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Sample records for advanced sic fibers

  1. Thermomechanical Behavior of Advanced SiC Fiber Multifilament Tows

    NASA Technical Reports Server (NTRS)

    Yun, Hee Mann; DiCarlo, James A.

    1997-01-01

    In order to relate single fiber behavior to multiple fiber behavior in composites, fast-fracture tensile strength, creep, and stress-rupture studies were conducted on advanced SiC fiber multifilament tows in the temperature range from 20 to 1400 C in air as well as in inert environments. For conditions of small fiber creep (short times and low temperatures), the tow results of this study confirm the ability of limited single fiber data to model the strength behavior of multiple fibers in a bundle. For conditions of high creep (long times and high temperatures), further studies are needed to explain tow rupture behavior being better than average single fiber behavior.

  2. Creep behavior for advanced polycrystalline SiC fibers

    SciTech Connect

    Youngblood, G.E.; Jones, R.H.; Kohyama, Akira

    1997-04-01

    A bend stress relaxation (BSR) test has been utilized to examine irradiation enhanced creep in polycrystalline SiC fibers which are under development for use as fiber reinforcement in SiC/SiC composite. Qualitative, S-shaped 1hr BSR curves were compared for three selected advanced SiC fiber types and standard Nicalon CG fiber. The temperature corresponding to the middle of the S-curve (where the BSR parameter m = 0.5) is a measure of a fiber`s thermal stability as well as it creep resistance. In order of decreasing thermal creep resistance, the measured transition temperatures were Nicalon S (1450{degrees}C), Sylramic (1420{degrees}C), Hi-Nicalon (1230{degrees}C) and Nicalon CG (1110{degrees}C).

  3. Creep behavior for advanced polycrystalline SiC fibers

    SciTech Connect

    Youngblood, G.E.; Jones, R.H.; Kohyama, Akira

    1997-08-01

    A bend stress relaxation (BSR) test is planned to examine irradiation enhanced creep in polycrystalline SiC fibers which are under development for use as fiber reinforcement in SiC/SiC composite. Baseline 1 hr and 100 hr BSR thermal creep {open_quotes}m{close_quotes} curves have been obtained for five selected advanced SiC fiber types and for standard Nicalon CG fiber. The transition temperature, that temperature where the S-shaped m-curve has a value 0.5, is a measure of fiber creep resistance. In order of decreasing thermal creep resistance, with the 100 hr BSR transition temperature given in parenthesis, the fibers ranked: Sylramic (1261{degrees}C), Nicalon S (1256{degrees}C), annealed Hi Nicalon (1215{degrees}C), Hi Nicalon (1078{degrees}C), Nicalon CG (1003{degrees}C) and Tyranno E (932{degrees}C). The thermal creep for Sylramic, Nicalon S, Hi Nicalon and Nicalon CG fibers in a 5000 hr irradiation creep BSR test is projected from the temperature dependence of the m-curves determined during 1 and 100 hr BSR control tests.

  4. Creep and Rupture Strength of an Advanced CVD SiC Fiber

    NASA Technical Reports Server (NTRS)

    Goldsby, J. C.; Yun, H. M.; DiCarlo, J. A.

    1997-01-01

    In the as-produced condition the room temperature strength (approx. 6 GPa) of Textron Specialty Materials' 50 microns CVD SiC fiber represents the highest value thus far obtained for commercially produced polycrystalline SiC fibers. To understand whether this strength can be maintained after composite processing conditions, high temperature studies were performed on the effects of time, stress, and environment on 1400 deg. C tensile creep strain and stress rupture on as-produced, chemically vapor deposited SiC fibers. Creep strain results were consistent, allowing an evaluation of time and stress effects. Test environment had no influence on creep strain but I hour annealing at 1600 deg. C in argon gas significantly reduced the total creep strain and increased the stress dependence. This is attributed to changes in the free carbon morphology and its distribution within the CVD SiC fiber. For the as-produced and annealed fibers, strength at 1400 deg. C was found to decrease from a fast fracture value of 2 GPa to a 100-hr rupture strength value of 0. 8 GPa. In addition a loss of fast fracture strength from 6 GPa is attributed to thermally induced changes in the outer carbon coating and microstructure. Scatter in rupture times made a definitive analysis of environmental and annealing effects on creep strength difficult.

  5. Interfacial studies of refractory glass-ceramic matrix/advanced SiC fiber-reinforced composites. Annual report, 1 Feb 91-1 Feb 92

    SciTech Connect

    Brennan, J.J.

    1992-04-30

    The main objective of this program is to characterize the chemistry and structure of new advanced small diameter silicon based fibers and how these factors influence the nature of the fiber/matrix interface in refractory glass-ceramic matrix composites. It is the nature of this interface that then determines to a great degree the composite thermal, environmental, and mechanical properties. The fibers under investigation during the second year of this program included the new experimental polymer derived crystalline SiC fibers from Dow Corning Corp., the Si-N-C-O 'Black' fibers from Textron Specialty Materials, as well as the new low oxygen radiation cured Nicalon SiC type fibers from Nippon Carbon Co. Since the availability of all of these fibers was extremely limited, emphasis was placed on the mechanical, chemical, and microstructural characterization of the fibers through tensile testing, SEM of fiber fracture characteristics, scanning Auger depth profiling of fiber surfaces, and TEM of fiber thin sections, as well as their fracture behavior, bonding characteristics, and interfacial compatibility with various glass-ceramic matrix materials. Results of these analyses are discussed. Crystalline SiC fibers, Textron 'Black' fibers, low oxygen Nicalon fibers, SiC fiber/glass-ceramic matrix interfaces, TEM fiber analyses.

  6. Characterization of multiple SiC and C coatings on SiC fibers for composites

    SciTech Connect

    Paulson, T.E.; Pantano, C.G.; Veitch, L.C.

    1995-12-31

    The timely analysis of materials is crucial as new composites are developed for advanced applications in the aerospace industry. Components of the composites, such as fiber coatings, the interface region between the fiber and the matrix material, and the stability of the fiber coatings and fibers, will influence the final properties of the composite materials. Analyzing non-standard surfaces, i.e. cylindrical vs. flat substrates, in order to properly assess the chemical and microstructural properties of the fibers and coatings is not a trivial task. Sample preparation such as cutting and polishing can destroy valuable information contained at interfaces and within multiple coatings. Existing analytical methods have been investigated where most of the sample preparation has been eliminated. For this study, alternating layers of SiC and C on Textron`s SCS-0 SiC fiber were characterized using Secondary Ion Mass Spectrometry depth profiling (12KeV Cs{sup +} primary beam, negative SIMS mode), Scanning Auger Microscopy and Scanning Electron Microscopy. Several of these fibers were also heat-treated in an oxygen environment at 1200{degrees}C for 1 to 50 hours. SIMS depth profiling and SEM were used to ascertain the oxidative stability of the multi-layer coating on SiC fibers.

  7. Tensile strength of SiC fibers

    SciTech Connect

    Zok, F.W.; Chen, X.; Weber, C.H.

    1995-07-01

    An experimental investigation has been conducted on the effects of gauge length on the tensile strength of SiC fibers. The results show that the overall strength distribution cannot be described solely in terms of the two-parameter Weibull function. The overall distribution is found to be consistent with two concurrent flaw populations, one of them being characteristic of the pristine fibers, and the other characteristic of the additional flaws introduced into the fiber during processing of the composite.

  8. THERMAL CONDUCTIVITY OF SIC AND C FIBERS

    SciTech Connect

    Youngblood, Gerald E.; Senor, David J.; Kowbel, W.; Webb, J.; Kohyama, Akira

    2000-09-01

    Several rod-shaped specimens with uniaxially packed fibers (Hi-Nicalon, Hi-Nicalon Type S, Tyranno SA and Amoco K1100 types) and a pre-ceramic polymer matrix have been fabricated. By using appropriate analytic models, the bare fiber thermal conductivity (Kf) and the interface thermal conductance (h) will be determined as a function of temperature up to 1000?C before and after irradiation for samples cut from these rods. Initial results are: (1) for unirradiated Hi-Nicalon SiC fiber, Kf varied from 4.3 up to 5.9 W/mK for the 27-1000?C range, (2) for unirradiated K1100 graphite fiber, Kf varied from 576 down to 242 W/mK for the 27-1000?C range, and (3) h = 43 W/cm2K at 27?C as a typical fiber/matrix interface conductance.

  9. Development of CVD Mullite Coatings for SiC Fibers

    SciTech Connect

    Sarin, V.K.; Varadarajan, S.

    2000-03-15

    A process for depositing CVD mullite coatings on SiC fibers for enhanced oxidation and corrosion, and/or act as an interfacial protective barrier has been developed. Process optimization via systematic investigation of system parameters yielded uniform crystalline mullite coatings on SiC fibers. Structural characterization has allowed for tailoring of coating structure and therefore properties. High temperature oxidation/corrosion testing of the optimized coatings has shown that the coatings remain adherent and protective for extended periods. However, preliminary tests of coated fibers showed considerable degradation in tensile strength.

  10. The Influence of SiC on the Ablation Response of Advanced Refractory Composite Materials

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1994-01-01

    In continuing our studies of advanced refractory composite materials we have recently completed an arc-jet test series of a diverse group of ceramics and ceramic matrix composites. The compositions range from continuous fiber reinforced ceramics to monoliths. Many of these materials contain SiC and one objective of this test series was to identify the influence of SiC oxidation mechanisms on material performance. Hence the arc heater was operated at two conditions; one in which the passive oxidation of SiC would be dominant and the other where the active oxidation of SiC would be dominant. It is shown here that the active oxidation mechanism of SiC does not dominate material performance when it is present at levels equal to or below 20 volume percent.

  11. Ultra High Temperature (UHT) SiC Fiber (Phase 2)

    NASA Technical Reports Server (NTRS)

    Dicarlo, James A.; Jacobson, Nathan S.; Lizcano, Maricela; Bhatt, Ramakrishna T.

    2015-01-01

    Silicon-carbide fiber-reinforced silicon-carbide ceramic matrix composites (SiCSiC CMC) are emerginglightweight re-usable structural materials not only for hot section components in gas turbine engines, but also for controlsurfaces and leading edges of reusable hypersonic vehicles as well as for nuclear propulsion and reactor components. Ithas been shown that when these CMC are employed in engine hot-section components, the higher the upper usetemperature (UUT) of the SiC fiber, the more performance benefits are accrued, such as higher operating temperatures,reduced component cooling air, reduced fuel consumption, and reduced emissions. The first generation of SiCSiC CMC with a temperature capability of 2200-2400F are on the verge of being introduced into the hot-section components ofcommercial and military gas turbine engines.Today the SiC fiber type currently recognized as the worlds best in terms ofthermo-mechanical performance is the Sylramic-iBN fiber. This fiber was previously developed by the PI at NASA GRC using patented processes to improve the high-cost commercial Sylramic fiber, which in turn was derived from anotherlow-cost low-performance commercial fiber. Although the Sylramic-iBN fiber shows state-of-the art creep and rupture resistance for use temperatures above 2550oF, NASA has shown by fundamental creep studies and model developmentthat its microstructure and creep resistance could theoretically be significantly improved to produce an Ultra HighTemperature (UHT) SiC fiber.This Phase II Seedling Fund effort has been focused on the key objective of effectively repeating the similar processes used for producing the Sylramic-iBN fiber using a design of experiments approach to first understand the cause of the less than optimum Sylramic-iBN microstructure and then attempting to develop processconditions that eliminate or minimize these key microstructural issues. In so doing, it is predicted that that theseadvanced process could result in an UHT SiC

  12. Advanced Engineering Fibers.

    ERIC Educational Resources Information Center

    Edie, Dan D.; Dunham, Michael G.

    1987-01-01

    Describes Clemson University's Advanced Engineered Fibers Laboratory, which was established to provide national leadership and expertise in developing the processing equipment and advance fibers necessary for the chemical, fiber, and textile industries to enter the composite materials market. Discusses some of the laboratory's activities in…

  13. Toughened Matrix SiC Fiber Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Levine, Stanley R.; Bhatt, Ramakrishna T.; Morscher, Gregory N.; Kiser, James D.

    2005-01-01

    First matrix cracking stress is a critical parameter for application of Sic fiber reinforced composites in highly stressed, environmentally demanding applications such as turbine blades. High matrix fracture toughness is a key property that contributes to high composite fracture stress. Silicon nitride offers reduced matrix elastic modulus, lower coefficient of thermal expansion, and potentially high fracture toughness compared to Sic matrices. All of these factors can be used to advantage to increase matrix fracture stress. As a first model system we are pursuing toughened silicon nitride matrix composites reinforced with SCS-9 fibers. Fabrication is by tape casting the matrix plies and tape lay-up with fiber plies followed by hot pressing at 1800 C. Progress toward this end will be reported.

  14. Advanced SiC composites for fusion applications

    SciTech Connect

    Snead, L.L.; Schwarz, O.J.

    1995-04-01

    This is a short review of the motivation for and progress in the development of ceramic matrix composites for fusion. Chemically vapor infiltrated silicon carbide (SiC) composites have been fabricated from continuous fibers of either SiC or graphite and tested for strength and thermal conductivity. Of significance is the the Hi-Nicalon{trademark} SiC based fiber composite has superior unirradiated properties as compared to the standard Nicalon grade. Based on previous results on the stability of the Hi-Nicalon fiber, this system should prove more resistant to neutron irradiation. A graphite fiber composite has been fabricated with very good mechnical properties and thermal conductivity an order of magnitude higher than typical SiC/SiC composites.

  15. Creep of chemically vapor deposited SiC fibers

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1984-01-01

    The creep, thermal expansion, and elastic modulus properties for chemically vapor deposited SiC fibers were measured between 1000 and 1500 C. Creep strain was observed to increase logarithmically with time, monotonically with temperature, and linearly with tensile stress up to 600 MPa. The controlling activation energy was 480 + or - 20 kJ/mole. Thermal pretreatments near 1200 and 1450 C were found to significantly reduce fiber creep. These results coupled with creep recovery observations indicate that below 1400 C fiber creep is anelastic with neglible plastic component. This allowed a simple predictive method to be developed for describing fiber total deformation as a function of time, temperature, and stress. Mechanistic analysis of the property data suggests that fiber creep is the result of beta-SiC grain boundary sliding controlled by a small percent of free silicon in the grain boundaries.

  16. New High-Performance SiC Fiber Developed for Ceramic Composites

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.; Yun, Hee Mann

    2002-01-01

    creates a more environmentally durable fiber surface not only because a more oxidation-resistant BN is formed, but also because this layer provides a physical barrier between contacting fibers with oxidation-prone SiC surface layers (refs. 3 and 4). This year, Glenn demonstrated that the in situ BN treatment can be applied simply to Sylramic fibers located within continuous multifiber tows, within woven fabric pieces, or even assembled into complex product shapes (preforms). SiC/SiC ceramic composite panels have been fabricated from Sylramic-iBN fabric and then tested at Glenn within the Ultra-Efficient Engine Technology Program. The test conditions were selected to simulate those experienced by hot-section components in advanced gas turbine engines. The results from testing at Glenn demonstrate all the benefits expected for the Sylramic-iBN fibers. That is, the composites displayed the best thermostructural performance in comparison to composites reinforced by Sylramic fibers and by all other currently available high-performance SiC fiber types (refs. 3 and 5). For these reasons, the Ultra-Efficient Engine Technology Program has selected the Sylramic-iBN fiber for ongoing efforts aimed at SiC/SiC engine component development.

  17. Thermostructural Properties Of Sic/Sic Panels With 2.5d And 3d Fiber Architectures

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; DeCarlo, J. A.; Bhatt, R. H.; Jaskowiak, M. H.

    2005-01-01

    CMC hot-section components in advanced engines for power and propulsion will typically require high cracking strength, high ultimate strength and strain, high creep- rupture resistance, and high thermal conductivity in all directions. In the past, NASA has demonstrated fabrication of a variety of SiC/SiC flat panels and round tubes with various 2D fiber architectures using the high-modulus high-performance Sylramic-iBN Sic fiber and Sic-based matrices derived by CVI, MI, and/or PIP processes. The thermo- mechanical properties of these CMC have shown state-of-the-art performance, but primarily in the in-plane directions. Currently NASA is extending the thermostructural capability of these SiC/SiC systems in the thru-thickness direction by using various 2.5D and 3D fiber architectures. NASA is also using specially designed fabrication steps to optimize the properties of the BN-based interphase and Sic-based matrices. In this study, Sylramic-iBN/SiC panels with 2D plain weave, 2.5D satin weave, 2.5D ply-to-ply interlock weave, and 3D angle interlock fiber architectures, all woven at AITI, were fabricated using matrix densification routes previously established between NASA and GEPSC for CVI-MI processes and between NASA and Starfire-Systems for PIP processes. Introduction of the 2.5 D fiber architecture along with an improved matrix process was found to increase inter-laminar tensile strength from 1.5 -2 to 3 - 4 ksi and thru-thickness thermal conductivity from 15-20 to 30-35 BTU/ft.hr.F with minimal reduction in in-plane strength and creep-rupture properties. Such improvements should reduce thermal stresses and increase the thermostructural operating envelope for SiC/SiC engine components. These results are analyzed to offer general guidelines for selecting fiber architectures and constituent processes for high-performance SiC/SiC engine components.

  18. Thermomechanical Performance of C and SiC Multilayer, Fiber-Reinforced, CVI SiC Matrix Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Singh, Mrityunjay

    2004-01-01

    Hybrid fiber approaches have been attempted in the past to alloy desirable properties of different fiber-types for mechanical properties, thermal stress management, and oxidation resistance. Such an approach has potential for the CrSiC and SiCrSiC composite systems. SiC matrix composites with different stacking sequences of woven C fiber (T300) layers and woven Sic fiber (Hi-NicalonTM) layers were fabricated using the standard CVI process. Delamination occurred to some extent due to thermal mismatch for all of the composites. However, for the composites with a more uniform stacking sequence, minimal delamination occurred, enabling tensile properties to be determined at room temperature and elevated temperatures (stress-rupture in air). Composites were seal-coated with a CVI SiC layer as well as a proprietary C-B-Si (CBS) layer. Definite improvement in rupture behavior was observed in air for composites with increasing SiC fiber content and a CBS layer. The results will be compared to standard C fiber reinforced CVI SiC matrix and Hi-Nicalon reinforced CVI SiC matrix composites.

  19. Fabrication And Evaluation Of Sic/Sic Tubes With Various Fiber Architectures

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; DiCarlo, J. A.; Fox, D. S.

    2003-01-01

    SiC/SiC composites are excellent material candidates for high temperature applications where the performance requirements are high strength, high creep-rupture resistance, high environmental durability, and high thermal conductivity. In the past, the NASA UEET program has demonstrated fabrication of high-performance SiC/SiC flat panels reinforced by Sylramic-iBN SiC fibers. Currently NASA UEET is scaling up this SiC/SiC system by fabrication of more complex shaped components using the same fiber type. This paper reports the effects of various fiber architectures on the processing, mechanical, and durability behavior of small-diameter 0.5" ID SiC/SiC tubes, which are potential sub-elements for leading edges and cooling channels in turbine vanes and blades. Nine different fiber architectures were utilized for construction of seamless tube preforms, from simple 2D jelly-rolling to complex braiding, pin-weaving, filament-winding and 3D orthogonal weaving with approximately 5% fibers in the thru-thickness direction. Using the BN interphase and Sic matrix processing steps established for the flat panels, SiC/SiC tubes were fabricated with wall thicknesses of approximately 60 mils and total fiber fractions of approximately 35%. The "D" split ring tests for hoop tensile properties, micro-structural examinations for relationship between fiber architecture formation and matrix infiltration, and the low-pressure burner rig tests for the high temperature durability under thru-thickness thermal gradient were conducted. The better matrix infiltration and higher hoop strength were achieved using the tri-axial braided and the three-float pin woven SiC/SiC tubes. In general, it needs not only higher hoop direction fibers but also axial direction fibers for the higher hoop strength and the better infiltration, respectively. These results are analyzed to offer general guidelines for selecting fiber pre-form architectures and SiC/SiC processes that maximize tube hoop strength, thru

  20. Improved BN Coatings on SiC Fibers in SiC Matrices

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Bhatt, Ramakrishna; Yun, Hee-Mann; DiCarlo, James A.

    2004-01-01

    Modifications of BN-based coatings that are used as interfacial layers between the fibers and matrices of SiCfiber/SiC-matrix composite materials have been investigated to improve the thermomechanical properties of these materials. Such interfacial coating layers, which are also known as interphases (not to be confused with interphase in the biological sense), contribute to strength and fracture toughness of a fiber/matrix composite material by providing for limited amounts of fiber/matrix debonding and sliding to absorb some of the energy that would otherwise contribute to the propagation of cracks. Heretofore, the debonding and sliding have been of a type called inside debonding because they have taken place predominantly on the inside surfaces of the BN layers that is, at the interfaces between the SiC fibers and the interphases. The modifications cause the debonding and sliding to include more of a type, called outside debonding, that takes place at the outside surfaces of the BN layers that is, at the interfaces between the interphases and the matrix (see figure). One of the expected advantages of outside debonding is that unlike in inside debonding, the interphases would remain on the crack-bridging fibers. The interphases thus remaining should afford additional protection against oxidation at high temperature and should delay undesired fiber/fiber fusion and embrittlement of the composite material. A secondary benefit of outside debonding is that the interphase/matrix interfaces could be made more compliant than are the fiber/interphase interfaces, which necessarily incorporate the roughness of the SiC fibers. By properly engineering BN interphase layers to favor outside debonding, it should be possible, not only to delay embrittlement at intermediate temperatures, but also to reduce the effective interfacial shear strength and increase the failure strain and toughness of the composite material. Two techniques have been proposed and partially experimentally

  1. Polycrystalline SiC fibers from organosilicon polymers

    NASA Technical Reports Server (NTRS)

    Lipowitz, Jonathan; Rabe, James A.; Zank, Gregg A.

    1991-01-01

    Various organosilicon polymers have been converted into small diameter, fine-grained silicon carbide fibers by melt spinning, crosslinking, and pyrolyzing to greater than 1600 C. The high pyrolysis temperature densifies the fiber and causes CO evolution which removes nearly all oxygen. An additive prevents the loss of strength normally associated with such treatments. Silicon carbide fibres with up to 2.6 GPa (380 ksi) tensile strength, greater than 420 GPa (greater than 60 Msi) elastic modulus, and 3.1-3.2 mg/cu m density have been prepared via this process. Their microstructure consists of greater than 95 wt pct B-SiC crystallites averaging 30-40 nm diameter, with varying amounts of graphitic carbon between the SiC grains. Under inert conditions, the fibers can be thermally aged at least 12 h/1800 C with minimal change in properties.

  2. Stressed-Oxidation Lifetime of Different SiC Fiber, CVI Matrix SiC Minicomposites in Air

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Martinez-Fernandez, Julian

    1998-01-01

    The stressed-oxidation lifetime properties of several minicomposites composed of single fiber tows with a CVI SiC matrix were compared. The minicomposites were made up of Nicalon(Tm) and Hi-Nicalon(Tm) SiC fibers with carbon or BN interphases. Constant load stress-rupture tests were performed between 600 and 13000 C in air for all of the minicomposite systems. Cyclic load testing was performed on the Hi-Nicalon minicomposite systems. The factors controlling the different lifetime behaviors: fiber rupture properties, interphase oxidation, fiber degradation, and fiber-matrix bonding, are discussed in light of different minicomposite constituents. All of the systems were subject to intermediate temperature embrittlement. The Hi-Nicalon fiber, BN interphase system, performed the best for constant load conditions. For cyclic load conditions, both the BN- interphase and C-interphase minicomposites displayed poor, but different failure behavior.

  3. Advances in infrared fibers

    NASA Astrophysics Data System (ADS)

    Tao, Guangming; Abouraddy, Ayman F.

    2015-05-01

    Infrared (IR) fibers that transmit radiation at wavelengths from ~ 2 μm up to ~ 25 μm, a spectrum that extends across both the mid-IR (MIR) and far-IR (FIR), has gained extensive attention concomitant with the recent availability of MIR semiconductors sources and detectors. Chalcogenide glasses (ChGs) are a leading candidate for IR fibers by virtue of their wide optical transmission windows and high nonlinearity in the IR region. After extensive studies since the 1960s, the development and applications of ChG IR fibers are primarily hindered by their unfavorable mechanical properties. Here, we summarize our recent advances in low-cost, robust multimaterial ChG IR fibers with broad transmission windows and low optical losses, based on our multimaterial fiber preforms produced by several fabrication methodologies. Hundreds of meters of fibers are thermally drawn in an ambient atmosphere with desired step-index structure from a macroscopic multimaterial preform that contains few grams of ChG. These simple and efficient processes overcome many of the traditional obstacles, and therefore enable rapid production in an industrial setting.

  4. The microstructures of SCS-6 and SCS-8 SiC reinforcing fibers

    SciTech Connect

    Sattler, M.L.; Kinney, J.H.; Zywicz, E. ); Alani, R. ); Nichols, M.C. )

    1992-01-01

    The microstructures of SCS-6 and SCS-8 SiC fibers have been examined and analyzed using high resolution transmission electron microscopy (HRTEM), microdiffraction, parallel electron energy loss spectroscopy (PEELS), x-ray diffraction and x-ray spectroscopy. The results of the study confirm findings from earlier studies wherein the microstructure of the fibers have been described as consisting of {beta}-SiC grown upon a monofilament turbostratic carbon core. The present study, however, provides much more detail regarding this microstructure. For example, PEELS spectroscopy and x-ray microscopy indicate that the composition of the SiC varies smoothly from SiC plus free C near the carbon core to SiC at the midradial boundary. The SiC stoichiometry is roughly preserved from the midradial boundary to the exterior interface. HRTEM, microdiffraction, and dark field images provide evidence that the excess carbon is amorphous free carbon which is most likely situated at the grain boundaries of the SiC. The x-ray microscopy results are also consistent with the presence of two phases near the core which consist of SiC and free carbon having density less than graphite (2.25 g/cc). This complex microstructure may explain the recent observations of nonplanar failure in composites fabricated with SCS fibers.

  5. Hi Nicalon{trademark} SiC fiber reinforced glass and glass-ceramic matrix composites

    SciTech Connect

    Tredway, W.K.

    1996-12-31

    A multi-year research program was conducted by a team consisting of Nippon Carbon Corporation, United Technologies Research Center (UTRC), the University of Tokyo, and the University of Delaware to study and analyze basic mechanisms of failure in SiC fiber reinforced glass matrix composites. This paper presents the results of one portion of this investigation performed by UTRC that studied the mechanical performance and in-situ carbon interfacial layer formation characteristics of glass and glass-ceramic matrix composites reinforced with Hi Nicalon{trademark} SiC fiber. The fiber was produced by Nippon Carbon Corp. and was supplied to UTRC for their use on the program.

  6. SiC (SCS-6) Fiber Reinforced-Reaction Formed SiC Matrix Composites: Microstructure and Interfacial Properties

    NASA Technical Reports Server (NTRS)

    Singh, M.; Dickerson, R. M.; Olmstead, Forrest A.; Eldridge, J. I.

    1997-01-01

    Microstructural and interfacial characterization of unidirectional SiC (SCS-6) fiber reinforced-reaction formed SiC (RFSC) composites has been carried out. Silicon-1.7 at.% molybdenum alloy was used as the melt infiltrant, instead of pure silicon, to reduce the activity of silicon in the melt as well as to reduce the amount of free silicon in the matrix. Electron microprobe analysis was used to evaluate the microstructure and phase distribution in these composites. The matrix is SiC with a bi-modal grain-size distribution and small amounts of MoSi2, silicon, and carbon. Fiber push-outs tests on these composites showed that a desirably low interfacial shear strength was achieved. The average debond shear stress at room temperature varied with specimen thickness from 29 to 64 MPa, with higher values observed for thinner specimens. Initial frictional sliding stresses showed little thickness dependence with values generally close to 30 MPa. Push-out test results showed very little change when the test temperature was increased to 800 C from room temperature, indicating an absence of significant residual stresses in the composite.

  7. Time/Temperature Dependent Tensile Strength of SiC and Al2O3-Based Fibers

    NASA Technical Reports Server (NTRS)

    Yun, Hee Mann; DiCarlo, James A.

    1997-01-01

    In order to understand and model the thermomechanical behavior of fiber-reinforced composites, stress-rupture, fast-fracture, and warm-up rupture studies were conducted on various advanced SiC and Al2O3-based fibers in the,temperature range from 20 to 1400 C in air as well as in inert environments. The measured stress-rupture, fast fracture, and warm-up rupture strengths were correlated into a single master time/temperature-dependent strength plot for each fiber type using thermal activation and slow crack growth theories. It is shown that these plots are useful for comparing and selecting fibers for CMC and MMC reinforcement and that, in comparison to stress rupture tests, the fast-fracture and warm-up tests can be used for rapid generation of these plots.

  8. Intermediate Temperature Stress Rupture of Woven SiC Fiber, BN Interphase, SiC Matrix Composites in Air

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Levine, Stanley (Technical Monitor)

    2000-01-01

    Tensile stress-rupture experiments were performed on woven Hi-Nicalon reinforced SiC matrix composites with BN interphases in air. Modal acoustic emission (AE) was used to monitor the damage accumulation in the composites during the tests and microstructural analysis was performed to determine the amount of matrix cracking that occurred for each sample. Fiber fractograph), was also performed for individual fiber failures at the specimen fracture surface to determine the strengths at which fibers failed. The rupture strengths were significantly worse than what would have been expected front the inherent degradation of the fibers themselves when subjected to similar rupture conditions. At higher applied stresses the rate of rupture "?as larger than at lower applied stresses. It was observed that the change in rupture rate corresponded to the onset of through-thickness cracking in the composites themselves. The primary cause of the sen,ere degradation was the ease with which fibers would bond to one another at their closest separation distances, less than 100 nanometers, when exposed to the environment. The near fiber-to-fiber contact in the woven tows enabled premature fiber failure over large areas of matrix cracks due to the stress-concentrations created b), fibers bonded to one another after one or a few fibers fail. i.e. the loss of global load sharing. An@, improvement in fiber-to-fiber separation of this composite system should result in improved stress- rupture properties. A model was den,eloped in order to predict the rupture life-time for these composites based on the probabilistic nature of indin,idual fiber failure at temperature. the matrix cracking state during the rupture test, and the rate of oxidation into a matrix crack. Also incorporated into the model were estimates of the stress-concentration that would occur between the outer rim of fibers in a load-bearing bundle and the unbridged region of a matrix crack after Xia et al. For the lower stresses

  9. Interfacial characterization of a SiC fiber-reinforced AlN composite

    SciTech Connect

    Park, K.; Vasilos, T.; Sung, C. . Dept. of Chemical and Nuclear Engineering)

    1995-01-01

    In this study, an attempt was made to improve the mechanical properties of AlN by the incorporation of SiC (SCS-6) fibers (TEXTRON Specialty Materials, Lowell, MA) in a unidirectional array. The SiC fibers are one of the most important reinforcements for ceramic- and metal-matrix composites due to high tensile strength (3,450 MPs), high tensile modulus (400 GPa), and low density (3.0 g/cc). The SiC fiber (15 vol %)-reinforced AlN composite was fabricated by hot-pressing in vacuum. The microstructure and chemistry of interfacial regions in as-fabricated and crept composite were characterized using analytical transmission electron microscopy, in order to investigate the nature of the reaction between the fiber and matrix during both composite fabrication and creep tests and to understand the reinforcing effects of SiC fiber in the AlN matrix. Interfacial characteristics of the composite play an important role in influencing the mechanical properties of the composite.

  10. Microstructural and strength stability of a developmental CVD SiC fiber

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Garg, Anita; Hull, David R.

    1995-01-01

    The effects of thermal exposure on the room temperature tensile strength and microstructure of a developmental 50 micron CVD SiC fiber have been studied. The fibers were heat treated between 600 and 2000 C in 0.1 MPa argon and air environments for up to 100 hr. In the as-fabricated condition, the fibers showed approximately 6 GPa tensile strength. After argon treatment, the fibers showed strength degradation after 1 hr exposure beyond 1000 C, but those exposed between 1600 and 2000 C retained approximately 2 GPa strength. TEM results showed microstructural changes both in the surface coating and SiC sheath. Flaws created by the rearrangement of carbon in the surface coating and growth of equiaxed SiC grain zone in the SiC sheath are the suggested mechanisms of strength degradation. After air treatment, fibers showed strength degradation after only 2 min exposure at 600 C. Strength retention after 2 min at 1500 C was approximately 2 GPa. Oxidation of the surface coating is the primary reason for strength degradation.

  11. Damping mechanisms in chemically vapor deposited SiC fibers

    NASA Technical Reports Server (NTRS)

    Dicarlo, James A.; Goldsby, Jon C.

    1993-01-01

    Evaluating the damping of reinforcement fibers is important for understanding their microstructures and the vibrational response of their structural composites. In this study the damping capacities of two types of chemically vapor deposited silicon carbide fibers were measured from -200 C to as high as 800 C. Measurements were made at frequencies in the range 50 to 15000 Hz on single cantilevered fibers. At least four sources were identified which contribute to fiber damping, the most significant being thermoelastic damping and grain boundary sliding. The mechanisms controlling all sources and their potential influence on fiber and composite performance are discussed.

  12. Graphene covered SiC powder as advanced photocatalytic material

    NASA Astrophysics Data System (ADS)

    Zhu, Kaixing; Guo, Liwei; Lin, Jingjing; Hao, Weichang; Shang, Jun; Jia, Yuping; Chen, Lianlian; Jin, Shifeng; Wang, Wenjun; Chen, Xiaolong

    2012-01-01

    Graphene covered SiC powder (GCSP) has been fabricated by well established method of high temperature thermal decomposition of SiC. The structural and photocatalystic characteristics of the prepared GCSP were investigated and compared with that of the pristine SiC powder. Under UV illumination, more than 100% enhancement in photocatalystic activity is achieved in degradation of Rhodamine B (Rh B) by GCSP catalyst than by pristine SiC powder. The possible mechanisms underlining the observed results are discussed. The results suggested that GCSP as a composite of graphene based material has great potential for use as a high performance photocatalyst.

  13. Interfacial properties of as-received and coated SiC (SCS-6) fiber reinforced reaction-formed SiC matrix composites

    SciTech Connect

    Gaeta, P.J.; Sisson, R.D. Jr.; Singh, M.; Eldridge, J.I.

    1995-10-01

    The possibility of improving the interfacial shear strength of the SiC fiber reinforced SiC matrix composite system was examined. A ceramic fiber coating was chosen based on availability and chemical stability with the fiber and matrix. Fiber push-out tests conducted on as-received and coated fiber reinforced composite samples allowed characterization of the interfacial shear strength. Average debond shear and frictional sliding stresses were calculated. The effects of sample thickness and second phase addition in the matrix were also evaluated. Tested samples were examined by SEM to determine the location of the interfacial failure and to determine if any interface reactions had occurred. The coating was then evaluated based on the resulting interfacial shear strength, failure location, and integrity of the interface as compared to those properties of samples reinforced with as-received fibers.

  14. SiC fiber reinforced reaction-bonded Si3N4 composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.

    1986-01-01

    A technique for fabricating strong and tough SiC fiber reinforced reaction bonded Si3N4 matrix composites (SiC/RBSN) was developed. Using this technique, composites containing approximately 23, 30, and 40 volume fractions of aligned 140 micron diameter, chemically vapor deposited SiC fibers were fabricated. The room temperature physical and mechanical properties were evaluated. The results for composite tensile strength, bend strength, and fracture strain indicate that the composite displays excellent properties when compared with the unreinforced matrix of comparable porosity. The composite stress at which the matrix first cracks and the ultimate composite fracture strength increase with increasing volume fraction of fibers, and the composite fails gracefully. The mechanical property data of this ceramic composite are compared with similar data for unreinforced commercially available Si3N4 materials and for SEP SiC/SiC composites.

  15. Advances In Optical Fiber Sensors

    NASA Astrophysics Data System (ADS)

    Cole, J. H.; Giallorenzi, T. G.; Bucaro, J. A.

    1981-07-01

    Over the past several years, a new non-communication optical fiber application has emerged. This application utilizes optical fibers for sensing. Initial interest centered around rate rotation sensing. Since that time, however, acoustic, magnetic, and temperature sensing utilizing optical fibers has evolved into a viable research effort with significant potential payoff. As an example, laboratory fiber optic acoustic sensors now rival the best sensitivity obtained with piezoelectric ceramics. These sensors possess a unique geometric versatility previously unavailable. In conjunction with the Defense Advanced Research Projects Agency (DARPA), the Navy has begun a Fiber Optic Sensor System (FOSS) program to develop associated technology necessary to realize these sensors. Substantial effort is ongoing at the Naval Research Laboratory (NRL) and other Navy laboratories with considerable contractual effort from universities and industry. This paper reviews the status of the FOSS program.

  16. Microstructural and strength stability of CVD SiC fibers in argon environment

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Hull, David R.

    1991-01-01

    The room temperature tensile strength and microstructure of three types of commercially available chemically vapor deposited silicon carbide fibers were measured after 1, 10, and 100 hour heat treatments under argon pressures of 0.1 to 310 MPa at temperatures to 2100 C. Two types of fiber had carbon-rich surface coatings and the other contained no coating. All three fiber types showed strength degradation beyond 1400 C. Time and temperature of exposure had greater influence on strength degradation than argon pressure. Recrystallization and growth of near stoichiometric SiC grains appears to be the dominant mechanism for the strength degradation.

  17. Microstructural and strength stability of CVD SiC fibers in argon environments

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Hull, David R.

    1991-01-01

    The room temperature tensile strength and microstructure of three types of commercially available chemically vapor deposited silicon carbide fibers were measured after 1, 10, and 100 hour heat treatments under argon pressures of 0.1 to 310 MPa at temperatures to 2100 C. Two types of fiber had carbon-rich surface coatings and the other contained no coating. All three fiber types showed strength degradation beyond 1400 C. Time and temperature of exposure had greater influence on strength degradation than argon pressure. Recrystallization and growth of near stoichiometric SiC grains appears to be the dominant mechanism for the strength degradation.

  18. Comparison of the Tensile, Creep, and Rupture Strength Properties of Stoichiometric SiC Fibers

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; DiCarlo, J. A.

    1999-01-01

    Tensile strength, creep strength, and rupture strength properties were measured for the following types of polymer-derived stoichiometric SiC fibers: Hi-Nicalon Type S from Nippon Carbon, Tyranno SA from Ube, and Sylramic from Dow Corning. Also included in this study were an earlier version of the SA fiber plus two recent developmental versions of the Sylramic fiber. The tensile strength measurements were made at room temperature on as-received fibers and on fibers after high-temperature inert exposure. The creep-rupture property data were obtained at 1400 deg C in air as well as, argon. Some fiber types showed strong effects of environment on their strength properties. These results are compared and discussed in terms of underlying mechanisms and implications for ceramic composites.

  19. Fiber optics for advanced aircraft

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert J.

    1988-01-01

    The increased use of composites makes the digital control more susceptible to electromagnetic effects. In order to provide the protection to the digital control additional shielding will be required as well as protective circuitry for the electronics. This results in increased weight and reduced reliability. The advantages that fiber optic technology provides for advanced aircraft applications is recognized. The use of optical signals to carry information between the aircraft and the control module provides immunity from contamination by electromagnetic sources as well as other important benefits such as reduced weight and volume resulting from the elimination of the shielding and the replacement of metal conductors with low weight glass fibers. In 1975 NASA began work to develop passive optical sensors for use with fiber optics in aircraft control systems. The problem now is to choose the best optical sensor concepts and evaluate them for use. In 1985 NASA and DOD entered into a joint program, Fiber Optic Control System Integration (FOCSI), to look at optical technology specifically for use in advanced aircraft systems. The results of this program are discussed. The conclusion of the study indicated that the use of fiber optic technology in advanced aircraft systems is feasible and desirable. The study pointed to a lack of available sensors from vendors capable of operating in the adverse environments of advanced aircraft.

  20. Fiber optics for advanced aircraft

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert J.

    1989-01-01

    The increased use of composites makes the digital control more susceptible to electromagnetic effects. In order to provide the protection to the digital control additional shielding will be required as well as protective circuitry for the electronics. This results in increased weight and reduced reliability. The advantages that fiber optic technology provides for advanced aircraft applications is recognized. The use of optical signals to carry information between the aircraft and the control module provides immunity from contamination by electromagnetic sources as well as other important benefits such as reduced weight and volume resulting from the elimination of the shielding and the replacement of metal conductors with low weight glass fibers. In 1975 NASA began work to develop passive optical sensors for use with fiber optics in aircraft control systems. The problem now is to choose the best optical sensor concepts and evaluate them for use. In 1985 NASA and DOD entered into a joint program, Fiber Optic Control System Integration (FOCSI), to look at optical technology specifically for use in advanced aircraft systems. The results of this program are discussed. The conclusion of the study indicated that the use of fiber optic technology in advanced aircraft systems is feasible and desirable. The study pointed to a lack of available sensors from vendors capable of operating in the adverse environments of advanced aircraft.

  1. Tensile behavior of irradiated SiC fibers

    NASA Astrophysics Data System (ADS)

    Osborne, M. C.; Snead, L. L.; Steiner, D.

    1995-03-01

    The strength and toughness of continuous fiber reinforced ceramic composites (CFCCs) are highly dependent on the fiber strength distribution. To first order, weaker fibers lead to low strength but higher toughness while stronger fibers lead to high strength composites of relatively low toughness. Toughness is associated with pullout of the fibers from the ceramic matrix. It has been shown previously that both strength and toughness of SiC/Nicalon TM composites are drastically changed following irradiation. Tensile results are presented for low oxygen Nicalon fibers neutron irradiated at damage levels of 0.013 displacements per atom (dpa), 0.13 dpa and 0.32 dpa. Single fibers were tensile tested and analyzed, using Weibull statistics, for mean strength and distribution. Tensile modulus was also determined. Using a diffractometer, the fiber grain size and percent crystallinity were determined. The initial results of these low fluence neutron irradiations exhibit no substantial degradation of the properties investigated. Therefore, continued research at higher doses is recommended.

  2. Oxidation of SiC Fiber-Reinforced SiC Matrix Composites with a BN Interphase

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth; Boyd, Meredith K.

    2010-01-01

    SiC-fiber reinforced SiC matrix composites with a BN interphase were oxidized in reduced oxygen partial pressures of oxygen to simulate the environment for hypersonic vehicle leading edge applications. The constituent fibers as well as composite coupons were oxidized in oxygen partial pressures ranging from 1000 ppm O2 to 5% O2 balance argon. Exposure temperatures ranged from 816 C to 1353 C (1500 F to 2450 F). The oxidation kinetics of the coated fibers were monitored by thermogravimetric analysis (TGA). An initial rapid transient weight gain was observed followed by parabolic kinetics. Possible mechanisms for the transient oxidation are discussed. One edge of the composite coupon seal coat was ground off to simulate damage to the composite which allowed oxygen ingress to the interior of the composite. Oxidation kinetics of the coupons were characterized by scanning electron microscopy since the weight changes were minimal. It was found that sealing of the coupon edge by silica formation occurred. Differences in the amount and morphology of the sealing silica as a function of time, temperature and oxygen partial pressure are discussed. Implications for use of these materials for hypersonic vehicle leading edge materials are summarized.

  3. Tensile behavior of irradiated SiC fibers

    SciTech Connect

    Osborne, M.C.; Steiner, D.; Snead, L.L.

    1994-09-01

    Tensile results are presented for low oxygen Nicalon fibers neutron irradiated at damage levels of 0.013 displacements per atom (dpa), 0.13 dpa and 0.32 dpa. Single fibers were tensile tested and analyzed, using Weibull statistics, for mean strength and distribution. Tensile modulus was also determined. Using a diffractometer, the fiber grain size and percent crystallinity were determined. The mean strength and modulus decreased by 20% but then increased with the highest damage level tested. Both grain size and crystallinity decreased as dose increased. These initial results of low level neutron irradiation of low oxygen Nicalon fibers exhibit no substantial degradation of the properties investigated. Therefore, continued research at higher doses is recommended.

  4. Light ion irradiation creep of SiC fibers in torsion

    NASA Astrophysics Data System (ADS)

    Scholz, R.

    1998-10-01

    Creep tests were conducted in torsion on TEXTRON type SCS-6™ silicon carbide (SiC) fibers during irradiation with 14 MeV deuterons for 450°C, 600°C and 800°C. The fibers, produced by chemical vapor deposition (CVD), should be representative of the chemical vapor infiltrated (CVI) matrix of a SiC/SiC composite. SiC is known to undergo irradiation induced swelling which occurs without an incubation dose for temperatures below about 1000°C [R.J. Price, J. Nucl. Mater. 33 (1969) 17]. Such swelling in SiC may mask the irradiation creep strain in a tensile experiment, but plays a minor role in torsional creep tests. The torsional irradiation creep curves are characterized by long lasting strain transients during which the creep rate slows down before reaching approximately constant values. The steady state torsional creep rate γ˙s exhibited a linear dependence on stress and particle flux and it decreased when the temperature was increased. The temperature dependence of γ˙s in the range 450-800°C is similar to that of swelling for neutron irradiated SiC.

  5. Effects of high pressure nitrogen on the thermal stability of SiC fibers

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.

    1991-01-01

    Polymer-derived SiC fibers were exposed to nitrogen gas pressures of 7 and 50 atm at temperatures up to 1800 C. The fiber weight loss, chemical composition, and tensile strength were then measured at room temperature in order to understand the effects of nitrogen exposure on fiber stability. High pressure nitrogen treatments limited weight loss to 3 percent or less for temperatures up to 1800 C. The bulk Si-C-O chemical composition of the fiber remained relatively constant up to 1800 C with only a slight increase in nitrogen content after treatment at 50 atm; however, fiber strength retention was significantly improved. To further understand the effects of the nitrogen atmosphere on the fiber stability, the results of previous high pressure argon treatments were compared to those of the high pressure nitrogen treatments. High pressure inert gas can temporarily maintain fiber strength by physically inhibiting the evolution of gaseous species which result from internal reactions. In addition to this physical effect, it would appear that high pressure nitrogen further improved fiber temperature capability by chemically reacting with the fiber surface, thereby reducing the rate of gas evolution. Subsequent low pressure argon treatments following the initial nitrogen treatments resulted in stronger fibers than after argon treatment alone, further supporting the chemical reaction mechanism and its beneficial effects on fiber strength.

  6. Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Phillips, Ronald E.

    1990-01-01

    The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2) sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix.

  7. Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Rhatt, R. T.; Phillips, R. E.

    1988-01-01

    The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2)sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix.

  8. Thermomechanical Characterization of SiC Fiber Tows and Implications for CMC

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; DiCarlo, J. A.

    1999-01-01

    In order to better understand SiC fiber behavior within CMC microstructures, mechanical tests were performed on multifilament tows consisting of different types of as produced and pretreated fibers. Tensile strengths of tows and single fibers were measured at room temperature for nonstoichiometric Hi-Nicalon and ZMI fibers and for stoichiometric Hi-Nicalon-S, Tyranno SA. and Sylramic fibers. Based on simple bundle theory, measured strengths for as-produced and sized tows were in general agreement with the single fiber results. However, after sizing removal under inert conditions, tow strengths for the coarser grained stoichiometric fibers were typically lower than those predicted from individual fiber data. This effect is attributed to enhanced fiber-fiber mechanical interaction caused by sizing removal from the rough surfaces of these fibers. In support of this, tow strengths remained high for those fiber types with fine grains or excess surface carbon; and, when re-coated with a BN interphase coating, tow strengths for the coarser grained fibers returned to their as-produced values. When the tows were pretreated in air at intermediate temperatures, tow strengths decreased in a manner that could be correlated with the oxidation characteristics of each fiber type as measured by thermogravimetric analysis. The creep and rupture properties of Hi-Nicalon and Sylramic tows were also measured in air and argon from 1200 to 1400 C. Although displaying transient and environmental effects similar to single fibers, the tows crept faster at short times and slower at long times. This resulted in the tow rupture strengths at long time being much greater than the rupture strengths of single fibers. The CMC implications of the tow results are discussed, as well as the benefits and limitations of tow testing.

  9. Thermomechanical Performance of Si-Ti-C-O and Sintered SiC Fiber-Bonded Ceramics at High Temperatures

    SciTech Connect

    Matsunaga, Tadashi; Lin, Hua-Tay; Singh, Mrityunjay; Kajii, Shinji; Matsunaga, Kenji; Ishikawa, Toshihiro

    2011-01-01

    The stress-temperature-lifetime response of Si-Ti-C-O fiber-bonded ceramic (Tyrannohex ) and sintered SiC fiber-bonded ceramic (SA-Tyrannohex ) materials were investigated in air from 500 to 1150 C and 500 to 1400 C, respectively. The apparent threshold stress of Si-Ti-C-O fiber-bonded ceramic was about 175 MPa in the 500-1150 C temperature range. When the applied stress of the sintered SiC fiber-bonded ceramic was below an apparent threshold stress (e.g., ~225MPa) for tests conducted 1150 C, no failures were observed for lifetimes up to 1000h. In the case of sintered SiC fiber-bonded ceramic, at the temperature of 1300 C, the apparent threshold stress decreased to 175 MPa. The decrease in strength seemed to be caused by grain growth which was confirmed from the SEM fractography. Both fiber-bonded ceramics exhibited much higher durability than a commercial SiC/SiC composite at temperatures above 500 C. In addition, results suggested that the sintered SiC fiber-bonded ceramic (SA-Tyrannohex) is more stable than a Hi-Nicalon/MI SiC composite with BN/SiC fiber coating at temperatures above 1300 C.

  10. Fiber/matrix interfaces for SiC/SiC composites: Multilayer SiC coatings

    SciTech Connect

    Halverson, H.; Curtin, W.A.

    1996-08-01

    Tensile tests have been performed on composites of CVI SiC matrix reinforced with 2-d Nicalon fiber cloth, with either pyrolitic carbon or multilayer CVD SiC coatings [Hypertherm High-Temperature Composites Inc., Huntington Beach, CA.] on the fibers. To investigate the role played by the different interfaces, several types of measurements are made on each sample: (i) unload-reload hysteresis loops, and (ii) acoustic emission. The pyrolitic carbon and multilayer SiC coated materials are remarkably similar in overall mechanical responses. These results demonstrate that low-modulus, or compliant, interface coatings are not necessary for good composite performance, and that complex, hierarchical coating structures may possibly yield enhanced high-temperature performance. Analysis of the unload/reload hysteresis loops also indicates that the usual {open_quotes}proportional limit{close_quotes} stress is actually slightly below the stress at which the 0{degrees} load-bearing fibers/matrix interfaces slide and are exposed to atmosphere.

  11. On He bubbles in neutron irradiated SYLRAMIC type SiC fibers

    SciTech Connect

    Gelles, David S; Youngblood, Gerald E

    2006-03-01

    SylramicTM type SiC fibers, which contain at least 2.3 wt% B, were examined by TEM following neutron irradiation to dose levels of ~7 dpa in HFIR at 800°C and to ~1 dpa in ATR at 1090°C. At these radiation damage dose levels, transmutation of the boron-10 component effectively “dopes” the Sylramic type fibers with up to 10,000 appm helium. Following irradiation at 800°C, bubble development was too fine to resolve even by high resolution TEM. However, following irradiation at 1090°C helium bubble development was resolvable, but complex. A fine dispersion of 1-nm bubbles was observed within the SiC grains and a coarse, non-uniform distribution of irregular 25-nm bubbles was observed on grain boundaries. In addition, some unusual arrays of planar 2.5-nm thick bubbles were observed in the SiC grains and equiaxed bubbles were observed in the boride precipitate particles contained within the fiber microstructure. Not unexpectedly, helium retention and bubble formation in β-SiC depends on details of the polycrystalline microstructure as well as the irradiation conditions.

  12. CHARACTERIZATION BY SEM OF THE PYROCARBON FIBER COATING IN 2D-SIC/CVI-SIC

    SciTech Connect

    Youngblood, Gerald E.

    2011-03-23

    The previous report examined electrical conductivity (EC) data from RT to 800°C for several forms of two-dimensional silicon carbide composite made with a chemical vapor infiltration (CVI) matrix (2D-SiC/CVI-SiC), an important quantity needed for the design of an FCI. We found that both in-plane and transverse EC-values for 2D-SiC/CVI-SiC strongly depended on the total thickness of the highly conductive pyrocarbon (PyC) fiber coating and the alignment of the carbon coating network. Furthermore, the transverse EC depended on the degree of interconnectivity of this network. For our EC-modeling efforts we used either “nominal” coating thickness values provided by the composite fabricator or we made thickness estimates based on a limited number of fiber cross-section examinations using SEM. Because of the importance of using a truly representative coating thickness value in our analysis, we examined numerous new SEM cross-sectional views to reassess the reliability of our limited number of original coating thickness measurements as well as to obtain an estimate of the variation in thickness values for different composite configurations.

  13. Technique for measuring irradiation creep in polycrystalline SiC fibers

    SciTech Connect

    Youngblood, G.E.; Hamilton, M.L.; Jones, R.H.

    1996-10-01

    A bend stress relaxation (BSR) test has been designed to examine irradiation enhanced creep in polycrystalline SiC fibers being considered for fiber reinforcement in SiC/SiC composite. Thermal creep results on Nicalon-CG and Hi-Nicalon were shown to be consistent with previously published data with Hi-Nicalon showing about a 100{degrees}C improvement in creep resistance. Preliminary data was also obtained on Nicalon-S that demonstrated that its creep resistance is greater than that of Hi-Nicalon.

  14. SiC Fiber-Reinforced Celsian Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    2003-01-01

    Celsian is a promising matrix material for fiber-reinforced composites for high temperature structural applications. Processing and fabrication of small diameter multifilament silicon carbide tow reinforced celsian matrix composites are described. Mechanical and microstructural properties of these composites at ambient and elevated temperatures are presented. Effects of high-temperature exposures in air on the mechanical behavior of these composites are also given. The composites show mechanical integrity up to 1100 C but degrade at higher temperatures in oxidizing atmospheres. A model has been proposed for the degradation of these composites in oxidizing atmospheres at high temperatures.

  15. Pressure effects on the thermal stability of SiC fibers

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.; Dicarlo, James A.

    1986-01-01

    Commercially available polymer derived SiC fibers were treated at temperatures from 1000 to 2200 C in vacuum and argon gas pressure of 1 and 1360 atm. Effects of gas pressure on the thermal stability of the fibers were determined through property comparison between the pressure treated fibers and vacuum treated fibers. Investigation of the thermal stability included studies of the fiber microstructure, weight loss, grain growth, and tensile strength. The 1360 atm argon gas treatment was found to shift the onset of fiber weight loss from 1200 to above 1500 C. Grain growth and tensile strength degradation were correlated with weight loss and were thus also inhibited by high pressure treatments. Additional heat treatment in 1 atm argon of the fibers initially treated at 1360 atm argon caused further weight loss and tensile strength degradation, thus indicating that high pressure inert gas conditions would be effective only in delaying fiber strength degradation. However, if the high gas pressure could be maintained throughout composite fabrication, then the composites could be processed at higher temperatures.

  16. Lifetime Response of a Hi-Nicalon Fiber-Reinforced Melt-Infiltrated SiC Matrix Composites

    SciTech Connect

    Becher, P.F.; Lin, H.T.; Singh, M.

    1999-04-25

    Lifetime studies in four-point flexure were performed on a Hi-NicalonTM fiber-reinforced SiC matrix composite over a temperature range of 700 degrees to 1150 degrees C in air. The composite consisted of ~40 vol. % Hi-NicalonTM fiber (8-harness weave) with a 0.5 Mu-m BN fiber coating and a melt-infiltration SiC matrix wand was tested with as-machined surfaces. Lifetime results indicated that the composite exhibited a stress-dependent lifetime at stress levels above an apparent fatigue limit, similar to the trend observed in CG-NicalonTM fiber reinforced CVI SiC matrix composites. At less than or equal to 950 degrees C, the lifetimes of Hi-Nicalon/MI SiC composites decreased with increasing applied stress level and test temperature. However, the lifetimes were extended as test temperature increased from 950 degees to 1150 degrees C as a result of surface crack sealing due to glass formation by the oxidation of Mi SiC matrix. The lifetime governing processes were, in general, attributed to the progressive oxidation of BN fiber coating and formation of glassy phase, which formed a strong bond between fiber and matrix, resulting in embrittlement of the composite with time.

  17. Thermal Stability of Hi-Nicalon SiC Fiber in Nitrogen and Silicon Environments

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.; Garg, A.

    1995-01-01

    The room temperature tensile strength of uncoated and two types of pyrolytic boron nitride coated (PBN and Si-rich PBN) Hi-Nicalon SiC fibers was determined after 1 to 400 hr heat treatments to 1800 C under N2 pressures of 0.1, 2, and 4 MPa, and under 0.1 Mpa argon and vacuum environments. In addition, strength stability of both uncoated and coated fibers embedded in silicon powder and exposed to 0.1 MPa N2 for 24 hrs at temperatures to 1400 C was investigated. The uncoated and both types of BN coated fibers exposed to N2 for 1 hr showed noticeable strength degradation above 1400 C and 1600 C, respectively. The strength degradation appeared independent of nitrogen pressure, time of heat treatment, and surface coatings. TEM microstructural analysis suggests that flaws created due to SiC grain growth are responsible for the strength degradation. In contact with silicon powder, the uncoated and both types of PBN coated fibers degrade rapidly above 1350 C.

  18. TENSILE STRENGTH AND FRACTURE SURFACE CHARACTERIZATION OF HI-NICALONTM SIC FIBERS

    SciTech Connect

    Youngblood, Gerald E.; Lewinsohn, Charles A.; Jones, Russell H.; Kohyama, Akira

    2000-06-30

    Dimensional, tensile strength and fracture surface characterizations were carried out for a particular batch (51 samples) of unirradiated Hi-Nicalon™ SiC fiber. This batch of SiC fibers is included in the radiation test matrix as part of the JUPITER 12J and 14J experiments. In general, filaments of Hi-Nicalon™ fiber with larger cross-sectional areas (equivalent diameters) had lower strengths than filaments with smaller cross-sectional areas. During tensile tests at room temperature, fracture originated at critical flaws that typically consisted of internal pores or carbonaceous inclusions. Well-demarcated mirror and hackle regions usually surrounded the critical flaws. With a few exceptions, the critical flaw size (ac) was linearly related to the mirror size (rm) by ac » 0.33rm. From fracture mechanics principles, values for the average mirror constant (Am) and effective fracture toughness for this batch of Hi-NicalonÔ fiber were estimated to be 2.99 ± 0.33 and 1.1 ± 0.2 MPa m1/2, respectively.

  19. Methods of radiation effects evaluation of SiC/SiC composite and SiC fibers

    SciTech Connect

    Youngblood, G.E.; Jones, R.H.

    1998-03-01

    This report covers material presented at the IEA/Jupiter Joint International Workshop on SiC/SiC Composites for Fusion structural Applications held in conjunction with ICFRM-8, Sendai, Japan, Oct. 23--24, 1997. Several methods for radiation effects evaluation of SiC fibers and fiber-reinforced SiC/SiC composite are presented.

  20. Strength degradation of SiC fiber during manufacture of titanium matrix composites by plasma spraying and hot pressing

    NASA Astrophysics Data System (ADS)

    Baik, K. H.; Grant, P. S.

    2001-12-01

    Titanium matrix composites (TMCs) reinforced with Sigma 1140+ SiC fiber have been manufactured by a combination of low pressure plasma spraying (LPPS spray/wind) and simultaneous fiber winding, followed by vacuum hot pressing (VHP). Fiber damage during TMC manufacture has been evaluated by measuring fiber tensile strength after fiber extraction from the TMCs at various processing stages, followed by fitting of these data to a Weibull distribution function. The LPPS spray/wind processing caused a decrease in mean fiber strength and Weibull modulus in comparison with as-received fibers. A number of fiber surface flaws, primarily in the outer C layer of the fiber, formed as a result of mechanical impact of poorly melted particles from the plasma spray. Coarse feedstock powders promoted an increase in the population of fiber surface flaws, leading to significant reduction in fiber strength. The VHP consolidation promoted further development of fiber surface flaws by fiber bending and stress localization because of nonuniform matrix shrinkage, resulting in further degradation in fiber strength. In the extreme case of fibers touching, the stress concentration on the fibers was sufficient to cause fiber cracking. Fractographic studies revealed that low strength fibers failed by surface flaw induced failure and contained a large fracture mirror zone. Compared with the more widely investigated foil-fiber-foil route to manufacture TMCs, LPPS/VHP resulted in less degradation in fiber strength for Sigma 1140+ fiber. Preliminary results for Textron SCS-6 fiber indicated a much greater tolerance to LPPS/VHP damage.

  1. Strength and conductivity of unidirectional copper composites reinforced by continuous SiC fibers

    NASA Astrophysics Data System (ADS)

    Kimmig, S.; Allen, I.; You, J. H.

    2013-09-01

    A SiC long fiber-reinforced copper composite offers a beneficial combination of high strength and high thermal conductivity at elevated temperatures. Both properties make the composite a promising material for the heat sink of high-heat-flux components. In this work, we developed a novel Cu/SiCf composite using the Sigma fiber. Based on HIP technique, a metallurgical process was established for fabricating high quality specimens using a TiC interface coating. Extensive tensile tests were conducted on the unidirectionally reinforced composite at 20 °C and 300 °C for a wide range of fiber volume fraction (Vf). In this paper, a large amount of test data is presented. The transversal thermal conductivity varies from 260 to 130 W/mK at 500 °C as Vf is increased from 13% to 37%. The tensile strength reached up to 1246 MPa at 20 °C for Vf = 37.6%, where the fracture strain was limited to 0.8%. The data of both elastic modulus and ultimate strength exhibited a good agreement with the rule-of-mixture predictions indicating a high quality of the materials. The strength of the composite with the Sigma fibers turned out to be superior to those of the SCS6 fibers at 300 °C, although the SCS6 fiber actually has a higher strength than the Sigma fiber. The fractographic pictures of tension test and fiber push-out test manifested a sufficient interfacial bonding. Unidirectional copper composite reinforced by long SiC fibers was fabricated using the Sigma SM1140+ fiber for a wide range of fiber volume fraction from 14% to 40%. Extensive tensile tests were carried out at RT and 300 °C. The data of ultimate strength as well as elastic modulus exhibited a good agreement with the rule-of-mixture predictions indicating a high quality of the materials. In terms of the tensile strength, the Cu/Sigma composite turned out to be superior to the previous Cu/SCS6 composite at 300 °C, while comparable at RT, although the SCS6 fiber has a higher strength than the Sigma fiber. Such a

  2. Interactions between SiC fibers and a titanium alloy during liquid infiltration

    SciTech Connect

    Warrier, S.G.; Lin, R.Y.

    1995-07-01

    The rapid interaction between SiC fibers (SCS-0) and a liquid titanium alloy has been investigated using an infrared processing technique. Experimental results revealed that dissolution of the fibers in the alloy occurred within seconds without forming a continuous layer of reaction products at the interface. Thermodynamic analysis indicated that SiC is unstable in the presence of liquid titanium and dissociates into Si and C in the metal. With increasing carbon concentration, TiC will form when the carbon solubility limit in Ti is exceeded. The Ti-rich corner of the Ti-Si-C phase diagram with supercooled liquid Ti at 1,300 C was used to illustrate the tendency of TiC formation in this system. The fiber-matrix interface comprised two distinct morphologies: uniform dissolution fronts and scalloped dissolution fronts. The uniformly dissolved domains are believed to be caused by an isothermal dissolution mechanism controlled by a zeroth-order chemical reaction, whereas the scalloped interfaces are believed to be caused by an accelerated dissolution mechanism resulting from localized heating. A model employing heat balance and reaction kinetics indicates that the conditions for accelerated dissolution are satisfied by the observed dissolution rates in the scalloped domains.

