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Sample records for aluminized teflon fep

  1. Effects of proton exposure on aluminized Teflon FEP film degradation

    NASA Astrophysics Data System (ADS)

    Li, Chun-dong; Yang, De-zhuang; He, Shi-yu

    2005-06-01

    Aluminized Teflon FEP films have been widely used on the exterior surfaces of spacecrafts. Under the radiation exposure of charged particles in the Earth radiation belt, Teflon FEP film could be deteriorated. In order to reveal the deterioration mechanism, effects of proton radiation on optical properties and microstructure of the Teflon FEP film were investigated. The energy of protons was chosen as 50 keV, and the flux was ϕ = 5 × 10 11 cm -2 s -1. The spectral reflectance ρλ of specimens before and after radiation exposure was measured in-situ in the wavelength region of 200-2500 nm. Experimental results showed that the proton exposure resulted in forming an absorption band in the wavelength region of 280-600 nm. XPS analysis demonstrated that the proton bombard went expelled fluorine atoms from the main-chains and activated the macromolecules in the surface layer of the Teflon FEP films, leading to formation of various active radicals and free carbon atoms. Some functional groups were also generated due to the implantation effect of the protons. The in-situ analysis of mass spectroscopy revealed that during the proton irradiation, a large amount of CF 3 free radicals were preferentially formed and readily outgassed from the film surface.

  2. 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.

  3. 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.

  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. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Erosion of FEP Teflon and PMMA by VUV radiation and hyperthermal O or Ar atoms.

    PubMed

    Zhang, Jianming; Lindholm, Ned F; Brunsvold, Amy L; Upadhyaya, Hari P; Minton, Timothy K; Tagawa, Masahito

    2009-03-01

    A combination of beam-surface-scattering, quartz-crystal-microbalance, and surface-recession experiments was conducted to study the effects of various combinations of O atoms [in the O((3)P) ground state], Ar atoms, and vacuum ultraviolet (VUV) light on fluorinated ethylene-propylene copolymer (FEP) Teflon and poly(methyl methacrylate) (PMMA). A laser-breakdown source was used to create hyperthermal beams containing O and O(2) or Ar. A D(2) lamp provided a source of VUV light. O atoms with 4 eV of translational energy or less did not react with a pristine FEP Teflon surface. Volatile O-containing reaction products were observed when the O-atom energy was higher than 4.5 eV, and the signal increased with the O-atom energy. Significant erosion of FEP Teflon ( approximately 20% of Kapton H) was observed when it was exposed to the hyperthermal O/O(2) beam with an average O-atom energy of 5.4 eV. FEP Teflon and PMMA that were exposed to VUV light alone exhibited much less mass loss. Collision-induced dissociation by hyperthermal Ar atoms also caused mass loss, similar in magnitude to that caused by VUV light. There were no observed synergistic effects when VUV light or Ar bombardment was combined with O/O(2) exposure. For both FEP Teflon and PMMA, the erosion yields caused by simultaneous exposure to O/O(2) and either VUV light or Ar atoms could be approximately predicted by adding the erosion yield caused by O/O(2), acting individually, to the erosion yield caused by the individual action of either VUV light or Ar atoms.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1994-11-01

    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.

  20. Gamma-radiation-induced grafting of binary mixture of methacrylic acid and 4-vinyl pyridine onto Teflon-FEP film as an effective polar membrane for separation processes

    NASA Astrophysics Data System (ADS)

    Kaur, Inderjeet; Rattan, Sunita; Chauhan, Sandeep; Gupta, Nitika

    2010-05-01

    Ionic bifunctional membranes have been synthesized by grafting binary mixture of methacrylic acid (MAAc) and 4-vinyl pyridine (4-VP) onto Teflon-FEP film by pre-irradiation method. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters. Maximum percentage of grafting of binary mixture (MAAc-co-4-VP) (71.29%) was obtained at an optimum total dose of 54.48 kGy and the total concentration was 9.49 mol/L ([4-VP] = 0.07 mol/L and [MAAc ] = 9.42 mol/L) in 5 ml of water. The effect of alcohols as additives to the reaction medium on percent grafting of the binary mixture has also been studied. The membranes were characterized by FTIR spectroscopy, scanning electron microscopy and thermogravimetric analysis. Swelling studies of the membranes were performed in different solvents such as water, benzene, carbon tetrachloride and dimethyl formamide (DMF). Maximum swelling was observed in DMF with minimum swelling in benzene. Metal ion (Cu 2+, Ni 2+ and Fe 2+) uptake studies show better affinity for Fe 2+ ions. Conductance measurements in different aqueous salt solution showed that these membranes have affinity for Na +/K + ions and Cl - ions and hence can be used in desalination/separation processes for the separation of both type of cationic and anionic ions.

  1. Teflon bonding of silicon solar cells

    NASA Astrophysics Data System (ADS)

    White, P. A.; Jones, D. E.

    The silicon adhesive used to bond the coverglass onto the solar cell can be replaced by a thin layer of FEP Teflon. The advantage of using Teflon as the adhesive is that it is supplied as a thin sheet in thicknesses of 25 or 50 microns and can be cut to size prior to use. Because the Teflon does not extrude from the join in the same manner as conventional adhesives, the cleanup after Teflon bonding is virtually nonexistent. It is considered that the use of a coverglass which is thermally matched to silicon will prevent the buildup of thermal stresses which could cause delamination. Work done to date on the Teflon bonding process including the results of some critical end of life tests is reviewed.

  2. Teflon haemoptysis.

    PubMed

    Aboudara, Matthew; Krimsky, William; Harley, Daniel

    2012-03-20

    Teflon-coated pledgeted sutures can be used to reinforce the bronchial anastomosis site following a pulmonary resection in order to prevent bronchopleural fistula formation. The authors describe the case of a 42-year-old woman with recurrent haemoptysis secondary to the erosion of a pledgeted suture through the distal trachea. The pledgeted suture was used to reinforce a defect in the wall of the distal trachea after a right upper lobectomy for stage 2a squamous cell carcinoma. Surgically, a completion pneumonectomy with carinal reconstruction was thought necessary to treat the haemoptysis. Given her age and potential surgical morbidities, the decision was made to perform serial bronchoscopies with careful pruning and eventual removal of the pledget by using the cryoprobe and a flexible scissors. This resulted in the eventual removal of the suture. Follow-up bronchoscopy 4 weeks postremoval demonstrated no residual defect on the airway wall.

  3. 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).

  4. 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.

  5. Silver-Teflon contamination UV radiation study

    NASA Technical Reports Server (NTRS)

    Muscari, J. A.

    1978-01-01

    Silver-Teflon (Ag/FEP) is planned to be used as the thermal control material covering the radiator surfaces on the shuttle orbiter payload bay doors. These radiators require the use of materials that have a very low solar absorptance and a high emittance for heat rejection. However, operationally, materials used on these critical radiator surfaces, such as silver-Teflon, will be exposed to a variety of conditions which include both the natural as well as the induced environments from the Shuttle Orbiter. A complete test facility was assembled, and detailed test procedures and a test matrix were developed. Measurements of low solar absorptance were taken before and after contamination, at intervals during irradiation, and after sample cleaning to fulfill all the requirements.

  6. 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.

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

    PubMed Central

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

    2014-01-01

    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 sandwiched 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

  8. 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.

  9. 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.

  10. 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]).

  11. 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.

  12. The Impact of FEP Legislation

    ERIC Educational Resources Information Center

    Adams, Arvil

    1975-01-01

    This testimony, before a public hearing of the New York City Commission on Human Rights in May 1974, had three express focuses: (1) on urban poverty among blacks in the non-south; (2) on the enforcement of Fair Employment Practice (FEP) legislation and its effect on the economic position of blacks and other minority groups; and, (3) on guidelines…

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Impact penetration experiments in teflon targets of variable thickness

    NASA Astrophysics Data System (ADS)

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

    1993-03-01

    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.

  20. 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.

  1. Teflon-packed flexible joint

    NASA Technical Reports Server (NTRS)

    Belmont, G. E.

    1969-01-01

    Teflon-packed flexible joint separates the movement of the shaker from the liquid nitrogen hose during the ground testing of cryogenic zero-g equipment. The joint allows the hose to lie on the floor in a stationary position as the shaker moves back and forth, thus, the hose is not subject to violent motion.

  2. 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.

  3. Whole-Teflon microfluidic chips.

    PubMed

    Ren, Kangning; Dai, Wen; Zhou, Jianhua; Su, Jing; Wu, Hongkai

    2011-05-17

    Although microfluidics has shown exciting potential, its broad applications are significantly limited by drawbacks of the materials used to make them. In this work, we present a convenient strategy for fabricating whole-Teflon microfluidic chips with integrated valves that show outstanding inertness to various chemicals and extreme resistance against all solvents. Compared with other microfluidic materials [e.g., poly(dimethylsiloxane) (PDMS)] the whole-Teflon chip has a few more advantages, such as no absorption of small molecules, little adsorption of biomolecules onto channel walls, and no leaching of residue molecules from the material bulk into the solution in the channel. Various biological cells have been cultured in the whole-Teflon channel. Adherent cells can attach to the channel bottom, spread, and proliferate well in the channels (with similar proliferation rate to the cells in PDMS channels with the same dimensions). The moderately good gas permeability of the Teflon materials makes it suitable to culture cells inside the microchannels for a long time.

  4. 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.

  5. Hydrophobic metallic nanorods with Teflon nanopatches.

    PubMed

    Khudhayer, Wisam J; Sharma, Rajesh; Karabacak, Tansel

    2009-07-08

    Introducing a hydrophobic property to vertically aligned hydrophilic metallic nanorods was investigated experimentally and theoretically. The platinum nanorod arrays were deposited on flat silicon substrates using a sputter glancing angle deposition technique (GLAD). Then a thin layer of Teflon (nanopatch) was partially deposited on the tips of platinum nanorods at a glancing angle of theta(dep) = 85 degrees for different deposition times. Teflon deposition on Pt nanorods at normal incidence (theta(dep) = 0 degrees) was also performed for comparison. Morphology and elemental analysis of Pt/Teflon nanocomposite structures were carried out using scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDAX), respectively. It was found that the GLAD technique is capable of depositing ultrathin isolated Teflon nanostructures on selective regions of nanorod arrays due to the shadowing effect during obliquely incident deposition. Contact angle measurements on nanocomposite Pt nanorods with Teflon nanopatches exhibited contact angle values as high as 138 degrees, indicating a significant increase in the hydrophobicity of originally hydrophilic Pt nanostructures that had an angle of about 52 degrees. The enhanced hydrophobicity of the Pt nanorod/Teflon nanopatch composite is attributed to the presence of nanostructured Teflon coating, which imparted a low surface energy. Surface energy calculations were performed on Pt nanorods, Teflon thin film, and Pt/Teflon composite using the two-liquid method to confirm the contact angle measurements. Furthermore, a new contact angle model utilizing Cassie and Baxter theory for heterogeneous surfaces was developed in order to explain the enhanced hydrophobicity of Pt/Teflon nanorods. According to our model, it is predicted that the solid-liquid interface is mainly at the Teflon tips when the composite nanorods are in contact with water.

  6. Hydrophobic metallic nanorods with Teflon nanopatches

    NASA Astrophysics Data System (ADS)

    Khudhayer, Wisam J.; Sharma, Rajesh; Karabacak, Tansel

    2009-07-01

    Introducing a hydrophobic property to vertically aligned hydrophilic metallic nanorods was investigated experimentally and theoretically. The platinum nanorod arrays were deposited on flat silicon substrates using a sputter glancing angle deposition technique (GLAD). Then a thin layer of Teflon (nanopatch) was partially deposited on the tips of platinum nanorods at a glancing angle of θdep = 85° for different deposition times. Teflon deposition on Pt nanorods at normal incidence (θdep = 0°) was also performed for comparison. Morphology and elemental analysis of Pt/Teflon nanocomposite structures were carried out using scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDAX), respectively. It was found that the GLAD technique is capable of depositing ultrathin isolated Teflon nanostructures on selective regions of nanorod arrays due to the shadowing effect during obliquely incident deposition. Contact angle measurements on nanocomposite Pt nanorods with Teflon nanopatches exhibited contact angle values as high as 138°, indicating a significant increase in the hydrophobicity of originally hydrophilic Pt nanostructures that had an angle of about 52°. The enhanced hydrophobicity of the Pt nanorod/Teflon nanopatch composite is attributed to the presence of nanostructured Teflon coating, which imparted a low surface energy. Surface energy calculations were performed on Pt nanorods, Teflon thin film, and Pt/Teflon composite using the two-liquid method to confirm the contact angle measurements. Furthermore, a new contact angle model utilizing Cassie and Baxter theory for heterogeneous surfaces was developed in order to explain the enhanced hydrophobicity of Pt/Teflon nanorods. According to our model, it is predicted that the solid-liquid interface is mainly at the Teflon tips when the composite nanorods are in contact with water.

  7. 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.

  8. Radiologic appearance of chronic parapharyngeal Teflon granuloma.

    PubMed

    Hacein-Bey, Lotfi; Conneely, Mark F; Hijaz, Tarek A; Leonetti, John P

    2010-01-01

    Although Teflon has been used for almost 5 decades to provide tissue augmentation in various surgical indications, including head and neck surgery, its use has significantly declined in the last 2 decades, primarily because of its implication in granuloma formation. Teflon granulomas have been shown to cause false positives on positron emission tomography imaging and have been reported to have a characteristic magnetic resonance imaging (MRI) appearance. We report a patient with a large chronic Teflon granuloma of the parapharyngeal space that caused significant bony erosion of the atlas vertebra. The lesion's MRI signal characteristics were indistinguishable from those of surrounding tissues, while it showed characteristic hyperdensity on computed tomography due to the presence of fluorine atoms within Teflon. As MRI may supersede or replace computed tomography for a number of indications, and as Teflon has been used in large numbers of patients whose records may not always be available, knowledge of these findings has clinical relevance.

  9. Characteristics of edge breakdowns on Teflon samples

    NASA Technical Reports Server (NTRS)

    Yadlowsky, E. J.; Hazelton, R. C.; Churchill, R. J.

    1980-01-01

    The characteristics of electrical discharges induced on silverbacked Teflon samples irradiated by a monoenergetic electron beam have been studied under controlled laboratory conditions. Measurements of breakdown threshold voltages indicate a marked anisotropy in the electrical breakdown properties of Teflon: differences of up to 10 kV in breakdown threshold voltage are observed depending on the sample orientation. The material anisotropy can be utilized in spacecraft construction to reduce the magnitude of discharge currents.

  10. 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

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

    NASA Astrophysics Data System (ADS)

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

    1995-02-01

    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

  12. 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.

  13. Staphylococcus aureus FepA and FepB proteins drive heme iron utilization in Escherichia coli.

    PubMed

    Turlin, Evelyne; Débarbouillé, Michel; Augustyniak, Katarzyna; Gilles, Anne-Marie; Wandersman, Cécile

    2013-01-01

    EfeUOB-like tripartite systems are widespread in bacteria and in many cases they are encoded by genes organized into iron-regulated operons. They consist of: EfeU, a protein similar to the yeast iron permease Ftrp1; EfeO, an extracytoplasmic protein of unknown function and EfeB, also an extracytoplasmic protein with heme peroxidase activity, belonging to the DyP family. Many bacterial EfeUOB systems have been implicated in iron uptake, but a prefential iron source remains undetermined. Nevertheless, in the case of Escherichia coli, the EfeUOB system has been shown to recognize heme and to allow extracytoplasmic heme iron extraction via a deferrochelation reaction. Given the high level of sequence conservations between EfeUOB orthologs, we hypothesized that heme might be the physiological iron substrate for the other orthologous systems. To test this hypothesis, we undertook characterization of the Staphylococcus aureus FepABC system. Results presented here indicate: i) that the S. aureus FepB protein binds both heme and PPIX with high affinity, like EfeB, the E. coli ortholog; ii) that it has low peroxidase activity, comparable to that of EfeB; iii) that both FepA and FepB drive heme iron utilization, and both are required for this activity and iv) that the E. coli FepA ortholog (EfeO) cannot replace FepA in FepB-driven iron release from heme indicating protein specificity in these activities. Our results show that the function in heme iron extraction is conserved in the two orthologous systems.

  14. Method of processing aluminous ores

    SciTech Connect

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

    1981-02-24

    A method is described for 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 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 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 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. 1 fig.

  15. 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.

  16. Terrestrial applications of FEP-encapsulated solar cell modules

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    FEP-encapsulated solar cell modules and arrays have been designed and built expressly for terrestrial applications. System design including solar cell array mechanical design and the approach to system sizing is outlined. Such solar cell systems have been installed at six sites. Individual modules have undergone marine environment tests. Results from seven months of operation indicate that the system is meeting its electrical design requirements. No mechanical degradation has been reported. An array on Mammoth Mountain, California has been damaged by rime ice but shows no loss in electrical output. Marine environment tests on single modules have shown that elements of the module must be completely sealed by the FEP. Based on the limited test data available, the FEP-encapsulated solar cell module appears well suited to terrestrial applications.

  17. 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.

  18. 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.

  19. 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.

  20. Coaxially electrospun PVDF-Teflon AF and Teflon AF-PVDF core-sheath nanofiber mats with superhydrophobic properties.

    PubMed

    Muthiah, Palanikkumaran; Hsu, Shu-Hau; Sigmund, Wolfgang

    2010-08-03

    This work reports the coaxial electrospinning of poly(vinylidene fluoride) (PVDF)-Teflon amorphous fluoropolymer (AF) and Teflon AF-PVDF core-sheath nanofiber mats yielding superhydrophobic properties. The coaxial electrospinning configuration allows for the electrospinning of Teflon AF, a nonelectrospinnable polymer, with the help of an electrospinnable PVDF polymer. PVDF-Teflon AF and Teflon AF-PVDF core-sheath fibers have been found to a have mean fiber diameter ranging from 400 nm to less than 100 nm. TEM micrographs exhibit a typical core-sheath fiber structure for these fibers, where the sheath fiber coats the core fiber almost thoroughly. Water contact angle measurements by sessile drop method on these core-sheath nanofiber mats exhibited superhydrophobic characteristics with contact angles close to or higher than 150 degrees. Surprisingly, PVDF-Teflon AF and Teflon AF-PVDF nanofiber mat surface properties were dominated by the fiber dimensions and less influenced by the type of sheath polymer. This suggests that highly fluorinated polymer Teflon AF does not advance the hydrophobicity beyond what surface physics and slightly fluorinated polymer PVDF can achieve. It is concluded that PVDF-Teflon AF and Teflon AF-PVDF core-sheath electrospun nanofiber mats may be used in lithium (Li)-air batteries.

  1. 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.

  2. An automated Teflon microfluidic peptide synthesizer.

    PubMed

    Zheng, Hui; Wang, Weizhi; Li, Xiaojun; Wang, Zihua; Hood, Leroy; Lausted, Christopher; Hu, Zhiyuan

    2013-09-07

    We present a microfluidic synthesizer made entirely of Teflon material for solid phase peptide synthesis (SPPS). Solvent-resistant perfluoroalkoxy (PFA) was used to construct chip-sized devices featuring multiple tri-layer pneumatic microvalves. Using these devices, model peptides were automatically synthesized and cleaved in situ in a continuous-flow manner. The total coupling and cleavage time was significantly reduced compared to conventional bulk reactors. The synthesis of a decapeptide, for instance, took less than 6 h using our device while it usually takes more than three days using conventional reactors.

  3. An unusual presentation of Teflon granuloma: case report and discussion.

    PubMed

    Pagedar, Nitin A; Listinsky, Catherine M; Tucker, Harvey M

    2009-01-01

    For more than 25 years, Teflon was the most commonly used material for injection laryngoplasty. However, the incidence of Teflon granuloma and the consequent deterioration of glottic function ultimately led to the development of other injectable materials, and as a result, Teflon granulomas are no longer frequently encountered. We present a case of Teflon granuloma that was unusual in that (1) a long period of time had elapsed between the injection and the granuloma formation and (2) there was no change in the patient's glottic function.

  4. Overexpression of the Novel MATE Fluoroquinolone Efflux Pump FepA in Listeria monocytogenes Is Driven by Inactivation of Its Local Repressor FepR

    PubMed Central

    Guérin, François; Galimand, Marc; Tuambilangana, Fabrice; Courvalin, Patrice; Cattoir, Vincent

    2014-01-01

    Whereas fluoroquinolone resistance mainly results from target modifications in gram-positive bacteria, it is primarily due to active efflux in Listeria monocytogenes. The aim of this study was to dissect a novel molecular mechanism of fluoroquinolone resistance in this important human pathogen. Isogenic L. monocytogenes clinical isolates BM4715 and BM4716, respectively susceptible and resistant to fluoroquinolones, were studied. MICs of norfloxacin and ciprofloxacin were determined in the presence or in the absence of reserpine (10 mg/L). Strain BM4715 was susceptible to norfloxacin (MIC, 4 mg/L) and ciprofloxacin (MIC, 0.5 mg/L) whereas BM4716 was highly resistant to both drugs (MICs 128 and 32 mg/L, respectively). Reserpine was responsible for a 16-fold decrease in both norfloxacin and ciprofloxacin MICs against BM4716 suggesting efflux associated resistance. Whole-genome sequencing of the strains followed by comparative genomic analysis revealed a single point mutation in the gene for a transcriptional regulator, designated fepR (for fluoroquinolone efflux protein regulator) belonging to the TetR family. The frame-shift mutation was responsible for the introduction of a premature stop codon resulting in an inactive truncated protein. Just downstream from fepR, the structural gene for an efflux pump of the MATE family (named FepA) was identified. Gene expression was quantified by qRT-PCR and demonstrated that fepA expression was more than 64-fold higher in BM4716 than in BM4715. The clean deletion of the fepR gene from BM4715 was responsible for an overexpression of fepA with resistance to norfloxacin and ciprofloxacin, confirming the role of FepR as a local repressor of fepA. In conclusion, we demonstrated that overexpression of the new MATE efflux pump FepA is responsible for fluoroquinolone resistance in L. monocytogenes and secondary to inactivation of the FepR repressor. PMID:25188450

  5. Treatment of recurrent trigeminal neuralgia due to Teflon granuloma.

    PubMed

    Capelle, Hans-Holger; Brandis, Almuth; Tschan, Christoph A; Krauss, Joachim K

    2010-08-01

    Recurrent trigeminal neuralgia after microvascular decompression (MVD) may be due to insufficient decompression, dislocation of the implant to pad the neurovascular contact, or the development of granuloma. Here, we report on our experience with Teflon granuloma including its treatment and histopathological examination. In a series of 200 patients with trigeminal neuralgia MVD was performed with Teflon felt according to Jannetta's technique. In three patients with recurrent facial pain Teflon granuloma was found to be the cause for recurrence. In each instance, the granuloma was removed for histopathological examination. Mean age at the first procedure was 62.3 years and at the second procedure 66.3 years. Recurrence of pain occurred between 1 and 8.5 years after the first procedure. MRI scans demonstrated local gadolineum enhancement in the cerebellopontine angle, and CT scans showed local calcification. Intraoperatively dense fibrous tissue was found at the site of the Teflon granuloma. Histopathological examination revealed foreign body granuloma with multinuclear giant cells, collagen-rich hyalinized scar tissue, focal hemosiderin depositions, and microcalcifications. The Teflon granuloma was completely removed, and a new Teflon felt was used for re-decompression. Patients were free of pain after the second procedure at a mean of 40.3 months of follow-up. Teflon granuloma is a rare cause for recurrent facial pain after MVD. Small bleeding into the Teflon felt at surgery might trigger its development. A feasible treatment option is surgical re-exploration, nerve preserving removal of the granuloma, and repeat MVD.

  6. 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.

  7. Effect of silicate and aluminate ion adsorption on the reaction of quartz and alumina with caustic solution

    SciTech Connect

    Thornton, S.D.

    1986-05-01

    Caustic consumption is recognized as a problem in enhanced oil recovery by alkaline flooding. Chemical reactions which cause caustic consumption are governed by equilibria between reservoir minerals and alkaline solution. Identification of the individual dissolving and precipitating minerals in a given brine and rock system is a critical step in predicting caustic consumption and scale formation in oil recovery by alkaline flooding. This work demonstrates that ion adsorption may have a significant effect on mineral/alkali equilibria. Powdered quartz and alumina were mixed with alkaline solutions containing 0.01 to 0.1 molar hydroxide ion and added silicate or aluminate ion. Each suspension was sealed in a Teflon bottle and shaken continuously for approximately 1 week at 24/sup 0/ or 70/sup 0/C. Samples of the supernatant were removed periodically and analyzed for the elements silicon and aluminum. The solubilities of quartz and alumina in caustic solutions were found to be reduced significantly by added aluminate and silicate ion, respectively. Adsorption of these ions onto the minerals was also measured. It is postulated that these ions form a protective aluminosilicate layer when they are adsorbed onto the mineral surface. Such an aluminosilicate layer will reduce mineral reactions during alkaline flooding. Two major conclusions result from this work. Adsorbed aluminate and silicate ions can reduce the solubilities of quartz and alumina, respectively. The effect of adsorption on mineral equilibria should be included in a mineral reaction model for alkaline flooding. 18 refs., 5 figs., 8 tabs.

  8. 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.

  9. 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)

  10. 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}.

  11. Structure of liquid tricalcium aluminate

    NASA Astrophysics Data System (ADS)

    Drewitt, James W. E.; Barnes, Adrian C.; Jahn, Sandro; Kohn, Simon C.; Walter, Michael J.; Novikov, Alexey N.; Neuville, Daniel R.; Fischer, Henry E.; Hennet, Louis

    2017-02-01

    The atomic-scale structure of aerodynamically levitated and laser-heated liquid tricalcium aluminate (Ca3Al2O6 ) was measured at 2073(30) K by using the method of neutron diffraction with Ca isotope substitution (NDIS). The results enable the detailed resolution of the local coordination environment around calcium and aluminum atoms, including the direct determination of the liquid partial structure factor, SCaCa(Q ) , and partial pair distribution function, gCaCa(r ) . Molecular dynamics (MD) simulation and reverse Monte Carlo (RMC) refinement methods were employed to obtain a detailed atomistic model of the liquid structure. The composition Ca3Al2O6 lies at the CaO-rich limit of the CaO:Al2O3 glass-forming system. Our results show that, although significantly depolymerized, liquid Ca3Al2O6 is largely composed of AlO4 tetrahedra forming an infinite network with a slightly higher fraction of bridging oxygen atoms than expected for the composition. Calcium-centered polyhedra exhibit a wide distribution of four- to sevenfold coordinated sites, with higher coordinated calcium preferentially bonding to bridging oxygens. Analysis of the MD configuration reveals the presence of ˜10 % unconnected AlO4 monomers and Al2O7 dimers in the liquid. As the CaO concentration increases, the number of these isolated units increases, such that the upper value for the glass-forming composition of CaO:Al2O3 liquids could be described in terms of a percolation threshold at which the glass can no longer support the formation of an infinitely connected AlO4 network.

  12. Anion-exchange synthesis of nanoporous FeP nanosheets as electrocatalysts for hydrogen evolution reaction.

    PubMed

    Xu, You; Wu, Rui; Zhang, Jingfang; Shi, Yanmei; Zhang, Bin

    2013-07-28

    Nanoporous FeP nanosheets are successfully synthesized via the anion-exchange reaction of inorganic-organic hybrid Fe18S25-TETAH (TETAH = protonated triethylenetetramine) nanosheets with P ions. The as-prepared nanoporous FeP nanosheets exhibit high electrochemical hydrogen evolution reaction activity in acidic medium.

  13. 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.

  14. 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.

  15. 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.

  16. [Questionnaire on parental attitudes and rearing practices (FEPS)].

    PubMed

    Richter-Appelt, Hertha; Schimmelmann, Benno Graf; Tiefensee, Jutta

    2004-01-01

    A positive parent-child relationship is one of the most important determinants of a healthy cognitive, emotional and social development. The relationship from parent to child is determined by parenting styles. Parenting styles are characterised by the two dimensions parental attitudes and rearing practices. The development and the psychometric properties of a questionnaire on parental attitudes and rearing practices (FEPS), which contains an extended version of the Parental Bonding Instrument by Parker et al. (PBI, 1979) and two scales on parental reinforcement and punishment behaviour, is presented. In a sample of 457 women and 159 men factorial and item analysis revealed four scales (care, autonomy, low punishment and low material reinforcement). The care dimension contained items of immaterial reinforcement on the positive pole and items of coldness and ignorance as means of punishment on the negative pole. Based on findings from its first application in a clinical study it can be assumed that the FEPS differentiates between clinical and non-clinical populations. Additionally, varying patterns of the four scales may emerge as risk factors for the development of certain psychiatric/psychological problems.

  17. 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

  18. Effect of electron irradiation in vacuum on FEP-A silicon solar cell covers

    NASA Technical Reports Server (NTRS)

    Marsik, S. J.; Broder, J. D.

    1975-01-01

    Fluorinated ethylene-propylene-A (FEP-A) covers on silicon solar cells were irradiated with 1-MeV electrons, in vacuum, to an accumulated fluence equivalent to approximately 28 years in synchronous orbit. The effect of irradiation on the light transmittance of FEP-A was checked by measuring the short-circuit current of the cells after each dose increment. The results indicate no apparent overall loss in transmission due to irradiation of FEP-A. Filter wheel measurements revealed some darkening of the FEP-A at the blue end of the spectrum. Although no delamination from the cell surface was observed while in vacuum, embrittlement of FEP-A occurred at the accumulated dose.

  19. An unusual crystal structure of ferric-enterobactin bound FepB suggests novel functions of FepB in microbial iron uptake.

    PubMed

    Li, Bingqing; Li, Ning; Yue, Yingying; Liu, Xiuhua; Huang, Yan; Gu, Lichuan; Xu, Sujuan

    2016-09-23

    Iron acquisition by siderophores is critical for the survival of most bacteria. Enterobactin is a kind of catechol siderophore that exhibits the highest affinity to iron atoms secreted by E. coli and several other species of Enterobacteriaceae. The periplasmic binding protein (PBP) FepB can transport ferric-enterobactin (Fe-Ent) from the outer membrane to the membrane-associated ATP-binding cassette transport system in E. coli. To elucidate this process, we solved the crystal structure of FepB in complex with Fe-Ent at a resolution of 1.8 Å. Consistent with previously reported NMR results, our crystal structure shows that, similar to the other type III PBPs, the FepB structure was folded with separated globular N- and C-termini linked by a long α-helix. Additionally, the structure showed that the Fe-Ent bound to the cleft between the N- and C-terminal domains. Exceptionally, FepB differs from the other known siderophore binding PBPs in that it forms a trimer by capturing four Fe-Ents that can each contribute to FepB trimerization. Dynamic light-scattering experiments are consistent with the structural observations and indicate that FepB forms a trimer in a Fe-Ent-dependent manner.

  20. EQUATION OF STATE OF SOLIDS. II ALUMINUM AND TEFLON

    DTIC Science & Technology

    The pressure-volume-energy (P-V-E) equation of state of aluminum and Teflon has been investigated. The P-V-E equation of state of a material is needed to solve nonreactive flow problems using computer codes such as PUFF. Explosively induced shock waves...solid and porous specimens of aluminum and Teflon. For aluminum it is found that the following P-V-E equation of state can reproduce the experimental

  1. Eu(2+) luminescence in strontium aluminates.

    PubMed

    Dutczak, D; Jüstel, T; Ronda, C; Meijerink, A

    2015-06-21

    The luminescence properties of Eu(2+) doped strontium aluminates are reported and reviewed for a variety of aluminates, viz. SrAl12O19, SrAl4O7, Sr4Al14O25, SrAl2O4 and Sr3Al2O6. The aim of the research is to investigate the role of local coordination and covalency of the aluminate host lattice, related to the Sr/Al ratio, on the optical properties of the Eu(2+) ion. The UV and VUV excited luminescence spectra as well as luminescence decay curves were recorded to characterize the luminescence properties of the investigated aluminates. The emission of Eu(2+) ions varies over a wide spectral range, from ultraviolet (UV) to red, for the series of aluminates. The variation in emission color can be related to the crystal-field splitting of the 5d levels and the covalent interaction with the surrounding oxygen anions. In the least covalent material, viz. SrAl12O19:Eu(2+), narrow line emission due to the (6)P7/2-(8)S7/2 transition occurs at 4 K, indicating that the 4f(6)5d excited state is situated above the (6)P7/2(4f(7)) excited state around 360 nm. The most alkaline material, viz. Sr3Al2O6:Eu(2+) is the most covalent host and exhibits several d-f emission bands in the yellow to red spectral range due to the Eu(2+) ions located on different crystallographic Sr(2+) sites. The Eu(2+) emission spectra in the other aluminates confirm the trend that with increasing Sr/Al ratio the Eu(2+) emission shifts to longer wavelengths. Interesting differences are observed for the Eu(2+) from different crystallographic sites which cannot always be related with apparent differences in the first oxygen coordination sphere. The discussion gives insight into how in a similar class of materials, strontium aluminates, the emission color of Eu(2+) can be tuned over a wide spectral region.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. Isolation of human monocytes by double gradient centrifugation and their differentiation to macrophages in teflon-coated cell culture bags.

    PubMed

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

    2014-09-09

    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.

  8. 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.

  9. Free-surface light emission from shocked Teflon

    NASA Astrophysics Data System (ADS)

    Gallagher, Kathleen G.; Yang, Wenbo; Ahrens, Thomas J.

    1994-07-01

    Shock initiated light emission experiments were performed on Teflon shock loaded to pressures up to ˜17 GPa. Radiances up to 600×106Wṡm-2/(ster ṡnm), were measured over a range of 390 to 820 nm. We have measured the spectra of light emitted upon reflection of the shock at the free surface and observed it to be distinctly non-thermal in nature. The lights appears to result from bond destruction such as observed in shock recovery experiments on Teflon and in quasistatic experiments conducted on other polymers.

  10. 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.

  11. 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

  12. A cluster of Teflon pledgets manifesting as an intrathoracic cavitary mass following lung resection.

    PubMed

    Lee, J-I; Park, K-Y; Park, C-H

    2010-06-01

    Teflon pledgets are widely used for hemostasis and the reinforcement of friable tissue in surgery. However, rare but serious complications caused by the erosion of Teflon pledgets have been reported. We present an unusual case of an intrathoracic cavitary mass that was formed by the erosion of a cluster of Teflon pledgets into the lung parenchyma eight years after a lung resection.

  13. 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.

  14. The relationship between zinc protoporphyrin (ZPP) and "free" erythrocyte protoporphyrin (FEP) in lead-exposed individuals.

    PubMed

    Karacić, V; Prpić-Majić, D; Telisman, S

    1980-01-01

    The relationship between zinc protoporphyrin (ZPP) and total erythrocyte protoporphyrin, measured as "free" erythrocyte protoporphyrin (FEP), was determined in 194 adult subjects with different occupational and non-occupational lead exposures. Furthermore, the ZPP-FEP comparison was considered with respect to the dose-effect relationship of ZPP and FEP with blood lead (PbB) for males and females, respectively. Bilirubin (Bil.) interferences in ZPP analysis were taken into account. A very close and highly significant relationship (r = 0.962, P < 0.001) was established between ZPP and FEP values. A significant correlation (P < 0.001) between log ZPP or log FEP and PbB (males r = 0.767 and 0.718; females r = 0.525 and 0.405) was also found. It was established, by both in vitro and in vivo studies, that Bil. interferes with the ZPP fluorescence readings; the relationship between "false" positive ZPP concentrations and Bil. concentrations (in vitro r = 0.987, in vivo r = 0.903) was highly significant (P < 0.001). A small but highly significant (r = 0.948, P < 0.001) influence of increased carboxyhemoglobin (COHb) concentrations on the decrease in hematofluorometer ZPP readings, due to inadequate oxygenation of the blood, was found. The results obtained confirm the usefullness of ZPP determinations using hematofluorometers for surveillance of increased lead absorption but stress that the interfering effect of Bil., and to a lesser extent of COHb, cannot be ignored.

  15. 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.

  16. Terrestrial applications of FEP-encapsulated solar cell modules. [systems design and power output characteristics

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    FEP-encapsulated solar cell modules and arrays have been designed and built expressly for terrestrial applications. System design including solar cell array mechanical design and the approach to system sizing is outlined. Such solar cell systems have been installed at six sites. Individual modules have undergone marine environment tests. Results from seven months of operation indicate that system is meeting its electrical design requirements. No mechanical degradation has been reported. The array on Mammoth Mountain, California has been damaged by rime ice but shows no loss in electrical output. Marine environment tests on single modules have shown that elements of the module must be completely sealed by the FEP. Based on the limited test data available, the FEP-encapsulated solar cell module appears well suited to terrestrial applications.

  17. 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.

  18. The ferric enterobactin transporter Fep is required for persistent Salmonella enterica serovar typhimurium infection.

    PubMed

    Nagy, Toni A; Moreland, Sarah M; Andrews-Polymenis, Helene; Detweiler, Corrella S

    2013-11-01

    Most bacterial pathogens require iron to grow and colonize host tissues. The Gram-negative bacterium Salmonella enterica serovar Typhimurium causes a natural systemic infection of mice that models acute and chronic human typhoid fever. S. Typhimurium resides in tissues within cells of the monocyte lineage, which limit pathogen access to iron, a mechanism of nutritional immunity. The primary ferric iron import system encoded by Salmonella is the siderophore ABC transporter FepBDGC. The Fep system has a known role in acute infection, but it is unclear whether ferric iron uptake or the ferric iron binding siderophores enterobactin and salmochelin are required for persistent infection. We defined the role of the Fep iron transporter and siderophores in the replication of Salmonella in macrophages and in mice that develop acute followed by persistent infections. Replication of wild-type and iron transporter mutant Salmonella strains was quantified in cultured macrophages, fecal pellets, and host tissues in mixed- and single-infection experiments. We show that deletion of fepB attenuated Salmonella replication and colonization within macrophages and mice. Additionally, the genes required to produce and transport enterobactin and salmochelin across the outer membrane receptors, fepA and iroN, are needed for colonization of all tissues examined. However, salmochelin appears to be more important than enterobactin in the colonization of the spleen and liver, both sites of dissemination. Thus, the FepBDGC ferric iron transporter and the siderophores enterobactin and salmochelin are required by Salmonella to evade nutritional immunity in macrophages and cause persistent infection in mice.

