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  • Weitere Quellen  (774)
  • NONMETALLIC MATERIALS
  • 1980-1984  (774)
  • 1950-1954
  • 1
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    An atomic oxygen facility for studying polymer materials for spacecraft applications (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: A nozzle beam facility utilizing microwave discharge on a helium carrier gas seeded with oxygen to produce atomic oxygen fluxes of the order of 10 to the 15th power atoms/cu cm/sec is described. In addition, limited test results obtained from exposing a graphite/epoxy composite and Kapton (H) film are presented in terms of mass loss measurements and changes in surface morphology.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Goddard Space Flight Center 13th Space Simulation Conf.; p 169-192
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  • 2
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    Thermal control coatings experiment (A0138-6) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The objectives of this LDEF experiment are to verify the validity of space environment simulation performed in the laboratory in order to measure the stability of the thermo-optical properties of thermal control coatings, and to compare the behavior in space of some materials for which the available ultraviolet solar simulation is inadequate (especially in the far ultraviolet). The experimental approach is to passively expose samples of the thermal coatings of interest. These coatings include black paint, aluminum paint, white paint, a solar absorber, an optical surface reflector, second surface mirrors, metal coatings, and silica fabrics. Preflight and postflight measurements of thermo-optical properties will be compared to determine the effects of space environment exposure.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 52-53
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  • 3
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    Atomic-oxygen stimulated outgassing (A0034) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective of this experiment is to determine if the impingement of atomic oxygen in near-Earth orbit is a major factor in producing optically damaging outgassed products. The expected results will be to obtain samples which have been exposed to atomic oxygen for long durations. Analysis of these samples will determine if the impingement of atomic oxygen on the thermal control surfaces stimulates a significant amount of outgassed products. This experiment will give a clearer picture of the contamination problem and will assist in assuring that future Shuttle payloads, such as the Space Telescope and High-Energy Astronomy Observatory, will not experience Skylab contamination levels. Selected thermal control surfaces will be exposed to the atomic oxygen in near-Earth orbit. Passive collecting samples will collect any induced outgassing resulting from oxygen impingement. The optical condition of the passive samples will be measured using a ground-based integrating sphere reflectometer and a directional reflectometer.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 11-13
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  • 4
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    Shuttle tile environments and loads (1982)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The Shuttle tile ascent environments are discussed and the procedures used to convert these environments into tile loads are outlined. Testing which was performed to quantify or verify the loads are discussed, along with the load combination rationale which was used. The discussion of the ascent environment is limited to the transonic/supersonic portion of the mission since mechanical design loads occur during this time, and to specific regions of the vehicle, in particular those regions in which undensified critical (black) tiles are located.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Shock and Vibration Inform. Center The Shock and Vibration Bull., No. 52. Part 2; p 111-125
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  • 5
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    Structural characteristics of the shuttle orbiter ceramic thermal protection system (1982)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The thermal protection system (TPS) of the Space Shuttle Orbiter is described as well as the results of dynamic reponse studies conducted in support of the efforts to certify the TPS for flight. The ceramic Thermal Protection System consists of ceramic tiles bonded to felt pads which are in turn bonded to the Orbiter substructure to protect the aluminum substructure from the heat of reentry.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Shock and Vibration Inform. Center The Shock and Vibration Bull., No. 52. Part 2; p 101-110
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  • 6
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    Fibrous ceramic insulation (1982)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-12
    Beschreibung: Some of the reusable heat shielding materials used to protect the Space Shuttles, their manufacturing processes, properties, and applications are discussed. Emphases is upon ceramic materials. Space Shuttle Orbiter tiles are discussed.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Advan. Mater. Technol.; p 261-274
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  • 7
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    Polymer research at NASA Langley Research Center (1982)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-12
    Beschreibung: Polymer synthesis programs involve the development of Novel thermoplastics, pseudothermoplastics, and thermosets. These systems are prepared to elucidate structure-property relationships involving thermal capabilities, toughness, processability and environmental stability. Easily processable polyimides, solvent-resistant polysulfones and polyphenylquinoxalines, and tougher high and intermediate temperature polymers were developed. Characterization efforts included high pressure liquid chromatography methodology, the development of toughness tests for fiber reinforced composites, a study of electrical properties of metal ion filled polyimides, and a study of the mutagenicity of aromatic diamines. Also the mechanism of cure/degradation of experimental polymers was studied by rheology, mechanical behavior, separation techniques and spectroscopy. The degradative crosslinking of alkyl-containing polyimides, the separation and identification of crosslinked phenylquinoxalines, the rheological behavior of hot-melt polyimides, and the elucidation of the cure of norbornene endcapped imides were also studied.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Advan. Mater. Technol.; p 29-48
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  • 8
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    Polymer materials research at NASA Ames Research Center (1982)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-12
    Beschreibung: Polymers that provide significant improvements in both efficiency and safety for civilian transport aircraft and military combat aircraft were developed. High strength to weight structures such as carbon fiber composites with long term durability are requirements common to both classes of aircraft. Aircraft safety improvements in fire resistance and crashworthiness of primary and secondary structures are long term objectives for transport aircraft. Void filler ballistic foams, intumescent coatings, and radiation-resistant transparent plastics contribute to vulnerability reduction in combat military aircraft. Low and high velocity impact tolerance, fire resistance, thermal stability, and long term durability of polymers and components are emphasized.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Advan. Mater. Technol.; p 49-64
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  • 9
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    Corrosion properties of second-generation conductive materials (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Since the introduction of silver-filled epoxy adhesives and silver-filled nitrocellulose lacquer as RFI control materials, a number of new materials have been introduced. The resin carriers have been changed in an effort to make the materials more usable or more EPA acceptable and the fillers have been varied in an effort to make the materials less costly. The corrosion-related properties of second-generation materials were assessed, including adhesives, caulks, and greases. Aluminum 2024 was used as the only substrate material. Ten days of salt fog was used as the corrosive environment. If a noble material such as silver, nickel, or carbon is sandwiched with aluminum an increase in dc resistance results given enough time. If this is unsatisfactory electrically it should either not be used or have all corrosive environments excluded.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Intern. Aerospace and Ground Conf. on Lightning and Static Elec.; 7 p
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  • 10
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    Synthesis of aminosilane and aromatic diamine intermediates for polymerization (1982)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The preparation of monomers for use in a study to improve properties of epoxy polymers and silicone elastomers is described. Various approaches to the solution of the synthesis of aminosilane and diamine curing agents were examined. Ortho-, meta-, and para-substituted diamines where X is CH2, C(CH3)2, O, S, NH, or SO2 and n = 0, 1, 2, and 3 were investigated.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: The 1981 NASA(ASEE Summer Fac. Fellowship Program; 9 p
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  • 11
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    Development of high strength, high temperature ceramics (1982)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Improvement in the high-pressure turbopumps, both fuel and oxidizer, in the Space Shuttle main engine were considered. The operation of these pumps is limited by temperature restrictions of the metallic components used in these pumps. Ceramic materials that retain strength at high temperatures and appear to be promising candidates for use as turbine blades and impellers are discussed. These high strength materials are sensitive to many related processing parameters such as impurities, sintering aids, reaction aids, particle size, processing temperature, and post thermal treatment. The specific objectives of the study were to: (1) identify and define the processing parameters that affect the properties of Si3N4 ceramic materials, (2) design and assembly equipment required for processing high strength ceramics, (3) design and assemble test apparatus for evaluating the high temperature properties of Si3N4, and (4) conduct a research program of manufacturing and evaluating Si3N4 materials as applicable to rocket engine applications.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Alabama Univ. in Huntsville The 1981 NASA(ASEE Summer Fac. Fellowship Program; 11 p
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  • 12