  3. Irradiation creep of advanced silicon carbide fibers

    NASA Astrophysics Data System (ADS)

    Scholz, R.; Youngblood, G. E.

    2000-12-01

    The bend stress relaxation (BSR) method was applied to study irradiation enhanced creep (IEC) of small diameter silicon carbide (SiC) fibers after 10 MeV proton irradiation. A first series of tests was conducted on Sylramic™ fibers irradiated at 600°C with average bending stresses of 400 and 667 MPa and for irradiation doses smaller than 0.04 dpa. The BSR results are compared to previously obtained torsional creep test results for the Textron SCS-6™ type SiC fibers by calculating the tensile equivalents for both testing methods. For the Sylramic fibers, the creep constant κ=4.7×10-6 Mpa-1 dpa-1, was a factor of 6 smaller than the κ-value determined for SCS-6 fibers at 600°C. In contrast, for T<900°C the κ-value determined by R.J. Price [Nucl. Technol. 35 (1977) 320] for high purity monolithic β-Si after 7.7 dpa neutron irradiation was only 0.4×10-6 MPa-1 dpa-1.

  4. Tensile Creep and Stress-rupture Behavior of Polymer Derived Sic Fibers

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; Goldsby, J. C.; Dicarlo, J. A.

    1994-01-01

    Tensile creep and stress-rupture studies were conducted on polymer derived Nicalon, Hi-Nicalon, and SiC/BN-coated Nicalon SiC fibers. Test conditions were temperatures from 1200 to 1400 C, stresses from 100 to 1600 MPa, stress application times up to 200 hours, and air, argon, and vacuum test environments. For all fibers, creep occurred predominantly in the primary stage. Hi-Nicalon had much higher 0.2 and 1 percent creep strengths than as-produced as well as-coated Nicalon fibers. The stress-rupture strength of Hi-Nicalon up to 100 hours was also higher than that of the coated and as-produced Nicalon fibers. SiC/BN coating on Nicalon increased only the short-term low-temperature rupture strength. Limited testing in argon and vacuum suggests that for all fiber types, creep and rupture resistances are reduced in comparison to the results in air. Possible mechanisms for the observed behavior are discussed.

  5. Microstructure and Tensile Properties of BN/SiC Coated Hi-Nicalon, and Sylramic SiC Fiber Preforms

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Chen, Yuan L.; Morscher, Gregory N.

    2001-01-01

    Batch to batch and within batch variations, and the influence of fiber architecture on room temperature physical and tensile properties of BN/SiC coated Hi-Nicalon and Sylramic SiC fiber preform specimens were determined. The three fiber architectures studied were plain weave (PW), 5-harness satin (5HS) and 8-harness satin (8HS) Results indicate that the physical properties vary up to 10 percent within a batch, and up to 20 percent between batches of preforms. Load-reload (Hysteresis) and acoustic emission methods were used to analyze damage accumulation occurring during tensile loading. Early acoustic emission activity, before observable hysteretic behavior, indicates that the damage starts with the formation of nonbridged tunnel cracks. These cracks then propagate and intersect the load bearing "0" fibers giving rise to hysteretic behavior, For the Hi-Nicalon preform specimens, the onset of "0" bundle cracking stress and strain appeared to be independent of the fiber architecture. Also, the "0" fiber bundle cracking strain remained nearly the same for the preform specimens of both fiber types. Transmission Electron Microscope (TEM) analysis indicates that the Chemical Vapor Infiltration (CVI) Boron Nitride (BN) interface coating is mostly amorphous and contains carbon and oxygen impurities, and the CVI SiC coating is crystalline. No reaction exists between the CVI BN and SiC coating.

  6. Mechanical properties of SiC fiber-reinforced reaction-bonded Si3N4 composites

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.

    1985-01-01

    The room temperature mechanical and physical properties of silicon carbide fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) have been evaluated. The composites contained 23 and 40 volume fraction of aligned 140 micro m diameter chemically vapor deposited SiC fibers. Preliminary results for composite tensile and bend strengths and fracture strain indicate that the composites displayed excellent properties when compared with unreinforced RBSN of comparable porosity. Fiber volume fraction showed little influence on matrix first cracking strain but did influence the stressed required for matrix first cracking and for ultimate composite fracture strength. It is suggested that by reducing matrix porosity and by increasing the volume fraction of the large diameter SiC fiber, it should be possible to further improve the composite stress at which the matrix first cracks.

  7. Mechanical properties of SiC fiber-reinforced reaction-bonded Si3N4 composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.

    1986-01-01

    The room temperature mechanical and physical properties of silicon carbide fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) have been evaluated. The composites contained 23 and 40 volume fraction of aligned 140 micro m diameter chemically vapor deposited SiC fibers. Preliminary results for composite tensile and bend strengths and fracture strain indicate that the composites displayed excellent properties when compared with unreinforced RBSN of comparable porosity. Fiber volume fraction showed little influence on matrix first cracking strain but did influence the stressed required for matrix first cracking and for ultimate composite fracture strength. It is suggested that by reducing matrix porosity and by increasing the volume fraction of the large diameter SiC fiber, it should be possible to further improve the composite stress at which the matrix first cracks.

  8. Experimental investigation of interface properties in SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

    SciTech Connect

    Eldridge, J.I.; Bhatt, R.T.

    1995-10-01

    Interfacial properties of 1-D SiC/RBSN composites were measured by the matrix crack spacing method and by the fiber push-out method, and the results were compared. The composites consisted of 8 to 33 vol% of aligned SCS-6 SiC fibers (142 {micro}m diameter) in a relatively porous (20 to 40 vol%) Si{sub 3}N{sub 4} matrix. The effects of fiber volume fraction and test temperature on the interfacial properties have been investigated. The advantages and limitations of both methods in evaluating the interface properties of fiber-reinforced ceramic matrix composites and the factors influencing the interfacial measurements are discussed.

  9. The HFIR 14J irradiation SiC/SiC composite and SiC fiber collaboration

    SciTech Connect

    Youngblood, G.E.; Jones, R.H.; Kohyama, Akira; Katoh, Yutai; Hasegawa, Akira; Snead, L.; Scholz, R.

    1998-09-01

    A short introduction with references establishes the current status of research and development of SiC{sub f}/SiC composites for fusion energy systems with respect to several key issues. The SiC fiber and composite specimen types selected for the JUPITER 14J irradiation experiment are presented together with the rationale for their selection.

  10. Effects of Interface Coating and Nitride Enhancing Additive on Properties of Hi-Nicalon SiC Fiber Reinforced Reaction-Bonded Silicon Nitride Composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishana T.; Hull, David R.; Eldridge, Jeffrey I.; Babuder, Raymond

    2000-01-01

    Strong and tough Hi-Nicalon SiC fiber reinforced reaction-bonded silicon nitride matrix composites (SiC/ RBSN) have been fabricated by the fiber lay-up approach. Commercially available uncoated and PBN, PBN/Si-rich PBN, and BN/SiC coated SiC Hi-Nicalon fiber tows were used as reinforcement. The composites contained approximately 24 vol % of aligned 14 micron diameter SiC fibers in a porous RBSN matrix. Both one- and two-dimensional composites were characterized. The effects of interface coating composition, and the nitridation enhancing additive, NiO, on the room temperature physical, tensile, and interfacial shear strength properties of SiC/RBSN matrix composites were evaluated. Results indicate that for all three coated fibers, the thickness of the coatings decreased from the outer periphery to the interior of the tows, and that from 10 to 30 percent of the fibers were not covered with the interface coating. In the uncoated regions, chemical reaction between the NiO additive and the SiC fiber occurs causing degradation of tensile properties of the composites. Among the three interface coating combinations investigated, the BN/SiC coated Hi-Nicalon SiC fiber reinforced RBSN matrix composite showed the least amount of uncoated regions and reasonably uniform interface coating thickness. The matrix cracking stress in SiC/RBSN composites was predicted using a fracture mechanics based crack bridging model.

  11. Impact behavior of a SiC fiber-reinforced reaction bonded Si3N4 composite

    NASA Technical Reports Server (NTRS)

    Grady, J.; Bhatt, R.; Klima, S.

    1989-01-01

    Impact tests were performed on a series of ceramic plate specimens. Monolithic (unreinforced) and composite specimens with various fiber layups were tested to determine the effect that the fiber reinforcement has on impact damage initiation and dynamic response of the ceramic materials. Results show that a porous surface layer of Si3N4 on the composite specimens can enhance the energy absorbing capability of the composite specimens. The addition of SiC fiber reinforcement to the RBSN matrix material is also shown to significantly change the mode of failure and reduce the extent of damage due to impact.

  12. Effect of Fiber Strength on the Room Temperature Tensile Properties of Sic/Ti-24Al-11Nb

    NASA Technical Reports Server (NTRS)

    Draper, S. L.; Brindley, P. K.; Nathal, M. V.

    1991-01-01

    SCA-6 SiC fibers of known strength were incorporated into SiC/Ti-24Al-11Nb (at. percent) composites and the effect of fiber strength variability on room temperature composite strength was investigated. Fiber was etched out of a composite fabricated by the powder cloth technique and the effect of the fabrication process on fiber strength was assessed. The strength of the composite was directly correlated with the strength of the as-received fiber. The strength of composite plates containing mixed fiber strengths was dominated by the lower strength fiber. Fabrication by the powder cloth technique resulted in only a slight degradation of fiber strength. The strength of the composite was found to be overestimated by the rule of mixtures strength calculation. Examination of failed tensile specimens revealed periodic fiber cracks and the failure mode was concluded to be cumulative. With the variation in fiber strength eliminated, the composite UTS was found to have a positive correlation with volume fraction of fiber.

  13. In situ TEM annealing of ion-amorphized Hi Nicalon S and Tyranno SA3 SiC fibers

    NASA Astrophysics Data System (ADS)

    Huguet-Garcia, J.; Jankowiak, A.; Miro, S.; Meslin, E.; Serruys, Y.; Costantini, J.-M.

    2016-05-01

    In this work, recrystallization of ion-amorphized Hi Nicalon Type S and Tyranno SA3 SiC fibers (4 MeV Au3+, 2 × 1015 cm-2) has been studied via in situ TEM annealing. Both fibers show a two-step recovery process of the radiation damage. First recovery stage starts at temperatures as low as 250 °C and implies recovery of the radiation swelling. Eventually the amorphous layer recrystallizes with no signs of polytype change (3C-SiC). Recrystallization temperatures yield 900-920 °C and 930 °C for the HNS and the TSA3 respectively. HNS fiber shows columnar recrystallization perpendicular to the amorphous-crystalline interphase with a grain growth rate of ∼20 nm min-1. On the other hand, recrystallization of TSA3 fiber is rather "spontaneous" with no preferential growth direction. The different recrystallization is attributed to the different microstructure of the fibers.

  14. Characterization of SiC fibers by soft x-ray photoelectron and photoabsorption spectroscopies and scanning Auger microscopy

    SciTech Connect

    Ma, Qing; McDowell, M.W.; Rosenberg, R.A.

    1996-08-01

    Synchrotron radiation soft x-ray photoelectron and photoabsorption spectroscopy was used to characterize commercially obtained SiC fibers produced by CVD on a W core and followed by a C passivating layer. Depth profiling of the fiber through the C/SiC interface was done by making Si 2p and C 1s core level PES and PAS, as well as scanning Auger microscopy, measurements following Ar{sup +} sputtering. No significant changes in either photoemission or absorption or Auger line shapes were observed versus depth, indicating no significant interfacial reaction. The line shapes of the carbonaceous coatings are predominantely graphite-like and those of the CVD SiC coatings are microcrystalline, with disorder present to some extent in both cases.

  15. SiC fiber and yttria-stabilized zirconia composite thick thermal barrier coatings fabricated by plasma spray

    NASA Astrophysics Data System (ADS)

    Ma, Rongbin; Cheng, Xudong; Ye, Weiping

    2015-12-01

    Approximately 4 mm-thick SiC fiber/yttria-stabilized zirconia (YSZ) composite thermal barrier coatings (TBCs) were prepared by atmospheric plasma spray (APS). The composite coatings have a 'reinforced concrete frame structure', which can protect the coating from failure caused by increasing thickness of coating. The SiC fiber plays an important role in reducing the residual stress level of the composite coatings. The thermal conductivity (TC) value of the composite coatings is 0.632 W/m K, which is about 50% reduction compared to that of typical APS YSZ TBCs. And the composite coatings have higher fracture toughness and better thermal shock resistance than the YSZ TBCs.

  16. Advanced fiber placement of composite fuselage structures

    NASA Technical Reports Server (NTRS)

    Anderson, Robert L.; Grant, Carroll G.

    1991-01-01

    The Hercules/NASA Advanced Composite Technology (ACT) program will demonstrate the low cost potential of the automated fiber placement process. The Hercules fiber placement machine was developed for cost effective production of composite aircraft structures. The process uses a low cost prepreg tow material form and achieves equivalent laminate properties to structures fabricated with prepreg tape layup. Fiber placement demonstrations planned for the Hercules/NASA program include fabrication of stiffened test panels which represent crown, keel, and window belt segments of a typical transport aircraft fuselage.

  17. Effects of Thermal Treatment on Tensile Creep and Stress-Rupture Behavior of Hi-Nicalon SiC Fibers

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; Goldsby, J. C.; Dicarlo, J. A.

    1995-01-01

    Tensile creep and stress-rupture studies were conducted on Hi-Nicalon SiC fibers at 1200 and 1400 C in argon and air. Examined were as-received fibers as well as fibers annealed from 1400 to 1800 C for 1 hour in argon before testing. The creep and rupture results for these annealed fibers were compared to those of the as-received fibers to determine the effects of annealing temperature, test temperature, and test environment. Argon anneals up to 1500 C degrade room temperature strength of Hi-Nicalon fibers, but improve fiber creep resistance in argon or air by as much as 100% with no significant degradation in rupture strength. Argon anneals above 1500 C continue to improve fiber creep resistance when tested in argon, but significantly degrade creep resistance and rupture strength when tested in air. Decrease in creep resistance in air is greater at 1200 C than at 1400 C. Mechanisms are suggested for the observed behavior.

  18. Advances in drilling with fiber lasers

    NASA Astrophysics Data System (ADS)

    Naeem, Mohammed

    2015-07-01

    High brightness quasi- continuous wave (QCW) and continuous wave (CW) fiber lasers are routinely being used for cutting and welding for a range of industrial applications. However, to date very little work has been carried out or has been reported on laser drilling with these laser sources. This work describes laser drilling ((trepan and percussion) of nickel based superalloys (thermal barrier coated and uncoated) with a high power QCW fiber laser. This presentation will highlight some of the most significant aspect of laser drilling, i.e. SmartPierceTM, deep hole drilling and small hole drilling. These advances in processing also demonstrate the potential for fiber laser processing when an advanced interface between laser and an open architecture controller are used.

  19. Burner rig thermal fatigue failure of SiC continuous fiber/Si{sub 3}N{sub 4} ceramic composites

    SciTech Connect

    Ertuerk, T.; Park, K.; Sung, C.

    1995-10-01

    The burner rig thermal fatigue properties of SiC continuous fiber/Si{sub 3}N{sub 4} ceramic composites were examined under impinged jet fuel flame, a constant applied tensile stress and thermal cycling in the temperature range 500--1,350 C. The SCS-9 SiC fiber/Si{sub 3}N{sub 4} composites failed within the flame impinged zone, whereas the SCS-6 fiber/Si{sub 3}N{sub 4} composites failed outside the flame impinged zone due to the high thermal stresses resulting from high-temperature gradients. Analytical transmission electron microscopy was sued to investigate the microstructure and chemistry of the fiber, matrix and fiber/matrix interface in the failed SCS-9 SiC fiber/Si{sub 3}N{sub 4} composites. The partial degradation of columnar structure of the fiber was interpreted as the dominant mechanism of burner rig thermal fatigue failure of SCS-9 SiC fiber/Si{sub 3}N{sub 4} composites.

  20. Optical Fiber Sensors for Advanced Civil Structures

    NASA Astrophysics Data System (ADS)

    de Vries, Marten Johannes Cornelius

    1995-01-01

    The objective of this dissertation is to develop, analyze, and implement optical fiber-based sensors for the nondestructive quantitative evaluation of advanced civil structures. Based on a comparative evaluation of optical fiber sensors that may be used to obtain quantitative information related to physical perturbations in the civil structure, the extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor is selected as the most attractive sensor. The operation of the EFPI sensor is explained using the Kirchhoff diffraction approach. As is shown in this dissertation, this approach better predicts the signal-to-noise ratio as a function of gap length than methods employed previously. The performance of the optical fiber sensor is demonstrated in three different implementations. In the first implementation, performed with researchers in the Civil Engineering Department at the University of Southern California in Los Angeles, optical fiber sensors were used to obtain quantitative strain information from reinforced concrete interior and exterior column-to-beam connections. The second implementation, performed in cooperation with researchers at the United States Bureau of Mines in Spokane, Washington, used optical fiber sensors to monitor the performance of roof bolts used in mines. The last implementation, performed in cooperation with researchers at the Turner-Fairbanks Federal Highway Administration Research Center in McLean, Virginia, used optical fiber sensors, attached to composite prestressing strands used for reinforcing concrete, to obtain absolute strain information. Multiplexing techniques including time, frequency and wavelength division multiplexing are briefly discussed, whereas the principles of operation of spread spectrum and optical time domain reflectometery (OTDR) are discussed in greater detail. Results demonstrating that spread spectrum and OTDR techniques can be used to multiplex optical fiber sensors are presented. Finally, practical

  1. Chemical Vapor Deposited SiC (SCS-0) Fiber-Reinforced Strontium Aluminosilicate Glass-Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1997-01-01

    Unidirectional SrO Al2O3 2SiO2 glass-ceramic matrix composites reinforced with uncoated Chemical Vapor Deposited (CVD) SiC (SCS-0) fibers have been fabricated by hot-pressing under appropriate conditions using the glass-ceramic approach. Almost fully dense composites having a fiber volume fraction of 0.24 have been obtained. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase observed in the matrix by x-ray diffraction. No chemical reaction was observed between the fiber and the matrix after high temperature processing. In three-point flexure, the composite exhibited a first matrix cracking stress of approx. 231 +/- 20 MPa and an ultimate strength of 265 +/- 17 MPa. Examination of fracture surfaces revealed limited short length fiber pull-out. From fiber push-out, the fiber/matrix interfacial debonding and frictional strengths were evaluated to be approx. 17.5 +/- 2.7 MPa and 11.3 +/- 1.6 MPa, respectively. Some fibers were strongly bonded to the matrix and could not be pushed out. The micromechanical models were not useful in predicting values of the first matrix cracking stress as well as the ultimate strength of the composites.

  2. Microwave absorbability of unidirectional SiC fiber composites as a function of the constituents’ properties

    NASA Astrophysics Data System (ADS)

    Wan, Guangchao; Jiang, Jianjun; He, Yun; Bie, Shaowei

    2016-06-01

    The electromagnetic properties of unidirectional SiC fibre composites can be efficiently tailored by adjusting the properties of the composite’s constituents making these composites potential microwave absorbers. In this study, the microwave absorbing properties of unidirectional SiC fibre composites were investigated based on the electromagnetic properties of the constituents at frequencies ranging from 8 to 18 GHz. The composite was composed of two types of SiC fibres that individually exhibit relatively high and low electrical conductivity. The matrix together with the low-conductivity SiC fibres were characterized by effective permittivity and conductivity which provided a theoretical calculation of the microwave reflectivity. The theoretical calculation was based on formulas about anisotropic unidirectional composites and was compared to the results obtained from numerical simulations. There was good agreement in the results obtained from both methods. It was found that the intensity of microwave absorption of the composite was dependent primarily on the properties of the high-conductivity SiC fibres. The absorption band appeared to be dependent on the effective permittivity of the matrix and the low-conductivity SiC fibres and the conductivity of the high-conductivity SiC fibres.

  3. Advanced radio over fiber network technologies.

    PubMed

    Novak, Dalma; Waterhouse, Rod

    2013-09-23

    The evolution of wireless communication networks supporting emerging broadband services and applications offers new opportunities for realizing integrated optical and wireless network infrastructures. We report on some of our recent activities investigating advanced technologies for next generation converged optical wireless networks. Developments in Active Antenna Systems, mobile fronthaul architectures, and 60 GHz fiber distributed wireless networks are described. We also discuss the potential for analog radio over fiber distribution links as a viable solution for meeting the capacity requirements of new network architectures. PMID:24104183

  4. Creep and Stress-strain Behavior After Creep from Sic Fiber Reinforced, Melt-infiltrated Sic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Pujar, Vijay

    2004-01-01

    Silicon carbide fiber (Hi-Nicalon Type S, Nippon Carbon) reinforced silicon carbide matrix composites containing melt-infiltrated Si were subjected to creep at 1315 C for a number of different stress conditions, This study is aimed at understanding the time-dependent creep behavior of CMCs for desired use-conditions, and also more importantly, how the stress-strain response changes as a result of the time-temperature-stress history of the crept material. For the specimens that did not rupture, fast fracture experiments were performed at 1315 C or at room temperature immediately following tensile creep. In many cases, the stress-strain response and the resulting matrix cracking stress of the composite change due to stress-redistribution between composite constituents during tensile creep. The paper will discuss these results and its implications on applications of these materials for turbine engine components.

  5. Advanced fiber/matrix material systems

    NASA Technical Reports Server (NTRS)

    Hartness, J. Timothy

    1991-01-01

    Work completed in Phase 1 of the NASA Advanced Composite Technology program is discussed. Two towpreg forms (commingled yarns and fused powder towpregs) are being characterized under the program. These towpregs will be used to evaluate textile fabrication technologies for advanced aircraft composite structures. The unique characteristic of both of these material forms is that both fiber and matrix resin are handled in a single operation such as weaving, braiding, or fiber placement. The evaluation of both commingled and fused powder towpreg is described. Various polymer materials are considered for both subsonic and supersonic applications. Polymers initially being evaluated include thermoplastic polyimides such as Larc-TPI and New-TPI, thermoplastics such as PEEK and PEKEKK as well as some toughened crosslinked polyimides. Preliminary mechanical properties as well as tow handling are evaluated.

  6. Effects of reaction layer on interfacial shear properties and strength of fiber in silicon-carbide (SiC) fiber-reinforced titanium alloy composite

    SciTech Connect

    Kagawa, Yutaka; Masuda, Chitoshi; Fujiwara, Chikara; Fukushima, Akira

    1996-12-31

    The effect of the interfacial thickness of the reaction layer on the interfacial shear properties and the tensile strength of double carbon-coated SCS-6 SiC fiber in Ti-15Mo-5Zr-3Al alloy matrix composite was examined. The major reaction layer thickness, that is, titanium-carbide (TiC) layer thickness, varied with heat-exposure temperature and time, respectively, and the resultant mean thickness of the reaction layer of the composite ranged from 0.4 to 1.7 {micro}m. The critical interfacial toughness, G{sub i}{sup c}, and the mean shear sliding resistance, {tau}{sub s}, were evaluated by the thin specimen pushout technique. Tensile strength of the silicon-carbide (SiC) fiber extracted from the titanium alloy matrix before and after the heat exposure was determined in relationship to the thickness of the reaction layer. The critical interface toughness, G{sub i}{sup c}, for the failure of the root of the reaction layer was {approx}4 J/m{sup 2}, and the average shear sliding resistance of the interface, {tau}{sub s}, was 102 to 118 MPa. The interfacial shear mechanical properties were adequate to prevent failure of the fiber due to the stress concentration caused by cracks that formed first in the reaction layer. The results showed that when the growth of reaction layer was within 1.7 {micro}m, the mean strength of the extracted fiber was unaffected by the existence of the reaction layer because of weak bonding between it and the fiber. However, with the increase of the reaction layer thickness, the strength distribution of the extracted fiber tended to Weibull bimodal distribution.

  7. Role of interfacial thermal barrier in the transverse thermal conductivity of uniaxial SiC fiber-reinforced reaction bonded silicon nitride

    NASA Technical Reports Server (NTRS)

    Bhatt, H.; Donaldson, K. Y.; Hasselman, D. P. H.; Bhatt, R. T.

    1992-01-01

    The transverse thermal conductivity of reaction-bonded Si3N4 is significantly affected by an interfacial barrier at the interface formed with SiC reinforcing fibers. A comparative study of composites with and without reinforcing-fiber carbon coatings found the coating to reduce effective thermal conductivity by a factor of about 2; this, however, is partially due to a thermal expansion-mismatch gap between fiber and matrix. HIPing of composites with coated fibers led to an enhancement of thermal conductivity via improved interfacial thermal contact and greater grain size and crystallinity of the fibers.

  8. Characterization of interfacial failure in SiC reinforced Si3N4 matrix composite material by both fiber push-out testing and Auger electron spectroscopy

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Honecy, F. S.

    1990-01-01

    AES depth profiling and a fiber push-out test for interfacial shear-strength determination have been used to ascertain the mechanical/chemical properties of the fiber/matrix interface in SiC-reinforced reaction-bonded Si3N4, with attention to the weak point where interfacial failure occurs. In the cases of both composite fracture and fiber push-outs, the interfacial failure occurred either between the two C-rich coatings that are present on the double-coated SiC fibers, or between the inner C-rich coating and the SiC fiber. Interface failure occurs at points of very abrupt concentration changes.

  9. Joining of SiC Fiber-Bonded Ceramics using Silver, Copper, Nickel, Palladium, and Silicon-Based Alloy Interlayers

    SciTech Connect

    Asthana, Rajiv; Singh, Mrityunjay; Lin, Hua-Tay; Matsunaga, Kenji; Ishikawa, Toshihiro

    2013-01-01

    SiC fiber-bonded ceramics, SA-Tyrannohex, (SA-THX) with perpendicular and parallel fiber orientations were brazed using Ag-, Ni- and Pd-base brazes, and four Si X (X: Ti, Cr, Y, Ta) eutectics. Outcomes were variable, ranging from bonded joints through partially bonded to un-bonded joints. Prominent Ti- and Si-rich interfaces developed with Cusil-ABA, Ticusil, and Copper-ABA and Ni- and Si-rich layers with MBF-20. Stress rupture tests at 650 and 750 C on Cusil-ABA-bonded joints revealed a temperature-dependent behavior for the perpendicular joints but not for the parallel joints with failure occurring at brazed interface. Higher-use temperatures can be targeted with eutectic Si Ti and Si Cr alloys.

  10. Oxidation effects on the mechanical properties of SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.

    1989-01-01

    The room temperature mechanical properties of SiC fiber reinforced reaction bonded silicon nitride composites were measured after 100 hrs exposure at temperatures to 1400 C in nitrogen and oxygen environments. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers in a reaction bonded Si3N4 matrix. The results indicate that composites heat treated in a nitrogen environment at temperatures to 1400 C showed deformation and fracture behavior equivalent to that of the as-fabricated composites. Also, the composites heat treated in an oxidizing environment beyond 400 C yielded significantly lower tensile strength values. Specifically in the temperature range from 600 to 1000 C, composites retained approx. 40 percent of their as-fabricated strength, and those heat treated in the temperatures from 1200 to 1400 C retained 70 percent. Nonetheless, for all oxygen heat treatment conditions, composite specimens displayed strain capability beyond the matrix fracture stress; a typical behavior of a tough composite.

  11. Microstructure and Tensile Properties of BN/SiC Coated Hi-Nicalon, and Sylramic SiC Fiber Preforms. Revised

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Chen, Yuan L.; Morscher, Gregory N.

    2002-01-01

    Batch to batch and within batch variations, and the influence of fiber architecture on room temperature physical and tensile properties of BN/SiC coated Hi-Nicalon and Sylramic SiC fiber preform specimens were determined. The three fiber architectures studied were plain weave (PW), 5-harness satin (5HS), and 8-harness satin (8HS). Results indicate that the physical properties vary up to 10 percent within a batch, and up to 20 percent between batches of preforms. Load-reload (Hysteresis) and acoustic emission methods were used to analyze damage accumulation occurring during tensile loading. Early acoustic emission activity, before observable hysteretic behavior, indicates that the damage starts with the formation of nonbridged tunnel cracks. These cracks then propagate and intersect the load bearing "0 deg" fibers giving rise to hysteretic behavior. For the Hi-Nicalon preform specimens, the onset of "0 deg" bundle cracking stress and strain appeared to be independent of the fiber architecture. Also, the "0 deg" fiber bundle cracking strain remained nearly the same for the preform specimens of both fiber types. TEM analysis indicates that the CVI BN interface coating is mostly amorphous and contains carbon and oxygen impurities, and the CVI SiC coating is crystalline. No reaction exists between the CVI BN and SiC coating.

  12. Dimensional stability and tensile strength of irradiated Nicalon-CG and Hi-Nicalon SiC fibers

    SciTech Connect

    Youngblood, G.E.; Henager, C.H. Jr.; Senor, D.J.; Newsome, G.A.; Woods, J.J.

    1997-05-01

    Nicalon-CG and Hi-Nicalon fibers were characterized by measuring their length, density, and tensile strength in the unirradiated, thermal annealed, and irradiated conditions. The irradiation was conducted in the EBR-II to a dose of 43 dpa-SiC at a nominal irradiation temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. The results indicate the fibers that perform best in an irradiation environment are those that approach stoichiometric and crystalline SiC. Hi-Nicalon exhibited negligible densification, accompanied by an increase in tensile strength after irradiation. Nicalon-CG possessed a higher tensile strength than hi-Nicalon in the unirradiated condition, but was significantly weakened in the annealed and irradiated conditions. In addition, Nicalon-CG exhibited unacceptable irradiation-induced shrinkage. Loss o fiber tensile strength after irradiation is shown to reduce the flexural strength of irradiated composites and Nicalon-CG fiber shrinkage observed in irradiated composites.

  13. The influence of fiber/matrix interface on the mechanical behavior of Nicalon SiC fiber reinforced glass-ceramic composites

    SciTech Connect

    Liu, Y.M.; Mitchell, T.E.; Wadley, H.N.G.

    1996-11-01

    Mechanical properties of unidirectional Nicalon SiC fiber reinforced Ca aluminosilicate (CAS/SiC) and Mg aluminosilicate (MAS/SiC) glass-ceramic composites were investigated by tensile testing and nondestructive laser-ultrasound technique. The Ba-stuffed MAS was either undoped or doped with 5% borosilicate glass. Degradation of elastic stiffness constant C{sub 11} in transverse direction due to interface damage was monitored in situ by measuring the laser- generated ultrasound wave velocity. The three composite materials show different characteristics of macroscopic deformation behavior, which is correlated strongly to interface degradation. A stronger reduction trend of the elastic constant C{sub 11} is associated with a larger degree of inelastic deformation. The fracture surfaces also reveal the close relation between fiber pullout length and interfacial characteristics. Interfaces of these composites were studied by TEM; their influence on inhibiting and deflecting matrix cracks is discussed.

  14. Matrix density effects on the mechanical properties of SiC fiber-reinforced silicon nitride matrix properties

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Kiser, Lames D.

    1990-01-01

    The room temperature mechanical properties were measured for SiC fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus were approx. 15 and 50 percent higher, respectively, and ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIPed composites appears to be related to a degradation in fiber strength at the HIP temperature. However, the density effect on matrix fracture strength was much less than would be expected based on typical monolithic Si3N4 behavior, suggesting that composite theory is indeed operating. Possible practical implications of these observations are discussed.

  15. Matrix density effects on the mechanical properties of SiC fiber-reinforced silicon nitride matrix properties

    SciTech Connect

    Bhatt, R.T.; Kiser, L.D.

    1990-08-01

    The room temperature mechanical properties were measured for SiC fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus were approx. 15 and 50 percent higher, respectively, and ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIPed composites appears to be related to a degradation in fiber strength at the HIP temperature. However, the density effect on matrix fracture strength was much less than would be expected based on typical monolithic Si3N4 behavior, suggesting that composite theory is indeed operating. Possible practical implications of these observations are discussed. 18 refs.

  16. The effect of neutron irradiation on silicon carbide fibers

    SciTech Connect

    Newsome, G.A.

    1997-01-01

    Nine types of SiC fiber have been exposed to neutron radiation in the Advanced Test Reactor at 250 C for various lengths of time ranging from 83 to 128 days. The effects of these exposures have been initially determined using scanning electron microscopy. The fibers tested were Nicalon{trademark} CG, Tyranno, Hi-Nicalon{trademark}, Dow Corning SiC, Carborundum SiC, Textron SCS-6, polymethysilane (PMS) derived SiC from the University of Michigan, and two types of MER SiC fiber. This covers a range of fibers from widely used commercial fibers to developmental fibers. Consistent with previous radiation experiments, Nicalon fiber was severely degraded by the neutron irradiation. Similarly, Tyranno suffered severe degradation. The more advanced fibers which approach the composition and properties of SiC performed well under irradiation. Of these, the Carborundum SiC fiber appeared to perform the best. The Hi-Nicalon and Dow Corning Fibers exhibited good general stability, but also appear to have some surface roughening. The MER fibers and the Textron SCS-6 fibers both had carbon cores which adversely influenced the overall stability of the fibers.

  17. Stress-Dependent Matrix Cracking in 2D Woven SiC-Fiber Reinforced Melt-Infiltrated SiC Matrix Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.

    2003-01-01

    The matrix cracking of a variety of SiC/SiC composites has been characterized for a wide range of constituent variation. These composites were fabricated by the 2-dimensional lay-up of 0/90 five-harness satin fabric consisting of Sylramic fiber tows that were then chemical vapor infiltrated (CVI) with BN, CVI with SiC, slurry infiltrated with SiC particles followed by molten infiltration of Si. The composites varied in number of plies, the number of tows per length, thickness, and the size of the tows. This resulted in composites with a fiber volume fraction in the loading direction that ranged from 0.12 to 0.20. Matrix cracking was monitored with modal acoustic emission in order to estimate the stress-dependent distribution of matrix cracks. It was found that the general matrix crack properties of this system could be fairly well characterized by assuming that no matrix cracks originated in the load-bearing fiber, interphase, chemical vapor infiltrated Sic tow-minicomposites, i.e., all matrix cracks originate in the 90 degree tow-minicomposites or the large unreinforced Sic-Si matrix regions. Also, it was determined that the larger tow size composites had a much narrower stress range for matrix cracking compared to the standard tow size composites.

  18. Microstructures of short-carbon-fiber-reinforced SiC composites prepared by hot-pressing

    SciTech Connect

    He Xiulan Guo Yingkui; Zhou Yu; Jia Dechang

    2008-12-15

    Microstructures of short-carbon-fiber-reinforced silicon carbide composites, prepared by hot-pressing with MgO-Al{sub 2}O{sub 3}-Y{sub 2}O{sub 3} as sintering additives, were investigated by means of X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy. The results showed that the composites could be densified at a relatively low temperature of 1800 deg. C via the liquid-phase-sintering mechanism. The amorphous interphase in the composites not only avoided the direct contact of the fibers with the matrix, but also improved the fiber/matrix bonding, so they could improve the densification of the composites and avoid the degeneration of the carbon fiber. The nano silicon carbide derived from polycarbosilane, could play a role of improving the relative density of the composites.

  19. Advances in fiber combined pump modules for fiber lasers

    NASA Astrophysics Data System (ADS)

    Crum, Trevor; Romero, Oscar; Li, Hanxuan; Jin, Xu; Towe, Terry; Chyr, Irving; Truchan, Tom; Liu, Daming; Cutillas, Serge; Johnson, Kelly; Park, Sang-Ki; Wolak, Ed; Miller, Robert; Bullock, Robert; Mott, Jeff; Fidric, Bernard; Harrison, James

    2009-02-01

    Fiber combining multiple pump sources for fiber lasers has enabled the thermal and reliability advantages of distributed architectures. Recently, mini-bar based modules have been demonstrated which combine the advantages of independent emitter failures previously shown in single-stripe pumps with improved brightness retention yielding over 2 MW/cm2Sr in compact economic modules. In this work multiple fiber-coupled mini-bars are fiber combined to yield an output of over 400 W with a brightness exceeding 1 MW/cm2Sr in an economic, low loss architecture.

  20. Neutron irradiation effects on the density, tensile properties and microstructural changes in Hi-Nicalon™ and Sylramic™ SiC fibers

    NASA Astrophysics Data System (ADS)

    Osborne, M. C.; Hubbard, C. R.; Snead, L. L.; Steiner, D.

    1998-03-01

    Tensile results are presented for ceramic grade (cg) Nicalon™, Hi-Nicalon™ and Sylramic™ SiC fibers which have all been neutron irradiated in the high flux isotope reactor (HFIR) at damage levels of 0.1, 0.5, 2 and 5 dpa. Single fibers were tensile tested and the results were analyzed using Weibull statistics. Fiber axial displacements were measured with a laser micrometer which allowed for the determination of the tensile moduli. Density changes were measured with a gradient column. Transmission electron microscopy (TEM) was performed to assess microstructural damage and X-ray diffraction (XRD) was used to measure uniform strain, degree of crystallinity, average coherence length and root-mean-square microstrain. The physical and tensile results indicate that cg Nicalon™ and Hi-Nicalon™ are unstable in a neutron field. Both fiber types densify by 3-5% which would be detrimental to a composite's matrix cracking stress due to weakening or debonding of the interface. The Sylramic™ swells which is similar behavior to the monolithic SiC. The failure strength of the Sylramic™ drops by 50% after an irradiation temperature of 500°C which would have little effect on the matrix cracking condition of a composite. The Sylramic™ fiber strength decrease would significantly reduce the ultimate composite strength but the composite strength would remain above the matrix cracking strength such that the fibers may still potentially be viable for fusion applications.

  1. Effects of Thermal Cycling on Thermal Expansion and Mechanical Properties of Sic Fiber-reinforced Reaction-bonded Si3n4 Composites

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.; Palczer, A. R.

    1994-01-01

    Thermal expansion curves for SiC fiber-reinforced reaction-bonded Si3N4 matrix composites (SiC/RBSN) and unreinforced RBSN were measured from 25 to 1400 C in nitrogen and in oxygen. The effects of fiber/matrix bonding and cycling on the thermal expansion curves and room-temperature tensile properties of unidirectional composites were determined. The measured thermal expansion curves were compared with those predicted from composite theory. Predicted thermal expansion curves parallel to the fiber direction for both bonding cases were similar to that of the weakly bonded composites, but those normal to the fiber direction for both bonding cases resulted in no net dimensional changes at room temperature, and no loss in tensile properties from the as-fabricated condition. In contrast, thermal cycling in oxygen for both composites caused volume expansion primarily due to internal oxidation of RBSN. Cyclic oxidation affected the mechanical properties of the weakly bonded SiC/RBSN composites the most, resulting in loss of strain capability beyond matrix fracture and catastrophic, brittle fracture. Increased bonding between the SiC fiber and RBSN matrix due to oxidation of the carbon-rich fiber surface coating and an altered residual stress pattern in the composite due to internal oxidation of the matrix are the main reasons for the poor mechanical performance of these composites.

  2. Design Curve Generation for 3D SiC Fiber Architecture

    NASA Technical Reports Server (NTRS)

    Lang, Jerry; Dicarlo, James A.

    2014-01-01

    The design tool provides design curves that allow a simple and quick way to examine multiple factors that can influence the processing and key properties of the preforms and their final SiC-reinforced ceramic composites without over obligating financial capital for the fabricating of materials. Tool predictions for process and fiber fraction properties have been validated for a HNS 3D preform.The virtualization aspect of the tool will be used to provide a quick generation of solid models with actual fiber paths for finite element evaluation to predict mechanical and thermal properties of proposed composites as well as mechanical displacement behavior due to creep and stress relaxation to study load sharing characteristic between constitutes for better performance.Tool predictions for the fiber controlled properties of the SiCSiC CMC fabricated from the HNS preforms will be valuated and up-graded from the measurements on these CMC

  3. Characterization of SiC (SCS-6) Fiber Reinforced Reaction-Formed Silicon Carbide Matrix Composites

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Dickerson, Robert M.

    1995-01-01

    Silicon carbide (SCS-6) fiber reinforced-reaction formed silicon carbide matrix composites were fabricated using NASA's reaction forming process. Silicon-2 at a percent of niobium alloy was used as an infiltrant instead of pure silicon to reduce the amount of free silicon in the matrix after reaction forming. The matrix primarily consists of silicon carbide with a bi-modal grain size distribution. Minority phases dispersed within the matrix are niobium disilicide (NbSi2), carbon and silicon. Fiber push-out tests on these composites determined a debond stress of approx. 67 MPa and a frictional stress of approx. 60 MPa. A typical four point flexural strength of the composite is 297 MPa (43.1 KSi). This composite shows tough behavior through fiber pull out.

  4. Characterization of SiC Fiber (SCS-6) Reinforced-Reaction-Formed Silicon Carbide Matrix Composites

    NASA Technical Reports Server (NTRS)

    Singh, M.; Dickerson, R. M.

    1996-01-01

    Silicon carbide fiber (SCS-6) reinforced-reaction-formed silicon carbide matrix composites were fabricated using a reaction-forming process. Silicon-2 at.% niobium alloy was used as an infiltrant instead of pure silicon to reduce the amount of free silicon in the matrix after reaction forming. The matrix primarily consists of silicon carbide with a bimodal grain size distribution. Minority phases dispersed within the matrix are niobium disilicide (NbSi2), carbon, and silicon. Fiber pushout tests on these composites determined a debond stress of approximately 67 MPa and a frictional stress of approximately 60 MPa. A typical four-point flexural strength of the composite is 297 MPa (43.1 KSi). This composite shows tough behavior through fiber pullout.

  5. Interfacial reaction kinetics of coated SiC fibers with various titanium alloys

    NASA Technical Reports Server (NTRS)

    Gundel, D. B.; Wawner, F. E.

    1991-01-01

    The kinetics of the reaction between the silicon carbide fibers and the titanium-based alloy matrix was investigated at temperatures from 800 to 1000 C for several titanium-based alloys (including Ti-1100 alloy and BETA 21S) and unalloyed Ti, reinforced with coated silicon carbide fiber SCS-6. The reaction zone growth kinetics was studied by exposing vacuum encapsulated samples to temperatures from 700 to 1000 C for times up to 150 hrs, followed by SAM observations of samples which were polished perpendicular to the fiber axis and etched. It was found that the reaction zone growth kinetics of the alpha (hcp) and beta (bcc) phases of unalloyed titanium reacting with SCS-6 fibers exhibited different values of the apparent activation energy and of the preexponential factor. Additions of other metals to Ti was found to slow down the reaction kinetics. Among the alloys studied, the Ti-1100 was the slowest reacting conventional alloy and the Ti-14Al-21Nb (in wt pct) was the slowest overall.

  6. Some properties of an advanced boron fiber. [high strength, splittable fibers

    NASA Technical Reports Server (NTRS)

    Behrendt, D. R.

    1979-01-01

    An advanced coreless boron fiber exhibits tensile strengths which are more than twice that of the normal CVD B/W fibers. The coreless fiber is made by the chemical removal of the tungsten boride core exposed by splitting the as-grown fiber. The easily splittable fiber is made by the chemical vapor deposition of boron on a larger than usual tungsten substrate. It is expected that the ease of splitting is related to residual stresses in these fibers. Measurements of the axial residual stresses in both the normal and the splittable fibers are presented and the results compared. Differences in these stresses are discussed in connection with the ease of splitting in the splittable fibers.

  7. Advances in sapphire optical fiber sensors

    NASA Technical Reports Server (NTRS)

    Wang, Anbo; Wang, George Z.; Gollapudi, Sridhar; May, Russell G.; Murphy, Kent A.; Claus, Richard O.

    1993-01-01

    We describe the development and testing of two sapphire fiber sensor designs intended for use in high temperature environments. The first is a birefringence-balanced polarimetric sapphire fiber sensor. In this sensor, two single crystal sapphire rods, acting as the birefringence sensing element, are connected to each other in such a way that the slow axis of the first rod is aligned along with the fast axis of the second rod, and the fast axis of the first rod is along the slow axis of the second rod. This sensor has been demonstrated for measurement of temperature up to 1500 C. The second is a sapphire-fiber-based intrinsic interferometric sensor. In this sensor, a length of uncoated, unclad, structural-graded multimode sapphire fiber is fusion spliced to a singlemode silica fiber to form a Fabry-Perot cavity. The reflections from the silica-to-sapphire fiber splice and the free endface of the sapphire fiber give rise to the interfering fringe output. This sensor has been demonstrated for the measurement of temperature above 1510 C, and a resolution of 0.1 C has been obtained.

  8. Chemical compatibility issues related to use of copper as an interfacial layer for SiC fiber reinforced Ti3Ai+Nb composite

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1991-01-01

    The reaction of Cu, a potential interfacial compliant layer for the Ti3Al plus Nb/SiC composite, with SiC, SCS-6 fiber, and the Ti3Al plus Nb matrix was examined at two temperatures: 1223 and 1273 K. Reaction of Cu with SiC resulted in the formation of a CuSi solution and free carbon, the reaction product being molten at 1273 K. Hot pressing the SCS-6 fiber in a Cu matrix at 1273 K resulted in cracking and delamination of the outer carbon-rich coating, thus allowing the Cu to penetrate to the SiC-carbon coating interface and react with SiC. In contrast, no such damage to the outer coating was observed at 1223 K. There was excessive reaction between Cu and the Ti3Al plus Nb matrix, the reaction product being molten both at 1223 and 1273 K. An interlayer of Nb between Cu and Ti3Al plus Nb matrix prevented the reaction between the two.

  9. Influence of interfacial shear strength on the mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.

    1990-01-01

    The influence of fiber/matrix interface microstructure and interfacial shear strength on the mechanical properties of a fiber-reinforced ceramic composite was evaluated. The composite consisted of approximately 30 vol percent uniaxially aligned 142 microns diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix (SiC/RBSN). The interface microstructure was varied by controlling the composite fabrication conditions and by heat treating the composite in an oxidizing environment. Interfacial shear strength was determined by the matrix crack spacing method. The results of microstructural examination indicate that the carbon-rich coating provided with the as-produced SiC fibers was stable in composites fabricated at 1200 C in a nitrogen or in a nitrogen plus 4 percent hydrogen mixture for 40 hr. However this coating degraded in composites fabricated at 1350 C in N2 + 4 percent H2 for 40 and 72 hr and also in composites heat treated in an oxidizing environment at 600 C for 100 hr after fabrication at 1200 C in a nitrogen. It was determined that degradation occurred by carbon removal which in turn had a strong influence on interfacial shear strength and other mechanical properties. Specifically, as the carbon coating was removed, the composite interfacial shear strength, primary elastic modulus, first matrix cracking stress, and ultimate tensile strength decreased, but the first matrix cracking strain remained nearly the same.

  10. SiC lightweight telescopes for advanced space applications. I - Mirror technology

    NASA Technical Reports Server (NTRS)

    Anapol, Michael I.; Hadfield, Peter

    1992-01-01

    A SiC based telescope is an extremely attractive emerging technology which offers the lightweight and stiffness features of beryllium, the optical performance of glass to diffraction limited visible resolution, superior optical/thermal stability to cryogenic temperatures, and the cost advantages of an aluminum telescope. SSG has developed various SiC mirrors with and without a silicon coating and tested these mirrors over temperature ranges from +50 C to -250 C. Our test results show less than 0.2 waves P-V in visible wavefront change and no hysteresis over this wide temperature range. Several SSG mirrors are representative of very lightweight SiC/Si mirrors including (1) a 9 cm diameter, high aspect ratio mirror weighing less than 30 grams and (2) a 23 cm diameter eggcrated mirror weighing less than 400 grams. SSG has also designed and analyzed a 0.6 meter SiC based, on axis, three mirror reimaging telescope in which the primary mirror weighs less than 6 kg and a 0.5 meter GOES-like scan mirror. SSG has also diamond turned several general aspheric SiC/Si mirrors with excellent cryo optical performance.

  11. Microwave joining of SiC ceramics and composites

    SciTech Connect

    Ahmad, I.; Silberglitt, R.; Tian, Y.L.; Katz, J.D.

    1997-04-01

    Potential applications of SiC include components for advanced turbine engines, tube assemblies for radiant burners and petrochemical processing and heat exchangers for high efficiency electric power generation systems. Reliable methods for joining SiC are required in order to cost-effectively fabricate components for these applications from commercially available shapes and sizes. This manuscript reports the results of microwave joining experiments performed using two different types of SiC materials. The first were on reaction bonded SiC, and produced joints with fracture toughness equal to or greater than that of the base material over an extended range of joining temperatures. The second were on continuous fiber-reinforced SiC/SiC composite materials, which were successfully joined with a commercial active brazing alloy, as well as by using a polymer precursor.

  12. Advanced fiber optic face plate quality detector design

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Su, Liping; Zhao, Jingxia

    2010-10-01

    A fiber optic face plate is defined by a plurality of fibers of transparent material that are fused and compressed together to transmit an image from one end to another end. Fiber optic face plates exhibit utility in the image intensifiers, cathoderay tubes, and other media displays. In this paper, the design of an advanced fiber optic face plate quality detector is presented. Modern optoelectronic imaging techniques are being used to form fiber optic plate transmission images that are suitable for analyzing the quality parameters of fiber optic face plate. The diffusing light from a halogen lamp is condensed by condenser lens then through a fiber optic face plate, a set of lenses are used to magnify the transmission image, a computer controls a long linear CCD to scan the transmission image, a data grabber captures the CCD's output data and the computer transforms the data into frame image for further analysis. Digital image processing techniques are adopted to analyze the transmission image to obtain the required quality parameters. The image analysis software combines the API that a company provided and programed API is used to acquire the quality parameter that a relevant criteria required. With the long linear CCD scanning and image analysis being computerized, it accomplishes the detection of quality parameters of fiber optic face plates automaticly. The detector can replace the manual detection method and can be widely used for the quality detection of fiber optic face plate. Manufacturers of fiber optic face plates can benefit from the detector for quality control.

  13. Scalable in situ growth of SnO2 nanoparticle chains on SiC ultrathin fibers via a facile sol-gel-flame method

    NASA Astrophysics Data System (ADS)

    Wang, Yingde; Wang, Bing; Lei, Yongpeng; Wu, Nan; Han, Cheng; Gou, Yanzi; Fang, Dong

    2015-04-01

    SnO2 nanoparticle chains (SNPCs) were controllably in situ grown on the electrospun SiC ultrathin fibers (SUFs) by a scalable sol-gel-flame method to form a flexible mat. While bulk SnO2 was obtained by relatively slow pyrolysis in conventional horizontal tube furnace. The effect of process parameters on the microstructure and morphology of SNPCs/SUFs mats was discussed. I-V characteristics of the SNPCs/SUFs mats revealed a nonlinear curve, indicating the formation of Schottky-type junctions. The composite fibers mats also exhibited broad and strong emission bands between 400 and 650 nm. This may be attributed to the existence of a large amount of oxygen vacancies and defects in SNPCs caused by the fast pyrolysis process. Such composite fibers mats may have great potentials in high-temperature gas sensors, light-emitting diodes and lithium-ion storages, etc.

  14. Methods for integrating optical fibers with advanced aerospace materials

    NASA Astrophysics Data System (ADS)

    Poland, Stephen H.; May, Russell G.; Murphy, Kent A.; Claus, Richard O.; Tran, Tuan A.; Miller, Mark S.

    1993-07-01

    Optical fibers are attractive candidates for sensing applications in near-term smart materials and structures, due to their inherent immunity to electromagnetic interference and ground loops, their capability for distributed and multiplexed operation, and their high sensitivity and dynamic range. These same attributes also render optical fibers attractive for avionics busses for fly-by-light systems in advanced aircraft. The integration of such optical fibers with metal and composite aircraft and aerospace materials, however, remains a limiting factor in their successful use in such applications. This paper first details methods for the practical integration of optical fiber waveguides and cable assemblies onto and into materials and structures. Physical properties of the optical fiber and coatings which affect the survivability of the fiber are then considered. Mechanisms for the transfer of the strain from matrix to fiber for sensor and data bus fibers integrated with composite structural elements are evaluated for their influence on fiber survivability, in applications where strain or impact is imparted to the assembly.

  15. Applications of fiber optic sensors in advanced engine controls

    NASA Astrophysics Data System (ADS)

    Nitka, Edward F., II

    1989-06-01

    Measured parameters, operating ranges, accuracy requirements, environmental constraints, and speed of response of fiber optic sensors are identified for three categories of engines. The three engine categories are: (1) current turbojet, turbofan, and turboprop engines; (2) next generation and turbofan engines to be built in the 1990s; and (3) advanced supersonic/hypersonic engines represented by ramjet, scramjet, and air-turbo-ramjet concepts. The key development and test efforts in engine control applications of fiber optic sensors are discussed.

  16. Recent advancement in optical fiber sensing for aerospace composite structures

    NASA Astrophysics Data System (ADS)

    Minakuchi, Shu; Takeda, Nobuo

    2013-12-01

    Optical fiber sensors have attracted considerable attention in health monitoring of aerospace composite structures. This paper briefly reviews our recent advancement mainly in Brillouin-based distributed sensing. Damage detection, life cycle monitoring and shape reconstruction systems applicable to large-scale composite structures are presented, and new technical concepts, "smart crack arrester" and "hierarchical sensing system", are described as well, highlighting the great potential of optical fiber sensors for the structural health monitoring (SHM) field.

  17. Hollow fiber membrane systems for advanced life support systems

    NASA Technical Reports Server (NTRS)

    Roebelen, G. J., Jr.; Lysaght, M. J.

    1976-01-01

    The practicability of utilizing hollow fiber membranes in vehicular and portable life support system applications is described. A preliminary screening of potential advanced life support applications resulted in the selection of five applications for feasibility study and testing. As a result of the feasibility study and testing, three applications, heat rejection, deaeration, and bacteria filtration, were chosen for breadboard development testing; breadboard hardware was manufactured and tested, and the physical properties of the hollow fiber membrane assemblies are characterized.

  18. Investigation of the reaction kinetics between SiC fibers and selectively alloyed titanium matrix composites and determination of their mechanical properties

    NASA Technical Reports Server (NTRS)

    Gundel, Douglas B.; Wawner, Franklin E., Jr.

    1990-01-01

    During high temperature exposure, an interfacial reaction occurs between SiC fiber reinforcement and titanium matrices which can be detrimental to the mechanical properties of the composite. The reaction kinetics between SCS-6 fibers and Ti-1100 were determined at 800 to 1000 C and found to be slower than those of other currently used titanium alloys (Ti-15-3, Ti-6-4). The experimentally determined reaction kinetics for Ti-1100 were extrapolated to 700 C and found to accurately predict reaction zone size after 1000 hours of exposure. Predictions of the time to consume the surface layer on the SCS-6 and SCS-9 fibers were made in an effort to estimate the time that the fiber will retain its strength in Ti-1100 during isothermal exposure at high temperatures. Using this approach, the strength of an SCS-6 fiber in Ti-1100 should be retained for over 20,000 hours at isothermal exposures less than 800 C. Strength predictions using the rule of mixtures for a unidirectional Ti-1100/SCS-6 composite are presented for short term exposures up to 700 C. Room temperature tests of an as-fabricated 20 volume percent fiber/Ti-1100 composite yielded a UTS of 226 ksi (1490 MPa) which is close to that predicted by the ROM.

  19. Recent advances toward a fiber optic sensor for nerve agent

    NASA Astrophysics Data System (ADS)

    Beshay, Manal; Cordero, Steven R.; Mukamal, Harold; Ruiz, David; Lieberman, Robert A.

    2008-04-01

    We report advances made on the development of a fiber optic nerve agent sensor having its entire length as the sensing element. Upon exposure to sarin gas or its simulant, diisopropyl fluorophosphate, the cladding changes color resulting in an alteration of the light intensity throughput. The optical fiber is multimode and consists of a fused-silica core and a nerve agent sensitive cladding. The absorption characteristics of the cladding affect the fiber's spectral attenuation and limit the length of light guiding fiber that can be deployed continuously. The absorption of the cladding is also dependent on the sensor formulation, which in turn influences the sensitivity of the fiber. In this paper, data related to the trade-off of sensitivity, spectral attenuation, and length of fiber challenged will be reported. The fiber is mass produced using a conventional fiber optic draw tower. This technology could be used to protect human resources and buildings from dangerous chemical attacks, particularly when large areas or perimeters must be covered. It may also be used passively to determine how well such areas have been decontaminated.

  20. Mechanics of advanced fiber reinforced lattice composites

    NASA Astrophysics Data System (ADS)

    Fan, Hua-Lin; Zeng, Tao; Fang, Dai-Ning; Yang, Wei

    2010-12-01

    Fiber reinforced lattice composites are light-weight attractive due to their high specific strength and specific stiffness. In the past 10 years, researchers developed three-dimensional (3D) lattice trusses and two-dimensional (2D) lattice grids by various methods including interlacing, weaving, interlocking, filament winding and molding hot-press. The lattice composites have been applied in the fields of radar cross-section reduction, explosive absorption and heat-resistance. In this paper, topologies of the lattice composites, their manufacturing routes, as well as their mechanical and multifunctional applications, were surveyed.

  1. Carpet Specifiers Guide. Ultron, Advanced Generation Nylon Carpet Fiber.

    ERIC Educational Resources Information Center

    Monsanto Textiles Co., Atlanta, GA.

    The purpose of this guide is to assist specifiers in properly specifying carpet made of Monsanto Ultron advanced generation nylon fiber. The guide describes a variety of conditions that should be considered in arriving at the proper selection and provides reference information and data, ranging from varying regulatory requirements, performance and…

  2. FIBER-TEX 1992: The Sixth Conference on Advanced Engineering Fibers and Textile Structures for Composites

    NASA Technical Reports Server (NTRS)

    Buckley, John D. (Editor)

    1993-01-01

    The FIBER-TEX 1992 proceedings contain the papers presented at the conference held on 27-29 Oct. 1992 at Drexel University. The conference was held to create a forum to encourage an interrelationship of the various disciplines involved in the fabrication of materials, the types of equipment, and the processes used in the production of advanced composite structures. Topics discussed were advanced engineering fibers, textile processes and structures, structural fabric production, mechanics and characteristics of woven composites, and the latest requirements for the use of textiles in the production of composite materials and structures as related to global activities focused on textile structural composites.

  3. U.S. Department of Energy Accident Resistant SiC Clad Nuclear Fuel Development

    SciTech Connect

    George W. Griffith

    2011-10-01

    A significant effort is being placed on silicon carbide ceramic matrix composite (SiC CMC) nuclear fuel cladding by Light Water Reactor Sustainability (LWRS) Advanced Light Water Reactor Nuclear Fuels Pathway. The intent of this work is to invest in a high-risk, high-reward technology that can be introduced in a relatively short time. The LWRS goal is to demonstrate successful advanced fuels technology that suitable for commercial development to support nuclear relicensing. Ceramic matrix composites are an established non-nuclear technology that utilizes ceramic fibers embedded in a ceramic matrix. A thin interfacial layer between the fibers and the matrix allows for ductile behavior. The SiC CMC has relatively high strength at high reactor accident temperatures when compared to metallic cladding. SiC also has a very low chemical reactivity and doesn't react exothermically with the reactor cooling water. The radiation behavior of SiC has also been studied extensively as structural fusion system components. The SiC CMC technology is in the early stages of development and will need to mature before confidence in the developed designs can created. The advanced SiC CMC materials do offer the potential for greatly improved safety because of their high temperature strength, chemical stability and reduced hydrogen generation.

  4. Factors Affecting Fiber Design and Selection for Advanced Ceramic Composites

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.

    1998-01-01

    Structural Ceramic Matrix Composites (CMC) have the potential for application in the hot sections of a variety of advanced propulsion and power systems. It is therefore necessary to have a general understanding of the key properties of CMC and Reinforcing Fibers. This need is complicated by the wide variety of application conditions and structural requirements for which CMC's will be used, and the proprietary concerns of the design engineers. CMC's, to be successful, must display properties which are competitive with the currently used high temperature structural materials: (i.e., Iron and Nickel based superalloys, tough monolithic ceramics, and carbon/carbon composites.) Structural CMC offers several areas of competition: (1) performance, (i.e., strength and strength retention, creep resistance, and thermal conductivity), (2) reliability (i.e., environmental durability, and damage tolerance) and (3) processing (i.e., capability for varying sizes and shapes, and cost effective fabrication). The presentation further discusses, and illustrates with fiber and CMC data the key fiber properties and processes which strongly affect each CMC area of competition. The presentation further discusses the current knowledge of the important factors which control the key fiber properties. A design guidelines for the optimum fiber characteristics is developed, and the currently available fibers are compared against those guidelines.

  5. Advances in Wearable Fiber-Shaped Lithium-Ion Batteries.

    PubMed

    Zhang, Ye; Zhao, Yang; Ren, Jing; Weng, Wei; Peng, Huisheng

    2016-06-01

    It is highly desirable to develop flexible and efficient energy-storage systems for widely used wearable electronic products. To this end, fiber-shaped lithium-ion batteries (LIBs) attract increasing interest due to their combined superiorities of miniaturization, adaptability, and weavability, compared with conventional bulky and planar structures. Recent advances in the fabrication, structure, mechanism, and properties of fiber-shaped LIBs are summarized here, with a focus on the electrode material. Remaining challenges and future directions are also highlighted to provide some useful insights from the viewpoint of practical applications. PMID:26643467

  6. Design Guidelines for In-Plane Mechanical Properties of SiC Fiber-Reinforced Melt-Infiltrated SiC Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Pujar, Vijay V.

    2008-01-01

    In-plane tensile stress-strain, tensile creep, and after-creep retained tensile properties of melt-infiltrated SiC-SiC composites reinforced with different fiber types were evaluated with an emphasis on obtaining simple or first-order microstructural design guidelines for these in-plane mechanical properties. Using the mini-matrix approach to model stress-strain behavior and the results of this study, three basic general design criteria for stress and strain limits are formulated, namely a design stress limit, a design total strain limit, and an after-creep design retained strength limit. It is shown that these criteria can be useful for designing components for high temperature applications.

  7. Microgel photonics and lab on fiber technology for advanced label-free fiber optic nanoprobes

    NASA Astrophysics Data System (ADS)

    Giaquinto, M.; Micco, A.; Aliberti, A.; Ricciardi, A.; Ruvo, M.; Cutolo, A.; Cusano, A.

    2016-05-01

    We experimentally demonstrate a novel optical fiber label free optrode platform resulting from the integration between two rapidly emerging technologies such as Lab-on-Fiber Technology (LOFT) and Microgel Photonics (MPs). The device consists of a microgel (MG) layer painted on a metallic slabs supporting plasmonic resonances, directly integrated on the optical fiber tip. A molecular binding event induces significant changes in the MG layer thickness (and consequently in its 'equivalent' refractive index) resulting in an evident wavelength shift of the resonant feature. As a case of study, glucose-responsive MGs have been synthesized by incorporating into the gel matrix boronic acid moieties, whose interaction with glucose rules the driving forces for gel swelling. Our results pave the way for new technological routes aimed to develop advanced label free fiber optic nanoprobes.

