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NASA NTRS1995

Recent Developments in the Use of Liquid Crystal Coatings for Full-Surface Shear Stress Vector Measurements

Under normal white-light illumination and oblique observation, liquid crystal coating (LCC) color-change response to shear depends on both shear stress magnitude as well as the direction of the applied shear relative to the observer's line of sight. These color-change responses were quantified by subjecting a LCC to a wall-jet shear flow and measuring scattered-light spectra using a fiber optic probe and spectrophotometer. At any fixed shear stress magnitude, the maximum color change was measured when the shear vector was aligned with and directed away from the observer; changes in the relative in-plane view angle to either side of this vector/observer aligned position resulted in symmetric Gaussian reductions in measured color change. For this vector/observer aligned orientation, color change was found to scale linearly with increasing shear stress magnitude over an eight-fold range. Based on these results, a surface shear stress vector measurement methodology, involving multiple oblique-view observations of the test surface, was formulated. In the present paper, the experimental approach and data analysis procedure required to extend this vector measurement methodology to full-surface applications will be outlined and progress towards demonstrating this areal capability will be reviewed.

Reda, D. C.↗

NASA NTRS2011

Visual hydrogen detector with variable reversibility

Methods, processes and compositions are provided for a visual or chemochromic hydrogen-detector with variable or tunable reversible color change. The working temperature range for the hydrogen detector is from minus 100.degree. C. to plus 500.degree. C. A hydrogen-sensitive pigment, including, but not limited to, oxides, hydroxides and polyoxo-compounds of tungsten, molybdenum, vanadium, chromium and combinations thereof, is combined with nano-sized metal activator particles and preferably, coated on a porous or woven substrate. In the presence of hydrogen, the composition rapidly changes its color from white or light-gray or light-tan to dark gray, navy-blue or black depending on the exposure time and hydrogen concentration in the medium. After hydrogen exposure ceases, the original color of the hydrogen-sensitive pigment is restored, and the visual hydrogen detector can be used repeatedly. By changing the composition of the hydrogen-sensitive pigment, the time required for its complete regeneration is varied from a few seconds to several days.

Muradov, Nazim↗

NASA NTRS2012

Visual hydrogen detector with variable reversibilty

Muradov, Nazim Z.↗

NASA NTRS2014

Methods of Forming Visual Hydrogen Detector with Variable Reversibility

Methods, processes and compositions are provided for a visual or chemochromic hydrogen-detector with variable or tunable reversible color change. The working temperature range for the hydrogen detector is from minus 100 C to plus 500 C. A hydrogen-sensitive pigment, including, but not limited to, oxides, hydroxides and polyoxo-compounds of tungsten, molybdenum, vanadium, chromium and combinations thereof, is combined with nano-sized metal activator particles and preferably, coated on a porous or woven substrate. In the presence of hydrogen, the composition rapidly changes its color from white or light-gray or light-tan to dark gray, navy-blue or black depending on the exposure time and hydrogen concentration in the medium. After hydrogen exposure ceases, the original color of the hydrogen-sensitive pigment is restored, and the visual hydrogen detector can be used repeatedly. By changing the composition of the hydrogen-sensitive pigment, the time required for its complete regeneration is varied from a few seconds to several days.

Muradov, Nazim Z.↗

NASA NTRS1986

On the colors of Jupiter's satellite Io - Irradiation of solid sulfur at 77 K

The colors of seven sulfur allotropes at 77 K have been investigated both before and after irradiation by a high-pressure mercury lamp. S8 is white at 77 K but turns intense yellow within a few minutes on irradiation through quartz or DURAN. On warming, the yellow species (presumably chain-like sulfur diradicals characterized by an absorption at 430 nm) decomposes near 260 K and polymeric sulfur (S-infinity) is formed; the sample color changes gradually to the very similar color of an S8-S-infinity mixture, resulting in no visually detectable color change with temperatures from 77 K to 260 K. This is consistent with the lack of posteclipse brightening on Io. Other sulfur forms also turn intense yellow (S7, S10), grayish yellow (S12, S20, S-infinity), or brownish yellow (S6) on irradiation at 77 K, and these colors also change to the normal colors of the starting materials on warming to 298 K. It is suggested that the yellowish features on Io are caused by the effect of solar radiation on elemental sulfur. The yellow color thus produced may subsequently be modified by deposits of SO2 frosts and volcanic ash.