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    Development of toughened epoxy polymers for high performance composite and ablative applications (1982)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: A survey of current procedures for the assessment of state of cure in epoxy polymers and for the evaluation of polymer toughness as related to nature of the crosslinking agent was made to facilitate a cause-effect study of the chemical modification of epoxy polymers. Various conformations of sample morphology were examined to identify testing variables and to establish optimum conditions for the selected physical test methods. Dynamic viscoelasticity testing was examined in conjunction with chemical analyses to allow observation of the extent of the curing reaction with size of the crosslinking agent the primary variable. Specifically the aims of the project were twofold: (1) to consider the experimental variables associated with development of "extent of cure" analysis, and (2) to assess methodology of fracture energy determination and to prescribe a meaningful and reproducible procedure. The following is separated into two categories for ease of presentation.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Alabama Univ. in Huntsville The 1981 NASA(ASEE Summer Fac. Fellowship Program; 17 p
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  • 13
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    Effects of solar radiation on glasses (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The effects of solar radiation and space environment on glasses in space flight by exposing glass specimens to the space environment was determined. The occurrence of optical, mechanical, and chemical property changes was analyzed. The property changes of samples receiving differing cumulative solar radiation exposure are compared.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 170-172
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  • 14
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    Ion-beam-textured and coated surfaces experiment (S1003) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective of this LDEF experiment is to measure the effects of exposure to the shuttle launch and near Earth space environments on the optical properties of ion beam textured high absorptance solar thermal control surfaces, the optical and electrical properties of ion beam sputtered conductive solar thermal control surfaces, and the weight loss of ion beam deposited oxide polymer films. The various types of surfaces to be tested include six major categories: (1) ion beam textured surfaces suitable for space solar thermal (solar concentration) application; (2) painted and/or state of the art solar thermal surfaces; (3) ion beam sputtered conductive coatings for thermal and space charge control (e.g., indium-oxide coated metalized FEP Teflon); (4) ion beam sputtered conductive coated solar sail materials for space charge control and cooling through emittance; (5) micrometeoroid sensitive samples whose optical properties change only as a result of micrometeoroid impact; and (6) Kapton coated with oxide polymer films to minimize oxygen degradation at near Earth orbit altitudes.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 62-65
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  • 15
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    Thermal control surface experiment (S0069) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The objectives of this LDEF experiment are to determine the effects of the near Earth orbital environment and the Shuttle induced environment in spacecraft thermal control surfaces. Spectral reflectance measurements will be obtained and used to differentiate between different solid state damage mechanisms of environmental damage to separate the effects of contamination from those of natural environment damage, and for comparison and correlation with laboratory test data.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 57-61
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  • 16
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    Exposure of spacecraft coatings (S0010) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The objectives of this LDEF experiment are to determine the effects of both the Shuttle-induced environment and the space radiation environment on selected sets of spacecraft thermal control coatings. The experimental approach is to passively expose samples of thermal control coatings to Shuttle-induced and space radiation environments and to return the samples for postflight evaluation and comparison with preflight measurements to determine the effects of the environmental exposure. Optical measurements of the samples will include total normal emittance and spectral reflectance. The experiment will utilize a 6 in. deep peripheral tray and an experiment exposure control canister (EECC). The EECC will provide protection for some of the samples against exposure to the launch and reentry environments. The EECC will be programmed to open about 2 weeks after LDEF deployment and close pior to LDEF retrieval by the Shuttle and reentry. Some samples will not be housed in the EECC and will be exposed to the Shuttle-induced environment during launch and reentry. Comparison of the data from these samples with data from samples in the EECC will yield information about possible contamination induced degradation effects.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Long Duration Exposure Facility (LDEF); p 54-56
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  • 17
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    Balloon materials degradation (S1006) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective of this experiment is to assess the effects of long-term exposure of candidate balloon films, tapes, and lines to the hostile environment above the Earth's atmosphere. Degradation of mechanical and radiometric properties will be observed by a series of tests on exposed materials. The experiment is passive and will test candidate balloon films, tapes, and lines. The experiment will occupy one-third of a 3-in.-deep peripheral tray. Two additional identical sets of material will be prepared. The first set will be tested immediately and the second will be held in a controlled environment until the recovery of the samples placed on orbit. Tests will then be performed on this second set to determine any effects of aging. The specimens that are recovered from the Long Duration Exposure Facility will also be tested and the effects of long-duration exposure noted. In addition to these specimens, another set of specimens will be exposed at an accelerated exposure facility and the results will be compared with those of specimens exposed in situ.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 49-51
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  • 18
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    Polymer matrix composites research at NASA Lewis Research Center (1982)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-12
    Beschreibung: The in situ polymerization of monomer reactants (PMR) approach was demonstrated to be a powerful approach for solving many of the processing difficulties associated with the use of high temperature resistant polymers as matrix resins in high performance composites. The PMR-15 polyimide provides the best overall balance of processing characteristics and elevated temperature properties. The excellent properties and commercial availability of composite materials based on PMR-15 led to their acceptance as viable engineering materials. The PMR-15 composites are used to produce a variety of high quality structural components.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Advan. Mater. Technol.; p 65-90
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  • 19
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    Corrosion protection coating (1982)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA Technol. Appl. Team; p 40
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  • 20
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    Crystallization of fluorozirconate glasses (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: The crystallization of a number of glasses of the fluorozirconate family has been studied (using powder X-ray diffraction and DSC) as a function of time and temperature of heating. The main crystalline phases were beta BaZrF6 and beta BaZr2F10. Stable and metastble transformations to the low-temperature alpha phases were also investigated. The size of crystallites in fully devitrified glasses was calculated (from line broadening of the X-ray diffraction peaks) to be about 60 nm.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Materials Research Bulletin (ISSN 0025-5408); 19; 5, 19; 577-590
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  • 21
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    Ion beam deposition of amorphous carbon films with diamond like properties (1982)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: Carbon films were deposited on silicon, quartz, and potassium bromide substrates from an ion beam. Growth rates were approximately 0.3 micron/hour. The films were featureless and amorphous and contained only carbon and hydrogen in significant amounts. The density and carbon/hydrogen ratio indicate the film is a hydrogen deficient polymer. One possible structure, consistent with the data, is a random network of methylene linkages and tetrahedrally coordinated carbon atoms.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 22
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    Surface crystallization of a fluoride glass (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Growth of crystals on the surface of a Zr-Ba-La fluoride glass was observed by optical and scanning electron microscopy. Small, dark crystal nucleated rapidly and grew to a size of about 10 microns; then they stopped growing, and wrinkled regions emerged, covering the entire crystal surface.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society, Communications (ISSN 0002-7820); 66; C-132
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  • 23
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    Siloxane containing addition polyimides (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Addition polyimide oligomers have been synthesized from bis(gamma-aminopropyl) tetramethyldisiloxane and 3, 3', 4, 4'-benzophenonetetracarboxylic dianhydride using a variety of latent crosslinking groups as endcappers. The prepolymers were isolated and characterized for solubility (in amide, chlorinated and ether solvents), melt flow and cure properties. The most promising systems, maleimide and acetylene terminated prepolymers, were selected for detailed study. Graphite cloth reinforced composites were prepared and properties compared with those of graphite/Kerimid 601, a commercially available bismaleimide. Mixtures of the maleimide terminated system with Kerimid 601, in varying proportions, were also studied.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Quarterly (ISSN 0036-0821); 15; 24-30
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  • 24
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    Thermoplastic composite matrices with improved solvent resistance (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: In order to improve solvent resistance of aromatic thermoplastic polymers, ethynyl-terminated aromatic sulfone polymers (ETS), sulfone/ester polymers (SEPE) containing pendent ethynyl groups, and phenoxy resin containing pendent ethynyl groups are synthesized. Cured polysulfones and phenoxy resins containing ethynyl groups on the ends or pendent on the molecules exhibited systematic behavior in solvent resistance, film flexibility, and toughness as a function of crosslink density. The film and composite properties of a cured solvent-resistant ETS were better than those of a commercially available solvent sensitive polysulfone. The study was part of a NASA program to better understand the trade-offs between solvent resistance, processability and mechanical properties which may be useful in designing composite structures for aerospace vehicles.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Journal (ISSN 0091-1062); 20; 18-23
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  • 25
