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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Chromate Removal by Long Life IX Resins Without Continuous pH Adjustment - 20083

Long life resins are available for chromate removal from water but have traditionally had the disadvantage of requiring pH adjustment, first to reduce pH before treatment, and then to raise pH following treatment. The requirement for double pH adjustment leads to a significant increase in TDS, added complexity, risks associated with the use of strong acids and bases, and the ongoing costs of purchasing and using these chemicals. The mechanism of removal in long life resins used for chromate removal is ion exchange, followed by reduction of hexavalent chromium to trivalent chromium, followed by immobilization of trivalent chromium within the IX resin polymer. The second step is rate limiting and pH dependent and is the reason why lowering pH before treatment has until now been necessary. However, there is a reasonably simple way to use these long life resins that does not require continuous pH adjustment. By taking a portion of the treatment vessels off line and soaking them in a low pH solution, the rate constant for the reduction step is increased sufficiently to catch up, making the ion exchange step the limiting factor. The long life resin is effectively regenerated by the low pH soaks. Rejuvenated resin beds can then be put back on line and operated at the natural pH of the feedwater. This method of operation is protected by US Patent no. US20150136706A1. (author)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Surface and Electrochemical Characteristics of Novel Chromate-Free Mn-V Oxyanion Sealed Tartaric–Sulfuric Acid Anodized Coating

In the present investigation, a novel chromate-free Mn and V oxyanions sealed tartaric–sulfuric acid anodic oxide coating (TSA) was developed on airframe grade aluminum alloy (AA2024). The results obtained from field emission scanning electron microscopy and energy-dispersive x-ray analysis showed effective surface modification of TSA after Mn-V oxyanions sealing (TSAMnVO). Potentiodynamic polarization results showed no significant difference in corrosion current density value (0.01 µA/cm{sup 2}) after 1 h and 336 h of immersion in 3.5% NaCl solution. EIS result exhibited barrier layer resistance (R{sub b}) value of TSAMnVO > 10{sup 6} kΩ cm{sup 2} even after 336 h of immersion in NaCl solution. The 3D profile and Raman analysis showed no significant difference in the topography and composition, respectively, on the surface of TSAMnVO even after 1000 h of salt spray test. TSAMnVO also showed excellent adhesion with aircraft grade epoxy primer as per the ASTM 3359. Tensile and constant amplitude fatigue test results of TSAMnVO exhibited ultimate tensile strength and number of cycles to failure comparable with chromic acid anodization (CAA) process. Hence, the developed novel TSAMnVO coating system eliminates the usage of chromate ions completely in anodization process since it provides comparable corrosion resistance and mechanical properties with CAA.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Using the red chromatic coordinate to characterize the phenology of forest canopy photosynthesis

Vegetation phenology has received increasing attention in climate change research. Near-surface sensing using digital repeat photography has proven to be useful for ecosystem-scale monitoring of vegetation phenology. However, our understanding of the link between phenological metrics derived from digital repeat photography and the phenology of forest canopy photosynthesis is still incomplete, especially for evergreen plant species. Using 49 site-years of digital images from the PhenoCam Network from eight evergreen needleleaf forest (ENF) and six deciduous broadleaf forest (DBF) sites in North America, we explored the potential of the green chromatic (GCC) and red chromatic coordinates (RCC) in tracking forest canopy photosynthesis by comparing camera-derived start- and end-of-growing season (SOS and EOS, respectively) with corresponding estimates derived from eddy covariance-derived daily gross primary productivity (GPP). We found that for DBF sites, both GCC and RCC performed comparable in capturing SOS and EOS. However, similar to earlier studies, GCC had limited potential in capturing GPP-based SOS or EOS for ENF sites. In contrast, we found RCC was a better predictor of both GPP-based SOS and EOS for ENF sites. Environmental and ecological explanations were both provided that phenological transitions derived from RCC were highly correlated with spring and autumn meteorological conditions, as well as having overall higher correlations with phenology based on LAI, a critical variable for describing canopy development. Our results demonstrate that RCC is an underappreciated metric for tracking vegetation phenology, especially for ENF sites where GCC failed to provide reliable estimates for GPP-based SOS or EOS. Our results improve confidence in using digital repeat photography to characterize the phenology of canopy photosynthesis across forest types.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Blue photons excited highly chromatic red light emitting K3La(PO4)2:Pr3+ phosphors for white light emitting diodes

