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Sample records for aluminized teflon fep

  1. Ground Laboratory Soft X-Ray Durability Evaluation of Aluminized Teflon FEP Thermal Control Insulation. Revised

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; deGroh, Kim K.; Stueber, Thomas J.; Sechkar, Edward A.; Hall, Rachelle L.

    1998-01-01

    Metallized Teflon fluorinated ethylene propylene (FEP) thermal control insulation is mechanically degraded if exposed to a sufficient fluence of soft x-ray radiation. Soft x-ray photons (4-8 A in wavelength or 1.55 - 3.2 keV) emitted during solar flares have been proposed as a cause of mechanical properties degradation of aluminized Teflon FEP thermal control insulation on the Hubble Space Telescope (HST). Such degradation can be characterized by a reduction in elongation-to-failure of the Teflon FEP. Ground laboratory soft x-ray exposure tests of aluminized Teflon FEP were conducted to assess the degree of elongation degradation which would occur as a result of exposure to soft x-rays in the range of 3-10 keV. Tests results indicate that soft x-ray exposure in the 3-10 keV range, at mission fluence levels, does not alone cause the observed reduction in elongation of flight retrieved samples. The soft x-ray exposure facility design, mechanical properties degradation results and implications will be presented.

  2. Synchrontron VUV and Soft X-Ray Radiation Effects on Aluminized Teflon FEP

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; Townsend, Jacqueline A.; Gaier, James R.; Jalics, Alice I.

    1998-01-01

    Surfaces of the aluminized Teflon FEP multi-layer thermal insulation on the Hubble Space Telescope (HST) were found to be cracked and curled in some areas at the time of the second servicing, mission in February 1997, 6.8 years after HST was deployed in low Earth orbit (LEO). As part of a test program to assess environmental conditions which would produce embrittlement sufficient to cause cracking of Teflon on HST, samples of Teflon FEP with a backside layer of vapor deposited aluminum were exposed to vacuum ultraviolet (VUV) and soft x-ray radiation of various energies using facilities at the National Synchrotron Light Source. Brookhaven National Laboratory. Samples were exposed to synchrotron radiation of narrow energy bands centered on energies between 69 eV and 1900 eV. Samples were analyzed for ultimate tensile strength and elongation. Results will be compared to those of aluminized Teflon FEP retrieved from HST after 3.6 years and 6.8 years on orbit and will he referenced to estimated HST mission doses of VUV and soft x-ray radiation.

  3. Ground Laboratory Soft X-Ray Durability Evaluation of Aluminized Teflon FEP Thermal Control Insulation

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; deGroh, Kim K.; Stueber, Thomas J.; Sechkar, Edward A.

    1998-01-01

    Metallized Teflon fluorinated ethylene propylene (FEP) thermal control insulation is mechanically degraded if exposed to a sufficient fluence of soft x-ray radiation. Soft x-ray photons (4-8 A in wavelength or 1.55 - 3.2 keV) emitted during solar flares have been proposed as a cause of mechanical properties degradation of aluminized Teflon FEP thermal control insulation on the Hubble Space Telescope (HST). Such degradation can be characterized by a reduction in elongation-to-failure of the Teflon FER Ground laboratory soft x-ray exposure tests of aluminized Teflon FEP were conducted to assess the degree of elongation degradation which would occur as a result of exposure to soft x-rays in the range of 3-10 keV. Tests results indicate that soft x-ray exposure in the 3-10 keV range, at mission fluence levels, does not alone cause the observed reduction in elongation of flight retrieved samples. The soft x-ray exposure facility design, mechanical properties degradation results and implications will be presented.

  4. Effect of X-Rays on the Mechanical Properties of Aluminized FEP Teflon(trademark)

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Brinkmeier, Michael R.; Gaier, Elizabeth M.

    1999-01-01

    Pieces of the multilayer insulation (MLI) that is integral to the thermal control of the Hubble Space Telescope (HST) have been returned by two servicing missions after 3.6 and 6.8 years in orbit. They reveal that the outer layer, which is made from 5 mil (0.13 mm) thick aluminized fluorinated ethylenepropylene (FEP) Teflon. has become severely embrittled. Although possible agents of this embrittlement include electromagnetic radiation across the entire solar spectrum, trapped particle radiation, atomic oxygen, and thermal cycling, intensive investigations have not yielded unambiguous causes. Previous studies utilizing monoenergetic photons in the 69-1900 eV range did not cause significant embrittlement, even at much higher doses than were experienced by the HST MLI. Neither did x-rays in the 3 to 10 keV range generated in a modified electron bean evaporator. An antidotal aluminized FEP sample that was exposed to an intensive dose from unfiltered Mo x-ray radiation from a rotating anode generator, however, did show the requisite embrittlement. Thus, a study was undertaken to determine the effects of x-ray exposure on the embrittlement of aluminized FEP in hopes that it might elucidate the HST MLI degradation mechanism. Tensile specimens of aluminized 5 mil thick FEP were exposed to a constant fluence of unfiltered x-ray radiation from a Mo target whose maximum energy ranged from 20-60 kV. Other samples were annealed, thermally cycled (100x) between 77-333 K, or cycled and irradiated. Tensile tests and density measurements were then performed on the samples. Only the samples which had been irradiated had the drastically reduced elongation-to-break, characteristic of the HST samples. Thermal cycling may accelerate the embrittlement, but the effect was near the scatter in the measurements. Annealing and thermal cycling had no apparent effect. Only the samples which had been irradiated and annealed showed significant density increases, likely implicating polymer chain

  5. Effect of X-Rays on the Mechanical Properties of Aluminized FEP Teflon(R)

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Brinkmeier, Michael R.; Gaier, Elizabeth M.

    1998-01-01

    Pieces of the multilayer insulation (MLI) that is integral to the thermal control of the Hubble Space Telescope (HST) have been returned by two servicing missions after 3.6 and 6.8 years in orbit. They reveal that the outer layer, which is made from 5 mil (0.13 mm)thick aluminized fluorinated ethylene propylene(FEP) Teflon(R), has become severely embrittled. Although possible agents of this embrittlement include electromagnetic radiation across the entire solar spectrum, trapped particle radiation, atomic oxygen, and thermal cycling, intensive investigations have not yielded unambiguous causes. Previous studies utilizing monoenergetic photons in the 69-1900 eV range did not cause significant embrittlement, even at much higher doses than were experienced by the HST MLI. Neither did x-rays in the 3 to 10 keV range generated in a modified electron beam evaporator. An antidotal aluminized FEP sample that was exposed to an intensive dose from unfiltered Mo x-ray radiation from a rotating anode generator, however, did show the requisite embrittlement. Thus, a study was undertaken to determine the effects of x-ray exposure on the embrittlement of aluminized FEP in hopes that it might elucidate the HST MLI degradation mechanism. Tensile specimens of aluminized 5 mil thick FEP were exposed to a constant fluence of unfiltered x-ray radiation from a Mo target whose maximum energy ranged from 20-60 kV. Other samples were annealed, thermally cycled (100x) between 77-333 K, or cycled and irradiated. Tensile tests and density measurements were then performed on the samples. Only the samples which had been irradiated had the drastically reduced elongation-to-break, characteristic of the HST samples. Thermal cycling may accelerate the embrittlement, but the effect was near the scatter in the measurements. Annealing and thermal cycling had no apparent effect. Only the samples which had been irradiated and annealed showed significant density increases, likely implicating polymer

  6. Synchrotron Vacuum Ultraviolet Light and Soft X-Ray Radiation Effects on Aluminized Teflon FEP Investigated

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; Townsend, Jacqueline A.; Gaier, James R.; Jalics, Alice I.

    1999-01-01

    Since the Hubble Space Telescope (HST) was deployed in low Earth orbit in April 1990, two servicing missions have been conducted to upgrade its scientific capabilities. Minor cracking of second-surface metalized Teflon FEP (DuPont; fluorinated ethylene propylene) surfaces from multilayer insulation (MLI) was first observed upon close examination of samples with high solar exposure retrieved during the first servicing mission, which was conducted 3.6 years after deployment. During the second HST servicing mission, 6.8 years after deployment, astronaut observations and photographic documentation revealed significant cracks in the Teflon FEP layer of the MLI on both the solar- and anti-solar-facing surfaces of the telescope. NASA Goddard Space Flight Center directed the efforts of the Hubble Space Telescope MLI Failure Review Board, whose goals included identifying the low-Earth-orbit environmental constituent(s) responsible for the cracking and embrittling of Teflon FEP which was observed during the second servicing mission. The NASA Lewis Research Center provided significant support to this effort. Because soft x-ray radiation from solar flares had been considered as a possible cause for the degradation of the mechanical properties of Teflon FEP (ref. 1), the effects of soft xray radiation and vacuum ultraviolet light on Teflon FEP were investigated. In this Lewisled effort, samples of Teflon FEP with a 100-nm layer of vapor-deposited aluminum (VDA) on the backside were exposed to synchrotron radiation of various vacuum ultraviolet and soft x-ray wavelengths between 18 nm (69 eV) and 0.65 nm (1900 eV). Synchrotron radiation exposures were conducted using the National Synchrotron Light Source at Brookhaven National Laboratory. Samples of FEP/VDA were exposed with the FEP surface facing the synchrotron beam. Doses and fluences were compared with those estimated for the 20-yr Hubble Space Telescope mission.

  7. On-Orbit Teflon FEP Degradation

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline A.; Hansen, Patricia A.; Dever, Joyce A.

    1998-01-01

    During the Hubble Space Telescope (HST) Second Servicing Mission (SM2), degradation of unsupported Teflon' FEP (fluorinated ethylene propylene), used as the outer layer of the multi-layer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for ground testing and evaluation. The results of the Teflon FEP sample evaluation and additional testing of pristine Teflon FEP led the investigative team to theorize that the HST damage was caused by thermal cycling with deep-layer damage from electron and proton radiation which allowed the propagation of cracks along stress concentrations, and that the damage increased with the combined total dose of electrons, protons, LTV and x-rays along with thermal cycling. This paper discusses the testing and evaluation of the Teflon FEP.

  8. Investigation of Teflon FEP Embrittlement on Spacecraft in Low-Earth Orbit

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Banks, Bruce A.

    1997-01-01

    Teflon fluorinated ethylene propylene (FEP) (DuPont) is commonly used on exterior spacecraft surfaces for thermal control in the low-Earth orbit environment. Silverized or aluminized Teflon FEP is used for the outer layers of the thermal control blanket because of its high reflectance, low solar absorptance, and high thermal emittance. Teflon FEP is also desirable because, compared with other spacecraft polymers (such as Kapton), it has relatively high resistance to atomic oxygen erosion. Because of its comparably low atomic oxygen erosion yield, Teflon FEP has been used unprotected in the space environment. Samples of Teflon FEP from the Long Duration Exposure Facility (LDEF) and the Hubble Space Telescope (retrieved during its first servicing mission) were evaluated for solar-induced embrittlement and for synergistic effects of solar degradation and atomic oxygen.

  9. Investigation of Teflon FEP embrittlement on spacecraft in low earth orbit

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Smith, Daniela C.

    1997-01-01

    Teflon(TM) fluorinated ethylene-propylene (FEP) is used on the exterior of spacecraft surfaces in the low earth orbit environment for thermal control. Silverized or aluminized Teflon(TM) FEP used in the Long Duration Exposure Facility (LDEF) and the Hubble Space Telescope (HST) provided evidence of the low earth orbit environments. Samples from the LDEF and HST were evaluated for solar induced embrittlement and for synergistic effects of solar degradation and atomic oxygen.

  10. Atomic oxygen interactions with FEP Teflon and silicones on LDEF

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Gebauer, Linda

    1991-01-01

    The Long Duration Exposure Facility (LDEF) spacecraft represents the first controlled unidirectional exposure of high-fluence atomic oxygen on fluorinated ethylene propylene (FEP Teflon) and silicones. The atomic oxygen erosion yield for FEP Teflon was found to be significantly in excess of previous low fluence orbital data and is an order of magnitude below that of polyimide Kapton. LDEF FEP Teflon erosion yield data as a function of angle of attack is presented. Atomic oxygen interaction with silicon polymers results in crazing of the silicones as well as deposition of dark contaminant oxidation products on adjoining surfaces. Documentation of results and possible mechanistic explanations are presented.

  11. On-Orbit Teflon(R) FEP Degradation

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline A.; Hansen, Patricia A.; Dever, Joyce A.

    1998-01-01

    During the Hubble Space Telescope (HST) Second Servicing Mission (SM2), degradation of unsupported Teflon(R) FEP (fluorinated ethylene propylene), used as the outer layer of the multi-layer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for ground testing and evaluation. The results of the Teflon(R) FEP sample evaluation and additional testing of pristine Teflon(R) FEP led the investigative team to theorize that the HST damage was caused by thermal cycling with deep-layer damage from electron and proton radiation which allowed the propagation of cracks along stress concentrations, and that the damage increased with the combined total dose of electrons, protons, UV and x-rays along with thermal cycling. This paper discusses the testing and evaluation of the Teflon(R) FEP.

  12. On-Orbit Teflon(trademark) FEP Degradation

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline A.; Hansen, Patricia A.; Dever, Joyce A.

    1998-01-01

    During the Hubble Space Telescope (HST) Second Servicing Mission (SM2), degradation of unsupported Teflon(trademark) FEP (fluorinated ethylene propylene), used as the outer layer of the multi-layer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for ground testing and evaluation. The results of the Teflon(trademark) FEP sample evaluation and additional testing of pristine Teflon(trademark) FEP led the investigative team to theorize that the HST damage was caused by thermal cycling with deep-layer damage from electron and proton radiation which allowed the propagation of cracks along stress concentrations, and that the damage increased with the combined total dose of electrons, protons, UV and x-rays along with thermal cycling. This paper discusses the testing and evaluation of the Teflon(trademark) FEP.

  13. On-Orbit Teflon(trademark) FEP Degradation

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline; Hansen, Patricia A.; Dever, Joyce A.

    1999-01-01

    During the Hubble Space Telescope (HST) Second Servicing Mission (SM2), degradation of unsupported Teflon(trademark) FEP (fluorinated ethylene propylene), used as the outer layer of the multi-layer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for ground testing and evaluation. The results of the Teflon(trademark) FEP sample evaluation and additional testing of pristine Teflon FEP led the investigative team to theorize that the HST damage was caused by thermal cycling with deep-layer damage from electron and proton radiation which allowed the propagation of cracks along stress concentrations, and that the damage increased with the combined total dose of electrons, protons, UV and x-rays along with thermal cycling. This paper discusses the testing and evaluation of the Teflon(trademark) FEP.

  14. Atomic oxygen interactions with FEP Teflon and silicones on LDEF

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Dever, Joyce A.; Gebauer, Linda; Hill, Carol M.

    1992-01-01

    The Long Duration Exposure Facility (LDEF) spacecraft has enabled the measurement of the effects of fixed orientation exposure of high fluence atomic oxygen on fluorinated ethylene propylene (FEP Teflon) and silicones. The atomic oxygen erosion yield for the FEP Teflon was found to be 3.64 x 10(exp -25) cm(exp 3)/atom. This erosion yield is significantly higher than that measured from previous low fluence orbital data. The FEP Teflon erosion yield was found to have the same dependence on oxygen arrival angle as Kapton and Mylar. Atomic oxygen interaction with silicon polymers results in the crazing of silicon. Released silicone contaminants were found to darken upon further atomic oxygen exposure.

  15. Physical and Thermal Properties Evaluated of Teflon FEP Retrieved From the Hubble Space Telescope During Three Servicing Missions

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; deGroh, Kim, K.; Sutter, James K.; Gaier, James R.; Messer, Russell, K.; Scheiman, Daniel A.; McClendon, Mark W.; Viens, Michael J.; Wang, L. Len; He, Charles C.; Gummow, Jonathan D.

    2002-01-01

    Mechanical properties of aluminized Teflon fluorinated ethylene propylene (FEP) thermal control materials on the Hubble Space Telescope (HST) exposed to low Earth orbit for up to 9.7 years have significantly degraded, with extensive cracking occurring on orbit. The NASA Glenn Research Center and the NASA Goddard Space Flight Center have collaborated on analyzing the physical and thermal properties of aluminized FEP (FEP-Al, DuPont) materials retrieved in December 1999 during HST's third servicing mission (SM3A). Comparisons have been made to properties of FEP-Al retrieved during the first and second HST servicing missions, SM1 and SM2, in order to determine degradation processes for FEP on HST.

  16. Soft X-Ray Exposure Testing of FEP Teflon for the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.

    1998-01-01

    The FEP Teflon (DuPont) multilayer insulation (MLI) thermal-control blanket material on the Hubble Space Telescope is degrading in the space environment. During the first Hubble servicing mission in 1993, after 3.6 years in low Earth orbit, aluminized and silvered FEP Teflon MLI thermal-control blanket materials were retrieved. These materials have been jointly analyzed by the NASA Lewis Research Center and the NASA Goddard Space Flight Center for degradation induced in the space environment (ref. 1). Solar-facing blanket materials were found to be embrittled with through-the-thickness cracking in the 5-mil FEP. During the second Hubble servicing mission in 1997, astronauts noticed that several blankets had large areas with tears. The torn FEP was curled up in some areas, exposing the underlying materials to the space environment. This tearing problem, and the associated curling up of torn areas, could lead to over-heating of the telescope and to particulate contamination. A Hubble Space Telescope MLI Failure Review Board was assembled by Goddard to investigate and identify the degradation mechanism of the FEP, to identify and characterize replacement materials, and to estimate the extent of damage at the time of the third servicing mission in 1999. A small piece of FEP retrieved during the second servicing mission is being evaluated by this failure review board along with materials from the first servicing mission. Since the first servicing mission, and as part of the failure review board, Lewis has been exposing FEP to soft x-rays to help determine the damage mechanisms of FEP in the space environment. Soft x-rays, which can penetrate into the bulk of FEP, are generated during solar flares and appear to be contributing to the degradation of the Hubble MLI.

  17. The Effect of Heating on the Degradation of Ground Laboratory and Space Irradiated Teflon(r) FEP

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Martin, Morgana

    2002-01-01

    The outer most layer of the multilayer insulation (MLI) blankets on the Hubble Space Telescope (HST) is back surface aluminized Teflon(R) FEP (fluorinated ethylene propylene). As seen by data collected after each of the three servicing missions and as observed during the second servicing mission (SM2), the FEP has become embrittled in the space environment, leading to degradation of the mechanical properties and severe on-orbit cracking of the FEP. During SM2, a sample of aluminized-FEP was retrieved from HST that had cracked and curled, exposing its aluminum backside to space. Because of the difference in optical properties between FEP and aluminum, this insulation piece reached 200 C on-orbit, which is significantly higher than the nominal MLI temperature extreme of 50 C. This piece was more brittle than other retrieved material from the first and third servicing missions (SM1 and SM3A, respectively). Due to this observation and the fact that Teflon thermal shields on the solar array bi-stems were heated on-orbit to 130 C, experiments have been conducted to determine the effect of heating on the degradation of FEP that has been irradiated in a ground laboratory facility or in space on HST. Teflon FEP samples were X-ray irradiated in a high vacuum facility in order to simulate the damage caused by radiation in the space environment. Samples of pristine FEP, X-ray irradiated FEP and FEP retrieved from the HST during SM3A were heat treated from 50 to 200 C at 25 intervals in a high vacuum facility and then tensile tested. In addition, samples were tested in a density gradient column to determine the effect of the radiation and heating on the density of FEP. Results indicate that although heating does not degrade the tensile properties of non-irradiated Teflon, there is a significant dependence of the percent elongation at failure of irradiated Teflon as a function of heating temperature. Irradiated Teflon was found to undergo increasing degradation in the elongation

  18. Investigation of Teflon FEP Embrittlement on Spacecraft in Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Smith, Daniela C.

    1997-01-01

    Teflon(registered trademark) FEP (fluorinated ethylene-propylene) is commonly used on exterior spacecraft surfaces in the low Earth orbit (LEO) environment for thermal control. Silverized or aluminized FEP is used for the outer layer of thermal control blankets because of its low solar absorptance and high thermal emittance. FEP is also preferred over other spacecraft polymers because of its relatively high resistance to atomic oxygen erosion. Because of its low atomic oxygen erosion yield, FEP has not been protected in the space environment. Recent, long term space exposures such as on the Long Duration Exposure Facility (LDEF, 5.8 years in space), and the Hubble Space Telescope (HST, after 3.6 years in space) have provided evidence of LEO environmental degradation of FEP. These exposures provide unique opportunities for studying environmental degradation because of the long durations and the different conditions (such as differences in altitude) of the exposures. Samples of FEP from LDEF and from HST (retrieved during its first servicing mission) have been evaluated for solar induced embrittlement and for synergistic effects of solar degradation and atomic oxygen. Micro-indenter results indicate that the surface hardness increased as the ratio of atomic oxygen fluence to solar fluence decreased for the LDEF samples. FEP multilayer insulation (MLI) retrieved from HST provided evidence of severe embrittlement on solar facing surfaces. Micro-indenter measurements indicated higher surface hardness values for these samples than LDEF samples, but the solar exposures were higher. Cracks induced during bend testing were significantly deeper for the HST samples with the highest solar exposure than for LDEF samples with similar atomic oxygen fluence to solar fluence ratios. If solar fluences are compared, the LDEF samples appear as damaged as HST samples, except that HST had deeper induced cracks. The results illustrate difficulties in comparing LEO exposed materials from

  19. Flexible, FEP-Teflon covered solar cell module development

    NASA Technical Reports Server (NTRS)

    Rauschenbach, H. S.; Cannady, M. D.

    1976-01-01

    Techniques and equipment were developed for the large scale, low-cost fabrication of lightweight, roll-up and fold-up, FEP-Teflon encapsulated solar cell modules. Modules were fabricated by interconnecting solderless single-crystal silicon solar cells and heat laminating them at approximately 300 C between layers of optically clear FEP and to a loadbearing Kapton substrate sheet. Modules were fabricated from both conventional and wraparound contact solar cells. A heat seal technique was developed for mechanically interconnecting modules into an array. The electrical interconnections for both roll-up and fold-up arrays were also developed. The use of parallel-gap resistance welding, ultrasonic bonding, and thermocompression bonding processes for attaching interconnects to solar cells were investigated. Parallel-gap welding was found to be best suited for interconnecting the solderless solar cells into modules. Details of the fabrication equipment, fabrication processes, module and interconnect designs, environmental test equipment, and test results are presented.

  20. Teflon FEP Analyzed After Retrieval From the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; deGroh, Kim K.; Townsend, Jacqueline A.; Hansen, Patricia A.; Banks, Bruce A.; Wang, Len; He, Charles

    1999-01-01

    During the Hubble Space Telescope (HST) Second Servicing Mission, 6.8 years after the telescope was deployed in low Earth orbit, degradation of unsupported Teflon FEP (DuPont; fluorinated ethylene propylene), used as the outer layer of the multilayer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer (see the photograph) was retrieved during the second servicing mission and returned to Earth for ground testing and evaluation. Also retrieved was a Teflon FEP radiator surface from a cryogen vent cover that was exposed to the space environment on the aft bulkhead of the HST. NASA Goddard Space Flight Center directed the efforts of the Hubble Space Telescope MLI Failure Review Board, whose goals included determining the FEP degradation mechanisms. As part of the investigations into the degradation mechanisms, specimens retrieved from the first and second HST servicing missions, 3.6 and 6.8 years after launch, respectively, were characterized through exhaustive mechanical, optical, and chemical testing. Testing led by Goddard included scanning electron microscopy, optical microscopy, tensile testing, solar absorptance measurements, time-of-flight secondary ion mass spectroscopy (TOF-SIMS), Fourier transform infrared microscopy (m-FTIR), attenuated total reflectance infrared microscopy (ATR/FTIR), and x-ray diffraction (XRD). The NASA Lewis Research Center contributed significantly to the analysis of the retrieved HST materials by leading efforts and providing results of bend testing, surface microhardness measurements, x-ray photoelectron spectroscopy, solid-state nuclear magnetic resonance spectroscopy, and density measurements. Other testing was conducted by Nano Instruments, Inc., and the University of Akron.

  1. Effect of Air and Vacuum Storage on the Tensile Properties of X-Ray Exposed Aluminized-FEP

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Gummow, Jonathan D.

    2000-01-01

    Metallized Teflon(Registered Trademark) FEP (fluorinated ethylene propylene), a common spacecraft thermal control material, from the exterior layer of the Hubble Space Telescope (HST) has become embrittled and suffers from extensive cracking. Teflon samples retrieved during Hubble servicing missions and from the Long Duration Exposure Facility (LDEF) indicate that there may be continued degradation in tensile properties over time. An investigation has been conducted to evaluate the effect of air and vacuum storage on the mechanical properties of x-ray exposed FEP. Aluminized-FEP (Al-FEP) tensile samples were irradiated with 15.3 kV Cu x-rays and stored in air or under vacuum for various time periods. Tensile data indicate that samples stored in air display larger decreases in tensile properties than for samples stored under vacuum. Air-stored samples developed a hazy appearance, which corresponded to a roughening of the aluminized surface. Optical property changes were also characterized. These findings indicate that air exposure plays a role in the degradation of irradiated FEP, therefore proper sample handling and storage is necessary with materials retrieved from space.

  2. Environmental Exposure Conditions for Teflon FEP on the Hubble Space Telescope Investigated

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; deGroh, Kim K.; Banks, Bruce A.; Townsend, Jacqueline a.; Barth, Janet L.; Thomson, Shaun; Gregory, Teri; Savage, William J.

    2000-01-01

    The Hubble Space Telescope (HST) was launched into low Earth orbit on April 24,1990. During the first servicing mission in December 1993 (3.6 years after launch), multilayer insulation (MLI) blankets were retrieved from the two magnetic sensing systems located on the light shield. Retrieval of one of the solar arrays during this mission also provided MLI blanket material from the solar array drive arm. These MLI materials were analyzed in ground-based facilities, and results indicate that the space-facing outer layer of the MLI, aluminized Teflon FEP (DuPont; fluorinated ethylene propylene), was beginning to degrade. Close inspection of the FEP revealed through-the-thickness cracks in areas with the highest solar exposure and stress concentration. During the second servicing mission in February 1997 (6.8 years after launch), astronauts observed and documented severe cracking in the outer layer of the MLI blankets on both the solar-facing and anti-solar-facing surfaces. During this second mission, some material from the outer layer of the light shield MLI was retrieved and subsequently analyzed in ground-based facilities. After the second servicing mission, a Failure Review Board was convened by NASA Goddard Space Flight Center to address the MLI degradation problem on HST. Members of the Electro-Physics Branch of the NASA Glenn Research Center at Lewis Field participated on this board. To determine possible degradation mechanisms, board researchers needed to consider all environmental constituents to which the FEP MLI surfaces were exposed. On the basis of measurements, models, and predictions, environmental exposure conditions for FEP surfaces on HST were estimated for various time periods from launch in 1990 through 2010, the planned end-of-life for HST. The table summarizes these data including the number and temperature ranges of thermal cycles; equivalent Sun hours; fluence and absorbed radiation dose from solar event x rays; fluence and absorbed dose from

  3. Degradation of Teflon(trademark) FEP Following Charged Particle Radiation and Rapid Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline; Powers, Charles; Viens, Michael; Ayres-Treusdell, Mary; Munoz, Bruno

    1999-01-01

    During the Second Servicing Mission (SM2) of the Hubble Space Telescope (HST) severe degradation was observed on the outer layer of the thermal control blankets. Astronaut observations and photographs revealed large cracks in the metallized Teflon(trademark) FEP (fluorinated ethylene propylene), the outer layer of the multi-layer insulation (MLI), in many locations around the telescope. In an effort to understand what elements of the space environment might cause such damage, pristine Teflon(trademark) FEP was tested for durability to radiation and thermal cycling. Specimens were subjected to electron and proton fluences comparable to those experienced by HST and were subsequently thermal cycled in a custom-built rapid thermal cycle chamber. Tensile tests of the specimens showed that radiation followed by thermal cycling significantly reduced the ultimate strength and elongation of Teflon(trademark) FEP.

  4. Degradation of Teflon(tm) FEP Following Charged Particle Radiation and Rapid Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline A.; Powers, Charles E.; Viens, Michael J.; Ayres-Treusdell, Mary T.; Munoz, Bruno

    1998-01-01

    During the Second Servicing Mission (SM2) of the Hubble Space Telescope (HST) severe degradation was observed on the outer layer of the thermal control blankets. Astronaut observations and photographs revealed large cracks in the metallized Teflon FEP (fluorinated ethylene propylene), the outer layer of the multi-layer insulation (MLI), in many locations around the telescope. In an effort to understand what elements of the space environment might cause such damage, pristine Teflon' FEP was tested for durability to radiation and thermal cycling. Specimens were subjected to electron and proton fluences comparable to those experienced by HST and were subsequently thermal cycled in a custom-built rapid thermal cycle chamber. Tensile tests of the specimens showed that radiation followed by thermal cycling significantly reduced the ultimate strength and elongation of Teflon FEP.

  5. Degradation of Teflon(tm) FEP Following Charged Particle Radiation and Rapid Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline A.; Powers, Charles E.; Viens, Michael J.; Ayres-Treusdell, Mary T.; Munoz, Bruno F.

    1998-01-01

    During the Second Servicing Mission (SM2) of the Hubble Space Telescope (HST) severe degradation was observed on the outer layer of the thermal control blankets. Astronaut observations and photographs revealed large cracks in the metallized Teflon' FEP (fluorinated ethylene propylene), the outer layer of the multi-layer insulation (MLI), in many locations around the telescope. In an effort to understand what elements of the space environment might cause such damage, pristine Teflon(registered trademark) FEP was tested for durability to radiation and thermal cycling. Specimens were subjected to electron and proton fluences comparable to those experienced by HST and were subsequently thermal cycled in a custom-built rapid thermal cycle chamber. Tensile tests of the specimens showed that radiation followed by thermal cycling significantly reduced the ultimate strength and elongation of Teflon(registered trademark) FEP.

  6. Degradation of Teflon(tm) FEP Following Charged Particle Radiation and Rapid Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline; Powers, Charles; Viens, Michael; Ayres-Treusdell, Mary; Munoz, Bruno

    1998-01-01

    During the Second Servicing Mission (SM2) of the Hubble Space Telescope (HST) severe degradation was observed on the outer layer of the thermal control blankets. Astronaut observations and photographs revealed large cracks in the metallized Teflon(R) FEP (fluorinated ethylene propylene), the outer layer of the multi-layer insulation (MLI), in many locations around the telescope. In an effort to understand what elements of the space environment might cause such damage, pristine Teflon(R) FEP was tested for durability to radiation and thermal cycling. Specimens were subjected to electron and proton fluences comparable to those experienced by HST and were subsequently thermal cycled in a custom-built rapid thermal cycle chamber. Tensile tests of the specimens showed that radiation followed by thermal cycling significantly reduced the ultimate strength and elongation of Teflon(R) FEP.

  7. Effect of Air and Vacuum Storage on the Degradation of X-Ray-Exposed Aluminized-Teflon Investigated

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Gummow, Jonathan D.

    2001-01-01

    Metalized Teflon FEP (fluorinated ethylene propylene, DuPont), a common thermal control material, has been found to degrade in the low-Earth-orbit space environment. The aluminized-FEP (Al-FEP) exterior layer on the Hubble Space Telescope has become extremely embrittled, with extensive cracking occurring on all sides of the telescope. This embrittlement has been primarily attributed to radiation exposure (x-rays from solar flares, electron/proton radiation, and possibly near-ultraviolet radiation) combined with thermal cycling. Limited samples of FEP tested after long-term exposure to low Earth orbit on the Hubble Space Telescope and on the Long Duration Exposure Facility indicated that there might be continued degradation in tensile properties over time. An investigation was conducted at the NASA Glenn Research Center to evaluate the effect of air and vacuum storage on the mechanical properties of x-ray-exposed FEP. Aluminized-FEP (5-mil-thick) tensile samples were x-ray exposed with 15.3-kV copper xrays for 2 hr, reducing the percent elongation to failure by approximately 50 percent in comparison to that for pristine Al-FEP. X-ray-exposed samples were stored in air or under vacuum for various time periods to see the effect of storage on tensile properties. Tensile results indicated that samples stored in air had larger decreases in tensile properties than samples stored under vacuum had, as seen in the graph. Samples stored under vacuum (for up to 400 hr) showed no further decrease in tensile properties over time, whereas samples stored in air (for up to 900 hr) appeared to show decreases in tensile properties over time. X-ray-exposed samples stored in air developed a hazy appearance in the exposed area, as seen in the photographs. When the source of the haziness was evaluated using scanning electron microscopy and atomic force microscopy, it was found to reside at the Al/FEP interface as witnessed by an increased surface roughness of the aluminized side of the

  8. A Comparison of Space and Ground Based Facility Environmental Effects for FEP Teflon. Revised

    NASA Technical Reports Server (NTRS)

    Rutledge, Sharon K.; Banks, Bruce A.; Kitral, Michael

    1998-01-01

    Fluorinated Ethylene Propylene (FEP) Teflon is widely used as a thermal control material for spacecraft, however, it is susceptible to erosion, cracking, and subsequent mechanical failure in low Earth orbit. One of the difficulties in determining whether FEP Teflon will survive during a mission is the wide disparity of erosion rates observed for this material in space and in ground based facilities. Each environment contains different levels of atomic oxygen, ions, and vacuum ultraviolet (VUV) radiation in addition to parameters such as the energy of the arriving species and temperature. These variations make it difficult to determine what is causing the observed differences in erosion rates. This paper attempts to narrow down which factors affect the erosion rate of FEP Teflon through attempting to change only one environmental constituent at a time. This was attempted through the use of a single simulation facility (plasma asher) environment with a variety of Faraday cages and VUV transparent windows. Isolating one factor inside of a radio frequency (RF) plasma proved to be very difficult. Two observations could be made. First, it appears that the erosion yield of FEP Teflon with respect to that of polyimide Kapton is not greatly affected by the presence or lack of VUV radiation present in the RF plasma and the relative erosion yield for the FEP Teflon may decrease with increasing fluence. Second, shielding from charged particles appears to lower the relative erosion yield of the FEP to approximately that observed in space, however it is difficult to determine for sure whether ions, electrons, or some other components are causing the enhanced erosion.

  9. Effects of Various Wavelength Ranges of Vacuum Ultraviolet Radiation on Teflon FEP Film Investigated

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; McCracken, Cara A.

    2004-01-01

    Teflon Fluorinated Ethylene Propylene (FTP) films (DuPont) have been widely used for spacecraft thermal control and have been observed to become embrittled and cracked upon exposure to the space environment. This degradation has been attributed to a synergistic combination of radiation and thermal effects. A research study was undertaken at the NASA Glenn Research Center to examine the effects of different wavelength ranges of vacuum ultraviolet (VUV) radiation on the degradation of the mechanical properties of FEP. This will contribute to an overall understanding of space radiation effects on Teflon FEP, and will provide information necessary to determine appropriate techniques for using laboratory tests to estimate space VUV degradation. Research was conducted using inhouse facilities at Glenn and was carried out, in part, through a grant with the Cleveland State University. Samples of Teflon FEP film of 50.8 microns thickness were exposed to radiation from a VUV lamp from beneath different cover windows to provide different exposure wavelength ranges: MgF2 (115 to 400 nm), crystalline quartz (140 to 400 nm), and fused silica (FS, 155 to 400 nm). Following exposure, FEP film specimens were tensile tested to determine the ultimate tensile strength and elongation at failure as a function of the exposure duration for each wavelength range. The graphs show the effect of ultraviolet exposure on the mechanical properties of the FEP samples.

  10. Mechanical Properties Degradation of Teflon(Trademark) FEP Returned from the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; deGroh, Kim K.; Townsend, Jacqueline A.; Wang, L. Len

    1998-01-01

    After 6.8 years on orbit, degradation has been observed in the mechanical properties of second-surface metalized Teflon(Reg) FEP (fluorinated ethylene propylene) used on the Hubble Space Telescope (HST) on the outer surface of the multi-layer insulation (MLI) blankets and on radiator surfaces. Cracking of FEP surfaces on HST was first observed upon close examination of samples with high solar exposure retrieved during the first servicing mission (SM1) conducted 3.6 years after HST was put into orbit. Astronaut observations and photographs from the second servicing mission (SM2), conducted after 6.8 years on orbit, revealed severe cracks in the FEP surfaces of the MLI on many locations around the telescope. This paper describes results of mechanical properties testing of FEP surfaces exposed for 3.6 years and 6.8 years to the space environment on HST. These tests include tensile testing, surface micro-hardness testing, and bend testing.

  11. Analyses of Hubble Space Telescope Aluminized-Teflon Insulation Retrieved After 19 Years of Space Exposure

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Waters, Deborah L.; Mohammed, Jelila S.; Perry, Bruce A.; Banks, Bruce A.

    2012-01-01

    Since its launch in April 1990, the Hubble Space Telescope (HST) has made many important observations from its vantage point in low Earth orbit (LEO). However, as seen during five servicing missions, the outer layer of multilayer insulation (MLI) has become successively more embrittled and has cracked in many areas. In May 2009, during the 5th servicing mission (called SM4), two MLI blankets were replaced with new insulation pieces and the space-exposed MLI blankets were retrieved for degradation analyses by teams at NASA Glenn Research Center (GRC) and NASA Goddard Space Flight Center (GSFC). The MLI blankets were from Equipment Bay 8, which received direct sunlight, and Equipment Bay 5, which received grazing sunlight. Each blanket contained a range of unique regions based on environmental exposure and/or physical appearance. The retrieved MLI blanket s aluminized-Teflon (DuPont) fluorinated ethylene propylene (Al-FEP) outer layers have been analyzed for changes in optical, physical, and mechanical properties, along with space induced chemical and morphological changes. When compared to pristine material, the analyses have shown how the Al-FEP was severely affected by the space environment. This paper reviews tensile properties, solar absorptance, thermal emittance, x-ray photoelectron spectroscopy (XPS) data and atomic oxygen erosion values of the retrieved HST blankets after 19 years of space exposure.

  12. Degradation of Hubble Space Telescope Metallized Teflon(trademark) FEP Thermal Control Materials

    NASA Technical Reports Server (NTRS)

    Hansen, Patricia A.; Townsend, Jacqueline A.; Yoshikawa, Yukio; Castro, J. David; Triolo, Jack J.; Peters, Wanda C.

    1998-01-01

    The mechanical and optical properties of the metallized Teflon Fluorinated Ethylene Propylene (FEP) thermal control materials on the Hubble Space Telescope (HST) have degraded over the seven years the telescope has been in orbit. Astronaut observations and photographic documentation from the Second Servicing Mission revealed severe cracks of the multi-layer insulation (MLI) blanket outer layer in many locations around the telescope, particularly on solar facing surfaces. Two samples, the outer Teflon FEP MLI layer and radiator surfaces, were characterized post- mission through exhaustive mechanical, thermal, chemical, and optical testing. The observed damage to the thermal control materials, the sample retrieval and handling, and the significant changes to the radiator surfaces of HST will be discussed. Each of these issues is addressed with respect to current and future mission requirements.

  13. An analysis of LDEF-exposed silvered FEP teflon thermal blanket material

    NASA Technical Reports Server (NTRS)

    Young, Philip R.; Slemp, Wayne S.

    1991-01-01

    The characterization of selected silvered fluorinated ethylene propylene (FEP) teflon thermal blanket material which received 5 years and 9 months of exposure to the LEO environment on the Long Duration Exposure Facility is reported. X-ray photoelectron spectroscopy, infrared, and thermal analyses did not detect a significant change at the molecular level as the result of this exposure. However, various microscopic analyses revealed a roughening of the coating surface due to atomic oxygen erosion which resulted in some materials changing from specular reflectors of visible radiation to diffuse reflectors. The potential effect of silicon-containing molecular contamination on these materials is addressed.

  14. Effects of Heating on Teflon(Registered Trademark) FEP Thermal Control Material from the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    deGroh, Kim; Gaier, James R.; Hall, Rachelle L.; Norris, Mary Jo; Espe, Matthew P.; Cato, Daveen R.

    1999-01-01

    Metallized Teflon(Registered Trademark) FEP (fluorinated ethylene propylene) thermal control material on the Hubble Space Telescope (HST) is degrading in the space environment. Teflon(Registered Trademark) FEP thermal control blankets (space-facing FEP) retrieved during the first servicing mission (SM1) were found to be embrittled on solar facing surfaces and contained microscopic cracks. During the second servicing mission (SM2) astronauts noticed that the FEP outer layer of the multi-layer insulation (MLI) covering the telescope was cracked in many locations around the telescope. Large cracks were observed on the light shield, forward shell and equipment bays. A tightly curled piece of cracked FEP from the light shield was retrieved during SM2 and was severely embrittled, as witnessed by ground testing. A Failure Review Board (FRB) was organized to determine the mechanism causing the MLI degradation. Density, x-ray crystallinity and solid state nuclear magnetic resonance (NMR) analyses of FEP retrieved during SM1 were inconsistent with results of FEP retrieved during SM2. Because the retrieved SM2 material curled while in space, it experienced a higher temperature extreme during thermal cycling, estimated at 200 C, than the SM1 material, estimated at 50 C. An investigation on the effects of heating pristine and FEP exposed on HST was therefore conducted. Samples of pristine. SM1, and SM2 FEP were heated to 200 C and evaluated for changes in density and morphology. Elevated temperature exposure was found to have a major impact on the density of the retrieved materials. Characterization of polymer morphology of as-received and heated FEP samples by NMR provided results that were consistent with the density results. These findings have provided insight to the damage mechanisms of FEP in the space environment.

  15. Insights Developed Into the Damage Mechanism of Teflon FEP Thermal Control Material on the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Gaier, James R.; Hall, Rachelle L.; Norris, mary Jo; Espe, Matthew P.; Cato, Daveen R.

    2000-01-01

    Metalized Teflon FEP (DuPont; fluorinated ethylene propylene) thermal control material on the Hubble Space Telescope (HST) has been found to degrade in the space environment. Teflon FEP thermal control blankets retrieved during the first servicing mission were found to be embrittled on solar-facing surfaces and to contain microscopic cracks (the FEP surface is exposed to the space environment). During the second servicing mission, astronauts noticed that the FEP outer layer of the multilayer insulation blanketing covering the telescope was cracked in many locations. Large cracks were observed on the light shield, forward shell, and equipment bays. A tightly curled piece of cracked FEP from the light shield was retrieved during the second mission. This piece was severely embrittled, as witnessed by ground testing. A Failure Review Board was organized by NASA Goddard Space Flight Center to determine the mechanism causing the multilayer insulation degradation. This board included members of the Electro-Physics Branch of the NASA Glenn Research Center at Lewis Field. Density measurements of the retrieved materials obtained under the review board's investigations indicated that FEP from the first servicing mission was essentially unchanged from pristine FEP but that the second servicing mission FEP had increased in density in comparison to pristine FEP (ref. 1). The results were consistent with crystallinity measurements taken using x-ray diffraction and with results from solid-state nuclear magnetic resonance tests (see the table and ref. 1). Because the second servicing mission FEP was embrittled and its density and crystallinity had increased in comparison to pristine FEP, board researchers expected that the first servicing mission FEP, which was also embrittled, would also have increased in crystallinity and density, but it did not. Because the retrieved second servicing mission material curled while in space, it experienced a higher temperature extreme during

  16. Effect of Solar Exposure on the Atomic Oxygen Erosion of Hubble Space Telescope Aluminized-Teflon Thermal Shields

    NASA Technical Reports Server (NTRS)

    Guo, Aobo; Ashmead, Claire C.; deGroh, Kim K.

    2012-01-01

    When exposed to low Earth orbital (LEO) environment, external spacecraft materials degrade due to radiation, thermal cycling, micrometeoroid and debris impacts, and atomic oxygen (AO) interaction. Collisions between AO and spacecraft can result in oxidation of external spacecraft surface materials, which can lead to erosion and severe structural and/or optical property deterioration. It is therefore essential to understand the AO erosion yield (Ey), the volume loss per incident oxygen atom (cu cm/atom), of polymers to assure durability of spacecraft materials. The objective of this study was to determine whether solar radiation exposure can increase the rate of AO erosion of polymers in LEO. The material studied was a section of aluminized-Teflon (DuPont) fluorinated ethylene propylene (Al-FEP) thermal shield exposed to space on the Hubble Space Telescope (HST) for 8.25 years. Retrieved samples were sectioned from the circular thermal shield and exposed to ground laboratory thermal energy AO. The results indicate that the average Ey of the solar facing HST Al-FEP was 1.9 10(exp -24)cu cm/atom, while the average Ey of the anti-solar HST Al-FEP was 1.5 10(exp -24)cu cm/atom. The Ey of the pristine samples was 1.6- 1.7 10(exp -24)cu cm/atom. These results indicate that solar exposure affects the post-flight erosion rate of FEP in a plasma asher. Therefore, it likely affects the erosion rate while in LEO.

  17. Effect of Solar Exposure on the Atomic Oxygen Erosion of Hubble Space Telescope Aluminized-Teflon Thermal Shields

    NASA Astrophysics Data System (ADS)

    Guo, Aobo; Ashmead, Claire C.; de Groh, Kim K.; Sechkar, Edward A.

    When exposed to low Earth orbit (LEO) environment, external spacecraft materials degrade due to radiation, thermal cycling, micrometeoroid and debris impacts, and interaction with atomic oxygen (AO). Collisions between AO and spacecraft can result in oxidation of external spacecraft surface materials, which can lead to erosion and severe structural and/or optical properties deterioration. It is therefore essential to understand the AO erosion yield (Ey), the volume loss per incident oxygen atom (cm3/atom) of polymers to assure durability of spacecraft materials. The objective of this study was to determine whether solar radiation exposure can increase the rate of AO erosion of polymers in LEO. The material studied was a section of aluminized-Teflon® fluorinated ethylene propylene (Al-FEP) thermal shield exposed to space on the Hubble Space Telescope (HST) for 8.25 years. Retrieved samples were sectioned from the circular thermal shield and exposed to ground laboratory thermal energy AO. The results indicate that the average Ey of the solar facing HST Al-FEP was 1.9 × 10-24 cm3/atom, while the average Ey of the anti-solar HST Al-FEP was 1.5 × 10-24 cm3/atom. The Ey of the pristine samples was 1.6 to 1.7 × 10-24 cm3/atom. These results indicate that solar exposure affects the post-flight erosion rate of FEP in a plasma asher. Therefore, it likely affects the erosion rate while in LEO.

  18. Analyses of Hubble Space Telescope Aluminized-Teflon Multilayer Insulation Blankets Retrieved After 19 Years of Space Exposure

    NASA Technical Reports Server (NTRS)

    de Groh, Kim K.; Perry, Bruce A.; Mohammed, Jelila S.; Banks, Bruce

    2015-01-01

    Since its launch in April 1990, the Hubble Space Telescope (HST) has made many important observations from its vantage point in low Earth orbit (LEO). However, as seen during five servicing missions, the outer layer of multilayer insulation (MLI) has become increasingly embrittled and has cracked in many areas. In May 2009, during the 5th servicing mission (called SM4), two MLI blankets were replaced with new insulation and the space-exposed MLI blankets were retrieved for degradation analyses by teams at NASA Glenn Research Center (GRC) and NASA Goddard Space Flight Center (GSFC). The retrieved MLI blankets were from Equipment Bay 8, which received direct sunlight, and Equipment Bay 5, which received grazing sunlight. Each blanket was divided into several regions based on environmental exposure and/or physical appearance. The aluminized-Teflon (DuPont, Wilmington, DE) fluorinated ethylene propylene (Al-FEP) outer layers of the retrieved MLI blankets have been analyzed for changes in optical, physical, and mechanical properties, along with chemical and morphological changes. Pristine and as-retrieved samples (materials) were heat treated to help understand degradation mechanisms. When compared to pristine material, the analyses have shown how the Al-FEP was severely affected by the space environment. Most notably, the Al-FEP was highly embrittled, fracturing like glass at strains of 1 to 8 percent. Across all measured properties, more significant degradation was observed for Bay 8 material as compared to Bay 5 material. This paper reviews the tensile and bend-test properties, density, thickness, solar absorptance, thermal emittance, x-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) elemental composition measurements, surface and crack morphologies, and atomic oxygen erosion yields of the Al-FEP outer layer of the retrieved HST blankets after 19 years of space exposure.

  19. Synthesis of perm-selective membranes by grafting acrylic acid into air-irradiated Teflon-FEP films

    NASA Astrophysics Data System (ADS)

    Bozzi, Annick; Chapiro, Adolphe

    Grafting acrylic acid into air-irradiated Teflon-FEP films was investigated. Pre-irradiation doses ranged from 0.5 to 10 kGy. Grafting occurred at 45 or 60°C. Homopolymerization inhibitors, ferrous ions or methylene blue, were added to the system. It was found that after completion of the reaction, within 40-100 min, membranes were obtained with very low electric resistivities. The influence of added inhibitors, pre-irradiation dose and grafting temperature was studied. From the results it is concluded that the initiating centers in air-irradiated Teflon-FEP are, on the one hand, peroxides of structure POOP', in which P is a polymeric radical and Pprime; a small fragment, and on the other trapped PO .2 radicals. The latter only react after losing their oxygen. In the presence of polymerization inhibitors, initiation involves a redox process which reduces the overall activation energy.

  20. Hubble Space Telescope Metallized Teflon(registered trademark) FEP Thermal Control Materials: On-Orbit Degradation and Post-Retrieval Analysis

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline A.; Hansen, Patricia A.; Dever, J. A.; deGroh, K. K.; Banks, B.; Wang, L.; He, C.

    1988-01-01

    During the Hubble Space Telescope (HST) Second Servicing Mission (SM2), degradation of unsupported Teflon(Registered Trademark) FEP (fluorinated ethylene propylene), used as the outer layer of the multilayer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for ground testing and evaluation. The results of the Teflon(Registered Trademark) FEP sample evaluation and additional testing of pristine Teflon(Registered Trademark) FEP led the investigative team to theorize that the HST damage was caused by thermal cycling with deep-layer damage from electron and proton radiation which allowed the propagation of cracks along stress concentrations , and that the damage increased with the combined total dose of electrons, protons, UV and x-rays along with thermal cycling. This paper discusses the testing and evaluation of the retrieved Teflon(Registered Trademark) FEP.

  1. Ground-based simulation of LEO environment: Investigations of a select LDEF material: FEP Teflon (trademark)

    NASA Technical Reports Server (NTRS)

    Cross, Jon B.; Koontz, Steven L.

    1993-01-01

    The Long Duration Exposure Facility (LDEF) has produced a wealth of data on materials degradation in the low earth orbit (LEO) space environment and has conclusively shown that surface chemistry (as opposed to surface physics-sputtering) is the key to understanding and predicting the degradation of materials in the LEO environment. It is also clear that materials degradation and spacecraft contamination are closely linked and that the fundamental mechanisms responsible for this linking are in general not well understood especially in the area of synergistic effects. The study of the fundamental mechanisms underlying materials degradation in LEO is hampered by the fact that the degradation process itself is not observed during the actual exposure to the environment. Rather the aftermath of the degradation process is studied, i.e., the material that remains after exposure is observed and mechanisms are proposed to explain the observed results. The EOIM-3 flight experiment is an attempt to bring sophisticated diagnostic equipment into the space environment and monitor the degradation process in real time through the use of mass spectrometry. More experiments of this nature which would include surface sensitive diagnostics (Auger and photoelectron spectroscopes) are needed to truly unravel the basic chemical mechanisms involved in the materials degradation process. Since these in-space capabilities will most likely not be available in the near future, ground-based LEO simulation facilities employing sophisticated diagnostics are needed to further advance the basic understanding of the materials degradation mechanisms. The LEO simulation facility developed at Los Alamos National Laboratory has been used to investigate the atomic oxygen/vacuum ultraviolet (AO/VUV) enhanced degradation of FEP Teflon. The results show that photo-ejection of polymer fragments occur at elevated temperature (200 C), that VUV synergistic rare gas sputtering of polymer fragments occur even at

  2. Beam-surface scattering studies of the individual and combined effects of VUV radiation and hyperthermal O, O2, or Ar on FEP Teflon surfaces.

    PubMed

    Brunsvold, Amy L; Zhang, Jianming; Upadhyaya, Hari P; Minton, Timothy K

    2009-01-01

    Beam-surface scattering experiments were used to probe products that scattered from FEP Teflon surfaces during bombardment by various combinations of atomic and molecular oxygen, Ar atoms, and vacuum ultraviolet (VUV) light. A laser-breakdown source was used to create hyperthermal (translational energies in the range 4-13 eV) beams of argon and atomic/molecular oxygen. The average incidence energy of these beams was tunable and was controlled precisely with a synchronized chopper wheel. A filtered deuterium lamp provided a source of VUV light in a narrow-wavelength range centered at 161 nm. Volatile products that exited the surfaces were monitored with a rotatable mass spectrometer detector. Hyperthermal O atoms with average translational energies above approximately 4 eV may react directly with a pristine FEP Teflon surface, and the reactivity appears to increase with the translational energy of the incident O atoms. VUV light or highly energetic collisions of O2 or Ar may break chemical bonds and lead to the ejection of volatile products; the ejection of volatile products is enhanced when the surface is subjected to VUV light and energetic collisions simultaneously. Exposure to VUV light or to hyperthermal O2 or Ar may increase the reactivity of an FEP Teflon surface to O atoms. PMID:20355771

  3. Vacuum Ultraviolet (VUV) radiation-induced degradation of Fluorinated Ethylene Propylene (FEP) Teflon aboard the Long Duration Exposure Facility (LDEF)

    NASA Technical Reports Server (NTRS)

    Brinza, David E.; Stiegman, A. E.; Staszak, Paul R.; Laue, Eric G.; Liang, Ranty H.

    1992-01-01

    Examination of fluorinated ethylene propylene (FEP) copolymer specimens recovered from the Long Duration Exposure Facility (LDEF) provides evidence for degradation attributed to extended solar vacuum ultraviolet (VUV) irradiation. Scanning electron microscope (SEM) images of sheared FEP film edges reveal the presence of a highly embrittled layer on the exposed surface of specimens obtained from the trailing edge of the LDEF. Similar images obtained for leading edge and control FEP films do not exhibit evidence for such an embrittled layer. Laboratory VUV irradiation of FEP films is found to produce a damage layer similar to that witnessed in the LDEF trailing edge films. Spectroscopic analyses of irradiated films provide data to advance a photochemical mechanism for degradation.

  4. Atomic Oxygen (ATOX) simulation of Teflon FEP and Kapton H surfaces using a high intensity, low energy, mass selected, ion beam facility

    NASA Technical Reports Server (NTRS)

    Vered, R.; Grossman, E.; Lempert, G. D.; Lifshitz, Y.

    1994-01-01

    A high intensity (greater than 10(exp 15) ions/sq cm) low energy (down to 5 eV) mass selected ion beam (MSIB) facility was used to study the effects of ATOX on two polymers commonly used for space applications (Kapton H and Teflon FEP). The polymers were exposed to O(+) and Ne(+) fluences on 10(exp 15) - 10(exp 19) ions/sq cm, using 30eV ions. A variety of analytical methods were used to analyze the eroded surfaces including: (1) atomic force microscopy (AFM) for morphology measurements; (2) total mass loss measurements using a microbalance; (3) surface chemical composition using x-ray photoelectron spectroscopy (XPS), and (4) residual gas analysis (RGA) of the released gases during bombardment. The relative significance of the collisional and chemical degradation processes was evaluated by comparing the effects of Ne(+) and O(+) bombardment. For 30 eV ions it was found that the Kapton is eroded via chemical mechanisms while Teflon FEP is eroded via collisional mechanisms. AFM analysis was found very powerful in revealing the evolution of the damage from its initial atomic scale (roughness of approx. 1 nm) to its final microscopic scale (roughness greater than 1 micron). Both the surface morphology and the average roughness of the bombarded surfaces (averaged over 1 micron x 1 micron images by the system's computer) were determined for each sample. For 30 eV a non linear increase of the Kapton roughness with the O(+) fluence was discovered (a slow increase rate for fluences phi less than 5 x 10(exp 17) O(+)/sq cm, and a rapid increase rate for phi greater than 5 x 10(exp 17) O(+)/sq cm). Comparative studies on the same materials exposed to RF and DC oxygen plasmas indicate that the specific details of the erosion depend on the simulation facility emphasizing the advantages of the ion beam facility.

  5. Thermal Contributions to the Degradation of Ground-Laboratory- and Space-Irradiated Teflon Investigated

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Martin, Morgana

    2003-01-01

    The Hubble Space Telescope (HST) is covered with two primary types of thermal control materials, radiators and multilayer insulation blankets, which passively control temperatures during orbit. Both of these thermal control materials utilize back-surface metalized Teflon FEP (DuPont, fluorinated ethylene propylene) as the exterior (spacefacing) layer because of its excellent optical properties (low solar absorptance and high thermal emittance). The aluminized-FEP (Al-FEP) outermost layer of the multilayer insulation blankets on the HST has become embrittled while in space, resulting in severe on-orbit cracking (see the photographs). During the second servicing mission, an extremely embrittled piece of Al-FEP was retrieved that had curled, exposing the backsurface aluminum to space (see the photograph on the right). Because the aluminum surface has a lower thermal emittance than the FEP, this curled piece reached 200 C during orbit, 150 C higher than the nominal temperature extreme. To better understand the effect of temperature on the rate of degradation, and on the mechanism of degradation, of this insulation material in the low-Earth-orbit environment, researchers at the NASA Glenn Research Center conducted experiments to determine the effect of heating on the degradation of FEP that has been irradiated in a ground laboratory facility or in space on the HST. For this study, Teflon FEP retrieved from the HST during the third servicing mission after 9.7 years of space exposure was provided to Glenn by the NASA Goddard Space Flight Center.

  6. Utilization of FEP energetics

    NASA Technical Reports Server (NTRS)

    Frederking, T. H. K.; Abbassi, P.; Afifi, F.; Khandhar, P. K.; Ono, D. Y.; Chen, W. E. W.

    1987-01-01

    The research and development work on Fountain Effect Pump Systems (FEP systems) has been of interest in the competition between mechanical pumps for He II and FEP units. The latter do not have moving parts. In the course of the work, the energetics have been addressed using one part of a simple four-changes-of-state cycle. One option is the FEP ideal change of state at constant chemical potential (mu). The other option is the two-state sequence mu-P with a d mu=0 state change followed by an isobar. Questions of pump behavior, of flow rate response to temperature difference at the hot end, and related questions of thermodynamic cycle completion and heat transfer have been addressed. Porous media data obtained elucidate differences between vapor-liquid phase separation (VLPS) and Zero Net Mass Transfer (ZNMF).

  7. CLAD DEGRADATION - FEPS SCREENING ARGUMENTS

    SciTech Connect

    R. Schreiner

    2004-10-21

    The purpose of this report is to evaluate and document the screening of the clad degradation features, events, and processes (FEPs) with respect to modeling used to support the Total System Performance Assessment-License Application (TSPA-LA). This report also addresses the effect of certain FEPs on both the cladding and the commercial spent nuclear fuel (CSNF), DOE-owned spent nuclear fuel (DSNF), and defense high-level waste (DHLW) waste forms, as appropriate to address the effects on multiple materials and both components (FEPs 2.1.09.09.0A, 2.1.09.11.0A, 2.1.11.05.0A, 2.1.12.02.0A, and 2.1.12.03.0A). These FEPs are expected to affect the repository performance during the postclosure regulatory period of 10,000 years after permanent closure. Table 1-1 provides the list of cladding FEPs, including their screening decisions (include or exclude). The primary purpose of this report is to identify and document the analysis, screening decision, and TSPA-LA disposition (for included FEPs) or screening argument (for excluded FEPs) for these FEPs related to clad degradation. In some cases, where a FEP covers multiple technical areas and is shared with other FEP reports, this report may provide only a partial technical basis for the screening of the FEP. The full technical basis for shared FEPs is addressed collectively by the sharing FEP reports. The screening decisions and associated TSPA-LA dispositions or screening arguments from all of the FEP reports are cataloged in a project-specific FEPs database.

  8. Teflon films for chemically-inert microfluidic valves and pumps.

    PubMed

    Grover, William H; von Muhlen, Marcio G; Manalis, Scott R

    2008-06-01

    We present a simple method for fabricating chemically-inert Teflon microfluidic valves and pumps in glass microfluidic devices. These structures are modeled after monolithic membrane valves and pumps that utilize a featureless polydimethylsiloxane (PDMS) membrane bonded between two etched glass wafers. The limited chemical compatibility of PDMS has necessitated research into alternative materials for microfluidic devices. Previous work has shown that spin-coated amorphous fluoropolymers and Teflon-fluoropolymer laminates can be fabricated and substituted for PDMS in monolithic membrane valves and pumps for space flight applications. However, the complex process for fabricating these spin-coated Teflon films and laminates may preclude their use in many research and manufacturing contexts. As an alternative, we show that commercially-available fluorinated ethylene-propylene (FEP) Teflon films can be used to fabricate chemically-inert monolithic membrane valves and pumps in glass microfluidic devices. The FEP Teflon valves and pumps presented here are simple to fabricate, function similarly to their PDMS counterparts, maintain their performance over extended use, and are resistant to virtually all chemicals. These structures should facilitate lab-on-a-chip research involving a vast array of chemistries that are incompatible with native PDMS microfluidic devices. PMID:18497911

  9. Space environmental effects on silvered Teflon thermal control surfaces

    NASA Technical Reports Server (NTRS)

    Hemminger, C. S.; Stuckey, W. K.; Uht, J. C.

    1992-01-01

    Cumulative space environmental effects on silver/fluorinated ethylene propylene (Ag/FEP) were a function of exposure orientation. Samples from nineteen silvered Teflon (Ag/FEP) thermal control surfaces recovered from the Long Duration Exposure Facility (LDEF) were analyzed to determine changes in this material as a function of position on the spacecraft. Although solar absorptance and infrared emittance of measured thermal blanket specimens are relatively unchanged from control specimen values, significant changes in surface morphology, composition, and chemistry were observed. We hypothesize that the FEP surfaces on the LDEF are degraded by UV radiation at all orientations, but that the damaged material has been removed by erosion from the blankets exposed to atomic oxygen flux and that contamination is masking the damage in some areas on the trays flanking the trailing edge.

  10. Whole Teflon valves for handling droplets.

    PubMed

    Cybulski, Olgierd; Jakiela, Slawomir; Garstecki, Piotr

    2016-06-21

    We propose and test a new whole-Teflon gate valve for handling droplets. The valve allows droplet plugs to pass through without disturbing them. This is possible due to the geometric design, the choice of material and lack of any pulses of flow generated by closing or opening the valve. The duct through the valve resembles a simple segment of tubing, without constrictions, change in lumen or side pockets. There are no extra sealing materials with different wettability or chemical resistance. The only material exposed to liquids is FEP Teflon, which is resistant to aggressive chemicals and fully biocompatible. The valve can be integrated into microfluidic systems: we demonstrate a complex system for culturing bacteria in hundreds of microliter droplet chemostats. The valve effectively isolates modules of the system to increase precision of operations on droplets. We verified that the valve allowed millions of droplet plugs to safely pass through, without any cross-contamination with bacteria between the droplets. The valve can be used in automating complex microfluidic systems for experiments in biochemistry, biology and organic chemistry. PMID:27182628

  11. Miscellaneous Waste-Form FEPs

    SciTech Connect

    A. Schenker

    2000-12-08

    The US DOE must provide a reasonable assurance that the performance objectives for the Yucca Mountain Project (YMP) potential radioactive-waste repository can be achieved for a 10,000-year post-closure period. The guidance that mandates this direction is under the provisions of 10 CFR Part 63 and the US Department of Energy's ''Revised Interim Guidance Pending Issuance of New US Nuclear Regulatory Commission (NRC) Regulations (Revision 01, July 22, 1999), for Yucca Mountain, Nevada'' (Dyer 1999 and herein referred to as DOE's Interim Guidance). This assurance must be demonstrated in the form of a performance assessment that: (1) identifies the features, events, and processes (FEPs) that might affect the performance of the potential geologic repository; (2) examines the effects of such FEPs on the performance of the potential geologic repository; (3) estimates the expected annual dose to a specified receptor group; and (4) provides the technical basis for inclusion or exclusion of specific FEPs.

  12. Clad Degradation - FEPs Screening Arguments

    SciTech Connect

    E. Siegmann

    2004-03-17

    The purpose of this report is to document the screening of the cladding degradation features, events, and processes (FEPs) for commercial spent nuclear fuel (CSNF). This report also addresses the effect of some FEPs on both the cladding and the CSNF, DSNF, and HLW waste forms where it was considered appropriate to address the effects on both materials together. This report summarizes the work of others to screen clad degradation FEPs in a manner consistent with, and used in, the Total System Performance Assessment-License Application (TSPA-LA). This document was prepared according to ''Technical Work Plan for Waste Form Degradation Modeling, Testing, and Analyses in Support of LA'' (BSC 2004a [DIRS 167796]).

  13. Analysis of Ag/FEP Thermal Control Blanket Performance From Multiple Satellites

    NASA Technical Reports Server (NTRS)

    Pippin, Gary; Normand, E.; Woll, S.; Munafo, Paul (Technical Monitor)

    2001-01-01

    Materials performance data from operational spacecraft and spacecraft experiments has slowly accumulated over the years. Much of this data is obtained indirectly by analyzing temperature measurements telemetered to ground. Due to the Space Transportation System (STS) program, materials performance data has also been obtained by flying materials on satellites, or on the Space Shuttle itself, for limited periods of time, and then returning the materials to ground for post-flight examination. During the course of NASA contract NAS8-98213, the authors have extended the analysis of data reported for selected materials flown on a variety of spacecraft over the past 30 years. In this paper we discuss changes in two properties of silver- or aluminum-backed (metallized) FEP Teflon due to exposure to specific environmental factors on-orbit. First, the change in solar absorptance (alpha(sub s)) of metallized FEP Teflon as a function of particulate radiation will be discussed. Data providing the change in solar absorptance of metallized FEP as a function of days on orbit has been published for NTS-2 satellite, several NavStar Global Positioning Satellites (GPS), the SCATHA experiment, and the ML-101 satellite. The unique approach that we have taken is to calculate the absorbed radiation dose within the Ag/FEP for the various satellite orbits, and to plot the change in solar absorptance, alpha(sub s), as a function of the dose; the behavior agrees with the same data from laboratory tests. Second, the variation of the atomic oxygen induced material recession rate of metallized FEP will be discussed. Data from certain Space Shuttle flights, a Lockheed experiment [approximately 105 days in low Earth orbit (LEO)], and the Long Duration Exposure Facility allows the variation of the material recession rate of Ag/FEP to be estimated under conditions that include atomic oxygen exposure.

  14. Analysis of Silverized Teflon Thermal Control Material Flown on the Long Duration Exposure Facility

    NASA Technical Reports Server (NTRS)

    Pippin, H. Gary

    1995-01-01

    Silver backed teflon (Ag/FEP) material used for thermal control on the Long Duration Exposure Facility (LDEF) has been examined in detail. Optical, mechanical, and chemical properties were characterized for specimens exposed to a variety of space environmental conditions. Recession rates were determined for this material. Samples were obtained from virtually every LDEF location except the Earth-end. Atomic oxygen exposed regions changed from specular to diffusely reflective.

  15. Gas and aerosol wall losses in Teflon film smog chambers

    SciTech Connect

    McMurry, P.H.; Grosjean, D.

    1985-12-01

    Large smog chambers (approx.60 m/sup 3/) constructed of FEP Teflon film are frequently used to study photochemistry and aerosol formation in model chemical systems. In a previous paper a theory for aerosol wall loss rates in Teflon film smog chambers was developed; predicted particle loss rates were in good agreement with measured rates. In the present paper, measurements of wall deposition rates and the effects of wall losses on measurements of gas-to-particle conversion in smog chambers are discussed. Calculations indicate that a large fraction of the aerosol formed in several smog chamber experiments was on the chamber walls at the end of the experiment. Estimated values for particulate organic carbon yield for several precursor hydrocarbons increased by factors of 1.3-6.0 when wall deposition was taken into account. The theory is also extended to loss rates of gaseous species. Such loss rates are either limited by diffusion through a concentration boundary layer near the surface or by uptake at the surface. It is shown that for a typical 60-m/sup 3/ Teflon film smog chamber, gas loss rates are limited by surface reaction rates if mass accommodation coefficients are less than 6 x 10/sup -6/. It follows that previously reported loss rates of several gases in a chamber of this type were limited by surface reactions.

  16. Degradation studies of SMRM teflon

    NASA Technical Reports Server (NTRS)

    Liang, Ranty H.; Oda, Keri L.; Chung, Shirley Y.; Gupta, Amitava

    1986-01-01

    Teflon samples returned from the Solar Max Satellite (SMS) suffered noticeable damage such as cracking and yellowing. This is in contrast to teflon exposed aboard STS-5 and STS-8 which showed no detectable changes. Selected teflon tape samples from SMS were studied to evaluate the extent and mechanism of degradation. ESCA studies revealed that these teflon samples contain hydrocarbon segments which were susceptible to oxygen atom degradation. Mechanical measurements also showed bulk property changes as a result of LEO exposure. A molecular model of material and energetic oxygen atom interaction was proposed. SMS data and the importance of developing correlation between accelerated exposure data from STS and ground-based testing and real time data will be presented.

  17. Teflon lubrication of liquid oxygen turbopump bearings

    NASA Technical Reports Server (NTRS)

    Naerheim, Y.; Stocker, P. J.

    1989-01-01

    Ball bearings with glass fiber reinforced Teflon ball retainers from hot-fired liquid oxygen turbopumps were analyzed by X-ray photoelectron spectroscopy to determine the extent of Teflon transfer and/or chemical reaction at the bearing surface. No Teflon, but metal fluorides could be found on the metal surface. This indicates that Teflon decomposes and reacts with the bearing steel to form fluorides. Hence, Teflon does not appear to function directly as a lubricant under these operating conditions.

  18. Reactive Air Aluminization

    SciTech Connect

    Choi, Jung-Pyung; Chou, Y. S.; Stevenson, Jeffry W.

    2011-10-28

    Ferritic stainless steels and other alloys are of great interest to SOFC developers for applications such as interconnects, cell frames, and balance of plant components. While these alloys offer significant advantages (e.g., low material and manufacturing cost, high thermal conductivity, and high temperature oxidation resistance), there are challenges which can hinder their utilization in SOFC systems; these challenges include Cr volatility and reactivity with glass seals. To overcome these challenges, protective coatings and surface treatments for the alloys are under development. In particular, aluminization of alloy surfaces offers the potential for mitigating both evaporation of Cr from the alloy surface and reaction of alloy constituents with glass seals. Commercial aluminization processes are available to SOFC developers, but they tend to be costly due to their use of exotic raw materials and/or processing conditions. As an alternative, PNNL has developed Reactive Air Aluminization (RAA), which offers a low-cost, simpler alternative to conventional aluminization methods.

  19. 29 CFR 1601.80 - Certified designated FEP agencies.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 4 2010-07-01 2010-07-01 false Certified designated FEP agencies. 1601.80 Section 1601.80 Labor Regulations Relating to Labor (Continued) EQUAL EMPLOYMENT OPPORTUNITY COMMISSION PROCEDURAL REGULATIONS FEP Agency Designation Procedures § 1601.80 Certified designated FEP agencies. The designated FEP agencies receiving certification by...

  20. 29 CFR 1601.80 - Certified designated FEP agencies.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 4 2013-07-01 2013-07-01 false Certified designated FEP agencies. 1601.80 Section 1601.80 Labor Regulations Relating to Labor (Continued) EQUAL EMPLOYMENT OPPORTUNITY COMMISSION PROCEDURAL REGULATIONS FEP Agency Designation Procedures § 1601.80 Certified designated FEP agencies. The designated FEP agencies receiving certification by...

  1. Thermal anomalies in stressed Teflon.

    NASA Technical Reports Server (NTRS)

    Lee, S. H.; Wulff, C. A.

    1972-01-01

    In the course of testing polytetrafluoroethylene (Teflon) as a calorimetric gasketing material, serendipity revealed a thermal anomaly in stressed film that occurs concomitantly with the well-documented 25 C transition. The magnitude of the excess energy absorption - about 35 cal/g - is suggested to be related to the restricted thermal expansion of the film.

  2. Vacuum ultraviolet radiation/atomic oxygen synergism in fluorinated ethylene propylene Teflon erosion

    NASA Technical Reports Server (NTRS)

    Stiegman, A. E.; Brinza, David E.; Laue, Eric G.; Anderson, Mark S.; Liang, Ranty H.

    1992-01-01

    A micrographic investigation is reported of samples of the fluorinated ethylene propylene (FEP) Teflon thermal-blanketing materials recovered from the Long-Duration Exposure Facility (LDEF) satellite. The samples are taken from the trailing edge and row 8 which correspond to exposures to vacuum UV (VUV) and VUV + atomic O, respectively. Data are taken from SEM and IR-spectra observations, and the LDEF leading-edge FEP shows a high degree of erosion, roughening, and sharp peaks angled in the direction of the flow of atomic O. The trailing edge sample influenced primarily by VUV shows a hard brittle layer and some cracked mosaic patterns. Comparisons to a reference sample suggest that the brittle layer is related to exposure to VUV and is removed by atomic-O impingement. Polymers that are stable to VUV radiation appear to be more stable in terms of atomic oxygen.

  3. Optical and electrical properties of ion beam textured Kapton and Teflon

    NASA Technical Reports Server (NTRS)

    Mirtich, M. J.; Sovey, J. S.

    1977-01-01

    An electron bombardment argon ion source was used to ion etch polyimide (Kapton) and fluorinated ethylene, FEP (Teflon). Samples of polyimide and FEP were exposed to (0.5-1.0) keV Ar ions at ion current densities of (1.0-1/8) mA/sq cm for various exposure times. Changes in the optical and electrical properties of the samples were used to characterize the exposure. Spectral reflectance and transmittance measurements were made between 0.33 and 2.16 micron m using an integrating sphere after each exposure. From these measurements, values of solar absorptance were obtained. Total emittance measurements were also recorded for some samples. Surface resistivity was used to determine changes in the electrical conductivity of the etched samples. A scanning electron microscope recorded surface structure after exposure. Spectral optical data, resistivity measurements, calculated absorptance and emittance measurements are presented along with photomicrographs of the surface structure for the various exposures to Ar ions.

