Science.gov

Sample records for 2-digit sic manufacturing

  1. Improved Method of Manufacturing SiC Devices

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S.

    2005-01-01

    The phrase, "common-layered architecture for semiconductor silicon carbide" ("CLASSiC") denotes a method of batch fabrication of microelectromechanical and semiconductor devices from bulk silicon carbide. CLASSiC is the latest in a series of related methods developed in recent years in continuing efforts to standardize SiC-fabrication processes. CLASSiC encompasses both institutional and technological innovations that can be exploited separately or in combination to make the manufacture of SiC devices more economical. Examples of such devices are piezoresistive pressure sensors, strain gauges, vibration sensors, and turbulence-intensity sensors for use in harsh environments (e.g., high-temperature, high-pressure, corrosive atmospheres). The institutional innovation is to manufacture devices for different customers (individuals, companies, and/or other entities) simultaneously in the same batch. This innovation is based on utilization of the capability for fabrication, on the same substrate, of multiple SiC devices having different functionalities (see figure). Multiple customers can purchase shares of the area on the same substrate, each customer s share being apportioned according to the customer s production-volume requirement. This makes it possible for multiple customers to share costs in a common foundry, so that the capital equipment cost per customer in the inherently low-volume SiC-product market can be reduced significantly. One of the technological innovations is a five-mask process that is based on an established set of process design rules. The rules provide for standardization of the fabrication process, yet are flexible enough to enable multiple customers to lay out masks for their portions of the SiC substrate to provide for simultaneous batch fabrication of their various devices. In a related prior method, denoted multi-user fabrication in silicon carbide (MUSiC), the fabrication process is based largely on surface micromachining of poly SiC

  2. 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.

  3. A 10-kW SiC Inverter with A Novel Printed Metal Power Module With Integrated Cooling Using Additive Manufacturing

    SciTech Connect

    Chinthavali, Madhu Sudhan; Ayers, Curtis William; Campbell, Steven L; Wiles, Randy H; Ozpineci, Burak

    2014-01-01

    With efforts to reduce the cost, size, and thermal management systems for the power electronics drivetrain in hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), wide band gap semiconductors including silicon carbide (SiC) have been identified as possibly being a partial solution. This paper focuses on the development of a 10-kW all SiC inverter using a high power density, integrated printed metal power module with integrated cooling using additive manufacturing techniques. This is the first ever heat sink printed for a power electronics application. About 50% of the inverter was built using additive manufacturing techniques.

  4. SiC for Space Optics

    NASA Astrophysics Data System (ADS)

    Wellman, John

    2012-01-01

    This paper describes SiC mirrors that are large, ultra-lightweight, and actively controlled, for use in space telescopes. "Advanced Hybrid Mirrors” (AHMs) utilize SiC substrates, with embedded solid-state actuators, bonded to Nanolaminate metal foil reflective surfaces. They use replication techniques for high optical quality as well as rapid, low cost manufacturing. AHMs up to 1.35m in size have been made and tested, demonstrating wavefront error to better than the visible diffraction limit. AHMs can be fabricated at production rates after the first unit delivery as fast as 48 day intervals. "Superpolished Si/SiC Active Mirrors” (SSAMs) are similar to AHMs but the SiC mirror substrates have a layer of Si deposited on them to enable direct superpolishing. SSAMs can be much larger, can operate over a wider temperature range, and are better suited to UV astronomy. To make SSAMs larger than 1.8 m, multiple substrates can be joined together, using brazing techniques. Using wavefront sensing and control technology to command the embedded solid-state actuators, final mirror figure will be set after launch. This gives the active SiC mirror the ability to correct nearly any optical error, occurring anywhere in the optical system. As a result, active SiC mirrors can be made to relaxed figure requirements, enabling optical replication, or speeding up polishing, while assuring excellent final performance. Active SiC mirrors will reduce cost, risk and schedule for future astrophysics missions. Their high control authority allows relaxation of fabrication and assembly tolerances from optical to mechanical levels, speeding I & T. They enable rapid system testing to within required performance levels, even in 1 G, lowering mission risk. They are lighter weight and more durable than glass mirrors.

  5. 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.

  6. 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.

  7. 40 CFR 372.23 - SIC and NAICS codes to which this Part applies.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... sale of household furniture and that manufacture custom made upholstered household furniture (previously classified under SIC 5712, Furniture Stores (upholstered, custom made furniture)); Except 337122... limited to facilities primarily engaged in the retail sale of household furniture and that...

  8. 40 CFR 372.23 - SIC and NAICS codes to which this Part applies.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... sale of household furniture and that manufacture custom made upholstered household furniture (previously classified under SIC 5712, Furniture Stores (upholstered, custom made furniture)); Except 337122... limited to facilities primarily engaged in the retail sale of household furniture and that...

  9. Current and future industrial energy service characterizations. Volume II. Energy data on the US manufacturing subsector

    SciTech Connect

    Krawiec, F.; Thomas, T.; Jackson, F.; Limaye, D.R.; Isser, S.; Karnofsky, K.; Davis, T.D.

    1980-10-01

    In order to characterize industrial energy service, current energy demand, its end uses, and cost of typical energy applications and resultant services in the industrial sector were examined and a projection of state industrial energy demands and prices to 1990 was developed. Volume II presents in Section 2 data on the US manufacturing subsector energy demand, intensity, growth rates, and cost for 1971, 1974, and 1976. These energy data are disaggregated not only by fuel type but also by user classifications, including the 2-digit SIC industry groups, 3-digit subgroups, and 4-digit SIC individual industries. These data characterize typical energy applications and the resultant services in this subsector. The quantities of fuel and electric energy purchased by the US manufacturing subsector were converted to British thermal units and reported in billions of Btu. The conversion factors are presented in Table 4-1 of Volume I. To facilitate the descriptive analysis, all energy cost and intensity data were expressed in constant 1976 dollars. The specific US industrial energy service characteristics developed and used in the descriptive analysis are presented in Volume I. Section 3 presents the computer program used to produce the tabulated data.

  10. 40 CFR 372.23 - SIC and NAICS codes to which this Part applies.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... primarily engaged in the retail sale of household furniture and that manufacture custom made upholstered household furniture (previously classified under SIC 5712, Furniture Stores (upholstered, custom made... Shops (remanufacturing)); 336—Transportation Equipment Manufacturing. 337—Furniture and Related...

  11. A Φ 3.5m diameter Sic telescope for Herschel mission

    NASA Astrophysics Data System (ADS)

    Sein, Emmanuel; Toulemont, Yves; Safa, Frederic; Duran, Michel; Deny, Pierre; de Chambure, Daniel; Passvogel, Thomas; Pilbratt, Goeran L.

    2003-03-01

    Since ten years ASTRIUM has developed sintered Silicon Carbide (SiC) technology for space applications. Its unique thermo-mechanical properties, associated with its polishing capability, make SiC an ideal material for building ultra-stable lightweight space based telescopes or mirrors. SiC is a cost effective alternative to Beryllium and the ultra-lighweighted ULE. In Complememt to the material manufacturing process, ASTRIUM has developed several assembly techniques (bolting, brazing, bonding) for manufacturing large and complex SiC assemblies. This technology is now perfectly mature and mastered. SiC is baselined for most of the telescopes that are developed by ASTRIUM. SiC has been identified as the most suitable material for manufacturing very large crygenic telescopes. In this paper we present the development of Φ 3.5 m telescope for Herschel Mission. Herschel main goal is to study how the first stars and galaxies were formed and evolved. The Herschel Space telescope, using silicon carbide technology will be the largest space imagery telescope ever launched. The Herschel telescope will weight 300 kg rather than the 1.5 tons required with standard technology. The Herschel telescope is to be delivered in 2005 for a launch planned for 2007.

  12. Saturn V S-IC Stage Liquid Oxygen Tank

    NASA Technical Reports Server (NTRS)

    1964-01-01

    This photograph depicts a forward skirt being placed on the liquid oxygen tank for Saturn V S-IC (first) stage in the Manufacturing Engineering Laboratory at the Marshall Space Flight Center. Thirty-three feet in diameter, the fuel tanks hold a total of 4,400,000 pounds of fuel. Although this tankage was assembled at MSFC, the elements were made by the Boeing Company at Wichita and the Michoud Operations at New Orleans.

  13. Spin transport in epitaxial graphene on SiC (0001)

    NASA Astrophysics Data System (ADS)

    Du, Yuchen; Neal, Adam T.; Capano, Mike; Ye, Peide

    2013-03-01

    Graphene has been identified as a promising material for future spintronics devices due to its low spin orbit coupling and long spin diffusion lengths, even at room temperature. However, any device application requires the use of large-area graphene compatible with wafer-scale manufacturing methods, such as graphene grown epitaxially on SiC. We study spin transport in epitaxial graphene grown on SiC (0001) as a step toward future spintronics devices. A non-local spin valve signal of 200m Ω is observed at 77K, with a signal of 50m Ω resolved at 145K. Assuming a contact polarization of 10%, the measured signal corresponds to a spin diffusion length of 130nm at T =77K. Hanle effect spin precession measurements are ongoing.

  14. Saturn V S-IC Stage Fuel Tank Components

    NASA Technical Reports Server (NTRS)

    1964-01-01

    The components of the Saturn V booster (S-IC stage) fuel tank are shown in this photograph. The liquid oxygen tank bulkhead on the left and both halves of the fuel tank were in the Marshall Space Flight Center (MSFC) Manufacturing Engineering Laboratory, building 4707. These components were used at MSFC in structural testing to prove that they could withstand the forces to which they were subjected in flight. Each S-IC stage has two tanks, one for kerosene and one for liquid oxygen, made from such components as these. Thirty-three feet in diameter, they hold a total of 4,400,000 pounds of fuel. Although this tankage was assembled at MSFC, the elements were made by the Boeing Company at Wichita and the Michoud Operations at New Orleans.

  15. Study of Erosive Wear Behaviour on SIC/SIC Composites

    NASA Astrophysics Data System (ADS)

    Suh, Min-Soo

    In the field of aerospace propulsion system, erosive wear on continuous silicon carbide (SiC) fibre-reinforced SiC (SiC/SiC) composites is of significant issue to achieve high energy efficiency. This paper proposes a crucial factor and a design guideline of SiC/SiC composites for higher erosion performance regarding cost effectiveness. Fabrication and evaluation of impacts and wear on SiC/SiC composites are successfully carried out. Erosive wear behaviours of the CVI and the LPS composites evidently show that the crucial fabrication factor against solid particle erosion (SPE). Erosive wear mechanisms on various SiC/SiC composites are determined based on the analysis of erosive wear behaviour. Designing guideline for the SiC/SiC composites for pursuit of high erosion performance is also proposed as focusing on the followings; volume fraction of matrix, strength of the matrix, bonding strength, and PyC interface.

  16. Nanostructured core-shell Ni deposition on SiC particles by alkaline electroless coating

    NASA Astrophysics Data System (ADS)

    Uysal, M.; Karslioğlu, R.; Alp, A.; Akbulut, H.

    2011-10-01

    In this study, core-shell nanostructured nickel formation on silicon carbide (SiC) ceramic powders was achieved through the electroless deposition method using alkaline solutions. To produce a nano core-shell Ni deposition on the SiC surfaces, process parameters such as pH values, the type of reducer material, deposition temperature, stirring rate and activation procedure among others were determined. Full coverage of core-shell nickel structures on SiC surfaces was achieved with a grain size of between 100 and 300 nm, which was approximately the same deposition thickness on the SiC surfaces. The surface morphology of the coated SiC particles showed a homogenous distribution of nanostructured nickel grains characterized by scanning electron microscopy and X-ray diffraction techniques. The nanostructures of the crystalline Ni coatings were observed to be attractive for achieving both good bonding and dense structure. The thin core shell-structure of Ni on the SiC surfaces was assessed as a beneficial reinforcement for possible metal matrix composite manufacturing.

  17. /SiC Composite to Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Hernandez, X.; Jiménez, C.; Mergia, K.; Yialouris, P.; Messoloras, S.; Liedtke, V.; Wilhelmi, C.; Barcena, J.

    2014-08-01

    In view of aerospace applications, an innovative structure for joining a Ti alloy to carbon fiber reinforced silicon carbide has been developed. This is based on the perforation of the CMC material, and this procedure results in six-fold increase of the shear strength of the joint compared to the unprocessed CMC. The joint is manufactured using the active brazing technique and TiCuAg as filler metal. Sound joints without defects are produced and excellent wetting of both the composite ceramic and the metal is observed. The mechanical shear tests show that failure occurs always within the ceramic material and not at the joint. At the CMC/filler, Ti from the filler metal interacts with the SiC matrix to form carbides and silicides. In the middle of the filler region depletion of Ti and formation of Ag and Cu rich regions are observed. At the filler/Ti alloy interface, a layered structure of the filler and Ti alloy metallic elements is formed. For the perforation to have a significant effect on the improvement of the shear strength of the joint appropriate geometry is required.

  18. 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.

  19. Photoluminescence of etched SiC nanowires

    NASA Astrophysics Data System (ADS)

    Stewart, Polite D., Jr.; Rich, Ryan; Zerda, T. W.

    2010-10-01

    SiC nanowires were produced from carbon nanotubes and nanosize silicon powder in a tube furnace at temperatures between 1100^oC and 1350^oC. SiC nanowires had average diameter of 30 nm and very narrow size distribution. The compound possesses a high melting point, high thermal conductivity, and excellent wear resistance. The surface of the SiC nanowires after formation is covered by an amorphous layer. The composition of that layer is not fully understood, but it is believed that in addition to amorphous SiC it contains various carbon and silicon compounds, and SiO2. The objective of the research was to modify the surface structure of these SiC nanowires. Modification of the surface was done using the wet etching method. The etched nanowires were then analyzed using Fourier Transform Infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and photoluminescence (PL). FTIR and TEM analysis provided valid proof that the SiC nanowires were successfully etched. Also, the PL results showed that the SiC nanowire core did possess a fluorescent signal.

  20. Influence of Ni-P Coated SiC and Laser Scan Speed on the Microstructure and Mechanical Properties of IN625 Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Sateesh, N. H.; Kumar, G. C. Mohan; Krishna, Prasad

    2015-12-01

    Nickel based Inconel-625 (IN625) metal matrix composites (MMCs) were prepared using pre-heated nickel phosphide (Ni-P) coated silicon carbide (SiC) reinforcement particles by Direct Metal Laser Sintering (DMLS) additive manufacturing process under inert nitrogen atmosphere to obtain interface influences on MMCs. The distribution of SiC particles and microstructures were characterized using optical and scanning electron micrographs, and the mechanical behaviours were thoroughly examined. The results clearly reveal that the interface integrity between the SiC particles and the IN625 matrix, the mixed powders flowability, the SiC ceramic particles and laser beam interaction, and the hardness, and tensile characteristics of the DMLS processed MMCs were improved effectively by the use of Ni-P coated SiC particles.

  1. 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.

  2. 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.

  3. 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.

  4. Fabrication of mullite-bonded porous SiC ceramics from multilayer-coated SiC particles through sol-gel and in-situ polymerization techniques

    NASA Astrophysics Data System (ADS)

    Ebrahimpour, Omid

    second part of the project. Alumina sol was synthesized by the hydrolysis of Aluminum isopropoxide using the Yoldas method. Alumina sol was homogenous and had a needle-like shape with a thickness of 2--3 nm. Crystalline changes during the heating process of alumina sol were studied using XRD. In addition, Fourier transform infrared (FTIR) spectroscopy was performed to identify the functional groups on the alumina sol surface as a function of temperature. In the third part of the project, the feasibility of the in-situ polymerization technique was investigated to fabricate porous SiC ceramics. In this part, the mixture of SiC and calcined alumina powders were coated by polyethylene via in-situ polymerizing referred to as the polymerization compounding process in a slurry phase. The polymerization was conducted under very moderate operational conditions using the Ziegler-Natta catalyst system. Differential scanning calorimetry (DSC) and TGA analysis and morphological studies (SEM and TEM) revealed the presence of a high density of polyethylene on the surface of SiC and alumina powders. The amount of polymer was controlled by the polymerization reaction time. Most parts of particles were coated by a thin layer of polyethylene and polymer. The porous SiC ceramics, which were fabricated by these treated particles showed higher mechanical and physical properties compared to the samples made without any treatment. The relative intensity of mullite was higher compared to the samples prepared by the traditional process. The effects of the sintering temperature, forming pressure and polymer content were also studied on the physical and mechanical properties of the final product. In the last phase of this research work, the focus of the investigation was to take advantage of both the sol-gel processing and in-situ polymerization method to develop a new process to manufacture mullite-bonded porous SiC ceramic with enhanced mechanical and physical properties. Therefore, first the SiC

  5. 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.

  6. Oxidation behaviour of SiC coatings

    NASA Astrophysics Data System (ADS)

    Mergia, K.; Lafatzis, D.; Moutis, N.; Speliotis, T.; Apostolopoulos, G.; Cousin, F.

    2008-08-01

    Amorphous silicon carbide (SiC) films were deposited on silicon substrates by radio-frequency magnetron sputtering. The films were oxidized in air in the temperature range 400-900 °C and for times from 1 to 16 h. Neutron reflectivity measurements provided information on the thickness, density and roughness of the SiC and on the formed SiO2 layers. Fourier transform infrared spectroscopy was used to determine the bond structure of the formed SiO2 and changes in the bonding of SiC after exposure at the oxidation temperature. The surface morphology of the oxidized films was characterized by atomic force microscopy measurements. The oxidation kinetics is initially fast and as the SiO2 layer is formed it slows down. The SiC consumption varies linearly with time at all oxidation temperatures. Exposure of the SiC at the oxidation temperature affects its density and to some degree its bond structure, while the formed SiO2 has density and bond structure as that formed by oxidation of Si under the same conditions.

  7. Fabrication of mullite-bonded porous SiC ceramics from multilayer-coated SiC particles through sol-gel and in-situ polymerization techniques

    NASA Astrophysics Data System (ADS)

    Ebrahimpour, Omid

    second part of the project. Alumina sol was synthesized by the hydrolysis of Aluminum isopropoxide using the Yoldas method. Alumina sol was homogenous and had a needle-like shape with a thickness of 2--3 nm. Crystalline changes during the heating process of alumina sol were studied using XRD. In addition, Fourier transform infrared (FTIR) spectroscopy was performed to identify the functional groups on the alumina sol surface as a function of temperature. In the third part of the project, the feasibility of the in-situ polymerization technique was investigated to fabricate porous SiC ceramics. In this part, the mixture of SiC and calcined alumina powders were coated by polyethylene via in-situ polymerizing referred to as the polymerization compounding process in a slurry phase. The polymerization was conducted under very moderate operational conditions using the Ziegler-Natta catalyst system. Differential scanning calorimetry (DSC) and TGA analysis and morphological studies (SEM and TEM) revealed the presence of a high density of polyethylene on the surface of SiC and alumina powders. The amount of polymer was controlled by the polymerization reaction time. Most parts of particles were coated by a thin layer of polyethylene and polymer. The porous SiC ceramics, which were fabricated by these treated particles showed higher mechanical and physical properties compared to the samples made without any treatment. The relative intensity of mullite was higher compared to the samples prepared by the traditional process. The effects of the sintering temperature, forming pressure and polymer content were also studied on the physical and mechanical properties of the final product. In the last phase of this research work, the focus of the investigation was to take advantage of both the sol-gel processing and in-situ polymerization method to develop a new process to manufacture mullite-bonded porous SiC ceramic with enhanced mechanical and physical properties. Therefore, first the SiC

  8. 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.

  9. 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.

  10. Manufacturing Success

    ERIC Educational Resources Information Center

    Reese, Susan

    2007-01-01

    According to the National Association of Manufacturers (NAM), "manufacturing is the engine that drives American prosperity". When NAM and its research and education arm, The Manufacturing Institute, released the handbook, "The Facts About Modern Manufacturing," in October 2006, NAM President John Engler noted, that manufacturing output in America…

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Effect of Steam Activation on Development of Light Weight Biomorphic Porous SiC from Pine Wood Precursor

    NASA Astrophysics Data System (ADS)

    Manocha, Satish M.; Patel, Hemang; Manocha, L. M.

    2013-02-01

    Biomorphic SiC materials with tailor-made microstructure and properties similar to ceramic materials manufactured by conventional method are a new class of materials derived from natural biopolymeric cellulose templates (wood). Porous silicon carbide (SiC) ceramics with wood-like microstructure have been prepared by carbothermal reduction of charcoal/silica composites at 1300-1600 °C in inert Ar atmosphere. The C/SiO2 composites were fabricated by infiltrating silica sol into porous activated biocarbon template. Silica in the charcoal/silica composite, preferentially in the cellular pores, was found to get transformed in forms of fibers and rods due to shrinkage during drying. The changes in the morphology of resulting porous SiC ceramics after heat treatment to 1600 °C, as well as the conversion mechanism of wood to activated carbon and then to porous SiC ceramic have been investigated using scanning electron microscope, x-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. Activation of carbon prior to silica infiltration has been found to enhance conversion of charcoal to SiC. The pore structure is found to be uniform in these materials than in those made from as-such charcoal/silica composites. This provides a low-cost and eco-friendly route to advanced ceramic materials, with near-net shape potential.

  18. Surface modification of SiC mirror by IARE method

    NASA Astrophysics Data System (ADS)

    Shen, Zhenfeng; Gao, Jinsong

    2011-02-01

    A method to prepare high quality SiC coating at low temperature using large aperture E-beam evaporation PVD equipment with ion assistance was developed for the surface modification of SiC mirror for space projects .This method was called Ion Assisted Reactive Evaporation (IARE). The modified SiC coating was prepared using CH4 and Si with Kaufman ion source by IARE at 300°C and it had met the requirements of applications. The SiC coating prepared by this method was amorphous. It was dense, homogeneous and easy to be polished. The surface modification of a SiC mirror was carried out using SiC coating by this method and achieved a fine surface modification effect. The surface roughness (rms) of the SiC substrate was reduced to 0.862nm, the scattering coefficient was reduced to 2.79% and the reflectance coated with Ag film was improved simultaneously after the surface modification. The effect of surface modification using SiC coating was close to that of using Si coating. It can be drawn that this technological method to preparation SiC coating for the surface modification of SiC mirror is reasonable and effective.

  19. Surface modification of SiC mirror by IARE method

    NASA Astrophysics Data System (ADS)

    Shen, Zhenfeng; Gao, Jinsong

    2010-10-01

    A method to prepare high quality SiC coating at low temperature using large aperture E-beam evaporation PVD equipment with ion assistance was developed for the surface modification of SiC mirror for space projects .This method was called Ion Assisted Reactive Evaporation (IARE). The modified SiC coating was prepared using CH4 and Si with Kaufman ion source by IARE at 300°C and it had met the requirements of applications. The SiC coating prepared by this method was amorphous. It was dense, homogeneous and easy to be polished. The surface modification of a SiC mirror was carried out using SiC coating by this method and achieved a fine surface modification effect. The surface roughness (rms) of the SiC substrate was reduced to 0.862nm, the scattering coefficient was reduced to 2.79% and the reflectance coated with Ag film was improved simultaneously after the surface modification. The effect of surface modification using SiC coating was close to that of using Si coating. It can be drawn that this technological method to preparation SiC coating for the surface modification of SiC mirror is reasonable and effective.

  20. Field emission spectroscopy of SiC

    NASA Astrophysics Data System (ADS)

    Nikiforov, K. A.; Trofimov, V. V.; Egorov, N. V.

    2016-08-01

    Experimental set up for the natural experiment and measurement model are presented to obtain the feld emission energy distribution spectrum out of silicon carbide in case of the macro-sample having a macroscopic shape of a tip. The prototype of feld emission 6H - SiC monolithic cathode is proposed for spectroscopy measurements, and characterised by current-voltage dependence at macroscale interelectrode distance.

  1. Point Defects in SiC

    NASA Astrophysics Data System (ADS)

    Zvanut, Mary Ellen

    2004-03-01

    Production of high frequency, high power electronic devices using wide bandgap semiconductors has spurred renewed interest in point defects in SiC. Recent electron paramagnetic resonance (EPR) spectroscopy studies focus on centers in as-grown high purity semi-insulating substrates because intrinsic defects are thought to compensate unavoidable shallow centers, thus creating the high resistivity required. The EPR studies address the chemical/structural composition of the defects, the defect level (energy with respect to a band edge with which the defect can accept or release an electron) and thermal stability. Thus far, the positively charged carbon vacancy, the Si vacancy, a carbon-vacancy/carbon antisite pair, and several as yet-unidentified centers have been observed in as-grown electronic-grade 4H-SiC [1-3]. The talk will review the types of defects recently identified in SiC and discuss their possible relationship to compensation. The photo-induced EPR experiments used to determine defect levels will be discussed, with a particular focus on the carbon vacancy. The use of high frequency EPR to resolve the many different types of centers in SiC will also be covered. Finally, the presentation will review the thermal stability of the intrinsic defects detected in as-grown 4H SiC. 1. M. E. Zvanut and V. V. Konovalov, Appl. Phys. Lett. 80, 410 (2002). 2. N.T. Son, Z. Zolnai, and E. Janzen, Phys. Rev. B64, 2452xx (2003). 3. W.E. Carlos, E.R. Glaser, and B.V. Shanabrook, in Proceedings of the 22nd conference on Defects in Semiconductors, Aarhus, Denmark, July 2003.

  2. 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

  3. 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.

  4. Functionally graded coatings on SiC fibers for protection in Ti-based metal matrix composites

    SciTech Connect

    Choy, K.L.

    1996-06-01

    The incorporation of SiC fibers in Ti-based alloys, has led to the development of high strength, low density and high creep resistant properties of titanium-based metal matrix composites (Ti-MMCs). These composites have applications in the aerospace industry as structural materials for aerojet components and compressor blades. The processing of Ti-based composites usually involves a consolidation stage using diffusion bonding or hot isostatic pressing where the consolidation temperatures are in excess of 800 C for a significant period of time. Severe interdiffusion and chemical reactions between the SiC and Ti-alloy matrices occur under such processing conditions, leading to the formation of brittle reaction layer and deterioration of the mechanical properties of the composites. In addition, the SiC/Ti interfacial reactions can also occur during in service if the operating temperature is above 700 C. A variety of approaches has been examined to prevent or reduce the SiC/Ti interfacial reactions in MMCs at elevated temperatures during material manufacturing and in service. Coating of the SiC fibers prior to incorporation into the Ti matrices seems to be the most viable approach to overcome this technical problem. This has prompted the development of functionally graded coatings onto SiC fibers. Functionally graded coating consists a systematic but continuous variation in the composition and microstructure across the coating thickness, resulting in a gradual change in properties. Consequently, this has led to the distinct multifunction characteristics. This work describes the influence of functionally graded coatings of C/TiC/(Ti,C)/Ti in preserving the surface integrity and strength of the as-received SiC fibers, and effectiveness to prevent deleterious reaction with Ti-matrix as compared with the unprotected SiC fibers.

  5. Polishing, coating, and integration of SiC mirrors for space telescopes

    NASA Astrophysics Data System (ADS)

    Rodolfo, Jacques

    2008-07-01

    In the last years, the technology of SiC mirrors took an increasingly significant part in the field of space telescopes. Sagem is involved in the JWST program to manufacture and test the optical components of the NIRSpec instrument. The instrument is made of 3 TMAs and 4 plane mirrors made of SiC. Sagem is in charge of the CVD cladding, the polishing, the coating of the mirrors and the integration and testing of the TMAs. The qualification of the process has been performed through the manufacturing and testing of the qualification model of the FOR TMA. This TMA has shown very good performances both at ambient and during the cryo test. The polishing process has been improved for the manufacturing of the flight model. This improvement has been driven by the BRDF performance of the mirror. This parameter has been deeply analysed and a model has been built to predict the performance of the mirrors. The existing Dittman model have been analysed and found to be optimistic.

  6. 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.

  7. 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.

  8. 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.

  9. Manufacturing technologies

    NASA Astrophysics Data System (ADS)

    The Manufacturing Technologies Center is at the core of Sandia National Laboratories' advanced manufacturing effort which spans the entire product realization process. The center's capabilities in product and process development are summarized in the following disciplines: (1) mechanical - rapid prototyping, manufacturing engineering, machining and computer-aided manufacturing, measurement and calibration, and mechanical and electronic manufacturing liaison; (2) electronics - advanced packaging for microelectronics, printed circuits, and electronic fabrication; and (3) materials - ceramics, glass, thin films, vacuum technology, brazing, polymers, adhesives, composite materials, and process analysis.

  10. Microstructural development to toughen SiC

    SciTech Connect

    Moberlychan, W.J.; Cannon, R.M.; Chan, L.H.; Cao, J.J.; Gilbert, C.J.; Ritchie, R.O.; De Jonghe, L.C.

    1996-12-31

    SiC offers a promise for high strength applications at high temperature; however, poor fracture resistance has inhibited its utility. Recent developments to control microstructure during hot pressing have improved fracture toughness > 3 fold, while also improving strength 50% above that of a commercial SiC, Hexoloy. This ABC-SiC (designated for the Al, B, and C additives) utilizes liquid phase sintering to obtain full densification at 1,650 C, and to induce the {beta}-3C to {alpha}-4H phase transformation below 1,900 C. Interlocking, plate-like, {alpha} grains, coupled with a thin ({approximately}1 nm) amorphous layer, provide for tortuous intergranular fracture and high toughness. This study focuses on the developing microstructure; how the {alpha}-4H polytype grow as a stacking modification of the {beta}-3C grains, and how amorphous grain boundaries and crystalline triple point phases develop and interact with the crack geometry. HR-TEM and Image-Filtered EELS characterize the amorphous grain boundaries. Field Emission-SEM, EDS and Auger Electron Spectroscopy characterize the fracture morphology and the chemistry of grain boundaries and triple points. Electron Diffraction and HR-TEM depict an epitaxial relationship between triple point phases (Al{sub 8}B{sub 4}C{sub 7} and Al{sub 4}O{sub 4}C) and matrix {alpha}-SiC grains, the development of which affects the mechanical toughening. The transformation to toughen SiC is compared to the well-studied transformation processing in Si{sub 3}N{sub 4}. A distinct advantage is the interlocked nature of the plate-like grains, which causes strong elastic bridging behind the crack tip.

  11. SiC reinforced aluminide composites

    NASA Technical Reports Server (NTRS)

    Brindley, Pamela K.

    1987-01-01

    The tensile properties of SiC fiber, Ti3Al+Nb and SiC/Ti3Al+Nb composite have been determined from 300 to 1365 K. The composite results compared favorably to rule-of-mixtures (ROM) predictions in the intermediate temperature regime of 475 to 700 K. Deviations from ROM are discussed. Composite tensile results were compared on a strength/density basis to wrought superalloys and found to be superior. Fiber-matrix compatibility was characterized for the composite at 1250 and 1365 K for 1 to 100 hours.

  12. Cable manufacture

    NASA Technical Reports Server (NTRS)

    Gamble, P.

    1972-01-01

    A survey is presented of flat electrical cable manufacturing, with particular reference to patented processes. The economics of manufacture based on an analysis of material and operating costs is considered for the various methods. Attention is given to the competitive advantages of the several processes and their resulting products. The historical area of flat cable manufacture is presented to give a frame of reference for the survey.

  13. 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.

  14. 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.

  15. Manufacturing technologies

    SciTech Connect

    1995-09-01

    The Manufacturing Technologies Center is an integral part of Sandia National Laboratories, a multiprogram engineering and science laboratory, operated for the Department of Energy (DOE) with major facilities at Albuquerque, New Mexico, and Livermore, California. Our Center is at the core of Sandia`s Advanced Manufacturing effort which spans the entire product realization process.

  16. Manufacturing Technology.

    ERIC Educational Resources Information Center

    Barnes, James L.

    This curriculum guide is designed to assist junior high school industrial arts teachers in planning new courses and revising existing courses in manufacturing technology. Addressed in the individual units of the guide are the following topics: introduction to manufacturing, materials processing, personnel management, production management,…

  17. Estimates of emergency operating capacity in US manufacturing and nonmanufacturing industries

    SciTech Connect

    Belzer, D.B. ); Serot, D.E. ); Kellogg, M.A. )

    1991-03-01

    Development of integrated mobilization preparedness policies requires planning estimates of available productive capacity during national emergency conditions. Such estimates must be developed in a manner that allows evaluation of current trends in capacity and the consideration of uncertainties in various data inputs and in engineering assumptions. This study, conducted by Pacific Northwest Laboratory (PNL), developed estimates of emergency operating capacity (EOC) for 446 manufacturing industries at the 4-digit Standard Industrial Classification (SIC) level of aggregation and for 24 key non-manufacturing sectors. This volume presents tabular and graphical results of the historical analysis and projections for each SIC industry. (JF)

  18. 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.

  19. Quantification Of 4H- To 3C-Polymorphism In Silicon Carbide (SiC) Epilayers And An Investigation Of Recombination-Enhanced Dislocation Motion In SiC By Optical Emission Microscopy (Oem) Techniques

    NASA Technical Reports Server (NTRS)

    Speer, Kevin M.

    2004-01-01

    Environments that impose operational constraints on conventional silicon-(Si) based semiconductor devices frequently appear in military- and space-grade applications. These constraints include high temperature, high power, and high radiation environments. Silicon carbide (SiC), an alternative type of semiconductor material, has received abundant research attention in the past few years, owing to its radiation-hardened properties as well as its capability to withstand high temperatures and power levels. However, the growth and manufacture of SiC devices is still comparatively immature, and there are severe limitations in present crystal growth and device fabrication processes. Among these limitations is a variety of crystal imperfections known as defects. These imperfections can be point defects (e.g., vacancies and interstitials), line defects (e.g., edge and screw dislocations), or planar defects (e.g., stacking faults and double-positioning boundaries). All of these defects have been experimentally shown to be detrimental to the performance of electron devices made from SiC. As such, it is imperative that these defects are significantly reduced in order for SiC devices to become a viable entity in the electronics world. The NASA Glenn High Temperature Integrated Electronics & Sensors Team (HTIES) is working to identify and eliminate these defects in SiC by implementing improved epitaxial crystal growth procedures. HTIES takes two-inch SiC wafers and etches patterns, producing thousands of mesas into each wafer. Crystal growth is then carried out on top of these mesas in an effort to produce films of improved quality-resulting in electron devices that demonstrate superior performance-as well as fabrication processes that are cost-effective, reliable, and reproducible. In this work, further steps are taken to automate HTIES' SiC wafer inspection system. National Instruments LabVIEW image processing and pattern recognition routines are developed that are capable of

  20. Measurement of Thermal Conductivity of Anisotropic SiC Crystal

    NASA Astrophysics Data System (ADS)

    Su, Guo-Ping; Zheng, Xing-Hua; Qiu, Lin; Tang, Da-Wei; Zhu, Jie

    2013-12-01

    Silicon carbide (SiC) crystals with excellent heat conduction and thermal stability can be widely used in microelectronic devices and integrated circuits. It is important for the study of a functional type SiC material to have accurate thermal-conductivity and thermal-diffusivity values of SiC crystal. A 3 ω technique is employed to determine the anisotropic thermal conductivity of SiC crystal. Three micrometal probes with different widths are deposited by chemical-vapor deposition on the surface of SiC crystal. Each micrometal probe is used as a heater, and also as a thermometer. The temperature fluctuation signals of a micrometal probe represent heat conduction in different directions in the specimen. Thermal conductivities both in the cross-plane and in-plane directions of SiC crystal are achieved through fitted values. The results indicate that thermal conductivities in three different directions of SiC crystal can be characterized using the metal heater construction.

  1. Manufacturing technology

    SciTech Connect

    Blaedel, K.L.

    1997-02-01

    The specific goals of the Manufacturing Technology thrust area are to develop an understanding of fundamental fabrication processes, to construct general purpose process models that will have wide applicability, to document our findings and models in journals, to transfer technology to LLNL programs, industry, and colleagues, and to develop continuing relationships with industrial and academic communities to advance our collective understanding of fabrication processes. Advances in four projects are described here, namely Design of a Precision Saw for Manufacturing, Deposition of Boron Nitride Films via PVD, Manufacturing and Coating by Kinetic Energy Metallization, and Magnet Design and Application.

  2. 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.

  3. Vitreous joining of SiC fiber reinforced SiC composites

    SciTech Connect

    Coon, D.N. . Dept. of Mechanical Engineering)

    1989-12-01

    Glass in the MgO--Li{sub 2}O--Al{sub 2}O{sub 3}--SiO{sub 2} system were developed to as brazing materials to join SiC fiber reinforced SiC composites. These glass materials will melt and flow at temperatures ranging from 1000{degree}C to 1200{degree}C, and are chemically compatible with SiC. The glass transition temperature and melting temperature can be altered by adjusting the MgO:Li{sub 2}O ratio. The glasses exhibited viscous deformation at their glass transition temperatures, 490{degree}C to 725{degree}C. The glasses were devitrified to develop crystalline phases based on {beta}{prime}-spodumene, {beta}{prime}-eucryptite, or a {beta}{prime}-spodumene-{beta}{prime}-eucryptite solid solution. Glass-ceramics, prepared by thermal treatment, exhibited no viscous deformation to temperature as high as 785{degree}C, and exhibited improved strength as the test temperature was increased. Joints were prepared by painting the composite surface with a slurry of the glass powder suspended in water. Joining temperature, joining time, glass composition, amount of joining glass, and post-joining heat treatments were the variables examined. Larger quantities of joining glass and shorter joining times were observed to improve joint strength. The addition of niobium oxide to the glass also improved joint strength. The niobium oxide also stabilizes the glass/composite interface at temperatures less than 1200{degree}C.

  4. 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.

  5. 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.

  6. Smart Manufacturing.

    PubMed

    Davis, Jim; Edgar, Thomas; Graybill, Robert; Korambath, Prakashan; Schott, Brian; Swink, Denise; Wang, Jianwu; Wetzel, Jim

    2015-01-01

    Historic manufacturing enterprises based on vertically optimized companies, practices, market share, and competitiveness are giving way to enterprises that are responsive across an entire value chain to demand dynamic markets and customized product value adds; increased expectations for environmental sustainability, reduced energy usage, and zero incidents; and faster technology and product adoption. Agile innovation and manufacturing combined with radically increased productivity become engines for competitiveness and reinvestment, not simply for decreased cost. A focus on agility, productivity, energy, and environmental sustainability produces opportunities that are far beyond reducing market volatility. Agility directly impacts innovation, time-to-market, and faster, broader exploration of the trade space. These changes, the forces driving them, and new network-based information technologies offering unprecedented insights and analysis are motivating the advent of smart manufacturing and new information technology infrastructure for manufacturing. PMID:25898070

  7. Smart Manufacturing.

    PubMed

    Davis, Jim; Edgar, Thomas; Graybill, Robert; Korambath, Prakashan; Schott, Brian; Swink, Denise; Wang, Jianwu; Wetzel, Jim

    2015-01-01

    Historic manufacturing enterprises based on vertically optimized companies, practices, market share, and competitiveness are giving way to enterprises that are responsive across an entire value chain to demand dynamic markets and customized product value adds; increased expectations for environmental sustainability, reduced energy usage, and zero incidents; and faster technology and product adoption. Agile innovation and manufacturing combined with radically increased productivity become engines for competitiveness and reinvestment, not simply for decreased cost. A focus on agility, productivity, energy, and environmental sustainability produces opportunities that are far beyond reducing market volatility. Agility directly impacts innovation, time-to-market, and faster, broader exploration of the trade space. These changes, the forces driving them, and new network-based information technologies offering unprecedented insights and analysis are motivating the advent of smart manufacturing and new information technology infrastructure for manufacturing.

  8. Manufacturing Aids

    NASA Astrophysics Data System (ADS)

    1983-01-01

    Contractor's work for Lewis Research Center on "thermal barrier" coatings designed to improve aircraft engine efficiency resulted in two related but separate spinoffs. The Materials and Manufacturing Technology Center of TRW, Inc. invented a robotic system for applying the coating, and in the course of that research found it necessary to develop a new, extremely accurate type of optical gage that offers multiple improvements in controlling the quality of certain manufactured parts.

  9. 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.

  10. 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.

  11. An Extension of SIC Predictions to the Wiener Coactive Model.

    PubMed

    Houpt, Joseph W; Townsend, James T

    2011-06-01

    The survivor interaction contrasts (SIC) is a powerful measure for distinguishing among candidate models of human information processing. One class of models to which SIC analysis can apply are the coactive, or channel summation, models of human information processing. In general, parametric forms of coactive models assume that responses are made based on the first passage time across a fixed threshold of a sum of stochastic processes. Previous work has shown that that the SIC for a coactive model based on the sum of Poisson processes has a distinctive down-up-down form, with an early negative region that is smaller than the later positive region. In this note, we demonstrate that a coactive process based on the sum of two Wiener processes has the same SIC form.

  12. Thermal Characterization of SiC Amorphous Thin Films

    NASA Astrophysics Data System (ADS)

    Jeong, Taehee; Zhu, Jian-Gang; Mao, Sining; Pan, Tao; Tang, Yun Jun

    2012-06-01

    The cross-plane thermal conductivity of SiC amorphous films was measured employing the transient thermoreflectance technique. The SiC films were deposited on silicon substrates by RF magnetron sputtering at room temperature. The thickness of the films was varied in the range from 100 nm to 2500 nm to analyze the size effect. The results found that the thermal conductivity of the SiC thin films is significantly smaller than that of the SiC material in bulk form. The small thermal conductivity stems from the structural disorder of the films, which was confirmed by high-resolution transmission electron microscopy and X-ray diffraction. In addition, the contribution of the thermal boundary resistance to the thermal conductivity of the films is discussed.

  13. Observations of Ag diffusion in ion implanted SiC

    NASA Astrophysics Data System (ADS)

    Gerczak, Tyler J.; Leng, Bin; Sridharan, Kumar; Hunter, Jerry L.; Giordani, Andrew J.; Allen, Todd R.

    2015-06-01

    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 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. Estimated diffusion coefficients suggest GB diffusion in bulk SiC does not properly describe the release observed from TRISO fuel.

  14. 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.

  15. 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.

  16. 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

  17. UV-induced SiC nanowire sensors

    NASA Astrophysics Data System (ADS)

    Peng, Gang; Zhou, Yingqiu; He, Yanlan; Yu, Xiaoyan; Zhang, Xue A.; Li, Gong Y.; Haick, Hossam

    2015-02-01

    Ultraviolet (UV)-induced sensors based on a single SiC nanowire (NW) were fabricated and the photoelectric properties including I-V characteristics and time response of the UV sensors were studied. SiC NWs (NWs) were prepared through pyrolyzing a polymer precursor with ferrocene as the catalyst by a CVD route. To elucidate the physical mechanism giving rise to the photoelectrical response in SiC NW sensors, three kinds of contacts between electrodes and SiC NW were prepared, i.e. Schottky contact, p-n junction contact, and Ohmic contact. The photoelectric measurements of the device with Schottky contact indicates the lowest dark current and the largest photocurrent. The results suggest that photocurrent generated at SiC NW-electrode contacts is a result of the photovoltaic effect, in which a built-in electric field accelerates photo generated charge carriers to the electronic contacts. The UV sensors based on SiC NWs could be applied in a harsh environment due to the excellent physical stability and photoelectric properties.

  18. Microgravity Manufacturing

    NASA Technical Reports Server (NTRS)

    Cooper, Ken; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    Manufacturing capability in outer space remains one of the critical milestones to surpass to allow humans to conduct long-duration manned space exploration. The high cost-to-orbit for leaving the Earth's gravitational field continues to be the limiting factor in carrying sufficient hardware to maintain extended life support in microgravity or on other planets. Additive manufacturing techniques, or 'chipless' fabrication, like RP are being considered as the most promising technologies for achieving in situ or remote processing of hardware components, as well as for the repair of existing hardware. At least three RP technologies are currently being explored for use in microgravity and extraterrestrial fabrication.

  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. 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. Improved processing of. alpha. -SiC

    SciTech Connect

    Dutta, S. )

    1988-05-01

    Improved processing techniques such as slurry pressing and hot isostatic pressing were used to minimize processing defects and to improve strength and reliability in fabricated SiC. For this purpose, compacts were fabricated by various consolidation techniques: (1) dry-pressing and sintering, (2) slurry-pressing and sintering, and (3) slurry-pressing and hot isostatic pressing. High density (>96% of theoretical) was produced by sintering at 2,150{degree} to 2,200{degree}C. By contrast, a much lower temperature (1,875{degree} to 1,900{degree}C) was required for high-density specimens by hot isostatic pressing. The isostatistically hot-pressed {alpha}-SiC exhibited an ultrafine-grained microstructure (0.3 to 3 {mu}m) compared to 1 to 17 {mu}m produced by sintering. Dry-pressing and sintering yielded an average flexure strength (4-point bend) as high as 348 MPa. On the other hand, slurry-pressing resulted in an {approx}25% improvement in strength, 348 to 428 MPa. Further, isostatic hot-pressing of slurry-pressed specimens exhibited an average strength as high as 655 MPa. This value was {approx}90% higher than the dry-pressed/sintered strength and {approx}60% higher than the slurry-pressed/sintered strength.

  2. 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.

  3. 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.

  4. 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.

  5. 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

    chemical interaction of CO gas with the monocrystalline silicon matrix. The discovery of this mechanism yields a new kind of template: namely, substrates with buffer transition layers for wide-gap semiconductor growth on silicon. The properties of a variety of heteroepitaxial films of wide-gap semiconductors (SiC, AlN, GaN and AlGaN) grown on a SiC/Si substrate by solid-phase epitaxy will be reported. Grown films contain no cracks and have a quality sufficient to manufacture micro- and opto-electronic devices. Also, the new abilities in the synthesis of large (150 mm diameter) low-defective SiC films on Si substrates will be demonstrated.

  6. 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.

  7. 29 CFR 510.21 - SIC codes.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR REGULATIONS IMPLEMENTATION OF THE MINIMUM WAGE PROVISIONS OF THE 1989 AMENDMENTS TO THE FAIR LABOR STANDARDS ACT IN PUERTO RICO... annual Census of Manufacturing Industries as a source of average hourly wage data by industry....

  8. 29 CFR 510.21 - SIC codes.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR REGULATIONS IMPLEMENTATION OF THE MINIMUM WAGE PROVISIONS OF THE 1989 AMENDMENTS TO THE FAIR LABOR STANDARDS ACT IN PUERTO RICO... annual Census of Manufacturing Industries as a source of average hourly wage data by industry....

  9. 29 CFR 510.21 - SIC codes.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR REGULATIONS IMPLEMENTATION OF THE MINIMUM WAGE PROVISIONS OF THE 1989 AMENDMENTS TO THE FAIR LABOR STANDARDS ACT IN PUERTO RICO... annual Census of Manufacturing Industries as a source of average hourly wage data by industry....

  10. 29 CFR 510.21 - SIC codes.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR REGULATIONS IMPLEMENTATION OF THE MINIMUM WAGE PROVISIONS OF THE 1989 AMENDMENTS TO THE FAIR LABOR STANDARDS ACT IN PUERTO RICO... annual Census of Manufacturing Industries as a source of average hourly wage data by industry....

  11. 29 CFR 510.21 - SIC codes.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR REGULATIONS IMPLEMENTATION OF THE MINIMUM WAGE PROVISIONS OF THE 1989 AMENDMENTS TO THE FAIR LABOR STANDARDS ACT IN PUERTO RICO... annual Census of Manufacturing Industries as a source of average hourly wage data by industry....

  12. Apparel Manufacture

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Marshall Space Flight Center teamed with the University of Alabama in Huntsville (UAH) in 1989 on a program involving development of advanced simulation software. Concurrently, the State of Alabama chartered UAH to conduct a technology advancement program in support of the state's apparel manufacturers. In 1992, under contract to Marshall, UAH developed an apparel-specific software package that allows manufacturers to design and analyze modules without making an actual investment -- it functions on ordinary PC equipment. By 1995, Marshall had responded to requests for the package from more than 400 companies in 36 states; some of which reported savings up to $2 million. The National Garment Company of Missouri, for example, uses the system to design and balance a modular line before committing to expensive hardware; for setting up sewing lines; and for determining the composition of a new team.

  13. Manufacturing technology

    SciTech Connect

    Leonard, J.A.; Floyd, H.L.; Goetsch, B.; Doran, L.

    1993-08-01

    This bulletin depicts current research on manufacturing technology at Sandia laboratories. An automated, adaptive process removes grit overspray from jet engine turbine blades. Advanced electronic ceramics are chemically prepared from solution for use in high- voltage varistors. Selective laser sintering automates wax casting pattern fabrication. Numerical modeling improves performance of photoresist stripper (simulation on Cray supercomputer reveals path to uniform plasma). And mathematical models help make dream of low- cost ceramic composites come true.

  14. Green Manufacturing

    SciTech Connect

    Patten, John

    2013-12-31

    Green Manufacturing Initiative (GMI): The initiative provides a conduit between the university and industry to facilitate cooperative research programs of mutual interest to support green (sustainable) goals and efforts. In addition to the operational savings that greener practices can bring, emerging market demands and governmental regulations are making the move to sustainable manufacturing a necessity for success. The funding supports collaborative activities among universities such as the University of Michigan, Michigan State University and Purdue University and among 40 companies to enhance economic and workforce development and provide the potential of technology transfer. WMU participants in the GMI activities included 20 faculty, over 25 students and many staff from across the College of Engineering and Applied Sciences; the College of Arts and Sciences' departments of Chemistry, Physics, Biology and Geology; the College of Business; the Environmental Research Institute; and the Environmental Studies Program. Many outside organizations also contribute to the GMI's success, including Southwest Michigan First; The Right Place of Grand Rapids, MI; Michigan Department of Environmental Quality; the Michigan Department of Energy, Labor and Economic Growth; and the Michigan Manufacturers Technical Center.

  15. 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{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.

  16. 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.

  17. 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.

