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Sample records for elevated-temperature structural materials

  1. The Effect of Elevated Temperature on Concrete Materials and Structures - a Literature Review.

    SciTech Connect

    Naus, Dan J

    2006-03-01

    The objective of this limited study was to provide an overview of the effects of elevated temperature on the behavior of concrete materials and structures. In meeting this objective the effects of elevated temperatures on the properties of ordinary Portland cement concrete constituent materials and concretes are summarized. The effects of elevated temperature on high-strength concrete materials are noted and their performance compared to normal strength concretes. A review of concrete materials for elevated-temperature service is presented. Nuclear power plant and general civil engineering design codes are described. Design considerations and analytical techniques for evaluating the response of reinforced concrete structures to elevated-temperature conditions are presented. Pertinent studies in which reinforced concrete structural elements were subjected to elevated temperatures are described.

  2. "Ultra"-Fast Fracture Strength of Advanced Structural Ceramic Materials Studied at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.

    1999-01-01

    The accurate determination of inert strength is important in reliable life prediction of structural ceramic components. At ambient temperature, the inert strength of a brittle material is typically regarded as free of the effects of slow crack growth due to stress corrosion. Therefore, the inert strength can be determined either by eliminating active species, especially moisture, with an appropriate inert medium, or by using a very high test rate. However, at elevated temperatures, the concept or definition of the inert strength of brittle ceramic materials is not clear, since temperature itself is a degrading environment, resulting in strength degradation through slow crack growth and/or creep. Since the mechanism to control strength is rate-dependent viscous flow, the only conceivable way to determine the inert strength at elevated temperatures is to utilize a very fast test rate that either minimizes the time for or eliminates slow crack growth. Few experimental studies have measured the elevated-temperature, inert (or "ultra"-fast fracture) strength of advanced ceramics. At the NASA Lewis Research Center, an experimental study was initiated to better understand the "ultra"-fast fracture strength behavior of advanced ceramics at elevated temperatures. Fourteen advanced ceramics - one alumina, eleven silicon nitrides, and two silicon carbides - have been tested using constant stress-rate (dynamic fatigue) testing in flexure with a series of stress rates including the "ultra"-fast stress rate of 33 000 MPa/sec with digitally controlled test frames. The results for these 14 advanced ceramics indicate that, notwithstanding possible changes in flaw populations as well as flaw configurations because of elevated temperatures, the strength at 33 000 MPa/sec approached the room-temperature strength or reached a higher value than that determined at the conventional test rate of 30 MPa/sec. On the basis of the experimental data, it can be stated that the elevated-temperature

  3. Elevated-Temperature Tribology of Metallic Materials

    SciTech Connect

    Blau, Peter Julian

    2010-01-01

    The wear of metals and alloys takes place in many forms, and the type of wear that dominates in each instance is influenced by the mechanics of contact, material properties, the interfacial temperature, and the surrounding environment. The control of elevated-temperature friction and wear is important for applications like internal combustion engines, aerospace propulsion systems, and metalworking equipment. The progression of interacting, often synergistic processes produces surface deformation, subsurface damage accumulation, the formation of tribolayers, and the creation of free particles. Reaction products, particularly oxides, play a primary role in debris formation and microstructural evolution. Chemical reactions are known to be influenced by the energetic state of the exposed surfaces, and that surface energy is in turn affected by localized deformation and fracture. At relatively low temperatures, work-hardening can occur beneath tribo-contacts, but exposure to high temperatures can modify the resultant defect density and grain structure to affect the mechanisms of re-oxidation. As research by others has shown, the rate of wear at elevated temperatures can either be enhanced or reduced, depending on contact conditions and nature of oxide layer formation. Furthermore, the thermodynamic driving force for certain chemical reactions is moderated by kinetics and microstructure. The role of deformation, oxidation, and tribo-corrosion in the elevated temperature tribology of metallic alloys will be exemplified by three examples involving sliding wear, single-point abrasion, and repetitive impact plus slip.

  4. Methods for structural design at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Ellison, A. M.; Jones, W. E., Jr.; Leimbach, K. R.

    1973-01-01

    A procedure which can be used to design elevated temperature structures is discussed. The desired goal is to have the same confidence in the structural integrity at elevated temperature as the factor of safety gives on mechanical loads at room temperature. Methods of design and analysis for creep, creep rupture, and creep buckling are presented. Example problems are included to illustrate the analytical methods. Creep data for some common structural materials are presented. Appendix B is description, user's manual, and listing for the creep analysis program. The program predicts time to a given creep or to creep rupture for a material subjected to a specified stress-temperature-time spectrum. Fatigue at elevated temperature is discussed. Methods of analysis for high stress-low cycle fatigue, fatigue below the creep range, and fatigue in the creep range are included. The interaction of thermal fatigue and mechanical loads is considered, and a detailed approach to fatigue analysis is given for structures operating below the creep range.

  5. 49 CFR 172.325 - Elevated temperature materials.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be...

  6. 49 CFR 172.325 - Elevated temperature materials.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be...

  7. 49 CFR 172.325 - Elevated temperature materials.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be...

  8. 49 CFR 172.325 - Elevated temperature materials.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be...

  9. 49 CFR 172.325 - Elevated temperature materials.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Elevated temperature materials. 172.325 Section... REQUIREMENTS, AND SECURITY PLANS Marking § 172.325 Elevated temperature materials. (a) Except as provided in paragraph (b) of this section, a bulk packaging containing an elevated temperature material must be...

  10. Cement minerals at elevated temperature: Thermodynamic and structural characteristics

    SciTech Connect

    Bruton, C.J.; Phillips, B.L.; Meike, A.; Martin, S.; Viani, B.E.

    1993-11-01

    Large quantities of cementitious materials may be used in the construction of a potential nuclear waste repository. Temperatures in the emplacement drifts may reach over 200 C owing to decay heat from radioactive waste for various ``extended-dry`` repository scenarios. Despite its potential significance, the mineralogic response of cement to elevated temperature is not well known. The chemistry of fluid introduced to the repository from cementitious materials can also have a significant impact on repository performance. The masses of water associated with the use of cementitious materials such as shotcrete, which includes both structural and pore water, can be sizable. Pore water may be driven out by heating, and structural water may be released through phase dehydration. An experimental and modeling program has been designed to elucidate the structural and thermodynamic response of cement minerals to elevated temperature. The components of the program include: (a) synthesis of hydrated Ca-silicates; (b) structural analysis of cement phases during heating and dehydration/rehydration; (c) mechanistic and thermodynamic descriptions of the hydration/dehydration behavior of hydrated Ca-silicates as a function of temperature, pressure and relative humidity; (d) study of naturally occurring hydrated Ca-silicates; and (e) measurements of thermodynamic data for hydrated Ca-silicates.

  11. Elevated Temperature Testing and Modeling of Advanced Toughened Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Keith, Theo G.

    2005-01-01

    The purpose of this report is to provide a final report for the period of 12/1/03 through 11/30/04 for NASA Cooperative Agreement NCC3-776, entitled "Elevated Temperature Testing and Modeling of Advanced Toughened Ceramic Materials." During this final period, major efforts were focused on both the determination of mechanical properties of advanced ceramic materials and the development of mechanical test methodologies under several different programs of the NASA-Glenn. The important research activities made during this period are: 1. Mechanical properties evaluation of two gas-turbine grade silicon nitrides. 2) Mechanical testing for fuel-cell seal materials. 3) Mechanical properties evaluation of thermal barrier coatings and CFCCs and 4) Foreign object damage (FOD) testing.

  12. 49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Bulk packaging for certain elevated temperature... Than Class 1 and Class 7 § 173.247 Bulk packaging for certain elevated temperature materials. When... constructed of carbon steel which is in elevated temperature material service is excepted from §...

  13. 49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Bulk packaging for certain elevated temperature... Than Class 1 and Class 7 § 173.247 Bulk packaging for certain elevated temperature materials. When... constructed of carbon steel which is in elevated temperature material service is excepted from §...

  14. 49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Bulk packaging for certain elevated temperature... Than Class 1 and Class 7 § 173.247 Bulk packaging for certain elevated temperature materials. When... constructed of carbon steel which is in elevated temperature material service is excepted from §...

  15. 49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Bulk packaging for certain elevated temperature... Than Class 1 and Class 7 § 173.247 Bulk packaging for certain elevated temperature materials. When... constructed of carbon steel which is in elevated temperature material service is excepted from §...

  16. Exfoliation and Dispersion of 2-Dimensional Materials by Elevating Temperature

    NASA Astrophysics Data System (ADS)

    Kwon, Sanghyuk; Kim, Jinseon; Kwon, Hyukjoon; Lee, Changgu; Graphene Engneering Lab Team

    It is known that graphene and other 2-dimensional materials are hard to dissolve in water without using chemicals or surfactants. Here, we present a facile method to exfoliate and disperse those materials in water by simply controlling temperature. Graphene, when sonicated in water at high temperature (60°C), was edge-functionalized due to the extremely high temperature and pressure locally induced by ultrasonic cavitation, and dissolved in water stably even for longer than 1 month. However, it was not dispersed at low temperature(30°C) because of less cavitation and reduced sonochemical reaction. Other 2-dimensional materials, such as h-BN, MoS2, and other layered metal chalcogenides, were also well dissolved in water as graphene, but even at low temperature. Their stable solution is from the electric double layer because their relatively high insulating property. Also elevated storage temperature (60°C) improved the long-term dispersion stability compared to lower storage temperature (20°C) Exfoliation and Dispersion of 2-Dimensional Materials by Elevating Temperature.

  17. Fretting fatigue of anisotropic materials at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Haradanahalli, Murthy N.

    The purpose of this research is to develop an experimental procedure to characterize the contact between blade and disk in aircraft turbo-machinery and to develop a model to predict the life of components based on contact conditions. An experimental setup has been developed to conduct fretting fatigue tests at 610°C. Fretting fatigue lives are characterized for the contacting pair of IN100 and single crystal nickel subjected to a range of loading conditions. A well characterized set of experiments has been conducted to obtain the friction coefficient in the slip zone. Material principal axes and the crystallographic plane of fracture were determined. A robust quasi-analytical approach, based on solution to singular integral equations, has been used to analyze the contact stresses. Different multi-axial fatigue parameters have been investigated for their ability to predict the initiation life of the specimens, after applying a stressed area correction factor using weakest link approach. Multiaxial fatigue parameters also predicted crack nucleation at the edge of contact, consistent with observations of the fractured specimens. Crack propagation lives were evaluated using conventional fracture mechanics, after making certain assumptions to simplify the problem. Total life was estimated as the sum of nucleation life and propagation life. These predicted lives were compared with experimentally observed failure lives. The quality of the comparison provides confidence in the notion that conventional life prediction tools can be used to assess fretting fatigue at elevated temperatures.

  18. The effects of elevated temperatures on the structural properties of fiber composite materials suitable for use in space shuttle and other space vehicles

    NASA Technical Reports Server (NTRS)

    Wright, M. A.

    1972-01-01

    The effects of high temperatures on the structural properties of fiber composite materials for use in spacecraft structures are investigated. Various mechanical properties of boron reinforced aluminum alloys were measured. It was observed that cycling these materials through temperatures that varied from room temperature to 425 C could seriously degrade the properties. The extent of the observed effects depended on alloy type and the maximum cyclic temperature used. Results are discussed in terms of upper and lower strength bonds calculated from the strengths of individual fibers.

  19. Design and analysis of aerospace structures at elevated temperatures. [aircraft, missiles, and space platforms

    NASA Technical Reports Server (NTRS)

    Chang, C. I.

    1989-01-01

    An account is given of approaches that have emerged as useful in the incorporation of thermal loading considerations into advanced composite materials-based aerospace structural design practices. Sources of structural heating encompass not only propulsion system heat and aerodynamic surface heating at supersonic speeds, but the growing possibility of intense thermal fluxes from directed-energy weapons. The composite materials in question range from intrinsically nonheat-resistant polymer matrix systems to metal-matrix composites, and increasingly to such ceramic-matrix composites as carbon/carbon, which are explicitly intended for elevated temperature operation.

  20. Creep performance of oxide ceramic fiber materials at elevated temperature in air and in steam

    NASA Astrophysics Data System (ADS)

    Armani, Clinton J.

    Structural aerospace components that operate in severe conditions, such as extreme temperatures and detrimental environments, require structural materials that have superior long-term mechanical properties and that are thermochemically stable over a broad range of service temperatures and environments. Ceramic matrix composites (CMCs) capable of excellent mechanical performance in harsh environments are prime candidates for such applications. Oxide ceramic materials have been used as constituents in CMCs. However, recent studies have shown that high-temperature mechanical performance of oxide-oxide CMCs deteriorate in a steam-rich environment. The degradation of strength at elevated temperature in steam has been attributed to the environmentally assisted subcritical crack growth in the oxide fibers. Furthermore, oxide-oxide CMCs have shown significant increases in steady-state creep rates in steam. The present research investigated the effects of steam on the high-temperature creep and monotonic tension performance of several oxide ceramic materials. Experimental facilities were designed and configured, and experimental methods were developed to explore the influence of steam on the mechanical behaviors of ceramic fiber tows and of ceramic bulk materials under temperatures in the 1100--1300°C range. The effects of steam on creep behavior of Nextel(TM)610 and Nextel(TM)720 fiber tows were examined. Creep rates at elevated temperatures in air and in steam were obtained for both types of fibers. Relationships between creep rates and applied stresses were modeled and underlying creep mechanisms were identified. For both types of fiber tows, a creep life prediction analysis was performed using linear elastic fracture mechanics and a power-law crack velocity model. These results have not been previously reported and have critical design implications for CMC components operating in steam or near the recommended design limits. Predictions were assessed and validated via

  1. Shell structures in aluminum nanocontacts at elevated temperatures

    PubMed Central

    2012-01-01

    Aluminum nanocontact conductance histograms are studied experimentally from room temperature up to near the bulk melting point. The dominant stable configurations for this metal show a very early crossover from shell structures at low wire diameters to ionic subshell structures at larger diameters. At these larger radii, the favorable structures are temperature-independent and consistent with those expected for ionic subshell (faceted) formations in face-centered cubic geometries. When approaching the bulk melting temperature, these local stability structures become less pronounced as shown by the vanishing conductance histogram peak structure. PMID:22325572

  2. In situ characterisation of nanostructured multiphase thermoelectric materials at elevated temperatures.

    PubMed

    Aminorroaya Yamini, S; Mitchell, D R G; Avdeev, M

    2016-12-07

    Multiphase thermoelectric materials have recently attracted considerable attention due to the high thermoelectric efficiencies which can be achieved in these compounds compared to their single-phase counterparts. However, there is very little known on the structural evolution of these phases as a function of temperature. In this work we performed an in situ high temperature structural characterisation of recently reported high efficiency p-type multiphase (PbTe)0.65(PbS)0.25(PbSe)0.1 compounds by hot stage transmission electron microscopy and high-resolution neutron powder diffraction. We observed the microstructural evolution of precipitates and determined the lattice parameters of phases as a function of temperature for materials, which have been heavily and lightly doped with sodium. The role of the sodium is to optimize the concentration of charge carriers. It has been shown to distribute heterogeneously between the phases in multiphase compounds. The dissolution of secondary phases is found to occur at elevated temperatures. Although sodium concentration produces no significant differences between the lattice constants of the phases and the dissolution sequence of precipitates, it affects quite significantly the kinetics of precipitation. The heavily doped samples reach structural thermodynamic equilibrium more quickly than the lightly doped compound. These results are a step forward in designing high performance multiphase thermoelectric materials.

  3. Effects of Elevated Temperatures and Thermal Cycling on Ceramic Composite Materials

    DTIC Science & Technology

    1989-12-01

    the facilities of the materials laboratory at will. Larry Zawada provided the plates for me to use and gave me much information on the processing and...Fabrication All plates were manufactured at the Air Force Materials Laboratory under the supervision of Mr. Larry Zawada . The following processing...the room temperature, elevated temperature, and thermal cycling I portions of this study were conducted. Specimen Preparation. Mr. Larry Zawada

  4. Analysis and testing of dynamic micromechanical behavior of composite materials at elevated temperatures

    SciTech Connect

    Pant, R.H.; Gibson, R.F.

    1996-10-01

    This paper describes the use of a recently developed high temperature impulse-frequency response apparatus to directly measure dynamic modulus and internal damping of high temperature composite materials, matrix materials, and reinforcing fibers as a function of temperature. An extensional vibration test was used for determination of the complex Young`s modulus of fiber specimens as a function of temperature. A flexural vibration test was used for determination of the complex flexural modulus of matrix and unidirectional composite specimens (0 and 90 deg fiber orientations) as a function of temperature. These results were obtained from tests done on two different fiber reinforced composite materials: boron/epoxy (B/E) and Silicon Carbide/Ti-6Al-4V (SiC/Ti). The results from these tests were then used to assess the validity of micromechanics predictions of composite properties at elevated temperatures. Micromechanics predictions of composite moduli and damping at elevated temperatures show good agreement with measured values for the 0 deg case (longitudinal) but only fair agreement for the 90 deg case (transverse). In both cases, the predictions indicate the correct trends in the properties.

  5. Geopolymeric materials prepared using Class F fly ash and elevated temperature curing

    SciTech Connect

    Bakharev, T. . E-mail: tanya.bakharev@eng.monash.edu.au

    2005-06-01

    This paper reports the results of the study of the influence of elevated temperature curing on phase composition, microstructure and strength development in geopolymer materials prepared using Class F fly ash and sodium silicate and sodium hydroxide solutions. In particular, the effect of storage at room temperature before the application of heat on strength development and phase composition was studied. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and SEM were utilised in this study. Long precuring at room temperature before application of heat was beneficial for strength development in all studied materials, as strength comparable to 1 month of curing at elevated temperature can develop in this case only after 24 h of heat curing. The main product of reaction in the geopolymeric materials was amorphous alkali aluminosilicate gel. However, in the case of sodium hydroxide activator in addition to it, traces of chabazite, Linde Type A, Na-P1 (gismondine) zeolites and hydroxysodalite were also present. The type of zeolite present and composition of aluminosilicate gel were dependent on the curing history.

  6. Material property data and their use in design and analysis for an elevated temperature solar code

    NASA Astrophysics Data System (ADS)

    Berman, I.

    1981-11-01

    Specific properties of the materials, temperatures, and operating parameters for elevated temperature solar thermal power plants are considered as a basis for developing standards of implementation. Physical and mechanical properties such as thermal conductivity, elastic modulus, expansion, strength, and creep are discussed and recommendations for ASME Code I and III materials are cited where feasible. Inelastic behavior tests involving beam bending, pipe ratcheting, torsion-torsion tests, and axial cyclic tests of various stainless steel specimens and Incoloy 800 material are reported. Peculiarities of problems for solar applications are noted to be a lack of information of basic material behavior due to the low amount of actual operational experience, a large number of transient temperature cycles, and primary creep.

  7. Effects of elevated temperatures on various restorative materials: an in vitro study.

    PubMed

    Bose, Raison S; Mohan, B; Lakshminarayanan, L

    2005-01-01

    In cases of mass disasters associated with fire, identification of the burnt victims can be a real challenge to the forensic team. Teeth and their restorations play a significant role to aid in the identification process, as various restorative materials have varying resistance to high temperatures. A study was undertaken to evaluate the changes taking place on teeth restored with amalgam, composites, glass ionomers, heat cure acrylic, and ceramics. The specimens were placed in a furnace and heated to predetermined temperatures of 200, 400, 600, 800, and 1000 degrees C and the changes were examined using a digital camera and stereomicroscope. Our observations show that while some restorations were able to withstand elevated temperatures, others were reduced to an unrecognizable mass at relatively low temperatures.

  8. Reliability and life prediction of ceramic composite structures at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Duffy, Stephen F.; Gyekenyesi, John P.

    1994-01-01

    Methods are highlighted that ascertain the structural reliability of components fabricated of composites with ceramic matrices reinforced with ceramic fibers or whiskers and subject to quasi-static load conditions at elevated temperatures. Each method focuses on a particular composite microstructure: whisker-toughened ceramics, laminated ceramic matrix composites, and fabric reinforced ceramic matrix composites. In addition, since elevated service temperatures usually involve time-dependent effects, a section dealing with reliability degradation as a function of load history has been included. A recurring theme throughout this chapter is that even though component failure is controlled by a sequence of many microfailure events, failure of ceramic composites will be modeled using macrovariables.

  9. Effect of Preloading on Fatigue Strength in Dynamic Fatigue Testing of Ceramic Materials at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Salem, Jonathan A.

    1995-01-01

    Previously derived solutions of fatigue strength as a function of preloading were verified by applying preloads to elevated temperature dynamic fatigue tests of 96 wt% alumina at 1000 C and NC 132 silicon nitride at 1100 C. The technique was found very useful in identification and control of the governing failure mechanism when multiple failure mechanisms, such as slow crack growth, creep and oxidation occurred simultaneously at elevated temperatures.

  10. Evaluation of pore structures and cracking in cement paste exposed to elevated temperatures by X-ray computed tomography

    SciTech Connect

    Kim, Kwang Yeom; Yun, Tae Sup; Park, Kwang Pil

    2013-08-15

    When cement-based materials are exposed to the high temperatures induced by fire, which can rapidly cause temperatures of over 1000 °C, the changes in pore structure and density prevail. In the present study, mortar specimens were subjected to a series of increasing temperatures to explore the temperature-dependent evolution of internal pore structure. High-performance X-ray computed tomography (CT) was used to observe the evolution of temperature-induced discontinuities at the sub-millimeter level. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to investigate the cause of physical changes in the heated mortar specimens. Results exhibit the changes in pore structure caused by elevated temperatures, and thermally induced fractures. We discuss the progressive formation of thermally induced fracture networks, which is a prerequisite for spalling failure of cement-based materials by fire, based on visual observations of the 3D internal structures revealed by X-ray CT.

  11. Apparatus for Measuring Spectral Emissivity of Solid Materials at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Ren, Dengfeng; Tan, Hong; Xuan, Yimin; Han, Yuge; Li, Qiang

    2016-05-01

    Spectral emissivity measurements at high temperature are of great importance for both scientific research and industrial applications. A method to perform spectral emissivity measurements is presented based on two sample heating methods, the flat plate and tubular furnace. An apparatus is developed to measure the normal spectral emissivity of solid material at elevated temperatures from 1073 K to 1873 K and wavelengths from 2 \\upmu hbox {m} to 25 \\upmu hbox {m}. Sample heating is accomplished by a torch flame or a high temperature furnace. Two different variable temperature blackbody sources are used as standard references and the radiance is measured by a FTIR spectrometer. Following calibration of the spectral response and background radiance of the spectrometer, the effect of the blackbody temperature interval on calibration results is discussed. Measurements are performed of the normal spectral emissivity of SiC and graphite over the prescribed temperature and wavelength range. The emissivity of SiC at high temperatures is compared with the emissivity at room temperature, and the influence of an oxide layer formed at the surface of SiC on the emissivity is studied. The effect of temperature on the emissivity of graphite is also investigated. Furthermore, a thorough analysis of the uncertainty components of the emissivity measurement is performed.

  12. Elevated temperature irradiation damage in CANDU spacer material Inconel X-750

    NASA Astrophysics Data System (ADS)

    Zhang, He K.; Yao, Zhongwen; Daymond, Mark R.; Kirk, Marquis A.

    2014-02-01

    Heavy ion irradiation induced damage in Inconel X-750 at low temperatures (60-400 °C) has been reported in our previous study. In the current investigation, the microstructure evolution and phase change during heavy (1 MeV Kr2+) irradiation at elevated temperatures (500 °C and 600 °C) were characterized under in situ observation of intermediate voltage electron microscope (IVEM) at Argonne National Laboratory. For each temperature, defect analyses using the weak beam dark field method were carried out at several doses, up to 5.4 dpa. Small defects (<5 nm) yielded from high temperature irradiation comprise mainly stacking fault tetrahedras (SFTs), small ⅓ <1 1 1> and ½ <1 1 0> type dislocation loops. Large interstitial Frank loops were observed and a clear characteristic for growth of loops was video-captured. Unfaulting of interstitial Frank loops was observed. The number density of the defects saturated at a relatively low dose of 0.68 dpa. No obvious change of defect fraction was found with increasing dose, but more complex dislocation structures formed at higher doses. In contrast to low temperature irradiation, the primary strengthening phase γ‧ was found to be stable during irradiation at temperatures >500 °C and was not disordered up to 5.4 dpa. No cavities were observed after the irradiation even at 600 °C.

  13. Structural characteristics and elevated temperature mechanical properties of AJ62 Mg alloy

    SciTech Connect

    Kubásek, J. Vojtěch, D.; Martínek, M.

    2013-12-15

    Structure and mechanical properties of the novel casting AJ62 (Mg–6Al–2Sr) alloy developed for elevated temperature applications were studied. The AJ62 alloy was compared to commercial casting AZ91 (Mg–9Al–1Zn) and WE43 (Mg–4Y–3RE) alloys. The structure was examined by scanning electron microscopy, x-ray diffraction and energy dispersive spectrometry. Mechanical properties were characterized by Viskers hardness measurements in the as-cast state and after a long-term heat treatment at 250 °C/150 hours. Compressive mechanical tests were also carried out both at room and elevated temperatures. Compressive creep tests were conducted at a temperature of 250 °C and compressive stresses of 60, 100 and 140 MPa. The structure of the AJ62 alloy consisted of primary α-Mg dendrites and interdendritic nework of the Al{sub 4}Sr and massive Al{sub 3}Mg{sub 13}Sr phases. By increasing the cooling rate during solidification from 10 and 120 K/s the average dendrite arm thickness decreased from 18 to 5 μm and the total volume fraction of the interdendritic phases from 20% to 30%. Both factors slightly increased hardness and compressive strength. The room temperature compressive strength and hardness of the alloy solidified at 30 K/s were 298 MPa and 50 HV 5, i.e. similar to those of the as-cast WE43 alloy and lower than those of the AZ91 alloy. At 250 °C the compressive strength of the AJ62 alloy decreased by 50 MPa, whereas those of the AZ91 and WE43 alloys by 100 and 20 MPa, respectively. The creep rate of the AJ62 alloy was higher than that of the WE43 alloy, but significantly lower in comparison with the AZ91 alloy. Different thermal stabilities of the alloys were discussed and related to structural changes during elevated temperature expositions. - Highlights: • Small effect of cooling rate on the compressive strength and hardness of AJ 62 • A bit lower compressive strength of AJ 62 compared to AZ91 at room temperature • Higher resistance of the AJ 62

  14. Microwave-enhanced electrochemical cycling performance of the LiNi0.2Mn1.8O4 spinel cathode material at elevated temperature.

    PubMed

    Raju, Kumar; Nkosi, Funeka P; Viswanathan, Elumalai; Mathe, Mkhulu K; Damodaran, Krishnan; Ozoemena, Kenneth I

    2016-05-14

    The well-established poor electrochemical cycling performance of the LiMn2O4 (LMO) spinel cathode material for lithium-ion batteries at elevated temperature stems from the instability of the Mn(3+) concentration. In this work, a microwave-assisted solid-state reaction has been used to dope LMO with a very low amount of nickel (i.e., LiNi0.2Mn1.8O4, herein abbreviated as LMNO) for lithium-ion batteries from Mn3O4 which is prepared from electrolytic manganese oxide (EMD, γ-MnO2). To establish the impact of microwave irradiation on the electrochemical cycling performance at an elevated temperature (60 °C), the Mn(3+) concentration in the pristine and microwave-treated LMNO samples was independently confirmed by XRD, XPS, (6)LiMAS-NMR and electrochemical studies including electrochemical impedance spectroscopy (EIS). The microwave-treated sample (LMNOmic) allowed for the clear exposure of the {111} facets of the spinel, optimized the Mn(3+) content, promoting structural and cycle stability at elevated temperature. At room temperature, both the pristine (LMNO) and microwave-treated (LMNOmic) samples gave comparable cycling performance (>96% capacity retention and ca. 100% coulombic efficiency after 100 consecutive cycling). However, at an elevated temperature (60 °C), the LMNOmic gave an improved cycling stability (>80% capacity retention and ca. 90% coulombic efficiency after 100 consecutive cycling) compared to the LMNO. For the first time, the impact of microwave irradiation on tuning the average manganese redox state of the spinel material to enhance the cycling performance of the LiNi0.2Mn1.8O4 at elevated temperature and lithium-ion diffusion kinetics has been clearly demonstrated.

  15. Sandwich-structured polymer nanocomposites with high energy density and great charge–discharge efficiency at elevated temperatures

    PubMed Central

    Li, Qi; Liu, Feihua; Yang, Tiannan; Gadinski, Matthew R.; Zhang, Guangzu; Chen, Long-Qing; Wang, Qing

    2016-01-01

    The demand for a new generation of high-temperature dielectric materials toward capacitive energy storage has been driven by the rise of high-power applications such as electric vehicles, aircraft, and pulsed power systems where the power electronics are exposed to elevated temperatures. Polymer dielectrics are characterized by being lightweight, and their scalability, mechanical flexibility, high dielectric strength, and great reliability, but they are limited to relatively low operating temperatures. The existing polymer nanocomposite-based dielectrics with a limited energy density at high temperatures also present a major barrier to achieving significant reductions in size and weight of energy devices. Here we report the sandwich structures as an efficient route to high-temperature dielectric polymer nanocomposites that simultaneously possess high dielectric constant and low dielectric loss. In contrast to the conventional single-layer configuration, the rationally designed sandwich-structured polymer nanocomposites are capable of integrating the complementary properties of spatially organized multicomponents in a synergistic fashion to raise dielectric constant, and subsequently greatly improve discharged energy densities while retaining low loss and high charge–discharge efficiency at elevated temperatures. At 150 °C and 200 MV m−1, an operating condition toward electric vehicle applications, the sandwich-structured polymer nanocomposites outperform the state-of-the-art polymer-based dielectrics in terms of energy density, power density, charge–discharge efficiency, and cyclability. The excellent dielectric and capacitive properties of the polymer nanocomposites may pave a way for widespread applications in modern electronics and power modules where harsh operating conditions are present. PMID:27551101

  16. Sandwich-structured polymer nanocomposites with high energy density and great charge-discharge efficiency at elevated temperatures.

    PubMed

    Li, Qi; Liu, Feihua; Yang, Tiannan; Gadinski, Matthew R; Zhang, Guangzu; Chen, Long-Qing; Wang, Qing

    2016-09-06

    The demand for a new generation of high-temperature dielectric materials toward capacitive energy storage has been driven by the rise of high-power applications such as electric vehicles, aircraft, and pulsed power systems where the power electronics are exposed to elevated temperatures. Polymer dielectrics are characterized by being lightweight, and their scalability, mechanical flexibility, high dielectric strength, and great reliability, but they are limited to relatively low operating temperatures. The existing polymer nanocomposite-based dielectrics with a limited energy density at high temperatures also present a major barrier to achieving significant reductions in size and weight of energy devices. Here we report the sandwich structures as an efficient route to high-temperature dielectric polymer nanocomposites that simultaneously possess high dielectric constant and low dielectric loss. In contrast to the conventional single-layer configuration, the rationally designed sandwich-structured polymer nanocomposites are capable of integrating the complementary properties of spatially organized multicomponents in a synergistic fashion to raise dielectric constant, and subsequently greatly improve discharged energy densities while retaining low loss and high charge-discharge efficiency at elevated temperatures. At 150 °C and 200 MV m(-1), an operating condition toward electric vehicle applications, the sandwich-structured polymer nanocomposites outperform the state-of-the-art polymer-based dielectrics in terms of energy density, power density, charge-discharge efficiency, and cyclability. The excellent dielectric and capacitive properties of the polymer nanocomposites may pave a way for widespread applications in modern electronics and power modules where harsh operating conditions are present.

  17. Micro-structural optimization of polybenzimidazole-based membranes for H2/CO2 separation at elevated temperatures

    SciTech Connect

    Singh, Rajinder P; Li, Xin; Dudeck, Kevin W; Benicewicz, Brian C; Berchtold, Kathryn A

    2012-06-12

    There is compelling need to develop novel separation methods to improve the energy efficiency of synthesis (syn) gas processing operations including H{sub 2} and H{sub 2}/CO production to meet power, chemicals, and fuel producer needs, as well as carbon capture and removal of other undesirable syngas impurities. To be technically and economically viable, a successful separation method must be applicable to industrially relevant gas streams at realistic process conditions and compatible with large gas volumes. H{sub 2} selective membrane technology is a promising method for syngas separations at elevated temperatures (>150 C) that could be positioned upstream or downstream of one or more of the water-gas-shift reactors (WGSRs) or integrated with a WGSR depending on application specific syngas processing. Polybenzimidazole (PBI)-based polymer chemistries are exceptional candidates for H{sub 2}/CO{sub 2} separations at elevated temperatures. In general, these materials possess excellent chemical resistance, very high glass transition temperatures (> 400 C), good mechanical properties, and an appropriate level of processability. Although commercially available PBI polymers have demonstrated commercially attractive H{sub 2}/CO{sub 2} selectivity, their H{sub 2} permeability is low. Our team s employing structural and chemical manipulations to tailor the polymer free-volume achitecture with the ultimate goal of enhancing H{sub 2} permselectivity while retaining the inherent hermochemical stability characteristics of PBI. We will discuss our synthetic approaches and their influences on the gas transport behavior of these PBI-based materials. In general, a decrease in H{sub 2}/CO{sub 2} selectivity was observed with an increase in H{sub 2} permeability. H{sub 2} permeability and H{sub 2}/CO{sub 2} selectivity at 250 C ranged from 50 to 1000 barrer and 5 to 45, respectively.

  18. Optical Properties Of Solid Particle Receiver Materials II: Diffuse Reflectance Of Norton Masterbeads At Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Stahl, K. A.; Griffin, J. W.; Pettit, R. B.

    1985-12-01

    An experimental system to measure the diffuse reflectance of a particulate sample over the wavelength range of 300 to 2500 nm at elevated temperatures up to 1000°C has been developed and implemented. A description of the experimental apparatus and measurement procedures, as well as optical reflectance data for the Masterbeadse, are presented. Using the high temperature measurement system, the diffuse reflectance of Masterbeads changed by less than 1% for sample temperatures from 150°C to 930°C. However, after heating a sample for three hours at 1000°C in air, the solar absorptance measured at room temperature decreased from an initial value of 0.93 to 0.89.

  19. Effects of elevated temperatures on different restorative materials: An aid to forensic identification processes

    PubMed Central

    Pol, Chetan A.; Ghige, Suvarna K.; Gosavi, Suchitra R.; Hazarey, Vinay K.

    2015-01-01

    Background: Heat-induced alterations to dental and restorative materials can be of great interest to forensic dentistry. Knowing the specific optical behavior of dental materials can be of high importance as recognition of changes induced by high temperatures can lead to the determination of material which was used in a dental restoration, facilitating identification of burned human remains. Aim: To observe the effects of predetermined temperatures (200°C–400°C–600°C–800°C–1000°C) on unrestored teeth and different restorative materials macroscopically and then examine them under a stereomicroscope for the purpose of identification. Materials and Methods: The study was conducted on 375 extracted teeth which were divided into five groups of 75 teeth each as follows: group 1- unrestored teeth, group 2- teeth restored with all-ceramic crowns, Group 3- with class I silver amalgam filling, group 4- with class I composite restoration, and group 5- with class I glass ionomer cement restoration. Results: Unrestored and restored teeth display a series of specific macroscopic & stereomicroscopic structural changes for each range of temperature. Conclusion: Dental tissues and restorative materials undergo a series of changes which correlate well with the various temperatures to which they were exposed. These changes are a consequence of the nature of the materials and their physicochemical characteristics. PMID:26005305

  20. 49 CFR 173.247 - Bulk packaging for certain elevated temperature materials.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... materials. 173.247 Section 173.247 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Bulk Packaging for Hazardous Materials...

  1. CO{sub 2}-gasification reactivity of different carbonaceous materials at elevated temperatures

    SciTech Connect

    Gu, J.; Wu, S.; Wu, Y.; Gao, J.

    2009-07-01

    At the atmospheric pressure and at the temperatures between 1,223 and 1,673 K, the CO{sub 2} gasification reactivity of seven different carbonaceous materials comprising coal tar pitch coke, petroleum coke, natural graphite, carbon black and three coal chars was investigated by using thermogravimetric analysis. Their crystalline structures were analyzed by X-ray diffraction (XRD). It is found that the reactivity of the chars, pitch coke and petroleum coke produced from liquid phase carbonization, is several times poorer than that of the coal chars produced from solid phase carbonization and even lower than that of natural graphite. At the same time, it is obtained that under the condition of the chemical reaction control, the apparent activation energies of the former are in the range of 135.82-174.92 kJ/mol, while those of the latter are between 89.95 kJ/mol and 110.05 kJ/mol. Besides, the reactivity of the sample has a certain correlation with the crystalline structure of the sample, i.e., the larger the fraction of the relatively better crystalline structure is, the poorer the reactivity of the sample is.

  2. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Yau, J. F.; Malik, S. N.; Kim, K. S.; Vanstone, R. H.; Laflen, J. H.

    1985-01-01

    The objective of the Elevated Temperature Crack Growth Project is to evaluate proposed nonlinear fracture mechanics methods for application to combustor liners of aircraft gas turbine engines. During the first year of this program, proposed path-independent (P-I) integrals were reviewed for such applications. Several P-I integrals were implemented into a finite-element postprocessor which was developed and verified as part of the work. Alloy 718 was selected as the analog material for use in the forthcoming experimental work. A buttonhead, single-edge notch specimen was designed and verified for use in elevated-temperature strain control testing with significant inelastic strains. A crack mouth opening displacement measurement device was developed for further use.

  3. Impact Testing of Stainless Steel Material at Room and Elevated Temperatures

    SciTech Connect

    Dana K. Morton; Spencer D. Snow; Tom E. Rahl; Robert K. Blandford

    2007-07-01

    Stainless steels are used for the construction of numerous spent nuclear fuel or radioactive material containers that may be subjected to high strains and moderate strain rates during accidental drop events. Mechanical characteristics of these base materials and their welds under dynamic loads in the strain rate range of concern are not well documented. However, three previous papers [1, 2, 3] reported on impact testing and analysis results performed at the Idaho National Laboratory using 304/304L and 316/316L stainless steel base material specimens that began the investigation of these characteristics. The goal of the work presented herein is to add the results of additional tensile impact testing for 304/304L and 316/316L stainless steel material specimens. Utilizing a drop-weight impact test machine and 1/4-inch to 1/2-inch thick dog-bone shaped test specimens, additional tests achieved target strain rates of 5, 10, and 22 per second at room temperature, 300, and 600 degrees Fahrenheit. Elevated true stress-strain curves for these materials at each designated strain rate and temperature are presented herein.

  4. Progress in understanding the mechanical behavior of pressure-vessel materials at elevated temperatures

    SciTech Connect

    Swindeman, R.W.; Brinkman, C.R.

    1981-01-01

    Progress during the 1970's on the production of high-temperature mechanical properties data for pressure vessel materials was reviewed. The direction of the research was toward satisfying new data requirements to implement advances in high-temperature inelastic design methods. To meet these needs, servo-controlled testing machines and high-resolution extensometry were developed to gain more information on the essential behavioral features of high-temperature alloys. The similarities and differences in the mechanical response of various pressure vessel materials were identified. High-temperature pressure vessel materials that have received the most attention included Type 304 stainless steel, Type 316 stainless steel, 2 1/4 Cr-1 Mo steel, alloy 800H, and Hastelloy X.

  5. Thermal Output of WK-Type Strain Gauges on Various Materials at Cryogenic and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Kowalkowski, Matthew K.; Rivers, H. Kevin; Smith, Russell W.

    1998-01-01

    Strain gage apparent strain (thermal output) is one of the largest sources of error associated with the measurement of strain when temperatures and mechanical loads are varied. In this paper, experimentally determined apparent strains of WK-type strain gages, installed on both metallic and composite-laminate materials of various lay-ups and resin systems for temperatures ranging from -450 F to 230 F are presented. For the composite materials apparent strain in both the 0 ply orientation angle and the 90 ply orientation angle were measured. Metal specimens tested included: aluminum-lithium alloy (Al-LI 2195-T87), aluminum alloy (Al 2219-T87), and titanium alloy. Composite materials tested include: graphite-toughened-epoxy (IM7/997- 2), graphite-bismaleimide (IM7/5260), and graphite-K3 (IM7/K3B). The experimentally determined apparent strain data are curve fit with a fourth-order polynomial for each of the materials studied. The apparent strain data and the polynomials that are fit to the data are compared with those produced by the strain gage manufacturer, and the results and comparisons are presented. Unacceptably high errors between the manufacture's data and the experimentally determined data were observed (especially at temperatures below - 270-F).

  6. Simultaneous moduli measurement of elastic materials at elevated temperatures using an ultrasonic waveguide method

    NASA Astrophysics Data System (ADS)

    Periyannan, Suresh; Balasubramaniam, Krishnan

    2015-11-01

    A novel technique for simultaneously measuring the moduli of elastic isotropic material, as a function of temperature, using two ultrasonic guided wave modes that are co-generated using a single probe is presented here. This technique can be used for simultaneously measuring Young's modulus (E) and shear modulus (G) of different materials over a wide range of temperatures (35 °C-1200 °C). The specimens used in the experiments have special embodiments (for instance, a bend) at one end of the waveguide and an ultrasonic guided wave generator/detector (transducer) at the other end for obtaining reflected signals in a pulse-echo mode. The orientation of the transducer can be used for simultaneously generating/receiving the L(0,1) and/or T(0,1) using a single transducer in a waveguide on one end. The far end of the waveguides with the embodiment is kept inside a heating device such as a temperature-controlled furnace. The time of flight difference, as a function of uniform temperature distribution region (horizontal portion) of bend waveguides was measured and used to determine the material properties. Several materials were tested and the comparison between values reported in the literature and measured values were found to be in agreement, for both elastic moduli (E and G) measurements, as a function of temperature. This technique provides significant reduction in time and effort over conventional means of measurement of temperature dependence of elastic moduli.

  7. Thermal stability of direct dental esthetic restorative materials at elevated temperatures.

    PubMed

    Robinson, F G; Rueggeberg, F A; Lockwood, P E

    1998-11-01

    With increasing use of direct esthetic restorative materials, the identity of a body may rely upon knowledge of temperature effects on this class of dental restorations. This research examined the effect of atmospheric gas on thermal decomposition and color change of a wide variety of direct esthetic restorative materials. Cured discs (4 x 1 and 8 x 1 mm) were made using manufacturer's directions: traditional glass ionomer (Fuji II), light-curable resonomer (Fuji II LC), compomer (Geristore), and three types of resin composites--highly filled, urethane-based (Occlusin), and two Bis-GMA/TEGDMA resins: hybrid (Herculite XRV) and microfill (Silux Plus). Three replications of each material were heated at 5 degrees C/min in a thermogravimetric analysis unit using either room air or nitrogen purge to simulate different thermal environments. First derivative values of percent weight loss with respect to temperature were obtained to determine temperatures associated with increased decomposition rates. Room-air heating showed greater numbers of decomposition events than did nitrogen-heated discs. The only material decomposing less than 200 degrees C in either atmosphere was traditional glass ionomer. The majority of decomposition occurred between 200 degrees and 500 degrees C for all materials. Only products containing glass ionomer components decomposed between 600 degrees and 800 degrees C. Room-air heating resulted in ash white discs at 800 degrees C and higher. Specimens heated in nitrogen were gray to black at 600 degrees C and higher. Heating atmosphere greatly affected color, and some products demonstrated distinguishing color changes: glass ionomers, in particular, showed characteristic color features. An atlas was constructed from color change of specimens recovered after 200 degrees, 400 degrees, 600 degrees, 800 degrees, and 1000 degrees C compared with non-heated controls.

  8. Tensile behavior of glass/ceramic composite materials at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Mandell, J. F.; Grande, D. H.; Jacobs, J.

    1987-01-01

    This paper describes the tensile behavior of high-temperature composite materials containing continuous Nicalon ceramic fiber reinforcement and glass and glass/ceramic matrices. The longitudinal properties of these materials can approach theoretical expectations for brittle matrix composites, failing at a strength and ultimate strain level consistent with those of the fibers. The brittle, high-modulus matrices result in a nonlinear stress-strain curve due to the onset of stable matrix cracking at 10 to 30 percent of the fiber strain to failure, and at strains below this range in off-axis plies. Current fibers and matrices can provide attractive properties well above 1000 C, but composites experience embrittlement in oxidizing atmospheres at 800 to 1000 C due to oxidation of a carbon interface reaction layer.The oxidation effect greatly increases the interface bond strength, causing composite embrittlement.

  9. Creep Performance of Oxide Ceramic Fiber Materials at Elevated Temperature in Air and in Steam

    DTIC Science & Technology

    2011-03-24

    performance in harsh environments are prime candidates for such applications . Oxide ceramic materials have been used as constituents in CMCs...since 1965, when the United States Air Force led the effort to bring high performance fiber composites to practical applications [26]. Today...bulk polycrystalline alumina cubes were performed in air and steam at 1100 and 1300°C. Both the bulk alumina and YAG specimens were processed in two

  10. Electrical Properties of Materials for Elevated Temperature Resistance Strain Gage Application. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Lei, Jih-Fen

    1987-01-01

    The objective was to study the electrical resistances of materials that are potentially useful as resistance strain gages at 1000 C. Transition metal carbides and nitrides, boron carbide and silicon carbide were selected for the experimental phase of this research. Due to their low temperature coefficient of resistance and good stability, TiC, ZrC, B sub 4 C and beta-SiC are suggested as good candidates for high temperature resistance strain gage applications.

  11. Design Issues for Using Magnetic Materials in Radiation Environments at Elevated Temperature

    NASA Technical Reports Server (NTRS)

    Bowman, Cheryl L.

    2013-01-01

    One of the challenges of designing motors and alternators for use in nuclear powered space missions is accounting for the effects of radiation. Terrestrial reactor power plants use distance and shielding to minimize radiation damage but space missions must economize volume and mass. Past studies have shown that sufficiently high radiation levels can affect the magnetic response of hard and soft magnetic materials. Theoretical models explaining the radiation-induced degradation have been proposed but not verified. This paper reviews the literature and explains the cumulative effects of temperature, magnetic-load, and radiation-level on the magnetic properties of component materials. Magnetic property degradation is very specific to alloy choice and processing history, since magnetic properties are very much entwined with specific chemistry and microstructural features. However, there is basic theoretical as well as supportive experimental evidence that the negative impact to magnetic properties will be minimal if the bulk temperature of the material is less than fifty percent of the Curie temperature, the radiation flux is low, and the demagnetization field is small. Keywords: Magnets, Permanent Magnets, Power Converters, Nuclear Electric Power Generation, Radiation Tolerance.

  12. Consideration of Conductive Motor Winding Materials at Room and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    de Groh, Henry C., III

    2015-01-01

    A brief history of conductive motor winding materials is presented, comparing various metal motor winding materials and their properties in terms of conductivity, density and cost. The proposed use of carbon nanotubes (CNTs) and composites incorporating CNTs is explored as a potential way to improve motor winding conductivity, density, and reduce motor size which are important to electric aircraft technology. The conductivity of pure Cu, a CNT yarn, and a dilute Cu-CNT composite was measured at room temperature and at several temperatures up to 340 C. The conductivity of the Cu-CNT composite was about 3 percent lower than pure copper's at all temperatures measured. The conductivity of the CNT yarn was about 200 times lower than copper's, however, the yarn's conductivity dropped less with increasing temperature compared to Cu. It is believed that the low conductivity of the yarn is due primarily to high interfacial resistances and the presence of CNTs with low, semiconductor like electrical properties (s-CNT). It is believed the conductivity of the CNT-Cu composite could be improved by not using s-CNT, and instead using only CNTs with high, metallic like electrical properties (m-CNT); and by increasing the vol% m-CNTs.

  13. Elevated Temperature, Residual Compressive Strength of Impact-Damaged Sandwich Structure Manufactured Out-of-Autoclave

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Sutter, James K.; Burke, Eric R.; Dixon, Genevieve D.; Gyekenyesi, Thomas G.; Smeltzer, Stanley S.

    2012-01-01

    Several 1/16th-scale curved sandwich composite panel sections of a 10 m diameter barrel were fabricated to demonstrate the manufacturability of large-scale curved sections using minimum gauge, [+60/-60/0]s, toughened epoxy composite facesheets co-cured with low density (50 kilograms per cubic meters) aluminum honeycomb core. One of these panels was fabricated out of autoclave (OoA) by the vacuum bag oven (VBO) process using Cycom(Registered Trademark) T40-800b/5320-1 prepreg system while another panel with the same lay-up and dimensions was fabricated using the autoclave-cure, toughened epoxy prepreg system Cycom(Registered Trademark) IM7/977-3. The resulting 2.44 m x 2 m curved panels were investigated by non-destructive evaluation (NDE) at NASA Langley Research Center (NASA LaRC) to determine initial fabrication quality and then cut into smaller coupons for elevated temperature wet (ETW) mechanical property characterization. Mechanical property characterization of the sandwich coupons was conducted including edge-wise compression (EWC), and compression-after-impact (CAI) at conditions ranging from 25 C/dry to 150 C/wet. The details and results of this characterization effort are presented in this paper.

  14. Simulation studies of chemical erosion on carbon based materials at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Kenmotsu, T.; Kawamura, T.; Li, Zhijie; Ono, T.; Yamamura, Y.

    1999-06-01

    We simulated the fluence dependence of methane reaction yield in carbon with hydrogen bombardment using the ACAT-DIFFUSE code. The ACAT-DIFFUSE code is a simulation code based on a Monte Carlo method with a binary collision approximation and on solving diffusion equations. The chemical reaction model in carbon was studied by Roth or other researchers. Roth's model is suitable for the steady state methane reaction. But this model cannot estimate the fluence dependence of the methane reaction. Then, we derived an empirical formula based on Roth's model for methane reaction. In this empirical formula, we assumed the reaction region where chemical sputtering due to methane formation takes place. The reaction region corresponds to the peak range of incident hydrogen distribution in the target material. We adopted this empirical formula to the ACAT-DIFFUSE code. The simulation results indicate the similar fluence dependence compared with the experiment result. But, the fluence to achieve the steady state are different between experiment and simulation results.

  15. Compatibility of strontium-90 fluoride with containment materials at elevated temperatures

    SciTech Connect

    Fullam, H.T.

    1981-08-01

    The use of /sup 90/SrF/sub 2/ as a heat-source fuel requires that the /sup 90/Sr be adequately contained during heat-source service. A program for determining the compatibility of /sup 90/SrF/sub 2/ with containment materials at heat-source operating temperatures is described. These compatibility studies included: initial and supplemental screening tests; WESF /sup 90/SrF/sub 2/ capsule demonstration tests; thermal gradient test; and long-term tests. TZM, Haynes Alloy 25, and Hastelloy C-276 were the three materitals selected for evaluation at 600/sup 0/, 800/sup 0/ and 1000/sup 0/C for periods up to 30,000 h. Results showed that all three alloys suffered substantial attack when exposed to the /sup 90/SrF/sub 2/, although the TZM was more resistant to attack than the Hastelloy C-276 and Haynes Alloy 25. The latter two alloys appeared to provide about equal resistance to fluoride attack for exposures longer than about 12,000 h. Attack of the alloys tested by the /sup 90/SrF/sub 2/ was due primarily to impurities.

  16. Alterations in gill structure in tropical reef fishes as a result of elevated temperatures

    PubMed Central

    Bowden, A.J.; Gardiner, N.M.; Couturier, C.S.; Stecyk, J.A.W.; Nilsson, G.E.; Munday, P.L.; Rummer, J.L.

    2015-01-01

    Tropical regions are expected to be some of the most affected by rising sea surface temperatures (SSTs) because seasonal temperature variations are minimal. As temperatures rise, less oxygen dissolves in water, but metabolic requirements of fish and thus, the demand for effective oxygen uptake, increases. Gill remodelling is an acclimation strategy well documented in freshwater cyprinids experiencing large seasonal variations in temperature and oxygen as well as an amphibious killifish upon air exposure. However, no study has investigated whether tropical reef fishes remodel their gills to allow for increased oxygen demands at elevated temperatures. We tested for gill remodelling in five coral reef species (Acanthochromis polyacanthus, Chromis atripectoralis, Pomacentrus moluccensis, Dascyllus melanurus and Cheilodipterus quinquelineatus) from populations in northern Papua New Guinea (2° 35.765′ S; 150° 46.193′ E). Fishes were acclimated for 12-14 days to 29 and 31 °C, encompassing their seasonal range (29-31 °C), and 33 and 34 °C to account for end-of-century predicted temperatures. We measured lamellar perimeter, cross-sectional area, base thickness, and length for five filaments on the 2nd gill arches and qualitatively assessed 3rd gill arches via scanning electron microscopy (SEM). All species exhibited significant differences in the quantitative measurements made on the lamellae, but no consistent trends with temperature were observed. SEM only revealed alterations in gill morphology in P. moluccensis. The overall lack of changes in gill morphology with increasing temperature suggests that these near-equatorial reef fishes may fail to maintain adequate O2 uptake under future climate scenarios unless other adaptive mechanisms are employed. PMID:24862962

  17. Elevated temperature annealing behaviors of bulk resistivity and space charge density (Neff) of neutron irradiated silicon detectors and materials

    NASA Astrophysics Data System (ADS)

    Z., Li

    1996-02-01

    The bulk resistivity of neutron irradiated detector grade silicon material has been measured under the condition of no or low electrical filed (electrical neutral bulk or ENB condition) after elevated temperature (T = 110°C) anneals (ETA). The ENB resistivity (ρ) for as-irradiated silicon material increases with neutron fluence at low fluences (Φn > 1013 n/cm2). The saturation of the ENB resistivity near the intrinsic value can be explained by the near perfect compensation of all neutron induced deep donors and acceptors in the ENB. After ETA, it has been observed that ρ increases with annealing time for silicon materials irradiated below the saturation and decreases with annealing time for those irradiated after saturation. For those irradiated near the saturation point, ρ increases with annealing time initially and decreases thereafter. This ETA behavior of ρ may be explained by the increase of net acceptor-like deep levels in silicon during the anneal, qualitatively consistent with the observed reverse annealing effect of the space charge density (Neff) in silicon detectors which is an increase of negative space charge density (acceptors) after long term room temperature (RTA) anneal and/or ETA. However, the amount of the increase of net hole concentration (p) of about 5 × 1011 cm-3, corresponding to 20 hours of ETA at 110°C for a fluence of 1.5 × 1014 n/cm2, is still much less than the corresponding increase of Neff of about 1.5 × 1013 cm-3. This suggests that while the ETA restores some of the free carrier concentration (namely holes), there is still a large degree of compensation. The space charge density is still dominated by the deep levels and Neff ≠ p.

  18. Chemical structure of cement aged at normal and elevated temperatures and pressures

    SciTech Connect

    Le Saout, Gwenn . E-mail: lesaout_gwenn@yahoo.fr; Lecolier, Eric; Rivereau, Alain; Zanni, Helene

    2006-01-15

    The prime objective of the plug-and-abandon operations is to provide zonal isolation for infinite time. Cement-based materials are generally used as plugging materials. Therefore, it is important to understand the physical and chemical processes causing cement degradation in the downhole environment. In this study, we have characterised a Class G oilwell cement immersed for 1 year in brine at T=293 K, p=10{sup 5} Pa and T=353 K, p=7x10{sup 6} Pa using NMR and XRD techniques. In order to have a better understanding of the {sup 27}Al NMR spectra, selective dissolution has been performed. The results show that after 1 year of immersion in brine at T=293 K, p=10{sup 5} Pa, monosulfate is converted to Friedel's salt. Leaching resulted in the disappearance of portlandite and the formation of calcite and a more polymerised calcium silicate hydrates (C-S-H). In the T=353 K, p=7x10{sup 6} Pa mineralogy, ettringite is converted to hydrogrossular.

  19. Investigation of Problems Associated with the Use of Alloyed Molybdenum Sheet in Structures at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Mathauser, Eldon E.; Stein, Bland A.; Rummler, Donald R.

    1960-01-01

    The results of an experimental study to explore the capabilities and limitations of thin Mo-0.5Ti molybdenum-alloy sheet for structural applications at high temperatures are presented. Evaluation tests at temperatures ranging from room temperature,to 3000 F were made on resistance-welded corrugated-core sandwiches that were coated with a commercially available oxidation resistant coating known as W-2 and on coated oxidation and tensile specimens. The performance of the corrugated-core sandwiches in compressive strength and static oxidation tests, tensile properties of the coated molybdenum sheet, and the life of the coated specimens in static oxidation tests are given. A description of the equipment and procedures utilized in performing the evaluation tests is included.

  20. Effect of elevated temperature on the composition, structure, and mechanical properties of diffusion chromized steel

    SciTech Connect

    Osintsev, V.D.

    1986-05-01

    The author studies the effect of operating temperature for equipment in contact sections of sulfuric acid workshops on the structure and mechanical properties of the chromized coatings and core of chromized articles. The ferrite lattice spacing was determined in a DRON-0.5 diffractometer according to the line in copper K /sub alpha/ radiation exposure was carried out after layer-by-layer anodic etching of the coating in an aqueous solution. It was shown that diffusion chromizing may lead to a reduction in strength properties compared with those of unchromized steel. As a base for chromized articles intended for operation at temperatures up to 475/sup 0/C it is desirable to use steels 09G2 or 09G25, or for operation at temperatures up to 540/sup 0/C, steels 12KhM and 12MKh.

  1. Experiments to study strain gage load calibrations on a wing structure at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Monaghan, R. C.; Fields, R. A.

    1973-01-01

    Laboratory experiments were performed to study changes in strain-gage bridge load calibrations on a wing structure heated to temperatures of 200 F, 400 F, and 600 F. Data were also obtained to define the experimental repeatability of strain-gage bridge outputs. Experiments were conducted to establish the validity of the superposition of bridge outputs due to thermal and mechanical loads during a heating simulation of Mach 3 flight. The strain-gage bridge outputs due to load cycle at each of the above temperature levels were very repeatable. A number of bridge calibrations were found to change significantly as a function of temperature. The sum of strain-gage bridge outputs due to individually applied thermal and mechanical loads compared well with that due to combined or superimposed loads. The validity of superposition was, therefore, established.

  2. In situ soft XAS study on nickel-based layered cathode material at elevated temperatures: A novel approach to study thermal stability

    DOE PAGES

    Yoon, Won -Sub; Yang, Xiao -Qing; Haas, Otto; ...

    2014-10-29

    Tracking thermally induced reactions has always been challenging for electrode materials of electrochemical battery systems. Traditionally, a variety of calorimetric techniques and in situ XRD at elevated temperatures has been used to evaluate the thermal stability of electrode materials. These techniques are capable of providing variations in heat capacity, mass and average bulk composition of materials only. Herein, we report investigation of thermal characteristics of Li0.33Ni0.8Co0.15Al0.05O2 by using in situ soft XAS measurements in combination with XRD. Fluorescence yield and partial electron yield measurements are used simultaneously to obtain element selective surface and bulk information. Fluorescence yield measurements reveal nomore » energy change of the absorption peak and thus no valence state change in the bulk. However, electron yield measurements indicate that NiO-type rock salt structure is formed at the surface at temperatures above 200°C while no evidence for a surface reaction near Co sites in investigated temperature range is found. These results clearly show that in situ soft XAS can give a unique understanding of the role of each element in the structural transformation under thermal abuse offering a useful guidance in developing new battery system with improved safety performance.« less

  3. Effect of service exposure on fatigue crack propagation of Inconel 718 turbine disc material at elevated temperatures

    SciTech Connect

    Jeong, Dae-Ho; Choi, Myung-Je; Goto, Masahiro; Lee, Hong-Chul; Kim, Sangshik

    2014-09-15

    In this study, the fatigue crack propagation behavior of Inconel 718 turbine disc with different service times from 0 to 4229 h was investigated at 738 and 823 K. No notable change in microstructural features, other than the increase in grain size, was observed with increasing service time. With increasing service time from 0 to 4229 h, the fatigue crack propagation rates tended to increase, while the ΔK{sub th} value decreased, in low ΔK regime and lower Paris' regime at both testing temperatures. The fractographic observation using a scanning electron microscope suggested that the elevated temperature fatigue crack propagation mechanism of Inconel 718 changed from crystallographic cleavage mechanism to striation mechanism in the low ΔK regime, depending on the grain size. The fatigue crack propagation mechanism is proposed for the crack propagating through small and large grains in the low ΔK regime, and the fatigue crack propagation behavior of Inconel 718 with different service times at elevated temperatures is discussed. - Highlights: • The specimens were prepared from the Inconel 718 turbine disc used for 0 to 4229 h. • FCP rates were measured at 738 and 823 K. • The ΔK{sub th} values decreased with increasing service time. • The FCP behavior showed a strong correlation with the grain size of used turbine disc.

  4. Elevated temperature envelope forming

    NASA Technical Reports Server (NTRS)

    Burg, Bruce M. (Inventor); Gane, David H. (Inventor); Starowski, Robert M. (Inventor)

    1992-01-01

    Elevated temperature envelope forming includes enclosing a part blank and form tool within an envelope sealed against the atmosphere, heat treating the combination while forming pressure holds the envelope and part against the form tool, and allowing part cool down to occur in an inert atmosphere with forming pressure removed. The forming pressure is provided by evacuating the envelope and may be aided by differential force applied between the envelope and the form tool.

  5. Microstructure and Property Evolution in Advanced Cladding and Duct Materials Under Long-Term Irradiation at Elevated Temperature: Critical Experiments

    SciTech Connect

    Was, Gary; Jiao, Zhijie; Allen, Todd; Yang, Yong

    2013-12-20

    The in-service degradation of reactor core materials is related to underlying changes in the irradiated microstructure. During reactor operation, structural components and cladding experience displacement of atoms by collisions with neutrons at temperatures at which the radiation-induced defects are mobile, leading to microstructure evolution under irradiation that can degrade material properties. At the doses and temperatures relevant to fast reactor operation, the microstructure evolves by microchemistry changes due to radiation-induced segregation, dislocation loop formation and growth, radiation induced precipitation, destabilization of the existing precipitate structure, as well as the possibility for void formation and growth. These processes do not occur independently; rather, their evolution is highly interlinked. Radiation-induced segregation of Cr and existing chromium carbide coverage in irradiated alloy T91 track each other closely. The radiation-induced precipitation of Ni-Si precipitates and RIS of Ni and Si in alloys T91 and HCM12A are likely related. Neither the evolution of these processes nor their coupling is understood under the conditions required for materials performance in fast reactors (temperature range 300-600°C and doses to 200 dpa and beyond). Further, predictive modeling is not yet possible, as models for microstructure evolution must be developed along with experiments to characterize these key processes and provide tools for extrapolation. To extend the range of operation of nuclear fuel cladding and structural materials in advanced nuclear energy and transmutation systems to that required for the fast reactor, the irradiation-induced evolution of the microstructure, microchemistry, and the associated mechanical properties at relevant temperatures and doses must be understood. This project builds upon joint work at the proposing institutions, under a NERI-C program that is scheduled to end in September, to understand the effects of

  6. Characterization of microstructure and property evolution in advanced cladding and duct: Materials exposed to high dose and elevated temperature

    SciTech Connect

    Allen, Todd R.; Kaoumi, Djamel; Wharry, Janelle P.; Jiao, Zhijie; Topbasi, Cem; Kohnert, Aaron; Barnard, Leland; Certain, Alicia; Field, Kevin G.; Was, Gary S.; Morgan, Dane L.; Motta, Arthur T.; Wirth, Brian D.; Yang, Y.

    2015-05-20

    Designing materials for performance in high-radiation fields can be accelerated through a carefully chosen combination of advanced multiscale modeling paired with appropriate experimental validation. Here, the studies reported in this work, the combined efforts of six universities working together as the Consortium on Cladding and Structural Materials, use that approach to focus on improving the scientific basis for the response of ferritic–martensitic steels to irradiation. A combination of modern modeling techniques with controlled experimentation has specifically focused on improving the understanding of radiation-induced segregation, precipitate formation and growth under radiation, the stability of oxide nanoclusters, and the development of dislocation networks under radiation. Experimental studies use both model and commercial alloys, irradiated with both ion beams and neutrons. Lastly, transmission electron microscopy and atom probe are combined with both first-principles and rate theory approaches to advance the understanding of ferritic–martensitic steels.

  7. Characterization of microstructure and property evolution in advanced cladding and duct: Materials exposed to high dose and elevated temperature

    DOE PAGES

    Allen, Todd R.; Kaoumi, Djamel; Wharry, Janelle P.; ...

    2015-05-20

    Designing materials for performance in high-radiation fields can be accelerated through a carefully chosen combination of advanced multiscale modeling paired with appropriate experimental validation. Here, the studies reported in this work, the combined efforts of six universities working together as the Consortium on Cladding and Structural Materials, use that approach to focus on improving the scientific basis for the response of ferritic–martensitic steels to irradiation. A combination of modern modeling techniques with controlled experimentation has specifically focused on improving the understanding of radiation-induced segregation, precipitate formation and growth under radiation, the stability of oxide nanoclusters, and the development of dislocationmore » networks under radiation. Experimental studies use both model and commercial alloys, irradiated with both ion beams and neutrons. Lastly, transmission electron microscopy and atom probe are combined with both first-principles and rate theory approaches to advance the understanding of ferritic–martensitic steels.« less

  8. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Kim, K. S.; Vanstone, R. H.

