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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

New Directions in Phthalocyanine Pigments

The objectives were the following: (1) investigation of the synthesis of new phthalocyanines; (2) characterization of the new phthalocyanines synthesized; (3) investigate the properties of the newly synthesized phthalocyanines with emphasis on UV protection of plastics and coatings; and (4) utilize quantum mechanics to evaluate the structural relationships with possible properties and synthetic approaches. The proposed research targeted the synthesis of phthalocyanines containing an aromatic bridge between two phthalocyanine rings. The goal was to synthesize pigments which would protect plastics when exposed to the photodegradation effects of the sun in space. The stability and extended conjugation of the phthalocyanines offer a unique opportunity for energy absorption and numerous radiative and non-radiative energy loss mechanisms. Although the original targeted phthalocyanines were changed early in the project, several new and unique phthalocyanine compounds were prepared. The basic goals of this work were met and some unique and unexpected outcomes of the work were the result of the integral use of quantum mechanics and molecular modeling with the synthetic effort.

Vandemark, Michael R.↗
NASA NTRS2013

Studying the Use of Photocatalytic Coatings to Increase Building/Structure Sustainability and Cleanliness at NASA Stennis Space Center

TiO2 coated surfaces demonstrated both visually through photographic representation, and quantitatively, through reflectance measurements that they improved upon the current state of cleanliness upon the surfaces that they were applied to. TiO2 has the potential to both maintain and increase building s sustainability and the overall appearance of cleanliness TiO2 coated slides degraded soot under UV light compared to soot samples on plain uncoated slides under the same conditions Degradation of soot by photocatalysis was far more apparent than degradation of soot by UV light alone This demonstration provides the foundation for a laboratory model that could be used to simulate real world applications for photocatalytic materials Additional research is required to better understand the full potential of TiO2

Underwood, Lauren↗
DOE OSTI2023

Cross-linkable nanocomposite anticorrosion coating

Nanocomposite anticorrosion coating can be achieved by depositing alternating, multilayers of a cross-linkable polymer and dispersed and aligned inorganic platelets followed by cross-linking of the cross-linkable polymer. The cross-linkable polymer can be an externally cross-linkable polymer that is cross-linked by diffusing a cross-linking agent into the deposited multilayer coating. Alternately, the cross-linkable polymer can be a functionalized cross-linkable polymer that is cross-linked by self-curing, thermal heat curing, or light (e.g., UV) following deposition of the multilayer coating.

Percival, Stephen John↗
DOE OSTI2021

Investigation of UV, ns-laser damage resistance of hafnia films produced by electron beam evaporation and ion beam sputtering deposition methods

Laser-induced damage in coating materials with a high index of refraction, such as hafnia, limits the performance of high power and high energy laser systems. Understanding the underlying physics responsible for laser damage holds the key for developing damage-resistant optical films. Previous studies have reported a substantial difference in laser damage onset for hafnia films produced by different deposition methods, yet the underlying mechanisms for the observed difference remain elusive. We combined laser damage testing with analytical characterizations and theoretical simulations to investigate the response of hafnia films produced by electron (e-) beam evaporation vs ion beam sputtering (IBS) methods upon UV ns-laser exposure. We found that e-beam produced hafnia films were overall more damage resistant; in addition, we observed a polarization anisotropy associated with the onset of damage in the e-beam films, while this effect was absent in the latter films. The observed differences can be attributed to the stark contrast in the pressure inside the pores inherent in both films. The high pressure inside the IBS-induced nanobubbles has been shown to reduce the threshold for laser-induced plasma breakdown leading to film damage. The polarization effects in the e-beam coatings can be related to the asymmetric electric field intensification induced by the columnar void structure. Our findings provide a fundamental basis for developing strategies to produce laser damage-resistant coatings for UV pulsed laser applications.

36 MATERIALS SCIENCE↗
NASA NTRS1989

Working group written presentation: Solar radiation

The members of the Solar Radiation Working Group arrived at two major solar radiation technology needs: (1) generation of a long term flight data base; and (2) development of a standardized UV testing methodology. The flight data base should include 1 to 5 year exposure of optical filters, windows, thermal control coatings, hardened coatings, polymeric films, and structural composites. The UV flux and wavelength distribution, as well as particulate radiation flux and energy, should be measured during this flight exposure. A standard testing methodology is needed to establish techniques for highly accelerated UV exposure which will correlate well with flight test data. Currently, UV can only be accelerated to about 3 solar constants and can correlate well with flight exposure data. With space missions to 30 years, acceleration rates of 30 to 100X are needed for efficient laboratory testing.