  19. 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

    2016-03-01

    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.

  20. 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).

  1. Ultraviolet irradiation at elevated temperatures and thermal cycling in vacuum of FEP-A covered silicon solar cells

    NASA Technical Reports Server (NTRS)

    Broder, J. D.; Marsik, S. J.

    1978-01-01

    Silicon solar cells covered with FEP-A were irradiated in vacuum with ultraviolet light and then subjected to thermal cycling. These accelerated laboratory conditions are believed to be equivalent to those experienced by FEP-A covered cells on the ATS-6 spacecraft and the results indicate a probable mechanism for the faster degradation of the FEP-A covered cells. Heat-bonded FEP-A covers apparently embrittle when exposed to four months of space UV radiation at elevated temperatures, and crack when subjected to thermal cycling during the eclipse period. Low energy proton radiation can then penetrate to the junction of the cell causing degradation of the open circuit voltage and maximum power to occur. An alternate method of application of FEP-A, such as with adhesives, may prevent such cracking.

  2. Aluminate solution decomposition new technology development

    SciTech Connect

    Abramov, V.Ya.; Stelmakova, G.D.

    1996-10-01

    Scientific Technical Centre Reactor together with SC Aluminy carried out the number of investigations in the field of aluminum solution decomposition new technology development. It was based on large prime ratio on one hand, and liquid-solid countercurrent flow movement on the other hand. Practically the suggested technology was considered to be the result of unstationary, mass-transfer theory, which had been checked up at 100 m3 plot scale plant. Hydrate washing was accomplished at the first stage under the condition of countercurrent flow and less than 1 m3 water discharge. The experiments of 3.2--3.3 caustic module aluminate solution decomposition were carried out at the second stage. While full reactor 20 hour regime operation the caustic module increased till 4.1. Usually it accounts 3.7 under the analogous conditions and time.

  3. 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.

  4. Structural, optical and photocatalytic activity of cerium doped zinc aluminate

    NASA Astrophysics Data System (ADS)

    Sumathi, Shanmugam; Kavipriya, A.

    2017-03-01

    Zinc aluminate and cerium-doped zinc aluminate nanoparticles are synthesised by co-precipitation method. Ammonium hydroxide is used as a precipitating agent. The synthesised compounds are characterised by powder X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FT-IR), Ultraviolet diffuse reflectance spectroscopy (UV-DRS), Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and Surface area measurements. The photocatalytic activity of zinc aluminate and cerium doped zinc aluminate nanoparticles are studied under the UV light and visible light taking methylene blue as a model pollutant. The amount of catalyst, concentration of dye solution and time are optimised under UV-light. Degradation of methylene blue under the UV-light is found to be 99% in 20 min with 10 mg of cerium doped catalyst. Compared to visible light degradation, the degradation of dye under UV-light is higher. Cerium doping in zinc aluminate (ZnAl2O4:Ce3+) increased the photocatalytic activity of zinc aluminate.

  5. Etude vibrationnelle d'aluminates et de gallates de terres rares—IV. Aluminates de samarium et d'europium

    NASA Astrophysics Data System (ADS)

    Saine, M. C.; Husson, E.

    In order to complete our studies on rare earth aluminates and gallates of perovskite structure, we have calculated a force field for orthorhombic SmAlO 3 and EuAlO 3. This force field is anisotropic with regard to the ab plane of the structure and is slightly weaker than the force field of the rhombohedral aluminates LaAlO 3 or NdAlO 3.

  6. 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.

  7. Infrared laser deposition of Teflon coatings on microstructures

    NASA Astrophysics Data System (ADS)

    Papantonakis, M. R.; HaglundJr., R. F.

    2006-01-01

    Polytetrafluoroethylene (PTFE, trade name Teflon) has a wide range of unique and desirable physical, electrical and chemical properties. Its tribological properties are well-suited to anti-stiction applications, and its chemical inertness commends it as a barrier and passivation layer. However, conventional thin-film techniques are not suited for depositing Teflon films on microstructures. Spin coating is impossible because of the well-known insolubility of PTFE. Plasma polymerization of fluorocarbon monomers, ion beam and rf sputtering produce PTFE films that are deficient in fluorine. Pulsed laser deposition (PLD) using excimer and Ti:sapphire lasers is unsatisfactory because UV or near-IR laser ablation "unzips" the PTFE, and requires high-temperature annealing to re-polymerize the deposited monomeric film. We have demonstrated that a completely dry, vapor-phase coating technique - resonant infrared pulsed laser deposition (RIR-PLD) at a wavelength of 8.26 μm -produces crystalline, smooth Teflon films at low process temperatures. Indeed, the films as deposited by RIR-PLD exhibit a surprising degree of crystallinity even at room temperature. The stoichiometry and local electronic structure are preserved during the laser vaporization process, as demonstrated by IR absorption and X-ray photoelectron spectroscopy. Films deposited on microscale structures show good adhesion, excellent smoothness, and a high degree of conformability to the structures. We also discuss experiments planned for the near future to compare the tribological properties of the PTFE films deposited by RIR-PLD with those of other tribological coatings. We will also discuss the implementation of RIR-PLD in practical processing schemes for MEMS applications, including the challenge in adapting existing solid-state mid-IR laser technology for this purpose.

  8. Living history in current orthopaedic hip surgery: intrapelvic teflon granuloma after total hip replacement.

    PubMed

    Gheorghiu, Daniel; Peter, Viju; Lynch, Martin

    2010-02-01

    The teflon hip arthroplasty design was used by Sir John Charnley in the early 60's but was taken off the market due to high complication rates. A case is reported of an intrapelvic granuloma after total hip arthroplasty following the use of a teflon socket. This appears to be the last surviving patient treated by Sir John Charnley using a Teflon hip socket design.

  9. Flexible circular waveguides at millimeter wavelengths from metallized Teflon tubing

    NASA Astrophysics Data System (ADS)

    Obrzut, J.; Goldsmith, P. F.

    1990-03-01

    Flexible waveguides for use at millimeter wavelengths have been fabricated by deposition of metallic film onto the composite-modified inside surface of Teflon tubing. The attenuation characteristics in the range 80 to 115 GHz show losses on the order of 0.1 dB/cm. Bending, twisting, and rotating to the limit of plastic mechanical stability (curvature radius typically greater than 8 cm) have a negligible effect on the attenuation, and bend angles less than 45 deg produce relatively small changes in the insertion phase.

  10. 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.

  11. 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.

  12. Dynamic electrowetting-on-dielectric (DEWOD) on unstretched and stretched teflon.

    PubMed

    Lee, Min Wook; Latthe, Sanjay S; Yarin, Alexander L; Yoon, Sam S

    2013-06-25

    Dynamic electrowetting-on-dielectric (DEWOD) of the unstretched and stretched Teflon is reported in the experiments with water drop impact and rebound. We explore experimentally and theoretically the situation with the capacitance different from the standard static electrowetting. Deionized water drops impact onto either an unstretched hydrophobic Teflon surface or Teflon stretched up to 250% strain normally to the impact direction. The surface roughness of the unstretched Teflon increased after stretching from 209.9 to 245.6 nm resulting in the increase in the equilibrium water contact angle from 96 ± 4° to 147 ± 5°, respectively. The electric arrangement used in the drop impact experiments on DEWOD results in a dramatically reduced capacitance and requires a much higher voltage to observe EW in comparison with the standard static case of a drop deposited on a dielectric layer and attached to an electrode. In the dynamic situation we found that as the EW sets in it can greatly reduce the superhydrophobicity of the unstretched and stretched Teflon. At 0 kV, the water drop rebound height (hmax) is higher for the stretched Teflon (hmax ≈ 5.13 mm) and lower for the unstretched Teflon (hmax ≈ 4.16 mm). The EW response of unstretched Teflon is weaker than that of the stretched one. At the voltage of 3 kV, the water drop sticks to the stretched Teflon without rebound, whereas water drops still partially rebound (hmax ≈ 2.8 mm) after a comparable impact onto the unstretched Teflon. We found a sharp dynamic EW response for the stretched Teflon. The contact angle of deionized water ranged from 147 ± 5° (superhydrophobic) to 67 ± 5° (partially hydrophilic) by applying external voltage of 0 and 3 kV, respectively. Dynamic electrowetting introduced in this work for the first time can be used to control spray cooling, painting, and coating and for drop transport in microfluidics.

  13. 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.

  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. 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.

  16. Nanoporous FeP nanorods grown on Ti plate as an enhanced binder-free hydrogen evolution cathode.

    PubMed

    Gao, J J; Luo, P; Qiu, H-J; Wang, Y

    2017-03-10

    A porous and interconnected nanorod-like FeP structure on titanium plate has been fabricated by a simple hydrothermal method and followed by a calcination process. The nanorod is assembled by many paralleled FeP nanowires with a porous structure. With the porous surface structure of FeP nanorods and the synergetic effect from the electronic conductive Ti support, this binder-free FeP electrode brings about a desirable electrocatalytic activity for the hydrogen evolution reaction (HER), showing a low onset overpotential of 23 mV and a small Tafel slope of 39 mV dec(-1). Meanwhile, its catalytic activity could be maintained almost unchanged for at least 12 h in an acidic solution. This work provides us an effective HER electrocatalyst which can be easily produced on a large scale and at low cost.

  17. Nanoporous FeP nanorods grown on Ti plate as an enhanced binder-free hydrogen evolution cathode

    NASA Astrophysics Data System (ADS)

    Gao, J. J.; Luo, P.; Qiu, H.-J.; Wang, Y.

    2017-03-01

    A porous and interconnected nanorod-like FeP structure on titanium plate has been fabricated by a simple hydrothermal method and followed by a calcination process. The nanorod is assembled by many paralleled FeP nanowires with a porous structure. With the porous surface structure of FeP nanorods and the synergetic effect from the electronic conductive Ti support, this binder-free FeP electrode brings about a desirable electrocatalytic activity for the hydrogen evolution reaction (HER), showing a low onset overpotential of 23 mV and a small Tafel slope of 39 mV dec‑1. Meanwhile, its catalytic activity could be maintained almost unchanged for at least 12 h in an acidic solution. This work provides us an effective HER electrocatalyst which can be easily produced on a large scale and at low cost.

  18. 40 CFR 721.10423 - Complex strontium aluminate, rare earth doped (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Complex strontium aluminate, rare... 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,...

  19. Confined Mobility of TonB and FepA in Escherichia coli Membranes

    PubMed Central

    Lill, Yoriko; Jordan, Lorne D.; Smallwood, Chuck R.; Newton, Salete M.; Lill, Markus A.; Klebba, Phillip E.; Ritchie, Ken

    2016-01-01

    The important process of nutrient uptake in Escherichia coli, in many cases, involves transit of the nutrient through a class of beta-barrel proteins in the outer membrane known as TonB-dependent transporters (TBDTs) and requires interaction with the inner membrane protein TonB. Here we have imaged the mobility of the ferric enterobactin transporter FepA and TonB by tracking them in the membranes of live E. coli with single-molecule resolution at time-scales ranging from milliseconds to seconds. We employed simple simulations to model/analyze the lateral diffusion in the membranes of E.coli, to take into account both the highly curved geometry of the cell and artifactual effects expected due to finite exposure time imaging. We find that both molecules perform confined lateral diffusion in their respective membranes in the absence of ligand with FepA confined to a region 0.180−0.007+0.006 μm in radius in the outer membrane and TonB confined to a region 0.266−0.009+0.007 μm in radius in the inner membrane. The diffusion coefficient of these molecules on millisecond time-scales was estimated to be 21−5+9 μm2/s and 5.4−0.8+1.5 μm2/s for FepA and TonB, respectively, implying that each molecule is free to diffuse within its domain. Disruption of the inner membrane potential, deletion of ExbB/D from the inner membrane, presence of ligand or antibody to FepA and disruption of the MreB cytoskeleton was all found to further restrict the mobility of both molecules. Results are analyzed in terms of changes in confinement size and interactions between the two proteins. PMID:27935943

  20. 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.

  1. Formation of droplet interface bilayers in a Teflon tube

    PubMed Central

    Walsh, Edmond; Feuerborn, Alexander; Cook, Peter R.

    2016-01-01

    Droplet-interface bilayers (DIBs) have applications in disciplines ranging from biology to computing. We present a method for forming them manually using a Teflon tube attached to a syringe pump; this method is simple enough it should be accessible to those without expertise in microfluidics. It exploits the properties of interfaces between three immiscible liquids, and uses fluid flow through the tube to pack together drops coated with lipid monolayers to create bilayers at points of contact. It is used to create functional nanopores in DIBs composed of phosphocholine using the protein α-hemolysin (αHL), to demonstrate osmotically-driven mass transfer of fluid across surfactant-based DIBs, and to create arrays of DIBs. The approach is scalable, and thousands of DIBs can be prepared using a robot in one hour; therefore, it is feasible to use it for high throughput applications. PMID:27681313

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

    PubMed

    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

    2012-03-06

    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. Formation of droplet interface bilayers in a Teflon tube

    NASA Astrophysics Data System (ADS)

    Walsh, Edmond; Feuerborn, Alexander; Cook, Peter R.

    2016-09-01

    Droplet-interface bilayers (DIBs) have applications in disciplines ranging from biology to computing. We present a method for forming them manually using a Teflon tube attached to a syringe pump; this method is simple enough it should be accessible to those without expertise in microfluidics. It exploits the properties of interfaces between three immiscible liquids, and uses fluid flow through the tube to pack together drops coated with lipid monolayers to create bilayers at points of contact. It is used to create functional nanopores in DIBs composed of phosphocholine using the protein α-hemolysin (αHL), to demonstrate osmotically-driven mass transfer of fluid across surfactant-based DIBs, and to create arrays of DIBs. The approach is scalable, and thousands of DIBs can be prepared using a robot in one hour; therefore, it is feasible to use it for high throughput applications.

  4. 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.

  5. Formation of droplet interface bilayers in a Teflon tube.

    PubMed

    Walsh, Edmond; Feuerborn, Alexander; Cook, Peter R

    2016-09-29

    Droplet-interface bilayers (DIBs) have applications in disciplines ranging from biology to computing. We present a method for forming them manually using a Teflon tube attached to a syringe pump; this method is simple enough it should be accessible to those without expertise in microfluidics. It exploits the properties of interfaces between three immiscible liquids, and uses fluid flow through the tube to pack together drops coated with lipid monolayers to create bilayers at points of contact. It is used to create functional nanopores in DIBs composed of phosphocholine using the protein α-hemolysin (αHL), to demonstrate osmotically-driven mass transfer of fluid across surfactant-based DIBs, and to create arrays of DIBs. The approach is scalable, and thousands of DIBs can be prepared using a robot in one hour; therefore, it is feasible to use it for high throughput applications.

  6. 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.

  7. 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

  8. [Aluminous cement for dental application (author's transl)].

    PubMed

    Takeda, S

    1982-01-01

    The various materials such as zinc oxide eugenol pastes, calcium hydroxide slurry and self hardening polymers have been used for the root canal filling and pulp capping. However, those materials have various problems in terms of biocompatibility and physical properties in clinical use. The development of root canal filling and pulp capping materials has been carried out with powder-liquid system which consisted of aluminous cement added to 20 wt% Ca (OH)2 and polyvinylalcohol solutions. The influence of polyvinylalcohol concentrations and L/P ratio on physical properties and biocompatibility were investigated. The results were as follows: 1. The initial setting time was showed between 3 and 20 minutes according to polyvinylalcohol concentration and L/P ratio and delayed linearly by increasing the L/P ratio. 2. The consistency was indicated between 18 and 51 mm with polyvinylalcohol concentration and L/P ratio. The lower the L/P ratio, the thicker was the consistency. 3. The solubilities in distilled water were 2.7-7.3% and 3.9-8.4%, respectively, after storage for 24 hours and 1 week, while those values in 199 medium were 2.9-6.2% and 4.4-9.9%, respectively, after storage for 24 hours and 1 week. 4. The pH values in distilled water were indicated high alkaline conditions of about 11.5 after storage for 24 hours and was not influenced by the repeated immersions. On the other hand, the pH values in 199 medium were showed high alkaline conditions of about 11.0 after storage for 24 hours, but decreased rapidly to the neutral conditions of about 8.0 with the repeated immersion. 5. The compressive strengths were increased by the use of higher polyvinylalcohol concentration and lower L/P ratio and indicated from 26 kg/cm2 and 278 kg/cm2. 6. By the use of the tissue culture method, mild response with the un-set cement was recognized from the morphological observation. In the case of the set cement, the cell morphological changes showed no significant difference in the

  9. 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.

  10. 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...

  11. 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.

  12. Neutron diffraction study of the Li-ion battery cathode Li2FeP2O7.

    PubMed

    Barpanda, Prabeer; Rousse, Gwenaëlle; Ye, Tian; Ling, Chris D; Mohamed, Zakiah; Klein, Yannick; Yamada, Atsuo

    2013-03-18

    With a combination of magnetic susceptibility measurements and low-temperature neutron diffraction analyses, the magnetic structure of Li2FeP2O7 cathode has been solved. This pyrophosphate Li2FeP2O7 compound stabilizes into a monoclinic framework (space group P2(1)/c), having a pseudolayered structure with the constituent Li/Fe sites distributed into MO6 and MO5 building units. The magnetic susceptibility follows a Curie-Weiss behavior above 50 K. Li2FeP2O7 shows a long-range antiferromagnetic ordering at T(N) = 9 K, as characterized by the appearance of distinct additional peaks in the neutron diffraction pattern below T(N). Its magnetic reflections can be indexed with a propagation vector k = (0,0,0). The magnetic moments inside the FeO6-FeO5 clusters are ferromagnetic, whereas these clusters are antiferromagnetic along the chains. The adjacent chains are in turn ferromagnetically arranged along the a-axis. The magnetic structure of Li2FeP2O7 cathode material is described focusing on their localized spin-spin exchange. The magnetic structure and properties have been generalized for Li2FeP2O7-Li2CoP2O7 binary solid solutions.

  13. 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)

  14. Enhanced absorption of microwaves within cylindrical holes in Teflon film.

    PubMed

    Alekseev, Stanislav I; Fesenko, Evgeny E; Ziskin, Marvin C

    2010-10-01

    Earlier publications demonstrated that 0.9 GHz microwave exposure induced notable changes of the conductivity of modified bilayer lipid membranes (BLM) formed in holes in thin Teflon film (TF). The aims of this study were: 1) to perform detailed calculations of the microwave field distributions in holes formed in TF, using the finite-difference time-domain technique and 2) to model microwave heating of the hole under the conditions used in the BLM experiments but in the absence of BLM in the hole. We found that with the E-field oriented perpendicular to the TF plane the local-specific absorption rate in holes increased significantly. The increase became larger with increasing electrolyte concentration and with decreasing diameter of the hole and frequency. The calculated temperature elevations in the hole were in good agreement with those determined experimentally. These findings allowed us to conclude that the microwave effects on BLM conductivity reported previously resulted mostly from the enhanced absorption of microwave energy by the membrane-forming holes and subsequent local temperature elevation in the holes.

  15. Direct deposition of patterned copper films on Teflon

    NASA Astrophysics Data System (ADS)

    Perry, W. L.; Chi, K. M.; Koda, T.; Hampden-Smith, M.; Rye, R.

    1993-05-01

    Current subtractive methods yielding patterned Cu features on PTFE substrates rely on wet Cu etching processes. We have developed three variations of a new dry, additive patterning process. The mechanisms for patterning include MgKα X-ray-induced cross-linking, e-beam-induced cross-linking, or laser patterning. The X-ray and e-beam patterning processes rely on irradiation followed by selective etching of the non-irradiated areas. The laser patterning begins by chemically etching PTFE which leaves a rough surface with good adhesion characteristics. An argon-ion laser beam is then used to selectively remove the etched layer, revealing the underlying surface which has physical properties closely resembling unmodified Teflon. Typical laser patterning conditions are scan rates of 0.005-5.5 mm/s, incident powers of 40-380 mW at 514 nm, and base pressures of 10 -2 Torr and at atmospheric pressure in air. In all cases, CVD from ( β-diketonate)CuL compounds is used to deposit copper only on the etched regions of the sample, leaving the irradiated regions copper-free. The advantages of this procedure are: (1) subtractive Cu wet etching of copper is avoided, so no masking techniques are necessary and no liquid waste is generated; (2) ten-micron-sized features can be produced; (3) excellent adhesion is obtained.

  16. High-resolution micropatterned Teflon AF substrates for biocompatible nanofluidic devices.

    PubMed

    Czolkos, Ilja; Hakonen, Bodil; Orwar, Owe; Jesorka, Aldo

    2012-02-14

    We describe a general photolithography-based process for the microfabrication of surface-supported Teflon AF structures. Teflon AF patterns primarily benefit from superior optical properties such as very low autofluorescence and a low refractive index. The process ensures that the Teflon AF patterns remain strongly hydrophobic in order to allow rapid lipid monolayer spreading and generates a characteristic edge morphology which assists directed cell growth along the structured surfaces. We provide application examples, demonstrating the well-controlled mixing of lipid films on Teflon AF structures and showing how the patterned surfaces can be used as biocompatible growth-directing substrates for cell culture. Chinese hamster ovary (CHO) cells develop in a guided fashion along the sides of the microstructures, selectively avoiding to grow over the patterned areas.

  17. 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

  18. Novel strategy involving surfactant-polymer combinations for enhanced stability of aqueous teflon dispersions.

    PubMed

    Sharma, Mukesh; Bharatiya, Bhavesh; Mehta, Krupali; Shukla, Atindra; Shah, Dinesh O

    2014-06-24

    Among various polymers, the Teflon surface possesses extreme hydrophobicity (low surface energy), which is of great interest to both industry and academia. In this report, we discuss the stability of aqueous Teflon dispersions (particle size range of 100-3000 nm) formulated by a novel strategy that involves distinct combinations of surfactant and polymer mixtures for dispersion stabilization. As a first step, the hydrophobic Teflon particles were wetted using a range of surfactants (ionic, Triton, Brij, Tween, and Pluronic series) bearing different hydrophobic-lipophilic balance (HLB) and further characterized by contact angle and liquid penetration in packed powder measurements. The interaction between hydrophobic chains of surfactants and the Teflon particle surface is the driving force resulting in wetting of the Teflon particle surface. Further, these wetted particles in aqueous solutions were mixed with various polymers, for example, poly(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), hydroxyethyl cellulose (HEC), and hydroxypropyl methyl cellulose (HPMC). The rate of sedimentation for the final dispersions was measured using a pan suspended into the dispersion from a transducer recording the increase in weight with time. A significant stability was noticed for Teflon particles suspended in surfactant + polymer mixtures, which was linearly proportional to the concentration of added polymer. The observed phenomenon can be possibly explained by molecular interactions between the hydrophobic chains of surfactant molecules and polar groups in the polymer architecture. Brij-O10 + HEC mixture was found to be the best surfactant-polymer combination for decreasing the sedimentation of the Teflon particles in the final dispersion. As measured by dynamic light scattering (DLS), the hydrodynamic volume of the Teflon particles increases up to ∼55% in the final formulation. These dispersions could be further explored for various technological applications such as

  19. 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.

  20. Evaluation of teflon-coated intraocular lenses in an organ culture method.

    PubMed

    Werner, L; Legeais, J M; Nagel, M D; Renard, G

    1999-09-05

    An amorphous and transparent form of Teflon is proposed as a coating of polymethylmethacrylate (PMMA) intraocular lenses (IOLs), rendering them highly hydrophobic. We used an organ culture method to evaluate cell adhesion, proliferation, and migration on Teflon-coated IOLs. Corneal explants from 14-day-old chicken embryos were placed on a semisolid culture medium and covered with uncoated PMMA (n = 36) and Teflon-coated PMMA (n = 36) IOLs and two controls, Thermanox (n = 84) and latex (n = 36). After incubation (7 days at 37 degrees C), a digital imaging system was used to measure the areas of the cell migration layers on the materials. The cells were then removed with tripsin-ethylenediaminetetraacetic acid and the cells detached at times up to 75 min were counted (Coulter(R) Multisizer System). The values were used to construct a cell disconnecting curve for each material. The areas of cell migration layers on uncoated and Teflon-coated IOLs were significantly different (p <.05). Cell disconnecting curves demonstrated that cells adhered less strongly to Teflon-coated IOLs than to the other materials. This organ culture method demonstrated that the coating of PMMA IOLs with Teflon AF(R) is correlated with antiadhesive and antiproliferative properties.

  1. 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.

  2. Ultraviolet irradiation at elevated temperatures and thermal cycling in vacuum of FEP-A covered silicon solar cells

    NASA Technical Reports Server (NTRS)

    Broder, J. D.; Marsik, S. J.

    1978-01-01

    Experiments were designed and performed on silicon solar cells covered with heat-bonded FEP-A in an effort to explain the rapid degeneration of open-circuit voltage and maximum power observered on cells of this type included in an experiment on the ATS-6 spacecraft. Solar cells were exposed to ultraviolet light in vacuum at temperatures ranging from 30 to 105 C. The samples were then subjected to thermal cycling from 130 to -130 C. Inspection following irradiation indicated that all the covers remained physically intact. However, during the temperature cycling heat-bonded covers showed cracking. The test showed that heat-bonded FEP-A covers embrittle during UV exposure and the embrittlement is dependent upon sample temperature during irradiation. The results of the experiment suggest a probable mechanism for the degradation of the FEP-A cells on ATS-6.

  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. Magnetic properties of some rare-earth nanostuctured aluminates

    NASA Astrophysics Data System (ADS)

    Lovchinov, V.; Petrov, D.; Simeonova, P.; Angelov, B.

    2010-11-01

    Nanocrystalline single-phase RAlO3 (R = Nd, Sm, Eu, Dy, Gd) has been prepared by modified Pechini's method. Malic acid has been used for the first time as a new complexing agent in the sol-gel process. It has facilited a low temperature synthesis of the compound. The characterization of the nanoparticles has been carried out by different methods. Using Physical Property Measurement System (PPMS-9 QD) the temperature and magnetic dependency of the susceptibility and magnetization of the nanostuctured aluminates were measured. The obtained results were compared with the existing ones for the single crystals and powder specimens of the same aluminates. The differences observed have been discussed in the framework of the molecular field theory for a two-sublattice system.

  5. 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.

  6. 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.

  7. Reevaluation of thermonuclear reaction rate of 50Fe(p, 𝜸)51Co

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Ping; He, Jian-Jun; Chai, Wan-Dong; Hou, Su-Qing; Zhang, Li-Yong

    2016-11-01

    The thermonuclear rate of the 50Fe(p, 𝜸)51Co reaction in the Type I X-ray bursts (XRBs) temperature range has been reevaluated based on a recent precise mass measurement at CSRe Lanzhou, where the proton separation energy Sp = 142±77 keV has been determined firstly for the 51Co nucleus. Comparing to the previous theoretical predictions, the experimental Sp value has much smaller uncertainty. Based on the nuclear shell model and mirror nuclear structure information, we have calculated two sets of thermonuclear rates for the 50Fe(p, 𝜸)51Co reaction by utilizing the experimental Sp value. It shows that the statistical-model calculations are not ideally applicable for this reaction primarily because of the low density of low-lying excited states in 51Co. In this work, we recommend that a set of new reaction rates based on the mirror structure of 51Cr should be incorporated in future astrophysical network calculations. Supported by Natural Science Foundation of Inner Mongolia Autonomous Region of China (2013MS0916) and National Natural Science Foundation of China (11490562, 11405228)

  8. Magnetic structure and magnon dynamics of the quasi-two-dimensional antiferromagnet FePS3

    NASA Astrophysics Data System (ADS)

    Lançon, D.; Walker, H. C.; Ressouche, E.; Ouladdiaf, B.; Rule, K. C.; McIntyre, G. J.; Hicks, T. J.; Rønnow, H. M.; Wildes, A. R.

    2016-12-01

    Neutron scattering from single crystals has been used to determine the magnetic structure and magnon dynamics of FePS3, an S =2 Ising-like quasi-two-dimensional antiferromagnet with a honeycomb lattice. The magnetic structure has been confirmed to have a magnetic propagation vector of kM=[01 1/2 ] and the moments are collinear with the normal to the a b planes. The magnon data could be modeled using a Heisenberg Hamiltonian with a single-ion anisotropy. Magnetic interactions up to the third in-plane nearest neighbor needed to be included for a suitable fit. The best fit parameters for the in-plane exchange interactions were J1=1.46 , J2=-0.04 , and J3=-0.96 meV. The single-ion anisotropy is large, Δ =2.66 meV, explaining the Ising-like behavior of the magnetism in the compound. The interlayer exchange is very small, J'=-0.0073 meV, proving that FePS3 is a very good approximation to a two-dimensional magnet.

  9. Inhibited Aluminization of an ODS FeCr Alloy

    SciTech Connect

    Vande Put Ep Rouaix, Aurelie; Pint, Bruce A

    2012-01-01

    Aluminide coatings are of interest for fusion energy applications both for compatibility with liquid Pb-Li and to form an alumina layer that acts as a tritium permeation barrier. Oxide dispersion strengthened (ODS) ferritic steels are a structural material candidate for commercial reactor concepts expected to operate above 600 C. Aluminizing was conducted in a laboratory scale chemical vapor deposition reactor using accepted conditions for coating Fe- and Ni-base alloys. However, the measured mass gains on the current batch of ODS Fe-14Cr were extremely low compared to other conventional and ODS alloys. After aluminizing at two different Al activities at 900 C and at 1100 C, characterization showed that the ODS Fe-14Cr specimens formed a dense, primarily AlN layer that prevented Al uptake. This alloy batch contained a higher (> 5000 ppma) N content than the other alloys coated and this is the most likely reason for the inhibited aluminization. Other factors such as the high O content, small ({approx} 140 nm) grain size and Y-Ti oxide nano-clusters in ODS Fe-14Cr also could have contributed to the observed behavior. Examples of typical aluminide coatings formed on conventional and ODS Fe- and Ni-base alloys are shown for comparison.

  10. 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.

  11. Effect of aluminizing treatment on the oxidation properties of 12Cr heat resisting steel

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Hwan; Wang, Jei-Pil; Kang, Chang-Yong

    2011-12-01

    In order to investigate the effect of aluminization on the oxidation properties of 12Cr martensitic heat resisting steel, a specimen was prepared by forging after centrifugal casting. After aluminizing treatment under various conditions, scanning electron microscopy observation, and hardness, line profile and x-ray diffraction analysis of the alloy layer were performed. The results confirmed that the thickness of the layer of Al13Fe4, with a Vickers hardness of over 880, increased with increasing aluminizing temperature and time. Moreover, it was concluded from the results of the oxidation experiment that the oxidation properties of the aluminized specimen were improved by up to approximately 30 %.

  12. Properties and transport behavior of perfluorotripentylamine (FC-70)-doped amorphous teflon AF 2400 films.

    PubMed

    Zhang, Hong; Hussam, Abul; Weber, Stephen G

    2010-12-22

    Teflon AF 2400 films are known to imbibe solvents, making films in the presence of solvents less fluorous than they might otherwise be. Herein, we demonstrate that doping films with perfluorotripentylamine (Fluorinert FC-70) maintains the fluorous nature of Teflon AF 2400 and improves transport selectivity for fluorine-containing organic compounds. Density measurements on the FC-70-doped films reveal that free volume decreases dramatically as the dopant concentration increases (0-12 wt %) and then increases to approach that of pure FC-70. Remarkably, films from 0 to 12 wt % FC-70 have the same w/v concentration of Teflon AF 2400, indicating that FC-70 fills the free volume of Teflon AF 2400. This is consistent with the observed increased storage modulus and significant decrease (compared to undoped films) of solute diffusion coefficients in the same range of FC-70 concentrations. In contrast, FC-70 at concentrations greater than 12 wt % dilutes Teflon AF 2400, leading to a decrease of storage modulus and dramatic increase in solute diffusion coefficients. Sorption of chloroform decreases from 11.8 g of chloroform/100 g of film (pure Teflon film) to 3.8 g of chloroform/100 g of film (27 wt % FC-70-doped Teflon film), less than the solubility of chloroform in pure FC-70 (4.06 g of chloroform/100 g of FC-70). Solute partition coefficients from chloroform to FC-70-doped films generally decrease with increased dopant concentration. However, within a series of toluenes and nitrobenzenes, selectivity for F-containing solutes over analogous H-containing solutes increases as dopant concentration increases if the substitution is on the aromatic ring but not if it is on the methyl group (toluene). Transport (partitioning × diffusion) rates, as they involve both thermodynamic and kinetic factors, are not simply related to composition.

  13. [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.

  14. The solution structure, binding properties, and dynamics of the bacterial siderophore-binding protein FepB.

    PubMed

    Chu, Byron C H; Otten, Renee; Krewulak, Karla D; Mulder, Frans A A; Vogel, Hans J

    2014-10-17

    The periplasmic binding protein (PBP) FepB plays a key role in transporting the catecholate siderophore ferric enterobactin from the outer to the inner membrane in Gram-negative bacteria. The solution structures of the 34-kDa apo- and holo-FepB from Escherichia coli, solved by NMR, represent the first solution structures determined for the type III class of PBPs. Unlike type I and II PBPs, which undergo large "Venus flytrap" conformational changes upon ligand binding, both forms of FepB maintain similar overall folds; however, binding of the ligand is accompanied by significant loop movements. Reverse methyl cross-saturation experiments corroborated chemical shift perturbation results and uniquely defined the binding pocket for gallium enterobactin (GaEnt). NMR relaxation experiments indicated that a flexible loop (residues 225-250) adopted a more rigid and extended conformation upon ligand binding, which positioned residues for optimal interactions with the ligand and the cytoplasmic membrane ABC transporter (FepCD), respectively. In conclusion, this work highlights the pivotal role that structural dynamics plays in ligand binding and transporter interactions in type III PBPs.

  15. Role of the Teflon deposit in the recurrence of vesicoureteral reflux.

    PubMed

    Oberritter, Zsolt; Somogyi, Reka; Juhasz, Zsolt; Pinter, Andrew B

    2008-05-01

    A relationship between the Teflon deposit, visible with ultrasound, and long-term success of subureteric Teflon injection (STING) treatment was investigated. The study included only those patients with primary vesicoureteral reflux (VUR), in whom the reflux had disappeared and the Teflon deposits were visible 6 weeks following STING treatment. Cessation of VUR was proven by voiding cysto-urethrography (VCUG) in 99 patients (143 ureters). Average follow-up time was 9 (4-12) years. Patients were divided into two groups: group I, deposits visible with ultrasound [deposit (+)], and group II, no visible deposits at the end of the follow-up period [deposit (-)]. Reflux recurrence, the occurrence of urinary tract infection (UTI), and pyelonephritis were investigated, and technetium scintigraphy scans were examined. The deposit (+) group included 43 patients (65 ureters), and the deposit (-) group contained 56 patients (78 ureters). In the deposit (+) group there were no recurrences of VUR; however, 17 recurrences were found in the deposit (-) group (P < 0.05). Dimercaptosuccinic acid (DMSA) scintigraphy scans and occurrence of UTI showed significant difference between the groups (P < 0.05). A close relationship was found between the disappearance of the Teflon deposit and the recurrence of VUR. Disappearance of the Teflon deposit and repeated bacteriuria is a warning sign of the recurrence of VUR; therefore, VCUG might be warranted for these patients.

  16. Higher quality quercetin sustained release ethyl cellulose nanofibers fabricated using a spinneret with a Teflon nozzle.

    PubMed

    Li, Chen; Wang, Zhuan-Hua; Yu, Deng-Guang

    2014-02-01

    This study investigates the usage of a spinneret with a Teflon nozzle for fabrication of higher quality drug sustained-release electrospun nanofibers. Ethyl cellulose (EC) and quercetin were used as a filament-forming polymer matrix and an active pharmaceutical ingredient, respectively. The electrospinning was conducted using both a traditional stainless steel spinneret and a spinneret with a Teflon nozzle. Experimental results demonstrated that a Teflon-fluid interface at the spinneret's nozzle provided a better performance for implementing electrospinning than a traditional metal-fluid interface in the following aspects: (1) keeping more electrical energy on the working fluids for an efficacious process; (2) exerting less negative effect on the fluid to draw it back to the tube; and (3) making less possibility of clogging. The resulted nanofibers from the spinneret with a Teflon nozzle exhibited higher quality than those from the traditional spinneret in those: (1) smaller diameter and narrower distribution, 520±70 nm for the former and 750±280 nm for the later, as indicated by the field emission scanning electron microscopic images; and (2) better sustained-release profiles of quercetin from the former than the latter, as demonstrated by the in vitro dissolution tests. The new protocols about usage of Teflon as a spinneret's nozzle and the related knowledge disclosed here should promote the preparation and application of electrospun functional nanofibers.

  17. 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.

  18. Randomised comparison of silicone versus Teflon cannulas for peripheral intravenous nutrition.

    PubMed Central

    Reynolds, J. V.; Walsh, K.; Ruigrok, J.; Hyland, J. M.