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    Polyimides formulated from a partially fluorinated diamine for aerospace tribological applications (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Preliminary pribological studies on polyimides formulated from the diamine 2,2-bis 4-(4-aminophenoxy)phenyl hexafluoropane (4-BDAF) indicate that polyimides formulated from this diamine have excellent potential for high temperature tribological applications. The dianhydrides used to make the polyimides were pyromellitic (PMDA) and benzophenonetetracarboxylic acid (BTDA). Friction and wear studies at 25 and 200 C indicate that polyimides formulated using 50 mole percent of the PMDA dianhydride and 50 mole percent of the BTDA dianhydride perform better than polyimides formulated solely with the BTDA dianhydride. Graphite fiber reinforced polyimide composites were formulated with the polyimide made from the BTDA dianhydride and both graphitic and non-graphitic fibers were evaluated. Graphitic fibers produced better tribological results, since thin, flowing, 'layer-like' transfer films were produced which did not build up with long sliding durations. Non-graphitic fibers did not produce this type of transfer. Previously announced in STAR as N83-22423
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: ASLE Transactions; 27; 189-196
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  • 26
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    Ceramic-coated metals can survive contact with hot working fluid (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Thermal barrier coatings (TBCs) have been developed as a means of protecting turbine blades and other engine hot section components whose surfaces are exposed to the most extreme operating conditions. By adding a thin, insulating ceramic oxide layer to an air-cooled turbine blade, the difference between the gas temperature and the metal temperature is further increased as a function of ceramic coating thickness, heat flux, and oxide thermal conductivity. An 0.04-cm thick ceramic layer can typically yield a 100-300 C temperature drop. Of the various techniques available for the deposition of thermal barrier coatings, the most common is that of plasma spraying. Significant improvements have been made in TBC durability through the use of bond coat compositions with increased oxidation resistance.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Research and Development (ISSN 0160-4074); 26; 122-125
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  • 27
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    New phosphorus-containing bisimide resins (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Phosphorus-based flame retardants have been effectively used in a wide variety of polymeric materials. Such additives, however, may either influence the decomposition reaction in polymers or lack durability due to a tendency to be leached out by solvents. Attention is given to the synthesis, characterization, thermal stability and degradation mechanisms of bisimide resins, and an evaluation is conducted of the flammability and mechanical properties of graphite cloth-reinforced laminates fabricated from one of the six phosphorus-containing bisimide resins considered.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: IN: Contemporary topics in polymer science. Volume 4. New York; 115-139
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  • 28
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    Thermal oxidative degradation reactions of linear perfluoroalkyl ethers (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Thermal and thermal oxidative stability studies were performed on linear perfluoroalkyl ether fluids. The effect on degradation by metal catalysts and degradation inhibitors is reported. The linear perfluoroalkyl ethers are inherently unstable at 316 C in an oxidizing atmosphere. The metal catalysts greatly increased the rate of degradation in oxidizing atmospheres. In the presence of these metals in an oxidizing atmosphere, the degradation inhibitors were highly effective in arresting degradation at 288 C. However, the inhibitors had only limited effectiveness at 316 C. The metals promote degradation by chain scission. Based on elemental analysis and oxygen consumption data, the linear perfluoroalkyl ether fluids have a structural arrangement based on difluoroformyl and tetrafluoroethylene oxide units, with the former predominating. Previously announced in STAR as N82-26468
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: I&EC - Industrial and Engineering Chemistry, Product Research and Development (ISSN 0196-4321); 22; 166-170
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  • 29
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    Large-area silicon sheet technology status in United States' Department of Energy photovoltaics programs (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: International Journal of Solar Energy (ISSN 0142-5919); 2; 171-187
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  • 30
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    Fracture mechanics of cellular glass (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The fracture mechanics of cellular glasses (for the structural substrate of mirrored glass for solar concentrator reflecting panels) are discussed. Commercial and developmental cellular glasses were tested and analyzed using standard testing techniques and models developed from linear fracture mechanics. Two models describing the fracture behavior of these materials were developed. Slow crack growth behavior in cellular glass was found to be more complex than that encountered in dense glasses or ceramics. The crack velocity was found to be strongly dependent upon water vapor transport to the tip of the moving crack. The existence of a static fatigue limit was not conclusively established, however, it is speculated that slow crack growth behavior in Region 1 may be slower, by orders of magnitude, than that found in dense glasses. Previously announced in STAR as N82-11209
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  • 31
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    Simulated space radiation effects on dielectrics and coatings (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Simulation tests of space radiation have been performed for specific organic and inorganic materials. The test results for fifteen materials exposed to protons and five exposed to electrons are presented.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: IEEE Transactions on Nuclear Science (ISSN 0018-9499); NS-30; 4090-409
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  • 32
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    The effect of annealing on the creep of plasma-sprayed ceramics (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The creep of plasma sprayed ZrO2-8Y2O3 was measured at temperatures from 98 to 1250 C (180 to 220 F), and compared to creep of identical samples after annealing at temperatures from 98 to 1316 C (1800 to 2400 F). Loads and temperatures which produced significant creep of as sprayed ceramics produced no creep after annealing. Previously announced in STAR as N83-24799
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 4; 819-827
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  • 33
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    Residual stress in plasma-sprayed ceramic turbine tip and gas-path seal specimens (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The residual stresses in a ceramic sheet material used for turbine blade tip gas path seals, were estimated. These stresses result from the plasma spraying process which leaves the surface of the sheet in tension. To determine the properties of plasma sprayed ZrO2-Y2O3 sheet material, its load deflection characteristics were measured. Estimates of the mechanical properties for sheet materials were found to differ from those reported for plasma sprayed bulk materials. Previously announced in STAR as N83-28380
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 4; 802-809
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  • 34
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    Correlation of compressive and shear stress with spalling of plasma-sprayed ceramic materials (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Ceramics on metal substrates for potential use as high temperature seals or other applications are exposed to forces originating from differences in thermal expansion between the ceramic and the metal substrate. This report develops a relationship between the difference in expansion of the ceramic and the substrate, defines conditions under which shear between the ceramic and the substrate occurs, and those under which bending forces are produced in the ceramic. The off-axis effect of compression forces resulting from high temperature plastic flow of the ceramic producing buckling of the ceramic is developed. Shear is associated with the edge or boundary stresses on the component while bending is associated with the distortion of an interior region. Both modes are significant in predicting life of the ceramic. Previously announced in STAR as N83-27016
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 4; 810-818
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  • 35
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    Life modeling of atmospheric and low pressure plasma-sprayed thermal-barrier coating (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The cycles-to-failure vs cycle duration data for three different thermal barrier coating systems, which consist of atmospheric pressure plasma-sprayed ZrO2-8 percent Y2O3 over similarly deposited or low pressure plasma sprayed Ni-base alloys, are presently analyzed by means of the Miller (1980) oxidation-based life model. Specimens were tested at 1100 C for heating cycle lengths of 1, 6, and 20 h, yielding results supporting the model's value.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 5; 470-478
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  • 36
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    Mechanical property measurements of plasma-sprayed thermal-barrier coatings subjected to oxidation (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Techniques have been developed for measuring the tensile properties of plasma-sprayed coatings which are used in thermal barrier applications. The measurements have included the average Young's modulus, bond strength and elongation at failure. The oxidation behavior of the bond coat plays an important role in the integrity and adhesion of plasma-sprayed thermal barrier coatings. This work studies the nature of the high temperature degradation on the mechanical properties of the coating. Furnace tests have been carried out on U-700 alloy with bond coats of NiCrAlY or NiCrAlZr and an overlay of ZrO2-8 percent Y2O3. Weight gain measurements on the coatings have been examined with relation to the adhesion strength and failure observations. The results from an initial study are reported in this work.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 5; 479-490
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  • 37
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    Ethynyl-terminated polyarylates - Synthesis and characterization (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Hydroxy-terminated polyarylates (HTPA) with number-average molecular weights of approximately 2500, 5000, 7500, and 10,000 were synthesized and converted to corresponding 4-ethynylbenzoyloxy-terminated polyarylates (ETPA) by reaction with 4-ethynylbenzoyl chloride. The terminal ethynyl groups were thermally reacted to provide chain extension and crosslinking. The cured ETPA exhibited higher glass transition temperatures (Tg) and better solvent resistance than a high molecular weight linear polyarylate. Solvent resistance was further improved by curing 2,2-bis(4-ethynylbenzoyloxy-4-prime-phenyl) propane, a coreactant, with ETPA at concentrations of approximately 10 percent (w/w).
