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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Magnetic whiskers of p-aminobenzoic acid and their use for preparation of filled and microchannel silicone rubbers

A thin cobalt layer has been formed on the surface of p-aminobenzoic acid whiskers by chemical vapor deposition (CVD). The metallized crystals have been oriented in liquid polydimethylsiloxane rubber by applying a dc magnetic field. After vulcanization, the filler has been removed by processing in an alcohol solution of trifluoroacetic acid. The cobalt deposition on the surface of the organic compound and the properties of metallized whiskers are investigated by optical microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Quantitative Nonlinear Optical Polarimetry with High Spatial Resolution

Nonlinear optical microscopy such as in the optical second-harmonic generation (SHG) modality has become a popular tool today for probing materials in the physical and biological sciences. While imaging and spectroscopy are widely used in the microscopy mode, nonlinear polarimetry, which can shed light on materials’ symmetry and microstructure, is relatively underdeveloped. This is partly because quantitative analytical modeling of the optical SHG response for anisotropic crystals and films largely assumes low-numerical aperture (NA) focusing of light, where the plane-wave approximation is sufficient. Tight focusing provides unique benefits in revealing out-of-plane polarization responses, which cannot be detected by near-plane-wave illumination at normal incidence. Here, we outline a method for quantitatively analyzing SHG polarimetry measurements obtained under high-NA focusing within a microscope geometry. Experiments and simulations of a variety of standard samples, from single crystals to thin films, are in good agreement, including measured and simulated spatial SHG maps of ferroelectric domains. A solution to the inverse problem is demonstrated, where the spatial distribution of an SHG tensor with unknown tensor coefficient magnitudes is determined by experimentally measured polarimetry. The ability to extract the out-of-plane component of the nonlinear polarization in normal incidence is demonstrated, which can be valuable for high-resolution polarimetry of 2D materials, thin films, heterostructures, and uniaxial crystals with a strong out-of-plane response.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Growth of LiNbO{sub 3}:Er Crystals and concentration dependences of their properties

A series of lithium niobate (LiNbO{sub 3}) crystals of congruent and stoichiometric compositions, doped with erbium, have been grown under non-steady-state thermal conditions. A series of LiNbO{sub 3}:Zn crystals, nominally pure LiNbO{sub 3} crystals of congruent and stoichiometric compositions, and a LiNbO{sub 3}:B crystal have also been grown. Both growth conditions and concentration dependences of physicochemical, ferroelectric, and structural characteristics of LiNbO{sub 3}:Er crystals are investigated. The growth regular domain microstructures and periodic nanostructures in LiNbO{sub 3}:Er crystals are analyzed by optical microscopy and atomic force microscopy (AFM). A comparative study of the optical homogeneity and photorefractive properties of LiNbO{sub 3}:Er crystals of congruent and stoichiometric compositions and the Raman spectra of LiNbO{sub 3} crystals of different compositions is performed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Hot Isostatic Pressing and Powder Feedstock on Porosity, Microstructure, and Mechanical Properties of Selective Laser Melted AlSi10Mg

AlSi10Mg tensile bars were additively manufactured using the powder-bed selective laser melting process. Samples were subjected to stress relief annealing and hot isostatic pressing. Tensile samples built using fresh, stored, and reused powder feedstock were characterized for microstructure, porosity, and mechanical properties. Fresh powder exhibited the best mechanical properties and lowest porosity while stored and reused powder exhibited inferior mechanical properties and higher porosity. The microstructure of stress relieved samples was fine and exhibited (001) texture in the z-build direction. Microstructure for hot isostatic pressed samples was coarsened with fainter (001) texture. To investigate surface and interior defects, scanning electron microscopy, optical fractography, and laser scanning microscopy techniques were employed. Hot isostatic pressing eliminated internal pores and reduced the size of surface porosity associated with the selective laser melting process. Hot isostatic pressing tended to increase ductility at the expense of decreasing strength. Furthermore, scatter in ductility of hot isostatic pressed parts suggests that the presence of unclosed surface porosity facilitated fracture with crack propagation inward from the surface of the part.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Author Contribution to the Pu Handbook II: Chapter 37 LLNL Integrated Sample Preparation Glovebox (TEM) Section