  8. High-power monolithic fiber amplifiers based on advanced photonic crystal fiber designs

    NASA Astrophysics Data System (ADS)

    Sipes, Donald L.; Tafoya, Jason D.; Schulz, Daniel S.; Alkeskjold, Thomas Tanggaard; Weirich, Johannes; Olausson, Christina B.

    2014-03-01

    We report on the development and performance of a fully monolithic PCF amplifier that has achieved over 400 W with near diffraction limited beam quality with an approximately 1GHz phase modulated input. The key components for these amplifiers are an advanced PCF fiber design that combines segmented acoustically tailored (SAT) fiber that is gain tailored, a novel multi fiber-coupled laser diode stack and a monolithic 6+1x1 large fiber pump/signal multiplexer. The precisely aligned 2-D laser diode emitter array found in laser diode stacks is utilized by way of a simple in-line imaging process with no mirror reflections to process a 2-D array of 380-450 elements into 3 400/440μm 0.22NA pump delivery fibers. The fiber combiner is an etched air taper design that transforms low numerical aperture (NA), large diameter pump radiation into a high NA, small diameter format for pump injection into an air-clad large mode area PCF, while maintaining a constant core size through the taper for efficient signal coupling and throughput. The fiber combiner has 6 400/440/0.22 core/clad/NA pump delivery fibers and a 25/440 PM step-index signal delivery fiber on the input side and a 40/525 PM undoped PCF on the output side. The etched air taper transforms the six 400/440 μm 0.22 NA pump fibers to the 525 μm 0.55 NA core of the PCF fiber with a measured pump combining efficiency of over 95% with a low brightness drop. The combiner also operates as a stepwise mode converter via a 30 μm intermediate core region in the combiner between the 20 μm core of the input fiber and the 40 μm fiber core of the PCF with a measured signal efficiency of 60% to 70% while maintaining polarization with a measured PER of 20 dB. These devices were integrated in to a monolithic fiber amplifier with high efficiency and near diffraction limited beam quality.

  9. Properties of advanced fibers for reinforcing metal and ceramic matrix composites

    SciTech Connect

    Porter, J.

    1993-12-31

    The mechanical properties of ceramic reinforcing fibers need to be well characterized before their incorporation into composite materials. Critical fiber properties include strength and Weibull modulus, bundle strength, modulus and creep resistance. Important composite properties include thermochemical stability, interface debond energy and interfacial sliding resistance. Tailoring these interfacial properties by fiber coating can, in turn, influence fiber properties. Methods of measuring strength related properties are addressed and the results of a computer simulation to assess the quality of measured data statistically are presented. The readily available monofilament fibers are mostly chemically vapor deposited (CVD) silicon carbide. Current aerospace programs have identified the need for new ceramic fibers as enabling materials for their success. Alternate fibers such as sapphire are therefore currently under development with several objectives including: a CTE greater than that of SiC, higher strength and creep resistance, and chemical stability in new candidate matrices. The strength of a ceramic fiber is statistical, being determined by the largest flaw in the flaw population of the tested length of fiber. In a brittle matrix material such as an intermetallic, for toughening by continuous fiber reinforcement, fibers need to exhibit pull-out during matrix crack propagation. However, the stress distribution along a bridging fiber has a maximum in the crack plane and for fiber failure to occur away from the crack plane, a prerequisite for pull-out, a weak link must also exist away from the crack plane.

  10. Advances in the Echidna fiber-positioning technology

    NASA Astrophysics Data System (ADS)

    Sheinis, Andrew; Saunders, Will; Gillingham, Peter; Farrell, Tony J.; Muller, Rolf; Smedley, Scott; Brzeski, Jurek; Waller, Lewis G.; Gilbert, James; Smith, Greg

    2014-07-01

    We present advances in the patented Echidna 'tilting spine' fiber positioner technology that has been in operation since 2007 on the SUBARU telescope in the FMOS system. The new Echidna technology is proposed to be implemented on two large fiber surveys: the Dark Energy Spectroscopic Instrument (DESI) (5000 fibers) as well the Australian ESO Positioner (AESOP) for 4MOST, a spectroscopic survey instrument for the VISTA telescope (~2500 fibers). The new 'superspine' actuators are stiffer, longer and more accurate than their predecessors. They have been prototyped at AAO, demonstrating reconfiguration times of ~15s for errors of <5 microns RMS. Laboratory testing of the prortotype shows accurate operation at temperatures of -10 to +30C, with an average heat output of 200 microwatts per actuator during reconfiguration. Throughput comparisons to other positioner types are presented, and we find that losses due to tilt will in general be outweighed by increased allocation yield and reduced fiber stress FRD. The losses from spine tilt are compensated by the gain in allocation yield coming from the greater patrol area, and quantified elsewhere in these proceedings. For typical tilts, f-ratios and collimator overspeeds, Echidna offers a clear efficiency gain versus current r-that or theta-phi positioners.

  11. Advances in fiber lasers for nonlinear microscopy

    NASA Astrophysics Data System (ADS)

    Wise, F. W.; Ouzounov, D.; Kieu, K.; Renninger, W.; Chong, A.; Liu, H.

    2008-02-01

    In the past 30 years major advances in medical imaging have been made in areas such as magnetic resonance imaging, computed tomography, and ultrasound. These techniques have become quite effective for structural imaging at the organ or tissue level, but do not address the clear need for imaging technologies that exploit existing knowledge of the genetic and molecular bases of disease. Techniques that can provide similar information on the cellular and molecular scale would be very powerful, and ultimately the extension of such techniques to in vivo measurements will be desired. The availability of these imaging capabilities would allow monitoring of the early stages of disease or therapy, for example. Optical techniques provide excellent imaging capabilities, with sub-micron spatial resolution, and are noninvasive. An overall goal of biomedical imaging is to obtain diagnostic or functional information about biological structures. The difficulty of acquiring high-resolution images of structures deep in tissue presents a major challenge, however, owing to strong scattering of light. As a consequence, optical imaging has been limited to thin (typically ~0.5 mm) samples or superficial tissue. In contrast, techniques such as ultrasound and magnetic resonance provide images of structures centimeters deep in tissue, with ~100-micron resolution. It is desirable to develop techniques that offer the resolution of optics with the depth-penetration of other techniques. Since 1990, a variety of nonlinear microscopies have been demonstrated. These include 2- and 3-photon fluorescence microscopy, and 2nd- and 3rd-harmonic generation microscopies. These typically employ femtosecond-pulse excitation, for maximum peak power (and thus nonlinear excitation) for a given pulse energy. A relative newcomer to the group is CARS microscopy [1], which exploits resonant vibrational excitation of molecules or bonds. The CARS signal contrast arises from intrinsic elements of cells, and thus

  12. High-temperature flow of SiC continuous fiber-glass ceramic matrix composites: The effect of interface/interphase ductility

    SciTech Connect

    Nair, B.G.; Cooper, R.F.; Almquist, J.N.; Plesha, M.E.

    1995-10-01

    The elevated temperature rheology of continuous SiC (Nicalon{reg_sign}) calcium aluminosilicate glass-ceramic matrix composites is evaluated in uniaxial compression creep experiments ({minus}{sigma}{sub 1} = 20-to-40 MPa; T = 1,300--1,320 C). The steady state strain rate is demonstrated to be highly sensitive to the orientation of the reinforcement relative to the maximum compressional stress, with highest bulk specimen strain rates noted for conditions in which the sliding between the fiber and the matrix is optimized s a kinetic flow response (i.e., a fiber orientation of approximately 40--50{degree} from {sigma}{sub 1}). One further discovers that the temperature sensitivity (i.e., activation energy) of flow increases as the amount of interface flow/sliding increases. The experimental results suggest that the high-temperature, low-stress interface response in this composite system is related to the ductile flow of the planar SiO{sub 2} reaction-layer interphase that exists (in addition to the well-recognized planar carbon interphase) in these materials. The results of these simple experiments are used to calibrate a microscale-to-macroscale rheologic model in which the fiber-matrix interface is described by a viscous constitutive relationship.

  13. FIBER-TEX 1991: The Fifth Conference on Advanced Engineering Fibers and Textile Structures for Composites

    SciTech Connect

    Buckley, J.D.

    1992-10-01

    This document is a compilation of papers presented at a joint NASA/North Carolina State University/DoD/Clemson University/Drexel University conference on Fibers, Textile Technology, and Composites Structures held at the College of Textiles Building on Centennial Campus of North Carolina State University, Raleigh, North Carolina on October 15-17, 1991. Conference papers presented information on advanced engineering fibers, textile processes and structures, structural fabric production, mechanics and characteristics of woven composites, pultruded composites, and the latest requirements for the use of textiles in the production of composite materials and structures. Separate abstracts have been prepared for papers in this report.

  14. FIBER-TEX 1991: The Fifth Conference on Advanced Engineering Fibers and Textile Structures for Composites

    NASA Technical Reports Server (NTRS)

    Buckley, John D. (Editor)

    1992-01-01

    This document is a compilation of papers presented at a joint NASA/North Carolina State University/DoD/Clemson University/Drexel University conference on Fibers, Textile Technology, and Composites Structures held at the College of Textiles Building on Centennial Campus of North Carolina State University, Raleigh, North Carolina on October 15-17, 1991. Conference papers presented information on advanced engineering fibers, textile processes and structures, structural fabric production, mechanics and characteristics of woven composites, pultruded composites, and the latest requirements for the use of textiles in the production of composite materials and structures.

  15. Thermal effects on the mechanical properties of SiC fiber reinforced reaction bonded silicon nitride matrix (SiC/RBSN) composites

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.; Phillips, R. E.

    1988-01-01

    The elevated temperature four-point flexural strength and the room temperature tensile and flexural strength properties after thermal shock were measured for ceramic composites consisting of 30 vol pct uniaxially aligned 142 micron diameter SiC fibers in a reaction bonded Si3N4 matrix. The elevated temperature strengths were measured after 15 min of exposure in air at temperatures to 1400 C. Thermal shock treatment was accomplished by heating the composite in air for 15 min at temperatures to 1200 C and then quenching in water at 25 C. The results indicate no significant loss in strength properties either at temperature or after thermal shock when compared with the strength data for composites in the as-fabricated condition.

  16. Advance study of fiber-reinforced self-compacting concrete

    SciTech Connect

    Mironova, M. Ivanova, M. Naidenov, V.; Georgiev, I.; Stary, J.

    2015-10-28

    Incorporation in concrete composition of steel macro- and micro – fiber reinforcement with structural function increases the degree of ductility of typically brittle cement-containing composites, which in some cases can replace completely or partially conventional steel reinforcement in the form of rods and meshes. Thus, that can reduce manufacturing, detailing and placement of conventional reinforcement, which enhances productivity and economic efficiency of the building process. In this paper, six fiber-reinforced with different amounts of steel fiber cement-containing self-compacting compositions are investigated. The results of some of their main strength-deformation characteristics are presented. Advance approach for the study of structural and material properties of these type composites is proposed by using the methods of industrial computed tomography. The obtained original tomography results about the microstructure and characteristics of individual structural components make it possible to analyze the effective macro-characteristics of the studied composites. The resulting analytical data are relevant for the purposes of multi-dimensional modeling of these systems. Multifactor structure-mechanical analysis of the obtained with different methods original scientific results is proposed. It is presented a conclusion of the capabilities and effectiveness of complex analysis in the studies to characterize the properties of self-compacting fiber-reinforced concrete.

  17. Advance study of fiber-reinforced self-compacting concrete

    NASA Astrophysics Data System (ADS)

    Mironova, M.; Ivanova, M.; Naidenov, V.; Georgiev, I.; Stary, J.

    2015-10-01

    Incorporation in concrete composition of steel macro- and micro - fiber reinforcement with structural function increases the degree of ductility of typically brittle cement-containing composites, which in some cases can replace completely or partially conventional steel reinforcement in the form of rods and meshes. Thus, that can reduce manufacturing, detailing and placement of conventional reinforcement, which enhances productivity and economic efficiency of the building process. In this paper, six fiber-reinforced with different amounts of steel fiber cement-containing self-compacting compositions are investigated. The results of some of their main strength-deformation characteristics are presented. Advance approach for the study of structural and material properties of these type composites is proposed by using the methods of industrial computed tomography. The obtained original tomography results about the microstructure and characteristics of individual structural components make it possible to analyze the effective macro-characteristics of the studied composites. The resulting analytical data are relevant for the purposes of multi-dimensional modeling of these systems. Multifactor structure-mechanical analysis of the obtained with different methods original scientific results is proposed. It is presented a conclusion of the capabilities and effectiveness of complex analysis in the studies to characterize the properties of self-compacting fiber-reinforced concrete.

  18. Advanced experiments with an erbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Marques, Paulo V. S.; Marques, Manuel B.; Rosa, Carla C.

    2014-07-01

    This communication describes an optical hands-on fiber laser experiment aimed at advanced college courses. Optical amplifiers and laser sources represent very important optical devices in numerous applications ranging from telecommunications to medicine. The study of advanced photonics experiments is particularly relevant at undergraduate and master level. This paper discusses the implementation of an optical fiber laser made with a cavity built with two tunable Bragg gratings. This scheme allows the students to understand the laser working principles as a function of the laser cavity set-up. One or both of the gratings can be finely tuned in wavelength through applied stress; therefore, the degree of spectral mismatch of the two gratings can be adjusted, effectively changing the cavity feedback. The impact of the cavity conditions on the laser threshold, spectrum and efficiency is analyzed. This experiment assumes that in a previous practice, the students should had already characterized the erbium doped fiber in terms of absorption and fluorescent spectra, and the spectral gain as a function of pump power.

  19. On fracture phenomena in advanced fiber composite materials.

    NASA Technical Reports Server (NTRS)

    Konish, H. J., Jr.; Swedlow, J. L.; Cruse, T. A.

    1972-01-01

    The extension of linear elastic fracture mechanics (LEFM) from metallic alloys to advanced fiber composite laminates is considered. LEFM is shown to be valid for both isotropic and anisotropic homogeneous continua; the applicability of LEFM to advanced fiber composites is thus dependent on the validity of a homogeneous model of such materials. An experimental program to determine the validity of such a model for graphite/epoxy laminates is reviewed. Such laminates are found to have an apparent fracture toughness, from which it is inferred that a homogeneous material model is valid for the particular specimen geometry and composite laminates considered. Strain energy release rates are calculated from the experimentally determined fracture toughness of the various laminates. These strain energy release rates are found to lie in one of two groups, depending upon whether crack extension required fiber failure or matrix failure. The latter case is further investigated. It is concluded that matrix failure is governed by the tensile stress normal to the crack path.

  20. Mechanical Properties of High Purity SiC Fiber-Reinforced CVI-SiC Matrix Composites

    SciTech Connect

    Hinoki, Tatsuya; Lara-Curzio, Edgar; Snead, Lance L.

    2003-07-15

    Mechanical properties of silicon carbide composites reinforced with highly crystalline fibers and fabricated by the chemical vapor infiltration method were evaluated. Materials used were SiC/SiC composites reinforced with unidirectional Hi-Nicalon Type-S fibers and unidirectional Tyranno SA fibers with various fiber/matrix interphase. Also, SiC/SiC composites reinforced with plain weave Tyranno SA fibers with carbon or multilayers of silicon carbide and carbon interphase were evaluated. In-plane tensile, transthickness tensile and interlaminar shear properties were evaluated by the in-plane tensile test, the transthickness tensile test, the diametral compression test and the compression test of double-notched specimens.The elastic modulus and proportional limit stress were improved by using high purity silicon carbide fibers. The in-plane tensile properties were insensitive to carbon interphase thickness for a range of thicknesses between 30 and 230 nm. It was found that the in-plane tensile strength of composites containing multilayers of silicon carbide and carbon coating of fibers and fiber bundles was superior to that of composites with carbon alone. Transthickness tensile strength and shear strength of high purity silicon carbide composites were successfully evaluated.

  1. Ion irradiation effects on third generation SiC fibers in elastic and inelastic energy loss regimes

    NASA Astrophysics Data System (ADS)

    Huguet-Garcia, J.; Jankowiak, A.; Miro, S.; Serruys, Y.; Costantini, J. M.

    2014-05-01

    Third generation silicon carbide fibers, mainly Hi-Nicalon Type S and Tyranno SA3, have improved the irradiation resistance of silicon carbide composites. In this work the microstructural evolution of these fibers due to ion irradiation is investigated in terms of Raman micro-spectrometry. In comparison with a 6H-SiC single crystal, similar amorphization kinetics have been found for increasing fluences of 4-MeV Au3+ ions. Also, in situ tensile tests have been performed to these micrometric fibers that allow real time tracking of their strain behavior under different in-core-like conditions. Tyranno SA3 fibers have been irradiated with 12-MeV C4+ at 300 MPa at RT and 1000 °C revealing a high influence of the irradiation temperature on the fiber residual strain.

  2. [INVITED] New advances in polymer fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Nogueira, Rogério; Oliveira, Ricardo; Bilro, Lúcia; Heidarialamdarloo, Jamshid

    2016-04-01

    During the last years, fiber Bragg gratings (FBGs) written in polymer optical fibers (POFs) have been pointed as an interesting alternative to silica FBGs for applications in sensors and in optical access networks. In order to use such components in real applications, the manipulation of POFs, as well as the increase of quality in the production of FBGs has to be achieved. In this article some of the recent advances regarding these two aspects are reported and include recent developments to produce smooth POFs end face with high quality, benefiting the current splicing process and the inscription of high quality FBGs in a few seconds. Furthermore, additional characterizations to strain, temperature, pressure, and humidity are also shown.

  3. Boron/aluminum graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1975-01-01

    Fabrication feasibility and potential of an adhesively bonded metal and resin matrix fiber-composite hybrid are determined as an advanced material for aerospace and other structural applications. The results show that using this hybrid concept makes possible a composite design which, when compared with nonhybrid composites, has greater transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  4. Bias in the Weibull Strength Estimation of a SiC Fiber for the Small Gauge Length Case

    NASA Astrophysics Data System (ADS)

    Morimoto, Tetsuya; Nakagawa, Satoshi; Ogihara, Shinji

    It is known that the single-modal Weibull model describes well the size effect of brittle fiber tensile strength. However, some ceramic fibers have been reported that single-modal Weibull model provided biased estimation on the gauge length dependence. A hypothesis on the bias is that the density of critical defects is very small, thus, fracture probability of small gauge length samples distributes in discrete manner, which makes the Weibull parameters dependent on the gauge length. Tyranno ZMI Si-Zr-C-O fiber has been selected as an example fiber. The tensile tests have been done on several gauge lengths. The derived Weibull parameters have shown a dependence on the gauge length. Fracture surfaces were observed with SEM. Then we classified the fracture surfaces into the characteristic fracture patterns. Percentage of each fracture pattern was found dependent on the gauge length, too. This may be an important factor of the Weibull parameter dependence on the gauge length.

  5. Fiber-Reinforced-Foam (FRF) Core Composite Sandwich Panel Concept for Advanced Composites Technologi

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Fiber-Reinforced-Foam (FRF) Core Composite Sandwich Panel Concept for Advanced Composites Technologies Project - Preliminary Manufacturing Demonstration Articles for Ares V Payload Shroud Barrel Acreage Structure

  6. Effects of Fiber Content on Mechanical Properties of CVD SiC Fiber-Reinforced Strontium Aluminosilicate Glass-Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1996-01-01

    Unidirectional CVD SiC(f)(SCS-6) fiber-reinforced strontium aluminosilicate (SAS) glass-ceramic matrix composites containing various volume fractions, approximately 16 to 40 volume %, of fibers were fabricated by hot pressing at 1400 C for 2 h under 27.6 MPa. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase formed, with complete absence of the undesired hexacelsian phase, in the matrix. Room temperature mechanical properties were measured in 3-point flexure. The matrix microcracking stress and the ultimate strength increased with increase in fiber volume fraction, reached maximum values for V(sub f) approximately equal to 0.35, and degraded at higher fiber loadings. This degradation in mechanical properties is related to the change in failure mode, from tensile at lower V(sub f) to interlaminar shear at higher fiber contents. The extent of fiber loading did not have noticeable effect on either fiber-matrix debonding stress, or frictional sliding stress at the interface. The applicability of micromechanical models in predicting the mechanical properties of the composites was also examined. The currently available theoretical models do not appear to be useful in predicting the values of the first matrix cracking stress, and the ultimate strength of the SCS-6/SAS composites.

  7. Boron/aluminum-graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1974-01-01

    An investigation was conducted to determine the fabrication feasibility and to assess the potential of adhesively-bonded metal and resin matrix fiber composite hybrids as an advanced material, for aerospace and other structural applications. The results of fabrication studies and of evaluation of physical and mechanical properties show that using this hybrid concept it is possible to design a composite which, when compared to nonhybrid composites, has improved transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for perdicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  8. Boron/aluminum-graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1974-01-01

    An investigation was conducted to determine the fabrication feasibility and to assess the potential of adhesively-bonded metal and resin matrix fiber composite hybrids as an advanced material, for aerospace and other structural applications. The results of fabrication studies and of evaluation of physical and mechanical properties show that using this hybrid concept it is possible to design a composite which, when compared to nonhybrid composites, has improved transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  9. US long distance fiber optic networks: Technology, evolution and advanced concepts. Volume 2: Fiber optic technology and long distance networks

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The study projects until 2000 the evolution of long distance fiber optic networks in the U.S. Volume 1 is the Executive Summary. Volume 2 focuses on fiber optic components and systems that are directly related to the operation of long-haul networks. Optimistic, pessimistic and most likely scenarios of technology development are presented. The activities of national and regional companies implementing fiber long haul networks are also highlighted, along with an analysis of the market and regulatory forces affecting network evolution. Volume 3 presents advanced fiber optic network concept definitions. Inter-LATA traffic is quantified and forms the basis for the construction of 11-, 15-, 17-, and 23-node networks. Using the technology projections from Volume 2, a financial model identifies cost drivers and determines circuit mile costs between any two LATAs. A comparison of fiber optics with alternative transmission concludes the report.

  10. Graphene nanoribbons as an advanced precursor for making carbon fiber.

    PubMed

    Xiang, Changsheng; Behabtu, Natnael; Liu, Yaodong; Chae, Han Gi; Young, Colin C; Genorio, Bostjan; Tsentalovich, Dmitri E; Zhang, Chenguang; Kosynkin, Dmitry V; Lomeda, Jay R; Hwang, Chih-Chau; Kumar, Satish; Pasquali, Matteo; Tour, James M

    2013-02-26

    Graphene oxide nanoribbons (GONRs) and chemically reduced graphene nanoribbons (crGNRs) were dispersed at high concentrations in chlorosulfonic acid to form anisotropic liquid crystal phases. The liquid crystal solutions were spun directly into hundreds of meters of continuous macroscopic fibers. The relationship of fiber morphology to coagulation bath conditions was studied. The effects of colloid concentration, annealing temperature, spinning air gap, and pretension during annealing on the fibers' performance were also investigated. Heat treatment of the as-spun GONR fibers at 1500 °C produced thermally reduced graphene nanoribbon (trGNR) fibers with a tensile strength of 378 MPa, Young's modulus of 36.2 GPa, and electrical conductivity of 285 S/cm, which is considerably higher than that in other reported graphene-derived fibers. This better trGNR fiber performance was due to the air gap spinning and annealing with pretension that produced higher molecular alignment within the fibers, as determined by X-ray diffraction and scanning electron microscopy. The specific modulus of trGNR fibers is higher than that of the commercial general purpose carbon fibers and commonly used metals such as Al, Cu, and steel. The properties of trGNR fibers can be further improved by optimizing the spinning conditions with higher draw ratio, annealing conditions with higher pretensions, and using longer flake GONRs. This technique is a new high-carbon-yield approach to make the next generation carbon fibers based on solution-based liquid crystal phase spinning. PMID:23339339

  11. Overview of advanced components for fiber optic systems

    NASA Technical Reports Server (NTRS)

    Depaula, Ramon P.; Stowe, David W.

    1986-01-01

    The basic operating principles and potential performance of several state-of-the-art fiber-optic devices are illustrated with diagrams and briefly characterized. Technologies examined include high-birefringence polarization-maintaining fibers and directional couplers, single-mode fiber polarizers and cut-off polarizers, optical-fiber modulators with radially poled piezoactive polymer (PVF2) jackets, and piezoelectric-squeezer polarization modulators. The need for improved manufacturing techniques to make such fiber-optic devices cost-competitive with their thin-film integrated-optics analogs is indicated.

  12. Nanosphere lithography for advanced all fiber Sers probes

    NASA Astrophysics Data System (ADS)

    Pisco, Marco; Galeotti, Francesco; Quero, Giuseppe; Grisci, Giorgio; Micco, Alberto; Mercaldo, L.; Delli Veneri, P.; Cusano, Andrea

    2016-05-01

    In this work, we report a straightforward and cost-effective fabrication route for the development of nano-patterned optical fiber tips. The technique is based on self-assembling polystyrene microspheres at the air/water interface and on their successive transferring on the fiber tip of single mode optical fiber. By applying to the fiber further treatments like particle size reduction, metal coating and sphere removal, different periodic structures have been conveniently realized. The morphological analysis reveals indeed the successful creation on the optical fiber tip of regular metallic-dielectric spheres' arrays as well as metallic patterns with dimensional features down to a submicron scale. Finally, as proof of concept, we demonstrated the capability of the realized patterns to work as efficient Surface Enhanced Raman Spectroscopy (SERS) fiber probes.

  13. Investigation of fatigue strength of multilayer advanced fiber composites

    NASA Technical Reports Server (NTRS)

    Thornton, H. R.; Kozik, T. J.

    1974-01-01

    The analytical characterization of a multilayer fiber composite plate (without hole) was accomplished for both static and dynamic loading conditions using the finite difference technique. Thornel 300/5208 composites with and without holes were subjected to static and tensile fatigue testing. Five (5) fiber orientations were submitted to test. Tensile fatigue testing also included three (3) loading conditions and two (2) frequencies. The low-cycle test specimens demonstrated a shorter tensile fatigue life than the high-cycle test specimens. Failure surfaces demonstrated effect of testing conditions. Secondary failure mechanisms, such as: delamination, fiber breakage, and edge fiber delamination were present. Longitudinal delamination between plies also occurred in these specimens.

  14. Nondestructive Evaluation of Advanced Fiber Reinforced Polymer Matrix Composites: A Technology Assessment

    NASA Technical Reports Server (NTRS)

    Yolken, H. Thomas; Matzkanin, George A.

    2009-01-01

    Because of their increasing utilization in structural applications, the nondestructive evaluation (NDE) of advanced fiber reinforced polymer composites continues to receive considerable research and development attention. Due to the heterogeneous nature of composites, the form of defects is often very different from a metal and fracture mechanisms are more complex. The purpose of this report is to provide an overview and technology assessment of the current state-of-the-art with respect to NDE of advanced fiber reinforced polymer composites.

  15. Properties of fiber composites for advanced flywheel energy storage devices

    SciTech Connect

    DeTeresa, S J; Groves, S E

    2001-01-12

    The performance of commercial high-performance fibers is examined for application to flywheel power supplies. It is shown that actual delivered performance depends on multiple factors such as inherent fiber strength, strength translation and stress-rupture lifetime. Experimental results for recent stress-rupture studies of carbon fibers will be presented and compared with other candidate reinforcement materials. Based on an evaluation of all of the performance factors, it is concluded that carbon fibers are preferred for highest performance and E-glass fibers for lowest cost. The inferior performance of the low-cost E-glass fibers can be improved to some extent by retarding the stress-corrosion of the material due to moisture and practical approaches to mitigating this corrosion are discussed. Many flywheel designs are limited not by fiber failure, but by matrix-dominated failure modes. Unfortunately, very few experimental results for stress-rupture under transverse tensile loading are available. As a consequence, significant efforts are made in flywheel design to avoid generating any transverse tensile stresses. Recent results for stress-rupture of a carbon fiber/epoxy composite under transverse tensile load reveal that these materials are surprisingly durable under the transverse loading condition and that some radial tensile stress could be tolerated in flywheel applications.

  16. US long distance fiber optic networks: Technology, evolution and advanced concepts. Volume 3: Advanced networks and economics

    NASA Technical Reports Server (NTRS)

    1986-01-01

    This study projects until 2000 the evolution of long distance fiber optic networks in the U.S. Volume 1 is the executive Summary. Volume 2 focuses on fiber optic components and systems that are directly related to the operation of long-haul networks. Optimistic, pessimistic and most likely scenarios of technology development are presented. The activities of national and regional companies implementing fiber long haul networks are also highlighted, along with an analysis of the market and regulatory forces affecting network evolution. Volume 3 presents advanced fiber optic network concept definitions. Inter-LATA traffic is quantified and forms the basis for the construction of 11-, 15-, 17-, and 23-node networks. Using the technology projections from Volume 2, a financial model identifies cost drivers and determines circuit mile costs between any two LATAs. A comparison of fiber optics with alternative transmission concludes the report.

  17. ADVANCES IN THE MEASUREMENT OF AMBIENT CARBON FIBERS

    EPA Science Inventory

    Methodologies that have been used in a number of passive collectors and active detectors for measuring ambient carbon fibers are summarized. The need for improved performance in terms of specificity, sensitivity, detection efficiency, accuracy, precision, speed, stability and ser...

  18. Advances in fiber optic sensors for in-vivo monitoring

    NASA Astrophysics Data System (ADS)

    Baldini, Francesco; Mignani, Anna G.

    1995-09-01

    Biomedical fiber-optic sensors are attractive for the measurement of both physical and chemical parameters as well as for spectral measurements directly performed on the patient. An overview of fiber-optic sensors for in vivo monitoring is given, with particular attention to the advantages that these sensors are able to offer in different fields of application such as cardiovascular and intensive care, angiology, gastroenterology, ophthalmology, oncology, neurology, dermatology, and dentistry.

  19. Advanced in In Situ Inspection of Automated Fiber Placement Systems

    NASA Technical Reports Server (NTRS)

    Juarez, Peter D.; Cramer, K. Elliott; Seebo, Jeffrey P.

    2016-01-01

    Automated Fiber Placement (AFP) systems have been developed to help take advantage of the tailorability of composite structures in aerospace applications. AFP systems allow the repeatable placement of uncured, spool fed, preimpregnated carbon fiber tape (tows) onto substrates in desired thicknesses and orientations. This automated process can incur defects, such as overlapping tow lines, which can severely undermine the structural integrity of the part. Current defect detection and abatement methods are very labor intensive, and still mostly rely on human manual inspection. Proposed is a thermographic in situ inspection technique which monitors tow placement with an on board thermal camera using the preheated substrate as a through transmission heat source. An investigation of the concept is conducted, and preliminary laboratory results are presented. Also included will be a brief overview of other emerging technologies that tackle the same issue. Keywords: Automated Fiber Placement, Manufacturing defects, Thermography

  20. Thermal degradation study of silicon carbide threads developed for advanced flexible thermal protection systems

    NASA Technical Reports Server (NTRS)

    Tran, Huy Kim; Sawko, Paul M.

    1992-01-01

    Silicon carbide (SiC) fiber is a material that may be used in advanced thermal protection systems (TPS) for future aerospace vehicles. SiC fiber's mechanical properties depend greatly on the presence or absence of sizing and its microstructure. In this research, silicon dioxide is found to be present on the surface of the fiber. Electron Spectroscopy for Chemical Analysis (ESCA) and Scanning Electron Microscopy (SEM) show that a thin oxide layer (SiO2) exists on the as-received fibers, and the oxide thickness increases when the fibers are exposed to high temperature. ESCA also reveals no evidence of Si-C bonding on the fiber surface on both as-received and heat treated fibers. The silicon oxide layer is thought to signal the decomposition of SiC bonds and may be partially responsible for the degradation in the breaking strength observed at temperatures above 400 C. The variation in electrical resistivity of the fibers with increasing temperature indicates a transition to a higher band gap material at 350 to 600 C. This is consistent with a decomposition of SiC involving silicon oxide formation.

  1. Advances in fiber optic-based UV resonance Raman spectroscopy techniques for anatomical and physiological investigations

    NASA Astrophysics Data System (ADS)

    Schulze, H. Georg; Barbosa, Christopher J.; Greek, L. Shane; Turner, Robin F. B.; Haynes, C. A.; Klein, Karl-Friedrich; Blades, Michael W.

    1999-04-01

    UV resonance Raman spectroscopy (UVRRS) is becoming a very popular spectroscopic method for bioanalytical investigations due to its high sensitivity, lack of fluorescence, and suitability for use in aqueous solutions. We have made a number of technological advances, especially the development of fiber-optic-based technologies, which permit the performance of remote/in-situ UVRRS measurements. We will be reporting on improved optical fiber probes and demonstrate their benefits in performing UVRRS on neurotransmitters, saliva, and urine.

  2. High performance fibers for structurally reliable metal and ceramic composites. [advanced gas turbine engine materials

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1984-01-01

    Very few of the commercially available high performance fibers with low densities, high Young's moduli, and high tensile strengths possess all the necessary property requirements for providing either metal matrix composites (MMC) or ceramic matrix composites (CMC) with high structural reliability. These requirements are discussed in general and examples are presented of how these property guidelines are influencing fiber evaluation and improvement studies at NASA aimed at developing structurally reliable MMC and CMC for advanced gas turbine engines.

  3. An Update on Design Tools for Optimization of CMC 3D Fiber Architectures

    NASA Technical Reports Server (NTRS)

    Lang, J.; DiCarlo, J.

    2012-01-01

    Objective: Describe and up-date progress for NASA's efforts to develop 3D architectural design tools for CMC in general and for SIC/SiC composites in particular. Describe past and current sequential work efforts aimed at: Understanding key fiber and tow physical characteristics in conventional 2D and 3D woven architectures as revealed by microstructures in the literature. Developing an Excel program for down-selecting and predicting key geometric properties and resulting key fiber-controlled properties for various conventional 3D architectures. Developing a software tool for accurately visualizing all the key geometric details of conventional 3D architectures. Validating tools by visualizing and predicting the Internal geometry and key mechanical properties of a NASA SIC/SIC panel with a 3D orthogonal architecture. Applying the predictive and visualization tools toward advanced 3D orthogonal SiC/SIC composites, and combining them into a user-friendly software program.

  4. Advances in Optical Fiber-Based Faraday Rotation Diagnostics

    SciTech Connect

    White, A D; McHale, G B; Goerz, D A

    2009-07-27

    In the past two years, we have used optical fiber-based Faraday Rotation Diagnostics (FRDs) to measure pulsed currents on several dozen capacitively driven and explosively driven pulsed power experiments. We have made simplifications to the necessary hardware for quadrature-encoded polarization analysis, including development of an all-fiber analysis scheme. We have developed a numerical model that is useful for predicting and quantifying deviations from the ideal diagnostic response. We have developed a method of analyzing quadrature-encoded FRD data that is simple to perform and offers numerous advantages over several existing methods. When comparison has been possible, we have seen good agreement with our FRDs and other current sensors.

  5. Advances in in situ inspection of automated fiber placement systems

    NASA Astrophysics Data System (ADS)

    Juarez, Peter D.; Cramer, K. Elliott; Seebo, Jeffrey P.

    2016-05-01

    Automated Fiber Placement (AFP) systems have been developed to help take advantage of the tailorability of composite structures in aerospace applications. AFP systems allow the repeatable placement of uncured, spool fed, preimpregnated carbon fiber tape (tows) onto substrates in desired thicknesses and orientations. This automated process can incur defects, such as overlapping tow lines, which can severely undermine the structural integrity of the part. Current defect detection and abatement methods are very labor intensive, and still mostly rely on human manual inspection. Proposed is a thermographic in situ inspection technique which monitors tow placement with an on board thermal camera using the preheated substrate as a through transmission heat source. An investigation of the concept is conducted, and preliminary laboratory results are presented. Also included will be a brief overview of other emerging technologies that tackle the same issue.

  6. Comparison of SiC mirror approaches

    NASA Astrophysics Data System (ADS)

    Carrigan, Keith; Riso, Michael; Khatri, Shayna; Douglas, Christopher

    2013-09-01

    Silicon Carbide (SiC) mirrors hold many advantages over traditional optical materials and are increasingly common in optical systems. The wide range of optical applications necessitates different approaches to the manufacturing and finishing of SiC mirrors. Three key advancements have led to this differentiation: 1) manufacturing of CVD clad SiC mirrors in near cost and schedule parity with Zerodur, 2) super-polish of amorphous Silicon claddings, 3) low-roughness polishing results of bare reaction-bonded SiC aspheres. Three approaches which utilize these advancements will be discussed, each with its own strengths and weaknesses for specific applications. The relative schedules and performance of these approaches will also be compared, with Zerodur used as a reference.

  7. [INVITED] New advances in fiber cavity ring-down technology

    NASA Astrophysics Data System (ADS)

    Silva, S. O.; Magalhães, R.; Marques, M. B.; Frazão, O.

    2016-04-01

    A brief review in the cavity ring-down technique (CRD) is presented. In this review, there will only be considered the conventional fiber CRD configuration, i.e., there will only be presented researches involving cavities with two couplers with 99:1 ratios, due to the large amount of publications involving this spectroscopy method. The presented survey is divided in different topics related to the measurement of physical parameters, such as strain and temperature, curvature, pressure, refractive index, gas and biochemical sensing.

  8. Assessment of fiber optic sensors and other advanced sensing technologies for nuclear power plants

    SciTech Connect

    Hashemian, H.M.

    1996-03-01

    As a result of problems such as calibration drift in nuclear plant pressure sensors and the recent oil loss syndrome in some models of Rosemount pressure transmitters, the nuclear industry has become interested in fiber optic pressure sensors. Fiber optic sensing technologies have been considered for the development of advanced instrumentation and control (I&C) systems for the next generation of reactors and in older plants which are retrofitted with new I&C systems. This paper presents the results of a six-month Phase I study to establish the state-of-the-art in fiber optic pressure sensing. This study involved a literature review, contact with experts in the field, an industrial survey, a site visit to a fiber optic sensor manufacturer, and laboratory testing of a fiber optic pressure sensor. The laboratory work involved both static and dynamic performance tests. This initial Phase I study has recently been granted a two-year extension by the U.S. Nuclear Regulatory Commission (NRC). The next phase will evaluate fiber optic pressure sensors in specific nuclear plant applications in addition to other advanced methods for monitoring critical nuclear plant equipment.

  9. Advances in hyperspectral imaging technologies for multichannel fiber sensing

    NASA Astrophysics Data System (ADS)

    Zakrzewski, Jay; Didona, Kevin

    2009-05-01

    A spectrograph's design, e.g. the opto-mechanical system beginning at the entrance slit, and ending at the back focal plane position, directly impacts system level performance parameters including the height of the useable aperture, spatial and spectral resolving power, optical throughput efficiency, and dynamic range. The efficiency and integrity of both spatial and spectral input image reproduction within the entire back focal plane area is an often overlooked parameter leading to unnecessary acceptance of sacrificed system level performance. Examples of input images include the slit apertured area of a scene captured by a camera lens, a single optical fiber core located within the entrance aperture area, or a linear array of optical fiber cores stacked along the spatial height of the entrance aperture area. This study evaluates the spectral and spatial imaging performance of several aberration corrected high reciprocal dispersion retro-reflective concentric, as well as aberration corrected Offner imaging spectrographs which produce minimal degradation over a large focal plane. Ray trace images and pixilated area maps demonstrating spatial and spectral reproduction accuracy over the entire back focal plane are presented.

  10. Advanced Constituents and Processes for Ceramic Composite Engine Components

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; DiCarlo, J. A.; Bhatt, R. T.

    2004-01-01

    The successful replacement of metal alloys by ceramic matrix composites (CMC) in hot-section engine components will depend strongly on optimizing the processes and properties of the CMC microstructural constituents so that they can synergistically provide the total CMC system with improved temperature capability and with the key properties required by the components for long-term structural service. This presentation provides the results of recent activities at NASA aimed at developing advanced silicon carbide (Sic) fiber-reinforced hybrid Sic matrix composite systems that can operate under mechanical loading and oxidizing conditions for hundreds of hours at 2400 and 2600 F, temperatures well above current metal capability. These SiC/SiC composite systems are lightweight (-30% metal density) and, in comparison to monolithic ceramics and carbon fiber-reinforced ceramic composites, are able to reliably retain their structural properties for long times under aggressive engine environments. It is shown that the improved temperature capability of the SiC/SiC systems is related first to the NASA development of the Sylramic-iBN Sic fiber, which displays high thermal stability, creep resistance, rupture resistance, and thermal conductivity, and possesses an in-situ grown BN surface layer for added environmental durability. This fiber is simply derived from Sylramic Sic fiber type that is currently produced at ATK COI Ceramics. Further capability is then derived by using chemical vapor infiltration (CVI) to form the initial portion of the hybrid Sic matrix. Because of its high creep resistance and thermal conductivity, the CVI Sic matrix is a required base constituent for all the high temperature SiC/SiC systems. By subsequently thermo- mechanical-treating the CMC preform, which consists of the S ylramic-iBN fibers and CVI Sic matrix, process-related defects in the matrix are removed, further improving matrix and CMC creep resistance and conductivity.

  11. High-rate-long-distance fiber-optic communication based on advanced modulation techniques.

    PubMed

    Ivankovski, Y; Mendlovic, D

    1999-09-10

    The presence of fiber attenuation and chromatic dispersion is one of the major design aspects of fiber-optic communication systems when one addresses high-rate and long-distance digital data transmission. Conventional digital communication systems implement a modulation technique that generates light pulses at the fiber input end and tries to detect them at the fiber output end. Here an advanced modulation transmission system is developed based on knowledge of the exact dispersion parameters of the fiber and the principles of space-time mathematical analogy. The information encodes the phase of the input light beam (a continuous laser beam). This phase is designed such that, when the signal is transmitted through a fiber with a given chromatic dispersion, high peak pulses emerge at the output, which follows a desired bit pattern. Thus the continuous input energy is concentrated into short time intervals in which the information needs to be represented at the output. The proposed method provides a high rate-distance product even for fibers with high dispersion parameters, high power at the output, and also unique protection properties. Theoretical analysis of the proposed method, computer simulations, and some design aspects are given. PMID:18324062

  12. Fiber-optic technologies for advanced thermo-therapy applied ex vivo to liver tumors

    NASA Astrophysics Data System (ADS)

    Tosi, D.; Perrone, G.; Vallan, A.; Braglia, A.; Liu, Y.; Macchi, E. G.; Braschi, G.; Gallati, M.; Cigada, A.; Poeggel, S.; Duraibabu, D. B.; Leen, G.; Lewis, E.

    2015-07-01

    Thermal ablation, using radiofrequency, microwave, and laser sources, is a common treatment for hepatic tumors. Sensors allow monitoring, at the point of treatment, the evolution of thermal ablation procedures. We present optical fiber sensors that allow advanced capabilities for recording the biophysical phenomena occurring in the tissue in real time. Distributed or quasi-distributed thermal sensors allow recording temperature with spatial resolution ranging from 0.1 mm to 5 mm. In addition, a thermally insensitive pressure sensor allows recording pressure rise, supporting advanced treatment of encapsulated tumors. Our investigation is focused on two case studies: (1) radiofrequency ablation of hepatic tissue, performed on a phantom with a stem-shaped applicator; (2) laser ablation of a liver phantom, performed with a fiber laser. The main measurement results are discussed, comparing the technologies used for the investigation, and drawing the potential for using optical fiber sensors for "smart"-ablation.

  13. Fiber optic (flight quality) sensors for advanced aircraft propulsion

    NASA Technical Reports Server (NTRS)

    Poppel, Gary L.

    1994-01-01

    Development of flight prototype, fiber-optic sensing system components for measuring nine sensed parameters (three temperatures, two speeds, three positions, and one flame) on an F404-400 aircraft engine is described. Details of each sensor's design, functionality, and environmental testing, and the electro-optics architecture for sensor signal conditioning are presented. Eight different optical sensing techniques were utilized. Design, assembly, and environmental testing of an engine-mounted, electro-optics chassis unit (EOU), providing MIL-C-1553 data output, are related. Interconnection cables and connectors between the EOU and the sensors are identified. Results of sensor/cable/circuitry integrated testing, and installation and ground testing of the sensor system on an engine in October 1993 and April 1994 are given, including comparisons with the engine control system's electrical sensors. Lessons learned about the design, fabrication, testing, and integration of the sensor system components are included.

  14. Fiber

    MedlinePlus

    ... it can help with weight control. Fiber aids digestion and helps prevent constipation . It is sometimes used ... fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in ...

  15. Performance and stability of advanced monolithic and fiber reinforced composite candle filters during PCFBC operation

    SciTech Connect

    Alvin, M.A.

    1996-12-31

    Advanced clay bonded silicon carbide, alumina/mullite and CVI-SiC fiber reinforced composite porous ceramic candle filters have been identified for use in pressurized circulating fluidized-bed combustion (PCFBC) systems where operating temperatures approach 870--900 C. In this paper the author will discuss the performance of these filter elements, and explore the response and stability of the advanced filter materials after 540 hours of operation in Foster Wheeler`s PCFBC system in Karhula, Finland. The potential use of the advanced filter materials for extended operating life in high temperature, pressurized, coal-fired process applications will also be addressed.

  16. Carbon fibers: Thermochemical recovery from advanced composite materials and activation to an adsorbent

    NASA Astrophysics Data System (ADS)

    Staley, Todd Andrew

    This research addresses an expanding waste disposal problem brought about by the increasing use of advanced composite materials, and the lack of technically and environmentally viable recycling methods for these materials. A thermochemical treatment process was developed and optimized for the recycling of advanced composite materials. Counter-current gasification was employed for the treatment of carbon fiber reinforced-epoxy resin composite wastes. These materials were treated, allowing the reclamation of the material's valuable components. As expected in gasification, the organic portion of the waste was thermochemically converted to a combustible gas with small amounts of organic compounds that were identified by GC/MS. These compounds were expected based on data in the literature. The composites contain 70% fiber reinforcement, and gasification yielded approximately 70% recovered fibers, representing nearly complete recovery of fibers from the waste. Through SEM and mechanical testing, the recovered carbon fibers were found to be structurally and mechanically intact, and amenable to re-use in a variety of applications, some of which were identified and tested. In addition, an application was developed for the carbon fiber component of the waste, as an activated carbon fiber adsorbent for the treatment of wastewaters. This novel class of adsorbent was found to have adsorption rates, for various organic molecules, up to a factor of ten times those of commercial granular activated carbon, and adsorption capacities similar to conventional activated carbons. Overall, the research addresses an existing environmental waste problem, employing a thermochemical technique to recycle and reclaim the waste. Components of the reclaimed waste material are then employed, after further modification, to address other existing and potential environmental waste problems.

  17. Raman Study of Uncoated and P-bn/sic-coated Hi-nicalon Reinforced Celsian Matrix Composites. Part 2; Residual Stress in the Fibers

    NASA Technical Reports Server (NTRS)

    Gouadec, Gwenael; Colomban, Philippe; Bansal, Narottam P.

    2000-01-01

    Band shifts on Raman spectra were used to assess, at a microscopic scale, the residual strain existing in Hi-Nicalon fibers reinforcing celsian matrix composites. Uncoated as well as p-BN/SiC- and p-B(Si)N/SiC-coated Hi-Nicalon fibers were used as the reinforcements. We unambiguously conclude that the fibers are in a state of compressive residual stress. Quantitative determination of the residual stress was made possible by taking into account the heating induced by laser probing and by using a reference line, of fixed wavenumber. We found fiber compressive residual stress values between 110 and 960 MPa depending on the fiber/matrix coating in the composite. A stress relaxation-like phenomenon was observed at the surface of p-BN/SiC-coated Hi-Nicalon fibers whereas the uncoated or p-B(Si)N/SiC-coated Hi-Nicalon fibers did not show any stress relaxation in the Celsian matrix composites.

  18. Microwave joining of SiC

    SciTech Connect

    Silberglitt, R.; Ahmad, I.; Tian, Y.L.

    1997-04-01

    The purpose of this work is to optimize the properties of SiC-SiC joints made using microwave energy. The current focus is on identification of the most effective joining methods for scale-up to large tube assemblies, including joining using SiC produced in situ from chemical precursors. During FY 1996, a new microwave applicator was designed, fabricated and tested that provides the capability for vacuum baking of the specimens and insulation and for processing under inert environment. This applicator was used to join continuous fiber-reinforced (CFCC) SiC/SiC composites using a polymer precursor to form a SiC interlayer in situ.

  19. Coherent Terahertz Wireless Signal Transmission Using Advanced Optical Fiber Communication Technology

    NASA Astrophysics Data System (ADS)

    Kanno, Atsushi; Kuri, Toshiaki; Morohashi, Isao; Hosako, Iwao; Kawanishi, Tetsuya; Yoshida, Yuki; Kitayama, Ken-ichi

    2015-02-01

    Coherent terahertz signal transmission with multilevel modulation and demodulation is demonstrated using an optical sub-harmonic IQ mixer (SHIQM), which consists of optical components in advanced optical fiber communication technologies. An optical-frequency-comb-employed signal generator is capable of vector modulation as well as frequency tunability. Digital signal processing (DSP) adopted from the recently developed optical digital coherent communication can easily demodulate multi-level modulated terahertz signals by using electrical heterodyning for intermediate-frequency (IF) down conversion. This technique is applicable for mobile backhauling in the next-generation mobile communication technology directly connected to an optical fiber network as a high-speed wireless transmission link.

  20. Hollow fiber membranes for advanced life support systems. [permeable capillaries for medical filtration

    NASA Technical Reports Server (NTRS)

    Roebelen, G. J., Jr.; Lysaght, M. J.

    1977-01-01

    This paper describes an investigation of the practicability of utilizing hollow fiber membranes in vehicular and portable life support system applications. A preliminary screening of potential advanced life support applications resulted in the selection of five applications for feasibility study and testing. As a result of the feasibility study and testing, three applications, heat rejection, deaeration, and bacteria filtration, were chosen for breadboard development testing. Breadboard hardware has been manufactured and tested, and the physical properties of the three hollow fiber membrane assemblies applicable to use aboard future spacecraft have been characterized.

  1. Fiber Optic Surface Plasmon Resonance-Based Biosensor Technique: Fabrication, Advancement, and Application.

    PubMed

    Liang, Gaoling; Luo, Zewei; Liu, Kunping; Wang, Yimin; Dai, Jianxiong; Duan, Yixiang

    2016-05-01

    Fiber optic-based biosensors with surface plasmon resonance (SPR) technology are advanced label-free optical biosensing methods. They have brought tremendous progress in the sensing of various chemical and biological species. This review summarizes four sensing configurations (prism, grating, waveguide, and fiber optic) with two ways, attenuated total reflection (ATR) and diffraction, to excite the surface plasmons. Meanwhile, the designs of different probes (U-bent, tapered, and other probes) are also described. Finally, four major types of biosensors, immunosensor, DNA biosensor, enzyme biosensor, and living cell biosensor, are discussed in detail for their sensing principles and applications. Future prospects of fiber optic-based SPR sensor technology are discussed. PMID:27119268

  2. Advanced spectral fiber optic sensor systems and their application in energy facility monitoring

    NASA Astrophysics Data System (ADS)

    Willsch, Reinhardt; Ecke, Wolfgang; Bosselmann, Thomas; Willsch, Michael; Lindner, Eric; Bartelt, Hartmut

    2011-06-01

    Various spectral-encoded fiber optic sensor concepts and advanced system solutions for application in energy facility monitoring have been investigated. The technological maturity, high performance and reliability of multiplexed fiber Bragg grating (FBG) sensor arrays and networks for the measurement of temperature, dynamic strain, air flow, and magnetic field distributions in electric power generators increasing their efficiency will be demonstrated by selected examples of field testing under harsh environmental conditions. For high-temperature combustion monitoring in gas turbines, beside silica FBGs with enhanced temperature stability also sapphire FBGs and Fabry-Perot sensors have been tested and evaluated as well as fiber-based black-body thermal radiation sensors. Finally, the potential of FBG sensors for application in cryo-energetic facilities such as super-conductive high-power motors and experimental nuclear fusion reactors will be discussed.

  3. Advanced end-to-end fiber optic sensing systems for demanding environments

    NASA Astrophysics Data System (ADS)

    Black, Richard J.; Moslehi, Behzad

    2010-09-01

    Optical fibers are small-in-diameter, light-in-weight, electromagnetic-interference immune, electrically passive, chemically inert, flexible, embeddable into different materials, and distributed-sensing enabling, and can be temperature and radiation tolerant. With appropriate processing and/or packaging, they can be very robust and well suited to demanding environments. In this paper, we review a range of complete end-to-end fiber optic sensor systems that IFOS has developed comprising not only (1) packaged sensors and mechanisms for integration with demanding environments, but (2) ruggedized sensor interrogators, and (3) intelligent decision aid algorithms software systems. We examine the following examples: " Fiber Bragg Grating (FBG) optical sensors systems supporting arrays of environmentally conditioned multiplexed FBG point sensors on single or multiple optical fibers: In conjunction with advanced signal processing, decision aid algorithms and reasoners, FBG sensor based structural health monitoring (SHM) systems are expected to play an increasing role in extending the life and reducing costs of new generations of aerospace systems. Further, FBG based structural state sensing systems have the potential to considerably enhance the performance of dynamic structures interacting with their environment (including jet aircraft, unmanned aerial vehicles (UAVs), and medical or extravehicular space robots). " Raman based distributed temperature sensing systems: The complete length of optical fiber acts as a very long distributed sensor which may be placed down an oil well or wrapped around a cryogenic tank.

  4. High Neutron Fluence Survivability Testing of Advanced Fiber Bragg Grating Sensors

    SciTech Connect

    Fielder, Robert S.; Klemer, Daniel; Stinson-Bagby, Kelly L.

    2004-02-04

    The motivation for the reported research was to support NASA space nuclear power initiatives through the development of advanced fiber optic sensors for space-based nuclear power applications. The purpose of the high-neutron fluence testing was to demonstrate the survivability of fiber Bragg grating (FBG) sensors in a fission reactor environment. 520 FBGs were installed in the Ford reactor at the University of Michigan. The reactor was operated for 1012 effective full power hours resulting in a maximum neutron fluence of approximately 5x1019 n/cm2, and a maximum gamma dose of 2x103 MGy gamma. This work is significant in that, to the knowledge of the authors, the exposure levels obtained are approximately 1000 times higher than for any previously published experiment. Four different fiber compositions were evaluated. An 87% survival rate was observed for fiber Bragg gratings located at the fuel centerline. Optical Frequency Domain Reflectometry (OFDR), originally developed at the NASA Langley Research Center, can be used to interrogate several thousand low-reflectivity FBG strain and/or temperature sensors along a single optical fiber. A key advantage of the OFDR sensor technology for space nuclear power is the extremely low mass of the sensor, which consists of only a silica fiber 125{mu}m in diameter. The sensors produced using this technology will fill applications in nuclear power for current reactor plants, emerging Generation-IV reactors, and for space nuclear power. The reported research was conducted by Luna Innovations and was funded through a Small Business Innovative Research (SBIR) contract with the NASA Glenn Research Center.

  5. High Neutron Fluence Survivability Testing of Advanced Fiber Bragg Grating Sensors

    NASA Astrophysics Data System (ADS)

    Fielder, Robert S.; Klemer, Daniel; Stinson-Bagby, Kelly L.

    2004-02-01

    The motivation for the reported research was to support NASA space nuclear power initiatives through the development of advanced fiber optic sensors for space-based nuclear power applications. The purpose of the high-neutron fluence testing was to demonstrate the survivability of fiber Bragg grating (FBG) sensors in a fission reactor environment. 520 FBGs were installed in the Ford reactor at the University of Michigan. The reactor was operated for 1012 effective full power hours resulting in a maximum neutron fluence of approximately 5×1019 n/cm2, and a maximum gamma dose of 2×103 MGy gamma. This work is significant in that, to the knowledge of the authors, the exposure levels obtained are approximately 1000 times higher than for any previously published experiment. Four different fiber compositions were evaluated. An 87% survival rate was observed for fiber Bragg gratings located at the fuel centerline. Optical Frequency Domain Reflectometry (OFDR), originally developed at the NASA Langley Research Center, can be used to interrogate several thousand low-reflectivity FBG strain and/or temperature sensors along a single optical fiber. A key advantage of the OFDR sensor technology for space nuclear power is the extremely low mass of the sensor, which consists of only a silica fiber 125μm in diameter. The sensors produced using this technology will fill applications in nuclear power for current reactor plants, emerging Generation-IV reactors, and for space nuclear power. The reported research was conducted by Luna Innovations and was funded through a Small Business Innovative Research (SBIR) contract with the NASA Glenn Research Center.

  6. Advances in electrospun carbon fiber-based electrochemical sensing platforms for bioanalytical applications.

    PubMed

    Mao, Xianwen; Tian, Wenda; Hatton, T Alan; Rutledge, Gregory C

    2016-02-01

    Electrochemical sensing is an efficient and inexpensive method for detection of a range of chemicals of biological, clinical, and environmental interest. Carbon materials-based electrodes are commonly employed for the development of electrochemical sensors because of their low cost, biocompatibility, and facile electron transfer kinetics. Electrospun carbon fibers (ECFs), prepared by electrospinning of a polymeric precursor and subsequent thermal treatment, have emerged as promising carbon systems for biosensing applications since the electrochemical properties of these carbon fibers can be easily modified by processing conditions and post-treatment. This review addresses recent progress in the use of ECFs for sensor fabrication and analyte detection. We focus on the modification strategies of ECFs and identification of the key components that impart the bioelectroanalytical activities, and point out the future challenges that must be addressed in order to advance the fundamental understanding of the ECF electrochemistry and to realize the practical applications of ECF-based sensing devices. PMID:26650731

  7. S-IC Static Test Stand

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Constructed in 1964, the S-IC Static Test Stand was designed to develop and test the first stage (S-IC) of the Saturn V launch vehicle. In the 1974 the test stand was modified to test the liquid hydrogen tank on the Space Shuttle External Tank. The facility was again modified in 1986 and its name was changed to the Advanced Engine Test Facility. These modifications were made to accommodate the Technology Test Bed engine which is a derivative of the Space Shuttle Main Engine.

  8. Low dose irradiation performance of SiC interphase SiC/SiC composites

    NASA Astrophysics Data System (ADS)

    Snead, L. L.; Osborne, M. C.; Lowden, R. A.; Strizak, J.; Shinavski, R. J.; More, K. L.; Eatherly, W. S.; Bailey, J.; Williams, A. M.

    1998-03-01

    Reduced oxygen Hi-Nicalon™ fiber reinforced composite SiC materials were densified with a chemically vapor infiltrated (CVI) silicon carbide (SiC) matrix and interphases of either `porous' SiC or multilayer SiC and irradiated to a neutron fluence of 1.1×10 25 n m -2 ( E>0.1 MeV) in the temperature range of 260 to 1060°C. The unirradiated properties of these composites are superior to previously studied ceramic grade Nicalon fiber reinforced/carbon interphase materials. Negligible reduction in the macroscopic matrix microcracking stress was observed after irradiation for the multilayer SiC interphase material and a slight reduction in matrix microcracking stress was observed for the composite with porous SiC interphase. The reduction in strength for the porous SiC interfacial material is greatest for the highest irradiation temperature. The ultimate fracture stress (in four point bending) following irradiation for the multilayer SiC and porous SiC interphase materials was reduced by 15% and 30%, respectively, which is an improvement over the 40% reduction suffered by irradiated ceramic grade Nicalon fiber materials fabricated in a similar fashion, though with a carbon interphase. The degradation of the mechanical properties of these composites is analyzed by comparison with the irradiation behavior of bare Hi-Nicalon fiber and Morton chemically vapor deposited (CVD) SiC. It is concluded that the degradation of these composites, as with the previous generation ceramic grade Nicalon fiber materials, is dominated by interfacial effects, though the overall degradation of fiber and hence composite is reduced for the newer low-oxygen fiber.

  9. Nanocrystalline SiC and Ti3SiC2 Alloys for Reactor Materials: Diffusion of Fission Product Surrogates

    SciTech Connect

    Henager, Charles H.; Jiang, Weilin

    2014-11-01

    MAX phases, such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been suggested in the literature as a possible fuel cladding material. Prior to the application, it is necessary to investigate diffusivities of fission products in the ternary compound at elevated temperatures. This study attempts to obtain relevant data and make an initial assessment for Ti3SiC2. Ion implantation was used to introduce fission product surrogates (Ag and Cs) and a noble metal (Au) in Ti3SiC2, SiC, and a dual-phase nanocomposite of Ti3SiC2/SiC synthesized at PNNL. Thermal annealing and in-situ Rutherford backscattering spectrometry (RBS) were employed to study the diffusivity of the various implanted species in the materials. In-situ RBS study of Ti3SiC2 implanted with Au ions at various temperatures was also performed. The experimental results indicate that the implanted Ag in SiC is immobile up to the highest temperature (1273 K) applied in this study; in contrast, significant out-diffusion of both Ag and Au in MAX phase Ti3SiC2 occurs during ion implantation at 873 K. Cs in Ti3SiC2 is found to diffuse during post-irradiation annealing at 973 K, and noticeable Cs release from the sample is observed. This study may suggest caution in using Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures. Further studies of the related materials are recommended.

  10. -SiC Composites

    NASA Astrophysics Data System (ADS)

    Chakraborty, Shirshendu; Debnath, Debashish; Mallick, Azizur Rahaman; Das, Probal Kumar

    2014-12-01

    ZrB2-SiC composites were hot pressed at 2473 K (2200 °C) with graded amounts (5 to 20 wt pct) of SiC and the effect of the SiC addition on mechanical properties like hardness, fracture toughness, scratch and wear resistances, and thermal conductivity were studied. Addition of submicron-sized SiC particles in ZrB2 matrices enhanced mechanical properties like hardness (15.6 to 19.1 GPa at 1 kgf), fracture toughness (2 to 3.6 MPa(m)1/2) by second phase dispersion toughening mechanism, and also improved scratch and wear resistances. Thermal conductivity of ZrB2-SiC (5 wt pct) composite was higher [121 to 93 W/m K from 373 K to 1273 K (100 °C to 1000 °C)] and decreased slowly upto 1273 K (1000 °C) in comparison to monolithic ZrB2 providing better resistance to thermal fluctuation of the composite and improved service life in UHTC applications. At higher loading of SiC (15 wt pct and above), increased thermal barrier at the grain boundaries probably reduced the thermal conductivity of the composite.

  11. Microstructure and mechanical properties of joints in sintered SiC fiber-bonded ceramics brazed with Ag Cu Ti alloy

    SciTech Connect

    Singh, Mrityunjay; Asthana, Rajiv; Ishikawa, Toshihiro; Matsunaga, Tadashi; Lin, Hua-Tay

    2012-01-01

    Active metal brazing of a new high thermal conductivity sintered SiC-polycrystalline fiber-bonded ceramic (SA-Tyrannohexs) has been carried out using a Ti-containing Ag Cu active braze alloy (Cusil-ABAs). The brazed composite joints were characterized using scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM EDS). The results show that this material can be successfully joined using judiciously selected off-the shelf active braze alloys to yield metallurgically sound joints possessing high integrity. Uniform and continuous joints were obtained irrespective of differences in the fiber orientation in the substrate material. Detailed interfacial microanalysis showed that the titanium reacts with C and Si to form TiC layer and a Ti Si compound, respectively. Furthermore, the evaluation of shear strength of the joints was also conducted at ambient and elevated temperatures in air using the single-lap offset (SLO) shear test. The perpendicular-type SA-Tyrannohex joints exhibited apparent shear strengths of about 42 MPa and 25 MPa at 650 1C and 750 1C, respectively. The fracture at the higher temperature occurred at the interface between the reactionformed TiC layer and braze. This might be caused by generation of stress intensity when a shear stress was applied, according to m-FEA simulation results.

