Fiber optics in field ion microscopy.
Fiber optic window fitted to stainless steel field ion microscope permitting use of direct contact photography for image recording
WINDOW↗
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Results for “Optical Microscopy”
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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Spontaneous Formation of Single-Crystalline Spherulites in a Chiral 2D Hybrid Perovskite
In two-dimensional (2D) chiral metal-halide perovskites (MHPs), chiral organic spacers induce structural chirality and chiroptical properties in the metal-halide sublattice. This structural chirality enables reversible crystalline-glass phase transitions in (S-NEA) 2 PbBr 4 , a prototypical chiral 2D MHP where NEA + represents 1-(1-naphthyl)ethylammonium. Here, in this study, we investigate two distinct spherulite states of (S-NEA) 2 PbBr 4 , exhibiting either radial-like or stripe-like banded patterns depending on the annealing conditions of the amorphous film. Despite similarities in optical absorption and photoluminescence, the stripe-like, banded spherulite exhibits higher crystallinity and improved optical transparency compared to those of radial-like spherulite. X-ray nanoprobe measurements reveal tilting-angle modulations in the octahedral plane of stripe-like spherulites, correlating with the film’s surface geometry. Transfer matrix calculations indicate that the optical contrast in stripe-like patterns, seen in bright-field optical microscopy, arises from optical interference effects, differing from the contrast mechanism observed in polymer spherulites. Ultrafast carrier dynamics experiments suggest that the stripe-like spherulites resemble single crystals more closely than radial-like spherulites, while electrical conductivity measurements show enhanced charge carrier transport in stripe-like spherulites. These findings offer insights into MHP spherulite states with a single composition but different morphologies, previously observed only in polymers, highlighting their potential for optoelectronic applications.
36 MATERIALS SCIENCE↗
The structure of extruded NiAl
The deformation structure of Ni-rich NiAl extruded at 550 C has been characterized by transmission electron microscopy and by optical microscopy. Dislocations having a(100) Burgers vectors were found as complex networks, tangles, and prismatic loops. a(110) dislocations, which were rare, were concluded to arise from reactions of a(100) dislocations. Evidence of recovery and recrystallization was obtained. Extrusion was deemed to have been possible by the operation of (hko)(001) slip systems (often in plane strain flow) plus diffusion-assisted processes.
Baker, I.↗
Visible-to-THz near-field nanoscopy
Optical microscopy has a key role in research, development and quality control across a wide range of scientific, technological and medical fields. However, diffraction limits the spatial resolution of conventional optical instruments to about half the illumination wavelength. A technique that surpasses the diffraction limit in the wide spectral range between visible and terahertz frequencies is scattering-type scanning near-field optical microscopy (s-SNOM). The basis of s-SNOM is an atomic force microscope in which the tip is illuminated with light from the visible to the terahertz spectral range. By recording the elastically tip-scattered light while scanning the sample below the tip, s-SNOM yields near-field optical images with a remarkable resolution of 10 nm, simultaneously with the standard atomic force microscopic topography image. This resolution is independent of the illumination wavelength, rendering s-SNOM a versatile nanoimaging and nanospectroscopy technique for fundamental and applied studies of materials, structures and phenomena. This Review presents an overview of the fundamental principles governing the measurement and interpretation of near-field contrasts and discusses key applications of s-SNOM. We also showcase emerging developments that enable s-SNOM to operate under various environmental conditions, including cryogenic temperatures, electric and magnetic fields, electrical currents, strain and liquid environments. Furthermore, all these recent developments broaden the applicability of s-SNOMs for exploring fundamental solid-state and quantum phenomena, biological matter, catalytic reactions and more.