    1995-01-01

    The use of peripheral intravenous nutrition using standard Teflon cannulas is limited by a high incidence of thrombophlebitis, with resultant frequent line changes and compromised nutritional therapy. Fine-bore silicone catheters may reduce the incidence of thrombophlebitis; we prospectively compared the silicone catheter with a Teflon cannula in a randomised trial. Seventy-nine surgical patients were randomised to receive peripheral nutrition (10 g nitrogen; 1770 kcal; 650 mOsm/l) either via a Teflon cannula (18G, 4.4 cm long) or via a silicone catheter (23G, 15 cm long). Compared with the group randomised to a standard Teflon cannula, patients fed via a silicone catheter had a significant (P < 0.001) improvement in (a) median time to survival of the first catheter (125 h vs 48 h); (b) incidence of catheter reinsertions (13% vs 75%); and (c) incidence of thrombophlebitis (10% vs 48%). Delivery of a moderately hypertonic nutritional solution through a fine-bore silicone catheter is safe, durable and well tolerated, with a low incidence of complications relative to a Teflon cannula. An expanded role for this catheter in nutritional therapy is feasible, which may reduce the requirement for central venous parenteral nutrition. PMID:8540665

  19. 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.

  20. [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.

  1. Dielectric dilatometry on thin Teflon-PTFE films prepared by pulsed-laser deposition

    NASA Astrophysics Data System (ADS)

    Schwoediauer, Reinhard; Bauer-Gogonea, Simona; Bauer, Stefan; Heitz, J.; Arenholz, Enno; Baeuerle, Dieter

    1999-12-01

    Polytetrafluoroethylene (Teflon PTFE) films were grown by pulsed-laser deposition (PLD). Films prepared by ablation from press-sintered targets are found to be highly crystalline, with spherulite sizes adjustable over more than one order in magnitude by suitable thermal annealing. As revealed by dielectric dilatometry, PLD-PTFE films show characteristics remarkably similar to those of conventional PTFE, i.e. the same structural first-order phase transitions. Dielectric losses are low and indicate no tendency to film oxidation. PLD-PTFE films additionally show an excellent charge-stability, comparable and even superior to commercially available Teflon-PTFE foils. PLD-PTFE enlarges the family of Teflon materials and may thus become interesting for potential miniaturized electret devices. Furthermore, dielectric dilatometry provides an elegant means for the determination of the coefficient of thermal expansion in thin nonpolar films.

  2. 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.

  3. Crystal structure control of aluminized clay minerals on the mobility of caesium in contaminated soil environments

    NASA Astrophysics Data System (ADS)

    Dzene, Liva; Ferrage, Eric; Viennet, Jean-Christophe; Tertre, Emmanuel; Hubert, Fabien

    2017-02-01

    Radioactive caesium pollution resulting from Fukushima Dai-ichi and Chernobyl nuclear plant accidents involves strong interactions between Cs+ and clays, especially vermiculite-type minerals. In acidic soil environments, such as in Fukushima area, vermiculite is subjected to weathering processes, resulting in aluminization. The crystal structure of aluminized clays and its implications for Cs+ mobility in soils remain poorly understood due to the mixture of these minerals with other clays and organic matter. We performed acidic weathering of a vermiculite to mimic the aluminization process in soils. Combination of structure analysis and Cs+ extractability measurements show that the increase of aluminization is accompanied by an increase in Cs+ mobility. Crystal structure model for aluminized vermiculite is based on the interstratification of unaltered vermiculite layers and aluminized layers within the same particle. Cs+ in vermiculite layers is poorly mobile, while the extractability of Cs+ is greatly enhanced in aluminized layers. The overall reactivity of the weathered clay (cation exchange capacity, Cs+ mobility) is then governed by the relative abundance of the two types of layers. The proposed layer model for aluminized vermiculite with two coexisting populations of caesium is of prime importance for predicting the fate of caesium in contaminated soil environments.

  4. Crystal structure control of aluminized clay minerals on the mobility of caesium in contaminated soil environments

    PubMed Central

    Dzene, Liva; Ferrage, Eric; Viennet, Jean-Christophe; Tertre, Emmanuel; Hubert, Fabien

    2017-01-01

    Radioactive caesium pollution resulting from Fukushima Dai-ichi and Chernobyl nuclear plant accidents involves strong interactions between Cs+ and clays, especially vermiculite-type minerals. In acidic soil environments, such as in Fukushima area, vermiculite is subjected to weathering processes, resulting in aluminization. The crystal structure of aluminized clays and its implications for Cs+ mobility in soils remain poorly understood due to the mixture of these minerals with other clays and organic matter. We performed acidic weathering of a vermiculite to mimic the aluminization process in soils. Combination of structure analysis and Cs+ extractability measurements show that the increase of aluminization is accompanied by an increase in Cs+ mobility. Crystal structure model for aluminized vermiculite is based on the interstratification of unaltered vermiculite layers and aluminized layers within the same particle. Cs+ in vermiculite layers is poorly mobile, while the extractability of Cs+ is greatly enhanced in aluminized layers. The overall reactivity of the weathered clay (cation exchange capacity, Cs+ mobility) is then governed by the relative abundance of the two types of layers. The proposed layer model for aluminized vermiculite with two coexisting populations of caesium is of prime importance for predicting the fate of caesium in contaminated soil environments. PMID:28233805

  5. Crystal structure control of aluminized clay minerals on the mobility of caesium in contaminated soil environments.

    PubMed

    Dzene, Liva; Ferrage, Eric; Viennet, Jean-Christophe; Tertre, Emmanuel; Hubert, Fabien

    2017-02-24

    Radioactive caesium pollution resulting from Fukushima Dai-ichi and Chernobyl nuclear plant accidents involves strong interactions between Cs(+) and clays, especially vermiculite-type minerals. In acidic soil environments, such as in Fukushima area, vermiculite is subjected to weathering processes, resulting in aluminization. The crystal structure of aluminized clays and its implications for Cs(+) mobility in soils remain poorly understood due to the mixture of these minerals with other clays and organic matter. We performed acidic weathering of a vermiculite to mimic the aluminization process in soils. Combination of structure analysis and Cs(+) extractability measurements show that the increase of aluminization is accompanied by an increase in Cs(+) mobility. Crystal structure model for aluminized vermiculite is based on the interstratification of unaltered vermiculite layers and aluminized layers within the same particle. Cs(+) in vermiculite layers is poorly mobile, while the extractability of Cs(+) is greatly enhanced in aluminized layers. The overall reactivity of the weathered clay (cation exchange capacity, Cs(+) mobility) is then governed by the relative abundance of the two types of layers. The proposed layer model for aluminized vermiculite with two coexisting populations of caesium is of prime importance for predicting the fate of caesium in contaminated soil environments.

  6. Chemical modifications at Teflon interfaces induced by MeV ion beams

    NASA Astrophysics Data System (ADS)

    Ingemarsson, P. Anders; Keane, Michael P.; Gelius, Ulrik

    1989-10-01

    The effect of MeV ion beams incident on Teflon surfaces was studied by x-ray photoelectron spectroscopy (XPS). Irradiation with 20-MeV 35Cl4+ was carried out at doses ranging from 1012 to 1014 ions/cm2. Residual gas analysis was performed during irradiation to identify molecular fragments released from the Teflon surface. XPS spectra were recorded before and after ion irradiation. On some substrates, gold thin films were evaporated before and after ion bombardment, respectively, to detect possible modifications in thin-film adhesion. Changes in the XPS spectra were interpreted in terms of chemical and structural shifts, and related to the observed adhesion modifications.

  7. Shock initiation of nano-Al/Teflon: High dynamic range pyrometry measurements

    NASA Astrophysics Data System (ADS)

    Wang, Jue; Bassett, Will P.; Dlott, Dana D.

    2017-02-01

    Laser-launched flyer plates (25 μm thick Cu) were used to impact-initiate reactive materials consisting of 40 nm Al particles embedded in TeflonAF polymer (Al/Teflon) on sapphire substrates at a stoichiometric concentration (2.3:1 Teflon:Al), as well as one-half and one-fourth that concentration. A high dynamic range emission spectrometer was used to time and spectrally resolve the emitted light and to determine graybody temperature histories with nanosecond time resolution. At 0.5 km s-1, first light emission was observed from Teflon, but at 0.6 km s-1, the emission from Al/Teflon became much more intense, so we assigned the impact threshold for Al/Teflon reactions to be 0.6 (±0.1) km s-1. The flyer plates produced a 7 ns duration steady shock drive. Emission from shocked Al/Teflon above threshold consisted of two bursts. At the higher impact velocities, the first burst started 15 ns after impact, peaked at 25 ns, and persisted for 75 ns. The second burst started at a few hundred nanoseconds and lasted until 2 μs. The 15 ns start time was exactly the time the flyer plate velocity dropped to zero after impact with sapphire. The first burst was associated with shock-triggered reactions and the second, occurring at ambient pressure, was associated with combustion of leftover material that did not react during shock. The emission spectrum was found to be a good fit to a graybody at all times, allowing temperature histories to be extracted. At 25 ns, the temperature at 0.7 km s-1 and the one-fourth Al load was 3800 K. Those temperatures increased significantly with impact velocity, up to 4600 K, but did not increase as much with Al load. A steady combustion process at 2800 (±100) K was observed in the microsecond range. The minimal dependence on Al loading indicates that these peak temperatures arise primarily from Al nanoparticles reacting almost independently, since the presence of nearby heat sources had little influence on the peak temperatures.

  8. THERMAL PROPERTIES OF DOUBLE-ALUMINIZED KAPTON AT LOW TEMPERATURES

    SciTech Connect

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

    2008-03-03

    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.

  9. 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.

  10. Tritium recovery from a breeder material: Gamma lithium aluminate

    NASA Astrophysics Data System (ADS)

    Roth, E.; Botter, F.; Briec, M.; Rostaing, M.; Werle, H.; Clemmer, R. G.

    1986-11-01

    This paper discusses phenomena that have been observed during tritium extraction from y-lithium aluminate, specifically: Increase of rate of extraction when adding hydrogen to the sweep gas formation of tritiated water in all cases permeation of tritium through gas pipes adsorption of tritiated water on gas lines.To minimize the blanket tritium inventory a flowchart is proposed whose specificity rests in the addition of hydrogen to the gas within the blanket, followed by recovery of the tritium after oxidation of hydrogen to water, electrolysis and reconcentration. This flowchart includes a provision for detritiation of the coolant which is separate from the purge gas.

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

    DOEpatents

    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.

  12. 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.

  13. Forecasting of radiation hazard, 1. Alerts on great FEP events beginning; probabilities of false and missed alerts

    NASA Astrophysics Data System (ADS)

    Dorman, L. I.; Pustil'Nik, L. A.; Sternlieb, A.; Zukerman, I. G.

    It is well known that in periods of great FEP fluxes of energetic particles can be so big that memory of computers and other electronics in space may be destroyed, satellites and spacecrafts became dead: according to NOAA Space Weather Scales are dangerous Solar Radiation Storms S5-extreme (flux level of particles with energy > 10 MeV more than 10^5), S4-severe (flux more than 10^4) and S3-strong (flux more than 10^3). In these periods is necessary to switch off some part of electronics for few hours to protect computer memories. These periods are also dangerous for astronauts on space-ships, and passengers and crew in commercial jets (especially during S5 storms). The problem is how to forecast exactly these dangerous phenomena. We show that exact forecast can be made by using high-energy particles (few GeV/nucleon and higher) which transportation from the Sun is characterized by much bigger diffusion coefficient than for small and middle energy particles. Therefore high energy particles came from the Sun much more early (8-20 minutes after acceleration and escaping into solar wind) than main part of smaller energy particles caused dangerous situation for electronics (about 30-60 minutes later). We describe here principles and experience of automatically working of program "FEP-Search". The positive result which shows the exact beginning of FEP event on the Emilio Segre' Observatory (2025 m above sea level, Rc=10.8 GV), is determined now automatically by simultaneously increasing on 2.5 St. Dev. in two sections of neutron supermonitor. The next 1-min data the program "FEP-Search" uses for checking that the observed increase reflects the beginning of real great FEP or not. If yes, automatically starts to work on line the programs "FEP-Research". We determine also the probabilities of false and missed alerts. The work of NM on Mt. Hermon is supported by Israel (Tel Aviv University and ISA) -- Italian (UNIRoma-Tre and IFSI-CNR) collaboration.

  14. 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.

  15. Improper Ferroelectricity in Stuffed Aluminate Sodalites for Pyroelectric Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Maeda, Yusaku; Wakamatsu, Toru; Konishi, Ayako; Moriwake, Hiroki; Moriyoshi, Chikako; Kuroiwa, Yoshihiro; Tanabe, Kenji; Terasaki, Ichiro; Taniguchi, Hiroki

    2017-03-01

    In the present study, we demonstrate ferroelectricity in stuffed aluminate sodalites (Ca1 -xSrx)8[AlO2]12(WO4)2 (x ≤0.2 ) (C1 -xSxAW ). Pyroelectric measurements clarify switchable spontaneous polarization in polycrystalline C1 -xSxAW , whose polarization values are on the order of 10-2 μ C /cm2 at room temperature. A weak anomaly in the dielectric permittivity at temperatures near the ferroelectric transition temperature suggests improper ferroelectricity of C1 -xSxAW for all investigated values of x . A comprehensive study involving synchrotron x-ray powder diffraction measurements, molecular dynamics simulations, and first-principles calculations clarifies that the ferroelectric phase transition of C1 -xSxAW is driven by the freezing of the fluctuations of WO4 tetrahedra in the voids of an [AlO2]12 12 - framework. The voltage response and electromechanical coupling factor of C1 -xSxAW estimated from the present results indicate that this material exhibits excellent performance as a pyroelectric energy harvester, suggesting that aluminate sodalites exhibit great promise as a class of materials for highly efficient energy-harvesting devices.

  16. Sonochemical synthesis of cobalt aluminate nanoparticles under various preparation parameters.

    PubMed

    Lv, Weizhong; Qiu, Qi; Wang, Fang; Wei, Shaohui; Liu, Bo; Luo, Zhongkuan

    2010-06-01

    Cobalt aluminate (CoAl(2)O(4)) nanoparticles were synthesized using a precursor method with the aid of ultrasound irradiation under various preparation parameters. The effects of the preparation parameters, such as the sonochemical reaction time and temperature, precipitation agents, calcination temperature and time on the formation of CoAl(2)O(4) were investigated. The precursor on heating yields nanosized CoAl(2)O(4) particles and both these nanoparticles and the precursor were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The use of ultrasound irradiation during the homogeneous precipitation of the precursor reduces the duration of the precipitation reaction. The mechanism of the formation of cobalt aluminate was investigated by means of Fourier transformation infrared spectroscopy (FT-IR) and EDX (energy dispersive X-ray). The thermal decomposition process and kinetics of the precursor of nanosized CoAl(2)O(4) were investigated by means of differential scanning calorimetry (DSC) and thermogravimetry (TG). The apparent activation energy (E) and the pre-exponential constant (A) were 304.26 kJ/mol and 6.441 x 10(14)s(-1), respectively. Specific surface area was investigated by means of Brunauer Emmett Teller (BET) surface area measurements.

  17. A high acid mesoporous USY zeolite prepared by alumination

    NASA Astrophysics Data System (ADS)

    Ma, Jinghong; Kang, Yuhong; Ma, Ning; Hao, Wenming; Wang, Yan; Li, Ruifeng

    2013-01-01

    A high-acidity HUSY zeolite with mesoporous structure was prepared by alumination with a dilute aqueous NaAlO2 solution and characterized by XRD, N2 adsorption, IR framework vibration and 29Si MAS NMR methods. The results indicated the extra-framework aluminum was reinserted into the tetrahedral framework through isomorphic substitution of framework Si (0Al) sites by Al ions, whereas the crystal and micropore structure were unaltered. FTIR spectra of hydroxyl vibrations and pyridine adsorbed on realuminated zeolites showed that the number of Brønsted acid sites and strong Lewis acid sites increased whereas weak Lewis acid sites decreased twice. The mesoporous structure composed of inter-and intra-crystalline pores in the aluminated HUSY increased the external surface area of the zeolite, improving accessibility of molecules to the active sites and enhancing its catalytic ability. The realuminated HUSY zeolite supported with Ru catalyst exhibited a higher catalytic activity for benzene hydrogenation than the parent HUSY zeolite; the reaction rate in comparison to the mesozeolite increased by 5.5 times.

  18. Flow ozonolysis using a semipermeable Teflon AF-2400 membrane to effect gas-liquid contact.

    PubMed

    O'Brien, Matthew; Baxendale, Ian R; Ley, Steven V

    2010-04-02

    A flow-through chemistry apparatus has been developed which allows gases and liquids to contact via a semipermeable Teflon AF-2400 membrane. In this preliminary investigation, the concept was proven by application to the ozonolysis of a series of alkenes.

  19. Alkali impregnated teflon as a filter for atmospheric SO 2 PIXE analysis

    NASA Astrophysics Data System (ADS)

    Matsuda, Yatsuka; Cahill, Thomas A.

    1985-02-01

    In order to collect SO 2 gas on a stretched Teflon filter impregnated with an alkali solution for a PIXE analysis, an impregnation method has been developed. In this article, the following points are presented. a) It has been found to be necessary to replace the air trapped in filter pores by methanol, and then to replace the methanol by an alkali solution, b) The resistance for air flow through an impregnated Teflon filter is not high and it has been checked that an ordinary pump can be used for the air sampling with the impregnated filter, with the usual flow rate aerosol sampling, c) The impurity levels of the reagents used for impregnants were small enough for sulfur analysis, d) The collection efficiencies of the impregnants, 20%NaOH + 10%glycerin and 20%NaOH + 10%TEA, which are the most suitable ones, did not decrease with flow rate in the range of 0-10 {1}/{min} per filter of 25 mm in diameter. A cross check experiment on the collection of ambient SO 2 gas with the three kinds of filter (A: 5%NaOH + 5%glycerin impregnated Whatman-41 filter, B: 20%NaOH + 10%TEA coated Nuclepore filter, C: 20%NaOH + 10%TEA impregnated stretched Teflon filter) was done. The results showed a satisfactory tolerance for the practical use of Teflon impregnated filter.

  20. Noncontact detection of Teflon inclusions in glass-fiber-reinforced polymer composites using terahertz imaging.

    PubMed

    Zhang, Jin; Wang, Jie; Han, Xiaohui; Cui, Hong-Liang; Shi, Changcheng; Zhang, Jinbo; Shen, Yan

    2016-12-20

    We employed terahertz (THz) time-domain spectroscopy (TDS) imaging technology, a new nondestructive testing method, to detect the inclusions of glass-fiber-reinforced polymer (GFRP) composites. The refractive index and absorption coefficient of two types of GFRP composites (epoxy GFRP composites and polyester GFRP composites) were first extracted, and GFRP composites with Teflon inclusions were examined, including an epoxy GFRP solid panel with a smaller Teflon inclusion hidden behind a larger Teflon inclusion, and polyester GFRP solid panels with Teflon inclusions of various sizes, at different depths. It was experimentally demonstrated that THz TDS imaging technology could clearly detect a smaller inclusion hidden behind a larger inclusion. When the reflected THz pulse from the inclusion did not overlap with that from the front surface of the sample, removal of the latter before Fourier transform was shown to be helpful in imaging the inclusions. With sufficiently strong incident THz radiation, inclusion insertion depth had little impact on the ability of the THz wave to detect inclusions. However, as the thickness of the inclusion became thinner, the inclusion detection ability of the THz wave deteriorated. In addition, with a combination of reflected C-scan imaging and B-scan imaging using the reflected time-domain waveform, both the lateral sizes and locations of the inclusions and the depths and thicknesses of the inclusions were clearly ascertained.

  1. A false-positive FDG uptake in Teflon granuloma: a case report.

    PubMed

    Bajin, Münir Demir; Hosal, Ali Sefik

    2013-01-01

    Positron emmision tomography (PET) is successfully used to monitor malignancies. Unfortunately it is not tumor specific. We present a case with history of rectum cancer and lentigo maligna who underwent PET-CT which revealed an increased uptake in the larynx. What was first considered as a third primary turned out to be a Teflon granuloma.

  2. Development of adsorbent from Teflon waste by radiation induced grafting: equilibrium and kinetic adsorption of dyes.

    PubMed

    Goel, N K; Kumar, Virendra; Pahan, S; Bhardwaj, Y K; Sabharwal, S

    2011-10-15

    Mutual radiation grafting technique was employed to graft polyacrylic acid (PAA) onto Polytetrafluoroethylene (Teflon) scrap using high energy gamma radiation. Polyacrylic acid-g-Teflon (PAA-g-Teflon) adsorbent was characterized by grafting extent measurement, FTIR spectroscopy, SEM and wet ability & surface energy analysis. The PAA-g-Teflon adsorbent was studied for dye adsorption from aqueous solution of basic dyes, namely, Basic red 29 (BR29) and Basic yellow 11 (BY11). The equilibrium adsorption data were analyzed by Langmuir and Freundlich adsorption isotherm models, whereas, adsorption kinetics was analyzed using pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models. Equilibrium adsorption of BR29 was better explained by Langmuir adsorption model, while that of BY11 by Freundlich adsorption model. The adsorption capacity for BY11 was more than for BR29. Separation factor (R(L)) was found to be in the range 0 < R(L) < 1, indicating favorable adsorption of dyes. Higher coefficient of determination (r(2) > 0.99) and better agreement between the q(e,cal) and q(e,exp) values suggested that pseudo-second order kinetic model better represents the kinetic adsorption data. The non-linearity obtained for intra-particle diffusion plot indicated, more than one process is involved in the adsorption of basic dyes. The desorption studies showed that ~95% of the adsorbed dye could be eluted in suitable eluent.

  3. 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.

  4. 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)

  5. Mylar and Teflon-AF as cell culture substrates for studying endothelial cell adhesion.

    PubMed

    Anamelechi, Charles C; Truskey, George A; Reichert, W Monty

    2005-12-01

    The textured and opaque nature of Dacron and ePTFE has prevented the use of these fabrics in conventional cell culture techniques normally employed to optimize cell attachment and retention. This lack of optimization has led, in part, to the poor performance of endothelialization strategies for improving vascular graft patency. Here we show that thin, transparent films of Mylar and Teflon-AF are viable in vitro cell culture mimics of Dacron and ePTFE vascular graft materials, particularly for the study of protein mediated endothelial cell (EC) attachment, spreading and adhesion. Glass substrates were used as controls. X-ray photoelectron spectroscopy (XPS) and contact angle analysis showed that Mylar and Teflon-AF have surface chemistries that closely match Dacron and ePTFE. (125)I radiolabeling was used to quantify fibronectin (FN) adsorption, and FN and biotinylated-BSA "dual ligand" co-adsorption onto glass, Mylar and Teflon-AF substrates. Native human umbilical vein endothelial cells (HUVEC) and streptavidin-incubated biotinylated-HUVEC (SA-b-HUVEC) spreading was measured using phase contrast microscopy. Cell retention and adhesion was determined using phase contrast microscopy under laminar flow. All surfaces lacking protein pre-treatment, regardless of surface type, showed the lowest degree of cell spreading and retention. Dual ligand treated Mylar films showed significantly greater SA-b-HUVEC spreading up to 2 h, but were similar to HUVEC on FN treated Mylar at longer times; whereas SA-b-HUVEC spreading on dual ligand treated Teflon-AF was never significantly different from HUVEC on FN treated Teflon-AF at any time point. SA-b-HUVEC retention was significantly greater on dual ligand treated Mylar compared to HUVEC on FN treated Mylar over the entire range of shear stresses tested (3.54-28.3 dynes/cm(2)); whereas SA-b-HUVEC retention to dual ligand and HUVEC retention to FN treated Teflon-AF gave similar results at each shear stress, with only the mid

  6. High temperature corrosion of hot-dip aluminized steel in Ar/1%SO2 gas

    NASA Astrophysics Data System (ADS)

    Abro, Muhammad Ali; Lee, Dong Bok

    2017-01-01

    Carbon steels were hot-dip aluminized in Al or Al-1at%Si baths, and corroded in Ar/1%SO2 gas at 700-800 °C for up to 50 h. The aluminized layers consisted of not only an outer Al(Fe) topcoat that had interdispersed needle-like Al3Fe particles but also an inner Al-Fe alloy layer that consisted of an outer Al3Fe layer and an inner Al5Fe2 layer. The Si addition in the bath made the Al(Fe) topcoat thin and nonuniform, smoothened the tongue-like interface between the Al-Fe alloy layer and the substrate, and increased the microhardness of the aluminized layer. The aluminized steels exhibited good corrosion resistance by forming thin α-Al2O3 scales, along with a minor amount of iron oxides on the surface. The interdiffusion that occurred during heating made the aluminized layer thick and diffuse, resulting in the formation of Al5Fe2, AlFe and AlFe3 layers. It also smoothened the tongue-like interface, and decreased the microhardness of the aluminized layer. The non-aluminized steel formed thick, nonadherent, nonprotective (Fe3O4, FeS)-mixed scales.

  7. Crystallographic features related to a van der Waals coupling in the layered chalcogenide FePS3

    NASA Astrophysics Data System (ADS)

    Murayama, Chisato; Okabe, Momoko; Urushihara, Daisuke; Asaka, Toru; Fukuda, Koichiro; Isobe, Masahiko; Yamamoto, Kazuo; Matsushita, Yoshitaka

    2016-10-01

    We investigated the crystallographic structure of FePS3 with a layered structure using transmission electron microscopy and powder X-ray diffraction. We found that FePS3 forms a rotational twin structure with the common axis along the c*-axis. The high-resolution transmission electron microscopy images revealed that the twin boundaries were positioned at the van der Waals gaps between the layers. The narrow bands of dark contrast were observed in the bright-field transmission electron microscopy images below the antiferromagnetic transition temperature, TN ≈ 120 K. Low-temperature X-ray diffraction showed a lattice distortion; the a- and b-axes shortened and lengthened, respectively, as the temperature decreased below TN. We propose that the narrow bands of dark contrast observed in the bright-field transmission electron microscopy images are caused by the directional lattice distortion with respect to each micro-twin variant in the antiferromagnetic phase.

  8. 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.

  9. 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.

  10. Absorption of CO2 in the ionic liquid 1-n-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([hmim][FEP]): a molecular view by computer simulations.

    PubMed

    Zhang, Xiaochun; Huo, Feng; Liu, Zhiping; Wang, Wenchuan; Shi, Wei; Maginn, Edward J

    2009-05-28

    Using a computational screening methodology, we predicted (AIChE J. 2008, 54, 2717) that the anion tris(pentafluoroethyl)trifluorophosphate ([FEP]) should increase the solubility of CO2 in ionic liquids (ILs) relative to a wide range of conventional anions. This prediction was confirmed experimentally. In this work, we develop a united-atom force field for the [FEP] anion and use the continuous fractional component Monte Carlo (CFC MC) method to predict CO2 absorption isotherms in 1-n-hexyl-3-methylimidazolium ([hmim]) [FEP] at 298.2 and 323.2 K and pressures up to 20.0 bar. The simulated isotherms overestimate the solubility of CO2 by about 20% but capture the experimental trends quite well. Additional Monte Carlo (MC) and molecular dynamics (MD) simulations are performed to study the mechanisms of CO2 absorption in [hmim][FEP] and [hmim][PF6]. The site-site radial distribution functions (RDFs) show that CO2 is highly organized around the [PF6] anion due to its symmetry and smaller size, while less ordered distributions were found around [FEP] and [hmim]. However, more CO2 can be found in the first coordination shell of [FEP] compared with [PF6]. The structures of ILs, illustrated by P-P radial distribution functions, change very little upon the addition of as much as 50 mol % CO2. An energetic analysis shows that the van der Waals interactions between CO2 and ILs are generally larger than electrostatic interactions.

  11. ePTFE/FEP-Covered Metallic Stents for Palliation of MalignantBiliary Disease: Can Tumor Ingrowth Be Prevented?

    SciTech Connect

    Hatzidakis, Adam Krokidis, Miltiadis; Kalbakis, Kostantinos; Romanos, Jiannis; Petrakis, Ioannis; Gourtsoyiannis, Nicholas

    2007-09-15

    Purpose. To determine the application and clinical effectiveness of ePTFE/FEP-covered metallic stents for palliation of malignant biliary disease, and to evaluate the efficiency of stent coverage in preventing tumor ingrowth. Methods. During a 3-year period, 36 patients with malignant obstructive jaundice were treated with ePTFE/FEP-covered stents, with or without proximal side holes. The stricture was located in the lower common bile duct (CBD) in 18 cases, the upper CBD in 9, the lower common hepatic duct (CHD) in 6, and the upper CHD in 3 patients. Results.Thirty-seven covered stents were percutaneously implanted. The technical success rate was 97%. Reintervention was required in 6 cases. The 30-day mortality rate was 40%, not procedure-related. Mean survival was 128 days. Primary patency rates were 100%,55.5%, and 25% at 3, 6, and 12 months, respectively, while the assisted patency rate was 100% at 12 months. Stents without side holes had higher primary patency rates compared with those with side holes, where occlusion was always due to tumor ingrowth. Tumor ingrowth did not occur in the completely covered stents. No stent dysfunction due to sludge incrustation was found.Complications were 1 case of arterial laceration that occurred during percutaneous transhepatic cholangiography, and a subcapsular hematoma and 1 case of bile peritonitis, that both occurred during primary stenting. No complications followed the secondary stenting technique. Conclusion. ePTFE/FEP-covered metallic stents are safe and effective for palliation of malignant biliary disease. The presence of the ePTFE/FEP coating is likely to prevent from tumor ingrowth.

  12. Oxidation Resistance of Low-Temperature Pack Aluminizing Coatings on Ni-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Yuan, Bifei; Yu, Longwen; Lu, Guiwu

    A nickel-base superalloy has been used to deposit the aluminide coating by low-temperature pack cementation process. The high temperature oxidation tests on aluminized alloys and the uncoated specimens are carried out at 1000°C for 10h. It is observed that a dense and protective Al2O3 surface layer is produced on the aluminized alloy, and the aluminizing process has greatly enhanced the high temperature oxidation resistance of the Ni-base superalloy at 1000°C. As a contrast, the uncoated specimen begins to be failure when treated only for 6h at the same temperature.

  13. Synthesis of lanthanum aluminate by reverse chemical precipitation using pseudoboehmite as alumina precursor.

    PubMed

    Wilson, Hernández Muñoz; Juan, Serrato Rodríguez; Juan, Muñoz Saldaña; Juan, Zárate Medina

    2016-11-01

    Lanthanum aluminate was synthesized by using reverse precipitation. A lanthanum nitrate salt in solution allowed the precipitation of lanthanum hydroxide onto the surface of the pseudoboehmite particles. Pseudoboehmite was previously synthesized out of aluminum sulfate which after characterization presents a poor crystallized structure. A Perovskite-type lanthanum aluminate was obtained at different temperature and calcination time. When calcination was set up to 1500°C to 3°C/min pure, high crystallinity and highly agglomerated lanthanum aluminate is obtained, relative density of 94% was reached.

  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. 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.

  16. 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.

  17. 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.

  18. Ethylene glycol contamination effects on first surface aluminized mirrors

    NASA Astrophysics Data System (ADS)

    Dunlop, Patrick; Probst, Ronald G.; Evatt, Matthew; Reddell, Larry; Sprayberry, David

    2016-07-01

    The Dark Energy Spectroscopic Instrument (DESI) is under construction for installation on the Mayall 4 Meter telescope. The use of a liquid cooling system is proposed to maintain the DESI prime focus assembly temperature within ±1°C of ambient. Due to concerns of fluid deposition onto optical surfaces from possible leaks, systematic tests were performed of the effects on first surface aluminized mirrors of ethylene glycol and two other candidate coolants. Objective measurement of scattering and reflectivity was an important supplement to visual inspection. Rapid cleanup of a coolant spill followed by a hand wash of the mirror limited surface degradation to the equivalent of a few months of general environmental exposure. Prolonged exposure to corrosive coolants dissolved the aluminum, necesitating mirror recoating.

  19. 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.

  20. 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

  1. [Effect of microwaves on bilayer lipid membranes: role of a membrane-forming hole in the Teflon film].

    PubMed

    Alekseev, S I; Ziskin, M S; Fesenko, E E

    2009-01-01

    The distributions of specific abcorption rate (SAR) and E-field in a membrane-forming hole of Teflon film and surrounding electrolyte were calculated for 0.9 GHz exposure. It was found that the specific absorption rate in the membrane-forming hole increased greatly with increasing thickness of the Teflon film, and electrolyte concentration and decreasing diameter of the hole. The previously demonstrated significant changes in the conductivity of modified bilayer lipid membranes induced by microwave exposure can be explained by a local increase in specific absorption rate and subsequent elevation of temperature in the membrane-forming hole of the Teflon film.

  2. 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

  3. Going outside the TonB box: identification of novel FepA-TonB interactions in vivo.

    PubMed

    Gresock, Michael G; Postle, Kathleen

    2017-03-06

    In Gram-negative bacteria, the cytoplasmic membrane protein TonB transmits energy derived from protonmotive force to energize transport of important nutrients through TonB-dependent transporters in the outer membrane. Each transporter consists of a beta-barrel domain and a lumen-occluding cork domain containing an essential sequence called the TonB box. To date, the only identified site of transporter-TonB interaction is between the TonB box and residues ∼158-162 of TonB. While the mechanism of ligand transport is a mystery, a current model based on site-directed spin labeling and molecular dynamics simulations is that, following ligand binding, the otherwise-sequestered TonB box extends into the periplasm for recognition by TonB, which mediates transport by pulling or twisting the cork. In this study, we tested that hypothesis with the outer membrane transporter FepA using in vivo photocrosslinking to explore interactions of its TonB box and determine whether additional FepA-TonB interaction sites exist. We found numerous specific sites of FepA interaction with TonB on the periplasmic face of the FepA cork in addition to the TonB box. Two residues, T32 and A33, might constitute a ligand-sensitive conformational switch. The fact that some interactions were enhanced in the absence of ligand and that other interactions did not require the TonB box argued against the current model and suggested that the transport process is more complex than originally conceived, with subtleties that might provide a mechanism for discrimination among ligand loaded transporters. These results constitute the first study on the dynamics of TonB-gated transporter interaction with TonB in vivoImportance The TonB system of Gram-negative bacteria has a non-canonical active transport mechanism involving signal transduction and proteins integral to both membranes. To achieve transport, the cytoplasmic membrane protein TonB physically contacts outer membrane transporters such as FepA. Only

  4. [Study on the Influence of Mineralizer on the Preparation of Calcium Aluminates Based on Infrared Spectroscopy].

    PubMed

    Fan, Wei; Wang, Liang; Zheng, Huai-li; Chen, Wei; Tang, Xiao-min; Shang, Juan-fang; Qian, Li

    2015-05-01

    In this study, effect of mineralizer on the structure and spectraproperties of calcium aluminates formation was extensively studied. Medium or low-grade bauxite and calcium carbonate were used as raw material and mineralizer CaF2 as additive. Calcium aluminates can be obtained after mixing fully, calcination and grinding. The prepared calcium aluminates can be directly used for the production of polyaluminiumchloride (PAC), polymeric aluminum sulfate, sodium aluminate and some other water treatment agents. The calcium aluminates preparation technology was optimized by investigating the mass ratio of raw materials (bauxiteand calcium carbonate) and mineralizer CaF2 dosage. The structure and spectra properties of bauxite and calcium aluminates were characterized by Fourier transform infrared(FTIR) spectroscopy analysis and the mineralization mechanism of the mineralizer was studied. FTIR spectra indicated that the addition of mineralizer promoted the decomposition and transformation of the diaspore, gibbsite and kaolinite, the decomposition of calcium carbonate, and more adequately reaction between bauxite and calcium carbonate. In addition, not only Ca in calcium carbonate and Si in bauxite were more readily reacted, but also Si-O, Si-O-Al and Al-Si bonds in the bauxite were more fractured which contributed to the release of Al in bauxite, and therefore, the dissolution rate of Al2O3 could be improved. The dissolution rate of Al2O3 can be promoted effectively when the mineralizer CaF2 was added in a mass ratio amount of 3%. And the mineralizer CaF2 cannot be fully functioned, when its dosage was in a mass percent of 1. 5%. Low-grade bauxite was easier to sinter for the preparation of calcium aluminates comparing with the highgrade one. The optimum material ratio for the preparation of calcium aluminates calcium at 1 250 °C was the mass ratio between bauxite and calcium carbonate of 1 : 0. 6 and mineralizer CaF2 mass ratio percent of 3%.

  5. Etude vibrationnelle d'aluminates et de gallates de terres rares—III. Aluminates et gallates de structure grenat

    NASA Astrophysics Data System (ADS)

    Saine, M. C.; Husson, E.; Brusset, H.; de, A. Cerez

    The i.r. absorption and Raman scattering spectra of some aluminium and gallium garnets have been studied. They show a stronger force field in the aluminates than in the gallates and the influence of the ionic radius of the Ln 3+ cation on the frequencies of the aluminium—oxygen or gallium—oxygen network. The study of the system Er 3Ga 5O 12-Er 3Al 5O 12 permitted us to propose an assignment of the different ranges of frequencies and to point out that the tetrahedra vibrations are higher than the octahedra ones. The i.r. spectrum of the perovskite NdGaO 3 is compared to the garnet Nd 3GasO 12 one.

  6. 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)

  7. Thermal conductance of Teflon and Polyethylene: Insight from an atomistic, single-molecule level

    NASA Astrophysics Data System (ADS)

    Buerkle, Marius; Asai, Yoshihiro

    2017-02-01

    The thermal transport properties of teflon (polytetrafluoroethylene) and its polyethylene counterparts are, while highly desirable and widely used, only superficially understood. Here, we aim therefore to provide rigorous insight from an atomistic point of view in context of single-molecule devices. We show that for vinyl polymers adsorbed on metal-surfaces the thermal transport strongly depends on the properties of the metal-molecule interface and that the reduced thermal conductance observed for teflon derivatives originates in a reduced phonon injection life time. In asymmetric molecules phonon blocking on the intra molecular interface leads to a further reduction of thermal conductance. For hetrojunctions with different electrode materials we find that thermal conductance is suppressed due to a reduced overlap of the available phonon modes in the different electrodes. A detailed atomistic picture is thereby provided by studying the transport through perfluorooctane and octane on a single-molecule level using first principles transport calculations and nonequilibrium molecular dynamic simulations.

