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Sample records for sylramic type sic

  1. Processing and Structural Advantages of the Sylramic-iBN SiC Fiber for SiC/SiC Components

    Science.gov (United States)

    Yun, H. M.; Dicarlo, J. A.; Bhatt, R. T.; Hurst, J. B.

    2008-01-01

    The successful high-temperature application of complex-shaped SiC/SiC components will depend on achieving as high a fraction of the as-produced fiber strength as possible during component fabrication and service. Key issues center on a variety of component architecture, processing, and service-related factors that can reduce fiber strength, such as fiber-fiber abrasion during architecture shaping, surface chemical attack during interphase deposition and service, and intrinsic flaw growth during high-temperature matrix formation and composite creep. The objective of this paper is to show that the NASA-developed Sylramic-iBN SiC fiber minimizes many of these issues for state-of-the-art melt-infiltrated (MI) SiC/BN/SiC composites. To accomplish this, data from various mechanical tests are presented that compare how different high performance SiC fiber types retain strength during formation of complex architectures, during processing of BN interphases and MI matrices, and during simulated composite service at high temperatures.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    DiCarlo, James A.; Yun, Hee Mann

    2002-01-01

    Sylramic-iBN fiber is a new type of small-diameter (10-mm) SiC fiber that was developed at the NASA Glenn Research Center and was recently given an R&D 100 Award for 2001. It is produced by subjecting commercially available Sylramic (Dow Corning, Midland, MI) SiC fibers, fabrics, or preforms to a specially designed high-temperature treatment in a controlled nitrogen environment for a specific time. It can be used in a variety of applications, but it currently has the greatest advantage as a reinforcement for SiC/SiC ceramic composites that are targeted for long-term structural applications at temperatures higher than the capability of metallic superalloys. The commercial Sylramic SiC fiber, which is the precursor for the Sylramic-iBN fiber, is produced by Dow Corning, Midland, Michigan. It is derived from polymers at low temperatures and then pyrolyzed and sintered at high temperatures using boron-containing sintering aids (ref. 1). The sintering process results in very strong fibers (>3 GPa) that are dense, oxygen-free, and nearly stoichiometric. They also display an optimum grain size that is beneficial for high tensile strength, good creep resistance, and good thermal conductivity (ref. 2). The NASA-developed treatment allows the excess boron in the bulk to diffuse to the fiber surface where it reacts with nitrogen to form an in situ boron nitride (BN) coating on the fiber surface (thus the product name of Sylramic-iBN fiber). The removal of boron from the fiber bulk allows the retention of high tensile strength while significantly improving creep resistance and electrical conductivity, and probably thermal conductivity since the grains are slightly larger and the grain boundaries cleaner (ref. 2). Also, as shown in the graph, these improvements allow the fiber to display the best rupture strength at high temperatures in air for any available SiC fiber. In addition, for CMC applications under oxidizing conditions, the formation of an in situ BN surface layer

  4. Preparation of SiC Compacts by the Rapid Proto typing Machine

    International Nuclear Information System (INIS)

    Abdelrahman, A.A.M.; Ahmed, A.Z.; Elmasry, M.A.A.

    2008-01-01

    The preparation of ceramic green bodies from powders by the rapid proto typing is a promising technique. In this work SiC green bodies were prepared from black SiC powder mixed with 10 wt % organic binder namely Ave be SP G20 starch. Different liquid binders were investigated and were successful in producing strong green bodies such as NH 4 OH in the ph range 9-10 or 1 % HCl solution in water and or a mixture of 1% NH 4 Cl and NH 4 OH in the ph range of 8.5 to 9. The green bodies were then preheated at 200 degree C to eliminate the starch by thermal decomposition. After that these parts were infiltrated using molten silicon at 1450 degree C in Argon atmosphere. Unfortunately it was impossible to infiltrate the green bodies using liquid silicon. Another technique was followed which is dipping of the green bodies in liquid silicon. This method was successful. The densities of the green and dipped bodies were determined and they were examined under the metallo graph and SEM. It was found that no SiC dissolved in the silicon after dipping. This was concluded from the presence of sharp corners of SiC grains

  5. Ohmic contact on n- and p-type ion-implanted 4H-SiC with low-temperature metallization process for SiC MOSFETs

    Science.gov (United States)

    Shimizu, Haruka; Shima, Akio; Shimamoto, Yasuhiro; Iwamuro, Noriyuki

    2017-04-01

    The ohmic contact on n- and p-type SiC regions with the same contact metal is a key process in regard to creating high-performance MOSFETs and insulated gate bipolar transistors (IGBTs). The dependence of the contact resistance on n- and p-type SiC regions on ion species, dose, and implantation temperature was investigated. The results of such an investigation revealed that the amorphization of the SiC surface and the generation of 3C-SiC produce a low contact resistance without the need for a high-temperature metallization process. The contact resistances of 2.1 × 10-6 Ω cm2 on the n-type SiC region and 1.3 × 10-3 Ω cm2 on the p-type SiC region were obtained with high-dose ion implantation at room temperature on the n-type SiC region, high-dose ion implantation at high temperature on the p-type SiC region, and a titanium-based contact electrode. A SiC MOSFET was fabricated with the low-temperature ohmic contact process. The positive-bias gate leakage current markedly increased. It can be deduced that high-dose ion implantation at room temperature on the n-type SiC region degrades surface roughness on the N+ source region.

  6. The Benefits of SiC MOSFETs in a T-Type Inverter for Grid-Tie Applications

    DEFF Research Database (Denmark)

    Anthon, Alexander; Zhang, Zhe; Andersen, Michael A. E.

    2016-01-01

    at the expense of increased switching losses since these outer switches must now block the full DC link voltage. Silicon Carbide (SiC) MOSFET devices potentially offer substantial advantage in this context with their lower switching losses, but the benefit of replacing all switching devices in a T-Type inverter...... measurements to precisely compare semiconductor losses for these two alternatives for a T-Type inverter operating at or near unity power factor. The results show that replacing only the DC bus connection switches with SiC devices significantly reduces the semiconductor losses, allowing either the converter...... power level or the switching frequency to be significantly increased for the same device losses. Hence the use of SiC MOSFETS for T-Type inverters can be seen to be an attractive and potentially cost effective alternative, since only two switching devices per phase leg need to be upgraded....

  7. A new type of white light-emitting diode light source basing on fluorescent SiC

    DEFF Research Database (Denmark)

    Ou, Haiyan; Ou, Yiyu; Lu, Weifang

    Most of the commercial white light-emitting diode (LED) light sources are made from phosphor coated blue-emitting gallium nitride (GaN) chips. This type white LED light source always has tradeoff between luminous efficacy and color rendering index (CRI). Furthermore, yellow-emitting phosphor decays...... much faster than the semiconductor chip, so the white color will turn into bluish over the time. This paper will propose a new type white LED light source: using fluorescent silicon carbide (SiC) to take the place of phosphor. This new type LED has the following advantages: a) SiC is a wide bandgap...... semiconductor material , so it is stable; b) Fluorescent SiC has very wide emission spectrum, and it could generate white light with very high CRI; c) It is a better substrate than sapphire for the GaN growth in terms of lattice match and thermal conductivity. This paper will cover: the growth of fluorescent Si...

  8. Growth of thick p-type SiC epitaxial layers by halide chemical vapor deposition

    Science.gov (United States)

    Fanton, M. A.; Weiland, B. E.; Redwing, J. M.

    2008-08-01

    The halide chemical vapor deposition process for single-crystal SiC achieves growth rates over 200 μm/h at temperatures approaching 2000 °C. This work examines the conditions required to produce 80-100-μm-thick heavily p-type doped layers on 4H-SiC substrates by using boron trichloride and trimethylaluminum at high growth temperatures. Dopant incorporation as a function of the dopant concentration in the growth ambient was evaluated by secondary ion mass spectrometry (SIMS). The maximum Al and B concentrations achieved were 5×10 17 and 4×10 19 atoms/cm 3, respectively. Low Al incorporation efficiency was attributed to the high growth temperature and reaction of Al with Cl to form volatile chloride species. Aluminum incorporation was consistent with incorporation as a simple solid solution, while B incorporation exhibited a much stronger interaction with the SiC matrix. Aluminum incorporation was found to be an order of magnitude higher on the Si-face of the substrate, while B incorporation was essentially the same on both the Si-face and C-face. Aluminum incorporation was increased by a factor of five as the C/Si ratio increased from 0.42 to 0.86, while boron incorporation showed no sensitivity to the C/Si ratio. The B concentrations measured by SIMS were of the same magnitude as the net acceptor concentrations estimated from capacitance-voltage measurements, indicating a significant fraction of the B dopant was activated.

  9. Titanium isotopic compositions of rare presolar SiC grain types from the Murchison meteorite

    Science.gov (United States)

    Nguyen, Ann N.; Nittler, Larry R.; Alexander, Conel M. O'D.; Hoppe, Peter

    2018-01-01

    We report the Ti isotopic compositions of 8 mainstream, 22 Y, 9 Z, and 26 AB presolar SiC grains from two SiC-rich residues of the Murchison CM2 meteorite together with Si, C and some Mg-Al isotopic data for the same grains. Mainstream, Y and Z grains are believed to originate in asymptotic giant branch (AGB) stars of varying metallicities, but the stellar sources of AB grains are poorly understood. We find that the 46,47,49Ti/48Ti ratios are correlated with 29Si/28Si for all of the grain types, indicating that these ratios are mainly dominated by Galactic chemical evolution (GCE). The mainstream, Y and Z grains all show enrichments in 50Ti from neutron capture nucleosynthesis. However, AGB models predict smaller excesses in 50Ti (and 49Ti) than are observed in these grains. For Z grains and especially for Y grains, the enhancement of 50Ti is greater than the enhancement in 30Si, indicating that the 13C neutron source produced a greater total fluence of neutrons than the 22Ne source in the low metallicity parent AGB stars. The Z grains plot below the mainstream correlation lines at more 48Ti- and 28Si-rich compositions in plots of 46,47,49Ti/48Ti vs. 29Si/28Si. On the other hand, the Y grains plot close to the mainstream correlation line. This could imply that the Ti isotopes evolved non-linearly at metallicities below ∼1/3 solar. The AB grains in this study have Ti isotopic compositions that fall along correlation lines defined by the mainstream grains, suggesting origins in close to solar metallicity stars. However, these grains fall below the mainstream correlation lines in plots of 46,49,50Ti/48Ti vs. 29Si/28Si and do not show enhancements in 50Ti, indicating that their parent stars did not undergo significant s-process nucleosynthesis. These data support origins of AB grains in J-type C stars rather than born-again AGB stars that undergo s-process nucleosynthesis. AB grains that do not have 50Ti excesses may provide the best measure of Si and Ti isotope GCE

  10. Diodes of nanocrystalline SiC on n-/n+-type epitaxial crystalline 6H-SiC

    Science.gov (United States)

    Zheng, Junding; Wei, Wensheng; Zhang, Chunxi; He, Mingchang; Li, Chang

    2018-03-01

    The diodes of nanocrystalline SiC on epitaxial crystalline (n-/n+)6H-SiC wafers were investigated, where the (n+)6H-SiC layer was treated as cathode. For the first unit, a heavily boron doped SiC film as anode was directly deposited by plasma enhanced chemical vapor deposition method on the wafer. As to the second one, an intrinsic SiC film was fabricated to insert between the wafer and the SiC anode. The third one included the SiC anode, an intrinsic SiC layer and a lightly phosphorus doped SiC film besides the wafer. Nanocrystallization in the yielded films was illustrated by means of X-ray diffraction, transmission electronic microscope and Raman spectrum respectively. Current vs. voltage traces of the obtained devices were checked to show as rectifying behaviors of semiconductor diodes, the conduction mechanisms were studied. Reverse recovery current waveforms were detected to analyze the recovery performance. The nanocrystalline SiC films in base region of the fabricated diodes are demonstrated as local regions for lifetime control of minority carriers to improve the reverse recovery properties.

  11. J-type Carbon Stars: A Dominant Source of 14 N-rich Presolar SiC Grains of Type AB

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Nan; Stephan, Thomas; Boehnke, Patrick; Nittler, Larry R.; Alexander, Conel M. O’D.; Wang, Jianhua; Davis, Andrew M.; Trappitsch, Reto; Pellin, Michael J.

    2017-07-20

    We report Mo isotopic data of 27 new presolar SiC grains, including 12 N-14-rich AB (N-14/N-15 > 440, AB2) and 15 mainstream (MS) grains, and their correlated Sr and Ba isotope ratios when available. Direct comparison of the data for the MS grains, which came from low-mass asymptotic giant branch (AGB) stars with large s-process isotope enhancements, with the AB2 grain data demonstrates that AB2 grains show near-solar isotopic compositions and lack s-process enhancements. The near-normal Sr, Mo, and Ba isotopic compositions of AB2 grains clearly exclude born-again AGB stars, where the intermediate neutron-capture process (i-process) takes place, as their stellar source. On the other hand, low-mass CO novae and early R-and J-type carbon stars show C-13 and N-14 excesses but no s-process enhancements and are thus potential stellar sources of AB2 grains. Because both early R-type carbon stars and CO novae are rare objects, the abundant J-type carbon stars (10%-15% of all carbon stars) are thus likely to be a dominant source of AB2 grains.

  12. Flash X-ray cinematography analysis of dwell and penetration of small caliber projectiles with three types of SiC ceramics

    Directory of Open Access Journals (Sweden)

    Elmar Strassburger

    2016-06-01

    Full Text Available In order to improve the performance of ceramic composite armor it is essential to know the mechanisms during each phase of the projectile–target interaction and their influence on the penetration resistance. Since the view on the crater zone and the tip of a projectile penetrating a ceramic is rapidly getting obscured by damaged material, a flash X-ray technique has to be applied in order to visualize projectile penetration. For this purpose, usually several flash X-ray tubes are arranged around the target and the radiographs are recorded on film. At EMI a flash X-ray imaging method has been developed, which provides up to eight flash radiographs in one experiment. A multi-anode 450 kV flash X-ray tube is utilized with this method. The radiation transmitted through the target is then detected on a fluorescent screen. The fluorescent screen converts the radiograph into an image in the visible wavelength range, which is photographed by means of a high-speed camera. This technique has been applied to visualize and analyze the penetration of 7.62 mm AP projectiles into three different types of SiC ceramics. Two commercial SiC grades and MICASIC (Metal Infiltrated Carbon derived SiC, a C-SiSiC ceramic developed by DLR, have been studied. The influences, not only of the ceramic but also the backing material, on dwell time and projectile erosion have been studied. Penetration curves have been determined and their relevance to the ballistic resistance is discussed.

  13. Characterizing the Soldering Alloy Type In–Ag–Ti and the Study of Direct Soldering of SiC Ceramics and Copper

    Directory of Open Access Journals (Sweden)

    Roman Koleňák

    2018-04-01

    Full Text Available The aim of the research was to characterize the soldering alloy In–Ag–Ti type, and to study the direct soldering of SiC ceramics and copper. The In10Ag4Ti solder has a broad melting interval, which mainly depends on its silver content. The liquid point of the solder is 256.5 °C. The solder microstructure is composed of a matrix with solid solution (In, in which the phases of titanium (Ti3In4 and silver (AgIn2 are mainly segregated. The tensile strength of the solder is approximately 13 MPa. The strength of the solder increased with the addition of Ag and Ti. The solder bonds with SiC ceramics, owing to the interaction between active In metal and silicon infiltrated in the ceramics. XRD analysis has proven the interaction of titanium with ceramic material during the formation of the new minority phases of titanium silicide—SiTi and titanium carbide—C5Ti8. In and Ag also affect bond formation with the copper substrate. Two new phases were also observed in the bond interphase—(CuAg6In5 and (AgCuIn2. The average shear strength of a combined joint of SiC–Cu, fabricated with In10Ag4Ti solder, was 14.5 MPa. The In–Ag–Ti solder type studied possesses excellent solderability with several metallic and ceramic materials.

  14. Stellar Origin of 15N-rich Presolar SiC Grains of Type AB: Supernovae with Explosive Hydrogen Burning

    Science.gov (United States)

    Liu, Nan; Nittler, Larry R.; Pignatari, Marco; O'D. Alexander, Conel M.; Wang, Jianhua

    2017-06-01

    We report C, N, and Si isotopic data for 59 highly 13C-enriched presolar submicron- to micron-sized SiC grains from the Murchison meteorite, including eight putative nova grains (PNGs) and 29 15N-rich (14N/15N ≤ solar) AB grains, and their Mg-Al, S, and Ca-Ti isotope data when available. These 37 grains are enriched in 13C, 15N, and 26Al with the PNGs showing more extreme enhancements. The 15N-rich AB grains show systematically higher 26Al and 30Si excesses than the 14N-rich AB grains. Thus, we propose to divide the AB grains into groups 1 (14N/15N PNG and found 32S and/or 50Ti enhancements. Interestingly, one AB1 grain had the largest 32S and 50Ti excesses, strongly suggesting a neutron-capture nucleosynthetic origin of the 32S excess and thus the initial presence of radiogenic 32Si (t 1/2 = 153 years). More importantly, we found that the 15N and 26Al excesses of AB1 grains form a trend that extends to the region in the N-Al isotope plot occupied by C2 grains, strongly indicating a common stellar origin for both AB1 and C2 grains. Comparison of supernova models with the AB1 and C2 grain data indicates that these grains came from supernovae that experienced H ingestion into the He/C zones of their progenitors.

  15. Stellar Origin of 15N-rich Presolar SiC Grains of Type AB: Supernovae with Explosive Hydrogen Burning

    International Nuclear Information System (INIS)

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

    2017-01-01

    We report C, N, and Si isotopic data for 59 highly 13 C-enriched presolar submicron- to micron-sized SiC grains from the Murchison meteorite, including eight putative nova grains (PNGs) and 29 15 N-rich ( 14 N/ 15 N ≤ solar) AB grains, and their Mg–Al, S, and Ca–Ti isotope data when available. These 37 grains are enriched in 13 C, 15 N, and 26 Al with the PNGs showing more extreme enhancements. The 15 N-rich AB grains show systematically higher 26 Al and 30 Si excesses than the 14 N-rich AB grains. Thus, we propose to divide the AB grains into groups 1 ( 14 N/ 15 N < solar) and 2 ( 14 N/ 15 N ≥ solar). For the first time, we have obtained both S and Ti isotopic data for five AB1 grains and one PNG and found 32 S and/or 50 Ti enhancements. Interestingly, one AB1 grain had the largest 32 S and 50 Ti excesses, strongly suggesting a neutron-capture nucleosynthetic origin of the 32 S excess and thus the initial presence of radiogenic 32 Si ( t 1/2 = 153 years). More importantly, we found that the 15 N and 26 Al excesses of AB1 grains form a trend that extends to the region in the N–Al isotope plot occupied by C2 grains, strongly indicating a common stellar origin for both AB1 and C2 grains. Comparison of supernova models with the AB1 and C2 grain data indicates that these grains came from supernovae that experienced H ingestion into the He/C zones of their progenitors.

  16. Radiation hardness of n-type SiC Schottky barrier diodes irradiated with MeV He ion microbeam

    Energy Technology Data Exchange (ETDEWEB)

    Pastuović, Željko, E-mail: zkp@ansto.gov.au [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Capan, Ivana [Material Physics Division, Institute Rudjer Boskovic, PO Box 180, 10000 Zagreb (Croatia); Cohen, David D. [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Forneris, Jacopo [Physics Department and NIS Excellence Centre, University of Torino, via P. Giuria 1, 10125 Torino (Italy); Iwamoto, Naoya; Ohshima, Takeshi [Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Siegele, Rainer [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Hoshino, Norihiro; Tsuchida, Hidekazu [Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka, Kanagawa 240-0196 (Japan)

    2015-04-01

    We studied the radiation hardness of 4H-SiC Schottky barrier diodes (SBD) for the light ion detection and spectroscopy in harsh radiation environments. n-Type SBD prepared on nitrogen-doped (∼4 × 10{sup 14} cm{sup −3}) epitaxial grown 4H-SiC thin wafers have been irradiated by a raster scanning alpha particle microbeam (2 and 4 MeV He{sup 2+} ions separately) in order to create patterned damage structures at different depths within a sensitive volume of tested diodes. Deep Level Transient Spectroscopy (DLTS) analysis revealed the formation of two deep electron traps in the irradiated and not thermally treated 4H-SiC within the ion implantation range (E1 and E2). The E2 state resembles the well-known Z{sub 1/2} center, while the E1 state could not be assigned to any particular defect reported in the literature. Ion Beam Induced Charge (IBIC) microscopy with multiple He ion probe microbeams (1–6 MeV) having different penetration depths in tested partly damaged 4H-SiC SBD has been used to determine the degradation of the charge collection efficiency (CCE) over a wide fluence range of damaging alpha particle. A non-linear behavior of the CCE decrease and a significant degradation of the spectroscopic performance with increasing He ion fluence were observed above the value of 10{sup 11} cm{sup −2}.

  17. Performance Evaluation of an Automotive-Grade, High Speed Gate Driver for SiC FETs, Type UCC27531, Over a Wide Temperature Range

    Science.gov (United States)

    Boomer, Kristen; Hammoud, Ahmad

    2015-01-01

    Silicon carbide (SiC) devices are becoming widely used in electronic power circuits as replacement for conventional silicon parts due to their attractive properties that include low on-state resistance, high temperature tolerance, and high frequency operation. These attributes have a significant impact by reducing system weight, saving board space, and conserving power. In this work, the performance of an automotive-grade high speed gate driver with potential use in controlling SiC FETs (field-Effect Transistors) in converters or motor control applications was evaluated under extreme temperatures and thermal cycling. The investigations were carried out to assess performance and to determine suitability of this device for use in space exploration missions under extreme temperature conditions.

  18. Irradiation damage of SiC semiconductor device (I)

    International Nuclear Information System (INIS)

    Park, Ji Yeon; Kim, Weon Ju

    2000-09-01

    This report reviewed the irradiation damage of SiC semiconductor devices and examined a irradiation behavior of SiC single crystal as a pre-examination for evaluation of irradiation behavior of SiC semiconductor devices. The SiC single was crystal irradiated by gamma-beam, N+ ion and electron beam. Annealing examinations of the irradiated specimens also were performed at 500 deg C. N-type 6H-SiC dopped with N+ ion was used and irradiation doses of gamma-beam, N+ion and electron beam were up to 200 Mrad, 1x10 16 N + ions/cm 2 and 3.6 x 10 17 e/cm 2 and 1.08 x 10 18 e/cm 2 , respectively. Irradiation damages were analyzed by the EPR method. Additionally, properties of SiC, information about commercial SiC single crystals and the list of web sites with related to the SiC device were described in the appendix

  19. Irradiation damage of SiC semiconductor device (I)

    Energy Technology Data Exchange (ETDEWEB)

    Park, Ji Yeon; Kim, Weon Ju

    2000-09-01

    This report reviewed the irradiation damage of SiC semiconductor devices and examined a irradiation behavior of SiC single crystal as a pre-examination for evaluation of irradiation behavior of SiC semiconductor devices. The SiC single was crystal irradiated by gamma-beam, N+ ion and electron beam. Annealing examinations of the irradiated specimens also were performed at 500 deg C. N-type 6H-SiC dopped with N+ ion was used and irradiation doses of gamma-beam, N+ion and electron beam were up to 200 Mrad, 1x10{sup 16} N{sup +} ions/cm{sup 2} and 3.6 x 10{sup 17} e/cm{sup 2} and 1.08 x 10{sup 18} e/cm{sup 2} , respectively. Irradiation damages were analyzed by the EPR method. Additionally, properties of SiC, information about commercial SiC single crystals and the list of web sites with related to the SiC device were described in the appendix.

  20. Microwave joining of SiC ceramics and composites

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, I.; Silberglitt, R.; Tian, Y.L. [FM Technologies, Inc., Fairfax, VA (United States); Katz, J.D. [Los Alamos National Lab., NM (United States)

    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.

  1. Designing the fiber volume ratio in SiC fiber-reinforced SiC ceramic composites under Hertzian stress

    International Nuclear Information System (INIS)

    Lee, Kee Sung; Jang, Kyung Soon; Park, Jae Hong; Kim, Tae Woo; Han, In Sub; Woo, Sang Kuk

    2011-01-01

    Highlights: → Optimum fiber volume ratios in the SiC/SiC composite layers were designed under Hertzian stress. → FEM analysis and spherical indentation experiments were undertaken. → Boron nitride-pyrocarbon double coatings on the SiC fiber were effective. → Fiber volume ratio should be designed against flexural stress. -- Abstract: Finite element method (FEM) analysis and experimental studies are undertaken on the design of the fiber volume ratio in silicon carbide (SiC) fiber-reinforced SiC composites under indentation contact stresses. Boron nitride (BN)/Pyrocarbon (PyC) are selected as the coating materials for the SiC fiber. Various SiC matrix/coating/fiber/coating/matrix structures are modeled by introducing a woven fiber layer in the SiC matrix. Especially, this study attempts to find the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics under Hertzian stress. The analysis is performed by changing the fiber type, fiber volume ratio, coating material, number of coating layers, and stacking sequence of the coating layers. The variation in the stress for composites in relation to the fiber volume ratio in the contact axial or radial direction is also analyzed. The same structures are fabricated experimentally by a hot process, and the mechanical behaviors regarding the load-displacement are evaluated using the Hertzian indentation method. Various SiC matrix/coating/fiber/coating/matrix structures are fabricated, and mechanical characterization is performed by changing the coating layer, according to the introduction (or omission) of the coating layer, and the number of woven fiber mats. The results show that the damage mode changes from Hertzian stress to flexural stress as the fiber volume ratio increases in composites because of the decreased matrix volume fraction, which intensifies the radial crack damage. The result significantly indicates that the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics should be designed for

  2. Stellar Origin of {sup 15}N-rich Presolar SiC Grains of Type AB: Supernovae with Explosive Hydrogen Burning

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Nan; Nittler, Larry R.; Alexander, Conel M. O’D.; Wang, Jianhua [Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington, DC 20015 (United States); Pignatari, Marco [E. A. Milne Centre for Astrophysics, Department of Physics and Mathematics, University of Hull, Hull HU6 7RX (United Kingdom)

    2017-06-10

    We report C, N, and Si isotopic data for 59 highly {sup 13}C-enriched presolar submicron- to micron-sized SiC grains from the Murchison meteorite, including eight putative nova grains (PNGs) and 29 {sup 15}N-rich ({sup 14}N/{sup 15}N ≤ solar) AB grains, and their Mg–Al, S, and Ca–Ti isotope data when available. These 37 grains are enriched in {sup 13}C, {sup 15}N, and {sup 26}Al with the PNGs showing more extreme enhancements. The {sup 15}N-rich AB grains show systematically higher {sup 26}Al and {sup 30}Si excesses than the {sup 14}N-rich AB grains. Thus, we propose to divide the AB grains into groups 1 ({sup 14}N/{sup 15}N < solar) and 2 ({sup 14}N/{sup 15}N ≥ solar). For the first time, we have obtained both S and Ti isotopic data for five AB1 grains and one PNG and found {sup 32}S and/or {sup 50}Ti enhancements. Interestingly, one AB1 grain had the largest {sup 32}S and {sup 50}Ti excesses, strongly suggesting a neutron-capture nucleosynthetic origin of the {sup 32}S excess and thus the initial presence of radiogenic {sup 32}Si ( t {sub 1/2} = 153 years). More importantly, we found that the {sup 15}N and {sup 26}Al excesses of AB1 grains form a trend that extends to the region in the N–Al isotope plot occupied by C2 grains, strongly indicating a common stellar origin for both AB1 and C2 grains. Comparison of supernova models with the AB1 and C2 grain data indicates that these grains came from supernovae that experienced H ingestion into the He/C zones of their progenitors.

  3. Stress Analysis of SiC MEMS Using Raman Spectroscopy

    Science.gov (United States)

    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.

  4. Polycrystalline SiC as source material for the growth of fluorescent SiC layers

    DEFF Research Database (Denmark)

    Kaiser, M.; Hupfer, T.; Jokubavicus, V.

    2013-01-01

    Polycrystalline doped SiC act as source for fluorescent SiC. We have studied the growth of individual grains with different polytypes in the source material. We show an evolution and orientation of grains of different polytypes in polycrystalline SiC ingots grown by the Physical Vapor Transport...... method. The grain influence on the growth rate of fluorescent SiC layers grown by a sublimation epitaxial process is discussed in respect of surface kinetics....

  5. Fiber Effects on Minicomposite Mechanical Properties for Several Silicon Carbide Fiber: Chemically Vapor-Infiltrated Silicon Carbide Matrix Systems

    Science.gov (United States)

    Morscher, Gregory N.; Martinez-Fernandez, Julian

    1999-01-01

    Several different types of SiC fiber tows were coated with BN and composited using chemically vapor-infiltrated SiC to form single-tow minicomposites. The types of SiC fiber included Nicalon(sup TM), Hi-Nicalon(sup TM), and the new Sylramic(sup TM) polycrystalline SiC fiber. The interfacial shear stresses were determined from unload-reload tensile hysteresis-loop tests. The ultimate stress and strain properties also were determined for the minicomposites. The ultimate strengths of the newer Hi-Nicalon and Sylramic fibers were superior to that of Nicalon minicomposites with similar fiber volume fractions. The Sylramic minicomposites had the lowest strain to failure and highest interfacial shear strength, respectively, because of the high modulus of the fiber and the rough surface of this fiber type. The apparent interfacial shear strength increased as the stress increased for the Sylramic minicomposites, which also was attributed to the surface roughness of this fiber.

  6. SiC MEMS For Harsh Environments

    National Research Council Canada - National Science Library

    Bradley, Kenneth

    2003-01-01

    This document is the final technical report for the SiC MEMS for Harsh Environments in-house research program jointly coordinated between AFRL/MNMF and AFRL/MLPS, and addresses the benefits of silicon carbide (SiC...

  7. Hoop Tensile Properties of Ceramic Matrix Composite Cylinders

    Science.gov (United States)

    Verrilli, Michael J.; DiCarlo, James A.; Yun, HeeMan; Barnett, Terry

    2004-01-01

    Tensile stress-strain properties in the hoop direction were obtained for 100-mm diameter SiC/SiC ceramic matrix composite cylinders using ring specimens machined form the cylinder ends. The cylinders were fabricated from 2D balanced SiC fabric with several material variants, including wall thickness (6,8, and 12 plies), SiC fiber type (Sylramic, Sylramic-iBN, Hi-Nicalon, and Hi-Nicalon S), fiber sizing type, and matrix type (full CVI SiC, and partial CVI SiC plus slurry cast + melt-infiltrated SiC-Si). Fiber ply splices existed in all the hoops. Tensile hoop measurements are made at room temperature and 1200 C using hydrostatic ring test facilities. The failure mode of the hoops, determined through microstructural examination, is presented. The hoop properties are compared with in-plane data measured on flat panels using same material variants, but containing no splices.

  8. Large area SiC coating technology of RBSC for semiconductor processing component

    International Nuclear Information System (INIS)

    Park, Ji Yeon; Kim, Weon Ju

    2001-06-01

    As the semiconductor process is developed for the larger area wafer and the larger-scale integration, the processing fixtures are required to have excellent mechanical and high temperature properties. This highlights the importance of silicon carbide-based materials as a substitute for quartz-based susceptors. In this study, SiC coating technology on reaction sintered (RS) SiC with thickness variation of +/- 10% within a diameter of 8 inch by low pressure chemical vapor deposition has been developed for making a plate type SiC fixture such as heater, baffle, etc., with a diameter of 12 inch. Additionally, a state of art on fabrication technology and products of the current commercial SiC fixtures has been described

  9. Precursor Selection for Property Optimization in Biomorphic SiC Ceramics

    Science.gov (United States)

    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.

  10. FABRICATION AND MATERIAL ISSUES FOR THE APPLICATION OF SiC COMPOSITES TO LWR FUEL CLADDING

    Directory of Open Access Journals (Sweden)

    WEON-JU KIM

    2013-08-01

    Full Text Available The fabrication methods and requirements of the fiber, interphase, and matrix of nuclear grade SiCf/SiC composites are briefly reviewed. A CVI-processed SiCf/SiC composite with a PyC or (PyC-SiCn interphase utilizing Hi-Nicalon Type S or Tyranno SA3 fiber is currently the best combination in terms of the irradiation performance. We also describe important material issues for the application of SiC composites to LWR fuel cladding. The kinetics of the SiC corrosion under LWR conditions needs to be clarified to confirm the possibility of a burn-up extension and the cost-benefit effect of the SiC composite cladding. In addition, the development of end-plug joining technology and fission products retention capability of the ceramic composite tube would be key challenges for the successful application of SiC composite cladding.

  11. Surface functionalization and biomedical applications based on SiC

    Energy Technology Data Exchange (ETDEWEB)

    Yakimova, R; Petoral, R M Jr; Yazdi, G R; Vahlberg, C; Spetz, A Lloyd; Uvdal, K [Department of Physics, Chemistry and Biology, Linkoeping University, SE-58183 Linkoeping (Sweden)

    2007-10-21

    The search for materials and systems, capable of operating long term under physiological conditions, has been a strategy for many research groups during the past years. Silicon carbide (SiC) is a material, which can meet the demands due to its high biocompatibility, high inertness to biological tissues and to aggressive environment, and the possibility to make all types of electronic devices. This paper reviews progress in biomedical and biosensor related research on SiC. For example, less biofouling and platelet aggregation when exposed to blood is taken advantage of in a variety of medical implantable materials while the robust semiconducting properties can be explored in surface functionalized bioelectronic devices. (review article)

  12. From SICs and MUBs to Eddington

    Energy Technology Data Exchange (ETDEWEB)

    Bengtsson, Ingemar, E-mail: ingemar@physto.se [Fysikum, Stockholms Universitet, S-106 91 Stockholm (Sweden)

    2010-11-01

    This is a survey of some very old knowledge about Mutually Unbiased Bases (MUB) and Symmetric Informationally Complete POVMs (SIC). In prime dimensions the former are closely tied to an elliptic normal curve symmetric under the Heisenberg group, while the latter are believed to be orbits under the Heisenberg group in all dimensions. In dimensions 3 and 4 the SICs are understandable in terms of elliptic curves, but a general statement escapes us. The geometry of the SICs in 3 and 4 dimensions is discussed in some detail.

  13. One-step deposition of ultrafiltration SiC membranes on macroporous SiC supports

    DEFF Research Database (Denmark)

    König, Katja; Boffa, Vittorio; Buchbjerg, Bjarke

    2014-01-01

    We fabricated nearly defect-free SiC membranes for potential ultrafiltration applications by conducting pyrolysis of allylhydrido polycarbosilane in the presence of submicron α-SiC particles. The SiC membranes were developed on commercial macroporous SiC supports by a low-temperature-process in w......We fabricated nearly defect-free SiC membranes for potential ultrafiltration applications by conducting pyrolysis of allylhydrido polycarbosilane in the presence of submicron α-SiC particles. The SiC membranes were developed on commercial macroporous SiC supports by a low......-temperature-process in which allylhydrido polycarbosilane acted to bond together crystalline α-SiC particles to form a porous layer. The suspensions of α-SiC powder and allylhydrido polycarbosilane in hexane or hexane/tetradecane were used for membrane fabrication by dip-coating. By using optimized hexane suspension with 5% w...

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

    International Nuclear Information System (INIS)

    Kageshima, H; Hibino, H; Tanabe, S

    2012-01-01

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

  15. Elaboration and characterization of luminescent porous SiC microparticles/poly vinyl alcohol thin films

    Science.gov (United States)

    Kaci, S.; Mansouri, H.; Bozetine, I.; Keffous, A.; Guerbous, L.; Siahmed, Y.; Aissiou, S.

    2017-02-01

    In this study, Morphological, optical and photoluminescence characterizations of nanostructured SiC micropowder embedded in PVA matrix and deposited as thin films on glass substrates are reported. we prepared the porous SiC microparticles/PVA thin films by spin coating method. The average size of SiC microparticles were 7 μm. An electroless method was used for producing porous silicon carbide powder under UV irradiation. Silver nanoparticles coated SiC powder was formed by polyol process. The etchant was composed of aqueous HF and different oxidants. Various porous morphologies were obtained and studied as a function of oxidant type, etching time, and wavelength of irradiation. We concluded that the chemical etching conditions of SiC powder seems to have a large impact on the resulting properties. We noticed that the best photoluminescence property was achieved when SiC powder was etched in HF/K2S2O8 at reaction temperature of 80 °C for t = 40min and under UV light of 254 nm.

  16. Preparation of biomorphic SiC ceramics

    Directory of Open Access Journals (Sweden)

    Egelja A.

    2008-01-01

    Full Text Available This paper deals with a new method for producing non-oxide ceramic using wood as a template. SiC with a woodlike microstructure has been prepared by carbothermal reduction reactions of Tilia wood/TEOS composite at 1873K. The porous carbon preform was infiltrated with TEOS (Si(OC2H54, as a source of silica, without pressure at 298K. The morphology of resulting porous SiC ceramics, as well as the conversion mechanism of wood to SiC ceramics, have been investigated by scanning electron microscopy (SEM/EDS and X-ray diffraction analysis (XRD. Obtained SiC ceramics consists of β-SiC with traces of α-SiC.