    1989-01-01

    Alloy 718 crack growth experiments were conducted to assess the ability of the selected path-independent (P-I) integrals to describe the elevated temperature crack growth behavior. These tests were performed on single edge notch (SEN) specimens under displacement control with multiple extensometers to monitor the specimen and crack mouth opening displacement (CMOD). The displacements in these tests were sufficiently high to induce bulk cyclic inelastic deformation of the specimen. Under these conditions, the linear elastic fracture mechanics (LEFM) parameter K does not correlate the crack growth data. The experimentally measured displacement gradients at the end of specimen gage length were used as the boundary conditions in elastic-plastic finite element method (FEM) analyses. These analyses were performed with a node release approach using CYANIDE, a GEAE FEM code, which included a gap element which is capable of efficiently simulating crack closure. Excellent correlation was obtained between the experimentally measured and predicted variation of stress and CMOD with crack length and the stress-CMOD loops for Alloy 718 tests conducted at 538 C. This confirmed the accuracy of the FEM crack growth simulation approach. The experimentally measured crack growth rate data correlated well the selected P-I integrals. These investigations have produced significant progress in developing P-I integrals as non-linear fracture mechanics parameters. The results suggest that this methodology has the potential of accurately describing elevated temperature crack growth behavior under the combined influence of thermal cycling and bulk elastic-inelastic deformation states.

  9. Elevated temperature fatigue testing of metals

    NASA Technical Reports Server (NTRS)

    Hirschberg, M. H.

    1981-01-01

    The major technology areas needed to perform a life prediction of an aircraft turbine engine hot section component are discussed and the steps required for life prediction are outlined. These include the determination of the operating environment, the calculation of the thermal and mechanical loading of the component, the cyclic stress-strain and creep behavior of the material required for structural analysis, and the structural analysis to determine the local stress-strain-temperature-time response of the material at the critical location in the components. From a knowledge of the fatigue, creep, and failure resistance of the material, a prediction of the life of the component is made. Material characterization and evaluation conducted for the purpose of calculating fatigue crack initiation lives of components operating at elevated temperatures are emphasized.

  10. Superplastic forming and diffusion bonding of rapidly solidified, dispersion strengthened aluminum alloys for elevated temperature structural applications

    NASA Technical Reports Server (NTRS)

    Ting, E. Y.; Kennedy, J. R.

    1989-01-01

    Rapidly solidified alloys, based upon the Al-Fe-V-Si system and designed for elevated temperature applications, were evaluated for superplasticity and diffusion bonding behavior. Alloys with 8, 16, 27, and 36 volume percent silicide dispersoids were produced; dispersoid condition was varied by rolling at 300, 400, and 500 C (572, 752, and 932 F). Superplastic behavior was evaluated at strain rates from 1 x 10(exp -6)/s to 8.5/s at elevated temperatures. The results indicate that there was a significant increase in elongation at higher strain rates and at temperatures above 600 C (1112 F). However, the exposure of the alloys to temperatures greater than 600 C (1112 F) resulted in the coarsening of the strengthening dispersoid and the degradation of mechanical properties. Diffusion bonding was possible using low gas pressure at temperatures greater than 600 C (1112 F) which also resulted in degraded properties. The bonding of Al-Fe-V-Si alloys to 7475 aluminum alloy was performed at 516 C (960 F) without significant degradation in microstructure. Bond strengths equal to 90 percent that of the base metal shear strength were achieved. The mechanical properties and microstructural characteristics of the alloys were investigated.

  11. Microstructure and Property Evolution in Advanced Cladding and Duct Materials Under Long-Term and Elevated Temperature Irradiation: Modeling and Experimental Investigation

    SciTech Connect

    Wirth, Brian; Morgan, Dane; Kaoumi, Djamel; Motta, Arthur

    2013-12-01

    irradiation. This project will focus on modeling microstructural and microchemical evolution of irradiated alloys by performing detailed modeling of such microstructure evolution processes coupled with well-designed in situ experiments that can provide validation and benchmarking to the computer codes. The broad scientific and technical objectives of this proposal are to evaluate the microstructure and microchemical evolution in advanced ferritic/martensitic and oxide dispersion strengthened (ODS) alloys for cladding and duct reactor materials under long-term and elevated temperature irradiation, leading to improved ability to model structural materials performance and lifetime. Specifically, we propose four research thrusts, namely Thrust 1: Identify the formation mechanism and evolution for dislocation loops with Burgers vector of a<100> and determine whether the defect microstructure (predominately dislocation loop/dislocation density) saturates at high dose. Thrust 2: Identify whether a threshold irradiation temperature or dose exists for the nucleation of growing voids that mark the beginning of irradiation-induced swelling, and begin to probe the limits of thermal stability of the tempered Martensitic structure under irradiation. Thrust 3: Evaluate the stability of nanometer sized Y- Ti-O based oxide dispersion strengthened (ODS) particles at high fluence/temperature. Thrust 4: Evaluate the extent to which precipitates form and/or dissolve as a function of irradiation temperature and dose, and how these changes are driven by radiation induced segregation and microchemical evolutions and determined by the initial microstructure.

  12. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Kim, K. S.; Vanstone, R. H.

    1992-01-01

    The purpose of this program was to extend the work performed in the base program (CR 182247) into the regime of time-dependent crack growth under isothermal and thermal mechanical fatigue (TMF) loading, where creep deformation also influences the crack growth behavior. The investigation was performed in a two-year, six-task, combined experimental and analytical program. The path-independent integrals for application to time-dependent crack growth were critically reviewed. The crack growth was simulated using a finite element method. The path-independent integrals were computed from the results of finite-element analyses. The ability of these integrals to correlate experimental crack growth data were evaluated under various loading and temperature conditions. The results indicate that some of these integrals are viable parameters for crack growth prediction at elevated temperatures.

  13. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1984-01-01

    A three year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for non-proportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved undertanding were through several critical non-proportional loading experiments. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C.

  14. Properties of Yttria-Tetragonal Zirconia Polycrystal (Y-TZP) Materials after Long-Term Exposure to Elevated Temperatures

    DTIC Science & Technology

    1989-03-01

    4. TITLE (and Subside) 5. TYPE OF REPORT & PERIOD COVERED PROPERTIES OF YTTRIA- TETRAGONAL ZIRCONIA Final Report POLYCRYSTAL (Y- TZP ) MATERIALS AFTER...ABSTRACT Due to an unusual combination of high strength and toughness, tetragonal zirconia polycrystal ( TZP ) materials are candidates for use in...phenomenon’s effect on the properties. Seven commercially available yttria- tetragonal zirconia polycrystal (Y- TZP ) materials were evaluated. Ro 9 E temperature

  15. 1-3 connectivity composite material made from lithium niobate and cement for ultrasonic condition monitoring at elevated temperatures.

    PubMed

    Shepherd, G; Cochran, A; Kirk, K J; McNab, A

    2002-05-01

    We have designed, manufactured and tested a piezoelectric composite material to operate at temperatures above 400 degrees C. The material is a 1-3 connectivity composite with pillars of Z-cut lithium niobate in a matrix of alumina cement. The composite material produced shorter pulses than a monolithic plate of lithium niobate and remained intact upon cooling. Results are presented from room temperature and high temperature testing. This material could be bonded permanently to a test object, making it possible to carry out condition monitoring over an extended period. A new excitation method was also developed to enable remote switching between array elements.

  16. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1985-01-01

    A 3 year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for nonproportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved understanding were through several critical nonproportional loading experiments. The direction of cracking observed on failed specimens was also recorded and used to guide the development of the theory. Cyclic deformation responses were permanently recorded digitally during each test. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C. In contrast to some other metals, loading path in nonproportional loading had little effect on fatigue lives. Strain rate had a small effect on fatigue lives at 649 C. Of the various correlating parameters the modified plastic work and octahedral shear stress were the most successful.

  17. Corrosion resistance and behavior of construction materials exposed to dilute sulfuric acid at elevated temperatures under static conditions

    SciTech Connect

    Nguyen, D.T.

    1994-10-01

    Laboratory investigation has been undertaken to determine the electrochemical behavior and corrosion resistance of various construction materials in a simulated hydrolysis environment (5 wt % sulfuric acid) at temperatures ranging from 90 to 220C. Tests were performed in an autoclave-type electrochemical cell. The corrosion behavior of the test materials was determined using computer-controlled DC potentiodynamic polarization. Corrosion rates of the test materials were determined using AC impedance techniques. Among the stainless steels tested, only alloy N08026 (Carpenter 20Mo-6) performed satisfactory up to a temperature of 100C. The alloy passivated spontaneously in the environment and corroded at a rate of less than 2 mpy. None of the stainless steels tested could be used at 120{degrees}C or above. A number of nickel-based alloys tested had good corrosion resistance up to 100C, but their corrosion rate exceeded 2 mpy at higher temperatures. Zirconium alloys were satisfactory up to 180C. Only tantalum and a tantalum-niobium alloy were satisfactory up to 220C.

  18. The mechanical properties of fluoride salts at elevated temperatures. [candidate thermal energy storage materials for solar dynamic systems

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Whittenberger, J. D.

    1989-01-01

    The deformation behavior of CaF2 and LiF single crystals compressed in the 111 and the 100 line directions, respectively, are compared with the mechanical properties of polycrystalline LiF-22 (mol pct) CaF2 eutectic mixture in the temperature range 300 to 1275 K for strain rates varying between 7 x 10 to the -7th and 0.2/s. The true stress-strain curves for the single crystals were found to exhibit three stages in an intermediate range of temperatures and strain rates, whereas those for the eutectic showed negative work-hardening rates after a maximum stress. The true stress-strain rate data for CaF2 and LiF-22 CaF2 could be represented by a power-law relation with the strain rate sensitivities lying between 0.05 and 0.2 for both materials. A similar relation was found to be unsatisfactory in the case of LiF.

  19. Elevated temperature strain gages

    NASA Technical Reports Server (NTRS)

    Brittain, J. O.; Geslin, D.; Lei, J. F.

    1985-01-01

    Materials were evaluated that could be used in manufacturing electrical resistance strain gages for static strain measurements at temperatures at or above 1273 K. Strain gage materials must have a characteristic response to strain, temperature and time that is reproducible or that varies in a predictable manner within specified limits. Several metallic alloys were evaluated, as well as a series of transition metal carbides, nitrides and silicides.

  20. Actinide Thermodynamics at Elevated Temperatures

    SciTech Connect

    Friese, Judah I.; Rao, Linfeng; Xia, Yuanxian; Bachelor, Paula P.; Tian, Guoxin

    2007-11-16

    The postclosure chemical environment in the proposed Yucca Mountain repository is expected to experience elevated temperatures. Predicting migration of actinides is possible if sufficient, reliable thermodynamic data on hydrolysis and complexation are available for these temperatures. Data are scarce and scattered for 25 degrees C, and nonexistent for elevated temperatures. This collaborative project between LBNL and PNNL collects thermodynamic data at elevated temperatures on actinide complexes with inorganic ligands that may be present in Yucca Mountain. The ligands include hydroxide, fluoride, sulfate, phosphate and carbonate. Thermodynamic parameters of complexation, including stability constants, enthalpy, entropy and heat capacity of complexation, are measured with a variety of techniques including solvent extraction, potentiometry, spectrophotometry and calorimetry

  1. RESEARCH ON THE BASIC NATURE OF STRESS CORROSION FOR VARIOUS STRUCTURAL ALLOYS AT ROOM AND ELEVATED TEMPERATURE,

    DTIC Science & Technology

    LIFE), GRAIN STRUCTURES(METALLURGY), FRACTURE(MECHANICS), TENSILE PROPERTIES , HEAT TREATMENT, TEMPERATURE, SEA WATER, CHLORIDES, SHEETS, STEEL, MOLYBDENUM ALLOYS, VANADIUM ALLOYS, ENVIRONMENTAL TESTS, MICROSTRUCTURE.

  2. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Malik, S. N.; Vanstone, R. H.; Kim, K. S.; Laflen, J. H.

    1985-01-01

    The purpose is to determine the ability of currently available P-I integrals to correlate fatigue crack propagation under conditions that simulate the turbojet engine combustor liner environment. The utility of advanced fracture mechanics measurements will also be evaluated during the course of the program. To date, an appropriate specimen design, a crack displacement measurement method, and boundary condition simulation in the computational model of the specimen were achieved. Alloy 718 was selected as an analog material based on its ability to simulate high temperature behavior at lower temperatures. Tensile and cyclic tests were run at several strain rates so that an appropriate constitutive model could be developed. Suitable P-I integrals were programmed into a finite element post-processor for eventual comparison with experimental data.

  3. Buckling tests of aluminium columns at elevated temperatures

    SciTech Connect

    Langhelle, N.K.; Amdahl, J.; Eberg, E.; Lundberg, S.

    1996-12-31

    Accidental fires are events with severe catastrophe potential for all offshore structures, and in particular for aluminium structures. Due to aluminium`s rapid strength degradation at elevated temperatures, this is particular true for aluminium structures. Accurate prediction of fire resistance is therefore essential. Experimental tests are needed to evaluate current design rules and state-of-the-art material models for aluminium under elevated temperatures. An experimental investigation was undertaken in order to study the behavior of AA 6082 alloy aluminium columns at elevated temperatures. Some of the tests were carried out at constant load with increasing temperature. Other tests experienced constant temperature and increasing load. Buckling tests at ambient temperature were also conducted. Particular emphasis was put on high temperature creep effects. The purpose of the tests was to provide data for verification of the material model implemented in the computer program USFOS, for analysis of progressive collapse analyses of space frame structures. The performance of the tempers T4 and T6 as well as columns with transversal welds are compared internally as well as to column buckling curves given in current design codes.

  4. The development of gamma-gamma-prime lamellar structures in a nickel-base superalloy during elevated temperature mechanical testing

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Ebert, L. J.

    1985-01-01

    The kinetics of the formation and subsequent development of the directional coarsening of the gamma-prime precipitate in model Ni-Al-Mo-Ta superalloy single crystals are examined during tensile creep under various stress levels at 982 and 1038 C. Special attention is given to the gamma and gamma-prime relation to creep time and strain in order to trace the changing gamma-gamma-prime morphology. Directional coarsening of gamma-prime is found to begin during primary creep and its rate is shown to increase with an increase in temperature or stress level. The length of gamma-prime thickness increased linearly with time up to a plateau reached after the onset of steady state creep. The raft thickness, equal to the gamma-prime size, remained constant at this initial value up through the onset of the tertiary creep. The interlaminar spacing indicates the stability of directionally coarsened structure.

  5. Effect of Isomeric Structures of Branched Cyclic Hydrocarbons on Densities and Equation of State Predictions at Elevated Temperatures and Pressures

    SciTech Connect

    Wu, Yue; Bamgbade, Babatunde A; Burgess, Ward A; Tapriyal, Deepak; Baled, Hseen O; Enick, Robert M; McHugh, Mark

    2013-07-25

    The cis and trans conformation of a branched cyclic hydrocarbon affects the packing and, hence, the density, exhibited by that compound. Reported here are density data for branched cyclohexane (C6) compounds including methylcyclohexane, ethylcyclohexane (ethylcC6), cis-1,2-dimethylcyclohexane (cis-1,2), cis-1,4-dimethylcyclohexane (cis-1,4), and trans-1,4-dimethylcyclohexane (trans-1,4) determined at temperatures up to 525 K and pressures up to 275 MPa. Of the four branched C6 isomers, cis-1,2 exhibits the largest densities and the smallest densities are exhibited by trans-1,4. The densities are modeled with the Peng–Robinson (PR) equation of state (EoS), the high-temperature, high-pressure, volume-translated (HTHP VT) PREoS, and the perturbed chain, statistical associating fluid theory (PC-SAFT) EoS. Model calculations highlight the capability of these equations to account for the different densities observed for the four isomers investigated in this study. The HTHP VT-PREoS provides modest improvements over the PREoS, but neither cubic EoS is capable of accounting for the effect of isomer structural differences on the observed densities. The PC-SAFT EoS, with pure component parameters from the literature or from a group contribution method, provides improved density predictions relative to those obtained with the PREoS or HTHP VT-PREoS. However, the PC-SAFT EoS, with either set of parameters, also cannot fully account for the effect of the C6 isomer structure on the resultant density.

  6. Effect of isomeric structures of branched cyclic hydrocarbons on densities and equation of state predictions at elevated temperatures and pressures.

    PubMed

    Wu, Yue; Bamgbade, Babatunde A; Burgess, Ward A; Tapriyal, Deepak; Baled, Hseen O; Enick, Robert M; McHugh, Mark A

    2013-07-25

    The cis and trans conformation of a branched cyclic hydrocarbon affects the packing and, hence, the density, exhibited by that compound. Reported here are density data for branched cyclohexane (C6) compounds including methylcyclohexane, ethylcyclohexane (ethylcC6), cis-1,2-dimethylcyclohexane (cis-1,2), cis-1,4-dimethylcyclohexane (cis-1,4), and trans-1,4-dimethylcyclohexane (trans-1,4) determined at temperatures up to 525 K and pressures up to 275 MPa. Of the four branched C6 isomers, cis-1,2 exhibits the largest densities and the smallest densities are exhibited by trans-1,4. The densities are modeled with the Peng-Robinson (PR) equation of state (EoS), the high-temperature, high-pressure, volume-translated (HTHP VT) PREoS, and the perturbed chain, statistical associating fluid theory (PC-SAFT) EoS. Model calculations highlight the capability of these equations to account for the different densities observed for the four isomers investigated in this study. The HTHP VT-PREoS provides modest improvements over the PREoS, but neither cubic EoS is capable of accounting for the effect of isomer structural differences on the observed densities. The PC-SAFT EoS, with pure component parameters from the literature or from a group contribution method, provides improved density predictions relative to those obtained with the PREoS or HTHP VT-PREoS. However, the PC-SAFT EoS, with either set of parameters, also cannot fully account for the effect of the C6 isomer structure on the resultant density.

  7. Dynamics across the structural transitions at elevated temperatures in Na0.7CoO2

    NASA Astrophysics Data System (ADS)

    Juranyi, Fanni; Månsson, Martin; Gavilano, Jorge L.; Mena, Mattia; Pomjakushina, Ekaterina; Medarde, Marisa; Sugiyama, Jun; Kamazawa, Kazuya; Batlogg, Bertram; Ott, Hans R.; Seydel, Tilo

    2015-01-01

    The layered transition-metal oxide Nax CoO2 has been studied extensively both for its correlated electronic properties as well as for potential battery applications. It was discovered that high-temperature Na ion vacancy order and dynamics can be very useful to tailor low-temperature properties of members of this compound family. We have studied the Na-ion dynamics on the atomic length-scale in the Na0.7 CoO2 compound by neutron spectroscopy. The temperature dependence of both the elastic and the inelastic intensities show steps at TA ≈ 290 K and TB ≈ 400 K. At TA the step is shown to be connected to low energy phonons, while at TB the Na ion diffusion suddenly gets fast enough, and the characteristic signal of quasielastic scattering appears. The current results further elucidate the subtle changes in the Na ion dynamics that have been revealed in our previous neutron diffraction studies [1], intimately connecting structural transformations at TA and TB with the opening-up of 1D and 2D Na-ion diffusion paths. Finally, the estimated diffusion coefficient above TB was found to differ from the one measured by muon-spin relaxation (μ+SR) [2] by about four orders of magnitude. However it might be that the present QENS data rather describe a fast localized prozess than a long range translational diffusion. Within this model the corresponding time scale (ℏ/E) would be in the order of 50 ps.

  8. Creep and Fracture Characteristics of Materials and Structures at Elevated Temperatures.

    DTIC Science & Technology

    1986-02-14

    uncracked specimens were tested to determine their resistance to shear loading. The results demonstrate the ability of this loading grip system to...polymodale (mode 1+11). Ś . Micanique, Materiaux , Electricit6 338, 101-112 (1978) 20 A.F.-C. Liu, Crack growth and failure of aluminum under in-plane...rigidly mounted by sandwiching between two aluminum pieces. Two strain gauges of resistance 120ohms were mounted on each face of the titanium alloy

  9. Buffer strips in composites at elevated temperature

    NASA Technical Reports Server (NTRS)

    Bigelow, C. A.

    1983-01-01

    The composite material 'buffer strip' concept is presently investigated at elevated temperatures for the case of graphite/polyimide buffer strip panels using a (45/0/45/90)2S layup, where the buffer strip material was 0-deg S-glass/polyimide. Each panel was loaded in tension until it failed, and radiographs and crack opening displacements were recorded during the tests to determine fracture onset, fracture arrest, and the extent of damage in the buffer strip after crack arrest. At 177 + or - 3 C, the buffer strips increased the panel strength by at least 40 percent in comparison with panels without buffer strips. Compared to similar panels tested at room temperature, those tested at elevated temperature had lower residual strengths, but higher failure strains.

  10. HCF + LCF Interactions at Elevated Temperature

    DTIC Science & Technology

    2005-03-02

    4V alloy is a material typically selected for the construction of the front, low- temperature , stages of aero-engines because this alloy shows high ...contribution of HCF cycles to combined HCF+LCF FCG rates is reduced at elevated temperature especially at high stress ratios. f) An increase in temperature ...433. [2] Arakere NK, Goswami T, Krohn J and Ramachandran N. “ High temperature fatigue crack growth behaviour” of Ti-6Al-4V. High Temperature

  11. Modeling of High-Strain-Rate Deformation, Fracture, and Impact Behavior of Advanced Gas Turbine Engine Materials at Low and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Shazly, Mostafa; Nathenson, David; Prakash, Vikas

    2003-01-01

    Gamma titanium aluminides have received considerable attention over the last decade. These alloys are known to have low density, good high temperature strength retention, and good oxidation and corrosion resistance. However, poor ductility and low fracture toughness have been the key limiting factors in the full utilization of these alloys. More recently, Gamma-met PX has been developed by GKSS, Germany. These alloys have been observed to have superior strengths at elevated temperatures and quasi-static deformation rates and good oxidation resistance at elevated temperatures when compared with other gamma titanium aluminides. The present paper discusses results of a study to understand dynamic response of gamma-met PX in uniaxial compression. The experiments were conducted by using a modified split Hopkinson pressure bar between room temperature and 900 C and strain rates of up to 3500 per second. The Gamma met PX alloy showed superior strength when compared to nickel based superalloys and other gamma titanium aluminides at all test temperatures. It also showed strain and strain-rate hardening at all levels of strain rates and temperatures and without yield anomaly up to 900 C. After approximately 600 C, thermal softening is observed at all strain rates with the rate of thermal softening increasing dramatically between 800 and 900 C. However, these flow stress levels are comparatively higher in Gamma met PX than those observed for other TiAl alloys.

  12. Effect of Elevated CO2 Concentration, Elevated Temperature and No Nitrogen Fertilization on Methanogenic Archaeal and Methane-Oxidizing Bacterial Community Structures in Paddy Soil.

    PubMed

    Liu, Dongyan; Tago, Kanako; Hayatsu, Masahito; Tokida, Takeshi; Sakai, Hidemitsu; Nakamura, Hirofumi; Usui, Yasuhiro; Hasegawa, Toshihiro; Asakawa, Susumu

    2016-09-29

    Elevated concentrations of atmospheric CO2 ([CO2]) enhance the production and emission of methane in paddy fields. In the present study, the effects of elevated [CO2], elevated temperature (ET), and no nitrogen fertilization (LN) on methanogenic archaeal and methane-oxidizing bacterial community structures in a free-air CO2 enrichment (FACE) experimental paddy field were investigated by PCR-DGGE and real-time quantitative PCR. Soil samples were collected from the upper and lower soil layers at the rice panicle initiation (PI) and mid-ripening (MR) stages. The composition of the methanogenic archaeal community in the upper and lower soil layers was not markedly affected by the elevated [CO2], ET, or LN condition. The abundance of the methanogenic archaeal community in the upper and lower soil layers was also not affected by elevated [CO2] or ET, but was significantly increased at the rice PI stage and significantly decreased by LN in the lower soil layer. In contrast, the composition of the methane-oxidizing bacterial community was affected by rice-growing stages in the upper soil layer. The abundance of methane-oxidizing bacteria was significantly decreased by elevated [CO2] and LN in both soil layers at the rice MR stage and by ET in the upper soil layer. The ratio of mcrA/pmoA genes correlated with methane emission from ambient and FACE paddy plots at the PI stage. These results indicate that the decrease observed in the abundance of methane-oxidizing bacteria was related to increased methane emission from the paddy field under the elevated [CO2], ET, and LN conditions.

  13. Effect of Elevated CO2 Concentration, Elevated Temperature and No Nitrogen Fertilization on Methanogenic Archaeal and Methane-Oxidizing Bacterial Community Structures in Paddy Soil

    PubMed Central

    Liu, Dongyan; Tago, Kanako; Hayatsu, Masahito; Tokida, Takeshi; Sakai, Hidemitsu; Nakamura, Hirofumi; Usui, Yasuhiro; Hasegawa, Toshihiro; Asakawa, Susumu

    2016-01-01

    Elevated concentrations of atmospheric CO2 ([CO2]) enhance the production and emission of methane in paddy fields. In the present study, the effects of elevated [CO2], elevated temperature (ET), and no nitrogen fertilization (LN) on methanogenic archaeal and methane-oxidizing bacterial community structures in a free-air CO2 enrichment (FACE) experimental paddy field were investigated by PCR-DGGE and real-time quantitative PCR. Soil samples were collected from the upper and lower soil layers at the rice panicle initiation (PI) and mid-ripening (MR) stages. The composition of the methanogenic archaeal community in the upper and lower soil layers was not markedly affected by the elevated [CO2], ET, or LN condition. The abundance of the methanogenic archaeal community in the upper and lower soil layers was also not affected by elevated [CO2] or ET, but was significantly increased at the rice PI stage and significantly decreased by LN in the lower soil layer. In contrast, the composition of the methane-oxidizing bacterial community was affected by rice-growing stages in the upper soil layer. The abundance of methane-oxidizing bacteria was significantly decreased by elevated [CO2] and LN in both soil layers at the rice MR stage and by ET in the upper soil layer. The ratio of mcrA/pmoA genes correlated with methane emission from ambient and FACE paddy plots at the PI stage. These results indicate that the decrease observed in the abundance of methane-oxidizing bacteria was related to increased methane emission from the paddy field under the elevated [CO2], ET, and LN conditions. PMID:27600710

  14. Proceedings of the ONR/NBS Workshop Contact Damage in Ceramic Materials at Elevated Temperatures Held at the National Bureau of Standards, Washington, DC 20234.

    DTIC Science & Technology

    1982-04-01

    sliding. In his talk on high temperature sliding, Rabinowicz emphasized the chemical nature of the contact surfaces and the importance of phase...obtained. Hence, the higher the chemical affinity of two metals the greater will be the degree of wear when the metals are rubbed together. Rabinowicz ... Rabinowicz also noted that structural changes during sliding influence the friction and wear behavior of materials. Changes in crystal structure, the

  15. Elevated temperature static and fatigue testing techniques

    NASA Astrophysics Data System (ADS)

    Harmon, D. M.; Coffey, F. J.; Antolovich, S. D.; Brown, R. C.

    Aircraft of the future, such as an aerospace vehicle or an advanced fighter, will have expanded operating envelopes and therefore, will be subject to extreme environmental conditions. They will experience high temperatures combined with high external loads. Due to the complexity of full scale testing with combined thermal and mechanical loads, subcomponent and coupon testing play an extremely important role in the verification of structural integrity. This paper describes testing facilities designed for elevated temperature testing of coupon specimens. These facilities are capable of simultaneously applying spectrum loads and a detailed thermal profile. A method is also outlined for developing realistic thermal and mechanical load profiles for advanced aircraft.

  16. Elevated-Temperature "Ultra" Fast Fracture Strength of Advanced Ceramics: An Approach to Elevated-Temperature "Inert" Strength

    NASA Technical Reports Server (NTRS)

    Choi, S. R.; Gyekenyesi, J. P.

    1999-01-01

    The determination of "ultra" fast fracture strengths of five silicon nitride ceramics at elevated temperatures has been made by using constant stress-rate ("dynamic fatigue") testing with a series of "ultra" fast test rates. The test material included four monolithic and one SiC whisker-reinforced composite silicon nitrides. Of the five test materials, four silicon nitrides exhibited the elevated -temperature strengths that approaches their respective room-temperature strengths at an "ultra" fast test rate of 3.3 x 10(exp 4) MPa/s. This implies that slow cracks growth responsible for elevated-temperature failure can be eliminated or minimized by using the "ultra" fast test rate. These ongoing experimental results have shed light on laying a theoretical and practical foundation on the concept and definition of elevated-temperature "inert" strength behavior of advanced ceramics.

  17. Molten Composition B Viscosity at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Zerkle, David K.; Núñez, Marcel P.; Zucker, Jonathan M.

    2016-10-01

    A shear-thinning viscosity model is developed for molten Composition B at elevated temperature from analysis of falling ball viscometer data. Results are reported with the system held at 85, 110, and 135°C. Balls of densities of 2.7, 8.0, and 15.6 g/cm3 are dropped to generate a range of strain rates in the material. Analysis of video recordings gives the speed at which the balls fall. Computer simulation of the viscometer is used to determine parameters for a non-Newtonian model calibrated to measured speeds. For the first time, viscosity is shown to be a function of temperature and strain rate-dependent maximum RDX (cyclotrimethylenetrinitramine) particle volume fraction.

  18. Highly durable polymer electrolyte membranes at elevated temperature: Cross-linked copolymer structure consisting of poly(benzoxazine) and poly(benzimidazole)

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Kon; Kim, Ki-Hyun; Park, Jung Ock; Kim, Kihyun; Ko, Taeyun; Choi, Seong-Woo; Pak, Chanho; Chang, Hyuk; Lee, Jong-Chan

    2013-03-01

    For polymer electrolyte membrane fuel cell (PEMFC) applications at elevated temperature (>100 °C), a series of cross-linked benzoxazine-benzimidazole copolymer, P(HFa-co-BI), membranes are prepared by casting a solution of poly[2,2‧-(m-phenylene)-5,5‧-bibenzimidazole] (PBI) and di-functional benzoxazine monomer, 6,6‧-(hexafluoroisopropylidene)bis(3-phenyl-3,4-dihydro-2H-benzoxazine) (HFa), in N,N-dimethylacetamide prior to stepwise heating to 250 °C. The films are also viable to manufacture to large quantities and area by roll-to-roll coating. The resulting cross-linked copolymer, P(HFa-co-BI), membranes are found to be thermally and mechanically stable. Although the proton conductivity values of P(HFa-co-BI) membranes are smaller than that of the PBI membrane, their cell performance (0.68 V at 0.2 A cm-2 at 150 °C) is close to that of PBI membrane and their long-term durability (ca. 3116 cycles on in situ accelerated lifetime mode of load cycling testing) is found to be far superior to the PBI membrane.

  19. Investigation of the formability of aluminium alloys at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Tisza, M.; Budai, D.; Kovács, P. Z.; Lukács, Zs

    2016-11-01

    Aluminium alloys are more and more widely applied in car body manufacturing. Increasing the formability of aluminium alloys are one of the most relevant tasks in todays’ research topics. In this paper, the focus will be on the investigation of the formability of aluminium alloys concerning those material grades that are more widely applied in the automotive industry including the 5xxx and 6xxx aluminium alloy series. Recently, besides the cold forming of aluminium sheets the forming of aluminium alloys at elevated temperatures became a hot research topic, too. In our experimental investigations, we mostly examined the EN AW 5754 and EN AW 6082 aluminium alloys at elevated temperatures. We analysed the effect of various material and process parameters (e.g. temperature, sheet thickness) on the formability of aluminium alloys with particular emphasis on the Forming Limit Diagrams at elevated temperatures in order to find the optimum forming conditions for these alloys.

  20. Properties of yttria-tetragonal zirconia polycrystal (Y-TZP) materials after long-term exposure to elevated temperatures. Final report

    SciTech Connect

    Swab, J.J.

    1989-03-01

    Seven commercially available yttria-tetragonal zirconia polycrystal (Y-TZP) materials were evaluated. Room temperature properties were measured before and after heat treatments at 1000C. Microstructure and phase stability were also examined. In all but one case, the Y-TZPs showed very little change in room temperature properties after long times at this temperature. Results show that pressure-assisted processing greatly improves the strength by reducing porosity and keeping the grain size extremely fine, but this reduces the toughness because finer grains are more difficult to transform. In addition, a small amount of cubic zirconia appears to enhance the toughness of fine-grained Y-TZP while maintaining good strength. During processing, a small amount of cubic zirconia is formed and allowed to grow. This creates regions poor in yttria which can transform spontaneously in the presence of a crack-tip stress field.

  1. A Study of Advanced Materials for Gas Turbine Coatings at Elevated Temperatures Using Selected Microstructures and Characteristic Environments for Syngas Combustion

    SciTech Connect

    Ravinder Diwan; Patrick Mensah; Guoqiang Li; Nalini Uppu; Strphen Akwaboa; Monica Silva; Ebubekir Beyazoglu; Ogad Agu; Naresh Polasa; Lawrence Bazille; Douglas Wolfe; Purush Sahoo

    2011-02-10

    Thermal barrier coatings (TBCs) that can be suitable for use in industrial gas turbine engines have been processed and compared with electron beam physical vapor deposition (EBPVD) microstructures for applications in advanced gas turbines that use coal-derived synthesis gas. Thermo-physical properties have been evaluated of the processed air plasma sprayed TBCs with standard APS-STD and vertically cracked APS-VC coatings samples up to 1300 C. Porosity of these selected coatings with related microstructural effects have been analyzed in this study. Wet and dry thermal cycling studies at 1125 C and spalling resistance thermal cycling studies to 1200 C have also been carried out. Type I and Type II hot corrosion tests were carried out to investigate the effects of microstructure variations and additions of alumina in YSZ top coats in multi-layered TBC structures. The thermal modeling of turbine blade has also been carried out that gives the capability to predict in-service performance temperature gradients. In addition to isothermal high temperature oxidation kinetics analysis in YSZ thermal barrier coatings of NiCoCrAlY bond coats with 0.25% Hf. This can affect the failure behavior depending on the control of the thermally grown oxide (TGO) growth at the interface. The TGO growth kinetics is seen to be parabolic and the activation energies correspond to interfacial growth kinetics that is controlled by the diffusion of O{sub 2} in Al{sub 2}O{sub 3}. The difference between oxidation behavior of the VC and STD structures are attributed to the effects of microstructure morphology and porosity on oxygen ingression into the zirconia and TGO layers. The isothermal oxidation resistance of the STD and VC microstructures is similar at temperatures up to 1200 C. However, the generally thicker TGO layer thicknesses and the slightly faster oxidation rates in the VC microstructures are attributed to the increased ingression of oxygen through the grain boundaries of the vertically

  2. Determination of Plate Compressive Strengths at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Heimerl, George J; Roberts, William M

    1950-01-01

    The results of local-instability tests of h-section plate assemblies and compressive stress-strain tests of extruded 75s-t6 aluminum alloy, obtained to determine flat-plate compressive strength under stabilized elevated temperature conditions, are given for temperatures up to 600 degrees F. The results show that methods available for calculating the critical compressive stress at room temperature can also be used at elevated temperatures if the applicable compressive stress-strain curve for the material is given.

  3. An experimental investigation into the behavior of glassfiber reinforced polymer elements at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Qian, Kenny Zongxi

    This thesis presents a literature review and results of an experimental study about the effects of high temperatures and cyclic loading on the physical and mechanical properties of pultruded glass fiber reinforced polymer (GFRP) square tubes used in civil engineering structural applications. Most laboratory researches have focused mainly on the effect of elevated temperature on the compressive strength of the GFRP square tubes. Limited research has focused on the tensile strength of GFRP coupons under elevated temperatures. Dynamic Mechanical Analyses (DMA) was performed to assess the viscoelastic behavior including the glass transition temperature of GFRP. Sixteen GFRP coupons were tested under elevated temperatures to investigate the tensile strength and the effect of elevated temperatures to the tensile strength of GFRP. The results of an experimental program performed on fifty GFRP square tubes with different designs in 1.83m at normal temperatures were discussed to investigate compression performance. Another experimental program was performed on 20 GFRP square tubes with different designs in 1.22m under elevated temperatures. The experiments results were discussed and showed that the compressive strength of GFRP material was influenced by several factors including the glass transition v temperature and the connection bolts. Failure modes under 25°C and 75°C were crushing and the failure modes with the temperatures above 75°C were not typical crushing due to the glass transition of GFRP. Sixteen GFRP square tubes with length of 0.61m were tested with the same experimental program under elevated temperatures as the control group. Twelve GFRP square tubes with the same size were subjected to cyclic loading under elevated temperatures to investigate the effect of the cyclic loading to the compression properties of GFRP material. According to the experimental results and the discussion, the stiffness was reduced by the cyclic loading. On the contrary, the

  4. Viscoelastoplastic Deformation and Damage Response of Titanium Alloy, Ti-6Al-4V, at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Arnold, Steven M.; Lerch, Bradley A.; Saleeb, Atef F.; Kasemer, Matthew P.

    2013-01-01

    Time-dependent deformation and damage behavior can significantly affect the life of aerospace propulsion components. Consequently, one needs an accurate constitutive model that can represent both reversible and irreversible behavior under multiaxial loading conditions. This paper details the characterization and utilization of a multi-mechanism constitutive model of the GVIPS class (Generalized Viscoplastic with Potential Structure) that has been extended to describe the viscoelastoplastic deformation and damage of the titanium alloy Ti-6Al-4V. Associated material constants were characterized at five elevated temperatures where viscoelastoplastic behavior was observed, and at three elevated temperatures where damage (of both the stiffness reduction and strength reduction type) was incurred. Experimental data from a wide variety of uniaxial load cases were used to correlate and validate the proposed GVIPS model. Presented are the optimized material parameters, and the viscoelastoplastic deformation and damage responses at the various temperatures.

  5. Performance evaluation of fiber Bragg gratings at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Juergens, Jeffrey; Adamovsky, Grigory; Floyd, Bertram

    2004-03-01

    The development of integrated fiber optic sensors for smart propulsion systems demands that the sensors be able to perform in extreme environments. In order to use fiber optic sensors effectively in an extreme environment one must have a thorough understanding of the sensor"s limits and how it responds under various environmental conditions. The sensor evaluation currently involves examining the performance of fiber Bragg gratings at elevated temperatures. Fiber Bragg gratings (FBG) are periodic variations of the refractive index of an optical fiber. These periodic variations allow the FBG to act as an embedded optical filter passing the majority of light propagating through a fiber while reflecting back a narrow band of the incident light. The peak reflected wavelength of the FBG is known as the Bragg wavelength. Since the period and width of the refractive index variation in the fiber determines the wavelengths that are transmitted and reflected by the grating, any force acting on the fiber that alters the physical structure of the grating will change what wavelengths are transmitted and what wavelengths are reflected by the grating. Both thermal and mechanical forces acting on the grating will alter its physical characteristics allowing the FBG sensor to detect both temperature variations and physical stresses, strain, placed upon it. This ability to sense multiple physical forces makes the FBG a versatile sensor. This paper reports on test results of the performance of FBGs at elevated temperatures. The gratings looked at thus far have been either embedded in polymer matrix materials or freestanding with the primary focus of this paper being on the freestanding FBGs. Throughout the evaluation process, various parameters of the FBGs performance were monitored and recorded. These parameters include the peak Bragg wavelength, the power of the Bragg wavelength, and total power returned by the FBG. Several test samples were subjected to identical test conditions to

  6. Performance Evaluation of Fiber Bragg Gratings at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Juergens, Jeffrey; Adamovsky, Grigory; Floyd, Bertram

    2004-01-01

    The development of integrated fiber optic sensors for smart propulsion systems demands that the sensors be able to perform in extreme environments. In order to use fiber optic sensors effectively in an extreme environment one must have a thorough understanding of the sensor s limits and how it responds under various environmental conditions. The sensor evaluation currently involves examining the performance of fiber Bragg gratings at elevated temperatures. Fiber Bragg gratings (FBG) are periodic variations of the refractive index of an optical fiber. These periodic variations allow the FBG to act as an embedded optical filter passing the majority of light propagating through a fiber while reflecting back a narrow band of the incident light. The peak reflected wavelength of the FBG is known as the Bragg wavelength. Since the period and width of the refractive index variation in the fiber determines the wavelengths that are transmitted and reflected by the grating, any force acting on the fiber that alters the physical structure of the grating will change what wavelengths are transmitted and what wavelengths are reflected by the grating. Both thermal and mechanical forces acting on the grating will alter its physical characteristics allowing the FBG sensor to detect both temperature variations and physical stresses, strain, placed upon it. This ability to sense multiple physical forces makes the FBG a versatile sensor. This paper reports on test results of the performance of FBGs at elevated temperatures. The gratings looked at thus far have been either embedded in polymer matrix materials or freestanding with the primary focus of this paper being on the freestanding FBGs. Throughout the evaluation process, various parameters of the FBGs performance were monitored and recorded. These parameters include the peak Bragg wavelength, the power of the Bragg wavelength, and total power returned by the FBG. Several test samples were subjected to identical test conditions to

  7. Constitutive Modeling and Testing of Polymer Matrix Composites Incorporating Physical Aging at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Veazie, David R.

    1998-01-01

    Advanced polymer matrix composites (PMC's) are desirable for structural materials in diverse applications such as aircraft, civil infrastructure and biomedical implants because of their improved strength-to-weight and stiffness-to-weight ratios. For example, the next generation military and commercial aircraft requires applications for high strength, low weight structural components subjected to elevated temperatures. A possible disadvantage of polymer-based composites is that the physical and mechanical properties of the matrix often change significantly over time due to the exposure of elevated temperatures and environmental factors. For design, long term exposure (i.e. aging) of PMC's must be accounted for through constitutive models in order to accurately assess the effects of aging on performance, crack initiation and remaining life. One particular aspect of this aging process, physical aging, is considered in this research.

  8. Application of non-porous alumina based ceramics as structural material for devices handling tritium at elevated temperatures

    SciTech Connect

    Yukhimchuk, A.A.; Maksimkin, I.P.; Baluev, V.V.; Boitsov, I.E.; Vertey, A.V.; Malkov, I.L.; Musyaev, R.K.; Popov, V.V.; Sitdikov, D.T.; Khapov, A.S.; Grishechkin, S.K.; Kiselev, V.G.

    2015-03-15

    The article presents results of comparative tests for the determination of deuterium fluxes permeating through walls of austenitic stainless steel AISI304 (DIN 1.4301) chamber and Al{sub 2}O{sub 3} based ceramic F99.7 chamber. Both chambers represent a piece of φ(ext)=26*φ(int)=22*117 mm{sup 3} tube with spherical bottom ending. It is shown that at 773 K and deuterium pressure of 1200 mbar the permeated deuterium flux through the stainless steel chamber constituted 8*10{sup -5} cm{sup 3}/s, while the flux through ceramic one it did not exceed the sensitivity of the measurement method threshold, namely about 1.5*10{sup -7} cm{sup 3}/s. The ceramic chamber turned out to survive more than 10{sup 3} cycles of heating up to 773 K with no damages. It did not lose its tightness up to 10 bar of internal deuterium pressure. The authors also present test results of a prototype bed for reversible tritium storage. The bed's case was made of alumina based ceramic F99.7, titanium being used as tritide making metal and high frequency induction used for heating the tritide metal. (authors)

  9. Effects of elevated carbon dioxide, elevated temperature, and rice growth stage on the community structure of rice root-associated bacteria.

    PubMed

    Okubo, Takashi; Tokida, Takeshi; Ikeda, Seishi; Bao, Zhihua; Tago, Kanako; Hayatsu, Masahito; Nakamura, Hirofumi; Sakai, Hidemitsu; Usui, Yasuhiro; Hayashi, Kentaro; Hasegawa, Toshihiro; Minamisawa, Kiwamu

    2014-01-01

    The effects of free-air carbon dioxide enrichment (FACE) and elevated soil and water temperature (warming) on the rice root-associated bacterial community were evaluated by clone library analysis of the 16S ribosomal RNA gene. Roots were sampled at the panicle initiation and ripening stages 41 and 92 days after transplanting (DAT), respectively. The relative abundances of the methanotrophs Methylosinus and Methylocystis were increased by warming and decreased by FACE at 92 DAT, which indicated that microbial methane (CH4) oxidation in rice roots may have been influenced by global warming. The relative abundance of Burkholderia kururiensis was increased by warming at 41 DAT and by FACE or warming at 92 DAT. The abundances of methanotrophs increased during rice growth, which was likely induced by an enhancement in the emission of CH4 from the paddy fields, suggesting that CH4 is one of the predominant factors affecting the structure of the microbial community in rice roots. Marked variations in the community structure were also observed during rice growth in other genera: Bradyrhizobium, Clostridium, and an unknown genus close to Epsilonproteobacteria were abundant at 92 DAT, whereas Achromobacter was abundant at 41 DAT. These results demonstrated that the community structures of rice root-associated bacteria were markedly affected by FACE, temperature, and the rice growth stage.

  10. Characterizing the effects of elevated temperature on the air void pore structure of advanced gas-cooled reactor pressure vessel concrete using x-ray computed tomography

    NASA Astrophysics Data System (ADS)

    Stein, R. C.; Petkovski, M.; Engelberg, D. L.; Leonard, F.; Withers, P. J.

    2013-07-01

    X-ray computed tomography (X-ray CT) has been applied to nondestructively characterise changes in the microstructure of a concrete used in the pressure vessel structure of Advanced Gas-cooled Reactors (AGR) in the UK. Concrete specimens were conditioned at temperatures of 105 °C and 250 °C, to simulate the maximum thermal load expected to occur during a loss of coolant accident (LOCA). Following thermal treatment, these specimens along with an unconditioned control sample were characterised using micro-focus X-ray CT with a spatial resolution of 14.6 microns. The results indicate that the air void pore structure of the specimens experienced significant volume changes as a result of the increasing temperature. The increase in the porous volume was more prevalent at 250 °C. Alterations in air void size distributions were characterized with respect to the unconditioned control specimen. These findings appear to correlate with changes in the uni-axial compressive strength of the conditioned concrete.

  11. Surface metallization on Si(001) at elevated temperatures studied by angle-resolved photoemission spectroscopy and near-edge x-ray absorption fine structure: Effect of thermal adatoms

    NASA Astrophysics Data System (ADS)

    Jeon, C.; Hwang, C. C.; Kang, T.-H.; Kim, K.-J.; Kim, B.; Kim, Y.; Noh, D. Y.; Park, C.-Y.

    2009-10-01

    We report the metallization of the Si(001)2×1 surface at elevated temperatures using angle-resolved photoemission spectroscopy (ARPES) and near-edge x-ray absorption fine structure (NEXAFS). A metallic state (Sm) over the EF , which corresponds to the empty (π∗) state of the 2×1 asymmetric dimer model, increases in the ARPES spectra, while the π∗ state decreases in the NEXAFS spectra with increasing temperature. Since Sm is observed even at 400 K, the structural phase transition at ˜900K [Phys. Rev. Lett. 91, 126103 (2003); Phys. Rev. Lett. 77, 3869 (1996)] is not related to the metallization. Thermal excitation seems to be too small to detect in ARPES in initial stage of the metallization and cannot account for the different behavior of Sm and the filled surface state of the up-dimer upon oxidation. We suggest, based on the existence of Sm even at 400 K and the oxidation behavior, that the metallization is attributed to thermal adatoms.

  12. Gas-Alloy Interactions at Elevated Temperatures

    SciTech Connect

    Arroyave, Raymundo; Gao, Michael

    2012-11-07

    The understanding of the stability of metals and alloys against oxidation and other detrimental reactions, to the catalysis of important chemical reactions and the minimization of defects associated with processing and synthesis have one thing in common: At the most fundamental level, all these scientific/engineering problems involve interactions between metals and alloys (in the solid or liquid state) and gaseous atmospheres at elevated temperatures. In this special issue, we have collected a series of articles that illustrate the application of different theoretical, computational, and experimental techniques to investigate gas-alloy interactions.

  13. Fatigue damage characterization of braided and woven fiber reinforced polymer matrix composites at room and elevated temperatures

    NASA Astrophysics Data System (ADS)

    Montesano, John

    The use of polymer matrix composites (PMC) for manufacturing primary load-bearing structural components has significantly increased in many industrial applications. Specifically in the aerospace industry, PMCs are also being considered for elevated temperature applications. Current aerospace-grade composite components subjected to fatigue loading are over-designed due to insufficient understanding of the material failure processes, and due to the lack of available generic fatigue prediction models. A comprehensive literature survey reveals that there are few fatigue studies conducted on woven and braided fabric reinforced PMC materials, and even fewer at elevated temperatures. It is therefore the objective of this study to characterize and subsequently model the elevated temperature fatigue behaviour of a triaxial braided PMC, and to investigate the elevated temperature fatigue properties of two additional woven PMCs. An extensive experimental program is conducted using a unique test protocol on the braided and woven composites, which consists of static and fatigue testing at various test temperatures. The development of mechanically-induced damage is monitored using a combination of non-destructive techniques which included infrared thermography, fiber optic sensors and edge replication. The observed microscopic damage development is quantified and correlated to the exhibited macroscopic material behaviour at all test temperatures. The fiber-dominated PMC materials considered in this study did not exhibit notable time- or temperature-dependent static properties. However, fatigue tests reveal that the local damage development is in fact notably influenced by temperature. The elevated temperature environment increases the toughness of the thermosetting polymers, which results in consistently slower fatigue crack propagation rates for the respective composite materials. This has a direct impact on the stiffness degradation rate and the fatigue lives for the braided

  14. Theoretical Determination of Lifetime of Compressed Plates at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Herrmann, George; Chu, Hu-Nan

    1959-01-01

    A method for the theoretical determination of the lifetime of com- pressed plates at elevated temperatures is presented. In this approach, linearized equations are used throughout with the assumption that the plate material is a standard linear solid. The critical time (lifetime) is determined by reducing the time-dependent behavior to the time- independent response of purely elastic buckling. Theoretically predicted lifetimes of 2024-T3 (formerly 24S-T3) aluminum-alloy plates at 450 F are compared with experimental values obtained in previous work.

  15. Promoted Metals Combustion at Ambient and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Engel, Carl D.; Herald, Stephen D.; Davis, S. Eddie

    2005-01-01

    Promoted combustion testing of materials, Test 17 of NASA STD-6001, has been used to assess metal propensity to burn in oxygen rich environments. An igniter is used at the bottom end of a rod to promote ignition, and if combustion is sustained, the burning progresses from the bottom to the top of the rod. The physical mechanisms are very similar to the upward flammability test, Test 1 of NASA STD-6001. The differences are in the normal environmental range of pressures, oxygen content, and sample geometry. Upward flammability testing of organic materials can exhibit a significant transitional region between no burning to complete quasi-state burning. In this transitional region, the burn process exhibits a probabilistic nature. This transitional region has been identified for metals using the promoted combustion testing method at ambient initial temperatures. The work given here is focused on examining the transitional region and the quasi-steady burning region both at conventional ambient testing conditions and at elevated temperatures. A new heated promoted combustion facility and equipment at Marshall Space Flight Center have just been completed to provide the basic data regarding the metals operating temperature limits in contact with oxygen rich atmospheres at high pressures. Initial data have been obtained for Stainless Steel 304L, Stainless Steel 321, Haynes 214, and Inconel 718 at elevated temperatures in 100-percent oxygen atmospheres. These data along with an extended data set at ambient initial temperature test conditions are examined. The pressure boundaries of acceptable, non-burning usage is found to be lowered at elevated temperature.

  16. Elevated temperature forming method and preheater apparatus

    DOEpatents

    Krajewski, Paul E; Hammar, Richard Harry; Singh, Jugraj; Cedar, Dennis; Friedman, Peter A; Luo, Yingbing

    2013-06-11

    An elevated temperature forming system in which a sheet metal workpiece is provided in a first stage position of a multi-stage pre-heater, is heated to a first stage temperature lower than a desired pre-heat temperature, is moved to a final stage position where it is heated to a desired final stage temperature, is transferred to a forming press, and is formed by the forming press. The preheater includes upper and lower platens that transfer heat into workpieces disposed between the platens. A shim spaces the upper platen from the lower platen by a distance greater than a thickness of the workpieces to be heated by the platens and less than a distance at which the upper platen would require an undesirably high input of energy to effectively heat the workpiece without being pressed into contact with the workpiece.

  17. Elevated temperature deformation of thoria dispersed nickel-chromium

    NASA Technical Reports Server (NTRS)

    Kane, R. D.; Ebert, L. J.

    1974-01-01

    The deformation behavior of thoria nickel-chromium (TD-NiCr) was examined over the temperature range 593 C (1100 F) to 1260 C (2300 F) in tension and compression and at 1093 C (2000 F) in creep. Major emphasis was placed on: (1) the effects of the material and test related variables (grain size, temperature, stress and strain rate) on the deformation process; and (2) the evaluation of single crystal TD-NiCr material produced by a directional recrystallization process. Elevated temperature yield strength levels and creep activation enthalpies were found to increase with increasing grain size reaching maximum values for the single crystal TD-NiCr. Stress exponent of the steady state creep rate was also significantly higher for the single crystal TD-NiCr as compared to that determined for the polycrystalline materials. The elevated temperature deformation of TD-NiCr was analyzed in terms of two concurrent, parallel processes: diffusion controlled grain boundary sliding, and dislocation motion.

  18. High strain rate behavior of pure metals at elevated temperature

    NASA Astrophysics Data System (ADS)

    Testa, Gabriel; Bonora, Nicola; Ruggiero, Andrew; Iannitti, Gianluca; Domenico, Gentile

    2013-06-01

    In many applications and technology processes, such as stamping, forging, hot working etc., metals and alloys are subjected to elevated temperature and high strain rate deformation process. Characterization tests, such as quasistatic and dynamic tension or compression test, and validation tests, such as Taylor impact and DTE - dynamic tensile extrusion -, provide the experimental base of data for constitutive model validation and material parameters identification. Testing material at high strain rate and temperature requires dedicated equipment. In this work, both tensile Hopkinson bar and light gas gun where modified in order to allow material testing under sample controlled temperature conditions. Dynamic tension tests and Taylor impact tests, at different temperatures, on high purity copper (99.98%), tungsten (99.95%) and 316L stainless steel were performed. The accuracy of several constitutive models (Johnson and Cook, Zerilli-Armstrong, etc.) in predicting the observed material response was verified by means of extensive finite element analysis (FEA).

  19. Elevated Temperature and Allelopathy Impact Coral Recruitment.

    PubMed

    Ritson-Williams, Raphael; Ross, Cliff; Paul, Valerie J

    2016-01-01

    As climate change continues to alter seawater temperature and chemistry on a global scale, coral reefs show multiple signs of degradation. One natural process that could facilitate the recovery of reef ecosystems is coral recruitment, which can be influenced by the benthic organisms in a local habitat. We experimentally tested both a global stressor (increased seawater temperature) and a local stressor (exposure to microcolin A, a natural product from a common marine benthic cyanobacterium) to determine how these stressors impacted coral larval sublethal stress, survival and settlement. Larvae of Porites astreoides had the same survival and settlement as the controls after exposure to increased temperature alone, but elevated temperature did cause oxidative stress. When exposed to natural concentrations of microcolin A, larval survival and settlement were significantly reduced. When larvae were exposed to these two stressors sequentially there was no interactive effect; but when exposed to both stressors simultaneously, there was a synergistic reduction in larval survival and an increase in oxidative stress more than in either stressor treatment alone. Increased seawater temperatures made larvae more susceptible to a concurrent local stressor disrupting a key process of coral reef recovery and resilience. These results highlight the importance of understanding how interactive stressors of varying spatial scales can impact coral demographics.

  20. Elevated Temperature and Allelopathy Impact Coral Recruitment

    PubMed Central

    Ritson-Williams, Raphael; Ross, Cliff; Paul, Valerie J.

    2016-01-01

    As climate change continues to alter seawater temperature and chemistry on a global scale, coral reefs show multiple signs of degradation. One natural process that could facilitate the recovery of reef ecosystems is coral recruitment, which can be influenced by the benthic organisms in a local habitat. We experimentally tested both a global stressor (increased seawater temperature) and a local stressor (exposure to microcolin A, a natural product from a common marine benthic cyanobacterium) to determine how these stressors impacted coral larval sublethal stress, survival and settlement. Larvae of Porites astreoides had the same survival and settlement as the controls after exposure to increased temperature alone, but elevated temperature did cause oxidative stress. When exposed to natural concentrations of microcolin A, larval survival and settlement were significantly reduced. When larvae were exposed to these two stressors sequentially there was no interactive effect; but when exposed to both stressors simultaneously, there was a synergistic reduction in larval survival and an increase in oxidative stress more than in either stressor treatment alone. Increased seawater temperatures made larvae more susceptible to a concurrent local stressor disrupting a key process of coral reef recovery and resilience. These results highlight the importance of understanding how interactive stressors of varying spatial scales can impact coral demographics. PMID:27926916

  1. Crushed salt reconsolidation at elevated temperatures.

    SciTech Connect

    Holcomb, David Joseph; Clayton, Daniel James; Lee, Moo Yul; Bronowski, David R.

    2010-06-01

    There is a long history of testing crushed salt as backfill for the Waste Isolation Pilot Plant program, but testing was typically done at 100 C or less. Future applications may involve backfilling crushed salt around heat-generating waste packages, where near-field temperatures could reach 250 C or hotter. A series of experiments were conducted to investigate the effects of hydrostatic stress on run-of-mine salt at temperatures up to 250 C and pressures to 20 MPa. The results of these tests were compared with analogous modeling results. By comparing the modeling results at elevated temperatures to the experimental results, the adequacy of the current crushed salt reconsolidation model was evaluated. The model and experimental results both show an increase in the reconsolidation rate with temperature. The current crushed salt model predicts the experimental results well at a temperature of 100 C and matches the overall trends, but over-predicts the temperature dependence of the reconsolidation. Further development of the deformation mechanism activation energies would lead to a better prediction of the temperature dependence by the crushed salt reconsolidation model.

  2. Thermal Behavior of Cylindrical Buckling Restrained Braces at Elevated Temperatures

    PubMed Central

    Talebi, Elnaz; Tahir, Mahmood Md.; Yasreen, Airil

    2014-01-01

    The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB) elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core's surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system. PMID:24526915

  3. Phase distribution and microstructural changes of self-compacting cement paste at elevated temperature

    SciTech Connect

    Ye, G. . E-mail: ye.guang@citg.tudelft.nl; Liu, X.; De Schutter, G.; Taerwe, L.; Vandevelde, P.

    2007-06-15

    Self-compacting concrete, as a new smart building material with various advanced properties, has been used for a wide range of structures and infrastructures. However little investigation have been reported on the properties of Self-compacting when it is exposed to elevated temperatures. Previous experiments on fire test have shown the differences between high performance concrete and traditional concrete at elevated temperature. This difference is largely depending on the microstructural properties of concrete matrix, i.e. the cement paste, especially on the porosity, pore size distribution and the connectivity of pores in cement pastes. In this contribution, the investigations are focused on the cement paste. The phase distribution and microstructural changes of self-compacting cement paste at elevated temperatures are examined by mercury intrusion porosimetry and scanning electron microscopy. The chemical decomposition of self-compacting cement paste at different temperatures is determined by thermogravimetric analysis. The experimental results of self-compacting cement paste are compared with those of high performance cement paste and traditional cement paste. It was found that self-compacting cement paste shows a higher change of the total porosity in comparison with high performance cement paste. When the temperature is higher than 700 deg. C, a dramatic loss of mass was observed in the self-compacting cement paste samples with addition of limestone filler. This implies that the SCC made by this type of self-compacting cement paste will probably show larger damage once exposed to fire. Investigation has shown that 0.5 kg/m{sup 3} of Polypropylene fibers in the self-compacting cement paste can avoid the damage efficiently.

  4. Strengths of serpentinite gouges at elevated temperatures

    USGS Publications Warehouse

    Moore, Diane E.; Lockner, D.A.; Ma, S.; Summers, R.; Byerlee, J.D.

    1997-01-01

    Serpentinite has been proposed as a cause of both low strength and aseismic creep of fault zones. To test these hypotheses, we have measured the strength of chrysotile-, lizardite-, and antigorite-rich serpentinite gouges under hydrothermal conditions, with emphasis on chrysotile, which has thus far received little attention. At 25??C, the coefficient of friction, ??, of chrysotile gouge is roughly 0.2, whereas the lizardite- and antigorite-rich gouges are at least twice as strong. The very low room temperature strength of chrysotile is a consequence of its unusually high adsorbed water content. When the adsorbed water is removed, chrysotile is as strong as pure antigorite gouge at room temperature. Heating to ???200??C causes the frictional strengths of all three gouges to increase. Limited data suggest that different polytypes of a given serpentine mineral have similar strengths; thus deformation-induced changes in polytype should not affect fault strength. At 25??C, the chrysotile gouge has a transition from velocity strengthening at low velocities to velocity weakening at high velocities, consistent with previous studies. At temperatures up to ???200??C, however, chrysotile strength is essentially independent of velocity at low velocities. Overall, chrysotile has a restricted range of velocity-strengthening behavior that migrates to higher velocities with increasing temperature. Less information on velocity dependence is available for the lizardite and antigorite gouges, but their behavior is consistent with that outlined for chrysotile. The marked changes in velocity dependence and strength of chrysotile with heating underscore the hazards of using room temperature data to predict fault behavior at depth. The velocity behavior at elevated temperatures does not rule out serpentinite as a cause of aseismic slip, but in the presence of a hydrostatic fluid pressure gradient, all varieties of serpentine are too strong to explain the apparent weakness of faults such

  5. Process Simulation of Aluminium Sheet Metal Deep Drawing at Elevated Temperatures

    SciTech Connect

    Winklhofer, Johannes; Trattnig, Gernot; Sommitsch, Christof

    2010-06-15

    Lightweight design is essential for an economic and environmentally friendly vehicle. Aluminium sheet metal is well known for its ability to improve the strength to weight ratio of lightweight structures. One disadvantage of aluminium is that it is less formable than steel. Therefore complex part geometries can only be realized by expensive multi-step production processes. One method for overcoming this disadvantage is deep drawing at elevated temperatures. In this way the formability of aluminium sheet metal can be improved significantly, and the number of necessary production steps can thereby be reduced. This paper introduces deep drawing of aluminium sheet metal at elevated temperatures, a corresponding simulation method, a characteristic process and its optimization. The temperature and strain rate dependent material properties of a 5xxx series alloy and their modelling are discussed. A three dimensional thermomechanically coupled finite element deep drawing simulation model and its validation are presented. Based on the validated simulation model an optimised process strategy regarding formability, time and cost is introduced.

  6. Elevated-temperature deflection-controlled test of modified 9 Cr-1 Mo steel beam

    SciTech Connect

    Gwaltney, R C; Battiste, R L; Yahr, G T; Peters, M L

    1983-05-01

    This report presents elevated-temperature test results and comparisons with analytic predictions for a simply supported modified 9 Cr-1 Mo steel beam subjected to a controlled center deflection history. The test was performed to provide an assessment of structural analysis methods and material relations for modified 9 Cr-1 Mo steel. The inelastic analysis predictions were obtained using the finite-element code ADINA. The analysis was done using a nonlinear, time-independent plasticity model and a creep strain-hardening model for the constitutive equations. The test contained three constant-deflection hold periods for a total of 504 h at a a temperature of 573{sup 0}C (1100{sup 0}F). The beam specimen was fabricated using plate stock of the modified 9 Cr-1 Mo steel at heat 30383. The structural deformation responses in terms of load and strain were measured during the test; results are provided in graphical form.

  7. Structural materials for space applications

    NASA Technical Reports Server (NTRS)

    Tenney, Darrel R.

    1989-01-01

    The long-term performance of structural materials in the space environment is a key research activity within NASA. The primary concerns for materials in low Earth orbit (LEO) are atomic oxygen erosion and space debris impact. Atomic oxygen studies have included both laboratory exposures in atomic oxygen facilities and flight exposures using the Shuttle. Characterization of atomic oxygen interaction with materials has included surface recession rates, residual mechanical properties, optical property measurements, and surface analyses to establish chemical changes. The Long Duration Exposure Facility (LDEF) is scheduled to be retrieved in 1989 and is expected to provide a wealth of data on atomic oxygen erosion in space. Hypervelocity impact studies have been conducted to establish damage mechanisms and changes in mechanical properties. Samples from LDEF will be analyzed to determine the severity of space debris impact on coatings, films, and composites. Spacecraft placed in geosynchronous Earth orbit (GEO) will be subjected to high doses of ionizing radiation which for long term exposures will exceed the damage threshold of many polymeric materials. Radiation interaction with polymers can result in chain scission and/or cross-linking. The formation of low molecular weight products in the epoxy plasticize the matrix at elevated temperatures and embrittle the matrix at low temperatures. This affects both the matrix-dominated mechanical properties and the dimensional stability of the composite. Embrittlement of the matrix at low temperatures results in enhanced matrix microcracking during thermal cycling. Matrix microcracking changes the coefficient of thermal expansion (CTE) of composite laminates and produces permanent length changes. Residual stress calculations were performed to estimate the conditions necessary for microcrack development in unirradiated and irradiated composites. The effects of UV and electron exposure on the optical properties of transparent

  8. Literature survey on oxidations and fatigue lives at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Liu, H. W.; Oshida, Y.

