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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Coherent femtosecond low-energy single-electron pulses for time-resolved diffraction and imaging: A numerical study

We numerically investigate the properties of coherent femtosecond single electron wave packets photoemitted from nanotips in view of their application in ultrafast electron diffraction and non-destructive imaging with low-energy electrons. For two different geometries, we analyze the temporal and spatial broadening during propagation from the needle emitter to an anode, identifying the experimental parameters and challenges for realizing femtosecond time resolution. The simple tip-anode geometry is most versatile and allows for electron pulses of several ten of femtosecond duration using a very compact experimental design, however, providing very limited control over the electron beam collimation. A more sophisticated geometry comprising a suppressor-extractor electrostatic unit and a lens, similar to typical field emission electron microscope optics, is also investigated, allowing full control over the beam parameters. Using such a design, we find {approx}230 fs pulses feasible in a focused electron beam. The main limitation to achieve sub-hundred femtosecond time resolution is the typical size of such a device, and we suggest the implementation of more compact electron optics for optimal performance.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Microstructure and surface morphology of InAsSbBi grown by molecular beam epitaxy

The physical and chemical properties of 210 nm thick InAsSbBi layers grown by molecular beam epitaxy at temperatures between 400 and 430 °C on (100) GaSb substrates are investigated using Rutherford backscattering, X-ray diffraction, transmission electron microscopy, Nomarski optical microscopy, and atomic force microscopy. The results indicate that the layers are nearly lattice matched, coherently strained, and contain dilute Bi mole fractions. Large surface droplets with diameters on the order of 1 μm and densities on the order of 106 cm−2 are observed when the InAsSbBi growth is performed with lean As overpressures around 1%. Surface droplets are not observed when the As overpressure is increased to 4%. Small crystalline droplets with diameters on the order of 70 nm and densities on the order of 1010 cm−2 are observed between the large droplets for InAsSbBi grown at 430 °C. Analysis of one of the small droplets indicates a misoriented zinc blende crystal structure composed primarily of In, Sb, and Bi, with a lattice constant of 6.543 ± 0.038 Å. Lateral modulation in the Bi mole fraction is observed in InAsSbBi layers grown at 400 °C.

Kosireddy, R. R.↗
DOE OSTI2013

Measurement and effects of polarization fields on one-monolayer-thick InN/GaN multiple quantum wells

Polarization fields associated with one-monolayer-thick InN/GaN multiple quantum wells (MQWs) cause shifts of the photoluminescence peak that depend on the GaN barrier layer thickness. Diffraction contrast and aberration-corrected scanning transmission electron microscopy show that the InN QWs are well defined and coherently strained. Mapping of electrostatic potential using off-axis electron holography shows that the electric fields inside the GaN barriers decrease from ~0.7 to ~0.2 MV/cm as the barrier layer thickness increases from 5 to 20 nm. Atomistic tight-binding calculations agree closely with experiment, and confirm that changes in optical emission of these III-nitride quantum wells result from changes in the spontaneous and piezoelectric polarization fields in the InN quantum wells and the GaN barrier layers. Overall, this QW system provides the basis for InN-based light-emitting devices operating across a useful band of wavelengths at room temperature.

Zhou, Lin↗
DOE OSTI2011

Incorporation of trace elements in Portland cement clinker: Thresholds limits for Cu, Ni, Sn or Zn

This paper aims at defining precisely, the threshold limits for several trace elements (Cu, Ni, Sn or Zn) which correspond to the maximum amount that could be incorporated into a standard clinker whilst reaching the limit of solid solution of its four major phases (C{sub 3}S, C{sub 2}S, C{sub 3}A and C{sub 4}AF). These threshold limits were investigated through laboratory synthesised clinkers that were mainly studied by X-ray Diffraction and Scanning Electron Microscopy. The reference clinker was close to a typical Portland clinker (65% C{sub 3}S, 18% C{sub 2}S, 8% C{sub 3}A and 8% C{sub 4}AF). The threshold limits for Cu, Ni, Zn and Sn are quite high with respect to the current contents in clinker and were respectively equal to 0.35, 0.5, 0.7 and 1 wt.%. It appeared that beyond the defined threshold limits, trace elements had different behaviours. Ni was associated with Mg as a magnesium nickel oxide (MgNiO{sub 2}) and Sn reacted with lime to form a calcium stannate (Ca{sub 2}SnO{sub 4}). Cu changed the crystallisation process and affected therefore the formation of C{sub 3}S. Indeed a high content of Cu in clinker led to the decomposition of C{sub 3}S into C{sub 2}S and of free lime. Zn, in turn, affected the formation of C{sub 3}A. Ca{sub 6}Zn{sub 3}Al{sub 4}O{sub 15} was formed whilst a tremendous reduction of C{sub 3}A content was identified. The reactivity of cements made with the clinkers at the threshold limits was followed by calorimetry and compressive strength measurements on cement paste. The results revealed that the doped cements were at least as reactive as the reference cement.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Microstructures and photocatalytic properties of Ag{sup +} and La{sup 3+} surface codoped TiO{sub 2} films prepared by sol-gel method

