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

    NASA Astrophysics Data System (ADS)

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

    2001-12-01

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

  5. Comparison of SiC mirror approaches

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  6. -SiC Composites

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  7. 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.

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

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... codes 20 through 39 to which this part applies. (a) SIC codes. Major group or industry code Exceptions... industry code Exceptions and/or limitations 311—Food Manufacturing Except 311119—Exception is limited to... under SIC 7334, Photocopying and Duplicating Services, (instant printing)); 324—Petroleum and...

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

    NASA Astrophysics Data System (ADS)

    Robichaud, Joseph L.

    2003-02-01

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

  10. 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.

  11. Thrust Structure of Saturn V S-IC Stage

    NASA Technical Reports Server (NTRS)

    1963-01-01

    This image illustrates technicians working on a full scale engineering mock-up of a Saturn V S-IC stage thrust structure nearing completion at the Manufacturing Engineering Laboratory at Marshall Space Flight Center. The booster, 33 feet in diameter and 138 feet long, was powered by five F-1 engines that provided 7,500,000 pounds of thrust to start the monstrous vehicle on its journey into space.

  12. 29 CFR 510.21 - SIC codes.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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

  13. SiC Micropipe Sprecta

    NASA Astrophysics Data System (ADS)

    Leff, David; Frasca, Albert

    1997-05-01

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

  14. 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.

  15. Industrial process profiles for environmental use: Chapter 30. The electronic component manufacturing industry. Final report

    SciTech Connect

    Not Available

    1983-04-01

    This report is one of a series constituting the catalog of Industrial Process Profiles for Environmental Use. Each industry sector is addressed as a separate chapter of the study. The catalog was developed for the purpose of compiling relevant information concerning air, water, and solid waste emissions from industries which employ similar technologies, have common types of environmental impacts, and supply their products for further processing or consumption to the same general population of customers. This report addresses the following segments of the electronic component manufacturing industry: semiconductors, SIC 3674; capacitors, SIC 3675; resistors, SIC 3676; transformer and inductors, SIC 3677; printed circuit boards, SIC 3679052; electron tubes, SIC 36711, 36713; and cathode ray tubes, SIC 36712, 3671385.

  16. Research on microwave joining of SiC

    SciTech Connect

    Silberglitt, R.

    1995-07-31

    Results: identification of optimum joining temperature range for reaction bonded Si carbide at 1420-1500 C; demonstration that specimens joined within this range have fracture roughness greater than as-received material; and demonstration of ability to use SiC formed in situ from the decomposition of polycarbosilane as a joining aid for sintered Si carbide. In the latter case, the interlayer material was also shown to fill any pores in the joining specimens near the interlayer. Together with the demonstration of leaktight joints between tube sections of reaction bonded and sintered SiC under the previous contract, these results provide the foundation for scaleup to joining of the larger and longer tubes needed for radiant burner and heat exchanger tube assemblies. The formation of SiC in situ is important because maintaining roundness of these large tubes is a technical challenge for the tube manufacturer, so that formation of a leaktight joint may require some degree of gap filling.

  17. Update on SIC-Based Inverter Technology

    SciTech Connect

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

    2009-01-01

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

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

    SciTech Connect

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

    1995-10-01

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

  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. 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…

  3. STS-70 Launch - Nikon E-2 Digital Image

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This test images was taken with a Nikon E-2 Digital Imaging System camera and are provided courtesy of Nikon (GIF 450x450 JPEG 1280x1000): The second Shuttle launch in 16 days hurtles off the pad into a sweltering summer sky. The unstable weather typical to Florida in the summertime didn't have a chance to coalesce and impact this morning's launch window, and the Space Shuttle Discovery began its planned seven-day, 22-hour flight on Mission STS-70 from Launch Pad 39B at 9:41:55.078 a.m. EDT, just seconds off schedule. On board for Discovery's 21st spaceflight are a crew of five: Commander Terence 'Tom' Henricks; Pilot Kevin R. Kregel; and Mission Specialists Nancy Jane Currie, Donald A. Thomas and Mary Ellen Weber. The crew's primary objective during the 70th Shuttle flight is to deploy the Tracking and Data Relay Satellite (TDRS-G), which will join a constellation of other TDRS spacecraft already on orbit. TDRS-G is destined to become an on- orbit, fully operational 'ready reserve' satellite, available along with one other ready reserve TDRS spacecraft to back up the two primary TDRS satellites positions, TDRS East over the Atlantic Ocean and TDRS West over the Pacific. Assured capability of the TDRS communications network is essential for linking Earth-orbiting spacecraft such as the Shuttle and the Hubble Space Telescope with the ground.

  4. STS-70 Launch - Nikon E-2 Digital Image

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This test image was taken with a Nikon E-2 Digital Imaging System camera and are provided courtesy of Nikon (GIF 450x450 JPEG 1280x1000): The second Shuttle launch in 16 days hurtles off the pad into a sweltering summer sky. The unstable weather typical to Florida in the summertime didn't have a chance to coalesce and impact this morning's launch window, and the Space Shuttle Discovery began its planned seven-day, 22-hour flight on Mission STS-70 from Launch Pad 39B at 9:41:55.078 a.m. EDT, just seconds off schedule. On board for Discovery's 21st spaceflight are a crew of five: Commander Terence 'Tom' Henricks; Pilot Kevin R. Kregel; and Mission Specialists Nancy Jane Currie, Donald A. Thomas and Mary Ellen Weber. The crew's primary objective during the 70th Shuttle flight is to deploy the Tracking and Data Relay Satellite (TDRS-G), which will join a constellation of other TDRS spacecraft already on orbit. TDRS-G is destined to become an on- orbit, fully operational 'ready reserve' satellite, available along with one other ready reserve TDRS spacecraft to back up the two primary TDRS satellites positions, TDRS East over the Atlantic Ocean and TDRS West over the Pacific. Assured capability of the TDRS communications network is essential for linking Earth-orbiting spacecraft such as the Shuttle and the Hubble Space Telescope with the ground.

  5. 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.

  6. 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.

  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. 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.

  9. Threshold-voltage bias-temperature instability in commercially-available SiC MOSFETs

    NASA Astrophysics Data System (ADS)

    Green, Ron; Lelis, Aivars; Habersat, Daniel

    2016-04-01

    This work reports on three important aspects of threshold-voltage instability in SiC power MOSFETs: (1) the threshold-voltage bias-temperature instability observed in commercial devices from two leading manufacturers, (2) a summary of the basic mechanisms driving this instability, and (3) the need for an improved test method for evaluating these devices. Even under significant overstress conditions, no negative threshold-voltage shift was observed in the most-recent-vintage commercial devices from one of the manufacturers during a -15 V, 175 °C negative-bias temperature stress lasting 120 h.

  10. 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

  11. 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.

  12. 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.

  13. Examples of conditional SIC-POVMs

    NASA Astrophysics Data System (ADS)

    Ohno, Hiromichi; Petz, Dénes

    2015-10-01

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

  14. Saturn V S-IC (First) Stage

    NASA Technical Reports Server (NTRS)

    1967-01-01

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

  15. Saturn V S-IC (First) Stage

    NASA Technical Reports Server (NTRS)

    1968-01-01

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

  16. Saturn V S-IC (First) Stage

    NASA Technical Reports Server (NTRS)

    2004-01-01

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

  17. S-IC Static Test Stand

    NASA Technical Reports Server (NTRS)

    1977-01-01

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

  18. Stacking faults in SiC nanowires.

    PubMed

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

    2008-07-01

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

  19. 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.

  20. In vitro cellular responses to silicon carbide particles manufactured through the Acheson process: impact of physico-chemical features on pro-inflammatory and pro-oxidative effects.

    PubMed

    Boudard, Delphine; Forest, Valérie; Pourchez, Jérémie; Boumahdi, Najih; Tomatis, Maura; Fubini, Bice; Guilhot, Bernard; Cottier, Michèle; Grosseau, Philippe

    2014-08-01

    Silicon carbide (SiC) an industrial-scale product manufactured through the Acheson process, is largely employed in various applications. Its toxicity has been poorly investigated. Our study aims at characterizing the physico-chemical features and the in vitro impact on biological activity of five manufactured SiC powders: two coarse powders (SiC C1/C2), two fine powders (SiC F1/F2) and a powder rich in iron impurities (SiC I). RAW 264.7 macrophages were exposed to the different SiC particles and the cellular responses were evaluated. Contrary to what happens with silica, no SiC cytotoxicity was observed but pro-oxidative and pro-inflammatory responses of variable intensity were evidenced. Oxidative stress (H₂O₂ production) appeared related to SiC particle size, while iron level regulated pro-inflammatory response (TNFα production). To investigate the impact of surface reactivity on the biological responses, coarse SiC C1 and fine SiC F1 powders were submitted to different thermal treatments (650-1400 °C) in order to alter the oxidation state of the particle surface. At 1400 °C a decrease in TNFα production and an increase in HO·, COO(·-) radicals production were observed in correlation with the formation of a surface layer of crystalline silica. Finally, a strong correlation was observed between surface oxidation state and in vitro toxicity. PMID:24603312

  1. 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.

  2. SOURCE ASSESSMENT: OVERVIEW AND PRIORITIZATION OF EMISSIONS FROM TEXTILE MANUFACTURING

    EPA Science Inventory

    The report gives an overview of air pollution emission levels and a ranking of the public health hazard potential of textile manufacturing operations. The textile industry was defined and categorized by Bureau of the Census Standard Industrial Classification (SIC) Codes. Flow cha...

  3. 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.

  4. 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.

  5. 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.

  6. Design of Twin Structures in SiC Nanowires

    SciTech Connect

    Yongfeng Zhang; Hanchen Huang

    2012-11-01

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

  7. 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.

  8. S-IC Test Stand Design Model

    NASA Technical Reports Server (NTRS)

    1962-01-01

    At its founding, the Marshall Space Flight Center (MSFC) inherited the Army's Jupiter and Redstone test stands, but much larger facilities were needed for the giant stages of the Saturn V. From 1960 to 1964, the existing stands were remodeled and a sizable new test area was developed. The new comprehensive test complex for propulsion and structural dynamics was unique within the nation and the free world, and they remain so today because they were constructed with foresight to meet the future as well as on going needs. Construction of the S-IC Static test stand complex began in 1961 in the west test area of MSFC, and was completed in 1964. The S-IC static test stand was designed to develop and test the 138-ft long and 33-ft diameter Saturn V S-IC first stage, or booster stage, weighing in at 280,000 pounds. Required to hold down the brute force of a 7,500,000-pound thrust produced by 5 F-1 engines, the S-IC static test stand was designed and constructed with the strength of hundreds of tons of steel and 12,000,000 pounds of cement, planted down to bedrock 40 feet below ground level. The foundation walls, constructed with concrete and steel, are 4 feet thick. The base structure consists of four towers with 40-foot-thick walls extending upward 144 feet above ground level. The structure was topped by a crane with a 135-foot boom. With the boom in the upright position, the stand was given an overall height of 405 feet, placing it among the highest structures in Alabama at the time. This photo is of the S-IC test stand design model created prior to construction.

  9. S-IC Test Stand Design Model

    NASA Technical Reports Server (NTRS)

    1962-01-01

    At its founding, the Marshall Space Flight Center (MSFC) inherited the Army's Jupiter and Redstone test stands, but much larger facilities were needed for the giant stages of the Saturn V. From 1960 to 1964, the existing stands were remodeled and a sizable new test area was developed. The new comprehensive test complex for propulsion and structural dynamics was unique within the nation and the free world, and they remain so today because they were constructed with foresight to meet the future as well as on going needs. Construction of the S-IC Static test stand complex began in 1961 in the west test area of MSFC, and was completed in 1964. The S-IC static test stand was designed to develop and test the 138-ft long and 33-ft diameter Saturn V S-IC first stage, or booster stage, weighing in at 280,000 pounds. Required to hold down the brute force of a 7,500,000-pound thrust produced by 5 F-1 engines, the S-IC static test stand was designed and constructed with the strength of hundreds of tons of steel and 12,000,000 pounds of cement, planted down to bedrock 40 feet below ground level. The foundation walls, constructed with concrete and steel, are 4 feet thick. The base structure consists of four towers with 40-foot-thick walls extending upward 144 feet above ground level. The structure was topped by a crane with a 135-foot boom. With the boom in the upright position, the stand was given an overall height of 405 feet, placing it among the highest structures in Alabama at the time. This photo is of the S-IC test stand design model.

  10. Infrared spectra of meteoritic SiC grains

    NASA Astrophysics Data System (ADS)

    Andersen, A. C.; Jäger, C.; Mutschke, H.; Braatz, A.; Clément, D.; Henning, Th.; Jørgensen, U. G.; Ott, U.

    1999-03-01

    We present here the first infrared spectra of meteoritic SiC grains. The mid-infrared transmission spectra of meteoritic SiC grains isolated from the Murchison meteorite were measured in the wavelength range 2.5-16.5 mu m, in order to make available the optical properties of presolar SiC grains. These grains are most likely stellar condensates with an origin predominately in carbon stars. Measurements were performed on two different extractions of presolar SiC from the Murchison meteorite. The two samples show very different spectral appearance due to different grain size distributions. The spectral feature of the smaller meteoritic SiC grains is a relatively broad absorption band found between the longitudinal and transverse lattice vibration modes around 11.3 mu m, supporting the current interpretation about the presence of SiC grains in carbon stars. In contrast to this, the spectral feature of the large (> 5 mu m) grains has an extinction minimum around 10 mu m. The obtained spectra are compared with commercially available SiC grains and the differences are discussed. This comparison shows that the crystal structure (e.g., beta -SiC versus alpha -SiC) of SiC grains plays a minor role on the optical signature of SiC grains compared to e.g. grain size.

  11. Synthesis of SiC nanorods from bleached wood pulp

    SciTech Connect

    Shin, Yongsoon; Wang, Chong M.; Samuels, William D.; Exarhos, Gregory J.

    2007-05-01

    Unbleached and bleached soft wood pulps have been used as templates and carbon precursors to produce SiC nanorods. Hydrolyzed tetraethylorthosilicate (TEOS), Silicic acid was infiltrated into the pulps followed by a carbothermal reduction to form SiC nanorods at 1400oC in Ar. Residual carbon formed along with SiC was removed by gasification at 700oC in air. The SiC materials prepared from unbleached pulp were non-uniform SiC with a thick SiO2 coating, while the SiC nanorods prepared from the bleached pulp were uniform and straight with dimensions of 250 nm in diameter and 5.0 mm long. The formation of uniform camelback structure of SiC in the reaction between silica and bleached pulp is attributed to more silica deposited in the amorphous region of cellulose.

  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. 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.

  14. 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,…

  15. Tensile strength of SiC fibers

    SciTech Connect

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

    1995-07-01

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

  16. Periodically twinned SiC nanowires.

    PubMed

    Wang, Dong-Hua; Xu, Di; Wang, Qing; Hao, Ya-Juan; Jin, Guo-Qiang; Guo, Xiang-Yun; Tu, K N

    2008-05-28

    Twinning has been recognized to be an important microstructural defect in nanoscale materials. Periodically twinned SiC nanowires were largely synthesized by the carbothermal reduction of a carbonaceous silica xerogel prepared from tetraethoxysilane and biphenyl with iron nitrate as an additive. The twinned β-SiC nanowires, with a hexagonal cross section, a diameter of 50-300 nm and a length of tens to hundreds of micrometers, feature a zigzag arrangement of periodically twinned segments with a rather uniform thickness along the entire growth length. Computer simulation has been used to generate three-dimensional atomic structures of the zigzag columnar twin structure by the stacking of hexagonal discs of {111} planes of SiC. A minimum surface energy and strain energy argument is proposed to explain the formation of periodic twins in the SiC nanowires. The thickness of the periodic twinned segments is found to be linearly proportional to the nanowire diameter, and a constant volume model is proposed to explain the relation. PMID:21730575

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Direct current conduction in SiC powders

    NASA Astrophysics Data System (ADS)

    Mârtensson, E.; Gäfvert, U.; Lindefelt, U.

    2001-09-01

    Silicon carbide (SiC) powder is used in nonlinear field grading materials. The composite material, consisting of an insulating polymer matrix filled with the SiC-grains, is usually a percolated system with established conducting paths. In order to explain the properties, the electrical characteristic and conduction mechanisms of the SiC powder itself are of interest. SiC powders have been studied by current-voltage measurements and the influences of grain size and doping have been investigated. The macroscopic current characteristics of green and black SiC powders can be described by the transport mechanisms at the grain contacts, which can be modeled by Schottky-like barriers. The SiC is heavily doped and tunneling by field emission is the dominating conduction mechanism over the major part of the nonlinear voltage range. It is suggested that preavalanche multiplication influences the current at the highest voltages, especially for p-type black SiC.

  2. F-1 Engine Installation to S-IC Stage

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Engineers and technicians at the Marshall Space Flight Center were installing an F-I engine on the Saturn V S-IC (first) stage thrust structure in building 4705. The S-IC (first) stage used five F-1 engines that produced a total thrust of 7,500,000 pounds as each engine produced 1,500,000 pounds of thrust. The S-IC stage lifted the Saturn V vehicle and Apollo spacecraft from the launch pad.

  3. 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

  4. 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.

  5. Graphene covered SiC powder as advanced photocatalytic material

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  6. 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.

  7. 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.

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

    SciTech Connect

    Henager, Charles H.; Jiang, Weilin

    2014-11-01

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

  9. 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)

  10. 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.

  11. Saturn V S-IC Stage LOX Tank

    NASA Technical Reports Server (NTRS)

    1964-01-01

    This image depicts the Saturn V S-IC (first) stage liquid oxygen (LOX) tank being lowered into the irner tank in a high bay at the Marshall Space Flight Center (MSFC). The S-IC stage utilized five F-1 engines that used liquid oxygen and kerosene as propellant and provided a combined thrust of 7,500,000 pounds.

  12. Alternate current characteristics of SiC powders

    NASA Astrophysics Data System (ADS)

    Mârtensson, E.; Gäfvert, U.; Önneby, C.

    2001-09-01

    Silicon carbide (SiC) powder is used in nonlinear field grading materials. The composite material, consisting of an insulating polymer matrix filled with the SiC grains, is usually a percolated system with established conducting paths. In order to explain the properties, the electrical characteristic of the SiC powder itself is of interest. The ac characteristics of SiC powders have been studied by dielectric response, capacitance-voltage, and ac-pulse measurements. The frequency, electric field, and pressure dependencies have been analyzed for green and black SiC, which have different doping. The ac characteristics of green and black SiC powders are governed by both the barrier regions at the SiC-grain contacts and the surrounding matrix. The nonlinear loss is determined by the conduction current at the contacts. Depending on the doping level of the SiC grains, the capacitance may be controlled by either the nonlinear capacitance of the barrier region or the linear capacitance of the surrounding matrix. Each contact zone may be modeled by a nonlinear resistance in parallel with both a nonlinear and a linear capacitance. The components are considered to be frequency independent. However, in order to explain the macroscopic frequency and field dependencies of the SiC powders, the use of a network of unique contact zones with dissimilar properties is suggested.

  13. 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. Growth Of Graphitic Polyhedra, SiC Platelets, And Carbon Nanotubes Filled With SiC Nanowires By Laser Ablation

    SciTech Connect

    Kokai, Fumio; Uchiyama, Kunihiro; Chigusa, Hajime; Nozaki, Iori; Noguchi, Eriko; Kameda, Yuto; Koshio, Akira

    2010-10-08

    Three characteristic silicon/carbon nanostructures, i.e., graphitic polyhedral (GP) particles, silicon carbide (SiC) platelets, and carbon nanotubes (CNTs) filled with SiC nanowires, were synthesized by the laser ablation of Si-C targets in the presence of high-pressure Ar gas up to 0.9 MPa. The growth of nanostructures was controlled merely by adjusting the Si content in graphite and the ambient Ar gas pressure. Deposits containing GP particles were purified by heat treatment at 550 deg. C in a pure oxygen atmosphere for 1 h. CNTs filled with SiC nanowires were grown without a catalyst. Unlike previous studies of CNTs filled with metals or compounds, all the CNTs checked by transmission electron microscopy contained SiC nanowires and no unfilled CNTs were produced. We discuss the growth mechanisms of the three nanostructures.

  16. Cryogenic optical testing of SiC mirrors for ASTRO-F and C/SiC composite mirrors for SPICA

    NASA Astrophysics Data System (ADS)

    Kaneda, Hidehiro; Nakagawa, Takao; Enya, Keigo; Onaka, Takashi

    2004-06-01

    Light-weight mirrors are developed for two Japanese infrared astronomical missions, ASTRO-F and SPICA. ASTRO-F is scheduled for launch in 2005, while the target year for launch of SPICA is 2010. The mirrors of the ASTRO-F telescope are made of a sandwich-type silicon carbide (SiC) material, comprising porous core and CVD coat of SiC on the surface. Cryogenic measurements of the ASTRO-F primary mirror and telescope assembly were performed extensively. As for the SPICA telescope, which has an aperture of 3.5-m diameter, carbon-fiber-reinforced SiC (C/SiC composite), as well as SiC, is one of the promising candidates for mirror material. C/SiC composite spherical test mirrors of 160-mm diameter has recently been manufactured and tested. This paper presents the experimental results of the cryogenic performance obtained for the sandwich-type SiC mirrors and the C/SiC composite mirrors.

  17. The fracture strength of plate and tubular forms of monolithic silicon carbide (SiC) produced by chemical vapor deposition (CVD)

    SciTech Connect

    Cockeram, B.V.

    2000-12-01

    The fracture strength of silicon carbide (SiC) plate deposits produced by Chemical Vapor Deposition (CVD) was determined from room-temperature to 1500 C using a standard 4-point flexural test method (ASTM Cl 161). CVD SiC materials produced by two different manufacturers are shown to have only slightly different flexural strength values, which appear to result from differences in microstructure. Although CVD deposition of SiC results in a textured grain structure, the flexural strength was shown to be independent of the CVD growth direction. The orientation of machining marks was shown to have the most significant influence on flexural strength, as expected. The fracture strength of tubular forms of SiC produced by CVD deposition directly onto a mandrel was comparable to flexural bars machined from a plate deposit. The tubular (o-ring) specimens were much smaller in volume than the flexural bars, and higher strength values are predicted based on Weibull statistical theory for the o-ring specimens. Differences in microstructure between the plate deposits and deposits made on a mandrel result in different flaw distributions and comparable strength values for the flexural bar and o-ring specimens. These results indicate that compression testing of o-rings provides a more accurate strength measurement for tubular product forms of SiC due to more representative flaw distributions.

