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  • PROPELLANTS AND FUELS  (7)
  • Inorganic Chemistry  (4)
  • 1990-1994  (9)
  • 1970-1974  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 1262-1268 
    ISSN: 0044-2313
    Keywords: Solid-State NMR ; Magic-Angle-Spinning NMR ; 11B MAS NMR ; chemical shifts, borates ; peroxoborates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 11B MAS NMR Studies on the Structure of Borate AnionsThe results of 11B MAS NMR studies on selected crystalline borates and peroxoborates show that the boron coordination number can be determined not only from the quadrupole coupling constant but also from the chemical shift values. Correspondingly, the B[3]:B[4] ratio can be determined quantitatively. In contrast to 27Al, 29Si, and 31P NMR data, however, the observed small variation of the 11B chemical shifts does not allow a more detailed information on the linkage of the coordination polyhedra and their environments. The method was applied to Ag borates with unknown structures. In the case of a borate with an Ag:B ratio of 1:3 the measured B[3]:B[4] ratio suggests a triborate structure of the anion.
    Notes: Die Ergebnisse von 11B-MAS-NMR-Untersuchungen an einer Reihe ausgewählter kristalliner Borate und Peroxoborate zeigen, daß sich die Koordinationszahl des Bor - ebenso wie aus den Quadrupolkopplungskonstanten - auch aus den chemischen Verschiebungswerten ermitteln läßt und eine quantitative Bestimmung der Anteile von B[3]:B[4] möglich ist. Die geringe Variation der 11B-Verschiebungswerte gestattet jedoch im Gegensatz zu entsprechenden 27Al-, 29Si- und 31P-NMR-Daten keine weiterführenden Aussagen über die Verknüpfung der Koordinationspolyeder bzw. über deren weitere Umgebung. Die Untersuchungen wurden auch auf Ag-Borate unbekannter Struktur ausgedehnt. Im Falle eines Borates mit einem Atomverhältnis Ag:B von 1:3 wurde aus dem ermittelten Mengenverhältnis B[3]:B[4] auf ein Triborat-Anion geschlossen.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 410 (1974), S. 129-137 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigations of Ternary Chalkogenides. XXIII. On the Structure of the Tl0,33TaSe2 - PhaseThe system Tl/Ta/Se, at low thallium concentrations gives rise to a phase with the empirical formula TlxTaSe2, in which x has values between 0.33 and 0.5. It crystallizes hexagonal (a = 3.473 Å; c = 8.393 Å; c/a = 2.42) with one formula weight per unit cell. The structure of this phase (space group D3h1-P6m2) consists of TaSe2 layers between which the thallium atoms are arranged in such a way, that both metals attain a trigonal-prismatic coordination concerning the selenium atoms. The interatomic distances as well as bonding resulting from them and the relations of this structure with similar structure types are discussed.
    Notes: Im System Tl/Ta/Se bildet sich bei kleinen Thalliumgehalten eine Phase der Zusammensetzung TlxTaSe2 mit x zwischen 0,33 und 0,5. Sie kristallisiert hexagonal mit a = 3,473 Å; c = 8,393 Å; c/a = 2,42 mit einer Formeleinheit in der Elementarzelle. Die Struktur dieser Phase (Raumgruppe D3h1-P6m2) baut sich aus TaSe2-Schichten auf, zwischen denen die Thalliumatome so eingelagert sind, daß sich für beide Metalle eine trigonal-prismatische Koordination gegenüber den Selenatomen ergibt. Die interatomaren Abstände, die sich daraus ergebenden Bindungsverhältnisse sowie die Beziehungen dieser Struktur zu ähnlichen Strukturtypen werden diskutiert.
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 398 (1973), S. 207-220 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Ternary Thallium Chalcogenides with Thallium Selenide Structure.By means of single crystal investigations, it has been confirmed that the compounds TlGaTe2, TIInSe2, and TIInTe2 crystallize in the TISe type (B37). As an univalent cation thallium is surrounded by eight chalcogen atoms. Gallium and indium are trivalent with tetrahedral coordination and covalent bonds. The interatomic distances as well as coordination and bonding resulting from them are discussed.
    Notes: Mit Hilfe von röntgenographischen Einkristalluntersuchungen wurde bestätigt, daß die Verbindungen TlGaTe2, TlInSe2 und TlInTe2 im TISe-Typ (B37) kristallisieren. Thallium ist darin als 1wertiges Kation von acht Chalkogenatomen umgeben, Gallium und Indium liegen 3wertig mit tetraedrischer Koordination und kovalenter Bindung vor. Dio interatomaren Abstände sowie die sich daraus ergebenden Koordinations- und Bindungsverhältnisse werden diskutiert.