  4. Impact penetration experiments in teflon targets of variable thickness

    NASA Technical Reports Server (NTRS)

    Hoerz, F.; Cintala, M. J.; Bernhard, R. P.; See, T. H.

    1993-01-01

    Approximately 20.4 sq m of Teflon thermal blankets on the nonspinning Long Duration Exposure Facility (LDEF) were exposed to the orbital debris and micrometeoroid environment in low-Earth orbit (LEO) for approximately 5.7 years. Each blanket consisted of an outer layer (approximately 125 micron thick) of FEP Teflon that was backed by a vapor-deposited metal mirror (Inconel; less than 1 micron thick). The inner surface consisted of organic binders and Chemglaze thermal protective paint (approximately 50 micron thick) resulting in a somewhat variable, total blanket thickness of approximately 180 to 200 microns. There was at least one of these blankets, each exposing approximately 1.2 sq m of surface area, on nine of LDEF's 12 principal pointing directions, the exceptions being Rows 3, 9, and 12. As a consequence, these blankets represent a significant opportunity for micrometeoroid and debris studies, in general, and specifically they provide an opportunity to address those issues that require information about pointing direction (i.e., spatial density of impact events as a function of instrument orientation). During deintegration of the LDEF spacecraft at KSC, all penetration holes greater than or equal to 300 micron in diameter were documented and were recently synthesized in terms of spatial density as a function of LDEF viewing direction by. The present report describes ongoing cratering and penetration experiments in pure Teflon targets, which are intended to establish the relationships between crater or penetration-hole diameters and the associated projectile dimensions at laboratory velocities (i.e., 6 km/s). The ultimate objective of these efforts is to extract reliable mass-frequencies and associated fluxes of hypervelocity particles in LEO.

  5. Technique for stripping Teflon insulated wire

    NASA Technical Reports Server (NTRS)

    Babb, B. D.

    1967-01-01

    Cryogenic stripping of Teflon insulated wire leaves no residue and produces no physical damage. After the wire is immersed in liquid nitrogen, bent slightly, and returned to room temperature, the Teflon is removed by fingernails or flat-nosed pliers.

  6. Degradation of FEP thermal control materials returned from the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    Zuby, Thomas M.; Degroh, Kim K.; Smith, Daniela C.

    1995-01-01

    After an initial 3.6 years of space flight, the Hubble Space Telescope was serviced through a joint effort with the NASA and the European Space Agency. Multi-layer insulation (MLI) was retrieved from the electronics boxes of the two magnetic sensing systems (MSS), also called the magnetometers, and from the returned solar array (SA-I) drive arm assembly. The top layer of each MLI assembly is fluorinated ethylene propylene (FEP, a type of Teflon). Dramatic changes in material properties were observed when comparing areas of high solar fluence to areas of low solar fluence. Cross sectional analysis shows atomic oxygen (AO) erosion values up to 25.4 mu m (1 mil). Greater occurrences of through-thickness cracking and surface microcracking were observed in areas of high solar exposure. Atomic force microscopy (AFM) showed increases in surface microhardness measurements with increasing solar exposure. Decreases in FEP tensile strength and elongation were measured when compared to non-flight material. Erosion yield and tensile results are compared with FEP data from the Long Duration Exposure Facility. AO erosion yield data, solar fluence values, contamination, micrometeoroid or debris impact sites, and optical properties are presented.

  7. Infusion thrombophlebitis: a prospective comparison of 645 Vialon and Teflon cannulae in anaesthetic and postoperative use.

    PubMed

    Gaukroger, P B; Roberts, J G; Manners, T A

    1988-08-01

    A prospective study of the incidence and severity of infusion thrombophlebitis in peripheral intravenous infusions used for anaesthetic and postoperative purposes in 645 patients was conducted over a four-month period. Conditions of insertion were carefully controlled while ward management was according to standard practice. A total of 330 polyurethane Vialon and 315 FEP-A Teflon cannulae were used. The results show that the nature of the cannula was the single most important factor in the incidence and severity of infusion thrombophlebitis, Vialon cannulae being associated with a 46% lower incidence than the Teflon type. Less important but significant factors included intravenous antibiotics, duration of infusion, cannula tip damage and caesarean section. Factors not associated with infusion thrombophlebitis included potassium therapy, blood transfusion or site of insertion in the upper limb. Heparinisation increased duration of infusion without affecting the incidence of infusion thrombophlebitis. PMID:3189736

  8. Degradation studies of SMRM Teflon

    NASA Technical Reports Server (NTRS)

    Liang, R. H.; Oda, K. L.; Chung, S. Y.

    1985-01-01

    A working group was organized to study materials and components of the Solar Max Satellite (SMS) that was returned by the STS 41C. These materials were exposed in space for 50 months and represent the only real time long term exposure data available to date. In the molecular modeling of material and energetic oxygen atom interaction, it is pointed out that the importance of developing correlation between accelerated exposure data from STS and some real time data. In particular, it was predicted that Teflon which showed no detectable degradation on various STS flights may be susceptible to atomic oxygen degradation under real time conditions. Initial inspection of returned SMS samples showed that Teflon suffered visual damage such as cracking and yellowing. The results of examination of these samples are given.

  9. Duplex aluminized coatings

    NASA Technical Reports Server (NTRS)

    Gedwill, M. A.; Grisaffe, S. J. (Inventor)

    1975-01-01

    The surface of a metallic base system is initially coated with a metallic alloy layer that is ductile and oxidation resistant. An aluminide coating is then applied to the metallic alloy layer. The chemistry of the metallic alloy layer is such that the oxidation resistance of the subsequently aluminized outermost layer is not seriously degraded.

  10. Thermal Contributions to the Degradation of Ground Laboratory and Space Irradiated Teflon

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Martin, Morgana

    2003-01-01

    The aluminized Teflon fluorinated ethylene propylene outer most layer of the multilayer insulation blankets on the Hubble Space Telescope has become embrittled resulting in severe on-orbit cracking. During the second servicing mission, a piece of aluminized fluorinated ethylene propylene was retrieved that had curled, exposing the back-surface aluminum to space. This extremely embrittled piece reached 200 C on-orbit, 150 C higher than the nominal temperature extreme. Therefore, experiments have been conducted to determine the effect of heating on the degradation of fluorinated ethylene propylene that has been irradiated in a ground laboratory facility or in space on Hubble Space Telescope. Samples of pristine, x-ray irradiated and Hubble Space Telescope retrieved fluorinated ethylene propylene were heat treated from 50 to 200 C at 25 C intervals in a high vacuum facility and tensile tested. Density measurements were also obtained. Results indicate that heating does not embrittle non-irradiated Teflon. However, there is a significant dependence of the embrittlement of irradiated Teflon on heating temperature, with near complete loss of elongation at 100 C and higher. Rate of degradation changes, which were consistent with the glass transition temperature for fluorinated ethylene propylene, were present in the data. The results support chain scission as the primary mechanism of degradation of fluorinated ethylene propylene on Hubble Space Telescope, and indicate the significance of the on-orbit temperature of fluorinated ethylene propylene with respect to its degradation in the space environment.

  11. Preventing Delamination of Silverized FEP Films

    NASA Technical Reports Server (NTRS)

    Domnikov, L.; May, J.; Gallego, R.

    1986-01-01

    Edge treatment inhibits attack by moisture. New technique prevents delamination by sealing edges where delamination starts. Samples of aluminum/FEP/silver laminate survive humidity tests and other environmental tests when edges of layers are covered by epoxy bead. Untreated laminates, in contrast, deteriorated seriously during such tests.

  12. Laser processing of polytetrafluoroethylene (Teflon) in air

    NASA Astrophysics Data System (ADS)

    Wang, Z. B.; Hong, Ming Hui; Lu, Yong Feng; Chong, Tow Chong

    2003-02-01

    Teflon, polytetrafluorethylene (PTFE), is an important material in bioscience and medical application due to its special characteristics (non-flammable, anti-adhesive, heat-resistant and bio-compatible). The advantages of ultrashort laser processing of Teflon include a minimal thermal penetration region and low processing temperatures, precision removal of material, and good-quality feature definition. In this paper, laser processing of Teflon by Ti:Sapphire femtosecond laser (780 nm, 110 fs), Nd:YAG laser (532 nm, 7 ns) and CO2 laser (10.6 μm, 10 μs) has been investigated. For femtosecond laser processing, clear ablation takes place and provides high-quality groove on Teflon surface. Both the groove depth and the width increase as the laser fluence increase, and decrease almost linearly as the scanning speed increase for laser fluence below 5.0 J/cm2. For Nd:YAG processing, Teflon surface roughness is improved but no clean ablation is accessible, which makes it difficult to micromachine Teflon by Nd:YAG laser. For CO2 laser processing, laser-induced bumps were formed on Teflon surface with controlled laser parameters. The physics mechanisms for different pulse duration laser processing of Teflon are also discussed.

  13. Transient Ablation of Teflon Hemispheres

    NASA Technical Reports Server (NTRS)

    Arai, Norio; Karashima, Kei-ichi; Sato, Kiyoshi

    1997-01-01

    For high-speed entry of space vehicles into atmospheric environments, ablation is a practical method for alleviating severe aerodynamic heating. Several studies have been undertaken on steady or quasi-steady ablation. However, ablation is a very complicated phenomenon in which a nonequilibrium chemical process is associated with an aerodynamic process that involves changes in body shape with time. Therefore, it seems realistic to consider that ablation is an unsteady phenomenon. In the design of an ablative heat-shield system, since the ultimate purpose of the heat shield is to keep the internal temperature of the space vehicle at a safe level during entry, the transient heat conduction characteristics of the ablator may be critical in the selection of the material and its thickness. This note presents an experimental study of transient ablation of Teflon, with particular emphasis on the change in body shape, the instantaneous internal temperature distribution, and the effect of thermal expansion on ablation rate.

  14. Viscoelastic Properties of Fluorinated Ethylene-Propylene (FEP) Random Copolymers

    NASA Astrophysics Data System (ADS)

    Curtin, Megan; Wright, Benjamin; Ozisik, Rahmi

    Florinated ethylene-propylene (FEP) random copolymers contain tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) repeat units. FEP is an excellent alternative to poly(tetrafluoroethylene), PTFE, which cannot be melt processed due to its high molecular weight and extensive crystallinity. On the other hand, FEP is a melt processible polymer and offers similar if not the same properties as PTFE. Many studies have been performed on FEP over the years, however, the properties of these polymers strongly depend on the HFP concentration and molecular weight (distribution). Just like PTFE, FEP cannot be dissolved in many solvents, therefore, obtaining molecular weight distribution of these polymers is not possible with commonly used methods. In the current study, we perform rheological analysis of various FEPs and obtain their molecular weight distributions by employing the Tuminello method. This material is based upon work supported by the National Science Foundation under Grant No. CMMI-1538730.

  15. A Model For The Burning of Teflon

    NASA Technical Reports Server (NTRS)

    Waller, Jess M.; Wilson, D. Bruce; Beeson, Harold D.; Fries, Joseph (Technical Monitor)

    2000-01-01

    Teflon has been identified as suitable material for use in oxygen-enriched atmospheres because of its low specific enthalpy of combustion that is, less than 1500 cal/gram. However, once ignited, Teflon burns in a heterogeneous reaction until total consumption or depletion of oxygen occurs. A model is developed for the burning of Teflon in pure, high-pressure oxygen, 3.4 to 68.9 MPa. The Teflon polymer chain dissociates via monomer units due to pyrolysis. These monomer units diffuse to the surface due to free convection. The model consists of coupled mass and energy balances for the polymer and an energy balance for the free convection of product gases. The model is used to obtain appropriate kinetic parameters for the dissociation and surface reactions. The model is validated against experimental measurements of Teflon discs supported on aluminum rods (2216) at oxygen pressures of 3.4, 6.8, 34.4, and 68.9 MPa. The model simulates the temperature distribution in the product gases above burning Teflon.

  16. Biphasic binding kinetics between FepA and its ligands.

    PubMed

    Payne, M A; Igo, J D; Cao, Z; Foster, S B; Newton, S M; Klebba, P E

    1997-08-29

    The Escherichia coli FepA protein is an energy- and TonB-dependent, ligand-binding porin that functions as a receptor for the siderophore ferric enterobactin and colicins B and D. We characterized the kinetic and thermodynamic parameters associated with the initial, energy-independent steps in ligand binding to FepA. In vivo experiments produced Kd values of 24, 185, and 560 nM for ferric enterobactin, colicin B, and colicin D, respectively. The siderophore and colicin B bound to FepA with a 1:1 stoichiometry, but colicin D bound to a maximum level that was 3-fold lower. Preincubation with ferric enterobactin prevented colicin B binding, and preincubation with colicin B prevented ferric enterobactin binding. Colicin B release from FepA was unexpectedly slow in vivo, about 10-fold slower than ferric enterobactin release. This slow dissociation of the colicin B.FepA complex facilitated the affinity purification of FepA and FepA mutants with colicin B-Sepharose. Analysis of a fluorescent FepA derivative showed that ferric enterobactin and colicin B adsorbed with biphasic kinetics, suggesting that both ligands bind in at least two distinct steps, an initial rapid stage and a subsequent slower step, that presumably establishes a transport-competent complex. PMID:9268330

  17. A Study to Analyze the Permeation of High Density Gases and Propellant Vapors Through Single Layer Teflon or Teflon Structure Materials and Laminations. Volume 1

    NASA Technical Reports Server (NTRS)

    Johnson, R. L.; Young, Donald L. (Technical Monitor)

    1967-01-01

    This report contains the results of a fifteen month analytical and experimental study of the leakage rate of the pressurant gases (N2, He) and the propellant vapors (N2O4,N2H4) through bladder structures consisting of two layers of Teflon separated by a metallic foil diffusion barrier containing microscopic or larger holes. Results were obtained for the steady state leakage rate through circular holes and long rectangular openings in the barrier for arbitrary thicknesses of the two Teflon layers. The effect of hole shape and relative hole position on the leakage rate were studied. The transient problem was analyzed and it was shown that steady state calculations are adequate for estimating the leakage rate. A computer program entitled "Diffusion Analyzer Program" was developed to calculate the leakage rate, both transient and steady state. Finally, the analytical results were compared to experimentally determined values of the leakage rate through a model laminated bladder structure. The results of the analysis are in good agreement with experiment. The experimental effort (Part II of the Bladder Permeation Program) measured the solubility, diffusion coefficient and permeability of helium, nitrogen and nitrogen tetroxide vapor through Teflon TFE and FEP membranes. Data were obtained in the temperature range of 25 to 100 C at pressures ranging from near vacuum to about 20 atmospheres. Results of the experimental effort were compared with the limited data previously reported. As a verification to the applicability of results to actual bladder systems, counter diffusion tests were performed with a laminated sample containing aluminum foil with a selected group of holes.

  18. Cratering and penetration experiments in Teflon targets at velocities from 1 to 7 km/s

    NASA Technical Reports Server (NTRS)

    Hoerz, Friedrich; Bernhard, Ronald P.; Cintala, Mark J.; See, Thomas H.

    1995-01-01

    Approximately 20 sq m of protective thermal blankets, largely composed of Teflon, were retrieved from the Long Duration Exposure Facility (LDEF) after the spacecraft had spent approximately 5.7 years in space. Examination of these blankets revealed that they contained thousands of hypervelocity impact features ranging from micron-sized craters to penetration holes several millimeters in diameter. We conducted impact experiments in an effort to reproduce such features and to -- hopefully -- understand the relationships between projectile size and the resulting crater or penetration-hole diameter over a wide range of impact velocity. Such relationships are needed to derive the size- and mass-frequency distribution and flux of natural and man-made particles in low-Earth orbit. Powder propellant and light-gas guns were used to launch soda-lime glass spheres of 3.175 mm (1/8 inch) nominal diameter (Dp) into pure Teflon FEP targets at velocities ranging from 1 to 7 km/s. Target thickness (T) was varied over more than three orders of magnitude from infinite halfspace targets (Dp/T less than 0.1) to very thin films (Dp/T greater than 100). Cratering and penetration of massive Teflon targets is dominated by brittle failure and the development of extensive spall zones at the target's front and, if penetrated, the target's rear side. Mass removal by spallation at the back side of Teflon targets may be so severe that the absolute penetration-hole diameter (Dh) can become larger than that of a standard crater (Dc) at relative target thicknesses of Dp/T = 0.6-0.9. The crater diameter is infinite halfspace Teflon targets increases -- at otherwise constant impact conditions -- with encounter velocity by a factor of V0.44. In contrast, the penetration-hole size is very thin foils (Dp/T greater than 50) is essentially unaffected by impact velocity. Penetrations at target thicknesses intermediate to these extremes will scale with variable exponents of V. Our experimental matrix is

  19. Teflon lined process pumps save over $25,000/yr in acid regeneration plant

    SciTech Connect

    Ross, L.; Gaines, A.

    1982-03-01

    Armco's Eastern Steel Division Works in Ashland, KY includes an acid regeneration plant that uses the spray/roaster process to recover hydrochloric acid and high purity iron oxides from spent pickling liquor. Two centrifugal pumps, one operating and one on standby, were used to pump the corrosive and erosive mixture at 175-200/sup 0/F to the spray nozzles in the roaster. The impeller, casing and other wetted parts were of an acid resistant exotic metal, but the pumps had a service life of only 2 to 3 months. The impellers had to be replaced after about six weeks because of wear that reduced the discharge pressure and impaired the performance of the spray nozzles. Maintaining the pumps and replacing them several times a year was extremely expensive, since each pump cost about $6000. A 3 X 1 1/2 X 8 1/2'' centrifugal pump specifically designed for severe corrosive service was installed on a trial basis in February 1980. The process pump is built to AVS standards and features a 3/16'' thick fluoropolymer liner molded in place to the ductile iron case, and a fully open faced ductile iron impeller encapsulated with fluoropolymer. The pumps have been available for a number of years with liners and impeller coverings of Du Pont's Teflon-FEP fluorocarbon, and the acid regenerating plant has been using them in various corrosive applications since the startup in 1972. The acid regeneration plant is very pleased with the trouble-free performance of the Teflon-FEP lined pumps. They are reliable, essentially maintenance free, and maintain the discharge pressures required for efficient operation of the spray nozzles.

  20. Fatigue testing of corrugated and Teflon hoses

    NASA Technical Reports Server (NTRS)

    Benner, Steve M.; Swanson, Theodore D.; Costello, Frederick A.

    1990-01-01

    Single and two-phase heat transport systems for the thermal control of large space facilities require fluid lines that traverse joints and either rotate or move in some other manner. Flexible hoses are being considered as one means of traversing these joints. To test the resilience of flexible hoses to bending stress, a test assembly was constructed to determine the number of flexing cycles the hoses could withstand before losing their ability to maintain a constant pressure. Corrugated metal hoses and Teflon hoses were tested at different pressures with nitrogen gas. The metal hoses had lives ranging from 30,000 to 100,000 flexing cycles. But, even after 400,000 cycles, the Teflon hoses remained essentially intact, though some leakage in the convoluted Teflon is noted.

  1. Mars containers - Dust on teflon sealing surfaces

    NASA Astrophysics Data System (ADS)

    Lauer, H. V., Jr.; Allton, J. H.

    As part of an evaluation of suitable hermetic seals for containers for Martian rock and soil samples, teflon o-ring static face seals were challenged with silica gel, basalt, and bentonite dust in several size ranges: 20-45 microns, 45-75 microns, and 75-125 microns. Seals were most tolerant of the soft bentonite dust and least tolerant of angular silica gel dust. Small amounts of 75-125 micron size particles can be accommodated by the teflon o-ring; however, the seals do not work well if smaller particles are concentrated enough to form layers more than 1 grain thick.

  2. Solar Effects on Tensile and Optical Properties of Hubble Space Telescope Silver-Teflon(Registered Trademark) Insulation

    NASA Technical Reports Server (NTRS)

    deGroh, Kim, K.; Dever, Joyce A.; Snyder, Aaron; Kaminski, Sharon; McCarthy, Catherine E.; Rapoport, Alison L.; Rucker, Rochelle N.

    2006-01-01

    A section of the retrieved Hubble Space Telescope (HST) solar array drive arm (SADA) multilayer insulation (MLI), which experienced 8.25 years of space exposure, was analyzed for environmental durability of the top layer of silver-Teflon (DuPont) fluorinated ethylene propylene (Ag-FEP). Because the SADA MLI had solar and anti-solar facing surfaces and was exposed to the space environment for a long duration, it provided a unique opportunity to study solar effects on the environmental degradation of Ag-FEP, a commonly used spacecraft thermal control material. Data obtained included tensile properties, solar absorptance, surface morphology and chemistry. The solar facing surface was found to be extremely embrittled and contained numerous through-thickness cracks. Tensile testing indicated that the solar facing surface lost 60% of its mechanical strength and 90% of its elasticity while the anti-solar facing surface had ductility similar to pristine FEP. The solar absorptance of both the solar facing surface (0.155 plus or minus 0.032) and the anti-solar facing surface (0.208 plus or minus 0.012) were found to be greater than pristine Ag-FEP (0.074). Solar facing and anti-solar facing surfaces were microscopically textured, and locations of isolated contamination were present on the anti-solar surface resulting in increased localized texturing. Yet, the overall texture was significantly more pronounced on the solar facing surface indicating a synergistic effect of combined solar exposure and increased heating with atomic oxygen erosion. The results indicate a very strong dependence of degradation, particularly embrittlement, upon solar exposure with orbital thermal cycling having a significant effect.

  3. Microfluidic Pumps Containing Teflon [Trademark] AF Diaphragms

    NASA Technical Reports Server (NTRS)

    Willis, Peter; White, Victor; Grunthaner, Frank; Ikeda, Mike; Mathies, Richard A.

    2009-01-01

    Microfluidic pumps and valves based on pneumatically actuated diaphragms made of Teflon AF polymers are being developed for incorporation into laboratory-on-a-chip devices that must perform well over temperature ranges wider than those of prior diaphragm-based microfluidic pumps and valves. Other potential applications include implanted biomedical microfluidic devices, wherein the biocompatability of Teflon AF polymers would be highly advantageous. These pumps and valves have been demonstrated to function stably after cycling through temperatures from -125 to 120 C. These pumps and valves are intended to be successors to similar prior pumps and valves containing diaphragms made of polydimethylsiloxane (PDMS) [commonly known as silicone rubber]. The PDMS-containing valves ae designed to function stably only within the temperature range from 5 to 80 C. Undesirably, PDMS membranes are somwehat porous and retain water. PDMS is especially unsuitable for use at temperatures below 0 C because the formation of ice crystals increases porosity and introduces microshear.

  4. Method of processing aluminous ores

    DOEpatents

    Loutfy, Raouf O.; Keller, Rudolf; Yao, Neng-Ping

    1981-01-01

    A method of producing aluminum chloride from aluminous materials containing compounds of iron, titanium and silicon comprising reacting the aluminous materials with carbon and a chlorine-containing gas at a temperature of about 900.degree. K. to form a gaseous mixture containing chlorides of aluminum, iron, titanium and silicon and oxides of carbon; cooling the gaseous mixture to a temperature of about 400.degree. K. or lower to condense the aluminum chlorides and iron chlorides while titanium chloride and silicon chloride remain in the gas phase to effect a separation thereof; heating the mixture of iron chlorides and aluminum chlorides to a temperature of about 800.degree. K. to form gaseous aluminum chlorides and iron chlorides; passing the heated gases into intimate contact with aluminum sulfide to precipitate solid iron sulfide and to form additional gaseous aluminum chlorides; and separating the gaseous aluminum chloride from the solid iron sulfide.

  5. Effects of the LDEF environment on the Ag/FEP thermal blankets

    NASA Technical Reports Server (NTRS)

    Levadou, Francois; Pippin, H. Gary

    1992-01-01

    This presentation was made by Francois Levadou at the NASA Langley Research Center LDEF materials workshop, November 19-22, 1991. It represents the results to date on the examination of silvered teflon thermal blankets primarily from the Ultra-heavy Cosmic Ray Experiment and also from the blanket from the Park Seed Company experiment. ESA/ESTEC and Boeing conducted a number of independent measurements on the blankets and in particular on the exposed fluorinated ethylene-propylene (FEP) layer of the blankets. Mass loss, thickness, and thickness profile measurements have been used by ESA, Boeing, and NASA LeRC to determine recession and average erosion yield under atomic oxygen exposure. Tensile strength and percent elongation to failure data, surface characterization by ESCA, and SEM images are presented. The Jet Propulsion Laboratory analysis of vacuum radiation effects is also presented. The results obtained by the laboratories mentioned and additional results from the Aerospace Corporation on samples provided by Boeing are quite similar and give confidence in the validity of the data.

  6. A study of the UV and VUV degradation of FEP

    NASA Technical Reports Server (NTRS)

    George, Graeme A.; Hill, David J. T.; Odonnell, James H.; Pomery, Peter J.; Rasoul, Firas A.

    1993-01-01

    UV and VUV degradation of fluorinated ethylene propylene (FEP) copolymer was studied using electron spin resonance (ESR) spectroscopy, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The ESR study revealed the formation of a terminal polymer radical. The stability of this radical was investigated under different environments. An XPS study of FEP film exposed to VUV and atomic oxygen showed that oxidation takes place on the polymer surface. The study revealed also that the percentage of CF2 in the polymer surface decreased with exposure time and the percentage of CF, CF3, and carbon attached to oxygen increased. SEM micrographs of FEP film exposed to VUV and atomic oxygen identified a rough surface with undulations similar to sand dunes.

  7. Comparison of type A and C Fluorinated Ethylene Propylene (FEP) as cover materials for silicon solar cells

    NASA Technical Reports Server (NTRS)

    Broder, J. D.

    1976-01-01

    Fluorinated ethylene propylene film (FEP, 0.0127 cm thick) was heat and pressure laminated to silicon solar cells as a low cost substitute for quartz covers. The FEP-C, treated on one side for bonding, was compared to FEP-A, an untreated FEP. With FEP-A, a silane adhesion promoter was applied to the cells. The FEP-C covers delaminated during accelerated temperature-humidity testing and Earth environmental exposure testing; FEP-A covers were unchanged. No differences were observed in peel tests, but FEP-A is superior in its resistance to tearing and in retention of transmission properties after exposure to ultraviolet radiation.

  8. DYNAMIC LOADING OF TEFLON AT 200?C

    SciTech Connect

    Urtiew, P A; Forbes, J W; Tarver, C M; Vandersall, K S; Garcia, F

    2007-06-13

    Dynamic loading experiments were performed on inert Teflon (Polytetrafluoroethylene) samples, initially heated to the temperature of 200 C, to test its behavior under these conditions for its use in other heated experiments. Tests were performed in the 100 mm diameter bore propellant driven gas gun with piezo-resistive manganin pressure gauges imbedded into the samples to measure loading pressures. Experimental data provided new information on the shock velocity - particle velocity relationship for the heated material and showed no adverse effect of temperature on the insulating properties of the material.

  9. Barriers to flashover discharge arcs on Teflon

    NASA Technical Reports Server (NTRS)

    Gossland, M.; Balmain, K. G.

    1982-01-01

    The effect of various barriers (empty gap, copper, Mylar, and nickel mesh) on the probability of simultaneous arc discharging of two physically separated pieces of electron-beam-charged Teflon was studied. For the empty gap barrier, it was found that simultaneous discharges rarely occur when the separation between the samples is greater than approximately 0.4 times the length of their common edge when this length is of the order of 1 cm. Evidence suggests that electromagnetic fields play a larger role than electrons in influencing the occurrence of simultaneous arc discharges.

  10. Unique Charge Storage Characteristics of FEP/THV/FEP Sandwich Electret Membrane Polarized by Thermally Charging Technology

    NASA Astrophysics Data System (ADS)

    Chen, Gang-Jin; Lei, Ming-Feng; Xiao, Hui-Ming; Wu, Ling

    2014-12-01

    Utilizing the synergy of three processes (space charge injection, dipole orientation and interfacial polarization) which determine the electret properties, a sandwich electret membrane FEP/THV/FEP (FEP: fluorinated ethylene propylene, THV: tetrafluoroethylene-hexafluoropropylene-vinylidene) is prepared by the laminating method and the thermal charging technology. The surface potential measurement indicates that the sandwich electret membrane exhibits excellent charge storage stability. When washing the sample surface with alcohol, its surface potential first undergoes decay to zero, and then quickly restores to a high value. The surface potential value is associated with the charging electric field and temperature. The best charging condition is 18.75 MV·m-1 and 130°C. A charge storage profile is proposed, and the experimental results are in good agreement with this profile.

  11. Hole schubweg in FEP (fluorinated ethylene propylene copolymer)

    NASA Astrophysics Data System (ADS)

    Wintle, H. J.

    We discuss four models to account for observations of a constant hole schubweg in FEP (fluorinated ethylene propylene copolymer). Inhomogeneity in the sample and one-dimensional chain transport seem unlikely, while conventional semiconductor theory demands a particular combination of properties. Tunnelling, influenced by the field to yield essentially unidirectional transport, matches the observations and gives a reasonable trap density ( N ≈ 10 19 cm -3, with wide limits of uncertainty).

  12. HNS/Teflon, a new heat resistant explosive

    NASA Technical Reports Server (NTRS)

    Heller, H.; Bertram, A. L.

    1973-01-01

    HNS/Teflon (90/10) is a new pressed explosive developed for use in the Apollo program. The major advantages of HNS/Teflon are (1) excellent thermal stability at elevated temperatures, (2) superior resistance to sublimation at high temperatures and low pressures and (3) ease of molding powder preparation, pressing and machining. The impact sensitivity of HNS/Teflon is between that of Comp B and Comp A-3 while its explosive performance is about the same as TNT. Under the severe environmental conditions of the moon's surface, this explosive successfully performed its intended function of generating seismic waves in the Apollo ALSEP and LSPE experiments. (Modified author abstract)

  13. FEPs Screening of Processes and Issues in Drip Shield and Waste Package Degradation

    SciTech Connect

    K. Mon

    2004-10-11

    The purpose of this report is to evaluate and document the inclusion or exclusion of features, events and processes (FEPs) with respect to drip shield and waste package modeling used to support the Total System Performance Assessment for License Application (TSPA-LA). Thirty-three FEPs associated with the waste package and drip shield performance have been identified (DTN: MO0407SEPFEPLA.000 [DIRS 170760]). A screening decision, either ''included'' or ''excluded,'' has been assigned to each FEP, with the technical bases for screening decisions, as required by the Nuclear Regulatory Commission (NRC) in 10 CFR 63.114 (d, e, and f) [DIRS 156605]. The FEPs analyses in this report address issues related to the degradation and potential failure of the drip shield and waste package over the post closure regulatory period of 10,000 years after permanent closure. For included FEPs, this report summarizes the disposition of the FEP in TSPA-LA. For excluded FEPs, this report provides the technical bases for the screening arguments for exclusion from TSPA-LA. The analyses are for the TSPA-LA base-case design (BSC 2004 [DIRS 168489]), where a drip shield is placed over the waste package without backfill over the drip shield (BSC 2004 [DIRS 168489]). Each FEP includes one or more specific issues, collectively described by a FEP name and description. The FEP description encompasses a single feature, event, or process, or a few closely related or coupled processes, provided the entire FEP can be addressed by a single specific screening argument or TSPA-LA disposition. The FEPs were assigned to associated Project reports, so the screening decisions reside with the relevant subject-matter experts.

  14. Combustion Synthesis of Magnesium Aluminate

    NASA Astrophysics Data System (ADS)

    Kale, M. A.; Joshi, C. P.; Moharil, S. V.

    2011-10-01

    In the system MgO-Al2O3, three compounds MgAl2O4, MgAl6O10 (also expressed as- Mg0.4Al2.4O4) and MgAl26O40 are well known. Importance of the first two is well established. Magnesium aluminate (MgAl2O4) spinel is a technologically important material due to its interesting thermal properties. The MgAl2O4 ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl2O4 is due to various applications such as humidity-sensing and PEM fuel cells, TL/OSL dosimetry of the ionizing radiations, white light source. Interest in the MgAl6O10 has aroused due to possible use as a substrate for GaN growth. Attempt was made to synthesize these compounds by the combustion synthesis using metal nitrates as oxidizer and urea as a fuel. Compounds MgAl2O4 and MgAl6O10 were formed in a single step, while MgAl26O40 was not formed by this procedure. Activation of MgAl6O10 by rare earth ions like Ce3+, Eu3+ and Tb3+ and ns2 ion Pb2+ could be achieved. Excitation bands for MgAl6O10 are at slightly shorter wavelengths compared to those reported for MgAl2O4.

  15. Combustion Synthesis of Magnesium Aluminate

    SciTech Connect

    Kale, M. A.; Joshi, C. P.; Moharil, S. V.

    2011-10-20

    In the system MgO-Al{sub 2}O{sub 3}, three compounds MgAl{sub 2}O{sub 4}, MgAl{sub 6}O{sub 10}(also expressed as-Mg{sub 0.4}Al{sub 2.4}O{sub 4}) and MgAl{sub 26}O{sub 40} are well known. Importance of the first two is well established. Magnesium aluminate (MgAl{sub 2}O{sub 4}) spinel is a technologically important material due to its interesting thermal properties. The MgAl{sub 2}O{sub 4} ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl{sub 2}O{sub 4} is due to various applications such as humidity-sensing and PEM fuel cells, TL/OSL dosimetry of the ionizing radiations, white light source. Interest in the MgAl{sub 6}O{sub 10} has aroused due to possible use as a substrate for GaN growth. Attempt was made to synthesize these compounds by the combustion synthesis using metal nitrates as oxidizer and urea as a fuel. Compounds MgAl{sub 2}O{sub 4} and MgAl{sub 6}O{sub 10} were formed in a single step, while MgAl{sub 26}O{sub 40} was not formed by this procedure. Activation of MgAl{sub 6}O{sub 10} by rare earth ions like Ce{sup 3+}, Eu{sup 3+} and Tb{sup 3+} and ns{sup 2} ion Pb{sup 2+} could be achieved. Excitation bands for MgAl{sub 6}O{sub 10} are at slightly shorter wavelengths compared to those reported for MgAl{sub 2}O{sub 4}.

  16. Kinetics of pack aluminization of nickel

    NASA Technical Reports Server (NTRS)

    Seigle, L. L.; Gupta, B. K.; Shankar, R.; Sarkhel, A. K.

    1978-01-01

    The kinetics of pack aluminization of unalloyed nickel in packs of varying aluminum activity with various halide activators were studied. Surface compositions of the coatings as functions of time, temperature, and pack composition were obtained in order to establish the boundary conditions for diffusion in the system. The structure of the packs was also examined in order to clarify the mechanism of aluminum transport. The results indicate that the kinetics of pack aluminization are controlled jointly by gas diffusion in the pack and solid diffusion in the coating. Levine and Caves' model for gas diffusion was combined with calculations of rates of diffusion in the solid to formulate a more complete theory for the kinetics of pack aluminization.

  17. Pitting corrosion of aluminized seals in molten carbonate fuel cells

    SciTech Connect

    Krumpelt, M.; Roche, M.F.; Bloom, I.

    1994-08-01

    The objective of this research is to gain a better understanding of the corrosion of the aluminized type 316 stainless steel employed in the seal areas of the molten carbonate fuel cell. The seals are formed between the aluminized Type 316 SS surface and the electrolyte (generally a mixture of molten alkali carbonates and lithium aluminate).

  18. Phosphate-bonded calcium aluminate cements

    DOEpatents

    Sugama, T.

    1993-09-21

    A method is described for making a rapid-setting phosphate-bonded cementitious material. A powdered aluminous cement is mixed with an aqueous solution of ammonium phosphate. The mixture is allowed to set to form an amorphous cementitious material which also may be hydrothermally treated at a temperature of from about 120 C to about 300 C to form a crystal-containing phosphate-bonded material. Also described are the cementitious products of this method and the cement composition which includes aluminous cement and ammonium polyphosphate. 10 figures.

  19. Phosphate-bonded calcium aluminate cements

    DOEpatents

    Sugama, Toshifumi

    1993-01-01

    A method is described for making a rapid-setting phosphate-bonded cementitious material. A powdered aluminous cement is mixed with an aqueous solution of ammonium phosphate. The mixture is allowed to set to form an amorphous cementitious material which also may be hydrothermally treated at a temperature of from about 120.degree. C. to about 300.degree. C. to form a crystal-containing phosphate-bonded material. Also described are the cementitious products of this method and the cement composition which includes aluminous cement and ammonium polyphosphate.

  20. Eigenvalue Detonation of Combined Effects Aluminized Explosives

    NASA Astrophysics Data System (ADS)

    Capellos, C.; Baker, E. L.; Nicolich, S.; Balas, W.; Pincay, J.; Stiel, L. I.

    2007-12-01

    Theory and performance for recently developed combined—effects aluminized explosives are presented. Our recently developed combined-effects aluminized explosives (PAX-29C, PAX-30, PAX-42) are capable of achieving excellent metal pushing, as well as high blast energies. Metal pushing capability refers to the early volume expansion work produced during the first few volume expansions associated with cylinder and wall velocities and Gurney energies. Eigenvalue detonation explains the observed detonation states achieved by these combined effects explosives. Cylinder expansion data and thermochemical calculations (JAGUAR and CHEETAH) verify the eigenvalue detonation behavior.

  1. Cratering and penetration experiments in aluminum and teflon: Implications for space-exposed surfaces

    NASA Astrophysics Data System (ADS)

    Hörz, Friedrich

    2012-04-01

    Whether a target is penetrated or not during hypervelocity impact depends strongly on typical impactor dimensions (Dp) relative to the absolute target thickness (T). We have therefore conducted impact experiments in aluminum1100 and TeflonFEP targets that systematically varied Dp/T (=D*), ranging from genuine cratering events in thick targets (Dp << T) to the nondisruptive passage of the impactor through very thin films (Dp >> T). The objectives were to (1) delineate the transition from cratering to penetration events, (2) characterize the diameter of the penetration hole (Dh) as a function of D*, and (3) determine the threshold target thickness that yields Dh = Dp. We employed spherical soda-lime glass (SLG) projectiles of Dp = 50-3175 μm at impact velocities (V) from 1 to 7 km s-1, and varied target thicknesses from microns to centimeters. The transition from cratering to penetration processes in thick targets forms a continuum in all morphologic aspects. The entrance side of the target resembles that of a standard crater even when the back of the target suffers substantial, physical perforations via spallation and plastic deformation. We thus suggest that the cratering-to-penetration transition does not occur when the target becomes physically perforated (i.e., at the "ballistic limit"), but when the shock pulse duration in the projectile (tp) is identical to that in the target (tt), i.e., tp = tt. This condition is readily calculated from equation-of-state data. As a consequence, in reconstructing impactor dimensions from observations of space-exposed substrates, we recommend that crater size (Dc) be used for the case of tp < tt, and that penetration hole diameter (Dh) be used when tp > tt. The morphologic evolution of the penetration hole and its size also forms a continuum that strongly depends on both the scaled parameter D* and on V, but it is independent of the absolute scale. The condition of Dh = Dp is approached at D* > 50. The dependence of Dh on T

  2. Embossed Teflon AF Laminate Membrane Microfluidic Diaphragm Valves

    NASA Technical Reports Server (NTRS)

    Willis, Peter; Hunt, Brian; White,Victor; Grunthaner, Frank

    2008-01-01

    A microfluidic system has been designed to survive spaceflight and to function autonomously on the Martian surface. It manipulates microscopic quantities of liquid water and performs chemical analyses on these samples to assay for the presence of molecules associated with past or present living processes. This technology lies at the core of the Urey Instrument, which is scheduled for inclusion on the Pasteur Payload of the ESA ExoMars rover mission in 2013. Fabrication processes have been developed to make the microfabricated Teflon-AF microfluidic diaphragm pumps capable of surviving extreme temperature excursions before and after exposure to liquid water. Two glass wafers are etched with features and a continuous Teflon membrane is sandwiched between them (see figure). Single valves are constructed using this geometry. The microfabricated devices are then post processed by heating the assembled device while applying pneumatic pressure to force the Teflon diaphragm against the valve seat while it is softened. After cooling the device, the embossed membrane retains this new shape. This solves previous problems with bubble introduction into the fluid flow where deformations of the membrane at the valve seat occurred during device bonding at elevated temperatures (100-150 C). The use of laminated membranes containing commercial Teflon AF 2400 sheet sandwiched between spun Teflon AF 1600 layers performed best, and were less gas permeable than Teflon AF 1600 membranes on their own. Spinning Teflon AF 1600 solution (6 percent in FLOURINERT(Registered TradeMark) FC40 solvent, 3M Company) at 500 rpm for 1.5 seconds, followed by 1,000 rpm for 3 seconds onto Borofloat glass wafers, results in a 10-micron-thick film of extremely smooth Teflon AF. This spinning process is repeated several times on flat, blank, glass wafers in order to gradually build a thick, smooth membrane. After running this process at least five times, the wafer and Teflon coating are heated under vacuum

  3. Theoretical equation of state for aluminized nitromethane

    SciTech Connect

    Jones, H.D.; Zerilli, F.J. )

    1991-04-01

    The simple fluid constituents of the reaction products of an aluminized nitromethane explosive are described by a perturbation technique based on their intermolecular interactions. Liquid metal constituents are treated with a Grover scaling model. Standard solid-state approaches are applied to the solid components of the reaction products. Calculated detonation velocities compared favorably with experimental data.

  4. The Enhanced Plan for Features, Events, and Processes (FEPS) at Yucca Mountain

    SciTech Connect

    G. Freeze

    2002-03-25

    A performance assessment is required to demonstrate compliance with the post-closure performance objectives for the Yucca Mountain Project (YMP), as stated in 10 CFR Part 63.1 13 (66 FR 55732, p. 55807). A performance assessment is defined in 10 CFR 63.2 (66 FR 55732, p. 55794) as an analysis that: (1) identifies the features, events, and processes (FEPs) that might affect the potential geologic repository; (2) examines the effects of those FEPs upon the performance of the potential geologic repository; and (3) estimates the expected dose incurred by a specified reasonably maximally exposed individual as a result of releases caused by significant FEPs. The performance assessment must also provide the technical basis for inclusion or exclusion of specific FEPs in the performance assessment as stated in 10 CFR 63.114 (66 FR 55732, p. 55807). An initial approach for FEP development, in support of the Total System Performance Assessment for the Site Recommendation (TSPA-SR) (CRWMS M&O 2000e), was documented in Freeze et al. (2001). The development of a comprehensive list of FEPs potentially relevant to the post-closure performance of the potential Yucca Mountain repository is an ongoing, iterative process based on site-specific information, design, and regulations. Although comprehensiveness of the FEPs list cannot be proven with absolute certainty, confidence can be gained through a combination of formal and systematic reviews (both top-down and bottom-up), audits, and comparisons with other FEP lists and through the application of more than one classification scheme. To support TSPA-SR, DOE used a multi-step approach for demonstrating comprehensiveness of the initial list of FEPs. Input was obtained from other international radioactive waste disposal programs as compiled by the Nuclear Energy Agency (NEA) of the Organization for Economic Co-operation and Development (OECD) to establish a general list of FEPs. The list was subsequently refined to include YMP

  5. Recession of FEP specimens from trays D11 and B7

    NASA Technical Reports Server (NTRS)

    Pippin, H. Gary

    1992-01-01

    We report work done at Boeing Defense and Space Group on analysis of silvered teflon specimens taken from selected locations of the Long Duration Exposure Facility under support from a contract provided by NASA LaRC. The samples discussed in this presentation were taken from the unexposed side of D11 and extended through the folded area of this blanket into the exposed area. Two similar areas were cut from blanket B7, one from the edge of the blanket near row six and one from the edge of the blanket near row eight and within a few centimeters of the copper grounding strap for B7. The specimens were each divided into three sections by cutting with a scapel. Two of the sections were mounted in a potting compound, which was cut and polished such that the cross-sectional thickness of each was exposed. One piece was mounted straight and the other was mounted in an attempt to configure the specimens such that it was bent with a radius of curvature similar to the on-orbit configuration. The third portion of each specimen was used for SEM images to help define the angle of exposure with respect to the ram at each location on the specimen. Photomicrographs were taken in cross section from the edge of the blanket through the curved transition region into the exposed area of the blanket. The thickness of the Fluorinated Ethylene Propylene (FEP) layer was determined at known distances from the edge of the blanket. SEM images were obtained at known distances to help define the angle with respect to ram and therefore establish the atomic oxygen fluence on each location and correlate this exposure with thickness. Thickness measurements made with a two to three centimeter distance minimized the uncertainty arising from variations in the as-manufactured thickness of each blanket. The nominal angle from ram of the exposed portion of each blanket, and the fact that the unexposed edge portions are approximately at right angles to the exposed portion were also used to help define the

  6. Measurements of prompt radiation induced conductivity in Teflon (PTFE).

    SciTech Connect

    Hartman, E. Frederick; Zarick, Thomas Andrew; Sheridan, Timothy J.; Preston, E.

    2013-05-01

    We performed measurements of the prompt radiation induced conductivity (RIC) in thin samples of Teflon (PTFE) at the Little Mountain Medusa LINAC facility in Ogden, UT. Three mil (76.2 microns) samples were irradiated with a 0.5 %CE%BCs pulse of 20 MeV electrons, yielding dose rates of 1E9 to 1E11 rad/s. We applied variable potentials up to 2 kV across the samples and measured the prompt conduction current. Details of the experimental apparatus and analysis are reported in this report on prompt RIC in Teflon.

  7. Temperature characteristics of microfiber coil resonators embedded in teflon

    NASA Astrophysics Data System (ADS)

    Chen, Ye; Ming, Yang; Guo, Wei; Xu, Fei; Lu, Yan-qing

    2011-12-01

    In this paper we investigate the temperature characteristic of an optical microfiber coil resonator (OMCR) which is wrapped on Teflon coated PMMA rob and embedded in low index polymer Teflon. The micro fiber used to fabricated the OMCR was 4 ~ 5μm in diameter and 14 mm in waist region length. The PMMA rob has a diameter of 2 mm. Our sample shows high temperature sensitivity as much as 80 pm/°C. The test result suggests OMCR could be of good value in application of temperature sensing.

  8. Protoporphyrin (FEP/ZPP) screening in industrial lead exposure

    SciTech Connect

    Saryan, L.A.

    1988-11-01

    Lead-acid battery manufacturers, as a group, are among the largest industrial users of lead in the United States, and every industry using this metal is confronted with a maze of federal regulations governing workplace conditions and employee health. In the biological testing category, particular emphasis has been placed on the periodic testing of blood for lead, to assess absorption of the metal, and protoporphyrin (abbreviated ZPP or FEP) testing as a means of monitoring the biological effects resulting from lead exposure. The protoporphyrin test, however, remains a matter of general confusion among industry managers and medical directors, and this article attempts to provide a concise and understandable explanation of this topic. 10 references, 3 figures, 1 table.

  9. Measurements of Gas-Wall Partitioning of Oxidized Species in Environmental Smog Chambers and Teflon Sampling Lines

    NASA Astrophysics Data System (ADS)

    Krechmer, J.; Pagonis, D.; Ziemann, P. J.; Jimenez, J. L.

    2015-12-01

    Environmental "smog" chambers have played an integral role in atmospheric aerosol research for decades. Recently, many works have demonstrated that the loss of gas-phase material to fluorinated ethylene propylene (FEP) chamber walls can have significant effects on secondary organic aerosol (SOA) yield results. The effects of gas-wall partitioning on highly oxidized species is still controversial, however. In this work we performed a series of experiments examining the losses of oxidized gas-phase compounds that were generated in-situ­ in an environmental chamber. The loss of species to the walls was measured using three chemical ionization mass spectrometry techniques: proton-transfer-reaction (PTR), nitrate (NO3-) ion, and iodide (I-). Many oxidized species have wall loss timescales ranging between 15 to 45 minutes and scale according to the molecule's estimated saturation concentration c* and functional groups. By comparing results of the different techniques, and in particular by the use of the "wall-less" NO3- source, we find that measuring species with high chamber wall-loss rates is complicated by the use of a standard ion-molecule reaction (IMR) region, as well as long Teflon sampling lines, which can be important sinks for gas-phase species. This effect is observed even for semi-volatile species and could have significant effects on ambient sampling techniques that make highly time-resolved measurements using long sampling lines, such as eddy covariance measurements.

  10. Isolation of Human Monocytes by Double Gradient Centrifugation and Their Differentiation to Macrophages in Teflon-coated Cell Culture Bags

    PubMed Central

    Menck, Kerstin; Behme, Daniel; Pantke, Mathias; Reiling, Norbert; Binder, Claudia; Pukrop, Tobias; Klemm, Florian

    2014-01-01

    Human macrophages are involved in a plethora of pathologic processes ranging from infectious diseases to cancer. Thus they pose a valuable tool to understand the underlying mechanisms of these diseases. We therefore present a straightforward protocol for the isolation of human monocytes from buffy coats, followed by a differentiation procedure which results in high macrophage yields. The technique relies mostly on commonly available lab equipment and thus provides a cost and time effective way to obtain large quantities of human macrophages. Briefly, buffy coats from healthy blood donors are subjected to a double density gradient centrifugation to harvest monocytes from the peripheral blood. These monocytes are then cultured in fluorinated ethylene propylene (FEP) Teflon-coated cell culture bags in the presence of macrophage colony-stimulating factor (M-CSF). The differentiated macrophages can be easily harvested and used for subsequent studies and functional assays. Important methods for quality control and validation of the isolation and differentiation steps will be highlighted within the protocol. In summary, the protocol described here enables scientists to routinely and reproducibly isolate human macrophages without the need for cost intensive tools. Furthermore, disease models can be studied in a syngeneic human system circumventing the use of murine macrophages. PMID:25226391

  11. Evaluation of Features, Events, and Processes (FEP) for the Biosphere Model

    SciTech Connect

    M. Wasiolek; P. Rogers

    2004-10-27

    The purpose of this analysis report is to evaluate and document the inclusion or exclusion of biosphere features, events, and processes (FEPs) with respect to modeling used to support the total system performance assessment (TSPA) for the license application (LA). A screening decision, either ''Included'' or ''Excluded'', is given for each FEP along with the corresponding technical basis for the excluded FEPs and the descriptions of how the included FEPs were incorporated in the biosphere model. This information is required by the U.S. Nuclear Regulatory Commission (NRC) regulations at 10 CFR 63.114 (d, e, and f) [DIRS 156605]. The FEPs addressed in this report concern characteristics of the reference biosphere, the receptor, and the environmental transport and receptor exposure pathways for the groundwater and volcanic ash exposure scenarios considered in biosphere modeling. This revision provides the summary of the implementation of included FEPs in TSPA-LA, (i.e., how the FEP is included); for excluded FEPs, this analysis provides the technical basis for exclusion from TSPA-LA (i.e., why the FEP is excluded). This report is one of the 10 documents constituting the biosphere model documentation suite. A graphical representation of the documentation hierarchy for the biosphere model is presented in Figure 1-1. This figure shows the interrelationships among the products (i.e., analysis and model reports) developed for biosphere modeling. The ''Biosphere Model Report'' describes in detail the biosphere conceptual model and mathematical model. The input parameter reports shown to the right of the ''Biosphere Model Report'' contain detailed descriptions of the model input parameters and their development. Outputs from these six reports are used in the ''Nominal Performance Biosphere Dose Conversion Factor Analysis and Disruptive Event Biosphere Dose Conversion Factor Analysis'' to generate the biosphere dose conversion factors (BDCFs), which are input parameters for

  12. In situ high-pressure study of FeP: Implications for planetary cores

    NASA Astrophysics Data System (ADS)

    Gu, Tingting; Wu, Xiang; Qin, Shan; Dubrovinsky, Leonid

    2011-02-01

    FeP with MnP-type structure is isostructural with high-pressure FeS polymorphs (both post-troilite FeS and FeS VI), which are believed to exist in planetary cores. Due to similar PTX phase diagrams of binary Fe-P and Fe-S, phosphorus can incorporate with iron-sulfur at planetary core conditions. To understand such substitution and the high-pressure behavior of FeP, we investigate the structural stability of FeP up to 15.6 GPa and 1800 ± 200 K by combined in situ powder X-ray diffraction and Mössbauer spectroscopy. Our experimental results show that FeP remains the MnP-type structure throughout the PT range covered. Isothermal equation of state of FeP is obtained with V0 of 92.91(8) Å 3, B0 of 205(7) GPa, and B0 of 4. The shortest axis of the MnP-type FeP cell, the b-axis, is the most compressible, due to the soft edge-sharing octahedra along the b-axis. Mössbauer results show that no electronic structure changes occur up to 15.6 GPa, but indicate decreasing distortion of FeP 6 octahedron with pressure increasing. The behavior of FeP is quite different from that of FeS under high pressure and high temperature, suggesting that phosphorus will have a significant impact on stability and electronic properties of FeS within terrestrial planet cores.

  13. Eigenvalue Detonation of Combined Effects Aluminized Explosives

    NASA Astrophysics Data System (ADS)

    Capellos, Christos; Baker, Ernest; Balas, Wendy; Nicolich, Steven; Stiel, Leonard

    2007-06-01

    This paper reports on the development of theory and performance for recently developed combined effects aluminized explosives. Traditional high energy explosives used for metal pushing incorporate high loading percentages of HMX or RDX, whereas blast explosives incorporate some percentage of aluminum. However, the high blast explosives produce increased blast energies, with reduced metal pushing capability due to late time aluminum reaction. Metal pushing capability refers to the early volume expansion work produced during the first few volume expansions associated with cylinder wall velocities and Gurney energies. Our Recently developed combined effects aluminized explosives (PAX-29C, PAX-30, PAX-42) are capable of achieving excellent metal pushing and high blast energies. Traditional Chapman-Jouguet detonation theory does not explain the observed detonation states achieved by these combined effects explosives. This work demonstrates, with the use of cylinder expansion data and thermochemical code calculations (JAGUAR and CHEETAH), that eigenvalue detonation theory explains the observed behavior.

  14. Fault Tree, Event Tree, and Piping and Instrumentation Diagram (FEP) editors, Version 4. 0

    SciTech Connect

    McKay, M.K.; Skinner, N.L.; Wood, S.T. )

    1992-05-01

    The Fault Tree, Event Tree, and Piping Instrumentation Diagram (FEP) editors allow the user to graphically build and edit fault trees, event trees, and piping instrumentation diagrams (P IDs). The software is designed to enable the use of graphical-based editors found in the Integrated Reliability and Risk Assessment System (IRRAS). FEP is made up of three separate editors (Fault Tree, Event Tree, and Piping Instrumentation Diagram) and a utility module. This reference manual provides a screen-by-screen walkthrough of the entire FEP System.

  15. Status of FEP encapsulated solar cell modules used in terrestrial applications

    NASA Technical Reports Server (NTRS)

    Ratajczak, A. F.; Forestieri, A. F.

    1974-01-01

    The Lewis Research Center has been engaged in transferring the FEP encapsulated solar cell technology developed for the space program to terrestrial applications. FEP encapsulated solar cell modules and arrays were designed and built expressly for terrestrial applications. Solar cell power systems were installed at three different land sites, while individual modules are undergoing marine environment tests. Four additional power systems are being completed for installation during the summer of 1974. These tests have revealed some minor problems which have been corrected. The results confirm the inherent utility of FEP encapsulated terrestrial solar cell systems.

  16. The aluminizing in powder technology of AISI 304 steel

    NASA Astrophysics Data System (ADS)

    Băitanu, D. B.; Găluşcă, D. G.; Achiţei, D. C.; Minciună, M. G.; Bakri Abdullah, Mohd Mustafa Al

    2016-06-01

    The paper presents a study about the aluminizing treatments applied to AISI 304 stainless steel, with the purpose to improve the corrosion resistance. The aluminizing is realized in a powder medium, composed by aluminium powder (with 99.95% purity), aluminium oxide Al2O3 and ammonium chloride NH4Cl. The structural characterization was made by scanning electronic microscopy to highlight the structure of layer after aluminizing, at different magnitudes.

  17. Mussel-inspired block copolymer lithography for low surface energy materials of teflon, graphene, and gold.

    PubMed

    Kim, Bong Hoon; Lee, Duck Hyun; Kim, Ju Young; Shin, Dong Ok; Jeong, Hu Young; Hong, Seonki; Yun, Je Moon; Koo, Chong Min; Lee, Haeshin; Kim, Sang Ouk

    2011-12-15

    Mussel-inspired interfacial engineering is synergistically integrated with block copolymer (BCP) lithography for the surface nanopatterning of low surface energy substrate materials, including, Teflon, graphene, and gold. The image shows the Teflon nanowires and their excellent superhydrophobicity. PMID:22021119

  18. Evaluation of Features, Events, and Processes (FEP) for the Biosphere Model

    SciTech Connect

    M. A. Wasiolek

    2003-10-09

    The purpose of this report is to document the evaluation of biosphere features, events, and processes (FEPs) that relate to the license application (LA) process as required by the U.S. Nuclear Regulatory Commission (NRC) regulations at 10 CFR 63.114 (d, e, and f) [DIRS 156605]. The evaluation determines whether specific biosphere-related FEPs should be included or excluded from consideration in the Total System Performance Assessment (TSPA). This analysis documents the technical basis for screening decisions as required at 10 CFR 63.114 (d, e, and f) [DIRS 156605]. For FEPs that are included in the TSPA, this analysis provides a TSPA disposition, which summarizes how the FEP has been included and addressed in the TSPA model, and cites the analysis reports and model reports that provide the technical basis and description of its disposition. For FEPs that are excluded from the TSPA, this analysis report provides a screening argument, which identifies the basis for the screening decision (i.e., low probability, low consequence, or by regulation) and discusses the technical basis that supports that decision. In cases, where a FEP covers multiple technical areas and is shared with other FEP analysis reports, this analysis may provide only a partial technical basis for the screening of the FEP. The full technical basis for these shared FEPs is addressed collectively by all FEP analysis reports that cover technical disciplines sharing a FEP. FEPs must be included in the TSPA unless they can be excluded by low probability, low consequence, or regulation. A FEP can be excluded from the TSPA by low probability per 10 CFR 63.114(d) [DIRS 156605], by showing that it has less than one chance in 10,000 of occurring over 10,000 years (or an approximately equivalent annualized probability of 10{sup -8}). A FEP can be excluded from the TSPA by low consequence per 10 CFR 63.114 (e or f) [DIRS 156605], by showing that omitting the FEP would not significantly change the magnitude and

  19. Fabrication and characterization of calcium aluminate glass fibers

    NASA Astrophysics Data System (ADS)

    Foy, Paul R.

    Calcium aluminate glasses (CAG) offer excellent chemical durability, high strength, broad spectral transparency, and a refractory nature. This makes them ideal candidates for fiber optic power delivery and sensor systems in the infrared spectrum. CAG also have the potential to form ultra-low loss optical materials. The fabrication of glass optical fibers from CAG was investigated in this study. High quality bulk glasses were obtained from the best industrial sources available. These glasses included silica and baria doped CAG compositions. A preform fabrication method was developed to obtain drawing samples. An optical fiber draw furnace was specially modified to achieve fiber drawing. A novel drawing method was also developed. Solid and hollow CAG waveguides, and CAG core/silica clad waveguides were obtained from drawing preforms. This represents the first successful fiber drawing of this glass system. Teflon coating for optical cladding and strength protection was also investigated. Infrared Spectroscopy was used to assess the attenuation in the drawn fibers. 7 dB/m at 2.7 mum with the baria doped CAG solid waveguide was recorded. This represents the lowest loss documented for fibers fabricated from CAG. Laser power propagation through solid and hollow waveguides was investigated. 24 Watts of CO2 laser power was delivered into a hollow baria doped CAG waveguide. 10.13 J/mm2 of 2.94 mum Erbium YAG laser power was delivered through solid baria doped CAG waveguide. Fiber strength testing was performed on the CAG fibers through four point bend testing. The best strength obtained was 1290 MPa for baria doped CAG. Glass stability was assessed using Differential Thermal Analysis. Fiber surface crystallization products were characterized using Energy Dispersive Analysis, Scanning Electron Microscopy, a specially modified Hot Stage X-Ray, and Guinier Camera X-Ray Analysis. The surface crystallization analysis revealed the formation of Ca3Al2O6 in the silica doped CAG

  20. THE DEVELOPMENT OF THE YUCCA MOUNTAIN PROJECT FEATURE, EVENT, AND PROCESS (FEP) DATABASE

    SciTech Connect

    G. Freeze; P. Swift; N. Brodsky

    2000-10-11

    A Total System Performance Assessment for Site Recommendation (TSPA-SR) has recently been completed (CRWMS M&O, 2000b) for the potential high-level waste repository at the Yucca Mountain site. The TSPA-SR is an integrated model of scenarios and processes relevant to the postclosure performance of the potential repository. The TSPA-SR scenarios and model components in turn include representations of all features, events, and processes (FEPs) identified as being relevant (i.e., screened in) for analysis. The process of identifying, classifying, and screening potentially relevant FEPs thus provides a critical foundation for scenario development and TSPA analyses for the Yucca Mountain site (Swift et al., 1999). The objectives of this paper are to describe (a) the identification and classification of the comprehensive list of FEPs potentially relevant to the postclosure performance of the potential Yucca Mountain repository, and (b) the development, structure, and use of an electronic database for storing and retrieving screening information about the inclusion and/or exclusion of these Yucca Mountain FEPs in TSPA-SR. The FEPs approach to scenario development is not unique to the Yucca Mountain Project (YMP). General systematic approaches are summarized in NEA (1992). The application of the FEPs approach in several other international radioactive waste disposal programs is summarized in NEA ( 1999).

  1. Near-infrared laser ablation of poly tetrafluoroethylene (Teflon) sensitized by nanoenergetic materials

    SciTech Connect

    Yang Yanqiang; Wang Shufeng; Sun Zhaoyong; Dlott, Dana D.

    2004-08-30

    Laser ablation of Teflon doped with size-selected (30-250 nm) Al nanoparticles is studied. Unlike pure Teflon, which requires a vacuum-ultraviolet or femtosecond excimer laser for ablation, this sensitized Teflon can be ablated with a near-infrared laser. Using 100 ps duration pulses, near-infrared ablation thresholds are lower by about a factor of 10 from excimer ablation of pure Teflon. A mechanism is discussed that involves Teflon decomposition by spherical shock fronts originating at each irradiated nanoparticle. Studies of the distance dependence of this process as a function of particle diameter and oxide layer thickness suggest ways of optimizing the ablation process.

  2. Durable Superhydrophobic Surfaces via Spontaneous Wrinkling of Teflon AF.

    PubMed

    Scarratt, Liam R J; Hoatson, Ben S; Wood, Elliot S; Hawkett, Brian S; Neto, Chiara

    2016-03-16

    We report the fabrication of both single-scale and hierarchical superhydrophobic surfaces, created by exploiting the spontaneous wrinkling of a rigid Teflon AF film on two types of shrinkable plastic substrates. Sub-100 nm to micrometric wrinkles were reproducibly generated by this simple process, with remarkable control over the size and hierarchy. Hierarchical Teflon AF wrinkled surfaces showed extremely high water repellence (contact angle 172°) and very low contact angle hysteresis (2°), resulting in droplets rolling off the surface at tilt angles lower than 5°. The wrinkling process intimately binds the Teflon AF layer with its substrate, making these surfaces mechanically robust, as revealed by macroscale and nanoscale wear tests: hardness values were close to that of commercial optical lenses and aluminum films, resistance to scratch was comparable to commercial hydrophobic coatings, and damage by extensive sonication did not significantly affect water repellence. By this fabrication method the size of the wrinkles can be reproducibly tuned from the nanoscale to the microscale, across the whole surface in one step; the fabrication procedure is extremely rapid, requiring only 2 min of thermal annealing to produce the desired topography, and uses inexpensive materials. The very low roll-off angles achieved in the hierarchical surfaces offer a potentially up-scalable alternative as self-cleaning and drag-reducing coatings. PMID:26910574

  3. Mobility of cations in magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Martinelli, J. R.; Sonder, E.; Weeks, R. A.; Zuhr, R. A.

    1986-04-01

    Transport of cations in magnesium aluminate spinel due to an applied electric field at approximately 1000 °C has been measured by observing changes in elemental concentrations near the cathode and anode surfaces using ion backscattering techniques. The results indicate that magnesium ions are the mobile species at 1000 °C and that these ions combine with ambient oxygen at the cathode surface to form a MgO layer. Quantitative interpretation of the data leads to the conclusion that the ionic transference number of spinel becomes approximately 0.5 after treatment in an electric field.

  4. Evaluation of Features, Events, and Processes (FEP) for the Biosphere Model

    SciTech Connect

    J. J. Tappen

    2003-02-16

    The purpose of this revision of ''Evaluation of the Applicability of Biosphere-Related Features, Events, and Processes (FEPs)'' (BSC 2001) is to document the screening analysis of biosphere-related primary FEPs, as identified in ''The Development of Information Catalogued in REV00 of the YMP FEP Database'' (Freeze et al. 2001), in accordance with the requirements of the final U.S. Nuclear Regulatory Commission (NRC) regulations at 10 CFR Part 63. This database is referred to as the Yucca Mountain Project (YMP) FEP Database throughout this document. Those biosphere-related primary FEPs that are screened as applicable will be used to develop the conceptual model portion of the biosphere model, which will in turn be used to develop the mathematical model portion of the biosphere model. As part of this revision, any reference to the screening guidance or criteria provided either by Dyer (1999) or by the proposed NRC regulations at 64 FR 8640 has been removed. The title of this revision has been changed to more accurately reflect the purpose of the analyses. In addition, this revision will address Item Numbers 19, 20, 21, 25, and 26 from Attachment 2 of ''U.S. Nuclear Regulatory Commission/U.S. Department of Energy Technical Exchange and Management Meeting on Total System Performance Assessment and Integration (August 6 through 10, 2001)'' (Reamer 2001). This Scientific Analysis Report (SAR) does not support the current revision to the YMP FEP Database (Freeze et al. 2001). Subsequent to the release of the YMP FEP Database (Freeze et al. 2001), a series of reviews was conducted on both the FEP processes used to support Total System Performance Assessment for Site Recommendation and to develop the YMP FEP Database. In response to observations and comments from these reviews, particularly the NRC/DOE TSPA Technical Exchange in August 2001 (Reamer 2001), several Key Technical Issue (KTI) Agreements were developed. ''The Enhanced Plan for Features, Events and Processes

  5. The iron uptake repressor Fep1 in the fission yeast binds Fe-S cluster through conserved cysteines.

    PubMed

    Kim, Hyo-Jin; Lee, Kang-Lok; Kim, Kyoung-Dong; Roe, Jung-Hye

    2016-09-01

    Iron homeostasis is tightly regulated since iron is an essential but toxic element in the cell. The GATA-type transcription factor Fep1 and its orthologs contribute to iron homeostasis in many fungi by repressing genes for iron uptake when intracellular iron is high. Even though the function and interaction partners of Fep1 have been elucidated extensively In Schizosaccharomyces pombe, the mechanism behind iron-sensing by Fep1 remains elusive. It has been reported that Fep1 interacts with Fe-S-containing monothiol glutaredoxin Grx4 and Grx4-Fra2 complex. In this study, we demonstrate that Fep1 also binds iron, in the form of Fe-S cluster. Spectroscopic and biochemical analyses of as isolated and reconstituted Fep1 suggest that the dimeric Fep1 binds Fe-S clusters. The mutation study revealed that the cluster-binding depended on the conserved cysteines located between the two zinc fingers in the DNA binding domain. EPR analyses revealed [Fe-S]-specific peaks indicative of mixed presence of [2Fe-2S], [3Fe-4S], or [4Fe-4S]. The finding that Fep1 is an Fe-S protein fits nicely with the model that the Fe-S-trafficking Grx4 senses intracellular iron environment and modulates the activity of Fep1. PMID:27444384

  6. Pack aluminization of nickel anode for molten carbonate fuel cells

    NASA Astrophysics Data System (ADS)

    Chun, H. S.; Park, G. P.; Lim, J. H.; Kim, K.; Lee, J. K.; Moon, K. H.; Youn, J. H.

    1994-04-01

    The aluminum pack cementation (pack aluminization) process on a porous nickel anode for molten carbonate fuel cells has been studied to improve anode creep resistance. The porous nickel substrates used in this study were fabricated by doctor blade equipment followed by sintering (850 C). Packs surrounding the Ni anode were made by mixing Al2O3 powder, Al powder, and NaCl as activator. The pack aluminization was performed at 700 to 850 C for 0.5-5.0 h. After pack aluminization, the principal Ni-Al intermetallic compounds detected were Ni3Al at 700 C, NiAl at 750 C and Ni3Al2 at 800 C. The aluminum content in the aluminized Ni anode was proportional to the square root of pack aluminizing time. With increasing the Al content in the anode, the creep of the anode decreased. It was nearly constant (2.0%) when the Al content was above 5.0%. Although the exchange current density (24 mA/sq cm) for the aluminized (2.5 wt.%) Ni anode was somewhat lower than that of the pure Ni anode (40 mA/sq cm), the performance of a single cell using an aluminized Ni anode was similar to that of the one with pure Ni anode.

  7. Characterization of the Cobalamin and Fep Operons in Methylobium petrolphilum PM1

    SciTech Connect

    Ewing, J

    2005-09-06

    The bacterium Methylobium petroleophilum PM1 is economically important due to its ability to degrade methyl tert-butyl ether (MTBE), a fuel additive. Because PM1 is a representative of all MTBE degraders, it is important to understand the transport pathways critical for the organism to survive in its particular environment. In this study, the cobalamin pathway and select iron transport genes will be characterized to help further understand all metabolic pathways in PM1. PM1 contains a total of four cobalamin operons. A single operon is located on the chromosome. Located on the megaplasmid are two tandem repeats of cob operons and a very close representative of the cob operon located on the chromosome. The fep operon, an iron transport mechanism, lies within the multiple copies of the cob operon. The cob operon and the fep operon appear to be unrelated except for a shared need for the T-on-B-dependent energy transduction complex to assist the operons in moving large molecules across the outer membrane of the cell. A genomic study of the cob and the fep operons with that of phylogenetically related organisms helped to confirm the identity of the cob and fep operons and to represent the pathways. More study of the pathways should be done to find the relationship that positions the two seemingly unrelated cob and fep genes together in what appears to be one operon.

  8. Sulfur and phosphorus in the Earth's core: The Fe-P-S system at 23 GPa

    NASA Astrophysics Data System (ADS)

    Stewart, A. J.; Schmidt, M. W.

    2007-07-01

    Phosphorus is an important element believed to be present in the Earth's core. As a non-metal, its solubility in iron is limited, leading to the precipitation of phosphides at high concentrations. Here we present experimental results for the iron-rich portions of the Fe-P and Fe-P-S systems at 23 GPa. We find a Fe-P eutectic point occurring at 9 wt% P and 1275°C at 23 GPa. Up to 4 wt% P is soluble in the Fe-rich solid coexisting with the eutectic liquid at these conditions. The ternary Fe-P-S system displays a simple cotectic between the Fe-P and Fe-S binary eutectics with minimum melting temperature on the S-side at 1075°C. At subsolidus conditions there is complete solid solution between Fe3P and Fe3S. The high solubility of phosphorus in iron along with its miscibility in Fe3S and iron-sulfur liquids at high pressures, combined with expectation of only minor concentrations in planetary cores, indicate phosphorus will not form a distinct phase within terrestrial planet cores.

  9. Experimental impacts into Teflon targets and LDEF thermal blankets

    NASA Technical Reports Server (NTRS)

    Hoerz, F.; Cintala, M. J.; Zolensky, M. E.; Bernhard, R. P.; See, T. H.

    1994-01-01

    The Long Duration Exposure Facility (LDEF) exposed approximately 20 sq m of identical thermal protective blankets, predominantly on the Ultra-Heavy Cosmic Ray Experiment (UHCRE). Approximately 700 penetration holes greater than 300 micron in diameter were individually documented, while thousands of smaller penetrations and craters occurred in these blankets. As a result of their 5.7 year exposure and because they pointed into a variety of different directions relative to the orbital motion of the nonspinning LDEF platform, these blankets can reveal important dynamic aspects of the hypervelocity particle environment in near-earth orbit. The blankets were composed of an outer teflon layer (approximately 125 micron thick), followed by a vapor-deposited rear mirror of silver (less than 1000 A thick) that was backed with an organic binder and a thermal protective paint (approximately 50 to 75 micron thick), resulting in a cumulative thickness (T) of approximately 175 to 200 microns for the entire blanket. Many penetrations resulted in highly variable delaminations of the teflon/metal or metal/organic binder interfaces that manifest themselves as 'dark' halos or rings, because of subsequent oxidation of the exposed silver mirror. The variety of these dark albedo features is bewildering, ranging from totally absent, to broad halos, to sharp single or multiple rings. Over the past year experiments were conducted over a wide range of velocities (i.e., 1 to 7 km/s) to address velocity dependent aspects of cratering and penetrations of teflon targets. In addition, experiments were performed with real LDEF thermal blankets to duplicate the LDEF delaminations and to investigate a possible relationship of initial impact conditions on the wide variety of dark halo and ring features.

  10. Terrestrial applications of FEP-encapsulated solar cell modules. [power systems using Fluorinated Ethylene Propylene encapsulation

    NASA Technical Reports Server (NTRS)

    Forestieri, A. F.; Ratajczak, A. F.