  18. Deposition of hydroxyapatite on SiC nanotubes in simulated body fluid.

    PubMed

    Taguchi, Tomitsugu; Miyazaki, Toshiki; Iikubo, Satoshi; Yamaguchi, Kenji

    2014-01-01

    SiC nanotubes can become candidate reinforcement materials for dental and orthopedic implants due to their light weight and excellent mechanical properties. However, the development of bioactive SiC materials has not been reported. In this study, hydroxyapatites were found on SiC nanotubes treated with NaOH and subsequently HCl solution after soaking in simulated body fluid. On the other hand, hydroxyapatites did not deposit on as-received SiC nanotubes, the SiC nanotubes with NH4OH solution treatment and SiC bulk materials with NaOH and subsequently HCl solution treatment. Therefore, we succeeded in the development of bioactive SiC nanotubes by downsizing SiC materials to nanometer size and treating with NaOH and subsequently HCl solutions for the first time.

  19. 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.

  20. 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.

  1. Effect of helium implantation on SiC and graphite

    NASA Astrophysics Data System (ADS)

    Guo, Hong-Yan; Ge, Chang-Chun; Xia, Min; Guo, Li-Ping; Chen, Ji-Hong; Yan, Qing-Zhi

    2015-03-01

    Effects of helium implantation on silicon carbide (SiC) and graphite were studied to reveal the possibility of SiC replacing graphite as plasma facing materials. Pressureless sintered SiC and graphite SMF-800 were implanted with He+ ions of 20 keV and 100 keV at different temperatures and different fluences. The He+ irradiation induced microstructure changes were studied by field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). Project supported by the ITER-National Magnetic Confinement Fusion Program, China (Grant Nos. 2010GB109000, 2011GB108009, and 2014GB123000) and the National Natural Science Foundation of China (Grant No. 11075119).

  2. Selective epitaxial growth of graphene on SiC

    SciTech Connect

    Camara, N.; Rius, G.; Godignon, P.; Huntzinger, J.-R.; Tiberj, A.; Camassel, J.

    2008-09-22

    We present a method of selective epitaxial growth of few layers graphene (FLG) on a ''prepatterned'' silicon carbide (SiC) substrate. The methods involves, successively, the sputtering of a thin aluminium nitride (AlN) layer on top of a monocrystalline SiC substrate and, then, patterning it with e-beam lithography and wet etching. The sublimation of few atomic layers of Si from the SiC substrate occurs only through the selectively etched AlN layer. The presence of the Raman G-band at {approx}1582 cm{sup -1} in the AlN-free areas is used to validate the concept. It gives absolute evidence of selective FLG growth.

  3. Selective epitaxial growth of graphene on SiC

    NASA Astrophysics Data System (ADS)

    Camara, N.; Rius, G.; Huntzinger, J.-R.; Tiberj, A.; Mestres, N.; Godignon, P.; Camassel, J.

    2008-09-01

    We present a method of selective epitaxial growth of few layers graphene (FLG) on a "prepatterned" silicon carbide (SiC) substrate. The methods involves, successively, the sputtering of a thin aluminium nitride (AlN) layer on top of a monocrystalline SiC substrate and, then, patterning it with e-beam lithography and wet etching. The sublimation of few atomic layers of Si from the SiC substrate occurs only through the selectively etched AlN layer. The presence of the Raman G-band at ˜1582cm-1 in the AlN-free areas is used to validate the concept. It gives absolute evidence of selective FLG growth.

  4. 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.

  5. 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.

  6. Manufacturing technology

    SciTech Connect

    Blaedel, K L

    1998-01-01

    The mission of the Manufacturing Technology thrust area at Lawrence Livermore National Laboratory (LLNL) has been to have an adequate base of manufacturing technology, not necessarily resident at LLNL, to conduct their future business. The specific goals were (1) to develop an understanding of fundamental fabrication processes; (2) to construct general purpose process models that have wide applicability; (3) to document their findings and models in journals; (4) to transfer technology to LLNL programs, industry, and colleagues; and (5) to develop continuing relationships with the industrial and academic communities to advance their collective understanding of fabrication processes. In support of this mission, two projects were reported here, each of which explores a way to bring higher precision to the manufacturing challenges that we face over the next few years. The first, ''A Spatial-Frequency-Domain Approach to Designing a Precision Machine Tools,'' is an overall view of how they design machine tools and instruments to make or measure workpieces that are specified in terms of the spatial frequency content of the residual errors of the workpiece surface. This represents an improvement of an ''error budget,'' a design tool that saw significant development in the early 1980's, and has been in active use since then. The second project, ''Micro-Drilling of ICF Capsules,'' is an attempt to define the current state in commercial industry for drilling small holes, particularly laser-drilling. The report concludes that 1-{micro}m diameter holes cannot currently be drilled to high aspect ratios, and then defines the engineering challenges that will have to be overcome to machine holes small enough for NIF capsules.

  7. 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.

  8. 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.

  9. -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.

  10. Performance of bulk SiC radiation detectors

    NASA Astrophysics Data System (ADS)

    Cunningham, W.; Gouldwell, A.; Lamb, G.; Scott, J.; Mathieson, K.; Roy, P.; Bates, R.; Thornton, P.; Smith, K. M.; Cusco, R.; Glaser, M.; Rahman, M.

    2002-07-01

    SiC is a wide-gap material with excellent electrical and physical properties that may make it an important material for some future electronic devices. The most important possible applications of SiC are in hostile environments, such as in car/jet engines, within nuclear reactors, or in outer space. Another area where the material properties, most notably radiation hardness, would be valuable is in the inner tracking detectors of particle physics experiments. Here, we describe the performance of SiC diodes irradiated in the 24 GeV proton beam at CERN. Schottky measurements have been used to probe the irradiated material for changes in I- V characteristics. Other methods, borrowed from III-V research, used to study the irradiated surface include atomic force microscope scans and Raman spectroscopy. These have been used to observe the damage to the materials surface and internal lattice structure. We have also characterised the detection capabilities of bulk semi-insulating SiC for α radiation. By measuring the charge collection efficiency (CCE) for variations in bias voltage, CCE values up to 100% have been measured.

  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 PAGES

    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. 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.

  14. PhySIC: a veto supertree method with desirable properties.

    PubMed

    Ranwez, Vincent; Berry, Vincent; Criscuolo, Alexis; Fabre, Pierre-Henri; Guillemot, Sylvain; Scornavacca, Celine; Douzery, Emmanuel J P

    2007-10-01

    This paper focuses on veto supertree methods; i.e., methods that aim at producing a conservative synthesis of the relationships agreed upon by all source trees. We propose desirable properties that a supertree should satisfy in this framework, namely the non-contradiction property (PC) and the induction property (PI). The former requires that the supertree does not contain relationships that contradict one or a combination of the source topologies, whereas the latter requires that all topological information contained in the supertree is present in a source tree or collectively induced by several source trees. We provide simple examples to illustrate their relevance and that allow a comparison with previously advocated properties. We show that these properties can be checked in polynomial time for any given rooted supertree. Moreover, we introduce the PhySIC method (PHYlogenetic Signal with Induction and non-Contradiction). For k input trees spanning a set of n taxa, this method produces a supertree that satisfies the above-mentioned properties in O(kn(3) + n(4)) computing time. The polytomies of the produced supertree are also tagged by labels indicating areas of conflict as well as those with insufficient overlap. As a whole, PhySIC enables the user to quickly summarize consensual information of a set of trees and localize groups of taxa for which the data require consolidation. Lastly, we illustrate the behaviour of PhySIC on primate data sets of various sizes, and propose a supertree covering 95% of all primate extant genera. The PhySIC algorithm is available at http://atgc.lirmm.fr/cgi-bin/PhySIC. PMID:17918032

  15. Construction Progress of S-IC Test Stand Towers

    NASA Technical Reports Server (NTRS)

    1963-01-01

    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 photograph taken April 17, 1963, gives a look at the four tower legs of the S-IC test stand at their completed height.

  16. Construction Progress of the S-IC Test Stand Tower

    NASA Technical Reports Server (NTRS)

    1963-01-01

    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 photograph, taken from ground level on May 7, 1963, gives a close look at one of the four towers legs of the S-IC test stand nearing its completed height.

  17. Construction Progress of the S-IC Test Stand Towers

    NASA Technical Reports Server (NTRS)

    1963-01-01

    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 photograph, taken April 4, 1963, gives a close up look at the ever-growing four towers of the S-IC Test Stand.

  18. 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

  19. Influence of defects in SiC (0001) on epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Guo, Yu; Guo, Li-Wei; Lu, Wei; Huang, Jiao; Jia, Yu-Ping; Sun, Wei; Li, Zhi-Lin; Wang, Yi-Fei

    2014-08-01

    Defects in silicon carbide (SiC) substrate are crucial to the properties of the epitaxial graphene (EG) grown on it. Here we report the effect of defects in SiC on the crystalline quality of EGs through comparative studies of the characteristics of the EGs grown on SiC (0001) substrates with different defect densities. It is found that EGs on high quality SiC possess regular steps on the surface of the SiC and there is no discernible D peak in its Raman spectrum. Conversely, the EG on the SiC with a high density of defects has a strong D peak, irregular stepped morphology and poor uniformity in graphene layer numbers. It is the defects in the SiC that are responsible for the irregular stepped morphology and lead to the small domain size in the EG.

  20. The 3.2m all SiC Telescope for SPICA

    NASA Astrophysics Data System (ADS)

    Castel, Didier; Sein, Emmanuel; Lopez, Sebastien; Nakagawa, Takao; Bougoin, Michel

    2012-09-01

    Placed on the Sun-Earth L2 Lagrange point, SPICA will operate in the 5 to 210 μm wavelength range. Astrium has been contracted by ESA/ JAXA to update the study of the SPICA telescope from a 3.5 m design (compatible to the Japanese HIIB launcher) to a 3.2 m design (compatible to the HII-A with the short 5S fairing): despite a similar fairing diameter, the shorter length of the fairing envelope results in a reduction of the M1-M2 distance and an associated diameter reduction of M1. Maximization of the M1-M2 distance within the constraints is important to maintain a reasonable polishing criteria of the main reflector. Therefore the M2 assembly sizing and the back focal length become main parameters for the telescope optical design. The main constraints are driven by the telescope requirements such as focal length, maximizing the diameter of M1 (3.2 m) and, M1 f-number (critical for the manufacturing aspects). The WFE must be below 350 nm rms, and operational temperature below 6K. . The main issues addressed in this paper are: - an improved telescope design based on the Astrium background in Silicon Carbide technology which has been tried-an-tested for mirrors and structural parts on several space projects, including HERSCHEL and Gaia (brazing, polishing, assembling, iso-static mountings). - performances which are taking advantage of the SiC properties ,such as homogeneity of the single-phase material inside the structure, and structural stability from ambient to the operational temperature range. Our study shows that the SiC telescope design can fulfil all the mechanical and optical requirements for SPICA. - the verification and optical tests definition which will be key elements in the qualification of the telescope to be incorporated in the logic of the satellite verification activity to be conducted in Japan.

  1. Cloud manufacturing: a new manufacturing paradigm

    NASA Astrophysics Data System (ADS)

    Zhang, Lin; Luo, Yongliang; Tao, Fei; Li, Bo Hu; Ren, Lei; Zhang, Xuesong; Guo, Hua; Cheng, Ying; Hu, Anrui; Liu, Yongkui

    2014-03-01

    Combining with the emerged technologies such as cloud computing, the Internet of things, service-oriented technologies and high performance computing, a new manufacturing paradigm - cloud manufacturing (CMfg) - for solving the bottlenecks in the informatisation development and manufacturing applications is introduced. The concept of CMfg, including its architecture, typical characteristics and the key technologies for implementing a CMfg service platform, is discussed. Three core components for constructing a CMfg system, i.e. CMfg resources, manufacturing cloud service and manufacturing cloud are studied, and the constructing method for manufacturing cloud is investigated. Finally, a prototype of CMfg and the existing related works conducted by the authors' group on CMfg are briefly presented.

  2. Oxygen Impurities and Defects in Epitaxial Layer SiC and SiC Wafer Characterized by Room and Low Temperatures FTIR

    NASA Technical Reports Server (NTRS)

    Lu, W. J.; Collins, W. E.; Shi, D. T.; Tung, Y. S.; Larkin, D. J.

    1998-01-01

    SiC as a highly promising semiconducting material has received increasing attention in the last decade. The impurities such as oxygen and hydrogen have a great effect in electronic properties of semiconducting materials. In this study, the FTIR spectra were measured at room temperature (25 C) and low temperature (-70 C) for an n-type SiC substrate, a p-type epitaxial layer SiC, and patterned Ta on a p-type epitaxial layer SiC sample. The oxygen related IR peaks were measured for all three samples at room and low temperatures. The peak at 1105 cm(exp -1) is the result of a substitutional carbon and a interstitial oxygen in SiC. The concentration of the impurity oxygen increases in the SiC epitaxial layer during the CVD and electron beam processes. For the n-type SiC substrate, this peak does not appear. The peak at 905 cm(exp -1) exists in the IR spectra only for two epitaxial layer on p-type SiC substrate samples. This peak is related to oxygen vacancy centers in SiC, which are introduced in the CVD epitaxial growth process. At low temperature, the peak at 1105 cm(exp -1) shifts down and the peak at 905 cm(exp -1) shifts up for the epitaxial layer SiC samples. It can be explained that, at low temperatures, the stress increases due to the distorted bonds. The study shows that FTIR is a very effective method to evaluate low concentration impurities in SiC.

  3. Pd/CeO2/SiC Chemical Sensors

    NASA Technical Reports Server (NTRS)

    Lu, Weijie; Collins, W. Eugene

    2005-01-01

    The incorporation of nanostructured interfacial layers of CeO2 has been proposed to enhance the performances of Pd/SiC Schottky diodes used to sense hydrogen and hydrocarbons at high temperatures. If successful, this development could prove beneficial in numerous applications in which there are requirements to sense hydrogen and hydrocarbons at high temperatures: examples include monitoring of exhaust gases from engines and detecting fires. Sensitivity and thermal stability are major considerations affecting the development of high-temperature chemical sensors. In the case of a metal/SiC Schottky diode for a number of metals, the SiC becomes more chemically active in the presence of the thin metal film on the SiC surface at high temperature. This increase in chemical reactivity causes changes in chemical composition and structure of the metal/SiC interface. The practical effect of the changes is to alter the electronic and other properties of the device in such a manner as to degrade its performance as a chemical sensor. To delay or prevent these changes, it is necessary to limit operation to a temperature <450 C for these sensor structures. The present proposal to incorporate interfacial CeO2 films is based partly on the observation that nanostructured materials in general have potentially useful electrical properties, including an ability to enhance the transfer of electrons. In particular, nanostructured CeO2, that is CeO2 with nanosized grains, has shown promise for incorporation into hightemperature electronic devices. Nanostructured CeO2 films can be formed on SiC and have been shown to exhibit high thermal stability on SiC, characterized by the ability to withstand temperatures somewhat greater than 700 C for limited times. The exchanges of oxygen between CeO2 and SiC prevent the formation of carbon and other chemical species that are unfavorable for operation of a SiC-based Schottky diode as a chemical sensor. Consequently, it is anticipated that in a Pd

  4. The physics of epitaxial graphene on SiC(0001).

    PubMed

    Kageshima, H; Hibino, H; Tanabe, S

    2012-08-01

    Various physical properties of epitaxial graphene grown on SiC(0001) are studied. First, the electronic transport in epitaxial bilayer graphene on SiC(0001) and quasi-free-standing bilayer graphene on SiC(0001) is investigated. The dependences of the resistance and the polarity of the Hall resistance at zero gate voltage on the top-gate voltage show that the carrier types are electron and hole, respectively. The mobility evaluated at various carrier densities indicates that the quasi-free-standing bilayer graphene shows higher mobility than the epitaxial bilayer graphene when they are compared at the same carrier density. The difference in mobility is thought to come from the domain size of the graphene sheet formed. To clarify a guiding principle for controlling graphene quality, the mechanism of epitaxial graphene growth is also studied theoretically. It is found that a new graphene sheet grows from the interface between the old graphene sheets and the SiC substrate. Further studies on the energetics reveal the importance of the role of the step on the SiC surface. A first-principles calculation unequivocally shows that the C prefers to release from the step edge and to aggregate as graphene nuclei along the step edge rather than be left on the terrace. It is also shown that the edges of the existing graphene more preferentially absorb the isolated C atoms. For some annealing conditions, experiments can also provide graphene islands on SiC(0001) surfaces. The atomic structures are studied theoretically together with their growth mechanism. The proposed embedded island structures actually act as a graphene island electronically, and those with zigzag edges have a magnetoelectric effect. Finally, the thermoelectric properties of graphene are theoretically examined. The results indicate that reducing the carrier scattering suppresses the thermoelectric power and enhances the thermoelectric figure of merit. The fine control of the Fermi energy position is thought to

  5. Advanced Manufacturing Technologies

    NASA Technical Reports Server (NTRS)

    Fikes, John

    2016-01-01

    Advanced Manufacturing Technologies (AMT) is developing and maturing innovative and advanced manufacturing technologies that will enable more capable and lower-cost spacecraft, launch vehicles and infrastructure to enable exploration missions. The technologies will utilize cutting edge materials and emerging capabilities including metallic processes, additive manufacturing, composites, and digital manufacturing. The AMT project supports the National Manufacturing Initiative involving collaboration with other government agencies.

  6. Effects of SiC on Properties of Cu-SiC Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Efe, G. Celebi; Altinsoy, I.; Ipek, M.; Zeytin, S.; Bindal, C.

    2011-12-01

    This paper was focused on the effects of particle size and distribution on some properties of the SiC particle reinforced Cu composites. Copper powder produced by cementation method was reinforced with SiC particles having 1 and 30 μm particle size and sintered at 700 °C. SEM studies showed that SiC particles dispersed in copper matrix homogenously. The presence of Cu and SiC components in composites were verified by XRD analysis technique. The relative densities of Cu-SiC composites determined by Archimedes' principle are ranged from 96.2% to 90.9% for SiC with 1 μm particle size, 97.0 to 95.0 for SiC with 30 μm particle size. Measured hardness of sintered compacts varied from 130 to 155 HVN for SiC having 1 μm particle size, 188 to 229 HVN for SiC having 1 μm particle size. Maximum electrical conductivity of test materials was obtained as 80.0% IACS (International annealed copper standard) for SiC with 1 μm particle size and 83.0% IACS for SiC with 30 μm particle size.

  7. Operating procedure for SiC defect detection: Data support document

    SciTech Connect

    Adams, C.C.; Partain, K.E.

    1989-09-29

    The feasibility of the Hg Intrusion QC method for measuring SiC coating defects for the MHTGR was conducted as a potential improvement for the Burn/Leach (B/L) QC method currently used. The purpose for evaluating the Hg Intrusion QC method as an alternative method was to determine if B/L QC method underestimated SiC coating defects. Some evidence in work conducted earlier, indicated that TRISO-coated fuel particles with low SiC coating defects measured by the B/L QC method showed higher releases of metallic fission products. These data indicated that the SiC coating defect fractions were higher than the B/L measured data indicated. Sample sizes used in the current study were too small to conclusively demonstrate that the B/L QC method under estimate SiC coating defects. However, observations made during this study indicated a need for an additional QC method to the B/L QC method to measure SiC coating defects for the higher quality MHTGR fuels. The B/L QC method is the best method for measuring SiC coating defects with missing SiC layers or broken SiC coatings (gross SiC defects). However, SiC coating defects with microcracks and other SiC defects not detected by the B/L method may contribute to the release of metallic fission products in-service. For these type of SiC coating defects, the Hg Intrusion QC method investigated in this study is feasible, but particle sample size should be increased to a much larger sample size (100,000 particles per test) for the MHTGR. 7 refs., 5 figs., 9 tabs.

  8. Desktop Manufacturing Technologies.

    ERIC Educational Resources Information Center

    Snyder, Mark

    1991-01-01

    Desktop manufacturing is the use of data from a computer-assisted design system to construct actual models of an object. Emerging processes are stereolithography, laser sintering, ballistic particle manufacturing, laminated object manufacturing, and photochemical machining. (SK)

  9. Focused thermal emission from a nanostructured SiC surface

    NASA Astrophysics Data System (ADS)

    Chalabi, Hamidreza; Alù, Andrea; Brongersma, Mark L.

    2016-09-01

    Incandescent sources that produce light from electrically heated filaments or films tend to feature low efficiencies and offer poor spectral and angular control. We demonstrate that a judicious nanostructuring of a SiC surface can focus thermal emission of a preselected spectral range to a well-defined height above the surface. SiC is known to support electromagnetic surface waves that afford the required thermal emission control. Here, we provide general design rules for this type of focusing element that can be extended to other material systems, such as metals supporting surface plasmon-polariton waves. These rules are verified using full-wave calculations of the spatial variation of thermal emission. The obtained results establish a foundation for developing more complex algorithms for the design of complex thermal lenses.

  10. Molten salt corrosion of SiC: Pitting mechanism

    NASA Technical Reports Server (NTRS)

    Jacobson, N. S.; Smialek, J. L.

    1985-01-01

    Thin films of Na2SO4 and Na2CO3 at 1000 C lead to severe pitting of sintered alpha-SiC. These pits are important as they cause a strength reduction in this material. The growth of product layers is related to pit formation for the Na2CO3 case. The early reaction stages involve repeated oxidation and dissolution to form sodium silicate. This results in severe grain boundary attack. After this a porous silica layer forms between the sodium silicate melt and the SiC. The pores in this layer appear to act as paths for the melt to reach the SiC and create larger pits.

  11. Oxidation of ZrB2-SiC

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Halbig, Michael C.

    2001-01-01

    In this paper the oxidation behavior of ZrB2-20 vol% SiC is examined. Samples were exposed in stagnant air in a zirconia furnace (Deltech, Inc.) at temperatures of 1327, 1627, and 1927 C for ten ten-minute cycles. Samples were removed from the furnace after one, five, and ten cycles. Oxidized material was characterized by mass change when possible, x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Oxidation kinetics, oxide scale development, and matrix recession were monitored as a function of time and temperature. Oxidation and recession rates of ZrB2 - 20 vol% SiC were adequately modeled by parabolic kinetics. Oxidation rates of this material are rapid, allowing only very short-term application in air or other high oxygen partial pressure environments.

  12. Excited States of the divacancy in SiC

    NASA Astrophysics Data System (ADS)

    Bockstedte, Michel; Garratt, Thomas; Ivady, Viktor; Gali, Adam

    2014-03-01

    The divacancy in SiC - a technologically mature material that fulfills the necessary requirements for hosting defect based quantum computing - is a good candidate for implementing a solid state quantum bit. Its ground state is isovalent to the NV center in diamond as demonstrated by density functional theory (DFT). Furthermore, coherent manipulation of divacancy spins in SiC has been demonstrated. The similarities to NV might indicate that the same inter system crossing (ICS) from the high to the low spin state is responsible for its spin-dependent fluorescent signal. By DFT and a DFT-based multi-reference hamiltonian we analyze the excited state spectrum of the defects. In contrast to the current picture of the spin dynamics of the NV center, we predict that a static Jahn-Teller effect in the first excited triplet states governs an ICS both with the excited and ground state of the divacancy.

  13. 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).

  14. High frequency ultrasonic characterization of sintered SiC

    NASA Technical Reports Server (NTRS)

    Baaklini, George Y.; Generazio, Edward R.; Kiser, James D.

    1987-01-01

    High frequency (60 to 160 MHz) ultrasonic nondestructive evaluation was used to characterize variations in density and microstructural constituents of sintered SiC bars. Ultrasonic characterization methods included longitudinal velocity, reflection coefficient, and precise attenuation measurements. The SiC bars were tailored to provide bulk densities ranging from 90 to 98 percent of theoretical, average grain sizes ranging from 3.0 to 12.0 microns, and average pore sizes ranging from 1.5 to 4.0 microns. Velocity correlated with specimen bulk density irrespective of specimen average grain size, average pore size, and average pore orientation. Attenuation coefficient was found to be sensitive to both density and average pore size variations, but was not affected by large differences in average grain size.

  15. 1 GHz, 200 C, SiC MESFET Clapp Oscillator

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Schwartz, Zachary D.

    2005-01-01

    A SiC Clapp oscillator frabricated on an alumina substrate with chip capacitors and spiral inductors is designed for high temperature operation at 1 gigahertz. The oscillator operated from 30 to 200 C with an output power of 21.8 dBm at 1 gigahertz and 200 C. The efficiency at 200 C is 15 percent. The frequency variation over the temperature range is less than 0.5 percent.

  16. SYLRAMIC™ SiC fibers for CMC reinforcement

    NASA Astrophysics Data System (ADS)

    Jones, Richard E.; Petrak, Dan; Rabe, Jim; Szweda, Andy

    2000-12-01

    Dow Corning researchers developed SYLRAMIC SiC fiber specifically for use in ceramic-matrix composite (CMC) components for use in turbine engine hot sections where excellent thermal stability, high strength and high thermal conductivity are required. This is a stoichiometric SiC fiber with a high degree of crystallinity, high tensile strength, high tensile modulus and good thermal conductivity. Owing to the small diameter, this textile-grade fiber can be woven into 2-D and 3-D structures for CMC fabrication. These properties are also of high interest to the nuclear community. Some initial studies have shown that SYLRAMIC fiber shows very good dimensional stability in a neutron flux environment, which offers further encouragement. This paper will review the properties of SYLRAMIC SiC fiber and then present the properties of polymer impregnation and pyrolysis (PIP) processed CMC made with this fiber at Dow Corning. While these composites may not be directly applicable to applications of interest to this audience, we believe that the properties shown will give good evidence that the fiber should be suitable for high temperature structural applications in the nuclear arena.

  17. Fractographic Analysis of HfB2-SiC and ZrB2-SiC Composites

    NASA Technical Reports Server (NTRS)

    Mecholsky, J.J., Jr.; Ellerby, D. T.; Johnson, S. M.; Stackpoole, M. M.; Loehman, R. E.; Arnold, Jim (Technical Monitor)

    2001-01-01

    Hafnium diboride-silicon carbide and zirconium diboride-silicon carbide composites are potential materials for high temperature leading edge applications on reusable launch vehicles. In order to establish material constants necessary for evaluation of in-situ fracture, bars fractured in four point flexure were examined using fractographic principles. The fracture toughness was determined from measurements of the critical crack sizes and the strength values, and the crack branching constants were established to use in forensic fractography of materials for future flight applications. The fracture toughnesses range from about 13 MPam (sup 1/2) at room temperature to about 6 MPam (sup 1/2) at 1400 C for ZrB2-SiC composites and from about 11 MPam (sup 1/2) at room temperature to about 4 MPam (sup 1/2) at 1400 C for HfB2-SiC composites.

  18. Current and future industrial energy service characterizations. Volume III. Energy data on 15 selected states' manufacturing subsector

    SciTech Connect

    Krawiec, F.; Thomas, T.; Jackson, F.; Limaye, D.R.; Isser, S.; Karnofsky, K.; Davis, T.D.

    1980-11-01

    An examination is made of the current and future energy demands, and uses, and cost to characterize typical applications and resulting services in the US and industrial sectors of 15 selected states. Volume III presents tables containing data on selected states' manufacturing subsector energy consumption, functional uses, and cost in 1974 and 1976. Alabama, California, Illinois, Indiana, Louisiana, Michigan, Missouri, New Jersey, New York, Ohio, Oregon, Pennsylvania, Texas, West Virginia, and Wisconsin were chosen as having the greatest potential for replacing conventional fuel with solar energy. Basic data on the quantities, cost, and types of fuel and electric energy purchased by industr for heat and power were obtained from the 1974 and 1976 Annual Survey of Manufacturers. The specific indutrial energy servic cracteristics developed for each selected state include. 1974 and 1976 manufacturing subsector fuels and electricity consumption by 2-, 3-, and 4-digit SIC and primary fuel (quantity and relative share); 1974 and 1976 manufacturing subsector fuel consumption by 2-, 3-, and 4-digit SIC and primary fuel (quantity and relative share); 1974 and 1976 manufacturing subsector average cost of purchsed fuels and electricity per million Btu by 2-, 3-, and 4-digit SIC and primary fuel (in 1976 dollars); 1974 and 1976 manufacturing subsector fuels and electric energy intensity by 2-, 3-, and 4-digit SIC and primary fuel (in 1976 dollars); manufacturing subsector average annual growth rates of (1) fuels and electricity consumption, (2) fuels and electric energy intensity, and (3) average cost of purchased fuels and electricity (1974 to 1976). Data are compiled on purchased fuels, distillate fuel oil, residual ful oil, coal, coal, and breeze, and natural gas. (MCW)

  19. Energy end-use requirements in manufacturing, volume 1

    NASA Astrophysics Data System (ADS)

    Limaye, D. R.; Isser, S.; Beatty, R.; Colville, G.; Lang, K.; Krawiec, F.

    1981-07-01

    A review and evaluation of existing industrial energy data bases were undertaken to assess their potential for supporting SERI research to analyze technical and economic feasibility of solar technologies, and to establish multilayer R and D programs for: solar thermal industrial electric power systems and solar IPH systems. In the review of existing industrial energy data bases, the level of detail, disaggregation, and primary sources of information were examined. The focus was on fuels and electric energy used for heat and power purchased by the manufacturing subsector and listed by 2-, 3-, and 4-digit SIC, primary fuel, and end use.

  20. Energy resource management for energy-intensive manufacturing industries

    SciTech Connect

    Brenner, C.W.; Levangie, J.

    1981-10-01

    A program to introduce energy resource management into an energy-intensive manufacturing industry is presented. The food industry (SIC No. 20) was chosen and 20 companies were selected for interviews, but thirteen were actually visited. The methodology for this program is detailed. Reasons for choosing the food industry are described. The substance of the information gained and the principal conclusions drawn from the interviews are given. Results of the model Energy Resource Management Plan applied to three companies are compiled at length. Strategies for dissemination of the information gained are described. (MCW)

  1. SiC Optically Modulated Field-Effect Transistor

    NASA Technical Reports Server (NTRS)

    Tabib-Azar, Massood

    2009-01-01

    An optically modulated field-effect transistor (OFET) based on a silicon carbide junction field-effect transistor (JFET) is under study as, potentially, a prototype of devices that could be useful for detecting ultraviolet light. The SiC OFET is an experimental device that is one of several devices, including commercial and experimental photodiodes, that were initially evaluated as detectors of ultraviolet light from combustion and that could be incorporated into SiC integrated circuits to be designed to function as combustion sensors. The ultraviolet-detection sensitivity of the photodiodes was found to be less than desired, such that it would be necessary to process their outputs using high-gain amplification circuitry. On the other hand, in principle, the function of the OFET could be characterized as a combination of detection and amplification. In effect, its sensitivity could be considerably greater than that of a photodiode, such that the need for amplification external to the photodetector could be reduced or eliminated. The experimental SiC OFET was made by processes similar to JFET-fabrication processes developed at Glenn Research Center. The gate of the OFET is very long, wide, and thin, relative to the gates of typical prior SiC JFETs. Unlike in prior SiC FETs, the gate is almost completely transparent to near-ultraviolet and visible light. More specifically: The OFET includes a p+ gate layer less than 1/4 m thick, through which photons can be transported efficiently to the p+/p body interface. The gate is relatively long and wide (about 0.5 by 0.5 mm), such that holes generated at the body interface form a depletion layer that modulates the conductivity of the channel between the drain and the source. The exact physical mechanism of modulation of conductivity is a subject of continuing research. It is known that injection of minority charge carriers (in this case, holes) at the interface exerts a strong effect on the channel, resulting in amplification

  2. 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

  3. 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.

  4. Atomic probe microscopy of 3C SiC films grown on 6H SiC substrates

    NASA Technical Reports Server (NTRS)

    Steckl, A. J.; Roth, M. D.; Powell, J. A.; Larkin, D. J.

    1993-01-01

    The surface of 3C SiC films grown on 6H SiC substrates has been studied by atomic probe microscopy in air. Atomic-scale images of the 3C SiC surface have been obtained by STM which confirm the 111 line type orientation of the cubic 3C layer grown on the 0001 plane type surface of the hexagonal 6H substrate. The nearest-neighbor atomic spacing for the 3C layer has been measured to be 3.29 +/- 0.2 A, which is within 7 percent of the bulk value. Shallow terraces in the 3C layer have been observed by STM to separate regions of very smooth growth in the vicinity of the 3C nucleation point from considerably rougher 3C surface regions. These terraces are oriented at right angles to the growth direction. Atomic force microscopy has been used to study etch pits present on the 6H substrate due to high temperature HCl cleaning prior to CVD growth of the 3C layer. The etch pits have hexagonal symmetry and vary in depth from 50 nm to 1 micron.

  5. Thermal expansion and elastic anisotropies of SiC as related to polytype structure

    NASA Technical Reports Server (NTRS)

    Li, Z.; Bradt, R. C.

    1989-01-01

    The concept of the fraction of hexagonal stacking is used to describe the anisotropic thermal expansion coefficients of polytypes of SiC. The single crystal elastic anisotropy for the SiC polytype structures and the temperature dependencies of the anisotropies are examined. The anisotropic thermoelastic stress index for the 3C and 6H SiC polytypes are illustrated graphically. It is shown that this index is useful for predicting the most desirable crystal growth orientations for SiC whisker incorporation into composite matrices.

  6. 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.

  7. High quality SiC microdisk resonators fabricated from monolithic epilayer wafers

    SciTech Connect

    Magyar, Andrew P.; Bracher, David; Lee, Jonathan C.; Hu, Evelyn L.; Aharonovich, Igor

    2014-02-03

    The exquisite mechanical properties of SiC have made it an important industrial material with applications in microelectromechanical devices and high power electronics. Recently, the optical properties of SiC have garnered attention for applications in photonics, quantum information, and spintronics. This work demonstrates the fabrication of microdisks formed from a p-N SiC epilayer material. The microdisk cavities fabricated from the SiC epilayer material exhibit quality factors of as high as 9200 and the approach is easily adaptable to the fabrication of SiC-based photonic crystals and other photonic and optomechanical devices.

  8. PROPERTIES AND BALLISTIC BEHAVIOR OF PRESSURELESS SINTERED SIC/TIB2 COMPOSITES

    SciTech Connect

    T.M. Lillo; H.S. Chu; B.Merkle; D. Bailey; W.M. Harrison

    2005-01-01

    Pressureless sintering of ceramics for armor applications offers the potential of greatly reduced cost and increased production volume. Previously it was shown that pure SiC could be made by pressureless sintering while achieving a ballistic performance slightly less than commercial SiC made by pressure-assisted densification (PAD). Additions of titanium diboride were made to pin the SiC grain size during pressureless sintering to achieve a final grain size closer to that found in PAD SiC and achieve improved ballistic performance. Silicon carbide/titanium diboride composites of various compositions were blended by various means, consolidated and pressureless sintered to near theoretical density. Additions of TiB2 were <10% by volume and increased the density of the material by less than 3% over that of pure SiC. Variations in the mixing techniques yielded composites with a range of TiB2 particle sizes. TiB2 additions hindered SiC grain growth and the formation of elongated grains during high temperature pressureless sintering. The microstructure of the composites is documented and compared to commercially available SiC material. The SiC/TiB2 composites demonstrated improved ballistic properties in Depth-of-Penetration (DOP) tests over pure, pressureless-sintered SiC material and approach that of SiC made by hot pressing.

  9. Point pinning centers in SiC doped MgB2 wires after HIP

    NASA Astrophysics Data System (ADS)

    Gajda, D.; Zaleski, A.; Morawski, A.; Cetner, T.; Thong, C. J.; Rindfleisch, M. A.

    2016-08-01

    In this study we show that dominant point pinning mechanisms in SiC doped MgB2 wires can be obtained by annealing in high isostatic pressure. The results indicate that the point pinning centers increase the critical current density in medium and high magnetic fields, but not at low magnetic fields. In addition, our study shows that dominant pinning mechanism changes from point to surface type with increase of magnetic fields. An MgB2 wire heat treated in a high pressure of 1.4 GPa shows a high critical current density of 100 A mm‑2 in 13 T at 4.2 K. Scanning electron microscope studies show that high isostatic pressure increases the density of the MgB2 material, eliminates voids, allows for small Si precipitates and homogeneous distribution of Si precipitates. Transport measurements E - B and E - I show that the MgB2 wires manufactured by Hyper Tech Research did not heat up after transition into a normal state. This is important for applications in coils.

  10. Point pinning centers in SiC doped MgB2 wires after HIP

    NASA Astrophysics Data System (ADS)

    Gajda, D.; Zaleski, A.; Morawski, A.; Cetner, T.; Thong, C. J.; Rindfleisch, M. A.

    2016-08-01

    In this study we show that dominant point pinning mechanisms in SiC doped MgB2 wires can be obtained by annealing in high isostatic pressure. The results indicate that the point pinning centers increase the critical current density in medium and high magnetic fields, but not at low magnetic fields. In addition, our study shows that dominant pinning mechanism changes from point to surface type with increase of magnetic fields. An MgB2 wire heat treated in a high pressure of 1.4 GPa shows a high critical current density of 100 A mm-2 in 13 T at 4.2 K. Scanning electron microscope studies show that high isostatic pressure increases the density of the MgB2 material, eliminates voids, allows for small Si precipitates and homogeneous distribution of Si precipitates. Transport measurements E - B and E - I show that the MgB2 wires manufactured by Hyper Tech Research did not heat up after transition into a normal state. This is important for applications in coils.

  11. Processing of laser formed SiC powder

    NASA Technical Reports Server (NTRS)

    Haggerty, J. S.; Bowen, H. K.

    1985-01-01

    Superior SiC characteristics can be achieved through the use of ideal constituent powders and careful post-synthesis processing steps. High purity SiC powders of approx. 1000 A uniform diameter, nonagglomerated and spherical were produced. This required major revision of the particle formation and growth model from one based on classical nucleation and growth to one based on collision and coalescence of Si particles followed by their carburization. Dispersions based on pure organic solvents as well as steric stabilization were investigated. Although stable dispersions were formed by both, subsequent part fabrication emphasized the pure solvents since fewer problems with drying and residuals of the high purity particles were anticipated. Test parts were made by the colloidal pressing technique; both liquid filtration and consolidation (rearrangement) stages were modeled. Green densities corresponding to a random close packed structure (approx. 63%) were achieved; this highly perfect structure has a high, uniform coordination number (greater than 11) approaching the quality of an ordered structure without introducing domain boundary effects. After drying, parts were densified at temperatures ranging from 1800 to 2100 C. Optimum densification temperatures will probably be in the 1900 to 2000 C range based on these preliminary results which showed that 2050 C samples had experienced substantial grain growth. Although overfired, the 2050 C samples exhibited excellent mechanical properties. Biaxial tensile strengths up to 714 MPa and Vickers hardness values of 2430 kg/sq mm 2 were both more typical of hot pressed than sintered SiC. Both result from the absence of large defects and the confinement of residual porosity (less than 2.5%) to small diameter, uniformly distributed pores.

  12. Plastic deformation of alumina reinforced with SiC whiskers

    SciTech Connect

    DeArellano-Lopez, A.R.; Dominguez-Rodriguez, A.; Goretta, K.C.; Routbort, J.L.

    1993-06-01

    Addition of small amounts of stiff reinforcement (SiC whiskers) to a polycrystalline AL{sub 2}O{sub 3} matrix partially inhibits grain boundary sliding because of an increase in threshold stress. When the concentration of whiskers is high enough, a pure diffusional mechanism takes over the control of plastic deformation of the composites. For higher whisker loadings, the materials creep properties depend on a microstructural feature different from the nominal grain size. A tentative correlation of this effective microstructural parameter with the spacing between the whiskers was established through a model.

  13. Corrosion of SiC by Molten Salt

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Smialek, James L.

    1987-01-01

    Advanced ceramic materials considered for wide range of applications as in gas turbine engines and heat exchangers. In such applications, materials may be in corrosive environments that include molten salts. Very corrosive to alloys. In order to determine extent of problem for ceramic materials, corrosion of SiC by molten salts studied in both jet fuel burners and laboratory furnaces. Surface of silicon carbide corroded by exposure to flame seeded with 4 parts per million of sodium. Strength of silicon carbide decreased by corrosion in flame and tube-furnace tests.

  14. 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

  15. Construction Progress of S-IC Test Stand Pump House

    NASA Technical Reports Server (NTRS)

    1963-01-01

    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. In addition to the stand itself, related facilities were constructed during this time. Built to the northeast east was a newly constructed Pump House. Its function was to provide water to the stand to prevent melting damage during testing. The water was sprayed through small holes in the stand's 1900 ton flame deflector at the rate of 320,000 gallons per minute. This photograph of the Pump House area was taken August 13, 1963. The massive round water storage tanks can be seen to the left of

  16. Blade Manufacturing Improvement: Remote Blade Manufacturing Demonstration

    SciTech Connect

    ASHWILL, THOMAS D.

    2003-05-01

    The objective of this program was to investigate manufacturing improvements for wind turbine blades. The program included a series of test activities to evaluate the strength, deflection, performance, and loading characteristics of the prototype blades. The original contract was extended in order to continue development of several key blade technologies identified in the project. The objective of the remote build task was to demonstrate the concept of manufacturing wind turbine blades at a temporary manufacturing facility in a rural environment. TPI Composites successfully completed a remote manufacturing demonstration in which four blades were fabricated. The remote demonstration used a manufacturing approach which relied upon material ''kits'' that were organized in the factory and shipped to the site. Manufacturing blades at the wind plant site presents serious logistics difficulties and does not appear to be the best approach. A better method appears to be regional manufacturing facilities, which will eliminate most of the transportation cost, without incurring the logistical problems associated with fabrication directly onsite. With this approach the remote facilities would use commonly available industrial infrastructure such as enclosed workbays, overhead cranes, and paved staging areas. Additional fatigue testing of the M20 root stud design was completed with good results. This design provides adhesive bond strength under fatigue loading that exceeds that of the fastener. A new thru-stud bonding concept was developed for the M30 stud design. This approach offers several manufacturing advantages; however, the test results were inconclusive.

  17. Measured Attenuation of Coplanar Waveguide on 6H, p-type SiC and High Purity Semi-Insulating 4H SiC through 800 K

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Schwartz, Zachary D.; Alterovitz, Samuel A.; Downey, Alan N.

    2004-01-01

    Wireless sensors for high temperature applications such as oil drilling and mining, automobiles, and jet engine performance monitoring require circuits built on wide bandgap semiconductors. In this paper, the characteristics of microwave transmission lines on 4H-High Purity Semi-Insulating SiC and 6H, p-type SiC is presented as a function of temperature and frequency. It is shown that the attenuation of 6H, p-type substrates is too high for microwave circuits, large leakage current will flow through the substrate, and that unusual attenuation characteristics are due to trapping in the SiC. The 4H-HPSI SiC is shown to have low attenuation and leakage currents over the entire temperature range.

  18. Highly flexible, nonflammable and free-standing SiC nanowire paper.

    PubMed

    Chen, Jianjun; Liao, Xin; Wang, Mingming; Liu, Zhaoxiang; Zhang, Judong; Ding, Lijuan; Gao, Li; Li, Ye

    2015-04-14

    Flexible paper-like semiconductor nanowire materials are expected to meet the criteria for some emerging applications, such as components of flexible solar cells, electrical batteries, supercapacitors, nanocomposites, bendable or wearable electronic or optoelectronic components, and so on. As a new generation of wide-bandgap semiconductors and reinforcements in composites, SiC nanowires have advantages in power electronic applications and nanofiber reinforced ceramic composites. Herein, free-standing SiC nanowire paper consisting of ultralong single-crystalline SiC nanowires was prepared through a facile vacuum filtration approach. The ultralong SiC nanowires were synthesized by a sol-gel and carbothermal reduction method. The flexible paper composed of SiC nanowires is ∼100 nm in width and up to several hundreds of micrometers in length. The nanowires are intertwisted with each other to form a three-dimensional network-like structure. SiC nanowire paper exhibits high flexibility and strong mechanical stability. The refractory performance and thermal stability of SiC nanowire paper were also investigated. The paper not only exhibits excellent nonflammability in fire, but also remains well preserved without visible damage when it is heated in an electric oven at a high temperature (1000 °C) for 3 h. With its high flexibility, excellent nonflammability, and high thermal stability, the free-standing SiC nanowire paper may have the potential to improve the ablation resistance of high temperature ceramic composites. PMID:25785912

  19. The Social Interactive Coding System (SICS): An On-Line, Clinically Relevant Descriptive Tool.

    ERIC Educational Resources Information Center

    Rice, Mabel L.; And Others

    1990-01-01

    The Social Interactive Coding System (SICS) assesses the continuous verbal interactions of preschool children as a function of play areas, addressees, script codes, and play levels. This paper describes the 26 subjects and the setting involved in SICS development, coding definitions and procedures, training procedures, reliability, sample…

  20. Highly flexible, nonflammable and free-standing SiC nanowire paper.

    PubMed

    Chen, Jianjun; Liao, Xin; Wang, Mingming; Liu, Zhaoxiang; Zhang, Judong; Ding, Lijuan; Gao, Li; Li, Ye

    2015-04-14

    Flexible paper-like semiconductor nanowire materials are expected to meet the criteria for some emerging applications, such as components of flexible solar cells, electrical batteries, supercapacitors, nanocomposites, bendable or wearable electronic or optoelectronic components, and so on. As a new generation of wide-bandgap semiconductors and reinforcements in composites, SiC nanowires have advantages in power electronic applications and nanofiber reinforced ceramic composites. Herein, free-standing SiC nanowire paper consisting of ultralong single-crystalline SiC nanowires was prepared through a facile vacuum filtration approach. The ultralong SiC nanowires were synthesized by a sol-gel and carbothermal reduction method. The flexible paper composed of SiC nanowires is ∼100 nm in width and up to several hundreds of micrometers in length. The nanowires are intertwisted with each other to form a three-dimensional network-like structure. SiC nanowire paper exhibits high flexibility and strong mechanical stability. The refractory performance and thermal stability of SiC nanowire paper were also investigated. The paper not only exhibits excellent nonflammability in fire, but also remains well preserved without visible damage when it is heated in an electric oven at a high temperature (1000 °C) for 3 h. With its high flexibility, excellent nonflammability, and high thermal stability, the free-standing SiC nanowire paper may have the potential to improve the ablation resistance of high temperature ceramic composites.

  1. Gadolinium and Dysprosium Isotopic Compositions in Stardust SiC Grains from the Murchison Meteorite

    NASA Astrophysics Data System (ADS)

    Avila, J. N.; Ireland, T. R.; Lugaro, M.; Gyngard, F.; Karakas, A.

    2016-08-01

    We report the results of Gd and Dy isotopic analyses performed in stardust SiC grains. We have compared the SiC data with new theoretical predictions of the evolution of Gd and Dy isotopic ratios in the envelopes of low-mass AGB stars.

  2. Iron and Nickel Isotope Measurements on SiC X Grains with CHILI

    NASA Astrophysics Data System (ADS)

    Kodolányi, J.; Stephan, T.; Trappitsch, R.; Hoppe, P.; Pignatari, M.; Davis, A. M.; Pellin, M. J.

    2016-08-01

    New measurements with CHILI on SiC X grains provide more detailed Fe and Ni isotope data than previous NanoSIMS analyses. The new data suggest that Fe-Ni fractionation may occur in supernova ejecta before SiC condensation.

  3. The first muon beam from a new highly-intense DC muon source, MuSIC

    NASA Astrophysics Data System (ADS)

    Tran, Nam Hoai; MuSIC Collaboration

    2012-09-01

    A new DC muon source, MuSIC, is now under construction at Research Center for Nuclear Physics (RCNP), Osaka University, Japan. The MuSIC adopts a new pion/muon collection system and a curved transport solenoid. These techniques are important in realization of future muon programs such as the muon to electron conversion experiments (COMET/Mu2e), neutrino factories, and muon colliders. The pion capture magnet and a part of the transport solenoid have been built and beam tests were carried out to assess the MuSIC's performance. Muon lifetime measurements and muonic X-ray measurements have been used for estimation of muon yield of the MuSIC. The result indicates that the MuSIC would be one of the most intense DC muon beams in the world.

  4. 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.

  5. Oxidation of SiC cladding under Loss of Coolant Accident (LOCA) conditions in LWRs

    SciTech Connect

    Lee, Y.; Yue, C.; Arnold, R. P.; McKrell, T. J.; Kazimi, M. S.

    2012-07-01

    An experimental assessment of Silicon Carbide (SiC) cladding oxidation rate in steam under conditions representative of Loss of Coolant Accidents (LOCA) in light water reactors (LWRs) was conducted. SiC oxidation tests were performed with monolithic alpha phase tubular samples in a vertical quartz tube at a steam temperature of 1140 deg. C and steam velocity range of 1 to 10 m/sec, at atmospheric pressure. Linear weight loss of SiC samples due to boundary layer controlled reaction of silica scale (SiO{sub 2} volatilization) was experimentally observed. The weight loss rate increased with increasing steam flow rate. Over the range of test conditions, SiC oxidation rates were shown to be about 3 orders of magnitude lower than the oxidation rates of zircaloy 4. A SiC volatilization correlation for developing laminar flow in a vertical channel is formulated. (authors)

  6. Hydrothermal corrosion of SiC in LWR coolant environments in the absence of irradiation

    NASA Astrophysics Data System (ADS)

    Terrani, K. A.; Yang, Y.; Kim, Y.-J.; Rebak, R.; Meyer, H. M.; Gerczak, T. J.

    2015-10-01

    Assessment of the thermodynamics of SiC corrosion under light water reactor coolant environments suggests that silica formation is always expected in the range of applicable pH and potential. Autoclave testing of SiC-based materials in the absence of ionizing radiation was performed. The kinetics data from these tests, when compared with kinetics of silica dissolution in water and post-exposure characterization of SiC samples, suggest that oxidation of SiC to form silica is the rate-limiting step for recession of SiC in high temperature water. Oxygen activity in water was determined to play an important role in SiC recession kinetics. A simplified model of a power loop shows the effect of silica dissolution from the hot region (resembling fuel) and deposition in the cold regions.

  7. The role of Pd in the transport of Ag in SiC

    NASA Astrophysics Data System (ADS)

    Olivier, E. J.; Neethling, J. H.