  18. 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

  19. 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.

  20. Fabrication of SiC whisker-reinforced SiC ceramics

    SciTech Connect

    Miyahara, Kaoru; Watanabe, Takashi; Koga, Shin; Sasa, Tadashi

    1992-10-01

    A fabrication process of SiC whisker-reinforced SiC ceramics consisting of whisker CVD-coating for the control of interfacial bonding, slurry-pressing and HIP consolidation has been developed. Microstructural observation confirmed the incorporation of the interfacial carbon layer in the composites brought about remarkable whisker bridging/pull-out in the fracture. Whisker-bridging was considered to be a predominant toughening mechanism. To optimize the interfacial properties, the effect of coating conditions, i.e., amount of coating and CVD temperature, on the fracture toughness were studied. The effect of whisker diameter on the fracture toughness and anisotropy in the fracture toughness were also investigated. 12 refs.

  1. 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.

  2. 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.

  3. 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.

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

    SciTech Connect

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

    1995-12-31

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

  5. 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.

  6. ICP Etching of SiC

    SciTech Connect

    Grow, J.M.; Lambers, E.S.; Ostling, M.; Pearton, S.J.; Ren, F.; Shul, R.J.; Wang, J.J.; Zetterling, C.-M.

    1999-02-04

    A number of different plasma chemistries, including NF{sub 3}/O{sub 2}, SF{sub 6}/O{sub 2}, SF{sub 6}/Ar, ICl, IBr, Cl{sub 2}/Ar, BCl{sub 3}/Ar and CH{sub 4}/H{sub 2}/Ar, have been investigated for dry etching of 6H and 3C-SiC in a Inductively Coupled Plasma tool. Rates above 2,000 {angstrom} cm{sup {minus}1} are found with fluorine-based chemistries at high ion currents. Surprisingly, Cl{sub 2}-based etching does not provide high rates, even though the potential etch products (SiCi{sub 4} and CCl{sub 4}) are volatile. Photoresist masks have poor selectivity over SiC in F{sub 2}-based plasmas under normal conditions, and ITO or Ni are preferred.

  7. 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.

  8. Ellipsometric study of cubic SiC

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Shoemaker, Neil S.; Powell, J. A.

    1990-01-01

    Variable angle spectroscopic ellipsometry (VASE) was applied to cubic SiC. This technique gives absolute values of the refractive index (n) and the extinction coefficient (k) of a substrate and/or a thin film of unknown material. The samples were grown by chemical vapor deposition (CVD) on p-type silicon. The substrate was aligned either on the (001) axis or 1 degree of (001). Several growth temperatures and growth durations were used. The samples were divided into two groups: (1) thick films of order 10 microns grown near optimal conditions of temperature, flow, and gas ratio; and (2) thin films of order 100 A grown at various temperatures. The ellipsometric results for samples in group 1 were analyzed using a two-phase model (substrate and ambient). Results show that for wavelengths in the visible, the refractive index of these CVD samples is equal to that reported for single crystal cubic SiC, within the experimental error, which is on the order of 1 percent. However, the extinction coefficient has a relatively large value, even above the band gap. The absorption is sample dependent and has a broad peak in the visible. The results for samples in group 2 were analyzed using a three-phase model (substrate, film, and ambient). The dielectric functions of the film, deducted from the measured n and k, were further analyzed using the effective medium approximation. The results show that the films contain 30 to 40 vol. percent amorphous silicon, i.e., silicon with only short-range order.

  9. Imaging of SiC in metal matrix composites

    SciTech Connect

    Radmilovic, V.; O`Keefe, M.A.; Thomas, G.

    1992-08-01

    TEM has advantages over XRD in determining lattice periodicity. This paper reports an attempt in matching a simulation to an experimental image of SiC in an Al-8.5wt%Fe-1.3 wt%V-1.7 wt%Si composite containing 15 wt% SiC particulates, processed by powder metallurgy. The hexagonal allotrope has predominantly the 6H polytype structure; 1/3 of the 15R polytype is also observed. This SiC structure represents the 87R polytype. 6 refs, 2 figs.

  10. 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.

  11. SiC Composite Turbine Vanes

    NASA Technical Reports Server (NTRS)

    Calomino, Anthony M.; Verilli, Michael J.

    2006-01-01

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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Compensation in epitaxial cubic SiC films

    NASA Technical Reports Server (NTRS)

    Segall, B.; Alterovitz, S. A.; Haugland, E. J.; Matus, L. G.

    1986-01-01

    Hall measurements on four n-type cubic SiC films epitaxially grown by chemical vapor deposition on SiC substrates are reported. The temperature dependent carrier concentrations indicate that the samples are highly compensated. Donor ionization energies, E sub D, are less than one half the values previously reported. The values for E sub D and the donor concentration N sub D, combined with results for small bulk platelets with nitrogen donors, suggest the relation E sub D (N sub D) = E sub D(O) - alpha N sub N sup 1/3 for cubic SiC. A curve fit gives alpha is approx 2.6x10/5 meV cm and E sub D (O) approx 48 meV, which is the generally accepted value of E sub D(O) for nitrogen donors in cubic SiC.

  18. Saturn V S-IC Stage Fuel Tank

    NASA Technical Reports Server (NTRS)

    1964-01-01

    This image shows the Saturn V S-IC-T stage (S-IC static test article) fuel tank being attached to the thrust structure in the vehicle assembly building at the Marshall Space Flight Center (MSFC). The S-IC stage utilized five F-1 engines that used liquid oxygen and kerosene as propellant and provided a combined thrust of 7,500,000 pounds.

  19. 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

  20. Electrical Characterization of Defects in SiC Schottky Barriers

    NASA Technical Reports Server (NTRS)

    Schnabel, C. M.; Tabib-Azar, M.; Raffaelle, R. P.; Su, H. B.; Dudley, M.; Neudeck, P. G.; Bailey, S.

    2005-01-01

    We have been investigating the effect of screw dislocation and other structural defects on the electrical properties of SiC. SiC is a wide-bandgap semiconductor that is currently received much attention due to its favorable high temperature behavior and high electric field breakdown strength. Unfortunately, the current state-of-the-art crystal growth and device processing methods produce material with high defect densities, resulting in a limited commercial viability

  1. Turbine Manufacture

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The machinery pictured is a set of Turbodyne steam turbines which power a sugar mill at Bell Glade, Florida. A NASA-developed computer program called NASTRAN aided development of these and other turbines manufactured by Turbodyne Corporation's Steam Turbine Division, Wellsville, New York. An acronym for NASA Structural Analysis Program, NASTRAN is a predictive tool which advises development teams how a structural design will perform under service use conditions. Turbodyne uses NASTRAN to analyze the dynamic behavior of steam turbine components, achieving substantial savings in development costs. One of the most widely used spinoffs, NASTRAN is made available to private industry through NASA's Computer Software Management Information Center (COSMIC) at the University of Georgia.

  2. The impact resistance of SiC and other mechanical properties of SiC and Si3N4

    NASA Technical Reports Server (NTRS)

    Bradt, R. C.

    1984-01-01

    Studies focused on the impact and mechanical behavior of SiC and Si3N4 at high temperatures are summarized. Instrumented Charpy impact testing is analyzed by a compliance method and related to strength; slow crack growth is related to processing, and creep is discussed. The transient nature of flaw populations during oxidation under load is emphasized for both SiC and Si3N4.

  3. 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.

  4. High temperature chemical compatibility between SiC composites and Be pebbles

    NASA Astrophysics Data System (ADS)

    Alves, L. C.; Paúl, A.; da Silva, M. R.; Alves, E.; Riccardi, B.; Soares, J. C.

    2003-09-01

    SiC composite reinforced fibres are still considered to be an important material to be used in nuclear fusion reactors due to their high temperature and low neutron activation properties. Two different kinds of SiC/SiC f composite were manufactured, one of them presenting an extra SiC coating obtained by chemical vapour deposition technique. Several samples of both materials were placed inside a Be pebble bed and the whole set-up annealed at 800 °C for 550 h in a reducing atmosphere, simulating fusion reactor conditions. Surface chemical reactions were investigated with nuclear microprobe analyses techniques and complemented with SEM analysis. For the uncoated samples, surface oxidation is accompanied by a strong C depletion and a Be diffusion. Two different behaviours were found for the coated samples. One of those samples showed extended regions where surface was left almost unaltered. The general behaviour, however, was an increase in the number and extension of the cracks already observed at the surface of the coated virgin samples.

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

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Singh, Mrityunjay

    2004-01-01

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

  6. Total displacement functions for SiC

    NASA Astrophysics Data System (ADS)

    Weber, W. J.; Williford, R. E.; Sickafus, K. E.

    1997-04-01

    Numerical solutions for the displacement functions in SiC are determined from the coupled integro-differential equations governing the total number of type- j atoms displaced in the collision cascade initiated by a primary knock-on atom (PKA) of type- i and energy E. Atomic scattering cross sections based on either the inverse power law screening potentials or the Ziegler, Biersack, and Littmark (ZBL) universal screening potential are used in the calculation of the displacement functions. The electronic stopping powers used in the calculations are either derived from the LSS and Bethe-Bloch theories or generated from the SRIM-96 electronic stopping power data base. The displacement functions determined using LSS/Bethe-Bloch electronic stopping powers are 25 to 100% larger than the displacement functions determined using the electronic stopping powers generated by SRIM-96. The total number of displaced atoms determined numerically for each PKA type, based on ZBL scattering cross sections and SRIM-96 electronic stopping powers, is in excellent agreement, over the entire range of PKA energies (10 eV to 10 MeV), with the total number of displacements determined by full cascade Monte Carlo simulations using the TRIM code in SRIM-96.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Saccharomyces cerevisiae Ime2 phosphorylates Sic1 at multiple PXS/T sites but is insufficient to trigger Sic1 degradation

    PubMed Central

    Sedgwick, Chantelle; Rawluk, Matthew; Decesare, James; Raithatha, Sheetal; Wohlschlegel, James; Semchuk, Paul; Ellison, Michael; Yates, John; Stuart, David

    2006-01-01

    The initiation of DNA replication in Saccharomyces cerevisiae depends upon the destruction of the Clb–Cdc28 inhibitor Sic1. In proliferating cells Cln–Cdc28 complexes phosphorylate Sic1, which stimulates binding of Sic1 to SCFCdc4 and triggers its proteosome mediated destruction. During sporulation cyclins are not expressed, yet Sic1 is still destroyed at the G1-/S-phase boundary. The Cdk (cyclin dependent kinase) sites are also required for Sic1 destruction during sporulation. Sic1 that is devoid of Cdk phosphorylation sites displays increased stability and decreased phosphorylation in vivo. In addition, we found that Sic1 was modified by ubiquitin in sporulating cells and that SCFCdc4 was required for this modification. The meiosis-specific kinase Ime2 has been proposed to promote Sic1 destruction by phosphorylating Sic1 in sporulating cells. We found that Ime2 phosphorylates Sic1 at multiple sites in vitro. However, only a subset of these sites corresponds to Cdk sites. The identification of multiple sites phosphorylated by Ime2 has allowed us to propose a motif for phosphorylation by Ime2 (PXS/T) where serine or threonine acts as a phospho-acceptor. Although Ime2 phosphorylates Sic1 at multiple sites in vitro, the modified Sic1 fails to bind to SCFCdc4. In addition, the expression of Ime2 in G1 arrested haploid cells does not promote the destruction of Sic1. These data support a model where Ime2 is necessary but not sufficient to promote Sic1 destruction during sporulation. PMID:16776651

  14. Growth and Features of Epitaxial Graphene on SiC

    NASA Astrophysics Data System (ADS)

    Kusunoki, Michiko; Norimatsu, Wataru; Bao, Jianfeng; Morita, Koichi; Starke, Ulrich

    2015-12-01

    Recent progress of epitaxial graphene on SiC was reviewed, focusing on its growth and structural and electronic features. Homogeneous graphene can be grown on SiC(0001) on a wafer scale, however on SiC(000bar{1}) multilayer but rotationally stacked graphene with monolayer like electronic property grows. HRTEM revealed the formation mechanism and structural features of graphene on the both surfaces. The high structural and electronic quality of the grown graphene is monitored by Raman spectroscopy and magneto-transport characterization. High-resolution ARPES measurements of the electronic dispersion around the bar{text{K}}-point retrieved the ABA and ABC stacked trilayer graphene. The measurements also directly revealed that electronic structures of graphene were manipulated by transfer doping and atomic intercalation. In particular, p- and n-doped regions on a meso-scale and the p-n junctions prepared on SiC via controlling intercalation of Ge exhibited ballistic transport and Klein tunneling, which predicted novel potentials on to epitaxial graphene on SiC.

  15. Recent Developments in SiC Device Research

    NASA Astrophysics Data System (ADS)

    Harris, C. I.; Konstantinov, A. O.

    Silicon Carbide is fast emerging as a mature semiconductor. The unique combination of material properties offered by SiC will allow it to establish itself in applications where the ever dominant Si is approaching the physical (not technical) limits of it's operation. Three key areas will be explored in this paper: (i) High power electronics. SiC devices operating at several kV and capable of MW power handling will revolutionise the way electrical power is transmitted and made use of. Recent progress supported by ABB in Sweden suggests these breakthroughs will begin to play a key role soon after the turn of the century. (ii) High frequency devices made from SiC will also play an increasingly important part in the mobile telecommunication revolution in which we currently live. Northrop Grumman in the USA have demonstrated the transmission of digital TV using SiC based devices. The high power density achieved from such devices make them also suitable for base stations for mobile telephones. (iii) Finally we look at some examples of how SiC is being used to develop new types of sensors that can be used in extreme environments such as high temperatures, high pressures or corrosive environments. Feedback from such sensors is seen as essential to understanding how we effect the world around us and thereby how we can limit pollution.

  16. TRISO coated fuel particles with enhanced SiC properties

    NASA Astrophysics Data System (ADS)

    López-Honorato, E.; Tan, J.; Meadows, P. J.; Marsh, G.; Xiao, P.

    2009-07-01

    The silicon carbide (SiC) layer used for the formation of TRISO coated fuel particles is normally produced at 1500-1650 °C via fluidized bed chemical vapor deposition from methyltrichlorosilane in a hydrogen environment. In this work, we show the deposition of SiC coatings with uniform grain size throughout the coating thickness, as opposed to standard coatings which have larger grain sizes in the outer sections of the coating. Furthermore, the use of argon as the fluidizing gas and propylene as a carbon precursor, in addition to hydrogen and methyltrichlorosilane, allowed the deposition of stoichiometric SiC coatings with refined microstructure at 1400 and 1300 °C. The deposition of SiC at lower deposition temperatures was also advantageous since the reduced heat treatment was not detrimental to the properties of the inner pyrolytic carbon which generally occurs when SiC is deposited at 1500 °C. The use of a chemical vapor deposition coater with four spouts allowed the deposition of uniform and spherical coatings.

  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. Research on microwave joining of SiC. Final report

    SciTech Connect

    1993-06-30

    Work on microwave joining of sintered SiC has showed that small samples could be jointed using Si interlayer (applied as pressed powder); SEM showed a smooth, homogeneous interlayer 50 {mu}m wide. Objective of this contract is to optimize these joints. Results showed that the interlayer could be reduced to 10-20 {mu}m using an oil-based slurry made from Si powder, and to less than 5 {mu}m by plasma spraying Si on one of the SiC surfaces. Direct joints were made in reaction bonded SiC, using the residual Si. Excellent joints with good mechanical properties were obtained in both small specimens and in small scale tube assemblies like in heat exchanger and radiant burner tubes. In situ reaction synthesis from powders to produce a SiC-TiC-SiC joint was demonstrated, as well feasibility of producing SiC from microwave-assisted decomposition of polymer precursors. Finally, new applicator designs, including a compound adjustable iris and a mitered bend single mode cavity, were demonstrated to provide improved heating of larger and longer specimens. This work provides the foundation for scaleup of microwave joining to SiC components for industrial applications.

  19. Modification Progress of the S-IC Test Stand

    NASA Technical Reports Server (NTRS)

    1975-01-01

    At its founding, the Marshall Space Flight Center (MSFC) inherited the Army's Jupiter and Redstone test stands, but much larger facilities were needed for the giant stages of the Saturn V. From 1960 to 1964, the existing stands were remodeled and a sizable new test area was developed. The new comprehensive test complex for propulsion and structural dynamics was unique within the nation and the free world, and they remain so today because they were constructed with foresight to meet the future as well as on going needs. Construction of the S-IC Static test stand complex began in 1961 in the west test area of MSFC, and was completed in 1964. The S-IC static test stand was originally designed to develop and test the 138-ft long and 33-ft diameter Saturn V S-IC first stage, or booster stage. Modifications to the S-IC Test Stand began in 1975 to accommodate space shuttle external tank testing. This photo depicts the continuation of the modification process as of July 14, 1975. The flame deflector originally used to provide water to the 5 F-1 engines of the S-IC stage during testing has been removed.

  20. 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.

  1. 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.

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

    SciTech Connect

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

    2014-04-01

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

  3. Structural Properties of Liquid SiC during Rapid Solidification

    PubMed Central

    Yan, WanJun; Gao, TingHong; Guo, XiaoTian; Qin, YunXiang; Xie, Quan

    2013-01-01

    The rapid solidification of liquid silicon carbide (SiC) is studied by molecular dynamic simulation using the Tersoff potential. The structural properties of liquid and amorphous SiC are analyzed by the radial distribution function, angular distribution function, coordination number, and visualization technology. Results show that both heteronuclear and homonuclear bonds exist and no atomic segregation occurs during solidification. The bond angles of silicon and carbon atoms are distributed at around 109° and 120°, respectively, and the average coordination number is <4. Threefold carbon atoms and fourfold silicon atoms are linked together by six typical structures and ultimately form a random network of amorphous structure. The simulated results help understand the structural properties of liquid and amorphous SiC, as well as other similar semiconductor alloys. PMID:24288474

  4. Aspects of SiC diode assembly using Ag technology

    NASA Astrophysics Data System (ADS)

    Mysliwiec, Marcin; Guziewicz, Marek; Kisiel, Ryszard

    2013-07-01

    The aim of our paper is to consider the possibility of applying pure Ag technology for assembly of SiC Schottky diode into a ceramic package able to work at temperatures up to 350°C. Ag micropowder was used for assembly SiC structure to DBC interposer of the ceramic package. Ag wire bonds as well as flip-chip technology using Ag balls were used as material for interconnection systems. The parameters of I-V characteristics were used as a quality factor to determine the Schottky diode after hermetization into ceramic package as well as after ageing in air at 350°C in comparison with characteristics of bare SiC diode.

  5. 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. Synthesis and properties of porous SiC ceramics

    NASA Astrophysics Data System (ADS)

    Kiselov, V. S.; Lytvyn, P. M.; Yukhymchuk, V. O.; Belyaev, A. E.; Vitusevich, S. A.

    2010-05-01

    Porous silicon carbide (SiC) ceramics are produced using carbon matrices derived from natural wood. Such material is especially promising as it is environmentally friendly with attractive physical properties, including a high level of biocompatibility, chemical inertness, and mechanical strength. We have developed a forced impregnation process with further synthesis of SiC using natural wood as well as a variety of industrial carbon materials and compared the properties of these ceramics. The structure and composition of the materials obtained were investigated by Raman scattering spectroscopy. The hardness of the samples was estimated using the Vickers technique. It was shown that the phase composition and mechanical properties of synthesized SiC ceramics can be effectively controlled by the initial Si contents and temperature of the synthesis process. A large variety of options are demonstrated for materials development taking into account an optimal porosity selection for various practical applications.

  7. 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.

  8. 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.

  9. Junction barrier Schottky diodes in 6H SiC

    NASA Astrophysics Data System (ADS)

    Zetterling, Carl-Mikael; Dahlquist, Fanny; Lundberg, Nils; Östling, Mikael; Rottner, Kurt; Ramberg, Lennart

    1998-09-01

    Junction barrier Schottky (JBS) diodes in 6H SiC have been fabricated and characterised electrically. This device, demonstrated in silicon technology, has the advantage of a low forward voltage drop comparable to that of Schottky diodes, as well as a high blocking voltage and low reverse leakage current of a pn junction. This is especially attractive for wide bandgap materials such as SiC in which pn junctions have a large forward voltage drop. The devices were capable of blocking up to 1100 V with a leakage current density of 0.15 A cm -2, limited by the leakage when the drift region was fully depleted, or breakdown of the SiC material itself. The forward conduction was limited by an on-resistance of 20 mΩ cm 2, resulting in forward voltage drops of 2.6 V at 100 A cm -2.

  10. Structural properties of liquid SiC during rapid solidification.

    PubMed

    Yan, WanJun; Gao, TingHong; Guo, XiaoTian; Qin, YunXiang; Xie, Quan

    2013-01-01

    The rapid solidification of liquid silicon carbide (SiC) is studied by molecular dynamic simulation using the Tersoff potential. The structural properties of liquid and amorphous SiC are analyzed by the radial distribution function, angular distribution function, coordination number, and visualization technology. Results show that both heteronuclear and homonuclear bonds exist and no atomic segregation occurs during solidification. The bond angles of silicon and carbon atoms are distributed at around 109° and 120°, respectively, and the average coordination number is <4. Threefold carbon atoms and fourfold silicon atoms are linked together by six typical structures and ultimately form a random network of amorphous structure. The simulated results help understand the structural properties of liquid and amorphous SiC, as well as other similar semiconductor alloys. PMID:24288474

  11. 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)

  12. 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.

  13. Elastic properties of SiC nanoscopic wires

    NASA Astrophysics Data System (ADS)

    Makeev, Maxim; Menon, Madhu; Srivastava, Deepak

    2006-03-01

    Mechanical properties of crystalline and amorphous SiC nanowires have been investigated using molecular dynamics simulations with the Tersoff bond-order interatomic potential. The crystalline and a-SiC nanowires of different diameters were studied under tension/compression, torsion, and bending. The bending and torsion rigidities are found to be strongly dependent on the wire size. This is unlike the Young's modulus computed from uniaxial loading curves. Atomistic relaxations effects near the thresholds of structural stability are investigated for the four employed load types. The mechanical properties of crystalline SiC nanowires are compared with a-SiC wires of the same radii.