Steudel, R.↗

DOE OSTI2022

Investigation of Inverse Temperature Effects During Thermal-Radiation Aging of Semicrystalline Cable Insulation

Inverse temperature effects were observed for semi-crystalline polymers subjected to combined thermal and irradiation aging. The mechanical durability of materials aged at low temperatures degrades with dose faster than at high temperatures. In this paper, two crosslinked polyethylene (XLPE) and two ethylene propylene rubber (EPR) type nuclear cable insulations were exposed to thermal-radiation aging at 100Gy/h up to 30Mrad and three temperatures (26°C, 50°C, 90°C). Their mass change and color change after aging were analyzed.

Ni, Yelin↗

NASA NTRS1988

Mass loss in a B2 IIIe star - Omega Orionis 1978-1984

A combination of long-term optical polarimetric, photometric, spectrometric, and UV spectral data has confirmed that all the observed portions of Omega Ori's outer atmosphere are variable on a variety of time scales. The shortest confirmed variations are detectable over a few hours, and the longest changes are observed on time scales of years. A straightforward interpretation of the available data is that the continuum polarization, continuum-magnitude changes, and color changes produced are in a presumably equatorial disk close to the stellar photosphere.

Sonneborn, George↗

NASA NTRS1994

Video Event Trigger

Video event trigger (VET) processes video image data to generate trigger signal when image shows significant change like motion or appearance, disappearance, change in color, change in brightness, or dilation of object. System aids in efficient utilization of image-data-storage and image-data-processing equipment in applications in which many video frames show no changes and are wasteful to record and analyze all frames when only relatively few frames show changes of interest. Applications include video recording of automobile crash tests, automated video monitoring of entrances, exits, parking lots, and secure areas.

Williams, Glenn L.↗

DOE OSTI2020

A Digital Imaging Method for Evaluating the Kinetics of Vapochromic Response

This work describes the use of a cell phone camera and the L*a*b method (color space specified by the International Commission on Illumination) to characterize the color change in different vapochromic systems. In this study we have developed a semi-automatic color change analysis software that digitally analyzes images (e.g., video frames) collected while a vapochromic material is absorbing vapor. The advantages of using this method, as compared to reflectance spectroscopy or transmission spectroscopy through a thin film, include low cost, convenience, portability, ease of sample preparation, the absence of need for specialized equipment, and the ease of simultaneously collecting data on different samples under identical conditions. In addition, this method arguably provides direct insight into what a human would observe when monitoring these color changes by eye. Limitations of the method also are discussed in this paper.

cell phone camera, colorimetric sensing, vapor det↗

NASA NTRS1998

Visualization and Measurement of Surface Shear Stress Vector Distributions Using Liquid Crystal Coatings

When a shear-sensitive liquid crystal coating is illuminated from the normal direction by white light and observed from an oblique above-plane view angle, its color-change response to shear depends on both shear stress vector magnitude and the direction of the applied shear vector relative to the observer's in-plane line of sight. At any point, the maximum color change is always seen or measured when the local shear vector is aligned with, and directed away from, the observer; the magnitude of the color change at this vector/observer aligned orientation scales directly with shear stress magnitude. Conversely, any point exposed to a shear vector with a component directed toward the observer exhibits a noncolor-change response, always characterized by a rusty red or brown color, independent of both shear magnitude and direction. Based on this knowledge, full-surface shear stress vector visualization and measurement methodologies were formulated and successfully demonstrated. The present paper reviews the observations and measurements that led to the development of these methodologies and applications of both are discussed.