    2013-01-01

    This paper presents results in support of a newly proposed transport mechanism to account for the release of Ag from intact TRISO particles during HTR reactor operation. The study reveals that the migration of Ag in polycrystalline SiC can occur in association with Pd, a relatively high yield metallic fission product. The migration takes place primarily along grain boundary routes, seen in the form of distinct Pd, Ag and Si containing nodules. Pd is known to rapidly migrate to the SiC and iPyC interface within TRISO particles during operation. It has been shown to chemically corrode the SiC to form palladium silicides. These palladium silicides are found present along SiC grain boundaries in nodule like form. It is suggested that Ag penetrates these nodules together with the palladium silicide, to form a Pd, Ag and Si solution capable of migrating along SiC grain boundaries over time.

  8. Amorphization resistance of nano-engineered SiC under heavy ion irradiation

    NASA Astrophysics Data System (ADS)

    Imada, Kenta; Ishimaru, Manabu; Xue, Haizhou; Zhang, Yanwen; Shannon, Steven C.; Weber, William J.

    2016-09-01

    Silicon carbide (SiC) with a high-density of planar defects (hereafter, 'nano-engineered SiC') and epitaxially-grown single-crystalline 3C-SiC were simultaneously irradiated with Au ions at room temperature, in order to compare their relative resistance to radiation-induced amorphization. It was found that the local threshold dose for amorphization is comparable for both samples under 2 MeV Au ion irradiation; whereas, nano-engineered SiC exhibits slightly greater radiation tolerance than single crystalline SiC under 10 MeV Au irradiation. Under 10 MeV Au ion irradiation, the dose for amorphization increased by about a factor of two in both nano-engineered and single crystal SiC due to the local increase in electronic energy loss that enhanced dynamic recovery.

  9. Optimized growth of graphene on SiC: from the dynamic flip mechanism

    NASA Astrophysics Data System (ADS)

    Wang, Dandan; Liu, Lei; Chen, Wei; Chen, Xiaobo; Huang, Han; He, Jun; Feng, Yuan-Ping; Wee, A. T. S.; Shen, D. Z.

    2015-02-01

    Thermal decomposition of single-crystal SiC is one of the popular methods for growing graphene. However, the mechanism of graphene formation on the SiC surface is poorly understood, and the application of this method is also hampered by its high growth temperature. In this study, based on the ab initio calculations, we propose a vacancy assisted Si-C bond flipping model for the dynamic process of graphene growth on SiC. The fact that the critical stages during growth take place at different energy costs allows us to propose an energetic-beam controlled growth method that not only significantly lowers the growth temperature but also makes it possible to grow high-quality graphene with the desired size and patterns directly on the SiC substrate.

  10. The microstructure origin of large strain plastically deformed SiC nanowires

    NASA Astrophysics Data System (ADS)

    Fu, X.; Jiang, J.; Hu, X.; Yuan, J.; Zhang, Y.; Han, X.; Zhang, Z.

    2008-08-01

    Surprisingly large strain plasticity has been demonstrated for ceramic SiC nanowires through in-situ deformation experiments near room temperature. This article reports a detailed electron energy-loss spectroscopy (EELS) study of deformation-induced localized plastic zones in a bent SiC nanowire. Both the 'red shift' of the plasmon peak and the characteristic fine structure at Si L-edge absorption are consistent with local amorphisation of SiC. The recorded C K-edge fine structure is processed to remove the contribution from the surface amorphous carbon and the extracted C K-edge fine structure has no characteristic sp2-related pre-edge peak and hence is also consistent with amorphous SiC. These results suggest that the large strain plasticity in SiC nanowires is enabled by crystalline-to-amorphous transition.

  11. Estimation of capacity utilization for selected U.S. manufacturing industries

    SciTech Connect

    Niefer, M.J.; Kokkelenberg, E.D.

    1995-03-01

    This paper reports results from the nonparametric estimation of plant-level capacity and capacity utilization for selected four-digit Standard Industrial Classification (SIC) industries for the years 1972-90. The estimates are constructed using establishment-level data from the Annual Survey of Manufactures (ASM) drawn from the Census Bureau`s Longitudinal Research Database (LRD). This work represents the first broad-scale application of the nonparametric measurement of capacity and capacity utilization to manufacturing plants. Given that the measures are largely untried, we attempt to assess the quality of the reported nonparametric measures.

  12. Streptococcal inhibitor of complement (SIC) inhibits the membrane attack complex by preventing uptake of C567 onto cell membranes.

    PubMed

    Fernie-King, B A; Seilly, D J; Willers, C; Würzner, R; Davies, A; Lachmann, P J

    2001-07-01

    Streptococcal inhibitor of complement (SIC) was first described in 1996 as a putative inhibitor of the membrane attack complex of complement (MAC). SIC is a 31 000 MW protein secreted in large quantities by the virulent Streptococcus pyogenes strains M1 and M57, and is encoded by a gene which is extremely variable. In order to study further the interactions of SIC with the MAC, we have made a recombinant form of SIC (rSIC) in Escherichia coli and purified native M1 SIC which was used to raise a polyclonal antibody. SIC prevented reactive lysis of guinea pig erythrocytes by the MAC at a stage prior to C5b67 complexes binding to cell membranes, presumably by blocking the transiently expressed membrane insertion site on C7. The ability of SIC and clusterin (another putative fluid phase complement inhibitor) to inhibit complement lysis was compared, and found to be equally efficient. In parallel, by enzyme-linked immunosorbent assay both SIC and rSIC bound strongly to C5b67 and C5b678 complexes and to a lesser extent C5b-9, but only weakly to individual complement components. The implications of these data for virulence of SIC-positive streptococci are discussed, in light of the fact that Gram-positive organisms are already protected against complement lysis by the presence of their peptidoglycan cell walls. We speculate that MAC inhibition may not be the sole function of SIC.

  13. Processing of laser formed SiC powder

    NASA Technical Reports Server (NTRS)

    Haggerty, J. S.; Bowen, H. K.

    1987-01-01

    Processing research was undertaken to demonstrate that superior SiC characteristics could be achieved through the use of ideal constituent powders and careful post-synthesis processing steps. Initial research developed the means to produce approximately 1000 A uniform diameter, nonagglomerated, spherical, high purity SiC powders. Accomplishing this goal required major revision of the particle formation and growth model from one based on classical nucleation and growth to one based on collision and coalescence of Si particles followed by their carburization. Dispersions based on pure organic solvents as well as steric stabilization were investigated. Test parts were made by the colloidal pressing technique; both liquid filtration and consolidation (rearrangement) stages were modeled. Green densities corresponding to a random close packed structure were achieved. After drying, parts were densified at temperatures ranging from 1800 to 2100 C. This research program accomplished all of its major objectives. Superior microstructures and properties were attained by using powders having ideal characteristics and special post-synthesis processing procedures.

  14. 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.

  15. 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.

  16. Multi-functional micro electromechanical devices and method of bulk manufacturing same

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S. (Inventor)

    2004-01-01

    A method of bulk manufacturing SiC sensors is disclosed and claimed. Materials other than SiC may be used as the substrate material. Sensors requiring that the SiC substrate be pierced are also disclosed and claimed. A process flow reversal is employed whereby the metallization is applied first before the recesses are etched into or through the wafer. Aluminum is deposited on the entire planar surface of the metallization. Photoresist is spun onto the substantially planar surface of the Aluminum which is subsequently masked (and developed and removed). Unwanted Aluminum is etched with aqueous TMAH and subsequently the metallization is dry etched. Photoresist is spun onto the still substantially planar surface of Aluminum and oxide and then masked (and developed and removed) leaving the unimidized photoresist behind. Next, ITO is applied over the still substantially planar surface of Aluminum, oxide and unimidized photoresist. Unimidized and exposed photoresist and ITO directly above it are removed with Acetone. Next, deep reactive ion etching attacks exposed oxide not protected by ITO. Finally, hot phosphoric acid removes the Al and ITO enabling wires to connect with the metallization. The back side of the SiC wafer may be also be etched.

  17. Energy Use in Manufacturing

    EIA Publications

    2006-01-01

    This report addresses both manufacturing energy consumption and characteristics of the manufacturing economy related to energy consumption. In addition, special sections on fuel switching capacity and energy-management activities between 1998 and 2002 are also featured in this report.

  18. Microstructure characterization of SiC nanowires as reinforcements in composites

    SciTech Connect

    Dong, Ronghua; Yang, Wenshu; Wu, Ping; Hussain, Murid; Xiu, Ziyang; Wu, Gaohui; Wang, Pingping

    2015-05-15

    SiC nanowires have been rarely investigated or explored along their axial direction by transmission electron microscopy (TEM). Here we report the investigation of the cross-section microstructure of SiC nanowires by embedding them into Al matrix. Morphology of SiC nanowires was cylindrical with smooth surface or bamboo shape. Cubic (3C-SiC) and hexagonal structure (2H-SiC) phases were detected by X-ray diffraction (XRD) analysis. High density stacking faults were observed in both the cylindrical and bamboo shaped nanowires which were perpendicular to their axial direction. Selected area electron diffraction (SAED) patterns of the cylindrical and bamboo shaped SiC nanowires both in the perpendicular and parallel direction to the axial direction were equivalent in the structure. After calculation and remodeling, it has been found that the SAED patterns were composed of two sets of diffraction patterns, corresponding to 2H-SiC and 3C-SiC, respectively. Therefore, it could be concluded that the SiC nanowires are composed of a large number of small fragments that are formed by hybrid 3C-SiC and 2H-SiC structures. - Graphical abstract: Display Omitted - Highlights: • Cross-section microstructure of SiC nanowires was observed in Al composite. • Cylindrical with smooth surface or bamboo shape SiC nanowires were found. • The cylindrical and bamboo shaped SiC nanowires were equivalent in structure. • Structure of SiC nanowires was remodeled. • SiC nanowires are composed of hybrid 3C-SiC and 2H-SiC structures.

  19. Workforce Development for Manufacturing

    ERIC Educational Resources Information Center

    Bernard, Rosalie

    2007-01-01

    In a recent skills gap report, the National Association of Manufacturers (NAM) noted some disturbing trends in the gap between the demand for highly skilled manufacturing workers and the potential supply. The NAM report notes that smaller manufacturers rank finding qualified workers ahead of energy costs, taxes and government regulations on the…

  20. History of the ISS/SIC: Antoine Depage, one of the founders of the ISS/SIC.

    PubMed

    Van Hee, R

    2002-10-01

    Antoine Depage, born near Brussels in 1862, was one of the founders and first Secretary General of the Société Internationale de Chirurgie (ISS-SIC). After an excellent medical education at the Free Brussels University, he became professor at the same university at the age of 27. Surgically trained by Prof. Thiriar, he became one of the leading Belgian surgeons at the end of the nineteenth century, and he published more than 100 articles in national and international journals. In 1907 he founded a school for nurses in Brussels, to be directed by Edith Cavell. He also vigorously transformed the organization of the public hospitals in the Belgian capital. During World War I Queen Elisabeth appointed him surgeon-in-chief of the Océan-hospital in De Panne, where more than 50,000 soldiers with wounds, fractures, cerebral trauma, nitrous gas intoxication, and infectious diseases, among other problems were treated. The results he and his team obtained were excellent, and mortality was low. Many surgeons, including Alexis Carrel, as well as distinguished political leaders came to visit him in the hospital barracks. After the war he was honored by many political and scientific organizations, including the Société Internationale de Chirurgie. He served our Society not only as Secretary General from 1902 to 1912 but became President of the 4th Congress of the ISS-SIC in New York. Antoine Depage died after a long illness in 1925. PMID:12205562

  1. In situ toughened SiC ceramics with Al-B-C additions and oxide-coated SiC platelet/SiC composites

    SciTech Connect

    Cao, J. |

    1996-12-01

    This work aimed at fabrication and characterization of high toughness SiC ceramics through the applications of in situ toughening and SiC platelet reinforcement. The processing-microstructure-property relations of hot pressed SiC with Al, B, and C additions (designated as ABC-SiC) were investigated. Through a liquid phase sintering mechanism, dense SiC was obtained by hot pressing at a temperature as low as 1,700 C with 3 wt% Al, 0.6 wt% B, and 2 wt% C additions. These sintering aids also enhanced the {beta}-to-{alpha} (3C-to-4H) phase transformation, which promoted SiC grains to grow into plate-like shapes. Under optimal processing conditions, the microstructure exhibited high-aspect-ratio plate-shaped grains with a thin (< 1 nm) Al-containing amorphous grain boundary film. The mechanical properties of the toughened SiC and the composites were evaluated in comparison with a commercial Hexoloy SiC under identical test conditions. The C-curve behavior was examined using the strength-indentation load relationship and compared with that directly measured using precracked compact tension specimens. The in situ toughened ABC-SiC exhibited much improved flaw tolerance and a significantly rising R-curve behavior. A steady-state toughness in excess of 9 MPam{sup 1/2} was recorded for the ABC-SiC in comparison to a single valued toughness below 3 MPam{sup 1/2} for the Hexoloy. Toughening in the ABC-SiC was mainly attributed to grain bridging and subsequent pullout of the plate-shaped grains. The high toughness ABC-SiC exhibited a bend strength of 650 MPa with a Weibull modulus of 19; in comparison, the commercial SiC showed a bend strength of 400 MPa with a Weibull modulus of 6. Higher fracture toughness was also achieved by the reinforcement of SiC platelets, encapsulated with alumina, yttria, or silica, in a SiC matrix.

  2. Manufacturing Planning Guide

    NASA Technical Reports Server (NTRS)

    Waid, Michael

    2011-01-01

    Manufacturing process, milestones and inputs are unknowns to first-time users of the manufacturing facilities. The Manufacturing Planning Guide aids in establishing expectations for both NASA and non-NASA facility customers. The potential audience for this guide includes both internal and commercial spaceflight hardware/software developers. It is intended to assist their project engineering personnel in manufacturing planning and execution. Material covered includes a roadmap of the manufacturing process, roles and responsibilities of facility and user, major milestones, facility capabilities, and inputs required by the facility. Samples of deliverables, products, and inputs necessary to define test scope, cost, and schedule are included as an appendix to the guide.

  3. Surface charges and optical characteristic of colloidal cubic SiC nanocrystals

    NASA Astrophysics Data System (ADS)

    Li, Yong; Chen, Changxin; Li, Jiang-Tao; Yang, Yun; Lin, Zhi-Ming

    2011-07-01

    Colloidal cubic silicon carbide (SiC) nanocrystals with an average diameter of 4.4 nm have been fabricated by anisotropic wet chemical etching of microsized cubic SiC powder. Fourier transform infrared spectra show that these cubic SiC nanocrystals contain carboxylic acid, SiH, CH, and CHx groups. UV/Vis absorption and photoluminescence (PL) spectroscopy clearly indicate that water and ethanol colloidal suspensions of the as-fabricated colloidal samples exhibit strong and above band gap blue and blue-green emissions. The cubic SiC nanocrystals show different surface charges in water and ethanol solutions due to the interaction of water molecules with polar Si-terminated surfaces of cubic SiC nanocrystals. The results explain the distinctive optical characteristics of colloidal cubic SiC nanocrystals in water and ethanol, and reveal that quantum confinement and surface charges play a great role in determining the optical characteristics of colloidal cubic SiC nanocrystals.

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

    NASA Astrophysics Data System (ADS)

    Xiao, H. Y.; Zhang, Y.; Snead, L. L.; Shutthanandan, V.; Xue, H. Z.; Weber, W. 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.

  5. Surface charges and optical characteristic of colloidal cubic SiC nanocrystals

    PubMed Central

    2011-01-01

    Colloidal cubic silicon carbide (SiC) nanocrystals with an average diameter of 4.4 nm have been fabricated by anisotropic wet chemical etching of microsized cubic SiC powder. Fourier transform infrared spectra show that these cubic SiC nanocrystals contain carboxylic acid, SiH, CH, and CHx groups. UV/Vis absorption and photoluminescence (PL) spectroscopy clearly indicate that water and ethanol colloidal suspensions of the as-fabricated colloidal samples exhibit strong and above band gap blue and blue-green emissions. The cubic SiC nanocrystals show different surface charges in water and ethanol solutions due to the interaction of water molecules with polar Si-terminated surfaces of cubic SiC nanocrystals. The results explain the distinctive optical characteristics of colloidal cubic SiC nanocrystals in water and ethanol, and reveal that quantum confinement and surface charges play a great role in determining the optical characteristics of colloidal cubic SiC nanocrystals. PMID:21762496

  6. Chemical reactivity of CVC and CVD SiC with UO2 at high temperatures

    DOE PAGES

    Silva, Chinthaka M.; Katoh, Yutai; Voit, Stewart L.; Snead, Lance L.

    2015-02-11

    Two types of silicon carbide (SiC) synthesized using two different vapor deposition processes were embedded in UO2 pellets and evaluated for their potential chemical reaction with UO2. While minor reactivity between chemical-vapor-composited (CVC) SiC and UO2 was observed at comparatively low temperatures of 1100 and 1300 C, chemical-vapor-deposited (CVD) SiC did not show any such reactivity, according to microstructural investigations. But, both CVD and CVC SiCs showed some reaction with UO2 at a higher temperature (1500 C). Elemental maps supported by phase maps obtained using electron backscatter diffraction indicated that CVC SiC was more reactive than CVD SiC at 1500more » C. Moreover, this investigation indicated the formation of uranium carbides and uranium silicide chemical phases such as UC, USi2, and U3Si2 as a result of SiC reaction with UO2.« less

  7. Application of rapid milling technology for fabrication of SiC nanoparticles.

    PubMed

    Kim, Jong-Woong; Shim, Jae-Shik; Kwak, Min-Gi; Hong, Sung-Jei; Cho, Hyun-Min

    2013-09-01

    SiC nanoparticles were successfully fabricated by a high energy ball milling method, so that can be used in the printed electronics to make SiC thin film patterns. Here we utilized the waste of Si sludge for making the SiC nanoparticles. In order to achieve uniform thin film from the nanoparticle ink, fine sized SiC nanoparticles less than 100 nm has to be uniformly dispersed. In this study, we employed the ultra apex milling (UAM) system for particle comminution and dispersion. We investigated the effects of milling parameters, e.g., size of ZrO2 bead and milling time. The size of the SiC particles reached about 103 nm after 4 hours of UAM, when the ZrO2 beads of 50 microm were used. Then SiC ink was formulated with organic solvents and a dispersing agent. A specially designed pattern was printed by an ink-jet printer for evaluating the feasibility of the SiC nanoparticle inks.

  8. Detection and analysis of particles with failed SiC in AGR-1 fuel compacts

    DOE PAGES

    Hunn, John D.; Baldwin, Charles A.; Gerczak, Tyler J.; Montgomery, Fred C.; Morris, Robert N.; Silva, Chinthaka M.; Demkowicz, Paul A.; Harp, Jason M.; Ploger, Scott A.

    2016-04-06

    As the primary barrier to release of radioactive isotopes emitted from the fuel kernel, retention performance of the SiC layer in tristructural isotropic (TRISO) coated particles is critical to the overall safety of reactors that utilize this fuel design. Most isotopes are well-retained by intact SiC coatings, so pathways through this layer due to cracking, structural defects, or chemical attack can significantly contribute to radioisotope release. In the US TRISO fuel development effort, release of 134Cs and 137Cs are used to detect SiC failure during fuel compact irradiation and safety testing because the amount of cesium released by a compactmore » containing one particle with failed SiC is typically ten or more times higher than that released by compacts without failed SiC. Compacts with particles that released cesium during irradiation testing or post-irradiation safety testing at 1600–1800 °C were identified, and individual particles with abnormally low cesium retention were sorted out with the Oak Ridge National Laboratory (ORNL) Irradiated Microsphere Gamma Analyzer (IMGA). X-ray tomography was used for three-dimensional imaging of the internal coating structure to locate low-density pathways through the SiC layer and guide subsequent materialography by optical and scanning electron microscopy. In addition, all three cesium-releasing particles recovered from as-irradiated compacts showed a region where the inner pyrocarbon (IPyC) had cracked due to radiation-induced dimensional changes in the shrinking buffer and the exposed SiC had experienced concentrated attack by palladium; SiC failures observed in particles subjected to safety testing were related to either fabrication defects or showed extensive Pd corrosion through the SiC where it had been exposed by similar IPyC cracking.« less

  9. Graphene nanoribbons anchored to SiC substrates

    NASA Astrophysics Data System (ADS)

    Le, Nam B.; Woods, Lilia M.

    2016-09-01

    Graphene nanoribbons are quasi-one-dimensional planar graphene allotropes with diverse properties dependent on their width and types of edges. Graphene nanoribbons anchored to substrates is a hybrid system, which offers novel opportunities for property modifications as well as experimental control. Here we present electronic structure calculations of zigzag graphene nanoribbons chemically attached via the edges to the Si or C terminated surfaces of a SiC substrate. The results show that the edge characteristics are rather robust and the properties are essentially determined by the individual nanoribbon. While the localized spin polarization of the graphene nanoribbon edge atoms is not significantly affected by the substrate, secondary energy gaps in the highest conduction and lowest valence region may emerge in the anchored structures. The van der Waals interaction together with the electrostatic interactions due to the polarity of the surface bonds are found to be important for the structure parameters and energy stability.

  10. Demonstration of SiC Pressure Sensors at 750 C

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S.; Lukco, Dorothy; Nguyen, Vu; Savrun, Ender

    2014-01-01

    We report the first demonstration of MEMS-based 4H-SiC piezoresistive pressure sensors tested at 750 C and in the process confirmed the existence of strain sensitivity recovery with increasing temperature above 400 C, eventually achieving near or up to 100% of the room temperature values at 750 C. This strain sensitivity recovery phenomenon in 4H-SiC is uncharacteristic of the well-known monotonic decrease in strain sensitivity with increasing temperature in silicon piezoresistors. For the three sensors tested, the room temperature full-scale output (FSO) at 200 psig ranged between 29 and 36 mV. Although the FSO at 400 C dropped by about 60%, full recovery was achieved at 750 C. This result will allow the operation of SiC pressure sensors at higher temperatures, thereby permitting deeper insertion into the engine combustion chamber to improve the accurate quantification of combustor dynamics.

  11. 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.

  12. Graphene nanoribbons anchored to SiC substrates.

    PubMed

    Le, Nam B; Woods, Lilia M

    2016-09-14

    Graphene nanoribbons are quasi-one-dimensional planar graphene allotropes with diverse properties dependent on their width and types of edges. Graphene nanoribbons anchored to substrates is a hybrid system, which offers novel opportunities for property modifications as well as experimental control. Here we present electronic structure calculations of zigzag graphene nanoribbons chemically attached via the edges to the Si or C terminated surfaces of a SiC substrate. The results show that the edge characteristics are rather robust and the properties are essentially determined by the individual nanoribbon. While the localized spin polarization of the graphene nanoribbon edge atoms is not significantly affected by the substrate, secondary energy gaps in the highest conduction and lowest valence region may emerge in the anchored structures. The van der Waals interaction together with the electrostatic interactions due to the polarity of the surface bonds are found to be important for the structure parameters and energy stability. PMID:27392014

  13. Electronic structure of Si vacancy centers in SiC

    NASA Astrophysics Data System (ADS)

    Soykal, Oney; Dev, Pratibha; Economou, Sophia

    2015-03-01

    The spin state of silicon vacancies in SiC is a promising candidate for applications in solid state quantum information technologies due to its long coherence time at room temperature, its technological availability and wide range of polytypism. Until recently, the electronic structure of this vacancy was not well understood. We have developed a group theoretical model that correctly predicts the spin 3/2 structure seen in recent experiments for the 4H-SiC defect. We have included several different mechanisms involved in the mixing of its spin states, such as crystal field splitting, spin-orbit coupling, spin-spin coupling, strain and Jahn-Teller interactions. We have also carried out DFT calculations that support and complement our analytical results.

  14. 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.

  15. Excitation and recombination photodynamics in colloidal cubic SiC nanocrystals

    NASA Astrophysics Data System (ADS)

    Fan, J. Y.; Li, H. X.; Cui, W. N.; Dai, D. J.; Chu, P. K.

    2010-11-01

    We studied the photodynamics of the different-sized colloidal cubic SiC nanocrystals in distinct polar and nonpolar solvents. The UV-visible absorption spectral study indicates that the SiC nanocrystals with an average size of 4 nm retain an indirect energy gap; whereas the smaller quantum dots about 1 nm in size exhibit discrete and sharp absorption features indicating their discrete energy levels and the result agrees well with theoretical results. The colloidal SiC nanocrystals exhibit triple-exponential photoluminescence decay with nanosecond-order lifetimes which show slight size-dependence.

  16. The intensive terahertz electroluminescence induced by Bloch oscillations in SiC natural superlattices.

    PubMed

    Sankin, Vladimir; Andrianov, Alexandr; Petrov, Alexey; Zakhar'in, Alexey; Lepneva, Ala; Shkrebiy, Pavel

    2012-10-09

    : We report on efficient terahertz (THz) emission from high-electric-field-biased SiC structures with a natural superlattice at liquid helium temperatures. The emission spectrum demonstrates a single line, the maximum of which shifts linearly with increases in bias field. We attribute this emission to steady-state Bloch oscillations of electrons in the SiC natural superlattice. The properties of the THz emission agree fairly with the parameters of the Bloch oscillator regime, which have been proven by high-field electron transport studies of SiC structures with natural superlattices.

  17. Diffusion of helium in SiC and implications for retention of cosmogenic He

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.; Watson, E. B.; Trappisch, R.; Thomas, J. B.; Chaussende, D.

    2016-11-01

    Diffusion of helium has been characterized in silicon carbide of cubic and hexagonal (4H and 6H) forms. Polished sections of SiC were implanted with 3He at 100 keV at a dose of 1 × 1015/cm2. The implanted SiC samples were sealed under vacuum in silica glass ampoules, and annealed in 1-atm furnaces. 3He distributions following all experiments were measured with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For He diffusion in cubic SiC and 4H hexagonal SiC we obtain the following Arrhenius relations: Dcubic = 1.83 ×10-6 exp (- 254 ± 10kJmol-1 /RT)m2s-1 . D4H = 4.78 ×10-7 exp (- 255 ± 29kJmol-1 /RT)m2s-1 . While He diffusion is considerably slower in SiC than in many silicate phases, He retentivity may be limited under some conditions. For example, helium will be lost from SiC grains over much shorter timescales than potential survival times of SiC presolar grains in the solar nebula. When exposed to impact heating followed by slow cooling, nearly complete loss of He from SiC grains near the site of impact will occur within several hours to a few days. For SiC grains at greater distance from impact sites, He would be better retained, depending on the rapidity of cooling. At tens of km away from a large impactor, where peak T would be ∼800 K, SiC grains would lose about 50% of their He if the grains cooled within a few thousand years, and 5% if they cooled within a few tens of years. At greater distances where heating is more modest (500 K and lower), SiC grains would be quite retentive of He even for cases of very slow cooling. Helium would also be retained in cases of impact heating followed by very rapid cooling. For these short heating pulses, 10 μm diameter SiC grains would retain more than 50% of their He for peak heating temperatures of 2173, 1973 and 1773 K for durations of 3, 10 and 60 s, respectively.

  18. Electrical Impact of SiC Structural Crystal Defects on High Electric Field Devices (Invited)

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.

    1999-01-01

    As illustrated by the invited paper at this conference and other works, SiC wafers and epilayers contain a variety of crystallographic imperfections, including micropipes, closed-core screw dislocations, grain boundaries, basal plane dislocations, heteropolytypic inclusions, and surfaces that are often damaged and contain atomically rough features like step bunching and growth pits or hillocks. Present understanding of the operational impact of various crystal imperfections on SiC electrical devices is reviewed, with an emphasis placed on high-field SiC power devices and circuits.

  19. 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.

  20. 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.

  1. Similarities and differences in sublimation growth of SiC and AlN

    NASA Astrophysics Data System (ADS)

    Epelbaum, B. M.; Bickermann, M.; Nagata, S.; Heimann, P.; Filip, O.; Winnacker, A.

    2007-07-01

    The similarities and differences in development of crystal growth of bulk silicon carbide (SiC) and aluminum nitride (AlN) are discussed. It is concluded that AlN is going to become the second crystal grown in production scale using PVT technique. The growth technology of AlN may take advantage of learning from SiC technology as the latter is based on significant advances achieved in the course of last 20 years. The main differences between two materials are in incongruent evaporation of SiC and in poor compatibility of AlN with regular high-temperature crucible materials.

  2. Thermal expansion and thermal expansion anisotropy of SiC polytypes

    NASA Technical Reports Server (NTRS)

    Li, Z.; Bradt, R. C.

    1987-01-01

    The principal axial coefficients of thermal expansion for the (3C), (4H), and (6H) polytypes of SiC are considered to identify the structural role of the stacking layer sequence as it affects the thermal expansion. A general equation based on the fractions of cubic and hexagonal layer stacking is developed that expresses the principal axial thermal expansion coefficients of all of the SiC polytypes. It is then applied to address the thermal expansion anisotropy of the noncubic SiC structures.

  3. The intensive terahertz electroluminescence induced by Bloch oscillations in SiC natural superlattices

    PubMed Central

    2012-01-01

    We report on efficient terahertz (THz) emission from high-electric-field-biased SiC structures with a natural superlattice at liquid helium temperatures. The emission spectrum demonstrates a single line, the maximum of which shifts linearly with increases in bias field. We attribute this emission to steady-state Bloch oscillations of electrons in the SiC natural superlattice. The properties of the THz emission agree fairly with the parameters of the Bloch oscillator regime, which have been proven by high-field electron transport studies of SiC structures with natural superlattices. PMID:23043773

  4. Exposure of epitaxial graphene on SiC(0001) to atomic hydrogen.

    PubMed

    Guisinger, Nathan P; Rutter, Gregory M; Crain, Jason N; First, Phillip N; Stroscio, Joseph A

    2009-04-01

    Graphene films on SiC exhibit coherent transport properties that suggest the potential for novel carbon-based nanoelectronics applications. Recent studies suggest that the role of the interface between single layer graphene and silicon-terminated SiC can strongly influence the electronic properties of the graphene overlayer. In this study, we have exposed the graphitized SiC to atomic hydrogen in an effort to passivate dangling bonds at the interface, while investigating the results utilizing room temperature scanning tunneling microscopy.

  5. Incorporation of oxygen in SiC implanted with hydrogen

    NASA Astrophysics Data System (ADS)

    Barcz, A.; Jakieła, R.; Kozubal, M.; Dyczewski, J.; Celler, G. K.

    2015-12-01

    Oxygen accumulation at buried implantation-damage layers was studied after post-implantation annealing of hydrogen- or deuterium-implanted 4H-SiC. In this study H+ or 2H+ implantation was carried out at energies E, from 200 keV to 1 MeV, to fluences D, ranging from 2 × 1016/cm2 to 1 × 1017/cm2. For comparison, the implantation was also done into float-zone (FZ) and Czochralski (CZ) silicon wafers. Post-implantation annealing at temperatures from 400 °C to 1150 °C was performed either in pure argon or in a water vapor. Characterization methods included SIMS, RBS and TEM. At sufficiently high doses, hydrogen implantation into semiconductors leads to the irreversible formation of a planar zone of microcavities, bubbles and other extended defects located at the maximum of deposited energy. This kind of highly perturbed layer, containing large amounts of agglomerated hydrogen is known to efficiently getter a number of impurities. Oxygen was detected in both CZ and FZ silicon subjected to Smart-Cut™ processing. We have identified, by SIMS profiling, a considerable oxygen peak situated at the interface between the SiC substrate and a layer implanted with 1 × 1017 H ions/cm2 and heated to 1150 °C in either H2O vapor or in a nominally pure Ar. In view of a lack of convincing evidence that a hexagonal SiC might contain substantial amounts of oxygen, the objective of the present study was to identify the source and possible transport mechanism of oxygen species to the cavity band. Through the analysis of several implants annealed at various conditions, we conclude that, besides diffusion from the bulk or from surface oxides, an alternative path for oxygen agglomeration is migration of gaseous O2 or H2O from the edge of the sample through the porous layer.

  6. New Laboratory Measurements of Rhomboidal SiC_3

    NASA Astrophysics Data System (ADS)

    Gottlieb, Carl A.; Thaddeus, Patrick

    2009-06-01

    Rhomboidal SiC_3, the highly polar planar ring with C_{2v} symmetry and a transannular C-C bond, was detected in our laboratory about 10 years ago, and soon afterwards was identified with a radio telescope in the expanding envelope of IRC+10216. Recently a sensitive spectral line survey of IRC+10216 was made with the Submillimeter Array (SMA) in the 300 - 355 GHz range with a 3^'' × 2^'' synthesized beam. Many new lines were detected in this survey. Most are from high rotational transitions of molecules that are known in IRC+10216, but some of the lines are quite narrow and more than 10 of these are unassigned. In support of the SMA observations we have extended the earlier laboratory measurements by Apponi et al. from 286 GHz and K_a ≤ 6, to 450 GHz and K_a ≤ 20 from rotational levels as high as 825 K above ground. As a result uncertainties in the predicted spectrum for lines with high K_a have been reduced by as much as two orders of magnitude, which should aid the assignment of SiC_3 in the SMA survey and in future observations with ALMA. A. J. Apponi, M. C. McCarthy, C. A. Gottlieb, and P. Thaddeus, Journ. Chem. Phys. 111, 3911 (1999). A. J. Apponi, M. C. McCarthy, C. A. Gottlieb, and P. Thaddeus, Astrophys. Journ. Lett. 516, L103 (1999). N. A. Patel, K. H. Young, S. Brünken, R. W. Wilson, P. Thaddeus, K. M. Menten, M. Reid, M. C. McCarthy, Dinh-V Trung, C. A. Gottlieb, and A. Hedden, Astrophys. Journ., in press (2009).

  7. D-region ion-neutral coupled chemistry (Sodankylä Ion Chemistry, SIC) within the Whole Atmosphere Community Climate Model (WACCM 4) - WACCM-SIC and WACCM-rSIC

    NASA Astrophysics Data System (ADS)

    Kovács, Tamás; Plane, John M. C.; Feng, Wuhu; Nagy, Tibor; Chipperfield, Martyn P.; Verronen, Pekka T.; Andersson, Monika E.; Newnham, David A.; Clilverd, Mark A.; Marsh, Daniel R.

    2016-09-01

    This study presents a new ion-neutral chemical model coupled into the Whole Atmosphere Community Climate Model (WACCM). The ionospheric D-region (altitudes ˜ 50-90 km) chemistry is based on the Sodankylä Ion Chemistry (SIC) model, a one-dimensional model containing 307 ion-neutral and ion recombination, 16 photodissociation and 7 photoionization reactions of neutral species, positive and negative ions, and electrons. The SIC mechanism was reduced using the simulation error minimization connectivity method (SEM-CM) to produce a reaction scheme of 181 ion-molecule reactions of 181 ion-molecule reactions of 27 positive and 18 negative ions. This scheme describes the concentration profiles at altitudes between 20 km and 120 km of a set of major neutral species (HNO3, O3, H2O2, NO, NO2, HO2, OH, N2O5) and ions (O2+, O4+, NO+, NO+(H2O), O2+(H2O), H+(H2O), H+(H2O)2, H+(H2O)3, H+(H2O)4, O3-, NO2-, O-, O2, OH-, O2-(H2O), O2-(H2O)2, O4-, CO3-, CO3-(H2O), CO4-, HCO3-, NO2-, NO3-, NO3-(H2O), NO3-(H2O)2, NO3-(HNO3), NO3-(HNO3)2, Cl-, ClO-), which agree with the full SIC mechanism within a 5 % tolerance. Four 3-D model simulations were then performed, using the impact of the January 2005 solar proton event (SPE) on D-region HOx and NOx chemistry as a test case of four different model versions: the standard WACCM (no negative ions and a very limited set of positive ions); WACCM-SIC (standard WACCM with the full SIC chemistry of positive and negative ions); WACCM-D (standard WACCM with a heuristic reduction of the SIC chemistry, recently used to examine HNO3 formation following an SPE); and WACCM-rSIC (standard WACCM with a reduction of SIC chemistry using the SEM-CM method). The standard WACCM misses the HNO3 enhancement during the SPE, while the full and reduced model versions predict significant NOx, HOx and HNO3 enhancements in the mesosphere during solar proton events. The SEM-CM reduction also identifies the important ion-molecule reactions that affect the partitioning of

  8. Recent achievements using chemical vapor composite silicon carbide (CVC SiC)

    NASA Astrophysics Data System (ADS)

    Goodman, William A.; Tanaka, Clifford

    2009-08-01

    This annual review documents our progress towards inexpensive mass production of silicon carbide mirrors and optical structures. Results are provided for a NASA Small Business Technology Transfer (STTR) X-Ray Mirror project. Trex partnered with the University of Alabama-Huntsville Center for Advanced Optics (UAH-CAO) to develop fabrication methods for polished cylindrical and conical chemical vapor composite (CVCTM) SiC mandrels. These mandrels are envisioned as pre-forms for the replication of fused silica x-ray optics to be eventually used in the International X-Ray Observatory (IXO). CVC SiCTM offers superior high temperature stability, thermal and mechanical performance and polishability required for this precision replication process. In this program, Trex fabricated prototype mandrels with design diameters of 10.5cm, 20cm and 45cm. UAH-CAO was Trex's university partner in this effort and worked on polishing and metrology of the unusual x-ray mandrel geometries. UAH-CAO successfully developed an innovative interferometric method for measuring the CVC SiCTM x-ray mandrels based on a precision cylindrical lens system. UAH-CAO also developed finishing and polishing methods for CVC SiCTM that utilized a Zeeko IRP200 computer controlled polishing tool. The three technologies key technologies demonstrated in this program (near net shape forming of CVC SiCTM mandrels, the x-ray mandrel metrology and free-form polishing capability on CVC SiCTM) could enable cost-effective manufacture of the x-ray mandrels required for the International X-Ray Observatory (IXO).

  9. Manufacturing with the Sun

    NASA Technical Reports Server (NTRS)

    Murphy, Lawrence M.; Hauser, Steven G.; Clyne, Richard J.

    1991-01-01

    Concentrated solar radiation is now a viable alternative source for many advanced manufacturing processes. Researchers at the National Renewable Energy Laboratory (NREL) have demonstrated the feasibility of processes such as solar induced surface transformation of materials (SISTM), solar based manufacturing, and solar pumped lasers. Researchers are also using sunlight to decontaminate water and soils polluted with organic compounds; these techniques could provide manufacturers with innovative alternatives to traditional methods of waste management. The solar technology that is now being integrated into today's manufacturing processes offer greater potential for tomorrow, especially as applied to the radiation abundant environment available in space and on the lunar surface.

  10. COMPATIBILITY OF INTERFACES AND FIBERS FOR SIC-COMPOSITES IN FUSION ENVIRONMENTS

    SciTech Connect

    Henager, Charles H.; Kurtz, Richard J.

    2008-02-14

    The use of SiC composites in fusion environments is predicated on stability under neutron irradiation, on outstanding high-temperature mechanical properties, and on chemical inertness and corrosion resistance. However, SiC is susceptible to many forms of corrosion in water and in water vapor where silica formation is required as a protective layer because silica forms stable hydroxides that are volatile, even at low temperatures. SiC composites have an additional concern that fine-grained fibers and weak interfaces provide the required fracture toughness, but these components may also exhibit susceptibility to corrosion that can compromise material properties. In this work we examine and review the compatibility of fibers and interfaces, as well as the SiC matrix, in proposed fusion environments including first wall, tritium breeding, and blanket modules and module coolants.

  11. Synthesis of One-Dimensional SiC Nanostructures from a Glassy Buckypaper

    SciTech Connect

    Ding, Mengning; Star, Alexander

    2013-02-21

    A simple and scalable synthetic strategy was developed for the fabrication of one-dimensional SiC nanostructures - nanorods and nanowires. Thin sheets of single-walled carbon nanotubes (SWNTs) were prepared by vacuum filtration and were washed repeatedly with sodium silicate (Na₂SiO₃) solution. The resulting “glassy buckypaper” was heated at 1300 - 1500 °C under Ar/H₂ to allow a solid state reaction between C and Si precursors to form a variety of SiC nanostructures. The morphology and crystal structures of SiC nanorods and nanowires were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive xray spectroscopy (EDX), electron diffraction (ED) and x-ray diffraction (XRD) techniques. Furthermore, electrical conductance measurements were performed on SiC nanorods, demonstrating their potential applications in high-temperature sensors and control systems.

  12. Amorphization resistance of nano-engineered SiC under heavy ion irradiation

    DOE PAGES

    Imada, Kenta; Ishimaru, Manabu; Xue, Haizhou; Zhang, Yanwen; Shannon, Steven C.; Weber, William J.

    2016-06-19

    Silicon carbide (SiC) with a high-density of planar defects (hereafter, ‘nano-engineered SiC’) and epitaxially-grown single-crystalline 3C-SiC were simultaneously irradiated with Au ions at room temperature, in order to compare their relative resistance to radiation-induced amorphization. Furthermore, it was found that the local threshold dose for amorphization is comparable for both samples under 2 MeV Au ion irradiation; whereas, nano-engineered SiC exhibits slightly greater radiation tolerance than single crystalline SiC under 10 MeV Au irradiation. Under 10 MeV Au ion irradiation, the dose for amorphization increased by about a factor of two in both nano-engineered and single crystal SiC due tomore » the local increase in electronic energy loss that enhanced dynamic recovery.« less

  13. Precursor Selection for Property Optimization in Biomorphic SiC Ceramics

    NASA Technical Reports Server (NTRS)

    Varela-Feria, F. M.; Lopez-Robledo, M. J.; Martinez-Fernandez, J.; deArellano-Lopez, A. R.; Singh, M.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Biomorphic SiC ceramics have been fabricated using different wood precursors. The evolution of volume, density and microstructure of the woods, carbon performs, and final SiC products are systematically studied in order to establish experimental guidelines that allow materials selection. The wood density is a critical characteristic, which results in a particular final SiC density, and the level of anisotropy in mechanical properties in directions parallel (axial) and perpendicular (radial) to the growth of the wood. The purpose of this work is to explore experimental laws that can help choose a type of wood as precursor for a final SiC product, with a given microstructure, density and level of anisotropy. Preliminary studies of physical properties suggest that not only mechanical properties are strongly anisotropic, but also electrical conductivity and gas permeability, which have great technological importance.

  14. Effects of Ni doping and structural defects on magnetic properties of annealed SiC films

    NASA Astrophysics Data System (ADS)

    Fu, Yuting; Jin, Xin; Sun, Ning; Li, Chunjing; An, Yukai; Liu, Jiwen

    2016-08-01

    Ni-doped SiC films deposited on Si (100) substrates prepared by RF-magnetron sputtering were discussed in this paper. The results show that with reference to the as-deposited as well as annealing at 800 °C. C atoms were substituted by Ni atoms in the 3Csbnd SiC lattice and Ni-related secondary phase cannot be detected. After annealing at 1200 °C, the crystal quality improved obviously while the majority of Ni atoms form the Ni2Si secondary phase. Temperature dependent on resistivity reveals that the conduction mechanism is dominated by Mott variable range hopping behavior for the Ni-doped SiC films, confirming that the carriers are localized. All the films are ferromagnetic at 300 K and annealing can evidently improve the room-temperature (RT) ferromagnetism. The bound magnetic polarons should be responsible for the RT ferromagnetism of the Ni-doped SiC films.

  15. SiC Nanowires with Tunable Hydrophobicity/Hydrophilicity and Their Application as Nanofluids.

    PubMed

    Chen, Junhong; Zhai, Famin; Liu, Meng; Hou, Xinmei; Chou, Kuo-Chih

    2016-06-14

    In this paper, several methods including HF, NaOH, TEOS, and PVP treatment were adopted to modify the wettability of silicon carbide (SiC) nanowires switching from hydrophobic to hydrophilic. The phase and microstructure investigated by XRD, FT-IR, XPS, TGA, SEM, and TEM demonstrated SiC nanowires switching from hydrophobic to hydrophilic due to the surface-tethered hydrophilic layer as well as increasing interspace between nanowires. Besides this, SiC nanowires with hydrophilicity may effectively improve the thermal conductivity of a fluid. The thermal conductivity of aqueous SiC nanowires after TEOS treatment with just 0.3 vol % was remarkably improved up to ca. 13.0%. PMID:27223246

  16. Numerical design of SiC bulk crystal growth for electronic applications

    SciTech Connect

    Wejrzanowski, T.; Grybczuk, M.; Kurzydlowski, K. J.; Tymicki, E.

    2014-10-06

    Presented study concerns numerical simulation of Physical Vapor Transport (PVT) growth of bulk Silicon Carbide (SiC) crystals. Silicon Carbide is a wide band gap semiconductor, with numerous applications due to its unique properties. Wider application of SiC is limited by high price and insufficient quality of the product. Those problems can be overcame by optimizing SiC production methods. Experimental optimization of SiC production is expensive because it is time consuming and requires large amounts of energy. Numerical modeling allows to learn more about conditions inside the reactor and helps to optimize the process at much lower cost. In this study several simulations of processes with different reactor geometries were presented along with discussion of reactor geometry influence on obtained monocrystal shape and size.

  17. SiC Nanowire Film Photodetectors: A Promising Candidate Toward High Temperature Photodetectors.

    PubMed

    Chong, Haining; Yang, Huijun; Yang, Weiyou; Zheng, Jinju; Shang, Minghui; Yang, Zuobao; Wei, Guodong; Gao, Fengmei

    2016-04-01

    In this study, UV photodetectors (PDs) based on SiC nanowire films have been successfully prepared by a simple and low-cost drip-coating method followed by sintering at 500 °C. The corresponding electrical characterizations clearly demonstrate that the SiC nanowire based PD devices can be regarded as a promising candidate for UV PDs. The PDs can exhibit the excellent performances of fast, high sensitivity, linearity, and stable response, which can thus achieve on-line monitoring of weak UV light. Furthermore, the SiC nanowire-based PDs enable us to fabricate detectors working under high temperature as high as 150 °C. The high photosensitivity and rapid photoresponse for the PDs can be attributed to the superior single crystalline quality of SiC nanowires and the ohmic contact between the electrodes and nanowires. PMID:27451712

  18. Highly flexible, nonflammable and free-standing SiC nanowire paper

    NASA Astrophysics Data System (ADS)

    Chen, Jianjun; Liao, Xin; Wang, Mingming; Liu, Zhaoxiang; Zhang, Judong; Ding, Lijuan; Gao, Li; Li, Ye

    2015-03-01

    Flexible paper-like semiconductor nanowire materials are expected to meet the criteria for some emerging applications, such as components of flexible solar cells, electrical batteries, supercapacitors, nanocomposites, bendable or wearable electronic or optoelectronic components, and so on. As a new generation of wide-bandgap semiconductors and reinforcements in composites, SiC nanowires have advantages in power electronic applications and nanofiber reinforced ceramic composites. Herein, free-standing SiC nanowire paper consisting of ultralong single-crystalline SiC nanowires was prepared through a facile vacuum filtration approach. The ultralong SiC nanowires were synthesized by a sol-gel and carbothermal reduction method. The flexible paper composed of SiC nanowires is ~100 nm in width and up to several hundreds of micrometers in length. The nanowires are intertwisted with each other to form a three-dimensional network-like structure. SiC nanowire paper exhibits high flexibility and strong mechanical stability. The refractory performance and thermal stability of SiC nanowire paper were also investigated. The paper not only exhibits excellent nonflammability in fire, but also remains well preserved without visible damage when it is heated in an electric oven at a high temperature (1000 °C) for 3 h. With its high flexibility, excellent nonflammability, and high thermal stability, the free-standing SiC nanowire paper may have the potential to improve the ablation resistance of high temperature ceramic composites.Flexible paper-like semiconductor nanowire materials are expected to meet the criteria for some emerging applications, such as components of flexible solar cells, electrical batteries, supercapacitors, nanocomposites, bendable or wearable electronic or optoelectronic components, and so on. As a new generation of wide-bandgap semiconductors and reinforcements in composites, SiC nanowires have advantages in power electronic applications and nanofiber

  19. Breakthrough in Power Electronics from SiC: May 25, 2004 - May 31, 2005

    SciTech Connect

    Marckx, D. A.

    2006-03-01

    This report explores the premise that silicon carbide (SiC) devices would reduce substantially the cost of energy of large wind turbines that need power electronics for variable speed generation systems.

  20. Dr. Wernher Von Braun leads a tour of the S-IC checkout area.

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Dr. Eberhard Rees, Charles Schultze, James Webb, Elmer Staats, Comptroller General of the United States, and Dr. Wernher Von Braun tour the S-IC checkout area in the Marshall Space Flight Center quality lab.

  1. High-Temperature SiC Power Module with Integrated SiC Gate Drivers for Future High-Density Power Electronics Applications

    SciTech Connect

    Whitaker, Mr. Bret; Cole, Mr. Zach; Passmore, Mr. Brandon; Mcnutt, Tyler; Lostetter, Dr. Alex; Ericson, Milton Nance; Frank, Steven; Britton Jr, Charles L; Marlino, Laura D; Mantooth, Alan; Francis, Matt; Lamichhane, Ranjan; Shepherd, Paul; Glover, Michael

    2014-01-01

    This paper presents a high-temperature capable intelligent power module that contains SiC power devices and SiC gate driver integrated circuits (ICs). The high-temperature capability of the SiC gate driver ICs allows for them to be packaged into the power module and be located physically close to the power devices. This provides a distinct advantage by reducing the gate driver loop inductance, which promotes high frequency operation, while also reducing the overall volume of the system through higher levels of integration. The power module was tested in a bridgeless-boost converter (Fig. 1) to determine the performance of the module in a system level application. The converter was operated with a switching frequency of 200 kHz with a peak output power of approximately 5 kW. The peak efficiency was found to be 97.5% at 2.9 kW.