    1974-01-01

    The NASA-Lewis Research Center program of transferring the FEP-encapsulated solar cell technology developed for the space program to terrestrial applications is presented. The electrical power system design and the array mechanical design are described, and power systems being tested are discussed. The latter are located at NOAA-RAMOS weather stations at Sterling, Va., and Mammoth Mountain, Calif.; on the roof of the Lewis Research Center; on a NOAA-Coast Guard buoy in the Gulf of Mexico; in a U.S. Forest Service mountaintop voice repeater station in the Inyo National Forest, Calif., and in a backpack charger for portable transmitter/receivers being used in the same place. Preliminary results of testing are still incomplete, but show that rime ice can cause cracks in modular cells without damaging the FEP though, which keeps the grid lines intact, and that electrically active elements of the module must be completely sealed from salt water to prevent FEP delamination.

  11. Modified Pechini synthesis of tricalcium aluminate powder

    SciTech Connect

    Voicu, Georgeta Ghitulica, Cristina Daniela; Andronescu, Ecaterina

    2012-11-15

    Tricalcium aluminate (Ca{sub 3}Al{sub 2}O{sub 6}-C{sub 3}A) was obtained by a modified Pechini synthesis in order to eliminate successive thermal treatments and intermediate grinding usually performed between the two sintering steps and in order to reduce the sintering temperature. Our results indicated that pure C{sub 3}A was obtained, by a single step thermal treatment at 1300 Degree-Sign C for 4 h and 1350 Degree-Sign C for 1 h. The synthesis was confirmed by XRD, FT-IR and free lime analyses. The morphology of synthesised C{sub 3}A was assessed by electron microscopy (SEM and TEM, HRTEM) and it was observed a high tendency of the particles to form aggregates and the individual particles seem to be single crystals. The bioactivity was assessed by specimen soaking in simulated body fluid (SBF) for 7 days; the hydrate (i.e. 3CaO Bullet-Operator Al{sub 2}O{sub 3} Bullet-Operator 6H{sub 2}O formed at the C{sub 3}A surface), can act as nucleation centers for the resulted phosphate phases. - Highlights: Black-Right-Pointing-Pointer A modified Pechini synthesis was used for obtained of tricalcium aluminate. Black-Right-Pointing-Pointer C{sub 3}A was obtained at 1300 Degree-Sign C/4 h and 1350 Degree-Sign C/1 h. Black-Right-Pointing-Pointer Were eliminated successive thermal treatments and intermediate grinding. Black-Right-Pointing-Pointer The morphology of synthesised C{sub 3}A was assessed by electron microscopy (SEM, TEM). Black-Right-Pointing-Pointer Was observed a high tendency of the particles to form aggregates.

  12. Roadmaps through free energy landscapes calculated using the multi-dimensional vFEP approach.

    PubMed

    Lee, Tai-Sung; Radak, Brian K; Huang, Ming; Wong, Kin-Yiu; York, Darrin M

    2014-01-14

    The variational free energy profile (vFEP) method is extended to two dimensions and tested with molecular simulation applications. The proposed 2D-vFEP approach effectively addresses the two major obstacles to constructing free energy profiles from simulation data using traditional methods: the need for overlap in the re-weighting procedure and the problem of data representation. This is especially evident as these problems are shown to be more severe in two dimensions. The vFEP method is demonstrated to be highly robust and able to provide stable, analytic free energy profiles with only a paucity of sampled data. The analytic profiles can be analyzed with conventional search methods to easily identify stationary points (e.g. minima and first-order saddle points) as well as the pathways that connect these points. These "roadmaps" through the free energy surface are useful not only as a post-processing tool to characterize mechanisms, but can also serve as a basis from which to direct more focused "on-the-fly" sampling or adaptive force biasing. Test cases demonstrate that 2D-vFEP outperforms other methods in terms of the amount and sparsity of the data needed to construct stable, converged analytic free energy profiles. In a classic test case, the two dimensional free energy profile of the backbone torsion angles of alanine dipeptide, 2D-vFEP needs less than 1% of the original data set to reach a sampling accuracy of 0.5 kcal/mol in free energy shifts between windows. A new software tool for performing one and two dimensional vFEP calculations is herein described and made publicly available. PMID:24505217

  13. Teflon Implants Versus Titanium Implants in Stapes Surgery.

    PubMed

    Bansal, Mohan

    2016-03-01

    Otosclerosis is the most common cause of bilateral gradually progressive conductive hearing loss with normal tympanic membrane and Eustachian tube. Otosclerosis surgical treatment is one of the most gratifying operations in Otorhinolaryngology. It is not only the surgical techniques but also the prosthesis which are evolving in the attempt of providing best hearing results. Teflon piston is the most commonly employed prosthesis in stapes surgery. Titanium pistons are relatively the new development in the evolution of stapes prosthesis. The aim of this review article is to know and compare the surgical technicalities and postoperative outcomes including hearing improvement after the use of Teflon and titanium stapes piston. The adverse reactions occurred during follow-up were taken into consideration. The data in this article are supported by a Medline search. The use of both the prosthesis gave good results in cases of otosclerosis. The placement of titanium soft clip design was found easier than the earlier àWengen design of clip piston. PMID:27066403

  14. Proton Radiography of Shape Charge Jets Penetrating Teflon and Explosive

    NASA Astrophysics Data System (ADS)

    Ferm, Eric N.; Burkett, Michael W.; Hull, Larry M.; Marr-Lyon, Mark; McNeil, Wendy V.; Morris, Chris L.; Rightley, Paul M.; Lansce Proton Radiography Team

    2011-06-01

    We have used proton radiography at the Los Alamos Neutron Science Center to observe viper shaped charge jets penetrating inert and explosive materials. A viper jet was observed penetrating both Teflon and PBX 9501. Radiographs captured the penetration events at several times and are analyzed to determine the density of the materials imaged at each time. The interfaces and shock waves in the flow are clearly evident in the images. Multiple time images allow the determination of the velocities of the interfaces and shock waves. Comparisons are made in the Teflon case with estimates of penetration rates and densities using the quasi-steady approximation analysis used in many terminal ballistics models. The PBX 9501 clearly detonated from the impact of the shape charge jet tip traveling at 9.1 mm/s. The detonation wave is examined to see what support it obtains from the pursing jet and the jet is examined to find the influence of the explosive products on penetration velocity. This experiment gives us experimental results of in-situ penetration process that can be used to verify common modeling techniques and fluid mechanic calculations of the penetration process.

  15. Femtosecond laser ablation of polytetrafluoroethylene (Teflon) in ambient air

    NASA Astrophysics Data System (ADS)

    Wang, Z. B.; Hong, M. H.; Lu, Y. F.; Wu, D. J.; Lan, B.; Chong, T. C.

    2003-05-01

    Teflon, polytetrafluorethylene (PTFE), is an important material in bioscience and medical application due to its special characteristics (bio-compatible, nonflammable, antiadhesive, and heat resistant). The advantages of ultrashort laser processing of Teflon include a minimal thermal penetration region and low processing temperatures, precision removal of material, and good-quality feature definition. In this paper, laser processing of PTFE in ambient air by a Ti:sapphire femtosecond laser (780 nm, 110 fs) is investigated. It is found that the pulse number on each irradiated surface area must be large enough for a clear edge definition and the ablated depth increases with the pulse number. The air ionization effect at high laser fluences not only degrades the ablated structures quality but also reduces the ablation efficiency. High quality microstructures are demonstrated with controlling laser fluence below a critical fluence to exclude the air ionization effect. The ablated microstructures show strong adhesion property to liquids and clear edges that are suitable for bio-implantation applications. Theoretical calculation is used to analyze the evolution of the ablated width and depth at various laser fluences.

  16. [Study on the compatibility of slip casting aluminous ceramic crowns

    PubMed

    Wan, Q B; Xue, M; You, L; Du, C S; Chao, Y L

    1997-03-01

    One of the key factors for a good slip casting aluminous ceramic crown is good compatibility between its core material and the veneering porcelain.The chemical and thermal compatibility of two slip casting aluminous ceramic crown systems(In-Ceram and GI-I) were investigated by means of SEM and EDAX,thermal shock tests were also performed to evaluate the crazing resistance.The results showed: the crazing resistance of In-Ceram was 158 degrees centigrade,and that of GI-I was degrees centigrade;there existed tightly bonded interfaces between the slip casting aluminous ceramic cores and the veneering porcelains in both of the two systems,where ion transferences were found.The results also suggested good compatibility of the two slip casting aluminous ceramic crown systems. PMID:15159959

  17. Determination of neutron absorbed doses in lithium aluminates.

    PubMed

    Delfín Loya, A; Carrera, L M; Ureña-Núñez, F; Palacios, O; Bosch, P

    2003-04-01

    Lithium-based ceramics have been proposed as tritium breeders for fusion reactors. The lithium aluminate (gamma phase) seems to be thermally and structurally stable, the damages produced by neutron irradiation depend on the absorbed dose. A method based on the measurement of neutron activation of foils through neutron capture has been developed to obtain the neutron absorbed dose in lithium aluminates irradiated in the thermal column facility and in the fixed irradiation system of a Triga Mark III Nuclear Reactor. PMID:12672632

  18. Impact of welan gum on tricalcium aluminate-gypsum hydration

    SciTech Connect

    Ma Lei Zhao Qinglin Yao Chukang; Zhou Mingkai

    2012-02-15

    The retarding effect of welan gum on tricalcium aluminate-gypsum hydration, as a partial system of ordinary Portland cement (OPC) hydration, was investigated with several methods. The tricalcium aluminate-gypsum hydration behavior in the presence or absence of welan gum was researched by field emission gun scanning electron microscopy, X-ray diffraction and zeta potential analysis. Meanwhile, we studied the surface electrochemical properties and adsorption characteristics of welan gum by utilizing a zeta potential analyzer and UV-VIS absorption spectrophotometer. By adding welan gum, the morphology change of ettringite and retardation of hydration stages in tricalcium aluminate-gypsum system was observed. Moreover, we detected the adsorption behavior and zeta potential inversion of tricalcium aluminate and ettringite, as well as a rapid decrease in the zeta potential of tricalcium aluminate-gypsum system. The reduction on nucleation rate of ettringite and hydration activity of C{sub 3}A was also demonstrated. Thus, through the adsorption effect, welan gum induces a retarding behavior in tricalcium aluminate-gypsum hydration. Highlights: Black-Right-Pointing-Pointer Adsorption characteristics of welan gum on C{sub 3}A and ettringite have been studied. Black-Right-Pointing-Pointer C{sub 3}A-gypsum hydration behavior and the hydration products are examined in L/S = 3. Black-Right-Pointing-Pointer Welan gum retards the process of C{sub 3}A-gypsum hydration. Black-Right-Pointing-Pointer The addition of welan gum changes the nucleation growth of ettringite.

  19. Degradation of Multi-Layer Insulation (MLI) Retrieved from the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    Mohammed, Jelila S.; deGroh, Kim, K.

    2011-01-01

    Multi-Layer Insulation (MLI) returned during Servicing Mission 4 are still being analyzed. Analysis has revealed degradation of optical, thermal, and mechanical properties, increased crystallinity, and reduction in fluorine/carbon ratio of aluminized-Teflon fluorinated ethylene propylene (Al-FEP) FEP. These material properties can be affected by high temperatures on orbit, increased radiation exposure, and in some cases contamination from materials in close proximity to the insulation on orbit. Preliminary results support conclusions of previous studies: areas of Al-FEP that received higher levels of solar exposure show more degradation (high temperatures and radiation combined).

  20. 77 FR 48107 - Workshop on Performance Assessments of Near-Surface Disposal Facilities: FEPs Analysis, Scenario...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-13

    ... Radioactive Waste.'' These regulations were published in the Federal Register on December 27, 1982 (47 FR..., Environmental Protection and Performance Assessment Directorate, Division of Waste Management and Environmental...-Surface Disposal Facilities: FEPs Analysis, Scenario and Conceptual Model Development, and Code...

  1. A wood and bark fuel economics computer program (FEP). Forest service research paper

    SciTech Connect

    Harpole, G.B.; Ince, P.J.; Tschernitz, J.L.; Bilek, E.

    1982-09-01

    Forest products harvesting and manufacturing processes are expected to provide large and continuing supplies of wood and bark residues. At the same time, the demand for wood residue-type materials for production of wood-fiber based products as well as wood and bark fuels is expected to create competing utilization alternatives. Primary objectives of the fuel economics computer program (FEP) presented here are: (1) to provide a means for assessing the relative energy values of fossil fuels and wood/bark fuels, and (2) to provide pre-engineering assessments of the potential investment that may be justified by benefits gained through modification of systems to burn wood/bark fuels. The FEP computer program utilizes readily available fuel and economics information, standard combustion equations, and discounted cash flow analytic techniques. Because the FEP program is designed for preliminary assessments of wood/bark fuel use opportunities it is suggested that more advanced engineering and financial analytic methods be used for further evaluation whenever favorable venture likelihoods are indicated by the FEP program.

  2. Room temperature ferromagnetism in Teflon due to carbon dangling bonds

    NASA Astrophysics Data System (ADS)

    Ma, Y. W.; Lu, Y. H.; Yi, J. B.; Feng, Y. P.; Herng, T. S.; Liu, X.; Gao, D. Q.; Xue, D. S.; Xue, J. M.; Ouyang, J. Y.; Ding, J.

    2012-03-01

    The ferromagnetism in many carbon nanostructures is attributed to carbon dangling bonds or vacancies. This provides opportunities to develop new functional materials, such as molecular and polymeric ferromagnets and organic spintronic materials, without magnetic elements (for example, 3d and 4f metals). Here we report the observation of room temperature ferromagnetism in Teflon tape (polytetrafluoroethylene) subjected to simple mechanical stretching, cutting or heating. First-principles calculations indicate that the room temperature ferromagnetism originates from carbon dangling bonds and strong ferromagnetic coupling between them. Room temperature ferromagnetism has also been successfully realized in another polymer, polyethylene, through cutting and stretching. Our findings suggest that ferromagnetism due to networks of carbon dangling bonds can arise in polymers and carbon-based molecular materials.

  3. Durability of monopolar Teflon-coated electromyographic needles.

    PubMed

    Mikolich, L M; Waylonis, G W

    1977-10-01

    The results of a two-year study on durability and cause of failure of electromyographic monopolar electrodes are reported. The electrodes were obtained from the regular stock of three different manufacturing sources. Durability is defined on the basis of the number of patients that could be examined before failure. The range was 3 to 110 with the averages 19.7, 33.8, and 62.5 for the three different manufacturers. Common causes of electrode failure included: Teflon retraction, 40.6%; tip dullness or burrs, 34.8%; structural failure of wire or pin, 13.1%; electrical artifacts, 9.7%; and bending of needle shank, 5.7%. Variations in manufactures' tip contour and bevel correlated with tip durability. PMID:907451

  4. Effective ultraviolet irradiation of platelet concentrates in teflon bags

    SciTech Connect

    Capon, S.M.; Sacher, R.A.; Deeg, H.J. )

    1990-10-01

    Several plastic materials used in blood storage were evaluated for their ability to transmit ultraviolet B (UVB) light. A plastic bag manufactured from sheets of transparent Teflon efficiently (78-86%) transmitted UVB light and was employed in subsequent functional studies of lymphocytes and platelets exposed to UVB light while contained in these bags. In vitro experiments showed a UVB dose-dependent abrogation of lymphocyte responder and stimulator functions, with concurrent preservation of platelet aggregation responses. In a phase I pilot study, UVB-treated platelet concentrates were administered to four bone marrow transplant recipients. Adverse effects attributable to the transfusions were not observed, and patients showed clinically effective transfusion responses. No patient developed lymphocytotoxic HLA or platelet antibodies. These studies suggest that platelets can be effectively irradiated with UVB light in a closed system. However, numerous variables, including container material, volume and composition of contents, steady exposure versus agitation, and exact UV wavelength, must be considered.

  5. Electrical properties of teflon and ceramic capacitors at high temperatures

    NASA Technical Reports Server (NTRS)

    Hammoud, A. N.; Baumann, E. D.; Myers, I. T.; Overton, E.

    1992-01-01

    Space power systems and components are often required to operate efficiently and reliably in harsh environments where stresses, such as high temperature, are encountered. These systems must, therefore, withstand exposure to high temperature while still providing good electrical and other functional properties. Experiments were carried out to evaluate Teflon and ceramic capacitors for potential use in high temperature applications. The capacitors were characterized in terms of their capacitance and dielectric loss as a function of temperature, up to 200 C. At a given temperature, these properties were obtained in a frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also performed in a temperature range from 25 to 200 C. The results obtained are discussed and conclusions are made concerning the suitability of the capacitors studied for high temperature applications.

  6. Heat-enhanced peptide synthesis on Teflon-patterned paper.

    PubMed

    Deiss, Frédérique; Yang, Yang; Matochko, Wadim L; Derda, Ratmir

    2016-06-14

    In this report, we describe the methodology for 96 parallel organic syntheses of peptides on Teflon-patterned paper assisted by heating with an infra-red lamp. SPOT synthesis is an important technology for production of peptide arrays on a paper-based support for rapid identification of peptide ligands, epitope mapping, and identification of bio-conjugation reactions. The major drawback of the SPOT synthesis methodology published to-date is suboptimal reaction conversion due to mass transport limitations in the unmixed reaction spot. The technology developed in this report overcomes these problems by changing the environment of the reaction from static to dynamic (flow-through), and further accelerating the reaction by selective heating of the reaction support in contact with activated amino acids. Patterning paper with Teflon allows for droplets of organic solvents to be confined in a zone on the paper array and flow through the paper at a well-defined rate and provide a convenient, power-free setup for flow-through solid-phase synthesis and efficient assembly of peptide arrays. We employed an infra-red (IR) lamp to locally heat the cellulosic support during the flow-through delivery of the reagents to each zone of the paper-based array. We demonstrate that IR-heating in solid phase peptide synthesis shortened the reaction time necessary for amide bond formation down to 3 minutes; in some couplings of alpha amino acids, conversion rates increased up to fifteen folds. The IR-heating improved the assembly of difficult sequences, such as homo-oligomers of all 20 natural amino acids. PMID:27184468

  7. Secondary electron emission from electrically charged fluorinated-ethylene-propylene Teflon for normal and non-normal electron incidence. M.S. Thesis; [spacecraft thermal coatings

    NASA Technical Reports Server (NTRS)

    Budd, P. A.

    1981-01-01

    The secondary electron emission coefficient was measured for a charged polymer (FEP-Teflon) with normally and obliquely incident primary electrons. Theories of secondary emission are reviewed and the experimental data is compared to these theories. Results were obtained for angles of incidence up to 60 deg in normal electric fields of 1500 V/mm. Additional measurements in the range from 50 to 70 deg were made in regions where the normal and tangential fields were approximately equal. The initial input angles and measured output point of the electron beam could be analyzed with computer simulations in order to determine the field within the chamber. When the field is known, the trajectories can be calculated for impacting electrons having various energies and angles of incidence. There was close agreement between the experimental results and the commonly assumed theoretical model in the presence of normal electric fields for angles of incidence up to 60 deg. High angle results obtained in the presence of tangential electric fields did not agree with the theoretical models.

  8. Mechanical strength and stability of lithium aluminate

    NASA Astrophysics Data System (ADS)

    Brimhall, J. L.

    1992-06-01

    Pacific Northwest Laboratory (PNL) investigated the strength and resistance to thermal shock of lithium aluminate annular pellets. The room temperature, axial compressive fracture strength of pellets made at Westinghouse Advanced Energy Systems (WAES) varied from 80 to 133 ksi. The strength at 430 C (806 F) was to 30 to 40 percent lower. The strength at 900 C (1652 F) showed a wide variation with one measurement near 90 ksi. These strength values are consistent with other data and predictions made in the literature when the grain size and porosity of the microstructure are taken into account. In diametral compression tests, the fracture strengths were much lower due to the existence of tensile stresses in some pellet regions from this type of loading. However, the fracture stresses were still generally higher than those reported in the literature; this fracture resistance probably reflects the better quality of the pellets tested in this study. Measurements on pellets made at PNL indicated lower strengths compared to the WAES material. This strength difference could be accounted for by different processing technologies: material made at PNL was cold-pressed and sintered with high porosity whereas the WAES material was isostatically hot-pressed with high density. Thermal shocking of the material by ramping to 900 C in two minutes did not have an observable effect on the microstructure or the strength of any of the pellets.

  9. Modeling spherical explosions with aluminized energetic materials

    NASA Astrophysics Data System (ADS)

    Massoni, J.; Saurel, R.; Lefrançois, A.; Baudin, G.

    2006-11-01

    This paper deals with the numerical solution and validation of a reactive flow model dedicated to the study of spherical explosions with an aluminized energetic material. Situations related to air blast as well as underwater explosions are examined. Such situations involve multiscale phenomena associated with the detonation reaction zone, the aluminium reaction zone, the shock propagation distance and the bubble oscillation period. A detonation tracking method is developed in order to avoid the detonation structure computation. An ALE formulation is combined to the detonation tracking method in order to solve the material interface between detonation products and the environment as well as shock propagation. The model and the algorithm are then validated over a wide range of spherical explosions involving several types of explosives, both in air and liquid water environment. Large-scale experiments have been done in order to determine the blast wave effects with explosive compositions of variable aluminium content. In all situations the agreement between computed and experimental results is very good.

  10. Mechanical strength and stability of lithium aluminate

    SciTech Connect

    Brimhall, J.L.

    1992-06-01

    Pacific Northwest Laboratory (PNL) investigated the strength and resistance to thermal shock of lithium aluminate annular pellets. The room temperature, axial compressive fracture strength of pellets made at Westinghouse Advanced Energy Systems (WAES) varied from 80 to 133 ksi. The strength at 430{degrees}C (806{degrees}F) was to 30 to 40% lower. The strength at 900{degrees}C (1652{degrees}F) showed a wide variation with one measurement near 90 ksi. These strength values are consistent with other data and predictions made in the literature when the grain size and porosity of the microstructure are taken into account. In diametral compression tests, the fracture strengths were much lower due to the existence of tensile stresses in some pellet regions from this type of loading. However, the fracture stresses were still generally higher than those reported in the literature; this fracture resistance probably reflects the better quality of the pellets tested in this study. Measurements on pellets made at PNL indicated lower strengths compared to the WAES material. This strength difference could be accounted for by different processing technologies: material made at PNL was cold-pressed and sintered with high porosity whereas the WAES material was isostatically hot-pressed with high density. Thermal shocking of the material by ramping to 900{degrees}C in two minutes did not have an observable effect on the microstructure or the strength of any of the pellets.

  11. Neutron irradiation of polycrystalline yttrium aluminate garnet, magnesium aluminate spinel and α-alumina.

    NASA Astrophysics Data System (ADS)

    Neeft, E. A. C.; Konings, R. J. M.; Bakker, K.; Boshoven, J. G.; Hein, H.; Schram, R. P. C.; van Veen, A.; Conrad, R.

    1999-08-01

    Polycrystalline pellets of yttrium aluminate garnet (Y 3Al 5O 12), magnesium aluminate spinel (MgAl 2O 4) and α-alumina (α-Al 2O 3) have been irradiated in the high flux reactor (HFR) at Petten to a neutron fluence of 1.7 × 10 26 m -2 ( E>0.1 MeV) at a temperature of about 815 K. Volume changes smaller than 1% have been measured for Y 3Al 5O 12 and MgAl 2O 4. Transmission electron microscopy (TEM) results of Y 3Al 5O 12 show no difference between the unirradiated TEM samples and neutron-irradiated samples. For MgAl 2O 4, dislocation loops in some grains are found in the irradiated samples. TEM results of Al 2O 3 show a dense network of dislocation loops after neutron irradiation. The increase in volume is 4.2% for a neutron fluence of 1.7 × 10 26 m -2.

  12. FT-IR TRANSMISSION SPECTROSCOPY FOR QUANTITATION OF AMMONIUM BISULFATE IN FINE PARTICULATE MATTER COLLECTED ON TEFLON FILTERS

    EPA Science Inventory

    A quantitative measurement method for fine particle bisulfatein ammonium bisulfate collected from the ambient air onto Teflon filters is described. nfrared absorbance measurements of the Teflon filters are made before and after particle collection. ubtraction of the two spectra r...

  13. Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

    SciTech Connect

    Orosco, Pablo; Barbosa, Lucía; Ruiz, María del Carmen

    2014-11-15

    Highlights: • Use of chlorination for the synthesis of magnesium aluminate spinel. • The reagents used were alumina, periclase and chlorine. • Isothermal and non-isothermal assays were performed in air and Cl{sub 2}–N{sub 2} flows. • The chlorination produced magnesium aluminate spinel at 700 °C. • Selectivity of the chlorination reaction to obtain spinel is very high. - Abstract: A pyrometallurgical route for the synthesis of magnesium aluminate spinel by thermal treatment of a mechanical mixture containing 29 wt% MgO (periclase) and 71 wt% Al{sub 2}O{sub 3} (alumina) in chlorine atmosphere was developed and the results were compared with those obtained by calcining the same mixture of oxides in air atmosphere. Isothermal and non-isothermal assays were performed in an experimental piece of equipment adapted to work in corrosive atmospheres. Both reagents and products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD) and X-ray fluorescence (XRF). Thermal treatment in Cl{sub 2} atmosphere of the MgO–Al{sub 2}O{sub 3} mixture produces magnesium aluminate spinel at 700 °C, while in air, magnesium spinel is generated at 930 °C. The synthesis reaction of magnesium aluminate spinel was complete at 800 °C.

  14. Surface Modification of Nickel Foams by a Slurry Aluminizing Process

    SciTech Connect

    Omar, H.; Papanastasiou, N.; Psyllaki, P.; Stergioudi, F.; Tsipas, D. N.; Tsipas, S. A.; Michailidis, N.

    2010-01-21

    A novel slurry-based process for aluminizing nickel foams while improving the mechanical properties and conserving the excellent ductility is reported. Cellular unalloyed nickel foams with 92% porosity and uniform pore size and distribution were used as a starting material. Several slurries of different compositions were examined to investigate the possibility of developing an aluminide-nickel intermetallic coating on a Ni foam without considerably degrading the original ductile properties of the foam. The process temperature was varying from 400 to 850 deg. C and the process holding time was ranging between 2h to 6h. Scanning electron microscopy with an energy dispersive X-ray spectrometry and X-Ray diffraction were applied to assess the effectiveness of the aluminizing process and determine both the optimum parameters of the procedure (slurry composition, holding temperature and time) and the concentration profiles across the coating cross-section. The mechanical behavior of the aluminized Ni-foams was evaluated by the conduction of micro-tension tests. The resulting Ni-foams after aluminization retain the pore structure of original Ni-foams and present a thick outer surface layer which consists of a range of aluminide phases. The mechanical properties of the Ni-foams aluminized in low process temperature were insignificantly affected.

  15. Fault Tree, Event Tree, and Piping and Instrumentation Diagram (FEP) editors, Version 4.0. Reference manual

    SciTech Connect

    McKay, M.K.; Skinner, N.L.; Wood, S.T.

    1992-05-01

    The Fault Tree, Event Tree, and Piping & Instrumentation Diagram (FEP) editors allow the user to graphically build and edit fault trees, event trees, and piping & instrumentation diagrams (P & IDs). The software is designed to enable the use of graphical-based editors found in the Integrated Reliability and Risk Assessment System (IRRAS). FEP is made up of three separate editors (Fault Tree, Event Tree, and Piping & Instrumentation Diagram) and a utility module. This reference manual provides a screen-by-screen walkthrough of the entire FEP System.

  16. Actinide-Aluminate Speciation in Alkaline Radioactive Waste

    SciTech Connect

    Dr. David L. Clark; Dr. Alexander M. Fedosseev

    2001-12-21

    Investigation of behavior of actinides in alkaline media containing AL(III) showed that no aluminate complexes of actinides in oxidation states (IIII-VIII) were formed in alkaline solutions. At alkaline precipitation IPH (10-14) of actinides in presence of AL(III) formation of aluminate compounds is not observed. However, in precipitates contained actinides (IIV)<(VI), and to a lesser degree actinides (III), some interference of components takes place that is reflected in change of solid phase properties in comparison with pure components or their mechanical mixture. The interference decreases with rise of precipitation PH and at PH 14 is exhibited very feebly. In the case of NP(VII) the individual compound with AL(III) is obtained, however it is not aluminate of neptunium(VII), but neptunate of aluminium(III) similar to neptunates of other metals obtained earlier.

  17. Parallel Syntheses of Peptides on Teflon-Patterned Paper Arrays (SyntArrays).

    PubMed

    Deiss, Frédérique; Yang, Yang; Derda, Ratmir

    2016-01-01

    Screening of peptides to find the ligands that bind to specific targets is an important step in drug discovery. These high-throughput screens require large number of structural variants of peptides to be synthesized and tested. This chapter describes the generation of arrays of peptides on Teflon-patterned sheets of paper. First, the protocol describes the patterning of paper with a Teflon solution to produce arrays with solvophobic barriers that are able to confine organic solvents. Next, we describe the parallel syntheses of 96 peptides on Teflon-patterned arrays using the SPOT synthesis method. PMID:26614081

  18. Development of aluminized coatings for MCFC wet seal applications

    SciTech Connect

    Yuh, C.Y.; Singh, P.; Paetsch, L.; Maru, H.C.

    1987-01-01

    The molten carbonate fuel cell (MCFC) wet seal are has been found to experience accelerated corrosion in the presence of molten electrolyte because of simultaneous exposure to reducing and oxidizing atmospheres. Development of protective coatings plays an important role in minimizing this corrosion. Various aluminizing processes, such as flame spraying, slurry spraying, pack cementation, and ion vapor deposition, have been evaluated for their effectiveness. Continuous interdiffusion of aluminum and substrate Fe, Ni, and Cr occurred during high-temperature corrosion tests. Among the four aluminizing methods, ion-vapor deposition (IVD) with subsequent diffusion bonding appears to provide the most protective coating in the MCFC wet seal environment.

  19. Limestone reaction in calcium aluminate cement–calcium sulfate systems

    SciTech Connect

    Bizzozero, Julien Scrivener, Karen L.

    2015-10-15

    This paper reports a study of ternary blends composed of calcium aluminate cement, calcium sulfate hemihydrate and limestone. Compressive strength tests and hydration kinetics were studied as a function of limestone and calcium sulfate content. The phase evolution and the total porosity were followed and compared to thermodynamic simulation to understand the reactions involved and the effect of limestone on these binders. The reaction of limestone leads to the formation of hemicarboaluminate and monocarboaluminate. Increasing the ratio between sulfate and aluminate decreases the extent of limestone reaction.

  20. Improvements in UV stability for FEP/Ag based thermal control materials

    NASA Astrophysics Data System (ADS)

    Grieser, James; Maas, Gerald

    2003-09-01

    Darkening of FEP/Ag based Thermal Control (TC) materials after UV exposure has been documented for several years. This End of Life (EOL) Solar Absorptance (α) increase and the corresponding performance degradation must be taken into account in the preliminary design of spacecraft. Astral Technology Unlimited, Inc. (ATU) has developed new processes and coatings to improve the UV stability of FEP/Ag based TC materials. Test results of this development effort are presented. Data for several new coating combinations along with data on the current "Industry Standard" material are compared for up to 27,000 Equivalent Sun Hours (ESH) of UV exposure. The resulting solar absorptance improvements are very dramatic and should allow future satellite designs with the EOL solar alpha to be nearly identical to the Beginning of Life (BOL) values. Satellites using these new TC materials can have optimum thermal-optical performance for the life of the spacecraft.

  1. Development of sulfonated FEP Nafion hybrid proton exchange membranes for PEFC

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Fujii, K.; Mitani, N.; Matsuura, A.; Kakigi, T.; Muto, F.; Li, J.; Oshima, A.; Washio, M.

    2007-12-01

    The performance of polymer electrolyte fuel cell (PEFC) is affected by an interfacial property between a proton exchange membrane (PEM) and electrodes. Thus, to develop a well-laminated membrane electrode assembly (MEA), a hybrid PEM (FN) was fabricated by mixing a radiation grafted membrane (sulfonated FEP) with ionomer (Nafion ® dispersion) which is applied to coat the interface of the PEM and electrodes. The obtained FN, sulfonated FEP and Nafion ®112 were characterized in terms of water uptake, ion exchange capacity (IEC), polarization performance and electrochemical impedance. FN showed high IEC and water uptake, which would induce the highest ionic conductivity (IC) among tested PEMs. In terms of FN, the interface between the PEM and electrodes should have been improved because FN showed the lowest charge transfer resistance than other tested PEMs. The high IC and improved interface between the PEM and electrodes resulted in the best cell performance of FN in tested PEMs.

  2. IMPACT OF INCREASED ALUMINATE CONCENTRATIONS ON PROPERTIES OF SALTSTONE MIXES

    SciTech Connect

    Harbour, J; Tommy Edwards, T; Erich Hansen, E; Vickie Williams, V

    2007-10-12

    One of the goals of the Saltstone variability study is to identify the operational and compositional variables that control or influence the important processing and performance properties of Saltstone mixes. The protocols developed in this variability study are ideally suited as a tool to assess the impact of proposed changes to the processing flow sheet for Liquid Waste Operations (LWO). One such proposal that is currently under consideration is to introduce a leaching step in the treatment of the High Level Waste (HLW) sludge to remove aluminum prior to vitrification at the Defense Waste Processing Facility (DWPF). This leachate would significantly increase the soluble aluminate concentrations as well as the free hydroxide ion concentration in the salt feed that will be processed at the Saltstone Processing Facility (SPF). Consequently, an initial study of the impact of increased aluminate concentration on the Saltstone grout properties was performed. The projected compositions and ranges of the aluminate rich salt stream (which includes the blending strategy) are not yet available and consequently, in this initial report, two separate salt stream compositions were investigated. The first stream starts with the previously projected baseline composition of the salt solution that will be fed to SPF from the Salt Waste Processing Facility (SWPF). The second stream is the solution that results from washing of the current Tank 51 sludge and subsequent transfer of the salt solution to Tank 11. The SWPF simulant has higher nitrate and lower free hydroxide than the Tank 11 simulant. In both of these cases, the aluminate was varied up to a maximum of 0.40 to 0.45M aluminate in order to evaluate the impact of increasing aluminate ion concentration on the grout properties. In general, the fresh grout properties of mixes made with SWPF and Tank 11 simulants were relatively insensitive to an increase in aluminate concentration in the salt solutions. However, the overall

  3. Passive immunization by recombinant ferric enterobactin protein (FepA) from Escherichia coli O157

    PubMed Central

    Larrie-Bagha, Seyed Mehdi; Rasooli, Iraj; Mousavi-Gargari, Seyed Latif; Rasooli, Zohreh; Nazarian, Shahram

    2013-01-01

    Background and Objectives Enterohemorrhagic Escherichia coli (EHEC) O157:H7 has been recognized as a major food borne pathogen responsible for frequent hemorrhagic colitis and hemolytic uremic syndrome in humans. Cattle are important reservoirs of E. coli O157:H7, in which the organism colonizes the intestinal tract and is shed in the feces. Objective Vaccination of cattle has significant potential as a pre-harvest intervention strategy for E. coli O157:H7. The aim of this study was to evaluate active and passive immunization against E. coli O157:H7 using a recombinant protein. Materials and Methods The recombinant FepA protein induced by IPTG was purified by nickel affinity chromatography. Antibody titre was determined by ELISA in FepA immunized rabbits sera. Sera collected from vaccinated animals were used for bacterial challenge in passive immunization studies. Results The results demonstrate that passive immunization with serum raised against FepA protects rabbits from subsequent infection. Conclusion Significant recognition by the antibody of ferric enterobactin binding protein may lead to its application in the restriction of Enterobacteriaceae propagation. PMID:23825727

  4. Theoretical study of atomic transport via interstitials in dilute Fe-P alloys

    NASA Astrophysics Data System (ADS)

    Meslin, E.; Fu, Chu-Chun; Barbu, A.; Gao, F.; Willaime, F.

    2007-03-01

    By combining density functional theory, empirical potential, and atomic transport model approaches, we investigate the energetics and the diffusion properties of P interstitials in dilute Fe-P alloys. Although P is a substitutional impurity in α -iron, when a self-interstitial atom (SIA) approaches a substitutional P, the P atom becomes interstitial with an energy gain of up to 1.0eV . The octahedral and the ⟨110⟩ mixed dumbbell are the lowest-energy configurations with similar stabilities. The P atoms are highly mobile in both configurations. The transitions between these two configurations also require low activation energies. The most likely mechanisms leading to long-distance diffusion of a P interstitial are proposed by ab initio calculations. The resulting effective diffusion energy estimated by the transport model is 0.19eV , which agrees with the result from resistivity recovery experiments, suggesting that the Fe-P mixed dumbbells are more mobile than the SIAs. The fast-migrating P interstitial can be deeply trapped by a substitutional P atom. The resulting complexes are very stable with a binding energy of around 1.0eV . Their mobilities are investigated by means of the dimer method using an Fe-P empirical potential. A comparison between the present predictions and existing experimental results is also discussed.

  5. Evidence of Ball-and-chain Transport of Ferric Enterobactin through FepA*

    PubMed Central

    Ma, Li; Kaserer, Wallace; Annamalai, Rajasekeran; Scott, Daniel C.; Jin, Bo; Jiang, Xiaoxu; Xiao, Qiaobin; Maymani, Hossein; Massis, Liliana Moura; Ferreira, Luiz C. S.; Newton, Salete M. C.; Klebba, Phillip E.

    2008-01-01

    The Escherichia coli iron transporter, FepA, has a globular N terminus that resides within a transmembrane β-barrel formed by its C terminus. We engineered 25 cysteine substitution mutations at different locations in FepA and modified their sulfhydryl side chains with fluorescein maleimide in live cells. The reactivity of the Cys residues changed, sometimes dramatically, during the transport of ferric enterobactin, the natural ligand of FepA. Patterns of Cys susceptibility reflected energy- and TonB-dependent motion in the receptor protein. During transport, a residue on the normally buried surface of the N-domain was labeled by fluorescein maleimide in the periplasm, providing evidence that the transport process involves expulsion of the globular domain from the β-barrel. Porin deficiency much reduced the fluoresceination of this site, confirming the periplasmic labeling route. These data support the previously proposed, but never demonstrated, ball-and-chain theory of membrane transport. Functional complementation between a separately expressed N terminus and C-terminal β-barrel domain confirmed the feasibility of this mechanism. PMID:17056600

  6. Analysis of Ag/FEP Control Blanket Performance from Multiple Satellites

    NASA Technical Reports Server (NTRS)

    Pippin, H. G.; Normand, E.; Wol, S. L.

    2001-01-01

    Published data reporting the change in solar absorptance as a function of time on orbit for certain satellites has been re-examined. The optical property change of metallized FEP as a function of total particulate radiation dose received by specific satellites has been estimated. Results tend to follow a common trend and a design curve has been constructed to estimate solar absorptance change as a function of radiation dose for metallized FEP at any altitude. Effects due to apparent contamination on several of the satellites are addressed and taken into account in determining property changes. Data from LDEF, ML-101, NavStar 1-5, NTS-2, the SCATHA experiment, and SOLRAD 11 are used as the basis of the design curve. A similar comparison is made between published atomic oxygen recession data from numerous Space Shuttle flights, a LEO experiment flown by Lockheed, and LDEF results. Variation of atomic oxygen recession rate of FEP as a function of exposure conditions is determined.

  7. Evaluation of non-specular reflecting silvered Teflon and filled adhesives

    NASA Technical Reports Server (NTRS)

    Bourland, G.; Cox, R. L.

    1981-01-01

    A non-specular silver-Teflon tape thermal control coating was tested to provide the data necessary to qualify it for use on the Space Shuttle Orbiter radiators. Effects of cure cycle temperature and pressure on optical and mechanical properties on the silver-Teflon tape were evaluated. The baseline Permacel P-223 adhesive, used with the specular silver-Teflon tape initially qualified for the Orbiter radiators, and four alternate metal-filled and unfilled adhesives were evaluated. Tests showed the cure process has no effect on the silver-Teflon optical properties, and that the baseline adhesive cure cycle gives best results. In addition the P-223 adhesive bond is more reproducible than the alternates, and the non-specular tape meets both the mechanical and the optical requirements of the Orbiter radiator coating specification. Existing Orbiter coating techniques were demonstrated to be effective in aplying the non-specular tape to a curved panel simulating the radiators. Author

  8. Deposition of superhydrophobic nanostructured Teflon-like coating using expanding plasma arc

    NASA Astrophysics Data System (ADS)

    Satyaprasad, A.; Jain, V.; Nema, S. K.

    2007-04-01

    A novel approach was used to grow nanostructured Teflon-like superhydrophobic coatings on stainless steel (SS). In this method Teflon tailings were pyrolyzed to generate fluorocarbon precursor molecules, and an expanding plasma arc (EPA) was used to polymerize these precursors to deposit Teflon-like coating. The coating shows super hydrophobic behavior with water contact angle (WCA) of 165°. The coating was observed to be uniform. It consists of nanostructured (˜80-200 nm) features, which were confirmed by scanning electron microscopy. The chemical bond state of the film was determined by XPS and FTIR, which indicate the dominance of -CF 2 groups in the deposited coating. The combination of nanofeature induced surface roughness and the low surface energy imparted by Teflon-like coating is responsible for the observed superhydrophobic nature.

  9. The development of an inert simulant for HNS/teflon explosive

    NASA Technical Reports Server (NTRS)

    Elban, W. L.

    1972-01-01

    The report describes the development and evaluation of an inert simulant for the thermally stable, heat-resistant plastic-bonded explosive HNS/Teflon. The simulant is made by dry blending vinylidene fluoride, melamine and Teflon which when compared has a pressed density and thermal properties corresponding closely to the explosive. In addition, the machinability and handling characteristics of the simulant are similar to the explosive.

  10. FINAL REPORT. ACTINIDE-ALUMINATE SPECIATION IN ALKALINE RADIOACTIVE WASTE

    EPA Science Inventory

    Investigation of behavior of actinides in alkaline media containing Al(III) showed that no aluminate complexes of actinides in oxidation states (III-VII) were formed in alkaline solutions. At alkaline precipitation (pH 10-14) of actinides in presence of Al(III) formation of alumi...

  11. SINTERING AND SULFATION OF CALCIUM SILICATE-ALUMINATE

    EPA Science Inventory

    The effect of sintering on the reactivity of solids at high temperature was studied. The nature of the interaction was studied with calcium silicate-aluminate reacting with SO2 between 665 and 800 C. The kinetics of the sintering and sulfation processes were measured independentl...

  12. A phase-field study of the aluminizing of nickel

    NASA Astrophysics Data System (ADS)

    Philippe, T.; Erdeniz, D.; Dunand, D. C.; Voorhees, P. W.

    2015-03-01

    A quantitative phase-field approach for multiphase systems that is based upon CALPHAD free energies is used to model the aluminization of nickel wires, wherein vapour-phase alloying is used to deposit Al on the surface of the Ni wire and then the wire is annealed so that to remove all Al gradients and achieve a homogenous Ni-Al alloy. Both processes are modelled and numerical results are compared with experiments. It is found that the kinetics of both processes is controlled by bulk diffusion. During aluminization at 1273 K, formation and growth of intermetallics, Ni2Al3 NiAl and Ni3Al, are strongly dependent on the Al content in the vapour phase. Ni2Al3 growth is very fast compared with NiAl and Ni3Al. It is also found that an intermediate Al content in the vapour phase is preferable for aluminization, since the Ni2Al3 coating thickness is difficult to control. Ni2Al3 is found to disappear in a few minutes during homogenization at 1373 K. Thereafter, the NiAl phase, in which the composition is highly non-uniform after aluminization, continues growing until the supersaturation in this phase vanishes. Then, NiAl coating disappears concomitantly with the growth of Ni3Al, which disappears thereafter. Finally, the Al concentration profile in Ni(Al) homogenizes.

  13. SINTERING AND SULFATION OF CALCIUM SILICATE-ALUMINATE

    EPA Science Inventory

    The paper gives results of a study of the effect of sintering on the reactivity of solids at high temperature. he nature of the interaction was studied with calcium silicate-aluminate reacting with SO2 between 665 and 800 C, where sintering progresses rapidly. The kinetics of the...

  14. DNA adsorption onto calcium aluminate and silicate glass surfaces.

    PubMed

    Carlson, Krista; Flick, Lisa; Hall, Matthew

    2014-05-01

    A common technique for small-scale isolation of genomic DNA is via adsorption of the DNA molecules onto a silica scaffold. In this work, the isolation capacities of calcium aluminate based glasses were compared against a commercially available silica scaffold. Silica scaffolds exhibit a negative surface at the physiological pH values used during DNA isolation (pH 5-9), while the calcium aluminate glass microspheres exhibit a positive surface charge. Isolation data demonstrates that the positively charged surface enhanced DNA adsorption over the negatively charged surface. DNA was eluted from the calcium aluminate surface by shifting the pH of the solution to above its IEP at pH 8. Iron additions to the calcium aluminate glass improved the chemical durability without compromising the surface charge. Morphology of the glass substrate was also found to affect DNA isolation; 43-106 μm diameter soda lime silicate microspheres adsorbed a greater quantity of genomic DNA than silica fibers with an average diameter of ∼2 μm. PMID:24309135

  15. The effect of Teflon coating on the resistance to sliding of orthodontic archwires.

    PubMed

    Farronato, Giampietro; Maijer, Rolf; Carìa, Maria Paola; Esposito, Luca; Alberzoni, Dario; Cacciatore, Giorgio

    2012-08-01

    Teflon is an anti-adherent and aesthetic material. The aim of this study was to evaluate, in vitro, the influence of Teflon coating on the resistance to sliding (RS) of orthodontic archwires. For this purpose, Teflon-coated archwires were examined using frictional resistance tests by means of a universal testing machine and compared with conventional uncoated wires. Twelve types of archwires with round and rectangular sections (0.014, 0.018, and 0.018 × 0.025 inches) and of different materials (stainless steel and nickel-titanium) were tested with two passive self-ligating brackets (SmartClip™ and Opal(®)) and one active self-ligating bracket (Quick(®)). Each archwire-bracket combination was tested 10 times under 8 simulated clinical scenarios. Statistical comparisons were conducted between the uncoated and Teflon-coated archwires using Wilcoxon and Mann-Whitney tests, and linear regression analysis. For all bracket-archwire combinations, Teflon-coated archwires resulted lower friction than the corresponding uncoated archwires (P < 0.01). The results showed that Teflon coating has the potential to reduce RS of orthodontic archwires. PMID:21478301

  16. Application of FEPs analysis to identify research priorities relevant to the safety case for an Australian radioactive waste facility

    SciTech Connect

    Payne, T.E.; McGlinn, P.J.

    2007-07-01

    The Australian Nuclear Science and Technology Organisation (ANSTO) has established a project to undertake research relevant to the safety case for the proposed Australian radioactive waste facility. This facility will comprise a store for intermediate level radioactive waste, and either a store or a near-surface repository for low-level waste. In order to identify the research priorities for this project, a structured analysis of the features, events and processes (FEPs) relevant to the performance of the facility was undertaken. This analysis was based on the list of 137 FEPs developed by the IAEA project on 'Safety Assessment Methodologies for Near Surface Disposal Facilities' (ISAM). A number of key research issues were identified, and some factors which differ in significance for the store, compared to the repository concept, were highlighted. For example, FEPs related to long-term groundwater transport of radionuclides are considered to be of less significance for a store than a repository. On the other hand, structural damage from severe weather, accident or human interference is more likely for a store. The FEPs analysis has enabled the scientific research skills required for the inter-disciplinary project team to be specified. The outcomes of the research will eventually be utilised in developing the design, and assessing the performance, of the future facility. It is anticipated that a more detailed application of the FEPs methodology will be undertaken to develop the safety case for the proposed radioactive waste management facility. (authors)

  17. Higher stabilities of positive and negative charge on tetrafluoroethylene-hexafluoropropylene copolymer (FEP) electrets treated with titanium-tetrachloride vapor

    NASA Astrophysics Data System (ADS)

    Rychkov, D.; Rychkov, A.; Efimov, N.; Malygin, A.; Gerhard, R.

    2013-08-01

    Tetrafluoroethylene-hexafluoropropylene copolymer (FEP) films were treated with titanium-tetrachloride vapor in a molecular-layer deposition process. As a result of the surface treatment, significant improvements of the thermal and temporal charge stability were observed. Charge-decay measurements revealed enhancements of the half-value temperatures and the relaxation times of positively charged FEP electrets by at least 120 °C and two orders of magnitude, respectively. Beyond previous publications on fluoropolymer electrets with surface modification, we here report enhanced charge stabilities of the FEP films charged in negative as well as in positive corona discharges. Even though the improvement for negatively charged FEP films is moderate (half-value temperature about 20 °C higher), our experiments show that the asymmetry in positive and negative charge stability that is typical for FEP electrets can be overcome by means of chemical surface treatments. The results are discussed in the context of the formation of modified surface layers with enhanced charge-trapping properties.

  18. Bonding of teflon to metals. (Latest citations from the Rubber and Plastics Research Association database). Published Search

    SciTech Connect

    Not Available

    1994-04-01

    The bibliography contains citations concerning the adhesion of Teflon to metal. Adhesion strength, bond mechanisms, and the effects on friction and lubrication are discussed. Metal films applied to Teflon products and Teflon films joined to metal are discussed. Joining processes, surface treatments, and reasons for failure are examined. Applications discussed include bearings, pipe linings, and bridge coatings. (Contains a minimum of 75 citations and includes a subject term index and title list.)

  19. [Teflon granuloma after microvascular decompression of the trigeminal nerve root in a patient with recurrent trigeminal neuralgia].

    PubMed

    Rzaev, D A; Kulikova, E V; Moysak, G I; Voronina, E I; Ageeva, T A

    2016-01-01

    The use of a Teflon implant for Jannetta surgery in patients with trigeminal neuralgia is complicated in rare cases by the development of a Teflon granuloma and can cause recurrent facial pain. The article presents a clinical case of a Teflon granuloma developed after microvascular decompression of the trigeminal nerve root, describes the surgical findings and histological picture, and analyzes the literature, causes of granuloma development, and recommendations for treatment of these patients. PMID:27070261

  20. Convenient surface functionalization of whole-Teflon chips with polydopamine coating

    PubMed Central

    Shen, Bo; Xiong, Bin; Wu, Hongkai

    2015-01-01

    This paper presents a convenient strategy to modify the surface of whole-Teflon microfluidic chips by coating the channel walls with a thin layer of polydopamine (PDA) film, which is formed by oxidation-induced self-polymerization of dopamine in alkaline solution. Two coating strategies, static incubation and dynamic flow, are demonstrated and used for tuning the physical and chemical properties of the coated channel walls. The functionalized surfaces were investigated with the contact angle, X-ray photoelectron spectroscopy, and atomic force microscopy measurements. The coating time was optimized according to the fluorescent intensity of the green fluorescent protein immobilized on the modified surface. Applications of the PDA-modified Teflon microchips in bioanalysis were demonstrated with a typical sandwich immunoassay. Moreover, long-term cell culture experiments on modified and native Teflon chips revealed that the chip biocompatibility can be greatly improved with PDA coating. The results indicate that the surface properties of the Teflon can be easily controlled by the PDA modification, thus greatly expanding the application scope of whole-Teflon chips for various chemical and biological research fields. PMID:26339312

  1. Nylon and teflon scribe effect on NBR to Chemlok 233 and NBR to NBR bond interfaces

    NASA Technical Reports Server (NTRS)

    Jensen, S. K.

    1990-01-01

    A study was requested by Manufacturing Engineering to determine what effects marking with nylon (6/6) and Teflon scribes may have on subsequent bonding. Witness panel bond specimens were fabricated by the development lab to test both acrylonitrile butadiene rubber (NBR) to Chemlok and NBR to NBR after controlled exposure. The nylon rod used as a scribe tool demonstrates virtually no bond deterioration when used to scribe lines on either the Chemlok to NBR surfaces or the NBR to NBR interface. Lab test results indicate that the nylon rod-exposed samples produce tensile and peel values very similar to the control samples and the Teflon exposed samples produce tensile and peel values much lower than the control samples. Visual observation of the failure surfaces of the tested samples shows that Teflon scribing produces an obvious contamination to the surface and the nylon produces no effect. Photographs of test samples are provided. It is concluded that Teflon stock used as a scribe tool on a Chemlok 233 to NBR surface or an NBR to NBR surface has a detrimental effect on the bond integrity on either of these bond interfaces. Therefore, it is recommended that the nylon rod continue to be used where a scribe line is required in the redesigned solid rocket motor segment insulation layup operations. The use of Teflon scribes should not be considered.

  2. Effect of X irradiation on optical properties of Teflon-AF

    NASA Astrophysics Data System (ADS)

    Jahan, M. S.; Ermer, D. R.; Cooke, D. W.

    1993-03-01

    Radiation effects in optical-grade amorphous fluoropolymer, Teflon-AF, is investigated by UV-visible absorption and electron spin resonance (ESR) measurements. When irradiated with low-energy (40 kVp) X-rays at room temperature in air, Teflon-AF is found to develop a broad, structureless UV-absorption band in the wavelength interval 200-350 nm. While the UV absorption increases as a function of X-ray dose, with relative rates of approx 2 × 10 -5 Gy -1 (1 × 10 -5 Gy -1) in Teflon-AF 1600 (Teflon-AF 2400), its optical transparency for a given dose of 67.5 kGy, however, remains unaffected. Additional measurements conducted using electron spin resonance (ESR) technique reveal that the observed UV absorption is caused by the X-ray induced peroxy radical (POO .˙). The results also suggest that the inclusion of dioxole monomer in the PTFE chain not only improves the optical clarity of Teflon-AF, as reported, but also increases its radiation tolerance. During a post-irradiation storage in air at RT for about 30 days the peroxy radical is observed to decay, with a concomitant decrease in UV absorption. A tentative model is proposed to explain the radiation damage and recovery mechanisms.

  3. A reactive flow model for heavily aluminized cyclotrimethylene-trinitramine

    SciTech Connect

    Kim, Bohoon; Lee, Kyung-Cheol; Yoh, Jack J.; Park, Jungsu

    2014-07-14

    An accurate and reliable prediction of reactive flow is a challenging task when characterizing an energetic material subjected to an external shock impact as the detonation transition time is on the order of a micro second. The present study aims at investigating the size effect behavior of a heavily aluminized cyclotrimethylene-trinitramine (RDX) which contains 35% of aluminum by using a detonation rate model that includes ignition and growth mechanisms for shock initiation and subsequent detonation. A series of unconfined rate stick tests and two-dimensional hydrodynamic simulations are conducted to construct the size effect curve which represents the relationship between detonation velocity and inverse radius of the charge. A pressure chamber test is conducted to further validate the reactive flow model for predicting the response of a heavily aluminized high explosive subjected to an external impact.

  4. Study of Detonation and Cylinder Velocities for Aluminized Explosives

    NASA Astrophysics Data System (ADS)

    Stiel, Leonard; Baker, Ernest

    2005-07-01

    The detonation properties of aluminized explosives have been studied using experimental data available in the literature and EXP-6 thermo-chemical potential calculations with the JAGUAR computer program. It has been found that the observed detonation velocity behavior for aluminized explosives can be accurately represented by a reaction zone model in which unreacted aluminum is initially in equilibrium with H-C-N-O compounds. The JAGUAR procedures have been modified to represent the aluminum reaction zone behavior and to enable specified temperature differences between the gas and aluminum particles in the initial portion of this reaction zone. The modified procedures enable isentropic expansion for incomplete or complete aluminum reaction in the zone, and result in close agreement with experimental cylinder test data for several explosives. In order to aid in the application of the model, constants of thermodynamic equations of state are related to the extent of aluminum reaction.

  5. Study of Detonation and Cylinder Velocities for Aluminized Explosives

    NASA Astrophysics Data System (ADS)

    Stiel, Leonard I.; Baker, Ernest L.; Capellos, Christos

    2006-07-01

    The detonation properties of aluminized explosives have been studied using experimental data and EXP-6 thermo-chemical potential calculations with the JAGUAR computer program. It has been found that the observed detonation velocity behavior for aluminized explosives can be accurately represented by a reaction zone model in which unreacted aluminum is initially in equilibrium with H-C-N-O compounds. The JAGUAR procedures have been modified to represent the reaction zone behavior and to enable specified temperature differences between the gas and aluminum particles in the initial portion of this reaction zone. The modified procedures enable isentropic expansion for incomplete or complete aluminum reaction in the zone, and result in close agreement with experimental cylinder test data.

  6. Morphological and microstructural studies on aluminizing coating of carbon steel

    SciTech Connect

    Samsu, Zaifol; Othman, Norinsan Kamil; Daud, Abd Razak; Hussein, Hishammuddin

    2013-11-27

    Hot dip aluminizing is one of the most effective methods of surface protection for steels and is gradually gaining popularity. The morphology and microstructure of an inter-metallic layer form on the surface of low carbon steel by hot dip aluminization treatment had been studied in detail. This effect has been investigated using optical and scanning electron microscopy, and X-ray diffraction. The result shows that the reaction between the steel and the molten aluminium leads to the formation of Fe–Al inter-metallic compounds on the steel surface. X-ray diffraction and electron microscopic studies showed that a two layer coating was formed consisting of an external Al layer and a (Fe{sub 2}Al{sub 5}) inter metallic on top of the substrate after hot dip aluminizing process. The inter-metallic layer is ‘thick’ and exhibits a finger-like growth into the steel. Microhardness testing shown that the intermetallic layer has high hardness followed by steel substrate and the lowest hardness was Al layer.

  7. Statistical Modeling of the Industrial Sodium Aluminate Solutions Decomposition Process

    NASA Astrophysics Data System (ADS)

    Živković, Živan; Mihajlović, Ivan; Djurić, Isidora; Štrbac, Nada

    2010-10-01

    This article presents the results of the statistical modeling of industrial sodium aluminate solution decomposition as part of the Bayer alumina production process. The aim of this study was to define the correlation dependence of degree of the aluminate solution decomposition on the following parameters of technological processes: concentration of the Na2O (caustic), caustic ratio and crystallization ratio, starting temperature, final temperature, average diameter of crystallization seed, and duration of decomposition process. Multiple linear regression analysis (MLRA) and artificial neural networks (ANNs) were used as the tools for the mathematical analysis of the indicated problem. On the one hand, the attempt of process modeling, using MLRA, resulted in a linear model whose correlation coefficient was equal to R 2 = 0.731. On the other hand, ANNs enabled, to some extent, better process modeling, with a correlation coefficient equal to R 2 = 0.895. Both models obtained using MLRA and ANNs can be used for the efficient prediction of the degree of sodium aluminate solution decomposition, as the function of the input parameters, under industrial conditions of the Bayer alumina production process.

  8. Aluminum hydroxide nucleation kinetics and mechanism during the electrodialysis decomposition of aluminate solutions

    NASA Astrophysics Data System (ADS)

    Lainer, Yu. A.; Gorichev, I. G.; Todorov, S. A.

    2008-08-01

    The kinetic laws of the electrodialysis decomposition of strong aluminate solutions are considered. Mathematical simulation is performed using the equations of the heterogeneous kinetics of aluminum hydroxide precipitation for the electrodialysis of aluminate solutions, and this simulation shows that the nature of the limiting stage is related to the instantaneous nucleation during the three-dimensional coalescence of particles. The electrodialysis precipitate is analyzed, and the possible commercial application of the decomposition of strong aluminate solutions by electrodialysis is considered.

  9. Thin teflon-like films for eliminating adhesion in released polysilicon microstructures

    SciTech Connect

    Smith, B.K.; Sniegowski, J.J.; LaVigne, G.

    1996-12-31

    This paper presents a method for depositing thin Teflon-like films using a commercial plasma reactor to eliminate adhesion or stiction in released polysilicon microstructures. A Lam 384T oxide etch system is used in a remote plasma mode with commercially available trifluoromethane (CHF{sub 3}) to deposit thin hydrophobic films around and under released microstructures. Hard, uniform, Teflon-like films which penetrate into undercuts beneath structures have been produced. Thus far, surfaces beneath gears as large as 1600 micron diameter with a gap of 2.0 microns are hydrophobic after being exposed to plasma treatment. These Teflon-like coatings have been shown to reduce the coefficient of friction from 1.0 to 0.07.

  10. [Case of polymer fume fever with interstitial pneumonia caused by inhalation of polytetrafluoroethylene (Teflon)].

    PubMed

    Son, Masami; Maruyama, Eiichi; Shindo, Yuichiro; Suganuma, Nobukazu; Sato, Shinji; Ogawa, Masahiro

    2006-07-01

    A 30-year old man was admitted to our hospital with cough, slight fever, and dyspnea that he had developed several hours after inhaling the fumes produced from a Teflon-coated pan, after evaporation of the water in the pan. Chest radiography revealed diffuse infiltrations, and a computed tomography (CT) scan revealed patchy interstitial shadows in both lungs. In pulmonary function tests, the diffusing capacity of the lungs showed a moderate decrease. Leukocytosis and slight hypoxemia were observed. The patient recovered clinically in a few days without any specific treatment. We speculated that the pulmonary problems in this patient may have been induced by the products of thermal degradation of Teflon that were present in the fumes. When Teflon is heated, the fumes generated cause an influenza like syndrome (polymer fume fever) or cause severe toxic effects such as pulmonary edema, pneumonitis, and death in the exposed individual. PMID:16922460

  11. Mechanical impact tests of materials in oxygen effects of contamination. [Teflon, stainless steel, and aluminum

    NASA Technical Reports Server (NTRS)

    Ordin, P. M.

    1980-01-01

    The effect of contaminants on the mechanical impact sensitivity of Teflon, stainless steel, and aluminum in a high-pressure oxygen environment was investigated. Uncontaminated Teflon did not ignite under the test conditions. The liquid contaminants - cutting oil, motor lubricating oil, and toolmaker dye - caused Teflon to ignite. Raising the temperature lowered the impact energy required for ignition. Stainless steel was insensitive to ignition under the test conditions with the contaminants used. Aluminum appeared to react without contaminants under certain test conditions; however, contamination with cutting oil, motor lubricating oil, and toolmakers dye increased the sensitivity of aluminum to mechanical impact. The grit contaminants silicon dioxide and copper powder did not conclusively affect the sensitivity of aluminum.

  12. Fluoresceination of FepA during Colicin B Killing: Effects of Temperature, Toxin and TonB

    PubMed Central

    Smallwood, Chuck R.; Marco, Amparo Gala; Xiao, Qiaobin; Trinh, Vy; Newton, Salete M. C.; Klebba, Phillip E.

    2009-01-01

    We studied the reactivity of 35 genetically engineered Cys sulfhydryl groups at different locations in Escherichia coli FepA. Modification of surface loop residues by fluorescein maleimide (FM) was strongly temperature-dependent in vivo, whereas reactivity at other sites was much less affected. Control reactions with bovine serum albumin showed that the temperature dependence of loop residue reactivity was unusually high, indicating that conformational changes in multiple loops (L2, L3, L4, L5, L7, L8, L10) transform the receptor to a more accessible form at 37 °C. At 0 °C colicin B binding impaired or blocked labeling at 8 of 10 surface loop sites, presumably by steric hindrance. Overall, colicin B adsorption decreased the reactivity of more than half of the 35 sites, in both the N - and C- domains of FepA. However, colicin B penetration into the cell at 37 °C did not augment the chemical modification of any residues in FepA. The FM modification patterns were similarly unaffected by the tonB locus. FepA was expressed at lower levels in a tonB host strain, but when we accounted for this decrease its FM-labeling was comparable whether TonB was present or absent. Thus we did not detect TonB-dependent structural changes in FepA, either alone or when it interacted with colicin B at 37 °C. The only changes in chemical modification were reductions from steric hindrance when the bacteriocin bound to the receptor protein. The absence of increases in the reactivity of N-domain residues argues against the idea (Devanathan and Postle, Mol. Microbiol. 65: 441–453, 2007) that the colicin B polypeptide traverses the FepA channel. PMID:19432807

  13. Placement of Teflon Sponges in Microvascular Decompression Procedure for Treatment of Hemifacial Spasm.

    PubMed

    Nan-Xiang, Xiong; Lv-An, Chen; Zhi-Jun, Chen; Hong-Yang, Zhao

    2016-07-01

    Background Hemifacial spasm (HFS) is generally treated by microvascular decompression (MVD). Inadequate separation of vessel and nerve or adhesive inflammation surrounding the nerve root may cause recurrence. Objective To explore a method to reduce the incidence of adhesions and to ensure sufficient separation of the offending vessel and nerve during MVD. Methods Fifty-one patients diagnosed with HFS were studied. During the MVD procedure, Teflon sponges were placed between the offending vessels and medulla oblongata to push compressing vessels away from the facial nerve without contacting the nerve. Results Our method of placement of the Teflon sponge effectively shifts the compressing artery and ensures that both the Teflon sponge and offending vessels do not contact the root exit zone. This method also ensures that the Teflon sponge is fixed in place. Conclusion The technique described for the treatment of HFS provides an effective, safe, and durable resolution to patient symptoms that minimizes surgical complications and may be useful in treating HFS. PMID:25798798

  14. An investigation of the adhesive bonding of Teflon solar cell covers

    NASA Technical Reports Server (NTRS)

    Rayl, G. J.

    1979-01-01

    The concept of introducing organic agents into silicone resins to stabilize these materials against the ravages of ultraviolet radiation is presented. A screening of coating materials, cover materials and ultraviolet screening agents is described. Fabrication processes were developed for the application of thin 25 micrometer coatings to Teflon. Temperature shock and temperature-humidity tests were conducted.

  15. Complications of intravenous therapy: a randomized prospective study--Vialon vs. Teflon.

    PubMed

    McKee, J M; Shell, J A; Warren, T A; Campbell, V P

    1989-01-01

    For the past two decades, the vast majority of vascular-access devices used in I.V. catheterization have been made of Teflon material. More recent developments in material science have produced the Vialon biomaterial currently used in the Insyte I.V. catheter. This prospective, randomized study compared the length of venous dwell time and rate of I.V.-related complications of Teflon peripheral I.V. catheters and Vialon peripheral I.V. catheters. The study population included only the most difficult peripheral I.V. access patients. Conditions of insertion, monitoring, and care were carefully controlled by the investigators. An alternate assignment scheme was used for randomization of eligible patients. Of 247 catheters evaluated over a six-week period in a 550-bed community tertiary care hospital, 191 were evaluable; of these, equivalent numbers were made of Vialon and Teflon. This investigation found that the incidence of phlebitis in the group receiving Vialon I.V. catheters was 36 percent lower than that of the group receiving Teflon I.V. catheters. PMID:2677289

  16. Evaluation of commercially supplied silver coated Teflon for spacecraft temperature control usage

    NASA Technical Reports Server (NTRS)

    Heaney, J. B.

    1974-01-01

    A series of tests are described which were performed to evaluate the acceptability of a commercially supplied silver backed teflon thermal control coating relative to teflon previously coated at GSFC. Optical measurements made on numerous samples indicate that the commercial material possesses an average solar absorptance of 0.085, an emittance of 0.76 and an average alpha/epsilon equal to 0.112, all of which are equivalent to the GSFC coated teflon. The emittance of the protective inconel backing was found to be 0.037. The coating is shown to have good adhesion at the Ag-teflon interface and exposure to UV irradiation uncovered no coating irregularities. Temperature cycling over the range -135 C to +200 C produced crazing in the evaporated Ag layer as expected but no delamination was observed. The suitability of Mystik no. 7366 and 3M no. 467 adhesives as bonding agents for the metallized polymer is demonstrated. Various problems associated with production reproducibility and selection of a proper bonding process are discussed.

  17. Demonstrating a Lack of Reactivity Using a Teflon-Coated Pan.

    ERIC Educational Resources Information Center

    Richmond, Thomas G.

    1995-01-01

    Illustrates the chemical resistance of polytetrafluoroethene to mineral acids using an ordinary Teflon-coated frying pan. The demonstration can also be used to lead to a discussion of the long lifetimes of fluorocarbons and chlorofluorocarbons in the atmosphere and their roles in the breakdown of the ozone layer. (AIM)

  18. Electroejaculation using standard nerve stimulation equipment and Teflon-coated needles.

    PubMed

    Ozkurkcugil, C; Cardenas, D; Hartsell, C; Berger, R E

    1993-12-01

    We attempted transperineal needle electroejaculation using a Digistim nerve stimulator and Teflon-coated needles in 12 anejaculatory men. We obtained semen in 11 men. Five of the 12 men also underwent electroejaculation using a transrectal probe. Comparable semen parameters were obtained by transrectal probe and transperineal needles. PMID:8243692

  19. MUTAGENICITY OF TEFLON-COATED GLASS FIBER FILTERS: A POTENTIAL PROBLEM AND SOLUTIONS

    EPA Science Inventory

    Teflon-coated glass fiber filters, used in studies of airborne particulate matter, were tested for mutagenic activity using the Salmonella/mammalian-microsome (Ames) assay. For each sample, eight blank filters were simultaneously extracted with dichloromethane (DCM), and the extr...

  20. Sorption of Water/Methanol on Teflon and Hydrocarbon Proton Exchange Membranes.

    PubMed

    He, Chenfeng; Mighri, Frej; Guiver, Michael D; Kaliaguine, Serge

    2016-05-18

    The sorption of water and methanol droplets on Teflon films, as well as on various representative classes of hydrocarbon-based proton exchange membranes (PEMs) was investigated using contact angle measurement (drop shape method) during wetting under ambient open-air conditions. Teflon films exhibited constant hydrophobic surfaces when contacted with water, but a significant sorption of methanol. The PEMs showed slow sorption of water, and a significant sorption of methanol. The differences in sorption of water and methanol on Teflon and PEMs arose from the match/compatibility in the surface free energies as well as polarities between a liquid and a membrane. The significant discrepancies in surface free energies and polarities between water (72.0 mJ m(-2) and 70.1%, respectively) and Teflon film (14.0 mJ m(-2) and 4.9%, respectively) lead to a highly hydrophobic surface and no discernible sorption of water on Teflon films, while the relative similarity or minor discrepancy in surface free energies and polarities between methanol (22.5 mJ m(-2) and 17.0%, respectively) and Teflon film (14.0 mJ m(-2) and 4.9%, respectively) results in a significant sorption of methanol on Teflon. The surface free energies of PEMs were calculated using the harmonic-mean approach, based on contact angle measurements using both water and diiodomethane as probes. The results show that PEMs have initial surface free energies ranging from 44.1 to 54.0 mJ m(-2) along with polarities in the range of 20.8 to 29.1%, for a selection of typical sulfonated polymers. The surface free energies of ionomers were principally contributed to by the nonpolar component, but the presence of polar groups in the polymer increased the polar component, leading to an increase in surface free energy. Of the PEMs investigated, sulfonated poly(aryl ether ether nitrile) has a higher surface energy than those of other ionomers with similar sulfonate contents. The compatibility between water/methanol and PEMs was

  1. 40 CFR 721.10423 - Complex strontium aluminate, rare earth doped (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... earth doped (generic). 721.10423 Section 721.10423 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10423 Complex strontium aluminate, rare earth doped... substances identified generically as complex strontium aluminate, rare earth doped (PMNs P-12-22, P-12-23,...

  2. Biocompatibility and durability of Teflon-coated platinum-iridium wires implanted in the vitreous cavity.

    PubMed

    Nishida, Kentaro; Sakaguchi, Hirokazu; Xie, Ping; Terasawa, Yasuo; Ozawa, Motoki; Kamei, Motohiro; Nishida, Kohji

    2011-12-01

    Teflon-coated platinum-iridium wires are placed in the vitreous as electrodes in artificial vision systems. The purpose of this study was to determine whether these wires have toxicity in the vitreous cavity, and to examine the durability of their coating when grasped by forceps. Rabbits were implanted with platinum-iridium wires that were 50 μm in diameter and coated with Teflon to a total diameter of 68 or 100 μm. To examine the biocompatibility, electroretinograms (ERGs) and fluorescein angiography (FA) were performed before and 1 week, 1, 3, and 6 months after the implantation of the electrode. After 6 months, the eyes were histologically examined with light microscopy. To check the durability, the surface of a coated wire was examined with scanning electron microscopy after grasping with different types of forceps. At all times after the implantation the amplitudes and implicit times of the ERGs recorded were not significantly different from those recorded before the implantation (P > 0.05). FA showed no notable change during the follow-up periods. Histological studies showed that the retinas were intact after 6 months of implantation. There was no damage to the Teflon-coated wire after grasping the wire with forceps with silicon-coated tips, while surface damage of the Teflon that did not extend to the platinum-iridium wire was found when grasped by vitreoretinal forceps. We conclude that Teflon-coated platinum-iridium wire is highly biocompatible in the vitreous for at least 6 months. Wires should be handled with vitreoretinal forceps with silicone-coated tips in order to avoid causing damage during wire manipulation. PMID:21769688

  3. Monolithic Teflon membrane valves and pumps for harsh chemical and low-temperature use.

    PubMed

    Willis, Peter A; Hunt, Brian D; White, Victor E; Lee, Michael C; Ikeda, Michael; Bae, Sam; Pelletier, Michael J; Grunthaner, Frank J

    2007-11-01

    Microfluidic diaphragm valves and pumps capable of surviving conditions required for unmanned spaceflight applications have been developed. The Pasteur payload of the European ExoMars Rover is expected to experience temperatures ranging between -100 degrees C and +50 degrees C during its transit to Mars and on the Martian surface. As such, the Urey instrument package, which contains at its core a lab-on-a-chip capillary electrophoresis analysis system first demonstrated by Mathies et al., requires valving and pumping systems that are robust under these conditions before and after exposure to liquid samples, which are to be analyzed for chemical signatures of past or present living processes. The microfluidic system developed to meet this requirement uses membranes consisting of Teflon and Teflon AF as a deformable material in the valve seat region between etched Borofloat glass wafers. Pneumatic pressure and vacuum, delivered via off-chip solenoid valves, are used to actuate individual on-chip valves. Valve sealing properties of Teflon diaphragm valves, as well as pumping properties from collections of valves, are characterized. Secondary processing for embossing the membrane against the valve seats after fabrication is performed to optimize single valve sealing characteristics. A variety of different material solutions are found to produce robust devices. The optimal valve system utilizes a membrane of mechanically cut Teflon sandwiched between two thin spun films of Teflon AF-1600 as a composite "laminated" diaphragm. Pump rates up to 1600 nL s(-1) are achieved with pumps of this kind. These high pumping rates are possible because of the very fast response of the membranes to applied pressure, enabling extremely fast pump cycling with relatively small liquid volumes, compared to analogous diaphragm pumps. The developed technologies are robust over extremes of temperature cycling and are applicable in a wide range of chemical environments. PMID:17960273

  4. Corrosion Evaluation and Durability Estimation of Aluminized Steel Drainage Pipes

    NASA Astrophysics Data System (ADS)

    Akhoondan, Mersedeh

    Aluminized steel pipes are expected to have a long service life, e.g. 75 years. Spiral ribbed aluminized pipes (SRAP) have been widely specified and used by the Florida Department of Transportation (FDOT) for drainage of runoff water. Confidence in the long term durability of SRAP has been challenged by recent unexpected early corrosion failures in various Florida locations. SRAP premature corrosion incidents have occurred in two modalities. Mode A has taken place in near-neutral soil environments and has often been associated with either gross manufacturing defects (i.e. helical cuts) or corrosion concentration at or near the ribs. Mode B took place in pipes in contact with limestone backfill and corrosion damage was in the form of perforations, not preferentially located at the ribs, and not necessarily associated with other deficiencies. These failures motivated this research. The objectives of this work are to establish to what extent the Mode A corrosion incidents can be ascribed to manufacturing defects, that can be rectified by appropriate quality control, as opposed to an intrinsic vulnerability to corrosion of regularly produced SRAP due to ordinary forming strains and to determine the mechanism responsible for Mode B corrosion including the role that limestone backfill played in that deterioration. To achieve those objectives, laboratory experiments were conducted to replicate the conditions for Mode A and Mode B. Overall, the findings of this and previous work suggest that much of the corrosion damage observed in the Mode A incidents were promoted more by manufacturing deficiencies and less by any possible inherent susceptibility of corrosion at the ribs of SRAP that was produced following appropriate quality control. Experiments to explore the causes of Mode B corrosion showed that high pH values, sufficient to cause dissolution of the passive film on aluminum, can develop under exposure of limestone to flowing natural water. The findings substantiate

  5. System and process for aluminization of metal-containing substrates

    SciTech Connect

    Chou, Yeong-Shyung; Stevenson, Jeffry W

    2015-11-03

    A system and method are detailed for aluminizing surfaces of metallic substrates, parts, and components with a protective alumina layer in-situ. Aluminum (Al) foil sandwiched between the metallic components and a refractory material when heated in an oxidizing gas under a compression load at a selected temperature forms the protective alumina coating on the surface of the metallic components. The alumina coating minimizes evaporation of volatile metals from the metallic substrates, parts, and components in assembled devices during operation at high temperature that can degrade performance.