Ag{sup +} and La{sup 3+} surface codoped TiO{sub 2} films were successfully prepared by the improved sol-gel and doping processes. The as-prepared specimens were characterized using differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (FE-SEM), X-ray energy dispersive spectroscopy (EDS), Brunauer-Emmett-Teller (BET) surface area, Photoluminescence spectrum (PL) and UV-vis diffuse reflectance spectroscopy. The photocatalytic activities of the films were evaluated by degradation of an organic dye in aqueous solution. The results of XRD, FE-SEM and BET analyses indicated that the TiO{sub 2} films were composed of nano-particles or aggregates with a size of less than 10 nm. With the codoping of Ag{sup +} and La{sup 3+}, TiO{sub 2} films with high photocatalytic activity and clearly responsive to the visible light were obtained. The improvement mechanism by ions doping was also discussed. - Graphical Abstract: The PL intensity of Ag{sup +} and La{sup 3+} surface codoped TiO{sub 2} was the lowest among all samples, indicating the recombination of electron and hole was effectively prohibited compared with pure TiO{sub 2}, Ag{sup +} and La{sup 3+} bulk codoped TiO{sub 2}. Highlights: > Ag{sup +} and La{sup 3+} codoping can reduce the crystal size of TiO{sub 2}. > Ag{sup +} and La{sup 3+} surface codoped TiO{sub 2} films have an obvious optical response red-shift. > Ag{sup +} and La{sup 3+} surface codoped TiO{sub 2} films can exhibit excellent photocatalytic activity under both UV and visible light irradiations.

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

Synthesis, structures and photocatalytic activities of microcrystalline ABi{sub 2}Nb{sub 2}O{sub 9} (A=Sr, Ba) powders

Microcrystalline ABi{sub 2}Nb{sub 2}O{sub 9} (A=Sr, Ba) photocatalysts were successfully synthesized by a citrate complex method. The as-prepared samples were characterized by the X-ray diffraction technique, BET surface area analysis, UV-vis diffuse reflectance spectrum, transmission electron microscopy, X-ray photoelectron spectroscopy and inductively coupled plasma-atomic emission spectrometry. The results indicated that single-phase orthorhombic SrBi{sub 2}Nb{sub 2}O{sub 9} could be obtained after being calcined above 650 {sup o}C, while BaBi{sub 2}Nb{sub 2}O{sub 9} was tetragonal. Based on the diffuse reflectance spectra, the band gaps of the obtained samples were calculated to be around 3.34-3.54 eV. For the photocatalytic redox reaction of methyl orange under UV-light irradiation, SrBi{sub 2}Nb{sub 2}O{sub 9} exhibited higher photocatalytic activity than that of BaBi{sub 2}Nb{sub 2}O{sub 9}. The effects of the crystallinities, BET surface areas and crystal structures of the samples on the photocatalytic activities were discussed in detail. -- Graphical abstract: Aurivillius-type ABi{sub 2}Nb{sub 2}O{sub 9} (A=Sr, Ba) photocatalysts were successfully synthesized by a citrate complex method. SrBi{sub 2}Nb{sub 2}O{sub 9} and BaBi{sub 2}Nb{sub 2}O{sub 9} showed different photocatalytic performances in the redox reaction of methyl orange (MO) under UV-light ({lambda}=254 nm), due to the different crystal structures of ABi{sub 2}Nb{sub 2}O{sub 9} (A=Sr, Ba). Display Omitted