The development of our Integrated Actinide Sample Preparation Laboratory (IASPL) commenced in 1998 driven by the need to perform transmission electron microscopy studies on naturally aged plutonium and its alloys looking for the microstructural effects of the radiological decay process (1). Remodeling and construction of a laboratory within the Chemistry and Materials Science Directorate facilities at LLNL was required to turn a standard radiological laboratory into a Radiological Materials Area (RMA) and Radiological Buffer Area (RBA) containing type I, II and III workplaces. Two inert atmosphere dry-train glove boxes with antechambers and entry/exit fumehoods (Figure 1), having a baseline atmosphere of 1 ppm oxygen and 1 ppm water vapor, a utility fumehood and a portable, and a third double-walled enclosure have been installed and commissioned. These capabilities, along with highly trained technical staff, facilitate the safe operation of sample preparation processes and instrumentation, and sample handling while minimizing oxidation or corrosion of the plutonium. In addition, we are currently developing the capability to safely transfer small metallographically prepared samples to a mini-SEM for microstructural imaging and chemical analysis. The gloveboxes continue to be the most crucial element of the laboratory allowing nearly oxide-free sample preparation for a wide variety of LLNL-based characterization experiments, which includes transmission electron microscopy, electron energy loss spectroscopy, optical microscopy, electrical resistivity, ion implantation, X-ray diffraction and absorption, magnetometry, metrological surface measurements, high-pressure diamond anvil cell equation-of-state, phonon dispersion measurements, X-ray absorption and emission spectroscopy, and differential scanning calorimetry. The sample preparation and materials processing capabilities in the IASPL have also facilitated experimentation at world-class facilities such as the Advanced Photon Source at Argonne National Laboratory, the European Synchrotron Radiation Facility in Grenoble, France, the Stanford Synchrotron Radiation Facility, the National Synchrotron Light Source at Brookhaven National Laboratory, the Advanced Light Source at Lawrence Berkeley National Laboratory, and the Triumph Accelerator in Canada.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2021

Detection and Aggregation of Listeria Monocytogenes Using Polyclonal Antibody Gold-Coated Magnetic Nanoshells Surface-Enhanced Raman Spectroscopy Substrates

Magnetic nanoshells with tailored surface chemistry can enhance bacterial detection and separation technologies. This work demonstrated a simple technique to detect, capture, and aggregate bacteria with the aid of end-functionalized polyclonal antibody gold-coated magnetic nanoshells (pAb-Lis-AuMNs) as surface-enhanced Raman spectroscopy (SERS) probes. Listeria monocytogenes were used as the pathogenic bacteria and the pAb-LisAuMNs, 300 nm diameter, were used as probes allowing facile magnetic separation and aggregation. An optimized covalent bioconjugation procedure between the magnetic nanoshells and the polyclonal antibody was performed at pH six via a carbodiimide crosslinking reaction. Spectroscopic and morphological characterization techniques confirmed the fabrication of stable pAb-Lis-AuMNs. The resulting pAb-Lis-AuMNs acted as a SERS probe for L. monocytogenes based on the targeted capture via surface binding interactions and magnetically induced aggregation. Label-free SERS measurements were recorded for the minimum detectable amount of L. monocytogenes based on the SERS intensity at the 1388 cm -1 Raman shift. L. monocytogenes concentrations exhibited detection limits in the range of 10 4 –10 7 CFU ml -1 , before and after aggregation. By fitting these concentrations, the limit of detection of this method was ~10 3 CFU ml -1 . Using a low-intensity magnetic field of 35 G, pAb-LisAuMNs aggregated L. monocytogenes as demonstrated with microscopy techniques, including SEM and optical microscopy. Overall, this work presents a label-free SERS probe method comprised of a surface-modified polyclonal antibody sub-micron magnetic nanoshell structures with high sensitivity and magnetic induced separation that could lead to the fabrication of multiple single-step sensors.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

A method to determine the number of nanoparticles in a cluster using conventional optical microscopes