    Additional Material: 8 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 771-776 
    ISSN: 0044-2313
    Keywords: Tetrahydroxoaluminate chloride, Na2[Al(OH)4]Cl ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Sodium Tetrahydroxoaluminate Chloride Na2[Al(OH)4]ClThe hitherto unknown compound Na2[Al(OH)4]Cl was prepared by crystallisation from a NaCl containing sodium aluminate solution. According to the X-ray single crystal investigation (tetragonal, space group P4/nmm, a = 7.541 Å, c = 5.059 Å, Z = 2) the compound represents the first example of a crystalline hydroxoaluminate with monomeric [Al(OH)4]- anions. Cl- shows a quadratic anti prismatic coordination to 4 Na+ and over hydrogen bonds to 4 O2- while Na+ is octahedrally coordinated by 4 O2- and 2 Cl- (axial). The results of the crystal structure analysis are confirmed by 27Al and 23Na MAS NMR investigations. Na2[Al(OH)4]Cl decomposes at about 200°C without intermediates under formation of β-NaAlO2 and NaCl.
    Notes: Die bisher unbekannte Verbindung Na2[Al(OH)4]Cl wurde durch Kristallisation aus mit NaCl versetzter Natriumaluminatlösung erhalten. Entsprechend der Röntgenstrukturanalyse an einem Einkristall (tetragonal, Raumgruppe P4/nmm, a = 7,541 Å, c = 5,059 Å, Z = 2) liegt mit dieser Verbindung erstmals ein Beispiel für ein kristallines Hydroxoaluminat mit monomeren [Al(OH)4]--Anionen vor. Cl- ist quadratisch antiprismatisch mit 4 Na+ sowie über Wasserstoffbrückenbindungen mit 4 O2- koordiniert, während Na+ oktaedrisch von 4 O2- und 2 Cl- (axial) umgeben ist. Die Ergebnisse der Kristallstrukturanalyse werden durch 27Al- und 23Na-MAS-NMR-Messungen bestätigt. Na2[Al(OH)4]Cl zersetzt sich ohne Zwischenprodukte bei 200°C zu β-NaAlO2 und NaCl.
    Additional Material: 5 Ill.
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  • 5
    Publication Date: 2016-06-07
    Description: A laser-based, forward-scatter diagnostic technique, employing a single laser sheet, has been developed to simultaneously measure the size and velocity of individual 10-150 micron droplets in a dilute polydisperse droplet stream (less than 1000 particles/cc) and to detect the presence of burning aluminum in these same droplets. Spectral emission from aluminum vapor in the 390-400 nm wavelength region is used as an indication of burning aluminum. The technique utilizes a 4-mm uniformly illuminated probe volume, eliminating trajectory-dependent particle sizing and size-dependent system detection bias. Particle sizing is based on a correlation of particle size with near-forward scattered light intensity. Calculations show average particle sizing variation to be within 3.5% over the expected range of refractive indices. Calibrations using a range of optical pinholes (10-100 micron) were used to verify the above sizing correlation.
    Keywords: PROPELLANTS AND FUELS
    Type: NASA Propulsion Engineering Research Center, Volume 2; p 153-157
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  • 6
    Publication Date: 2019-07-13
    Description: Secondary atomization and ignition characteristics of aluminum/hydrocarbon gel propellants were investigated. Models of gel droplet shell formation were applied to aluminum/liquid hydrocarbon propellants to examine the effects of solid loading and ultimate particle size on the minimum droplet diameter permitting secondary atomization. A one-dimensional model of a gel-fueled rocket combustion chamber was developed. A model for radiant heat transfer from hot aluminum oxide particles to the chamber walls is included. A two-dimensional, two-phase nozzle code was used to estimate nozzle two-phase losses and overall engine performance.
    Keywords: PROPELLANTS AND FUELS
    Type: NASA-CR-196850 , NAS 1.26:196850
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  • 7
    Publication Date: 2019-07-13
    Description: Over the past six months, experimental investigations were continued and theoretical work on the secondary atomization process was begun. Final shakedown of the sizing/velocity measuring system was completed and the aluminum combustion detection system was modified and tested. Atomizer operation was improved to allow steady state operation over long periods of time for several slurries. To validate the theoretical modeling, work involving carbon slurry atomization and combustion was begun and qualitative observations were made. Simultaneous measurements of aluminum slurry droplet size distributions and detection of burning aluminum particles were performed at several axial locations above the burner. The principle theoretical effort was the application of a rigid shell formation model to aluminum slurries and an investigation of the effects of various parameters on the shell formation process. This shell formation model was extended to include the process leading up to droplet disruption, and previously developed analytical models were applied to yield theoretical aluminum agglomerate ignition and combustion times. The several theoretical times were compared with the experimental results.