  17. SiC MEMS For Harsh Environments

    National Research Council Canada - National Science Library

    Bradley, Kenneth

    2003-01-01

    ... (specifically high temperature) material for both structural and electronic devices. Although shock testing of SiC MEMS devices under this program was not accomplished, subsequent work allowed for this testing to occur, with positive results...

  18. A study of SiC decomposition under laser irradiation

    Science.gov (United States)

    Adelmann, B.; Hellmann, R.

    2017-06-01

    In this experimental study we investigate the laser induced thermal decomposition of 4H-Sic under ambient conditions using fiber laser. Using a unique two-color pyrometer setup, we measure the temporal evolution of the temperature in the irradiated zone and determine the decomposition rate for various laser power levels. We find that the temporal evolution of the temperature in the irradiated area exhibits an initial heating phase up to about 1300 K, being characterized by an unaffected SiC surface. Upon an expeditious temperature increase, a decomposition phase follows with temperatures above 1700 K, being accompanied by carbonization of the SiC surface. The decomposed volume depends linearly on the duration of the decomposition phase and increases linearly with laser power. The temperature evaluation of the decomposition speed reveals an Arrhenius-type behavior allowing the calculation of the activation energy for the decomposition under ambient conditions to 613 kJ/mol in the temperature range between 2140 and 2420 K.

  19. Experimental determination of grain density function of AZ91/SiC composite with different mass fractions of SiC and undercoolings using heterogeneous nucleation model

    Directory of Open Access Journals (Sweden)

    J. Lelito

    2011-02-01

    Full Text Available The grain density, Nv, in the solid state after solidification of AZ91/SiC composite is a function of maximum undercooling, ΔT, of a liquid alloy. This type of function depends on the characteristics of heterogeneous nucleation sites and number of SiC present in the alloy. The aim of this paper was selection of parameters for the model describing the relationship between the grain density of primary phase and undercooling. This model in connection with model of crystallisation, which is based on chemical elements diffusion and grain interface kinetics, can be used to predict casting quality and its microstructure. Nucleation models have parameters, which exact values are usually not known and sometimes even their physical meaning is under discussion. Those parameters can be obtained after mathematical analysis of the experimental data. The composites with 0, 1, 2, 3 and 4wt.% of SiC particles were prepared. The AZ91 alloy was a matrix of the composite reinforcement SiC particles. This composite was cast to prepare four different thickness plates.They were taken from the region near to the thermocouple, to analyze the undercooling for different composites and thickness plates and its influence on the grain size. The microstructure and thermal analysis gave set of values that connect mass fraction of SiC particles, and undercooling with grain size. These values were used to approximate nucleation model adjustment parameters. Obtained model can be very useful in modelling composites microstructure.

  20. Cl-intercalated graphene on SiC: Influence of van der Waals forces

    KAUST Repository

    Cheng, Yingchun

    2013-01-01

    The atomic and electronic structures of Cl-intercalated epitaxial graphene on SiC are studied by first-principles calculations. By increasing the Cl concentration, doping levels from n-type to slightly p-type are achieved on the SiC(0001) surface, while a wider range of doping levels is possible on the SiC(0001̄) surface. We find that the Cl atoms prefer bonding to the substrate rather than to the graphene. By varying the Cl concentration the doping level can be tailored. Consideration of van der Waals forces improves the distance between the graphene and the substrate as well as the binding energy, but it is not essential for the formation energy. For understanding the doping mechanism the introduction of non-local van der Waals contributions to the exchange correlation functional is shown to be essential. Copyright © EPLA, 2013.

  1. Neutron displacement damage cross sections for SiC

    International Nuclear Information System (INIS)

    Huang Hanchen; Ghoniem, N.

    1993-01-01

    Calculations of neutron displacement damage cross sections for SiC are presented. We use Biersack and Haggmark's empirical formula in constructing the electronic stopping power, which combines Lindhard's model at low PKA energies and Bethe-Bloch's model at high PKA energies. The electronic stopping power for polyatomic materials is computed on the basis of Bragg's Additivity Rule. A continuous form of the inverse power law potential is used for nuclear scattering. Coupled integro-differential equations for the number of displaced atoms j, caused by PKA i, are then derived. The procedure outlined above gives partial displacement cross sections, displacement cross sections for each specie of the lattice, and for each PKA type. The corresponding damage rates for several fusion and fission neutron spectra are calculated. The stoichiometry of the irradiated material is investigated by finding the ratio of displacements among various atomic species. The role of each specie in displacing atoms is also investigated by calculating the fraction of displacements caused by each PKA type. The study shows that neutron displacement damage rates of SiC in typical magnetic fusion reactor first walls will be ∝10-15 dpa MW -1 m 2 ; in typical lead-protected inertial confinement fusion reactor first walls they will be ∝15-20 dpa MW -1 m 2 . For fission spectra, we find that the neutron displacement damage rate of SiC is ∝74 dpa per 10 27 n/m 2 in FFTF, ∝39 dpa per 10 27 n/m 2 in HFIR, and 25 dpa per 10 27 n/m 2 in NRU. Approximately 80% of displacement atoms are shown to be of the carbon-type. (orig.)

  2. SiC synthesis using natural Mg-silicates

    Directory of Open Access Journals (Sweden)

    Devečerski A.

    2012-01-01

    Full Text Available The silicon carbide powders are prepared by carbothermal reduction of domestic mineral resources (white and brown sepiolite, at relatively low temperatures (1200 - 1600oC. Carbothermal reduction process is greatly influenced by chemical composition of sepiolites and type of carbon used. Obtained SiC powders consist of fine β-SiC particles and did not retain the fibrous morphology of sepiolites. Catalytical influence of Fe is attributed to formation of iron-silicide and its potentionaly important role in removal of Mg-species, i.e. reduction of Mg2SiO4 and MgO into Mg(g.

  3. Simulations of Proton Implantation in Silicon Carbide (SiC)

    Science.gov (United States)

    2016-03-31

    Simulations of Proton Implantation in Silicon Carbide (SiC) Jonathan P. McCandless, Hailong Chen, Philip X.-L. Feng Electrical Engineering, Case...of implanting protons (hydrogen ions, H+) into SiC thin layers on silicon (Si) substrate, and explore the ion implantation conditions that are...relevant to experimental radiation of SiC layers. Keywords: silicon carbide (SiC); radiation effects; ion implantation; proton ; stopping and range of

  4. A Grande Reportagem no contexto informativo SIC

    OpenAIRE

    Colaço, Vanessa Alexandra Francisco

    2014-01-01

    Os telespectadores querem ver grandes reportagens? Como evoluíram as audiências da Grande Reportagem SIC? É este o produto premium da estação? Terá este formato um investimento e continuidade garantidas? Estas são algumas das questões formuladas e às quais se procurou dar resposta neste Relatório de Estágio. Neste trabalho traça-se o perfil do programa Grande Reportagem SIC, clarificando a linha editorial que lhe serviu de base, procurando perceber as suas dinâmicas e passando em revista mome...

  5. Highly flexible and robust N-doped SiC nanoneedle field emitters

    KAUST Repository

    Chen, Shanliang

    2015-01-23

    Flexible field emission (FE) emitters, whose unique advantages are lightweight and conformable, promise to enable a wide range of technologies, such as roll-up flexible FE displays, e-papers and flexible light-emitting diodes. In this work, we demonstrate for the first time highly flexible SiC field emitters with low turn-on fields and excellent emission stabilities. n-Type SiC nanoneedles with ultra-sharp tips and tailored N-doping levels were synthesized via a catalyst-assisted pyrolysis process on carbon fabrics by controlling the gas mixture and cooling rate. The turn-on field, threshold field and current emission fluctuation of SiC nanoneedle emitters with an N-doping level of 7.58 at.% are 1.11 V μm-1, 1.55 V μm-1 and 8.1%, respectively, suggesting the best overall performance for such flexible field emitters. Furthermore, characterization of the FE properties under repeated bending cycles and different bending states reveal that the SiC field emitters are mechanically and electrically robust with unprecedentedly high flexibility and stabilities. These findings underscore the importance of concurrent morphology and composition controls in nanomaterial synthesis and establish SiC nanoneedles as the most promising candidate for flexible FE applications. © 2015 Nature Publishing Group All rights reserved.

  6. Ag Transport Through Non-Irradiated and Irradiated SiC

    Energy Technology Data Exchange (ETDEWEB)

    Szlufarska, Izabela [Univ. of Wisconsin, Madison, WI (United States); Morgan, Dane [Univ. of Wisconsin, Madison, WI (United States); Blanchard, James [Univ. of Wisconsin, Madison, WI (United States)

    2016-01-11

    Silicon carbide is the main barrier to diffusion of fission products in the current design of TRistuctural ISOtropic (TRISO) coated fuel particles, and Ag is one of the few fission products that have been shown to escape through this barrier. Because the SiC coating in TRISO is exposed to radiation throughout the lifetime of the fuel, understanding of how radiation changes the transport of the fission products is essential for the safety of the reactor. The goals of this project are: (i) to determine whether observed variation in integral release measurements of Ag through SiC can be explained by differences in grain size and grain boundary (GB) types among the samples; (2) to identify the effects of irradiation on diffusion of Ag through SiC; (3) to discover phenomena responsible for significant solubility of Ag in polycrystalline SiC. To address these goals, we combined experimental analysis of SiC diffusion couples with modeling studies of diffusion mechanisms through bulk and GBs of this material. Comparison between results obtained for pristine and irradiated samples brings in insights into the effects of radiation on Ag transport.

  7. Ag Transport Through Non-Irradiated and Irradiated SiC

    International Nuclear Information System (INIS)

    Szlufarska, Izabela; Morgan, Dane; Blanchard, James

    2016-01-01

    Silicon carbide is the main barrier to diffusion of fission products in the current design of TRistuctural ISOtropic (TRISO) coated fuel particles, and Ag is one of the few fission products that have been shown to escape through this barrier. Because the SiC coating in TRISO is exposed to radiation throughout the lifetime of the fuel, understanding of how radiation changes the transport of the fission products is essential for the safety of the reactor. The goals of this project are: (i) to determine whether observed variation in integral release measurements of Ag through SiC can be explained by differences in grain size and grain boundary (GB) types among the samples; (2) to identify the effects of irradiation on diffusion of Ag through SiC; (3) to discover phenomena responsible for significant solubility of Ag in polycrystalline SiC. To address these goals, we combined experimental analysis of SiC diffusion couples with modeling studies of diffusion mechanisms through bulk and GBs of this material. Comparison between results obtained for pristine and irradiated samples brings in insights into the effects of radiation on Ag transport.

  8. About SIC POVMs and discrete Wigner distributions

    International Nuclear Information System (INIS)

    Colin, Samuel; Corbett, John; Durt, Thomas; Gross, David

    2005-01-01

    A set of d 2 vectors in a Hilbert space of dimension d is called equiangular if each pair of vectors encloses the same angle. The projection operators onto these vectors define a POVM which is distinguished by its high degree of symmetry. Measures of this kind are called symmetric informationally complete, or SIC POVMs for short, and could be applied for quantum state tomography. Despite its simple geometrical description, the problem of constructing SIC POVMs or even proving their existence seems to be very hard. It is our purpose to introduce two applications of discrete Wigner functions to the analysis of the problem at hand. First, we will present a method for identifying symmetries of SIC POVMs under Clifford operations. This constitutes an alternative approach to a structure described before by Zauner and Appleby. Further, a simple and geometrically motivated construction for an SIC POVM in dimensions two and three is given (which, unfortunately, allows no generalization). Even though no new structures are found, we hope that the re-formulation of the problem may prove useful for future inquiries

  9. Universal Converter Using SiC

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. Theoretical investigation of the breakdown electric field of SiC polymorphs

    Science.gov (United States)

    Yamaguchi, Kikou; Kobayashi, Daisuke; Yamamoto, Tomoyuki; Hirose, Kazuyuki

    2018-03-01

    The breakdown electric field of several SiC polymorphs has been investigated theoretically using a concept of "recovery rate," which is obtained by first principles calculations. A good relationship between the experimental breakdown electric fields and the calculated recovery rate of 4H-, 6H-, and 3C-SiC was obtained. In order to examine the stability of SiC polymorphs, the total electronic energies of various types of SiC crystal structures were calculated. Here, two candidates of polymorphs-GeS-type- and 2H-SiC-with energies comparable to those of experimentally well-established structures, have been obtained. The breakdown electric fields of these two polymorphs were estimated using a relationship obtained from the results of 4H-, 6H-, and 3C-SiC. This indicates that one of these polymorphs, GeS-type-SiC, has higher breakdown electric field than any other SiC polymorphs. In addition to the investigation with the recovery rate, relationship between experimental breakdown electric field and calculated band gap with recently developed accurate electron-correlation potential has been also discussed.

  11. An Updated Subsequent Injury Categorisation Model (SIC-2.0): Data-Driven Categorisation of Subsequent Injuries in Sport.

    Science.gov (United States)

    Toohey, Liam A; Drew, Michael K; Fortington, Lauren V; Finch, Caroline F; Cook, Jill L

    2018-03-03

    Accounting for subsequent injuries is critical for sports injury epidemiology. The subsequent injury categorisation (SIC-1.0) model was developed to create a framework for accurate categorisation of subsequent injuries but its operationalisation has been challenging. The objective of this study was to update the subsequent injury categorisation (SIC-1.0 to SIC-2.0) model to improve its utility and application to sports injury datasets, and to test its applicability to a sports injury dataset. The SIC-1.0 model was expanded to include two levels of categorisation describing how previous injuries relate to subsequent events. A data-driven classification level was established containing eight discrete injury categories identifiable without clinical input. A sequential classification level that sub-categorised the data-driven categories according to their level of clinical relatedness has 16 distinct subsequent injury types. Manual and automated SIC-2.0 model categorisation were applied to a prospective injury dataset collected for elite rugby sevens players over a 2-year period. Absolute agreement between the two coding methods was assessed. An automated script for automatic data-driven categorisation and a flowchart for manual coding were developed for the SIC-2.0 model. The SIC-2.0 model was applied to 246 injuries sustained by 55 players (median four injuries, range 1-12), 46 (83.6%) of whom experienced more than one injury. The majority of subsequent injuries (78.7%) were sustained to a different site and were of a different nature. Absolute agreement between the manual coding and automated statistical script category allocation was 100%. The updated SIC-2.0 model provides a simple flowchart and automated electronic script to allow both an accurate and efficient method of categorising subsequent injury data in sport.

  12. Ceramic Matrix Characterization Under a Gas Turbine Combustion and Loading Environment

    Science.gov (United States)

    2014-03-17

    consisting of a silicon carbide matrix reinforced by boron nitride coated Hi-Nicalon type S TM SiC fiber under tension-tension fatigue loading in...were not covered by this research. One thing that would be of interest would be to x - ray the material before testing in the combustion environment to...made up of woven Sylramic SiC (silicon carbide ) fibers situated in an SiC matrix using chemical vapor infiltration (CVI). The specimens used in this

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

    Directory of Open Access Journals (Sweden)

    Douzery Emmanuel JP

    2008-10-01

    _IST infers much more informative supertrees than PhySIC, while preserving low type I error compared to the well-known MRP method. Two biological case studies on animals confirm that the STC preprocess successfully detects anomalies in the source trees while STC+PhySIC_IST provides well-resolved supertrees agreeing with current knowledge in systematics. Conclusion The paper introduces and tests two new methodologies, PhySIC_IST and STC, that demonstrate the interest in inferring non-plenary supertrees as well as preprocessing the source trees. An implementation of the methods is available at: http://www.atgc-montpellier.fr/physic_ist/.

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

    Science.gov (United States)

    Scornavacca, Celine; Berry, Vincent; Lefort, Vincent; Douzery, Emmanuel J P; Ranwez, Vincent

    2008-10-04

    supertrees than PhySIC, while preserving low type I error compared to the well-known MRP method. Two biological case studies on animals confirm that the STC preprocess successfully detects anomalies in the source trees while STC+PhySIC_IST provides well-resolved supertrees agreeing with current knowledge in systematics. The paper introduces and tests two new methodologies, PhySIC_IST and STC, that demonstrate the interest in inferring non-plenary supertrees as well as preprocessing the source trees. An implementation of the methods is available at: http://www.atgc-montpellier.fr/physic_ist/.

  15. Hoop Tensile Characterization Of SiC/SiC Cylinders Fabricated From 2D Fabric

    Science.gov (United States)

    Verrilli, Michael J.; Yun, HeeMann; DiCarlo, James A.; Barnett, Terry R.

    2002-01-01

    Tensile stress-strain properties in the hoop direction were obtained for 100-mm diameter SiC/SiC cylinders using ring specimens machined from the cylinder ends. The cylinders were fabricated from 2D balanced fabric with several material variants, including wall thickness (6, 8, and 12 plies), Sic fiber type (Sylramic, Sylramic-iBN, Hi-Nicalon, and Hi-Nicalon S), fiber sizing type, and matrix type (full CVI Sic, and partial CVI plus melt-infiltrated SiC-Si). Fiber ply splices existed in the all the hoops. Tensile hoop measurements were made at room temperature and 1200 C using hydrostatic ring test facilities. The hoop results are compared with in-plane data measured on flat panels using same material variants, but containing no splices.

  16. SiC Power MOSFET with Improved Gate Dielectric

    Energy Technology Data Exchange (ETDEWEB)

    Sbrockey, Nick M. [Structured Materials Industries, Inc., Piscataway, NJ (United States); Tompa, Gary S. [Structured Materials Industries, Inc., Piscataway, NJ (United States); Spencer, Michael G. [Structured Materials Industries, Inc., Piscataway, NJ (United States); Chandrashekhar, Chandra M.V. S. [Structured Materials Industries, Inc., Piscataway, NJ (United States)

    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.

  17. SiC Multi-Chip Power Modules as Power-System Building Blocks

    Science.gov (United States)

    Lostetter, Alexander; Franks, Steven

    2007-01-01

    and difficulty of designing new, highly reliable power systems would be reduced considerably. Several prototype DC-to-DC power-converter modules containing SiC power-switching devices were designed and built to demonstrate the feasibility of the SiC MCPM concept. In anticipation of a future need for operation at high temperature, the circuitry in the modules includes high-temperature inductors and capacitors. These modules were designed to be stacked to construct a system of four modules electrically connected in series and/or parallel. The packaging of the modules is designed to satisfy requirements for series and parallel interconnection among modules, high power density, high thermal efficiency, small size, and light weight. Each module includes four output power connectors two for serial and two for parallel output power connections among the modules. Each module also includes two signal connectors, electrically isolated from the power connectors, that afford four zones for signal interconnections among the SOI controllers. Finally, each module includes two input power connectors, through which it receives power from an in-line power bus. This design feature is included in anticipation of a custom-designed power bus incorporating sockets compatible with snap-on type connectors to enable rapid replacement of failed modules.

  18. Selected mechanical properties of aluminum composite materials reinforced with SiC particles

    Directory of Open Access Journals (Sweden)

    A. Kurzawa

    2008-07-01

    Full Text Available This work presents the results of research concerning influence of ceramic particles’ content of silicon carbide on selected mechanical properties of type AW-AlCu4Mg2Mn - SiC composite materials. Composites produced of SiC particles with pressure infiltration method of porous preform and subject to hot plastic forming in the form of open die forging were investigated. The experimental samples contained from 5% up to 45% of reinforcing SiC particles of 8÷10μm diameter. Studies of strength properties demonstrated that the best results, in case of tensile strength as well as offset yield strength, might be obtained while applying reinforcement in the amount of 20-25% vol. of SiC. Application of higher than 25% vol. contents of reinforcing particles leads to gradual strength loss. The investigated composites were characterized by very high functional properties, such as hardness and abrasive wear resistance, whose values increase strongly with the increase of reinforcement amount. The presented results of the experiments shall allow for a more precise component selection of composite materials at the stage of planning and design of their properties.

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

    Science.gov (United States)

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

    1987-01-01

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

  20. Comparative optical investigations of sintered and monocrystalline black and green silicon carbide (SiC)

    International Nuclear Information System (INIS)

    Werheit, H.; Schwetz, K.A.

    2004-01-01

    Crystalline SiC appears in many different polytypes of cubic, hexagonal, and rhombohedral structures. These polytypes are colorless transparent or exhibit various colors evoked by doping with different elements. Dense sintered S-SiC (solid-state sintered) and LPS-SiC (liquid-phase sintered) were known in black color only, but recently a new liquid-phase sintering process was developed to achieve green LPS-SiC as well. Whereas in S-SiC the polycrystalline grains are homogeneously doped with 0.2 wt% boron, in the LPS-types the SiC grains contain up to 1.2 wt% Al, 0.3 wt% N and 0.1% O having a structure comprising a SiC(Al,N,O) mixed crystal shell and a pure SiC core. The difference in color of polycrystalline SiC bodies seems to result from small amounts of carbon in the sintered specimens (0.2-0.5 wt% C). Green sintered LPS-SiC is obtained, after free carbon has largely been removed by a suitable oxidation process prior to sintering. To get information on the various types of sintered SiC, the optical extinction and absorption spectra of black and green sintered SiC and green Acheson-SiC single crystals were quantitatively measured in the spectral range between about 1.4 and 4.1 eV. While the absorption coefficients of the single crystals vary between about 50 and 200 cm -1 , the extinction coefficients of the sintered materials are between 2000 and 7000 cm -1 . Nevertheless the absorption bands in the more or less transparent region of the green and black materials can easily be attributed to one another. Hence, the reason for these absorption processes must be assumed to be the same. In the same way, position and slope of the absorption edges are correlated amongst green or black SiC, irrespective of, whether the material is single crystal or sintered

  1. 500?C SiC JFET Driver Circuits and Packaging, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — In the proposed development, SiC JFET control circuitry and normally-off SiC JFET power switch will be integrated in a single SiC chip that will provide digital...

  2. Preparation and performance of Pt/PTFE/Foam SiC as a hydrophobic catalyst for LPCE

    Energy Technology Data Exchange (ETDEWEB)

    He, Jianchao; Wang, Heyi, E-mail: hywang@caep.cn; Xiao, Chengjian; Li, Jiamao; Chen, Ping; Hou, Jingwei

    2016-12-15

    Highlights: • A new type of foam material, Foam SiC with three-dimensional network structure, was chosen as the carrier of catalyst. • Foam SiC was hydrophobic treated by PTFE, and achieved a good hydrophobic property. • Pt/PTFE/Foam SiC was prepared by impregnation method with Pt-organic solution and gaseous phase reduction method. • The hydrophobic catalysts were packed with Dixon phosphor bronze gauze rings (about 3 mm × 3 mm) in LPCE system to test the catalytic performance. • The effect of different size of the catalyst on LPCE was been tested. - Abstract: Platinum catalysts supported on a composite of polytetrafluoroethylene (PTFE) and Foam SiC (Pt/PTFE/Foam SiC) have been proposed and prepared by an impregnation method. The as-prepared Pt/PTFE/Foam SiC was characterized by compression load testing, dynamic contact angle measurement, SEM, XRD, and TEM. The results show that the catalyst prepared by triple hydrophobic treatment had an initial contact angle of 134.2°, a good compression performance of 3.2 MPa, and platinum nanoparticles of 12.1 nm (average size). The catalytic activity of the catalyst was tested with different packing methods, reaction temperatures, and gas-liquid ratios. An excellent hydrogen isotope exchange performance was observed using a hydrophilic packing material-to-catalyst ratio of 25% and reaction temperature of 80 °C. Pt/PTFE/Foam SiC may be used as a hydrophobic catalyst for a water detritiation system (WDS) via a liquid-phase catalytic exchange process (LPCE).

  3. Preparation and performance of Pt/PTFE/Foam SiC as a hydrophobic catalyst for LPCE

    International Nuclear Information System (INIS)

    He, Jianchao; Wang, Heyi; Xiao, Chengjian; Li, Jiamao; Chen, Ping; Hou, Jingwei

    2016-01-01

    Highlights: • A new type of foam material, Foam SiC with three-dimensional network structure, was chosen as the carrier of catalyst. • Foam SiC was hydrophobic treated by PTFE, and achieved a good hydrophobic property. • Pt/PTFE/Foam SiC was prepared by impregnation method with Pt-organic solution and gaseous phase reduction method. • The hydrophobic catalysts were packed with Dixon phosphor bronze gauze rings (about 3 mm × 3 mm) in LPCE system to test the catalytic performance. • The effect of different size of the catalyst on LPCE was been tested. - Abstract: Platinum catalysts supported on a composite of polytetrafluoroethylene (PTFE) and Foam SiC (Pt/PTFE/Foam SiC) have been proposed and prepared by an impregnation method. The as-prepared Pt/PTFE/Foam SiC was characterized by compression load testing, dynamic contact angle measurement, SEM, XRD, and TEM. The results show that the catalyst prepared by triple hydrophobic treatment had an initial contact angle of 134.2°, a good compression performance of 3.2 MPa, and platinum nanoparticles of 12.1 nm (average size). The catalytic activity of the catalyst was tested with different packing methods, reaction temperatures, and gas-liquid ratios. An excellent hydrogen isotope exchange performance was observed using a hydrophilic packing material-to-catalyst ratio of 25% and reaction temperature of 80 °C. Pt/PTFE/Foam SiC may be used as a hydrophobic catalyst for a water detritiation system (WDS) via a liquid-phase catalytic exchange process (LPCE).

  4. Advances in wide bandgap SiC for optoelectronics

    DEFF Research Database (Denmark)

    Ou, Haiyan; Ou, Yiyu; Argyraki, Aikaterini

    2014-01-01

    Silicon carbide (SiC) has played a key role in power electronics thanks to its unique physical properties like wide bandgap, high breakdown field, etc. During the past decade, SiC is also becoming more and more active in optoelectronics thanks to the progress in materials growth and nanofabrication...

  5. Challenges in Switching SiC MOSFET without Ringing

    DEFF Research Database (Denmark)

    Li, Helong; Munk-Nielsen, Stig

    2014-01-01

    Switching SiC MOSFET without ringing in high frequency applications is important for meeting the EMI (ElectroMagnetic Interference) standard. Achieving a clean switching waveform of SiC MOSFET without additional components is becoming a challenge. In this paper, the switching oscillation mechanism...

  6. Tema 8. Principis físics dels semiconductors (Resum)

    OpenAIRE

    Beléndez Vázquez, Augusto

    2011-01-01

    Resum del "Tema 8. Principis físics dels semiconductors" de l'assignatura "Fonaments Físics de l'Enginyeria I" de "Grau en Enginyeria en So i Imatge" impartit a l'Escola Politècnica Superior de la Universitat d'Alacant.

  7. Energy efficiency improvement target for SIC 34 - fabricated metal products

    Energy Technology Data Exchange (ETDEWEB)

    Byrer, T. G.; Billhardt, C. F.; Farkas, M. S.

    1977-03-15

    A March 15, 1977 revision of a February 15, 1977 document on the energy improvement target for the Fabricated Metal Products industry (SIC 34) is presented. A net energy savings in 1980 of 24% as compared with 1972 energy consumption in SIC 34 is considered a realistic goal. (ERA citation 04:045008)

  8. New constructions of approximately SIC-POVMs via difference sets

    Science.gov (United States)

    Luo, Gaojun; Cao, Xiwang

    2018-04-01

    In quantum information theory, symmetric informationally complete positive operator-valued measures (SIC-POVMs) are related to quantum state tomography (Caves et al., 2004), quantum cryptography (Fuchs and Sasaki, 2003) [1], and foundational studies (Fuchs, 2002) [2]. However, constructing SIC-POVMs is notoriously hard. Although some SIC-POVMs have been constructed numerically, there does not exist an infinite class of them. In this paper, we propose two constructions of approximately SIC-POVMs, where a small deviation from uniformity of the inner products is allowed. We employ difference sets to present the first construction and the dimension of the approximately SIC-POVMs is q + 1, where q is a prime power. Notably, the dimension of this framework is new. The second construction is based on partial geometric difference sets and works whenever the dimension of the framework is a prime power.

  9. Pulsed Capacitance Measurement of Silicon Carbide (SiC) Schottky Diode and SiC Metal Oxide Semiconductor

    National Research Council Canada - National Science Library

    Griffin, Timothy E

    2006-01-01

    The incremental capacitance C was measured for a silicon carbide (SiC) Schottky diode during a reverse-biasing pulse and for two SiC n-MOS transistors during a negative pulse to their source with the drain grounded...

  10. Comparative study of the structural damage of nano-structured and micro-structured ceramics SiC under irradiation

    International Nuclear Information System (INIS)

    Leconte, Y.; Herlin-Boime, N.; Reynaud, C.; Monnet, I.; Levalois, M.; Morales, M.; Portier, X.; Thome, L.

    2006-01-01

    In order to know if the nano-structured ceramics SiC are possible materials for the future nuclear applications, SiC pellets have been submitted to low and mean energy irradiation experiments. These samples have been characterized by grazing X-ray diffraction and confocal Raman spectroscopy as well as conventional SiC ceramic pellets as reference. The low energy irradiations have allowed to exceed the amorphization threshold and to obtain a total disorder in the two types of samples. At the mean energies, this amorphization has not been obtained in spite of the doses generating a number of dpa superior to those of the low energies. The hypothesis of a synergy between the effects of the electronic and nuclear energy losses is advanced. (O.M.)

  11. Influence of SiC coating thickness on mechanical properties of SiCf/SiC composite

    Science.gov (United States)

    Yu, Haijiao; Zhou, Xingui; Zhang, Wei; Peng, Huaxin; Zhang, Changrui

    2013-11-01

    Silicon carbide (SiC) coatings with varying thickness (ranging from 0.14 μm to 2.67 μm) were deposited onto the surfaces of Type KD-I SiC fibres with native carbonaceous surface using chemical vapour deposition (CVD) process. Then, two dimensional SiC fibre reinforced SiC matrix (2D SiCf/SiC) composites were fabricated using polymer infiltration and pyrolysis (PIP) process. Influences of the fibre coating thickness on mechanical properties of SiC fibre and SiCf/SiC composite were investigated using single-filament test and three-point bending test. The results indicated that flexural strength of the composites initially increased with the increasing CVD SiC coating thickness and reached a peak value of 363 MPa at the coating thickness of 0.34 μm. Further increase in the coating thickness led to a rapid decrease in the flexural strength of the composites. The bending modulus of composites showed a monotonic increase with increasing coating thickness. A chemical attack of hydrogen or other ions (e.g. a C-H group) on the surface of SiC fibres during the coating process, owing to the formation of volatile hydrogen, lead to an increment of the surface defects of the fibres. This was confirmed by Wang et al. [35] in their work on the SiC coating of the carbon fibre. In the present study, the existing ˜30 nm carbon on the surface of KD-I fibre [36] made the fibre easy to be attacked. Deposition of non-stoichiometric SiC, causing a decrease in strength. During the CVD process, a small amount of free silicon or carbon always existed [35]. The existence of free silicon, either disordered the structure of SiC and formed a new source of cracks or attacked the carbon on fibre surface resulting in properties degeneration of the KD-I fibre. The effect of residual stress. The different thermal expansion coefficient between KD-I SiC fibre and CVD SiC coating, which are 3 × 10-6 K-1 (RT ˜ 1000 °C) and 4.6 × 10-6 K-1 (RT ˜ 1000 °C), respectively, could cause residual stress

  12. The Effect of Fiber Architecture on Matrix Cracking in Sic/sic Cmc's

    Science.gov (United States)

    Morscher, Gregory N.

    2005-01-01

    Applications incorporating silicon carbide fiber reinforced silicon carbide matrix composites (CMC's) will require a wide range of fiber architectures in order to fabricate complex shape. The stress-strain response of a given SiC/SiC system for different architectures and orientations will be required in order to design and effectively life-model future components. The mechanism for non-linear stress-strain behavior in CMC's is the formation and propagation of bridged-matrix cracks throughout the composite. A considerable amount of understanding has been achieved for the stress-dependent matrix cracking behavior of SiC fiber reinforced SiC matrix systems containing melt-infiltrated Si. This presentation will outline the effect of 2D and 3D architectures and orientation on stress-dependent matrix-cracking and how this information can be used to model material behavior and serve as the starting point foe mechanistic-based life-models.

  13. Prevalence of Complement-Mediated Cell Lysis-like Gene (sicG) in Streptococcus dysgalactiae subsp. equisimilis Isolates From Japan (2014-2016).

    Science.gov (United States)

    Takahashi, Takashi; Fujita, Tomohiro; Shibayama, Akiyoshi; Tsuyuki, Yuzo; Yoshida, Haruno

    2017-07-01

    Streptococcus dysgalactiae subsp. equisimilis (SDSE; a β-hemolytic streptococcus of human or animal origin) infections are emerging worldwide. We evaluated the clonal distribution of complement-mediated cell lysis-like gene (sicG) among SDSE isolates from three central prefectures of Japan. Group G/C β-hemolytic streptococci were collected from three institutions from April 2014 to March 2016. Fifty-five strains (52 from humans and three from animals) were identified as SDSE on the basis of 16S rRNA sequencing data.; they were obtained from 25 sterile (blood, joint fluid, and cerebrospinal fluid) and 30 non-sterile (skin-, respiratory tract-, and genitourinary tract-origin) samples. emm genotyping, multilocus sequence typing, sicG amplification/sequencing, and random amplified polymorphic DNA (RAPD) analysis of sicG-positive strains were performed. sicG was detected in 30.9% of the isolates (16 human and one canine) and the genes from the 16 human samples (blood, 10; open pus, 3; sputum, 2; throat swab, 1) and one canine sample (open pus) showed the same sequence pattern. All sicG-harboring isolates belonged to clonal complex (CC) 17, and the most prevalent emm type was stG6792 (82.4%). There was a significant association between sicG presence and the development of skin/soft tissue infections. CC17 isolates with sicG could be divided into three subtypes by RAPD analysis. CC17 SDSE harboring sicG might have spread into three closely-related prefectures in central Japan during 2014-2016. Clonal analysis of isolates from other areas might be needed to monitor potentially virulent strains in humans and animals. © The Korean Society for Laboratory Medicine

  14. Fabrication of large aperture SiC brazing mirror

    Science.gov (United States)

    Li, Ang; Wang, Peipei; Dong, Huiwen; Wang, Peng

    2016-10-01

    The SiC brazing mirror is the mirror whose blank is made by assembling together smaller SiC pieces with brazing technique. Using such kinds of joining techniques, people can manufacture large and complex SiC assemblies. The key technologies of fabricating and testing SiC brazing flat mirror especially for large aperture were studied. The SiC brazing flat mirror was ground by smart ultrasonic-milling machine, and then it was lapped by the lapping smart robot and measured by Coordinate Measuring Machine (CMM). After the PV of the surface below 4um, we did classic coarse polishing to the surface and studied the shape of the polishing tool which directly effects removal amount distribution. Finally, it was figured by the polishing smart robot and measured by Fizeau interferometer. We also studied the influence of machining path and removal functions of smart robots on the manufacturing results and discussed the use of abrasive in this process. At last, an example for fabricating and measuring a similar SiC brazing flat mirror with the aperture of 600 mm made by Shanghai Institute of Ceramics was given. The mirror blank consists of 6 SiC sectors and the surface was finally processed to a result of the Peak-to-Valley (PV) 150nm and Root Mean Square (RMS) 12nm.

  15. Compatibility of SiC and SiC Composites with Molten Lead

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Carbon surface diffusion and SiC nanocluster self-ordering

    International Nuclear Information System (INIS)

    Pezoldt, J.; Trushin, Yu.V.; Kharlamov, V.S.; Schmidt, A.A.; Cimalla, V.; Ambacher, O.

    2006-01-01

    The process of the spatial ordering of SiC nanoclusters on the step edges on Si surfaces was studied by means of multi-scale computer simulation. The evolution of cluster arrays on an ideal flat surface and surfaces with terraces of various widths was performed by kinetic Monte Carlo (KMC) simulations based on quantitative studies of potential energy surfaces (PES) by molecular dynamics (MD). PES analysis revealed that certain types of steps act as strong trapping centres for both Si and C adatoms stimulating clusters nucleation. Spatial ordering of the SiC nanoclusters at the terrace edges can be achieved if the parameters of the growth process (substrate temperature, carbon flux) and substrate (steps direction and terrace widths) are adjusted to the surface morphology. Temperature ranges for growth regimes with and without formation of cluster chains were determined. Cluster size distributions and the dependence of optimal terrace width for self ordering on the deposition parameters were obtained

  17. Structural and optical characterization of GaN heteroepitaxial films on SiC substrates

    Energy Technology Data Exchange (ETDEWEB)

    Morse, M. [Department of Electrical and Computer Engineering, Duke University, 128 Hudson Hall, Durham, NC (United States) and Department of Physics, Duke University, 128 Hudson Hall, Durham, NC (United States)]. E-mail: michael.morse@duke.edu; Wu, P. [Department of Electrical and Computer Engineering, Duke University, 128 Hudson Hall, Durham, NC (United States); Department of Physics, Duke University, 128 Hudson Hall, Durham, NC (United States); Choi, S. [Department of Electrical and Computer Engineering, Duke University, 128 Hudson Hall, Durham, NC (United States); Department of Physics, Duke University, 128 Hudson Hall, Durham, NC (United States); Kim, T.H. [Department of Electrical and Computer Engineering, Duke University, 128 Hudson Hall, Durham, NC (United States); Department of Physics, Duke University, 128 Hudson Hall, Durham, NC (United States); Brown, A.S. [Department of Electrical and Computer Engineering, Duke University, 128 Hudson Hall, Durham, NC (United States) and Department of Physics, Duke University, 128 Hudson Hall, Durham, NC (United States)]. E-mail: abrown@ee.duke.edu; Losurdo, M. [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, via Orabona, 4-70126 Bari (Italy); Bruno, G. [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, via Orabona, 4-70126 Bari (Italy)

    2006-10-31

    We have estimated the threading dislocation density and type via X-ray diffraction and Williamson-Hall analysis to elicit qualitative information directly related to the electrical and optical quality of GaN epitaxial layers grown by PAMBE on 4H- and 6H-SiC substrates. The substrate surface preparation and buffer choice, specifically: Ga flashing for SiC oxide removal, controlled nitridation of SiC, and use of AlN buffer layers all impact the resultant screw dislocation density, but do not significantly influence the edge dislocation density. We show that modification of the substrate surface strongly affects the screw dislocation density, presumably due to impact on nucleation during the initial stages of heteroepitaxy.