  2. Manufacturers' support policies.

    PubMed

    1992-09-01

    Choosing an effective plan for supporting a medical device is critical to its safe use, cost-effectiveness, and longevity. Hospitals can choose from a variety of support providers, including manufacturers, third-party service vendors, or hospital clinical engineering (CE) departments. However, if the hospital plans to use a third-party service vendor or its own CE department to provide support, the manufacturer's cooperation or assistance will still be needed to implement the support plan effectively. Over the years, ECRI has received many comments from hospitals about the way in which manufacturers respond to their equipment support needs. We have learned that some manufacturers are not willing to assist third-party service vendors or in-house service programs or do not always deliver the support they promise. Also, hospitals do not always consider their support needs before purchase, when they have the most leverage to negotiate flexible support arrangements. To help foster better equipment support and customer satisfaction, we polled manufacturers that have participated in recent Health Devices Evaluations to obtain detailed information about their policies toward manufacturers' contract, third-party, and in-house support. Ready access to this information will help hospitals evaluate whether manufacturers' support policies will meet their needs, and it will allow them to minimize problems by working with the manufacturer to negotiate optimal support arrangements during the purchase process. In this article, we briefly discuss the factors to consider when evaluating support alternatives and manufacturers' support policies. We also present the questions posed to each manufacturer on our Manufacturers' Support Policies Questionnaire, along with a summary of the responses that we received for each question.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1428903

  3. Si Isotopic Ratios in Mainstream Presolar SIC Grains Revisited

    NASA Astrophysics Data System (ADS)

    Lugaro, Maria; Zinner, Ernst; Gallino, Roberto; Amari, Sachiko

    1999-12-01

    Although mainstream SiC grains, the major group of presolar SiC grains found in meteorites, are believed to have originated in the expanding envelope of asymptotic giant branch (AGB) stars during their late carbon-rich phases, their Si isotopic ratios show a distribution that cannot be explained by nucleosynthesis in this kind of star. Previously, this distribution has been interpreted to be the result of contributions from many AGB stars of different ages whose initial Si isotopic ratios vary owing to the Galactic chemical evolution of the Si isotopes. This paper presents a new interpretation based on local heterogeneities of the Si isotopes in the interstellar medium at the time the parent stars of the mainstream grains were born. Recently, several authors have presented inhomogeneous chemical evolution models of the Galactic disk in order to account for the well-known evidence that F and G dwarfs of similar age show an intrinsic scatter in their elemental abundances. First we report new calculations of the s-process nucleosynthesis of the Si and Ti isotopes in four AGB models (1.5, 3, and 5 Msolar with Z=0.02; 3 Msolar with Z=0.006). These calculations are based on the release of neutrons in the He intershell by the 13C source during the interpulse periods followed by a second small burst of neutrons released in the convective thermal pulse by the marginal activation of the 22Ne source. In the 1.5 and 3 Msolar models with solar metallicity the predicted shifts of the Si isotopic ratios in the stars' envelope are much smaller (<30‰ for the 29Si/28Si ratio and <40‰ for the 30Si/28Si ratio; the two ratios are normalized to solar) than the range observed in the mainstream grains (up to 180‰). Isotopic shifts are of the same order as in the SiC grains for the 5 Msolar and Z=0.006 models, but the slope of the 29Si/28Si versus 30Si/28Si correlation line is much smaller than that of the grains. We also show that none of the models can reproduce the correlations

  4. Ultra-Low-Cost Room Temperature SiC Thin Films

    NASA Technical Reports Server (NTRS)

    Faur, Maria

    1997-01-01

    The research group at CSU has conducted theoretical and experimental research on 'Ultra-Low-Cost Room Temperature SiC Thin Films. The effectiveness of a ultra-low-cost room temperature thin film SiC growth technique on Silicon and Germanium substrates and structures with applications to space solar sells, ThermoPhotoVoltaic (TPV) cells and microelectronic and optoelectronic devices was investigated and the main result of this effort are summarized.

  5. The development of chemically vapor deposited mullite coatings for the corrosion protection of SiC

    SciTech Connect

    Auger, M.; Hou, P.; Sengupta, A.; Basu, S.; Sarin, V.

    1998-05-01

    Crystalline mullite coatings have been chemically vapor deposited onto SiC substrates to enhance the corrosion and oxidation resistance of the substrate. Current research has been divided into three distinct areas: (1) Development of the deposition processing conditions for increased control over coating`s growth rate, microstructure, and morphology; (2) Analysis of the coating`s crystal structure and stability; (3) The corrosion resistance of the CVD mullite coating on SiC.

  6. Fuel Tank Assembly of the Saturn V S-IC Stage

    NASA Technical Reports Server (NTRS)

    1964-01-01

    The fuel tank assembly of the Saturn V S-IC (first) stage is readied to be mated to the liquid oxygen tank at the Marshall Space Flight Center. The fuel tank carried kerosene as its fuel. The S-IC stage utilized five F-1 engines that used kerosene and liquid oxygen as propellant. Each engine provided 1,500,000 pounds of thrust. This stage lifted the entire vehicle and Apollo spacecraft from the launch pad.

  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. Phosphorus doping of 4H SiC by liquid immersion excimer laser irradiation

    SciTech Connect

    Ikeda, Akihiro; Nishi, Koji; Ikenoue, Hiroshi; Asano, Tanemasa

    2013-02-04

    Phosphorus doping of 4H SiC is performed by KrF excimer laser irradiation of 4H SiC immersed in phosphoric acid. Phosphorus is incorporated to a depth of a few tens of nanometers at a concentration of over 10{sup 20}/cm{sup 3} without generating significant crystal defects. Formation of a pn junction diode with an ideality factor of 1.06 is demonstrated.

  9. 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.

  10. A SiC MOSFET Based Inverter for Wireless Power Transfer Applications

    SciTech Connect

    Onar, Omer C; Chinthavali, Madhu Sudhan; Campbell, Steven L; Ning, Puqi; White, Cliff P; Miller , John M.

    2014-01-01

    In a wireless power transfer (WPT) system, efficiency of the power conversion stages is crucial so that the WPT technology can compete with the conventional conductive charging systems. Since there are 5 or 6 power conversion stages, each stage needs to be as efficient as possible. SiC inverters are crucial in this case; they can handle high frequency operation and they can operate at relatively higher temperatures resulting in reduces cost and size for the cooling components. This study presents the detailed power module design, development, and fabrication of a SiC inverter. The proposed inverter has been tested at three center frequencies that are considered for the WPT standardization. Performance of the inverter at the same target power transfer level is analyzed along with the other system components. In addition, another SiC inverter has been built in authors laboratory by using the ORNL designed and developed SiC modules. It is shown that the inverter with ORNL packaged SiC modules performs simular to that of the inverter having commercially available SiC modules.

  11. 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.

  12. Effect of Ductile Agents on the Dynamic Behavior of SiC3D Network Composites

    NASA Astrophysics Data System (ADS)

    Zhu, Jingbo; Wang, Yangwei; Wang, Fuchi; Fan, Qunbo

    2016-07-01

    Co-continuous SiC ceramic composites using pure aluminum, epoxy, and polyurethane (PU) as ductile agents were developed. The dynamic mechanical behavior and failure mechanisms were investigated experimentally using the split Hopkinson pressure bar (SHPB) method and computationally by finite element (FE) simulations. The results show that the SiC3D/Al composite has the best overall performance in comparison with SiC3D/epoxy and SiC3D/PU composites. FE simulations are generally consistent with experimental data. These simulations provide valuable help in predicting mechanical strength and in interpreting the experimental results and failure mechanisms. They may be combined with micrographs for fracture characterizations of the composites. We found that interactions between the SiC phase and ductile agents under dynamic compression in the SHPB method are complex, and that interfacial condition is an important parameter that determines the mechanical response of SiC3D composites with a characteristic interlocking structure during dynamic compression. However, the effect of the mechanical properties of ductile agents on dynamic behavior of the composites is a second consideration in the production of the composites.

  13. Packaging Technologies for 500C SiC Electronics and Sensors

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu

    2013-01-01

    Various SiC electronics and sensors are currently under development for applications in 500C high temperature environments such as hot sections of aerospace engines and the surface of Venus. In order to conduct long-term test and eventually commercialize these SiC devices, compatible packaging technologies for the SiC electronics and sensors are required. This presentation reviews packaging technologies developed for 500C SiC electronics and sensors to address both component and subsystem level packaging needs for high temperature environments. The packaging system for high temperature SiC electronics includes ceramic chip-level packages, ceramic printed circuit boards (PCBs), and edge-connectors. High temperature durable die-attach and precious metal wire-bonding are used in the chip-level packaging process. A high temperature sensor package is specifically designed to address high temperature micro-fabricated capacitive pressure sensors for high differential pressure environments. This presentation describes development of these electronics and sensor packaging technologies, including some testing results of SiC electronics and capacitive pressure sensors using these packaging technologies.

  14. Amorphous carbon for structured step bunching during graphene growth on SiC

    NASA Astrophysics Data System (ADS)

    Palmer, James; Kunc, Jan; Hu, Yike; Hankinson, John; Guo, Zelei; Berger, Claire; de Heer, Walt

    2014-03-01

    Structured growth of high quality graphene is necessary for technological development of carbon based materials. Specifically, control of the bunching and placement of surface steps under epitaxial graphene on SiC is an important consideration for graphene device production. We demonstrate lithographically patterned evaporated amorphous carbon as a method to pin SiC surface steps. Evaporated amorphous carbon is an ideal step-flow barrier on SiC due to its chemical compatibility with graphene growth and its structural stability at high temperatures, as well as its patternability. The amorphous carbon is deposited in vacuum on SiC prior to graphene growth. In the graphene furnace at temperatures above 1200°C, mobile SiC steps accumulate at these amorphous carbon barriers, forming an aligned step free region for graphene growth at temperatures above 1330°C. AFM imaging and Raman spectroscopy support the formation of quality step-free graphene sheets grown on SiC with the step morphology aligned to the carbon grid.

  15. The Development of SiC MOSFET-based Switching Power Amplifiers for Fusion Science

    NASA Astrophysics Data System (ADS)

    Prager, James; Ziemba, Timothy; Miller, Kenneth; Picard, Julian

    2015-11-01

    Eagle Harbor Technologies (EHT), Inc. is developing a switching power amplifier (SPA) based on silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET). SiC MOSFETs offer many advantages over IGBTs including lower drive energy requirements, lower conduction and switching losses, and higher switching frequency capabilities. When comparing SiC and traditional silicon-based MOSFETs, SiC MOSFETs provide higher current carrying capability allowing for smaller package weights and sizes and lower operating temperature. EHT has conducted single device testing that directly compares the capabilities of SiC MOSFETs and IGBTs to demonstrate the utility of SiC MOSFETs for fusion science applications. These devices have been built into a SPA that can drive resistive loads and resonant tank loads at 800 V, 4.25 kA at pulse repetition frequencies up to 1 MHz. During the Phase II program, EHT will finalize the design of the SPA. In Year 2, EHT will replace the SPAs used in the HIT-SI lab at the University of Washington to allow for operation over 100 kHz. SPA prototype results will be presented. This work is supported under DOE Grant # DE-SC0011907.

  16. The role of carbon surface diffusion on the growth of epitaxial graphene on SiC.

    SciTech Connect

    Thurmer, Konrad; Ohta, Taisuke; Nie, Shu; Bartelt, Norman Charles; Kellogg, Gary Lee

    2010-03-01

    Growth of high quality graphene films on SiC is regarded as one of the more viable pathways toward graphene-based electronics. Graphitic films form on SiC at elevated temperature because of preferential sublimation of Si. Little is known, however, about the atomistic processes of interrelated SiC decomposition and graphene growth. We have observed the formation of graphene on SiC by Si sublimation in an Ar atmosphere using low energy electron microscopy, scanning tunneling microcopy and atomic force microscopy. This work reveals that the growth mechanism depends strongly on the initial surface morphology, and that carbon diffusion governs the spatial relationship between SiC decomposition and graphene growth. Isolated bilayer SiC steps generate narrow ribbons of graphene, whereas triple bilayer steps allow large graphene sheets to grow by step flow. We demonstrate how graphene quality can be improved by controlling the initial surface morphology specifically by avoiding the instabilities inherent in diffusion-limited growth.

  17. Modeling and testing miniature torsion specimens for SiC joining development studies for fusion

    DOE PAGES

    Henager, Jr., C. H.; Nguyen, Ba N.; Kurtz, Richard J.; Roosendaal, T. J.; Borlaug, B. A.; Ferraris, Monica; Ventrella, A.; Katoh, Yutai

    2015-08-05

    The international fusion community has designed a miniature torsion specimen for neutron irradiation studies of joined SiC and SiC/SiC composite materials. For this research, miniature torsion joints based on this specimen design were fabricated using displacement reactions between Si and TiC to produce Ti3SiC2 + SiC joints with SiC and tested in torsion-shear prior to and after neutron irradiation. However, many miniature torsion specimens fail out-of-plane within the SiC specimen body, which makes it problematic to assign a shear strength value to the joints and makes it difficult to compare unirradiated and irradiated strengths to determine irradiation effects. Finite elementmore » elastic damage and elastic–plastic damage models of miniature torsion joints are developed that indicate shear fracture is more likely to occur within the body of the joined sample and cause out-of-plane failures for miniature torsion specimens when a certain modulus and strength ratio between the joint material and the joined material exists. The model results are compared and discussed with regard to unirradiated and irradiated test data for a variety of joint materials. The unirradiated data includes Ti3SiC2 + SiC/CVD-SiC joints with tailored joint moduli, and includes steel/epoxy and CVD-SiC/epoxy joints. Finally, the implications for joint data based on this sample design are discussed.« less

  18. Si/C hybrid nanostructures for Li-ion anodes: An overview

    NASA Astrophysics Data System (ADS)

    Terranova, Maria Letizia; Orlanducci, Silvia; Tamburri, Emanuela; Guglielmotti, Valeria; Rossi, Marco

    2014-01-01

    This review article summarizes recent and increasing efforts in the development of novel Li ion cell anode nanomaterials based on the coupling of C with Si. The rationale behind such efforts is based on the fact that the Si-C coupling realizes a favourable combination of the two materials properties, such as the high lithiation capacity of Si and the mechanical and conductive properties of C, making Si/C hybrid nanomaterials the ideal candidates for innovative and improved Li-ion anodes. Together with an overview of the methodologies proposed in the last decade for material preparation, a discussion on relationship between organization at the nanoscale of the hybrid Si/C systems and battery performances is given. An emerging indication is that the enhancement of the batteries efficiency in terms of mass capacity, energy density and cycling stability, resides in the ability to arrange Si/C bi-component nanostructures in pre-defined architectures. Starting from the results obtained so far, this paper aims to indicate some emerging directions and to inspire promising routes to optimize fabrication of Si/C nanomaterials and engineering of Li-ion anodes structures. The use of Si/C hybrid nanostructures could represents a viable and effective solution to the foreseen limits of present lithium ion technology.

  19. Sizing SiC Storage Inverters for Fast Grid Frequency Support

    SciTech Connect

    Hoke, Anderson; Bennion, Kevin; Gevorgian, Vahan; Chakraborty, Sudipta; Muljadi, Eduard

    2015-11-02

    As wind and solar displace synchronous generators whose inertia stabilizes the AC grid frequency on fast time scales, it has been proposed to use energy storage systems (ESSs) to mitigate frequency transient events. Such events require a rapid surge of power from the ESS, but they occur only rarely. The high temperature tolerance of SiC MOSFETs and diodes presents an opportunity for innovative ESS inverter designs. Herein we investigate a SiC ESS inverter design such that the SiC device ratings are obeyed during mild frequency events but are exceeded during rare, major events, for a potentially more economical inverter design. In support of this proposal we present: 1. An analysis of four years of grid frequency events in the U.S. Western Interconnection. 2. A switch-level ESS inverter simulation using SiC devices with detailed loss estimates. 3. Thermal analysis of the SiC power modules during a worst-case frequency event, showing that the modules can likely withstand the brief overcurrent. This analysis supports the conclusion that it may be advantageous for economical designs (acknowledging the increased risks) to undersize the SiC switches when designing inverters to perform active power control for grid frequency support. Such a strategy may result in SiC-based designs being more competitive with less costly silicon IGBT-based designs.

  20. Effect of Ductile Agents on the Dynamic Behavior of SiC3D Network Composites

    NASA Astrophysics Data System (ADS)

    Zhu, Jingbo; Wang, Yangwei; Wang, Fuchi; Fan, Qunbo

    2016-10-01

    Co-continuous SiC ceramic composites using pure aluminum, epoxy, and polyurethane (PU) as ductile agents were developed. The dynamic mechanical behavior and failure mechanisms were investigated experimentally using the split Hopkinson pressure bar (SHPB) method and computationally by finite element (FE) simulations. The results show that the SiC3D/Al composite has the best overall performance in comparison with SiC3D/epoxy and SiC3D/PU composites. FE simulations are generally consistent with experimental data. These simulations provide valuable help in predicting mechanical strength and in interpreting the experimental results and failure mechanisms. They may be combined with micrographs for fracture characterizations of the composites. We found that interactions between the SiC phase and ductile agents under dynamic compression in the SHPB method are complex, and that interfacial condition is an important parameter that determines the mechanical response of SiC3D composites with a characteristic interlocking structure during dynamic compression. However, the effect of the mechanical properties of ductile agents on dynamic behavior of the composites is a second consideration in the production of the composites.

  1. Modeling and testing miniature torsion specimens for SiC joining development studies for fusion

    NASA Astrophysics Data System (ADS)

    Henager, C. H.; Nguyen, B. N.; Kurtz, R. J.; Roosendaal, T. J.; Borlaug, B. A.; Ferraris, M.; Ventrella, A.; Katoh, Y.

    2015-11-01

    The international fusion community has designed a miniature torsion specimen for neutron irradiation studies of joined SiC and SiC/SiC composite materials. Miniature torsion joints based on this specimen design were fabricated using displacement reactions between Si and TiC to produce Ti3SiC2 + SiC joints with SiC and tested in torsion-shear prior to and after neutron irradiation. However, many miniature torsion specimens fail out-of-plane within the SiC specimen body, which makes it problematic to assign a shear strength value to the joints and makes it difficult to compare unirradiated and irradiated strengths to determine irradiation effects. Finite element elastic damage and elastic-plastic damage models of miniature torsion joints are developed that indicate shear fracture is more likely to occur within the body of the joined sample and cause out-of-plane failures for miniature torsion specimens when a certain modulus and strength ratio between the joint material and the joined material exists. The model results are compared and discussed with regard to unirradiated and irradiated test data for a variety of joint materials. The unirradiated data includes Ti3SiC2 + SiC/CVD-SiC joints with tailored joint moduli, and includes steel/epoxy and CVD-SiC/epoxy joints. The implications for joint data based on this sample design are discussed.

  2. Nanoscale SiC production by ballistic ion beam mixing of C/Si multilayer structures

    NASA Astrophysics Data System (ADS)

    Battistig, G.; Zolnai, Z.; Németh, A.; Panjan, P.; Menyhárd, M.

    2016-05-01

    The ion beam-induced mixing process using Ar+, Ga+, and Xe+ ion irradiation has been used to form SiC rich layers on the nanometer scale at the interfaces of C/Si/C/Si/C multilayer structures. The SiC depth distributions were determined by Auger electron spectroscopy (AES) depth profiling and were compared to the results of analytical models developed for ballistic ion mixing and local thermal spike induced mixing. In addition, the measured SiC depth distributions were correlated to the Si and C mixing profiles simulated by the TRIDYN code which can follow the ballistic ion mixing process as a function of ion fluence. Good agreement has been found between the distributions provided by AES depth profiling and TRIDYN on the assumption that the majority of the Si (C) atoms transported to the neighboring C (Si) layer form the SiC compound. The ion beam mixing process can be successfully described by ballistic atomic transport processes. The results show that SiC production as a function of depth can be predicted, and tailored compound formation on the nanoscale becomes feasible, thus leading to controlled synthesis of protective SiC coatings at room temperature.

  3. SiC detector damage and characterization for high intensity laser-plasma diagnostics

    NASA Astrophysics Data System (ADS)

    Torrisi, L.; Cannavò, A.

    2016-05-01

    Silicon-Carbide (SiC) detectors are always more extensively employed as diagnostics in laser-generated plasma due to their remarkable properties such as their high band gap, high carrier velocity, high detection efficiency, high radiation resistance and low leakage current at room temperature. SiC detectors, in comparison with Si detectors, have the advantage of being insensitive to visible light, having low reverse current at high temperature and high radiation hardness. A similar energy resolution characterizes the two types of detectors, being 0.8% in Si and 1.0% in SiC, as measured detecting 5.8 MeV alpha particles. Generally, SiC detectors are employed as laser-plasma diagnostics in time-of-flight configuration, permitting the simultaneous detection of photons, electrons and ions based on discrimination of velocity. SiC detectors can be employed in the proportionality regime, because their response is proportional to the radiation energy deposited in the active layer. Using thin absorbers in front of the detectors makes it possible to have further information on the radiation nature, intensity and energy. Surface characterization of SiC before and after prolonged exposure to hot plasma laser generated shows the formation of bulk defects and thin film deposition on the detector surface limiting the device functionality.

  4. Clean Energy Manufacturing Initiative

    SciTech Connect

    2013-04-01

    The initiative will strategically focus and rally EERE’s clean energy technology offices and Advanced Manufacturing Office around the urgent competitive opportunity for the United States to be the leader in the clean energy manufacturing industries and jobs of today and tomorrow.

  5. Heat pipe manufacturing study

    NASA Technical Reports Server (NTRS)

    Edelstein, F.

    1974-01-01

    Heat pipe manufacturing methods are examined with the goal of establishing cost effective procedures that will ultimately result in cheaper more reliable heat pipes. Those methods which are commonly used by all heat pipe manufacturers have been considered, including: (1) envelope and wick cleaning, (2) end closure and welding, (3) mechanical verification, (4) evacuation and charging, (5) working fluid purity, and (6) charge tube pinch off. The study is limited to moderate temperature aluminum and stainless steel heat pipes with ammonia, Freon-21 and methanol working fluids. Review and evaluation of available manufacturers techniques and procedures together with the results of specific manufacturing oriented tests have yielded a set of recommended cost-effective specifications which can be used by all manufacturers.

  6. Theoretical and electron paramagnetic resonance studies of hyperfine interaction in nitrogen doped 4H and 6H SiC

    SciTech Connect

    Szász, K.; Gali, A.

    2014-02-21

    Motivated by recent experimental findings on the hyperfine signal of nitrogen donor (N{sub C}) in 4 H and 6 H SiC, we calculate the hyperfine tensors within the framework of density functional theory. We find that there is negligible hyperfine coupling with {sup 29}Si isotopes when N{sub C} resides at h site both in 4 H and 6 H SiC. We observe measurable hyperfine coupling to a single {sup 29}Si at k site in 4 H SiC and k{sub 1} site in 6 H SiC. Our calculations unravel that such {sup 29}Si hyperfine coupling does not occur at k{sub 2} site in 6 H SiC. Our findings are well corroborated by our new electron paramagnetic resonance studies in nitrogen doped 6 H SiC.

  7. Microwave Absorption Properties of Ni-Foped SiC Powders in the 2-18 GHz Frequency Range

    NASA Astrophysics Data System (ADS)

    Jin, Hai-Bo; Li, Dan; Cao, Mao-Sheng; Dou, Yan-Kun; Chen, Tao; Wen, Bo; Simeon, Agathopoulos

    2011-03-01

    Ni-doped SiC powder with improved dielectric and microwave absorption properties was prepared by self-propagating high-temperature synthesis (SHS). The XRD analysis of the as-synthesized powders suggests that Ni is accommodated in the sites of Si in the lattice of SiC, which shrinks in the presence of Ni. The experimental results show an improvement in the dielectric properties of the Ni-doped SiC powder in the frequency range of 2-18 GHz. The bandwidth of the reflection loss below -10 dB is broadened from 3.04 (for pure SiC) to 4.56 GHz (for Ni-doped SiC), as well as the maximum reflection loss of produced powders from 13.34 to 22.57 dB, indicating that Ni-doped SiC could be used as an effective microwave absorption material.

  8. Flexible Manufacturing Systems: What's in It for the Manufacturer.

    ERIC Educational Resources Information Center

    Chowdhury, A. R.; Peckman, Donald C.

    1987-01-01

    The authors define the Flexible Manufacturing System and outline its history. They describe what the processing time includes and provide advantages and disadvantages of Flexible Manufacturing Systems compared to conventional manufacturing. (CH)

  9. SiC Die Attach for High-Temperature Applications

    NASA Astrophysics Data System (ADS)

    Drevin-Bazin, A.; Lacroix, F.; Barbot, J.-F.

    2013-11-01

    Eutectic solders AuIn19 and AuGe12 and nanosilver paste were investigated for SiC die attach in high-temperature (300°C) applications. The soldering or sintering conditions were optimized through die shear tests performed at room temperature. In particular, application of static pressure (3.5 MPa) during sintering resulted in greatly improved mechanical behavior of the nanosilver-based joint. Microstructural study of the eutectic solders showed formation of Au-rich grains in AuGe die attach and significant diffusion of Au and In through the Ni layer in AuIn19 die attach, which could lead to formation of intermetallic compounds. Die shear tests versus temperature showed that the behaviors of the studied die attaches are different; nevertheless they present suitable shear strengths required for high-temperature applications. The mechanical behavior of joints under various levels of thermal and mechanical stress was also studied. Creep experiments were carried out on the eutectic solders to describe the thermomechanical behavior of the complete module; only one creep mechanism was observed in the working range.

  10. Exciton-polariton state in nanocrystalline SiC films

    NASA Astrophysics Data System (ADS)

    Semenov, A. V.; Lopin, A. V.

    2016-05-01

    We studied the features of optical absorption in the films of nanocrystalline SiC (nc-SiC) obtained on the sapphire substrates by the method of direct ion deposition. The optical absorption spectra of the films with a thickness less than ~500 nm contain a maximum which position and intensity depend on the structure and thickness of the nc-SiC films. The most intense peak at 2.36 eV is observed in the nc-SiC film with predominant 3C-SiC polytype structure and a thickness of 392 nm. Proposed is a resonance absorption model based on excitation of exciton polaritons in a microcavity. In the latter, under the conditions of resonance, there occurs strong interaction between photon modes of light with λph=521 nm and exciton of the 3С polytype with an excitation energy of 2.36 eV that results in the formation of polariton. A mismatch of the frequencies of photon modes of the cavity and exciton explains the dependence of the maximum of the optical absorption on the film thickness.

  11. Development of Cu Reinforced SiC Particulate Composites

    NASA Astrophysics Data System (ADS)

    Singh, Harshpreet; Kumar, Lailesh; Nasimul Alam, Syed

    2015-02-01

    This paper presents the results of Cu-SiCp composites developed by powder metallurgy route and an attempt has been made to make a comparison between the composites developed by using unmilled Cu powder and milled Cu powder. SiC particles as reinforcement was blended with unmilled and as-milled Cu powderwith reinforcement contents of 10, 20, 30, 40 vol. % by powder metallurgy route. The mechanical properties of pure Cu and the composites developed were studied after sintering at 900°C for 1 h. Density of the sintered composites were found out based on the Archimedes' principle. X-ray diffraction of all the composites was done in order to determine the various phases in the composites. Scanning electron microscopy (SEM) and EDS (electron diffraction x-ray spectroscopy) was carried out for the microstructural analysis of the composites. Vickers microhardness tester was used to find out the hardness of the samples. Wear properties of the developed composites were also studied.

  12. Rapid small lot manufacturing

    SciTech Connect

    Harrigan, R.W.

    1998-05-09

    The direct connection of information, captured in forms such as CAD databases, to the factory floor is enabling a revolution in manufacturing. Rapid response to very dynamic market conditions is becoming the norm rather than the exception. In order to provide economical rapid fabrication of small numbers of variable products, one must design with manufacturing constraints in mind. In addition, flexible manufacturing systems must be programmed automatically to reduce the time for product change over in the factory and eliminate human errors. Sensor based machine control is needed to adapt idealized, model based machine programs to uncontrolled variables such as the condition of raw materials and fabrication tolerances.

  13. Matrix-grain-bridging contributions to the toughness of SiC composites with alumina-coated SiC platelets

    SciTech Connect

    Cao, J.J.; He, Y.; MoberlyChan, W.J.; De Jonghe, L.C. |

    1996-05-01

    Silicon carbide composites were fabricated through the incorporation of alumina-coated SiC platelets into a SiC matrix. Mechanical properties were evaluated in direct comparison with a commercial Hexoloy SiC. The fracture toughness of the composite, with a fine grained {beta}-SiC matrix, was twice that of the commercial material. The alumina-coating on the platelets provided a weak interface to promote crack deflection and platelet bridging, as well as easing densification of the composites. On the other hand, a three-fold increase in fracture toughness (9.1 MPa {radical}m) of an in situ toughened monolithic SiC was achieved by processing at higher temperatures, promoting the {beta}-to-{alpha} phase transformation and forming a microstructure containing high-aspect-ration plate-shaped grains. Efforts were made to combine the effects of coated-platelets reinforcement and in situ toughening in the matrix. Moderate high toughness (8 MPa {radical}m) was achieved by coupled toughening. The contribution of matrix-grain-bridging, however, was limited by the processing temperature at which the oxide coating was stable.

  14. Experimental Investigation of Mechanical and Thermal properties of sisal fibre reinforced composite and effect of sic filler material

    NASA Astrophysics Data System (ADS)

    Surya Teja, Malla; Ramana, M. V.; Sriramulu, D.; Rao, C. J.

    2016-09-01

    With a view of exploring the potential use of natural recourses, we made an attempt to fabricate sisal fibre polymer composites by hand lay-up method. Natural fiber composites are renewable, cheap and biodegradable. Their easy availability, lower density, higher specific properties, lower cost, satisfactory mechanical and thermal properties, non-corrosive nature, makes them an attractive ecological alternative to glass, carbon or other man-made synthetic fibers. In this work, the effect of SiC on mechanical and thermal properties of natural sisal fiber composites are investigated. The composite has been made with and without SiC incorporating natural sisal fiber with polyester as bonding material. The experimental outcomes exhibited that the tensile strength of composite with 10%SiC 2.53 times greater than that of composite without SiC. The impact strength of composite with 10% SiC is 1.73 times greater than that of composite without SiC plain polyester. Thermal properties studied include thermal conductivity, specific heat capacity, thermal diffusivity, thermal degradation and stability. Three different samples with 0%, 5%, 10% SiC powder are considered. With the addition of SiC filler powder, thermal conductivity increases, specific heat capacity gradually increases then decreases, thermal diffusivity increases and thermal stability improves with Sic powder.

  15. The streptococcal inhibitor of complement (SIC) protects Streptococcus pyogenes from bacteriocin-like inhibitory substance (BLIS) from Streptococcus salivarius.

    PubMed

    Minami, Masaaki; Ohmori, Daisuke; Tatsuno, Ichiro; Isaka, Masanori; Kawamura, Yoshiaki; Ohta, Michio; Hasegawa, Tadao

    2009-09-01

    Streptococcus salivarius inhibits the growth of Streptococcus pyogenes in vitro. Streptococcus pyogenes has various virulence factors, including the streptococcus inhibitor of complement (SIC). Although SIC inhibits the activity of the peptides LL-37 and NAP1, the relationship between SIC and the bacteriocin-like inhibitory substance (BLIS) has not been elucidated. Here, we evaluated whether S. salivarius BLIS affects S. pyogenes SIC. We created three deltasic mutant strains from three S. pyogenes strains and performed deferred antagonism assays. The test strains were BLIS-positive S. salivarius JCM5707 and BLIS-negative S. salivarius NCU12. Deferred antagonism assays with JCM5707 showed that the inhibitory zones in the three deltasic mutant strains were wider than those in the three wild-type strains. Streptococcus pyogenes was cultured in BLIS-containing broth and the change in SIC in the supernatant was assessed by two-dimensional gel electrophoresis (2-DE). The 2-DE analysis of S. pyogenes exoproteins with the JCM5707 supernatant showed reduced SIC compared with those without the JCM5707 supernatant. Changes in sic mRNA levels affected by S. salivarius BLIS were evaluated by a reverse transcriptase-PCR. The sic mRNA level was affected more by the BLIS-positive S. salivarius than by the BLIS-negative strain. Our result indicates that SIC plays a role in the inhibition of S. salivarius BLIS. PMID:19594623

  16. SiC JFET Transistor Circuit Model for Extreme Temperature Range

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.

    2008-01-01

    A technique for simulating extreme-temperature operation of integrated circuits that incorporate silicon carbide (SiC) junction field-effect transistors (JFETs) has been developed. The technique involves modification of NGSPICE, which is an open-source version of the popular Simulation Program with Integrated Circuit Emphasis (SPICE) general-purpose analog-integrated-circuit-simulating software. NGSPICE in its unmodified form is used for simulating and designing circuits made from silicon-based transistors that operate at or near room temperature. Two rapid modifications of NGSPICE source code enable SiC JFETs to be simulated to 500 C using the well-known Level 1 model for silicon metal oxide semiconductor field-effect transistors (MOSFETs). First, the default value of the MOSFET surface potential must be changed. In the unmodified source code, this parameter has a value of 0.6, which corresponds to slightly more than half the bandgap of silicon. In NGSPICE modified to simulate SiC JFETs, this parameter is changed to a value of 1.6, corresponding to slightly more than half the bandgap of SiC. The second modification consists of changing the temperature dependence of MOSFET transconductance and saturation parameters. The unmodified NGSPICE source code implements a T(sup -1.5) temperature dependence for these parameters. In order to mimic the temperature behavior of experimental SiC JFETs, a T(sup -1.3) temperature dependence must be implemented in the NGSPICE source code. Following these two simple modifications, the Level 1 MOSFET model of the NGSPICE circuit simulation program reasonably approximates the measured high-temperature behavior of experimental SiC JFETs properly operated with zero or reverse bias applied to the gate terminal. Modification of additional silicon parameters in the NGSPICE source code was not necessary to model experimental SiC JFET current-voltage performance across the entire temperature range from 25 to 500 C.

  17. 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.

  18. 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.

  19. Effect of SiC particles on microarc oxidation process of magnesium matrix composites

    NASA Astrophysics Data System (ADS)

    Wang, Y. Q.; Wang, X. J.; Gong, W. X.; Wu, K.; Wang, F. H.

    2013-10-01

    SiC particles are an important reinforced phase in metal matrix composites. Their effect on the microarc oxidation (MAO, also named plasma electrolytic oxidation-PEO) process of SiCp/AZ91 Mg matrix composites (MMCs) was studied and the mechanism was revealed. The corrosion resistance of MAO coating was also investigated. Voltage-time curves during MAO were recorded to study the barrier film status on the composites. Scanning electron microscopy was used to characterize the existing state of SiC particles in MAO. Energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy were used to analyze the chemical composition of the coating. Corrosion resistance of the bare and coated composites was evaluated by potentiodynamic polarization curves in 3.5% NaCl solution. Results showed that the integrality and electrical insulation properties of the barrier film on the composites were destroyed by the SiC particles. Consequently, the sparking discharge at the early stage of MAO was inhibited, and the growth efficiency of the MAO coating decreased with the increase in the volume fraction of SiC particles. SiC particles did not exist stably during MAO; they were oxidized or partially oxidized into SiO2 before the overall sparking discharge. The transformation from semi-conductive SiC to insulating SiO2 by oxidation restrained the current leakage at the original SiC positions and then promoted sparking discharge and coating growth. The corrosion current density of SiCp/AZ91 MMCs was reduced by two orders of magnitude after MAO treatment. However, the corrosion resistances of the coated composites were lower than that of the coated alloy.

  20. Wear Behaviour of Al-6061/SiC Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Mishra, Ashok Kumar; Srivastava, Rajesh Kumar

    2016-06-01

    Aluminium Al-6061 base composites, reinforced with SiC particles having mesh size of 150 and 600, which is fabricated by stir casting method and their wear resistance and coefficient of friction has been investigated in the present study as a function of applied load and weight fraction of SiC varying from 5, 10, 15, 20, 25, 30, 35 and 40 %. The dry sliding wear properties of composites were investigated by using Pin-on-disk testing machine at sliding velocity of 2 m/s and sliding distance of 2000 m over a various loads of 10, 20 and 30 N. The result shows that the reinforcement of the metal matrix with SiC particulates up to weight percentage of 35 % reduces the wear rate. The result also show that the wear of the test specimens increases with the increasing load and sliding distance. The coefficient of friction slightly decreases with increasing weight percentage of reinforcements. The wear surfaces are examined by optical microscopy which shows that the large grooved regions and cavities with ceramic particles are found on the worn surface of the composite alloy. This indicates an abrasive wear mechanism, which is essentially a result of hard ceramic particles exposed on the worn surfaces. Further, it was found from the experimentation that the wear rate decreases linearly with increasing weight fraction of SiC and average coefficient of friction decreases linearly with increasing applied load, weight fraction of SiC and mesh size of SiC. The best result has been obtained at 35 % weight fraction and 600 mesh size of SiC.

  1. Agile manufacturing concept

    NASA Astrophysics Data System (ADS)

    Goldman, Steven L.

    1994-03-01

    The initial conceptualization of agile manufacturing was the result of a 1991 study -- chaired by Lehigh Professor Roger N. Nagel and California-based entrepreneur Rick Dove, President of Paradigm Shifts, International -- of what it would take for U.S. industry to regain global manufacturing competitiveness by the early twenty-first century. This industry-led study, reviewed by senior management at over 100 companies before its release, concluded that incremental improvement of the current system of manufacturing would not be enough to be competitive in today's global marketplace. Computer-based information and production technologies that were becoming available to industry opened up the possibility of an altogether new system of manufacturing, one that would be characterized by a distinctive integration of people and technologies; of management and labor; of customers, producers, suppliers, and society.

  2. Computers in Manufacturing.

    ERIC Educational Resources Information Center

    Hudson, C. A.

    1982-01-01

    Advances in factory computerization (computer-aided design and computer-aided manufacturing) are reviewed, including discussions of robotics, human factors engineering, and the sociological impact of automation. (JN)

  3. 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.

  4. High-Temperature SiC Power Module with Integrated SiC Gate Drivers for Future High-Density Power Electronics Applications

    SciTech Connect

    Whitaker, Mr. Bret; Cole, Mr. Zach; Passmore, Mr. Brandon; Martin, Daniel; Mcnutt, Tyler; Lostetter, Dr. Alex; Ericson, Milton Nance; Frank, Steven Shane; Britton Jr, Charles L; Marlino, Laura D; Mantooth, Alan; Francis, Dr. Matt; Lamichhane, Ranjan; Shepherd, Dr. Paul; Glover, Dr. Michael

    2014-01-01

    This paper presents the testing results of an all-silicon carbide (SiC) intelligent power module (IPM) for use in future high-density power electronics applications. The IPM has high-temperature capability and contains both SiC power devices and SiC gate driver integrated circuits (ICs). The high-temperature capability of the SiC gate driver ICs allows for them to be packaged into the power module and be located physically close to the power devices. This provides a distinct advantage by reducing the gate driver loop inductance, which promotes high frequency operation, while also reducing the overall volume of the system through higher levels of integration. The power module was tested in a bridgeless-boost converter to showcase the performance of the module in a system level application. The converter was initially operated with a switching frequency of 200 kHz with a peak output power of approximately 5 kW. The efficiency of the converter was then evaluated experimentally and optimized by increasing the overdrive voltage on the SiC gate driver ICs. Overall a peak efficiency of 97.7% was measured at 3.0 kW output. The converter s switching frequency was then increased to 500 kHz to prove the high frequency capability of the power module was then pushed to its limits and operated at a switching frequency of 500 kHz. With no further optimization of components, the converter was able to operate under these conditions and showed a peak efficiency of 95.0% at an output power of 2.1 kW.

  5. Manufacturing information system

    NASA Astrophysics Data System (ADS)

    Allen, D. K.; Smith, P. R.; Smart, M. J.

    1983-12-01

    The size and cost of manufacturing equipment has made it extremely difficult to perform realistic modeling and simulation of the manufacturing process in university research laboratories. Likewise the size and cost factors, coupled with many uncontrolled variables of the production situation has even made it difficult to perform adequate manufacturing research in the industrial setting. Only the largest companies can afford manufacturing research laboratories; research results are often held proprietary and seldom find their way into the university classroom to aid in education and training of new manufacturing engineers. It is the purpose for this research to continue the development of miniature prototype equipment suitable for use in an integrated CAD/CAM Laboratory. The equipment being developed is capable of actually performing production operations (e.g. drilling, milling, turning, punching, etc.) on metallic and non-metallic workpieces. The integrated CAD/CAM Mini-Lab is integrating high resolution, computer graphics, parametric design, parametric N/C parts programmings, CNC machine control, automated storage and retrieval, with robotics materials handling. The availability of miniature CAD/CAM laboratory equipment will provide the basis for intensive laboratory research on manufacturing information systems.

  6. GEM detector conductor manufacturing experience

    SciTech Connect

    Martovetsky, N.N.; Pace, J.R.; Reardon, P.J.; Richied, D.E.; Camille, R.J.; Marston, P.G.; Smith, B.A.; Deis, G.A.; Bohanan, J.S.; Gertsen, J.H.

    1994-10-07

    Feasibility studies and manufacturing experience on the GEM Magnet superconductor are presented, including all components - NbTi strand, cable, conduit manufacture, cable pulling, and aluminum sheath application.

  7. Surface characteristics and corrosion behaviour of WE43 magnesium alloy coated by SiC film

    NASA Astrophysics Data System (ADS)

    Li, M.; Cheng, Y.; Zheng, Y. F.; Zhang, X.; Xi, T. F.; Wei, S. C.

    2012-01-01

    Amorphous SiC film has been successfully fabricated on the surface of WE43 magnesium alloy by plasma enhanced chemical vapour deposition (PECVD) technique. The microstructure and elemental composition were analyzed by transmission electron microscopy (TEM), glancing angle X-ray diffraction (GAXRD) and X-ray photoelectron spectroscopy (XPS), respectively. The immersion test indicated that SiC film could efficiently slow down the degradation rate of WE43 alloy in simulated body fluid (SBF) at 37 ± 1 °C. The indirect toxicity experiment was conducted using L929 cell line and the results showed that the extraction medium of SiC coated WE43 alloys exhibited no inhibitory effect on L929 cell growth. The in vitro hemocompatibility of the samples was investigated by hemolysis test and blood platelets adhesion test, and it was found that the hemolysis rate of the coated WE43 alloy decreased greatly, and the platelets attached on the SiC film were slightly activated with a round shape. It could be concluded that SiC film prepared by PECVD made WE43 alloy more appropriate to biomedical application.

  8. 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.

  9. Fabrication and properties of ultraviolet photo-detectors based on SiC nanowires

    NASA Astrophysics Data System (ADS)

    Peng, Gang; Zhou, YingQiu; He, YanLan; Yu, XiaoYan; Li, GongYi

    2012-07-01

    A new type of ultraviolet photo-detectors (UVPDs) based on a bundle of highly aligned SiC nanowires was fabricated and the photo-electric properties of the UVPDs including I-V characteristics and time response were studied in this work. SiC nanowires were prepared by pyrolysis of a polymer precursor with ferrocene as the catalyst by a CVD route. The diameters of SiC nanowires varied from 100 to 200 nm while they were some centimeters long and the SiC nanowires were with zinc blended cubic form ( β-SiC) tested by X-ray diffraction. A bundle of nanowires was fixed onto two legs' base by conductive silver paste to form the UVPDs. The electrical measurement of the device showed a significant increase of current when the device was exposed to 254 nm UV light, and the rising time of the device is very short, but the falling time is relatively long. Our results show that the UVPDs based on SiC nanowires have excellent electrical and optical properties which can be potentially applied.

  10. Grain boundary diffusion of Ag through polycrystalline SiC in TRISO fuel particles

    NASA Astrophysics Data System (ADS)

    Deng, Jie; Ko, Hyunseok; Demkowicz, Paul; Morgan, Dane; Szlufarska, Izabela

    2015-12-01

    The effective diffusivity and release fraction of Ag in polycrystalline SiC are evaluated using a kinetic Monte Carlo model. The effects of various grain boundary network properties on the transport of Ag across the SiC layer have been examined, including fraction of grain boundary type, spread in grain boundary diffusivities and distribution of grain boundary types. It is shown that the effective diffusivity and release fraction of Ag can exhibit a large variability due to changes in the GB structure of SiC, and this variability is almost independent of temperature fluctuation. The present results suggest that the variation in properties of grain boundary networks in SiC may contribute to the spread in the Ag diffusivity and release fraction measured in TRISO particles. It is also found that the grain boundary diffusion alone may be insufficient to account for the Ag diffusivities and release fractions measured in integral release experiments. Additional factors such as irradiation and temperature distribution may also play an important role in Ag transport across the SiC layer.

  11. Silicon Carbide (SiC) MOSFET-based Full-Bridge for Fusion Science Applications

    NASA Astrophysics Data System (ADS)

    Ziemba, Timothy; Miller, Kenneth; Prager, James; Picard, Julian; Hashim, Akel

    2014-10-01

    Switching power amplifiers (SPAs) have a wide variety of applications within the fusion science community, including feedback and control systems for dynamic plasma stabilization in tokamaks, inductive and arc plasma sources, Radio Frequency (RF) helicity and flux injection, RF plasma heating and current drive schemes, ion beam generation, and RF pre-ionizer systems. SiC MOSFETs offer many advantages over IGBTs including lower drive energy requirements, lower conduction and switching losses, and higher switching frequency capabilities. When comparing SiC and traditional silicon-based MOSFETs, SiC MOSFETs provide higher current carrying capability allowing for smaller package weights and sizes and lower operating temperature. Eagle Harbor Technologies (EHT) is designing, constructing, and testing a SiC MOSFET-based full-bridge SPA. EHT will leverage the proprietary gate drive technology previously developed with the support of a DOE SBIR, which will enable fast, efficient switching in a small form factor. The primary goal is to develop a SiC MOSFET-based SPA for fusion science applications. Work supported in part by the DOE under Contract Number DE-SC0011907.

  12. Anisotropic mechanical properties of hexagonal SiC sheet: a molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Yu, Ming; Liu, Emily; Zhang, Congyan

    2015-03-01

    The anisotropic mechanical properties of hexagonal SiC sheet have been studied using an efficient quantum mechanics molecular dynamics scheme based on a robust semi-empirical Hamiltonian (refereed as SCED-LCAO) [PRB 74, 15540; PHYSE 42, 1]. It was found that the SiC sheet could sustain the heavy load up to about 20 %. In particular, it was found that the SiC sheet also shows large difference in the strain direction. It will quickly crack after 20 % of strain in armchair the direction, but it will be slowly destroyed after 30% in the zigzag direction, indicating the anisotropic nature of the mechanical properties of the SiC sheet. The nominal and 2D membrane stresses will be analyzed, from where we will obtain the 2D Young's modulus at infinitesimal strain and the third-order (effective nonlinear) elastic modulus for the SiC sheet. The detail results and discussions will be reported in the presentation.

  13. CVD of SiC and AlN using cyclic organometallic precursors

    NASA Technical Reports Server (NTRS)

    Interrante, L. V.; Larkin, D. J.; Amato, C.

    1992-01-01

    The use of cyclic organometallic molecules as single-source MOCVD precursors is illustrated by means of examples taken from our recent work on AlN and SiC deposition, with particular focus on SiC. Molecules containing (AlN)3 and (SiC)2 rings as the 'core structure' were employed as the source materials for these studies. The organoaluminum amide, (Me2AlNH2)3, was used as the AlN source and has been studied in a molecular beam sampling apparatus in order to determine the gas phase species present in a hot-wall CVD reactor environment. In the case of SiC CVD, a series of disilacyclobutanes (Si(XX')CH2)2 (with X and X' = H, CH3, and CH2SiH2CH3), were examined in a cold-wall, hot-stage CVD reactor in order to compare their relative reactivities and prospective utility as single-source CVD precursors. The parent compound, disilacyclobutane, (SiH2CH2)2, was found to exhibit the lowest deposition temperature (ca. 670 C) and to yield the highest purity SiC films. This precursor gave a highly textured, polycrystalline film on the Si(100) substrates.

  14. High-fluence Si-implanted diamond: Optimum implantation temperature for SiC formation

    SciTech Connect

    Weishart, H.; Eichhorn, F.; Heera, V.; Pecz, B.; Barna, A.; Skorupa, W.

    2005-08-15

    In this paper the authors investigate the effect of implantation temperature on the structural properties of diamond implanted with high fluences of Si between 5.3x10{sup 17} Si cm{sup -2} and 1x10{sup 18} Si cm{sup -2}. In order to reduce radiation-induced damage and to enhance SiC formation the implantations were performed at elevated temperatures in the range from 900 to 1200 deg. C. Subsequently, all samples were annealed for 10 min at 1500 deg. C in a rf-heated furnace. X-ray diffraction revealed the formation of cubic SiC nanocrystallites in a buried layer inside the implanted diamond. The implantation-induced damage was assessed by analyzing graphitization of the surface-near layer using Raman spectroscopy. With increasing Si fluence the implantation-induced damage rises and the nearly perfect alignment of the formed SiC crystallites within the host diamond lattice deteriorates. However, raising the implantation temperature from 900 to 1000 deg. C reduces the damage in the diamond and increases the amount, size, and epitaxial alignment of the crystalline SiC precipitates. Further increase of the implantation temperature gives no improvement in the quality of the SiC-rich layer. Instead, the damaged diamond converts into graphite and the formation of SiC crystallites is obstructed.

  15. Microstructures of diffusion bonded SiC ceramics using Ti and Mo interlayers

    NASA Astrophysics Data System (ADS)

    Jung, Yang-Il; Kim, Sun-Han; Kim, Hyun-Gil; Park, Jeong-Yong; Kim, Weon-Ju

    2013-10-01

    SiC plates were diffusion bonded using metallic interlayers of Ti and Mo foils. For the joining, a uniaxial pressure of ∼7 MPa was applied at 1400 °C for 1 h in a vacuum. The interfacial microstructures along with their atomic compositions of the SiC/SiC joints were analyzed. For the Ti interlayer, Ti was converted into a Ti3SiC2 phase owing to the diffusion of silicon and carbon from the SiC part. A crystallographic orientation relationship was found between the SiC and Ti3SiC2 grains. At the middle of the Ti interlayer, a TiSi2 phase also existed, forming a dual-phase region. For the Mo interlayer, the diffusion of silicon into Mo induced the formation of the Mo5Si3C phase at the SiC/Mo interface. An unreacted metallic phase was still observed in the middle of the Mo insert. The shear strengths of the joints were 67 MPa and 76 MPa for the Ti and Mo interlayers, respectively.