    1984-01-01

    Nickel-base superalloys are the most complex and the most widely used for high temperature applications such as aircraft engine components. The desirable properties of nickel-base superalloys at high temperatures are tensile strength, thermomechanical fatigue resistance, low thermal expansion, as well as oxidation resistance. At elevated temperature, fatigue cracks are often initiated by grain boundary oxidation, and fatigue cracks often propagate along grain boundaries, where the oxidation rate is higher. Oxidation takes place at the interface between metal and gas. Properties of the metal substrate, the gaseous environment, as well as the oxides formed all interact to make the oxidation behavior of nickel-base superalloys extremely complicated. The important topics include general oxidation, selective oxidation, internal oxidation, grain boundary oxidation, multilayer oxide structure, accelerated oxidation under stress, stress-generation during oxidation, composition and substrate microstructural changes due to prolonged oxidation, fatigue crack initiation at oxidized grain boundaries and the oxidation accelerated fatigue crack propagation along grain boundaries.

  9. Elevated temperature mechanical properties of line pipe steels

    NASA Astrophysics Data System (ADS)

    Jacobs, Taylor Roth

    The effects of test temperature on the tensile properties of four line pipe steels were evaluated. The four materials include a ferrite-pearlite line pipe steel with a yield strength specification of 359 MPa (52 ksi) and three 485 MPa (70 ksi) yield strength acicular ferrite line pipe steels. Deformation behavior, ductility, strength, strain hardening rate, strain rate sensitivity, and fracture behavior were characterized at room temperature and in the temperature range of 200--350 °C, the potential operating range for steels used in oil production by the steam assisted gravity drainage process. Elevated temperature tensile testing was conducted on commercially produced as-received plates at engineering strain rates of 1.67 x 10 -4, 8.33 x 10-4, and 1.67 x 10-3 s-1. The acicular ferrite (X70) line pipe steels were also tested at elevated temperatures after aging at 200, 275, and 350 °C for 100 h under a tensile load of 419 MPa. The presence of serrated yielding depended on temperature and strain rate, and the upper bound of the temperature range where serrated yielding was observed was independent of microstructure between the ferrite-pearlite (X52) steel and the X70 steels. Serrated yielding was observed at intermediate temperatures and continuous plastic deformation was observed at room temperature and high temperatures. All steels exhibited a minimum in ductility as a function of temperature at testing conditions where serrated yielding was observed. At the higher temperatures (>275 °C) the X52 steel exhibited an increase in ductility with an increase in temperature and the X70 steels exhibited a maximum in ductility as a function of temperature. All steels exhibited a maximum in flow strength and average strain hardening rate as a function of temperature. The X52 steel exhibited maxima in flow strength and average strain hardening rate at lower temperatures than observed for the X70 steels. For all steels, the temperature where the maximum in both flow

  10. Ultra-Fast Fracture Strength of Advanced Ceramics at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Salem, Jonathan A.

    1998-01-01

    An attempt was made to determine elevated-temperature, 'ultra'-fast fracture strengths of one alumina, two silicon nitrides and one silicon carbide by using constant stress-rate ('dynamic fatigue') testing with a series of 'ultra'-fast test rates. Of the materials tested, the alumina exhibited a convergence of strength at stress rates below 3.3 x 10(exp 4) MPa/s. The strength approached approximately the room-temperature inert strength. By contrast, the silicon nitrides and silicon carbide did not reveal a strength approach, but exhibited elevated-temperature strengths 10 and 20% lower than their respective room-temperature strengths. Although the analytical results imply that the elevated-temperature 'inert' strength of a ceramic material can be obtained by using sufficiently high stress rates, the experimental testing rates were only sufficient to demonstrate convergence for the alumina.

  11. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1982-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons and methods for making such materials. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  12. Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Park, Jingee; Lee, Jongshin; You, Bongsun; Choi, Seogou; Kim, Youngsuk

    2007-05-01

    Using lightweight materials is the emerging need in order to reduce the vehicle's energy consumption and pollutant emissions. Being a lightweight material, magnesium alloys are increasingly employed in the fabrication of automotive and electronic parts. Presently, magnesium alloys used in automotive and electronic parts are mainly processed by die casting. The die casting technology allows the manufacturing of parts with complex geometry. However, the mechanical properties of these parts often do not meet the requirements concerning the mechanical properties (e.g. endurance strength and ductility). A promising alternative can be forming process. The parts manufactured by forming could have fine-grained structure without porosity and improved mechanical properties such as endurance strength and ductility. Because magnesium alloy has low formability resulted form its small slip system at room temperature it is usually formed at elevated temperature. Due to a rapid increase of usage of magnesium sheets in automotive and electronic industry it is necessary to assure database for sheet metal formability and plastic yielding properties in order to optimize its usage. Especially, plastic yielding criterion is a critical property to predict plastic deformation of sheet metal parts in optimizing process using CAE simulation. Von-Mises yield criterion generally well predicts plastic deformation of steel sheets and Hill'1979 yield criterion predicts plastic deformation of aluminum sheets. In this study, using biaxial tensile test machine yield loci of AZ31 magnesium alloy sheet were obtained at elevated temperature. The yield loci ensured experimentally were compared with the theoretical predictions based on the Von-Mises, Hill, Logan-Hosford, and Barlat model.

  13. Integrated research in constitutive modelling at elevated temperatures, part 1

    NASA Technical Reports Server (NTRS)

    Haisler, W. E.; Allen, D. H.

    1986-01-01

    Topics covered include: numerical integration techniques; thermodynamics and internal state variables; experimental lab development; comparison of models at room temperature; comparison of models at elevated temperature; and integrated software development.

  14. Mechanisms of time-dependent crack growth at elevated temperature

    SciTech Connect

    Saxena, A.; Stock, S.R.

    1990-04-15

    Objective of this 3-y study was to conduct creep and creep-fatigue crack growth experiments and to characterize the crack tip damage mechanisms in a model material (Cu-1wt%Sb), which is known to cavitate at grain boundaries under creep deformation. Results were: In presence of large scale cavitation damage and crack branching, time rate of creep crack growth da/dt does not correlate with C[sub t] or C[sup *]. When cavitation damage is constrained, da/dt is characterized by C[sub t]. Area fraction of grain boundary cavitated is the single damage parameter for the extent of cavitation damage ahead of crack tips. C[sub t] is used for the creep-fatigue crack growth behavior. In materials prone to rapid cavity nucleation, creep cracks grow faster initially and then reach a steady state whose growth rate is determined by C[sub t]. Percent creep life exhausted correlates with average cavity diameter and fraction of grain boundary area occupied by cavities. Synchrotron x-ray tomographic microscopy was used to image individual cavities in Cu-1wt% Sb. A methodology was developed for predicting the remaining life of elevated temperature power plant components; (C[sub t])[sub avg] was used to correlate creep-fatigue crack growth in Cr-Mo and Cr-Mo-V steel and weldments.

  15. Electromigration in Sintered Nanoscale Silver Films at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Calata, Jesus N.; Lu, Guo-Quan; Ngo, Khai; Nguyen, Luu

    2014-01-01

    Sintered nanoscale silver is a promising interconnection material for semiconductor devices because it provides improved joint properties compared with solder and wire bonds. It has higher electrical and thermal conductivity and is capable of higher operating temperature. Joints with die shear strength above 20 MPa can be formed at around 250°C even without applied pressure. Sintered silver joints were also found to be an order of magnitude more reliable than solder joints and wire bonds. In this work, the electromigration behavior of sintered nanosilver material under conditions of high applied current density and elevated temperature was investigated. Thin strips of sintered nanosilver formed on ceramic substrates were tested under current densities exceeding 150 kA/cm2 at temperatures of 150°C and above. Results based on the percentage change in sample resistance showed that the sintered silver lasted at least ten times longer than aluminum wire bonds. Examination of failed strips revealed that hairline cracks formed during sintering were the main cause of failure. Otherwise, defect-free samples exhibited a 10-fold increase in lifetime over wire bonds under similar conditions.

  16. Growth rate of Enterobacteriaceae at elevated temperatures: limitation by methionine.

    PubMed

    Ron, E Z

    1975-10-01

    The effect of elevated temperatures on growth rate was studied in five strains of Enterobacteriaceae. In all the strains tested a shift to the elevated temperature resulted in an immediate decrease in growth rate which was due to limitation in the availability of endogenous methionine. The first biosynthetic enzyme of the methionine pathway-homoserine transsuccinylase-was studied in extracts of Aerobacter aerogenes, Salmonella typhimurium, and Escherichia coli and was shown to be temperature sensitive in all of them.

  17. Elevated Temperature, Notched Compression Performance of Out of Autoclave Processed Composites

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Sutter, James K.; Dixon, Genevieve D.; Smeltzer, Satn S.

    2013-01-01

    Curved honeycomb sandwich panels composed of carbon fiber reinforced toughened-epoxy polymer facesheets are being evaluated for potential use as payload fairing components on the NASA heavy-lift space launch system (HL-SLS). These proposed composite sandwich panels provide the most efficient aerospace launch structures, and offer mass and thermal advantages when compared with existing metallic payload fairing structures. NASA and industry are investigating recently developed carbon fiber epoxy prepreg systems which can be fabricated using out-of autoclave (OOA) processes. Specifically, OOA processes using vacuum pressure in an oven and thereby significantly reducing the cost associated with manufacturing large (up to 10 m diameter) composite structures when compared with autoclave. One of these OOA composite material systems, CYCOM(R) 5320-1, was selected for manufacture of a 1/16th scale barrel portion of the payload fairing; such that, the system could be compared with the well-characterized prepreg system, CYCOM(R) 977-3, typically processed in an autoclave. Notched compression coupons for each material were obtained from the minimum-gauge flat laminate [60/-60/0]S witness panels produced in this manufacturing study. The coupons were also conditioned to an effective moisture equilibrium point and tested according to ASTM D6484M-09 at temperatures ranging from 25 C up to 177 C. The results of this elevated temperature mechanical characterization study demonstrate that, for thin coupons, the OHC strength of the OOA laminate was equivalent to the flight certified autoclave processed composite laminates; the limitations on the elevated temperature range are hot-wet conditions up to 163 C and are only within the margins of testing error. At 25 C, both the wet and dry OOA material coupons demonstrated greater OHC failure strengths than the autoclave processed material laminates. These results indicate a substantial improvement in OOA material development and

  18. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1982-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  19. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1983-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  20. Lightweight Materials & Structures

    NASA Video Gallery

    The Lightweight Materials and Structures (LMS) project will mature high-payoff structures and materials technologies that have direct application to NASA’s future space exploration needs.One of the...

  1. Elevated temperature crack growth in advanced powder metallurgy aluminum alloys

    NASA Technical Reports Server (NTRS)

    Porr, William C., Jr.; Gangloff, Richard P.

    1990-01-01

    Rapidly solidified Al-Fe-V-Si powder metallurgy alloy FVS0812 is among the most promising of the elevated temperature aluminum alloys developed in recent years. The ultra fine grain size and high volume fraction of thermally stable dispersoids enable the alloy to maintain tensile properties at elevated temperatures. In contrast, this alloy displays complex and potentially deleterious damage tolerant and time dependent fracture behavior that varies with temperature. J-Integral fracture mechanics were used to determine fracture toughness (K sub IC) and crack growth resistance (tearing modulus, T) of extruded FVS0812 as a function of temperature. The alloy exhibits high fracture properties at room temperature when tested in the LT orientation, due to extensive delamination of prior ribbon particle boundaries perpendicular to the crack front. Delamination results in a loss of through thickness constraint along the crack front, raising the critical stress intensity necessary for precrack initiation. The fracture toughness and tensile ductility of this alloy decrease with increasing temperature, with minima observed at 200 C. This behavior results from minima in the intrinsic toughness of the material, due to dynamic strain aging, and in the extent of prior particle boundary delaminations. At 200 C FVS0812 fails at K levels that are insufficient to cause through thickness delamination. As temperature increases beyond the minimum, strain aging is reduced and delamination returns. For the TL orientation, K (sub IC) decreased and T increased slightly with increasing temperature from 25 to 316 C. Fracture in the TL orientation is governed by prior particle boundary toughness; increased strain localization at these boundaries may result in lower toughness with increasing temperature. Preliminary results demonstrate a complex effect of loading rate on K (sub IC) and T at 175 C, and indicate that the combined effects of time dependent deformation, environment, and strain aging

  2. Novel silica surface charge density mediated control of the optical properties of embedded optically active materials and its application for fiber optic pH sensing at elevated temperatures.

    PubMed

    Wang, Congjun; Ohodnicki, Paul R; Su, Xin; Keller, Murphy; Brown, Thomas D; Baltrus, John P

    2015-02-14

    Silica and silica incorporated nanocomposite materials have been extensively studied for a wide range of applications. Here we demonstrate an intriguing optical effect of silica that, depending on the solution pH, amplifies or attenuates the optical absorption of a variety of embedded optically active materials with very distinct properties, such as plasmonic Au nanoparticles, non-plasmonic Pt nanoparticles, and the organic dye rhodamine B (not a pH indicator), coated on an optical fiber. Interestingly, the observed optical response to varying pH appears to follow the surface charge density of the silica matrix for all the three different optically active materials. To the best of our knowledge, this optical effect has not been previously reported and it appears universal in that it is likely that any optically active material can be incorporated into the silica matrix to respond to solution pH or surface charge density variations. A direct application of this effect is for optical pH sensing which has very attractive features that can enable minimally invasive, remote, real time and continuous distributed pH monitoring. Particularly, as demonstrated here, using highly stable metal nanoparticles embedded in an inorganic silica matrix can significantly improve the capability of pH sensing in extremely harsh environments which is of increasing importance for applications in unconventional oil and gas resource recovery, carbon sequestration, water quality monitoring, etc. Our approach opens a pathway towards possible future development of robust optical pH sensors for the most demanding environmental conditions. The newly discovered optical effect of silica also offers the potential for control of the optical properties of optically active materials for a range of other potential applications such as electrochromic devices.

  3. Mesoscale Molecular Dynamics of Geomaterials: the Glass Transition, Long-Range Structure of Amorphous Silicates and Relation between Structure, Dynamics and Properties of geomaterials at elevated Temperature and Pressure

    SciTech Connect

    Frank Spera

    2006-07-31

    Objectives: Our aims were (1) Large particle-number Molecular Dynamics (MD) simulations of molten silicate and aluminosilicate geomaterials (e.g., CaAl{sub 2}Si{sub 2}O{sub 8}, MgSiO{sub 3}, Mg{sub 2}SiO{sub 4}) with emphasis on understanding the connection between atomic structure and properties at temperatures and pressures characteristic of Earth's mantle (2) Study of the transport properties and equations of state for silicate liquids based on the MD results (3) Development of geochemical models for the evolution of crustal magma bodies undergoing simultaneous assimilation, fractional crystallization, periodic recharge and periodic eruption and application to magmatic systems (4) Study of current-day rates of generation and eruption of magma on earth.

  4. Materials and structures

    NASA Technical Reports Server (NTRS)

    Saito, Theodore T.; Langenbeck, Sharon L.; Al-Jamily, Ghanim; Arnold, Joe; Barbee, Troy; Coulter, Dan; Dolgin, Ben; Fichter, Buck; George, Patricia; Gorenstein, Paul

    1992-01-01

    Materials and structures technology covers a wide range of technical areas. Some of the most pertinent issues for the Astrotech 21 missions include dimensionally stable structural materials, advanced composites, dielectric coatings, optical metallic coatings for low scattered light applications, low scattered light surfaces, deployable and inflatable structures (including optical), support structures in 0-g and 1-g environments, cryogenic optics, optical blacks, contamination hardened surfaces, radiation hardened glasses and crystals, mono-metallic telescopes and instruments, and materials characterization. Some specific examples include low coefficients of thermal expansion (CTE) structures (0.01 ppm/K), lightweight thermally stable mirror materials, thermally stable optical assemblies, high reliability/accuracy (1 micron) deployable structures, and characterization of nanometer level behavior of materials/structures for interferometry concepts. Large filled-aperture concepts will require materials with CTE's of 10(exp 9) at 80 K, anti-contamination coatings, deployable and erectable structures, composite materials with CTE's less than 0.01 ppm/K and thermal hysteresis, 0.001 ppm/K. Gravitational detection systems such as LAGOS will require rigid/deployable structures, dimensionally stable components, lightweight materials with low conductivity, and high stability optics. The Materials and Structures panel addressed these issues and the relevance of the Astrotech 21 mission requirements by dividing materials and structures technology into five categories. These categories, the necessary development, and applicable mission/program development phasing are summarized. For each of these areas, technology assessments were made and development plans were defined.

  5. Gas Generation Testing of Neptunium Oxide at Elevated Temperature

    SciTech Connect

    Duffey, JM

    2004-01-30

    Elevated temperature gas generation tests have been conducted using neptunium dioxide produced on a laboratory scale using the HB-Line Phase II flowsheet. These tests were performed to determine what effect elevated temperatures would have on the neptunium dioxide in comparison to neptunium dioxide tested at ambient temperature. The headspace gas compositions following storage at elevated temperatures associated with normal conditions of transport (NCT) have been measured. These test results show an increase in hydrogen generation rate at elevated temperature and significant removal of oxygen from the headspace gas. The elevated temperature gas generation tests described in this report involved heating small test vessels containing neptunium dioxide and measuring the headspace gas pressure and composition at the end of the test period. Four samples were used in these tests to evaluate the impact of process variables on the gas generation rate. Two samples were calcined to 600 degrees Celsius and two were calcined to 650 degrees Celsius. Each test vessel contained approximately 9.5 g of neptunium dioxide. Following exposure to 75 per cent relative humidity (RH) for five days, these samples were loaded in air and then heated to between 105 and 115 degrees Celsius for about one month. At the conclusion of the test period, the headspace gas of each container was analyzed using a micro-gas chromatograph installed in the glovebox where the experiments were conducted. The pressure, volume, and composition data for the headspace gas samples were used to calculate average H2 generation rates.

  6. Elevated Temperature Compressive Properties of Zr-Modified Nial

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Noebe, R. D.

    1996-01-01

    Small Zr additions are known to substantially affect the deformation behavior and strength of polycrystalline NiAl, yet little information is currently available regarding the high-temperature properties of such alloys. Utilizing prealloyed powder technology, a series of four NiAl alloys have been produced containing from 0.05 to 0.7 at. pct Zr. The creep behavior of these alloys was characterized in compression between 1000 and 1400 K at strain rates ranging from approx. O.1 to 10(exp -9)/ sec. All the Zr-modified alloys were significantly stronger than binary NiAl under lower temperature and faster strain-rate conditions; however, the single-phase materials (Zr less than or equal to 0.1 at. pct) and binary NiAl had similar strengths at high temperatures and slow strain rates. The two-phase NiAl-Ni, AlZr alloys containing 0.3 and 0.7 at. pct Zr had nearly identical strengths. While the two-phase alloys were stronger than the single-phase materials at all test conditions, the degree of microstructural damage in the two-phase alloys due to internal oxidation during testing appeared to increase with Zr level. Balancing the poor oxidation behavior with the consistent strength advantage of the two-phase alloys, it is concluded that optimum elevated-temperature properties could be obtained in Heusler-strengthened NiAl containing between 0.1 and 0.3 at. pct Zr.

  7. An x-ray absorption spectroscopy study of Mo oxidation in Pb at elevated temperatures

    SciTech Connect

    Liu, Shanshan; Olive, Daniel; Terry, Jeff; Segre, Carlo U.

    2009-06-30

    The corrosion of fuel cladding and structural materials by lead and lead-bismuth eutectic in the liquid state at elevated temperatures is an issue that must be considered when designing advanced nuclear systems and high-power spallation neutron targets. In this work, lead corrosion studies of molybdenum were performed to investigate the interaction layer as a function of temperature by X-ray absorption spectroscopy. In situ X-ray absorption measurements on a Mo substrate with a 3-6 {micro}m layer of Pb deposited by thermal evaporation were performed at temperatures up to 900 C and at a 15{sup o} angle to the incident X-rays. The changes in the local atomic structure of the corrosion layer are visible in the difference extended X-ray absorption fine structure and the linear combination fitting of the X-ray absorption near-edge structure to as-deposited molybdenum sample and molybdenum oxide (MoO{sub 2} and MoO{sub 3}) standards. The data are consistent with the appearance of MoO{sub 3} in an intermediate temperature range (650-800 C) and the more stable MoO{sub 2} phase dominating at high and low temperatures.

  8. Effect of curing conditions on the dimensional and thermal stability of calcium phosphate cement for elevated temperature applications

    SciTech Connect

    Blom, Johan; Rahier, Hubert; Wastiels, Jan

    2014-12-15

    Calcium phosphate cements (CPCs) are attractive materials for elevated temperature applications, like moulds to process thermoplastics up to 300 °C. The CPC resulting from the reaction of wollastonite with phosphoric acid cured at room temperature however contains hydrated phases like brushite, and is thus not stable when exposed to temperatures above 200 °C. A non-contact method based on digital image correlation demonstrated that isothermal curing at 60 °C reduces the thermal shrinkage up to 300 °C by 25%. This curing method results in the direct formation of the more stable monetite in a shorter curing time. The correlated results of TGA, pH of the filtration water, and DSC analysis on partially cured material indicate this. XRD diffractograms and SEM images in combination with EDX show the evolution of the transformation of wollastonite into monetite, and the structure and morphology of the formed material.

  9. The Mechanisms of Elevated Temperature Property Losses in High Performance Structural Epoxy Resin Matrix Materials after Exposures to High Humidity Environments

    DTIC Science & Technology

    1977-03-01

    tensile measurements, infrared spectroscopy , heat distortion tests, bomb creep tests, scanning electron microscopy, polarized-light photomlcroscopy, and... bsorption rate and raised the absorption level to values higher than equilibrium values for humidity only conditions. It was subsequently found that... Spectroscopy to detent any evidence of chemnical changes occurring 1<, 2 7 AFML-TR-76-153 during stress-temperature-humidity exposures. This

  10. Elevated temperature creep properties for selected active metal braze alloys

    SciTech Connect

    Stephens, J.J.

    1997-02-01

    Active metal braze alloys reduce the number of processes required for the joining of metal to ceramic components by eliminating the need for metallization and/or Ni plating of the ceramic surfaces. Titanium (Ti), V, and Zr are examples of active element additions which have been used successfully in such braze alloys. Since the braze alloy is expected to accommodate thermal expansion mismatch strains between the metal and ceramic materials, a knowledge of its elevated temperature mechanical properties is important. In particular, the issue of whether or not the creep strength of an active metal braze alloy is increased or decreased relative to its non-activated counterpart is important when designing new brazing processes and alloy systems. This paper presents a survey of high temperature mechanical properties for two pairs of conventional braze alloys and their active metal counterparts: (a) the conventional 72Ag-28Cu (Cusil) alloy, and the active braze alloy 62.2Ag- 36.2Cu-1.6Ti (Cusil ABA), and (b) the 82Au-18Ni (Nioro) alloy and the active braze alloy Mu-15.5M-0.75Mo-1.75V (Nioro ABA). For the case of the Cusil/Cusil ABA pair, the active metal addition contributes to solid solution strengthening of the braze alloy, resulting in a higher creep strength as compared to the non-active alloy. In the case of the Nioro/Nioro ABA pair, the Mo and V additions cause the active braze alloy to have a two-phase microstructure, which results in a reduced creep strength than the conventional braze alloy. The Garofalo sinh equation has been used to quantitatively describe the stress and temperature dependence of the deformation behavior. It will be observed that the effective stress exponent in the Garofalo sinh equation is a function of the instantaneous value of the stress argument.

  11. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R. G.; Wiberley, S. E.

    1985-01-01

    Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

  12. Crack Growth Processes at Elevated Temperatures in Advanced Materials

    DTIC Science & Technology

    1991-01-01

    34C. 9 The dependence of U = AK./AK on 1/Kr, for SEN specimens of 27 titanium alloys. (a) CORONA -5 and (b) 2411. 10 The dependence of U = AK.,/AK on 1...the slope of the line modified. Similar results are shown for the titanium alloys CORONA -5 and 2411 in Fig. 9. Closure levels have also been measured... CORONA -5 Ti-6AI-4V(RA) Crack growth rate 5.5±2 3.5±2 5.0±2 3.0±2 Mode 1 closure 5.8±0.5 not meas. = 6.7 not meas. Microstructure 4.0±0.5 4.0±0.5 6.6±1.5

  13. Crack Growth Processes at Elevated Temperatures in Advanced Materials

    DTIC Science & Technology

    1992-02-01

    aluminum alloys, 8 CORONA -5, the titanium aluminide alloy 2411, fine grained Astroloy, and partially stabilized zirconia . This similarity in closure...4V C equiaxed cx-P, recryst. annealed, ingot 6 CORONA -5 C lamellar (x-P, ingot 7 AI-Fe-X A dispersion strengthed, P/M 5 8 Super ca2 A equiaxed a-P...temperature through two a+13 titanium alloys, Ti-6AI-4V (RA) [1] and CORONA -5, [2] and two a2 +13 titanium aluminide alloys, Super Alpha 2, I [3] and 2411

  14. Bioinspired structural materials

    NASA Astrophysics Data System (ADS)

    Wegst, Ulrike G. K.; Bai, Hao; Saiz, Eduardo; Tomsia, Antoni P.; Ritchie, Robert O.

    2015-01-01

    Natural structural materials are built at ambient temperature from a fairly limited selection of components. They usually comprise hard and soft phases arranged in complex hierarchical architectures, with characteristic dimensions spanning from the nanoscale to the macroscale. The resulting materials are lightweight and often display unique combinations of strength and toughness, but have proven difficult to mimic synthetically. Here, we review the common design motifs of a range of natural structural materials, and discuss the difficulties associated with the design and fabrication of synthetic structures that mimic the structural and mechanical characteristics of their natural counterparts.

  15. Bioinspired structural materials.

    PubMed

    Wegst, Ulrike G K; Bai, Hao; Saiz, Eduardo; Tomsia, Antoni P; Ritchie, Robert O

    2015-01-01

    Natural structural materials are built at ambient temperature from a fairly limited selection of components. They usually comprise hard and soft phases arranged in complex hierarchical architectures, with characteristic dimensions spanning from the nanoscale to the macroscale. The resulting materials are lightweight and often display unique combinations of strength and toughness, but have proven difficult to mimic synthetically. Here, we review the common design motifs of a range of natural structural materials, and discuss the difficulties associated with the design and fabrication of synthetic structures that mimic the structural and mechanical characteristics of their natural counterparts.

  16. Hot deformation behaviour of alloys for applications at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Voyzelle, Benoit

    The present study investigated the deformation behaviour, microstructure evolution and fracture behaviour under hot working conditions of alloys designed for elevated-temperature applications. For this purpose, iron-aluminum and titanium-aluminum alloys were selected and their compositions are: Fe-8.5wt%Al-5.5Cr-2.0Mo-0.2Zr-0.03C, Fe-16.5Al-5.5Cr-1.0Nb-0.05C and Ti-33.3Al-2.8Mn-4.8Nb. These alloys were tested in the as-cast condition and in the form of hot-rolled + annealed plate for the iron-aluminum alloys and in the HIP'ed condition for the titanium-aluminum alloy. Isothermal compression tests were carried out with a Gleeble 2000 over a range of temperatures from 800 to 1250°C and constant strain rates from 10-3 to 10 s-1. In general, the flow curves are marked by a peak stress and softening which decline as temperature rises, and a flow stress which diminishes with rise in temperature and decrease in strain rate. The flow behaviour at peak stress (sigmap) and 0.5 true strain of these materials was described well by the Zener-Hollomon parameter Z=3˙exp /RTQHW , where Z=K3sinha sn . A numerical curve-fitting method was used to yield values of the following parameters: (i) stress exponent, n and (ii) activation energy, QHW . The dynamic material modeling approach was performed to extract from hot compression data: (i) the strain rate sensitivity parameter, m, (ii) the efficiency of power dissipation, eta, and (iii) the instability parameter, xi. The microstructure evolution and fracture behaviour were assessed using optical and electron microscopy. The deformation processes occuring were determined by correlation of the sigma-epsilon curves, m and microstructural observations. The resulting deformation map indicates that at lower temperatures and higher strain rates, the dominant restoration occurs by dynamic recovery, while at lower strain rates and higher temperatures dynamic recrystallization is the operative mode. At the highest temperatures, dynamic

  17. Composite structural materials. [aircraft structures

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1980-01-01

    The use of filamentary composite materials in the design and construction of primary aircraft structures is considered with emphasis on efforts to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, and reliability and life prediction. The redesign of a main spar/rib region on the Boeing 727 elevator near its actuator attachment point is discussed. A composite fabrication and test facility is described as well as the use of minicomputers for computer aided design. Other topics covered include (1) advanced structural analysis methids for composites; (2) ultrasonic nondestructive testing of composite structures; (3) optimum combination of hardeners in the cure of epoxy; (4) fatigue in composite materials; (5) resin matrix characterization and properties; (6) postbuckling analysis of curved laminate composite panels; and (7) acoustic emission testing of composite tensile specimens.

  18. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R.; Wiberley, S. E.

    1986-01-01

    Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

  19. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Wiberley, S. E.

    1978-01-01

    The purpose of the RPI composites program is to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, reliability and life prediction. Concommitant goals are to educate engineers to design and use composite materials as normal or conventional materials. A multifaceted program was instituted to achieve these objectives.

  20. Mechanical properties of polyimide coated optical fibers at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Huang, Lei; Dyer, Robert S.; Lago, Ralph J.; Stolov, Andrei A.; Li, Jie

    2016-03-01

    High temperature mechanical strength and reliability of optical fibers have become important subjects as optical fibers are increasingly used for harsher environments. Theories and models of fiber mechanical properties established for traditional telecommunications applications may need to be validated for applications at elevated temperatures. In this paper, we describe the test setup for high temperature tensile strength of fiber and report initial results of dynamic tensile strength of polyimide coated optical fiber at 300 and 350ºC for different heating time intervals. The results are compared with room temperature strength data, data available in the literature, and our earlier work on thermogravimetric analysis (TGA) weight loss of the polyimide coating and the observations on surface morphology at elevated temperatures. Interesting observations are discussed and possible explanations are proposed.

  1. Upsettability and forming limit of magnesium alloys at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Park, Heung Sik; Kim, Si Pom; Park, Young Chul; Park, Joon Hong; Baek, Seung Gul

    2012-11-01

    In recent years, Magnesium (Mg) and its alloys have become a center of special interest in the automotive industry. Due to their high specific mechanical properties, they offer a significant weight saving potential in modern vehicle constructions. Most Mg alloys show very good machinability and processability, and even the most complicated die casting parts can be easily produced. In this study, Microstructure, Vickers hardness and tensile tests were examined and performed for each specimen to verify effects of forming conditions. Also to verify upsettability and forming limit of the specimen at room temperature and elevated temperature, upsetting experiments were performed. For comparison, experiments at elevated temperature were performed for various Mg alloy, such as AZ31, AZ91, and AM50. The experimental results were compared with those of CAE analysis to propose forming limit of Magnesium alloys.

  2. Modal Acoustic Emission of Damage Accumulation in Woven SiC/SiC at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Morscher, G. N.

    1998-01-01

    Ceramic matrix composites exhibit significant nonlinear stress-strain behavior that makes them attractive as potential materials for many high temperature applications. The mechanisms for this nonlinear stress-strain behavior are all associated with various types of damage in the composites, e.g. transverse matrix cracks and individual fiber failures. Modal acoustic emission has been employed to aid in discerning the damage accumulation that occurs during elevated temperature tensile stress-rupture of woven Hi-Nicalon fiber, BN interphase, SiC matrix composites. It is shown that modal acoustic emission is an effective monitor of the relative damage accumulation in the composites and locator of the damage and failure events as a function of strain (stress), time at temperature, and temperature gradients along the length of the elevated temperature test specimen.

  3. Elevated-temperature fracture resistances of monolithic and composite ceramics using chevron-notched bend tests

    NASA Technical Reports Server (NTRS)

    Ghosh, Asish; Jenkins, Michael G.; Ferber, Mattison K.; Peussa, Jouko; Salem, Jonathan A.

    1992-01-01

    The quasi-static fracture behaviors of monolithic ceramics (SiC, Si3N4, MgAl2O4), self-reinforced monoliths (acicular grained Si3N4, acicular grained mullite), and ceramic matrix composites (SiC whisker/Al2O3 matrix, TiB2 particulate/SiC matrix, SiC fiber/CVI SiC matrix, Al2O3 fiber/CVI SiC matrix) were measured over the temperature range of 20 to 1400 C. The chevron notched, bend bar test geometry was essential for characterizing the elevated temperature fracture resistances of this wide range of quasi-brittle materials during stable crack growth. Fractography revealed the differences in the fracture behavior of the different materials at the various temperatures. The fracture resistances of the self-reinforced monoliths were comparable to those of the composites and the fracture mechanisms were found to be similar at room temperature. However at elevated temperatures the differences of the fracture behavior became apparent where the superior fracture resistance of the self-reinforced monoliths were attributed to the minor amounts of glassy, intergranular phases which were often more abundant in the composites and affected the fracture behavior when softened by elevated temperatures.

  4. Elevated Temperature Crack Growth Studies of Advanced Titanium Aluminides.

    DTIC Science & Technology

    1987-09-01

    titanium aluminide in gas turbine engines would reduce the United States dependence on foreign sources for superalloy constituent elements, and would...ELVTDTEMPERATURE CRACK GROWTH STUDIES OF ADVANCED 1I TITANIUM ALUMINIDES (U) SYSTRAN CORP DAYTON ON VENKATARAMAN SEP 87 AFUAL-TR-87-4t82 F32615-86-C...ELEVATED TEMPERATURE CRACK GROWTH STUDIES OF ADVANCED TITANIUM ALUMINIDES DTIC Dr. Srivathsan Venkataraman e’.- Systran Corporation 4126 Linden Avenue

  5. Corrosion resistant coatings suitable for elevated temperature application

    DOEpatents

    Chan, Kwai S [San Antonio, TX; Cheruvu, Narayana Sastry [San Antonio, TX; Liang, Wuwei [Austin, TX

    2012-07-31

    The present invention relates to corrosion resistance coatings suitable for elevated temperature applications, which employ compositions of iron (Fe), chromium (Cr), nickel (Ni) and/or aluminum (Al). The compositions may be configured to regulate the diffusion of metals between a coating and a substrate, which may then influence coating performance, via the formation of an inter-diffusion barrier layer. The inter-diffusion barrier layer may comprise a face-centered cubic phase.

  6. Diffusive Gas Loss from Silica Glass Ampoules at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Palosz, W.

    1998-01-01

    Changes in the pressure of hydrogen, helium and neon due to diffusion through the wall of silica crystal growth ampoules at elevated temperatures were determined experimentally. We show that, while both He- and Ne-losses closely follow conventional model of diffusive gas permeation through the wall, hydrogen losses, in particular at low fill pressures, can be much larger. This is interpreted in terms of the high solubility of hydrogen in silica glasses.

  7. Intrinsic relationship between electronic structures and phase transition of SrBi{sub 2−x}Nd{sub x}Nb{sub 2}O{sub 9} ceramics from ultraviolet ellipsometry at elevated temperatures

    SciTech Connect

    Duan, Z. H.; Jiang, K.; Xu, L. P.; Li, Y. W.; Hu, Z. G. Chu, J. H.

    2014-02-07

    The ferroelectric orthorhombic to paraelectric tetragonal phase transition of SrBi{sub 2−x}Nd{sub x}Nb{sub 2}O{sub 9} (x = 0, 0.05, 0.1, and 0.2) layer-structured ceramics has been investigated by temperature-dependent spectroscopic ellipsometry. Based on the analysis of dielectric functions from 0 to 500 °C with double Tauc-Lorentz dispersion model, the interband transitions located at ultraviolet region have shown an abrupt variation near the Curie temperature. The changes of dielectric functions are mainly due to the thermal-optical and/or photoelastic effect. Moreover, the characteristic alteration in interband transitions can be ascribed to distortion of NbO{sub 6} octahedron and variation of hybridization between Bi 6s and O 2p states during the structure transformation.

  8. Performance of MOV Stem Lubricants at Elevated Temperatures

    SciTech Connect

    DeWall, Kevin George; Nitzel, Michael Everett; Watkins, John Clifford

    2001-07-01

    This paper documents the results of recent tests sponsored by the U. S. Nuclear Regulatory Commission (NRC) and performed by the Idaho National Engineering and Environmental Laboratory (INEEL). These tests address the effectiveness of the lubricant used on the threaded portion of the valve stem, where the stem nut turns on the stem. Recent testing indicates that an elevated temperature environment can lead to significant increases in the friction coefficient at the stem/stem-nut interface. Most valve actuator qualification tests are performed at room temperature. Similarly, in-service tests are run at ambient plant temperatures, usually 70 to 100°F. Since design conditions can lead to valve operating temperatures in the 200 to 300°F range, it is important to know whether a temperature-induced increase in friction at the stem/stem-nut interface will prevent the required operation of critical valves. Lubricant aging is another phenomenon that might have deleterious effects on the thrust output of a valve actuator. Laboratory experience and field experience both indicate that after long periods in elevated temperature environments, the lubricants may lose their lubrication qualities. The scope of the current test program includes testing of five different lubricants on four different valve stems. Pending completion of the testing, results of the tests conducted using two of the four stems are discussed. The test series included collection of baseline data at room temperature, single step temperature tests where the temperature of the test setup was elevated directly to 250°F, and step testing where the temperature was elevated in steps to 130, 190, and 250°F, then returned to 70°F. All greases tested showed evidence of physical change after elevated temperature tests. Except for one particular lubricant, all of the greases tested showed increased coefficients of friction at elevated temperatures. Numerous other preliminary conclusions are presented

  9. Nitrogen ion beam synthesis of InN in InP(100) at elevated temperature

    SciTech Connect

    Dhara, S.; Magudapathy, P.; Kesavamoorthy, R.; Kalavathi, S.; Sastry, V.S.; Nair, K.G.M.; Hsu, G.M.; Chen, L.C.; Chen, K.H.; Santhakumar, K.; Soga, T.

    2006-06-12

    The InN phase is grown in crystalline InP(100) substrates by 50 keV N{sup +} implantation at an elevated temperature of 400 deg. C followed by annealing at 525 deg. C in N{sub 2} ambient. Crystallographic structural and Raman scattering studies are performed for the characterization of grown phases. Temperature- and power-dependent photoluminescence studies show direct band-to-band transition peak {approx}1.06 eV at temperatures {<=}150 K. Implantations at an elevated temperature with a low ion beam current and subsequent low temperature annealing step are found responsible for the growth of high-quality InN phase.

  10. Dynamic restoration mechanism of a Fe{sub 3}Al based alloy during elevated temperature deformation

    SciTech Connect

    Chen, M.; Shan, A.; Lin, D.

    1995-08-01

    By TEM and metallographic examination, the authors found that dynamic recovery and following continuous recrystallization, which connects with the elevated temperature ductility, takes place in a Fe{sub 3}Al based alloy during elevated temperature deformation. Dynamic restoration consists of the following process: (1) by climbing or cross-slipping, glide dislocations change into dislocation arrays, (2) the dislocation array attracts lattice dislocations, (3) with increasing dislocation density, a non-equilibrium sub boundary forms, which is easy to migrate, slide or rotate under external force, and (4) when the misorientation angle of the sub boundary increases to a critical value, the sub boundary changes into a grain boundary with continuous misfit. By relaxation, the boundary then changes into a grain boundary consisting of periodical structure units.

  11. Comparative performance of geopolymers made with metakaolin and fly ash after exposure to elevated temperatures

    SciTech Connect

    Kong, Daniel L.Y.; Sanjayan, Jay G. Sagoe-Crentsil, Kwesi

    2007-12-15

    This paper presents the results of a study on the effect of elevated temperatures on geopolymers manufactured using metakaolin and fly ash of various mixture proportions. Both types of geopolymers (metakaolin and fly ash) were synthesized with sodium silicate and potassium hydroxide solutions. The strength of the fly ash-based geopolymer increased after exposure to elevated temperatures (800 deg. C). However, the strength of the corresponding metakaolin-based geopolymer decreased after similar exposure. Both types of geopolymers were subjected to thermogravimetric, scanning electron microscopy and mercury intrusion porosimetry tests. The paper concludes that the fly ash-based geopolymers have large numbers of small pores which facilitate the escape of moisture when heated, thus causing minimal damage to the geopolymer matrix. On the other hand, metakaolin geopolymers do not possess such pore distribution structures. The strength increase in fly ash geopolymers is also partly attributed to the sintering reactions of un-reacted fly ash particles.

  12. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    The promise of filamentary composite materials, whose development may be considered as entering its second generation, continues to generate intense interest and applications activity. Fiber reinforced composite materials offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been achieved since the initial developments in the mid 1960's. Rather limited applications to primary aircraft structure have been made, however, mainly in a material-substitution mode on military aircraft, except for a few experiments currently underway on large passenger airplanes in commercial operation. To fulfill the promise of composite materials completely requires a strong technology base. NASA and AFOSR recognize the present state of the art to be such that to fully exploit composites in sophisticated aerospace structures, the technology base must be improved. This, in turn, calls for expanding fundamental knowledge and the means by which it can be successfully applied in design and manufacture.

  13. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1984-01-01

    Progress is reported in studies of constituent materials composite materials, generic structural elements, processing science technology, and maintaining long-term structural integrity. Topics discussed include: mechanical properties of high performance carbon fibers; fatigue in composite materials; experimental and theoretical studies of moisture and temperature effects on the mechanical properties of graphite-epoxy laminates and neat resins; numerical investigations of the micromechanics of composite fracture; delamination failures of composite laminates; effect of notch size on composite laminates; improved beam theory for anisotropic materials; variation of resin properties through the thickness of cured samples; numerical analysis composite processing; heat treatment of metal matrix composites, and the RP-1 and RP2 gliders of the sailplane project.

  14. Dynamic Fracture Initiation Toughness of a Gamma (Met-PX) Titanium Aluminide at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Shazly, Mostafa; Prakash, Vikas; Draper, Susan

    2009-06-01

    Recently, a new generation of titanium aluminide alloy named Gamma-Met PX (GKSS, Geesthacht, Germany) has been developed with better rolling and postrolling characteristics. Previous work on this alloy has shown the material to have higher strengths at room and elevated temperatures when compared with other gamma titanium aluminides. In particular, this new alloy has shown increased ductility at elevated temperatures under both quasistatic and high-strain-rate uniaxial compressive loading. However, its high-strain-rate tensile ductility at room and elevated temperatures is limited to ~1 pct. In the present article, the results of a study investigating the effects of the loading rate and test temperature on the dynamic fracture initiation toughness in Gamma-Met PX are presented. A modified split Hopkinson pressure bar (MSHPB) was used along with high-speed photography, to determine the dynamic fracture initiation toughness. Three-point-bend fracture tests were conducted at impact speeds in the range 1 to 3.6 m/s and at test temperatures up to 1200 °C. Furthermore, the effect of long-time high-temperature air exposure on the fracture toughness was investigated. The results show that the dynamic fracture initiation toughness decreases at test temperatures beyond 600 °C. Moreover, the dynamic fracture initiation toughness was found to decrease with increasing exposure time. The reasons behind this drop are analyzed and discussed.

  15. Establishing isothermal contact at a known temperature under thermal equilibrium in elevated temperature instrumented indentation testing

    NASA Astrophysics Data System (ADS)

    Hou, X. D.; Alvarez, C. L. M.; Jennett, N. M.

    2017-02-01

    Instrumented indentation testing (IIT) at elevated temperatures has proved to be a useful tool to study plastic and elastic deformation and understand the performance of material components at (or nearer to) the actual temperatures experienced in-service. The value of elevated temperature IIT data, however, depends on the ability not only to achieve a stable, isothermal indentation contact at thermal equilibrium when taking data, but to be able to assign a valid temperature to that contact (and so to the data). The most common method found in the current literature is to use the calculated thermal drift rate as an indicator, but this approach has never been properly validated. This study proves that using the thermal drift rate to determine isothermal contact may lead to large errors in the determination of the real contact temperature. Instead, a more sensitive and validated method is demonstrated, based upon using the indenter tip and the tip heater control thermocouple as a reproducible and calibrated contact temperature sensor. A simple calibration procedure is described, along with step by step guidance to establish an isothermal contact at a known temperature under thermal equilibrium when conducting elevated temperature IIT experiments.

  16. Electrospun melamine resin-based multifunctional nonwoven membrane for lithium ion batteries at the elevated temperatures

    NASA Astrophysics Data System (ADS)

    Wang, Qingfu; Yu, Yong; Ma, Jun; Zhang, Ning; Zhang, Jianjun; Liu, Zhihong; Cui, Guanglei

    2016-09-01

    A flame retardant and thermally dimensional stable membrane with high permeability and electrolyte wettability can overcome the safety issues of lithium ion batteries (LIBs) at elevated temperatures. In this work, a multifunctional thermoset nonwoven membrane composed of melamine formaldehyde resin (MFR) nano-fibers was prepared by a electro-spinning method. The resultant porous nonwoven membrane possesses superior permeability, electrolyte wettability and thermally dimensional stability. Using the electrospun MFR membrane, the LiFePO4/Li battery exhibits high safety and stable cycling performance at the elevated temperature of 120 °C. Most importantly, the MFR membrane contains lone pair electron in the nitrogen element, which can chelate with Mn2+ ions and suppress their transfer across the separator. Therefore, the LiMn2O4/graphite cells with the electrospun MFR multifunctional membranes reveal an improved cycle performance even at high temperature. This work demonstrated that electrospun MFR is a promising candidate material for high-safety separator of LIBs with stable cycling performance at elevated temperatures.

  17. Structural Materials: 95. Concrete

    SciTech Connect

    Naus, Dan J

    2012-01-01

    Nuclear power plant concrete structures and their materials of construction are described, and their operating experience noted. Aging and environmental factors that can affect the durability of the concrete structures are identified. Basic components of a program to manage aging of these structures are identified and described. Application of structural reliability theory to devise uniform risk-based criteria by which existing facilities can be evaluated to achieve a desired performance level when subjected to uncertain demands and to quantify the effects of degradation is outlined. Finally, several areas are identified where additional research is desired.

  18. Complexation of neptunium(V) with fluoride in aqueous solutions at elevated temperatures

    SciTech Connect

    Tian, Guoxin; Rao, Linfeng; Xia, Yuanxian; Friese, Judah I.

    2009-02-01

    Over the past several decades, the production and testing of nuclear weapons in the U.S. have created significant amounts of high-level nuclear wastes (HLW) that are currently stored in underground tanks across the U.S. DOE (Department of Energy) sites. Eventually, the HLW will be made into the waste form and disposed of in geological repositories for HLW. Among the radioactive materials, neptunium is of great concern in the post-closure chemical environment in the repository because of the long half-life of 237Np (2.14•106 years) and the high mobility of Np(V), the most stable oxidation state of neptunium. It is estimated that 237Np, together with 129I and 99Tc, will be the major contributors to the potential total annual dose from the repository beyond 10000 years [1]. Due to the high radiation energy released from the HLW, the postclosure repository is expected to remain at elevated temperatures for thousands of years [1]. If the waste package is breached and becomes in contact with groundwater, neptunium, as well as other radioactive materials will be in aqueous solutions at elevated temperatures. Interactions of radioactive materials with the chemical components in groundwater play an important role in determining their migration in the repository. To predict the migration behavior of neptunium, it is necessary to have sufficient and reliable thermodynamic data on its complexation with the ligands that are present in the groundwater of the repository (e.g., OH–, F–, SO42– ,PO43– and CO32) at elevated temperatures. However, such data are scarce and scattered for 25°C, and nearly nonexistent for elevated temperatures [2]. To provide reliable thermodynamic data, we have conducted investigations of the complexation of actinides, including thorium, uranium, neptunium and plutonium, at elevated temperatures. Thermodynamic parameters, including formation constants, enthalpy and heat capacity of complexation are experimentally determined. This paper

  19. Mechanical Properties of T650-35/AFR-PE-4 at Elevated Temperatures for Lightweight Aeroshell Designs

    NASA Technical Reports Server (NTRS)

    Whitley, Karen S.; Collins, TImothy J.

    2006-01-01

    Considerable efforts have been underway to develop multidisciplinary technologies for aeroshell structures that will significantly increase the allowable working temperature for the aeroshell components, and enable the system to operate at higher temperatures while sustaining performance and durability. As part of these efforts, high temperature polymer matrix composites and fabrication technologies are being developed for the primary load bearing structure (heat shield) of the spacecraft. New high-temperature resins and composite material manufacturing techniques are available that have the potential to significantly improve current aeroshell design. In order to qualify a polymer matrix composite (PMC) material as a candidate aeroshell structural material, its performance must be evaluated under realistic environments. Thus, verification testing of lightweight PMC's at aeroshell entry temperatures is needed to ensure that they will perform successfully in high-temperature environments. Towards this end, a test program was developed to characterize the mechanical properties of two candidate material systems, T650-35/AFR-PE-4 and T650-35/RP46. The two candidate high-temperature polyimide resins, AFR-PE-4 and RP46, were developed at the Air Force Research Laboratory and NASA Langley Research Center, respectively. This paper presents experimental methods, strength, and stiffness data of the T650-35/AFR-PE-4 material as a function of elevated temperatures. The properties determined during the research test program herein, included tensile strength, tensile stiffness, Poisson s ratio, compressive strength, compressive stiffness, shear modulus, and shear strength. Unidirectional laminates, a cross-ply laminate and two eight-harness satin (8HS)-weave laminates (4-ply and 10-ply) were tested according to ASTM standard methods at room and elevated temperatures (23, 316, and 343 C). All of the relevant test methods and data reduction schemes are outlined along with

  20. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1979-01-01

    A multifaceted program is described in which aeronautical, mechanical, and materials engineers interact to develop composite aircraft structures. Topics covered include: (1) the design of an advanced composite elevator and a proposed spar and rib assembly; (2) optimizing fiber orientation in the vicinity of heavily loaded joints; (3) failure mechanisms and delamination; (4) the construction of an ultralight sailplane; (5) computer-aided design; finite element analysis programs, preprocessor development, and array preprocessor for SPAR; (6) advanced analysis methods for composite structures; (7) ultrasonic nondestructive testing; (8) physical properties of epoxy resins and composites; (9) fatigue in composite materials, and (10) transverse thermal expansion of carbon/epoxy composites.

  1. Composite Structural Materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

    1984-01-01

    The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

  2. Technology for Elevated Temperature Tests of Structural Panels

    NASA Technical Reports Server (NTRS)

    Thornton, E. A.

    1999-01-01

    A technique for full-field measurement of surface temperature and in-plane strain using a single grid imaging technique was demonstrated on a sample subjected to thermally-induced strain. The technique is based on digital imaging of a sample marked by an alternating line array of La2O2S:Eu(+3) thermographic phosphor and chromium illuminated by a UV lamp. Digital images of this array in unstrained and strained states were processed using a modified spin filter. Normal strain distribution was determined by combining unstrained and strained grid images using a single grid digital moire technique. Temperature distribution was determined by ratioing images of phosphor intensity at two wavelengths. Combined strain and temperature measurements demonstrated on the thermally heated sample were DELTA-epsilon = +/- 250 microepsilon and DELTA-T = +/- 5 K respectively with a spatial resolution of 0.8 mm.

  3. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    Research in the basic composition, characteristics, and processng science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to problems. Detailed descriptions of the progress achieved in the various component parts of his program are presented.

  4. Grain boundary oxidation and fatigue crack growth at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Liu, H. W.; Oshida, Y.

    1986-01-01

    Fatigue crack growth rate at elevated temperatures can be accelerated by grain boundary oxidation. Grain boundary oxidation kinetics and the statistical distribution of grain boundary oxide penetration depth were studied. At a constant delta K-level and at a constant test temperature, fatigue crack growth rate, da/dN, is a function of cyclic frequency, nu. A fatigue crack growth model of intermittent micro-ruptures of grain boundary oxide is constructed. The model is consistent with the experimental observations that, in the low frequency region, da/dN is inversely proportional to nu, and fatigue crack growth is intergranular.

  5. Elevated temperature alters carbon cycling in a model microbial community

    NASA Astrophysics Data System (ADS)

    Mosier, A.; Li, Z.; Thomas, B. C.; Hettich, R. L.; Pan, C.; Banfield, J. F.

    2013-12-01

    Earth's climate is regulated by biogeochemical carbon exchanges between the land, oceans and atmosphere that are chiefly driven by microorganisms. Microbial communities are therefore indispensible to the study of carbon cycling and its impacts on the global climate system. In spite of the critical role of microbial communities in carbon cycling processes, microbial activity is currently minimally represented or altogether absent from most Earth System Models. Method development and hypothesis-driven experimentation on tractable model ecosystems of reduced complexity, as presented here, are essential for building molecularly resolved, benchmarked carbon-climate models. Here, we use chemoautotropic acid mine drainage biofilms as a model community to determine how elevated temperature, a key parameter of global climate change, regulates the flow of carbon through microbial-based ecosystems. This study represents the first community proteomics analysis using tandem mass tags (TMT), which enable accurate, precise, and reproducible quantification of proteins. We compare protein expression levels of biofilms growing over a narrow temperature range expected to occur with predicted climate changes. We show that elevated temperature leads to up-regulation of proteins involved in amino acid metabolism and protein modification, and down-regulation of proteins involved in growth and reproduction. Closely related bacterial genotypes differ in their response to temperature: Elevated temperature represses carbon fixation by two Leptospirillum genotypes, whereas carbon fixation is significantly up-regulated at higher temperature by a third closely related genotypic group. Leptospirillum group III bacteria are more susceptible to viral stress at elevated temperature, which may lead to greater carbon turnover in the microbial food web through the release of viral lysate. Overall, this proteogenomics approach revealed the effects of climate change on carbon cycling pathways and other

  6. Full-field measurement of surface topographies and thin film stresses at elevated temperatures by digital gradient sensing method.

    PubMed

    Zhang, Changxing; Qu, Zhe; Fang, Xufei; Feng, Xue; Hwang, Keh-Chih

    2015-02-01

    Thin film stresses in thin film/substrate systems at elevated temperatures affect the reliability and safety of such structures in microelectronic devices. The stresses result from the thermal mismatch strain between the film and substrate. The reflection mode digital gradient sensing (DGS) method, a real-time, full-field optical technique, measures deformations of reflective surface topographies. In this paper, we developed this method to measure topographies and thin film stresses of thin film/substrate systems at elevated temperatures. We calibrated and compensated for the air convection at elevated temperatures, which is a serious problem for optical techniques. We covered the principles for surface topography measurements by the reflection mode DGS method at elevated temperatures and the governing equations to remove the air convection effects. The proposed method is applied to successfully measure the full-field topography and deformation of a NiTi thin film on a silicon substrate at elevated temperatures. The evolution of thin film stresses obtained by extending Stoney's formula implies the "nonuniform" effect the experimental results have shown.

  7. Description of a system for interlocking elevated temperature mechanical tests

    SciTech Connect

    Schmale, D.T.; Poulter, G.A.

    1995-07-01

    Long term mechanical creep and fatigue testing at elevated temperatures requires reliable systems with safeguards to prevent destruction of equipment, loss of data and negative environmental impacts. Toward this goal, a computer controlled system has been developed and built for interlocking tests run on elevated temperature mechanical test facilities. Sensors for water flow, water pressure, water leakage, temperature, power and hydraulic status are monitored to control specimen heating equipment through solid state relays and water solenoid valves. The system is designed to work with the default interlocks present in the RF generators and mechanical tests systems. Digital hardware consists of two National Instruments 1/0 boards mounted in a Macintosh IIci computer. Software is written in National Instruments LabVIEW. Systems interlocked include two MTS closed loop servo controlled hydraulic test frames, one with an RF generator and one with both an RF generator and a quartz lamp furnace. Control for individual test systems is modularized making the addition of more systems simple. If any of the supporting utilities fail during tests, heating systems, chill water and hydraulics are powered down, minimizing specimen damage and eliminating equipment damage. The interlock control is powered by an uninterruptible power supply. Upon failure the cause is documented in an ASCII file.

  8. Measurements of Young's and shear moduli of rail steel at elevated temperatures.

    PubMed

    Bao, Yuanye; Zhang, Haifeng; Ahmadi, Mehdi; Karim, Md Afzalul; Felix Wu, H

    2014-03-01

    The design and modelling of the buckling effect of Continuous Welded Rail (CWR) requires accurate material constants, especially at elevated temperatures. However, such material constants have rarely been found in literature. In this article, the Young's moduli and shear moduli of rail steel at elevated temperatures are determined by a new sonic resonance method developed in our group. A network analyser is used to excite a sample hanged inside a furnace through a simple tweeter type speaker. The vibration signal is picked up by a Polytec OFV-5000 Laser Vibrometer and then transferred back to the network analyser. Resonance frequencies in both the flexural and torsional modes are measured, and the Young's moduli and shear moduli are determined through the measured resonant frequencies. To validate the measured elastic constants, the measurements have been repeated by using the classic sonic resonance method. The comparisons of obtained moduli from the two methods show an excellent consistency of the results. In addition, the material elastic constants measured are validated by an ultrasound test based on a pulse-echo method and compared with previous published results at room temperature. The measured material data provides an invaluable reference for the design of CWR to avoid detrimental buckling failure.

  9. Automated Measurement of Crack Length and Load Line Displacement at Elevated Temperature,

    DTIC Science & Technology

    1988-02-01

    LINE DISPLACEMENT AT ELEVATED TEMPERATURE Test results reported in the literature show that, in creep cracking tests at elevated temperature under steady...set-up developed for elevated temperature creep cracking test in which crack length was measured with the electrical potential drop method and load...reported in the literature show that in creep cracking tests at elevated temperature under steady load, the crack growth rate correlates best with the

  10. Capacity fade of Sony 18650 cells cycled at elevated temperatures. Part II. Capacity fade analysis

    NASA Astrophysics Data System (ADS)

    Ramadass, P.; Haran, Bala; White, Ralph; Popov, Branko N.

    A complete capacity fade analysis was carried out for Sony 18650 cells cycled at elevated temperatures. The major causes of capacity loss were identified and a complete capacity fade balance was carried out to account for the total capacity loss of Li-ion battery as a function of cycle number and temperature. The three most significant parameters that cause capacity loss were loss of secondary active material (LiCoO 2/carbon) and primary active material (Li +) and the rate capability losses. Intrinsic capacity measurements for both positive and negative electrode has been used to estimate the capacity loss due to secondary active material and a charge balance gives the capacity lost due to primary active material (Li +). Capacity fade has been quantified with secondary active material loss dominating the other losses.

  11. Mechanical properties of long carbon fiber reinforced thermoplastic (LFT) at elevated temperature

    NASA Astrophysics Data System (ADS)

    Wang, Qiushi

    Long fiber reinforced thermoplastics (LFT) possess high specific modulus and strength, superior damage tolerance and fracture toughness and have found increasing use in transportation, military, and aerospace applications. However, one of the impediments to utilizing these materials is the lack of performance data in harsh conditions, especially at elevated temperature. In order to quantify the effect of temperature on the mechanical properties of carbon fiber reinforced thermoplastic composites, carbon fiber PAA composite plates containing 20% and 30% carbon fiber were produced using extrusion/compression molding process and tested at three representative temperatures, room temperature (RT 26°C), middle temperature (MID 60°C) and glass transition temperature (Tg 80°C). A heating chamber was designed and fabricated for the testing at elevated temperature. As temperature increases, flexural modulus, flexural strength, tensile modulus and tensile strength decrease. The highest reduction observed in stiffness (modulus) values of 30% CF/PAA at Tg in the 00 orientation is 75%. The reduction values were larger for the transverse (perpendicular to flow direction) samples than the longitudinal (flow direction) samples. The property reduction in 30% CF/PAA is larger than 20% CF/PAA. Furthermore, an innovative method was developed to calculate the fiber content in carbon fiber reinforced composites by burning off the neat resin and sample in a tube furnace. This method was proved to be accurate (within 1.5 wt. % deviation) by using burning off data obtained from CF/Epoxy and CF/Vinyl Ester samples. 20% and 30% carbon/PAA samples were burned off and carbon fiber content was obtained using this method. The results of the present study will be helpful in determining the end-user applications of these composite materials. Keywords: Long Carbon Fibers, Elevated Temperature, Mechanical Properties, Burn off Test.

  12. Complexation of Neptunium(V) with Fluoride at Elevated Temperatures

    SciTech Connect

    Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian; Friese, Judah I.

    2008-06-16

    Complexation of neptunium(V) with fluoride at elevated temperatures was studied by spectrophotometry and microcalorimetry. Two successive complexes, NpO{sub 2}F(aq) and NpO{sub 2}F{sub 2}{sup -}, were identified by spectrophotometry in the temperature range of 10-70 C. Thermodynamic parameters, including the equilibrium constants and enthalpy of complexation between Np(V) and fluoride at 10-70 C were determined. Results show that the complexation of Np(V) with fluoride is endothermic and that the complexation is enhanced by the increase in temperature - a two-fold increase in the stability constants of NpO{sub 2}F(aq) and more than five-fold increase in the stability constants of NpO{sub 2}F{sub 2}{sup -} as the temperature is increased from 10 to 70 C.

  13. Hydrologic property alterations due to elevated temperatures at Yucca Mountain

    SciTech Connect

    Flint, A.L.; Nash, M.H.; Nash, M.S.

    1994-12-31

    Yucca Mountain is currently being evaluated as a potential site for a high level nuclear waste repository. The pre-emplacement hydrologic properties of the rock are important in determining the suitability of the site; however, post emplacement thermal loads and associated drying may permanently alter the character of the rock. A preliminary study was undertaken to determine the effects of elevated temperatures on hydrologic properties of the welded Topopah Spring member of the Paintbrush Tuff and a zeolitic, nonwelded tuff from the Tuffaceous Beds of Calico Hills. Rock outcrop samples were collected and dried in the laboratory at different temperatures (up to 400 degrees C). Hydrologic and physical properties -were tested before and after each of the drying cycles.

  14. Thermodynamics of Neptunium (V) Complexes with Phosphate at Elevated Temperatures

    SciTech Connect

    Xia, Y.; Friese, Judah I.; Bachelor, Paula P.; Moore, Dean A.; Rao, Linfeng

    2009-06-01

    Abstract – The complexation of Np(V) with phosphate at elevated temperatures was studied by a synergistic extraction method. A mixed buffer solution of TRIS and MES was used to maintain an appropriate pH value during the distribution experiments. The distribution ratio of Np(V) between the organic and aqueous phases was found to decrease as the concentrations of phosphate were increased. Stability constants of the 1:1 and 1:2 Np(V)-HPO42- complexes, dominant in the aqueous phase under the experimental conditions, were calculated from the effect of [HPO42-] on the distribution ratio. The thermodynamic parameters including enthalpy and entropy of complexation between Np(V) and HPO42- at 25o C – 55o C were calculated by the temperature coefficient method.

  15. Characteristics of mercury desorption from sorbents at elevated temperatures

    SciTech Connect

    Ho, T.C.; Yang, P.; Kuo, T.H.; Hopper, J.R.

    1998-12-31

    This study investigated the dynamic desorption characteristics of mercury during the thermal treatment of mercury-loaded sorbents at elevated temperatures under fixed-bed operations. Experiments were carried out in a 25.4 mm ID quartz bed enclosed in an electric furnace. Elemental mercury and mercuric chloride were tested with activated carbon and bauxite. The experimental results indicated that mercury desorption from sorbents was strongly affected by the desorption temperature and the mercury-sorbent pair. Elemental mercury was observed to desorb faster than mercuric chloride and activated carbon appeared to have higher desorption limits than bauxite at low temperatures. A kinetic model considering the mechanisms of surface equilibrium, pore diffusion and external mass transfer was proposed to simulate the observed desorption profiles. The model was found to describe reasonably well the experimental results.

  16. Compressive Strength of Stainless-Steel Sandwiches at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Mathauser, Eldon E.; Pride, Richard A.

    1959-01-01

    Experimental results are presented from crippling tests of stainless-steel sandwich specimens in the temperature range from 80 F to 1,200 F. The specimens included resistance-welded 17-7 PH stainless-steel sandwiches with single-corrugated cores, type 301 stainless-steel sandwiches with double-corrugated cores, and brazed 17-7 PH stainless-steel sandwiches with honeycomb cores. The experimental strengths are compared with predicted buckling and crippling strengths. The crippling strengths were predicted from the calculated maximum strength of the individual plate elements of the sandwiches and from a correlation procedure which gives the elevated-temperature crippling strength when the experimental room-temperature crippling strengths are known. Photographs of some of the tested specimens are included to show the modes of failure.

  17. Tolerance of LSS Plant Component to Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Ushakova, S. A.; Tikhomirov, A. A.

    2002-06-01

    Stability of LSS based on biological regeneration of water, air and food subject to damaging factors is largely dependent on the behavior of the photosynthesizing component represented, mainly, by higher plants. The purpose of this study is to evaluate the tolerance of uneven-aged wheat and radish cenoses to temperature effects different in time and value. Estimation of thermal tolerance of plants demonstrated that exposure for 20 h to the temperature increasing to 45°C brought about irreversible damage both in photosynthetic processes (up to 80% of initial value) and the processes of growth and development. Kinetics of visible photosynthesis during exposure to elevated temperatures can be used to evaluate critical exposure time within the range of which the damage of metabolic processes is reversible. With varying light intensity and air temperature it is possible to find a time period admissible for the plants to stay under adverse conditions without considerable damage of metabolic processes.