Reda, Daniel C.↗

NASA NTRS2003

Fiber-Optic Ammonia Sensors

Reversible, colorimetric fiber-optic sensors are undergoing development for use in measuring concentrations of ammonia in air at levels relevant to human health [0 to 50 parts per million (ppm)]. A sensor of this type includes an optical fiber that has been modified by replacing a portion of its cladding with a polymer coat that contains a dye that reacts reversibly with ammonia and changes color when it does so. The change in color is measured as a change in the amount of light transmitted from one end of the fiber to the other. Responses are reversible and proportional to the concentration of ammonia over the range from 9 to 175 ppm and in some cases the range of reversibility extends up to 270 ppm. The characteristic time for the response of a sensor to rise from 10 to 90 percent of full scale is about 25 seconds. These sensors are fully operational in pure carbon dioxide and are not adversely affected by humidity. This work was done by Michael T. Carter

Carter, Michael T.↗

DOE OSTI2021

1,3,5-Trichloro-2,4,6-Trinitrobenzene: The Elusive Impurity Standard

1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is an insensitive high explosive synthesized in two steps; 1,3,5-trichloro-2,4,6-trinitrobenzene (TCTNB) is the only intermediate. Due to solubility limitations, TATB is often dissolved in dimethylsulfoxide (DMSO) for liquid chromatography-mass spectrometry (LC–MS) analyses; however, DMSO is capable of participating in a wide variety of reactions. Intending to use it as an impurity standard, TCTNB was dissolved in DMSO. A stark color change from colorless to yellow accompanied by wavelength and ion chromatogram changes occurred over 24 hours. Three compounds were identified as causing the color change. All three were present in both acetone and DMSO solutions, but, overtime the absorbance spectra of the DMSO solution changed indicating an underlying reaction occurs between these compounds and DMSO. The chemical formulas of impurities present in the TCTNB sample as well as reaction products are identified via quadrupole time of flight mass spectrometry. The chemical structures are also proposed. The combination of the solvent system, ionization technique, and halogenated/nitrated aromatic ring structures resulted in substitutions of both the chlorine and nitro groups to hydroxyl groups. Furthermore, three proposed structures were closely related to TCTNB, but only one was detected at a consistent mass and absorbance wavelength in both acetone and DMSO. This compound had undergone a chlorine to hydroxyl substitution and should be utilized for TCTNB detection.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1973

Collection and analysis of remotely sensed data from the Rhode River Estuary Watershed

The remote sensing study to survey the Rhode River watershed for spray irrigation with secondarily treated sewage is reported. The standardization of Autumn coloration changes with Munsell color chips is described along with the mapping of old field vegetation for the spray irrigation project. The interpretation and verification of salt marsh vegetation by remote sensing of the water shed is discussed.

Jenkins, D. W.↗

NASA NTRS1977

Survey of the BY Draconis syndrome among dMe stars

Results are reported for a BVr photometric survey of 22 dK, dKe, dM, and dMe stars conducted to search for slow quasi-sinusoidal fluctuations in V (the BY Draconis syndrome). The (B-V) and (V-r) color indices are determined in an attempt to detect wavelength-dependent color changes produced by starspots and to infer starspot temperatures. It is found that nine of the stars exhibit variations in V of the order of 0.05 to 0.10 magnitude on a time scale of days or weeks, that at least three more display changes in mean light level over a period of years, that the stars generally tend to become redder at minimum light, and that some of the stars show no detectable color changes over their photometric cycle. The color data are taken to suggest a probable temperature difference of about 200 to 500 K between the stellar photospheres and starspots if the V variations are attributed to dark spots. It is concluded that the BY Draconis syndrome is clearly a very common occurrence among dMe stars.

Bopp, B. W.↗

DOE OSTI2021

Quantitative Microstructural Characterization of Plutonium Oxalate Auto-Degradation and Evidence for PuO2 Nanocrystal Formation

It has been known since the 1950s that plutonium oxalate powders change color and lose mass over time when stored at room temperature in air. Despite several studies monitoring these changes, there are still discrepancies in the literature regarding the speciation of intermediate and final products that result from this decomposition. Presented here for the first time is a comprehensive series of time-resolved powder X-ray diffraction experiments coupled with solid-state optical spectroscopy and electron microscopy of aged plutonium (III) and (IV) oxalate powders. These data provide fresh insight into the chemical and structural changes that occur in these solids over time at room temperature and represent new evidence suggesting both plutonium (III) and plutonium (IV) oxalates decompose to form nanocrystalline plutonium oxide in the solid state.