  12. Microstructure and Mechanical Properties of Joints in Sintered SiC Fiber-Bonded Ceramics Brazed with Ag-Cu-Ti Alloy

    SciTech Connect

    Singh, Mrityunjay; Matsunaga, Tadashi; Lin, Hua-Tay; Asthana, Rajiv; Ishikawa, Toshihiro

    2012-01-01

    Active metal brazing of a new high thermal conductivity sintered SiC-polycrystalline fiber-bonded ceramic (SA-Tyrannohex{reg_sign}) has been carried out using a Ti-containing Ag-Cu active braze alloy (Cusil-ABA{reg_sign}). The brazed composite joints were characterized using scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDS). The results show that this material can be successfully joined using judiciously selected off-the shelf active braze alloys to yield metallurgically sound joints possessing high integrity. Uniform and continuous joints were obtained irrespective of differences in the fiber orientation in the substrate material. Detailed interfacial microanalysis showed that the titanium reacts with C and Si to form TiC layer and a Ti-Si compound, respectively. Furthermore, the evaluation of shear strength of the joints was also conducted at ambient and elevated temperatures in air using the single-lap offset (SLO) shear test. The perpendicular-type SA-Tyrannohex joints exhibited apparent shear strengths of about 42 MPa and 25 MPa at 650 C and 750 C, respectively. The fracture at the higher temperature occurred at the interface between the reaction-formed TiC layer and braze. This might be caused by generation of stress intensity when a shear stress was applied, according to {mu}-FEA simulation results.

  13. Cyclic Fiber Push-In Test Monitors Evolution of Interfacial Behavior in Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I.

    1998-01-01

    SiC fiber-reinforced ceramic matrix composites are being developed for high-temperature advanced jet engine applications. Obtaining a strong, tough composite material depends critically on optimizing the mechanical coupling between the reinforcing fibers and the surrounding matrix material. This has usually been accomplished by applying a thin C or BN coating onto the surface of the reinforcing fibers. The performance of these fiber coatings, however, may degrade under cyclic loading conditions or exposure to different environments. Degradation of the coating-controlled interfacial behavior will strongly affect the useful service lifetime of the composite material. Cyclic fiber push-in testing was applied to monitor the evolution of fiber sliding behavior in both C- and BN-coated small-diameter (15-mm) SiC-fiber-reinforced ceramic matrix composites. The cyclic fiber push-in tests were performed using a desktop fiber push-out apparatus. At the beginning of each test, the fiber to be tested was aligned underneath a 10- mm-diameter diamond punch; then, the applied load was cycled between selected maximum and minimum loads. From the measured response, the fiber sliding distance and frictional sliding stresses were determined for each cycle. Tests were performed in both room air and nitrogen. Cyclic fiber push-in tests of C-coated, SiC-fiber-reinforced SiC showed progressive increases in fiber sliding distances along with decreases in frictional sliding stresses for continued cycling in room air. This rapid degradation in interfacial response was not observed for cycling in nitrogen, indicating that moisture exposure had a large effect in immediately lowering the frictional sliding stresses of C-coated fibers. These results indicate that matrix cracks bridged by C-coated fibers will not be stable, but will rapidly grow in moisture-containing environments. In contrast, cyclic fiber push-in tests of both BN-coated, SiC-fiber-reinforced SiC and BNcoated, SiC-fiber

  14. Annual Conference on Composites and Advanced Ceramic Materials, 11th, Cocoa Beach, FL, Jan. 18-23, 1987, Proceedings

    SciTech Connect

    Not Available

    1987-08-01

    The present conference on advanced ceramic materials discusses topics in the fields of NDE, coating/joining/tribology techniques, fracture and interface phenomena, whisker- and particulate-reinforced composites, fiber and whisker properties, SiC and Si/sub 3/N/sub 4/, glass/glass-ceramic matrix composites, alumina-matrix composites, ceramic materials for space structures, and SiC- and Si/sub 3/N/sub 4/-matrix composites. Attention is given to ceramic characterization by thermal wave imaging, an advanced ceramic-to-metal joining process, the fracture modes of brittle-matrix unidirectional composites, the oxidation of SiC-containing composites, particulate matter in SiC whiskers, corrosion reactions in SiC ceramics, melt-infiltrated ceramic-matrix composites, environmental effects in toughened ceramics, and a ceramic composite heat exchanger.

  15. Fiber-Based, Spatially and Temporally Shaped Picosecond UV Laser for Advanced RF Gun Applications

    SciTech Connect

    Shverdin, M Y; Anderson, S G; Betts, S M; Gibson, D J; Hartemann, F V; Hernandez, J E; Johnson, M; Jovanovic, I; Messerly, M; Pruet, J; Tremaine, A M; McNabb, D P; Siders, C W; Barty, C J

    2007-06-08

    The fiber-based, spatially and temporally shaped, picosecond UV laser system described here has been specifically designed for advanced rf gun applications, with a special emphasis on the production of high-brightness electron beams for free-electron lasers and Compton scattering light sources. The laser pulse can be shaped to a flat-top in both space and time with a duration of 10 ps at full width of half-maximum (FWHM) and rise and fall times under 1 ps. The expected pulse energy is 50 {micro}J at 261.75 nm and the spot size diameter of the beam at the photocathode is 2 mm. A fiber oscillator and amplifier system generates a chirped pump pulse at 1047 nm; stretching is achieved in a chirped fiber Bragg grating. A single multi-layer dielectric grating based compressor recompresses the input pulse to 250 fs FWHM and a two stage harmonic converter frequency quadruples the beam. Temporal shaping is achieved with a Michelson-based ultrafast pulse stacking device with nearly 100% throughput. Spatial shaping is achieved by truncating the beam at the 20% energy level with an iris and relay-imaging the resulting beam profile onto the photocathode. The integration of the system, as well as preliminary laser measurements will be presented.

  16. SiC Technology

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.

    1998-01-01

    Silicon carbide (SiC)-based semiconductor electronic devices and circuits are presently being developed for use in high-temperature, high-power, and/or high-radiation conditions under which conventional semiconductors cannot adequately perform. Silicon carbide's ability to function under such extreme conditions is expected to enable significant improvements to a far-ranging variety of applications and systems. These range from greatly improved high-voltage switching [1- 4] for energy savings in public electric power distribution and electric motor drives to more powerful microwave electronics for radar and communications [5-7] to sensors and controls for cleaner-burning more fuel-efficient jet aircraft and automobile engines. In the particular area of power devices, theoretical appraisals have indicated that SiC power MOSFET's and diode rectifiers would operate over higher voltage and temperature ranges, have superior switching characteristics, and yet have die sizes nearly 20 times smaller than correspondingly rated silicon-based devices [8]. However, these tremendous theoretical advantages have yet to be realized in experimental SiC devices, primarily due to the fact that SiC's relatively immature crystal growth and device fabrication technologies are not yet sufficiently developed to the degree required for reliable incorporation into most electronic systems [9]. This chapter briefly surveys the SiC semiconductor electronics technology. In particular, the differences (both good and bad) between SiC electronics technology and well-known silicon VLSI technology are highlighted. Projected performance benefits of SiC electronics are highlighted for several large-scale applications. Key crystal growth and device-fabrication issues that presently limit the performance and capability of high temperature and/or high power SiC electronics are identified.

  17. Feasibility and process scale-up low cost alumina fibers for advanced Re-usable Surface Insulation (RSI)

    NASA Technical Reports Server (NTRS)

    Pearson, A.

    1975-01-01

    The objective of this program was to establish feasibility of a process to produce low cost aluminum oxide fibers having sufficient strength, flexibility, and thermal stability for multiple re-use at temperatures to 1480 C in advanced RSI type heat shields for reentry vehicles. Using bench-scale processing apparatus, the Alcoa 'Saphiber' process was successfully modified to produce nominally 8 microns diameter polycrystalline alpha-alumina fiber. Thermal stability was demonstrated in vacuum reheating tests to 1371 C and in atmospheric reheating to 1483 C. Individual fiber properties of strength, modulus, and flexibility were not determined because of friability and short length of the fiber. Rigidized tile produced from fiber of nominally 8, 20 and 40 micron diameter had thermal conductivities significantly higher than those of RSI SiO2 or mullite at relatively low temperature but became comparable above about 1000 C. Tile densities were high due to short fiber length, especially in the coarser diameter fiber. No significant effect of fiber diameter on thermal properties could be determined form the data. Mechanical properties of tiles deteriorated as fiber diameter increased.

  18. Hollow Fiber Spacesuit Water Membrane Evaporator Development and Testing for Advanced Spacesuits

    NASA Technical Reports Server (NTRS)

    Bue, Grant C.; Trevino, Luis A.; Tsioulos, Gus; Settles, Joseph; Colunga, Aaron; Vogel, Matthew; Vonau, Walt

    2010-01-01

    The spacesuit water membrane evaporator (SWME) is being developed to perform the thermal control function for advanced spacesuits to take advantage of recent advances in micropore membrane technology in providing a robust heat-rejection device that is potentially less sensitive to contamination than is the sublimator. Principles of a sheet membrane SWME design were demonstrated using a prototypic test article that was tested in a vacuum chamber at JSC in July 1999. The Membrana Celgard X50-215 microporous hollow fiber (HoFi) membrane was selected after recent contamination tests as the most suitable candidate among commercial alternatives for HoFi SWME prototype development. A design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape, was developed into a full-scale prototype consisting 14,300 tube bundled into 30 stacks, each of which are formed into a chevron shape and separated by spacers and organized into three sectors of ten nested stacks. Vacuum chamber testing has been performed characterize heat rejection as a function of inlet water temperature and water vapor backpressure and to show contamination resistance to the constituents expected to be found in potable water produced by the distillation processes. Other tests showed the tolerance to freezing and suitability to reject heat in a Mars pressure environment.

  19. Development of SiC Large Tapered Crystal Growth

    NASA Technical Reports Server (NTRS)

    Neudeck, Phil

    2011-01-01

    Research Focus Area: Power Electronics, Temperature Tolerant Devices. Demonstrate initial feasibility of totally new "Large Tapered Crystal" (LTC) process for growing vastly improved large-diameter wide-band gap wafers. Addresses Targets: The goal of this research is to experimentally investigate and demonstrate feasibility of the key unproven LTC growth processes in SiC. Laser-assisted growth of long SiC fiber seeds. Radial epitaxial growth enlargement of seeds into large SiC boules. Uniqueness and Impacts open a new technology path to large-diameter SiC and GaN wafers with 1000-fold defect density improvement at 2-4 fold lower cost. Leapfrog improvement in wide band gap power device capability and cost.

  20. Fiber

    MedlinePlus

    ... broccoli, spinach, and artichokes legumes (split peas, soy, lentils, etc.) almonds Look for the fiber content of ... salsa, taco sauce, and cheese for dinner. Add lentils or whole-grain barley to your favorite soups. ...

  1. Fiber

    MedlinePlus

    ... short period of time can cause intestinal gas ( flatulence ), bloating , and abdominal cramps . This problem often goes ... 213. National Research Council. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and ...

  2. Review of data on irradiation creep of monolithic SiC

    SciTech Connect

    Garner, F.A.; Youngblood, G.E.; Hamilton, M.L.

    1996-04-01

    An effort is now underway to design an irradiation creep experiment involving SiC composites to SiC fibers. In order to successfully design such an experiment, it is necessary to review and assess the available data for monolithic SiC to establish the possible bounds of creep behavior for the composite. The data available show that monolithic SiC will indeed creep at a higher rate under irradiation compared to that of thermal creep, and surprisingly, it will do so in a temperature-dependant manner that is typical of metals.

  3. SSG SiC Optical Systems in Space

    NASA Technical Reports Server (NTRS)

    Robichaud, Joseph; Keys, Andrew S. (Technical Monitor)

    2002-01-01

    Silicon Carbide (SiC) materials provide a number of benefits for space based optical systems. SSG Precision Optronics has extensive experience in the areas of design, fabrication, integration, and test of SiC optical systems. This expertise has been applied to produce a number of SiC-based instruments, including the Miniature Infrared Camera and Spectrometer (MICAS) and Advanced Land Imager (ALI) optical systems which have flown as part of NASA's New Millennium program. Our presentation will provide an overview of SSG's experience in the development of these SiC flight systems.

  4. Recent advances in reaction bonded silicon carbide optics and optical systems

    NASA Astrophysics Data System (ADS)

    Robichaud, Joseph; Schwartz, Jay; Landry, David; Glenn, William; Rider, Brian; Chung, Michael

    2005-08-01

    SSG Precision Optronics, Inc. (SSG) has recently developed a number of Reaction Bonded (RB) Silicon Carbide (SiC) optical systems for space-based remote sensing and astronomical observing applications. RB SiC's superior material properties make it uniquely well suited to meet the image quality and long term dimensional stability requirements associated with these applications. An overview of the RB SiC manufacturing process is presented, along with a summary description of recently delivered RB SiC flight hardware. This hardware includes an RB SiC telescope and Pointing Mirror Assembly (PMA) for the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) mission and an imaging telescope for the Long-Range Reconnaissance Imager (LORRI) mission. SSG continues to advance the state-of-the-technology with SiC materials and systems. A summary of development activities related to a low-cost, fracture tough, fiber reinforced RB SiC material formulation, novel tooling to produce monolithic, partially closed back mirror geometries, and extension of the technology to large aspheric mirrors is also provided.

  5. Pressure driven spinning: A multifaceted approach for preparing nanoscaled functionalized fibers, scaffolds, and membranes with advanced materials

    PubMed Central

    Jayasinghe, Suwan N.; Suter, Nicolai

    2010-01-01

    Electrospinning, a flexible jet-based fiber, scaffold, and membrane fabrication approach, has been elucidated as having significance to the heath sciences. Its capabilities have been most impressive as it possesses the ability to spin composite fibers ranging from the nanometer to the micrometer scale. Nonetheless, electrospinning has limitations and hazards, negating its wider exploration, for example, the inability to handle highly conducting suspensions, to its hazardous high voltage. Hence, to date electrospinning has undergone an exhaustive research regime to a point of cliché. Thus, in the work reported herein we unveil a competing technique to electrospinning, which has overcome the above limitations and hazards yet comparable in capabilities. The fiber preparation approach unearthed herein is referred to as “pressure driven spinning (PDS).” The driving mechanism exploited in this fiber spinning process is the pressurized by-pass flow. This mechanism allows the drawing of either micro- or nanosized fibers while processing polymeric suspensions containing a wide range of advanced materials spanning structural, functional, and biological entities. Similar to electrospinning if the collection time of these continuous formed fibers is varied, composite scaffolds and membranes are generated. In keeping with our interests, multicompositional structural entities such as these could have several applications in biology and medicine, for example, ranging from the development of three-dimensional cultures (including disease models) to the development of synthetic tissues and organ structures to advanced approaches for controlled and targeted therapeutics. PMID:20644675

  6. Multiplexed Optical Fiber Sensors for Coal Fired Advanced Fossil Energy Systems

    SciTech Connect

    Wang, Anbo; Pickrell, Gary

    2012-03-31

    This report summarizes technical progress on the program Multiplexed Optical Fiber Sensors for Coal Fired Advanced Fossil Energy Systems funded by the National Energy Technology Laboratory of the U.S. Department of Energy, and performed jointly by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering and the Department of Materials Science and Engineering at Virginia Tech. This three-year project started on October 1, 2008. In the project, a fiber optical sensing system based on intrinsic Fabry-Perot Interferometer (IFPI) was developed for strain and temperature measurements for Ultra Supercritical boiler condition assessment. Investigations were focused on sensor design, fabrication, attachment techniques and novel materials for high temperature and strain measurements. At the start of the project, the technical requirements for the sensing technology were determined together with our industrial partner Alstom Power. As is demonstrated in Chapter 4, all the technical requirements are successfully met. The success of the technology extended beyond laboratory test; its capability was further validated through the field test at DOE NETL, in which the sensors yielded distributed temperature mapping of a testing coupon installed in the turbine test rig. The measurement results agreed well with prior results generated with thermocouples. In this project, significant improvements were made to the IFPI sensor technology by splicing condition optimization, transmission loss reduction, sensor signal demodulation and sensor system design.

  7. Polypropylene/glass fiber hierarchical composites incorporating inorganic fullerene-like nanoparticles for advanced technological applications.

    PubMed

    Díez-Pascual, Ana M; Naffakh, Mohammed

    2013-10-01

    Novel isotactic polypropylene (iPP)/glass fiber (GF) laminates reinforced with inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles as environmentally friendly fillers have been successfully fabricated by simple melt-blending and fiber impregnation in a hot-press without the addition of any compatibilizer. The influence of IF-WS2 concentration on the morphology, viscosity. and thermal and mechanical behavior of the hierarchical composites has been investigated. Results revealed an unprecedented 62 °C increase in the degradation temperature of iPP/GF upon addition of only 4.0 wt % IF-WS2. The coexistence of both micro- and nanoscale fillers resulted in synergistic effects on enhancing the stiffness, strength, crystallinity, thermal stability, glass transition (Tg) and heat distortion temperature (HDT) of the matrix. The approach used in this work is an efficient, versatile, scalable and economic strategy to improve the mechanical and thermal behavior of GF-reinforced thermoplastics with a view to extend their use in advanced technological applications. This new type of composite materials shows great potential to improve the efficiency and sustainability of many forms of transport. PMID:24015820

  8. Optical coherence tomography demonstrating macular retinal nerve fiber thinning in advanced optic disc drusen

    PubMed Central

    Hassan, Ali; Gouws, Pieter

    2014-01-01

    Optic disc drusen (ODD) are extracellular proteinaceous excrescences in the optic nerve head. They enlarge over time and can cause damage to nerve fibers with resulting loss of visual field. The authors report a case of advanced ODD in which macular optical coherence tomography demonstrated retinal nerve fiber thinning. A single case report of a 42-year-old woman with known ODD presented to the eye clinic with worsening field of vision which was impacting on her daily life. The patient was subject to full ophthalmic examination as well as Goldmann visual field testing, optic disc photography and optical coherence tomography (OCT) of both her optic discs and maculae. ODD although rare, can be visually devastating. No treatment is currently available however patients should be counseled about progressive nature of ODD and the potential for visual loss. OCT imaging of the maculae as well as optic discs may serve a role in monitoring the damage disc drusen cause to the eye. PMID:25136235

  9. Optical coherence tomography demonstrating macular retinal nerve fiber thinning in advanced optic disc drusen.

    PubMed

    Hassan, Ali; Gouws, Pieter

    2014-05-01

    Optic disc drusen (ODD) are extracellular proteinaceous excrescences in the optic nerve head. They enlarge over time and can cause damage to nerve fibers with resulting loss of visual field. The authors report a case of advanced ODD in which macular optical coherence tomography demonstrated retinal nerve fiber thinning. A single case report of a 42-year-old woman with known ODD presented to the eye clinic with worsening field of vision which was impacting on her daily life. The patient was subject to full ophthalmic examination as well as Goldmann visual field testing, optic disc photography and optical coherence tomography (OCT) of both her optic discs and maculae. ODD although rare, can be visually devastating. No treatment is currently available however patients should be counseled about progressive nature of ODD and the potential for visual loss. OCT imaging of the maculae as well as optic discs may serve a role in monitoring the damage disc drusen cause to the eye. PMID:25136235

  10. Full-Scale Hollow Fiber Spacesuit Water Membrane Evaporator Prototype Development and Testing for Advanced Spacesuits

    NASA Technical Reports Server (NTRS)

    Bue, Grant; Trevino, Luis; Tsioulos, Gus; Mitchell, Keith; Dillon, Paul; Weaver, Gregg

    2009-01-01

    The spacesuit water membrane evaporator (SWME) is being developed to perform the thermal control function for advanced spacesuits to take advantage of recent advances in micropore membrane technology in providing a robust heat-rejection device that is potentially less sensitive to contamination than is the sublimator. Principles of a sheet membrane SWME design were demonstrated using a prototypic test article that was tested in a vacuum chamber at JSC in July 1999. The Membrana Celgard X50-215 microporous hollow fiber (HoFi) membrane was selected after recent contamination tests as the superior candidate among commercial alternatives for HoFi SWME prototype development. Although a number of design variants were considered, one that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape, was deemed best for further development. An analysis of test data showed that eight layer stacks of the HoFi sheets that had good exposure on each side of the stack would evaporate water with high efficiency. A design that has 15,000 tubes, with 18 cm of exposed tubes between headers has been built and tested that meets the size, weight, and performance requirements of the SWME. This full-scale prototype consists of 30 stacks, each of which are formed into a chevron shape and separated by spacers and organized into three sectors of ten nested stacks. Testing has been performed to show contamination resistance to the constituents expected to be found in potable water produced by the distillation processes. Other tests showed the sensitivity to surfactants.

  11. A New Method to Grow SiC: Solvent-Laser Heated Floating Zone

    NASA Technical Reports Server (NTRS)

    Woodworth, Andrew A.; Neudeck, Philip G.; Sayir, Ali

    2012-01-01

    The solvent-laser heated floating zone (solvent-LHFZ) growth method is being developed to grow long single crystal SiC fibers. The technique combines the single crystal fiber growth ability of laser heated floating zone with solvent based growth techniques (e.g. traveling solvent method) ability to grow SiC from the liquid phase. Initial investigations reported in this paper show that the solvent-LHFZ method readily grows single crystal SiC (retains polytype and orientation), but has a significant amount of inhomogeneous strain and solvent rich inclusions.

  12. Smart Materials for Advanced Applications: Self-Decontaminating Polymers, Photofunctional Composites, and Electroconductive Fibers

    NASA Astrophysics Data System (ADS)

    Little, Brian Kevin

    2011-12-01

    Materials capable of providing multifunctional properties controllable by some external stimulus (pH, light, temperature, etc) are highly desirable and obtainable given recent advancements in material science. Development of these so called "Smart" materials spanned across many disciplines of science with applications in industrial areas such as medical, military, security, and environmental. Furthermore, next-generation materials require the ability to not only sense/respond to changes in their external/internal environment, but process information in regards to these changes and adapt accordingly in a dynamic fashion, autonomously, so called "Intelligent" materials. Findings reported in this manuscript detail the synthesis, characterization, and application of smart materials in the following three areas: (1) self-cleaning polymers (2) photoresponsive composites and (3) electroconductive fibers. Self-Cleaning Polymers: Self-decontaminating polymers are unique materials capable of degrading toxic organic chemicals (TOCs). Barriers composed of or coated with our photochemical reactive polymer matrix could be applied to multiple surfaces for defense against TOCs; for example, military garments for protection against chemical warfare agents. This study investigates conditions necessary for formation of peroxides via O2 reduction induced by long-lived, strongly reducing benzophenyl ketyl (BPK) polymer radicals. Photolysis of aqueous solutions composed of sulphonated poly(ether etherketone), SPEEK, and poly(vinyl alcohol), PVA lead to the formation of the BPK radicals. Experiments investigate the formation and decomposition of peroxides in aqueous solutions of SPEEK/PVA under photolysis. Photofunctional Composites: Photoresponsive nanoporous (PN) films and powders were studied and evaluated as possible additives to sensitize the initiation of CH3NO2 via a mechanism involving coalescence of reaction sites. Such materials consist of a 3-D mesoporous silica framework

  13. Compatibility of SiC and SiC Composites with Molten Lead

    SciTech Connect

    H Tunison

    2006-03-07

    The choice of structural material candidates to contain Lead at 1000 C are limited in number. Silicon carbide composites comprise one choice of possible containment materials. Short term screening studies (120 hours) were undertaken to study the behavior of Silicon Carbide, Silicon Nitride, elemental Silicon and various Silicon Carbide fiber composites focusing mainly on melt infiltrated composites. Isothermal experiments at 1000 C utilized graphite fixtures to contain the Lead and material specimens under a low oxygen partial pressure environment. The corrosion weight loss values (grams/cm{sup 2} Hr) obtained for each of the pure materials showed SiC (monolithic CVD or Hexoloy) to have the best materials compatibility with Lead at this temperature. Increased weight loss values were observed for pure Silicon Nitride and elemental Silicon. For the SiC fiber composite samples those prepared using a SiC matrix material performed better than Si{sub 3}N{sub 4} as a matrix material. Composites prepared using a silicon melt infiltration process showed larger corrosion weight loss values due to the solubility of silicon in lead at these temperatures. When excess silicon was removed from these composite samples the corrosion performance for these material improved. These screening studies were used to guide future long term exposure (both isothermal and non-isothermal) experiments and Silicon Carbide composite fabrication work.

  14. Experimental demonstration of large capacity WSDM optical access network with multicore fibers and advanced modulation formats.

    PubMed

    Li, Borui; Feng, Zhenhua; Tang, Ming; Xu, Zhilin; Fu, Songnian; Wu, Qiong; Deng, Lei; Tong, Weijun; Liu, Shuang; Shum, Perry Ping

    2015-05-01

    Towards the next generation optical access network supporting large capacity data transmission to enormous number of users covering a wider area, we proposed a hybrid wavelength-space division multiplexing (WSDM) optical access network architecture utilizing multicore fibers with advanced modulation formats. As a proof of concept, we experimentally demonstrated a WSDM optical access network with duplex transmission using our developed and fabricated multicore (7-core) fibers with 58.7km distance. As a cost-effective modulation scheme for access network, the optical OFDM-QPSK signal has been intensity modulated on the downstream transmission in the optical line terminal (OLT) and it was directly detected in the optical network unit (ONU) after MCF transmission. 10 wavelengths with 25GHz channel spacing from an optical comb generator are employed and each wavelength is loaded with 5Gb/s OFDM-QPSK signal. After amplification, power splitting, and fan-in multiplexer, 10-wavelength downstream signal was injected into six outer layer cores simultaneously and the aggregation downstream capacity reaches 300 Gb/s. -16 dBm sensitivity has been achieved for 3.8 × 10-3 bit error ratio (BER) with 7% Forward Error Correction (FEC) limit for all wavelengths in every core. Upstream signal from ONU side has also been generated and the bidirectional transmission in the same core causes negligible performance degradation to the downstream signal. As a universal platform for wired/wireless data access, our proposed architecture provides additional dimension for high speed mobile signal transmission and we hence demonstrated an upstream delivery of 20Gb/s per wavelength with QPSK modulation formats using the inner core of MCF emulating a mobile backhaul service. The IQ modulated data was coherently detected in the OLT side. -19 dBm sensitivity has been achieved under the FEC limit and more than 18 dB power budget is guaranteed. PMID:25969194

  15. Advanced signaling technologies for high-speed digital fiber-optic links.

    PubMed

    Stark, Andrew J; Isautier, Pierre; Pan, Jie; Pavan, Sriharsha Kota; Filer, Mark; Tibuleac, Sorin; Lingle, Robert; de Salvo, Richard; Ralph, Stephen E

    2014-09-01

    We summarize the most recent research of the Georgia Tech Terabit Optical Networking Consortium and the state-of-the-art in fiber telecommunications. These results comprise high-capacity single-mode fiber systems with digital coherent receivers and shorter-reach multimode fiber links with vertical cavity surface emitting lasers. We strongly emphasize the capabilities that sophisticated digital signal processing and electronics add to these fiber-based data transport links. PMID:25321383

  16. Processing and Properties of SiC/MoSi2-SiC Composites Fabricated by Melt Infiltration

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Hebsur, Mohan G.

    2000-01-01

    Hi-Nicalon SiC fiber reinforced MoSi2-SiC matrix composites (SiC/MoSi2-SiC) have been fabricated by the melt infiltration approach. The composite consists of approximately 60 vol%, 2-D woven BN/SiC coated Hi-Nicalon SiC fibers and approximately 40 vol% MoSi2-SiC matrix. The room temperature tensile properties and thermal conductivity of the SiC/MoSi2-SiC composites were measured and compared with those of the melt infiltrated SiC/SiC composites. The influence oi fiber architecture on tensile properties was also evaluated. Results indicate that the primary modulus, stress corresponding to deviation from linearity, and transverse thermal conductivity values for the SiC/MoSi2-SiC composites are significantly lower than those for the SiC/SiC composites. Microcracking of the matrix due to the large difference in thermal expansion between MoSi2 and SiC appears to be the reason for the lower matrix dominated properties of SiC/MoSi2-SiC composites.

  17. Assessment of Silicon Carbide Composites for Advanced Salt-Cooled Reactors

    SciTech Connect

    Katoh, Yutai; Wilson, Dane F; Forsberg, Charles W

    2007-09-01

    The Advanced High-Temperature Reactor (AHTR) is a new reactor concept that uses a liquid fluoride salt coolant and a solid high-temperature fuel. Several alternative fuel types are being considered for this reactor. One set of fuel options is the use of pin-type fuel assemblies with silicon carbide (SiC) cladding. This report provides (1) an initial viability assessment of using SiC as fuel cladding and other in-core components of the AHTR, (2) the current status of SiC technology, and (3) recommendations on the path forward. Based on the analysis of requirements, continuous SiC fiber-reinforced, chemically vapor-infiltrated SiC matrix (CVI SiC/SiC) composites are recommended as the primary option for further study on AHTR fuel cladding among various industrially available forms of SiC. Critical feasibility issues for the SiC-based AHTR fuel cladding are identified to be (1) corrosion of SiC in the candidate liquid salts, (2) high dose neutron radiation effects, (3) static fatigue failure of SiC/SiC, (4) long-term radiation effects including irradiation creep and radiation-enhanced static fatigue, and (5) fabrication technology of hermetic wall and sealing end caps. Considering the results of the issues analysis and the prospects of ongoing SiC research and development in other nuclear programs, recommendations on the path forward is provided in the order or priority as: (1) thermodynamic analysis and experimental examination of SiC corrosion in the candidate liquid salts, (2) assessment of long-term mechanical integrity issues using prototypical component sections, and (3) assessment of high dose radiation effects relevant to the anticipated operating condition.

  18. Novel Modified Optical Fibers for High Temperature In-Situ Miniaturized Gas Sensors in Advanced Fossil Energy Systems

    SciTech Connect

    Pickrell, Gary; Scott, Brian

    2014-06-30

    This report covers the technical progress on the program “Novel Modified Optical Fibers for High Temperature In-Situ Miniaturized Gas Sensors in Advanced Fossil Energy Systems”, funded by the National Energy Technology Laboratory of the U.S. Department of Energy, and performed by the Materials Science & Engineering and Electrical & Computer Engineering Departments at Virginia Tech, and summarizes technical progress from July 1st, 2005 –June 30th, 2014. The objective of this program was to develop novel fiber materials for high temperature gas sensors based on evanescent wave absorption in optical fibers. This project focused on two primary areas: the study of a sapphire photonic crystal fiber (SPCF) for operation at high temperature and long wavelengths, and a porous glass based fiber optic sensor for gas detection. The sapphire component of the project focused on the development of a sapphire photonic crystal fiber, modeling of the new structures, fabrication of the optimal structure, development of a long wavelength interrogation system, testing of the optical properties, and gas and temperature testing of the final sensor. The fabrication of the 6 rod SPCF gap bundle (diameter of 70μm) with a hollow core was successfully constructed with lead-in and lead-out 50μm diameter fiber along with transmission and gas detection testing. Testing of the sapphire photonic crystal fiber sensor capabilities with the developed long wavelength optical system showed the ability to detect CO2 at or below 1000ppm at temperatures up to 1000°C. Work on the porous glass sensor focused on the development of a porous clad solid core optical fiber, a hollow core waveguide, gas detection capabilities at room and high temperature, simultaneous gas species detection, suitable joining technologies for the lead-in and lead-out fibers and the porous sensor, sensor system sensitivity improvement, signal processing improvement, relationship between pore structure and fiber

  19. Advanced risk assessment of the effects of graphite fibers on electronic and electric equipment

    NASA Technical Reports Server (NTRS)

    Pocinki, L.; Cornell, M.; Kaplan, L.

    1980-01-01

    An assessment of the risk associated with accidents involving aircraft with carbon fiber composite structural components is examined. The individual fiber segments cause electrical and electronic equipment to fail under certain operating conditions. A Monte Carlo simulation model was used to computer the risk. Aircraft accidents with fire, release of carbon fiber material, entrainment of carbon fibers in a smoke plume transport of fibers downwind, transfer of some fibers/into the the interior of buildings, failures of electrical and electronic equipment, and economic impact of failures are discussed. Risk profiles were prepared for individual airports and the Nation. The vulnerability of electrical transmission equipment to carbon fiber incursion and aircraft accident total costs is investigated.

  20. In-situ sensor monitoring of resin film infusion of advanced fiber architecture preforms

    SciTech Connect

    Kranbuehl, D.E.; Hood, D.; Rogozinski, J.

    1995-12-01

    Resin transfer molding (RTM) of advanced fiber architecture stitched preforms is being developed as a smart cost-effective manufacturing technique for fabricating damage tolerant composite structures with geometrically complex reinforcements. Dry textile preforms are infiltrated with resin and cured in a single step process, thus eliminating separate prepreg manufacture and ply-by-ply lay-up. The number of parameters that must be controlled during infiltration and cure make trial-and-error methods of process cycle optimization extremely inefficient. In situ cure monitoring sensors and an analytical processing model are a superior alternative for the determination of optimum processing cycles, quality assurance, and automated process control. Resin transfer molding experiments have been conducted in a manufacturing plant with a reactive epoxy resin and carbon fabric preforms. Frequency dependent electromagnetic sensing (FDEMS) was used to monitor in situ resin position, viscosity and degree of cure in situ in the mold during the Resin Transfer Molding infiltration and cure process. A science based multi-dimensional model of Resin Transfer Molding (RTM) was used to predict the infiltration behavior, as well as viscosity and degree of cure as the resin flows and cures in the dry textile preform.

  1. More than meets the eye in bacterial cellulose: biosynthesis, bioprocessing, and applications in advanced fiber composites.

    PubMed

    Lee, Koon-Yang; Buldum, Gizem; Mantalaris, Athanasios; Bismarck, Alexander

    2014-01-01

    Bacterial cellulose (BC) nanofibers are one of the stiffest organic materials produced by nature. It consists of pure cellulose without the impurities that are commonly found in plant-based cellulose. This review discusses the metabolic pathways of cellulose-producing bacteria and the genetic pathways of Acetobacter xylinum. The fermentative production of BC and the bioprocess parameters for the cultivation of bacteria are also discussed. The influence of the composition of the culture medium, pH, temperature, and oxygen content on the morphology and yield of BC are reviewed. In addition, the progress made to date on the genetic modification of bacteria to increase the yield of BC and the large-scale production of BC using various bioreactors, namely static and agitated cultures, stirred tank, airlift, aerosol, rotary, and membrane reactors, is reviewed. The challenges in commercial scale production of BC are thoroughly discussed and the efficiency of various bioreactors is compared. In terms of the application of BC, particular emphasis is placed on the utilization of BC in advanced fiber composites to manufacture the next generation truly green, sustainable and renewable hierarchical composites. PMID:23897676

  2. SiC optics for EUV, UV, and visible space missions

    NASA Astrophysics Data System (ADS)

    Robichaud, Joseph L.

    2003-02-01

    An overview of silicon carbide (SiC) materials is provided, focusing on reaction bonded (RB) SiC and its properties. The Miniature Infrared Camera and Spectrometer (MICAS) and Advanced Land Imager (ALI) SiC space instruments produced by SSGPO and flown under NASA's New Millennium Program are described, and some of the mission requirements associated with UV and extreme UV (EUV) applications are reviewed. Manufacturing options associated with SiC reflectors are reviewed and the optical performance demonstrated with these materials is presented. In order to review the suitability of these materials to UV and EUV missions microroughness and surface scatter results are shown.

  3. A NEW TYPE OF SIC COMPOSITE FOR FUSION

    SciTech Connect

    Youngblood, Gerald E.; Jones, Russell H.

    2001-04-01

    A new type of SiC composite called Tyrannohex™ is potentially suitable as a fusion reactor structural material. Tyrannohex™ composite plates are made by hot-pressing layups of Tyranno™ SA precursor fibers into various 1D and 2D configurations. The fiber-bonded composite plates contain nearly 100% fiber volume, so take advantage of the outstanding high temperature strength and creep properties of the Tyranno™ SA fiber, a nearly stoichiometric SiC fiber. The hot-pressed plates are dense, strong, rigid, tough, thermally conductive and have high temperature stability. The microstructure and thermal conductivity of a SA-Tyrannohex™ material with a 2D-woven configuration was evaluated prior to irradiation testing. The microstructure contained some small, flat interlaminar pores and intrabundle needle-like pores, and the transverse thermal conductivity was 25 and 21 W/mK at ambient and 1000°C, respectively. These results suggest that careful control of the fiber-bonded interlayers and the fiber architecture are critical to achieve both high thermal conductivity and toughness in Tyrannohex™ type materials.

  4. US long distance fiber optic networks: Technology, evolution and advanced concepts. Volume 1: Executive summary

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Over the past two decades, fiber optics has emerged as a highly practical and cost-efficient communications technology. Its competitiveness vis-a-vis other transmission media, especially satellite, has become a critical question. This report studies the likely evolution and application of fiber optic networks in the United States to the end of the century. The outlook for the technology of fiber systems is assessed and forecast, scenarios of the evolution of fiber optic network development are constructed, and costs to provide service are determined and examined parametrically as a function of network size and traffic carried. Volume 1 consists of the Executive Summary. Volume 2 focuses on fiber optic technology and long distance fiber optic networks. Volume 3 develops a traffic and financial model of a nationwide long distance transmission network. Among the study's most important conclusions are: revenue requirements per circuit for LATA-to-LATA fiber optic links are less than one cent per call minute; multiplex equipment, which is likely to be required in any competing system, is the largest contributor to circuit costs; the potential capacity of fiber optic cable is very large and as yet undefined; and fiber optic transmission combined with other network optimization schemes can lead to even lower costs than those identified in this study.

  5. Study of Extra-Solar Planets with the Advanced Fiber Optic Echelle

    NASA Technical Reports Server (NTRS)

    Noyes, Robert W.; Boyce, Joseph M. (Technical Monitor)

    2002-01-01

    This is the final report of NASA Grant NAG5-7505, for 'Study of Extra-solar Planets with the Advanced Fiber Optic Echelle'. This program was funded in response to our proposal submitted under NASA NRA 97-OSS-06, with a total period of performance from June 1, 1998 through Feb 28 2002. Principal Investigator is Robert W. Noyes; co-Investigators are Sylvain G. Korzennik (SAO), Peter Niserison (SAO), and Timothy M. Brown (High Altitude Observatory). Since the start of this program we have carried out more than 30 observing runs, typically of 5 to 7 days duration. We obtained a total of around 2000 usable observations of about 150 stars, where a typical observation consists of 3 exposures of 10 minutes each. Using this data base we detected thc two additional planetary companions to the star Upsilon Andromedae. This detection was made independently of, and essentially simultaneously with, a similar detection by the Berkeley group (Marcy et al): the fact that two data sets were completely independent and gave essentially the same orbital parameters for this three-planet system gave a strong confirmation of this important result. We also extended our previous detection of the planet orbiting Rho Coronae Borealis to get a better determination of its orbital eccentricity: e=0.13 +/- 0.05. We detected a new planet in orbit around the star HD 89744, with orbital period 256 days, semi-major axis 0.88 AU, eccentricity 0.70, and minimum mass m sini = 7.2 m(sub Jup). This discovery is significant because of the very high orbital eccentricity, arid also because HD 89744 has both high metallicity [Fe/H] and at the same time a low [C/Fe] abundance ratio.

  6. Focused ion beam 3D nano-patterned optical fiber tips for advanced beam profile engineering

    NASA Astrophysics Data System (ADS)

    Janeiro, Ricardo; Flores, Raquel; Ribeiro, Ana R.; Jorge, Pedro; Viegas, Jaime

    2015-03-01

    Focused ion beam (FIB) patterning of 3D topography on optical fiber tips for application in stand-alone, rugged and simplified setups for optical tweezers cell sorters, optical near-field lithography and optical beam profile engineering are reported. We demonstrate various configurations based on single-step FIB patterning, multiple-step FIB processing and hybrid approaches based on optical fiber pre- and post-FIB treatment with either etching, fusion splicing, photopolymerization or electroplating steps for optical fiber texture, topography and composition engineering. Different conductive coatings for minimal charge accumulation and beam drift are studied with the relative merits compared. Furthermore optimal beam parameters for accurate pattern replication and positioning are also presented. Measured experimental field profiles are compared with numerical simulations of fabricated optical fiber tips for fabrication accuracy evaluation. Applications employing these engineered fiber tips in the field of optical tweezers, optical vortex generation, photolithography, photo-polymerization and beam forming are presented.

  7. SiC growth by Solvent-Laser Heated Floating Zone

    NASA Technical Reports Server (NTRS)

    Woodworth, Andrew A.; Neudeck, Philip G.; Sayir, Ali; Spry, David J.; Trunek, Andrew J.; Powell, J. Anthony

    2011-01-01

    In an effort to grow single crystal SiC fibers for seed crystals the following two growth methods have been coupled in this work: traveling solvent and laser heated floating zone to create the solvent-laser heated floating zone (Solvent-LHFZ) crystal growth method. This paper discusses the results of these initial experiments, which includes: source material, laser heating, and analysis of the first ever Solvent-LHFZ SiC crystals (synchrotron white beam x-ray topography confirmed).

  8. Modeling the Elastic Modulus of 2D Woven CVI SiC Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.

    2006-01-01

    The use of fiber, interphase, CVI SiC minicomposites as structural elements for 2D-woven SiC fiber reinforced chemically vapor infiltrated (CVI) SiC matrix composites is demonstrated to be a viable approach to model the elastic modulus of these composite systems when tensile loaded in an orthogonal direction. The 0deg (loading direction) and 90deg (perpendicular to loading direction) oriented minicomposites as well as the open porosity and excess SiC associated with CVI SiC composites were all modeled as parallel elements using simple Rule of Mixtures techniques. Excellent agreement for a variety of 2D woven Hi-Nicalon(TradeMark) fiber-reinforced and Sylramic-iBN reinforced CVI SiC matrix composites that differed in numbers of plies, constituent content, thickness, density, and number of woven tows in either direction (i.e, balanced weaves versus unbalanced weaves) was achieved. It was found that elastic modulus was not only dependent on constituent content, but also the degree to which 90deg minicomposites carried load. This depended on the degree of interaction between 90deg and 0deg minicomposites which was quantified to some extent by composite density. The relationships developed here for elastic modulus only necessitated the knowledge of the fractional contents of fiber, interphase and CVI SiC as well as the tow size and shape. It was concluded that such relationships are fairly robust for orthogonally loaded 2D woven CVI SiC composite system and can be implemented by ceramic matrix composite component modelers and designers for modeling the local stiffness in simple or complex parts fabricated with variable constituent contents.

  9. Additive Manufacturing of SiC Based Ceramics and Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Halbig, Michael Charles; Singh, Mrityunjay

    2015-01-01

    Silicon carbide (SiC) ceramics and SiC fiber reinforcedSiC ceramic matrix composites (SiCSiC CMCs) offer high payoff as replacements for metals in turbine engine applications due to their lighter weight, higher temperature capability, and lower cooling requirements. Additive manufacturing approaches can offer game changing technologies for the quick and low cost fabrication of parts with much greater design freedom and geometric complexity. Four approaches for developing these materials are presented. The first two utilize low cost 3D printers. The first uses pre-ceramic pastes developed as feed materials which are converted to SiC after firing. The second uses wood containing filament to print a carbonaceous preform which is infiltrated with a pre-ceramic polymer and converted to SiC. The other two approaches pursue the AM of CMCs. The first is binder jet SiC powder processing in collaboration with rp+m (Rapid Prototyping+Manufacturing). Processing optimization was pursued through SiC powder blending, infiltration with and without SiC nano powder loading, and integration of nanofibers into the powder bed. The second approach was laminated object manufacturing (LOM) in which fiber prepregs and laminates are cut to shape by a laser and stacked to form the desired part. Scanning electron microscopy was conducted on materials from all approaches with select approaches also characterized with XRD, TGA, and bend testing.

  10. Ab initio prediction of SiC nanotubes with negative strain energy

    SciTech Connect

    Alfieri, G.; Kimoto, T.

    2014-01-20

    Single-layer SiC nanotubes (SiCNTs) are known to be metastable structures that is why only nanotubular fibers or polygrained nanotubes have been obtained experimentally. In this study, we report on how hydrogen helps to overcome the metastability of SiCNTs. Starting from SiC graphitic sheets, we analyzed the impact of either partial or full hydrogenation on the electronic properties and structural stability of SiCNTs. It is shown that, in general, hydrogenation widens the band gap of both SiC graphitic sheets and nanotubes and, irrespective of the difference in chirality and diameter, leads to the formation of energetically stable SiCNTs.

  11. Tga Characteristic and Fabrication of Porous SiC Ceramics

    NASA Astrophysics Data System (ADS)

    Kim, Seong Hoon; Yoon, Han Ki; Kim, Seon Jin; Park, Yi Hyun

    The long-range aim of this research is to develop porous ceramics with high strength, excellent thermal resistance and chemical stability at high temperature in environmental industry. The Cf/SiC was made by hot pressing method with SiC powder whose particle size is 50nm and less on the average also Al2O3, Y2O3 and SiO2 as additive. The carbon fibers of oxidation property are investigated by TGA for finding out decarburization point. As a result, decarburization point selected the specific temperature of TGA curve and the Cf/SiC composites occurred perfectly decarburization at carbon fibers so the clearly porous SiC ceramics were formed many holes of 3-5µm diameters through length direction by its reaction.

  12. SiC Composite Turbine Vanes

    NASA Technical Reports Server (NTRS)

    Calomino, Anthony M.; Verilli, Michael J.

    2006-01-01

    Turbine inlet guide vanes have been fabricated from composites of silicon carbide fibers in silicon carbide matrices. A unique design for a cloth made from SiC fibers makes it possible to realize the geometric features necessary to form these vanes in the same airfoil shapes as those of prior metal vanes. The fiber component of each of these vanes was made from SiC-fiber cloth coated with boron nitride. The matrix was formed by chemical-vapor infiltration with SiC, then slurry-casting of SiC, followed by melt infiltration with silicon. These SiC/SiC vanes were found to be capable of withstanding temperatures 400 F (222 C) greater than those that can be withstood by nickel-base-superalloy turbine airfoils now in common use in gas turbine engines. The higher temperature capability of SiC/SiC parts is expected to make it possible to use them with significantly less cooling than is used for metallic parts, thereby enabling engines to operate more efficiently while emitting smaller amounts of NOx and CO. The SiC/SiC composite vanes were fabricated in two different configurations. Each vane of one of the configurations has two internal cavities formed by a web between the suction and the pressure sides of the vane. Each vane of the other configuration has no web (see Figure 1). It is difficult to fabricate components having small radii, like those of the trailing edges of these vanes, by use of stiff stoichiometric SiC fibers currently preferred for SiC/SiC composites. To satisfy the severe geometric and structural requirements for these vanes, the aforementioned unique cloth design, denoted by the term Y-cloth, was conceived (see Figure 2). In the regions away from the trailing edge, the Y-cloth features a fiber architecture that had been well characterized and successfully demonstrated in combustor liners. To form a sharp trailing edge (having a radius of 0.3 mm), the cloth was split into two planes during the weaving process. The fiber tows forming the trailing

  13. Industrial fiber beam delivery system for ultrafast lasers: applications and recent advances

    NASA Astrophysics Data System (ADS)

    Eilzer, Sebastian; Funck, Max C.; Wedel, Björn

    2016-03-01

    Fiber based laser beam delivery is the method of choice for high power laser applications whenever great flexibility is required. For cw-lasers fiber beam delivery has long been established but has recently also become available for ultrafast lasers. Using micro-structured hollow core fibers that guide the laser beam mostly inside a hollow core, nonlinear effects and catastrophic damage that arise in conventional glass fibers can be avoided. Today, ultrafast pulses with several 100 μJ and hundreds of MW can be transmitted in quasi single mode fashion. In addition, the technology opens new possibilities for beam delivery systems as the pulse propagation inside the fiber can be altered on purpose. For example to shorten the pulse duration of picosecond lasers down into the femtosecond regime. We present a modular fiber beam delivery system for micromachining applications with industrial pico- and femtosecond lasers that is flexibly integrated into existing applications. Micro-structured hollow core fibers inside the sealed laser light cable efficiently guide high-power laser pulses over distances of several meters with excellent beam quality, while power, pulse duration and polarization are maintained. Robust and stable beam transport during dynamic operation as in robot or gantry systems will be discussed together with optional pulse compression.

  14. Synthesis of high performance ceramic fibers by chemical vapor deposition for advanced metallics reinforcing

    NASA Technical Reports Server (NTRS)

    Revankar, Vithal; Hlavacek, Vladimir

    1991-01-01

    The chemical vapor deposition (CVD) synthesis of fibers capable of effectively reinforcing intermetallic matrices at elevated temperatures which can be used for potential applications in high temperature composite materials is described. This process was used due to its advantage over other fiber synthesis processes. It is extremely important to produce these fibers with good reproducible and controlled growth rates. However, the complex interplay of mass and energy transfer, blended with the fluid dynamics makes this a formidable task. The design and development of CVD reactor assembly and system to synthesize TiB2, CrB, B4C, and TiC fibers was performed. Residual thermal analysis for estimating stresses arising form thermal expansion mismatch were determined. Various techniques to improve the mechanical properties were also performed. Various techniques for improving the fiber properties were elaborated. The crystal structure and its orientation for TiB2 fiber is discussed. An overall view of the CVD process to develop CrB2, TiB2, and other high performance ceramic fibers is presented.

  15. High-power fused assemblies enabled by advances in fiber-processing technologies

    NASA Astrophysics Data System (ADS)

    Wiley, Robert; Clark, Brett

    2011-02-01

    The power handling capabilities of fiber lasers are limited by the technologies available to fabricate and assemble the key optical system components. Previous tools for the assembly, tapering, and fusion of fiber laser elements have had drawbacks with regard to temperature range, alignment capability, assembly flexibility and surface contamination. To provide expanded capabilities for fiber laser assembly, a wide-area electrical plasma heat source was used in conjunction with an optimized image analysis method and a flexible alignment system, integrated according to mechatronic principles. High-resolution imaging and vision-based measurement provided feedback to adjust assembly, fusion, and tapering process parameters. The system was used to perform assembly steps including dissimilar-fiber splicing, tapering, bundling, capillary bundling, and fusion of fibers to bulk optic devices up to several mm in diameter. A wide range of fiber types and diameters were tested, including extremely large diameters and photonic crystal fibers. The assemblies were evaluated for conformation to optical and mechanical design criteria, such as taper geometry and splice loss. The completed assemblies met the performance targets and exhibited reduced surface contamination compared to assemblies prepared on previously existing equipment. The imaging system and image analysis algorithms provided in situ fiber geometry measurement data that agreed well with external measurement. The ability to adjust operating parameters dynamically based on imaging was shown to provide substantial performance benefits, particularly in the tapering of fibers and bundles. The integrated design approach was shown to provide sufficient flexibility to perform all required operations with a minimum of reconfiguration.

  16. [Research advances of retinal nerve fiber layer thickness and its association with myopia].

    PubMed

    Kang, M T; Ran, A R; Wang, N L; Li, S M

    2016-05-11

    Recently, the distribution characteristics of retinal nerve fiber layer thickness in myopic population have raised scholars' attention. The retinal nerve fiber layer thickness is varied with different refractive statuses, and is correlated to many factors like age, eye elongation, and fundus changes. Further exploration of the relationship between myopia and retinal structure and function will promote our understanding and knowledge of the pathogenesis of myopia. The article reviews the structure characteristics of the retinal nerve fiber layer, its associations with demographic characteristics, its characteristics in myopia, and the structural-functional relationship.(Chin J Ophthalmol, 2016, 52: 396-400). PMID:27220715

  17. Fiber-optic Raman spectroscopy for cure monitoring of advanced polymer composites

    SciTech Connect

    Myrick, M.L.; Angel, S.M.; Lyon, R.E.; Vess, T.M.

    1991-12-16

    The curing reaction of an epoxy matrix used for wet filament-wound composites was monitored using Raman spectroscopy measured over fiber optics. The resin system consists of the diglycidyl ether of bisphenol-A in combination with a polyethertriamine hardener in a 1:1 stoichiometric ratio. The extent of chemical reaction of the epoxy as a function of time was measurable through changes in peak heights of several vibrational modes. A Raman peak associated with a phenyl ring vibration in epoxide component was used as in internal reference to correct for density changes and instrumental variations. Temperature measurements were made over the same fiber optics used to obtain the cure chemistry data by measuring the intensity of anti-Stokes Raman scattering from the epoxy. Both single-fiber and dual-fiber probes were evaluated.

  18. Heatshield material selection for advanced ballistic reentry vehicles. [rayon fiber cloth impregnated with phenolic resin

    NASA Technical Reports Server (NTRS)

    Legendre, P. J.; Holtz, T.; Sikra, J. C.

    1980-01-01

    The Performance of staple rayon fiber and AVTEX continuous rayon fiber was evaluated as precursor materials for heatshields. The materials studied were referenced to the IRC FM5055A heatshield materials flown during the past decade. Three different arc jet facilities were used to simulate portions of the reentry environment. The IRC FM5055A and the AVTEX FM5055G, both continuous rayon fiber woven materials having the phenolic impregnant filled with carbon particles were compared. The AVTEX continuous fiber, unfilled material FM5822A was also examined to a limited extent. Test results show that the AVTEX FM5055G material provided a close substitute for the IRC FM5055A material both in terms of thermal protection and roll torque performance.

  19. Basic failure mechanisms in advanced composites. [composed of epoxy resins reinforced with carbon fibers

    NASA Technical Reports Server (NTRS)

    Mazzio, V. F.; Mehan, R. L.; Mullin, J. V.

    1973-01-01

    The fundamental failure mechanisms which result from the interaction of thermal cycling and mechanical loading of carbon-epoxy composites were studied. This work was confined to epoxy resin uniderictionally reinforced with HTS carbon fibers, and consists of first identifying local fiber, matrix and interface failure mechanisms using the model composite specimen containing a small number of fibers so that optical techniques can be used for characterization. After the local fracture process has been established for both mechanical loading and thermal cycling, engineering composite properties and gross fracture modes are then examined to determine how the local events contribute to real composite performance. Flexural strength in high fiber content specimens shows an increase in strength with increased thermal cycling. Similar behavior is noted for 25 v/o material up to 200 cycles; however, there is a drastic reduction after 200 cycles indicating a major loss of integrity probably through the accumulation of local cleavage cracks in the tensile region.

  20. Assessment of Japanese technology in advanced glass and ceramic fibers. Final report

    SciTech Connect

    Messier, D.R.

    1992-06-01

    Summarized herein are the findings from a two month trip to Japan from mid-September to mid-November 1991 to evaluate Japanese technology in oxynitride glasses and fibers and in carbide and nitride fibers and whiskers. The information discussed was obtained through visits to universities, companies, Government institutes, and through attendance at three conferences. It was learned that the development of a process for the production of oxynitride glass fibers is still being actively pursued and that, while high temperature instability problems are well-recognized, the production of carbide or nitride fibers with good high temperature stability is still several years away. Also discussed are new developments in several research areas including ceramic matrix composites, sol-gel technology, ceramic powder preparation, and high strength ceramics.

  1. Development of fiber optic sensors for advanced aircraft testing and control

    NASA Astrophysics Data System (ADS)

    Meller, Scott A.; Jones, Mark E.; Wavering, Thomas A.; Kozikowski, Carrie L.; Murphy, Kent A.

    1999-02-01

    Optical fiber sensors, because of the small size, low weight, extremely high information carrying capability, immunity to electromagnetic interference, and large operational temperature range, provide numerous advantages over conventional electrically based sensors. This paper presents preliminary results from optical fiber sensor design for monitoring acceleration on aircraft. Flight testing of the final accelerometer design will be conducted on the F-18 Systems Research Aircraft at NASA Dryden Flight Research Center in Edwards, CA.

  2. Advanced Measurements of Silicon Carbide Ceramic Matrix Composites

    SciTech Connect

    Farhad Farzbod; Stephen J. Reese; Zilong Hua; Marat Khafizov; David H. Hurley

    2012-08-01

    Silicon carbide (SiC) is being considered as a fuel cladding material for accident tolerant fuel under the Light Water Reactor Sustainability (LWRS) Program sponsored by the Nuclear Energy Division of the Department of Energy. Silicon carbide has many potential advantages over traditional zirconium based cladding systems. These include high melting point, low susceptibility to corrosion, and low degradation of mechanical properties under neutron irradiation. In addition, ceramic matrix composites (CMCs) made from SiC have high mechanical toughness enabling these materials to withstand thermal and mechanical shock loading. However, many of the fundamental mechanical and thermal properties of SiC CMCs depend strongly on the fabrication process. As a result, extrapolating current materials science databases for these materials to nuclear applications is not possible. The “Advanced Measurements” work package under the LWRS fuels pathway is tasked with the development of measurement techniques that can characterize fundamental thermal and mechanical properties of SiC CMCs. An emphasis is being placed on development of characterization tools that can used for examination of fresh as well as irradiated samples. The work discuss in this report can be divided into two broad categories. The first involves the development of laser ultrasonic techniques to measure the elastic and yield properties and the second involves the development of laser-based techniques to measurement thermal transport properties. Emphasis has been placed on understanding the anisotropic and heterogeneous nature of SiC CMCs in regards to thermal and mechanical properties. The material properties characterized within this work package will be used as validation of advanced materials physics models of SiC CMCs developed under the LWRS fuels pathway. In addition, it is envisioned that similar measurement techniques can be used to provide process control and quality assurance as well as measurement of

  3. CONTACT RESISTANCE AT A CVD-SIC/NI INTERFACE

    SciTech Connect

    Youngblood, Gerald E.; Thomsen, Edwin C.

    2011-04-17

    The primary objectives of this task are: (1) to assess the properties and behavior of SiCf/SiC composites made from SiC fibers (with various SiC-type matrices, fiber coatings and architectures) before and after irradiation, and (2) to develop analytic models that describe these properties as a function of temperature and dose as well as composite architecture. In support of the U.S. dual-coolant lead-lithium (DCLL) fusion reactor blanket concept, recent efforts have focused on examining the electrical conductivity properties of SiCf/SiC composites considered for application in FCI-structures.

  4. Coatings for Graphite Fibers

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Scola, D. A.; Veltri, R. D.

    1980-01-01

    Several approaches for applying high resistance coatings continuously to graphite yarn were investigated. Two of the most promising approaches involved (1) chemically vapor depositing (CVD) SiC coatings on the surface of the fiber followed by oxidation, and (2) drawing the graphite yarn through an organo-silicone solution followed by heat treatments. In both methods, coated fibers were obtained which exhibited increased electrical resistances over untreated fibers and which were not degraded. This work was conducted in a previous program. In this program, the continuous CVD SiC coating process used on HTS fiber was extended to the coating of HMS, Celion 6000, Celion 12000 and T-300 graphite fiber. Electrical resistances three order of magnitude greater than the uncoated fiber were measured with no significant degradation of the fiber strength. Graphite fibers coated with CVD Si3N4 and BN had resistances greater than 10(exp 6) ohm/cm. Lower pyrolysis temperatures were used in preparing the silica-like coatings also resulting in resistances as high as three orders of magnitude higher than the uncoated fiber. The epoxy matrix composites prepared using these coated fibers had low shear strengths indicating that the coatings were weak.

  5. Thermophysical and mechanical properties of near-stoichiometric fiber CVI SiC/SiC composites after neutron irradiation at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Katoh, Yutai; Snead, Lance L.; Nozawa, Takashi; Kondo, Sosuke; Busby, Jeremy T.

    2010-08-01

    Thermophysical and mechanical properties of high purity chemically vapor-deposited (CVD) SiC and chemically vapor-infiltrated SiC matrix, pyrocarbon/SiC multilayered interphase composites with Hi-Nicalon™ Type-S and Tyranno™-SA3 SiC fibers were evaluated following neutron irradiation. Specimens including statistically significant population of tensile bars were irradiated up to 5.3 displacement-per-atom at ˜220 to ˜1080 °C in the Advanced Test Reactor at Idaho National Laboratory and High Flux Isotope Reactor at Oak Ridge National Laboratory. Thermal diffusivity/conductivity of all materials decreased during irradiation. The reciprocal thermal diffusivity linearly increased with temperature from ambient to the irradiation temperature. The magnitude of defect thermal resistance was distinctively different among materials and its ranking was Hi-Nicalon™ Type-S > Tyranno™-SA3 > CVD SiC regardless of irradiation condition. Dynamic Young's modulus decrease for the irradiated CVD SiC exhibited explicit correlation with swelling. No significant effects of neutron irradiation on tensile properties of the composites were revealed, except for an anomaly case for the Hi-Nicalon™ Type-S composite irradiated in a specific condition. According to the single filament tensile evaluation, fibers of both types retained the original strength during irradiation at intermediate temperatures but significantly deteriorated during bare fiber irradiation at ˜910 °C. However, fiber strength deterioration was not observed when irradiated in composite form. Irradiation effects on the fiber-matrix interface properties were discussed based on results from the composite and single filament tensile tests, the hysteresis analysis, and the fracture surface examination.

  6. X-ray fluorescence microtomography of SiC shells

    SciTech Connect

    Ice, G.E.; Chung, J.S.; Nagedolfeizi, M.

    1997-04-01

    TRISCO coated fuel particles contain a small kernel of nuclear fuel encapsulated by alternating layers of C and SiC. The TRISCO coated fuel particle is used in an advanced fuel designed for passive containment of the radioactive isotopes. The SiC layer provides the primary barrier for radioactive elements in the kernel. The effectiveness of this barrier layer under adverse conditions is critical to containment. The authors have begun the study of SiC shells from TRISCO fuel. They are using the fluorescent microprobe beamline 10.3.1. The shells under evaluation include some which have been cycled through a simulated core melt-down. The C buffer layers and nuclear kernels of the coated fuel have been removed by laser drilling through the SiC and then exposing the particle to acid. Elements of interest include Ru, Sb, Cs, Ce and Eu. The radial distribution of these elements in the SiC shells can be attributed to diffusion of elements in the kernel during the melt-down. Other elements in the shells originate during the fabrication of the TRISCO particles.

  7. Fatigue behavior of SiC reinforced titanium composites

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.; Grimes, H. H.

    1979-01-01

    The low cycle axial fatigue properties of 25 and 44 fiber volume percent SiC/Ti(6Al-4V) composites were measured at room temperature and at 650 deg C. The S-N curves for the composites showed no anticipated improvement over bulk matrix behavior at room temperature. Although axial and transverse tensile strength results suggest a degradation in SiC fiber strength during composite fabrication, it appears that the poor fatigue life of the composites was caused by a reduced fatigue resistance of the reinforced Ti(6Al-4V) matrix. The reduced matrix behavior was due, to the presence of flawed and fractured fibers created near the specimen surfaces by preparation techniques and to the large residual tensile stresses that can exist in fiber reinforced matrices. The effects of fatigue testing at high temperature are discussed.

  8. Fatigue behavior of SiC reinforced titanium composites

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.; Grimes, H. H.