  14. Saturn V S-IC (First Stage) Structural Arrangement

    NASA Technical Reports Server (NTRS)

    1968-01-01

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

  15. Spin effects in thermoelectric phenomena in SiC nanoribbons.

    PubMed

    Zberecki, K; Swirkowicz, R; Wierzbicki, M; Barnaś, J

    2015-01-21

    Using ab initio methods we calculate the thermoelectric and spin thermoelectric properties of zigzag SiC nanoribbons, asymmetrically terminated with hydrogen. Such nanoribbons display a ferromagnetic ground state, with edge magnetic moments oriented in parallel. Both thermopower and spin thermopower have been determined as a function of chemical potential and temperature. To find the thermoelectric efficiency, the total heat conductance has been calculated, i.e. the electronic and phonon contributions. Numerical results for SiC nanoribbons are compared with those for graphene and silicene ones. PMID:25473937

  16. Plasma synthesis and characterization of ultrafine SiC

    SciTech Connect

    Vogt, G.J.; Phillips, D.S.; Taylor, T.N.

    1986-01-01

    Ultrafine SiC powders have been prepared by gas phase synthesis from silane and methane in an argon thermal rf-plasma. Bulk properties of the powders were determined by elemental analysis, x-ray diffractin, helium pycnometry, and BET surface area measurements. The near-surface composition and structure of the particles were examined by x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). In addition to free silicon and carbon particles in the powders, free carbon and various silicon/carbon/oxygen species were found on the surface of the SiC particles.

  17. The Commercialization of the SiC Flame Sensor

    NASA Astrophysics Data System (ADS)

    Fedison, Jeffrey B.

    2002-03-01

    The technical and scientific steps required to produce large quantities of SiC flame sensors is described. The technical challenges required to understand, fabricate, test and package SiC photodiodes in 1990 were numerous since SiC device know how was embryonic. A sense of urgency for a timely replacement of the Geiger Muller gas discharge tube soon entered the scene. New dual fuel GE Power Systems gas turbines, which were designed to lean burn either natural gas or oil for low NOx emissions required a much higher sensitivity sensor. Joint work between GE CRD and Cree Research sponsored by the GE Aircraft Engine Division developed the know how for the fabrication of high sensitivity, high yield, reliable SiC photodiodes. Yield issues were uncovered and overcome. The urgency for system insertion required that SiC diode and sensor circuitry development needed to be carried out simultaneously with power plant field tests of laboratory or prototype sensor assemblies. The sensor and reliability specifications were stringent since the sensors installed on power plant turbine combustor walls are subjected to high levels of vibration, elevated temperatures, and high pressures. Furthermore a fast recovery time was required to sense flame out in spite of the fact that the amplifier circuit needed have high gain and high dynamic range. SiC diode technical difficulties were encountered and overcome. The science of hydrocarbon flames will also be described together with the fortunate overlap of the strong OH emission band with the SiC photodiode sensitivity versus wavelength characteristic. The extremely low dark current (<1pA/cm^2) afforded by the wide band gap and the 3eV sensitivity cutoff at 400nm made if possible to produce low amplifier offsets, high sensitivity and high dynamic range along with immunity to black body radiation from combustor walls. Field tests at power plants that had experienced turbine tripping, whenever oil fuel and/or oil with steam injection for

  18. Gas Sensing Diode Comprising SiC

    NASA Technical Reports Server (NTRS)

    Hunter, Gary William (Inventor)

    2001-01-01

    A diode for sensing hydrogen and hydrocarbons and the process for manufacturing the diode are disclosed. The diode is a Schottky diode which has a palladium chrome contact on the C-face of an n-type 6H Silicon carbide epilayer. The epilayer is grown on the C-face of a 6H silicon carbide substrate. The diode is capable of measuring low concentrations of hydrogen and hydrocarbons at high temperatures, for example, 800 degrees C. The diode is both sensitive and stable at elevated temperatures.

  19. Fe Isotopic Composition of Presolar SiC Mainstream Grains

    NASA Technical Reports Server (NTRS)

    Tripa, C. E.; Pellin, M. J.; Savina, M. R.; Davis, A. M.; Lewis, R. S.; Clayton, R. N.

    2002-01-01

    Iron isotopic distribution was measured in SiC mainstream grains from the Murchison meteorite by time-of-flight resonance ionization mass spectrometry. All grains exhibit 54Fe depletions of 50 to 200, lower than what are predicted by calculations of s-process nucleosynthesis in AGB stars. Additional information is contained in the original extended abstract.

  20. Development of SiC Mirror for ASTRO-F

    NASA Astrophysics Data System (ADS)

    Kaneda, H.; Onaka, T.; Yamashiro, R.

    2000-12-01

    The development of the light-weight silicon carbide mirrors for the ASTRO-F mission is described in this paper. These mirrors are made of a sandwich-type SiC material, consisting of light porous core and dense CVD (chemical vapor deposition) coat of SiC. The primary mirror has a diameter of 710 mm and weighs only 11 kg. Combined with the secondary mirror of the same type, they form Ritchey-Chretien type telescope (F/6), which is cooled down to 5.8 K. Fabrication of the small-scale test SiC mirror has been successful which shows very little deformation of the figure at liquid-helium temperatures. Another type of the SiC coated mirror has been tested which has the same size as flight model, but of which core is made of graphite. At present, polishing of the flight-model primary mirror is going on. Construction of the flight model telescope system will be finished in 2001.

  1. 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.

  2. Observations of Ag diffusion in ion implanted SiC

    DOE PAGESBeta

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

    2015-03-17

    The nature and magnitude of Ag diffusion in SiC has been a topic of interest in connection with the performance of tristructural isotropic (TRISO) coated particle fuel for high temperature gas-cooled nuclear reactors. Ion implantation diffusion couples have been revisited to continue developing a more complete understanding of Ag fission product diffusion in SiC. Ion implantation diffusion couples fabricated from single crystal 4H-SiC and polycrystalline 3C-SiC substrates and exposed to 1500–1625°C, were investigated in this study by transmission electron microscopy and secondary ion mass spectrometry (SIMS). The high dynamic range of SIMS allowed for multiple diffusion régimes to be investigated,more » including enhanced diffusion by implantation-induced defects and grain boundary (GB) diffusion in undamaged SiC. Lastly, estimated diffusion coefficients suggest GB diffusion in bulk SiC does not properly describe the release observed from TRISO fuel.« less

  3. Low damage, highly anisotropic dry etching of SiC

    SciTech Connect

    Wang, J.J.; Hong, J.; Lambers, E.S.; Pearton, S.J.; Ren, F.; Ostling, M.; Zetterling, C.M.; Grow, J.M.; Shul, R.J.

    1998-03-01

    A parametric study of the etching characteristics of 6H p{sup +} and n{sup +} SiC and thin film SiC{sub 0.5}N{sub 0.5} in Inductively Coupled Plasma NF{sub 3}/O{sub 2} and NF{sub 3}/Ar discharges has been performed. The etch rates in both chemistries increase monotonically with NF{sub 3} percentage and rf chuck power. The etch rates go through a maximum with increasing ICP source power, which is explained by a trade-off between the increasing ion flux and the decreasing ion energy. The anisotropy of the etched features is also a function of ion flux, ion energy and atomic fluorine neutral concentration. Indium-tin-oxide (ITO) masks display relatively good etch selectivity over SiC (maximum of {approximately} 70:1), while photoresist etches more rapidly than SiC. The surface roughness of SiC is essentially independent of plasma composition for NF3/O2 discharges, while extensive surface degradation occurs for SiCN under high NF{sub 3}:O{sub 2} conditions.

  4. Towards SiC Surface Functionalization: An Ab Initio Study

    SciTech Connect

    Cicero, G; Catellani, A

    2005-01-28

    We present a microscopic model of the interaction and adsorption mechanism of simple organic molecules on SiC surfaces as obtained from ab initio molecular dynamics simulations. Our results open the way to functionalization of silicon carbide, a leading candidate material for bio-compatible devices.

  5. -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.

  6. Stress Analysis of SiC MEMS Using Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ness, Stanley J.; Marciniak, M. A.; Lott, J. A.; Starman, L. A.; Busbee, J. D.; Melzak, J. M.

    2003-03-01

    During the fabrication of Micro-Electro-Mechanical Systems (MEMS), residual stress is often induced in the thin films that are deposited to create these systems. These stresses can cause the device to fail due to buckling, curling, or fracture. Industry is looking for ways to characterize the stress during the deposition of thin films in order to reduce or eliminate device failure. Micro-Raman spectroscopy has been successfully used to characterize poly-Si MEMS devices made with the MUMPS® process. Raman spectroscopy was selected because it is nondestructive, fast and has the potential for in situ stress monitoring. This research attempts to use Raman spectroscopy to analyze the stress in SiC MEMS made with the MUSiC® process. Raman spectroscopy is performed on 1-2-micron-thick SiC thin films deposited on silicon, silicon nitride, and silicon oxide substrates. The most common poly-type of SiC found in thin film MEMS made with the MUSiC® process is 3C-SiC. Research also includes baseline spectra of 6H, 4H, and 15R poly-types of bulk SiC.

  7. Optimizing Graphene Morphology on SiC(0001)

    NASA Astrophysics Data System (ADS)

    Hannon, James

    2009-03-01

    Many schemes to integrate graphene with microelectronics assume that reliable wafer-scale synthesis processes will be developed. One promising route to wafer-scale synthesis is to form graphene overlayers from the decomposition of SiC at high temperature. We have shown that, even at 1200 C, limited diffusion at the SiC surface leads to pit formation and a non-uniform graphene film thickness [1]. In this talk I will describe our efforts to improve both graphene domain size and thickness uniformity. One way we achieve this is by forming graphene in a background pressure of disilane, which hinders SiC decomposition. Even in rather low Si partial pressures (e.g. 1e-5 Torr), the SiC decomposition temperature can shifted several hundred degrees higher in temperature [2]. Using in situ low-energy electron microscopy (LEEM), we show that this effect can be exploited to form large graphene domains (larger than 10 um) with controlled layer thickness (e.g. 1 ML). Work performed in collaboration with R.M. Tromp. [4pt] [1] J.B. Hannon and R.M. Tromp, Phys. Rev. B77, 241404(R) 2008[0pt] [2] R.M. Tromp and J.B. Hannon, in press.

  8. Fission-product SiC reaction in HTGR fuel

    SciTech Connect

    Montgomery, F.

    1981-07-13

    The primary barrier to release of fission product from any of the fuel types into the primary circuit of the HTGR are the coatings on the fuel particles. Both pyrolytic carbon and silicon carbide coatings are very effective in retaining fission gases under normal operating conditions. One of the possible performance limitations which has been observed in irradiation tests of TRISO fuel is chemical interaction of the SiC layer with fission products. This reaction reduces the thickness of the SiC layer in TRISO particles and can lead to release of fission products from the particles if the SiC layer is completely penetrated. The experimental section of this report describes the results of work at General Atomic concerning the reaction of fission products with silicon carbide. The discussion section describes data obtained by various laboratories and includes (1) a description of the fission products which have been found to react with SiC; (2) a description of the kinetics of silicon carbide thinning caused by fission product reaction during out-of-pile thermal gradient heating and the application of these kinetics to in-pile irradiation; and (3) a comparison of silicon carbide thinning in LEU and HEU fuels.

  9. Exploring Manufacturing Technology.

    ERIC Educational Resources Information Center

    Iley, John; And Others

    These teacher's materials for an eight-unit course were developed to help students develop technological literacy, career exploration, and problem-solving skills relative to the manufacturing industries. The eight units include an overview of manufacturing, manufacturing enterprises and systems, manufacturing materials and selection, manufacturing…

  10. 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.

  11. First principle identification of SiC monolayer as an efficient catalyst for CO oxidation

    NASA Astrophysics Data System (ADS)

    Sinthika, S.; Reddy, C. Prakash; Thapa, Ranjit

    2015-06-01

    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 O2 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 CO2 formation. Overall metal free SiC monolayer can be used as efficient catalyst for CO oxidation.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  13. 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

  14. Construction Progress of the S-IC Test Stand

    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 shows the progress of the S-IC test stand as of October 22, 1963. Spherical liquid hydrogen tanks can be seen to the left. Just to the lower front of those are the cylindrical liquid oxygen (LOX) tanks.

  15. 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.

  16. Construction Progress of the S-IC Test Stand

    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 March 29, 1963, gives a close up look at two of the ever-growing four towers of the S-IC Test Stand.

  17. Construction Progress of the S-IC Test Stand

    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 shows the progress of the S-IC test stand as of October 10, 1963. Spherical liquid hydrogen tanks can be seen to the left.

  18. Construction Progress of the S-IC Test Stand

    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 shows the progress of the S-IC test stand as of November 20, 1963.

  19. 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.

  20. Construction Progress of the S-IC Test Stand

    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 shows the progress of the S-IC test stand as of October 10, 1963. Kerosene storage tanks can be seen to the left.

  1. Construction Progress of the S-IC Test Stand

    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 February 25, 1963, gives a close up look at two of the ever-growing four towers of the S-IC Test Stand.

  2. Construction Progress of the S-IC Test Stand

    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 May 7, 1963, gives a close look at the four concrete tower legs of the S-IC test stand at their completed height.

  3. 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.

  4. Estimating HUC 2-digit sustainable water use over the continental United States using GRACE

    NASA Astrophysics Data System (ADS)

    Solander, K.; Reager, J. T., II; Famiglietti, J. S.

    2015-12-01

    Managing water resources so that supplies meet demands over the long-term is of increasing importance due to greater demands from a growing population and shifts in supplies due to climate change. Although the technology and infrastructure to determine spatially-distributed total surface water and groundwater supplies does not currently exist, satellite measurements of water resources have been useful for providing regional or global assessments of sustainable surface water or groundwater use. Here, we apply an innovative technique using GRACE to evaluate the sustainable use of both surface water and groundwater for the continental United States. Annual total water availability was estimated from the difference between the annual maximum and minimum change in total water storage as determined from GRACE. The available portion partitioned to humans was compared to the amount of water being used based on county-level USGS water use estimates to assess total water use sustainability at the HUC 2-digit spatial scale. This evaluation was conducted for a given wet, normal, and dry year according to GRACE records. Projected estimates of precipitation due to climate change across these regions were then used to compare present and future total water use sustainability. Such information is critical to better manage these resources so respective allocations to humans and the environment are more in line with the given quantities available at different spatial scales.

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

    SciTech Connect

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

    2004-08-01

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

  6. 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.

  7. 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)

  8. 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)

  9. 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.

  10. 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.

  11. 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

  12. Understanding carrier injection effects upon the Reststrahlen band of SiC using transient infrared spectroscopy (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Spann, Bryan T.; Compton, Ryan; Dunkelberger, Adam D.; Long, James P.; Klein, Paul; Ratchford, Daniel; Caldwell, Josh D.; Owrutsky, Jeff

    2015-09-01

    Sub-diffractional confinement of light has led to advancements in imaging, metamaterials, nano-manufacturing, plasmonics, and other fields. One potential route to sub-diffractional confinement is via stimulated surface phonon polaritons (SPhPs). SPhPs couple infrared photons with optical phonons and consequently their lifetimes can be longer than surface plasmon polaritons (SPPs), whose lifetimes are dominated by electron scattering events. Thus, materials capable of generating SPhPs are of general interest to study. SPhPs are activated by photons with energies near the Reststrahlen band of semiconductors such as SiC. In this work we examine aspects of carrier dynamics by photo-injecting electrons into the SiC conduction band using a pulsed 355 nm laser and probe the resulting dynamics near the Reststrahlen band using a tunable CO2 laser. The fluence of the pump laser was varied to provide photo-injection levels ranging from ~1x10^17 to 1x10^19 free carriers. Probing the excited-state dynamics near the blue-edge of the Reststrahlen band resulted in complex transient behavior, showing both positive and negative changes in transient reflectance depending on the level of photo-injected carriers and probe energy. Numerical calculations of the SiC reflectance spectra with different doping levels were done to simulate the initial photo-injection level provided by the transient experiment. The computed spectra and the experimentally measured excited spectra for different photo-injection levels were compared and resulted in qualitative agreement.

  13. 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.

  14. 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.

  15. Feed Formulation and Manufacture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter provides information on feed formulation and manufacture. To formulate and manufacture high quality fish feeds, including tilapia feeds, one should have knowledge of nutrient requirements, nutrient composition, digestibility, and availability of feed ingredients; impacts of manufacturin...

  16. 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).

  17. Interstitial H and H2 in SiC

    NASA Astrophysics Data System (ADS)

    Kaukonen, M.; Fall, C. J.; Lento, J.

    2003-08-01

    The properties of hydrogen in 3C and 4H type silicon carbide (SiC) are studied theoretically at the density functional level. We find that only singly positive or negative charge states of hydrogen are thermodynamically stable in SiC. The transition from the positive to the negative charge state (+/-) is at 0.9 and 1.3 eV above the valence band maximum in 3C and 4H structures, respectively. The diffusion barrier for the proton is 0.5 eV (being, however, anisotropic in 4H). For the negative H- the diffusion barrier is found to be considerably higher, of the order of 3 eV.

  18. Nucleation and growth of polycrystalline SiC

    NASA Astrophysics Data System (ADS)

    Kaiser, M.; Schimmel, S.; Jokubavicius, V.; Linnarsson, M. K.; Ou, H.; Syväjärvi, M.; Wellmann, P.

    2014-03-01

    The nucleation and bulk growth of polycrystalline SiC in a 2 inch PVT setup using isostatic and pyrolytic graphite as substrates was studied. Textured nucleation occurs under near-thermal equilibrium conditions at the initial growth stage with hexagonal platelet shaped crystallites of 4H, 6H and 15R polytypes. It is found that pyrolytic graphite results in enhanced texturing of the nucleating gas species. Reducing the pressure leads to growth of the crystallites until a closed polycrystalline SiC layer containing voids with a rough surface is developed. Bulk growth was conducted at 35 mbar Ar pressure at 2250°C in diffusion limited mass transport regime generating a convex shaped growth form of the solid-gas interface leading to lateral expansion of virtually [001] oriented crystallites. Growth at 2350°C led to the stabilization of 6H polytypic grains. The micropipe density in the bulk strongly depends on the substrate used.

  19. Tga Characteristic and Fabrication of Porous SiC Ceramics

    NASA Astrophysics Data System (ADS)

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

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

  20. 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.

  1. The SiC Direct Target Prototype for SPES

    SciTech Connect

    Rizzi, V.; Andrighetto, A.; Barbui, M.; Carturan, S.; Cinausero, M.; Giacchini, M.; Gramegna, F.; Lollo, M.; Maggioni, G.; Prete, G.; Tonezzer, M.; Antonucci, C.; Cevolani, S.; Petrovich, C.; Biasetto, L.; Colombo, P.; Manzolaro, M.; Meneghetti, M.; Celona, L.; Chines, F.

    2007-10-26

    A R and D study for the realization of a Direct Target is in progress within the SPES project for RIBs production at the Laboratori Nazionali of Legnaro. A proton beam (40 MeV energy, 0.2 mA current) is supposed to impinge directly on a UCx multiple thin disks target, the power released by the proton beam is dissipated mainly through irradiation. A SiC target prototype with a 1:5 scale has been developed and tested. Thermal, mechanical and release calculations have been performed to fully characterize the prototype. An online test has been performed at the HRIBF facility of the Oak Ridge National Laboratory (ORNL), showing that our SiC target can sustain a proton beam current considerably higher than the maximum beam current used with the standard HRIBF target configuration.

  2. Saturn V S-IC Stage Test Firing

    NASA Technical Reports Server (NTRS)

    1965-01-01

    The Saturn V first stages were test fired at the Mississippi Test Facility and at the Marshall Space Flight Center (MSFC). Five F-1 engines powered the first stage, each developing 1.5 million pounds of thrust. The first stage, known as the S-IC stage, burned over 15 tons of propellant per second during its 2.5 minutes of operation to take the vehicle to a height of about 36 miles and to a speed of about 6,000 miles per hour. The stage was 138 feet long and 33 feet in diameter. This photograph shows the test firing of an F-1 engine at the MSFC's S-IC Static Test Firing Facility.

  3. 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.

  4. 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.

  5. Toughened Matrix SiC Fiber Reinforced Composites

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  6. Sputter deposition of SiC coating on silicon wafers

    NASA Technical Reports Server (NTRS)

    Robson, M. T.; Blue, C. A.; Warrier, S. G.; Lin, R. Y.

    1992-01-01

    A study is conducted of the effect of substrate temperature during coating on the properties of coated SiC films on Si wafers, using a scratch test technique. While specimen temperature during coating has little effect on deposition rate, it significantly affects the durability of the coating. Scratch test damage to both film coating and substrate decreased with increasing deposition temperature, perhaps due to the rapid diffusion of the deposited atoms.

  7. Construction Progress of the S-IC Test Stand

    NASA Technical Reports Server (NTRS)

    1961-01-01

    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 September 5, 1961, shows pumps used for extracting water emerging form a disturbed natural spring that occurred during the excavation of the site. The pumping became a daily ritual and the site is still pumped today.

  8. Bilateral comparison of an IPRT between KRISS and SIC

    NASA Astrophysics Data System (ADS)

    Yang, I.; Sánchez, C. A.

    2013-09-01

    As a follow-up of a memorandum of understanding signed in 2009 between KRISS of Korea and SIC of Colombia, the two national metrology institutes carried out a bilateral comparison of calibration of an industrial platinum resistance thermometer (IPRT). A protocol that was similar to that of APMP.T-S6 has been agreed and followed in the comparison. The method of the calibration at each laboratory was calibration by comparison against calibrated reference thermometers. The nominal temperatures of the comparison were nine temperatures, including the ice point, between -50 °C and 500 °C. One commercially-available IPRT with α ˜ 0.00385 °C-1 that was prepared by KRISS was calibrated by comparison firstly at KRISS, and then at SIC, and finally at KRISS to assess the drift of the artifact during the comparison. At KRISS, an ice-point bath, three liquid baths and a salt bath were used to provide isothermal environment for the comparison. At SIC, an ice-point bath, two liquid baths and a vertical furnace with a metal equalizing block were used. The claimed uncertainty with k=2 of the calibration at KRISS, excluding the longterm instability and hysteresis of the traveling IPRT, was 30 mK, and that at SIC was 120 mK. The capability of the calibration of the two laboratories from -50 °C to 500 °C showed a good agreement within the claimed uncertainty of the calibration. The largest deviation of the two calibration results was 75 mK at 500 °C.