Corbey, Jordan F.↗

DOE OSTI2021

Tamper-Indicating Enclosures with Visually Obvious Tamper Response (Final Project Report)

Sandia National Laboratories is developing a new method for detecting penetration of tamper - indicating enclosures (TIEs). This method incorporates the use of "bleeding" materials (analogous to visually obvious, colorful bruised skin that doesn't heal) into the design of TIEs. As designed, it will allow inspectors to use simple visual observation to detect attempts to penetrate the external surfaces of a TIE, without providing adversaries the ability to repair damage. A material of this type can enhance tamper indication of current TIEs used to support treaty verification regimes. Current TIE inspections are time - consuming and rely on subjective visual assessment by an inspector, equipment such as eddy current or camera devices, or involve approaches that may be limited due to application environment. The complexities and requirements that volumetric sealing methods (or TIEs) must address are: (1) enclosures that are non - standard in size/shape; (2) enclosures that may be inspectorate - or facility - owned; (3) finding tamper attempts that are difficult and time consuming for an inspector to locate; (4) enclosures that are reliable and durable enough to survive the conditions that exist in the operating environment (including facility handling); and (5) methods that prevent adversaries from repairing penetrations. Early project R&D [1] focused on encapsulated transition metals. Due to the challenges associated with the transition metal - based approach, a mitigation approach was investigated resulting in two separate research paths — one that involves fabricating custom TIE molds that meet the specific (size and shape) needs of safeguards equipment a nd one that can be deployed as a sprayed on or painted coating to an existing TIE or surface. The "custom mold" approach is based on creating thin layers of materials that , when penetrated, expose an inner material to O 2 which causes an irreversible color change. The "in-situ coating" approach is based on applying a sensor solution containing color changing microcapsules that bleed when the microcapsule is ruptured. The anticipated benefits of this work are passive, flexible, scalable, robust , cost-effective TIEs with visually obvious responses to tamper attempts. This provides more efficient and effective monitoring , as inspectors will require little or no additional equipment and will be able to detect tamper without extensive time - consuming visual examination. Applications include custom TIEs (cabinets , equipment enclosures or seal bodies ), or spray-coating/painting onto facility-owned items, walls or structures, or circuit boards. The paper describes research and testing completed to-date on the method and integration of select system components.

36 MATERIALS SCIENCE↗

NASA NTRS1988

The NASA Infrared Telescope Facility Comet Halley monitoring program. II - Postperihelion results

Postperihelion 1-20-micron magnitudes of Comet Halley obtained at the NASA Infrared Telescope Facility are presented. These magnitudes complement the preperihelion magnitudes published earlier by Tokunaga et al.(1986). The time period covered in this program was March 1986 through June 1987. While no systematic near-infrared color change was found during the preperihelion passage, a distinct J-H, H-K color change occurred during the postperihelion passage after July 1986. This indicates that there was a change in either the composition or particle size of the cometary dust, or both.

Tokunaga, A. T.↗

NASA NTRS2022

Reversible Colorimetric Sensing of Volatile Analytes By Wicking in Close Proximity to A Photonic Film

Isolation of volatile analytes from environmental or biological fluids is a rate-determining step that can delay the response time for continuous sensing. In this paper, we demonstrate a colorimetric sensing system that enables the rapid detection of gas-phase analytes released from a flowing micro-volume fluid sample. The sensor platform is an analyte-responsive metal-insulator-metal (MIM) thin-film structure integrated with a large area quartz micropillar array. This allows precise planar alignment and microscale separation (310 μm) of the optical and fluidic structures. This configuration offers rapid and homogeneous color changes over large areas that permits detection by low-resolution optics or eye, which is well-suited to portable/wearable devices. For our proof-of-principle demonstration, we utilized a poly(methyl methacrylate) (PMMA) spacer and evaluated the sensor's response (color change) to ethanol vapor. We show that the RGB color value is quantitatively linked to the spacer swelling, which is reversible and repeatable. The optofluidic platform reduces the sensor response time from minutes to seconds compared with experiments using a conventional chamber. The sensor's concentration-dependent response was examined, confirming the potential of the reported sensing platform for continuous, compact, and quantitative colorimetric analysis of volatile analytes in low-volume samples, such as biofluids.

Timothy J. Palinski↗