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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Data analysis for lidar and quartz crystal microbalance systems

Results are presented of the analysis of data taken on the stratospheric aerosol, using lidar, Quartz Crystal Microbalance (QCM), and the SAGE and SAM II satellite systems. The main objective of the work reported has been to use the data, taken with the NASA-LaRC instruments to study the stratospheric effects of volcanic eruptions during the period between the launch of the SAGE and SAM II satellite systems and October 1980. Four significant volcanic eruptions, for which data are available, occurred during this period--Soufriere, Sierra Negra, Mt. St. Helens, and Ulawun. Data on these have been analyzed to determine the changes in stratospheric mass loading produced by the eruptions, and to study the dispersion of the newly injected material.

Kent, G. S.↗
NASA NTRS1992

Post-flight analyses of the crystals from the M0003-14 quartz crystal microbalance experiment

Quartz Crystal Microbalances constructed by QCM Research were flown on the leading and trailing edges of the Long Duration Exposure Facility (LDEF) as one of the sub-experiments of M0003. Response of the crystals coated with 150 A of IN2O3ZnS was recorded during the first 424 days of the mission. A second QCM with crystals coated with 150 A was also flown but not monitored. The flight data and temperature profiles will be presented. After the flight, the QCM's were disassembled and analyzed. The samples included the crystals from the leading and trailing edge samples of both types of coatings along with the reference crystals which were inside the QCM housing. Analyses were performed by scanning electron microscopy, energy dispersive x ray analysis, x ray photoelectron spectroscopy, ion microprobe mass analysis, and reflectance spectroscopy in the infrared and ultraviolet/visible region. The crystals were contaminated predominantly with silicone compounds. The contamination is higher on the leading edge than on the trailing edge, and higher on the exposed crystal than on the reference crystals. No significant differences in composition of the In2O3 crystals were noted. Differences in the reflectance and surface analysis of the Zns crystals will be discussed.

Stuckey, W. K.↗
NASA NTRS1993

Post-flight analyses of the crystals from the M0003-14 quartz crystal microbalance experiment

Quartz Crystal Microbalances constructed by QCM Research were flown on the leading and trailing edges of LDEF as one of the sub-experiments of M0003. Response of the crystals coated with 150 A of In2O3 was recorded during the first 424 days of the mission. A second QCM with crystals coated with 150 A of ZnS was also flown but not monitored. After the flight, the QCM's were disassembled and analyzed in The Aerospace Corporation laboratories. The samples included the crystals from the leading and trailing edge samples of both types of coatings along with the reference crystals, which were inside the QCM housing. Analyses were performed by scanning electron microscopy, energy dispersive x-ray analyses, x-ray photoelectron spectroscopy, ion microprobe mass analysis, and reflectance spectroscopy in the infrared and UV/visible regions. The crystals are contaminated predominantly with silicone compounds. The contamination is higher on the leading edge than on the trailing edge and higher on the exposed crystals than on the reference crystals.

Stuckey, W. K.↗
NASA NTRS1996

Some Sources of Contaminants in the Shuttle Bay Measured with Temperature-Controlled Quartz Crystal Microbalances (TQCM)

The sources of molecular deposits on a Temperature-Controlled Quartz Crystal Microbalance (TQCM) attached to the shuttle bay wall at some distance from the payload and pointing out of the bay have been investigated. Explored as possible sources are: (1) the outgassing of the shuttle tiles treated with the water proofing di-methyl-ethoxy-silane (DMES) compound, scattered back by the ambient molecules into the bay; (2) The ambient scattered return flux of the outgassing, from the RTV 560 silicone which is used as the adhesive for the tiles; (3) the ambient scattered return flux of the payload outgassing; (4) the return C, flux from outgassing source originating near, below, or adjacent to the package containing the TQCM; and (5) the self-scattering of venting plumes and outgassing above the monitor package depositing on the TQCM. In all of these sources, the magnitudes of the outgassing, of the leakage rates, and venting had to be estimated in the absence of data. The resulting analyses which can be useful for similar investigations, indicates that the outgassin- from the tiles, the RTV, the payloads, or the shuttle may not have been the sources of the deposit (about 1 micro g/cm(sup 2) during a the period from bay door opening and payload release from the bay). It appears more probable that the origin is the self- and/or ambient-scattered return fluxes originating near, below, or internal to the monitor package.