  16. A new approach for fabrications of SiC based photodetectors.

    PubMed

    Aldalbahi, Ali; Li, Eric; Rivera, Manuel; Velazquez, Rafael; Altalhi, Tariq; Peng, Xiaoyan; Feng, Peter X

    2016-01-01

    We report on a new approach to quickly synthesize high-quality single crystalline wide band gap silicon carbide (SiC) films for development of high-performance deep ultraviolet (UV) photodetectors. The fabricated SiC based UV photodetectors exhibited high response while maintaining cost-effectiveness and size miniaturization. Focus of the experiments was on studies of electrical and electronic properties, as well as responsivity, response and recovery times, and repeatability of the deep UV photodetectors. Raman scattering spectroscopy and scanning electron microscope (SEM) were used to characterize the SiC materials. Analyses of the SEM data indicated that highly flat SiC thin films have been obtained. Based on the synthesized SiC, deep UV detectors are designed, fabricated, and tested with various UV wavelength lights at different radiation intensities. Temperature effect and bias effect on the photocurrent strength and signal-to-noise ratio, humidity effect on the response time and recovery time of the fabricated detectors have been carefully characterized and discussed. The detectors appear to have a very stable baseline and repeatability. The obtained responsivity is more than 40% higher compared to commercial detectors. The good performance of the photodetectors at operating temperature up to 300 °C remains nearly unchanged. PMID:26988399

  17. A new approach for fabrications of SiC based photodetectors

    PubMed Central

    Aldalbahi, Ali; Li, Eric; Rivera, Manuel; Velazquez, Rafael; Altalhi, Tariq; Peng, Xiaoyan; Feng, Peter X.

    2016-01-01

    We report on a new approach to quickly synthesize high-quality single crystalline wide band gap silicon carbide (SiC) films for development of high-performance deep ultraviolet (UV) photodetectors. The fabricated SiC based UV photodetectors exhibited high response while maintaining cost-effectiveness and size miniaturization. Focus of the experiments was on studies of electrical and electronic properties, as well as responsivity, response and recovery times, and repeatability of the deep UV photodetectors. Raman scattering spectroscopy and scanning electron microscope (SEM) were used to characterize the SiC materials. Analyses of the SEM data indicated that highly flat SiC thin films have been obtained. Based on the synthesized SiC, deep UV detectors are designed, fabricated, and tested with various UV wavelength lights at different radiation intensities. Temperature effect and bias effect on the photocurrent strength and signal-to-noise ratio, humidity effect on the response time and recovery time of the fabricated detectors have been carefully characterized and discussed. The detectors appear to have a very stable baseline and repeatability. The obtained responsivity is more than 40% higher compared to commercial detectors. The good performance of the photodetectors at operating temperature up to 300 °C remains nearly unchanged. PMID:26988399

  18. Design Study of Small Lead-Cooled Fast Reactors Using SiC Cladding and Structure

    SciTech Connect

    Abu Khalid Rivai; Minoru Takahashi

    2006-07-01

    Effects of SiC cladding and structure on neutronics of reactor core for small lead-cooled fast reactors have been investigated analytically. The fuel of this reactor was uranium nitride with {sup 235}U enrichment of 11% in inner core and 13% in outer core. The reactors were designed by optimizing the use of natural uranium blanket and nitride fuel to prolong the fuel cycle. The fuels can be used without re-shuffling for 15 years. The coolant of this reactor was lead. A calculation was also conducted for steel cladding and structure type as comparison with SiC cladding and structure type. The results of calculation indicated that the neutron energy spectrum of the core using SiC was slightly softer than that using steel. The SiC type reactor was designed to have criticality at the beginning of cycle (BOC), although the steel type reactor could not have critical condition with the same size and geometry. In other words, the SiC type core can be designed smaller than the steel type core. The result of the design analysis showed that neutron flux distributions and power distribution was made flatter because the outer core enrichment was higher than inner core. The peak power densities could remain constant over the reactor operation. The consumption capability of uranium was quite high, i.e. 13% for 125 MWt reactor and 25% for 375 MWt reactor at EOC. (authors)

  19. Development of multi-functional NITE-porous SiC for ceramic insulators

    NASA Astrophysics Data System (ADS)

    Park, Yi-Hyun; Hinoki, Tatsuya; Kohyama, Akira

    2009-04-01

    Porous silicon carbide (SiC) ceramics are being considered as functional materials for advanced energy systems due to their low thermal and electrical conductivity, low thermal-expansion coefficient, good thermal-shock resistance, and excellent mechanical and chemical stability at elevated temperature. However, conventional processing routes for SiC are complicated and conventional porous SiC shows poor mechanical and chemical stability at high temperature. Therefore, it is desirable to develop a simple fabrication method. In this study, porous SiC ceramic have been fabricated based on the NITE process, a recently developed processing technique for high performance SiC f/SiC composites. Ceramic porosity was calculated from relative and theoretical density, which was obtained by the rule of mixture. The port shape and size distribution were examined by optical microscopy and scanning electron microscopy. Mechanic properties were evaluated using three-point bend and tensile testing. Thermal conductivity was measured by the laser flash method from room temperature to 900 °C.

  20. Effect of a metal electrode on the radiation tolerance of a SiC neutron detector

    NASA Astrophysics Data System (ADS)

    Park, Junesic; Shin, Hee-Sung; Kim, Ho-Dong; Kim, Han Soo; Park, Se Hwan; Lee, Cheol Ho; Kim, Yong Kyun

    2012-08-01

    The Korea Atomic Energy Research Institute (KAERI) has developed a silicon carbide (SiC) diode as a neutron detector that can be used in harsh environments such as nuclear reactor cores and spent fuel. The radiation tolerance of the SiC detector was studied in the present work. Especially, the effect of a metal electrode on the radiation tolerance of the SiC detector was studied. Four different types of SiC detectors were fabricated, and the operation properties of the detectors were measured and compared before and after neutron irradiations of 2.16 × 1015 n/cm2 and 5.40 × 1017 n/cm2. From the comparison, the detector with a Ti/Au electrode structure showed the highest radiation tolerance among detectors. A detector assembly was fabricated using two types of SiC p-i-n diode detectors: one containing 6LiF and the other without it. Signals from the detectors were measured in the current mode to minimize the noise of the detector. Signal currents from detectors were measured for neutron fluxes ranging from 5.54 × 106 n/cm2 s to 2.86 × 108 n/cm2 s and gamma doses up to 100 Gy/h.

  1. C/sic Life Prediction for Propulsion Applications

    NASA Technical Reports Server (NTRS)

    Levine, Stanley R.; Verrilli, Michael J.; Opila, Elizabeth J.; Halbig, Michael C.; Calomino, Anthony M.; Thomas, David J.

    2002-01-01

    Accurate life prediction is critical to successful use of ceramic matrix composites (CMC). The tools to accomplish this are immature and not oriented toward the behavior of carbon fiber reinforced silicon carbide (C/SiC), the primary system of interest for many reusable and single mission launch vehicle propulsion and airframe applications. This paper describes an approach and process made to satisfy the need to develop an integrated life prediction system that addresses mechanical durability and environmental degradation of C/SiC. Issues such as oxidation, steam and hydrogen effects on material behavior are discussed. Preliminary tests indicate that steam will aggressively remove SiC seal coat and matrix in line with past experience. The kinetics of water vapor reaction with carbon fibers is negligible at 600 C, but comparable to air attack at 1200 C. The mitigating effect of steam observed in fiber oxidation studies has also been observed in stress rupture tests. Detailed microscopy of oxidized specimens is being carried out to develop the oxidation model. Carbon oxidation kinetics are reaction controlled at intermediate temperatures and diffusion controlled at high temperatures (approximately 1000 C). Activation energies for T-300 and interface pyrolytic carbon were determined as key inputs to the oxidation model. Crack opening as a function of temperature and stress was calculated. Mechanical property tests to develop and verify the probabilistic life model are very encouraging except for residual strength prediction. Gage width is a key variable governing edge oxidation of seal coated specimens. Future efforts will include architectural effects, enhanced coatings, biaxial tests, and LCF. Modeling will need to account for combined effects.

  2. C/SIC Life Prediction for Propulsion Applications

    NASA Technical Reports Server (NTRS)

    Levine, Stanley R.; Verrilli, Michael J.; Opula, Elizabeth J.; Halbig, Michael C.; Calomino, Anthony M.; Thomas, David J.

    2002-01-01

    Accurate life prediction is critical to successful use of ceramic matrix composites (CMC). The tools to accomplish this are immature and not oriented toward the behavior of carbon fiber reinforced silicon carbide (C/SiC), the primary system of interest for many reusable and single mission launch vehicle propulsion and airframe applications. This paper describes an approach and progress made to satisfy the need to develop an integrated life prediction system that addresses mechanical durability and environmental degradation of C/SiC. Issues such as oxidation, steam and hydrogen effects on material behavior are discussed. Preliminary tests indicate that stream will aggressively remove SiC seal coat and matrix in line with past experience. The kinetics of water vapor reaction with carbon fibers is negligible at 600 C, but comparable to air attack at 1200 C. The mitigating effect of steam observed in fiber oxidation studies has also been observed in stress rupture tests. Detailed microscopy of oxidized specimens is being carried out to develop the oxidation model. Carbon oxidation kinetics are reaction controlled at intermediate temperatures and diffusion controlled at high temperatures (approx. 1000 C). Activation energies for T-300 and interface pyrolytic carbon were determined as key inputs to the oxidation model. Crack opening as a function of temperature and stress was calculated. Mechanical property tests to develop and verify the probabilistic life model are very encouraging except for residual strength prediction. Gage width is a key variable governing edge oxidation of seal coated specimens. Future efforts will include architectural effects, enhanced coatings, biaxial tests, and LCF. Modeling will need to account for combined effects.

  3. 75 FR 104 - Manufacturing & Services' Sustainable Manufacturing Initiative; Update

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-04

    ... International Trade Administration Manufacturing & Services' Sustainable Manufacturing Initiative; Update ACTION: Notice and request for input on proposed new areas of work for the Sustainable Manufacturing Initiative... (ITA) Manufacturing & Services Unit held a Sustainability and U.S. Competitiveness Summit on October...

  4. National Center for Manufacturing Sciences: Environmentally conscious manufacturing

    NASA Technical Reports Server (NTRS)

    Vinton, Clare

    1995-01-01

    The purpose of this presentation is to share the results and some of the thinking of the Environmentally Conscious Manufacturing - Strategic Initiative Group (ECM-SIG) at the National Center for Manufacturing Sciences (NCMS). NCMS is a consortium of more than 185 North American Manufacturing organizations comprised of about 75 percent for profit manufacturing companies and about 25 percent nonprofit organizations that support manufacturing activities. NCMS conducts collaborative R&D programs designed to improve global competitiveness of its members and other North American manufacturers to address common issues that are important to manufacturing industries. NCMS is an industry driven organization whose agenda is established by industry with input from appropriate government agencies.

  5. Additive Manufacturing Infrared Inspection

    NASA Technical Reports Server (NTRS)

    Gaddy, Darrell

    2014-01-01

    Additive manufacturing is a rapid prototyping technology that allows parts to be built in a series of thin layers from plastic, ceramics, and metallics. Metallic additive manufacturing is an emerging form of rapid prototyping that allows complex structures to be built using various metallic powders. Significant time and cost savings have also been observed using the metallic additive manufacturing compared with traditional techniques. Development of the metallic additive manufacturing technology has advanced significantly over the last decade, although many of the techniques to inspect parts made from these processes have not advanced significantly or have limitations. Several external geometry inspection techniques exist such as Coordinate Measurement Machines (CMM), Laser Scanners, Structured Light Scanning Systems, or even traditional calipers and gages. All of the aforementioned techniques are limited to external geometry and contours or must use a contact probe to inspect limited internal dimensions. This presentation will document the development of a process for real-time dimensional inspection technique and digital quality record of the additive manufacturing process using Infrared camera imaging and processing techniques.

  6. Enlargement of Step-Free SiC Surfaces by Homoepitaxial Web-Growth of Thin SiC Cantilevers

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Powell, J. Anthony; Beheim, Glenn M.; Benavage, Emye L.; Abel, Phillip B.; Trunek, Andrew J.; Spry, David J.; Dudley, Michael; Vetter, William M.

    2002-01-01

    Lateral homoepitaxial growth of thin cantilevers emanating from mesa patterns that were reactive ion etched into on-axis commercial SiC substrates prior to growth is reported. The thin cantilevers form after pure stepflow growth removes almost all atomic steps from the top surface of a mesa, after which additional adatoms collected by the large step-free surface migrate to the mesa sidewall where they rapidly incorporate into the crystal near the top of the mesa sidewall. The lateral propagation of the step-free cantilevered surface is significantly affected by pregrowth mesa shape and orientation, with the highest lateral expansion rates observed at the inside concave comers of V-shaped pregrowth mesas with arms lengthwise oriented along the {1100} direction. Complete spanning of the interiors of V's and other mesa shapes with concave comers by webbed cantilevers was accomplished. Optical microscopy, synchrotron white beam x-ray topography and atomic force microscopy analysis of webbed regions formed over a micropipe and closed-core screw dislocations show that c-axis propagation of these defects is terminated by the webbing. Despite the nonoptimized process employed in this initial study, webbed surfaces as large as 1.4 x 10(exp -3) square centimeters, more than four times the pregrowth mesa area, were grown. However, the largest webbed surfaces were not completely free of bilayer steps, due to unintentional growth of 3C-SiC that occurred in the nonoptimized process. Further process optimization should enable larger step-free webs to be realized.

  7. Methods for growth of relatively large step-free SiC crystal surfaces

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor)

    2002-01-01

    A method for growing arrays of large-area device-size films of step-free (i.e., atomically flat) SiC surfaces for semiconductor electronic device applications is disclosed. This method utilizes a lateral growth process that better overcomes the effect of extended defects in the seed crystal substrate that limited the obtainable step-free area achievable by prior art processes. The step-free SiC surface is particularly suited for the heteroepitaxial growth of 3C (cubic) SiC, AlN, and GaN films used for the fabrication of both surface-sensitive devices (i.e., surface channel field effect transistors such as HEMT's and MOSFET's) as well as high-electric field devices (pn diodes and other solid-state power switching devices) that are sensitive to extended crystal defects.

  8. 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

  9. Plasmon-assisted photoluminescence enhancement of SiC nanocrystals by proximal silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhang, N.; Dai, D. J.; Fan, J. Y.

    2012-10-01

    Plasmon-enhanced photoluminescence has wide application potential in many areas, whereas the underlying mechanism is still in debate. We report the photoluminescence enhancement in SiC nanocrystal-Ag nanoparticle coupled system spaced by the poly(styrene sulfonic acid) sodium salt/poly(allylamine hydrochloride) polyelectrolyte bilayers. The integrated luminescence intensity can be improved by up to 17 times. Our analysis indicates that the strong coupling between the SiC nanocrystals and the surface plasmon oscillation of the silver nanoparticles is the major cause of the luminescence enhancement. These findings will help to understand the photoluminescence enhancement mechanism as well as widen the applications of the SiC nanocrystals in photonics and life sciences.

  10. The Oxidation Rate of SiC in High Pressure Water Vapor Environments

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Robinson, R. Craig

    1999-01-01

    CVD SiC and sintered alpha-SiC samples were exposed at 1316 C in a high pressure burner rig at total pressures of 5.7, 15, and 25 atm for times up to 100h. Variations in sample emittance for the first nine hours of exposure were used to determine the thickness of the silica scale as a function of time. After accounting for volatility of silica in water vapor, the parabolic rate constants for Sic in water vapor pressures of 0.7, 1.8 and 3.1 atm were determined. The dependence of the parabolic rate constant on the water vapor pressure yielded a power law exponent of one. Silica growth on Sic is therefore limited by transport of molecular water vapor through the silica scale.

  11. Layered SiC Sheets: A Potential Catalyst for Oxygen Reduction Reaction

    NASA Astrophysics Data System (ADS)

    Zhang, P.; Xiao, B. B.; Hou, X. L.; Zhu, Y. F.; Jiang, Q.

    2014-01-01

    The large-scale practical application of fuel cells cannot come true if the high-priced Pt-based electrocatalysts for oxygen reduction reaction (ORR) cannot be replaced by other efficient, low-cost, and stable electrodes. Here, based on density functional theory (DFT), we exploited the potentials of layered SiC sheets as a novel catalyst for ORR. From our DFT results, it can be predicted that layered SiC sheets exhibit excellent ORR catalytic activity without CO poisoning, while the CO poisoning is the major drawback in conventional Pt-based catalysts. Furthermore, the layered SiC sheets in alkaline media has better catalytic activity than Pt(111) surface and have potential as a metal-free catalyst for ORR in fuel cells.

  12. Inside a Diamond Planet: Experimental Investigation of High P-T SiC

    NASA Astrophysics Data System (ADS)

    Daviau, K.; Du, Z.; Lee, K. K. M.

    2015-12-01

    The discovery of hundreds of diverse extrasolar planetary systems implies that there are many worlds in the universe unlike our own. Models indicate that carbon-rich planets, composed largely of SiC and C, may be abundant around carbon rich stars (Kuchner and Seager 2005, Moriarty et al 2014). In order to understand the structure and evolution of such an unfamiliar planet, the basic thermodynamic phase relations of the major materials present must first be constrained. Using the laser heated diamond anvil cell (LHDAC) in combination with Raman analysis and X-Ray diffraction, this study investigates the high pressure and temperature phase diagram of SiC. Microprobe and diffraction data indicate that SiC decomposes at high P-T and that the change follows a negative Clapeyron slope. This has interesting implications for the interior "mantle" structure and dynamics of a SiC-based planet.

  13. Investigation of reactivity between SiC and Nb-1Zr in planned irradiation creep experiments

    SciTech Connect

    Lewinsohn, C.A.; Hamilton, M.L.; Jones, R.H.

    1997-08-01

    Thermodynamic calculations and diffusion couple experiments showed that SiC and Nb-1Zr were reactive at the upper range of temperatures anticipated in the planned irradiation creep experiment. Sputter-deposited aluminum oxide (Al{sub 2}O{sub 3}) was selected as a diffusion barrier coating. Experiments showed that although the coating coarsened at high temperature it was an effective barrier for diffusion of silicon from SiC into Nb-1Zr. Therefore, to avoid detrimental reactions between the SiC composite and the Nb-1Zr pressurized bladder during the planned irradiation creep experiment, a coating of Al{sub 2}O{sub 3} will be required on the Nb-1Zr bladder.

  14. Stellar Origins of C-13 and N-15-Enriched Presolar SiC Grains

    NASA Technical Reports Server (NTRS)

    Liu, Nan; Nittler, Larry R.; Alexander, Conel M. O’D.; Wang, Jianhua; Pignatari, Marco; Jose, Jordi; Nguyen, Ann

    2016-01-01

    Extreme excesses of 13 C ( C (12 C/ 13 C<10) and 15 N ( N (14 N/ 15 N< 20) in rare presolar SiC 20) in rare presolar SiClar SiC grains have been considered diagnostic of an origin in classical novae [1], though an origin in core-collapse supernovae (CCSNe) has also been proposed [2]. We report multi-element isotopic data for 19 13 C- and 15 N-enriched presolar SiC grains(12 C/13 C<16 and 14 N/ 15 N<150) from an acid resistant residue of the Murchison meteorite. These grains are enriched in 13 C and15 N, but with quite diverse Si isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures.

  15. Al4SiC4 wurtzite crystal: Structural, optoelectronic, elastic, and piezoelectric properties

    NASA Astrophysics Data System (ADS)

    Pedesseau, L.; Even, J.; Modreanu, M.; Chaussende, D.; Sarigiannidou, E.; Chaix-Pluchery, O.; Durand, O.

    2015-12-01

    New experimental results supported by theoretical analyses are proposed for aluminum silicon carbide (Al4SiC4). A state of the art implementation of the density functional theory is used to analyze the experimental crystal structure, the Born charges, the elastic properties, and the piezoelectric properties. The Born charge tensor is correlated to the local bonding environment for each atom. The electronic band structure is computed including self-consistent many-body corrections. Al4SiC4 material properties are compared to other wide band gap wurtzite materials. From a comparison between an ellipsometry study of the optical properties and theoretical results, we conclude that the Al4SiC4 material has indirect and direct band gap energies of about 2.5 eV and 3.2 eV, respectively.

  16. Interstellar SiC with unusual isotopic compositions - Grains from a supernova?

    NASA Technical Reports Server (NTRS)

    Amari, Sachiko; Hoppe, Peter; Zinner, Ernst; Lewis, Roy S.

    1992-01-01

    Results are presented from an ion microprobe mass spectrometric analyses of five SiC grains from the Murchison carbonaceous meteorite. Unlike most interstellar SiC grains from primitive meteorites, the five grains from the Murchison meteorite show large excesses of C-12 (up to 28 times solar) and N-15 (up to 22 times solar), depletion in Si-29 and Si-30 (up to 59 percent), Al-26/Al-27 ratios between 0.1 and 0.6, and Ti-49 excesses up to 95 percent; in addition, one grain has a large Ca-44 excess (300 percent). The Ca and Ti anomalies point toward explosive nucleosynthesis in supernovae and the in situ decay of the radioactive precursors Ti-44 and V-49 in SiC grains formed in supernova ejecta. However, there is no simple formation scenario that can give a consistent explanation for the isotopic compositions of these grains.

  17. Microporous layer based on SiC for high temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Lobato, Justo; Zamora, Héctor; Cañizares, Pablo; Plaza, Jorge; Rodrigo, Manuel Andrés

    2015-08-01

    This work reports the evaluation of Silicon Carbide (SiC) for its application in microporous layers (MPL) of HT-PEMFC electrodes and compares results with those obtained using conventional MPL based on Vulcan XC72. Influence of the support load on the MPL prepared with SiC was evaluated, and the MPL were characterized by XRD, Hg porosimetry and cyclic voltammetries. In addition, a short lifetest was carried out to evaluate performance in accelerated stress conditions. Results demonstrate that SiC is a promising alternative to carbonaceous materials because of its higher electrochemical and thermal stability and the positive effect on mass transfer associated to its different pore size distribution. Ohmic resistance is the most significant challenge to be overcome in further studies.

  18. 78 FR 67117 - Manufacturing Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-08

    ... International Trade Administration Manufacturing Council AGENCY: International Trade Administration, U.S. Department of Commerce. ACTION: Notice of an Opportunity to Apply for Membership on the Manufacturing Council.... manufacturing industry to fill five vacant positions on the Manufacturing Council (Council). The purpose of...

  19. Microstructural analysis of fracture toughness variation in 2XXX-series aluminum alloy composites reinforced with SiC whiskers

    NASA Astrophysics Data System (ADS)

    Lee, Sunghak; Kim, Tae Hyung; Kwon, Dongil

    1994-10-01

    The effects of local microstructure on fracture properties in powder-metallurgy (P/M)-processed 2124/SiC/15w and 2009/SiC/15w composites are analyzed in this study. Ductility and fracture toughness of the 2009/SiC/15w, in which dispersoid-forming elements such as manganese and iron were nearly absent, were greater than in the 2124/SiC/15w, while its tensile and yield strengths were somewhat less. Microstructural examination and fracture parameter analysis revealed that the improved fracture toughness of the 2009/SiC/15w compared to the 2124/SiC/15w was due to the increase in the critical microstructural distance, l* when manganese-containing particles are absent. 2009/SiC/15w was also heat-treated in T4P and overaged (OA) conditions. The OA 2009 composite showed lower fracture toughness than the 2009-T4P composite and the critical fracture strain of the OA condition was much lower, too. Detailed fractographic analyses indicated that interface precipitates facilitate premature SiC whisker failure in the OA condition.

  20. NanoSIMS Isotopic Analysis of Small Presolar SiC Grains from the Murchisonand Indarch Meteorites

    NASA Astrophysics Data System (ADS)

    Amari, S.; Jennings, C.; Nguyen, A.; Stadermann, F. J.; Zinner, E.; Lewis, R. S.

    2002-03-01

    Carbon and N isotopic measurements were made with the NanoSIMS ion microprobe on small (0.25-0.6 µm) presolar SiC grains from the Murchison and Indarch meteorites. Indarch also contains silicon nitride grains with the isotopic signature of mainstream SiC.

  1. Purity and radioactive decay behaviour of industrial 2D-reinforced SiC f/SiC composites

    NASA Astrophysics Data System (ADS)

    Scholz, H. W.; Zucchetti, M.; Casteleyn, K.; Adelhelm, C.

    1994-09-01

    Ceramic matrix composites based on SiC with continuous fibres (SiC f/SiC) are considered promising structural materials for future fusion devices. It was still to clarify, whether impurities in industrial SiC f/SiC could jeopardise radiological advantages. Experimental impurity analyses revealed a two-dimensionally reinforced SiC f/SiC with the matrix produced by CVI as very pure. Chemo-spectrometric methods were combined with radioactivation methods (CPAA, NAA). A quantification of the main constituents Si, C and O was added. Calculations with the FISPACT-2.4 code and EAF-2 library identified elements detrimental for different low-activation criteria. For the neutron exposure, EEF reactor-study first wall and blanket conditions were simulated. The calculated SiC f/ SiC included 48 trace elements. Even under conservative assumptions, all low-activation limits of European interest are fulfilled. Exclusively the hands-on recycling limit for the First Wall can intrinsically not be satisfied with SiC. The theoretical goal of a SiC f/SiC depleted of 28Si (isotopic tailoring) is critically discussed.

  2. Environmentally sound manufacturing

    NASA Technical Reports Server (NTRS)

    Caddy, Larry A.; Bowman, Ross; Richards, Rex A.

    1994-01-01

    The NASA/Thiokol/industry team has developed and started implementation of an environmentally sound manufacturing plan for the continued production of solid rocket motors. They have worked with other industry representatives and the U.S. Environmental Protection Agency to prepare a comprehensive plan to eliminate all ozone depleting chemicals from manufacturing processes and to reduce the use of other hazardous materials used to produce the space shuttle reusable solid rocket motors. The team used a classical approach for problem solving combined with a creative synthesis of new approaches to attack this problem. As our ability to gather data on the state of the Earth's environmental health increases, environmentally sound manufacturing must become an integral part of the business decision making process.

  3. Environmentally sound manufacturing

    NASA Astrophysics Data System (ADS)

    Caddy, Larry A.; Bowman, Ross; Richards, Rex A.

    The NASA/Thiokol/industry team has developed and started implementation of an environmentally sound manufacturing plan for the continued production of solid rocket motors. They have worked with other industry representatives and the U.S. Environmental Protection Agency to prepare a comprehensive plan to eliminate all ozone depleting chemicals from manufacturing processes and to reduce the use of other hazardous materials used to produce the space shuttle reusable solid rocket motors. The team used a classical approach for problem solving combined with a creative synthesis of new approaches to attack this problem. As our ability to gather data on the state of the Earth's environmental health increases, environmentally sound manufacturing must become an integral part of the business decision making process.

  4. High temperature characterization of SiC BJTs for power switching applications

    NASA Astrophysics Data System (ADS)

    Sheng, K.; Yu, L. C.; Zhang, J.; Zhao, J. H.

    2006-06-01

    SiC as a wide bandgap semiconductor material has attracted great interest in high power density and high temperature applications. Development of SiC-based power semiconductor devices has made remarkable progress and specific on-resistance ˜100 times lower than the best available silicon-based has been experimentally demonstrated [Zhao JH, Tone K, Li X, Alexandrov P, Fursin L, Weiner M. 3.6 m cm 2, 1726 V 4H-SiC normally-off trenched-and-implanted vertical JFETs and circuit applications. IEE Proc - Circ, Dev Syst 2004;151(3):231-7]. However, progress in characterization and application of such devices in power electronics applications at a practically useful power level has so far been limited. In this paper, SiC BJTs with a blocking voltage of >1800 V are characterized in power switching applications for temperatures up to 275 °C. Inductive switching speeds under different load current and DC bus voltage conditions are studied. This is the first time a SiC switch has been characterized at a practically useful power level (300 V, 7 A) and a temperature substantially higher than any commercial power device is capable of. Current switching times of ˜10 ns have been demonstrated across the full temperature range. Switching speed of the SiC BJT has been found to remain virtually unchanged even at 275 °C. In addition, due to the lack of storage charge at even high temperature, switching storage time is negligible for the SiC BJT. The fast and stable switching speed of the SiC BJT at high temperature demonstrated in this paper makes the device an attractive candidate for high temperature, high frequency and high power density power electronics applications.

  5. Probing the interaction at the C 60-SiC nanomesh interface

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Chen, Shi; Zhang, Hong Liang; Xu, Hai; Qi, Dong Chen; Gao, Xing Yu; Loh, Kian Ping; Wee, Andrew Thye Shen

    2007-07-01

    Synchrotron-based high-resolution photoemission spectroscopy (PES) and in situ scanning tunneling microscopy (STM) are used to investigate the interaction at the C 60-SiC nanomesh interface during the sequential deposition and subsequent desorption of C 60 molecules. A weak charge transfer occurs at the C 60-nanomesh interface, involving electrons transferring from nanomesh to C 60 overlayer. The interface interaction originated from the weak charge transfer at the C 60-nanomesh interface is stronger than C 60 intermolecular interaction (e.g., van-der-Waals force), facilitating the layer-by-layer growth for the first two layers of C 60 on SiC nanomesh. The highly corrugated nanomesh surface results in an anisotropic diffusion and high diffusion barrier of C 60 on top, and thereby leads to the formation of irregularly shaped C 60 islands under submonolayer condition. In contrast, C 60 diffusion on HOPG and Ag(1 1 1) surfaces is rather isotropic, resulting in the formation of hexagonally shaped C 60 islands with smooth domain boundaries. STM results show the partial desorption of C 60 molecules from the SiC nanomesh surface after annealing the 1 ML C 60 sample (complete wetting layer of C 60 on SiC nanomesh) at around 150 °C for 20 min. Thorough desorption of C 60 molecules and full recovery of the clean SiC nanomesh are observed after annealing at around 200 °C for 20 min. In situ PES and STM experiments clearly demonstrate that C 60 adsorption and desorption processes do not affect the underlying SiC nanomesh structure, revealing its thermal stability and chemical inertness to C 60 molecules.

  6. ATS materials/manufacturing

    SciTech Connect

    Karnitz, M.A.; Wright, I.G.; Ferber, M.K.

    1997-11-01

    The Materials/Manufacturing Technology subelement is a part of the base technology portion of the Advanced Turbine Systems (ATS) Program. The work in this subelement is being performed predominantly by industry with assistance from national laboratories and universities. The projects in this subelement are aimed toward hastening the incorporation of new materials and components in gas turbines. Work is currently ongoing on thermal barrier coatings (TBCs), the scale-up of single crystal airfoil manufacturing technologies, materials characterization, and technology information exchange. This paper presents highlights of the activities during the past year. 12 refs., 24 figs., 4 tabs.

  7. Manufacturing and producibility technology

    NASA Technical Reports Server (NTRS)

    Hankins, J. D.; Dreshfield, R. L.

    1985-01-01

    Activities of the manufacturing/producibility working group within the Advanced High-Pressure O2/H2 Technology Program are summarized. The objectives of the M/P working group are: to develop and evaluate process and manufacturing techniques for advanced propulsion hardware design and selected materials; and to optimize the producibility of (SSME) components and assemblies by improved performance, increased life, greater reliability, and/or reduced cost. The technologies being developed include: plasma arc, laser, and inertia welding; combustion chamber and turbine blade coatings; coating processes; high performance alloy electroforming; and process control technology.

  8. Photovoltaic manufacturing technology

    SciTech Connect

    Wohlgemuth, J.H.; Whitehouse, D.; Wiedeman, S.; Catalano, A.W.; Oswald, R. )

    1991-12-01

    This report identifies steps leading to manufacturing large volumes of low-cost, large-area photovoltaic (PV) modules. Both crystalline silicon and amorphous silicon technologies were studied. Cost reductions for each step were estimated and compared to Solarex Corporation's manufacturing costs. A cost model, a simple version of the SAMICS methodology developed by the Jet Propulsion Laboratory (JPL), projected PV selling prices. Actual costs of materials, labor, product yield, etc., were used in the cost model. The JPL cost model compared potential ways of lowering costs. Solarex identified the most difficult technical challenges that, if overcome, would reduce costs. Preliminary research plans were developed to solve the technical problems. 13 refs.

  9. Broadband Antireflection and Light Extraction Enhancement in Fluorescent SiC with Nanodome Structures

    PubMed Central

    Ou, Yiyu; Zhu, Xiaolong; Jokubavicius, Valdas; Yakimova, Rositza; Mortensen, N. Asger; Syväjärvi, Mikael; Xiao, Sanshui; Ou, Haiyan

    2014-01-01

    We demonstrate a time-efficient and low-cost approach to fabricate Si3N4 coated nanodome structures in fluorescent SiC. Nanosphere lithography is used as the nanopatterning method and SiC nanodome structures with Si3N4 coating are formed via dry etching and thin film deposition process. By using this method, a significant broadband surface antireflection and a considerable omnidirectional luminescence enhancement are obtained. The experimental observations are then supported by numerical simulations. It is believed that our fabrication method will be well suitable for large-scale production in the future. PMID:24722521

  10. Laser processing for bevel termination of high voltage pn junction in SiC

    NASA Astrophysics Data System (ADS)

    Kubiak, A.; Ruta, Ł.; Rosowski, A.; French, P.

    2016-04-01

    Proper edge termination of the p-n junction in silicon carbide is a key requirement in the fabrication of discrete devices able to withstand high voltages in reverse polarization. Due to the hardness of SiC the creation of the bevel termination remains difficult using mechanical machining. The use of laser beam sources with medium wavelength (532 nm) gives new possibilities in the machining of the silicon carbide. The paper presents the fabrication of the bevel termination structure in SiC using a green DPSS laser equipped with scanner and dedicated rotating sample holder. Characterization of the resulting structures proves the high potential of the proposed approach.

  11. System for the growth of bulk SiC crystals by modified CVD techniques

    NASA Technical Reports Server (NTRS)

    Steckl, Andrew J.

    1994-01-01

    The goal of this program was the development of a SiC CVD growth of films thick enough to be useful as pseudo-substrates. The cold-walled CVD system was designed, assembled, and tested. Extrapolating from preliminary evaluation of SiC films grown in the system at relatively low temperatures indicates that the growth rate at the final temperatures will be high enough to make our approach practical. Modifications of the system to allow high temperature growth and cleaner growth conditions are in progress. This program was jointly funded by Wright Laboratory, Materials Directorate and NASA LeRC and monitored by NASA.

  12. PhySIC_IST: cleaning source trees to infer more informative supertrees

    PubMed Central

    Scornavacca, Celine; Berry, Vincent; Lefort, Vincent; Douzery, Emmanuel JP; Ranwez, Vincent

    2008-01-01

    Background Supertree methods combine phylogenies with overlapping sets of taxa into a larger one. Topological conflicts frequently arise among source trees for methodological or biological reasons, such as long branch attraction, lateral gene transfers, gene duplication/loss or deep gene coalescence. When topological conflicts occur among source trees, liberal methods infer supertrees containing the most frequent alternative, while veto methods infer supertrees not contradicting any source tree, i.e. discard all conflicting resolutions. When the source trees host a significant number of topological conflicts or have a small taxon overlap, supertree methods of both kinds can propose poorly resolved, hence uninformative, supertrees. Results To overcome this problem, we propose to infer non-plenary supertrees, i.e. supertrees that do not necessarily contain all the taxa present in the source trees, discarding those whose position greatly differs among source trees or for which insufficient information is provided. We detail a variant of the PhySIC veto method called PhySIC_IST that can infer non-plenary supertrees. PhySIC_IST aims at inferring supertrees that satisfy the same appealing theoretical properties as with PhySIC, while being as informative as possible under this constraint. The informativeness of a supertree is estimated using a variation of the CIC (Cladistic Information Content) criterion, that takes into account both the presence of multifurcations and the absence of some taxa. Additionally, we propose a statistical preprocessing step called STC (Source Trees Correction) to correct the source trees prior to the supertree inference. STC is a liberal step that removes the parts of each source tree that significantly conflict with other source trees. Combining STC with a veto method allows an explicit trade-off between veto and liberal approaches, tuned by a single parameter. Performing large-scale simulations, we observe that STC+PhySIC_IST infers much

  13. Plasmon-enhanced nonlinear optical properties of SiC nanoparticles

    NASA Astrophysics Data System (ADS)

    Zakharko, Y.; Nychyporuk, T.; Bonacina, L.; Lemiti, M.; Lysenko, V.

    2013-02-01

    An original plasmonic nano-Ag/SiNx substrate was elaborated to strongly enhance the nonlinear response of SiC NPs for the first time. A plasmon-induced two order of magnitude increase of second-harmonic generation and two-photon excited photoluminescence was experimentally achieved. The measured enhancement factors were correlated with local field intensities theoretically estimated by finite-difference time-domain calculations. The obtained plasmon-enhanced nonlinear response of the SiC nanostructures make them promising in nonlinear optics applications.

  14. Realizing stable fully spin polarized transport in SiC nanoribbons with dopant

    NASA Astrophysics Data System (ADS)

    Tao, Xixi; Hao, Hua; Wang, Xianlong; Zheng, Xiaohong; Zeng, Zhi

    2016-06-01

    Intrinsic half-metallicity recently reported in zigzag edged SiC nanoribbons is basically undetectable due to negligible energy difference between the antiferromagnetic (AFM) and ferromagnetic (FM) configurations. In this Letter, by density functional theory calculations, we demonstrate a scheme of N doping at the carbon edge to selectively close the edge state channel at this edge and achieve 100% spin filtering, no matter whether it is in an AFM state or FM state. This turns SiC nanoribbon into a promising material for obtaining stable and completely spin polarized transport and may find application in spintronic devices.

  15. Femtosecond laser damage threshold and nonlinear characterization in bulk transparent SiC materials

    SciTech Connect

    DesAutels, G. Logan; Finet, Marc; Ristich, Scott; Whitaker, Matt; Brewer, Chris; Juhl, Shane; Walker, Mark; Powers, Peter

    2008-01-15

    Semi-insulating and conducting SiC crystalline transparent substrates were studied after being processed by femtosecond (fs) laser radiation (780 nm at 160 fs). Z-scan and damage threshold experiments were performed on both SiC bulk materials to determine each sample's nonlinear and threshold parameters. 'Damage' in this text refers to an index of refraction modification as observed visually under an optical microscope. In addition, a study was performed to understand the damage threshold as a function of numerical aperture. Presented here for the first time, to the best of our knowledge, are the damage threshold, nonlinear index of refraction, and nonlinear absorption measured values.

  16. Rapid Fabrication of Lightweight SiC Optics using Reactive Atom Plasma (RAP) Processing

    NASA Technical Reports Server (NTRS)

    Fiske, Peter S.

    2006-01-01

    Reactive Atom Plasma (RAP) processing is a non-contact, plasma-based processing technology that can be used to generate damage-free optical surfaces. We have developed tools and processes using RAP that allow us to shape extremely lightweight mirror Surfaces made from extremely hard-to-machine materials (e.g. SiC). We will describe our latest results using RAP in combination with other technologies to produce finished lightweight SiC mirrors and also discuss applications for RAP in the rapid fabrication of mirror segments for reflective and grazing incidence telescopes.

  17. Construction Progress of the S-IC Test Stand Complex Bunker House

    NASA Technical Reports Server (NTRS)

    1963-01-01

    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. In addition to the S-IC stand, additional related facilities were built during this time frame. Built to the east of the S-IC stand, the block house served as the control room. To the south of the blockhouse was a newly constructed pump house used for delivering water to the S-IC stand during testing. North of the massive test stand, the F-1 Engine test stand was built for testing a single F-1 engine. Just southeast of the S-IC stand a concrete bunker house was constructed. The bunker housed

  18. Effects of irradiation on the mechanical behavior of twined SiC nanowires

    SciTech Connect

    Jin Enze; Niu Lisha; Lin Enqiang; Duan Zheng

    2013-03-14

    Irradiation is known to bring new features in one-dimensional nano materials. In this study, we used molecular dynamics simulations to investigate the irradiation effects on twined SiC nanowires. Defects tend to accumulate from outside toward inside of the twined SiC nanowires with increasing irradiation dose, leading to a transition from brittle to ductile failure under tensile load. Atomic chains are formed in the ductile failure process. The first-principles calculations show that most of the atomic chains are metallic.

  19. Stability and electronic properties of SiC nanowire adsorbed on MoS2 monolayer

    NASA Astrophysics Data System (ADS)

    Sharma, Munish; Pooja, Kumar, Ashok; Ahluwalia, P. K.

    2015-06-01

    Structural stability and electronic properties of silicon carbide (SiC) nano-wire on MoS2 monolayer are investigated within the framework of density functional theory (DFT). The preferred binding site for the SiC nano-wire is predicted to be hollow site of monolayer. In the electronic band structure the states in valence band near Fermi level are mainly due to nano-wire leading to reduction of band gap relative to monolayer. These results provide a platform for their applications in optoelectronic devices.

  20. Performance Comparison Study of SiC and Si Technology for an IPM Drive System

    SciTech Connect

    Chinthavali, Madhu Sudhan; Otaduy, Pedro J; Ozpineci, Burak

    2010-01-01

    The impact of the new SiC material based devices on a full system needs to be evaluated in order to assess the benefits of replacing Silicon (Si) devices with WBG devices. In this paper the results obtained with a full-system model simulated for an aggressive US06 drive cycle are presented. The system model includes a motor/generator model and inverter loss model developed using actual measured data. The results provide an insight to the difference in performance of a permanent magnet traction drive system using SiC versus Si devices.

  1. Study of Ac Dielectrophoretic Process of SiC Nanowires: A Universal Method for Alignment of Semiconductor Nanowires.

    PubMed

    Yao, Limei; Cui, Yan; Cong, Haining; Zheng, Jinju; Shang, Minghui; Yang, Zuobao; Yang, Weiyou; Wei, Guodong; Gao, Fengmei

    2016-04-01

    In this study, the dielectrophoretic processes of SiC nanowires suspended in three typical solvents, (highly purified water, ethanol and isopropanol) were systematically investigated. Optical microscope and SEM characterizations were used to observe the order of SiC nanowires on the surface of gold microchannels. The gold microchannels were induced by Ac dielectrophoresis of the corresponding dispersion solutions of SiC nanowires, with a concentration of 0.1 mg/mL. The study shows that the dielectrophoresis process is an effective way of synthesizing highly oriented SiC nanoarrays using isopropanol solution. The results also show that the arrangement of SiC nanowires on the interdigital electrode configuration not only depend on the kind of solvent used, but also on the applied frequency (1000 Hz~1 MHz) and voltage (1 V~20 V). PMID:27451739

  2. Experimental evidence of α → β phase transformation in SiC quantum dots and their size-dependent luminescence

    SciTech Connect

    Guo, Xiaoxiao; Dai, Dejian; Fan, Baolu; Fan, Jiyang

    2014-11-10

    Phase transformation can occur among different SiC polytypes under extreme conditions such as high pressure or temperature. It remains unknown whether phase transformation can occur under normal conditions. We demonstrate that the α → β phase transformation can occur at ambient temperature and pressure in nanoscale SiC. The microstructural characterization and light absorption and emission spectroscopy demonstrate the occurrence of this phase transformation. It is found that the quantum-confinement luminescence dominates in larger SiC quantum dots (QDs) and the surface-defect luminescence dominates in ultrasmall SiC QDs. The rare phenomenon of multiple-phonon-assisted light absorption is observed in the SiC QDs.

  3. Study of Ac Dielectrophoretic Process of SiC Nanowires: A Universal Method for Alignment of Semiconductor Nanowires.

    PubMed

    Yao, Limei; Cui, Yan; Cong, Haining; Zheng, Jinju; Shang, Minghui; Yang, Zuobao; Yang, Weiyou; Wei, Guodong; Gao, Fengmei

    2016-04-01

    In this study, the dielectrophoretic processes of SiC nanowires suspended in three typical solvents, (highly purified water, ethanol and isopropanol) were systematically investigated. Optical microscope and SEM characterizations were used to observe the order of SiC nanowires on the surface of gold microchannels. The gold microchannels were induced by Ac dielectrophoresis of the corresponding dispersion solutions of SiC nanowires, with a concentration of 0.1 mg/mL. The study shows that the dielectrophoresis process is an effective way of synthesizing highly oriented SiC nanoarrays using isopropanol solution. The results also show that the arrangement of SiC nanowires on the interdigital electrode configuration not only depend on the kind of solvent used, but also on the applied frequency (1000 Hz~1 MHz) and voltage (1 V~20 V).

  4. MG63 Osteoblast-Like Cells Response of SiC Coating for Carbon/carbon Composites

    NASA Astrophysics Data System (ADS)

    Zhang, Lei-Lei; Li, He-Jun; Li, Ke-Zhi; Lu, Jin-Hua; Shen, Xue-Tao; Lan, Feng-Tao

    A SiC coating for carbon/carbon (C/C) composites was produced by pack cementation to use as a bonding and buffer layer between C/C composites and bioactive ceramic for application in orthopaedic implants. The microstructure and MG63 osteoblast-like cell responses of the coating were investigated. The results confirmed that the SiC coating displayed a dense and uniform microstructure. MG63 cells attached and spread favorably on SiC coating, and cell proliferation was better on SiC coating than on uncoated C/C composites surface. The SiC coated C/C composites have the potential to be used in artificial implants.

  5. Nanomechanical properties of SiC films grown from C{sub 60} precursors using atomic force microscopy

    SciTech Connect

    Morse, K.; Balooch, M.; Hamza, A.V.; Belak, J.

    1994-12-01

    The mechanical properties of SiC films grown via C{sub 60} precursors were determined using atomic force microscopy (AFM). Conventional silicon nitride and modified diamond cantilever AFM tips were employed to determine the film hardness, friction coefficient, and elastic modulus. The hardness is found to be between 26 and 40 GPa by nanoindentation of the film with the diamond tip. The friction coefficient for the silicon nitride tip on the SiC film is about one third that for silicon nitride sliding on a silicon substrate. By combining nanoindentation and AFM measurements an elastic modulus of {approximately}300 GPa is estimated for these SiC films. In order to better understand the atomic scale mechanisms that determine the hardness and friction of SiC, we simulated the molecular dynamics of a diamond indenting a crystalline SiC substrate.

  6. Assessment of U.S. Manufacturing Capability for Next-Generation Wind Turbine Drivetrains

    SciTech Connect

    Cotrell, J.; Stelhy, T.

    2013-09-01

    Robust U.S. wind turbine manufacturing capabilities and supply chains are important for the United States to reduce the cost of electricity generated from wind turbines. These capabilities and supply chains are also critical to the invention and commercialization of new wind turbine technologies while providing high-quality jobs. The development of advanced drivetrain technologies for windturbine applications is advancing the state of the art for drivetrain design by producing higher capacity and operating reliability than conventional drivetrains. Advanced drivetrain technologies such as medium-speed and direct-drive generators, silicon-carbide (SiC) IGBT-based power electronics, and high torque density speed increasers require different manufacturing and supply chaincapabilities that present both risks and opportunities for U.S. wind turbine manufacturers and the wind industry as a whole. The primary objective of this project is to assess how advanced drivetrain technologies and trends will impact U.S. wind turbine manufacturing and its supply chains. The U.S. Department of Energy and other industry participants will use the information from this study toidentify domestic manufacturing gaps, barriers, and opportunities for developing U.S. wind turbine manufacturing capabilities and supply chains for next-generation drivetrain technologies. This report also includes recommendations for prioritizing technology areas for possible investments by public, private, or nonprofit entities that will reduce the cost of wind-generated electricity. Suchinvestments foster opportunities to invent and commercialize new wind turbine technologies, and provide high-quality jobs in the United States.

  7. Manufacturing Technology. Curriculum Guide.

    ERIC Educational Resources Information Center

    North Dakota State Board for Vocational Education, Bismarck.

    This guide provides the basic foundation to develop a one-semester course based on the cluster concept, manufacturing technology. One of a set of six guides for an industrial arts curriculum at the junior high school level, it suggests activities that allow students (1) to become familiar with and use some of the tools, materials, and processes…

  8. Illinois Manufacturing Technology Curriculum.

    ERIC Educational Resources Information Center

    Cliffe, Roger; And Others

    This manufacturing technology curriculum involves students in learning problem-solving, communication, team building, quality control, safety, math, science, and technical skills. The document begins with a section on implementation, which gives background information on the purposes and development of the curriculum, explains its rationale,…

  9. Manufacturing and Merchandising Careers

    ERIC Educational Resources Information Center

    Ryan, Peter J.; And Others

    1977-01-01

    Anyone with a flair for business, product development, or promotion might consider a manufacturing or merchandising occupation. The music industry offers many career opportunities for administrators, salespersons, marketing specialists--the record industry offers positions from promotion manager to rack jobber. Describes instrument company…

  10. Drug development and manufacturing

    SciTech Connect

    Warner, Benjamin P.; McCleskey, T. Mark; Burrell, Anthony K.

    2015-10-13

    X-ray fluorescence (XRF) spectrometry has been used for detecting binding events and measuring binding selectivities between chemicals and receptors. XRF may also be used for estimating the therapeutic index of a chemical, for estimating the binding selectivity of a chemical versus chemical analogs, for measuring post-translational modifications of proteins, and for drug manufacturing.

  11. Turbine airfoil manufacturing technology

    SciTech Connect

    Kortovich, C.

    1995-12-31

    The specific goal of this program is to define manufacturing methods that will allow single crystal technology to be applied to complex-cored airfoils components for power generation applications. Tasks addressed include: alloy melt practice to reduce the sulfur content; improvement of casting process; core materials design; and grain orientation control.