  8. Measurement of the optical performance of liquid scintillator filled Teflon-fiber tubes

    SciTech Connect

    Zaman, S.M.

    1990-05-01

    A study of the optical performance of a liquid scintillator (BC517L) filled Teflon tube of inner diameter 0.06 cm, was carried out using a rectangular array of those tubes. Two experimental methods, the cosmic ray telescope and the direct scouce method, were used in measuring the light output (in photoelectrons) and the light attenuation length through the scintillator. Results showed the light output from this array for minimum ionizing charged particles to ba a fraction of a photoelectron (about 10{sup {minus}2}) and the attenuation length to be about 20.0 cm, for high energy particles, suggesting a limiting value for the tube diameter of the Teflon that can be used in scintillating fiber calorimeters for high energy physics experiments. 18 refs., 16 figs., 4 tabs.

  9. A Teflon microreactor with integrated piezoelectric actuator to handle solid forming reactions.

    PubMed

    Kuhn, Simon; Noël, Timothy; Gu, Lei; Heider, Patrick L; Jensen, Klavs F

    2011-08-07

    We present a general inexpensive method for realizing a Teflon stack microreactor with an integrated piezoelectric actuator for conducting chemical synthesis with solid products. The microreactors are demonstrated with palladium-catalyzed C-N cross-coupling reactions, which are prone to clogging microchannels by forming insoluble salts as by-products. Investigations of the ultrasonic waveform applied by the piezoelectric actuator reveal an optimal value of 50 kHz at a load power of 30 W. Operating the system at these conditions, the newly developed Teflon microreactor handles the insoluble solids formed and no clogging is observed. The investigated reactions reach full conversion in very short reaction times and high isolated yields are obtained (>95% yield).

  10. Nanopatterning of mobile lipid monolayers on electron-beam-sculpted Teflon AF surfaces.

    PubMed

    Shaali, Mehrnaz; Lara-Avila, Samuel; Dommersnes, Paul; Ainla, Alar; Kubatkin, Sergey; Jesorka, Aldo

    2015-02-24

    Direct electron-beam lithography is used to fabricate nanostructured Teflon AF surfaces, which are utilized to pattern surface-supported monolayer phospholipid films with 50 nm lateral feature size. In comparison with unexposed Teflon AF coatings, e-beam-irradiated areas show reduced surface tension and surface potential. For phospholipid monolayer spreading experiments, these areas can be designed to function as barriers that enclose unexposed areas of nanometer dimensions and confine the lipid film within. We show that the effectiveness of the barrier is defined by pattern geometry and radiation dose. This surface preparation technique represents an efficient, yet simple, nanopatterning strategy supporting studies of lipid monolayer behavior in ultraconfined spaces. The generated structures are useful for imaging studies of biomimetic membranes and other specialized surface applications requiring spatially controlled formation of self-assembled, molecularly thin films on optically transparent patterned polymer surfaces with very low autofluorescence.

  11. Thermal conductance of Teflon and Polyethylene: Insight from an atomistic, single-molecule level

    PubMed Central

    Buerkle, Marius; Asai, Yoshihiro

    2017-01-01

    The thermal transport properties of teflon (polytetrafluoroethylene) and its polyethylene counterparts are, while highly desirable and widely used, only superficially understood. Here, we aim therefore to provide rigorous insight from an atomistic point of view in context of single-molecule devices. We show that for vinyl polymers adsorbed on metal-surfaces the thermal transport strongly depends on the properties of the metal-molecule interface and that the reduced thermal conductance observed for teflon derivatives originates in a reduced phonon injection life time. In asymmetric molecules phonon blocking on the intra molecular interface leads to a further reduction of thermal conductance. For hetrojunctions with different electrode materials we find that thermal conductance is suppressed due to a reduced overlap of the available phonon modes in the different electrodes. A detailed atomistic picture is thereby provided by studying the transport through perfluorooctane and octane on a single-molecule level using first principles transport calculations and nonequilibrium molecular dynamic simulations. PMID:28150738

  12. The Reduction of Sulfuryl Chloride at Teflon-Bonded Carbon Cathodes

    DTIC Science & Technology

    1980-07-01

    corresponding vide high electronic conduction. While still moist, the lithium - thionyl chloride system. One reason for the electrode was pressed to whatever...curves were measured for sulfuryl chloride re- duction at Teflon-bonded carbon cathodes fabricated using a number of differ- ent carbon powders. Lithium ...electrochemical performance against lithium counterelectrodes. When sulfuryl chloride is reduced at the optimized cathode (against a lithium anode), the main

  13. The Reduction of Sulfuryl Chloride at Teflon-Bonded Carbon Cathodes.

    DTIC Science & Technology

    1981-01-01

    lower priority, by both Governmental and industrial organizations, than the corresponding lithium - thionyl chloride system. One reason for the...S. Gilman, "Teflon-Bonded Cathodes in Lithium - Thionyl Chloride Cells," Proc. Tenth Intersociety Energy Conversion Engineering Conference, p. 437 (1975...0. L. Holleck, and D. E. Toland, "Reactions in Lithium Thionyl Chloride Cells," Proc. 27th Power Sources Symposium, p. 28 (1976). 11 4i CI Cw-4 0 0 -4

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

    PubMed

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

    2014-01-06

    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.

  15. Development of an Automated All-Teflon HPLC System for the Analysis of Precious Geological and Extraterrestrial Materials

    NASA Astrophysics Data System (ADS)

    Ireland, T. J.; Dauphas, N.; Tissot, F. L. H.

    2012-03-01

    We outline the development and progress toward building an automated all-Teflon HPLC system for the analysis of precious geological and extraterrestrial samples. Our system has several traits that distinguish it from traditional column setups.

  16. 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.

  17. Bioglue-Coated Teflon Sling Technique in Microvascular Decompression for Hemifacial Spasm Involving the Vertebral Artery

    PubMed Central

    Lee, Seong Ho; Park, Jae Sung

    2016-01-01

    Objective Microvascular decompression (MVD) for hemifacial spasm (HFS) involving the vertebral artery (VA) can be technically challenging. We investigated the therapeutic effects of a bioglue-coated Teflon sling technique on the VA during MVD in 42 cases. Methods A bioglue-coated Teflon sling was crafted by the surgeon and applied to patients in whom neurovascular compression was caused by the VA. The radiologic data, intra-operative findings with detailed introduction of the procedure, and the clinical outcomes of each patient were reviewed and analyzed. Results The 42 patients included in the analysis consisted of 22 females and 20 males, with an average follow-up duration of 76 months (range 24–132 months). Intraoperative investigation revealed that an artery other than the VA was responsible for the neurovascular compression in all cases : posterior inferior cerebellar artery (PICA) in 23 patients (54.7%) and anterior inferior cerebellar artery (AICA) in 11 patients (26.2%). All patients became symptom-free after MVD. Neither recurrence nor postoperative neurological deficit was noted during the 2-year follow-up, except in one patient who developed permanent deafness. Cerebrospinal fluid (CSF) leak occurred in three patients, and one required dural repair. Conclusion Transposition of the VA using a bioglue-coated Teflon sling is a safe and effective surgical technique for HFS involving the VA. A future prospective study to compare clinical outcomes between groups with and without use of this novel technique is required. PMID:27651870

  18. Silver-coated Teflon hollow waveguides for the delivery of terahertz radiation

    NASA Astrophysics Data System (ADS)

    Melzer, Jeffrey E.; Navarro-Cía, Miguel; Mitrofanov, Oleg; Harrington, James A.

    2014-02-01

    Significant research exists regarding the successful implementation of hollow waveguides for the low-loss transmission of infrared radiation in applications ranging from laser power delivery to spectroscopy. With the continued development of terahertz (THz) technologies and applications, it is often advantageous to have a waveguide for the transmission of THz radiation. This study focuses on the fabrication of novel silver-coated polytetrafluoroethylene (PTFE) waveguides for the transmission of terahertz radiation. The hollow structure described in this paper is made by depositing a thin film of Ag on the outer surface of a dielectric tube. This is in contrast to depositing metallic and dielectric thin film coatings on the inner surface of capillary tubing as is commonly done for IR and some THz transmissive waveguides. In this work, the Teflon tubing itself is the dielectric layer that is used to enhance the reflectivity of the Ag. Theoretical loss calculations will be presented and compared to the loss obtained for the guides measured at THz frequencies. In addition the spectra of the guides in the infrared region are also measured as a means to study the uniformity of the Teflon "layer" and to confirm the wall thickness of the Teflon tubing. The surface topography of the silver / PTFE waveguides is obtained and the resulting surface roughness related scattering losses are calculated. The implications of the terahertz fiber for applications ranging from nondestructive evaluation (NDE), security, and medical imaging are briefly discussed.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  20. 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.

  1. 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

  2. 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

  3. 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.

  4. Development of a Blue Emitting Calcium-Aluminate Phosphor

    PubMed Central

    Kim, Doory; Kim, Han-Eol; Kim, Chang-Hong

    2016-01-01

    We report methodological advances that enhance the phosphorescence efficiency of a blue-emitting calcium aluminate phosphor (CaAl2O4: Eu2+, Nd3+). The investigation of long-persistence blue-emitting phosphors is highly desirable due to their promising applications, such as white LEDs; however, the development of highly efficient blue-emitting phosphors is still challenging. Here, we have quantitatively characterized the phosphorescence properties of the blue-emitting phosphor CaAl2O4:Eu2+, Nd3+ with various compositions and directly related these properties to the quality of its luminescence. We optimized the composition of the activator Eu2+ and the co-activator Nd3+, the doping conditions with alkaline earth metals, alkali metals, and Si to create crystallographic distortions and, finally, the flux conditions to find the best parameters for bright and persistent blue-emitting phosphors. Our research has identified several doping compositions with good to excellent performance, with which we have demonstrated bright and persistent phosphors with afterglow characteristics superior to those of conventional phosphors. PMID:27648560

  5. Impact initiation of reactive aluminized fluorinated acrylic nanocomposites

    SciTech Connect

    White, Bradley W.; Crouse, Christopher A.; Spowart, Jonathan E.; Aydelotte, Brady; Thadhani, Naresh N.

    2016-04-18

    The initiation of aluminized fluorinated acrylic (AlFA) nanocomposites during modified Taylor impact tests was investigated. Samples were impacted against a steel or sapphire anvil at a nominal velocity of 150 m/s. A framing camera was used to capture head-on and side-profile impact images for the sapphire window and steel plate rigid anvils, respectively. Correlations were drawn between both experimental setups to determine the initiation locations and reaction times. Reactions were found to initiate at an intermediate radius on the impact face of the pellet at a time near full compaction. From simulations, the highest strains and temperatures were found at radii similar to those observed in experiments at the time of ignition. Off-normal impacts produced higher localized straining and temperatures on one-half of the pellet. As a result, the copper projectile, used for delivery, was revealed to aid in a shear assisted reaction by helping to drive the pellet material outward as the projectile deformed radially.

  6. Impact initiation of reactive aluminized fluorinated acrylic nanocomposites

    DOE PAGES

    White, Bradley W.; Crouse, Christopher A.; Spowart, Jonathan E.; ...

    2016-04-18

    The initiation of aluminized fluorinated acrylic (AlFA) nanocomposites during modified Taylor impact tests was investigated. Samples were impacted against a steel or sapphire anvil at a nominal velocity of 150 m/s. A framing camera was used to capture head-on and side-profile impact images for the sapphire window and steel plate rigid anvils, respectively. Correlations were drawn between both experimental setups to determine the initiation locations and reaction times. Reactions were found to initiate at an intermediate radius on the impact face of the pellet at a time near full compaction. From simulations, the highest strains and temperatures were found atmore » radii similar to those observed in experiments at the time of ignition. Off-normal impacts produced higher localized straining and temperatures on one-half of the pellet. As a result, the copper projectile, used for delivery, was revealed to aid in a shear assisted reaction by helping to drive the pellet material outward as the projectile deformed radially.« less

  7. Forecast of solar radiation storms by on-line NM one-minute data, 1. automatically search of great FEP event beginning

    NASA Astrophysics Data System (ADS)

    Dorman, L. I.; Pustilnik, L. A.; Sternlieb, A.; Zukerman, I. G.

    2001-08-01

    It is well known that in periods of great FEP fluxes of energetic particles can be so big that memory of computers and other electronics in space may be destroyed, satellites and spacecrafts became dead: according to NOAA Space Weather Scales are dangerous Solar Radiation Storms S5extreme (flux level of particles with energy > 10 MeV more than 105 ), S4-severe (flux more than 104 ) and S3-strong (flux more than 103 3). In these periods is necessary to switch off some part of electronics for few hours to protect computer memories. These periods are also dangerous for astronauts on space-ships, and passengers and crew in commercial jets (especially during S5 storms). The problem is how to forecast exactly these dangerous phenomena. We show that exact forecast can be made by using high-energy particles (few GeV/nucleon and higher) which transportation from the Sun is characterized by much bigger diffusion coefficient than for small and middle energy particles. Therefore high energy particles came from the Sun much more early (8-20 minutes after acceleration and escaping into solar wind) than main part of smaller energy particles caused dangerous situation for electronics (about 30-60 minutes later). We describe here principles and experience of automatically working of program "FEP-Search". The positive result which shows the exact beginning of FEP event on the Emilio Segre' Observatory (2025 m above sea level, Rc = 10.8 GV), is determined now automatically by simultaneously increasing on 2.5 St. Dev. in two sections of neutron supermonitor. The next 1-min data the program "FEP-Search" uses for checking that the observed increase reflects the beginning of real great FEP or not. If yes, automatically starts to work on line the programs "FEP-Research".

  8. Origins of saccharide-dependent hydration at aluminate, silicate, and aluminosilicate surfaces

    PubMed Central

    Smith, Benjamin J.; Rawal, Aditya; Funkhouser, Gary P.; Roberts, Lawrence R.; Gupta, Vijay; Israelachvili, Jacob N.; Chmelka, Bradley F.

    2011-01-01

    Sugar molecules adsorbed at hydrated inorganic oxide surfaces occur ubiquitously in nature and in technologically important materials and processes, including marine biomineralization, cement hydration, corrosion inhibition, bioadhesion, and bone resorption. Among these examples, surprisingly diverse hydration behaviors are observed for oxides in the presence of saccharides with closely related compositions and structures. Glucose, sucrose, and maltodextrin, for example, exhibit significant differences in their adsorption selectivities and alkaline reaction properties on hydrating aluminate, silicate, and aluminosilicate surfaces that are shown to be due to the molecular architectures of the saccharides. Solid-state 1H, 13C, 29Si, and 27Al nuclear magnetic resonance (NMR) spectroscopy measurements, including at very high magnetic fields (19 T), distinguish and quantify the different molecular species, their chemical transformations, and their site-specific adsorption on different aluminate and silicate moieties. Two-dimensional NMR results establish nonselective adsorption of glucose degradation products containing carboxylic acids on both hydrated silicates and aluminates. In contrast, sucrose adsorbs intact at hydrated silicate sites and selectively at anhydrous, but not hydrated, aluminate moieties. Quantitative surface force measurements establish that sucrose adsorbs strongly as multilayers on hydrated aluminosilicate surfaces. The molecular structures and physicochemical properties of the saccharides and their degradation species correlate well with their adsorption behaviors. The results explain the dramatically different effects that small amounts of different types of sugars have on the rates at which aluminate, silicate, and aluminosilicate species hydrate, with important implications for diverse materials and applications. PMID:21562207

  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. [Selective Heating of Membrane-forming Holes in Teflon Film Exposed to Decimeter Waves].

    PubMed

    Alekseev, S I; Fesenko, E E; Fesenko, E E

    2015-01-01

    Calculations of heating of membrane-forming holes in Teflon film exposed to decimeter waves were performed. The dependence of the temperature increment in holes on the geometry of holes, electrolyte concentration, and decimeter wave frequency was studied. The kinetics of heating depending on the hole diameter was also obtained. It was concluded that the observed in the experiment effects of the decimeter wave on bilayer lipid membranes resulted from the elevated concentration of decimeter electromagnetic waves in membrane-forming hole that led to selective heating of electrolyte in hole and bilayer lipid membranes.

  11. Studies of erosion of solar max samples of Kapton and Teflon

    NASA Technical Reports Server (NTRS)

    Fristrom, R. M.; Benson, R. C.; Bargeron, C. B.; Phillips, T. E.; Vest, C. E.; Hoshall, C. H.; Satkiewicz, F. G.; Uy, O. M.

    1985-01-01

    Several samples of Kapton and Teflon which was exposed to solar radiation were examined. The samples represent material behavior in near Earth space. Clues to the identity of erosive processes and the responsible species were searched for. Interest centered around oxygen atoms which are ubiquitous at these altitudes and are known to erode some metal surfaces. Three diagnostic methods were employed: optical microscopy, scanning electron microscopy, and fourier transform infrared spectroscopy. Two types of simulation were used: a flow containing low energy oxygen atoms and bombardment with 3000 volt Ar ions. Results and conclusions are presented.

  12. 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

  13. 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.

  14. 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.

  15. Microstructure and creep resistance of a diffusionally aluminized Ni-base superalloy

    NASA Astrophysics Data System (ADS)

    Sah, Injin; Kim, Sung Hwan; Jang, Changheui

    2016-11-01

    An aluminide layer was formed on a wrought Ni-base superalloy by the diffusional aluminizing method, which involves a physical vapor deposition of Al followed by two-step heat treatment in vacuum. Microstructural analysis revealed the presence of an aluminide layer, inter-diffusion zone (IDZ), and affected substrate, all of which developed due to the inter-diffusion of deposited Al and elements in the matrix. In addition, a wide carbide free zone, in which grain boundaries were mostly denuded of carbides, was found below the IDZ. Depth profiling analysis using a glow discharge spectrometer confirmed the reduced carbon content in the carbide free zone. At 900 °C, the diffusionally aluminized specimens showed a decrease in creep-rupture life caused by the presence of the carbide free zone. Fracture surface and cross-section microstructure observation confirmed the detrimental effect of the carbide free zone on the creep resistance of the diffusionally aluminized Alloy 617.

  16. Role of Adsorption Phenomena in Cubic Tricalcium Aluminate Dissolution.

    PubMed

    Myers, Rupert J; Geng, Guoqing; Li, Jiaqi; Rodríguez, Erich D; Ha, Juyoung; Kidkhunthod, Pinit; Sposito, Garrison; Lammers, Laura N; Kirchheim, Ana Paula; Monteiro, Paulo J M

    2017-01-10

    The workability of fresh Portland cement (PC) concrete critically depends on the reaction of the cubic tricalcium aluminate (C3A) phase in Ca- and S-rich pH >12 aqueous solution, yet its rate-controlling mechanism is poorly understood. In this article, the role of adsorption phenomena in C3A dissolution in aqueous Ca-, S-, and polynaphthalene sulfonate (PNS)-containing solutions is analyzed. The zeta potential and pH results are consistent with the isoelectric point of C3A occurring at pH ∼12 and do not show an inversion of its electric double layer potential as a function of S or Ca concentration, and PNS adsorbs onto C3A, reducing its zeta potential to negative values at pH >12. The S and Ca K-edge X-ray absorption spectroscopy (XAS) data obtained do not indicate the structural incorporation or specific adsorption of SO4(2-) on the partially dissolved C3A solids analyzed. Together with supporting X-ray ptychography and scanning electron microscopy results, a model for C3A dissolution inhibition in hydrated PC systems is proposed whereby the formation of an Al-rich leached layer and the complexation of Ca-S ion pairs onto this leached layer provide the key inhibiting effect(s). This model reconciles the results obtained here with the existing literature, including the inhibiting action of macromolecules such as PNS and polyphosphonic acids upon C3A dissolution. Therefore, this article advances the understanding of the rate-controlling mechanism in hydrated C3A and thus PC systems, which is important to better controlling the workability of fresh PC concrete.

  17. Microwave absorption in single crystals of lanthanum aluminate

    NASA Astrophysics Data System (ADS)

    Zuccaro, Claudio; Winter, Michael; Klein, Norbert; Urban, Knut

    1997-12-01

    A very sensitive dielectric resonator technique is employed to measure loss tangent tan δ and relative permittivity ɛr of lanthanum aluminate (LaAlO3) single crystals at 4-300 K and 4-12 GHz. A variety of single crystals grown by different techniques and purchased from different suppliers are considered. For T>150 K the loss tangent tan δ is almost sample independent with linear frequency dependence and monotonous temperature variation from 8×10-6 at 300 K to 2.5×10-6 at 150 K and 4.1 GHz. In this temperature range the experimental data are explained by a model based on lifetime broadened two-phonon difference processes. The loss tangent below 150 K is characterized by a peak in tan δ(T) at about 70 K. The height of this peak is frequency and strongly sample dependent. This leads to a variation of the loss tangent from 10-6 to 1.5×10-5 at 77 K and 8.6 GHz, the lowest values are generally achieved with Verneuil grown crystals and approach the intrinsic lower limit predicted by the phonon model. The peak is explained by defect dipole relaxation (local motions of ions). The activation energy of the relaxation process is determined from the measured data to be 31 meV. This low value indicates that the defect dipoles are associated with interstitials, possibly impurities in interstitial positions. Considering absorption due to phonons and due to defect dipole relaxation the loss tangent is calculated for a wide frequency range.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Acute silicosis in teflon-coated pan manufacturing due to metal sandblasting.

    PubMed

    Köksal, Nurhan; Kahraman, Hasan

    2011-01-01

    Sandblasting is one of the occupational causes of silicosis. This report details three cases diagnosed as silicosis caused by sandblasting in Teflon-coated pan manufacturing: Case 1--A 24-year-old man admitted with dyspnea and cough; Case 2--An 18-year-old man admitted with shortness of breath and fever; and Case 3--A 25-year-old man admitted with dyspnea and weight loss. Chest examinations of the first and second cases revealed crackles in both lungs, but the third case was normal, no crackles. Chest x-rays showed bilateral reticulonodular densities and hilar enlargement in all cases. They were clinically and radiologically diagnosed as silicosis due to occupational exposure. All cases had worked in the sandblasting unit at a Teflon-coated pan manufacturing factory for one to three years. Silicosis is a preventable occupational lung disease, but no effective treatment is available for the disease yet. Improving workplace conditions is the most effective way to prevent silicosis.

  3. Resistance of Spores of Bacillus subtilis var. niger on Kapton and Teflon Film to High Temperature and Dry Heat

    PubMed Central

    Bruch, Mary K.; Smith, Frederick W.

    1968-01-01

    To determine parameters that would assure sterility of a sealed seam of film for application in “split-seam entry,” spores of Bacillus subtilis var. niger were sprayed onto pieces of Kapton and Teflon film. Short-time, high-temperature (200 to 270 C) exposures were made with film pieces between aluminum blocks in a hot-air oven, and the D and z values were determined after subculture of surviving spores. The use of Kapton film allowed the study of high temperatures, since it is not heat sealable and could be used to make thin packages for heat treatment. Spores on Teflon were dry-heat treated in a package designed to simulate an actual seam to be sealed. The z values of 29.1 C (52.4 F) for spores on Kapton and 139 C (250.4 F) for spores on Teflon were calculated. Images Fig. 1 Fig. 2 Fig. 3 PMID:4973071

  4. 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

  5. Topotactic Conversion of α-Fe2O3 Nanowires into FeP as a Superior Fluorosensor for Nucleic Acid Detection: Insights from Experiment and Theory.

    PubMed

    Yang, Li; Liu, Danni; Hao, Shuai; Qu, Fengli; Ge, Ruixiang; Ma, Yongjun; Du, Gu; Asiri, Abdullah M; Chen, Liang; Sun, Xuping

    2017-02-21

    Nanostructures possess distinct quenching ability toward fluorophores with different emission frequencies and have been intensively used as nanoquenchers for homogeneous nucleic acid detection. Complete understanding of such a sensing system will provide significant guidance for the design of superior sensing materials, which is still lacking. In this Letter, we demonstrate the development of FeP nanowires as a nanoquencher for high-performance fluorescent nucleic acid detection with much superior performance to α-Fe2O3 counterparts. The whole detection process is complete within 1 min, and this fluorosensor presents a detection limit as low as 4 pM with strong discrimination of single-point mutation. Electrochemical tests and density functional theory calculations reveal that FeP NWs are superior in both conductivity for facilitated electron diffusion and hydrogen-evolving catalytic activity for favorable electron depletion, providing further experimental and theoretical insights into the enhanced sensing performance of the FeP nanosensor. Both faster electron transfer kinetics and stronger electron-consuming ability via catalyzed proton reduction enable FeP nanowires to be a superb nucleic acid nanosensor for applications.

  6. 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.

  7. 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

  8. Specific heat of Teflon, Torlon 4203 and Torlon 4301 in the range of 30-400 mK

    NASA Astrophysics Data System (ADS)

    Singh, V.; Garai, A.; Mathimalar, S.; Dokania, N.; Nanal, V.; Pillay, R. G.; Ramakrishnan, S.

    2015-04-01

    The specific heat of amorphous polymers, Teflon, Torlon 4203 and Torlon 4301, has been measured in the range of 30-400 mK using thermal relaxation calorimetric technique. The data is consistent with the tunneling state models used to explain the observed unusual low temperature specific heat of amorphous polymers. Below 100 mK, the specific heat of Torlon 4301 is ∼3 times higher than that of Torlon 4203. Teflon has the lowest specific heat, ∼10 times lower than that of Torlon 4301.

  9. Experimental validation of a numerical model predicting the charging characteristics of Teflon and Kapton under electron beam irradiation

    NASA Technical Reports Server (NTRS)

    Hazelton, R. C.; Yadlowsky, E. J.; Churchill, R. J.; Parker, L. W.; Sellers, B.

    1981-01-01

    The effect differential charging of spacecraft thermal control surfaces is assessed by studying the dynamics of the charging process. A program to experimentally validate a computer model of the charging process was established. Time resolved measurements of the surface potential were obtained for samples of Kapton and Teflon irradiated with a monoenergetic electron beam. Results indicate that the computer model and experimental measurements agree well and that for Teflon, secondary emission is the governing factor. Experimental data indicate that bulk conductivities play a significant role in the charging of Kapton.

  10. 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.

  11. 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

  12. Hydrogen Incorporation in Aluminous MgSiO3-Perovskite

    NASA Astrophysics Data System (ADS)

    Smyth, J. R.; Jacobsen, S. D.; Huss, G. R.; Miyajima, N.; Pamato, M. G.

    2013-12-01

    We have synthesized hydrous, aluminum-bearing MgSiO3 perovskite samples at 25GPa and various temperatures from 1600 to 2200C in a multi-anvil press and have characterized the samples by single-crystal X-ray diffraction, Raman spectroscopy, electron microprobe (EPMA), transmission electron microscopy (TEM), and secondary ion mass spectroscopy (SIMS). Perovskite crystals range up to 100 micrometers in size and contain 1 - 2.5% by weight Al2O3. SIMS analyses with a probe spot of approximately 10 micron square indicate up to several thousand ppm by weight H2O which corresponds to one H per Al atom in the structure. Microprobe chemical analysis and crystal structure refinement from single crystal X-ray data indicates that Al substitutes in the Si site, but not in the Mg site. However, Raman spectroscopy indicates the presence of micro-inclusions of brucite, super-hydrous phase B (SHyB), magnesite, and stishovite in most samples. Some of the perovskite crystals in the samples synthesized at temperatures above 2100 C exhibit rounded inclusions that are interpreted to be melt that quenched to perovskite plus brucite, phase D, and/or stishovite. Nearly all spectra show O-H stretching bands that are associated with brucite and/or Shy-B. None of the samples show a Raman peak in the O-H stretching region (3000 to 3700 cm-1) that correlates in intensity with perovskite Raman lattice modes. Our provisional interpretation is that the MgSiO3-perovskite structure incorporates very little H2O (<100 ppmw) and that most of the H in the samples is contained in brucite, phase D, superhydrous phase B (SHyB) or aluminous stishovite. This implies that the magnesium silicate perovskite phase in the lower mantle is unlikely to be a significant host for H in the lower mantle. However, phase D may be stabilized to higher temperatures by incorporation of Al and is extremely hydrous so that two modal percent of phase D may allow the lower mantle to contain several thousand ppmw H2O. Such a small

  13. Crystal growth and characterization of LaMAl 11O 19 lanthanum aluminates

    NASA Astrophysics Data System (ADS)

    Laville, F.; Lejus, A. M.

    1983-10-01

    New magnetoplumbite-type lanthanum aluminates with the formula LaMAl 11O 19 (M 2+ = Ni 2+, Co 2+, Fe 2+, Mg 1- xMn x, 0≤ x ≤1, have been grown as large single crystals using the Verneuil process or the floating zone method. Some characteristics of these crystals are given.

  14. Wear Resistance and Wear Mechanism of a Hot Dip Aluminized Steel in Sliding Wear Test

    NASA Astrophysics Data System (ADS)

    Xue, Zhiyong; Hao, Xiaoyang; Huang, Yao; Gu, Lingyun; Ren, Yu; Zheng, Ruipeng

    2016-12-01

    Sliding wear experiments were conducted on a hot dip aluminized steel to investigate its wear resistance and wear mechanism. The wear tests were also carried out on a hot dip galvanized steel and the base material (steel Q345) as a comparison. Results show that the wear resistance and hardness of the hot dip aluminized steel are significantly higher than that of the hot dip galvanized steel and the steel Q345 at room temperature. The better wear resistance of the hot dip aluminized steel attributes mainly to the formation of a transition layer containing abundant Fe-Al intermetallic compounds and the transformation of wear-resisting oxides during the friction process. The main phase in the transition layer is Fe2Al5. The thickness of the transition layer is about 90-120 μm. When the wear load increases from 3 N to 19 N, the wear type of the aluminized layer transform from adhesive wear (3 N) into abrasive wear (7 N) and finally into slight wear mixed with oxidation (higher than 11 N).

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. Software framework for the upcoming MMT Observatory primary mirror re-aluminization

    NASA Astrophysics Data System (ADS)

    Gibson, J. Duane; Clark, Dusty; Porter, Dallan

    2014-07-01

    Details of the software framework for the upcoming in-situ re-aluminization of the 6.5m MMT Observatory (MMTO) primary mirror are presented. This framework includes: 1) a centralized key-value store and data structure server for data exchange between software modules, 2) a newly developed hardware-software interface for faster data sampling and better hardware control, 3) automated control algorithms that are based upon empirical testing, modeling, and simulation of the aluminization process, 4) re-engineered graphical user interfaces (GUI's) that use state-of-the-art web technologies, and 5) redundant relational databases for data logging. Redesign of the software framework has several objectives: 1) automated process control to provide more consistent and uniform mirror coatings, 2) optional manual control of the aluminization process, 3) modular design to allow flexibility in process control and software implementation, 4) faster data sampling and logging rates to better characterize the approximately 100-second aluminization event, and 5) synchronized "real-time" web application GUI's to provide all users with exactly the same data. The framework has been implemented as four modules interconnected by a data store/server. The four modules are integrated into two Linux system services that start automatically at boot-time and remain running at all times. Performance of the software framework is assessed through extensive testing within 2.0 meter and smaller coating chambers at the Sunnyside Test Facility. The redesigned software framework helps ensure that a better performing and longer lasting coating will be achieved during the re-aluminization of the MMTO primary mirror.

  20. 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.

  1. Measurements of particle emission from discharge sites in Teflon irradiated by high energy electron beams

    NASA Technical Reports Server (NTRS)

    Hazelton, R. C.; Churchill, R. J.; Yadlowsky, E. J.

    1979-01-01

    Anomalous behavior of synchronous orbit satellites manifested by overall degradation of system performance and reduced operating life is associated with electrical discharges resulting from differential charging of the spacecraft surface by fluxes of high energy electrons. During a laboratory simulation silver-backed Teflon samples have been irradiated by electron beams having energies in the range 16-26 keV. Charged particles emitted from the resultant electrical discharges have been measured with a biased Faraday cup and retarding potential analyser. Measurements indicate the presence of two distinct fluxes of particles, the first being an early pulse (0-600ns) of high energy (about 7keV) electrons, while the second is a late pulse (1-5 microseconds) of low energy electrons (less than 1eV) and ions (70eV) leaving the discharge site as a quasi plasma. Calculations indicate an electrostatic field as the dominant accelerating mechanism for charged particles.

  2. Characterization of electrical discharges on Teflon dielectrics used as spacecraft thermal control

    NASA Technical Reports Server (NTRS)

    Yadlowsky, E. J.; Hazelton, R. C.; Churchill, R. J.

    1979-01-01

    The dual effects of system degradation and reduced life of synchronous-orbit satellites as a result of differential spacecraft charging underscore the need for a clearer understanding of the prevailing electrical discharge phenomena. In a laboratory simulation, the electrical discharge current, surface voltage, emitted particle fluxes, and photo-emission associated with discharge events on electron beam irradiated silver-backed Teflon samples were measured. Sample surface damage was examined with optical and electron beam microscopes. The results are suggestive of a model in which the entire sample surface is discharged by lateral sub-surface currents flowing from a charge deposition layer through a localized discharge channel to the back surface of the sample. The associated return current pulse appears to have a duration which may be a signature by which different discharge processes may be characterized.

  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. 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.

  5. Production of biologically inert Teflon thin layers on the surface of allergenic metal objects by pulsed laser deposition technology

    NASA Astrophysics Data System (ADS)

    Hopp, B.; Smausz, T.; Kresz, N.; Nagy, P. M.; Juhász, A.; Ignácz, F.; Márton, Z.

    Allergic-type diseases are current nowadays, and they are frequently caused by certain metals. We demonstrated that the metal objects can be covered by Teflon protective thin layers using a pulsed laser deposition procedure. An ArF excimer laser beam was focused onto the surface of pressed PTFE powder pellets; the applied fluences were 7.5-7.7 J/cm2. Teflon films were deposited on fourteen-carat gold, silver and titanium plates. The number of ablating pulses was 10000. Post-annealing of the films was carried out in atmospheric air at oven temperatures between 320 and 500 °C. The thickness of the thin layers was around 5 μm. The prepared films were granular without heat treatment or after annealing at a temperature below 340 °C. At 360 °C a crystalline, contiguous, smooth, very compact and pinhole-free thin layer was produced; a melted and re-solidified morphology was observed above 420 °C. The adhesion strength between the Teflon films and the metal substrates was determined. This could exceed 1-4 MPa depending on the treatment temperature. It was proved that the prepared Teflon layers can be suitable for prevention of contact between the human body and allergen metals and so for avoidance of metal allergy.

  6. 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.

  7. Bilayer lipid membranes supported on Teflon filters: a functional environment for ion channels.

    PubMed

    Phung, Thai; Zhang, Yanli; Dunlop, James; Dalziel, Julie

    2011-03-15

    Many ion channel proteins have binding sites for toxins and pharmaceutical drugs and therefore have much promise as the sensing entity in high throughput technologies and biosensor devices. Measurement of ionic conductance changes through ion channels requires a robust biological membrane with sufficient longevity for practical applications. The conventional planar BLM is 100-300 μm in diameter and typically contains fewer than a dozen channels whereas pharmaceutical screening methods in cells use current recordings for many ion channels. We present a new, simple method for the fabrication of a disposable porous-supported bilayer lipid membrane (BLM) ion channel biosensor using hydrated Teflon (polytetrafluoroethylene, PTFE) filter material (pore size 5 μm, filter diameter=1 mm). The lipid layer was monitored for its thickness and mechanical stability by electrical impedance spectroscopy. The results showed membrane capacitances of 1.8±0.2 nF and membrane resistances of 25.9±4.1 GΩ, indicating the formation of lipid bilayers. The current level increased upon addition of the pore-forming peptide gramicidin. Following addition of liposomes containing voltage-gated sodium channels, small macroscopic sodium currents (1-80 pA) could be recorded. By preloading the porous Teflon with sodium channel proteoliposomes, prior to BLM formation, currents of 1-10 nA could be recorded in the presence of the activator veratridine that increased with time, and were inhibited by tetrodotoxin. A lack of rectification suggests that the channels incorporated in both orientations. This work demonstrates that PTFE filters can support BLMs that provide an environment in which ion channels can maintain their functional activity relevant for applications in drug discovery, toxin detection, and odour sensing.

  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. 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.

  10. Development of a New Design Concept (Replaceable Knee and Elbow patches) for the Standard Aluminized Proximity Coat/Trouser Ensemble.

    DTIC Science & Technology

    1991-06-28

    DEVELOPMENT OF A NEW DESIGN CONCEPT (REPLACEABLE KNEE AND ELBOW PATCHES) FOR THE STANDARD ALUMINIZED PROXIMITYCOAT/TROUSER ENSEMBLE o :~ 91-10527 T...New Design Concept (Replaceable Knee and Elbow Patches) for the Standard Aluminized Proximity Coatf PR 90-3-13 Trouser Ensemble. 6. AUTHOR(S) William...Havy Clothirq aid TVX ile Reearch Facility (MCM) ws tasked by the ArFoarc to develop and evaluate a rmvable knee and elbow patcdeign concept far

  11. The importance of protonation and tautomerization in relative binding affinity prediction: a comparison of AMBER TI and Schrödinger FEP

    NASA Astrophysics Data System (ADS)

    Hu, Yuan; Sherborne, Brad; Lee, Tai-Sung; Case, David A.; York, Darrin M.; Guo, Zhuyan

    2016-07-01

    In drug discovery, protonation states and tautomerization are easily overlooked. Through a Merck-Rutgers collaboration, this paper re-examined the initial settings and preparations for the Thermodynamic Integration (TI) calculation in AMBER Free-Energy Workflows, demonstrating the value of careful consideration of ligand protonation and tautomer state. Finally, promising results comparing AMBER TI and Schrödinger FEP+ are shown that should encourage others to explore the value of TI in routine Structure-based Drug Design.