  18. Polymer precursors for SiC ceramic materials

    Science.gov (United States)

    Litt, Morton H.

    1986-01-01

    Work on precursor polymers to SiC was performed, concentrating on polymers made from decamethyl cyclohexasilyene units. The initial approach was to synthesize mixed diphenyl decamethyl cyclohexasilane, dephenylate, and polymerize. This produced polymers which had yields of up to 50 percent SiC. (Theoretical yield is 75 percent). The present approach is to make the polymer through the intermediate trans-1,4-diphenyl decamethyl cyclohexasilane. This should produce a crystalline polymer and high strength fibers. These will be thermally decomposed to SiC fibers. This requires new chemistry which is currently being studied.

  19. Comparative study by IBIC of Si and SiC diodes irradiated with high energy protons

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Lopez, J., E-mail: fjgl@us.es [Dpto. Física Atómica, Molecular y Nuclear, Universidad de Sevilla, 41080 Sevilla (Spain); CNA (U. Sevilla, J. Andalucia, CSIC), Av. Thomas A. Edison 7, 41092 Sevilla (Spain); Jimenez-Ramos, M.C.; Rodriguez-Ramos, M. [CNA (U. Sevilla, J. Andalucia, CSIC), Av. Thomas A. Edison 7, 41092 Sevilla (Spain); Ceballos, J. [Institute of Microelectronics of Seville, IMSE-CNM (CSIC/University of Seville), Seville 41092 (Spain); Linez, F. [Department of Applied Physics, Aalto University, 02150 Espoo (Finland); Raisanen, J. [Department of Physics, University of Helsinki, Helsinki 00014 (Finland)

    2016-04-01

    The transport properties of a series of Si and SiC diodes have been studied using the Ion Beam Induced Charge (IBIC) technique. Structural defects were induced into the samples during the irradiation with 17 MeV protons. The experimental values of the charge collection efficiency (CCE) vs bias voltages have been analyzed using a modified drift-diffusion model, which takes into account the recombination of carriers in the neutral and depletion regions. From these simulations, we have obtained the values of the carrier’s lifetime for pristine and irradiated diodes, which are found to degrade faster in the case of the SiC samples. However, the decrease of the CCE at high bias voltages is more important for the Si detectors, indicative of the lower radiation hardness of this material compared to SiC. The nature of the proton-induced defects on Si wafers has been studied by Positron Annihilation Spectroscopy (PAS) and Doppler Broadening Spectroscopy (DBS). The results suggest that the main defect detected by the positrons in p-type samples is the divacancy while for n-type at least a fraction of the positron annihilate in another defect. The concentration of defects is much lower than the number of vacancies predicted by SRIM.

  20. Characteristics of Commercial SiC and Synthetic SiC as an Aggregate in Geopolymer Composites

    Science.gov (United States)

    Irfanita, R.; Afifah, K. N.; Asrianti; Subaer

    2017-03-01

    This main objective of this study is to investigate the effect silicon carbide (SiC) as an aggregate on the mechanical strength and microstructure of the geopolymer composites. The geopolymers binder were produced by using alkaline activation method of metakaolin and cured at 70oC for 2 hours. In this study commercial and synthetic SiC were used as aggregate to produce composite structure. Synthetic SiC was produced from rice husk ash and coconut shell carbon calcined at 750oC for 2 hours. The addition of SiC in geopolymers paste was varied from 0.25g, 0.50g to 0.75g to form geopolymers composites. The chemical compositions and crystallinity level of SiC and the resulting composites were measured by means of Rigaku MiniFlexII X-Ray Diffraction (XRD). The microstructure of SiC and the composites were examined by using Tescan Vega3SB Scanning Electron Microscopy (SEM). The physical and mechanical properties of the samples were determined based on apparent porosity, bulk density, and three bending flexural strength measurements. The results showed that the commercial and synthetic SiC were effectively produced geopolymers composites with different microstructure, physical and mechanical strength.

  1. Characterization of SiC based composite materials by the infiltration of ultra-fine SiC particles

    International Nuclear Information System (INIS)

    Lee, J.K.; Lee, S.P.; Byun, J.H.

    2010-01-01

    The fabrication route of SiC materials by the complex compound of ultra-fine SiC particles and oxide additive materials has been investigated. Especially, the effect of additive composition ratio on the characterization of SiC materials has been examined. The characterization of C/SiC composites reinforced with plain woven carbon fabrics was also investigated. The fiber preform for C/SiC composites was prepared by the infiltration of complex mixture into the carbon fabric structure. SiC based composite materials were fabricated by a pressure assisted liquid phase sintering process. SiC materials possessed a good density higher than about 3.0 Mg/m 3 , accompanying the creation of secondary phase by the chemical reaction of additive materials. C/SiC composites also represented a dense morphology in the intra-fiber bundle region, even if this material had a sintered density lower than that of monolithic SiC materials. The flexural strength of SiC materials was greatly affected by the composition ratio of additive materials.

  2. SiC Avalanche Photodiodes and Arrays Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Aymont Technology, Inc. (Aymont) will demonstrate the feasibility of SiC p-i-n avalanche photodiodes (APD) arrays. Aymont will demonstrate 4 x 4 arrays of 2 mm2 APDs...

  3. SiC flame sensors for gas turbine control systems

    Science.gov (United States)

    Brown, Dale M.; Downey, Evan; Kretchmer, Jim; Michon, Gerald; Emily Shu; Schneider, Don

    1998-05-01

    The research and development activities carried out to develop a SiC flame sensor for gas turbines utilized for power generation are discussed. These activities included the fabrication and characterization of SiC UV photodiodes and small SiC signal diodes as well as the designing and testing of production flame detector assemblies. The characteristics that make this solid state flame detector particularly useful for dry low NO x (DLN) premixed oil and natural gas fuels will be described. Since this device provides both analog dc and ac output signals, turbine combustor mode tracking, combustion flame dynamics and flame intensity tracking have been demonstrated. Sensors designed for production have been built, qualified and field tested. These sensors are now being installed in gas turbine power plants and are a component part of the turbine control system. This development has resulted in the first commercialized turbine control application to use SiC electronic devices.

  4. Visible Blind SiC Array with Low Noise Readout

    Data.gov (United States)

    National Aeronautics and Space Administration — We have designed and fabricated a Focal Plane Array (FPA) and low noise preamp board. We wish to complete the development of the SiC array test assembly and perform...

  5. Broadband antireflection nanodome structures on SiC substrate

    DEFF Research Database (Denmark)

    Ou, Yiyu; Zhu, Xiaolong; Møller, Uffe Visbech

    2013-01-01

    Nanodome structures are demonstrated on the SiC substrate by using nanosphere lithography and dry etching. Significant surface antireflection has been observed over a broad spectral range from 400 nm to 1600 nm.......Nanodome structures are demonstrated on the SiC substrate by using nanosphere lithography and dry etching. Significant surface antireflection has been observed over a broad spectral range from 400 nm to 1600 nm....

  6. Preparation of SiC and Ag/SiC coatings on TRISO surrogate particles by Pulsed Laser Deposition

    International Nuclear Information System (INIS)

    Lustfeld, Martin; Reinecke, Anne-Maria; Lippman, Wolfgang; Hurtado, Antonio; Ruiz-Moreno, Ana

    2014-01-01

    Recently published research results suggest significant advantages of using nanocrystalline instead of coarse grained SiC for nuclear applications. In this work it was attempted to prepare nanocrystalline SiC coatings on TRISO surrogate kernels using the pulsed laser deposition (PLD) process. As a plasma-based physical vapor deposition process, PLD allows the synthesis of dense and stoichiometric coatings in the amorphous or nanocrystalline phase. Two different types of TRISO surrogate kernels were used with outer diameters of 500 pm and 800 μm, respectively: plain Al 2 O 3 kernels and ZrO 2 kernels coated with TRISO-like buffer and pyrolytic carbon (PyC) layers. In a second step, the PLD process was used for the preparation of multilayer coatings consisting of a Ag layer buried with a SiC layer. The samples were analyzed regarding their morphology, microstructure, crystalline phase and chemical composition using scanning electron microscopy (SEM), laser scanning microscopy (LSM), x-ray diffraction (XRD) and energy- dispersive x-ray spectroscopy (EDX). The samples will be used in future work for out-of-pile investigations of both thermal stability and Ag retention capability of nanocrystalline SiC layers. X-ray diflraction measurements did not confirm nano crystallinity of the SiC coatings, but rather indicated that the coatings were mainly amorphous possibly with a little fraction of the nanocrystalline phase. Further analyses showed that some of the SiC coatings had an adequate stoichiometric composition and that Ag/SiC multilayer coatings were successfully produced by PLD. Coatings on TRISO- like buffer and PyC layers exhibited good adhesion to the substrate while coatings on Al 2 O 3 kernels were susceptible to delamination. The results suggest that PLD is generally suitable for SiC coating of TRISO particles. However, further optimization of the process parameters such as the coating temperature is needed to obtain fine- grained non-columnar SiC layers that

  7. Formation of SiC using low energy CO2 ion implantation in silicon

    International Nuclear Information System (INIS)

    Sari, A.H.; Ghorbani, S.; Dorranian, D.; Azadfar, P.; Hojabri, A.R.; Ghoranneviss, M.

    2008-01-01

    Carbon dioxide ions with 29 keV energy were implanted into (4 0 0) high-purity p-type silicon wafers at nearly room temperature and doses in the range between 1 x 10 16 and 3 x 10 18 ions/cm 2 . X-ray diffraction analysis (XRD) was used to characterize the formation of SiC in implanted Si substrate. The formation of SiC and its crystalline structure obtained from above mentioned technique. Topographical changes induced on silicon surface, grains and evaluation of them at different doses observed by atomic force microscopy (AFM). Infrared reflectance (IR) and Raman scattering measurements were used to reconfirm the formation of SiC in implanted Si substrate. The electrical properties of implanted samples measured by four point probe technique. The results show that implantation of carbon dioxide ions directly leads to formation of 15R-SiC. By increasing the implantation dose a significant changes were also observed on roughness and sheet resistivity properties.

  8. Research on SiC Whisker Prepared by H-PSO

    Directory of Open Access Journals (Sweden)

    WANG Yao

    2017-10-01

    Full Text Available SiC whiskers were prepared on the matrix of graphite by using high hydrogenous silicone oil(PSO as raw material. The effect of surface conditions of graphite and heating temperature on the growth of SiC whisker was mainly studied in this paper. The main factor which affects the nucleation and growth of SiC whisker is the heating temperature, with the heating temperature rising, the production of SiC whisker increases. The surface condition of graphite matrix also influences the growth of SiC whisker. With the nucleation points provided by graphite matrix defects increasing, the production of SiC whisker incleases and SiC whisker starts to overlap with each other. The formation process of SiC whisker includes two steps:nucleation and growth. SiC whisker nucleates at low temperature and grows at high temperature, which follows the VLS (vapor-liquid-solid growth mechanism.

  9. A dual-phase microstructural approach to damage and fracture of Ti3SiC2/SiC joints

    Science.gov (United States)

    Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.

    2018-02-01

    The microcracking mechanisms responsible for Ti3SiC2/SiC joint damage observed at the macroscopic scale after neutron irradiation experiments are investigated in detail. A dual-phase microstructural approach to damage and fracture of Ti3SiC2/SiC joints is developed that uses a finely discretized two-phase domain based on a digital image of an actual microstructure involving embedded Ti3SiC2 and SiC phases. The behaviors of SiC and Ti3SiC2 in the domain are described by the continuum damage mechanics (CDM) model reported in Nguyen et al., J. Nucl. Mater., 2017, 495:504-515. This CDM model describes microcracking damage in brittle ceramics caused by thermomechanical loading and irradiation-induced swelling. The dual-phase microstructural model is applied to predict the microcracking mechanisms occurring in a typical Ti3SiC2/SiC joint subjected to heating to 800 °C followed by irradiation-induced swelling at this temperature and cooling to room temperature after the applied swelling has reached the maximum swelling levels observed in the experiments for SiC and Ti3SiC2. The model predicts minor damage of the joint after heating but significant microcracking in the SiC phase and along the boundaries between SiC and Ti3SiC2 as well as along the bonding joint during irradiation-induced swelling and cooling to room temperature. These predictions qualitatively agree with the limited experimental observations of joint damage at this irradiation temperature.

  10. Quantitative Analysis of Efficiency Improvement of a Propulsion Drive by Using SiC Devices: A Case of Study

    Directory of Open Access Journals (Sweden)

    Kundan Kumar

    2017-01-01

    Full Text Available One of the emerging research topics in the propulsion drive of the electric vehicles is the improvement in the efficiency of its component parts, namely, the propulsion motor and the associated inverter. This paper is focused on the efficiency of the inverter and analyzes the improvement that follows from the replacement of the silicon (Si IGBT devices with silicon carbide (SiC MOSFETs. To this end, the paper starts by deriving the voltage-current solicitations of the inverter over the working torque-speed plane of the propulsion motor. Then, a proper model of the power losses in the inverter over a supply period of the motor is formulated for the two types of device, including the integrated freewheeling diode. By putting together the voltage-current solicitations and the device power losses, the efficiency maps of the Si IGBT and SiC MOSFET inverters are calculated and compared over the torque-speed plane. The results for the Si IGBT inverter are supported by measurements executed on a marketed C-segment compact electric car, while the SiC MOSFET loss model is validated by an on-purpose built test bench. Finally, the overall efficiency of the propulsion drive is calculated by accounting for the motor efficiency. Main outcomes of the paper is a quantitative evaluation of both the improvement in the efficiency achievable with the SiC MOSFETs and the ensuing increase in the electric car range.

  11. Alkali (Li, K and Na) and alkali-earth (Be, Ca and Mg) adatoms on SiC single layer

    Science.gov (United States)

    Baierle, Rogério J.; Rupp, Caroline J.; Anversa, Jonas

    2018-03-01

    First-principles calculations within the density functional theory (DFT) have been addressed to study the energetic stability, and electronic properties of alkali and alkali-earth atoms adsorbed on a silicon carbide (SiC) single layer. We observe that all atoms are most stable (higher binding energy) on the top of a Si atom, which moves out of the plane (in the opposite direction to the adsorbed atom). Alkali atoms adsorbed give raise to two spin unpaired electronic levels inside the band gap leading the SiC single layer to exhibit n-type semiconductor properties. For alkaline atoms adsorbed there is a deep occupied spin paired electronic level inside the band gap. These finding suggest that the adsorption of alkaline and alkali-earth atoms on SiC layer is a powerful feature to functionalize two dimensional SiC structures, which can be used to produce new electronic, magnetic and optical devices as well for hydrogen and oxygen evolution reaction (HER and OER, respectively). Furthermore, we observe that the adsorption of H2 is ruled by dispersive forces (van der Waals interactions) while the O2 molecule is strongly adsorbed on the functionalized system.

  12. Rheology of partially solidified AlSi7Mg0. 3 and the influence of SiC additions

    Energy Technology Data Exchange (ETDEWEB)

    Loue, W.R.; Landkroon, S.; Kool, W.H. (Delft Univ. of Technology (Netherlands))

    1992-05-01

    The rheology of a partially solidified AlSi7Mg0.3 alloy and the effect of SiC additions were investigated using a high-temperature, Searle-type viscometer. During continuous cooling, the viscosity increases gradually with increasing fraction of solidified alloy, until a critical fraction of solidified alloy is reached above which the viscosity sharply increases. The viscosity strongly decreases with increasing shear rate. This shear thinning behaviour is dependent on the time used for changing the shear rate. During isothermal holding, the viscosity gradually decreases towards a quasi-steady state value. The kinetics for reaching this value are independent of stirring speed, but are accelerated by the addition of SiC particles. However, the final viscosity does not seem to be affected by the presence of SiC. After stopping the shearing action, the viscosity increases with time. The increase in viscosity is reduced by the presence of SiC. The restoration time between the resumption of stirring and the re-attainment of quasi-steady state viscosity is much shorter than the corresponding holding time at rest. (orig.).

  13. Hysteresis in the Active Oxidation of SiC

    Science.gov (United States)

    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.

  14. X-ray fluorescence microtomography of SiC shells

    Energy Technology Data Exchange (ETDEWEB)

    Ice, G.E.; Chung, J.S. [Oak Ridge National Lab., TN (United States); Nagedolfeizi, M. [Univ. of Tennessee, Knoxville, TN (United States)

    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.

  15. Formation of SiC thin films by chemical vapor deposition with vinylsilane precursor

    Science.gov (United States)

    Doi, Takuma; Takeuchi, Wakana; Jin, Yong; Kokubun, Hiroshi; Yasuhara, Shigeo; Nakatsuka, Osamu; Zaima, Shigeaki

    2018-01-01

    We have examined the formation of SiC thin films by chemical vapor deposition (CVD) using vinylsilane and investigated the chemical bonding state and crystallinity of the prepared SiC thin films. We achieved the formation of a Si–H–less SiC film at growth temperatures as low as 600 °C. Also, we investigated the in situ doping effect of N by the incorporation of NH3 gas in the SiC growth and demonstrated that the chemical composition of N in SiC thin films was controlled by adjusting the NH3 flow rate. In addition, we examined the growth of SiC thin films on a Cu substrate and achieved the formation of a SiC thin film while avoiding any significant reaction between SiC and Cu at a growth temperature of 700 °C.

  16. Synthesis and properties of porous SiC ceramics

    Science.gov (United States)

    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.

  17. Determination of irradiation temperature using SiC temperature monitors

    International Nuclear Information System (INIS)

    Maruyama, Tadashi; Onose, Shoji

    1999-01-01

    This paper describes a method for detecting the change in length of SiC temperature monitors and a discussion is made on the relationship between irradiation temperature and the recovery in length of SiC temperature monitors. The SiC specimens were irradiated in the experimental fast reactor JOYO' at the irradiation temperatures around 417 to 645degC (design temperature). The change in length of irradiated specimens was detected using a dilatometer with SiO 2 glass push rod in an infrared image furnace. The temperature at which recovery in macroscopic length begins was obtained from the annealing intersection temperature. The results of measurements indicated that a difference between annealing intersection temperature and the design temperature sometimes reached well over ±100degC. A calibration method to obtain accurate irradiation temperature was presented and compared with the design temperature. (author)

  18. Laser composite surfacing of stainless steel with SiC

    Science.gov (United States)

    Dutta Majumdar, J.; Chandra, B. Ramesh; Nath, A. K.; Manna, I.

    2006-07-01

    In the present study, an attempt has been made to improve wear resistance of AISI 304 stainless steel by laser composite surfacing with SiC. Laser processing has been carried out by pre-deposition of Fe + SiC powders (in the ratio of 85:15 and thickness of 100 m) on AISI 304 stainless steel substrate and subsequently, melting it using a 2 kW continuous wave CO2 laser. Following laser processing, a detailed characterization and evaluation of mechanical/electrochemical properties of the composite layer were undertaken to study the influence of laser processing on the characteristics and properties of the composite layer. Microstructure of the composite layer consisted of uniformly dispersed SiC particles in grain refined -Fe dendrites. Laser composite surfacing led to a significant improvement in microhardness and wear resistance as compared to as-received substrate. However, pitting corrosion property was marginally deteriorated due to laser composite surfacing.

  19. Rare earth element abundances in presolar SiC

    Science.gov (United States)

    Ireland, T. R.; Ávila, J. N.; Lugaro, M.; Cristallo, S.; Holden, P.; Lanc, P.; Nittler, L.; Alexander, C. M. O'D.; Gyngard, F.; Amari, S.

    2018-01-01

    Individual isotope abundances of Ba, lanthanides of the rare earth element (REE) group, and Hf have been determined in bulk samples of fine-grained silicon carbide (SiC) from the Murchison CM2 chondrite. The analytical protocol involved secondary ion mass spectrometry with combined high mass resolution and energy filtering to exclude REE oxide isobars and Si-C-O clusters from the peaks of interest. Relative sensitivity factors were determined through analysis of NIST SRM reference glasses (610 and 612) as well as a trace-element enriched SiC ceramic. When normalised to chondrite abundances, the presolar SiC REE pattern shows significant deficits at Eu and Yb, which are the most volatile of the REE. The pattern is very similar to that observed for Group III refractory inclusions. The SiC abundances were also normalised to s-process model predictions for the envelope compositions of low-mass (1.5-3 M⊙) AGB stars with close-to-solar metallicities (Z = 0.014 and 0.02). The overall trace element abundances (excluding Eu and Yb) appear consistent with the predicted s-process patterns. The depletions of Eu and Yb suggest that these elements remained in the gas phase during the condensation of SiC. The lack of depletion in some other moderately refractory elements (like Ba), and the presence of volatile elements (e.g. Xe) indicates that these elements were incorporated into SiC by other mechanisms, most likely ion implantation.

  20. High Temperature Memories in SiC Technology

    OpenAIRE

    Ekström, Mattias

    2014-01-01

    This thesis is part of the Working On Venus (WOV) project. The aim of the project is to design electronics in silicon carbide (SiC) that can withstand the extreme surface environmen  of Venus. This thesis investigates some possible computer memory technologies that could survive on the surface of Venus. A memory must be able to function at 460 °C and after a total radiation dose of at least 200 Gy (SiC). This thesis is a literature survey. The thesis covers several Random-Access Memory (RAM) ...

  1. Packaging Technology for SiC High Temperature Electronics

    Science.gov (United States)

    Chen, Liang-Yu; Neudeck, Philip G.; Spry, David J.; Meredith, Roger D.; Nakley, Leah M.; Beheim, Glenn M.; Hunter, Gary W.

    2017-01-01

    High-temperature environment operable sensors and electronics are required for long-term exploration of Venus and distributed control of next generation aeronautical engines. Various silicon carbide (SiC) high temperature sensors, actuators, and electronics have been demonstrated at and above 500 C. A compatible packaging system is essential for long-term testing and application of high temperature electronics and sensors in relevant environments. This talk will discuss a ceramic packaging system developed for high temperature electronics, and related testing results of SiC integrated circuits at 500 C facilitated by this high temperature packaging system, including the most recent progress.

  2. A comparative study on the tensile and impact properties of Kevlar, carbon, and S-glass/epoxy composites reinforced with SiC particles

    Science.gov (United States)

    Bulut, Mehmet; Alsaadi, Mohamad; Erkliğ, Ahmet

    2018-02-01

    Present study compares the tensile and impact characteristics of Kevlar, carbon and glass fiber reinforced composites with addition of microscale silicon carbide (SiC) within the common matrix of epoxy. The variation of tensile and impact strength values was explored for different content of SiC in the epoxy resin by weight (0, 5, 10, 15 and 20 wt%). Resulting failure characteristics were identified by assisting Charpy impact tests. The influence of interfacial adhesion between particle and fiber/matrix on failure and tensile properties was discussed from obtained results and scanning electron microscopy (SEM) figures. It is concluded from results that the content of SiC particles, and fiber types used as reinforcement are major parameters those effecting on tensile and impact resistance of composites as a result of different interface strength properties between particle-matrix and particle-fiber.

  3. Comparison of Microstructure and Mechanical Properties of A356/SiC Metal Matrix Composites Produced by Two Different Melting Routes

    Directory of Open Access Journals (Sweden)

    Shashi Prakash Dwivedi

    2014-01-01

    Full Text Available A356/SiC metal matrix composites with different weight percent of SiC particles were fabricated by two different techniques such as mechanical stir casting and electromagnetic stir casting. The results of macrostructure, microstructure, and XRD study revealed uniform distribution, grain refinement, and low porosity in electromagnetic stir casing samples. The mechanical results showed that the addition of SiC particles led to the improvement in tensile strength, hardness, toughness, and fatigue life. It indicates that type of fabrication process and percentage of reinforcement are the effective factors influencing the mechanical properties. It is observed that when percentage of reinforcement increases in electromagnetic stir casting, best mechanical properties are obtained.

  4. Residual stresses and mechanical properties of Si3N4/SiC multilayered composites with different SiC layers

    International Nuclear Information System (INIS)

    Liua, S.; Lia, Y.; Chena, P.; Lia, W.; Gaoa, S.; Zhang, B.; Yeb, F.

    2017-01-01

    The effect of residual stresses on the strength, toughness and work of fracture of Si3N4/SiC multilayered composites with different SiC layers has been investigated. It may be an effective way to design and optimize the mechanical properties of Si3N4/SiC multilayered composites by controlling the properties of SiC layers. Si3N4/SiC multilayered composites with different SiC layers were fabricated by aqueous tape casting and pressureless sintering. Residual stresses were calculated by using ANSYS simulation, the maximum values of tensile and compressive stresses were 553.2MPa and −552.1MPa, respectively. Step-like fracture was observed from the fracture surfaces. Fraction of delamination layers increased with the residual stress, which can improve the reliability of the materials. Tensile residual stress was benefit to improving toughness and work of fracture, but the strength of the composites decreased. [es

  5. Fe Isotopic Composition of Presolar SiC Mainstream Grains

    Science.gov (United States)

    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.

  6. Emanation thermal analysis of SiC based materials

    Czech Academy of Sciences Publication Activity Database

    Bálek, V.; Zeleňák, V.; Mitsuhashi, T.; Bakardjieva, Snejana; Šubrt, Jan; Haneda, H.

    2002-01-01

    Roč. 67, č. 1 (2002), s. 83-89 ISSN 1418-2874 R&D Projects: GA MŠk ME 180 Grant - others:EFDA(XE) TTMA-001 Institutional research plan: CEZ:AV0Z4032918 Keywords : emanation thermal analysis * SEM * SiC nanocomposites Subject RIV: CA - Inorganic Chemistry Impact factor: 0.598, year: 2002

  7. High temperature flow behaviour of SiC reinforced lithium

    Indian Academy of Sciences (India)

    The compressive flow behaviour of lithium aluminosilicate (LAS) glass, with and without SiC particulate reinforcements, was studied. The LAS glass crystallized to spodumene during high-temperature testing. The flow behaviour of LAS glass changed from Newtonian to non-Newtonian due to the presence of crystalline ...

  8. Investigation of thermoelectric SiC ceramics for energy harvesting ...

    Indian Academy of Sciences (India)

    Investigation of thermoelectric SiC ceramics for energy harvesting applications on supersonic vehicles leading–edges. XIAO-YI HANa, b,∗. , JUN WANGa and HAI-FENG CHENGa. aScience and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and. Engineering ...

  9. Nucleation and growth of polycrystalline SiC

    DEFF Research Database (Denmark)

    Kaiser, M.; Schimmel, S.; Jokubavicius, V.

    2014-01-01

    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 ...

  10. High temperature flow behaviour of SiC reinforced lithium ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The compressive flow behaviour of lithium aluminosilicate (LAS) glass, with and without SiC particulate reinforcements, was studied. The LAS glass crystallized to β spodumene during high-temperature testing. The flow behaviour of LAS glass changed from Newtonian to non-Newtonian due to the presence of.

  11. Microstructure and mechanical properties of SiC materials

    International Nuclear Information System (INIS)

    Yarahmadi, M.

    1985-01-01

    The effect of the microstructure on the mechanical properties of SiC materials of different chemical composition (SSiC, SiSiC, and RSiC) was investigated. Furthermore, the creep strength was determined on oxidized samples and on non-pretreated samples. (HSCH)

  12. High temperature flow behaviour of SiC reinforced lithium ...

    Indian Academy of Sciences (India)

    Unknown

    Verdier (1996) explored the effect of SiC particulate rein- forcements in oxynitride glasses. Like in silicate compo- sites, non-Newtonian behaviour was observed in oxynitride glasses but instead of shear thinning they observed shear thickening. This was attributed to change in composition of grain boundary glass coupled ...

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

    Science.gov (United States)

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

    2007-10-01

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

  14. Construction Progress of S-IC Test Stand Towers

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  16. Construction Progress of the S-IC Test Stand

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    1963-01-01

    At its founding, the Marshall Space Flight Center (MSFC) inherited the Army's Jupiter and Redstone test stands, but much larger facilities were needed for the giant stages of the Saturn V. From 1960 to 1964, the existing stands were remodeled and a sizable new test area was developed. The new comprehensive test complex for propulsion and structural dynamics was unique within the nation and the free world, and they remain so today because they were constructed with foresight to meet the future as well as on going needs. Construction of the S-IC Static test stand complex began in 1961 in the west test area of MSFC, and was completed in 1964. The S-IC static test stand was designed to develop and test the 138-ft long and 33-ft diameter Saturn V S-IC first stage, or booster stage, weighing in at 280,000 pounds. Required to hold down the brute force of a 7,500,000-pound thrust produced by 5 F-1 engines, the S-IC static test stand was designed and constructed with the strength of hundreds of tons of steel and 12,000,000 pounds of cement, planted down to bedrock 40 feet below ground level. The foundation walls, constructed with concrete and steel, are 4 feet thick. The base structure consists of four towers with 40-foot-thick walls extending upward 144 feet above ground level. The structure was topped by a crane with a 135-foot boom. With the boom in the upright position, the stand was given an overall height of 405 feet, placing it among the highest structures in Alabama at the time. This photograph, taken April 4, 1963, gives a close up look at the ever-growing four towers of the S-IC Test Stand.

  18. Water absorption in thermally grown oxides on SiC and Si: Bulk oxide and interface properties

    Science.gov (United States)

    Liu, Gang; Xu, Can; Yakshinskiy, Boris; Wielunski, Leszek; Gustafsson, Torgny; Bloch, Joseph; Dhar, Sarit; Feldman, Leonard C.

    2014-11-01

    We combine nuclear reaction analysis and electrical measurements to study the effect of water exposure (D2O) on the n-type 4H-SiC carbon face (000 1 ¯ ) MOS system and to compare to standard silicon based structures. We find that: (1) The bulk of the oxides on Si and SiC behave essentially the same with respect to deuterium accumulation; (2) there is a significant difference in accumulation of deuterium at the semiconductor/dielectric interface, the SiC C-face structure absorbs an order of magnitude more D than pure Si; (3) standard interface passivation schemes such as NO annealing greatly reduce the interfacial D accumulation; and (4) the effective interfacial charge after D2O exposure is proportional to the total D amount at the interface.

  19. A comparative study on electrical characteristics of 1-kV pnp and npn SiC bipolar junction transistors

    Science.gov (United States)

    Okuda, Takafumi; Kimoto, Tsunenobu; Suda, Jun

    2018-04-01

    We investigate the electrical characteristics of 1-kV pnp SiC bipolar junction transistors (BJTs) and compare them with those of npn SiC BJTs. The base resistance, current gain, and blocking capability are characterized. It is found that the base resistance of pnp SiC BJTs is two orders of magnitude lower than that of npn SiC BJTs. However, the obtained current gains are low below unity in pnp SiC BJTs, whereas npn SiC BJTs exhibit a current gain of 14 without surface passivation. The reason for the poor current gain of pnp SiC BJTs is discussed.

  20. Grain-boundary type and distribution in silicon carbide coatings and wafers

    Science.gov (United States)

    Cancino-Trejo, Felix; López-Honorato, Eddie; Walker, Ross C.; Ferrer, Romelia Salomon

    2018-03-01

    Silicon carbide is the main diffusion barrier against metallic fission products in TRISO (tristructural isotropic) coated fuel particles. The explanation of the accelerated diffusion of silver through SiC has remained a challenge for more than four decades. Although, it is now well accepted that silver diffuse through SiC by grain boundary diffusion, little is known about the characteristics of the grain boundaries in SiC and how these change depending on the type of sample. In this work five different types (coatings and wafers) of SiC produced by chemical vapor deposition were characterized by electron backscatter diffraction (EBSD). The SiC in TRISO particles had a higher concentration of high angle grain boundaries (aprox. 70%) compared to SiC wafers, which ranged between 30 and 60%. Similarly, SiC wafers had a higher concentration of low angle grain boundaries ranging between 15 and 30%, whereas TRISO particles only reached values of around 7%. The same trend remained when comparing the content of coincidence site lattice (CSL) boundaries, since SiC wafers showed a concentration of more than 30%, whilst TRISO particles had contents of around 20%. In all samples the largest fractions of CSL boundaries (3 ≤ Σ ≤ 17) were the Σ3 boundaries. We show that there are important differences between the SiC in TRISO particles and SiC wafers which could explain some of the differences observed in diffusion experiments in the literature.

  1. A nanomechanical Raman spectroscopy based assessment of stress distribution in irradiated and corroded SiC

    Science.gov (United States)

    Mohanty, Debapriya Pinaki; Wang, Hao; Okuniewski, Maria; Tomar, Vikas

    2017-12-01

    Silicon carbide (SiC) composites are under consideration for cladding and structural materials in various types of reactors. The effects of ion irradiation and corrosion on stress distribution due to mechanical loading on chemical vapor deposited (CVD) SiC were investigated in this paper by using nanomechanical Raman spectroscopy (NMRS). The stress distribution was analyzed as a function of the oxide formation on a corroded specimen and as a function of ion-induced irradiation damage in an irradiated specimen. A finite element method (FEM) based model was developed based on local mechanical properties measured using nanoindentation to predict the NMRS measured stress distribution. The stress distribution was also predicted theoretically by using a stress concentration factor, which is a function of sample geometry and boundary conditions. The maximum stress obtained theoretically was in good agreement with the FEM model and NMRS based measurements. FEM results captured the stress variation trends and maximum stress value in the analyzed samples. NMRS measurements predicted that corrosion had a greater influence on increasing the maximum value of stress in comparison to ion irradiation. The increase in stress attributed to corrosion in comparison to ion irradiated samples was approximately 10%-20%.

  2. SiC: An Agent Based Architecture for Preventing and Detecting Attacks to Ubiquitous Databases

    Science.gov (United States)

    Pinzón, Cristian; de Paz, Yanira; Bajo, Javier; Abraham, Ajith; Corchado, Juan M.

    One of the main attacks to ubiquitous databases is the structure query language (SQL) injection attack, which causes severe damages both in the commercial aspect and in the user’s confidence. This chapter proposes the SiC architecture as a solution to the SQL injection attack problem. This is a hierarchical distributed multiagent architecture, which involves an entirely new approach with respect to existing architectures for the prevention and detection of SQL injections. SiC incorporates a kind of intelligent agent, which integrates a case-based reasoning system. This agent, which is the core of the architecture, allows the application of detection techniques based on anomalies as well as those based on patterns, providing a great degree of autonomy, flexibility, robustness and dynamic scalability. The characteristics of the multiagent system allow an architecture to detect attacks from different types of devices, regardless of the physical location. The architecture has been tested on a medical database, guaranteeing safe access from various devices such as PDAs and notebook computers.

  3. MAX Phase Modified SiC Composites for Ceramic-Metal Hybrid Cladding Tubes

    International Nuclear Information System (INIS)

    Jung, Yang-Il; Kim, Sun-Han; Park, Dong-Jun; Park, Jeong-Hwan; Park, Jeong-Yong; Kim, Hyun-Gil; Koo, Yang-Hyun

    2015-01-01

    A metal-ceramic hybrid cladding consists of an inner zirconium tube, and an outer SiC fiber-matrix SiC ceramic composite with surface coating as shown in Fig. 1 (left-hand side). The inner zirconium allows the matrix to remain fully sealed even if the ceramic matrix cracks through. The outer SiC composite can increase the safety margin by taking the merits of the SiC itself. In addition, the outermost layer prevents the dissolution of SiC during normal operation. On the other hand, a ceramic-metal hybrid cladding consists of an outer zirconium tube, and an inner SiC ceramic composite as shown in Fig. 1 (right-hand side). The outer zirconium protects the fuel rod from a corrosion during reactor operation, as in the present fuel claddings. The inner SiC composite, additionally, is designed to resist the severe oxidation under a postulated accident condition of a high-temperature steam environment. Reaction-bonded SiC was fabricated by modifying the matrix as the MAX phase. The formation of Ti 3 SiC 2 was investigated depending on the compositions of the preform and melt. In most cases, TiSi 2 was the preferential phase because of its lowest melting point in the Ti-Si-C system. The evidence of Ti 3 SiC 2 was the connection with the pressurizing

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

    Science.gov (United States)

    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.