  12. Virtual manufacturing in reality

    NASA Astrophysics Data System (ADS)

    Papstel, Jyri; Saks, Alo

    2000-10-01

    SMEs play an important role in manufacturing industry. But from time to time there is a shortage in resources to complete the particular order in time. Number of systems is introduced to produce digital information in order to support product and process development activities. Main problem is lack of opportunity for direct data transition within design system modules when needed temporary extension of design capacity (virtuality) or to implement integrated concurrent product development principles. The planning experience in the field is weakly used as well. The concept of virtual manufacturing is a supporting idea to solve this problem. At the same time a number of practical problems should be solved like information conformity, data transfer, unified technological concepts acceptation etc. In the present paper the proposed ways to solve the practical problems of virtual manufacturing are described. General objective is to introduce the knowledge-based CAPP system as missing module for Virtual Manufacturing in the selected product domain. Surface-centered planning concept based on STEP- based modeling principles, and knowledge-based process planning methodology will be used to gain the objectives. As a result the planning module supplied by design data with direct access, and supporting advising environment is expected. Mould producing SME would be as test basis.

  13. Advanced Computing for Manufacturing.

    ERIC Educational Resources Information Center

    Erisman, Albert M.; Neves, Kenneth W.

    1987-01-01

    Discusses ways that supercomputers are being used in the manufacturing industry, including the design and production of airplanes and automobiles. Describes problems that need to be solved in the next few years for supercomputers to assume a major role in industry. (TW)

  14. Reusing Old Manufacturing Buildings

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2014-01-01

    This article presents an interesting design challenge for students, one that will certainly let them integrate subject matter and get a sense of pride for doing something useful in their own community. The author would be willing to bet that the average town or city has some old red brick manufacturing building(s) that have seen much better days.…

  15. Manufacturing (Industrial) Technician.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document contains 35 units to consider for use in a tech prep competency profile for the occupation of manufacturing (industrial) technician. All the units listed will not necessarily apply to every situation or tech prep consortium, nor will all the competencies within each unit be appropriate. Several units appear within each specific…

  16. MEGARA optical manufacturing process

    NASA Astrophysics Data System (ADS)

    Carrasco, E.; Páez, G.; Granados, F.; Percino, E.; Castillo-Domínguez, E.; Avilés, J. L.; García-Vargas, M. L.; Gil de Paz, A.; Gallego, J.; Iglesias-Páramo, J.; Cedazo, R.

    2014-07-01

    MEGARA is the future visible integral-field and multi-object spectrograph for the GTC 10.4-m telescope located in La Palma. INAOE is a member of the MEGARA Consortium and it is in charge of the Optics Manufacturing work package. MEGARA passed the Optics Detailed Design Review in May 2013, and the blanks of the main optics have been already ordered and their manufacturing is in progress. Except for the optical fibers and microlenses, the complete MEGARA optical system will be manufactured in Mexico, shared between the workshops of INAOE and CIO. This includes a field lens, a 5-lenses collimator, a 7-lenses camera and a complete set of volume phase holographic gratings with 36 flat windows and 24 prisms, being all these elements very large and complex. Additionally, the optical tests and the complete assembly of the camera and collimator subsystems will be carried out in Mexico. Here we describe the current status of the optics manufacturing process.

  17. 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

  18. Comparison of the dynamic fatigue behavior of two monolithic SiC and an Al{sub 2}O{sub 3}/SiC composite

    SciTech Connect

    Breder, K.; Tennery, V.J.

    1994-09-01

    Two monolithic silicon carbides, NT230 siliconized SiC from Norton Saint Gobain and sintered {beta}-SiC from Coors, and a silicon carbide particulate reinforced alumina ceramic composite from Lanxide, which all are candidate materials for pressurized heat exchangers in coal-fired power plants have been evaluated. The fast fracture flexure strength was measured as a function of temperature. All candidate materials retained a sufficient strength level up to 1400C. The susceptibility to slow crack growth (SCG) was evaluated by the dynamic fatigue method at 1100C and 1400C. None of the materials exhibited SCG at 1100C. At 1400C the siliconized SiC ceramic showed limited SCG and the composite ceramic exhibited creep damage when stressed to 50% of fast fracture strength at the intermediate and slow stressing rates. This prevented the evaluation of the SCG properties of this material at 1400C. Fractography supported the mechanical observations and with the exception of the specimens which exhibited creep damage, only the siliconized SiC showed a small SCG damage zone at long times at 1400C.

  19. 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

  20. Effect of SiC interlayer between Ti6Al4V alloy and hydroxyapatite films.

    PubMed

    Azem, Funda Ak; Birlik, Isil; Braic, Viorel; Toparli, Mustafa; Celik, Erdal; Parau, Anca; Kiss, Adrian; Titorencu, Irina; Vladescu, Alina

    2015-04-01

    Bioactive coatings are frequently used to improve the osseointegration of the metallic implants used in dentistry or orthopaedics. Among different types of bioactive coatings, hydroxyapatite (Ca10(PO4)6(OH)2) is one of the most extensively used due to its chemical similarities to the components of bones and teeth. In this article, production and characterization of hydroxyapatite films deposited on Ti6Al4V alloy prepared by magnetron sputtering were reported. Besides, SiC was deposited on substrate surface to study the interlayer effect. Obtained coatings were annealed at 600 °C for 30 and 120 min in a mixed atmosphere of N2 + H2O vapours with the heating rate of 12 °C min(-1). The effects of SiC interlayer and heat treatment parameters on the structural, mechanical and corrosion properties were investigated. After heat treatment process, the crystalline hydroxyapatite was obtained. Additionally, cell viability tests were performed. The results show that the presence of the SiC interlayer contributes a decrease in surface roughness and improves the mechanical properties and corrosion performance of the hydroxyapatite coatings. Biological properties were not affected by the presence of the SiC interlayer. PMID:25934259

  1. Relaxations of fluorouracil tautomers by decorations of fullerene-like SiCs: DFT studies

    NASA Astrophysics Data System (ADS)

    Kouchaki, Alireza; Gülseren, Oğuz; Hadipour, Nasser; Mirzaei, Mahmoud

    2016-06-01

    Decorations of silicon carbide (SiC) fullerene-like nanoparticles by fluorouracil (FU) and its tautomers are investigated through density functional theory (DFT) calculations. Two models of fullerene-like particles including Si12C8 and Si8C12 are constructed to be counterparts of decorated hybrid structures, FU@Si12C8 and FU@Si8C12, respectively. The initial models including original FU and tautomeric structures and SiC nanoparticles are individually optimized and then combined for further optimizations in the hybrid forms. Covalent bonds are observed for FU@Si12C8 hybrids, whereas non-covalent interactions are seen for FU@Si8C12 ones. The obtained properties indicated that Si12C8 model could be considered as a better counterpart for interactions with FU structures than Si8C12 model. The results also showed significant effects of interactions on the properties of atoms close to the interacting regions in nanoparticles. Finally, the tautomeric structures show different behaviors in interactions with SiC nanoparticles, in which the SiC nanoparticles could be employed to detect the situations of tautomeric processes for FU structures.

  2. Deposition of nanocrystalline SiC films using helicon wave plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lu, Wanbing; Yu, Wei; Ma, Luo; Wu, Liping; Fu, Guangsheng

    2008-11-01

    Hydrogenated nanocrystalline SiC films have been deposited by using helicon wave plasma enhanced chemical vapor deposition (HW-PECVD) in H2, SiH4 and CH4 gas mixtures at different RF powers. Their structural and optical properties have been investigated by Fourier transform infrared absorption (FTIR), atomic force microscopy (AFM) and ultraviolet-visible (UV-VIS) transmission spectra. The results indicate that RF power has an important influence on properties of the deposited films. It is found that in a 300 °C low substrate temperature, only amorphous SiC can be deposited at the radio frequency (RF) power of lower than 400 W, while nanocrystalline SiC can be grown at the RF power of equal to or higher than 400 W. The analyses show that the high plasma density of helicon wave plasma source and the high hydrogen dilution condition are two key factors for depositing nanocrystalline SiC films at a low temperature.

  3. 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.

  4. Few layer graphene synthesis via SiC decomposition at low temperature and low vacuum

    NASA Astrophysics Data System (ADS)

    Kayali, Emre; Mercan, Elif; Emre Oren, Ersin; Cambaz Buke, Goknur

    2016-04-01

    Based on the large-scale availability and good electrical properties, the epitaxial graphene (EG) on SiC exhibits a big potential for future electronic devices. However, it is still necessary to work continuously on lowering the formation temperature and vacuum values of EG while improving the quality and increasing the lateral size to fabricate high-performance electronic devices at reduced processing costs. In this study, we investigated the effect of the presence of Mo plate and hydrogen atmosphere as well as the vacuum annealing durations on SiC decomposition. Our studies showed that the graphene layers can be produced at lower annealing temperatures (1200 °C) and vacuum values (10-4 Torr) in the presence of Mo plate and hydrogen. For high quality continuous graphene formation, Mo plate should be in contact with SiC. If there is a gap between Mo and SiC, non-wetting oxide droplets on few layer graphene (FLG) are recorded. Moreover, it is found that the morphology of these islands can be controlled by changing the annealing time and atmosphere conditions, and applying external disturbances such as vibration.

  5. TEM Observation of the Ti Interlayer Between SiC Substrates During Diffusion Bonding

    NASA Technical Reports Server (NTRS)

    Tsuda, Hiroshi; Mori, Shigeo; Halbig, Michael C.; Singh, Mori

    2012-01-01

    Diffusion bonding was carried out to join SiC to SiC substrates using titanium interlayers. In this study, 10 m and 20 m thick physical vapor deposited (PVD) Ti surface coatings, and 10 and 20 m thick Ti foils were used. Diffusion bonding was performed at 1250 C for PVD Ti coatings and 1200 C for Ti foil. This study investigates the microstructures of the phases formed during diffusion bonding through TEM and selected-area diffraction analysis of a sample prepared with an FIB, which allows samples to be taken from the reacted area. In all samples, Ti3SiC2, Ti5Si3Cx and TiSi2 phases were identified. In addition, TiC and unknown phases also appeared in the samples in which Ti foils were used as interlayers. Furthermore, Ti3SiC2 phases show high concentration and Ti5Si3Cx formed less when samples were processed at a higher temperature and thinner interlayer samples were used. It appears that the formation of microcracks is caused by the presence of intermediate phase Ti5Si3Cx, which has anisotropic thermal expansion, and by the presence of an unidentified Ti-Si-C ternary phase with relatively low Si content.

  6. Time-Domain Thermoreflectance Measurements of Thermal Transport in Amorphous SiC Thin Films

    NASA Astrophysics Data System (ADS)

    Daly, Brian; Hondongwa, Donald; King, Sean

    2010-03-01

    We present ultrafast optical pump-probe measurements of thermal transport in a series of amorphous SiC samples. The samples were grown on Si wafers by plasma enhanced chemical vapor deposition utilizing various combinations of methylsilanes and H2 and He diluent gases. The sample films were well characterized and found to have densities (1.3 -- 2.3 g cm-3) and dielectric constants (4.0 -- 7.2) that spanned a wide range of values. Prior to their measurement, the samples were coated with 40-70 nm of polycrystalline Al. The pump-probe measurements were performed at room temperature using a modelocked Ti:sapphire laser that produced sub-picosecond pulses of a few nJ. The pulses heat the Al coating, causing a transient reflectivity change. As the Al film cools into the SiC film, the reflectivity change can be measured, giving a measure of the thermal effusivity of the SiC film. We then extract values for the thermal conductivity of the SiC films and find that it varies from less than half of the thermal conductivity of amorphous SiO2 for the lower density materials to somewhat larger than amorphous SiO2 for the highest density films.

  7. Simulating structural transitions with kinetic Monte Carlo: The case of epitaxial graphene on SiC

    NASA Astrophysics Data System (ADS)

    Deretzis, I.; La Magna, A.

    2016-03-01

    We have developed a kinetic Monte Carlo numerical scheme, specifically suited to simulate structural transitions in crystalline materials, and implemented it for the case of epitaxial graphene on SiC. In this process, surface Si atoms selectively sublimate, while the residual C atoms rearrange from a position occupied in the SiC hexagonal lattice to the graphene honeycomb structure, modifying their hybridization (from s p3 to s p2 ) and bond partners (from Si-C to C-C). The model is based on the assumption that the Monte Carlo particles follow the evolution of their reference crystal until they experience a thermally activated reversible transition to another crystal structure. We demonstrate that, in a formulation based on three parallel lattices, the method is able to recover the complex evolution steps of epitaxial graphene on SiC. Moreover, the simulation results are in noteworthy agreement with the overall experimental scenario, both when varying the structural properties of the material (e.g., the initial surface configuration or polarity) as well as the process conditions (e.g., the temperature and pressure).

  8. Dimensional isotropy of 6H and 3C SiC under neutron irradiation

    NASA Astrophysics Data System (ADS)

    Snead, Lance L.; Katoh, Yutai; Koyanagi, Takaaki; Terrani, Kurt; Specht, Eliot D.

    2016-04-01

    This investigation experimentally determines the as-irradiated crystal axes dimensional change of the common polytypes of SiC considered for nuclear application. Single crystal α-SiC (6H), β-SiC (3C), CVD β-SiC, and single crystal Si have been neutron irradiated near 60 °C from 2 × 1023 to 2 × 1026 n/m2 (E > 0.1 MeV), or about 0.02-20 dpa, in order to study the effect of irradiation on bulk swelling and strain along independent crystalline axes. Single crystal, powder diffractometry and density measurement have been carried out. For all neutron doses where the samples remained crystalline all SiC materials demonstrated equivalent swelling behavior. Moreover the 6H-SiC expanded isotropically. The magnitude of the swelling followed a ∼0.77 power law against dose consistent with a microstructure evolution driven by single interstitial (carbon) mobility. Extraordinarily large ∼7.8% volume expansion in SiC was observed prior to amorphization. Above ∼0.9 × 1025 n/m2 (E > 0.1 MeV) all SiC materials became amorphous with an identical swelling: a 11.7% volume expansion, lowering the density to 2.84 g/cm3. The as-amorphized density was the same at the 2 × 1025 and 2 × 1026 n/m2 (E > 0.1 MeV) dose levels.

  9. CO oxidation catalyzed by silicon carbide (SiC) monolayer: A theoretical study.

    PubMed

    Wang, Nan; Tian, Yu; Zhao, Jingxiang; Jin, Peng

    2016-05-01

    Developing metal-free catalysts for CO oxidation has been a key scientific issue in solving the growing environmental problems caused by CO emission. In this work, the potential of the silicon carbide (SiC) monolayer as a metal-free catalyst for CO oxidation was systematically explored by means of density functional theory (DFT) computations. Our results revealed that CO oxidation reaction can easily proceed on SiC nanosheet, and a three-step mechanism was proposed: (1) the coadsorption of CO and O2 molecules, followed by (2) the formation of the first CO2 molecule, and (3) the recovery of catalyst by a second CO molecule. The last step is the rate-determining one of the whole catalytic reaction with the highest barrier of 0.65eV. Remarkably, larger curvature is found to have a negative effect on the catalytic performance of SiC nanosheet for CO oxidation. Therefore, our results suggested that flat SiC monolayer is a promising metal-free catalyst for CO oxidation.

  10. Synthesis and characterization of AA 6061- Graphene - SiC hybrid nanocomposites processed through microwave sintering

    NASA Astrophysics Data System (ADS)

    Jauhari, Siddhartha; Prashantha Kumar, H. G.; Xavior, . M. Anthony

    2016-09-01

    As one of the most essential industrial and engineering materials, Aluminum alloy 6061 have been extensively used in automobile industries and many engineering applications due to its impending properties like low density, good structural rigidity, feasibility to incorporate and enhance the strength by addition of various reinforcing materials. The essential criteria in enhancing the properties without sacrificing the ductility is always challenging in Aluminum and its alloys based composites. In the recent years, enormous research has been carried on ceramic based and carbon based reinforcement materials used in Aluminum metal matrix composites. But the combination of both is never tried so far due to lack of processing methods. The current research work is carried out to process, synthesize and perform the characterization of Al 6061 matrix nanocomposites with Graphene of flake size 10 μm and SiC of particle size 10 pm as reinforcement combinations in various proportions (weight percentage) which are carried out through powder metallurgy (PM) approach. The powders are processed through ultrasonic liquid processing method and the mixtures were ball milled by adding SiC particles followed by uniaxial hot compaction. Thus prepared compacts are sintered (conventional and microwave) and mechanical properties like hardness, density are investigated as a function of Graphene and SiC concentrations (weight fraction). Relevant strengthening mechanism involved in the Al6061 - Graphene -SiC composites in comparison with monolithic Al 6061 alloy were discussed.

  11. Temperature dependence of a microstructured SiC coherent thermal source

    NASA Astrophysics Data System (ADS)

    Hervé, Armande; Drévillon, Jérémie; Ezzahri, Younès; Joulain, Karl; De Sousa Meneses, Domingos; Hugonin, Jean-Paul

    2016-09-01

    By ruling a grating on a polar material that supports surface phonon-polaritons such as silicon carbide (SiC), it is possible to create directional and monochromatic thermal sources. So far, most of the studies have considered only materials with room temperature properties as the ones tabulated in Palik's handbooks. Recently, measurements have provided experimental data of the SiC dielectric function at different temperatures. Here we study, numerically, the effect of the temperature dependence of the dielectric function on the thermal emission of SiC gratings (1D grating, in a first approach), heated at different temperatures. When materials are heated, the position of the grating emissivity peak shifts towards higher wavelength values. A second consequence of the temperature dependence of optical properties is that room temperature designed gratings are not optimal for higher temperatures. However, by modifying the grating parameters, it is possible to find an emission peak, with a maximum of emissivity near 1, for each temperature. We tried first to catch some patterns in the emissivity variation. Then, we obtained a grating, which leads to an optimum emissivity for all available temperature data for SiC.

  12. Topology of charge density and elastic properties of Ti3SiC2 polymorphs

    SciTech Connect

    Yu, Rong; Zhang, Xiao Feng; He, Lian Long; Ye, Heng Qiang

    2004-06-24

    Using an all-electron, full potential first-principles method, we have investigated the topology of charge density and elastic properties of the two polymorphs, alpha and beta, of Ti3SiC2. The bonding effect was analyzed based on Bader's quantum theory of ''atoms in molecules'' (AIM). It was found that the Ti-Si bonding effect is significantly weaker in beta than in alpha, giving less stabilizing effect for beta. The Si-C bonds, which are absent in alpha, are formed in beta and provide additional stabilizing effect for beta. In contrast to conventional thinking, there is no direction interaction between Ti atoms in both alpha and beta. The calculated elastic properties are in good agreement with the experimental results, giving the bulk modulus of about 180 GPa and the Poisson's ratio of 0.2. The beta phase is generally softer than the alpha phase. As revealed by the direction dependent Young's modulus, there is only slight elastic anisotropy in Ti3SiC2. For alpha, Young's modulus is minimum in the c direction and maximum in the directions 42o from c. For beta, the maximum lies in the c direction, in part due to the formation of Si-C bonds in this direction.

  13. Laboratory astrochemistry: catalytic conversion of acetylene to polycyclic aromatic hydrocarbons over SiC grains.

    PubMed

    Zhao, T Q; Li, Q; Liu, B S; Gover, R K E; Sarre, P J; Cheung, A S-C

    2016-02-01

    Catalytic conversion reactions of acetylene on a solid SiC grain surface lead to the formation of polycyclic aromatic hydrocarbons (PAHs) and are expected to mimic chemical processes in certain astrophysical environments. Gas-phase PAHs and intermediates were detected in situ using time-of-flight mass spectrometry, and their formation was confirmed using GC-MS in a separate experiment by flowing acetylene gas through a fixed-bed reactor. Activation of acetylene correlated closely with the dangling bonds on the SiC surface which interact with and break the C-C π bond. The addition of acetylene to the resulting radical site forms a surface ring structure which desorbs from the surface. The results of HRTEM and TG indicate that soot and graphene formation on the SiC surface depends strongly on reaction temperature. We propose that PAHs as seen through the 'UIR' emission bands can be formed through decomposition of a graphene-like material, formed on the surface of SiC grains in carbon-rich circumstellar envelopes. PMID:26752613

  14. CO oxidation catalyzed by silicon carbide (SiC) monolayer: A theoretical study.

    PubMed

    Wang, Nan; Tian, Yu; Zhao, Jingxiang; Jin, Peng

    2016-05-01

    Developing metal-free catalysts for CO oxidation has been a key scientific issue in solving the growing environmental problems caused by CO emission. In this work, the potential of the silicon carbide (SiC) monolayer as a metal-free catalyst for CO oxidation was systematically explored by means of density functional theory (DFT) computations. Our results revealed that CO oxidation reaction can easily proceed on SiC nanosheet, and a three-step mechanism was proposed: (1) the coadsorption of CO and O2 molecules, followed by (2) the formation of the first CO2 molecule, and (3) the recovery of catalyst by a second CO molecule. The last step is the rate-determining one of the whole catalytic reaction with the highest barrier of 0.65eV. Remarkably, larger curvature is found to have a negative effect on the catalytic performance of SiC nanosheet for CO oxidation. Therefore, our results suggested that flat SiC monolayer is a promising metal-free catalyst for CO oxidation. PMID:27135172

  15. The SIC Are Dying: New Federal Industry Code on the Way.

    ERIC Educational Resources Information Center

    Quint, Barbara

    1996-01-01

    Standard Industrial Classification (SIC) codes have structured most federal and many private collections of industry statistics. This article introduces the new industry classification hierarchy called the North American Industry Classification System (NAICS) and its effects on searchers. A sidebar includes sources of information on the new code.…

  16. 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.

  17. 40 CFR 372.23 - SIC and NAICS codes to which this Part applies.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Retail Stores, NEC); Except 339115—Exception is limited to lens grinding facilities that are primarily engaged in the retail sale of eyeglasses and contact lenses to prescription for individuals (previously classified under SIC 5995, Optical Goods Stores (optical laboratories grinding of lenses to...

  18. 40 CFR 372.23 - SIC and NAICS codes to which this Part applies.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Retail Stores, NEC); Except 339115—Exception is limited to lens grinding facilities that are primarily engaged in the retail sale of eyeglasses and contact lenses to prescription for individuals (previously classified under SIC 5995, Optical Goods Stores (optical laboratories grinding of lenses to...

  19. Magnetic anisotropy of rare-earth magnets calculated by SIC and OEP

    NASA Astrophysics Data System (ADS)

    Akai, Hisazumi; Ogura, Masako

    We have pointed out in our previous study that the chemical bonding between N and Sm plays an important role in the magnetic anisotropy change of Sm2Fe17 from in-plane to uniaxial ones caused by the introducing of N. This effect of N insertion was discussed in terms of change in the electronic structure calculated in the framework of LDA+SIC. The main issue here is whether the 4f states are dealt with properly in SIC. In the present study, we examine the applicability of SIC for the evaluation of the magnetic anisotropy of rare-earth (RE) magnets by comparing the results with various methods, in particular, the optimized effective potential (OEP) method. In this study, OEP is applied only on the RE sites. Admittedly, this is a drawback from the viewpoint of the consistent treatment of uncertainly inherent in the so-called KLI (Krieger-Li-Iafrate) constants. Putting this aside for the moment, we have calculated the electronic structure of RE magnets R2Fe17Nx and RCo5 (R=light RE), by OEP with exact-exchange (EXX) combined with Colle-Salvetti correlation. Our preliminary results have shown considerable differences between the SIC and OEP calculations. We will discuss the meaning of this discrepancy. This work was supported by the Elements Strategy Initiative Center for Magnetic Materials under the outsourcing project of MEXT and by a Grant-in-Aid for Scientific Research (No. 26400330) from MEXT.

  20. Photocatalytic reduction of CO₂with SiC recovered from silicon sludge wastes.

    PubMed

    Yang, T-C; Chang, F-C; Peng, C-Y; Wang, H Paul; Wei, Y-L

    2015-01-01

    In the present study, silicon carbide (SiC) recovered from silicon sludge wastes is used as catalysts for photocatalytic reduction of CO₂. By X-ray diffraction, it is clear that the main components in the silicon sludge wastes are silicon and SiC. The grain size of the SiC separated from the sludge waste is in the range of 10-20 µm in diameter (observed by scanning electron microscopy). By solid state nuclear magnetic resonance, it is found that α-SiC is the main crystallite in the purified SiC. The α-SiC has the band-gap of 3.0 eV. To yield C₁-C₂chemicals from photocatalytic reduction of CO₂, hydrogen is provided by simultaneous photocatalytic splitting of H₂O. Under the light (253-2000 nm) illumination, 12.03 and 1.22 µmol/h g cat of formic and acetic acids, respectively, can be yielded. PMID:25241807

  1. Modeling and Testing Miniature Torsion Specimens for SiC Joining Development Studies for Fusion

    SciTech Connect

    Henager, Charles H.; Nguyen, Ba Nghiep; Kurtz, Richard J.; Roosendaal, Timothy J.; Borlaug, Brennan A.; Ferraris, Monica; Ventrella, Andrea; Katoh, Yutai

    2015-08-19

    The international fusion community has designed a miniature torsion specimen for neutron irradiation studies of joined SiC and SiC/SiC composite materials. Miniature torsion joints based on this specimen design were fabricated using displacement reactions between Si and TiC to produce Ti3SiC2 + SiC joints with CVD-SiC and tested in torsion-shear prior to and after neutron irradiation. However, many of these miniature torsion specimens fail out-of-plane within the CVD-SiC specimen body, which makes it problematic to assign a shear strength value to the joints and makes it difficult to compare unirradiated and irradiated joint strengths to determine the effects of the irradiation. Finite element elastic damage and elastic-plastic damage models of miniature torsion joints are developed that indicate shear fracture is likely to occur within the body of the joined sample and cause out-of-plane failures for miniature torsion specimens when a certain modulus and strength ratio between the joint material and the joined material exists. The model results are compared and discussed with regard to unirradiated and irradiated joint test data for a variety of joint materials. The unirradiated data includes Ti3SiC2 + SiC/CVD-SiC joints with tailored joint moduli, and includes steel/epoxy and CVD-SiC/epoxy joints. The implications for joint data based on this sample design are discussed.

  2. An improved model for current voltage characteristics of submicron SiC MESFETs

    NASA Astrophysics Data System (ADS)

    Riaz, Mohammad; Ahmed, Muhammad Mansoor; Munir, Usama

    2016-07-01

    This paper presents an improved model to simulate I - V characteristics of submicron SiC MESFETs, designed for microwave power applications. The proposed model adequately addresses a non-ideal Schottky behavior, commonly observed in submicron devices, by adjusting the device biasing through simulation variables. Swarm optimization technique has been applied to investigate gate length (Lg) dependent performance of various SiC MESFETs models. It has been found that the proposed model provides an improved accuracy, ranging from 7% to 24%, compared to the best models available in the literature. This enhanced performance is primarily associated with the extra control, provided by the proposed model to simulate the movement of the depletion region in the channel as a function of applied voltages. An attempt has been made to identify the location underneath the Schottky barrier gate, where the depletion region gets its maximum height and thus controls the saturation current of the channel. Physical and electrical parameters of various SiC MESFETs having Lg = 0.4 μm, 0.5 μm, 0.6 μm and 0.7 μm have also been assessed. An accurate assessment of the physical parameters of the device exhibits the validity of the model for submicron SiC MESFETs.

  3. Conformal Thin Film Packaging for SiC Sensor Circuits in Harsh Environments

    NASA Technical Reports Server (NTRS)

    Scardelletti, Maximilian C.; Karnick, David A.; Ponchak, George E.; Zorman, Christian A.

    2011-01-01

    In this investigation sputtered silicon carbide annealed at 300 C for one hour is used as a conformal thin film package. A RF magnetron sputterer was used to deposit 500 nm silicon carbide films on gold metal structures on alumina wafers. To determine the reliability and resistance to immersion in harsh environments, samples were submerged in gold etchant for 24 hours, in BOE for 24 hours, and in an O2 plasma etch for one hour. The adhesion strength of the thin film was measured by a pull test before and after the chemical immersion, which indicated that the film has an adhesion strength better than 10(exp 8) N/m2; this is similar to the adhesion of the gold layer to the alumina wafer. MIM capacitors are used to determine the dielectric constant, which is dependent on the SiC anneal temperature. Finally, to demonstrate that the SiC, conformal, thin film may be used to package RF circuits and sensors, an LC resonator circuit was fabricated and tested with and without the conformal SiC thin film packaging. The results indicate that the SiC coating adds no appreciable degradation to the circuits RF performance. Index Terms Sputter, silicon carbide, MIM capacitors, LC resonators, gold etchants, BOE, O2 plasma

  4. The correlation of epitaxial graphene properties and morphology of SiC (0001)

    SciTech Connect

    Guo, Y.; Guo, L. W. E-mail: xlchen@iphy.ac.cn; Huang, J.; Jia, Y. P.; Lin, J. J.; Lu, W.; Li, Z. L.; Yang, R.; Chen, X. L. E-mail: xlchen@iphy.ac.cn

    2014-01-28

    The electronic properties of epitaxial graphene (EG) on SiC (0001) depend sensitively on the surface morphology of SiC substrate. Here, 2–3 layers of graphene were grown on on-axis 6H-SiC with different step densities realized through controlling growth temperature and ambient pressure. We show that epitaxial graphene on SiC (0001) with low step density and straight step edge possesses fewer point defects laying mostly on step edges and higher carrier mobility. A relationship between step density and EG mobility is established. The linear scan of Raman spectra combined with the atomic force microscopy morphology images revealed that the Raman fingerprint peaks are nearly the same on terraces, but shift significantly while cross step edges, suggesting the graphene is not homogeneous in strain and carrier concentration over terraces and step edges of substrates. Thus, control morphology of epitaxial graphene on SiC (0001) is a simple and effective method to pursue optimal route for high quality graphene and will be helpful to prepare wafer sized graphene for device applications.

  5. 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.

  6. Impact of SiC Devices on Hybrid Electric and Plug-In Hybrid Electric Vehicles

    SciTech Connect

    Zhang, Hui; Tolbert, Leon M; Ozpineci, Burak

    2008-01-01

    The application of SiC devices (as battery interface, motor controller, etc.) in a hybrid electric vehicle (HEV) will benefit from their high-temperature capability, high-power density, and high efficiency. Moreover, the light weight and small volume will affect the whole power train system in a HEV, and thus performance and cost. In this work, the performance of HEVs is analyzed using PSAT (powertrain system analysis tool, vehicle simulation software). Power loss models of a SiC inverter are incorporated into PSAT powertrain models in order to study the impact of SiC devices on HEVs. Two types of HEVs are considered. One is the 2004 Toyota Prius HEV, the other is a plug-in HEV (PHEV), whose powertrain architecture is the same as that of the 2004 Toyota Prius HEV. The vehicle-level benefits from the introduction of the SiC devices are demonstrated by simulations. Not only the power loss in the motor controller but also those in other components in the vehicle powertrain are reduced. As a result, the system efficiency is improved and the vehicles consume less energy and emit less harmful gases. It also makes it possible to improve the system compactness with simplified thermal management system. For the PHEV, the benefits are more distinct. Especially, the size of battery bank can be reduced for optimum design.

  7. Zirconia toughened SiC whisker reinforced alumina composites small business innovation research

    NASA Technical Reports Server (NTRS)

    Loutfy, R. O.; Stuffle, K. L.; Withers, J. C.; Lee, C. T.

    1987-01-01

    The objective of this phase 1 project was to develop a ceramic composite with superior fracture toughness and high strength, based on combining two toughness inducing materials: zirconia for transformation toughening and SiC whiskers for reinforcement, in a controlled microstructure alumina matrix. The controlled matrix microstructure is obtained by controlling the nucleation frequency of the alumina gel with seeds (submicron alpha-alumina). The results demonstrate the technical feasibility of producing superior binary composites (Al2O3-ZrO2) and tertiary composites (Al2O3-ZrO2-SiC). Thirty-two composites were prepared, consolidated, and fracture toughness tested. Statistical analysis of the results showed that: (1) the SiC type is the key statistically significant factor for increased toughness; (2) sol-gel processing with a-alumina seed had a statistically significant effect on increasing toughness of the binary and tertiary composites compared to the corresponding mixed powder processing; and (3) ZrO2 content within the range investigated had a minor effect. Binary composites with an average critical fracture toughness of 6.6MPam sup 1/2, were obtained. Tertiary composites with critical fracture toughness in the range of 9.3 to 10.1 MPam sup 1/2 were obtained. Results indicate that these composites are superior to zirconia toughened alumina and SiC whisker reinforced alumina ceramic composites produced by conventional techniques with similar composition from published data.

  8. Photoelectrochemical etching of silicon carbide (SiC) and its characterization

    NASA Technical Reports Server (NTRS)

    Collins, D. M.; Harris, G. L.; Wongchotigul, K.

    1995-01-01

    Silicon carbide (SiC) is an attractive semiconductor material for high speed, high density, and high temperature device applications due to its wide bandgap (2.2-3.2 eV), high thermal conductivity, and high breakdown electric field (4 x 10(exp 6) V/cm). An instrumental process in the fabrication of semiconductor devices is the ability to etch in a highly controlled and selective manner for direct patterning techniques. A novel technique in etching using electrochemistry is described. This procedure involves the ultraviolet (UV) lamp-assisted photoelectrochemical etching of n-type 3C- and 6H-SiC to enhance the processing capability of device structures in SiC. While under UV illumination, the samples are anodically biased in an HF based aqueous solution since SiC has photoconductive properties. In order for this method to be effective, the UV light must be able to enhance the production of holes in the SiC during the etching process thus providing larger currents with light from the photocurrents generated than those currents with no light. Otherwise dark methods would be used as in the case of p-type 3C-SiC. Experiments have shown that the I/V characteristics of the SiC-electrolyte interface reveal a minimum etch voltage of 3 V and 4 V for n- and p-type 3C-SiC, respectively. Hence it is possible for etch-stops to occur. Etch rates calculated have been as high as 0.67 micrometer/min for p-type, 1.4 micrometer/min for n-type, and 1.1 micrometer/min for pn layer. On n-type 3C- SiC, an oxide formation is present where after etching a yellowish layer corresponds to a low Si/C ratio and a white layer corresponds to a high Si/C ratio. P-type 3C-SiC shows a grayish layer. Additionally, n-type 6H-SiC shows a brown layer with a minimum etch voltage of 3 V.

  9. Additive manufacturing of ceramic structures by laser engineered net shaping

    NASA Astrophysics Data System (ADS)

    Niu, Fangyong; Wu, Dongjiang; Ma, Guangyi; Zhang, Bi

    2015-11-01

    Ceramic is an important material with outstanding physical properties whereas impurities and porosities generated by traditional manufacturing methods limits its further industrial applications. In order to solve this problem, direct fabrication of Al2O3 ceramic structures is conducted by laser engineered net shaping system and pure ceramic powders. Grain refinement strengthening method by doping ZrO2 and dispersion strengthening method by doping SiC are proposed to suppress cracks in fabricating Al2O3 structure. Phase compositions, microstructures as well as mechanical properties of fabricated specimens are then analyzed. The results show that the proposed two methods are effective in suppressing cracks and structures of single-bead wall, arc and cylinder ring are successfully deposited. Stable phase of α-Al2O3 and t-ZrO2 are obtained in the fabricated specimens. Micro-hardness higher than 1700 HV are also achieved for both Al2O3 and Al2O3/ZrO2, which are resulted from fine directional crystals generated by the melting-solidification process. Results presented indicate that additive manufacturing is a very attractive technique for the production of high-performance ceramic structures in a single step.

  10. Computers in manufacturing

    NASA Astrophysics Data System (ADS)

    Hudson, C. A.

    1982-02-01

    CAD/CAM advances and applications for enhancing productivity in industry are explored. Wide-spread use of CAD/CAM devices are projected to occur by the time period 1992-1997, resulting in a higher percentage of technicians in the manufacturing process, while the cost of computers and software will continue to fall and become more widely available. Computer aided design is becoming a commercially viable system for design and geometric modeling, engineering analysis, kinematics, and drafting, and efforts to bridge the gap between CAD and CAM are indicated, with particular attention given to layering, wherein individual monitoring of different parts of the manufacturing process can be effected without crossover of unnecessary information. The potentials and barriers to the use of robotics are described, with the added optimism that displaced workers to date have moved up to jobs of higher skill and interest.

  11. Perspectives on Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Bourell, David L.

    2016-07-01

    Additive manufacturing (AM) has skyrocketed in visibility commercially and in the public sector. This article describes the development of this field from early layered manufacturing approaches of photosculpture, topography, and material deposition. Certain precursors to modern AM processes are also briefly described. The growth of the field over the last 30 years is presented. Included is the standard delineation of AM technologies into seven broad categories. The economics of AM part generation is considered, and the impacts of the economics on application sectors are described. On the basis of current trends, the future outlook will include a convergence of AM fabricators, mass-produced AM fabricators, enabling of topology optimization designs, and specialization in the AM legal arena. Long-term developments with huge impact are organ printing and volume-based printing.

  12. Chemical reactivity of CVC and CVD SiC with UO2 at high temperatures

    SciTech Connect

    Silva, Chinthaka M.; Katoh, Yutai; Voit, Stewart L.; Snead, Lance L.

    2015-02-11

    Two types of silicon carbide (SiC) synthesized using two different vapor deposition processes were embedded in UO2 pellets and evaluated for their potential chemical reaction with UO2. While minor reactivity between chemical-vapor-composited (CVC) SiC and UO2 was observed at comparatively low temperatures of 1100 and 1300 C, chemical-vapor-deposited (CVD) SiC did not show any such reactivity, according to microstructural investigations. But, both CVD and CVC SiCs showed some reaction with UO2 at a higher temperature (1500 C). Elemental maps supported by phase maps obtained using electron backscatter diffraction indicated that CVC SiC was more reactive than CVD SiC at 1500 C. Moreover, this investigation indicated the formation of uranium carbides and uranium silicide chemical phases such as UC, USi2, and U3Si2 as a result of SiC reaction with UO2.

  13. Photon absorption and emission properties of 7 Å SiC nanoclusters: Electronic gap, surface state, and quantum size effect

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoxiao; Chen, Xifang; Fan, Baolu; Zhang, Yumeng; Fan, Jiyang

    2016-07-01

    People know little experimentally about the physical properties of the SiC nanoclusters with sizes of a couple of angstroms. Herein, we study the electronic structure and light absorption/emission properties of the SiC nanoclusters with an average diameter of 7 Å that are fabricated by diminishing the sizes of the SiC microcrystals under high pressure and high temperature. The results reveal that the SiC nanoclusters have an indirect energy gap of 5.1 eV. Unlike the case of larger SiC nanocrystals, the luminescence of the SiC nanoclusters is dominated by two types of oxygen-related surface defects, and the maximum of their photoluminescence/photoluminescence excitation spectrum lies at 4.1/3.3 and 3.8/3.0 eV, respectively. The energy gap of the SiC nanoparticles with reference to bulk value is found to be inversely proportional to the diameter to the power 0.97, which shows slower increase of energy gap with decreasing size than what is predicted by using the first-principles calculations.

  14. Microstructure of TRISO Coated Particles from the AGR-1 Experiment I: SiC Grain Size and Grain Boundary Character

    SciTech Connect

    Rita Kirchhofer; John D, Hunn; Paul A. Demkowicz; James I. Cole; Brian P. Gorman

    2013-01-01

    Pre-irradiation SiC microstructures in TRISO coated fuel particles from the AGR-1 experiment were quantitatively characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). From EBSD it was determined that only the cubic polymorph of as-deposited SiC was present and the SiC had a high fraction of CSL S3 grain boundaries. Additionally, the local area misorientation (LAM), which is a qualitative measurement of strain in the SiC lattice, was mapped for each fuel variant. The morphology of the SiC / IPyC interfaces were characterized by TEM following site-specific focused ion beam (FIB) specimen preparation. It was determined that the SiC layer had a heavily faulted microstructure typical of CVD deposited SiC and that the average grain diameter increased from the SiC/IPyC interface for all the fuel variants, except V3 that showed a constant grain size across the layer.

  15. Epitaxial Growth of beta-Silicon Carbide (SiC) on a Compliant Substrate via Chemical Vapor Deposition (CVD)

    NASA Technical Reports Server (NTRS)

    Mitchell, Sharanda L.

    1996-01-01

    Many lattice defects have been attributed to the lattice mismatch and the difference in the thermal coefficient of expansion between SiC and silicon (Si). Stacking faults, twins and antiphase boundaries are some of the lattice defects found in these SiC films. These defects may be a partial cause of the disappointing performance reported for the prototype devices fabricated from beta-SiC films. The objective of this research is to relieve some of the thermal stress due to lattice mismatch when SiC is epitaxially grown on Si. The compliant substrate is a silicon membrane 2-4 microns thick. The CVD process includes the buffer layer which is grown at 1360 C followed by a very thin epitaxial growth of SiC. Then the temperature is raised to 1500 C for the subsequent growth of SiC. Since silicon melts at 1415 C, the SiC will be grown on molten Silicon which is absorbed by a porous graphite susceptor eliminating the SiC/Si interface. We suspect that this buffer layer will yield less stressed material to help in the epitaxial growth of SiC.

  16. Evaluation of sintering effects on SiC incorporated UO2 kernels under Ar and Ar-4%H2 environments

    SciTech Connect

    Silva, Chinthaka M; Lindemer, Terrence; Hunt, Rodney Dale; Collins, Jack Lee; Terrani, Kurt A; Snead, Lance Lewis

    2013-01-01

    Silicon carbide (SiC) is suggested as an oxygen getter in UO2 kernels used for TRISO particle fuels to lower oxygen potential and prevent kernel migration during irradiation. Scanning electron microscopy and X-ray diffractometry analyses performed on sintered kernels verified that internal gelation process can be used to incorporate SiC in urania fuel kernels. Sintering in either Ar or Ar-4%H2 at 1500 C lowered the SiC content in the UO2 kernels to some extent. Formation of UC was observed as the major chemical phase in the process, while other minor phases such as U3Si2C2, USi2, U3Si2, and UC2 were also identified. UC formation was presumed to be occurred by two reactions. The first was the SiC reaction with its protective SiO2 oxide layer on SiC grains to produce volatile SiO and free carbon that subsequently reacted with UO2 to form UC. The second process was direct UO2 reaction with SiC grains to form SiO, CO, and UC, especially in Ar-4%H2. A slightly higher density and UC content was observed in the sample sintered in Ar-4%H2, but the use of both atmospheres produced kernels with ~95% of theoretical density. It is suggested that incorporating CO in the sintering gas would prevent UC formation and preserve the initial SiC content.

  17. Advancements in asphere manufacturing

    NASA Astrophysics Data System (ADS)

    Fess, Edward; DeFisher, Scott

    2013-09-01

    Aspheric optics can pose as a challenge to the manufacturing community due to the surface shape and level of quality required. The aspheric surface may have inflection points that limit the usable tool size during manufacturing, or there may be a stringent tolerance on the slope for mid-spatial frequencies that may be problematic for sub-aperture finishing techniques to achieve. As aspheres become more commonplace in the optics community, requests for more complex aspheres have risen. OptiPro Systems has been developing technologies to create a robust aspheric manufacturing process. Contour deterministic microgrinding is performed on a Pro80 or eSX platform. These platforms utilize software and the latest advancements in machine motion to accurately contour the aspheric shape. Then the optics are finished using UltraForm Finishing (UFF), which is a sub-aperture polishing process. This process has the capability to adjust the diameter and compliance of the polishing lap to allow for finishing over a wide range of shapes and conditions. Finally, the aspheric surfaces are qualified using an OptiTrace contact profilometer, or an UltraSurf non-contact 3D surface scanner. The OptiTrace uses a stylus to scan across the surface of the part, and the UltraSurf utilizes several different optical pens to scan the surface and generate a topographical map of the surface under test. This presentation will focus on the challenges for asphere manufacturing, how OptiPro has implemented its technologies to combat these challenges, and provide surface data for analysis.

  18. Electrohydrodynamic Printing and Manufacturing

    NASA Technical Reports Server (NTRS)

    Aksay, Ilhan A. (Inventor); Saville, Dudley A. (Inventor); Poon, Hak Fei (Inventor); Korkut, Sibel (Inventor); Chen, Chuan-hua (Inventor)

    2014-01-01

    An stable electrohydrodynamic filament is obtained by causing a straight electrohydrodynamic filament formed from a liquid to emerge from a Taylor cone, the filament having a diameter of from 10 nm to 100.mu.m. Such filaments are useful in electrohydrodynamic printing and manufacturing techniques and their application in liquid drop/particle and fiber production, colloidal deployment and assembly, and composite materials processing.

  19. Near-Interface Defects in SiO2/SiC MOS Devices

    NASA Astrophysics Data System (ADS)

    Basile, A. F.; Mooney, P. M.

    2012-02-01

    The implementation of SiO2/SiC MOSFETS for high power applications has been hindered by the high density of near-interface states. We have developed a method to distinguish both the energy and spatial distribution of defect states near insulator-semiconductor interfaces through a comparison of the thermal emission energy extracted from constant capacitance transient spectroscopy (CCDLTS) measurements and the interface Fermi energy (FP). The dependence of FP on trap filling voltage at the CCDLTS peak temperature is determined from temperature-dependent 1MHz C-V curves. Capture by tunneling into oxide traps is detected in 4H- and 6H-SiC capacitors fabricated by oxidation followed by NO-annealing, with the difference in thermal emission energies consistent with the conduction band offsets of the two polytypes at the SiO2/SiC interface. Comparison with results from first principles calculations suggests that the observed oxide traps are CO=CO and interstitial Si [1]. SiC defects having energies close to the SiC conduction band are suggested to be carbon di-interstitial defects, (C2)i, introduced during standard oxidation [1]. Well-known traps introduced in SiC by ion-implantation are observed in 4H-SiC MOS capacitors fabricated by N-implantation followed by standard oxidation, thus validating this new method [2]. *A.F. Basile, et al., J. Appl. Phys. 109, 064514 (2011) *A.F. Basile, et al., J. Appl. Phys. 109, 114505 (2011).

  20. Diffusion of fission products and radiation damage in SiC

    NASA Astrophysics Data System (ADS)

    Malherbe, Johan B.

    2013-11-01

    A major problem with most of the present nuclear reactors is their safety in terms of the release of radioactivity into the environment during accidents. In some of the future nuclear reactor designs, i.e. Generation IV reactors, the fuel is in the form of coated spherical particles, i.e. TRISO (acronym for triple coated isotropic) particles. The main function of these coating layers is to act as diffusion barriers for radioactive fission products, thereby keeping these fission products within the fuel particles, even under accident conditions. The most important coating layer is composed of polycrystalline 3C-SiC. This paper reviews the diffusion of the important fission products (silver, caesium, iodine and strontium) in SiC. Because radiation damage can induce and enhance diffusion, the paper also briefly reviews damage created by energetic neutrons and ions at elevated temperatures, i.e. the temperatures at which the modern reactors will operate, and the annealing of the damage. The interaction between SiC and some fission products (such as Pd and I) is also briefly discussed. As shown, one of the key advantages of SiC is its radiation hardness at elevated temperatures, i.e. SiC is not amorphized by neutrons or bombardment at substrate temperatures above 350 °C. Based on the diffusion coefficients of the fission products considered, the review shows that at the normal operating temperatures of these new reactors (i.e. less than 950 °C) the SiC coating layer is a good diffusion barrier for these fission products. However, at higher temperatures the design of the coated particles needs to be adapted, possibly by adding a thin layer of ZrC.

  1. Aluminum Nitride-Silicon Carbide Alloy Crystals Grown on SiC Substrates by Sublimation

    SciTech Connect

    Gu, Z; Du, Li; Edgar, J H; Payzant, E Andrew; Walker, Larry R; Liu, R; Engelhard, M H

    2005-01-01

    AlN-SiC alloy crystals, with a thickness greater than 500μm, were grown on 4H- and 6H-SiC substrates from a mixture of AlN and SiC powders by the sublimation-recondensation method at 1860-1990 C. On-axis SiC substrates produced a rough surface covered with hexagonal grains, while 6H- and 4H- off-axis SiC substrates with different miscut angles (8 or 3.68 ) formed a relatively smooth surface with terraces and steps. The substrate misorientation ensured that the AlNSiC alloy crystals grew two dimensionally as identified by scanning electron microscopy (SEM). Xray diffraction (XRD) and transmission electron microscopy (TEM) confirmed that the AlN-SiC alloys had the wurtzite structure. Electron probe microanalysis (EPMA) and x-ray photoelectron spectroscopy (XPS) demonstrated that the resultant alloy crystals had non-stoichiometric ratios of Al:N and Si:C and a uniform composition throughout the alloy crystal from the interface to the surface. The composition ratio of Al:Si of the alloy crystals changed with the growth temperature, and differed from the original source composition, which was consistent with the results predicted by thermodynamic calculation of the solid-vapor distribution of each element. XPS detected the bonding between Si-C, Si-N, Si-O for the Si 2p spectra. The dislocation density decreased with the growth, which was lower than 10^6cm-2 at the alloy surface, more than two orders of magnitude lower compared to regions close to the crystal/substrate interface, as determined by TEM.

  2. Aluminum Nitride-Silicon Carbide Alloy Crystals Grown on SiC Substrates by Sublimation

    SciTech Connect

    Gu, Zheng; Du, L; Edgar, James H.; Payzant, Edward A.; Walker, L. R.; Liu, R.; Engelhard, Mark H.

    2005-12-20

    AlN-SiC alloy crystals, with a thickness greater than 500 m, were grown on 4H- and 6H-SiC substrates from a mixture of AlN and SiC powders by the sublimation-recondensation method at 1860-1990 C. On-axis SiC substrates produced a rough surface covered with hexagonal grains, while 6H- and 4H- off-axis SiC substrates with different miscut angles (8? or 3.68?) formed a relatively smooth surface with terraces and steps. The substrate misorientation ensured that the AlN-SiC alloy crystals grew two dimensionally as identified by scanning electron microscopy (SEM). X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed that the AlN-SiC alloys had the wurtzite structure. Electron probe microanalysis (EPMA) and x-ray photoelectron spectroscopy (XPS) demonstrated that the resultant alloy crystals had non-stoichiometric ratios of Al:N and Si:C and a uniform composition throughout the alloy crystal from the interface to the surface. The composition ratio of Al:Si of the alloy crystals changed with the growth temperature, and differed from the original source composition, which was consistent with the results predicted by thermodynamic calculation of the solid-vapor distribution of each element. XPS detected the bonding between Si-C, Si-N, Si-O for the Si 2p spectra. The dislocation density decreased with the growth, which was lower than 106 cm-2 at the alloy surface, more than two orders of magnitude lower compared to regions close to the crystal/substrate interface, as determined by TEM.