  6. Shock-induced cation disorder in magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Chen, Q. Y.; Meng, C. M.; Lu, T. C.; Xu, M.; Qi, J. Q.; Tan, J. J.

    2010-12-01

    An increase in lattice constants and an order-disorder phase transition were observed in the magnesium aluminate spinel (MgAl2O4) powders after shock compression. Theoretical calculations on the basis of density functional theory confirm that the remarkable volume expansion in shocked MgAl2O4 powders is closely related to the substantial site disorder in the MgAl2O4 lattice. The calculations also show that the partially inverse MgAl2O4 spinel with an inversion index of 0.7 represents the greatest disordered metastable phase and the most unstable structure.

  7. Thermal Properties of Double-Aluminized Kapton at Low Temperatures

    NASA Technical Reports Server (NTRS)

    Tuttle, J.; DiPirro, M.; Canavan, E.; Hait, T.

    2007-01-01

    Double-aluminized kapton (DAK) is commonly used in multi-layer insulation blankets in cryogenic systems. NASA plans to use individual DAK sheets in lightweight deployable shields for satellites carrying instruments. A set of these shields will reflect away thermal radiation from the sun, the earth, and the instrument's warm side and allow the instrument's cold side to radiate its own heat to deep space. In order to optimally design such a shield system, it is important to understand the thermal characteristics of DAK down to low temperatures. We describe experiments which measured the thermal conductivity and electrical resistivity down to 4 Kelvin and the emissivity down to 10 Kelvin.

  8. Aluminized film, seam sealing tests and observations. Final report

    SciTech Connect

    Not Available

    1994-06-16

    The purpose of this work was to investigate various seam sealing techniques, reinforcing methods, fitting installations, seam tolerances and geometric configurations pertinent to an aluminized plastic laminate. The program seeks a successful fabricating method for producing low-diffusion, cylindrical, spar liners to contain pressurized GH{sub 2} and GO{sub 2}. The test plan included: (1) seaming techniques on metallized Mylar film; (2) ``double patches`` for end fittings; (3) stainless steel bulkhead fitting assembly with seals; (4) minimum run tolerance on linear shear seam; (5) peel seam vs. inverted seal seam fabrication.

  9. Noncontact temperature measurement of aluminized polymer for space applications

    NASA Astrophysics Data System (ADS)

    Pollard, William, Jr.; Hannas, Benjamin

    2002-03-01

    An existing fiber-optic/infrared (F-O/IR) temperature measurement system was adapted to measure the surface temperature of a thin-film aluminized polymer. The polymer under study, Kapton by Dupont, is used commonly in the aerospace industry for applications such as solar sails and solar shields. A cold plate was developed and implemented to control environmental effects on infrared data. Spectral characterization of the optical properties of Kapton was conducted to improve measurement accuracy. The instrument provides a non-contact means for accurate temperature measurement of very thin polymer membranes without distorting surface contour.

  10. Thermal Properties of Double-Aluminized Kapton at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Tuttle, J.; DiPirro, M.; Canavan, E.; Hait, T.

    2008-03-01

    Double-aluminized kapton (DAK) is commonly used in multi-layer insulation blankets in cryogenic systems. NASA plans to use individual DAK sheets in lightweight deployable shields for satellites carrying instruments. A set of these shields will reflect away thermal radiation from the sun, the earth, and the instrument's warm side and allow the instrument's cold side to radiate its own heat to deep space. In order to optimally design such a shield system, it is important to understand the thermal characteristics of DAK down to low temperatures. We describe experiments which measured the thermal conductivity and electrical resistivity down to 4 Kelvin and the emissivity down to 10 Kelvin.

  11. Porous electrolyte retainer for molten carbonate fuel cell. [lithium aluminate

    DOEpatents

    Singh, R.N.; Dusek, J.T.

    1979-12-27

    A porous tile for retaining molten electrolyte within a fuel cell is prepared by sintering particles of lithium aluminate into a stable structure. The tile is assembled between two porous metal plates which serve as electrodes with fuels gases such as H/sub 2/ and CO opposite to oxidant gases such as O/sub 2/ and CO/sub 2/. The tile is prepared with a porosity of 55 to 65% and a pore size distribution selected to permit release of sufficient molten electrolyte to wet but not to flood the adjacent electrodes.

  12. High energy excitations measured by neutron spectroscopy in FePS3

    NASA Astrophysics Data System (ADS)

    Rule, K C; Wildes, A R; Bewley, R I; Visser, D; Hicks, T J

    2009-03-01

    The quasi-two-dimensional antiferromagnet FePS3 has been investigated using inelastic neutron spectroscopy with the time-of-flight spectrometer HET at the ISIS spallation neutron source. In the paramagnetic regime, two clearly resolved, high energy excitations were observed in the low scattering angle detector banks at 195(5) meV and 430(10) meV. The absence of these transitions from the high angle detector banks indicates that they are likely to be due to the crystal fields and magnetic in origin. The two transitions most probably represent electronic transitions in the Fe2+ ion among the low lying crystal field and spin-orbit split levels raised from the ground state. It has not yet been determined why the energies are greater than those observed in a comparable Raman experiment.

  13. High energy excitations measured by neutron spectroscopy in FePS(3).

    PubMed

    Rule, K C; Wildes, A R; Bewley, R I; Visser, D; Hicks, T J

    2009-03-25

    The quasi-two-dimensional antiferromagnet FePS(3) has been investigated using inelastic neutron spectroscopy with the time-of-flight spectrometer HET at the ISIS spallation neutron source. In the paramagnetic regime, two clearly resolved, high energy excitations were observed in the low scattering angle detector banks at 195(5) meV and 430(10) meV. The absence of these transitions from the high angle detector banks indicates that they are likely to be due to the crystal fields and magnetic in origin. The two transitions most probably represent electronic transitions in the Fe(2+) ion among the low lying crystal field and spin-orbit split levels raised from the ground state. It has not yet been determined why the energies are greater than those observed in a comparable Raman experiment. PMID:21817456

  14. Concerted loop motion triggers induced fit of FepA to ferric enterobactin

    PubMed Central

    Smallwood, Chuck R.; Jordan, Lorne; Trinh, Vy; Schuerch, Daniel W.; Gala, Amparo; Hanson, Mathew; Shipelskiy, Yan; Majumdar, Aritri; Newton, Salete M.C.

    2014-01-01

    Spectroscopic analyses of fluorophore-labeled Escherichia coli FepA described dynamic actions of its surface loops during binding and transport of ferric enterobactin (FeEnt). When FeEnt bound to fluoresceinated FepA, in living cells or outer membrane fragments, quenching of fluorophore emissions reflected conformational motion of the external vestibular loops. We reacted Cys sulfhydryls in seven surface loops (L2, L3, L4, L5, L7 L8, and L11) with fluorophore maleimides. The target residues had different accessibilities, and the labeled loops themselves showed variable extents of quenching and rates of motion during ligand binding. The vestibular loops closed around FeEnt in about a second, in the order L3 > L11 > L7 > L2 > L5 > L8 > L4. This sequence suggested that the loops bind the metal complex like the fingers of two hands closing on an object, by individually adsorbing to the iron chelate. Fluorescence from L3 followed a biphasic exponential decay as FeEnt bound, but fluorescence from all the other loops followed single exponential decay processes. After binding, the restoration of fluorescence intensity (from any of the labeled loops) mirrored cellular uptake that depleted FeEnt from solution. Fluorescence microscopic images also showed FeEnt transport, and demonstrated that ferric siderophore uptake uniformly occurs throughout outer membrane, including at the poles of the cells, despite the fact that TonB, its inner membrane transport partner, was not detectable at the poles. PMID:24981231

  15. On the kinetics of the pack - Aluminization process

    NASA Technical Reports Server (NTRS)

    Sivakumar, R.; Seigle, L. L.

    1976-01-01

    An investigation has been made of the aluminization of unalloyed Ni in fluoride-activated packs of varying Al activity. In packs of low Al activity, in which the ratio of Al to Ni was less than 50 at. pct, the specimen surface quickly came to equilibrium with the pack and remained close to equilibrium for the duration of normal coating runs. In these packs the kinetics of aluminization was controlled by diffusion in the solid. In packs of higher Al activity the surface of the specimen did not come to equilibrium with the pack and the kinetics of the process was governed by a combination of solid and gas diffusion rates. Under most conditions however, the surface composition was time-invariant and a steady-state appeared to exist at the pack-coating interface. By combining Levine and Caves' model for gaseous diffusion in pure-Al packs with calculations of solid diffusion rates some success has been achieved in explaining the results.

  16. High-temperature oxidation behavior of aluminized AISI 4130 steel

    NASA Astrophysics Data System (ADS)

    Badaruddin, Mohammad; Wang, Chaur Jeng; Wardono, Herry; Tarkono, Asmi, Dwi

    2016-02-01

    AISI 4130 steel was dipped into a molten aluminum bath at 700°C for 16 s to produce an aluminide coating on the steel substrate. The coating, which consisted of an Al-rich layer and an FeAl3 and Fe2Al5 intermetallic layer, strongly adhered to the steel substrate. High-temperature oxidation of the bare steel and aluminized steel was performed by thermogravimetry at 850°C for 49 h in static air. The oxidation products were characterized by scanning electron microscopy and energy-dispersive spectroscopy. The aluminide coating could increase the oxidation resistance of the bare steel by a factor of ˜19. The increase in high-temperature oxidation resistance of the aluminized steel is attributed to the formation of protective alumina scale (α-Al2O3). Although iron oxide nodules grew on the aluminide coating surface, the oxidation rate of the aluminide coatings was very low. After 49 h of oxidation, agglomerates of α-Al2O3 fine grains grew on the rod-shaped FeAl phases.

  17. Atomic oxygen undercutting of LDEF aluminized Kapton multilayer insulation

    NASA Astrophysics Data System (ADS)

    Degroh, Kim K.

    1991-06-01

    Atomic oxygen undercutting is a potential threat to vulnerable spacecraft materials which have been shielded with an atomic oxygen protective coating. This is due to atomic oxygen attack of oxidizable materials at the point of microscopic defects in the protective coatings which occur during fabrication and handling, or from micrometeoroid and debris bombardment in space. An aluminized Kapton multilayer insulation sample which was flown on the leading edge of the Long Duration Exposure Facility (LDEF) was used to study low Earth orbit (LEO) directed ram oxygen undercutting. Cracks in the aluminized coatings around the vent holes provided excellent locations for evaluation of atomic oxygen undercutting. The undercutting profiles were compared to Monte Carlo models which predict LEO ram atomic oxygen attack. The shape of the undercurrent profile was found to vary with crack width, which is proportional to the number of atomic oxygen atoms entering the crack. The resulting atomic oxygen undercut profiles which occurred on LDEF indicated wide undercut cavities in spite of the fixed ram orientation. Potential causes of the observed undercutting profiles will be presented. Implications of the undercutting profiles relevant to Space Station Freedom will also be discussed.

  18. Cratering and penetration experiments in teflon targets at velocities from 1 to 7 km/s

    NASA Technical Reports Server (NTRS)

    Horz, Friedrich; Cintala, Mark; Bernhard, Ronald P.; Cardenas, Frank; Davidson, William; Haynes, Gerald; See, Thomas H.; Winkler, Jerry; Knight, Jeffrey

    1994-01-01

    Approximately 20 sq m of protective thermal blankets, largely composed of Teflon, were retrieved from the Long Duration Exposure Facility after the spacecraft spent approximately 5.7 years in space. Examination of these blankets revealed that they contained thousands of hypervelocity impact features ranging from micron-sized craters to penetration holes several millimeters in diameter. We conducted impact experiments to reproduce such features and to understand the relationships between projectile size and the resulting crater or penetration hole diameter over a wide range of impact velocities. Such relationships are needed to derive the size and mass frequency distribution and flux of natural and man-made particles in low-earth orbit. Powder propellant and light-gas guns were used to launch soda-lime glass spheres into pure Teflon targets at velocities ranging from 1 to 7 km/s. Target thickness varied over more than three orders of magnitude from finite halfspace targets to very thin films. Cratering and penetration of massive Teflon targets is dominated by brittle failure and the development of extensive spall zones at the target's front and, if penetrated, the target's rear side. Mass removal by spallation at the back side of Teflon targets may be so severe that the absolute penetration hole diameter can become larger than that of a standard crater. The crater diameter in infinite halfspace Teflon targets increases, at otherwise constant impact conditions, with encounter velocity by a factor of V (exp 0.44). In contrast, the penetration hole size in very thin foils is essentially unaffected by impact velocity. Penetrations at target thicknesses intermediate to these extremes will scale with variable exponents of V. Our experimental matrix is sufficiently systematic and complete, up to 7 km/s, to make reasonable recommendations for velocity-scaling of Teflon craters and penetrations. We specifically suggest that cratering behavior and associated equations apply

  19. Late ureteral obstruction in an adult who had STING/Teflon in childhood: Should we expect an epidemic?

    PubMed Central

    Rosenberg, Shilo; Lorber, Amitay; Landau, Ezekiel H.; Pode, Dov; Gofrit, Ofer N.; Hidas, Guy; Duvdevani, Mordechai; Sfoungaristos, Stavros

    2015-01-01

    We present a case of left renal colic in a 25-year-old female patient. She had subureteral injection of Teflon (STING) at the age of 10 due to vesico-ureteral reflux (VUR) disease and recurrent urinary tract infections. Renal colic was the result of late ureteral obstruction due to Teflon-induced periureteral foreign body reaction. To our knowledge, this is the longest interval between STING and ureteral obstruction reported and the first case of delayed ureteral obstruction caused by Teflon. Monitoring the upper tracts of patients after STING should go beyond childhood. PMID:26664516

  20. Single versus double occlusive dressing technique to minimize infusion thrombophlebitis: Vialon and Teflon cannulae reassessed.

    PubMed

    Myles, P S; Buckland, M R; Burnett, W J

    1991-11-01

    Infusion thrombophlebitis is the commonest complication of intravenous cannulation. This study was undertaken to prospectively evaluate a double-occlusive dressing technique and a new cannula, bismuth oxide-Teflon (Critikon Inc., Aust.), comparing it to Vialon (Deseret Medical Inc., Utah, USA). The study group of two hundred patients had a 16 gauge intravenous cannula inserted in theatre using a standard technique. The incidence of thrombophlebitis was determined on a daily basis. Cannula tips were sent for culture on removal. Vialon was found to be superior to Teflon after day 1. Although a double-occlusive dressing technique increased the duration of cannulation (50.9 vs. 41.9 hours, P less than 0.05), there was no difference in the incidence of thrombophlebitis. Neither cannula material nor dressing technique had an influence on the results of cannula tip culture (6% incidence). There was no evidence of bacteraemia in any case. PMID:1750632

  1. Teflon cylindrical phantom for delivery quality assurance of stereotactic body radiotherapy (SBRT).

    PubMed

    Lack, Danielle W; Kakakhel, Ali; Starin, Ross; Snyder, Michael

    2014-01-01

    At our institution the standard delivery quality assurance (DQA) procedure for tomotherapy plans is accomplished with a water equivalent phantom, EDR2 film, and ion chamber point-dose measurements. Most plans deliver at most 5 Gy to the dose plane; however, recently a stereotactic body radiotherapy (SBRT) protocol has produced plans delivering upwards of 12 Gy to the film plane. EDR2 film saturates at a dose of ~ 7 Gy, requiring a modification of our DQA procedure for SBRT plans. To reduce the dose to the film plane and accommodate a possible move to SBRT using Varian RapidArc, a Teflon phantom has been constructed and tested. Our Teflon phantom is cylindrical in shape and of a similar design to the standard phantom. The phantom was MVCT scanned on the TomoTherapy system with images imported into the TomoTherapy and Varian Eclipse planning systems. Phantom images were smoothed to reduce artifacts for treatment planning purposes. Verification SBRT plans were delivered with film and point-dose benchmarked against the standard procedure. Verification tolerance criteria were 3% dose difference for chamber measurements and a gamma pass rate > 90% for film (criteria: 3 mm DTA, 3% dose difference, 10% threshold). The phantom sufficiently reduced dose to the film plane for DQA of SBRT plans. Both planning systems calculated accurate point doses in phantom, with the largest differences being 2.4% and 4.4% for TomoTherapy and Rapid Arc plans. Measured dose distributions correlated well with planning system calculations (γ < 1 for > 95%). These results were comparable to the standard phantom. The Teflon phantom appears to be a potential option for SBRT DQA. Preliminary data show that the planning systems are capable of calculating point doses in the Teflon, and the dose to the film plane is reduced sufficiently to allow for a direct measured DQA without the need for dose rescaling. PMID:24423855

  2. A rotating-disk study on Teflon-bonded porous zinc electrodes

    NASA Astrophysics Data System (ADS)

    Duffield, A.; Mitchell, P. J.; Hampson, N. A.; Kumar, N.; Shield, D. W.

    1985-07-01

    Microcomputer-controlled, rotating-disk experiments have been carried out on Teflon-bonded porous electrodes fabricated from a 5 percent PTFE suspension + ZnO. The effect of using 1 percent mercuric oxide as an additive on this type of electrode has been examined. Plots of i exp -1 vs omega exp -1/2 on electrodes containing mercuric oxide show intercepts through the origin for low overpotentials, implying that quasi-reversible kinetics prevail.

  3. Thin teflon-like films for MEMS: Film properties and reliability studies

    SciTech Connect

    Smith, B.K.; LaVigne, G.; Sniegowski, J.J.; Brown, C.D.

    1998-07-01

    This work presents film properties and initial reliability studies for thin Teflon-like films applied to a unique test vehicle, the Sandia-designed and fabricated microengine. Results on microengines coated with the film show a factor of three improvement in their lifetime and an order of magnitude reduction in the coefficient of friction when compared to uncoated samples. Coefficients Of Friction (COF) of 0.07 for the Teflon-like film and 1.0 for uncoated samples are extracted from models which match the measured behavior of working microengines. These films, deposited form a plasma source, exhibit the ability to penetrate into very narrow, deep channels common to many MEMS devices. For as-deposited film, both the refractive index at 1.4 and the contact angle with water at 108{degree} show the film to be very similar to bulk Teflon PTFE. Film stability as a function of temperature has been examined using Fourier Transformation Infrared (FTIR) spectroscopy. The film structure as observed by the fluorine-carbon (F-C) peak is stable up to 200 C, but starts decomposing above 250 C. Film composition has been examined using X-ray photoelectron spectroscopy (XPS) and is quite different for directly exposed surfaces compared with deep, narrow channels where the deposition process is diffusion limited.

  4. Penetration experiments in aluminum and Teflon targets of widely variable thickness

    NASA Technical Reports Server (NTRS)

    Hoerz, F.; Cintala, Mark J.; Bernhard, R. P.; See, T. H.

    1994-01-01

    The morphologies and detailed dimensions of hypervelocity craters and penetration holes on space-exposed surfaces faithfully reflect the initial impact conditions. However, current understanding of this postmortem evidence and its relation to such first-order parameters as impact velocity or projectile size and mass is incomplete. While considerable progress is being made in the numerical simulation of impact events, continued impact simulations in the laboratory are needed to obtain empirical constraints and insights. This contribution summarizes such experiments with Al and Teflon targets that were carried out in order to provide a better understanding of the crater and penetration holes reported from the Solar Maximum Mission (SMM) and the Long Duration Exposure Facility (LDEF) satellites. A 5-mm light gas gun was used to fire spherical soda-lime glass projectiles from 50 to 3175 microns in diameter (D(sub P)), at a nominal 6 km/s, into Al (1100 series; annealed) and Teflon (Teflon(sup TFE)) targets. Targets ranged in thickness (T) from infinite halfspace targets (T approx. equals cm) to ultrathin foils (T approx. equals micron), yielding up to 3 degrees of magnitude variation in absolute and relative (D(sub P)/T) target thickness. This experimental matrix simulates the wide range in D(sub P)/T experienced by a space-exposed membrane of constant T that is being impacted by projectiles of widely varying sizes.

  5. Multi-domain CGFS-type glutaredoxin Grx4 regulates iron homeostasis via direct interaction with a repressor Fep1 in fission yeast

    SciTech Connect

    Kim, Kyoung-Dong; Kim, Hyo-Jin; Lee, Kyung-Chang; Roe, Jung-Hye

    2011-05-20

    Research highlights: {yields} Monothiol glutaredoxin Grx4 allows Fep1-mediated de-repression of iron uptake genes at low iron. {yields} Grx4 directly interacts with Fep1 in vivo and in vitro. {yields} The Cys172 in the CGFS motif of Grx4 is necessary for cell proliferation and iron regulation. {yields} The Cys172 of Grx4 is required for normal interaction with Fep1. -- Abstract: The fission yeast Schizosaccharomyces pombe contains two CGFS-type monothiol glutaredoxins, Grx4 and Grx5, which are localized primarily in the nucleus and mitochondria, respectively. We observed involvement of Grx4 in regulating iron-responsive gene expression, which is modulated by a repressor Fep1. Lack of Grx4 caused defects not only in growth but also in the expression of both iron-uptake and iron-utilizing genes regardless of iron availability. In order to unravel how Grx4 is involved in Fep1-mediated regulation, interaction between them was investigated. Co-immunoprecipitation and bimolecular fluorescence complementation (BiFC) revealed that Grx4 physically interacts with Fep1 in vivo. BiFC revealed localized nuclear dots produced by interaction of Grx4 with Fep1. Mutation of cysteine-172 in the CGFS motif to serine (C172S) produced effects similarly observed under Grx4 depletion, such as the loss of iron-dependent gene regulation and the absence of nuclear dots in BiFC analysis. These results suggest that the ability of Grx4 to bind iron, most likely Fe-S cofactor, could be critical in interacting with and modulating the activity of Fep1.

  6. Development of a communications Front End Processor (FEP) for the VAX-11/780 using an LSI-11/23

    NASA Astrophysics Data System (ADS)

    Masty, A. F.

    1983-12-01

    A Communications Front-End Processor (FEP) was implemented for a Digital Equipment Corporation (DEC) VAX-11/780 using a DEC LSI-11/23 microcomputer. The LSI-11/23 serviced eight DEC VT-100 terminals and communicated with the VAX-11/780 over an Able Computer Technology, Inc. Direct Memory Access (DMA) interface. This investigation proceeded from a FEP design provided in a previous work and culminated in the Telecon "C' compiler language coding of those design specifications. The design was translated into structure charts defining software module functions and interfaces. Program Design Language (PDL) was then used to outline the processing steps in a structured programming format for each software module. A data dictionary was constructed to document the data and functional module interfaces. The code was implemented in a "top-down' manner.

  7. Method of winning aluminum metal from aluminous ore

    DOEpatents

    Loutfy, Raouf O.; Keller, Rudolf; Yao, Neng-Ping

    1981-01-01

    Aluminous ore such as bauxite containing alumina is blended with coke or other suitable form of carbon and reacted with sulfur gas at an elevated temperature. For handling, the ore and coke can be extruded into conveniently sized pellets. The reaction with sulfur gas produces molten aluminum sulfide which is separated from residual solid reactants and impurities. The aluminum sulfide is further increased in temperature to cause its decomposition or sublimation, yielding aluminum subsulfide liquid (AlS) and sulfur gas that is recycled. The aluminum monosulfide is then cooled to below its disproportionation temperature to again form molten aluminum sulfide and aluminum metal. A liquid-liquid or liquid-solid separation, depending on the separation temperature, provides product aluminum and aluminum sulfide for recycle to the disproportionation step.

  8. Lattice site of helium implanted in magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Alien, W. R.

    1993-01-01

    The lattice site of helium implanted at 60 keV in magnesium aluminate spinel (MgAl 2O 4) has been investigated with channeling effect measurements that apply the ion-induced 3He(d, p) 4He nuclear reaction. Within the spinel crystal structure, numerous interstices characterized by octahedral anion coordination are intrinsically unfilled by cations. For implantation at 300 K, a typical helium atom locates centrally in one of these vacant octahedral interstices with a probability of approximately 95%. Significant occupation of other lattice sites of either high or low symmetry was rejected. In particular, helium neither clusters in defect complexes nor locates in tetrahedral interstices or substitutional sites.

  9. On the Compressive and Tensile Strength of Magnesium Aluminate Spinel

    NASA Astrophysics Data System (ADS)

    Paris, V.; Hayun, S.; Dariel, M. P.; Frage, N.; Zaretsky, E.

    2009-12-01

    Magnesium aluminate spinel is a strong polycrystalline transparent ceramic. Spinel is an attractive material for armor applications and its behavior under shock wave loading is of obvious interest. The purpose of the present study was to determine the Hugoniot elastic limit (HEL) of this material, its Hugoniot response above the HEL, and its spall strength. Planar impact experiments were performed over the 2 to 40 GPa stress range using the Velocity Interferometer System for Any Reflector (VISAR) as a principal diagnostics tool. According to these tests, spinel has a HEL of about 11.3 GPa. The spall strength of the material was found to be close to zero at low, about 2 GPa, impact stress.

  10. Synthesis and optical study of barium magnesium aluminate blue phosphors

    NASA Astrophysics Data System (ADS)

    Jeet, Suninder; Sharma, Manoj; Pandey, O. P.

    2015-05-01

    Europium doped barium magnesium aluminate (BaMgAl10O17:Eu2+) phosphor was prepared via solution combustion method at 550°C using urea as a fuel. Morphological and optical properties of the prepared sample was studied by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Photoluminescence spectroscopy (PL). XRD result showed the formation of pure phase BaMgAl10O17(JCPDS 26-0163) along with an additional phase BaAl2O4(JCPDS 01-082-1350). TEM image indicated the formation of faceted particles with average particle size 40 nm. From PL spectra, a broad emission band obtained at about 450 nm attributes to 4f6 5d → 4f7 transition of Eu2+ which lies in the blue region of the visible spectrum.

  11. Synthesis and optical study of barium magnesium aluminate blue phosphors

    SciTech Connect

    Jeet, Suninder Pandey, O. P.; Sharma, Manoj

    2015-05-15

    Europium doped barium magnesium aluminate (BaMgAl{sub 10}O{sub 17}:Eu{sup 2+}) phosphor was prepared via solution combustion method at 550°C using urea as a fuel. Morphological and optical properties of the prepared sample was studied by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Photoluminescence spectroscopy (PL). XRD result showed the formation of pure phase BaMgAl{sub 10}O{sub 17}(JCPDS 26-0163) along with an additional phase BaAl{sub 2}O{sub 4}(JCPDS 01-082-1350). TEM image indicated the formation of faceted particles with average particle size 40 nm. From PL spectra, a broad emission band obtained at about 450 nm attributes to 4f{sup 6} 5d → 4f{sup 7} transition of Eu{sup 2+} which lies in the blue region of the visible spectrum.

  12. Method of winning aluminum metal from aluminous ore

    DOEpatents

    Loutfy, R.O.; Keller, R.; Yao, N.P.

    Aluminous ore such as bauxite containing alumina is blended with coke or other suitable form of carbon and reacted with sulfur gas at an elevated temperature. For handling, the ore and coke can be extruded into conveniently sized pellets. The reaction with sulfur gas produces molten aluminum sulfide which is separated from residual solid reactants and impurities. The aluminum sulfide is further increased in temperature to cause its decomposition or sublimation, yielding aluminum subsulfide liquid (A1S) and sulfur gas that is recycled. The aluminum monosulfide is then cooled to below its disproportionation temperature to again form molten aluminum sulfide and aluminum metal. A liquid-liquid or liquid-solid separation, depending on the separation temperature, provides product aluminum and aluminum sulfide for recycle to the disproportionation step.

  13. Free Energy Perturbation Hamiltonian Replica-Exchange Molecular Dynamics (FEP\\H-REMD) for absolute ligand binding free energy calculations.

    SciTech Connect

    Jiang, W.; Roux, B.

    2010-09-01

    Free Energy Perturbation with Replica Exchange Molecular Dynamics (FEP/REMD) offers a powerful strategy to improve the convergence of free energy computations. In particular, it has been shown previously that a FEP/REMD scheme allowing random moves within an extended replica ensemble of thermodynamic coupling parameters '{lambda}' can improve the statistical convergence in calculations of absolute binding free energy of ligands to proteins [J. Chem. Theory Comput. 2009, 5, 2583]. In the present study, FEP/REMD is extended and combined with an accelerated MD simulations method based on Hamiltonian replica-exchange MD (H-REMD) to overcome the additional problems arising from the existence of kinetically trapped conformations within the protein receptor. In the combined strategy, each system with a given thermodynamic coupling factor {lambda} in the extended ensemble is further coupled with a set of replicas evolving on a biased energy surface with boosting potentials used to accelerate the interconversion among different rotameric states of the side chains in the neighborhood of the binding site. Exchanges are allowed to occur alternatively along the axes corresponding to the thermodynamic coupling parameter {lambda} and the boosting potential, in an extended dual array of coupled {lambda}- and H-REMD simulations. The method is implemented on the basis of new extensions to the REPDSTR module of the biomolecular simulation program CHARMM. As an illustrative example, the absolute binding free energy of p-xylene to the nonpolar cavity of the L99A mutant of the T4 lysozyme was calculated. The tests demonstrate that the dual {lambda}-REMD and H-REMD simulation scheme greatly accelerates the configurational sampling of the rotameric states of the side chains around the binding pocket, thereby improving the convergence of the FEP computations.

  14. Synthesis of Li2FeP2O7/Carbon nanocomposite as cathode materials for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Nagano, Hiroaki; Taniguchi, Izumi

    2015-12-01

    A Li2FeP2O7/Carbon (C) nanocomposite was successfully synthesized via a combination of spray pyrolysis and wet ball milling followed by annealing from a precursor solution; in which LiNO3, H3PO4 and Fe(NO3)3·9H2O were stoichiometrically dissolved into distilled water. Ascorbic acid was added to the precursor solution as a reduction agent. The peaks of the Li2FeP2O7/C nanocomposite obtained by X-ray diffraction analysis were indexed to the monoclinic structure with the space group P21/c. The Li2FeP2O7/C nanocomposite cathode delivered a first discharge capacity of 100 mAh g-1 at 0.05 C, which corresponded to 91% of its theoretical capacity. After various higher discharge rates from 0.05 to 2 C in the cycle performance test, a discharge capacity of 93 mAh g-1 was achieved at 0.05 C, which showed an excellent capacity retention (93%) after 29 cycles.

  15. Formation of copper aluminate spinel and cuprous aluminate delafossite to thermally stabilize simulated copper-laden sludge.

    PubMed

    Hu, Ching-Yao; Shih, Kaimin; Leckie, James O

    2010-09-15

    The study reported herein indicated the stabilization mechanisms at work when copper-laden sludge is thermally treated with gamma-alumina and kaolinite precursors, and evaluated the prolonged leachability of their product phases. Four copper-containing phases - copper oxide (CuO), cuprous oxide (Cu(2)O), copper aluminate spinel (CuAl(2)O(4)), and cuprous aluminate delafossite (CuAlO(2)) - were found in the thermal reactions of the investigated systems. These phases were independently synthesized for leaching by 0.1M HCl aqueous solution, and the relative leachabilities were found to be CuAl(2)O(4)

  16. The effects of aluminum particle size on aluminized propellant combustion

    NASA Astrophysics Data System (ADS)

    Dokhan, Allan

    The goal of this thesis was to: test current ideas regarding the complex behavior of aluminized propellant combustion, extend understanding to conditions not previously clarified, and demonstrate the applicability of the results in the tailoring of propellant formulations to specific applicational needs. The study focused on ammonium perchlorate (AP), hydrocarbon binder, aluminum (Al) formulations. All formulations had 11% polybutadiene (PBAN) binder and 89% solids (i.e., 18% Al and 71% AP). The primary propellant formulations were Al and fine AP (fAP) particle sizes. The values of these variables were chosen according to current practical standards and ideas on how to tailor the Al behavior. Bimodal size distributions were used for AP and Al. For bimodal Al formulations, the coarse Al particle size was 30mum (nominal) and the fine Al particle size was 0.1mum (nominal), and for bimodal AP, the cAP particle size was 400mum (nominal) and the fAP particle size was either 82.5mum or 10mum (nominal). The effects of the Al particle size, Al c/f ratio, fAP particle size and the AP c/f ratio were examined for monomodal and bimodal aluminized propellants. This experimental investigation challenges conventional thinking with regards to the mechanisms involved with Al combustion and provides guidelines in formulating propellants with minimal losses in performance. The results showed the existence of an intense aluminized burning region (ABR) very close to the propellant surface with ultra-fine Al (UFAl) and 3mum Al that encouraged heat feedback to the flame front and to the propellant surface in the form of radiation and conduction. The high burning rates observed with UFAl were part of a continuum of reducing the size of the Al particles, which also lead to the presence of a dense ABR close to the propellant surface. It was also shown that major modification to the burning rates could be achieved by moderate amounts of UFAl and/or significant reduction in the AP c/f ratio. A

  17. Teflon probing for the flow characterization of arc-heated wind tunnel facilities

    NASA Astrophysics Data System (ADS)

    Gulli, Stefano; Ground, Cody; Crisanti, Matthew; Maddalena, Luca

    2014-02-01

    The experimental flow characterization of the arc-heated wind tunnel of the University of Texas at Arlington is investigated in this work using ablative Teflon probes in combination with total pressure measurements. A parallel analytical work, focused on the dimensional analysis of the ablation process, has been conducted with the purpose of improving existing semi-empirical correlations for the heat blockage due to the mass injection inside the boundary layer. A control volume analysis at the receding surface of the specimens is used to calculate the wall heat transfer for a non-ablating probe by including the blockage effect. The new correlations, obtained for the convective blockage, show an improvement of the correlation coefficient of 110 % with respect to those available in literature, once a new blowing parameter containing the stagnation pressure is introduced. A correlation developed by NASA during the Round-Robin program, which relates the Teflon mass loss rate to the total pressure and cold-wall heat flux measured experimentally, is also used to predict the wall heat transfer referred to the ablation temperature of Teflon. For both approaches, a simplified stagnation point convective heat transfer equation allows the average stagnation enthalpy to be calculated. Several locations downstream of the nozzle exit have been surveyed, and selected points of the facility's performance map have been used for the experimental campaign. The results show that both approaches provide similar results in terms of stagnation heat flux and enthalpy prediction with uncertainties comparable to those provided by standard intrusive heat flux probes ( δ q max < 25 %). The analysis of the Teflon's ablated surface does not reveal significant flow non-uniformities, and a 1.14 heat flux enhancement factor due to the shock-shock interaction is detectable at x = 3.5 in. from the nozzle exit plane. The results show the use of ablative probes for the flow characterization of arc

  18. Fast surface temperature measurement of Teflon propellant-in-pulsed ablative discharges using HgCdTe photovoltaic cells

    SciTech Connect

    Antonsen, Erik L.; Burton, Rodney L.; Reed, Garrett A.; Spanjers, Gregory G.

    2006-10-15

    High-speed mercury cadmium telluride photovoltaic detectors, sensitive to infrared emission, are investigated as a means of measuring surface temperature on a microsecond time frame during pulsed ablative discharges with Teflon trade mark sign as the ablated material. Analysis is used to derive a governing equation for detector output voltage for materials with wavelength dependent emissivity. The detector output voltage is experimentally calibrated against thermocouples embedded in heated Teflon. Experimental calibration is performed with Teflon that has been exposed to {approx}200 pulsed discharges and non-plasma-exposed Teflon and is compared to theoretical predictions to analyze emissivity differences. The diagnostic capability is evaluated with measurements of surface temperature from the Teflon propellant of electric micropulsed plasma thrusters. During the pulsed current discharge, there is insufficient information to claim that the surface temperature is accurately measured. However, immediately following the discharge, the postpulse cooling curve is measured. The statistical spread of postpulse surface temperature from shot to shot, most likely due to arc constriction and localization, is investigated to determine an operational envelope for postpulse temperature and mass ablation. This information is useful for determining postpulse ablation contributions to mass loss as well as evaluation of theoretical discharge models currently under development.

  19. Reducing DRIFT backgrounds with a submicron aluminized-mylar cathode

    NASA Astrophysics Data System (ADS)

    Battat, J. B. R.; Daw, E.; Dorofeev, A.; Ezeribe, A. C.; Fox, J. R.; Gauvreau, J.-L.; Gold, M.; Harmon, L.; Harton, J.; Lafler, R.; Landers, J.; Lauer, R. J.; Lee, E. R.; Loomba, D.; Lumnah, A.; Matthews, J.; Miller, E. H.; Mouton, F.; Murphy, A. St. J.; Paling, S. M.; Phan, N.; Sadler, S. W.; Scarff, A.; Schuckman, F. G.; Snowden-Ifft, D.; Spooner, N. J. C.; Walker, D.

    2015-09-01

    Background events in the DRIFT-IId dark matter detector, mimicking potential WIMP signals, are predominantly caused by alpha decays on the central cathode in which the alpha particle is completely or partially absorbed by the cathode material. We installed a 0.9 μm thick aluminized-mylar cathode as a way to reduce the probability of producing these backgrounds. We study three generations of cathode (wire, thin-film, and radiologically clean thin-film) with a focus on the ratio of background events to alpha decays. Two independent methods of measuring the absolute alpha decay rate are used to ensure an accurate result, and agree to within 10%. Using alpha range spectroscopy, we measure the radiologically cleanest cathode version to have a contamination of 3.3±0.1 ppt 234U and 73±2 ppb 238U. This cathode reduces the probability of producing an RPR from an alpha decay by a factor of 70±20 compared to the original stainless steel wire cathode. First results are presented from a texturized version of the cathode, intended to be even more transparent to alpha particles. These efforts, along with other background reduction measures, have resulted in a drop in the observed background rate from 500/day to 1/day. With the recent implementation of full-volume fiducialization, these remaining background events are identified, allowing for background-free operation.

  20. Structure and mechanical properties of irradiated magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Devanathan, R.; Yu, N.; Sickafus, K. E.; Nastasi, M.

    1996-09-01

    The relationship between structure and mechanical properties of MgAl 2O 4 spinel single crystals following 400 keV Xe 2+ irradiation at 100 K to doses up to 1 × 10 20 ions/m 2 was examined. The structural changes in the irradiated layer were studied using electron diffraction from cross-sectional samples. The nano-indentation technique was used to determine the mechanical properties. At low doses, the material transformed into a metastable crystalline phase characterized by the rearrangement of cations. At the onset of this transformation, the Young's modulus and hardness rose to values about 10 and 15% higher, respectively, than those of the unirradiated crystal. Upon further irradiation, the metastable crystal became amorphous. The Young's modulus and hardness of the amorphous state were about 30 and 60% less, respectively, than the corresponding values of unirradiated spinel. These results, in conjunction with the findings of a recent computer simulation study, provide important insights into the exceptional radiation resistance of magnesium aluminate spinel.

  1. Hard transparent domes and windows from magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    DiGiovanni, Anthony A.; Fehrenbacher, Larry; Roy, Don W.

    2005-05-01

    Transparent magnesium aluminate spinel is an attractive material for use in a wide range of optical applications including windows, domes, armor, and lenses, which require excellent transmission from the visible through to the mid IR. Theoretical transmission is very uniform and approaches 87% between 0.3 to 5 microns. Transmission characteristics rival that of ALON and sapphire in the mid-wave IR, making it especially attractive for the everincreasing performance requirements of current and next-generation IR imaging systems. Future designs in missile technology will require materials that can meet stringent performance demands in both optical and RF wavelengths. Loss characteristics for spinel are being investigated to meet those demands. Technology Assessment and Transfer Inc. (TA&T), have established a 9000 ft2 production facility for optical quality spinel based on the traditional hot-pressing followed by hot isostatic pressing (HIPing) route. Additionally, TA&T is developing pressureless sintering - a highly scalable, near net shape processing method based on traditional ceramic processing technology - to fabricate optical components. These two main processing approaches allow the widest variety of applications to be addressed using a range of optical components and configurations. The polycrystalline nature of spinel facilitates near net shape processing, which provides the potential to fabricate physically larger optical parts or larger quantities of parts at significantly lower costs compared to single crystal materials such as sapphire. Current research is focused at optimizing the processing parameters for both synthesis routes to maximize strength and transparency while minimizing the cost of fabrication.

  2. Sintering and sulfation of calcium silicate: Calcium aluminate

    SciTech Connect

    Borgwardt, R.H.; Rochelle, G.T.

    1990-01-01

    The effect of sintering on the reactivity of solids at high temperature was studied. The nature of the interaction was studied with calcium silicate-aluminate reacting with SO2 between 665 and 800 C. The kinetics of the sintering and sulfation processes were measured independently in terms of the common variables, temperature and specific surface area. Surface reduction parameters were evaluated by the German-Munir sinter model, modified to account for a strong catalytic effect of H2O vapor. Sulfation parameters were determined from a series of conversion vs. time measurements at various temperatures using calcined solids of known surface area. These show product layer diffusion through CaSO4 to be the probable controlling process above 670 C and diffusion through a mixture of CaSO3 and CaSO4 controlling below that temperature. Like sintering, sulfation was enhanced by the presence of H2O in the feed gas. With 7% H2O vapor, the enhancement factor for sulfation was 1.5 at 665 C and estimated to be 5.0 at higher temperatures where only CaSO4 is formed. A combined sinter/sulfation model, based on the parameters evaluated for the independent processes, is compared to sulfation rates measured for the uncalcined solid when sintering is occurring simultaneously.

  3. Double mutagenesis of a positive charge cluster in the ligand-binding site of the ferric enterobactin receptor, FepA.

    PubMed

    Newton, S M; Allen, J S; Cao, Z; Qi, Z; Jiang, X; Sprencel, C; Igo, J D; Foster, S B; Payne, M A; Klebba, P E

    1997-04-29

    Siderophores and colicins enter bacterial cells through TonB-dependent outer membrane proteins. Using site-directed substitution mutagenesis, we studied ligand recognition by a prototypic Escherichia coli siderophore receptor, FepA, that binds the iron chelate ferric enterobactin and colicins B and D. These genetic experiments identified a common binding site for two of the three ligands, containing multiple positive charges, within cell surface residues of FepA. Elimination of single residues in this region did not impair the adsorption or transport of ferric enterobactin, but double mutagenesis in the charge cluster identified amino acids (Arg-286 and Arg-316) that participate in siderophore binding and function in FepA-mediated killing by colicins B and D. Ferric enterobactin binding, furthermore, prevented covalent modification of FepA within this domain by either a fluorescent probe or an arginine-specific reagent, corroborating the involvement of this site in ligand recognition. These results identify, for the first time, residues in a TonB-dependent outer membrane protein that participate in ligand binding. They also explain the competition between ferric enterobactin and the colicins on the bacterial cell surface: all three ligands interact with the same arginine residues within FepA during their penetration through the outer membrane. PMID:9114029

  4. Medicated Janus fibers fabricated using a Teflon-coated side-by-side spinneret.

    PubMed

    Yu, Deng-Guang; Yang, Chen; Jin, Miao; Williams, Gareth R; Zou, Hua; Wang, Xia; Bligh, S W Annie

    2016-02-01

    A family of medicated Janus fibers that provides highly tunable biphasic drug release was fabricated using a side-by-side electrospinning process employing a Teflon-coated parallel spinneret. The coated spinneret facilitated the formation of a Janus Taylor cone and in turn high quality integrated Janus structures, which could not be reliably obtained without the Teflon coating. The fibers prepared had one side consisting of polyvinylpyrrolidone (PVP) K60 and ketoprofen, and the other of ethyl cellulose (EC) and ketoprofen. To modulate and tune drug release, PVP K10 was doped into the EC side in some cases. The fibers were linear and had flat morphologies with an indent in the center. They provide biphasic drug release, with the PVP K60 side dissolving very rapidly to deliver a loading dose of the active ingredient, and the EC side resulting in sustained release of the remaining ketoprofen. The addition of PVP K10 to the EC side was able to accelerate the second stage of release; variation in the dopant amount permitted the release rate and extent this phase to be precisely tuned. These results offer the potential to rationally design systems with highly controllable drug release profiles, which can complement natural biological rhythms and deliver maximum therapeutic effects. PMID:26674839

  5. UV and IR laser radiation's interaction with metal film and teflon surfaces

    NASA Astrophysics Data System (ADS)

    Fedenev, A. V.; Alekseev, S. B.; Goncharenko, I. M.; Koval', N. N.; Lipatov, E. I.; Orlovskii, V. M.; Shulepov, M. A.; Tarasenko, V. F.

    2003-04-01

    The interaction of Xe ([lambda] [similar] 1.73 [mu]m) and XeCl (0.308 [mu]m) laser radiation with surfaces of metal and TiN-ceramic coatings on glass and steel substrates has been studied. Correlation between parameters of surface erosion versus laser-specific energy was investigated. Monitoring of laser-induced erosion on smooth polished surfaces was performed using optical microscopy. The correlation has been revealed between characteristic zones of thin coatings damaged by irradiation and energy distribution over the laser beam cross section allowing evaluation of defects and adhesion of coatings. The interaction of pulsed periodical CO2 ([lambda] [similar] 10.6 [mu]m), and Xe ([lambda] [similar] 1.73 [mu]m) laser radiation with surfaces of teflon (polytetrafluoroethylene—PTFE) has been studied. Monitoring of erosion track on surfaces was performed through optical microscopy. It has been shown that at pulsed periodical CO2-radiation interaction with teflon the sputtering of polymer with formation of submicron-size particles occurs. Dependencies of particle sizes, form, and sputtering velocity on laser pulse duration and target temperature have been obtained.

  6. Percutaneous Palliation of Pancreatic Head Cancer: Randomized Comparison of ePTFE/FEP-Covered Versus Uncovered Nitinol Biliary Stents

    SciTech Connect

    Krokidis, Miltiadis; Fanelli, Fabrizio; Orgera, Gianluigi; Tsetis, Dimitrios; Mouzas, Ioannis; Bezzi, Mario; Kouroumalis, Elias; Pasariello, Roberto; Hatzidakis, Adam

    2011-04-15

    The purpose of this study was to compare the clinical effectiveness of expanded polytetrafluoroethylene/fluorinated-ethylene-propylene (ePTFE/FEP)-covered stents with that of uncovered nitinol stents for the palliation of malignant jaundice caused by inoperable pancreatic head cancer. Eighty patients were enrolled in a prospective randomized study. Bare nitinol stents were used in half of the patients, and ePTFE/FEP-covered stents were used in the remaining patients. Patency, survival, complications, and mean cost were calculated in both groups. Mean patency was 166.0 {+-} 13.11 days for the bare-stent group and 234.0 {+-} 20.87 days for the covered-stent group (p = 0.007). Primary patency rates at 3, 6, and 12 months were 77.5, 69.8, and 69.8% for the bare-stent group and 97.5, 92.2, and 87.6% for the covered-stent group, respectively. Mean secondary patency was 123.7 {+-} 22.5 days for the bare-stent group and 130.3 {+-} 21.4 days for the covered-stent group. Tumour ingrowth occurred exclusively in the bare-stent group in 27.5% of cases (p = 0.002). Median survival was 203.2 {+-} 11.8 days for the bare-stent group and 247.0 {+-} 20 days for the covered-stent group (p = 0.06). Complications and mean cost were similar in both groups. Regarding primary patency and ingrowth rate, ePTFE/FEP-covered stents have shown to be significantly superior to bare nitinol stents for the palliation of malignant jaundice caused by inoperable pancreatic head cancer and pose comparable cost and complications. Use of a covered stent does not significantly influence overall survival rate; nevertheless, the covered endoprosthesis seems to offer result in fewer reinterventions and better quality of patient life.

  7. Regions of Escherichia coli TonB and FepA proteins essential for in vivo physical interactions.

    PubMed Central

    Larsen, R A; Foster-Hartnett, D; McIntosh, M A; Postle, K

    1997-01-01

    The transport of Fe(III)-siderophore complexes and vitamin B12 across the outer membrane of Escherichia coli is an active transport process requiring a cognate outer membrane receptor, cytoplasmic membrane-derived proton motive force, and an energy-transducing protein anchored in the cytoplasmic membrane, TonB. This process requires direct physical contact between the outer membrane receptor and TonB. Previous studies have identified an amino-terminally located region (termed the TonB box) conserved in all known TonB-dependent outer membrane receptors as being essential for productive energy transduction. In the present study, a mutation in the TonB box of the ferric enterochelin receptor FepA resulted in the loss of detectable in vivo chemical cross-linking between FepA and TonB. Protease susceptibility studies indicated this effect was due to an alteration of conformation rather than the direct disruption of a specific site of physical contact. This suggested that TonB residue 160, implicated in previous studies as a site of allele-specific suppression of TonB box mutants, also made a conformational rather than a direct contribution to the physical interaction between TonB and the outer membrane receptors. This possibility was supported by the finding that TonB carboxyl-terminal truncations that retained Gln-160 were unable to participate in TonB-FepA complex formation, indicating that this site alone was not sufficient to support the physical interactions involved in energy transduction. These studies indicated that the final 48 residues of TonB were essential to this physical interaction. This region contains a putative amphipathic helix which could facilitate TonB-outer membrane interaction. Amino acid replacements at one site in this region were found to affect energy transduction but did not appear to greatly alter TonB conformation or the formation of a TonB-FepA complex. The effects of amino acid substitutions at several other TonB sites were also examined

  8. Amorphization of rare earth aluminate garnets by ionic irradiation and decay of 244Cm admixture

    SciTech Connect

    Livshits, T. S.; Lizin, A. A.; Zhang, J. M.; Ewing, R. C.

    2010-08-29

    The stability of synthetic REE-aluminate garnets irradiated by accelerated Kr2+ ions and affected by alpha decay of ²⁴⁴Cm (T1/2 = 18.1 yr) has been studied. The dose of irradiation sufficient for the complete disordering of the aluminate garnet structure is 0.40–0.55 displacements per atom. This value increases with rising temperature due to the increasing intensity of recovery from radiation damage to the lattice by heating. The critical temperature above which the structure of REE-aluminate is not damaged by radiation is 550°C. The amorphization dose for aluminates with garnet structure is two to three times higher than of that previously studied ferrites; the critical temperature of both is similar. In resistance to radiation, aluminate garnets do not yield to zirconolite and exceed titanate pyrochlore. Heating to 250°C does not lead to substantial recovery from radiation defects in the garnet structure. The radiation impact on matrices of real actinide (An) wastes is lower than that related to ion irradiation and ²⁴⁴Cm doping, and this facilitates a higher radiation resistance of garnets containing HLW.

  9. Structural Characterization of Spinel Zinc Aluminate Nanoparticles Prepared By Coprecipitation Method

    NASA Astrophysics Data System (ADS)

    Sunder, Shyam; Rohilla, Sunil; Kumar, Sushil; Aghamkar, Praveen

    2011-12-01

    Zinc aluminate is well known wide bandgap semiconductor with cubic spinel structure and transparent for wavelength greater than 320 nm. Therefore, ZnAl2O4 can be used for ultraviolet photoelectronic devices. Furthermore, spinel zinc aluminate is useful in many reactions as catalytic support. Moreover, zinc aluminate can be used as second phase in glaze layer of white ceramics to improve wear resistance and to preserve whiteness. In present study cubic spinel zinc aluminate nanoparticles have been synthesized from aqueous solution of Zn(NO3)2.6H2O (0.1 M) and Al(NO3)2.9H2O (0.2 M) using chemical coprecipitation technique. Ammonium hydroxide was used as precipitating agent and pH was maintained between 8 to 9. The precipitated slurry was filtered and washed several times with deionized double distilled water and dried at 110 °C. The fine powder was annealed at different temperatures from 600 °C to 900 °C for 4h in temperature controlled furnace. Structural characterization of annealed samples was carried out via X-ray Diffraction (XRD), and Fourier Transform Infrared spectroscopy (FTIR). XRD patterns reveal that zinc aluminate samples were cubic spinel nanoparticles and grain size determined by Debye-Scherrer formula is from 5 to 16 nm.

  10. Rugae-like FeP nanocrystal assembly on a carbon cloth: an exceptionally efficient and stable cathode for hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Yang, Xiulin; Lu, Ang-Yu; Zhu, Yihan; Min, Shixiong; Hedhili, Mohamed Nejib; Han, Yu; Huang, Kuo-Wei; Li, Lain-Jong

    2015-06-01

    There is a strong demand to replace expensive Pt catalysts with cheap metal sulfides or phosphides for hydrogen generation in water electrolysis. Earth-abundant Fe can be electroplated on carbon cloth (CC) to form high surface area rugae-like FeOOH assembly. Subsequent gas phase phosphidation converts the FeOOH to FeP or FeP2 and the morphology of the crystal assembly is controlled by the phosphidation temperature. FeP prepared at 250 °C presents lower crystallinity and that prepared at higher temperatures of 400 °C and 500 °C possesses higher crystallinity, but lower surface area. The phosphidation at 300 °C produces nanocrystalline FeP and preserves the high-surface area morphology; thus, it exhibits the highest HER efficiency in 0.5 M H2SO4, i.e., the required overpotential to reach 10 and 20 mA cm-2 is 34 and 43 mV, respectively. These values are lowest among the reported non-precious metal phosphides on CC. The Tafel slope for FeP prepared at 300 °C is around 29.2 mV dec-1, which is comparable to that of Pt/CC; this indicates that the hydrogen evolution for our best FeP is limited by the Tafel reaction (same as Pt). Importantly, the FeP/CC catalyst exhibits much better stability in a wide-range working current density (up to 1 V cm-2), suggesting that it is a promising replacement of Pt for HER.There is a strong demand to replace expensive Pt catalysts with cheap metal sulfides or phosphides for hydrogen generation in water electrolysis. Earth-abundant Fe can be electroplated on carbon cloth (CC) to form high surface area rugae-like FeOOH assembly. Subsequent gas phase phosphidation converts the FeOOH to FeP or FeP2 and the morphology of the crystal assembly is controlled by the phosphidation temperature. FeP prepared at 250 °C presents lower crystallinity and that prepared at higher temperatures of 400 °C and 500 °C possesses higher crystallinity, but lower surface area. The phosphidation at 300 °C produces nanocrystalline FeP and preserves the high

  11. The Na2FeP2O7-carbon nanotubes composite as high rate cathode material for sodium ion batteries

    NASA Astrophysics Data System (ADS)

    Longoni, Gianluca; Wang, Ji Eun; Jung, Young Hwa; Kim, Do Kyung; Mari, Claudio M.; Ruffo, Riccardo

    2016-01-01

    Among the viable positive electrode materials recently proposed for Na-ion secondary batteries, Na2FeP2O7 was investigated thanks to its facile preparation, the use of highly abundant and low cost raw materials, and the highest thermal stability among all others cathode materials. In the present work the electrochemical features of the Na2FeP2O7 are improved by synthesizing a Na2FeP2O7-carbon nanotubes composite with prominent high-rate performances. The material shows a reversible specific capacity of 86 mAh g-1 for 140 cycles at 1C and 68 mAh g-1 at 10C. An in depth investigation about the Na+ diffusion rates inside the material was conducted by electrochemical impedance spectroscopy.

  12. Terraced copper growth deposited onto Teflon AF1600 by the excimer laser irradiation of Cu(hfac)TMVS

    SciTech Connect

    Popovici, D.; Piyakis, K.; Sacher, E.; Meunier, M.

    1996-12-31

    The authors are studying the feasibility of constructing Cu/fluoropolymer multilayer devices, in an effort to reduce both metal R and insulator C, a necessary condition in VLSI and GSI microelectronic applications. The laser chemical vapor deposition (LCVD) of the organometallic precursor Cu(hfac)TMVS (hexafluoroacetylacetonate)(trimethylvinylsilane) is used to grow copper films on a Teflon AF1600 substrate. Exposure to excimer laser radiation at 248 nm results in a terraced copper growth. A simple model, based on interference effects in the Teflon and copper layers, is presented to account for this structure.

  13. Rugae-like FeP nanocrystal assembly on a carbon cloth: an exceptionally efficient and stable cathode for hydrogen evolution.

    PubMed

    Yang, Xiulin; Lu, Ang-Yu; Zhu, Yihan; Min, Shixiong; Hedhili, Mohamed Nejib; Han, Yu; Huang, Kuo-Wei; Li, Lain-Jong

    2015-07-01

    There is a strong demand to replace expensive Pt catalysts with cheap metal sulfides or phosphides for hydrogen generation in water electrolysis. Earth-abundant Fe can be electroplated on carbon cloth (CC) to form high surface area rugae-like FeOOH assembly. Subsequent gas phase phosphidation converts the FeOOH to FeP or FeP2 and the morphology of the crystal assembly is controlled by the phosphidation temperature. FeP prepared at 250 °C presents lower crystallinity and that prepared at higher temperatures of 400 °C and 500 °C possesses higher crystallinity, but lower surface area. The phosphidation at 300 °C produces nanocrystalline FeP and preserves the high-surface area morphology; thus, it exhibits the highest HER efficiency in 0.5 M H2SO4, i.e., the required overpotential to reach 10 and 20 mA cm(-2) is 34 and 43 mV, respectively. These values are lowest among the reported non-precious metal phosphides on CC. The Tafel slope for FeP prepared at 300 °C is around 29.2 mV dec(-1), which is comparable to that of Pt/CC; this indicates that the hydrogen evolution for our best FeP is limited by the Tafel reaction (same as Pt). Importantly, the FeP/CC catalyst exhibits much better stability in a wide-range working current density (up to 1 V cm(-2)), suggesting that it is a promising replacement of Pt for HER. PMID:26058361

  14. Er3+ fluorescence in rare-earth aluminate glass

    NASA Astrophysics Data System (ADS)

    Weber, Richard; Hampton, Scott; Nordine, Paul C.; Key, Thomas; Scheunemann, Richard

    2005-08-01

    Er3+ ion fluorescence was excited with a 980-nm pump laser in Er-doped rare-earth aluminate (REAl) glasses with Er-dopant concentrations from 0.5-30mol% (oxides basis). The spectral and decay characteristics were measured at ˜1550nm from Er3+I13/24 and at ˜2750nm from Er3+I11/24. Red and green light emissions were also observed, from Er3+F9/24 and S3/24+H11/22, respectively. The fluorescence decay rates are described by a model that yields an accurate fit of results at Er concentrations from 0.5to7mol%. The radiative lifetime of Er3+I13/24 in Er:REAl glass is 6.12±0.26ms. Hydroxyl ion quenching occurs at a rate given by 9.88×10-20 aOHnEr Hz, where aOH is the glass absorption coefficient (in cm-1) at a wavelength of 2950nm and nEr is the total Er ion concentration. The I13/24 upconversion rate constant increases with the Er concentration to 1.35+0.05×10-18width="0.3em"/>cm3/s at and above 7-mol% Er2O3. Er3+I11/24 fluorescence decays primarily by multiphonon quenching to I13/24, at 7700±800Hz, a rate that is slightly less than in tellurite glasses. The addition of 20-mol% silica to the glass has only a small influence on the fluorescence decay rates and greatly improves glass formation from the liquid to allow melting and casting of Er-doped REAl glass from platinum crucibles. The application of these Er-doped glasses in laser and optical device applications is briefly discussed.

  15. Rare earth activated yttrium aluminate phosphors with modulated luminescence.

    PubMed

    Muresan, L E; Popovici, E J; Perhaita, I; Indrea, E; Oro, J; Casan Pastor, N

    2016-06-01

    Yttrium aluminate (Y3 A5 O12 ) was doped with different rare earth ions (i.e. Gd(3+) , Ce(3+) , Eu(3+) and/or Tb(3+) ) in order to obtain phosphors (YAG:RE) with general formula,Y3-x-a Gdx REa Al5 O12 (x = 0; 1.485; 2.97 and a = 0.03). The synthesis of the phosphor samples was done using the simultaneous addition of reagents technique. This study reveals new aspects regarding the influence of different activator ions on the morpho-structural and luminescent characteristics of garnet type phosphor. All YAG:RE phosphors are well crystallized powders containing a cubic-Y3 Al5 O12 phase as major component along with monoclinic-Y4 Al2 O9 and orthorhombic-YAlO3 phases as the impurity. The crystallites dimensions of YAG:RE phosphors vary between 38 nm and 88 nm, while the unit cell slowly increase as the ionic radius of the activator increases. Under UV excitation, YAG:Ce exhibits yellow emission due to electron transition in Ce(3+) from the 5d level to the ground state levels ((2) F5/2 , (2) F7/2 ). The emission intensity of Ce(3+) is enhanced in the presence of the Tb(3+) ions and is decreased in the presence of Eu(3+) ions due to some radiative or non-radiative processes that take place between activator ions. By varying the rare earth ions, the emission colour can be modulated from green to white and red. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26553167

  16. Fluorous Polymeric Membranes for Ionophore-Based Ion-Selective Potentiometry: How Inert is Teflon AF?

    PubMed Central

    Lai, Chun-Ze; Koseoglu, Secil S.; Lugert, Elizabeth C.; Boswell, Paul G.; Rábai, József; Lodge, Timothy P.; Bühlmann, Philippe

    2011-01-01

    Fluorous media are the least polar and polarizable condensed phases known. Their use as membrane materials considerably increases the selectivity and robustness of ion-selective electrodes (ISEs). In this research, a fluorous amorphous perfluoropolymer was used for the first time as a matrix for an ISE membrane. Electrodes for pH measurements with membranes composed of poly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole]-co-poly(tetrafluoroethylene) (87% dioxole monomer content; known as Teflon AF2400) as polymer matrix, a linear perfluorooligoether as plasticizer, sodium tetrakis[3,5-bis(perfluorohexyl)phenyl]borate providing for ionic sites, and bis[(perfluorooctyl)propyl]-2,2,2-trifluoroethylamine as H+-ionophore were investigated. All electrodes had excellent potentiometric selectivities, showed Nernstian responses to H+ over a wide pH range, exhibited enhanced mechanical stability and maintained their selectivity over at least four weeks. For membranes of low ionophore concentration, the polymer affected the sensor selectivity noticeably at polymer concentrations exceeding 15%. Also, the membrane resistance increased quite strongly at high polymer concentrations, which cannot be explained by the Mackie–Meares obstruction model. The selectivities and resistances depend on the polymer concentration because of a functional group associated with Teflon AF2400, with a concentration of one functional group per 854 monomer units of the polymer. In the fluorous environment of these membranes, this functional group binds to Na+, K+, Ca2+, and the unprotonated ionophore with binding constants of 103.5, 101.8, 106.8 and 104.4 M−1, respectively. Potentiometric and spectroscopic evidence indicates that these functional groups are COOH groups formed by the hydrolysis of carboxylic acid fluoride (COF) groups originally present in Teflon AF2400. The use of higher ionophore concentrations removes the undesirable effect of these COOH groups almost completely

  17. Improving electrochemical properties of AISI 1045 steels by duplex surface treatment of plasma nitriding and aluminizing

    NASA Astrophysics Data System (ADS)

    Haftlang, Farahnaz; Habibolahzadeh, Ali; Sohi, Mahmoud Heydarzadeh

    2015-02-01

    Improvement in electrochemical behavior of AISI 1045 steel after applying aluminum nitride coating was investigated in 3.5% NaCl solution, using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analyses. Aluminum nitride coating was applied on the steel surface by duplex treatment of pack aluminizing and plasma nitriding. Some specimens were plasma nitrided followed by aluminizing (PN-Al), while the others were pack aluminized followed by plasma nitriding (Al-PN). Topological and structural studies of the modified surfaces were conducted using scanning electron microscope (SEM) equipped by energy dispersive X-ray spectroscope (EDS), and X-ray diffractometer (XRD). The electrochemical measurements showed that the highest corrosion and polarization (Rp) resistances were obtained in PN-Al specimens, having single phase superficial layer of AlN. Pitting mechanism was dominant reason of lower corrosion resistance in the Al-PN specimens.

  18. Method of preparing a sintered lithium aluminate structure for containing electrolyte

    DOEpatents

    Sim, James W.; Kinoshita, Kimio

    1981-01-01

    A porous sintered tile is formed of lithium aluminate for retaining molten lectrolyte within a fuel cell. The tile is prepared by reacting lithium hydroxide in aqueous solution with alumina particles to form beta lithium aluminate particles. The slurry is evaporated to dryness and the solids dehydrated to form a beta lithium aluminate powder. The powder is compacted into the desired shape and sintered at a temperature in excess of 1200 K. but less than 1900 K. to form a porous integral structure that is subsequently filled with molten electrolyte. A tile of this type is intended for use in containing molten alkali metal carbonates as electolyte for use in a fuel cell having porous metal or metal oxide electrodes for burning a fuel gas such as hydrogen and/or carbon monoxide with an oxidant gas containing oxygen.

  19. Interfacial interactions between an alkali-free borosilicate viscous sealing glass and aluminized ferritic stainless steel

    NASA Astrophysics Data System (ADS)

    Hsu, Jen-Hsien; Kim, Cheol-Woon; Brow, Richard K.

    2014-03-01

    An alkali-free, alkaline earth borosilicate glass (designated G73) has been developed as a viscous sealant for use with solid oxide fuel cells (SOFC). In this work, the interfacial interactions that occur between this viscous sealant and aluminized ferritic stainless steel (SS441) under SOFC operational conditions are described. YSZ/glass/aluminized SS441 sandwich seals were held at 800 °C in air for up to 1000 h, and the interfaces were analyzed using analytical scanning electron microscopy (ASEM). Interfacial reactions were also characterized by X-ray diffraction (XRD) analyses of heat-treated mixtures of glass and alumina powders. The results show that the glass reacted with aluminum from the steel to form BaAl2Si2O8 crystals at the glass/metal interface and that the aluminum concentration in the aluminized steel was significantly depleted with time.

  20. MBE Growth of AlN Nanowires on Si Substrates by Aluminizing Nucleation.

    PubMed

    E, Yanxiong; Hao, Zhibiao; Yu, Jiadong; Wu, Chao; Liu, Runze; Wang, Lai; Xiong, Bing; Wang, Jian; Han, Yanjun; Sun, Changzheng; Luo, Yi

    2015-12-01

    By introducing an aluminization process to achieve nucleation of nanowires (NWs), spontaneous growth of AlN NWs on Si substrates has been realized by plasma-assisted molecular beam epitaxy. The AlN NWs are grown from the nuclei formed by the aluminization process, and the NW density and diameter can be controlled by the aluminization parameters. The influence of growth conditions on the morphologies of AlN NWs is carefully investigated. Island-like films are found to grow between the NWs due to poor migration ability of Al adatoms. The films are proved to be Al-polar different from the N-polar AlN NWs, which can explain the absence of newly formed NWs. Increasing the V/III ratio can efficiently suppress the growth of Al-polar AlN films. PMID:26437653

  1. MBE Growth of AlN Nanowires on Si Substrates by Aluminizing Nucleation

    NASA Astrophysics Data System (ADS)

    E, Yanxiong; Hao, Zhibiao; Yu, Jiadong; Wu, Chao; Liu, Runze; Wang, Lai; Xiong, Bing; Wang, Jian; Han, Yanjun; Sun, Changzheng; Luo, Yi

    2015-10-01

    By introducing an aluminization process to achieve nucleation of nanowires (NWs), spontaneous growth of AlN NWs on Si substrates has been realized by plasma-assisted molecular beam epitaxy. The AlN NWs are grown from the nuclei formed by the aluminization process, and the NW density and diameter can be controlled by the aluminization parameters. The influence of growth conditions on the morphologies of AlN NWs is carefully investigated. Island-like films are found to grow between the NWs due to poor migration ability of Al adatoms. The films are proved to be Al-polar different from the N-polar AlN NWs, which can explain the absence of newly formed NWs. Increasing the V/III ratio can efficiently suppress the growth of Al-polar AlN films.

  2. Study of optical properties of cerium ion doped barium aluminate phosphor

    NASA Astrophysics Data System (ADS)

    Lohe, P. P.; Omanwar, S. K.; Bajaj, N. S.; Belsare, P. D.

    2016-05-01

    In the recent years due to their various optical and technological applications aluminate materials have attracted attention of several researchers. When these materials are doped with rare earth ions they show properties favorable for many optical applications such as high quantum efficiencies. These materials are used in various applications such as lamp phosphors, optically and thermoluminescence dosimeter etc Barium aluminate BaAl2O4 doped with Ce is well known long lasting phosphor. This paper reports synthesis of BaAl2O4: Ce phosphor prepared by a simple combustion synthesis. The samples were characterized for the phase purity, chemical bonds and luminescent properties.

  3. Direct measurement of electrostatic fields using single Teflon nanoparticle attached to AFM tip

    PubMed Central

    2013-01-01

    Abstract A single 210-nm Teflon nanoparticle (sTNP) was attached to the vertex of a silicon nitride (Si3N4) atomic force microscope tip and charged via contact electrification. The charged sTNP can then be considered a point charge and used to measure the electrostatic field adjacent to a parallel plate condenser using 30-nm gold/20-nm titanium as electrodes. This technique can provide a measurement resolution of 250/100 nm along the X- and Z-axes, and the minimum electrostatic force can be measured within 50 pN. PACS 07.79.Lh, 81.16.-c, 84.37. + q PMID:24314111

  4. Electrical characterization of glass, teflon, and tantalum capacitors at high temperatures

    NASA Technical Reports Server (NTRS)

    Hammoud, A. N.; Baumann, E. D.; Myers, I. T.; Overton, E.

    1991-01-01

    Dielectric materials and electrical components and devices employed in radiation fields and the space environment are often exposed to elevated temperatures among other things. Therefore, these systems must withstand the high temperature exposure while still providing good electrical and other functional properties. Experiments were carried out to evaluate glass, teflon, and tantalum capacitors for potential use in high temperature applications. The capacitors were characterized in terms of their capacitance and dielectric loss as a function of temperature up to 200 C. At a given temperature, these properties were obtained in a frequency range of 50 Hz to 100 kHz. The DC leakage current measurements were also performed in a temperature range from 20 to 200 C. The obtained results are discussed and conclusions are made concerning the suitability of the capacitors investigated for high temperature applications.

  5. Neutron energy spectrum adjustment using deposited metal films on Teflon in the miniature neutron source reactor.

    PubMed

    Nassan, L; Abdallah, B; Omar, H; Sarheel, A; Alsomel, N; Ghazi, N

    2016-01-01

    The focus of this article was on the experimental estimation of the neutron energy spectrum in the inner irradiation site of the miniature neutron source reactor (MNSR), using, for the first time, a selected set of deposited metal films on Teflon (DMFTs) neutron detectors. Gold, copper, zinc, titanium, aluminum, nickel, silver, and chromium were selected because of the dependence of their neutron cross-sections on neutron energy. Emphasis was placed on the usability of this new type of neutron detectors in the total neutron energy spectrum adjustment. The measured saturation activities per target nucleus values of the DMFTs, and the calculated neutron spectrum in the inner irradiation site using the MCNP-4C code were used as an input for the STAY'SL computer code during the adjustment procedure. The agreement between the numerically calculated and experimentally adjusted spectra results was discussed. PMID:26562448

  6. Clotting Problems with the Teflon-Silastic Arteriovenous Shunt in Patients on Regular Haemodialysis

    PubMed Central

    Papadimitriou, M.; Carroll, R. N. P.; Kulatilake, A. E.