    1979-01-01

    The low cycle axial fatigue properties of 25 and 44 fiber volume percent SiC/Ti(6Al-4V) composites were measured at room temperature and at 650 C. At room temperature, the S-N curves for the composites showed no anticipated improvement over bulk matrix behavior. Although axial and transverse tensile strength results suggest a degradation in SiC fiber strength during composite fabrication, it appears that the poor fatigue life of the composites was caused by a reduced fatigue resistance of the reinforced Ti(6Al-4V) matrix. Microstructural studies indicate that the reduced matrix behavior was due, in part, to the presence of flawed and fractured fibers created near the specimen surfaces by preparation techniques. Another possible contributing factor is the large residual tensile stresses that can exist in fiber-reinforced matrices. These effects, as well as the effects of fatigue testing at high temperature, are discussed.

  9. Advances in high-power 9XXnm laser diodes for pumping fiber lasers

    NASA Astrophysics Data System (ADS)

    Skidmore, Jay; Peters, Matthew; Rossin, Victor; Guo, James; Xiao, Yan; Cheng, Jane; Shieh, Allen; Srinivasan, Raman; Singh, Jaspreet; Wei, Cailin; Duesterberg, Richard; Morehead, James J.; Zucker, Erik

    2016-03-01

    A multi-mode 9XXnm-wavelength laser diode was developed to optimize the divergence angle and reliable ex-facet power. Lasers diodes were assembled into a multi-emitter pump package that is fiber coupled via spatial and polarization multiplexing. The pump package has a 135μm diameter output fiber that leverages the same optical train and mechanical design qualified previously. Up to ~ 270W CW power at 22A is achieved at a case temperature ~ 30ºC. Power conversion efficiency is 60% (peak) that drops to 53% at 22A with little thermal roll over. Greater than 90% of the light is collected at < 0.12NA at 16A drive current that produces 3.0W/(mm-mr)2 radiance from the output fiber.

  10. Advanced Interrogation of Fiber-Optic Bragg Grating and Fabry-Perot Sensors with KLT Analysis

    PubMed Central

    Tosi, Daniele

    2015-01-01

    The Karhunen-Loeve Transform (KLT) is applied to accurate detection of optical fiber sensors in the spectral domain. By processing an optical spectrum, although coarsely sampled, through the KLT, and subsequently processing the obtained eigenvalues, it is possible to decode a plurality of optical sensor results. The KLT returns higher accuracy than other demodulation techniques, despite coarse sampling, and exhibits higher resilience to noise. Three case studies of KLT-based processing are presented, representing most of the current challenges in optical fiber sensing: (1) demodulation of individual sensors, such as Fiber Bragg Gratings (FBGs) and Fabry-Perot Interferometers (FPIs); (2) demodulation of dual (FBG/FPI) sensors; (3) application of reverse KLT to isolate different sensors operating on the same spectrum. A simulative outline is provided to demonstrate the KLT operation and estimate performance; a brief experimental section is also provided to validate accurate FBG and FPI decoding. PMID:26528975

  11. Advanced Interrogation of Fiber-Optic Bragg Grating and Fabry-Perot Sensors with KLT Analysis.

    PubMed

    Tosi, Daniele

    2015-01-01

    The Karhunen-Loeve Transform (KLT) is applied to accurate detection of optical fiber sensors in the spectral domain. By processing an optical spectrum, although coarsely sampled, through the KLT, and subsequently processing the obtained eigenvalues, it is possible to decode a plurality of optical sensor results. The KLT returns higher accuracy than other demodulation techniques, despite coarse sampling, and exhibits higher resilience to noise. Three case studies of KLT-based processing are presented, representing most of the current challenges in optical fiber sensing: (1) demodulation of individual sensors, such as Fiber Bragg Gratings (FBGs) and Fabry-Perot Interferometers (FPIs); (2) demodulation of dual (FBG/FPI) sensors; (3) application of reverse KLT to isolate different sensors operating on the same spectrum. A simulative outline is provided to demonstrate the KLT operation and estimate performance; a brief experimental section is also provided to validate accurate FBG and FPI decoding. PMID:26528975

  12. Recent advances in very highly nonlinear chalcogenide photonic crystal fibers and their applications

    NASA Astrophysics Data System (ADS)

    Méchin, David; Brilland, Laurent; Troles, Johann; Chartier, Thierry; Besnard, Pascal; Canat, Guillaume; Renversez, Gilles

    2012-02-01

    Perfos and the laboratory Glasses and Ceramics Group of University of Rennes 1 have worked together to develop a new fabrication technique for chalcogenide preforms based on the glass-casting process. Various fiber profiles have been designed by the Fresnel Institute and fiber losses have been significantly improved, approaching those of the material losses. Using this technology, we have manufactured an AsSe CPCF exhibiting a nonlinear coefficient γ of 46 000 W-1km-1. Self-phase modulation, Raman effect, Brillouin effect, Four-Wave Mixing have been observed leading to the demonstration of various optical functions such four-wave mixing based wavelength conversion at 1.55 μm by FOTON, the demonstration of Raman Shifts and the generation of a mid-IR supercontinuum source by ONERA and the demonstration of a Brillouin fiber laser by FOTON.

  13. Prismatic sealed nickel-cadmium batteries utilizing fiber structured electrodes. I - New advances in cell design

    NASA Astrophysics Data System (ADS)

    Haschka, Friedrich; Benczur-Urmossy, Gabor; Anderman, Menahem

    Prismatic sealed Ni/Cd cells of fiber structured electrodes offer the potential to fully recharge a battery in a uniquely short time. It was demonstrated that the cells show excellent cycle life. The design is not restricted to 20 Ah rated capacity. Cells of 50 Ah have been built and tested in an electric hybrid vehicle. A specially designed ultra high-power cell of 45 Ah rated capacity for APU cranking in commerical aircraft supplies 50 percent more peak power than vented Ni/Cd sintered plate aircraft cells. The fiber structured sealed FNC-RECOM cell will not require any maintenance.

  14. Advanced Fiber-optic Monitoring System for Space-flight Applications

    NASA Technical Reports Server (NTRS)

    Hull, M. S.; VanTassell, R. L.; Pennington, C. D.; Roman, M.

    2005-01-01

    Researchers at Luna Innovations Inc. and the National Aeronautic and Space Administration s Marshall Space Flight Center (NASA MSFC) have developed an integrated fiber-optic sensor system for real-time monitoring of chemical contaminants and whole-cell bacterial pathogens in water. The system integrates interferometric and evanescent-wave optical fiber-based sensing methodologies with atomic force microscopy (AFM) and long-period grating (LPG) technology to provide versatile measurement capability for both micro- and nano-scale analytes. Sensors can be multiplexed in an array format and embedded in a totally self-contained laboratory card for use with an automated microfluidics platform.

  15. Nanocrystalline SiC and Ti3SiC2 Alloys for Reactor Materials: Thermal and Mechanical Properties

    SciTech Connect

    Henager, Charles H.; Alvine, Kyle J.; Roosendaal, Timothy J.; Shin, Yongsoon; Nguyen, Ba Nghiep; Borlaug, Brennan A.; Jiang, Weilin

    2014-04-01

    SiC-polymers (pure polycarbosilane and polycarbosilane filled with SiC-particles) are being combined with Si and TiC powders to create a new class of polymer-derived ceramics for consideration as advanced nuclear materials in a variety of applications. Compared to pure SiC these materials have increased fracture toughness with only slightly reduced thermal conductivity. Future work with carbon nanotube (CNT) mats will be introduced with the potential to increase the thermal conductivity and the fracture toughness. At present, this report documents the fabrication of a new class of monolithic polymer derived ceramics, SiC + SiC/Ti3SiC2 dual phase materials. The fracture toughness of the dual phase material was measured to be significantly greater than Hexoloy SiC using indentation fracture toughness testing. However, thermal conductivity of the dual phase material was reduced compared to Hexoloy SiC, but was still appreciable, with conductivities in the range of 40 to 60 W/(m K). This report includes synthesis details, optical and scanning electron microscopy images, compositional data, fracture toughness, and thermal conductivity data.

  16. Distributed Brillouin fiber optic strain monitoring applications in advanced composite materials

    NASA Astrophysics Data System (ADS)

    Bastianini, Filippo; Cargnelutti, Mario; Di Tommaso, Angelo; Toffanin, Massimo

    2003-08-01

    Composite materials based on glass, carbon and aramid fibers have many advantages such as fast application, lightweight and corrosion resistance, and are widely diffused for manufacturing of tanks, pipings and for restoration, upgrade and seismic retrofit of structures and historical heritage. As several questions regarding long term durability of composite strengthenings remains still unsolved, monitoring of strain and temperature is strongly recommended, respectively to assess proper load transfer and no glass phase transition of the polymeric matrix. In this research work strain and temperature distributed sensing trough Brillouin scattering in single-mode optical fibers was used in different tests in order to understand the influence of different fiber coatings and embedding techniques. Pressure tests were performed on a GFRP piping with inhomogeneous strengthening layout and Brillouin strain data were compared with conventional strain gages. A smart CFRP material has been also developed and evaluated in a seismic retrofit application on an historical building dated 1500 that was seriously damaged in the earthquake of 1997. The developed embedding technique has been demonstrated successful to obtain fiber-optic smart composites with low optical losses, and the data comparison between Brillouin and resistive strain gauges confirms Brillouin technique is very effective for composite monitoring.

  17. Recent advances in electron-beam curing of carbon fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Coqueret, Xavier; Krzeminski, Mickael; Ponsaud, Philippe; Defoort, Brigitte

    2009-07-01

    Cross-linking polymerization initiated by high-energy radiation is a very attractive technique for the fabrication of high-performance composite materials. The method offers many advantages compared to conventional energy- and time-consuming thermal curing processes. Free radical and cationic poly-addition chemistries have been investigated in some details by various research groups along the previous years. A high degree of control over curing kinetics and material properties can be exerted by adjusting the composition of matrix precursors as well as by acting on process parameters. However, the comparison with state-of-the-art thermally cured composites revealed the lower transverse mechanical properties of radiation-cured composites and the higher brittleness of the radiation-cured matrix. Improving fiber-matrix adhesion and upgrading polymer network toughness are thus two major challenges in this area. We have investigated several points related to these issues, and particularly the reduction of the matrix shrinkage on curing, the wettability of carbon fibers, the design of fiber-matrix interface and the use of thermoplastic toughening agents. Significant improvements were achieved on transverse strain at break by applying original surface treatments on the fibers so as to induce covalent coupling with the matrix. A drastic enhancement of the K IC value exceeding 2 MPa m 1/2 was also obtained for acrylate-based matrices toughened with high T g thermoplastics.

  18. Advanced development of the Nested Fiber Filter: Phase 1, Evaluation of cleaning methods. Final report

    SciTech Connect

    Litt, R.D.; Conkle, H.N.; Glover, R.C.; Jordan, H.

    1990-08-01

    Battelle has completed Phase I of the DOE program to evaluate cleaning methods for the Nested Fiber Filter (NFF). The results of the investigations into fly ash bonding mechanisms, and mechanical vibration and acoustic vibration techniques led to the conclusion that acoustic cleaning with a pulse combustor is the preferred integrated system for high-temperature, high-pressure applications.

  19. Advanced development of the Nested Fiber Filter: Phase 1, Evaluation of cleaning methods

    SciTech Connect

    Litt, R.D.; Conkle, H.N.; Glover, R.C.; Jordan, H.

    1990-08-01

    Battelle has completed Phase I of the DOE program to evaluate cleaning methods for the Nested Fiber Filter (NFF). The results of the investigations into fly ash bonding mechanisms, and mechanical vibration and acoustic vibration techniques led to the conclusion that acoustic cleaning with a pulse combustor is the preferred integrated system for high-temperature, high-pressure applications.

  20. Advances towards the qualification of an aircraft fuel tank inert environment fiber optic oxygen sensor system

    NASA Astrophysics Data System (ADS)

    Mendoza, Edgar A.; Esterkin, Yan; Kempen, Cornelia; Sun, Songjian; Susko, Kenneth; Goglia, John

    2011-06-01

    An all optical pressure and temperature compensated fiber optic oxygen sensor (FOxSenseTM) system is under qualification for use in the in-situ closed-loop-control of the inert atmosphere environment inside fuel tanks of military and commercial aircraft. The all-optical oxygen environment control sensor is a passive, intrinsically safe, fiber-optic sensor device with no electrical connections leading to the sensors installed within the fuel tanks of an aircraft. To control the fuel tank environment, an array of multiple sensors is deployed throughout the fuel tanks of an aircraft, and a remote multi-channel optoelectronic system is used to monitor the status of all the sensors in real time to provide feedback oxygen environment information to the on-board inert gas generating system (OBIGS). Qualification testing of the all optical sensor have demonstrated the ability to monitor the oxygen environment inside a simulated fuel tank environment in the oxygen range from 0% to 21% oxygen concentrations, temperatures from (-) 40°C to (+) 60°C, and altitudes from sea level to 40,000 feet. Fiber optic oxygen sensors with built-in temperature compensation as well as the conduit fiber optic cables have passed DO-160E including acoustic noise and burn test.

  1. Advanced Fiber Optic-Based Sensing Technology for Unmanned Aircraft Systems

    NASA Technical Reports Server (NTRS)

    Richards, Lance; Parker, Allen R.; Piazza, Anthony; Ko, William L.; Chan, Patrick; Bakalyar, John

    2011-01-01

    This presentation provides an overview of fiber optic sensing technology development activities performed at NASA Dryden in support of Unmanned Aircraft Systems. Examples of current and previous work are presented in the following categories: algorithm development, system development, instrumentation installation, ground R&D, and flight testing. Examples of current research and development activities are provided.

  2. Advanced fiber information systems seed coat neps baseline response from diverse mediums

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An extensive literature search has revealed that no papers have been published regarding selectivity calculation of the AFIS seed coat neps (SCN) determination over interfering material in cotton. A prerequisite to selectivity measurements is to identify suitable fiber medium(s) that give baseline ...

  3. Polymer-Derived Ceramic Fibers

    NASA Astrophysics Data System (ADS)

    Ichikawa, Hiroshi

    2016-07-01

    SiC-based ceramic fibers are derived from polycarbosilane or polymetallocarbosilane precursors and are classified into three groups according to their chemical composition, oxygen content, and C/Si atomic ratio. The first-generation fibers are Si-C-O (Nicalon) fibers and Si-Ti-C-O (Tyranno Lox M) fibers. Both fibers contain more than 10-wt% oxygen owing to oxidation during curing and lead to degradation in strength at temperatures exceeding 1,300°C. The maximum use temperature is 1,100°C. The second-generation fibers are SiC (Hi-Nicalon) fibers and Si-Zr-C-O (Tyranno ZMI) fibers. The oxygen content of these fibers is reduced to less than 1 wt% by electron beam irradiation curing in He. The thermal stability of these fibers is improved (they are stable up to 1,500°C), but their creep resistance is limited to a maximum of 1,150°C because their C/Si atomic ratio results in excess carbon. The third-generation fibers are stoichiometric SiC fibers, i.e., Hi-Nicalon Type S (hereafter Type S), Tyranno SA, and Sylramic™ fibers. They exhibit improved thermal stability and creep resistance up to 1,400°C. Stoichiometric SiC fibers meet many of the requirements for the use of ceramic matrix composites for high-temperature structural application. SiBN3C fibers derived from polyborosilazane also show promise for structural applications, remain in the amorphous state up to 1,800°C, and have good high-temperature creep resistance.

  4. Advanced Lithium Battery Cathodes Using Dispersed Carbon Fibers as the Current Collector

    SciTech Connect

    Martha, Surendra K; Kiggans, Jim; Nanda, Jagjit; Dudney, Nancy J

    2011-01-01

    To fabricate LiFePO4 battery cathodes, highly conductive carbon fibers of 10-20 m in diameter have been used to replace a conventional aluminum (Al) foil current collector. This disperses the current collector throughout the cathode sheet and increases the contact area with the LiFePO4 (LFP) particles. In addition, the usual organic binder plus carbon-black can be replaced by a high temperature binder of <5 weight % carbonized petroleum pitch (P-pitch). Together these replacements increase the specific energy density and energy per unit area of the electrode. Details of the coating procedure, characterization and approach for maximizing the energy density are discussed. In a side-by-side comparison with conventional cathodes sheets of LFP on Al foil, the carbon fiber composite cathodes have a longer cycle life, higher thermal stability, and high capacity utilization with little sacrifice of the rate performance.

  5. Potential for integrated optical circuits in advanced aircraft with fiber optic control and monitoring systems

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert

    1991-01-01

    The current Fiber Optic Control System Integration (FOCSI) program is reviewed and the potential role of IOCs in FOCSI applications is described. The program is intended for building, environmentally testing, and demonstrating operation in piggyback flight tests (no active control with optical sensors) of a representative sensor system for propulsion and flight control. The optical sensor systems are to be designed to fit alongside the bill-of-materials sensors for comparison. The sensors are to be connected to electrooptic architecture cards which will contain the optical sources and detectors to recover and process the modulated optical signals. The FOCSI program is to collect data on the behavior of passive optical sensor systems in a flight environment and provide valuable information on installation amd maintenance problems for this technology, as well as component survivability (light sources, connectors, optical fibers, etc.).

  6. Experimentation and analysis of mechanical behavior modification of titanium matrix composites through controlled fiber placement

    NASA Astrophysics Data System (ADS)

    Bowman, Cheryl Lynne

    Titanium composites reinforced with SiC fibers in a uniaxial direction are being considered for various high temperature applications which require high specific strength or stiffness in the primary loading direction. However the very low tensile and creep strength of these composites in the transverse direction (loading perpendicular to the fiber axis) limits their use in many practical applications. Recent advances in composite fabrication techniques have provided not only better control of fiber volume fraction and distribution, but also the ability to control the relative fiber placement. The goal of this research was produce continuously reinforced SiC/Ti composites with precise fiber arrangement in order to ascertain the significance of fiber arrangements on transverse mechanical properties. In this study, TIMETAL 21S and Ti-6-4 composites reinforced with SCS-6 SiC fibers were produced with six distinct fiber placement arrangements. The effect of fiber placement on uniaxial tensile and creep behaviors was assessed and the results compared to analytical predictions. Consistent with analytical predictions, the fiber arrangements used in this study did not significantly change the longitudinal tensile behavior, but differences were obtained in the transverse loading response. For example, a diamond (non-equilateral triangle) fiber packing was found to have a higher transverse ultimate tensile strength and better transverse creep resistance than a rectangular fiber packing arrangement for a given volume fraction and fiber spacing (within-ply vs. between-ply). Initially this result appeared to be in contrast to previous computational and analytical simulations which predicted more favorable mechanical behavior for rectangular-type arrangements. However, this experimental/predictive conflict was resolved, in part, by simply defining a fiber spacing ratio which could describe both rectangular type and diamond-type arrangements. The computationally efficient

  7. 29 CFR 510.21 - SIC codes.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR... in that census are organized by Standard Industrial Classification (SIC), the statistical... (SIC) code level.” (b) The Standard Industrial Classification (SIC) codes listed in appendix A and...

  8. Properties of SiC-SiC composites produced using CVR converted graphite cloth to SiC cloth

    SciTech Connect

    Kowbel, W.; Kyriacou, C.; Gao, F.; Bruce, C.A.; Withers, J.C.

    1995-10-01

    Nicalon fiber is the primary reinforcement in SiC-SiC composites currently produced by a variety of techniques including CVI and polymer infiltration. Low strength retention at high temperatures of the Nicalon fibers limits the choice of manufacturing processes which can be employed to produce low cost SiC-SiC composites. MER has developed a new SiC reinforcement based upon a conversion of low cost carbon fabric to SiC via a Chemical Vapor Reaction (CVR) process. This new SiC filaments exhibit an excellent creep resistance at temperatures up to 1,600 C. Several SiC-SiC composites were fabricated using graphite fabric converted to SiC fabric utilizing the CVR process combined with a slurry infiltration and CVI densification. A correlation between processing conditions, microstructure and properties of the SiC-SiC composites are discussed in detail.

  9. Enhanced thermal conductivity of CVD SiC via beryllium and boron dopings

    SciTech Connect

    Kowbel, W.; Gao, F.; Withers, J.C.

    1995-10-01

    SiC-SiC composites exhibit excellent mechanical and corrosion properties, which are desired for a variety of advanced applications including fusion reactors, heat exchangers and advanced turbine engines. However, SiC-SiC composites fabricated by the CVI methods have unacceptably low through-the-thickness thermal conductivity, which limits their use in these applications. CVD SiC co-deposition with either beryllium or boron compounds significantly enhanced the thermal conductivity of CVD SiC at temperatures up to 1,000 C. Results pertinent to the doping processes and the measured thermal conductivity of doped CVD SiC are reported. Mechanisms for the enhanced thermal conductivity of the CVD SiC are discussed based on the microstructural characteristics of the doped specimens.

  10. Combined-load stress-strain relationship for advanced fiber composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sullivan, T. L.

    1975-01-01

    It was demonstrated experimentally that only one test specimen is required to determine the combined-load stress-strain relationships of a given fiber composite system. These relationships were determined using a thin angle-plied laminate tube and subjecting it to a number of combined-loading conditions. The measured data obtained are compared with theoretical predictions. Some important considerations associated with such a test are identified, and the significance of combined-load stress-strain relationships in certain practical designs are discussed.

  11. Infiltration/cure modeling of resin transfer molded composite materials using advanced fiber architectures

    NASA Technical Reports Server (NTRS)

    Loos, Alfred C.; Weideman, Mark H.; Long, Edward R., Jr.; Kranbuehl, David E.; Kinsley, Philip J.; Hart, Sean M.

    1991-01-01

    A model was developed which can be used to simulate infiltration and cure of textile composites by resin transfer molding. Fabric preforms were resin infiltrated and cured using model generated optimized one-step infiltration/cure protocols. Frequency dependent electromagnetic sensing (FDEMS) was used to monitor in situ resin infiltration and cure during processing. FDEMS measurements of infiltration time, resin viscosity, and resin degree of cure agreed well with values predicted by the simulation model. Textile composites fabricated using a one-step infiltration/cure procedure were uniformly resin impregnated and void free. Fiber volume fraction measurements by the resin digestion method compared well with values predicted using the model.

  12. Optical fiber evanescent wave adsorption sensors for high-temperature gas sensing in advanced coal-fired power plants

    SciTech Connect

    Buric, M.; Ohodnicky, P.; Duy, J.

    2012-01-01

    Modern advanced energy systems such as coal-fired power plants, gasifiers, or similar infrastructure present some of the most challenging harsh environments for sensors. The power industry would benefit from new, ultra-high temperature devices capable of surviving in hot and corrosive environments for embedded sensing at the highest value locations. For these applications, we are currently exploring optical fiber evanescent wave absorption spectroscopy (EWAS) based sensors consisting of high temperature core materials integrated with novel high temperature gas sensitive cladding materials. Mathematical simulations can be used to assist in sensor development efforts, and we describe a simulation code that assumes a single thick cladding layer with gas sensitive optical constants. Recent work has demonstrated that Au nanoparticle-incorporated metal oxides show a potentially useful response for high temperature optical gas sensing applications through the sensitivity of the localized surface plasmon resonance absorption peak to ambient atmospheric conditions. Hence, the simulation code has been applied to understand how such a response can be exploited in an optical fiber based EWAS sensor configuration. We demonstrate that interrogation can be used to optimize the sensing response in such materials.

  13. Plasma and laser kinetics and field emission from carbon nanotube fibers for an Advanced Noble Gas Laser (ANGL)

    NASA Astrophysics Data System (ADS)

    Moran, Paul J.; Lockwood, Nathaniel P.; Lange, Matthew A.; Hostutler, David A.; Guild, Eric M.; Guy, Matthew R.; McCord, John E.; Pitz, Greg A.

    2016-03-01

    A metastable argon laser operating at 912 nm has been demonstrated by optically pumping with a pulsed titanium sapphire laser to investigate the temporal dynamics of an Advanced Noble Gas Laser (ANGL). Metastable argon concentrations on the order of 1011 cm-3 were maintained with the use of a radio frequency (RF) capacitively coupled discharge. The end-pumped laser produced output powers under 2 mW of average power with pulse lengths on the order of 100 ns. A comparison between empirical results and a four level laser model using longitudinally average pump and inter-cavity intensities is made. An alternative, highly-efficient method of argon metastable production for ANGL was explored using carbon nanotube (CNT) fibers.

  14. SiC Micropipe Sprecta

    NASA Astrophysics Data System (ADS)

    Leff, David; Frasca, Albert

    1997-05-01

    This report focuses on the spectral response of 4H SiC PN junction micropipes when reverse and forward biased. Reverse biased 4H SiC PN junctions give a very strong UV line, 385nm (3.22eV), and blue line, 475nm (2.61eV). In the forward bias direction the spectra do not contain the UV, only the blue line, 490nm (2.53eV), with considerably better resolution. For isolating and measuring the micropipe spectra and structure, a sample fixture was fabricated from a power transistor case. In order to activate the micropipes in the SEM, a vacuum feed-thru was made from another power transistor case. The emitter and base leads were used as the vacuum feed-thru and were used to mount a very fine spring for making contact to the 1mm X 1mm PN junction on the SiC chip. In our attempts to study these pipes and their properties, we utilized the SE, BSE, and X-ray detectors on the SEM, a stereo microscope, and a grading monochrometer. From the utilization of this equipment, we found the locations of the micropipes, the forward and reverse bias spectrum, and the possible structural faults in the SiC. Thanks to Dr. Philip Neudeck at LeRC, and Dr. Kenneth Bladh of Wittenberg.

  15. Microbubble enhanced ozonation process for advanced treatment of wastewater produced in acrylic fiber manufacturing industry.

    PubMed

    Zheng, Tianlong; Wang, Qunhui; Zhang, Tao; Shi, Zhining; Tian, Yanli; Shi, Shanshan; Smale, Nicholas; Wang, Juan

    2015-04-28

    This work investigated microbubble-ozonation for the treatment of a refractory wet-spun acrylic fiber wastewater in comparison to macrobubble-ozonation. CODcr, NH3-N, and UV254 of the wastewater were removed by 42%, 21%, and 42%, respectively in the microbubble-ozonation, being 25%, 9%, and 35% higher than the removal rates achieved by macrobubble-ozonation at the same ozone dose. The microbubbles (with average diameter of 45μm) had a high concentration of 3.9×10(5) counts/mL at a gas flow rate of 0.5L/min. The gas holdup, total ozone mass-transfer coefficient, and average ozone utilization efficiency in the microbubble-ozonation were 6.6, 2.2, and 1.5 times higher than those of the macrobubble-ozonation. Greater generation of hydroxyl radicals and a higher zeta potential of the bubbles were also observed in the microbubble ozonation process. The biodegradability of the wastewater was also significantly improved by microbubble-ozonation, which was ascribed to the enhanced degradation of alkanes, aromatic compounds, and the many other bio-refractory organic compounds in the wastewater. Microbubble-ozonation can thus be a more effective treatment process than traditional macrobubble-ozonation for refractory wastewater produced by the acrylic fiber manufacturing industry. PMID:25681716

  16. Non-destructive measurements in advanced composite materials and structures using a fiber optic sensing system

    NASA Astrophysics Data System (ADS)

    Aeby, Ian

    1989-06-01

    The implementation of a distributed fiber optic sensing system for monitoring strain, temperature, and absorbed moisture at multiple discrete locations throughout an organic matrix composite structure is discussed. The system consists of a network of passive fiber optic sensors fabricated along a continuous single or dual channel waveguide that is embedded within the composite part during manufacture. The single channel sensor networks are interrogated by a conventional optical time domain reflectometer (OTDR) while the dual channel networks are operated as coupled mode systems. In either case, physical information is encoded as relative changes in the amplitude of the signal returned from individual sensors. Operational theory, design and experimentally observed characteristics of each of the sensor types as well as the overall system are presented. Distributed sensors capable of measuring strain in the range of 1.8 microstrain to tens of millistrain, temperature from zero to 170 C with one tenth of a degree C resolution, and absorbed moisture from zero to two weight percent at up to ten discrete locations have been achieved.

  17. Progress report on understanding AFIS seed coat nep levels in pre-opened slivers on the Advanced Fiber Information System (AFIS)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Advanced Fiber Information System (AFIS) is utilized in this segment of the research project to study how seed coat neps are measured. A patent search was conducted, and studied to assist with the understanding of the AFIS measurement of this impurity in raw cotton. The older AFIS 2 is primari...

  18. PIP processing, microstructure and properties of Si{sub 3}N{sub 4} fiber and Al{sub 2}O{sub 3} fiber reinforced silicon nitride

    SciTech Connect

    Schwab, S.T.; Page, R.A.; Davidson, D.L.; Graef, R.C.

    1995-10-01

    Polymer infiltration/pyrolysis (PIP) processing has the potential to become an affordable means of manufacturing continuous fiber-reinforced ceramic-matrix components. The PIP method is very similar to the well-known polymer-matrix and carbon-carbon composite manufacturing techniques, the major difference being the use of a preceramic polymer in place of the organic polymer or carbon precursor. To date, the majority of research in the field of preceramic polymers has centered on precursors to silicon carbide (SiC). The Southwest Research institute (SwRI) has focused on the development of polymeric precursors to silicon nitride (Si{sub 3}N{sub 4}) because its high-temperature strength, resistance to oxidation, and other properties make it an attractive candidate for many advanced high-temperature structural applications. PIP Si{sub 3}N{sub 4} composites with NICALON SiC fiber reinforcement have exhibited good fracture toughness (K{sub IC} {approximately} 16 MPa {center_dot} m{sup 1/2}). The authors report here processing, microstructure and preliminary mechanical properties of two new PIP Si{sub 3}N{sub 4} composites. One is reinforced with Tonen Si{sub 3}N{sub 4} fiber (plain weave) while the other is reinforced with ALMAX Al{sub 2}O{sub 3} fiber (8 Harness satin weave).

  19. Hollow Fiber Spacesuit Water Membrane Evaporator Development and Testing for Advanced Spacesuits

    NASA Technical Reports Server (NTRS)

    Bue, Grant C.; Trevino, Luis; Tsioulos, Gus; Settles, Joseph; Colunga, Aaron; Vogel, Matthew; Vonau, Walt

    2010-01-01

    Grant Bue and Matthew Vogel presented the two types of Spacesuit Water Membrane Evaporators (SWME) that were developed based on hydrophobic microporous membranes. One type, the Sheet Membrane (SaM) SWME, is composed of six concentric Teflon sheet membranes fixed on cylindrical-supporting screens to form three concentric annular water channels. Those water channels are surrounded by vacuum passages to draw off the water vapor that passes through the membrane. The other type, the Hollow Fiber (HoFi) SWME, is composed of more than 14,000 tubes. Water flows through the tubes and water vapor passes through the tube wall to the shell side that vents to the vacuum of space. Both SWME types have undergone testing to baseline the performance at predicted operating temperatures and flow rates; the units also have been subjected to contamination testing and other conditions to test resiliency.

  20. Interfacial reactions in titanium/SCS fiber composites during fabrication

    NASA Technical Reports Server (NTRS)

    Warrier, S. G.; Lin, R. Y.

    1993-01-01

    The objectrive of the study was to determine the effect of titanium concentration and different pyrocarbon fiber coatings on the morphology and the extent of fiber-matrix reactions in Ti/SiC composites fabricated by rapid infrared forming (RIF). It is found that the extent of fiber-matrix reactions in Ti/SiC composites fabricated by the RIF technique is noticeably affected by both an increase in Ti content and by the processing temperature. Uncoated SiC fibers extensively react with the titanium alloy matrix at 1200 C, whereas no reaction occurs when coated SiC fibers are used.

  1. Fiber coatings for ceramic matrix composites

    SciTech Connect

    Carpenter, H.W.; Bohlen, J.W.

    1992-08-01

    Two fiber coating concepts for ceramic matrix composites were successfully demonstrated in a preliminary study. These coatings were designed to promote toughness in composites and resist oxidation. The concepts were: (1) thin, multiple unbonded layers, and (2) a single porous layer that provided low interfacial strengths between the fiber and matrix. Chemical vapor deposited (CVD) SiC and sol-gel derived oxides were used to produce the fiber coatings. Specimens consisted of a single coated monofilament fiber and a sheath of CVD SiC to represent the matrix. Results from flexure tests showed that matrix cracks were deflected and that fibers debonded the same as in specimens made using carbon-coated fibers. Crack deflection and fiber debonding were also evident after exposure in air at elevated temperatures. 5 refs.

  2. Fabrication of SiC matrix composites by liquid phase infiltration with a polymeric precursor

    SciTech Connect

    Interrante, L.V.; Whitmarsh, C.W.; Sherwood, W.

    1995-10-01

    A process for the fabrication of SiC matrix composites has been developed which employs a liquid, highly branched, polycarbosilane (AHPCS). This polymer thermosets on heating at 200--400 C (or at 100 C with catalyst) and yields an amorphous SiC with low excess C and O content in 60--80% yield on pyrolysis to 1,000 C. Preforms consisting of C-coated Nicalon SiC fiber cloth, unidirectional Textron SiC SCS-6 fiber layups, or Mo boats packed with SiC whiskers, were infiltrated with the polymer, cured in an autoclave, and pyrolized to 1,000 C. Five to eight infiltration cycles gave net shape composites with final densities at 85--94% of theoretical. The results of 4-point flexure tests on the as-prepared Nicalon composites indicate flexure strengths (aver. 378 MPa) that are comparable to or better than similarly reinforced CVI-SiC matrix composites. The whisker and SCS-6 composites showed a small weight loss (10--20%) on heating to 1,500 C in Ar and little or no weight change or obvious embrittlement in air at 1,000 C.

  3. Near-surface and bulk behavior of Ag in SiC

    SciTech Connect

    Xiao, Haiyan; Zhang, Yanwen; Snead, Lance Lewis; Shutthanandan, Vaithiyalingam; Xue, Haizhou; Weber, William J

    2012-01-01

    The diffusive release of fission products, such as Ag, from TRISO particles at high temperatures has raised concerns regarding safe and economic operation of advanced nuclear reactors. Understanding the mechanisms of Ag diffusion is thus of crucial importance for effective retention of fission products. Two mechanisms, i.e., grain boundary diffusion and vapor or surface diffusion through macroscopic structures such as nano-pores or nano-cracks, remain in debate. In the present work, an integrated computational and experimental study of the near-surface and bulk behavior of Ag in silicon carbide (SiC) has been carried out. The ab initio calculations show that Ag prefers to adsorb on the SiC surface rather than in the bulk, and the mobility of Ag on the surface is high. The energy barrier for Ag desorption from the surface is calculated to be 0.85-1.68 eV, and Ag migration into bulk SiC through equilibrium diffusion process is not favorable. Experimentally, Ag ions are implanted into SiC to produce Ag profiles buried in the bulk and peaked at the surface. High-temperature annealing leads to Ag release from the surface region instead of diffusion into the interior of SiC. It is suggested that surface diffusion through mechanical structural imperfection, such as vapor transport through cracks in SiC coatings, may be a dominating mechanism accounting for Ag release from the SiC in the nuclear reactor.

  4. Advanced risk assessment of the effects of graphite fibers on electronic and electric equipment, phase 1. [simulating vulnerability to airports and communities from fibers released during aircraft fires

    NASA Technical Reports Server (NTRS)

    Pocinki, L. S.; Kaplan, L. D.; Cornell, M. E.; Greenstone, R.

    1979-01-01

    A model was developed to generate quantitative estimates of the risk associated with the release of graphite fibers during fires involving commercial aircraft constructed with graphite fiber composite materials. The model was used to estimate the risk associated with accidents at several U.S. airports. These results were then combined to provide an estimate of the total risk to the nation.

  5. Stability of SiC and its Composites at High Neutron Fluence

    SciTech Connect

    Katoh, Yutai; Nozawa, Takashi; Snead, Lance Lewis; Ozawa, Kazumi; Tanigawa, H.

    2011-01-01

    High purity chemically vapor-deposited (CVD) silicon carbide (SiC) and near-stoichiometric SiC fiber, chemically vapor-infiltrated (CVI) SiC matrix composite were evaluated following neutron irradiation to {approx}28 dpa at 300 and 650 C and to {approx}41 dpa at 800 C, respectively. The irradiated swelling, thermal conductivity, and elastic modulus indicated no additional changes in these properties at high fluences after saturation at low fluences. With a statistically meaningful sample population, no change in flexural strength of CVD SiC was observed after 300 C irradiation. A slight decrease in strength was observed after 650 C irradiation but was attributed to an experimental artifact; specifically, a reaction between samples and the capsule components. The Hi-Nicalon{trademark} Type-S, CVI SiC composite retained the pre-irradiation strength and the non-linear fracture mode. The electrical resistivity measurement revealed a relatively minor effect of irradiation. Overall, irradiation-insensitivity of the high purity SiC ceramics and composite to neutron irradiation to doses 30-40 dpa at temperatures 300-800 C was demonstrated.

  6. Preparation of silicon carbide fibers

    DOEpatents

    Wei, G.C.

    1983-10-12

    Silicon carbide fibers suitable for use in the fabrication of dense, high-strength, high-toughness SiC composites or as thermal insulating materials in oxidizing environments are fabricated by a new, simplified method wherein a mixture of short-length rayon fibers and colloidal silica is homogenized in a water slurry. Water is removed from the mixture by drying in air at 120/sup 0/C and the fibers are carbonized by (pyrolysis) heating the mixture to 800 to 1000/sup 0/C in argon. The mixture is subsequently reacted at 1550 to 1900/sup 0/C in argon to yield pure ..beta..-SiC fibers.

  7. a Study on the Role of Sintering Additives for Fabrication of sic Ceramic

    NASA Astrophysics Data System (ADS)

    Yoon, Han Ki; Lee, Young Ju; Cho, Ho Jun; Kim, Tae Gyu

    Silicon carbide (SiC) materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine. The SiC ceramics have been fabricated by a NITE (Nano Infiltration Transient Eutectic Phase) Process, using Nano-SiC powder. The sintering additives used for forming liquid phase under sintering process, used the sintering additives ratios were an Al2O3-Y2O3 system or add SiO2 contents. A major R&D focus for the SiC ceramics is the production to obtain high purity SiC ceramics. In this study, we investigated roles of the sintering additives(Al2O3:Y2O3) to fabrication of the SiC ceramics. The effects of SiO2 contents and density properties of the SiC ceramics were also investigated. To investigate the effects of SiO2, Al2O3/Y2O3 composition were fixed and then SiO2 ratios were changed as several kinds, and to confirm the effects of sintering additives ratios (Al2O3:Y2O3) they were changed between 4:6 and 6:4 in x wt.%.

  8. High-temperature corrosion of Nicalon reg sign /SiC composites

    SciTech Connect

    Lowden, R.A.; James, R.D.

    1991-08-01

    The elevated-temperature stability of Nicalon{reg sign} (Nippon Carbon Company, Tokyo, Japan)/SiC composites with a graphitic carbon interface layer in oxidizing and simulated fossil fuel environments was investigated. Composite specimens with and without an external SiC surface coating were oxidizing in air and exposed to a variety of combustion environments at a temperature of 1273 K. A burner rig furnace was constructed for simulating corrosive fossil fuel environments containing water vapor, sulfur, and sodium. The mechanical properties of unprotected Nicalon{reg sign}/SiC specimens were degraded after short periods of exposure, due to the oxidation of the carbon interface coating. Longer exposures resulted in the oxidation of the fibers and matrix to form silica, which with time bonded the components together and produced brittle behavior. Combustion environments hastened the embrittlement of composites without an external SiC coating. Conversely, the specimens protected by a chemical vapor deposition (CVD) SiC surface coating exhibited only small decreases in strength after oxidation or corrosion in combustion environments. The SiC layer sealed off the surface of the composites, protecting the exposed fibers' ends, and thus prevented oxidation at the fiber-matrix interface. 26 refs., 11 figs., 1 tab.

  9. Advanced communication systems: A report on fiber optic technology and its possible applications in the gas industry

    NASA Astrophysics Data System (ADS)

    Ziolkowski, C. J.; Rush, W. F.; Saha, N. C.

    1987-08-01

    The applicability of fiber optic technology to the area of natural gas distribution is examined. The basic technology of fiber optics is outlined. Some of the commercially available products are examined. The two areas where fiber optics might be successfully applied to gas distribution needs are the remote control of district pressure regulators and the lease of communication capability to interested parties.

  10. Advances in Using Fiber-Optic Distributed Temperature Sensing to Identify the Mixing of Waters

    NASA Astrophysics Data System (ADS)

    Briggs, M. A.; Day-Lewis, F. D.; Rosenberry, D. O.; Harvey, J. W.; Lane, J. W., Jr.; Hare, D. K.; Boutt, D. F.; Voytek, E. B.; Buckley, S.

    2014-12-01

    Fiber-optic distributed temperature sensing (FO-DTS) provides thermal data through space and time along linear cables. When installed along a streambed, FO-DTS can capture the influence of upwelling groundwater (GW) as thermal anomalies. The planning of labor-intensive physical measurements can make use of FO-DTS data to target areas of focused GW discharge that can disproportionately affect surface-water (SW) quality and temperature. Typical longitudinal FO-DTS spatial resolution ranges 0.25 to1.0 m, and cannot resolve small-scale water-column mixing or sub-surface diurnal fluctuations. However, configurations where the cable is wrapped around rods can improve the effective vertical resolution to sub-centimeter scales, and the pipes can be actively heated to induce a thermal tracer. Longitudinal streambed and high-resolution vertical arrays were deployed at the upper Delaware River (PA, USA) and the Quashnet River (MA, USA) for aquatic habitat studies. The resultant datasets exemplify the varied uses of FO-DTS. Cold anomalies found along the Delaware River steambed coincide with zones of known mussel populations, and high-resolution vertical array data showed relatively stable in-channel thermal refugia. Cold anomalies at the Quashnet River identified in 2013 were found to persist in 2014, and seepage measurements and water samples at these locations showed high GW flux with distinctive chemistry. Cable location is paramount to seepage identification, particularly in faster flowing deep streams such as the Quashnet and Delaware Rivers where steambed FO-DTS identified many seepage zones with no surface expression. The temporal characterization of seepage dynamics are unique to FO-DTS. However, data from Tidmarsh Farms, a cranberry bog restoration site in MA, USA indicate that in slower flowing shallow steams GW inflow affects surface temperature; therefore infrared imaging can provide seepage location information similar to FO-DTS with substantially less effort.

  11. Ceramic matrix composites -- Advanced high-temperature structural materials

    SciTech Connect

    Lowden, R.A.; Ferber, M.K.; Hellmann, J.R.; Chawla, K.K.; DiPietro, S.G.

    1995-10-01

    This symposium on Ceramic Matrix Composites: Advanced High-Temperature Structural Materials was held at the 1994 MRS Fall Meeting in Boston, Massachusetts on November 28--December 2. The symposium was sponsored by the Department of Energy`s Office of Industrial Technology`s Continuous Fiber Ceramic Composites Program, the Air Force Office of Scientific Research, and NASA Lewis Research Center. Among the competing materials for advanced, high-temperature applications, ceramic matrix composites are leading candidates. The symposium was organized such that papers concerning constituents--fibers and matrices--were presented first, followed by composite processing, modeling of mechanical behavior, and thermomechanical testing. More stable reinforcements are necessary to enhance the performance and life of fiber-reinforced ceramic composites, and to ensure final acceptance of these materials for high-temperature applications. Encouraging results in the areas of polymer-derived SiC fibers and single crystal oxide filaments were given, suggesting composites with improved thermomechanical properties and stability will be realized in the near future. The significance of the fiber-matrix interface in the design and performance of these materials is evident. Numerous mechanical models to relate interface properties to composite behavior, and interpret test methods and data, were enthusiastically discussed. One issue of great concern for any advanced material for use in extreme environments is stability. This theme arose frequently throughout the symposium and was the topic of focus on the final day. Fifty nine papers have been processed separately for inclusion on the data base.

  12. Effects of Irradiation and Post-Irradiation Annealing on the Thermal Conductivity/ Diffusivity of Monolithic SIC and SIC/SIC Composites

    SciTech Connect

    Youngblood, Gerald E.; Senor, David J.; Jones, Russell H.

    2004-08-01

    Laser flash thermal diffusivity measurements were made on high-purity monolithic CVD-SiC (impurity concentration <5 wppm) and 2D f-SiC/PyC/ICVI-SiC composite samples (plain weave Hi-Nicalon (Trademark) fabric layers with 0-90 layup made by the isothermal chemical vapor infiltration process and with either a “thick” 1.0 µm or a “thin” 0.11 µm PyC fiber coating) before and after irradiation in the HFIR reactor (250 to 800°C, 4-8 dpa-SiC) and after post-irradiation annealing composite samples to 1200°C. Thermal conductivity in SiC is controlled by phonon transport. Point defects introduced into SiC during neutron irradiation are effective scattering centers for phonons, and as a consequence the thermal conductivity is sharply reduced. For irradiation temperatures below ~800°C, the accumulation of point defects (in SiC mostly single or small clusters of interstitials and isolated vacancies) saturates when the interstitial-vacancy recombination rate equals the defect production rate. For saturation conditions, the relative reduction in the SiC thermal conductivity decreases in a manner similar to its swelling reduction with increasing irradiation temperature. Examination of SiC swelling data at various irradiation temperatures and doses indicates that saturation occurs for ~2 dpa-SiC at 200°C and decreases continuously to ~0.4 dpa-SiC at 800°C. Based on a model that assumes a uniform distribution of the phonon scattering defects, the calculated defect concentration for unirradiated CVD-SiC was less than 1 appm, which is consistent with the manufacturer’s value of <5 wppm impurities. The defect concentrations estimated for the irradiated CVD-SiC samples decreased continuously from ~25,000 to 940 appm as the irradiation temperature increased from 252 to 800°C. The small intrinsic defect concentration in comparison to the rather large extrinsic irradiation-induced defect concentrations illustrates why CVD-SiC makes an ideal irradiation damage monitor.

  13. Synthesis of multifilament silicon carbide fibers by chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Revankar, Vithal; Hlavacek, Vladimir

    1991-01-01

    A process for development of clean silicon carbide fiber with a small diameter and high reliability is presented. An experimental evaluation of operating conditions for SiC fibers of good mechanical properties and devising an efficient technique which will prevent welding together of individual filaments are discussed. The thermodynamic analysis of a different precursor system was analyzed vigorously. Thermodynamically optimum conditions for stoichiometric SiC deposit were obtained.

  14. Update on SIC-Based Inverter Technology

    SciTech Connect

    Chinthavali, Madhu Sudhan; Zhang, Hui; Tolbert, Leon M; Ozpineci, Burak

    2009-01-01

    This paper presents a study of silicon carbide (SiC) technology which includes device characterization and modeling, inverter simulation, and test results for several prototype inverters. The static and dynamic characteristics of discrete devices and half bridge modules are presented. Test results of a 55 kW hybrid inverter with SiC Schottky diodes and an 18 kW all-SiC inverter using SiC JFETs and Schottky diodes are demonstrated.

  15. Synergistically toughening effect of SiC whiskers and nanoparticles in Al2O3-based composite ceramic cutting tool material

    NASA Astrophysics Data System (ADS)

    Liu, Xuefei; Liu, Hanlian; Huang, Chuanzhen; Wang, Limei; Zou, Bin; Zhao, Bin

    2016-06-01

    In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiCnp advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vol% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730±95 MPa and fracture toughness is 5.6±0.6 MPa·m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.

  16. Elevated temperature tensile and creep behavior of a SiC fiber-reinforced titanium metal matrix composite. Final Report, 22 Dec. 1994 M.S. Thesis, 7 May 1993

    NASA Technical Reports Server (NTRS)

    Thurston, Rita J.

    1995-01-01

    In this research program, the tensile properties and creep behavior in air of (0)(sub 4), (0/90)(sub s) and (90)(sub 4) SCS-9/Beta 21S composite layups with 0.24 volume fraction fiber were evaluated. Monotonic tensile tests at 23, 482, 650 and 815 C yielded the temperature dependence of the elastic modulus, proportional limit, ultimate tensile strength and total strain at failure. At 650 C, the UTS of the (0)(sub 4) and (0/90)(sub s) layups decreases by almost 50 percent from the room temperature values, indicating that operating temperatures should be less than 650 C to take advantage of the specific tensile properties of these composites.

  17. Fabrication of fiber-reinforced composites by chemical vapor infiltration

    SciTech Connect

    Besmann, T.M.; McLaughlin, J.C.; Probst, K.J.; Anderson, T.J.; Starr, T.L.

    1997-12-01

    Silicon carbide-based heat exchanger tubes are of interest to energy production and conversion systems due to their excellent high temperature properties. Fiber-reinforced SiC is of particular importance for these applications since it is substantially tougher than monolithic SiC, and therefore more damage and thermal shock tolerant. This paper reviews a program to develop a scaled-up system for the chemical vapor infiltration of tubular shapes of fiber-reinforced SiC. The efforts include producing a unique furnace design, extensive process and system modeling, and experimental efforts to demonstrate tube fabrication.

  18. Making Ceramic Fibers By Chemical Vapor

    NASA Technical Reports Server (NTRS)

    Revankar, Vithal V. S.; Hlavacek, Vladimir

    1994-01-01

    Research and development of fabrication techniques for chemical vapor deposition (CVD) of ceramic fibers presented in two reports. Fibers of SiC, TiB2, TiC, B4C, and CrB2 intended for use as reinforcements in metal-matrix composite materials. CVD offers important advantages over other processes: fibers purer and stronger and processed at temperatures below melting points of constituent materials.

  19. Advanced SiC/SiC Ceramic Composites For Gas-Turbine Engine Components

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; DiCarlo, J. A.; Easler, T. E.

    2004-01-01

    NASA Glenn Research Center (GRC) is developing a variety of advanced SiC/SiC ceramic composite (ASC) systems that allow these materials to operate for hundreds of hours under stress in air at temperatures approaching 2700 F. These SiC/SiC composite systems are lightweight (approximately 30% metal density) and, in comparison to monolithic ceramics and carbon fiber-reinforced ceramic composites, are able to reliably retain their structural properties for long times under aggressive gas-turbine engine environments. The key for the ASC systems is related first to the NASA development of the Sylramic-iBN Sic fiber, which displays higher thermal stability than any other SiC- based ceramic fibers and possesses an in-situ grown BN surface layer for higher environmental durability. This fiber is simply derived from Sylramic Sic fiber type that is currently produced at ATK COI Ceramics (COIC). Further capability is then derived by using chemical vapor infiltration (CVI) and/or polymer infiltration and pyrolysis (PIP) to form a Sic-based matrix with high creep and rupture resistance as well as high thermal conductivity. The objectives of this study were (1) to optimize the constituents and processing parameters for a Sylramic-iBN fiber reinforced ceramic composite system in which the Sic-based matrix is formed at COIC almost entirely by PIP (full PIP approach), (2) to evaluate the properties of this system in comparison to other 2700 F Sylramic-iBN systems in which the matrix is formed by full CVI and CVI + PIP, and (3) to examine the pros and cons of the full PIP approach for fabricating hot-section engine components. A key goal is the development of a composite system with low porosity, thereby providing high modulus, high matrix cracking strength, high interlaminar strength, and high thermal conductivity, a major property requirement for engine components that will experience high thermal gradients during service. Other key composite property goals are demonstration at

  20. Reactive sintering of SiC

    NASA Technical Reports Server (NTRS)

    Kim, Y. W.; Lee, J. G.

    1984-01-01

    Investigation of the sintering processes involved in the sintering of SiC revealed a connection between the types and quantities of sintering additives or catalysts and densification, initial shrinkage, and weight loss of the sintered SiC material. By sintering processes, is meant the methods of mass transport, namely solid vapor transport and grain boundary diffusion.

  1. MRS International Meeting on Advanced Materials, 1st, Tokyo, Japan, June 2, 3, 1988, Proceedings. Volume 4 - Composites corrosion/Coating of advanced materials

    SciTech Connect

    Kimura, Shiushichi; Kobayashi, Akira; Nii, Kazuyoshi; Saito, Yasutoshi; Umekawa, Sokichi.

    1989-01-01

    The present conference on metal-matrix composites (MMCs) and ceramic-matrix composites (CMCs) discusses electrodeposited C/Cu MMCs, the quasi-liquid hot press method for SiC/Al composites, die-cast MMCs for tribological applications, the solidification-processing of monotectic alloy matrix composites, the fracture of SiC whisker-reinforced Al-alloy MMCs, the elastic constants of a graphite/magnesium composite, and an elastoplastic analysis of metal/plastic/metal sandwich plates in three-point bending. Also discussed are the fabrication of diamond particle-dispersed glass composites in space, heat-resistant graphite fiber-reinforced phosphate ceramic CMCs, the high-temperature creep of SiC-reinforced alumina CMCs, flexible carbon fiber-reinforced exfoliated graphite composites, and the application of advanced CMCs to advanced railway systems, the corrosion and oxidation of SiC, Si{sub 3}N{sub 4}, and other structural ceramics, corrosion properties of advanced alloys, and novel coating systems for advanced materials.

  2. Formation of boron nitride coatings on silicon carbide fibers using trimethylborate vapor

    NASA Astrophysics Data System (ADS)

    Yuan, Mengjiao; Zhou, Tong; He, Jing; Chen, Lifu

    2016-09-01

    High quality boron nitride (BN) coatings have been grown on silicon carbide (SiC) fibers by carbothermal nitridation and at atmospheric pressure. SiC fibers were first treated in chlorine gas to form CDC (carbide-derived carbon) film on the fiber surface. The CDC-coated SiC fibers were then reacted with trimethylborate vapor and ammonia vapor at high temperature, forming BN coatings by carbothermal reduction. The FT-IR, XPS, XRD, SEM, TEM and AES were used to investigate the formation of the obtained coatings. It has been found that the obtained coatings are composed of phase mixture of h-BN and amorphous carbon, very uniform in thickness, have smooth surface and adhere well with the SiC fiber substrates. The BN-coated SiC fibers retain ∼80% strength of the as-received SiC fibers and show an obvious interfacial debonding and fiber pullout in the SiCf/SiOC composites. This method may be useful for the large scale production of high quality BN coating on silicon carbide fiber.

  3. Characterization of SiC f/SiC and CNT/SiC composite materials produced by liquid phase sintering

    NASA Astrophysics Data System (ADS)

    Lee, J. K.; Lee, S. P.; Cho, K. S.; Byun, J. H.; Bae, D. S.

    2011-10-01

    This paper dealt with the microstructure and mechanical properties of SiC based composites reinforced with different reinforcing materials. The composites were fabricated using reinforcing materials of carbon nanotubes (CNT) and Tyranno Lox-M SiC chopped fibers. The volume fraction of carbon nanotubes was also varied in this composite system. An Al 2O 3-Y 2O 3 powder mixture was used as a sintering additive in the consolidation of the SiC matrix. The characterization of the composites was investigated by means of SEM and three point bending tests. These composites showed a dense morphology of the matrix region, by the creation of a secondary phase. The composites reinforced with SiC chopped fibers possessed a flexural strength of about 400 MPa at room temperature. The flexural strength of the carbon nanotubes composites had a tendency to decrease with increased volume fraction of the reinforcing material.

  4. Preparation of anti-oxidative carbon fiber at high temperature

    NASA Astrophysics Data System (ADS)

    Kim, Bo-Hye; Kim, Su Yeun; Kim, Chang Hyo; Yang, Kap Seung; Lee, Young-Jun

    2010-11-01

    In this paper, carbon fibers with improved thermal stability and oxidation resistive properties were prepared and evaluated their physical performances under oxidation condition. Carbon fibers were coated with SiC particles dispersed in a polyacrylonitrile solution and then followed by pyrolyzed at 1400 °C to obtain the SiC nanoparticle deposition on the surface of the carbon fiber. The SiC coated carbon fiber showed extended oxidation resistive property as remaining 80-88% of the original weight even at high temperature 1000 °C under air, as compared with the control of zero weight at 600 °C. The effects of the coating conditions on the oxidation resistive properties of the coated fibers were studied in detail.

  5. Full-field characterization of thermal diffusivity in continuous- fiber ceramic composite materials and components

    SciTech Connect

    Steckenrider, J.S.; Ellingson, W.A.; Rothermel, S.A.

    1995-05-01

    Continuous-fiber ceramic matrix composites (CFCCs) are currently being developed for various high-temperature applications, including use in advanced heat engines. Among the material classes of interest for such applications are silicon carbide (SiC)-fiber-reinforced SiC (SiC{sub (f)}/SiC), SiC-fiber-reinforced silicon nitride (SiC {sub (f)}/Si{sub 3}N{sub 4}), aluminum oxide (Al{sub 2}O{sub 3})-fiber-reinforced Al{sub 2}O{sub 3} (Al{sub 2}O{sub 3}{sub (f)}/Al{sub 2}O{sub 3}), and others. In such composites, the condition of the interfaces (between the fibers and matrix) are critical to the mechanical and thermal behavior of the component (as are conventional mechanical defects such as cracks, porosity, etc.). For example, oxidation of this interface (especially on carbon coated fibers) can seriously degrade both mechanical and thermal properties. Furthermore, thermal shock damage can degrade the matrix through extensive crack generation. A nondestructive evaluation method that could be used to assess interface condition, thermal shock damage, and to detect other ``defects`` would thus be very beneficial, especially if applicable to full-scale components. One method under development uses infrared thermal imaging to provide ``single-shot`` full-field assessment of the distribution of thermal properties in large components by measuring thermal diffusivity. By applying digital image filtering, interpolation, and least-squares-estimation techniques for noise reduction, we can achieve acquisition and analysis times of minutes or less with submillimeter spatial resolution. The system developed at Argonne has been used to examine the effects of thermal shock, oxidation treatment, density variations, and variations in oxidation resistant coatings in a full array of test specimens. Subscale CFCC components with nonplanar geometries have also been studied for manufacturing-induced variations in thermal properties.

  6. Creep deformation of grain boundary in a highly crystalline SiC fibre.

    PubMed

    Shibayama, Tamaki; Yoshida, Yutaka; Yano, Yasuhide; Takahashi, Heishichiro

    2003-01-01

    Silicon carbide (SiC) matrix composites reinforced by SiC fibres (SiC/SiC composites) are currently being considered as alternative materials in high Ni alloys for high-temperature applications, such as aerospace components, gas-turbine energy-conversion systems and nuclear fusion reactors, because of their high specific strength and fracture toughness at elevated temperatures compared with monolithic SiC ceramics. It is important to evaluate the creep properties of SiC fibres under tensile loading in order to determine their usefulness as structural components. However, it would be hard to evaluate creep properties by monoaxial tensile properties when we have little knowledge on the microstructure of crept specimens, especially at the grain boundary. Recently, a simple fibre bend stress relaxation (BSR) test was introduced by Morscher and DiCarlo to address this problem. Interpretation of the fracture mechanism at the grain boundary is also essential to allow improvement of the mechanical properties. In this paper, effects of stress applied by BSR test on microstructural evolution in advanced SiC fibres, such as Tyranno-SA including small amounts of Al, are described and discussed along with the results of microstructure analysis on an atomic scale by using advanced microscopy. PMID:12741492

  7. Refractory Oxide Coatings on Sic Ceramics

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.; Jacobson, Nathan S.; Miller, Robert A.

    1994-01-01

    Silicon carbide with a refractory oxide coating is potentially a very attractive ceramic system. It offers the desirable mechanical and physical properties of SiC and the environmental durability of a refractory oxide. The development of a thermal shock resistant plasma-sprayed mullite coating on SiC is discussed. The durability of the mullite/SiC in oxidizing, reducing, and molten salt environments is discussed. In general, this system exhibits better behavior than uncoated SiC. Areas for further developments are discussed.

  8. An advanced 500-MHZ-bandwidth fiber-optic signal link for EMP and general laboratory applications

    NASA Astrophysics Data System (ADS)

    Blackburn, J. C.

    1981-07-01

    Means have been found to control modal noise in a fiber-optic system using single-mode lasers. Laser coherence is reduced by dithering, and careful attention is given to fiber connections. These techniques, in combination with miniaturization, have produced a compact wideband analog fiber-optic link that is well suited to signal transmission where dielectric transmission is dictated by electrical noise, need for complete isolation, TEMPEST considerations, or a requirement for wide bandwidth. The optical transmitter has a volume of 550 cc, contains an optically remote-controlled 0- to 45-dB input attenuator and calibrator, and will operate for 2 hr on its internal batteries. Maximum input sensitivity is a few millivolts into 50 ohms, system risetime in 0.8 ns, and dynamic range is greater than 30 dB. Transmission distances up to kilometers are possible, although fiber dispersion will reduce bandwidth at long distances.

  9. SiC nanowires: A photocatalytic nanomaterial

    SciTech Connect

    Zhou Weimin; Yan Lijun; Wang Ying; Zhang Yafei

    2006-07-03

    Single-crystal {beta}-SiC nanowires coated with amorphous SiO{sub 2} were synthesized by a simple thermal evaporation technique. The photocatalytic activity of the SiC nanowires was characterized by measuring the photodegradation rate of acetaldehyde catalyzed by SiC as a function of UV irradiation time. It exhibited excellent photocatalytic activity, leading to the efficient decomposition of acetaldehyde by irradiation with UV light. The progress of the photocatalytic reaction can be monitored by the evolution of one of the products, CO{sub 2}. It has been observed that the as-synthesized SiC nanowires (with the SiO{sub 2} coating) have higher catalytic activity than the HF-etched, oxide-free SiC nanowires.

  10. Fabrication of commercial-scale fiber-reinforced hot-gas filters by chemical vapor deposition

    SciTech Connect

    White, L.R.

    1992-11-01

    Goal was to fabricate a filter for removing particulates from hot gases; principal applications would be in advanced utility processes such as pressurized fluidized bed combustion or coal gasification combined cycle systems. Filters were made in two steps: make a ceramic fiber preform and coat it with SiC by chemical vapor infiltration (CVD). The most promising construction was felt/filament wound. Light, tough ceramic composite filters can be made; reinforcement by continuous fibers is needed to avoid brittleness. Direct metal to filter contact does not damage the top which simplifies installation. However, much of the filter surface of felt/filament wound structures is closed over by the CVD coating, and the surface is rough and subject to delamination. Recommendations are given for improving the filters.

  11. Fiber coatings and the fracture behavior of a continuous fiber ceramic composite

    SciTech Connect

    Miller, J.H.; Lowden, R.A.; Liaw, P.K.

    1995-10-01

    Fiber coatings have been used to modify fiber-matrix interfacial forces, and thus control mechanical properties of continuous fiber ceramic composites. It has been shown that the properties and thickness of the interlayer influence composite properties such as matrix cracking and ultimate strength, toughness and interlaminar shear. The effects of fiber coating properties and thickness on fiber-reinforced SiC matrix composites fabricated employing CVI techniques have been examined. Correlations between interface condition, mechanical properties and failure mechanisms have been made.

  12. SEM analysis of ion implanted SiC

    NASA Astrophysics Data System (ADS)

    Malherbe, Johan B.; van der Berg, N. G.; Botha, A. J.; Friedland, E.; Hlatshwayo, T. T.; Kuhudzai, R. J.; Wendler, E.; Wesch, W.; Chakraborty, P.; da Silveira, E. F.