  3. Effects of thermal annealing on photoluminescence of Si+/C+ implanted SiO2 films

    NASA Astrophysics Data System (ADS)

    Chen, Yin-Yu; Chao, Der-Sheng; Tsai, Hsu-Sheng; Liang, Jenq-Horng

    2016-04-01

    The mechanisms of photoluminescence (PL) originating from Si+/C+ implanted SiO2 are still unclear and need to be clarified. Thus, the purpose of this study is to thoroughly investigate the effects of ion implantation and post-annealing temperature on microstructures and PL characteristics of the Si+/C+ implanted SiO2 films. A comparative analysis was also conducted to clarify the different optical properties between the Si+ and Si+/C+ implanted SiO2 films. In this study, thermally-grown SiO2 films on Si substrates were used as the matrix materials. The Si+ ions and C+ ions were separately implanted into the SiO2 films at room temperature. After ion implantation, the post-annealing treatments were carried out using the furnace annealing (FA) method at various temperatures (600-1100 °C) for 1 h in a N2 ambient. The PL characteristics of the implanted SiO2 films were analyzed using a fluorescence spectrophotometer. The results revealed that the distinct PL peaks were observed at approximately 310, 450 and 650 nm in the Si+-implanted SiO2 films, which can be attributed to the defects, the so-called oxygen deficiency centers (ODCs) and non-bridging oxygen hole centers (NBOHCs), in the materials. In contrast to the Si+ ion implantation, the SiO2 films which were sequentially implanted with Si+ and C+ ions and annealed at 1100 °C can emit white light corresponding to the PL peaks located at around 420, 520 and 720 nm, those can be assigned to the Si-C bonding, C-C graphite-like structure (sp2), and Si nanocrystals, respectively. Moreover, a correlation between the optical properties, microstructures, and bonding configurations of the Si+/C+ implanted SiO2 films was also established in this study.

  4. Manufactured Homes Tool

    2005-03-09

    The MH Tool software is designed to evaluate existing and new manufactured homes for structural adequacy in high winds. Users define design elements of a manufactured home and then select the hazard(s) for analysis. MH Tool then calculates and reports structural analysis results for the specified design and hazard Method of Solution: Design engineers input information (geometries, materials, etc.) describing the structure of a manufactured home, from which the software automatically creates a mathematical model.more » Windows, doors, and interior walls can be added to the initial design. HUD Code loads (wind, snow loads, interior live loads, etc.) are automatically applied. A finite element analysis is automatically performed using a third party solver to find forces and stresses throughout the structure. The designer may then employ components of strength (and cost) most appropriate for the loads that must be carried at each location, and then re-run the analysis for verification. If forces and stresses are still within tolerable limits (such as the HUD requirements), construction costs would be reduced without sacrificing quality.« less

  5. Advanced manufacturing: Technology diffusion

    SciTech Connect

    Tesar, A.

    1995-12-01

    In this paper we examine how manufacturing technology diffuses rom the developers of technology across national borders to those who do not have the capability or resources to develop advanced technology on their own. None of the wide variety of technology diffusion mechanisms discussed in this paper are new, yet the opportunities to apply these mechanisms are growing. A dramatic increase in technology diffusion occurred over the last decade. The two major trends which probably drive this increase are a worldwide inclination towards ``freer`` markets and diminishing isolation. Technology is most rapidly diffusing from the US In fact, the US is supplying technology for the rest of the world. The value of the technology supplied by the US more than doubled from 1985 to 1992 (see the Introduction for details). History shows us that technology diffusion is inevitable. It is the rates at which technologies diffuse to other countries which can vary considerably. Manufacturers in these countries are increasingly able to absorb technology. Their manufacturing efficiency is expected to progress as technology becomes increasingly available and utilized.

  6. Synthesis of ZrB2 and ZrB2-SiC Powders Using a Sucrose-Containing System.

    PubMed

    Wang, Tingyu; Zhang, Yun; Li, Junping; Zhao, Bin; Li, Ruixing; Yin, Shu; Feng, Zhihai; Sato, Tsugio; Cai, Hongnian

    2015-09-01

    ZrB2 and ZrB2-SiC powders are synthesized by a sol-gel method from zirconium n-propoxide, tetraethyl orthosilicate (only for ZrB2-SiC), boric acid, and sucrose. After reduction at 1550 degrees C, both ZrB2 and ZrB2-SiC are unconsolidated, soft gray powders. The ZrB2-SiC particles have an equiaxed shape with a diameter of about 800 nm and a uniform size distribution. The SiC may be very finely distributed, because we barely find SiC among ZrB2 particles when using energy dispersive X-ray spectroscopy (EDS), although both ZrB2 and SiC are identified by X-ray diffractometry (XRD). PMID:26716344

  7. 77 FR 2275 - Manufacturing Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-17

    ... manufacturing and alternative energy manufacturing sectors. Additional factors that may be considered in the... Washington, DC. The next meeting is scheduled to take place on January 20, 2012 in Washington, DC. See 76...

  8. Dermatitis in rubber manufacturing industries

    SciTech Connect

    White, I.R.

    1988-01-01

    This review describes the history of rubber technology and the manufacturing techniques used in rubber manufacturing industries. The important aspects of the acquisition of allergic and irritant contact dermatitis within the industry are presented for the reader.

  9. 75 FR 80040 - Manufacturing Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-21

    ... International Trade Administration Manufacturing Council AGENCY: International Trade Administration, U.S... Manufacturing Council. SUMMARY: On November 23, 2010, the Department of Commerce's International Trade Administration published a notice in the Federal Register (75 FR 71417) soliciting applications to fill...

  10. 75 FR 30781 - Manufacturing Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-02

    ... International Trade Administration Manufacturing Council AGENCY: International Trade Administration, U.S... Manufacturing Council. SUMMARY: On March 16, 2010, the Department of Commerce's International Trade Administration published a notice in the Federal Register (75 FR 12507) soliciting applications for membership...

  11. 77 FR 69794 - Manufacturing Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-21

    ... International Trade Administration Manufacturing Council AGENCY: International Trade Administration, U.S... Manufacturing Council. SUMMARY: On September 14, 2012, the Department of Commerce's International Trade Administration (ITA) published a notice in the Federal Register (77 FR 56811) soliciting applications...

  12. 77 FR 66179 - Manufacturing Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-02

    ... International Trade Administration Manufacturing Council AGENCY: International Trade Administration, U.S... manufacturing council. SUMMARY: On September 14, 2012, the Department of Commerce's International Trade Administration published a notice in the Federal Register (77 FR 56811) soliciting applications for...

  13. Manufacturing a Superconductor in School.

    ERIC Educational Resources Information Center

    Barrow, John

    1989-01-01

    Described is the manufacture of a superconductor from a commercially available kit using equipment usually available in schools or easily obtainable. The construction is described in detail including equipment, materials, safety procedures, tolerances, and manufacture. (Author/CW)

  14. Energy 101: Clean Energy Manufacturing

    SciTech Connect

    2015-07-09

    Most of us have a basic understanding of manufacturing. It's how we convert raw materials, components, and parts into finished goods that meet our essential needs and make our lives easier. But what about clean energy manufacturing? Clean energy and advanced manufacturing have the potential to rejuvenate the U.S. manufacturing industry and open pathways to increased American competitiveness. Watch this video to learn more about this exciting movement and to see some of these innovations in action.

  15. Synthesis and Characterization of Ti3SiC2 Particulate-Reinforced Novel Zn Matrix Composites

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Habib, M. A.; Dunnigan, R.; Kaabouch, N.; Ghosh, S.

    2015-10-01

    In this paper, we report the synthesis and characterization of novel Ti3SiC2-reinforced Zn matrix composites. All the composites were hot pressed at 500 °C for 5 min at a uniaxial pressure of ~150 MPa. Microstructure analysis by scanning electron microscopy and phase analysis by x-ray diffraction confirmed that there was minimal interfacial reaction between Ti3SiC2 particles and Zn matrix. The addition of Ti3SiC2 improved the tribological performance of these composites against alumina substrates but did not have any beneficial effect on the mechanical performance.

  16. The influence of ZrB2-SiC powders mechanical treatment on the structure of sintered ceramic composites

    NASA Astrophysics Data System (ADS)

    Buyakova, S.; Burlachenko, A.; Mirovoi, Yu; Sevostiyanova, I.; Kulkov, S.

    2016-07-01

    The effect of mechanical treatment by planetary ball milling on the properties of hot pressed ZrB2 - SiC ceramics was studied. It was shown that material densification after mechanical treatment is finished at initial stages of sintering process. Addition of SiC leads to an essential increase of sample density to 99% of theoretically achievable for powder with 2% of SiC, as compared with ZrB2 with the density less than 76%. It was demonstrated that all defects that were accumulated during mechanical treatment are annealed during hot pressing, and there are no changes of CDD values in sintered ceramics.

  17. 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.

  18. Decision Guidance for Sustainable Manufacturing

    ERIC Educational Resources Information Center

    Shao, Guodong

    2013-01-01

    Sustainable manufacturing has significant impacts on a company's business performance and competitiveness in today's world. A growing number of manufacturing industries are initiating efforts to address sustainability issues; however, to achieve a higher level of sustainability, manufacturers need methodologies for formally describing, analyzing,…

  19. 77 FR 56811 - Manufacturing Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-14

    ... International Trade Administration Manufacturing Council AGENCY: International Trade Administration, U.S. Department of Commerce. ACTION: Notice of an Opportunity to Apply for Membership on the Manufacturing Council... ] Manufacturing Council (Council) for a two-year term to begin in fall 2012. The purpose of the Council is...

  20. 76 FR 33244 - Manufacturing Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-08

    ... International Trade Administration Manufacturing Council AGENCY: International Trade Administration, U.S. Department of Commerce. ACTION: Notice of an Opportunity To Apply for Membership on the Manufacturing Council... Manufacturing Council (Council). The purpose of the Council is to advise the Secretary of Commerce on...

  1. Out of bounds additive manufacturing

    DOE PAGES

    Holshouser, Chris; Newell, Clint; Palas, Sid; Love, Lonnie J.; Kunc, Vlastimil; Lind, Randall F.; Lloyd, Peter D.; Rowe, John C.; Blue, Craig A.; Duty, Chad E.; et al

    2013-03-01

    Lockheed Martin and Oak Ridge National Laboratory are working on an additive manufacturing system capable of manufacturing components measured not in terms of inches or feet, but multiple yards in all dimensions with the potential to manufacture parts that are completely unbounded in size.

  2. Manufacturing Curriculum Grant. Final Report.

    ERIC Educational Resources Information Center

    Scarborough, Jule Dee

    A manufacturing curriculum for secondary vocational programs was designed to bridge the gap between grades 9-10 level courses and the community college-level curriculum of the Illinois Plan for Industrial Education. During the project, a literature review of manufacturing curriculum materials was conducted, a manufacturing conceptual framework was…

  3. Developing Critical L2 Digital Literacy through the Use of Computer-Based Internet-Hosted Learning Management Systems such as Moodle

    NASA Astrophysics Data System (ADS)

    Meurant, Robert C.

    Second Language (L2) Digital Literacy is of emerging importance within English as a Foreign Language (EFL) in Korea, and will evolve to become regarded as the most critical component of overall L2 English Literacy. Computer-based Internet-hosted Learning Management Systems (LMS), such as the popular open-source Moodle, are rapidly being adopted worldwide for distance education, and are also being applied to blended (hybrid) education. In EFL Education, they have a special potential: by setting the LMS to force English to be used exclusively throughout a course website, the meta-language can be made the target L2 language. Of necessity, students develop the ability to use English to navigate the Internet, access and contribute to online resources, and engage in computer-mediated communication. Through such pragmatic engagement with English, students significantly develop their L2 Digital Literacy.

  4. Electronic Transitions of Jet-cooled SiC2, Si2Cn (n=1-3), Si3Cn (n = 1,2), and SiC6H4 between 250 and 710 nm

    NASA Astrophysics Data System (ADS)

    Steglich, M.; Maier, J. P.

    2015-03-01

    Electronic transitions of the title molecules were measured between 250 and 710 nm using a mass-resolved 1 + 1’ resonant two-photon ionization technique at a resolution of 0.1 nm. Calculations at the B3LYP/aug-cc-pVQZ level of theory support the analyses. Because of their spectral properties, SiC2, linear Si2C2, Si3C, and SiC6H4 are interesting target species for astronomical searches in the visible spectral region. Of special relevance is the Si-C2-Si chain, which features a prominent band at 516.4 nm of a strong transition (f = 0.25). This band and one from SiC6H4 at 445.3 nm were also investigated at higher resolution (0.002 nm).

  5. Metal Additive Manufacturing: A Review

    NASA Astrophysics Data System (ADS)

    Frazier, William E.

    2014-06-01

    This paper reviews the state-of-the-art of an important, rapidly emerging, manufacturing technology that is alternatively called additive manufacturing (AM), direct digital manufacturing, free form fabrication, or 3D printing, etc. A broad contextual overview of metallic AM is provided. AM has the potential to revolutionize the global parts manufacturing and logistics landscape. It enables distributed manufacturing and the productions of parts-on-demand while offering the potential to reduce cost, energy consumption, and carbon footprint. This paper explores the material science, processes, and business consideration associated with achieving these performance gains. It is concluded that a paradigm shift is required in order to fully exploit AM potential.

  6. Manufactured soil screening test

    SciTech Connect

    1999-05-01

    The purpose of this technical note is to provide a screening test that can be used to evaluate the potential for manufacturing artificial soil using dredged material, cellulose waste materials (e.g., yard waste compost, sawdust, wastepaper), and biosolids (e.g., N-Viro-reconditioned sewage sludge, BIONSOIL-reconstituted cow manure). This procedure will allow the most productive blend of any dredged material (uncontaminated or contaminated), cellulose, and biosolids to be determined and recommended for use in an environmentally productive and beneficial manner.

  7. Manufacturing of microarrays.

    PubMed

    Petersen, David W; Kawasaki, Ernest S

    2007-01-01

    DNA microarray technology has become a powerful tool in the arsenal of the molecular biologist. Capitalizing on high precision robotics and the wealth of DNA sequences annotated from the genomes of a large number of organisms, the manufacture of microarrays is now possible for the average academic laboratory with the funds and motivation. Microarray production requires attention to both biological and physical resources, including DNA libraries, robotics, and qualified personnel. While the fabrication of microarrays is a very labor-intensive process, production of quality microarrays individually tailored on a project-by-project basis will help researchers shed light on future scientific questions.

  8. Packaging Technology Developed for High-Temperature SiC Sensors and Electronics

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Lei, Jih-Fen

    2000-01-01

    A ceramic- and thick-film-materials-based prototype electronic package designed for silicon carbide (SiC) high-temperature sensors and electronics has been successfully tested at 500 C in an oxygen-containing air environment for 500 hours. This package was designed, fabricated, assembled, and electronically evaluated at the NASA Glenn Research Center at Lewis Field with an in-house-fabricated SiC semiconductor test chip. High-temperature electronics and sensors are necessary for harsh-environment space and aeronautical applications, such as space missions to the inner solar system or the emission control electronics and sensors in aeronautical engines. Single-crystal SiC has such excellent physical and chemical material properties that SiC-based semiconductor electronics can operate at temperatures over 600 C, which is significantly higher than the limit for Si-based semiconductor devices. SiC semiconductor chips were recently demonstrated to be operable at temperatures as high as 600 C, but only in the probe station environment because suitable packaging technology for sensors and electronics at temperatures of 500 C and beyond did not exist. Thus, packaging technology for SiC-based sensors and electronics is immediately needed for both application and commercialization of high-temperature SiC sensors and electronics. In response to this need, researchers at Glenn designed, fabricated, and assembled a prototype electronic package for high-temperature electronics, sensors, and microelectromechanical systems (MEMS) using aluminum nitride (AlN) substrate and gold (Au) thick-film materials. This prototype package successfully survived a soak test at 500 C in air for 500 hours. Packaging components tested included thick-film high-temperature metallization, internal wire bonds, external lead bonds, and a SiC diode chip die-attachment. Each test loop, which was composed of thick-film printed wire, wire bond, and lead bond was subjected to a 50-mA direct current for 250

  9. Construction Progress of the S-IC Test Stand-Crane Control

    NASA Technical Reports Server (NTRS)

    1963-01-01

    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, taken at the S-IC test stand on October 2, 1963, is of a crane control. It was from here that the massive cranes were operated. Seen in the background is the F-1 Test Stand. Designed to assist in the development of the F-1 Engine, the F-1 test stand is a vertical engine firing test stand, 239 feet in elevation and 4,600 square feet in area at the base. Capability was provided for static firing of 1.5 million pounds of thrust using liquid oxygen and kerosene. Like the S-IC stand

  10. Construction Progress of the S-IC Test Stand-Pump House

    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. In addition to the stand itself, related facilities were constructed during this time. Built directly east of the test stand was the Block House, which served as the control center for the test stand. The two were connected by a narrow access tunnel which housed the cables for the controls. Again to the east, just south of the Block House, was a newly constructed Pump House. Its function was to provide water to the stand to prevent melting damage during testing. The water was sprayed through

  11. SIC-BASED HYDROGEN SELECTIVE MEMBRANES FOR WATER-GAS-SHIFT REACTION

    SciTech Connect

    Paul K.T. Liu

    2003-12-01

    A hydrogen selective membrane as a membrane reactor (MR) can significantly improve the power generation efficiency with a reduced capital and operating cost for the waster-gas-shift reaction. Existing hydrogen selective ceramic membranes are not suitable for the proposed MR due to their poor hydrothermal stability. In this project we have focused on the development of innovative silicon carbide (SiC) based hydrogen selective membranes, which can potentially overcome this technical barrier. SiC macro-porous membranes have been successfully fabricated via extrusion of commercially available SiC powder. Also, an SiC hydrogen selective thin film was prepared via our CVD/I technique. This composite membrane demonstrated excellent hydrogen selectivity at high temperature ({approx}600 C). More importantly, this membrane also exhibited a much improved hydrothermal stability at 600 C with 50% steam (atmospheric pressure) for nearly 100 hours. In parallel, we have explored an alternative approach to develop a H{sub 2} selective SiC membrane via pyrolysis of selected pre-ceramic polymers and sol-gel techniques. Building upon the positive progress made in the membrane development study, we conducted an optimization study to develop an H{sub 2} selective SiC membrane with sufficient hydrothermal stability suitable for the WGS environment. In addition, mathematical simulation has been performed to compare the performance of the membrane reactor (MR) vs conventional packed bed reactor for WGS reaction. Our result demonstrates that >99.999% conversion can be accomplished via WGS-MR using the hydrogen selective membrane developed by us. Further, water/CO ratio can be reduced, and >97% hydrogen recovery and <200 ppm CO can be accomplished according to the mathematical simulation. Thus, we believe that the operating economics of WGS can be improved significantly based upon the proposed MR concept. In parallel, gas separations and hydrothermal and long-term-storage stability of the

  12. Distribution of Pd, Ag & U in the SiC Layer of an Irradiated TRISO Fuel Particle

    SciTech Connect

    Thomas M. Lillo; Isabella J. van Rooyen

    2014-08-01

    The distribution of silver, uranium and palladium in the silicon carbide (SiC) layer of an irradiated TRISO fuel particle was studied using samples extracted from the SiC layer using focused ion beam (FIB) techniques. Transmission electron microscopy in conjunction with energy dispersive x-ray spectroscopy was used to identify the presence of the specific elements of interest at grain boundaries, triple junctions and precipitates in the interior of SiC grains. Details on sample fabrication, errors associated with measurements of elemental migration distances and the distances migrated by silver, palladium and uranium in the SiC layer of an irradiated TRISO particle from the AGR-1 program are reported.

  13. Synthesis of the tube-brush-shaped SiC nanowire array on carbon fiber and its photoluminescence properties.

    PubMed

    Chen, Jianjun; Wu, Renbing; Pan, Yi

    2010-10-01

    Tube-brush-shaped nanostructure of SiC nanowires was synthesized on polyacrylonitrile-based carbon fibers. The morphology and microstructure of the nanowires were characterized by X-ray powder diffraction, field emission scanning electron microscopy and high-resolution transmission electron microscopy. A quasi-periodically twin structure with (111) plane as the boundary along the SiC nanowires was observed. The vapor-solid growth mechanism of the SiC nanowire brush is also discussed. Moreover, some separated blue-shifted photoluminescence peaks around 469 nm were measured. The separated blue-shifted emission peaks are attributed to the quantum confinement of nanoscaled twin segments along each nanowire rather than the apparent diameters of the nanowires. The SiC nanowire brushes hopefully can find potential applications in nanotechnology. PMID:21137760

  14. Pitting Corrosion in CVD SiC at 300°C in Deoxygenated High-Purity Water

    SciTech Connect

    Henager, Charles H.; Schemer-Kohrn, Alan L.; Pitman, Stan G.; Senor, David J.; Geelhood, Ken J.; Painter, Chad L.

    2008-08-15

    SiC is a candidate for nuclear applications at elevated temperatures but has not been fully studied under typical light-water reactor operating conditions, such as moderate temperatures and high pressures. Coupons of high-purity chemical vapor deposited SiC were exposed to deoxygenated, pressurized water at 573K and 100 Bar for up to 4000 hours. Ceramographic examination of the exposed SiC surfaces revealed both embryonic and large, d > 300 µm, pits on the surface. The pits were characterized using scanning electron microscopy for structure and chemistry analysis. Pit densities were also determined by standard counting methods. The chemical analysis revealed that the pits are associated with the formation of silica and subsequent loss of Si, which is expected due to several suggested reactions between SiC and water.

  15. Tailored growth of in situAl4SiC4 in laser melted aluminum melt

    NASA Astrophysics Data System (ADS)

    Chang, Fei; Gu, Dongdong

    2015-04-01

    The crystallization and growth of in situ crystals during non-equilibrium laser rapid melting/solidification process is an important research topic in the fields of both Applied Physics and Materials Science. The present paper studies the development mechanisms of in situ formed Al4SiC4 ceramic phase within the selective laser melted SiC/AlSi10Mg composites. Two different-structured Al4SiC4 having strip and particle morphologies were disclosed and their growth mechanisms were influenced by laser linear energy density (LED). An elevated LED resulted in a larger degree formation of strip-structured Al4SiC4 with the gradually coarsened crystal sizes in its length and thickness. The homogeneously dispersed particle-shaped Al4SiC4 exhibited a considerably refined nanostructure with a proper increase in LED, but showing a significant coarsening of particles at an excessive LED.

  16. Comparative studies of monoclinic and orthorhombic WO3 films used for hydrogen sensor fabrication on SiC crystal

    NASA Astrophysics Data System (ADS)

    Zuev, V. V.; Grigoriev, S. N.; Romanov, R. I.; Fominski, V. Y.; Volosova, M. A.; Demin, M. V.

    2016-09-01

    Amorphous WOx films were prepared on the SiC crystal by using two different methods, namely, reactive pulsed laser deposition (RPLD) and reactive deposition by ion sputtering (RDIS). After deposition, the WOx films were annealed in an air. The RISD film possessed a m-WO3 structure and consisted of closely packed microcrystals. Localized swelling of the films and micro-hills growth did not destroy dense crystal packing. RPLD film had layered β-WO3 structure with relatively smooth surface. Smoothness of the films were destroyed by localized swelling and the micro-openings formation was observed. Comparative study of m-WO3/SiC, Pt/m-WO3/SiC, and P-WO3/SiC samples shows that structural characteristics of the WO3 films strongly influence on the voltage/current response as well as on the rate of current growth during H2 detection at elevated temperatures.

  17. The application of PCMMcs and SiC by commercially direct dual-complex coating on textile polymer

    NASA Astrophysics Data System (ADS)

    Koo, Kang; Choe, Jongdeok; Park, Youngmi

    2009-07-01

    To enhance the thermal insulation effect, waterproof/breathable fabrics were directly top dual-coated by the dry coating method with ceramic materials (silicon carbide, SiC). The fabric was base coated by the wet coating method with 5 wt% phase-change material microcapsules (PCMMcs) and tested for the emission of far-infrared (FIR) radiation. With increasing SiC content, the fabric altered some of the physical properties by increasing the FIR emissivity, emission power, water vapor transmission rate (WVTR) and heat release capacity. Scanning electron microscopy (SEM) analysis revealed the presence of the PCMMcs and SiC particles at the cross-section and surface of the coating, respectively, which exhibited a rugged and blocky shape. The results indicated that SiC addition did not affect the water entry pressure (WEP) in the fabric structure, but did alter the following physical properties: WVTR, interactions between the macromolecule chains and the susceptibility to humidity.

  18. Polyolefin catalyst manufacturing

    SciTech Connect

    Inkrott, K.E.; Scinta, J.; Smith, P.D. )

    1989-10-16

    Statistical process control (SPC) procedures are absolutely essential for making new-generation polyolefin catalysts with the consistent high quality required by modern polyolefin processes. Stringent quality assurance is critical to the production of today's high-performance catalysts. Research and development efforts during the last 20 years have led to major technological improvements in the polyolefin industry. New generation catalysts, which once were laboratory curiosities, must now be produced commercially on a regular and consistent basis to meet the increasing requirements of the plastics manufacturing industry. To illustrate the more stringent requirements for producing the new generation polyolefin catalysts, the authors compare the relatively simple, first-generation polypropylene catalyst production requirements with some of the basic requirements of manufacturing a more complex new-generation catalyst, such as Catalyst Resources Inc.'s LYNX 900. The principles which hold true for the new-generation catalysts such as LYNX 900 are shown to apply equally to the scale-up of other advanced technology polyolefin catalysts.

  19. Effects of Atmosphere and Ultraviolet Light Irradiation on Chemical Mechanical Polishing Characteristics of SiC Wafers

    NASA Astrophysics Data System (ADS)

    Ohnishi, Osamu; Doi, Toshiro; Kurokawa, Syuhei; Yamazaki, Tsutomu; Uneda, Michio; Yin, Tao; Koshiyama, Isamu; Ichikawa, Koichiro; Aida, Hideo

    2012-05-01

    To establish a high-efficiency and high-quality polishing process by controlling the workpiece environment, a prototype chemical mechanical polishing (CMP) machine that can perform double-side CMP simultaneously in a sealed pressure chamber was developed. Using this new machine, polishing experiments on single crystalline silicon carbide (SiC) wafers were carried out. The results showed that applying a highly pressurized O2 gas and ultraviolet light irradiation were effective in SiC CMP.

  20. Fracture strain of SiC nanowires and direct evidence of electron-beam induced amorphisation in the strained nanowires.

    PubMed

    Wang, Shiliang; Wu, Yueqin; Lin, Liangwu; He, Yuehui; Huang, Han

    2015-04-01

    SiC nanowires with diameters ranging from 29 to 270 nm exhibit an average strain of 5.5% with a maximum of up to 7.0%. The brittle fracture of the nano-wires being measured was confirmed by transmission electron microscopy (TEM) analysis. This study demonstrates that amorphisation occurs in the stained SiC nanowires during normal TEM examination, which could be induced by electron irradiation. PMID:25367627

  1. Integrating post-manufacturing issues into design and manufacturing decisions

    NASA Technical Reports Server (NTRS)

    Eubanks, Charles F.

    1996-01-01

    An investigation is conducted on research into some of the fundamental issues underlying the design for manufacturing, service and recycling that affect engineering decisions early in the conceptual design phase of mechanical systems. The investigation focuses on a system-based approach to material selection, manufacturing methods and assembly processes related to overall product requirements, performance and life-cycle costs. Particular emphasis is placed on concurrent engineering decision support for post-manufacturing issues such as serviceability, recyclability, and product retirement.

  2. Theoretical study on the possible use of SiC microparticles as photothermal agents for the heating of bacteria

    NASA Astrophysics Data System (ADS)

    Rosenberg, M.; Petrie, T. A.

    2012-02-01

    Gold nanoparticles exhibiting surface plasmon resonances have been considered as photothermal agents for the selective destruction of bacteria by visible to near-infrared radiation. Here, we consider theoretically the possible complementary use of sub-micron silicon carbide (SiC) particles as photothermal agents for the heating of bacteria by pulsed mid-infrared (MIR) radiation. A SiC microparticle can exhibit surface phonon resonances in the MIR. Similar to the effect of surface plasmon resonances in gold nanoparticles, this could lead to enhanced absorption at the resonant wavelength and strong heating of the microparticle locally. If the heating is sufficient, this might lead to damage of bacterial cells adjacent to SiC particles. We estimate the heating of sub-micron SiC particles in a water medium under various pulse lengths of radiation at wavelength 10.6 µm. Noting that SiC is being investigated as a biocompatible material that could be functionalized for biomedical applications, and that an appropriately roughened SiC surface could be expected to exhibit similar surface phonon resonances, we speculate that enhanced heating under MIR radiation may be useful for in vitro sterilization of such surfaces.

  3. Ab initio potential energy surface and vibration-rotation energy levels of silicon dicarbide, SiC2.

    PubMed

    Koput, Jacek

    2016-10-01

    The accurate ground-state potential energy surface of silicon dicarbide, SiC2 , has been determined from ab initio calculations using the coupled-cluster approach. Results obtained with the conventional and explicitly correlated coupled-cluster methods were compared. The core-electron correlation, higher-order valence-electron correlation, and scalar relativistic effects were taken into account. The potential energy barrier to the linear SiCC configuration was predicted to be 1782 cm(-1) . The vibration-rotation energy levels of the SiC2 , (29) SiC2 , (30) SiC2 , and SiC(13) C isotopologues were calculated using a variational method. The experimental vibration-rotation energy levels of the main isotopologue were reproduced to high accuracy. In particular, the experimental energy levels of the highly anharmonic vibrational ν3 mode of SiC2 were reproduced to within 6.7 cm(-1) , up to as high as the v3  = 16 state.

  4. Ab initio potential energy surface and vibration-rotation energy levels of silicon dicarbide, SiC2.

    PubMed

    Koput, Jacek

    2016-10-01

    The accurate ground-state potential energy surface of silicon dicarbide, SiC2 , has been determined from ab initio calculations using the coupled-cluster approach. Results obtained with the conventional and explicitly correlated coupled-cluster methods were compared. The core-electron correlation, higher-order valence-electron correlation, and scalar relativistic effects were taken into account. The potential energy barrier to the linear SiCC configuration was predicted to be 1782 cm(-1) . The vibration-rotation energy levels of the SiC2 , (29) SiC2 , (30) SiC2 , and SiC(13) C isotopologues were calculated using a variational method. The experimental vibration-rotation energy levels of the main isotopologue were reproduced to high accuracy. In particular, the experimental energy levels of the highly anharmonic vibrational ν3 mode of SiC2 were reproduced to within 6.7 cm(-1) , up to as high as the v3  = 16 state. PMID:27481562

  5. An improved design of TRISO particle with porous SiC inner layer by fluidized bed-chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liu, Rongzheng; Liu, Malin; Chang, Jiaxing; Shao, Youlin; Liu, Bing

    2015-12-01

    Tristructural-isotropic (TRISO) particle has been successful in high temperature gas cooled reactor (HTGR), but an improved design is required for future development. In this paper, the coating layers are reconsidered, and an improved design of TRISO particle with porous SiC inner layer is proposed. Three methods of preparing the porous SiC layer, called high methyltrichlorosilane (MTS) concentration method, high Ar concentration method and hexamethyldisilane (HMDS) method, are experimentally studied. It is indicated that porous SiC layer can be successfully prepared and the density of SiC layer can be adjusted by tuning the preparation parameters. Microstructure and characterization of the improved TRISO coated particle are given based on scanning electron microscope (SEM), X-ray diffraction (XRD), Raman scattering and energy dispersive X-ray (EDX) analysis. It can be found that the improved TRISO coated particle with porous SiC layer can be mass produced successfully. The formation mechanisms of porous SiC layer are also discussed based on the fluidized bed-chemical vapor deposition principle.

  6. Fabrication and Evaluation of a High Performance SiC Inverter for Wireless Power Transfer Applications

    SciTech Connect

    Onar, Omer C; Campbell, Steven L; Ning, Puqi; Miller, John M; Liang, Zhenxian

    2013-01-01

    In this study, a high power density SiC high efficiency wireless power transfer converter system via inductive coupling has been designed and developed. The detailed power module design, cooling system design and power stage development are presented. The successful operation of rated power converter system demonstrates the feasible wireless charging plan. One of the most important part of this study is the wind bandgap devices packaged at the Oak Ridge National Laboratory (ORNL) using the in-house packaging technologies by employing the bare SiC dies acquired from CREE, which are rated at 50 A / 1200 V each. These packaged devices are also inhouse tested and characterized using ORNL s Device Characterization Facility. The successful operation of the proposed inverter is experimentally verified and the efficiency and operational characteristics of the inverter are also revealed.

  7. Vector Magnetometry Using Silicon Vacancies in 4 H -SiC Under Ambient Conditions

    NASA Astrophysics Data System (ADS)

    Niethammer, Matthias; Widmann, Matthias; Lee, Sang-Yun; Stenberg, Pontus; Kordina, Olof; Ohshima, Takeshi; Son, Nguyen Tien; Janzén, Erik; Wrachtrup, Jörg

    2016-09-01

    Point defects in solids promise precise measurements of various quantities. Especially magnetic field sensing using the spin of point defects has been of great interest recently. When optical readout of spin states is used, point defects achieve optical magnetic imaging with high spatial resolution at ambient conditions. Here, we demonstrate that genuine optical vector magnetometry can be realized using the silicon vacancy in SiC, which has an uncommon S =3 /2 spin. To this end, we develop and experimentally test sensing protocols based on a reference field approach combined with multifrequency spin excitation. Our work suggests that the silicon vacancy in an industry-friendly platform, SiC, has the potential for various magnetometry applications under ambient conditions.

  8. Ubiquitous interstellar diamond and SiC in primitive chondrites - Abundances reflect metamorphism

    NASA Technical Reports Server (NTRS)

    Huss, Gary R.

    1990-01-01

    It is shown here that interstellar diamond and SiC were incorporated into all groups of chondrite meteorites. Abundances rapidly go to zero with increasing metamorphic grade, suggesting that metamorphic destruction is responsible for the apparent absence of these grains in most chondrites. In unmetamorphosed chondrites, abundances normalized to matrix content are similar for different classes. Diamond samples from chondrites of different classes have remarkably similar noble-gas constants and isotropic compositions, although constituent diamonds may have come from many sources. SiC seems to be more diverse, partly because grains are large enough to measure individually, but average characteristics seem to be similar from meteorite to meteorite. These observations suggest that various classes of chondritic meteorites sample the same solar system-wide reservoir of interstellar grains.

  9. On the doping limit for strain stability retention in phosphorus doped Si:C

    NASA Astrophysics Data System (ADS)

    Chuang, Yao-Teng; Hu, Kuan-Kan; Woon, Wei-Yen

    2014-07-01

    Strain stability of phosphorus doped pseudomorphically strained Si:C alloy is investigated via high-resolution X-ray diffractometry, Fourier transform infrared spectroscopy, and Hall measurement. Significant strain relaxations are found under post-annealing treatment far below β-SiC precipitation threshold temperature, especially for the highest phosphorus doped case. Most of the substitutional carbon is retained and no further β-SiC formation can be found for all samples investigated. Volume compensation through gettering of interstitial atoms around substitutional carbon is considered as a probable mechanism for the observed strain relaxation. The strain relaxation effect can be further reduced with HF treatment prior to post-annealing process. We found an upper limit for ion implant dose (<1 × 1014 atom/cm2) for the retention of strain stability in phosphorus doped Si:C.

  10. Silicon Carbide (SiC) Power Processing Unit (PPU) for Hall Effect Thrusters

    NASA Technical Reports Server (NTRS)

    Reese, Bradley

    2015-01-01

    Arkansas Power Electronics International (APEI), Inc., is developing a high-efficiency, radiation-hardened 3.8-kW SiC power supply for the PPU of Hall effect thrusters. This project specifically targets the design of a PPU for the high-voltage Hall accelerator (HiVHAC) thruster, with target specifications of 80- to 160-V input, 200- to 700-V/5A output, efficiency greater than 96 percent, and peak power density in excess of 2.5 kW/kg. The PPU under development uses SiC junction field-effect transistor power switches, components that APEI, Inc., has irradiated under total ionizing dose conditions to greater than 3 MRad with little to no change in device performance.

  11. Depth dependence of defect density and stress in GaN grown on SiC

    SciTech Connect

    Faleev, N.; Temkin, H.; Ahmad, I.; Holtz, M.; Melnik, Yu.

    2005-12-15

    We report high resolution x-ray diffraction studies of the relaxation of elastic strain in GaN grown on SiC(0001). The GaN layers were grown with thickness ranging from 0.29 to 30 {mu}m. High level of residual elastic strain was found in thin (0.29 to 0.73 {mu}m thick) GaN layers. This correlates with low density of threading screw dislocations of 1-2x10{sup 7} cm{sup -2}, observed in a surface layer formed over a defective nucleation layer. Stress was found to be very close to what is expected from thermal expansion mismatch between the GaN and SiC. A model based on generation and diffusion of point defects accounts for these observations.

  12. 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.

  13. Interfacial Charge States in Graphene on SiC Studied by Noncontact Scanning Nonlinear Dielectric Potentiometry

    NASA Astrophysics Data System (ADS)

    Yamasue, Kohei; Fukidome, Hirokazu; Funakubo, Kazutoshi; Suemitsu, Maki; Cho, Yasuo

    2015-06-01

    We investigate pristine and hydrogen-intercalated graphene synthesized on a 4 H -SiC (0001 ) substrate by using noncontact scanning nonlinear dielectric potentiometry (NC-SNDP). Permanent dipole moments are detected at the pristine graphene-SiC interface. These originate from the covalent bonds of carbon atoms of the so-called buffer layer to the substrate. Hydrogen intercalation at the interface eliminates these covalent bonds and the original quasi-(6 ×6 ) corrugation, which indicates the conversion of the buffer layer into a second graphene layer by the termination of Si bonds at the interface. NC-SNDP images suggest that a certain portion of the Si dangling bonds remains even after hydrogen intercalation. These bonds are thought to act as charged impurities reducing the carrier mobility in hydrogen-intercalated graphene on SiC.

  14. On the doping limit for strain stability retention in phosphorus doped Si:C

    SciTech Connect

    Chuang, Yao-Teng; Hu, Kuan-Kan; Woon, Wei-Yen

    2014-07-21

    Strain stability of phosphorus doped pseudomorphically strained Si:C alloy is investigated via high-resolution X-ray diffractometry, Fourier transform infrared spectroscopy, and Hall measurement. Significant strain relaxations are found under post-annealing treatment far below β-SiC precipitation threshold temperature, especially for the highest phosphorus doped case. Most of the substitutional carbon is retained and no further β-SiC formation can be found for all samples investigated. Volume compensation through gettering of interstitial atoms around substitutional carbon is considered as a probable mechanism for the observed strain relaxation. The strain relaxation effect can be further reduced with HF treatment prior to post-annealing process. We found an upper limit for ion implant dose (<1 × 10{sup 14} atom/cm{sup 2}) for the retention of strain stability in phosphorus doped Si:C.

  15. Thermal detection mechanism of SiC based hydrogen resistive gas sensors

    NASA Astrophysics Data System (ADS)

    Fawcett, Timothy J.; Wolan, John T.; Lloyd Spetz, Anita; Reyes, Meralys; Saddow, Stephen E.

    2006-10-01

    Silicon carbide (SiC) resistive hydrogen gas sensors have been fabricated and tested. Planar NiCr contacts were deposited on a thin 3C-SiC epitaxial film grown on thin Si wafers bonded to polycrystalline SiC substrates. At 673K, up to a 51.75±0.04% change in sensor output current and a change in the device temperature of up to 163.1±0.4K were demonstrated in response to 100% H2 in N2. Changes in device temperature are shown to be driven by the transfer of heat from the device to the gas, giving rise to a thermal detection mechanism.

  16. The astrophysical interpretation of isotope anomalies in graphite and SiC grains of chondrites

    NASA Technical Reports Server (NTRS)

    Lavrukhina, A. K.

    1993-01-01

    The C, N, and Mg isotopic compositions in graphite and SiC grains of carbonaceous chondrites can be explained by nuclear processes in massive O,B stars of second generation passed a stage of WR star with intensive stellar wind, where grain condensation had taken place. The interstellar graphite and SiC grains with anomalous isotopic compositions of C, N, Ne, and Si and other elements of nucleosynthetic origin, found in non-equilibrated chondrites, are most suitable for determination of astro-physical objects, where nucleosynthesis had taken place. Two objects were examined: (1) massive O,B stars of second generation passed a stage of WR star with intensive stellar wind (O,B-WR model) and (2) low-mass stars (1 less than or equal to M/solar mass less than or equal to 3) during thermally pulsing asymptotic giant branch phase (TP-AGB model).

  17. A model for thermal oxidation of Si and SiC including material expansion

    NASA Astrophysics Data System (ADS)

    Christen, T.; Ioannidis, A.; Winkelmann, C.

    2015-02-01

    A model based on drift-diffusion-reaction kinetics for Si and SiC oxidation is discussed, which takes the material expansion into account with an additional convection term. The associated velocity field is determined self-consistently from the local reaction rate. The approach allows a calculation of the densities of volatile species in an nm-resolution at the oxidation front. The model is illustrated with simulation results for the growth and impurity redistribution during Si oxidation and for carbon and silicon emission during SiC oxidation. The approach can be useful for the prediction of Si and/or C interstitial distribution, which is particularly relevant for the quality of metal-oxide-semiconductor electronic devices.

  18. First-principles investigation of the intrinsic defects in Ti3SiC2

    NASA Astrophysics Data System (ADS)

    Zhao, Shijun; Xue, Jianming; Wang, Yugang; Huang, Qing

    2014-03-01

    First-principles calculations have been carried out to investigate intrinsic defects including vacancies, interstitials, antisite defects, Frenkel and Schottky defects in the 312 MAX phase Ti3SiC2. The formation energies of defects are obtained according to the elemental chemical potentials which are determined by the phase stability conditions. The most stable self-interstitials are all found in the hexahedral position surrounded by two Ti(2) and three Si atoms. For the entire elemental chemical potential range considered, our results demonstrated that Si and C related defects, including vacancies, interstitials and Frenkel defects are the most dominant defects. Besides, the present calculations also reveal that the formation energies of C and Si Frenkel defects are much lower than those of all Schottky defects considered. In addition, the calculated profiles of densities of states for the defective Ti3SiC2 indicate that these defects should have great influence on its thermal and electrical properties.

  19. Low activation brazing materials and techniques for SiC f/SiC composites

    NASA Astrophysics Data System (ADS)

    Riccardi, B.; Nannetti, C. A.; Petrisor, T.; Sacchetti, M.

    2002-12-01

    A low activation brazing technique for silicon carbide fiber reinforced silicon carbide matrix composites (SiC f/SiC) is presented; this technique is based on the use of the 78Si-22Ti (wt%) eutectic alloy. The joints obtained take advantage of a melting point able to avoid composite fibre-interface degradation. All the joints showed absence of discontinuities and defects at the interface and a fine eutectic structure. Moreover, the joint layer appeared well adherent both to the matrix and the fibre interphase and the brazing alloy infiltration looked sufficiently controlled. The joints of SiC f/SiC composites showed 71±10 MPa almost pure shear strength at RT and up to 70 MPa at 600 °C.

  20. Dissimilar joint characteristics of SiC and WC-Co alloy by laser brazing

    NASA Astrophysics Data System (ADS)

    Nagatsuka, K.; Sechi, Y.; Nakata, K.

    2012-08-01

    SiC and WC-Co alloys were joined by laser brazing with an active braze metal. The braze metal based on eutectic Ag-Cu alloy with additional Ti as an active element ranging from 0 to 2.8 mass% was sandwiched by the SiC block and WC-Co alloy plate. The brazing was carried out by selective laser beam irradiation on the WC-Co alloy plate. The content of Ti in the braze metal was required to exceed 0.6 mass% in order to form a brazed joint with a measurable shear strength. The shear strength increased with increasing Ti content up to 2.3 mass%Ti and decreased with a higher content.

  1. Intercalation of graphene on SiC(0001) via ion implantation

    NASA Astrophysics Data System (ADS)

    Stöhr, Alexander; Forti, Stiven; Link, Stefan; Zakharov, Alexei A.; Kern, Klaus; Starke, Ulrich; Benia, Hadj M.

    2016-08-01

    Electronic devices based on graphene technology are catching on rapidly and the ability to engineer graphene properties at the nanoscale is becoming, more than ever, indispensable. Here, we present a procedure of graphene functionalization on SiC(0001) that paves the way towards the fabrication of complex graphene electronic chips. The procedure resides on the well-known ion-implantation technique. The efficiency of the working principle is demonstrated by the intercalation of the epitaxial graphene layer on SiC(0001) with Bi atoms, which was not possible following standard procedures. The investigation of the obtained graphene system reveals no clear spin-orbit coupling enhancement expected by theory in addition to the presence of residual structural defects. Our graphene/SiC(0001) intercalation procedure puts forward the ion-beam lithography to nanostructure and functionalize desired graphene chips.

  2. Controllable growth of vertically aligned graphene on C-face SiC

    PubMed Central

    Liu, Yu; Chen, Lianlian; Hilliard, Donovan; Huang, Qing-song; Liu, Fang; Wang, Mao; Böttger, Roman; Hübner, René; N’Diaye, Alpha T.; Arenholz, Elke; Heera, Viton; Skorupa, Wolfgang; Zhou, Shengqiang

    2016-01-01

    We investigated how to control the growth of vertically aligned graphene on C-face SiC by varying the processing conditions. It is found that, the growth rate scales with the annealing temperature and the graphene height is proportional to the annealing time. Temperature gradient and crystalline quality of the SiC substrates influence their vaporization. The partial vapor pressure is crucial as it can interfere with further vaporization. A growth mechanism is proposed in terms of physical vapor transport. The monolayer character of vertically aligned graphene is verified by Raman and X-ray absorption spectroscopy. With the processed samples, d0 magnetism is realized and negative magnetoresistance is observed after Cu implantation. We also prove that multiple carriers exist in vertically aligned graphene. PMID:27708399

  3. Fabrication of SiC aspheric mirrors with low mid-spatial error

    NASA Astrophysics Data System (ADS)

    Tinker, Flemming; Xin, Kai

    2013-09-01

    Recent experience with finishing off-axis parabolas and other conic surfaces is demonstrated by some examples that illustrate surface accuracy - not only in terms of traditional metrics, but also in terms of specified ranges of spatial frequency. Particular attention is given to the topic of interferometric metrology, and the extent to which we can effectively characterize mid-spatial frequency errors. The presence of mid-spatial errors can appear even more dominant in hard ceramics like SiC as compared with glass - reasons for this are suggested. This paper will discuss how controlled force grinding, robotic polishing, and surface smoothing can be employed to minimize and mitigate mid-spatial errors in fast silicon carbide aspheric mirrors. Recent experience and results are presented on two SiC mirrors finished by Aperture Optical Sciences Inc.

  4. Evidence for near-infrared photoluminescence of nitrogen vacancy centers in 4 H -SiC

    NASA Astrophysics Data System (ADS)

    Zargaleh, S. A.; Eble, B.; Hameau, S.; Cantin, J.-L.; Legrand, L.; Bernard, M.; Margaillan, F.; Lauret, J.-S.; Roch, J.-F.; von Bardeleben, H. J.; Rauls, E.; Gerstmann, U.; Treussart, F.

    2016-08-01

    We present evidence of near-infrared photoluminescence (PL) signature of nitrogen vacancy centers (NCVSi) - in silicon carbide (SiC). This center exhibits an S =1 ground state spin similar to the NV- center in diamond. We have performed photoluminescence excitation measurements at cryogenic temperature and demonstrated efficient photoexcitation of distinct photoluminescence from (NCVSi)- in 4 H -SiC. Furthermore, by correlating the energies of measured zero phonon lines (ZPLs) with theoretical values derived from hybrid density functional theory each of the ZPLs has been associated to the respective occupation of hexagonal (h ) and quasicubic (k ) lattice sites in close analogy to neutral divacancy centers (VCVSi) 0 in the same material. Finally, with the appropriate choice of excitation energy we demonstrated the selective excitation of (NCVSi) - PL with no contamination by (VCVSi) 0 PL, thereby opening the way towards the optical detection of (NCVSi) - electron spin resonance.

  5. A model for thermal oxidation of Si and SiC including material expansion

    SciTech Connect

    Christen, T. Ioannidis, A.; Winkelmann, C.

    2015-02-28

    A model based on drift-diffusion-reaction kinetics for Si and SiC oxidation is discussed, which takes the material expansion into account with an additional convection term. The associated velocity field is determined self-consistently from the local reaction rate. The approach allows a calculation of the densities of volatile species in an nm-resolution at the oxidation front. The model is illustrated with simulation results for the growth and impurity redistribution during Si oxidation and for carbon and silicon emission during SiC oxidation. The approach can be useful for the prediction of Si and/or C interstitial distribution, which is particularly relevant for the quality of metal-oxide-semiconductor electronic devices.

  6. Multilayer epitaxial graphene grown on the SiC (000- 1) surface; structure and electronic properties

    SciTech Connect

    Sprinkle, M.; Hicks, J.; Tejeda, A.; Taleb-Ibrahimi, A.; Le Fevre, P.; Bertran, F.; Tinkey, H.; Clark, M.C.; Soukiassian, P.; Martinotti, D.; Hass, J.; Conrad, E.H.

    2010-10-22

    We review the progress towards developing epitaxial graphene as a material for carbon electronics. In particular, we discuss improvements in epitaxial graphene growth, interface control and the understanding of multilayer epitaxial graphene's (MEG's) electronic properties. Although graphene grown on both polar faces of SiC will be discussed, our discussions will focus on graphene grown on the (000{bar 1}) C-face of SiC. The unique properties of C-face MEG have become apparent. These films behave electronically like a stack of nearly independent graphene sheets rather than a thin Bernal stacked graphite sample. The origins of multilayer graphene's electronic behaviour are its unique highly ordered stacking of non-Bernal rotated graphene planes. While these rotations do not significantly affect the inter-layer interactions, they do break the stacking symmetry of graphite. It is this broken symmetry that leads to each sheet behaving like isolated graphene planes.