Highlights: • K{sub 3}La(PO{sub 4}){sub 2}:Pr{sup 3+} phosphors were investigated as an alternative for red light. • Highly chromatic red emission was realized upon blue excitation. • The phosphor has high color purity ∼ 97.8% and yield ∼27%. - Abstract: Highly chromatic blue photons excited red emitting K{sub 3}La(PO{sub 4}){sub 2}:Pr{sup 3+} (0–1.8 mol%) phosphors were synthesized by solution combustion method. The resulted phosphors showed peanut like morphology and had a monoclinic phase with space group P2{sub 1}/m. The photoluminescence studies disclosed that the phosphor emits red light due to the {sup 1}D{sub 2} → {sup 3}H{sub 4} and {sup 1}D{sub 2} → {sup 3}H{sub 5} transition of the Pr{sup 3+} ions under blue photons excitation. The optimal concentration for the Pr{sup 3+} ions were optimized to be 1.2 mol% after which concentration quenching occurred. Dipole-dipole interaction among the dopant ions was found to be responsible for the concentration quenching. X-ray photoelectron spectroscopy results depicted that Pr was present in the (+3) valance state in the phosphor. The photometric results suggest that the phosphor with a high color purity ∼ 97.8% and enough quantum yield ∼27% could be an eventual choice as the red component for white light emitting diodes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Realizing string-net condensation: Fibonacci anyon braiding for universal gates and sampling chromatic polynomials

Abstract The remarkable complexity of a topologically ordered many-body quantum system is encoded in the characteristics of its anyons. Quintessential predictions emanating from this complexity employ the Fibonacci string net condensate (Fib SNC) and its anyons: sampling Fib-SNC would estimate chromatic polynomials while exchanging its anyons would implement universal quantum computation. However, physical realizations remained elusive. We introduce a scalable dynamical string net preparation (DSNP) that constructs Fib SNC and its anyons on reconfigurable graphs suitable for near-term superconducting processors. Coupling the DSNP approach with composite error-mitigation on deep circuits, we create, measure, and braids Fibonacci anyons; charge measurements show 94% accuracy, and exchanging the anyons yields the expected golden ratioϕwith 98% average accuracy. We then sample the Fib SNC to estimate chromatic polynomial atϕ + 2 for several graphs. Our results establish the proof of principle for using Fib-SNC and its anyons for fault-tolerant universal quantum computation and aim at a classically hard problem.

Science & Technology - Other Topics↗
DOE OSTI2016

Chromatic-aberration-corrected diffractive lenses for ultra-broadband focusing

We exploit the inherent dispersion in diffractive optics to demonstrate planar chromatic-aberration-corrected lenses. Specifically, we designed, fabricated and characterized cylindrical diffractive lenses that efficiently focus the entire visible band (450 nm to 700 nm) onto a single line. These devices are essentially pixelated, multi-level microstructures. Experiments confirm an average optical efficiency of 25% for a three-wavelength apochromatic lens whose chromatic focus shift is only 1.3 μm and 25 μm in the lateral and axial directions, respectively. Super-achromatic performance over the continuous visible band is also demonstrated with averaged lateral and axial focus shifts of only 1.65 μm and 73.6 μm, respectively. These lenses are easy to fabricate using single-step grayscale lithography and can be inexpensively replicated. Furthermore, these devices are thin (<3 μm), error tolerant, has low aspect ratio (<1:1) and offer polarization-insensitive focusing, all significant advantages compared to alternatives that rely on metasurfaces. Lastly, our design methodology offers high design flexibility in numerical aperture and focal length, and is readily extended to 2D.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Chromatic instabilities in cesium-doped tungsten bronze nanoparticles

Nanoparticles of alkali-doped tungsten bronzes are an excellent near-infrared shielding material, but exhibit slight chromatic instabilities typically upon applications of strong ultra-violet light or heating in humid environment, which acts detrimentally to long-life commercial applications. Origin of the chromatic instabilities in cesium-doped tungsten bronze has been investigated, and it has been found that the coloration and bleaching processes comprised electronic exchanges which accelerate or depress the polaron excitation and the localized surface plasmon resonance. Coloration on UV illumination is evidenced by electron diffraction as due to the formation of H{sub x}WO{sub 3}, which is considered to take place in the surface Cs-deficient WO{sub 3} region via the double charge injection mechanism. On the other hand, bleaching on heating in air and in humid environment is shown to accompany the extraction of Cs and electrons from Cs{sub 0.33}WO{sub 3} by X-ray photoelectron spectroscopy and X-ray diffraction analysis and is concluded to be an oxidation of Cs{sub 0.33}WO{sub 3} on the particle surface.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Variation in band gap of lanthanum chromate by transition metals doping LaCr{sub 0.9}A{sub 0.1}O{sub 3} (A:Fe/Co/Ni)