  12. The importance of protonation and tautomerization in relative binding affinity prediction: a comparison of AMBER TI and Schrödinger FEP.

    PubMed

    Hu, Yuan; Sherborne, Brad; Lee, Tai-Sung; Case, David A; York, Darrin M; Guo, Zhuyan

    2016-07-01

    In drug discovery, protonation states and tautomerization are easily overlooked. Through a Merck-Rutgers collaboration, this paper re-examined the initial settings and preparations for the Thermodynamic Integration (TI) calculation in AMBER Free-Energy Workflows, demonstrating the value of careful consideration of ligand protonation and tautomer state. Finally, promising results comparing AMBER TI and Schrödinger FEP+ are shown that should encourage others to explore the value of TI in routine Structure-based Drug Design.

  13. The reactivity of the 1,4-biradical formed by Norrish type reactions of aqueous valerophenone: a QM/MM-based FEP study.

    PubMed

    Shen, Lin; Fang, Wei-Hai

    2011-02-04

    In the present work, Norrish type reactions of aqueous valerophenone and the reactivity of the triplet 1,4-biradical formed by the 1,5-H shift have been studied with the free energy perturbation (FEP) method that is based on the combined scheme of quantum mechanics (QM) and molecular mechanics (MM). The fluctuation and diffusion of the solvent molecules were found to have an important influence on Norrish type reactions of valerophenone. The α C-C bond cleavages were predicted to be not in competition with the 1,5-H shift, which is consistent with the experimental findings that Norrish type II quantum yield is close to unity. The triplet lifetime of aqueous valerophenone was experimentally inferred to be 52 ns, which is nearly reproduced by the QM/MM-FEP calculated rate constant of 2.33 × 10(7) s(-1). The calculated results show that branch ratios of the subsequent reactions from the triplet 1,4-biradical are mainly controlled by the equilibrium populations of its stable conformations. The ratio of cleavage to cyclization measured experimentally is well reproduced by the present QM/MM-FEP calculations. However, the absolute quantum yields of cleavage and cyclization reactions are underestimated theoretically and the reason for this is discussed.

  14. 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.

  15. Calcium aluminates for quick cesium trapping, application for nuclear power plants

    SciTech Connect

    Capmas, A.; Dubourg, M.; Boch, P.

    1993-12-31

    It has recently been shown that cesium dissolved in water could be trapped in a solid structure by adding cementitious calcium aluminates and fume silica. Calcium aluminates are heat resistant and widely used as refractory products. Extensive studies on the rheological properties has been achieved. It is now possible to obtain flow properties to such an extent as to percolate a slurry through broken structures and give high mechanical strength in a short time. This along with the other properties of thermal shock resistance and cesium trapping makes a solution possible for nuclear building safety as a preventitive or a curative material. For example, at Chernobyl, this material could improve safety by remote casting techniques, construction of a structure which could serve as as ash tray under the coruim. Remotelly controlled equipment needed for this are in operation in more than 50 standardized PWR`s. The equipment performs maintenance and inspection tasks with low radiation exposure.

  16. 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.

  17. 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.

  18. 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.

  19. Sodium aluminate leaching and desilication in lime-soda sinter process for alumina from coal wastes

    NASA Astrophysics Data System (ADS)

    Padilla, R.; Sohn, H. Y.

    1985-12-01

    Sodium aluminate in the sinter produced from coal wastes using the lime-soda sinter process can be leached with dilute alkaline solutions. The extraction of alumina by leaching with water and sodium hydroxide solutions was comparable to extraction by leaching with Na2CO3 solutions. However, leaching with water dissolved the least amount of silica. The optimal conditions for water leaching were determined to be temperatures of 60 to 70 °C and times of 30 to 40 minutes. The sodium aluminate solution obtained under these conditions readily responded to desilication with Ca(OH)2 suspensions at atmospheric pressure, reducing the silica-to-alumina ratio to less than 10-3, which is lower than the specification for reduction-grade alumina.

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

    DOE PAGES

    Li, Xufan; Budai, John D.; Liu, Feng; ...

    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

  1. 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.

  2. Atomistic modeling of an impurity element and a metal-impurity system: pure P and Fe-P system.

    PubMed

    Ko, Won-Seok; Kim, Nack J; Lee, Byeong-Joo

    2012-06-06

    An interatomic potential for pure phosphorus, an element that has van der Waals, covalent and metallic bonding character, simultaneously, has been developed for the purpose of application to metal-phosphorus systems. As a simplification, the van der Waals interaction, which is less important in metal-phosphorus systems, was omitted in the parameterization process and potential formulation. On the basis of the second-nearest-neighbor modified embedded-atom method (2NN MEAM) interatomic potential formalism applicable to both covalent and metallic materials, a potential that can describe various fundamental physical properties of a wide range of allotropic or transformed crystalline structures of pure phosphorus could be developed. The potential was then extended to the Fe-P binary system describing various physical properties of intermetallic compounds, bcc and liquid alloys, and also the segregation tendency of phosphorus on grain boundaries of bcc iron, in good agreement with experimental information. The suitability of the present potential and the parameterization process for atomic scale investigations about the effects of various non-metallic impurity elements on metal properties is demonstrated.

  3. Development of LiCl-containing calcium aluminate cement for bone repair and remodeling applications.

    PubMed

    Acuña-Gutiérrez, I O; Escobedo-Bocardo, J C; Almanza-Robles, J M; Cortés-Hernández, D A; Saldívar-Ramírez, M M G; Reséndiz-Hernández, P J; Zugasti-Cruz, A

    2017-01-01

    The effect of LiCl additions on the in vitro bioactivity, hemolysis, cytotoxicity, compressive strength and setting time of calcium aluminate cements was studied. Calcium aluminate clinker (AC) was obtained via solid state reaction from reagent grade chemicals of CaCO3 and Al2O3. Calcium aluminate cements (CAC) were prepared by mixing the clinker with water or aqueous LiCl solutions (0.01, 0.0125 or 0.015M (M)) using a w/c ratio of 0.4. After 21days of immersion in a simulated body fluid (SBF) at physiological conditions of temperature and pH, a Ca-P rich layer, identified as hydroxyapatite (HA), was formed on the cement without LiCl and on the cement prepared with 0.01M of LiCl solution. This indicates the high bioactivity of these cements. The cements setting times were significantly reduced using LiCl. The measured hemolysis percentages, all of them lower than 5%, indicated that the cements were not hemolytic. The compressive strength of the cements was not negatively affected by the LiCl additions. The obtained cement when a solution of LiCl 0.010M was added, presented high compressive strength, appropriated bioactivity, no cytotoxicity and low setting time, making this material a potentially bone cement.

  4. 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.

  5. Structure and mechanical properties of ceramic coatings fabricated by plasma electrolytic oxidation on aluminized steel

    NASA Astrophysics Data System (ADS)

    Wu, Zhenqiang; Xia, Yuan; Li, Guang; Xu, Fangtao

    2007-08-01

    Ceramic coatings were formed by plasma electrolytic oxidation (PEO) on aluminized steel. Characteristics of the average anodic voltages versus treatment time were observed during the PEO process. The micrographs, compositions and mechanical properties of ceramic coatings were investigated. The results show that the anodic voltage profile for processing of aluminized steel is similar to that for processing bulk Al alloy during early PEO stages and that the thickness of ceramic coating increases approximately linearly with the Al layer consumption. Once the Al layer is completely transformed, the FeAl intermetallic layer begins to participate in the PEO process. At this point, the anodic voltage of aluminized steel descends, and the thickness of ceramic coating grows more slowly. At the same time, some micro-cracks are observed at the Al 2O 3/FeAl interface. The final ceramic coating mainly consists of γ-Al 2O 3, mullite, and α-Al 2O 3 phases. PEO ceramic coatings have excellent elastic recovery and high load supporting performance. Nanohardness of ceramic coating reaches about 19.6 GPa.

  6. 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.

  7. 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'.

  8. The compressibility of a natural composition calcium ferrite-type aluminous phase to 70 GPa

    NASA Astrophysics Data System (ADS)

    Ono, Shigeaki; Hirose, Kei; Kikegawa, Takumi; Saito, Yoko

    2002-08-01

    In situ X-ray diffraction (XRD) experiments of a calcium ferrite-type aluminous phase that is a sodium host mineral of subducted oceanic crusts into the Earth's lower mantle have been carried out using a laser-heated diamond anvil cell (LHDAC), up to a pressure of 70 GPa with synchrotron radiation source at the Photon Factory (PF) in Japan. The sample was heated using a Nd:YAG laser at each pressure increment to relax the deviatoric stress in the sample. XRD measurements were carried out at 300 K using an angle-dispersive technique. The pressure was determined from an internal platinum pressure calibrant. A Birch-Murnaghan equation of state (EOS) was determined from the experimental unit cell parameters: volume V0=244.07 (±55) Å 3, density ρ0=4.143 g/cm 3, bulk modulus K0=253 (±14) GPa, and K0'=3.6 (±0.6). When the first pressure derivative of the bulk modulus K0' was fixed at 4, the value of K0=243 (±2) GPa was obtained. The density of the calcium ferrite-type aluminous phase is lower than those of co-existing Mg-, Ca-perovskite, and hexagonal aluminous phase in subducted oceanic crusts.

  9. 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.

  10. Solidification and immobilization of MSWI fly ash through aluminate geopolymerization: Based on partial charge model analysis.

    PubMed

    Zheng, Lei; Wang, Wei; Gao, Xingbao

    2016-12-01

    This study presents an integrated synopsis of the solidification and immobilization mechanisms of fly ash-based geopolymers. A rational analysis of the ion reactions involved in geopolymerization was conducted using the partial charge model (PCM). The following conclusions were obtained: (1) heavy metal cations cannot be immobilized as counter cations through exchange with Na(+); (2) isomorphous substitution of heavy metals in the geopolymer can be expected from the condensation reaction between the hydrolyzed heavy metal species and aluminosilicate; (3) the hydrolyzed species condensation could result in solidification and immobilization and be promoted by aluminates; and (4) a geopolymer with the highest immobilization and solidification efficiency can be obtained at an intermediate pH value. The partial charges on the framework of Si, Al, and O in the primary building blocks of aluminosilicate and heavy metal-doped aluminosilicate were confirmed through XPS and (29)Si NMR spectroscopy analyses. The effects of activator dosage and types on fly ash-based geopolymers were also investigated, and the results verify the PCM analysis. A geopolymer with the highest strength was produced at an intermediate alkaline dosage. Silicate or aluminate introduced into the activator improved the strength and immobilization efficiency, and aluminate exhibited better performance. Heavy metals bound to the exchangeable or acid-soluble fraction were transformed into aluminosilicate species during geopolymerization.

  11. Flow-through synthesis on Teflon-patterned paper to produce peptide arrays for cell-based assays.

    PubMed

    Deiss, Frédérique; Matochko, Wadim L; Govindasamy, Natasha; Lin, Edith Y; Derda, Ratmir

    2014-06-16

    A simple method is described for the patterned deposition of Teflon on paper to create an integrated platform for parallel organic synthesis and cell-based assays. Solvent-repelling barriers made of Teflon-impregnated paper confine organic solvents to specific zones of the patterned array and allow for 96 parallel flow-through syntheses on paper. The confinement and flow-through mixing significantly improves the peptide yield and simplifies the automation of this synthesis. The synthesis of 100 peptides ranging from 7 to 14 amino acids in length gave over 60% purity for the majority of the peptides (>95% yield per coupling/deprotection cycle). The resulting peptide arrays were used in cell-based screening to identify 14 potent bioactive peptides that support the adhesion or proliferation of breast cancer cells in a 3D environment. In the future, this technology could be used for the screening of more complex phenotypic responses, such as cell migration or differentiation.

  12. Nanoimprint of large-area optical gratings on a conventional photoresist using a teflon-coated nanoimprint mold

    NASA Astrophysics Data System (ADS)

    Jugessur, A. S.; Zhang, A.; Lyu, Y.

    2016-03-01

    Nanoimprint Lithography is a promising high-throughput technology for the fabrication of optical nanostructures over large areas in the centimeter range. However, there are limitations (cost, proprietary and tool specific) of the commercial transfer resist. In this work, the photo-resist AZ1518 is investigated as a viable nanoimprint resist mask with a tefloncoated silicon mold. The results are comparable with a commercial nanoimprint resist. To our knowledge, the application of a conventional photoresist as the nanoimprint mask with teflon-coated mold is novel, providing a critical solution for cost-effective, flexible and high-throughput fabrication of optical nanostructures over large areas. Periodic gratings with lateral width of 100 nm and 200 nm pitch have been fabricated using this approach. The nanoimprint process parameters (pressure and temperature) are optimized to improve the release of the mold from the resist. In addition, the Teflon-coated mold improves the release process to avoid tearing of the mask.

  13. 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.

  14. Forecasting of radiation hazard: 1. Alerts on great FEP events beginning; probabilities of false and missed alerts; on-line determination of solar energetic particle spectrum by using spectrographic method

    NASA Astrophysics Data System (ADS)

    Dorman, L. I.; Pustil'Nik, L. A.; Sternlieb, A.; Zukerman, I. G.

    We show that exact forecast can be made by using high-energy particles (few GeV/nucleon and higher) which transportation from the Sun is characterized by much bigger diffusion coefficient than for small and middle energy particles. Therefore, high-energy particles came from the Sun much more early (8 20 min after acceleration and escaping into solar wind) than main part of smaller energy particles caused dangerous situation for electronics (more than 30 60 min later). We describe here principles and experience of automatically working of program “FEP-Search”. The positive result which shows the exact beginning of FEP event on the Emilio Segre’ Observatory (2025 m above sea level, Rc = 10.8 GV), is determined now automatically by simultaneously increasing on 2.5 St. Dev. in two sections of neutron supermonitor. The next 1-min data the program “FEP-Search” uses for checking that the observed increase reflects the beginning of real great FEP or not. If yes, automatically starts to work on line the programs “FEP-Research”. We determine also the probabilities of false and missed alerts. The first of programs “FEP-Research” is the program “FEP-Research/Spectrum”. We consider two variants: (1) quiet period (no change in cut-off rigidity), (2) disturbed period (characterized with possible changing of cut-off rigidity). We describe the method of determining of the spectrum of FEP in the 1-st variant (for this we need data for at least two components with different coupling functions). For the 2-nd variant we need data for at least three components with different coupling functions. We show that for these purposes can be used data of total intensity and some different multiplicities, but better to use data from two or three NM with different cut-off rigidities. We describe in details the algorithms of the program “FEP-Research/Spectrum”. We show how worked this program on examples of some historical great FEP events.

  15. Fabrication of flexible photonic crystal using alumina ball inserted Teflon tube

    NASA Astrophysics Data System (ADS)

    Watanabe, Yoshimi; Hotta, Takehiro; Sato, Hisashi

    2010-09-01

    In our previous paper, it was found that cotton yarn/TiO2-dispersed resin photonic crystals were fabricated successfully by applying textile technology. However, it is difficult to apply for practical use because these photonic crystals cannot change their shape flexibly. In this study, we fabricate the flexible photonic crystals using high-dielectric constant fibers. The high-dielectric constant fibers were made by inserting alumina balls into Teflon tubes. The crossed linear-fiber laminated fabric and multilayered woven fabric with an fcc lattice structure were structured by aligning high-dielectric constant fibers periodically. These photonic crystals consist of air and high-dielectric constant fibers. The attenuation of transmission amplitude through the photonic crystals was measured. The photonic crystal of crossed linear-fiber laminated fabric exhibits a forbidden gap in the range from 16 to 18 GHz range. On the other hand, the photonic crystal of multilayered woven fabric, which was fabricated by the same parameter with crossed linear-fiber laminated fabric, also exhibits a forbidden gap in the range from 13 to 16 GHz range. Thus, we can successfully fabricate flexible photonic crystals of woven fabric using high-dielectric constant fibers.

  16. 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.

  17. 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.

  18. Short-term hearing results after primary stapedotomy with nitinol and teflon-platinum prostheses for otosclerosis.

    PubMed

    Gouveris, Haralampos; Tóth, Miklós; Koutsimpelas, Dimitrios; Schmidtmann, Irene; Mann, Wolf J

    2013-08-01

    The aim of this study is to determine differences in postoperative air-bone gap (ABG) after placement of teflon-platinum or nitinol middle ear prostheses in primary stapedotomy patients with otosclerosis. Thirty otosclerosis patients (24 female, 6 male; age 10-61 years) with primary stapedotomy were studied prospectively. Before and after surgery, the mean and standard deviations of the ABG were measured at eight frequencies (0.25-4 kHz). Patients were randomized into one of two groups receiving either teflon-platinum or nitinol prostheses. Hearing results were assessed 1 year after surgery. To assess the joint influence of treatment and frequency on ABG reduction, a linear mixed model was used (significance level was p = 5%). The Tukey-Kramer method was used to adjust for multiple comparisons. Significant differences were found between treatment groups (p < 0.0001) and between frequencies within the same treatment group (p < 0.0001) but no interaction (p = 0.7963), i.e. the reduction of the conductive components over frequencies was nearly parallel in both groups. Overall, patients in the Teflon group had a larger reduction of conductive components, on average 8.0 dB more reduction, than patients in the nitinol group. However, after adjusting for multiple comparisons, we could not identify a single frequency with a significant difference in reduction of conductive components. Use of the teflon-platinum prosthesis results in statistically non-significant better ABG closure at 0.25-4 kHz 1 year postoperatively than the use of the nitinol prosthesis.

  19. Fast Surface Temperature Measurement of Teflon Propellant in Pulsed Ablative Discharges Using HgCdTe Photovoltaic Cells (PREPRINT)

    DTIC Science & Technology

    2006-01-01

    performed using crossed tungsten wires of 80 µm diameter. Current up to 1.2 A is run through each wire to induce thermal emission. The signal is maximized...2 second intervals. A typical calibration takes about 10 hours. A slow heating scheme is used to increase accuracy by reducing transient thermal ...Reasons why the two curves might not match include Teflon expansion out of the viewing hole (which causes a change in the optical path), targeting errors

  20. 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.

  1. Graphite-Teflon composite bienzyme electrodes for the determination of L-lactate: application to food samples.

    PubMed

    Serra, B; Reviejo, A J; Parrado, C; Pingarrón, J M

    1999-05-31

    A bienzyme amperometric graphite-Teflon composite biosensor, in which lactate oxidase (LOD) and peroxidase, together with the mediator ferrocene, are incorporated into the electrode matrix, was developed for the determination of L-lactate in food samples such as wine and yogurt by using both batch- and flow-injection modes. This bienzyme electrode was fabricated by simple physical inclusion of the enzymes and the mediator in the bulk of the graphite-Teflon matrix. A Teflon content of 70%, an applied potential of 0.00 V, and a pH of 7.4 were employed as working conditions. The composite bioelectrode exhibited long-term operation because of the renewability of its surface by polishing. Reproducible amperometric responses were achieved with different electrodes fabricated from different composite matrices, and no significant loss of the enzyme activity occurred after 6 months of storage at 4 degrees C. Detection limits for L-lactate of 1.4 and 0.9 microM were obtained by batch amperometry in stirred solutions and flow-injection with amperometric detection, respectively. An interferences study with different substances which may be present in wine and yogurt together with L-lactic acid demonstrated very good selectivity for the determination of this analyte. The bienzyme composite electrode was applied to the determination of L-lactic acid in red wine and shaken yogurt, and the methods were validated by comparing these results with those obtained by applying a recommended reference method.

  2. 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.

  3. The stabilities of gibbsite, boehmite, aluminous goethites and aluminous hematites in bauxites, ferricretes and laterites as a function of water activity, temperature and particle size

    NASA Astrophysics Data System (ADS)

    Trolard, Fabienne; Tardy, Yves

    1987-04-01

    Stability relationships between Al-goethite, Al-hematite, boehmite and gibbsite are presented in terms of water activity [H 2O], temperature ( T), grain size and bulk-composition in the system Fe 2O 3-Al 2O 3-H 2O at a total pressure of 1 bar. Al-goethite and Al-hematite are treated as ideal solid solutions, the former of the end-members FeOOH (goethite) and AlOOH (diaspore) and the latter of the end-members Fe 2O 3 (hematite) and Al 2O 3 (corundum). Using log K sp provided by the literature for the various phases involved, the common associations observed in laterites, bauxites and ferricretes do not have stability fields over geologically reasonable intervals of [H 2O] and T. Consequently a new internally consistent set of log Ksp values is proposed and used, and allows such associations to have actual stability fields in the appropriate diagrams. The new log Ksp values used in the calculations are such that the solubilities of the end members are greater than those commonly listed. This is in agreement with natural observations which show that such minerals, are generally poorly crystallized and of very small size. The assumption of an ideal solid solution in aluminous goethite and aluminous hematite combined with the new log Ksp values leads to prediction of composition limits for these two minerals which agree well with observed values. The fact that an ideal solid solution must extend continuously from one end-member to the other is masked by the appearance of other stability fields ( e.g. gibbsite or boehmite) which cross and overlap a part of the solid solution stability fields of AlOOH-FeOOH and Fe 2O 3-Al 2O 3.

  4. A Study of Pack Aluminizing Process for NiCrAlY Coatings Using Response Surface Methodology

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Huang, Xiao; Liu, Rong; Yang, Qi

    2014-01-01

    Aluminizing process is widely used to provide additional Al deposition onto superalloy surface for enhanced oxidation and corrosion resistance. In this research, an aluminizing process—pack cementation process, is used to deposit Al onto the surface of NiCrAlY coatings for increasing environmental protection. The experiment is designed using Box-Behnken approach, in which three parameters, the Al content, Ni content of the pack powder, and the temperature of the process, are selected as factors; and the thickness and Al/Ni ratio of the coatings are selected as responses. The effects of the factors on the responses are analyzed and modeled empirically. It is found that these empirical models correlate well with the results from additional sets of experiment. These models can be used to produce aluminized NiCrAlY coatings with specific thicknesses and Al/Ni ratios.

  5. 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.

  6. Calcium aluminate coated and uncoated free form fabricated CoCr implants: a comparative study in rabbit.

    PubMed

    Palmquist, A; Jarmar, T; Hermansson, L; Emanuelsson, L; Taylor, A; Taylor, M; Engqvist, H; Thomsen, P

    2009-10-01

    The purpose of this study was to compare the integration in bone of uncoated free form fabricated cobalt chromium (CoCr) implants to the same implant with a calcium aluminate coating. The implants of cylindrical design with a pyramidal surface structure were press-fit into the limbs of New Zealand white rabbits. After 6 weeks, the rabbits were sacrificed, and samples were retrieved and embedded. Ground sections were subjected to histological analysis and histomorphometry. The section counter part was used for preparing an electron transparent transmission electron microscopy sample by focused ion beam milling. Calcium aluminate dip coating provided a significantly greater degree of bone contact than that of the native CoCr. The gibbsite hydrate formed in the hardening reaction of the calcium aluminate was found to be the exclusive crystalline phase material in direct contact with bone.

  7. FeP nanoparticles film grown on carbon cloth: an ultrahighly active 3D hydrogen evolution cathode in both acidic and neutral solutions.

    PubMed

    Tian, Jingqi; Liu, Qian; Liang, Yanhui; Xing, Zhicai; Asiri, Abdullah M; Sun, Xuping

    2014-12-10

    In this Letter, we demonstrate the direct growth of FeP nanoparticles film on carbon cloth (FeP/CC) through low-temperature phosphidation of its Fe3O4/CC precursor. Remarkably, when used as an integrated 3D hydrogen evolution cathode, this FeP/CC electrode exhibits ultrahigh catalytic activity comparable to commercial Pt/C and good stability in acidic media. This electrode also performs well in neutral solutions. This work offers us the most cost-effective and active 3D cathode toward electrochemical water splitting for large-scale hydrogen fuel production.

  8. Evaluation of attenuated PSM photomask blanks with TF11 chrome and FEP-171 resist on a 248 nm DUV laser pattern generator

    NASA Astrophysics Data System (ADS)

    Xing, Kezhao; Björnborg, Charles; Karlsson, Henrik; Paulsson, Adisa; Rosendahl, Anna; Beiming, Peter; Vedenpää, Jukka; Walford, Jonathan; Newman, Tom

    2007-10-01

    Tighter requirements on mask resolution, CD and image positioning accuracy at and beyond the 45 nm technology node push the development of improved photomask blanks. One such blank for attenuated phase-shift masks (att-PSM) provides a thinner chrome film, named TF11, with higher chrome etch rate compared to the previous generation Att- PSM blank (NTAR5 chrome film) from the same supplier. Reduced stress in the chrome film also results in less image placement error induced by the material. FEP-171 is the positive chemically amplified resist (PCAR) that is most commonly used in advanced mask manufacturing with both 50 keV variable shaped e-beam (VSB) and DUV laser pattern generators. TF11 allows an FEP-171 resist film down to about 2000 Å thickness with sufficient etch resistance, while the standard resist thickness for NTAR5 is around 3000 Å. This work has experimentally evaluated the use of TF11 chrome and FEP-171 resist together with a 248 nm DUV laser pattern generator, the Sigma7500. First, patterning performance in resist with thicknesses from 2000 Å to 2600 Å, in steps of 100 Å, was tested with respect to swing curve and basic lithographic parameters including resolution, CD linearity, CD iso-dense bias and dose sensitivity. Patterning results on mask showed a swing minimum at around 2200 Å and a swing maximum at around 2500 Å, which correspond to reflectivity measurements for 248 nm wavelength performed by the blank supplier. It was concluded that the overall patterning performance was best close to the swing maximum. Thereafter the patterning performance using TF11 at two resist thicknesses, 2000 Å and 2550 Å, was studied in more detail and compared to performance using NTAR5 with 3200 Å resist. The evaluation showed that the Sigma7500-II offers good compatibility with TF11, especially using the optimized FEP-171 resist thickness of 2550 Å. It also showed that the patterning capability of the Sigma7500-II using TF11 and 2550 Å resist is improved

  9. 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.

  10. Adsorption/desorption phenomena on pure and Teflon AF-coated titania surfaces studied by dynamic contact angle analysis.

    PubMed

    Rupp, F; Axmann, D; Ziegler, C; Geis-Gerstorfer, J

    2002-12-15

    As a result of inflammatory processes, plaque formation on dental titanium implants often leads to clinically pathogenic situations. This special biofilm formation on (bio)materials in contact with saliva is initiated by ionic and protein interactions. In this interfacial process, albumin becomes a main constituent of dental pellicle. Interfacial reactions change the surface characteristics. They determine the following steps of macromolecular adsorption and bacterial adhesion. This work focuses on the dynamic contact angle analysis (DCA), which is a tool for online measurements of dynamic changes of wettability without disturbing the interface during detection. Repeatability of the DCA method has been assessed according to the Bland and Altman method. The kinetics and equilibrium data of shifts in the wetting tension hysteresis indicate ionic influences at the titanium/bovine serum albumin (BSA) interface: the Ca-mediated increase of the BSA adsorption on titanium and the adsorption maximum at the isoelectric point (IEP) of BSA. Ti was surface modified by Teflon AF polymeric coatings. The result of the assessment gives reason to consider Teflon AF as a reference material for DCA repeatability studies. This surface modification caused drastic changes in the dynamic interfacial reactions. Shifts in the wetting tensions during DCA adsorption-desorption experiments clearly demonstrated the partially irreversible adsorption of BSA on Teflon AF. In contrast, reversible adsorption behavior was detected on pure Ti surfaces. These findings strengthen the hypothesis that the analysis of dynamic changes in wetting tension and wetting tension hysteresis is a sensitive analytical method for the detection of dynamic interfacial changes at biomaterial/biosystem interfaces during the initial steps of biofilm formation.

  11. 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.

  12. A New Method for Determining the Equation of State of Aluminized Explosive

    NASA Astrophysics Data System (ADS)

    Zhou, Zheng-Qing; Nie, Jian-Xin; Guo, Xue-Yong; Wang, Qiu-Shi; Ou, Zhuo-Cheng; Jiao, Qing-Jie

    2015-01-01

    The time-dependent Jones—Wilkins—Lee equation of state (JWL-EOS) is applied to describe detonation state products for aluminized explosives. To obtain the time-dependent JWL-EOS parameters, cylinder tests and underwater explosion experiments are performed. According to the result of the wall radial velocity in cylinder tests and the shock wave pressures in underwater explosion experiments, the time-dependent JWL-EOS parameters are determined by iterating these variables in AUTODYN hydrocode simulations until the experimental values are reproduced. In addition, to verify the reliability of the derived JWL-EOS parameters, the aluminized explosive experiment is conducted in concrete. The shock wave pressures in the affected concrete bodies are measured by using manganin pressure sensors, and the rod velocity is obtained by using a high-speed camera. Simultaneously, the shock wave pressure and the rod velocity are calculated by using the derived time-dependent JWL equation of state. The calculated results are in good agreement with the experimental data.

  13. Reaction temperature variations on the crystallographic state of spinel cobalt aluminate.

    PubMed

    Taguchi, Minori; Nakane, Takayuki; Hashi, Kenjiro; Ohki, Shinobu; Shimizu, Tadashi; Sakka, Yoshio; Matsushita, Akiyuki; Abe, Hiroya; Funazukuri, Toshitaka; Naka, Takashi

    2013-05-21

    In this study, we report a rapid and simple technique for obtaining cobalt aluminate having a spinel structure. The products were prepared from a hydroxide precursor synthesized by coprecipitation of cobalt (Co(2+)) and aluminum (Al(3+)) nitrates with an alkaline solution. The chosen precursor enabled low temperature fabrication of cobalt aluminate with a spinel structure by sintering it for 2 hours at low temperatures (>400 °C). Crystallographic and thermal analyses suggest that the low-temperature-sintered products contain Co(3+) ions stabilized by chemisorbed water and/or hydroxide groups, which was not observed for products sintered at temperatures higher than 1000 °C. The color of the products turned from clear blue (Thenard's blue) to dark green when sintering temperatures were below 1000 °C. Magnetic quantities, Curie constants, and Weiss temperatures show a strong dependence on the sintering temperature. These findings suggest that there are mixed valent states, i.e. Co(2+) and Co(3+), and unique cation distributions at the different crystallographic sites in the spinel structure, especially in the products sintered at lower temperatures.

  14. 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.

    2016-10-01

    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.

  15. 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.

  16. IMPACT OF TIME / TEMPERATURE CURING CONDITIONS AND ALUMINATE CONCENTRATIONS ON SALTSTONE PROPERTIES

    SciTech Connect

    Harbour, J.; Edwards, T.; Williams, V.

    2009-05-05

    This report addresses the impact of (1) the time and temperature curing conditions (profile) and (2) the impact of higher aluminate concentrations in the decontaminated salt solution on Saltstone processing and performance properties. The results demonstrate that performance properties as well as some of the processing properties of Saltstone are highly sensitive to the conditions of time and temperature under which curing occurs. This sensitivity is in turn dependent on the concentration of aluminate in the salt feed solution. In general, the performance properties and indicators (Young's modulus, compressive strength and total porosity) are reduced when curing is initially carried out under high temperature. However, this reduction in performance properties is dependent on the sequence of temperatures (the time/temperature profile) experienced during the curing process. That is, samples that are subjected to a 1, 2, 3 or 4 day curing time at 60 C followed by final curing at 22 C lead to performance properties that are significantly different than the properties of grouts allowed to cure for 1, 2, 3 or 4 days at 22 C followed by a treatment at 60 C. The performance properties of Saltstone cured in the sequence of higher temperature first are generally less (and in some cases significantly less) than performance properties of Saltstone cured only at 22 C. This loss in performance was shown to be mitigated by increased slag content or cement content in the premix at the expense of fly ash. For the sequence in which the Saltstone is initially cured at 22 C followed by a higher temperature cure, the performance properties can be equal to or greater than the properties observed with curing only at 22 C curing. The results in this report indicate that in order to meaningfully measure and report the performance properties of Saltstone, one has to know the time/temperature profile conditions under which the Saltstone will be cured. This will require thermal modeling and

  17. THz polariton laser using an intracavity Mg:LiNbO3 crystal with protective Teflon coating.

    PubMed

    Ortega, Tiago A; Pask, Helen M; Spence, David J; Lee, Andrew J

    2017-02-20

    An enhancement in the performance of a THz polariton laser based on an intracavity magnesium-doped lithium niobate crystal (Mg:LiNbO3) in surface-emitted (SE) configuration is demonstrated resulting from the deposition of a protective Teflon coating on the total internal reflection surface of the crystal. In this cavity geometry the resonating fields undergo total internal reflection (TIR) inside the lithium niobate, and laser damage to that surface can be a limiting factor in performance. The protective layer prevents laser damage to the crystal surface, enabling higher pump power, yielding higher THz output power and wider frequency tuning range. With the unprotected crystal, narrow-band THz output tunable from 1.50 to 2.81 THz was produced, with maximum average output power of 20.1 µW at 1.76 THz for 4 W diode pump power (limited by laser damage to the crystal). With the Teflon coating, no laser damage to the crystal was observed, and the system produced narrow-band THz output tunable from 1.46 to 3.84 THz, with maximum average output power of 56.8 µW at 1.76 THz for 6.5 W diode pump power. This is the highest average output power and the highest diode-to-terahertz conversion efficiency ever reported for an intracavity terahertz polariton laser.

  18. Nongray-radiative and convective-conductive thermal coupling in Teflon-glazed, selective-black, flat-plate solar collectors

    NASA Astrophysics Data System (ADS)

    Edwards, D. K.; Rhee, S. J.

    1984-05-01

    An analysis is presented comparing Teflon film with glass for the inner glazing of a double-glazed selective-black, flat-plate solar collector. The effect of spacing between glazings and between the inner glazing and absorber plate is examined. It is shown that a 12.5-micron Teflon film is superior to glass for the inner glazing of a selective-black collector, because the advantage of its high solar transparency overwhelms the disadvantage of its infrared transparency. A too-small spacing between a selective-black absorber and its inner cover short-circuits the desirable thermal radiation resistance offered by a selective-black absorber plate. Account is taken of spectral variations in the radiation properties of glass, Teflon, and the absorber plate. Allowance is made for the fact that critical Rayleigh number is lower for a plastic film inner glazing than for a glass one.

  19. 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.

  20. 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.

  1. Etude vibrationnelle d'aluminates et de gallates de terres rares—I. Alluminates de structure pérovskite

    NASA Astrophysics Data System (ADS)

    Saine, M. C.; Husson, E.; Brusset, H.; Cerez, A.

    The i.r. spectra of some aluminates of rhomboedral and orthorhombic perovskite types are presented and analysed. The complete vibrational analysis of NdAlO 3 is presented and a force field is proposed for this type of compounds; the potential energy distribution is given and the normal modes are drawn using ORTEP program.

  2. Scaling the Teflon Peaks: Granite, Glaciers, and the Highest Relief in North America

    NASA Astrophysics Data System (ADS)

    Ward, D.; Anderson, R. S.; Haeussler, P. J.

    2010-12-01

    the glacial buzzsaw hypothesis, except where resistant granite has been exhumed among the weaker rocks. Differential erosion has progressively localized divides on the plutons as they were exhumed, leading to focused glaciation there. However, glacier long profiles provide evidence that glacial incision is less efficient on the granite. Cirques cannot form on the steep valley walls that are maintained by detachment of rock slabs along sheeting joints. The strong granites can therefore sustain steep walls that act as Teflon, efficiently shedding snow to the valley below. These avalanches can greatly enhance the health and the erosive power of the modern glaciers in parts of the range. During glaciations, mass is removed efficiently from the surrounding sedimentary landscape, promoting isostatic uplift of the granitic massifs. We conclude that, in places such as Denali, unusual combinations of tectonic uplift rate and rock strength have enacted a set of feedbacks that allowed the development of the highest relief in North America by enhancing glacial erosion in the valleys while preserving the peaks.

  3. LDEF - 69 Months in Space. First Post-Retrieval Symposium. Proceeding of a symposium held in Kissimmee, Florida, 2-8 June 1991.

    DTIC Science & Technology

    1992-01-01

    is attributed to atomic oxygen (AO) impingement. Forward-facing surfaces of silvered Teflon (Ag/FEP) second surface mirror thermal blankets on...not exposed to significant fluences of atomic oxygen have been initiated. Silvered Teflon (Ag/FEP) Second Surface Mirror Thermal Blankets Properties...FEP second surface mirror blanket composition and function, and refs. 9 and 10, respectively. As noted previously in this paper, silvered Teflon

  4. 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...

  5. 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.

  6. Stabilization of ambient sensitive atomic layer deposited lanthanum aluminates by annealing and in situ capping

    NASA Astrophysics Data System (ADS)

    Swerts, J.; Gielis, S.; Vereecke, G.; Hardy, A.; Dewulf, D.; Adelmann, C.; Van Bael, M. K.; Van Elshocht, S.

    2011-03-01

    We have studied the effect of air exposure on lanthanum aluminates (LaAlOx) deposited by atomic layer deposition. Fourier transform infrared spectroscopy and thermal desorption spectroscopy of as-deposited LaAlOx showed that H2O is absorbed during air exposure and that the amount of absorbed H2O increases with increasing La atomic percent. C was found to be incorporated already during deposition in the form of carbonates. H2O and CO2 are outgassed during postdeposition annealing in an inert atmosphere. After a 700 °C postdeposition anneal, the LaAlOx becomes resistant against H2O absorption due to film densification. Alternatively, in situ capping of the LaAlOx with a ˜2 nm thin Al2O3 film protects the LaAlOx against H2O absorption, but it also hinders the outgassing of the C contaminants during a postdeposition anneal.