  18. Microchip electrophoresis at elevated temperatures and high separation field strengths.

    PubMed

    Mitra, Indranil; Marczak, Steven P; Jacobson, Stephen C

    2014-02-01

    We report free-solution microchip electrophoresis performed at elevated temperatures and high separation field strengths. We used microfluidic devices with 11 cm long separation channels to conduct separations at temperatures between 22 (ambient) and 45°C and field strengths from 100 to 1000 V/cm. To evaluate separation performance, N-glycans were used as a model system and labeled with 8-aminopyrene-1,3,6-trisulfonic acid to impart charge for electrophoresis and render them fluorescent. Typically, increased diffusivity at higher temperatures leads to increased axial dispersion and poor separation performance; however, we demonstrate that sufficiently high separation field strengths offset the impact of increased diffusivity in order to maintain separation efficiency. Efficiencies for these free-solution separations are the same at temperatures of 25, 35, and 45°C with separation field strengths ≥ 500 V/cm.

  19. Elevated temperature fracture of RS/PM aluminum alloy 8009

    NASA Technical Reports Server (NTRS)

    Porr, William C., Jr.; Yang, Leng; Gangloff, Richard P.

    1991-01-01

    The fracture behavior of advanced powder metallurgy Al-Fe-V-Si alloy 8009 (previously called FVS0812) is being characterized under monotonic loads, as a function of temperature. Particular attention is focused on contributions to the fracture mechanism from the fine grained dispersoid strengthened microstructure, dissolved solute from rapid solidification, and the moist air environment. Time-dependent crack growth is characterized in advanced aluminum alloys at elevated temperatures with the fracture mechanics approach, and cracking mechanisms are examined with a metallurgical approach. Specific tasks were to obtain standard load crack growth experimental information from a refined testing system; to correlate crack growth kinetics with the j-integral and time dependent C(sub t)(t); and to investigate the intermediate temperature embrittlement of 8009 alloy in order to understand crack growth mechanisms.

  20. Tension-Compression Fatigue Behavior of 2D and 3D Polymer Matrix Composites at Elevated Temperature

    DTIC Science & Technology

    2015-09-21

    performance in elevated temperature environments. High- temperature polymer matrix composites (HTPMCs) are being considered for such applications . However...the polymer matrix in most HTPMCs cannot operate at temperatures required for many aerospace structural applications . Continuous research seeks to...temperature polymer matrix composites (HTPMCs) applications , other polyimide resins replacement are being researched and developed due to the carcinogenic

  1. Zeta Potential in Intact Natural Carbonates at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Al-Mahrouqi, D.; Vinogradov, J.; Jackson, M.

    2015-12-01

    Measurements of zeta potential have been used to monitor subsurface flows in many natural brine systems. Numerous studies report zeta potentials in carbonates using crushed samples at low ionic strength and laboratory temperatures. However, natural brines have much higher salinity; moreover, temperatures are considerably higher in many subsurface settings. The variation of zeta potentials with temperature has not been examined in natural carbonates. We report zeta potential values interpreted from streaming potential measurements in two intact carbonate rock samples, saturated with artificial brines at elevated temperatures. We measure streaming potential using an experimental set-up that incorporates in-situ measurements of saturated rock conductivity, brine temperature, brine pH, brine electrical conductivity, pressure difference and voltage at temperatures up to 120oC. The streaming potential measurements are complemented with brine effluent studies. We find that the interpreted zeta potential is negative and decreases in magnitude with increasing temperature at low ionic strength (0.01M) and independent of temperature at high ionic strength (0.5M); consistent with published zeta potential in intact natural sandstones. The concentration of Ca2+ (main potential determining ion) also decreases with temperature at low ionic strength, but remains constant at high ionic strength. The temperature dependence of the zeta potential is consistent between two different natural carbonate samples and can be explained by the temperature dependence of pCa2+. We suggest that zeta potential of carbonate is independent of temperature or pH when pCa2+ remains constant. A linear variation of pH vs. pCa2+ is exhibited, at ambient and elevated temperatures, when pCa2+ is allowed to change with pH. This linear variation explains the numerous published data that shows apparent relationship between zeta potential of carbonates and pH.

  2. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, Robert G.; Wiberley, Stephen E.

    1987-01-01

    The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

  3. Artificially structured magnetic materials

    SciTech Connect

    Falco, C.M.

    1990-09-28

    This document reports the progress made during the first six months of the current three-year DOE grant on Artificially Structured Magnetic Materials.'' However, because some of the results of our previous three-year DOE grant on Artificially Structured Superconductors'' continue to emerge, both topics are addressed in this Progress Report. This report describes progress with DOE funding during the current calendar year; description of the research to be conducted during the remaining six months of the current grant year; a description of the status of the graduate students working on this research; lists of the invited talks, seminars and colloquia, of other recognition of our research, and of the publications crediting DOE sponsorship; and a summary of current and pending federal support. Since the research proposed to be conducted during the next 2 1/2 years is described in detail in our DOE proposal, it is only briefly reviewed here.

  4. In Situ Microstructural Control and Mechanical Testing Inside the Transmission Electron Microscope at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Wang, Baoming; Haque, M. A.

    2015-08-01

    With atomic-scale imaging and analytical capabilities such as electron diffraction and energy-loss spectroscopy, the transmission electron microscope has allowed access to the internal microstructure of materials like no other microscopy. It has been mostly a passive or post-mortem analysis tool, but that trend is changing with in situ straining, heating and electrical biasing. In this study, we design and demonstrate a multi-functional microchip that integrates actuators, sensors, heaters and electrodes with freestanding electron transparent specimens. In addition to mechanical testing at elevated temperatures, the chip can actively control microstructures (grain growth and phase change) of the specimen material. Using nano-crystalline aluminum, nickel and zirconium as specimen materials, we demonstrate these novel capabilities inside the microscope. Our approach of active microstructural control and quantitative testing with real-time visualization can influence mechanistic modeling by providing direct and accurate evidence of the fundamental mechanisms behind materials behavior.

  5. On the interaction of water-soluble binders and nano silicon particles: alternative binder towards increased cycling stability at elevated temperatures.

    PubMed

    Klamor, S; Schröder, M; Brunklaus, G; Niehoff, P; Berkemeier, F; Schappacher, F M; Winter, M

    2015-02-28

    Silicon based composites are among the most promising negative electrodes for lithium ion battery applications due to their high theoretical capacities. One major drawback of silicon based anodes are their large volume changes during lithiation and delithiation. Although many efforts have been made in view of new binder materials and improved electrolytes, the resulting battery cell suffers from severe capacity fading at ambient or elevated temperatures, respectively. The strong reactivity with the electrolyte is considered to be responsible for the reduced cycle life at elevated temperatures. In this work we introduce silicon composite anodes with a novel composition based on a gellan gum binder material that show an improved cycling performance at ambient temperature and at 60 °C. To elucidate the influence of the binder material, we investigated the structure of the silicon based composite anodes in order to understand the nature of the interaction of the gellan gum based binder polymers with the silicon particles in comparison with a common CMC binder. Also the influence of the choice of binder on the interactions at the interface between electrode surface and electrolyte were studied. A combination of powerful techniques including solid state NMR, TEM and EELS, XPS as well as FTIR were applied.

  6. The Effects of Elevated Temperatures on the Response of Resins Under Dynamic and Static Loadings

    NASA Technical Reports Server (NTRS)

    Gilat, Amos

    2005-01-01

    The overall objective of the research is to experimentally study the combined effects of temperature and strain rate on the response of two resins that are commonly used for the matrix material in composites. The resins are loaded at various temperatures in shear and in tension over a wide range of strain rates. These two types of loadings provide an opportunity to examine also the effect that temperature might have on the effects of the hydrostatic stress component on the material response. The experimental data provide the information needed for NASA scientists for the development of a nonlinear, strain rate, and temperature dependent deformation and strength models for composites that can subsequently be used in design. This year effort was directed into the development and testing of the epoxy resin at elevated temperatures. Two types of epoxy resins were tested in shear at high strain rates of about 10(exp-4)/s and elevated temperatures of 50 and 8OC. The results show that the temperature significantly affects the response of epoxy.

  7. The Deformation of the Multi-Layered Panel of Sheet Metals Under Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Wook; Woo, Dong-Uk

    A Molten Carbonate Fuel Cell (MCFC) stack consists of several layered unit cells. In each unit cell, the stiff structure of the separator plate contains the softer components, such as electrodes. When surface pressure acts on the stack over an extended period of time at elevated temperatures, the stiffness of the separator plate tends to degrade. Moreover, the demands for large electrode area (to increase the electric capacity of a unit cell) and thinner separator plates (to reduce weight) complicate the design of a separator plate with high stiffness. To evaluate the stiffness of the separator plate at elevated temperatures, we design and test a tiny, multi-layered separator plate specimen using a three-point bending tool. To determine the optimal structure of the separator plate, we investigate three design factors: angle, pitch and height. We adopt the Taguchi method to evaluate the experiments, and use finite element analysis to examine the experimental results. Based on these results, pitch is the most effective of these factors. As the pitch narrows, the stiffness of the separator plate increases. Therefore, we propose the pitch factor as a design criterion for the separator plate of the MCFC stack.

  8. Dynamic restoration mechanisms in {alpha}-zirconium at elevated temperatures

    SciTech Connect

    Perez-Prado, M.T. . E-mail: tpprado@cenim.csic.es; Barrabes, S.R.; Kassner, M.E.; Evangelista, E.

    2005-02-01

    The creep behavior of {alpha}-zirconium at high temperatures is not understood. Recently, steady-state stress exponents between 5 and 7 have been suggested over a range of elevated temperatures, indicating the predominance of dislocation climb (dynamic recovery) as the restoration mechanism. However, the activation energies are significantly higher than those of self-diffusion of pure Zr, as expected from climb-controlled mechanisms. This discrepancy and the observations of increased high-angle grain boundary area with straining have been attributed to the possible occurrence of discontinuous recrystallization and/or grain growth as additional restoration mechanisms. Tension, torsion and creep tests to small and large strains were performed at temperatures from 400 to 800 deg C. The microstructure of the deformed samples was characterized by optical microscopy, transmission electron microscopy, as well as texture analysis using X-ray and electron backscatter diffraction. Dynamic recovery through dislocation climb appears to be the prevailing restoration mechanism. The increase in high angle boundary area with larger strains is a consequence of geometric dynamic recrystallization.

  9. Combined Mode I and Mode II Fracture of Plasma-Sprayed Thermal Barrier Coatings at Ambient and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

    2003-01-01

    The mode I, mode II, and combined mode I-mode II fracture behavior of ZrO2- 8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. Precracks were introduced in test specimens using the single-edge-v-notched beam (SEVNB) method incorporated with final diamond polishing to achieve sharp crack tips. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of K(sub I)/K(sub II) were also determined. The mixed-mode fracture behaviors of the coating material were compared with those of monolithic advanced ceramics determined previously. The mixed-mode fracture behavior of the plasma-sprayed thermal barrier coating material was predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

  10. Combined Mode I and Mode II Fracture of Plasma-Sprayed Thermal Barrier Coatings at Ambient and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

    2003-01-01

    The mode I, mode II, and combined mode I-mode II fracture behavior of ZrO2 - 8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. Precracks were introduced in test specimens using the single-edge-v-notched beam (SEVNB) method incorporated with final diamond polishing to achieve sharp crack tips. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of KI/KII were also determined. The mixed-mode fracture behaviors of the coating material were compared with those of monolithic advanced ceramics determined previously. The mixed-mode fracture behavior of the plasma- sprayed thermal barrier coating material was predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

  11. Experimental Comparison of the Effects of Nanometric and Micrometric Particulates on the Tensile Properties and Fracture Behavior of Al Composites at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Ahmed, Adnan; Neely, Andrew J.; Shankar, Krishna

    2011-03-01

    This article studies the influence of nanometric (n-SiCp) and micrometric-scale SiC particulates ( μ-SiCp) on the tensile properties of the Al 7075 alloy. The unreinforced Al and its composites were synthesized using the powder metallurgy (P/M) route and were tested uniaxially in tension at both room and elevated temperatures. Aging behavior was studied to observe any effect of the reinforcement on the aging kinetics and hardness of the composites. X-ray diffraction was performed to determine the crystal structures of the raw materials and any reaction phase formed in the composites. The n-SiCp were not dispersed uniformly in the Al matrix and clustered mainly at the grain boundaries. The stiffness of the composites increased and the ductility decreased with an increase in the volume fraction of the n-SiCp. The n-SiCp proved to be a better reinforcement than the traditional μ-SiCp in terms of imparting higher ductility to the composite. Fractography and microscopy using optical, scanning electron, and transmission electron microscopes were performed for failure and microstructural analysis of all the materials. At room temperature, the fracture altered from ductile in the unreinforced Al to brittle in the composites. At an elevated temperature, the fracture mechanism transformed from brittle to ductile rupture in the composites.

  12. The effect of hydrogen on the fracture toughness of alloy X-750 at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Symons, Douglas M.

    Ni-Cr-Fe alloys are widely used in pressurized water nuclear reactors (PWR). These alloys are susceptible to stress corrosion cracking (SCC) in PWR environments. There have been numerous mechanisms of crack advance proposed to describe the SCC of the nickel-base alloys in a PWR environment including slip/film rupture/oxidation and hydrogen embrittlement. It has also been suggested that there is not sufficient evidence to implicate hydrogen in the PWR SCC of nickel-base alloys. This program evaluated the effect of hydrogen on the embrittlement of a nickel-base alloy, alloy X-750, at elevated temperatures with a hydrogen concentration typical of what may be developed from the corrosion reaction. Fracture toughness values and the tearing resistance of alloy X-750 were evaluated in hydrogen gas and in air 260°C and 338°C. It was shown that at 260°C and 338°C alloy X-750 was severely embrittled in high pressure hydrogen gas. Further, the fracture morphology changed from predominantly transgranular ductile dimple fracture in air to predominantly intergranular fracture in hydrogen. The fracture morphology in hydrogen was similar to that found for PWR SCC of this material. This work supports a hydrogen-enhanced fracture mechanism contributing to the SCC of nickel-base alloys at elevated temperatures.

  13. Factor Study for the Separator Plate of Mcfc Having Uniform Stiffness at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Wook; Kim, Jung-Hyun; Jun, Joong-Hwan

    A molten carbonate fuel cell (MCFC) is composed of several stacks of unit cells. A unit cell is composed of two electrodes and a matrix that is inserted between separator plates. Separator plates should properly contact the electrodes to reduce the electricity loss arising from contact resistance. To this end, a pressure of about 2 kgf/cm2 is usually applied on the top of the stack, which results in the separator plates being somewhat compacted. Furthermore, the stiffness of the separator plates becomes degraded at elevated temperatures due to softening of the plate materials. Therefore, a nonuniform temperature distribution across the separator plates induced by exothermic reactions of the oxidant and reactant gases leads to a non-uniform plate stiffness. This study has firstly evaluated the change in separator plate stiffness as temperature changes by applying pressure to the plates. Secondly, using the Taguchi method, several design factors that affect stiffness have been investigated to determine which has the most influence. Based on these results, a new design for the separators, which allows for uniform stiffness at elevated temperatures, has been proposed.

  14. Duration of Exposure to Elevated Temperature Affects Competitive Interactions in Juvenile Reef Fishes

    PubMed Central

    Warren, Donald T.; Donelson, Jennifer M.; McCormick, Mark I.; Ferrari, Maud C. O.; Munday, Philip L.

    2016-01-01

    Climate change will affect key ecological processes that structure natural communities, but the outcome of interactions between individuals and species will depend on their thermal plasticity. We tested how short- and long-term exposure to projected future temperatures affects intraspecific and interspecific competitive interactions in two species of coral reef damselfishes. In conspecific contests, juvenile Ambon damselfish, Pomacentrus amboinensis, exhibited no change in aggressive interactions after 4d exposure to higher temperatures. However, after 90d of exposure, fish showed a nonadaptive reduction in aggression at elevated temperatures. Conversely, 4d exposure to higher temperature increased aggression towards conspecifics in the lemon damselfish, Pomacentrus moluccensis. 90d exposure began to reduce this pattern, but overall there was little effect of temperature. Aggression in interspecific contests increased with short-term exposure, but was significantly lower after long-term exposure indicative of acclimation. Our results show how the length of exposure to elevated temperature can affect the outcome of competitive interactions. Furthermore, we illustrate that results from intraspecific contests may not accurately predict interspecific interactions, which will challenge our ability to generalise the effects of warming on competitive interactions. PMID:27736924

  15. Intelligent materials and structures revisited

    NASA Astrophysics Data System (ADS)

    Shahinpoor, Mohsen

    1996-02-01

    Presented are new definitions and interpretations for smartness and intelligence associated with materials, structures, and material systems (MS & MS). These newly proposed definitions complement and augment the present notion of smart and/or intelligent materials, structures and material systems, as accepted by our scientific community. These new definitions numerically quantify the concepts of smartness and intelligence for materials, structures and material systems. In this context amino acid sequences and structures such as proteins are proposed to be the smartest material family and are given an MSQ of 1000. Correspondingly, ribonucleic acid sequences such as RNA and DNA macromolecular assemblies and structures are proposed to be the most intelligent material family and are given an MIQ of 1000. In the same category the proteins are given an MIQ of about 700. Ionic polymeric gels, shape memory alloys, electromagnetic (electrostrictive, piezoelectric, ferroelectric, ferromagnetic) materials, electrorheological fluids and magnetorheological fluids are then categorized under this hierarchy of smart/intelligent materials with MSQs and MIQs of smaller values. A similar classification is also applied to smart/intelligent structures with reference to simple cells such as bacteria and viruses such as T4 Bacteriophages. A number of examples are presented and the corresponding MSQs and MIQs are estimated to show that materials, structure and material systems can truly be numerically categorized in connection with their smartness and intelligence and thus be compared with biological and botanical structures and material systems.

  16. Smart materials and structures

    NASA Technical Reports Server (NTRS)

    Rogowski, Robert S.; Heyman, Joseph S.

    1993-01-01

    Embedded optical fibers allow not only the cure-monitoring and in-service lifetime measurements of composite materials, but the NDE of material damage and degradation with aging. The capabilities of such damage-detection systems have been extended to allow the quantitative determination of 2D strain in materials by several different methods, including the interferometric and the numerical. It remains to be seen, what effect the embedded fibers have on the strength of the 'smart' materials created through their incorporation.

  17. Trihalomethane hydrolysis in drinking water at elevated temperatures.

    PubMed

    Zhang, Xiao-Lu; Yang, Hong-Wei; Wang, Xiao-Mao; Karanfil, Tanju; Xie, Yuefeng F

    2015-07-01

    Hydrolysis could contribute to the loss of trihalomethanes (THMs) in the drinking water at elevated temperatures. This study was aimed at investigating THM hydrolysis pertaining to the storage of hot boiled water in enclosed containers. The water pH value was in the range of 6.1-8.2 and the water temperature was varied from 65 to 95 °C. The effects of halide ions, natural organic matter, and drinking water matrix were investigated. Results showed that the hydrolysis rates declined in the order following CHBrCl2 > CHBr2Cl > CHBr3 > CHCl3. THM hydrolysis was primarily through the alkaline pathway, except for CHCl3 in water at relatively low pH value. The activation energies for the alkaline hydrolysis of CHCl3, CHBrCl2, CHBr2Cl and CHBr3 were 109, 113, 115 and 116 kJ/mol, respectively. No hydrolysis intermediates could accumulate in the water. The natural organic matter, and probably other constituents, in drinking water could substantially decrease THM hydrolysis rates by more than 50%. When a drinking water was at 90 °C or above, the first order rate constants for THM hydrolysis were in the magnitude of 10(-2)‒10(-1) 1/h. When the boiled real tap water was stored in an enclosed container, THMs continued increasing during the first few hours and then kept decreasing later on due to the competition between hydrolysis and further formation. The removal of THMs, especially brominated THMs, by hydrolysis would greatly reduce one's exposure to disinfection by-products by consuming the boiled water stored in enclosed containers.

  18. Factors Controlling Elevated Temperature Strength Degradation of Silicon Carbide Composites

    NASA Technical Reports Server (NTRS)

    2005-01-01

    For 5 years, the cooperative agreement NCC3-763 has focused on the development and understanding of Sic-based composites. Most of the work was performed in the area of SiC fiber-reinforced composites for UEET and NGLT and in collaboration with Goodrich Corporation under a partially reimbursable Space Act Agreement. A smaller amount of work was performed on C fiber-reinforced SiC matrix composites for NGLT. Major accomplishments during this agreement included: Improvements to the interphase used in melt-infiltrated (MI) SiC/SiC composites which increases the life under stressed-oxidation at intermediate temperatures referred to as "outside-debonding". This concept is currently in the patent process and received a Space Act Award. Mechanistic-based models of intermediate temperature degradation for MI SiC/SiC Quantification and relatively robust relationships for matrix crack evolution under stress in SiC/SiC composites which serve as the basis for stress-strain and elevated temperature life models The furthering of acoustic emission as a useful tool in composite damage evolution and the extension of the technique to other composite systems Development of hybrid C-SiC fiber-reinforced SiC matrix composites Numerous presentations at conferences, industry partners, and government centers and publications in recognized proceedings and journals. Other recognition of the author's accomplishments by NASA with a TGIR award (2004), NASA's Medal for Public Service (2004), and The American Ceramic Society s Richard M. Fulrath Award (2005). The following will briefly describe the work of the past five years in the three areas of interest: SiC/SiC composite development, mechanistic understanding and modeling of SiC/SiC composites, and environmental durability of C/SiC composites. More detail can be found in the publications cited at the end of this report.

  19. Behavior of reinforcement SCC beams under elevated temperatures

    NASA Astrophysics Data System (ADS)

    Fathi, Hamoon; Farhang, Kianoosh

    2015-09-01

    This experimental study focuses on the behavior of heated reinforced concrete beams. Four types of concrete mixtures were used for the tested self-compacting concrete beams. A total of 72 reinforced concrete beams and 72 standard cylindrical specimens were tested. The compressive strength under uniaxial loading at 23 °C ranged from 30 to 45 MPa. The specimens were exposed to different temperatures. The test parameters of interest were the compressive strength and the temperature of the specimens. The effect of changes in the parameters was examined so as to control the behavior of the tested concrete and that of the reinforced concrete beam. The results indicated that flexibility and compressive strength of the reinforced concrete beams decreased at higher temperatures. Furthermore, heating beyond 400 °C produced greater variations in the structural behavior of the materials in both the cylindrical samples and the reinforced concrete beams.

  20. Elevated temperature stress strain behavior of beryllium powder product

    SciTech Connect

    Abeln, S.P.; Field, R.; Mataya, M.C.

    1995-09-01

    Several grades of beryllium powder product were tested under isothermal conditions in compression over a temperature range of room temperature to 1000 C and a strain rate range from 0.001 s{sup {minus}1} to 1 s{sup {minus}1}. Samples were compressed to a total strain of 1 (64% reduction in height). It is shown that all the grades are strain rate sensitive and that strain rate sensitivity increases with temperature. Yield points were exhibited by some grades up to a temperature of 500 C, and appeared to be primarily dependent on prior thermal history which determined the availability of mobile dislocations. Serrated flow in the form of stress drops was seen in all the materials tested and was most pronounced at 500 C. The appearance and magnitude of the stress drops were dependent on accumulated strain, strain rate, sample orientation, and composition. The flow stress and shape of the flow curves differed significantly from grade to grade due to variations in alloy content, the size and distribution of BeO particles, aging precipitates, and grain size. The ductile-brittle transition temperature (DBTT) was determined for each grade of material and shown to be dependent on composition and thermal treatment. Structure/property relationships are discussed using processing history, microscopy (light and transmission), and property data.

  1. Experimental and Computational Investigation of High Entropy Alloys for Elevated-Temperature Applications

    SciTech Connect

    Liaw, Peter; Zhang, Fan; Zhang, Chuan; Wang, Gongyao; Xie, Xie; Diao, Haoyan; Kuo, Chih-Hsiang; An, Zhinan; Hemphill, Michael

    2016-07-30

    tomography (APT), and transmission electron microscopy (TEM). In-situ neutron diffraction experiments were conducted to study the strengthening effect of B2 phase on tensile properties of Al0.3CoCrFeNi HEAs directly. The results shows the creep behavior of Al0.3CoCrFeNi is superior to conventional alloys, and the heat treatment introduces secondary B2 phase into the FCC matrix, which increase the yielding strength, decrease the ductility, diminish the serrated flow during compression tests at high temperatures. In summary, the outcomes of the development of the HEAs with creep resistance include: (1) Suitable candidates, for the application to boilers and steam and gas turbines at temperatures above 760 °C and a stress of 35 MPa. (2) Fundamental understanding on the precipitate stability and deformation mechanisms of both single-phase and precipitate-strengthened alloys at room and elevated temperatures, and (3) The demonstration of an integrated approach, coupling modeling [thermodynamic calculations and crystal-plasticity finite-element modeling (CPFEM)] and focused experiments, to identify HEAs that outperform conventional alloys for high-temperature applications, which will be applicable for the discovery and development of other high-temperature materials in the power-generating industry.

  2. Generation of Constant Life Diagram under Elevated Temperature Ratcheting of 316LN Stainless Steel

    NASA Astrophysics Data System (ADS)

    Sarkar, Aritra; Nagesha, A.; Sandhya, R.; Mathew, M. D.

    2016-04-01

    Combined influence of mean stress and stress amplitude on the cyclic life under elevated temperature (823-923 K) ratcheting of 316LN austenitic stainless steel is discussed. Constant life Haigh diagrams have been generated, using different combinations of stress amplitude and mean stress. In the plastic domain, the allowable stress was found to increase or decrease with mean stress depending on the temperature and combination of mean stress - stress amplitude employed. Strong influence of dynamic strain aging (DSA) was found at 823 K which affected the mode of deformation of the material in comparison with 923 K. Failure mode expressed through a fracture mechanism map was found to change from fatigue to necking depending on the test temperature as well as combinations of mean stress and stress amplitude. Occurrence of DSA at 823 K proved to be beneficial by way of extending the safe zone of operation to higher R-ratios in comparison with 923 K.

  3. An assessment of buffer strips for improving damage tolerance of composite laminates at elevated temperature

    NASA Technical Reports Server (NTRS)

    Bigelow, C. A.

    1981-01-01

    Buffer strips greatly improve the damage tolerance of graphite/epoxy laminates loaded in tension. Graphite/polyimide buffer strip panels were made and tested to determine their residual strength at ambient and elevated (177 C) temperature. Each panel was cut in the center to represent damage. Panels were radiographed and crack-opening displacements were recorded to indicate fracture, fracture arrest, and the extent of damage in the buffer strip after arrest. All panels had the same buffer strip spacing and width. The buffer strip material was 0 deg S-glass/PMR-15. The buffer strips were made by replacing narrow strips of the 0 deg graphite plies with strips of the 0 deg S-glass on either a one-for-one or a two-for-one basis. Half of the panels were heated to 177 + or - 3 C before and during the testing. Elevated temperature did not alter the fracture behavior of the buffer configuration.

  4. Microstructure and tensile properties of tungsten at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Shen, Tielong; Dai, Yong; Lee, Yongjoong

    2016-01-01

    In order to support the development of the 5 MW spallation target for the European Spallation Source, the effect of fabrication process on microstructure, ductile-to-brittle transition temperature (DBTT), tensile and fracture behaviour of powder-metallurgy pure tungsten materials has been investigated. A hot-rolled (HR) tungsten piece of 12 mm thickness and a hot-forged (HF) piece of about 80 mm thickness were used to simulate the thin and thick blocks in the target. The two tungsten pieces were characterized with metallography analysis, hardness measurement and tensile testing. The HR piece exhibits an anisotropic grain structure with an average size of about 330 × 140 × 40 μm in rolling, long transverse and short transverse (thickness) directions. The HF piece possesses a bimodal grain structure with about 310 × 170 × 70 μm grain size in deformed part and about 25 μm sized grains remained from sintering process. Hardness (HV0.2) of the HR piece is slightly greater than that of the HF one. The ductility of the HR tungsten specimens is greater than that of the HF tungsten. For the HF tungsten piece, specimens with small grains in gauge section manifest lower ductility but higher strength. The DBTT evaluated from the tensile results is 250-300 °C for the HR tungsten and about 350 °C for the HF tungsten.

  5. Selection of flowing liquid lead target structural materials for accelerator driven transmutation applications

    NASA Astrophysics Data System (ADS)

    Park, John J.; Buksa, John J.

    1995-09-01

    The beam entry window and container for a liquid lead spallation target will be exposed to high fluxes of protons and neutrons that are both higher in magnitude and energy than have been experienced in proton accelerators and fission reactors, as well as in a corrosive environment. The structural material of the target should have a good compatibility with liquid lead, a sufficient mechanical strength at elevated temperatures, a good performance under an intense irradiation environment, and a low neutron absorption cross section; these factors have been used to rank the applicability of a wide range of materials for structural containment. Nb-1Zr has been selected for use as the structural container for the LANL ABC/ATW molten lead target. Corrosion and mass transfer behavior for various candidate structural materials in liquid lead are reviewed, together with the beneficial effects of inhibitors and various coatings to protect substrate against liquid lead corrosion. Mechanical properties of some candidate materials at elevated temperatures and the property changes resulting from 800 MeV proton irradiation are also reviewed.

  6. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1979-01-01

    Technology utilization of fiber reinforced composite materials is discussed in the areas of physical properties, and life prediction. Programs related to the Composite Aircraft Program are described in detail.

  7. Investigation of the Compressive Strength and Creep Lifetime of 2024-T3 Aluminum-Alloy Plates at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Mathauser, Eldon E; Deveikis, William D

    1957-01-01

    The results of elevated-temperature compressive strength and creep tests of 2024-t3 (formerly 24s-t3) aluminum alloy plates supported in v-grooves are presented. The strength-test results indicate that a relation previously developed for predicting plate compressive strength for plates of all materials at room temperature is also satisfactory for determining elevated-temperature strength. Creep-lifetime results are presented for plates in the form of master creep-lifetime curves by using a time-temperature parameter that is convenient for summarizing tensile creep-rupture data. A comparison is made between tensile and compressive creep lifetime for the plates and a method that made use of isochronous stress-strain curves for predicting plate-creep failure stresses is investigated.

  8. Evolution of Intermetallics, Dispersoids, and Elevated Temperature Properties at Various Fe Contents in Al-Mn-Mg 3004 Alloys

    NASA Astrophysics Data System (ADS)

    Liu, K.; Chen, X.-G.

    2016-12-01

    Nowadays, great interests are rising on aluminum alloys for the applications at elevated temperature, driven by the automotive and aerospace industries requiring high strength, light weight, and low-cost engineering materials. As one of the most promising candidates, Al-Mn-Mg 3004 alloys have been found to possess considerably high mechanical properties and creep resistance at elevated temperature resulted from the precipitation of a large number of thermally stable dispersoids during heat treatment. In present work, the effect of Fe contents on the evolution of microstructure as well as high-temperature properties of 3004 alloys has been investigated. Results show that the dominant intermetallic changes from α-Al(MnFe)Si at 0.1 wt pct Fe to Al6(MnFe) at both 0.3 and 0.6 wt pct Fe. In the Fe range of 0.1-0.6 wt pct studied, a significant improvement on mechanical properties at elevated temperature has been observed due to the precipitation of dispersoids, and the best combination of yield strength and creep resistance at 573 K (300 °C) is obtained in the 0.3 wt pct Fe alloy with the finest size and highest volume fraction of dispersoids. The superior properties obtained at 573 K (300 °C) make 3004 alloys more promising for high-temperature applications. The relationship between the Fe content and the dispersoid precipitation as well as the materials properties has been discussed.

  9. Elevated temperature tribology of cobalt and tantalum-based alloys

    SciTech Connect

    Scharf, T. W.; Prasad, S. V.; Kotula, P. G.; Michael, J. R.; Robino, C. V.

    2014-12-31

    This paper describes the friction and wear behavior of a Co–Cr alloy sliding on a Ta–W alloy. Measurements were performed in a pin-on-flat configuration with a hemispherically tipped Co-base alloy pin sliding on a Ta–W alloy flat from ambient to 430°C. Focused ion beam-scanning electron microscopy (FIB-SEM) and cross-sectional transmission electron microscopy (TEM) were used to identify the friction-induced changes to the chemistry and crystal structure in the subsurface regions of wear tracks. During sliding contact, transfer of material varied as a function of the test temperature, either from pin-to-flat, flat-to-pin, or both, resulting in either wear loss and/or volume gain. Friction coefficients (μ) and wear rates also varied as a function of test temperature. The lowest friction coefficient (μ=0.25) and wear rate (1×10–4 mm3/N•m) were observed at 430°C in argon atmosphere. This was attributed to the formation of a Co-base metal oxide layer (glaze), predominantly (Co, Cr)O with Rocksalt crystal structure, on the pin surface. Part of this oxide film transferred to the wear track on Ta–W, providing a self-mated oxide-on-oxide contact. Once the oxide glaze is formed, it is able to provide friction reduction for the entire temperature range of this study, ambient to 430°C. Furthermore, the results of this study indicate that glazing the surfaces of Haynes alloys with continuous layers of cobalt chrome oxide prior to wear could protect the cladded surfaces from damage.

  10. Elevated temperature tribology of cobalt and tantalum-based alloys

    DOE PAGES

    Scharf, T. W.; Prasad, S. V.; Kotula, P. G.; ...

    2014-12-31

    This paper describes the friction and wear behavior of a Co–Cr alloy sliding on a Ta–W alloy. Measurements were performed in a pin-on-flat configuration with a hemispherically tipped Co-base alloy pin sliding on a Ta–W alloy flat from ambient to 430°C. Focused ion beam-scanning electron microscopy (FIB-SEM) and cross-sectional transmission electron microscopy (TEM) were used to identify the friction-induced changes to the chemistry and crystal structure in the subsurface regions of wear tracks. During sliding contact, transfer of material varied as a function of the test temperature, either from pin-to-flat, flat-to-pin, or both, resulting in either wear loss and/or volumemore » gain. Friction coefficients (μ) and wear rates also varied as a function of test temperature. The lowest friction coefficient (μ=0.25) and wear rate (1×10–4 mm3/N•m) were observed at 430°C in argon atmosphere. This was attributed to the formation of a Co-base metal oxide layer (glaze), predominantly (Co, Cr)O with Rocksalt crystal structure, on the pin surface. Part of this oxide film transferred to the wear track on Ta–W, providing a self-mated oxide-on-oxide contact. Once the oxide glaze is formed, it is able to provide friction reduction for the entire temperature range of this study, ambient to 430°C. Furthermore, the results of this study indicate that glazing the surfaces of Haynes alloys with continuous layers of cobalt chrome oxide prior to wear could protect the cladded surfaces from damage.« less

  11. Elevated Temperature Primary Load Design Method Using Pseudo Elastic-Perfectly Plastic Model

    SciTech Connect

    Carter, Peter; Sham, Sam; Jetter, Robert I

    2012-01-01

    A new primary load design method for elevated temperature service has been developed. Codification of the procedure in an ASME Boiler and Pressure Vessel Code, Section III Code Case is being pursued. The proposed primary load design method is intended to provide the same margins on creep rupture, yielding and creep deformation for a component or structure that are implicit in the allowable stress data. It provides a methodology that does not require stress classification and is also applicable to a full range of temperature above and below the creep regime. Use of elastic-perfectly plastic analysis based on allowable stress with corrections for constraint, steady state stress and creep ductility is described. This approach is intended to ensure that traditional primary stresses are the basis for design, taking into account ductility limits to stress re-distribution and multiaxial rupture criteria.

  12. Elevated temperature slow plastic deformation of NiAl-TiB2 particulate composites at 1200 and 1300 K

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Viswanadham, R. K.; Mannan, S. K.; Sprissler, B.

    1990-01-01

    Elevated temperature compression testing has been conducted in air at 1200 and 1300 K with strain rates varying from about 10 to the -4th to about 10 to the -7th/sec on NiAl-TiB2 particulate composites. These materials, which consisted of a B2 crystal structure intermetallic Ni-50 at. pct Al matrix and from 0 to 30 vol pct of approximately 1- micron diameter TiB2 particles, were fabricated by XD synthesis and hot pressed to full density. Flow strength of the composites increased with volume fraction of the strengthening phase with NiAl-30TiB2 being approximately three times stronger than NiAl. Comparison of the light optical and TEM microstructures of as-received and tested samples revealed that reactions did not occur between the two phases, and NiAl-TiB2 interfaces were not cracked during deformation. Additional TEM indicated that the particles stabilize a vastly different microstructure in the NiAl matrix of the composites than that formed in unreinforced NiAl.

  13. Influence of Elevated Temperatures on Pet-Concrete Properties

    NASA Astrophysics Data System (ADS)

    Albano, C.; Camacho, N.; Hernández, M.; Matheus, A.; Gutiérrez, A.

    2008-08-01

    Lightweight aggregate is an important material in reducing the unit weight of concrete complying with special concrete structures of large high-rise buildings. Besides, the use of recycled PET bottles as lightweight aggregate in concrete is an effective contribution for environment preservation. So, the objective of the present work was to study experimentally the flexural strength of the PET -concrete blends and the thermal degradation of the PET in the concrete, when the blends with 10 and 20% in volume of PET were exposed to different temperatures (200, 400, 600 °C). The flexural strength of concrete-PET exposed to a heat source is strongly dependent on the temperature, water/cement ratio, as well as the content and particle size of PET. However, the activation energy is affected by the temperature, location of the PET particles on the slabs and the water/cement ratio. Higher water content originates thermal and hydrolytic degradation on the PET, while on the concrete, a higher vapor pressure which causes an increase in crack formation. The values of the activation energy are higher on the center of the slabs than on the surface, since concrete is a poor heat conductor.

  14. Microscopic evaluation of vesicles shed by erythrocytes at elevated temperatures.

    PubMed

    Moore, Timothy; Sorokulova, Iryna; Pustovyy, Oleg; Globa, Ludmila; Pascoe, David; Rudisill, Mary; Vodyanoy, Vitaly

    2013-11-01

    The images of human erythrocytes and vesicles were analyzed by a light microscopy system with spatial resolution of better than 90 nm. The samples were observed in an aqueous environment and required no freezing, dehydration, staining, shadowing, marking, or any other manipulation. Temperature elevation resulted in significant concentration increase of structurally transformed erythrocytes (echinocytes) and vesicles in the blood. The process of vesicle separation from spiculated erythrocytes was video recorded in real time. At a temperature of 37°C, mean vesicle concentrations and diameters were found to be 1.50 ± 0.35 × 10(6) vesicles per microliter and 0.365 ± 0.065 μm, respectively. The vesicle concentration increased approximately threefold as the temperature increased from 37 to 40°C. It was estimated that 80% of all vesicles found in the blood are smaller than 0.4 μm. Accurate account of vesicle numbers and dimensions suggest that 86% of the lost erythrocyte material is lost not by vesiculation but by another, as yet, unknown mechanism.

  15. Phonons in Si24 at simultaneously elevated temperature and pressure

    NASA Astrophysics Data System (ADS)

    Tong, Xiao; Xu, Xiaolin; Fultz, B.; Zhang, Haidong; Strobel, Timothy A.; Kim, Duck Young

    2017-03-01

    Raman spectroscopy was used to measure the frequencies of phonons in Si24 with an open clathrate structure at temperatures from 80 to 400 K with simultaneous pressures of 0 to 8 GPa. The frequency shifts of the different phonons were substantially different under either temperature or pressure. The quasiharmonic behavior was isolated by varying pressure at low temperatures, and the anharmonic behavior was isolated by varying temperature at low pressures. Phonon modes dominated by bond bending were anomalous, showing stiffening with temperature and softening with pressure. Both the quasiharmonic behavior and the anharmonic behavior changed markedly with simultaneous changes in temperature Δ T and pressure Δ P . With Δ T =320 K and Δ P =8 GPa , some frequency shifts that scaled with the product Δ T Δ P were as large as the shifts from Δ T and Δ P alone. The thermodynamic entropy of this material likely has a dependence on Δ T and Δ P that cannot be obtained by adding effects from quasiharmonicity and phonon-phonon anharmonicity.

  16. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1983-01-01

    Transverse properties of fiber constituents in composites, fatigue in composite materials, matrix dominated properties of high performance composites, numerical investigation of moisture effects, numerical investigation of the micromechanics of composite fracture, advanced analysis methods, compact lug design, and the RP-1 and RP-2 sailplanes projects are discussed.

  17. Elastic Properties and Internal Friction of Two Magnesium Alloys at Elevated Temperatures

    SciTech Connect

    Freels, M.; Liaw, P. K.; Garlea, E.; Morrell, J. S.; Radiovic, M.

    2011-06-01

    The elastic properties and internal friction of two magnesium alloys were studied from 25 C to 450 C using Resonant Ultrasound Spectroscopy (RUS). The Young's moduli decrease with increasing temperature. At 200 C, a change in the temperature dependence of the elastic constants is observed. The internal friction increases significantly with increasing temperature above 200 C. The observed changes in the temperature dependence of the elastic constants and the internal friction are the result of anelastic relaxation by grain boundary sliding at elevated temperatures. Elastic properties govern the behavior of a materials subjected to stress over a region of strain where the material behaves elastically. The elastic properties, including the Young's modulus (E), shear modulus (G), bulk modulus (B), and Poisson's ratio (?), are of significant interest to many design and engineering applications. The choice of the most appropriate material for a particular application at elevated temperatures therefore requires knowledge of its elastic properties as a function of temperature. In addition, mechanical vibration can cause significant damage in the automotive, aerospace, and architectural industries and thus, the ability of a material to dissipate elastic strain energy in materials, known as damping or internal friction, is also important property. Internal friction can be the result of a wide range of physical mechanisms, and depends on the material, temperature, and frequency of the loading. When utilized effectively in engineering applications, the damping capacity of a material can remove undesirable noise and vibration as heat to the surroundings. The elastic properties of materials can be determined by static or dynamic methods. Resonant Ultrasound Spectroscopy (RUS), used in this study, is a unique and sophisticated non-destructive dynamic technique for determining the complete elastic tensor of a solid by measuring the resonant spectrum of mechanical resonance for a

  18. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1981-01-01

    The composite aircraft program component (CAPCOMP) is a graduate level project conducted in parallel with a composite structures program. The composite aircraft program glider (CAPGLIDE) is an undergraduate demonstration project which has as its objectives the design, fabrication, and testing of a foot launched ultralight glider using composite structures. The objective of the computer aided design (COMPAD) portion of the composites project is to provide computer tools for the analysis and design of composite structures. The major thrust of COMPAD is in the finite element area with effort directed at implementing finite element analysis capabilities and developing interactive graphics preprocessing and postprocessing capabilities. The criteria for selecting research projects to be conducted under the innovative and supporting research (INSURE) program are described.

  19. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1983-01-01

    Progress and plans are reported for investigations of: (1) the mechanical properties of high performance carbon fibers; (2) fatigue in composite materials; (3) moisture and temperature effects on the mechanical properties of graphite-epoxy laminates; (4) the theory of inhomogeneous swelling in epoxy resin; (5) numerical studies of the micromechanics of composite fracture; (6) free edge failures of composite laminates; (7) analysis of unbalanced laminates; (8) compact lug design; (9) quantification of Saint-Venant's principles for a general prismatic member; (10) variation of resin properties through the thickness of cured samples; and (11) the wing fuselage ensemble of the RP-1 and RP-2 sailplanes.

  20. Materials, structures, and devices for high-speed electronics

    NASA Technical Reports Server (NTRS)

    Woollam, John A.; Snyder, Paul G.

    1992-01-01

    Advances in materials, devices, and instrumentation made under this grant began with ex-situ null ellipsometric measurements of simple dielectric films on bulk substrates. Today highly automated and rapid spectroscopic ellipsometers are used for ex-situ characterization of very complex multilayer epitaxial structures. Even more impressive is the in-situ capability, not only for characterization but also for the actual control of the growth and etching of epitaxial layers. Spectroscopic ellipsometry has expanded from the research lab to become an integral part of the production of materials and structures for state of the art high speed devices. Along the way, it has contributed much to our understanding of the growth characteristics and material properties. The following areas of research are summarized: Si3N4 on GaAs, null ellipsometry; diamondlike carbon films; variable angle spectroscopic ellipsometry (VASE) development; GaAs-AlGaAs heterostructures; Ta-Cu diffusion barrier films on GaAs; GaAs-AlGaAs superlattices and multiple quantum wells; superconductivity; in situ elevated temperature measurements of III-V's; optical constants of thermodynamically stable InGaAs; doping dependence of optical constants of GaAs; in situ ellipsometric studies of III-V epitaxial growth; photothermal spectroscopy; microellipsometry; and Si passivation and Si/SiGe strained-layer superlattices.

  1. Small Bioactive Lipoplex (SBL) Nanoparticles Self-Assembled at Elevated Temperature and Pressure

    NASA Astrophysics Data System (ADS)

    Huang, Leaf

    2009-03-01

    Conventional lipoplex (cationic liposome/DNA complex) serves well for gene transfer in cultured cells. However, their in vivo gene delivery activity is limited due to its relatively large size (>100 nm). This is due to incomplete charge neutralization as a result of the steric hindrance during the complexation between DNA and liposomes. Behr et al hypothesized that monomolecular DNA condensate can be prepared if the DNA sees the cationic lipid as monomers. Indeed, small nanoparticles (˜30 nm) were prepared by using a single-chain cationic amphiphile which has a high solubility at the physiological condition. To stabilize the monomolecular condensate, Behr has included a SH group in the cationic amphiphile which could be oxidized to form a dimer. Unfortunately, the stabilized nanoparticles showed no transfection activity when delivered into cells. We hypothesized that similar small lipoplex can be prepared by using a double-chain cationic amphiphile if both DNA and the amphiphile can be soluble in the same solvent. A hydrofluorocarbon HFC-152a is an excellent solvent for the cationic lipid DOTAP at an elevated temperature (˜35 ^oC) and pressure (˜300 atm). Since the solvent can accommodate small amounts of water, DNA or siRNA could be introduced into the system to allow lipoplex formation. The resulting Small Bioactive Lipoplex (SBL) is 30-50 nm in diameter and can transfect cultured cells. Freeze-fracture electron microscopy showed that SBL are solid nanoparticles without any lipid bilayer structure. Since plasmid DNA is fragile at elevated temperature and pressure, we have concentrated our effort in siRNA which is stable under the same conditions. The new formulation shows great promise as an in vivo delivery vector when small particles are required for efficient penetration into the tissues.

  2. Dynamic Fracture Initiation Toughness at Elevated Temperatures With Application to the New Generation of Titanium Aluminide Alloys. Chapter 8

    NASA Technical Reports Server (NTRS)

    Shazly, Mostafa; Prakash, Vikas; Draper, Susan; Shukla, Arun (Editor)

    2006-01-01

    Recently, a new generation of titanium aluminide alloy, named Gamma-Met PX, has been developed with better rolling and post-rolling characteristics. I'revious work on this alloy has shown the material to have higher strengths at room and elevated temperatures when compared with other gamma titanium aluminides. In particular, this new alloy has shown increased ductility at elevated temperatures under both quasi-static and high strain rate uniaxial compressive loading. However, its high strain rate tensile ductility at room and elevated temperatures is limited to approx. 1%. In the present chapter, results of a study to investigate the effects of loading rate and test temperature on the dynamic fracture initiation toughness in Gamma-Met PX are presented. Modified split Hopkinson pressure bar was used along with high-speed photography to determine the crack initiation time. Three-point bend dynamic fracture experiments were conducted at impact speeds of approx. 1 m/s and tests temperatures of up-to 1200 C. The results show that thc dynamic fracture initiation toughness decreases with increasing test temperatures beyond 600 C. Furthermore, thc effect of long time high temperature air exposure on the fracture toughness was investigated. The dynamic fracture initiation toughness was found to decrease with increasing exposure time. The reasons behind this drop are analyzed and discussed.

  3. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, Robert G.; Wiberley, Stephen E.

    1988-01-01

    A decade long program to develop critical advanced composite technology in the areas of physical properties, structural concept and analysis, manufacturing, reliability, and life predictions is reviewed. Specific goals are discussed. The status of the chemical vapor deposition effects on carbon fiber properties; inelastic deformation of metal matrix laminates; fatigue damage in fibrous MMC laminates; delamination fracture toughness in thermoplastic matrix composites; and numerical analysis of composite micromechanical behavior are presented.

  4. LTA structures and materials technology

    NASA Technical Reports Server (NTRS)

    Mayer, N. J.

    1975-01-01

    The state-of-the-art concerning structures and materials technology is reviewed. It is shown that many present materials developments resulting from balloon and aircraft research programs can be applied to new concepts in LTA vehicles. Both buoyant and semi-buoyant vehicles utilize similar approaches to solving structural problems and could involve pressurized non-rigid and unpressurized rigid structures. System designs common to both and vital to structural integrity include much of the past technology as well. Further research is needed in determination of structural loads, especially in future design concepts.

  5. Hypersonic Materials and Structures

    NASA Technical Reports Server (NTRS)

    Glass, David E.

    2016-01-01

    Thermal protection systems (TPS) and hot structures are required for a range of hypersonic vehicles ranging from ballistic reentry to hypersonic cruise vehicles, both within Earth's atmosphere and non-Earth atmospheres. The focus of this presentation is on air breathing hypersonic vehicles in the Earth's atmosphere. This includes single-stage to orbit (SSTO), two-stage to orbit (TSTO) accelerators, access to space vehicles, and hypersonic cruise vehicles. This paper will start out with a brief discussion of aerodynamic heating and thermal management techniques to address the high heating, followed by an overview of TPS for rocket-launched and air-breathing vehicles. The argument is presented that as we move from rocket-based vehicles to air-breathing vehicles, we need to move away from the insulated airplane approach used on the Space Shuttle Orbiter to a wide range of TPS and hot structure approaches. The primary portion of the paper will discuss issues and design options for CMC TPS and hot structure components, including leading edges, acreage TPS, and control surfaces. The current state-of-the-art will be briefly discussed for some of the components.

  6. Effects of elevated temperature on the viscoplastic modeling of graphite/polymeric composites

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.

    1991-01-01

    To support the development of new materials for the design of next generation supersonic transports, a research program is underway at NASA to assess the long term durability of advanced polymer matrix composites (PMC's). One of main objectives of the program was to explore the effects of elevated temperature (23 to 200 C) on the constitutive model's material parameters. To achieve this goal, test data on the observed nonlinear, stress-strain behavior of IM7/5260 and IM7/8320 composites under tension and compression loading were collected and correlated against temperature. These tests, conducted under isothermal conditions using variable strain rates, included such phenomena as stress relaxation and short term creep. The second major goal was the verification of the model by comparison of analytical predictions and test results for off axis and angle ply laminates. Correlation between test and predicted behavior was performed for specimens of both material systems over a range of temperatures. Results indicated that the model provided reasonable predictions of material behavior in load or strain controlled tests. Periods of loading, unloading, stress relaxation, and creep were accounted for.

  7. Advanced composite structural concepts and materials technologies for primary aircraft structures: Advanced material concepts

    NASA Technical Reports Server (NTRS)

    Lau, Kreisler S. Y.; Landis, Abraham L.; Chow, Andrea W.; Hamlin, Richard D.

    1993-01-01

    To achieve acceptable performance and long-term durability at elevated temperatures (350 to 600 F) for high-speed transport systems, further improvements of the high-performance matrix materials will be necessary to achieve very long-term (60,000-120,000 service hours) retention of mechanical properties and damage tolerance. This report emphasizes isoimide modification as a complementary technique to semi-interpenetrating polymer networks (SIPN's) to achieve greater processibility, better curing dynamics, and possibly enhanced thermo-mechanical properties in composites. A key result is the demonstration of enhanced processibility of isoimide-modified linear and thermo-setting polyimide systems.

  8. Wood properties of Scots pines (Pinus sylvestris) grown at elevated temperature and carbon dioxide concentration.

    PubMed

    Kilpeläinen, Antti; Peltola, Heli; Ryyppö, Aija; Sauvala, Kari; Laitinen, Kaisa; Kellomäki, Seppo

    2003-09-01

    Impacts of elevated temperature and carbon dioxide concentration ([CO2]) on wood properties of 15-year-old Scots pines (Pinus sylvestris L.) grown under conditions of low nitrogen supply were investigated in open-top chambers. The treatments consisted of (i) ambient temperature and ambient [CO2] (AT+AC), (ii) ambient temperature and elevated [CO2] (AT+EC), (iii) elevated temperature and ambient [CO2] (ET+AC) and (iv) elevated temperature and elevated [CO2] (ET+EC). Wood properties analyzed for the years 1992-1994 included ring width, early- and latewood width and their proportions, intra-ring wood density (minimum, maximum and mean, as well as early- and latewood densities), mean fiber length and chemical composition of the wood (cellulose, hemicellulose, lignin and acetone extractive concentration). Absolute radial growth over the 3-year period was 54% greater in AT+EC trees and 30 and 25% greater in ET+AC and ET+EC trees, respectively, than in AT+AC trees. Neither elevated temperature nor elevated [CO2] had a statistically significant effect on ring width, early- and latewood widths or their proportions. Both latewood density and maximum intra-ring density were increased by elevated [CO2], whereas fiber length was increased by elevated temperature. Hemicellulose concentration decreased and lignin concentration increased significantly in response to elevated temperature. There were no statistically significant interaction effects of elevated temperature and elevated [CO2] on the wood properties, except on earlywood density.

  9. Sputtering graphite coating to improve the elevated-temperature cycling ability of the LiMn2O4 electrode.

    PubMed

    Wang, Jiexi; Zhang, Qiaobao; Li, Xinhai; Wang, Zhixing; Guo, Huajun; Xu, Daguo; Zhang, Kaili

    2014-08-14

    To improve the cycle performance of LiMn2O4 at elevated temperature, a graphite layer is introduced to directly cover the surface of a commercial LiMn2O4-based electrode via room-temperature DC magnetron sputtering. The as-modified cathodes display improved capacity retention as compared to the bare LiMn2O4 cathode (BLMO) at 55 °C. When sputtering graphite for 30 min, the sample shows the best cycling performance at 55 °C, maintaining 96.2% capacity retention after 200 cycles. Reasons with respect to the graphite layer for improving the elevated-temperature performance of LiMn2O4 are systematically investigated via the methods of cyclic voltammetry, electrochemical impedance spectroscopy, X-ray photoelectron spectrometry, scanning and transmission electron microscopy, X-ray diffraction and inductively coupled plasma-atomic emission spectrometry. The results demonstrate that the graphite coated LiMn2O4 cathode has much less increased electrode polarization and electrochemical impedance than BLMO during the elevated-temperature cycling process. Furthermore, the graphite layer is able to alleviate the severe dissolution of manganese ions into the electrolyte and mitigate the morphological and structural degradation of LiMn2O4 during cycling. A model for the electrochemical kinetics process is also suggested for explaining the roles of the graphite layer in suppressing the Mn dissolution.

  10. Microplastic Deformation of Submicrocrystalline Copper at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Dudarev, E. F.; Pochivalova, G. P.; Tabachenko, A. N.; Maletkina, T. Yu.; Skosyrskii, A. B.; Osipov, D. A.

    2017-02-01

    of investigations of submicrocrystalline copper subjected to cold rolling after abc pressing by methods of backscatter electron diffraction and x-ray diffraction analysis are presented. It is demonstrated that after such combined intensive plastic deformation, the submicrocrystalline structure with average grain-subgrain structure elements having sizes of 0.63 μm is formed with relative fraction of high-angle grain boundaries of 70% with texture typical for rolled copper. Results of investigation of microplastic deformation of copper with such structure at temperatures in the interval 295-473 K and with submicrocrystalline structure formed by cold rolling of coarse-grained copper are presented.

  11. Static tensile and tensile creep testing of four boron nitride coated ceramic fibers at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Coguill, Scott L.; Adams, Donald F.; Zimmerman, Richard S.

    1989-01-01

    Six types of uncoated ceramic fibers were static tensile and tensile creep tested at various elevated temperatures. Three types of boron nitride coated fibers were also tested. Room temperature static tensile tests were initially performed on all fibers, at gage lengths of 1, 2, and 4 inches, to determine the magnitude of end effects from the gripping system used. Tests at one elevated temperature, at gage lengths of 8 and 10 inches, were also conducted, to determine end effects at elevated temperatures. Fiber cross sectional shapes and areas were determined using scanning electron microscopy. Creep testing was typically performed for 4 hours, in an air atmosphere.

  12. Elevated Temperature Fatigue Endurance of Three Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Verrilli, Michael J.

    2007-01-01

    High-cycle fatigue endurance of three candidate materials for the acoustic liners of the Enabling Propulsion Materials Nozzle Program was investigated. The ceramic matrix composite materials investigated were N720/AS (Nextel 720, 3M Corporation), Sylramic S200 (Dow Corning), and UT 22. High-cycle fatigue tests were conducted in air at 910 C on as-machined specimens and on specimens subjected to tensile cyclic load excursions every 160 hr followed by thermal exposure at 910 C in a furnace up to total exposure times of 2066 and 4000 hr. All the fatigue tests were conducted in air at 100 Hz with a servohydraulic test machine. In the as-machined condition, among the three materials investigated only the Sylramic S200 exhibited a deterministic type of high-cycle fatigue behavior. Both the N720/AS and UT-22 exhibited significant scatter in the experimentally observed high-cycle fatigue lives. Among the thermally exposed specimens, N720/AS and Sylramic S200 materials exhibited a reduction in the high-cycle fatigue lives, particularly at the exposure time of 4000 hr.

  13. Fire retardancy with structural materials

    NASA Technical Reports Server (NTRS)

    Gardner, R. E.

    1971-01-01

    Impregnating wood with chemicals to reduce or prevent combustion is discussed. Basic types of materials for fireproofing purposes and methods of applications are described. It is concluded that effective fireproofing materials have been developed and their application to wooden structures represents acceptable safety management procedures.

  14. Analytical ultrasonics for structural materials

    NASA Technical Reports Server (NTRS)

    Kupperman, D. S.

    1986-01-01

    The application of ultrasonic velocity and attenuation measurements to characterize the microstructure of structural materials is discussed. Velocity measurements in cast stainless steel are correlated with microstructural variations ranging from equiaxed (elastically isotropic) to columnar (elastically anisotropic) grain structure. The effect of the anisotropic grain structure on the deviation of ultrasonic waves in cast stainless steel is also reported. Field-implementable techniques for distinguishing equiaxed from columnar grain structures in cast strainless steel structural members are presented. The application of ultrasonic velocity measurements to characterize structural ceramics in the green state is also discussed.

  15. Optimal lattice-structured materials

    NASA Astrophysics Data System (ADS)

    Messner, Mark C.

    2016-11-01

    This work describes a method for optimizing the mesostructure of lattice-structured materials. These materials are periodic arrays of slender members resembling efficient, lightweight macroscale structures like bridges and frame buildings. Current additive manufacturing technologies can assemble lattice structures with length scales ranging from nanometers to millimeters. Previous work demonstrates that lattice materials have excellent stiffness- and strength-to-weight scaling, outperforming natural materials. However, there are currently no methods for producing optimal mesostructures that consider the full space of possible 3D lattice topologies. The inverse homogenization approach for optimizing the periodic structure of lattice materials requires a parameterized, homogenized material model describing the response of an arbitrary structure. This work develops such a model, starting with a method for describing the long-wavelength, macroscale deformation of an arbitrary lattice. The work combines the homogenized model with a parameterized description of the total design space to generate a parameterized model. Finally, the work describes an optimization method capable of producing optimal mesostructures. Several examples demonstrate the optimization method. One of these examples produces an elastically isotropic, maximally stiff structure, here called the isotruss, that arguably outperforms the anisotropic octet truss topology.

  16. Optimal lattice-structured materials

    DOE PAGES

    Messner, Mark C.

    2016-07-09

    This paper describes a method for optimizing the mesostructure of lattice-structured materials. These materials are periodic arrays of slender members resembling efficient, lightweight macroscale structures like bridges and frame buildings. Current additive manufacturing technologies can assemble lattice structures with length scales ranging from nanometers to millimeters. Previous work demonstrates that lattice materials have excellent stiffness- and strength-to-weight scaling, outperforming natural materials. However, there are currently no methods for producing optimal mesostructures that consider the full space of possible 3D lattice topologies. The inverse homogenization approach for optimizing the periodic structure of lattice materials requires a parameterized, homogenized material model describingmore » the response of an arbitrary structure. This work develops such a model, starting with a method for describing the long-wavelength, macroscale deformation of an arbitrary lattice. The work combines the homogenized model with a parameterized description of the total design space to generate a parameterized model. Finally, the work describes an optimization method capable of producing optimal mesostructures. Several examples demonstrate the optimization method. One of these examples produces an elastically isotropic, maximally stiff structure, here called the isotruss, that arguably outperforms the anisotropic octet truss topology.« less

  17. Optimal lattice-structured materials

    SciTech Connect

    Messner, Mark C.

    2016-07-09

    This paper describes a method for optimizing the mesostructure of lattice-structured materials. These materials are periodic arrays of slender members resembling efficient, lightweight macroscale structures like bridges and frame buildings. Current additive manufacturing technologies can assemble lattice structures with length scales ranging from nanometers to millimeters. Previous work demonstrates that lattice materials have excellent stiffness- and strength-to-weight scaling, outperforming natural materials. However, there are currently no methods for producing optimal mesostructures that consider the full space of possible 3D lattice topologies. The inverse homogenization approach for optimizing the periodic structure of lattice materials requires a parameterized, homogenized material model describing the response of an arbitrary structure. This work develops such a model, starting with a method for describing the long-wavelength, macroscale deformation of an arbitrary lattice. The work combines the homogenized model with a parameterized description of the total design space to generate a parameterized model. Finally, the work describes an optimization method capable of producing optimal mesostructures. Several examples demonstrate the optimization method. One of these examples produces an elastically isotropic, maximally stiff structure, here called the isotruss, that arguably outperforms the anisotropic octet truss topology.

  18. Integrated research in constitutive modelling at elevated temperatures, part 2

    NASA Technical Reports Server (NTRS)

    Haisler, W. E.; Allen, D. H.

    1986-01-01

    Four current viscoplastic models are compared experimentally with Inconel 718 at 1100 F. A series of tests were performed to create a sufficient data base from which to evaluate material constants. The models used include Bodner's anisotropic model; Krieg, Swearengen, and Rhode's model; Schmidt and Miller's model; and Walker's exponential model.

  19. Hypervelocity impact damage response and characterization of thin plate targets at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Corbett, Brooke Myers

    The performance of a typical International Space Station (ISS) shield against the meteoroid and orbital debris (M/OD) impact threat is generally modeled by damage equations for the outer shield and the rear pressure wall. In their current forms, these damage equations neglect the on-orbit temperature extremes witnessed by the ISS. To address IF and HOW temperature extremes affect the performance of the ISS' typical M/OD shield, a comprehensive study was undertaken that investigated hole diameters in .063" thick 6061-T6 aluminum targets impacted at velocities from ˜2-7 km/s at 20°C, 110°C, and 210°C. Robust graphical and analytical analyses confirmed the existence of a statistically significant temperature effect, i.e., hole diameters in heated targets were larger than those in room temperature targets. A new temperature-dependent model was found via multivariable regression analysis that incorporates a linear velocity term and a temperature term based on a form of the cumulative distribution function. Numerical modeling of hypervelocity impacts (HVI) into elevated temperature targets was also performed to determine whether or not currently available material and failure models can adequately simulate the differences observed between room and elevated temperature target hole diameters. Statistical analyses showed that AUTODYN simulated the heated data almost as well as the room temperature data. However, the slightly worse Goodness of Fit (GOF) values between the heated empirical vs. simulated comparisons suggest that the simulations do not completely account for the observed temperature effect. A series of materials tests and observations were carried out on the post-impacted target plates to help explain the empirical data results with respect to material variability and deformation features. Rockwell B and K macro-hardness tests revealed that the hardness values for the targets impacted at 110°C were statistically significantly higher compared to those

  20. Compressive Strength of Epoxy Resin Chocks Subjected to Elevated Temperatures.

    DTIC Science & Technology

    1984-09-01

    9 2. Pour-In-Place Chock (PIPC) .... ............. 11 3. Atomic Model of Liquid Resin DGEBA ... ......... 18 4. Properties of CHOCKFAST...resin is known as diglycidyl ether of bisphenol A ( DGEBA ) which is the general constituent of CHOCKFAST ORANGE. Due to the confidentiality that... DGEBA occurs by reacting epichlorohydrin with bisphenol A in the presence of sodium hydroxide. The raw material epichlorohydrin is synthesized from

  1. Polymeric Binders which Reversibly Dissociate at Elevated Temperatures

    DTIC Science & Technology

    1978-05-01

    materials must be used which are capable of regenerating the free isocyana.e on heating and will not undergo undesirable side reactions . The most widely...such as imidazole, indazole and benzotriazole, exhibit a marked tendency to dissociate at temperatures as low as 80*C to 100*C. With 4,5...only undergo a Diels-Alder reaction at room temperature with a variety of dienes, but it will also react with other functional groups. Many of these

  2. A Modified Johnson-Cook Model for Sheet Metal Forming at Elevated Temperatures and Its Application for Cooled Stress-Strain Curve and Spring-Back Prediction

    SciTech Connect

    Duc-Toan, Nguyen; Tien-Long, Banh; Young-Suk, Kim; Dong-Won, Jung

    2011-08-22

    In this study, a modified Johnson-Cook (J-C) model and an innovated method to determine (J-C) material parameters are proposed to predict more correctly stress-strain curve for tensile tests in elevated temperatures. A MATLAB tool is used to determine material parameters by fitting a curve to follow Ludwick's hardening law at various elevated temperatures. Those hardening law parameters are then utilized to determine modified (J-C) model material parameters. The modified (J-C) model shows the better prediction compared to the conventional one. As the first verification, an FEM tensile test simulation based on the isotropic hardening model for boron sheet steel at elevated temperatures was carried out via a user-material subroutine, using an explicit finite element code, and compared with the measurements. The temperature decrease of all elements due to the air cooling process was then calculated when considering the modified (J-C) model and coded to VUMAT subroutine for tensile test simulation of cooling process. The modified (J-C) model showed the good agreement between the simulation results and the corresponding experiments. The second investigation was applied for V-bending spring-back prediction of magnesium alloy sheets at elevated temperatures. Here, the combination of proposed J-C model with modified hardening law considering the unusual plastic behaviour for magnesium alloy sheet was adopted for FEM simulation of V-bending spring-back prediction and shown the good comparability with corresponding experiments.