Hillenbrand, Rainer [CIC nanoGUNE BRTA and Departm↗
Exobiology study - Analytical systems for biological study of Mars. The role of electron microscopy and electron optical techniques in exobiology
Electron microscopy and optical techniques for biological Mars studies
MARS PROBE↗
Microscopic analysis of irradiated UN–Mo–W for space nuclear propulsion
Nuclear propulsion is an effective method of providing thrust in deep space, allowing for shorter mission duration for long-term surface missions to Mars. The fuel for nuclear propulsion systems must exhibit superior mechanical and thermal properties, to decrease the possibility of fuel failure and to increase reactor efficiency. Here, the objective of the Sirius project is to fabricate and irradiate cermet fuels at the Idaho National Laboratory Transient Reactor Facility to determine the properties of the fuel after irradiation at prototypical nuclear propulsion start-up conditions. The Sirius project featured 3 test capsules, Sirius-1 featured uranium nitride fuel dispersed in a matrix of tungsten and rhenium, while Sirius-2A and -2B featured uranium nitride-molybdenum-tungsten fuel (UN-Mo-W). The fuel samples from the Sirius-2A and -2B capsules were examined after irradiation using optical microscopy, scanning electron microscopy, and X-ray diffraction analyses. The mechanical properties of the fuel from Sirius-2A and -2B are discussed in a previous work. In this study, the results of the optical microscopy, scanning electron microscopy, and X-ray diffraction analyses are discussed.
11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Exobiology study- analytical systems for biological study of mars, the role of electron microscopy and electron optical techniques in exobiology
Electron microscopy and electron optics in exobiology
ELECTRON MICROSCOPY↗
Iridium, shocked minerals, and trace elements across the Cretaceous/Tertiary boundary at Maud Rise, Wedell Sea, and Walvis Ridge, South Atlantic Ocean
Sediments spanning a 5 meter section across the Cretaceous-Tertiary boundary at ODP holes 689B and 690D, Maud Rise, Wedell Sea and hole 527, Walvis Ridge, are being analyzed for shock deformation, PGE's and other trace elements (including REE's). Mineral separates from each sample were studied with optical microscopy to determine the distribution and microstructural state of quartz and feldspar present in the sediments. Samples from Maud Rise were taken of the K/T transition and at about 50 cm intervals above and below it. These samples consist of carbonate-rich sediments, with the K/T transition marked by a change from white Maastrichtian oozes to a greenish ooze with higher concentrations of altered volcanic clay and vitric ash. The Walvis Ridge site is characterized by more clay-rich sediments with average carbonate content about 60 to 70 percent. Initial results from RNAA studies indicate that iridium is present in all the Maud Rise samples in concentrations equal to or greater than 0.01 ppb (whole-rock basis). Preliminary results from optical microscopy indicate the occurrence of shock mosaicism in quartz and feldspar in all of the samples studied. The pervasiveness of shock mosaicism and presence of planar features to 2 meters from the K/T boundary indicates that a single impact or volcanic explosion 66 ma may be ruled out as responsible for the K/T event. A similar conclusion may be drawn independently from the distribution of iridium and other trace elements. Regardless of the source of the shock waves and sediment contamination, multiple events are required over a ca.0.5 my timespan; currently we favor endogenous sources.
Huffman, Alan R.↗
Analytical systems for biological study of mars. the role of electron microscopy and electron optical techniques in exobiology
Electron microscopy and electron optical techniques in exobiology
OPTICAL METHOD↗
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↗
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↗
Development of In-situ Digital Microscopy Capabilities for Electrochemical Testing
In-situ digital optical microscopy data was successfully collected during the potentiodynamic polarization of iron in corrosive NaCl solution. This report serves as a foundation for future, more comprehensive experiments that correlate electrochemical responses to near-real time surface morphology tracking. The development of in-situ microscopy and roughness collection will help realize increases in data acquisition of the surface morphology during electrochemical experiments.