Scialdone, John J.↗
NASA NTRS1995

Use of the quartz crystal microbalance to determine the monomeric friction coefficient of polyimides

When a thin film of polymer is coated on to a quartz crystal microbalance (QCM), the QCM can be used to detect the rate of increase in weight of the polymer film as the volatile penetrant diffuses into the polymer. From this rate information the diffusion coefficient of the penetrant into the polymer can be computed. Calculations requiring this diffusion coefficient lead to values which approximate the monomeric friction coefficient of the polymer. This project has been concerned with the trial of crystal oscillating circuits suitable for driving polymer coated crystals in an atmosphere of penetrant. For these studies done at room temperature, natural rubber was used as an easily applied polymer that is readily penetrated by toluene vapors, qualities anticipated with polyimides when they are tested at T(g) in the presence of toluene. Three quartz crystal oscillator circuits were tested. The simplest circuit used +/- 5 volt dc and had a transistor to transistor logic (TTL) inverter chip that provides a 180 deg phase shift via a feed back loop. This oscillator circuit was stable but would not drive the crystal when the crystal was coated with polymer and subjected to toluene vapors. Removal of a variable resistor from this circuit increased stability but did not otherwise increase performance. Another driver circuit tested contained a two stage differential input, differential output, wide band video amplifier and also contain a feed back loop. The circuit voltage could not be varied and operated at +/- 5 volts dc; this circuit was also stable but failed to oscillate the polymer coated crystal in an atmosphere saturated with toluene vapors. The third oscillator circuit was of similar construction and relied on the same video amplifier but allowed operation with variable voltage. This circuit would drive the crystal when the crystal was submerged in liquid toluene and when the crystal was coated with polymer and immersed in toluene vapors. The frequency readings obtained when using this oscillating circuit are highly variable. This circuit requires further modification to stabilize frequency readings before its use in studies to determine the diffusion coefficient of penetrant molecules into a polymer film coated on a QCM.

Bechtold, Mary M.↗
NASA NTRS1996

Methods of Measuring Vapor Pressures of Lubricants With Their Additives Using TGA and/or Microbalances

The life of a space system may be critically dependent on the lubrication of some of its moving parts. The vapor pressure, the quantity of the available lubricant, the temperature and the exhaust venting conductance passage are important considerations in the selection and application of a lubricant. In addition, the oil additives employed to provide certain properties of low friction, surface tension, antioxidant and load bearing characteristics, are also very important and need to be known with regard to their amounts and vapor pressures. This paper reports on the measurements and analyses carried out to obtain those parameters for two often employed lubricants, the Apiezon(TM)-C and the Krytox(TM) AB. The measurements were made employing an electronic microbalance and a thermogravimetric analyzer (TGA) modified to operate in a vacuum. The results have been compared to other data on these oils when available. The identification of the mass fractions of the additives in the oil and their vapor pressures as a function of the temperature were carried out. These may be used to estimate the lubricant life given its quantity and the system vent exhaust conductance. It was found that the Apiezon(TM)-C has three main components with different rates of evaporation while the Krytox(TM) did not indicate any measurable additive.

Scialdone, John J.↗
NASA NTRS1997

Gas Dynamics, Characterization, and Calibration of Fast Flow Flight Cascade Impactor Quartz Crystal Microbalances (QCM) for Aerosol Measurements

During recent high altitude flights, we have tested the aerosol section of the fast flow flight cascade impactor quartz crystal microbalance (QCM) on loan to Howard University from NASA. The aerosol mass collected during these flights was disappointingly small. Increasing the flow through the QCM did not correct the problem. It was clear that the instrument was not being operated under proper conditions for aerosol collect ion primarily because the gas dynamics is not well understood. A laboratory study was therefore undertaken using two different fast flow QCM's in an attempt to establish the gas flow characteristics of the aerosol sections and its effect on particle collection, Some tests were made at low temperatures but most of the work reported here was carried out at room temperature. The QCM is a cascade type impactor originally designed by May (1945) and later modified by Anderson (1966) and Mercer et al (1970) for chemical gas analysis. The QCM has been used extensively for collecting and sizing stratospheric aerosol particles. In this paper all flow rates are given or corrected and referred to in terms of air at STP. All of the flow meters were kept at STP. Although there have been several calibration and evaluation studies of moderate flow cascade impactors of less than or equal to 1 L/rein., there is little experimental information on the gas flow characteristics for fast flow rates greater than 1 L/rein.

Grant, J.R.↗
NASA NTRS2004

Quartz Crystal Microbalance Operation and In Situ Calibration

Quartz crystal microbalances (QCMs) are commonly used to measure the rate of deposition of molecular species on a surface. The measurement is often used to select materials with a low outgassing rate for applications where the material has a line of sight to a contamination-sensitive surface. A quantitative, in situ calibration of the balance, or balances, using a pure material for which the enthalpy of sublimation is known, is described in this Technical Memorandum. Supporting calculations for surface dwell times of deposited materials and the effusion cell Clausing factor are presented along with examples of multiple QCM measurements of outgassing from a common source.