  7. 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.

  8. 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.

  9. Optical properties of rare earth doped strontium aluminate (SAO) phosphors: A review

    NASA Astrophysics Data System (ADS)

    Kshatri, D. S.; Khare, A.

    2014-11-01

    After the first news on rare earth (RE) doped strontium aluminate (SAO) phosphors in late 1990s, researchers all over the world geared up to develop stable and efficient persistent phosphors. Scientists studied various features of long lasting phosphors (LLP) and tried to earmark appropriate mechanism. However, about two decades after the discovery of SrAl2O4: Eu2+, Dy3+, the number of persistent luminescent materials is not significant. In this review, we present an overview of the optical characteristics of RE doped SAO phosphors in terms of photoluminescence (PL), thermoluminescence (TL) and afterglow spectra. Also, we refresh the work undertaken to study diverse factors like dopant concentration, temperature, surface energy, role of activator, etc. Simultaneously, some of our important findings on SAO are reported and discussed in the end.

  10. Poly(carboxylate ether)-based superplasticizer achieves workability retention in calcium aluminate cement

    PubMed Central

    Akhlaghi, Omid; Menceloglu, Yusuf Ziya; Akbulut, Ozge

    2017-01-01

    Calcium aluminate cement (CAC) suffers from loss of workability in less than an hour (~15 minutes) after first touch of water. Current superplasticizers that are utilized to modify the viscosity of cement admixtures are designed to target ordinary Portland cement (OPC). The high affinity between these superplasticizers and cement particles were found to be detrimental in CAC systems. Utilization of a monomer that, instead, facilitates gradual adsorption of a superplasticizer provides workability retention. For the first time in literature, we report a superplasticizer that caters to the properties of CAC such as high rate of surface development and surface charge. While neat CAC was almost unworkable after 1 hour, with the addition of only 0.4% of the optimized superplasticizer, 90% fluidity retention was achieved. PMID:28134316

  11. 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.

  12. Poly(carboxylate ether)-based superplasticizer achieves workability retention in calcium aluminate cement

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Omid; Menceloglu, Yusuf Ziya; Akbulut, Ozge

    2017-01-01

    Calcium aluminate cement (CAC) suffers from loss of workability in less than an hour (~15 minutes) after first touch of water. Current superplasticizers that are utilized to modify the viscosity of cement admixtures are designed to target ordinary Portland cement (OPC). The high affinity between these superplasticizers and cement particles were found to be detrimental in CAC systems. Utilization of a monomer that, instead, facilitates gradual adsorption of a superplasticizer provides workability retention. For the first time in literature, we report a superplasticizer that caters to the properties of CAC such as high rate of surface development and surface charge. While neat CAC was almost unworkable after 1 hour, with the addition of only 0.4% of the optimized superplasticizer, 90% fluidity retention was achieved.

  13. 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.

  14. Formation of Apollo 14 aluminous mare basalts by replenishment fractional crystallization and assimilation of precursor crust

    NASA Technical Reports Server (NTRS)

    Dickinson, Tammy L.; Nelson, Dennis O.

    1991-01-01

    Apollo 14 aluminous mare basalts (AMB) have been the subject of considerable controversy. These basalts were divided into 5 distinct groups on the basis of RE and HFS element abundances. The groups are similar in major element compositions but display an 8 fold variation in REE abundances. Open-system processes were explored which are common on Earth: combined replenishment fractional crystallization (RFC); and assimilation fractional crystallization (AFC), where the assimilant is a partial melt of precursor crust. RFC often produces decoupled major and trace element variations, while AFC can produce significant variation in incompatible trace element ratios. A model was envisioned by which magmas of Group 5 composition were emplaced in shallow chambers. The Apollo 14 AMB was modeled by RFC using a parental magma of Group 5 composition with the fractionating assemblage consisting of 60 pct. Px, 30 pct. Plag, and 3 pct. Il.

  15. 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

  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. Steric Effects on the Structures, Reactivity, and Coordination Chemistry of Tris(2-pyridyl)aluminates.

    PubMed

    García-Rodríguez, Raúl; Wright, Dominic S

    2015-10-12

    Introducing substituents in the 6-position of the 2-pyridyl rings of tris(pyridyl)aluminate anions, of the type [EtAl(2-py')3 ](-) (py'=a substituted 2-pyridyl group), has a large impact on their metal coordination characteristics. This is seen most remarkably in the desolvation of the THF solvate [EtAl(6-Me-2-py)3 Li⋅THF] to give the monomer [EtAl(6-Me-2-py)3 Li] (1), containing a pyramidal, three-coordinate Li(+) cation. Similar monomeric complexes are observed for [EtAl(6-CF3 -2-py)3 Li] (2) and [EtAl(6-Br-2-py)3 Li] (3), which contain CF3 and Br substituents (R). This steric influence can be exploited in the synthesis of a new class of terminal Al-OH complexes, as is seen in the controlled hydrolysis of 2 and 3 to give [EtAl(OH)(6-R-2-py)2 ](-) anions, as in the dimer [EtAl(OH)(6-Br-2-py)2 Li]2 (5). Attempts to deprotonate the Al-OH group of 5 using Et2 Zn led only to the formation of the zincate complex [LiZn(6-Br-py)3 ]2 (6), while reactions of the 6-Br substituted 3 and the unsubstituted complex [EtAl(2-py)3 Li] with MeOH give [EtAl(OMe)(6-Br-2-py)2 Li]2 (7) and [EtAl(OMe)(2-py)2 Li]2 (8), respectively, having similar dimeric arrangements to 5. The combined studies presented provide key synthetic methods for the functionalization and elaboration of tris(pyridyl)aluminate ligands.

  18. Petrogenesis of coexisting high-silica aluminous and peralkaline rhyolites from Yunshan (Yongtai), southeastern China

    NASA Astrophysics Data System (ADS)

    Hong, Wentao; Xu, Xisheng; Zou, Haibo

    2013-09-01

    The Late Cretaceous bimodal Yunshan (Yongtai) volcanics in Fujian province contain peralkaline rhyolites, the only presence of such rhyolites in southeastern China. Whole-rock and mineral chemical compositions are analyzed for the coexisting aluminous (metaluminous to weakly peraluminous)-peralkaline high-silica rhyolites from the Yunshan volcanics. They are sparsely porphyritic, and contain K-feldspar, ferromagnesian minerals, quartz, magnetite, and titanomagnetite phenocrysts, as well as accessory minerals such as fayalite, chevkinite, apatite and zircon. The mineral assemblage indicates an oxidizing pre-eruption condition. These rhyolites exhibit diagnostic geochemical features of A-type granites, such as elevated 104 * Ga/Al (mostly greater than 2.6) and FeOT/(FeOT + MgO) ratios, enrichment in high field strength elements (HFSE) such as Zr (>400 ppm) and Nb, and strong depletion in Al2O3 (<13 wt%), CaO, Ba and Sr. On the basis of their petrographic and geochemical characteristics, it is suggested that the rhyolite magmas are derived from partial melting of H2O-poor (meta) granitic igneous rocks in the deep crust, and cannot be fractionated from the coeval Yunshan mafic magmas. Geochemical variations of major and trace elements indicate the possible fractionation of K-feldspar, calcium-rich pyroxene, Fe-Ti oxides and minor chevkinite during the magma evolution. In peralkaline rhyolites, we found that the pre-existing Fe-Ti oxide and hedenbergite phenocrysts had been transformed into aegirine + oxide and aegirine + oxide + fluorite assemblages, respectively. These mineral assemblages are the products of the subsolidus reaction of pre-existing phenocrysts and extraneous Na-F-rich fluids. Such Na-F-rich fluids may be derived from the degassing of the subvolcanic rocks. The reactions indicate that the Yunshan peralkaline rhyolites could be generated through the reaction of highly fractionated aluminous silica magmas and Na-F-rich fluids.

  19. 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.

  20. 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.

  1. Modeling kinetics for the reaction of aluminum and teflon and the simulation of its energetic flow motion

    NASA Astrophysics Data System (ADS)

    Yoo, Sunhee; Stewart, D. Scott; Choi, Sungjin; Lambert, David

    2012-03-01

    Simulations with reduced kinetic models are used to study shock ignition and detonation in reactive materials that may support non-classical detonation. Porous aluminum Teflon oxidizer mixtures that support combustion reactions in air are considered, as a member of a class of materials with intrinsic interest. We recast a phenomenological theory [4] with realistic kinetics with end products whose primary components are AlF3, CO, CO2 and Al2O3. Intermediate products include at least thirty elementary reactions; a sub-set can be selected to simplify, but a hard problem remains. Results of the multi-species evolution and its impact on rapid self-oxidizing combustion and possible detonation conditions and the computational methods are presented.

  2. Evaluation of a teflon based ultraviolet light system on the disinfection of water in a textile air washer

    SciTech Connect

    Smith, J.E.; Whisnant, R.B.

    1987-08-01

    The report provides an in-depth evaluation of an ultraviolet (UV) disinfection unit as applied to the treatment of cooling water in a textile air washer system. The UV unit tests used a teflon tube to transport the aquatic phase. The unit reduced microbial populations and maintained an average level of 10,000 Colony formed unites/mL for the 6-month testing period, without the addition of biocides. No cleaning or other maintenance was required of the wetted surfaces during the testing period. Slime deposits observed on walls of the air washer during chemical treatment were also eliminated. The UV unit can be utilized on both cooling towers and air washers without extensive installation.

  3. Flow synthesis using gaseous ammonia in a Teflon AF-2400 tube-in-tube reactor: Paal-Knorr pyrrole formation and gas concentration measurement by inline flow titration.

    PubMed

    Cranwell, Philippa B; O'Brien, Matthew; Browne, Duncan L; Koos, Peter; Polyzos, Anastasios; Peña-López, Miguel; Ley, Steven V

    2012-08-14

    Using a simple and accessible Teflon AF-2400 based tube-in-tube reactor, a series of pyrroles were synthesised in flow using the Paal-Knorr reaction of 1,4-diketones with gaseous ammonia. An inline flow titration technique allowed measurement of the ammonia concentration and its relationship to residence time and temperature.

  4. Computational modeling and preliminary iroN, fepA, and cirA gene expression in Salmonella Enteritidis under iron-deficiency-induced conditions.

    PubMed

    Zárate-Bonilla, Lina J; Del Portillo, Patricia; Sáenz-Suárez, Homero; Gonzáles-Santos, Janneth; Barreto-Sampaio, George E; Poutou-Piñales, Raúl A; Rey, Andrés Felipe; Rey, Jairo Guillermo

    2014-01-01

    Salmonellosis outbreaks in Europe, the United States, and Latin America have been associated with contaminated food derivatives including meat from the poultry industry. Salmonella grown under iron-limiting conditions has the capability to increase concentration of several iron-regulated outer-membrane proteins to augment the acquisition of the metal. These proteins have been proved to have immunogenic properties. Our aim was to increase the relative expression of iroN, fepA, and cirA in Salmonella Enteritidis domestic strain. Furthermore, we proposed a 3-dimensional structure model for each protein to predict and locate antigenic peptides. Our eventual objective is to produce an effective vaccine against regional avian salmonellosis. Two simple factorial designs were carried out to discriminate between 2 nitrogen sources and determine chelating-agent addition timing to augment relative gene expression. Two antigenic peptides located at the external face of each protein and 2 typical domains of iron-regulated outer-membrane proteins, plug and TonB-dep-Rec, were identified from the 3-dimensional models. Tryptone was selected as the best nitrogen source based on growth rate (μx = 0.36 h(-1)) and biomass productivity (Px = 0.9 g•h(-1)•L(-1)) as determined by a general factorial design. Optimum timing for chelating agent addition was in the middle of the log phase, which allowed relative expressions at 4 h of culture. Increase in iroN, fepA, and cirA relative expression was favored by the length of log phase and the addition of chelating agent, which decreased chelating toxicity and enhanced cell growth rate.

  5. Heat capacities of aqueous sodium hydroxide/aluminate mixtures and prediction of the solubility constant of boehmite up to 300 °C

    NASA Astrophysics Data System (ADS)

    Schrödle, Simon; Königsberger, Erich; May, Peter M.; Hefter, Glenn

    2010-04-01

    A modified commercial (Setaram C80) calorimeter has been used to measure the isobaric volumetric heat capacities of concentrated alkaline sodium aluminate solutions at ionic strengths from 1 to 6 mol kg -1, with up to 40 mol.% substitution of hydroxide by aluminate, at temperatures from 50 to 300 °C and a pressure of 10 MPa. Apparent molar heat capacities for the mixtures, C pϕ, derived from these data were found to depend linearly on the aluminate substitution level, i.e., they followed Young's rule. These quantities were used to estimate the apparent molar heat capacities of pure, hypothetical sodium aluminate solutions, C pϕ ('NaAl(OH) 4'(aq)). Slopes of the Young's rule plots were invariant with ionic strength at a given temperature but depended linearly on temperature. The heat capacities of ternary aqueous sodium hydroxide/aluminate mixtures could therefore be modelled using only two parameters in addition to those needed for the correlation of C pϕ (NaOH(aq)) reported previously from these laboratories. An assessment of the standard thermodynamic quantities for boehmite, gibbsite and the aluminate ion yielded a set of recommended values that, together with the present heat capacity data, accurately predicts the solubility of gibbsite and boehmite at temperatures up to 300 °C.

  6. Fast in situ x-ray-diffraction studies of chemical reactions: A synchrotron view of the hydration of tricalcium aluminate

    NASA Astrophysics Data System (ADS)

    Jupe, A. C.; Turrillas, X.; Barnes, P.; Colston, S. L.; Hall, C.; Häusermann, D.; Hanfland, M.

    1996-06-01

    We report observations on the early hydration of tricalcium aluminate, the most reactive component of Portland cement, using rapid-energy dispersive diffraction on a high brilliance synchrotron source. In situ observations of the hydration process over short time scales, and through bulk samples, reveal an intermediate calcium aluminate hydrate appearing just prior to the formation of the final stable hydrate, demonstrating the nucleating role of this intermediate. The superior quality of the data is sufficient to yield concentration versus time plots for each phase over the whole hydration sequence. This improvement derives from being able to use smaller diffracting volumes and consequent removal of time smearing due to inhomogenetics, and thus now offers the possibility of extending the technique in terms of time resolution and diversity of system.

  7. Modified sol-gel prepared Sr(II)-added nickel aluminate nanocatalysts for selective oxidation of benzyl alcohol.

    PubMed

    Kumar, R Thinesh; Vijaya, J Judith; Kennedy, L John

    2013-04-01

    A series of Sr(II)-added nickel aluminate nanocatalysts with different molar ratios of Ni:Sr (1.0:0.0, 0.9:0.1, 0.8:0.2, 0.7:0.3, 0.6:0.4 and 0.5:0.5) keeping the molar ratio of aluminum constant were synthesized by modified sol-gel method using ethylenediamine and sintered at 900 degrees C. The samples were labeled as NiSA1-900, NiSA2-900, NiSA3-900, NiSA4-900, NiSA5-900, NiSA6-900, respectively. The catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), nitrogen adsorption/desorption isotherms and tested for the catalytic oxidation of benzyl alcohol. Influence of the reaction parameters (molar ratio of Sr(II) added to nickel aluminate nanocatalyst, reaction time, reaction temperature and solvent effect) on the catalytic oxidation of benzyl alcohol were studied. It was observed that the addition of Sr(II) improves the performance of the nickel aluminate nanocatalysts towards the selective oxidation of benzyl alcohol and decreases the grain size. Higher activity was obtained for the conversion of benzyl alcohol to benzaldehyde for 0.3 molar percentage Sr(II) added nickel aluminate catalyst (NiSA4-900). Stability and reusability of the catalyst was also investigated.

  8. Etude vibrationnelle d'aluminates et de gallates de terres rares—II. Gallates de structure pérovskite

    NASA Astrophysics Data System (ADS)

    Saine, M. C.; Husson, E.; Brusset, H.

    The i.r. spectra of some gallates LnGaO 3 (Ln = La, Pr, Nd) with perovskite structure and the Raman spectrum of NdGaO 3 are presented and analysed. The force field, calculated for the three compounds, is stronger than for homologous aluminates. The GaO bonds which are parallel to the C2 axis are stronger than the others, thus showing the existence of a privileged direction. This effect decreases from La to Nd compounds.

  9. 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.

  10. 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].

  11. 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.

  12. 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.

  13. Hot alkali carbonation of sodium metaphosphate modified fly ash/calcium aluminate blend hydrothermal cements

    SciTech Connect

    Sugama, T.

    1996-11-01

    Sodium metaphosphate-modified fly ash/calcium aluminate blend (SFCB) cements were prepared by autoclaving for 1 day at 300 C and their resistance was evaluated in a highly concentrated Na{sub 2}CO{sub 3} solution at 300 C. The hydroxyapatite and analcime phases formed in the autoclaved SFCB cements played an essential role in conferring resistance to the degradation of cements caused by alkali carbonation. Although the carbonating reaction of the analcime phase led to the formation of cancrinite, this analcime cancrinite transformation did not show any influence on the changes in the mechanical and physical properties of the cements. Additionally, there was no formation of the water-soluble calcium bicarbonate in the cements exposed for 28 days. Contrarily, the conventional class G cement systems were very vulnerable to a hot alkali carbonation. The major reason for the damage caused by carbonation of the cements was the fact that the xonotlite phase formed in the 300{degree} autoclaved cements was converted into two carbonation products, calcite and pectolite. Furthermore, the reaction between calcite and carbonic acid derived from Na{sub 2}CO{sub 3} led to the formation of water-soluble calcium bicarbonate, thereby causing the alteration of dense structures into porous ones and the loss of strength of cements.

  14. Superplastic flow in a non-stoichiometric ceramic: Magnesium aluminate spinel

    SciTech Connect

    Lappalainen, R.; Pannikkat, A.; Raj, R. . Dept. of Materials Science and Engineering)

    1993-04-01

    Tensile superplastic deformation of ceramics is often limited by their susceptibility to intergranular cavitation. However, the authors find that fine grained magnesium aluminate spinel exhibits unusual superplastic ductility at strain rates of up to 5 [times] 10[sup [minus]4]s[sup [minus]1] and at temperatures below 1,280 C. The ductility is all the more remarkable because the flow stress of the spinel was in the range of several hundred MPa. The authors propose that the unusual cavitation resistance of interfaces in spinel is related to its non-stoichiometry. They further propose that the non-linear threshold stress like rheology which they have measured is related to an electrical double (barrier) layer which is postulated to form to compensate the net charge at interfaces of non-stoichiometric ceramics. They estimate that a boundary double layer potential, [psi][sub b], of 5-50 mV can account for this threshold stress. The phenomenological characteristics of superplastic flow in the spinel are shared by other non-stoichiometric ceramics such as yttria stabilized zirconia, hydroxyapatite and zinc sulfide.

  15. 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.

  16. First-principles study of iron spin crossover in the new hexagonal aluminous phase

    NASA Astrophysics Data System (ADS)

    Hsu, Han

    2017-01-01

    The new hexagonal aluminous (NAL) phase, chemical formula A B2C6O12 (A = Na+, K+, Ca2 +; B = Mg2 +, Fe2 +, Fe3 +; C = Al3 +, Si4 +, Fe3 +), is considered a major component (˜20 vol%) of mid-ocean ridge basalt (MORB) under the lower-mantle condition. As MORB can be transported back into the Earth's lower mantle via subduction, a thorough knowledge of the NAL phase is essential to fully understand the fate of subducted MORB and its role in mantle dynamics and heterogeneity. In this Rapid Communication, the complicated spin crossover of the Fe-bearing NAL phase is revealed by a series of local density approximation + self-consistent Hubbard U (LDA+Us c) calculations. Only the ferric iron (Fe3 +) substituting Al/Si in the octahedral (C ) site undergoes a crossover from the high-spin (HS) to the low-spin (LS) state at ˜40 GPa, while iron substituting Mg in the trigonal-prismatic (B ) site remains in the HS state, regardless of its oxidation state (Fe2 + or Fe3 +). The volume/elastic anomalies and the iron nuclear quadrupole splittings determined by calculations are in great agreement with room-temperature experiments. The calculations further predict that the HS-LS transition pressure of the NAL phase barely increases with temperature due to the three nearly degenerate LS states of Fe3 +, suggesting that the elastic anomalies of this mineral can occur at the top lower mantle.

  17. Crystal field parameters with Wannier functions: Application to rare-earth aluminates

    NASA Astrophysics Data System (ADS)

    Novák, P.; Knížek, K.; Kuneš, J.

    2013-05-01

    A method to calculate the crystal field parameters is proposed and applied to trivalent rare-earth impurities in yttrium aluminate and to Tb3+ ion in TbAlO3. To determine crystal field parameters local Hamiltonian expressed in the basis of Wannier functions is expanded in a series of spherical tensor operators. Wannier functions are obtained by transforming the Bloch functions calculated using the density functional theory based program. The results show that the crystal field is continuously decreasing as the number of 4f electrons increases and that the hybridization of 4f states with the states of oxygen ligands is important. The method contains a single adjustable parameter characterizing the 4f-ligand charge transfer. Theory is confronted with experiment for Nd3+ and Er3+ ions in the YAlO3 matrix and for the Tb3+ ion in TbAlO3, and a good agreement within a few meV is found.

  18. 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.

  19. Corrosion behaviour of aluminized martensitic and austenitic steels in liquid Pb-Bi

    NASA Astrophysics Data System (ADS)

    Deloffre, Ph.; Balbaud-Célérier, F.; Terlain, A.

    2004-11-01

    The Pb-Bi liquid alloy is under consideration as a spallation target material in the hybrid systems due to its suitable nuclear and physical properties. In order to limit the risks of corrosion of the structural elements in contact with the liquid Pb-Bi, protection by means of aluminized coatings was investigated for 316L austenitic steel and T91 martensitic steel. For both steels, no damages were observed after immersions in static Pb-Bi up to 500 °C for low oxygen concentrations and long durations. However, at 600 °C in the same conditions, a non-uniform degradation of the coatings was observed. Only coated 316L was tested in dynamic conditions. The results were generally satisfying for temperatures from 350 to 600 °C and for fluid velocities up to 2.3 m s -1. However, in both the IPPE loops and the CICLAD device, some localized damage of the coatings, attributed to erosion, was observed.

  20. 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}.

  1. 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.

  2. Effect of 14-MeV neutrons on strontium-aluminate-based long-lasting phosphor

    NASA Astrophysics Data System (ADS)

    Toh, K.; Shikama, T.; Katsui, H.; Nagata, S.; Tsuchiya, B.; Yamauchi, M.; Nishitani, T.

    2009-04-01

    Long-lasting phosphor (LLP) emits photons for a long period of time after the cessation of irradiation without external excitation. LLP exhibits not only a long-lasting emission but also strong fluorescence. The fluorescence and long-lasting emission properties of two types of strontium-aluminate-based LLPs - SrAl 2O 4:Eu 2+, Dy 3+ and Sr 4Al 14O 25:Eu 2+, Dy 3+ - are examined under 14-MeV neutron irradiation. The fluorescent spectra of the LLPs have characteristic peaks due to their dopants and the fluorescent intensity of Sr 4Al 14O 25:Eu 2+, Dy 3+ shows good radiation resistance for the neutrons, with a slight change after increasing the irradiation fluence up to 10 19 n/m 2. Long-lasting emissions are exhibited after neutron irradiation, and the emission spectra have one peak due to Eu 2+. A peak due to Dy 3+ ends immediately when the irradiation is stopped. Further, it is found that there is an optimum neutron fluence at which the longest decay time is obtained.

  3. Long lasting phosphorescence and photostimulated luminescence in Tb-ion-activated reduced calcium aluminate glasses

    NASA Astrophysics Data System (ADS)

    Kinoshita, Takeru; Yamazaki, Masaaki; Kawazoe, Hiroshi; Hosono, Hideo

    1999-10-01

    Long lasting phosphorescence (LLP) and photostimulated luminescence (PSL) were found in reduced calcium aluminate glasses activated with Tb3+ ions. The LLP from Tb3+ was observed by illuminating the Tb3+ 4f→5d charge transfer band with ultraviolet (UV) 254 nm light, while the PSL was seen by stimulating the UV-illuminated glasses with 633 nm light. The decay curve of the LLP was fitted with a second-order kinetic for the initial period (030 min). An electron paramagnetic resonance (EPR) signal, which is attributed to an F+-like center associated with Ca2+ ions, was induced by illumination with UV light and its intensity decay was fitted with a first-order kinetic similarly to the later stage of the LLP. The appearance of the PSL by illumination is accompanied by a distinct intensity reduction of the EPR signal due to the F+-like center. The thermoluminescence spectra of the specimen illuminated with UV light at 77 K consist of two components peaking at ˜240 and ˜390 K. The low temperature component and the high temperature component were attributed to an F-like center and an F+-like center, respectively. These results lead to a conclusion that electrons of the F-like center and the F+-like center contribute predominantly to the emergence of the LLP and the PSL, respectively.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. FEP regimen (epidoxorubicin, etoposide and cisplatin) in advanced gastric cancer, with or without low-dose GM-CSF: an Italian Trial in Medical Oncology (ITMO) study.

    PubMed Central

    Bajetta, E.; Di Bartolomeo, M.; Carnaghi, C.; Buzzoni, R.; Mariani, L.; Gebbia, V.; Comella, G.; Pinotti, G.; Ianniello, G.; Schieppati, G.; Bochicchio, A. M.; Maiorino, L.

    1998-01-01

    The new regimens developed over the last few years have led to an improvement in the treatment of advanced gastric cancer, and our previous experience confirmed the fact that the combination of etoposide, doxorubicin and cisplatin (EAP regimen) is an active treatment that leads to interesting complete remission rates. The primary end point of the present multicentre, randomized, parallel-group phase II study was to determine the activity of the simplified 2-day EAP schedule in patients with locally advanced or metastatic gastric cancer, and to verify whether the addition of low doses of granulocyte-macrophage colony-stimulating factor (GM-CSF) made it possible to increase dose intensity. Of the 62 enrolled patients, 30 were randomized to receive epirubicin 35 mg m(-2), etoposide 120 mg m(-2) and cisplatin 45 mg m(-2) (FEP) on days 1 and 2 every 28 days and 32 to receive the same schedule plus subcutaneous GM-CSF (molgramostin) 150 microg day(-1) on days 5-14 every 21 days. The patients were stratified by age and the number of disease sites. The characteristics of the patients were well balanced between the two groups. The objective response rate of the patients as a whole was 34% (21 out of 62; 95% confidence interval 22-46), with only one complete remission. The median response duration was 4.5 months (range 1-24 months). The median time to treatment failure was 5 months (range 1-14 months), without any difference between the two groups. The median survival of the patients as a whole was 9 months. Full doses were administered in 92% and 94% of the cycles in the control and GM-CSF arms respectively. The average dose intensity calculated for all drugs was 0.96% in the control and 1.27% in the GM-CSF group. CTC-NCI grade 3-4 neutropenia was reported in 39% vs 45% of patients, thrombocytopenia in 11% vs 35% (P = 0.020) and anaemia in 7% vs 35% (P = 0.014). The FEP combination is as active (OR: 34%) in the treatment of patients with advanced gastric cancer as the EAP

  9. Effect of different Bacillus subtilis lipopeptides on surface hydrophobicity and adhesion of Bacillus cereus 98/4 spores to stainless steel and Teflon.

    PubMed

    Shakerifard, Parvin; Gancel, Frédérique; Jacques, Philippe; Faille, Christine

    2009-01-01

    Various lipopeptides produced by Bacillus subtilis were examined for their ability to modify the surface hydrophobicity of two substrata, stainless steel (SS) and Teflon. These modifications were evaluated by water contact angle measurements. The effects depended on the lipopeptide, its concentration, and the tested substratum. Treatment of SS with different concentrations of surfactin S1 showed an increase of the hydrophobicity between 1 and 100 mg l(-1). On the same substratum, fengycin increased hydrophobicity up to its critical micelle concentration (6.25 mg l(-1)). With higher concentrations of fengycin, hydrophobicity decreased. Surfactin, mycosubtilin, and iturin A decreased hydrophobicity on Teflon. The different effects of these three families of lipopeptides were related to their structural differences. A good correlation was shown between hydrophobicity modifications of surfaces and the attachment of B. cereus 98/4 spores. Enhancement in the hydrophobicity of the surfaces increased the number of adhering spores.

  10. Electro-optical response of polymer-dispersed liquid crystal single layers of large nematic droplets oriented by rubbed teflon nanolayers

    NASA Astrophysics Data System (ADS)

    Marinov, Y. G.; Hadjichristov, G. B.; Petrov, A. G.; Marino, S.; Versace, C.; Scaramuzza, N.

    2013-02-01

    The surface orienting effect of rubbed teflon nanolayers on the morphology and electro-optical (EO) response of polymer-dispersed liquid crystal (PDLC) single layers of large nematic droplets was studied experimentally. In PDLC composites of the nematic liquid crystal (LC) E7 and NOA65 polymer, single droplets of LC with diameters as larger as 10 μm were confined in layers with a thickness of 10 μm, and the nematic director field was efficiently modified by nanostructuring teflon rubbing of the glass plates of the PDLC cell. For layered PDLCs arranged and oriented in this way, the modulated EO response by the dielectric oscillations of the nematic director exhibits a selective amplitude-frequency modulation controllable by both temperature and voltage applied, and is simply related to the LC droplet size. That may be of practical interest for PDLC-based modulators operating in the infrasound frequency range.

  11. Temporal and storage effects on ultra-low volume droplets of insecticides collected on Teflon-coated slides.

    PubMed

    Farooq, Muhammad; Lloyd, Aaron M; Estep, Alden S; Walker, Todd W; Hughes, Tony

    2013-12-01

    Use of microscope slides is the most commonly used method to field-assess the droplet spectrum of ultra-low volume (ULV) sprays. Due to absence of analysis facilities during military deployments, slides must be stored and shipped, and the impact of delays in processing and storage conditions on droplets is unknown. This study was designed to evaluate the effect of storage temperatures and duration on droplets on Teflon-coated slides. Treatments included BVA-13 mineral oil, Kontrol 30-30 (30% permethrin), and Fyfanon (96.5% malathion), 2 slide wrapping techniques (proper and improper), and 2 storage temperatures (23 and 45 degrees C), replicated 6 times. The same areas of a slide were measured at different times for 56-58 days using the DropVision droplet measurement system. Regardless of the wrapping technique, droplets of BVA-13, Fyfanon, and Kontrol 30-30 on slides stored at 45 degrees C reduced significantly after 1, 2, and 1 day, respectively, but droplets on slides stored at 23 degrees C were not significantly affected. The results of this study may assist vector control professionals to accurately interpret the droplet size and help in the effective dispersal of ULV-applied insecticides.

  12. 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.

  13. 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.

  14. Droplet sampling of an oil-based and two water-based antievaporant ultra-low volume insecticide formulations using Teflon- and magnesium oxide-coated slides.

    PubMed

    Chaskopoulou, Alexandra; Latham, Mark D; Pereira, Roberto M; Koehler, Philip G

    2013-06-01

    We estimated the diameters below which 50% and 90% of the volume of droplets exist (Dv50 and Dv90, respectively) of 1 oil-based (Permanone 30-30) and 2 water-based (AquaReslin, Aqua-K-Othrine) antievaporant aerosols (with the Film Forming Aqueous Spray Technology [FFAST]) using Teflon- and magnesium oxide (MgO)-coated slides and determined whether the aging of the droplets on the slides (up to 60 min) exhibited any significant effect on Dv50 and Dv90 calculations. There were no significant differences in either Dv50 or Dv90 estimates on MgO-coated slides at 0 min and 60 min for all 3 products tested. On Teflon-coated slides, the only product that showed significant difference between 0 min and 60 min in both Dv50 and Dv90 estimates was Aqua-K-Othrine, perhaps due to a difference in formulation components. Specifically, both values corresponding to Dv50 and Dv90 at 60 min decreased by approximately 50% when compared to the values at 0 min. For the other 2 products, AquaReslin and Permanone, aging of droplets on Teflon up to 60 min did not have any significant effect on Dv50 and Dv90 values. To further investigate the behavior of Aqua-K-Othrine droplets on Teflon-coated slides we observed the droplets immediately after spraying and at 10-min intervals under different conditions of temperature and humidity. The majority of the shrinkage occurred within the 1st 10 min after impaction on the slides under all conditions tested. So in most field situations where slides are read several hours or days after collection, this shrinkage would not be observed. The MgO-coated slides should be the preferred field method for sampling droplets of Aqua-K-Othirne with the FFAST antievaporant technology.

  15. Escherichia coli ghosts or live E. coli expressing the ferri-siderophore receptors FepA, FhuE, IroN and IutA do not protect broiler chickens against avian pathogenic E. coli (APEC).

    PubMed

    Tuntufye, Huruma Nelwike; Ons, Ellen; Pham, Anh Dao Nguyen; Luyten, Tom; Van Gerven, Nani; Bleyen, Nele; Goddeeris, Bruno Maria

    2012-10-12

    The aim of this study was to investigate if immunization with the ferri-siderophore receptors FepA, FhuE, IroN and IutA could protect chickens against avian pathogenic Escherichia coli (APEC) infection. The antigens were administered as recombinant proteins in the outer membrane (OM) of E. coli strain BL21 Star DE3. In a first immunization experiment, live E. coli expressing all 4 recombinant ferri-siderophore receptors (BL21(L)) were given intranasally. In a second immunization experiment, a mixture of E. coli ghosts containing recombinant FepA and IutA and ghosts containing recombinant FhuE and IroN was evaluated. For both experiments non-recombinant counterparts of the tentative vaccines were administered as placebo. At the time of challenge, the IgG antibody response for BL21(L) and a mixture of E. coli ghosts containing recombinant FepA and IutA and ghosts containing recombinant FhuE and IroN was significantly higher in all immunized groups as compared to the negative control groups (LB or PBS) confirming successful immunization. Although neither of the tentative vaccines could prevent lesions and mortality upon APEC infection, immunization with bacterial ghosts resulted in a decrease in mortality from 50% (PBS) to 31% (non-recombinant ghosts) or 20% (recombinant ghosts) and these differences were not found to be significant.

  16. 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.

  17. The deposition of anti-adhesive ultra-thin teflon-like films and their interaction with polymers during hot embossing

    NASA Astrophysics Data System (ADS)

    Jaszewski, R. W.; Schift, H.; Schnyder, B.; Schneuwly, A.; Gröning, P.

    1999-04-01

    The chemical and physical interactions of ultra-thin teflon-like films at interfaces are a surface science problem with many technological implications. Such films are the material of choice for protective layers and anti-adhesive coatings. During the replication of microstructures in polymers by hot embossing, interfacial forces between the master and the replica need to be reduced by an anti-adhesive layer, in order to ensure a clean demolding process. In this work, we investigated two different teflon-like films, one obtained by ion sputtering, and the other by plasma polymerization. Using both deposition methods, we deposited thin fluorinated films on nickel substrates and conducted depth-resolved X-ray Photoelectron Spectroscopy (XPS) measurements for a detailed comparison. In a subsequent step, nickel surfaces covered by both anti-adhesive coatings were hot embossed into two different polymers. The chemical composition of both the anti-adhesive film and the polymer replicas was monitored, as a function of the number of embossings made with the same Polytetrafluoroethylene (PTFE)-treated nickel stamp. During the embossing process, a transfer of material was found to occur from the teflon-like film to the embossed polymer, consisting of fluorinated entities or small polymer chains. The influence of the operating parameters on these phenomena was also investigated and resulted in a better understanding of the film/polymer interactions under pressure and at high temperature.

  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. 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

  20. 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.

  1. Color-Center Production and Formation in Electron-Irradiated Magnesium Aluminate Spinel and Ceria

    DOE PAGES

    Costantini, Jean-Marc; Lelong, Gerald; Guillaumet, Maxime; ...

    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

  2. Color-Center Production and Formation in Electron-Irradiated Magnesium Aluminate Spinel and Ceria

    SciTech Connect

    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 calculations 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.

  3. 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.

  4. Study on the structure and electrical behaviour of zinc aluminate ceramics irradiated with gamma radiation

    NASA Astrophysics Data System (ADS)

    Abd El All, S.; Fawzy, Y. H. A.; Radwan, R. M.

    2007-09-01

    The preparation process of zinc aluminate (ZnAl2 O4) ceramic powder, as well as the sintering temperature have been consequently governed using scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. A broad exothermic peak in the range 223-310 °C is observed due to the crystallization of ZnAl2O4 powder. Then the final resultant powder was irradiated with gamma rays at different doses from 30 to 150 kGy. The effect of gamma irradiation on the structure and the electrical behaviour of ZnAl2O4 ceramics has been obtained. The induced changes in the structure have been studied via SEM, XRD and FTIR spectrometers. The obtained results reveal no changes in the spinel phase of ZnAl2O4, while some displacements of the constituent individual atoms for the irradiated samples are observed. The I-V characteristic curves and the dielectric properties of the prepared ceramic powder have been measured for unirradiated and irradiated samples. These curves exhibit nonlinearity of this type of ceramics, where the dc current gradually increases with the increase in the dose. The irradiation of ZnAl2O4 with gamma radiation was found to increase the nonlinearity of the I-V curves. The dielectric constant and loss were found to decrease as the dose increases. Therefore, the irradiation of ZnAl2O4 with gamma rays can improve its utility as an electronic protector in electrical circuits against sudden overvoltage.