  5. POWDER INJECTION MOLDING OF SIC FOR THERMAL MANAGEMENT V

    Directory of Open Access Journals (Sweden)

    Valmikanathan Onbattuvelli

    2012-06-01

    Full Text Available Silicon carbide (SiC exhibits many functional properties that are relevant to applications in electronics, aerospace, defense and automotive industries. However, the successful translation of these properties into final applications lies in the net-shaping of ceramics into fully dense microstructures. Increasing the packing density of the starting powders is one effective route to achieve high sintered density and dimensional precision. The present paper presents an in-depth study on the effects of nanoparticle addition on the powder injection molding process (PIM of SiC powder-polymer mixtures. In particular, bimodal mixtures of nanoscale and sub-micrometer particles are found to have significantly increased powder packing characteristics (solids loading in the powder-polymer mixtures. The influence of nanoparticle addition on the multi-step PIM process is examined. The above results provide new perspectives which could impact a wide range of materials, powder processing techniques and applications.

  6. Deposition of SiC thin films by PECVD

    CERN Document Server

    Cho, N I; Kim, C K

    1999-01-01

    The SiC films were deposited on Si substrate by the decomposition of CH sub 3 SiCl sub 3 (methylthrichlorosilane) molecules in a high frequency discharge field. From the Raman spectra, it is conjectured that the deposited film are formed into the polycrystalline structure. The photon absorption measurement reveal that the band gap of the electron energy state are to be 2.4 eV for SiC, and 2.6 eV for Si sub 0 sub . sub 4 C sub 0 sub . sub 6 , respectively. In the high power density regime, methyl-radicals decompose easily and increases the carbon concentration in plasma and result in the growing films.

  7. Structure of MnSi on SiC(0001)

    Science.gov (United States)

    Meynell, S. A.; Spitzig, A.; Edwards, B.; Robertson, M. D.; Kalliecharan, D.; Kreplak, L.; Monchesky, T. L.

    2016-11-01

    We report on the growth and magnetoresistance of MnSi films grown on SiC(0001) by molecular beam epitaxy. The growth resulted in a textured MnSi(111) film with a predominantly [1 1 ¯0 ] MnSi (111 )∥[11 2 ¯0 ] SiC(0001) epitaxial relationship, as demonstrated by transmission electron microscopy, reflection high energy electron diffraction, and atomic force microscopy. The 500 ∘C temperature required to crystallize the film leads to a dewetting of the MnSi layer. Although the sign of the lattice mismatch suggested the films would be under compressive stress, the films acquire an in-plane tensile strain likely driven by the difference in thermal expansion coefficients between the film and substrate during annealing. As a result, the magnetoresistive response demonstrates that the films possess a hard-axis out-of-plane magnetocrystalline anisotropy.

  8. SiC Particle Reinforced Al Matrix Composite by SIMA

    Science.gov (United States)

    Aydın, Emirhan; Yuksel, Caglar; Erzi, Eray; Dispinar, Derya

    Strain Induced Melt Activated (SIMA) method is one of the most commonly used techniques for producing near-net-shape parts. The alloy is heated to liquid+solid region and then forged into the die cavity. In this way, homogeneously distributed spherical structure can be obtained. There are no works in the literature on the use of SIMA to produce p/MMC. A cast alloy (A380) and a wrought alloy (A6063) was selected. There different SiC particle size were sieved to be in the range of 50-120 μm. The highest wettability was obtained in 6063 however there was almost no binding in A380. Impact and wear tests were carried to characterise the properties of SiC p/MMC.

  9. Effect of Si3N4 Addition on Oxidation Resistance of ZrB2-SiC Composites

    Directory of Open Access Journals (Sweden)

    Manab Mallik

    2017-06-01

    Full Text Available The oxidation behavior of ZrB2-20 vol % SiC and ZrB2-20 vol % SiC-5 vol % Si3N4 composites prepared by hot-pressing and subjected to isothermal exposure at 1200 or 1300 °C for durations of 24 or 100 h in air, as well as cyclic exposure at 1300 °C for 24 h, have been investigated. The oxidation resistance of the ZrB2-20 vol % SiC composite has been found to improve by around 20%–25% with addition of 5 vol % Si3N4 during isothermal or cyclic exposures at 1200 or 1300 °C. This improvement in oxidation resistance has been attributed to the formation of higher amounts of SiO2 and Si2N2O, as well as a greater amount of continuity in the oxide scale, because these phases assist in closing the pores and lower the severity of cracking by exhibiting self-healing type behavior. For both the composites, the mass changes are found to be higher during cyclic exposure at 1300 °C by about 2 times compared to that under isothermal conditions.

  10. A comprehensive molecular dynamics study on the self-assembly and properties of SiC based cage structures

    Science.gov (United States)

    Zhang, Congyan; Xin, Zihua; Yu, Ming; Jayanthi, C. S.; Wu, S. Y.; Shanghai University Collaboration

    2014-03-01

    A molecular dynamics study to investigate a plausible way of fabricating SiC based cage structures has been performed. In this work, the existence of the stable SiC based cage nanostructures SimCn with the size up to about 2.05nm in diameter and the compositions n/(n +m) from 0.4 to 0.6 has been demonstrated using an efficient semi-empirical Hamiltonian method (SCED-LCAO) [PRB 74, 15540 (2006)]. The structural properties are analyzed in terms of the composition, the bonding nature, the surface environment, the local strain, and types of ring structures. It is found that the sp2 bonding nature between Si and C atoms and the environmental mediation are two key factors for the self-assembly of the stable SiC based cage structures. In particular, the transition from one stable cage structure to another of similar composition might occur due to the mending process in the self-assembly. The first and second authors acknowledge the support from the NSFC (grant No.: 61176118) and 085 project of Shanghai University (China) for this work.

  11. Packaging Technologies for 500 C SiC Electronics and Sensors: Challenges in Material Science and Technology

    Science.gov (United States)

    Chen, Liang-Yu; Neudeck, Philip G.; Behelm, Glenn M.; Spry, David J.; Meredith, Roger D.; Hunter, Gary W.

    2015-01-01

    This paper presents ceramic substrates and thick-film metallization based packaging technologies in development for 500C silicon carbide (SiC) electronics and sensors. Prototype high temperature ceramic chip-level packages and printed circuit boards (PCBs) based on ceramic substrates of aluminum oxide (Al2O3) and aluminum nitride (AlN) have been designed and fabricated. These ceramic substrate-based chip-level packages with gold (Au) thick-film metallization have been electrically characterized at temperatures up to 550C. The 96 alumina packaging system composed of chip-level packages and PCBs has been successfully tested with high temperature SiC discrete transistor devices at 500C for over 10,000 hours. In addition to tests in a laboratory environment, a SiC junction field-effect-transistor (JFET) with a packaging system composed of a 96 alumina chip-level package and an alumina printed circuit board was tested on low earth orbit for eighteen months via a NASA International Space Station experiment. In addition to packaging systems for electronics, a spark-plug type sensor package based on this high temperature interconnection system for high temperature SiC capacitive pressure sensors was also developed and tested. In order to further significantly improve the performance of packaging system for higher packaging density, higher operation frequency, power rating, and even higher temperatures, some fundamental material challenges must be addressed. This presentation will discuss previous development and some of the challenges in material science (technology) to improve high temperature dielectrics for packaging applications.

  12. Modelling of ion implantation in SiC crystals

    Energy Technology Data Exchange (ETDEWEB)

    Chakarov, Ivan [SILVACO International, 4701 Patrick Henry Drive, Building 2, Santa Clara, CA 95054 (United States)]. E-mail: ivan.chakarov@silvaco.com; Temkin, Misha [SILVACO International, 4701 Patrick Henry Drive, Building 2, Santa Clara, CA 95054 (United States)

    2006-01-15

    An advanced electronic stopping model for ion implantation in SiC has been implemented within the binary collision approximation. The model has been thoroughly tested and validated for Al implantation into 4H-, 6H-SiC under different initial implant conditions. A very good agreement between calculated and experimental profiles has been achieved. The model has been integrated in an industrial technology CAD process simulator.

  13. Modelling of ion implantation in SiC crystals

    International Nuclear Information System (INIS)

    Chakarov, Ivan; Temkin, Misha

    2006-01-01

    An advanced electronic stopping model for ion implantation in SiC has been implemented within the binary collision approximation. The model has been thoroughly tested and validated for Al implantation into 4H-, 6H-SiC under different initial implant conditions. A very good agreement between calculated and experimental profiles has been achieved. The model has been integrated in an industrial technology CAD process simulator

  14. Behaviors of SiC fibers at high temperature

    International Nuclear Information System (INIS)

    Colin, C.; Falanga, V.; Gelebart, L.

    2010-01-01

    On the one hand, considering the improvements of mechanical and thermal behaviours of the last generation of SiC fibers (Hi-Nicalon S, Tyranno SA3); on the other hand, regarding physical and chemical properties and stability under irradiation, SiC/SiC composites are potential candidates for nuclear applications in advanced fission and fusion reactors. CEA must characterize and optimize these composites before their uses in reactors. In order to study this material, CEA is developing a multi-scale approach by modelling from fibers to bulk composite specimen: fibres behaviours must be well known in first. Thus, CEA developed a specific tensile test device on single fibers at high temperature, named MecaSiC. Using this device, we have already characterized the thermoelastic and thermoelectric behaviours of SiC fibers. Additional results about the plastic properties at high temperatures were also obtained. Indeed, we performed tensile tests between 1200 degrees C up to 1700 degrees C to characterize this plastic behaviour. Some thermal annealing, up to 3 hours at 1700 degrees C, had been also performed. Furthermore, we compare the mechanical behaviours with the thermal evolution of the electric resistivity of these SiC fibers. Soon, MecaSiC will be coupled to a new charged particle accelerator. Thus, in this configuration, we will be able to study in-situ irradiation effects on fibre behaviours, as swelling or creep for example

  15. Surface engineering of SiC via sublimation etching

    International Nuclear Information System (INIS)

    Jokubavicius, Valdas; Yazdi, Gholam R.; Ivanov, Ivan G.; Niu, Yuran; Zakharov, Alexei; Iakimov, Tihomir; Syväjärvi, Mikael; Yakimova, Rositsa

    2016-01-01

    Highlights: • Comparison of 6H-, 4H- and 3C-SiC sublimation etching. • Effects of Si-C and Si-C-Ta chemical systems on etching mechanisms. • Effect of etching ambient on surface reconstruction. • Application of etched 4H-SiC surface for the growth of graphene nanoribbons is illustrated. - Abstract: We present a technique for etching of SiC which is based on sublimation and can be used to modify the morphology and reconstruction of silicon carbide surface for subsequent epitaxial growth of various materials, for example graphene. The sublimation etching of 6H-, 4H- and 3C-SiC was explored in vacuum (10 −5 mbar) and Ar (700 mbar) ambient using two different etching arrangements which can be considered as Si-C and Si-C-Ta chemical systems exhibiting different vapor phase stoichiometry at a given temperature. The surfaces of different polytypes etched under similar conditions are compared and the etching mechanism is discussed with an emphasis on the role of tantalum as a carbon getter. To demonstrate applicability of such etching process graphene nanoribbons were grown on a 4H-SiC surface that was pre-patterned using the thermal etching technique presented in this study.

  16. Surface engineering of SiC via sublimation etching

    Energy Technology Data Exchange (ETDEWEB)

    Jokubavicius, Valdas, E-mail: valjo@ifm.liu.se [Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping (Sweden); Yazdi, Gholam R.; Ivanov, Ivan G. [Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping (Sweden); Niu, Yuran; Zakharov, Alexei [Max Lab, Lund University, S-22100 Lund (Sweden); Iakimov, Tihomir; Syväjärvi, Mikael; Yakimova, Rositsa [Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping (Sweden)

    2016-12-30

    Highlights: • Comparison of 6H-, 4H- and 3C-SiC sublimation etching. • Effects of Si-C and Si-C-Ta chemical systems on etching mechanisms. • Effect of etching ambient on surface reconstruction. • Application of etched 4H-SiC surface for the growth of graphene nanoribbons is illustrated. - Abstract: We present a technique for etching of SiC which is based on sublimation and can be used to modify the morphology and reconstruction of silicon carbide surface for subsequent epitaxial growth of various materials, for example graphene. The sublimation etching of 6H-, 4H- and 3C-SiC was explored in vacuum (10{sup −5} mbar) and Ar (700 mbar) ambient using two different etching arrangements which can be considered as Si-C and Si-C-Ta chemical systems exhibiting different vapor phase stoichiometry at a given temperature. The surfaces of different polytypes etched under similar conditions are compared and the etching mechanism is discussed with an emphasis on the role of tantalum as a carbon getter. To demonstrate applicability of such etching process graphene nanoribbons were grown on a 4H-SiC surface that was pre-patterned using the thermal etching technique presented in this study.

  17. Modeling SiC swelling under irradiation: Influence of amorphization

    CERN Document Server

    Romano, A; Defranceschi, M; Yip, S

    2003-01-01

    Irradiation-induced swelling of SiC is investigated using a molecular dynamics simulation-based methodology. To mimic the effect of heavy ion irradiation extended amorphous areas of various sizes are introduced in a crystalline SiC sample, and the resulting configurations are relaxed using molecular dynamics at constant pressure. Simulation results compare very well with data from existing ion implantation experiments. Analysis of the relaxed configurations shows very clearly that SiC swelling does not scale linearly with the amorphous fraction introduced. Two swelling regimes are observed depending on the size of the initial amorphous area: for small amorphous zones swelling scales like the amorphous fraction to the power 2/3, while for larger areas it scales like the amorphous fraction to the powers 2/3 and 4/3. Similar dependences on the amorphous fraction are obtained for the number of homonuclear bonds present in the initial amorphous volume and for the number of short bonds created at the interface betw...

  18. Spherical nanostructured Si/C composite prepared by spray drying technique for lithium ion batteries anode

    Energy Technology Data Exchange (ETDEWEB)

    Chen Libao [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Xie Xiaohua [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Wang Baofeng [Department of Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang Ke [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Xie Jingying [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China) and Graduate School of Chinese Academy of Sciences, Beijing 100049 (China)]. E-mail: jyxie@mail.sim.ac.cn

    2006-07-15

    Spherical nanostructured Si/C composite was prepared by spray drying technique, followed by heat treatment, in which nanosized silicon and fine graphite particles were homogeneously embedded in carbon matrix pyrolyzed by phenol formaldehyde resin. Cyclic voltammetry tests showed two pairs of redox peaks corresponding to lithiation and delithiation of Si/C composite. The Si/C composite exhibited a reversible capacity of 635 mAh g{sup -1} and good cycle performance used in lithium ion batteries. To improve cycle performance of this Si/C composite further, the carbon-coated Si/C composite was synthesized by the second spray drying and heat treatment processing. The cycle performance of carbon-coated Si/C composite was improved significantly, which was attributed to the formation of stable SEI passivation layers on the outer surface of carbon shell which protected the bared silicon from exposing to electrolyte directly.

  19. Protein SIC Secreted fromForms Complexes with Extracellular Histones That Boost Cytokine Production

    DEFF Research Database (Denmark)

    Westman, Johannes; Chakrakodi, Bhavya; Snäll, Johanna

    2018-01-01

    determine the amplitude of such responses and influence the outcome of the disease. Here, we report that protein SIC, Streptococcal Inhibitor of Complement, an abundant secreted protein fromStreptococcus pyogenes, binds to extracellular histones, a group of danger signals released during necrotizing tissue...... damage. This interaction leads to the formation of large aggregatesin vitro. Extracellular histones and SIC are abundantly expressed and seen colocalized in biopsies from patients with necrotizing soft-tissue infections caused byS. pyogenes. In addition, binding of SIC to histones neutralized...... their antimicrobial activity. Likewise, the ability of histones to induce hemolysis was inhibited in the presence of SIC. However, when added to whole blood, SIC was not able to block the pro-inflammatory effect of histones. Instead SIC boosted the histone-triggered release of a broad range of cytokines...

  20. SiC Optically Modulated Field-Effect Transistor

    Science.gov (United States)

    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

  1. Characterization of femtosecond-laser-induced periodic structures on SiC substrates

    Science.gov (United States)

    Miyagawa, Reina; Ohno, Yutaka; Deura, Momoko; Yonenaga, Ichiro; Eryu, Osamu

    2018-02-01

    We investigated the crystalline state of femtosecond-laser-induced periodic structures using a transmission electron microscope (TEM). The core of the 200-nm-pitch periodic nanostructures on SiC retained a high crystalline quality continued from the SiC substrate, where the crystal orientation was aligned with that of the SiC substrate. These results suggest that the periodic nanostructures were formed by periodic etching and not by rearrangement. At high laser power, microstructures with sizes larger than 2 µm were formed on the periodic nanostructures. The microstructures were amorphous and extended from the amorphous SiC layer that covered the periodic nanostructures.

  2. Formation and characterization of porous SiC by anodic oxidation using potassium persulfate solution

    Science.gov (United States)

    Iwasa, Y.; Kamiyama, S.; Iwaya, M.; Takeuchi, T.; Akasaki, I.

    2018-01-01

    The formation process of porous SiC by anodic oxidation was investigated, aiming at the generation of pure white light with a high color rendering index (CRI) and high luminous efficiency. The efficiency of white light emission from porous SiC and its wavelength are strongly dependent on the porous structure such as the average pore size and porosity. In this study, we examined the structure and optical properties of porous SiC by adding potassium persulfate (K2S2O8) as an oxidant in HF solution to control the porosity of porous SiC formed by anodic oxidation. By increasing the amount of the oxidant, we enhanced the integrated light emission intensity of porous SiC to 81 times that of bulk SiC. Through the study of porous SiC we demonstrated that the peak wavelength of the porous SiC could be controlled from 370 to 500 nm. Porous SiC created by anodic oxidation was thus proven to have great potential for realizing high-CRI white light generation using LEDs.

  3. New Possibilities of Power Electronic Structures Using SiC Technology

    Directory of Open Access Journals (Sweden)

    Robert Sul

    2006-01-01

    Full Text Available This paper is dedicated to the recent unprecedented boom of SiC electronic technology. The contribution deals with brief survey of those properties. 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 given for several large-scale applications on the end of the contribution. The basic properties of SiC material have been discussed already on the beginning of 80’s, also at our university.

  4. Small Incision Cataract Surgery (SICS with Clear Corneal Incision and SICS with Scleral Incision – A Comparative Study

    Directory of Open Access Journals (Sweden)

    Md Shafiqul Alam

    2014-01-01

    Full Text Available Background: Age related cataract is the leading cause of blindness and visual impairment throughout the world. With the advent of microsurgical facilities simple cataract extraction surgery has been replaced by small incision cataract surgery (SICS with posterior chamber intra ocular lens implant, which can be done either with clear corneal incision or scleral incision. Objective: To compare the post operative visual outcome in these two procedures of cataract surgery. Materials and method: This comparative study was carried out in the department of Ophthalmology, Delta Medical College & Hospital, Dhaka, Bangladesh, during the period of January 2010 to December 2012. Total 60 subjects indicated for age related cataract surgery irrespective of sex with the age range of 40-80 years with predefined inclusion and exclusion criteria were enrolled in the study. Subjects were randomly and equally distributed in 2 groups; Group A for SICS with clear corneal incision and group B for SICS with scleral incision. Post operative visual out come was evaluated by determining visual acuity and astigmatism in different occasions and was compared between groups. Statistical analysis was done by SPSS for windows version12. Results: The highest age incidence (43.3% was found between 61 to 70 years of age group. Among study subjects 40 were male and 20 were female. Preoperative visual acuity and astigmatism were evenly distributed between groups. Regarding postoperative unaided visual outcome, 6/12 or better visual acuity was found in 19.98% cases in group A and 39.6% cases in group B at 1st week. At 6th week 6/6 vision was found in 36.3% in Group A and 56.1% in Group B and 46.2% in group A and 66% in group B without and with correction respectively. With refractive correction, 6/6 vision was attained in 60% subjects of group A and 86.67% of group B at 8th week. Post operative visual acuity was statistically significant in all occasions. Postoperative astigmatism of

  5. Examining of abrasion resistance of hybrid composites reinforced with SiC and Cgr particles

    Directory of Open Access Journals (Sweden)

    M. Łągiewka

    2008-08-01

    Full Text Available The presented work discusses the influence of the type and volume percentage of particulate reinforcement consisting of mixed silicon carbide and graphite on the abrasion wear of hybrid composites with AlMg10 matrix. Also the macro photos of frictional surfaces have been shown and the results of hardness measurements have been presented. The performed examinations have allowed for stating that the mixture of SiC and Cgr particles changes in favour the tribological properties of the matrix alloy. It has been also proved that introducing hard reinforcing particles along with soft lubricating ones allows for achieving the material exhibiting high abrasion resistance, and moreover, the graphite particles protect the abraded surface from the destructive action of silicon carbide particles. Also hardness measurements have been performed and the resulting conclusion is that the composite hardness increases with an increase in volume fraction of the reinforcing particles.

  6. White light emission from fluorescent SiC with porous surface

    DEFF Research Database (Denmark)

    Lu, Weifang; Ou, Yiyu; Fiordaliso, Elisabetta Maria

    2017-01-01

    the bulk fuorescent SiC layer. A high color rendering index of 81.1 has been achieved. Photoluminescence spectra in porous layers fabricated in both commercial n-type and lab grown N-B co-doped 6H-SiC show two emission peaks centered approximately at 460nm and 530nm. Such bluegreen emission phenomenon can......, the photoluminescence intensity from the porous layer was signifcant enhanced by a factor of more than 12. Using a porous layer of moderate thickness (~10µm), high-quality white light emission was realized by combining the independent emissions of blue-green emission from the porous layer and yellow emission from...

  7. Influence of the growth-surface on the incorporation of phosphorus in SiC

    International Nuclear Information System (INIS)

    Rauls, E.; Gerstmann, U.; Frauenheim, Th.

    2005-01-01

    Phosphorus is a common and desired n-type dopant of SiC, but it turned out that doping by diffusion or during growth is rarely successful. To avoid the efforts and the creation of damage if ion implantation is used instead, these techniques were, though, highly desirable. In this work, we have investigated theoretically the experimental observation that phosphorus obviously hardly diffuses into the material. Not the diffusivity of the dopant but its addiction to occupy a three-fold coordinated surface site are critical, together with the way the surface affects the bulk migration barriers of the dopants. Whereas the most common growth direction for 4H-SiC, the polar silicon terminated (0001) surface, seems to be least appropriate for the incorporation of phosphorus atoms, growth along the nonpolar [112-bar 0] provides a good possibility to achieve efficient P-doping during growth

  8. Extraction method of interfacial injected charges for SiC power MOSFETs

    Science.gov (United States)

    Wei, Jiaxing; Liu, Siyang; Li, Sheng; Song, Haiyang; Chen, Xin; Li, Ting; Fang, Jiong; Sun, Weifeng

    2018-01-01

    An improved novel extraction method which can characterize the injected charges along the gate oxide interface for silicon carbide (SiC) power metal-oxide-semiconductor field-effect transistors (MOSFETs) is proposed. According to the different interface situations of the channel region and the junction FET (JFET) region, the gate capacitance versus gate voltage (Cg-Vg) curve of the device can be divided into three relatively independent parts, through which the locations and the types of the charges injected in to the oxide above the interface can be distinguished. Moreover, the densities of these charges can also be calculated by the amplitudes of the shifts in the Cg-Vg curve. The correctness of this method is proved by TCAD simulations. Moreover, experiments on devices stressed by unclamped-inductive-switching (UIS) stress and negative bias temperature stress (NBTS) are performed to verify the validity of this method.

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

    Science.gov (United States)

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

    2004-01-01

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

  10. Low Activation Joining of SiC/SiC Composites for Fusion Applications: Modeling Thermal and Irradiation-induced Swelling Effects on Integrity of Ti3SiC2/SiC Joint

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.; Ferraris, M.; Katoh, Yutai

    2017-03-31

    This work developed a continuum damage mechanics model that incorporates thermal expansion combined with irradiation-induced swelling effects to study the origin of cracking observed in recent irradiation experiments. Micromechanical modeling using an Eshelby-Mori-Tanaka approach was used to compute the thermoelastic properties of the Ti3SiC2/SiC joint needed for the model. In addition, a microstructural dual-phase Ti3SiC2/SiC model was developed to determine irradiation-induced swelling of the composite joint at a given temperature resulting from differential swelling of SiC and the Ti3SiC2 MAX phase. Three cases for the miniature torsion hourglass (THG) specimens containing a Ti3SiC2/SiC joint were analyzed corresponding to three irradiation temperatures: 800oC, 500oC, and 400oC.

  11. SiC MOSFETs based split output half bridge inverter

    DEFF Research Database (Denmark)

    Li, Helong; Munk-Nielsen, Stig; Beczkowski, Szymon

    2014-01-01

    output. The double pulse test shows the devices' current during commutation process and the reduced switching losses of SiC MOSFETs compared to that of the traditional half bridge. The efficiency comparison is presented with experimental results of half bridge power inverter with split output...... and traditional half bridge inverter, from switching frequency 10 kHz to 100 kHz. The experimental results comparison shows that the half bridge with split output has an efficiency improvement of more than 0.5% at 100 kHz switching frequency....

  12. SiC epitaxy growth using chloride-based CVD

    International Nuclear Information System (INIS)

    Henry, Anne; Leone, Stefano; Beyer, Franziska C.; Pedersen, Henrik; Kordina, Olof; Andersson, Sven; Janzén, Erik

    2012-01-01

    The growth of thick epitaxial SiC layers needed for high-voltage, high-power devices is investigated with the chloride-based chemical vapor deposition. High growth rates exceeding 100 μm/h can be obtained, however to obtain device quality epilayers adjustments of the process parameters should be carried out appropriately for the chemistry used. Two different chemistry approaches are compared: addition of hydrogen chloride to the standard precursors or using methyltrichlorosilane, a molecule that contains silicon, carbon and chlorine. Optical and electrical techniques are used to characterize the layers.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  15. Correlated silicon and titanium isotopic compositions of presolar SiC grains from the Murchison CM2 chondrite

    Science.gov (United States)

    Gyngard, Frank; Amari, Sachiko; Zinner, Ernst; Marhas, Kuljeet Kaur

    2018-01-01

    We report correlated Si, and Ti isotopic compositions and elemental concentrations of 238 presolar SiC grains from the Murchison CM2 meteorite. Combined with measurements of the C and N isotopic compositions of these 238 grains, 220 were determined to be of type mainstream, 10 type AB, 4 type Y and 4 type Z. SiC grains of diameter ≳2.5 μm, to ensure enough material to attempt Ti measurements, were randomly chosen without any other prejudice. The Ti isotopic compositions of the majority of the grains are characterized by enrichments in 46Ti, 47Ti, 49Ti, and 50Ti relative to 48Ti, and show linear isotopic correlations indicative of galactic chemical evolution and neutron capture of the grains parent stars. The variability in the observed Ti signal as a function of depth in most of the grains indicates the presence of distinct subgrains, likely TiC that have been previously observed in TEM studies. Vandium-51 concentrations correlate with those of Ti, indicating V substitutes for Ti in the TiC matrix in many of the grains. No isotopic anomalies in 52Cr/53Cr ratios were observed, and Cr concentrations did not correlate with those of either Ti or V.

  16. Volume production of high quality SiC substrates and epitaxial layers: Defect trends and device applications

    Science.gov (United States)

    Müller, St. G.; Sanchez, E. K.; Hansen, D. M.; Drachev, R. D.; Chung, G.; Thomas, B.; Zhang, J.; Loboda, M. J.; Dudley, M.; Wang, H.; Wu, F.; Byrappa, S.; Raghothamachar, B.; Choi, G.

    2012-08-01

    We review the progress of silicon carbide (SiC) bulk growth by the sublimation method, highlighting recent advances at Dow Corning, which resulted in the commercial release of 100 mm n-type 4H-SiC wafers with median micropipe densities (MPD) in production wafers etch pit analysis of 100 mm wafers demonstrate threading screw dislocation densities RMS) ≤1 nm as measured by atomic force microscopy (AFM), and carrier lifetimes consistently in the range of 2-3 μs has been demonstrated.

  17. Study of indentation induced cracks in MoSi2-reaction bonded SiC ...

    Indian Academy of Sciences (India)

    Mo melt into a preform of commercial SiC and petroleum coke powder. The infiltrated sample had a density > 92% of the theoretical density (TD) and microstructurally contained SiC, MoSi2, residual Si and unreacted C. The material was tested for indentation fracture toughness at room temperature with a Vicker's indenter ...

  18. Synthesis of SiC from rice husk in a plasma reactor

    Indian Academy of Sciences (India)

    Abstract. A new route for production of SiC from rice husk is reported by employing thermal plasma technique. The formation of -SiC is observed in a short time of 5 min. The samples are characterized by XRD and SEM.

  19. A DfT architecture for 3D-SICs based on a standardizable die wrapper

    NARCIS (Netherlands)

    Marinissen, E.J.; Chi, C.C.; Konijnenburg, M.; Verbree, J.

    2011-01-01

    Process technology developments enable the creation of three-dimensional stacked ICs (3D-SICs) interconnected by means of Through-Silicon Vias (TSVs). This paper presents a 3D Design-for-Test (DfT) architecture for such 3D-SICs that allows prebond die testing as well as mid-bond and post-bond stack

  20. Development of Simulink-Based SiC MOSFET Modeling Platform for Series Connected Devices

    DEFF Research Database (Denmark)

    Tsolaridis, Georgios; Ilves, Kalle; Reigosa, Paula Diaz

    2016-01-01

    A new MATLAB/Simulink-based modeling platform has been developed for SiC MOSFET power modules. The modeling platform describes the electrical behavior f a single 1.2 kV/ 350 A SiC MOSFET power module, as well as the series connection of two of them. A fast parameter initialization is followed...

  1. Tema 8. Principis físics dels semiconductors (Guia del tema)

    OpenAIRE

    Beléndez Vázquez, Augusto

    2011-01-01

    Guia del "Tema 8. Principis físics dels semiconductors" de l'assignatura "Fonaments Físics de l'Enginyeria I" de "Grau en Enginyeria en So i Imatge" impartit a l'Escola Politècnica Superior de la Universitat d'Alacant.

  2. [Application of Raman spectroscopy to investigation of CVD-SIC fiber].

    Science.gov (United States)

    Liu, Bin; Yang, Yan-Qing; Luo, Xian; Huang, Bin

    2011-11-01

    The CVD-SiC fiber was studied by using laser Raman spectra. It was found that the sharp TO peak exists in the first SiC deposit layer, indicating the larger SiC grains. But the second SiC deposit layer is with small grains. Raman peak of carbon and silicon was detected respectively in the first and second layer. Compared with that of the single SiC fiber, the TO peaks move to the high wave number for the SiC fiber in SiC(f)/Ti-6Al-4V composite. It indicates that the compressive thermal residual stress is present in the SiC fiber during the fabrication of the composite because of the mismatched coefficient of thermal expansion between Ti-6Al-4V matrix and SiC fiber. The average thermal residual stress of the SiC fiber in SiC(f)/Ti-6Al-4V composite was calculated to be 318 MPa and the residual stress in first deposit layer is 436 MPa which is much higher than that in the second layer.

  3. Reliability Concerns for Flying SiC Power MOSFETs in Space

    Science.gov (United States)

    Galloway, K. F.; Witulski, A. F.; Schrimpf, R. D.; Sternberg, A. L.; Ball, D. R.; Javanainen, A.; Reed, R. A.; Sierawski, B. D.; Lauenstein, J-M

    2018-01-01

    SiC power MOSFETs are space-ready in terms of typical reliability measures. However, single event burnout (SEB) often occurs at voltages 50% or lower than specified breakdown. Data illustrating burnout for 1200 V devices is reviewed and the space reliability of SiC MOSFETs is discussed.

  4. Fabrication of SiC nanopillars by inductively coupled SF6/O2 plasma etching

    Science.gov (United States)

    Choi, J. H.; Latu-Romain, L.; Bano, E.; Dhalluin, F.; Chevolleau, T.; Baron, T.

    2012-06-01

    In this paper, we demonstrate a top-down fabrication technique for nanometre scale silicon carbide (SiC) pillars using inductively coupled plasma etching. A set of experiments in SF6-based plasma was carried out in order to realize high aspect ratio SiC nanopillars. The etched SiC nanopillars using a small circular mask pattern (115 nm diameter) show high aspect ratio (7.4) with a height of 2.2 µm at an optimum bias voltage (300 V) and pressure (6 mTorr). Under the optimal etching conditions using a large circular mask pattern with 370 nm diameter, the obtained SiC nanopillars exhibit high anisotropy features (6.4) with a large etch depth (>7 µm). The etch characteristic of the SiC nanopillars under these conditions shows a high etch rate (550 nm min-1) and a high selectivity (over 60 for Ni). We also studied the etch profile of the SiC nanopillars and mask evolution over the etching time. As the mask pattern size shrinks in nanoscale, vertical and lateral mask erosion plays a crucial role in the etch profile of the SiC nanopillars. Long etching process makes the pillars appear with a hexagonal shape, coming from the crystallographic structure of α-SiC. It is found that the feature of pillars depends not only on the etching process parameters, but also on the crystallographic structure of the SiC phase.

  5. High Temperature Oxidation Property of SiC Coating Layer Fabricated by Aerosol Deposition Process

    Directory of Open Access Journals (Sweden)

    Ham G.-S.

    2017-06-01

    Full Text Available This study investigated the high temperature oxidation property of SiC coated layer fabricated by aerosol deposition process. SiC coated layer could be successfully manufactured by using pure SiC powders and aerosol deposition on the Zr based alloy in an optimal process condition. The thickness of manufactured SiC coated layer was measured about 5 μm, and coating layer represented high density structure. SiC coated layer consisted of α-SiC and β-SiC phases, the same as the initial powder. The initial powder was shown to have been crushed to the extent and was deposited in the form of extremely fine particles. To examine the high temperature oxidation properties, oxidized weight gain was obtained for one hour at 1000°C by using TGA. The SiC coated layer showed superior oxidation resistance property than that of Zr alloy (substrate. The high temperature oxidation mechanism of SiC coated layer on Zr alloy was suggested. And then, the application of aerosol deposited SiC coated layer was also discussed.

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

    DEFF Research Database (Denmark)

    Ou, Yiyu; Zhu, Xiaolong; Jokubavicius, Valdas

    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...... in the future....

  7. Research Progress of Optical Fabrication and Surface-Microstructure Modification of SiC

    Directory of Open Access Journals (Sweden)

    Fang Jiang

    2012-01-01

    Full Text Available SiC has become the best candidate material for space mirror and optical devices due to a series of favorable physical and chemical properties. Fine surface optical quality with the surface roughness (RMS less than 1 nm is necessary for fine optical application. However, various defects are present in SiC ceramics, and it is very difficult to polish SiC ceramic matrix with the 1 nm RMS. Surface modification of SiC ceramics must be done on the SiC substrate. Four kinds of surface-modification routes including the hot pressed glass, the C/SiC clapping, SiC clapping, and Si clapping on SiC surface have been reported and reviewed here. The methods of surface modification, the mechanism of preparation, and the disadvantages and advantages are focused on in this paper. In our view, PVD Si is the best choice for surface modification of SiC mirror.

  8. A Short-Circuit Safe Operation Area Identification Criterion for SiC MOSFET Power Modules

    DEFF Research Database (Denmark)

    Reigosa, Paula Diaz; Iannuzzo, Francesco; Luo, Haoze

    2017-01-01

    -circuit-current-based criterion; and 2) the gate-voltage-based criterion. The applicability of these two criteria makes possible the SCSOA evaluation of SiC MOSFETs with some safety margins in order to avoid unnecessary failures during their SCSOA characterization. SiC MOSFET power modules from two different manufacturers...

  9. Study of indentation induced cracks in MoSi2-reaction bonded SiC ...

    Indian Academy of Sciences (India)

    Unknown

    SiC ceramics. O P CHAKRABARTI*, P K DAS and S MONDAL. Central Glass and Ceramic Research Institute, Kolkata 700 032, India. Abstract. MoSi2–RBSC composite samples were prepared by infiltration of Si–2 at.% Mo melt into a preform of commercial SiC and petroleum coke powder. The infiltrated sample had a ...