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

The Imaging and Coherence Beamline I13 at Diamond

The coherence and imaging beamline I13 is dedicated to hard x-ray imaging on the micro- and nano-lengthscale, performing microscopy either in direct or reciprocal space. For both, lens-based and lensless imaging, two independent stations will be operated in a separate building at a distance of 250 m from the source. The imaging branch will perform in-line phase contrast imaging and tomography over a large field of view in the 6- to 35-keV energy range. In addition, it will be possible to switch to full-field microscopy with 50-nm spatial resolution. Other microscopies will be developed according to the scientific needs. Resolution beyond the limitations given by the detector and x-ray optics will be achieved with techniques working in the far field. Coherent x-ray diffraction (CXRD) and other coherent diffraction imaging techniques such as ptychography will also be implemented on the same 'coherence' branch. The beamline hosts a number of innovative features such as the so-called 'mini-beta' layout for electron optics in the storage ring or new concepts for beamline instrumentation. The stations will be operational in 2011.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Synthesis, characterization and photocatalytic properties of novel zinc germanate nano-materials

We report the first instance of a hydrothermal synthesis of zinc germanate (Zn{sub 2}GeO{sub 4}) nano-materials having a variety of morphologies and photochemical properties in surfactant, template and catalyst-free conditions. A systematic variation of synthesis conditions and detailed characterization using X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, Raman spectroscopy, electron microscopy, X-ray photoelectron spectroscopy and small angle X-ray scattering led to a better understanding of the growth of these particles from solution. At 140 {sup o}C, the zinc germanate particle morphology changes with pH from flower-shaped at pH 6.0, to poly-disperse nano-rods at pH 10 when the Zn to Ge ratio in the synthesis solution is 2. When the Zn to Ge ratio is reduced to 1.25, mono-disperse nano-rods could be prepared at pH 7.5. Nanorod formation is also independent of the addition of cetyltrimethylammonium bromide (CTAB), in contrast to previous reports. Photocatalytic tests show that Zn{sub 2}GeO{sub 4} nano-rods (by weight) and flower shaped (by surface area) are the most active for methylene blue dye degradation among the synthesized zinc germanate materials. -- Graphical abstract: Zinc germanate materials were synthesized possessing unique morphologies dependent on the hydrothermal synthesis conditions in the absence of surfactant, catalyst or template. These novel materials are characterized and evaluated for their photocatalytic activities. Display Omitted highlights: > Zinc germanate synthesized hydrothermally (surfactant free) with unique morphologies. > Flower-shaped, nano-rods, globular particles obtained dependent on synthesis pH. > At 140 {sup o}C, they possess the rhombohedral crystal irrespective of synthesis conditions. > They are photocatalytically active for the degradation of methylene blue. > Potential applications could be photocatalytic water splitting and CO{sub 2} reduction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Microwave-assisted hydrothermal synthesis of marigold-like ZnIn{sub 2}S{sub 4} microspheres and their visible light photocatalytic activity

Marigold-like ZnIn{sub 2}S{sub 4} microspheres were synthesized by a microwave-assisted hydrothermal method with the temperature ranging from 80 to 195 Degree-Sign C. X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen sorption analysis, UV-visible spectroscopy, scanning electron microscopy and transmission electron microscopy were used to characterize the products. It was found that the crystallographic structure and optical property of the products synthesized at different temperatures were almost the same. The degradation of methyl orange (MO) under the visible light irradiation has been used as a probe reaction to investigate the photocatalytic activity of as-prepared ZnIn{sub 2}S{sub 4}, which shows that the ZnIn{sub 2}S{sub 4} sample synthesized at 195 Degree-Sign C shows the best photocatalytic activity for MO degradation. In addition, the photocatalytic activities of all the samples prepared by the microwave-assisted hydrothermal method are better than those prepared by a normal hydrothermal method, which could be attributed to the formation of more defect sites during the microwave-assisted hydrothermal treatment. - Graphical abstract: Marigold-like ZnIn{sub 2}S{sub 4} microspheres were synthesized by a fast microwave-assisted hydrothermal method at 80-195 Degree-Sign C with a very short reaction time of 10 min. The as-prepared ZnIn{sub 2}S{sub 4} sample can be used as visible light photocatalyst for degradation of organic dyes. Highlights: Black-Right-Pointing-Pointer ZnIn{sub 2}S{sub 4} microspheres were synthesized by microwave-assisted hydrothermal method. Black-Right-Pointing-Pointer The crystal structure and optical property of the products were almost the same. Black-Right-Pointing-Pointer Increment of the temperature renders high surface area due to the bubbling effect. Black-Right-Pointing-Pointer The ZnIn{sub 2}S{sub 4} synthesized at 195 Degree-Sign C shows the best visible catalytic activity for MO.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Properties of mortars made by uncalcined FGD gypsum-fly ash-ground granulated blast furnace slag composite binder