Albyn, K. C.↗
NASA NTRS2003

Quartz Microbalance Study of 400-angstrom Thick Films near the lambda Point

In a recent measurement we observed the thinning of an adsorbed helium film induced by the confinement of critical fluctuations a few millikelvin below the lambda point. A capacitor set-up was used to measure this Casimir effect. In this poster we will present our measurement of an adsorbed helium film of 400 angstroms near the lambda point with a quartz microbalance. For films this thick, we must take into account the non-linear dynamics of the shear waves in the fluid. In spite of the added complications, we were able to confirm the thinning of the film due to the Casimir effect and the onset of the superfluid transition. In addition, we observe a sharp anomaly at the bulk lambda point, most likely related to critical dissipation of the first sound. This work is carried out in collaboration with Rafael Garcia, Stephen Jordon and John Lazzaretti. This work is funded by NASA's Office of Biological and Physical Research under grant.

Chan, Moses H. W.↗
NASA NTRS2022

A Method for Incorporating Quartz Crystal Microbalance Thermo-Gravimetric Assessment Data in Contamination Modeling

The science objectives of increasingly ambitious space missions require meeting stringent contamination requirements. Contamination transport models are based on established principles such as Fick’s law for contamination diffusion within the source material, Arrhenius factors to account for temperature variations and free molecular transport for spacecraft operating in vacuum. In addition to the science principles, empirical data obtained from ASTM E1559 testing is used for engineering contamination modeling. The ASTM E1559 test provides outgassing rate data for materials at expected spacecraft temperatures during a mission. Multiple quartz crystal microbalances (QCMs) can be operated at different temperatures to measure the amount of contamination condensation that can occur on various spacecraft surfaces. At the conclusion of the ASTM E1559 test a thermo-gravimetric assessment (TGA) can be performed by heating the QCMs at a linear rate to obtain contamination desorption data. This TGA data provides a wealth of information that can be incorporated into contamination models. A method for applying this data is presented.

Anderson, John R↗
NASA NTRS1967

Crystal microbalance measures condensable molecular fluxes

Quartz crystal quantitatively measures molecular fluxes emanating from and condensing on spacecraft surfaces. Vibrating in a thickness shear mode, the crystal is frequency sensitive to changes in mass on its surface and can measure a fractional monolayer of a condensate.

Stephens, J. B.↗
NASA NTRS1972

Quartz microbalance studies of an adsorbed helium film.

The resonant frequency of a quartz crystal oscillating in the thickness-shear mode changes by virtue of the mass loading due to any type of film laid down on its surfaces. For a helium film only the normal fraction remains rigidly coupled to the substrate motion. Adsorption isotherms of He-4 measured with this technique show clear departures from conventional nonsuperfluid behavior. We attribute this effect to the onset and presence of superfluidity in the film.

Chester, M.↗
NASA NTRS1970

Microbalance

A reed is vibrated by the minute vibrations of a base frame which, in turn, is vibrated by a driver mechanism. The vibration of the reed is picked off and fed back to the driver means, causing the base frame to be vibrated at the resonant frequency of the reed. A counter is connected to the feedback loop to measure the frequency of the reed oscillations. By adding the mass to be weighed to the reed, the resonant frequency of the reed will be changed, which will in turn change the reading at the counter by an amount which is proportional to the added mass.

Heflinger, L. O.↗
NASA NTRS1984

Crystal Microbalance Monitors Relative Humidity

Sensor monitors water evaporation in industrial drying processes. Measured adsorption isotherm for instrument essentially linear over entire range of relative humidity. Testing at each temperature setting less than half hour for full relative-humidity range, with estimated frequency response time less than 10 seconds. Used to measure relative humidity of ambient atmosphere near drying paper, food textile fabrics and pulp to optimize water-drying portion of processing cycle.

Yang, L. C.↗
NASA NTRS1991

A 200 MHz surface acoustic wave resonator mass microbalance

The development of a 200 MHz SAW instrument based on an SAW resonator instead of a conventional delay line is reported. The instrument is small, compact, and uses two separate 200 MHz resonataor crystals which operate in the dual difference mode. The difference frequency stability is better than 5 x 10 to the -9th (+ or - 1 Hz) which is comparable to a 10 MHz bulk crystal and at least an order of magnitude better than other commercially available SAW delay lines that operate at comparable frequencies. The mass sensitivity is about 9 x 10 to the 10th Hz sq cm/g. Response to temperature change is found to be about 20 Hz/C from -30 C to 30 C. Response to pressure is found to be linear from 760 to 415 Torr at 3 Hz/Torr. Detection limits for HCl vapors were determined to be in the low ppb range using an SAW resonator coated with triethanolamine.

Bowers, W. D.↗