Slemp, Wayne S.↗
NASA NTRS1991

Optical design considerations for next-generation space and lunar telescopes

The paper discusses the optical requirements for future large space or lunar telescopes and their influence upon the fundamental system parameters. Two telescope concepts, a four-reflection three-mirror telescope, and a spherical-primary four-mirror telescope are introduced. Both have the potential for extreme high performance, and both use four reflections to accomplish this. Considering the present available coating capabilities, the reflectivity loss in the lower UV region due to the additional reflections, compared to a two-mirror system, seriously affects the utility of four-mirror telescopes for this part of the spectrum. Separate telescopes for the UV and for longer wavelengths may therefore be a practical solution, unless significant advances in coating technology are made in the foreseeable future.

Korsch, Dietrich↗
NASA NTRS1991

Evaluation of optically transparent polyetherimide films for applications in space

Several series of aromatic polyetherimide films have been synthesized and characterized with the objective of obtaining maximum optical transparency for applications in space. Incorporation of phenoxy groups into aromatic polyimides has resulted in a reduction in the color intensity of these films compared to commercial polyimide film by reducing electronic interactions between polymer chains. The resulting lightly colored to colorless polyetherimide films have been characterized by UV-visible and infrared spectroscopy before and after exposure to varying doses of UV and electron irradiation designed to simulate use as second-surface mirror thermal control coatings. After exposure to 300 equivalent solar hours UV irradiation and 1 MeV electron irradiation, the polyetherimides were 2.2 to 2.6 times more transparent than commercial polyimide film of the same thickness.

St. Clair, Anne K.↗
NASA NTRS2003

Electrical Properties and Manufacturability of ITO-MgF2 and Related Transparent Arcproof Spacecraft Coatings

To investigate the applicability of co-deposited indium tin oxide and magnesium fluoride as a transparent arcproof coating on the exterior of PowerSphere microsatellites. This included testing coating performance after deposition on flexible polymeric substrates, determining whether ultraviolet (UV) radiation present during deposition might affect the UV-curing resin contained in the substrate, and preparation of coated polymeric samples for radiation damage studies by the PowerSphere team.

Hambourger, Paul D.↗
NASA NTRS2022

Vitrolube NPI-1220 Solid Lubricant Performance After Ultraviolet and Salt Fog Test Exposures

Vitrolube NPI-1220 is a ceramic-bonded solid lubricant produced by National Process Industries, Inc. (NPI) that uses molybdenum disulfide (MoS2) and graphite as lubricating pigments. It is applied to many space flight components, including nickel-alloy and stainless-steel components. Various applications, such as the powered nut and bolt assemblies in the international space station (ISS) (Illi, 1999), the Space Launch System (SLS) sliding bellows, and the SLS ball strut tie-rod assembly (BSTRA) use Vitrolube. No engineering data exists regarding possible Vitrolube degradation after extended exposure to coastal environments encountered by flight hardware on test stands or launch pads. Such environments include ultraviolet (UV) ray, high humidity, and salt exposures. In this study, nickel-alloy disks coated with Vitrolube by NPI, are exposed to controlled UV ray and ‘salt fog’ environments in facilities at Marshall Space Flight Center (MSFC). The exposed disks are run in tribological pin-on-disk tests to quantify any difference in coating lubricity and/or wear compared to coated disks that were not exposed to those environments.

Tribology↗
NASA NTRS2012

Thermally Resilient, Broadband Optical Absorber from UV to IR Derived from Carbon Nanostructures

Optical absorber coatings have been developed from carbon-based paints, metal blacks, or glassy carbon. However, such materials are not truly black and have poor absorption characteristics at longer wavelengths. The blackness of such coatings is important to increase the accuracy of calibration targets used in radiometric imaging spectrometers since blackbody cavities are prohibitively large in size. Such coatings are also useful potentially for thermal detectors, where a broadband absorber is desired. Au-black has been a commonly used broadband optical absorber, but it is very fragile and can easily be damaged by heat and mechanical vibration. An optically efficient, thermally rugged absorber could also be beneficial for thermal solar cell applications for energy harnessing, particularly in the 350-2,500 nm spectral window. It has been demonstrated that arrays of vertically oriented carbon nanotubes (CNTs), specifically multi-walled-carbon- nanotubes (MWCNTs), are an exceptional optical absorber over a broad range of wavelengths well into the infrared (IR). The reflectance of such arrays is 100x lower compared to conventional black materials, such as Au black in the spectral window of 350-2,500 nm. Total hemispherical measurements revealed a reflectance of approximately equal to 1.7% at lambda approximately equal to 1 micrometer, and at longer wavelengths into the infrared (IR), the specular reflectance was approximately equal to 2.4% at lambda approximately equal to 7 micrometers. The previously synthesized CNTs for optical absorber applications were formed using water-assisted thermal chemical vapor deposition (CVD), which yields CNT lengths in excess of 100's of microns. Vertical alignment, deemed to be a critical feature in enabling the high optical absorption from CNT arrays, occurs primarily via the crowding effect with thermal CVD synthesized CNTs, which is generally not effective in aligning CNTs with lengths less than 10 m. Here it has been shown that the electric field inherent in a plasma yields vertically aligned CNTs at small length scales (less than 10 m), which still exhibit broadband, and high-efficiency optical absorption characteristics from the ultraviolet (UV) to IR. A thin and yet highly absorbing coating is extremely valuable for detector applications for radiometry in order to enhance sensitivity. A plasma-based process also increases the potential of forming the optical absorbers at lower synthesis temperatures in the future, increasing the prospects of integrating the absorbers with flexible substrates for low-cost solar cell applications, for example.