Highlights: Black-Right-Pointing-Pointer The mortar with uncalcined FGD gypsum has suitable workability. Black-Right-Pointing-Pointer The strength of mortar with uncalcined FGD gypsum is higher than that of mortar without uncalcined FGD gypsum. Black-Right-Pointing-Pointer The dry shrinkage of mortar with uncalcined FGD gypsum is lower than that of mortar without uncalcined FGD gypsum. Black-Right-Pointing-Pointer The leaching of sulfate ion of mortar is studied. - Abstract: A series of novel mortars were developed from composite binder of uncalcined FGD gypsum, fly ash (FA) and ground granulated blast furnace slag (GGBFS) for the good utilization of flue gas desulphurization (FGD) gypsum. At a fixed ratio (20%) of GGBFS to the composite binder, keeping consistency of the mortar between 9.5 and 10.0 cm, the properties of the composite mortar were studied. The results show that higher water/binder (W/B) is required to keep the consistency when increasing the percentage of FGD gypsum. No obvious influences of the W/B and content of FGD gypsum on the bleeding of paste were observed which keeps lower than 2% under all experimental conditions tried. The highest compressive and flexural strengths (ratio is 20% FGD gypsum, 20% GGBFS and 60% FA) are 22.6 and 4.3 MPa at 28 days, respectively. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicate that massive ettringite crystals and C-S-H gels exist in the hydration products. At 90 days the mortars with FGD gypsum is dramatically smaller drying shrinkage (563-938 micro strain) than that without FGD gypsum (about 2250 micro strain). The release of the SO{sub 4}{sup 2-} from the mortar was analyzed, indicating that the dissolution of sulfate increases with FGD gypsum. The concentration of SO{sub 4}{sup 2-} releasing from the mortar with 10% FGD gypsum is almost equal to that obtained from the mortar without FGD gypsum. The release of SO{sub 4}{sup 2-} from the mortar with 20% FGD gypsum is 9200 mg{center_dot}m{sup -2}, which is lower than that from the mortar with 95% cement clinker and 5% FGD gypsum.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Three-dimensional coherent X-ray diffractive imaging of whole frozen-hydrated cells

Here, a structural understanding of whole cells in three dimensions at high spatial resolution remains a significant challenge and, in the case of X-rays, has been limited by radiation damage. By alleviating this limitation, cryogenic coherent diffractive imaging (cryo-CDI) can in principle be used to bridge the important resolution gap between optical and electron microscopy in bio-imaging. Here, the first experimental demonstration of cryo-CDI for quantitative three-dimensional imaging of whole frozen-hydrated cells using 8 Kev X-rays is reported. As a proof of principle, a tilt series of 72 diffraction patterns was collected from a frozen-hydrated Neospora caninum cell and the three-dimensional mass density of the cell was reconstructed and quantified based on its natural contrast. This three-dimensional reconstruction reveals the surface and internal morphology of the cell, including its complex polarized sub-cellular structure. Finally, it is believed that this work represents an experimental milestone towards routine quantitative three-dimensional imaging of whole cells in their natural state with spatial resolutions in the tens of nanometres.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2011

Synthesis and structural characterization of Al{sub 7}C{sub 3}N{sub 3}-homeotypic aluminum silicon oxycarbonitride, (Al{sub 7-x}Si{sub x})(O{sub y}C{sub z}N{sub 6-y-z}) (x{approx}1.2, y{approx}1.0 and z{approx}3.5)