  3. A Modified Johnson-Cook Model for Sheet Metal Forming at Elevated Temperatures and Its Application for Cooled Stress-Strain Curve and Spring-Back Prediction

    NASA Astrophysics Data System (ADS)

    Duc-Toan, Nguyen; Tien-Long, Banh; Young-Suk, Kim; Dong-Won, Jung

    2011-08-01

    In this study, a modified Johnson-Cook (J-C) model and an innovated method to determine (J-C) material parameters are proposed to predict more correctly stress-strain curve for tensile tests in elevated temperatures. A MATLAB tool is used to determine material parameters by fitting a curve to follow Ludwick's hardening law at various elevated temperatures. Those hardening law parameters are then utilized to determine modified (J-C) model material parameters. The modified (J-C) model shows the better prediction compared to the conventional one. As the first verification, an FEM tensile test simulation based on the isotropic hardening model for boron sheet steel at elevated temperatures was carried out via a user-material subroutine, using an explicit finite element code, and compared with the measurements. The temperature decrease of all elements due to the air cooling process was then calculated when considering the modified (J-C) model and coded to VUMAT subroutine for tensile test simulation of cooling process. The modified (J-C) model showed the good agreement between the simulation results and the corresponding experiments. The second investigation was applied for V-bending spring-back prediction of magnesium alloy sheets at elevated temperatures. Here, the combination of proposed J-C model with modified hardening law considering the unusual plastic behaviour for magnesium alloy sheet was adopted for FEM simulation of V-bending spring-back prediction and shown the good comparability with corresponding experiments.

  4. Low-cycle fatigue of two austenitic alloys in hydrogen gas and air at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Jaske, C. E.; Rice, R. C.

    1976-01-01

    The low-cycle fatigue resistance of type 347 stainless steel and Hastelloy Alloy X was evaluated in constant-amplitude, strain-controlled fatigue tests conducted under continuous negative strain cycling at a constant strain rate of 0.001 per sec and at total axial strain ranges of 1.5, 3.0, and 5.0 percent in both hydrogen gas and laboratory air environments in the temperature range 538-871 C. Elevated-temperature, compressive-strain hold-time experiments were also conducted. In hydrogen, the cyclic stress-strain behavior of both materials at 538 C was characterized by appreciable cyclic hardening at all strain ranges. At 871 C neither material hardened significantly; in fact, at 5% strain range 347 steel showed continuous cyclic softening until failure. The fatigue resistance of 347 steel was slightly higher than that of Alloy X at all temperatures and strain ranges. Ten-minute compressive hold time experiments at 760 and 871 C resulted in increased fatigue lives for 347 steel and decreased fatigue lives for Alloy X. Both alloys showed slightly lower fatigue resistance in air than in hydrogen. Some fractographic and metallographic results are also given.

  5. Behavior of gamma TiAl subjected to impact damage and elevated temperature fatigue

    SciTech Connect

    Harding, T.S.; Jones, J.W.

    1999-12-31

    Gamma titanium aluminide has received significant attention in recent years as a candidate material for use in aerospace and industrial gas turbine engine applications. It is well known that fatigue crack growth rates in {gamma}-TiAl alloys are very sensitive to stress intensity range and that there is a small difference between threshold stress intensity range and apparent fracture toughness in these materials. The result is limited damage tolerance and dramatic reductions in fatigue lifetime in the presence of extrinsic damage, such as that produced from an impact event. To apply a damage tolerance approach to this situation would require improved crack detection techniques and would increase the life cycle cost of the engine by decreasing the inspection interval. Using a threshold-based approach, on the other hand, would ensure that pre-existing or service indices cracks would not grow and that failure by fatigue would not occur. The present study investigates the feasibility of using a threshold calculation to estimate the fatigue strength reduction caused by impact damage at elevated temperatures (600 C). The results are part of a larger investigation into the feasibility of using {gamma}-TiAl for low-pressure turbine blades.

  6. Surface mapping of field-induced piezoelectric strain at elevated temperature employing full-field interferometry.

    PubMed

    Stevenson, Tim; Quast, Tatjana; Bartl, Guido; Schmitz-Kempen, Thorsten; Weaver, Paul M

    2015-01-01

    Piezoelectric actuators and sensors are widely used for flow control valves, including diesel injectors, ultrasound generation, optical positioning, printing, pumps, and locks. Degradation and failure of material and electrical properties at high temperature typically limits these applications to operating temperatures below 200°C, based on the ubiquitous Pb(Zr,Ti)O3 ceramic. There are, however, many applications in sectors such as automotive, aerospace, energy and process control, and oil and gas, where the ability to operate at higher temperatures would open up new markets for piezoelectric actuation. Presented here is a review of recent progress and initial results toward a European effort to develop measurement techniques to characterize high-temperature materials. Full-field, multi-wavelength absolute length interferometry has, for the first time, been used to map the electric-field-induced piezoelectric strain across the surface of a PZT ceramic. The recorded variation as a function of temperature has been evaluated against a newly developed commercial single-beam system. Conventional interferometry allows measurement of the converse piezoelectric effect with high precision and resolution, but is often limited to a single point, average measurement and to limited sample environments because of optical aberrations in varying atmospheres. Here, the full-field technique allows the entire surface to be analyzed for strain and, in a bespoke sample chamber, for elevated temperatures.

  7. Effect of Particle Size on Wear of Particulate Reinforced Aluminum Alloy Composites at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Kumar, Suresh; Pandey, Ratandeep; Panwar, Ranvir Singh; Pandey, O. P.

    2013-11-01

    The present paper describes the effect of particle size on operative wear mechanism in particle reinforced aluminum alloy composites at elevated temperatures. Two composites containing zircon sand particles of 20-32 μm and 106-125 μm were fabricated by stir casting process. The dry sliding wear tests of the developed composites were performed at low and high loads with variation in temperatures from 50 to 300 °C. The transition in wear mode from mild-to-severe was observed with variation in temperature and load. The wear at 200 °C presented entirely different wear behavior from the one at 250 °C. The wear rate of fine size reinforced composite at 200 °C at higher load was substantially lower than that of coarse size reinforced composite. Examination of wear tracks and debris revealed that delamination occurs after run in wear mode followed by formation of smaller size wear debris, transfer of materials from the counter surfaces and mixing of these materials on the contact surfaces. The volume loss was observed to increase with increase in load and temperature. Composite containing bigger size particles exhibit higher loss under similar conditions.

  8. Effect of Load Rate on Ultimate Tensile Strength of Ceramic Matrix Composites at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.

    2001-01-01

    The strengths of three continuous fiber-reinforced ceramic composites, including SiC/CAS-II, SiC/MAS-5 and SiC/SiC, were determined as a function of test rate in air at 1100 to 1200 C. All three composite materials exhibited a strong dependency of strength on test rate, similar to the behavior observed in many advanced monolithic ceramics at elevated temperatures. The application of the preloading technique as well as the prediction of life from one loading configuration (constant stress-rate) to another (constant stress loading) suggested that the overall macroscopic failure mechanism of the composites would be the one governed by a power-law type of damage evolution/accumulation, analogous to slow crack growth commonly observed in advanced monolithic ceramics. It was further found that constant stress-rate testing could be used as an alternative to life prediction test methodology even for composite materials, at least for short range of lifetimes and when ultimate strength is used as the failure criterion.

  9. Time-dependent deformation at elevated temperatures in basalt from El Hierro, Stromboli and Teide volcanoes

    NASA Astrophysics Data System (ADS)

    Benson, P. M.; Fahrner, D.; Harnett, C. E.; Fazio, M.

    2014-12-01

    Time dependent deformation describes the process whereby brittle materials deform at a stress level below their short-term material strength (Ss), but over an extended time frame. Although generally well understood in engineering (where it is known as static fatigue or "creep"), knowledge of how rocks creep and fail has wide ramifications in areas as diverse as mine tunnel supports and the long term stability of critically loaded rock slopes. A particular hazard relates to the instability of volcano flanks. A large number of flank collapses are known such as Stromboli (Aeolian islands), Teide, and El Hierro (Canary Islands). Collapses on volcanic islands are especially complex as they necessarily involve the combination of active tectonics, heat, and fluids. Not only does the volcanic system generate stresses that reach close to the failure strength of the rocks involved, but when combined with active pore fluid the process of stress corrosion allows the rock mass to deform and creep at stresses far lower than Ss. Despite the obvious geological hazard that edifice failure poses, the phenomenon of creep in volcanic rocks at elevated temperatures has yet to be thoroughly investigated in a well controlled laboratory setting. We present new data using rocks taken from Stromboli, El Heirro and Teide volcanoes in order to better understand the interplay between the fundamental rock mechanics of these basalts and the effects of elevated temperature fluids (activating stress corrosion mechanisms). Experiments were conducted over short (30-60 minute) and long (8-10 hour) time scales. For this, we use the method of Heap et al., (2011) to impose a constant stress (creep) domain deformation monitored via non-contact axial displacement transducers. This is achieved via a conventional triaxial cell to impose shallow conditions of pressure (<25 MPa) and temperature (<200 °C), and equipped with a 3D laboratory seismicity array (known as acoustic emission, AE) to monitor the micro

  10. Elevated temperature triggers human respiratory syncytial virus F protein six-helix bundle formation

    SciTech Connect

    Yunus, Abdul S.; Jackson, Trent P.; Crisafi, Katherine; Burimski, Irina; Kilgore, Nicole R.; Zoumplis, Dorian; Allaway, Graham P.; Wild, Carl T.; Salzwedel, Karl

    2010-01-20

    Human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infection in infants, immunocompromised patients, and the elderly. The RSV fusion (F) protein mediates fusion of the viral envelope with the target cell membrane during virus entry and is a primary target for antiviral drug and vaccine development. The F protein contains two heptad repeat regions, HR1 and HR2. Peptides corresponding to these regions form a six-helix bundle structure that is thought to play a critical role in membrane fusion. However, characterization of six-helix bundle formation in native RSV F protein has been hindered by the fact that a trigger for F protein conformational change has yet to be identified. Here we demonstrate that RSV F protein on the surface of infected cells undergoes a conformational change following exposure to elevated temperature, resulting in the formation of the six-helix bundle structure. We first generated and characterized six-helix bundle-specific antibodies raised against recombinant peptides modeling the RSV F protein six-helix bundle structure. We then used these antibodies as probes to monitor RSV F protein six-helix bundle formation in response to a diverse array of potential triggers of conformational changes. We found that exposure of 'membrane-anchored' RSV F protein to elevated temperature (45-55 deg. C) was sufficient to trigger six-helix bundle formation. Antibody binding to the six-helix bundle conformation was detected by both flow cytometry and cell-surface immunoprecipitation of the RSV F protein. None of the other treatments, including interaction with a number of potential receptors, resulted in significant binding by six-helix bundle-specific antibodies. We conclude that native, untriggered RSV F protein exists in a metastable state that can be converted in vitro to the more stable, fusogenic six-helix bundle conformation by an increase in thermal energy. These findings help to better define the mechanism of

  11. Elevated Temperature Tensile Tests on DU–10Mo Rolled Foils

    SciTech Connect

    Schulthess, Jason

    2014-09-01

    Tensile mechanical properties for uranium-10 wt.% molybdenum (U–10Mo) foils are required to support modeling and qualification of new monolithic fuel plate designs. It is expected that depleted uranium-10 wt% Mo (DU–10Mo) mechanical behavior is representative of the low enriched U–10Mo to be used in the actual fuel plates, therefore DU-10Mo was studied to simplify material processing, handling, and testing requirements. In this report, tensile testing of DU-10Mo fuel foils prepared using four different thermomechanical processing treatments were conducted to assess the impact of foil fabrication history on resultant tensile properties.

  12. Response of ferritic steels to nonsteady loading at elevated temperatures

    SciTech Connect

    Swindeman, R.W.

    1984-04-01

    High-temperature operating experience is lacking in pressure vessel materials that have strength levels above 586 MPa. Because of their tendency toward strain softening, we have been concerned about their behavior under nonsteady loading. Testing was undertaken to explore the extent of softening produced by monotonic and cyclic strains. The specific materials included bainitic 2 1/4Cr-1Mo steel, a micro-alloyed version of 2 1/4Cr-1Mo steel, a micro-alloyed version of 2 1/4Cr-1Mo steel containing vanadium, titanium, and boron, and a martensitic 9Cr-1Mo-V-Nb steel. Tests included tensile, creep, variable stress creep, relaxation, strain cycling, stress cycling, and non-isothermal creep ratchetting experiments. We found that these steels had very low uniform elongation and exhibited small strains to the onset of tertiary creep compared to annealed 2 1/4Cr-1Mo steel. Repeated relaxation test data also indicated a limited capacity for strain hardening. Reversal strains produced softening. The degree of softening increased with increased initial strength level. We concluded that the high strength bainitic and martensitic steels should perform well when used under conditions where severe cyclic operation does not occur.

  13. Code qualification of structural materials for AFCI advanced recycling reactors.

    SciTech Connect

    Natesan, K.; Li, M.; Majumdar, S.; Nanstad, R.K.; Sham, T.-L.

    2012-05-31

    This report summarizes the further findings from the assessments of current status and future needs in code qualification and licensing of reference structural materials and new advanced alloys for advanced recycling reactors (ARRs) in support of Advanced Fuel Cycle Initiative (AFCI). The work is a combined effort between Argonne National Laboratory (ANL) and Oak Ridge National Laboratory (ORNL) with ANL as the technical lead, as part of Advanced Structural Materials Program for AFCI Reactor Campaign. The report is the second deliverable in FY08 (M505011401) under the work package 'Advanced Materials Code Qualification'. The overall objective of the Advanced Materials Code Qualification project is to evaluate key requirements for the ASME Code qualification and the Nuclear Regulatory Commission (NRC) approval of structural materials in support of the design and licensing of the ARR. Advanced materials are a critical element in the development of sodium reactor technologies. Enhanced materials performance not only improves safety margins and provides design flexibility, but also is essential for the economics of future advanced sodium reactors. Code qualification and licensing of advanced materials are prominent needs for developing and implementing advanced sodium reactor technologies. Nuclear structural component design in the U.S. must comply with the ASME Boiler and Pressure Vessel Code Section III (Rules for Construction of Nuclear Facility Components) and the NRC grants the operational license. As the ARR will operate at higher temperatures than the current light water reactors (LWRs), the design of elevated-temperature components must comply with ASME Subsection NH (Class 1 Components in Elevated Temperature Service). However, the NRC has not approved the use of Subsection NH for reactor components, and this puts additional burdens on materials qualification of the ARR. In the past licensing review for the Clinch River Breeder Reactor Project (CRBRP) and the

  14. Enhanced thermoelectric performance of carbon nanotubes at elevated temperature.

    PubMed

    Jiang, P H; Liu, H J; Fan, D D; Cheng, L; Wei, J; Zhang, J; Liang, J H; Shi, J

    2015-11-07

    The electronic and transport properties of the (10, 0) single-walled carbon nanotube are studied by performing first-principles calculations and semi-classical Boltzmann theory. It is found that the (10, 0) tube exhibits a considerably large Seebeck coefficient and electrical conductivity which are highly desirable for good thermoelectric materials. Together with the lattice thermal conductivity predicted by non-equilibrium molecular dynamics simulations, the room temperature ZT value of the (10, 0) tube is estimated to be 0.15 for p-type carriers. Moreover, the ZT value exhibits strong temperature dependence and can reach to 0.77 at 1000 K. Such a ZT value can be further enhanced to as high as 1.9 by isotopic substitution and chemisorptions of hydrogen on the tube surface.

  15. Deflagration Behavior of PBX 9501 at Elevated Temperature and Pressure

    SciTech Connect

    Maienschein, J L; Koerner, J G

    2008-04-15

    We report the deflagration behavior of PBX 9501 at pressures up to 300 MPa and temperatures of 150-180 C where the sample has been held at the test temperature for several hours before ignition. The purpose is to determine the effect on the deflagration behavior of material damage caused by prolonged exposure to high temperature. This conditioning is similar to that experienced by an explosive while it being heated to eventual explosion. The results are made more complicated by the presence of a significant thermal gradient along the sample during the temperature ramp and soak. Three major conclusions are: the presence of nitroplasticizer makes PBX 9501 more thermally sensitive than LX-04 with an inert Viton binder; the deflagration behavior of PBX 9501 is more extreme and more inconsistent than that of LX-04; and something in PBX 9501 causes thermal damage to 'heal' as the deflagration proceeds, resulting in a decelerating deflagration front as it travels along the sample.

  16. Permittivity measurement of thermoplastic composites at elevated temperature.

    PubMed

    Ku, H S; Horsfield, B; Ball, J A; Siores, E

    2001-01-01

    The material properties of greatest importance in microwave processing of a dielectric are the complex relative permittivity epsilon = epsilon'-jepsilon", and the loss tangent, tan delta = epsilon"/epsilon'. This paper describes two convenient laboratory based methods to obtain epsilon', epsilon" and hence tan delta of fibre-reinforced thermoplastic (FRTP) composites. One method employs a microwave network analyzer in conjunction with a waveguide transmission technique, chosen because it provides the widest possible frequency range with high accuracy. The values of the dielectric constant and dielectric loss of glass fibre reinforced (33%) low density polyethylene, LDPE/GF (33%), polystyrene, PS/GF (33%), and Nylon 66/GF (33%), were obtained. Results are compared with those obtained by another method using a high-temperature dielectric probe.

  17. Failure modes at room and elevated temperatures. Technical report

    SciTech Connect

    Braun, L.M.

    1995-04-01

    Successful development of reliable ceramic composites will depend on an understanding of matrix cracking and damage mechanisms in these materials. Therefore, the objective of the Failure Models subtask is to investigate failure and damage mechanisms in fiber reinforced ceramic composites. Issues such as how fiber coatings, the fiber/matrix interface, residual stresses, and fiber volume fraction affect frictional stresses, fiber debonding, fiber pull-out and failure modes will be examined. The effect of these microstructural parameters on matrix crack initiation, propagation and damage will also be determined. The resulting observations and measurements data will be used to develop theoretical models for damage mechanisms in fiber reinforced composites. This report presents results concerning the effect of temperature on the failure modes of continuous fiber ceramic composites performed during the last quarter of FY 1993 and FY 1994. The Raman stress measurements and calculations were performed during the last quarter of FY 1994 and the first quarter of FY 1995.

  18. Coupled Effect of Elevated Temperature and Cooling Conditions on the Properties of Ground Clay Brick Mortars

    NASA Astrophysics Data System (ADS)

    Ali Abd El Aziz, Magdy; Abdelaleem, Salh; Heikal, Mohamed

    2013-12-01

    When a concrete structure is exposed to fire and cooling, some deterioration in its chemical resistivity and mechanical properties takes place. This deterioration can reach a level at which the structure may have to be thoroughly renovated or completely replaced. In this investigation, four types of cement mortars, ground clay bricks (GCB)/sand namely 0/3, 1/2, 2/1 and 3/0, were used. Three different cement contents were used: 350, 400 and 450 kg/m3. All the mortars were prepared and cured in tap water for 3 months and then kept in laboratory atmospheric conditions up to 6 months. The specimens were subjected to elevated temperatures up to 700°C for 3h and then cooled by three different conditions: water, furnace, and air cooling. The results show that all the mortars subjected to fire, irrespective of cooling mode, suffered a significant reduction in compressive strength. However, the mortars cooled in air exhibited a relativity higher reduction in compressive strength rather than those water or furnace cooled. The mortars containing GCB/sand (3/0) and GCB/sand (1/2) exhibited a relatively higher thermal stability than the others.

  19. Apparatus for direct measurement of ash fusion and sintering behavior at elevated temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Khan, M. Rashid

    1989-10-01

    Ash fusion, sintering, and deposition may impose serious operational difficulties in conventional and advanced coal-combustion systems. Conventional ash fusion techniques (e.g., ASTM methods) determine the qualitative behavior of ash samples at atmospheric pressure. Presently, there is no known available technique that can measure the behavior of coal ash at elevated temperatures and pressures. In the literature, methods based on electrical resistance or shrinkage of coal ash have been reported at atmospheric pressure (elevated temperatures) conditions. A high-pressure microdilatometer (HPMD) has been developed to investigate ash fusion and sintering behavior at elevated pressures and temperatures by the simultaneous measurement of the temperature of initial contraction and electrical resistivity of samples. This novel technique facilitates the measurement of ash properties over a wide range of temperature, pressure, and gas atmosphere (oxidizing, reducing, or inert). The operating principle of the HPMD includes measuring the temperature at which there is a significant ``shift'' in the electrical resistivity (and/or sample volume) that represents ash sintering and fusion. Sintering occurs through the formation of solid-state, particle-to-particle ``necks'' or the appearance of a molten phase, which allows a path for electrical conductance. The ability to perform both resistivity and shrinkage measurements simultaneously or independently at elevated pressures makes the HPMD truly unique. The HPMD can also be used to investigate the swelling and softening behavior of pyrolyzing coal at elevated pressures and relatively rapid heating rates. The HPMD can provide insights into the sintering/fusion of coal ash or coal swelling at a range of conditions: (a) the influences of various gas atmospheres can be investigated, (b) the effects of pressure can be studied, (c) different temperature/heating rate schemes can be used (constant rates, isothermal holds below or above the

  20. A Specially Constructed Metallograph for Use at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Jenkins, Joe E; Buchele, Donald R; Long, Roger A

    1951-01-01

    A Metallographic microscope was developed with provision for heating a specimen to 1800 F in protective atmospheres, that is, vacuum or gas. A special objective was constructed of reflecting elements with an unusually long working distance (7/16 in.) and a high numerical aperture (0.5). Changes in specimen microstructure were observed and recorded on 35-millimeter motion-picture film. The resulting pictures were projected as motion pictures and individual frames were cut and enlargements made for close observation. Structural changes upon heating a 0.35-percent annealed carbon steel and a 5-percent tin phosphor bronze specimen were observed and recorded. Newly formed microstructure were revealed by selective vacuum etching and specimen relief resulting from recrystallization and varying grain orientation.

  1. Dolomite-magnesian calcite relations at elevated temperatures and CO2 pressures

    USGS Publications Warehouse

    Graf, D.L.; Goldsmith, J.R.

    1955-01-01

    The equilibrium thermal decomposition curve of dolomite has been determined up to a CO2 pressure of 20,000 lb/in.2, at which pressure dolomite decomposes at 857??C. Equilibrium was approached from both directions, by the breakdown and by the solid-state synthesis of dolomite. At elevated temperatures and pressures, calcites in equilibrium with periclase as well as those in equilibrium with dolomite contain Mg in solid solution. In the former, the Mg content increases with increasing CO2 pressure, and decreases with increasing temperature. In the latter, it is a function of temperature only. The exsolution curve of dolomite and magnesian calcite has been determined between 500?? and 800??C; at 500?? dolomite is in equilibrium with a magnesian calcite containing ~6 mol per cent MgCO2; at 800??, ~22 mol per cent. There appears to be a small but real deviation from the ideal 1 : 1 Ca : Mg ratio of dolomite, in the direction of excess Ca, for material in equilibrium with magnesian calcite at high temperature. The experimental findings indicate that very little Mg is stable in the calcites of sedimentary environments, but that an appreciable amount is stable under higher-temperature metamorphic conditions, if sufficient CO2 pressure is maintained. ?? 1955.

  2. CHARACTERIZATION OF ELEVATED TEMPERATURE PROPERTIES OF HEAT EXCHANGER AND STEAM GENERATOR ALLOYS

    SciTech Connect

    J.K. Wright; L.J. Carroll; C.J. Cabet; T. Lillo; J.K. Benz; J.A. Simpson; A. Chapman; R.N. Wright

    2012-10-01

    The Next Generation Nuclear Plant project is considering Alloy 800H and Alloy 617 for steam generator and intermediate heat exchangers. It is envisioned that a steam generator would operate with reactor outlet temperatures from 750 to 800 C, while an intermediate heat exchanger for primary to secondary helium would operate up to an outlet temperature of 950 C. Although both alloys are of interest due in part to their technical maturity, a number of specific properties require further characterization for design of nuclear components. Strain rate sensitivity of both alloys has been characterized and is found to be significant above 600 C. Both alloys also exhibit dynamic strain aging, characterized by serrated flow, over a wide range of temperatures and strain rates. High temperature tensile testing of Alloy 617 has been conducted over a range of temperatures. Dynamic strain aging is a concern for these materials since it is observed to result in reduced ductility for many solid solution alloys. Creep, fatigue, and creep-fatigue properties of Alloy 617 have been measured as well, with the goal of determining the influence of the temperature, strain rate and atmosphere on the creep fatigue life of Alloy 617. Elevated temperature properties and implications for codification of the alloys will be described.

  3. Numerical Modeling of Magnesium Alloy Sheet Metal Forming at Elevated Temperature

    SciTech Connect

    Lee, Myeong-Han; Oh, Soo-Ik; Kim, Heon-Young; Kim, Hyung-Jong; Choi, Yi-Chun

    2007-05-17

    The development of light-weight vehicle is in great demand for enhancement of fuel efficiency and dynamic performance. The vehicle weight can be reduced effectively by using lightweight materials such as magnesium alloys. However, the use of magnesium alloys in sheet forming processes is still limited because of their low formability at room temperature and the lack of understanding of the forming process of magnesium alloys at elevated temperatures. In this study, uniaxial tensile tests of the magnesium alloy AZ31B-O at various temperatures were performed to evaluate the mechanical properties of this alloy relevant for forming of magnesium sheets. To construct a FLD (forming limit diagram), a forming limit test were conducted at temperature of 100 and 200 deg. C. For the evaluation of the effects of the punch temperature on the formability of a rectangular cup drawing with AZ31B-O, numerical modelling was conducted. The experiment results indicate that the stresses and possible strains of AZ31B-O sheets largely depend on the temperature. The stress decreases with temperature increase. Also, the strain increase with temperature increase. The numerical modelling results indicate that formability increases with the decrease in the punch temperature at the constant temperature of the die and holder.

  4. Development of optical tools for the characterization of selective solar absorber at elevated temperature

    NASA Astrophysics Data System (ADS)

    Giraud, Philemon; Braillon, Julien; Delord, Christine; Raccurt, Olivier

    2016-05-01

    Durability of solar components for CSP (Concentrated Solar Power Plant) technologies is a key point to lower cost and ensure their large deployment. These technologies concentrated the solar radiation by means of mirrors on a receiver tube where it is collected as thermal energy. The absorbers are submitted to strong environmental constraints and the degradation of their optical properties (emittance and solar absorbance) have a direct impact on performance. The objective is to develop new optical equipment for characterization of this solar absorber in condition of use that is to say in air and at elevated temperature. In this paper we present two new optical test benches developed for optical characterization of solar absorbers in condition of use up to 800°C. The first equipment is an integrated sphere with heated sample holder which measures the hemispherical reflectance between 280 and 2500 nm to calculate the solar absorbance at high temperature. The second optical test bench measures the emittance of samples up to 1000°C in the range of 1.25 to 28.57 µm. Results of high temperature measurements on a series of metallic absorbers with selective coating and refractory material for high thermal receiver are presented.

  5. Engineered Kluyveromyces marxianus for pyruvate production at elevated temperature with simultaneous consumption of xylose and glucose.

    PubMed

    Zhang, Biao; Zhu, Yelin; Zhang, Jia; Wang, Dongmei; Sun, Lianhong; Hong, Jiong

    2017-01-01

    Xylose and glucose from lignocellulose are sustainable sources for production of pyruvate, which is the starting material for the synthesis of many drugs and agrochemicals. In this study, the pyruvate decarboxylase gene (KmPDC1) and glycerol-3-phosphate dehydrogenase gene (KmGPD1) of Kluyveromyces marxianus YZJ051 were disrupted to prevent ethanol and glycerol accumulation. The deficient growth of PDC disruption was rescued by overexpressing mutant KmMTH1-ΔT. Then pentose phosphate pathway and xylitol dehydrogenase SsXYL2-ARS genes were overexpressed to obtain strain YZB053 which produced pyruvate with xylose other than glucose. It produced 24.62g/L pyruvate from 80g/L xylose with productivity of 0.51g/L/h at 42°C. Then, xylose-specific transporter ScGAL2-N376F was overexpressed to obtain strain YZB058, which simultaneously consumed 40g/L glucose and 20g/L xylose and produced 29.21g/L pyruvate with productivity of 0.81g/L/h at 42°C. Therefore, a platform for pyruvate production from glucose and xylose at elevated temperature was developed.

  6. Strength, Fracture Toughness, and Slow Crack Growth of Zirconia/alumina Composites at Elevated Temperature

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.

    2003-01-01

    Various electrolyte materials for solid oxide fuel cells were fabricated by hot pressing 10 mol% yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina particulates and platelets each containing 0 to 30 mol% alumina. Flexure strength and fracture toughness of platelet composites were determined as a function of alumina content at 1000 C in air and compared with those of particulate composites determined previously. In general, elevated-temperature strength and fracture toughness of both composite systems increased with increasing alumina content. For a given alumina content, flexure strength of particulate composites was greater than that of platelet composites at higher alumina contents (greater than or equal to 20 mol%), whereas, fracture toughness was greater in platelet composites than in particulate composites, regardless of alumina content. The results of slow crack growth (SCG) testing, determined at 1000 C via dynamic fatigue testing for three different composites including 0 mol% (10-YSZ matrix), 30 mol % particulate and 30 mol% platelet composites, showed that susceptibility to SCG was greatest with SCG parameter n = 6 to 8 for both 0 and 30 mol% particulate composites and was least with n = 33 for the 30 mol% platelet composite.

  7. Elevated Temperature Fracture Toughness and Fatigue Testing of Steels for Geothermal Applications

    SciTech Connect

    Cutler, R.A.; Goodman, E.C.; Hendrickson, R.R.

    1981-10-01

    Conventional drill bit steels exhibit increased wear and decreased toughness when run at elevated temperatures in geothermal wells. Bits are therefore run at lower speeds and lighter loads, resulting in lower penetration rates for geothermal drilling than for conventional rock drilling. Carpenter EX-00053, Timken CBS 600, Timken CBS 1000M and Vasco X-2M steels with improved hot hardness (improved wear resistance), were tested in conjunction with the steels used for cones (AISI 4829, 3915 and EX55) in conventional roller cones and lugs (AISI 8620, 9315 and EX55) in conventional roller cone rock bits. Short-rod fracture toughness measurements were made on each of these steels between room temperature and 400{degree}C. Fatigue crack resistance was determined at 300{degree}C for high-temperature steels and at room temperature for conventional steels. Scanning electron microscopy analyses of the fractured short-rod specimens were correlated with observed crack behavior from the test records. Materials testing results are discussed and steel selections made for improved geothermal bits. Carpenter EX-00053 and Timken CBS 1000M steels meet all design requirements for use in stabilizers, lugs and cones at temperatures to 400{degree}C. It is recommended that EX-00053 and CBS 1000M be manufactured for geothermal drilling at the Geysers site. [DJE 2005

  8. Effects of Elevated Temperature on Concrete with Recycled Coarse Aggregates

    NASA Astrophysics Data System (ADS)

    Salau, M. A.; Oseafiana, O. J.; Oyegoke, T. O.

    2015-11-01

    This paper discusses the effects of heating temperatures of 200°C, 400°C and 600°C each for 2 hours at a heating rate of 2.5°C/min on concrete with the content of Natural Coarse Aggregates (NCA) partially replaced with Recycled Coarse Aggregates (RCA), obtained from demolished building in the ratio of 0%, 15% and 30%.There was an initial drop in strength from 100°C to 200°C which is suspected to be due to the relatively weak interfacial bond between the RCA and the hardened paste within the concrete matrix;a gradual increase in strength continued from 200°C to 450°C and steady drop occurred again as it approached 600°C.With replacement proportion of 0%, 15% and 30% of NCA and exposure to peak temperature of 600°C, a relative concrete strength of 23.6MPa, 25.3MPa and 22.2MPa respectively can be achieved for 28 days curing age. Furthermore, RAC with 15% NCA replacement when exposed to optimum temperature of 450°C yielded high compressive strength comparable to that of control specimen (normal concrete). In addition, for all concrete samples only slight surface hairline cracks were noticed as the temperature approached 400°C. Thus, the RAC demonstrated behavior just like normal concrete and may be considered fit for structural use.

  9. Large deformation micromechanics of particle filled acrylics at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Gunel, Eray Mustafa

    The main aim of this study is to investigate stress whitening and associated micro-deformation mechanism in thermoformed particle filled acrylic sheets. For stress whitening quantification, a new index was developed based on image histograms in logarithmic scale of gray level. Stress whitening levels in thermoformed acrylic composites was observed to increase with increasing deformation limit, decreasing forming rate and increasing forming temperatures below glass transition. Decrease in stress whitening levels above glass transition with increasing forming temperature was attributed to change in micro-deformation behavior. Surface deformation feature investigated with scanning electron microscopy showed that source of stress whitening in thermoformed samples was a combination of particle failure and particle disintegration depending on forming rate and temperature. Stress whitening level was strongly correlated to intensity of micro-deformation features. On the other hand, thermoformed neat acrylics displayed no surface discoloration which was attributed to absence of micro-void formation on the surface of neat acrylics. Experimental damage measures (degradation in initial, secant, unloading modulus and strain energy density) have been inadequate in describing damage evolution in successive thermoforming applications on the same sample at different levels of deformation. An improved version of dual-mechanism viscoplastic material model was proposed to predict thermomechanical behavior of neat acrylics under non-isothermal conditions. Simulation results and experimental results were in good agreement and failure of neat acrylics under non-isothermal conditions ar low forming temperatures were succesfully predicted based on entropic damage model. Particle and interphase failure observed in acrylic composites was studied in a multi-particle unit cell model with different volume fractions. Damage evolution due to particle failure and interphase failure was simulated

  10. Modifications of system for elevated temperature tensile testing and stress-strain measurement of metal matrix composites

    SciTech Connect

    Diaz, J.O.

    1994-09-01

    Composites consisting of tungsten alloy wires in superalloy matrices are being studied because they offer the potential for increased strength compared to current materials used at temperatures up to a least 1093{degrees}C (2000{degrees}F). Previous research at the NASA Lewis Research Center and at other laboratories in the U.S., Europe, and Japan has demonstrated laboratory feasibility for fiber reinforced superalloys (FRS). The data for the mechanical and physical properties used to evaluate candidate materials is limited and a need exists for a more detailed and complete data base. The focus of this work was to develop a test procedure to provide a more complete FRS data base to quantitatively evaluate the composite`s potential for component applications. This paper will describe and discuss the equipment and procedures under development to obtain elevated temperature tensile stress-strain, strength and modulus data for the first generation of tungsten reinforced superalloy composite (TFRS) materials. Tensile stress-strain tests were conducted using a constant crosshead speed tensile testing machine and a modified load-strain measuring apparatus. Elevated temperature tensile tests were performed using a resistance wound commercial furnace capable of heating tests specimens up to 1093{degrees}C (2000{degrees}F). Tensile stress-strain data were obtained for hollow tubular stainless steel specimens serving as a prototype for future composite specimens.

  11. Heat shock protein concentration and clarity of porcine lenses incubated at elevated temperatures

    PubMed Central

    Dzialoszynski, T. M.; Milne, K.J.; Trevithick, J.R.

    2016-01-01

    Purpose To quantify the concentration of heat shock proteins in lenses in lens organ culture at elevated temperatures, and to examine the relation between elevated temperature and lens clarity. Methods Pig lenses obtained from a local abattoir were dissected aseptically and incubated in medium M199 without serum for 4 days to stabilize, and lenses with protein leakage of less than 10 mg/l were obtained for heat shock exposure. Heat shock was performed by incubation for 1 h in M199 without serum at various temperatures ranging from 37 °C to 55 °C. After incubation for 24 h, cataract blurring of the images was assessed using Scantox™ and Scion Image analysis of the lens photographs. Lens homogenates were subsequently analyzed for Hsp70 and Hsp27 with western blotting. Results The degree of cataract blurring of the images increased with increasing temperature, but the two functional measures provided different results. Focal length inconsistency, as assessed with the back vertex distance standard error of the mean (BVD SEM; the variability in focal lengths measured at 20 equally spaced locations across the lens, Scantox™), increased nearly linearly with the heat treatment temperature. In contrast, decreased clarity, evident by a fuzzy image with lower contrast, was not markedly altered as the temperature rose until a threshold of approximately 47.5 °C. The inducible isoform of the Hsp70 family (Hsp70) of heat shock proteins was increased at all temperatures above the control except those above 50 °C. Changes in Hsp27 were less clear as the protein content increased only at the incubation temperatures of 39 °C and 48.5 °C. Conclusions The porcine lens demonstrates subtle changes in the variability of the focal length, and the variability increases as the incubation temperature rises. In contrast, lens clarity is relatively stable at temperatures up to 47.5 °C, above which dramatic changes, indicative of the formation of cataracts, occur. The lens content

  12. DDT in fuel air mixtures at elevated temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Card, J.; Rival, D.; Ciccarelli, G.

    2005-11-01

    An experimental study was carried out to investigate flame acceleration and deflagration-to-detonation transition (DDT) in fuel air mixtures at initial temperatures up to 573 K and pressures up to 2 atm. The fuels investigated include hydrogen, ethylene, acetylene and JP-10 aviation fuel. The experiments were performed in a 3.1-m long, 10-cm inner-diameter heated detonation tube equipped with equally spaced orifice plates. Ionization probes were used to measure the flame time-of-arrival from which the average flame velocity versus propagation distance could be obtained. The DDT composition limits and the distance required for the flame to transition to detonation were obtained from this flame velocity data. The correlation developed by Veser et al. (run-up distance to supersonic flames in obstacle-laden tubes. In the proceedings of the 4th International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions, France (2002)) for the flame choking distance proved to work very well for correlating the detonation run-up distance measured in the present study. The only exception was for the hydrogen air data at elevated initial temperatures which tended to fall outside the scatter of the hydrocarbon mixture data. The DDT limits obtained at room temperature were found to follow the classical d/λ = 1 correlation, where d is the orifice plate diameter and λ is the detonation cell size. Deviations found for the high-temperature data could be attributed to the one-dimensional ZND detonation structure model used to predict the detonation cell size for the DDT limit mixtures. This simple model was used in place of actual experimental data not currently available.

  13. Elevated temperature fretting fatigue of nickel based alloys

    NASA Astrophysics Data System (ADS)

    Gean, Matthew C.

    This document details the high temperature fretting fatigue of high temperature nickel based alloys common to turbine disk and blade applications. The research consists of three area of focus: Experiments are conducted to determine quantitatively the fretting fatigue lives of advanced nickel based alloys; Analytical tools are developed and used to investigate the fretting fatigue response of the material; Fractographic analysis of the experimental results is used to improve the analytical models employed in the analysis of the experiments. Sixty three fretting fatigue experiments were conducted at 649 °C using a polycrystalline Nickel specimen in contact with directionally solidified and single crystal Nickel pads. Various influences on the fretting fatigue life are investigated. Shot peened Rene' 95 had better fretting fatigue life compared to shot peened Rene' 88. Shot peening produced a 2x increase in life for Rene' 95, but only a marginal improvement in the fretting fatigue life for Rene' 88. Minor cycles in variable amplitude loading produces significant damage to the specimen. Addition of occasional overpeaks in load produces improvements in fretting fatigue life. Contact tractions and stresses are obtained through a variety of available tools. The contact tractions can be efficiently obtained for limited geometries, while FEM can provide the contact tractions for a broader class of problems, but with the cost of increased CPU requirements. Similarly, the subsurface contact stresses can be obtained using the contact tractions as a boundary condition with either a semi-analytical FFT method or FEM. It is found that to calculate contact stresses the FFT was only marginally faster than FEM. The experimental results are combined with the analysis to produce tools that are used to design against fretting fatigue. Fractographic analysis of the fracture surface indicates the nature of the fretting fatigue crack behavior. Interrupted tests were performed to analyze

  14. Composite structural materials. [aircraft applications

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1981-01-01

    The development of composite materials for aircraft applications is addressed with specific consideration of physical properties, structural concepts and analysis, manufacturing, reliability, and life prediction. The design and flight testing of composite ultralight gliders is documented. Advances in computer aided design and methods for nondestructive testing are also discussed.

  15. Hydrolytic Stability of 3-Aminopropylsilane Coupling Agent on Silica and Silicate Surfaces at Elevated Temperatures.

    PubMed

    Okhrimenko, Denis V; Budi, Akin; Ceccato, Marcel; Cárdenas, Marité; Johansson, Dorte B; Lybye, Dorthe; Bechgaard, Klaus; Andersson, Martin P; Stipp, Susan L S

    2017-03-08

    3-Aminopropylsilane (APS) coupling agent is widely used in industrial, biomaterial, and medical applications to improve adhesion of polymers to inorganic materials. However, during exposure to elevated humidity and temperature, the deposited APS layers can decompose, leading to reduction in coupling efficiency, thus decreasing the product quality and the mechanical strength of the polymer-inorganic material interface. Therefore, a better understanding of the chemical state and stability of APS on inorganic surfaces is needed. In this work, we investigated APS adhesion on silica wafers and compared its properties with those on complex silicate surfaces such as those used by industry (mineral fibers and fiber melt wafers). The APS was deposited from aqueous and organic (toluene) solutions and studied with surface sensitive techniques, including X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), streaming potential, contact angle, and spectroscopic ellipsometry. APS configuration on a model silica surface at a range of coverages was simulated using density functional theory (DFT). We also studied the stability of adsorbed APS during aging at high humidity and elevated temperature. Our results demonstrated that APS layer formation depends on the choice of solvent and substrate used for deposition. On silica surfaces in toluene, APS formed unstable multilayers, while from aqueous solutions, thinner and more stable APS layers were produced. The chemical composition and substrate roughness influence the amount of deposited APS. More APS was deposited and its layers were more stable on fiber melt than on silica wafers. The changes in the amount of adsorbed APS can be successfully monitored by streaming potential. These results will aid in improving industrial- and laboratory-scale APS deposition methods and increasing adhesion and stability, thus increasing the quality and effectiveness of materials where APS is used as a coupling agent.

  16. Effects of primary recoil energy on the production rate of mobile defects during elevated temperature irradiation

    SciTech Connect

    Okamoto, P.R.; Rehn, L.E.; Averback, R.S.

    1984-11-01

    Radiation-induced segregation rates in a Ni-12.7 at.% Si alloy have been measured as a function of temperature using ions of various masses and energies. An analysis of the segregation kinetics using a simple analytical model yielded the relative efficiency of each of the ions for producing mobile defects directly from ratios of their measured segregation rates. In this paper, we also show that the relative efficiencies can also be determined from measured shifts in the peak segregation temperature. Both methods yield a strong decrease in efficiency with increasing ion mass. The reduction in efficiency for the heavior ions was found to be significantly larger than that measured at very low temperatures by resistivity techniques. The latter are often used as a basis for correlating damage structures produced at elevated temperatures. Differences between the low and high temperature measurements indicate that relative efficiencies determined from segregation measurements are more reliable for correlating microstructural changes that are produced in different irradiation environments at high temperatures.

  17. Thermo-elastic behavior of deformed woven fabric composites at elevated temperatures: Part 1

    SciTech Connect

    Vu-Khanh, T.; Liu, B.

    1994-12-31

    This paper presents the results of a study on the effects of temperature on the thermo-elastic properties of woven fabric composites. The thermo-mechanical behavior of woven fabric composites is characterized by a laminate composed of four fictional unidirectional plies, called the sub-plies model. The model allows determination of the thermo-elastic properties of deformed fabric composites (non-orthogonal structure) and direct use of layered shell elements in finite element codes. A special procedure is also proposed to measure the fiber undulation effect and to predict the on-axis thermo-elastic coefficients of the equivalent constituent plies. The thermo-elastic behavior at elevated temperature was investigated on graphite/epoxy fabric composites. Experimental measurements were carried out from 23 C to 177 C. The results revealed that the equivalent thermal expansion coefficients of the sub-plies remain almost constant over a wide range of temperature. However, the equivalent elastic moduli and Poison`s ratio of the sub-plies vary nonlinearly with temperature. Semiempirical equations based on the experimental data were also developed to predict the equivalent on-axis thermo-elastic properties of the fictional constituent plies in the sub-plies model as a function of temperature.

  18. Microstructural changes to AlCu6Ni1 alloy after prolonged annealing at elevated temperature.

    PubMed

    Wierzbińska, M; Sieniawski, J

    2010-03-01

    This work presents results of microstructure examination of AlCu(6)Ni(1) aluminium alloy. The commercial AlCu(4)Ni(2)Mg(2) (M-309) alloy is widely used for elements of aircraft and automotive engines. Modification its chemical composition was aimed at improving the stability of mechanical properties of the alloy subjected to long-term exposure to high temperature. The alloy after standard T6 heat treatment (solution heat treated at 818 K/10 h/water quenched followed by ageing at 498 K/8 h/air cooled) was annealed for 150 h at elevated temperature of 573 K corresponding to the maximum value at which structural elements of jet piston engines made of aluminium alloys operate. It was found that applied heat treatment caused an increasing in the particles of hardening phase (theta'-Al(2)Cu) size. The significant growth of the length of theta'-Al(2)Cu precipitations was observed in particularly. Nevertheless, it did not strongly result in change of its shape - the 'crystallites' and 'rods' were still characteristic of hardening phase morphology. The phenomena of the growth of theta'-Al(2)Cu precipitates caused decreasing the mechanical properties of the alloy, what is the subject of further investigations by the authors.

  19. Bone as a Structural Material.

    PubMed

    Zimmermann, Elizabeth A; Ritchie, Robert O

    2015-06-24

    As one of the most important natural materials, cortical bone is a composite material comprising assemblies of tropocollagen molecules and nanoscale hydroxyapatite mineral crystals, forming an extremely tough, yet lightweight, adaptive and multi-functional material. Bone has evolved to provide structural support to organisms, and therefore its mechanical properties are vital physiologically. Like many mineralized tissues, bone can resist deformation and fracture from the nature of its hierarchical structure, which spans molecular to macroscopic length-scales. In fact, bone derives its fracture resistance with a multitude of deformation and toughening mechanisms that are active at most of these dimensions. It is shown that bone's strength and ductility originate primarily at the scale of the nano to submicrometer structure of its mineralized collagen fibrils and fibers, whereas bone toughness is additionally generated at much larger, micro- to near-millimeter, scales from crack-tip shielding associated with interactions between the crack path and the microstructure. It is further shown how the effectiveness with which bone's structural features can resist fracture at small to large length-scales can become degraded by biological factors such as aging and disease, which affect such features as the collagen cross-linking environment, the homogeneity of mineralization, and the density of the osteonal structures.

  20. High temperature structural insulating material

    DOEpatents

    Chen, Wayne Y.

    1987-01-06

    A high temperature structural insulating material useful as a liner for cylinders of high temperature engines through the favorable combination of high service temperature (above about 800.degree. C.), low thermal conductivity (below about 0.2 W/m.degree. C.), and high compressive strength (above about 250 psi). The insulating material is produced by selecting hollow ceramic beads with a softening temperature above about 800.degree. C., a diameter within the range of 20-200 .mu.m, and a wall thickness in the range of about 2-4 .mu.m; compacting the beads and a compatible silicate binder composition under pressure and sintering conditions to provide the desired structural form with the structure having a closed-cell, compact array of bonded beads.

  1. High temperature structural insulating material

    DOEpatents

    Chen, Wayne Y.

    1987-01-01

    A high temperature structural insulating material useful as a liner for cylinders of high temperature engines through the favorable combination of high service temperature (above about 800.degree. C.), low thermal conductivity (below about 0.2 W/m.degree. C.), and high compressive strength (above about 250 psi). The insulating material is produced by selecting hollow ceramic beads with a softening temperature above about 800.degree. C., a diameter within the range of 20-200 .mu.m, and a wall thickness in the range of about 2-4 .mu.m; compacting the beads and a compatible silicate binder composition under pressure and sintering conditions to provide the desired structural form with the structure having a closed-cell, compact array of bonded beads.

  2. High temperature structural insulating material

    DOEpatents

    Chen, W.Y.

    1984-07-27

    A high temperature structural insulating material useful as a liner for cylinders of high temperature engines through the favorable combination of high service temperature (above about 800/sup 0/C), low thermal conductivity (below about 0.2 W/m/sup 0/C), and high compressive strength (above about 250 psi). The insulating material is produced by selecting hollow ceramic beads with a softening temperature above about 800/sup 0/C, a diameter within the range of 20-200 ..mu..m, and a wall thickness in the range of about 2 to 4 ..mu..m; compacting the beads and a compatible silicate binder composition under pressure and sintering conditions to provide the desired structural form with the structure having a closed-cell, compact array of bonded beads.

  3. Elevated temperature alters proteomic responses of individual organisms within a biofilm community

    DOE PAGES

    Mosier, Annika C.; Li, Zhou; Thomas, Brian C.; ...

    2014-07-22

    Microbial communities that underpin global biogeochemical cycles will likely be influenced by elevated temperature associated with environmental change. In this paper, we test an approach to measure how elevated temperature impacts the physiology of individual microbial groups in a community context, using a model microbial-based ecosystem. The study is the first application of tandem mass tag (TMT)-based proteomics to a microbial community. We accurately, precisely and reproducibly quantified thousands of proteins in biofilms growing at 40, 43 and 46 °C. Elevated temperature led to upregulation of proteins involved in amino-acid metabolism at the level of individual organisms and the entiremore » community. Proteins from related organisms differed in their relative abundance and functional responses to temperature. Elevated temperature repressed carbon fixation proteins from two Leptospirillum genotypes, whereas carbon fixation proteins were significantly upregulated at higher temperature by a third member of this genus. Leptospirillum group III bacteria may have been subject to viral stress at elevated temperature, which could lead to greater carbon turnover in the microbial food web through the release of viral lysate. Finally, overall, these findings highlight the utility of proteomics-enabled community-based physiology studies, and provide a methodological framework for possible extension to additional mixed culture and environmental sample analyses.« less

  4. Elevated temperature alters proteomic responses of individual organisms within a biofilm community

    SciTech Connect

    Mosier, Annika C.; Li, Zhou; Thomas, Brian C.; Hettich, Robert L.; Pan, Chongle; Banfield, Jillian F.

    2014-07-22

    Microbial communities that underpin global biogeochemical cycles will likely be influenced by elevated temperature associated with environmental change. In this paper, we test an approach to measure how elevated temperature impacts the physiology of individual microbial groups in a community context, using a model microbial-based ecosystem. The study is the first application of tandem mass tag (TMT)-based proteomics to a microbial community. We accurately, precisely and reproducibly quantified thousands of proteins in biofilms growing at 40, 43 and 46 °C. Elevated temperature led to upregulation of proteins involved in amino-acid metabolism at the level of individual organisms and the entire community. Proteins from related organisms differed in their relative abundance and functional responses to temperature. Elevated temperature repressed carbon fixation proteins from two Leptospirillum genotypes, whereas carbon fixation proteins were significantly upregulated at higher temperature by a third member of this genus. Leptospirillum group III bacteria may have been subject to viral stress at elevated temperature, which could lead to greater carbon turnover in the microbial food web through the release of viral lysate. Finally, overall, these findings highlight the utility of proteomics-enabled community-based physiology studies, and provide a methodological framework for possible extension to additional mixed culture and environmental sample analyses.

  5. Elevated temperature alters proteomic responses of individual organisms within a biofilm community

    PubMed Central

    Mosier, Annika C; Li, Zhou; Thomas, Brian C; Hettich, Robert L; Pan, Chongle; Banfield, Jillian F

    2015-01-01

    Microbial communities that underpin global biogeochemical cycles will likely be influenced by elevated temperature associated with environmental change. Here, we test an approach to measure how elevated temperature impacts the physiology of individual microbial groups in a community context, using a model microbial-based ecosystem. The study is the first application of tandem mass tag (TMT)-based proteomics to a microbial community. We accurately, precisely and reproducibly quantified thousands of proteins in biofilms growing at 40, 43 and 46 °C. Elevated temperature led to upregulation of proteins involved in amino-acid metabolism at the level of individual organisms and the entire community. Proteins from related organisms differed in their relative abundance and functional responses to temperature. Elevated temperature repressed carbon fixation proteins from two Leptospirillum genotypes, whereas carbon fixation proteins were significantly upregulated at higher temperature by a third member of this genus. Leptospirillum group III bacteria may have been subject to viral stress at elevated temperature, which could lead to greater carbon turnover in the microbial food web through the release of viral lysate. Overall, these findings highlight the utility of proteomics-enabled community-based physiology studies, and provide a methodological framework for possible extension to additional mixed culture and environmental sample analyses. PMID:25050524

  6. Increased anthocyanin accumulation in aster flowers at elevated temperatures due to magnesium treatment.

    PubMed

    Shaked-Sachray, Liat; Weiss, David; Reuveni, Moshe; Nissim-Levi, Ada; Oren-Shamir, Michal

    2002-04-01

    Temperature is one of the main external factors affecting anthocyanin accumulation in plant tissues: low temperatures cause an increase and elevated temperatures cause a decrease in anthocyanin concentration. Several metals have been shown to increase the half-life time of anthocyanins, by forming complexes with them. We studied the combined effect of elevated temperatures and increased metal concentrations on the accumulation of anthocyanins in aster 'Sungal' flowers. It has been found that magnesium treatment of aster plants or detached flower buds, partially prevents colour fading at elevated temperatures. Anthocyanin concentration of aster 'Sungal' flowers grown at 29 degrees C/21 degrees C day/night, respectively, was about half that of flowers grown at 17 degrees C/9 degrees C. The activity of phenylalanine ammonia-lyase (PAL) and chalcone isomerase (CHI) decreased as the temperature increased. Treatment of both whole plants and detached flower buds grown at elevated temperatures in the presence of magnesium salts, increased flower anthocyanin concentration by up to 80%. Measurement of magnesium following these treatments revealed an increased level of the metal in the petals, suggesting a direct effect. Magnesium treatment does not seem to cause increased synthesis of anthocyanin through a stress-related reaction, since the activities of both PAL and CHI did not increase due to this treatment. The results of this study show that increasing magnesium levels in aster petals prevents the deleterious effect of elevated temperatures on anthocyanin accumulation, thus enhancing flower colour.

  7. Spatial and temporal characteristics of elevated temperatures in municipal solid waste landfills.

    PubMed

    Jafari, Navid H; Stark, Timothy D; Thalhamer, Todd

    2017-01-01

    Elevated temperatures in waste containment facilities can pose health, environmental, and safety risks because they generate toxic gases, pressures, leachate, and heat. In particular, MSW landfills undergo changes in behavior that typically follow a progression of indicators, e.g., elevated temperatures, changes in gas composition, elevated gas pressures, increased leachate migration, slope movement, and unusual and rapid surface settlement. This paper presents two MSW landfill case studies that show the spatial and time-lapse movements of these indicators and identify four zones that illustrate the transition of normal MSW decomposition to the region of elevated temperatures. The spatial zones are gas front, temperature front, and smoldering front. The gas wellhead temperature and the ratio of CH4 to CO2 are used to delineate the boundaries between normal MSW decomposition, gas front, and temperature front. The ratio of CH4 to CO2 and carbon monoxide concentrations along with settlement strain rates and subsurface temperatures are used to delineate the smoldering front. In addition, downhole temperatures can be used to estimate the rate of movement of elevated temperatures, which is important for isolating and containing the elevated temperature in a timely manner.

  8. Space Shuttle Orbiter - Leading edge structural design/analysis and material allowables

    NASA Technical Reports Server (NTRS)

    Johnson, D. W.; Curry, D. M.; Kelly, R. E.

    1986-01-01

    Reinforced Carbon-Carbon (RCC), a structural composite whose development was targeted for the high temperature reentry environments of reusable space vehicles, has successfully demonstrated that capability on the Space Shuttle Orbiter. Unique mechanical properties, particularly at elevated temperatures up to 3000 F, make this material ideally suited for the 'hot' regions of multimission space vehicles. Design allowable characterization testing, full-scale development and qualification testing, and structural analysis techniques will be presented herein that briefly chart the history of the RCC material from infancy to eventual multimission certification for the Orbiter. Included are discussions pertaining to the development of the design allowable data base, manipulation of the test data into usable forms, and the analytical verification process.

  9. Modal Acoustic Emission Used at Elevated Temperatures to Detect Damage and Failure Location in Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.

    1999-01-01

    Ceramic matrix composites are being developed for elevated-temperature engine applications. A leading material system in this class of materials is silicon carbide (SiC) fiber-reinforced SiC matrix composites. Unfortunately, the nonoxide fibers, matrix, and interphase (boron nitride in this system) can react with oxygen or water vapor in the atmosphere, leading to strength degradation of the composite at elevated temperatures. For this study, constant-load stress-rupture tests were performed in air at temperatures ranging from 815 to 960 C until failure. From these data, predictions can be made for the useful life of such composites under similar stressed-oxidation conditions. During these experiments, the sounds of failure events (matrix cracking and fiber breaking) were monitored with a modal acoustic emission (AE) analyzer through transducers that were attached at the ends of the tensile bars. Such failure events, which are caused by applied stress and oxidation reactions, cause these composites to fail prematurely. Because of the nature of acoustic waveform propagation in thin tensile bars, the location of individual source events and the eventual failure event could be detected accurately.

  10. Surface film formation on nickel electrodes in a propylene carbonate solution at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Mogi, Ryo; Inaba, Minoru; Iriyama, Yasutoshi; Abe, Takeshi; Ogumi, Zempachi

    The effect of temperature on surface film formation on nickel electrode was studied in 1 mol dm -3 bis(perfluoroethylsulfonyl)imide dissolved in propylene carbonate by atomic force microscopy (AFM) and ac impedance spectroscopy. Cyclic voltammetry measurements revealed that electrolyte decomposition reactions are accelerated at elevated temperatures, especially at 60 and 80 °C. In situ AFM measurements showed that the film formation is fast and the resulting surface film is thicker at 80 °C than at room temperature. Furthermore, it was confirmed by ac impedance measurements that the resistance of surface film was very low at elevated temperatures. These results were discussed in relation to superior cycling characteristics of lithium deposition and dissolution at the elevated temperatures.

  11. Elevated Temperature and CO2 Stimulate Late-Season Photosynthesis But Impair Cold Hardening in Pine.

    PubMed

    Chang, Christine Y; Fréchette, Emmanuelle; Unda, Faride; Mansfield, Shawn D; Ensminger, Ingo

    2016-10-01

    Rising global temperature and CO2 levels may sustain late-season net photosynthesis of evergreen conifers but could also impair the development of cold hardiness. Our study investigated how elevated temperature, and the combination of elevated temperature with elevated CO2, affected photosynthetic rates, leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening in Eastern white pine (Pinus strobus). We designed an experiment where control seedlings were acclimated to long photoperiod (day/night 14/10 h), warm temperature (22°C/15°C), and either ambient (400 μL L(-1)) or elevated (800 μmol mol(-1)) CO2, and then shifted seedlings to growth conditions with short photoperiod (8/16 h) and low temperature/ambient CO2 (LTAC), elevated temperature/ambient CO2 (ETAC), or elevated temperature/elevated CO2 (ETEC). Exposure to LTAC induced down-regulation of photosynthesis, development of sustained nonphotochemical quenching, accumulation of soluble carbohydrates, expression of a 16-kD dehydrin absent under long photoperiod, and increased freezing tolerance. In ETAC seedlings, photosynthesis was not down-regulated, while accumulation of soluble carbohydrates, dehydrin expression, and freezing tolerance were impaired. ETEC seedlings revealed increased photosynthesis and improved water use efficiency but impaired dehydrin expression and freezing tolerance similar to ETAC seedlings. Sixteen-kilodalton dehydrin expression strongly correlated with increases in freezing tolerance, suggesting its involvement in the development of cold hardiness in P. strobus Our findings suggest that exposure to elevated temperature and CO2 during autumn can delay down-regulation of photosynthesis and stimulate late-season net photosynthesis in P. strobus seedlings. However, this comes at the cost of impaired freezing tolerance. Elevated temperature and CO2 also impaired freezing tolerance. However, unless the frequency and timing of extreme low

  12. Thermodynamics of actinide complexation in solution at elevated temperatures: application of variable-temperature titration calorimetry.

    PubMed

    Rao, Linfeng

    2007-06-01

    Studies of actinide complexation in solution at elevated temperatures provide insight into the effect of solvation and the energetics of complexation, and help to predict the chemical behavior of actinides in nuclear waste processing and disposal where temperatures are high. This tutorial review summarizes the data on the complexation of actinides at elevated temperatures and describes the methodology for thermodynamic measurements, with the emphasis on variable-temperature titration calorimetry, a highly valuable technique to determine the enthalpy and, under appropriate conditions, the equilibrium constants of complexation as well.

  13. Subtelomeric repeat amplification is associated with growth at elevated temperature in yku70 mutants of Saccharomyces cerevisiae.

    PubMed Central

    Fellerhoff, B; Eckardt-Schupp, F; Friedl, A A

    2000-01-01

    Inactivation of the Saccharomyces cerevisiae gene YKU70 (HDF1), which encodes one subunit of the Ku heterodimer, confers a DNA double-strand break repair defect, shortening of and structural alterations in the telomeres, and a severe growth defect at 37 degrees. To elucidate the basis of the temperature sensitivity, we analyzed subclones derived from rare yku70 mutant cells that formed a colony when plated at elevated temperature. In all these temperature-resistant subclones, but not in cell populations shifted to 37 degrees, we observed substantial amplification and redistribution of subtelomeric Y' element DNA. Amplification of Y' elements and adjacent telomeric sequences has been described as an alternative pathway for chromosome end stabilization that is used by postsenescence survivors of mutants deficient for the telomerase pathway. Our data suggest that the combination of Ku deficiency and elevated temperature induces a potentially lethal alteration of telomere structure or function. Both in yku70 mutants and in wild type, incubation at 37 degrees results in a slight reduction of the mean length of terminal restriction fragments, but not in a significant loss of telomeric (C(1-3)A/TG(1-3))(n) sequences. We propose that the absence of Ku, which is known to bind to telomeres, affects the telomeric chromatin so that its chromosome end-defining function is lost at 37 degrees. PMID:10757752

  14. Effect of viscous grain bridging on cyclic fatigue-crack growth in monolithic ceramics at elevated temperatures

    SciTech Connect

    McNaney, J.M.; Gilbert, C.J.; Ritchie, R.O. . Dept. of Materials Science and Mineral Engineering)

    1999-07-09

    The bridging tractions developed behind a crack tip are considered for a stationary crack under cyclic loading conditions at elevated temperatures in high-toughness, monolithic ceramics. Assuming a temperature range where the grain-boundary phases are sufficiently soft such that bridging can occur due to a viscous layer in the boundary, a viscoelastic model is developed in which bridging forces associated with the shear resistance of the grain-boundary phase are transmitted across the surfaces of a crack. Throughout the work, cyclic and static damage mechanisms which may be operating ahead of the crack tip (e.g. creep cavitation) are ignored in order to focus exclusively on the role of viscous grain bridging. A primary goal is to incorporate microstructural details like grain shape, grain-boundary thickness, and glass viscosity, as well as the effects of external variables such as loading rate and temperature. A fully self-consistent numerical approach is adopted, which does not require any prescribed assumptions as to the shape of the crack-opening profile. The self-consistent solution is compared to an analytical solution for a simplified parabolic approximation of the crack-flank opening displacements. The model is applicable to a wide range of ceramic materials at elevated temperatures, and rationalizes the frequency and temperature sensitivity not generally observed in ceramics at room temperature. Solutions identify a non-dimensional group associated with microstructure and external loading conditions, and solutions are presented over a range of this parameter.

  15. Forming-Limit Diagrams for Magnesium AZ31B and ZEK100 Alloy Sheets at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Antoniswamy, Aravindha R.; Carpenter, Alexander J.; Carter, Jon T.; Hector, Louis G.; Taleff, Eric M.