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Polymer Science: Polymer Chemistry Edition (ISSN 0360-6376); 22; 3011-302
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  • 38
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    The development of aerospace polyimide adhesives (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Few materials are available which can be used as aerospace adhesives at temperatures in the range of 300 C. The Materials Division at NASA-Langley Research Center developed several high temperature polyimide adhesives to fulfill the stringent needs of current aerospace programs. These adhesives are the result of a decade of basic research studies on the structure property relationships of both linear and addition aromatic polyimides. The development of both in house and commercially available polyimides is reviewed with regards to their potential for use as aerospace adhesives.
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  • 39
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    Polyimides - Tribological properties and their use as lubricants (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Friction, wear, and wear mechanisms of several different polyimide films, solid bodies, composites, and bonded solid lubricant films are compared and discussed. In addition, the effect of such parameters as temperatures, type of atmosphere, contact stress, and specimen configuration are investigated. A friction and wear transition occurs in some polyimides at elevated temperatures and this transition is related to molecular relaxations that occur in polyimides. Friction and wear data from an accelerated test (pin-on-disk) are compared to similar data from an end use test device (plain spherical bearing), and to other polymers investigated in a similar geometry.
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  • 40
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    Polyimide characterization studies - Effect of pendant alkyl groups (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The effect on selected polyimide properties when pendant alkyl groups were attached to the polymer backbone was investigated. A series of polymers were prepared using benzophenone tetracarboxylic acid dianhydride (BTDA) and seven different p-alkyl-m,p'-diaminobenzophenone monomers. The alkyl groups varied in length from C(1) (methyl) to C(9) (nonyl). The polyimide prepared from BTDA and m,p'-diaminobenzophenone was included as a control. All polymers were characterized by various chromatographic, spectroscopic, thermal, and mechanical techniques. Increasing the length of the pendant alkyl group resulted in a systematic decrease in glass transition temperature (Tg) for vacuum cured films. A 70 C decrease in Tg to 193 C was observed for the nonyl polymer compared to the Tg for the control. A corresponding systematic increase in Tg indicative of crosslinking, was observed for air cured films. Thermogravimetric analysis revealed a slight sacrifice in thermal stability with increasing alkyl length. No improvement in film toughness was observed.
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  • 41
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    Rheological characterization of addition polyimide matrix resins and prepregs (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Although graphite-reinforced polyimide matrix composites offer outstanding specific strength and stiffness, together with high thermal oxidative stability, processing problems connected with their rheological behavior remain to be addressed. The present rheological studies on neat polyimide resin systems encountered outgassing during cure. A staging technique has been developed which can successfully handle polyimide samples, and novel methods were applied to generate rheological curves for graphite-reinforced prepregs. The commercial graphite/polyimide systems studied were PRM 15, LARC 160, and V378A.
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  • 42
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    A thermoplastic polyimidesulfone (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A polymer system has been prepared which has the excellent thermoplastic properties generally associated with polysulfones, and the solvent resistance and thermal stability of aromatic polyimides. This material, with improved processability over the base polyimide, can be processed in the 260-325 C range in such a manner as to yield high quality, tough unfilled moldings; strong, high-temperature-resistant adhesive bonds; and well consolidated, graphite-fiber-reinforced moldings (composites). The unfilled moldings have physical properties that are similar to aromatic polysulfones which demonstrates the potential as an engineering thermoplastic. The adhesive bonds exhibit excellent retention of initial strength levels even after thermal aging for 5000 hours at 232 C. The graphite-fiber-reinforced moldings have mechanical properties which makes this polymer attractive for the fabrication of structural composites.
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  • 43
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    Spherical microglass particle impingement studies of thermoplastic materials at normal incidence (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Light optical and scanning electron microscope studies were conducted to characterize the erosion resistance of polymethyl methacrylate (PMMA), polycarbonate (PC), polytetrafluoroethylene (PTFE) and ultra-high-molecular-weight-polyethylene (UHMWPE). Erosion was caused by a jet of spherical micro-glass beads at normal impact. During the initial stages of damage, the surfaces of these materials were studied using a profilometer. Material buildup above the original surface was observed on PC and PMMA. As erosion progressed, this buildup disappeared as the pit became deeper. Little or no buildup was observed on PTFE and on UHMWPE. UHMWPE and PTFE are the most resistant materials and PMMA the least. Favorable properties for high erosion resistance seem to be high values of ultimate elongation, and strain energy and a low value of the modulus of elasticity. Erosion-rate-versus-time curves of PC and PTFE exhibit incubation, acceleration and steady state periods. A continuously increasing erosion rate period was observed however for PMMA instead of a steady state period. At early stages of damage and at low impact pressure material removal mechanisms appear to be similar to those for metallic materials.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: ASLE Transactions; 27; 373-379
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  • 44
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    Thermogravimetric analysis of silicon carbide-silicon nitride polycarbosilazane precursor during pyrolysis from ambient to 1000 C (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Thermogravimetric analysis data are presented on the unmeltable polycarbosilazane precursor of silicon carbide-silicon nitride fibers, over the room temperature-1000 C range in a nitrogen atmosphere, in order to establish the weight loss at various temperatures during the precursor's pyrolysis to the fiber material. The fibers obtained by this method are excellent candidates for use in applications where the oxidation of carbon fibers (above 400 C) renders them unsuitable.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Materials Science Letters (ISSN 0261-8028); 3; 802-804
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  • 45
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    Ultrasonic mixing of epoxy curing agents (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A new technique for mixing solid curing agents into liquid epoxy resins using ultrasonic energy was developed. This procedure allows standard curing agents such as 4,4 prime-diaminodiphenyl sulfone (4,4 prime-DDS) and its 3,3 prime-isomer, (3,3 prime-DDS) to be mixed without prior melting of the curing agent. It also allows curing agents with very high melt temperatures such as 4,4 prime-diaminodiphenyl sulfone (4,4 prime-DDS) and its 3,3 prime-isomer, (3,3 prime-DDS) to be mixed without prior melting of the curing agent. It also allows curing agents with very high melt temperatures such as 4,4 prime-diaminobenzophenone (4,4 prime-DABP) (242 C) to be mixed without premature curing. Four aromatic diamines were ultrasonically blended into MY-720 epoxy resin. These were 4, 4 prime-DDS; 3,3 prime-DDA; 4, 4 prime-DABP and 3,3 prime-DABP. Unfilled moldings were cast and cured for each system and their physical and mechanical properties compared. Previously announced in STAR as N83-27018
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Quarterly (ISSN 0036-0821); 14; 46-50
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  • 46
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    Hardness of dense beta-Si3N4 (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The effects of small changes in the concentration of an oxygen content densification aid on the room temperature microhardness of hot isostatically pressed and sintered beta-Si3N4 ceramics are studied. The compositions studied were Si3N4 containing 7 wt. pct BeSiN2, a fixed nonoxide densification aid, and 1.9-3.7 wt. pct oxygen as a second, variable densification aid. A proportional relationship between high density and high oxygen content, regardless of heat treatment type, is noted.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Materials Science Letters (ISSN 0261-8028); 2; 657-659
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  • 47
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    Stability of silica heat shield materials in the Space Shuttle environment (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Sample tiles of Space Shuttle reusable surface insulation (RSI) and fibrous refractory composite insulation (FRCI) have been alternately exposed to simulated mission heating and the Kennedy Space Center launch-pad environment for up to 50 cycles. The two types of tiles were coated with an identical glass composition. The coating on RSI tiles was prone to cracking in the test environment while the same coating on FRCI was not. Absorption of water contaminated with environmental deposits resulted in accelerated devitrification in the RSI tiles. Devitrification in FRCI tiles was significantly less. The rate of environmental degradation of tiles appeared to be dependent on the amount of water absorption.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 4; 564-577
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  • 48
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    Surface chemistry, friction, and wear of Ni-Zn and Mn-Zn ferrites in contact with metals (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to the surfaces of the ferrites in sliding. Previously announced in STAR as N83-19901
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 4; 674-693
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  • 49
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    Shrinkage of amorphous silica fibers (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: By the application of a new technique, the viscosity of amorphous silica fibers was determined in the 1100-1350 C temperature range. An equation was derived that describes the kinetics of shrinkage of the fibers in terms of their radius, viscosity, and surface tension.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 4; 492-501
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  • 50
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    Phase distributions in plasma-sprayed zirconia-yttria (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The distribution of phases in plasma-sprayed zirconia-yttria has been determined over a range of yttria levels from 0 to 26.1 molpct YO(1.5) using room temperature X-ray diffractometry. Pure, plasma-sprayed zirconia is composed almost entirely of the monoclinic phase. At levels of yttria between 4 and 10 percent, a quenched-in tetragonal phase predominates, and at higher levels the cubic phase predominates. The phase distributions are compared with previously reported test lives of thermal barrier coatings formed from these materials. Regions of optimal lives were found to correlate with regions having high amounts of the tetragonal phase, small but nonzero amounts of the monoclinic phase, and little or none of the cubic phase. Possible relationships between phase composition and coating performance are discussed.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society Bulletin (ISSN 0002-7812); 62; 1355-135
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  • 51
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    Development of plane strain fracture toughness test for ceramics using Chevron notched specimens (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Chevron-notched four-point-bend and short-bar specimens have been used to determine the fracture toughness of sintered aluminum oxide and hot-pressed silicon nitride ceramics. The fracture toughness for Si3N4 is found to be essentially independent of the specimen size and chevron notch configuration, with values ranging from 4.6 to 4.9 MNm exp -3/2. In contrast, significant specimen size and notch geometry effects have been observed for Al2O3, with the fracture toughness ranging from 3.1 to 4.7 MNm exp -3/2. These effects are attributed to a rising crack growth resistance curve for the Al2O3 tested.