    1969-01-01

    Episodes of clotting that occurred in 22 patients on regular haemodialysis were studied over a six-month period. The venous pressure during dialysis and the radiology of the Teflon-Silastic arteriovenous shunt were found to be satisfactory guides for the management of the shunt. The failure of the shunt during the early stage was mainly due to technical reasons. Histological study of the excised vessels in removed long-term shunts showed that these had failed because of rigidity and thickening of the vessel wall due to calcium and iron deposits or chronic inflammation, or both. ImagesFig. 1Fig. 2Fig. 3Fig. 4Fig. 5Fig. 6Fig. 7Fig. 8Fig. 9Fig. 10Fig. 11 PMID:5776208

  7. The "Teflon basin" myth: Snow-soil interactions in mountain catchments in the western US

    NASA Astrophysics Data System (ADS)

    Williams, M. W.; Cowie, R. M.

    2015-12-01

    In much of western North America, snow and snowmelt provide the primary means for storage of winter precipitation, effectively transferring water from the relatively wet winter season to the typically dry summers. A common assumption is that high-elevation catchments in the western United States behave like "Teflon basins" and that water released from seasonal storage in snow packs flows directly into streams with little or no interaction with underlying soils. Here I present information from a variety of catchments in the Colorado Front Range on snowmelt/soil interactions using isotopic, geochemical, nutrient and hydrometric data in 2- and 3- component hydrograph separations, along with end-member mixing analysis (EMMA). For most catchments we measured these parameters in weekly precipitation, the seasonal snowpack, snowmelt before contact with the ground, discharge, springs, soil solution, and groundwater. We ran EMMA at the catchment scale for catchments that represent the rain-snow transition zone in the montane forest, the seasonally snow covered sub-alpine to alpine transition zone, and a high-elevation alpine zone near the continental divide. In all catchments three end-members were the source waters for about 95% of discharge. Two end-members were the same in all catchments, snow and groundwater. For the alpine catchment talus springs was the third water source, while rain was the third water source in the two lower-elevation catchments. For all three catchments, soil solution plotted with stream waters along or near a line connecting the snow and groundwater end-members. Thus, for seasonally snow-covered catchments from montane to alpine ecosystems, snowmelt infiltrates underlying soils before snowmelt recharges groundwater reservoirs and contributes to surface flows. Seasonally snow-covered catchments are not Teflon basins. Rather, snowmelt infiltrates soils where solute concentrations are changed by biological and geochemical processes.

  8. A Novel Teflon-membrane Gas Tension Device for Denitrification-studies in Oxygen Minimum Zones

    NASA Astrophysics Data System (ADS)

    Reed, A. C.; McNeil, C. L.; D'Asaro, E. A.; Altabet, M. A.; Johnson, B.; Bourbonnais, A.

    2014-12-01

    Oxygen Minimum Zones (OMZs) are global hotspots for the biogeochemical transformation of biologically-available forms of nitrogen to unusable nitrogen-gas. We present a new Teflon-membrane based Gas Tension Device (GTD) for measuring the excess N2 signal generated by denitrification and anammox in OMZs, with a hydrostatic pressure-independent response and a depth range from 0 - 550 m, a significant advancement from previous GTD models. The GTD consists of a 4/1000" thick by 2" diameter Teflon-membrane with a water-side plenum connected to SeaBird 5T pump. Dissolved gases in the water equilibrate across the membrane with a low-dead-volume housing connected to a high-precision quart pressure sensor. Laboratory data characterizing the GTD will be presented. The e-folding (response) time ranges from 14 min at continuous (100%) pumping to 28 min at pulse (10%) pumping. We also demonstrate the pressure dependence of the partial pressures from Henry's Law in the laboratory for pure nitrogen, pure oxygen, and standard atmospheric ratios of gases. GTD's were field tested on two floats deployed in the Eastern Tropical North Pacific (ETNP) OMZ for 15 days that targeted a productive mesoscale surface eddy originating from the Mexican coast. We anticipated that high organic carbon export should stimulate denitrification within the OMZ below. The floats profiled between the surface and 400 m depth and concurrently measured T, S, PAR, O2 (SBE 43 and Optode), and nitrate (SUNA). The N2-profiles from the GTDs are validated against independently measured N2/Ar ratio data collected during the deployment.

  9. Effects of pressure, oxygen concentration, and forced convection on flame spread rate of Plexiglas, Nylon and Teflon

    NASA Technical Reports Server (NTRS)

    Notardonato, J. J.; Burkhardt, L. A.; Cochran, T. H.

    1974-01-01

    Experiments were conducted in which the burning of cylindrical materials in a flowing oxidant stream was studied. Plexiglas, Nylon, and Teflon fuel specimens were oriented such that the flames spread along the surface in a direction opposed to flowing gas. Correlations of flame spread rate were obtained that were power law relations in terms of pressure, oxygen concentration, and gas velocity.

  10. Charge-Exchange Processes of Titanium-Doped Aluminate Crystals

    NASA Astrophysics Data System (ADS)

    Wong, Wing Cheong

    1995-01-01

    Titanium exists in more than one charge state in the aluminate crystals: it is stable as Ti^ {3+} and Ti^{4+}. Other than the intense Ti^{4+ } absorption, a ubiquitous absorption/luminescence excitation band in the UV region is identified as a titanium -bound exciton in Al_2rm O_3, Y_3Al_5rm O_{12}, {rm YAlO}_3, MgAl_2O _4, and LaMgAl_{11} {rm O}_{19}. One -step and two-step photoconductivities of Ti^ {3+} are measured and compared. While the selectivity of the two-step process is demonstrated, its use in locating the energy threshold is hampered by the small Franck-Condon factor for the transition between the Ti^{3+} ^2{ rm E} excited state and Ti^ {4+}. The titanium-bound exciton band, together with the one-step photocurrent signal, makes it possible to determine the photoionization energy threshold accurately. The charge-transfer transition energy thresholds of Ti^{4+} are obtained from the emission and the luminescence excitation spectra. Locally and non-locally charge compensated Ti^{4+ } are found in Al_2{rm O}_3. The luminescence kinetics for the two kinds of Ti^{4+} are well explained by a three-level system with a lower triplet excited state and a higher singlet excited state. These charge-exchange threshold energies can be deduced from the Born-Haber thermodynamical cycle. The electrostatic site potentials are calculated and from it, the calculated photoionization and charge-transfer energy thresholds are found to be consistent with the experimental results. The deficiency of this model is pointed out and possible improvement is discussed. Quantitatively, the sum of the two charge-exchange energy thresholds is close to the band-gap energy of the host crystal. This offers a convenient way for material characterization. Provided that any two of the three quantities (band-gap energy, photoionization energy threshold, and charge-transfer transition energy threshold) have been found, the third quantity can be calculated. In addition, the trapping of charge

  11. Pichia pastoris Fep1 is a [2Fe-2S] protein with a Zn finger that displays an unusual oxygen-dependent role in cluster binding.

    PubMed

    Cutone, Antimo; Howes, Barry D; Miele, Adriana E; Miele, Rossella; Giorgi, Alessandra; Battistoni, Andrea; Smulevich, Giulietta; Musci, Giovanni; di Patti, Maria Carmela Bonaccorsi

    2016-01-01

    Fep1, the iron-responsive GATA factor from the methylotrophic yeast Pichia pastoris, has been characterised both in vivo and in vitro. This protein has two Cys2-Cys2 type zinc fingers and a set of four conserved cysteines arranged in a Cys-X5-Cys-X8-Cys-X2-Cys motif located between the two zinc fingers. Electronic absorption and resonance Raman spectroscopic analyses in anaerobic and aerobic conditions indicate that Fep1 binds iron in the form of a [2Fe-2S] cluster. Site-directed mutagenesis shows that replacement of the four cysteines with serine inactivates this transcriptional repressor. Unexpectedly, the inactive mutant is still able to bind a [2Fe-2S] cluster, employing two cysteine residues belonging to the first zinc finger. These two cysteine residues can act as alternative cluster ligands selectively in aerobically purified Fep1 wild type, suggesting that oxygen could play a role in Fep1 function by causing differential localization of the [Fe-S] cluster. PMID:27546548

  12. Pichia pastoris Fep1 is a [2Fe-2S] protein with a Zn finger that displays an unusual oxygen-dependent role in cluster binding

    PubMed Central

    Cutone, Antimo; Howes, Barry D.; Miele, Adriana E.; Miele, Rossella; Giorgi, Alessandra; Battistoni, Andrea; Smulevich, Giulietta; Musci, Giovanni; di Patti, Maria Carmela Bonaccorsi

    2016-01-01

    Fep1, the iron-responsive GATA factor from the methylotrophic yeast Pichia pastoris, has been characterised both in vivo and in vitro. This protein has two Cys2-Cys2 type zinc fingers and a set of four conserved cysteines arranged in a Cys-X5-Cys-X8-Cys-X2-Cys motif located between the two zinc fingers. Electronic absorption and resonance Raman spectroscopic analyses in anaerobic and aerobic conditions indicate that Fep1 binds iron in the form of a [2Fe-2S] cluster. Site-directed mutagenesis shows that replacement of the four cysteines with serine inactivates this transcriptional repressor. Unexpectedly, the inactive mutant is still able to bind a [2Fe-2S] cluster, employing two cysteine residues belonging to the first zinc finger. These two cysteine residues can act as alternative cluster ligands selectively in aerobically purified Fep1 wild type, suggesting that oxygen could play a role in Fep1 function by causing differential localization of the [Fe-S] cluster. PMID:27546548

  13. Fast lithium intercalation chemistry of the hierarchically porous Li2FeP2O7/C composite prepared by an iron-reduction method

    NASA Astrophysics Data System (ADS)

    Tan, L.; Zhang, S.; Deng, C.

    2015-02-01

    Lithium iron pyrophosphate has drawn great attention because of its interesting physical and electrochemical properties, whereas its high rate capability is far from satisfactory. We synthesize nano-Li2FeP2O7/C with hierarchical pore via a low cost method which uses iron powder instead of Vitamin C as the reducing agent. The hierarchical pore is constructed through a "combustion" mechanism according to the thermogravimetric and morphological characterizations. The phase-pure nanoparticles of Li2FeP2O7 are embedded in the three-dimensional network of amorphous carbon. The hierarchical pore together with the two-dimensional diffusion channel of lithium in Li2FeP2O7 is beneficial to lithium diffusion capability which is evaluated by the lithium diffusion coefficients calculated from the results of GITT measurements. The fast lithium intercalation chemistry facilitates the reversible de/intercalation of lithium, resulting in the high cycling stability and rate-capability. After 100 cycles at the current density of 1C, 93.8% of the initial capacity is retained. The discharge capacity is 62.1 mAh g-1 at the current density of 4C. Therefore, the hierarchically porous nano-Li2FeP2O7/C is a promising cathode material for advanced rechargeable lithium ion battery.

  14. Lithium aluminate/zirconium material useful in the production of tritium

    DOEpatents

    Cawley, W.E.; Trapp, T.J.

    1984-10-09

    A composition is described useful in the production of tritium in a nuclear reactor. Lithium aluminate particles are dispersed in a matrix of zirconium. Tritium produced by the reactor of neutrons with the lithium are absorbed by the zirconium, thereby decreasing gas pressure within capsules carrying the material.

  15. Effect of aluminized fabrics on radiant protective performance of fire proximity suit materials.

    PubMed

    Jin, Lu; Park, Pyoung Kyu; Hong, Kyoung A; Yoon, Kee Jong

    2015-03-01

    Radiant heat may be a significant component of heat exposure in the case of proximity firefighting. To combat high levels of radiant heat, fire proximity suits made of aluminized fabrics (Al-Fb) are commonly used due to their proven radiant protective performance (RPP). In this study RPP of various Al-Fb prepared using different aluminized films (Al-Fl) such as double-sided aluminized film and single-sided aluminized film and different base fabrics such as woven, knit, and nonwoven fabrics are compared. The effect of flexing on RPP and flame protective performance (FPP) of Al-Fb is also examined. The results show that RPP of Al-Fl is affected by the protective film to protect against mechanical or physical damages, and also by their structure such as whether the second reflective aluminum layer is present or not. In addition RPP of Al-Fb is also influenced by the base fabric, especially its surface roughness. The increased surface roughness combined with the damage caused to the aluminum layer after flexing result in reduction of RPP of Al-Fb. The contribution of Al-Fl to FPP of Al-Fb is not as significant as to RPP. Finally, based on the results, some points that may be important in developing and designing fire proximity suits are recommended. PMID:25324564

  16. Lithium aluminate/zirconium material useful in the production of tritium

    DOEpatents

    Cawley, W.E.; Trapp, T.J.

    A composition is described useful in the production of tritium in a nuclear reactor. Lithium aluminate particles are dispersed in a matrix of zirconium. Tritium produced by the reactor of neutrons with the lithium are absorbed by the zirconium, thereby decreasing gas pressure within capsules carrying the material.

  17. Lithium aluminate/zirconium material useful in the production of tritium

    DOEpatents

    Cawley, William E.; Trapp, Turner J.

    1984-10-09

    A composition is described useful in the production of tritium in a nuclear eactor. Lithium aluminate particles are dispersed in a matrix of zirconium. Tritium produced by the reactor of neutrons with the lithium are absorbed by the zirconium, thereby decreasing gas pressure within capsules carrying the material.

  18. Preliminary Safety Analysis of the Gorleben Site: Safety Concept and Application to Scenario Development Based on a Site-Specific Features, Events and Processes (FEP) Database - 13304

    SciTech Connect

    Moenig, Joerg; Beuth, Thomas; Wolf, Jens; Lommerzheim, Andre; Mrugalla, Sabine

    2013-07-01

    Based upon the German safety criteria, released in 2010 by the Federal Ministry of the Environment (BMU), a safety concept and a safety assessment concept for the disposal of heat-generating high-level waste have both been developed in the framework of the preliminary safety case for the Gorleben site (Project VSG). The main objective of the disposal is to contain the radioactive waste inside a defined rock zone, which is called containment-providing rock zone. The radionuclides shall remain essentially at the emplacement site, and at the most, a small defined quantity of material shall be able to leave this rock zone. This shall be accomplished by the geological barrier and a technical barrier system, which is required to seal the inevitable penetration of the geological barrier by the construction of the mine. The safe containment has to be demonstrated for probable and less probable evolutions of the site, while evolutions with very low probability (less than 1 % over the demonstration period of 1 million years) need not to be considered. Owing to the uncertainty in predicting the real evolution of the site, plausible scenarios have been derived in a systematic manner. Therefore, a comprehensive site-specific features, events and processes (FEP) data base for the Gorleben site has been developed. The safety concept was directly taken into account, e.g. by identification of FEP with direct influence on the barriers that provide the containment. No effort was spared to identify the interactions of the FEP, their probabilities of occurrence, and their characteristics (values). The information stored in the data base provided the basis for the development of scenarios. The scenario development methodology is based on FEP related to an impairment of the functionality of a subset of barriers, called initial barriers. By taking these FEP into account in their probable characteristics the reference scenario is derived. Thus, the reference scenario describes a

  19. Radiation grafted and sulfonated (FEP-g-polysterene) - An alternative to perfluorinated membranes for PEM fuel cells?

    NASA Astrophysics Data System (ADS)

    Buechi, F. N.; Gupta, B.; Rouilly, M.; Hauser, P. C.; Chapiro, A.; Scherer, G. G.

    Partially fluorinated proton exchange membranes (PEMs) were synthesized for fuel cell applications by simultaneous radiation grafting of styrene on FEP films followed by sulfonation. Properties of the synthesized membranes can be tailored by varying the degree of grafting and crosslinking. The performance of these membranes was tested in H2/O2 fuel cells. Long time testing showed steady performance for high grafted membranes over periods of more than 300 h at a cell temperature of 60 C. Low grafted membranes and the Morgane CDS membrane showed considerable decay of cell power on the same time scale. A fast degradation of all membranes occurred at a cell temperature of 80 C. It is noted that grafting in film form makes this process a potentially cheap and easy technique for the preparation of solid polymer fuel cell electrolytes.

  20. The effect of the initial exciton numbers on {sup 54,56}Fe(p, xp) Pre-Equilibrium Reactions

    SciTech Connect

    Boeluekdemir, M. H.; Tel, E.; Ayd Latin-Small-Letter-Dotless-I n, A.; Okuducu, S.; Kaplan, A.

    2011-02-15

    In pre-equilibrium nuclear reactions, the geometry-dependent hybrid model is applied with the use of the neutron and proton densities to investigate the effect of initial exciton numbers on the nucleon emission spectra. The initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained within the Skryme-Hartree-Fock method with SKM* and SLy4 forces on target nuclei in the {sup 54,56}Fe(p, xp) reaction at 61.5-MeV incident proton energy by using a new calculationmethod of Tel et al. Also, the differences between the initial exciton numbers for protons and neutrons as a function of nuclear radius, focusing on systematic discrepancies correlated to differences in the proton and neutron densities have been investigated.

  1. Theoretical study of the hydrolysis of ethyl benzoate in acidic aqueous solution using the QM/MC/FEP method

    NASA Astrophysics Data System (ADS)

    Kaweetirawatt, Thanayuth; Kokita, Yohei; Iwai, Shiho; Sumimoto, Michinori; Hori, Kenji

    2012-09-01

    The hydrolysis of ethyl benzoate in acidic condition was theoretically studied for models with two (2W) or three water (3WA) molecules at the B3LYP/6-311++G(d,p) levels of theory. Activation free energy of solvation in aqueous solution (ΔG‡cal) was calculated using the QM/MC/FEP method. The value of the 2W model in aqueous solution was calculated to be smaller by more than 5.0 kcal mol-1 than the observed value (26.0 kcal mol-1 at 298 K). The position of the third water molecule in the 3WA model plays an essential role in producing the ΔG‡cal value (26.4 kcal mol-1) consistent with the experimental value.

  2. Investigation of background radical sources in a teflon-film irradiation chamber

    SciTech Connect

    Glasson, W.A.; Dunker, A.M. )

    1988-09-01

    In attempts to model hydrocarbon/NOx irradiations carried out in smog chambers, workers have found it necessary to postulate background free radical sources. Without such radical sources, it has not been possible to obtain agreement between the predictions of chemical mechanisms and the chamber data. The background radical sources appear to be specific to chambers and are not used when applying chemical mechanisms to simulate the atmosphere. Until recently, there were no experimental measurements of the radical sources, and as a result assumptions on the nature and magnitude of the sources varied. Differences in these assumptions are responsible for some of the differences in the predictions of chemical mechanisms in atmospheric simulations. Experimental determinations of the background radical sources in different chambers are, therefore, imperative for the effective use of chamber experiments in developing and evaluating chemical mechanisms for smog formation. In this work, they have conducted a detailed study of the background radical sources in a small Teflon-film chamber. The purpose was to determine the usefulness of such chambers for quantitative studies of smog formation. Values for the background radical sources were derived from the experimental data by simulations with a detailed chemical mechanism, and the uncertainties in these values were estimated as well. The effects of various parameters, such as light intensity and NO and NO{sub 2} concentrations, on the radical sources were studied to provide the necessary information for taking these sources into account in modeling future chamber experiments.

  3. Energy response of CaSO4:Dy teflon TLD disk dosimeters to photons and electrons.

    PubMed

    Sharada, K S

    1983-01-01

    The photon energy response of CaSO4:Dy teflon disk dosimeters used widely in radiation dosimetry is computed using the energy absorption coefficient values for calcium, sulfur, oxygen, and carbon taken from J. H. Hubbell's tables. For fluorine, the energy absorption coefficients were obtained from the values given by F. H. Attix for CaF2 and Ca. The energy response of the radiation-monitoring disk for the range of 10 keV to 10 MeV, relative to air, is computed and plotted. The response is maximum between 20 and 30 keV and then gradually falls to a constant at 200 keV to 10 MeV. This computed response for different energies is compared with the experimental TL response of the dosimeter. The electron energy response of these TLD disks is computed using the stopping-power values for the different component elements. The electron stopping power for sulfur and calcium from 10 keV to 10 MeV is computed using the Bethe-Bloch formula. Those for oxygen and carbon are taken from the tables given by M. J. Berger and S. M. Seltzer. For fluorine, the values are computed from those for Li and LiF given in the same tables. This calculated response is compared with the experimental beta response of the TL dosimeter. PMID:6823508

  4. Bacterial survival in evaporating deposited droplets on a teflon-coated surface.

    PubMed

    Xie, Xiaojian; Li, Yuguo; Zhang, Tong; Fang, Herbert H P

    2006-12-01

    Understanding of bacterial survival in aerosols is crucial for controlling infection transmission via airborne aerosols and/or large droplets routes. The cell viability changes of four bacteria species (Escherichia coli K12 JM109; Acinetobacter sp. 5A5; Pseudomonas oleovorans X5; and Staphylococcus aureus X8), three Gram-negative and one Gram-positive, in a large evaporating droplet of size 1,800 microm in diameter on teflon-coated slides were measured using the LIVE/DEAD BacLight solution and a microscope. Droplets of three levels of salinity (0, 0.9, and 36% w/v) were tested. All four species survived well during the droplet evaporation process, but died mostly at the time when droplets were dried out at 40-45 min. The final bacteria survival rate after droplets were completely dried was dependent on bacteria species and the salinity of the suspension solution. Droplet evaporation over the first 35-40 min had no adverse effect on bacterial survival for the droplets tested. The lethal effect of desiccation was found to be the most important death mechanism. PMID:17053902

  5. Infiltration during intravenous therapy in neonates: comparison of Teflon and Vialon catheters.

    PubMed

    Stanley, M D; Meister, E; Fuschuber, K

    1992-09-01

    Infiltration is a frequent complication of intravenous therapy using peripheral venous lines in neonatal patients. In a randomized trial of two catheter materials, Vialon (Becton Dickinson) and Teflon (DuPont), we studied 19 putative risk factors for infiltration, including 11 infusates, in 772 peripheral venous lines in patients aged 1 to 67 days. The best-fit Cox regression model identified six significant predictors of infiltration (P less than .05): catheter material, age, anatomic insertion site, hyperalimentation, and use of furosemide and dopamine. For the subsample of patients weighing less than or equal to 1500 g, a second Cox regression model identified time spent inserting the catheter and the number of insertion attempts as additional significant predictors. These multivariate models showed that Vialon catheter material reduced the risk of infiltration by 18% (95% CI, 1% to 32% reduction) in the total sample and by 35% (95% CI, 15% to 50% reduction) in the higher risk low-weight (less than or equal to 1500 g) subsample. PMID:1523447

  6. High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers

    NASA Technical Reports Server (NTRS)

    Hammoud, A. N.; Baumann, E. D.; Overton, E.; Myers, I. T.; Suthar, J. L.; Khachen, W.; Laghari, J. R.

    1992-01-01

    Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments.

  7. Electric field modulation of magnetic anisotropy and microwave absorption properties in Fe50Ni50/Teflon composite films

    NASA Astrophysics Data System (ADS)

    Xia, Zhenjun; He, Jun; Ou, Xiulong; Wang, Yu; He, Shuli; Zhao, Dongliang; Yu, Guanghua

    2016-05-01

    Fe50Ni50 nanoparticle films with the size about 6 nm were deposited by a high energetic cluster deposition source. An electric field of about 0 - 40 kV was applied on the sample platform when the films were prepared. The field assisted deposition technique can dramatically induce in-plane magnetic anisotropy. To probe the microwave absorption properties, the Fe50Ni50 nanoparticles were deliberately deposited on the dielectric Teflon sheet. Then the laminated Fe50Ni50/Teflon composites were used to do reflection loss scan. The results prove that the application of electric field is an effective avenue to improve the GHz microwave absorption performance of our magnetic nanoparticles films expressed by the movement of reflection loss peak to high GHz region for the composites.

  8. Experimental evaluation of a fixed collector employing vee-trough concentrator and vacuum tube receivers

    NASA Technical Reports Server (NTRS)

    Selcuk, M. K.

    1977-01-01

    A test bed for experimental evaluation of a fixed solar collector which combines an evacuated glass tube solar receiver with a flat plate/black chrome plated copper absorber and an asymmetric vee-trough concentrator was designed and constructed. Earlier predictions of thermal performance were compared with test data acquired for a bare vacuum tube receiver; and receiver tubes with Alzak aluminum, aluminized FEP Teflon film laminated sheet metal and second surface ordinary mirror reflectors. Test results and system economics as well as objectives of an ongoing program to obtain long-term performance data are discussed.

  9. Mass transfer in fuel cells. [electron microscopy of components, thermal decomposition of Teflon, water transport, and surface tension of KOH solutions

    NASA Technical Reports Server (NTRS)

    Walker, R. D., Jr.

    1973-01-01

    Results of experiments on electron microscopy of fuel cell components, thermal decomposition of Teflon by thermogravimetry, surface area and pore size distribution measurements, water transport in fuel cells, and surface tension of KOH solutions are described.

  10. Multi-dimensional hydrodynamic simulations aimed at characterizing heavily aluminized RDX

    NASA Astrophysics Data System (ADS)

    Yoh, Jack J.; Kim, Bohoon; Kim, Minsung

    2015-06-01

    An accurate and reliable prediction of reactive flow is a challenging task for an energetic material subjected to an external shock impact. The present study aims at simulating the shock induced detonation of heavily aluminized RDX which contains 35% of aluminum. A series of gap tests with the longitudinal simulations involving gap substances are conducted to understand the inherent initiation process that depends on the shock propagation through multi-material domain and the high strain dynamics of nearby confinement materials. A pressure chamber test is used to validate the blast wave calculation of the sample charge, and a full 3-D hydrodynamic simulation is performed to predict fragmentation of an explosively loaded steel casing. The paper provides an elaborate description of how a heavily aluminized RDX is characterized in terms of its thermo-chemical response and multi-material interaction with inert confinement materials.

  11. Highly reflective and adhesive surface of aluminized polyvinyl chloride film by vacuum evaporation

    NASA Astrophysics Data System (ADS)

    Li, Denian; Tai, Qile; Feng, Qiang; Li, Qi; Xu, Xizhe; Li, Hairong; Huang, Jing; Dong, Lijie; Xie, Haian; Xiong, Chuanxi

    2014-08-01

    Aluminized poly(vinyl chloride) (PVC) film with high reflectivity and strong adhesion was facilely fabricated by vacuum evaporation. The technical study revealed that both alkali-pretreatment of the PVC matrix and thermal annealing after aluminization could greatly promote the peeling adhesion force of this metal/polymer composite by producing interfacial active chemical groups and removing the inner stress, respectively. Reflectivity test and AFM study indicated that the reflecting capacitance of the aluminum coating was closely related to the surface roughness, which can be easily controlled by modulating deposition of aluminum. Moreover, the formation of aluminum layer follows an island model process, and a continuous and smooth coating with highest reflectivity and lowest surface resistance was achieved at deposition time of 60 s. We anticipate that the cost-effective metallized PVC film by this strategy may find extensive applications in light harvesting, solar energy, and flexible mirrors, among others.

  12. Removal of methyl orange from aqueous solutions through adsorption by calcium aluminate hydrates.

    PubMed

    Zhang, Ping; Wang, Tianqi; Qian, Guangren; Wu, Daishe; Frost, Ray L

    2014-07-15

    Methyl orange (MO) is a kind of anionic dye and widely used in industry. In this study, tricalcium aluminate hydrates (Ca-Al-LDHs) are used as an adsorbent to remove methyl orange (MO) from aqueous solutions. The resulting products were studied by X-ray diffraction (XRD), infrared spectroscopy (MIR), thermal analysis (TG-DTA) and scanning electron microscope (SEM). The XRD results indicated that the MO molecules were successfully intercalated into the tricalcium aluminate hydrates, with the basal spacing of Ca-Al-LDH expanding to 2.48 nm. The MIR spectrum for CaAl-MO-LDH shows obvious bands assigned to the N=N, N=H stretching vibrations and S=O, SO3(-) group respectively, which are considered as marks to assess MO(-) ion intercalation into the interlayers of LDH. The overall morphology of CaAl-MO-LDH displayed a "honey-comb" like structure, with the adjacent layers expanded. PMID:24863763

  13. Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders

    SciTech Connect

    Chavda, Mehul A.; Bernal, Susan A.; Apperley, David C.; Kinoshita, Hajime; Provis, John L.

    2015-04-15

    The conversion of hexagonal calcium aluminate hydrates to cubic phases in hydrated calcium aluminate cements (CAC) can involve undesirable porosity changes and loss of strength. Modification of CAC by phosphate addition avoids conversion, by altering the nature of the reaction products, yielding a stable amorphous gel instead of the usual crystalline hydrate products. Here, details of the environments of aluminium and phosphorus in this gel were elucidated using solid-state NMR and complementary techniques. Aluminium is identified in both octahedral and tetrahedral coordination states, and phosphorus is present in hydrous environments with varying, but mostly low, degrees of crosslinking. A {sup 31}P/{sup 27}Al rotational echo adiabatic passage double resonance (REAPDOR) experiment showed the existence of aluminium–phosphorus interactions, confirming the formation of a hydrated calcium aluminophosphate gel as a key component of the binding phase. This resolves previous disagreements in the literature regarding the nature of the disordered products forming in this system.

  14. Coating Prospects in Corrosion Prevention of Aluminized Steel and Its Coupling with Magnesium

    NASA Astrophysics Data System (ADS)

    Sun, Fuyan

    In this study, a plasma electrolytic oxidation (PEO) process was used to form oxide coating on aluminized steel, heated aluminized steel and magnesium. A potentiodynamic polarization corrosion test was employed to investigate the general corrosion properties. Galvanic corrosion of steel samples and magnesium samples was studied by zero resistance ammeter (ZRA) tests and boiling tests. Scanning electron microscopy (SEM) and EDS were used to investigate the coating microstructure and the coating/substrate interface. In general, the PEO coatings on all three substrate can help prevent general corrosion. 6-min coated magnesium with unipolar current mode performs best in most galvanic couplings for preventing both general corrosion and galvanic corrosion. Factors which could influence galvanic corrosion behaviors of tested samples were discussed based on area ratios of anode/cathode and cell potential driving force during the ZRA corrosion tests and boiling tests.

  15. Scale-up of Lithium Aluminate Pellet Manufacturing with a Flowable Powder

    SciTech Connect

    Hollenberg, Glenn W.; Bagaasen, Larry M.; Kurosky, Randal P.; Tonn, D.; Carty, W.

    2004-01-01

    Thin-walled, high-density lithium aluminate pellets are challenging to manufacture for nuclear reactor applications. The key to scale-up of production was the development of flowable, high density, lithium aluminate powder that permitted (1) automated isostatic pressing, (2) low compaction during pressing, (3) low shrinkage during firing, (4) elimination of chlorine-containing fumed alumina and (5) near-net shape forming. A triple spray drying process was developed that included: (I) a unique-feedstock blend cycle, (II) a post-calcination grinding cycle, and (III) a high-pH final cycle with high solids loading slurry that was spray dried into flowable high-density spheres with large, uniform diameters. Today, pellet manufacturing at a rate of more than 400,000 per year is possible.

  16. Crystal structures and optical properties of new quaternary strontium europium aluminate luminescent nanoribbons

    DOE PAGESBeta

    Li, Xufan; Budai, John D.; Liu, Feng; Chen, Yu-Sheng; Howe, Jane Y.; Sun, Chengjun; Tischler, Jonathan Zachary; Meltzer, Richard; Pan, Zhengwei

    2014-11-12

    We report the synthesis and characterizations of three series of quaternary strontium europium aluminate (Sr-Eu-Al-O; SEAO) luminescent nanoribbons that show blue, green, and yellow luminescence from localized Eu2+ luminescent centers. These three series of SEAO nanoribbons are: blue luminescent, tetragonal Sr1-xEuxAl6O10 (01-xEuxAl2O4 (01-xEuxAl2O4 (0

  17. Boundary conditions for diffusion in the pack-aluminizing of nickel.

    NASA Technical Reports Server (NTRS)

    Sivakumar, R.; Seigle, L. L.; Menon, N. B.

    1973-01-01

    The surface compositions of nickel specimens coated for various lengths of time in aluminizing packs at 2000 F were studied, in order to obtain information about the kinetics of the pack-cementation process in the formation of aluminide coatings. The results obtained indicate that the surface compositions of the coated nickel specimens are independent of time, at least for time between 0.5 and 20 hrs. Another important observation is that the specimens gained weight during the coating process.

  18. Comparative study between REAP 200 and FEP171 CAR with 50-kV raster e-beam system for sub-100-nm technology

    NASA Astrophysics Data System (ADS)

    Baik, Ki-Ho; Lem, Homer Y.; Dean, Robert L.; Osborne, Stephen; Mueller, Mark; Abboud, Frank E.

    2003-08-01

    In this paper, a process established with a positive-tone chemically amplified resist (CAR) from TOK REAP200 and Fujifilm Arch FEP171 and 50kV MEBES system is discussed. This TOK resist is developed for raster scan 50 kV e-beam systems. It has high contrast, good coating characteristics, good dry etch selectivity, and high environmental stability. In the mask industries, the most popular positive tone CAR is FEP171, which is a high activation energy type CAR. REAP (Raster E-beam Advanced Process) 200 is low activation energy type and new acetal protecting polymer. In this study, we compared to these different type resists in terms of contrast, PAB and PEB latitude, resist profile, footing, T-topping, PED stability, LER, Global CDU (Critical Dimension Uniformity) and resolution. The REAP200 Resist obtained 75nm isolated lines and spaces, 90nm dense patterns with vertical profile, and a good stability of delay time.

  19. [Dimensions of parental rearing styles in alcohol dependent patients: first results of the questionnaire on parental attitudes and rearing practices (FEPS)].

    PubMed

    Lotzin, Annett; Kriston, Levente; Richter-Appelt, Hertha; Leichsenring, Irina; Ramsauer, Brigitte; Schäfer, Ingo

    2013-07-01

    To date no instrument for the assessment of parenting styles is available in the German -language area that has been validated in patients with addictive disorders. Therefore the aim of this study was the confirmatory evaluation of the factor structure of the Questionnaire on Parental Attitudes and Rearing Practices (FEPS) in 186 alcohol dependent patients. The model as proposed by the test developers with the 4 factors Care, Autonomy, Low Punishment, and Low Material Reinforcement showed acceptable fit when residual correlations were allowed (mother: χ(2)/df=1,92, RMSEA=0,07, TLI=0,79; father: χ(2)/df=1,75, RMSEA=0,07, TLI=0,82). All factors showed sufficient factor reliabilities as well as good to very good internal consistencies. Factor loadings, discriminations and difficulties of the indicators could be regarded as good, with the exception of 2 items. These results indicate the factorial validity of the FEPS in patients with alcohol dependence. PMID:23446826

  20. Computer modelling of the reduction of rare earth dopants in barium aluminate

    SciTech Connect

    Rezende, Marcos V. dos S; Valerio, Mario E.G.; Jackson, Robert A.

    2011-08-15

    Long lasting phosphorescence in barium aluminates can be achieved by doping with rare earth ions in divalent charge states. The rare earth ions are initially in a trivalent charge state, but are reduced to a divalent charge state before being doped into the material. In this paper, the reduction of trivalent rare earth ions in the BaAl{sub 2}O{sub 4} lattice is studied by computer simulation, with the energetics of the whole reduction and doping process being modelled by two methods, one based on single ion doping and one which allows dopant concentrations to be taken into account. A range of different reduction schemes are considered and the most energetically favourable schemes identified. - Graphical abstract: The doping and subsequent reduction of a rare earth ion into the barium aluminate lattice. Highlights: > The doping of barium aluminate with rare earth ions reduced in a range of atmospheres has been modelled. > The overall solution energy for the doping process for each ion in each reducing atmosphere is calculated using two methods. > The lowest energy reduction process is predicted and compared with experimental results.

  1. IMPACT OF ALUMINATE IONS ON THE PROPERTIES OF SALTSTONE GROUT MIXES

    SciTech Connect

    Harbour, J; Tommy Edwards, T; Erich Hansen, E; Vickie Williams, V

    2008-02-21

    It is important to identify and control the operational and compositional variables that impact the important processing and performance properties of Saltstone grout mixes. The grout that is produced at the Saltstone Production Facility (SPF) is referred to as Saltstone and is a waste form that immobilizes low concentrations of radionuclides as well as certain toxic metals. The Saltstone will be disposed of in vaults at Savannah River Site (SRS). An effort referred to as the Saltstone Variability Study has been initiated to achieve this goal. The protocols developed in this variability study are also ideally suited as a tool to assess the impact of proposed changes to the processing flow sheet for Liquid Waste Operations at SRS. One such proposal that is currently under consideration is to introduce a leaching step in the treatment of the High Level Waste (HLW) sludge to remove aluminum prior to vitrification at the Defense Waste Processing Facility (DWPF). This leachate would significantly increase the soluble aluminate concentration in the salt feed that will be processed at the SPF. Consequently, an initial study of the impact of increased aluminate concentration on the Saltstone grout properties was performed. Prior work by Lukens (1) showed that aluminate in the salt solutions increases the amount of heat generation.

  2. Behaviour of SS316, with and without aluminization, in stagnant Pb17Li

    NASA Astrophysics Data System (ADS)

    Schreinlechner, I.; Sattler, P.

    1992-09-01

    Austenitic SS316 sheet material, partly aluminized, was tested in static Pb17Li (83 at% Pb and 17 at% Li), at 500°C. After 1000 h of exposure polished cross sections of pieces of the sample with and without aluminization were analysed by electron microscopy and compared with the as-received sample. The unprotected surface revealed the expected depletion of alloying elements and the formation of a porous ferritic zone to a depth of ≈ 200 μm into which Pb has penetrated. The aluminized suface does not show any attack by Pb17Li nor penetration of Pb into the grain boundaries. An intermediate layer is found between the matrix and the aluminum surface layer, with distinct borders on either side, consisting of Al+Ni-rich areas, believed to be an AlNi alloy between Cr-rich areas. Quantitative analyses revealed identical concentrations of Al and Ni, for exposed as well as unexposed samples, indicating no counter diffusion to have taken place during the test.

  3. Chemical and radiation stability of 244Cm-doped aluminate perovskite

    NASA Astrophysics Data System (ADS)

    Livshits, T. S.; Lizin, A. A.; Tomilin, S. V.

    2014-11-01

    Aluminate perovskite with a 75% simulator of actinide-REE (Nd, Sm, Ce) fraction of high-level radioactive wastes (HLW) from reprocessing of spent nuclear fuel (SNF) has been synthesized and studied. The radiation stability of perovskite in the process of 244Cm decay ( T 1/2 = 18 yr) was investigated. Its structure has been amorphized at accumulated dose of 2.3 × 1018 α-decays/g, or 0.26 displacements per atom (dpa). The critical temperature above which amorphization does not occur at any dose is estimated to be 500°C. Radiation resistance of aluminate perovskite is close to previously studied titanate pyrochlore and ferrite garnet. The stability of perovskite in water before and after amorphization has been studied as well. The leach rate of Cm by water (90°C) from crystalline perovskite in runs 3-14 days long was 10-2-10-3 g/m2. This value is close to the stability of titanate pyrochlore and aluminate garnet. The intensity of element leaching from perovskite after amorphization of its structure increases 10-100 times and thus is higher than for other previously studied actinide phases.

  4. Microstructure characterization of oxidation of aluminized coating prepared by a combined process

    NASA Astrophysics Data System (ADS)

    Liu, H. B.; Tao, J.; Xu, J.; Chen, Z. F.; Sun, X. J.; Xu, Z.

    2008-08-01

    Alumina layer is a good candidate for the tritium penetration barrier that is important in the control of tritium losses due to permeation through structural materials used in high-temperature gas-cooled reactors and in fusion reactors. This paper describes the microstructure of the oxide film of the tritium penetration barrier formed on 316L stainless steel, which was prepared by a combined process, namely, aluminizing and oxidizing treatments using a double glow plasma technology. Microstructure and phase structure of the coatings investigated were examined by scanning electronic microscope (SEM), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM), respectively. The chemical composition and the chemical states of Al, O elements in the oxidation film were identified by X-ray photoelectron spectroscopy (XPS). After aluminization, the typical microstructure of the coating mainly consisted of an outer high aluminum-containing intermetallic compound layer (Fe 2Al 5 and FeAl) and intermediate ferritic stainless steel (α Fe(Al))layer followed by the austenitic substrate. After the combined process, an oxide layer that consisted of Al 2O 3 and spinel FeAl 2O 4 had been successfully formed on the aluminizing coating surface, with an amorphous outmost surface and an underlying subsurface nanocrystalline structure.

  5. Supercritical fluid-mediated alumination of mesoporous silica and its beneficial effect on hydrothermal stability.

    PubMed

    O'Neil, Adam S; Mokaya, Robert; Poliakoff, Martyn

    2002-09-11

    We have investigated the use of supercritical fluids (SCFs) as carriers/solvents during the postsynthesis alumination of mesoporous silica. SCFs were found to be ideally suited for transport of Al into mesoporous silica and to lead to Al-grafted aluminosilicate materials that exhibit exceptional hydrothermal (steam) stability even for highly aluminated materials. The improvements in steam stability arising from the use of SCFs as grafting media (as compared to aqueous or organic solvents) are remarkable, especially for Al-grafted MCM-41 materials with high (Si/Al < or = 10) Al contents. It is proposed that under supercritical fluid conditions Al is sorbed on the surface of the pore walls of the host Si-MCM-41 with little penetration into the pore wall region, that is, the low solvating power of SCFs ensures the deposition of Al onto rather than into the silica framework. This is because the host silica framework cannot undergo any significant hydrolysis (to allow penetration of Al into the pore wall region) during the SCF-mediated alumination. Removal of the Al (i.e., dealumination) which occurs during steaming is therefore less detrimental to the structural integrity of SCF-grafted Al-MCM-41 materials since any dealumination that occurs will not involve removal of Al from deep within the pore walls. PMID:12207501

  6. Phase transformation of alumina coating by plasma assisted tempering of aluminized P91 steels

    NASA Astrophysics Data System (ADS)

    Jamnapara, N. I.; Mukherjee, S.; Khanna, A. S.

    2015-09-01

    α-Al2O3 coating on aluminized surfaces are considered candidate coatings for blanket applications in fusion reactor. In order to generate α-Al2O3, aluminized P91 steel samples were subjected to normalizing and tempering treatments at 980 °C and 750 °C respectively. Oxygen plasma has been used during tempering treatment of aluminized P91 steel samples at 750 °C for 1 h. The resulting alumina coating on plasma tempered samples were compared with those of thermally tempered samples. The alumina films were characterized using XRD, XPS, and SEM-EDS techniques. Results indicate that the thermally tempered samples had θ-Al2O3 coating while the plasma tempered samples had α-Al2O3 coating after heat treatment. Such transformation of alumina phase was not visible without plasma. A hypothesis of θ to α-Al2O3 transformation in plasma is proposed. This paper emphasizes the role of plasma processing on generation of an improved insulation coating for TBM applications in fusion reactors.

  7. The synthesis and spectroscopic characterisation of hydrotalcite formed from aluminate solutions.

    PubMed

    Palmer, Sara J; Grand, Laure M; Frost, Ray L

    2011-06-01

    Raman spectroscopy has been used to characterise nine hydrotalcites prepared from aluminate and magnesium solutions (magnesium chloride and seawater). The aluminate hydrotalcites are proposed to have the following formula Mg(6)Al(2)(OH)(16)(CO(3)(2-))·xH(2)O, Mg(6)Al(2)(OH)(16)(CO(3)(2-),SO(4)(2-))·xH(2)O, and Mg(6)Al(2)(OH)(16)(SO(4)(2-))·xH(2)O. The synthesis of these hydrotalcites using seawater results in the intercalation of sulfate anions into the hydrotalcite interlayer. The spectra have been used to assess the molecular assembly of the cations and anions in the hydrotalcite structures. The spectra have been conveniently subdivided into spectral features based upon the carbonate anion, the hydroxyl units and water units. This investigation has shown the ideal conditions to form hydrotalcite from aluminate solutions is at pH 14 using a magnesium chloride solution at a volumetric ratio of 1:1. Changes in synthesis conditions resulted in the formation of impurity products aragonite, thenardite, and gypsum. PMID:21429789

  8. Ion microprobe analyses of aluminous lunar glasses - A test of the 'rock type' hypothesis

    NASA Technical Reports Server (NTRS)

    Meyer, C., Jr.

    1978-01-01

    Previous soil survey investigations found that there are natural groupings of glass compositions in lunar soils and that the average major element composition of some of these groupings is the same at widely separated lunar landing sites. This led soil survey enthusiasts to promote the hypothesis that the average composition of glass groupings represents the composition of primary lunar 'rock types'. In this investigation the trace element composition of numerous aluminous glass particles was determined by the ion microprobe method as a test of the above mentioned 'rock type' hypothesis. It was found that within any grouping of aluminous lunar glasses by major element content, there is considerable scatter in the refractory trace element content. In addition, aluminous glasses grouped by major elements were found to have different average trace element contents at different sites (Apollo 15, 16 and Luna 20). This evidence argues that natural groupings in glass compositions are determined by regolith processes and may not represent the composition of primary lunar 'rock types'.

  9. The Formation and Evolution of Planetary Systems (FEPS): Discovery of an Unusual Debris System Associated with HD 12039

    NASA Astrophysics Data System (ADS)

    Mamajek, E. E.; Hines, D. C.; Backman, D. E.; Bouwman, J.; Hillenbrand, L. A.; Carpenter, J. M.; Meyer, M. R.; Kim, J. S.; Silverstone, M. D.; Rodmann, J.; Wolf, S.; Brooke, T. Y.; Padgett, D. L.; Henning, Th.; Moro-Martin, A.; Stobie, E.; Gordon, K. D.; Morrison, J.; Muzerolle, J.; Su, K.

    2005-12-01

    We report the discovery of a debris system associated with the ˜ 30 Myr old G3/5V star HD 12039 using Spitzer Space Telescope observations from 3.6 -- 160μ m. An observed infrared excess (L IR/L* = 1×10-4) above the expected photosphere for λ ≳ 14μ m is fit by thermally emitting material with a color temperature of T ˜ 110 K, warmer than the majority of debris disks identified to date around Sun-like stars. The object is not detected at 70μ m with a 3σ upper limit 6 times the expected photospheric flux. The spectrum of the infrared excess can be explained by warm, optically thin material comprised of blackbody-like grains of size ≳ 7 μ m that reside in a belt orbiting the star at 4--6 AU. An alternate model dominated by smaller grains, near the blow-out size a ˜ 0.5μ m, located at 30-40AU is also possible, but requires the dust to have been produced recently since such small grains will be expelled from the system by radiation pressure in ˜ few × 102yrs. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. FEPS is pleased to acknowledge support through NASA contracts 1224768, 1224634, 1224566 administered through JPL.

  10. Aluminizing Oil Casing Steel N80 by a Low-Temperature Pack Processing Modified with Zinc Addition

    NASA Astrophysics Data System (ADS)

    Huang, Min; Wang, Yu; Zhang, Xiao Yong

    Different aluminide coatings were prepared on oil casing steel N80 at a relatively lower temperature of 530°C for 2 h by pack powder modified with different content of zinc (Zn). The cross-sectional microstructure, element distribution and properties of as-aluminized oil casing steel N80 were investigated by SEM, EDS, micro-hardness test and electrochemical corrosion measurement. Results show that aluminide coating with around 50 μm in thickness can be successfully achieved by a low-temperature pack aluminizing processing with the addition of Zn. Zn in the pack powder can enhance the uniformity and continuity of the coating layer, while it has little effect on the thickness of as-packed coating with the increasing content of Zn from 38.8 wt.% to 84.4 wt.%. As the content of Zn is over 58.8 wt.%, two layer coating consisting of pure Zn layer and Fe-Al aluminide layer can be formed on oil casing steel N80 substrate. Furthermore, oil casing steel N80 with aluminizing coating shows a higher microhardness than that of original one except in the depth range of pure Zn layer, but the microhardness of oil casing steel substrate does not decrease after aluminizing which can be inferred that low-temperature aluminizing processing reported here will not bring any damages on the mechanical properties of oil casing steel N80. Additionally, a lower self-corrosion current density of oil casing steel N80 with aluminizing coating also indicates that low-temperature aluminizing processing is helpful to the corrosion resistance of oil casing steel N80.

  11. Postoperative early hemolytic anemia due to inverted teflon felt strip after emergency repair for type A dissection.

    PubMed

    Hata, M; Yoshitake, I; Wakui, S; Unosawa, S; Hata, H; Shiono, M

    2012-10-01

    A 39-year-old man underwent emergency surgery for type A acute aortic dissection complicated by paraplegia. However, hemolytic anemia increased significantly due to severe stenosis of the proximal anastomosis one month after surgery. He finally underwent a redo procedure 4 months after the initial operation whereupon it was verified that half of the inner felt strip used for proximal stump fixation had turned up and was protruding into the inner lumen. We report here on a rare case of survival of postoperative early hemolytic anemia due to severe graft stenosis caused by an inverted inner Teflon felt strip without any extra vascular compression. PMID:21766281

  12. Using FEP's List and a PA Methodology for Evaluating Suitable Areas for the LLW Repository in Italy

    SciTech Connect

    Risoluti, P.; Ciabatti, P.; Mingrone, G.

    2002-02-26

    In Italy following a referendum held in 1987, nuclear energy has been phased out. Since 1998, a general site selection process covering the whole Italian territory has been under way. A GIS (Geographic Information System) methodology was implemented in three steps using the ESRI Arc/Info and Arc/View platforms. The screening identified approximately 0.8% of the Italian territory as suitable for locating the LLW Repository. 200 areas have been identified as suitable for the location of the LLW Repository, using a multiple exclusion criteria procedure (1:500,000), regional scale (1:100.000) and local scale (1:25,000-1:10,000). A methodology for evaluating these areas has been developed allowing, along with the evaluation of the long term efficiency of the engineered barrier system (EBS), the characterization of the selected areas in terms of physical and safety factors and planning factors. The first step was to identify, on a referenced FEPs list, a group of geomorphological, geological, hydrogeological, climatic and human behavior caused process and/or events, which were considered of importance for the site evaluation, taking into account the Italian situation. A site evaluation system was established ascribing weighted scores to each of these processes and events, which were identified as parameters of the new evaluation system. The score of each parameter is ranging from 1 (low suitability) to 3 (high suitability). The corresponding weight is calculated considering the effect of the parameter in terms of total dose to the critical group, using an upgraded AMBER model for PA calculation. At the end of the process an index obtained by a score weighted sum gives the degree of suitability of the selected areas for the LLW Repository location. The application of the methodology to two selected sites is given in the paper.

  13. Methods of use of calcium hexa aluminate refractory linings and/or chemical barriers in high alkali or alkaline environments

    DOEpatents

    McGowan, Kenneth A; Cullen, Robert M; Keiser, James R; Hemrick, James G; Meisner, Roberta A

    2013-10-22

    A method for improving the insulating character/and or penetration resistance of a liner in contact with at least one of an alkali and/or alkaline environments is provided. The method comprises lining a surface that is subject to wear by an alkali environment and/or an alkaline environment with a refractory composition comprising a refractory aggregate consisting essentially of a calcium hexa aluminate clinker having the formula CA.sub.6, wherein C is equal to calcium oxide, wherein A is equal to aluminum oxide, and wherein the hexa aluminate clinker has from zero to less than about fifty weight percent C.sub.12A.sub.7, and wherein greater than 98 weight percent of the calcium hexa aluminate clinker having a particle size ranging from -20 microns to +3 millimeters, for forming a liner of the surface. This method improves the insulating character/and or penetration resistance of the liner.

  14. X- and gamma-ray response of the TLD badge based on CaSO4:Dy Teflon TLD discs.

    PubMed

    Vohra, K G; Pradhan, A S; Bhatt, R C

    1982-09-01

    A TLD badge based on CaSO4: Dy Teflon TLD discs has been designed for personnel monitoring of radiation workers encountering X-rays of effective energies above 20 keV. The badge had two Teflon TLD discs, one of which is used bare (without any filter) and other which is used with a metal filter. By taking into account the TL readout of both of these discs, the problems of photon energy dependence as well as directional dependence of the badge have been reduced to a minimum. The uncertainty due to photon energy dependence above 29 KeV (eff.) was found to be within a value of +/- 15% (at an angle of incidence of 45 degrees). The directional dependence of the badge is within +/- 30% in the energy range from 35 KeV to 1.25 MeV. The badge is designed so as to provide approximate information on the effective photon energy of the X-ray exposures. PMID:7174332

  15. Development of thrombophlebitis in peripheral veins with Vialon and PTFE-Teflon cannulas: a double-blind, randomised, controlled trial.

    PubMed Central

    Payne-James, J. J.; Rogers, J.; Bray, M. J.; Rana, S. K.; McSwiggan, D.; Silk, D. B.

    1991-01-01

    A series of 54 normal subjects were randomised to have either a Vialon or a PTFE-Teflon peripheral vein cannula inserted in a vein in each forearm to observe the development of thrombophlebitis. Cannulas were inspected twice daily for up to 5 days to observe the development of three signs, erythema, oedema or hardness and one symptom, pain. Each sign and symptom was recorded twice daily at three points, the cannula insertion site, the mid-point of the cannula and the cannula tip. The degree of change was recorded as less than 1, 1-2 and greater than 2 cm. Any cannula causing any sign greater than 2 cm was removed. By the end of the study over 40% of both types of cannula had been removed. There were no significant differences between the numbers of each type of cannula removed at any time point throughout the duration of the study. There were no significant differences in the amounts of erythema or hardness, but minimally increased swelling was observed at the mid-point of the PTFE-Teflon cannulas (P = 0.022). Despite the theoretical superiority of Vialon as a cannula material, under controlled conditions there appears to be little difference in its inherent capacity to cause the thrombophlebitis. PMID:1929137

  16. Development of thrombophlebitis in peripheral veins with Vialon and PTFE-Teflon cannulas: a double-blind, randomised, controlled trial.

    PubMed

    Payne-James, J J; Rogers, J; Bray, M J; Rana, S K; McSwiggan, D; Silk, D B

    1991-09-01

    A series of 54 normal subjects were randomised to have either a Vialon or a PTFE-Teflon peripheral vein cannula inserted in a vein in each forearm to observe the development of thrombophlebitis. Cannulas were inspected twice daily for up to 5 days to observe the development of three signs, erythema, oedema or hardness and one symptom, pain. Each sign and symptom was recorded twice daily at three points, the cannula insertion site, the mid-point of the cannula and the cannula tip. The degree of change was recorded as less than 1, 1-2 and greater than 2 cm. Any cannula causing any sign greater than 2 cm was removed. By the end of the study over 40% of both types of cannula had been removed. There were no significant differences between the numbers of each type of cannula removed at any time point throughout the duration of the study. There were no significant differences in the amounts of erythema or hardness, but minimally increased swelling was observed at the mid-point of the PTFE-Teflon cannulas (P = 0.022). Despite the theoretical superiority of Vialon as a cannula material, under controlled conditions there appears to be little difference in its inherent capacity to cause the thrombophlebitis. PMID:1929137

  17. Dynamic apparent transition resistance data in spot welding of aluminized 22MnB5.

    PubMed

    Kaars, Jonny; Mayr, Peter; Koppe, Kurt

    2016-09-01

    In-situ resistance measurements of aluminized 22MnB5 steel using a current ramp of 500 A/ms at welding force levels from 2 kN to 8 kN were conducted to obtain data on the dynamic resistance behaviour in spot welding of the material for varying mechanical and electrical loads. The data has been successfully used to calibrate a numerical transition resistance model (KMK-model, Kaars et al., 2016 [1]) in Kaars et al. (2016) [2]. PMID:27547795

  18. Acyl silicates and acyl aluminates as activated intermediates in peptide formation on clays

    NASA Technical Reports Server (NTRS)

    White, D. H.; Kennedy, R. M.; Macklin, J.

    1984-01-01

    Glycine reacts with heating on dried clays and other minerals to give peptides in much better yield than in the absence of mineral. This reaction was proposed to occur by way of an activated intermediate such as an acyl silicate or acyl aluminate analogous to acyl phosphates involved in several biochemical reactions including peptide bond synthesis. The proposed mechanism has been confirmed by trapping the intermediate, as well as by direct spectroscopic observation of a related intermediate. The reaction of amino acids on periodically dried mineral surfaces represents a widespead, geologically realistic setting for prebiotic peptide formation via in situ activation.

  19. Precipitation of copper and chromium impurities in lanthanum magnesium aluminate crystals during thermochemical reduction

    SciTech Connect

    Ballesteros, C. ); Gonzalez, R. ); Chen, Y. ); Kokta, M.R. )

    1993-02-01

    Thermochemical reduction at high temperatures has been performed on chromium-doped lanthanum magnesium aluminate crystals. Analytical transmission-electron-microscopy and optical-absorption techniques were used to characterize the crystals. Copper impurities inherently present in the crystals began to aggregate and form Cu-rich particles at 1500 K near the surface region. Below 1870 K there was no evidence of chromium precipitates being formed. However, Cr-rich particles were formed at 2020 K. The distribution of the precipitates was very inhomogeneous and the precipitates were also concentrated near the surface region.

  20. Geochronology of high-K aluminous mare basalt clasts from Apollo 14 breccia 14304

    NASA Technical Reports Server (NTRS)

    Shih, C.-Y.; Bansal, B. M.; Nyquist, L. E.; Bogard, D. D.; Dasch, E. J.

    1987-01-01

    Two aluminous mare basalt clasts of high K abundances from Apollo 14 breccia 14304 (the 14304,127 and 14304,128 samples) were characterized with respect to the Rb and Sr concentrations and isotopic compositions, and the Rb-Sr, K-Ar, and Sm-Nd isotopic age determinations were carried out. The results suggest that these high-K basalts were melts derived from mantle material and that they have experienced about ten-fold Rb/Sr and K/La enrichments at approximately the time of crystallization.

  1. Geochronology of high-K aluminous mare basalt clasts from Apollo 14 breccia 14304

    NASA Astrophysics Data System (ADS)

    Shih, C.-Y.; Nyquist, L. E.; Bogard, D. D.; Dasch, E. J.; Bansal, B. M.; Wiesmann, H.

    1987-12-01

    Two aluminous mare basalt clasts of high K abundances from Apollo 14 breccia 14304 (the 14304,127 and 14304,128 samples) were characterized with respect to the Rb and Sr concentrations and isotopic compositions, and the Rb-Sr, K-Ar, and Sm-Nd isotopic age determinations were carried out. The results suggest that these high-K basalts were melts derived from mantle material and that they have experienced about ten-fold Rb/Sr and K/La enrichments at approximately the time of crystallization.

  2. Solid reaction products and aluminate solutions that form during the operation of an air-aluminum chemical power supply

    NASA Astrophysics Data System (ADS)

    Okorokova, N. S.; Sevruk, S. D.; Suvorova, E. V.; Farmakovskaya, A. A.

    2015-12-01

    A solution to the set of problems concerning the solid reaction products and the aluminate solutions that form during the operation of an aluminum-closed power supply system for self-contained objects is proposed. The system is based on a resource-saving technology using an aluminum energy carrier in an air-aluminum chemical power supply and related energy installations. The boundaries of the metastable and labile state regions of aluminate solutions and the real degrees of supersaturation that can be attained when aluminum is dissolved in an electrolyte during the operation of an air-aluminum chemical power supply are determined.

  3. Pure and Sr(II)-added copper aluminate nanocomposites: structural, electrical and alcohol sensing studies.

    PubMed

    Kumar, R Thinesh; Vijaya, J Judith; Kennedy, L John

    2013-08-01

    The effect of ethylenediamine addition in the sol-gel method for the preparation of pure and Sr(II)-added nano copper aluminate (CuAl2O4) composites for the enhancement in their structural, electrical, and alcohol sensing properties were investigated. The effect of addition of Sr(II) to pure CuAl2O4 in both the methods were also discussed. X-ray diffraction, scanning electron microscopy, nitrogen adsorption/desorption isotherms, temperature dependant conductance measurements and thermoelectric power measurements were used to characterize the composites prepared. Among the composites, 0.8 molar ratio strontium added copper aluminate composite prepared by modified sol-gel method showed the highest sensitivity towards alcohols. The stability, response and recovery of MS-CuSA5 were also discussed. The response and recovery characteristics showed that the order of sensing alcohols by the composites was butanol > isopropanol > ethanol > methanol, which could be explained on the basis of oxidation of alcohols. PMID:23882857

  4. First-Principles Study of the Elastic Properties of Aluminous Phases at High Temperature and Pressure

    NASA Astrophysics Data System (ADS)

    Stackhouse, S.; Liu, T.

    2014-12-01

    Seismic studies report the presence of regions below Africa and the Pacific, which exhibit shear-wave velocity reductions of about 3 percent. These so-called large low shear velocity provinces (LLSVPs), cover approximately half of the core-mantle boundary, making them an important interface between the core and lowermost mantle. The fact that they exhibit different seismic properties indicates that they are different from surrounding mantle, either in temperature and/or composition. The reported sharpness of the boundaries of large low shear velocity provinces suggests that they are at least in part compositional anomalies. One potential explanation is that they comprise the relics of subducted slabs, and thus have mid-ocean ridge basalt (MORB). The high temperature and pressure seismic properties of MORB phases, needed to compare with seismic observations, are unknown. Here we report the high temperature and pressure elastic properties of several aluminous phases, which comprise about 20 percent of MORB material. In particular, we have looked at MgAl2O4, NaMg2Al5SiO12, and KMg2Al5SiO12, with the calcium ferrite (CF) and new aluminous (NAL) structure. These should provide further constraints to aid the interpretation of seismic observations, contributing to the thermal vs compositional anomaly debate.

  5. Shear bond strength of novel calcium aluminate-based cement (EndoBinder) to root dentine

    PubMed Central

    Garcia, Lucas da Fonseca Roberti; Rossetto, Hebert Luis; Pires-de-Souza, Fernanda de Carvalho Panzeri

    2014-01-01

    Objective: To evaluate the shear bond strength of a novel calcium aluminate-based cement, EndoBinder (EB), to dentine in comparison with Grey and White Mineral Trioxide Aggregate (MTA). Materials and Methods: Root canal hemi-sections obtained from 30 extracted molar teeth were embedded in self-polymerized acrylic resin and were grounded wet in order to obtain a flat dentine surface. Next, the roots were randomly assigned into three groups (n = 10), according to the cement used, as follows: EB: EndoBinder; WMTA: White MTA and GMTA: Grey MTA. The shear bond strength test was performed using a Universal Testing Machine (0.5 mm/min) and the data were submitted to statistical analysis (1-way ANOVA and Tukey tests, P < 0.05). Results: EB presented the highest shear bond strength values; however, there was no statistically significant difference in comparison with GMTA (P > 0.05). WMTA presented the lowest mean values, which were significant in comparison with EB (P < 0.05). Conclusions: The novel calcium aluminate-based cement presented higher shear bond strength than WMTA, and should be considered as a promising alternative in endodontic therapy. PMID:25512731

  6. Investigation of calcium aluminates by IR spectroscopy in diffusely scattered light

    SciTech Connect

    Medin, A.S.; Borovkov, V.Yu.; Nissenbaum, V.D.; Yakerson, V.I.; Kazanskii, V.B.

    1989-01-01

    The hydroxyl covering and the adsorption sites for CO and H/sub 2/O on aluminum-calcium catalysts and supports with developed surfaces have been studied by IR spectroscopy in diffusely scattered light. The presence of several types of surface OH groups, viz., terminal groups bonded to calcium ions with different types of coordination, bridging OH groups, and groups appearing in (CaOH)/sup +/ groupings, which perform the role of compensating cations in the zeolite-like structure of calcium aluminates, has been established. The shifts of the bands of the OH groups upon the adsorption of C/sub 6/H/sub 6/ and cyclo-C/sub 6/H/sub 12/ point out their weakly acidic or basic character. When calcium aluminates are dehydroxylated, aprotic sites appear on their surfaces, and the rehydration of such surfaces is accompanied by the formation of OH groups and the weakening of the Al-O-M bonds (M = Al, Ca) with the appearance of additional sites for the strong adsorption of water.

  7. Systems analysis programs for hands-on integrated reliability evaluations (SAPHIRE) Version 5.0. Fault tree, event tree, and piping & instrumentation diagram (FEP) editors reference manual: Volume 7

    SciTech Connect

    McKay, M.K.; Skinner, N.L.; Wood, S.T.

    1994-07-01

    The Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) refers to a set of several microcomputer programs that were developed to create and analyze probabilistic risk assessments (PRAs), primarily for nuclear power plants. The Fault Tree, Event Tree, and Piping and Instrumentation Diagram (FEP) editors allow the user to graphically build and edit fault trees, and event trees, and piping and instrumentation diagrams (P and IDs). The software is designed to enable the independent use of the graphical-based editors found in the Integrated Reliability and Risk Assessment System (IRRAS). FEP is comprised of three separate editors (Fault Tree, Event Tree, and Piping and Instrumentation Diagram) and a utility module. This reference manual provides a screen-by-screen guide of the entire FEP System.

  8. Thermochemical properties of gibbsite, bayerite, boehmite, diaspore, and the aluminate ion between 0 and 350/degree/C

    SciTech Connect

    Apps, J.A.; Neil, J.M.; Jun, C.H.

    1989-01-01

    A requirement for modelling the chemical behavior of groundwater in a nuclear waste repository is accurate thermodynamic data pertaining to the participating minerals and aqueous species. In particular, it is important that the thermodynamic properties of the aluminate ion be accurately determined, because most rock forming minerals in the earth's crust are aluminosilicates, and most groundwaters are neutral to slightly alkaline, where the aluminate ion is the predominant aluminum species in solution. Without a precise knowledge of the thermodynamic properties of the aluminate ion aluminosilicate mineral solubilities cannot be determined. The thermochemical properties of the aluminate ion have been determined from the solubilities of the aluminum hydroxides and oxyhydroxides in alkaline solutions between 20 and 350/degree/C. An internally consistent set of thermodynamic properties have been determined for gibbsite, boehmite, diaspore and corundum. The thermodynamic properties of bayerite have been provisionally estimated and a preliminary value for ..delta..G/sub f, 298//sup 0/ of nordstrandite has been determined. 205 refs., 17 figs., 25 tabs.

  9. Recovery of iron and calcium aluminate slag from high-ferrous bauxite by high-temperature reduction and smelting process

    NASA Astrophysics Data System (ADS)

    Zhang, Ying-yi; Lü, Wei; Qi, Yuan-hong; Zou, Zong-shu

    2016-08-01

    A high-temperature reduction and smelting process was used to recover iron and calcium aluminate slag from high-ferrous bauxite. The effects of w(CaO)/ w(SiO2) ratio, anthracite ratio, and reduction temperature and time on the recovery and size of iron nuggets and on the Al2O3 grade of the calcium aluminate slag were investigated through thermodynamic calculations and experiments. The optimized process conditions were the bauxite/anthracite/slaked lime weight ratio of 100:16.17:59.37, reduction temperature of 1450°C and reduction time of 20 min. Under these conditions, high-quality iron nuggets and calcium aluminate slag were obtained. The largest size and the highest recovery rate of iron nuggets were 11.42 mm and 92.79wt%, respectively. The calcium aluminate slag mainly comprised Ca2SiO4 and Ca12Al14O33, with small amounts of FeAl2O4, CaAl2O4, and Ca2Al2SiO7.

  10. Gaskets of teflon-bonded EPDM halt leakage from acid lines - low sealing force design eliminates flange distress

    SciTech Connect

    Walker, I.S.; Gaines, A.

    1987-11-01

    The W.R. Grace Chemical Division plant in Lake Charles, LA had to stop producing catalysts for the oil refining industry whenever a piping system for 98% sulfuric acid developed a leak. Gaskets of a nonasbestos material were being used between the flanges of the steel pipe lined with TFE or polypropylene. The flange bolts were kept tight, but the gaskets usually failed to maintain a leaktight seal with the acid at 60 psi for more than a few weeks or months. The acid lines had to be drained before the faulty gasket could be replaced, and production downtime would range from one to three hours. In July 1986, the plant decided to try a chemical resistant gasket of Teflon molded and bonded to a core of Shore A 65-66 durometer EPDM rubber in the acid lines. The resilient gasket also has patented double convex rings on both faces for optimum sealing with only one-eighth the bolt tightening torque commonly required with flat-faced gaskets. The low sealing force requirement prolongs the life of the gasket, eliminates plastic cold flow at the flange of lined steel pipe, and avoids stresses that can damage thermoplastic and fiberglass piping systems. The gasket has a temperature range of {minus}4 to 210{degree}F and is available in 1/2 through 12 inch sizes that conform to ANSI B16.1 flange dimensions. Alternative gasket materials are Kynar PVDF-bonded EPDM and EPDM without a fluoropolymer laminate. The Teflon-bonded EPDM gaskets eliminated unscheduled catalyst production downtime due to leakage from the sulfuric acid piping system. The plant maintains an inventory of the low torque gasket, but has never had to replace any that have been in service since July 1986.

  11. The Effect of Simulated Lunar Dust on the Absorptivity, Emissivity, and Operating Temperature on AZ-93 and Ag/FEP Thermal Control Surfaces

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Siamidis, John; Panko, Scott R.; Rogers, Kerry J.; Larkin, Elizabeth M. G.

    2008-01-01

    JSC-1AF lunar simulant has been applied to AZ-93 and AgFEP thermal control surfaces on aluminum or composite substrates in a simulated lunar environment. The temperature of these surfaces was monitored as they were heated with a solar simulator and cooled in a 30 K coldbox. Thermal modeling was used to determine the absorptivity ( ) and emissivity ( ) of the thermal control surfaces in both their clean and dusted states. Then, a known amount of power was applied to the samples while in the coldbox and the steady state temperatures measured. It was found that even a submonolayer of simulated lunar dust can significantly degrade the performance of both white paint and second-surface mirror type thermal control surfaces under these conditions. Contrary to earlier studies, dust was found to affect as well as . Dust lowered the emissivity by as much as 16 percent in the case of AZ-93, and raised it by as much as 11 percent in the case of AgFEP. The degradation of thermal control surface by dust as measured by / rose linearly regardless of the thermal control coating or substrate, and extrapolated to degradation by a factor 3 at full coverage by dust. Submonolayer coatings of dust were found to not significantly change the steady state temperature at which a shadowed thermal control surface will radiate.

  12. Effect of Annealing on Mechanical Properties and Formability of Cold Rolled Thin Sheets of Fe-P P/M Alloys

    NASA Astrophysics Data System (ADS)

    Trivedi, Shefali; Ravi Kumar, D.; Aravindan, S.

    2016-08-01

    Phosphorus in steel is known to increase strength and hardness and decrease ductility. Higher phosphorus content (more than 0.05%), however, promotes brittle behavior due to segregation of Fe3P along the grain boundaries which makes further mechanical working of these alloys difficult. In this work, thin sheets of Fe-P alloys (with phosphorus in range of 0.1-0.35%) have been developed through processing by powder metallurgy followed by hot rolling and cold rolling. The effect of phosphorus content and annealing parameters (temperature and time) on microstructure, mechanical properties, formability in biaxial stretching and fracture behavior of the cold rolled and annealed sheets has been studied. A comparison has also been made between the properties of the sheets made through P/M route and the conventional cast route with similar phosphorus content. It has been shown that thin sheets of Fe-P alloys with phosphorous up to 0.35% possessing a good combination of strength and formability can be produced through rolling of billets of these alloys made through powder metallurgy technique without the problem of segregation.

  13. EVALUATION OF A TEFLON HELIX LIQUID-LIQUID EXTRACTOR FOR CONCENTRATION OF TRACE ORGANICS FROM WATER INTO METHYLENE CHLORIDE (JOURNAL VERSION)

    EPA Science Inventory

    A continuous liquid-liquid extraction system (CLLE) for concentrating trace organics from water into methylene chloride for analysis was designed, built and evaluated. The CLLE uses Teflon coils for phase contact and gravity phase separation. The system includes a self-contained ...

  14. Studies on operational and dynamic response characteristics of the potentiometric carbon dioxide gas-sensing probe by using a Teflon membrane

    SciTech Connect

    Roditaki, A.; Nikolelis, D.P.; Papastathopoulos, D.S. )

    1993-03-01

    The performance and dynamic response characteristics of the potentiometric carbon dioxide gas sensor with an alternative to the commercially available silicon rubber membrane are studied in this paper. This study was performed in the course to choose a low cost membrane and possibly to further optimize the time response of this sensor. The membrane used was a microporous Teflon membrane which is used in ammonia gas sensors. The results have shown that the CO[sub 2] gas-sensing probe with the Teflon membrane shows similar performance characteristics as the silicon rubber membrane, but improved stability with time. Convolution mathematics were also used to study the dynamic response characteristics of the gas sensor with the Teflon membrane and the results have shown that practically similar time constants are obtained as when a silicon rubber membrane is used. Therefore, the less costly membrane can replace the silicon rubber membrane when CO[sub 2] is being monitored and a gas-sensing probe can be constructed through this means, by using a Teflon membrane and a 1 mM NaHCO[sub 3]-100 mM NaCl internal filling solution. 10 refs., 5 figs.

  15. Production of Magnesium by Vacuum Aluminothermic Reduction with Magnesium Aluminate Spinel as a By-Product

    NASA Astrophysics Data System (ADS)

    Wang, Yaowu; You, Jing; Peng, Jianping; Di, Yuezhong

    2016-03-01

    The Pidgeon process currently accounts for 85% of the world's magnesium production. Although the Pidgeon process has been greatly improved over the past 10 years, such production still consumes much energy and material and creates much pollution. The present study investigates the process of producing magnesium by employing vacuum aluminothermic reduction and by using magnesite as material and obtaining magnesium aluminate spinel as a by-product. The results show that compared with the Pidgeon process, producing magnesium by vacuum aluminothermic reduction can save materials by as much as 50%, increase productivity up to 100%, and save energy by more than 50%. It can also reduce CO2 emission by up to 60% and realize zero discharge of waste residue. Vacuum aluminothermic reduction is a highly efficient, low-energy-consumption, and environmentally friendly method of producing magnesium.