  9. SiC device development for high temperature sensor applications

    NASA Technical Reports Server (NTRS)

    Shor, J. S.; Goldstein, David; Kurtz, A. D.; Osgood, R. M.

    1992-01-01

    Progress made in the processing and characterization of 3C-SiC for high temperature sensor applications is reviewed. Piezoresistance properties of silicon carbide and the temperature coefficient of resistivity of n-type beta-SiC are presented. In addition, photoelectrical etching and dopant selective etch-stops in SiC and high temperature Ohmic contacts for n-type beta-SiC sensors are discussed.

  10. Construction Progress of the S-IC Test Stand

    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, depicts the progress of the stand as of January 14, 1963, with its four towers prominently rising.

  11. Construction Progress of the S-IC Test Stand

    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 this photo, taken June 24, 1963, the four tower legs of the test stand can be seen at their maximum height.

  12. Construction Progress of the S-IC Test Stand

    NASA Technical Reports Server (NTRS)

    1961-01-01

    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 shows the construction progress as of August 5, 1961. Heavy equipment continues to clear the test stand site.

  13. Construction Progress of the S-IC Test Stand

    NASA Technical Reports Server (NTRS)

    1962-01-01

    At its founding, the Marshall Space Flight Center (MSFC) inherited the Army's Jupiter and Redstone test stands, but much larger facilities were needed for the giant stages of the Saturn V. From 1960 to 1964, the existing stands were remodeled and a sizable new test area was developed. The new comprehensive test complex for propulsion and structural dynamics was unique within the nation and the free world, and they remain so today because they were constructed with foresight to meet the future as well as on going needs. Construction of the S-IC Static test stand complex began in 1961 in the west test area of MSFC, and was completed in 1964. The S-IC static test stand was designed to develop and test the 138-ft long and 33-ft diameter Saturn V S-IC first stage, or booster stage, weighing in at 280,000 pounds. Required to hold down the brute force of a 7,500,000-pound thrust produced by 5 F-1 engines, the S-IC static test stand was designed and constructed with the strength of hundreds of tons of steel and 12,000,000 pounds of cement, planted down to bedrock 40 feet below ground level. The foundation walls, constructed with concrete and steel, are 4 feet thick. The base structure consists of four towers with 40-foot-thick walls extending upward 144 feet above ground level. The structure was topped by a crane with a 135-foot boom. With the boom in the upright position, the stand was given an overall height of 405 feet, placing it among the highest structures in Alabama at the time. This construction photo depicts the progress of the stand site as of October 8, 1962.

  14. SiC device development for high temperature sensor applications

    NASA Astrophysics Data System (ADS)

    Shor, J. S.; Goldstein, David; Kurtz, A. D.; Osgood, R. M.

    1992-09-01

    Progress made in the processing and characterization of 3C-SiC for high temperature sensor applications is reviewed. Piezoresistance properties of silicon carbide and the temperature coefficient of resistivity of n-type beta-SiC are presented. In addition, photoelectrical etching and dopant selective etch-stops in SiC and high temperature Ohmic contacts for n-type beta-SiC sensors are discussed.

  15. 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…

  16. Synchronistic preparation of fibre-like SiC and cubic-ZrO{sub 2}/SiC composite from zircon via carbothermal reduction process

    SciTech Connect

    Xu, Youguo; Liu, Yangai; Huang, Zhaohui; Fang, Minghao; Hu, Xiaozhi; Yin, Li; Huang, Juntong

    2013-01-15

    Graphical abstract: Display Omitted Highlights: ► Zircon carbothermal reduction was carried out in a tailor-made device at high-temperature air atmosphere. ► Fibre-like SiC and cubic-ZrO{sub 2}/SiC composite were obtained synchronically. ► Zirconium and silicon in zircon ore was initial separated. ► [SiO{sub 4}] was mutated to fibre-like SiC, while [ZrO{sub 8}] was transformed to cubic ZrO{sub 2}. ► The SiC were surprisingly enriched in the reducing atmosphere charred coal particles layers by gas–solid reaction. -- Abstract: Fibre-like SiC and cubic-ZrO{sub 2}/SiC composite were prepared respectively from zircon with yttrium oxide addition via carbothermal reduction process at 1600 °C for 4 h in an air atmosphere furnace, where the green samples were immerged in charred coal particles inside a high-temperature enclosed corundum crucible. The reaction products were characterized by XRD, XRF, XPS and SEM. The results indicate that ZrO{sub 2} in the products was mainly existed in the form of cubic phase. The reacted samples mainly contain cubic ZrO{sub 2}, β-SiC and trace amounts of zircon, with the SiC accounting for 14.8 wt%. Furthermore, a large quantity of fibre-like SiC was surprisingly found to concentrate in the charred coal particles layers around the samples. This study obtains fibre-like SiC and cubic-ZrO{sub 2}/SiC composite synchronically from zircon via carbothermal reduction process, which also bring a value-added high-performance application for natural zircon.

  17. The influence of SiC particle size and volume fraction on the thermal conductivity of spark plasma sintered UO2-SiC composites

    NASA Astrophysics Data System (ADS)

    Yeo, Sunghwan; Baney, Ronald; Subhash, Ghatu; Tulenko, James

    2013-11-01

    This study examines the influence of Silicon Carbide (SiC) particle addition on thermal conductivity of UO2-SiC composite pellets. UO2 powder and β-SiC particles of different sizes and of different volume fractions were mechanically mixed and sintered at 1350-1450 °C for 5 min by Spark Plasma Sintering (SPS). The particle size (0.6-55 μm diameter) and volume fraction (5-20%) of SiC were systematically varied to investigate their influence on the resulting UO2-SiC composite pellet microstructure and the thermal properties. It was found that SiC particle size less than 16.9 μm with larger volume fraction is more effective for improving the thermal conductivity of the fuel pellets. Scanning Electron Microscopy examination revealed micro-cracking and interfacial debonding in the composites containing larger size SiC particles (16.9 and 55 μm) which resulted in reduced thermal conductivity. For the UO2-SiC composite pellets containing 1 μm diameter SiC particles, the thermal conductivity increased almost linearly with volume fraction of particles. However, the addition of a larger volume fraction of SiC reduces the amount of heavy metal in the composite pellet and therefore a higher U-235 enrichment is necessary to compensate for the heavy metal loss. The experimental thermal conductivity values of the UO2-SiC composite pellets are in good agreement with the theoretical values based on the available model in the literature.

  18. Atmospheric pressure growth of graphene on SiC(0001)

    NASA Astrophysics Data System (ADS)

    Seyller, Thomas

    2009-03-01

    Graphene, a single monolayer of sp^2-bonded carbon, is a very unique 2-dimensional electron gas system with electronic properties fundamentally different to other 2DEG systems [1]. Several production routes exist for graphene. Among them, the solid-state decomposition of hexagonal silicon carbide (SiC) surfaces [2] is particularly attractive for the development of graphene based electronics [3,4]. The first part of the presentation gives a brief summary of recent studies on the structural and electronic properties of graphene and few-layer graphene grown on SiC(0001) under ultra-high vacuum (UHV) conditions. The second part of the talk is devoted to recent progress in the growth of large domain graphene films on SiC(0001) in Ar atmosphere. It is shown that growth in Ar ambient leads to a significant improvement of the surface morphology and domain size as well as carrier mobility. [4pt] [1] A.H. Castro Neto, et al., Reviews of Modern Physics, in print (arXiv:0709.1163v2); and references therein. [0pt] [2] A. Charrier, et al., J. Appl. Phys. 92 (2002) 2479. [0pt] [3] C. Berger et al., J. Phys. Chem. B 108 (2004) 19912; C. Berger, et al., Science 312 (2006) 1191. [0pt] [4] A.K. Geim and K.S. Novoselov, Nature Mat. 6 (2007) 183.

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

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Martinez-Fernandez, Julian

    1998-01-01

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

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. Construction Progress of the S-IC Test Stand

    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 of the stand 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. In this photo of the S-IC test stand, taken October 2, 1963, the flame deflector can be seen in the bottom center portion

  5. Construction Progress of the S-IC Test Stand

    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 the early stages of excavation, a natural spring was disturbed that caused a water problem which required constant pumping from the site and is even pumped to this day. Behind this reservoir of pumped water is the S-IC test stand boasting its ever-growing four towers as of March 29, 1963.

  6. Construction Progress of the S-IC Test Stand

    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 northeast of the stand 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. In this photo, taken September 5, 1963, the flame deflector is being installed in the S-IC test stand.

  7. Construction Progress of the S-IC Test Stand

    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 of the stand 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. In this photo of the S-IC test stand, taken September 25, 1963, the flame deflector can be seen rotated to the outside on

  8. Reaction channels and spectroscopic constants of astrophysical relevant Silicon bearing molecules SiC3H,+ and SiC3H

    NASA Astrophysics Data System (ADS)

    Inostroza Pino, N.; Cardenas, C.; Fuentealba, P.

    2014-10-01

    Reaction channels and spectroscopic properties of a series of silicon-carbon-bearing isomers of SiC3H+ and SiC3H, which are suitable species for astrophysical detection in carbon-rich sources, are calculated with correlated ab initio CCSD(T) and density functional theory methods. We present four isomers of SiC3H+ for which the electronic ground states have closed-shell configurations. For SiC3H, we considered the same structures in order to present a complete study. The global minimum among the SiC3H+ isomers corresponds to the rhomboidal structure with a transannular bond in a 1A1 electronic state (rb3-SiC3H+ C2v X1A1). The next minima correspond to a second rhomboid 1A1 isomer and a linear isomer (X1Σ+) with relative energies 0.86 and 0.93 eV, respectively at the CCSD(T)/cc-pvTZ level of theory. The most stable mono-hydrogenated silicon carbon isomer is linear, followed by two rhomboidal isomers, rb2-SiC3H and rb3-SiC3H (0.23 and 0.31 eV). For each structure, a set of spectroscopic parameters including their equilibrium structures, rotational constants, harmonic frequencies and dipole moment is presented. Furthermore, we discuss plausible formation pathways of SiC3H+ isomers which are classified as charge-exchange, ion-neutral and dissociative recombination reactions. These results show one favourable pathway to produce rb3-SiC3H+ from rb-SiC3-3s. The formation energy of the cation's isomers coming from neutral isomers as linear l1-SiC3H, rb3-SiC3H and rb2-SiC3H plus H+ as reactants (charge-exchange reaction) are 203.8 kcal mol-1 (8.84eV), 175.4 kcal mol-1 (7.60 eV) and 195.2 kcal mol-1 (8.46 eV), which provides us with evidence of the endergonic character of these reactions. As a consequence, it does not seem to be feasible to produce a cation from neutral reactant plus H+ by a charge-exchange reaction that was proposed by UMIST.

  9. Liquid infiltration and pyrolysis of SiC matrix composite materials

    SciTech Connect

    Casadio, S.; Nanneti, C.A.; Donato, A.

    1995-12-01

    SiC matrix composites were prepared by prepregging carbon and Nicalon fibre cloths with polycarbosilane (PCS) solution or nanosized SiC powder dispersion in PCS solution. After consolidation of the stacked cloths and pyrolysis, densification of the matrix was accomplished by multiple infiltration/pyrolysis steps with PCS solution. The pyrolysis behaviour of the SiC nanopowder/PCS matrix material was investigated in comparison to PCS.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Presolar SiC in chondrites - How variable and how many sources?

    NASA Astrophysics Data System (ADS)

    Alexander, C. M. O'd.

    1993-06-01

    The carbon and silicon isotropic compositions of 246 isotopically anomalous SiC grains measured in low concentration residues are reported. The residues were prepared from nine chondrites, namely, 6 unequilibrated ordinary chondrites (UOCs), Qingzhen (EH3), Leoville (CV3), and Murchison (CM2). Murchison is used as a standard to which all the other meteorites studied are compared. The range of isotopic compositions exhibited by UOC SiC is found to be similar to Murchison, except in Inman. Inman SiC has a distinctly different distribution of its silicon isotopic composition compared to the other meteorites. Residues from Qingzhen and Leoville produce only one anomalous SiC grain each.

  15. 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.

  16. 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.

  17. Particles cellulation composite (PCC): Dispersion morphology of SiC particles in Si{sub 3}N{sub 4}/SiC composites

    SciTech Connect

    Yamada, K.; Kamiya, N.

    1995-10-01

    Dispersion morphology of fine SiC particles in Si{sub 3}N{sub 4}/xSiC (x = 0, 10, 20, 30wt%, average size: 0.03 {micro} m) composites was statistically analyzed, and typical properties of the composites such as creep, electric and thermal conductivity were investigated. The dispersion morphology of SiC particles was analyzed by observing the ECR-plasma etched surface of the sintered composites using scanning electron microscopy. SiC particles in Si{sub 3}N{sub 4}/SiC composites were distributed both within Si{sub 3}N{sub 4} grains and on Si{sub 4}N{sub 4} grain boundary, but 90% or more of them was located on the grain boundary. For the composites with 20--30 wt%SiC, the SiC particles on the grain boundary clearly formed a three-dimensional network structure surrounding a few or more Si{sub 3}N{sub 4} crystalline grains. A Si{sub 3}N{sub 4}/SiC composite with a three-dimensional network structure of SiC particles, named particles cellulation composite (PCC), was artificially made by pressing the granulated Si{sub 3}N{sub 4} powder (less than 500 {micro} m diameter) discontinuously coated with SiC particles (average size: 0.4 {micro}m). The creep deformation of PCC was reduced to about 60% of that of the composites with SiC particles randomly dispersed. Electrical and thermal properties were also improved. These results suggest that the formation of three-dimensional network structure by the second phase particles in a composite would considerably improve its mechanical property as well as electrical and thermal properties.

  18. 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.

  19. 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.

  20. 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.

  1. Manufacturing with the Sun

    NASA Astrophysics Data System (ADS)

    Murphy, L. M.; Hauser, S. G.; Clyne, R. J.

    1992-05-01

    Concentrated solar radiation is now a viable alternative energy 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 offers even greater potential for tomorrow, especially as applied to the radiation-abundant environment available in space and on the lunar surface.

  2. 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.

  3. Thermomechanical Behavior of Advanced SiC Fiber Multifilament Tows

    NASA Technical Reports Server (NTRS)

    Yun, Hee Mann; DiCarlo, James A.

    1997-01-01

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

  4. Construction Progress of the S-IC Test Stand

    NASA Technical Reports Server (NTRS)

    1961-01-01

    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 this photograph taken on August 5th, 1961, a back hoe is nearly submerged in water in the test stand site. During the initial digging, the disturbance of a natural spring contributed to constant water problems during the construction process. It was necessary to pump the water from the site on a daily basis and is still pumped from the site today.

  5. Construction Progress of the S-IC Test Stand

    NASA Technical Reports Server (NTRS)

    1961-01-01

    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 shows the construction progress of the test stand as of August 14, 1961. Water gushing in from the disturbance of a natural spring contributed to constant water problems during the construction process. It was necessary to pump water from the site on a daily basis and is still pumped from the site today. The equipment is partially submerged in the water emerging from the spring.

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

    SciTech Connect

    Youngblood, Gerald E.; Thomsen, Edwin C.

    2011-04-17

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

  7. Construction Progress of the S-IC Test Stand

    NASA Technical Reports Server (NTRS)

    1961-01-01

    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 September 5, 1961, shows the construction of forms which became the concrete foundation for the massive stand. The lower right hand corner reveals a pump used for extracting water emerging from a disturbed natural spring that occurred during excavation of the site. The pumping became a daily ritual and the site is still pumped today.

  8. 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

  9. 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.

  10. 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

  11. Construction Progress S-IC Test Stand Block House Interior

    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 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. This photograph, taken August 12, 1963, offers a view of the Block House interior.

  12. Construction Progress of the S-IC Test Stand

    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. After a six month delay in construction due to size reconfiguration of the Saturn booster, the site was revisited for modifications in March 1962. The original foundation walls built in the prior year were torn down and re-poured to accommodate the larger boosters. This photo depicts that modification progress as of June 13,1962.

  13. Construction Progress of the S-IC Test Stand

    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. After a 6 month delay in construction due to size reconfiguration of the Saturn booster, the site was revisited for modifications. The original foundation walls built in the prior year had to be torn down and re-poured to accommodate the larger booster. The demolition can be seen in this photograph taken on May 21, 1962.

  14. 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.

  15. 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…

  16. 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

  17. 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.

  18. Manufacturing Education Curriculum Project.

    ERIC Educational Resources Information Center

    Umstattd, William D.

    The Manufacturing Education Curriculum Project's feasibility study concerned with industrial arts curriculum development in manufacturing for the senior high school level is described. The need for an industrial arts curriculum which meets and reflects present and future trends is discussed in the introduction, followed by a review of the…

  19. Developments in Agile Manufacturing

    SciTech Connect

    Clinesmith, M.G.

    1993-09-01

    As part of a project design initiative, Sandia National Laboratories and AlliedSignal Inc. Kansas City Division have joined efforts to develop a concurrent engineering capability for the manufacturing of complex precision components. The primary effort of this project, called Agile Manufacturing, is directed toward: (1) Understand the error associated with manufacturing and inspection. (2) Develop methods for correcting error. (3) Integrate diverse software technologies into a compatible process. The Agile Manufacturing System (AMS) is a system that integrates product design, manufacturing, and inspection into a closed loop, concurrent engineering process. The goal of developing the Agile Manufacturing System is to: (1) Optimize accuracy in manufacturing and inspection. (A) Use of softgage software for product evaluation. This will ensure ANSI Y14.5 compliance. (B) Establish and monitor bias between CMM and machine center. (C) Map probe deflection error and apply correction to inspection results. This applies to both on machine probing and CMM inspections. (D) Inspection process. (2) Compress the cycle time from product concept to production level manufacturing and verification. (3) Create a self-correcting process that feeds inspection results back into the machining process. (4) Link subordinate processes (cutting/probing path, softgage model, etc.) to the solid model definition.

  20. Manufacturing research strategic plan

    SciTech Connect

    1995-11-01

    This plan provides an overall strategic roadmap for the DOE-defense programs advanced manufacturing research program which supports the national science based stockpile stewardship program. This plan represents a vision required to develop the knowledge base needed to ensure an enduring national capability to rapidly and effectively manufacture nuclear weapons.

  1. Computer Aided Manufacturing.

    ERIC Educational Resources Information Center

    Insolia, Gerard

    This document contains course outlines in computer-aided manufacturing developed for a business-industry technology resource center for firms in eastern Pennsylvania by Northampton Community College. The four units of the course cover the following: (1) introduction to computer-assisted design (CAD)/computer-assisted manufacturing (CAM); (2) CAM…

  2. 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)

  3. Mechanical and microstructural characterization of Al7075/SiC nanocomposites fabricated by dynamic compaction

    NASA Astrophysics Data System (ADS)

    Atrian, A.; Majzoobi, G. H.; Enayati, M. H.; Bakhtiari, H.

    2014-03-01

    This paper describes the synthesis of Al7075 metal matrix composites reinforced with SiC, and the characterization of their microstructure and mechanical behavior. The mechanically milled Al7075 micron-sized powder and SiC nanoparticles are dynamically compacted using a drop hammer device. This compaction is performed at different temperatures and for various volume fractions of SiC nanoparticles. The relative density is directly related to the compaction temperature rise and indirectly related to the content of SiC nanoparticle reinforcement, respectively. Furthermore, increasing the amount of SiC nanoparticles improves the strength, stiffness, and hardness of the compacted specimens. The increase in hardness and strength may be attributed to the inherent hardness of the nanoparticles, and other phenomena such as thermal mismatch and crack shielding. Nevertheless, clustering of the nanoparticles at aluminum particle boundaries make these regions become a source of concentrated stress, which reduces the load carrying capacity of the compacted nanocomposite.

  4. 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.

  5. 'Buffer-layer' technique for the growth of single crystal SiC on Si

    NASA Astrophysics Data System (ADS)

    Addamiano, A.; Sprague, J. A.

    1984-03-01

    The nature of the buffer layers needed for the single-crystal deposition of cubic SiC on Si substrates has been studied. The preparation of chemically formed surface layers of SiC on (100) Si wafers is described. The reaction-grown films of SiC were examined by reflection high-energy electron diffraction using an incident electron energy of 200 keV and by SEM using incident electron energies of 20 and 200 keV. It is concluded that the buffer layer obtained at about 1400 C is a stressed monocrystalline layer of cubic SiC whose crystals contain considerable imperfections. The stresses are due to quenching to room temperature because of the large difference between the thermal expansion coefficients of Si and SiC.

  6. 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.

  7. 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.

  8. Laser assisted direct manufacturing

    NASA Astrophysics Data System (ADS)

    Bertrand, Ph.; Smurov, I.

    2007-06-01

    Direct Laser Manufacturing (DLM) with coaxial powder injection (TRUMPF DMD 505 installation) was applied for fabrication of 3D objects from metallic and ceramic powder. One of the advantages of DLM is the possibility to build functionally graded objects in one-step manufacturing cycle by application of a 2-channel powder feeder. Several models with different types of material gradients (smooth, sharp, periodic) and multi-layered structures were manufactured from SS, stellite (Cobalt alloy), Cu and W alloys. Technology of Selective Laser Melting (SLM) was applied for manufacturing of net shaped objects from different powders (PHENIX PM-100 machine) : Inox 904L, Ni625, Cu/Sn, W and Zr02-Y2O3. Performance and limitations of SLM technology for fabrication of elements for chemical and mechanical industries are analysed. Two-component objects (Stainless steel /Cu - H13/CuNi) were fabricated in a two-step manufacturing cycle.

  9. 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.

  10. Mechanical properties of SiC long fibre reinforced copper

    NASA Astrophysics Data System (ADS)

    Brendel, A.; Paffenholz, V.; Köck, Th.; Bolt, H.

    2009-04-01

    SiC fibre reinforced copper is a potential novel heat sink material for the divertor of future fusion reactors to reinforce the zone between plasma facing material (W) and heat sink material (CuCrZr). The metal matrix composite (MMC) should be able to withstand heat loads up to 15 MW/m 2 at operating temperatures of up to 550 °C. SCS6 fibres were coated by magnetron sputtering with a titanium interlayer and the copper matrix was deposited by electroplating. The composite was consolidated by hot-isostatic pressing. The average ultimate tensile strength of composite samples with 20% fibre reinforcement is 640 MPa and for the Young's modulus 162 GPa was determined. The Young's modulus decreases with increasing temperature and reaches 113 GPa at 550 °C. Fracture area analysis after tensile tests show the failure of the SCS 6 fibres at the interface between the two outer carbon layers. Titanium as interlayer led to an improved bonding between the outer carbon coating of the SiC fibres and the copper matrix.