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  • 52
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    Microstructural characterization of SiC (SCS) filaments (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Microstructural features of SiC('SCS') fibers demonstrating growth properties have been investigated using scanning and transmission electron microscopy. An etchant of fused KOH:KNO3 was developed which adequately brought out previously undetermined features.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Quarterly (ISSN 0036-0821); 14; 39-45
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  • 53
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    Dynamic and static fatigue of a machinable glass ceramic (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The dynamic and static fatigue behavior of a machinable glass ceramic was investigated to assess its susceptibility to stress corrosion-induced delayed failure. Fracture mechanics techniques were used to analyze the results so that lifetime predictions for components of this material could be made. The resistance to subcritical crack growth of this material was concluded to be only moderate and was found to be dependent on the size of its microstructure.
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  • 54
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    Friction and wear of ceramics (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The adhesion, friction, wear and lubricated behaviors of both oxide and non-oxide ceramics are reviewed. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as with metals. Grit size effects in two- and three-body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Wear (ISSN 0043-1648); 100; 333-353
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  • 55
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    Synthesis and characterization of a melt processable polyimide (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A melt processable polyimide which contains sulfur and oxygen bridges between the aromatic rings (BDSDA/APB) was synthesized and characterized. Its physical, mechanical, thermal and flow properties were determined as was its resistance to some of the more commonly used solvents. The melt flow properties were measured for the temperature range 250 C - 350 C and under the conditions (stress/strain) encountered in commercial processes.
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  • 56
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    Effects of intermediate-energy electrons on mechanical and molecular properties of a polyetherimide (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An experiment, using 100-keV electrons and 10 to the 9th -rad doses, was conducted on Ultem polyetherimide film. Mechanical, electron paramagnetic resonance, and infrared spectroscopic data suggested that the radiation produced crosslinking and embrittlement of the material.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: IEEE Transactions on Nuclear Science (ISSN 0018-9499); NS-31; 1293-129
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  • 57
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    Performance of thermal barrier coatings in high heat flux environments (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 C after 0.5 sec in the flame. An as-sprayed ZrO2-8 percent Y2O3 specimens survived 3000 of the 0.5 sec cycles with falling. Surface spalling was observed when 2.5 sec cycles were employed but this was attributed to uneven heating caused by surface roughness. This surface spalling was prevented by smoothing the surface with silicon carbide paper or by laser glazing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as 1 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12 percent Y2O3 or ZrO2-2O percent Y2O3 were shown to be unsuited for use under the high heat flux conditions of this study.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Thin Solid Films (ISSN 0040-6090); 119; 195-202
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  • 58
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    Surface tension of ZrF4-BaF2-LaF3 glass (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A solidified pendant drop technique is presently used in the measurement of surface tension of a 62 mol pct ZrF4, 33 mol pct BaF2, 5 mol pct LaF3 heavy metal-fluoride glass, in keeping with a requirement from a comparison experiment planned for microgravity conditions aboard the Space Shuttle. The surface tension at 550 C is 0.174 + or - 0.005 J/sq m.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society, Communications (ISSN 0002-7820); 67; C-197
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  • 59
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    Siloxane containing addition polyimides. II - Acetylene terminated polyimides (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Acetylene terminated polyimide oligomers having a range of molecular weights have been synthesized by reacting bis (gamma-aminopropyl) tetramethyldisiloxane, aminophenylacetylene and 3, 3', 4, 4' benzophenonetetracarboxylic dianhydride in different molar ratios. The prepolymers were isolated and characterized for melt flow and cure properties. They show promise as adhesives for bonding titanium to titanium and as matrix resins for graphite cloth reinforced composites. The most promising system has been blended in varying proportions with Thermid 600, a commercially available acetylene terminated polyimide oligomer, and the mixtures have been tested for application as composite matrix resins.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Quarterly (ISSN 0036-0821); 16; 6-12
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  • 60
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    Preparation and properties of silane-endcapped polyimide adhesives (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Silane-endcapped polyimide high temperature adhesive formulations were prepared by reacting anhydride-terminated poly(amic acid), obtained from benzophenonetetracarboxylic dianhydride and a diamine (3,3'-, 3,4'- or 4,4'-diaminodiphenylmethane and 3,3', 3,4'- or 4,4'-diaminobenzophenone) with varying amounts of gama-aminopropyltriethoxysilane in dimethylacetamide. Resin properties were evaluated by torsional braid analysis and thermogravimetric analysis. Lap shear strengths of some of the adhesive bonds were determined at room temperature and at 177 C before and after ageing at 200 C for 2500 h and after boiling in water for 72 h.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: International Journal of Adhesion and Adhesives (ISSN 0143-7496); 4; 129-132
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  • 61
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    Demonstration of a silicon nitride attrition mill for production of fine pure Si and Si3N4 powders (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: To avoid metallic impurities normally introduced by milling ceramic powders in conventional steel hardware, an attrition mill (high-energy stirred ball mill) was constructed with the wearing parts (mill body, stirring arms, and media) made from silicon nitride. Commercial silicon and Si3N4 powders were milled to fine uniform particles with only minimal contamination - primarily from wear of the sintered Si3N4 media.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society Bulletin (ISSN 0002-7812); 63; 1176-117
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  • 62
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    Recycling used lubricating oil at the deep space stations (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A comparison is made of the lubricating oil recycling methods used in the Deep Space Station 43 test and the basic requirements which could favor recycling of oil for continuous reuse. The basic conditions for successful recycling are compared to the conditions that exist in the Deep Space Network (DSN). This comparison shows that to recycle used oil in the DSN would not only be expensive but also nonproductive.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 239-246
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  • 63
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    Thermal stability and aging of some new anaerobic adhesives for structural binding (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Polyurethane-modified high impact anaerobic adhesives have been chosen for a bonding application where impact cushion is critical. These adhesives meet all the requirements for high rate production and automatic assembly techniques. With aluminum adherends, one selected adhesive cured at room temperature with the recommended activator retained sixty percent of its original impact strength after twenty-six week aging at 100 C. The impact strength aging, the thermogravimetric analysis results, the outgassing data, and other observations made in this work indicate that the adhesives cured by simple heating give a more durable bond than that cured with an activator at room temperature.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Quarterly; 11; July 198
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  • 64
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    Synthesis of perfluoroalkylether triazine elastomers (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: A method of perfluoroalkylether triazine elastomer synthesis is described. To form an elastomer, the resultant polymer is heated in a closed oven at slightly reduced pressures for 1-day periods at 100, 130 and 150 C. A high-molecular-weight perfluoroalkylether triazine elastomer is produced that exhibits thermal and oxidative stability. This material is potentially useful in applications such as high-temperature seals, 'O' rings, and wire enamels.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Polymer Science; vol. 18
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  • 65
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    Release-rate calorimetry of multilayered materials for aircraft seats (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Multilayered samples of contemporary and improved fire-resistant aircraft seat materials were evaluated for their rates of heat release and smoke generation. Top layers with glass-fiber block cushion were evaluated to determine which materials, based on their minimum contributions to the total heat release of the multilayered assembly, may be added or deleted. The smoke and heat release rates of multilayered seat materials were then measured at heat fluxes of 1.5 and 3.5 W/cm2. Abrasion tests were conducted on the decorative fabric covering and slip sheet to ascertain service life and compatibility of layers
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Quarterly; 11; Apr. 198
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  • 66