We present a method that uses conventional optical microscopes to determine the number of nanoparticles in a cluster, which is typically not possible using traditional image-based optical methods due to the diffraction limit. The method, called through-focus scanning optical microscopy (TSOM), uses a series of optical images taken at varying focus levels to achieve this. The optical images cannot directly resolve the individual nanoparticles, but contain information related to the number of particles. The TSOM method makes use of this information to determine the number of nanoparticles in a cluster. Initial good agreement between the simulations and the measurements is also presented. The TSOM method can be applied to fluorescent and non-fluorescent as well as metallic and non-metallic nano-scale materials, including soft materials, making it attractive for tag-less, high-speed, optical analysis of nanoparticles down to 45 nm diameter.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1999

Analyses of Contaminated Solar Array Handrail Samples Retrieved from Mir

In January 1998 during, the STS-89 mission, an eight section Russian solar array panel was retrieved after more than ten years exposure to the orbital space environment on the Russian space station Mir. Two darkened handrail samples from the Russian solar array have been evaluated for contamination: a section of a white paint covered rigid handrail and a section of woven fabric over-wrapped around a flexible handhold. The handrail samples were evaluated using optical microscopy (OM), field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). Optical properties were also obtained. Microscopy has shown the discolored areas to have thick layers of contaminant that has crazed and spalled off in regions. Energy dispersive spectroscopy revealed that the brown contaminant is composed of oxidized silicon. No silicon was present on the unexposed fabric over-wrap, and very small amounts were present in the white paint. Therefore, the contaminant layer on both samples is attributed to silicone contamination from other spacecraft materials that have been oxidized by atomic oxygen while in orbit. A significant source of the silicone contamination appears to be from the solar array itself.

deGroh, Kim K.↗
DOE OSTI2021

Near-field infrared microscopy: A novel analytic mapping technique to nanocharacterize calcium silicate-based cement materials

Infrared imaging via scattering-type scanning near-field optical microscopy (s-SNOM) allows chemical mapping of organic and inorganic materials with nanoscale spatial resolution. However, its potential adaptation to the complex multiphase structure of Portland cement is yet to be explored. Here we demonstrate the successful implementation of s-SNOM to spatially resolve coexisting chemical phases in tricalcium silicate, Portland cement's main compound, with 20-nm resolution. We found that s-SNOM is sensitive to different anhydrous polymorphic phases, revealing nanoscale domains that are ‘invisible’ to other microscopic techniques. Furthermore, s-SNOM's ability to distinguish the unhydrated and hydrated phases signifies its great promise as an analytical tool to study the complex hydration process of cement. The key to s-SNOM's application was nano-modifying the surface roughness of the cement samples, allowing nanoscale infrared imaging without topographical artifacts. Our study opens a window for infrared spectral microscopy in cement and other porous inorganic materials.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Growth of single and bilayer graphene by filtered cathodic vacuum arc technique

The authors present a viable process to grow the high quality graphene films with control over number of layers by the filtered cathodic vacuum arc (FCVA) technique. In the FCVA process, the different carbon concentrations can be controlled by precisely tuning the arc time (1–4 s). The arc generated carbon was deposited on the nickel catalyst at 800 °C, annealed for 10 min, and cooled down to room temperature in the presence of hydrogen gas, resulting in the graphene films with control over number of layers. Prior to arcing, hydrogen etching of nickel was carried out to clean the surface of the substrate. A growth model to prepare the high quality graphene has also been proposed. The as-grown graphene films were transferred to different substrates and are characterized by Raman spectroscopy, optical microscopy, high resolution transmission electron microscopy, and atomic force microscopy to determine the number of layers present in these films. Raman spectra of the prepared graphene films exhibit change in the G peak position from 1582.4 to 1578.1 cm{sup −1}, two-dimensional (2D) peak shifts from 2688.5 to 2703.8 cm{sup −1}, the value of I{sub 2D}/I{sub G} increased from 0.38 to 3.82, and the full width at half maxima of 2D peak changed from 41 to 70 cm{sup −1}, for different layers of graphene films. The high resolution transmission electron microscopy image revealed that the graphene films prepared for 1 and 2 s arc times have single and bi- or trilayered structures, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2025