    2013-11-01

    SiC is a material used in two future energy production technologies, firstly as a photovoltaic layer to harness the UV spectrum in high efficient power solar cells, and secondly as a diffusion barrier material for radioactive fission products in the fuel elements of the next generation of nuclear power plants. For both applications, there is an interest in the implantation of reactive and non-reactive ions into SiC and their effects on the properties of the SiC. In this study 360 keV Ag+, I+ and Xe+ ions were separately implanted into 6H-SiC and in polycrystalline SiC at various substrate temperatures. The implanted samples were also annealed in vacuum at temperatures ranging from 900 °C to 1600 °C for various times. In recent years, there had been significant advances in scanning electron microscopy (SEM) with the introduction of an in-lens detector combined with field emission electron guns. This allows defects in solids, such as radiation damage created by the implanted ions, to be detected with SEM. Cross-sectional SEM images of 6H-SiC wafers implanted with 360 keV Ag+ ions at room temperature and at 600 °C and then vacuum annealed at different temperatures revealed the implanted layers and their thicknesses. A similar result is shown of 360 keV I+ ions implanted at 600 °C into 6H-SiC and annealed at 1600 °C. The 6H-SiC is not amorphized but remained crystalline when implanting at 600 °C. There are differences in the microstructure of 6H-SiC implanted with silver at the two temperatures as well as with reactive iodine ions. Voids (bubbles) are created in the implanted layers into which the precipitation of silver and iodine can occur after annealing of the samples. The crystallinity of the substrate via implantation temperature caused differences in the distribution and size of the voids. Implantation of xenon ions in polycrystalline SiC at 350 °C does not amorphize the substrate as is the case with room temperature heavy ion bombardment. Subsequent

  13. Diffusion of Ag, Au and Cs implants in MAX phase Ti3SiC2

    NASA Astrophysics Data System (ADS)

    Jiang, Weilin; Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R.; Zhang, Chonghong; Gou, Jie

    2015-07-01

    MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti3SiC2/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including X-ray diffraction, electron backscatter diffraction, energy dispersive X-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti3SiC2 within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti3SiC2 was also observed. Cs out-diffusion and release from Ti3SiC2 occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

  14. Diffusion of Ag, Au and Cs implants in MAX phase Ti3SiC2

    SciTech Connect

    Jiang, Weilin; Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R.; Zhang, Chonghong; Gou, Jie

    2015-05-16

    MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti3SiC2/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including x-ray diffraction, electron backscatter diffraction, energy dispersive x-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti3SiC2 within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti3SiC2 was also observed. Cs out-diffusion and release from Ti3SiC2 occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

  15. Development of Sic Gas Sensor Systems

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Neudeck, P. G.; Okojie, R. S.; Beheim, G. M.; Thomas, V.; Chen, L.; Lukco, D.; Liu, C. C.; Ward, B.; Makel, D.

    2002-01-01

    Silicon carbide (SiC) based gas sensors have significant potential to address the gas sensing needs of aerospace applications such as emission monitoring, fuel leak detection, and fire detection. However, in order to reach that potential, a range of technical challenges must be overcome. These challenges go beyond the development of the basic sensor itself and include the need for viable enabling technologies to make a complete gas sensor system: electrical contacts, packaging, and transfer of information from the sensor to the outside world. This paper reviews the status at NASA Glenn Research Center of SiC Schottky diode gas sensor development as well as that of enabling technologies supporting SiC gas sensor system implementation. A vision of a complete high temperature microfabricated SiC gas sensor system is proposed. In the long-term, it is believed that improvements in the SiC semiconductor material itself could have a dramatic effect on the performance of SiC gas sensor systems.

  16. Fabrication of TI/SIC Surface Nano-Composite Layer by Friction Stir Processing

    NASA Astrophysics Data System (ADS)

    Shamsipur, Ali; Kashani-Bozorg, Seyed Farshid; Zareie-Hanzaki, Abbas

    In the present investigation, novel Ti/SiC surface nano-composite layer was successfully fabricated by dispersing nano-sized SiC particles into commercially pure titanium plates employing friction stir processing technique. The process parameters such as tool rotation and advancing speeds were adjusted to produce defect-free surface composite layer, however, uniform distribution of the nano-size SiC particles in a matrix of titanium was achieved after the second pass. The micro hardness value of the Ti/SiC nano-composite surface layer was found to be 534 HV; this is 3.3 times higher than that of the commercially pure titanium substrate. No reaction was detected between SiC powders and the titanium matrix after friction stir processing.

  17. SiC MODIFICATIONS TO MELCOR FOR SEVERE ACCIDENT ANALYSIS APPLICATIONS

    SciTech Connect

    Brad J. Merrill; Shannon M Bragg-Sitton

    2013-09-01

    The Department of Energy (DOE) Office of Nuclear Energy (NE) Light Water Reactor (LWR) Sustainability Program encompasses strategic research focused on improving reactor core economics and safety margins through the development of an advanced fuel cladding system. The Fuels Pathway within this program focuses on fuel system components outside of the fuel pellet, allowing for alteration of the existing zirconium-based clad system through coatings, addition of ceramic sleeves, or complete replacement (e.g. fully ceramic cladding). The DOE-NE Fuel Cycle Research & Development (FCRD) Advanced Fuels Campaign (AFC) is also conducting research on materials for advanced, accident tolerant fuels and cladding for application in operating LWRs. To aide in this assessment, a silicon carbide (SiC) version of the MELCOR code was developed by substituting SiC in place of Zircaloy in MELCOR’s reactor core oxidation and material property routines. The purpose of this development effort is to provide a numerical capability for estimating the safety advantages of replacing Zr-alloy components in LWRs with SiC components. This modified version of the MELCOR code was applied to the Three Mile Island (TMI-2) plant accident. While the results are considered preliminary, SiC cladding showed a dramatic safety advantage over Zircaloy cladding during this accident.

  18. Mechanism of interface formation in a silicon carbide fiber-reinforced magnesuium aluminosilicate

    SciTech Connect

    Kumar, A.; Knowles, K.M.

    1995-12-01

    The formation of sliding interfacial layers is a major key to the success of fiber-reinforced glass-ceramics. This paper reports the mechanism of formation of fiber-matrix interfaces during oxidizing heat treatments in a SiC fiber-reinforced magnesium aluminosilicate.

  19. Cryogenic Performance of Trex SiC Mirror

    NASA Technical Reports Server (NTRS)

    Foss, Colby; Kane, Dave; Bray, Donald; Hadaway, James

    2005-01-01

    Low cost, high performance lightweight Silicon Carbide (Sic) mirrors provide an alternative to Beryllium mirrors. A Trex Enterprises 0.25m diameter lightweight Sic mirror using its patented Chemical Vapor Composites (CVC) technology was evaluated for its optical performance. CVC Sic is chemically pure, thermally stable, and mechanically stiff. CVC technology yields higher growth rate than that of CVD Sic. NASA has funded lightweight optical materials technology development efforts involving Sic mirrors for future space based telescope programs. As part of these efforts, a Trex Sic was measured interferometrically from room temperature to 30 degrees Kelvin. This paper will discuss the test goals, the test instrumentation, test results, and lessons learned.

  20. Comparison of various advanced oxidation processes and chemical treatment methods for COD and color removal from a polyester and acetate fiber dyeing effluent.

    PubMed

    Azbar, N; Yonar, T; Kestioglu, K

    2004-04-01

    In this paper, a comparison of various advanced oxidation processes (O3, O3/UV, H2O2/UV, O3/H2O2/UV, Fe2+/H2O2) and chemical treatment methods using Al2(SO4)3.18H2O, FeCl3 and FeSO4 for the chemical oxygen demand (COD) and color removal from a polyester and acetate fiber dyeing effluent is undertaken. Advanced oxidation processes (AOPs) showed a superior performance compared to conventional chemical treatment, which maximum achievable color and COD removal for the textile effluent used in this study was 50% and 60%, respectively. Although O3/H2O2/UV combination among other AOPs methods studied in this paper was found to give the best result (99% removal for COD and 96% removal for color), use of Fe2+/H2O2 seems to show a satisfactory COD and color removal performance and to be economically more viable choice for the acetate and polyester fiber dyeing effluent on the basis of 90% removal. PMID:14720544

  1. The effect of processing on strength of Nicalon fibers in Nicalon fiber-SiC matrix composites

    SciTech Connect

    Singh, D.; Singh, J.P.

    1991-12-01

    Degradation of strength of Nicalon (silicon carbide) fibers during processing of Nicalon fiber-SiC matrix composites was studied. Strength distribution of as-fabricated Nicalon fibers was obtained via bundle tests. Whereas, strengths of fractured fibers in Nicalon fiber-reinforced SiC matrix composite specimens were estimated by measuring fracture mirror radii. Comparison of fracture probability plots indicate significant differences in the behavior of the as-fabricated fibers and those in the composite. Possible causes leading to these differences are discussed.

  2. Epoxy/Glass Fiber Laminated Composites Integrated with Amino Functionalized ZrO2 for Advanced Structural Applications.

    PubMed

    Halder, Sudipta; Ahemad, Soyeb; Das, Subhankar; Wang, Jialai

    2016-01-27

    This work demonstrates the successful silanization of ZrO2 nanoparticles (ZN) and their incorporation in glass fiber/epoxy composites. Microscopic investigation under transmission electron microscope elucidates antiaggregation and size enhancement of silanized ZrO2 nanoparticles (SZNs). FTIR spectroscopy has been used to demonstrate the chemical nature of the SZNs prepared. EDX results reveal the presence of Si onto SZNs. Incorporation of SZNs shows a strong influence on tensile and flexural properties of hybrid multiscale glass fiber composite (SZGFRP) compared to that of the neat epoxy glass fiber composite (GFRP). A significant variation of tensile strength, stiffness, and toughness of ∼27%, 62%, and 110% is observed with respect to GFRP. Strength and modulus under bending are also enhanced to ∼22% and ∼38%, respectively. Failure mechanisms obtained from macroscopic and microscopic investigation demonstrate reduced interfacial delamination for SZGFRP. Additionally, increased roughness of the fiber surface in SZGFRP laminates produces better interfacial bonding arising from SZN incorporation in laminates. This symptomatic behavior exposes the espousal of organically modified ZrO2 to enhance the interfacial bonding for their use in next generation hybrid laminates. PMID:26714570

  3. Processes and applications of silicon carbide nanocomposite fibers

    NASA Astrophysics Data System (ADS)

    Shin, D. G.; Cho, K. Y.; Jin, E. J.; Riu, D. H.

    2011-10-01

    Various types of SiC such as nanowires, thin films, foam, and continuous fibers have been developed since the early 1980s, and their applications have been expanded into several new applications, such as for gas-fueled radiation heater, diesel particulate filter (DPF), ceramic fiber separators and catalyst/catalyst supports include for the military, aerospace, automobile and electronics industries. For these new applications, high specific surface area is demanded and it has been tried by reducing the diameter of SiC fiber. Furthermore, functional nanocomposites show potentials in various harsh environmental applications. In this study, silicon carbide fiber was prepared through electrospinning of the polycarbosilane (PCS) with optimum molecular weight distribution which was synthesized by new method adopting solid acid catalyst such as ZSM-5 and γ-Al2O3. Functional elements such as aluminum, titanium, tungsten and palladium easily doped in the precursor fiber and remained in the SiC fiber after pyrolysis. The uniform SiC fibers were produced at the condition of spinning voltage over 20 kV from the PCS solution as the concentration of 1.3 g/ml in DMF/Toluene (3:7) and pyrolysis at 1200°C. Pyrolyzed products were processed into several interesting applications such as thermal batteries, hydrogen sensors and gas filters.

  4. High temperature characterization of reaction sintered SiC based materials

    NASA Astrophysics Data System (ADS)

    Lee, S. P.; Jin, J. O.; Park, J. S.; Kohyama, A.; Katoh, Y.; Yoon, H. K.; Bae, D. S.; Kim, I. S.

    2004-08-01

    Monolithic SiC and SiC f/SiC composite materials have been fabricated by a reaction sintering process. The mechanical properties of RS-SiC f/SiC composites reinforced with Hi-Nicalon SiC fiber have been investigated at elevated temperatures, in conjunction with a detailed analysis of their microstructures. The effect of heat treatment on the microstructure and strength of RS-SiC material was also examined. The characterization of RS-SiC based materials was evaluated by means of SEM, EDS and three point bend test. The RS-SiC material showed an average density of 3.0 Mg/cm 3 and an average strength of about 550 MPa. However, the strength of RS-SiC material decreased with increasing heat treatment times. The RS-SiC f/SiC composite also experienced a reduction of room temperature strength at a test temperature of 1300 °C, owing to the creation of internal defects such as matrix oxidation, interfacial debonding and fiber degradation.

  5. Update on Development of SiC Multi-Chip Power Modules

    NASA Technical Reports Server (NTRS)

    Lostetter, Alexander; Cilio, Edgar; Mitchell, Gavin; Schupbach, Roberto

    2008-01-01

    Progress has been made in a continuing effort to develop multi-chip power modules (SiC MCPMs). This effort at an earlier stage was reported in 'SiC Multi-Chip Power Modules as Power-System Building Blocks' (LEW-18008-1), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 28. The following recapitulation of information from the cited prior article is prerequisite to a meaningful summary of the progress made since then: 1) SiC MCPMs are, more specifically, electronic power-supply modules containing multiple silicon carbide power integrated-circuit chips and silicon-on-insulator (SOI) control integrated-circuit chips. SiC MCPMs are being developed as building blocks of advanced expandable, reconfigurable, fault-tolerant power-supply systems. Exploiting the ability of SiC semiconductor devices to operate at temperatures, breakdown voltages, and current densities significantly greater than those of conventional Si devices, the designs of SiC MCPMs and of systems comprising multiple SiC MCPMs are expected to afford a greater degree of miniaturization through stacking of modules with reduced requirements for heat sinking; 2) The stacked SiC MCPMs in a given system can be electrically connected in series, parallel, or a series/parallel combination to increase the overall power-handling capability of the system. In addition to power connections, the modules have communication connections. The SOI controllers in the modules communicate with each other as nodes of a decentralized control network, in which no single controller exerts overall command of the system. Control functions effected via the network include synchronization of switching of power devices and rapid reconfiguration of power connections to enable the power system to continue to supply power to a load in the event of failure of one of the modules; and, 3) In addition to serving as building blocks of reliable power-supply systems, SiC MCPMs could be augmented with external control circuitry to make them

  6. Effects of specimen configuration and fiber orientation on in-plane shear testing methods for advanced composite panels

    NASA Astrophysics Data System (ADS)

    Iwai, H.; Uemura, M.

    The mechanical in-plane shear testing method for unidirectional CFRP panels has not yet been authorized internationally because of its difficulty in obtaining the uniform shear stress field. A revised picture-frame fixture was proposed earlier to obtain the essential in-plane shear properties along fibers, but the specimen configuration included curved corners which exhibit stress concentration. In the present paper, an attempt is offered to simplify the specimen configuration in order to obtain more uniform shear stress distribution than seen in the previous specimens used in the picture frame fixture. Furthermore, a proposal is offered where the fiber direction is changed perpendicularly in rail shear methods. The experiments on unidirectional CFRP specimens together with the numerical FEM analyses were carried out in order to verify the advantages of such revisions by which the higher true shear strengths were obtained without stress concentration.

  7. Solute embrittlement of SiC

    NASA Astrophysics Data System (ADS)

    Enrique, Raúl A.; Van der Ven, Anton

    2014-09-01

    The energies and stresses associated with the decohesion of β-SiC in the presence of mobile Pd and Ag impurities are studied from first principles. Density functional theory calculations are parameterized with a generalized cohesive zone model and are analyzed within a thermodynamic framework that accounts for realistic boundary conditions in the presence of mobile impurities. We find that Pd impurities will embrittle SiC when Pd is in equilibrium with metallic Pd precipitates. Our thermodynamic analysis predicts that Pd embrittles SiC by substantially reducing the maximum stress of decohesion as a result of a phase transition between decohering planes involving an influx of Pd atoms. The methods presented in this work can be applied to study the thermodynamics of decohesion of SiC in other aggressive environments containing oxygen and water, for example, and yield environment dependent cohesive zone models for use in continuum approaches to study crack propagation and fracture.

  8. Solute embrittlement of SiC

    SciTech Connect

    Enrique, Raúl A.; Van der Ven, Anton

    2014-09-21

    The energies and stresses associated with the decohesion of β-SiC in the presence of mobile Pd and Ag impurities are studied from first principles. Density functional theory calculations are parameterized with a generalized cohesive zone model and are analyzed within a thermodynamic framework that accounts for realistic boundary conditions in the presence of mobile impurities. We find that Pd impurities will embrittle SiC when Pd is in equilibrium with metallic Pd precipitates. Our thermodynamic analysis predicts that Pd embrittles SiC by substantially reducing the maximum stress of decohesion as a result of a phase transition between decohering planes involving an influx of Pd atoms. The methods presented in this work can be applied to study the thermodynamics of decohesion of SiC in other aggressive environments containing oxygen and water, for example, and yield environment dependent cohesive zone models for use in continuum approaches to study crack propagation and fracture.

  9. Advanced X-Ray scattering methods for the study of structure and its evolution in soft materials with fiber symmetry

    NASA Astrophysics Data System (ADS)

    Stribeck, Norbert

    2010-11-01

    Three recently developed evaluation methods for the automated quantitative analysis of X-ray scattering data (small-angle (SAXS) and wide-angle (WAXS)) are presented. They are applicable to extensive series of 2D patterns that are recorded in studies of polymer materials with uniaxial symmetry. The experiments comprise time-resolved studies (melting, crystallization, mechanical properties and fatigue) as well as microbeam-scanning for the study of nanostructure gradients. The methods appear suitable to manage the data flood from modern synchrotron radiation setups aiming at the extraction of quantitative information on the structure evolution inside the material. In microbeam-scanning experiments the recorded scattering patterns are smeared. It is proposed to reconstruct desmeared scattering patterns by an X-ray scattering fiber-computer-tomography (XS-FCT). Reconstruction aberrations yield additional structure information. The true structure variation along the fiber radius is established. Compared to general tomography the experiment is faster by a factor of 100, and reconstruction is faster by a factor of 104. In WAXS fiber patterns should first be mapped into reciprocal space before analysis. After having corrected an erroneous tilt-angle equation, automatic tilt-angle tracking and mapping becomes possible. If polymers fail at low strain, the determination of strain and of structural parameters from the scattering patterns require very high accuracy because the observed variations are subtle. Suitable methods are presented both for the high-precision determination of the macroscopic strain, and for the determination of subtle variations of structure parameters.

  10. Advances in performance and beam quality of 9xx-nm laser diodes tailored for efficient fiber coupling

    NASA Astrophysics Data System (ADS)

    Lauer, Christian; König, Harald; Grönninger, Günther; Hein, Sebastian; Gomez-Iglesias, Alvaro; Furitsch, Michael; Maric, Josip; Kissel, Heiko; Wolf, Paul; Biesenbach, Jens; Strauss, Uwe

    2012-03-01

    The impact of new direct-diode and fiber laser systems on industrial manufacturing drives the demand for highbrightness diode laser pump sources suitable for simple fiber coupling with high efficiency. Within the German funded project HEMILAS laser mini-bars with different bar geometries and small fill factors were investigated. We present results on 9xx nm bars with tailored beam parameter products for simplified coupling to fibers with core diameters of 200μm and 300μm with a numerical aperture of 0.22 and compare beam quality parameters, brightness, conversion efficiency, and thermal performance of different bar designs. Optimized epitaxy structures yield conversion efficiency maxima above 66%. The slow axis divergence angle of mini-bars with a fill factor of 10% featuring five 100μm wide and 4mm long emitters based on this epitaxy structure stays below 7°, which corresponds to a beam parameter product of 15mm mrad, up to very high output power of over 45W. This result was achieved for mounting on actively cooled submounts using hard solder. A similar bar with 5mm cavity length and using soft soldering reached an output power of 60W at the same beam parameter product. At 4mm cavity length, no COMD failures were observed up to currents exceeding the thermal rollover and the maximum output cw power was 95W.

  11. Carbothermal synthesis of coatings on silicon carbide fibers

    NASA Astrophysics Data System (ADS)

    Chen, Linlin

    Four kinds of protective coatings---carbide derived carbon (CDC), boron nitride (BN), Al-O-N and BN doped Al-O-N (BAN) have been successfully synthesized on the surface of SiC fibers on the target to enhance the mechanical properties and oxidation resistance of the coated SiC fibers for the application as the reinforcements in the Ceramic Matrix Composites (CMCs) in the high temperatures. First of all, CDC coatings have been uniformly produced on Tyranno ZMI SiC fibers with good thickness control within nanometer accuracy by the chlorination in the temperature range of 550--700°C at atmospheric pressure. Kinetics of the carbon coating growth on the fibers has been systematically studied and thus a good foundation was set up for the further coating synthesis. BN coatings have been synthesized on the surface of SiC powders, fibers and fabrics by a novel carbothermal nitridation method. Non-bridging has been achieved in the BN-coated fiber tows by the nitridation in ammonia at atmospheric pressure in a temperature below 1200°C, which is lower compared to the traditional BN synthesis method and does not cause the degradation of the coated-fibers. BN coatings on the carbon nanotubes have also been formed and unlike the common methods, no additional dopant (such as metal catalyst) is introduced into the system during the BN coatings syntheses, thus the contamination of the final product is avoided. A novel Al-O-N coating has been explored with the most impressive point is that a more than 65% improvement in the tensile strength (up to ˜5.1GPa) and a three-time increase in the Weibull modulus compared to the as-received fibers are resulted by the formation of 200nm Al-O-N coating on the SiC fibers. It exceeds the strength of all other small diameter SiC fibers reported in the literature. Furthermore, BAN coating has also been produced on the surface of SiC fibers and about 20% enhancement in mechanical strength is achieved compared to that of the original fibers

  12. Ceramic fiber reinforced filter

    DOEpatents

    Stinton, David P.; McLaughlin, Jerry C.; Lowden, Richard A.

    1991-01-01

    A filter for removing particulate matter from high temperature flowing fluids, and in particular gases, that is reinforced with ceramic fibers. The filter has a ceramic base fiber material in the form of a fabric, felt, paper of the like, with the refractory fibers thereof coated with a thin layer of a protective and bonding refractory applied by chemical vapor deposition techniques. This coating causes each fiber to be physically joined to adjoining fibers so as to prevent movement of the fibers during use and to increase the strength and toughness of the composite filter. Further, the coating can be selected to minimize any reactions between the constituents of the fluids and the fibers. A description is given of the formation of a composite filter using a felt preform of commercial silicon carbide fibers together with the coating of these fibers with pure silicon carbide. Filter efficiency approaching 100% has been demonstrated with these filters. The fiber base material is alternately made from aluminosilicate fibers, zirconia fibers and alumina fibers. Coating with Al.sub.2 O.sub.3 is also described. Advanced configurations for the composite filter are suggested.

  13. Examples of conditional SIC-POVMs

    NASA Astrophysics Data System (ADS)

    Ohno, Hiromichi; Petz, Dénes

    2015-10-01

    The state of a quantum system is a density matrix with several parameters. The concern herein is how to recover the parameters. Several possibilities exist for the optimal recovery method, and we consider some special cases. We assume that a few parameters are known and that the others are to be recovered. The optimal positive-operator-valued measure (POVM) for recovering unknown parameters with an additional condition is called a conditional symmetric informationally complete POVM (SIC-POVM). In this paper, we study the existence or nonexistence of conditional SIC-POVMs. We provide a necessary condition for existence and some examples.

  14. Saturn V S-IC (First) Stage

    NASA Technical Reports Server (NTRS)

    1967-01-01

    This illustration shows a cutaway drawing with callouts of the major components for the S-IC (first) stage of the Saturn V launch vehicle. The S-IC stage is 138 feet long and 33 feet in diameter, producing more than 7,500,000 pounds of thrust through five F-1 engines powered by liquid oxygen and kerosene. Four of the engines are mounted on an outer ring and gimball for control purposes. The fifth engine is rigidly mounted in the center. When ignited, the roar produced by the five engines equals the sound of 8,000,000 hi-fi sets.

  15. Saturn V S-IC (First) Stage

    NASA Technical Reports Server (NTRS)

    1968-01-01

    This is a cutaway view of the Saturn V first stage, known as the S-IC, detailing the five F-1 engines and fuel cells. The S-IC stage is 138 feet long and 33 feet in diameter, producing more than 7,500,000 pounds of thrust through the five F-1 engines that are powered by liquid oxygen and kerosene. Four of the engines are mounted on an outer ring and gimbal for control purposes. The fifth engine is rigidly mounted in the center. When ignited, the roar produced by the five engines equals the sound of 8,000,000 hi-fi sets.

  16. Saturn V S-IC (First) Stage

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This cutaway illustration shows the Saturn V S-IC (first) stage with detailed callouts of the components. The S-IC Stage is 138 feet long and 33 feet in diameter, producing 7,500,000 pounds of thrust through five F-1 engines that are powered by liquid oxygen and kerosene. Four of the engines are mounted on an outer ring and gimbal for control purposes. The fifth engine is rigidly mounted in the center. When ignited, the roar produced by the five engines equals the sound of 8,000,000 hi-fi sets.

  17. Stacking faults in SiC nanowires.

    PubMed

    Wallis, K L; Wieligor, M; Zerda, T W; Stelmakh, S; Gierlotka, S; Palosz, B

    2008-07-01

    SiC nanowires were obtained by a reaction between vapor silicon and multiwall carbon nanotubes, CNT, in vacuum at 1200 degrees C. Raman and IR spectrometry, X-ray diffraction and high resolution transmission electron microscopy, HRTEM, were used to characterize properties of SiC nanowires. Morphology and chemical composition of the nanowires was similar for all samples, but concentration of structural defects varied and depended on the origin of CNT. Stacking faults were characterized by HRTEM and Raman spectroscopy, and both techniques provided complementary results. Raman microscopy allowed studying structural defects inside individual nanowires. A thin layer of amorphous silicon carbide was detected on the surface of nanowires. PMID:19051903

  18. Annual Conference on Composites and Advanced Ceramic Materials, 13th, Cocoa Beach, FL, Jan. 15-18, 1989, Collection of Papers. Parts 1 2

    SciTech Connect

    Not Available

    1989-10-01

    The present conference on advanced ceramics discusses topics in matrix-infiltration and processing techniques, the failure analysis of monolithic ceramics, the processing of polycrystalline oxide-matrix ceramic composites, the processing and properties of monolithic ceramics, ceramic composite interface phenomena, and ceramic NDE and characterization. Attention is given to chemical vapor infiltration for composites, dense ceramics via controlled melt oxidation, supertough silicon nitride, the properties of pressureless-sintered alumina-matrix/30 vol pct SiC composites, and toughening in metal particulate/glass-ceramic composites. Also discussed are the joining of silicon nitride for heat-engine applications, nitridation mechanisms in silicon powder compacts, the synthesis and properties of ceramic fibers, a technique for interfacial bond strength measurement, the degradation of SiC whiskers at elevated temperatures, and the correlation of NDE and fractography in Si3N4.

  19. Joining of SiC ceramics and SiC/SiC composites

    SciTech Connect

    Rabin, B.H.

    1996-08-01

    This project has successfully developed a practical and reliable method for fabricating SiC ceramic-ceramic joints. This joining method will permit the use of SiC-based ceramics in a variety of elevated temperature fossil energy applications. The technique is based on a reaction bonding approach that provides joint interlayers compatible with SiC, and excellent joint mechanical properties at temperatures exceeding 1000{degrees}C. Recent emphasis has been given to technology transfer activities, and several collaborative research efforts are in progress. Investigations are focusing on applying the joining method to sintered {alpha}-SiC and fiber-reinforced SiC/SiC composites for use in applications such as heat exchangers, radiant burners and gas turbine components.

  20. Recent developments in SiC monofilament reinforced Si sub 3 N sub 4 composites

    SciTech Connect

    Thomson, B.; LeCoistaouec, J.F. )

    1991-04-01

    The use of SiC monofilament to reinforce a Si{sub 3}N{sub 4} matrix has led to a refractory ceramic composite with outstanding high temperature properties. These composites provide many of the properties required for future generation aerospace applications and make viable candidates for structural applications where use temperatures exceed 1,350C. SiC/Si{sub 3}N{sub 4} composites are fabricated by using collimated fibers and a matrix slurry to produce preform tapes. Fully densified composites are achieved by hot pressing of tapes. Various aspects of the work related to shape forming, fabrication techniques, joining and processing considerations are addresses. Data are presented on high temperature tensile strength, impact characteristics, and environmental behavior. Recent developments are centered about the use of 75 {mu}m diameter SiC monofilaments in conjunction with hot isostatic pressing techniques to produce more complex shapes and improved properties.

  1. Joining of SiC ceramics and SiC/SiC composites

    SciTech Connect

    Rabin, B.H.

    1995-08-01

    This project has successfully developed a practical and reliable method for fabricating SiC ceramic-ceramic joints. This joining method has the potential to facilitate the use of SiC-based ceramics in a variety of elevated temperature fossil energy applications. The technique is based on a reaction bonding approach that provides joint interlayers compatible with SiC, and excellent joint mechanical properties at temperatures exceeding 1000{degrees}C. Recent efforts have focused on transferring the joining technology to industry. Several industrial partners have been identified and collaborative research projects are in progress. Investigations are focusing on applying the joining method to sintered a-SiC and fiber-reinforced SiC/SiC composites for use in applications such as heat exchangers, radiant burners and gas turbine components.

  2. Fatigue behavior of SiC reinforced Ti/6Al-4V/ at 650 C

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.; Grimes, H. H.

    1982-01-01

    Axial, low cycle fatigue properties of 25 and 44 fiber vol pct SiC/Ti(6Al-4V) composites, measured at 650 C, were compared with the fatigue properties of unreinforced Ti(6Al-4V) at the same temperature. A prior study of the fatigue behavior of this composite system at room temperature indicated that the SiC fiber reinforcement did not provide the anticipated improvement of fatigue resistance of this alloy. At 650 C, the composite fatigue properties degraded somewhat from those at room temperature. However, these properties degraded more for the unreinforced matrix at 650 C with the result that the composite fatigue strength was two to three times the fatigue strength of the matrix alloy. The reasons for this reversal are discussed in terms of crack initiation at broken fibers and residual matrix stresses.

  3. Environmental effects on the tensile strength of chemically vapor deposited silicon carbide fibers

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.; Kraitchman, M. D.

    1985-01-01

    The room temperature and elevated temperature tensile strengths of commercially available chemically vapor-deposited (CVD) silicon carbide fibers were measured after 15 min heat treatment to 1600 C in various environments. These environments included oxygen, air, argon and nitrogen at one atmosphere and vacuum at 10/9 atmosphere. Two types of fibers were examined which differed in the SiC content of their carbon-rich coatings. Threshold temperature for fiber strength degradation was observed to be dependent on the as-received fiber-flaw structure, on the environment and on the coating. Fractographic analyses and flexural strength measurements indicate that tensile strength losses were caused by surface degradation. Oxidation of the surface coating is suggested as one possible degradation mechanism. The SiC fibers containing the higher percentage of SiC near the surface of the carbon-rich coating show better strength retention and higher elevated temperature strength.

  4. Universal Converter Using SiC

    SciTech Connect

    Dallas Marckx; Brian Ratliff; Amit Jain; Matthew Jones

    2007-01-01

    The grantee designed a high power (over 1MW) inverter for use in renewable and distributed energy systems, such as PV cells, fuel cells, variable speed wind turbines, micro turbines, variable speed gensets and various energy storage methods. The inverter uses 10,000V SiC power devices which enable the use of a straight-forward topology for medium voltage (4,160VAC) without the need to cascade devices or topologies as is done in all commercial, 4,160VAC inverters today. The use of medium voltage reduces the current by nearly an order of magnitude in all current carrying components of the energy system, thus reducing size and cost. The use of SiC not only enables medium voltage, but also the use of higher temperatures and switching frequencies, further reducing size and cost. In this project, the grantee addressed several technical issues that stand in the way of success. The two primary issues addressed are the determination of real heat losses in candidate SiC devices at elevated temperature and the development of high temperature packaging for SiC devices.

  5. Passive SiC irradiation temperature monitor

    SciTech Connect

    Youngblood, G.E.

    1996-04-01

    A new, improved passive irradiation temperature monitoring method was examined after an irradiation test at 627{degrees}C. The method is based on the analysis of thermal diffusivity changes during postirradiation annealing of polycrystalline SiC. Based on results from this test, several advantages for using this new method rather than a method based on length or lattice parameter changes are given.

  6. Microwave joining of SiC

    SciTech Connect

    Silberglitt, R.; Ahmad, I.; Black, W.M.

    1995-05-01

    The purpose of this work is to optimize the properties of SiC-SiC joints made using microwave energy. The current focus is on optimization of time-temperature profiles, production of SiC from chemical precursors, and design of new applicators for joining of long tubes.

  7. Fiber Optic Control System integration for advanced aircraft. Electro-optic and sensor fabrication, integration, and environmental testing for flight control systems

    NASA Technical Reports Server (NTRS)

    Seal, Daniel W.; Weaver, Thomas L.; Kessler, Bradley L.; Bedoya, Carlos A.; Mattes, Robert E.

    1994-01-01

    This report describes the design, development, and testing of passive fiber optic sensors and a multiplexing electro-optic architecture (EOA) for installation and flight test on a NASA-owned F-18 aircraft. This hardware was developed under the Fiber Optic Control Systems for Advanced Aircraft program, part of a multiyear NASA initiative to design, develop, and demonstrate through flight test 'fly-by-light' systems for application to advanced aircraft flight and propulsion control. This development included the design and production of 10 passive optical sensors and associated multiplexed EOA hardware based on wavelength division multiplexed (WDM) technology. A variety of sensor types (rotary position, linear position, temperature, and pressure) incorporating a broad range of sensor technologies (WDM analog, WDM digital, analog microbend, and fluorescent time rate of decay) were obtained from different manufacturers and functionally integrated with an independently designed EOA. The sensors were built for installation in a variety of aircraft locations, placing the sensors in a variety of harsh environments. The sensors and EOA were designed and built to have the resulting devices be as close as practical to a production system. The integrated system was delivered to NASA for flight testing on a NASA-owned F-18 aircraft. Development and integration testing of the system provided valuable information as to which sensor types were simplest to design and build for a military aircraft environment and which types were simplest to operate with a multiplexed EOA. Not all sensor types met the full range of performance and environmental requirements. EOA development problems provided information on directions to pursue in future fly-by-light flight control development programs. Lessons learned in the development of the EOA and sensor hardware are summarized.

  8. Design of Twin Structures in SiC Nanowires

    SciTech Connect

    Yongfeng Zhang; Hanchen Huang

    2012-11-01

    With covalent bonding, SiC has high mechanical strength and a large energy gap in electronic band structure. Nanoscale SiC, in the form of nanowires, has increased mechanical toughness and variable band gaps. Further, introduction of twin boundaries into cubic SiC nanowires can result in improvement in both mechanical and electronic properties. This review presents effects of twin boundaries on properties of cubic SiC nanowires, including mechanical and electronic properties. Further, this review presents recent developments in introducing twin boundaries into cubic SiC nanowires, controllably and uncontrollably.

  9. Development of SiC Large Tapered Crystal Growth

    NASA Technical Reports Server (NTRS)

    Neudeck, Phil

    2010-01-01

    Majority of very large potential benefits of wide band gap semiconductor power electronics have NOT been realized due in large part to high cost and high defect density of commercial wafers. Despite 20 years of development, present SiC wafer growth approach is yet to deliver majority of SiC's inherent performance and cost benefits to power systems. Commercial SiC power devices are significantly de-rated in order to function reliably due to the adverse effects of SiC crystal dislocation defects (thousands per sq cm) in the SiC wafer.

  10. Advanced noise reduction techniques for ultra-low phase noise optical-to-microwave division with femtosecond fiber combs.

    PubMed

    Zhang, Wei; Xu, Zhenyu; Lours, Michel; Boudot, Rodolphe; Kersalé, Yann; Luiten, Andre N; Le Coq, Yann; Santarelli, Giorgio

    2011-05-01

    We report what we believe to be the lowest phase noise optical-to-microwave frequency division using fiber-based femtosecond optical frequency combs: a residual phase noise of -120 dBc/Hz at 1 Hz offset from an 11.55 GHz carrier frequency. Furthermore, we report a detailed investigation into the fundamental noise sources which affect the division process itself. Two frequency combs with quasi-identical configurations are referenced to a common ultrastable cavity laser source. To identify each of the limiting effects, we implement an ultra-low noise carrier-suppression measurement system, which avoids the detection and amplification noise of more conventional techniques. This technique suppresses these unwanted sources of noise to very low levels. In the Fourier frequency range of ∼200 Hz to 100 kHz, a feed-forward technique based on a voltage-controlled phase shifter delivers a further noise reduction of 10 dB. For lower Fourier frequencies, optical power stabilization is implemented to reduce the relative intensity noise which causes unwanted phase noise through power-to-phase conversion in the detector. We implement and compare two possible control schemes based on an acousto-optical modulator and comb pump current. We also present wideband measurements of the relative intensity noise of the fiber comb. PMID:21622045

  11. Room Temperature Tensile Behavior and Damage Accumulation of Hi-Nicalon Reinforced SiC Matrix Composites

    NASA Technical Reports Server (NTRS)

    Morscher, G. N.; Gyekenyesi, J. Z.

    1998-01-01

    Composites consisting of woven Hi-Nicalon fibers, BN interphases, and different SiC matrices were studied in tension at room temperature. Composites with SiC matrices processed by CVI and melt infiltration were compared. Monotonic and load/unload/reload tensile hysteresis experiments were performed. A modal acoustic emission (AE) analyzer was used to monitor damage accumulation during the tensile test. Post test polishing of the tensile gage sections was performed to determine the extent of cracking. The occurrence and location of cracking could easily be determined using modal AE. The loss of modulus could also effectively be determined from the change in the velocity of sound across the sample. Finally, the stresses where cracks appear to intersect the load-bearing fibers correspond with high temperature low cycle fatigue run out stresses for these materials.

  12. S-IC Test Stand Design Model

    NASA Technical Reports Server (NTRS)

    1962-01-01

    At its founding, the Marshall Space Flight Center (MSFC) inherited the Army's Jupiter and Redstone test stands, but much larger facilities were needed for the giant stages of the Saturn V. From 1960 to 1964, the existing stands were remodeled and a sizable new test area was developed. The new comprehensive test complex for propulsion and structural dynamics was unique within the nation and the free world, and they remain so today because they were constructed with foresight to meet the future as well as on going needs. Construction of the S-IC Static test stand complex began in 1961 in the west test area of MSFC, and was completed in 1964. The S-IC static test stand was designed to develop and test the 138-ft long and 33-ft diameter Saturn V S-IC first stage, or booster stage, weighing in at 280,000 pounds. Required to hold down the brute force of a 7,500,000-pound thrust produced by 5 F-1 engines, the S-IC static test stand was designed and constructed with the strength of hundreds of tons of steel and 12,000,000 pounds of cement, planted down to bedrock 40 feet below ground level. The foundation walls, constructed with concrete and steel, are 4 feet thick. The base structure consists of four towers with 40-foot-thick walls extending upward 144 feet above ground level. The structure was topped by a crane with a 135-foot boom. With the boom in the upright position, the stand was given an overall height of 405 feet, placing it among the highest structures in Alabama at the time. This photo is of the S-IC test stand design model created prior to construction.

  13. S-IC Test Stand Design Model

    NASA Technical Reports Server (NTRS)

    1962-01-01

    At its founding, the Marshall Space Flight Center (MSFC) inherited the Army's Jupiter and Redstone test stands, but much larger facilities were needed for the giant stages of the Saturn V. From 1960 to 1964, the existing stands were remodeled and a sizable new test area was developed. The new comprehensive test complex for propulsion and structural dynamics was unique within the nation and the free world, and they remain so today because they were constructed with foresight to meet the future as well as on going needs. Construction of the S-IC Static test stand complex began in 1961 in the west test area of MSFC, and was completed in 1964. The S-IC static test stand was designed to develop and test the 138-ft long and 33-ft diameter Saturn V S-IC first stage, or booster stage, weighing in at 280,000 pounds. Required to hold down the brute force of a 7,500,000-pound thrust produced by 5 F-1 engines, the S-IC static test stand was designed and constructed with the strength of hundreds of tons of steel and 12,000,000 pounds of cement, planted down to bedrock 40 feet below ground level. The foundation walls, constructed with concrete and steel, are 4 feet thick. The base structure consists of four towers with 40-foot-thick walls extending upward 144 feet above ground level. The structure was topped by a crane with a 135-foot boom. With the boom in the upright position, the stand was given an overall height of 405 feet, placing it among the highest structures in Alabama at the time. This photo is of the S-IC test stand design model.

  14. Deuteron irradiation creep of chemically vapor deposited silicon carbide fibers

    NASA Astrophysics Data System (ADS)

    Scholz, R.

    1998-03-01

    Irradiation creep tests were conducted on Textron SCS-6 silicon carbide (SiC) fibers during irradiation with 14 MeV deuterons at 450 and 600°C. The fibers are produced by a CVD procedure; their microstructure may therefore be representative for the matrix of a SiC composite. There is a significant radiation induced increase in creep deformation. Both quantities, irradiation creep strain and creep rate, are higher at 450°C than at 600°C for doses <0.07 dpa.

  15. Infrared spectra of meteoritic SiC grains

    NASA Astrophysics Data System (ADS)

    Andersen, A. C.; Jäger, C.; Mutschke, H.; Braatz, A.; Clément, D.; Henning, Th.; Jørgensen, U. G.; Ott, U.

    1999-03-01

    We present here the first infrared spectra of meteoritic SiC grains. The mid-infrared transmission spectra of meteoritic SiC grains isolated from the Murchison meteorite were measured in the wavelength range 2.5-16.5 mu m, in order to make available the optical properties of presolar SiC grains. These grains are most likely stellar condensates with an origin predominately in carbon stars. Measurements were performed on two different extractions of presolar SiC from the Murchison meteorite. The two samples show very different spectral appearance due to different grain size distributions. The spectral feature of the smaller meteoritic SiC grains is a relatively broad absorption band found between the longitudinal and transverse lattice vibration modes around 11.3 mu m, supporting the current interpretation about the presence of SiC grains in carbon stars. In contrast to this, the spectral feature of the large (> 5 mu m) grains has an extinction minimum around 10 mu m. The obtained spectra are compared with commercially available SiC grains and the differences are discussed. This comparison shows that the crystal structure (e.g., beta -SiC versus alpha -SiC) of SiC grains plays a minor role on the optical signature of SiC grains compared to e.g. grain size.

  16. Synthesis of SiC nanorods from bleached wood pulp

    SciTech Connect

    Shin, Yongsoon; Wang, Chong M.; Samuels, William D.; Exarhos, Gregory J.

    2007-05-01

    Unbleached and bleached soft wood pulps have been used as templates and carbon precursors to produce SiC nanorods. Hydrolyzed tetraethylorthosilicate (TEOS), Silicic acid was infiltrated into the pulps followed by a carbothermal reduction to form SiC nanorods at 1400oC in Ar. Residual carbon formed along with SiC was removed by gasification at 700oC in air. The SiC materials prepared from unbleached pulp were non-uniform SiC with a thick SiO2 coating, while the SiC nanorods prepared from the bleached pulp were uniform and straight with dimensions of 250 nm in diameter and 5.0 mm long. The formation of uniform camelback structure of SiC in the reaction between silica and bleached pulp is attributed to more silica deposited in the amorphous region of cellulose.

  17. Auger analysis of a fiber/matrix interface in a ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Honecy, Frank S.; Pepper, Stephen V.

    1988-01-01

    Auger electron spectroscopy (AES) depth profiling was used to characterize the fiber/matrix interface of an SiC fiber, reaction bonded Si3N4 matrix composite. Depth profiles of the as received double coated fiber revealed concentration oscillations which disappeared after annealing the fiber in the environment used to fabricate the composite. After the composite was fractured, the Auger depth profiles showed that failure occurred in neither the Beta-SiC fiber body nor in the Si3N4 matrix but, concurrently, at the fiber coating/matrix interface and within the fiber coating itself.

  18. Glass-clad semiconductor core optical fibers

    NASA Astrophysics Data System (ADS)

    Morris, Stephanie Lynn

    Glass-clad optical fibers comprising a crystalline semiconductor core have garnered considerable recent attention for their potential utility as novel waveguides for applications in nonlinear optics, sensing, power delivery, and biomedicine. As research into these fibers has progressed, it has become evident that excessive losses are limiting performance and so greater understanding of the underlying materials science, coupled with advances in fiber processing, is needed. More specifically, the semiconductor core fibers possess three performance-limiting characteristics that need to be addressed: (a) thermal expansion mismatches between crystalline core and glass cladding that lead to cracks, (b) the precipitation of oxide species in the core upon fiber cooling, which results from partial dissolution of the cladding glass by the core melt, and (c) polycrystallinity; all of which lead to scattering and increased transmission losses. This dissertation systematically studies each of these effects and develops both a fundamental scientific understanding of and practical engineering methods for reducing their impact. With respect to the thermal expansion mismatch and, in part, the dissolution of oxides, for the first time to our knowledge, oxide and non-oxide glass compositions are developed for a series of semiconductor cores based on two main design criteria: (1) matching the thermal expansion coefficient between semiconductor core and glass cladding to minimize cracking and (2) matching the viscosity-temperature dependences, such that the cladding glass draws into fiber at a temperature slightly above the melting point of the semiconductor in order to minimize dissolution and improve the fiber draw process. The x[Na 2O:Al2O3] + (100 - 2x)SiO2 glass compositional family was selected due to the ability to tailor the glass properties to match the aforementioned targets through slight variations in composition and adjusting the ratios of bridging and non-bridging oxygen

  19. Fiber Optic Fourier Transform Infrared Spectroscopic Techniques for Advanced On-Line Chemical Analysis in Semiconductor Fabrication Tools

    NASA Astrophysics Data System (ADS)

    Kester, Michael; Trygstad, Marc; Chabot, Paul

    2003-09-01

    A unique analytical methodology has recently been developed to perform real-time, on-line chemical analysis of bath solutions in semiconductor fabrication tools. A novel, patented fiber optic sensor is used to transmit infrared light directly through the tube walls of the circulating bath solutions within the fabrication tool in a completely non-invasive, non-extractive way. The sensor simply "clips" onto the tubing, thus permitting immediate analysis of the bath composition by Fourier Transform infrared (FTIR) spectroscopy. The infrared spectrometer is capable of multiplexing up to eight "Clippir™" sensor heads to a single interferometer using fiber optic cables. The instrument can analyze almost any bath solution utilized today. The analysis is performed using the near-infrared (NIR) portion of the electromagnetic spectrum, where absorption bands related to molecular vibrations can be found. The Fourier Transform infrared spectrometer gives access to absorption bands over a wide range of frequencies (or wavelengths), and the absorptions are correlated to concentrations using a chemometric approach employing a partial least-squares algorithm. Models are generated from this approach for each chemistry to be analyzed. This paper will review the analytical technology necessary to make such measurements, and discuss the instrument performance criteria required to achieve accurate and precise measurements of bath chemistries. The ability to measure non-infrared absorbing compounds will be discussed, as will the nature of the influence of sample temperature on measurement. Issues critical to the development of robust models and their direct implementation on multiple channels and even different instruments will be considered.

  20. Strength distribution of reinforcing fibers in a Nicalon fiber/chemically vapor infiltrated silicon carbide matrix composite

    NASA Technical Reports Server (NTRS)

    Eckel, Andrew J.; Bradt, Richard C.

    1989-01-01

    The strength distribution of fibers within a two-dimensional laminate ceramic/ceramic composite consisting of an eight harness satin weave of Nicalon continuous fiber within a chemically vapor infiltrated SiC matrix was determined from analysis of the fracture mirrors of the fibers. Comparison of the fiber strengths and the Weibull moduli with those for Nicalon fibers prior to incorporation into composites suggests that possible fiber damage may occur either during the weaving or during another stage of the composite manufacture. Observations also indicate that it is the higher-strength fibers which experience the greatest extent of fiber pullout and thus make a larger contribution to the overall composite toughness than do the weaker fibers.

  1. Reaction-bonded Si3N4 and SiC matrix composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Behrendt, Donald R.

    1992-01-01

    A development status evaluation is presented for the reaction-bonded SiC- and Si3N4-matrix types of fiber-reinforced ceramic-matrix composite (FRCMC). A variety of reaction-bonding methods are being pursued for FRCMC fabrication: CVI, CVD, directed metal oxidation, and self-propagating high-temperature synthesis. Due to their high specific modulus and strength, toughness, and fabricability, reaction-bonded FRCMC are important candidate materials for such heat-engine components as combustor liners, nozzles, and turbine and stator blading. The improvement of long-term oxidative stability in these composites is a major goal of current research.

  2. Kinetics of fiber solidification

    PubMed Central

    Mercader, C.; Lucas, A.; Derré, A.; Zakri, C.; Moisan, S.; Maugey, M.; Poulin, P.

    2010-01-01

    Many synthetic or natural fibers are produced via the transformation of a liquid solution into a solid filament, which allows the wet processing of high molecular weight polymers, proteins, or inorganic particles. Synthetic wet-spun fibers are used in our everyday life from clothing to composite reinforcement applications. Spun fibers are also common in nature. Silk solidification results from the coagulation of protein solutions. The chemical phenomena involved in the formation of all these classes of fibers can be quite different but they all share the same fundamental transformation from a liquid to a solid state. The solidification process is critical because it governs the production rate and the strength that fibers can sustain to be drawn and wound. An approach is proposed in this work to investigate the kinetics of fiber solidification. This approach consists in circulating solidifying fibers in the extensional flow of a surrounding liquid. Such as polymers in extensional flows, the fibers break if resultant drag forces exceed the fiber tensile strength. The solidification kinetics of nanotube composite fibers serves as a validation example of this approach. The method could be extended to other systems and advance thereby the science and technology of fiber and textile materials. It is also a way to directly visualize the scission of chain-like systems in extensional flows. PMID:20937910

  3. Kinetics of fiber solidification.

    PubMed

    Mercader, C; Lucas, A; Derré, A; Zakri, C; Moisan, S; Maugey, M; Poulin, P

    2010-10-26

    Many synthetic or natural fibers are produced via the transformation of a liquid solution into a solid filament, which allows the wet processing of high molecular weight polymers, proteins, or inorganic particles. Synthetic wet-spun fibers are used in our everyday life from clothing to composite reinforcement applications. Spun fibers are also common in nature. Silk solidification results from the coagulation of protein solutions. The chemical phenomena involved in the formation of all these classes of fibers can be quite different but they all share the same fundamental transformation from a liquid to a solid state. The solidification process is critical because it governs the production rate and the strength that fibers can sustain to be drawn and wound. An approach is proposed in this work to investigate the kinetics of fiber solidification. This approach consists in circulating solidifying fibers in the extensional flow of a surrounding liquid. Such as polymers in extensional flows, the fibers break if resultant drag forces exceed the fiber tensile strength. The solidification kinetics of nanotube composite fibers serves as a validation example of this approach. The method could be extended to other systems and advance thereby the science and technology of fiber and textile materials. It is also a way to directly visualize the scission of chain-like systems in extensional flows. PMID:20937910

  4. SiC Multi-Chip Power Modules as Power-System Building Blocks

    NASA Technical Reports Server (NTRS)

    Lostetter, Alexander; Franks, Steven

    2007-01-01

    The term "SiC MCPMs" (wherein "MCPM" signifies "multi-chip power module") denotes electronic power-supply modules containing multiple silicon carbide power devices and silicon-on-insulator (SOI) control integrated-circuit chips. SiC MCPMs are being developed as building blocks of advanced expandable, reconfigurable, fault-tolerant power-supply systems. Exploiting the ability of SiC semiconductor devices to operate at temperatures, breakdown voltages, and current densities significantly greater than those of conventional Si devices, the designs of SiC MCPMs and of systems comprising multiple SiC MCPMs are expected to afford a greater degree of miniaturization through stacking of modules with reduced requirements for heat sinking. Moreover, the higher-temperature capabilities of SiC MCPMs could enable operation in environments hotter than Si-based power systems can withstand. The stacked SiC MCPMs in a given system can be electrically connected in series, parallel, or a series/parallel combination to increase the overall power-handling capability of the system. In addition to power connections, the modules have communication connections. The SOI controllers in the modules communicate with each other as nodes of a decentralized control network, in which no single controller exerts overall command of the system. Control functions effected via the network include synchronization of switching of power devices and rapid reconfiguration of power connections to enable the power system to continue to supply power to a load in the event of failure of one of the modules. In addition to serving as building blocks of reliable power-supply systems, SiC MCPMs could be augmented with external control circuitry to make them perform additional power-handling functions as needed for specific applications: typical functions could include regulating voltages, storing energy, and driving motors. Because identical SiC MCPM building blocks could be utilized in a variety of ways, the cost

  5. Tensile deformation damage in SiC reinforced Ti-15V-3Cr-3Al-3Sn

    NASA Technical Reports Server (NTRS)

    Lerch, Bradley A.; Saltsman, James F.

    1991-01-01

    The damage mechanisms of a laminated, continuous SiC fiber reinforced Ti-15V-3Cr-3Al-3Sn (Ti-15-3) composite were investigated. Specimens consisting of unidirectional as well as cross-ply laminates were pulled in tension to failure at room temperature and 427 C and subsequently examined metallographically. Selected specimens were interrupted at various strain increments and examined to document the development of damage. When possible, a micromechanical stress analysis was performed to aid in the explanation of the observed damage. The analyses provide average constituent microstresses and laminate stresses and strains. It was found that the damage states were dependent upon the fiber architecture.

  6. Atomic layer deposited titanium dioxide coatings on KD-II silicon carbide fibers and their characterization

    NASA Astrophysics Data System (ADS)

    Cao, Shiyi; Wang, Jun; Wang, Hao

    2016-03-01

    To provide oxidation protection and/or to act as an interfacial coating, titanium oxide (TiO2) coatings were deposited on KD-II SiC fibers by employing atomic layer deposition (ALD) technique with tetrakis(dimethylamido)titanium (TDMAT) and water (H2O) as precursors. The average deposition rate was about 0.08 nm per cycle, and the prepared coatings were smooth, uniform and conformal, shielding the fibers entirely. The as-deposited coatings were amorphous regardless of the coating thickness, and changed to anatase and rutile crystal phase after annealing at 600 °C and 1000 °C, respectively. The oxidation measurement suggests that the TiO2 coating enhanced the oxidation resistance of SiC fibers obviously. SiC fibers coated with a 70-nm-thick TiO2 layer retained a relatively high tensile strength of 1.66 GPa even after exposition to air at 1400 °C for 1 h, and thick silica layer was not observed. In contrast, uncoated SiC fibers were oxidized dramatically through the same oxidation treatment, covered with a macro-cracked thick silica film, and the tensile strength was not measurable due to interfilament adhesion. The above results indicate that TiO2 films deposited by ALD are a promising oxidation resistance coating for SiC fibers.

  7. Constituent Effects on the Stress-Strain Behavior of Woven Melt-Infiltrated SiC Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Eldridge, Jeff I.; Levine, Stanley (Technical Monitor)

    2001-01-01

    The stress-strain behavior of 2D woven SiC fiber reinforced, melt-infiltrated SiC matrix composites with BN interphases were studied for composites fabricated with different fiber tow ends per unit length, different composite thickness, and different numbers of plies. In general, the stress-strain behavior, i.e., the 'knee' in the curve and the final slope of the stress-strain curve, was controlled by the volume fraction of fibers. Some of the composites exhibited debonding and sliding in between the interphase and the matrix rather than the more common debonding and sliding interface between the fiber and the interphase. Composites that exhibited this 'outside debonding' interface, in general, had lower elastic moduli and higher ultimate strains as well as longer pull-out lengths compared to the 'inside debonding' interface composites. Stress-strain curves were modeled where matrix crack formation as a function of stress was approximated from the acoustic emission activity and the measured crack density from the failed specimens. Interfacial shear strength measurements from individual fiber push-in tests were in good agreement with the interfacial shear strength values used to model the stress-strain curves.

  8. Periodically twinned SiC nanowires.

    PubMed

    Wang, Dong-Hua; Xu, Di; Wang, Qing; Hao, Ya-Juan; Jin, Guo-Qiang; Guo, Xiang-Yun; Tu, K N

    2008-05-28

    Twinning has been recognized to be an important microstructural defect in nanoscale materials. Periodically twinned SiC nanowires were largely synthesized by the carbothermal reduction of a carbonaceous silica xerogel prepared from tetraethoxysilane and biphenyl with iron nitrate as an additive. The twinned β-SiC nanowires, with a hexagonal cross section, a diameter of 50-300 nm and a length of tens to hundreds of micrometers, feature a zigzag arrangement of periodically twinned segments with a rather uniform thickness along the entire growth length. Computer simulation has been used to generate three-dimensional atomic structures of the zigzag columnar twin structure by the stacking of hexagonal discs of {111} planes of SiC. A minimum surface energy and strain energy argument is proposed to explain the formation of periodic twins in the SiC nanowires. The thickness of the periodic twinned segments is found to be linearly proportional to the nanowire diameter, and a constant volume model is proposed to explain the relation. PMID:21730575

  9. The friction and wear of TPS fibers

    NASA Technical Reports Server (NTRS)

    Bascom, W. D.; Wong, S.

    1987-01-01

    The sliding friction behavior of single filaments of SiO2, SiC, and an aluminoborosilicate has been determined. These fibers are used in thermal protection systems (TPS) and are subject to damage during weaving and aero-maneuvering. All fibers exhibited stick-slip friction indicating the successive formation and rupture of strong junctions between the contacting filaments. The static frictional resistance of the sized SiC filament was 4X greater than for the same filament after heat cleaning. This result suggests that the sizing is an organic polymer with a high shear yield strength. Heat cleaning exposes the SiC surface and/or leaves an inorganic residue so that the adhesional contact between filaments has a low fracture energy and frictional sliding occurs by brittle fracture. The frictional resistances of the sized and heat cleaned SiO2 and glass filaments were all comparable to that of the heat cleaned SiC. It would appear that the sizings as well as the heat cleaned surfaces of the silica and glass have low fracture energies so that the sliding resistance is determined by brittle fracture.

  10. Large-area SiC membrane produced by plasma enhanced chemical vapor deposition at relatively high temperature

    SciTech Connect

    Liu, Yu; Xie, Changqing

    2015-09-15

    Advances in the growth of silicon carbide (SiC) thin films with outstanding thermal and mechanical properties have received considerable attention. However, the fabrication of large-area free-standing SiC membrane still remains a challenge. Here, the authors report a plasma enhanced chemical vapor deposition process at a relatively high temperature to improve the free-standing SiC membrane area. A systematic study on the microstructural, mechanical, and optical properties of hydrogenated polycrystalline silicon carbide (poly-SiC{sub x}:H) thin films deposited at 600 °C with different annealing temperatures has been performed. In the as-deposited state, SiC{sub x}:H thin films show a polycrystalline structure. The crystallinity degree can be further improved with the increase of the postdeposition annealing temperature. The resulting process produced free-standing 2-μm-thick SiC membranes up to 70 mm in diameter with root mean square roughness of 3.384 nm and optical transparency of about 70% at 632.8 nm wavelength. The large-area SiC membranes made out of poly-SiC{sub x}:H thin films deposited at a relatively high temperature can be beneficial for a wide variety of applications, such as x-ray diffractive optical elements, optical and mechanical filtering, lithography mask, lightweight space telescopes, etc.

  11. Evaluation of two fiber optic-based solar collection and distribution systems for advanced space life support

    NASA Technical Reports Server (NTRS)

    Jack, D. A.; Nakamura, T.; Sadler, P.; Cuello, J. L.

    2002-01-01

    Growing plants in an enclosed controlled environment is crucial in developing bioregenerative life-support systems (BLSS) for space applications. The major challenge currently facing a BLSS is the extensive use of highly energy-intensive electric light sources, which leads to substantial energy wastes through heat dissipations by these lamps. An alternative lighting strategy is the use of a solar irradiance collection, transmission, and distribution system (SICTDS). Two types of fiber optic-based SICTDS, a Fresnel-lens Himawari and a parabolic-mirror optical waveguide (OW) lighting system, were evaluated. The overall efficiency for the OW SICTDS of 40.5% exceeded by 75% that for the Himawari of 23.2%. The spectral distributions of the light delivered by the Himawari and the OW SICTDS were almost identical and had practically no difference from that of terrestrial solar radiation. The ratios of photosynthetically active radiation (PAR) to total emitted radiation (k) of 0.39 +/- 0.02 for the Himawari and 0.41 +/- 0.04 for the OW SICTDS were statistically indistinguishable, were not significantly different from that of 0.042 +/- 0.01 for terrestrial solar radiation, and were comparable to that of 0.35 for a high-pressure sodium (HPS) lamp. The coefficients of variation (CV) of 0.34 and 0.39 for PPF distributions, both at 50 mm X 50 mm square grid arrays, corresponding to the Himawari and the OW SICTDS, respectively, were comparable with each other but were both significantly greater than the CV of 0.08 corresponding to the HPS lamp. The average fresh weight or dry weight of lettuce grown in the solar chamber with either the Himawari or the OW SICTDS showed no statistical difference from the average fresh weight or dry weight of lettuce grown in the reference chamber with the HPS lamp. The results of this study suggest that an SICTDS could help reduce the electric power demand in a BLSS.

  12. SiC nanowires synthesized from graphene and silicon vapors

    NASA Astrophysics Data System (ADS)

    Weichenpei, Luo; Gong-yi, Li; Zengyong, Chu; Tianjiao, Hu; Xiaodong, Li; Xuefei, Zhang

    2016-04-01

    The preparation of silicon carbide (SiC) nanowires is basically important for its potential applications in nanodevices, nanocomposites, etc. In the present work, a simple route was reported to synthesize SiC nanowires by heating commercial graphene with silicon vapors and no catalyst. Characterization by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, electron energy scattering, X-ray diffraction, and Raman dispersive spectrum demonstrates the products are composed of β-SiC crystal. The SiC nanowires have the average diameter of about 50 nm and length of tens of micrometers. The vapor-solid mechanism was employed to interpret the SiC nanowires growth. Gaseous SiO which was produced by the reaction of Si powders with its surface oxidation reacted with the solid graphene to form SiC crystal nuclei. And SiC crystal nuclei would act as active sites for further growing into nanowires.

  13. Ultralight, Strong, Three-Dimensional SiC Structures.

    PubMed

    Chabi, Sakineh; Rocha, Victoria G; García-Tuñón, Esther; Ferraro, Claudio; Saiz, Eduardo; Xia, Yongde; Zhu, Yanqiu

    2016-02-23

    Ultralight and strong three-dimensional (3D) silicon carbide (SiC) structures have been generated by the carbothermal reduction of SiO with a graphene foam (GF). The resulting SiC foams have an average height of 2 mm and density ranging between 9 and 17 mg cm(-3). They are the lightest reported SiC structures. They consist of hollow struts made from ultrathin SiC flakes and long 1D SiC nanowires growing from the trusses, edges, and defect sites between layers. AFM results revealed an average flake thickness of 2-3 nm and lateral size of 2 μm. In-situ compression tests in the scanning electron microscope (SEM) show that, compared with most of the existing lightweight foams, the present 3D SiC exhibited superior compression strengths and significant recovery after compression strains of about 70%. PMID:26580985

  14. Direct current conduction in SiC powders

    NASA Astrophysics Data System (ADS)

    Mârtensson, E.; Gäfvert, U.; Lindefelt, U.