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    Morphological and frictional behavior of sputtered MoS2 films (1982)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: (Previously announced in STAR as N82-22387)
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 67
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    Phase stability in plasma-sprayed, partially stabilized zirconia-yttria (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 68
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    Novel improved PMR polyimides (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The development of a class of high-temperature-resistant resins known as PMR polyimides has been reported by Serafini et al. (1972). Serafini and Vannucci (1975) found that the lower formulated molecular weight (FMW) compositions exhibited increased resin flow, but with some sacrifice in elevated temperature thermo-oxidative stability. Vannucci (1977) reported that the resin flow characteristics of the PMR composition having an FMW of 1500 could be varied by controlling the degree of resin advancement or imidization. The current investigation is concerned with an alternative approach to obtain improved flow PMR polyimides without sacrificing the desirable thermo-oxidative characteristics. The new approach is based on the utilization of a chemically compatible flow modifying agent. This agent is N-phenylnadimide (PN). The determination of the processing characteristics and properties of PN modified PMR/Celion 6000 composites is discussed.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Journal; 17; Nov
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  • 69
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    Behavior of bubbles in glassmelts. III - Dissolution and growth of a rising bubble containing a single gas (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Finite difference solutions of the mass transport equations governing the dissolution (growth) of a rising gas bubble, containing a single gas, in a glassmelt were obtained. These solutions were compared with those obtained from an approximate procedure for a range of the controlling parameters. Applications were made to describe various aspects of O2 and CO2 gas-bubble behavior in a soda-lime-silicate melt.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society; vol. 64
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  • 70
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    The generation and morphology of single-crystal silicon carbide wear particles under adhesive conditions (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Sliding friction experiments were performed in vacuum at room temperature on a plane-type SiC surface in contact with iron-based binary alloys. Multiangular and spherical wear particles were found to form as a result of multipass sliding. The multiangular particles were produced by primary and secondary cracking of the 0001, 10(-)10, and 11(-)20 plane-type cleavage planes under the Hertzian stress field or local inelastic deformation zone. When alloy surfaces are in contact with silicon carbide under a load of 0.2 N, the alloy around the contact area is subjected to stresses that are close to the elastic limit in the elastic deformation region and/or exceed it. It was also found that spherical wear particles may be produced by two mechanisms: a penny-shaped fracture along the circular stress trajectories under the local inelastic deformation zone, and the attrition and fatigue of wear particles.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Wear; 67; Apr. 1
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  • 71
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    Dissolution of multicomponent bubbles (1980)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The behavior of an isolated, stationary, multicomponent gas bubble in a glassmelt containing several dissolved gases is considered. The relevant mass-transport equations are formulated and calculations are performed for the case of two diffusing gases using a quasi-stationary model and a numerical solution of the exact mass-transfer equations. The results obtained from these two approaches are compared. The factors which govern the dissolution or growth of a bubble are thermodynamic and kinetic in origin. The tendency of a bubble to grow or shrink at long times is controlled by departure from overall equilibrium, whereas the short-time bubble dynamics may be dominated by kinetic effects. As a result of the existence of these dual influences, maxima and/or minima occur in the functional dependence of the bubble radius on time.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society; vol. 63
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  • 72
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    Photosensitized oxidation of unsaturated polymers (1980)
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    Publikationsdatum: 2011-08-17
    Beschreibung: A review of the photosensitized oxidation of singlet oxygenation of unsaturated hydrocarbon polymers and of their model compounds is presented. The cis and trans forms of 1,4-polyisoprene, 1,4-polybutadiene and 1,2-poly(1,4-hexadiene) are studied, and their microstructural changes which occur on reaction with (IO2) in solution were investigated by infrared, (H-1) and (C-13) NMR spectroscopy. The polymers yielded allylic hydroperoxides with shifted double bonds according to the 'ene' mechanism of simple olefins. It was shown that single oxygenation of unsaturated polymers is similar to their low molecular weight analogs, and that the differences are due to secondary processes affecting the (IO2)-reacted polymers.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Pure and Applied Chemistry; 52; 1980
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  • 73
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    Effect of CeO2, MgO and Y2O3 additions on the sinterability of a milled Si3N4 with 14.5 wt% SiO2 (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The sinterability of alpha Si3N4 with 0-5.07 equivalent per cent of CeO2, MgO, or Y2O3 has been studied in the temperature range 1650-1820 C by density measurements and X-ray diffraction analysis. Maximum densities were obtained in the range 1765-1820 C and were 99.6% of theoretical with 2.5% CeO2; 98.5% of theoretical with 1.24 to 1.87% MgO, and 99.2% of theoretical with 2.5% Y2O3. Densities 94% or more of theoretical value were obtained with as little as 0.62 equivalent per cent additive.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Materials Science; 16; Mar. 198
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  • 74
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    Performance of Chevron-notch short bar specimen in determining the fracture toughness of silicon nitride and aluminum oxide (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Ease of preparation and testing are advantages unique to the chevron-notch specimen used for the determination of the plane strain fracture toughness of extremely brittle materials. During testing, a crack develops at the notch tip and extends stably as the load is increased. For a given specimen and notch configuration, maximum load always occurs at the same relative crack length independent of the material. Fracture toughness is determined from the maximum load with no need for crack length measurement. Chevron notch acuity is relatively unimportant since a crack is produced during specimen loading. In this paper, the authors use their previously determined stress intensity factor relationship for the chevron-notch short bar specimen to examine the performance of that specimen in determining the plane strain fracture toughness of silicon nitride and aluminum oxide.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Testing and Evaluation; 8; May 1980
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  • 75
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    Fracture toughness determination of Al2O3 using four-point-bend specimens with straight-through and chevron notches (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society; vol. 63
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  • 76
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    Physical aging of linear and network epoxy resins (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Network and linear epoxy resins principally based on the diglycidyl ether of bisphenol-A and its oligomers are prepared and studied using diamine and anhydride crosslinking agents. Rubber modified epoxies and a carbon fiber reinforced composite are also investigated. All materials display time-dependent changes when stored at temperatures below the glass transition temperature after quenching (sub-T/g/ annealing). Solvent sorption experiments initiated after different sub-T(g) annealing times demonstrate that the rate of solvent uptake can be indirectly related to the free volume of the epoxy resins. Residual thermal stresses and water are found to have little effect on the physical aging process, which affects the sub-T(g) properties of uniaxial carbon fiber reinforced epoxy material. Finally, the importance of the recovery phenomenon which affects the durability of epoxy glasses is considered.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 77
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    An overview of the nonequilibrium behavior of polymer glasses (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is pointed out that research efforts are at present being directed in two areas, one comprising experimental studies of this phenomenon in various glassy polymer systems and the other involving the development of a quantitative theory capable of satisfactorily predicting aging behavior for a variety of polymer materials under different conditions. Recent work in both these areas is surveyed. The basic principles of nonequilibrium behavior are outlined, with emphasis placed on changes in material properties with annealing below the glass transition temperature. Free volume theory and thermodynamic theory are discussed.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 78
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    Effect of gamma irradiation on the friction and wear of ultrahigh molecular weight polyethylene (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The effect of sterilization gamma irradiation on the friction and wear properties of ultrahigh molecular weight polyethylene (UHMWPE) sliding against stainless steel 316L in dry air at 23 C is investigated, the results to be used in the development of artificial joints which are to surgically replace diseased human joints. A pin-on-disk sliding friction apparatus is used, a constant sliding speed in the range 0.061-0.27 m/s is maintained, a normal load of 1 kgf is applied with dead weight, and the irradiation dose levels are: 0, 2.5, and 5.0 Mrad. Wear and friction data and conditions for each of the ten tests are summarized, and include: (1) wear volume as a function of the sliding distance for the irradiation levels, (2) incremental wear rate, and (3) coefficient of friction as a function of the sliding distance. It is shown that (1) the friction and wear properties of UHMWPE are not significantly changed by the irradiation doses of 2.5 and 5.0 Mrad, (2) the irradiation increases the amount of insoluble gel as well as the amount of low molecular weight material, and (3) after run-in the wear rate is either steady or gradually decreases as a function of the sliding distance.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Wear; 70; July 15
