -- Graphical Abstract: Ibuprofen delivery from the parent and amino-modified spherical MCM-41 materials with 100 nm (small) and 500 nm (large) particle sizes. Display Omitted Highlights: {yields} Spherical type MCM-41 and SBA-15 with different particle sizes were modified by APTES. {yields} Adsorption and release rate of ibuprofen were compared. {yields} High degree of ibuprofen loading, slow release rate for MCM-41, the opposite for SBA-15. {yields} MCM-41 with 100 nm particles was more stable and showed slower release rate

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

Synthesis and characterization of Pd-poly(N-vinyl-2-pyrrolidone)/KIT-5 nanocomposite as a polymer-inorganic hybrid catalyst for the Suzuki-Miyaura cross-coupling reaction

Composite poly(N-vinyl-2-pyrrolidone)/KIT-5 (PVP/KIT-5) was prepared by in situ polymerization method and used as a support for palladium nanoparticles obtained through the reduction of Pd(OAc){sub 2} by hydrazine hydrate. The physical and chemical properties of the catalyst were investigated by XRD, FT-IR, UV-vis, TG, BET, SEM, and TEM techniques. The catalytic performance of this novel heterogeneous catalyst was determined for the Suzuki-Miyaura cross-coupling reaction between aryl halides and phenylboronic acid in the presence of water at room temperature. The stability of the nanocomposite catalyst was excellent and could be reused 8 times without much loss of activity in the Suzuki-Miyaura cross-coupling reaction. - Graphical Abstract: Pd-poly(N-vinyl-2-pyrrolidone)/KIT-5 was prepared as an organic-inorganic hybrid catalyst for the Suzuki-Miyaura reaction. The stability of the catalyst was excellent and could be reused 8 times in the Suzuki-Miyaura reaction. Highlights: > Pd-poly(N-vinyl-2-pyrrolidone)/KIT-5 was prepared as a novel nanocomposite. > Nanocomposite was prepared based on a cage-type mesoporous system. > Catalyst showed excellent activity for Suzuki-Miyaura reaction in water. > Stability of the catalyst was excellent and could be reused 8 times.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