  11. Infrared surface phonon polariton waveguides on SiC Substrate

    NASA Astrophysics Data System (ADS)

    Yang, Yuchen; Manene, Franklin M.; Lail, Brian A.

    2015-08-01

    Surface plasmon polariton (SPP) waveguides harbor many potential applications at visible and near-infrared (NIR) wavelengths. However, dispersive properties of the metal in the waveguide yields weakly coupled and lossy plasmonic modes in the mid and long wave infrared range. This is one of the major reasons for the rise in popularity of surface phonon polariton (SPhP) waveguides in recent research and micro-fabrication pursuit. Silicon carbide (SiC) is a good candidate in SPhP waveguides since it has negative dielectric permittivity in the long-wave infrared (LWIR) spectral region, indicative that coupling to surface phonon polaritons is realizable. Introducing surface phonon polaritons for waveguiding provides good modal confinement and enhanced propagation length. A hybrid waveguide structure at long-wave infrared (LWIR) is demonstrated in which an eigenmode solver approach in Ansys HFSS was applied. The effect of a three layer configuration i.e., silicon wire on a benzocyclobutene (BCB) dielectric slab on SiC, and the effects of varying their dimensions on the modal field distribution and on the propagation length, is presented.

  12. 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.

  13. 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.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1998-03-01

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

  16. Study of CVD SiC thin film for space mirror

    NASA Astrophysics Data System (ADS)

    Zhang, Jianhan; Zhang, Yumin; Han, Jiecai; He, Xiaodong

    2006-01-01

    The performance of space mirror lied on the properties of the mirror surface material to a great extent. In this paper, the silicon carbide thin film deposited on reaction-bonded silicon carbide (RBSC) space mirror blank was produced by Chemical Vapor Deposition (CVD) process. Some mechanical and physical properties of the SiC thin film were tested because they were important to study ability to work of space mirror. The result of XRD phase analysis indicated that the component of the SiC thin film was β-SiC. The micro hardness of the film was tested. The thickness of SiC thin film was tested using needle touch contour graph. The results showed that the thickness of SiC film was about 20 μm and film was even in the macro scope. The adhesion strength of SiC thin film and RBSC substrate was tested by scratch method and the results showed that was excellent. The residual stress of SiC thin film was tested by X-ray, at the same time; the origin of residual stress and the calculation of thermal stress were discussed. In the room temperature, the residual stress of the SiC film was compressive. After precision grinding, the surface topography and roughness of the SiC thin film was tested by Atomic Force Microscope (AFM). The results showed that the surface of SiC thin film had extremely low surface roughness and high surface form accuracy. The thermal shock resistance of SiC film was fine by tested.

  17. 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.

  18. 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

  19. 75 FR 104 - Manufacturing & Services' Sustainable Manufacturing Initiative; Update

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-04

    ... of Trade Policy Analysis, 202-482-2831. SUPPLEMENTARY INFORMATION: ITA's Manufacturing and Services... 18, 2009. Matthew Howard, Office of Trade Policy Analysis. BILLING CODE 3510-DR-P ... International Trade Administration Manufacturing & Services' Sustainable Manufacturing Initiative; Update...

  20. 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)

  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. 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.

  3. Compositional Heterogeneity in Orgueil SiC: Further Comparisons with Murchison

    NASA Astrophysics Data System (ADS)

    Huss, G. R.; Deloule, E.; Hutcheon, I. D.; Wasserburg, G. J.

    1993-07-01

    Interstellar SiC recovered from primitive chondrites is characterized by large enrichments in ^13C and ^14N, and by Si isotope compositions distinct from solar that define a linear array on a Si 3-isotope plot [1-3]. While most SiC >2 micrometers fit this description, the total population of presolar SiC is not homogeneous. A comparison [4] of C, N, Mg, and Si isotopic characteristic of 2-6 micrometer SiC crystals from Orgueil with Murchison SiC [2,3] found two significant differences: 1) Orgueil SiC do not exhibit the clustering on either an Si 3-isotope plot or on a plot of delta^29Si vs. delta^13C shown by large Murchison SiC, and 2) there were no Orgueil SiC with delta^15N between 0 and -350 per mil. The interpretation of these differences was tempered by the relatively small number of Orgueil SiC that had been measured. We report here new Si and C isotope data for an additional 70 Orgueil SiC grains, making a total of ~110 grains measured to date. We have extended our study to smaller grains, measuring 15 grains less than 2 micrometers. The great majonty (~90%) of Orgueil SiC have roughly similar isotopic compositions and define the main population (Fig. 1). Among the remaining SiC grains, one is extremely enriched in ^28Si (Fig. 1 inset) and extremely depleted in ^13C, like the Murchison 'X' grains [3]. Four grains have delta^13C<0 and Si compositions similar to Murchison 'Y' grains [5]. Two Orgueil SiC ('Z' grains) have delta^29Si ~-75 per mil and delta^30Si ~-34per mil and fall in a previously unoccupied region of Si isotope space. Unlike 'Y' grains, 'Z' grains have delta^13C > 0. Eight Orgueil SiC have extreme enrichments in ^13C (8000 per mil < delta^13C < 3000 per mil); six of the eight lie on the ^28Si-rich end of the Si isotope array (Fig. 1), five with delta^29Si <--4 per mil and the sixth with delta^29Si=13 per mil. The new data reveal a compositional variability among Orgueil SiC larger than ~2 micrometers at least as great as that found for

  4. The Manufacturing Game

    ERIC Educational Resources Information Center

    Fenn, Margaret

    1972-01-01

    Article describes management training through playing a game which involves the creation and operation of a business organization devoted to manufacturing and sales. Precise details on setting up the game are given. (Author/PD)

  5. 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)

  6. 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.

  7. Comparing SiC switching power devices: MOSFET, NPN transistor and GTO thyristor

    NASA Astrophysics Data System (ADS)

    Huang, Alex Q.; Zhang, Bo

    2000-02-01

    This paper for the first time systematically analyzed the operation mechanism of SiC NPN transistors. Theoretical device figure-of-merits for switching power devices based on the conduction loss and switching loss were developed. The on-state loss and the switching loss of 4.5-kV SiC switching power devices (MOSFET, NPN transistor and GTO thyristor) were then compared by using theoretical and numerical calculations. Special emphasis is placed on comparing the total power loss of the devices at a given current density. Theoretical analyses and simulation results show that GTO thyristors have a large switching loss due to the long current tail at turn-off, hence restricting its maximum operation frequency. High voltage SiC MOSFETs have a large on-state power dissipation at high current levels due to the resistive nature of the drift region, restricting their applications at high current densities. SiC NPN transistors have a comparable switching loss as that of SiC MOSFETs, but at the same time, SiC NPN transistors have the lowest on-state loss. This study indicates that SiC NPN transistor is the most attractive switching power device at 4.5 kV.

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

    SciTech Connect

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

    2012-01-01

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

  9. 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

  10. Theoretical studies on Si-C bond cleavage in organosilane precursors during polycondensation to organosilica hybrids.

    PubMed

    Shirai, Soichi; Goto, Yasutomo; Mizoshita, Norihiro; Ohashi, Masataka; Tani, Takao; Shimada, Toyoshi; Hyodo, Shi-aki; Inagaki, Shinji

    2010-05-20

    Molecular orbital theory calculations were carried out to predict the occurrence of Si-C bond cleavage in various organosilane precursors during polycondensation to organosilica hybrids under acidic and basic conditions. On the basis of proposed mechanisms for cleavage of the Si-C bonds, the proton affinity (PA) of the carbon atom at the ipso-position and the PA of the carbanion generated after Si-C cleavage were chosen as indices for Si-C bond stability under acidic and basic conditions, respectively. The indices were calculated using a density functional theory (DFT) method for model compounds of organosilane precursors (R-Si(OH)(3)) having organic groups (R) of benzene (Ph), biphenyl (Bp), terphenyl (Tph), naphthalene (Nph), N-methylcarbazole (MCz), and anthracene (Ant). The orders for the predicted stability of the Si-C bond were Ph > Nph > Bp > Ant > Tph > MCz for acidic conditions and Ph > MCz > Bp > Nph > Tph > Ant for basic conditions. These behaviors were primarily in agreement with experimental results where cleavage of the Si-C bonds occurred for Tph (both acidic and basic), MCz (acidic), and Ant (basic). The Si-C bond cleavage of organosilane precursors during polycondensation is qualitatively predicted from these indices based on our theoretical approach. PMID:20429568

  11. Material science and device physics in SiC technology for high-voltage power devices

    NASA Astrophysics Data System (ADS)

    Kimoto, Tsunenobu

    2015-04-01

    Power semiconductor devices are key components in power conversion systems. Silicon carbide (SiC) has received increasing attention as a wide-bandgap semiconductor suitable for high-voltage and low-loss power devices. Through recent progress in the crystal growth and process technology of SiC, the production of medium-voltage (600-1700 V) SiC Schottky barrier diodes (SBDs) and power metal-oxide-semiconductor field-effect transistors (MOSFETs) has started. However, basic understanding of the material properties, defect electronics, and the reliability of SiC devices is still poor. In this review paper, the features and present status of SiC power devices are briefly described. Then, several important aspects of the material science and device physics of SiC, such as impurity doping, extended and point defects, and the impact of such defects on device performance and reliability, are reviewed. Fundamental issues regarding SiC SBDs and power MOSFETs are also discussed.

  12. Influence of SiC Particles Distribution and Their Weight Percentage on 7075 Al Alloy

    NASA Astrophysics Data System (ADS)

    Bhushan, Rajesh Kumar; Kumar, Sudhir

    2011-03-01

    The stir casting method was used for fabrication of 7075 aluminum alloy with 10 wt.% SiC particles of size 20-40 μm. The research objective of this paper are to achieve uniform distribution of SiC particles in the 7075 aluminum alloy matrix, characterization, and analysis of mechanical properties of composite formed. Experiments were carried out at stirring speeds of 500, 650, 750 rpm, and stirring period of 10 min. Microstructures of aluminum alloy and composites with 5, 10 wt.% SiC reinforcements were examined. The results reveal that composite produced at stirring speed of 650 rpm and stirring time of 10 min has uniform distribution of SiC particles. XRD and EDAX analysis were carried out for 7075 Al alloy and composite with 10 wt.% SiC reinforcement. No adverse reaction was observed in XRD and EDAX of composite with 10 wt.% SiC reinforcement. Tensile strength and hardness increased by 12.74% and 10.48%, respectively, with the increase in percentage of SiC reinforcement from 5 to 15 wt.%.

  13. SiC nanoparticles as potential carriers for biologically active substances

    NASA Astrophysics Data System (ADS)

    Guevara-Lora, Ibeth; Czosnek, Cezary; Smycz, Aleksandra; Janik, Jerzy F.; Kozik, Andrzej

    2009-01-01

    Silicon carbide SiC thanks to its many advantageous properties has found numerous applications in diverse areas of technology. In this regard, its nanosized forms often with novel properties have been the subject of intense research in recent years. The aim of this study was to investigate the binding of biologically active substances onto SiC nanopowders as a new approach to biomolecule immobilization in terms of their prospective applications in medicine or for biochemical detection. The SiC nanoparticles were prepared by a two-stage aerosol-assisted synthesis from neat hexamethyldisiloxane. The binding of several proteins (bovine serum albumin, high molecular weight kininogen, immunoglobulin G) on SiC particle surfaces was demonstrated at the levels of 1-2 nanograms per mg of SiC. These values were found to significantly increase after suitable chemical modifications of nanoparticle surfaces (by carbodiimide or 3-aminopropyltrietoxysilane treatment). The study of SiC biocompatibility showed a lack of cytotoxicity against macrophages-like cells below the concentration of 1 mg nanoparticles per mL. In summary, we demonstrated the successful immobilization of the selected substances on the SiC nanoparticles. These results including the cytotoxicity study make nano-SiC highly attractive for potential applications in medicine, biotechnology or molecular detection.

  14. 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. PMID:24205600

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    DOE PAGESBeta

    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

  17. Identifying radiation induced point defect in SiC nanowires: computational modeling

    NASA Astrophysics Data System (ADS)

    Uu, Ming

    SiC nanowires (NWs) are expected to possess higher radiation tolerance compared to their crystalline counterpart due to their efficiency in eliminating point defects generated by the radiations. In this study, we will develop a computational modeling scheme to identify the radiation induced point defects in SiC NWs. A preliminary study on the hexagonal 2H-SiC NWs has demonstrated that the point defects on the surface of the SiC NWs only create local distortions and will not cause the destruction of the entire structure of the SiC NWs. It is also found that the local strain created by the antisite, the C-vacancy, and the Si-interstitial defects induces a few impurity states inside the energy gap, while defects such as the Si-vacancy and C-interstitial defects tend to produce a small tail at the top of the valence band. These observations suggest that the electronic properties of the SiC NWs will not be affected to any great extent by these types of points defects on the surface of the SiC NWs, and therefore the SiC NWs are expected to be tolerant or resistant responding to these types of radiation effect.

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

    SciTech Connect

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

    1992-01-01

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

  19. 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.

  20. Plasma-aided manufacturing

    NASA Astrophysics Data System (ADS)

    Shohet, J. L.

    1993-12-01

    Plasma-aided manufacturing is used for producing new materials with unusual and superior properties, for developing new chemical compounds and processes, for machining, and for altering and refining materials and surfaces. Plasma-aided manufacturing has direct applications to semiconductor fabrication, materials synthesis, welding, lighting, polymers, anti-corrosion coatings, machine tools, metallurgy, electrical and electronics devices, hazardous waste removal, high performance ceramics, and many other items in both the high-technology and the more traditional industries in the United States.

  1. Holonic Manufacturing Paint Shop

    NASA Astrophysics Data System (ADS)

    Lind, Morten; Roulet-Dubonnet, Olivier; Nyen, Per Åge; Gellein, Lars Tore; Lien, Terje; Skavhaug, Amund

    In pursuit of flexibility and agility within discrete manufacturing, the surrounding logistics and handling processes of a paint shop is under construction as a laboratory prototype application. Holonic Manufacturing seems to be a promising strategic paradigm and architecture to use for a system characterised by production logistics and control. This paper describes the physical devices to be used; the desired functionality; and the basic logic control designed. Additionally, the ideas for holonification based on the already designed logic control is presented.

  2. Study of the effects of SiC filler on the internal charging of LDPE in space environment

    NASA Astrophysics Data System (ADS)

    Dong, Lei; Tan, Zhenyu; Tang, Fule

    2015-05-01

    The systematic investigation on the effects of the parameters of SiC filler on the internal charging of low density polyethylene (LDPE) has been performed. The injected current density and the absorbed dose rate in LDPE are calculated by means of the Monte Carlo method based on Geant4 code. Using these obtained quantities and taking into account the high-field conductivity, the electric field distributions in the LDPEs with SiC fillers of the different parameters have been calculated. The following significant results are given. With the increase of SiC filler concentration, the obvious increase of the electric field appears at increasingly small depth in LDPE. At lower SiC filler concentrations, large incident current density leads to large electric field magnitude Emax, but at higher SiC filler concentrations, Emax values under different incident current densities become close to each other. In addition, large particulate size of SiC has a substantial effect on the electric field distributions at high SiC filler concentrations, the contribution of black SiC to the decrease in the electric field is superior to that of green SiC, and the addition of β-form SiC leads to significant low Emax, compared to that by adding α-form SiC.

  3. Effect of grain size on microstructure, properties, and surface roughness of reaction bonded SiC ceramics

    NASA Astrophysics Data System (ADS)

    Aghajanian, Michael; Emmons, Craig; Rummel, Steve; Barber, Paul; Robb, Chris; Hibbard, Doug

    2013-09-01

    Silicon carbide (SiC) based ceramics have received significant study for optical applications due to high specific stiffness, high thermal conductivity, and low coefficient of thermal expansion (CTE). Reaction bonded SiC ceramics, which are composites of SiC and Si, are of particular interest due to large size and complex shape capability. The behavior of these ceramics is very much affected by the grain size of the SiC phase. The present work examines SiC grain sizes ranging from 6 to 50 μm, with the goal of optimizing properties and finishing capability for optical uses. Microstructures are reviewed; physical, mechanical and thermal properties are presented; and post-polishing surface roughness data are provided. In particular, results demonstrate that properties can be tailored by SiC particle size selection, and that measureable enhancement in surface roughness can be achieved by moving to smaller SiC grain size.

  4. 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.

  5. Interstellar grains in meteorites. I - Isolation of SiC, graphite, and diamond; size distributions of SiC and graphite. II - SiC and its noble gases

    NASA Astrophysics Data System (ADS)

    Amari, Sachiko; Lewis, Roy S.; Anders, Edward

    1994-01-01

    A new separation procedure is described that permits recovery of grains of interstellar graphite, diamond and SiC from primitive meteorites in greater than 90 percent purity and with yields generally of 70 percent or more. The method relies mainly on a set of progressively more corrosive 'selective solvents' to remove phases one by one, but also includes grain size and density separations. The procedure is applied here to the Murchison C2M meteorite to analyze He, Ne, Ar, Kr, and Xe. The results indicate that the SIC grains are pristine circumstellar condensates from red giant carbon stars representing a range of masses, metallicities, temperatures, and neutron densities. The results suggest that gas-rich SiC grains predate the solar system by at least 130 Ma and possibly up to 2000 Ma.

  6. 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.

  7. 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.

  8. Graphene Nanoribbons Anchored to a SiC Substrate

    NASA Astrophysics Data System (ADS)

    Woods, Lilia; Le, Nam

    Due to their exceptional fundamental characteristics graphene nanoribbons play a major role in the development of future nano-technological applications. The high chemical reactivity of the graphene nanoribbon edges can be utilized to create modified materials. Using first principles simulations we explore this possibility to construct patterned systems composed of anchored ribbons of zigzag edges covalently bonded to a SiC substrate. The hybrid edge states are found to possess interesting electronic and magnetic properties, which alter the overall behavior of the entire system as compared to the behavior of the individual components. It is found that the van der Waals interactions are important for the overall stability and structure of the anchored ribbons. Also, spin-polarization effects play a profound role in the electronic structure and associated density of states. The hybrid graphene/SiC zigzag edges are analyzed in terms of their transport characteristics as well.

  9. Interaction Of Water Molecules With SiC(001) Surfaces

    SciTech Connect

    Cicero, G; Catellani, A; Galli, G

    2004-08-10

    We have investigated the interaction of water molecules with the polar Si- and C- terminated surfaces of cubic Silicon Carbide by means of ab initio molecular dynamics simulations at finite temperature. Different water coverages were considered, from {1/4} to a complete monolayer. Irrespective of coverage, we find that water dissociates on the silicon terminated surfaces, leading to important changes in both its structural and electronic properties. On the contrary, the carbon terminated surface remains inert when exposed to water. We propose experiments to reveal the ionic and electronic structure of wet Si-terminated surfaces predicted by our calculations, which at full coverage are notably different from those of hydrated Si(001) substrates. Finally, we discuss the implications of our results for SiC surface functionalization.

  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. 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

  12. 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.

  13. Saturn V S-IC Stage at Dynamic Test Stand

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Engineers and technicians at the Marshall Space Flight Center placed a Saturn V ground test booster (S-IC-D) into the dynamic test stand. The stand was constructed to test the integrity of the vehicle. Forces were applied to the tail of the vehicle to simulate the engines thrusting, and various other flight factors were fed to the vehicle to test reactions. The Saturn V launch vehicle, with the Apollo spacecraft, was subjected to more than 450 hours of shaking. The photograph shows the 300,000 pound S-IC stage being lifted from its transporter into place inside the 360-foot tall test stand. This dynamic test booster has one dummy F-1 engine and weight simulators are used at the other four engine positions.

  14. Angular Effects on F+ Etching SiC: MD Study

    NASA Astrophysics Data System (ADS)

    Chen, Xu; Tian, Shuping; He, Pingni; Zhao, Chengli; Sun, Weizhong; Zhang, Junyuan; Chen, Feng; Gou, Fujun

    2012-12-01

    Molecular dynamics (MD) simulations were performed to investigate F+ continuously bombarding SiC surfaces with energies of 100 eV at different incident angles at 300 K. The simulated results show that the steady-state uptake of F atoms increases with increasing incident angle. With the steady-state etching established, a Si-C-F reactive layer is formed. It is found that the etching yield of Si is greater than that of C. In the F-containing reaction layer, the SiF species is dominant with incident angles less than 30°. For all incident angles, the CF species is dominant over CF2 and CF3.

  15. Fatigue behavior of SiC reinforced titanium composites

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  16. Fatigue behavior of SiC reinforced titanium composites

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  17. 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.

  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. Improvement of the thermal design in the SiC PVT growth process

    NASA Astrophysics Data System (ADS)

    Yan, J.-Y.; Chen, Q.-S.; Jiang, Y.-N.; Zhang, H.

    2014-01-01

    The physical vapor transport (PVT) method is used to grow silicon carbide (SiC) crystals, which are difficult to be grown by other methods. In this paper, a field-coordination theory is involved to optimize the SiC PVT growth process. By using a finite volume-based computational method, we calculate the flow field as well as species concentration field before and after improvement of the thermal design, respectively. The shape of the SiC crystal grown using the improved thermal design is also shown.

  20. Design and fabrication of large-scale lightweight SiC space mirror

    NASA Astrophysics Data System (ADS)

    Zhang, Jianhan; Zhang, Yumin; Han, Jiecai; He, Xiaodong; Yao, Wang

    2006-02-01

    Silicon carbide is a new type of optics material developed in recent years because it offered some advantages over other traditional optical substrate materials such as low density, low thermal expansion coefficient, high thermal conductivity, big special heat, big modulus of elasticity and potential cost and schedule. So in this paper, the silicon carbide space mirror was fabricated by both reaction bonded (RB) and chemical vapor deposition (CVD) process. The green body of the space mirror was prepared by silicon carbide powder, carbon powder, dilution and solidified agent using slip casting method. The space mirror blank was prepared by green body and pure silicon powder. They were laid in vacuum sintering furnace and sintered at 1500°C. In this temperature, silicon was melting then infiltrated in SiC green body and reacted with carbon to generate the new SiC, at the same time, bonded original SiC powder, in the end, the nonporous SiC/Si space mirror blank was fabricated. The reaction bonded silicon carbide (RBSiC) was consistent with original SiC powder, new generated SiC and unreacted Si. Because RBSiC was SiC/Si two-phase structure, the hardness difference between SiC and Si made the space mirror difficult to achieve precision optical surface by grinding. So a full density SiC thin film was coated on the surface of space mirror blank with RBSiC by chemical vapor deposition (CVD) process. The raw material was CH3SiCl3. The hydrogen (H2) was catalyst. The deposition temperature was 1300°C. The cooling rate could be controlled. The SiC space mirror was honeycomb open back lightweight structure. The honeycomb cellar could be triangle, rectangle, hexogen and sector. The biggest diameter of SiC space mirror blank which has been fabricated is approach one meter by forgoing process. In order to the forgoing process was feasible, a flat round SiC space mirror with 250mm diameter. The space mirror was composed of a 4mm thick round plane faceplate and hexagonal cellar

  1. 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.