On the scale of heterogeneity in composite electrodes of batteries

An electrode in cylindrical or pouch cell batteries contains millions of active particles embedded in a conductive network. Battery performance, such as voltage, capacity, and cyclic efficiency, is a collective response of the particle network. We use optical microscopy to measure the local, heterogeneous state of charge of individual particles upon charging and discharging. The optical reflectivity is proportional to Li composition in the ternary oxide LiNi x Mn y Co z O 2 (NMC) cathode. Through clustering analysis, we determine the scale of heterogeneity where a representative volume in the composite electrode contains 100 to 1,000 particles. The heterogeneous activity in the particle network can be described by Weibull defect population at the particle interface with the conductive matrix.

batteries↗
DOE OSTI2014

Near-field resonance shifts of ferroelectric barium titanate domains upon low-temperature phase transition

Scattering scanning near-field optical microscopy (s-SNOM) has been established as an excellent tool to probe domains in ferroelectric crystals at room temperature. Here, we apply the s-SNOM possibilities to quantify low-temperature phase transitions in barium titanate single crystals by both temperature-dependent resonance spectroscopy and domain distribution imaging. The orthorhombic-to-tetragonal structural phase transition at 263 K manifests in a change of the spatial arrangement of ferroelectric domains as probed with a tunable free-electron laser. More intriguingly, the domain distribution unravels non-favored domain configurations upon sample recovery to room temperature as explainable by increased sample disorder. Ferroelectric domains and topographic influences are clearly deconvolved even at low temperatures, since complementing our s-SNOM nano-spectroscopy with piezoresponse force microscopy and topographic imaging using one and the same atomic force microscope and tip.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Low vacuum annealing of polymer at low temperatures towards direct and scalable growth of graphene

Highlights: • Low Temperature and pressure growth process. • Synthesis of transfer free single layer graphene in the absence of reducing gases. • Sandwich structure growth process. - Abstract: A transfer-free method is demonstrated for the synthesis of graphene flakes directly on insulating substrate (SiO{sub 2}/Si) by carbon decomposition and diffusion through a layer of nickel. The 100 nm nickel catalyst was deposited on the top of SiO{sub 2} (300 nm)/Si substrate. The sandwich structure was prepared wherein spin-coated polymer was used as a carbon source for the graphene formation. The carbon molecules decomposed and diffused into the nickel layer during annealing of sandwich structures in low vacuum (∼5 × 10{sup −1} Pa) at 600–750 °C for 10 min. When cooled to room temperature (25 °C), graphene is formed at the interface between Ni and SiO{sub 2}/Si, the nickel film was removed by chemical etching. The observed graphene on SiO{sub 2}/Si substrates is confirmed by optical microscopy, Raman spectroscopy and atomic force microscopy. The Raman spectroscopy mapping over a 55 × 55 μm{sup 2} area confirmed the good quality of graphene flakes obtained.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Preparation of GaN on GaAs (100) substrate by annealing and post-nitridation

Preparation of GaN on GaAs (100) substrate by annealing and post-nitridation process has been studied. X-ray diffraction analysis confirmed the formation β-Ga{sub 2}O{sub 3} phase on annealed substrate. Nitridation of annealed samples resulted in formation hexagonal structure of GaN. Morphological changes of annealed and nitridated samples were analyzed using optical microscopy, scanning electron microscopy, atomic force microscopy. Chemical composition and elemental impurities were analysed by energy dispersive x-ray diffraction. The room-temperature photoluminescence study of annealed samples shows broad emission from 300 nm to 500 nm related to of β-Ga{sub 2}O{sub 3}, whereas nitridated samples show near band edge emission at 370 nm (3.36 eV) which corresponds to GaN.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Morphology, structure, and mechanical properties of the surface of PbTe crystals after etching with H{sub 2}O{sub 2}–HBr–ethylene glycol solutions