    2013-11-01

    Modern design and manufacturing methodologies for magnesium (Mg) sheet panels require formability data for use in computer-aided design and computer-aided engineering tools. To meet this need, forming-limit diagrams (FLDs) for AZ31B and ZEK100 wrought Mg alloy sheets were developed at elevated temperatures for strain rates of 10-3 and 10-2 s-1. The elevated temperatures investigated range from 250 to 450 °C for AZ31B and 300 to 450 °C for ZEK100. The FLDs were generated using data from uniaxial tension, biaxial bulge, and plane-strain bulge tests, all carried out until specimen rupture. The unique aspect of this study is that data from materials with consistent processing histories were produced using consistent testing techniques across all test conditions. The ZEK100 alloy reaches greater major true strains at rupture, by up to 60%, than the AZ31B alloy for all strain paths at all temperatures and strain rates examined. Formability limits decrease only slightly with a decrease in temperature, less than 30% decrease for AZ31B and less than 35% decrease for ZEK100 as the temperature decreases from 450 to 300 °C. This suggests that forming processes at 250-300 °C are potentially viable for manufacturing complex Mg components.

  16. Directionally Solidified NiAl-Based Alloys Studied for Improved Elevated-Temperature Strength and Room-Temperature Fracture Toughness

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

    2000-01-01

    Efforts are underway to replace superalloys used in the hot sections of gas turbine engines with materials possessing better mechanical and physical properties. Alloys based on the intermetallic NiAl have demonstrated potential; however, they generally suffer from low fracture resistance (toughness) at room temperature and from poor strength at elevated temperatures. Directional solidification of NiAl alloyed with both Cr and Mo has yielded materials with useful toughness and elevated-temperature strength values. The intermetallic alloy NiAl has been proposed as an advanced material to extend the maximum operational temperature of gas turbine engines by several hundred degrees centigrade. This intermetallic alloy displays a lower density (approximately 30-percent less) and a higher thermal conductivity (4 to 8 times greater) than conventional superalloys as well as good high-temperature oxidation resistance. Unfortunately, unalloyed NiAl has poor elevated temperature strength (approximately 50 MPa at 1027 C) and low room-temperature fracture toughness (about 5 MPa). Directionally solidified NiAl eutectic alloys are known to possess a combination of high elevated-temperature strength and good room-temperature fracture toughness. Research has demonstrated that a NiAl matrix containing a uniform distribution of very thin Cr plates alloyed with Mo possessed both increased fracture toughness and elevated-temperature creep strength. Although attractive properties were obtained, these alloys were formed at low growth rates (greater than 19 mm/hr), which are considered to be economically unviable. Hence, an investigation was warranted of the strength and toughness behavior of NiAl-(Cr,Mo) directionally solidified at faster growth rates. If the mechanical properties did not deteriorate with increased growth rates, directional solidification could offer an economical means to produce NiAl-based alloys commercially for gas turbine engines. An investigation at the NASA Glenn

  17. Response of AM fungi spore population to elevated temperature and nitrogen addition and their influence on the plant community composition and productivity

    PubMed Central

    Zhang, Tao; Yang, Xue; Guo, Rui; Guo, Jixun

    2016-01-01

    To examine the influence of elevated temperature and nitrogen (N) addition on species composition and development of arbuscular mycorrhizal fungi (AMF) and the effect of AMF on plant community structure and aboveground productivity, we conducted a 5-year field experiment in a temperate meadow in northeast China and a subsequent greenhouse experiment. In the field experiment, N addition reduced spore population diversity and richness of AMF and suppressed the spore density and the hyphal length density (HLD). Elevated temperature decreased spore density and diameter and increased the HLD, but did not affect AMF spore population composition. In the greenhouse experiment, AMF altered plant community composition and increased total aboveground biomass in both elevated temperature and N addition treatments; additionally, AMF also increased the relative abundance and aboveground biomass of the grasses Leymus chinensis (Poaceae) and Setaria viridis (Gramineae) and significantly reduced the relative abundance and aboveground biomass of the Suaeda corniculata (Chenopodiaceae). Although elevated temperature and N addition can affect species composition or suppress the development of AMF, AMF are likely to play a vital role in increasing plant diversity and productivity. Notably, AMF might reduce the threat of climate change induced degradation of temperate meadow ecosystems. PMID:27098761

  18. Response of AM fungi spore population to elevated temperature and nitrogen addition and their influence on the plant community composition and productivity

    NASA Astrophysics Data System (ADS)

    Zhang, Tao; Yang, Xue; Guo, Rui; Guo, Jixun

    2016-04-01

    To examine the influence of elevated temperature and nitrogen (N) addition on species composition and development of arbuscular mycorrhizal fungi (AMF) and the effect of AMF on plant community structure and aboveground productivity, we conducted a 5-year field experiment in a temperate meadow in northeast China and a subsequent greenhouse experiment. In the field experiment, N addition reduced spore population diversity and richness of AMF and suppressed the spore density and the hyphal length density (HLD). Elevated temperature decreased spore density and diameter and increased the HLD, but did not affect AMF spore population composition. In the greenhouse experiment, AMF altered plant community composition and increased total aboveground biomass in both elevated temperature and N addition treatments; additionally, AMF also increased the relative abundance and aboveground biomass of the grasses Leymus chinensis (Poaceae) and Setaria viridis (Gramineae) and significantly reduced the relative abundance and aboveground biomass of the Suaeda corniculata (Chenopodiaceae). Although elevated temperature and N addition can affect species composition or suppress the development of AMF, AMF are likely to play a vital role in increasing plant diversity and productivity. Notably, AMF might reduce the threat of climate change induced degradation of temperate meadow ecosystems.

  19. Effect of Load Rate on Tensile Strength of Various CFCCs at Elevated Temperatures: An Approach to Life Prediction Testing

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.

    2001-01-01

    Strength of three continuous fiber-reinforced ceramic composites, including SiC/CAS-11, SiC/MAS-5 and SiC/SiC, was determined as a function of test rate in air at 1100 - 1200 C. All three composite materials exhibited a strong dependency of strength on test rate, similar to the behavior observed in many advanced monolithic ceramics at elevated temperatures. The application of the preloading technique as well as the prediction of life from one loading configuration (constant stress-rate) to another (constant stress loading) suggested that the overall macroscopic failure mechanism of the composites would be the one governed by a power-law tyw of damage evolution/accumulation, analogous to slow crack growth commonly observed in advanced monolithic ceramics. It was further found that constant stress-rate testing could be used as an alternative to life prediction test methodology even for the composite materials at least for the short range of lifetime.

  20. Apparent activation energy of subcritical crack growth of SiC/SiC composites at elevated temperatures

    SciTech Connect

    Chou, Y.S.; Stackpoole, M.M.; Bordia, R.

    1995-04-01

    The purpose of this study is to investigate the environmental effect of oxygen-containing gases on the subcritical crack growth of continuous fiber (Nicalon {open_quotes}SiC{close_quotes}) reinforced ceramic matrix (SiC) composites at elevated temperatures. This is a continuing project and the primary goal for this time period is to obtain an apparent activation energy for SiC/SiC materials with two different interfaces: carbon and boron nitride coatings. In the past six months, the authors have conducted studies of subcritical crack growth on SiC/SiC composite materials in a corrosive (O{sub 2}) as well as an inert (Ar) atmosphere for temperatures ranging from 800 to 1100{degree}C.

  1. Selected durability studies of geopolymer concrete with respect to carbonation, elevated temperature, and microbial induced corrosion

    NASA Astrophysics Data System (ADS)

    Badar, Mohammad Sufian

    This thesis reports a comprehensive study related to the experimental evaluation of carbonation in reinforced geopolymer concrete, the evaluation of geopolymer concretes at elevated temperature, and the resistance of geopolymer concrete to microbial induced corrosion (MIC). Carbonation: Reinforced concretes, made of geopolymer, prepared from two class F fly ashes and one class C fly ash, were subjected to accelerated carbonation treatment for a period of 450 days. Electrochemical, microstructure and pore structure examinations were performed to evaluate the effect of corrosion caused due to carbonation. GPC specimens prepared from class F fly ash exhibited lower corrosion rates by a factor of 21, and higher pH values (pH>12) when compared with concrete specimens prepared from class C Fly ash (GPCMN). Microstructure and pore characterization of GPC prepared using class F fly ash revealed lower porosity by a factor of 2.5 as compared with thier counterparts made using GPC-MN. The superior performace of GPC prepared with the class F fly ash could be attributed to the dense pore structure and formation of the protective layer of calcium and sodium alumino silicate hydrates (C/N-A-S-H) geopolymeric gels around the steel reinforcement. Elevated Temperature: Geopolymers are an emerging class of cementitious binders which possess a potential for high temperature resistance that could possibly be utilized in applications such as nozzles, aspirators and refractory linings. This study reports on the results of an investigation into the performance of a fly ash based geopolymer binder in high temperature environments. Geopolymer concrete (GPC) was prepared using eleven types of fly ashes obtained from four countries. High content alumina and silica sand was used in the mix for preparing GPC. GPC was subjected to thermal shock tests following ASTM C 1100-88. The GPC samples prepared with tabular alumina were kept at 1093° C and immediately quenched in water. GPC specimens

  2. Physical and chemical changes in whey protein concentrate stored at elevated temperature and humidity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The chemistry of whey protein concentrate (WPC) under adverse storage conditions was monitored to provide information on shelf life in hot, humid areas. WPC34 (34.9 g protein/100 g) and WPC80 (76.8 g protein/100 g) were stored for up to 18 mo under ambient conditions and at elevated temperature and...

  3. Physiological, biochemical and molecular responses of the potato (Solanum tuberosum L.) plant to moderately elevated temperature.

    PubMed

    Hancock, Robert D; Morris, Wayne L; Ducreux, Laurence J M; Morris, Jenny A; Usman, Muhammad; Verrall, Susan R; Fuller, John; Simpson, Craig G; Zhang, Runxuan; Hedley, Pete E; Taylor, Mark A

    2014-02-01

    Although significant work has been undertaken regarding the response of model and crop plants to heat shock during the acclimatory phase, few studies have examined the steady-state response to the mild heat stress encountered in temperate agriculture. In the present work, we therefore exposed tuberizing potato plants to mildly elevated temperatures (30/20 °C, day/night) for up to 5 weeks and compared tuber yield, physiological and biochemical responses, and leaf and tuber metabolomes and transcriptomes with plants grown under optimal conditions (22/16 °C). Growth at elevated temperature reduced tuber yield despite an increase in net foliar photosynthesis. This was associated with major shifts in leaf and tuber metabolite profiles, a significant decrease in leaf glutathione redox state and decreased starch synthesis in tubers. Furthermore, growth at elevated temperature had a profound impact on leaf and tuber transcript expression with large numbers of transcripts displaying a rhythmic oscillation at the higher growth temperature. RT-PCR revealed perturbation in the expression of circadian clock transcripts including StSP6A, previously identified as a tuberization signal. Our data indicate that potato plants grown at moderately elevated temperatures do not exhibit classic symptoms of abiotic stress but that tuber development responds via a diversity of biochemical and molecular signals.

  4. Test System for Elevated Temperature Characterization of Thin Metallic Foils (Preprint)

    DTIC Science & Technology

    2010-01-01

    19428-2959, USA. 13. Hartman, G.A., Zawada , L.P., and Russ, S.M., “Techniques for Elevated Temperature Testing of Advanced Ceramic Composite...CT, 1988, pp. 31-38. 14. Butkus, L.M., Zawada , L.P., and Hartman, G.A., “Fatigue Test Methodology and Resutls for Ceramic Matrix Composites at

  5. CHARACTERISTICS OF MERCURY DESORPTION FROM SORBENTS AT ELEVATED TEMPERATURES. (R822721C697)

    EPA Science Inventory

    This study investigated the dynamic desorption characteristics of mercury during the thermal treatment of mercury-loaded sorbents at elevated temperatures under fixed-bed operations. Experiments were carried out in a 25.4 mm ID quartz bed enclosed in an electric furnace. ...

  6. CHARACTERISTICS OF MERCURY DESORPTION FROM SORBENTS AT ELEVATED TEMPERATURES. (R826694C697)

    EPA Science Inventory

    This study investigated the dynamic desorption characteristics of mercury during the thermal treatment of mercury-loaded sorbents at elevated temperatures under fixed-bed operations. Experiments were carried out in a 25.4 mm ID quartz bed enclosed in an electric furnace. ...

  7. The Application of Laser Speckle Interferometry to Measure Strain at Elevated Temperatures and Various Loading Rates

    DTIC Science & Technology

    1990-05-01

    MTL TR 90-23 lAD IAD- A225 583 JILL COPY THE APPLICATION OF LASER SPECKLE INTERFEROMETRY TO MEASURE STRAIN AT ELEVATED TEMPERATURES AND VARIOUS...specimen was visable. Then LSI was used to measure further straining in the necking regions. The second question to be answered was whc:’,- cr LSI

  8. Immobilization of imidazole moieties in polymer electrolyte composite membrane for elevated temperature fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Ke; Zhou, Bei; Ye, Gongbo; Pan, Mu; Zhang, Haining

    2015-12-01

    Development of membrane electrolyte with reasonable proton conductivity at elevated temperature without external humidification is essential for practical applications of elevated temperature proton exchange membrane fuel cells. Herein, a novel polymer electrolyte composite membrane using imidazole as anhydrous proton carriers for elevated temperature fuel cells is investigated. The imidazole moieties are immobilized inside the Nafion/poly(tetrafluoroethylene) (PTFE) composite membrane through in situ formation of imidazole functionalized silica nanoparticles in Nafion dispersion. The thus-formed membrane exhibits strong Coulombic interaction between negatively charged sulfonic acid groups of Nafion and protonated imidazole moieties, leading to an anhydrous proton conductivity of 0.018 S cm-1 at 180 °C. With the introduction of PTFE matrix, the mechanical strength of the membrane is greatly improved. The peak power density of a single cell assembled from the hybrid membrane is observed to be 130 mW cm-2 under 350 mA cm-2 at 110 °C without external humidification and it remains stable for 20 h continuous operation. The obtained results demonstrate that the developed composite membranes could be utilized as promising membrane electrolytes for elevated temperature fuel cells.

  9. Rod-type extensometers in long-term elevated temperature service

    NASA Astrophysics Data System (ADS)

    Dubois, A. O.; Nelson, P. H.; Hood, M.; Binnall, E.

    1982-09-01

    At Stripa, Sweden, 35 rod type extensometers were used to measure displacements within the granite rock mass surrounding electrical heaters emplaced in the floor of an underground entry. The performance of currently available rock instrumentation when subjected to long term service at elevated temperatures are thermomechanically evaluated.

  10. Modeling of the viscoelastic behavior of a polyimide matrix at elevated temperature

    NASA Astrophysics Data System (ADS)

    Crochon, Thibaut

    Use of Polymer Matrix Composite Materials (PMCMs) in aircraft engines requires materials able to withstand extreme service conditions, such as elevated temperatures, high mechanical loadings and an oxidative environment. In such an environment, the polymer matrix is likely to exhibit a viscoelastic behavior dependent on the mechanical loading and temperature. In addition, the combined effects of elevated temperature and the environment near the engines are likely to increase physical as well as chemical aging. These various parameters need to be taken into consideration for the designer to be able to predict the material behavior over the service life of the components. The main objective of this thesis was to study the viscoelastic behavior of a high temperature polyimide matrix and develop a constitutive theory able to predict the material behavior for every of service condition. Then, the model had to have to be implemented into commercially available finite-element software such as ABAQUS or ANSYS. Firstly, chemical aging of the material at service temperature was studied. To that end, a thermogravimetric analysis of the matrix was conducted on powder samples in air atmosphere. Two kinds of tests were performed: i) kinetic tests in which powder samples were heated at a constant rate until complete sublimation; ii) isothermal tests in which the samples were maintained at a constant temperature for 24 hours. The first tests were used to develop a degradation model, leading to an excellent fit of the experimental data. Then, the model was used to predict the isothermal data but which much less success, particularly for the lowest temperatures. At those temperatures, the chemical degradation was preceded by an oxidation phase which the model was not designed to predict. Other isothermal degradation tests were also performed on tensile tests samples instead of powders. Those tests were conducted at service temperature for a much longer period of time. The samples

  11. Explosive scabbling of structural materials

    DOEpatents

    Bickes, Jr., Robert W.; Bonzon, Lloyd L.

    2002-01-01

    A new approach to scabbling of surfaces of structural materials is disclosed. A layer of mildly energetic explosive composition is applied to the surface to be scabbled. The explosive composition is then detonated, rubbleizing the surface. Explosive compositions used must sustain a detonation front along the surface to which it is applied and conform closely to the surface being scabbled. Suitable explosive compositions exist which are stable under handling, easy to apply, easy to transport, have limited toxicity, and can be reliably detonated using conventional techniques.

  12. Method of binding structural material

    DOEpatents

    Wagh, Arun S.; Antink, Allison L.

    2007-12-25

    A structural material of a polystyrene base and the reaction product of the polystyrene base and a solid phosphate ceramic. The ceramic is applied as a slurry which includes one or more of a metal oxide or a metal hydroxide with a source of phosphate to produce a phosphate ceramic and a poly (acrylic acid or acrylate) or combinations or salts thereof and polystyrene or MgO applied to the polystyrene base and allowed to cure so that the dried aqueous slurry chemically bonds to the polystyrene base. A method is also disclosed of applying the slurry to the polystyrene base.

  13. Fatigue of a 3D Orthogonal Non-crimp Woven Polymer Matrix Composite at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Wilkinson, M. P.; Ruggles-Wrenn, M. B.

    2017-02-01

    Tension-tension fatigue behavior of two polymer matrix composites (PMCs) was studied at elevated temperature. The two PMCs consist of the NRPE polyimide matrix reinforced with carbon fibers, but have different fiber architectures: the 3D PMC is a singly-ply non-crimp 3D orthogonal weave composite and the 2D PMC, a laminated composite reinforced with 15 plies of an eight harness satin weave (8HSW) fabric. In order to assess the performance and suitability of the two composites for use in aerospace components designed to contain high-temperature environments, mechanical tests were performed under temperature conditions simulating the actual operating conditions. In all elevated temperature tests performed in this work, one side of the test specimen was at 329 °C while the other side was open to ambient laboratory air. The tensile stress-strain behavior of the two composites was investigated and the tensile properties measured for both on-axis (0/90) and off-axis (±45) fiber orientations. Elevated temperature had little effect on the on-axis tensile properties of the two composites. The off-axis tensile strength of both PMCs decreased slightly at elevated temperature. Tension-tension fatigue tests were conducted at elevated temperature at a frequency of 1.0 Hz with a ratio of minimum stress to maximum stress of R = 0.05. Fatigue run-out was defined as 2 × 105 cycles. Both strain accumulation and modulus evolution during cycling were analyzed for each fatigue test. The laminated 2D PMC exhibited better fatigue resistance than the 3D composite. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. Post-test examination under optical microscope revealed severe delamination in the laminated 2D PMC. The non-crimp 3D orthogonal weave composite offered improved delamination resistance.

  14. The Environmental Cost of Misinformation: Why the Recommendation to Use Elevated Temperatures for Handwashing is Problematic

    PubMed Central

    Carrico, Amanda R.; Spoden, Micajah; Wallston, Kenneth A.; Vandenbergh, Michael P.

    2013-01-01

    Multiple government and health organizations recommend the use of warm or hot water in publications designed to educate the public on best practices for washing one’s hands. This is despite research suggesting that the use of an elevated water temperature does not improve handwashing efficacy, but can cause hand irritation. There is reason to believe that the perception that warm or hot water is more effective at cleaning one’s hands is pervasive, and may be one factor that is driving up unnecessary energy consumption and greenhouse gas emissions. We examine handwashing practices and beliefs about water temperature using a survey of 510 adults in the United States. The survey included measures of handwashing frequency, duration, the proportion of time an elevated temperature was used, and beliefs about water temperature and handwashing efficacy. We also estimate the energy consumed and resultant carbon dioxide equivalent emissions (CO2eq) in the U.S. due to the use of elevated temperatures during handwashing. Participants used an elevated temperature 64% of the time, causing 6.3 million metric tons (MMt) of CO2eq which is 0.1% of total annual emissions and 0.3% of commercial and residential sector emissions. Roughly 69% of the sample believed that elevated temperatures improve handwashing efficacy. Updating these beliefs could prevent 1 MMt of CO2eq annually, exceeding the total emissions from many industrial sources in the U.S. including the Lead and Zinc industries. In addition to causing skin irritation, the recommendation to use an elevated temperature during handwashing contributes to another major threat to public health—climate change. Health and consumer protection organizations should consider advocating for the use of a “comfortable” temperature rather than warm or hot water. PMID:23814480

  15. Plastic Responses to Elevated Temperature in Low and High Elevation Populations of Three Grassland Species

    PubMed Central

    Frei, Esther R.; Ghazoul, Jaboury; Pluess, Andrea R.

    2014-01-01

    Local persistence of plant species in the face of climate change is largely mediated by genetic adaptation and phenotypic plasticity. In species with a wide altitudinal range, population responses to global warming are likely to differ at contrasting elevations. In controlled climate chambers, we investigated the responses of low and high elevation populations (1200 and 1800 m a.s.l.) of three nutrient-poor grassland species, Trifolium montanum, Ranunculus bulbosus, and Briza media, to ambient and elevated temperature. We measured growth-related, reproductive and phenological traits, evaluated differences in trait plasticity and examined whether trait values or plasticities were positively related to approximate fitness and thus under selection. Elevated temperature induced plastic responses in several growth-related traits of all three species. Although flowering phenology was advanced in T. montanum and R. bulbosus, number of flowers and reproductive allocation were not increased under elevated temperature. Plasticity differed between low and high elevation populations only in leaf traits of T. montanum and B. media. Some growth-related and phenological traits were under selection. Moreover, plasticities were not correlated with approximate fitness indicating selectively neutral plastic responses to elevated temperature. The observed plasticity in growth-related and phenological traits, albeit variable among species, suggests that plasticity is an important mechanism in mediating plant responses to elevated temperature. However, the capacity of species to respond to climate change through phenotypic plasticity is limited suggesting that the species additionally need evolutionary adaptation to adjust to climate change. The observed selection on several growth-related and phenological traits indicates that the study species have the potential for future evolution in the context of a warming climate. PMID:24901500

  16. The rheology of structured materials

    NASA Astrophysics Data System (ADS)

    Sun, Ning

    2000-10-01

    In this work, the rheological properties of structured materials are studied via both theoretical (continuum mechanics and molecular theory) and experimental approaches. Through continuum mechanics, a structural model, involving shear-induced structural breakdown and buildup, is extended to model biofluids. In particular, we study the cases of steady shear flow, hysteresis, yield stress, small amplitude oscillatory flow as well as non-linear viscoelasticity. Model predictions are successfully compared with experimental data on complex materials such as blood and a penicillin suspension. Next, modifications are introduced into the network model. A new formulation involving non-affine motion is proposed and its applications are presented. The major improvement is that a finite elongational viscosity is predicted for finite elongational rate, contrary to infinite elongational viscosities existing at some elongational rates predicted by most previous network models. Comparisons with experimental data on shear viscosity, primary normal stress coefficient and elongational viscosity are given, in terms of the same set of model parameters. Model predictions for the stress growth are also shown. The model is successfully tested with data on a polyisobutylene solution (S1), on a polystyrene solution and on a poly-alpha-methylstyrene solution. A further extension of the network model is related to the prediction of the stress jump phenomenon which is defined as the instantaneous gain or loss of stress on startup or cessation of a deformation. It is not predicted by most existing models. In this work, the internal viscosity idea used in the dumbbell model is incorporated into the transient network model. Via appropriate approximations, a closed form constitutive equation, which predicts a stress jump, is obtained. Successful comparisons with the available stress jump measurements are given. In addition, the model yields good quantitative predictions of the standard steady

  17. Life prediction methodology for thermal-mechanical fatigue and elevated temperature creep design

    NASA Astrophysics Data System (ADS)

    Annigeri, Ravindra

    Nickel-based superalloys are used for hot section components of gas turbine engines. Life prediction techniques are necessary to assess service damage in superalloy components resulting from thermal-mechanical fatigue (TMF) and elevated temperature creep. A new TMF life model based on continuum damage mechanics has been developed and applied to IN 738 LC substrate material with and without coating. The model also characterizes TMF failure in bulk NiCoCrAlY overlay and NiAl aluminide coatings. The inputs to the TMF life model are mechanical strain range, hold time, peak cycle temperatures and maximum stress measured from the stabilized or mid-life hysteresis loops. A viscoplastic model is used to predict the stress-strain hysteresis loops. A flow rule used in the viscoplastic model characterizes the inelastic strain rate as a function of the applied stress and a set of three internal stress variables known as back stress, drag stress and limit stress. Test results show that the viscoplastic model can reasonably predict time-dependent stress-strain response of the coated material and stress relaxation during hold times. In addition to the TMF life prediction methodology, a model has been developed to characterize the uniaxial and multiaxial creep behavior. An effective stress defined as the applied stress minus the back stress is used to characterize the creep recovery and primary creep behavior. The back stress has terms representing strain hardening, dynamic recovery and thermal recovery. Whenever the back stress is greater than the applied stress, the model predicts a negative creep rate observed during multiple stress and multiple temperature cyclic tests. The model also predicted the rupture time and the remaining life that are important for life assessment. The model has been applied to IN 738 LC, Mar-M247, bulk NiCoCrAlY overlay coating and 316 austenitic stainless steel. The proposed model predicts creep response with a reasonable accuracy for wide range of

  18. Ab initio studies of equations of state and chemical reactions of reactive structural materials

    NASA Astrophysics Data System (ADS)

    Zaharieva, Roussislava

    subject of studies of the shock or thermally induced chemical reactions of the two solids comprising these reactive materials, from first principles, is a relatively new field of study. The published literature on ab initio techniques or quantum mechanics based approaches consists of the ab initio or ab initio-molecular dynamics studies in related fields that contain a solid and a gas. One such study in the literature involves a gas and a solid. This is an investigation of the adsorption of gasses such as carbon monoxide (CO) on Tungsten. The motivation for these studies is to synthesize alternate or synthetic fuel technology by Fischer-Tropsch process. In this thesis these studies are first to establish the procedure for solid-solid reaction and then to extend that to consider the effects of mechanical strain and temperature on the binding energy and chemisorptions of CO on tungsten. Then in this thesis, similar studies are also conducted on the effect of mechanical strain and temperature on the binding energies of Titanium and hydrogen. The motivations are again to understand the method and extend the method to such solid-solid reactions. A second motivation is to seek strained conditions that favor hydrogen storage and strain conditions that release hydrogen easily when needed. Following the establishment of ab initio and ab initio studies of chemical reactions between a solid and a gas, the next step of research is to study thermally induced chemical reaction between two solids (Ni+Al). Thus, specific new studies of the thesis are as follows: (1) Ab initio Studies of Binding energies associated with chemisorption of (a) CO on W surfaces (111, and 100) at elevated temperatures and strains and (b) adsorption of hydrogen in titanium base. (2) Equations of state of mixtures of reactive material structures from ab initio methods. (3) Ab initio studies of the reaction initiation, transition states and reaction products of intermetallic mixtures of (Ni+Al) at elevated

  19. Carbon structural materials for fusion reactors

    SciTech Connect

    Virgiliev, Yu.S.; Kurolenkin, E.I.

    1993-12-31

    This report describes properties of several structural carbon materials being investigated as materials for fusion reactors. Materials include: graphite, graphite doped with boron and titanium; and C-C composites. Radiation effects and additive effects are described.

  20. Method and structure for passivating semiconductor material

    DOEpatents

    Pankove, Jacques I.

    1981-01-01

    A structure for passivating semiconductor material comprises a substrate of crystalline semiconductor material, a relatively thin film of carbon disposed on a surface of the crystalline material, and a layer of hydrogenated amorphous silicon deposited on the carbon film.

  1. The effects of physical aging at elevated temperatures on the viscoelastic creep on IM7/K3B

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Feldman, Mark

    1994-01-01

    Physical aging at elevated temperature of the advanced composite IM7/K3B was investigated through the use of creep compliance tests. Testing consisted of short term isothermal, creep/recovery with the creep segments performed at constant load. The matrix dominated transverse tensile and in-plane shear behavior were measured at temperatures ranging from 200 to 230 C. Through the use of time based shifting procedures, the aging shift factors, shift rates and momentary master curve parameters were found at each temperature. These material parameters were used as input to a predictive methodology, which was based upon effective time theory and linear viscoelasticity combined with classical lamination theory. Long term creep compliance test data was compared to predictions to verify the method. The model was then used to predict the long term creep behavior for several general laminates.

  2. Ultimate Tensile Strength as a Function of Test Rate for Various Ceramic Matrix Composites at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.; Gyekenyesi, John P.

    2002-01-01

    Ultimate tensile strength of five different continuous fiber-reinforced ceramic composites, including SiC/BSAS (2D 2 types), SiC/MAS-5 (2D), SiC/SiC (2D enhanced), and C/SiC(2D) was determined as a function of test rate at I 100 to 1200 'C in air. All five composite materials exhibited a significant dependency of ultimate strength on test rate such that the ultimate strength decreased with decreasing test rate, similar to the behavior observed in many advanced monolithic ceramics at elevated temperatures. The application of the preloading technique as well as the prediction of life from one loading configuration (constant stress rate) to another (constant stress loading) for SiC/BSAS suggested that the overall macroscopic failure mechanism of the composites would be the one governed by a power-law type of damage evolution/accumulation, analogous to slow crack growth commonly observed in advanced monolithic ceramics.

  3. Infrared spectroscopic studies of the effect of elevated temperature on the association of pyroglutamic acid with clay and other minerals

    NASA Technical Reports Server (NTRS)

    Macklin, J. W.; White, D. H.

    1985-01-01

    Fourier transform i.r. measurements of L-pyroglutamic acid dispersed in a matrix of a clay, silica or alumina have been obtained at various temperatures between 25 and 220 degrees C. The i.r. spectrum of L-pyroglutamic acid varies in a manner dependent upon the matrix material and shows considerable change as the temperature of the mixtures is increased. The differences in the spectrum at elevated temperatures are explained in terms of a chemical reaction between hydroxyl groups in the matrix and the carboxylic acid. The i.r. spectra of trimethylsilyl derivatives of L-pyroglutamic acid and aluminum pyroglutamate were also measured to assist the understanding of spectra and interpretation of the spectral changes dependent upon increasing temperature.

  4. Effects of elevated temperature postharvest on color aspect, physiochemical characteristics, and aroma components of pineapple fruits.

    PubMed

    Liu, Chuanhe; Liu, Yan

    2014-12-01

    In this work, 2 separate experiments were performed to describe the influence of elevated temperature treatments postharvest on the color, physiochemical characteristics and aroma components of pineapple fruits during low-temperature seasons. The L* (lightness) values of the skin and pulp of pineapple fruits were decreased. The a* (greenness-redness) and b* (blueness-yellowness) values of the skin and pulp were all markedly increased. The elevated temperature significantly increased the contents of total soluble solids (TSS) and slightly affected contents of vitamin C (nonsignificant). Titratable acidity (TA) of pineapple fruits were notably decreased, whereas the values of TSS/TA of pineapple fruits were significantly increased. The firmness of the pineapple fruits decreased and more esters and alkenes were identified. The total relative contents of esters were increased, and the total relative contents of alkenes were decreased.

  5. Elevated Temperature Strength of Fine-Grained INCONEL Alloy MA754

    SciTech Connect

    T.C. Totemeier; T.M. Lillo; J.A. Simpson

    2005-09-01

    Elevated temperature tensile and creep-rupture tests were performed on INCONEL alloy MA754 in an as-rolled, fine-grained condition. Tensile tests were performed at 25, 800, 900, and 1000°C; creep-rupture tests were performed at 800, 900, and 1000°C. The elevated temperature strength in the fine-grained condition was approximately 25% of the standard, coarse-grained annealed condition. While good ductility was observed in tensile tests at a nominal strain rate of 1×10-3 sec-1, ductility in creep-rupture tests was very low, with failure elongations less than 5% and no reduction in area. Creep deformation appeared to occur solely by cavity formation and growth.

  6. Effect of hydrogen on the integrity of aluminium-oxide interface at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Li, Meng; Xie, De-Gang; Ma, Evan; Li, Ju; Zhang, Xi-Xiang; Shan, Zhi-Wei

    2017-02-01

    Hydrogen can facilitate the detachment of protective oxide layer off metals and alloys. The degradation is usually exacerbated at elevated temperatures in many industrial applications; however, its origin remains poorly understood. Here by heating hydrogenated aluminium inside an environmental transmission electron microscope, we show that hydrogen exposure of just a few minutes can greatly degrade the high temperature integrity of metal-oxide interface. Moreover, there exists a critical temperature of ~150 °C, above which the growth of cavities at the metal-oxide interface reverses to shrinkage, followed by the formation of a few giant cavities. Vacancy supersaturation, activation of a long-range diffusion pathway along the detached interface and the dissociation of hydrogen-vacancy complexes are critical factors affecting this behaviour. These results enrich the understanding of hydrogen-induced interfacial failure at elevated temperatures.

  7. Microstructural stability of wrought, laser and electron beam glazed NARloy-Z alloy at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Singh, J.; Jerman, G.; Bhat, B.; Poorman, R.

    1993-01-01

    Microstructure of wrought, laser, and electron-beam glazed NARloy-Z(Cu-3 wt.% Ag-0.5 wt.% Zr) was investigated for thermal stability at elevated temperatures (539 to 760 C (1,100 to 1,400 F)) up to 94 h. Optical and scanning electron microscopy and electron probe microanalysis were employed for studying microstructural evolution and kinetics of precipitation. Grain boundary precipitation and precipitate free zones (PFZ's) were observed in the wrought alloy after exposing to temperatures above 605 C (1,120 F). The fine-grained microstructure observed in the laser and electron-beam glazed NARloy-Z was much more stable at elevated temperatures. Microstructural changes correlated well with hardness measurements.

  8. Effect of hydrogen on the integrity of aluminium–oxide interface at elevated temperatures

    PubMed Central

    Li, Meng; Xie, De-Gang; Ma, Evan; Li, Ju; Zhang, Xi-Xiang; Shan, Zhi-Wei

    2017-01-01

    Hydrogen can facilitate the detachment of protective oxide layer off metals and alloys. The degradation is usually exacerbated at elevated temperatures in many industrial applications; however, its origin remains poorly understood. Here by heating hydrogenated aluminium inside an environmental transmission electron microscope, we show that hydrogen exposure of just a few minutes can greatly degrade the high temperature integrity of metal–oxide interface. Moreover, there exists a critical temperature of ∼150 °C, above which the growth of cavities at the metal–oxide interface reverses to shrinkage, followed by the formation of a few giant cavities. Vacancy supersaturation, activation of a long-range diffusion pathway along the detached interface and the dissociation of hydrogen-vacancy complexes are critical factors affecting this behaviour. These results enrich the understanding of hydrogen-induced interfacial failure at elevated temperatures. PMID:28218260

  9. Fatigue crack growth at elevated temperature 316 stainless steel and H-13 steel

    NASA Technical Reports Server (NTRS)

    Chen, W. C.; Liu, H. W.

    1976-01-01

    Crack growths were measured at elevated temperatures under four types of loading: pp, pc, cp, and cc. In H-13 steel, all these four types of loading gave nearly the same crack growth rates, and the length of hold time had negligible effects. In AISI 316 stainless steel, the hold time effects on crack growth rate were negligible if the loading was tension-tension type; however, these effects were significant in reversed bending load, and the crack growth rates under these four types of loading varied considerably. Both tensile and compressive hold times caused increased crack growth rate, but the compressive hold period was more deleterious than the tensile one. Metallographic examination showed that all the crack paths under different types of loading were largely transgranular for both CTS tension-tension specimens and SEN reversed cantilever bending specimens. In addition, an electric potential technique was used to monitor crack growth at elevated temperature.

  10. Improved Mechanical Properties of Various Fabric-Reinforced Geocomposite at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Samal, Sneha; Phan Thanh, Nhan; Petríková, Iva; Marvalová, Bohadana

    2015-07-01

    This article signifies the improved performance of the various types of fabric reinforcement of geopolymer as a function of physical, thermal, mechanical, and heat-resistant properties at elevated temperatures. Geopolymer mixed with designed Si:Al ratios of 15.6 were synthesized using three different types of fabric reinforcement such as carbon, E-glass, and basalt fibers. Heat testing was conducted on 3-mm-thick panels with 15 × 90 mm surface exposure region. The strength of carbon-based geocomposite increased toward a higher temperature. The basalt-reinforced geocomposite strength decreased due to the catastrophic failure in matrix region. The poor bridging effect and dissolution of fabric was observed in the E-glass-reinforced geocomposite. At an elevated temperature, fiber bridging was observed in carbon fabric-reinforced geopolymer matrix. Among all the fabrics, carbon proved to be suitable candidate for the high-temperature applications in thermal barrier coatings and fire-resistant panels.

  11. Separation of CO{sub 2} from CO{sub 2}/N{sub 2} mixture using supported polymeric liquid membranes at elevated temperatures

    SciTech Connect

    Jeong, S.H.; Lee, K.H.

    1999-09-01

    Novel supported polymeric liquid (SPL) membranes have been prepared and shown to be applicable for the separation of CO{sub 2} from mixtures with N{sub 2} at the elevated temperature encountered in flue gas. The membranes were fabricated by immobilizing polystyrene, polyethylene, and polydimethylsiloxane into the pores of borosilicate glass supports. At 250 C, the CO{sub 2} permeability and CO{sub 2}/N{sub 2} separation factors were 3000--9000 barrer and 1.7--3.7, respectively. It was shown that polymers which have a lower T{sub g} or melting temperature than the operating temperature can be used as SPL membrane materials at elevated temperatures.

  12. Mechanical properties of turbine blade alloys in hydrogen at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Deluca, D. P.

    1981-01-01

    The mechanical properties of single crystal turbine blade alloys in a gaseous hydrogen environment were determined. These alloys are proposed for use in space propulsion systems in pure or partial high pressure hydrogen environments at elevated temperatures. Mechanical property tests included: tensile, creep, low fatigue (LCF), and crack growth. Specimens were in both transverse and longitudinal directions relative to the casting solidification direction. Testing was conducted on solid specimens exposed to externally pressurized environments of gaseous hydrogen and hydrogen-enriched steam.

  13. Alternative solvents for elevated-temperature solid-phase parallel synthesis. Application to thionation of amides.

    PubMed

    Coats, Steven J; Link, Jeffrey S; Hlasta, Dennis J

    2003-03-06

    A new class of higher-boiling solvents was investigated for elevated-temperature solid-phase parallel synthesis. Extremely low vapor pressures at high temperature and a broader range of solvent effect tuning make this new class of solvents an ideal choice for high-temperature parallel solid-phase synthesis. Benzyl benzoate is identified as a superior high-boiling solvent for parallel solid-phase Lawesson's thionation reactions.

  14. Feasibility demonstration of a hyperfiltration technique to reclaim shower wastewater at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Hester, J. C.; Brandon, C. A.

    1972-01-01

    A feasibility demonstration of a hyperfiltration technique to determine its capability to reclaim shower wastewater at elevated temperature was conducted. Approximately twenty (20) gallons of typical shower water were processed through a dynamically formed membrane at a temperature of 167 F. Chemical and bacterial analyses of the product water are presented which show compliance with all potable water requirements established for extended manned space missions. In addition, subsystem characteristics and capabilities are discussed.

  15. Guidelines and procedures for design of Class 1 elevated temperature nuclear system components

    SciTech Connect

    Not Available

    1986-09-01

    This standard provides guidelines and procedures which may be used by the manufacturer in satisfying the requirements given for design of class 1 elevated temperature nuclear system components. Guidance is given regarding planning and control of design analysis. A sequence for calculations is recommended. Methods of analysis, including procedures to account for environmental effects, are given which are acceptable in principle to the owner. A format is provided for use in documentation of design analyses.

  16. Elucidating the Effect of Alloying Elements on the Behavior of Austenitic Stainless Steels at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Naghizadeh, Meysam; Mirzadeh, Hamed

    2016-12-01

    The effect of carbon and molybdenum on elevated temperature behavior of austenitic stainless steels was studied. It was revealed that carbon does not alter the overall grain coarsening behavior but molybdenum significantly retards the growth of grains toward higher temperatures and slower kinetics and effectively increases the grain growth activation energy due to an interaction energy between Mo and grain boundaries. These observations were based on especial activation energy plots, which facilitate the interpretation of results.

  17. Application of X-ray Absorption Spectroscopy to the study of nuclear structural materials

    NASA Astrophysics Data System (ADS)

    Liu, Shanshan

    One of key technologies for the next generation nuclear systems are advanced materials, including high temperature structural materials, fast neutron resistance core materials and so on. Local structure determination in these systems, which often are crystallographically intractable, is critical to gaining an understanding of their properties. In this thesis, X-ray Absorption Spectroscopy (XAS), including Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES), is used to examine the geometric and electronic structure of nuclear structural materials under varying conditions. The thesis is divided into two main sections. The first examines the structural analysis of nanostructured ferritic alloys (NFA) which are dispersion strengthened by an ultra high density of Y-Ti-O enriched nano-features, resulting in remarkable high temperature creep strength and radiation damage resistance. Titanium and Yttrium K-edge XAS shows commercial alloys MA957 and J12YWT more closely resemble the as received Fe-14Cr-3W-0.4Ti (wt. %) powders, and mechanically alloyed (MA) powders with 0.25Y2O3 (wt. %). It shows that a significant fraction of substitutional Ti remains dissolved in the (BCC) ferrite matrix. In contrast, annealed powders and hot isostatic press (HIP) consolidated alloys show high temperature heat treatments shift the Y and Ti to more oxidized states that are consistent with combinations of Y2Ti2O7 and, especially, TiO. The second section describes corrosion studies of Pb with 316L stainless steel, molybdenum and spinet (MgAl2O4) at high temperature by XAS. The corrosion of fuel cladding and structural materials by liquid lead at elevated temperatures is an issue that must be considered when designing advanced nuclear systems and high-power spallation neutron targets. The results of ex-situ studies show that a Mo substrate retained a smooth and less corroded surface than 316L stainless steel sample at elevated temperature. In

  18. Interlaminar Fracture Toughness of CF/PEI and GF/PEI Composites at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Kim, Ki-Young; Ye, Lin; Phoa, Kim-Meng

    2004-05-01

    An experimental study has been conducted to assess temperature effects on mode-I and mode-II interlaminar fracture toughness of carbon fibre/polyetherimide (CF/PEI) and glass fibre/polyetherimide (GF/PEI) thermoplastic composites. Mode-I double cantilever beam (DCB) and mode-II end notched flexure (ENF) tests were carried out in a temperature range from 25 to 130°C. For both composite systems, the initiation toughness, G IC, ini and G IIC, ini, of mode-I and mode-II interlaminar fracture decreased with an increase in temperature, while the propagation toughness, G IC, prop and G IIC, prop, displayed a reverse trend. Three main mechanisms were identified to contribute to the interlaminar fracture toughness, namely matrix deformation, fibre/matrix interfacial failure and fibre bridging during the delamination process. At delamination initiation, the weakened fibre/matrix interface at elevated temperatures plays an overriding role with the delamination growth initiating at the fibre/matrix interface, rather than from a blunt crack tip introduced by the insert film, leading to low values of G IC, ini and G IIC, ini. On the other hand, during delamination propagation, enhanced matrix deformation at elevated temperatures and fibre bridging promoted by weakened fibre/matrix interface result in greater G IC, prop values. Meanwhile enhanced matrix toughness and ductility at elevated temperatures also increase the stability of mode-II crack growth.

  19. Carbohydrate concentrations and freezing stress resistance of silver birch buds grown under elevated temperature and ozone.

    PubMed

    Riikonen, Johanna; Kontunen-Soppela, Sari; Vapaavuori, Elina; Tervahauta, Arja; Tuomainen, Marjo; Oksanen, Elina

    2013-03-01

    The effects of slightly elevated temperature (+0.8 °C), ozone (O3) concentration (1.3 × ambient O3 concentration) and their combination on over-wintering buds of Betula pendula Roth were studied after two growing seasons of exposure in the field. Carbohydrate concentrations, freezing stress resistance (FSR), bud dry weight to fresh weight ratio, and transcript levels of cytochrome oxidase (COX), alternative oxidase (AOX) and dehydrin (LTI36) genes were studied in two clones (clones 12 and 25) in December. Elevated temperature increased the bud dry weight to fresh weight ratio and the ratio of raffinose family oligosaccharides to sucrose and the transcript levels of the dehydrin (LTI36) gene (in clone 12 only), but did not alter the FSR of the buds. Genotype-specific alterations in carbohydrate metabolism were found in the buds grown under elevated O3. The treatments did not significantly affect the transcript level of the COX or AOX genes. No clear pattern of an interactive effect between elevated temperature and O3 concentration was found. According to these data, the increase in autumnal temperatures and slightly increasing O3 concentrations do not increase the risk for freeze-induced damage in winter in silver birch buds, although some alterations in bud physiology occur.

  20. Compartment-specific transcriptomics in a reef-building coral exposed to elevated temperatures.

    PubMed

    Mayfield, Anderson B; Wang, Yu-Bin; Chen, Chii-Shiarng; Lin, Chung-Yen; Chen, Shu-Hwa

    2014-12-01

    Although rising ocean temperatures threaten scleractinian corals and the reefs they construct, certain reef corals can acclimate to elevated temperatures to which they are rarely exposed in situ. Specimens of the model Indo-Pacific reef coral Pocillopora damicornis collected from upwelling reefs of Southern Taiwan were previously found to have survived a 36-week exposure to 30°C, a temperature they encounter infrequently and one that can elicit the breakdown of the coral-dinoflagellate (genus Symbiodinium) endosymbiosis in many corals of the Pacific Ocean. To gain insight into the subcellular pathways utilized by both the coral hosts and their mutualistic Symbiodinium populations to acclimate to this temperature, mRNAs from both control (27°C) and high (30°C)-temperature samples were sequenced on an Illumina platform and assembled into a 236 435-contig transcriptome. These P. damicornis specimens were found to be ~60% anthozoan and 40% microbe (Symbiodinium, other eukaryotic microbes, and bacteria), from an mRNA-perspective. Furthermore, a significantly higher proportion of genes from the Symbiodinium compartment were differentially expressed after two weeks of exposure. Specifically, at elevated temperatures, Symbiodinium populations residing within the coral gastrodermal tissues were more likely to up-regulate the expression of genes encoding proteins involved in metabolism than their coral hosts. Collectively, these transcriptome-scale data suggest that the two members of this endosymbiosis have distinct strategies for acclimating to elevated temperatures that are expected to characterize many of Earth's coral reefs in the coming decades.

  1. Materials research at Stanford University. [composite materials, crystal structure, acoustics

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Research activity related to the science of materials is described. The following areas are included: elastic and thermal properties of composite materials, acoustic waves and devices, amorphous materials, crystal structure, synthesis of metal-metal bonds, interactions of solids with solutions, electrochemistry, fatigue damage, superconductivity and molecular physics and phase transition kinetics.

  2. Bio-inspired variable structural color materials.

    PubMed

    Zhao, Yuanjin; Xie, Zhuoying; Gu, Hongcheng; Zhu, Cun; Gu, Zhongze

    2012-04-21

    Natural structural color materials, especially those that can undergo reversible changes, are attracting increasing interest in a wide variety of research fields. Inspired by the natural creatures, many elaborately nanostructured photonic materials with variable structural colors were developed. These materials have found important applications in switches, display devices, sensors, and so on. In this critical review, we will provide up-to-date research concerning the natural and bio-inspired photonic materials with variable structural colors. After introducing the variable structural colors in natural creatures, we will focus on the studies of artificial variable structural color photonic materials, including their bio-inspired designs, fabrications and applications. The prospects for the future development of these fantastic variable structural color materials will also be presented. We believe this review will promote the communications among biology, bionics, chemistry, optical physics, and material science (196 references).

  3. NASICON-Structured Materials for Energy Storage.

    PubMed

    Jian, Zelang; Hu, Yong-Sheng; Ji, Xiulei; Chen, Wen

    2017-02-21

    The demand for electrical energy storage (EES) is ever increasing, which calls for better batteries. NASICON-structured materials represent a family of important electrodes due to its superior ionic conductivity and stable structures. A wide range of materials have been considered, where both vanadium-based and titanium-based materials are recommended as being of great interest. NASICON-structured materials are suitable for both the cathode and the anode, where the operation potential can be easily tuned by the choice of transition metal and/or polyanion group in the structure. NASICON-structured materials also represent a class of solid electrolytes, which are widely employed in all-solid-state ion batteries, all-solid-state air batteries, and hybrid batteries. NASICON-structured materials are reviewed with a focus on both electrode materials and solid-state electrolytes.

  4. Chapter 7: Materials for Launch Vehicle Structures

    NASA Technical Reports Server (NTRS)

    Henson, Grant; Jone, Clyde S. III

    2017-01-01

    This chapter concerns materials for expendable and reusable launch vehicle (LV) structures. An emphasis is placed on applications and design requirements, and how these requirements are met by the optimum choice of materials. Structural analysis and qualification strategies, which cannot be separated from the materials selection process, are described.

  5. Simulation studies on sputtering and reflection from compound materials at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Kenmotsu, T.; Kawamura, T.; Li, Zhijie; Ono, T.; Yamamura, Y.

    Using the ACAT code, we have calculated the energy spectra of boronized graphite under D + ion bombardment. In the case of light ion sputtering, high energy tail of the energy spectra drop sharply compared with the Thompson formula because most sputtered atoms are not due to collision cascade. In this work, we derived a new fitting formula based on the Falcon-Sigmund model instead of the Thompson formula. This fitting formula is in good agreement with the energy spectra in the high energy part. Furthermore, we have simulated surface compositional change in the Hirooka experiment under D + ion bombardment at high temperature. We have applied the ACAT-DIFFUSE code to calculate the compositional change of a boronized graphite. The ACAT-DIFFUSE is a simulation code based on a Monte Carlo method with a binary collision approximation and solves diffusion equations. The ACAT-DIFFUSE was developed to estimate chemical reaction such as methane production. In the present work, we obtained the result which has about 20% in surface composition change.

  6. Heat Transfer Retardation at Elevated Temperatures. Phase I. Analysis of Heat Transfer Retardation Configurations and Materials.

    DTIC Science & Technology

    1983-09-01

    aluminum foil (0.002 in. thick). The other configuration tested was formed with alternate layers of an insulating paper (" Fiberfrax " paper, which has...because " Fiberfrax " has a density of about 15 Ibm/ft3 , as compared to the Dynaquartz density of 4 to 7 lbm/ft 3 depending on the compaction. Thus the

  7. Properties of materials in high pressure hydrogen at room and elevated temperatures

    NASA Technical Reports Server (NTRS)

    Harris, J. A., Jr.

    1972-01-01

    Experimental efforts in this program for this period. Mechanical property tests of wrought and cast nickel-base alloys and one wrought cobalt-base alloy were conducted in 34.5 MN/sq m (5000-psig) helium and hydrogen or hydrogen mixtures. Comparison of test results was made to determine degradation of properties due to the hydrogen environments. All testing was conducted on solid specimens exposed to external gaseous pressure. Specific mechanical properties determined and the testing methods used are summarized.

  8. Properties of materials in high pressure hydrogen at cryogenic, room, and elevated temperatures

    NASA Technical Reports Server (NTRS)

    Harris, J. A., Jr.; Vanwanderham, M. C.

    1973-01-01

    Various tests were conducted to determine the mechanical properties of 12 alloys that are commonly used or proposed for use in pressurized gaseous hydrogen or hydrogen containing environments. Properties determined in the hydrogen environments were compared to properties determined in a pure helium environment at the same conditions to establish environmental degradation. The specific mechanical properties tested include: high-cycle fatigue, low-cycle fatigue, fracture mechanics, creep-rupture, and tensile.

  9. Range-Wide Latitudinal and Elevational Temperature Gradients for the World's Terrestrial Birds: Implications under Global Climate Change

    PubMed Central

    La Sorte, Frank A.; Butchart, Stuart H. M.; Jetz, Walter; Böhning-Gaese, Katrin

    2014-01-01

    Species' geographical distributions are tracking latitudinal and elevational surface temperature gradients under global climate change. To evaluate the opportunities to track these gradients across space, we provide a first baseline assessment of the steepness of these gradients for the world's terrestrial birds. Within the breeding ranges of 9,014 bird species, we characterized the spatial gradients in temperature along latitude and elevation for all and a subset of bird species, respectively. We summarized these temperature gradients globally for threatened and non-threatened species and determined how their steepness varied based on species' geography (range size, shape, and orientation) and projected changes in temperature under climate change. Elevational temperature gradients were steepest for species in Africa, western North and South America, and central Asia and shallowest in Australasia, insular IndoMalaya, and the Neotropical lowlands. Latitudinal temperature gradients were steepest for extratropical species, especially in the Northern Hemisphere. Threatened species had shallower elevational gradients whereas latitudinal gradients differed little between threatened and non-threatened species. The strength of elevational gradients was positively correlated with projected changes in temperature. For latitudinal gradients, this relationship only held for extratropical species. The strength of latitudinal gradients was better predicted by species' geography, but primarily for extratropical species. Our findings suggest threatened species are associated with shallower elevational temperature gradients, whereas steep latitudinal gradients are most prevalent outside the tropics where fewer bird species occur year-round. Future modeling and mitigation efforts would benefit from the development of finer grain distributional data to ascertain how these gradients are structured within species' ranges, how and why these gradients vary among species, and the capacity

  10. Range-wide latitudinal and elevational temperature gradients for the world's terrestrial birds: implications under global climate change.

    PubMed

    La Sorte, Frank A; Butchart, Stuart H M; Jetz, Walter; Böhning-Gaese, Katrin

    2014-01-01

    Species' geographical distributions are tracking latitudinal and elevational surface temperature gradients under global climate change. To evaluate the opportunities to track these gradients across space, we provide a first baseline assessment of the steepness of these gradients for the world's terrestrial birds. Within the breeding ranges of 9,014 bird species, we characterized the spatial gradients in temperature along latitude and elevation for all and a subset of bird species, respectively. We summarized these temperature gradients globally for threatened and non-threatened species and determined how their steepness varied based on species' geography (range size, shape, and orientation) and projected changes in temperature under climate change. Elevational temperature gradients were steepest for species in Africa, western North and South America, and central Asia and shallowest in Australasia, insular IndoMalaya, and the Neotropical lowlands. Latitudinal temperature gradients were steepest for extratropical species, especially in the Northern Hemisphere. Threatened species had shallower elevational gradients whereas latitudinal gradients differed little between threatened and non-threatened species. The strength of elevational gradients was positively correlated with projected changes in temperature. For latitudinal gradients, this relationship only held for extratropical species. The strength of latitudinal gradients was better predicted by species' geography, but primarily for extratropical species. Our findings suggest threatened species are associated with shallower elevational temperature gradients, whereas steep latitudinal gradients are most prevalent outside the tropics where fewer bird species occur year-round. Future modeling and mitigation efforts would benefit from the development of finer grain distributional data to ascertain how these gradients are structured within species' ranges, how and why these gradients vary among species, and the capacity

  11. Characterization of lignin derived from water-only and dilute acid flowthrough pretreatment of poplar wood at elevated temperatures

    SciTech Connect

    Zhang, Libing; Yan, Lishi; Wang, Zheming; Laskar, Dhrubojyoti D.; Swita, Marie S.; Cort, John R.; Yang, Bin

    2015-12-01

    In this study, flowthrough pretreatment of biomass has high potential to valorize lignin derivatives to high-value products, which is vital to enhance the economy of biorefinery plants. Comprehensive understanding of lignin behaviors and solubilization chemistry in aqueous pretreatment such as water-only and dilute acid flowthrough pretreatment is of fundamental importance to achieve the goal of providing flexible platform for lignin utilization. In this study, the effects of flowthrough pretreatment conditions on lignin separation from poplar wood were reported as well as the characteristics of three sub-sets of lignin produced from the pretreatment, including residual lignin in pretreated solid residues (ReL), recovered insoluble lignin in pretreated liquid (RISL), and recovered soluble lignin in pretreatment liquid (RSL). Both the water-only and 0.05% (w/w) sulfuric acid pretreatments were performed at temperatures from 160 to 270°C on poplar wood in a flowthrough reactor system for 2-10 min. Results showed that water-only flowthrough pretreatment primarily removed syringyl (S units). Increased temperature and/or the addition of sulfuric acid enhanced the removal of guaiacyl (G units) compared to water-only pretreatments at lower temperatures, resulting in nearly complete removal of lignin from the biomass. Results also suggested that more RISL was recovered than ReL and RSL in both dilute acid and water-only flowthrough pretreatment at elevated temperatures. NMR spectra of the RISL revealed significant β-O-4 cleavage, α-β deoxygenation to form cinnamyl-like end groups, and slight β-5 repolymerization in both water-only and dilute acid flowthrough pretreatments. In conclusion, elevated temperature and/or dilute acid greatly enhanced lignin removal to almost 100% by improving G unit removal besides S unit removal in flowthrough system. A new lignin chemistry transformation pathway was proposed and revealed the complexity of lignin structural change during

  12. Structural Integrity of Intelligent Materials and Structures

    DTIC Science & Technology

    1998-03-01

    Laminates," International Journal for Numerical Methods and Engineering (in press). 3. "Coupled Thermomechanical Simulation of Shape Memory Alloys...interpolation polynomials," AIAA Journal , 30, No 11, Nov. 1992. 5. Chang, Fu-Kuo, Perez, J.L., and Chang, K.Y., "Analysis of thick laminated composites...34 Journals of Composite Materials, 24, 801-822, August 1990. 6. Christensen, R.M., Mechanics of Composite Materials, John Wiley & Sons, NY 1979. 7

  13. Structural material irradiations in FFTF

    SciTech Connect

    Not Available

    1985-01-01

    Information is presented concerning the Materials Open Test Assembly (MOTA); instrumentation and control system; MOTA neutronic data; pressurized tube specimens; stress-rupture measurements for reactor materials; miniature specimen design; the Interim Examination and Maintenance (IEM) cell at the FFTF; support services; and general information concerning the FFTF.

  14. Compartment-specific transcriptomics in a reef-building coral exposed to elevated temperatures

    PubMed Central

    Mayfield, Anderson B; Wang, Yu-Bin; Chen, Chii-Shiarng; Lin, Chung-Yen; Chen, Shu-Hwa

    2014-01-01

    Although rising ocean temperatures threaten scleractinian corals and the reefs they construct, certain reef corals can acclimate to elevated temperatures to which they are rarely exposed in situ. Specimens of the model Indo-Pacific reef coral Pocillopora damicornis collected from upwelling reefs of Southern Taiwan were previously found to have survived a 36-week exposure to 30°C, a temperature they encounter infrequently and one that can elicit the breakdown of the coral–dinoflagellate (genus Symbiodinium) endosymbiosis in many corals of the Pacific Ocean. To gain insight into the subcellular pathways utilized by both the coral hosts and their mutualistic Symbiodinium populations to acclimate to this temperature, mRNAs from both control (27°C) and high (30°C)-temperature samples were sequenced on an Illumina platform and assembled into a 236 435-contig transcriptome. These P. damicornis specimens were found to be ∼60% anthozoan and 40% microbe (Symbiodinium, other eukaryotic microbes, and bacteria), from an mRNA-perspective. Furthermore, a significantly higher proportion of genes from the Symbiodinium compartment were differentially expressed after two weeks of exposure. Specifically, at elevated temperatures, Symbiodinium populations residing within the coral gastrodermal tissues were more likely to up-regulate the expression of genes encoding proteins involved in metabolism than their coral hosts. Collectively, these transcriptome-scale data suggest that the two members of this endosymbiosis have distinct strategies for acclimating to elevated temperatures that are expected to characterize many of Earth's coral reefs in the coming decades. PMID:25354956

  15. Environment assisted crack growth in nickel-base superalloys at elevated temperature

    NASA Astrophysics Data System (ADS)

    Evans, Jeffrey Lee

    The environmental effect on the fatigue crack growth rate of Ni-base superalloys at elevated temperature was evaluated in this study. A set of crack growth tests was performed on the turbine disk alloy ME3 at 704°C (1300°F) in vacuum and in air at 0 and 10 second hold times using two microstructures developed with two different cooling rates from the solution heat treat temperature. Fatigue crack growth tests were also conducted at 25°C (77°F) with the two microstructures. Also, a set of oxidation experiments was conducted in order to evaluate the high temperature oxidation behavior of ME3. The microstructure was analyzed and the main differences between the two cooling rates were in the amounts of minor phase particles and size of secondary gamma prime particles. The crack growth rate results suggest that there is no measurable effect of environment or microstructure at room temperature. For the tests conducted in air at elevated temperature, both hold time and microstructural effects were evident. A coupling effect was also observed between the microstructure and the environment. The samples that were slow cooled, and had larger secondary gamma prime particles, had slower crack growth rates and less intergranular fracture in air than the fast cooled samples. A possible explanation for this would be excess free chromium available along grain boundaries due to its low solubility in gamma prime, providing for greater oxidation resistance. An elevated temperature fatigue crack growth rate model for Ni-base superalloys is also proposed.

  16. Effects of selected thermophilic microorganisms on crude oils at elevated temperatures and pressures

    SciTech Connect

    Premuzic, E.T.; Lin, M.S.

    1992-01-01

    The objective of this program is to determine the chemical and physical effects of thermophilic and thermoadapted organisms on crude oils and cores at elevated temperatures and pressures. Ultimately a data base will be generated which will be used in technical and economic feasibility studies leading to field applications. Progress to date are described for: construction of core-flooding systems; studies of trends in biochemical interactions between different microorganisms and crude oils; and comparative studies of interaction between different crude oils and microorganisms.

  17. Large-strain cyclic response and martensitic transformation of austenitic stainless steel at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Hamasaki, H.; Nakano, T.; Ishimaru, E.; Yoshida, F.

    2016-08-01

    Cyclic tension-compression tests were carried out for austenitic stainless steel (SUS304) at elevated temperatures. The significant Bauschinger effect was found in the obtained stress-strain curve. In addition, stagnation of deformation induced martensitic transformation was observed just after stress reversal until the equivalent stress reached the maximum value in the course of experiment. The constitutive model for SUS304 at room temperature was developed, in which homogenized stress of SUS304 was expressed by the weighed summation of stresses of austenite and martensite phases. The calculated stress-strain curves and predicted martensite volume fraction were well correlated with those experimental results.

  18. Shape of isolated domains in lithium tantalate single crystals at elevated temperatures

    SciTech Connect

    Shur, V. Ya. Akhmatkhanov, A. R.; Baturin, I. S.; Chezganov, D. S.; Lobov, A. I.; Smirnov, M. M.

    2013-12-09

    The shape of isolated domains has been investigated in congruent lithium tantalate (CLT) single crystals at elevated temperatures and analyzed in terms of kinetic approach. The obtained temperature dependence of the growing domain shape in CLT including circular shape at temperatures above 190 °C has been attributed to increase of relative input of isotropic ionic conductivity. The observed nonstop wall motion and independent domain growth after merging in CLT as opposed to stoichiometric lithium tantalate have been attributed to difference in wall orientation. The computer simulation has confirmed applicability of the kinetic approach to the domain shape explanation.

  19. Effects of nuclear radiation and elevated temperature storage on electroexplosive devices

    NASA Technical Reports Server (NTRS)

    Menichelli, V. J.

    1976-01-01

    Aerospace type electroexplosive devices (EEDs) were subjected to nuclear radiation. Components and chemicals used in the EEDs were also included. The kind of radiation and total dosage administered were those which may be experienced in a space flight of 10 years duration, based on information available at this time. After irradiation, the items were stored in elevated constant-temperature ovens to accelerate early effects of the exposure to radiation. Periodically, samples were withdrawn for visual observation and testing. Significant changes occurred which were attributed to elevated-temperature storage and not radiation.

  20. The effect of elevated temperature and substrate on free-living Symbiodinium cultures

    NASA Astrophysics Data System (ADS)

    Nitschke, M. R.; Davy, S. K.; Cribb, T. H.; Ward, S.

    2015-03-01

    Elevated temperatures can produce a range of serious, deleterious effects on marine invertebrate— Symbiodinium symbioses. The responses of free-living Symbiodinium to elevated temperature, however, have been little studied, especially in the context of their natural habitat. In this study, we investigated physiological responses of two Symbiodinium cultures to elevated temperature, an exclusively free-living ITS2 clade A (strain HI-0509) and the symbiosis-forming ITS2 type A1 (strain CCMP2467). Free-living Symbiodinium strains have recently been isolated from benthic sediments, and both cultures were therefore grown with or without a microhabitat of carbonate sediment at 25, 28 or 31 °C. Maximum quantum yield of photosystem II ( F v/ F m) and specific growth rate were measured as response variables. In culture, Symbiodinium cells exhibit motility in a helical swimming pattern, and therefore, revolutions per minute (RPM) were also measured with video microscopy. The exclusively free-living clade A was physiologically superior to Symbiodinium A1 across all measured variables and treatment combinations. F v/ F m remained relatively stable through time (at approximately 0.55) and was not substantially affected by temperature or the presence or the absence of sediment. Populations of the exclusively free-living Symbiodinium A reproduced faster with sediment than without and exhibited high levels of motility across all treatments (surpassing 300 RPM). In contrast, the F v/ F m of A1 dropped to 0.42 in sediment (relative to cultures without sediment) and exhibited dramatic declines in cell concentration, most severely at 31 °C. A > 50 % reduction in motility was also observed at 31 °C. Even in the absence of sediment, elevated temperature was observed to reduce population growth and cell motility of type A1. We suggest that vital behaviours linked to motility (such as vertical migration and the locating of potential hosts) may become impaired during future thermal

  1. Reduced thermal resistance of the silicon-synthetic diamond composite substrates at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Goyal, V.; Subrina, S.; Nika, D. L.; Balandin, A. A.