Transition metal (Fe, Co, Ni) doped lanthanum chromate (LaCrO{sub 3}) nanoparticles (NPs) were prepared by gel combustion method and calcinated at 800°C. Microstructural studies were carried by XRD and SEM/EDS techniques. The results of structural characterization show the formation of all samples in single phase without any impurity. Optical properties were studied by UV- visible and photoluminescence techniques. The energy band gap was calculated and the variation was observed with the doping of transition metal ions. Photoluminescence spectra show the emission peak maxima for the pure LaCrO{sub 3} at about 315 nm. Influence of Fe, Co, Ni doping was studied and compared with pure lanthanum chromate nanoparticles.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Chromatic matching in a plasma undulator

The principle of chromatic matching, i.e., using two laser modes of different geometric mode numbers and different colors so that they copropagate at the same group velocity, is proposed in order to realize the plasma undulator concept. Chromatic matching allows one to overcome group velocity slippage, whereby lower-order modes outrun higher-order ones, allowing for extended interaction lengths. The dephasing limit can be mitigated by using a special tapering of the plasma channel such that the electron bunch propagates in phase with the laser mode in addition to maintaining a constant undulator frequency. Finally, controlled dephasing is proposed as a means to induce chirp in the generated X-ray spectrum.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

A STUDY OF GRAVITATIONAL LENS CHROMATICITY WITH THE HUBBLE SPACE TELESCOPE

We report Hubble Space Telescope observations of six gravitational lenses with the Advanced Camera for Surveys. We measured the flux ratios between the lensed images in seven filters from 8140 #Angstrom# to 2200 #Angstrom#. In three of the systems, HE0512-3329, B1600+434, and H1413+117, we were able to construct UV extinction curves partially overlapping the 2175 #Angstrom# feature and characterize the properties of the dust relative to the Galaxy and the Magellanic Clouds. In HE1104-1804, we detect chromatic microlensing and use it to study the physical properties of the quasar accretion disk. For a Gaussian model of the disk exp (- r{sup 2}/2r{sup 2}{sub s}), scaling with wavelength as r{sub s} {proportional_to}{lambda}{sup p}, we estimate r{sub s} ({lambda}3363) = 4{sup +4}{sub -2} (7 {+-} 4) light days and p = 1.1 {+-} 0.6 (1.0 {+-} 0.6) for a logarithmic (linear) prior on r{sub s} . The remaining two systems, FBQ0951+2635 and SBS1520+530, yielded no useful estimates of extinction or chromatic microlensing.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Strong chromatic microlensing in HE0047–1756 and SDSS1155+6346

We use spectra of the double-lensed quasars HE0047–1756 and SDSS1155+6346 to study their unresolved structure through the impact of microlensing. There is no significant evidence of microlensing in the emission line profiles except for the Lyα line of SDSS1155+6346, which shows strong differences in the shapes for images A and B. However, the continuum of the B image spectrum in SDSS1155+6346 is strongly contaminated by the lens galaxy, and these differences should be considered with caution. Using the flux ratios of the emission lines for image pairs as a baseline to remove macro-magnification and extinction, we have detected strong chromatic microlensing in the continuum measured by CASTLES (www.cfa.harvard.edu/castles/) in both lens systems, with amplitudes 0.09(λ16000) ≲ |Δm| ≲ 0.8(λ5439) for HE0047–1756, and 0.2(λ16000) ≲ |Δm| ≲ 0.8(λ5439) for SDSS1155+6346. Using magnification maps to simulate microlensing and modeling the accretion disk as a Gaussian source (I ∝ exp(–R {sup 2}/2r {sub s}{sup 2})) of size r {sub s} ∝ λ {sup p}, we find r {sub s} = 2.5{sub −1.4}{sup +3.0} √(M/0.3M{sub ⊙}) lt-day and p = 2.3 ± 0.8 at the rest frame for λ = 2045 for HE0047–1756 (log prior) and r {sub s} = 5.5{sub −3.3}{sup +8.2} √(M/0.3M{sub ⊙}) lt-day and p = 1.5 ± 0.6 at the rest frame of λ = 1398 for SDSS1155+6346 (log prior). Contrary to other studied lens systems, the chromaticity detected in HE0047–1756 and SDSS1155+6346 is large enough to fulfill the thin disk prediction. The inferred sizes, however, are very large compared to the predictions of this model, especially in the case of SDSS1155+6346.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

Ultrafast spatiotemporal laser pulse engineering using chromatic dispersion.