    2001-09-01

    Silicon carbide (SiC) powder is used in nonlinear field grading materials. The composite material, consisting of an insulating polymer matrix filled with the SiC-grains, is usually a percolated system with established conducting paths. In order to explain the properties, the electrical characteristic and conduction mechanisms of the SiC powder itself are of interest. SiC powders have been studied by current-voltage measurements and the influences of grain size and doping have been investigated. The macroscopic current characteristics of green and black SiC powders can be described by the transport mechanisms at the grain contacts, which can be modeled by Schottky-like barriers. The SiC is heavily doped and tunneling by field emission is the dominating conduction mechanism over the major part of the nonlinear voltage range. It is suggested that preavalanche multiplication influences the current at the highest voltages, especially for p-type black SiC.

  15. F-1 Engine Installation to S-IC Stage

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Engineers and technicians at the Marshall Space Flight Center were installing an F-I engine on the Saturn V S-IC (first) stage thrust structure in building 4705. The S-IC (first) stage used five F-1 engines that produced a total thrust of 7,500,000 pounds as each engine produced 1,500,000 pounds of thrust. The S-IC stage lifted the Saturn V vehicle and Apollo spacecraft from the launch pad.

  16. Sensor-model prediction, monitoring and in-situ control of liquid RTM advanced fiber architecture composite processing

    NASA Astrophysics Data System (ADS)

    Kranbuehl, D.; Kingsley, P.; Hart, S.; Loos, A.; Hasko, G.; Dexter, B.

    In-situ frequency dependent electromagnetic sensors (FDEMS) and the Loos resin transfer model have been used to select and control the processing properties of an epoxy resin during liquid pressure RTM impregnation and cure. Once correlated with viscosity and degree of cure the FDEMS sensor monitors and the RTM processing model predicts the reaction advancement of the resin, viscosity and the impregnation of the fabric. This provides a direct means for predicting, monitoring, and controlling the liquid RTM process in-situ in the mold throughout the fabrication process and the effects of time, temperature, vacuum and pressure. Most importantly, the FDEMS-sensor model system has been developed to make intelligent decisions, thereby automating the liquid RTM process and removing the need for operator direction.

  17. Sensor-model prediction, monitoring and in-situ control of liquid RTM advanced fiber architecture composite processing

    NASA Technical Reports Server (NTRS)

    Kranbuehl, D.; Kingsley, P.; Hart, S.; Loos, A.; Hasko, G.; Dexter, B.

    1992-01-01

    In-situ frequency dependent electromagnetic sensors (FDEMS) and the Loos resin transfer model have been used to select and control the processing properties of an epoxy resin during liquid pressure RTM impregnation and cure. Once correlated with viscosity and degree of cure the FDEMS sensor monitors and the RTM processing model predicts the reaction advancement of the resin, viscosity and the impregnation of the fabric. This provides a direct means for predicting, monitoring, and controlling the liquid RTM process in-situ in the mold throughout the fabrication process and the effects of time, temperature, vacuum and pressure. Most importantly, the FDEMS-sensor model system has been developed to make intelligent decisions, thereby automating the liquid RTM process and removing the need for operator direction.

  18. Early implementation of SiC cladding fuel performance models in BISON

    SciTech Connect

    Powers, Jeffrey J.

    2015-09-18

    SiC-based ceramic matrix composites (CMCs) [5–8] are being developed and evaluated internationally as potential LWR cladding options. These development activities include interests within both the DOE-NE LWR Sustainability (LWRS) Program and the DOE-NE Advanced Fuels Campaign. The LWRS Program considers SiC ceramic matrix composites (CMCs) as offering potentially revolutionary gains as a cladding material, with possible benefits including more efficient normal operating conditions and higher safety margins under accident conditions [9]. Within the Advanced Fuels Campaign, SiC-based composites are a candidate ATF cladding material that could achieve several goals, such as reducing the rates of heat and hydrogen generation due to lower cladding oxidation rates in HT steam [10]. This work focuses on the application of SiC cladding as an ATF cladding material in PWRs, but these work efforts also support the general development and assessment of SiC as an LWR cladding material in a much broader sense.

  19. Evaluation of two fiber optic-based solar collection and distribution systems for advanced space life support.

    PubMed

    Jack, D A; Nakamura, T; Sadler, P; Cuello, J L

    2002-01-01

    Growing plants in an enclosed controlled environment is crucial in developing bioregenerative life-support systems (BLSS) for space applications. The major challenge currently facing a BLSS is the extensive use of highly energy-intensive electric light sources, which leads to substantial energy wastes through heat dissipations by these lamps. An alternative lighting strategy is the use of a solar irradiance collection, transmission, and distribution system (SICTDS). Two types of fiber optic-based SICTDS, a Fresnel-lens Himawari and a parabolic-mirror optical waveguide (OW) lighting system, were evaluated. The overall efficiency for the OW SICTDS of 40.5% exceeded by 75% that for the Himawari of 23.2%. The spectral distributions of the light delivered by the Himawari and the OW SICTDS were almost identical and had practically no difference from that of terrestrial solar radiation. The ratios of photosynthetically active radiation (PAR) to total emitted radiation (k) of 0.39 +/- 0.02 for the Himawari and 0.41 +/- 0.04 for the OW SICTDS were statistically indistinguishable, were not significantly different from that of 0.042 +/- 0.01 for terrestrial solar radiation, and were comparable to that of 0.35 for a high-pressure sodium (HPS) lamp. The coefficients of variation (CV) of 0.34 and 0.39 for PPF distributions, both at 50 mm X 50 mm square grid arrays, corresponding to the Himawari and the OW SICTDS, respectively, were comparable with each other but were both significantly greater than the CV of 0.08 corresponding to the HPS lamp. The average fresh weight or dry weight of lettuce grown in the solar chamber with either the Himawari or the OW SICTDS showed no statistical difference from the average fresh weight or dry weight of lettuce grown in the reference chamber with the HPS lamp. The results of this study suggest that an SICTDS could help reduce the electric power demand in a BLSS. PMID:12807140

  20. Corrosion pitting of SiC by molten salts

    NASA Technical Reports Server (NTRS)

    Jacobson, N. S.; Smialek, J. L.

    1986-01-01

    The corrosion of SiC by thin films of Na2CO3 and Na2SO4 at 1000 C is characterized by a severe pitting attack of the SiC substrate. A range of different Si and SiC substrates were examined to isolate the factors critical to pitting. Two types of pitting attack are identified: attack at structural discontinuities and a crater-like attack. The crater-like pits are correlated with bubble formation during oxidation of the SiC. It appears that bubbles create unprotected regions, which are susceptible to enhanced attack and, hence, pit formation.

  1. Paralinear Oxidation of CVD SiC in Water Vapor

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Hann, Raiford E., Jr.

    1997-01-01

    The oxidation kinetics of CVD SiC were monitored by thermogravimetric analysis (TGA) in a 50% H2O/50% O2 gas mixture flowing at 4.4 cm/s for temperatures between 1200 and 1400 C. Paralinear weight change kinetics were observed as the water vapor oxidized the SiC and simultaneously volatilized the silica scale. The long-term degradation rate of SiC is determined by the volatility of the silica scale. Rapid SiC surface recession rates were estimated from these data for actual aircraft engine combustor conditions.

  2. SiC Power MOSFET with Improved Gate Dielectric

    SciTech Connect

    Sbrockey, Nick M; Tompa, Gary S; Spencer, Michael G; Chandrashekhar, Chandra MVS

    2010-08-23

    In this STTR program, Structured Materials Industries (SMI), and Cornell University are developing novel gate oxide technology, as a critical enabler for silicon carbide (SiC) devices. SiC is a wide bandgap semiconductor material, with many unique properties. SiC devices are ideally suited for high-power, highvoltage, high-frequency, high-temperature and radiation resistant applications. The DOE has expressed interest in developing SiC devices for use in extreme environments, in high energy physics applications and in power generation. The development of transistors based on the Metal Oxide Semiconductor Field Effect Transistor (MOSFET) structure will be critical to these applications.

  3. An orthogonal wavelet division multiple-access processor architecture for LTE-advanced wireless/radio-over-fiber systems over heterogeneous networks

    NASA Astrophysics Data System (ADS)

    Mahapatra, Chinmaya; Leung, Victor CM; Stouraitis, Thanos

    2014-12-01

    The increase in internet traffic, number of users, and availability of mobile devices poses a challenge to wireless technologies. In long-term evolution (LTE) advanced system, heterogeneous networks (HetNet) using centralized coordinated multipoint (CoMP) transmitting radio over optical fibers (LTE A-ROF) have provided a feasible way of satisfying user demands. In this paper, an orthogonal wavelet division multiple-access (OWDMA) processor architecture is proposed, which is shown to be better suited to LTE advanced systems as compared to orthogonal frequency division multiple access (OFDMA) as in LTE systems 3GPP rel.8 (3GPP, http://www.3gpp.org/DynaReport/36300.htm). ROF systems are a viable alternative to satisfy large data demands; hence, the performance in ROF systems is also evaluated. To validate the architecture, the circuit is designed and synthesized on a Xilinx vertex-6 field-programmable gate array (FPGA). The synthesis results show that the circuit performs with a clock period as short as 7.036 ns (i.e., a maximum clock frequency of 142.13 MHz) for transform size of 512. A pipelined version of the architecture reduces the power consumption by approximately 89%. We compare our architecture with similar available architectures for resource utilization and timing and provide performance comparison with OFDMA systems for various quality metrics of communication systems. The OWDMA architecture is found to perform better than OFDMA for bit error rate (BER) performance versus signal-to-noise ratio (SNR) in wireless channel as well as ROF media. It also gives higher throughput and mitigates the bad effect of peak-to-average-power ratio (PAPR).

  4. Progress on matrix SiC processing and properties for fully ceramic microencapsulated fuel form

    NASA Astrophysics Data System (ADS)

    Terrani, K. A.; Kiggans, J. O.; Silva, C. M.; Shih, C.; Katoh, Y.; Snead, L. L.

    2015-02-01

    The consolidation mechanism and resulting properties of the silicon carbide (SiC) matrix of fully ceramic microencapsulated (FCM) fuel form are discussed. The matrix is produced via the nano-infiltration transient eutectic-forming (NITE) process. Coefficient of thermal expansion, thermal conductivity, and strength characteristics of this SiC matrix have been characterized in the unirradiated state. An ad hoc methodology for estimation of thermal conductivity of the neutron-irradiated NITE-SiC matrix is also provided to aid fuel performance modeling efforts specific to this concept. Finally, specific processing methods developed for production of an optimal and reliable fuel form using this process are summarized. These various sections collectively report the progress made to date on production of optimal FCM fuel form to enable its application in light water and advanced reactors.

  5. Preceramic Polymers for Use as Fiber Coatings

    NASA Technical Reports Server (NTRS)

    Heimann, P. J.; Hurwitz, F. I.; Wheeler, D.; Eldridge, J.; Baranwal, R.; Dickerson, R.

    1996-01-01

    Polymeric precursors to Si-C-O, SI-B-N and Si-C were evaluated for use as ceramic interfaces in ceramic matrix composites. Use of the preceramic polymers allows for easy dip coating of fibers from dilute solutions of a polymer, which are then pyrolyzed to obtain the ceramic. SCS-0 fibers (Textron Specialty Materials, Lowell, MA) were coated with polymers from three systems: polysilsesquioxanes, polyborosilazanes and polycarbosilanes. The polysilsesquioxane systems were shown to produce either silicon oxycarbide or silicon oxynitride, depending on the pyrolysis conditions, and demonstrated some promise in an RBSN (reaction-bonded silicon nitride) matrix model system. Polyborosilazanes were shown, in studies of bulk polymers, to give rise to oxidation resistant Si-B-N ceramics which remain amorphous to temperatures of 1600 C, and should therefore provide a low modulus interface. Polycarbosilanes produce amorphous carbon-rich Si-C materials which have demonstrated oxidation resistance.

  6. Investigation of interfacial shear strength in a SiC fibre/Ti-24Al-11Nb composite by a fibre push-out technique

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Brindley, P. K.

    1989-01-01

    A fiber push-out technique applied at several sample thicknesses was used to determine both the debond shear stress and the frictional shear stress at the fiber-matrix interface at room temperautre for a unidirectional SiC fiber-reinforced T-24Al-11Nb (in at. pct) composite prepared by a powder cloth technique. The push-out technique measures the separate contributions of bond strength and friction to the mechanical shear strength at the fiber-matrix interface. It was found that the fiber-matrix bond shear strength of this material is significantly higher than the fiber-matrix frictional shear stress (119.2 and 47.8 MPa, respectively).

  7. Neutron irradiation effects on high Nicalon silicon carbide fibers

    SciTech Connect

    Osborne, M.C.; Steiner, D.; Snead, L.L.

    1996-10-01

    The effects of neutron irradiation on the mechanical properties and microstructure of SiC and SiC-based fibers is a current focal point for the development of radiation damage resistant SiC/SiC composites. This report discusses the radiation effects on the Nippon Carbon Hi-Nicalon{trademark} fiber system and also discusses an erratum on earlier results published by the authors on this material. The radiation matrix currently under study is also summarized.

  8. SiC Recession Due to SiO2 Scale Volatility Under Combustor Conditions

    NASA Technical Reports Server (NTRS)

    Robinson, Raymond Craig

    1997-01-01

    One of today's most important and challenging technological problems is the development of advanced materials and processes required to design and build a fleet of supersonic High Speed Civil Transport (HSCT) airliners, a follow-up to the Concorde SST. The innovative combustor designs required for HSCT engines will need high-temperature materials with long-term environmental stability. Higher combustor liner temperatures than today's engines and the need for lightweight materials will require the use of advanced ceramic-matrix composites (CMC's) in hot-section components. The HSCT is just one example being used to demonstrate the need for such materials. This thesis evaluates silicon carbide (SiC) as a potential base material for HSCT and other similar applications. Key issues are the environmental durability for the materials of interest. One of the leading combustor design schemes leads to an environment which will contain both oxidizing and reducing gas mixtures. The concern is that these environments may affect the stability of the silica (SiO2) scale on which SiC depends for environmental protection. A unique High Pressure Burner Rig (HPBR) was developed to simulate the combustor conditions of future gas turbine engines, and a series of tests were conducted on commercially available SiC material. These tests are intended as a feasibility study for the use of these materials in applications such as the HSCT. Linear weight loss and surface recession of the SiC is observed as a result of SiO2 volatility for both fuel-lean and fuel-rich gas mixtures. These observations are compared and agree well with thermogravimetric analysis (TGA) experiments. A strong Arrhenius-type temperature dependence exists. In addition, the secondary dependencies of pressure and gas velocity are defined. As a result, a model is developed to enable extrapolation to points outside the experimental space of the burner rig, and in particular, to potential gas turbine engine conditions.

  9. Dietary Fiber

    MedlinePlus

    Fiber is a substance in plants. Dietary fiber is the kind you eat. It's a type of carbohydrate. You may also see it listed on a food label as soluble fiber or insoluble fiber. Both types have important health benefits. Good sources of dietary fiber include Whole grains Nuts ...

  10. Intermediate Temperature Stress Rupture of a Woven Hi-Nicalon, BN-Interphase, SiC Matric Composite in Air

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Hurst, Janet; Brewer, David

    1999-01-01

    Woven Hi-Nicalon (TM) reinforced melt-infiltrated SiC matrix composites were tested under tensile stress-rupture conditions in air at intermediate temperatures. A comprehensive examination of the damage state and the fiber properties at failure was performed. Modal acoustic emission analysis was used to monitor damage during the experiment. Extensive microscopy of the composite fracture surfaces and the individual fiber fracture surfaces was used to determine the mechanisms leading to ultimate failure. The rupture properties of these composites were significantly worse than expected compared to the fiber properties under similar conditions. This was due to the oxidation of the BN interphase. Oxidation occurred through the matrix cracks that intersected the surface or edge of a tensile bar. These oxidation reactions resulted in minor degradation to fiber strength and strong bonding of the fibers to one another at regions of near fiber-to-fiber contact. It was found that two regimes for rupture exist for this material: a high stress regime where rupture occurs at a fast rate and a low stress regime where rupture occurs at a slower rate. For the high stress regime, the matrix damage state consisted of through thickness cracks. The average fracture strength of fibers that were pulled-out (the final fibers to break before ultimate failure) was controlled by the slow-crack growth rupture criterion in the literature for individual Hi-Nicalon (TM) fibers. For the low stress regime, the matrix damage state consisted of microcracks which grew during the rupture test. The average fracture strength of fibers that were pulled-out in this regime was the same as the average fracture strength of individual fibers pulled out in as-produced composites tested at room temperature.

  11. Saturn V S-IC Stage LOX Tank

    NASA Technical Reports Server (NTRS)

    1964-01-01

    This image depicts the Saturn V S-IC (first) stage liquid oxygen (LOX) tank being lowered into the irner tank in a high bay at the Marshall Space Flight Center (MSFC). The S-IC stage utilized five F-1 engines that used liquid oxygen and kerosene as propellant and provided a combined thrust of 7,500,000 pounds.

  12. Alternate current characteristics of SiC powders

    NASA Astrophysics Data System (ADS)

    Mârtensson, E.; Gäfvert, U.; Önneby, C.

    2001-09-01

    Silicon carbide (SiC) powder is used in nonlinear field grading materials. The composite material, consisting of an insulating polymer matrix filled with the SiC grains, is usually a percolated system with established conducting paths. In order to explain the properties, the electrical characteristic of the SiC powder itself is of interest. The ac characteristics of SiC powders have been studied by dielectric response, capacitance-voltage, and ac-pulse measurements. The frequency, electric field, and pressure dependencies have been analyzed for green and black SiC, which have different doping. The ac characteristics of green and black SiC powders are governed by both the barrier regions at the SiC-grain contacts and the surrounding matrix. The nonlinear loss is determined by the conduction current at the contacts. Depending on the doping level of the SiC grains, the capacitance may be controlled by either the nonlinear capacitance of the barrier region or the linear capacitance of the surrounding matrix. Each contact zone may be modeled by a nonlinear resistance in parallel with both a nonlinear and a linear capacitance. The components are considered to be frequency independent. However, in order to explain the macroscopic frequency and field dependencies of the SiC powders, the use of a network of unique contact zones with dissimilar properties is suggested.

  13. Method of preparing fiber reinforced ceramic material

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T. (Inventor)

    1987-01-01

    Alternate layers of mats of specially coated SiC fibers and silicon monotapes are hot pressed in two stages to form a fiber reinforced ceramic material. In the first stage a die is heated to about 600 C in a vacuum furnace and maintained at this temperature for about one-half hour to remove fugitive binder. In the second stage the die temperature is raised to about 1000 C and the layers are pressed at between 35 and 138 MPa. The resulting preform is placed in a reactor tube where a nitriding gas is flowed past the preform at 1100 to 1400 C to nitride the same.

  14. Fiber Creep Evaluation by Stress Relaxation Measurements

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Dicarlo, James A.; Wagner, Timothy

    1991-01-01

    A simple bend stress relaxation (BSR) test has been used to measure the creep related properties of a chemically vapor-deposited SiC fiber. Time, temperature, and strain dependent BSR data were analyzed to ascertain the ability of the stress relaxation results to predict tensile creep as a function of the same parameters. The predictions compared very well to actual creep data obtained by axial measurements, indicating that the BSR test could be used for determining both creep and stress relaxation of polycrystalline ceramic fibers under tensile loading.

  15. Crack initiation in borosilicate glass-SiC fiber composites

    SciTech Connect

    Dutton, R.E.; Pagano, N.J.; Kim, R.Y.

    1996-04-01

    The initiation of matrix microcracking was investigated in unidirectional glass matrix composites having controlled fiber spacing. Observations were taken from composites consisting of regular arrays of TiB{sub 2}-coated SIGMA 1240 and carbon-coated SCS-6 monofilament SiC fibers in a series of borosilicate glasses. The thermal expansion mismatch between the fibers and glass matrix was varied such that the resulting radial stresses after processing ranged from tensile to compressive. The glass strongly bonds to the TiB{sub 2}-coated SIGMA 1240 fiber but weakly bonds to the carbon coating of the SCS-6 fiber, allowing the investigation of the effects of bonding at the fiber/matrix interface. The observed crack initiation stresses of the various composites are compared to predictions based on a previously developed semiempirical model and used to study the influence of the volume fraction of fibers, residual stress state and interface strength.

  16. Integrated optics for fiber optic sensors

    NASA Technical Reports Server (NTRS)

    Minford, W. J.; Depaula, R. P.

    1991-01-01

    Recent progress achieved in the field of fiber-optic sensor applications is discussed with emphasis placed on LiNbO3-based integrated optics (IO). Particular consideration is given to advanced electromagnetic-field sensors, an integrated laser vibrometer system, and a fiber-optic gyroscope system. It is shown that the multifunction IO chips have enabled high perforamance fiber-optic sensors (e.g., fiber-optic gyros), provided advanced and unique signal processing capabilities and advanced architectures, and have a potential of making fiber-optic sensors at low cost.

  17. Porous silicon carbide (SiC) semiconductor device

    NASA Technical Reports Server (NTRS)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1994-01-01

    A semiconductor device employs at least one layer of semiconducting porous silicon carbide (SiC). The porous SiC layer has a monocrystalline structure wherein the pore sizes, shapes, and spacing are determined by the processing conditions. In one embodiment, the semiconductor device is a p-n junction diode in which a layer of n-type SiC is positioned on a p-type layer of SiC, with the p-type layer positioned on a layer of silicon dioxide. Because of the UV luminescent properties of the semiconducting porous SiC layer, it may also be utilized for other devices such as LEDs and optoelectronic devices.

  18. Cryogenic optical testing of SiC mirrors for ASTRO-F and C/SiC composite mirrors for SPICA

    NASA Astrophysics Data System (ADS)

    Kaneda, Hidehiro; Nakagawa, Takao; Enya, Keigo; Onaka, Takashi

    2004-06-01

    Light-weight mirrors are developed for two Japanese infrared astronomical missions, ASTRO-F and SPICA. ASTRO-F is scheduled for launch in 2005, while the target year for launch of SPICA is 2010. The mirrors of the ASTRO-F telescope are made of a sandwich-type silicon carbide (SiC) material, comprising porous core and CVD coat of SiC on the surface. Cryogenic measurements of the ASTRO-F primary mirror and telescope assembly were performed extensively. As for the SPICA telescope, which has an aperture of 3.5-m diameter, carbon-fiber-reinforced SiC (C/SiC composite), as well as SiC, is one of the promising candidates for mirror material. C/SiC composite spherical test mirrors of 160-mm diameter has recently been manufactured and tested. This paper presents the experimental results of the cryogenic performance obtained for the sandwich-type SiC mirrors and the C/SiC composite mirrors.

  19. Processing of sintered alpha SiC

    NASA Technical Reports Server (NTRS)

    Storm, R. S.

    1984-01-01

    Processing methods of sintered alpha SiC for engine applications are developed in a cost effective manner, using a submicron sized powder blended with sintering aids (boron and carbon). The processes for forming a green powder compact, such as dry pressing, cold isostatic pressing and green machining, slip casting, aqueous extrusion, plastic extrusion, and injection molding, are described. Dry pressing is the simplest route to component fabrication, and is carried out at approximately 10,000 psi pressure, while in the cold isostatic method the pressure could go as high as 20,000 psi. Surfactants are added to control settling rates and casting characteristics in the slip casting. The aqueous extrusion process is accomplished by a hydraulic ram forcing the aqueous mixture through a die. The plastic forming processes of extrusion and injection molding offer the potential of greater diversity in shape capacity. The physical properties of sintered alpha SiC (hardness, Young's modulus, shear modulus, and thermal diffusivity) are extensively tested. Corrosion resistance test results of silicon carbide are included.

  20. UV laser drilling of SiC for semiconductor device fabrication

    NASA Astrophysics Data System (ADS)

    Krüger, Olaf; Schöne, Gerd; Wernicke, Tim; John, Wilfred; Würfl, Joachim; Tränkle, Günther

    2007-04-01

    Pulsed UV laser processing is used to drill micro holes in silicon carbide (SiC) wafers supporting AlGaN/GaN transistor structures. Direct laser ablation using nanosecond pulses has been proven to provide an efficient way to create through and blind holes in 400 µm thick SiC. When drilling through, openings in the front pads are formed, while blind holes stop ~40 µm before the backside and were advanced to the electrical contact pad by subsequent plasma etching without an additional mask. Low induction connections (vias) between the transistor's source pads and the ground on the backside were formed by metallization of the holes. Micro vias having aspect ratios of 5-6 have been processed in 400 µm SiC. The process flow from wafer layout to laser drilling is available including an automated beam alignment that allows a positioning accuracy of ±1 µm with respect to existing patterns on the wafer. As proven by electrical dc and rf measurements the laser-assisted via technologies have successfully been implemented into fabrication of AlGaN/GaN high-power transistors.

  1. Effects of heat treatment on the mechanical properties of SiC p/6061 Al composite

    NASA Astrophysics Data System (ADS)

    Aldun, D.; Martin, P.; Sun, J.

    1992-10-01

    Metal-matrix composites have been receiving considerable attention as light-weight materials for use in many advanced technology applications. Silicon carbide (SiC) particles and whiskers have several advantages over other discontinuous reinforcements. Studies have shown that heat treatment can change the mechanical properties of metal-matrix composites. Modified heat treatments were developed for SiC p/6061 Al composites through a series of heat treatment with varied solution temperatures and aging time. Mechanical tests were conducted to determine the mechanical properties of the composites in three conditions; as-received, annealed, and heat treated. The modified heat treatments resulted in increases in the yield strength of up to 12% over the manufacturer’s reported yield strength for the standard T6 heat treatment. The trends which occur during heat treatment of SiC p/6061 Al are simular to those which occur during heat treatment of aluminum alloys. In addition, the relationship between the mechanical properties and the heat treatment parameters was documented. Throughout this study, the values of elastic modules were rather erratic compared to the strength values. Scanning Electron Microscope fractographic analysis revealed various fracture initiation sites, such as particle clusters and iron inclusions.

  2. Transient Infrared Studies of Carrier Injection Effects on the Reststrahlen Band of SiC

    NASA Astrophysics Data System (ADS)

    Spann, Bryan; Compton, Ryan; Dunkelberger, Adam; Long, James; Klein, Paul; Caldwell, Josh; Owrutsky, Jeff

    2015-03-01

    Sub-diffraction light confinement has led to advances in imaging, metamaterials, and plasmonics among other fields. A phenomenon that can provide sub-diffraction light is the surface phonon polariton (SPhP). SPhPs couple infrared photons with optical phonons. Because SPhPs are coupled directly to phonons, lifetimes can be longer than that of surface plasmon polaritons (SPPs) whose lifetimes are dominated by electron scattering. SiC is one material that exhibits SPhPs. SiC SPhPs are activated by photons with energies near the Reststrahlen band. In this study we investigate aspects of carrier dynamics by photo-injecting free carriers into the SiC conduction band using a pulsed 355 nm pump laser and probe the resulting dynamics near the Reststrahlen band using a tunable CO2 laser. Variable pump fluences provided free carrier densities of 1x1017 to 1x1019. Probing the excited state dynamics near the Reststrahlen band revealed complex transient behavior resulting in positive and negative changes in transient reflectance depending on the photo-injection level and the probe energy. Numerical simulations were carried out to mimic the initial photo-injection level provided by the transient experiment and resulted in qualitative agreement with the experiment. National Research Council Postdoctoral Fellow

  3. Biomechanical fatigue analysis of an advanced new carbon fiber/flax/epoxy plate for bone fracture repair using conventional fatigue tests and thermography.

    PubMed

    Bagheri, Zahra S; El Sawi, Ihab; Bougherara, Habiba; Zdero, Radovan

    2014-07-01

    The current study is part of an ongoing research program to develop an advanced new carbon fiber/flax/epoxy (CF/flax/epoxy) hybrid composite with a “sandwich structure” as a substitute for metallic materials for orthopedic long bone fracture plate applications. The purpose of this study was to assess the fatigue properties of this composite, since cyclic loading is one of the main types of loads carried by a femur fracture plate during normal daily activities. Conventional fatigue testing, thermographic analysis, and scanning electron microscopy (SEM) were used to analyze the damage progress that occurred during fatigue loading. Fatigue strength obtained using thermography analysis (51% of ultimate tensile strength) was confirmed using the conventional fatigue test (50–55% of ultimate tensile strength). The dynamic modulus (E⁎) was found to stay almost constant at 47 GPa versus the number of cycles, which can be related to the contribution of both flax/epoxy and CF/epoxy laminae to the stiffness of the composite. SEM images showed solid bonding at the CF/epoxy and flax/epoxy laminae, with a crack density of only 0.48% for the plate loaded for 2 million cycles. The current composite plate showed much higher fatigue strength than the main loads experienced by a typical patient during cyclic activities; thus, it may be a potential candidate for bone fracture plate applications. Moreover, the fatigue strength from thermographic analysis was the same as that obtained by the conventional fatigue tests, thus demonstrating its potential use as an alternate tool to rapidly evaluate fatigue strength of composite biomaterials. PMID:24918250

  4. Growth Of Graphitic Polyhedra, SiC Platelets, And Carbon Nanotubes Filled With SiC Nanowires By Laser Ablation

    SciTech Connect

    Kokai, Fumio; Uchiyama, Kunihiro; Chigusa, Hajime; Nozaki, Iori; Noguchi, Eriko; Kameda, Yuto; Koshio, Akira

    2010-10-08

    Three characteristic silicon/carbon nanostructures, i.e., graphitic polyhedral (GP) particles, silicon carbide (SiC) platelets, and carbon nanotubes (CNTs) filled with SiC nanowires, were synthesized by the laser ablation of Si-C targets in the presence of high-pressure Ar gas up to 0.9 MPa. The growth of nanostructures was controlled merely by adjusting the Si content in graphite and the ambient Ar gas pressure. Deposits containing GP particles were purified by heat treatment at 550 deg. C in a pure oxygen atmosphere for 1 h. CNTs filled with SiC nanowires were grown without a catalyst. Unlike previous studies of CNTs filled with metals or compounds, all the CNTs checked by transmission electron microscopy contained SiC nanowires and no unfilled CNTs were produced. We discuss the growth mechanisms of the three nanostructures.

  5. Advances in SiC/SiC Composites for Aero-Propulsion

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.

    2013-01-01

    In the last decade, considerable progress has been made in the development and application of ceramic matrix composites consisting of silicon carbide (SiC) based matrices reinforced by small-diameter continuous-length SiC-based fibers. For example, these SiC/SiC composites are now in the early stages of implementation into hot-section components of civil aero-propulsion gas turbine engines, where in comparison to current metallic components they offer multiple advantages due to their lighter weight and higher temperature structural capability. For current production-ready SiC/SiC, this temperature capability for long time structural applications is 1250 degC, which is better than 1100 degC for the best metallic superalloys. Foreseeing that even higher structural reliability and temperature capability would continue to increase the advantages of SiC/SiC composites, progress in recent years has also been made at NASA toward improving the properties of SiC/SiC composites by optimizing the various constituent materials and geometries within composite microstructures. The primary objective of this chapter is to detail this latter progress, both fundamentally and practically, with particular emphasis on recent advancements in the materials and processes for the fiber, fiber coating, fiber architecture, and matrix, and in the design methods for incorporating these constituents into SiC/SiC microstructures with improved thermo-structural performance.

  6. The Effect of Excess Carbon on the Crystallographic, Microstructural, and Mechanical Properties of CVD Silicon Carbide Fibers

    SciTech Connect

    Marzik, J V; Croft, W J; Staples, R J; MoberlyChan, W J

    2006-12-05

    Silicon carbide (SiC) fibers made by chemical vapor deposition (CVD) are of interest for organic, ceramic, and metal matrix composite materials due their high strength, high elastic modulus, and retention of mechanical properties at elevated processing and operating temperatures. The properties of SCS-6{trademark} silicon carbide fibers, which are made by a commercial process and consist largely of stoichiometric SiC, were compared with an experimental carbon-rich CVD SiC fiber, to which excess carbon was added during the CVD process. The concentration, homogeneity, and distribution of carbon were measured using energy dispersive x-ray spectroscopy (SEM/EDS). The effect of excess carbon on the tensile strength, elastic modulus, and the crystallographic and microstructural properties of CVD silicon carbide fibers was investigated using tensile testing, x-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

  7. Strong fibers

    SciTech Connect

    Li, Che-Yu.

    1991-03-01

    This program was directed to a new and generic approach to the development of new materials with novel and interesting properties, and to the precision fabrication of these materials in one and two-dimensional forms. Advanced deposition processes and microfabrication technology were used to produce fibers and grids of metals, semiconductors, ceramics, and mixtures of controlled composition and structure, and with new and interesting mechanical and physical properties. Deposition processes included electron beam evaporation, co-deposition of mixtures by dual electron beam evaporation, thermal evaporation, sputtering of a single element or compound, sputtering of a single element in a gaseous atmosphere to produce compounds, plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), and selective tungsten chemical vapor deposition (W-CVD). The approach was to use the deposition processes in coordination with patterns generated by optical lithography to produce fibers with transverse dimensions in the micron range, and lengths from less than a millimeter to several centimeters. The approach is also applicable to the production of two-dimensional grids and particulates of controlled sizes and geometries.

  8. Mullite fiber reinforced reaction bonded Si3N4 composites

    NASA Technical Reports Server (NTRS)

    Saleh, T.; Sayir, A.; Lightfoot, A.; Haggerty, J.

    1996-01-01

    Fracture toughnesses of brittle ceramic materials have been improved by introducing reinforcements and carefully tailored interface layers. Silicon carbide and Si3N4 have been emphasized as matrices of structural composites intended for high temperature service because they combine excellent mechanical, chemical, thermal and physical properties. Both matrices have been successfully toughened with SiC fibers, whiskers and particles for ceramic matrix composite (CMC) parts made by sintering, hot pressing or reaction forming processes. These SiC reinforced CMCs have exhibited significantly improved toughnesses at low and intermediate temperature levels, as well as retention of properties at high temperatures for selected exposures; however, they are vulnerable to attack from elevated temperature dry and wet oxidizing atmospheres after the matrix has cracked. Property degradation results from oxidation of interface layers and/or reinforcements. The problem is particularly acute for small diameter (-20 tim) polymer derived SiC fibers used for weavable toes. This research explored opportunities for reinforcing Si3N4 matrices with fibers having improved environmental stability; the findings should also be applicable to SiC matrix CMCs.

  9. Fabrication of SiC whisker-reinforced SiC ceramics

    SciTech Connect

    Miyahara, Kaoru; Watanabe, Takashi; Koga, Shin; Sasa, Tadashi

    1992-10-01

    A fabrication process of SiC whisker-reinforced SiC ceramics consisting of whisker CVD-coating for the control of interfacial bonding, slurry-pressing and HIP consolidation has been developed. Microstructural observation confirmed the incorporation of the interfacial carbon layer in the composites brought about remarkable whisker bridging/pull-out in the fracture. Whisker-bridging was considered to be a predominant toughening mechanism. To optimize the interfacial properties, the effect of coating conditions, i.e., amount of coating and CVD temperature, on the fracture toughness were studied. The effect of whisker diameter on the fracture toughness and anisotropy in the fracture toughness were also investigated. 12 refs.

  10. Active Oxidation of SiC

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Myers,Dwight L.; Harder, Bryan J.

    2011-01-01

    The high temperature oxidation of silicon carbide occurs in either a passive or active mode, depending on temperature and oxygen potential. Passive oxidation forms a protective oxide film which limits attack of the SiC:SiC(s) + 3/2 O2(g) = SiO2(s) + CO(g.) Active oxidation forms a volatile oxide and leads to extensive attack of the SiC: SiC(s) + O2(g) = SiO(g) + CO(g). The transition points and rates of active oxidation are a major issue. Previous studies are reviewed and the leading theories of passive/active transitions summarized. Comparisons are made to the active/passive transitions in pure Si, which are relatively well-understood. Critical questions remain about the difference between the active-to-passive transition and passive-to-active transition. For Si, Wagner [2] points out that the active-to-passive transition is governed by the criterion for a stable Si/SiO2 equilibria and the passive-to-active transition is governed by the decomposition of the SiO2 film. This suggests a significant oxygen potential difference between these two transitions and our experiments confirm this. For Si, the initial stages of active oxidation are characterized by the formation of SiO(g) and further oxidation to SiO2(s) as micron-sized rods, with a distinctive morphology. SiC shows significant differences. The active-to-passive and the passive-to-active transitions are close. The SiO2 rods only appear as the passive film breaks down. These differences are explained in terms of the reactions at the SiC/SiO2 interface. In order to understand the breakdown of the passive film, pre-oxidation experiments are conducted. These involve forming dense protective scales of 0.5, 1, and 2 microns and then subjecting the samples with these scales to a known active oxidation environment. Microstructural studies show that SiC/SiO2 interfacial reactions lead to a breakdown of the scale with a distinct morphology.

  11. Microchemical analysis of the SCS-6 silicon carbide fiber

    SciTech Connect

    Ning, Xian Jie; Pirouz, P. . Dept. of Materials Science and Engineering); Farmer, S.C. )

    1993-08-01

    A detailed quantitative study of the microstructural variation of chemical composition of chemically vapor-deposited commercial SiC SCS-6 fiber is presented. Chemical etching and various electron-optical techniques including scanning electron microscopy, transmission electron microscopy scanning Auger microscopy, Auger electron spectroscopy, and parallel electron energy loss spectroscopy are used to analyze the chemical composition of the as-received fiber. In addition, some results on stereology of the high-temperature annealed fiber are presented. The results show that the carbon-to-silicon atom ratio in the SiC layers decreases in a stepwise fashion from [approximately] 3:2 to [approximately] 1:1 in going from the innermost layer to the outermost layer.

  12. Microchemical analysis of the SCS-6 silicon carbide fiber

    NASA Technical Reports Server (NTRS)

    Ning, Xian-Jie; Pirouz, Pirouz; Farmer, Serene C.

    1993-01-01

    A detailed quantitative study of the microstructural variation of chemical composition of chemically vapor-deposited commercial SiC SCS-6 fiber is presented. Chemical etching and various electron-optical techniques including SEM, TEM, scanning Auger microscopy, AES, and parallel electron energy loss spectroscopy are used to analyze the chemical composition of the as-received fiber. In addition, some results on stereology of the high-temperature annealed fiber are presented. The results show that the carbon-to-silicon atom ratio in the SiC layers decreases in a stepwise fashion from about 3:2 to about 1:1 in going from the innermost layer to the outermost layer.

  13. Fiber biology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton fiber cells arising from seed epidermis is the most important agricultural textile commodity in the world. To produce fully mature fibers, approximately two months of fiber developmental process are required. The timing of four distinctive fiber development stages consisting of initiation, ...

  14. ICP Etching of SiC

    SciTech Connect

    Grow, J.M.; Lambers, E.S.; Ostling, M.; Pearton, S.J.; Ren, F.; Shul, R.J.; Wang, J.J.; Zetterling, C.-M.

    1999-02-04

    A number of different plasma chemistries, including NF{sub 3}/O{sub 2}, SF{sub 6}/O{sub 2}, SF{sub 6}/Ar, ICl, IBr, Cl{sub 2}/Ar, BCl{sub 3}/Ar and CH{sub 4}/H{sub 2}/Ar, have been investigated for dry etching of 6H and 3C-SiC in a Inductively Coupled Plasma tool. Rates above 2,000 {angstrom} cm{sup {minus}1} are found with fluorine-based chemistries at high ion currents. Surprisingly, Cl{sub 2}-based etching does not provide high rates, even though the potential etch products (SiCi{sub 4} and CCl{sub 4}) are volatile. Photoresist masks have poor selectivity over SiC in F{sub 2}-based plasmas under normal conditions, and ITO or Ni are preferred.

  15. Investigation of fiber/matrix interfacial mechanical behavior in ceramic matrix composites by cyclic fiber push-in testing

    SciTech Connect

    Eldridge, J.I.; Bhatt, R.T.; Bansal, N.P.; Olmstead, F.A.

    1996-12-31

    Cyclic fiber push-in testing is used to examine the stability of interfacial frictional sliding stresses and fiber debond lengths with continued push-in load/unload cycles. The measured response to applying load cycling to a single fiber reveals the susceptibility of the fiber/matrix interface to degrade under cyclic loading conditions, and thus, helps evaluate the contribution of the interface to the cyclic fatigue behavior of the composite after the occurrence of matrix cracks. From cyclic push-in testing in room temperature air, decreasing interfacial sliding stresses and increasing debond lengths are observed with continued load cycling for SCS-6 SiC fiber reinforced reaction-bonded silicon nitride (SCS-6/RBSN), whereas stable interfacial sliding stresses and no increase in debond lengths are observed with continued load cycling for SCS-6 SiC fiber reinforced strontium aluminosilicate (SCS-6/SAS). These results indicate that fiber-bridged matrix cracks should be stable under cyclic fatigue loading conditions in SCS-6/SAS, but should exhibit increasing crack opening displacements and fiber pull-out with continued cycling in SCS-6/RBSN. In addition, changing the test environment from room air to nitrogen significantly affects the cyclic push-in test results for SCS-6/RBSN, but not for SCS-6/SAS. The different responses to this change in test environment are attributed to different locations of interfacial failure.

  16. Advanced composite combustor structural concepts program

    NASA Technical Reports Server (NTRS)

    Sattar, M. A.; Lohmann, R. P.

    1984-01-01

    An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's.

  17. Ellipsometric study of cubic SiC

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Shoemaker, Neil S.; Powell, J. A.

    1990-01-01

    Variable angle spectroscopic ellipsometry (VASE) was applied to cubic SiC. This technique gives absolute values of the refractive index (n) and the extinction coefficient (k) of a substrate and/or a thin film of unknown material. The samples were grown by chemical vapor deposition (CVD) on p-type silicon. The substrate was aligned either on the (001) axis or 1 degree of (001). Several growth temperatures and growth durations were used. The samples were divided into two groups: (1) thick films of order 10 microns grown near optimal conditions of temperature, flow, and gas ratio; and (2) thin films of order 100 A grown at various temperatures. The ellipsometric results for samples in group 1 were analyzed using a two-phase model (substrate and ambient). Results show that for wavelengths in the visible, the refractive index of these CVD samples is equal to that reported for single crystal cubic SiC, within the experimental error, which is on the order of 1 percent. However, the extinction coefficient has a relatively large value, even above the band gap. The absorption is sample dependent and has a broad peak in the visible. The results for samples in group 2 were analyzed using a three-phase model (substrate, film, and ambient). The dielectric functions of the film, deducted from the measured n and k, were further analyzed using the effective medium approximation. The results show that the films contain 30 to 40 vol. percent amorphous silicon, i.e., silicon with only short-range order.

  18. Imaging of SiC in metal matrix composites

    SciTech Connect

    Radmilovic, V.; O`Keefe, M.A.; Thomas, G.

    1992-08-01

    TEM has advantages over XRD in determining lattice periodicity. This paper reports an attempt in matching a simulation to an experimental image of SiC in an Al-8.5wt%Fe-1.3 wt%V-1.7 wt%Si composite containing 15 wt% SiC particulates, processed by powder metallurgy. The hexagonal allotrope has predominantly the 6H polytype structure; 1/3 of the 15R polytype is also observed. This SiC structure represents the 87R polytype. 6 refs, 2 figs.

  19. Report on status of execution of SiC step document

    SciTech Connect

    Katoh, Yutai; Terrani, Kurt A.

    2015-02-01

    Advanced fuel claddings made entirely or mainly of silicon carbide (SiC) ceramics and/or composites are considered very attractive elements of the accident-tolerant fuels for the light water reactors. In order to translate the promise of SiC composite materials into a reliable fuel cladding, a coordinated program of component level design and materials development must be carried out with many key feasibility issues addressed a-priori to inform the process. With the primary objective of developing a draft blueprint of a technical program that addresses the critical feasibility issues; assesses design and performance issues related with manufacturing, operating, and off-normal events; and advances the technological readiness levels in essential technology elements, a draft plan for the Systematic Technology Evaluation Program for SiC/SiC Composite Accident-Tolerant LWR Fuel Cladding and Core Structures was developed in the FY-14 Advanced Fuels Campaign of the U.S. Department of Energy’s Fuel Cycles Research and Development Program. This document summarizes the status of execution of the technical plan within the activities at the Oak Ridge National Laboratory.

  20. Studies on non-oxide coating on carbon fibers using plasma enhanced chemical vapor deposition technique

    NASA Astrophysics Data System (ADS)

    Patel, R. H.; Sharma, S.; Prajapati, K. K.; Vyas, M. M.; Batra, N. M.

    2016-05-01

    A new way of improving the oxidative behavior of carbon fibers coated with SiC through Plasma Enhanced Chemical Vapor Deposition technique. The complete study includes coating of SiC on glass slab and Stainless steel specimen as a starting test subjects but the major focus was to increase the oxidation temperature of carbon fibers by PECVD technique. This method uses relatively lower substrate temperature and guarantees better stoichiometry than other coating methods and hence the substrate shows higher resistance towards mechanical and thermal stresses along with increase in oxidation temperature.

  1. Scanning acoustic microscopy of SCS-6 silicon carbide fiber

    SciTech Connect

    Sathish, S.; Cantrell, J.H.; Yost, W.T.

    1996-01-01

    Scanning acoustic microscopy of SCS-6 silicon carbide fiber reveals large radial variations in acoustic reflectivity associated with the chemical composition and microstructure of a given fiber region. Rayleigh wave fringe patterns observed in each of five subregions are used to calculate the average Young modulus of that subregion. The Young modulus is found to increase monotonically from 40 GPa in the carbon core to a value of 413 GPa in the stoichiometric SiC region. The effective Young modulus of the fiber as a whole is estimated from the moduli of the individual regions and it is compared with mechanical measurements reported in the literature.

  2. Oxidation-resistant interfacial coatings for continuous fiber ceramic composites

    SciTech Connect

    Stinton, D.P.; Besmann, T.M.; Bleier, A.; Shanmugham, S.; Liaw, P.K.

    1995-08-01

    Continuous fiber ceramic composites mechanical behavior are influenced by the bonding characteristics between the fiber and the matrix. Finite modeling studies suggest that a low-modulus interfacial coating material will be effective in reducing the residual thermal stresses that are generated upon cooling from processing temperatures. Nicalon{trademark}/SiC composites with carbon, alumina and mullite interfacial coatings were fabricated with the SiC matrix deposited using a forced-flow, thermal gradient chemical vapor infiltration process. Composites with mullite interfacial coatings exhibited considerable fiber pull-out even after oxidation and have potential as a composite system.

  3. Electron microscopy and microanalysis of the fiber-matrix interface in monolithic silicone carbide-based ceramic composite material for use in a fusion reactor application.

    PubMed

    Toplisek, Tea; Drazic, Goran; Novak, Sasa; Kobe, Spomenka

    2008-01-01

    A composite material made from continuous monolithic silicone carbide (SiC) fibers and a SiC-based matrix (SiC(f)/SiC), was prepared using a novel technique, i.e. adapted dip coating and infiltration of SiC fibers with a water suspension containing SiC particles and a sintering additive. This kind of material could be used in the first-wall blanket of a future fusion reactor. Using magnetron sputtering, the SiC fibers were coated with various thin layers (TiC, CrN, CrC, WC, DLC-diamond-like carbon) of the interface material by physical vapor deposition (PVD). Using scanning and transmission electron microscopy and microanalysis, detailed microstructural studies of the fiber-matrix interface were performed. Both samples, with coated and uncoated fibers, were examined under a load. The microcracks introduced by the Vickers indenter continued their path through the fibers, and thus caused the failure of the composite material, in the case of the uncoated fibers or deviated from their primary direction at the fiber-matrix interface in the case of the coated fibers. PMID:18172883

  4. Factors affecting pressure infiltration of packed SiC particulates by liquid aluminum

    SciTech Connect

    Narciso, J.; Alonso, A.; Pamies, A.; Garcia-Cordovilla, C.; Louis, E.

    1995-04-01

    Pressure infiltration is being currently used to evaluate the wettability of ceramic particles and fibers by liquid metals. The objective of this work is to investigate the effect of type and surface condition of the particulates and infiltration atmosphere on pressure infiltration of packed SiC particulates by pure liquid aluminum, Fourteen SiC particulates from five different suppliers, of green (high purity) and black (low purity) types, were used. Two of the particulates were subjected to either low or high-temperature heat treatments in order to either bum organic residues or promote oxidation. Infiltrations were carried out in air, argon, argon/hydrogen, and nitrogen/hydrogen atmospheres. The results indicate that the threshold pressure does not depend appreciably on the type of particulate. A heat treatment at 600 C improves the infiltration performance of particulates having a large amount of organic residues, whereas oxidation at 1,000 C decreases the threshold pressure. The results also illustrate the effects of the infiltration atmosphere; in particular, it is shown that inert or reducing atmospheres improve wettability.

  5. Observations of Ag diffusion in ion implanted SiC

    SciTech Connect

    Gerczak, Tyler J.; Leng, Bin; Sridharan, Kumar; Jerry L. Hunter, Jr.; Giordani, Andrew J.; Allen, Todd R.

    2015-03-17

    The nature and magnitude of Ag diffusion in SiC has been a topic of interest in connection with the performance of tristructural isotropic (TRISO) coated particle fuel for high temperature gas-cooled nuclear reactors. Ion implantation diffusion couples have been revisited to continue developing a more complete understanding of Ag fission product diffusion in SiC. Ion implantation diffusion couples fabricated from single crystal 4H-SiC and polycrystalline 3C-SiC substrates and exposed to 1500–1625°C, were investigated in this study by transmission electron microscopy and secondary ion mass spectrometry (SIMS). The high dynamic range of SIMS allowed for multiple diffusion régimes to be investigated, including enhanced diffusion by implantation-induced defects and grain boundary (GB) diffusion in undamaged SiC. Lastly, estimated diffusion coefficients suggest GB diffusion in bulk SiC does not properly describe the release observed from TRISO fuel.

  6. Compensation in epitaxial cubic SiC films

    NASA Technical Reports Server (NTRS)

    Segall, B.; Alterovitz, S. A.; Haugland, E. J.; Matus, L. G.

    1986-01-01

    Hall measurements on four n-type cubic SiC films epitaxially grown by chemical vapor deposition on SiC substrates are reported. The temperature dependent carrier concentrations indicate that the samples are highly compensated. Donor ionization energies, E sub D, are less than one half the values previously reported. The values for E sub D and the donor concentration N sub D, combined with results for small bulk platelets with nitrogen donors, suggest the relation E sub D (N sub D) = E sub D(O) - alpha N sub N sup 1/3 for cubic SiC. A curve fit gives alpha is approx 2.6x10/5 meV cm and E sub D (O) approx 48 meV, which is the generally accepted value of E sub D(O) for nitrogen donors in cubic SiC.

  7. Saturn V S-IC Stage Fuel Tank

    NASA Technical Reports Server (NTRS)

    1964-01-01

    This image shows the Saturn V S-IC-T stage (S-IC static test article) fuel tank being attached to the thrust structure in the vehicle assembly building at the Marshall Space Flight Center (MSFC). The S-IC stage utilized five F-1 engines that used liquid oxygen and kerosene as propellant and provided a combined thrust of 7,500,000 pounds.

  8. Synthesis of micro-sized interconnected Si-C composites

    DOEpatents

    Wang, Donghai; Yi, Ran; Dai, Fang

    2016-02-23

    Embodiments provide a method of producing micro-sized Si--C composites or doped Si--C and Si alloy-C with interconnected nanoscle Si and C building blocks through converting commercially available SiO.sub.x (0

  9. Electrical Characterization of Defects in SiC Schottky Barriers

    NASA Technical Reports Server (NTRS)

    Schnabel, C. M.; Tabib-Azar, M.; Raffaelle, R. P.; Su, H. B.; Dudley, M.; Neudeck, P. G.; Bailey, S.

    2005-01-01

    We have been investigating the effect of screw dislocation and other structural defects on the electrical properties of SiC. SiC is a wide-bandgap semiconductor that is currently received much attention due to its favorable high temperature behavior and high electric field breakdown strength. Unfortunately, the current state-of-the-art crystal growth and device processing methods produce material with high defect densities, resulting in a limited commercial viability

  10. Sequential injection chromatography with a miniaturized multi-channel fiber optic detector for separation and quantification of propranolol and hydrochlorothiazide

    PubMed Central

    2011-01-01

    Background Sequential injection chromatography (SIC) is a new alternative separation technology. It has some advantages over high performance liquid chromatography (HPLC) regarding simplicity, inexpensiveness, portability, ease of use, maintenance requirement and operation time. In contrast, SIC has had suffered from some limitations. Results The current work involves four achievements. (a) One of the limitations of SIC has been overcome. A higher pressure resistant selection valve with additional ports was installed in an SIC system. This development allows propelling solution without showing solution leakage. (b) A new inexpensive rapid and green method for the separation and quantification of propranolol (PRP) and hydrochlorothiazide (HTZ) in their formulations was optimized and validated. (c) A miniaturized multi-channel fiber optic detector was coupled with the newly developed SIC system to detect PRP and HTZ at 270 and 290 nm, respectively. This issue enhanced the sensitivity rather than using a single-channel detector. (d) A comparative study on the efficiency of the SIC method with that of previous HPLC methods was conducted. Conclusions Besides the benefits of the instrumentation of SIC, the proposed method is rapider and more reagent-saving than previous HPLC methods. The total volume of consumed reagents and sample was 4.04 mL. The sample frequency was 22 samples/h. Other such analytical characters of the SIC method as resolution, peak symmetry, numbers of theoretical plates, linearity range, accuracy, precision and limits of detection and quantification recorded comparable results. PMID:21658210

  11. Reaction-Based SiC Materials for Joining Silicon Carbide Composites for Fusion Energy

    SciTech Connect

    Lewinsohn, Charles A.; Jones, Russell H.; Singh, M.; Serizawa, H.; Katoh, Y.; Kohyama, A.

    2000-09-01

    The fabrication of large or complex silicon carbide-fiber-reinforced silicon carbide (SiC/SiC) components for fusion energy systems requires a method to assemble smaller components that are limited in size by manufacturing constraints. Previous analysis indicates that silicon carbide should be considered as candidate joint materials. Two methods to obtain SiC joints rely on a reaction between silicon and carbon to produce silicon carbide. This report summarizes preliminary mechanical properties of joints formed by these two methods. The methods appear to provide similar mechanical properties. Both the test methods and materials are preliminary in design and require further optimization. In an effort to determine how the mechanical test data is influenced by the test methodology and specimen size, plans for detailed finite element modeling (FEM) are presented.

  12. MODELING THE TRANSVERSE THERMAL CONDUCTIVITY OF 2-D SICF/SIC COMPOSITES MADE WITH WOVEN FABRIC

    SciTech Connect

    Youngblood, Gerald E; Senor, David J; Jones, Russell H

    2004-06-01

    The hierarchical two-layer (H2L) model describes the effective transverse thermal conductivity (Keff) of a 2D-SiCf/SiC composite plate made from stacked and infiltrated woven fabric layers in terms of constituent properties and microstructural and architectural variables. The H2L model includes the effects of fiber-matrix interfacial conductance, high fiber packing fractions within individual tows and the non-uniform nature of 2D fabric/matrix layers that usually include a significant amount of interlayer porosity. Previously, H2L model Keff-predictions were compared to measured values for two versions of 2D Hi-Nicalon/PyC/ICVI-SiC composite, one with a “thin” (0.11m) and the other with a “thick” (1.04m) pyrocarbon (PyC) fiber coating, and for a 2D Tyranno SA/”thin” PyC/FCVI-SIC composite. In this study, H2L model Keff-predictions were compared to measured values for a 2D-SiCf/SiC composite made using the ICVI-process with Hi-Nicalon type S fabric and a “thin” PyC fiber coating. The values of Keff determined for the latter composite were significantly greater than the Keff-values determined for the composites made with either the Hi-Nicalon or the Tyranno SA fabrics. Differences in Keff-values were expected for the different fiber types, but major differences also were due to observed microstructural and architectural variations between the composite systems, and as predicted by the H2L model.

  13. Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites: Influence of Interface Modification

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Eldridge, Jeffrey I.

    1998-01-01

    Unidirectional celsian matrix composites having 42-45 vol % of uncoated or BN-SIC coated Hi-Nicalon fibers were tested in three-point bend at room temperature. The uncoated fiber-reinforced composites showed catastrophic failure with strength of 210 35 MPa and a flat fracture surface. In contrast, composites reinforced with coated fibers exhibited graceful failure with extensive fiber pullout. Values of first matrix cracking stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01%, respectively, with ultimate strength as high as 960 MPa. The elastic Young modulus of the uncoated and coated fiber-reinforced composites were 184 +/- 4 GPa and 165 +/- 5 GPa, respectively. Fiber push-through tests and microscopic examination indicated no chemical reaction at the uncoated or coated fiber-matrix interface. The low strength of composite with uncoated fibers is due to degradation of the fiber strength from mechanical damage during processing. Because both the coated- and uncoated-fiber-reinforced composites exhibited weak interfaces, the beneficial effect of the BN-SIC dual layer is primarily the protection of fibers from mechanical damage during processing.

  14. Associations of Pd, U and Ag in the SiC layer of neutron-irradiated TRISO fuel

    SciTech Connect

    Lillo, Thomas; Rooyen, Isabella Van

    2015-05-01

    Knowledge of the associations and composition of fission products in the neutron irradiated SiC layer of high-temperature gas reactor TRISO fuel is important to the understanding of various aspects of fuel performance that presently are not well understood. Recently, advanced characterization techniques have been used to examine fuel particles from the Idaho National Laboratory’s AGR-1 experiment. Nano-sized Ag and Pd precipitates were previously identified in grain boundaries and triple points in the SiC layer of irradiated TRISO nuclear fuel. Continuation of this initial research is reported in this paper and consists of the characterization of a relatively large number of nano-sized precipitates in three areas of the SiC layer of a single irradiated TRISO nuclear fuel particle using standardless EDS analysis on focused ion beam-prepared transmission electron microscopy samples. Composition and distribution analyses of these precipitates, which were located on grain boundaries, triple junctions and intragranular precipitates, revealed low levels, generally <10 atomic %, of palladium, silver and/or uranium with palladium being the most common element found. Palladium by itself, or associated with either silver or uranium, was found throughout the SiC layer. A small number of precipitates on grain boundaries and triple junctions were found to contain only silver or silver in association with palladium while uranium was always associated with palladium but never found by itself or in association with silver. Intergranular precipitates containing uranium were found to have migrated ~23 μm along a radial direction through the 35 μm thick SiC coating during the AGR-1 experiment while silver-containing intergranular precipitates were found at depths up to ~24 μm in the SiC layer. Also, Pd-rich, nano-precipitates (~10 nm in diameter), without evidence for the presence of either Ag or U, were revealed in intragranular regions throughout the SiC layer. Because not all

  15. Associations of Pd, U and Ag in the SiC layer of neutron-irradiated TRISO fuel

    NASA Astrophysics Data System (ADS)

    Lillo, T. M.; van Rooyen, I. J.

    2015-05-01

    Knowledge of the associations and composition of fission products in the neutron irradiated SiC layer of high-temperature gas reactor TRISO fuel is important to the understanding of various aspects of fuel performance that presently are not well understood. Recently, advanced characterization techniques have been used to examine fuel particles from the Idaho National Laboratory's AGR-1 experiment. Nano-sized Ag and Pd precipitates were previously identified in grain boundaries and triple points in the SiC layer of irradiated TRISO nuclear fuel. Continuation of this initial research is reported in this paper and consists of the characterization of a relatively large number of nano-sized precipitates in three areas of the SiC layer of a single irradiated TRISO nuclear fuel particle using standardless EDS analysis on focused ion beam-prepared transmission electron microscopy samples. Composition and distribution analyses of these precipitates, which were located on grain boundaries, triple junctions and intragranular precipitates, revealed low levels, generally <10 atomic %, of palladium, silver and/or uranium with palladium being the most common element found. Palladium by itself, or associated with either silver or uranium, was found throughout the SiC layer. A small number of precipitates on grain boundaries and triple junctions were found to contain only silver or silver in association with palladium while uranium was always associated with palladium but never found by itself or in association with silver. Intergranular precipitates containing uranium were found to have migrated ∼23 μm along a radial direction through the 35 μm thick SiC coating during the AGR-1 experiment while silver-containing intergranular precipitates were found at depths up to ∼24 μm in the SiC layer. Also, Pd-rich, nano-precipitates (∼10 nm in diameter), without evidence for the presence of either Ag or U, were revealed in intragranular regions throughout the SiC layer. Because not

  16. The impact resistance of SiC and other mechanical properties of SiC and Si3N4

    NASA Technical Reports Server (NTRS)

    Bradt, R. C.

    1984-01-01

    Studies focused on the impact and mechanical behavior of SiC and Si3N4 at high temperatures are summarized. Instrumented Charpy impact testing is analyzed by a compliance method and related to strength; slow crack growth is related to processing, and creep is discussed. The transient nature of flaw populations during oxidation under load is emphasized for both SiC and Si3N4.

  17. Refinement of the Microstructure of Sn-Ag-Bi-In Solder, by Addition of SiC Nanoparticles, to Reduce Electromigration Damage Under High Electric Current

    NASA Astrophysics Data System (ADS)

    Kim, Youngseok; Nagao, Shijo; Sugahara, Tohru; Suganuma, Katsuaki; Ueshima, Minoru; Albrecht, Hans-Juergen; Wilke, Klaus; Strogies, Joerg

    2014-12-01

    The trends of miniaturization, multi-functionality, and high performance in advanced electronic devices require higher densities of I/O gates and reduced area of soldering of interconnections. This increases the electric current density flowing through the interconnections, increasing the risk of interconnection failure caused by electromigration (EM). Accelerated directional atomic diffusion in solder materials under high current induces substantial growth of intermetallic compounds (IMCs) at the anode, and also void and crack formation at the cathode. In the work discussed in this paper, addition of SiC nanoparticles to Sn-Ag-Bi-In (SABI) lead-free solder refined its microstructure and improved its EM reliability under high current stress. Electron backscattering diffraction analysis revealed that the added SiC nanoparticles refined solder grain size after typical reflow. Under current stress, SABI joints with added nano-SiC had lifetimes almost twice as long as those without. Comparison of results from high-temperature aging revealed direct current affected evolution of the microstructure. Observations of IMC growth indicated that diffusion of Cu in the SiC composite solder may not have been reduced. During current flow, however, only narrow voids were formed in solder containing SiC, thus preventing the current crowding caused by bulky voids in the solder without SiC.

  18. Advanced Ceramic Matrix Composites with Multifunctional and Hybrid Structures

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Morscher, Gregory N.

    2004-01-01

    Ceramic matrix composites are leading candidate materials for a number of applications in aeronautics, space, energy, and nuclear industries. Potential composite applications differ in their requirements for thickness. For example, many space applications such as "nozzle ramps" or "heat exchangers" require very thin (< 1 mm) structures whereas turbine blades would require very thick parts (> or = 1 cm). Little is known about the effect of thickness on stress-strain behavior or the elevated temperature tensile properties controlled by oxidation diffusion. In this study, composites consisting of woven Hi-Nicalon (trademark) fibers a carbon interphase and CVI SiC matrix were fabricated with different numbers of plies and thicknesses. The effect of thickness on matrix crack formation, matrix crack growth and diffusion kinetics will be discussed. In another approach, hybrid fiber-lay up concepts have been utilized to "alloy" desirable properties of different fiber types for mechanical properties, thermal stress management, and oxidation resistance. Such an approach has potential for the C(sub I)-SiC and SiC(sub f)-SiC composite systems. CVI SiC matrix composites with different stacking sequences of woven C fiber (T300) layers and woven SiC fiber (Hi-Nicalon (trademark)) layers were fabricated. The results will be compared to standard C fiber reinforced CVI SiC matrix and Hi-Nicalon reinforced CVI SiC matrix composites. In addition, shear properties of these composites at different temperatures will also be presented. Other design and implementation issues will be discussed along with advantages and benefits of using these materials for various components in high temperature applications.