36 MATERIALS SCIENCE↗
Thermal Inspection for the Assessment of Adhesively Bonded Metal Adherents
Certification of adhesively bonded structures is currently a challenge for aircraft manufacturers. The ability to certify bonds in primary structure can reduce dependence on fasteners and this will enable more efficient manufacturing. For example, drilling holes and installing fasteners in bonded joints can be a potentially significant bottleneck in airframe manufacturing. In addition, fasteners increase the airframe weight and can add stress concentration areas. Reducing fastener count can accelerate manufacturing and improve aircraft performance. NASA is currently investigating nondestructive evaluation (NDE) techniques to assess bond integrity. For example, bond thickness influences bond strength and therefore NDE techniques are being investigated to determine bond thickness. For bonded metal structures, there is a large difference in the thermal diffusivity between the 7075 aluminum alloy metal adherends and aircraft grade adhesive. Multi-layered thermal models show a large variation in the thermal response for bondline adhesive thicknesses that vary from 100 to 300 microns for adherend thicknesses of 0.163 cm. Experimental through-transmission thermal measurements reveal promise to quantitatively characterize the bondline thickness. Results were validated with X-ray computed tomography and optical microscopy measurements, and influence of porosity on the thermal model and measurements are investigated.
bondline thickness↗
Thermal Inspection for the Assessment of Adhesively Bonded Metal Adherends
Certification of adhesively bonded structures is currently a challenge for aircraft manufacturers. The ability to certify bonds in primary structure can reduce dependence on fasteners and this will enable more efficient manufacturing. For example, drilling holes and installing fasteners in bonded joints can be a potentially significant bottleneck in airframe manufacturing. In addition, fasteners increase the airframe weight and can add stress concentration areas. Reducing fastener count can accelerate manufacturing and improve aircraft performance. NASA is currently investigating nondestructive evaluation (NDE) techniques to assess bond integrity. For example, bond thickness influences bond strength and therefore NDE techniques are being investigated to determine bond thickness. For bonded metal structures, there is a large difference in the thermal diffusivity between the 7075 aluminum alloy metal adherends and aircraft grade adhesive. Multi-layered thermal models show a large variation in the thermal response for bondline adhesive thicknesses that vary from 100 to 300 microns for adherend thicknesses of 0.163 cm. Experimental through-transmission thermal measurements reveal promise to quantitatively characterize the bondline thickness. Results were validated with X-ray computed tomography and optical microscopy measurements, and influence of porosity on the thermal model and measurements are investigated.
X-ray computed tomography↗
Compatibility of molten plutonium with wrought and additively manufactured metal crucibles
Understanding plutonium’s interaction with metals is crucial for optimizing pyrochemical operations, nuclear fuel containment, and various actinide processing techniques. Traditionally, tantalum crucibles are employed for plutonium processing due to their high durability, excellent temperature stability, and low solubility in plutonium. However, tantalum faces challenges such as plutonium wetting and diffusion, making surface coatings particularly important for crucibles in pyrochemical applications to enhance corrosion resistance against plutonium. Tantalum is also expensive and difficult to machine, prompting the need for advanced manufacturing techniques to address these challenges. Here, in this work, we investigate the interaction of Pu with tantalum and titanium crucibles fabricated using both traditional machining methods and laser powder bed fusion (LPBF) additive manufacturing (AM). LPBF-AM is an advanced technique that allows for the creation of complex geometries from traditionally difficult-to-machine metals by using a high-powered laser to build parts. Previous studies of conventional manufactured tantalum have utilized oxidation and carburization of the surface to mitigate plutonium wetting; however, no studies of surface modified LPBF-AM material have been undertaken. These studies are crucial, given the typical differences in the grain structure between conventional and LPBF-AM materials. All crucibles underwent differential scanning calorimetry to confirm the melting of plutonium. Subsequently, the crucibles were sectioned and mounted in epoxy for microstructural analysis using optical microscopy and scanning electron microscopy. This investigation, comparing the performance of wrought vs AM metal crucibles, provides a basis for future tooling applications in actinide processing techniques and can address the challenges associated with traditional machining, particularly in pyrochemical applications.