    Keywords: PROPELLANTS AND FUELS
    Type: NASA-CR-192231 , NAS 1.26:192231 , TR-91-008
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  • 8
    Publication Date: 2019-07-13
    Description: During this reporting period, theoretical work on the secondary atomization process was continued and the experimental apparatus was improved. A one-dimensional model of a rocket combustor, incorporating multiple droplet size classes, slurry combustion, secondary atomization, radiation heat transfer, and two-phase slip between slurry droplets and the gas flow was derived and a computer code was written to implement this model. The STANJAN chemical equilibrium solver was coupled with this code to yield gas temperature, density, and composition as functions of axial location. Preliminary results indicate that the model is performing correctly, given current model assumptions. Radiation heat transfer in the combustion chamber is treated as an optically-thick participating media problem requiring a solution of the radiative transfer equation. A cylindrical P sub 1 approximation was employed to yield an analytical expression for chamber-wall heat flux at each axial location. The code exercised to determine the effects of secondary atomization intensity, defined as the number of secondary drops produced per initial drop, on chamber burnout distance and final Al2O3 agglomerate diameter. These results indicate that only weak secondary atomization is required to significantly reduce these two parameters. Stronger atomization intensities were found to yield decreasing marginal benefits. The experimental apparatus was improved to reduce building vibration effects on the optical system alignment. This was accomplished by mounting the burner and the transmitting/receiving optics on a single frame supported by vibration-isolation legs. Calibration and shakedown tests indicate that vibration problems were eliminated and that the system is performing correctly.
    Keywords: PROPELLANTS AND FUELS
    Type: NASA-CR-190613 , NAS 1.26:190613 , PSU-TR-92-010
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  • 9
    Publication Date: 2019-07-13
    Description: Experimental and analytical investigations focusing on aluminum/hydrocarbon gel droplet secondary atomization and its effects on gel-fueled rocket engine performance are being conducted. A single laser sheet sizing/velocimetry diagnostic technique, which should eliminate sizing bias in the data collection process, has been designed and constructed to overcome limitations of the two-color forward-scatter technique used in previous work. Calibration of this system is in progress and the data acquisition/validation code is being written. Narrow-band measurements of radiant emission, discussed in previous reports, will be used to determine if aluminum ignition has occurred in a gel droplet. A one-dimensional model of a gel-fueled rocket combustion chamber, described in earlier reports, has been exercised in conjunction with a two-dimensional, two-phase nozzle code to predict the performance of an aluminum/hydrocarbon fueled engine. Estimated secondary atomization effects on propellant burnout distance, condensed particle radiation losses to the chamber walls, and nozzle two phase flow losses are also investigated. Calculations indicate that only modest secondary atomization is required to significantly reduce propellant burnout distances, aluminum oxide residual size, and radiation heat losses. Radiation losses equal to approximately 2-13 percent of the energy released during combustion were estimated, depending on secondary atomization intensity. A two-dimensional, two-phase nozzle code was employed to estimate radiation and nozzle two phase flow effects on overall engine performance. Radiation losses yielded a one percent decrease in engine Isp. Results also indicate that secondary atomization may have less effect on two-phase losses than it does on propellant burnout distance and no effect if oxide particle coagulation and shear induced droplet breakup govern oxide particle size. Engine Isp was found to decrease from 337.4 to 293.7 seconds as gel aluminum mass loading was varied from 0-70 wt percent. Engine Isp efficiencies, accounting for radiation and two phase flow effects, on the order of 0.946 were calculated for a 60 wt percent gel, assuming a fragmentation ratio of five.
    Keywords: PROPELLANTS AND FUELS
    Type: NASA-CR-195107 , NAS 1.26:195107
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  • 10
    Publication Date: 2019-07-13
    Description: Experimental and analytical investigations focusing on secondary atomization and ignition characteristics of aluminum/liquid hydrocarbon slurry propellants were conducted. Experimental efforts included the application of a laser-based, two-color, forward-scatter technique to simultaneously measure free-flying slurry droplet diameters and velocities for droplet diameters in the range of 10-200 microns. A multi-diffusion flame burner was used to create a high-temperature environment into which a dilute stream of slurry droplets could be introduced. Narrowband measurements of radiant emission were used to determine if ignition of the aluminum in the slurry droplet had occurred. Models of slurry droplet shell formation were applied to aluminum/liquid hydrocarbon propellants and used to ascertain the effects of solids loading and ultimate particle size on the minimum droplet diameter that will permit secondary atomization. For a 60 weight-percent Al slurry, the limiting critical diameter was predicted to be 34.7 microns which is somewhat greater than the 20-25 micron limiting diameters determined in the experiments. A previously developed model of aluminum ignition in a slurry droplet was applied to the present experiments and found to predict ignition times in reasonable agreement with experimental measurements. A model was also developed that predicts the mechanical stress in the droplet shell and a parametric study was conducted. A one-dimensional model of a slurry-fueled rocket combustion chamber was developed. This model includes the processes of liquid hydrocarbon burnout, secondary atomization, aluminum ignition, and aluminum combustion. Also included is a model for radiant heat transfer from the hot aluminum oxide particles to the chamber walls. Exercising this model shows that only a modest amount of secondary atomization is required to reduce residence times for aluminum burnout, and thereby maintain relatively short chamber lengths. The model also predicts radiant heat transfer losses to the walls to be only approximately 3 percent of the fuel energy supplied. Additional work is required to determine the effects of secondary atomization on two-phase losses in the nozzle.
    Keywords: PROPELLANTS AND FUELS
    Type: NASA-CR-192285 , NAS 1.26:192285
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