  16. Aqueous Cr (VI) removal by Friedel's salt adsorbent prepared from calcium aluminate-rich cementitious materials.

    PubMed

    Jiang, Yonghai; Yang, Yu; Qian, Guangren; Hou, Hetian; Xi, Beidou; Xu, Yunfeng

    2015-01-01

    This research paper investigated a novel absorbent of calcium aluminate-rich cementitious materials (Friedel's salt adsorbent, FA) for aqueous hexavalent chromium (VI) removal. The adsorption kinetics showed that the maximum adsorption capacities of FA were 3.36, 14.66, and 26.17 mg/g when the initial Cr(VI) concentration was 10, 50, and 100 mg/L, respectively. The adsorption fitted with the pseudo-second-order kinetic model, suggesting the important roles of intercalation in the adsorption process with increasing Cr(VI) concentrations. This Friedel's salt adsorbent is suggested as an adaptive and effective adsorbent for Cr(VI) removal in contaminated groundwater. PMID:25798557

  17. Development of MnCoO Coating with New Aluminizing Process for Planar SOFC Stacks

    SciTech Connect

    Choi, Jung-Pyung; Weil, K. Scott; Chou, Y. S.; Stevenson, Jeffry W.; Yang, Zhenguo

    2011-03-22

    Low-cost, chromia-forming steels find widespread use in SOFCs at operating temperatures below 800°C, because of their low thermal expansion mismatch and low cost. However, volatile Cr-containing species originating from this scale poison the cathode material in the cells and subsequently cause power degradation in the devices. To prevent this, a conductive manganese cobaltite coating has been developed. However, this coating is not compatible with forming hermetic seals between the interconnect or window frame component and ceramic cell. This coating reacts with sealing materials. Thus, a new aluminizing process has been developed for the sealing regions in these parts, as well as for other metallic stack and balance-of-plant components. From this development, the sealing performance and SOFC stack performance became very stable.

  18. Calibration of the BKW--EOS and application to aluminized composite explosives

    SciTech Connect

    Hobbs, M.L.; Baer, M.R.

    1993-04-01

    The Becker-Kistiakowsky-Wilson equation of state (BKW-EOS) has been calibrated over a wide initial density range near C-J states using measured detonation properties from 62 explosives at III total initial densities. Values for the empirical BKW constants {alpha}, {beta}, {kappa}, and {theta} were 0.5, 0.298, 10.5, and 6620, respectively. Covolumes were assumed to be invariant. Model evaluation includes comparison to measurements from 91 explosives composed of combinations of Al, B, Ba, C, Ca, Cl, F, H, N, 0, P, Pb, and Si at 147 total initial densities. Adequate agreement between predictions and measurements were obtained with a few exceptions for nonideal explosives. However, detonation properties for the nonideal explosives can be predicted adequately by assuming partial equilibrium. The partial equilibrium assumption was applied to aluminized composites of RDX, HMX, TNETB, and TNT to predict detonation velocity and temperature.

  19. Calibration of the BKW--EOS and application to aluminized composite explosives

    SciTech Connect

    Hobbs, M.L.; Baer, M.R.

    1993-01-01

    The Becker-Kistiakowsky-Wilson equation of state (BKW-EOS) has been calibrated over a wide initial density range near C-J states using measured detonation properties from 62 explosives at III total initial densities. Values for the empirical BKW constants [alpha], [beta], [kappa], and [theta] were 0.5, 0.298, 10.5, and 6620, respectively. Covolumes were assumed to be invariant. Model evaluation includes comparison to measurements from 91 explosives composed of combinations of Al, B, Ba, C, Ca, Cl, F, H, N, 0, P, Pb, and Si at 147 total initial densities. Adequate agreement between predictions and measurements were obtained with a few exceptions for nonideal explosives. However, detonation properties for the nonideal explosives can be predicted adequately by assuming partial equilibrium. The partial equilibrium assumption was applied to aluminized composites of RDX, HMX, TNETB, and TNT to predict detonation velocity and temperature.

  20. Acyl Silicates and Acyl Aluminates as Activated Intermediates in Peptide Formation on Clays

    NASA Astrophysics Data System (ADS)

    White, David H.; Kennedy, Robert M.; Macklin, John

    1984-12-01

    Glycine reacts with heating on dried clays and other minerals to give peptides in much better yield than in the absence of mineral. This reaction was proposed to occur by way of an activated intermediate such as an acyl silicate or acyl aluminate (i.e., the anhydride of a carboxylic acid with Si-OH or Al-OH), analogous to acyl phosphates involved in several biochemical reactions including peptide bond synthesis. We confirmed the proposed mechanism by trapping the intermediate, as well as by direct spectroscopic observation of a related intermediate. The reaction of amino acids on periodically dried mineral surfaces represents a widespread, geologically realistic setting for prebiotic peptide formation via in situ activation.

  1. Post-stishovite transition in hydrous aluminous SiO2

    NASA Astrophysics Data System (ADS)

    Umemoto, Koichiro; Kawamura, Katsuyuki; Hirose, Kei; Wentzcovitch, Renata M.

    2016-06-01

    Lakshtanov et al. (2007) showed that incorporation of aluminum and some water into SiO2 significantly reduces the post-stishovite transition pressure in SiO2. This discovery suggested that the ferroelastic post-stishovite transition in subducted MORB crust could be the source of reflectors/scatterers with low shear velocities observed in the mid to upper lower mantle. A few years later, a similar effect was observed in anhydrous Al-bearing silica. In this paper, we show by first principles static calculations and by molecular dynamics using inter-atomic potentials that hydrogen bonds and hydrogen mobility play a crucial role in lowering the post-stishovite transition pressure. A cooperative redistribution of hydrogen atoms is the main mechanism responsible for the transition pressure reduction in hydrous aluminous stishovite. The effect is enhanced by increasing hydrogen concentration. This perspective suggests a potential relationship between the depth of seismic scatterers and the water content in stishovite.

  2. Electron energy-loss spectroscopy study of thin film hafnium aluminates for novel gate dielectrics.

    PubMed

    Stemmer, S; Chen, Z Q; Zhu, W J; Ma, T P

    2003-04-01

    We have used conventional high-resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS) in scanning transmission electron microscopy to investigate the microstructure and electronic structure of hafnia-based thin films doped with small amounts (6.8 at.%) of Al grown on (001) Si. The as-deposited film is amorphous with a very thin (approximately 0.5 nm) interfacial SiOx layer. The film partially crystallizes after annealing at 700 degrees C and the interfacial SiO2-like layer increases in thickness by oxygen diffusion through the Hf-aluminate layer and oxidation of the silicon substrate. Oxygen K-edge EELS fine-structures are analysed for both films and interpreted in the context of the films' microstructure. We also discuss valence electron energy-loss spectra of these ultrathin films. PMID:12694419

  3. Defects and radiation induced electronic processes in magnesium aluminate spinel of different compositions

    NASA Astrophysics Data System (ADS)

    Gritsyna, V. T.; Kazarinov, Y. G.; Kobyakov, V. A.; Sickafus, K. E.

    The time dependence of the formation and decay of irradiation-induced optical absorption centers in magnesium aluminate spinel single crystals of different compositions (MgO.1.0Al(2)O(3) and MgO.2.5Al(2)O(3)) was investigated. The kinetics of accumulation of X-ray irradiation-induced absorption bands is consistent with the mechanism of trap filling with free charge carriers through the conduction band. The model includes Coulomb blocking effects on spatially correlated defects. The observed two-stage decay of absorption bands after termination of X-ray irradiation is explained by electron hole recombination between centers of two different distances and/or different potential barriers. UV-irradiation confirms the existence of charge exchange between complex spatially correlated defects.

  4. On the Compressive and Tensile Dynamic Strength of Magnesium Aluminate Spinel

    NASA Astrophysics Data System (ADS)

    Hayun, Shmuel; Paris, Vitaly; Dariel, Moshe; Zaretsky, Eugene; Frage, Nahum

    2009-06-01

    Polycrystalline transparent Magnesium Aluminate Spinel (MAS) is an attractive material for a wide range of optical, electronic, structural and armor applications. Transparent MAS samples of 20-30 mm diameter and 3-5 mm thickness has been successfully fabricated by means of Field Assisted Sintering Technology. The dynamic response of MAS was investigated by plate impact experiments. The values of the Hugoniot Elastic Limit (HEL) and the spall strength were derived from the VISAR records of the velocities of the free sample surface or of the sample/window (PMMA) interface. The dependence of the HEL and the spall strength on the impact stress, as well as, correlation between the spall strength and the width of the loading pulse are discussed.

  5. Radiation-induced disordering in magnesium aluminate spinel subjected to ionizing radiation

    NASA Astrophysics Data System (ADS)

    Shimada, M.; Matsumura, S.; Yasuda, K.; Kinoshita, C.; Chimi, Y.; Ishikawa, N.; Iwase, A.

    2004-08-01

    An analytical electron microscope study was carried out on single crystal specimens of magnesium aluminate spinel irradiated with 200 MeV Xe 14+ ions up to 5.0 × 10 15 and 2.0 × 10 16 ions/m 2 at ambient temperature. Bright-field images showed structurally disordered columns of about 4-5 nm in diameter along ion tracks. Tiny pits were observed on the incident surface of the columns. Quantitative HARECXS analysis of atomic configurations revealed that disordering proceeds in more extended regions over 10 nm in diameter. The configurations of Al 3+ ions are more disordered than that of Mg 2+ ions. The disordered areas are appeared to overlap each other in the specimen irradiated with 2.0 × 10 16 ions/m 2.

  6. Life Model of Hollow Cathodes Using a Barium Calcium Aluminate Impregnated Tungsten Emitter

    NASA Technical Reports Server (NTRS)

    Kovaleski, S. D.; Burke, Tom (Technical Monitor)

    2001-01-01

    Hollow cathodes with barium calcium aluminate impregnated tungsten emitters for thermionic emission are widely used in electric propulsion. These high current, low power cathodes are employed in ion thrusters, Hall thrusters, and on the International Space Station in plasma contactors. The requirements on hollow cathode life are growing more stringent with the increasing use of electric propulsion technology. The life limiting mechanism that determines the entitlement lifetime of a barium impregnated thermionic emission cathode is the evolution and transport of barium away from the emitter surface. A model is being developed to study the process of barium transport and loss from the emitter insert in hollow cathodes. The model accounts for the production of barium through analysis of the relevant impregnate chemistry. Transport of barium through the approximately static gas is also being treated. Finally, the effect of temperature gradients within the cathode are considered.

  7. Water solubility in aluminous orthopyroxene and the origin of Earth's asthenosphere.

    PubMed

    Mierdel, Katrin; Keppler, Hans; Smyth, Joseph R; Langenhorst, Falko

    2007-01-19

    Plate tectonics is based on the concept of rigid lithosphere plates sliding on a mechanically weak asthenosphere. Many models assume that the weakness of the asthenosphere is related to the presence of small amounts of hydrous melts. However, the mechanism that may cause melting in the asthenosphere is not well understood. We show that the asthenosphere coincides with a zone where the water solubility in mantle minerals has a pronounced minimum. The minimum is due to a sharp decrease of water solubility in aluminous orthopyroxene with depth, whereas the water solubility in olivine continuously increases with pressure. Melting in the asthenosphere may therefore be related not to volatile enrichment but to a minimum in water solubility, which causes excess water to form a hydrous silicate melt. PMID:17234945

  8. An internally consistent model for the thermodynamic properties of Fe-Mg-titanomagnetite-aluminate spinels

    NASA Astrophysics Data System (ADS)

    Sack, Richard O.; Ghiorso, Mark S.

    1991-02-01

    A model is developed for the thermodynamic properties of Fe2+-Mg2+-aluminate-titanate-ferrite spinels of space group Fd3m. The model incorporates an expression for the configurational entropy of mixing which accounts for long-range order over tetrahedral and octahedral sites. Short-range order or departures from cubic symmetry are not considered. The non-configurational Gibbs energy is formulated as a second degree Taylor expansion in six linearly independent composition and ordering variables. The model parameters are calibrated to reproduce miscibility gap constraints, order-disorder phenomena in MgAl2O4 and MgFe2O4, and Fe2+-Mg2+ partitioning data between olivine and: (1) aluminate spinels; (2) ferrite spinels; (3) titanate spinels; (4) mixed aluminate-ferrite spinels. This calibration is achieved without invoking non-configurational excess entropies of mixing. The model predicts that the ordering state of FeAl2O4 is more normal than that of MgAl2O4. It also successfully accounts for heat of solution measurements and activity-composition relations in the constituent binaries. Phase equilibrium constraints require that the structure of Fe3O4 is more inverse than random at all temperatures and that Mg2+ has a strong tetrahedral site preference with respect to that of Fe2+. The analysis suggests that in the titanates short range order on octahedral sites may be significant at temperatures as high as 1300° C. Constraints developed from calibrating the thermodynamic properties of Fe2+-Mg2+-aluminatetitanate-ferrite spinel solid solutions permit extension of the database of Berman (1988) to include estimates of the end-member properties of hercynite (FeAl2O4), ulvöspinel (Fe2TiO4), MgFe2O4 and cubic Mg2TiO4. In constructing these estimates, provision is made for low-temperature magnetic entropy contributions and the energetic consequences of disordering the aluminates and the ferrites. These estimates are consistent with all of the available low

  9. Production of Magnesium by Vacuum Aluminothermic Reduction with Magnesium Aluminate Spinel as a By-Product

    NASA Astrophysics Data System (ADS)

    Wang, Yaowu; You, Jing; Peng, Jianping; Di, Yuezhong

    2016-06-01

    The Pidgeon process currently accounts for 85% of the world's magnesium production. Although the Pidgeon process has been greatly improved over the past 10 years, such production still consumes much energy and material and creates much pollution. The present study investigates the process of producing magnesium by employing vacuum aluminothermic reduction and by using magnesite as material and obtaining magnesium aluminate spinel as a by-product. The results show that compared with the Pidgeon process, producing magnesium by vacuum aluminothermic reduction can save materials by as much as 50%, increase productivity up to 100%, and save energy by more than 50%. It can also reduce CO2 emission by up to 60% and realize zero discharge of waste residue. Vacuum aluminothermic reduction is a highly efficient, low-energy-consumption, and environmentally friendly method of producing magnesium.

  10. Improved performance of strontium aluminate luminous coating on the ceramic surface

    NASA Astrophysics Data System (ADS)

    Gao, Fang; Xiong, Zhaoxian; Xue, Hao; Liu, Yongxi

    2009-03-01

    Phosphor of strontium aluminate co-actived by Eu2+ and Dy3+ is one kind of important afterglow luminescent materials. In this paper, the phosphors were used with transparent glaze for an inorganic luminous coating on the ceramic surface, which was stable even at high temperature. The chemical structure and microstructure of the luminous coating were identified with X-ray diffraction (XRD) and observed with scanning electron microscopy (SEM), respectively. The photoluminescence of the coating was measured by a HITACHI F-4500 fluorescence spectrophotometer. The afterglow property was recorded by a ST-86LA-3 brightness meter. The samples behaved good performances such as high lighting brightness and long after-glowing time.

  11. Exposing elusive cationic magnesium-chloro aggregates in aluminate complexes through donor control.

    PubMed

    Brouillet, Etienne V; Kennedy, Alan R; Koszinowski, Konrad; McLellan, Ross; Mulvey, Robert E; Robertson, Stuart D

    2016-04-01

    The cationic magnesium moiety of magnesium organohaloaluminate complexes, relevant to rechargeable Mg battery electrolytes, typically takes the thermodynamically favourable dinuclear [Mg2Cl3](+) form in the solid-state. We now report that judicious choice of Lewis donor allows the deliberate synthesis and isolation of the hitherto only postulated mononuclear [MgCl](+) and trinuclear [Mg3Cl5](+) modifications, forming a comparable series with a common aluminate anion [(Dipp)(Me3Si)NAlCl3](-). By pre-forming the Al-N bond prior to introduction of the Mg source, a consistently reproducible protocol is reported. Usage of the green solvent 2-methyltetrahydrofuran in place of THF in the context of Mg/Al battery electrolyte type complexes is also promoted. PMID:26916737

  12. Pre-desilication and digestion of gibbsitic bauxite with lime in sodium aluminate liquor

    NASA Astrophysics Data System (ADS)

    Pan, Xiao-lin; Yu, Hai-yan; Dong, Kai-wei; Tu, Gan-feng; Bi, Shi-wen

    2012-11-01

    The effect of lime on the pre-desilication and digestion of gibbsitic bauxite in synthetic sodium aluminate liquor at different temperatures was investigated. The bauxite is comprised of gibbsite, aluminogoethite, hematite, kaolin, quartz, and minor boehmite. Lime increases the desilication efficiency of the bauxite during the pre-desilication process by promoting the conversion of sodalite and cancrinite to hydrogarnet. Desilication reactions during the digestion process promoted by lime result in the loss of Al2O3 entering the red mud, but the amount of aluminogoethite-to-hematite conversion promoted by lime leads to the increase of aluminogoethitic Al2O3 entering the digested liquor. The alumina digestion rate at 245°C is higher than that at 145°C due to the more pronounced conversion of aluminogoethite to hematite. The soda consumption during the digestion process decreases due to lime addition, especially at higher temperatures.

  13. Laser-Induced Fluorescence Photogrammetry for Dynamic Characterization of Transparent and Aluminized Membrane Structures

    NASA Technical Reports Server (NTRS)

    Dorrington, Adrian A.; Jones, Thomas W.; Danehy, Paul M.; Pappa, Richard S.

    2003-01-01

    Photogrammetry has proven to be a valuable tool for static and dynamic profiling of membrane based inflatable and ultra-lightweight space structures. However, the traditional photogrammetric targeting techniques used for solid structures, such as attached retro-reflective targets and white-light dot projection, have some disadvantages and are not ideally suited for measuring highly transparent or reflective membrane structures. In this paper, we describe a new laser-induced fluorescence based target generation technique that is more suitable for these types of structures. We also present several examples of non-contact non-invasive photogrammetric measurements of laser-dye doped polymers, including the dynamic measurement and modal analysis of a 1m-by-1m aluminized solar sail style membrane.

  14. Evaluation of cytotoxicity, antimicrobial activity and physicochemical properties of a calcium aluminate-based endodontic material

    PubMed Central

    SILVA, Emmanuel João Nogueira Leal; HERRERA, Daniel Rodrigo; ROSA, Tiago Pereira; DUQUE, Thais Mageste; JACINTO, Rogério Castilho; GOMES, Brenda Paula Figueiredo de Almeida; ZAIA, Alexandre Augusto

    2014-01-01

    A calcium aluminate-based endodontic material, EndoBinder, has been developed in order to reduce MTA negative characteristics, preserving its biological properties and clinical applications. Objectives The aim of this study was to evaluate the cytotoxicity, antimicrobial activity, pH, solubility and water sorption of EndoBinder and to compare them with those of white MTA (WMTA). Material and Methods Cytotoxicity was assessed through a multiparametric analysis employing 3T3 cells. Antimicrobial activity against Enterococcus faecalis (ATCC 29212), Staphylococcus aureus. (ATCC 25923) and Candida albicans (ATCC 10556) was determined by the agar diffusion method. pH was measured at periods of 3, 24, 72 and 168 hours. Solubility and water sorption evaluation were performed following ISO requirements. Data were statistically analyzed by ANOVA and Tukey`s test with a significance level of 5%. Results EndoBinder and WMTA were non-cytotoxic in all tested periods and with the different cell viability parameters. There was no statistical differences between both materials (P>.05). All tested materials were inhibitory by direct contact against all microbial strains tested. EndoBinder and WMTA presented alkaline pH in all tested times with higher values of pH for WMTA (P<.05). Both materials showed values complying with the solubility minimum requirements. However, EndoBinder showed lower solubility than WMTA (P<.05). No statistical differences were observed regarding water sorption (P>.05). Conclusion Under these experimental conditions, we concluded that the calcium aluminate-based endodontic material EndoBinder demonstrated suitable biological and physicochemical properties, so it can be suggested as a material of choice in root resorption, perforations and root-end filling. PMID:24626250

  15. Chitosan-collagen biomembrane embedded with calcium-aluminate enhances dentinogenic potential of pulp cells.

    PubMed

    Soares, Diana Gabriela; Rosseto, Hebert Luís; Basso, Fernanda Gonçalves; Scheffel, Débora Salles; Hebling, Josimeri; Costa, Carlos Alberto de Souza

    2016-01-01

    The development of biomaterials capable of driving dental pulp stem cell differentiation into odontoblast-like cells able to secrete reparative dentin is the goal of current conservative dentistry. In the present investigation, a biomembrane (BM) composed of a chitosan/collagen matrix embedded with calcium-aluminate microparticles was tested. The BM was produced by mixing collagen gel with a chitosan solution (2:1), and then adding bioactive calcium-aluminate cement as the mineral phase. An inert material (polystyrene) was used as the negative control. Human dental pulp cells were seeded onto the surface of certain materials, and the cytocompatibility was evaluated by cell proliferation and cell morphology, assessed after 1, 7, 14 and 28 days in culture. The odontoblastic differentiation was evaluated by measuring alkaline phosphatase (ALP) activity, total protein production, gene expression of DMP-1/DSPP and mineralized nodule deposition. The pulp cells were able to attach onto the BM surface and spread, displaying a faster proliferative rate at initial periods than that of the control cells. The BM also acted on the cells to induce more intense ALP activity, protein production at 14 days, and higher gene expression of DSPP and DMP-1 at 28 days, leading to the deposition of about five times more mineralized matrix than the cells in the control group. Therefore, the experimental biomembrane induced the differentiation of pulp cells into odontoblast-like cells featuring a highly secretory phenotype. This innovative bioactive material can drive other protocols for dental pulp exposure treatment by inducing the regeneration of dentin tissue mediated by resident cells. PMID:27119587

  16. Zircon saturation in silicate melts: a new and improved model for aluminous and alkaline melts

    NASA Astrophysics Data System (ADS)

    Gervasoni, Fernanda; Klemme, Stephan; Rocha-Júnior, Eduardo R. V.; Berndt, Jasper

    2016-03-01

    The importance of zircon in geochemical and geochronological studies, and its presence not only in aluminous but also in alkaline rocks, prompted us to think about a new zircon saturation model that can be applied in a wide range of compositions. Therefore, we performed zircon crystallization experiments in a range of compositions and at high temperatures, extending the original zircon saturation model proposed by Watson and Harrison (Earth Planet Sci Lett 64:295-304, 1983) and Boehnke et al. (Chem Geol 351:324-334, 2013). We used our new data and the data from previous studies in peraluminous melts, to describe the solubility of zircon in alkaline and aluminous melts. To this effect, we devised a new compositional parameter called G [ {( {3 \\cdot {{Al}}2 {{O}}3 + {{SiO}}2 )/({{Na}}2 {{O}} + {{K}}2 {{O}} + {{CaO}} + {{MgO}} + {{FeO}}} )} ] (molar proportions), which enables to describe the zircon saturation behaviour in a wide range of rock compositions. Furthermore, we propose a new zircon saturation model, which depends basically on temperature and melt composition, given by (with 1σ errors): ln [ {{Zr}} ] = ( {4.29 ± 0.34} ) - ( {1.35 ± 0.10} ) \\cdot ln G + ( {0.0056 ± 0.0002} ) \\cdot T( °C ) where [Zr] is the Zr concentration of the melt in µg/g, G is the new parameter representing melt composition and T is the temperature in degrees Celsius. The advantages of the new model are its straightforward use, with the G parameter being calculated directly from the molar proportions converted from electron microprobe measurements, the temperature calculated given in degrees Celsius and its applicability in a wider range of rocks compositions. Our results confirm the high zircon solubility in peralkaline rocks and its dependence on composition and temperature. Our new model may be applied in all intermediate to felsic melts from peraluminous to peralkaline compositions.

  17. CITRIC ACID AS A SET RETARDER FOR CALCIUM ALUMINATE PHOSPHATE CEMENTS.

    SciTech Connect

    SUGAMA,T.; BROTHERS, L.E.

    2005-01-01

    Citric acid added as set retarder significantly contributed to enhancing the setting temperature and to extending the thickening time of a calcium aluminate phosphate (CaP) geothermal cement slurry consisting of calcium aluminate cement (CAC) as the base reactant and sodium polyphosphate (NaP) solution as the acid reactant. The set-retarding activity of citric acid was due to the uptake of Ca{sup 2+} ions from the CAC by carboxylic acid groups within the citric acid. This uptake led to the precipitation of a Ca-complexed carboxylate compound as a set-retarding barrier layer on the CAC grains' surfaces. However, this barrier layer was vulnerable to disintegration by the attack of free Ca{sup 2+} ions from CAC, and also to degradation at elevated temperature, thereby promoting the generation of exothermic energy from acid-base reactions between the CAC and NaP after the barrier was broken. The exothermic reaction energy that was promoted in this way minimized the loss in strength of the citric acid-retarded cement. The phase composition assembled in both retarded and non-retarded cements after autoclaving at 180 C encompassed three reaction products, hydroxyapatite (HOAp), hydrogrossular and boehmite, which are responsible for strengthening the autoclaved cement. The first two reaction products were susceptible to reactions with sulfuric acid and sodium sulfate to form crystalline bassanite scale as the corrosion product. The boehmite phase possessed a great resistance to acid and sulfate. Although the bassanite scales clinging to the cement's surfaces were the major factor governing the loss in weight, they served in protecting the cement from further acid- and sulfate-corrosion until their spallation eventually occurred. Nevertheless, the repetitive processes of HOAp and hydrogrossular {yields} bassanite {yields} spallation played an important role in extending the useful lifetime of CaP cement in a low pH environment at 180 C.

  18. BRAIN CHOLINESTERASE INHIBITION AND DEPRESSION OF THE PHOTIC AFTER DISCHARGE (PHAD) OF FLASH EVOKED POTENTIALS (FEPS) IN LONG EVANS RATS FOLLOWING ACUTE OR REPEATED EXPOSURES TO A MIXTURE OF CARBARYL AND PROPOXUR.

    EPA Science Inventory

    Carbaryl and propoxur are N-methyl carbamate pesticides (NMCs) which are part of the EPA’s cumulative risk assessments for NMCs. These NMCs inhibit cholinesterase (ChE) activity and may lead to cholinergic disruption of CNS function. We used decreases in the PhAD of FEPs to indic...

  19. Modifying candle soot with FeP nanoparticles into high-performance and cost-effective catalysts for the electrocatalytic hydrogen evolution reaction.

    PubMed

    Zhang, Zhe; Hao, Jinhui; Yang, Wenshu; Lu, Baoping; Tang, Jilin

    2015-03-14

    Developing inexpensive and highly efficient non-precious-metal electrocatalysts has been proposed as a promising alternative to platinum-based catalysts for the hydrogen evolution reaction (HER). Herein, we report novel FeP NPs supported on inexpensive and available candle soot (FeP-CS) derived from Fe3O4-CS hybrid precursors obtained after a phosphidation reaction. As HER electrocatalysts, the FeP-CS hybrids exhibit high electrocatalytic ability for HER with a Tafel slope of 58 mV dec(-1), a low onset overpotential of 38 mV, a large exchange current density of 2.2 × 10(-1) mA cm(-2) and an overpotential of 112 mV to obtain a current of 10 mA cm(-2). The present work shows significant advance in designing and developing non-precious-metal electrocatalysts for hydrogen evolution reaction. PMID:25685982

  20. Formation of magnesium aluminate (spinel) in cast SiC particulate-reinforced Al(A356) metal matrix composites

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Wang, Zhirui; Weatherly, George C.

    1992-05-01

    Transmission (TEM) and scanning electron microscopy (SEM) are employed to study the SiC/Al-alloy interface in a cast SiCp/Al(A356) metal matrix composite (MMC). Magnesium aluminate (spinel), MgAl2O4, was found at the interface as a reaction product after material processing. Comparisons of the crystal structure, structure factor, and interface reaction ther-modynamics between MgAl2O4 and MgO have been carried out. The results from these com-parisons confirm the experimental observation; i.e., the favored interface phase is magnesium aluminate (spinel). Based on the thermodynamic analysis, the presence of oxygen in various forms in the system during processing, such as SiO2, A12O3, and MgO, is believed to be the source which supplies the oxygen for the formation of MgAl2O4.

  1. A Numerical Study on Internal-Blast-Field Characteristics and Dynamic Response of Concrete by Aluminized Explosive

    NASA Astrophysics Data System (ADS)

    Song, P.; Xiao, C.; Gu, X. H.

    2011-09-01

    Three energy release models of aluminized explosive with combustion effects were compared and analyzed, including Miller-Extension model, Additional energy model, Ignition and growth model (Lee-Tarver model). The Ignition and growth model is one three-form equation of reaction rate, which can describe unsteady detonation process of non-ideal explosives well. So, in this paper, the energy release model of aluminized explosive based on the Lee-Tarver rate equation was utilized and an internal-blast dynamic model of concrete was established. Moreover, the smoothed particle hydrodynamics (SPH) method was adopted to research blast field and damage effects of concrete, which widens SPH method for study on explosion of non-ideal explosive in a confined medium, and provides an important way to evaluate the damage effect of internal-blast of concrete.

  2. Graphite-teflon composite bienzyme electrodes for the determination of cholesterol in reversed micelles. Application to food samples.

    PubMed

    Peña, N; Ruiz, G; Reviejo, A J; Pingarrón, J M

    2001-03-15

    A bienzyme amperometric composite biosensor for the determination of free and total cholesterol in food samples is reported. Cholesterol oxidase and horseradish peroxidase, together with potassium ferrocyanide as a mediator, are incorporated into a graphite-70% Teflon matrix. The compatibility of this biosensor design with predominantly nonaqueous media allows the use of reversed micelles as working medium. The reversed micelles are formed with ethyl acetate as continuous phase (in which cholesterol is soluble), a 4% final concentration of 0.05 mol L(-1) phosphate buffer solution, pH 7.4, as dispersed phase, and 0.1 mol L(-1) AOT as emulsifying agent. Studies on the repeatability of the amperometric response obtained at +0.10 V, with and without regeneration of the electrode surface by polishing, on the useful lifetime of one single biosensor and on the reproducibility in the fabrication of different pellets illustrate the robustness of the biosensor design. Determination of free and total cholesterol in food samples such as butter, lard, and egg yoke was carried out, and the obtained results were advantageously compared with those provided by using a commercial Boehringer test kit. PMID:11305650

  3. Fabrication and characterization of ZnO nanowires by wet oxidation of Zn thin film deposited on Teflon substrate

    NASA Astrophysics Data System (ADS)

    Farhat, O. F.; Halim, M. M.; Abdullah, M. J.; Ali, M. K. M.; Ahmed, Naser M.; Bououdina, M.

    2015-10-01

    In this study, ZnO nanowires (NWs) were successfully grown for the first time on to Teflon substrate by a wet oxidation of a Zn thin film coated by RF sputtering technique. The sputtered Zn thin film was oxidized at 100 °C for 5 h under water-vapour using a horizontal furnace. This oxidation process transformed Zn thin film into ZnO with wire-like nanostructure. XRD analysis confirms the formation of single nanocrystalline ZnO phase having a low compressive strain. FESEM observations reveal high density of ZnO NWs with diameter ranging from 34 to 52 nm and length about 2.231 μm, which are well distributed in different direction. A flexible ZnO NWs-based metal-semiconductor-metal UV photodetector was fabricated. Photo-response and sensitivity measurements under low power illumination (375 nm, 1.5 mW/cm2) showed a high sensitivity of 2050%, which can be considered a relatively fast response and baseline recovery for UV detection.

  4. Merging drops in a Teflon tube, and transferring fluid between them, illustrated by protein crystallization and drug screening.

    PubMed

    Feuerborn, A; Prastowo, A; Cook, P R; Walsh, E

    2015-01-01

    The ability to manipulate drops with small volumes has many practical applications. Current microfluidic devices generally exploit channel geometry and/or active external equipment to control drops. Here we use a Teflon tube attached to a syringe pump and exploit the properties of interfaces between three immiscible liquids to create particular fluidic architectures. We then go on to merge any number of drops (with volumes of micro- to nano-liters) at predefined points in time and space in the tube; for example, 51 drops were merged in a defined order to yield one large drop. Using a different architecture, specified amounts of fluid were transferred between 2 nl drops at specified rates; for example, 2.5 pl aliquots were transferred (at rates of ~500 fl s(-1)) between two drops through inter-connecting nano-channels (width ~40 nm). One proof-of-principle experiment involved screening conditions required to crystallize a protein (using a concentration gradient created using such nano-channels). Another demonstrated biocompatibility; drugs were mixed with human cells grown in suspension or on surfaces, and the treated cells responded like those grown conventionally. Although most experiments were performed manually, moderate high-throughput potential was demonstrated by mixing ~1000 different pairs of 50 nl drops in ~15 min using a robot. We suggest this reusable, low-cost, and versatile methodology could facilitate the introduction of microfluidics into workflows of many experimental laboratories. PMID:26246015

  5. Grade-2 Teflon (AF1601) PCF for optical communication using 2D FDTD technique: a simplest design

    NASA Astrophysics Data System (ADS)

    Muduli, N.; Achary, J. S. N.; Padhy, Hemanta ku.

    2016-04-01

    A nonlinear ytterbium-doped rectangular proposed PCF structure of inner and outer cladding is used to analyze effective mode field area (Aeff), nonlinear coefficient (γ), dispersion (D), and confinement loss (CL) in a wide range of wavelength. The fabrication of PCF structure is due to different size doped air hole, pitch, and air hole diameter in a regular periodic geometrical array fashion. The various property of PCF structure such as mode field area, nonlinear coefficient, dispersion, and confinement loss are analyzed by implementing 2D FDTD technique. The above PCF property investigated using suitable parameters like Λ1, ?, ?, and ? in three different situations is discussed in simulation. The high nonlinear coefficient and dispersion property of PCF structure are tailored by setting the cladding parameter. However, highly nonlinear fibers with nonzero dispersion at the wavelength of 1.55 μm are very attractive for a range of optical communication application such as laser amplifier, pulse compression, wavelength conversion, all optical switching, and supercontinuum generation. So our newly proposed ytterbium-doped PCF seems to be most suitable exclusively for supercontinuum generation and nonlinear fiber optics. Finally, it is observed that ytterbium-doped Teflon (AF1601) PCF has more nonlinear coefficient (γ(λ) = 65.27 W-1 km-1) as compared to pure silica PCF (γ(λ) = 52 W-1 km-1) design to have same mode field area (Aeff) 1.7 μm2 at an operating wavelength of 1.55 μm.

  6. Formation of calcium aluminates in the lime sinter process. [Extraction of alumina from fly ash

    SciTech Connect

    Chou, K.S.

    1980-03-01

    A study of the formation of several calcium aluminates from pure components in the lime sinter process was undertaken to determine the kinetics of formation and subsequent leaching using a dilute sodium carbonate solution. The composition CaO 61.98%, SiO/sub 2/ 26.67%, and Al/sub 2/O/sub 3/ 11.53% was used. Isothermal sintering runs of 0.2 to 10.0 h were carried out at 1200, 1250, 1300, and 1350/sup 0/C. When the sintering temperature was below the eutectic temperature (1335/sup 0/C), the ternary mixture behaved like two binary systems, i.e. CaO-Al/sub 2/O/sub 3/ and CaO-SiO/sub 2/. Only one compound, 3CaO.SiO/sub 2/, was formed between CaO and SiO/sub 2/. With lower sintering temperature and shorter sintering time, the ..beta..-phase was dominant. However, when both temperature and time increased, more and more of the ..beta..-C/sub 2/S was transformed into the ..gamma..-phase. Several different aluminates were formed during the sintering of CaO and Al/sub 2/O/sub 3/. The compounds CaO.Al/sub 2/O/sub 3/ and 3CaO.Al/sub 2/O/sub 3/ were observed at all tested sintering temperatures, while the 5CaO.3Al/sub 2/O/sub 3/ phase was found only at 1200/sup 0/C and 12CaO.7Al/sub 2/O/sub 3/ at 1250/sup 0/C or higher. The first compound formed between CaO and Al/sub 2/O/sub 3/ was probably 12CaO.7Al/sub 2/O/sub 3/, but the amount did not increase immediately with time. The first dominant compound between CaO and Al/sub 2/O/sub 3/ was CaO.3Al/sub 2/O/sub 3/. When the calcium ion diffused through the product layer of CaO.Al/sub 2/O/sub 3/, 3CaO.Al/sub 2/O/sub 3/ was formed. If unreacted Al/sub 2/O/sub 3/ were present after the formation of CaO.Al/sub 2/O/sub 3/, CaO.2Al/sub 2/O/sub 3/ would form. Subsequent leaching of the sinters showed that the extractable alumina in the products increased with both sintering temperature and time, reaching a max of about 90%. These extraction data corresponded very well to the quantities of aluminates in the sinters. 59 figures, 13 tables.

  7. Formation of Nickel, Cobalt, Copper, and Iron Aluminates from α- and γ-Alumina-Supported Oxides: A Comparative Study

    NASA Astrophysics Data System (ADS)

    Bolt, P. H.; Habraken, F. H. P. M.; Geus, J. W.

    1998-01-01

    The rates of metal aluminate formation inMeOx/Al2O3systems (Me=Ni, Co, Cu, Fe) at 500-1000°C in O2or N2atmospheres were compared, using bothα-Al2O3andγ-Al2O3substrates. Interfacial reaction toMeAl2O4was assessed using Rutherford backscattering spectrometry and X-ray diffraction. The lateral homogeneity of the samples was investigated using scanning electron microscopy. The spinel formation rate follows the sequence FeAl2O4aluminate was accompanied by a severe rupture of the top layer (∼1 μm) of the substrate. Penetration of transition metal ions intoγ-Al2O3substrates is notable at considerably lower temperatures than withα-Al2O3substrates, mainly due to grain boundary diffusion. Annealing conditions that favor the formation of transition metal cations of a low valency (Co2+, Cu+) are beneficial for reactions to aluminates.

  8. BLENDED CALCIUM ALUMINATE-CALCIUM SULFATE CEMENT-BASED GROUT FOR P-REACTOR VESSEL IN-SITU DECOMMISSIONING

    SciTech Connect

    Langton, C.; Stefanko, D.

    2011-03-10

    The objective of this report is to document laboratory testing of blended calcium aluminate - calcium hemihydrate grouts for P-Reactor vessel in-situ decommissioning. Blended calcium aluminate - calcium hemihydrate cement-based grout was identified as candidate material for filling (physically stabilizing) the 105-P Reactor vessel (RV) because it is less alkaline than portland cement-based grout which has a pH greater than 12.4. In addition, blended calcium aluminate - calcium hemihydrate cement compositions can be formulated such that the primary cementitious phase is a stable crystalline material. A less alkaline material (pH {<=} 10.5) was desired to address a potential materials compatibility issue caused by corrosion of aluminum metal in highly alkaline environments such as that encountered in portland cement grouts [Wiersma, 2009a and b, Wiersma, 2010, and Serrato and Langton, 2010]. Information concerning access points into the P-Reactor vessel and amount of aluminum metal in the vessel is provided elsewhere [Griffin, 2010, Stefanko, 2009 and Wiersma, 2009 and 2010, Bobbitt, 2010, respectively]. Radiolysis calculations are also provided in a separate document [Reyes-Jimenez, 2010].

  9. Corrosion Resistant Ceramic Coating for X80 Pipeline Steel by Low-Temperature Pack Aluminizing and Oxidation Treatment

    NASA Astrophysics Data System (ADS)

    Min, Huang; Qian-Gang, Fu; Yu, Wang; Wen-Wu, Zhong

    2013-12-01

    In this paper, we discuss the formation of ceramic coatings by a combined processing of low-temperature pack aluminizing and oxidation treatment on the surface of X80 pipeline steel substrates in order to improve the corrosion resistance ability of X80 pipeline steel. First, Fe-Al coating consisting of FeAl3 and Fe2Al5 was prepared by a low-temperature pack aluminizing at 803 K which was fulfilled by adding zinc in the pack powder. Pre-treatment of X80 pipeline steel was carried out through surface mechanical attrition treatment (SMAT). Further oxidation treatment of as-aluminized sample was carried out in the CVD reactor at 833 K under oxygen containing atmosphere. After 1 h duration in these conditions, ceramic coating consisting of α-Al2O3 was formed by in situ oxidation reaction of Fe-Al coating. Those coatings have been characterized by different techniques including X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscope (EDS), respectively. Ceramic coating shows a dense and uniform microstructure, and exhibits good coherences with X80 pipeline steel substrates. By electrochemical corrosion test, the self-corrosion current density of X80 pipeline steel with as-obtained ceramics coating in 3.5% NaCl solution shows an obvious decrease. The formation of α-Al2O3 ceramic coating is considered as the main reason for the corrosion resistance improvement of X80 pipeline steel.

  10. Approach for determination of detonation performance and aluminum percentage of aluminized-based explosives by laser-induced breakdown spectroscopy.

    PubMed

    Rezaei, Amir Hossein; Keshavarz, Mohammad Hossein; Tehrani, Masoud Kavosh; Reza Darbani, Seyyed Mohammad; Farhadian, Amir Hossein; Mousavi, Seyyed Jabbar; Mousaviazar, Ali

    2016-04-20

    Energetic materials containing aluminum powder are hazardous compounds, which have wide applications as propellants, explosives, and pyrotechnics. This work introduces a new method on the basis of the laser-induced breakdown spectroscopy technique in air and argon atmospheres to investigate determination of aluminum content and detonation performance of 1,3,5-trinitro-1,3,5-triazine (RDX)-based aluminized explosives. Plasma emission of aluminized RDX explosives are recorded where atomic lines of Al, C, H, N, and O, as well as molecular bands of AlO and CN are identified. The formation mechanism of AlO and CN molecular bands is affected by the aluminum percentage and oxygen content present in the composition and plasma. Relative intensity of the Al/O is used to determine detonation velocity and pressure of the RDX/Al samples. The released energy in the laser-induced plasma of aluminized RDX composition is related to the heat of explosion and percentage of aluminum. PMID:27140093

  11. Characterization of mechanical properties of aluminized coatings in advanced gas turbine blades using a small punch method

    SciTech Connect

    Sugita, Y.; Ito, M.; Sakurai, S.; Bloomer, T.E.; Kameda, J. |

    1997-04-01

    Advanced technologies of superalloy casting and coatings enable one to enhance the performance of combined cycle gas turbines for electric power generation by increasing the firing temperature. This paper describes examination of the microstructure/composition and mechanical properties (22--950 C) in aluminized CoCrAlY coatings of advanced gas turbine blades using scanning Auger microprobe and a small punch (SP) testing method. Aluminized coatings consisted of layered structure divided into four regimes: (1) Al enriched and Cr depleted region, (2) Al and Cr graded region, (3) fine grained microstructure with a mixture of Al and Cr enriched phases and (4) Ni/Co interdiffusion zone adjacent to the interface. SP specimens were prepared in order that the specimen surface would be located in the various coating regions. SP tests indicated strong dependence of the fracture properties on the various coatings regimes. Coatings 1 and 2 with very high microhardness showed much easier formation of brittle cracks in a wide temperature range, compared to coatings 3 and 4 although the coating 2 had ductility improvement at 950 C. The coating 3 had lower room temperature ductility than the coating 4. However, the ductility in the coating 3 exceeded that in the region 4 above 730 C due to a precipitous ductility increase. The integrity of aluminized coatings while in-service is discussed in light of the variation of the low cycle fatigue life as well as the ductility in the layered structure.

  12. Selected laboratory evaluations of the whole-water sample-splitting capabilities of a prototype fourteen-liter Teflon churn splitter

    USGS Publications Warehouse

    Horowitz, A.J.; Smith, J.J.; Elrick, K.A.

    2001-01-01

    A prototype 14-L Teflon? churn splitter was evaluated for whole-water sample-splitting capabilities over a range of sediment concentratons and grain sizes as well as for potential chemical contamination from both organic and inorganic constituents. These evaluations represent a 'best-case' scenario because they were performed in the controlled environment of a laboratory, and used monomineralic silica sand slurries of known concentration made up in deionized water. Further, all splitting was performed by a single operator, and all the requisite concentration analyses were performed by a single laboratory. The prototype Teflon? churn splitter did not appear to supply significant concentrations of either organic or inorganic contaminants at current U.S. Geological Survey (USGS) National Water Quality Laboratory detection and reporting limits when test samples were prepared using current USGS protocols. As with the polyethylene equivalent of the prototype Teflon? churn, the maximum usable whole-water suspended sediment concentration for the prototype churn appears to lie between 1,000 and 10,000 milligrams per liter (mg/L). Further, the maximum grain-size limit appears to lie between 125- and 250-microns (m). Tests to determine the efficacy of the valve baffle indicate that it must be retained to facilitate representative whole-water subsampling.

  13. Deposition of thick and adherent Teflon-like coating on industrial scale stainless steel shell using pulsed dc and RF PECVD

    NASA Astrophysics Data System (ADS)

    Satyaprasad, A.; Nema, S. K.; Sinha, N. K.; Raj, Baldev

    2010-04-01

    A unique combination of pulsed dc and radio frequency (RF) discharge deposition was used to deposit thick (˜5 μm) and adherent (2-4 MPa) Teflon-like coatings on a stainless steel (SS) shell of 2 m diameter size, through plasma enhanced chemical vapor deposition (PECVD). The details of deposition on such a big industrial scale component are reported for the first time. In this method, highly adherent thin interface layers were grown on SS shell that was electrically grounded, using pulsed dc discharge, followed by RF discharge deposition to build up the required coating thickness. The fluorocarbon precursor molecules, required for the deposition of Teflon-like coating, are generated indigenously by pyrolyzing the Teflon powder. The deposited coating was studied for its chemical bond state, surface roughness (Ra), morphology, thickness, and adhesive strength. These studies were carried out by using XPS, AFM, SEM, etc. The adhesive strength of the coating was measured by pin-pull test as per ASTM D4541 standard test. The coatings deposited with pulsed dc discharge were observed to have higher adhesive strength when compared with those deposited with RF discharge.

  14. NHEXAS PHASE I REGION 5 STUDY--STANDARD OPERATING PROCEDURE--ANALYSIS OF TEFLON FILTERS USED IN PERSONAL AIR MONITORING SAMPLERS FOR LEAD, ARSENIC, CADMIUM, AND CHROMIUM (RTI/ACS-AP-209-111)

    EPA Science Inventory

    This protocol provides guidelines for the analysis of Teflon filter samples for toxic metals, either by graphite furnace atomic absorption spectrometry (GFAAS) or by hydride generation atomic fluorescence spectrometry (HGAFS). This method involves the extraction of analytes from ...

  15. Combustion synthesis of γ-lithium aluminate by using various fuels

    NASA Astrophysics Data System (ADS)

    Li, Fei; Hu, Keao; Li, Jianlin; Zhang, Dong; Chen, Gang

    2002-01-01

    Combustion synthesis, which is a quick and straightforward preparation process to produce homogeneous, crystalline and unagglomerated multicomponent oxide ceramic powders without the intermediate decomposition and/or calcining steps, was used to prepare γ-lithium aluminate. Lithium nitrate and aluminium nitrate were used as the starting materials and various organic compounds, such as citric acid, urea, carbohydrazide, glycine and alanine, as the fuels. The mixture of nitrate and fuel could be ignited at 450 °C, but only urea and carbohydrazide could be reacted with the mixed nitrates to result in dry, loose and white γ-LiAlO 2 powders. In this study, the effects of fuel type and ratio of fuel to nitrates on the phase formation of γ-LiAlO 2 powder were investigated and also discussed. Additionally, the phase and morphology of the γ-LiAlO 2 powder synthesized by the combustion reaction were compared with that by the conventional solid state reaction.

  16. Diffusion of lithium-6 isotopes in lithium aluminate ceramics using neutron depth profiling

    NASA Astrophysics Data System (ADS)

    McWhinney, Hylton G.; James, William D.; Schweikert, Emile A.; Williams, John R.; Hollenberg, Glen; Welsh, John; Sereatan, Washington

    1993-07-01

    Lithium Ceramics offer tremendous potential as a source for the production of tritium ( 3H) for fusion power reactors. Their successful application will depend to a great extent upon the diffusion properties of the 6Li within the matrix. Consequently knowledge od 6Li concentration gradients in the ceramic matrices is an important requirement in the continued development of the technology. In this investigation, the neutron depth profile (NDP) technique has been applied to the study of concentration profiles of 6Li in lithium aluminate ceramics, doped with 1.8%, 50% and 95% 6Li isotopic concentrations. Specimen for analysis were prepared at Battelle (PNL) as pellet discs. Samples for diffusion studies were arranged as diffusion couples in the following manner: 1.8% 6Li discs/85% 6Li powder. Experiments were performed at the Texas A&M Nuclear Science Center Reactor Building, utilizing 1 MW equivalent thermal neutron fluxes 3 × 10 11n/ m2s. The depth probed by the technique is approximately 15 μ.m. Diffusion coefficients are in the range of 2.1 × 10 -12 to 7.0 × 10 -11m2s-1 for 1.8% 6Li-doped ceramics annealed at 1200 and 1400° C, for 4 to 48-h anneal times.

  17. Tritium permeation barrier-aluminized coating prepared by Al-plating and subsequent oxidation process

    NASA Astrophysics Data System (ADS)

    Guikai, Zhang; Ju, Li; Chang'an, Chen; Sanping, Dou; Guoping, Ling

    2011-10-01

    Aluminum rich coatings forming Al 2O 3 on surface are widely applied as tritium permeation barrier (TPB) on structural materials in fusion reactor. In this work, we proposed a new three-step method for preparing such aluminum rich coating on HR-2 steel: ambient temperature melts salt electroplating followed by heat treating and artificial oxidation at 700 °C. Al deposition from AlCl 3/EMIC was performed with a deposition rate of 15 μm/h. After heat treated for 2 h, the aluminized coating appeared homogeneous, with thickness of 11-13 μm and free of visible porosity, and exhibited a three-layer structure. After oxidized in 10 -2 Pa O 2 for 80 h, the finally fabricated coating showed a double-layered structure consisting of an outer γ-A1 2O 3 layer with thickness of 0.1 μm and inner (Fe,Cr,Mn,Ni)Al/(Fe,Cr,Mn,Ni) 3Al layer of 32 μm thickness, without any visible defects. The deuterium permeation rate through the coated HR-2 steel was reduced by 2-3 orders of magnitude at 600-727 °C.

  18. Defect sites in highly siliceous HZSM-5 zeolites: A study performed by alumination and IR spectroscopy

    SciTech Connect

    Yamagishi, Kouji; Namba, Seitaro; Yashima, Tatsuaki )

    1991-01-24

    The concentration of oxygen atoms on defect sites in a highly siliceous HZSM-5 type zeolite was estimated by the {sup 18}O-exchange reaction between C{sup 18}O{sub 2} and the zeolite. The concentration of oxygen atoms on defect sites could be controlled by means of changes of the gel composition and of the use of various silica sources in the hydrothermal synthesis. The relationship between the concentration of oxygen atoms on defect sites in a highly siliceous HZSM-5 and the concentration of aluminum introduced into the framework of the HZSM-5 by an alumination was examined. The concentration of the framework aluminum was the same as one-fourth that of the oxygen atoms on defect sites. These results suggest that the defect sites into which aluminum atoms are introduced tetrahedrally can be identified with hydroxyl nests that consist of four silanol groups. The existence of hydroxyl nests could be confirmed by IR spectroscopy. From the {sup 18}O-exchange reaction and IR measurements, the authors conclude that the sharp band at 3,740 cm{sup {minus}1} can be attributed to both isolated SiOH groups on the external surface and intracrystalline isolated SiOH groups and that the broad band at 3,505 cm{sup {minus}1} can be attributed to the SiOH groups in hydroxyl nests.

  19. Aluminizing a Ni sheet through severe plastic deformation induced by ball collisions

    NASA Astrophysics Data System (ADS)

    Romankov, S.; Shchetinin, I. V.; Park, Y. C.

    2015-07-01

    Aluminizing a Ni sheet was performed through severe plastic deformation induced by ball collisions. The Ni sheet was fixed in the center of a mechanically vibrated vial between two connected parts. The balls were loaded into the vial on both sides of the Ni disk. Al disks, which were fixed on the top and the bottom of the vial, served as the sources of Al contamination. During processing, the Ni sheet was subject to intense ball collisions. The Al fragments were transferred and alloyed to the surface of the Ni sheet by these collisions. The combined effects of deformation-induced plastic flow, mechanical intermixing, and grain refinement resulted in the formation of a dense, continuous nanostructured Al layer on the Ni surface on both sides of the sheet. The Al layer consisted of Al grains with an average size of about 40 nm. The Al layer was reinforced with nano-sized Ni flakes that were introduced from the Ni surface during processing. The local amorphization at the Ni/Al interface revealed that the bonding between Ni and Al was formed by mechanical intermixing of atomic layers at the interface. The hardness of the fabricated Al layer was 10 times that of the initial Al plate. The ball collisions destroyed the initial rolling texture of the Ni sheet and induced the formation of the mixed [1 0 0] + [1 1 1] fiber texture. The laminar rolling structure of the Ni was transformed into an ultrafine grain structure.

  20. A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel.

    PubMed

    Gilbert, C A; Smith, R; Kenny, S D; Murphy, S T; Grimes, R W; Ball, J A

    2009-07-01

    Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters. PMID:21828490

  1. A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Gilbert, C. A.; Smith, R.; Kenny, S. D.; Murphy, S. T.; Grimes, R. W.; Ball, J. A.

    2009-07-01

    Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters.

  2. Crystal structures and optical properties of new quaternary strontium europium aluminate luminescent nanoribbons

    SciTech Connect

    Li, Xufan; Budai, John D.; Liu, Feng; Chen, Yu-Sheng; Howe, Jane Y.; Sun, Chengjun; Tischler, Jonathan Zachary; Meltzer, Richard; Pan, Zhengwei

    2014-11-12

    We report the synthesis and characterizations of three series of quaternary strontium europium aluminate (Sr-Eu-Al-O; SEAO) luminescent nanoribbons that show blue, green, and yellow luminescence from localized Eu2+ luminescent centers. These three series of SEAO nanoribbons are: blue luminescent, tetragonal Sr1-xEuxAl6O10 (01-xEuxAl2O4 (01-xEuxAl2O4 (0

  3. Novel porous calcium aluminate/phosphate nanocomposites: in situ synthesis, microstructure and permeability.

    PubMed

    Yang, Jingzhou; Hu, Xiaozhi; Huang, Juntong; Chen, Kai; Huang, Zhaohui; Liu, Yangai; Fang, Minghao; Sun, Xudong

    2016-02-14

    Permeable porous nanomaterials have extensive applications in engineering fields. Here, we report a novel system of porous calcium aluminate/phosphate (CaAl-CaP) nanocomposites fabricated by pore generator free processing. The CaAl rich samples have close micropores and are not permeable. Interestingly, the CaP rich composites have a unique three-dimensional nanosieve structure with interconnected nanopores and exhibit excellent liquid permeability and adsorbability. The pore size has a narrow distribution of 200-500 nm. The CaAl nanoplatelets in the CaP rich composite have a thickness of 202 nm, a diameter of 1600 nm and an aspect ratio of 8. The porosity is from 19% to 40%. The bending strength and compressive strength are 40.3 MPa and 195 MPa, respectively. The CaP rich nanocomposite is highly permeable so that a water droplet can completely penetrate in 10 seconds (1 mm thick disk). The blue dye can be desorbed in 45 min by ultrasonic vibration. Given the nanosieve porous structure, good permeability/adsorbability and high mechanical properties, the CaP rich nanocomposite has big potential in applications for chemical engineering, biomedical engineering and energy/environmental engineering. PMID:26805036

  4. Metal-insulator transition at lanthanum aluminate-strontium titanate interface induced by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Dai, Weitao; Cen, Cheng

    The formation of two-dimensional electron gas (2DEG) at lanthanum aluminate (LAO)-strontium titanate (STO) interface, as well as the 2DEG's unique characters in metal-insulator transition, have evoked widespread interest. Highly insulating interfaces are obtained for the structures with LAO thickness below 3 unit cell (uc) and abrupt transition from an insulating to conducting interface was observed for samples with thicker LAO layers. For 3uc LAO/STO samples, reversible nanoscale control of the metal-insulator transition was implemented by a conductive AFM writing. Our research furtherly discovered a very stable metal-insulator transition can be achieved by oxygen plasma (OP) treatment for samples with thicker LAO layers. AFM imaging and XPS measurement demonstrated the low energy OP treatment altered only the surface bonds, which confirmed the importance of surface properties in the heterostructures. Then microscale Hall bars were patterned at the interface and imaged by electrostatic force microscope. Their transport and magnetic properties were measured. This research will promote deeper understanding about the interfacial metal-insulator transition mechanism and open new device opportunities. This work is supported by the Department of Energy Grant No. DE-SC-0010399 and National Science Foundation Grant No. NSF-1454950.

  5. Complex interaction of aluminous metasedimentary xenoliths and siliceous magma; an example from Mt. Amiata (Central Italy)

    NASA Astrophysics Data System (ADS)

    van Bergen, Manfred J.; Barton, Michael

    1984-12-01

    Aluminous, silica-deficient metasedimentary xenoliths in siliceous lavas of Mt. Amiata have preserved composite zoning-patterns indicative for complex processes of magma-rock interaction. Petrographic observations and small-scale mineralogical and chemical differences between up to five distinct zones (including the core and envelope of lava) provide evidence that: 1. Partial melt formed in and extracted from the xenoliths was more mafic than the host magma and had a Mg/Fe ratio higher than that of the restite, at least during the peak of thermometamorphism. 2. Liquid-state interdiffusion occurred at the interface between partial melt and the enclosing magma. 3. Certain mineral phases in the restite (notably, hercynitic spinel) became unstable in the presence of a siliceous liquid. Quartz-poor muscovite-biotite schists are considered to be the most likely parent rocks and it is believed that release of volatiles from decomposing micas played a significant role in the high-temperature metamorphic evolution of the xenoliths and their interaction with the magma. The conditions favourable for assimilation were enhanced by injection of mafic magma into the magma chamber. Although this concurrent operation of magma-mixing precludes a quantitative estimate of contamination from the wall-rocks (which was probably of minor importance) the present example indicates that dry acid magma may potentially become more mafic by interaction with partially melted hydrous rocks.

  6. Microstructure and atomic disordering of magnesium aluminate spinel irradiated with swift heavy ions

    NASA Astrophysics Data System (ADS)

    Yamamoto, T.; Shimada, M.; Yasuda, K.; Matsumura, S.; Chimi, Y.; Ishikawa, N.

    2006-04-01

    We have investigated the microstructure and atomic disordering of nearly stoichiometric magnesium aluminate spinel (MgO · 1.1Al2O3), irradiated with 200 MeV Xe14+ ions (Se = 25 keV/nm). Transmission electron microscopy techniques of bright-field (BF) and high-resolution (HR) imaging, as well as high angular resolution electron channeling X-ray spectroscopy (HARECXS) were employed for quantitative analysis of radiation-induced structural change. BF images of ion tracks show columnar dark contrast of ∼4 nm in diameter accompanying distinct black or white dots at the incident surface. Clear lattice fringes are observed in HR images even inside the ion tracks, indicating that the spinel crystals are not amorphized but partially disordered along the ion tracks. HARECXS analysis showed that cation disordering progresses successively with ion fluence, and the disordered regions are found to extend over 12.8 ± 0.9 nm in diameter for Al ions and 9.6 ± 0.6 nm for Mg ions along the ion tracks. This chemically disordered region is much larger than the strained volume detected by BF and HR images.

  7. Mechanical properties and microstructure of α-alumina and magnesium aluminate spinel irradiated with He ions

    NASA Astrophysics Data System (ADS)

    Izumi, Koichiro; Yasuda, Kazuhiro; Kinoshita, Chiken; Kutsuwada, Masanori

    1998-10-01

    Mechanical properties of α-alumina, stoichiometric- and nonstoichiometric-magnesium aluminate spinel single crystals were examined by using ultra-microhardness technique. The samples were irradiated with 100 keV He + ions at temperatures of 300-870 K and to fluences up to 2 × 10 20 He +/m 2. Apparent hardness, Δ H, in α-alumina increases with fluence in three stages, while that of spinel crystals increases monotonically with fluence. We have also evaluated elastic modulus, plastic and elastic energies, and plastic and elastic indentation depths through the analysis of load-displacement curves. These analyses showed that plastic and elastic hardening are responsible for the variation of Δ H of α-alumina, and that plastic hardening is the main cause of hardening in spinel crystals. Corresponding TEM observations suggested the importance of point defects and/or `invisible' defect clusters for radiation hardening compared to `visible' dislocation loops. The relationship between microstructure and mechanical properties is given for various ceramics.

  8. Coprecipitation Synthesis of Superplastic 3 Mol. % Yttria -- Stabilized Tetragonal Zirconia Polycrystalline / Magnesium Aluminate Spinel Nanocomposite

    NASA Astrophysics Data System (ADS)

    Opoku, Michael

    3 mole % Yttria-stabilized tetragonal zirconia polycrystalline/Magnesium aluminate spinel (3Y-TZP/MgAl2O4) nanocomposite have exhibited high strain rate superplasticity at 1.7x10--2 --3.3x10--1 s --1. Low strain rate superplasticity (10--5--10 --3 s--1) has been the main drawback of using superplastic ceramics in industries. Microstructural design of 3Y-TZP/MgAl2O4 composite is a key in obtaining high strain rate superplasticity within the range of 10 --2--100 s--1 ). 3Y-TZP/MgAl2O4 may experience a surge in its application at high temperature if the microstructure is designed to exhibit high strain rates at low temperatures. In the present study, the reverse coprecipitation synthesis technique was adopted to synthesize nanocomposite powders containing 70%3Y-TZP/30%MgAl 2O4 and 60%3Y-TZP/40%MgAl2O4 with microstructural characteristics suitable for superplastic application. It was expected that the coprecipitation synthesis technique route will yield highly homogeneous nanocrystalline composite powders, which could be sintered into a dense component with high thermal stability of the small grains. Microstructual features observed after processing powders of 3Y-TZP/MgAl2O4 revealed that the coprecipitation synthesis is a suitable technique for processing nanocomposite powders for superplastic application.

  9. Cation disordering in magnesium aluminate spinel crystals induced by electron or ion irradiation

    NASA Astrophysics Data System (ADS)

    Soeda, Takeshi; Matsumura, Syo; Kinoshita, Chiken; Zaluzec, Nestor J.

    2000-12-01

    Structural changes in magnesium aluminate spinel (MgO · nAl 2O 3) single crystals, which were irradiated with 900 keV electrons or 1 MeV Ne + ions at 873 K, were examined by electron channeling enhanced X-ray microanalysis. Unirradiated MgO · Al 2O 3 has a tendency to form the normal spinel configuration, where Mg 2+ ions and Al 3+ ions occupy mainly the tetrahedral and the octahedral sites, respectively. Electron irradiation induces simple cation disordering between the tetrahedral sites and the octahedral sites in MgO · Al 2O 3. In addition to cation disordering, slight evacuation of cations from the tetrahedral sites to the octahedral sites occurs in a peak-damaged area in MgO · Al 2O 3 irradiated with Ne + ions. In contrast, cation disordering is suppressed in MgO · 2.4Al 2O 3 irradiated with electrons. The structural vacancies, present in the non-stoichiometric compound, appear to be effective in promoting irradiation damage recovery through interstitial-vacancy recombination.

  10. Atomistic structures of metastable and amorphous phases in ion-irradiated magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Ishimaru, Manabu; Hirotsu, Yoshihiko; Afanasyev-Charkin, Ivan V.; Sickafus, Kurt E.

    2002-02-01

    Ion-beam-induced microstructures in magnesium aluminate (MgAl2O4) spinel have been examined using transmission electron microscopy (TEM). Irradiations were performed at cryogenic temperature (~120 K) on MgAl2O4 spinel single-crystal surfaces with (111) orientation, using 180 keV neon (Ne+) ions to ion fluences ranging from 1016 to 1017 Ne+ cm-2. Cross-sectional TEM observations indicated that the MgAl2O4 spinel transforms first into a metastable crystalline phase and then into an amorphous phase under these irradiation conditions. On the basis of selected-area electron diffraction and high-resolution TEM, we concluded that Ne-ion-beam irradiation induces an ordered spinel-to-disordered rock-salt-like structural phase transformation. Atomistic structures of amorphous MgAl2O4 were also examined on the basis of atomic pair distribution functions. We compared the experimentally obtained results with previous theoretically calculated results for the metastable and amorphous phases of MgAl2O4, and discussed the validity of the proposed ion-beam-induced structural changes in MgAl2O4 spinel.

  11. Diffusion kinetics of Fe 2+ and Mg in aluminous spinel . experimental determination and applications

    NASA Astrophysics Data System (ADS)

    Liermann, Hanns-Peter; Ganguly, Jibamitra

    2002-09-01

    The diffusion coefficients of Fe 2+ and Mg in aluminous spinel at ˜20 kb, 950 to 1325°C, and at 30 kb, 1125°C have been determined via diffusion couple experiments and numerical modeling of the induced diffusion profiles. The oxygen fugacity, fO 2, was constrained by graphite encapsulating materials. The retrieved self-diffusion coefficients of Fe 2+ and Mg at ˜20 kb, 950 to 1325°C, fit well the Arrhenian relation, D = D 0exp(-Q/RT), where Q is the activation energy, with D 0(Fe) = 1.8 (±2.8) × 10 -5, D 0(Mg) = 1.9 (±1.4) × 10 -5 cm 2/s, Q(Fe) = 198 ± 19, and Q(Mg) = 202 ± 8 kJ/mol. Comparison with the data at 30 kb suggests an activation volume of ˜5 cm 3/mol. From analysis of compositional zoning in natural olivine-spinel assemblages in ultramafic rocks, previous reports concluded that D(Fe-Mg) in spinel with Cr/(Cr + Al) ≤0.5 is ˜10 times that in olivine. The diffusion data in spinel and olivine have been applied to the problems of preservation of Mg isotopic inhomogeneity in spinel within the plagioclase-olivine inclusions in Allende meteorite and cooling rates of terrestrial ultramafic rocks.

  12. EFFECTS OF XE ION IRRADIATION AND SUBSEQUENT ANNEALING ON THE PROPERTIES OF MAGNESIUM-ALUMINATE SPINEL

    SciTech Connect

    I. AFANASYEV; ET AL

    2000-04-01

    Single crystals of magnesium-aluminate spinel MgAl{sub 2}O{sub 4} were irradiated with 340 keV Xe{sup 2} ions at {minus}173 C ({approximately} 100 K). A fluence of 1 x 10{sup 20} Xe/m{sup 2} created an amorphous layer at the surface of the samples. The samples were annealed for 1 h at different temperatures ranging from 130 C to 880 C. Recrystallization took place in the temperature interval between 610 C and 855 C. Transmission electron microscopy (TEM) images show two distinct layers near the surface: (1) a polycrystalline layer with columnar grain structure; and (2) a buried damaged layer epitaxial with the substrate. After annealing at 1100 C for 52 days, the profile of implanted Xe ions did not change, which means that Xe ions are not mobile in the spinel structure up to 1100 C. The thickness of the buried damaged layer decreased significantly in the 1100 C annealed sample comparing to the sample annealed for 1 h at 855 C.

  13. Persistent luminescence strontium aluminate nanoparticles as reporters in lateral flow assays.

    PubMed

    Paterson, Andrew S; Raja, Balakrishnan; Garvey, Gavin; Kolhatkar, Arati; Hagström, Anna E V; Kourentzi, Katerina; Lee, T Randall; Willson, Richard C

    2014-10-01

    Demand for highly sensitive, robust diagnostics and environmental monitoring methods has led to extensive research in improving reporter technologies. Inorganic phosphorescent materials exhibiting persistent luminescence are commonly found in electroluminescent displays and glowing paints but are not widely used as reporters in diagnostic assays. Persistent luminescence nanoparticles (PLNPs) offer advantages over conventional photoluminescent probes, including the potential for enhanced sensitivity by collecting time-resolved measurements or images with decreased background autofluorescence while eliminating the need for expensive optical hardware, superior resistance to photobleaching, amenability to quantitation, and facile bioconjugation schemes. We isolated rare-earth doped strontium aluminate PLNPs from larger-particle commercial materials by wet milling and differential sedimentation and water-stabilized the particles by silica encapsulation using a modified Stöber process. Surface treatment with aldehyde silane followed by reductive amination with heterobifunctional amine-poly(ethylene glycol)-carboxyl allowed covalent attachment of proteins to the particles using standard carbodiimide chemistry. NeutrAvidin PLNPs were used in lateral flow assays (LFAs) with biotinylated lysozyme as a model analyte in buffer and monoclonal anti-lysozyme HyHEL-5 antibodies at the test line. Preliminary experiments revealed a limit of detection below 100 pg/mL using the NeutrAvidin PLNPs, which was approximately an order of magnitude more sensitive than colloidal gold. PMID:25247754

  14. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    SciTech Connect

    Esro, M.; Adamopoulos, G.; Mazzocco, R.; Kolosov, O.; Krier, A.; Vourlias, G.; Milne, W. I.

    2015-05-18

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (La{sub x}Al{sub 1−x}O{sub y}) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the La{sub x}Al{sub 1−x}O{sub y} films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlO{sub y} dielectrics exhibit a wide band gap (∼6.18 eV), high dielectric constant (k ∼ 16), low roughness (∼1.9 nm), and very low leakage currents (<3 nA/cm{sup 2}). TFTs employing solution processed LaAlO{sub y} gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (∼10 V), high on/off current modulation ratio of >10{sup 6}, subthreshold swing of ∼650 mV dec{sup −1}, and electron mobility of ∼12 cm{sup 2} V{sup −1} s{sup −1}.

  15. Transparent magnesium aluminate spinel: a prospective biomaterial for esthetic orthodontic brackets.

    PubMed

    Krishnan, Manu; Tiwari, Brijesh; Seema, Saraswathy; Kalra, Namitha; Biswas, Papiya; Rajeswari, Kotikalapudi; Suresh, Madireddy Buchi; Johnson, Roy; Gokhale, Nitin M; Iyer, Satish R; Londhe, Sanjay; Arora, Vimal; Tripathi, Rajendra P

    2014-11-01

    Adult orthodontics is recently gaining popularity due to its importance in esthetics, oral and general health. However, none of the currently available alumina or zirconia based ceramic orthodontic brackets meet the esthetic demands of adult patients. Inherent hexagonal lattice structure and associated birefringence limits the visible light transmission in polycrystalline alumina and make them appear white and non transparent. Hence focus of the present study was to assess the feasibility of using magnesium aluminate (MgAl2O4) spinel; a member of the transparent ceramic family for esthetic orthodontic brackets. Transparent spinel specimens were developed from commercially available white spinel powder through colloidal shaping followed by pressureless sintering and hot isostatic pressing at optimum conditions of temperature and pressure. Samples were characterized for chemical composition, phases, density, hardness, flexural strength, fracture toughness and optical transmission. Biocompatibility was evaluated with in-vitro cell line experiments for cytotoxicity, apoptosis and genotoxicity. Results showed that transparent spinel samples had requisite physico-chemical, mechanical, optical and excellent biocompatibility for fabricating orthodontic brackets. Transparent spinel developed through this method demonstrated its possibility as a prospective biomaterial for developing esthetic orthodontic brackets. PMID:25027301

  16. Novel porous calcium aluminate/phosphate nanocomposites: in situ synthesis, microstructure and permeability

    NASA Astrophysics Data System (ADS)

    Yang, Jingzhou; Hu, Xiaozhi; Huang, Juntong; Chen, Kai; Huang, Zhaohui; Liu, Yangai; Fang, Minghao; Sun, Xudong

    2016-02-01

    Permeable porous nanomaterials have extensive applications in engineering fields. Here, we report a novel system of porous calcium aluminate/phosphate (CaAl-CaP) nanocomposites fabricated by pore generator free processing. The CaAl rich samples have close micropores and are not permeable. Interestingly, the CaP rich composites have a unique three-dimensional nanosieve structure with interconnected nanopores and exhibit excellent liquid permeability and adsorbability. The pore size has a narrow distribution of 200-500 nm. The CaAl nanoplatelets in the CaP rich composite have a thickness of 202 nm, a diameter of 1600 nm and an aspect ratio of 8. The porosity is from 19% to 40%. The bending strength and compressive strength are 40.3 MPa and 195 MPa, respectively. The CaP rich nanocomposite is highly permeable so that a water droplet can completely penetrate in 10 seconds (1 mm thick disk). The blue dye can be desorbed in 45 min by ultrasonic vibration. Given the nanosieve porous structure, good permeability/adsorbability and high mechanical properties, the CaP rich nanocomposite has big potential in applications for chemical engineering, biomedical engineering and energy/environmental engineering.

  17. In situ absorption of molybdate and vanadate during precipitation of hydrotalcite from sodium aluminate solutions

    NASA Astrophysics Data System (ADS)

    Smith, Howard D.; Parkinson, Gordon M.; Hart, Robert D.

    2005-02-01

    Reaction with seawater to produce the layered double hydroxide hydrotalcite is an important means for amelioration of Bayer process wastewater prior to its disposal into the marine environment. This reaction has been synthesised under controlled conditions to elucidate the principal mechanisms involved, particularly those related to absorption of transition metals that are removed from solution. Magnesium-aluminium layered double hydroxides precipitated from reaction between magnesium chloride and synthetic sodium aluminate solution in the presence of transition metal oxyanions have been prepared and characterised using thermal, X-ray and microscopic techniques. The layered double hydroxide precipitated at pH >13 is found to consist of nano-sized hexagonal crystals of final magnesium-aluminium ratio of 2:1, while that precipitated at pH<9.5 has a less well defined crystal structure and final ratio of 4:1. In situ absorption of transition metals from solution into hydrotalcite during precipitation is a pH dependent process. Transition metals are found to replace carbonate in the interlayer space but have little or no overall effect on crystal size or structure. Interlayer distance remains constant in the presence of transition metals, suggesting that these species are intercalated as simple monomeric or dimeric oxyanions, rather than larger polymeric forms.

  18. Apollo 14 aluminous mare basalts and their possible relationship to KREEP

    NASA Astrophysics Data System (ADS)

    Dickinson, T.; Taylor, G. J.; Keil, K.; Schmitt, R. A.; Hughes, S. S.; Smith, M. R.