  2. 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

  3. Evolution of SiC Nanocluster from Carbon Fullerene: A Density Functional Theoretic Study

    SciTech Connect

    Huda, M. N.; Ray, A. K.

    2008-01-01

    Stability of SiC fullerene type structures is still an unsolved issue as no experimental confirmation has been reported so far regarding its existence. However, theoretical reports are available in the literature where carbon fullerenes were taken as base models for SiC fullerene structures. In this present Letter we show by a systematic study on the C{sub 20} fullerene that this approach may not always produce the ground state structure in fullerene form. Instead, the energetically favorable structure could be highly distorted and open structure. However, we observed a very systematic linear trend in the evolution of binding energies of SiC clusters from the carbon fullerene.

  4. 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.

  5. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  7. Dry Sliding Wear Behavior of a Novel 6351 Al-(Al4SiC4 + SiC) Hybrid Composite

    NASA Astrophysics Data System (ADS)

    Show, Bijay Kumar; Mondal, Dipak Kumar; Maity, Joydeep

    2014-03-01

    In this research study, the dry sliding wear behaviors of 6351 Al alloy and its composites with single and hybrid reinforcements (ex situ SiC and in situ Al4SiC4) were investigated at low sliding speed (1 ms-1) against a hardened EN 31 disk at different loads. In general, the wear mechanism involved adhesion (coupled with subsurface cracking) and microcutting-abrasion at lower loads. With higher loads, abrasive wear involving microcutting and microplowing along with adherent oxide formation was observed. At higher loads, the abrasive wear mechanism caused rapid wear loss initially up to a certain sliding distance beyond which, by virtue of frictional heat generation and associated temperature rise, an adherent oxide layer was developed at the pin surface, which drastically reduced the wear loss. Moreover, the overall wear rates of all the composites (either single or hybrid reinforcement) were found to be lower than that of the 6351 Al alloy at all applied loads. The ex situ SiC particles were found to resist abrasive wear; while, in situ Al4SiC4 particles offered resistance to adhesive wear. Accordingly, the 6351 Al-(SiC + Al4SiC4) hybrid composite exhibited the best wear resistance among all composites.

  8. Effects of SiC Particle Size and Process Parameters on the Microstructure and Hardness of AZ91/SiC Composite Layer Fabricated by FSP

    NASA Astrophysics Data System (ADS)

    Asadi, P.; Givi, M. K. Besharati; Abrinia, K.; Taherishargh, M.; Salekrostam, R.

    2011-12-01

    In this study, friction stir processing (FSP) was employed to develop a composite layer on the surface of as-cast AZ91 magnesium alloy using SiC particles (5 μm and 30 nm). The effects of the rotational and traverse speeds and the FSP pass number on the microstructure and microhardness of the friction stir processed (FSPed) layer with and without SiC particles were investigated. Optical microscopy and scanning electron microscopy (SEM) were employed for microstructural analysis. FSP produces a homogeneous microstructure by eliminating the precipitates near the grain boundaries. The analyses showed that the effects of the rotational and traverse speeds on the microstructure of specimens produced without nano-sized SiC particles are considerable; however, they are negligible in the specimens with particles. While the second FSP pass enhances the microstructure and microhardness of the samples with SiC particles, it has no significant effect on such properties in the samples without SiC particles.

  9. 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.

  10. 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.

  11. Analysis on partial thermal resistances of packaged SiC schottky barrier diodes at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Kim, Taehwa; Funaki, Tsuyoshi

    2016-04-01

    This paper investigates the temperature dependence of partial thermal resistances of a packaged SiC schottky barrier diode (SBD) for high temperature applications. Transient thermal resistances of the packaged SiC SBD were measured and characterized in temperature range from 27 to 275 °C. The partial thermal resistances were extracted and analyzed using the cumulative and differential thermal structure functions. The extracted partial thermal resistances were compared to the results from the finite difference thermal model, and both results were in good agreement. The temperature dependence of the partial thermal resistance of the SiC device and the Si3N4 substrate contributes to the overall thermal characteristics variation of the packaged SiC SBD.

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

    SciTech Connect

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

    1995-10-01

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

  13. Codeposition of SiC particles with electrolytic cobalt in the presence of Cs + ions

    NASA Astrophysics Data System (ADS)

    Rudnik, Ewa; Burzyńska, Lidia; Jędruch, Jacek; Błaż, Ludwik

    2009-05-01

    Electrodeposition of SiC particles with cobalt matrix in the presence of cesium ions was studied. The influence of Cs + concentration (0-37.6 mM) on the cathodic polarization curves was determined in galvanostatic and potentiodynamic measurements. It was found that the presence of Cs + in the solution enhanced adsorption of Co 2+ ions on SiC, but preferential cesium adsorption occurred simultaneously. The last phenomena resulted in cesium incorporation in the composite coating. Surface charge of SiC powder and amounts of functional groups on SiC surface were determined. The particles incorporation into deposits was only little dependent on cesium concentration in the bath. Structure of the composite coatings was studied by microscopic observations. Microhardness of the deposits was also determined.

  14. 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.

  15. Magnetic, optical and electrical characterization of SiC doped with scandium during the PVT growth

    NASA Astrophysics Data System (ADS)

    Racka, K.; Avdonin, A.; Sochacki, M.; Tymicki, E.; Grasza, K.; Jakieła, R.; Surma, B.; Dobrowolski, W.

    2015-03-01

    Scandium is introduced into bulk SiC during the physical vapor transport (PVT) growth. SiC crystals grown with different Sc contents (from 0.5 wt% up to 2.5 wt%, added to the SiC source material) are studied. Magnetic properties of SiC doped with scandium during the PVT growth are reported for the first time. The presence of antiferromagnetic interactions between magnetic moments of Sc ions is concluded from the temperature dependence of magnetic susceptibility. Detailed PL spectra of 4H-/6H-SiC:B and 4H-/6H-SiC:Sc crystals are presented. A new energy level of 35-37 meV is found on SiC:Sc samples and its possible assignment to a complex defect, consisting of nitrogen donor and scandium acceptor, is proposed.

  16. Study of Compressive Strength of sic in Impact Experiments with Divergent Flow

    NASA Astrophysics Data System (ADS)

    Paris, V.; Frage, N.; Zaretsky, E.

    2009-12-01

    The axisymmetric divergent flow was generated in SiC samples by impact of convex copper flyer plates (radius of curvature ranging from 88 to 550 mm) having velocities from 550 to 700 m/s. The sample-window (sapphire) interface velocities or the velocities of the free surface of the nickel witness plate were continuously monitored by VISAR. The maximum shear stress achieved under different confining stress just prior to the sample failure is associated with the compressive failure threshold of the SiC. Both the compressive failure threshold of SiC and the parameters of its inelastic deformation were found by matching the results of the AUTODYN-2D numerical simulation with the experimentally obtained waveforms. The compressive failure threshold of SiC is characterized by a transition from brittle-like behavior below the confining stress of 1.4-1.5 GPa to the ductile-like one at higher confining stress.

  17. Study of Compressive Strength of SiC In Impact Experiments with Divergent Flow

    NASA Astrophysics Data System (ADS)

    Paris, Vitaly; Frage, Naum; Zaretsky, Eugene

    2009-06-01

    The axisymmetric divergent flow was generated in SiC specimens by impact of spherical (radius of curvature ranging from 170 to 550 mm) copper impactors having velocities 550 to 700 m/s. The specimen-window (sapphire) interface velocities or the velocities of the free surface of the nickel witness plate were continuously monitored by VISAR. The maximum, just prior to the failure, shear stress values achieved in the SiC under different confining stresses are associated with the failure threshold of the material. Both the compressive failure threshold of SiC and the parameters of its inelastic deformation were found by matching the results of the AUTODYN numerical simulation to the experimentally obtained waveforms. The compressive failure threshold of SiC is characterized by a transition from apparently pressure-dependent behavior below the confining stress equal to 1.5 GPa to a pressure-independent behavior at higher confining stresses.

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

    DOE PAGESBeta

    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

  19. 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

  20. 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.

  1. 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.

  2. Grain boundary effects on defect production and mechanical properties of irradiated nanocrystalline SiC

    SciTech Connect

    Jin Enze; Niu Lisha; Lin Enqiang; Song Xiaoxiong

    2012-05-15

    Grain boundaries (GBs) are known to play an important role in determining the mechanical and functional properties of nanocrystalline materials. In this study, we used molecular dynamics simulations to investigate the effects of damaged GBs on the mechanical properties of SiC that is irradiated by 10 keV Si atoms. The results reveal that irradiation promotes GB sliding and reduces the ability of GBs to block dislocations, which improves the deformation ability of nanocrystalline SiC. However, irradiation causes local rearrangements in disordered clusters and pinning of dislocations in the grain region, which restrains its deformation. These two mechanisms arise from the irradiation effects on GBs and grains, and these mechanisms compete in nanocrystalline SiC during irradiation. The irradiation effects on GBs dominate at low irradiation doses, and the effects on grains dominate at high doses; the result of these combined effects is a peak ductility of 0.09 dpa in nanocrystalline SiC.

  3. Grain boundary effects on defect production and mechanical properties of irradiated nanocrystalline SiC

    NASA Astrophysics Data System (ADS)

    Jin, Enze; Niu, Li-Sha; Lin, Enqiang; Song, Xiaoxiong

    2012-05-01

    Grain boundaries (GBs) are known to play an important role in determining the mechanical and functional properties of nanocrystalline materials. In this study, we used molecular dynamics simulations to investigate the effects of damaged GBs on the mechanical properties of SiC that is irradiated by 10 keV Si atoms. The results reveal that irradiation promotes GB sliding and reduces the ability of GBs to block dislocations, which improves the deformation ability of nanocrystalline SiC. However, irradiation causes local rearrangements in disordered clusters and pinning of dislocations in the grain region, which restrains its deformation. These two mechanisms arise from the irradiation effects on GBs and grains, and these mechanisms compete in nanocrystalline SiC during irradiation. The irradiation effects on GBs dominate at low irradiation doses, and the effects on grains dominate at high doses; the result of these combined effects is a peak ductility of 0.09 dpa in nanocrystalline SiC.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  5. 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.

  6. Selective Growth of Graphene by Pulsed Laser Annealing Ion Implanted SiC

    NASA Astrophysics Data System (ADS)

    Berke, Kara; Wang, Xiaotie; Rudawski, Nick; Venkatachalam, Dinesh; Fridmann, Joel; Gila, Brent; Ren, Fan; Elliman, Rob; Hebard, Arthur; Appleton, Bill

    2014-03-01

    We report a method for site-selective graphene growth on SiC for direct nano-scale patterning of graphene. Crystalline SiC was implanted with Si and C ions to amorphize the sample surface, then subjected to pulsed laser annealing (PLA); graphene growth occurred only where ions were implanted. PLA parameters including the fluence, number of pulses, and annealing environment were investigated to optimize the growth process. Our previous work involving Au, Cu, and Ge implants in SiC suggested that both the implanted species and surface amorphization affect graphene growth. In this work, we show that surface amorphization alone, without the presence of foreign ionic species, can be used with PLA to create site-selective graphene growth on SiC. Samples were characterized using Raman spectroscopy and cross-sectional transmission electron microscopy. also affiliated with Raith USA, Incorporated.

  7. 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.

  8. 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

  9. Theoretical analysis of short-circuit capability of SiC power MOSFETs

    NASA Astrophysics Data System (ADS)

    Shoji, Tomoyuki; Soeno, Akitaka; Toguchi, Hiroaki; Aoi, Sachiko; Watanabe, Yukihiko; Tadano, Hiroshi

    2015-04-01

    The short-circuit capability of Si power devices, defined in terms of critical energy density, is the product of the heat capacity in the heat generation region and the increase in temperature. However, for SiC power devices, the heat generation region is significantly smaller than that for Si power devices, because the drift-region thickness is about 10 times less in SiC power devices. Therefore, the formulae used for Si devices are not directly applicable to SiC devices. In this study, analytical formulae are derived for the short-circuit capability of a SiC power device and its dependence on the ambient temperature and the thickness of the n- drift region, on the basis of the thermal diffusion equation. The calculated results are found to be in good agreement with those of direct measurements.

  10. Micro/nanoscale mechanical and tribological characterization of SiC for orthopedic applications.

    PubMed

    Li, Xiaodong; Wang, Xinnan; Bondokov, Robert; Morris, Julie; An, Yuehuei H; Sudarshan, Tangali S

    2005-02-15

    Micro/nanomechanical and tribological characterization of SiC has been carried out. For comparison, measurements on SiC, CoCrMo, Ti-6Al-4V, and stainless steel have also been made. Hardness and elastic modulus of these materials were measured by nanoindentation using a nanoindenter. The nanoindentation impressions were imaged using an atomic force microscope (AFM). Scratch, friction, and wear properties were measured using an accelerated microtribometer. Scratch and wear damages were studied using a scanning electron microscope (SEM). It is found that SiC exhibits higher hardness, elastic modulus, scratch resistance as well as lower friction with fewer and smaller debris particles compared to other materials. These results show that SiC possesses superior mechanical and tribological properties that make it an ideal material for use in orthopedic and other biomedical applications. PMID:15538716

  11. 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

  12. Light and heavy element isotopic compositions of mainstream SiC grains.

    SciTech Connect

    Amari, S.; Clayton, R. N.; Davis, A. M.; Lewis, R. S.; Pellin, M. J.

    1999-02-03

    Although a variety of types of pre-solar SiC grains have been classified by their C, N, and Si isotopic composition, the majority of such grains are so-called mainstream grains and are believed to have come from asymptotic giant branch stars [1]. We have previously reported the Mo isotopic compositions of presolar SiC grains whose C, N, and Si isotopic compositions were not known [2]. Since most presolar SiC grains fall in the mainstream group, we assumed that these grains were mainstream. The excellent match of the Mo isotopic data with expectations for nucleosynthesis in AGB stars was consistent with this identification. In order to better understand the distribution of isotopic compositions in presolar grains, we have begun to measure heavy element isotopic compositions of presolar SiC grains of known C, N and Si isotopic composition.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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...

  18. Manufacturing Laboratory (Fact Sheet)

    SciTech Connect

    Not Available

    2011-10-01

    This fact sheet describes the purpose, lab specifications, applications scenarios, and information on how to partner with NREL's Manufacturing Laboratory at the Energy Systems Integration Facility. The Manufacturing Laboratory at NREL's Energy Systems Integration Facility (ESIF) focuses on developing methods and technologies that will assist manufacturers of hydrogen and fuel cell technologies, as well as other renewable energy technologies, to scale up their manufacturing capabilities to volumes that meet DOE and industry targets. Specifically, the manufacturing activity is currently focused on developing and validating quality control techniques to assist manufacturers of low temperature and high temperature fuel cells in the transition from low to high volume production methods for cells and stacks. Capabilities include initial proof-of-concept studies through prototype system development and in-line validation. Existing diagnostic capabilities address a wide range of materials, including polymer films, carbon and catalyst coatings, carbon fiber papers and wovens, and multi-layer assemblies of these materials, as well as ceramic-based materials in pre- or post-fired forms. Work leading to the development of non-contact, non-destructive techniques to measure critical dimensional and functional properties of fuel cell and other materials, and validation of those techniques on the continuous processing line. This work will be supported by materials provided by our partners. Looking forward, the equipment in the laboratory is set up to be modified and extended to provide processing capabilities such as coating, casting, and deposition of functional layers, as well as associated processes such as drying or curing. In addition, continuous processes are used for components of organic and thin film photovoltaics (PV) as well as battery technologies, so synergies with these important areas will be explored.

  19. 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.

  20. 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.

  1. Microwave-assisted pyrolysis of SiC and its application to joining

    SciTech Connect

    Ahmad, I.; Silberglitt, R.; Shan, T.A.

    1995-07-01

    Microwave energy has been used to pyrolyze silicon carbide from commercially available polycarbosilane precursor. The pyrolysis was performed on SiC surfaces having various surface treatments, to identify conditions which improve the wetting and adherence. Grinding and etching of the surfaces in hydrofluoric (HF) acid promotes the bonding of precursor derived ceramic to the SiC ceramic. Finally, the polycarbosilane precursor mixed with fine silicon carbide powder was used as the interlayer material to join silicon carbide specimens.

  2. 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).

  3. 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.

  4. Installation of the F-1 Engine to the Saturn V S-IC Stage for Testing

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Engineers at the Marshall Space Flight Center install the F-1 engines on the S-IC stage thrust structure at the S-IC static test stand. Engines are installed on the stage after it has been placed in the test stand. Five F-1 engines, each weighing 10 tons, gave the booster a total thrust of 7,500,000 pounds, roughly equivalent to 160 million horsepower.

  5. 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.

  6. Installation of the F-1 Engine to the Saturn V S-IC Stage for Testing

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Engineers at the Marshall Space Flight Center install the F-1 engines on the S-IC stage thrust structure at the S-IC static test stand. Engines are installed on the stage after it has been placed in the test stand. This image shows a close-up of an F-1 engine. Five F-1 engines, each weighing 10 tons, gave the booster a total thrust of 7,500,000 pounds, roughly equivalent to 160 million horsepower.

  7. 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.

  8. 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.

  9. Energy consumption in manufacturing

    NASA Astrophysics Data System (ADS)

    Schmid, S. R.

    2012-04-01

    Energy sources, in the form of coal, oil, natural gas, solar or nuclear power, are global commodities, and as demand is projected to rise in the coming decades, so will costs. As such, an understanding of the energy needs of manufacturing processes and the ability to reduce the energy and carbon footprints are essential for sustainability reasons. Energy source effects are quantified in a number of measures. Models of energy needs by manufacturing processes are then examined, along with models incorporating the use of ancillary equipment such as pumps, filters, blowers, lighting, etc. Finally, the successful application of the tribological principles to influence energy consumption is discussed.

  10. Photovoltaic Manufacturing Technology

    NASA Astrophysics Data System (ADS)

    Easoz, J. R.; Herlocher, R. H.

    1991-12-01

    This report examines the cost-effective manufacture of dendritic-web-based photovoltaic modules. It explains how process changes can increase production and reduce manufacturing costs. Long-range benefits of these improved processes are also discussed. Problems are identified that could impede increasing production and reducing costs; approaches to solve these problems are presented. These approaches involve web growth throughput, cell efficiency, process yield, silicon use, process control, automation, and module efficiency. Also discussed are the benefits of bifacial module design, unique to the dendritic web process.

  11. 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.

  12. 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.

  13. 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.

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

    SciTech Connect

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

    2011-01-01

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

  15. 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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

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

  18. 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.

  19. 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.

  20. 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.

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

    DOE PAGESBeta

    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

  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. Mechanical and Thermal Properties of Hot-Pressed ZrB2-SiC Composites

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  4. Effects of SiC whiskers and particles on precipitation in aluminum matrix composites

    NASA Astrophysics Data System (ADS)

    Papazian, John M.

    1988-12-01

    The age-hardening precipitation reactions in aluminum matrix composites reinforced with discontinuous SiC were studied using a calorimetric technique. Composites fabricated with 2124, 2219, 6061, and 7475 alloy matrices were obtained from commercial sources along with unreinforced control materials fabricated in a similar manner. The 7475 materials were made by a casting process while the others were made by powder metallurgy: the SiC reinforcement was in the form of whiskers or particulate. It was found that the overall age-hardening sequence of the alloy was not changed by the addition of SiC, but that the volume fractions of various phases and the precipitation kinetics were substantially modified. Precipitation and dissolution kinetics were generally accelerated. A substantial portion of this acceleration was found to be due to the powder metallurgy process employed to make the composites, but the formation kinetics of some particular precipitate phases were also strongly affected by the presence of SiC. It was observed that the volume fraction of GP zones able to form in the SiC containing materials was significantly reduced. The presence of SiC particles also caused normally quench insensitive materials such as 6061 to become quench sensitive. The microstructural origins of these effects are discussed.

  5. 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.

  6. Synthesis and Characterization of SiC Ceramics for High Temperature Resistant Coatings and Matrix

    NASA Astrophysics Data System (ADS)

    Watanabe, Hiroyuki; Kobayashi, Satoshi; Fukushima, Manabu; Wakayama, Shuichi

    SiC ceramics are expected as oxidation resistant coating material for Carbon/Carbon (C/C) composites. In the present study, SiC ceramics were synthesized through Sol-Gel method with low environmental impact. The gels were synthesized from ethylalcohol, methyltriethoxysilane (MTES), hydrochloric acid (HCl) and purified water (H2O), and it was pyrolyzed at 1000, 1500 and 1700°C. The structures of gels after heat treatment were analyzed by X-ray diffraction (XRD). XRD results indicated that βup-SiC were obtained in the present method and crystallization was increased with increasing heat treatment temperature. There was little weight change in synthesized SiC obtained at 1000°C in air, which results in lower weight changes in SiC coated C/C composites comparing with bare C/C composites. However, SiC coated C/C composites were also oxidized because of the generation of cracks during heat treatment at 1000°C. Residual tensile strength of SiC coated C/C composites were also higher than that of bare C/C composites after 5 minutes oxidation.

  7. 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.

  8. The status of SiC bulk growth from an industrial point of view

    NASA Astrophysics Data System (ADS)

    Müller, St. G.; Glass, R. C.; Hobgood, H. M.; Tsvetkov, V. F.; Brady, M.; Henshall, D.; Jenny, J. R.; Malta, D.; Carter, C. H.