A new aluminum silicon oxycarbonitride, (Al{sub 5.8}Si{sub 1.2})(O{sub 1.0}C{sub 3.5}N{sub 1.5}), has been synthesized and characterized by X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS). The title compound is hexagonal with space group P6{sub 3}/mmc and unit-cell dimensions a=0.322508(4) nm, c=3.17193(4) nm and V=0.285717(6) nm{sup 3}. The atom ratios of Al:Si and those of O:C:N were, respectively, determined by EDX and EELS. The initial structural model was successfully derived from the XRPD data by the direct methods and further refined by the Rietveld method. The crystal is most probably composed of four types of domains with nearly the same fraction, each of which is isotypic to Al{sub 7}C{sub 3}N{sub 3} with space group P6{sub 3}mc. The existence of another new oxycarbonitride (Al{sub 6.6}Si{sub 1.4})(O{sub 0.7}C{sub 4.3}N{sub 2.0}), which must be homeotypic to Al{sub 8}C{sub 3}N{sub 4}, has been also demonstrated by XRPD and TEM. - Graphical abstract: A new oxycarbonitride discovered in the Al-Si-O-C-N system, (Al{sub 7-x}Si{sub x})(O{sub y}C{sub z}N{sub 6-y-z}) (x{approx}1.2, y{approx}1.0 and z{approx}3.5). The crystal is composed of four types of domains (I, II, III and IV), and hence the structure is represented by a split-atom model. Individual crystal structures can be regarded as layered structures, which consist of A-type [(Al, Si){sub 4}(O, C, N){sub 4}] unit layers and B-type [(Al, Si)(O, C, N){sub 2}] single layers. Highlights: > (Al{sub 5.8}Si{sub 1.2})(O{sub 1.0}C{sub 3.5}N{sub 1.5}) as a new aluminum silicon oxycarbonitride. > Crystal structure is determined and represented by a split-atom model. > Existence of another new oxycarbonitride (Al{sub 6.6}Si{sub 1.4})(O{sub 0.7}C{sub 4.3}N{sub 2.0}) is demonstrated. > Both new materials are formed by oxidation and nitridation of (Al, Si){sub 6}(O, C){sub 5}.

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

Original electrochemical mechanisms of CaSnO{sub 3} and CaSnSiO{sub 5} as anode materials for Li-ion batteries

Calcium stannate (CaSnO{sub 3}) and malayaite (CaSnSiO{sub 5}) were synthesized by means of a high temperature solid-state reaction. Their crystal structures and morphologies were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy; their electrochemical properties were analyzed by galvanostatic tests. The amorphization of the initial electrode materials was followed by XRD. The first discharge of the oxides CaSnO{sub 3} and CaSnSiO{sub 5} shows a plateau at low potential, which is due to the progressive formation of Li-Ca-Sn and/or Li-Sn alloys as shown by {sup 119}Sn Moessbauer spectroscopy. The results reveal similar electrochemical mechanisms for CaSnO{sub 3} and CaSnSiO{sub 5} but they completely differ from those related to SnO{sub 2}. - Graphical abstract: {sup 119}Sn Moessbauer spectra at the end of the first discharge of CaSnO{sub 3} (dashed line) and CaSnSiO{sub 5} (solid line) anodes for Li-ion batteries. Inset shows that relative amounts of Sn(0) based alloys formed during the first discharge are similar for CaSnO{sub 3} and CaSnSiO{sub 5} pristine materials. Highlights: > CaSnSiO{sub 5} and CaSnO{sub 3} as anode materials for Li-ion batteries. > X-ray diffraction and Moessbauer spectroscopy, to explain the electrochemical mechanisms. > Similar mechanisms for the two compounds but different from those of SnO{sub 2} due to Ca.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

2.8 {mu}m emission from type-I quantum wells grown on InAs{sub x}P{sub 1-x}/InP metamorphic graded buffers

We report 2.8 {mu}m emission from compressively strained type-I quantum wells (QWs) grown on InP-based metamorphic InAs{sub x}P{sub 1-x} step-graded buffers. High quality metamorphic graded buffers showed smooth surface morphology and low threading dislocation densities of approximately 2.5 Multiplication-Sign 10{sup 6} cm{sup -2}. High-resolution x-ray diffraction scans showed strong satellites from multiple quantum wells grown on metamorphic buffers, and cross-sectional transmission electron microscopy revealed smooth and coherent quantum well interfaces. Room-temperature photoluminescence emission at 2.8 {mu}m with a narrow linewidth ({approx}50 meV) shows the promise of metamorphic growth for mid-infrared laser diodes on InP.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Strain-associated nanoscale fluctuating lithium transport within single-crystalline LiNi 1/3 Mn 1/3 Co 1/3 O 2 cathode particles