    1985-02-01

    Thirty-six aluminous mare basalt fragments from breccia 14321 and other Apollo 14 basalts are statistically divided into two broad groups, comprising five subgroups, using La, Sm, and Yb data. Major element compositions, petrographic characteristics, and mineral compositions are similar for the five groups. However, there is an eight-fold increase in REE abundances from Group 5 to Group 1, with Group 1 having a REE pattern similar to KREEP. Groups 1 to 3 may be related by partial melting of a source similar to that proposed by Unruh et al. (1984) for feldspathic basalt 12038. However, Groups 4 and 5 cannot be as closely matched by larger degrees of partial melting of this source. Groups 1 to 4 could also be produced by assimilation of a KREEP component by a magma similar in composition to Group 5. Such a magma can be produced by partial melting of an olivine-orthopyroxene source that crystallized from a magma with chondritic relative REE abundances.

  19. Persistent Luminescence Strontium Aluminate Nanoparticles as Reporters in Lateral Flow Assays

    PubMed Central

    2015-01-01

    Demand for highly sensitive, robust diagnostics and environmental monitoring methods has led to extensive research in improving reporter technologies. Inorganic phosphorescent materials exhibiting persistent luminescence are commonly found in electroluminescent displays and glowing paints but are not widely used as reporters in diagnostic assays. Persistent luminescence nanoparticles (PLNPs) offer advantages over conventional photoluminescent probes, including the potential for enhanced sensitivity by collecting time-resolved measurements or images with decreased background autofluorescence while eliminating the need for expensive optical hardware, superior resistance to photobleaching, amenability to quantitation, and facile bioconjugation schemes. We isolated rare-earth doped strontium aluminate PLNPs from larger-particle commercial materials by wet milling and differential sedimentation and water-stabilized the particles by silica encapsulation using a modified Stöber process. Surface treatment with aldehyde silane followed by reductive amination with heterobifunctional amine-poly(ethylene glycol)-carboxyl allowed covalent attachment of proteins to the particles using standard carbodiimide chemistry. NeutrAvidin PLNPs were used in lateral flow assays (LFAs) with biotinylated lysozyme as a model analyte in buffer and monoclonal anti-lysozyme HyHEL-5 antibodies at the test line. Preliminary experiments revealed a limit of detection below 100 pg/mL using the NeutrAvidin PLNPs, which was approximately an order of magnitude more sensitive than colloidal gold. PMID:25247754

  20. Nanoscale calcium aluminate coated graphite for improved performance of alumina based monolithic refractory composite

    SciTech Connect

    Mukhopadhyay, S.

    2013-07-15

    Graphical abstract: - Highlights: • Sol–gel Ca-doped γ-Al{sub 2}O{sub 3} accomplished graphite retention. • Nanocoating considerably improved matrix-aggregate bonding. • Less porous simulated matrix upgraded slag resistance. - Abstract: The synthesis and properties of high alumina castable containing nanostructured calcium aluminate coated graphite were studied in terms of slag resistance and overall physical characteristics. Raman spectroscopy, BET surface area and field emission scanning electron microscopy (FESEM) were performed to exclusively understand the coating characteristics and its compatibility in refractory composite. The coating not only secured graphite in castable for prolonged period but also noticeably improved matrix to aggregate contact. The microstructural aspects of castables were investigated, with special emphasis on a representative matrix prepared and infiltrated with slag at elevated temperature. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) of fired composite containing surface-treated graphite was quite prospective. It circumvented the problems of incorporating as-received graphite in castables and should be in the attention of refractory researchers and producers.

  1. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    NASA Astrophysics Data System (ADS)

    Esro, M.; Mazzocco, R.; Vourlias, G.; Kolosov, O.; Krier, A.; Milne, W. I.; Adamopoulos, G.

    2015-05-01

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (LaxAl1-xOy) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the LaxAl1-xOy films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlOy dielectrics exhibit a wide band gap (˜6.18 eV), high dielectric constant (k ˜ 16), low roughness (˜1.9 nm), and very low leakage currents (<3 nA/cm2). TFTs employing solution processed LaAlOy gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (˜10 V), high on/off current modulation ratio of >106, subthreshold swing of ˜650 mV dec-1, and electron mobility of ˜12 cm2 V-1 s-1.

  2. Effective fingerprint recognition technique using doped yttrium aluminate nano phosphor material.

    PubMed

    Darshan, G P; Premkumar, H B; Nagabhushana, H; Sharma, S C; Prashanth, S C; Prasad, B Daruka

    2016-02-15

    First time the yttrium aluminate nanoparticles are used to improve the fingerprint quality. Eco-friendly green combustion process is used to synthesize YAlO3:Sm(3+) (0.5-11mol%) nanophosphor using green tea leaf extract as non-toxic and eco-friendly fuel. Powder X-ray diffraction study confirms the orthorhombic phase. The average sizes of the crystallites were found to be in the range 20-35nm. The emission peaks centered at 564, 601 and 647nm is attributed to 4f-4f (4)G5/2→(6)HJ=5/2,7/2,9/2 forbidden transitions of Sm(3+) ions. Judd-Ofelt theory is applied to experimental data for providing qualitative support by determining J-O intensity parameters. The Commission International De I-Eclairage chromaticity co-ordinates are very close to National Television System Committee standard value of white emission (x=0.296, y=0.237). Further, correlated color temperature is found to be ∼11,900K. A simple, fast, highly sensitive and low-cost method for the detection and enhancement of fingermarks in a broad range of surfaces is developed and constitutes an alternative to traditional luminescent powders. PMID:26619131

  3. Investigation Into Gas-Sensing Mechanism of Nanostructured Magnesium Aluminate as a Function of Temperature.

    PubMed

    Nithyavathy, N; Arunmetha, S; Dhineshbabu, N R; Rajendran, V

    2015-07-01

    In this study, we used a new simple chemical method to synthesise nanostructured magnesium aluminate (NMA) powder. Sol-gel technique followed by sonication was used to develop different sensor samples namely NMA573, NMA873, and NMA1 073 by calcination at temperatures of 573, 873, and 1073 K respectively. Average crystallite size of 18-27 nm and specific surface area of 68.09 to 61.84 m2 g(-1) was obtained for the sensor samples. The existence of functional groups at 800 and 550 cm-1 corresponding respectively to AIO6 group and the lattice vibration of MgO4 stretching were confirmed through FTIR studies; SEM/EDX confirm the spherical morphology with elemental composition Mg, Al and O at different calcination temperatures. UV-Vis absorption spectra show band gap energy as 3.50, 3.48, and 3.44 eV for the sensor samples NMA573, NMA873, and NMA1 073 respectively. The effect of polyethylene glycol on the gas-sensing behaviour was studied in all the sensor samples. In particular, NMA1073 was found to have better resistance and sensor response for CO gas than NMA573 and NMA873. The effect of increase in calcination temperature of the sensor samples on the structural, morphological, optical, and gas response properties were carried out extensively to explore its gas sensing applications. PMID:26373088

  4. An Internal Thermal Environment Model of an Aluminized Solid Rocket Motor with Experimental Validation

    NASA Technical Reports Server (NTRS)

    Martin, Heath T.

    2015-01-01

    Due to the severity of the internal solid rocket motor (SRM) environment, very few direct measurements of that environment exist; therefore, the appearance of such data provides a unique opportunity to assess current thermal/fluid modeling capabilities. As part of a previous study of SRM internal insulation performance, the internal thermal environment of a laboratory-scale SRM featuring aluminized propellant was characterized with two types of custom heat-flux calorimeters: one that measured the total heat flux to a graphite slab within the SRM chamber and another that measured the thermal radiation flux. Therefore, in the current study, a thermal/fluid model of this lab-scale SRM was constructed using ANSYS Fluent to predict not only the flow field structure within the SRM and the convective heat transfer to the interior walls, but also the resulting dispersion of alumina droplets and the radiative heat transfer to the interior walls. The dispersion of alumina droplets within the SRM chamber was determined by employing the Lagrangian discrete phase model that was fully coupled to the Eulerian gas-phase flow. The P1-approximation was engaged to model the radiative heat transfer through the SRM chamber where the radiative contributions of the gas phase were ignored and the aggregate radiative properties of the alumina dispersion were computed from the radiative properties of its individual constituent droplets, which were sourced from literature. The convective and radiative heat fluxes computed from the thermal/fluid model were then compared with those measured in the lab-scale SRM test firings and the modeling approach evaluated.

  5. Copper aluminate spinel in the stabilization and detoxification of simulated copper-laden sludge.

    PubMed

    Tang, Yuanyuan; Shih, Kaimin; Chan, King

    2010-06-01

    This study aims to evaluate the feasibility of stabilizing copper-laden sludge by the application of alumina-based ceramic products. The processing temperature, material leaching behaviour, and the effect of detoxification were investigated in detail. CuO was used to simulate the copper-laden sludge and X-ray Diffraction was performed to monitor the incorporation of copper into the copper aluminate spinel (CuAl(2)O(4)) phase in ceramic products. It was found that the development of CuAl(2)O(4) increased with elevating temperatures up to and including 1000 degrees C in the 3h short-sintering scheme. When the sintering temperature went above 1000 degrees C, the CuAl(2)O(4) phase began to decompose due to the high temperature transformation to CuAlO(2). The leachability and leaching behaviour of CuO and CuAl(2)O(4) were compared by usage of a prolonged leaching test modified from US EPA's toxicity characteristic leaching procedure. The leaching results show that CuAl(2)O(4) is superior to CuO for the purpose of copper immobilization over longer leaching periods. Furthermore, the detoxification effect of CuAl(2)O(4) was tested through bacterial adhesion with Escherichia coli K12, and the comparison of bacterial adhesion on CuO and CuAl(2)O(4) surfaces shows the beneficial detoxification effect in connection with the formation of the CuAl(2)O(4) spinel. This study demonstrates the feasibility of transforming copper-laden sludge into the spinel phase by using readily available and inexpensive ceramic materials, and achieving a successful reduction of metal mobility and toxicity. PMID:20478609

  6. Effect of Composition and Impurities on the Phosphorescence of Green-Emitting Alkaline Earth Aluminate Phosphor

    PubMed Central

    Kim, Doory; Kim, Han-Eol; Kim, Chang-Hong

    2016-01-01

    Recent improvements to SrAl2O4:Eu2+, Dy3+ phosphors have enabled the use of luminescent hosts with a stable crystal structure and high physical and chemical stability, thus overcoming the bottleneck in the applicability of ZnS:Cu phosphors. However, enhancement of afterglow lifetime and brightness in SrAl2O4:Eu2+, Dy3+ phosphors remains a challenging task. Here, we have improved the afterglow characteristics in terms of persistence time and brightness by a systematic investigation of the composition of Eu-doped alkaline earth aluminate SrAl2O4:Eu2+, Dy3+ crystals. We found that a Dy3+/Eu2+ ratio of ~2.4 and ~0.935 mol Eu2+ (per mol of SrAl2O4) gave the brightest and longest emissions (11% and 9% increase for each). Doping with Si4+ also resulted in a slight increase in brightness up to ~15%. Doping with alkali metal or alkaline earth metal significantly enhanced the phosphorescence intensity. In particular, doping with 0.005 mol Li+ (per mol of SrAl2O4) alone boosted the phosphorescence intensity to 239% of the initial value, as compared to that observed for the non-doped crystal, while doping with 0.01 mol Mg2+ and 0.005 mol Li+ (per 1 mol SrAl2O4) boosted the phosphorescence intensity up to 313% of the initial value. The results of this investigation are expected to act as a guideline for the synthesis of bright and long persistent phosphors, and facilitate the development of persistent phosphors with afterglow characteristics superior to those of conventional phosphors. PMID:26731086

  7. Optical transitions in magnesium aluminate spinel crystals of different compositions exposed to irradiation

    NASA Astrophysics Data System (ADS)

    Gritsyna, V. T.; Afanasyev-Charkin, I. V.; Kazarinov, Yu. G.; Sickafus, K. E.

    2004-06-01

    Optical absorption of magnesium aluminate spinel single crystals of different compositions MgO · nAl 2O 3 ( n=1.0 and 2.5) were investigated after irradiation with neutrons, X-rays and the UV-light to elucidate existence of specific absorption bands related to lattice defects. The radiation induced absorption envelope is shifted to higher energy and is larger in intensity in non-stoichiometric spinel in comparison with stoichiometric one at the same irradiation conditions. Deconvolution of difference optical spectra of irradiated crystals shows the shift of the F-type centers from 4.75 and 5.3 eV in stoichiometric crystals to 5.08 and 5.63 eV in MgO · 2.5Al 2O 3 for F +- and F-centers, respectively. The absorption bands at 3.1 and 3.78 eV are present in both stoichiometric and non-stoichiometric crystals and are identified as V-type centers. By changing the irradiation time and using isochronal annealing it was revealed that additional bands appear in optical absorption spectra at 4.15 eV for MgO · 1.0Al 2O 3 crystals and at 4.46 eV for MgO · 2.5Al 2O 3 crystals. From the shift of the band energy position and the high intensity of this band in non-stoichiometric spinel crystals, it could be identified with electronic centers related to lattice defects.

  8. A nuclear magnetic resonance study of amorphous and crystalline lanthanum-aluminates

    SciTech Connect

    Iuga, D.; Simon, S.; Boer, E. de; Kentgens, A.P.M.

    1999-09-09

    Lanthanum-aluminates of the composition (1 {minus} x)Al{sub 2}O{sub 3}{center_dot}xLa{sub 2}O{sub 3} (0 < x < 0.7) were prepared by sol-gel synthesis. Subsequent heat-treatment temperatures ranging from 200 to 1,200 C were applied. The resulting samples were characterized by X-ray powder diffraction and {sup 27}Al MAS NMR. The most complex spectra were analyzed by MQMAS NMR in order to get insight in the number of sites and the possible distribution of the NMR parameters in the amorphous samples. Analysis of the MQMAS spectra, taking the efficiency of this experiment for different sites into account, helped to resolve ambiguities in the MAS spectra, which could otherwise not be deconvoluted in a unique way. The analyses show that, except for the sample with the lowest La (x = 0.085) concentration, hardly any pentacoordinated aluminum is observed over the whole temperature treatment range. For all samples the concentration of six-coordinated aluminum decreases as the heating temperature increases until the point where crystallization occurs. The concentration of 4-fold coordinated aluminum shows the opposite behavior. When crystallization occurs, a remarkable transformation between four- and six-coordinated aluminum takes place. Crystallization of the samples occurs at lower temperatures for samples with high amounts of lanthanum. At low La content crystallization is shifted to higher temperatures and thus the lower Al (four and five) coordinations are maintained over a larger temperature range. Storage of the samples in a water-saturated atmosphere leads to a conversion of four- to six-coordinated aluminum. This shows that the low-coordinated Al atoms are accessible to water molecules and must therefore be situated at the surface.

  9. X-AFm stabilization as a mechanism of bypassing conversion phenomena in calcium aluminate cements

    SciTech Connect

    Falzone, Gabriel; Balonis, Magdalena; Sant, Gaurav

    2015-06-15

    Phase conversion phenomena are often observed in calcium aluminate cements (CACs), when the water-rich hydrates (e.g., CAH{sub 10}, C{sub 2}AH{sub 8}) formed at early ages, at temperatures ≤ 30 °C, expel water in time to form more compact, less water-rich structures (C{sub 3}AH{sub 6}). The phase conversions follow a path regulated by the thermodynamic stabilities (solubilities) of phases. Based on this premise, it is proposed that conversion phenomena in CACs can be bypassed by provoking the precipitation of phases more preferred than those typically encountered along the conversion pathway. Therefore, X-AFm formation (where in this case, X = NO{sub 3}{sup −}) triggered by the sequential addition of calcium nitrate (Ca(NO{sub 3}){sub 2} = CN) additives is identified as a new means of bypassing conversion. A multi-method approach comprising X-ray diffraction (XRD), thermal analytics, and evaluations of the compressive strength is applied to correlate phase balances and properties of CAC systems cured at 25 °C and 45 °C. The results highlight the absence of the C{sub 3}AH{sub 6} phase across all systems and the curing conditions considered, with enhanced strengths being noted, when sufficient quantities of CN are added. The experimental outcomes are supported by insights gained from thermodynamic calculations which highlight thermodynamic selectivity as a means of regulating and controlling the evolutions of solid phase balances using inorganic salts in CACs, and more generally in cementing material systems.

  10. Hydrogen production from steam reforming of acetic acid over Cu-Zn supported calcium aluminate.

    PubMed

    Mohanty, Pravakar; Patel, Madhumita; Pant, Kamal K

    2012-11-01

    Hydrogen can be produced by catalytic steam reforming (CSR) of biomass-derived oil. Typically bio oil contains 12-14% acetic acid; therefore, this acid was chosen as model compound for reforming of biooil with the help of a Cu-Zn/Ca-Al catalyst for high yield of H(2) with low CH(4) and CO content. Calcium aluminate support was prepared by solid-solid reaction at 1350°C. X-ray diffraction indicates 12CaO·7Al(2)O(3) as major, CaA(l4)O(7) and Ca(5)A(l6)O(14) as minor phases. Cu and Zn were loaded onto the support by wet-impregnation at 10 and 1wt.%, respectively. The catalysts were characterized by Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy TEM and the surface area for both support and Cu-Zn were 10.5 and 5.8m(2)/g, respectively. CSR was carried out in a tubular fixed bed reactor (I.D.=19mm) at temperatures between 600 and 800°C with 3-g loadings and (H(2)O/acetic acid) wt. ratio of 9:1. Significantly high (80%) yield of hydrogen was obtained over Cu-Zn/Ca-Al catalyst, as incorporation of Zn enhanced the H(2) yield by reducing deactivation of the catalyst. The coke formation on the support (Ca-12/Al-7) surface was negligible due to the presence of excess oxygen in the 12CaO·7Al(2)O(3) phase. PMID:22944490

  11. Transition of Blast Furnace Slag from Silicates-Based to Aluminates-Based: Viscosity

    NASA Astrophysics Data System (ADS)

    Yan, Zhiming; Lv, Xuewei; Liang, Dong; Zhang, Jie; Bai, Chenguang

    2016-05-01

    The effect of Al2O3 and the Al2O3/SiO2(A/S) ratio on the viscosity of the CaO-SiO2-Al2O3-MgO-TiO2 slag system was studied in the present work. At a fixed CaO/SiO2(C/S) ratio of 1.20, 9 mass pct MgO, and 1 mass pct TiO2, the viscosity increases with an increase in Al2O3 content at a range of 16 to 24 mass pct due to the polymerization of the aluminosilicate structures, while it decreases when the Al2O3 is higher than 24 mass pct, which means that Al2O3 acts as a network modifier at higher content. Increasing A/S from 0.47 to 0.92 causes a slight decrease in viscosity of the slags and has an opposite effect when A/S is more than 0.92. The free running temperature increases with the Al2O3 content and appears to show a peak at an A/S ratio of 0.92. The change of the apparent activation energy is in accordance with the change of viscosity. When Al2O3 content is more than 24 mass pct with low SiO2, CaO content ranges from 35 to 45 mass pct, and the slag transform from silicates-based to aluminates-based can still get a good operation region. Four different viscosity models were employed to predict the viscosity and RIBOUD's model was found to be the best in predicting the viscosity by comparing the estimated viscosity with the measured viscosity.

  12. Effect of Composition and Impurities on the Phosphorescence of Green-Emitting Alkaline Earth Aluminate Phosphor.

    PubMed

    Kim, Doory; Kim, Han-Eol; Kim, Chang-Hong

    2016-01-01

    Recent improvements to SrAl2O4:Eu2+, Dy3+ phosphors have enabled the use of luminescent hosts with a stable crystal structure and high physical and chemical stability, thus overcoming the bottleneck in the applicability of ZnS:Cu phosphors. However, enhancement of afterglow lifetime and brightness in SrAl2O4:Eu2+, Dy3+ phosphors remains a challenging task. Here, we have improved the afterglow characteristics in terms of persistence time and brightness by a systematic investigation of the composition of Eu-doped alkaline earth aluminate SrAl2O4:Eu2+, Dy3+ crystals. We found that a Dy3+/Eu2+ ratio of ~2.4 and ~0.935 mol Eu2+ (per mol of SrAl2O4) gave the brightest and longest emissions (11% and 9% increase for each). Doping with Si4+ also resulted in a slight increase in brightness up to ~15%. Doping with alkali metal or alkaline earth metal significantly enhanced the phosphorescence intensity. In particular, doping with 0.005 mol Li+ (per mol of SrAl2O4) alone boosted the phosphorescence intensity to 239% of the initial value, as compared to that observed for the non-doped crystal, while doping with 0.01 mol Mg2+ and 0.005 mol Li+ (per 1 mol SrAl2O4) boosted the phosphorescence intensity up to 313% of the initial value. The results of this investigation are expected to act as a guideline for the synthesis of bright and long persistent phosphors, and facilitate the development of persistent phosphors with afterglow characteristics superior to those of conventional phosphors. PMID:26731086

  13. Color-Center Production and Formation in Electron-Irradiated Magnesium Aluminate Spinel and Ceria

    DOE PAGESBeta

    Costantini, Jean-Marc; Lelong, Gerald; Guillaumet, Maxime; Weber, William J.; Takaki, Seiya; Yasuda, Kazuhiro

    2016-06-20

    Single crystals of magnesium aluminate spinel (MgAl2O4) with (100) or (110) orientations and cerium dioxide or ceria (CeO2) were irradiated by 1.0-MeV and 2.5-MeV electrons in a high fluence range. Point-defect production was studied by off-line UV-visible optical spectroscopy after irradiation. For spinel, regardless of both crystal orientation and electron energy, two characteristic broad bands centered at photon energies of 5.4 eV and 4.9 eV were assigned to F and F+ centers (neutral and singly-ionized oxygen vacancies), respectively, on the basis of available literature data. No clear differences in colour-centre formation were observed for the two crystal orientations. Using calculationsmore » of displacement cross sections by elastic collisions, these results are consistent with a very large threshold displacement energy (200 eV) for oxygen atoms at RT. A third very broad band centered at 3.7 eV might be attributed either to an oxygen hole center (V-type center) or an F2 dimer center (oxygen di-vacancy). The onset of recovery of these color centers took place at 200°C with almost full bleaching at 600°C. Activation energies (~0.3-0.4 eV) for defect recovery were deduced from the isochronal annealing data by using a first-order kinetics analysis. For ceria, a sub band-gap absorption feature peaked at ~3.1 eV was recorded for 2.5-MeV electron irradiation only. Assuming a ballistic process, we suggest that the latter defect might result from cerium atom displacement on the basis of computed cross sections.« less

  14. Color-center production and recovery in electron-irradiated magnesium aluminate spinel and ceria

    NASA Astrophysics Data System (ADS)

    Costantini, Jean-Marc; Lelong, Gérald; Guillaumet, Maxime; Weber, William J.; Takaki, Seiya; Yasuda, Kazuhiro

    2016-08-01

    Single crystals of magnesium aluminate spinel (MgAl2O4) with (1 0 0) or (1 1 0) orientations and cerium dioxide or ceria (CeO2) were irradiated by 1.0 MeV and 2.5 MeV electrons in a high-fluence range. Point-defect production was studied by off-line UV–visible optical spectroscopy after irradiation. For spinel, regardless of both crystal orientation and electron energy, two characteristic broad bands centered at photon energies of 5.4 eV and 4.9 eV were assigned to F and F+ centers (neutral and singly ionized oxygen vacancies), respectively, on the basis of available literature data. No clear differences in color-center formation were observed for the two crystal orientations. Using calculations from displacement cross sections by elastic collisions, these results are consistent with a very large threshold displacement energy (200 eV) for oxygen atoms at room temperature. A third very broad band centered at 3.7 eV might be attributed either to an oxygen hole center (V-type center) or an F2 dimer center (oxygen di-vacancy). The onset of recovery of these color centers took place at 200 °C with almost full bleaching at 600 °C. Activation energies (~0.3–0.4 eV) for defect recovery were deduced from the isochronal annealing data by using a first-order kinetics analysis. For ceria, a sub-band-gap absorption feature, which peaked at ~3.1 eV, was recorded for 2.5 MeV electron irradiation only. Assuming a ballistic process, we suggest that the latter defect might result from cerium atom displacement on the basis of computed cross sections.

  15. Color-center production and recovery in electron-irradiated magnesium aluminate spinel and ceria.

    PubMed

    Costantini, Jean-Marc; Lelong, Gérald; Guillaumet, Maxime; Weber, William J; Takaki, Seiya; Yasuda, Kazuhiro

    2016-08-17

    Single crystals of magnesium aluminate spinel (MgAl2O4) with (1 0 0) or (1 1 0) orientations and cerium dioxide or ceria (CeO2) were irradiated by 1.0 MeV and 2.5 MeV electrons in a high-fluence range. Point-defect production was studied by off-line UV-visible optical spectroscopy after irradiation. For spinel, regardless of both crystal orientation and electron energy, two characteristic broad bands centered at photon energies of 5.4 eV and 4.9 eV were assigned to F and F(+) centers (neutral and singly ionized oxygen vacancies), respectively, on the basis of available literature data. No clear differences in color-center formation were observed for the two crystal orientations. Using calculations from displacement cross sections by elastic collisions, these results are consistent with a very large threshold displacement energy (200 eV) for oxygen atoms at room temperature. A third very broad band centered at 3.7 eV might be attributed either to an oxygen hole center (V-type center) or an F2 dimer center (oxygen di-vacancy). The onset of recovery of these color centers took place at 200 °C with almost full bleaching at 600 °C. Activation energies (~0.3-0.4 eV) for defect recovery were deduced from the isochronal annealing data by using a first-order kinetics analysis. For ceria, a sub-band-gap absorption feature, which peaked at ~3.1 eV, was recorded for 2.5 MeV electron irradiation only. Assuming a ballistic process, we suggest that the latter defect might result from cerium atom displacement on the basis of computed cross sections. PMID:27319289

  16. A force field for tricalcium aluminate to characterize surface properties, initial hydration, and organically modified interfaces in atomic resolution.

    PubMed

    Mishra, Ratan K; Fernández-Carrasco, Lucia; Flatt, Robert J; Heinz, Hendrik

    2014-07-21

    Tricalcium aluminate (C3A) is a major phase of Portland cement clinker and some dental root filling cements. An accurate all-atom force field is introduced to examine structural, surface, and hydration properties as well as organic interfaces to overcome challenges using current laboratory instrumentation. Molecular dynamics simulation demonstrates excellent agreement of computed structural, thermal, mechanical, and surface properties with available experimental data. The parameters are integrated into multiple potential energy expressions, including the PCFF, CVFF, CHARMM, AMBER, OPLS, and INTERFACE force fields. This choice enables the simulation of a wide range of inorganic-organic interfaces at the 1 to 100 nm scale at a million times lower computational cost than DFT methods. Molecular models of dry and partially hydrated surfaces are introduced to examine cleavage, agglomeration, and the role of adsorbed organic molecules. Cleavage of crystalline tricalcium aluminate requires approximately 1300 mJ m(-2) and superficial hydration introduces an amorphous calcium hydroxide surface layer that reduces the agglomeration energy from approximately 850 mJ m(-2) to 500 mJ m(-2), as well as to lower values upon surface displacement. The adsorption of several alcohols and amines was examined to understand their role as grinding aids and as hydration modifiers in cement. The molecules mitigate local electric fields through complexation of calcium ions, hydrogen bonds, and introduction of hydrophobicity upon binding. Molecularly thin layers of about 0.5 nm thickness reduce agglomeration energies to between 100 and 30 mJ m(-2). Molecule-specific trends were found to be similar for tricalcium aluminate and tricalcium silicate. The models allow quantitative predictions and are a starting point to provide fundamental understanding of the role of C3A and organic additives in cement. Extensions to impure phases and advanced hydration stages are feasible. PMID:24828263

  17. Influence of phosphorus addition on the surface tension of liquid iron and segregation of phosphorus on the surface of Fe-P alloy

    SciTech Connect

    Xue, X.M.; Jiang, H.G.; Ding, B.Z.; Hu, Z.Q.; Sui, Z.T.

    1996-02-01

    This article presents a study of the surface tension and phosphorus surface segregation in Fe-P alloys. The surface tension was measured by the sessile drop technique. The result of the dynamic surface tension for the low phosphorus content alloys shows that the alloy surface vaporization has a clear effect on the surface tension and causes a positive surface tension temperature coefficient. However, from this article, it is evident that phosphorus in liquid iron acts as a surface active element similar to arsenic. The surface segregation was determined using Auger electron spectroscopy. The result on the surface analysis of as-solidified sample indicates that the adsorption of impurity elements, such as oxygen, carbon, and nitrogen, can conceal phosphorus segregation on the free surface. Phosphorus segregation was also examined in the samples as-cleaned by Ar{sup +} and then treated 30 minutes at 650 C. Phosphorus was found to segregate extensively on the surface of the alloys. On the basis of the analysis of the published data, the surface active intensity sequence of some nonmetallic elements was arrayed, and the surface active intensity of fluorine and boron in liquid iron was estimated.

  18. Sm-Nd and Rb-Sr isotopic systematics of the Pea Ridge Fe-P deposit and related rocks, southeast Missouri

    SciTech Connect

    Marikos, M.A.; Barton, M.D. . Dept. of Geosciences)

    1993-03-01

    Pea ridge is a discordant Middle Proterozoic Fe-P deposit hosted in rhyolite tuffs and flows of the 1.4--1.5 Ga St. Francois terrane. Host rocks and the deposit are cut by basalt and aplite/pegmatite dikes. The deposit overlies a blind pluton which is partially surrounded by a trachytic ring complex. In the deposit, which is mined for Fe, early Qtz+Amph+Mag+Ap rock is cut by Mag+Ap+Qtz rock. Subsequently, portions of the deposit and host rocks were brecciated, oxidized and silicified to produce a complex suite of rocks enriched in Hem+Qtz+Ksp+Mu. Late breccia pipes/dikes cut the complex and were mineralized with Bar+Ksp+Flu+Chl+Cc+REE-phosphates. Sm/Nd and Rb/Sr isotopic systematics have been studied to: (1) constrain source(s) of igneous rocks and deposit components, (2) refine ages of magmatism, mineralization, and later hydrothermal activity, (3) begin regional comparison of isotopic systematics in SE Missouri Fe deposits, and (4) complement ongoing Missouri DGLS/USGS studies. Fourteen combined Sm-Nd and Rb-Sr analyses were done on materials including two host rhyolites, two nearby trachytes, two gneiss samples representing plausible basement, two intramineral dikes, and six samples of mineralization.

  19. Analysis of the Erwinia chrysanthemi ferrichrysobactin receptor gene: resemblance to the Escherichia coli fepA-fes bidirectional promoter region and homology with hydroxamate receptors.

    PubMed Central

    Sauvage, C; Franza, T; Expert, D

    1996-01-01

    The fct cbsCEBA operon from the Erwinia chrysanthemi 3937 chrysobactin-dependent iron assimilation system codes for transport and biosynthetic functions. The sequence of the fct outer membrane receptor gene was determined. The fct promoter region displays a strong resemblance to the Escherichia coli bidirectional intercistronic region controlling the expression of the fepA-entD and fes-entF operons. An apparent Fur-binding site was shown to confer iron regulation on an fct::lac fusion expressed on a low-copy-number plasmid in a Fur-proficient E. coli strain. The fct gene consists of an open reading frame encoding a 735-amino-acid polypeptide with a signal sequence of 38 residues. The Fct protein has 36% sequence homology with the E. coli ferrichrome receptor FhuA and the Yersinia enterocolitica ferrioxamine receptor FoxA. On the basis of secondary-structure predictions and these homologies, we propose a two-dimensional folding model for Fct. PMID:8576065

  20. A prospective, within-patient comparison between metal butterfly needles and Teflon cannulae in subcutaneous infusion of drugs to terminally ill hospice patients.

    PubMed

    Ross, J R; Saunders, Y; Cochrane, M; Zeppetella, G

    2002-01-01

    We performed a prospective study of hospice in-patients requiring a syringe driver (SD), to determine the site duration and tolerability of metal butterfly needles compared to Teflon cannulae. Using patients as their own control, prescribed medications were divided equally between two SDs (Graseby MS16a), for delivery over 24 h. A butterfly infusion (Flosafer, 25 gauge) was connected to one SD and a Teflon cannula (Abbocath-T, 24 gauge), to the second. These were inserted subcutaneously (s.c.) on opposite sides of the body at comparable sites; oedematous, broken or painful sites were excluded. SD sites were examined at 4-hourly intervals. The study was terminated when both devices had required resiting. Needle and cannula times were compared using the Wilcoxon signed rank test. Thirty patients entered the study, 13 males and 17 females, mean age (standard deviation): 70 (11) years. Thirteen patients completed the study. Nine patients died and eight patients discontinued the study before both needle and cannula had been resited. All 30 patients are included in the analysis. The time from insertion to resiting of the cannula was significantly longer than the needle: P < 0.0002, median (range) 93.5 (22.8-263.5) h versus 42.8 (7.5-162.3) h, respectively. The cost of the needle versus cannula is 1.93 Pounds versus 2.51 Pounds, respectively. Teflon cannulae have a median life span twice that of metal butterfly needles and are a cost-effective alternative for administration of medications by s.c. infusion in terminally ill patients. PMID:11963447

  1. Vacuum Ultraviolet Radiation and Atomic Oxygen Durability Evaluation of HST Bi-Stem Thermal Shield Materials

    NASA Technical Reports Server (NTRS)

    Dever, Joyce; deGroh, Kim K.

    2002-01-01

    Bellows-type thermal shields were used on the bi-stems of replacement solar arrays installed on the Hubble Space Telescope (HST) during the first HST servicing mission (SMI) in December 1993. These thermal shields helped reduce the problem of thermal gradient- induced jitter observed with the original HST solar arrays during orbital thermal cycling and have been in use on HST for eight years. This paper describes ground testing of the candidate solar array bi-stem thermal shield materials including backside aluminized Teflon(R)FEP (fluorinated ethylene propylene) with and without atomic oxygen (AO) and ultraviolet radiation protective surface coatings for durability to AO and combined AO and vacuum ultraviolet (VOV) radiation. NASA Glenn Research Center (GRC) conducted VUV and AO exposures of samples of candidate thermal shield materials at HST operational temperatures and pre- and post-exposure analyses as part of an overall program coordinated by NASA Goddard Space Flight Center (GSFC) to determine the on-orbit durability of these materials. Coating adhesion problems were observed for samples having the AO- and combined AO/UV-protective coatings. Coating lamination occurred with rapid thermal cycling testing which simulated orbital thermal cycling. This lack of adhesion caused production of coating flakes from the material that would have posed a serious risk to HST optics if the coated materials were used for the bi-stem thermal shields. No serious degradation was observed for the uncoated aluminized Teflon(R) as evaluated by optical microscopy, although atomic force microscopy (AFM) microhardness testing revealed that an embrittled surface layer formed on the uncoated Teflon(R) surface due to vacuum ultraviolet radiation exposure. This embrittled layer was not completely removed by AO erosion, No cracks or particle flakes were produced for the embrittled uncoated material upon exposure to VUV and AO at operational temperatures to an equivalent exposure of

  2. Characterization of magnetite in silico-aluminous fly ash by SEM, TEM, XRD, magnetic susceptibility, and Moessbauer spectroscopy

    SciTech Connect

    Gomes, S.; Francois, M.; Abdelmoula, M.; Refait, P.; Pellissier, C.; Evrard, O.

    1999-11-01

    Spinel magnetite contained in a silico-aluminous fly ash (originating from la Maxe's power plant, near Metz in the east of France) issued from bituminous coal combustion has been studied by scanning and transmission electron microscopy linked with energy dispersive spectroscopy. X-ray diffraction, susceptibility measurements, and Moessbauer spectroscopy. The results show that in this magnetite Mg is strongly substituted for Fe and the chemical formula is closer to MgFe{sub 2}O{sub 4} than Fe{sub 3}O{sub 4}. Magnetite also contains Mn, Ca, and Si elements, but at a lower proportion. The results are compatible with the chemical formula Fe{sub 2.08}Mg{sub 0.75}Mn{sub 0.11}Ca{sub 0.04}Si{sub 0.02}O{sub 4} and crystallochemical formula [Fe{sup 2{minus}}{sub 0.92}Ca{sup 2+}{sub 0.06}Si{sup 4+}{sub 0.02}]{sup tetra}[Fe{sup 3+}Fe{sup 2+}{sub 0.16}Mg{sup 2+}{sub 0.73}Mn{sup 2+}{sub 0.11}]{sup octa}O{sub 4}, showing the cation distribution on octahedral and tetrahedral sites of the spinel structure. The reason Mg element is not incorporated in soluble surface salt and in glass composition of the silico-aluminous fly ashes is now understood.

  3. More complete desilication of aluminate solution is the key-factor to radical improvement of alumina refining

    SciTech Connect

    Rayzman, V.

    1996-10-01

    A conventional aluminate solution obtained in the Bayer process is characterized by an Al{sub 2}O{sub 3}:SiO{sub 2} (mass) ratio of about 300--350:1. This ratio level is sufficient to produce of alumina low in SiO{sub 2} because silicon during the Al(OH){sub 3} precipitation remains in a spent (mother) liquor. However, there are important reasons to believe that the rise in the rate of aluminum hydroxide precipitation and, consequently, Al{sub 2}O{sub 3} yield are limited by excessive SiO{sub 2} concentration. Moreover, a sodium desilication product formed during heating and evaporation of the spent liquor fouls heat exchanger surfaces. From the aforesaid, it might be assumed that more complete desilication of aluminate solution is a method for radically improving the Bayer process. It is known the technology used in the sintering process that provides increasing the Al{sub 2}O{sub 3}:SiO{sub 2} (mass) ratio in solution to 1,000:1 and more. This method can be applied to the Bayer process with some modifications. As a result the great improvements of the Bayer process parameters are expected.

  4. Simulated Solar Flare X-Ray and Thermal Cycling Durability Evaluation of Hubble Space Telescope Thermal Control Candidate Replacement Materials

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Banks, Bruce A.; Sechkar, Edward A.; Scheiman, David A.

    1998-01-01

    During the Hubble Space Telescope (HST) second servicing mission (SM2), astronauts noticed that the multilayer insulation (MLI) covering the telescope was damaged. Large pieces of the outer layer of MLI (aluminized Teflon fluorinated ethylene propylene (Al-FEP)) were torn in several locations around the telescope. A piece of curled up Al-FEP was retrieved by the astronauts and was found to be severely embrittled, as witnessed by ground testing. Goddard Space Flight Center (GSFC) organized a HST MLI Failure Review Board (FRB) to determine the damage mechanism of FEP in the HST environment, and to recommend replacement insulation material to be installed on HST during the third servicing mission (SM3) in 1999. Candidate thermal control replacement materials were chosen by the FRB and tested for environmental durability under various exposures and durations. This paper describes durability testing of candidate materials which were exposed to charged particle radiation, simulated solar flare x-ray radiation and thermal cycling under load. Samples were evaluated for changes in solar absorptance and tear resistance. Descriptions of environmental exposures and durability evaluations of these materials are presented.

  5. Improvement in reliability of amorphous indium-gallium-zinc oxide thin-film transistors with Teflon/SiO2 bilayer passivation under gate bias stress

    NASA Astrophysics Data System (ADS)

    Fan, Ching-Lin; Tseng, Fan-Ping; Li, Bo-Jyun; Lin, Yu-Zuo; Wang, Shea-Jue; Lee, Win-Der; Huang, Bohr-Ran

    2016-02-01

    The reliability of amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) with Teflon/SiO2 bilayer passivation prepared under positive and negative gate bias stresses (PGBS and NGBS, respectively) was investigated. Heavier electrical degradation was observed under PGBS than under NGBS, indicating that the environmental effects under PGBS are more evident than those under NGBS. The device with bilayer passivation under PGBS shows two-step degradation. The positive threshold voltage shifts during the initial stressing period (before 500 s), owing to the charges trapped in the gate insulator or at the gate insulator/a-IGZO active layer interface. The negative threshold voltage shift accompanies the increase in subthreshold swing (SS) for the continuous stressing period (after 500 s) owing to H2O molecules from ambience diffused within the a-IGZO TFTs. It is believed that Teflon/SiO2 bilayer passivation can effectively improve the reliability of the a-IGZO TFTs without passivation even though the devices are stressed under gate bias.

  6. Development of a high analytical performance-tyrosinase biosensor based on a composite graphite-Teflon electrode modified with gold nanoparticles.

    PubMed

    Carralero, V; Mena, M L; Gonzalez-Cortés, A; Yáñez-Sedeño, P; Pingarrón, J M

    2006-12-15

    The design of a new tyrosinase biosensor with improved stability and sensitivity is reported. The biosensor design is based on the construction of a graphite-Teflon composite electrode matrix in which the enzyme and colloidal gold nanoparticles are incorporated by simple physical inclusion. Experimental variables such as the colloidal gold loading into the composite matrix, the enzyme loading and the potential applied to the bioelectrode were optimized. The Tyr-Au(coll)-graphite-Teflon biosensor exhibited suitable amperometric responses at -0.10 V for the different phenolic compounds tested (catechol; phenol; 3,4-dimethylphenol; 4-chloro-3-methylphenol; 4-chlorophenol; 4-chloro-2-methylphenol; 3-methylphenol and 4-methylphenol). The limits of detection obtained were 3 nM for catechol, 3.3 microM for 4-chloro-2-methylphenol, and approximately 20 nM for the rest of phenolic compounds. The presence of colloidal gold into the composite matrix gives rise to enhanced kinetics of both the enzyme reaction and the electrochemical reduction of the corresponding o-quinones at the electrode surface, thus allowing the achievement of a high sensitivity. The biosensor exhibited an excellent renewability by simple polishing, with a lifetime of at least 39 days without apparent loss of the immobilized enzyme activity. The usefulness of the biosensor for the analysis of real samples was evaluated by performing the estimation of the content of phenolic compounds in water samples of different characteristics. PMID:16569498

  7. Processing method and process modeling of large aperture transparent magnesium aluminate spinel domes

    NASA Astrophysics Data System (ADS)

    Yu, Jian; McWilliams, Brandon; Kilczewski, Steven; Gilde, Gary; Lidie, Ashley; Sands, James

    2009-05-01

    Polycrystalline spinel serves as an alternative to materials such as sapphire and magnesium fluoride that are currently being used in electromagnetic window applications such as missile domes, where high strength, high hardness and high transmittance in the visible and infrared spectra are required. The cubic crystal lattice of spinel imparts an isotropy to the bulk optical property, which eliminates optical distortion due to birefringence that occurs in sapphire and other non-cubic materials. The current study is to find a reliable manufacturing process to produce large magnesium aluminate spinel domes from powder consolidation efficiently. A binder-less dry ball milling process was used to deflocculate the spinel powder to increase its fluidity in an effort to ease the shape-forming. Dry ball milling time trials were conducted at several intervals to determine the appropriate level of time required to break up both the hard and soft agglomerates associated with the virgin spinel powder. The common problems encountered in dry powder shape-forming are crack growth and delamination of the green body during cold isostatic pressing (CIPing). The cracking and the delamination are due to the buildup of stress gradients on the green body that are created by the frictional force between the powder and the die wall or mold wall. To understand the stresses during the CIPing process, a finite element analysis of stresses on the green body was conducted. The simulation was used to evaluate the effect of die tooling and process characteristics on the development of stress gradients in the green body dome. Additionally, the effect of friction between the die wall and powder was examined by the simulation. It was found that by mitigating the frictional forces, cracking and delamination on the green body could be eliminated. A stepped-pressure CIPing technique was developed to reduce stress gradient build-up during CIPing. Also, oleic acid lubricant was applied to the die wall to

  8. Kinetics of calcium sulfoaluminate formation from tricalcium aluminate, calcium sulfate and calcium oxide

    SciTech Connect

    Li, Xuerun Zhang, Yu; Shen, Xiaodong Wang, Qianqian; Pan, Zhigang

    2014-01-15

    The formation kinetics of tricalcium aluminate (C{sub 3}A) and calcium sulfate yielding calcium sulfoaluminate (C{sub 4}A{sub 3}$) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C{sub 3}A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction 3Ca{sub 3}Al{sub 2}O{sub 6} + CaSO{sub 4} → Ca{sub 4}Al{sub 6}O{sub 12}(SO{sub 4}) + 6CaO was the primary reaction < 1350 °C with and activation energy of 231 ± 42 kJ/mol; while the decomposition reaction 2Ca{sub 4}Al{sub 6}O{sub 12}(SO{sub 4}) + 10CaO → 6Ca{sub 3}Al{sub 2}O{sub 6} + 2SO{sub 2} ↑ + O{sub 2} ↑ primarily occurred beyond 1350 °C with an activation energy of 792 ± 64 kJ/mol. The optimal formation region for C{sub 4}A{sub 3}$ was from 1150 °C to 1350 °C and from 6 h to 1 h, which could provide useful information on the formation of C{sub 4}A{sub 3}$ containing clinkers. The Jander diffusion model was feasible for the formation and decomposition of calcium sulfoaluminate. Ca{sup 2+} and SO{sub 4}{sup 2−} were the diffusive species in both the formation and decomposition reactions. -- Highlights: •Formation and decomposition of calcium sulphoaluminate were studied. •Decomposition of calcium sulphoaluminate combined CaO and yielded C{sub 3}A. •Activation energy for formation was 231 ± 42 kJ/mol. •Activation energy for decomposition was 792 ± 64 kJ/mol. •Both the formation and decomposition were controlled by diffusion.

  9. Evaluation program for secondary spacecraft cells. Initial evaluation tests of General Electric Company standard and teflonated negative electrode 20.0 ampere-hour, nickel-cadmium spacecraft cells with auxiliary electrodes

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The standard plate cells exhibited higher average end-of-charge (EOC) voltages than the cells with teflonated negative plates; they also delivered a higher capacity output in ampere hours following these charges. All the cells reached a pressure of 20 psia before reaching the voltage limit of 1.550 volts during the pressure versus capacity test. The average ampere hours in and voltages at this pressure were 33.6 and 1.505 volts respectively for the teflonated negative plate cells and 35.5 and 1.523 volts for the standard plate cells. All cells exhibited pressure decay in the range of 1 to 7 psia during the last 30 minutes of the 1-hour open circuit stand. Average capacity out for the teflonated and standard negative plate cells was 29.4 and 29.9 ampere hours respectively.

  10. Effect of aluminizing of Cr-containing ferritic alloys on the seal strength of a novel high-temperature solid oxide fuel cell sealing glass

    SciTech Connect

    Chou, Y. S.; Stevenson, Jeffry W.; Singh, Prabhakar

    2008-12-01

    A novel high-temperature alkaline-earth silicate sealing glass was developed for solid oxide fuel cell (SOFC) applications. The glass was used to join two metallic coupons of Cr-containing ferritic stainless steel for seal strength evaluation. In previous work, SrCrO4 was found to form along the glass/steel interface, which led to severe strength degradation. In the present study, aluminization of the steel surface was investigated as a remedy to minimize or prevent the strontium chromate formation. Three different processes for aluminization were evaluated with Crofer22APU stainless steel: pack cementation, vapor phase deposition, and aerosol spraying. It was found that pack cementation resulted in a rough surface with occasional cracks in the Al-diffused region. Vapor phase deposition yielded a smoother surface, but the resulting high Al content increased the coefficient of thermal expansion (CTE), resulting in failure of joined coupons. Aerosol spraying of an Al-containing salt resulted in formation of a thin aluminum oxide layer without any surface damage. The room temperature seal strength was evaluated in the as-fired state and in environmentally aged conditions. In contrast to earlier results with uncoated Crofer22APU, the aluminized samples showed no strength degradation even for samples aged in air. Interfacial and chemical compatibility was also investigated. The results showed aluminization to be a viable candidate approach to minimize undesirable chromate formation between alkaline earth silicate sealing glass and Cr-containing interconnect alloys for SOFC applications.

  11. Effect of aluminizing of Cr-containing ferritic alloys on the seal strength of a novel high-temperature solid oxide fuel cell sealing glass

    NASA Astrophysics Data System (ADS)

    Chou, Yeong-Shyung; Stevenson, Jeffry W.; Singh, Prabhakar

    A novel high-temperature alkaline earth silicate sealing glass was developed for solid oxide fuel cell (SOFC) applications. The glass was used to join two metallic coupons of Cr-containing ferritic stainless steel for seal strength evaluation. In previous work, SrCrO 4 was found to form along the glass/steel interface, which led to severe strength degradation. In the present study, aluminization of the steel surface was investigated as a remedy to minimize or prevent the strontium chromate formation. Three different processes for aluminization were evaluated with Crofer22APU stainless steel: pack cementation, vapor-phase deposition, and aerosol spraying. It was found that pack cementation resulted in a rough surface with occasional cracks in the Al-diffused region. Vapor-phase deposition yielded a smoother surface, but the resulting high Al content increased the coefficient of thermal expansion (CTE), resulting in the failure of joined coupons. Aerosol spraying of an Al-containing salt resulted in the formation of a thin aluminum oxide layer without any surface damage. The room temperature seal strength was evaluated in the as-fired state and in environmentally aged conditions. In contrast to earlier results with uncoated Crofer22APU, the aluminized samples showed no strength degradation even for samples aged in air. Interfacial and chemical compatibility was also investigated. The results showed aluminization to be a viable candidate approach to minimize undesirable chromate formation between alkaline earth silicate sealing glass and Cr-containing interconnect alloys for SOFC applications.

  12. MSFC Analysis of Thermal Control Materials on MISSE

    NASA Technical Reports Server (NTRS)

    Finckenor, Miria

    2006-01-01

    Many different passive thermal control materials were flown as part of the Materials on International Space Station Experiment, including coatings, anodizes, and multi-layer insulation materials. Engineers and scientists at the Marshall Space Flight Center have analyzed a number of these materials, including: Zinc oxide/potassium silicate coating, Zinc orthotitanate/potassium silicate coating, Sulfuric acid anodized aluminum, Various coatings for part marking, automated rendezvous and capture, and astronaut visual aids, FEP Teflon with silver/Inconel backing, and Beta cloth with and without aluminization. These and other material samples were exposed to the low Earth orbital environment of atomic oxygen, ultraviolet radiation, thermal cycling, and hard vacuum, though atomic oxygen exposure was very limited for some samples. Solar absorptance, infrared emittance, and mass measurements indicate the durability of these materials to withstand the space environment. The effect of contamination from an active space station on the performance of white thermal control coatings is discussed.

  13. Oxidation of Uncoated and Aluminized 9-12% Cr Boiler Steels at 550-650 °C

    NASA Astrophysics Data System (ADS)

    Metsäjoki, J.; Huttunen-Saarivirta, E.; Lepistö, T.

    2011-03-01

    In this paper, oxidation behavior of 9-12% Cr steels P91 and HCM12A is studied in air and in a mixture of air and water vapor. Comparison is made between these steels in uncoated condition and coated with aluminum diffusion coating by a slurry method. Oxidation tests were carried out at 550, 600, and 650 °C for a discontinued duration of 1000 h; every 250 h the specimens were slowly cooled to room temperature and weighed. SEM + EDS and XRD characterization were performed after 500 and 1000 h. The results showed that oxidation rate of uncoated P91 and HCM12A was significantly higher in the mixture of air and water vapor than in air. Oxidation resistance of the studied materials improved substantially when they were aluminized.

  14. Density functional theory studies of structural properties, energies and natural band orbital for two new aluminate compounds

    NASA Astrophysics Data System (ADS)

    Sahebalzamani, Hajar; Ghammamy, Shahriare; Mehrani, Kheyrollah; Jahandide, Shahram; Salimi, Farshid

    2012-05-01

    Two new aluminate compounds was prepared by the reaction of AlCl3 with KX (X = SCN-, CN-) in a 1:1 mole ratio. In these salts the aluminum atom is surrounded by three chlorine atoms and a ligand (X = SCN-, CN-). In AlCl3SCN anion, the SCN coordinates to the Al through sulfur and AlCl3CN anion the CN- coordinates to the Al center through carbon. The molecular geometry, vibrational frequencies, energies and natural bond orbital (NBO) in the ground state are calculated by using the DFT (B3LYP) methods with 6-311G* basis sets. The geometries and normal modes of vibrations obtained from B3LYP calculations are in good agreement with the experimentally observed data.

  15. Surface studies on aluminized and thermally oxidized superalloy 690 substrates interacted with simulated nuclear waste and sodium borosilicate melt

    NASA Astrophysics Data System (ADS)

    Yusufali, C.; Kshirsagar, R. J.; Mishra, R. K.; Kaushik, C. P.; Sengupta, P.; Dutta, R. S.; Dey, G. K.

    2014-04-01

    Aluminized and thermally oxidized Ni-Cr-Fe based superalloy 690 substrates with Al2O3 layer on top have been exposed in nitrate based environment (simulated high level nuclear liquid waste) at 373 K for 216 hours and sodium borosilicate melt at 1248 K for 192 hours. The surfaces of exposed samples have been characterized by using Electron probe micro-analyzer (EPMA). Elemental X-ray mapping on coated specimen that exposed in simulated nuclear waste solution revealed that the surface is enriched with Ni, Cr and Al. X-ray mapping on surface of the specimen that interacted with sodium borosilicate melt indicated that the surface is composed of Al, Fe, Ni and Cr.

  16. Surface studies on aluminized and thermally oxidized superalloy 690 substrates interacted with simulated nuclear waste and sodium borosilicate melt

    SciTech Connect

    Yusufali, C. Sengupta, P.; Dutta, R. S.; Dey, G. K.; Kshirsagar, R. J.; Mishra, R. K.; Kaushik, C. P.

    2014-04-24

    Aluminized and thermally oxidized Ni-Cr-Fe based superalloy 690 substrates with Al{sub 2}O{sub 3} layer on top have been exposed in nitrate based environment (simulated high level nuclear liquid waste) at 373 K for 216 hours and sodium borosilicate melt at 1248 K for 192 hours. The surfaces of exposed samples have been characterized by using Electron probe micro-analyzer (EPMA). Elemental X-ray mapping on coated specimen that exposed in simulated nuclear waste solution revealed that the surface is enriched with Ni, Cr and Al. X-ray mapping on surface of the specimen that interacted with sodium borosilicate melt indicated that the surface is composed of Al, Fe, Ni and Cr.

  17. Studies of composite ion exchange membranes formed from gamma radiation initiated formed from gamma radiation initiated grafting of polymers to modified expanded teflon membranes

    SciTech Connect

    Blubaugh, E.A.; Ramos, B.L.; Heineman, W.R.

    1995-12-31

    This report will present our results for evaluating expanded Teflon as a matrix for polymer grafting. The porosity of the ePTFE starting material was kept constant. However, the volume percent of monomer to solvent and the radiation dosage levels were varied. Also, the monomers used were styrene and (2-dimethylaminoethyl methacrylate) and the influence on the microscopic characteristics of the composite polymers was evaluated via gravimetric determinations and Scanning Electron Microscopy (SEM), respectively. The grafted polystyrene or poly-(2-dimethylaminoethyl methacrylate) must be further modified chemically. The polystyrene must be sulfonated and the poly-(2-dimethylaminoethyl methacrylate) must be quatemized via 2-Bromobutane. These chemical modifications convert the polystyrene into polystyrene-sulfonate (a cation exchanger) and the conversion of poly-(2-dimethylaminoethyl methacrylate) to poly-(2-dimethyl-butyl ammonium ethyl methacrylate) bromide (an anion exchange medium). These polymer composites were evaluated as to their ion-exchange ability, via the electrochemical activity displayed through exchanged electroactive ions.

  18. Infrared, spectral, directional-hemispherical reflectance of fused silica, Teflon polytetrafluoroethylene polymer, chrome oxide ceramic particle surface, Pyromark 2500 paint, Krylon 1602 paint, and Duraflect coating.

    PubMed

    Persky, Merle J; Szczesniak, Martin

    2008-04-01

    Infrared, spectral, directional-hemispherical reflectivity measurements of polished fused silica, Teflon polytetrafluoroethylene polymer, chrome oxide ceramic particle surface, Pyromark 2500 paint, Krylon 1602 paint, and Duraflect coating are provided. The reflectance was measured with an estimated accuracy of 0.01 to 0.02 units and a precision of 0.005 units. All the surfaces were measured at ambient temperatures. Additionally, the chrome oxide ceramic particle surface was measured at 486 K and the Pyromark 2500 at four temperatures to 877 K. Polarization measurements are also provided for fused silica, Duraflect, chrome oxide ceramic particle surface, and Pyromark 2500 paint. Separate diffuse and specular reflectance components for the Duraflect and chrome oxide ceramic surfaces are included. Fresnel-based predictions for fused silica parallel and perpendicular polarized reflections are compared to measurements. It is notable that the Pyromark 2500 and chrome oxide ceramic particle surfaces exhibit a significant lack of manufacturing repeatability. PMID:18382562

  19. Total rock dissolution using ammonium bifluoride (NH4HF2) in screw-top Teflon vials: a new development in open-vessel digestion.

    PubMed

    Zhang, Wen; Hu, Zhaochu; Liu, Yongsheng; Chen, Haihong; Gao, Shan; Gaschnig, Richard M

    2012-12-18

    Complete sample digestion is a prerequisite for achieving reproducible and accurate analytical results for geological samples. Open-vessel acid digestions successfully dissolve mafic samples, but this method cannot achieve complete dissolution of felsic samples, because of the presence of refractory minerals such as zircon. In this study, an efficient and simplified digestion technique using the solid compound NH(4)HF(2) in a screw-top vial has been developed for multielement analysis of different types of rock samples. NH(4)HF(2) has a higher boiling point (239.5 °C) than conventional acids such as HF, HNO(3) and HCl, which allows for an elevated digestion temperature in open vessels, enabling the decomposition of refractory phases. Similar to HF, HNO(3) and HCl, ultrapure NH(4)HF(2) can be produced using a conventional PFA sub-boiling (heating and cooling) purification system. A digestion time of 2-3 h for 200 mg NH(4)HF(2) in a Savillex Teflon vial at 230 °C is sufficient to digest 50 mg of the felsic rock GSP-2, which is ~6 times faster than using conventional closed-vessel acid digestion at 190 °C (high-pressure PTFE digestion bomb). The price of a Savillex Teflon vial is far less than the price of a high-pressure PTFE digestion bomb (consisting of a PTFE inner vessel and an outer stainless steel pressure jacket). Moreover, the NH(4)HF(2)-open-vessel acid digestion is not hampered by the formation of insoluble fluorides. We have successfully applied the NH(4)HF(2)-open-vessel acid digestion to the digestion of a series of international geological reference materials, including mafic to felsic igneous rocks and shales. This method provides an effective, simple, economical, and comparatively safe dissolution method that combines the advantages of both the open- and closed-vessel digestion methods. PMID:23176404

  20. Evaluation of Surlyn 8920 as PHE Visor Material and Evaluations of New Adhesives for Improving Bonding Between Teflon and Stainless Steel at Cryogenic Temperature

    NASA Technical Reports Server (NTRS)

    Ray, Asit K.

    1991-01-01

    Two studies are presented, and in the first study, Surlyn 8920 (an ionic and amorphous low density polyethylene made by Dupont) was evaluated as a possible replacement of Plexyglass G as PHE visor material. Four formulations of the polymer were made by adding different amounts of UV stabilizer, energy quencher, and antioxident in a Brabender Plasticorder. The formulated polymers were molded in the form of sheets in a compression molder. Cut samples from the molded sheets were exposed in a weatherometer and tested on Instron Tensile Tester for strength and elongation. Specially molded samples of the formulated polymers were subjected to Charpy Impact Tests. In the second study, preliminary evaluations of adhesives for improvement of bonding between Teflon and stainless steel (SS) were performed. Kapton, a high temperature polyimide made by Dupont, and a rubber based adhesive made by Potter Paint Co., were evaluated against industrial quality epoxy, the current material used to bond Teflon and SS. The degreased surfaces of the SS discs were etched mechanically, with a few of these etched chemically. The surfaces of the SS discs were etched mechanically, with a few of these etched chemically. Bonding strengths were evaluated using lap shear tests on the Instron Tensile Tester for the samples bonded by Kapton and industrial quality epoxy. Bond strengths were also evaluated using a pull test on the Instron for the samples bonded by Potter adhesive (CWL-152) and industrial quality epoxy. Based on limited lap shear data, Kapton gave bond strength favorable compared to that of industrial epoxy. Based on limited pull test data, Kapton bonded and CWL-152 bonded samples showed poor strength compared to epoxy bonded sample.

  1. Reactions of vibrationally excited hydrogen and deuterium molecules with atoms and radicals. Heterogeneous relaxation of the vibrational energy of H/sub 2/ and D/sub 2/ on quartz and teflon surfaces

    SciTech Connect

    Gershenzon, Yu.M.; Ivanov, A.V.; Kucheryavyi, S.I.; Lyapunov, A.Ya.; Rozenshtein, V.B.

    1987-03-01

    The ESR method was used to measure the probability of relaxation of the vibrational energy of H/sub 2/(v = 1) and D/sub 2/(v = 1) molecules during collisions with the surfaces of quartz and F32-L and F4-D Teflons. The results indicate that this relaxation proceeds by an adsorption-phonon mechanism

  2. Shock wave dynamics of novel aluminized detonations and empirical model for temperature evolution from post-detonation combustion fireballs

    NASA Astrophysics Data System (ADS)

    Gordon, J. Motos

    Optical forensics of explosion events can play a vital role in investigating the chain of events leading up to the explosion by possibly identifying key spectral characteristics and even molecules in the post-detonation fireball that may serve as the fingerprint for a particular explosive type used. This research characterizes the blast wave and temperature evolution of an explosion fireball in order to improve the classification of aluminized conventional munitions based on a single explosive type such as RDX. High speed 4 kHz visible imagery is collected for 13 field detonations of aluminized novel munitions to study fireball and shock wave dynamics. The 238 mus temporal resolution visible imagery and the 12 ms temporal resolution FTS spectra are the data sets upon which shock wave dynamics and the time dependence of the fireball temperature are studied, respectively. The Sedov-Taylor point blast theory is fitted to data where a constant release (s = 1) of energy upon detonation suggests shock energies of 0.5--8.9 MJ corresponding to efficiencies of 2--15 percent of the RDX heats of detonation with blast dimensionalities indicative of the spherical geometry observed in visible imagery. A drag model fit to data shows initial shock wave speeds of Mach 4.7--8.2 and maximum fireball radii ranging from 4.3--5.8 m with most of the radii reached by 50 ms upon detonation. Initial shock speeds are four times lower than theoretical maximum detonation speed of RDX and likely contributes to the low efficiencies. An inverse correlation exists between blast wave energy and overall aluminum or liner content in the test articles. A two-color best fit Planckian is used to extract temperature profiles from collected Fourier-transform spectrometer spectra. The temperatures decay from initial values of 1290--1850 K to less than 1000 K within 1 s after detonation. A physics-based low-dimensionality empirical model is developed to represent the temperature evolution of post

  3. The Electronic Structure of Iron in Aluminous (Mg,Fe)SiO3 Perovskite at High-Pressures and Temperatures

    NASA Astrophysics Data System (ADS)

    Jackson, J. M.; Sturhahn, W.; Lerche, M.; Li, J.

    2006-12-01

    Knowledge of iron valences and spin states in silicate perovskite is relevant to our understanding of the physical and chemical properties of Earth's lower mantle such as transport properties, mechanical behavior, and element partitioning. Recent studies have proposed that aluminous ferromagnesium silicate perovskite (Al- Pv) is the principle sink for ferric iron in Earth's lower mantle [e.g. 1]. Also of geophysical interest is the electronic spin state of Al-Pv under lower mantle conditions. To date, simultaneous high-pressure and high- temperature measurements of the hyperfine parameters to identify the valence and spin states of iron in Al-Pv have not been reported. In this study, we have measured the electronic structure of the iron component of an aluminous Fe-bearing silicate perovskite sample, (Mg0.88Fe0.09)(Si0.94Al0.10)O3, close to a pyrolite composition, using synchrotron Mössbauer spectroscopy (SMS) and laser heated diamond anvil cells. Recent developments in SMS have enabled in situ measurements of small samples (< 10 μm) with relatively low 57Fe contents (< 10 at.%) to Mbar pressures [e.g. 2,3]. The samples were first synthesized in a multi-anvil apparatus [3], and the perovskite structure was confirmed by X-ray diffraction. The sample was loaded into a diamond anvil cell sandwiched between NaCl insulating layers. Measurements were carried out to 65 GPa and up to 2000 K at beamline 3-ID of the Advanced Photon Source. Spectra were collected before, during, and after laser heating, at each pressure point. Synchrotron Mössbauer spectra were also collected on decreasing pressure. Evaluation of the spectra provided the isomer shift (relative to stainless steel) and the quadrupole splitting of the iron component in silicate perovskite, which gives information on valence and spin states under lower mantle conditions. This work is supported by NSF through COMPRES and the U.S. DOE-BES, Office of Science, under Contract No. W-31-109-ENG-38. [1] Mc

  4. Electrocautery Devices With Feedback Mode and Teflon-Coated Blades Create Less Surgical Smoke for a Quality Improvement in the Operating Theater

    PubMed Central

    Kisch, Tobias; Liodaki, Eirini; Kraemer, Robert; Mailaender, Peter; Brandenburger, Matthias; Hellwig, Veronika; Stang, Felix H.

    2015-01-01

    Abstract Monopolar electrocautery is a fast and elegant cutting option. However, as it creates surgical smoke containing polycyclic aromatic hydrocarbons (PAHs), it may be hazardous to the health of the surgical team. Although new technologies, such as feedback mode (FM) and Teflon-coated blades (TBs), reduce tissue damage, their impact on surgical smoke creation has not yet been elucidated. Therefore, we analyzed the plume at its source. The aim of this study was to evaluate if electrocautery FM and TBs create less surgical smoke. Porcine tissue containing skin was cut in a standardized manner using sharp-edged Teflon-coated blades (SETBs), normal-shaped TBs, or stainless steel blades (SSBs). Experiments were performed using FM and pure-cut mode. Surgical smoke was sucked through filters or adsorption tubes. Subsequently, filters were scanned and analyzed using a spectrophotometer. A high-performance liquid chromatography (HPLC-UV) was performed to detect benzo[a]pyrene (BaP) and phenanthrene as 2 of the most critical PAHs. Temperature changes at the cutting site were measured by an infrared thermometer. In FM, more surgical smoke was created using SSB compared with TBs (P < 0.001). Furthermore, differences between FM and pure-cut mode were found for SSB and TB (P < 0.001), but not for SETB (P = 0.911). Photometric analysis revealed differences in the peak heights of the PAH spectrum. In HLPC-UV, the amount of BaP and phenanthrene detected was lower for TB compared with SSB. Tissue temperature variations increased when SSB was used in FM and pure-cut mode. Furthermore, different modes revealed higher temperature variations with the use of SETB (P = 0.004) and TB (P = 0.005) during cutting, but not SSB (P = 0.789). We found that the use of both TBs and FM was associated with reduced amounts of surgical smoke created during cutting. Thus, the surgical team may benefit from the adoption of such new technologies, which could contribute to the

  5. Wear Behavior and Mechanism of Fe-Al Intermetallic Coating Prepared by Hot-Dip Aluminizing and Diffusion

    NASA Astrophysics Data System (ADS)

    Zhang, Q. Y.; Zhou, Y.; Liu, J. Q.; Chen, K. M.; Mo, J. G.; Cui, X. H.; Wang, S. Q.

    2016-05-01

    A Fe-Al intermetallic compound coating was prepared on AISI H13 steel by hot-dip aluminizing and subsequent high-temperature diffusion. Dry sliding wear tests of the Fe-Al intermetallic coating were performed at 298 K to 873 K (25 °C to 600 °C). The wear behavior of the Fe-Al intermetallic coating was noticed to vary markedly with the temperature and load. At 298 K (25 °C), the wear rate rapidly increased with an increase of the load. As the temperature was elevated, the wear rate dramatically decreased except for the cases under 300 N at 473 K and 673 K (200 °C and 400 °C). The Fe-Al intermetallic coating possessed an excellent elevated-temperature wear performance, especially at 673 K to 873 K (400 °C to 600 °C), but worse room-temperature one, which were noticed to be attributed to the existence and inexistence of thin tribo-oxide layers, respectively. Such a thin tribo-oxide layer was considered to provide a protection for the intermetallic compound. When the tribo-oxide layer did not form at room temperature or the formed one was massively delaminated above the critical load at elevated temperatures, Fe-Al intermetallic coating possessed poor wear resistance.

  6. Corrosion of Aluminized and Uncoated 9-12% Cr Boiler Steels in Simulated Biomass andWaste Combustion Conditions

    NASA Astrophysics Data System (ADS)

    Metsäjoki, Jarkko; Huttunen-Saarivirta, Elina; Lepistö, T.

    2011-04-01

    Coatings are seen a promising way to improve the corrosion resistance of relatively cheap power plant steels to enable higher steam temperatures than currently in use. In this research, 9-12% Cr steels P91 and HCM12A are coated with aluminium diffusion coating by a slurry method and exposed for 336 hours at 833 K and 883 K to atmospheres containing varying amounts of O2, H2O, HCl and SO2. Corrosion behaviour of the coated steels is compared to that of those steels in an uncoated condition. Characterization is performed by weighing, SEM + EDS and XRD. The results show that corrosion resistance of P91 and HCM12A is significantly improved by the aluminium diffusion coating at high temperatures in atmospheres containing HCl and SO2. The corrosion rate of the aluminized specimens slightly increases with increase in test temperature but remains virtually the same irrespective of the composition of the atmosphere. On the other hand, the corrosion rate of the uncoated specimens is dependent on both the atmosphere and the temperature. The steels undergo active oxidation that results in formation of non-protective, thick and layered scales in HCl containing atmospheres. SO2 addition slightly decreases the corrosion rate although it is anyway higher than that in SO2 containing atmosphere without HCl.

  7. In situ neutron powder diffraction investigation of the hydration of tricalcium aluminate in the presence of gypsum

    SciTech Connect

    Hartman, M.R. . E-mail: michael.hartman@nist.gov; Berliner, R.

    2005-11-15

    The hydration of a 1:3 molar ratio of tricalcium aluminate, Ca{sub 3}Al{sub 2}O{sub 6}, to gypsum, CaSO{sub 4}.2D{sub 2}O, was investigated at temperatures of 25, 50, and 80 deg. C using time-of-flight powder neutron diffraction combined with multiphase Rietveld structural refinement. It was shown that ettringite, Ca{sub 6}[Al(OD){sub 6}]{sub 2}(SO{sub 4}){sub 3}.{approx}26D{sub 2}O, was the first and only hydration product of the system, in contrast to a prior investigation which suggested the occurrence of a precursor phase prior to the formation of ettringite. Kinetics data showed that the hydration reaction is very sensitive to temperature: hydration at 25 deg. C was characterized by a single kinetic regime while hydration at higher temperatures consisted of two distinct kinetic regimes. The presence of two kinetic regimes was attributed to a change in either the dimensionality of the growth process or a change in the rate controlling mechanism in the hydration reaction.

  8. Effects of Xe ion irradiation and subsequent annealing on the structural properties of magnesium-aluminate spinel

    NASA Astrophysics Data System (ADS)

    Afanasyev-Charkin, Ivan V.; Dickerson, Robert M.; Wayne Cooke, D.; Bennett, Bryan L.; Gritsyna, Vasily T.; Sickafus, Kurt E.

    2001-02-01

    Single crystals of magnesium-aluminate spinel MgAl 2O 4 were irradiated with 340 keV Xe ++ ions at -173°C (˜100 K). A fluence of 1×10 20 Xe/m 2 created an amorphous layer at the surface of the samples. The samples were annealed for 1 h at different temperatures ranging from 130°C to 880°C. Recrystallization took place in the temperature interval between 610°C and 855°C. Transmission electron microscopy (TEM) images show two distinct layers near the surface: (1) a polycrystalline layer with columnar grain structure; and (2) a buried damaged layer epitaxial with the substrate. After annealing at 1100°C for 52 days, the profile of implanted Xe ions did not change, which means that Xe ions are not mobile in the spinel structure up to 1100°C. The thickness of the buried damaged layer decreased significantly in the 1100°C annealed sample comparing to the sample annealed for 1 h at 855°C.

  9. Disordering and annealing effects of magnesium aluminate spinel implanted with high-flux 60 keV Cu -

    NASA Astrophysics Data System (ADS)

    Lee, C. G.; Takeda, Y.; Kishimoto, N.

    2002-05-01

    Magnesium aluminate spinel of single crystal MgO n(Al 2O 3) was implanted with 60 keV Cu - at a flux up to 100 μA/cm 2, and effects of damage accumulation on the lattice were studied by Rutherford backscattering spectrometry (RBS)/channeling measurements. No complete amorphization was observed in the spinel over the flux range examined in this study, although the crystalline lattice was significantly damaged. The damaged region on the Al sublattice extended to a deeper region with increasing flux. Fluence- and flux dependence of Al damage peak is greatly influenced by the stoichiometry n of spinel. The Al damage peak of MgO1.0(Al 2O 3) is smaller for higher flux and fluence. It is understood that recombination of radiation-induced interstitials with structural vacancies effectively reduces damage of the Al sublattice. In the case of MgO2.4(Al 2O 3), the Al damage peak, however, increases with increasing fluence and flux. The results of RBS/channeling indicate that the recombination mechanism is more effective in the stoichiometric spinel than the nonstoichiometric one.

  10. Radiation-induced swelling and softening in magnesium aluminate spinel irradiated with high-flux Cu - ions

    NASA Astrophysics Data System (ADS)

    Lee, C. G.; Ohmura, T.; Takeda, Y.; Matsuoka, S.; Kishimoto, N.