    2000-04-01

    Silicon-carbide-based device technology as well as the volume production of nitride-based, high brightness blue and green LEDs fabricated on SiC substrates has made tremendous progress within the last several years. The commercial availability of large, high-quality SiC substrates is a key issue for the realization of the full potential of this technology. The current status of SiC bulk sublimation growth for the industrial production of 50 mm diameter 4H and 6H wafers and the quality improvement of 75 mm wafers is reviewed. Results at Cree show a continous reduction of the micropipe density in SiC substrates, demonstrating micropipe free material of a 25 mm diameter and densities as low as 1.1 cm -2 for an entire 50 mm 4H-SiC wafer. We present results of modeling the relevant heat transfer processes during crystal growth and the thermoelastic stress in the growing crystal. The effect on dislocation generation is discussed. The recent interest in SiC for the production of a unique gemstone material (moissanite) additionally increases the demand for high-quality SiC bulk material.

  9. 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.

  10. Crystallization of ion-beam-synthesized SiC layer by thermal annealing

    NASA Astrophysics Data System (ADS)

    Wu, W.; Chen, D. H.; Cheung, W. Y.; Xu, J. B.; Wong, S. P.; Kwok, R. W. M.; Wilson, I. H.

    Synthesis of β-phase silicon carbide (SiC) layers has been achieved by high-dose carbon ion beam implantation into (100) silicon wafers with two different ion implantation energies, 40 keV and 65 keV. Subsequent furnace annealing was carried out in N2 at temperatures ranging from 600 to 1200 °C for 2 h. Rutherford backscattering spectrometry (RBS) analysis revealed carbon distribution and the formation of an SiC layer. Infrared spectroscopy (IR) exhibited a sharp absorption peak produced by the Si-C bond at 795 cm-1 with full width at half maximum (FWHM) of about 35 cm-1. A layer of crystalline SiC was formed after annealing the as-implanted sample at 1000 °C for 2 h. The influence of annealing temperature on the surface morphology and the dynamics of the crystallization procedure was studied by atomic force microscopy (AFM). A study of grain size and roughness revealed that the morphology of the SiC layer was largely dependent on annealing temperature, and the average grain size increased as the annealing temperature was raised. At about 900 °C, a layer of nanocrystalline SiC was formed on the sample surface, containing columnar grains with a FWHM of tens of nanometers and a height of less than ten nanometers.

  11. Do SiC grains in Orgueil differ from those in Murchison?

    NASA Technical Reports Server (NTRS)

    Huss, Gary R.; Hutcheon, Ian D.; Wasserburg, G. J.

    1993-01-01

    Studies of individual presolar SiC grains have shown that most are enriched in Si-29, Si-30, and C-13, and depleted in N-15, compared to solar-system abundances and that many have large excesses of Mg-26, most plausibly from in situ decay of Al-26. Stone et al., observed that Si from a family of platy SiC grains define a linear array on a 3-isotope plot that does not pass through normal solar-system Si. In contrast, Si-isotope data from over 100 3-4 micron SiC grains from Murchison from an elongate ellipse enclosing the Stone et al. linear array but also including 'normal' solar-system Si. To investigate whether this difference in Si isotopes indicates different populations of SiC in the two meteorites and to improve the characterization of Orgueil SiC, we used the PANURGE ion microprobe to measure Si, C, N, and Mg isotopes and Al and Na concentrations in a suite of 2-5 micron SiC grains from a new sample of Orgueil.

  12. 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.

  13. Study of silicon carbide (SiC) polytype heterojunctions

    NASA Astrophysics Data System (ADS)

    Eshun, Ebenezer Emmanuel

    2001-12-01

    The results of a study of the chemical vapor deposition (CVD) growth and characterization of SiC polytype heterojunctions are presented. Device quality alpha-SiC has been grown at 1580°C, with p-type background between 6 x 1014cm-3 and 5 x 1015cm-3. N-type device layers have also been grown using nitrogen as a dopant gas. These materials were characterized by various methods including photoluminescence, atomic force microscopy, scanning electron microscopy, secondary ion mass spectroscopy, reflection high energy electron diffraction, C-V and I-V measurements. The above results along with a pre-growth hydrogen/propane etch study were used as a baseline for developing a growth process for the SiC polytype heterojunctions. High quality heterojunctions have been obtained with almost no polytype inclusions. Characterizations were performed to study the heterojunctions, which included an oxidation study to map polytype inclusions in the layers grown under different conditions resulting in a high (>95%) polytype homogeneity. Transmission electron microscopy (TEM) shows no visible defects and/or columnar growth features, a sign of high quality crystalline films. TEM diffraction patterns obtained are very strong, further indicating high quality 3C-SiC epitaxial layers. X-ray rocking and reciprocal space mapping (RSM) were further used in characterizing the SiC polytype heterojunctions. The FWHM of the x-ray scans are very narrow, between 0.01° and 0.02°, an excellent figure further indicating high quality crystalline 3C-SiC epitaxial layers. Iso-intensity contours from the RSM show very little broadening in o which is due to the mosaic nature of the samples. The o-2theta direction shows almost no broadening implying that there is almost no strain in the material. In addition, the electrical quality of the heterojunctions was obtained by the fabrication and characterization of MESFETs made by growing a 0.6 mum n-type 3C-SiC on a semi-insulating 4H-SiC substrate

  14. Expert Systems Application In Manufacturing

    NASA Astrophysics Data System (ADS)

    Som, Pradip; Chitturi, Ramesh; Babu, A. J. G.

    1987-05-01

    Expert system, a special branch of Artificial Intelligence finds its way in the domain of manufacturing. This paper presents the basic ideas and features of the expert systems, problems in manufacturing and application of expert systems in manufacturing. As the process planning is an important phase in manufacturing, the suitability of expert systems for process planning area has been highlighted. Several expert systems, developed to solve manufacturing problems are also discussed in the paper.

  15. SiC devices: Physics and numerical simulation

    NASA Astrophysics Data System (ADS)

    Ruff, Martin; Mitlehner, Heinz; Helbig, Reinhard

    1994-06-01

    The important material parameters for 6H silicon carbide (6H-SiC) are extracted from the literature and implemented into the 2-D device simulation programs PISCES and BREAKDOWN and into the 1-D program OSSI Simulations of 6H-SiC p-n junctions show the possibility to operate corresponding devices at temperatures up to 1000 K thanks to their low reverse current densities. Comparison of a 6H-SiC 1200 V p-n(-)-n(+) diode with a corresponding silicon (Si) diode shows the higher switching performance of the 6H-SiC diode, while the forward power loss is somewhat higher than in Si due to the higher built-in voltage of the 6H-SiC p-n junction. This disadvantage can be avoided by a 6H-SiC Schottky diode. The on-resistances of Si, 3C-SiC, and 6H-SiC vertical power MOSFET's are compared by analytical calculations. At room temperature, such SiC MOSFET's can operate up to blocking capabilities of 5000 V with an on-resistance below 0.1 (Omega) sq cm, while Si MOSFET's are limited to below 500 V. This is checked by calculating the characteristics of a 6H-SiC 1200 V MOSFET with PISCES. In the voltage region below 200 V, Si is superior due to its higher mobility and lower threshold voltage. Electric fields in the order of 4 x 10(exp 6) V/cm occur in the gate oxide of the mentioned 6H-SiC MOSFET as well as in a field plate oxide used to passivate its planar junction. To investigate the high frequency performance of SiC devices, a heterobipolartransistor with a 6H-SiC emitter is considered. Base and collector are assumed to be out of 3C-SiC. Frequencies up to 10 GHz with a very high output power are obtained on the basis of analytical considerations.

  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. 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)

  18. 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…

  19. 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.

  20. 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.…

  1. 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…

  2. Drug development and manufacturing

    DOEpatents

    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.

  3. 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…

  4. 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,…

  5. Rapid response manufacturing (RRM)

    SciTech Connect

    Cain, W.D.; Waddell, W.L.

    1997-02-18

    US industry is fighting to maintain its competitive edge in the global market place. Today markets fluctuate rapidly. Companies, to survive, have to be able to respond with quick-to-market, improved, high quality, cost efficient products. The way products are developed and brought to market can be improved and made more efficient through the proper incorporation of emerging technologies. The RRM project was established to leverage the expertise and resources of US private industries and federal agencies to develop, integrate, and deploy new technologies that meet critical needs for effective product realization. The RRM program addressed a needed change in the US Manufacturing infrastructure that will ensure US competitiveness in world market typified by mass customization. This project provided the effort needed to define, develop and establish a customizable infrastructure for rapid response product development design and manufacturing. A major project achievement was the development of a broad-based framework for automating and integrating the product and process design and manufacturing activities involved with machined parts. This was accomplished by coordinating and extending the application of feature-based product modeling, knowledge-based systems, integrated data management, and direct manufacturing technologies in a cooperative integrated computing environment. Key technological advancements include a product model that integrates product and process data in a consistent, minimally redundant manner, an advanced computer-aided engineering environment, knowledge-based software aids for design and process planning, and new production technologies to make products directly from design application software.

  6. Manufacturing of SiCp Reinforced Magnesium Composite Tubes by Hot Extrusion Processes

    NASA Astrophysics Data System (ADS)

    Hwang, Yeong-Maw; Huang, Song-Jeng; Huang, Yu-San

    2011-05-01

    Magnesium alloys have higher specific strength compared with other metals, such as aluminum, copper and steel. Nevertheless, their ductility is still not good for further metal forming and their strength is not large enough for real structure applications. The aim of this paper is to develop magnesium alloy composite tubes reinforced with SiC particulates by the stir-casting method and hot extrusion processes. At first, AZ61/SiCp composite ingots reinforced with 5 wt% SiC particulates are fabricated by the melt-stirring technique. Then, finite element simulations are conducted to analyze the plastic flow of magnesium alloy AZ61 within the die and the temperature distribution of the products. AZ61/SiCp composite tubes are manufactured by hot extrusion using a specially designed die-set for obtaining uniform thickness distribution tubes. Finally, the mechanical properties of the reinforced AZ61/SiCp composite and Mg alloy AZ61 tubes are compared with those of the billets to manifest the advantages of extrusion processes and reinforcement of SiC particulates. The microstructures of the billet and extruded tubes are also observed. Through the improvement of the strength of the tube product, its life cycle can be extended and the energy consumption can be reduced, and eventually the environmental sustainability is achieved.

  7. Manufacturing of SiCp Reinforced Magnesium Composite Tubes by Hot Extrusion Processes

    SciTech Connect

    Hwang, Yeong-Maw; Huang, Song-Jeng; Huang, Yu-San

    2011-05-04

    Magnesium alloys have higher specific strength compared with other metals, such as aluminum, copper and steel. Nevertheless, their ductility is still not good for further metal forming and their strength is not large enough for real structure applications. The aim of this paper is to develop magnesium alloy composite tubes reinforced with SiC particulates by the stir-casting method and hot extrusion processes. At first, AZ61/SiCp composite ingots reinforced with 5 wt% SiC particulates are fabricated by the melt-stirring technique. Then, finite element simulations are conducted to analyze the plastic flow of magnesium alloy AZ61 within the die and the temperature distribution of the products. AZ61/SiCp composite tubes are manufactured by hot extrusion using a specially designed die-set for obtaining uniform thickness distribution tubes. Finally, the mechanical properties of the reinforced AZ61/SiCp composite and Mg alloy AZ61 tubes are compared with those of the billets to manifest the advantages of extrusion processes and reinforcement of SiC particulates. The microstructures of the billet and extruded tubes are also observed. Through the improvement of the strength of the tube product, its life cycle can be extended and the energy consumption can be reduced, and eventually the environmental sustainability is achieved.

  8. 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.

  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. 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.

  11. Exciton-polariton state in nanocrystalline SiC films

    NASA Astrophysics Data System (ADS)

    Semenov, А. V.; Lopin, А. 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.

  12. 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.

  13. 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

  14. Epitaxial graphene on SiC: from carrier density engineering to quasi-free standing graphene by atomic intercalation

    NASA Astrophysics Data System (ADS)

    Forti, S.; Starke, U.

    2014-03-01

    Epitaxial graphene (EG) on SiC has been proven to be an excellent material to investigate the fundamental physical properties of graphene and also to directly implement new findings into devices realized on the versatile platform of SiC. Within this framework, this work aims to review some of the recent major achievements accomplished in the field of EG on SiC, related to the growth of EG on the SiC(0 0 0 1) surface, the control of its doping level, the decoupling of the graphene from the substrate and the intercalation of foreign atomic species at the interface.

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

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Hebsur, Mohan G.

    2000-01-01

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

  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. 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.

  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. 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.

  20. 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.

  1. 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.

  2. 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.

  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. Technology for Manufacturing Efficiency

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The Ground Processing Scheduling System (GPSS) was developed by Ames Research Center, Kennedy Space Center and divisions of the Lockheed Company to maintain the scheduling for preparing a Space Shuttle Orbiter for a mission. Red Pepper Software Company, now part of PeopleSoft, Inc., commercialized the software as their ResponseAgent product line. The software enables users to monitor manufacturing variables, report issues and develop solutions to existing problems.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. Manufactured Homes Tool

    SciTech Connect

    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. 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.

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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.

  16. 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)

  17. Safe food manufacturing.

    PubMed

    Shapiro, A; Mercier, C

    1994-03-31

    Food safety is a growing preoccupation of the health authorities and the major food companies in any European country. All the aspects of food manufacturing, from the raw materials until the product is consumed have to insure they are innoxious to human health, eliminate any harmful effects related either to food handling or consumption in domestic or common eating places, as well as protect, as much as possible, our environment. Thus, the food manufacturer has to examine step-by-step the security of the agro-cultures, their composition, but also the possible residues of pollutants and contaminants, or chemicals used to protect them against various pests and determine the possible loss or retention of these substances during technological processes. Animal raw materials should not contain veterinary drug residues or an abnormal amount of some components that result from inadequate feeding. Care should be taken to ensure the security of foods manufactured by biotechnology processes. The organisms and the whole processes used in food biotechnologies should eliminate any impurities. Any minor food ingredients, such as food additives, are under a permanent revision from the point of view of their safety. The industry reacts immediately if any justification requires that a particular food additive should not be used. In other words all the raw materials must conform to their specifications. Technological processes must create a food with an adequate microbiological quality, e.g. free of pathogens and their toxic metabolites. Any danger of microbiological contamination or accidental pollution, such as mechanical particles, chemical substances, etc. should be eliminated. The particular role of food packaging is crucial, since this is a barrier to protect the food against further parasites or microbial contamination and preserve the food from alterations due to enzymatic reactions that require particular oxygen and water activity conditions. The packaging should also

  18. 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.

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

    PubMed

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

    2003-01-01

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

  20. 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

  1. 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)

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

    SciTech Connect

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

    1995-10-01

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

  3. 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.

  4. A new approach for fabrications of SiC based photodetectors

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  5. Removal of Flame Deflector From the S-IC Test Stand

    NASA Technical Reports Server (NTRS)

    1975-01-01

    At its founding, the Marshall Space Flight Center (MSFC) inherited the Army's Jupiter and Redstone test stands, but much larger facilities were needed for the giant stages of the Saturn V. From 1960 to 1964, the existing stands were remodeled and a sizable new test area was developed. The new comprehensive test complex for propulsion and structural dynamics was unique within the nation and the free world, and they remain so today because they were constructed with foresight to meet the future as well as on going needs. Construction of the S-IC Static test stand complex began in 1961 in the west test area of MSFC, and was completed in 1964. The S-IC static test stand was originally designed to develop and test the 138-ft long and 33-ft diameter Saturn V S-IC first stage, or booster stage. Modifications to the S-IC Test Stand began in 1975 to accommodate space shuttle external tank testing. This photo depicts the removal of the flame deflector which was originally used to provide water to the 5 F-1 engines of the S-IC stage during testing.

  6. First Saturn V S-IC Stage Five F-1 Engine Testing

    NASA Technical Reports Server (NTRS)

    1965-01-01

    This photograph depicts a dramatic view of the first test firing of all five F-1 engines for the Saturn V S-IC stage at the Marshall Space Flight Center. The testing lasted a full duration of 6.5 seconds. It also marked the first test performed in the new S-IC static test stand and the first test using the new control blockhouse. The S-IC stage is the first stage, or booster, of a 364-foot long rocket that ultimately took astronauts to the Moon. Operating at maximum power, all five of the engines produced 7,500,000 pounds of thrust. Required to hold down the brute force of a 7,500,000-pound thrust, the S-IC static test stand was designed and constructed with the strength of hundreds of tons of steel and cement, planted down to bedrock 40 feet below ground level. The structure was topped by a crane with a 135-foot boom. With the boom in the up position, the stand was given an overall height of 405 feet, placing it among the highest structures in Alabama at the time. When the Saturn V S-IC first stage was placed upright in the stand , the five F-1 engine nozzles pointed downward on a 1,900 ton, water-cooled deflector. To prevent melting damage, water was sprayed through small holes in the deflector at the rate 320,000 gallons per minute.

  7. 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.

  8. 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

  9. 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.

  10. 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...

  11. 77 FR 2275 - Manufacturing Council

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-17

    ... 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...

  12. Out of bounds additive manufacturing

    SciTech Connect

    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.; Peter, William H.; Dehoff, Ryan R.

    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.

  13. 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…

  14. 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,…

  15. 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.

  16. Precise Measurement for Manufacturing

    NASA Technical Reports Server (NTRS)

    2003-01-01

    A metrology instrument known as PhaseCam supports a wide range of applications, from testing large optics to controlling factory production processes. This dynamic interferometer system enables precise measurement of three-dimensional surfaces in the manufacturing industry, delivering speed and high-resolution accuracy in even the most challenging environments.Compact and reliable, PhaseCam enables users to make interferometric measurements right on the factory floor. The system can be configured for many different applications, including mirror phasing, vacuum/cryogenic testing, motion/modal analysis, and flow visualization.

  17. Evaporation in space manufacturing

    NASA Technical Reports Server (NTRS)

    Li, C. H.

    1974-01-01

    'Normal evaporation' equations for predicting the compositional changes with time and temperature have been developed and correlated with actual experimental data. An evaporative congruent temperature is defined and used to explain, predict, or plan space experiments on anomalous constitutional melting (on cooling) or solidification (on heating). Uneven evaporation causes reactive jetting forces capable of initiating new convection currents, nongravitational accelerations, surface vibrations, or other disturbances. Applications of evaporation to space manufacturing are described concerning evaporative purification, surface cooling, specimen selection, particles splitting, freezing data interpretation, material loss and dimensional control, and surface contamination or compositional changes.

  18. 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.

  19. 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.

  20. Proteomic study of human bronchial epithelial cells exposed to SiC nanoparticles

    NASA Astrophysics Data System (ADS)

    Tokarski, Caroline; Hirano, Seishiro; Rolando, Christian

    2011-07-01

    The presented work proposes an optimized methodology for the study of cell exposure to nanomaterials at protein level. The study was investigated on proteins extracted from human bronchial epithelial cells exposed and non-exposed to silicon carbide nanoparticles (SiC). The analytical strategy was based on high resolution measurement using Fourier transform mass spectrometer 9.4 T. The methodology proposed succeeds in identifying over 300 proteins; most of the identified proteins are present in both exposed and non exposed cells to SiC nanoparticles. More interestingly, cytokines as Macrophage migration inhibitory factor protein could be identified only in the cells exposed to SiC nanoparticles indicating cell inflammatory response.

  1. 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.

  2. Femtosecond laser modification aiming at the enhancement of local electric conductivities in SiC

    NASA Astrophysics Data System (ADS)

    Deki, Manato; Yamamoto, Minoru; Ito, Takuto; Tomita, Takuro; Matsuo, Shigeki; Hashimoto, Shuichi; Kitada, Takahiro; Isu, Toshiro; Onoda, Shinobu; Ohshima, Takeshi

    2011-12-01

    Femtosecond laser modification was used to enhance the local electrical conductivities in silicon carbide (SiC). Current-voltage (I-V) characteristics of the laser-modified regions were measured between the ion-implanted metal contacts on SiC. The currents of modified lines increased more than six orders of magnitude when compared with those of the non-irradiated SiC. The current sharply increased in the fluence range from 3.3 to 6.7 J/cm2. From the I-V characteristics and scanning elctroron microscope (SEM) observations, we conclude that the modification related to the formation of the classical laser-induced periodic structures causes the drastic increase of electrical conductivities.

  3. SiC polytypes process affected by Ge predeposition on Si(111) substrates

    NASA Astrophysics Data System (ADS)

    Nader, Richard; Moussaed, Elie; Kazan, Michel; Pezoldt, Joerg; Masri, Pierre

    2008-08-01

    Structural and optical measurements were performed on silicon carbide (SiC) samples containing several polytypes. The SiC samples investigated were grown on (111) Si substrates by solid source molecular beam epitaxy (SSMBE). Several quantities of Ge were predeposited before the growth procedure. The influence of Ge on the SiC polytypes formation was studied by X-Ray, FTIR and μ-Raman characterizations methods. The spectra of the samples with less than one Ge monolayer exhibit a mixture of 2H, 15R and 3C-SiC polytypes. This mixture is due to the mismatch between the heterostructure layers. We propose that the Ge predeposition in the heterostructure can be used to stabilize and unify the polytypes formation.

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

    PubMed Central

    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. PMID:24448069

  5. 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.

  6. Investigation of Thermal Properties of SiC Ceramics Containing Carbon Nanostructures by Photothermal Measurements

    NASA Astrophysics Data System (ADS)

    Kaźmierczak-Bałata, Anna; Mazur, Jacek; Bodzenta, Jerzy; Trefon-Radziejewska, Dominika; Drewniak, Łukasz

    2014-12-01

    This work presents an analysis of the influence of graphene reinforcement on properties of silicon carbide composites. Samples were prepared by a spark plasma sintering method. The density and hardness were obtained in the preliminary experiments. The thermal diffusivity was determined by the continuous wave photothermal technique with detection based on infrared radiometry. The thermal diffusivity is in the range of (0.48 to 0.57) cms for samples prepared from granulated SiC and in the range of (0.56 to 0.71) cms for samples prepared from SiC powder. Thermal properties are correlated with the density of SiC ceramics. The thermal diffusivity of samples with a higher density is lower in comparison to samples with a lower density.

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

    NASA Astrophysics Data System (ADS)

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

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

  8. 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.