We discuss a new method for manipulating the optical field distribution in time and space at the focal plane of a chromatic lens. Chromatic dispersion and aberration make it possible to control the photon distribution in both time and space by properly controlling the amplitude and phase of the incident laser pulse, including shortening a laser pulse or generating a specific time-dependent transverse distribution. As an example, we discuss the generation of a quasi-three-dimensional ellipsoidal photon distribution and a proof-of-principle experiment, where favourable agreement between theoretical calculations and the data is observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Single bunch transverse instability in a circular accelerator with chromaticity and space charge

The transverse instability of a bunch in a circular accelerator is elaborated in this paper. A new tree-modes model is proposed and developed to describe the most unstable modes of the bunch. This simple and flexible model includes chromaticity and space charge, and can be used with any bunch and wake forms. The dispersion equation for the bunch eigentunes is obtained in form of a third-order algebraic equation. The known head-tail and TMCI modes appear as the limiting cases which are distinctly bounded at zero chromaticity only. It is shown that the instability parameters depend only slightly on the bunch model but they are rather sensitive to the wake shape. In particular, space charge effects are investigated in the paper and it is shown that their influence depends on sign of wake field enhancing the bunch stability if the wake is negative. In addition, the resistive wall wake is considered in detail including a comparison of single and collective effects. A comparison of the results with earlier publications is carried out.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Chromatic effects on the PSF and shear measurement for the Roman Space Telescope High-Latitude Wide Area Survey

Weak gravitational lensing (WL) is a key cosmological probe that requires precise measurement of galaxy images to infer shape distortions, or shear, and constrain cosmology. Accurate estimation of the point spread function (PSF) is crucial for shear measurement, but the wavelength dependence of the PSF introduces chromatic biases that can systematically impact shear inference. We focus on biases arising from spectral energy distribution (SED) differences between stars, used for PSF modelling, and galaxies, used for shear measurement. We investigate these effects in Roman’s four design reference mission WL bands (Y106, J129, H158, F184) and wide filter (W146). Using Roman-like image simulations, we quantify the induced shear biases and compare them to requirements on those biases. Multiplicative biases over all galaxies hover around ~0.2 per cent in the WL bands and 2 per cent in the wide filter, exceeding the mission requirement of |m| < 0.032 per cent and relaxed requirement of |m| < 0.1 per cent⁠. In individual redshift bins, biases can reach 0.4–0.9 per cent for the WL bands and 3–6 per cent for the wide filter. Additive biases remain acceptable in the WL bands but exceed systematic limits in the wide filter. We develop and test PSF-level corrections, showing that a first-order correction reduces biases within survey requirements for the WL bands; however, higher-order terms are necessary for the wide filter. Our results highlight the necessity of chromatic corrections for precision WL with Roman and provide a framework for mitigating these biases. Finally, we compare analytical colour-based corrections to self-organizing maps and find that both methods effectively reduce biases.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

First cosmology results using Type IA supernovae from the dark energy survey: effects of chromatic corrections to supernova photometry on measurements of cosmological parameters

Abstract Calibration uncertainties have been the leading systematic uncertainty in recent analyses using Type Ia supernovae (SNe Ia) to measure cosmological parameters. To improve the calibration, we present the application of spectral energy distribution-dependent ‘chromatic corrections’ to the SN light-curve photometry from the Dark Energy Survey (DES). These corrections depend on the combined atmospheric and instrumental transmission function for each exposure, and they affect photometry at the 0.01 mag (1 per cent) level, comparable to systematic uncertainties in calibration and photometry. Fitting our combined DES and low-z SN Ia sample with baryon acoustic oscillation (BAO) and cosmic microwave background (CMB) priors for the cosmological parameters Ωm (the fraction of the critical density of the universe comprised of matter) and w (the dark energy equation of state parameter), we compare those parameters before and after applying the corrections. We find the change in w and Ωm due to not including chromatic corrections is −0.002 and 0.000, respectively, for the DES-SN3YR sample with BAO and CMB priors, consistent with a larger DES-SN3YR-like simulation, which has a w-change of 0.0005 with an uncertainty of 0.008 and an Ωm change of 0.000 with an uncertainty of 0.002. However, when considering samples on individual CCDs we find large redshift-dependent biases (∼0.02 in distance modulus) for SN distances.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Chromatic patchy particles: Effects of specific interactions on liquid structure