  10. Computational Modeling of Radiation Phenomenon in SiC for Nuclear Applications

    Science.gov (United States)

    Ko, Hyunseok

    Silicon carbide (SiC) material has been investigated for promising nuclear materials owing to its superior thermo-mechanical properties, and low neutron cross-section. While the interest in SiC has been increasing, the lack of fundamental understanding in many radiation phenomena is an important issue. More specifically, these phenomena in SiC include the fission gas transport, radiation induced defects and its evolution, radiation effects on the mechanical stability, matrix brittleness of SiC composites, and low thermal conductivities of SiC composites. To better design SiC and SiC composite materials for various nuclear applications, understanding each phenomenon and its significance under specific reactor conditions is important. In this thesis, we used various modeling approaches to understand the fundamental radiation phenomena in SiC for nuclear applications in three aspects: (a) fission product diffusion through SiC, (b) optimization of thermodynamic stable self-interstitial atom clusters, (c) interface effect in SiC composite and their change upon radiation. In (a) fission product transport work, we proposed that Ag/Cs diffusion in high energy grain boundaries may be the upper boundary in unirradiated SiC at relevant temperature, and radiation enhanced diffusion is responsible for fast diffusion measured in post-irradiated fuel particles. For (b) the self-interstitial cluster work, thermodynamically stable clusters are identified as a function of cluster size, shape, and compositions using a genetic algorithm. We found that there are compositional and configurational transitions for stable clusters as the cluster size increases. For (c) the interface effect in SiC composite, we investigated recently proposed interface, which is CNT reinforced SiC composite. The analytical model suggests that CNT/SiC composites have attractive mechanical and thermal properties, and these fortify the argument that SiC composites are good candidate materials for the cladding

  11. SiC Formation Through Interface Reaction between C60 and Si in Plasma Environment

    Science.gov (United States)

    Ding, Fang; Meng, Liang; Zhu, Xiaodong

    2007-02-01

    The formation of SiC through the interface reaction between C60 and Si in a plasma-assisted chemical vapour deposition system (PACVD) is investigated with a C60 film previously deposited on Si wafers. The composition and structure of the deposited samples were characterized by micro-Raman spectroscopy and X-ray diffraction (XRD). The results showed that SiC film was formed successfully in hydrogen plasma at a substrate temperature of 800°C. The hydrogen atoms in plasma were found to enhance the production of SiC. Furthermore, the effects of the added CH4 on the formation of film were studied. Introduction of CH4 simultaneously with H2 at the beginning would suppress the formation of the initial layer of SiC due to a carbon-rich environment on the substrate, which would be disadvantageous to the further growth of the SiC film.

  12. Influence of stirring speed on SiC particles distribution in A356 liquid

    Directory of Open Access Journals (Sweden)

    Yao Shasha

    2012-05-01

    Full Text Available A straight-blade mechanical stirrer was designed to stir A356-3.5vol%SiCp liquid in a cylindrical crucible with the capability of systematically investigating the influence of rotating speed of stirrer on the distribution of SiC particles in A356 liquid. The experimental results show that the vertical distribution of SiC particles in A356 liquid can be uniform when the rotating speed of stirrer is 200 rpm, but the radial distribution of SiC particles in A356 liquid is always nonhomogeneous regardless of the rotating speed of stirrer. The radial centrifugalization ratio of SiC particles in A356 liquid between the center and the periphery of crucible increases with the rotating speed of stirrer. The results were explained in the light of SiC particles motion subject to a combination of stirring and centrifugal effect.

  13. Infrared surface phonon polariton waveguides on SiC Substrate

    Science.gov (United States)

    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.

  14. A Kochen–Specker inequality from a SIC

    Energy Technology Data Exchange (ETDEWEB)

    Bengtsson, Ingemar [Stockholms Universitet, Fysikum, S-10691 Stockholm (Sweden); Blanchfield, Kate, E-mail: kate@fysik.su.se [Stockholms Universitet, Fysikum, S-10691 Stockholm (Sweden); Cabello, Adán [Departamento de Física Aplicada II, Universidad de Sevilla, E-41012 Sevilla (Spain); Stockholms Universitet, Fysikum, S-10691 Stockholm (Sweden)

    2012-01-09

    Yu and Oh (eprint) have given a state-independent proof of the Kochen–Specker theorem in three dimensions using only 13 rays. The proof consists of showing that a non-contextual hidden variable theory necessarily leads to an inequality that is violated by quantum mechanics. We give a similar proof making use of 21 rays that constitute a SIC (symmetric informationally-complete positive operator-valued measure) and a complete set of MUB (mutually unbiased bases). A theory-independent inequality is also presented using the same 21 rays, as required for experimental tests of contextuality. -- Highlights: ► We find a state-independent Kochen–Specker inequality in dimension 3 with 21 rays. ► The rays constitute a SIC (9 rays) and a complete set of MUB (12 rays). ► Orthogonalities among the rays produce the Hesse configuration. ► The rays also give a state-independent non-contextual hidden variable inequality. ► We show that both inequalities are violated by quantum mechanics.

  15. Cohort profile: the Social Inequality in Cancer (SIC) cohort study.

    Science.gov (United States)

    Nordahl, Helene; Hvidtfeldt, Ulla Arthur; Diderichsen, Finn; Rod, Naja Hulvej; Osler, Merete; Frederiksen, Birgitte Lidegaard; Prescott, Eva; Tjønneland, Anne; Lange, Theis; Keiding, Niels; Andersen, Per Kragh; Andersen, Ingelise

    2014-12-01

    The Social Inequality in Cancer (SIC) cohort study was established to determine pathways through which socioeconomic position affects morbidity and mortality, in particular common subtypes of cancer. Data from seven well-established cohort studies from Denmark were pooled. Combining these cohorts provided a unique opportunity to generate a large study population with long follow-up and sufficient statistical power to develop and apply new methods for quantification of the two basic mechanisms underlying social inequalities in cancer-mediation and interaction. The SIC cohort included 83 006 participants aged 20-98 years at baseline. A wide range of behavioural and biological risk factors such as smoking, physical inactivity, alcohol intake, hormone replacement therapy, body mass index, blood pressure and serum cholesterol were assessed by self-administered questionnaires, physical examinations and blood samples. All participants were followed up in nationwide demographic and healthcare registries. For those interested in collaboration, further details can be obtained by contacting the Steering Committee at the Department of Public Health, University of Copenhagen, at inan@sund.ku.dk. © The Author 2014; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association.

  16. Mechanical properties of SiC long fibre reinforced copper

    Energy Technology Data Exchange (ETDEWEB)

    Brendel, A. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany)], E-mail: Annegret.Brendel@ipp.mpg.de; Paffenholz, V.; Koeck, Th.; Bolt, H. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany)

    2009-04-30

    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{sup 2} at operating temperatures of up to 550 deg. 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 deg. 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.

  17. Introduction of nano-laminate Ti3SiC2 and SiC phases into Cf-C composite by liquid silicon infiltration method

    Directory of Open Access Journals (Sweden)

    Omid Yaghobizadeh

    2017-03-01

    Full Text Available The material Cf-C-SiC-Ti3SiC2 is promising for high temperature application. Due to the laminated structure and special properties, the Ti3SiC2 is one of the best reinforcements for Cf-C-SiC composites. In this paper, Cf-C-SiC-Ti3SiC2 composites were fabricated by liquid silicon infiltration (LSI method; the effect of the TiC amount on the various composites properties were studied. For samples with 0, 50 and 90 vol.% of TiC, the results show that bending strength are 168, 190, and 181 MPa; porosities are 3.2, 4.7, and 9%; the fracture toughness are 6.1, 8.9, and 7.8 MPa∙m1/2; interlaminar shear strength are 27, 36, and 30 MPa; the amount of the MAX phase are 0, 8.5, and 5.6 vol.%, respectively. These results show that amount of TiC is not the main effective parameter in synthesis of Ti3SiC2. The existence of carbon promotes the synthesis of Ti3SiC2 indicating that only sufficient carbon content can lead to the appearance of Ti3SiC2 in the LSI process.

  18. Improved thermoelectric performance of CdO by adding SiC fibers versus by adding SiC nanoparticles inclusions

    Science.gov (United States)

    Liang, S.; Li, Longjiang

    2018-03-01

    We report the improved thermoelectric (TE) performance of CdO by alloying with SiC fibers. In contrast to the lowered thermoelectric figure of merit (ZT) in a CdO matrix with SiC nanoparticle composites, an appreciable ZT value increment of about 36% (from 0.32 to 0.435) at 1000 K was obtained in the CdO matrix with SiC fiber composites. Both kinds of composites show substantially decreased thermal conductivity due to additional phonon scattering by the nano-inclusions. Compared to the very high electrical resistivity (ρ ˜ 140 μΩ m) for 5 at. % SiC nanoparticle composites, SiC fiber composites favorably maintained a very low ρ (˜30 μΩ m) even with 5 at. % SiC at 1000 K. We think the substantial difference of specific surface areas of these two nano-inclusions (30 m2/g for fibers vs 300 m2/g for nanoparticles) might play a crucial role to fine tune the TE performance. Larger interface could be inductive to diffusion and electron acceptor activation, which affect carrier mobility considerably. This work might hint at an alternative approach to improve TE materials' performance.

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

    International Nuclear Information System (INIS)

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

    1998-01-01

    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 x 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. (orig.)

  20. The spin relaxation of nitrogen donors in 6H SiC crystals as studied by the electron spin echo method

    Science.gov (United States)

    Savchenko, D.; Shanina, B.; Kalabukhova, E.; Pöppl, A.; Lančok, J.; Mokhov, E.

    2016-04-01

    We present the detailed study of the spin kinetics of the nitrogen (N) donor electrons in 6H SiC wafers grown by the Lely method and by the sublimation "sandwich method" (SSM) with a donor concentration of about 1017 cm-3 at T = 10-40 K. The donor electrons of the N donors substituting quasi-cubic "k1" and "k2" sites (Nk1,k2) in both types of the samples revealed the similar temperature dependence of the spin-lattice relaxation rate (T1-1), which was described by the direct one-phonon and two-phonon processes induced by the acoustic phonons proportional to T and to T9, respectively. The character of the temperature dependence of the T1-1 for the donor electrons of N substituting hexagonal ("h") site (Nh) in both types of 6H SiC samples indicates that the donor electrons relax through the fast-relaxing centers by means of the cross-relaxation process. The observed enhancement of the phase memory relaxation rate (Tm-1) with the temperature increase for the Nh donors in both types of the samples, as well as for the Nk1,k2 donors in Lely grown 6H SiC, was explained by the growth of the free electron concentration with the temperature increase and their exchange scattering at the N donor centers. The observed significant shortening of the phase memory relaxation time Tm for the Nk1,k2 donors in the SSM grown sample with the temperature lowering is caused by hopping motion of the electrons between the occupied and unoccupied states of the N donors at Nh and Nk1,k2 sites. The impact of the N donor pairs, triads, distant donor pairs formed in n-type 6H SiC wafers on the spin relaxation times was discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Cao, J. [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering]|[Lawrence Berkeley National Lab., CA (United States). Materials Sciences Div.

    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. Fabrication of SiC hardened bodies with geopolymer binders using a warm press method

    Science.gov (United States)

    Hashimoto, Shinobu; Kubota, Kosuke; Ando, Kotaro; Tsutani, Masaki; Diko, Yusuke; Honda, Sawao; Iwamoto, Yuji

    2017-09-01

    Novel SiC hardened bodies with geopolymer binders using a warm press method were fabricated. In this study, two methods were tried. The first method used a conventional powder mixture consisted of SiC and geopolymer particles as starting materials. In the second method, SiC particles was first immersed in hydrochloric acid solution with 2.5 mol/L and then heated at 1200 °C for 6 h to form a reactive aluminosilicate layer at the surface of SiC particles. Subsequently, the resultant SiC particles mixed with a fixed amount of sodium hydroxide solution with various concentrations were put into a steel mold which was set in the warm press device. This second method was defined as a chemical assist processing. As this warm press condition, heating temperature was 130 °C and pressed at 240 MPa for 30 min simultaneously. When a powder mixture consisted of geopolymer and SiC particles was used, the compressive strength of the hardened bodies decreased with the amount of SiC particles. On the contrary, when the chemical assist processing method was selected, the compressive strength of the hardened bodies increased with the concentration of the sodium hydroxide solution. When the sodium hydroxide solution was 4 mol/L was used, the compressive strength of the hardened body reached to 170 MPa which was the maximum value in this study.

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

    Science.gov (United States)

    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.

  4. Fluorescent SiC as a New Platform for Visible and Infrared Emitting Applications as Well as Prospective Photovoltaics

    DEFF Research Database (Denmark)

    Syvaejaervi, Mikael; Sun, Jianwu; Wellmann, Peter

    of the polytypes covers a broad range of emission in the visible and infrared region, and the fluorescent SiC can act as a base material for SiC based light emitting materials having benefits of the SiC properties such as chemical stability, high thermal conduction and matching with nitride growth for LED......Fluorescent SiC is a novel materials system which may be a new platform for visible and infrared emitting applications. Although SiC is an indirect bandgap semiconductor, the donor acceptor pair emissions involving deep acceptors could become efficient if the acceptor envelope function...... are sufficiently localized. Nitrogen and boron co-doped SiC exhibits a high efficient donor acceptor pair emission at room temperature. Such donor acceptor pair emission exhibits a broad emission band in the wavelength ranging from visible to infrared region depending on the SiC polytypes. In 6H-SiC the emission...

  5. Theoretical predictions of a bucky-diamond SiC cluster

    Science.gov (United States)

    Yu, Ming; Jayanthi, C. S.; Wu, S. Y.

    2012-06-01

    A study of structural relaxations of SinCm clusters corresponding to different compositions, different relative arrangements of Si/C atoms, and different types of initial structure, reveals that the SinCm bucky-diamond structure can be obtained for an initial network structure constructed from a truncated bulk 3C-SiC for a magic composition corresponding to n = 68 and m = 79. This study was performed using a semi-empirical Hamiltonian (SCED-LCAO) since it allowed an extensive search of different types of initial structures. However, the bucky-diamond structure predicted by this method was also confirmed by a more accurate density functional theory (DFT) based method. The bucky-diamond structure exhibited by a SiC-based system represents an interesting paradigm where a Si atom can form three-coordinated as well as four-coordinated networks with carbon atoms and vice versa and with both types of network co-existing in the same structure. Specifically, the bucky-diamond structure of the Si68C79 cluster consists of a 35-atom diamond-like inner core (four-atom coordinations) suspended inside a 112-atom fullerene-like shell (three-atom coordinations).

  6. Theoretical predictions of a bucky-diamond SiC cluster.

    Science.gov (United States)

    Yu, Ming; Jayanthi, C S; Wu, S Y

    2012-06-15

    A study of structural relaxations of Si(n)C(m) clusters corresponding to different compositions, different relative arrangements of Si/C atoms, and different types of initial structure, reveals that the Si(n)C(m) bucky-diamond structure can be obtained for an initial network structure constructed from a truncated bulk 3C-SiC for a magic composition corresponding to n = 68 and m = 79. This study was performed using a semi-empirical Hamiltonian (SCED-LCAO) since it allowed an extensive search of different types of initial structures. However, the bucky-diamond structure predicted by this method was also confirmed by a more accurate density functional theory (DFT) based method. The bucky-diamond structure exhibited by a SiC-based system represents an interesting paradigm where a Si atom can form three-coordinated as well as four-coordinated networks with carbon atoms and vice versa and with both types of network co-existing in the same structure. Specifically, the bucky-diamond structure of the Si(68)C(79) cluster consists of a 35-atom diamond-like inner core (four-atom coordinations) suspended inside a 112-atom fullerene-like shell (three-atom coordinations).

  7. Residual stresses and mechanical properties of Si3N4/SiC multilayered composites with different SiC layers; Las tensiones residuales y las propiedades mecánicas de compuestos multicapa de Si3N4/SiC con diferentes capas de SiC

    Energy Technology Data Exchange (ETDEWEB)

    Liua, S.; Lia, Y.; Chena, P.; Lia, W.; Gaoa, S.; Zhang, B.; Yeb, F.

    2017-11-01

    The effect of residual stresses on the strength, toughness and work of fracture of Si3N4/SiC multilayered composites with different SiC layers has been investigated. It may be an effective way to design and optimize the mechanical properties of Si3N4/SiC multilayered composites by controlling the properties of SiC layers. Si3N4/SiC multilayered composites with different SiC layers were fabricated by aqueous tape casting and pressureless sintering. Residual stresses were calculated by using ANSYS simulation, the maximum values of tensile and compressive stresses were 553.2MPa and −552.1MPa, respectively. Step-like fracture was observed from the fracture surfaces. Fraction of delamination layers increased with the residual stress, which can improve the reliability of the materials. Tensile residual stress was benefit to improving toughness and work of fracture, but the strength of the composites decreased. [Spanish] Se ha investigado el efecto de las tensiones residuales en la resistencia, dureza y trabajo de fractura de los compuestos multicapa de Si3N4/SiC con diferentes capas de SiC. Puede ser una manera eficaz de diseñar y optimizar las propiedades mecánicas de los compuestos multicapa de Si3N4/SiC mediante el control de las propiedades de las capas de SiC. Los compuestos multicapa de Si3N4/SiC con diferentes capas de SiC se fabricaron por medio de colado en cinta en medio acuoso y sinterización sin presión. Las tensiones residuales se calcularon mediante el uso de la simulación ANSYS, los valores máximos de las fuerzas de tracción y compresión fueron 553,2 MPa y −552,1 MPa, respectivamente. Se observó una fractura escalonada a partir de las superficies de fractura. La fracción de capas de deslaminación aumenta con la tensión residual, lo que puede mejorar la fiabilidad de los materiales. La fuerza de tracción residual era beneficiosa para la mejora de la dureza y el trabajo de fractura, pero la resistencia de los compuestos disminuyó.

  8. Localized Surface Plasmon on 6H SiC with Ag Nanoparticles

    DEFF Research Database (Denmark)

    Wei, Yi; Fadil, Ahmed; Ou, Haiyan

    2017-01-01

    Silver (Ag) nanoparticles (NPs) were deposited on the surface of bulk Nitrogen-Boron co-doped 6H silicon carbide (SiC), and the Ag NPs were observed to induce localized surface plasmons (LSP) resonances on the SiC substrate, which was expected to improve the internal quantum efficiency (IQE...... of an Ag nanoparticle on the SiC substrate, it is predicted that when the diameter of the cross section on the xy plane of the Ag nanoparticle is greater than 225 nm, the LSP starts to enhance the PL intensity. With implementation of a 3rd order exponential decay fitting model to the TRPL results...

  9. A route to strong p-doping of epitaxial graphene on SiC

    KAUST Repository

    Cheng, Yingchun

    2010-11-09

    The effects of Au intercalation on the electronic properties of epitaxialgraphenegrown on SiC{0001} substrates are studied using first principles calculations. A graphenemonolayer on SiC{0001} restores the shape of the pristine graphene dispersion, where doping levels between strongly n-doped and weakly p-doped can be achieved by altering the Au coverage. We predict that Au intercalation between the two C layers of bilayer graphenegrown on SiC{0001} makes it possible to achieve a strongly p-doped graphene state, where the p-doping level can be controlled by means of the Au coverage.

  10. Structural and thermal characterization of polyvinylalcohol grafted SiC nanocrystals

    DEFF Research Database (Denmark)

    Saini, Isha; Sharma, Annu; Dhiman, Rajnish

    2017-01-01

    In the present work, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, x-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to ascertain the grafting of an organic layer of polyvinyl alcohol (PVA) onto the surface...... of semiconducting SiC nanocrystals using a novel method. FTIR spectroscopy reveals the introduction of new peaks corresponding to various functional groups of PVA alongwith the presence of characteristic Si-C vibrational peak in the spectra of grafted SiC nanocrystals. Raman spectra depict the presence of changes...

  11. Effects of SiC and MgO on aluminabased ceramic foams filters

    Directory of Open Access Journals (Sweden)

    CAO Da-li

    2007-11-01

    Full Text Available Alumina-based foam ceramic filters were fabricated by using alumina, SiC, magnesia powder as major materials. It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals. The influences of SiC and magnesia content, the sintering temperatures on ceramic properties were discussed. Aluminabased foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times. Its main phases after 1 hour sintering at 1 500 consist of alumina, silicon carbide, spinel and mullite.

  12. Conformers of hydrogenated SiC honeycomb structure: A first principles study

    Directory of Open Access Journals (Sweden)

    Seemita Banerjee

    2013-08-01

    Full Text Available The structural and electronic properties of fully hydrogenated SiC graphane-like nano-structures have been investigated. The objective of this study is to underscore the relative stability of different conformers of hydrogenated SiC sheet. All calculations are carried out using plane wave based pseudo-potential approach under the density functional theory. The results reveal that the fully hydrogenated SiC sheet forms five stable isomers, and the chair conformer is most stable. Further study through molecular dynamic simulation strategy demonstrates that even at room temperature the chair conformer remains stable.

  13. Pulsed laser deposition of SiC thin films at medium substrate temperatures

    International Nuclear Information System (INIS)

    Katharria, Y.S.; Kumar, Sandeep; Choudhary, R.J.; Prakash, Ram; Singh, F.; Lalla, N.P.; Phase, D.M.; Kanjilal, D.

    2008-01-01

    Systematic studies of thin silicon carbide (SiC) films deposited on Si (100) substrates using pulsed laser deposition technique at room temperature, 370 deg. C and 480 deg. C are carried out. X-ray photoelectron spectroscopy showed the formation of SiC bonds in the films at these temperatures along with some graphitic carbon clusters. Fourier transform infrared analysis also confirmed the formation of SiC nanocrystallites in the films. Transmission electron microscopy and electron diffraction were used to study the structural properties of nanocrystallites formed in the films. Surface morphological analysis using atomic force microscopy revealed the growth of smooth films

  14. Effect of SiC addition to the characteristics of Al-11Zn-6.7Mg composite produced by squeeze casting for ballistic application

    Science.gov (United States)

    Adiputra, R. F.; Wijanarko, R.; Angela, I.; Sofyan, B. T.

    2018-01-01

    Aluminium composite material as an alternative to steel used in body of tactical vehicles has been studied. Addition of SiC was expected to have strengthening effect on the composite matrix therefore improving its ballistic performance. Composites of Al-11Zn-6.7Mg matrix and SiC strengthening particles with the fraction of 0, 10, and 15 vol. % were fabricated through squeeze casting process. Composite samples were then precipitation strengthened at 130 °C for 102 h to further improve their toughness. Final products were characterized by using chemical composition testing, optical microscopy, Scanning Electron Microscope – Energy Dispersive Spectroscopy (SEM-EDS) and quantitative metallography to calculate porosity, hardness test, impact test, and type III ballistic test in accordance with NIJ 0108.04 standard. The results showed that increase in SiC volume fraction from 0 to 10 and 15 vol. % managed to improve the hardness from 73 to 85 and 87 HRB, respectively, while on the other hand reduced the impact values from 12,278.69 to 11,290.35 and 9,924.54 J/m2. SEM-EDS observation confirmed the presence of Mg3Zn3Al2 intermetallic compound which formed during solidification and indicated the precipitation of MgZn2 precipitates during ageing. The ballistic testing demonstrated a promising result of the potential of Al-11Zn-6.7Mg composite strengthened by 15 vol. % SiC to withstand penetration of type III bullet (7.62 mm).

  15. Development of high thermal conductive SiC fiber reinforced SiC matrix composites for fusion reactors (Thesis)

    International Nuclear Information System (INIS)

    Taguchi, Tomitsugu

    2006-07-01

    A 3 dimensional model (after cubic model) was developed to quantitatively predict the thermal conductivity of SiC fiber-reinforced SiC matrix (SiC/SiC) composites. The cubic model showed that thermal conductivity of the composites increased by decreasing the porosity and ensphering the shape of pore. The SiC/SiC composites were fabricated by chemical vapor infiltration (CVI) and reaction bonding (RB) processes. The thermal conductivity of the composites by RB process was higher than that by CVI process. The reason is that the porosity of the composites by RB process was lower than that by CVI process and the shape of pore in the composites by RB process was almost sphere. The thermal conductivity of the SiC/SiC composite by RB process was consistent with the estimated value by the cubic model. The cubic model also showed that the thermal conductivity of the composites increased by introducing a high thermal conductive new phase parallel to the direction of heat flow. To verify the prediction, a SiC/SiC composite with carbon nano-fiber (CNF) were fabricated by RB process. The thermal conductivity of the SiC/SiC composite with CNF was approximately 90 W/mK at room temperature. The thermal conductivity of the SiC/SiC composite was coincided with the estimated value by the cubic model. They concluded that the cubic model was useful for predicting the thermal conductivity of fiber-reinforced composites. (author)

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

    Science.gov (United States)

    Ebrahimpour, Omid

    In this work, mullite-bonded porous silicon carbide (SiC) ceramics were prepared via a reaction bonding technique with the assistance of a sol-gel technique or in-situ polymerization as well as a combination of these techniques. In a typical procedure, SiC particles were first coated by alumina using calcined powder and alumina sol via a sol-gel technique followed by drying and passing through a screen. Subsequently, they were coated with the desired amount of polyethylene via an in-situ polymerization technique in a slurry phase reactor using a Ziegler-Natta catalyst. Afterward, the coated powders were dried again and passed through a screen before being pressed into a rectangular mold to make a green body. During the heating process, the polyethylene was burnt out to form pores at a temperature of about 500°C. Increasing the temperature above 800°C led to the partial oxidation of SiC particles to silica. At higher temperatures (above 1400°C) derived silica reacted with alumina to form mullite, which bonds SiC particles together. The porous SiC specimens were characterized with various techniques. The first part of the project was devoted to investigating the oxidation of SiC particles using a Thermogravimetric analysis (TGA) apparatus. The effects of particle size (micro and nano) and oxidation temperature (910°C--1010°C) as well as the initial mass of SiC particles in TGA on the oxidation behaviour of SiC powders were evaluated. To illustrate the oxidation rate of SiC in the packed bed state, a new kinetic model, which takes into account all of the diffusion steps (bulk, inter and intra particle diffusion) and surface oxidation rate, was proposed. Furthermore, the oxidation of SiC particles was analyzed by the X-ray Diffraction (XRD) technique. The effect of different alumina sources (calcined Al2O 3, alumina sol or a combination of the two) on the mechanical, physical, and crystalline structure of mullite-bonded porous SiC ceramics was studied in the

  17. Ultra-Lightweight, High Efficiency Silicon-Carbide (SIC) Based Power Electronic Converters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business of Innovation Research Phase I proposal seeks to investigate and prove the feasibility of developing highly efficient, ultra-lightweight SiC...

  18. Carbon Nanotube (CNT) and Carbon Fiber Reinforced SiC Optical Components, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — M Cubed has developed and patented technology to make carbon fiber reinforced SiC composites and components. In addition, the feasibility of doubling the toughness...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  20. Silicon Carbide (SiC) Power Processing Unit (PPU) for Hall Effect Thrusters, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — In this SBIR project, APEI, Inc. is proposing to develop a high efficiency, rad-hard 3.8 kW silicon carbide (SiC) Power Processing Unit (PPU) for Hall Effect...

  1. Promise and Challenges of High-Voltage SiC Bipolar Power Devices

    Directory of Open Access Journals (Sweden)

    Tsunenobu Kimoto

    2016-11-01

    Full Text Available Although various silicon carbide (SiC power devices with very high blocking voltages over 10 kV have been demonstrated, basic issues associated with the device operation are still not well understood. In this paper, the promise and limitations of high-voltage SiC bipolar devices are presented, taking account of the injection-level dependence of carrier lifetimes. It is shown that the major limitation of SiC bipolar devices originates from band-to-band recombination, which becomes significant at a high-injection level. A trial of unipolar/bipolar hybrid operation to reduce power loss is introduced, and an 11 kV SiC hybrid (merged pin-Schottky diodes is experimentally demonstrated. The fabricated diodes with an epitaxial anode exhibit much better forward characteristics than diodes with an implanted anode. The temperature dependence of forward characteristics is discussed.

  2. Ultra-Lightweight, High Efficiency Silicon-Carbide (SIC) Based Power Electronic Converters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In Phase I of this project, APEI, Inc. proved the feasibility of creating ultra-lightweight power converters (utilizing now emerging silicon carbide [SiC] power...

  3. Ultra-Lightweight, High Efficiency Silicon-Carbide (SIC) Based Power Electronic Converters, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business of Innovation Research Phase I proposal seeks to investigate and prove the feasibility of developing highly efficient, ultra-lightweight SiC...

  4. SiC Armor Tiles via Magnetic Compaction and Pressureless Sintering

    National Research Council Canada - National Science Library

    Chelluri, Bhanu; Knoth, Ed A; Franks, L. P

    2008-01-01

    The purpose of the SBIR, entitled "Continuous Dynamic Processing of Ceramic Tiles for Ground Vehicle Protection", was to create a high rate, cost effective manufacturing method for producing silicon carbide (SiC...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Preparation and infrared absorption properties of buried SiC layers

    International Nuclear Information System (INIS)

    Yan Hui; Chen Guanghua; Wong, S.P.; Kwok, R.W.M.

    1997-01-01

    Buried SiC layers were formed by using a metal vapor vacuum arc (MEVVA) ion source, with C + ions implanted into Si substrates under different doses. In the present study, the extracted voltage was 50 kV and the ion dose was varied from 3.0 x 10 17 to 1.6 x 10 18 cm -2 . According to infrared absorption measurements, it was fount that the structure of the buried SiC layers depended on the ion dose. Moreover, the results also demonstrated that the buried SiC layers including cubic crystalline SiC could be synthesized at an averaged substrate temperature of lower than 400 degree C with the MEVVA ion source

  7. Light extraction efficiency enhancement for fluorescent SiC based white light-emitting diodes

    DEFF Research Database (Denmark)

    Ou, Haiyan; Ou, Yiyu; Argyraki, Aikaterini

    Fluorescent SiC based white light-emitting diodes(LEDs) light source, as an innovative energy-efficient light source, would even have longer lifetime, better light quality and eliminated blue-tone effect, compared to the current phosphor based white LED light source. In this paper, the yellow....... At a device level, the focus is on improving the light extraction efficiency due to the rather high refractive index of SiC by nanostructuring the surface of SiC. Both periodic nanostructures made by e-beam lithography and nanosphere lithography and random nanostructures made by self-assembled Au nanosphere...... mask and a thin layer of Al film have been investigated and all of them showed much enhanced extraction efficiency. All these good results pave the way to a very promising fluorescent SiC based white LED light source...

  8. Fluorescent SiC with pseudo-periodic moth-eye structures

    DEFF Research Database (Denmark)

    Ou, Yiyu; Aijaz, Imran; Ou, Haiyan

    2012-01-01

    to enhance the extraction efficiency, we present a simple method to fabricate the pseudo-periodic moth-eye structures on the surface of the fluorescent SiC. A thin gold layer is deposited on the fluorescent SiC first. Then the thin gold layer is treated by rapid thermal processing. After annealing, the thin......-eye structure as an effective and simple method to enhance the extraction efficiency of fluorescent SiC based white LEDs.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only....... material much superior to the phosphors in terms of high color rendering index value and long lifetime. The light extraction efficiency of the fluorescent SiC based all semiconductor LED light sources is usually low due to the large refractive index difference between the semiconductor and air. In order...

  9. Decentralized Nonlinear Controller Based SiC Parallel DC-DC Converter, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is aimed at demonstrating the feasibility of a Decentralized Control based SiC Parallel DC-DC Converter Unit (DDCU) with targeted application for...

  10. Synthesis of boron nitride nanotubes with SiC nanowire as template

    International Nuclear Information System (INIS)

    Zhong, B.; Song, L.; Huang, X.X.; Wen, G.W.; Xia, L.

    2011-01-01

    Highlights: → Boron nitride nanotubes (BNNTs) have been fabricated using SiC nanowires as template. → SiC nanowires could be effectively etched out by the vapors decomposed from ammonia borane, leading to the formation of BNNTs. → A template self-sacrificing mechanism is responsible for the formation of BNNTs. -- Abstract: A novel template method for the preparation of boron nitride nanotubes (BNNTs) using SiC nanowire as template and ammonia borane as precursor is reported. We find out that the SiC nanowires could be effectively etched out by the vapors decomposed from ammonia borane, leading to the formation of BNNTs. The as-prepared products are well characterized by means of complementary analytical techniques. A possible formation mechanism is disclosed. The method developed here paves the way for large scale production of BNNTs.

  11. In-situ neutron powder diffraction study of Ti3SiC2 synthesis

    International Nuclear Information System (INIS)

    Wu, E.; Kisi, E.H.; Kennedy, S.J.; Studer, A.J.

    2000-01-01

    Full text: The synthesis of Ti 3 SiC 2 by pressureless reactive sintering Ti/SiC/C mixtures under an Ar atmosphere has been studied by in-situ neutron diffraction. The intermediate phases TiC x and Ti 5 Si 5 C x (x ≤ 1) form first at ∼ 800 - 1400 deg C. These phases are consumed in the formation of Ti 3 SiC 2 , at ∼ 1500 deg C. An amount of TiC x remains in the sample after sintering, primarily as a surface layer. The studies appear to support a suggestion that these intermediate phases react to form Ti 3 SiC 2 through a diffusion controlled process. Prolonged step-wise heating under argon in some experiments results in decomposition of Ti 3 SiC 2 above ∼ 1400 deg C and significant disproportionation of the sample

  12. Deposition of thin ultrafiltration membranes on commercial SiC microfiltration tubes

    DEFF Research Database (Denmark)

    Facciotti, Marco; Boffa, Vittorio; Magnacca, Giuliana

    2014-01-01

    Porous SiC based materials present high mechanical, chemical and thermal robustness, and thus have been largely applied to water-filtration technologies. In this study, commercial SiC microfiltration tubes with nominal pore size of 0.04 m were used as carrier for depositing thin aluminium oxide....... After 5 times coating, a 5.6 µm thick γ-Al2O3 layer was obtained. This membrane shows retention of ~75% for polyethylene glycol molecules with Mn of 8 and 35 kDa, indicating that, despite their intrinsic surface roughness, commercial SiC microfiltration tubes can be applied as carrier for thin...... ultrafiltration membranes. This work also indicates that an improvement of the commercial SiC support surface smoothness may greatly enhance permeance and selectivity of Υ-Al2O3 ultrafiltration membranes by allowing the deposition of thinner defect-free layers....

  13. Novel microstructural growth in the surface of Inconel 625 by the addition of SiC under electron beam melting

    Science.gov (United States)

    Ahmad, M.; Ali, G.; Ahmed, Ejaz; Haq, M. A.; Akhter, J. I.

    2011-06-01

    Electron beam melting is being used to modify the microstructure of the surfaces of materials due to its ability to cause localized melting and supercooling of the melt. This article presents an experimental study on the surface modification of Ni-based superalloy (Inconel 625) reinforced with SiC ceramic particles under electron beam melting. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction techniques have been applied to characterize the resulted microstructure. The results revealed growth of novel structures like wire, rod, tubular, pyramid, bamboo and tweezers type morphologies in the modified surface. In addition to that fibrous like structure was also observed. Formation of thin carbon sheet has been found at the regions of decomposed SiC. Electron beam modified surface of Inconel 625 alloy has been hardened twice as compared to the as-received samples. Surface hardening effect may be attributed to both the formation of the novel structures as well as the introduction of Si and C atom in the lattice of Inconel 625 alloy.

  14. Conversion of wood flour/SiO2/phenolic composite to porous SiC ceramic containing SiC whiskers

    Directory of Open Access Journals (Sweden)

    Li Zhong

    2013-01-01

    Full Text Available A novel wood flour/SiO2/phenolic composite was chosen to be converted into porous SiC ceramic containing SiC whiskers via carbothermal reduction. At 1550°C the composite is converted into porous SiC ceramic with pore diameters of 10~40μm, and consisting of β-SiC located at the position of former wood cell walls. β-SiC wire-like whiskers of less than 50 nm in diameter and several tens to over 100 μm in length form within the pores. The surface of the resulting ceramic is coated with β-SiC necklace-like whiskers with diameters of 1~2μm.

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

    International Nuclear Information System (INIS)

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

    2012-01-01

    Highlights: ► Ag release from SiC poses problems in safe operation of nuclear reactors. ► Near-surface and bulk behavior of Ag are studied by ab initio and ion beam methods. ► Ag prefers to adsorb on the surface rather than in the bulk SiC. ► At high temperature Ag desorbs from the surface instead of diffusion into bulk SiC. ► Surface diffusion may be a dominating mechanism accounting for Ag release from SiC. - Abstract: 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.

  16. Effect of dopants on the morphology of porous SiC

    DEFF Research Database (Denmark)

    Lu, Weifang; Iwasa, Yoshimi; Ou, Yiyu

    Porous SiC samples with different doping level were fabricated and investigated by using anodic oxidation method. The morphology of the porous structures was explained by space charge layer width, which was affected by the free carrier-dopants concentration.......Porous SiC samples with different doping level were fabricated and investigated by using anodic oxidation method. The morphology of the porous structures was explained by space charge layer width, which was affected by the free carrier-dopants concentration....

  17. SiC fibre by chemical vapour deposition on tungsten filament

    Indian Academy of Sciences (India)

    A CVD system for the production of continuous SiC fibre was set up. The process of SiC coating on 19 m diameter tungsten substrate was studied. Methyl trichloro silane (CH3SiCl3) and hydrogen reactants were used. Effect of substrate temperature (1300–1500°C) and concentration of reactants on the formation of SiC ...

  18. Manufacturing: SiC Power Electronics for Variable Frequency Motor Drives

    Energy Technology Data Exchange (ETDEWEB)

    Horowitz, Kelsey A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Bench Reese, Samantha R [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Remo, Timothy W [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-08-15

    This brochure, published as an annual research highlight of the Clean Energy Manufacturing Analysis Center (CEMAC), summarizes CEMAC analysis of silicon carbide (SiC) power electronics for variable frequency motor drives. The key finding presented is that variations in manufacturing expertise, yields, and access to existing facilities impact regional costs and manufacturing location decisions for SiC ingots, wafers, chips, and power modules more than do core country-specific factors such as labor and electricity costs.

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

    Energy Technology Data Exchange (ETDEWEB)

    Auger, M.; Hou, P.; Sengupta, A.; Basu, S.; Sarin, V. [Boston Univ., MA (United States)

    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.