  5. Formation of lead-aluminate ceramics: Reaction mechanisms in immobilizing the simulated lead sludge.

    PubMed

    Lu, Xingwen; Shih, Kaimin

    2015-11-01

    We investigated a strategy of blending lead-laden sludge and an aluminum-rich precursor to reduce the release of hazardous lead from the stabilized end products. To quantify lead transformation and determine its incorporation behavior, PbO was used to simulate the lead-laden sludge fired with γ-Al2O3 by Pb/Al molar ratios of 1/2 and 1/12 at 600-1000 °C for 0.25-10 h. The sintered products were identified and quantified using Rietveld refinement analysis of X-ray diffraction data from the products generated under different conditions. The results indicated that the different crystallochemical incorporations of hazardous lead occurred through the formation of PbAl2O4 and PbAl12O19 in systems with Pb/Al ratios of 1/2 and 1/12, respectively. PbAl2O4 was observed as the only product phase at temperature of 950 °C for 3h heating in Pb/Al of 1/2 system. For Pb/Al of 1/12 system, significant growth of the PbAl12O19 phase clearly occurred at 1000 °C for 3 h sintering. Different product microstructures were found in the sintered products between the systems with the Pb/Al ratios 1/2 and 1/12. The leaching performances of the PbO, Pb9Al8O21, PbAl2O4 and PbAl12O19 phases were compared using a constant pH 4.9 leaching test over 92 h. The leachability data indicated that the incorporation of lead into PbAl12O19 crystal is a preferred stabilization mechanism in aluminate-ceramics.

  6. 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

    2017-04-01

    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.

  7. 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.

  8. 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.

  9. 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.

  10. Stabilizing cadmium into aluminate and ferrite structures: Effectiveness and leaching behavior.

    PubMed

    Su, Minhua; Shih, Kaimin; Kong, Lingjun

    2017-02-01

    The inappropriate disposal of sludge, particularly for those enriched in heavy metals, is highly hazardous to the environment. Thermally converting sludge into useful products is a highly promising technique as heavy metals are immobilized and organic substances are mineralized. This work investigated the feasibility of stabilizing simulated cadmium-laden sludge by sintering with Al-and Fe-rich precursors. To simulate the process, cadmium oxide was alternatively mixed and sintered with γ-Al2O3 and α-Fe2O3. Cadmium was crystallographically incorporated into aluminate (CdAl4O7) monoclinic structure and ferrite (CdFe2O4) spinel, dependent on the type of precursor used. The CdFe2O4 formation was initialed at about 150-300 °C lower than that of CdAl4O7. With Rietveld refinement analysis of the collated XRD data, the weight percentages of crystalline phases in the fired samples were quantified. To evaluate the cadmium incorporation efficiency, a transformation ratio (TR) index was devised. The TR values revealed that, to effectively incorporate cadmium, 950 °C was favored by γ-Al2O3 and 850 °C was for α-Fe2O3 within a 3-h sintering treatment. Constant pH leaching test (CPLT) was used to assess the metal stabilization effects, revealing a remarkable reduction of cadmium by transformation into CdAl4O7 and CdFe2O4. Both CdAl4O7 and CdFe2O4 were incongruently dissolved in an acid solution. The overall finding indicated a potentially feasible technology in cadmium-laden sludge stabilization.

  11. 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.

  12. 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

  13. Chemical alteration of poly(tetrafluoroethylene) TFE teflon induced by exposure to electrons and inert-gas ions.

    PubMed

    Everett, Michael L; Hoflund, Gar B

    2005-09-08

    In this study the chemical alterations of poly(tetrafluoroethylene) (TFE Teflon) by approximately 1.0-keV electrons and 1.0-keV He and Ar ions have been examined using X-ray photoelectron spectroscopy (XPS). The initial F/C atom ratio of 1.99 decreases to a steady-state value of 1.48 after 48 h of electron exposure. Exposure to either He+ or Ar+ decreases the initial F/C atom ratio from approximately 2 to a steady-state value of 1.12. The high-resolution XPS C 1s data indicate that new chemical states of carbon form as the F is removed and that the relative amounts of these states depend on the F content of the near-surface region. These states are most likely due to C bonded only to one F atom, C bonded only to other C atoms and C that have lost a pair of electrons through emission of F-. Exposures of the electron-damaged and He+- or Ar+-damaged surfaces to research-grade O2 result in chemisorption of very small amounts of O indicating that large quantities of reactive sites are not formed during the chemical erosion. Further exposure to the electron or ion fluxes quickly removes this chemisorbed oxygen. Exposure of the He+-damaged surface to air at room temperature results in the chemisorption of a larger amount of O than the O2 exposure but no N is adsorbed. The chemical alterations due to electrons and ions are compared with those caused by hyperthermal (approximately 5 eV) atomic oxygen (AO) and vacuum ultraviolet (VUV) radiation. The largest amount of damage is caused by AO followed by VUV, inert-gas ions, and then electrons.

  14. Characterization of In Vitro Interactions between a Truncated TonB Protein from Escherichia coli and the Outer Membrane Receptors FhuA and FepA

    PubMed Central

    Moeck, Gregory S.; Letellier, Lucienne

    2001-01-01

    High-affinity iron uptake in gram-negative bacteria depends upon TonB, a protein which couples the proton motive force in the cytoplasmic membrane to iron chelate receptors in the outer membrane. To advance studies on TonB structure and function, we expressed a recombinant form of Escherichia coli TonB lacking the N-terminal cytoplasmic membrane anchor. This protein (H6-′TonB; Mr, 24,880) was isolated in a soluble fraction of lysed cells and was purified by virtue of a hexahistidine tag located at its N terminus. Sedimentation experiments indicated that the H6-′TonB preparation was almost monodisperse and the protein was essentially monomeric. The value found for the Stokes radius (3.8 nm) is in good agreement with the value calculated by size exclusion chromatography. The frictional ratio (2.0) suggested that H6-′TonB adopts a highly asymmetrical form with an axial ratio of 15. H6-′TonB captured both the ferrichrome-iron receptor FhuA and the ferric enterobactin receptor FepA from detergent-solubilized outer membranes in vitro. Capture was enhanced by preincubation of the receptors with their cognate ligands. Cross-linking assays with the purified proteins in vitro demonstrated that there was preferential interaction between TonB and ligand-loaded FhuA. Purified H6-′TonB was found to be stable and thus shows promise for high-resolution structural studies. PMID:11292793

  15. 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.

  16. Effect of B2O3 content on structure and spectroscopic properties of neodymium-doped calcium aluminate glasses

    NASA Astrophysics Data System (ADS)

    Kang, Shuai; Wang, Xue; Xu, Wenbin; Wang, Xin; He, Dongbing; Hu, Lili

    2017-04-01

    Nd2O3-doped calcium aluminate glasses was synthesized with the following compositions: (100-x)(33Al2O3-62CaO-2MgO-3BaO)-xB2O3-0.5Nd2O3 (x = 0, 2.5, 5, 7.5, 10). The Raman, absorption, and emission spectra were measured to characterize the structure and spectroscopic properties of these glasses. The glass thermal stability was studied using differential scanning calorimetry (DSC) tests. Both the Raman spectra and DSC results indicated a decrease in the non-bridging oxygens (NBOs) in the [AlO4]- network with an increase in the B2O3 content. The J-O intensity parameter Ω2, covalency degree of the Nd-O bond, and emission bandwidth of the Nd3+ ions decreased with the B2O3 content. The stimulated emission cross-section and optical gain property increased with an increase in the B2O3 content. The tunable gain property and broadband emission feature of the Nd3+-doped CaO-Al2O3-B2O3-MgO-BaO calcium aluminate glass suggested a potential application to a high-energy ultra-short-pulse laser.

  17. Cytotoxicity of a calcium aluminate cement in comparison with other dental cements and resin-based materials.

    PubMed

    Franz, Alexander; Konradsson, Katarina; König, Franz; Van Dijken, Jan W V; Schedle, Andreas

    2006-02-01

    The objective of this study was to compare the cytotoxic effects of a calcium aluminate cement with several currently used direct restorative materials. Specimens of three composites (QuiXfil, Tetric Ceram, Filtek Supreme), one zinc phosphate cement (Harvard Cement), one glass ionomer cement (Ketac Molar), and one calcium aluminate cement (DoxaDent), were used fresh or after 7-days' preincubation in cell culture medium at 37 degrees C, pH 7.2. PVC strips for ISO 10993-5 cytotoxicity test were used as positive control and glass specimens as negative control. L-929 fibroblasts (5-ml aliquots, containing 3 x 10(4) cells/ml), cultivated in DMEM with 10% FCS, 1% glutamine, and 1% penicillin/streptomycin at 37 degrees C/5% CO2 and trypsinized, were exposed to the specimens for 72 h. The cells were harvested, centrifuged, and resuspended in 500 microl DMEM and then counted in 500 microl DMEM for 30 s with a flow cytometer at 488 nm. The analysis of variance comparing the six materials showed different influences on L-929 fibroblast cytotoxicity (p <0.0001). The cytotoxicity of all specimens diminished with increasing preincubation time (p <0.0001). Fresh DoxaDent exhibited the lowest cytotoxicity, followed by QuiXfil. Ketac Molar showed the highest cytotoxicity. After 7 days of preincubation, Harvard Cement and Filtek Supreme demonstrated more cytotoxicity than the other materials (p <0.005).

  18. Synthesis of zinc aluminate with high surface area by microwave hydrothermal method applied in the transesterification of soybean oil (biodiesel)

    SciTech Connect

    Quirino, M.R.; Oliveira, M.J.C.; Keyson, D.; Lucena, G.L.; Oliveira, J.B.L.; Gama, L.

    2016-02-15

    Highlights: • ZnAl{sub 2}O{sub 4} spinel was synthesized by the microwave hydrothermal method in only 15 or 30 min. • The powders show high specific surface area. • ZAT{sub b}15 showed activity of 52.22% for the conversion of soybean oil into biodiesel. - Abstract: Zinc aluminate is a material with high thermal stability and high mechanical strength that, owing to these properties, is used as a catalyst or support. In this work, zinc aluminate spinel was synthesized by the microwave hydrothermal method in only 15 or 30 min at a low temperature (150 °C) without templates, using only Al(NO{sub 3}){sub 3}·9H{sub 2}O, Zn(NO{sub 3}){sub 2}·6H{sub 2}O, and urea as precursors and applied in the transesterification of soybean oil. X-ray diffraction analysis showed that ZnAl{sub 2}O{sub 4} had a cubic structure without secondary phases. The nitrogen adsorption measurements (BET) revealed a high surface area (266.57 m{sup 2} g{sup −1}) for the nanopowder synthesized in 15 min. This powder showed activity of 52.22% for the catalytic conversion of soybean oil into biodiesel by transesterification.

  19. Differences in the Nature of Active Sites for Methane Dry Reforming and Methane Steam Reforming over Nickel Aluminate Catalysts

    DOE PAGES

    Rogers, Jessica L.; Mangarella, Michael C.; D’Amico, Andrew D.; ...

    2016-07-20

    In this paper, the Pechini synthesis was used to prepare nickel aluminate catalysts with the compositions NiAl4O7, NiAl2O4, and Ni2Al2O5. The samples have been characterized by N2 physisorption, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS). Characterization results indicate unique structural properties and excellent regeneration potential of nickel aluminates. Prepared samples were tested when unreduced and reduced prior to reaction for methane dry reforming and methane steam reforming reactivity. NiAl2O4 in the reduced and unreduced state as well as NiAl4O7 in the reduced state are activemore » and stable for methane dry reforming due to the presence of 4-fold coordinated oxidized nickel. The limited amount of metallic nickel in these samples minimizes carbon deposition. Finally, on the other hand, the presence of metallic nickel is required for methane steam reforming. Ni2Al2O5 in the reduced and unreduced states and NiAl2O4 in the reduced state are found to be active for methane steam reforming due to the presence of sufficiently small nickel nanoparticles that catalyze the reaction without accumulating carbonaceous deposits.« less

  20. 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.

  1. Usefulness of an aluminized polyester film for reducing heat in polyethylene calf hutches.

    PubMed

    Binion, W R; Friend, T H; Holub, G A

    2014-11-01

    This study determined the efficacy of a radiant barrier material used in the construction industry to moderate summer temperatures in polyethylene calf hutches. The cover consisted of a single layer of two-sided reflective aluminized polyester film with a center polyester scrim reinforcement (reflectivity = 95%). At each of two dairies, six hutches containing a young calf were either uncovered (control) or had reflective covers across the top and sides of the hutch, leaving the front, back, and 1.2 × 1.8-m attached outdoor wire pen exposed. Duplicate loggers mounted 20 cm above the flooring in the center of each hutch recorded interior temperature at 30-min intervals over 22 days during late August to early September. The mean daily interior peak temperatures in each of the hutches over 21 days of observation were significantly less (P < 0.001) in the hutches with reflective covers (37.48 ± 0.14 °C) than in the uncovered hutches (41.65 ± 0.45 °C) and did not differ (P = 0.77) between dairies. The mean daily interior peak temperatures in each of the hutches over the warmest 10 days of observation were significantly less (P < 0.001) in hutches with reflective covers (40.15 °C ± 0.16) than in the uncovered hutches (44.93 ± 0.47 °C). The mean interior ceiling temperatures in each of the hutches over 4 days of observation were significantly lower (P < 0.001) in the hutches with reflective covers (37.82 ± 0.36 °C) than in the uncovered hutches (46.89 ± 0.47 °C). The reflective cover used in this study moderated interior hutch temperatures but showed signs of delamination after 22 days and was relatively expensive, so more suitable material needs to be identified.

  2. 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.

  3. Effect of Co2+ Ions Doping on the Structural and Optical Properties of Magnesium Aluminate

    NASA Astrophysics Data System (ADS)

    Kanwal, Kiran; Ismail, Bushra; Rajani, K. S.; Kissinger, N. J. Suthan; Zeb, Aurang

    2017-02-01

    Cobalt-doped nanosized magnesium aluminate (Mg1-xCoxAl2O4) samples having different compositions (x = 0.2, 0.4, 0.6, 0.8, 1.0) were synthesized by a chemical co-precipitation method. All samples were characterized by means of x-ray diffraction (XRD), scanning electron microscopy, Fourier transform infrared spectroscopy, ultra violet-visible spectroscopy, photoluminescence and diffused reflectance spectroscopy. The results of XRD revealed that the samples were spinel single phase cubic close packed crystalline materials. The lattice constant and x-ray density were found to be affected by the ionic radii of the doped metal cations. Using the Debye-Scherrer formula, the calculated crystalline size was found to be Co2+ ion concentration-dependent and varied between 32 nm and 40 nm. Nano-dimensions and phase of the Mg1-xCoxAl2O4 samples were analyzed and the replacement of Mg2+ ions with Co2+ ions was confirmed by elemental analysis. Three strong absorption bands at 540 nm, 580 nm and 630 nm were observed for the doped samples which are attributed to the three spin-allowed 4T1g (4F) → 4T2g, 4A2g, 4T1g (4P) electronic transitions of Co2+ at tetrahedral lattice sites. Nanophosphors have optical properties different from bulk because of spatial confinement and non-radiative relaxation. Decreases in particle size can increase the surface area and the defects, which can in turn increase the luminescent efficiency to make it very useful for tunable laser operations, persistent phosphorescence, color centers, photoconductivity and luminescence for display technology. MgAl2O4 was doped with Co2+ ions using a co-precipitation method and the optical absorption studies revealed that there is a decrease of band gap due to the increase of Co2+ content. The emission intensity of this phosphor is observed at 449 nm with a sharp peak attributed to the smaller size of the particles and the homogeneity of the powder.

  4. 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

  5. Amelioration de la procedure d'essai d'eclatement de joints d'etancheite a base de teflon

    NASA Astrophysics Data System (ADS)

    Benabdallah, Samir

    The objective of this work is to improve a HOt Blow-out Test procedure to determine the maximum operating temperature of Teflon-based gaskets. In parallel, an experimental fixture is developed to measure the thermal expansion coefficient of such material. This study aims to analyze the relaxation of PTFE gasketed joints due to creep at high temperature. The determination of the safe operating temperature limit of PTFE-based gaskets requires a good knowledge of its capacity to resist creep-relaxation due to temperature exposure in the short and long term. The aim of this work is to improve the HOBT standard procedure « Standard Test Method for Hot Blowout and Thermal Cycling Performance for Polytetrafluoroethylene (PTFE) Sheet or Sheet-Like Gaskets» which is under adoption by the ASTM F03 gasket committee. Based on a previous work, the introduction of a fixed number of cycles of heating and cooling in the HOBT test procedure has shown that the cumulative permanent deformation (ratcheting damage) which has impact on reduction of the gasket stress can be taken into account. The effect of holding temperature for a short period of time will be investigated. The modified HOBT rig allows measurement of the gasket compression during the test in order to accurately quantify the cumulative permanent deformation. Several types of PTFE-based gaskets will be tested in order to cover a wide range of gaskets to justify the generalization of the modified procedure. The different steps to achieve this project are listed below: 1. Improve the HOBT test rig by implementing a device to measure gasket compression and it variation with the thermal cycles. 2. Study the effects of the number of thermal cycling and the holding temperature on the gasket stress and the cumulative permanent deformation and the short term creep on the hot blowout characteristics of PTFE-based gaskets. 3. Development of a small fixture to measure the coefficient of thermal expansion of gasketing materials

  6. Coating of TiO 2 photocatalysts on super-hydrophobic porous teflon membrane by an ion assisted deposition method and their self-cleaning performance

    NASA Astrophysics Data System (ADS)

    Yamashita, H.; Nakao, H.; Takeuchi, M.; Nakatani, Y.; Anpo, M.

    2003-05-01

    By means of an ion assisted deposition method, a TiO 2 photocatalyst was prepared at relatively lower temperature on porous Teflon sheets (PTS) that are good candidates for the coating materials with super-hydrophobic surfaces. UV light irradiation of TiO 2 photocatalyst on PTS led to the photocatalytic degradation of organic pollutants (self-cleaning), which wear off the water-repellent property of the original PTS surface. The PTS surface loading of a small amount of TiO 2 photocatalyst can keep the super-hydrophobic properties of PTS for a long time because of the photocatalytic degradation of the accumulated pollutants.

  7. Large broadband visible to infrared plasmonic absorption from Ag nanoparticles with a fractal structure embedded in a Teflon AFxAE matrix

    NASA Astrophysics Data System (ADS)

    Biswas, A.; Eilers, H.; Hidden, F.; Aktas, O. C.; Kiran, C. V. S.

    2006-01-01

    An unusual almost flat broadband plasmonic absorption, ranging from 400nm to well beyond 2500nm, was observed in a 150nm thin film of Ag nanoparticles embedded in a Teflon AF® matrix. The nanocomposites were synthesized by a simple single-step vapor-phase codeposition method. The Ag nanoparticles of various sizes and shapes, and thus various resonance frequencies, form a fractal percolating network. The broadband absorption, attributed to plasmon excitations within the nanoparticles, could be useful for multicolor applications in the visible and infrared wavelengths region.

  8. Characterization of plasma-enhanced teflon AF for sensing benzene, toluene, and xylenes in water with near-IR surface plasmon resonance.

    PubMed

    Erickson, Tim A; Nijjar, Rajvir; Kipper, Matt J; Lear, Kevin L

    2014-02-01

    Near-IR surface plasmon resonance is used to characterize Teflon AF films for refractive index-based detection of the aromatic hydrocarbon contaminants benzene, toluene, and xylenes in water. The technique requires no sample preparation, and film sensitivity is found to be enhanced by oxygen plasma etching. A diffusion equation model is used to extract the diffusion and partition coefficients, which indicate film enrichment factors exceeding two orders of magnitude, permitting a limit of detection of 183, 105 and 55 ppb for benzene, toluene, and xylenes, respectively. The effect of other potential interfering contaminants is quantified.

  9. Evolution of aluminide coating microstructure on nickel-base cast superalloy CM-247 in a single-step high-activity aluminizing process

    SciTech Connect

    Das, D.K.; Joshi, S.V.; Singh, V.

    1998-08-01

    This study deals with the aluminizing of a directionally cast Ni-base superalloy, namely CM-247, by a single-step process using a high-activity pack. It is observed that significant incorporation of Al into the substrate surface during aluminizing continues over a period of about 1 hour and is not restricted merely to the first few minutes, as reported in the literature. Based on the microstructural details of the coatings formed at various stages of aluminizing, it is concluded that the coating growth in the above process takes place primarily by inward Al diffusion initially, followed by an intermediate stage when the growth involves both inward Al and outward Ni diffusion. In the final stages, the outward diffusion of Ni dominates the coating formation process. The above mechanism of coating formation is different from the one that prevails in the conventional two-step high-activity coating process in that the reaction front for the formation of NiAl remains spatially stationary despite the outward diffusion of nickel during the intermediate stage. It is also shown in the present study that the content of the Al source in the pack affects the coating structure significantly. It is further demonstrated that the microstructure of the aluminide coatings depends not only on the amount of Al incorporated in the sample during aluminizing but also on the time over which the uptake of this Al takes place.

  10. Aluminizing and boroaluminizing treatments of Mar-M247 and their effect on hot corrosion resistance in Na2SO4-NaCl molten salt

    NASA Astrophysics Data System (ADS)

    Cho, J. H.; Kim, T. W.; Son, K. S.; Yoon, J. H.; Kim, H. S.; Leisk, G. G.; Mitton, D. B.; Latanision, R. M.

    2003-06-01

    The effect of surface modifications of Mar-M247 superalloy on hot corrosion resistance was examined in Na2SO4-NaCl molten salt. The Mar-M247 was aluminized and boroaluminized by pack cementation in Ar and underwent a cyclic hot corrosion test in Na2SO4-NaCl molten salt. The XRD results showed that a Ni2Al3 phase was formed between the aluminized layer and the substrate when the surface modification temperature was below 1273 K. However, a NiAl phase formed when the temperature was above 1273 K. The intensity of the XRD peak in the NiAl phase increased after post heat treatment. Hot corrosion resistance increased for the specimens containing NiAl rather than Ni2Al3 phase. The ductile NiAl phase suppressed the potential for crack initiation during thermal cycling. Post heat treatment increased the corrosion resistance of the aluminized layer for Mar-M247, which underwent surface modification at 1273 K and above. In the boroaluminized Mar-M247 specimens, corrosion resistance decreased as a result of the blocking of outward diffusion of Cr by boron and decreased cohesion between the oxide scale and the aluminized layer during thermal cycling.

  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. 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.

  13. Chemical speciation in concentrated alkaline aluminate solutions in sodium, potassium and caesium media. Interpretation of the unusual variations of the observed hydroxide activity.

    PubMed

    Sipos, Pál; Schibeci, Mark; Peintler, Gábor; May, Peter M; Hefter, Glenn

    2006-04-21

    A detailed electrochemical investigation using H2/Pt electrode potentiometry as well as Raman and NMR spectroscopy was carried out to develop a comprehensive chemical explanation for the unusual patterns of hydroxide concentrations observed in strongly alkaline, highly concentrated aluminate solutions (Bayer-liquors). For this, aluminate solutions with various alkaline metal background cations were investigated. The effect of the temperature on the observed patterns was also studied, and for comparison with solutions of similar concentrations, the chemical speciation of borate solutions was also studied. The formation of the NaOH 0 ion-pair has been proven with the formation constant (defined in terms of activities) beta 0 = 0.78 +/- 0.08. The formation of analogous KOH 0 or CsOH 0 ion-pairs under the experimental conditions applied is negligible. Assuming the formation of the NaAl(OH)4 (0) ion-pair is not necessary for modeling the experimental findings, as its formation causes only secondary effects on the potentiometric patterns. It has also been shown that all experimental data can be interpreted quantitatively if the formation of the doubly charged dimeric aluminate species is included in the calculation of the changes in the mean activity coefficients. The formation constant of the aluminate dimer could not be estimated purely from the H2/Pt potentiometric data but a lower limit for its formation constant (defined in terms of activities) has been derived. These conclusions are in full congruency with those derived from the Raman spectra of solutions with similar concentrations, so the two independent experimental methods lead to the same set of chemical species in highly concentrated alkaline aluminate solutions.

  14. 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.

  15. Polyelectrolyte gels comprising a lipophilic, cost-effective aluminate as fluorine-free absorbents for chlorinated hydrocarbons and diesel fuel.

    PubMed

    Wrede, Michael; Ganza, Viktoria; Bucher, Janina; Straub, Bernd F

    2012-07-25

    Superabsorbent polymers comprising a lipophilic, halogen-free, and cost-effective aluminate ("altebate") anion have been synthesized. The polyelectrolytes are based on octadecyl acrylate monomers, 0.8-1 mol % ethylene dimethacrylate cross-linker, and 5 mol % N-3-acroyloxypropyl trialkylammonium altebate. At 30 °C, swelling degrees of 70 (chlorobenzene), 102 (CHCl3), 130 (THF), 163 (ClCH2CH2Cl), 171 (dichlorobenzene), and 208 (CH2Cl2) have been determined. The polyelectrolyte absorbs reversibly diesel fuel with a swelling degree of 34, even in the presence of water. Swelling times and critical swelling temperatures have also been determined. The challenges for the development of oil absorbents are discussed.

  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. Recent progress in advanced optical materials based on gadolinium aluminate garnet (Gd3Al5O12)

    PubMed Central

    Li, Ji-Guang; Sakka, Yoshio

    2015-01-01

    This review article summarizes the recent achievements in stabilization of the metastable lattice of gadolinium aluminate garnet (Gd3Al5O12, GAG) and the related developments of advanced optical materials, including down-conversion phosphors, up-conversion phosphors, transparent ceramics, and single crystals. Whenever possible, the materials are compared with their better known YAG and LuAG counterparts to demonstrate the merits of the GAG host. It is shown that novel emission features and significantly improved luminescence can be attained for a number of phosphor systems with the more covalent GAG lattice and the efficient energy transfer from Gd3+ to the activator. Ce3+ doped GAG-based single crystals and transparent ceramics are also shown to simultaneously possess the advantages of high theoretical density, fast scintillation decay, and high light yields, and hold great potential as scintillators for a wide range of applications. The unresolved issues are also pointed out. PMID:27877750

  18. High-T sub c thin films on low microwave loss alkaline-rare-earth-aluminate crystals

    SciTech Connect

    Sobolewski, R.; Gierlowski, P.; Kula, W.; Zarembinski, S.; Lewandowski, S.J.; Berkowski, M.; Pajaczkowska, A. ); Gorshunov, B.P.; Lyudmirsky, D.B.; Sirotinsky, O.I. )

    1991-03-01

    This paper reports on the alkaline-rare-earth aluminates (K{sub 2}NiF{sub 4}-type perovskites) which are an excellent choice as the substrate material for the growth of high-T{sub c} thin films suitable for microwave and far-infrared applications. The CaNdAlO{sub 4}, and SrLaAlO{sub 4} single crystals have been grown by Czochralski pulling and fabricated into the form of (001) oriented wafers. The Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O films deposited on these substrates by a single-target magnetron sputtering exhibited very good superconducting and structural properties.

  19. Recent progress in advanced optical materials based on gadolinium aluminate garnet (Gd3Al5O12).

    PubMed

    Li, Ji-Guang; Sakka, Yoshio

    2015-02-01

    This review article summarizes the recent achievements in stabilization of the metastable lattice of gadolinium aluminate garnet (Gd3Al5O12, GAG) and the related developments of advanced optical materials, including down-conversion phosphors, up-conversion phosphors, transparent ceramics, and single crystals. Whenever possible, the materials are compared with their better known YAG and LuAG counterparts to demonstrate the merits of the GAG host. It is shown that novel emission features and significantly improved luminescence can be attained for a number of phosphor systems with the more covalent GAG lattice and the efficient energy transfer from Gd(3+) to the activator. Ce(3+) doped GAG-based single crystals and transparent ceramics are also shown to simultaneously possess the advantages of high theoretical density, fast scintillation decay, and high light yields, and hold great potential as scintillators for a wide range of applications. The unresolved issues are also pointed out.

  20. High-field 19.6 T 27Al solid-state MAS NMR of in vitro aluminated brain tissue

    NASA Astrophysics Data System (ADS)

    Bryant, Pamela L.; Lukiw, Walter J.; Gan, Zhehong; Hall, Randall W.; Butler, Leslie G.

    2004-10-01

    The combination of 27Al high-field solid-state NMR (19.6 T) with rapid spinning speeds (17.8 kHz) is used to acquire 27Al NMR spectra of total RNA human brain temporal lobe tissues exposed to 0.10 mM Al 3+ (as AlCl 3) and of human retinal pigment epithelial cells (ARPE-19), grown in 0.10 mM AlCl 3. The spectra of these model systems show multiple Al 3+ binding sites, good signal/noise ratios and apparent chemical shift dispersions. A single broad peak (-3 to 11 ppm) is seen for the aluminated ARPE-19 cells, consistent with reported solution-state NMR chemical shifts of Al-transferrin. The aluminated brain tissue has a considerably different 27Al MAS NMR spectrum. In addition to the transferrin-type resonance, additional peaks are seen. Tentative assignments include: -9 to -3 ppm, octahedral AlO 6 (phosphate and water); 9 ppm, condensed AlO 6 units (Al-O-Al bridges); 24 ppm, tetrahedral AlO 3N and/or octahedral Al-carbonate; and 35 ppm, more N-substituted aluminum and /or tetrahedral AlO 4. Thus, brain tissue is susceptible to a broad range of coordination by aluminum. Furthermore, the moderate 27Al C Q values (all less than 10 MHz) suggest future NMR studies may be performed at 9.4 T and a spin rate of 20 kHz.

  1. Differences in the Nature of Active Sites for Methane Dry Reforming and Methane Steam Reforming over Nickel Aluminate Catalysts

    SciTech Connect

    Rogers, Jessica L.; Mangarella, Michael C.; D’Amico, Andrew D.; Gallagher, James R.; Dutzer, Michael R.; Stavitski, Eli; Miller, Jeffrey T.; Sievers, Carsten

    2016-07-20

    In this paper, the Pechini synthesis was used to prepare nickel aluminate catalysts with the compositions NiAl4O7, NiAl2O4, and Ni2Al2O5. The samples have been characterized by N2 physisorption, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS). Characterization results indicate unique structural properties and excellent regeneration potential of nickel aluminates. Prepared samples were tested when unreduced and reduced prior to reaction for methane dry reforming and methane steam reforming reactivity. NiAl2O4 in the reduced and unreduced state as well as NiAl4O7 in the reduced state are active and stable for methane dry reforming due to the presence of 4-fold coordinated oxidized nickel. The limited amount of metallic nickel in these samples minimizes carbon deposition. Finally, on the other hand, the presence of metallic nickel is required for methane steam reforming. Ni2Al2O5 in the reduced and unreduced states and NiAl2O4 in the reduced state are found to be active for methane steam reforming due to the presence of sufficiently small nickel nanoparticles that catalyze the reaction without accumulating carbonaceous deposits.

  2. Effects of sulfur impurity on the scale adhesion behavior of a desulfurized Ni-based superalloy aluminized by chemical vapor deposition

    SciTech Connect

    Lee, W.Y.; Wright, I.G.; Pint, B.A.; Liwa, P.K.

    1998-03-01

    The surface of a single-crystal Ni-based superalloy, which contained a bulk sulfur content of {approximately} 0.4 ppmw, was aluminized in a hot-wall chemical vapor deposition (CVD) reactor, using AlCl{sub 3} and H{sub 2} as gaseous precursors, at 1,100 C. The chemical composition and microstructure of the resulting aluminide coating were characterized with particular emphasis on sulfur incorporation as an impurity during aluminizing. Depth profiling by glow-discharge mass spectroscopy (GDMS) was used as a qualitative means of assessing the level of sulfur in the coating structure. Sulfur contamination, which was initially observed at the coating surface and the substrate-coating interface, could be reduced by some minor reactor modifications. With the reduced sulfur content, scale adhesion on the surface of the aluminide grains of the coating was significantly improved during cyclic oxidation, whereas scale spallation at the coating`s grain boundaries became more apparent.

  3. 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.

  4. Influence of chlorinated paraffin/titanium additives on burning and radiance performances of Magnesium/Teflon/Viton(MTV) foil-type composition

    NASA Astrophysics Data System (ADS)

    Du, Jun; Guan, Hua; Song, Dong-ming; Liu, Hui

    2017-01-01

    The influence of chlorinated paraffin/titanium (C24H29Cl21/Ti) additives on burning and radiance performances of Magnesium/Teflon/Viton™ (MTV) foil-type was investigated via a high-speed camera, high-temperature differential thermobalance, far-infrared thermal imager and Fourier Transform Infrared (FTIR) remote-sensing spectrometer. We found that the burning temperature, radiance brightness, radiance area and radiance intensity after addition of C24H29Cl21/Ti are improved by 124-196 °C (8-13%), 300-475 W·m-2·sr-1 (12-19%), 943-1422 mm2 (67-101%) and 3.17-4.99 W·sr-1 (88-138%), respectively, and are maximized at the addition ratio of 10%. The substances formed by adding C24H29Cl21/Ti could improve the middle and far infrared radiation.

  5. One-step generation of engineered drug-laden poly(lactic-co-glycolic acid) micropatterned with Teflon chips for potential application in tendon restoration.

    PubMed

    Shi, Xuetao; Zhao, Yihua; Zhou, Jianhua; Chen, Song; Wu, Hongkai

    2013-11-13

    Regulating cellular behaviors such as cellular spatial arrangement and cellular phenotype is critical for managing tissue microstructure and biological function for engineered tissue regeneration. We herein pattern drug-laden poly(lactic-co-glycolic acid) (PLGA) into grooves using novel Teflon stamps (that possess excellent properties of resistance to harsh organic solvents and molecular adsorption) for engineered tendon-repair therapeutics. The drug release and biological properties of melatonin-laden PLGA grooved micropatterns are investigated. The results reveal that fibroblasts cultured on the melatonin-laden PLGA groove micropatterns not only display significant cell alignment that mimics the cell behavior in native tendon, but also promote the secretion of a major extracellular matrix in tendon, type I collagen, indicating great potential for the engineering of functional tendon regeneration.

  6. 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

    NASA Astrophysics Data System (ADS)

    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.

  7. Adsorption of insulin with varying self-association profiles to a solid Teflon surface--influence on protein structure, fibrillation tendency and thermal stability.

    PubMed

    Jorgensen, Lene; Bennedsen, Pernille; Hoffmann, Søren Vrønning; Krogh, Rasmus Linnemann; Pinholt, Charlotte; Groenning, Minna; Hostrup, Susanne; Bukrinsky, Jens T

    2011-04-18

    Interfaces are present in the preparation of pharmaceutical products and are well known for having an influence on the physical stability of proteins. The aim of this study was to examine the conformation (i.e. secondary and tertiary structures) and fibrillation tendency, overall aggregation tendency and thermal stability of adsorbed human insulin at a solid particulate Teflon surface. The effects of changes in the association degree of insulin on the structure and stability have been determined. Using SEC-HPLC, association profiles were determined for insulin aspart, zinc-free human insulin and human insulin with two Zn(2+) per hexamer in concentrations ranging from 0.1 mg/ml to 20 mg/ml. Insulin aspart was 100% monomeric, regardless of concentration. In contrast, human insulin went from 100% monomer to 80% hexamer, and 20% dimer/monomer and zinc-free human insulin from 100% monomer to 70% dimer and 30% monomer with increasing concentration. The secondary structure of the insulins changed upon adsorption, but only minor differences were observed among the insulins. Structural changes were observed when the insulin-surface ratio was varied, but at no point did the structure resemble that of fibrillated insulin in solution. The presence of particles resulted in increased fibrillation of human insulin. The lag-time of fibrillation decreased, when the amount of particles present was increased. In conclusion, the type and association degree of the three insulin variants has no major influence on the secondary structure observed after adsorption of insulin at the solid Teflon surface. However, the presence of particles increases the tendency of insulin to fibrillate.

  8. 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

  9. Ion beam damage assessment and waveguide formation induced by energetic Si-ion irradiation in lanthanum aluminate crystal

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Huang, Q.; Crespillo, M. L.; Qiao, M.; Liu, P.; Wang, X. L.

    2017-02-01

    Lanthanum aluminate (LaAlO3) crystal has emerged as one of the most valuable functional-materials, and its physical, electronic and optical properties strongly depend on the crystal structure, which can be easily altered in an irradiation environment and therefore affect the performance of LaAlO3-based devices. On the other hand, the preparation of LaAlO3 waveguide is also a scientific challenge for its potential application prospects in optoelectronics field. In this work, the damage evolution behavior of LaAlO3 crystal under Si-ion irradiation has been discussed in detail utilizing complementary characterization techniques, and then, single-mode waveguide of LaAlO3 crystal in the visible band can be obtained based on ion-irradiation-induced lattice damage behavior. Waveguide optical-coupling techniques are used to show its competitive features. Thus, novel optical waveguides with optimized features in LaAlO3 crystals can be tailored by a proper selection of ion mass, energy and fluence using the modification of the target material during ion irradiation process.

  10. 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.

  11. Effect of Surface Aluminizing on Long-Term High-Temperature Thermal Stability of TC4 Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Dai, Jingjie; Zhu, Jiyun; Zhuang, Lei; Li, Shouying

    2016-12-01

    Aluminum (Al)-rich titanium (Ti)-Al alloyed coating was fabricated on the surface of TC4 Ti alloy to improve the high-temperature stability of TC4 Ti alloy by means of arc-added glow discharge plasma technology. Microstructure, room-temperature properties and long-term high-temperature oxidation behavior of the alloyed sample were investigated. The results show that a uniform and compact Ti-Al alloyed coating with about 30μm thickness formed on the surface of TC4 Ti alloy. Microhardness and room-temperature wear resistance of the alloyed sample improved significantly. Long-term oxidation behaviors of the samples in air at 800∘C for 1000h show that the mass gain of the alloyed sample was 0.3686mg/cm2, while that of the substrate was 18.2095mg/cm2. Arc-added glow discharge plasma aluminizing improved high-temperature oxidation resistance of TC4 Ti alloy significantly.