Solid-state lithium diffusion dynamics are critical for the rate capability and longevity of Li-ion batteries. Conventionally, nanoscale lithium diffusion within individual battery particles has been simplified as being primarily driven by concentration gradients, despite the associated processes inducing local lattice expansion, contraction, and strain fields. Using operando scanning transmission soft X-ray microscopy with high spatial resolution and chemical sensitivity to track nanoscale intraparticle lithium transport, and post-cycling Bragg coherent diffraction X-ray imaging to directly reveal three-dimensional intraparticle strain fields, we uncover strain-associated lithium transport dynamics within single-crystalline LiNi 1/3 Mn 1/3 Co 1/3 O 2 (scNMC) particles during cycling. Contrary to the expected thermodynamic solid-solution behavior of scNMC, our observations reveal near-uniform but fluctuating regions of lithium-dense and lithium-dilute areas during cycling. These fluctuations suggest that nanoscale lithium diffusion can proceed counter to concentration gradients. Additionally, we demonstrate that an increased presence of lithium-dilute regions near the surface enhances lithium surface insertion kinetics, emphasizing the importance of controlling surface lithium distribution to improve rate performance. Our study provides insights into nanoscale solid-state ion transport, with potential applications in batteries, solid-state fuel cells, and memristors.

Lee, Danwon [Seoul National Univ. (Korea, Republic↗
DOE OSTI2011

Room Temperature Ferromagnetism in Cu Doped ZnO Thin Films

We report on the growth of Cu doped ZnO thin films for different Cu concentration from 0.1%, to10% by RF magnetron sputtering. The X-ray diffraction study has shown single phase wurtzite type ZnO thin films with no evidence of copper/copper oxide or any other secondary phases. Room temperature ferromagnetism was observed in RF sputtered Cu doped ZnO films with magnetic moment per Cu atom first increasing and then decreasing with an increasing Cu content. Decrease of band gap with Cu doping, indicating strong p-d mixing of O and Cu is clear by the absorption spectroscopy study. The surface morphology by AFM of pure and Cu doped ZnO thin films show average grain size of 110nm and RMS surface roughness of 2.15 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2011

TEM and Moessbauer Study of Nano Sized Fe{sub 2}MnAl Flakes

Magnetic and structural properties of L21 ordered Fe{sub 2}MnAl Heusler alloy have been studied by X-ray diffraction, Transmission electron microscopy (TEM), Moessbauer spectroscopy and DC magnetization. Structural texturing induced by ball milling is destroyed on heating while Moessbauer and DC magnetization studies show magnetic texturing persists after thermal treatment. TEM shows large distribution in particle size with an average size of 27 nm. Thermal annealing of ball milled sample results L2{sub 1} ordering and the needle shaped particle contributes spin texturing.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Development and calibration of mirrors and gratings for the Soft X-ray materials science beamline at the Linac Coherent Light Source free-electron laser

This article discusses the development and calibration of the x-ray reflective and diffractive elements for the Soft X-ray Materials Science (SXR) beamline of the Linac Coherent Light Source (LCLS) free-electron laser (FEL), designed for operation in the 500 – 2000 eV region. The surface topography of three Si mirror substrates and two Si diffraction grating substrates was examined by atomic force microscopy (AFM) and optical profilometry. The figure of the mirror substrates was also verified via surface slope measurements with a long trace profiler. A boron carbide (B 4 C) coating especially optimized for the LCLS FEL conditions was deposited on all SXR mirrors and gratings. Coating thickness uniformity of 0.14 nm root mean square (rms) across clear apertures extending to 205 mm length was demonstrated for all elements, as required to preserve the coherent wavefront of the LCLS source. The reflective performance of the mirrors and the diffraction efficiency of the gratings were calibrated at beamline 6.3.2 at the Advanced Light Source synchrotron. To verify the integrity of the nanometer-scale grating structure, the grating topography was examined by AFM before and after coating. This is to our knowledge the first time B 4 C-coated diffraction gratings are demonstrated for operation in the soft x-ray region.

36 MATERIALS SCIENCE↗