  20. Passivation of surface-nanostructured f-SiC and porous SiC

    DEFF Research Database (Denmark)

    Ou, Haiyan; Lu, Weifang; Ou, Yiyu

    The further enhancement of photoluminescence from nanostructured fluorescent silicon carbide (f-SiC) and porous SiC by using atomic layer deposited (ALD) Al2O3 is studied in this paper.......The further enhancement of photoluminescence from nanostructured fluorescent silicon carbide (f-SiC) and porous SiC by using atomic layer deposited (ALD) Al2O3 is studied in this paper....

  1. Temperature Dependence of Mechanical Properties of TRISO SiC Coatings

    International Nuclear Information System (INIS)

    Kim, Do Kyung; Park, Kwi Il; Lee, Hyeon Keun; Seong, Young Hoon; Lee, Seung Jun

    2009-04-01

    SiC coating layer has been introduced as protective layer in TRISO nuclear fuel particle of high temperature gas cooled reactor (HTGR) due to excellent mechanical stability at high temperature. It is important to study for high temperature stability in SiC coating layers, because TRISO fuel particles were operating at high temperature around 1000 .deg. C. In this study, the nanoindentation test and micro tensile test were conducted in order to measure the mechanical properties of SiC coating layers at elevated temperature. SiC coating film was fabricated on the carbon substrate using chemical vapor deposition process with different microstructures and thicknesses. Nanoindentation test was performed for the analysis of the hardness, modulus and creep properties up to 500 .deg. C. Impression creep method applied to nanoindentation and creep properties of SiC coating layers were characterized by nanoindentation creep test. The fracture strength of SiC coating layers was measured by the micro tensile method at room temperature and 500 .deg. C. From the results, we can conclude that the hardness and fracture strength are decreased with temperature and no significant change in the modulus is observed with increase in temperature. The deformation mechanism for indentation creep and creep rate changes as the testing temperature increased

  2. Development of evaluation method of high temperature mechanical properties of TRISO SiC coating layers

    International Nuclear Information System (INIS)

    Kim, Do Kyung; Lee, Hyeon Keun; Kim, Dong Seok; Lee, Ji Seok; Park, Kwi Il

    2010-05-01

    SiC coating layer has been introduced as protective layer in TRISO nuclear fuel particle of high temperature gas cooled reactor (HTGR) due to excellent mechanical stability at high temperature. It is important to study for high temperature stability in SiC coating layers, because TRISO fuel particles were operating at high temperature around 1000 .deg. C. In this study, the nanoindentation test and micro tensile test were conducted in order to measure the mechanical properties of SiC coating layers at elevated temperature. SiC coating film was fabricated on the carbon substrate using chemical vapor deposition process with different microstructures and thicknesses. Nanoindentation test was performed for the analysis of the hardness, modulus and creep properties up to 500 .deg. C. Impression creep method applied to nanoindentation and creep properties of SiC coating layers were characterized by nanoindentation creep test. The fracture strength of SiC coating layers was measured by the micro tensile method at room temperature and 500 .deg. C. From the results, we can conclude that the hardness and fracture strength are decreased with temperature and no significant change in the modulus is observed with increase in temperature. The deformation mechanism for indentation creep and creep rate changes as the testing temperature increased

  3. Hydrogen generation due to water splitting on Si - terminated 4H-Sic(0001) surfaces

    Science.gov (United States)

    Li, Qingfang; Li, Qiqi; Yang, Cuihong; Rao, Weifeng

    2018-02-01

    The chemical reactions of hydrogen gas generation via water splitting on Si-terminated 4H-SiC surfaces with or without C/Si vacancies were studied by using first-principles. We studied the reaction mechanisms of hydrogen generation on the 4H-SiC(0001) surface. Our calculations demonstrate that there are major rearrangements in surface when H2O approaches the SiC(0001) surface. The first H splitting from water can occur with ground-state electronic structures. The second H splitting involves an energy barrier of 0.65 eV. However, the energy barrier for two H atoms desorbing from the Si-face and forming H2 gas is 3.04 eV. In addition, it is found that C and Si vacancies can form easier in SiC(0001)surfaces than in SiC bulk and nanoribbons. The C/Si vacancies introduced can enhance photocatalytic activities. It is easier to split OH on SiC(0001) surface with vacancies compared to the case of clean SiC surface. H2 can form on the 4H-SiC(0001) surface with C and Si vacancies if the energy barriers of 1.02 and 2.28 eV are surmounted, respectively. Therefore, SiC(0001) surface with C vacancy has potential applications in photocatalytic water-splitting.

  4. Packaging Technologies for 500C SiC Electronics and Sensors

    Science.gov (United States)

    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.

  5. Velcro-Inspired SiC Fuzzy Fibers for Aerospace Applications.

    Science.gov (United States)

    Hart, Amelia H C; Koizumi, Ryota; Hamel, John; Owuor, Peter Samora; Ito, Yusuke; Ozden, Sehmus; Bhowmick, Sanjit; Syed Amanulla, Syed Asif; Tsafack, Thierry; Keyshar, Kunttal; Mital, Rahul; Hurst, Janet; Vajtai, Robert; Tiwary, Chandra Sekhar; Ajayan, Pulickel M

    2017-04-19

    The most recent and innovative silicon carbide (SiC) fiber ceramic matrix composites, used for lightweight high-heat engine parts in aerospace applications, are woven, layered, and then surrounded by a SiC ceramic matrix composite (CMC). To further improve both the mechanical properties and thermal and oxidative resistance abilities of this material, SiC nanotubes and nanowires (SiCNT/NWs) are grown on the surface of the SiC fiber via carbon nanotube conversion. This conversion utilizes the shape memory synthesis (SMS) method, starting with carbon nanotube (CNT) growth on the SiC fiber surface, to capitalize on the ease of dense surface morphology optimization and the ability to effectively engineer the CNT-SiC fiber interface to create a secure nanotube-fiber attachment. Then, by converting the CNTs to SiCNT/NWs, the relative morphology, advantageous mechanical properties, and secure connection of the initial CNT-SiC fiber architecture are retained, with the addition of high temperature and oxidation resistance. The resultant SiCNT/NW-SiC fiber can be used inside the SiC ceramic matrix composite for a high-heat turbo engine part with longer fatigue life and higher temperature resistance. The differing sides of the woven SiCNT/NWs act as the "hook and loop" mechanism of Velcro but in much smaller scale.

  6. Preparation of biomorphic SiC ceramic by carbothermal reduction of oak wood charcoal

    Energy Technology Data Exchange (ETDEWEB)

    Qian Junmin; Wang Jiping; Jin Zhihao

    2004-04-25

    Highly porous silicon carbide (SiC) ceramic with woodlike microstructure has been prepared at 1400-1600 deg. C by carbothermal reduction reaction of charcoal/silica composites in static argon atmosphere. These composites were fabricated by infiltrating silica sol into a porous biocarbon template from oak wood using a vacuum/pressure infiltration process. The morphology of resulting porous SiC ceramic, as well as the conversion mechanism of wood to porous SiC ceramic, have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Experimental results show that the biomorphic cellular morphology of oak wood charcoal is remained in the porous SiC ceramic with high precision that consists of {beta}-SiC with traces of {alpha}-SiC. Silica in the charcoal/silica composites exists in the cellular pores in form of fibers and rods. The SiC strut material is formed by gas-solid reaction between SiO (g) and C (s) during the charcoal-to-ceramic conversion. The densification of SiC strut material may occur at moderate temperatures and holding time.

  7. High temperature oxidation behavior of SiC coating in TRISO coated particles

    International Nuclear Information System (INIS)

    Liu, Rongzheng; Liu, Bing; Zhang, Kaihong; Liu, Malin; Shao, Youlin; Tang, Chunhe

    2014-01-01

    Highlights: • High temperature oxidation tests of SiC coating in TRISO particles were carried out. • The dynamic oxidation process was established. • Oxidation mechanisms were proposed. • The existence of silicon oxycarbides at the SiO 2 /SiC interface was demonstrated. • Carbon was detected at the interface at high temperatures and long oxidation time. - Abstract: High temperature oxidation behavior of SiC coatings in tristructural-isotropic (TRISO) coated particles is crucial to the in-pile safety of fuel particles for a high temperature gas cooled reactor (HTGR). The postulated accident condition of air ingress was taken into account in evaluating the reliability of the SiC layer. Oxidation tests of SiC coatings were carried out in the ranges of temperature between 800 and 1600 °C and time between 1 and 48 h in air atmosphere. Based on the microstructure evolution of the oxide layer, the mechanisms and kinetics of the oxidation process were proposed. The existence of silicon oxycarbides (SiO x C y ) at the SiO 2 /SiC interface was demonstrated by X-ray photospectroscopy (XPS) analysis. Carbon was detected by Raman spectroscopy at the interface under conditions of very high temperatures and long oxidation time. From oxidation kinetics calculation, activation energies were 145 kJ/mol and 352 kJ/mol for the temperature ranges of 1200–1500 °C and 1550–1600 °C, respectively

  8. Applications, Prospects and Challenges of Silicon Carbide Junction Field Effect Transistor (SIC JFET

    Directory of Open Access Journals (Sweden)

    Frederick Ojiemhende Ehiagwina

    2016-09-01

    Full Text Available Properties of Silicon Carbide Junction Field Effect Transistor (SiC JFET such as high switching speed, low forward voltage drop and high temperature operation have attracted the interest of power electronic researchers and technologists, who for many years developed devices based on Silicon (Si.  A number of power system Engineers have made efforts to develop more robust equipment including circuits or modules with higher power density. However, it was realized that several available power semiconductor devices were approaching theoretical limits offered by Si material with respect to capability to block high voltage, provide low on-state voltage drop and switch at high frequencies. This paper presents an overview of the current applications of SiC JFET in circuits such as inverters, rectifiers and amplifiers. Other areas of application reviewed include; usage of the SiC JFET in pulse signal circuits and boost converters. Efforts directed toward mitigating the observed increase in electromagnetic interference were also discussed. It also presented some areas for further research, such as having more applications of SiC JFET in harsh, high temperature environment. More work is needed with regards to SiC JFET drivers so as to ensure stable and reliable operation, and reduction in the prices of SiC JFETs through mass production by industries.

  9. Crystal growth and characterization of fluorescent SiC

    DEFF Research Database (Denmark)

    Wellmann, P.; Kaiser, M.; Hupfer, T.

    Silicon carbide (SiC) is widely used as substrate for nitride based light emitting diodes (LEDs). For today’s white LEDs mainly a sandwich structure of a blue or ultra violet LED and a yellowish phosphorus is used. In the frame of European project we study a concept to implement the functionality......-SiC co-doped with nitrogen and boron has been achieved [1][2]. The source is the rate determining step, and is expected to be determining the fluorescent properties by introducing dopants to the layer from the source. The optimization process of the polycrystalline, co-doped SiC:B,N source material...... and its impact on the FSPG epitaxial process, in particular the influence on the brightness of the is presented. In particular, the doping properties of the poly-SiC source material influence on the brightness of the fluorescent 6H-SiC. In addition we have investigated how the grain orientation...

  10. Development of Cu Reinforced SiC Particulate Composites

    Science.gov (United States)

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

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Rongzheng; Liu, Malin, E-mail: liumalin@tsinghua.edu.cn; Chang, Jiaxing; Shao, Youlin; Liu, Bing

    2015-12-15

    Tristructural-isotropic (TRISO) particle has been successful in high temperature gas cooled reactor (HTGR), but an improved design is required for future development. In this paper, the coating layers are reconsidered, and an improved design of TRISO particle with porous SiC inner layer is proposed. Three methods of preparing the porous SiC layer, called high methyltrichlorosilane (MTS) concentration method, high Ar concentration method and hexamethyldisilane (HMDS) method, are experimentally studied. It is indicated that porous SiC layer can be successfully prepared and the density of SiC layer can be adjusted by tuning the preparation parameters. Microstructure and characterization of the improved TRISO coated particle are given based on scanning electron microscope (SEM), X-ray diffraction (XRD), Raman scattering and energy dispersive X-ray (EDX) analysis. It can be found that the improved TRISO coated particle with porous SiC layer can be mass produced successfully. The formation mechanisms of porous SiC layer are also discussed based on the fluidized bed-chemical vapor deposition principle. - Graphical abstract: An improved design of TRISO particle with porous SiC inner layer to replace the inner porous pyrolytic carbon layer was proposed and prepared by FB-CVD method. This new design is aimed to reduce the total internal pressure of the particles by reducing the formation of CO and to reduce the risks of amoeba effect. - Highlights: • An improved design of TRISO particle with porous SiC inner layer was proposed. • Three methods of preparing porous SiC layer are proposed and experimentally studied. • The density of porous SiC layer can be controlled by adjusting experimental parameters. • Formation mechanisms of porous SiC layer were given based on the FB-CVD principle. • TRISO particles with porous SiC inner layer were mass produced successfully.

  12. Dual ohmic contact to N- and P-type silicon carbide

    Science.gov (United States)

    Okojie, Robert S. (Inventor)

    2013-01-01

    Simultaneous formation of electrical ohmic contacts to silicon carbide (SiC) semiconductor having donor and acceptor impurities (n- and p-type doping, respectively) is disclosed. The innovation provides for ohmic contacts formed on SiC layers having n- and p-doping at one process step during the fabrication of the semiconductor device. Further, the innovation provides a non-discriminatory, universal ohmic contact to both n- and p-type SiC, enhancing reliability of the specific contact resistivity when operated at temperatures in excess of 600.degree. C.

  13. Loss Model and Efficiency Analysis of Tram Auxiliary Converter Based on a SiC Device

    Directory of Open Access Journals (Sweden)

    Hao Liu

    2017-12-01

    Full Text Available Currently, the auxiliary converter in the auxiliary power supply system of a modern tram adopts Si IGBT as its switching device and with the 1700 V/225 A SiC MOSFET module commercially available from Cree, an auxiliary converter using all SiC devices is now possible. A SiC auxiliary converter prototype is developed during this study. The author(s derive the loss calculation formula of the SiC auxiliary converter according to the system topology and principle and each part loss in this system can be calculated based on the device datasheet. Then, the static and dynamic characteristics of the SiC MOSFET module used in the system are tested, which aids in fully understanding the performance of the SiC devices and provides data support for the establishment of the PLECS loss simulation model. Additionally, according to the actual circuit parameters, the PLECS loss simulation model is set up. This simulation model can simulate the actual operating conditions of the auxiliary converter system and calculate the loss of each switching device. Finally, the loss of the SiC auxiliary converter prototype is measured and through comparison it is found that the loss calculation theory and PLECS loss simulation model is valuable. Furthermore, the thermal images of the system can prove the conclusion about loss distribution to some extent. Moreover, these two methods have the advantages of less variables and fast calculation for high power applications. The loss models may aid in optimizing the switching frequency and improving the efficiency of the system.

  14. A study on the high densification process of CVI SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Doo Jin; Son, Ji Hye; Jun, Jin O. [Yonsei University, Seoul (Korea)

    2002-03-01

    A novel process called in-situ whisker growing and matrix filling was designed to overcome the problem of conventional ICVI process which make composites porous. Fiber reinforced SiC matrix composites were successfully fabricated by the process in the present study. Methyltrichlorosilane(CH{sub 3}SiCl{sub 3},MTS) was chosen as a source precursor of SiC. Hydrogen was used as a dilute gas for the in-situ whisker growing process and nitrogen was used as a dilute gas for the SiC matrix filling process. In order to increase the fracture toughness of the composites, the fibers were coated with a thin pyrolytic carbon layer at 1000 .deg. C before ICVI process. In case of the monolithic SiC-SiC composites, SiC whisker was grown at the temperature of 1100 .deg. C with the input gas ratio of 15. SiC-SiC composites obtained by the suggested process were denser than the composites obtained by conventional ICVI process. Also, in case of the stacked SiC-SiC composites, SiC whisker was grown at the temperature of 1100 .deg. C with the input gas ratio of 20 and 30. In addition, the SiC whisker was also grown at 1150 .deg.C with the input gas ratio of 20. The optimum condition of the in-situ whisker growing for the following matrix filling process is 1100 .deg. C, {alpha}=20, and 2hr. The designed process, in-situ whisker growing and matrix filling, was confirmed as a novel process which can fabricate high density fiber reinforced SiC matrix composites. 40 refs., 24 figs., 7 tabs. (Author)

  15. SiC Coating Process Development Using H-PCS in Supercritical CO2

    International Nuclear Information System (INIS)

    Park, Kwangheon; Jung, Wonyoung

    2013-01-01

    We tried SiC coating using supercritical fluids. Supercritical fluids are the substance exists over critical temperature and critical pressure. It is hard to expect that there would be a big change as single-solvent as the fluid is incompressible and the space between the molecules is almost steady. But the fluid which is being supercritical can bring a great change when it is changed its pressure near its critical point, showing its successive change in the density, viscosity, diffusion coefficient and the polarity. We have tested the 'H-PCS into SiC' coating experiment with supercritical CO 2 which has the high penetration, low viscosity as well as the high density and the high solubility that shows the property of the fluid. This experiment is for SiC coating using H-PCS in supercritical CO 2 . It shows the clear difference that the penetration of H-PCS into the SiC between dip coating method and using the supercritical CO 2 If we can make a metal cladding with SiC composites as a protective layer, the use of the cladding will be very broad and diverse. Inherent safe nuclear fuels can be possible that can stand under severe accident conditions. SiC is known to be one of a few materials that maintain very corrosion-resistant properties under tough corrosive environments. The metal cladding with SiC composites as a protective layer will be a high-tech product that can be used in many applications including chemical, material, and nuclear engineering and etc

  16. Thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap semiconductors SiC, GaN, and ZnO

    Directory of Open Access Journals (Sweden)

    Zheng Huang

    2015-09-01

    Full Text Available We have investigated the thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap(n-type semiconductors SiC, GaN, and ZnO based on first-principles calculations and Boltzmann transport theory. Our results show that the thermoelectric performance increases from 3C to 6H, 4H, and 2H structures with an increase of hexagonality for SiC. However, for GaN and ZnO, their power factors show a very weak dependence on the polytype. Detailed analysis of the thermoelectric properties with respect to temperature and carrier concentration of 4H-SiC, 2H-GaN, and 2H-ZnO shows that the figure of merit of these three compounds increases with temperature, indicating the promising potential applications of these thermoelectric materials at high temperature. The significant difference of the polytype-dependent thermoelectric properties among SiC, GaN, and ZnO might be related to the competition between covalency and ionicity in these semiconductors. Our calculations may provide a new way to enhance the thermoelectric properties of wide-band-gap semiconductors through atomic structure design, especially hexagonality design for SiC.

  17. SiC Conversion Coating Prepared from Silica-Graphite Reaction

    Directory of Open Access Journals (Sweden)

    Back-Sub Sung

    2017-01-01

    Full Text Available The β-SiC conversion coatings were successfully synthesized by the SiO(v-graphite(s reaction between silica powder and graphite specimen. This paper is to describe the effects on the characteristics of the SiC conversion coatings, fabricated according to two different reaction conditions. FE-SEM, FE-TEM microstructural morphologies, XRD patterns, pore size distribution, and oxidation behavior of the SiC-coated graphite were investigated. In the XRD pattern and SAD pattern, the coating layers showed cubic SiC peak as well as hexagonal SiC peak. The SiC coatings showed somewhat different characteristics with the reaction conditions according to the position arrangement of the graphite samples. The SiC coating on graphite, prepared in reaction zone (2, shows higher intensity of beta-SiC main peak (111 in XRD pattern as well as rather lower porosity and smaller main pore size peak under 1 μm.

  18. Methodology Development for SiC Sensor Signal Modelling in the Nuclear Reactor Radiation Environments

    International Nuclear Information System (INIS)

    Cetnar, J.; Krolikowski, I.P.

    2013-06-01

    This paper deals with SiC detector simulation methodology for signal formation by neutrons and induced secondary radiation as well as its inverse interpretation. The primary goal is to achieve the SiC capability of simultaneous spectroscopic measurements of neutrons and gamma-rays for which an appropriate methodology of the detector signal modelling and its interpretation must be adopted. The process of detector simulation is divided into two basically separate but actually interconnected sections. The first one is the forward simulation of detector signal formation in the field of the primary neutron and secondary radiations, whereas the second one is the inverse problem of finding a representation of the primary radiation, based on the measured detector signals. The applied methodology under development is based on the Monte Carlo description of radiation transport and analysis of the reactor physics. The methodology of SiC detector signal interpretation will be based on the existing experience in neutron metrology developed in the past for various neutron and gamma-ray detection systems. Since the novel sensors based on SiC are characterised by a new structure, yet to be finally designed, the methodology for particle spectroscopic fluence measurement must be developed while giving a productive feed back to the designing process of SiC sensor, in order to arrive at the best possible design. (authors)

  19. Epitaxy relationships between Ge-islands and SiC(0 0 0 1)

    Energy Technology Data Exchange (ETDEWEB)

    Ait-Mansour, K. [Faculte des Sciences, LPSE, UMR CNRS 7014, 4, rue des Freres Lumiere, 68093 Mulhouse, Cedex (France)]. E-mail: k.ait-mansour@uha.fr; Dentel, D. [Faculte des Sciences, LPSE, UMR CNRS 7014, 4, rue des Freres Lumiere, 68093 Mulhouse, Cedex (France); Kubler, L. [Faculte des Sciences, LPSE, UMR CNRS 7014, 4, rue des Freres Lumiere, 68093 Mulhouse, Cedex (France); Diani, M. [Departement de Physique, Faculte des Sciences et Techniques, LSGM, BP 416, Tanger, Maroc (Morocco); Bischoff, J.L. [Faculte des Sciences, LPSE, UMR CNRS 7014, 4, rue des Freres Lumiere, 68093 Mulhouse, Cedex (France); Bolmont, D. [Faculte des Sciences, LPSE, UMR CNRS 7014, 4, rue des Freres Lumiere, 68093 Mulhouse, Cedex (France)

    2005-03-15

    Reflection high-energy electron diffraction (RHEED) has been used to determine epitaxy relationships and in-plane orientations between Ge and SiC(0 0 0 1). Three monolayers of Ge have been deposited at 500 deg. C on a graphitized SiC (6{radical}3 x 6{radical}3)R30 deg. reconstructed surface, this surface supporting epitaxial Ge island growth in a Volmer-Weber mode. Nucleation of relaxed Ge-islands gives rise to transmission electron diffraction patterns allowing to deduce that pure Ge grows according to only one epitaxy relationship Ge{l_brace}1 1 1{r_brace}//SiC(0 0 0 1). These {l_brace}1 1 1{r_brace}-Ge-islands have two in-plane orientations, a preferential one, Ge<-1-12>//SiC<1-100> and a minority one, Ge<-1-12>//SiC<10-10>, deduced one from the other by a 30 deg. rotation around the <1 1 1>-Ge (or [0 0 0 1]-SiC) growth axis. Due to the three-fold symmetry of the {l_brace}1 1 1{r_brace}-Ge plane, each in-plane orientation is degenerated into two twin orientations, differing by a 180 deg. angle around Ge<111>.

  20. Preparation of Diffusion Couples (I) to Study Ag/Pd Migration in SiC

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B. G.; Yeo, S.; Kim, Y. K.; Kim, Y. J.; Kim, H. M.; Cho, M. S. [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    It has been observed in reactor experiments that although the SiC layer can retain most fission products, some species such as Ag can escape from fuel particles. In particular, because of a strong γ-ray emitter and a long half-life of 250 days of {sup 110m}Ag, the release of {sup 110m}Ag from intact TRISO fuel is especially a concern as {sup 110m}Ag in the primary coolant loop can plate out on the turbine system of VHTR causing safety and maintenance concerns and an increased risk of radiation exposure. In order to improve reactor operation and reduce safety and maintenance concerns, there were many efforts to understand Ag diffusion mechanism and release rates. In this study, spherical diffusion couples using surrogate TRISO particles were successfully prepared to trap Ag or/and Pd between IPyC layer and SiC layer, and SiC layers using silver nitrate, palladium nitrate hydrate, and polycarbosilane (PCS). These diffusion couples will provide the opportunity to investigate diffusion mechanism and to determine diffusion coefficients of Ag or/and Pd as FPs in SiC and the role of the Pd for Ag migration in SiC layer.

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

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  2. Thermal conductivity analysis of SiC ceramics and fully ceramic microencapsulated fuel composites

    International Nuclear Information System (INIS)

    Lee, Hyeon-Geun; Kim, Daejong; Lee, Seung Jae; Park, Ji Yeon; Kim, Weon-Ju

    2017-01-01

    Highlights: • Thermal conductivity of SiC ceramics and FCM pellets was measured and discussed. • Thermal conductivity of FCM pellets was analyzed by the Maxwell-Eucken equation. • Effective thermal conductivity of TRISO particles applied in this study was assumed. - Abstract: The thermal conductivity of SiC ceramics and FCM fuel composites, consisting of a SiC matrix and TRISO coated particles, was measured and analyzed. SiC ceramics and FCM pellets were fabricated by hot press sintering with Al 2 O 3 and Y 2 O 3 sintering additives. Several factors that influence thermal conductivity, specifically the content of sintering additives for SiC ceramics and the volume fraction of TRISO particles and the matrix thermal conductivity of FCM pellets, were investigated. The thermal conductivity values of samples were analyzed on the basis of their microstructure and the arrangement of TRISO particles. The thermal conductivity of the FCM pellets was compared to that predicted by the Maxwell-Eucken equation and the thermal conductivity of TRISO coated particles was calculated. The thermal conductivity of FCM pellets in various sintering conditions was in close agreement to that predicted by the Maxwell-Eucken equation with the fitted thermal conductivity value of TRISO particles.

  3. Direct growth of graphene on SiC(0001) by KrF-excimer-laser irradiation

    Science.gov (United States)

    Hattori, Masakazu; Ikenoue, Hiroshi; Nakamura, Daisuke; Furukawa, Kazuaki; Takamura, Makoto; Hibino, Hiroki; Okada, Tatsuo

    2016-02-01

    In this report, we propose a direct patterning method of graphene on the SiC(0001) surface by KrF-excimer-laser irradiation. In this method, Si atoms are locally sublimated from the SiC surface in the laser-irradiated area, and direct graphene growth is induced by the rearrangement of surplus carbon on the SiC surface. Using Raman microscopy, we demonstrated the formation of graphene by laser irradiation and observed the growth process by transmission electron microscopy and conductive atomic force microscopy. When SiC was irradiated by 5000 shots of the laser beam with a fluence of 1.2 J/cm2, two layers of graphene were synthesized on the SiC(0001) surface. The number of graphene layers increased from 2 to 5-7 with an increase in the number of laser shots. Based on the results of conductive-atomic force microscopy measurements, we conclude that graphene formation was initiated from the step area, after which the graphene grew towards the terrace area by further Si evaporation and C recombination with increasing laser irradiation.

  4. Anodization Mechanism on SiC Nanoparticle Reinforced Al Matrix Composites Produced by Power Metallurgy.

    Science.gov (United States)

    Ferreira, Sonia C; Conde, Ana; Arenas, María A; Rocha, Luis A; Velhinho, Alexandre

    2014-12-19

    Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiC np ) produced by powder metallurgy (PM) were anodized under voltage control in tartaric-sulfuric acid (TSA). In this work, the influence of the amount of SiC np on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050) anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiC np . The current peaks and the steady-state current density recorded at each voltage step increases with the SiC np volume fraction due to the oxidation of the SiC np . The formation mechanism of the anodic film on Al/SiC np composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiC np in the anodic film.

  5. Friction Stir Processing of Copper-Coated SiC Particulate-Reinforced Aluminum Matrix Composite

    Directory of Open Access Journals (Sweden)

    Chih-Wei Huang

    2018-04-01

    Full Text Available In the present work, we proposed a novel friction stir processing (FSP to produce a locally reinforced aluminum matrix composite (AMC by stirring copper-coated SiC particulate reinforcement into Al6061 alloy matrix. Electroless-plating process was applied to deposit the copper surface coating on the SiC particulate reinforcement for the purpose of improving the interfacial adhesion between SiC particles and Al matrix. The core-shell SiC structure provides a layer for the atomic diffusion between aluminum and copper to enhance the cohesion between reinforcing particles and matrix on one hand, the dispersion of fine copper in the Al matrix during FSP provides further dispersive strengthening and solid solution strengthening, on the other hand. Hardness distribution and tensile results across the stir zone validated the novel concept in improving the mechanical properties of AMC that was realized via FSP. Optical microscope (OM and Transmission Electron Microscopy (TEM investigations were conducted to investigate the microstructure. Energy dispersive spectrometer (EDS, electron probe micro-analyzer (EPMA, and X-ray diffraction (XRD were explored to analyze the atomic inter-diffusion and the formation of intermetallic at interface. The possible strengthening mechanisms of the AMC containing Cu-coated SiC particulate reinforcement were interpreted. The concept of strengthening developed in this work may open a new way of fabricating of particulate reinforced metal matrix composites.

  6. Direct growth of graphene on SiC(0001) by KrF-excimer-laser irradiation

    International Nuclear Information System (INIS)

    Hattori, Masakazu; Ikenoue, Hiroshi; Nakamura, Daisuke; Okada, Tatsuo; Furukawa, Kazuaki; Takamura, Makoto; Hibino, Hiroki

    2016-01-01

    In this report, we propose a direct patterning method of graphene on the SiC(0001) surface by KrF-excimer-laser irradiation. In this method, Si atoms are locally sublimated from the SiC surface in the laser-irradiated area, and direct graphene growth is induced by the rearrangement of surplus carbon on the SiC surface. Using Raman microscopy, we demonstrated the formation of graphene by laser irradiation and observed the growth process by transmission electron microscopy and conductive atomic force microscopy. When SiC was irradiated by 5000 shots of the laser beam with a fluence of 1.2 J/cm 2 , two layers of graphene were synthesized on the SiC(0001) surface. The number of graphene layers increased from 2 to 5–7 with an increase in the number of laser shots. Based on the results of conductive-atomic force microscopy measurements, we conclude that graphene formation was initiated from the step area, after which the graphene grew towards the terrace area by further Si evaporation and C recombination with increasing laser irradiation.

  7. Effects of sic buffer layer on the optical properties of ZnO films grown on Si (1 1 1) substrates

    International Nuclear Information System (INIS)

    Zhang Yang; Zheng Haiwu; Su Jianfeng; Lin Bixi; Fu Zhuxi

    2007-01-01

    ZnO films have been grown by a sol-gel process on Si (1 1 1) substrates with and without SiC buffer layers. The influence of SiC buffer layer on the optical properties of ZnO films grown on Si (1 1 1) substrates was investigated. The intensity of the E 2 (high) phonon peak in the micro-Raman spectrum of ZnO film with the SiC buffer layer is stronger than that of the sample without the SiC buffer layer, and the breadth of E 2 (high) phonon peak of ZnO film with the SiC buffer layer is narrower than that of the sample without the SiC buffer layer. These results indicated that the crystalline quality of the sample with the SiC buffer layer is better than that of the sample without the SiC buffer layer. In photoluminescence spectra, the intensity of free exciton emission from ZnO films with the SiC buffer was much stronger than that from ZnO film without the SiC buffer layer, while the intensity of deep level emission from sample with the SiC buffer layer was about half of that of sample without the SiC buffer layer. The results indicate the SiC buffer layer improves optical qualities of ZnO films on Si (1 1 1) substrates

  8. Friction stir spot welding of 2024-T3 aluminum alloy with SiC nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Paidar, Moslem; Sarab, Mahsa Laali [Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2016-01-15

    In this study, the Friction stir spot welding (FSSW) of 2024-T3 aluminum alloy with 1.6 mm thickness was investigated. The effects of the silicon carbide (SiC) nanoparticles on the metallurgical and mechanical properties were discussed. The effects of particles on tension shear and wear tests were also investigated. The process was conducted at a constant rotational speed of 1000 rpm. Results showed that adding SiC nanoparticles to the weld during FSSW had a major effect on the mechanical properties. In fact, the addition of nanoparticles as barriers prevented grain growth in the Stir zone (SZ). The data obtained in the tensile-shear and wear tests showed that tensile-shear load and wear resistance increased with the addition of SiC nanoparticles, which was attributed to the fine grain size produced in the SZ.

  9. Characteristics of hot-pressed fiber-reinforced ceramics with SiC matrix

    Science.gov (United States)

    Miyoshi, Tadahiko; Kodama, Hironori; Sakamoto, Hiroshi; Goto, Akihiro; Iijima, Shiroo

    1989-11-01

    Silicon carbide ceramics’ matrix composites with SiC or C filaments were fabricated through hot pressing, and the effects of the filament pullout on their fracture toughness were experimentally investigated. The C-rich coating layers on the SiC filaments were found to have a significant effect on the frictional stress at the filament/matrix interfaces, through assising the filamet pullout from the matrix. Although the coating layers were apt to burn out in the sintering process of SiC matrix compposites, a small addition of carbon to the raw materials was found to be effective for the retention of the layers on the fibers, thus increasing the fracture toughness of the composites. The fracture toughness of the C filament/SiC matrix composite increased with temperature due to the larger interfacial frictional stress at higher temperatures, because of the higher thermal expansion of the filament in the radial direction than that of the matrix.

  10. Oxidation of BN-coated SiC fibers in ceramic matrix composites

    International Nuclear Information System (INIS)

    Sheldon, B.W.; Sun, E.Y.

    1996-01-01

    Thermodynamic calculations were performed to analyze the simultaneous oxidation of BN and SiC. The results show that, with limited amounts of oxygen present, the formation of SiO 2 should occur prior to the formation of B 2 O 3 . This agrees with experimental observations of oxidation in glass-ceramic matrix composites with BN-coated SiC fibers, where a solid SiO 2 reaction product containing little or no boron has been observed. The thermodynamic calculations suggest that this will occur when the amount of oxygen available is restricted. One possible explanation for this behavior is that SiO 2 formation near the external surfaces of the composite closes off cracks or pores, such that vapor phase O 2 diffusion into the composite occurs only for a limited time. This indicates that BN-coated SiC fibers will not always oxidize to form significant amounts of a low-melting, borosilicate glass

  11. Growth of graphene from SiC{0001} surfaces and its mechanisms

    International Nuclear Information System (INIS)

    Norimatsu, Wataru; Kusunoki, Michiko

    2014-01-01

    Graphene, a one-atom-layer carbon material, can be grown by thermal decomposition of SiC. On Si-terminated SiC(0001), graphene nucleates at steps and grows layer-by-layer, and as a result a homogeneous monolayer or bilayer can be obtained. We demonstrate this mechanism both experimentally and theoretically. On the C-face (000 1-bar ), multilayer graphene nucleates not only at steps, but also on the terraces. These differences reflect the distinct differences in the reactivity of these faces. Due to its high quality and structural controllability, graphene on SiC{0001} surfaces will be a platform for high-speed graphene device applications. (paper)

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

    Science.gov (United States)

    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.

  13. Pseudo Dirac dispersion in Mn-intercalated graphene on SiC

    KAUST Repository

    Kahaly, M. Upadhyay

    2013-07-01

    The atomic and electronic structures of bulk C6Mn, bulk C 8Mn, and Mn-intercalated graphene on SiC(0 0 0 1) and SiC(0001̄) are investigated by density functional theory. We find for both configurations of Mn-intercalated graphene a nonmagnetic state, in agreement with the experimental situation for SiC(0 0 0 1), and explain this property. The electronic structures around the Fermi energy are dominated by Dirac-like cones at energies consistent with data from angular resolved photoelectron spectroscopy [Gao et al., ACS Nano. 6 (2012) 6562]. However, our results demonstrate that the corresponding states trace back to hybridized Mn d orbitals, and not to the graphene. © 2013 Elsevier B.V. All rights reserved.

  14. Effect of silicon source and carbon source on the morphology of SiC powders

    Science.gov (United States)

    Wang, Zhao; Wang, Shu-lin; Ji, Jia-you; Xu, Man

    2017-11-01

    Silicon carbide (SiC) powders were prepared by carbothermal reduction method with silica fume and carbon-white as the silicon source; glucose, phenolic resin, polyvinyl pyrrolidone (PVP) as carbon source. The effects of reaction temperature, silicon source and carbon source on the morphology of silicon carbide powder were investigated. The result shows that: The optimum temperature for preparation of silicon carbide powder was 1400 °C When the glucose was used as carbon source, the morphology of SiC powder was greatly affected by the kinds of silicon sources; When the phenolic resin and PVP were used as carbon source, the morphology of SiC powder was greatly influenced by the carbon source.

  15. ToF-MEIS stopping measurements in thin SiC films

    International Nuclear Information System (INIS)

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

    2014-01-01

    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

  16. Preparation of Al-based metal matrix composites reinforced by Cu coated SiC particles

    Energy Technology Data Exchange (ETDEWEB)

    Wang Hailong; Zhang Rui; Xu Hongliang; Lu Hongxia; Guan Shaokang [Coll. of Materials Engineering, Zhengzhou Univ., HEN (China)

    2005-07-01

    In order to improve the interfacial behavior between SiC and Al, a surface layer of Cu was coated on SiC particles. The influence of pH value on the coating process was analyzed. A powder metallurgy method was used to prepare the Al-based metal matrix composites (MMCs). SEM, XRD techniques were used to characterize the sintered compacts. It was found that the optimized pH value during the coating process was 1{proportional_to}2. The specimen showed the maximum density when sintered at 750 C. Inter-metallic compound of Al{sub 3.21}Si{sub 0.47} was detected which contributed to the enhancement at the interface between SiC and Al. The hardness of the composites is improved to 90 MPa. (orig.)