  12. The effect of the host composition on the lifetime decay properties of barium/strontium aluminates compounds

    NASA Astrophysics Data System (ADS)

    Rezende, Marcos V. dos S.; Andrade, A. B.; Valerio, Mário E. G.; Montes, Paulo J. R.

    2014-03-01

    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). Ba1-xSrxAl2O4 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 Eu2+ and Eu3+ transitions, although no Eu2+ 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. Electrocautery Devices With Feedback Mode and Teflon-Coated Blades Create Less Surgical Smoke for a Quality Improvement in the Operating Theater.

    PubMed

    Kisch, Tobias; Liodaki, Eirini; Kraemer, Robert; Mailaender, Peter; Brandenburger, Matthias; Hellwig, Veronika; Stang, Felix H

    2015-07-01

    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 primary

  14. 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

  15. Evaluation of Commerical Nonstick Coatings for US Army Field-Feeding Cookware

    DTIC Science & Technology

    2002-06-01

    polytetrafluoroethylene ( PTFE ). Other fluoropolymer that are considered Teflon ® are Dupont’s FEP , Tefzel® ETFE, and PFA . PTFE , the original resin, was...surfaces. Typical commercial grade Teflon ® or PTFE coatings were assumed inadequate for the rigors or Army field use however; the latest improvements on...Innovative Teflon ® formulations were also explored. The commercial market for Teflon ® -type polytetrafluoroethylene ( PTFE ) coatings has advanced

  16. 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

  17. 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

  18. Generation of microgrooved silica nanotube membranes with sustained drug delivery and cell contact guidance ability by using a Teflon microfluidic chip

    PubMed Central

    Chen, Song; Shi, Xuetao; Chinnathambi, Shanmugavel; Wu, Hongkai; Hanagata, Nobutaka

    2013-01-01

    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. PMID:27877563

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Host-mediated synthesis of cobalt aluminate/γ-alumina nanoflakes: a dispersible composite pigment with high catalytic activities.

    PubMed

    Dandapat, Anirban; De, Goutam

    2012-01-01

    Cobalt aluminate/γ-alumina (CoAl(2)O(4)/γ-Al(2)O(3)) nanocomposite pigment with mesoporous structure has been synthesized. The method simply involves adsorption of Co(2+) ion on the surface of a commercially available boehmite (AlOOH) powder followed by the reaction of Co(2+) and AlOOH at relatively low temperature (500 °C) to obtain CoAl(2)O(4)/γ-Al(2)O(3) composite nanopowders. The formation of γ-Al(2)O(3) from boehmite induces the in situ generation of isostructural CoAl(2)O(4) (both crystallize as cubic spinel) at such a low temperature. The obtained intense blue powder of optimal composition (53.6 wt % CoAl(2)O(4) in γ-Al(2)O(3)) can be dispersed in glycerol and characterized by UV-visible, X-ray diffraction, Raman spectroscopy, TEM, and nitrogen sorption analyses. Raman studies confirm the formation of CoAl(2)O(4) phase in γ-Al(2)O(3). TEM studies reveal the formation of flake shaped (5-10 nm in width and 10-25 nm in length) nanopowders, and these flakes are assembled to form mesoporous structure. The specific surface area, total pore volume and average pore diameter of this powder are estimated to be ~118 m(2) g(-1), 0.1375 cm(3) g(-1), and 4.65 nm, respectively. This composite nanopowder has been used as an active catalyst for the decomposition of H(2)O(2) at room temperature and the decomposition follows the first order kinetics with rate constant value close to 2.3 × 10(-2) min(-1). This pigment nanopowder can be reused for several cycles without noticeable degradation of its original catalytic activity.

  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. 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.

  6. 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.

  7. 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.

  8. The investigation of dielectric properties and ac conductivity of new ceramic diphosphate Ag0.6Na0.4FeP2O7 using impedance spectroscopy method

    NASA Astrophysics Data System (ADS)

    Nasri, S.; Megdiche, M.; Gargouri, M.

    2016-10-01

    In this paper, Ag0.6Na0.4FeP2O7 has been synthesized by solid state reaction method. The ceramic compound was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrational spectroscopy and impedance measurements. In fact, the investigated sample has shown single phase type monoclinic structure with P21/C space group. The frequency-dependent electrical data are analyzed in the frame-work of conductivity and electric modulus formalisms. The real and imaginary parts of complex impedance are well fitted to equivalent circuit model based on the Z-View-software. Besides, the observed frequency dependence of conductivity is found to obey Jonscher's universal law. The temperature dependence of both ac conductivity and the parameter s is reasonably well interpreted by the correlated barrier hopping (CBH). The theoretical fitting between the proposed model and the experimental data showed good agreement. The contribution of single polaron and bipolaron hopping to a.c. conductivity in present compound is also studied. The ionic conductivity is discussed on the basis of the structural characteristics of the sample.

  9. Agglomerates, smoke oxide particles, and carbon inclusions in condensed combustion products of an aluminized GAP-based propellant

    NASA Astrophysics Data System (ADS)

    Ao, Wen; Liu, Peijin; Yang, Wenjing

    2016-12-01

    In solid propellants, aluminum is widely used to improve the performance, however the condensed combustion products especially the large agglomerates generated from aluminum combustion significantly affect the combustion and internal flow inside the solid rocket motor. To clarify the properties of the condensed combustion products of aluminized propellants, a constant-pressure quench vessel was adopted to collect the combustion products. The morphology and chemical compositions of the collected products, were then studied by using scanning electron microscopy coupled with energy dispersive (SEM-EDS) method. Various structures have been observed in the condensed combustion products. Apart from the typical agglomerates or smoke oxide particles observed before, new structures including the smoke oxide clusters, irregular agglomerates and carbon-inclusions are discovered and investigated. Smoke oxide particles have the highest amount in the products. The highly dispersed oxide particle is spherical with very smooth surface and is on the order of 1-2 μm, but due to the high temperature and long residence time, these small particles will aggregate into smoke oxide clusters which are much larger than the initial particles. Three types of spherical agglomerates have been found. As the ambient gas temperature is much higher than the boiling point of Al2O3, the condensation layer inside which the aluminum drop is burning would evaporate quickly, which result in the fact that few "hollow agglomerates" has been found compared to "cap agglomerates" and "solid agglomerates". Irregular agglomerates usually larger than spherical agglomerates. The formation of irregular agglomerates likely happens by three stages: deformation of spherical aluminum drops; combination of particles with various shape; finally production of irregular agglomerates. EDS results show the ratio of O to Al on the surface of agglomerates is lower in comparison to smoke oxide particles. C and O account for

  10. 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

  11. 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

  12. The Insulation of Copper Wire by the Electrostatic Coating Process.

    DTIC Science & Technology

    1983-06-30

    Propvlene) FEP is based on duPont’s TeflonFEP . It has the best electrical, chemical, friction and release properties of all Liquinite coatings...ETFE (ethylene-tetrafluoroethylene copolymer), PFA (perfluoroalkoxy resin), ECTFE (ethylene-chlorotrifluoroethylene), and FEP (fluorinated ethylene...cure. PPS/ PTFE Grades of PPS modified with PTFE are available for improved friction, wear and release properties and physical and temperature

  13. High temperature oxidation and sodium chloride-induced accelerated corrosion of hot-dip aluminized 9chromium-1molybdenum and 310 stainless steel

    NASA Astrophysics Data System (ADS)

    Tsaur, Charng-Cheng

    The behaviors of high temperature corrosion on hot-dip aluminized on 9Cr-1Mo and 310 stainless steels when catalyzed by NaCl and cyclic heating environment were studied experimentally. The corrosion behavior and morphological development were investigated by weight gain kinetics, metallographs, depths of attack, metal losses, and X-ray analyses. The results of 310SS deposited with salt mixtures show that weight gain kinetics in simple oxidation reveals a steady-state parabolic rate law after 3 hr, while the kinetics with salt deposits display multi-stage growth rates. NaCl is the main corrosive specie in high-temperature corrosion involving mixtures of NaCl/Na2SO 4 and is responsible for the formation of internal attack. Uniform internal attack is the typical morphology of NaCl-induced hot corrosion, while the extent of intergranular attack is more pronounced as the content of Na 2SO4 in the mixture is increased. The thermal-cycling test results of 310SS deposited NaCl and coated 7wt%Si/93wt%Al show that the aluminized layers have good corrosion resistance during the first four cycles of testing, while degradation occurs after testing for five cycles. The reason for degradation of aluminized layers is attributed to the formation of inter-connecting voids caused by aluminum inward diffusion, chloridation/oxidation cyclic reactions and the penetration of molten NaCl through the voids into the alloy substrate. The 9Cr-1Mo steels coated with 7wt%Si/93wt%Al oxidized at 750, 850, and 950°C in static air show that oxidation kinetics followed a parabolic rate law at 750 and 850°C. The cracks propagated through the Fex Aly layer due to the growth of brittle FeAl2 and Fe2Al5 at 750 and 850°C. The voids condensed in the interface of intermetallics and substrate are attributed to the Kirkendall effect. At 950°C, the fast growing aluminide layer has a different expansion coefficient than oxide scale, leading to scale cracking, oxygen penetration, and internal oxidized

  14. 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.

  15. Combined Effects Aluminized Explosives

    DTIC Science & Technology

    2010-07-01

    to traditional blast explosives. Traditional Chapman - Jouguet detonation theory does not explain the observed detonation states achieved by these...aluminum Hugoniot for a given explosive and does not represent traditional Chapman - Jouguet sonic conditions. It appears that with small aluminum particles...the never achieved 100% aluminum reaction Chapman - Jouguet (C-J) point for which the calculated detonation velocity is 8.21 km/s: P = 358 kbar and T

  16. Basic performance of a multilayer insulation system containing 20 to 160 layers. [thermal effectiveness of aluminized Mylar-silk net system

    NASA Technical Reports Server (NTRS)

    Stochl, R. J.

    1974-01-01

    An experimental investigation was conducted to determine the thermal effectiveness of an aluminized Mylar-silk net insulation system containing up to 160 layers. The experimentally measured heat flux was compared with results predicted by using (1) a previously developed semi-empirical equation and (2) an effective-thermal-conductivity value. All tests were conducted at a nominal hot-boundary temperature of 294 K (530 R) with liquid hydrogen as the heat sink. The experimental results show that the insulation performed as expected and that both the semi-empirical equation and effective thermal conductivity of a small number of layers were adequate in predicting the thermal performance of a large number of layers of insulation.

  17. 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.

  18. Developpement d'un catalyseur nickel-alumine efficace pour le reformage de diesel a la vapeur d'eau et etude du systeme reactionnel

    NASA Astrophysics Data System (ADS)

    Fauteux-Lefebvre, Clemence

    Le developpement de sources d'energie alternatives fiables et efficaces est aujourd'hui une necessite. L' interet dans le reformage d'hydrocarbures liquides est ainsi croissant puisqu'il s'agit d'une voie pour l'alimentation des piles a combustible. Les piles a combustible ont une efficacite pour la conversion d'energie en electricite plus grande que celle des moteurs a combustion et font ainsi partie de la recherche de solution en efficacite energetique. Ces piles consomment de l'hydrogene comme combustible pour produire de l'electricite, d'ou l'interet pour le reformage. En effet, cette reaction permet de produire de l'hydrogene et du monoxyde de carbone (un autre combustible des piles a combustible a electrolyte solide) a partir d'hydrocarbure liquide, notamment le diesel. Les piles pourraient donc etre integrees avec une unite de reformage leur fournissant directement le combustible necessaire a partir de diesel. Dans ce projet de recherche, un nouveau catalyseur de nickel sous forme de spinelle nickel-alumine (spinelle NiAl2O4 sur support d'alumine et de zircone stabilisee avec yttria) a ete developpe et teste en laboratoire pour du reformage de propane, d'hydrocarbures liquides et de diesel, a la vapeur d'eau. Par ailleurs, une methode d'ajout des reactifs novatrice a ete utilisee afin de diminuer la pyrolyse precedant le reformage, en utilisant une emulsion. Les resultats de reformage d'hydrocarbures purs ont montre des concentrations tres pres de l'equilibre thermodynamique et une activite constante sans desactivation du catalyseur ni formation de carbone, et ce avec des ratios H2O/C de moins de 2.5 et des temperatures d'operation variant entre 630 °C et 750 °C. Lors de tests effectues en utilisant du diesel fossile, a 705°C, avec un debit volumique des reactifs de plus de 50 000 cm3gcat-1h-1 et un ratio H2O/C de moins de 2.5, l'activite a ete maintenue pendant plus de 15 heures, malgre une operation en cycles. L'analyse du catalyseur apres cette

  19. High-resolution study of {sup 56}Fe{yields}{sup 56}Mn Gamow-Teller transition by the combined analysis of {sup 56}Fe({sup 3}He, t){sup 56}Co and 56Fe(P, p'){sup 56}Fe reactions

    SciTech Connect

    Nagashimaa, M.; Shimbara, Y.; Fujita, H.; Fujita, Y.; Adachi, T.; Hatanaka, K.; Hirota, K.; Matsubara, H.; Nakanishi, K.; Okamura, H.; Ong, H. J.; Sakemic, Y.; Shimizu, Y.; Suzuki, T.; Tamii, A.; Yosoi, M.; Botha, N. T.; Neveling, R.; Ganioglu, E.; Susoy, G.

    2010-08-12

    The Gamow-Teller (GT) transitions in the {beta}{sup +}(electron capture) direction from the ground state of {sup 56}Fe to the excited states of {sup 56}Mn play an important role in the core collapse of presupernova. Assuming that isospin analogous transitions in isobars have corresponding strengths, we deduced these GT strengths by combining the results of the {sup 56}Fe(p, p'){sup 56}Fe experiment performed at 200 MeV and 0 deg. and the {sup 56}Fe({sup 3}He, t){sup 56}Co experiment in the {beta}{beta} direction at 140 MeV/u and 0 deg. The ground state of {sup 56}Fe has the isospin value of T = 2, while the GT states in {sup 56}Mn have T = 3. In order to identify the analogous T = 2{yields}3, GT transitions in the {sup 56}Fe(p, p'){sup 56}Fe and the {sup 56}Fe({sup 3}He, t){sup 56}Co measurements, we used the fact that the isospin Clebsch-Gordan (CG) coefficients for these T = 2{yields}3 transitions are different in these measurements. Then the GT transition strengths B(GT) in the {beta}{sup +} direction can be deduced from the B(GT) values of the corresponding transitions well determined in the {sup 56}Fe({sup 3}He, t){sup 56}Co measurement assuming the isospin symmetry and correcting the difference of CG coefficients.

  20. Nickel-doped zinc aluminate oxides: starch-assisted synthesis, structural, optical properties, and their catalytic activity in oxidative coupling of methane

    NASA Astrophysics Data System (ADS)

    Visinescu, Diana; Papa, Florica; Ianculescu, Adelina C.; Balint, Ioan; Carp, Oana

    2013-03-01

    Nanosized nickel-substituted zinc aluminate oxides were obtained by the gradual insertion of nickel cations within the zinc aluminate lattice, using starch as active ingredient. The obtained (Ni x Zn1- x Al2)-starch ( x = 0.1, 0.2, 0.4, 0.6, 0.8, 1) gel precursors were characterized through infrared spectroscopy and thermal analysis. The thermal behavior of the precursors are influenced by the nickel content, the DTA curves for the richer nickel samples revealing stronger, faster and overlapping exothermic reactions, that can be completed at lower temperatures. The corresponding spinelic oxides were obtained after calcination treatments at 800 °C and analyzed by means of NIR-UV-Vis spectroscopy, XRD measurements, SEM, TEM, and HRTEM investigations. The spinelic structure for all oxide samples is confirmed by XRD analysis, although small amounts of NiO cannot be neglected. TEM/HRTEM analysis revealed mesopores embedded in plate-like large (68.8 nm) particles of Ni0.2Zn0.8Al2O4 sample and smaller (15.7 nm) uniform equiaxial particles, with a more pronounced tendency of agglomeration for Ni0.8Zn0.2Al2O4 oxide. A formation mechanism for Ni0.2Zn0.8Al2O4 oxides was proposed based on DTA/TG, XRD, and SEM analyses. NIR-UV-Vis spectra for Ni x Zn1- x Al2O4 showed a significant presence of tetrahedral nickel cations that augments with nickel concentration increase. CIE- L * a * b * color parameters shown a variation of the lightness and also of the green and blue color components with x, the best color characteristics being obtained for x = 0.6. The oxides with a substitution degree x = 0.2 and 0.8 tested in the oxidative coupled of methane reaction (OCM) showed positive catalytic activity and selectivity due to an interesting synergetic effect of Zn(II) and Ni(II) ions.

  1. 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.

  2. 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.

  3. 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.

  4. a New Red Phosphor of the Mn Activated Non-Stoichiometric Strontium Aluminate 3SrO•5Al2O3 for High Color Rendering White Leds

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Zhang, Yao; Liu, Fayong; Deng, Xiaorong; Xue, Shaochan; Luo, Anqi; Jiang, Yang; Chen, Shifu; Zhang, Wenhua

    2013-05-01

    A new red phosphor of strontium aluminate activated by Mn4+ was developed for high color rendering and warm white light-emitting diodes. The phosphor composition and conditions for synthesis were optimized through solid-state reaction. Meanwhile, the structure and morphology were investigated with XRD and SEM analysis. The results show that the 3SrO•5Al2O3 activated by 0.0005 M Mn fired at 1300°C in air ambient by adopting 2.5 wt.% AlF3 as flux exhibits most efficient luminescence. A white LED device prototype with CIE (0.3291, 0.3571), CCT 5639 K, CRI Ra 92.6, and efficacy 63 lm/W driven at 20 mA has been packaged by pre-coating the red phosphor combined with a yellow one Y3Al5O12:Ce3+ on a blue InGaN chip. The analysis of critical distance and luminescence quench reveal that the mechanism of energy transfer for luminescence is through dipole-dipole interaction.

  5. Preparation of iron aluminate (FeAl2O4) nanoparticles from FeAl2O4 hollow particles fabricated by using a spray pyrolysis process

    NASA Astrophysics Data System (ADS)

    Yun, Jaecheol; Kim, Yangdo; Park, Dahee; Yun, Jung-Yeul

    2015-05-01

    Iron aluminate (FeAl2O4) hollow particles with a spinel structure were synthesized by using a spray pyrolysis process. FeAl2O4 hollow particles were formed at a reaction temperature of 900 °C at a flow rate of 40 L/min as a result of the rapid solvent evaporation and decomposition gases from the droplets in the spray solution prepared from metal salts and organic reagents. FeAl2O4 hollow particles were fabricated at a reaction temperature of 900 °C with a flow rate of 40 L/min. The FeAl2O4 hollow particles were heat treated for 3 hours at 600 °C in a 5% H2/Ar atmosphere to form the crystal particles. Subsequently, FeAl2O4 nanoparticles were fabricated from the FeAl2O4 hollow particles by using the wet milling process. After milling for 60 minutes, transmission electron microscopy revealed the FeAl2O4 particles to have a mean size of approximately 50 nm. The FeAl2O4 nanoparticles were fabricated successfully by using a two-step process, spray pyrolysis and wet milling.

  6. Solution combustion synthesis of strontium aluminate, SrAl2O4, powders: single-fuel versus fuel-mixture approach.

    PubMed

    Ianoş, Robert; Istratie, Roxana; Păcurariu, Cornelia; Lazău, Radu

    2016-01-14

    The solution combustion synthesis of strontium aluminate, SrAl2O4, via the classic single-fuel approach and the modern fuel-mixture approach was investigated in relation to the synthesis conditions, powder properties and thermodynamic aspects. The single-fuel approach (urea or glycine) did not yield SrAl2O4 directly from the combustion reaction. The absence of SrAl2O4 was explained by the low amount of energy released during the combustion process, in spite of the highly negative values of the standard enthalpy of reaction and standard Gibbs free energy. In the case of single-fuel recipes, the maximum combustion temperatures measured by thermal imaging (482 °C - urea, 941 °C - glycine) were much lower than the calculated adiabatic temperatures (1864 °C - urea, 2147 °C - glycine). The fuel-mixture approach (urea and glycine) clearly represented a better option, since (α,β)-SrAl2O4 resulted directly from the combustion reaction. The maximum combustion temperature measured in the case of a urea and glycine fuel mixture was the highest one (1559 °C), which was relatively close to the calculated adiabatic temperature (1930 °C). The addition of a small amount of flux, such as H3BO3, enabled the formation of pure α-SrAl2O4 directly from the combustion reaction.

  7. Structure of Calcium Aluminate Decahydrate (CaAl2O4.10D2O) from Neutron and X-ray Powder Diffraction Data

    SciTech Connect

    Christensen,A.; Lebech, B.; Sheptyakov, D.; Hanson, J.

    2007-01-01

    Calcium aluminate decahydrate is hexagonal with the space group P63/m and Z = 6. The compound has been named CaAl2O4{center_dot}10H2O (CAH10) for decades and is known as the product obtained by hydration of CaAl2O4 (CA) in the temperature region 273-288 K - one of the main components in high-alumina cements. The lattice constants depend on the water content. Several sample preparations were used in this investigation: one CAH10, three CAD10 and one CA(D/H)10, where the latter is a zero-matrix sample showing no coherent scattering contribution from the D/H atoms in a neutron diffraction powder pattern. The crystal structure including the positions of the H/D atoms was determined from analyses of four neutron diffraction powder patterns by means of the ab initio crystal structure determination program FOX and the FULLPROF crystal structure refinement program. Additionally, eight X-ray powder diffraction patterns (Cu K[alpha]1 and synchrotron X-rays) were used to establish phase purity. The analyses of these combined neutron and X-ray diffraction data clearly show that the previously published positions of the O atoms in the water molecules are in error. Thermogravimetric analysis of the CAD10 sample preparation used for the neutron diffraction studies gave the composition CaAl2(OD)8(D2O)2{center_dot}2.42D2O. Neutron and X-ray powder diffraction data gave the structural formula CaAl2(OX)8(X2O)2{center_dot}[gamma]X2O (X = D, H and D/H), where the [gamma] values are sample dependent and lie between 2.3 and 3.3.

  8. α-Tricalcium phosphate cements modified with β-dicalcium silicate and tricalcium aluminate: physicochemical characterization, in vitro bioactivity and cytotoxicity.

    PubMed

    Correa, Daniel; Almirall, Amisel; Carrodeguas, Raúl García; dos Santos, Luis Alberto; De Aza, Antonio H; Parra, Juan; Morejón, Lizette; Delgado, José Angel

    2015-01-01

    Biocompatibility, injectability and in situ self-setting are characteristics of calcium phosphate cements which make them promising materials for a wide range of clinical applications in traumatology and maxillo-facial surgery. One of the main disadvantages is their relatively low strength which restricts their use to nonload-bearing applications. α-Tricalcium phosphate (α-C3P) cement sets into calcium-deficient hydroxyapatite (CDHA), which is biocompatible and plays an essential role in the formation, growth and maintenance of tissue-biomaterial interface. β-Dicalcium silicate (β-C2S) and tricalcium aluminate (C3A) are Portland cement components, these compounds react with water to form hydrated phases that enhance mechanical strength of the end products. In this study, setting time, compressive strength (CS) and in vitro bioactivity and biocompatibility were evaluated to determine the influence of addition of β-C2S and C3A to α-C3P-based cement. X-ray diffraction and scanning electron microscopy were used to investigate phase composition and morphological changes in cement samples. Addition of C3A resulted in cements having suitable setting times, but low CS, only partial conversion into CDHA and cytotoxicity. However, addition of β-C2S delayed the setting times but promoted total conversion into CDHA by soaking in simulated body fluid and strengthened the set cement over the limit strength of cancellous bone. The best properties were obtained for cement added with 10 wt % of β-C2S, which showed in vitro bioactivity and cytocompatibility, making it a suitable candidate as bone substitute.

  9. A fixed tilt solar collector employing reversible vee-trough reflectors and vacuum tube receivers for solar heating and cooling systems

    NASA Technical Reports Server (NTRS)

    Selcuk, M. K.

    1977-01-01

    The usefulness of vee-trough concentrators in improving the efficiency and reducing the cost of collectors assembled from evacuated tube receivers was studied in the vee-trough/vacuum tube collector (VTVTC) project. The VTVTC was analyzed rigorously and various mathematical models were developed to calculate the optical performance of the vee-trough concentrator and the thermal performance of the evacuated tube receiver. A test bed was constructed to verify the mathematical analyses and compare reflectors made out of glass, Alzak and aluminized FEP Teflon. Tests were run at temperatures ranging from 95 to 180 C. Vee-trough collector efficiencies of 35 to 40% were observed at an operating temperature of about 175 C. Test results compared well with the calculated values. Predicted daily useful heat collection and efficiency values are presented for a year's duration of operation temperatures ranging from 65 to 230 C. Estimated collector costs and resulting thermal energy costs are presented. Analytical and experimental results are discussed along with a complete economic evaluation.

  10. Hubble Space Telescope Bi-Stem Thermal Shield Analyses

    NASA Technical Reports Server (NTRS)

    Finlay, Katherine A.

    2004-01-01

    The Hubble Space Telescope (HST) was launched April 24, 1990, and was deployed April 25 into low Earth orbit (LEO). It was soon discovered that the metal poles holding the solar arrays were expanding and contracting as the telescope orbited the Earth passing between the sunlight and the Earth s shadow. The expansion and contraction, although very small, was enough to cause the telescope to shake because of thermal-induced jitters, a detrimental effect when trying to take pictures millions of miles away. Therefore, the European Space Agency (ESA, the provider of the solar arrays) built new solar arrays (SA-11) that contained bi-stem thermal shields which insulated the solar array metal poles. These thermal shields were made of 2 mil thick aluminized-Teflon fluorinated ethylene propylene (FEP) rings fused together into a circular bellows shape. The new solar arrays were put on the HST during an extravehicular activity (EVA), also called an astronaut space walk, during the first servicing mission (SM1) in December 1993. An on-orbit photograph of the HST with the SA-11, and a close up of the bellows-like structure of the thermal shields is provided in Figure 1.

  11. Characterization of white Portland cement hydration and the C-S-H structure in the presence of sodium aluminate by {sup 27}Al and {sup 29}Si MAS NMR spectroscopy

    SciTech Connect

    Andersen, Morten Daugaard; Jakobsen, Hans J.; Skibsted, Joergen

    2004-05-01

    The effects of hydrating a white Portland cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO{sub 2}) at 5 and 20 deg. C are investigated by {sup 27}Al and {sup 29}Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO{sub 2} accelerates the hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO{sub 4}/AlO{sub 4} tetrahedra. The C-S-H phases are investigated in detail and it is shown that the Al/Si ratio for the chains of tetrahedra is quite constant during the time studied for the hydration (6 h to 2 years) but increases for higher concentration of the NaAlO{sub 2} solution. The average chain lengths of 'pure' silicate and SiO{sub 4}/AlO{sub 4} tetrahedra demonstrate that Al acts as a linker for the silicate chains, thereby producing aluminosilicate chains with longer average chain lengths. Finally, it is shown that NaAlO{sub 2} reduces the quantity of ettringite and results in larger quantities of monosulfate and a calcium aluminate hydrate phase.

  12. Microstructural evolution and hardness of TiAl3 and TiAl2 phases on Ti-45Al-2Nb-2Mn-1B by plasma pack aluminizing

    NASA Astrophysics Data System (ADS)

    Rastkar, Ahmad Reza; Parseh, Pejman; Darvishnia, Naser; Hadavi, Seyed Mohammad Mehdi

    2013-07-01

    The surface of Ti-45Al-2Nb-2Mn-1B (at%) titanium aluminide was aluminized in a so called plasma pack aluminizing by packing the substrate in a mixture of aluminum copper alloy and application of an 18 kHz pulsed DC glow discharge plasma in argon gas. The plasma energy provided the necessary heat for melting and mutual diffusion of titanium and aluminum at the surface of titanium aluminide alloy in less than 1 h without any further heat treatment. The microstructure and hardness of different phases on the surface of Ti-45Al-2Nb-2Mn-1B alloy were characterized using optical and electron microscopy, X-ray diffraction (XRD), EDX analysis and Vickers microhardness tests. The thickness of the surface layers was up to 300 μm. The surface layers consisted mainly of TiAl3 and TiAl2 compounds. These compounds appeared in blocky and round shapes with different micrometer sizes in a matrix of aluminum alloy phase. The hardness of the surface layers was up to 600 HV0.1, which was higher than that of Ti-45Al-2Nb-2Mn-1B substrate (330 HV0.1).

  13. The stability of hibonite, melilite and other aluminous phases in silicate melts: Implications for the origin of hibonite-bearing inclusions from carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Beckett, J. R.; Stolper, E.

    1994-01-01

    are generally lower than predicted and melilite initially condenses with or even after spinel. Simple thermochemical modes for the substitution of trace elements into the Ca site of meteoritic hibonites suggest that virtually all Eu is divalent in early condensate hibonites but that Eu(2+)/Eu(#+) 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 phase condense. The relative sizes of Eu and Yb anomalies in meteoritic hibonites and inclusions may be partly due to this effect.

  14. The stability of hibonite, melilite and other aluminous phases in silicate melts: Implications for the origin of hibonite-bearing inclusions from carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Beckett, J. R.; Stolper, E.

    1994-01-01

    equilibration temperatures are generally lower than predicted and melilite initially condenses with or even after spinel. Simple thermochemical modes for the substitution of trace elements into the Ca site of meteoritic hibonites suggest that virtually all Eu is divalent in early condensate hibonites but that Eu(2+)/Eu(#+) 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 phase condense. The relative sizes of Eu and Yb anomalies in meteoritic hibonites and inclusions may be partly due to this effect.

  15. Characterization and origin of the Taishanmiao aluminous A-type granites: implications for Early Cretaceous lithospheric thinning at the southern margin of the North China Craton

    NASA Astrophysics Data System (ADS)

    Wang, Changming; Chen, Liang; Bagas, Leon; Lu, Yongjun; He, Xinyu; Lai, Xiangru

    2016-07-01

    Late Mesozoic magmatic rocks from the Taishanmiao Batholith were collected for LA-ICP-MS dating, Sr-Nd-Hf isotope systematics, and whole-rock major and trace element geochemistry to help understand the nature of collisional and extensional events along the southern margin of the North China Craton. The batholith consists of three texturally distinguishable phases of a 125 ± 1 Ma medium- to coarse-grained syenogranite, a 121 ± 1 Ma fine- to medium-grained syenogranite, and a 113 ± 1 Ma porphyritic monzogranite. Most of the units in the batholith are syenogranitic in composition with high levels of silica (70-78 wt% SiO2), alkalis (8.0-8.6 wt% Na2O + K2O), Fe* (FeOT/(FeOT + MgO) = 0.76-0.90), and depletion in CaO (0.34-1.37 wt%), MgO (0.12-0.52 wt%), TiO2 (0.09-0.40 wt%), and A/CNK (Al2O3/(Na2O + K2O + CaO)) molar ratios of 1.00-1.11. All samples have high proportions of Ga, Nb, Zr, Ga/Al, and REE, and depletions in Ba, Sr, Eu, and compatible elements, indicating that the batholith consists of A-type granites. The zircon saturation temperature for these units yields a mean value of 890 °C, and zircons with Early Cretaceous magmatic ages have ɛNd( t) values of -14.0 to -12.0, ɛHf( t) values ranging from -18.7 to -2.1, and corresponding Hf model ages of 2339-1282 Ma. These geochemical and isotopic characteristics allowed us to conclude that the primary magma for the Taishanmiao Batholith originated from partial melting of Precambrian crustal rocks in the medium-lower crust. However, the high Nb and Ta contents and low normalized Nb/Ta values for the Taishanmiao granites are due to fractionation in Nb- and Ta-rich amphibole (or biotite). It is further proposed that these aluminous A-type granites were generated in an extensional tectonic setting during the Early Cretaceous, which was induced by lithospheric thinning and asthenospheric upwelling beneath eastern China toward the Paleo-Pacific Plate.

  16. Use of a single-bowl continuous-flow centrifuge for dewatering suspended sediments: effect on sediment physical and chemical characteristics

    USGS Publications Warehouse

    Rees, T.F.; Leenheer, J.A.; Ranville, J.F.

    1991-01-01

    Sediment-recovery efficiency of 86-91% is comparable to that of other types of CFC units. The recovery efficiency is limited by the particle-size distribution of the feed water and by the limiting particle diameter that is retained in the centrifuge bowl. Contamination by trace metals and organics is minimized by coating all surfaces that come in contact with the sample with either FEP or PFA Teflon and using a removable FEP Teflon liner in the centrifuge bowl. -from Authors

  17. Coated Aluminized Film Resists Corrosion

    NASA Technical Reports Server (NTRS)

    Rockoff, H. J.

    1982-01-01

    Commercially available corrosion-protection coating allows less costly metals - aluminum in particular used in heat-reflecting films for thermal barriers. Previously, such films had to incorporate gold as reflective layer to withstand humidity, moisture, and salt spray without corroding. This protective coating prevents corrosion of metalized films during evironmental exposure yet remains flexible, thermally stable and clear.

  18. The role of impurities, LIF, and processing on the sintering, microstructure, and optical properties of transparent polycrystalline magnesium aluminate (MgAl2O4) spinel

    NASA Astrophysics Data System (ADS)

    Rubat du Merac, Marc

    Transparent polycrystalline magnesium aluminate (MgAl2O4) spinel has an exceptional combination of properties that is well-suited to fulfill demanding optical applications that few other materials can satisfy. However, spinel is inherently difficult to densify due to high defect formation energies, variable stoichiometry, and extreme sensitivity to powder and processing parameters. In addition, the LiF sintering additive typically required to impart transparency degrades optical and mechanical properties, precluding wider application. Furthermore, there remains a fundamental lack of understanding of the processing-structure-property relationships required to obtain high transparency and good mechanical properties. In this work, hot-press experiments were designed to determine the role of impurities and LiF and the key variables required to obtain transparent spinel. Hot-pressed compacts were characterized with electron microscopy, chemical spectroscopy, and spectrophotometry, and impurities present in parts-per-million in starting powders were found to cause restricted grain size and opacity. LiF addition was found to reduce the content of some impurities by one order of magnitude, counteract absorption, and impart transparency, but also to cause grain coarsening, grain-boundary embrittlement, and scatter. Thermal analysis and residual gas analysis of prepared powders in combination with thermodynamic modeling demonstrated for the first time the specific mechanism by which LiF acts as a cleanser. LiF reacts with impurities to form volatile fluorides, and the temperature at which pressure is applied during hot-pressing determines the extent to which compact-scale differential sintering either traps LiF and volatile fluorides or allows their removal, the latter enabling transparency. The main cause of absorption in hot-pressed spinel compacts was found to be carbon contamination from graphitic hot-press components and it could be completely eliminated with proper

  19. Multielectrode Teflon electrochemical nanocatalyst investigation system

    PubMed Central

    Hodnik, Nejc

    2015-01-01

    The most common approach in the search for the optimal low temperature fuel cell catalyst remains “trial and error”. Therefore, large numbers of different potential catalytic materials need to be screened. The well-established and most commonly used method for testing catalytic electrochemical activity under well-defined hydrodynamics is still thin film rotating disc electrode (TF-RDE). Typically this method is very time consuming and is subjected to impurity problems. In order to avoid these issues a new multielectrode electrochemical cell design is presented, where 8 different electrocatalysts can be measured simultaneously at identical conditions. The major advantages over TF-RDE method are: • Faster catalyst screening times. • Greater impurity tolerance. • The option of internal standard. PMID:26150990

  20. Détermination de l'énergie de surface d'alumines et de titanates de baryum utilisés pour la préparation de céramiques : influence d'un traitement thermique

    NASA Astrophysics Data System (ADS)

    Papirer, E.; Perrin, J. M.; Siffert, B.; Philipponneau, G.

    1991-05-01

    Surface characteristics of powders used for the preparation of ceramics determine the physical interactions potential between constituents and condition, in particular, the stability of slurries. Inverse Gas Chromatography (I.G.C.) applied to aluminas and barium titanates, appears to be a well suited method for the measurement, on the one hand, of the dispersive component (γ^D_S) of the surface energy and, on the other hand, of a specific interaction parameter (I_{sp}) which accounts for all possible interactions, except London interactions. It is shown that, firstly, the chemical surface composition (presence of impurities or Ba/Ti ratios) influences strongly the values of γ^D_S and I_{sp} and, secondly, the heat treatment of certain aluminas (below 500 °C) modifies in an unexpected way the same values. In that case, the results may be explained supposing the existence, on the alumina surfaces, of a thin hydrated oxide layer which is formed during ageing in humid atmosphere. This layer, of the boehmite type, transforms into γ alumina around 350-400 °C, a transformation accompanied by important variations of γ^D_S This study underlines the importance of a thorough physico-chemical control of the ceramic powders and of their conditioning. Les caractéristiques de surface des poudres entrant dans la préparation des céramiques déterminent les capacités d'interactions physiques entre constituants et conditionnent, en particulier, la stabilité des barbotines. La chromatographie gazeuse inverse (C.G.I.), appliquée aux alumines et aux titanates de baryum, s'avère comme une méthode de choix pour la mesure d'une part, de la composante dispersive (γ^D_S) de l'énergie de surface et d'autre part, d'un paramètre d'interaction spécifique (I_{sp}) qui rend compte de toutes les possibilités d'interactions à l'exception de celles de London. On montre, premièrement, que la composition chimique de surface (présence d'impuretés, ou rapport Ba/Ti) influe