    2010-07-01

    The authors report results of experimental investigation of thermal conductivity of synthetic diamond-silicon composite substrates. Although composite substrates are more thermally resistive than silicon at room temperature they outperform conventional wafers at elevated temperatures owing to different thermal conductivity dependence on temperature. The crossover point is reached near ˜360 K and can be made even lower by tuning the polycrystalline-grain size, film thickness, and interface quality. The reduction of thermal resistance of composite wafers at temperatures, typical for operation of electronic chips, may lead to better thermal management and new phonon-engineered methods for the electron mobility enhancement.

  2. Seawater Acidification and Elevated Temperature Affect Gene Expression Patterns of the Pearl Oyster Pinctada fucata

    PubMed Central

    Liu, Wenguang; Huang, Xiande; Lin, Jianshi; He, Maoxian

    2012-01-01

    Oceanic uptake of anthropogenic carbon dioxide results in decrease in seawater pH and increase in temperature. In this study, we demonstrated the synergistic effects of elevated seawater temperature and declined seawater pH on gene expression patterns of aspein, calmodulin, nacrein, she-7-F10 and hsp70 in the pearl oyster Pinctada fucata. Under ‘business-as-usual’ scenarios, four treatments were examined: (1) ambient pH (8.10) and ambient temperature (27°C) (control condition), (2) ambient pH and elevated temperature (+3°C), (3) declined pH (7.70) and ambient temperature, (4) declined pH and elevated temperature. The results showed that under warming and acidic seawater conditions, expression of aspein and calmodulin showed no significant differences among different time point in condition 8.10 T. But the levels of aspein and calmodulin in conditions 8.10 T+3, 7.70 T and 7.70 T+3, and levels of nacrein, she-7-F10 in all the four treatments changed significantly. Low pH and pH×temperature interaction influenced the expression of aspein and calmodulin significantly after hours 48 and 96. Significant effects of low pH and pH×temperature interaction on the expression of nacrein were observed at hour 96. The expression level of she-7-F10 was affected significantly by pH after hours 48 and 96. The expression of hsp70 was significantly affected by temperature, pH, temperature×pH interaction at hour 6, and by temperature×pH interaction at hour 24. This study suggested that declined pH and pH×temperature interaction induced down regulation of calcification related genes, and the interaction between declined seawater pH and elevated temperature caused up regulation of hsp70 in P. facata. These results demonstrate that the declined seawater pH and elevated temperature will impact the physiological process, and potentially the adaptability of P. fucata to future warming and acidified ocean. PMID:22438983

  3. Note: A method for minimizing oxide formation during elevated temperature nanoindentation

    SciTech Connect

    Cheng, I. C.; Hodge, A. M.; Garcia-Sanchez, E.

    2014-09-15

    A standardized method to protect metallic samples and minimize oxide formation during elevated-temperature nanoindentation was adapted to a commercial instrument. Nanoindentation was performed on Al (100), Cu (100), and W (100) single crystals submerged in vacuum oil at 200 °C, while the surface morphology and oxidation was carefully monitored using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The results were compared to room temperature and 200 °C nanoindentation tests performed without oil, in order to evaluate the feasibility of using the oil as a protective medium. Extensive surface characterization demonstrated that this methodology is effective for nanoscale testing.

  4. Electrorheological Material Based Smart Structures

    DTIC Science & Technology

    2007-11-02

    based in-situ structural vibration monitoring, and real-time neural network based vibration control. In order to facilitate the basic science...structural vibration model was developed and tested with corresponding experimentation. Novel fiber-optic sensors and neural network controllers were also

  5. Microstructural characteristics of adiabatic shear localization in a metastable beta titanium alloy deformed at high strain rate and elevated temperatures

    SciTech Connect

    Zhan, Hongyi; Zeng, Weidong; Wang, Gui; Kent, Damon; Dargusch, Matthew

    2015-04-15

    The microstructural evolution and grain refinement within adiabatic shear bands in the Ti6554 alloy deformed at high strain rates and elevated temperatures have been characterized using transmission electron microscopy. No stress drops were observed in the corresponding stress–strain curve, indicating that the initiation of adiabatic shear bands does not lead to the loss of load capacity for the Ti6554 alloy. The outer region of the shear bands mainly consists of cell structures bounded by dislocation clusters. Equiaxed subgrains in the core area of the shear band can be evolved from the subdivision of cell structures or reconstruction and transverse segmentation of dislocation clusters. It is proposed that dislocation activity dominates the grain refinement process. The rotational recrystallization mechanism may operate as the kinetic requirements for it are fulfilled. The coexistence of different substructures across the shear bands implies that the microstructural evolution inside the shear bands is not homogeneous and different grain refinement mechanisms may operate simultaneously to refine the structure. - Graphical abstract: Display Omitted - Highlights: • The microstructure within the adiabatic shear band was characterized by TEM. • No stress drops were observed in the corresponding stress–strain curve. • Dislocation activity dominated the grain refinement process. • The kinetic requirements for rotational recrystallization mechanism were fulfilled. • Different grain refinement mechanisms operated simultaneously to refine the structure.

  6. Enhancement of photoheterotrophic biohydrogen production at elevated temperatures by the expression of a thermophilic clostridial hydrogenase.

    PubMed

    Lo, Shou-Chen; Shih, Shau-Hua; Chang, Jui-Jen; Wang, Chun-Ying; Huang, Chieh-Chen

    2012-08-01

    The working temperature of a photobioreactor under sunlight can be elevated above the optimal growth temperature of a microorganism. To improve the biohydrogen productivity of photosynthetic bacteria at higher temperatures, a [FeFe]-hydrogenase gene from the thermophile Clostridium thermocellum was expressed in the mesophile Rhodopseudomonas palustris CGA009 (strain CGA-CThydA) using a log-phase expression promoter P( pckA ) to drive the expression of heterogeneous hydrogenase gene. In contrast, a mesophilic Clostridium acetobutylicum [FeFe]-hydrogenase gene was also constructed and expressed in R. palustris (strain CGA-CAhydA). Both transgenic strains were tested for cell growth, in vivo hydrogen production rate, and in vitro hydrogenase activity at elevated temperatures. Although both CGA-CThydA and CGA-CAhydA strains demonstrated enhanced growth over the vector control at temperatures above 38 °C, CGA-CThydA produced more hydrogen than the other strains. The in vitro hydrogenase activity assay, measured at 40 °C, confirmed that the activity of the CGA-CThydA hydrogenase was higher than the CGA-CAhydA hydrogenase. These results showed that the expression of a thermophilic [FeFe]-hydrogenase in R. palustris increased the growth rate and biohydrogen production at elevated temperatures. This transgenic strategy can be applied to a broad range of purple photosynthetic bacteria used to produce biohydrogen under sunlight.

  7. Physiological acclimation to elevated temperature in a reef-building coral from an upwelling environment

    NASA Astrophysics Data System (ADS)

    Mayfield, A. B.; Fan, T.-Y.; Chen, C.-S.

    2013-12-01

    Recent work has found that pocilloporid corals from regions characterized by unstable temperatures, such as those exposed to periodic upwelling, display a remarkable degree of phenotypic plasticity. In order to understand whether important reef builders from these upwelling reefs remain physiologically uncompromised at temperatures they will experience in the coming decades as a result of global climate change, a long-term elevated temperature experiment was conducted with Pocillopora damicornis specimens collected from Houbihu, a small embayment within Nanwan Bay, southern Taiwan that is characterized by 8-9 °C temperature changes during upwelling events. Upon nine months of exposure to nearly 30 °C, all colony (mortality and surface area), polyp ( Symbiodinium density and chlorophyll a content), tissue (total thickness), and molecular (gene expression and molecular composition)-level parameters were documented at similar levels between experimental corals and controls incubated at 26.5 °C, suggesting that this species can readily acclimate to elevated temperatures that cause significant degrees of stress, or even bleaching and mortality, in conspecifics of other regions of the Indo-Pacific. However, the gastrodermal tissue layer was relatively thicker in corals of the high temperature treatment sampled after nine months, possibly as an adaptive response to shade Symbiodinium from the higher photosynthetically active radiation levels that they were experiencing at that sampling time. Such shading may have prevented high light and high temperature-induced photoinhibition, and consequent bleaching, in these samples.

  8. Coralline algal physiology is more adversely affected by elevated temperature than reduced pH

    PubMed Central

    Vásquez-Elizondo, Román Manuel; Enríquez, Susana

    2016-01-01

    In this study we analyzed the physiological responses of coralline algae to ocean acidification (OA) and global warming, by exposing algal thalli of three species with contrasting photobiology and growth-form to reduced pH and elevated temperature. The analysis aimed to discern between direct and combined effects, while elucidating the role of light and photosynthesis inhibition in this response. We demonstrate the high sensitivity of coralline algae to photodamage under elevated temperature and its severe consequences on thallus photosynthesis and calcification rates. Moderate levels of light-stress, however, were maintained under reduced pH, resulting in no impact on algal photosynthesis, although moderate adverse effects on calcification rates were still observed. Accordingly, our results support the conclusion that global warming is a stronger threat to algal performance than OA, in particular in highly illuminated habitats such as coral reefs. We provide in this study a quantitative physiological model for the estimation of the impact of thermal-stress on coralline carbonate production, useful to foresee the impact of global warming on coralline contribution to reef carbon budgets, reef cementation, coral recruitment and the maintenance of reef biodiversity. This model, however, cannot yet account for the moderate physiological impact of low pH on coralline calcification. PMID:26740396

  9. Use of stable tracer studies to evaluate pesticide photolysis at elevated temperatures.

    PubMed

    Hebert, V R; Hoonhout, C; Miller, G C

    2000-05-01

    New methods were developed to determine photolysis rates of medium-weight pesticides in the gas phase using elevated air temperatures and solid-phase microextraction (SPME). A 57-L glass chamber was constructed that utilized collimated xenon arc irradiation that could heat chamber air to increase the amount of pesticide in the gas phase. Gas-phase photolysis rates were determined at various air temperatures by comparing the rate of loss of each of the tested pesticides to a photochemically stable tracer, hexachlorobenzene. Interval sampling of gas-phase constituents was performed using SPME immediately followed by GC-ECD or GC-MSD analysis. The two pesticides under examination were the dinitroaniline herbicide trifluralin and the organophosphorus insecticide chlorpyrifos. The gas-phase photolysis for trifluralin was found to be rapid with half-lives of 22-24 min corrected for sunlight. These results were comparable to photochemical lifetime estimates from other investigators under sunlight conditions. Elevating temperatures from 60 to 80 degrees C did not affect photolysis rates, and these rates could be extrapolated to environmental temperatures. From 60 to 80 degrees C, gas-phase chlorpyrifos photolysis lifetimes were observed to range from 1.4 to 2.2 h corrected for sunlight and will thus be important together with hydroxyl radical reactions for removing this substance from the atmosphere. At these elevated temperatures, pesticides and tracer compounds were found to be substantially in the gas phase, and possible effects on reaction rates from wall interactions were minimized.

  10. Improving xylitol production at elevated temperature with engineered Kluyveromyces marxianus through over-expressing transporters.

    PubMed

    Zhang, Jia; Zhang, Biao; Wang, Dongmei; Gao, Xiaolian; Hong, Jiong

    2015-01-01

    Three transporter genes including Kluyveromyces marxianus aquaglyceroporin gene (KmFPS1), Candida intermedia glucose/xylose facilitator gene (CiGXF1) or glucose/xylose symporter gene (CiGXS1) were over-expressed in K. marxianus YZJ017 to improve xylitol production at elevated temperatures. The xylitol production of YZJ074 that harbored CiGXF1 was improved to 147.62g/L in Erlenmeyer flask at 42°C. In fermenter, 99.29 and 149.60g/L xylitol were produced from 99.55 and 151.91g/L xylose with productivity of 4.14 and 3.40g/L/h respectively at 42°C. Even at 45°C, YZJ074 could produce 101.30g/L xylitol from 101.41g/L xylose with productivity of 2.81g/L/h. Using fed-batch fermentation through repeatedly adding non-sterilized substrate directly, YZJ074 could produce 312.05g/L xylitol which is the highest yield reported to date. The engineered strains YZJ074 which can produce xylitol at elevated temperatures is an excellent foundation for xylitol bioconversion.

  11. ELEVATED TEMPERATURE SENSORS FOR ON-LINE CRITICAL EQUIPMENT HEALTH MONITORING

    SciTech Connect

    James Sebastian

    2005-03-01

    The objective of this research program is to improve high temperature piezoelectric aluminum nitride (AlN) sensor technology to make it useful for instrumentation and health monitoring of current and future electrical power generation equipment. The program will extend the temperature range of the sensor from approximately 700 C to above 1000 C, and ultrasonic coupling to objects at these temperatures will be investigated and tailored for use with the sensor. The chemical vapor deposition (CVD) AlN deposition process was successfully transferred from film production on tungsten carbide substrates to titanium alloy and silicon carbide (SiC) substrates in the first year of the program, and additional substrates were evaluated. In the second year of the program, additional substrate research was performed with the goal of improving the performance of using SiC substrates. While greatly improved bandwidth was achieved, sensor survival at elevated temperature remains problematic. The elevated temperature coupling work continued with significant experimentation. Molten glasses were found to work within a limited temperature range, but metal foils applied with heat and pressure were found to have superior performance overall. The final year of the program will be dedicated to making further advances in AlN/ substrate behavior, and the design and implementation of a sensor demonstration experiment at very high temperature in a simulated industrial application.

  12. Ratchetting behavior of type 304 stainless steel at room and elevated temperatures

    SciTech Connect

    Ruggles, M.; Krempl, E.

    1988-01-01

    The zero-to-tension ratchetting behavior was investigated under uniaxial loading at room temperature and at 550, 600 and 650/degree/ C. In History I the maximum stress level of ratchetting was equal to the stress reached in a tensile test at one percent strain. For History II the maximum stress level was established as the stress reached after a 2100 s relaxation at one percent strain. Significant ratchetting was observed for History I at room temperature but not at the elevated temperatures. The accumulated ratchet strain increases with decreasing stress rate. Independent of the stress rates used insignificant ratchet strain was observed at room temperature for History II. This observation is explained in the context of the viscoplasticity theory based on overstress by the exhaustion of the viscous contribution to the stress during relaxation. The viscous part of the stress is the driving force for the ratchetting in History I. Strain aging is presumably responsible for the lack of short-time inelastic deformation resulting in a nearly rate-independent behavior at the elevated temperatures. 26 refs., 7 figs., 1 tab.

  13. Dry Sliding Wear Behavior of Hafnium-Based Bulk Metallic Glass at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Keshri, Anup Kumar; Behl, Lovish; Lahiri, Debrupa; Dulikravich, George S.; Agarwal, Arvind

    2016-09-01

    Dry sliding wear behavior of hafnium-based bulk metallic glass was studied at two loads (5 and 15 N) and two temperatures (298 and 673 K) using aluminum oxide (Al2O3) ball as a wear counterpart. At 5 N load, wear reduced by ~71% on increasing the temperature from 298 to 673 K. At a higher load of 15 N, the weight loss reduction was much lower (45%) on increasing the temperature from 298 to 673 K. Decreased wear weight loss on increasing the temperature was attributed to the increased hardness of the Hf-based metallic glass at high temperatures. Micro-hardness of the alloy at 293 K was found to be 636 Hv, which gradually increased to 655 Hv on annealing at 673 K. Improvement in the hardness at elevated temperature is attributed to: (1) free volume annihilation, (2) surface oxide formation and (3) nano-crystallites precipitation. Reduced wear at elevated temperature resulted in smaller volume of debris generation that restricted three-body wear to obtain lower coefficient of friction (COF) (0.25-0.35) compared to COF (0.65-0.75) at room temperature.

  14. Low cycle fatigue behavior of polycrystalline Ni3Al alloys at ambient and elevated temperatures

    NASA Astrophysics Data System (ADS)

    Webb, Graham; Antolovich, Stephen D.

    1994-11-01

    The low cycle fatigue (LCF) resistance of polycrystalline Ni3Al has been evaluated at ambient, intermediate (300 °C), and elevated (600 °C) temperatures using strain rates of 10-2/s and 10-4/s. Testing was conducted on a binary and a Cr-containing alloy of similar stoichiometry and B content (hypostoichiometric, 200 wppm B). Test results were combined with electron microscope investigations in order to evaluate microstructural changes during LCF. At ambient and intermediate temperatures, the cyclic constitutive response of both alloys was similar, and the LCF behavior was virtually rate independent. Under these conditions, the alloys rapidly hardened and then gradually softened for the remainder of the life. Initial hardening resulted from the accumulation of dislocation debris within the deformed microstructure, whereas softening was related to localized disordering. For these experimental conditions, crack initiation resulted within persistent slip bands (PSBs). At the elevated temperature, diffusion-assisted deformation resulted in a rate-dependent constitutive response and crack-initiation characteristics. At the high strain rate (10-2/s), continuous cyclic hardening resulted from the accumulation of dislocation debris. At the low strain rate (10-4/s), the diffusion of dislocation debris to grain boundaries resulted in cyclic softening. The elevated temperature LCF resistance was determined by the effect of the constitutive response on the driving force for environmental embrittlement. Chromium additions were observed to enhance LCF performance only under conditions where crack initiation was environmentally driven.

  15. Static tensile and tensile creep testing of five ceramic fibers at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Zimmerman, Richard S.; Adams, Donald F.

    1988-01-01

    Static tensile and tensile creep testing of five ceramic fibers at elevated temperature was performed. J.P. Stevens, Co., Astroquartz 9288 glass fiber, Nippon Carbon, Ltd., (Dow Corning) Nicalon NLM-102 silicon carbide fiber, and 3M Company Nextel 312, 380, and 480 alumina/silica/boria fibers were supplied in unsized tows. Single fibers were separated from the tows and tested in static tension and tensile creep. Elevated test temperatures ranged from 400 to 1300 C and varied for each fiber. Room temperature static tension was also performed. Computer software was written to reduce all single fiber test data into engineering constants using ASTM Standard Test Method D3379-75 as a reference. A high temperature furnace was designed and built to perform the single fiber elevated temperature testing up to 1300 C. A computerized single fiber creep apparatus was designed and constructed to perform four fiber creep tests simultaneously at temperatures up to 1300 C. Computer software was written to acquire and reduce all creep data.

  16. Static tensile and tensile creep testing of five ceramic fibers at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Zimmerman, Richard S.; Adams, Donald F.

    1989-01-01

    Static tensile and tensile creep testing of five ceramic fibers at elevated temperature was performed. J.P. Stevens, Co., Astroquartz 9288 glass fiber; Nippon Carbon, Ltd., (Dow Corning) nicalon NLM-102 silicon carbide fiber; and 3M Company Nextel 312, 380, and 480 alumina/silica/boria fibers were supplied in unsized tows. Single fibers were separated from the tows and tested in static tension and tensile creep. Elevated test temperatures ranged from 400 C to 1300 C and varied for each fiber. Room temperature static tension was also performed. Computer software was written to reduce all single fiber test data into engineering constants using ASTM Standard Test Method D3379-75 as a reference. A high temperature furnace was designed and built to perform the single fiber elevated temperature testing up to 1300 C. A computerized single fiber creep apparatus was designed and constructed to perform four fiber creep tests simultaneously at temperatures up to 1300 C. Computer software was written to acquire and reduce all creep data.

  17. Lifetimes statistics for single Kevlar 49 aramid filaments in creep-rupture at elevated temperatures

    SciTech Connect

    Wu, H.F.

    1987-01-01

    Kevlar 49 fibrous composites are routinely fabricated to have strengths above 1.5 GPa(200 ksi), but in many applications one would like to sustain such stresses for long time periods, sometimes at elevated temperatures. Thus the temperature dependence of the creep-rupture process in the fibers is of interest. Experimental data are presented for the lifetime of single Kevlar 49 filaments under constant stress at elevated temperatures. The goal of this research was to fully characterize the statistical strength and lifetime behavior of single filaments in order to separate fiber effects from fiber/matrix interactions in the creep-rupture lifetime of Kevlar 49/epoxy composites as described for example in Phoenix and Wu (1983). First we conducted experiments to determine distributions for the strength of filaments from the two distinct spools as a function of temperature. As expected, the data could generally be fitted by a two-parameter Weibull distribution. Lifetime experiments at 80 and 130/sup 0/C were conducted at several stress levels chosen as suitable fractions of the Weibull scale parameter for short-term strength for that temperature. The lifetime data were well modelled by a two-parameter Weibull distribution with large variability.

  18. Coralline algal physiology is more adversely affected by elevated temperature than reduced pH

    NASA Astrophysics Data System (ADS)

    Vásquez-Elizondo, Román Manuel; Enríquez, Susana

    2016-01-01

    In this study we analyzed the physiological responses of coralline algae to ocean acidification (OA) and global warming, by exposing algal thalli of three species with contrasting photobiology and growth-form to reduced pH and elevated temperature. The analysis aimed to discern between direct and combined effects, while elucidating the role of light and photosynthesis inhibition in this response. We demonstrate the high sensitivity of coralline algae to photodamage under elevated temperature and its severe consequences on thallus photosynthesis and calcification rates. Moderate levels of light-stress, however, were maintained under reduced pH, resulting in no impact on algal photosynthesis, although moderate adverse effects on calcification rates were still observed. Accordingly, our results support the conclusion that global warming is a stronger threat to algal performance than OA, in particular in highly illuminated habitats such as coral reefs. We provide in this study a quantitative physiological model for the estimation of the impact of thermal-stress on coralline carbonate production, useful to foresee the impact of global warming on coralline contribution to reef carbon budgets, reef cementation, coral recruitment and the maintenance of reef biodiversity. This model, however, cannot yet account for the moderate physiological impact of low pH on coralline calcification.

  19. Coralline algal physiology is more adversely affected by elevated temperature than reduced pH.

    PubMed

    Vásquez-Elizondo, Román Manuel; Enríquez, Susana

    2016-01-07

    In this study we analyzed the physiological responses of coralline algae to ocean acidification (OA) and global warming, by exposing algal thalli of three species with contrasting photobiology and growth-form to reduced pH and elevated temperature. The analysis aimed to discern between direct and combined effects, while elucidating the role of light and photosynthesis inhibition in this response. We demonstrate the high sensitivity of coralline algae to photodamage under elevated temperature and its severe consequences on thallus photosynthesis and calcification rates. Moderate levels of light-stress, however, were maintained under reduced pH, resulting in no impact on algal photosynthesis, although moderate adverse effects on calcification rates were still observed. Accordingly, our results support the conclusion that global warming is a stronger threat to algal performance than OA, in particular in highly illuminated habitats such as coral reefs. We provide in this study a quantitative physiological model for the estimation of the impact of thermal-stress on coralline carbonate production, useful to foresee the impact of global warming on coralline contribution to reef carbon budgets, reef cementation, coral recruitment and the maintenance of reef biodiversity. This model, however, cannot yet account for the moderate physiological impact of low pH on coralline calcification.

  20. Elevated-Temperature Ferritic and Martensitic Steels and Their Application to Future Nuclear Reactors

    SciTech Connect

    Klueh, RL

    2005-01-31

    In the 1970s, high-chromium (9-12% Cr) ferritic/martensitic steels became candidates for elevated-temperature applications in the core of fast reactors. Steels developed for conventional power plants, such as Sandvik HT9, a nominally Fe-12Cr-1Mo-0.5W-0.5Ni-0.25V-0.2C steel (composition in wt %), were considered in the United States, Europe, and Japan. Now, a new generation of fission reactors is in the planning stage, and ferritic, bainitic, and martensitic steels are again candidates for in-core and out-of-core applications. Since the 1970s, advances have been made in developing steels with 2-12% Cr for conventional power plants that are significant improvements over steels originally considered. This paper will review the development of the new steels to illustrate the advantages they offer for the new reactor concepts. Elevated-temperature mechanical properties will be emphasized. Effects of alloying additions on long-time thermal exposure with and without stress (creep) will be examined. Information on neutron radiation effects will be discussed as it applies to ferritic and martensitic steels.

  1. Response and Tolerance Mechanism of Cotton Gossypium hirsutum L. to Elevated Temperature Stress: A Review

    PubMed Central

    Zahid, Kashif Rafiq; Ali, Farhan; Shah, Farooq; Younas, Muhammad; Shah, Tariq; Shahwar, Durri; Hassan, Waseem; Ahmad, Zahoor; Qi, Chao; Lu, Yanli; Iqbal, Amjad; Wu, Wei

    2016-01-01

    Cotton is an important multipurpose crop which is highly sensitive to both biotic and abiotic stresses. Proper management of this cash crop requires systematic understanding of various environmental conditions that are vital to yield and quality. High temperature stress can severely affect the viability of pollens and anther indehiscence, which leads to significant yield losses. Cotton can respond to withstand adverse environmental condition in several phases among which the accumulation of chemicals is extremely vital. Calcium, kinases, reactive oxygen species, carbohydrate, transcription factors, gene expression regulation, and plant hormones signaling pathways are playing a handy role in activating the major genes responsible to encounter and defend elevated temperature stress. The production of heat shock proteins is up-regulated when crops are unleashed to high temperature stress. Molecular breeding can play a functional role to identify superior genes for all the important attributes as well as provide breeder ready markers for developing ideotypes. The development of high-temperature resistant transgenic cultivars of cotton can grant a stability benefit and can also ameliorate the production capacity in response to elevated temperature. PMID:27446165

  2. Materials and structures/ACEE

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Light weight composites made from graphite fibers, glass, or man made materials held in an epoxy matrix, and their application to airframe design are reviewed. The Aircraft Energy Efficiency program is discussed. Characteristics of composites, acceptable risks, building parts and confidence, and aeroelastic tailoring are considered.

  3. Engineering Data on New Aerospace Structural Materials.

    DTIC Science & Technology

    1975-06-01

    SResults of Charpy V n4~ tdh teots at room temperature in both i the Iongiuia ln o~ rnvredrcin t iven to Table XXXIV. `W4161~i. P~lt-0f s 164 -bitrd type...checked,,periodically. In each "case, the dynamic load-control accuracy is bettet •han + 3 porcent of the test ,• load. "For elevated temperature

  4. Long-term performance of ceramic matrix composites at elevated temperatures: Modelling of creep and creep rupture

    SciTech Connect

    Curtin, W.A.; Fabeny, B.; Ibnabdeljalil, M.; Iyengar, N.; Reifsnider, K.L.

    1996-07-31

    The models developed, contain explicit dependences on constituent material properties and their changes with time, so that composite performance can be predicted. Three critical processes in ceramic composites at elevated temperatures have been modeled: (1) creep deformation of composite vs stress and time-dependent creep of fibers and matrix, and failure of these components; (2) creep deformation of ``interface`` around broken fibers; and (3) lifetime of the composite under conditions of fiber strength loss over time at temperature. In (1), general evolution formulas are derived for relaxation time of matrix stresses and steady-state creep rate of composite; the model is tested against recent data on Ti-MMCs. Calculations on a composite of Hi-Nicalon fibers in a melt-infiltrated SiC matrix are presented. In (2), numerical simulations of composite failure were made to map out time-to-failure vs applied load for several sets of material parameters. In (3), simple approximate relations are obtained between fiber life and composite life that should be useful for fiber developers and testers. Strength degradation data on Hi-Nicalon fibers is used to assess composite lifetime vs fiber lifetime for Hi-Nicalon fiber composites.

  5. Mechanisms of time-dependent crack growth at elevated temperature. Final project report, July 1, 1986--August 31, 1989

    SciTech Connect

    Saxena, A.; Stock, S.R.

    1990-04-15

    Objective of this 3-y study was to conduct creep and creep-fatigue crack growth experiments and to characterize the crack tip damage mechanisms in a model material (Cu-1wt%Sb), which is known to cavitate at grain boundaries under creep deformation. Results were: In presence of large scale cavitation damage and crack branching, time rate of creep crack growth da/dt does not correlate with C{sub t} or C{sup *}. When cavitation damage is constrained, da/dt is characterized by C{sub t}. Area fraction of grain boundary cavitated is the single damage parameter for the extent of cavitation damage ahead of crack tips. C{sub t} is used for the creep-fatigue crack growth behavior. In materials prone to rapid cavity nucleation, creep cracks grow faster initially and then reach a steady state whose growth rate is determined by C{sub t}. Percent creep life exhausted correlates with average cavity diameter and fraction of grain boundary area occupied by cavities. Synchrotron x-ray tomographic microscopy was used to image individual cavities in Cu-1wt% Sb. A methodology was developed for predicting the remaining life of elevated temperature power plant components; (C{sub t}){sub avg} was used to correlate creep-fatigue crack growth in Cr-Mo and Cr-Mo-V steel and weldments.

  6. The elevated-temperature mechanical behavior of as-cast and wrought Ti-6Al-4V-1B

    SciTech Connect

    Chen, Wei; Boehlert, C. J.; Howe, Jane Y; Payzant, E Andrew

    2011-01-01

    This work studied the effect of processing on the elevated-temperature [728 K (455 C)] fatigue deformation behavior of Ti-6Al-4V-1B for maximum applied stresses between 300 to 700 MPa (R = 0.1, 5 Hz). The alloy was evaluated in the as-cast form as well as in three wrought forms: cast-and-extruded, powder metallurgy (PM) rolled, and PM extruded. Processing caused significant differences in the microstructure, which in turn impacted the fatigue properties. The PM-extruded material exhibited a fine equiaxed {alpha} + {beta} microstructure and the greatest fatigue resistance among all the studied materials. The {beta}-phase field extrusion followed by cooling resulted in a strong {alpha}-phase texture in which the basal plane was predominately oriented perpendicular to the extrusion axis. The TiB whiskers were also aligned in the extrusion direction. The {alpha}-phase texture in the extrusions resulted in tensile-strength anisotropy. The tensile strength in the transverse orientation was lower than that in the longitudinal orientation, but the strength in the transverse orientation remained greater than that for the as-cast Ti-6Al-4V. The ratcheting behavior during fatigue is also discussed.

  7. Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

    SciTech Connect

    Huang, Shenyan; Gao, Yanfei; An, Ke; Zheng, Lili; Wu, Wei; Teng, Zhenke; Liaw, Peter K

    2014-10-22

    In this study, the ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticity theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.

  8. Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

    DOE PAGES

    Huang, Shenyan; Gao, Yanfei; An, Ke; ...

    2014-10-22

    In this study, the ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticitymore » theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.« less

  9. Deformation mechanisms in a precipitation-strengthened ferritic super alloy revealed by in situ neutron dffraction studies at elevated temperatures

    SciTech Connect

    Huang, Shenyan; Gao, Yanfei; An, Ke; Zheng, Lili; Teng, Zhenke; Wu, Wei; Liaw, Peter K.

    2015-01-01

    The ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)AlB2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticity theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.

  10. Durability of Composite Materials and Structures

    DTIC Science & Technology

    2009-11-02

    Michigan State University Composite Materials and Structures Center 2100 Engineering Building , East Lansing, MI 48824-1226 6.1 Objectives The...DATES COVERED (From - To) February 7, 2005 - January 31. 2009 4. TITLE AND SUBTITLE DURABILITY OF COMPOSITE MATERIALS AND STRUCTURES 5a...Manager: Dr. Yapa D.S. Rajapakse Office of Naval Research 875 N. Randolph Street Arlington, VA 22203-1995 DURABILITY OF COMPOSITE MATERIALS AND

  11. Growth kinetics of SiO2 on (001) Si catalyzed by Cu3Si at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Huang, H. Y.; Chen, L. J.

    2000-08-01

    The oxidation of Si catalyzed by 170-nm-thick Cu3Si at elevated temperatures has been investigated by transmission electron microscopy, glancing angle x-ray diffraction, and Auger electron spectroscopy. For wet oxidation at 140-180 °C, the thickness of the oxide was found to increase parabolically with time with an activation energy of 0.4±0.2 eV. The activation energy is close to that of diffusivity of Cu in Si. At 180-200 °C, the growth rate became slower with increasing temperature. The growth of oxide tended to be discontinuous at the surface as the oxidation temperature was increased to a temperature at or higher than 300 °C. The anomalously fast growth of oxide at low temperatures is attributed to the presence of filamentary structures of Cu clusters in the oxide to expedite the diffusion of the oxidants through oxide. At 200-250 °C, more Cu atoms diffuse to the Cu3Si/Si interface and less Cu atoms stay in the oxide, which slows down the oxide growth. The lack of filamentary structures of Cu as diffusion paths retards the growth of SiO2. At 300 °C or higher temperatures, the lack of filamentary structures of Cu clusters stopped the growth of continuous oxide layer altogether.

  12. Intrinsically Survivable Structural Composite Materials

    DTIC Science & Technology

    2001-02-01

    Coefficient 14 2.2.2 Low-Temperature Precure Treatment (LTPT) 16 2.2.3 Investigation of Several Commercially Available Organoclays 18 2.2.4 High-Shear...of material. Additional commercially available organoclay samples all flocculated to a greater extent than the original S30A. Other attempts to...nanocomposites. A series of epoxy-organosilicate nanocomposites have been successfully prepared with the nanosheets of the nano- organoclay uniformly and

  13. Structures and materials technology for hypersonic aerospacecraft

    NASA Technical Reports Server (NTRS)

    Mccomb, Harvey G., Jr.; Murrow, Harold N.; Card, Michael F.

    1990-01-01

    Major considerations in structural design of a transatmospheric aerospacecraft are discussed. The general direction of progress in structures and materials technology is indicated, and technical areas in structures and materials where further research and development is necessary are indicated. Various structural concepts under study and materials which appear to be most applicable are discussed. Structural design criteria are discussed with particular attention to the factor-of-safety approach and the probabilistic approach. Structural certification requirements for the aerospacecraft are discussed. The kinds of analyses and tests which would be required to certify the structural integrity, safety, and durability of the aerospacecraft are discussed, and the type of test facility needed to perform structural certification tests is identified.

  14. Natural Kenaf Fiber Reinforced Composites as Engineered Structural Materials

    NASA Astrophysics Data System (ADS)

    Dittenber, David B.

    The objective of this work was to provide a comprehensive evaluation of natural fiber reinforced polymer (NFRP)'s ability to act as a structural material. As a chemical treatment, aligned kenaf fibers were treated with sodium hydroxide (alkalization) in different concentrations and durations and then manufactured into kenaf fiber / vinyl ester composite plates. Single fiber tensile properties and composite flexural properties, both in dry and saturated environments, were assessed. Based on ASTM standard testing, a comparison of flexural, tensile, compressive, and shear mechanical properties was also made between an untreated kenaf fiber reinforced composite, a chemically treated kenaf fiber reinforced composite, a glass fiber reinforced composite, and oriented strand board (OSB). The mechanical properties were evaluated for dry samples, samples immersed in water for 50 hours, and samples immersed in water until saturation (~2700 hours). Since NFRPs are more vulnerable to environmental effects than synthetic fiber composites, a series of weathering and environmental tests were conducted on the kenaf fiber composites. The environmental conditions studied include real-time outdoor weathering, elevated temperatures, immersion in different pH solutions, and UV exposure. In all of these tests, degradation was found to be more pronounced in the NFRPs than in the glass FRPs; however, in nearly every case the degradation was less than 50% of the flexural strength or stiffness. Using a method of overlapping and meshing discontinuous fiber ends, large mats of fiber bundles were manufactured into composite facesheets for structural insulated panels (SIPs). The polyisocyanurate foam cores proved to be poorly matched to the strength and stiffness of the NFRP facesheets, leading to premature core shear or delamination failures in both flexure and compressive testing. The NFRPs were found to match well with the theoretical stiffness prediction methods of classical lamination

  15. Effects of multigenerational exposure to elevated temperature on reproduction, oxidative stress, and Cu toxicity in Daphnia magna.

    PubMed

    Bae, Eunhye; Samanta, Palas; Yoo, Jisu; Jung, Jinho

    2016-10-01

    This study evaluated the effect of temperature (20 and 25°C) on reproduction, oxidative stress, and copper (Cu) toxicity in Daphnia magna across three generations (F0, F1, and F2). Exposing D. magna to elevated temperature significantly decreased the number of offspring per female per day, the time to first brood, and body length compared to exposure to the optimal temperature (p<0.05). In addition, elevated temperature induced a significantly higher production of reactive oxygen species and lipid peroxidation (p<0.05). These findings suggest that D. magna likely responded to thermal stress by investing more energy into defense mechanisms, rather than growth and reproduction. In addition, oxidative stress at the elevated temperature gradually increased with each generation, possibly owing to the reduced fitness of the offspring. Exposing D. magna to 25°C (EC50=34±3µgL(-1)) substantially increased the median effective concentration of Cu in all generations compared to exposure to 20°C (EC50=25±3µgL(-1)), indicating a decrease in acute toxicity at elevated temperature. However, elevated temperature significantly increased the oxidative stress induced by a sublethal concentration of Cu (10µgL(-1)). The interaction between elevated temperature and Cu exposure appears to be synergistic; however, this needs to be confirmed using multiple generations in a long-term experiment.

  16. Composite materials for space structures

    NASA Technical Reports Server (NTRS)

    Tenney, D. R.; Sykes, G. F.; Bowles, D. E.

    1985-01-01

    The use of advanced composites for space structures is reviewed. Barriers likely to limit further applications of composites are discussed and highlights of research to improve composites are presented. Developments in composites technology which could impact spacecraft systems are reviewed to identify technology needs and opportunities.

  17. Effect of the Zener-Hollomon parameter on the formability of AA6082-T6 formed at elevated temperature

    NASA Astrophysics Data System (ADS)

    Novella, Michele F.; Ghiotti, Andrea; Bruschi, Stefania

    2016-10-01

    Material formability is one of the main research topics in metal forming, but it is usually regarded as a secondary concern in processes carried out at high temperature. Though usually entailing higher material ductility, the high temperature used in hot forging can lead to the phenomenon of hot shortness, with fall of material formability due to the microstructural changes during the deformation. Hot metal formability modelling can imply three main issues: (i) the lack of models expressly developed for high temperatures, (ii) the exponential increase of the experimental effort which is needed for the model calibration, since different thermo-mechanical conditions need to be tested, according to the process window parameters, and consequently (iii) the more complex model calibration, especially if inverse analysis techniques are used. In this work the formability of the AA6082-T6 aluminum alloy is investigated by means of tensile tests carried out at different temperatures and strain rates. The hot shortness onset is identified as well as the negative strain rate influence on the material maximum strain at fracture. A linear dependency of the material formability on the Zener-Hollomon parameter is established for temperatures below the hot shortness point, allowing a significant simplification of the experiments needed for the calibration. A new formability model is proposed to overcome the limits of the linear correlation thanks to the introduction of a critical value of the Zener-Hollomon parameter. The Oyane-Sato damage criterion is then extended to hot conditions using the afore mentioned Zener-Hollomon dependency. Finally, the approach is validated on the reference industrial case: the cross wedge rolling of AA6082-T6 round bars carried out at elevated temperature showing axial cracking due to Mannesmann effect.

  18. Determination of design allowable strength properties of elevated-temperature alloys. Part 1: Coated columbium alloys

    NASA Technical Reports Server (NTRS)

    Favor, R. J.; Maykuth, D. J.; Bartlett, E. S.; Mindlin, H.

    1972-01-01

    A program to determine the characteristics of two coated columbium alloy systems for spacecraft structures is discussed. The alloy was evaluated as coated base material, coated butt-welded material, and material thermal/pressure cycled prior to testing up to 30 cycles. Evaluation was by means of tensile tests covering the temperature range to 2400 F. Design allowables were computed and are presented as tables of data. The summary includes a room temperature property table, effect of temperature curves, and typical stress-strain curves.

  19. Effects of surface condition on the corrosion of candidate structural materials in a simulated HTGR-GT environment

    SciTech Connect

    Thompson, L.D.

    1980-02-01

    A simulated high-temperature gas-cooled reactor (HTGR) helium environment was used to study the effects of surface finish conditions on the subsequent elevated-temperature corrosion behavior of key candidate structural materials. The environment contained helium with 500 ..mu..atm H/sub 2//50 ..mu..atm CO/50 ..mu..atm CH/sub 4//<0.5 ..mu..atm H/sub 2/O at 900/sup 0/C with total test exposure durations of 3000 hours. Specimens with lapped, grit-blasted, pickled, and preoxidized surface conditions were studied. Materials tested included two cast superalloys, IN 100 and IN 713LC; one centrifugally cast high-temperature alloy, HK 40 one oxice-dispersion-strengthened alloy, Inconel MA 754; and three wrought high-temperature alloys, Hastelloy Alloy X, Inconel Alloy 617, and Alloy 800H.

  20. Biomimetic photonic materials with tunable structural colors.

    PubMed

    Xu, Jun; Guo, Zhiguang

    2013-09-15

    Nature is a huge gallery of art involving nearly perfect structures and forms over the millions of years developing. Inspiration from natural structures exhibiting structural colors is first discussed. We give some examples of natural one-, two-, and three-dimensional photonic structures. This review article presents a brief summary of recent progress on bio-inspired photonic materials with variable structural colors, including the different facile and efficient routes to construct the nano-architectures, and the development of the artificial variable structural color photonic materials. Besides the superior optical properties, the excellent functions such as robust mechanical strength, good wettability are also mentioned, as well as the technical importance in various applications. This review will provide significant insight into the fabrication, design and application of the structural color materials.

  1. Radiation Effects on Spacecraft Structural Materials

    SciTech Connect

    Wang, Jy-An J.; Ellis, Ronald J.; Hunter, Hamilton T.; Singleterry, Robert C. Jr.

    2002-07-01

    Research is being conducted to develop an integrated technology for the prediction of aging behavior for space structural materials during service. This research will utilize state-of-the-art radiation experimental apparatus and analysis, updated codes and databases, and integrated mechanical and radiation testing techniques to investigate the suitability of numerous current and potential spacecraft structural materials. Also included are the effects on structural materials in surface modules and planetary landing craft, with or without fission power supplies. Spacecraft structural materials would also be in hostile radiation environments on the surface of the moon and planets without appreciable atmospheres and moons around planets with large intense magnetic and radiation fields (such as the Jovian moons). The effects of extreme temperature cycles in such locations compounds the effects of radiation on structural materials. This paper describes the integrated methodology in detail and shows that it will provide a significant technological advance for designing advanced spacecraft. This methodology will also allow for the development of advanced spacecraft materials through the understanding of the underlying mechanisms of material degradation in the space radiation environment. Thus, this technology holds a promise for revolutionary advances in material damage prediction and protection of space structural components as, for example, in the development of guidelines for managing surveillance programs regarding the integrity of spacecraft components, and the safety of the aging spacecraft. (authors)

  2. LTA structures and materials technology. [airships

    NASA Technical Reports Server (NTRS)

    Mayer, N. J.

    1975-01-01

    The state-of-the-art concerning structures and materials technology is reviewed. It is shown that many present materials developments resulting from balloon and aircraft research programs can be applied to new concepts in LTA vehicles. Both buoyant and semi-buoyant vehicles will utilize similar approaches to solving structural problems and could involve pressurized non-rigid and unpressurized rigid structures. System designs common to both and vital to structural integrity will include much of the past technology as well. Further research is needed in determination of structural loads, especially in future design concepts.

  3. A zero density change phase change memory material: GeTe-O structural characteristics upon crystallisation.

    PubMed

    Zhou, Xilin; Dong, Weiling; Zhang, Hao; Simpson, Robert E

    2015-06-11

    Oxygen-doped germanium telluride phase change materials are proposed for high temperature applications. Up to 8 at.% oxygen is readily incorporated into GeTe, causing an increased crystallisation temperature and activation energy. The rhombohedral structure of the GeTe crystal is preserved in the oxygen doped films. For higher oxygen concentrations the material is found to phase separate into GeO2 and TeO2, which inhibits the technologically useful abrupt change in properties. Increasing the oxygen content in GeTe-O reduces the difference in film thickness and mass density between the amorphous and crystalline states. For oxygen concentrations between 5 and 6 at.%, the amorphous material and the crystalline material have the same density. Above 6 at.% O doping, crystallisation exhibits an anomalous density change, where the volume of the crystalline state is larger than that of the amorphous. The high thermal stability and zero-density change characteristic of Oxygen-incorporated GeTe, is recommended for efficient and low stress phase change memory devices that may operate at elevated temperatures.

  4. Space structures concepts and materials

    NASA Technical Reports Server (NTRS)

    Nowitzky, A. M.; Supan, E. C.

    1988-01-01

    An extension is preseted of the evaluation of graphite/aluminum metal matrix composites (MMC) for space structures application. A tubular DWG graphite/aluminum truss assembly was fabricated having the structural integrity and thermal stability needed for space application. DWG is a proprietary thin ply continuous graphite reinforced aluminum composite. The truss end fittings were constructed using the discontinuous ceramic particulate reinforced MMC DWAl 20 (trademark). Thermal stability was incorporated in the truss by utilizing high stiffness, negative coefficient of thermal expansion (CTE) P100 graphite fibers in a 6061 aluminum matrix, crossplied to provide minimized CTE in the assembled truss. Tube CTE was designed to be slightly negative to offset the effects of the end fitting and sleeve, CTE values of which are approx. 1/2 that of aluminum. In the design of the truss configuration, the CTE contribution of each component was evaluated to establish the component dimension and layup configuration required to provide a net zero CTE in the subassemblies which would then translate to a zero CTE for the entire truss bay produced.

  5. Uncertainty Of The Measurement Of DC Conductivity Of Eramics At Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Štubňa, Igor; Trnovcová, Viera; Vozár, Libor; Csáki, Štefan

    2015-01-01

    The electrical DC conductivity is measured at room and elevated temperatures on green ceramic samples prepared from kaolin. The arrangement of the sample, with two platinum wire electrodes inserted in the kaolin prism that was used is suitable for measurements of temperature dependences of the DC conductivity from 20 °C to 1100 °C in the air. The uncertainty analysis taking into account thermal expansion of the sample, homogeneity of the temperature field, measurement regime, corrosion of the electrodes, and overlapping of the electrodes is done for 1000 °C. Uncertainties connected with current and voltage measurements and uncertainties connected with the instruments that were used are also considered. The sum of all the partial uncertainties gives an expanded uncertainty of the conductivity measurement. The uncertainty varies with temperature and reaches the value of ˜ 6.5% at 1000 °C.

  6. Fuel/cladding compatibility in irradiated metallic fuel pins at elevated temperatures

    SciTech Connect

    Tsai, Hanchung.

    1990-04-01

    Over fifty fuel/cladding compatibility tests on irradiated metallic fuel specimens have been conducted in an in-cell facility at elevated temperatures. At temperatures below 700--725{degree}C, no fuel/cladding interaction was noted in tests up to 7 h. Liquid-phase cladding penetration occurred in some of the tests at temperatures greater than 725--750{degree}C. The effective rates of liquid- phase cladding penetration of six different fuel/cladding combinations during 1-h testing are reported. After the initial liquefaction at the fuel/cladding interface, which may be affected by the solid-state diffusional interaction during the steady-state irradiation, the rate of further cladding penetration stays constant or decreases with time. There was no runaway cladding penetration in the latter part of a heating cycle.

  7. Gas diffusion electrode setup for catalyst testing in concentrated phosphoric acid at elevated temperatures

    SciTech Connect

    Wiberg, Gustav K. H. E-mail: m.arenz@chem.ku.dk; Fleige, Michael; Arenz, Matthias E-mail: m.arenz@chem.ku.dk

    2015-02-15

    We present a detailed description of the construction and testing of an electrochemical cell setup allowing the investigation of a gas diffusion electrode containing carbon supported high surface area catalysts. The setup is designed for measurements in concentrated phosphoric acid at elevated temperature, i.e., very close to the actual conditions in high temperature proton exchange membrane fuel cells (HT-PEMFCs). The cell consists of a stainless steel flow field and a PEEK plastic cell body comprising the electrochemical cell, which exhibits a three electrode configuration. The cell body and flow field are braced using a KF-25 vacuum flange clamp, which allows an easy assembly of the setup. As demonstrated, the setup can be used to investigate temperature dependent electrochemical processes on high surface area type electrocatalysts, but it also enables quick screening tests of HT-PEMFC catalysts under realistic conditions.

  8. Fundamental studies of ceramic/metal interfacial reactions at elevated temperatures.

    SciTech Connect

    McDeavitt, S. M.; Billings, G. W.; Indacochea, J. E.

    2000-12-14

    This work characterizes the interfaces resulting from exposing oxide and non-oxide ceramic substrates to zirconium metal and stainless steel-zirconium containing alloys. The ceramic/metal systems together were preheated at about 600 C and then the temperatures were increased to the test maximum temperature, which exceeded 1800 C, in an atmosphere of high purity argon. Metal samples were placed onto ceramic substrates, and the system was heated to elevated temperatures past the melting point of the metallic specimen. After a short stay at the peak temperature, the system was cooled to room temperature and examined. The chemical changes across the interface and other microstructural developments were analyzed with energy dispersive spectroscopy (EDS). This paper reports on the condition of the interfaces in the different systems studied and describes possible mechanisms influencing the microstructure.

  9. THERMODYNAMICS OF NEPTUNIUM(V) FLOURIDE AND SULFATE AT ELEVATED TEMPERATURES

    SciTech Connect

    L. Rao; G. Tian; Y. Xia; J.I. Friese

    2006-03-06

    Complexation of neptunium(V) with fluoride and sulfate at elevated, temperatures was studied by microcalorimetry. Thermodynamic parameters, including the equilibrium constants and enthalpy of protonation of fluoride and sulfate, and the enthalpy of complexation between Np(V) and fluoride and sulfate at 25-70 C were determined. Results show that the complexation of Np(V) with fluoride and sulfate is endothermic and that the complexation is enhanced by the increase in temperature--a threefold increase in the stability constants of NpO{sub 2}F(aq) and NpO{sub 2}SO{sub 4}{sup -} as the temperature is increased from 25 to 70 C.

  10. Direct Selective Laser Sintering/Melting of High Density Alumina Powder Layers at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Deckers, J.; Meyers, S.; Kruth, J. P.; Vleugels, J.

    Direct selective laser sintering (SLS) or selective laser melting (SLM) are additive manufacturing techniques that can be used to produce three-dimensional ceramic parts directly, without the need for a sacrificial binder. In this paper, a low laser energy density is applied to SLS/SLM high density powder layers of sub-micrometer alumina at elevated temperatures (up to 800̊C). In order to achieve this, a furnace was designed and built into a commercial SLS machine. This furnace was able to produce a homogeneously heated cylindrical zone with a height of 60 mm and a diameter of 32 mm. After optimizing the layer deposition and laser scanning parameters, two ceramic parts with a density up to 85% and grain sizes as low as 5 μm were successfully produced.

  11. Photoluminescence in silicon implanted with erbium ions at an elevated temperature

    SciTech Connect

    Sobolev, N. A. Kalyadin, A. E.; Shek, E. I.; Sakharov, V. I.; Serenkov, I. T.; Vdovin, V. I.; Parshin, E. O.; Makoviichuk, M. I.

    2011-08-15

    Photoluminescence spectra of n-type silicon upon implantation with erbium ions at 600 Degree-Sign C and oxygen ions at room temperature and subsequent annealings at 1100 Degree-Sign C in a chlorine-containing atmosphere have been studied. Depending on the annealing duration, photoluminescence spectra at 80 K are dominated by lines of the Er{sup 3+} ion or dislocation-related luminescence. The short-wavelength shift of the dislocation-related luminescence line observed at this temperature is due to implantation of erbium ions at an elevated temperature. At room temperature, lines of erbium and dislocation-related luminescence are observed in the spectra, but lines of near-band-edge luminescence predominate.

  12. Fatigue life prediction of an intermetallic matrix composite at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Bartolotta, P. A.

    1991-01-01

    A strain-based fatigue life prediction method is proposed for an intermetallic matrix composite (IMC) under tensile cyclic loadings at elevated temperatures. Styled after the 'Universal Slopes' method, the model utilizes the composite's tensile properties to estimate fatigue life. Factors such as fiber volume ratio (Vf), number of plys and temperature dependence are implicitly incorporated into the model through these properties. The model constants are determined by using unidirectional fatigue data at temperatures of 425 and 815 C. Fatigue lives from two independent sources are used to verify the model at temperatures of 650 and 760 C. Cross-ply lives at 760 C are also predicted. It is demonstrated that the correlation between experimental and predicted lives is within a factor of two.

  13. Modeling the effects of elevated temperatures on action potential propagation in unmyelinated axons

    NASA Astrophysics Data System (ADS)

    Ganguly, Mohit; Jenkins, Michael W.; Chiel, Hillel J.; Jansen, E. Duco

    2016-03-01

    Infrared lasers (λ=1.87 μm) are capable of inducing a thermally mediated nerve block in Aplysia and rat nerves. While this block is spatially precise and reversible in sensory and motor neurons, the mechanism of block is not clearly understood. Model predictions show that, at elevated temperatures, the rates of opening and closing of the voltage gated ion channels are disrupted and normal functioning of the gates is hindered. A model combining NEURON with Python is presented here that can simulate the behavior of unmyelinated nerve axons in the presence of spatially and temporally varying temperature distributions. Axon behavior and underlying mechanism leading to conduction block is investigated. The ability to understand the photothermal interaction of laser light and temperature dependence of membrane ion channels in-silico will help speed explorations of parameter space and guide future experiments testing the feasibility of selectively blocking pain conduction fibers (Photonic Analgesia of Nerves (PAIN)) in humans.

  14. Role of oxygen in wetting of copper nanoparticles on silicon surfaces at elevated temperature

    PubMed Central

    Ghosh, Tapas

    2017-01-01

    Copper nanoparticles have been deposited on silicon surfaces by a simple galvanic displacement reaction, and rapid thermal annealing has been performed under various atmospheric conditions. In spite of the general tendency of the agglomeration of nanoparticles to lower the surface energy at elevated temperatures, our plan-view and cross-sectional transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis shows that the thermal oxidation of the copper nanoparticles and formation of cupric oxide (CuO) on silicon surfaces leads to wetting rather than agglomeration. In contrast, agglomeration has been observed when copper nanoparticles were annealed in a nitrogen environment. The lattice transformation from cubic Cu to monoclinic CuO, and hence the change in surface energy of the particles, assists the wetting process. The occurrence of wetting during the oxidation step implies a strong interaction between the oxidized film and the silicon surface. PMID:28326232

  15. Influence of elevated temperature and acid mine drainage on mortality of the crayfish Cambarus bartonii

    USGS Publications Warehouse

    Hartman, K.J.; Hom, C.D.; Mazik, P.M.

    2010-01-01

    Effects of elevated temperature and acid mine drainage (AMD) on crayfish mortality were investigated in the Stony River, Grant County, West Virginia. During summers 2003 and 2004, four-week in situ bioassays were performed along a thermal and AMD gradient with the native crayfish Cambarus bartonii. Crayfish mortality was analyzed in conjunction with temperature and AMD related variables (pH, specific conductivity). Mortality was significantly higher (48-88%) at sites with high temperatures during 2003 (max = 33.0??C), but no significant differences were observed in 2004 (max = 32.0??C). Temperatures were higher in 2003 than 2004 due to increased discharge from a cooling reservoir flowing into the river. Additionally, duration of high temperature was approximately four days in 2003 as compared with only one day in 2004. No significant relationship between acid mine drainage variables and crayfish mortality was apparent.

  16. Acoustic inspection of bond strength of steel-reinforced mortar after exposure to elevated temperatures

    PubMed

    Chiang; Tsai; Kan

    2000-03-01

    In order to evaluate the bond strength between the reinforcement and concrete after fire damage, a combination of acoustic through-transmission and pull-out tests were used. Previous studies have shown a 25% decrease in the ultrasonic pulse velocity at 90% of the maximum load at room temperature. The specimens were kept in the oven at an elevated temperature for 1, 2, or 3 h. They were then removed and cooled to room temperature. Inspection was conducted using a high-power ultrasonic pulse velocity system while a pull-out load was applied. The correlation between preheated temperature, acoustic wave velocity, and the applied load was analyzed. Initial results show that bond strength and pulse velocity decreased substantially as the temperature or the heating time increased.

  17. Nucleation and growth of cracks in vitreous-bonded aluminum oxide at elevated temperatures

    SciTech Connect

    Jakus, K.; Wiederhorn, S.M.; Hockey, B.J.

    1986-10-01

    The nucleation and growth of cracks was studied at elevated temperatures on a grade of vitreous-bonded aluminium oxide that contained approx. =8 vol% glass at the grain boundaries. Cracks were observed to nucleate within the vitreous phase, close to the tensile surface of the flexural test specimens used in these experiments. Crack nucleation occurred at a strain of approx. =0.08% to 0.12% which corresponded to a crack nucleation time of approx. =35% of the time to failure by creep rupture. Once nucleated, cracks propagated along grain boundaries, as long as the stress for crack propagation was maintained. The crack velocity for cracks that were nucleated by the creep process was found to be linearly proportional to the apparent stress intensity factor, whereas for cracks that were nucleated by indentation, the crack velocity was proportional to the fourth power of the apparent stress intensity factor.

  18. Fatigue life prediction of an intermetallic matrix composite at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Bartolotta, Paul A.

    1991-01-01

    A strain-based fatigue life prediction method is proposed for an intermetallic matrix composite (IMC) under tensile cyclic loadings at elevated temperatures. Styled after the Universal Slopes method, the model utilizes the composite's tensile properties to estimate fatigue life. Factors such as fiber volume ratio, number of plys and temperature dependence are implicitly incorporated into the model through these properties. The model constants are determined by using unidirectional fatigue data at temperatures of 425 and 815 C. Fatigue lives from two independent sources are used to verify the model at temperatures of 650 and 760 C. Cross-ply lives at 760 C are also predicted. It is demonstrated that the correlation between experimental and predicted lives is within a factor of two.

  19. Application of path-independent integrals to elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Kim, K. S.; Van Stone, R. H.

    1990-01-01

    The applicability of the J-integral in elasto-plastic fracture mechanics is limited to isothermal, monotonic loading conditions from the theoretical viewpoint, while in many applications, for instance gas turbine engines, crack growth occurs in the presence of cyclic inelastic loading, thermomechanical loading and temperature gradients. A number of path-independent (P-I) integrals have been proposed which do not have the restrictions of the J-integral. A review indicates that four of these integrals, although they are not the classical conservation integrals, are path-independent under these complex loading conditions. This paper describes a combined analytical and experimental effort to evaluate the ability of these four P-I integrals to correlate the crack growth data of Alloy 718 at elevated temperatures. Results for uniform temperature, 538 C, cases indicate that all these integrals are capable of correlating the crack growth data over a wide range of cyclic plasticity.

  20. Computational and Experimental Design of Fe-Based Superalloys for Elevated-Temperature Applications

    SciTech Connect

    Liaw, Peter K.; Fine, Morris E.; Ghosh, Gautam; Asta, Mark D.; Liu, Chain T.; Sun, Zhiqian; Huang, Shenyan; Teng, Zhenke; Wang, Gongyao

    2012-04-13

    Analogous to nickel-based superalloys, Fe-based superalloys, which are strengthened by coherent B2- type precipitates are proposed for elevated-temperature applications. During the period of this project, a series of ferritic superalloys have been designed and fabricated by methods of vacuum-arc melting and vacuum-induction melting. Nano-scale precipitates were characterized by atom-probe tomography, ultrasmall- angle X-ray scattering, and transmission-electron microscopy. A duplex distribution of precipitates was found. It seems that ferritic superalloys are susceptible to brittle fracture. Systematic endeavors have been devoted to understanding and resolving the problem. Factors, such as hot rolling, precipitate volume fractions, alloy compositions, precipitate sizes and inter-particle spacings, and hyperfine cooling precipitates, have been investigated. In order to understand the underlying relationship between the microstructure and creep behavior of ferric alloys at elevated temperatures, in-situ neutron studies have been carried out. Based on the current result, it seems that the major role of β' with a 16%-volume fraction in strengthening ferritic alloys is not load sharing but interactions with dislocations. The oxidation behavior of one ferritic alloy, FBB8 (Fe-6.5Al-10Ni-10Cr-3.4Mo-0.25Zr-0.005B, weight percent), was studied in dry air. It is found that it possesses superior oxidation resistance at 1,023 and 1,123 K, compared with other creep-resistant ferritic steels [T91 (modified 9Cr-1Mo, weight percent) and P92 (9Cr-1.8W-0.5Mo, weight percent)]. At the same time, the calculation of the interfacial energies between the -iron and B2-type intermetallics (CoAl, FeAl, and NiAl) has been conducted.

  1. Effects of episodic low aragonite saturation and elevated temperature on the physiology of Stylophora pistillata

    NASA Astrophysics Data System (ADS)

    Lürig, M.; Kunzmann, A.

    2015-05-01

    As global climate change is predicted to gradually alter the oceans' carbonate system and water temperature, knowledge about the effects an altered marine environment has on the physiology of reef building (hermatypic) coral species is more widely established. However, although it is recognized that seawater temperature and the carbonate system of a coral reef can change rapidly and with great amplitude, little is known about how the interaction of these natural fluctuations with long term effects of climate change may affect the metabolism and productivity of hermatypic corals. To investigate this, we acclimated the hermatypic coral Stylophora pistillata to a "worst case" scenario for carbon dioxide emissions (aragonite saturation state [ΩARAG] = 1.6), and tested how exposure to short term (24 h) elevated temperature (+ 3 °C) and further lowered ΩARAG (-1 unit) affected its photosynthesis and respiration. While episodic exposure to very low ΩARAG had only little effect on S. pistillata's physiology, short term heat stress caused a shift from net oxygen production to consumption and partial coral bleaching. Higher gross coral respiration, and lowered photosynthetic activity under episodically elevated temperature may have been the result of photoinhibition and partial coral bleaching. These findings suggest that fluctuating environmental conditions in combination with a low ΩARAG background signal may impair basic metabolic processes in calcifying corals. In a future high-CO2 world short term stress could be relevant for reef ecosystem processes, and may affect the resilience of coral reefs to other external influences and effects of climate change.

  2. The effect of elevated temperature on Barley yellow dwarf virus-PAV in wheat.

    PubMed

    Nancarrow, Narelle; Constable, Fiona E; Finlay, Kyla J; Freeman, Angela J; Rodoni, Brendan C; Trebicki, Piotr; Vassiliadis, Simone; Yen, Alan L; Luck, Jo E

    2014-06-24

    Barley yellow dwarf virus-PAV (BYDV-PAV) is associated with yellow dwarf disease, one of the most economically important diseases of cereals worldwide. In this study, the impact of current and future predicted temperatures for the Wimmera wheat growing district in Victoria, Australia on the titre of BYDV-PAV in wheat was investigated. Ten-day old wheat (Triticum aestivum, cv. Yitpi) seedlings were inoculated with BYDV-PAV and grown at ambient (5.0-16.1°C, night-day) or elevated (10.0-21.1°C, night-day) temperature treatments, simulating the current Wimmera average and future daily temperature cycles, respectively, during the wheat-growing season. Whole above-ground plant samples were collected from each temperature treatment at 0 (day of inoculation), 3, 6, 9, 12, 15, 18, 21 and 24 days after inoculation and the titre of BYDV-PAV was measured in each sample using a specific one-step multiplex normalised reverse transcription quantitative PCR (RT-qPCR) assay. Physical measurements, including plant height, dry weight and tiller number, were also taken at each sampling point. The titre of BYDV-PAV was significantly greater in plants grown in the elevated temperature treatment than in plants grown in the ambient treatment on days 6, 9 and 12. Plants grown at elevated temperature were significantly bigger and symptoms associated with BYDV-PAV were visible earlier than in plants grown at ambient temperature. These results may have important implications for the epidemiology of yellow dwarf disease under future climates in Australia.

  3. Changes in CdS/CdTe Solar Cells Subjected to Elevated Temperature, Voltage and Illumination

    NASA Astrophysics Data System (ADS)

    Demtsu, Samuel; Nagle, Tim

    2003-10-01

    CdTe/CdS solar cells have been known to exhibit degradation in performance after being subjected to elevated temperature, voltage and illumination. These conditions are collectively referred to as "stress". We have studied and presented CdTe/CdS cell degradation under different stress conditions of devices from First Solar Inc., the University of South Florida and the University of Toledo. All cells were stressed in the light (close to 100 mW/cm2) for 56 days at elevated temperature of 900C at two different biases, short circuit (SC) and open circuit (OC). The stress condition surpasses the operation conditions expected in the field. To characterize the cells, we have measured current density as function of the applied voltage (JV), capacitance vs bias voltage (CV) and quantum efficiency (QE) measurements before and after exposure to stress. To investigate the spatial non-uniformity of photocurrent collection induced by stress we have done Light Beam-Induced Current (LBIC) measurement. The effect of the stress on the photovoltaic parameters short-circuit current (Jsc), open-circuit voltage (Voc), Fill-Factor (FF), and efficiency is presented and discussed. Carrier density as a function of the distance from the semiconductor junction is extracted from the C-V measurements. We have seen some variations between cells and degradation was not monotonic with stress time. The highly probable explanation for the degradation of the cells after the stress is that mobile copper ions diffuse out of the back contact towards the primary junction leaving a depletion of Cu in the back contact, which increases the contact barrier.