The morphology and microstructure of PbTe surfaces polished with H{sub 2}O{sub 2}–HBr–ethylene glycol solutions have been studied by atomic force and electron microscopy techniques. The surface of PbTe single crystals after chemical–mechanical and dynamic chemical polishing with bromine-releasing etchants has been examined by optical microscopy and profilometry. The structural perfection and composition of the PbTe surface after chemical treatment have been determined by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The mechanical properties of the crystals have been studied using microindentation. Using X-ray microanalysis, we have monitored the concentrations of the host elements (Pb and Te) and possible contamination with chemical compounds present in the etchants and the solutions used to rinse the samples.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Radically Tunable n-Type Organic Semiconductor via Polymorph Control

Polymorphism has emerged as an important design consideration in organic semiconductors (OSCs). Previously, in many OSCs, even small changes in molecular stacking can cause drastic changes to the optical and electronic properties. However, investigation into n-type semiconductors has significantly lagged behind their p-type counterparts. In this work, we present the prolific polymorphism of 2-dimensional quinoidal terthiophene (2DQTT-o-B) and systematically investigate each of 5 polymorphs, 3 of which have been previously unreported. Grazing incidence X-ray diffraction provided a key method to understanding the structure of each polymorph. Via the polymorphic transitions mapped, we tuned the electron mobility by 5 orders of magnitude, from 5.63 × 10 –5 to 0.22 cm 2 V –1 s –1 . These were accompanied by modifications to the optical properties, namely we observed substantial differences in the refractive index noted by intensity differences under polarized optical microscopy and a large shift in optical band gap from 1.18 eV up to 1.40 eV. Lastly, we suggest that changes to these properties may be related to the unique quinoidal to aromatic transition observed in quinoidal molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Rapid Accumulation of Soil Inorganics on Plastics: Implications for Plastic Degradation and Contaminant Fate

As plastics degrade in the environment, chemical oxidation of the plastic surface enables inorganics to adsorb and form inorganic coatings, likely through a combination of adsorption of minerals and in situ mineral formation. The presence of inorganic coatings on aged plastics has negative implications for plastics fate, hindering our ability to recycle weathered plastics and increasing the potential for plastics to adsorb contaminants. Here, inorganic coatings formed on terrestrially weathered polyethylene were characterized using synchrotron spectroscopy and microscopy techniques across spatial scales including optical microscopy, nano-X-ray-fluorescence mapping (nano-XRF), nano-X-ray absorption near edge structure (nano-XANES), and high-energy resolution fluorescence detected-XANES (HERFD-XANES). Results indicate a heterogeneous elemental distribution and speciation which includes inorganics common to soil terrestrial environments including iron oxides and oxyhydroxides, aluminosilicates, and carbonates.

36 MATERIALS SCIENCE↗
NASA NTRS2002

A Deuterium NMR Study of Bent-Core Liquid Crystals: Synthesis and Characterization of Deuterium-Labeled Oxadiazole-Containing Liquid Crystals - 1

We have synthesized two deuterated boomerang-shaped liquid crystals based on 2,5-bis(4-hydroxyphenyl)-1,3,4-oxadiazole (ODBP). Deuterium was introduced in the rigid 2,5-diphenyl-1,3,4-oxadiazole core and in the aromatic ring of the terminal 4-dodecyloxyphenyl moiety using standard acid catalyzed deuterium exchange conditions. Both compounds, ([4,4'(1,3,4-oxadiazole-2,5-diyl-d4)] di-4-dodecyloxybenzoate: ODBP-d4-Ph-O-C12) and ([4,4'(1,3,4-oxadiazole-2,5-diyl)] di-4-dodecyloxy-benzoate-d4; ODBP-Ph-d4-O-C12) were investigated by nuclear magnetic resonance, optical microscopy and differential scanning calorimetry. The optical textures and thermal behavior of both compounds were found to be identical to the non-deuterated analog [4,4(1,3,4-oxadiazole-2,5-diyl)] di-4-dodecyloxybenzoate (ODBP-Ph-O-C12) which we reported earlier. These compounds exhibit behavior indicative of a biaxial nematic liquid crystal phase, which we hope to confirm using deuterium NMR spectroscopy in the next phase of this study.

Dingemans, Theo J.↗