  17. Origin of the high p-doping in F intercalated graphene on SiC

    KAUST Repository

    Cheng, Yingchun

    2011-08-04

    The atomic and electronic structures of F intercalated epitaxialgraphene on a SiC(0001) substrate are studied by first-principles calculations. A three-step fluorination process is proposed. First, F atoms are intercalated between the graphene and the SiC, which restores the Dirac point in the band structure. Second, saturation of the topmost Si dangling bonds introduces p-doping up to 0.37 eV. Third, F atoms bond covalently to the graphene to enhance the p-doping. Our model explains the highly p-doped state of graphene on SiC after fluorination [A. L. Walter et al., Appl. Phys. Lett. 98, 184102 (2011)].

  18. Friction stir spot welding of 2024-T3 aluminum alloy with SiC nanoparticles

    International Nuclear Information System (INIS)

    Paidar, Moslem; Sarab, Mahsa Laali

    2016-01-01

    In this study, the Friction stir spot welding (FSSW) of 2024-T3 aluminum alloy with 1.6 mm thickness was investigated. The effects of the silicon carbide (SiC) nanoparticles on the metallurgical and mechanical properties were discussed. The effects of particles on tension shear and wear tests were also investigated. The process was conducted at a constant rotational speed of 1000 rpm. Results showed that adding SiC nanoparticles to the weld during FSSW had a major effect on the mechanical properties. In fact, the addition of nanoparticles as barriers prevented grain growth in the Stir zone (SZ). The data obtained in the tensile-shear and wear tests showed that tensile-shear load and wear resistance increased with the addition of SiC nanoparticles, which was attributed to the fine grain size produced in the SZ

  19. SiC 10um-Pitch UV Imaging Array and APD with Active Pixel Readout, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — CoolCAD Electronics, LLC, proposes to design and fabricate a SiC UV detector array with a 10μm pixel pitch, sensitive to EUV, VUV and Deep UV. SiC is a visible-blind...

  20. Proposal of a SiC disposal canister for very deep borehole disposal

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Heui-Joo; Lee, Minsoo; Lee, Jong-Youl; Kim, Kyungsu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    In this paper authors proposed a silicon carbide, SiC, disposal canister for the DBD concept in Korea. A. Kerber et al. first proposed the SiC canister for a geological disposal of HLW, CANDU or HTR spent nuclear fuels. SiC has some drawbacks in welding or manufacturing a large canister. Thus, we designed a double layered disposal canister consisting of a stainless steel outer layer and a SiC inner layer. KAERI has been interested in developing a very deep borehole disposal (DBD) of HLW generated from pyroprocessing of PWR spent nuclear fuel and supported the relevant R and D with very limited its own budget. KAERI team reviewed the DBD concept proposed by Sandia National Laboratories (SNL) and developed its own concept. The SNL concept was based on the steel disposal canister. The authors developed a new technology called cold spray coating method to manufacture a copper-cast iron disposal canister for a geological disposal of high level waste in Korea. With this method, 8 mm thin copper canister with 400 mm in diameter and 1200 mm in height was made. In general, they do not give any credit on the lifetime of a disposal canister in DBD concept unlike the geological disposal. In such case, the expensive copper canister should be replaced with another one. We designed a disposal canister using SiC for DBD. According to an experience in manufacturing a small size canister, the fabrication of a large-size one is a challenge. Also, welding of SiC canister is not easy. Several pathways are being paved to overcome it.

  1. A survey of SiC power MOSFETs short-circuit robustness and failure mode analysis

    DEFF Research Database (Denmark)

    Ceccarelli, L.; Reigosa, P. D.; Iannuzzo, F.

    2017-01-01

    The aim of this paper is to provide an extensive overview about the state-of-art commercially available SiC power MOSFET, focusing on their short-circuit ruggedness. A detailed literature investigation has been carried out, in order to collect and understand the latest research contribution withi...... this topic and create a survey of the present scenario of SiC MOSFETs reliability evaluation and failure mode analysis, pointing out the evolution and improvements as well as the future challenges in this promising device technology....

  2. Neurocisticercosis racemosa (sic), diagnóstico orientado por neuroimágenes

    OpenAIRE

    Carlos Hugo Zapata; Sergio Alberto Vargas; Carlos Santiago Uribe

    2017-01-01

    La neurocisticercosis es la primera causa de parasitosis del sistema nervioso central y de epilepsia adquirida en países en desarrollo. Sus manifestaciones clínicas, especialmente de la variante racemosa (sic), son pleomorfas e inespecíficas, características que hacen de su diagnóstico un desafío para el clínico. El objetivo de este informe fue describir dos casos de neurocisticercosis racemosa (sic), en los cuales las neuroimágenes permitieron hacer el diagnóstico definitivo. El primer ca...

  3. A Novel DBC Layout for Current Imbalance Mitigation in SiC MOSFET Multichip Power Modules

    DEFF Research Database (Denmark)

    Li, Helong; Munk-Nielsen, Stig; Beczkowski, Szymon

    2016-01-01

    This letter proposes a novel direct bonded copper (DBC) layout for mitigating the current imbalance among the paralleled SiC MOSFET dies in multichip power modules. Compared to the traditional layout, the proposed DBC layout significantly reduces the circuit mismatch and current coupling effect......, which consequently improves the current sharing among the paralleled SiC MOSFET dies in power module. Mathematic analysis and circuit model of the DBC layout are presented to elaborate the superior features of the proposed DBC layout. Simulation and experimental results further verify the theoretical...... analysis and current balancing performance of the proposed DBC layout....

  4. A Novel DBC Layout for Current Imbalance Mitigation in SiC MOSFET Multichip Power Modules

    DEFF Research Database (Denmark)

    Li, Helong; Munk-Nielsen, Stig; Beczkowski, Szymon

    2016-01-01

    This paper proposes a novel Direct Bonded Copper (DBC) layout for mitigating the current imbalance among the paralleled SiC MOSFET dies in multichip power modules. Compared to the traditional layout, the proposed DBC layout significantly reduces the circuit mismatch and current coupling effect......, which consequently improves the current sharing among the paralleled SiC MOSFET dies in power module. Mathematic analysis and circuit model of the DBC layout are presented to elaborate on the superior features of the proposed DBC layout. Simulation and experimental results further verify the theoretical...... analysis and current balancing performance of the proposed DBC layout....

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Seleção/Filtragem de Informação no Universo SIC - TV

    OpenAIRE

    Silva, Joana Bárbara Assunção dos Santos

    2012-01-01

    Relatório de Estágio apresentado para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Jornalismo Realizado no âmbito do Mestrado em Jornalismo, este relatório pretende caracterizar o percurso de estágio que, ao longo de seis meses, concretizei na estação de televisão SIC. Proponho uma reflexão teoricamente sustentada sobre as ocorrências que acompanhei na secção Agenda/Planeamento e que mereceram destaque nos serviços noticiosos da SIC. Exploro e probl...

  7. Control of SiC Based Front-End Rectifier under Unbalanced Supply Voltage

    DEFF Research Database (Denmark)

    Maheshwari, Ramkrishan; Trintis, Ionut; Gohil, Ghanshyamsinh Vijaysinh

    2015-01-01

    A voltage source converter is used as a front end converter typically. In this paper, a converter which is realized using SiC MOSFET is considered. Due to SiC MOSFET, a switching frequency more than 50 kHz can be achieved. This can help increasing the current control loop bandwidth, which is not ...... together with a positive-sequence current controller for the front-end rectifier. A gain in the feedforward term can be changed to control the negative-sequence current. Simulation results are presented to verify the theory....

  8. Switching Investigations on a SiC MOSFET in a TO-247 Package

    DEFF Research Database (Denmark)

    Anthon, Alexander; Hernandez Botella, Juan Carlos; Zhang, Zhe

    2014-01-01

    package, has a major influence on the switching energy. Crucial design guidelines for an improved double pulse test circuit are introduced which are used for practical investigations on the switching behavior. Switching energies of a SiC MOSFET in a TO-247 package is measured depending on varying gate......This paper deals with the switching behavior of a SiC MOSFET in a TO-247 package. Based on simulations, critical parasitic inductances in the circuit layout are analyzed and their effect on the switching losses highlighted. Especially the common source inductance, a critical parameter in a TO-247...

  9. Role of Defects in Swelling and Creep of Irradiated SiC

    Energy Technology Data Exchange (ETDEWEB)

    Szlufarska, Izabela [Univ. of Wisconsin, Madison, WI (United States); Voyles, Paul [Univ. of Wisconsin, Madison, WI (United States); Sridharan, Kumar [Univ. of Wisconsin, Madison, WI (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-01-16

    Silicon carbide is a promising cladding material because of its high strength and relatively good corrosion resistance. However, SiC is brittle and therefore SiC-based components need to be carefully designed to avoid cracking and failure by fracture. In design of SiC-based composites for nuclear reactor applications it is essential to take into account how mechanical properties are affected by radiation and temperature, or in other words, what strains and stresses develop in this material due to environmental conditions. While thermal strains in SiC can be predicted using classical theories, radiation-induced strains are much less understood. In particular, it is critical to correctly account for radiation swelling and radiation creep, which contribute significantly to dimensional instability of SiC under radiation. Swelling typically increases logarithmically with radiation dose and saturates at relatively low doses (damage levels of a few dpa). Consequently, swelling-induced stresses are likely to develop within a few months of operation of a reactor. Radiation-induced volume swelling in SiC can be as high as 2%, which is significantly higher than the cracking strain of 0.1% in SiC. Swelling-induced strains will lead to enormous stresses and fracture, unless these stresses can be relaxed via some other mechanism. An effective way to achieve stress relaxation is via radiation creep. Although it has been hypothesized that both radiation swelling and radiation creep are driven by formation of defect clusters, existing models for swelling and creep in SiC are limited by the lack of understanding of specific defects that form due to radiation in the range of temperatures relevant to fuel cladding in light water reactors (LWRs) (<1000°C). For example, defects that can be detected with traditional transmission electron microscopy (TEM) techniques account only for 10-45% of the swelling measured in irradiated SiC. Here, we have undertaken an integrated experimental and

  10. Energy efficiency improvement target for SIC 34 - fabricated metal products. Revised target support document

    Energy Technology Data Exchange (ETDEWEB)

    Byrer, T. G.; Billhardt, C. F.; Farkas, M. S.

    1977-02-15

    In accordance with section 374 of the Energy Policy and Conservation Act (EPCA), Pub. L. 94-163, the Federal Energy Administration (FEA) proposed industrial energy efficiency improvement targets for the ten most energy-consumptive manufacturing industries in the U.S. Following public hearings and a review of the comments made, the final targets for Fabricated Metal Products (SIC 34) were established and are described. Using 1972 data on the energy consumed to produce specific metal products, it was concluded that a 24% reduction in energy consumption for SIC 34 is a viable goal for achievement by 1980. (ERA citation 04:045006)

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

    Science.gov (United States)

    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

  12. High efficiency battery converter with SiC devices for residential PV systems

    DEFF Research Database (Denmark)

    Pham, Cam; Teodorescu, Remus; Kerekes, Tamas

    2013-01-01

    The demand for high efficiency and higher power density is a challenge for Si-based semiconductors due to the physical characteristics of material. These can be overcome by employing wide-band-gap materials like SiC. This paper compares a second generator SiC MOSFETs against a normally-on Trench ...... JFETs and theirs performances in a high efficiency battery converter for residential photovoltaic systems. The prototypes are 3 kW converters with more than 98% efficiency and high simplicity and power density....

  13. Al-doped single-crystalline SiC nanowires synthesized by pyrolysis of polymer precursors.

    Science.gov (United States)

    Yang, Weiyou; Gao, Fengmei; Fan, Yi; An, Linan

    2010-07-01

    Al-doped 6H-SiC nanowires are synthesized by catalyst-assisted pyrolysis of polymer precursors. The obtained nanowires were characterized using scanning electron microscopy, X-ray diffraction, transmission electron microscopy and selective area electron diffraction. We demonstrate that doping concentrations can be controlled by tailoring the Al concentrations in the precursors. We also find that Al-doping has a profound effect on the morphology and emission behavior of the SiC nanowires. The current results suggest a simple technique for synthesizing Al-doped SiC nanomaterials in a controlled manner, which are promising for applications in optical and electronic nanodevices.

  14. Improvement of Strength and Oxidation Resistance for SiC/graphite Composites by SiC coating

    Science.gov (United States)

    Yang, Wanli; Shi, Zhongqi; Li, Hongwei; Li, Zhen; Jin, Zhihao; Qiao, Guanjun

    2011-03-01

    SiC/graphite composites with exelent machinable properties and thermal shock behaviour were successfully fabricated by pressureless sintering at 1700°C in nitrogen atmosphere. A dipping infiltration process was applied to improve the strength and oxidation resistance of the composites. Dense SiC coating was covered on the composites' surface by heat-treating at 1400°C in nitrogen atmosphere with dipping infiltration of silica sol and phenolic resin solutions. The flexural strength of the SiC coated composites were improved from 60 MPa to 140 MPa obviously, and the weight loss of the SiC coated composites was reduced more than 20 % comparing with the uncoated composites by oxidation resistance testing at 1000 °C for 24 h in air. SEM micrographs shows that SiC coating was surrounded the surface of pores and XRD pattern revealed that the new layer was SiC.

  15. Effect of oxygen on the processes of ion beam synthesis of buried SiC layers in silicon

    International Nuclear Information System (INIS)

    Artamonov, V.V.; Valakh, M.Ya.; Klyuj, N.I.; Mel'nik, V.P.; Romanyuk, A.B.; Romanyuk, B.N.; Yukhimchuk, V.A.

    1998-01-01

    The properties of Si-structures with buried silicon carbide (SiC) layers created by high dose carbon implantation into Cz-Si or Fz-Si wafers followed by high-temperature annealing were studied by Raman and infrared spectroscopy. Effect of additional oxygen implantation on the peculiarities of SiC layer formation was also studied. It was shown that under the same implantation and post-implantation annealing conditions the buried SiC layers are more effectively formed in Cz-Si or in Si subjected to additional oxygen implantation. Thus, oxygen in silicon promotes the SiC layer formation due to SiO x precipitate creation and accommodation of the crystal volume in the region where SiC phase is formed

  16. Nickel matrix composite electro coatings containing high concentration of incorporated Sic; Rivestimenti lettrolitici compositi a matrice di nichel, a elevata concentrazione di particelli incorporate di SiC

    Energy Technology Data Exchange (ETDEWEB)

    Psarrou, S.; Spyrellis, N. [National Technical University of Athens (Greece)

    1999-08-01

    This paper gives the results of the study on the preparation of nickel matrix composite electro coatings, containing incorporate silicon carbide (SiC) microparticles under either direct current (D.C.) or pulse current (P.C.) conditions. It is proved that the applicability of pulse plating techniques modifies significantly the control of metal electro crystallization procedure. Under specific preparation conditions, the application of pulse current results to Ni/SiC composite coatings with better surface morphology, higher incorporation percentages and more uniform distribution of the insert SiC microparticles in the metallic matrix than the direct current technique. Pulse electrolysis is thus a powerful mean of perturbing the absorption-desorption phenomena occurring at the nickel/electrolyte interface and hence influences the incorporation procedure to a significant grade. [Italian] Questo articolo fornisce i risultati di uno studio condotto sulla preparazione di elettrodepositi compositi a matrice di nichel per incorporazione di microparticelle di carburo di silicio (SiC), ottenuti sia in condizione di corrente diretta (C.D.) sia di corrente a impulsi (C.P.). E' ormai appurato che l'applicazione della tecnica ad impulsi modifica in modo rilevante il controllo della fase di elettrocristallizazione del metallo. La corrente ad impulsi, in particolare e specifiche condizioni operative, porta all'ottenimento di rivestimenti compositi Ni/SiC con migliorata morfologia superficiale, inoltre la percentuale di particelle incorporate e' piu' elevata e la distribuzione di micro particelle inerti di SiC nella matrice metallica e' piu' uniforme rispetto ai codepositi ottenuti con la tecnica a corrente diretta. L'elettrolisi a impulsi e' quindi uno strumento efficace per perturbare i fenomeni di absorbimento-desorbimento che avvengono all'interfaccia nichel/elettrolita e influenza significativamente il meccanismo di

  17. Micromechanics of fiber pull-out and crack bridging in SCS-6 SiC- CVD SiC composite system at high-temperature

    International Nuclear Information System (INIS)

    El-Azab, A.; Ghoniem, N.M.

    1993-01-01

    A micro mechanical model is developed to study fiber pull-out and crack bridging in fiber reinforced SiC-SiC composites with time dependent thermal creep. By analyzing the creep data for monolithic CVD SiC (matrix) and the SCS-6 SiC fibers in the temperature range 900-1250 degrees C, it is found that the matrix creep rates can be ignored in comparison to those of fibers. Two important relationships are obtained: (1) a time dependent relation between the pull-out stress and the relative sliding distance between the fiber and matrix for the purpose of analyzing pull-out experiments, and (2) the relation between the bridging stress and the crack opening displacement to be used in studying the mechanics and stability of matrix crack bridged by fibers at high temperatures. The present analysis can also be applied to Nicalon-reinforced CVD SiC matrix system since the Nicalon fibers exhibit creep characteristics similar to those of the SCS-6 fibers

  18. Tribo-mechanical behaviour of SiC filled glass-epoxy composites at ...

    African Journals Online (AJOL)

    Polymer matrix composites are a promising candidate in tribological applications due to possibility of tailoring their properties with special fillers. Several methods have been developed to improve their performance. For instance, the introduction of ceramics such (SiC, Al2O3, TiC, etc.) as within the matrix notably increases ...

  19. Biomimetic synthesis of cellular SiC based ceramics from plant ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. A novel biomimetic approach in designing and fabricating engineering ceramic materials has gained much interest in recent times. Following this approach, synthesis has been made of dense Si–SiC duplex ceramic composites and highly porous SiC ceramics in the image of the morphological features inherent in ...

  20. Transformation from amorphous to nano-crystalline SiC thin films ...

    Indian Academy of Sciences (India)

    Silicon carbide (SiC) thin films were deposited on Si(111) by the hot wire chemical vapour deposition (HWCVD) technique using silane (SiH4) and methane (CH4) gases without hydrogen dilution. The effects of SiH4 to CH4 gas flow ratio (R) on the structural properties, chemical composition and photoluminescence (PL) ...

  1. Porous SiC ceramics fabricated by quick freeze casting and solid state sintering

    Directory of Open Access Journals (Sweden)

    Feng Wang

    2017-06-01

    Full Text Available Porous SiC ceramics with uniform microstructure were fabricated by quick freezing in liquid nitrogen and solid state sintering. Poly (vinyl alcohol (PVA was added as binder and pore morphology controller in this work. The microstructure and mechanical properties of porous SiC ceramics could be controlled by the composition of the aqueous slurries. Both solid content of the slurries and PVA content impacted on the pore structures and mechanical properties of the porous SiC ceramics. The solid content of slurries and PVA content varied from 60 to 67.5 wt% and 2–6 wt%, respectively. Besides, the grain morphology of ceramics was also tailored by changing the sintering temperature from 2050 to 2150 °C. Porous SiC ceramics with an average porosity of 42.72%, flexural strength of 59.28 MPa were obtained at 2150 °C from 67.5 wt% slurries with 2 wt% PVA.

  2. AlGaN/GaN-based HEMT on SiC substrate for microwave ...

    Indian Academy of Sciences (India)

    (HEMT) on SiC substrate is proposed and its DC as well as microwave characteristics are dis- cussed for Si3N4 and ... From DC characteristics, the saturation drain currents are measured to be 600 mA/mm and. 550 mA/mm for ..... figure 12 from a family of Mason's unilateral gain (MUG) curves for both passivated devices.

  3. Fabrication and characterization of Ti3SiC2–SiC nanocomposite by ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 34; Issue 7. Fabrication and characterization of Ti3SiC2–SiC nanocomposite by in situ reaction synthesis of TiC/Si/Al powders. Baoyan Liang Mingzhi Wang Xiaopu Li Yunchao Mu. Volume 34 Issue 7 December 2011 pp 1309-1311 ...

  4. Photoluminescence topography of fluorescent SiC and its corresponding source crystals

    DEFF Research Database (Denmark)

    Wilhelm, M.; Kaiser, M.; Jokubavicus, V.

    2013-01-01

    The preparation and application of co-doped polycrystalline SiC as source in sublimation growth of fluorescent layers is a complex topic. Photoluminescence topographies of luminescent 6H-SiC layers and their corresponding source crystals have been studied in order to investigate the dependence...

  5. Silicon Carbide (SiC) Power Processing Unit (PPU) for Hall Effect Thrusters, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — In this SBIR project, APEI, Inc. is proposing to develop a high efficiency, rad-hard 3.8 kW silicon carbide (SiC) power supply for the Power Processing Unit (PPU) of...

  6. Substrate temperature effect on F+ etching of SiC: Molecular dynamics simulation

    NARCIS (Netherlands)

    Lu, X.; Ning, J.; Qin, Y.; Qian, Q.; Chuanwu, Z.; Ying, Y.; Ming, J.; Gou, F.

    2009-01-01

    In this study, we performed molecular dynamics simulations to investigate F+ continuously bombarding SiC surfaces at temperatures of 100, 400, 600 and 800 K with the energy of 150 eV. The simulation results show that the etch rate of Si atoms is more than that of C atoms. With increasing

  7. A Fast Electro-Thermal Co-Simulation Modeling Approach for SiC Power MOSFETs

    DEFF Research Database (Denmark)

    Ceccarelli, Lorenzo; Bahman, Amir Sajjad; Iannuzzo, Francesco

    2017-01-01

    the FEM simulation of the DUT’s structure, performed in ANSYS Icepack. A MATLAB script is used to process the simulation data and feed the needed settings and parameters back into the simulation. The parameters for a CREE 1.2 kV/30 A SiC MOSFET have been identified and the electro-thermal model has been...

  8. Laser alloying of AI with mixed Ni, Ti and SiC powders

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2010-03-01

    Full Text Available Laser alloying of aluminium AA1200 was performed with a 4.4kW Rofin Sinar Nd:YAG laser to improve the surface hardness. Alloying was carried out by depositing Ni, Ti and SiC powders of different weight ratios on the aluminum substrate. The aim...

  9. Laser alloying of Al with mixed Ni, Ti and SiC powders

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2010-11-01

    Full Text Available Laser alloying of aluminium AA1200 was performed with a 4.4kW Rofin Sinar Nd:YAG laser to improve the surface hardness. Alloying was carried out by depositing Ni, Ti and SiC powders of different weight ratios on the aluminium substrate. The aim...

  10. Biomimetic synthesis of cellular SiC based ceramics from plant ...

    Indian Academy of Sciences (India)

    Unknown

    ing oxidized. 3.3 Porous cellular SiC ceramics. Outward movement and reaction of residual Si-phase of biomorphic Si–SiC ceramic specimens occurred when they were positioned in the axial direction in intimate contact with powdered carbon during heating. The den- sity and porosity of the Si-depleted material were found.

  11. Synthesis of SiC from rice husk in a plasma reactor

    Indian Academy of Sciences (India)

    Unknown

    air pollution and ash disposal has proven to be an unsatis- factory solution. Fortunately, rice husk contains the nece- ssary carbon and silica, intimately dispersed, to provide a nearly ideal source material for production of SiC, an industrially important ceramic material. Rice husk was first used by Cutler (1973) as a starting ...

  12. SiC MODIFICATIONS TO MELCOR FOR SEVERE ACCIDENT ANALYSIS APPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Brad J. Merrill; Shannon M Bragg-Sitton

    2013-09-01

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

  13. Omnidirectional luminescence enhancement of fluorescent SiC via pseudoperiodic antireflective subwavelength structures

    DEFF Research Database (Denmark)

    Ou, Yiyu; Jokubavicius, Valdas; Yakimova, Rositza

    2012-01-01

    In the present work, an approach of fabricating pseudoperiodic antireflective subwavelength structures (ARS) on fluorescent SiC by using self-assembled etch mask is demonstrated. By applying the pseudoperiodic (ARS), the average surface reflectance at 6° incidence over the spectral range of 390...

  14. Transformation from amorphous to nano-crystalline SiC thin films ...

    Indian Academy of Sciences (India)

    Administrator

    Auger electron spectroscopy showed that the carbon incorporation in the film structure was strongly dependent on the gas flow ratio. A similar broad visible room-temperature PL with two peaks was observed for all SiC films. The main PL emission was correlated to the band to band transition in uniform a-SiC phase and the ...

  15. Transformation from amorphous to nano-crystalline SiC thin films ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Silicon carbide (SiC) thin films were deposited on Si(111) by the hot wire chemical vapour deposi- tion (HWCVD) technique using silane (SiH4) and methane (CH4) gases without hydrogen dilution. The effects of SiH4 to CH4 gas flow ratio (R) on the structural properties, chemical composition and ...

  16. SiC nanocrystals as Pt catalyst supports for fuel cell applications

    DEFF Research Database (Denmark)

    Dhiman, Rajnish; Morgen, Per; Skou, E.M.

    2013-01-01

    A robust catalyst support is pivotal to Proton Exchange Membrane Fuel Cells (PEMFCs) to overcome challenges such as catalyst support corrosion, low catalyst utilization and overall capital cost. SiC is a promising candidate material which could be applied as a catalyst support in PEMFCs. Si......C nanocrystals are here synthesized using nano-porous carbon black (Vulcan XC-72) as a template using two different reactions, which result in particle sizes in the ranges of 50-150 nm (SiC-SPR) and 25-35 nm (SiC-NS). Pt nano-catalysts of size 5-8 nm and 4-5 nm have successfully been uniformly deposited...... on the nanocrystals of SiC-SPR and SiC-NS by the polyol method. The SiC substrates are subjected to an acid treatment to introduce the surface groups, which help to anchor the Pt nano-catalysts. These SiC based catalysts have been found to have a higher electrochemical activity than commercially available Vulcan...

  17. A Comparison of SiC Power Switches for High-Rel Defense Applications (preprint)

    Science.gov (United States)

    2007-07-01

    junction transistor ( BJT ). The VJFET is principally valued for having demonstrated the highest current and voltage combinations, positive...for defense applications. They are the vertical junction field effect transistor (VJFET), the metal-oxide-semiconductor FET (MOSFET), and the bipolar...most technologically ready SiC power switch, the vertical junction field effect transistor (VJFET), has been demonstrated in preproduction devices at

  18. PSpice Modeling Platform for SiC Power MOSFET Modules with Extensive Experimental Validation

    DEFF Research Database (Denmark)

    Ceccarelli, Lorenzo; Iannuzzo, Francesco; Nawaz, Muhammad

    2016-01-01

    The aim of this work is to present a PSpice implementation for a well-established and compact physics-based SiC MOSFET model, including a fast, experimental-based parameter extraction procedure in a MATLAB GUI environment. The model, originally meant for single-die devices, has been used...

  19. SiC fibre by chemical vapour deposition on tungsten filament

    Indian Academy of Sciences (India)

    Unknown

    MS received 26 December 2000; revised 15 March 2001. Abstract. A CVD system for the production of continuous SiC fibre ... Mercury acts as gas tight seal and facilitates electrical resistance heating of the fibre. ... com, Inc., Atlantic Research Corporation, USA) are com- mercially available for last 15 years. Microstructure,.

  20. Synthesis of SiC from rice husk in a plasma reactor

    Indian Academy of Sciences (India)

    Unknown

    nearly ideal source material for production of SiC, an industrially important ceramic material. Rice husk was first used by Cutler (1973) as a starting material for the production of silicon carbide. Since the rice husk route appears to be promising, much attention has been paid to it (Mansour and Hanna 1979; Nutt 1988; Patel ...

  1. Precession electron diffraction for SiC grain boundary characterization in unirradiated TRISO fuel

    International Nuclear Information System (INIS)

    Lillo, T.M.; Rooyen, I.J. van; Wu, Y.Q.

    2016-01-01

    Highlights: • SiC grain orientation determined by TEM-based precession electron diffraction. • Orientation data improved with increasing TEM sample thickness. • Fraction of low angle grain boundaries lower from PED data than EBSD data. • Fractions of high angle and CSL-related boundaries similar to EBSD data. - Abstract: Precession electron diffraction (PED), a transmission electron microscopy-based technique, has been evaluated for the suitability for evaluating grain boundary character in the SiC layer of tristructural isotropic (TRISO) fuel. This work reports the effect of transmission electron microscope (TEM) lamella thickness on the quality of data and establishes a baseline comparison to SiC grain boundary characteristics, in an unirradiated TRISO particle, determined previously using a conventional electron backscatter diffraction (EBSD) scanning electron microscope (SEM)-based technique. In general, it was determined that the lamella thickness produced using the standard focused ion beam (FIB) fabrication process (∼80 nm), is sufficient to provide reliable PED measurements, although thicker lamellae (∼120 nm) were found to produce higher quality orientation data. Also, analysis of SiC grain boundary character from the TEM-based PED data showed a much lower fraction of low-angle grain boundaries compared to SEM-based EBSD data from the SiC layer of a TRISO-coated particle made using the same fabrication parameters and a SiC layer deposited at a slightly lower temperature from a surrogate TRISO particle. However, the fractions of high-angle and coincident site lattice (CSL)-related grain boundaries determined by PED are similar to those found using SEM-based EBSD. Since the grain size of the SiC layer of TRSIO fuel can be as small as 250 nm (Kirchhofer et al., 2013), depending on the fabrication parameters, and since grain boundary fission product precipitates in irradiated TRISO fuel can be nano-sized, the TEM-based PED orientation data

  2. Evolution of Radiation Induced Defects in SiC: A Multiscale Simulation Approach

    Science.gov (United States)

    Jiang, Hao

    Because of various excellent properties, SiC has been proposed for many applications in nuclear reactors including cladding layers in fuel rod, fission products container in TRISO fuel, and first wall/blanket in magnetic controlled fusion reactors. Upon exposure to high energy radiation environments, point defects and defect clusters are generated in materials in amounts significantly exceeding their equilibrium concentrations. The accumulation of defects can lead to undesired consequences such as crystalline-to-amorphous transformation1, swelling, and embrittlement, and these phenomena can adversely affect the lifetime of SiC based components in nuclear reactors. It is of great importance to understand the accumulation process of these defects in order to estimate change in properties of this material and to design components with superior ability to withstand radiation damages. Defect clusters are widely in SiC irradiated at the operation temperatures of various reactors. These clusters are believed to cause more than half of the overall swelling of irradiated SiC and can potentially lead to lowered thermal conductivity and mechanical strength. It is critical to understand the formation and growth of these clusters. Diffusion of these clusters is one importance piece to determine the growth rate of clusters; however it is unclear so far due to the challenges in simulating rare events. Using a combination of kinetic Activation Relaxation Technique with empirical potential and ab initio based climbing image nudged elastic band method, I performed an extensive search of the migration paths of the most stable carbon tri-interstitial cluster in SiC. This research reveals paths with the lowest energy barriers to migration, rotation, and dissociation of the most stable cluster. Based on these energy barriers, I concluded defect clusters are thermally immobile at temperatures lower than 1500 K and can dissociate into smaller clusters and single interstitials at

  3. Elaboration of silicon carbides nano particles (SiC): from the powder synthesis to the sintered ceramic; Elaboration de ceramiques nanostructurees en carbure de silicium (SiC): de la synthese de poudre a la ceramique frittee

    Energy Technology Data Exchange (ETDEWEB)

    Reau, A. [CEA Saclay, Dept. des Materiaux pour le Nucleaire (DEN/DANS/DMN/SRMA), 91 - Gif-sur-Yvette (France)

    2008-07-01

    Materials for the reactor cores of the fourth generation will need materials supporting high temperatures with fast neutrons flux. SiC{sub f}/SiC ceramics are proposed. One of the possible elaboration process is to fill SiC fiber piece with nano particles SiC powder and to strengthen by sintering. The aim of this thesis is to obtain a nano structured SiC ceramic as a reference for the SiC{sub f}/SiC composite development and to study the influence of the fabrication parameters. (A.L.B.)

  4. Fracture Mechanisms For SiC Fibers And SiC/SiC Composites Under Stress-Rupture Conditions at High Temperatures

    Science.gov (United States)

    DiCarlo, James A.; Yun, Hee Mann; Hurst, Janet B.; Viterna, L. (Technical Monitor)

    2002-01-01

    The successful application of SiC/SiC ceramic matrix composites as high-temperature structural materials depends strongly on maximizing the fracture or rupture life of the load-bearing fiber and matrix constituents. Using high-temperature data measured under stress-rupture test conditions, this study examines in a mechanistic manner the effects of various intrinsic and extrinsic factors on the creep and fracture behavior of a variety of SiC fiber types. It is shown that although some fiber types fracture during a large primary creep stage, the fiber creep rate just prior to fracture plays a key role in determining fiber rupture time (Monkman-Grant theory). If it is assumed that SiC matrices rupture in a similar manner as fibers with the same microstructures, one can develop simple mechanistic models to analyze and optimize the stress-rupture behavior of SiC/SiC composites for applied stresses that are initially below matrix cracking.

  5. Preparation and characterization of the electrodeposited Cr-Al{sub 2}O{sub 3}/SiC composite coating

    Energy Technology Data Exchange (ETDEWEB)

    Gao Jifeng, E-mail: readlot@tom.com [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Suo Jinping, E-mail: jpsuo@yahoo.com.cn [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2011-09-01

    To increase the SiC content in Cr-based coatings, Cr-Al{sub 2}O{sub 3}/SiC composite coatings were plated in Cr(VI) baths which contained Al{sub 2}O{sub 3}-coated SiC powders. The Al{sub 2}O{sub 3}-coated SiC composite particles were synthesized by calcining the precursor prepared by heterogeneous deposition method. The transmission electron microscopy analysis of the particles showed that the nano-SiC particle was packaged by alumina. The zeta potential of the particles collected from the bath was up to +23 mV, a favorable condition for the co-deposition of the particles and chromium. Pulse current was used during the electrodeposition. Scanning Electron Microscopy (SEM) indicated that the coating was compact and combined well with the substrate. Energy dispersive X-ray analysis of Cr-Al{sub 2}O{sub 3}/SiC coatings demonstrated that the concentration of SiC in the coating reached about 2.5 wt.%. The corrosion behavior of the composite coating was studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The data obtained suggested that the Al{sub 2}O{sub 3}/SiC particles significantly enhanced the corrosion resistance of the composite coating in 0.05 M HCl solution.

  6. Mechanical performance of SiC based MEMS capacitive microphone for ultrasonic detection in harsh environment

    Science.gov (United States)

    Zawawi, S. A.; Hamzah, A. A.; Mohd-Yasin, F.; Majlis, B. Y.

    2017-08-01

    In this project, SiC based MEMS capacitive microphone was developed for detecting leaked gas in extremely harsh environment such as coal mines and petroleum processing plants via ultrasonic detection. The MEMS capacitive microphone consists of two parallel plates; top plate (movable diaphragm) and bottom (fixed) plate, which separated by an air gap. While, the vent holes were fabricated on the back plate to release trapped air and reduce damping. In order to withstand high temperature and pressure, a 1.0 μm thick SiC diaphragm was utilized as the top membrane. The developed SiC could withstand a temperature up to 1400°C. Moreover, the 3 μm air gap is invented between the top membrane and the bottom plate via wafer bonding. COMSOL Multiphysics simulation software was used for design optimization. Various diaphragms with sizes of 600 μm2, 700 μm2, 800 μm2, 900 μm2 and 1000 μm2 are loaded with external pressure. From this analysis, it was observed that SiC microphone with diaphragm width of 1000 μm2 produced optimal surface vibrations, with first-mode resonant frequency of approximately 36 kHz. The maximum deflection value at resonant frequency is less than the air gap thickness of 8 mu;m, thus eliminating the possibility of shortage between plates during operation. As summary, the designed SiC capacitive microphone has high potential and it is suitable to be applied in ultrasonic gas leaking detection in harsh environment.

  7. Construction Progress of the S-IC Test Stand Spherical Hydrogen Tank

    Science.gov (United States)

    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. This photograph taken September 18, 1963 shows a spherical hydrogen tank being constructed next to the S-IC test stand.

  8. Construction Progress of the S-IC Test Stand Hydrogen Tanks

    Science.gov (United States)

    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. In the center portion of this photograph, taken September 5, 1963, the spherical hydrogen storage tanks are being constructed. One of the massive tower legs of the S-IC test stand is visible to the far right.

