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  • 1
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    Long-term stability and properties of zirconia ceramics for heavy duty diesel engine components (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Physical, mechanical, and thermal properties of commercially available transformation-toughened zirconia are measured. Behavior is related to the material microstructure and phase assemblage. The stability of the materials is assessed after long-term exposure appropriate for diesel engine application. Properties measured included flexure strength, elastic modulus, fracture toughness, creep, thermal shock, thermal expansion, internal friction, and thermal diffusivity. Stability is assessed by measuring the residual property after 1000 hr/1000C static exposure. Additionally static fatigue and thermal fatigue testing is performed. Both yttria-stabilized and magnesia-stabilized materials are compared and contrasted. The major limitations of these materials are short term loss of properties with increasing temperature as the metastable tetragonal phase becomes more stable. Fine grain yttria-stabilized material (TZP) is higher strength and has a more stable microstructure with respect to overaging phenomena. The long-term limitation of Y-TZP is excessive creep deformation. Magnesia-stabilized PSZ has relatively poor stability at elevated temperature. Overaging, decomposition, and/or destabilization effects are observed. The major limitation of Mg-PSZ is controlling unwanted phase changes at elevated temperature.
    Keywords: URBAN TECHNOLOGY AND TRANSPORTATION
    Type: NASA-CR-174943 , DOE/NASA/0305-1 , NAS 1.26:174943
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  • 2
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    Space processing of chalcogenide glasses (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: Manufacture of chalcogenide glasses in space will eliminate many of the causes of optical non-homogeneity and contamination that are inherent in earth-bound manufacture. A program is outlined to demonstrate the feasibility of various techniques and processes that will be utilized to manufacture chalcogenide glasses in space. Amorphous character, purity, and homogeneity parameters are being investigated at various stages of the glass forming process. These parameters in merit index form will serve to provide guidelines for the design of the actual melting experiment in space, and for the optimization of the exact chalcogenide composition to be included in the space experiments.
    Keywords: MATERIALS, NONMETALLIC
    Type: NASA. Marshall Space Flight Center Proc. of the 3d Space Processing Symp. on Skylab Results, Vol. 2; p 925-938
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  • 3
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    Long-term stability and properties of commercial zirconia ceramics (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Keywords: NONMETALLIC MATERIALS
    Type: Society of Automotive Engineers, Inc. Proc. of the 21st Automotive Technol. Develop. Contractors' Meeting; p 193-200
    Format: text
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  • 4
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    Theoretical study of production of unique glasses in space (1974)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Analytical functional relationships describing homogeneous nucleation and crystallization in various supercooled liquids were developed. The time and temperature dependent relationships of nucleation and crystallization (intrinsic properties) are being used to relate glass forming tendency to extrinsic parameters such as cooling rate through computer simulation. Single oxide systems are being studied initially to aid in developing workable kinetic models and to indicate the primary materials parameters affecting glass formation. The theory and analytical expressions developed for simple systems is then extended to complex oxide systems. A thorough understanding of nucleation and crystallization kinetics of glass forming systems provides a priori knowledge of the ability of a given system to form a glass.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-CR-120417 , AR-1
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  • 5
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    Space processing of chalcogenide glass (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The manner in which the weightless, containerless nature of in-space processing can be successfully utilized to improve the quality of infrared transmitting chalcogenide glasses is determined. The technique of space processing chalcogenide glass was developed, and the process and equipment necessary to do so was defined. Earthbound processing experiments with As2S3 and G28Sb12Se60 glasses were experimented with. Incorporated into these experiments is the use of an acoustic levitation device.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA-CR-150311
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  • 6
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    Space processing of chalcogenide glasses (1975)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Chalcogenide glasses are discussed as good infrared transmitters, possessing the strength, corrosion resistance, and scale-up potential necessary for large 10.6-micron windows. The disadvantage of earth-produced chalcogenide glasses is shown to be an infrared absorption coefficient which is unacceptably high relative to alkali halides. This coefficient is traced to optical nonhomogeneities resulting from environmental and container contamination. Space processing is considered as a means of improving the infrared transmission quality of chalcogenides and of eliminating the following problems: optical inhomogeneities caused by thermal currents and density fluctuation in the l-g earth environment; contamination from the earth-melting crucible by oxygen and other elements deleterious to infrared transmission; and, heterogeneous nucleation at the earth-melting crucible-glass interface.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA-CR-120745 , AR-1
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  • 7
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    Theoretical study of production of unique glasses in space (1975)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The potential of producing the glassy form of selected materials in the weightless, containerless nature of space processing is examined through the development of kinetic relationships describing nucleation and crystallization phenomena. Transformation kinetics are applied to a well-characterized system (SiO2), an excellent glass former (B2O3), and a poor glass former (Al2O3) by conventional earth processing methods. Viscosity and entropy of fusion are shown to be the primary materials parameters controlling the glass forming tendency. For multicomponent systems diffusion-controlled kinetics and heterogeneous nucleation effects are considered. An analytical empirical approach is used to analyze the mullite system. Results are consistent with experimentally observed data and indicate the promise of mullite as a future space processing candidate.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA-CR-143978
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  • 8
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    Space processing of chalcogenide glass (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The manner in which the weightless, containerless nature of in-space processing can be successfully utilized to improve the quality of infrared transmitting chalcogenide glasses was investigated. The following conclusions were reached: (1) Laboratory experiments have established the techniques, processes and equipment necessary for the production of high purity chalcogenide glasses. (2) Processing techniques have been successfully adopted for Ge28Sb12Se60 glass in a 1-g environment. (3) The Ge28Sb12Se60 glasses that have been processed have optical transmission around 63% (5 mm thick). (4) Laboratory experiments have established that the use of precursor materials in powdered form increases the oxygen contamination of the processed glass. This indicates that high purity precursor materials in bar or pellet form should be used. (5) Modifications were made on the MSFC acoustic levitator in an attempt to improve levitation stability during long-time experiments. Room temperature experiments on As2S3 glasses and high temperature experiments on polystyrene were conducted.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA-CR-144278 , ASR-2
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