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  • 79
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    Sinterability, strength and oxidation of alpha silicon carbide powders (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: An investigation is made of pressureless sintering of commercially available alpha-SiC powders at temperatures between 1900 and 2150 C for periods of 10 to 240 min under one atmosphere of argon pressure. It is found that alpha-SiC powder containing boron and carbon sintering aids is sinterable at 2150 C for a period of 30 min to a high final density (greater than 96 percent of theoretical). In alpha-SiC powder containing aluminum and carbon sintering aids, the final density achieved is only about 80 percent of theoretical. Determinations are made of room temperature and high temperature (1370 C) flexure strength and oxidation resistance on sintered high density (more than 96 percent of theoretical) alpha-SiC (boron, carbon) material. It is found that both the strength and the resistance to oxidation are equivalent and comparable to those of the sintered alpha-SiC which represents the state of the art.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Materials Science (ISSN 0022-2461); 19; 1307-131
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  • 80
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    Study of molecular deformation mechanisms in the glassy state. I - Temperature effect on stress-birefringence and strain-birefringence responses of poly(methyl methacrylate) (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Polymer Science: Polymer Physics Edition (ISSN 0098-1273); 21; 1647-166
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  • 81
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    Electrically conductive black optical paint (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: An electrically conductive flat black paint has been developed for use on the Galileo spacecraft which will orbit Jupiter in the late 1980s. The paint, designed for equipment operating in high-energy radiation fields, has multipurpose functions. Its electrical conductivity keeps differential charging of the spacecraft external surfaces and equipment to a minimum, preventing the buildup of electrostatic fields and arcing. Its flat black aspect minimizes the effects of stray light and unwanted reflectances, when used in optical instruments and on sunshades. Its blackness is suitable, also, for thermal control, when the paint is put on spacecraft surfaces. The paint has good adherence properties, as measured by tape tests, when applied properly to a surface. The electrically conductive paint which was developed has the following characteristics: an electrical resistivity of 5 x 10 to the 7th ohms per square; a visual light total reflectance of approximately 5 percent; an infrared reflectance of 0.13 measured over a spectrum from 10 to the (-5.5) power to 0.001 meter; a solar absorptivity, alpha-s, of 0.93, and a thermal emissivity, epsilon, of 0.87, resulting in an alpha-s/epsilon of 1.07. The formula for making the paint and the process for applying it are described.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 82
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    Characteristics of Si3N4-SiO2-Ce2O3 compositions sintered in high-pressure nitrogen (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Full-density Si3N4-SiO2-Ce2O3 compositions were prepared by sintering with 2.5 MPa nitrogen pressure at temperatures of 1900 and 2090 C. Room-temperature flexural strengths near 700 MPa for sintered material compared favorably with the strength of hot-pressed material. At 1370 C, where flexural strengths as high as 363 MPa were obtained, it was observed that the coarsest structure was the strongest and the finest structure was the weakest. One of the compositions tested, Si3N4-8.7 wt pct SiO2-8.3 wt pct-Ce2O3, was found to have excellent 200-h oxidation resistance at 700, 1000, and 1370 C, without incidence of 700 to 1000 C phase instability and cracking.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society, Journal (ISSN 0002-7820); 66; 835-841
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  • 83
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    Performance of laser-glazed zirconia thermal barrier coatings in cyclic oxidation and corrosion burner rig tests (1982)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: (Previously announced in STAR as N82-22346)
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 84
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    Some properties of r.f.-sputtered hafnium nitride coatings (1982)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: (Previously announced in STAR as N82-21331)
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 85
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    Sputtered silicon nitride coatings for wear protection (1982)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: (Previously announced in STAR as N82-20314)
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 86
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    The combined effects of Fe and H2 on the nitridation of silicon (1982)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: In view of the support offered by previous work for the suggestion that Fe may affect alpha-Si3N4 formation and microstructural development, a two-part study was conducted to differentiate the effects of H2 and Fe in, first, the nitridation of pure and of Fe-containing powder in N2 and N2-4% H2, and then the nitridation of (1 1 1) Si single crystal wafers with and without Fe powder on the surface. The degree of nitridation is most strongly affected by H2 at 1200 C, but by Fe at 1375 C, where Fe-containing samples in either atmosphere were almost completely nitrided. While neither H2 nor Fe alone changed the ratio of alpha-Si3N4 to beta-Si3N4, the combination of H2 and Fe increased it at both temperatures.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Materials Science Letters; 1; Aug. 198
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  • 87
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    Experimental studies of the vapor phase nucleation of refractory compounds. I - The condensation of SiO (1982)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The critical partial pressure of SiO necessary to initiate avalanche nucleation in the SiO-H2 system is measured as a function of the ambient temperature in the range 750-1000 K. Results show that the condensate produced at low temperatures is Si2O3, while a mixture of Si2O3 and amorphous SiO2 is produced at high temperatures. A surface energy of approximately 500 ergs/sq cm for the particles is found by analyzing the critical partial pressure vs temperature using classical nucleation theory. It is concluded that classical nucleation theory is not applicable to this system, because several inconsistencies in the thermodynamic analysis are demonstrated, and it is suggested that a kinetic theory of nucleation may be the preferential way to describe the condensation process.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Chemical Physics; 77; Sept. 1
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  • 88
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    Infrared spectroscopic analysis of the effects of simulated space radiation on a polyimide (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Infrared spectroscopic techniques have been used to study the effects of electron radiation on the polyimide PMDA-p,p-prime- ODA. The radiation exposures were made at various dose rates, for a total dose approximately equal to that for 30 years of exposure to electron radiation in geosynchronous earth orbit. At high dose rates the major effect was probably the formation of a polyisoimide or a charged quaternary amine, and at the low dose rates the effect was a reduction in the amount or aromatic ether linkage. In addition, the effects of dose rate for a small total dose were studied. Elevated temperatures occurred at high dose rates and were, in part, probably the cause of the radiation product. The data suggest that dose rates for accelerated simulations of the space environment should not exceed 100,000 rads/sec.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 89
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    Adhesive and composite evaluation of acetylene-terminated phenylquinoxaline resins (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A series of acetylene-terminated phenylquinoxaline (ATPQ) oligomers of various molecular weights were prepared and subsequently chain extended by the thermally induced reaction of the ethynyl groups. The processability and thermal properties of these oligomers and their cured resins were compared with that of a relatively high molecular weight linear polyphenylquinoxaline (PPQ) with the same chemical backbone. The ATPQ oligomers exhibited significantly better processability than the linear PPQ but the PPQ displayed substantially better thermooxidative stability. Adhesive (Ti/Ti) and composite (graphite filament reinforcement) work was performed to evaluate the potential of these materials for structural applications. The PPQ exhibited better retention of adhesive and laminate properties than the ATPQ resins at 260 C after aging for 500 hr at 260 C in circulating air.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Polymer Engineering and Science; 21; 16, N; Nov. 198
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  • 90
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    Compliance calibration of the short rod chevron-notch specimen for fracture toughness testing of brittle materials (1982)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The short rod chevron-notch specimen has the advantages of (1) crack development at the chevron tip during the early stage of test loading, and (2) convenient calculation of plane-strain fracture toughness from the maximum test load and from a calibration factor which depends only on the specimen geometry and manner of loading. For generalized application, calibration of the specimen over a range of specimen proportions and chevron-notch configurations is necessary. Such was the objective of this investigation, wherein calibration of the short rod specimen was made by means of experimental compliance measurements converted into dimensionless stress intensity factor coefficients.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: International Journal of Fracture; 18; Feb. 198