  9. Controlling corrosion of WC-Co by using an amorphous SiC coating

    NASA Astrophysics Data System (ADS)

    Yeo, Sunmog; Park, Jae-Won

    2012-07-01

    A reduction of WC-Co corrosion was investigated using a potentiodynamic electrochemical test. SiC layers with different thicknesses from 1 to 5 µm were coated on WC-Co by using an ionbeam mixing process. I-V characterization measurements were performed on the SiC-coated WCCo at different conditions: NaOH and H2SO4 solutions and room temperature and 70 °C. The I-V measurements demonstrated that the corrosion current density decreased and the corrosion potential increased as the SiC coating layers got thicker. This finding is evidence that SiC coating layers contact well electrically to WC-Co surfaces and enhance the corrosion properties of WC-Co.

  10. 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.

  11. 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

  12. Men Working on Mock-Up of S-IC Thrust Structure

    NASA Technical Reports Server (NTRS)

    1963-01-01

    This photograph depicts Marshall Space Flight Center employees, James Reagin, machinist (top); Floyd McGinnis, machinist; and Ernest Davis, experimental test mechanic (foreground), working on a mock up of the S-IC thrust structure. The S-IC stage is the first stage, or booster, of the 364-foot long Saturn V rocket that ultimately took astronauts to the Moon. The S-IC stage, burned over 15 tons of propellant per second during its 2.5 minutes of operation to take the vehicle to a height of about 36 miles and to a speed of about 6,000 miles per hour. The stage was 138 feet long and 33 feet in diameter. Operating at maximum power, all five of the engines produced 7,500,000 pounds of thrust.

  13. ToF-MEIS stopping measurements in thin SiC films

    NASA Astrophysics Data System (ADS)

    Linnarsson, M. K.; Khartsev, S.; Primetzhofer, D.; Possnert, G.; Hallén, A.

    2014-08-01

    Electronic stopping in thin, amorphous, SiC films has been studied by time-of-flight medium energy ion scattering and conventional Rutherford backscattering spectrometry. Amorphous SiC films (8, 21 and 36 nm) were prepared by laser ablation using a single crystalline silicon carbide target. Two kinds of substrate films, one with a lower atomic mass (carbon) and one with higher atomic mass (iridium) compared to silicon has been used. Monte Carlo simulations have been used to evaluate electronic stopping from the shift in energy for the signal scattered from Ir with and without SiC. The two kinds of samples are used to illustrate the strength and challenges for ToF-MEIS compared to conventional RBS.

  14. Boron and nitrogen impurities in SiC nanoribbons: an ab initio investigation

    NASA Astrophysics Data System (ADS)

    Costa, C. D.; Morbec, J. M.

    2011-05-01

    Using ab initio calculations based on density-functional theory we have performed a theoretical investigation of substitutional boron and nitrogen impurities in silicon carbide (SiC) nanoribbons. We have considered hydrogen terminated SiC ribbons with zigzag and armchair edges. In both systems we verify that the boron and nitrogen atoms energetically prefer to be localized at the edges of the nanoribbons. However, while boron preferentially substitutes a silicon atom, nitrogen prefers to occupy a carbon site. In addition, our electronic-structure calculations indicate that (i) substitutional boron and nitrogen impurities do not affect the semiconducting character of the armchair SiC nanoribbons, and (ii) the half-metallic behavior of the zigzag nanoribbons is maintained in the presence of substitutional boron impurities. In contrast, nitrogen atoms occupying edge carbon sites transform half-metallic zigzag nanoribbons into metallic systems.

  15. Boron and nitrogen impurities in SiC nanoribbons: an ab initio investigation.

    PubMed

    Costa, C D; Morbec, J M

    2011-05-25

    Using ab initio calculations based on density-functional theory we have performed a theoretical investigation of substitutional boron and nitrogen impurities in silicon carbide (SiC) nanoribbons. We have considered hydrogen terminated SiC ribbons with zigzag and armchair edges. In both systems we verify that the boron and nitrogen atoms energetically prefer to be localized at the edges of the nanoribbons. However, while boron preferentially substitutes a silicon atom, nitrogen prefers to occupy a carbon site. In addition, our electronic-structure calculations indicate that (i) substitutional boron and nitrogen impurities do not affect the semiconducting character of the armchair SiC nanoribbons, and (ii) the half-metallic behavior of the zigzag nanoribbons is maintained in the presence of substitutional boron impurities. In contrast, nitrogen atoms occupying edge carbon sites transform half-metallic zigzag nanoribbons into metallic systems. PMID:21540516

  16. Positron diffraction study of SiC(0 0 0 1) surface

    NASA Astrophysics Data System (ADS)

    Kawasuso, A.; Maekawa, M.; Yoshikawa, M.; Ichimiya, A.

    2005-05-01

    Surface structures of 6H SiC(0 0 0 1) after heat treatment in a UHV has been studied using reflection high-energy positron diffraction (RHEPD). After heat treatment at 900 °C, a typical interference effect of positron waves due to Si adatoms appears in the total reflection region of the rocking curve. The further heat treatment at 1100 °C results in surface graphitization. The rocking curve is well reproduced by theoretical calculation assuming the graphite monolayer on SiC substrate. The interlayer distance is fairly large (2.5-3.2 Å), which is comparable to that in the graphite monocrystal suggesting that the weak binding of the graphite monolayer to the SiC surface by the van der Waals force.

  17. 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.

  18. Liquid-Solid Reactions and Microstructure of SiC-5120 Steel Composite Brake Material

    NASA Astrophysics Data System (ADS)

    Li, Jingyang; Ru, Hongqiang; Yang, Hong; Liu, Yinong

    2012-02-01

    This study investigated solid-liquid reactions between SiC preform and molten 5120 steel during infiltration casting of SiC-steel composite for heavy duty brake applications. The reactions between SiC and the molten steel resulted in the formation of three distinctive microstructural regions, including the α 1-Fe(Si)-graphite region, the pearlite region, and the ferrite-pearlite region. The phase structures were identified by means of X-ray diffraction, X-ray energy dispersive spectrometry, and metallographic examination. These observations reveal that SiC was decomposed via reactions with the molten steel. The diffusion of C and Si into the molten steel and selective solidification led to the formation of different regions with varied C and Si contents. The microstructures produced during the solidification sequence are identified to be the ferrite-pearlite → pearlite → α 1-Fe(Si) + graphite and cementite.

  19. 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.

  20. 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.

  1. 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.

  2. Scalable nanostructuring on polymer by a SiC stamp: optical and wetting effects

    NASA Astrophysics Data System (ADS)

    Argyraki, Aikaterini; Lu, Weifang; Petersen, Paul M.; Ou, Haiyan

    2015-08-01

    A method for fabricating scalable antireflective nanostructures on polymer surfaces (polycarbonate) is demonstrated. The transition from small scale fabrication of nanostructures to a scalable replication technique can be quite challenging. In this work, an area per print corresponding to a 2-inch-wafer, is presented. The initial nanopatterning is performed on SiC in a 2-step process. Depending on the nanostructures the transmission of the SiC surface can be increased or suppressed (average height of nanostructures ~300nm and ~600nm, respectively) while the reflectance is decreased, when compared to a bare surface. The reflectance of SiC can be reduced down to 0.5% when the ~600nm nanostructures are applied on the surface (bare surface reflectance 25%). The texture of the green SiC color is changed when the different nanostructures are apparent. The ~600nm SiC nanostructures are replicated on polymer through a process flow that involved hot embossing and galvanization. The resulted polymer structures have similar average height and exhibit more rounded edges than the initial SiC nanostructures. The polymer surface becomes antireflective and hydrophobic after nanostructuring. The contact angle changes from 68 (bare) to 123 (nanostructured) degrees. The optical effect on the polymer surface can be maximized by applying a thin aluminum (Al) layer coating on the nanostructures (bare polymer reflectance 11%, nanostructured polymer reflectance 5%, Al coated nanostructured polymer reflectance 3%). The optical measurements were performed with an integrating sphere and a spectrometer. The contact angles were measured with a drop shape analyzer. The nanostructures were characterized with scanning electron microscopy.

  3. Magnet cable manufacturing

    SciTech Connect

    Royet, J.

    1990-10-01

    The cable is the heart of a superconducting accelerator magnet. Since the initial development of the Rutherford Cable more than twenty years ago, many improvements in manufacturing techniques have increased the current carrying capacity. When the Tevatron cable was specified fifteen years ago the current carrying capacity was 1800 A/mm{sup 2} at a field of 5.3T. During the intervening years it has been increased to 3000 A/mm{sup 2}. These improvements were due to refinements in the fabrication of the strands and the formation of the cable from the strands. The metallurgists were able to impart significant gains in performance by improving the homogeneity of the conductor. The engineers and technicians who designed and built the modern cabling machines made an enormous contribution by significantly reducing the degradation of wire performance that occurs when the wire was cabled. The fact that these gains were made while increasing the speed of cabling is one of the technological advances that made accelerators like the SSC possible. This article describes the cabling machines that were built to manufacture the cable for the full scale SSC prototype magnets and the low beta quadrupoles for the Fermilab Tevatron. This article also presents a compendium of the knowledge that was gained in the struggle to make high performance cable to exacting dimensional standards and at the throughput needed for the SSC. The material is an important part of the technology transfer from the Department of energy Laboratories to Industry.

  4. 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.

  5. OPINION: Safe exponential manufacturing

    NASA Astrophysics Data System (ADS)

    Phoenix, Chris; Drexler, Eric

    2004-08-01

    In 1959, Richard Feynman pointed out that nanometre-scale machines could be built and operated, and that the precision inherent in molecular construction would make it easy to build multiple identical copies. This raised the possibility of exponential manufacturing, in which production systems could rapidly and cheaply increase their productive capacity, which in turn suggested the possibility of destructive runaway self-replication. Early proposals for artificial nanomachinery focused on small self-replicating machines, discussing their potential productivity and their potential destructiveness if abused. In the light of controversy regarding scenarios based on runaway replication (so-called 'grey goo'), a review of current thinking regarding nanotechnology-based manufacturing is in order. Nanotechnology-based fabrication can be thoroughly non-biological and inherently safe: such systems need have no ability to move about, use natural resources, or undergo incremental mutation. Moreover, self-replication is unnecessary: the development and use of highly productive systems of nanomachinery (nanofactories) need not involve the construction of autonomous self-replicating nanomachines. Accordingly, the construction of anything resembling a dangerous self-replicating nanomachine can and should be prohibited. Although advanced nanotechnologies could (with great difficulty and little incentive) be used to build such devices, other concerns present greater problems. Since weapon systems will be both easier to build and more likely to draw investment, the potential for dangerous systems is best considered in the context of military competition and arms control.

  6. 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.

  7. Investigation of thermal properties of SiC using photothermal method

    NASA Astrophysics Data System (ADS)

    Bodzenta, J.; Kaźmierczak-Bałata, A.

    2006-11-01

    A photothermal measurements were carried out for a few samples of silicon carbide (SiC). Thickness of the SiC plates was about 1 mm. Samples were highly inhomogeneous and differed in crystal structure. Experimental setup was typical for such investigation. The photothermal signal was measured using mirage detection. Experiment was performed for two configurations: probing beam was running over and under the sample surface. Analysis of experimental data was done according to one dimensional model of thermal wave propagation in multilayer system. Thermal diffusivities and optical absorption coefficients of the samples were determined based on multiparameter fitting procedure.

  8. Quasi-Freestanding multilayer graphene films on the carbon face of SiC

    SciTech Connect

    Siegel, D. A.; Hwang, C. G.; Fedorov, A. V.; Lanzara, A.

    2010-06-30

    The electronic band structure of as-grown and doped graphene grown on the carbon face of SiC is studied by high-resolution angle-resolved photoemission spectroscopy, where we observe both rotations between adjacent layers and AB-stacking. The band structure of quasi-freestanding AB-bilayers is directly compared with bilayer graphene grown on the Si-face of SiC to study the impact of the substrate on the electronic properties of epitaxial graphene. Our results show that the C-face films are nearly freestanding from an electronic point of view, due to the rotations between graphene layers.

  9. Elevated temperature mechanical behavior of monolithic and SiC whisker-reinforced silicon nitrides

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Choi, Sung R.; Sanders, William A.; Fox, Dennis S.

    1991-01-01

    The mechanical behavior of a 30 volume percent SiC whisker reinforced silicon nitride and a similar monolithic silicon nitride were measured at several temperatures. Measurements included strength, fracture toughness, crack growth resistance, dynamic fatigue susceptibility, post oxidation strength, and creep rate. Strength controlling defects were determined with fractographic analysis. The addition of SiC whiskers to silicon nitride did not substantially improve the strength, fracture toughness, or crack growth resistance. However, the fatigue resistance, post oxidation strength, and creep resistance were diminished by the whisker addition.

  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. 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.

  12. 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.

  13. Investigation of compaction and sintering behavior of SiC powder after ultra-fine treatment.

    PubMed

    Guo, Xing-Zhong; Yang, Hui

    2004-08-01

    Silicon carbide ceramics were prepared with SiC powder treated by the fluidized bed opposed jet mill as raw materials, and the effects of the ultra-fine treatment mechanism on the compaction and sintering behavior of SiC ceramics were investigated. The results showed that the compacts had higher density and microstructure homogeneity when the sintering temperature of the compact was decreased; and that the surface microstructure, densification and mechanical properties of the sintered body could be ameliorated obviously. PMID:15236481

  14. 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.

  15. 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.

  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. Spallation recoil II: Xenon evidence for young SiC grains

    NASA Astrophysics Data System (ADS)

    Ott, U.; Altmaier, M.; Herpers, U.; Kuhnhenn, J.; Merchel, S.; Michel, R.; Mohapatra, R. K.

    2005-11-01

    We have determined the recoil range of spallation xenon produced by irradiation of Ba glass targets with ˜1190 and ˜268 MeV protons, using a catcher technique, where spallation products are measured in target and catcher foils. The inferred range for 126Xe produced in silicon carbide is ˜0.19 μm, which implies retention of ˜70% for 126Xe produced in "typical" presolar silicon carbide grains of 1 μm size. Recoil loss of spallation xenon poses a significantly smaller problem than loss of the spallation neon from SiC grains. Ranges differ for the various Xe isotopes and scale approximately linearly as function of the mass difference between the target element, Ba, and the product. As a consequence, SiC grains of various sizes will have differences in spallation Xe composition. In an additional experiment at ˜66 MeV, where the recoil ranges of 22Na and 127Xe produced on Ba glass were determined using γ-spectrometry, we found no evidence for recoil ranges being systematically different at this lower energy. We have used the new data to put constraints on the possible presolar age of the SiC grains analyzed for Xe by Lewis et al. (1994). Uncertainties in the composition of the approximately normal Xe component in SiC (Xe-N) constitute the most serious problem in determining an age, surpassing remaining uncertainties in Xe retention and production rate. A possible interpretation is that spallation contributions are negligible and that trapped 124Xe/126Xe is ˜5% lower in Xe-N than in Q-Xe. But also for other reasonable assumptions for the 124Xe/126Xe ratio in Xe-N (e.g., as in Q-Xe), inferred exposure ages are considerably shorter than theoretically expected lifetimes for interstellar grains. A short presolar age is in line with observations by others (appearance, grain size distribution) that indicate little processing in the interstellar medium (ISM) of surviving (crystalline) SiC. This may be due to amorphization of SiC in the ISM on a much shorter time scale

  18. Fabrication of SiC Blue LEDs Using Off-Oriented Substrates

    NASA Astrophysics Data System (ADS)

    Matsushita, Yasuhiko; Nakata, Toshitake; Uetani, Takahiro; Yamaguchi, Takao; Niina, Tatsuhiko

    1990-02-01

    SiC blue LEDs were fabricated by the dipping technique, using 6H-SiC substrates whose (000\\bar{1})C face varied toward the [11\\bar{2}0] or [10\\bar{1}0] direction. The surface morphology of the epitaxial layers on the off-oriented substrates was a striped pattern perpendicular to the off-axis direction. By using off-oriented substrates, the degradation of SiC blue LEDs can be greatly reduced. High-efficiency blue LEDs (12 mcd at 20 mA) were fabricated by increasing the amount of Al dopant in the n-type layer.

  19. 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

  20. Fuel Tank Assembly for 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 supported with the aid of a C frame on the transporter was readied to be transported to the Marshall Space Flight Center, building 4705. The fuel tank carried kerosene (RP-1) as its fuel. The S-IC stage utilized five F-1 engines that used kerosene and liquid oxygen as propellant and each engine provided 1,500,000 pounds of thrust. This stage lifted the entire vehicle and Apollo spacecraft from the launch pad.

  1. SICS--a cost effective alternative to phacoemulsification for developing countries in Nepal.

    PubMed

    Nowak, Rafał

    2008-01-01

    Millions of people worldwide are blind from mature cataracts. The developing countries cannot afford expensive modern technologies to treat these cases. A cost effective, fast, machine independent procedure is necessary The purpose of this study is to describe such a technique, little known in Poland--manual small incision cataract surgery (SICS), where the whole nucleus is removed through a self-sealing sclero-corneal tunnel. Within the last several years SICS has become the main way of cataract removal in underserved populations of Asia, with Nepal as an example. Thus, the developing countries have developed a cost effective alternative to phacoemulsification with a very good clinical outcome. PMID:18669094

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

    SciTech Connect

    Tredway, W.K.

    1996-12-31

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

  3. Identification of luminescent surface defect in SiC quantum dots

    NASA Astrophysics Data System (ADS)

    Dai, Dejian; Guo, Xiaoxiao; Fan, Jiyang

    2015-02-01

    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(OH) → π*(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.

  4. Homogenization of the melting depth in SiC on Si structures during flash lamp irradiation

    NASA Astrophysics Data System (ADS)

    Voelskow, Matthias; Skorupa, Wolfgang; Smith, Mark P.; McMahon, Richard A.

    2005-12-01

    Flash lamp annealing of heteroepitaxial silicon carbide on silicon structures involves melting the silicon below the SiC layer but the faceted nature of the liquid-solid interface leads to unacceptable surface roughness. This letter describes a method of controlling melting by using a melt stop created at a controlled depth below the Si /SiC interface by implanting a high dose of carbon, which significantly increases the silicon melting temperature. Results confirm the effectiveness of this approach for increasing surface uniformity, making liquid phase processing compatible with standard device fabrication techniques.

  5. 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

  6. Moissanite (SiC) from kimberlites: Polytypes, trace elements, inclusions and speculations on origin

    NASA Astrophysics Data System (ADS)

    Shiryaev, A. A.; Griffin, W. L.; Stoyanov, E.

    2011-03-01

    An extensive collection of moissanite (SiC) grains from the Mir, Aikhal and Udachnaya kimberlite pipes of Yakutia has been characterized in terms of structural perfection, defects and the major- and trace-element chemistry of SiC and its included phases. The natural grains are clearly distinct from synthetic SiC produced by various methods. Most of the natural SiC grains are 6H and 15R polytypes. Some of the grains (< 10%) show extremely complex Raman spectra indicating strongly disordered structures. Some grains also show zoning in impurities, C-isotope composition and cathodoluminescence brightness. Inclusions are heterogeneously distributed within the natural SiC; their size varies from a few nanometers to hundreds of microns. The most abundant inclusions in SiC are Si metal and iron silicide (FeSi 2); a Si-C-O phase with stoichiometry close to Si 4(C,O) 7 probably is related to the silicon oxycarbides. FeSi 2 commonly appears to have exsolved from Si metal; in some cases Ti metal then has exsolved from FeSi 2 to form symplectites. Trace elements are strongly concentrated in the inclusions of FeSi 2 and Si 4(C,O) 7. The trace-element patterns of these phases are generally similar in the different kimberlites, but there are some consistent minor differences between localities. The trace-element patterns of FeSi 2 and Si 4(C,O) 7 are strongly enriched in LREE/HREE and are broadly similar to the patterns of kimberlites, carbonatites and some diamond-forming fluids. However, extreme negative anomalies in Eu (and Sm) suggest highly reducing conditions. Yb also shows strong negative anomalies in FeSi 2 from all three localities, and in Si 4(C,O) 7 from Aikhal and Mir, but not in those from Udachnaya. Trace-element chemistry and the nature of the inclusions provide a reliable basis for distinguishing natural and synthetic SiC. Textural and chemical features and the presence of oxidation products (Si 4(C,O) 7 and SiO 2) suggest that moissanite grew at high temperatures

  7. 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

  8. 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.

  9. Development of SiC ultra light mirror for large space telescope and for extremely huge ground based telescope

    NASA Astrophysics Data System (ADS)

    Ebizuka, Noboru; Dai, Yutang; Eto, Hiroaki; Lin, Weimin; Ebisuzaki, Toshikazu; Omori, Hitoshi; Handa, Thoshikazu; Takami, Hideki; Takahashi, Yoshiyuki

    2003-02-01

    Ultra lightweight mirrors of silicon carbide (SiC) are used for a large number of space telescopes, and SiC is also candidate as hopeful material for segmented mirrors of the next generation ground based telescopes from 20 to 100 m in diameter. However, an SiC mirror is difficult to shape because the material is very hard and brittle. We are developing an SiC mirror by means of an ultra-precision rotary grinding machine (800 mm in diameter) and the ELID (ELectrolytic In-process Dressing) grinding method. The method is suitable for fabrications of very hard materials, such as crystalline silicon and sapphire, ceramics, glasses, hard metals and so on. In this study, we present results of test fabrication for the SiC mirrors by means of ELID grinding method and evaluations of the profile deformation of the lightweight mirrors by using FEM simulation method.

  10. 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.

  11. Study of properties of SiC layer in TRISO coated particles grown using different alkyl-silicon compounds

    NASA Astrophysics Data System (ADS)

    Prakash, Jyoti; Ghosh, Sunil; Venugopalan, Ramani; Sathiyamoorthy, D.

    2013-06-01

    The silicon carbide (SiC) layer used for the formation of Tri-isostatic (TRISO) coated fuel particles is normally produced at high temperatures via fluidized bed chemical vapor deposition from methyltrichlorosilane (MTS) in a hydrogen environment. In this work, we show the deposition of uniform SiC layers using different organosilicon precursors such as MTS and hexamethyldisilane (HMDS) via spouted bed chemical vapor deposition. From the X-ray diffraction pattern it could be inferred that the SiC deposits obtained through different precursors have the β-SiC phase. The microstructure and mechanical properties of the fabricated SiC coating were studied. The hardness and fracture toughness of the fabricated SiC coatings using MTS and HMDS were nearly the same and close to the theoretical value for pure silicon carbide.

  12. 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.

  13. 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

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

    SciTech Connect

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

    1995-10-01

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

  15. 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.

  16. 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...

  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. 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.

  20. 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.