  4. Effects of selected thermophilic microorganisms on crude oils at elevated temperatures and pressures. Final report

    SciTech Connect

    Premuzic, E.T.; Lin, M.S.

    1995-07-01

    During the past several years, a considerable amount of work has been carried out showing that microbially enhanced oil recovery (MEOR) is promising and the resulting biotechnology may be deliverable. At the Brookhaven National Laboratory (BNL), systematic studies have been conducted which dealt with the effects of thermophilic and thermoadapted bacteria on the chemical and physical properties of selected types of crude oils at elevated temperatures and pressures. Particular attention was paid to heavy crude oils from Venezuela, California, Alabama, Arkansas, Wyoming, Alaska, and other oil producing areas. Current studies indicate that during the biotreatment several chemical and physical properties of crude oils are affected. The oils are (1) emulsified; (2) acidified; (3) there is a qualitative and quantitative change in light and heavy fractions of the crudes; (4) there are chemical changes in fractions containing sulfur compounds; (5) there is an apparent reduction in the concentration of trace metals; (6) the qualitative and quantitative changes appear to be microbial species dependent; and (7) there is a distinction between {open_quotes}biodegraded{close_quotes} and {open_quotes}biotreated{close_quotes} oils. Preliminary results indicate the introduced microorganisms may become the dominant species in the bioconversion of oils. These studies also indicate the biochemical interactions between crude oils and microorganisms follow distinct trends, characterized by a group of chemical markers. Core-flooding experiments have shown significant additional crude oil recoveries are achievable with thermophilic microorganisms at elevated temperatures similar to those found in oil reservoirs. In addition, the biochemical treatment of crude oils has technological applications in downstream processing of crude oils such as in upgrading of low grade oils and the production of hydrocarbon based detergents.

  5. Correlation between mobile continents and elevated temperatures in the subcontinental mantle

    NASA Astrophysics Data System (ADS)

    Jain, Charitra; Rozel, Antoine; Tackley, Paul

    2016-04-01

    Rolf et al. (EPSL, 2012) and Coltice et al. (Science, 2012) have previously shown that continents exert a first order influence on Earth's mantle flow by affecting convective wavelength and surface heat flow. With stationary continents, Heron and Lowman (JGR, 2014) highlighted the decreasing role of continental insulation on subcontinental temperatures with higher Rayleigh number (Ra). However, the question whether there exists a correlation between mobile continents and elevated temperatures in the subcontinental mantle or not remains to be answered. By systematically varying parameters like core-mantle boundary (CMB) temperature, continental size, and mantle heating modes (basal and internal); we model thermo-chemical mantle convection with 2D spherical annulus geometry (Hernlund and Tackley, PEPI 2008) using StagYY (Tackley, PEPI 2008). Starting with a simple incompressible model having mobile continents, we observe this correlation. Furthermore, this correlation still holds when the model complexity is gradually increased by introducing internal heating, compressibility, and melting. In general, downwellings reduce the mantle temperature away from the continents, thereby resulting in correlation between mobile continents and elevated temperatures in the subcontinental mantle. For incompressible models (Boussinesq approximation), correlation exists and the dominant degree of convection varies with the continental distribution. When internal heating is switched on, correlation is observed but it is reduced as there are less cold regions in the mantle. Even for compressible models with melting, big continents are able to focus the heat underneath them. The dominant degree of convection changes with continental breakup. Additionally, correlation is observed to be higher in the upper mantle (300 - 1000 km) compared to the lower mantle (1000 - 2890 km). At present, mobile continents in StagYY are simplified into a compositionally distinct field drifting at the top of

  6. Fatigue Life Prediction of 2D Woven Ceramic-Matrix Composites at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2017-02-01

    In this paper, the fatigue life of 2D woven ceramic-matrix composites, i.e., SiC/SiC, SiC/Si-N-C, SiC/Si-B4C, and Nextel 610™/Aluminosilicate, at room and elevated temperatures has been predicted using the micromechanics approach. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. The Budiansky-Hutchinson-Evans shear-lag model was used to describe the microstress field of the damaged composite considering fibers failure. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. The interface shear stress and fibers strength degradation model and oxidation region propagation model have been adopted to analyze the fatigue and oxidation effects on fatigue life of the composite, which is controlled by interface frictional slip and diffusion of oxygen gas through matrix multicrackings. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperatures, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composites fatigue fractures. The fatigue life S-N curves of 2D SiC/SiC, SiC/Si-N-C, SiC/Si-B4C, and Nextel 610™/Aluminosilicate composites at room temperature and 800, 1000 and 1200 °C in air and steam have been predicted.

  7. Fatigue Life Prediction of 2D Woven Ceramic-Matrix Composites at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2017-03-01

    In this paper, the fatigue life of 2D woven ceramic-matrix composites, i.e., SiC/SiC, SiC/Si-N-C, SiC/Si-B4C, and Nextel 610™/Aluminosilicate, at room and elevated temperatures has been predicted using the micromechanics approach. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. The Budiansky-Hutchinson-Evans shear-lag model was used to describe the microstress field of the damaged composite considering fibers failure. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. The interface shear stress and fibers strength degradation model and oxidation region propagation model have been adopted to analyze the fatigue and oxidation effects on fatigue life of the composite, which is controlled by interface frictional slip and diffusion of oxygen gas through matrix multicrackings. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperatures, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composites fatigue fractures. The fatigue life S- N curves of 2D SiC/SiC, SiC/Si-N-C, SiC/Si-B4C, and Nextel 610™/Aluminosilicate composites at room temperature and 800, 1000 and 1200 °C in air and steam have been predicted.

  8. Characterization of Compressive Creep Behavior of Oxide/Oxide Composite with Monazite Coating at Elevated Temperature

    DTIC Science & Technology

    2006-03-01

    Materials, and Structures: A. Ed. Mrityunjay Singh and Todd Jensen. Westerville, OH: The American Ceramic Society, 2001. 5. Antti, M-L, E. Lara-Curzio... Emmanuel E. Boakye, Pavel Mogilevsky, and Michael K. Cinibulk. “Effectiveness of Monazite Coatings in Oxide/Oxide Composites after Long-Term Exposure

  9. Characterization of lignin derived from water-only and dilute acid flowthrough pretreatment of poplar wood at elevated temperatures

    DOE PAGES

    Zhang, Libing; Yan, Lishi; Wang, Zheming; ...

    2015-12-01

    In this study, flowthrough pretreatment of biomass has high potential to valorize lignin derivatives to high-value products, which is vital to enhance the economy of biorefinery plants. Comprehensive understanding of lignin behaviors and solubilization chemistry in aqueous pretreatment such as water-only and dilute acid flowthrough pretreatment is of fundamental importance to achieve the goal of providing flexible platform for lignin utilization. In this study, the effects of flowthrough pretreatment conditions on lignin separation from poplar wood were reported as well as the characteristics of three sub-sets of lignin produced from the pretreatment, including residual lignin in pretreated solid residues (ReL),more » recovered insoluble lignin in pretreated liquid (RISL), and recovered soluble lignin in pretreatment liquid (RSL). Both the water-only and 0.05% (w/w) sulfuric acid pretreatments were performed at temperatures from 160 to 270°C on poplar wood in a flowthrough reactor system for 2-10 min. Results showed that water-only flowthrough pretreatment primarily removed syringyl (S units). Increased temperature and/or the addition of sulfuric acid enhanced the removal of guaiacyl (G units) compared to water-only pretreatments at lower temperatures, resulting in nearly complete removal of lignin from the biomass. Results also suggested that more RISL was recovered than ReL and RSL in both dilute acid and water-only flowthrough pretreatment at elevated temperatures. NMR spectra of the RISL revealed significant β-O-4 cleavage, α-β deoxygenation to form cinnamyl-like end groups, and slight β-5 repolymerization in both water-only and dilute acid flowthrough pretreatments. In conclusion, elevated temperature and/or dilute acid greatly enhanced lignin removal to almost 100% by improving G unit removal besides S unit removal in flowthrough system. A new lignin chemistry transformation pathway was proposed and revealed the complexity of lignin structural change

  10. Revolutionary opportunities for materials and structures study

    SciTech Connect

    Schweiger, F.A.

    1987-02-01

    The revolutionary opportunities for materials and structures study was performed to provide Government and Industry focus for advanced materials technology. Both subsonic and supersonic engine studies and aircraft fuel burn and DOC evaluation are examined. Year 2010 goal materials were used in the advanced engine studies. These goal materials and improved component aero yielded subsonic fuel burn and DOC improvements of 13.4 percent and 5 percent, respectively and supersonic fuel burn and DOC improvements of 21.5 percent and 18 percent, respectively. Conclusions are that the supersonic study engine yielded fuel burn and DOC improvements well beyond the program goals; therefore, it is appropriate that advanced material programs be considered.

  11. Revolutionary opportunities for materials and structures study

    NASA Technical Reports Server (NTRS)

    Schweiger, F. A.

    1987-01-01

    The revolutionary opportunities for materials and structures study was performed to provide Government and Industry focus for advanced materials technology. Both subsonic and supersonic engine studies and aircraft fuel burn and DOC evaluation are examined. Year 2010 goal materials were used in the advanced engine studies. These goal materials and improved component aero yielded subsonic fuel burn and DOC improvements of 13.4 percent and 5 percent, respectively and supersonic fuel burn and DOC improvements of 21.5 percent and 18 percent, respectively. Conclusions are that the supersonic study engine yielded fuel burn and DOC improvements well beyond the program goals; therefore, it is appropriate that advanced material programs be considered.

  12. Investigation of Structure, Properties and Deformation Mechanisms of Elevated Temperature Al Alloys with High Specific Properties

    DTIC Science & Technology

    2007-11-02

    Al2Mg3Zn3), S(Al2CuMg) and Al3(Sc, Zr) phases in L7 alloy. Dispersed precipitates of intermetallic phases strengthen the solid solution at heat...scandium intermetallics from the melt and dispersion strengthening as a result of formation of secondary particles of Al3(Sc, Zr) during artificial ageing...Al3(Sc1-xZrx) (Fig.1.2) is a reason for additional strengthening of studied alloys along with strengthening by dispersion particles of η′ phase

  13. Mechanical Properties and Fatigue Behavior of Unitized Composite Airframe Structures at Elevated Temperature

    DTIC Science & Technology

    2014-03-27

    matrix (typically a polymer , metal, or ceramic resin) and the reinforcement (can also be polymeric , metallic, or ceramic) in the form of fibers, whiskers...when all absorbed water was evaporated. Weight loss stabilized in less than 9 days as shown in Figure 12. The specimens were then removed 27 from the...The tension-tension fatigue behavior of newly developed polymer matrix composites (PMCs) and that of a unitized composite was studied. The PMCs

  14. Polymorphism and the crystal structures of InSb at elevated temperature and pressure

    NASA Technical Reports Server (NTRS)

    Yu, S.-C.; Spain, I. L.; Skelton, E. F.

    1978-01-01

    The paper presents polycrystalline X-ray diffraction data for three high-pressure phases of InSb. The study employed two types of diamond-anvil pressure cells. The X-ray diffraction parameters were recorded at different fixed pressures and temperatures on flat film. The experiment utilized Zr-filtered Mo radiation. The intensities were estimated from the X-ray photographs using a semiautomated microdensitometer.

  15. Multiphase Ceramics for Mechanical and Structural Reliability at Low and Elevated Temperatures

    DTIC Science & Technology

    1994-06-30

    example of PSZ uses MgO as the stabilizer. The second class. ’ tetragonal zirconia polycrystals’ ( TZP ). consists entirely (or nearly so) of tetragonal ...Mazdiyasni, C. T. Lynch and J. S. Smith II, " Cubic Phase Stabilization of Translucent Yttria- Zirconia at Very Low Temperatures", J. Am. Ceram. Soc., 50[10...toughness and Iracture strength of the composite increased. Similar results were reported by 8 French. et. al. 1992). for the cubic zirconia + alumina

  16. Plastics as structural materials for aircraft

    NASA Technical Reports Server (NTRS)

    Kline, G M

    1937-01-01

    The purpose here is to consider the mechanical characteristics of reinforced phenol-formaldehyde resin as related to its use as structural material for aircraft. Data and graphs that have appeared in the literature are reproduced to illustrate the comparative behavior of plastics and materials commonly used in aircraft construction. Materials are characterized as to density, static strength, modulus of elasticity, resistance to long-time loading, strength under repeated impact, energy absorption, corrosion resistance, and ease of fabrication.

  17. Creep-fatigue criteria and inelastic behavior of modified 9Cr-1Mo steel at elevated temperatures. Final report

    SciTech Connect

    Ruggles, M.B.; Ogata, T.

    1994-02-01

    The ever increasing demand for safety requires that stringent and conservative methodology be developed for design and analysis of reactor components. At present modified 9Cr-1Mo steel is a candidate material for construction of steam generators in fast breeder reactors. Therefore high-temperature material properties and extensive insight into deformation behavior and creep-fatigue life are required to develop design guidelines for use of modified 9Cr-1Mo steel in actual plant components. However, existing information on creep-fatigue and deformation response of modified 9Cr-1Mo steel is insufficient, and further experimental and modeling efforts are needed. A joint effort between the Electric Power Research Institute (EPRI) in the United States and the Central Research Institute of Electric Power Industry (CRIEPI) in Japan was started in 1991 to investigate the inelastic behavior of and to develop creep-fatigue criteria for modified 9Cr-1Mo steel at elevated temperatures. The current program focuses on uniaxial and biaxial fatigue, creep, and creep-fatigue tests. Results of this effort are presented in this report. Section 2 introduces the test material and experimental arrangement. Uniaxial exploratory deformation tests and unified constitutive equations for inelastic analysis of modified 9Cr-1Mo steel are presented in Sections 3 and 4, respectively. Axial fatigue and creep-fatigue test results are discussed in Section 5. Section 6 is devoted to constant stress creep tests. Biaxial fatigue and creep-fatigue tests are described in Section 7. Progress in creep-fatigue life evaluation is reported in Section 8.

  18. Foreign Object Damage Behavior of a SiC/SiC Composite at Ambient and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Pereira, J. Michael; Gyekenyesi, John P.; Choi, Sung R.

    2004-01-01

    Foreign object damage (FOD) behavior of a gas-turbine grade SiC/SiC ceramic matrix composite (CMC) was determined at 25 and 1316 C, employing impact velocities from 115 to 440 meters per second by 1.59-mm diameter stell-ball projectiles. Two different types of specimen support were used at each temperature: fully supported and partially supported. For a given temperature, the degree of post-impact strength degradation increased with increasing impact velocity, and was greater in a partially supported configuration than in a fully supported one. The elevated-temperature FOD resistance of the composite, particularly under partially supported loading at higher impact velocities greater than or equal to 350 meters per second, was significantly less than the ambient-temperature counterpart, attributed to a weakening effect of the composite. For fully supported loading, frontal contact stress played a major role in generating composite damage; whereas, for partially supported loading, both frontal contact and backside bending stresses were combined sources of damage generation. The SiC/SiC composite was able to survive higher energy impacts without complete structural failure but suffered more strength affecting damage from low energy impacts than AS800 and SN282 silicon nitrides.

  19. Development of the Structural Materials Information Center

    SciTech Connect

    Oland, C.B.; Naus, D.J.

    1990-01-01

    The US Nuclear Regulatory Commission has initiated a Structural Aging Program at the Oak Ridge National Laboratory to identify potential structural safety issues related to continued service of nuclear power plants and to establish criteria for evaluating and resolving these issues. One of the tasks in this program focuses on the establishment of a Structural Materials Information Center where data and information on the time variation of concrete and other structural material properties under the influence of pertinent environmental stressors and aging factors are being collected and assembled into a data base. This data base will be used to assist in the prediction of potential long-term deterioration of critical structural components in nuclear power plants and to establish limits on hostile environmental exposure for these structures and materials. Two complementary data base formats have been developed. The Structural Materials Handbook is an expandable, hard-copy reference document that contains complete sets of data and information for selected portland cement concrete, metallic reinforcement, prestressing tendon, and structural steel materials. Baseline data, reference properties and environmental information are presented in the handbook as tables, notes and graphs. The handbook, which will be published in four volumes, serves as the information source for the electronic data base. The Structural Materials Electronic Data Base is accessible by an IBM-compatible personal computer and provides an efficient means for searching the various data base files to locate materials with similar properties. Properties will be reported in the International System of Units (SI) and in customary units whenever possible. 7 refs., 3 figs., 4 tabs.

  20. Materials support for HITAF

    SciTech Connect

    Breder, K.; Tennery, V.J.

    1994-09-01

    The primary objective of this work is to compare the mechanical performance of structural ceramic materials which are being proposed for use in the air heater of a coal fired high temperature advanced furnace (HITAF) for power generation. The effort is focused on providing preliminary evaluations of key mechanical properties required of ceramic materials for this application. The critical properties studied include fast fracture strength distribution at room temperature and two elevated temperatures, any trends in slow crack growth (SCG) susceptibility at elevated temperatures, and preliminary creep behavior. In addition residual fast fracture strength of a limited number of specimens corroded in a coal ash environment will be evaluated at a later stage in the project.

  1. Smart materials and structures: what are they?

    NASA Astrophysics Data System (ADS)

    Spillman, W. B., Jr.; Sirkis, J. S.; Gardiner, P. T.

    1996-06-01

    There has been considerable discussion in the technical community on a number of questions concerned with smart materials and structures, such as what they are, whether smart materials can be considered a subset of smart structures, whether a smart structure and an intelligent structure are the same thing, etc. This discussion is both fueled and confused by the technical community due to the truly multidisciplinary nature of this new field. Smart materials and structures research involves so many technically diverse fields that it is quite common for one field to completely misunderstand the terminology and start of the art in other fields. In order to ascertain whether a consensus is emerging on a number of questions, the technical community was surveyed in a variety of ways including via the internet and by direct contact. The purpose of this survey was to better define the smart materials and structures field, its current status and its potential benefits. Results of the survey are presented and discussed. Finally, a formal definition of the field of smart materials and structures is proposed.

  2. The effect of elevated temperatures on the dentin adhesion of resin composites.

    PubMed

    Brackett, William W; Covey, David A; Haisch, Larry D

    2003-01-01

    Although resin composite restorations may undergo relatively extreme temperature changes in the oral cavity, little is known about the effects of temperature on their adhesion to tooth structure. This study evaluated the effect of temperature on shear bond strength to dentin of three commercial resin dentin adhesives through testing of matured specimens over the 20 degrees to 55 degrees C temperature range. A significant difference (p < 0.05) was observed between 20 degrees C and 55 degrees C for all the materials, and for one of the materials, a significant difference was also observed between 20 degrees C and 37 degrees C.

  3. Integrated design of structures, controls, and materials

    NASA Technical Reports Server (NTRS)

    Blankenship, G. L.

    1994-01-01

    In this talk we shall discuss algorithms and CAD tools for the design and analysis of structures for high performance applications using advanced composite materials. An extensive mathematical theory for optimal structural (e.g., shape) design was developed over the past thirty years. Aspects of this theory have been used in the design of components for hypersonic vehicles and thermal diffusion systems based on homogeneous materials. Enhancement of the design methods to include optimization of the microstructure of the component is a significant innovation which can lead to major enhancements in component performance. Our work is focused on the adaptation of existing theories of optimal structural design (e.g., optimal shape design) to treat the design of structures using advanced composite materials (e.g., fiber reinforced, resin matrix materials). In this talk we shall discuss models and algorithms for the design of simple structures from composite materials, focussing on a problem in thermal management. We shall also discuss methods for the integration of active structural controls into the design process.

  4. Evaluation of Three Constitutive Models for the Prediction of Hastelloy X Elevated Temperature Cyclic Response

    NASA Technical Reports Server (NTRS)

    Moreno, V.

    1983-01-01

    The approach for the method development assumes that, for a thermally loaded structure, the overall strain history is defined by linear elastic analysis. The local stress history at a fatigue critical location is then determined from a one dimensional material behavior model and the local strain and temperature conditions. Three material models are currently being evaluated to assess their ability to predict relevant high temperature cyclic material response characteristics. They are: a time independent classical plasticity and creep representation, a time dependent viscoplastic model capable of predicting combined creep and plasticity effects, and an approximate elastic analysis approach that uses a series of stress-strain curves and a cyclic hardening model to determine reverse plasticity.

  5. OSMOTIC COEFFICIENTS, SOLUBILITIES, AND DELIQUESCENCE RELATIONS IN MIXED AQUEOUS SALT SOLUTIONS AT ELEVATED TEMPERATURE

    SciTech Connect

    M.S. Gruszkiewicz; D.A. Palmer

    2006-02-22

    While thermodynamic properties of pure aqueous electrolytes are relatively well known at ambient temperature, there are far fewer data for binary systems extending to elevated temperatures and high concentrations. There is no general theoretically sound basis for prediction of the temperature dependence of ionic activities, and consequently temperature extrapolations based on ambient temperature data and empirical equations are uncertain and require empirical verification. Thermodynamic properties of mixed brines in a wide range of concentrations would enhance the understanding and precise modeling of the effects of deliquescence of initially dry solids in humid air in geological environments and in modeling the composition of waters during heating, cooling, evaporation or condensation processes. These conditions are of interest in the analysis of waters on metal surfaces at the proposed radioactive waste repository at Yucca Mountain, Nevada. The results obtained in this project will be useful for modeling the long-term evolution of the chemical environment, and this in turn is useful for the analysis of the corrosion of waste packages. In particular, there are few reliable experimental data available on the relationship between relative humidity and composition that reveals the eutonic points of the mixtures and the mixture deliquescence RH. The deliquescence RH for multicomponent mixtures is lower than that of pure component or binary solutions, but is not easy to predict quantitatively since the solutions are highly nonideal. In this work we used the ORNL low-temperature and high-temperature isopiestic facilities, capable of precise measurements of vapor pressure between ambient temperature and 250 C for determination of not only osmotic coefficients, but also solubilities and deliquescence points of aqueous mixed solutions in a range of temperatures. In addition to standard solutions of CaCl{sub 2}, LiCl, and NaCl used as references, precise direct

  6. Elevated Temperature and CO2 Stimulate Late-Season Photosynthesis But Impair Cold Hardening in Pine[OPEN

    PubMed Central

    2016-01-01

    Rising global temperature and CO2 levels may sustain late-season net photosynthesis of evergreen conifers but could also impair the development of cold hardiness. Our study investigated how elevated temperature, and the combination of elevated temperature with elevated CO2, affected photosynthetic rates, leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening in Eastern white pine (Pinus strobus). We designed an experiment where control seedlings were acclimated to long photoperiod (day/night 14/10 h), warm temperature (22°C/15°C), and either ambient (400 μL L−1) or elevated (800 μmol mol−1) CO2, and then shifted seedlings to growth conditions with short photoperiod (8/16 h) and low temperature/ambient CO2 (LTAC), elevated temperature/ambient CO2 (ETAC), or elevated temperature/elevated CO2 (ETEC). Exposure to LTAC induced down-regulation of photosynthesis, development of sustained nonphotochemical quenching, accumulation of soluble carbohydrates, expression of a 16-kD dehydrin absent under long photoperiod, and increased freezing tolerance. In ETAC seedlings, photosynthesis was not down-regulated, while accumulation of soluble carbohydrates, dehydrin expression, and freezing tolerance were impaired. ETEC seedlings revealed increased photosynthesis and improved water use efficiency but impaired dehydrin expression and freezing tolerance similar to ETAC seedlings. Sixteen-kilodalton dehydrin expression strongly correlated with increases in freezing tolerance, suggesting its involvement in the development of cold hardiness in P. strobus. Our findings suggest that exposure to elevated temperature and CO2 during autumn can delay down-regulation of photosynthesis and stimulate late-season net photosynthesis in P. strobus seedlings. However, this comes at the cost of impaired freezing tolerance. Elevated temperature and CO2 also impaired freezing tolerance. However, unless the frequency and timing of extreme low

  7. Finite Element Analysis of the Random Response Suppression of Composite Panels at Elevated Temperatures using Shape Memory Alloy Fibers

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Zhong, Z. W.; Mei, Chuh

    1994-01-01

    A feasibility study on the use of shape memory alloys (SMA) for suppression of the random response of composite panels due to acoustic loads at elevated temperatures is presented. The constitutive relations for a composite lamina with embedded SMA fibers are developed. The finite element governing equations and the solution procedures for a composite plate subjected to combined acoustic and thermal loads are presented. Solutions include: 1) Critical buckling temperature; 2) Flat panel random response; 3) Thermal postbuckling deflection; 4) Random response of a thermally buckled panel. The preliminary results demonstrate that the SMA fibers can completely eliminate the thermal postbuckling deflection and significantly reduce the random response at elevated temperatures.

  8. Defense activation triggers differential expression of phospholipase-C (PLC) genes and elevated temperature induces phosphatidic acid (PA) accumulation in tomato

    PubMed Central

    Abd-El-Haliem, Ahmed; Meijer, Harold J.G.; Tameling, Wladimir I.L.; Vossen, Jack H.; Joosten, Matthieu H.A.J.

    2012-01-01

    Recently, we provided the first genetic evidence for the requirement of tomato PLC4 and PLC6 genes in defense activation and disease resistance. The encoded enzymes were catalytically active as they were able to degrade phosphatidylinositol (PI), thereby producing diacylglycerol (DG). Here we report differential PLC gene expression following the initiation of defense signaling by the interaction between Cladosporium fulvum resistance (R) protein Cf-4 and its matching effector Avr4 in tomato hybrid seedlings that express both Cf-4 and Avr4. Furthermore, we observed that PLC3 and PLC6 gene expression is upregulated by elevated temperature in the control seedlings. This upregulation coincides with an increase in the levels of phosphatidic acid (PA) and a decrease in the levels of PI and phosphatidylinositol phosphate (PIP). The decrease in PI and PIP levels matches with the activation of PLC. In addition, the levels of the structural phospholipids phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) declined transiently during recovery after the exposure to elevated temperature., Further studies will be required to explain the mechanism causing the sustained accumulation of PA during recovery, combined with a reduction in the levels of structural phospholipids. PMID:22899083

  9. Physical and chemical changes in whey protein concentrate stored at elevated temperature and humidity.

    PubMed

    Tunick, Michael H; Thomas-Gahring, Audrey; Van Hekken, Diane L; Iandola, Susan K; Singh, Mukti; Qi, Phoebe X; Ukuku, Dike O; Mukhopadhyay, Sudarsan; Onwulata, Charles I; Tomasula, Peggy M

    2016-03-01

    In a case study, we monitored the physical properties of 2 batches of whey protein concentrate (WPC) under adverse storage conditions to provide information on shelf life in hot, humid areas. Whey protein concentrates with 34.9 g of protein/100g (WPC34) and 76.8 g of protein/100g (WPC80) were stored for up to 18 mo under ambient conditions and at elevated temperature and relative humidity. The samples became yellower with storage; those stored at 35 °C were removed from the study by 12 mo because of their unsatisfactory appearance. Decreases in lysine and increases in water activity, volatile compound formation, and powder caking values were observed in many specimens. Levels of aerobic mesophilic bacteria, coliforms, yeast, and mold were <3.85 log10 cfu/g in all samples. Relative humidity was not a factor in most samples. When stored in sealed bags, these samples of WPC34 and WPC80 had a shelf life of 9 mo at 35 °C but at least 18 mo at lower temperatures, which should extend the market for these products.

  10. Fatigue Hysteresis of Carbon Fiber-Reinforced Ceramic-Matrix Composites at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Li, Longbiao

    2016-02-01

    When the fiber-reinforced ceramic-matrix composites (CMCs) are first loading to fatigue peak stress, matrix multicracking and fiber/matrix interface debonding occur. Under fatigue loading, the stress-strain hysteresis loops appear as fiber slipping relative to matrix in the interface debonded region upon unloading/reloading. Due to interface wear at room temperature or interface oxidation at elevated temperature, the interface shear stress degredes with increase of the number of applied cycles, leading to the evolution of the shape, location and area of stress-strain hysteresis loops. The evolution characteristics of fatigue hysteresis loss energy in different types of fiber-reinforced CMCs, i.e., unidirectional, cross-ply, 2D and 2.5D woven, have been investigated. The relationships between the fatigue hysteresis loss energy, stress-strain hysteresis loops, interface frictional slip, interface shear stress and interface radial thermal residual stress, matrix stochastic cracking and fatigue peak stress of fiber-reinforced CMCs have been established.

  11. Elevated temperature creep properties of the 54Fe-29Ni-17Co "Kovar" alloy.

    SciTech Connect

    Stephens, John Joseph, Jr.; Rejent, Jerome Andrew; Schmale, David T.

    2009-01-22

    The outline of this presentation is: (1) Applications of Kovar Alloy in metal/ceramic brazing; (2) Diffusion bonding of precision-photoetched Kovar parts; (3) Sample composition and annealing conditions; (4) Intermediate temperature creep properties (350-650 C); (5) Power law creep correlations--with and without modulus correction; (6) Compressive stress-strain properties (23-900 C); (7) Effect of creep deformation on grain growth; and (8) Application of the power law creep correlation to the diffusion bonding application. The summary and conclusions are: Elevated temperature creep properties of Kovar from 750-900 C obey a power law creep equation with a stress exponent equal to 4.9, modulus compensated activation energy of 47.96 kcal/mole. Grain growth in Kovar creep samples tested at 750 and 800 C is quite sluggish. Significant grain growth occurs at 850 C and above, this is consistent with isothermal grain growth studies performed on Kovar alloy wires. Finite element analysis of the diffusion bonding of Kovar predict that stresses of 30 MPa and higher are needed for good bonding at 850 C, we believe that 'sintering' effects must be accounted for to allow FEA to be predictive of actual processing conditions. Additional creep tests are planned at 250-650 C.

  12. Aluminum-Silicon Alloy Having Improved Properties at Elevated Temperatures and Articles Cast Therefrom

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A. (Inventor); Chen, Po-Shou (Inventor)

    2002-01-01

    An aluminum alloy suitable for high temperature applications, such as heavy duty pistons and other internal combustion applications. having the following composition, by weight percent (wt %): Silicon: 11.0-14.0; Copper: 5.6-8.0; Iron: 0-0.8; Magnesium: 0.5-1.5; Nickel: 0.05-0.9; Manganese: 0.5-1.5; Titanium: 0.05-1.2; Zirconium: 0.12-1.2; Vanadium: 0.05-1.2; Zinc: 0.005-0.9; Strontium: 0.001-0.1; Aluminum: balance. In this alloy the ratio of silicon:magnesium is 10-25, and the ratio of copper:magnesium is 4-15. After an article is cast from this alloy, the article is treated in a solutionizing step which dissolves unwanted precipitates and reduces any segregation present in the original alloy. After this solutionizing step, the article is quenched, and is then aged at an elevated temperature for maximum strength.

  13. Elevated temperature increases carbon and nitrogen fluxes between phytoplankton and heterotrophic bacteria through physical attachment.

    PubMed

    Arandia-Gorostidi, Nestor; Weber, Peter K; Alonso-Sáez, Laura; Morán, Xosé Anxelu G; Mayali, Xavier

    2017-03-01

    Quantifying the contribution of marine microorganisms to carbon and nitrogen cycles and their response to predicted ocean warming is one of the main challenges of microbial oceanography. Here we present a single-cell NanoSIMS isotope analysis to quantify C and N uptake by free-living and attached phytoplankton and heterotrophic bacteria, and their response to short-term experimental warming of 4 °C. Elevated temperature increased total C fixation by over 50%, a small but significant fraction of which was transferred to heterotrophs within 12 h. Cell-to-cell attachment doubled the secondary C uptake by heterotrophic bacteria and increased secondary N incorporation by autotrophs by 68%. Warming also increased the abundance of phytoplankton with attached heterotrophs by 80%, and promoted C transfer from phytoplankton to bacteria by 17% and N transfer from bacteria to phytoplankton by 50%. Our results indicate that phytoplankton-bacteria attachment provides an ecological advantage for nutrient incorporation, suggesting a mutualistic relationship that appears to be enhanced by temperature increases.

  14. Elevated-temperature-induced acceleration of PACT clearing process of mouse brain tissue

    NASA Astrophysics Data System (ADS)

    Yu, Tingting; Qi, Yisong; Zhu, Jingtan; Xu, Jianyi; Gong, Hui; Luo, Qingming; Zhu, Dan

    2017-01-01

    Tissue optical clearing technique shows a great potential for neural imaging with high resolution, especially for connectomics in brain. The passive clarity technique (PACT) is a relative simple clearing method based on incubation, which has a great advantage on tissue transparency, fluorescence preservation and immunostaining compatibility for imaging tissue blocks. However, this method suffers from long processing time. Previous studies indicated that increasing temperature can speed up the clearing. In this work, we aim to systematacially and quantitatively study this influence based on PACT with graded increase of temperatures. We investigated the process of optical clearing of brain tissue block at different temperatures, and found that elevated temperature could accelerate the clearing process and also had influence on the fluorescence intensity. By balancing the advantages with drawbacks, we conclude that 42–47 °C is an alternative temperature range for PACT, which can not only produce faster clearing process, but also retain the original advantages of PACT by preserving endogenous fluorescence well, achieving fine morphology maintenance and immunostaining compatibility.

  15. Significantly improved cyclability of lithium manganese oxide under elevated temperature by an easily oxidized electrolyte additive

    NASA Astrophysics Data System (ADS)

    Zhu, Yunmin; Rong, Haibo; Mai, Shaowei; Luo, Xueyi; Li, Xiaoping; Li, Weishan

    2015-12-01

    Spinel lithium manganese oxide, LiMn2O4, is a promising cathode for lithium ion battery in large-scale applications, because it possesses many advantages compared with currently used layered lithium cobalt oxide (LiCoO2) and olivine phosphate (LiFePO4), including naturally abundant resource, environmental friendliness and high and long work potential plateau. Its poor cyclability under high temperature, however, limits its application. In this work, we report a significant cyclability improvement of LiMn2O4 under elevated temperature by using dimethyl phenylphonite (DMPP) as an electrolyte additive. Charge/discharge tests demonstrate that the application of 0.5 wt.% DMPP yields a capacity retention improvement from 16% to 82% for LiMn2O4 after 200 cycles under 55 °C at 1 C (1C = 148 mAh g-1) between 3 and 4.5 V. Electrochemical and physical characterizations indicate that DMPP is electrochemically oxidized at the potential lower than that for lithium extraction, forming a protective cathode interphase on LiMn2O4, which suppresses the electrolyte decomposition and prevents LiMn2O4 from crystal destruction.

  16. Shock Sensitivity of LX-04 Containing Delta Phase HMX at Elevated Temperatures

    SciTech Connect

    Urtiew, P A; Forbes, J W; Tarver, C M; Vandersall, K S; Garcia, F; Greenwood, D W; Hsu, P C; Maienschein, J L

    2003-07-11

    LX-04 is a widely used HMX-based plastic bonded explosive, which contains 85 weight % HMX and 15 weight % Viton binder. The sensitivity of LX-04 to a single stimulus such as heat, impact, and shock has been previously studied. However, hazard scenarios can involve multiple stimuli, such as heating to temperatures close to thermal explosion conditions followed by fragment impact, producing a shock in the hot explosive. The sensitivity of HMX at elevated temperatures is further complicated by the beta to delta solid-state phase transition, which occurs at approximately 165 C. This paper presents the results of shock initiation experiments conducted with LX-04 preheated to 190 C, as well as density measurements and small scale safety test results of the {delta} phase HMX at room temperature. This work shows that LX-04 at 190 C is more shock sensitive than LX-04 at 150 C or 170 C due to the volume increase during the {beta} to {delta} solid phase transition, which creates more hot spots, and the faster growth of reaction during shock compression.

  17. 'Effects of Elevated Temperature on Dehalococcoides Dechlorination Performance and DNA and RNA Biomarker Abundance

    SciTech Connect

    Fletcher, Kelly E; Costanza, Jed; Cruz-Garcia, Claribel; Ramaswamy, Nivedhya; Pennell, Kurt; Loeffler, Frank E

    2011-01-01

    Coupling thermal treatment with microbial reductive dechlorination is a promising remedy for tetrachloroethene (PCE) and trichloroethene (TCE) contaminated source zones. Laboratory experiments evaluated Dehalococcoides (Dhc) dechlorination performance, viability, and biomarker gene (DNA) and transcript (mRNA) abundances during exposure to elevated temperatures. The PCE-dechlorinating consortia BDI and OW produced ethene when incubated at temperatures of 30 C, but vinyl chloride (VC) accumulated when cultures were incubated at 35 or 40 C. Cultures incubated at 40 C for less than 49 days resumed VC dechlorination following cooling; however, incubation at 45 C resulted in complete loss of dechlorination activity. Dhc 16S rRNA, bvcA, and vcrA gene abundances in cultures showing complete dechlorination to ethene at 30 C exceeded those measured in cultures incubated at higher temperatures, consistent with observed dechlorination activities. Conversely, biomarker gene transcript abundances per cell in cultures incubated at 35 and 40 C were generally at least one order-of-magnitude greater than those measured in ethene-producing cultures incubated at 30 C. Even in cultures accumulating VC, transcription of the vcrA gene, which is implicated in VC-to-ethene dechlorination, was up-regulated. Temperature stress caused the up-regulation of Dhc reductive dehalogenase gene expression indicating that Dhc gene expression measurements should be interpreted cautiously as Dhc biomarker gene transcript abundances may not correlate with dechlorination activity.

  18. Microstructure and Elevated Temperature Properties of Die-cast AZ91- xNd Magnesium Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Wang, Limin; An, Jian; Liu, Yongbing

    2008-10-01

    The effect of Nd addition on the microstructure and mechanical properties of a die-cast AZ91 alloy was investigated in the present work. The results show that the die-cast AZ91 alloy is composed of α-Mg matrix and γ-Mg17Al12 phase. Nd addition into the AZ91 alloy leads to the formation of rare earth containing intermetallic phase. Al4Nd phase forms when Nd content is less than or equal to 1.0 wt.%. Al2Nd phase appears simultaneously when Nd content reaches to 3.0 wt.%. The size and volume fraction of γ-Mg17Al12 phase decrease, because of the newly formed Al-Nd phase. And the γ-Mg17Al12 phase distributes from reticular to dispersive. Nd addition has a little effect on the room temperature properties of the die-cast AZ91 alloy, but greatly improves the elevated temperature properties. The tensile strength of AZ91-0.5Nd and AZ91-1.0Nd alloy tested at 150 °C is even close to the room temperature strength. The AZ91-1.0Nd alloy has the optimal properties.

  19. Contrasting effects of elevated temperature and invertebrate grazing regulate multispecies interactions between decomposer fungi.

    PubMed

    A'Bear, A Donald; Murray, William; Webb, Rachel; Boddy, Lynne; Jones, T Hefin

    2013-01-01

    Predicting the influence of biotic and abiotic factors on species interactions and ecosystem processes is among the primary aims of community ecologists. The composition of saprotrophic fungal communities is a consequence of competitive mycelial interactions, and a major determinant of woodland decomposition and nutrient cycling rates. Elevation of atmospheric temperature is predicted to drive changes in fungal community development. Top-down regulation of mycelial growth is an important determinant of, and moderator of temperature-driven changes to, two-species interaction outcomes. This study explores the interactive effects of a 4 °C temperature increase and soil invertebrate (collembola or woodlice) grazing on multispecies interactions between cord-forming basidiomycete fungi emerging from colonised beech (Fagus sylvatica) wood blocks. The fungal dominance hierarchy at ambient temperature (16 °C; Phanerochaete velutina > Resinicium bicolor > Hypholoma fasciculare) was altered by elevated temperature (20 °C; R. bicolor > P. velutina > H. fasciculare) in ungrazed systems. Warming promoted the competitive ability of the fungal species (R. bicolor) that was preferentially grazed by all invertebrate species. As a consequence, grazing prevented the effect of temperature on fungal community development and maintained a multispecies assemblage. Decomposition of fungal-colonised wood was stimulated by warming, with implications for increased CO2 efflux from woodland soil. Analogous to aboveground plant communities, increasing complexity of biotic and abiotic interactions appears to be important in buffering climate change effects on soil decomposers.

  20. Elevated-temperature-induced acceleration of PACT clearing process of mouse brain tissue

    PubMed Central

    Yu, Tingting; Qi, Yisong; Zhu, Jingtan; Xu, Jianyi; Gong, Hui; Luo, Qingming; Zhu, Dan

    2017-01-01

    Tissue optical clearing technique shows a great potential for neural imaging with high resolution, especially for connectomics in brain. The passive clarity technique (PACT) is a relative simple clearing method based on incubation, which has a great advantage on tissue transparency, fluorescence preservation and immunostaining compatibility for imaging tissue blocks. However, this method suffers from long processing time. Previous studies indicated that increasing temperature can speed up the clearing. In this work, we aim to systematacially and quantitatively study this influence based on PACT with graded increase of temperatures. We investigated the process of optical clearing of brain tissue block at different temperatures, and found that elevated temperature could accelerate the clearing process and also had influence on the fluorescence intensity. By balancing the advantages with drawbacks, we conclude that 42–47 °C is an alternative temperature range for PACT, which can not only produce faster clearing process, but also retain the original advantages of PACT by preserving endogenous fluorescence well, achieving fine morphology maintenance and immunostaining compatibility. PMID:28139694

  1. Effect of elevated temperature and enhanced drainage on carbon balance of tundra microcosms

    SciTech Connect

    Johnson, L.C.; Shaver, G.R.; Giblin, A.E.; Nadelhoffer, K.J.; Rastetter, E.B.; Laundre, J.A.; Murray, G.L. )

    1994-06-01

    We tested effects of temperature and drainage on C balance of intact soil and tundra vegetation over a simulated season. We measured C budgets (CO[sub 2] and CH[sub 4] emissions and dissolved CO[sub 2], CH[sub 4] and DOC in soil water) of Eriophorum vaginatum tussock and moss-dominated interussock microcosms at two temperatures (7[degrees] and 15[degrees]C, season maxima) and two water regimes (saturated and field capacity). Net ecosystem productivity was strongly affected by water. Averaged over temperature and microhabitat, the rate of net C loss from microcosms at field capacity was [approximately]5[times] the saturated microcosms. Only saturated, 15[degrees]C tussock microcosms showed net C storage integrated over the whole season. Ecosystem respiration was strongly affected by water and less by temperature. Respiration rates at field capacity were [approximately]2[times] the rates under saturated conditions. Elevated temperature caused a 1.5[times] increase. Other C components were <20% of gaseous CO[sub 2] losses. Results indicate that C in tundra exists in a fragile balance between storage and release that is controlled mainly by water regime.

  2. Do colonization by dark septate endophytes and elevated temperature affect pathogenicity of oomycetes?

    PubMed

    Tellenbach, Christoph; Sieber, Thomas N

    2012-10-01

    Phialocephala subalpina is one of the most frequent dark septate root endophytes in tree roots but its function in forest ecosystems is largely unknown. A full-factorial infection experiment was performed, using six P. subalpina isolates, two pathogenic oomycetes (Phytophthora plurivora [syn. Phytophthora citricola s.l.] and Elongisporangium undulatum [syn. Pythium undulatum]) and two temperature regimes (17.9 and 21.6 °C) to examine the ability of P. subalpina to protect Norway spruce seedlings against root pathogens. Seedling survival, disease intensity and seedling growth were affected by P. subalpina genotype, temperature and pathogen species. Some P. subalpina isolates effectively reduced mortality and disease intensity caused by the two pathogens. Elevated temperature adversely affected seedling growth but did not aggravate the effect of the pathogens. Elongisporangium undulatum but not P. plurivora significantly reduced plant growth. Colonization density of P. subalpina measured by quantitative PCR was not affected by temperature or the presence of the pathogens. In conclusion, P. subalpina confers an indirect benefit to its host and might therefore be tolerated in natural ecosystems, despite negative effects on plant health and plant growth.

  3. Production of hydrogen bromide by bromine-methane reactions at elevated temperature.

    SciTech Connect

    Bradshaw, Robert W.; Larson, Richard S.

    2003-05-01

    Hydrogen bromide is a potentially useful intermediate for hydrogen production by electrolysis because it has a low cell potential and is extremely soluble in water. Processes have been proposed to exploit these properties, but among the important issues to be resolved is the efficiency of HBr production from hydrocarbon precursors. This investigation evaluated a fundamental facet of such a technology by studying the reaction of methane and bromine at elevated temperature to determine the yield and kinetics of HBr formation. Laboratory experimentation and computational chemistry were combined to provide a description of this reaction for possible application to reactor design at a larger scale. Experimental studies with a tubular flow reactor were used to survey a range of reactant ratios and reactor residence times at temperatures between 500 C and 800 C. At temperatures near 800 C with excess methane, conversions of bromine to HBr exceeded 90% and reaction products included solid carbon (soot) in stoichiometric amounts. At lower temperatures, HBr conversion was significantly reduced, the products included much less soot, and the formation of bromocarbon compounds was indicated qualitatively. Calculations of chemical equilibrium behavior and reaction kinetics for the experimental conditions were performed using the Sandia CHEMKIN package. An elementary multistep mechanism for the gas-phase chemistry was used together with a surface mechanism that assumed facile deposition of radical species at the reactor walls. Simulations with the laminar-flow boundary-layer code of the CHEMKIN package gave reasonable agreement with experimental data.

  4. Control of Thermal Deflection, Panel Flutter and Acoustic Fatigue at Elevated Temperatures Using Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Mei, Chuh; Huang, Jen-Kuang

    1996-01-01

    The High Speed Civil Transport (HSCT) will have to be designed to withstand high aerodynamic load at supersonic speeds (panel flutter) and high acoustic load (acoustic or sonic fatigue) due to fluctuating boundary layer or jet engine acoustic pressure. The thermal deflection of the skin panels will also alter the vehicle's configuration, thus it may affect the aerodynamic characteristics of the vehicle and lead to poor performance. Shape memory alloys (SMA) have an unique ability to recover large strains completely when the alloy is heated above the characteristic transformation (austenite finish T(sub f)) temperature. The recovery stress and elastic modulus are both temperature dependent, and the recovery stress also depends on the initial strain. An innovative concept is to utilize the recovery stress by embedding the initially strained SMA wire in a graphite/epoxy composite laminated panel. The SMA wires are thus restrained and large inplane forces are induced in the panel at elevated temeperatures. By embedding SMA in composite panel, the panel becomes much stiffer at elevated temperatures. That is because the large tensile inplane forces induced in the panel from the SMA recovery stress. A stiffer panel would certainly yield smaller dynamic responses.

  5. Elevated-temperature fracture toughness and fatigue testing of steels for geothermal applications. Annual progress report

    SciTech Connect

    Cutler, R.A.; Goodman, E.C.; Guest, R.V.; Hendrickson, R.R.; Leslie, W.C.

    1980-11-01

    Conventional drill bit steels exhibit increased wear and decreased toughness when run at elevated temperatures in geothermal wells. Bits are therefore run at lower speeds and lighter loads, resulting in lower penetration rates for geothermal wells than for conventional rock drilling. Carpenter EX-00053, Timken CBS 600, Timken CBS 1000M and Vasco X-2M, steels with improved hot hardness (improved wear resistance), were tested in conjunction with the steels used for cones (AISI 4820 and 9315) and lugs (AISI 8620 and 9315) in conventional roller cone rock bits. Shortrod fracture toughness measurements were made on each of these steels between room temperature and 400/sup 0/C. Fatigue crack resistance was determined at 300/sup 0/C for high-temperature steels and at room temperature for conventional steels. Scanning electron microscopy analyses of the fractured short-rod specimens were correlated with observed crack behavior from the test records. Test results are discussed, recommendations made for further testing and preliminary steel selections made for improved geothermal bits.

  6. Effects of selected thermophilic microorganisms on crude oils at elevated temperatures and pressures. 1991 annual report

    SciTech Connect

    Premuzic, E.T.; Lin, M.S.

    1993-10-01

    During the past several years, a considerable amount of work has been carried out showing that microbially enhanced oil recovery (MEOR) is promising and the resulting biotechnology may be deliverable. In this laboratory systematic studies are being conducted which deal with the effects of thermophilic and thermoadapted bacteria on the chemical and physical properties of selected types of crude oils at elevated temperatures and pressures. Particular attention is being paid to heavy crude oils such as Boscan and Cerro Negro (Venezuela), Monterey (California) and those from Alabama and Arkansas. Current studies indicate that during the biotreatment several properties of crude oils are affected. The oils are (1) emulsified; (2) acidified; (3) there is a qualitative and quantitative change in light and heavy fractions of the crudes; (4) there are chemical changes in fractions containing sulfur compounds; (5) there is an apparent solubilization of trace metals; and (6) the qualitative and quantitative chemical and physical changes appear to be microbial species dependent. Effects on heavy crude oils are also compared to those on lighter oils such as oils from the Wyoming petroleum reserve. Microbial oil interactions are monitored routinely by a consortium of analytical techniques which are continuously upgraded and are capable of multiparameter analysis. The results generated in fiscal year 1991, describing (1) through (6), are presented and discussed in this report.

  7. Rheological and Mechanical Property Measurements of PMDI Foam at Elevated Temperatures

    SciTech Connect

    Nemer, Martin Bernard; Brooks, Carlton F.; Shelden, Bion; Soehnel, Melissa Marie; Barringer, David Alan

    2014-10-01

    A study was undertaken to determine the viscosity of liquefied 20 lb/ft3 poly methylene diisocyanate (PMDI) foam and the stress required to puncture solid PMDI foam at elevated temperatures. For the rheological measurements the foam was a priori liquefied in a pressure vessel such that the volatiles were not lost in the liquefaction process. The viscosity of the liquefied PMDI foam was found to be Newtonian with a power law dependence on temperature log10(μ/Pa s) = 20.6 – 9.5 log10(T/°C) for temperatures below 170 °C. Above 170 °C, the viscosity was in the range of 0.3 Pa s which is close to the lower measurement limit (≈ 0.1 Pa s) of the pressurized rheometer. The mechanical pressure required to break through 20lb/ft3 foam was 500-800 psi at temperatures from room temperature up to 180 °C. The mechanical pressure required to break through 10 lb/ft3 was 170-300 psi at temperatures from room temperature up to 180 °C. We have not been able to cause gas to break through the 20 lb/ft3 PMDI foam at gas pressures up to 100 psi.

  8. An automated flow calorimeter for heat capacity and enthalpy measurements at elevated temperatures and pressures

    SciTech Connect

    Yesavage, V.F.

    1990-08-31

    The need for highly accurate thermal property data for a broad range of new application fluids is well documented. To facilitate expansion of the current thermophysical database, an automated flow calorimeter was developed for the measurement of highly accurate isobaric heat capacities and enthalpies of fluids at elevated temperatures and pressures. The experimental technique utilizes traditional electrical power input, adiabatic flow calorimetry with a precision metering pump that eliminates the need for on-line flow rate monitoring. In addition, a complete automation system, greatly simplifies the operation of the apparatus and increases the rapidity of the measurement process. The range over which the instrument was tested, was 300--600 K and 0--12 Mpa, although the calorimeter should perform up to the original design goals of 700 K and 30 MPa. The new flow calorimeter was evaluated by measuring the mean, isobaric, specific heat capacities of liquid water and n-pentane. These experiments yielded an average deviation from the standard literature data of +0.02% and a total variation of 0.05%. Additional data analysis indicated that the overall measurement uncertainty was conservatively estimated as 0.2% with an anticipated precision of 0.1--0.15% at all operating conditions. 44 refs., 27 figs., 2 tabs.

  9. Defect Monitoring at Elevated Temperatures (>500 °C) Using AN Array of Ultrasonic Waveguides

    NASA Astrophysics Data System (ADS)

    Jarvis, A. J. C.; Cegla, F. B.

    2011-06-01

    This paper describes the development of an array of ultrasonic waveguides that can be permanently installed on high temperature pipework. The work was motivated by the need for monitoring of thermal fatigue cracks in power station boiler outlet pipes. The defect monitoring concept is described and simulated results are presented for the operating envelope of the array. The effects of component geometry, array location and signal to noise ratios on measured defect size were investigated. Results show that the array is capable of measuring defects ranging from the size of an ultrasonic wavelength to 40 percent thickness of the component to within ±0.2 mm of the defect length. Experimental tests using a prototype array attached to a 30 mm thick steel plate containing a 5 mm deep and 0.3 mm wide notch in a furnace at 550 °C showed that monitoring at elevated temperatures is possible. A mean defect length of 5.09 mm with standard deviation of 0.13 mm was measured over a 2 week period. Further tests at even higher temperatures (up to 730 °C) were used to accelerate creep in the attachment mechanism and showed that long-term exposure to temperatures at 550 °C should not have a detrimental effect on the system.

  10. Hindered diffusion of asphaltenes at elevated temperature and pressure. Semiannual report, March 20 - September 20, 1996

    SciTech Connect

    Guin, J.A.; Geelen, R.; Gregory, C.; Yang, X.

    1996-11-01

    The objectives are to: investigate the hindered diffusion of coal and petroleum asphaltenes in the pores of catalyst particles at elevated temperature and pressures; and examine the effects of concentration, temperature, solvent type, and pressure on the intraparticle diffusivity of asphaltenes. Progress was made in several areas during this time period. The high temperature/high pressure autoclave has been received from Parr Instrument Company and is in the process of being set up and checked out. During this time period we mainly worked in two areas. In the first area, we performed some measurements on the adsorption isotherms of the model compound quinoline in cyclohexane onto a Criterion 324 catalyst at three temperatures. We are looking at the effect of temperature on the adsorption isotherms of several model compounds. This area is important since the adsorptive uptake of asphaltenes is being studied and the model compound systems lend insight as to how we may expect the more complex asphaltene systems to behave during adsorption on the surface of the porous particles. We found that even for the simple model compound quinoline, the adsorption behavior vs. temperature was quite 0563 complex. The second area explored during this time period was the application of a mathematical model to adsorptive uptake data for asphaltenes on Criterion 324 catalyst particles. This adsorptive uptake data was obtained during the previous time period and was analyzed by mathematical modeling during the current time period. The detailed findings in both of these areas are presented in this report.

  11. Reduced group delay dispersion in quantum dot passively mode-locked lasers operating at elevated temperature

    NASA Astrophysics Data System (ADS)

    Mee, J. K.; Raghunathan, R.; Murrell, D.; Braga, A.; Li, Y.; Lester, L. F.

    2014-09-01

    A detailed study of the pulse characteristics emitted from a monolithic Quantum Dot (QD) passively Mode-Locked Laser (MLL) has been performed using a state-of-the-art Frequency Resolved Optical Gating (FROG) pulse measurement system. While traditionally the time-domain pulse characteristics of semiconductor MLLs have been studied using digital sampling oscilloscope or intensity autocorrelation techniques, the FROG measurements allow for simultaneous characterization of time and frequency, which has been shown to be necessary and sufficient for true determination of mode-locked stability. In this paper, FROG pulse measurements are presented on a two-section QD MLL operating over wide temperature excursions. The FROG measurement allows for extraction of the temporal and spectral intensity and phase profiles from which the Group Delay Dispersion (GDD) can be determined. The magnitude of the GDD is found to decrease from 16.1 to 3.5 ps/nm when the temperature is increased from 20 to 50 oC, mirroring the trend of pulse width reduction at elevated temperature, which has been shown to correlate strongly with reduced unsaturated absorption. The possibility to further optimize pulse generation via intra-cavity dispersion compensation in a novel three-section MLL design is also examined, and shows strong potential toward providing valuable insight into the optimal cavity designs and operating parameters for QD MLLs.

  12. Elevated temperature strengthening of a melt spun austenitic steel by TiB2

    NASA Technical Reports Server (NTRS)

    Michal, G. M.; Glasgow, T. K.; Moore, T. J.

    1986-01-01

    Mechanical properties of an iron-based alloy containing (by wt pct) 33Ni, 2Al, 6Ti, and 2B (resulting in an alloy containing 10 vol pct TiB2) were evaluated by hardness and tensile testing. The alloy was cast as a ribbon using a dual 'free-jet' variation of Jech et al. (1984) method of chill-block melt-spinning against a copper wheel; to simulate thermal cycles the alloy ribbon would experience during compaction into shapes, various segments of the ribbon were annealed under a vacuum at temperatures ranging from 500 to 1150 C. The results show that maximum strengths at 650 and 760 C were developed in ribbons annealed at 1100 C; in these ribbons an optimal combination of grain coarsening with minimum TiB2 particle growth was observed. However, the elevated-temperature strength of the TiB2-strengthened alloy under optimal annealing conditions was poorer than that of conventional iron-based superalloys strengthened by gamma-prime precipitates.

  13. Dynamic measurement of drilling fluid rheology at elevated temperature and pressure

    SciTech Connect

    Moussa, M.M.; Al-Marhoun, M.A.

    1985-03-01

    Due to instability and degradation of the conventional drilling fluids specially under high shear rate, elevated temperatures and chemically complex environments of deep and geothermal wells, it is essential to modify and develop stable batches of clay suspensions that can perform adequately under these conditions. To obtain batches, a reliable set-up should be designed and constructed to examine and measure all the properties that may possibly change under the prevailing conditions. A scaled dynamic flow loop is designed and built in the Department of Petroleum Engineering at the University of Petroleum and Minerals, Dhahran. This set-up can simulate efficiently the bottomhole condition e.g. high temperature up to 450/sup 0/F, high shear rate up to 50,000 sec/sup -1/. The system pressure is maintained above the saturation pressure of water at the test temperature. Dynamic filteration rate and the corrosion rate is monitored instantaneously at wide range of bottomhole conditions. The flow parameters NandK,/tau/, ..gamma.. etc., are obtained by measuring ..delta..P across the 3-tube viscometer using the DP 15-150 pressure differential transducers. The ambient properties are measured by Baroid multi-speed viscometer and compared with data obtained from the loop. Two batches composed of sepiolite and polymer were tested. Effective viscosity is increased significantly at high temperature for the first and second batches. The consistency and thermal stability of these fluids may be attributed to the transfer of sepiolite to smectite at high temperature and high shear.

  14. Microstructure and elevated temperature wear behavior of induction melted Fe-based composite coating

    NASA Astrophysics Data System (ADS)

    Hu, Ge; Meng, Huimin; Liu, Junyou

    2014-10-01

    Fe-based composite coating prepared onto the component of guide wheel using ultrasonic frequency inductive cladding (UFIC) technique has been investigated in terms of microstructure, phase constitutions, microhardness and elevated temperature wear behavior by scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), Vickers microhardness tester and ball-on-disc wear tester. The results indicated that the primary phase in the coating contained austenite γ-Fe, eutectic γ-Fe/(Cr,Fe)2B, boride (Cr,Fe)2B and precipitation enriched in Mo. The average microhardness of the coating was 760 ± 10 HV0.2, which was three times higher than that of the substrate. With increasing temperature, the friction coefficients of the coating and high-chromium cast iron decreased gradually while the wear rates increased during dry sliding wear condition. The relative wear resistance of the coating was 1.63 times higher than that of the high-chromium cast iron at 500 °C, which was ascribed to the hard borides with high thermal stability uniformly embedded in the coating and the formation of dense transfer layer formed onto the worn surface. The high temperature wear mechanism of the coating was dominated by mild abrasive wear. The study revealed that Fe-based composite coating had excellent high temperature wear resistance under dry sliding wear condition.

  15. Elevated-temperature tensile and creep properties of several ferritic stainless steels

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1977-01-01

    The elevated-temperature mechanical properties of several ferritic stainless steels were determined. The alloys evaluated included Armco 18SR, GE 1541, and NASA-18T-A. Tensile and creep strength properties at 1073 and 1273 K and residual room temperature tensile properties after creep testing were measured. In addition, 1273 K tensile and creep tests and residual property testing were conducted with Armco 18SR and GE 1541 which were exposed for 200 hours to a severe oxidizing environment in automotive thermal reactors. Aside from the residual tensile properties for Armco 18SR, prior exposure did not affect the mechanical properties of either alloy. The 1273 K creep strength parallel to the sheet-rolling direction was similar for all three alloys. At 1073 K, NASA-18T-A had better creep strength than either Armco 18SR or GE 1541. NASA-18T-A possesses better residual properties after creep testing than either Armco 18SR or Ge 1541.

  16. Dynamic and structural control utilizing smart materials and structures

    NASA Technical Reports Server (NTRS)

    Rogers, C. A.; Robertshaw, H. H.

    1989-01-01

    An account is given of several novel 'smart material' structural control concepts that are currently under development. The thrust of these investigations is the evolution of intelligent materials and structures superceding the recently defined variable-geometry trusses and shape memory alloy-reinforced composites; the substances envisioned will be able to autonomously evaluate emergent environmental conditions and adapt to them, and even change their operational objectives. While until now the primary objective of the developmental efforts presently discussed has been materials that mimic biological functions, entirely novel concepts may be formulated in due course.

  17. Vapor-phase testing of the memory-effects in benzene- and toluene-imprinted polymers conditioned at elevated temperature.

    PubMed

    Azenha, Manuel; Schillinger, Eric; Sanmartin, Esther; Regueiras, M Teresa; Silva, Fernando; Sellergren, Börje

    2013-11-13

    The preparation of polymers imprinted with common aromatic solvents such as benzene and toluene is an under-exploited subject of research. The present study was aimed at the understanding of whether true solvent memory effects can be achieved by molecular imprinting, as well as if they are stable at elevated temperature. A set of copolymers, comprising low and high cross-linking levels, was prepared from four different combinations of functional monomer and cross-linker, namely methacrylic acid (MAA)/ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA)/EGDMA, MAA/divinyl benzene (DVB) and MMA/DVB. Each possible combination was prepared separately in benzene, toluene and acetonitrile. The obtained materials were applied as coatings onto nickel-titanium (Ni-Ti) alloy wires which were incorporated into solid-phase microextraction devices and finally tested for their ability to competitively adsorb vapors from the headspace of an aqueous solution containing a few volatile organic compounds. Porosity analysis showed that, regardless of the solvent used, only a high cross-linking level permitted the preparation of mesoporous copolymers (BJH radius typically in the range 13-15 nm), a requirement for providing accessibility to the targeted nanoscale-imprinted cavities. A noticeable exception was, however, observed for the MMA/DVB copolymers which exhibited much diminished BJH radius. The porosity data correlated well with the extraction profiles found, which suggested the presence of benzene-imprinted sites in all the highly cross-linked copolymers prepared in benzene, except for the MMA/DVB copolymers. Concerning the effect of an elevated conditioning temperature on the memory-effects created by the imprinting process, the results were clearly indicative that the tested copolymers, including the more robust highly cross-linked ones, are not suitable for high temperature applications such as solid-phase microextraction coupled to gas chromatography.

  18. Zeolitic materials with hierarchical porous structures.

    PubMed

    Lopez-Orozco, Sofia; Inayat, Amer; Schwab, Andreas; Selvam, Thangaraj; Schwieger, Wilhelm

    2011-06-17

    During the past several years, different kinds of hierarchical structured zeolitic materials have been synthesized due to their highly attractive properties, such as superior mass/heat transfer characteristics, lower restriction of the diffusion of reactants in the mesopores, and low pressure drop. Our contribution provides general information regarding types and preparation methods of hierarchical zeolitic materials and their relative advantages and disadvantages. Thereafter, recent advances in the preparation and characterization of hierarchical zeolitic structures within the crystallites by post-synthetic treatment methods, such as dealumination or desilication; and structured devices by in situ and ex situ zeolite coatings on open-cellular ceramic foams as (non-reactive as well as reactive) supports are highlighted. Specific advantages of using hierarchical zeolitic catalysts/structures in selected catalytic reactions, such as benzene to phenol (BTOP) and methanol to olefins (MTO) are presented.

  19. Active Structural Fibers for Multifunctional Composite Materials

    DTIC Science & Technology

    2014-05-06

    1. Lin, Y., Zhi, Z. and Sodano, 2012, “Barium Titanate and Barium Strontium Titanate Coated Carbon Fibers for Multifunctional Structural Capacitors...Multifunctional Structural Capacitors Consisting of Barium Titanate and Barium Strontium Titanate Coated Carbon Fibers, 18 th International Conference on... Strontium Titanate Coated SiC Fibers,” Electronic Materials and Applications 2011, Jan. 19 th –21 st Orlando, FL (Invited). 9. Lin, Y., Shaffer

  20. Microplastic deformation of submicrocrystalline and coarse-grained titanium at room and elevated temperatures

    NASA Astrophysics Data System (ADS)

    Dudarev, E. F.; Pochivalova, G. P.; Kolobov, Yu. R.; Bakach, G. P.; Skosyrskii, A. B.; Zhorovkov, M. F.

    2012-12-01

    Results obtained from a comparison study on the deformation behavior of submicrocrystalline and coarsegrained titanium in the temperature interval 295-773 K are presented. The microplastic strain mechanisms underlying a change in the deformation behavior of submicrocrystalline titanium in the melting temperature interval 0.35-0.40 Т m and a reduction in the strain hardening effect due to formation of submicrocrystalline structure of the material are examined. A multiscale model for development of microplastic deformation in submicrocrystalline metals and alloys is offered.