We study the structural and thermodynamic properties of patchy particle liquids, with a special focus on the role of “color,” i.e., specific interactions between individual patches. A possible experimental realization of such “chromatic” interactions is by decorating the particle patches with single-stranded DNA linkers. The complementarity of the linkers can promote selective bond formation between predetermined pairs of patches. By using MD simulations, we compare the local connectivity, the bond orientation order, and other structural properties of the aggregates formed by the “colored” and “colorless” systems. The analysis is done for spherical particles with two different patch arrangements (tetrahedral and cubic). It is found that the aggregated (liquid) phase of the “colorless” patchy particles is better connected, denser and typically has stronger local order than the corresponding “colored” one. This, in turn, makes the colored liquid less stable thermodynamically. Specifically, we predict that in a typical case the chromatic interactions should increase the relative stability of the crystalline phase with respect to the disordered liquid, thus expanding its region in the phase diagram.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Effects of dimensionality on the electronic structure of Ruddlesden-Popper chromates Sr n+1 ⁢Cr n ⁢O 3⁢n+1

Transition-metal oxides host a wide variety of electronic phenomena that can be significantly influenced by the effective dimensionality of the system under consideration. These include charge, spin, and orbital orderings, as well as unconventional superconductivity. In this context, the Ruddlesden-Popper chromates Sr n+1 Cr n O 3n+1 emerge as a particularly intriguing series of materials. Formally, the chromium atom displays a rather special 4+ oxidation state throughout the entire series. However, the effective dimensionality changes from quasi-2D to 3D as n increases from 1 to ∞. As a result, the insulating antiferromagnetic behavior observed for n = 1, 2, 3 transforms into itinerant antiferromagnetism with reduced transition temperature for the n = ∞ end member of the series, i.e., the perovskite SrCrO 3 . Further, distinct orbital orderings with exotic singlet states have been predicted for these systems. However, the lack of single-crystal bulk or thin-film samples has made experimental progress difficult. Here we demonstrate the synthesis of thin films of the perovskite SrCrO 3 and the associated layered chromates via oxide molecular beam epitaxy for n = 1 to n = 5. Our electrical transport measurements reveal a gradual evolution from a strongly insulating state in Sr 2 CrO 4 to a metallic state in the end member SrCrO 3 . X-ray absorption spectroscopy measurements demonstrate a varying hybridization strength of the Cr 4+ valence electrons across the series, helping to explain the trend in conduction. Finally, density functional theory calculations further confirm the observed transport trend and identify additional distortions present in the system.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A spectroscopic study of the chromatic properties of GafChromic™EBT3 films

Purpose: This work provides an interpretation of the chromatic properties of GafChromic™EBT3 films based on the chemical nature of the polydiacetylene (PDA) molecules formed upon interaction with ionizing radiation. The EBT3 films become optically less transparent with increasing radiation dose as a result of the radiation-induced polymerization of diacetylene monomers. In contrast to empirical quantification of the chromatic properties, less attention has been given to the underlying molecular mechanism that induces the strong decrease in transparency. Methods: Unlaminated GafChromic™EBT3 films were irradiated with a 6 MV photon beam to dose levels up to 20 Gy. The optical absorption properties of the films were investigated using visible (vis) spectroscopy. The presence of PDA molecules in the active layer of the EBT3 films was investigated using Raman spectroscopy, which probes the vibrational modes of the molecules in the layer. The vibrational modes assigned to PDA’s were used in a theoretical vis-absorption model to fit our experimental vis-absorption spectra. From the fit parameters, one can assess the relative contribution of different PDA conformations and the length distribution of PDA’s in the film. Results: Vis-spectroscopy shows that the optical density increases with dose in the full region of the visible spectrum. The Raman spectrum is dominated by two vibrational modes, most notably by the ν(C≡C) and the ν(C=C) stretching modes of the PDA backbone. By fitting the vis-absorption model to experimental spectra, it is found that the active layer contains two distinct PDA conformations with different absorption properties and reaction kinetics. Furthermore, the mean PDA conjugation length is found to be 2–3 orders of magnitude smaller than the crystals PDA’s are embedded in. Conclusions: Vis- and Raman spectroscopy provided more insight into the molecular nature of the radiochromic properties of EBT3 films through the identification of the excited states of PDA and the presence of two PDA conformations. The improved knowledge on the molecular composition of EBT3’s active layer provides a framework for future fundamental modeling of the dose–response.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