    2004-03-01

    Magnesium aluminate spinel of single crystal was irradiated with 60 keV Cu - at a flux up to 6.2 × 10 18 ions/m 2 s, to a total fluence of 3 × 10 20 ions/m 2, in order to study changes in hardness and step-height swelling by high-flux implantation. Hardness determined by nano-indentation measurements steeply decreased with implantation. There is a strong negative correlation between flux dependences of the hardness and the step-height swelling: the former decreases as the latter increases. The Rutherford backscattering spectrometry (RBS)/channeling measurements showed that the spinel is not completely amorphized over the flux range in this study, and the radiation-induced softening observed is not due to amorphization. Results of optical absorbance suggested that radiation-induced point defects and their clusters on the anion sublattices of the spinel played an important role in the radiation-induced swelling under high-flux ion implantation.

  11. Preparation, luminescence and defect studies of Eu{sup 2+}-activated strontium hexa-aluminate phosphor prepared via combustion method

    SciTech Connect

    Singh, Vijay; Gundu Rao, T.K.; Zhu Junjie . E-mail: jjzhu@nju.edu.cn

    2006-08-15

    Preparation of Eu{sup 2+} ions activated strontium hexa-aluminate phosphor using the combustion method is described. An efficient phosphor can be prepared by this method at reaction temperatures as low as 500 deg. C in a few minutes. Powder X-ray diffraction (XRD), transmission electron microscopy, scanning electron microscope analysis were used to characterize the as prepared product and the optical properties were studied by photoluminescence (PL) spectra. Thermally stimulated luminescence studies also have been carried out on SrAl{sub 12}O{sub 19}:Eu{sup 2+} phosphor. The TSL glow curve is broad and indicates two dominant peaks at 206 and 345 deg. C. Defect centres formed in irradiated phosphor have been studied using the technique of electron spin resonance. One of the centres is characterized by an isotropic g-value of 2.0055 and is assigned to a F{sup +} centre. The two annealing stages of F{sup +} centre in the region 125-230 and 340-390 deg. C appear to correlate with the release of carriers resulting in TSL peaks at 206 and 345 deg. C, respectively. - Graphical abstract: SEM image of SrAl{sub 12}O{sub 19}:Eu.

  12. The effect of the host composition on the lifetime decay properties of barium/strontium aluminates compounds

    SciTech Connect

    Rezende, Marcos V. dos S.; Andrade, A. B.; Valerio, Mário E. G.; Montes, Paulo J. R

    2014-03-14

    This paper reports the influence of the structural change on the luminescence of Eu-doped barium/strontium aluminates when excited with monochromatic X-rays (also known as X-ray excited optical luminescence—XEOL). Ba{sub 1−x}Sr{sub x}Al{sub 2}O{sub 4} samples, with 0 < x < 1, were produced via proteic sol-gel route and it was observed that the XEOL emission spectra are composed by the Eu{sup 2+} and Eu{sup 3+} transitions, although no Eu{sup 2+} was observed in the X-ray absorption spectra. The XEOL intensities while the sample is under irradiation decreased as a function of the irradiation time, indicating the buildup of radiation damage. The saturation level of the XEOL is directly correlated to the amount of damages induced by the irradiation and the sample composition. The Ba-rich samples are the ones with higher XEOL yield. X-ray induced long lasting phosphorescence (LLP) was also observed for all samples and it was found that the duration of the phosphorescence emission also depends on the sample composition. In Sr-rich samples, the LLP has a slower decay time constant than in Ba-rich samples. A model of the radiation induced luminescence is presented and all these features are discussed in terms of the energetic costs and the type of defects generated in the sample.

  13. CaO-based pellets supported by calcium aluminate cements for high-temperature CO2 capture.

    PubMed

    Manovic, Vasilije; Anthony, Edward J

    2009-09-15

    The development of highly efficient CaO-based pellet sorbents, using inexpensive raw materials (limestones) or the spent sorbent from CO2 capture cycles, and commercially available calcium aluminate cements (CA-14, CA-25, Secar 51, and Secar 80), is described here. The pellets were prepared using untreated powdered limestones or their corresponding hydrated limes and were tested for their CO2 capture carrying capacities for 30 carbonation/calcination cycles in a thermogravimetric analyzer (TGA). Their morphology was also investigated by scanning electron microscopy (SEM) and their compositions before and after carbonation/calcination cycleswere determined by X-ray diffraction (XRD). Pellets prepared in this manner showed superior behavior during CO2 capture cycles compared to natural sorbents, with the highest conversions being > 50% after 30 cycles. This improved performance was attributed to the resulting substructure of the sorbent particles, i.e., a porous structure with nanoparticles incorporated. During carbonation/calcination cycles mayenite (Ca12Al14O33) was formed, which is believed to be responsible for the favorable performance of synthetic CaO-based sorbents doped with alumina compounds. An added advantage of the pellets produced here is their superior strength, offering the possibility of using them in fluidized bed combustion (FBC) systems with minimal sorbent loss due to attrition. PMID:19806751

  14. Effect of substitution of Co 2+ ions on the structural and electrical properties of nanosized magnesium aluminate

    NASA Astrophysics Data System (ADS)

    Ahmad, Javed; Awan, Muhammad Qadeer; Mazhar, Muhammad Ehsan; Ashiq, Muhammad Naeem

    2011-01-01

    Cobalt substituted nanosized magnesium aluminates having a nominal composition MgAl 2- xCo xO 4 where x = 0.0, 0.5, 1.0, 1.5, 2.0 were synthesized by the chemical co-precipitation method. Aluminium (Al 3+) ions were completely and successfully substituted by Co 2+ ions, which yielded an electron rich terminal compound MgCo 2O 4. All the samples were characterized by means of X-ray diffraction (XRD), thermogravimetry and differential thermal analysis (TG/DTA) and dc electrical resistivity measurements. The investigated samples were found to be spinel single phase cubic close packed crystalline materials as demonstrated by XRD data. Using the Debye Scherer formula, the calculated crystallite size was found Co 2+ concentration dependent and varied between 7 and 19 nm. The lattice constant, X-ray density and bulk density were found to increase while percentage porosity decreases on increasing the Co 2+ concentration. The dc electrical resistivity was found to decrease as a function of temperature as expected for a typical semiconductor. The doped Co 2+ ions are believed to form small polarons and hopping of these small polarons between the adjacent sites seems to be partially responsible for conduction in the system. The activation energy of hopping of small polarons was also calculated.

  15. Role of microstructure and thermal transport in determining the rate of hot spot growth in aluminized PBX

    NASA Astrophysics Data System (ADS)

    Joshi, Kaushik; Chaudhuri, Santanu

    The mechanisms of initiation and propagation of a hot spot in non-ideal explosives with aluminum additives are poorly understood due to greater complexity introduced by the different thermal and mechanical behavior of the components. In aluminized composites such as PBXN-109, the binder, RDX and Aluminum phases have been studied separately. However, not much is known about deflection of hot spots in the microstructured composite. Especially, the role of adhesion, debonding and thermal conductivity of binder phase is critical in moderating the sensitivity of such interfaces. Using reactive molecular dynamics simulations, the primary binder interfaces in PBXN-109 was investigated. Depending on the temperature of the growing hot spot reaching an RDX or Al/Al2O3 grain, the thermal conductivity and viscoplastic behavior of the binder interface determine the attenuation of reaction front and thermal shock leading the hot spot. Different mechanisms like melt-dispersion and failure of oxide layer for the release of Al in the hot spot regions remain underexplored to connect the chemistry to the microstructure. Although Al/Al2O3/RDX and Al/Al2O3/HTPB interfaces are chemically stable, the hot spot melts the AlxOy layers and create shear bands in aluminum domain due to thermomechanical strain created due to different thermal environment. In a shock-compressed microstructure without voids, the cohesive interaction and chemical composition of such interfaces for different phases of RDX will be presented.

  16. Detection of Amines and Ammonia with an Ambient Pressure Mass Spectrometer using a Corona Discharge Ion Source, in an Urban Atmosphere and in a Teflon Film Chamber

    NASA Astrophysics Data System (ADS)

    Alves, M.; Hanson, D. R.; Grieves, C.; Ortega, J. V.

    2015-12-01

    Amines and ammonia are an important group of molecules that can greatly affect atmospheric particle formation that can go on to impact cloud formation and their scattering of thermal and solar radiation, and as a result human health and ecosystems. In this study, an Ambient Pressure Mass Spectrometer (AmPMS) that is selective and sensitive to molecules with a high proton affinity, such as amines, was coupled with a newly built corona discharge ion source. AmPMS was used to monitor many different nitrogenous compound that are found in an urban atmosphere (July 2015, Minneapolis), down to the single digit pmol/mol level. Simultaneous to this, a proton transfer mass spectrometer also sampled the atmosphere through an inlet within 20 m of the AmPMS inlet. In another set of studies, a similar AmPMS was attached to a large Teflon film chamber at the Atmospheric Chemistry Division at NCAR (August 2015, Boulder). Exploratory studies are planned on the sticking of amines to the chamber walls as well as oxidizing the amine and monitoring products. Depending on the success of these studies, results will be presented on the reversability of amine partitioning and mass balance for these species in the chamber.

  17. Generation of microgrooved silica nanotube membranes with sustained drug delivery and cell contact guidance ability by using a Teflon microfluidic chip

    NASA Astrophysics Data System (ADS)

    Chen, Song; Shi, Xuetao; Chinnathambi, Shanmugavel; Wu, Hongkai; Hanagata, Nobutaka

    2013-02-01

    Silica nanotubes have been extensively applied in the biomedical field. However, very little attention has been paid to the fabrication and application of micropatterned silica nanotubes. In the present study, microgrooved silica nanotube membranes were fabricated in situ by microgrooving silica-coated collagen hybrid fibril hydrogels in a Teflon microfluidic chip followed by calcination for removal of collagen fibrils. Scanning electron microscopy images showed that the resulting silica nanotube membranes displayed a typical microgroove/ridge surface topography with ˜50 μm microgroove width and ˜120 μm ridge width. They supported adsorption of bone morphogenetic protein 2 (BMP-2) and exhibited a sustained release behavior for BMP-2. After culturing with osteoblast MC3T3-E1 cells, they induced an enhanced osteoblast differentiation due to the release of biologically active BMP-2 and a strong contact guidance ability to directly align and elongate osteoblasts due to the presence of microgrooved surface topography, indicating their potential application as a multi-functional cell-supporting matrix for tissue generation.

  18. Quantification of Gas-Wall Partitioning in Teflon Environmental Chambers Using Rapid Bursts of Low-Volatility Oxidized Species Generated in Situ.

    PubMed

    Krechmer, Jordan E; Pagonis, Demetrios; Ziemann, Paul J; Jimenez, Jose L

    2016-06-01

    Partitioning of gas-phase organic compounds to the walls of Teflon environmental chambers is a recently reported phenomenon than can affect the yields of reaction products and secondary organic aerosol (SOA) measured in laboratory experiments. Reported time scales for reaching gas-wall partitioning (GWP) equilibrium (τGWE) differ by up to 3 orders of magnitude, however, leading to predicted effects that vary from substantial to negligible. A new technique is demonstrated here in which semi- and low-volatility oxidized organic compounds (saturation concentration c* < 100 μg m(-3)) were photochemically generated in rapid bursts in situ in an 8 m(3) environmental chamber, and then their decay in the absence of aerosol was measured using a high-resolution chemical ionization mass spectrometer (CIMS) equipped with an "inlet-less" NO3(-) ion source. Measured τGWE were 7-13 min (rel. std. dev. 33%) for all compounds. The fraction of each compound that partitioned to the walls at equilibrium follows absorptive partitioning theory with an equivalent wall mass concentration in the range 0.3-10 mg m(-3). Measurements using a CIMS equipped with a standard ion-molecule reaction region showed large biases due to the contact of compounds with walls. On the basis of these results, a set of parameters is proposed for modeling GWP in chamber experiments. PMID:27138683

  19. No More HF: Teflon-Assisted Ultrafast Removal of Silica to Generate High-Surface-Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance.

    PubMed

    Singh, Dheeraj Kumar; Krishna, Katla Sai; Harish, Srinivasan; Sampath, Srinivasan; Eswaramoorthy, Muthusamy

    2016-02-01

    An innovative technique to obtain high-surface-area mesostructured carbon (2545 m(2)  g(-1)) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10 min) with complete elimination of toxic HF usage. The obtained carbon material (JNC-1) displays excellent CO2 capture ability (ca. 26.2 wt % at 0 °C under 0.88 bar CO2 pressure), which is twice that of CMK-3 obtained by the HF etching method (13.0 wt %). JNC-1 demonstrated higher H2 adsorption capacity (2.8 wt %) compared to CMK-3 (1.2 wt %) at -196 °C under 1.0 bar H2 pressure. The bimodal pore architecture of JNC-1 led to superior supercapacitor performance, with a specific capacitance of 292 F g(-1) and 182 F g(-1) at a drain rate of 1 A g(-1) and 50 A g(-1) , respectively, in 1 m H2 SO4 compared to CMK-3 and activated carbon. PMID:26836336

  20. Reaction of aluminous perovskite and water at high pressure and temperature and water transport into the lower mantle

    NASA Astrophysics Data System (ADS)

    Ohira, I.; Ohtani, E.; Sakai, T.; Miyahara, M.; Hirao, N.; Ohishi, Y.; Nishijima, M.

    2012-12-01

    Water cycle is an important issue in earth science, because water can affect rheological properties and melting temperature of the mantle. It has been clarified that water can be transported to at least deep upper mantle and the transition zone (e.g., Ono, 1998). The transition zone is believed to be a water reservoir in the earth, because wadsleyite and ringwoodite which compose the transition zone can contain 1 to 3 wt.% water (Inoue et al., 1995; Kohlstedt et al., 1996). However, it has been a debated matter whether water can be transported into the lower mantle and the core. Here we report the phase relation and mineral chemistry of MgSiO3-perovskite and delta-AlOOH obtained from a combination of in-situ X-ray diffraction measurements at high-pressure and high-temperature, and chemical analyses using scanning transmission electron microscope with an EDS detector (STEM-EDS). We used MgSiO3-Al2O3-H2O gel-samples for high-temperature and high-pressure experiments at the SPring-8 BL10XU. The bulk composition of the starting gel sample was 70 mol% MgSiO3 - 30 mol% Al2O3. H2O contents of the starting gel samples were 1.5 wt.%, 6.0wt.% and 7.0 wt.%. A double sided laser heating diamond anvil cell was used for generation of high pressure and temperature. The YAG (Nd) or fiber laser was used for heating the sample. A Pt foil or powder was mixed with the sample for the absorber of the laser. In situ X-ray diffraction was conducted in the pressure and temperature ranges of 55~87 GPa and 1700~2400 K. We observed a clear coexistence of perovskite and delta-AlOOH at 68 GPa and 2000 K. The chemical analysis of the recovered sample revealed that MgSiO3-perovskite coexisting with delta-AlOOH contains 6.6±2.2 mol.% Al2O3 and delta-AlOOH phase contains about 50 mol.% MgSiO3. Our results revealed a new reaction of aluminous perovskite and water to form a mixture of alumina-depleted perovskite and Mg, Si-bearing delta-AlOOH along the mantle geotherm under the lower mantle

  1. The effects of re-firing process under oxidizing atmosphere and temperatures on the properties of strontium aluminate phosphors

    SciTech Connect

    Karacaoglu, Erkul; Karasu, Bekir

    2013-10-15

    Graphical abstract: The comparative emission spectra of standard and re-fired Phosphor A under oxidizing atmosphere at various temperatures. The colour of Phosphor A re-fired at higher temperatures above 900 °C shifted from yellowish-green to bluish-green in the dark. But, the bluish-green emission could only be seen when it was exposed to UV and disappeared as soon as the light source was removed. Moreover, the emission intensities decreased as the re-firing temperatures increased. This could be attributed to the oxidation of Eu{sup 2+} during the re-firing process. It is well known fact from the literature that the reduction of Eu{sup 3+} to Eu{sup 2+} in appropriate host materials needs an annealing process in a reducing atmosphere such as H{sub 2}, H{sub 2}/N{sub 2} mixture or CO. Up to now, the reduction phenomena of Eu{sup 3+} → Eu{sup 2+} in air have been found in phosphates (Ba{sub 3}(PO{sub 4}){sub 2}:Eu), sulphates (BaSO{sub 4}:Eu), borates (SrB{sub 4}O{sub 7}:Eu, SrB{sub 6}O{sub 10}:Eu and BaB{sub 8}O{sub 13}:Eu) and aluminates (Sr{sub 4}Al{sub 14}O{sub 25}:Eu). Interestingly, an apparent blue shift in the phosphorescence spectrum was observed in the samples re-fired at 1000 °C and above, indicating a minimal effect on the oxidation state or the electronic energy levels of the co-doped Dy{sup 3+} ions, which were thought to act as long-lived hole traps resulting in long afterglow. - Highlights: • This study examines the effects re-firing at oxidizing atmosphere of photoluminescence of three different commercial SrAl{sub 2}O{sub 4}:Eu{sup 2+},Dy{sup 3+}-phosphors. • All the commercial SrAl{sub 2}O{sub 4}:Eu{sup 2+},Dy{sup 3+}-phosphors completely lost their phosphorescence after being re-fired at 1300 °C. • Oxidizing environment and re-firing temperature naturally affecting the valance of Eu{sup 2+} may cause the basic lattice structure to be modified and also limit their applications at higher temperatures, such as third firing vetrosa d

  2. Geochronological and geochemical constraints on the petrogenesis of late Triassic aluminous A-type granites in southeast China

    NASA Astrophysics Data System (ADS)

    Sun, Yang; Ma, Changqian; Liu, Yuanyuan; She, Zhenbing

    2011-11-01

    The late Permian-Triassic granites in the South China Block (SCB) have important tectonic significance for the evolution of East Asia. Most of the intrusive bodies in the central SCB consist of S-type granites. Here, we report the first unambiguous discovery of Wengshan aluminous A-type granites in southwest Zhejiang Province, southeast China. SHRIMP and LA-ICP-MS zircon U-Pb analyses yielded similar ages about 224 Ma for two samples from the Wengshan pluton, in concordance with peak time of late Indosinian (234-205 Ma) tectonic magmatic activity in the SCB. The Wengshan granites are peraluminous with A/CNK values ranging from 1.09 to 1.24, enriched in K, Rb, Th, REE and Zr + Nb + Ce + Y, have elevated FeO tot/MgO and Ga/Al ratios, and are depleted in Mg, Ca, Mn, Ba, Sr, P and Ti. In addition, they show high zircon saturation temperatures (820-878 °C). Their REE patterns are highly fractionated, with (La/Yb) N ratios of 36.89-101.24 and strongly negative Eu anomalies (Eu/Eu * = 0.28 - 0.53). In-situ zircon Hf isotopic analyses indicate that the Wengshan granites have ɛ Hf( t) values ranging from -15.9 to -12.7 and two-stage depleted mantle Hf model ages from 2.05 to 2.26 Ga. Sr-Nd isotope systematics are characterized by a high initial 87Sr/ 86Sr ratios of 0.7092-0.7218 and a low ɛNd( t) values of -15.0 to -12.1, with two-stage depleted mantle Nd model ages of 1.99-2.22 Ga, consistent with those of Paleoproterozoic basement rocks in the area. It is inferred that the Wengshan granite magma formed by partial melting of Paleoproterozoic metasedimentary sources in Cathaysia Block. Meanwhile, the underplating of mafic magma in the lower crust may provide the heat source for the formation of the Wengshan granites. The data show that the Wengshan granites, unlike other S-type granites in the SCB, are late Triassic aluminous A-type granite. Therefore they may indicate distinct geodynamic significance. Our study of the Wengshan A-type granites (224 Ma), together with

  3. Low temperature synthesis of nanocrystalline magnesium aluminate with high surface area by surfactant assisted precipitation method: Effect of preparation conditions

    SciTech Connect

    Mosayebi, Zeinab; Rezaei, Mehran; Hadian, Narges; Kordshuli, Fazlollah Zareie; Meshkani, Fereshteh

    2012-09-15

    Highlights: ► MgAl{sub 2}O{sub 4} showed a high surface area and nanocrystalline structure. ► Addition of polymeric surfactant affected the structural properties of MgAl{sub 2}O{sub 4}. ► MgAl{sub 2}O{sub 4} prepared with surfactant showed a hollow cylindrical shape. -- Abstract: A surfactant assisted co-precipitation method was employed for the low temperature synthesis of magnesium aluminate spinel with nanocrystalline size and high specific surface area. Pluronic P123 triblock copolymer and ammonia solution were used as surfactant and precipitation agent, respectively. The prepared samples were characterized by thermal gravimetric and differential thermal gravimetric analyses (TG/DTG), X-ray diffraction (XRD), N{sub 2} adsorption (BET) and transmission electron microscopy (TEM) techniques. The effects of several process parameters such as refluxing temperature, refluxing time, pH, P123 to metals mole ratio (P123/metals) and calcination temperature on the structural properties of the samples were investigated. The obtained results showed that, among the process parameters pH and refluxing temperature have a significant effect on the structural properties of samples. The results revealed that increase in pH from 9.5 to 11 and refluxing temperature from 40 °C to 80 °C increased the specific surface area of prepared samples in the range of 157–188 m{sup 2} g{sup −1} and 162–184 m{sup 2} g{sup −1}, respectively. The XRD analysis showed the single-phase MgAl{sub 2}O{sub 4} was formed at 700 °C.

  4. Determination of trace rare earth elements in gadolinium aluminate by inductively coupled plasma time of flight mass spectrometry

    NASA Astrophysics Data System (ADS)

    Saha, Abhijit; Deb, S. B.; Nagar, B. K.; Saxena, M. K.

    An analytical methodology was developed for the precise quantification of ten trace rare earth elements (REEs), namely, La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, and Tm, in gadolinium aluminate (GdAlO3) employing an ultrasonic nebulizer (USN)-desolvating device based inductively coupled plasma mass spectrometry (ICP-MS). A microwave digestion procedure was optimized for digesting 100 mg of the refractory oxide using a mixture of sulphuric acid (H2SO4), phosphoric acid (H3PO4) and water (H2O) with 1400 W power, 10 min ramp and 60 min hold time. An USN-desolvating sample introduction system was employed to enhance analyte sensitivities by minimizing their oxide ion formation in the plasma. Studies on the effect of various matrix concentrations on the analyte intensities revealed that precise quantification of the analytes was possible with matrix level of 250 mg L- 1. The possibility of using indium as an internal standard was explored and applied to correct for matrix effect and variation in analyte sensitivity under plasma operating conditions. Individual oxide ion formation yields were determined in matrix matched solution and employed for correcting polyatomic interferences of light REE (LREE) oxide ions on the intensities of middle and heavy rare earth elements (MREEs and HREEs). Recoveries of ≥ 90% were achieved for the analytes employing standard addition technique. Three real samples were analyzed for traces of REEs by the proposed method and cross validated for Eu and Nd by isotope dilution mass spectrometry (IDMS). The results show no significant difference in the values at 95% confidence level. The expanded uncertainty (coverage factor 1σ) in the determination of trace REEs in the samples were found to be between 3 and 8%. The instrument detection limits (IDLs) and the method detection limits (MDLs) for the ten REEs lie in the ranges 1-5 ng L- 1 and 7-64 μg kg- 1 respectively.

  5. The influence of lithium fluoride on in vitro biocompatibility and bioactivity of calcium aluminate-pMMA composite cement.

    PubMed

    Oh, S H; Choi, S Y; Choi, S H; Lee, Y K; Kim, K N

    2004-01-01

    The objective of this study is to assess the influence of lithium fluoride on in vitro biocompatibility and bioactivity of calcium aluminate (CA)-polymethylmethacrylate (PMMA) composite cement exhibiting quick setting time ( < 15 min), low exothermic temperature (< 47 degrees C), and high compressive strength (> 100 MPa). The biocompatibility was measured by examining cytotoxicity tests such as the agar diffusion test with L929 cell line and the hemolysis test with fresh rabbit blood. To estimate the bioactivity of CA-PMMA composite cement, we determined hydroxyapatite (HAp) formation on the surface of composite cement in the simulated body (SBF) solution by using thin-film XRD, XPS, SEM, EPMA and ICP-AES. The results of biocompatibility tests indicated that all experimental compositions of this study had no cytotoxicity and no hemolysis so that there was no cytotoxicity with regard to non-reacted monomers (MMA and TEGDMA) and lithium fluoride. The results of bioactivity tests revealed that CA-PMMA composite cement without lithium fluoride did not form HAp on its surface after 60 days of soaking in the SBF. On the other hand, LiAl2(OH)7 . 2H2O and HAp were formed on the surface of CA-PMMA composite cement including 1.0% by weight of lithium fluoride after 7 and 15 days of soaking in the SBF, respectively. The 5 microm of LiAl2(OH)7 . 2H2O and HAp mixed layers were formed on the surface of specimen after 60 days of soaking in the SBF. PMID:15338588

  6. Growth of epitaxial films of sodium potassium tantalate and niobate on single-crystal lanthanum aluminate [100] substrates

    SciTech Connect

    Thomas, George H.; Specht, Eliot D; Larese, John Z; Xue, Ziling; Beach, David B

    2008-01-01

    Epitaxial films of sodium potassium tantalate (Na{sub 0.5}K{sub 0.5}TaO{sub 3}, NKT) and sodium potassium niobate (Na{sub 0.5}K{sub 0.5}NbO{sub 3}, NKN) were grown on single-crystal lanthanum aluminate (LAO) (100) (indexed as a pseudo-cubic unit cell) substrates via an all-alkoxide solution (methoxyethoxide complexes in 2-methoxyethanol) deposition route for the first time. X-ray diffraction studies indicated that the onset of crystallization in powders formed from hydrolyzed gel samples was 550 C. {sup 13}C nuclear magnetic resonance studies of solutions of methoxyethoxide complexes indicated that mixed-metal species were formed, consistent with the low crystallization temperatures observed. Thermal gravimetric analysis with simultaneous mass spectrometry showed the facile loss of the ligand (methoxyethoxide) at temperatures below 400 C. Crystalline films were obtained at temperatures as low as 650 C when annealed in air. {theta}-2{theta} x-ray diffraction patterns revealed that the films possessed c-axis alignment in that only (h00) reflections were observed. Pole-figures about the NKT or NKN (220) reflection indicated a single in-plane, cube-on-cube epitaxy. The quality of the films was estimated via {omega} (out-of-plane) and {psi} (in-plane) scans and full-widths at half-maximum (FWHMs) were found to be reasonably narrow ({approx}1{sup o}), considering the lattice mismatch between the films and the substrate.

  7. Homoleptic borates and aluminates containing the difluorophosphato ligand - [M(O2PF2)x](y-) - synthesis and characterization.

    PubMed

    Schulz, Christoph; Eiden, Philipp; Klose, Petra; Ermantraut, Andreas; Schmidt, Michael; Garsuch, Arnd; Krossing, Ingo

    2015-04-21

    Weakly coordinating anions (WCAs) with the difluorophosphato ligand (O2PF2) were the target of this study. Initial experiments were conducted towards the preparation of homoleptic aluminates of the well-studied [Al(OR)4](-)-type. The preparation of the initial target structure Li[Al(O2PF2)4] failed due to the remaining Lewis acidic character of the central aluminum atom. Instead, the formation of Li3[Al(O2PF2)6] and Al(O2PF2)3 was observed with hexacoordinate aluminum atoms and verified by NMR, IR and X-ray crystallography. A possible mechanism towards these compounds was postulated in the solvent induced dismutation of the tetracoordinate Li[Al(O2PF2)4]. A singly charged WCA was realized by the exchange of the central aluminum atom for boron. The [B(O2PF2)4](-) anion was prepared starting from BH3·S(CH3)2 and boron tribromide leading to the protic room temperature Ionic Liquid (IL) [H(S(CH3)2)][B(O2PF2)4] and the neat liquid Brønsted acid H[B(O2PF2)4], respectively, representing a significantly improved synthesis with regard to the first experiments of Dove et al. The basicity of the [B(O2PF2)4](-) anion and its WCA quality were investigated on the basis of the IR-spectroscopic NH-scale and the salt [H(N(Oct)3)][B(O2PF2)4] that places it better than all oxyanions and close to the carboranate based WCAs. A pathway to the solvent free pure Li[B(O2PF2)4] salt was established on a multi-gram scale with excellent purities enabling electrochemical applications (verified by NMR, IR, X-ray crystallography and cyclovoltammetry). PMID:25785817

  8. Polymorphism of the iron doped strontium aluminate SrAl 1.5Fe 0.5O 4

    NASA Astrophysics Data System (ADS)

    Desmoulins, H.; Malo, S.; Boudin, S.; Caignaert, V.; Hervieu, M.

    2009-07-01

    The partial substitution of Al by Fe atoms in SrAl 2O 4 allowed to stabilize four stuffed tridymite derivative structures SrAl 1.5Fe 0.5O 4. The different phases have been characterized by TEM and XRPD techniques. Two are isotypes of those observed for the undoped oxides, namely the hexagonal phase with √{3}A× √{3}A× C (with A and C being the tridymite unit cell parameters) and space group P6 3 and the monoclinic one with A× √{3}A× C, β≈93° and space group P2 1, with a synthesis temperature lower than the one required for SrAl 2O 4. By annealing, two original phases, denoted O 1 and O 2, are obtained; they are metrically similar (3 A× √{3}A× C and β≈90°) and only differ by their space groups. The TEM study showed that the transitions between the different phases follow topotactic mechanisms, through the formation of twinning boundaries, antiphase boundaries and planar defects. The annealed sample exhibits a mesomorph state and a reversible transition from this semi-ordered state to a crystalline phase. This dynamic transition takes place over a very wide temperature range from 620 to 1120 °C. The reversibility of the transition has been studied by DSC measurements. The crystallization energy of the orthorhombic phases is of the order of 10 J/g, at T≈622 °C as T decreases. The variation of the peak height observed as the annealing temperature increases is explained by the complex microstructures, which create an ill-defined energy barrier. Structural models related to the stuffed tridymite derivative structures are proposed for the new forms of the ferri-aluminate.

  9. Atomically smooth and homogeneously N-polar AlN film grown on silicon by alumination of Si{sub 3}N{sub 4}

    SciTech Connect

    Hu, Jiannan; Hao, Zhibiao; Niu, Lang; Yanxiong E,; Wang, Lai; Luo, Yi

    2013-04-08

    By using an alumination process of Si{sub 3}N{sub 4} at high temperature with aluminum flux irradiation for sufficient time, homogeneously N-polar and atomically smooth AlN film has been realized on silicon substrate with inversion domain suppressed to less than 3.0 Multiplication-Sign 10{sup 6} cm{sup -2} and root mean square surface roughness of {approx}0.4 nm. A general interface model is proposed to explain the mechanism of polarity determination. The sharp AlN(0001)/Si(111) interface exhibits 5:4 coincidence domain matching, resulting in an almost fully relaxed AlN film.

  10. Bonding Preferences of Non-Bridging Oxygens in Calcium Aluminosilicate Glass: Evidence from O-17 MAS and 3QMAS NMR on Calcium Aluminate Glass

    NASA Astrophysics Data System (ADS)

    Allwardt, J. R.; Lee, S.; Stebbins, J.

    2001-12-01

    Non-bridging oxygens (NBO's) play a significant role in the thermodynamic and transport properties in glasses and silicate melts. Previous oxygen-17 (O-17) triple quantum magic angle spinning (3QMAS NMR) data have shown the presence of NBO's in several calcium aluminosilicate (CAS) glasses on the CaAl2O4-SiO2 join (Stebbins and Xu 1997). The observed chemical shifts of these glasses are similar to those for the NBO in calcium silicate glasses (Stebbins et al. 1997 and Stebbins et al 1999); however, a recent O-17 MAS NMR study of crystalline CaAl2O4 showed that the NBO peak in an associated impurity phase is shifted to a higher frequency by 30 to 40 ppm from that of CAS and Ca-silicate glasses (Stebbins et al. in press). This finding suggests that Si is the preferred network cation for NBO's in aluminosilicate glasses and melts at the glass transition temperature. The preference for Si over that of Al as the network cation host for NBO's has also been suggested by Raman and other spectroscopic techniques (Mysen 1988). To investigate this apparent preference for Si-NBO, O-17 3QMAS and MAS experiments were conducted to examine the location of the NBO peak in the spectra of a calcium aluminate glass. Since the CaAl2O4 glass is difficult to make by conventional cooling methods, the binary eutectic composition (63CaO-37Al2O3) was chosen. The resulting O-17 MAS spectrum shows an intense, relatively narrow peak centered at 72 ppm, which nearly coincides with the peak location and width of the Al-O-Al peak in the crystalline Ca-aluminates (Stebbins et al. in press.) (70 ppm). There is a broader, less intense peak centered at 155 ppm that is assigned to the Al-NBO peak. This peak is in approximately the same location as that for a Ca-aluminate phase reported by Stebbins et al. (in press) (137 ppm). In addition, our 3QMAS data show that the peak maximum of the NBO in the Ca-aluminate (-85 and 150 ppm in isotropic and MAS dimensions, respectively) differs significantly from

  11. Emergence of electrophilic alumination as the counterpart of established nucleophilic lithiation: an academic sojourn in organometallics with William Kaska as fellow traveler.

    PubMed

    Eisch, John J

    2015-04-21

    William Kaska pursued doctoral studies with John Eisch in mechanistic organometallic chemistry, first with organolithium reactions at St. Louis University and then at the University of Michigan with organoaluminum reactions. Thereby he revealed the change in mechanism from nucleophilic lithiation and carbolithiation to that of electrophilic alumination, carboalumination and hydroalumination of organic substrates, which reactions were previously observed by Karl Ziegler in his empirical studies of organoaluminum reactions. Our findings were the first mechanistic studies attempting to set such Ziegler chemistry on a modern theoretical basis. PMID:25820225

  12. Complex permittivity of lanthanum aluminate in the 20 to 300 K temperature range from 26.5 to 40.0 GHz

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Ebihara, B. T.; Heinen, V. O.; Chorey, C. M.

    1990-01-01

    Dielectric constants of microwave substrates are required in the design of superconducting microwave circuits at various temperatures. In this paper, the results are reported of a study of the complex permittivity of the newly developed lanthanum aluminate (LaAlO3) substrate, in the 20 to 300 K temperature range at frequencies from 26.5 to 40.0 GHz. The value of the complex permittivity was obtained by measuring the sample scattering parameters using a microwave waveguide technique. It is observed that, while the dielectric constant did not change appreciably with frequency, its value decreased by approximately 14 percent from room temperature to 20 K.

  13. Silver-Teflon coating improvement

    NASA Technical Reports Server (NTRS)

    Reed, M. W.

    1976-01-01

    Approximately forty adhesives were subjected to laboratory screening. Seven candidate adhesives were selected from the screening tests and evaluated in a thermal vacuum test on radiator panels similar to the anticipated flight hardware configuration. Several classes of adhesives based on epoxide, polyester, silicone, and urethane resin systems were tested. These included contact adhesives, heat cured adhesives, heat and pressure cured adhesives, pressure sensitive adhesives, and two part paint-on or spray-on adhesives. The panels were tested in a space environmental simulation laboratory chamber during the July 9-20, 1973 time span.

  14. The influence of starch oxidization and aluminate coupling agent on interfacial interaction, rheological behavior, mechanical and thermal properties of poly(propylene carbonate)/starch blends

    NASA Astrophysics Data System (ADS)

    Jiang, Guo; Zhang, Shui-Dong; Huang, Han-Xiong; The Key Laboratory of Polymer Processing Engineering of the Ministry of Education Team

    Poly(propylene carbonate) (PPC) is a kind of new biodegradable polymer that is synthesized by copolymerization of propylene oxide and carbon dioxide. In this work, PPC end-capped with maleic anhydride (PPCMA)/thermoplastic starch (TPS), PPCMA/thermoplastic oxidized starch (TPOS) and PPCMA/AL-TPOS (TPOS modified by aluminate coupling agent) blends were prepared by melt blending to improve its thermal and mechanical properties. FTIR results showed that there existed hydrogen-bonding interaction between PPCMA and starch. SEM observation revealed that the compatibility between PPCMA and TPOS was improved by the oxidation of starch. The enhanced interfacial interactions between PPCMA and TPOS led to a better performance of PPC blends such as storage modulus (G'), loss modulus (G''), complex viscosity (η*), tensile strength and thermal properties. Furthermore, the modification of TPOS by aluminate coupling agent (AL) facilitated the dispersion of oxidized starch in PPC matrix, and resulted in increasing the tensile strength and thermal stability. National Natural Science Foundation of China, National Science Fund of Guangdong Province.

  15. Photocatalytic NO{sub x} abatement by calcium aluminate cements modified with TiO{sub 2}: Improved NO{sub 2} conversion

    SciTech Connect

    Pérez-Nicolás, M.; Navarro-Blasco, I.; Fernández, J.M.

    2015-04-15

    Photocatalytic activity of TiO{sub 2} was studied in two types of calcium aluminate cement (CAC) under two different curing regimes. The effect of the TiO{sub 2} addition on the setting time, consistency and mechanical properties of the CACs was evaluated. The abatement of gaseous pollutants (NO{sub x}) under UV irradiation was also assessed. These cementitious matrices were found to successfully retain NO{sub 2}: more abundant presence of aluminates in white cement (w-CAC, iron-lean) helped to better adsorb NO{sub 2}, thus improving the conversion performance of the catalyst resulting in a larger NO{sub x} removal under UV irradiation. As evidenced by XRD, SEM, EDAX and zeta potential analyses, the presence of ferrite in dark cement (d-CAC, iron-reach) induced a certain chemical interaction with TiO{sub 2}. The experimental findings suggest the formation of new iron titanate phases, namely pseudobrookite. The reduced band-gap energy of these compounds compared with that of TiO{sub 2} accounts for the photocatalytic activity of these samples.

  16. A novel synthetic route for magnesium aluminate (MgAl2O4) nanoparticles using sol-gel auto combustion method and their photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Nassar, Mostafa Y.; Ahmed, Ibrahim S.; Samir, Ihab

    2014-10-01

    In this paper a novel and inexpensive route for the preparation of spinel magnesium aluminate nanoparticles (MgAl2O4) is proposed. Magnesium aluminate photocatalyst was synthesized via sol-gel auto combustion method using oxalic acid, urea, and citric acid fuels at 350 °C. Subsequently, the burnt samples were calcined at different temperatures. The pure spinel MgAl2O4 with average crystallite size 27.7, 14.6 and 15.65 nm was obtained at 800 °C calcinations using the aforementioned fuels, respectively. The obtained samples were characterized by powder X-ray diffraction, Fourier transform infrared, UV-Vis spectroscopy, transmission electron microscope, scanning electron microscope. The photo catalytic activity of MgAl2O4 product was studied by performing the decomposition of Reactive Red Me 4BL dye under UV illumination or sunlight irradiation. The dye considerably photocatalytically degraded by 90.0% and 95.45% under UV and sunlight irradiation, respectively, within ca. 5 h with pseudo first order rate constants of 5.85 × 10-3 and 8.38 × 10-3 min-1, respectively.

  17. A novel synthetic route for magnesium aluminate (MgAl2O4) nanoparticles using sol-gel auto combustion method and their photocatalytic properties.

    PubMed

    Nassar, Mostafa Y; Ahmed, Ibrahim S; Samir, Ihab

    2014-10-15

    In this paper a novel and inexpensive route for the preparation of spinel magnesium aluminate nanoparticles (MgAl2O4) is proposed. Magnesium aluminate photocatalyst was synthesized via sol-gel auto combustion method using oxalic acid, urea, and citric acid fuels at 350°C. Subsequently, the burnt samples were calcined at different temperatures. The pure spinel MgAl2O4 with average crystallite size 27.7, 14.6 and 15.65nm was obtained at 800°C calcinations using the aforementioned fuels, respectively. The obtained samples were characterized by powder X-ray diffraction, Fourier transform infrared, UV-Vis spectroscopy, transmission electron microscope, scanning electron microscope. The photo catalytic activity of MgAl2O4 product was studied by performing the decomposition of Reactive Red Me 4BL dye under UV illumination or sunlight irradiation. The dye considerably photocatalytically degraded by 90.0% and 95.45% under UV and sunlight irradiation, respectively, within ca. 5h with pseudo first order rate constants of 5.85×10(-3) and 8.38×10(-3)min(-1), respectively. PMID:24835935

  18. SO 2 adsorption and thermal stability and reducibility of sulfates formed on the magnesium-aluminate spinel sulfur-transfer catalyst

    NASA Astrophysics Data System (ADS)

    Wang, Jin-an; Li, Cheng-lie

    2000-07-01

    Magnesium-aluminate spinel used as a sulfur-transfer catalyst in the fluid catalytic cracking units for SO x emission control was prepared by the precipitation method. The crystalline structure, textural property, and surface dehydroxylation of the sample were characterized by thermogravimetry-derivative thermogravimetry (TG-DTG), differential thermal analysis (DTA), X-ray diffraction (XRD), liquid N 2 adsorption-desorption and infrared spectroscopy (IR) measurements. The behavior of SO 2 adsorption and oxidation on the surface of catalyst was evaluated with IR from 50°C to 600°C. Particularly, the thermal stability and H 2-reducibility of the formed sulfite or sulfate during SO 2 adsorption or oxidation were tested under various conditions. In the absence of oxygen in the feed mixture, weak physically adsorbed SO 2 species and surface sulfite were identified. In the case of SO 2 oxidative adsorption, both surface sulfate and bulk-like sulfate were formed. When the sulfated sample was reduced with hydrogen, the surface sulfite and sulfates were completely removed below 550°C in vacuum. The bulk-like sulfate, however, showed a high ability to resist H 2-reduction, which indicates that the reducibility of bulk-like sulfate formed on magnesium-aluminate spinel must be enhanced when it is used as a sulfur-transfer catalyst.

  19. Structural and luminescent properties of Eu2+ and Nd3+-doped mixed alkaline earth aluminates prepared by the sol-gel method.

    PubMed

    Čelan Korošin, Nataša; Bukovec, Nataša; Bukovec, Peter

    2015-01-01

    Alkaline earth aluminates with the overall nominal compositions Mg0.5Sr0.5Al2O4 (MSA), Ca0.5Mg0.5Al2O4 (CMA) and Ca0.5Sr0.5Al2O4 (CSA) doped with 0.5 mol% of Eu2+ and 0.25 mol% of Nd3+ ions were obtained by a modified aqueous sol-gel method and annealed in a reducing atmosphere at 900, 1000, 1100 and 1300 °C. The sample structures were investigated by XRD. Solid solubility was only confirmed for the CSA samples. UV-excited luminescence was observed in the blue region (λ = 440 nm) in the samples of CMA containing the monoclinic CaAl2O4 phase and in the green region (λ = 512 nm) in the samples of MSA containing hexagonal or monoclinic phases of SrAl2O4. The CSA samples, besides the blue region, exhibited an extended shoulder in the green region, which proved the existence of some pure strontium phases. Co-doped Nd3+ ions did not affect the wavelength of the emitted light, but the persistent luminescence at room temperature was greatly extended with respect to the aluminates doped with Eu2+ ions only. PMID:26085411

  20. Studies on densification, mechanical, micro-structural and structure–properties relationship of magnesium aluminate spinel refractory aggregates prepared from Indian magnesite

    SciTech Connect

    Ghosh, Chandrima; Ghosh, Arup; Haldar, Manas Kamal

    2015-01-15

    The present work intends to study the development of magnesium aluminate spinel aggregates from Indian magnesite in a single firing stage. The raw magnesite has been evaluated in terms of chemical analysis, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction. The experimental batch containing Indian magnesite and calcined alumina has been sintered in the temperature range of 1550 °C–1700 °C. The sintered material has been characterized in terms of physico-chemical properties like bulk density, apparent porosity, true density, relative density and thermo-mechanical/mechanical properties like hot modulus of rupture, thermal shock resistance, cold modulus of rupture and structural properties by X-ray diffraction in terms of phase identification and evaluation of crystal structure parameters of corresponding phases by Rietveld analysis. The microstructures developed at different temperatures have been analyzed by field emission scanning electron microscope study and compositional analysis of the developed phase has been carried out by energy dispersive X-ray study. - Highlights: • The studies have been done to characterize the developed magnesium aluminate spinel. • The studies reveal correlation between refractory behavior of spinel and developed microstructures. • The studies show the values of lattice parameters of developed phases.

  1. Arc track resistant polymers for space applications

    NASA Technical Reports Server (NTRS)

    Haghighat, Ross

    1995-01-01

    The properties and test methods of aorimide polymers, kapton, and fep teflon are given in table format. Graphic depiction of an atomic oxygen resistance comparison, arc track resistance set-up and arc incident vs. propagation are given.

  2. The stability of hibonite and other aluminous phases in silicate melts: Implications for the origin of hibonite-bearing inclusions

    NASA Technical Reports Server (NTRS)

    Beckett, J. R.; Stolper, E.

    1993-01-01

    Phase fields in which hibonite (Hib) and silicate melt coexist with spinel (Sp), CaAl4O7 (CA2), gehlenitic melilite (Mel), anorthite (An), or corundum (Cor) in the system CaO-MgO-Al203-SiO2-TiO2 (CMAST) were determined and activity models developed for Mel and Hib solid solutions. Experimentally determined partition coefficients for Ti between Hib and coexisting melt, D sub t, vary from 0.8 to 2.1 and generally decrease with increasing TiO2 content in the liquid (L). Based on Ti partioning between Hib and melt, bulk inclusion compositions and Hib-saturated liquid use phase diagrams, the Hib in Fluffy Type A inclusions (FTA's) from Allende and at least some of the Hib from Hib-rich inclusions is relict; much of the Hib from Hib-glass spherules probably crystallized from a melt under nonequilibrium conditions. Bulk compositions for all of these Ca-Al-rich inclusions (CAI's) are consistent with an origin as Mel + Hib + Sp + perovskite (Pv) proto-inclusions in which Mel was partially altered. In some cases, the proto-inclusion was partially or completely melted with vaporization occurring over a period of time sufficient to remove any Na introduced by the alteration process but frequently insufficient to dissolve all of the original hibonite. If equilibration temperatures based on Hib-bearing CAI's reflect condensation in a cooling gas of solar composition, then Hib + Cor condensed at approximately 1260 C (referenced to 10 exp -3 atm) and Hib + Sp + Mel at approximately 1215 +/- 10 C. Simple thermochemical models for the substitution of trace elements into the Ca-site of meteoritic Hib suggest that virtually all Eu is divalent in early condensate Hibs but that Eu(2+)/Eu(3+) decreases by a factor of 20 or more during the course of condensation, primarily because the ratio is proportional to the partial pressure of Al, which decreases dramatically as aluminous phases condense. The relative sizes of Eu and Yb anomalies in meteoritic Hibs and CAI's may be influenced by

  3. Effect of particle size on the experimental dissolution and auto-aluminization processes of K-vermiculite

    NASA Astrophysics Data System (ADS)

    Viennet, Jean-Christophe; Hubert, Fabien; Tertre, Emmanuel; Ferrage, Eric; Robin, Valentin; Dzene, Liva; Cochet, Carine; Turpault, Marie-Pierre

    2016-05-01

    In acidic soils, the fixation of Al in the interlayer spaces of 2:1 clay minerals and the subsequent formation of hydroxyl interlayer minerals (HIMs) are known to reduce soil fertility. The resulting crystal structure of HIMs consist of complex mixed-layer minerals (MLMs) with contrasting relative proportions of expandable, hydroxy-interlayers (HI) and illite layers. The present study aims to experimentally assess the influence of particle size on the formation of such complex HIMs for vermiculite saturated with potassium (K). Based on chemical and structural data, this study reports the dissolution and Al-interlayer occupancy of three size fractions (0.1-0.2, 1-2 and 10-20 μm) of K-vermiculite, which were obtained at pH = 3 by using stirred flow-through reactors. The Al-interlayer occupancies were ordered 0.1-0.2 μm < 10-20 μm < 1-2 μm even though the dissolution rate (in molvermiculite g-1 s-1) increases with decreasing particle size. For fine particles (0.1-0.2 μm), a rapid but low Al-interlayer occupancy during the transitory state and a null rate in the steady-state were evidenced and interpreted as indicating (i) a rapid but limited K+ interlayer exchange during the first step of the overall reactions and (ii) a stoichiometric dissolution of the crystal (TOT layer + interlayer) in the steady-state. By contrast, although the stoichiometric dissolution of the TOT layer is reached in the steady-state for the coarsest fractions (10-20 and 1-2 μm), the Al-interlayer occupancies continue to evolve due to the exchange of interlayer K+, which continues to progress for a longer duration. The mechanism of auto-aluminization is interpreted in the present study as multiple processes that involve (i) the dissolution of the mineral under acidic conditions, (ii) the interlayer diffusion of initial interlayer cations and their exchange with those from the aqueous phase and (iii) the fixation of interlayer aluminum. Competition between the kinetics of ion

  4. Evaluation of Thermal Control Coatings and Polymeric Materials Exposed to Ground Simulated Atomic Oxygen and Vacuum Ultraviolet Radiation

    NASA Technical Reports Server (NTRS)

    Kamenetzky, R. R.; Vaughn, J. A.; Finckenor, M. M.; Linton, R. C.

    1995-01-01

    Numerous thermal control and polymeric samples with potential International Space Station applications were evaluated for atomic oxygen and vacuum ultraviolet radiation effects in the Princeton Plasma Physics Laboratory 5 eV Neutral Atomic Oxygen Facility and in the MSFC Atomic Oxygen Drift Tube System. Included in this study were samples of various anodized aluminum samples, ceramic paints, polymeric materials, and beta cloth, a Teflon-impregnated fiberglass cloth. Aluminum anodizations tested were black duranodic, chromic acid anodize, and sulfuric acid anodize. Paint samples consisted of an inorganic glassy black paint and Z-93 white paint made with the original PS7 binder and the new K2130 binder. Polymeric samples evaluated included bulk Halar, bulk PEEK, and silverized FEP Teflon. Aluminized and nonaluminized Chemfab 250 beta cloth were also exposed. Samples were evaluated for changes in mass, thickness, solar absorptance, and infrared emittance. In addition to material effects, an investigation was made comparing diffuse reflectance/solar absorptance measurements made using a Beckman DK2 spectroreflectometer and like measurements made using an AZ Technology-developed laboratory portable spectroreflectometer.

  5. Influence of self heating and Li{sub 2}SO{sub 4} addition on the microstructural development of calcium aluminate cement

    SciTech Connect

    Gosselin, Christophe Gallucci, Emmanuel; Scrivener, Karen

    2010-10-15

    Hydrated Calcium Aluminate Cement (CAC) is known to have a complex microstructure involving different phase assemblages strongly dependant on the temperature. This work presents an experimental approach to study the microstructure of CAC pastes from the first minute of hydration with controlled time-temperature histories up to several months of curing. The self heating usually occurring in the CAC concrete is considered and its influence on the growth and assemblage of the hydration products and subsequent space filling is shown. Quantification of the degree of CA hydration by BSE image analysis is used to understand the evolution of phases throughout the hydration process. Lithium sulphate is commonly used to control the setting time of CAC based materials. It is shown that this promotes the formation of more stable hydrates, but slightly reduces the extent of CA hydration.

  6. Synergistic use of Knudsen effusion quadrupole mass spectrometry, solid-state galvanic cell and differential scanning calorimetry for thermodynamic studies on lithium aluminates

    NASA Astrophysics Data System (ADS)

    Rakshit, S. K.; Naik, Y. P.; Parida, S. C.; Dash, Smruti; Singh, Ziley; Sen, B. K.; Venugopal, V.

    2008-06-01

    Three ternary oxides LiAl 5O 8(s), LiAlO 2(s) and Li 5AlO 4(s) in the system Li-Al-O were prepared by solid-state reaction route and characterized by X-ray powder diffraction method. Equilibrium partial pressure of CO 2(g) over the three-phase mixtures {LiAl 5O 8(s)+Li 2CO 3(s)+5Al 2O 3(s)}, {LiAl 5O 8(s)+5LiAlO 2(s)+2Li 2CO 3(s)} and {LiAlO 2(s)+Li 5AlO 4(s)+2Li 2CO 3(s)} were measured using Knudsen effusion quadrupole mass spectrometry (KEQMS). Solid-state galvanic cell technique based on calcium fluoride electrolyte was used to determine the standard molar Gibbs energies of formations of these aluminates. The standard molar Gibbs energies of formation of these three aluminates calculated from KEQMS and galvanic cell measurements were in good agreement. Heat capacities of individual ternary oxides were measured from 127 to 868 K using differential scanning calorimetry. Thermodynamic tables representing the values of Δ fH0(298.15 K), S0(298.15 K) S0( T), Cp0( T), H0( T), { H0( T)- H0(298.15 K)}, G0( T), Δ fH0( T), Δ fG 0( T) and free energy function (fef) were constructed using second law analysis and FACTSAGE thermo-chemical database software.

  7. Reactive molecular dynamics simulation on the disintegration of Kapton, POSS polyimide, amorphous silica, and teflon during atomic oxygen impact using the ReaxFF reactive force-field method.

    PubMed

    Rahnamoun, A; van Duin, A C T

    2014-04-17

    Atomic oxygen (AO) is the most abundant element in the low Earth orbit (LEO). It is the result of the dissociation of molecular oxygen by ultraviolet radiation from the sun. In the LEO, it collides with the materials used on spacecraft surfaces and causes degradation of these materials. The degradation of the materials on the surface of spacecrafts at LEO has been a significant problem for a long time. Kapton polyimide, polyhedral oligomeric silsesquioxane (POSS), silica, and Teflon are the materials extensively used in spacecraft industry, and like many other materials used in spacecraft industry, AO collision degradation is an important issue in their applications on spacecrafts. To investigate the surface chemistry of these materials in exposure to space AO, a computational chemical evaluation of the Kapton polyimide, POSS, amorphous silica, and Teflon was performed in separate simulations under similar conditions. For performing these simulations, the ReaxFF reactive force-field program was used, which provides the computational speed required to perform molecular dynamics (MD) simulations on system sizes sufficiently large to describe the full chemistry of the reactions. Using these simulations, the effects of AO impact on different materials and the role of impact energies, the content of material, and temperature of material on the behavior of the materials are studied. The ReaxFF results indicate that Kapton is less resistant than Teflon toward AO damage. These results are in good agreement with experiment. These simulations indicate that the amorphous silica shows the highest stability among these materials before the start of the highly exothermic silicon oxidation. We have verified that adding silicon to the bulk of the Kapton structure enhances the stability of the Kapton against AO impact. Our canonical MD simulations demonstrate that an increase in the heat transfer in materials during AO impact can provide a considerable decrease in the

  8. Synthesis and characterization of metal complexes containing tetrazolate, poly(tetrazolyl)borate, and poly(azolyl)aluminate ligands as high energy density materials

    NASA Astrophysics Data System (ADS)

    Snyder, Christopher James

    A series of heavy alkaline earth metal tetrazolate complexes has been synthesized that contain metal ions saturated by aqua ligands. Tetrazolates with small ring-core carbon substituents favor formation of two dimensional polymers with micro3-coordination of the tetrazolate to the metal centers. Tetrazolates with bulkier groups block coordination to the 1- and 4-nitrogen atoms, resulting in monomer formation. The first example of a trihydro(tetrazolyl)borate was prepared, and its bonding is heavily influenced by the basic BH3 moiety. 18-Crown-6 adducts of dihydrobis(tetrazolyl)borate complexes have been prepared that contain B-N bonding to the 2-nitrogen atoms, due to bulky ring-core atom substituents. A series of alkali metal hydrotris(tetrazolyl)borate complexes has been prepared by closely monitoring the reactions by electrospray ionization-mass spectrometry. The lithium hydrotris(tetrazolyl)borate complex contains kappa3-N,N,N bonding that is analgous to the bonding mode of hydrotris(pyrazolyl)borate ligands. The 18-crown-6 adducts of the sodium and potassium hydrotris(tetrazolyl)borate salts adopt eta 2-N,N and kappa2-N,H coordination modes, respectively, due to steric hindrances between the 18-crown-6 and hydrotris(tetrazolyl)borate ligands. The bonding modes of the hydrotris(tetrazolyl)borate complexes are stabilized by many hydrogen-bonding and dihydrogen-bonding contacts between the hydrotris(tetrazolyl)borate ligand and the ancillary ligand on the metal center. A series of poly(pyrazolyl)aluminate complexes containing aluminum-hydrogen bonds has been prepared, and these complexes exhibit similar coordination modes to their poly(pyrazolyl)borate analogues. Pyrazolyl exchange processes occur at room temperature in solution due to the weak Al-N and Al-H bonds. Salt metathesis of the new complexes with metal(II) halides yielded ligand, hydride, or pyrazolate transfer, depending on the metal and reaction conditions. The reactivity of 5-substituted tetrazoles

  9. Microstructural and compositional change of NaOH-activated high calcium fly ash by incorporating Na-aluminate and co-existence of geopolymeric gel and C-S-H(I)

    SciTech Connect

    Oh, Jae Eun; Moon, Juhyuk; Oh, Sang-Gyun; Clark, Simon M.; Monteiro, Paulo J.M.

    2012-05-15

    This study explores the reaction products of alkali-activated Class C fly ash-based aluminosilicate samples by means of high-resolution synchrotron X-ray diffraction (HSXRD), scanning electron microscope (SEM), and compressive strength tests to investigate how the readily available aluminum affects the reaction. Class C fly ash-based aluminosilicate raw materials were prepared by incorporating Na-aluminate into the original fly ashes, then alkali-activated by 10 M NaOH solution. Incorporating Na-aluminate reduced the compressive strength of samples, with the reduction magnitude relatively constant regardless of length of curing period. The HSXRD provides evidence of the co-existence of C-S-H with geopolymeric gels and strongly suggests that the C-S-H formed in the current system is C-S-H(I). The back-scattered electron images suggest that the C-S-H(I) phase exists as small grains in a finely intermixed form with geopolymeric gels. Despite providing extra source of aluminum, adding Na-aluminate to the mixes did not decrease the Si/Al ratio of the geopolymeric gel.

  10. Synergistic use of Knudsen effusion quadrupole mass spectrometry, solid-state galvanic cell and differential scanning calorimetry for thermodynamic studies on lithium aluminates

    SciTech Connect

    Rakshit, S.K. Naik, Y.P.; Parida, S.C.; Dash, Smruti; Singh, Ziley; Sen, B.K.; Venugopal, V.

    2008-06-15

    Three ternary oxides LiAl{sub 5}O{sub 8}(s), LiAlO{sub 2}(s) and Li{sub 5}AlO{sub 4}(s) in the system Li-Al-O were prepared by solid-state reaction route and characterized by X-ray powder diffraction method. Equilibrium partial pressure of CO{sub 2}(g) over the three-phase mixtures {l_brace}LiAl{sub 5}O{sub 8}(s)+Li{sub 2}CO{sub 3}(s)+5Al{sub 2}O{sub 3}(s){r_brace}, {l_brace}LiAl{sub 5}O{sub 8}(s)+5LiAlO{sub 2}(s)+2Li{sub 2}CO{sub 3}(s){r_brace} and {l_brace}LiAlO{sub 2}(s)+Li{sub 5}AlO{sub 4}(s)+2Li{sub 2}CO{sub 3}(s){r_brace} were measured using Knudsen effusion quadrupole mass spectrometry (KEQMS). Solid-state galvanic cell technique based on calcium fluoride electrolyte was used to determine the standard molar Gibbs energies of formations of these aluminates. The standard molar Gibbs energies of formation of these three aluminates calculated from KEQMS and galvanic cell measurements were in good agreement. Heat capacities of individual ternary oxides were measured from 127 to 868 K using differential scanning calorimetry. Thermodynamic tables representing the values of {delta}{sub f}H{sup 0}(298.15 K), S{sup 0}(298.15 K) S{sup 0}(T), C{sub p}{sup 0}(T), H{sup 0}(T), {l_brace}H{sup 0}(T)-H{sup 0}(298.15 K){r_brace}, G{sup 0}(T), {delta}{sub f}H{sup 0}(T), {delta}{sub f}G{sup 0}(T) and free energy function (fef) were constructed using second law analysis and FACTSAGE thermo-chemical database software. - Graphical abstract: Comparison of {delta}{sub f}G{sub m}{sup 0} of ternary oxides determined from KEQMS and solid-state galvanic cell techniques. (O) KEQMS, (9632;) solid-state galvanic cell and solid line: combined fit of both the experimental data.

  11. Studies on sintering additives for hydroxyapatite, and controlled porosity structures of calcium aluminates and polypropylene-tricalcium phosphate for bone graft applications

    NASA Astrophysics Data System (ADS)

    Kalita, Samar Jyoti

    Tissue engineering has made a significant contribution in developing new biomaterials that can restore the structural features and physiological functions of natural tissues. Various materials, such as metals, ceramics, polymers and composites have been developed for their use in hard tissue engineering applications. Part A of this thesis describes my research on HAp ceramics. HAp, a bioactive ceramic, is known for its osteoconductivity, but shows poor mechanical performance. This program aimed at improving mechanical performance of synthetic HAp by introducing small quantities of various sintering additives. A range of oxide-based sintering additives were selected and prepared. Dense compacts were prepared using a uniaxial press with an average green density of 1.6 g/cc. Results showed that some of these sintering additives improved densification, hardness and compression strength of synthetic HAp compared to the pure composition. A maximum bulk density of 3.06 g/cc was achieved for 2.5 wt% addition of MgO. A Microhardness of 4.9 GPa (505 HV) was measured for 2.5 wt% addition of BaO, and the highest compression strength (220MPa) was reported for 2.5 wt% addition of CaO. Cytotoxicity and cell proliferation studies with a modified human osteoblast (HOB) cell-line (OPC1) proved most of these materials non-toxic and biocompatible. Microscopic observation revealed that bone cells were attached and grew well on most of these ceramic matrices. Part B describes my work on development of controlled porosity polypropylene-tricalcium phosphate composite scaffolds via the fused deposition modeling (FDM) process. Hg-porosimetry was performed to determine pore size and their distribution. Uniaxial compression testing performed on samples with 36 vol% porosity and pore size of 160 mum showed the best compressive strength of 12.7 MPa. Part C includes my research on development of "3-D honeycomb" porous calcium aluminate structures via the indirect FDM process. Samples of 29% and

  12. ANALYSIS OF DUST DELIQUESCENCE FOR FEP SCREENING

    SciTech Connect

    C. Bryan

    2005-08-26

    The purpose of this report is to evaluate the potential for penetration of the Alloy 22 (UNS N06022) waste package outer barrier by localized corrosion due to the deliquescence of soluble constituents in dust present on waste package surfaces. The results support a recommendation to exclude deliquescence-induced localized corrosion (pitting or crevice corrosion) of the outer barrier from the total system performance assessment for the license application (TSPA-LA). Preparation of this report, and supporting laboratory studies and calculations, were performed as part of the planned effort in Work Package AEBM21, as implemented in ''Technical Work Plan for: Screening Evaluation for Dust Deliquescence and Localized Corrosion'' (BSC 2004 [DIRS 172804]), by Bechtel SAIC Company, LLC, and staff from three national laboratories: Sandia National Laboratories, Lawrence Livermore National Laboratory (LLNL), and Lawrence Berkeley National Laboratory (LBNL). The analysis and conclusions presented in this report are quality affecting, as determined in the controlling technical work plan. A summary of background information, based on work that was not performed under a quality assurance program, is provided as Appendix E. In this instance, the use of unqualified information is provided for transparency and corroboration only, and is clearly separated from uses of qualified information. Thus, the qualification status of this information does not affect the conclusions of this report. The acceptance criteria addressed in Sections 4.2 and 7.2 were changed from the technical work plan in response to review comments received during preparation of this report.

  13. A compact, higher order, high temperature superconductor microstrip bandpass filter on a two-inch lanthanum aluminate substrate for personal communication service applications

    NASA Astrophysics Data System (ADS)

    Pal, Srikanta; Stevens, Chris; Edwards, David

    2005-10-01

    A practical design methodology for a compact parallel-coupled microstrip bandpass filter structure with steep attenuation is introduced using a computer-aided full wave electromagnetic simulation based on the method of moments. The structure consists of an array of fully aligned half-wavelength spiral meander line resonators. Aimed at application in the front-end receiver of digital cellular communication service, a 12-pole high temperature superconductor filter with 2.27% fractional bandwidth at 883.0 MHz was designed. The filter is fabricated using thallium-barium-calcium-copper oxide (TBCCO) thin films on a two-inch lanthanum aluminate (LaAlO3) wafer. The S-parameter measurements show a good agreement with the simulated results. At 70 K, the 12-pole filter shows less than 0.4 dB insertion loss, 0.3 dB passband ripple, better than 12 dB return loss. The out of band rejection at 3 MHz below the passband edges is more than 60.0 dB. In order to estimate the power handling capability of the filter, the third-order intermodulation distortion was measured. A sensitivity analysis for the observed frequency shift in the filter is reported. Also from this analysis an approach for using the same design in 0.5% FBW applications is discussed.

  14. Comparative study of radiation-induced damage in magnesium aluminate spinel by means of IL, CL and RBS/C techniques

    NASA Astrophysics Data System (ADS)

    Jozwik, Iwona; Jagielski, Jacek; Gawlik, Grzegorz; Jozwik, Przemyslaw; Ratajczak, Renata; Panczer, Gerard; Moncoffre, Nathalie; Wajler, Anna; Sidorowicz, Agata; Thomé, Lionel

    2016-03-01

    A comparative study of damage accumulation in magnesium aluminate spinel (MgAl2O4) has been conducted using ionoluminescence (IL), cathodoluminescence (CL) and Rutherford Backscattering Spectrometry/channeling (RBS/C) techniques. MgAl2O4 single crystal and polycrystalline samples were irradiated with 320 keV Ar+ ions at fluencies ranging from 1 × 1012 to 2 × 1016 cm-2 in order to create various levels of radiation damage. RBS/C measurements provided quantitative data about damage concentration in the samples. These values were then compared to the luminescence measurements. The results obtained by IL and RBS/C methods demonstrate a two-step character of damage buildup process. The CL data analysis points to the three-step damage accumulation mechanism involving the first defect transformation at fluencies of about 1013 cm-2 and second at about 1015 cm-2. The rate of changes resulting from the formation of nonluminescent recombination centers is clearly nonlinear and cannot be described in terms of continuous accumulation of point defects. Both, IL and CL techniques, appear as new, complementary tools bringing new possibilities in the damage accumulation studies in single- and polycrystalline materials.

  15. Two-dimensional zeolite-like network in the new caesium copper aluminate Cs2CuAl4O8.

    PubMed

    Shvanskaya, Larisa; Yakubovich, Olga; Massa, Werner; Vasiliev, Alexander

    2015-10-01

    Monoclinic dicaesium copper tetraaluminate, Cs2CuAl4O8, space group P2(1)/c, a = 8.4551 (7), b = 10.012 (1), c = 17.073 (2) Å, β = 101.643 (9)°, Z = 6, was obtained by high-temperature crystallization from a phosphate flux. Its microporous crystal structure presents the first example of double layers built from [AlO4] tetrahedra combined in 4-, 6- and 8-rings, topologically similar to those found in the ATT-type zeolites and isostructural minerals armstrongite, davanite and dalyite. These layers show a rare arrangement of three [AlO4] tetrahedra sharing one oxygen vertex. The aluminate slabs are further linked by chains of edge-sharing [CuO4] square planes to form a mixed anionic three-dimensional framework with Cs(+) cations in channels and cavities. An unusually short Cu···Cs distance of 3.166 Å is ascribed to the strong Jahn-Teller effect of Cu(2+). The magnetic subsystem demonstrates properties of an alternating antiferromagnetic chain with a gap in the spectrum of magnetic excitations. PMID:26428399

  16. Rétention de sels simples par une membrane chargée d'ultrafiltration à base d'alumine gamma

    NASA Astrophysics Data System (ADS)

    Benalla, R.; Persin, M.; Toreis, N.; Sarrazin, J.; Larbot, A.; Bouhaouss, A.

    1999-09-01

    Filtration of different electrolytes solutions was performed by means of a γ alumina ultrafiltration membrane. The experimental determination of the rejection rate for the salts leads to their phenomenologic parameters σ and P. The observed rejection are in agreement with a Donnan mechanism of exclusion of the coion outside of the membrane pore. Une membrane d'ultrafiltration en alumine γ a été utilisée pour la filtration de différentes solutions salines. Les rétentions des différents sels ont été d'abord mesurées à l'aide de cette membrane puis les coefficients de réflexion σ et les perméabilités P pour chaque sel ont été déterminées. La rétention des sels peut être expliquée par un mécanisme d'exclusion de type Donnan.

  17. Synthesis and hydration behavior of calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cement

    SciTech Connect

    Kang, Eun-Hee; Yoo, Jun-Sang; Kim, Bo-Hye; Choi, Sung-Woo; Hong, Seong-Hyeon

    2014-02-15

    Calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cements were prepared by solid state reaction and polymeric precursor methods, and their phase evolution, morphology, and hydration behavior were investigated. In polymeric precursor method, a nearly single phase Ca{sub 7}ZrAl{sub 6}O{sub 18} was obtained at relatively lower temperature (1200 °C) whereas in solid state reaction, a small amount of CaZrO{sub 3} coexisted with Ca{sub 7}ZrAl{sub 6}O{sub 18} even at higher temperature (1400 °C). Unexpectedly, Ca{sub 7}ZrAl{sub 6}O{sub 18} synthesized by polymeric precursor process was the large-sized and rough-shaped powder. The planetary ball milling was employed to control the particle size and shape. The hydration behavior of Ca{sub 7}ZrAl{sub 6}O{sub 18} was similar to that of Ca{sub 3}Al{sub 2}O{sub 6} (C3A), but the hydration products were Ca{sub 3}Al{sub 2}O{sub 6}·6H{sub 2}O (C3AH6) and several intermediate products. Thus, Zr (or ZrO{sub 2}) stabilized the intermediate hydration products of C3A.

  18. Long-term behavior of CaO-based pellets supported by calcium aluminate cements in a long series of CO{sub 2} capture cycles

    SciTech Connect

    Manovic, V.; Anthony, E.J.

    2009-10-15

    A series of carbonation/calcination tests consisting of 1000 cycles was performed with CaO-based pellets prepared using hydrated lime and calcium aluminate cement. The change in CO{sub 2} carrying capacity of the sorbent was investigated in a thermogravimetric analyzer (TGA) apparatus and the morphology of residues after those cycles in the TGA was examined by scanning electron microscopy (SEM). Larger quantities of sorbent pellets underwent 300 carbonation/calcination cycles in a tube furnace (TF), and their properties were examined by nitrogen physisorption tests (BET and BJH). The crushing strength of the pellets before and after the CO{sub 2} cycles was determined by means of a custom-made strength testing apparatus. The results showed high CO{sub 2} carrying capacity in long series of cycles with an extremely high residual activity of the order of 28%. This superior performance is a result of favorable morphology due to the existence of large numbers of nanosized pores suitable for carbonation. This morphology is relatively stable during cycles due to the presence of mayenite (Ca{sub 12}Al{sub 14}O{sub 33}) in the CaO structure. However, the crushing tests showed that pellets lost strength after 300 carbonation/calcination cycles, and this appears to be due to the cracks formed in the pellets. This effect was not observed in smaller particles suitable for use in fluidized bed (FBC) systems.

  19. An in situ synchrotron X-ray diffraction investigation of lepidocrocite and ferrihydrite-seeded Al(OH) 3 crystallisation from supersaturated sodium aluminate liquor

    NASA Astrophysics Data System (ADS)

    Webster, Nathan A. S.; Loan, Melissa J.; Madsen, Ian C.; Knott, Robert B.; Brodie, Greta M.; Kimpton, Justin A.

    2012-02-01

    Lepidocrocite and ferrihydrite-seeded Al(OH) 3 crystallisation from supersaturated sodium aluminate liquor at 70 °C was investigated using in situ synchrotron X-ray diffraction. The presence of iron oxides and oxyhydroxides in the Bayer process has implications for the nucleation and growth of scale on process equipment, and a greater understanding of the effect they have on Al(OH) 3 crystallisation may allow for development of methods for Al(OH) 3 scale prevention. The early stages of both crystallisation reactions were characterised by nucleation of gibbsite on the seed material. This was followed by a rapid increase in gibbsite concentration, which coincided with the appearance of the bayerite and nordstrandite polymorphs of Al(OH) 3. The lepidocrocite-seeded reaction then proceeded via a mechanism similar to that which has been observed previously for goethite, hematite and magnetite-seeded Al(OH) 3 crystallisation. Different behaviour was observed in the ferrihydrite-seeded experiment, with nucleation as well as growth occurring during the period of rapid increase in gibbsite concentration, followed by a period of diffusion controlled growth.

  20. Comparative study of radiation-induced damage in magnesium aluminate spinel by means of IL, CL and RBS/C techniques

    NASA Astrophysics Data System (ADS)

    Jozwik, Iwona; Jagielski, Jacek; Gawlik, Grzegorz; Jozwik, Przemyslaw; Ratajczak, Renata; Panczer, Gerard; Moncoffre, Nathalie; Wajler, Anna; Sidorowicz, Agata; Thomé, Lionel

    2016-06-01

    A comparative study of damage accumulation in magnesium aluminate spinel (MgAl2O4) has been conducted using ionoluminescence (IL), cathodoluminescence (CL) and Rutherford Backscattering Spectrometry/channeling (RBS/C) techniques. MgAl2O4 single crystal and polycrystalline samples were irradiated with 320 keV Ar+ ions at fluencies ranging from 1 × 1012 to 2 × 1016 cm-2 in order to create various levels of radiation damage. RBS/C measurements provided quantitative data about damage concentration in the samples. These values were then compared to the luminescence measurements. The results obtained by IL and RBS/C methods demonstrate a two-step character of damage buildup process. The CL data analysis points to the three-step damage accumulation mechanism involving the first defect transformation at fluencies of about 1013 cm-2 and second at about 1015 cm-2. The rate of changes resulting from the formation of nonluminescent recombination centers is clearly nonlinear and cannot be described in terms of continuous accumulation of point defects. Both, IL and CL techniques, appear as new, complementary tools bringing new possibilities in the damage accumulation studies in single- and polycrystalline materials.