Actinides↗
Hemicellulose Modulates Nanoscale Lignin Architecture in Synthetic Plant Cell Walls
Cellulose, hemicellulose, and lignin─the most abundant biopolymers on Earth─compose the structural matrix of plant biomass, providing renewable resources critical to bioenergy and sustainable materials. Despite their importance, the nanoscale mechanochemical processes underlying lignocellulose assembly during plant secondary cell wall formation remain poorly understood, hindering advancements in biomass conversion technologies. Here, in this study, we synthesize a biomimetic model system comprising cellulose–hemicellulose nanofibrils (CHN) to examine guaiacyl lignin polymerization in a physiologically relevant context. Using advanced nanocharacterization─scattering-type scanning near-field optical microscopy (s-SNOM) with infrared nanospectroscopy coupled to solid-state nuclear magnetic resonance (NMR)─we reveal that hemicellulose presence considerably modulates lignin deposition and alters its interunit bond distribution. Specifically, hemicellulose-rich environments dramatically reduce lignin deposition by approximately 50% and yield highly condensed lignin structures characterized by severely reduced β–O–4′ linkages (<2%) and suppressed β–β′ linkages. Conversely, cellulose-alone scaffolds support notably higher β–O–4′ content (∼10%), resulting in a more uniform nanoscale lignin coating. Our work helps explain how accessible hemicellulose sites, both sterically and chemically, direct radical coupling during lignification, fundamentally reshaping lignin’s nanoscale architecture. These findings deepen our mechanistic understanding of plant cell wall biosynthesis and inform strategies aimed at enhancing biomass deconstruction efficiency for sustainable bioenergy applications.
NMR↗
Modal focal adaptive optics for Bessel-focus two-photon fluorescence microscopy
Adaptive optics (AO) improves the spatial resolution of microscopy by correcting optical aberrations. While its application has been well established in microscopy modalities utilizing a circular pupil, its adaptation to systems with non-circular pupils, such as Bessel-focus two-photon fluorescence microscopy (2PFM) with an annular pupil, remains relatively uncharted. Herein, we present a modal focal AO (MFAO) method for Bessel-focus 2PFM. Measuring and correcting aberration using a spatial light modulator placed in conjugation with the focal plane of the microscope objective, MFAO employs Zernike annular polynomials — a first in AO implementation — to achieve performance on par with a previous zonal AO method, but with a notably simplified optical configuration. We validated the performance of MFAO in correcting artificial and sample-induced aberrations, as well as in in vivo imaging of zebrafish larvae and mouse brains. By expanding the application of modal AO to annular pupils as well as aberration measurement and correction to a wavefront modulator at the objective focal plane, MFAO represents a notable advancement in the implementation of AO in microscopy.
47 OTHER INSTRUMENTATION↗
Unequal {110} Facets: The Potential Role of Intraparticle Heterogeneity and Facet Termination in Photoelectrochemical Activity of Single BiVO 4 Particles
BiVO 4 photoanodes are promising for solar water splitting, with photogenerated electrons and holes preferentially reacting at top {010} and lateral {110} facets, respectively. However, the mechanisms driving this facet-dependent reactivity remain unclear. Here, in this study, we investigate facet-dependent photocurrent and material heterogeneity using correlative scanning photoelectrochemical microscopy (SPCM), electron beam induced current (EBIC) mapping, and mid-IR scattering scanning near-field optical microscopy (s-SNOM). SPCM measurements of 62 BiVO 4 particles confirmed higher photocurrents at lateral {110} facets compared to top {010} facets, but unexpectedly revealed variations in photocurrent among lateral facets within the same particle. Variations in lateral facet surface termination could explain the intraparticle-level reactivity heterogeneity, consistent with theoretical predictions. Nano-FTIR spectroscopy and Raman microspectroscopy indicated significant materials chemistry heterogeneity within individual particles and facets that could be attributed to variations in lattice vibration distortions that enhance the overlap between Bi 6s and O 2p orbitals. The increased orbital overlap is significant as it potentially increases hole mobility in the valence band and potentially explains the lateral facet-dependent charge separation efficiency observed in photocurrent maps. Facet-dependent electrical and EBIC measurements showed no space charge regions at interfacet junctions or metal-BiVO 4 contacts under vacuum, suggesting that photogenerated holes beneath top {010} facets are unlikely to transport to lateral {110} facets to drive water/sulfite oxidation. These findings indicate the potential influence of distinct bulk properties and surface termination chemistries across different particles and facets, highlighting the importance of carefully controlling defects and surface chemistry during sample growth to optimize photocatalytic performance.
BiVO4↗