Kaul, Anupama B.↗
DOE OSTI2026

Artificial Soiling Replication of Field Losses on Commercial Photovoltaic Modules

Here, this study demonstrates the capabilities of an indoor artificial soiling approach developed to closely replicate the natural, cyclic soil accumulation processes in the field-dust suspension, deposition, and sedimentation/cementation-for a subtropical climate. In this work, a near-field environment is replicated in an artificial soiling cubic chamber through controlled regulation of humidity, temperature, dust type, and dust concentration, based on site-specific historical climate data. Two different models (MA and MB) of full-size commercial photovoltaic modules from a single manufacturer, installed side by side in the mid-Atlantic United States, were retrieved and subjected to artificial soiling experiments and various characterization measurements, including short-circuit current, colorimetry, reflectance, X-ray fluorescence, laser diffraction, and optical microscopy. Both in the field and in our improved field-representative artificial soiling tests, the MA model experienced roughly twice the soiling loss as the MB model. To closely replicate the field soiling losses for a site-specific climate, it is critical to include: 1) The use of field-collected dust with identical dust chemistry and particle distribution instead of standardized ISO 12103 Arizona Road dusts, 2) the use of only a small amount of field-collected dust inside the chamber during the deposition process (e.g., 0.15 g), and 3) the preconditioning of the surface coating for the partial/full dose of UV stress as experienced in the field during sunlight exposure and the abrasion as experienced in the field during regular module cleaning activities, if/as needed. The field-representative artificial soiling method developed here could potentially be adopted for rank ordering of various antisoiling coatings developed by researchers and industry stakeholders.

14 SOLAR ENERGY↗
DOE OSTI2022

UV‐induced degradation of high‐efficiency silicon PV modules with different cell architectures

Abstract Degradation from ultraviolet (UV) radiation has become prevalent in the front of solar cells due to the introduction of UV‐transmitting encapsulants in photovoltaic (PV) module construction. Here, we examine UV‐induced degradation (UVID) in various commercial, unencapsulated crystalline silicon cell technologies, including bifacial silicon heterojunction (HJ), interdigitated back contact (IBC), passivated emitter and rear contact (PERC), and passivated emitter rear totally diffused (PERT) solar cells. We performed UV exposure tests using UVA‐340 fluorescent lamps at 1.24 W·m −2 (at 340 nm) and 45°C through 4.02 MJ·m −2 (2000 h). Our results showed that modern cell architectures are more vulnerable to UVID, leading to a significant power decrease (−3.6% on average; −11.8% maximum) compared with the conventional aluminum back surface field (Al‐BSF) cells (<−1% on average). The power degradation is largely caused by the decrease in short‐circuit current and open‐circuit voltage. A greater power decrease is observed in bifacial cells with rear‐side exposure compared with those with front‐side exposure, indicating that the rear side is more susceptible to UV damage. Secondary ion mass spectroscopy (SIMS) confirmed an increase in hydrogen concentration near the Si/passivation interface in HJ and IBC cells after UV exposure; the excess of hydrogen could result in hydrogen‐induced degradation and subsequently cause higher recombination losses. Additionally, surface oxidation and hot‐carrier damage were identified in PERT cells. Using a spectral‐based analysis, we obtained an acceleration factor of 5× between unpackaged cells (containing a silicon nitride antireflective coating on the front) in the UV test and an encapsulated module (with the front glass and encapsulant blocking 90% of the UV at 294 nm and 353 nm, respectively) in outdoor conditions. From the analytical calculations, we show that a UV‐blocking encapsulant can reduce UV transmission in the module by an additional factor of ~50.