  19. Total displacement functions for SiC

    NASA Astrophysics Data System (ADS)

    Weber, W. J.; Williford, R. E.; Sickafus, K. E.

    1997-04-01

    Numerical solutions for the displacement functions in SiC are determined from the coupled integro-differential equations governing the total number of type- j atoms displaced in the collision cascade initiated by a primary knock-on atom (PKA) of type- i and energy E. Atomic scattering cross sections based on either the inverse power law screening potentials or the Ziegler, Biersack, and Littmark (ZBL) universal screening potential are used in the calculation of the displacement functions. The electronic stopping powers used in the calculations are either derived from the LSS and Bethe-Bloch theories or generated from the SRIM-96 electronic stopping power data base. The displacement functions determined using LSS/Bethe-Bloch electronic stopping powers are 25 to 100% larger than the displacement functions determined using the electronic stopping powers generated by SRIM-96. The total number of displaced atoms determined numerically for each PKA type, based on ZBL scattering cross sections and SRIM-96 electronic stopping powers, is in excellent agreement, over the entire range of PKA energies (10 eV to 10 MeV), with the total number of displacements determined by full cascade Monte Carlo simulations using the TRIM code in SRIM-96.

  20. SPHERICAL INDENTATION OF SiC

    SciTech Connect

    Wereszczak, Andrew A; Johanns, Kurt E

    2007-01-01

    Instrumented Hertzian indentation testing was performed on several grades of SiCs and the results and preliminary interpretations are presented. The grades included hot-pressed and sintered compositions. One of the hot-pressed grades was additionally subjected to high temperature heat treatment to produce a coarsened grain microstructure to enable the examination of exaggerated grain size on indentation response. Diamond spherical indenters were used in the testing. Indentation load, indentation depth of penetration, and acoustic activity were continually measured during each indentation test. Indentation response and postmortem analysis of induced damage (e.g., ring/cone, radial and median cracking, quasi-plasticity) are compared and qualitatively as a function of grain size. For the case of SiC-N, the instrumented spherical indentation showed that yielding initiated at an average contact stress 12-13 GPa and that there was another event (i.e., a noticeable rate increase in compliance probably associated with extensive ring and radial crack formations) occurring around an estimated average contact stress of 19 GPa.

  1. Dietary Fiber

    MedlinePlus

    Fiber is a substance in plants. Dietary fiber is the kind you eat. It's a type of carbohydrate. You may also see it listed on a food label as soluble ... types have important health benefits. Good sources of dietary fiber include Whole grains Nuts and seeds Fruit and ...

  2. Specialty fiber optic applications for harsh and high radiation environments

    NASA Astrophysics Data System (ADS)

    Risch, Brian G.

    2015-05-01

    Since the first commercial introduction in the 1980s, optical fiber technology has undergone an almost exponential growth. Currently over 2 billion fiber kilometers are deployed globally with 2014 global optical fiber production exceeding 300 million fiber kilometers. 1 Along with the staggering growth in optical fiber production and deployment, an increase in optical fiber technologies and applications has also followed. Although the main use of optical fibers by far has been for traditional data transmission and communications, numerous new applications are introduced each year. Initially the practical application of optical fibers was limited by cost and sensitivity of the optical fibers to stress, radiation, and other environmental factors. Tremendous advances have taken place in optical fiber design and materials allowing optical fibers to be deployed in increasingly harsh environments with exposure to increased mechanical and environmental stresses while maintaining high reliability. With the increased reliability, lower cost, and greatly expanded range of optical fiber types now available, new optical fiber deployments in harsh and high radiation environments is seeing a tremendous increase for data, communications, and sensing applications. An overview of key optical fiber applications in data, communications, and sensing for harsh environments in industrial, energy exploration, energy generation, energy transmission, and high radiation applications will be presented. Specific recent advances in new radiation resistant optical fiber types, other specialty optical fibers, optical fiber coatings, and optical fiber cable materials will be discussed to illustrate long term reliability for deployment of optical fibers in harsh and high radiation environments.

  3. Developing Accurate Spatial Maps of Cotton Fiber Quality Parameters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Awareness of the importance of cotton fiber quality (Gossypium, L. sps.) has increased as advances in spinning technology require better quality cotton fiber. Recent advances in geospatial information sciences allow an improved ability to study the extent and causes of spatial variability in fiber p...

  4. Pre-Finishing of SiC for Optical Applications

    NASA Technical Reports Server (NTRS)

    Rozzi, Jay; Clavier, Odile; Gagne, John

    2011-01-01

    13 Manufacturing & Prototyping A method is based on two unique processing steps that are both based on deterministic machining processes using a single-point diamond turning (SPDT) machine. In the first step, a high-MRR (material removal rate) process is used to machine the part within several microns of the final geometry. In the second step, a low-MRR process is used to machine the part to near optical quality using a novel ductile regime machining (DRM) process. DRM is a deterministic machining process associated with conditions under high hydrostatic pressures and very small depths of cut. Under such conditions, using high negative-rake angle cutting tools, the high-pressure region near the tool corresponds to a plastic zone, where even a brittle material will behave in a ductile manner. In the high-MRR processing step, the objective is to remove material with a sufficiently high rate such that the process is economical, without inducing large-scale subsurface damage. A laser-assisted machining approach was evaluated whereby a CO2 laser was focused in advance of the cutting tool. While CVD (chemical vapor deposition) SiC was successfully machined with this approach, the cutting forces were substantially higher than cuts at room temperature under the same machining conditions. During the experiments, the expansion of the part and the tool due to the heating was carefully accounted for. The higher cutting forces are most likely due to a small reduction in the shear strength of the material compared with a larger increase in friction forces due to the thermal softening effect. The key advantage is that the hybrid machine approach has the potential to achieve optical quality without the need for a separate optical finishing step. Also, this method is scalable, so one can easily progress from machining 50-mm-diameter samples to the 250-mm-diameter mirror that NASA desires.

  5. SiC protective coating for photovoltaic retinal prosthesis

    NASA Astrophysics Data System (ADS)

    Lei, Xin; Kane, Sheryl; Cogan, Stuart; Lorach, Henri; Galambos, Ludwig; Huie, Philip; Mathieson, Keith; Kamins, Theodore; Harris, James; Palanker, Daniel

    2016-08-01

    Objective. To evaluate plasma-enhanced, chemically vapor deposited (PECVD) amorphous silicon carbide (α-SiC:H) as a protective coating for retinal prostheses and other implantable devices, and to study their failure mechanisms in vivo. Approach. Retinal prostheses were implanted in rats sub-retinally for up to 1 year. Degradation of implants was characterized by optical and scanning electron microscopy. Dissolution rates of SiC, SiN x and thermal SiO2 were measured in accelerated soaking tests in saline at 87 °C. Defects in SiC films were revealed and analyzed by selectively removing the materials underneath those defects. Main results. At 87 °C SiN x dissolved at 18.3 ± 0.3 nm d‑1, while SiO2 grown at high temperature (1000 °C) dissolved at 0.104 ± 0.008 nm d‑1. SiC films demonstrated the best stability, with no quantifiable change after 112 d. Defects in thin SiC films appeared primarily over complicated topography and rough surfaces. Significance. SiC coatings demonstrating no erosion in accelerated aging test for 112 d at 87 °C, equivalent to about 10 years in vivo, can offer effective protection of the implants. Photovoltaic retinal prostheses with PECVD SiC coatings exhibited effective protection from erosion during the 4 month follow-up in vivo. The optimal thickness of SiC layers is about 560 nm, as defined by anti-reflective properties and by sufficient coverage to eliminate defects.

  6. Fiber coupler end face wavefront surface metrology

    NASA Astrophysics Data System (ADS)

    Compertore, David C.; Ignatovich, Filipp V.; Marcus, Michael A.

    2015-09-01

    Despite significant technological advances in the field of fiber optic communications, one area remains surprisingly `low-tech': fiber termination. In many instances it involves manual labor and subjective visual inspection. At the same time, high quality fiber connections are one of the most critical parameters in constructing an efficient communication link. The shape and finish of the fiber end faces determines the efficiency of a connection comprised of coupled fiber end faces. The importance of fiber end face quality becomes even more critical for fiber connection arrays and for in the field applications. In this article we propose and demonstrate a quantitative inspection method for the fiber connectors using reflected wavefront technology. The manufactured and polished fiber tip is illuminated by a collimated light from a microscope objective. The reflected light is collected by the objective and is directed to a Shack-Hartmann wavefront sensor. A set of lenses is used to create the image of the fiber tip on the surface of the sensor. The wavefront is analyzed by the sensor, and the measured parameters are used to obtain surface properties of the fiber tip, and estimate connection loss. For example, defocus components in the reflected light indicate the presence of bow in the fiber end face. This inspection method provides a contact-free approach for quantitative inspection of fiber end faces and for estimating the connection loss, and can potentially be integrated into a feedback system for automated inspection and polishing of fiber tips and fiber tip arrays.

  7. Fiber optics for controls

    NASA Technical Reports Server (NTRS)

    Seng, Gary T.

    1987-01-01

    The challenge of those involved in control-system hardware development is to accommodate an ever-increasing complexity in aircraft control, while limiting the size and weight of the components and improving system reliability. A technology that displays promise towards this end is the area of fiber optics for controls. The primary advantages of employing optical fibers, passive optical sensors, and optically controlled actuators are weight and volume reduction, immunity from electromagnetic effects, superior bandwidth capabilities, and freedom from short circuits and sparking contacts. Since 1975, NASA Lewis has performed in-house, contract, and grant research in fiber optic sensors, high-temperature electro-optic switches, and fly-by-light control-system architecture. Passive optical sensor development is an essential yet challenging area of work and has therefore received much attention during this period. A major effort to develop fly-by-light control-system technology, known as the Fiber-Optic Control System Integration (FOCSI) program, was initiated in 1985 as a cooperative effort between NASA and DOD. Phase 1 of FOCSI, completed in 1986, was aimed at the design of a fiber-optic integrated propulsion/flight control system. Phase 2, yet to be initiated, will provide subcomponent and system development, and a system engine test. In addition to a summary of the benefits of fiber optics, the FOCSI program, sensor advances, and future directions in the NASA Lewis program will be discussed.

  8. SiC Homoepitaxy, Etching and Graphene Epitaxial Growth on SiC Substrates Using a Novel Fluorinated Si Precursor Gas (SiF4)

    NASA Astrophysics Data System (ADS)

    Rana, Tawhid; Chandrashekhar, M. V. S.; Daniels, Kevin; Sudarshan, Tangali

    2016-04-01

    Tetrafluorosilane (SiF4 or TFS), a novel precursor gas, has been demonstrated to perform three primary operations of silicon carbide-related processing: SiC etching, SiC epitaxial growth and graphene epitaxial growth. TFS etches SiC substrate vigorously in a H2 ambient by efficient Si removal from the surface, where SiC etch rate is a function of TFS gas concentration. In this SiC etching process, Si is removed by TFS and C is removed by H2. When propane is added to a H2 and TFS gas mixture, etching is halted and high-quality SiC epitaxy takes place in a Si droplet-free condition. TFS's ability to remove Si can also be exploited to grow epitaxial graphene in a controllable manner in an inert (Ar) ambient. Here, TFS enhances graphene growth by selective etching of Si from the SiC surface.

  9. Nuclear Reaction Analysis of Helium Retention in 6H SiC as a function of irradiation and annealing

    NASA Astrophysics Data System (ADS)

    Bissell, L. J.; Smith, R. J.; Shutthanadan, V.; Adams, E. M.; Thevuthasan, S.; Jiang, W.; Weber, W. J.; Zhang, Y.

    2002-10-01

    Silicon carbide has been proposed as a coating material in nuclear fuel, and silicon carbide composites have been proposed as cladding material in advanced gas-cooled and light water reactors. As such, the effects of irradiation and fission gases on the performance of SiC in the reactor environment are critical in several ways. Since He serves as a fission gas, low-energy He (< 50 keV) will be colliding with coolant gas and outer surface cladding layers. As such, it is important to understand He retention in SiC under advanced reactor operating conditions. We investigated He retention in single crystal 6H SiC as a function of irradiation dose and annealing temperature using nuclear reaction analysis (NRA) via the 3He(D,alpha)1H reaction. Helium ions with 40 keV energy were implanted in the SiC to a depth of ˜360 nm at room temperature under high vacuum conditions. The samples were then transferred to another high vacuum chamber where the NRA was performed using a 1.0 MeV D+ beam. Helium retention was studied as a function of D+ irradiation dose from 5 x 10^(16) to 4 x 10^(18) D+ /cm2, and as a function of annealing temperature ranging from 300 1600 K. No significant helium loss was observed under this dosage range, and only annealing temperatures above 1400 K caused measurable loss of helium. These results will be discussed along with the details associated with the 3He(D,alpha)1H nuclear reaction.

  10. CVD of silicon carbide on structural fibers - Microstructure and composition

    NASA Technical Reports Server (NTRS)

    Veitch, Lisa C.; Terepka, Francis M.; Gokoglu, Suleyman A.

    1992-01-01

    Structural fibers are currently being considered as reinforcements for intermetallic and ceramic materials. Some of these fibers, however, are easily degraded in a high temperature oxidative environment. Therefore, coatings are needed to protect the fibers from environmental attack. Silicon carbide (SiC) was chemically vapor deposited (CVD) on Textron's SCS6 fibers. Fiber temperatures ranging from 1350 to 1500 C were studied. Silane (SiH4) and propane (C2H8) were used for the source gases and different concentrations of these source gases were studied. Deposition rates were determined for each group of fibers at different temperatures. Less variation in deposition rates were observed for the dilute source gas experiments than the concentrated source gas experiments. A careful analysis was performed on the stoichiometry of the CVD SiC coating using electron microprobe. Microstructures for the different conditions were compared. At 1350 C, the microstructures were similar; however, at higher temperatures, the microstructure for the more concentrated source gas group were porous and columnar in comparison to the cross sections taken from the same area for the dilute source gas group.

  11. CVD of silicon carbide on structural fibers: Microstructure and composition

    NASA Technical Reports Server (NTRS)

    Veitch, Lisa C.; Terepka, Francis M.; Gokoglu, Suleyman A.

    1992-01-01

    Structural fibers are currently being considered as reinforcements for intermetallic and ceramic materials. Some of these fibers, however, are easily degraded in a high temperature oxidative environment. Therefore, coatings are needed to protect the fibers from environmental attack. Silicon carbide (SiC) was chemically vapor deposited (CVD) on Textron's SCS6 fibers. Fiber temperatures ranging from 1350 to 1500 C were studied. Silane (SiH4) and propane (C2H8) were used for the source gases and different concentrations of these source gases were studied. Deposition rates were determined for each group of fibers at different temperatures. Less variation in deposition rates were observed for the dilute source gas experiments than the concentrated source gas experiments. A careful analysis was performed on the stoichiometry of the CVD SiC coating using electron microprobe. Microstructures for the different conditions were compared. At 1350 C, the microstructures were similar; however, at higher temperatures, the microstructure for the more concentrated source gas group were porous and columnar in comparison to the cross sections taken from the same area for the dilute source gas group.

  12. Saccharomyces cerevisiae Ime2 phosphorylates Sic1 at multiple PXS/T sites but is insufficient to trigger Sic1 degradation

    PubMed Central

    Sedgwick, Chantelle; Rawluk, Matthew; Decesare, James; Raithatha, Sheetal; Wohlschlegel, James; Semchuk, Paul; Ellison, Michael; Yates, John; Stuart, David

    2006-01-01

    The initiation of DNA replication in Saccharomyces cerevisiae depends upon the destruction of the Clb–Cdc28 inhibitor Sic1. In proliferating cells Cln–Cdc28 complexes phosphorylate Sic1, which stimulates binding of Sic1 to SCFCdc4 and triggers its proteosome mediated destruction. During sporulation cyclins are not expressed, yet Sic1 is still destroyed at the G1-/S-phase boundary. The Cdk (cyclin dependent kinase) sites are also required for Sic1 destruction during sporulation. Sic1 that is devoid of Cdk phosphorylation sites displays increased stability and decreased phosphorylation in vivo. In addition, we found that Sic1 was modified by ubiquitin in sporulating cells and that SCFCdc4 was required for this modification. The meiosis-specific kinase Ime2 has been proposed to promote Sic1 destruction by phosphorylating Sic1 in sporulating cells. We found that Ime2 phosphorylates Sic1 at multiple sites in vitro. However, only a subset of these sites corresponds to Cdk sites. The identification of multiple sites phosphorylated by Ime2 has allowed us to propose a motif for phosphorylation by Ime2 (PXS/T) where serine or threonine acts as a phospho-acceptor. Although Ime2 phosphorylates Sic1 at multiple sites in vitro, the modified Sic1 fails to bind to SCFCdc4. In addition, the expression of Ime2 in G1 arrested haploid cells does not promote the destruction of Sic1. These data support a model where Ime2 is necessary but not sufficient to promote Sic1 destruction during sporulation. PMID:16776651

  13. Growth and Features of Epitaxial Graphene on SiC

    NASA Astrophysics Data System (ADS)

    Kusunoki, Michiko; Norimatsu, Wataru; Bao, Jianfeng; Morita, Koichi; Starke, Ulrich

    2015-12-01

    Recent progress of epitaxial graphene on SiC was reviewed, focusing on its growth and structural and electronic features. Homogeneous graphene can be grown on SiC(0001) on a wafer scale, however on SiC(000bar{1}) multilayer but rotationally stacked graphene with monolayer like electronic property grows. HRTEM revealed the formation mechanism and structural features of graphene on the both surfaces. The high structural and electronic quality of the grown graphene is monitored by Raman spectroscopy and magneto-transport characterization. High-resolution ARPES measurements of the electronic dispersion around the bar{text{K}}-point retrieved the ABA and ABC stacked trilayer graphene. The measurements also directly revealed that electronic structures of graphene were manipulated by transfer doping and atomic intercalation. In particular, p- and n-doped regions on a meso-scale and the p-n junctions prepared on SiC via controlling intercalation of Ge exhibited ballistic transport and Klein tunneling, which predicted novel potentials on to epitaxial graphene on SiC.

  14. Recent Developments in SiC Device Research

    NASA Astrophysics Data System (ADS)

    Harris, C. I.; Konstantinov, A. O.

    Silicon Carbide is fast emerging as a mature semiconductor. The unique combination of material properties offered by SiC will allow it to establish itself in applications where the ever dominant Si is approaching the physical (not technical) limits of it's operation. Three key areas will be explored in this paper: (i) High power electronics. SiC devices operating at several kV and capable of MW power handling will revolutionise the way electrical power is transmitted and made use of. Recent progress supported by ABB in Sweden suggests these breakthroughs will begin to play a key role soon after the turn of the century. (ii) High frequency devices made from SiC will also play an increasingly important part in the mobile telecommunication revolution in which we currently live. Northrop Grumman in the USA have demonstrated the transmission of digital TV using SiC based devices. The high power density achieved from such devices make them also suitable for base stations for mobile telephones. (iii) Finally we look at some examples of how SiC is being used to develop new types of sensors that can be used in extreme environments such as high temperatures, high pressures or corrosive environments. Feedback from such sensors is seen as essential to understanding how we effect the world around us and thereby how we can limit pollution.

  15. TRISO coated fuel particles with enhanced SiC properties

    NASA Astrophysics Data System (ADS)

    López-Honorato, E.; Tan, J.; Meadows, P. J.; Marsh, G.; Xiao, P.

    2009-07-01

    The silicon carbide (SiC) layer used for the formation of TRISO coated fuel particles is normally produced at 1500-1650 °C via fluidized bed chemical vapor deposition from methyltrichlorosilane in a hydrogen environment. In this work, we show the deposition of SiC coatings with uniform grain size throughout the coating thickness, as opposed to standard coatings which have larger grain sizes in the outer sections of the coating. Furthermore, the use of argon as the fluidizing gas and propylene as a carbon precursor, in addition to hydrogen and methyltrichlorosilane, allowed the deposition of stoichiometric SiC coatings with refined microstructure at 1400 and 1300 °C. The deposition of SiC at lower deposition temperatures was also advantageous since the reduced heat treatment was not detrimental to the properties of the inner pyrolytic carbon which generally occurs when SiC is deposited at 1500 °C. The use of a chemical vapor deposition coater with four spouts allowed the deposition of uniform and spherical coatings.

  16. Hysteresis in the Active Oxidation of SiC

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Harder, Bryan J.; Myers, Dwight L.

    2011-01-01

    Si and SiC show both passive oxidation behavior where a protective film of SiO2 forms and active oxidation behavior where a volatile suboxide SiO(g) forms. The active-to-passive and passive-to-active oxidation transitions are explored for both Si and SiC. Si shows a dramatic difference between the P(O2) for the two transitions of 10-4 bar. The active-to-passive transition is controlled by the condition for SiO2/Si equilibrium and the passive-to-active transition is controlled by the decomposition of SiO2. In the case of SiC, the P(O2) for these transitions are much closer. The active-to-passive transition appears to be controlled by the condition for SiO2/SiC equilibrium. The passive-to-active transition appears to be controlled by the interfacial reaction of SiC and SiO2 and subsequent generation of gases at the interface which leads to scale breakdown.

  17. Research on microwave joining of SiC. Final report

    SciTech Connect

    1993-06-30

    Work on microwave joining of sintered SiC has showed that small samples could be jointed using Si interlayer (applied as pressed powder); SEM showed a smooth, homogeneous interlayer 50 {mu}m wide. Objective of this contract is to optimize these joints. Results showed that the interlayer could be reduced to 10-20 {mu}m using an oil-based slurry made from Si powder, and to less than 5 {mu}m by plasma spraying Si on one of the SiC surfaces. Direct joints were made in reaction bonded SiC, using the residual Si. Excellent joints with good mechanical properties were obtained in both small specimens and in small scale tube assemblies like in heat exchanger and radiant burner tubes. In situ reaction synthesis from powders to produce a SiC-TiC-SiC joint was demonstrated, as well feasibility of producing SiC from microwave-assisted decomposition of polymer precursors. Finally, new applicator designs, including a compound adjustable iris and a mitered bend single mode cavity, were demonstrated to provide improved heating of larger and longer specimens. This work provides the foundation for scaleup of microwave joining to SiC components for industrial applications.

  18. Modification Progress of the S-IC Test Stand

    NASA Technical Reports Server (NTRS)

    1975-01-01

    At its founding, the Marshall Space Flight Center (MSFC) inherited the Army's Jupiter and Redstone test stands, but much larger facilities were needed for the giant stages of the Saturn V. From 1960 to 1964, the existing stands were remodeled and a sizable new test area was developed. The new comprehensive test complex for propulsion and structural dynamics was unique within the nation and the free world, and they remain so today because they were constructed with foresight to meet the future as well as on going needs. Construction of the S-IC Static test stand complex began in 1961 in the west test area of MSFC, and was completed in 1964. The S-IC static test stand was originally designed to develop and test the 138-ft long and 33-ft diameter Saturn V S-IC first stage, or booster stage. Modifications to the S-IC Test Stand began in 1975 to accommodate space shuttle external tank testing. This photo depicts the continuation of the modification process as of July 14, 1975. The flame deflector originally used to provide water to the 5 F-1 engines of the S-IC stage during testing has been removed.

  19. Fiber sensing with photorefractive fiber

    NASA Astrophysics Data System (ADS)

    Yu, Francis T. S.; Guo, Ruyan; Wang, Bo; Liu, Yuexin

    2002-11-01

    Optical fibers have been widely used for transmitting temporal signal. However, the transmission of spatial signal has not been fully exploited. Although multimode fiber has a large space-bandwidth product, transmitting spatial signals by using a fiber is rather difficult. When a laser beam is lached into a multimode fiber, the exit light field produces a complicated speckle pattern caused by the modal phasing of the fiber. It is difficult to recover the transmitted informati from the speckle field. However, the fiber speckle field can be used to fiber sensing with a hologrpahic method. In other words, if a hologram is made with the speckle fiber field, the information of the fiber status can be recovered. Thus by reading the hologram by the same speckle field, the reference beam can be reconstructed, which represents the detection of the speckle field. In other words, instead of exploiting the temporal content, the spatial content from a multimode fiber can be exploited for sensing. Our analyses and experimentations have shown that the fiber specklegram sensor (FSS) is highly senstiive to perturbation, and it is less vulnerable to the environment factors. Applications of the FSS to temperature, transversal displacement, and dynamic sensing are also included.

  20. TiC growth in C fiber/Ti alloy composites during liquid infiltration

    NASA Technical Reports Server (NTRS)

    Warrier, S. G.; Lin, R. Y.

    1993-01-01

    A cylindrical model is developed for predicting the reaction zone thickness of carbon fiber-reinforced Ti-matrix composites, and good agreement is obtained between its predicted values and experimental results. The reaction-rate constant for TiC formation is estimated to be 1.5 x 10 exp -9 sq cm/sec. The model is extended to evaluate the relationship between C-coating thicknesses on SiC fibers and processing times.

  1. Advanced Power Electronics Components

    NASA Technical Reports Server (NTRS)

    Schwarze, Gene E.

    2004-01-01

    This paper will give a description and status of the Advanced Power Electronics Materials and Components Technology program being conducted by the NASA Glenn Research Center for future aerospace power applications. The focus of this research program is on the following: 1) New and/or significantly improved dielectric materials for the development of power capacitors with increased volumetric efficiency, energy density, and operating temperature. Materials being investigated include nanocrystalline and composite ceramic dielectrics and diamond-like carbon films; 2) New and/or significantly improved high frequency, high temperature, low loss soft magnetic materials for the development of transformers/inductors with increased power/energy density, electrical efficiency, and operating temperature. Materials being investigated include nanocrystalline and nanocomposite soft magnetic materials; 3) Packaged high temperature, high power density, high voltage, and low loss SiC diodes and switches. Development of high quality 4H- and 6H- SiC atomically smooth substrates to significantly improve device performance is a major emphasis of the SiC materials program; 4) Demonstration of high temperature (> 200 C) circuits using the components developed above.

  2. Structural Properties of Liquid SiC during Rapid Solidification

    PubMed Central

    Yan, WanJun; Gao, TingHong; Guo, XiaoTian; Qin, YunXiang; Xie, Quan

    2013-01-01

    The rapid solidification of liquid silicon carbide (SiC) is studied by molecular dynamic simulation using the Tersoff potential. The structural properties of liquid and amorphous SiC are analyzed by the radial distribution function, angular distribution function, coordination number, and visualization technology. Results show that both heteronuclear and homonuclear bonds exist and no atomic segregation occurs during solidification. The bond angles of silicon and carbon atoms are distributed at around 109° and 120°, respectively, and the average coordination number is <4. Threefold carbon atoms and fourfold silicon atoms are linked together by six typical structures and ultimately form a random network of amorphous structure. The simulated results help understand the structural properties of liquid and amorphous SiC, as well as other similar semiconductor alloys. PMID:24288474

  3. Large And Highly Stable Structures Made Of SiC

    NASA Astrophysics Data System (ADS)

    Bougoin, M.; Lavenac, J.

    2012-07-01

    The Boostec® SiC material appears very attractive for manufacturing large space telescopes, thanks to its high specific stiffness and its thermal stability. Its physical properties are perfectly isotropic and it is remarkably more stable than the glass-ceramics in time and also against space radiations. This sintered SiC material has been fully qualified for application at cryogenic temperature. Thanks to its good mechanical strength and toughness, it can be used for making not only the mirrors but also the structure and the focal plane hardware of the optical instruments, thus making “all in SiC” and possibly “athermal” telescopes. The present paper describes the Boostec® SiC properties and then its manufacturing technology. Some examples of the structures of the Multi Spectral Imaging instruments of Sentinel-2 and also the very large Gaia one are further developed.

  4. Aspects of SiC diode assembly using Ag technology

    NASA Astrophysics Data System (ADS)

    Mysliwiec, Marcin; Guziewicz, Marek; Kisiel, Ryszard

    2013-07-01

    The aim of our paper is to consider the possibility of applying pure Ag technology for assembly of SiC Schottky diode into a ceramic package able to work at temperatures up to 350°C. Ag micropowder was used for assembly SiC structure to DBC interposer of the ceramic package. Ag wire bonds as well as flip-chip technology using Ag balls were used as material for interconnection systems. The parameters of I-V characteristics were used as a quality factor to determine the Schottky diode after hermetization into ceramic package as well as after ageing in air at 350°C in comparison with characteristics of bare SiC diode.

  5. Synthesis and properties of porous SiC ceramics

    NASA Astrophysics Data System (ADS)

    Kiselov, V. S.; Lytvyn, P. M.; Yukhymchuk, V. O.; Belyaev, A. E.; Vitusevich, S. A.

    2010-05-01

    Porous silicon carbide (SiC) ceramics are produced using carbon matrices derived from natural wood. Such material is especially promising as it is environmentally friendly with attractive physical properties, including a high level of biocompatibility, chemical inertness, and mechanical strength. We have developed a forced impregnation process with further synthesis of SiC using natural wood as well as a variety of industrial carbon materials and compared the properties of these ceramics. The structure and composition of the materials obtained were investigated by Raman scattering spectroscopy. The hardness of the samples was estimated using the Vickers technique. It was shown that the phase composition and mechanical properties of synthesized SiC ceramics can be effectively controlled by the initial Si contents and temperature of the synthesis process. A large variety of options are demonstrated for materials development taking into account an optimal porosity selection for various practical applications.

  6. SIC-POVMS and MUBS: Geometrical Relationships in Prime Dimension

    SciTech Connect

    Appleby, D. M.

    2009-03-10

    The paper concerns Weyl-Heisenberg covariant SIC-POVMs (symmetric informationally complete positive operator valued measures) and full sets of MUBs (mutually unbiased bases) in prime dimension. When represented as vectors in generalized Bloch space a SIC-POVM forms a d{sup 2}-1 dimensional regular simplex (d being the Hilbert space dimension). By contrast, the generalized Bloch vectors representing a full set of MUBs form d+1 mutually orthogonal d-1 dimensional regular simplices. In this paper we show that, in the Weyl-Heisenberg case, there are some simple geometrical relationships between the single SIC-POVM simplex and the d+1 MUB simplices. We go on to give geometrical interpretations of the minimum uncertainty states introduced by Wootters and Sussman, and by Appleby, Dang and Fuchs, and of the fiduciality condition given by Appleby, Dang and Fuchs.

  7. SiC IR emitter design for thermophotovoltaic generators

    NASA Astrophysics Data System (ADS)

    Fraas, Lewis M.; Ferguson, Luke; McCoy, Larry G.; Pernisz, Udo C.

    1996-02-01

    An improved ceramic spine disc burner/emitter for use in a thermophotovoltaic (TPV) generator is described. A columnar infrared (IR) emitter consisting of a stack of silicon carbide (SiC) spine discs provides for both high conductance for the combustion gases and efficient heat transfer from the hot combustion gases to the emitter. Herein, we describe the design, fabrication, and testing of this SiC burner as well as the characterization of the IR spectrum it emits. We note that when the SiC column is surrounded with fused silica heat shields, these heat shields suppress the emitted power beyond 4 microns. Thus, a TPV generator using GaSb photovoltaic cells covered by simple dielectric filters can convert over 30% of the emitted IR radiation to DC electric power.

  8. Junction barrier Schottky diodes in 6H SiC

    NASA Astrophysics Data System (ADS)

    Zetterling, Carl-Mikael; Dahlquist, Fanny; Lundberg, Nils; Östling, Mikael; Rottner, Kurt; Ramberg, Lennart

    1998-09-01

    Junction barrier Schottky (JBS) diodes in 6H SiC have been fabricated and characterised electrically. This device, demonstrated in silicon technology, has the advantage of a low forward voltage drop comparable to that of Schottky diodes, as well as a high blocking voltage and low reverse leakage current of a pn junction. This is especially attractive for wide bandgap materials such as SiC in which pn junctions have a large forward voltage drop. The devices were capable of blocking up to 1100 V with a leakage current density of 0.15 A cm -2, limited by the leakage when the drift region was fully depleted, or breakdown of the SiC material itself. The forward conduction was limited by an on-resistance of 20 mΩ cm 2, resulting in forward voltage drops of 2.6 V at 100 A cm -2.

  9. Structural properties of liquid SiC during rapid solidification.

    PubMed

    Yan, WanJun; Gao, TingHong; Guo, XiaoTian; Qin, YunXiang; Xie, Quan

    2013-01-01

    The rapid solidification of liquid silicon carbide (SiC) is studied by molecular dynamic simulation using the Tersoff potential. The structural properties of liquid and amorphous SiC are analyzed by the radial distribution function, angular distribution function, coordination number, and visualization technology. Results show that both heteronuclear and homonuclear bonds exist and no atomic segregation occurs during solidification. The bond angles of silicon and carbon atoms are distributed at around 109° and 120°, respectively, and the average coordination number is <4. Threefold carbon atoms and fourfold silicon atoms are linked together by six typical structures and ultimately form a random network of amorphous structure. The simulated results help understand the structural properties of liquid and amorphous SiC, as well as other similar semiconductor alloys. PMID:24288474

  10. Influence of fiber packing structure on permeability

    NASA Technical Reports Server (NTRS)

    Cai, Zhong; Berdichevsky, Alexander L.

    1993-01-01

    The study on the permeability of an aligned fiber bundle is the key building block in modeling the permeability of advanced woven and braided preforms. Available results on the permeability of fiber bundles in the literature show that a substantial difference exists between numerical and analytical calculations on idealized fiber packing structures, such as square and hexagonal packing, and experimental measurements on practical fiber bundles. The present study focuses on the variation of the permeability of a fiber bundle under practical process conditions. Fiber bundles are considered as containing openings and fiber clusters within the bundle. Numerical simulations on the influence of various openings on the permeability were conducted. Idealized packing structures are used, but with introduced openings distributed in different patterns. Both longitudinal and transverse flow are considered. The results show that openings within the fiber bundle have substantial effect on the permeability. In the longitudinal flow case, the openings become the dominant flow path. In the transverse flow case, the fiber clusters reduce the gap sizes among fibers. Therefore the permeability is greatly influenced by these openings and clusters, respectively. In addition to the porosity or fiber volume fraction, which is commonly used in the permeability expression, another fiber bundle status parameter, the ultimate fiber volume fraction, is introduced to capture the disturbance within a fiber bundle.

  11. Elastic properties of SiC nanoscopic wires

    NASA Astrophysics Data System (ADS)

    Makeev, Maxim; Menon, Madhu; Srivastava, Deepak

    2006-03-01

    Mechanical properties of crystalline and amorphous SiC nanowires have been investigated using molecular dynamics simulations with the Tersoff bond-order interatomic potential. The crystalline and a-SiC nanowires of different diameters were studied under tension/compression, torsion, and bending. The bending and torsion rigidities are found to be strongly dependent on the wire size. This is unlike the Young's modulus computed from uniaxial loading curves. Atomistic relaxations effects near the thresholds of structural stability are investigated for the four employed load types. The mechanical properties of crystalline SiC nanowires are compared with a-SiC wires of the same radii.

  12. Saturn V S-IC (First Stage) Structural Arrangement

    NASA Technical Reports Server (NTRS)

    1968-01-01

    This illustration, with callouts, shows the structural arrangement of the major components for the S-IC (first) stage of the Saturn V launch vehicle. The S-IC stage was 138 feet long and 33 feet in diameter, and produced more than 7,500,000 pounds of thrust through five F-1 engines that were powered by liquid oxygen and kerosene. Four of the engines were mounted on an outer ring and gimbal for control purposes. The fifth engine was rigidly mounted in the center. When ignited, the roar produced by the five engines equaled the sound of 8,000,000 hi-fi sets.

  13. Spin effects in thermoelectric phenomena in SiC nanoribbons.

    PubMed

    Zberecki, K; Swirkowicz, R; Wierzbicki, M; Barnaś, J

    2015-01-21

    Using ab initio methods we calculate the thermoelectric and spin thermoelectric properties of zigzag SiC nanoribbons, asymmetrically terminated with hydrogen. Such nanoribbons display a ferromagnetic ground state, with edge magnetic moments oriented in parallel. Both thermopower and spin thermopower have been determined as a function of chemical potential and temperature. To find the thermoelectric efficiency, the total heat conductance has been calculated, i.e. the electronic and phonon contributions. Numerical results for SiC nanoribbons are compared with those for graphene and silicene ones. PMID:25473937

  14. Plasma synthesis and characterization of ultrafine SiC

    SciTech Connect

    Vogt, G.J.; Phillips, D.S.; Taylor, T.N.

    1986-01-01

    Ultrafine SiC powders have been prepared by gas phase synthesis from silane and methane in an argon thermal rf-plasma. Bulk properties of the powders were determined by elemental analysis, x-ray diffractin, helium pycnometry, and BET surface area measurements. The near-surface composition and structure of the particles were examined by x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). In addition to free silicon and carbon particles in the powders, free carbon and various silicon/carbon/oxygen species were found on the surface of the SiC particles.

  15. CVD scaled up for commercial production of bulk SiC

    SciTech Connect

    Not Available

    1993-03-01

    A recent development at Morton International's Advanced Materials group is having a revolutionary impact on the materials world. The firm has successfully scaled production of bulk, cubic ([beta]), chemically vapor deposited (CVD) silicon carbide (SiC) to support commercial requirements. To date, they have produced free standing CVD SiC substrates in sheets up to 60 in. across and over one inch thick. The material can also be grown as smaller near-net-shape parts in many different popular geometries. The parts produced by the process are monolithic. Commercially known as CVD SILICON CARBIDE, the material is single phase, theoretically dense, and 99.999% pure, [beta]-SiC. These characteristics lead to superior product attributes such as high values of hardness, flexural strength, and thermal conductivity. Additionally, the product has demonstrated superior oxidation resistance, and polishability. Several markets have shown an interest in the material including: optics, wear parts, information storage, and electronic packaging. Other applications for the material are emerging on what seems like a daily basis.

  16. Band Engineering and Magnetic Doping of Epitaxial Graphene on SiC (0001)

    NASA Astrophysics Data System (ADS)

    Kong, Byoung Don; Jayasekera, Thushari; Kim, Ki Wook; Buongiorno Nardelli, M.

    2010-03-01

    Advances in the epitaxial growth of graphene films on SiC have the potential to open new classes of device applications that may revolutionize the semiconductor roadmap for future decades. However, this progress will require an in-depth understanding and utilization of the electronic processes that take place at the nanoscale, in particular the role of the interface buffer layer, where most of the electronic properties of the system can be controlled. In analogy with the formation of the Schottky barrier in metal-insulator interfaces (the energetic barrier the electrons have to overcome to go from the valence band of the metal to the conduction band of the insulator) here we demonstrate the ability to tune and control the band alignment and the magnetic doping at the heterojunction between graphene and SiC, a fundamental requirement for improving device efficiency and applicability. Using first principles calculations, we will show how the surface electrostatic distribution can be used to tune the valence band offset by introducing surface impurities such as B, Al, N, and P. Similarly, we will demonstrate how the introduction of magnetic impurities in the buffer layer can tune the spintronic behavior of the epitaxial graphene layer. This work was supported, in part, by the NERC/NIST SWAN-NRI and the DARPA/HRL CERA programs.

  17. Electronic stopping powers for heavy ions in SiC and SiO{sub 2}

    SciTech Connect

    Jin, K.; Xue, H.; Zhang, Y. Weber, W. J.; Zhu, Z.; Grove, D. A.; Xue, J.

    2014-01-28

    Accurate information on electronic stopping power is fundamental for broad advances in materials science, electronic industry, space exploration, and sustainable energy technologies. In the case of slow heavy ions in light targets, current codes and models provide significantly inconsistent predictions, among which the Stopping and Range of Ions in Matter (SRIM) code is the most commonly used one. Experimental evidence, however, has demonstrated considerable errors in the predicted ion and damage profiles based on SRIM stopping powers. In this work, electronic stopping powers for Cl, Br, I, and Au ions are experimentally determined in two important functional materials, SiC and SiO{sub 2}, based on a single ion technique, and new electronic stopping power values are derived over the energy regime from 0 to 15 MeV, where large deviations from the SRIM predictions are observed. As an experimental validation, Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) are utilized to measure the depth profiles of implanted Au ions in SiC for energies from 700 keV to 15 MeV. The measured ion distributions by both RBS and SIMS are considerably deeper than the SRIM predictions, but agree well with predictions based on our derived stopping powers.

  18. Electronic Stopping Powers For Heavy Ions In SiC And SiO2

    SciTech Connect

    Jin, Ke; Zhang, Y.; Zhu, Zihua; Grove, David A.; Xue, H.; Xue, Jianming; Weber, William J.

    2014-01-24

    Accurate information on electronic stopping power is fundamental for broad advances in materials science, electronic industry, space exploration, and sustainable energy technologies. In the case of slow heavy ions in light targets, current codes and models provide significantly inconsistent predictions, among which the Stopping and Range of Ions in Matter (SRIM) code is the most commonly used one. Experimental evidence, however, has demonstrated considerable errors in the predicted ion and damage profiles based on SRIM stopping powers. In this work, electronic stopping powers for Cl, Br, I, and Au ions are experimentally determined in two important functional materials, SiC and SiO2, based on a single ion technique, and new electronic stopping power values are derived over the energy regime from 0 to 15 MeV, where large deviations from the SRIM predictions are observed. As an experimental validation, Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) are utilized to measure the depth profiles of implanted Au ions in SiC for energies from 700 keV to 15MeV. The measured ion distributions by both RBS and SIMS are considerably deeper than the SRIM predictions, but agree well with predictions based on our derived stopping powers.

  19. SIC-LSD study of transition metal valencies in oxide materials

    NASA Astrophysics Data System (ADS)

    Petit, Leon; Schulthess, Thomas; Svane, Axel; Janotti, Anderson; Szotek, Zdzislawa; Temmerman, Walter

    2005-03-01

    The electronic and magnetic properties of transition metal (TM) oxide materials are largely determined by the degree of localization of the TM d-electrons. With the self-interaction corrected (SIC) local spin density (LSD) approximation, we are able to differentiate between various localization/delocalization scenarios based on total energy considerations, and thus to determine the ground state valency onfiguration from the global energy minimum. Using the SIC-LSD, we studied the valencies of TM (Co, Mn) impurities in ZnO. We find the position of the TM(0/+) donor level to be such that the TM^2+ configuration is energetically most favourable both in n-type ZnO, and in ZnO without additional codopants, whilst in p-type ZnO one additional d-electron prefers to delocalize with the resulting TM^3+ groundstate configuration. We furthermore investigated the possibility of ferromagnetic order in the corresponding groundstate scenarios. Work supported in part by the Defense Advanced Research Agency and by the Division of Materials Science and Engineering, US Department of Energy. The Oak Ridge National Laboratory is managed by UT-Battelle LLC for the Department of Energy under Contract No. DE-AC05-00OR22725.

  20. Theory and practice of SiC growth on Si and its applications to wide-gap semiconductor films

    NASA Astrophysics Data System (ADS)

    Kukushkin, S. A.; Osipov, A. V.

    2014-08-01

    The recent advances in epitaxial SiC films' growth on Si are overviewed. The basic classical methods currently used for SiC films' growth are discussed and their advantages and disadvantages are explored. The basic idea and the theoretical background for a new method of the synthesis of epitaxial SiC films on Si are given. It will be shown that the new method is significantly different from the classical techniques of thin-film growth where the evaporation of the atoms onto the substrate surface is exploited. The new method is based on the substitution of some atoms in the silicon matrix by the carbon atoms to form the molecules of silicon carbide. It will be shown that the following process of SiC nucleation happens gradually without destroying the crystalline structure of the silicon matrix, and the orientation of a grown film is imposed by the original crystalline structure of the silicon matrix (not only by the substrate surface as in conventional methods of film growth). A comparison of the new method with other epitaxy techniques will be given. The new method of solid-phase epitaxy based on the substitution of atoms and on the creation of dilatation dipoles solves one of the major problems in heteroepitaxy. It provides the synthesis of low-defective unstrained epitaxial films with a large difference between the lattice parameters of the film and the substrate without using any additional buffer layers. This method has another unique feature distinguishing it from the classical techniques of SiC films' growth—it allows the growing of SiC films of hexagonal polytypes. A new kind of phase transformation in solids owing to the chemical transformation of one substance into another will be described theoretically and revealed experimentally. This type of phase transformation, and the mechanism of a broad class of heterogeneous chemical reactions between gas and solid phases, will be illustrated by an example of the growth of SiC epitaxial layers due to the

  1. Fiber optics for controls

    NASA Technical Reports Server (NTRS)

    Seng, Gary T.

    1990-01-01

    The design, development, and testing of a fiber optic integrated propulsion/flight control system for an advanced supersonic dash aircraft (flies at supersonic speeds for short periods of time) is the goal of the joint NASA/DOD Fiber Optic Control System Integration (FOCSI) program. Phase 1 provided a comparison of electronic and optical control systems, identified the status of current optical sensor technology, defined the aircraft sensor/actuator environment, proposed architectures for fully optical control systems, and provided schedules for development. Overall, it was determined that there are sufficient continued efforts to develop such a system. It was also determined that it is feasible to build a fiber optic control system for the development of a data base for this technology, but that further work is necessary in sensors, actuators, and components to develop an optimum design, fully fiber optic integrated control system compatible with advanced aircraft environments. Phase 2 is to design, construct, and ground test a fly by light control system. Its first task is to provide a detailed design of the electro-optic architecture.

  2. Fiber waveguide sensors for intelligent materials

    NASA Technical Reports Server (NTRS)

    Flax, A. R.; Claus, R. O.

    1988-01-01

    This report, an addendum to the six month report submitted to NASA Langley Research Center in December 1987, covers research performed by the Fiber and Electro-Optics Research Center (FEORC) at Virginia Tech for the NASA Langley Research Center, Grant NAG1-780, for the period from December 1987 to June 1988. This final report discusses the research performed in the following four areas as described in the proposal: Fabrication of Sensor Fibers Optimized for Embedding in Advanced Composites; Fabrication of Sensor Fiber with In-Line Splices and Evaluation via OTR methods; Modal Domain Optical Fiber Sensor Analysis; and Acoustic Fiber Waveguide Implementation.

  3. The Commercialization of the SiC Flame Sensor

    NASA Astrophysics Data System (ADS)

    Fedison, Jeffrey B.

    2002-03-01

    The technical and scientific steps required to produce large quantities of SiC flame sensors is described. The technical challenges required to understand, fabricate, test and package SiC photodiodes in 1990 were numerous since SiC device know how was embryonic. A sense of urgency for a timely replacement of the Geiger Muller gas discharge tube soon entered the scene. New dual fuel GE Power Systems gas turbines, which were designed to lean burn either natural gas or oil for low NOx emissions required a much higher sensitivity sensor. Joint work between GE CRD and Cree Research sponsored by the GE Aircraft Engine Division developed the know how for the fabrication of high sensitivity, high yield, reliable SiC photodiodes. Yield issues were uncovered and overcome. The urgency for system insertion required that SiC diode and sensor circuitry development needed to be carried out simultaneously with power plant field tests of laboratory or prototype sensor assemblies. The sensor and reliability specifications were stringent since the sensors installed on power plant turbine combustor walls are subjected to high levels of vibration, elevated temperatures, and high pressures. Furthermore a fast recovery time was required to sense flame out in spite of the fact that the amplifier circuit needed have high gain and high dynamic range. SiC diode technical difficulties were encountered and overcome. The science of hydrocarbon flames will also be described together with the fortunate overlap of the strong OH emission band with the SiC photodiode sensitivity versus wavelength characteristic. The extremely low dark current (<1pA/cm^2) afforded by the wide band gap and the 3eV sensitivity cutoff at 400nm made if possible to produce low amplifier offsets, high sensitivity and high dynamic range along with immunity to black body radiation from combustor walls. Field tests at power plants that had experienced turbine tripping, whenever oil fuel and/or oil with steam injection for

  4. Small Business Innovations (Fiber Optics)

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Foster-Miller, Inc. Waltham, MA developed the In-Situ Fiber Optic Polymer Reaction Monitor which could lead to higher yields and lower costs in complex composite manufacturing. The monitor, developed under a Small Business Innovation Research (SBIR) contract with Langley Research Center, uses an infrared, fiber optic sensor to track the molecular vibrational characteristics of a composite part while it is being cured. It is the first analytical system capable of directly measuring the chemistry of advanced composite materials.

  5. Short-term inhalation and in vitro tests as predictors of fiber pathogenicity.

    PubMed Central

    Cullen, R T; Miller, B G; Davis, J M; Brown, D M; Donaldson, K

    1997-01-01

    A wide range of fiber types was tested in two in vitro assays: toxicity to A549 epithelial cells, as detachment from substrate, and the production of the proinflammatory cytokine tumor necrosis factor (TNF) by rat alveolar macrophages. Three of the fibers were also studied in vivo, using short-term inhalation followed by a) bronchoalveolar lavage to assess the inflammatory response and b) measurement of cell proliferation in terminal bronchioles and alveolar ducts, using incorporation of bromodeoxyuridine (BrdU). The amount of TNF produced by macrophages in vitro depended on the fiber type, with the man-made vitreous fibers, and refractory ceramic fibers being least stimulatory and silicon carbide (SiC) whiskers providing the greatest stimulation. In the epithelial detachment assay there were dose-dependent differences in the toxicity of the various fibers, with long amosite being the most toxic. However, there was no clear relationship to known chronic pathogenicity. Fibers studied by short-term inhalation produced some inflammation, but there was no clear discrimination between the responses to code 100/475 glass fibers and the more pathogenic amosite and SiC. However, measurements of BrdU uptake into lung cells showed that amosite and SiC produced a greater reaction than code 100/475, which itself caused no more proliferation than that seen in untreated lungs. These results mirror the pathogenicity ranking of the fibers in long-term experiments. In conclusion, the only test to show potential as a predictive measure of pathogenicity was that of cell proliferation in lungs after brief inhalation exposure (BrdU assay). We believe that this assay should be validated with a wider range of fibers, doses, and time points. PMID:9400730

  6. Fiber optic control system integration

    NASA Technical Reports Server (NTRS)

    Poppel, G. L.; Glasheen, W. M.; Russell, J. C.

    1987-01-01

    A total fiber optic, integrated propulsion/flight control system concept for advanced fighter aircraft is presented. Fiber optic technology pertaining to this system is identified and evaluated for application readiness. A fiber optic sensor vendor survey was completed, and the results are reported. The advantages of centralized/direct architecture are reviewed, and the concept of the protocol branch is explained. Preliminary protocol branch selections are made based on the F-18/F404 application. Concepts for new optical tools are described. Development plans for the optical technology and the described system are included.

  7. Composites for Advanced Space Transportation Systems - (CASTS). [graphite fiber/polyimide matrix composites and polyimide adhesives for the space shuttle orbiter

    NASA Technical Reports Server (NTRS)

    Davis, J. G., Jr.

    1979-01-01

    The CASTS Project initiated to develop graphite fiber/polyimide matrix (GR/PI) composite structures with 589K operational capability for aerospace vehicles is described. Near term tasks include screening composites and adhesives for 589K service, developing fabrication procedures and specifications, developing design allowables test methods and data, design and test of structural elements, and construction of a full scale aft body flap for the space shuttle orbiter vehicle for ground testing. Far term tasks include research efforts directed at new materials, manufacturing procedures and design/analysis methodology. Specific results discussed include: (1) identification of four GR/PI composites and three PI adhesives with 589K service potential for periods ranging from 125 to 500 hours; (2) development of an adhesive formulation suitable for bonding reusable surface insulation (RSI) titles to 589K (GR/PI) substructure; (3) the capability to fabricate and nondestructively inspect laminates, hat section shaped stiffeners, honeycomb sandwich panels, and chopped fiber moldings; and (4) test methods for measuring design allowables at 117K.

  8. Advanced cogeneration research study: Executive summary

    NASA Technical Reports Server (NTRS)

    Bluhm, S. A.; Moore, N.; Rosenberg, L.; Slonski, M.

    1983-01-01

    This study provides a broad based overview of selected areas relevant to the development of a comprehensive Southern California Edison (SCE) advanced cogeneration project. The areas studied are: (1) Cogeneration potential in the SCE service territory; (2) Advanced cogeneration technologies; and (3) Existing cogeneration computer models. An estimated 3700 MW sub E could potentially be generated from existing industries in the Southern California Edison service territory using cogeneration technology. Of this total, current technology could provide 2600 MW sub E and advanced technology could provide 1100 MW sub E. The manufacturing sector (SIC Codes 20-39) was found to have the highest average potential for current cogeneration technology. The mining sector (SIC Codes 10-14) was found to have the highest potential for advanced technology.

  9. Fe Isotopic Composition of Presolar SiC Mainstream Grains

    NASA Technical Reports Server (NTRS)

    Tripa, C. E.; Pellin, M. J.; Savina, M. R.; Davis, A. M.; Lewis, R. S.; Clayton, R. N.

    2002-01-01

    Iron isotopic distribution was measured in SiC mainstream grains from the Murchison meteorite by time-of-flight resonance ionization mass spectrometry. All grains exhibit 54Fe depletions of 50 to 200, lower than what are predicted by calculations of s-process nucleosynthesis in AGB stars. Additional information is contained in the original extended abstract.

  10. Development of SiC Mirror for ASTRO-F

    NASA Astrophysics Data System (ADS)

    Kaneda, H.; Onaka, T.; Yamashiro, R.

    2000-12-01

    The development of the light-weight silicon carbide mirrors for the ASTRO-F mission is described in this paper. These mirrors are made of a sandwich-type SiC material, consisting of light porous core and dense CVD (chemical vapor deposition) coat of SiC. The primary mirror has a diameter of 710 mm and weighs only 11 kg. Combined with the secondary mirror of the same type, they form Ritchey-Chretien type telescope (F/6), which is cooled down to 5.8 K. Fabrication of the small-scale test SiC mirror has been successful which shows very little deformation of the figure at liquid-helium temperatures. Another type of the SiC coated mirror has been tested which has the same size as flight model, but of which core is made of graphite. At present, polishing of the flight-model primary mirror is going on. Construction of the flight model telescope system will be finished in 2001.

  11. Saturn V Stage I (S-IC) Overview

    NASA Technical Reports Server (NTRS)

    Interbartolo, Michael

    2009-01-01

    Objectives include: a) Become familiar with the Saturn V Stage I (S-IC) major structural components: Forward Skirt, Oxidizer Tank, Intertank, Fuel Tank, and Thrust Structure. b) Gain a general understanding of the Stage I subsystems: Fuel, Oxidizer, Instrumentation, Flight Control, Environmental Control, Electrical, Control Pressure, and Ordinance.

  12. Observations of Ag diffusion in ion implanted SiC

    DOE PAGESBeta

    Gerczak, Tyler J.; Leng, Bin; Sridharan, Kumar; Jerry L. Hunter, Jr.; Giordani, Andrew J.; Allen, Todd R.

    2015-03-17

    The nature and magnitude of Ag diffusion in SiC has been a topic of interest in connection with the performance of tristructural isotropic (TRISO) coated particle fuel for high temperature gas-cooled nuclear reactors. Ion implantation diffusion couples have been revisited to continue developing a more complete understanding of Ag fission product diffusion in SiC. Ion implantation diffusion couples fabricated from single crystal 4H-SiC and polycrystalline 3C-SiC substrates and exposed to 1500–1625°C, were investigated in this study by transmission electron microscopy and secondary ion mass spectrometry (SIMS). The high dynamic range of SIMS allowed for multiple diffusion régimes to be investigated,more » including enhanced diffusion by implantation-induced defects and grain boundary (GB) diffusion in undamaged SiC. Lastly, estimated diffusion coefficients suggest GB diffusion in bulk SiC does not properly describe the release observed from TRISO fuel.« less

  13. Low damage, highly anisotropic dry etching of SiC

    SciTech Connect

    Wang, J.J.; Hong, J.; Lambers, E.S.; Pearton, S.J.; Ren, F.; Ostling, M.; Zetterling, C.M.; Grow, J.M.; Shul, R.J.

    1998-03-01

    A parametric study of the etching characteristics of 6H p{sup +} and n{sup +} SiC and thin film SiC{sub 0.5}N{sub 0.5} in Inductively Coupled Plasma NF{sub 3}/O{sub 2} and NF{sub 3}/Ar discharges has been performed. The etch rates in both chemistries increase monotonically with NF{sub 3} percentage and rf chuck power. The etch rates go through a maximum with increasing ICP source power, which is explained by a trade-off between the increasing ion flux and the decreasing ion energy. The anisotropy of the etched features is also a function of ion flux, ion energy and atomic fluorine neutral concentration. Indium-tin-oxide (ITO) masks display relatively good etch selectivity over SiC (maximum of {approximately} 70:1), while photoresist etches more rapidly than SiC. The surface roughness of SiC is essentially independent of plasma composition for NF3/O2 discharges, while extensive surface degradation occurs for SiCN under high NF{sub 3}:O{sub 2} conditions.

  14. Towards SiC Surface Functionalization: An Ab Initio Study

    SciTech Connect

    Cicero, G; Catellani, A

    2005-01-28

    We present a microscopic model of the interaction and adsorption mechanism of simple organic molecules on SiC surfaces as obtained from ab initio molecular dynamics simulations. Our results open the way to functionalization of silicon carbide, a leading candidate material for bio-compatible devices.

  15. -SiC nanocomposite coatings synthesized by co-electrodeposition

    NASA Astrophysics Data System (ADS)

    Masoudi, Mehran; Hashim, Mansor; Kamari, Halimah Mohamed

    2014-08-01

    In the present work, Ni-Al2O3, Ni-SiC and novel Ni-Al2O3-SiC metal matrix composite (MMC) coatings were electrodeposited onto pure copper samples using a modified Watt's nickel electroplating bath containing nano alumina and silicon carbide particles with an average particle size of 50 nm. The composition, crystalline structure and surface morphology of the deposits were characterized by X-ray diffractometry (XRD), energy-dispersive X-ray spectroscopy (EDS) and field emission scanning electron microscopy (FESEM). The results indicated that Ni-Al2O3-SiC hybrid composite films with an acceptable homogeneity and granular structure having 9.2 and 7.7 % vol. Al2O3 and SiC nanoparticles, respectively were developed successfully. The nanoparticles incorporated in the nickel layer effectively increased the micro hardness and wear resistance owing to dispersion and grain-refinement strengthening, changing the nickel matrix morphology as well as the texture and preferred grain growth direction from <100> to the close-packed <111>. The oxidation resistance of the Ni-Al2O3-SiC hybrid composite coatings was measured to be approximately 41 % greater than the unreinforced Ni deposit and almost 30 % better than the Ni-Al2O3 composite coatings.

  16. Stress Analysis of SiC MEMS Using Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ness, Stanley J.; Marciniak, M. A.; Lott, J. A.; Starman, L. A.; Busbee, J. D.; Melzak, J. M.

    2003-03-01

    During the fabrication of Micro-Electro-Mechanical Systems (MEMS), residual stress is often induced in the thin films that are deposited to create these systems. These stresses can cause the device to fail due to buckling, curling, or fracture. Industry is looking for ways to characterize the stress during the deposition of thin films in order to reduce or eliminate device failure. Micro-Raman spectroscopy has been successfully used to characterize poly-Si MEMS devices made with the MUMPS® process. Raman spectroscopy was selected because it is nondestructive, fast and has the potential for in situ stress monitoring. This research attempts to use Raman spectroscopy to analyze the stress in SiC MEMS made with the MUSiC® process. Raman spectroscopy is performed on 1-2-micron-thick SiC thin films deposited on silicon, silicon nitride, and silicon oxide substrates. The most common poly-type of SiC found in thin film MEMS made with the MUSiC® process is 3C-SiC. Research also includes baseline spectra of 6H, 4H, and 15R poly-types of bulk SiC.

  17. Optimizing Graphene Morphology on SiC(0001)

    NASA Astrophysics Data System (ADS)

    Hannon, James

    2009-03-01

    Many schemes to integrate graphene with microelectronics assume that reliable wafer-scale synthesis processes will be developed. One promising route to wafer-scale synthesis is to form graphene overlayers from the decomposition of SiC at high temperature. We have shown that, even at 1200 C, limited diffusion at the SiC surface leads to pit formation and a non-uniform graphene film thickness [1]. In this talk I will describe our efforts to improve both graphene domain size and thickness uniformity. One way we achieve this is by forming graphene in a background pressure of disilane, which hinders SiC decomposition. Even in rather low Si partial pressures (e.g. 1e-5 Torr), the SiC decomposition temperature can shifted several hundred degrees higher in temperature [2]. Using in situ low-energy electron microscopy (LEEM), we show that this effect can be exploited to form large graphene domains (larger than 10 um) with controlled layer thickness (e.g. 1 ML). Work performed in collaboration with R.M. Tromp. [4pt] [1] J.B. Hannon and R.M. Tromp, Phys. Rev. B77, 241404(R) 2008[0pt] [2] R.M. Tromp and J.B. Hannon, in press.

  18. Fission-product SiC reaction in HTGR fuel

    SciTech Connect

    Montgomery, F.

    1981-07-13

    The primary barrier to release of fission product from any of the fuel types into the primary circuit of the HTGR are the coatings on the fuel particles. Both pyrolytic carbon and silicon carbide coatings are very effective in retaining fission gases under normal operating conditions. One of the possible performance limitations which has been observed in irradiation tests of TRISO fuel is chemical interaction of the SiC layer with fission products. This reaction reduces the thickness of the SiC layer in TRISO particles and can lead to release of fission products from the particles if the SiC layer is completely penetrated. The experimental section of this report describes the results of work at General Atomic concerning the reaction of fission products with silicon carbide. The discussion section describes data obtained by various laboratories and includes (1) a description of the fission products which have been found to react with SiC; (2) a description of the kinetics of silicon carbide thinning caused by fission product reaction during out-of-pile thermal gradient heating and the application of these kinetics to in-pile irradiation; and (3) a comparison of silicon carbide thinning in LEU and HEU fuels.

  19. Advanced composite combustor structural concepts program. Final Report

    SciTech Connect

    Sattar, M.A.; Lohmann, R.P.

    1984-12-01

    An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's.

  20. First principle identification of SiC monolayer as an efficient catalyst for CO oxidation

    SciTech Connect

    Sinthika, S. E-mail: sinthika90@gmail.com; Thapa, Ranjit E-mail: sinthika90@gmail.com; Reddy, C. Prakash

    2015-06-24

    Using density functional theory, we investigated the electronic properties of SiC monolayer and tested its catalytic activity toward CO oxidation. The planar nature of a SiC monolayer is found to stable and is a high band gap semiconductor. CO interacts physically with SiC surface, whereas O{sub 2} is adsorbed with moderate binding. CO oxidation on SiC monolayer prefers the Eley Rideal mechanism over the Langmuir Hinshelwood mechanism, with an easily surmountable activation barrier during CO{sub 2} formation. Overall metal free SiC monolayer can be used as efficient catalyst for CO oxidation.