  7. Precipitation Sequence of a SiC Particle Reinforced Al-Mg-Si Alloy Composite

    NASA Astrophysics Data System (ADS)

    Shen, Rujuan; Wang, Yihan; Guo, Baisong; Song, Min

    2016-10-01

    In this study, the precipitation sequence of a 5 vol.% SiC particles reinforced Al-1.12 wt.%Mg-0.77 wt.%Si alloy composite fabricated by traditional powder metallurgy method was investigated by transmission electron microscopy and hardness measurements. The results indicated that the addition of SiC reinforcements not only suppresses the initial aging stage but also influences the subsequent precipitates. The precipitation sequence of the composite aged at 175 °C can be described as: Guinier-Preston (G.P.) zone → β″ → β' → B', which was confirmed by high-resolution transmission electron microscopy. This work might provide the guidance for the design and fabrication of hardenable automobile body sheet by Al-based composites with enhanced mechanical properties.

  8. 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.

  9. Identification of luminescent surface defect in SiC quantum dots

    SciTech Connect

    Dai, Dejian; Guo, Xiaoxiao; Fan, Jiyang

    2015-02-02

    The surface defect that results in the usually observed blue luminescence in the SiC quantum dots (QDs) remains unclear. We experimentally identify that the surface defect C=O (in COO) is responsible for this constant blue luminescence. The HO···C=O [n{sub (OH)} → π*{sub (CO)}] interaction between the hydroxyl and carbonyl groups changes the energy levels of C=O and makes the light absorption/emission arise at around 326/438 nm. Another surface defect (Si–Si) is identified and its light absorption contributes to both C=O-related luminescence and quantum-confinement luminescence of the SiC QDs.

  10. Epitaxial graphene on SiC formed by the surface structure control technique

    NASA Astrophysics Data System (ADS)

    Aritsuki, Takuya; Nakashima, Takeshi; Kobayashi, Keisuke; Ohno, Yasuhide; Nagase, Masao

    2016-06-01

    The thermal decomposition of silicon carbide (SiC) is a promising method for producing wafer-scale single-crystal graphene. The optimal growth condition for high-mobility epitaxial graphene fabricated by infrared rapid thermal annealing is discussed in this paper. The surface structures, such as step–terrace and graphene coverage structures, on a non-off-axis SiC(0001) substrate were well controlled by varying the annealing time in a range below 10 min. The mobility of graphene grown at 1620 °C for 5 min in 100 Torr Ar ambient had a maximum value of 2089 cm2 V‑1 s‑1. We found that the causes of the mobility reduction were low graphene coverage, high sheet carrier density, and nonuniformity of the step structure.

  11. Fabrication of a single layer graphene by copper intercalation on a SiC(0001) surface

    SciTech Connect

    Yagyu, Kazuma; Tochihara, Hiroshi; Tomokage, Hajime; Suzuki, Takayuki; Tajiri, Takayuki; Kohno, Atsushi; Takahashi, Kazutoshi

    2014-02-03

    Cu atoms deposited on a zero layer graphene grown on a SiC(0001) substrate, intercalate between the zero layer graphene and the SiC substrate after the thermal annealing above 600 °C, forming a Cu-intercalated single layer graphene. On the Cu-intercalated single layer graphene, a graphene lattice with superstructure due to moiré pattern is observed by scanning tunneling microscopy, and specific linear dispersion at the K{sup ¯} point as well as a characteristic peak in a C{sub 1s} core level spectrum, which is originated from a free-standing graphene, is confirmed by photoemission spectroscopy. The Cu-intercalated single layer graphene is found to be n-doped.

  12. Spin centres in SiC for all-optical nanoscale quantum sensing under ambient conditions

    NASA Astrophysics Data System (ADS)

    Anisimov, A. N.; Babunts, R. A.; Kidalov, S. V.; Mokhov, E. N.; Soltamov, V. A.; Baranov, P. G.

    2016-07-01

    Level anticrossing (LAC) spectroscopy was demonstrated on a family of uniaxially oriented spin colour centres with S = 3/2 in the ground and excited states in hexagonal 4H-, 6H- and rhombic 15R- SiC polytypes. It was shown that these centres exhibit unique characteristics such as optical spin alignment up to the temperatures of 250 ◦C. A sharp variation of the IR photoluminescence intensity in the vicinity of LAC with the record contrast was observed, which can be used for a purely all-optical sensing of the magnetic field and temperature without applying radiofrequency field. A distinctive feature of the LAC signal is weak dependence on the direction of the magnetic field that allows one to monitor the LAC signals in the nonoriented systems, such as powder of SiC nanocrystals.

  13. 75 FR 38078 - Manufacturing and Services' Manufacture America Initiative and Events

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-01

    ... International Trade Administration Manufacturing and Services' Manufacture America Initiative and Events ACTION... manufacturing. SUMMARY: The International Trade Administration's Manufacturing and Services Unit is launching a... government agencies as well as universities. To address these challenges, the Manufacturing and...

  14. Molecular dynamics simulations of swift heavy ion induced defect recovery in SiC

    SciTech Connect

    Backman, Marie; Toulemonde, Marcel; Pakarinen, Olli H; Juslin, Niklas; Djurabekova, Flyura; Nordlund, Kai; Debelle, Aurelien; Weber, William J

    2013-01-01

    Swift heavy ions induce a high density of electronic excitations that can cause the formation of amorphous ion tracks in insulators. No ion tracks have been observed in the semiconductor SiC, but recent experimental work suggests that irradiation damaged SiC can undergo defect recovery under swift heavy ion irradiation. It is believed that local heating of the lattice due to the electronic energy deposition can anneal, and thereby recover, some of the disordered structure. We simulate the local heating due to the ions by the inelastic thermal spike model and perform molecular dynamics simulations of dierent model damage states to study the defect recovery on an atomistic level. We find significant recovery of point defects and a disordered layer, as well as recrystallization at the amorphous-to-crystalline interface of an amorphous layer. The simulation results support the swift heavy ion annealing hypothesis.Swift heavy ions induce a high density of electronic excitations that can cause the formation of amorphous ion tracks in insulators. No ion tracks have been observed in the semiconductor SiC, but recent experimental work suggests that irradiation damaged SiC can undergo defect recovery under swift heavy ion irradiation. It is believed that local heating of the lattice due to the electronic energy deposition can anneal, and thereby recover, some of the disordered structure. We simulate the local heating due to the ions by the inelastic thermal spike model and perform molecular dynamics simulations of dierent model damage states to study the defect recovery on an atomistic level. We find significant recovery of point defects and a disordered layer, as well as recrystallization at the amorphous-to-crystalline interface of an amorphous layer. The simulation results support the swift heavy ion annealing hypothesis.

  15. Graphene on SiC(0001) inspected by dynamic atomic force microscopy at room temperature

    PubMed Central

    Telychko, Mykola; Berger, Jan; Majzik, Zsolt; Jelínek, Pavel

    2015-01-01

    Summary We investigated single-layer graphene on SiC(0001) by atomic force and tunneling current microscopy, to separate the topographic and electronic contributions from the overall landscape. The analysis revealed that the roughness evaluated from the atomic force maps is very low, in accord with theoretical simulations. We also observed that characteristic electron scattering effects on graphene edges and defects are not accompanied by any out-of-plane relaxations of carbon atoms. PMID:25977861

  16. Saturn V S-IC (First) Stage for Apollo 8 in the Vehicle Assembly Building

    NASA Technical Reports Server (NTRS)

    1967-01-01

    The S-IC stage being erected for the final assembly of the Saturn V launch vehicle for the Apollo 8 mission (AS-503), is photographed in the Vehicle Assembly Building (VAB) high bay at the Kennedy Space Center. The Apollo 8 mission was the first Saturn V manned mission with astronauts Frank Borman, James A. Lovell, and William Anders. They escaped Earth's gravity and traveled to lunar vicinity. The launch of Apollo 8 occurred on December 21, 1968.

  17. Enhanced functionality in GaN and SiC devices by using novel processing

    NASA Astrophysics Data System (ADS)

    Pearton, S. J.; Abernathy, C. R.; Gila, B. P.; Ren, F.; Zavada, J. M.; Park, Y. D.

    2004-11-01

    Some examples of recent advances in enhancing or adding functionality to GaN and SiC devices through the use of novel processing techniques are discussed. The first example is the use of ion implantation to incorporate transition metals such as Mn, Cr and Co at atomic percent levels in the wide bandgap semiconductors to produce room temperature ferromagnetism. A discussion is given of the phase space within which single-phase material can be obtained and the requirements for demonstrating the presence of a true dilute magnetic semiconductor. The ability to make GaN and SiC ferromagnetic leads to the possibility of magnetic devices with gain, spin FETs operating at low voltages and spin polarized light emitters. The second example is the use of novel oxides such as Sc 2O 3 and MgO as gate dielectrics or surface passivants on GaN. True inversion behavior has been demonstrated in gated MOS-GaN diodes with implanted n-regions supplying the minority carriers need for inversion. These oxide layers also effectively mitigate current collapse in AlGaN/GaN HEMTs through their passivation of surface states in the gate-drain region. The third example is the use of laser drilling to make through-wafer via holes in SiC, sapphire and GaN. The ablation rate is sufficiently high that this maskless, serial process appears capable of achieving similar throughput to the more conventional approach of plasma etching of vias. The fourth example is the use of either ungated AlGaN/GaN HEMTs or simple GaN and SiC Schottky diodes as sensors for chemicals, biogens, radiation, combustion gases or strain. The sensitivity of either the channel carrier density or the barrier height to changes in surface condition make these materials systems ideal for compact robust sensors capable of operating at elevated temperatures.

  18. High Power Silicon Carbide (SiC) Power Processing Unit Development

    NASA Technical Reports Server (NTRS)

    Scheidegger, Robert J.; Santiago, Walter; Bozak, Karin E.; Pinero, Luis R.; Birchenough, Arthur G.

    2015-01-01

    NASA GRC successfully designed, built and tested a technology-push power processing unit for electric propulsion applications that utilizes high voltage silicon carbide (SiC) technology. The development specifically addresses the need for high power electronics to enable electric propulsion systems in the 100s of kilowatts. This unit demonstrated how high voltage combined with superior semiconductor components resulted in exceptional converter performance.

  19. TRANSMUTATIONS IN SiC IRRADIATED IN ARIES-IV FIRST WALL

    SciTech Connect

    Heinisch, Howard L.

    2001-04-01

    The change in concentrations of elements due to transmutations resulting from neutron irradiation in the first wall of the ARIES-IV conceptual fusion energy device were determined as a function of neutron dose. SiC burns out at a rate of about 0.5% per effective full power year. The largest impurity concentration is that of He, but several other elements burn in at rates of hundreds of appm/efpy.

  20. Towards an Optimal Gradient-dependent Energy Functional of the PZ-SIC Form

    DOE PAGES

    Jónsson, Elvar Örn; Lehtola, Susi; Jónsson, Hannes

    2015-06-01

    Results of Perdew–Zunger self-interaction corrected (PZ-SIC) density functional theory calculations of the atomization energy of 35 molecules are compared to those of high-level quantum chemistry calculations. While the PBE functional, which is commonly used in calculations of condensed matter, is known to predict on average too high atomization energy (overbinding of the molecules), the application of PZ-SIC gives a large overcorrection and leads to significant underestimation of the atomization energy. The exchange enhancement factor that is optimal for the generalized gradient approximation within the Kohn-Sham (KS) approach may not be optimal for the self-interaction corrected functional. The PBEsol functional, wheremore » the exchange enhancement factor was optimized for solids, gives poor results for molecules in KS but turns out to work better than PBE in PZ-SIC calculations. The exchange enhancement is weaker in PBEsol and the functional is closer to the local density approximation. Furthermore, the drop in the exchange enhancement factor for increasing reduced gradient in the PW91 functional gives more accurate results than the plateaued enhancement in the PBE functional. A step towards an optimal exchange enhancement factor for a gradient dependent functional of the PZ-SIC form is taken by constructing an exchange enhancement factor that mimics PBEsol for small values of the reduced gradient, and PW91 for large values. The average atomization energy is then in closer agreement with the high-level quantum chemistry calculations, but the variance is still large, the F2 molecule being a notable outlier.« less

  1. Notes on the plasma resonance peak employed to determine doping in SiC

    DOE PAGES

    Engelbrecht, J. A. A.; van Rooyen, I. J.; Henry, A.; Janzen, E.; Sephton, B.

    2015-07-23

    In this study, the doping level of a semiconductor material can be determined using the plasma resonance frequency to obtain the carrier concentration associated with doping. This paper provides an overview of the procedure for the three most common polytypes of SiC. Results for 3C-SiC are presented and discussed. In phosphorus doped samples analysed, it is submitted that the 2nd plasma resonance cannot be detected due to high values of the free carrier damping constant γ.

  2. Towards an Optimal Gradient-dependent Energy Functional of the PZ-SIC Form

    SciTech Connect

    Jónsson, Elvar Örn; Lehtola, Susi; Jónsson, Hannes

    2015-06-01

    Results of Perdew–Zunger self-interaction corrected (PZ-SIC) density functional theory calculations of the atomization energy of 35 molecules are compared to those of high-level quantum chemistry calculations. While the PBE functional, which is commonly used in calculations of condensed matter, is known to predict on average too high atomization energy (overbinding of the molecules), the application of PZ-SIC gives a large overcorrection and leads to significant underestimation of the atomization energy. The exchange enhancement factor that is optimal for the generalized gradient approximation within the Kohn-Sham (KS) approach may not be optimal for the self-interaction corrected functional. The PBEsol functional, where the exchange enhancement factor was optimized for solids, gives poor results for molecules in KS but turns out to work better than PBE in PZ-SIC calculations. The exchange enhancement is weaker in PBEsol and the functional is closer to the local density approximation. Furthermore, the drop in the exchange enhancement factor for increasing reduced gradient in the PW91 functional gives more accurate results than the plateaued enhancement in the PBE functional. A step towards an optimal exchange enhancement factor for a gradient dependent functional of the PZ-SIC form is taken by constructing an exchange enhancement factor that mimics PBEsol for small values of the reduced gradient, and PW91 for large values. The average atomization energy is then in closer agreement with the high-level quantum chemistry calculations, but the variance is still large, the F2 molecule being a notable outlier.

  3. Charge trapping behavior and its origin in Al2O3/SiC MIS system

    NASA Astrophysics Data System (ADS)

    Liu, Xin-Yu; Wang, Yi-Yu; Peng, Zhao-Yang; Li, Cheng-Zhan; Wu, Jia; Bai, Yun; Tang, Yi-Dan; Liu, Ke-An; Shen, Hua-Jun

    2015-08-01

    Charge trapping behavior and its origin in Al2O3/SiC MOS structure are investigated by analyzing the capacitance-voltage (C-V) hysteresis and the chemical composition of the interface. The C-V hysteresis is measured as a function of oxide thickness series for an Al2O3/SiC MIS capacitor. The distribution of the trapped charges, extracted from the C-V curves, is found to mainly follow a sheet charge model rather than a bulk charge model. Therefore, the electron injection phenomenon is evaluated by using linear fitting. It is found that most of the trapped charges are not distributed exactly at the interface but are located in the bulk of the Al2O3 layers, especially close to the border. Furthermore, there is no detectable oxide interface layer in the x-ray photoelectron spectroscope (XPS) and transmission electron microscope (TEM) measurements. In addition, Rutherford back scattering (RBS) analysis shows that the width of the Al2O3/SiC interface is less than 1 nm. It could be concluded that the charge trapping sites in Al2O3/SiC structure might mainly originate from the border traps in Al2O3 film rather than the interface traps in the interfacial transition layer. Project supported by the National Natural Science Foundation of China (Grant No. 61106080) and the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. 2013ZX02305).

  4. Controlled synthesis and decoupling of monolayer graphene on SiC(0001)

    SciTech Connect

    Oida, S.; Hannon, J. B.; Tromp, R. M.

    2014-04-21

    We describe a process for the growth of a single, electronically decoupled graphene layer on SiC(0001). The method involves annealing in disilane to (1) prepare flat, clean substrates, (2) grow a single graphene layer, and (3) electronically decouple the graphene from the substrate. This approach uses a single process gas, at μTorr pressures, with modest substrate temperatures, thus affecting a drastic simplification over other processes described in the literature.

  5. A Highly intense DC muon source, MuSIC and muon CLFV search

    NASA Astrophysics Data System (ADS)

    Hino, Y.; Kuno, Y.; Sato, A.; Sakamoto, H.; Matsumoto, Y.; Tran, N. H.; Hashim, I. H.; Fukuda, M.; Hayashida, Y.; Ogitsu, T.; Yamamoto, A.; Yoshida, M.

    2014-08-01

    MuSIC is a new muon facility, which provides the world's highest intense muon beam with continuous time structure at Research Center of Nuclear Physics (RCNP), Osaka University. It's intensity is designed to be 108 muons per second with only 0.4 kW proton beam. Such a high intense muon beam is very important for searches of rare decay processes, for example search for the muon to electron conversion.

  6. Oxidation of SiC investigated by ellipsometry and Rutherford backscattering spectrometry

    SciTech Connect

    Szilagyi, E.; Petrik, P.; Lohner, T.; Koos, A. A.; Fried, M.; Battistig, G.

    2008-07-01

    Oxidation of SiC was performed in Ar-O{sub 2} mixture of atmospheric pressure at 1100 deg. C and compared with that of Si. The partial pressure of O{sub 2} varied from 100 to 1000 mbar, while the oxidation time ranged from 0.5 to 45 h. The thickness of the oxide films was determined by spectroscopic ellipsometry and Rutherford backscattering spectrometry. The time and the pressure dependence of the oxidation kinetics of SiC are well described by the modified Deal-Grove model. In the diffusion-limited region, even for the faster case, the oxidation kinetics of the C-terminated face of SiC is not clearly limited by oxygen indiffusion, as for pure silicon. To interpret the ellipsometry spectra, two models of possible structure were used. In the case of the one-layer model, for layer thicknesses above 30 nm, the refractive index of the oxide layers is identical to that of thermally oxidized Si, and it increases rapidly with decreasing thickness below about 15 nm. This increase is significantly larger for C-terminated than for Si-terminated faces, and this difference can be explained by a transition layer introduced into the two-layer model. This model contains a pure SiO{sub 2} layer and a transition layer modeled by a mixture of 50 % SiO{sub 2} and 50 % SiC. The transition layer is thicker on the C-terminated surface than on the Si-terminated one. The thickness ratio of the transition layers is slightly larger than the surface roughness ratio on the two different sides determined by atomic force microscopy. The density of the oxide films, which can be determined from the backscattering and spectroscopic ellipsometry spectra, decreases with decreasing thickness below about 30 nm. For thicker films, the density of the oxide is equal to the bulk density of SiO{sub 2}.

  7. Processing and characterization of SiC platelet/SiC composites

    SciTech Connect

    Cao, J.J.; MoberlyChan, W.J.; De Jonghe, L.C.; Dalgleish, B.; Niu, M.Y.

    1995-03-01

    Hot pressed {beta}-SiC and SiC matrix composites containing encapsulated {alpha}-SiC platelets were prepared and investigated. The Microstructures were characterized using electron microscopy, Auger electron spectroscopy, and x-ray diffraction. Prior to hot pressing, the platelets were either encapsulated with hydrated aluminum sulfate or yttrium hydroxycarbonate (later calcined to form alumina or yttria) from aqueous solutions, or oxidized to form a silica layer. The effect of these interfacial layers on toughness was described.

  8. Modeling and testing miniature torsion specimens for SiC joining development studies for fusion

    SciTech Connect

    Henager, Jr., C. H.; Nguyen, Ba N.; Kurtz, Richard J.; Roosendaal, T. J.; Borlaug, B. A.; Ferraris, Monica; Ventrella, A.; Katoh, Yutai

    2015-08-05

    The international fusion community has designed a miniature torsion specimen for neutron irradiation studies of joined SiC and SiC/SiC composite materials. For this research, miniature torsion joints based on this specimen design were fabricated using displacement reactions between Si and TiC to produce Ti3SiC2 + SiC joints with SiC and tested in torsion-shear prior to and after neutron irradiation. However, many miniature torsion specimens fail out-of-plane within the SiC specimen body, which makes it problematic to assign a shear strength value to the joints and makes it difficult to compare unirradiated and irradiated strengths to determine irradiation effects. Finite element elastic damage and elastic–plastic damage models of miniature torsion joints are developed that indicate shear fracture is more likely to occur within the body of the joined sample and cause out-of-plane failures for miniature torsion specimens when a certain modulus and strength ratio between the joint material and the joined material exists. The model results are compared and discussed with regard to unirradiated and irradiated test data for a variety of joint materials. The unirradiated data includes Ti3SiC2 + SiC/CVD-SiC joints with tailored joint moduli, and includes steel/epoxy and CVD-SiC/epoxy joints. Finally, the implications for joint data based on this sample design are discussed.

  9. Dimensional isotropy of 6H and 3C SiC under neutron irradiation

    DOE PAGES

    Snead, Lance L.; Katoh, Yutai; Koyanagi, Takaaki; Terrani, Kurt A.; Specht, Eliot D.

    2016-01-16

    This investigation experimentally determines the as-irradiated crystal axes dimensional change of the common polytypes of SiC considered for nuclear application. Single crystal α-SiC (6H), β-SiC (3C), CVD β-SiC, and single crystal Si have been neutron irradiated near 60 °C from 2 × 1023 to 2 × 1026 n/m2 (E > 0.1 MeV), or about 0.02–20 dpa, in order to study the effect of irradiation on bulk swelling and strain along independent crystalline axes. Single crystal, powder diffractometry and density measurement have been carried out. For all neutron doses where the samples remained crystalline all SiC materials demonstrated equivalent swelling behavior.more » Moreover the 6H–SiC expanded isotropically. The magnitude of the swelling followed a ~0.77 power law against dose consistent with a microstructure evolution driven by single interstitial (carbon) mobility. Extraordinarily large ~7.8% volume expansion in SiC was observed prior to amorphization. Above ~0.9 × 1025 n/m2 (E > 0.1 MeV) all SiC materials became amorphous with an identical swelling: a 11.7% volume expansion, lowering the density to 2.84 g/cm3. As a result, the as-amorphized density was the same at the 2 × 1025 and 2 × 1026 n/m2 (E > 0.1 MeV) dose levels.« less

  10. 250 degrees C SiC High Density Power Module Development

    SciTech Connect

    Ning, Puqi; Wang, Fei; Ngo, Khai

    2011-01-01

    Taking full advantage of SiC devices, a team from Oak Ridge National Laboratory, the University of Tennessee and Virginia Polytechnic Institute and State University have designed, developed, and tested a phase-leg power module based on a high temperature wirebond package. Details of the layout, gate drive, and cooling system designs are described. Continuous power tests confirmed that our design process produced a high density power module that operated successfully at high junction temperatures.

  11. SiC Sensors in Extreme Environments: Real-time Hydrogen Monitoring for Energy Plant Applications

    NASA Astrophysics Data System (ADS)

    Ghosh, Ruby

    2008-03-01

    Clean, efficient energy production, such as the gasification of coal (syngas), requires physical and chemical sensors for exhaust gas monitoring as well as real-time control of the combustion process. Wide-bandgap semiconducting materials systems can meet the sensing demands in these extreme environments consisting of chemically corrosive gases at high temperature and pressure. We have developed a SiC based micro-sensor for detection of hydrogen containing species with millisecond response at 600 C. The sensor is a Pt-SiO2-SiC device with a dense Pt catalytic sensing film, capable of withstanding months of continuous high temperature operation. The device was characterized in robust sensing module that is compatible with an industrial reactor. We report on the performance of the SiC sensor in a simulated syngas ambient at 370 C containing the common interferants CO2, CH4 and CO [1]. In addition we demonstrate that hours of exposure to >=1000 ppm H2S and 15% water vapor does not degrade the sensor performance. To elucidate the mechanisms responsible for the hydrogen response of the sensor we have modeled the hydrogen adsorptions kinetics at the internal Pt-SiO2 interface, using both the Tempkin and Langmuir isotherms. Under the conditions appropriate for energy plant applications, the response of our sensor is significantly larger than that obtained from ultra-high vacuum electrochemical sensor measurements at high temperatures. We will discuss the role of morphology, at the nano to micro scale, on the enhanced catalytic activity observed for our Pt sensing films in response to a heated hydrogen gas stream at atmospheric pressure. [1] R. Loloee, B. Chorpening, S. Beers & R. Ghosh, Hydrogen monitoring for power plant applications using SiC sensors, Sens. Actuators B:Chem. (2007), doi:10.1016/j.snb.2007.07.118

  12. 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.

  13. Turbine airfoil manufacturing technology

    SciTech Connect

    Kortovich, C.

    1995-10-01

    The efficiency and effectiveness of the gas turbine engine is directly related to the turbine inlet temperatures. The ability to increase these temperatures has occurred as a result of improvements in materials, design, and processing techniques. A generic sequence indicating the relationship of these factors to temperature capability is schematically shown in Figure 1 for aircraft engine and land based engine materials. A basic contribution that is not captured by the Figure is the significant improvement in process and manufacturing capability that has accompanied each of these innovations. It is this capability that has allowed the designs and innovations to be applied on a high volume, cost effective scale in the aircraft gas turbine market.

  14. Manufacture of Probiotic Bacteria

    NASA Astrophysics Data System (ADS)

    Muller, J. A.; Ross, R. P.; Fitzgerald, G. F.; Stanton, C.

    Lactic acid bacteria (LAB) have been used for many years as natural biopreservatives in fermented foods. A small group of LAB are also believed to have beneficial health effects on the host, so called probiotic bacteria. Probiotics have emerged from the niche industry from Asia into European and American markets. Functional foods are one of the fastest growing markets today, with estimated growth to 20 billion dollars worldwide by 2010 (GIA, 2008). The increasing demand for probiotics and the new food markets where probiotics are introduced, challenges the industry to produce high quantities of probiotic cultures in a viable and stable form. Dried concentrated probiotic cultures are the most convenient form for incorporation into functional foods, given the ease of storage, handling and transport, especially for shelf-stable functional products. This chapter will discuss various aspects of the challenges associated with the manufacturing of probiotic cultures.

  15. Technique for microswitch manufacture

    NASA Astrophysics Data System (ADS)

    Kitamura, T.; Kiyoyama, S.

    1983-05-01

    A five-step technique for microswitch manufacture is described: (1) A clad board is inlaid with a precious metal and the board is pressed. (2) One end of the fixed contact containing a precious metal inlay section is curved, and this edge of the precious metal inlay section becomes a fixed contact. (3) Inserts are formed in the unit body and terminal strips are placed through the top and bottom of the base and held. (4) The unit body is held by the base and the sequential contact strips are cut off. (5) Movable stripes are attached to the support of the terminal strips on the movable side and movable contacts are placed opposite the fixed contacts.

  16. REGIONAL MANUFACTURING TECHNICAL DEVELOPMENT

    SciTech Connect

    EASON, H.A.

    1997-02-21

    This project covers four CRADAS (Cooperative Research and Development Agreements) which were initiated in 1991 and 1993. The two CRADAS with the state of Tennessee and the state of Florida were to provide technical assistance to small manufacturers in those states and the CRADA with the Tennessee Technology Foundation was to engage in joint economic development activities within the state. These three CRADAS do not fit the traditional definition of CRADAS and would be administered by other agreement mechanisms, today. But in these early days of technology transfer efforts, the CRADA mechanism was already developed and usable. The CRADA with Coors Ceramics is a good example of a CRADA and was used to develop nondestructive testing technology for ceramic component inspection. The report describes the background of this project, its economic impact, and its benefits to the U. S. Department of Energy.

  17. Technique for microswitch manufacture

    NASA Technical Reports Server (NTRS)

    Kitamura, T.; Kiyoyama, S.

    1983-01-01

    A five-step technique for microswitch manufacture is described: (1) A clad board is inlaid with a precious metal and the board is pressed. (2) One end of the fixed contact containing a precious metal inlay section is curved, and this edge of the precious metal inlay section becomes a fixed contact. (3) Inserts are formed in the unit body and terminal strips are placed through the top and bottom of the base and held. (4) The unit body is held by the base and the sequential contact strips are cut off. (5) Movable stripes are attached to the support of the terminal strips on the movable side and movable contacts are placed opposite the fixed contacts.

  18. Direct growth of freestanding GaN on C-face SiC by HVPE

    PubMed Central

    Tian, Yuan; Shao, Yongliang; Wu, Yongzhong; Hao, Xiaopeng; Zhang, Lei; Dai, Yuanbin; Huo, Qin

    2015-01-01

    In this work, high quality GaN crystal was successfully grown on C-face 6H-SiC by HVPE using a two steps growth process. Due to the small interaction stress between the GaN and the SiC substrate, the GaN was self-separated from the SiC substrate even with a small thickness of about 100 μm. Moreover, the SiC substrate was excellent without damage after the whole process so that it can be repeatedly used in the GaN growth. Hot phosphoric acid etching (at 240 °C for 30 min) was employed to identify the polarity of the GaN layer. According to the etching results, the obtained layer was Ga-polar GaN. High-resolution X-ray diffraction (HRXRD) and electron backscatter diffraction (EBSD) were done to characterize the quality of the freestanding GaN. The Raman measurements showed that the freestanding GaN film grown on the C-face 6H-SiC was stress-free. The optical properties of the freestanding GaN layer were determined by photoluminescence (PL) spectra. PMID:26034939

  19. Radiative thermal rectification between SiC and SiO2.

    PubMed

    Joulain, Karl; Ezzahri, Younès; Drevillon, Jérémie; Rousseau, Benoît; De Sousa Meneses, Domingos

    2015-11-30

    By means of fluctuational electrodynamics, we calculate radiative heat flux between two planar materials respectively made of SiC and SiO2. More specifically, we focus on a first (direct) situation where one of the two materials (for example SiC) is at ambient temperature whereas the second material is at a higher one, then we study a second (reverse) situation where the material temperatures are inverted. When the two fluxes corresponding to the two situations are different, the materials are said to exhibit thermal rectification, a property with potential applications in thermal regulation. Rectification variations with temperature and separation distance are reported here. Calculations are performed using material optical data experimentally determined by Fourier transform emission spectrometry of heated materials between ambient temperature (around 300 K) and 1480 K. It is shown that rectification is much more important in the near-field domain, i.e. at separation distances smaller than the thermal wavelength. In addition, we see that the larger is the temperature difference, the larger is rectification. Large rectification is finally interpreted due to a weakening of the SiC surface polariton when temperature increases, a weakening which affects much less SiO2 resonances.

  20. The synthesis of nanostructured SiC from waste plastics and silicon powder

    NASA Astrophysics Data System (ADS)

    Ju, Zhicheng; Xu, Liqiang; Pang, Qiaolian; Xing, Zheng; Ma, Xiaojian; Qian, Yitai

    2009-09-01

    Waste plastics constitute a growing environmental problem. Therefore, the treatment of waste plastics should be considered. Here we synthesize 3C-SiC nanomaterials coexisting with amorphous graphite particles utilizing waste plastics and Si powder at 350-500 °C in a stainless steel autoclave. 3C-SiC could be finally obtained after refluxing with aqueous HClO4 (70 wt%) at 180 °C. X-ray powder diffraction patterns indicate that the product is 3C-SiC with the calculated lattice constant a = 4.36 Å. Transmission electron microscopy (TEM) images show that the SiC samples presented two morphologies: hexagonal platelets prepared by the waste detergent bottles or beverage bottles and nanowires prepared by waste plastic bags respectively. The corresponding selected area electron diffraction (SAED) pattern indicates that either the entire hexagonal platelet or the nanowire is single crystalline. High-resolution TEM shows the planar surfaces of the SiC platelet correspond to {111} planes; the lateral surfaces are {110} planes and the preferential growth direction of the nanowires is along [111]. The output of SiC was ~39% based on the amount of Si powder.

  1. Combustion synthesis as a novel method for production of 1-D SiC nanostructures.

    PubMed

    Huczko, Andrzej; Bystrzejewski, Michał; Lange, Hubert; Fabianowska, Agnieszka; Cudziło, Stanisław; Panas, Andrzej; Szala, Mateusz

    2005-09-01

    1-D nanostructures of cubic phase silicon carbide (beta-SiC) were efficiently produced by combustion synthesis of mixtures containing Si-containing compounds and halocarbons in a calorimetric bomb. The influence of the operating parameters on 1-D SiC formation yield was studied. The heat release, the heating rate, and the chamber pressure increase were monitored during the process. The composition and structural features of the products were characterized by elemental analysis, X-ray diffraction, differential thermal analysis/ thermogravimetric technique, Raman spectroscopy, scanning and transmission electron microscopy, and energy-dispersive X-ray spectrometry. This self-induced growth process can produce SiC nanofibers and nanotubes ca. 20-100 nm in diameter with the aspect ratio higher than 1000. Bulk scale Raman studies showed the product to be comprised of mostly cubic polytype of SiC and that finite size effects are present. We believe that the nucleation mechanism involving radical gaseous species is responsible for 1-D nanostructures growth. The present study has enlarged the family of nanofibers and nanotubes available and offers a possible, new general route to 1-D crystalline materials. PMID:16853065

  2. Biomorphous SiC ceramics prepared from cork oak as precursor

    NASA Astrophysics Data System (ADS)

    Yukhymchuk, V. O.; Kiselov, V. S.; Valakh, M. Ya.; Tryus, M. P.; Skoryk, M. A.; Rozhin, A. G.; Kulinich, S. A.; Belyaev, A. E.

    2016-04-01

    Porous ceramic materials of SiC were synthesized from carbon matrices obtained via pyrolysis of natural cork as precursor. We propose a method for the fabrication of complex-shaped porous ceramic hardware consisting of separate parts prepared from natural cork. It is demonstrated that the thickness of the carbon-matrix walls can be increased through their impregnation with Bakelite phenolic glue solution followed by pyrolysis. This decreases the material's porosity and can be used as a way to modify its mechanical and thermal characteristics. Both the carbon matrices (resulted from the pyrolysis step) and the resultant SiC ceramics are shown to be pseudomorphous to the structure of initial cork. Depending on the synthesis temperature, 3C-SiC, 6H-SiC, or a mixture of these polytypes, could be obtained. By varying the mass ratio of initial carbon and silicon components, stoichiometric SiC or SiC:С:Si, SiC:С, and SiC:Si ceramics could be produced. The structure, as well as chemical and phase composition of the prepared materials were studied by means of Raman spectroscopy and scanning electron microscopy.

  3. Biomorphous SiC ceramics prepared from cork oak as precursor

    NASA Astrophysics Data System (ADS)

    Yukhymchuk, V. O.; Kiselov, V. S.; Valakh, M. Ya.; Tryus, M. P.; Skoryk, M. A.; Rozhin, A. G.; Kulinich, S. A.; Belyaev, A. E.

    2016-04-01

    Porous ceramic materials of SiC were synthesized from carbon matrices obtained via pyrolysis of natural cork as precursor. We propose a method for the fabrication of complex-shaped porous ceramic hardware consisting of separate parts prepared from natural cork. It is demonstrated that the thickness of the carbon-matrix walls can be increased through their impregnation with Bakelite phenolic glue solution followed by pyrolysis. This decreases the material's porosity and can be used as a way to modify its mechanical and thermal characteristics. Both the carbon matrices (resulted from the pyrolysis step) and the resultant SiC ceramics are shown to be pseudomorphous to the structure of initial cork. Depending on the synthesis temperature, 3C-SiC, 6H-SiC, or a mixture of these polytypes, could be obtained. By varying the mass ratio of initial carbon and silicon components, stoichiometric SiC or SiC:C:Si, SiC:C, and SiC:Si ceramics could be produced. The structure, as well as chemical and phase composition of the prepared materials were studied by means of Raman spectroscopy and scanning electron microscopy.

  4. Direct growth of freestanding GaN on C-face SiC by HVPE.

    PubMed

    Tian, Yuan; Shao, Yongliang; Wu, Yongzhong; Hao, Xiaopeng; Zhang, Lei; Dai, Yuanbin; Huo, Qin

    2015-06-02

    In this work, high quality GaN crystal was successfully grown on C-face 6H-SiC by HVPE using a two steps growth process. Due to the small interaction stress between the GaN and the SiC substrate, the GaN was self-separated from the SiC substrate even with a small thickness of about 100 μm. Moreover, the SiC substrate was excellent without damage after the whole process so that it can be repeatedly used in the GaN growth. Hot phosphoric acid etching (at 240 °C for 30 min) was employed to identify the polarity of the GaN layer. According to the etching results, the obtained layer was Ga-polar GaN. High-resolution X-ray diffraction (HRXRD) and electron backscatter diffraction (EBSD) were done to characterize the quality of the freestanding GaN. The Raman measurements showed that the freestanding GaN film grown on the C-face 6H-SiC was stress-free. The optical properties of the freestanding GaN layer were determined by photoluminescence (PL) spectra.

  5. Small scale rotational disorder observed in epitaxial graphene on SiC(0001)

    NASA Astrophysics Data System (ADS)

    Walter, Andrew L.; Bostwick, Aaron; Speck, Florian; Ostler, Markus; Kim, Keun Su; Chang, Young Jun; Moreschini, Luca; Innocenti, Davide; Seyller, Thomas; Horn, Karsten; Rotenberg, Eli

    2013-02-01

    Interest in the use of graphene in electronic devices has motivated an explosion in the study of this remarkable material. The simple, linear, Dirac cone band structure offers a unique possibility to investigate its finer details by angle-resolved photoelectron spectroscopy (ARPES). Indeed, ARPES has been performed on graphene grown on metal substrates but electronic applications require an insulating substrate. Epitaxial graphene grown by the thermal decomposition of silicon carbide (SiC) is an ideal candidate for this due to the large scale, uniform, graphene layers produced. The experimental spectral function of epitaxial graphene on SiC has been extensively studied. However, until now the cause of an anisotropy in the spectral width of the Fermi surface has not been determined. In the current work we show, by comparison of the spectral function to a semi-empirical model, that the anisotropy is due to small scale rotational disorder (˜± 0.15°) of graphene domains in graphene grown on SiC(0001) samples. The complicated shape described by the line-width is accurately reproduced by the semi-empirical model only when rotational disorder is included. While spectra from rare regions of the sample containing only one or two rotational domains is also presented. In addition to the direct benefit in the understanding of graphene's electronic structure this work suggests a mechanism to explain similar variations in related ARPES data.

  6. 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.

  7. Seeded growth of AlN on SiC substrates and defect characterization

    NASA Astrophysics Data System (ADS)

    Lu, P.; Edgar, J. H.; Cao, C.; Hohn, K.; Dalmau, R.; Schlesser, R.; Sitar, Z.

    2008-05-01

    In this study, seeded sublimation growth of aluminum nitride (AlN) on SiC substrates was investigated. Large diameter (15-20 mm) and thick (1-2 mm) AlN layers were demonstrated on Si-face, 3.5° off-axis 6H-SiC (0 0 0 1). A c-axis growth rate of 15-20 μm/h was achieved at 1830 °C, and the surface morphology was highly textured: step features were formed with a single facet on the top of the layer. High-resolution X-ray diffraction (HRXRD), X-ray photoelectron spectroscopy (XPS), and molten KOH/NaOH etching were employed to characterize the AlN layers. The AlN crystals grew highly orientated along the c-axis, however, the impurities of Si (3-6 at%) and C (5.9-8 at%) from the SiC changed the lattice constants of AlN and shifted the AlN (0 0 .2) 2 θ value from pure AlN toward SiC. All the growth surfaces had Al-polarity and the dislocation density decreased from 10 8 to 10 6 cm -2 as the film thickness increased from 30 μm to 2 mm.

  8. Effect of SiC Particles on the Electrical Conductivity of Epoxy Composites

    NASA Astrophysics Data System (ADS)

    Rogti, F.; David, E.

    2016-09-01

    In this paper, the behavior of the electrical conductivity of epoxy/silicon carbide (SiC) composites as a function of weight fraction and particle size of SiC at room temperature has been investigated. Composite samples were prepared by a mixture composed of the same amount of hardener and resin (5 mg) with different amounts (ranging from 5 mg to 7 mg) of silicon carbide powder with different grain sizes (400 and 800 grit). The conduction current was measured under different applied voltages from 1 to 10 kV (corresponding to applied electrical fields from 0.04 kV/mm to 0.4 kV/mm), and the composites microstructure was characterized by scanning electron microscopy. It was shown that the electrical conductivity of epoxy/SiC composites was found to increase when the weight fraction of SiC was increased and also to increase non-linearly as a function of the electrical field.

  9. A SiC NMOS Linear Voltage Regulator for High-Temperature Applications

    SciTech Connect

    Valle-Mayorga, JA; Rahman, A; Mantooth, HA

    2014-05-01

    The first SiC integrated circuit linear voltage regulator is reported. The voltage regulator uses a 20-V supply and generates an output of 15 V, adjustable down to 10 V. It was designed for loads of up to 2 A over a temperature range of 25-225 degrees C. It was, however, successfully tested up to 300 degrees C. The voltage regulator demonstrated load regulations of 1.49% and 9% for a 2-A load at temperatures of 25 and 300 degrees C, respectively. However, the load regulation is less than 2% up to 300 degrees C for a 1-A load. The line regulation with a 2-A load at 25 and 300 degrees C was 17 and 296 mV/V, respectively. The regulator was fabricated in a Cree 4H-SiC 2-mu m experimental process and consists of 1000, 32/2-mu m NMOS depletion MOSFETs as the pass device, an integrated error amplifier with enhancement MOSFETs, and resistor loads, and uses external feedback and compensation networks to ensure operational integrity. It was designed to be integrated with high-voltage vertical power MOSFETs on the same SiC substrate. It also serves as a guide to future attempts for voltage regulation in any type of integrated SiC circuitry.

  10. Characterization of paramagnetic defect centers in three polytypes of dry heat treated, oxidized SiC

    NASA Astrophysics Data System (ADS)

    Macfarlane, P. J.; Zvanut, M. E.

    2000-10-01

    This work describes the characterization of defect centers in 3C-SiC, 4H-SiC, and 6H-SiC. The different SiC crystal structures are examined with electron paramagnetic resonance after thermal oxidation, and after dry (<1 ppm H2O) N2 or O2 heat treatment. The centers are described by g values that range from 2.0025 to 2.0029, which are typical of C dangling bonds. Because the centers are activated in ambients that eliminate H2O and are passivated in ambients that contain H2O, it is suggested that the centers are C dangling bonds created during the dry heat treatment when hydrogen or a hydrogenous species releases from C bonds. The activation characteristics for the centers is the same for both 6H and 3C polytypes; however, centers in the 6H-SiC samples are passivated at lower temperatures than the centers in the 3C-SiC samples. The passivation behavior is attributed to differences in the hydrogen diffusion rates in these materials rather than significant differences in the chemistry of the centers. Etching studies conducted with hydrofluoric acid indicate that the centers are not located in the SiO2, but are located in the SiC at a distance of, at most, 200 nm from the SiO2/SiC interface.

  11. 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.

  12. Adhesion of ZrN and SiC thin films on titanium and nickel alloys

    SciTech Connect

    Gruss, K.A.; James, R.D.; Davis, R.F.

    1996-12-31

    Chemically inert ceramic coatings are currently being investigated to extend the lifetime of metallic components operating in severe environments. Polycrystalline ZrN and amorphous SiC coatings were deposited by cathodic arc evaporation and by PACVD, respectively, on Titanium Grade 12 and Incoloy 825 metal substrates. The structure of the coatings was verified by SEM and XRD. Residual stress analyses were performed on the ZrN coatings via XRD using the sin{sup 2} {phi} method. Compressive stresses of 3.7 GPa and 2.5 GPa were calculated in the ZrN on the Incoloy and Titanium substrates, respectively. Studies of the interfacial chemistry via AES revealed chemically abrupt interfaces. Scratch tests were employed to assess the critical load for interfacial failure and fracture mechanisms for the various coating systems. Critical loads, characterized by a kidney-shaped crack patterns found in the scratch tracks, occurred at 12 N for ZrN on Titanium and 20 N for ZrN on Incoloy. Interfacial failure of SiC on Titanium was dominated by brittle fracture of the SiC coating at 3N loads.

  13. 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

  14. Numerical simulation of armor capability of AI2O3 and SiC armor tiles

    NASA Astrophysics Data System (ADS)

    Rashid, T.; Aleem, M. A.; Akbar, S.; Rauf, A.; Shuaib, M.

    2016-08-01

    Alumina and Silicon Carbide armor plates have been tested numerically against 7.62x51 (mm x mm) armor piercing (AP) projectiles. A 2-D problem with axial symmetry has been designedand the simulations were carried out using commercial software ANSYS AUTODYN. Experiments were modeled for Alumina (99.5%), Alumina (99.7%) and SiC with a range of tile thicknesses (5, 10, 15 and 20 mm). The projectile was chosen as 7.62 x 51AP bullet (initial velocity 810 m/sec)with two different core materials Steel 4340 and WC, however, casing material was copper for both cores. SiC showed better defense against AP bullet as compared to Al2O3. The residual velocity and momentum of the bullet were found to decrease with increasing tile thickness. SiC tiles with thickness 15mm and 20 mm successfully sustained penetration against steel 4340 and WC core bullets, respectively. However none of the Alumina targets succeeded in stopping the bullet.

  15. Radiative thermal rectification between SiC and SiO2.

    PubMed

    Joulain, Karl; Ezzahri, Younès; Drevillon, Jérémie; Rousseau, Benoît; De Sousa Meneses, Domingos

    2015-11-30

    By means of fluctuational electrodynamics, we calculate radiative heat flux between two planar materials respectively made of SiC and SiO2. More specifically, we focus on a first (direct) situation where one of the two materials (for example SiC) is at ambient temperature whereas the second material is at a higher one, then we study a second (reverse) situation where the material temperatures are inverted. When the two fluxes corresponding to the two situations are different, the materials are said to exhibit thermal rectification, a property with potential applications in thermal regulation. Rectification variations with temperature and separation distance are reported here. Calculations are performed using material optical data experimentally determined by Fourier transform emission spectrometry of heated materials between ambient temperature (around 300 K) and 1480 K. It is shown that rectification is much more important in the near-field domain, i.e. at separation distances smaller than the thermal wavelength. In addition, we see that the larger is the temperature difference, the larger is rectification. Large rectification is finally interpreted due to a weakening of the SiC surface polariton when temperature increases, a weakening which affects much less SiO2 resonances. PMID:26698789

  16. Manufacturing consumption of energy 1994

    SciTech Connect

    1997-12-01

    This report provides estimates on energy consumption in the manufacturing sector of the U.S. economy based on data from the Manufacturing Energy Consumption Survey. The sample used in this report represented about 250,000 of the largest manufacturing establishments which account for approximately 98 percent of U.S. economic output from manufacturing, and an expected similar proportion of manufacturing energy use. The amount of energy use was collected for all operations of each establishment surveyed. Highlights of the report include profiles for the four major energy-consuming industries (petroleum refining, chemical, paper, and primary metal industries), and an analysis of the effects of changes in the natural gas and electricity markets on the manufacturing sector. Seven appendices are included to provide detailed background information. 10 figs., 51 tabs.

  17. Additive manufacturing of optical components

    NASA Astrophysics Data System (ADS)

    Heinrich, Andreas; Rank, Manuel; Maillard, Philippe; Suckow, Anne; Bauckhage, Yannick; Rößler, Patrick; Lang, Johannes; Shariff, Fatin; Pekrul, Sven

    2016-08-01

    The development of additive manufacturing methods has enlarged rapidly in recent years. Thereby, the work mainly focuses on the realization of mechanical components, but the additive manufacturing technology offers a high potential in the field of optics as well. Owing to new design possibilities, completely new solutions are possible. This article briefly reviews and compares the most important additive manufacturing methods for polymer optics. Additionally, it points out the characteristics of additive manufactured polymer optics. Thereby, surface quality is of crucial importance. In order to improve it, appropriate post-processing steps are necessary (e.g. robot polishing or coating), which will be discussed. An essential part of this paper deals with various additive manufactured optical components and their use, especially in optical systems for shape metrology (e.g. borehole sensor, tilt sensor, freeform surface sensor, fisheye lens). The examples should demonstrate the potentials and limitations of optical components produced by additive manufacturing.

  18. Manufacturing consumption of energy 1991

    SciTech Connect

    Not Available

    1994-12-01

    This report provides estimates on energy consumption in the manufacturing sector of the US economy. These estimates are based on data from the 1991 Manufacturing Energy Consumption Survey (MECS). This survey--administered by the Energy End Use and Integrated Statistics Division, Office of Energy Markets and End Use, Energy Information Administration (EIA)--is the most comprehensive source of national-level data on energy-related information for the manufacturing industries.

  19. Wireless technology for integrated manufacturing

    SciTech Connect

    Manges, W.W.; Allgood, G.O.; Shourbaji, A.A.

    1996-08-01

    This paper describes the ground breaking work in Oak Ridge facilities that now leads us to the brink of the wireless revolution in manufacturing. The focus is on solving tough technological problems necessary for success and addressing the critical issues of throughput, security, reliability, and robustness in applying wireless technology to manufacturing processes. Innovative solutions to these problems are highlighted through detailed designs and testbed implementations that demonstrate key concepts. The DOE-Oak Ridge complex represented by the Oak Ridge Centers for Manufacturing Technologies (ORCMT) continues to develop these technologies and will continue to focus on solving tough manufacturing problems.

  20. Industrial Arts 7-9. Manufacturing: Metalwork, Plastics, Woodwork, Manufacturing.

    ERIC Educational Resources Information Center

    Manitoba Dept. of Education, Winnipeg. Div. of Vocational Education.

    This curriculum guide provides materials for the industrial arts (grades 7-9) subject cluster of manufacturing. This subject cluster has four areas of study: metalwork, plastics, woodwork, and manufacturing. Introductory materials include an overview of the industrial arts curriculum in its entirety, a listing of program objectives for each of the…