14 SOLAR ENERGY↗
NASA NTRS1993

Optical Technologies for UV Remote Sensing Instruments

Over the last decade significant advances in technology have made possible development of instruments with substantially improved efficiency in the UV spectral region. In the area of optical coatings and materials, the importance of recent developments in chemical vapor deposited (CVD) silicon carbide (SiC) mirrors, SiC films, and multilayer coatings in the context of ultraviolet instrumentation design are discussed. For example, the development of chemically vapor deposited (CVD) silicon carbide (SiC) mirrors, with high ultraviolet (UV) reflectance and low scatter surfaces, provides the opportunity to extend higher spectral/spatial resolution capability into the 50-nm region. Optical coatings for normal incidence diffraction gratings are particularly important for the evolution of efficient extreme ultraviolet (EUV) spectrographs. SiC films are important for optimizing the spectrograph performance in the 90 nm spectral region. The performance evaluation of the flight optical components for the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument, a spectroscopic instrument to fly aboard the Solar and Heliospheric Observatory (SOHO) mission, designed to study dynamic processes, temperatures, and densities in the plasma of the upper atmosphere of the Sun in the wavelength range from 50 nm to 160 nm, is discussed. The optical components were evaluated for imaging and scatter in the UV. The performance evaluation of SOHO/CDS (Coronal Diagnostic Spectrometer) flight gratings tested for spectral resolution and scatter in the DGEF is reviewed and preliminary results on resolution and scatter testing of Space Telescope Imaging Spectrograph (STIS) technology development diffraction gratings are presented.

Keski-Kuha, R. A. M.↗
DOE OSTI2020

Shape-Selective Mesoscale Nanoarchitectures: Preparation and Photocatalytic Performance

We create ordered arrays of shape-selective gold-titania composite nanomaterials at the mesoscale (100 &micro;m to 5 mm) by a combination of both bottom-up and top-down approaches for exquisite control of the size, shape, and arrangement of nanomaterials. Lithographic techniques along with wet chemical synthetic methods were combined to create these composite nanomaterials. The photocatalytic activity of these TiO 2, TiO 2 -Au and SiO 2 -TiO 2 -Au nano-composite mesoscale materials was monitored by the photodegradation of a model analyte, methyl orange, under UV and visible (Vis) illumination. Bare TiO 2 - and SiO 2 -TiO 2 -coated pillar arrays showed significant activity toward methyl orange in UV light with degradation rates on the order of 10 &minus;4 &ndash;10 &minus;3 min &minus;1 . The photocatalytic activity of these arrays was also found to depend on the nanoparticle shape, in which particles with more edges and corners were found to be more reactive than spherical particles (i.e., the photocatalytic activity decreased as follows: diamonds > squares > triangles > spheres). SiO 2 -TiO 2 -Au nano-composite pillar arrays were tested in both UV and Vis light and showed increased activity in Vis light but decreased activity in UV light as compared to the bare semiconductor arrays. Additionally, the Au nanorod-functionalized nanoarrays exhibit a strong shape-dependence in their photocatalytic activity toward methyl orange degradation in Vis light.

36 MATERIALS SCIENCE↗
NASA NTRS2001

Effects of Electrons, Protons, and Ultraviolet Radiation on Thermophysical Properties of Polymeric Films

The response of coated thin polymer films to ultraviolet (UV), electron and proton radiation simultaneously has been evaluated, with selected measurements in situ. Exposure was intended to simulate the electron and proton radiation environment near the Earth-Sun Lagrangian points (LI and L2) for five years and approximately 1000 equivalent solar hours (ESH) UV. These orbital environments are relevant to several potential missions such as the Next Generation Space Telescope and Geomagnetic Storm Warning, both of which may use thin film based structures for a sunshade and solar sail, respectively. The thin film candidates (12.5 micrometers thick) consisted of commercially available materials (Kapton(R) E, HN, Upilex(R) S, CP-1, CP-2, TOR-RC, and TOR-LMBP) that were metalized on one side with vapor deposited aluminum. All of the films are aromatic polyimides, with the exception of TORLMBP, which is a copoly(arylene ether benzimidazole). The films were exposed as second surface mirrors and the effects of the exposure on solar absorptance, thermal emittance, and tensile properties were determined. The in situ changes in solar absorptance from Kapton(R) and Upilex(R) were less than 0. 1, whereas the solar absorptance of TOR and CP films increased by more than 0.3 without saturating. The thermal emittance measurements also showed that the Kapton(R) and Upilex(R) materials increased only 1-2%, but the remaining materials increased 5-8%. Based on tensile property measurements made in air following the test, the failure stress of every type of polymer film decreased as a result of irradiation. The polymers most stable in reflectance, namely Upilex(R) and Kapton(R), were also the strongest in tension before irradiation, and they retained the greatest percentage of tensile strength. The films less stable in reflectance were also weaker in tension, and lost more tensile strength as a result of irradiation. The apparent failure strain (as a percent of original gage length) of every type of polymer film except TOR-RC, decreased as a result of irradiation.

Russell, Dennis A.↗