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  • 91
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    Short-term stability of high-silica glasses (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The devitrification characteristics of high-silica (70-90%) glasses for use in potential higher temperature coatings on advanced insulation systems for space vehicles were determined at 1260 C after 24 h. These data indicate that additives can be used to maintain the stability of these coatings relative to cristobalite formation.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings; 2; July-Aug
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  • 92
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    Dynamics of solid dispersions in oil during the lubrication of point contacts. II - Molybdenum disulfide (1982)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: (Previously announced in STAR as N81-20275)
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 93
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    Test methodology for evaluation of fireworthy aircraft seat cushions (1982)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Aircraft seat materials were evaluated in terms of their thermal performance. The materials were evaluated using (a) thermogravimetric analysis, (b) differential scanning calorimetry, (c) a modified NBS smoke chamber to determine the rate of mass loss and (d) the NASA T-3 apparatus to determine the thermal efficiency. In this paper, the modified NBS smoke chamber will be described in detail since it provided the most conclusive results. The NBS smoke chamber was modified to measure the weight loss of materials when exposed to a radiant heat source over the range of 2.5 to 7.5 W/cm sq. This chamber has been utilized to evaluate the thermal performance of various heat blocking layers utilized to protect the polyurethane cushioning foam used in aircraft seats. Various kinds of heat blocking layers were evaluated by monitoring the weight loss of miniature seat cushions when exposed to the radiant heat. The effectiveness of aluminized heat blocking systems was demonstrated when compared to conventional heat blocking layers such as neoprene. All heat blocking systems showed good fire protection capabilities when compared to the state-of-the-art, i.e., wool-nylon over polyurethane foam.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Fire and Flammability; 13; Jan. 198
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  • 94
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    The failure strengths of perfect diamond crystals (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Finite elasticity analysis is extended to the 110 direction, where off axis strain symmetry is not present, and the third order elastic data are obtained for diamond. The compressive yield strengths of perfect diamond crystals loaded in the 100, 110, and 111 directions are predicted to be 2.2, 5.6, and 2.8 Mbars, respectively, while the corresponding tensile fracture strengths are 1.0, 0.5, and 0.5 Mbars. From these results and from Hertz theory it is predicted that ring fracture of spherically tipped diamonds pressed against a flat will occur at pressures of 1.8-1.9 Mbars, substantially below the yield pressure (above 3 Mbars). Modification of the tip shape leads to a predicted increase in the pressure at which fracture occurs.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Scripta Metallurgica; 15; May 1981
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  • 95
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    Microstructure and property characterization of sintered Si3N4, SiC, and SiAlON (1982)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Commercially-produced, pressureless sintered Si3N4, SiC, and SiAlON were characterized with respect to density, phases present, bend strength, and oxidation resistance. The room-temperature bend strengths of sintered Si3N4, SiC, and SiAlON are comparable. However, the room-temperature strengths are much lower (approximately 40 to 50%) than the room-temperature strength of hot-pressed Si3N4 (NC-132). The strength loss in Si3N4 and SiAlON materials at high temperature was attributed to a viscous grain-boundary phase, retained during cooling from the sintering temperature. The oxidation resistance of sintered alpha-SiC was the best of any materials tested.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society; vol. 65
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  • 96
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    Behavior of bubbles in glassmelts. II - Dissolution of a stationary bubble containing a diffusing and a nondiffusing gas (1980)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The effect of a foreign nondiffusing gas on the rate of shrinkage of an oxygen bubble in a soda-lime-silica melt was studied. The rate of change of bubble radius with time was computed using the quasi-stationary approximation. The effects of melt undersaturation and initial fraction of foreign gas in the bubble are considered and compared with those calculated using previously derived expressions.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society; vol. 63
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  • 97
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    Molecular deformation and stress-strain behavior of poly(bisphenol-A-diphenyl sulfone) (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The strain-birefringence response of poly(bisphenol-A-diphenyl sulfone) is found to be independent of temperature at temperatures below -100 C; at higher temperatures, the response becomes slightly dependent on temperature, with lower birefringence seen at higher temperatures. The stress-strain behavior and the stress-birefringence response both depend on temperature over the entire testing temperature range (-179 C to 150 C) studied; this dependence, however, is not pronounced. The evidence is seen as suggesting that the polymer molecules respond to deformation by undergoing conformational rearrangements; the mode of the molecular deformation remains unchanged for temperatures of -100 C or lower. At higher temperatures, the average length of the chain segments involved in the rearrangement increases. The stress-strain response is attributed mainly to chain orientation. The entropic contribution deriving from chain orientation at temperatures below -100 C is still substantial. The modest temperature dependence of the stress-strain response suggests that the energy barriers for the chain segments involved in the rearrangement are relatively low.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Applied Physics (ISSN 0021-8979); 54; Oct. 198
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  • 98
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    Photothermal degradation of ethylene/vinylacetate copolymer (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Photothermal degradation studies were conducted on a 'stabilized' formulation of ethylene/vinyl acetate copolymer (EVA) in the temperature range 25-105 C under three different oxygen environments (in open air, with limited access to O2, and in a dark closed stagnant oven). These studies were performed in order to evaluate the utility of EVA as an encapsulation material for photovoltaic modules. Results showed that at low temperature (25 C), slow photooxidation of the polymer occurred via electronic energy transfer involving the UV absorber incorporated in the polymer. However, no changes in the physical properties of the bulk polymer were detected up to 1500 hours of irradiation. At elevated temperatures, leaching and evaporation of the additives occurred, which ultimately resulted in the chemical crosslinking of the copolymer and the formation of volatile photoproducts such as acetic acid.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 99
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    The structure of boron in boron fibres (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The structure of noncrystalline, chemically vapour-deposited boron fibres was investigated by computer modelling the experimentally obtained X-ray diffraction patterns. The diffraction patterns from the models were computed using the Debye scattering equation. The modelling was done utilizing the minimum nearest-neighbour distance, the density of the model, and the broadening and relative intensity of the various peaks as boundary conditions. The results suggest that the fibres consist of a continuous network of randomly oriented regions of local atomic order, about 2 nm in diameter, containing boron atoms arranged in icosahedra. Approximately half of these regions have a tetragonal structure and the remaining half a distorted rhombohedral structure. The model also indicates the presence of many partial icosahedra and loose atoms not associated with any icosahedra. The partial icosahedra and loose atoms indicated in the present model are in agreement with the relaxing sub-units which have been suggested to explain the anelastic behavior of fibre boron and the loosely bound boron atoms which have been postulated to explain the strengthening mechanism in boron fibres during thermal treatment.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Materials Science (ISSN 0022-2461); 18; Sept
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    A new brominated polymeric additive for flame retardant glass-filled polybutylene terephthalate (1982)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Attention is called to the undesirable effects (poor ultraviolet light stability and blooming) sometimes introduced by brominated flame retarders. A brominated polymeric additive (BPA) with little or none of these undesirable side effects is compared with decabromobiphenyl oxide (DBBPO). The additive bears the product name F-2300. It is found to be more easily dispersed than DBBPO. The F-2300 is as effective as the DBBPO in the oxygen index test. The improved efficiency of the F-2300 may be explained by its better dispersion in polybutylene terephthalate (PBT). Glass-filled PBT containing F-2300 is found to be more resistant to UV degradation than DBBPO-containing formulas. Formulations with F-2300 therefore have a longer useful outdoor life. F-2300 is a diglycidyl-type polymer containing 50 percent aromatically bound bromine. Its melting point is 112 C, and it is stable up to 372 C. It is pointed out that since its melts at a relatively low temperature, it can be introduced into the formulation as a large agglomerate and still be dispersed evenly throughout the polymer.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Fire Retardant Chemistry; 9; Aug. 198
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