  9. Interface and interaction of graphene layers on SiC(0001[combining macron]) covered with TiC(111) intercalation.

    Science.gov (United States)

    Wang, Lu; Wang, Qiang; Huang, Jianmei; Li, Wei-Qi; Chen, Guang-Hui; Yang, Yanhui

    2017-10-11

    It is important to understand the interface and interaction between the graphene layer, titanium carbide [TiC(111)] interlayer, and silicon carbide [SiC(0001[combining macron])] substrates in epitaxial growth of graphene on silicon carbide (SiC) substrates. In this study, the fully relaxed interfaces which consist of up to three layers of TiC(111) coatings on the SiC(0001[combining macron]) as well as the graphene layers interactions with these TiC(111)/SiC(0001[combining macron]) were systematically studied using the density functional theory-D2 (DFT-D2) method. The results showed that the two layers of TiC(111) coating with the C/C-terminated interfaces were thermodynamically more favorable than one or three layers of TiC(111) on the SiC(0001[combining macron]). Furthermore, the bonding of the Ti-hollow-site stacked interfaces would be a stronger link than that of the Ti-Fcc-site stacked interfaces. However, the formation of the C/Ti/C and Ti/C interfaces implied that the first upper carbon layer can be formed on TiC(111)/SiC(0001[combining macron]) using the decomposition of the weaker Ti-C and C-Si interfacial bonds. When growing graphene layers on these TiC(111)/SiC(0001[combining macron]) substrates, the results showed that the interaction energy depended not only on the thickness of the TiC(111) interlayer, but also on the number of graphene layers. Bilayer graphene on the two layer thick TiC(111)/SiC(0001[combining macron]) was thermodynamically more favorable than a monolayer or trilayer graphene on these TiC(111)/SiC(0001[combining macron]) substrates. The adsorption energies of the bottom graphene layers with the TiC(111)/SiC(0001[combining macron]) substrates increased with the decrease of the interface vertical distance. The interaction energies between the bottom, second and third layers of graphene on the TiC(111)/SiC(0001[combining macron]) were significantly higher than that of the freestanding graphene layers. All of these findings provided

  10. Qualification of SiC materials for fusion and fission reactors

    International Nuclear Information System (INIS)

    Ryazanov, Alexander

    2009-01-01

    Ceramic materials such as silicon carbide (SiC) and SiC/SiC composites are both considered, due to their high-temperature strength, pseudo-ductile fracture behavior and low-induced radioactivity, as candidate materials for fusion reactor (test blanket module for ITER) and high temperature gas-cooled reactors (HTGR). The radiation swelling and creep of SiC are very important physical phenomena that determine the radiation resistance of them in these reactors. Other important problem which exists especially in fusion reactor is an effect of accumulation of high concentrations of helium atoms in SiC (up to 15000-20000 at.ppm) due to (n,α) nuclear reaction on physical mechanical properties. An understanding of the physical mechanism of this phenomenon is very important for the investigations of helium atom effect on radiation swelling in SiC. In this report a compilation of non-irradiated and irradiated properties of SiC are provided and analyzed in terms of their application to fusion and high temperature gas cooled reactors. Special topic of this report is oriented on the micro structural changes in chemically vapor-deposited (CVD) high-purity beta-SiC during neutron and ion irradiations at elevated temperatures. The evolutions of various radiation induced defects including dislocation loops, network dislocations and cavities are presented here as a function of irradiation temperature and fluencies. These observations are discussed in relation with such irradiation phenomena in SiC as low temperature swelling and cavity swelling. One of the main difficulties in the radiation damage studies of SiC materials lies in the absence of theoretical models and interpretation of many physical mechanisms of radiation phenomena including the radiation swelling and creep. The point defects in ceramic materials are characterized by the charge states and they can have an effective charge. The internal effective electrical field is formed due to the accumulation of charged point

  11. Construction Progress of the S-IC and F-1 Test Stands

    Science.gov (United States)

    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. North of the massive S-IC test stand, the F-1 Engine test stand was built. Designed to assist in the development of the F-1 Engine, the F-1 test stand is a vertical engine firing test stand, 239 feet in elevation and 4,600 square feet in area at the base. Capability was provided for static firing of 1.5 million pounds of thrust using liquid oxygen and kerosene. Like the S-IC stand, the foundation of the F

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

    Science.gov (United States)

    1963-01-01

    At its founding, the Marshall Space Flight Center (MSFC) inherited the Army's Jupiter and Redstone test stands, but much larger facilities were needed for the giant stages of the Saturn V. From 1960 to 1964, the existing stands were remodeled and a sizable new test area was developed. The new comprehensive test complex for propulsion and structural dynamics was unique within the nation and the free world, and they remain so today because they were constructed with foresight to meet the future as well as on going needs. Construction of the S-IC Static test stand complex began in 1961 in the west test area of MSFC, and was completed in 1964. The S-IC static test stand was designed to develop and test the 138-ft long and 33-ft diameter Saturn V S-IC first stage, or booster stage, weighing in at 280,000 pounds. Required to hold down the brute force of a 7,500,000-pound thrust produced by 5 F-1 engines, the S-IC static test stand was designed and constructed with the strength of hundreds of tons of steel and 12,000,000 pounds of cement, planted down to bedrock 40 feet below ground level. The foundation walls, constructed with concrete and steel, are 4 feet thick. The base structure consists of four towers with 40-foot-thick walls extending upward 144 feet above ground level. The structure was topped by a crane with a 135-foot boom. With the boom in the upright position, the stand was given an overall height of 405 feet, placing it among the highest structures in Alabama at the time. This photo, taken at the S-IC test stand on October 2, 1963, is of a crane control. It was from here that the massive cranes were operated. Seen in the background is the F-1 Test Stand. Designed to assist in the development of the F-1 Engine, the F-1 test stand is a vertical engine firing test stand, 239 feet in elevation and 4,600 square feet in area at the base. Capability was provided for static firing of 1.5 million pounds of thrust using liquid oxygen and kerosene. Like the S-IC stand

  13. Nature of the Insulating Ground State of the Two-Dimensional Sn Atom Lattice on SiC(0001).

    Science.gov (United States)

    Yi, Seho; Lee, Hunpyo; Choi, Jin-Ho; Cho, Jun-Hyung

    2016-07-28

    Semiconductor surfaces with narrow surface bands provide unique playgrounds to search for Mott-insulating state. Recently, a combined experimental and theoretical study of the two-dimensional (2D) Sn atom lattice on a wide-gap SiC(0001) substrate proposed a Mott-type insulator driven by strong on-site Coulomb repulsion U within a single-band Hubbard model. However, our systematic density-functional theory (DFT) study with local, semilocal, and hybrid exchange-correlation functionals shows that the Sn dangling-bond state largely hybridizes with the substrate Si 3p and C 2p states to split into three surface bands due to the crystal field. Such a hybridization gives rise to the stabilization of the antiferromagnetic order via superexchange interactions. The band gap and the density of states predicted by the hybrid DFT calculation agree well with photoemission data. Our findings not only suggest that the Sn/SiC(0001) system can be represented as a Slater-type insulator driven by long-range magnetism, but also have an implication that taking into account long-range interactions beyond the on-site interaction would be of importance for properly describing the insulating nature of Sn/SiC(0001).

  14. Neutralization of an epitaxial graphene grown on a SiC(0001) by means of palladium intercalation

    Science.gov (United States)

    Yagyu, Kazuma; Takahashi, Kazutoshi; Tochihara, Hiroshi; Tomokage, Hajime; Suzuki, Takayuki

    2017-03-01

    Pd-intercalated graphene grown on a SiC(0001) substrate was investigated using STM, angle-resolved photoemission spectroscopy, and XPS. Pd atoms deposited at room temperature on a zero layer graphene grown on a SiC(0001) substrate were intercalated between the zero layer graphene and the SiC substrate after the thermal annealing above 700 °C, forming a Pd-intercalated single layer graphene. No charge transfer occurred between the intercalated Pd layer and the graphene, which resulted in the formation of the electrically neutral graphene. The Pd-intercalated graphene remained electrically neutral throughout the annealing temperature range between 700 and 1100 °C. The charge transfer, however, occurred between the intercalated Pd layer and the SiC substrate, which caused a band bending confirmed in the core level spectra measured by XPS.

  15. High Temperature All Silicon-Carbide (SiC) DC Motor Drives for Venus Exploration Vehicles, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project seeks to prove the feasibility of creating high-temperature silicon-carbide (SiC) based motor drives for...

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

    International Nuclear Information System (INIS)

    Koo, Kang; Choe, Jongdeok; Park, Youngmi

    2009-01-01

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

  17. Tribology of silicon-thin-film-coated SiC ceramics and the effects of high energy ion irradiation

    International Nuclear Information System (INIS)

    Kohzaki, Masao; Noda, Shoji; Doi, Harua

    1990-01-01

    The sliding friction coefficients and specific wear of SiC ceramics coated with a silicon thin film (Si/SiC) with and without subsequent Ar + irradiation against a diamond pin were measured with a pin-on-disk tester at room temperature in laboratory air of approximately 50% relative humidity without oil lubrication for 40 h. The friction coefficient of Ar + -irradiated Si/SiC was about 0.05 with a normal load of 9.8 N and remained almost unchanged during the 40 h test, while that of SiC increased from 0.04 to 0.12 during the test. The silicon deposition also reduced the specific wear of SiC to less than one tenth of that of the uncoated SiC. Effectively no wear was detected in Si/SiC irradiated to doses of over 2x10 16 ions cm -2 . (orig.)

  18. High Quality, Low-Scatter SiC Optics Suitable for Space-based UV & EUV Applications, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — SSG Precision Optronics proposes the development and demonstration of a new optical fabrication process for the production of EUV quality Silicon Carbide (SiC)...

  19. High Quality, Low-Scatter SiC Optics Suitable for Space-based UV & EUV Applicati, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — SSG Precision Optronics proposes the development of a novel optical manufacturing process that will allow the production of state-of-the-art Silicon Carbide (SiC)...

  20. Comparative assessment of 3.3kV/400A SiC MOSFET and Si IGBT power modules

    DEFF Research Database (Denmark)

    Ionita, Claudiu; Nawaz, Muhammad; Ilves, Kalle

    2017-01-01

    to withstand short-circuit (SC) events under hard switch fault condition is also investigated. The SiC MOSFET power modules survived short circuit tests performed at a DC-link voltage of 1.5 kV and a pulse duration of 3 μs with a measured short-circuit energy of 6.4 J. The SiC power module failed when......In this paper, a comparative evaluation between a commercial 3.3 kV/400 A Si-IGBT and a 3.3 kV/400 A SiC MOSFET power module in half-bridge configuration is presented. With a constant current of 250 A, a lower forward voltage (VDS) drop of 1.6 V is obtained for SiC MOSFET at 300 K compared to Si...

  1. A study of metal-ceramic wettability in SiC-Al using dynamic melt infiltration of SiC

    Science.gov (United States)

    Asthana, R.; Rohatgi, P. K.

    1993-01-01

    Pressure-assisted infiltration with a 2014 Al alloy of plain and Cu-coated single crystal platelets of alpha silicon carbide was used to study particulate wettability under dynamic conditions relevant to pressure casting of metal-matrix composites. The total penetration length of infiltrant metal in porous compacts was measured at the conclusion of solidification as a function of pressure, infiltration time, and SiC size for both plain and Cu-coated SiC. The experimental data were analyzed to obtain a threshold pressure for the effect of melt intrusion through SiC compacts. The threshold pressure was taken either directly as a measure of wettability or converted to an effective wetting angle using the Young-Laplace capillary equation. Cu coating resulted in partial but beneficial improvements in wettability as a result of its dissolution in the melt, compared to uncoated SiC.

  2. A high-performance alginate hydrogel binder for the Si/C anode of a Li-ion battery.

    Science.gov (United States)

    Liu, Jie; Zhang, Qian; Wu, Zhan-Yu; Wu, Jiao-Hong; Li, Jun-Tao; Huang, Ling; Sun, Shi-Gang

    2014-06-18

    An alginate hydrogel binder is prepared through the cross linking effect of Na alginate with Ca(2+) ions, which leads to a remarkable improvement in the electrochemical performance of the Si/C anode of a Li-ion battery.

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

    Energy Technology Data Exchange (ETDEWEB)

    Thomas M. Lillo; Isabella J. van Rooyen

    2014-08-01

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

  4. NOAA JPSS Visible Infrared Imaging Radiometer Suite (VIIRS) Sea Ice Characterization (SIC) Environmental Data Record (EDR) from IDPS

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains an Environmental Data Record (EDR) of Sea Ice Characterization (SIC) from the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument...

  5. SUPERPOLISHED SI COATED SIC OPTICS FOR RAPID MANUFACTURE OF LARGE APERTURE UV AND EUV TELESCOPES, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — SSG/Tinsley proposes an innovative optical manufacturing process that will allow the advancement of state-of-the-art Silicon Carbide (SiC) mirrors for large aperture...

  6. Direct Detection of Unnatural DNA Nucleotides dNaM and d5SICS using the MspA Nanopore.

    Directory of Open Access Journals (Sweden)

    Jonathan M Craig

    Full Text Available Malyshev et al. showed that the four-letter genetic code within a living organism could be expanded to include the unnatural DNA bases dNaM and d5SICS. However, verification and detection of these unnatural bases in DNA requires new sequencing techniques. Here we provide proof of concept detection of dNaM and d5SICS in DNA oligomers via nanopore sequencing using the nanopore MspA. We find that both phi29 DNA polymerase and Hel308 helicase are capable of controlling the motion of DNA containing dNaM and d5SICS through the pore and that single reads are sufficient to detect the presence and location of dNaM and d5SICS within single molecules.

  7. Electromagnetic interference shielding performance of nano-layered Ti3SiC2 ceramics at high-temperatures

    Directory of Open Access Journals (Sweden)

    Sigong Li

    2018-01-01

    Full Text Available The X-band electromagnetic interference (EMI shielding properties of nano-layered Ti3SiC2 ceramics were evaluated from room temperature up to 800°C in order to explore the feasibility of Ti3SiC2 as efficient high temperature EMI shielding material. It was found that Ti3SiC2 exhibits satisfactory EMI shielding effectiveness (SE close to 30 dB at room temperature and the EMI SE shows good temperature stability. The remarkable EMI shielding properties of Ti3SiC2 can be mainly attributed to high electrical conductivity, high dielectric loss and more importantly the multiple reflections due to the layered structure.

  8. FE simulation of the indentation deformation of SiC modified vinylester composites in respect to their abrasive wear performance

    Directory of Open Access Journals (Sweden)

    2008-10-01

    Full Text Available The abrasive sliding friction and wear behaviours of silicon carbide (SiC filled vinylester (VE composites were investigated. The average grain size of the incorporated SiC particles was varied, holding the volume content of them in every case at 16 vol%. Mechanical properties (hardness, compression modulus, yield stress of the filled and neat VE were determined. The tribological properties were investigated in block (composite – on – ring (steel test configuration. The steel counter bodies were covered with abrasive papers of different graining. Coefficient of friction (COF and specific wear rate of the VE + SiC composites were determined. It was observed that the wear resistance increases with increasing average filler grain size and with decreasing abrasiveness of the counter surface. The COF of the VE + SiC composites is independent of the size of the incorporated particles, but it is strongly influenced by the abrasiveness of the counter body. The worn surfaces of the VE + SiC systems were analysed in scanning electron microscope (SEM to deduce the typical wear mechanisms. The size effect of the SiC filler particles onto the abrasive wear characteristics was investigated by assuming that the roughness peaks of the abrasive paper and the indenter of the microhardness test cause similar micro scaled contact deformations in the composites. Therefore FE method was used to simulate the micro scaled deformation process in the VE + SiC systems during microindentation tests. The FE results provided valuable information on how to explain the size effect of the incorporated SiC filler.

  9. Characteristic electron energy loss spectra in SiC buried layers formed by C+ implantation into crystalline silicon

    International Nuclear Information System (INIS)

    Yan Hui; Chen Guanghua; Kwok, R.W.M.

    1998-01-01

    SiC buried layers were synthesized by a metal vapor vacuum arc ion source, with C + ions implanted into crystalline Si substrates. According to X-ray photoelectron spectroscopy, the characteristic electron energy loss spectra of the SiC buried layers were studied. It was found that the characteristic electron energy loss spectra depend on the profiles of the carbon content, and correlate well with the order of the buried layers

  10. Improvements in mechanical properties in SiC by the addition of TiC particles

    International Nuclear Information System (INIS)

    Wei, G.C.; Becher, P.F.

    1984-01-01

    Silicon carbide ceramics containing up to 24.6 vol% dispersed TiC particles yielded fully dense composites by hot-pressing at 2000 0 C with 1 wt% Al and 1 wt% C added. The microstructure consists of fine TiC particles in a fine-grained SiC matrix. Addition of TiC particles increases the critical fracture toughness of SiC (to approx. =6 MPa /SUP ./ m /SUP 1/2/ at 24.6 vol% TiC) and yields high flexure strength (greater than or equal to 680 MPa), with both properties increasing with increasing volume fraction of TiC. The strengths at high temperatures are also improved by the TiC additions. Observations of the fracture path indicate that the improved toughness and strength are a result of crack deflection by the TiC particles

  11. Suppressed compressibility of quantum Hall effect edge states in epitaxial graphene on SiC

    Science.gov (United States)

    Slizovskiy, Sergey; Fal'ko, Vladimir I.

    2018-02-01

    We determine conditions for the formation of compressible stripes near the quantum Hall effect (QHE) edges of top-gated epitaxial graphene on Si-terminated SiC (G/SiC) and compare those to graphene exfoliated onto insulating substrate in the field-effect-transistor (GraFET) geometry. For G/SiC, a large density of localized surface states on SiC just underneath graphene layer and charge transfer between them lead both to doping of graphene and to screening of potential profile near its edge. This suppresses formation of compressible stripes near QHE edges in graphene, making them much narrower than the corresponding compressible stripes in GraFETs.

  12. Modulated SiC nanowires: Molecular dynamics study of their thermal properties

    Science.gov (United States)

    Termentzidis, Konstantinos; Barreteau, Thibaut; Ni, Yuxiang; Merabia, Samy; Zianni, Xanthippi; Chalopin, Yann; Chantrenne, Patrice; Volz, Sebastian

    2013-03-01

    The thermal conductivity of diameter and polytype modulated SiC nanowires is predicted using nonequilibrium molecular dynamics. For the polytype modulated nanowires, the two main SiC polytypes, zinc blende (3C) and wurtzite (2H) were considered. We show that the thermal conductivity of the diameter modulated nanowires may be even smaller than that of the constant diameter nanowire with the small section. This remarkable reduction in thermal conduction is attributed to a significant thermal boundary resistance displayed by the constriction, as measured by independent molecular-dynamics simulations. The constriction resistance is related to the confinement of low-frequency modes, as shown by vibrational density-of-states calculations. We used Monte Carlo simulations to conclude that the value of the constriction resistance may be explained by the specular reflections of this class of modes on the surface surrounding the constriction.

  13. Production of Rare Earth Isotope Beams for Radiotracer-DLTS on SiC

    CERN Multimedia

    2002-01-01

    Electrical properties of semiconductors are extremely sensitive to minor traces of impurities and defects. This fact allows to intentionally modify material properties and is thus the very basis of semiconductor electronics and optoelectronics. In the present project, electronic properties and doping effects of rare-earth elements in the technologically important semiconductor SiC are to be investigated using optical and electrical characterization techniques like Photoluminescence, Deep Level Transient Spectroscopy and Thermal Admittance Spectroscopy. By using the elemental transmutation of radioactive isotopes as a tracer, it will be guaranteed that the impurity-related band gap states can definitively be distinguished from intrinsic or process-induced defects. For SiC up to now only detailed investigation of Er- related deep levels have been reported, preliminary data exist for Sm- and Gd- impurities. In this project we propose the implantation of Pr and Eu isotopes for detailed level studies.

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

    Science.gov (United States)

    Reese, Bradley

    2015-01-01

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

  15. Fabrication of a single layer graphene by copper intercalation on a SiC(0001) surface

    International Nuclear Information System (INIS)

    Yagyu, Kazuma; Tochihara, Hiroshi; Tomokage, Hajime; Suzuki, Takayuki; Tajiri, Takayuki; Kohno, Atsushi; Takahashi, Kazutoshi

    2014-01-01

    Cu atoms deposited on a zero layer graphene grown on a SiC(0001) substrate, intercalate between the zero layer graphene and the SiC substrate after the thermal annealing above 600 °C, forming a Cu-intercalated single layer graphene. On the Cu-intercalated single layer graphene, a graphene lattice with superstructure due to moiré pattern is observed by scanning tunneling microscopy, and specific linear dispersion at the K ¯ point as well as a characteristic peak in a C 1s core level spectrum, which is originated from a free-standing graphene, is confirmed by photoemission spectroscopy. The Cu-intercalated single layer graphene is found to be n-doped

  16. In-pile Hydrothermal Corrosion Evaluation of Coated SiC Ceramics and Composites

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, David [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Ang, Caen [Univ. of Tennessee, Knoxville, TN (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Linton, Kory D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Terrani, Kurt A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-09-01

    Hydrothermal corrosion accelerated by water radiolysis during normal operation is among the most critical technical feasibility issues remaining for silicon carbide (SiC) composite-based cladding that could provide enhanced accident-tolerance fuel technology for light water reactors. An integrated in-pile test was developed and performed to determine the synergistic effects of neutron irradiation, radiolysis, and pressurized water flow, all of which are relevant to a typical pressurized water reactor (PWR). The test specimens were chosen to cover a range of SiC materials and a variety of potential options for environmental barrier coatings. This document provides a summary of the irradiation vehicle design, operations of the experiment, and the specimen loading into the irradiation vehicle.

  17. Band-gap modulation of graphane-like SiC nanoribbons under uniaxial elastic strain

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Ben-Ling, E-mail: jsblgao@gmail.com [Department of Physics, Huaiyin Institute of Technology, Huaian 223003 (China); Department of Physics, Nanjing University, Nanjing 210093 (China); Xu, Qing-Qiang [Department of Physics, Xuzhou Normal University, Xuzhou 221009 (China); Ke, San-Huang, E-mail: shke@tongji.edu.cn [MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Beijing Computational Science Research Center, 3 Heqing Road, Beijing 100084 (China); Xu, Ning [Department of Physics, Yancheng Institute of Technology, Yancheng 224051 (China); Hu, Guang; Wang, Yanzong; Liang, Feng; Tang, Yalu [Department of Physics, Huaiyin Institute of Technology, Huaian 223003 (China); Xiong, Shi-Jie [Department of Physics, Nanjing University, Nanjing 210093 (China)

    2014-01-24

    The band-gap modulation of zigzag and armchair graphane-like SiC nanoribbons (GSiCNs) under uniaxial elastic strain is investigated using the density functional theory. The results show that band gap of both structures all decreases when being compressed or tensed. In compression, both zigzag and armchair GSiCNs are semiconductors with a direct band gap. However, in tension, the armchair GSiCNs undergo a direct-to-indirect band-gap transition but the zigzag GSiCNs still have a direct band gap. These results are also proved by HSE06 method. This implies a potential application of the graphane-like SiC nanoribbons in the future pressure sensor and optical electronics nanodevices.

  18. Development of nanoporous TiO2 and SiC membranes for membrane filtration

    DEFF Research Database (Denmark)

    König, Katja; Vigna, Erika; Farsi, Ali

    Reverse osmosis membranes are increasingly used for the production of drinking water (desalination of sea water or brackish water), for demineralisation of water in industrial processes (boiled feed water, microelectronics production) as well as in food processing and pharmaceutical production....... Today´s reverse osmosis membranes are made of polymers; however, these membranes have several technical limitations, for example, low water fluxes and high sensitivity to oxidizing chemicals. Since membrane fouling is still a major problem in reverse osmosis desalination plants, replacement of polymer...... reverse osmosis membranes by ceramic counterparts would provide higher fluxes and allow more efficient cleaning of the membranes. The aim of this work was to prepare defect-free nanoporous ceramic (TiO2 and SiC) layers on macroporous SiC supports by using electrophoretic deposition and dip...

  19. Synthesis of tubular SiC thick CVD coatings for thermo-structural applications

    International Nuclear Information System (INIS)

    Drieux, P.

    2013-01-01

    The goal of this study was to synthesize monolithic SiC tubes to improve sealing of the SiC/SiC composite of a nuclear fuel cladding structure. Tubes of 8 mm inner diameter and several hundred micrometers in thickness have been produced by atmospheric pressure chemical vapor deposition (APCVD) from a mixture CH 3 SiHCl 2 /H 2 . The method has been developed so as to produce continuous SiC tubes of up to thirty centimeters long. The chemical composition and microstructure of the tubes were determined by microprobe, Raman spectroscopy, XRD and electron microscopy (SEM, TEM). The mechanical properties of the tubes were characterized by nano-indentation tests and through compression C-ring. The thermomechanical behavior was also studied. The method includes consideration of a thermo-kinetic study, followed by a gas phase analysis by IRTF and 2D modeling of the reactor. (author) [fr

  20. Multilayer epitaxial graphene grown on the SiC (000- 1) surface; structure and electronic properties

    Energy Technology Data Exchange (ETDEWEB)

    Sprinkle, M.; Hicks, J.; Tejeda, A.; Taleb-Ibrahimi, A.; Le Fevre, P.; Bertran, F.; Tinkey, H.; Clark, M.C.; Soukiassian, P.; Martinotti, D.; Hass, J.; Conrad, E.H. (CNRS-UMR); (CEAS); (GIT)

    2010-10-22

    We review the progress towards developing epitaxial graphene as a material for carbon electronics. In particular, we discuss improvements in epitaxial graphene growth, interface control and the understanding of multilayer epitaxial graphene's (MEG's) electronic properties. Although graphene grown on both polar faces of SiC will be discussed, our discussions will focus on graphene grown on the (000{bar 1}) C-face of SiC. The unique properties of C-face MEG have become apparent. These films behave electronically like a stack of nearly independent graphene sheets rather than a thin Bernal stacked graphite sample. The origins of multilayer graphene's electronic behaviour are its unique highly ordered stacking of non-Bernal rotated graphene planes. While these rotations do not significantly affect the inter-layer interactions, they do break the stacking symmetry of graphite. It is this broken symmetry that leads to each sheet behaving like isolated graphene planes.

  1. Comparative Study of Si and SiC MOSFETs for High Voltage Class D Audio Amplifiers

    DEFF Research Database (Denmark)

    Nielsen, Dennis; Knott, Arnold; Andersen, Michael A. E.

    2014-01-01

    Silicon (Si) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) are traditional utilised in class D audio amplifiers. It has been proposed to replace the traditional inefficient electrodynamic transducer with the electrostatic transducer. This imposes new high voltage requirements...... on the MOSFETs of class D amplifiers, and significantly reduces the selection of suitable MOSFETs. As a consequence it is investigated, if Silicon-Carbide (SiC) MOSFETs could represent a valid alternative. The theory of pulse timing errors are revisited for the application of high voltage and capactive loaded...... class D amplifiers. It is shown, that SiC MOSFETs can compete with Si MSOFETs in terms of THD. Validation is done using simulations and a 500 V amplifier driving a 100 nF load. THD+N below 0.3 % is reported...

  2. Construction Progress of the S-IC Test Stand Complex-Aerial

    Science.gov (United States)

    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. The F-1 Engine test stand was built north of the massive S-IC test stand. The F-1 test stand is a vertical engine firing test stand, 239 feet in elevation and 4,600 square feet in area at the base, and

  3. Construction Progress of the S-IC Test Stand Complex-Aerial View

    Science.gov (United States)

    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. The F-1 Engine test stand was built north of the massive S-IC test stand. The F-1 test stand is a vertical engine firing test stand, 239 feet in elevation and 4,600 square feet in area at the base, and

  4. Progress on matrix SiC processing and properties for fully ceramic microencapsulated fuel form

    International Nuclear Information System (INIS)

    Terrani, K.A.; Kiggans, J.O.; Silva, C.M.; Shih, C.; Katoh, Y.; Snead, L.L.

    2015-01-01

    The consolidation mechanism and resulting properties of the silicon carbide (SiC) matrix of fully ceramic microencapsulated (FCM) fuel form are discussed. The matrix is produced via the nano-infiltration transient eutectic-forming (NITE) process. Coefficient of thermal expansion, thermal conductivity, and strength characteristics of this SiC matrix have been characterized in the unirradiated state. An ad hoc methodology for estimation of thermal conductivity of the neutron-irradiated NITE–SiC matrix is also provided to aid fuel performance modeling efforts specific to this concept. Finally, specific processing methods developed for production of an optimal and reliable fuel form using this process are summarized. These various sections collectively report the progress made to date on production of optimal FCM fuel form to enable its application in light water and advanced reactors

  5. Preparation and characterization of core-shell structured α-Fe2O3/SiC spheres

    International Nuclear Information System (INIS)

    Wu Xiangyang; Jin Guoqiang; Guan Lianxiu; Cao Hu; Guo Xiangyun

    2006-01-01

    Fe 2 O 3 /SiC composite microspheres with a core-shell structure were prepared by the carbothermal reduction reaction between poly(styrene sulfonic acid) iron salt and silica. X-ray diffraction, scanning electron microscope and magnetic properties measurement system were employed to characterize the morphology, structure and magnetic properties of the microspheres. From the results, the microspheres with a diameter of 150-400 μm have an α-Fe 2 O 3 core and a SiC shell of tens of microns in thickness. The magnetism of the core-shell structured spheres at 10 4 Oe is much larger than that of pure α-Fe 2 O 3 spheres prepared under the same conditions and the increment in magnetism is attributed to the introduction of iron silicides and SiC. By further chemical treatment, the α-Fe 2 O 3 /SiC microspheres can change into SiC hollow spheres, which have diameters similar to the magnetic spheres and mainly consist of irregular SiC particles. The formation mechanism of the composite and hollow spheres was also discussed

  6. Effect of organic additives on mechanical properties of SiC ceramics prepared by a modified gelcasting method

    Directory of Open Access Journals (Sweden)

    Feng Wang

    2016-12-01

    Full Text Available A novel and simple gel system of isobutylene and maleic anhydride (PIBM was used to prepare SiC ceramics. The rheological behaviour of the SiC slurries was investigated as function of organic additives. The SiC slurries with 0.2 wt.% PIBM and 0.2 wt.% tetramethylammonium hydroxide (TMAH showed low viscosity, which was favourable for casting SiC green bodies. In order to obtain homogeneous green bodies, polyvinyl alcohol (PVA was used to assist the dispersion of carbon black in the slurries, and polyethylene glycol (PEG was added to inhibit the surface exfoliation of green bodies. The content of PVA was controlled carefully to avoid the warpage of green bodies during the drying process. Finally, homogeneous defect-free SiC green bodies were successfully fabricated via aqueous gelcasting. The SiC ceramics sintered at 2100 °C (prepared from slurries with solid content of 60 wt.% showed an average flexural strength of 305.7 MPa with porosity of 19.92%.

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

    Science.gov (United States)

    Koput, Jacek

    2016-10-05

    The accurate ground-state potential energy surface of silicon dicarbide, SiC2 , has been determined from ab initio calculations using the coupled-cluster approach. Results obtained with the conventional and explicitly correlated coupled-cluster methods were compared. The core-electron correlation, higher-order valence-electron correlation, and scalar relativistic effects were taken into account. The potential energy barrier to the linear SiCC configuration was predicted to be 1782 cm(-1) . The vibration-rotation energy levels of the SiC2 , (29) SiC2 , (30) SiC2 , and SiC(13) C isotopologues were calculated using a variational method. The experimental vibration-rotation energy levels of the main isotopologue were reproduced to high accuracy. In particular, the experimental energy levels of the highly anharmonic vibrational ν3 mode of SiC2 were reproduced to within 6.7 cm(-1) , up to as high as the v3  = 16 state. © 2016 Wiley Periodicals, Inc.

  8. Design, preparation and microwave absorbing properties of resin matrix composites reinforced by SiC fibers with different electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Haitao, E-mail: xzddlht@163.com [Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073 (China); Science and Technology on Scramjet Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073 (China); Cheng, Haifeng; Tian, Hao [Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    2014-01-15

    Highlights: • SSMASs have better microwave absorbing properties in smaller thickness. • SSMASs can be realized by SiC fibers with different electrical resistivity. • Resistivity of SiC fibers can be regulated by adjusting surface characteristics. • The bandwidth of SSMASs at reflectivity below −10 dB can reach 11.6 GHz. -- Abstract: One kind of sandwich structure microwave absorbing structures (SSMASs) derived from Salisbury absorbers is reported. The impedance characteristics of SSMASs are analyzed, and the mechanisms of broadening microwave absorbing bandwidth are interpreted by Smith chart. In order to realize SSMASs, high electrical resistivity SiC fibers with Si–C–O surface layers and low electrical resistivity SiC fibers with pyrocarbon surface layers are employed and analyzed by SEM, XPS, AES and HRTEM. The conductive model of SiC fibers with pyrocarbon layers is built and electrical resistivity simulation is done. The SSMASs are fabricated by employing plain woven SiC fiber fabrics with high and low electrical resistivity as reinforcements of dielectric layers and lossy layer, respectively. The microwave absorbing properties of SSMASs are measured and compared with simulated results. The results show that the experimental and simulated results are in good agreement, the SSMASs have better wideband microwave absorbing properties, and the microwave absorbing bandwidth at reflectivity below −10 dB can reach 11.6 GHz.

  9. A Highly intense DC muon source, MuSIC and muon CLFV search

    International Nuclear Information System (INIS)

    Hino, Y.; Kuno, Y.; Sato, A.; Sakamoto, H.; Matsumoto, Y.; Tran, N.H.; Hashim, I.H.; Fukuda, M.; Hayashida, Y.; Ogitsu, T.; Yamamoto, A.; Yoshida, M.

    2014-01-01

    MuSIC is a new muon facility, which provides the world's highest intense muon beam with continuous time structure at Research Center of Nuclear Physics (RCNP), Osaka University. It's intensity is designed to be 10 8 muons per second with only 0.4 kW proton beam. Such a high intense muon beam is very important for searches of rare decay processes, for example search for the muon to electron conversion

  10. Hardness and elastic modulus of amorphous and nanocrystalline SiC and Si films

    Czech Academy of Sciences Publication Activity Database

    Kulykovskyy, Valeriy; Vorlíček, Vladimír; Boháč, Petr; Stranyánek, Martin; Čtvrtlík, Radim; Kurdyumov, A.; Jastrabík, Lubomír

    2008-01-01

    Roč. 202, - (2008), s. 1738-1745 ISSN 0257-8972 R&D Projects: GA MŠk OC 097; GA MŠk OC 095; GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100522 Keywords : sputtering * hardness * nanocrystalline SiC films * nanocomposites * amorphous Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.860, year: 2008

  11. SiC Sensors in Extreme Environments: Real-time Hydrogen Monitoring for Energy Plant Applications

    Science.gov (United States)

    Ghosh, Ruby

    2008-03-01

    Clean, efficient energy production, such as the gasification of coal (syngas), requires physical and chemical sensors for exhaust gas monitoring as well as real-time control of the combustion process. Wide-bandgap semiconducting materials systems can meet the sensing demands in these extreme environments consisting of chemically corrosive gases at high temperature and pressure. We have developed a SiC based micro-sensor for detection of hydrogen containing species with millisecond response at 600 C. The sensor is a Pt-SiO2-SiC device with a dense Pt catalytic sensing film, capable of withstanding months of continuous high temperature operation. The device was characterized in robust sensing module that is compatible with an industrial reactor. We report on the performance of the SiC sensor in a simulated syngas ambient at 370 C containing the common interferants CO2, CH4 and CO [1]. In addition we demonstrate that hours of exposure to >=1000 ppm H2S and 15% water vapor does not degrade the sensor performance. To elucidate the mechanisms responsible for the hydrogen response of the sensor we have modeled the hydrogen adsorptions kinetics at the internal Pt-SiO2 interface, using both the Tempkin and Langmuir isotherms. Under the conditions appropriate for energy plant applications, the response of our sensor is significantly larger than that obtained from ultra-high vacuum electrochemical sensor measurements at high temperatures. We will discuss the role of morphology, at the nano to micro scale, on the enhanced catalytic activity observed for our Pt sensing films in response to a heated hydrogen gas stream at atmospheric pressure. [1] R. Loloee, B. Chorpening, S. Beers & R. Ghosh, Hydrogen monitoring for power plant applications using SiC sensors, Sens. Actuators B:Chem. (2007), doi:10.1016/j.snb.2007.07.118

  12. High Power Silicon Carbide (SiC) Power Processing Unit Development

    Science.gov (United States)

    Scheidegger, Robert J.; Santiago, Walter; Bozak, Karin E.; Pinero, Luis R.; Birchenough, Arthur G.

    2015-01-01

    NASA GRC successfully designed, built and tested a technology-push power processing unit for electric propulsion applications that utilizes high voltage silicon carbide (SiC) technology. The development specifically addresses the need for high power electronics to enable electric propulsion systems in the 100s of kilowatts. This unit demonstrated how high voltage combined with superior semiconductor components resulted in exceptional converter performance.

  13. Construction Progress of the S-IC Test Stand-Steel Reinforcements

    Science.gov (United States)

    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 15, 1961, shows the installation of the reinforcing steel prior to the pouring of the concrete foundation walls.

  14. Direct microwave annealing of SiC substrate for rapid synthesis of quality epitaxial graphene

    Czech Academy of Sciences Publication Activity Database

    Cichoň, Stanislav; Macháč, P.; Fekete, Ladislav; Lapčák, L.

    2016-01-01

    Roč. 98, Mar (2016), s. 441-448 ISSN 0008-6223 R&D Projects: GA MŠk LO1409; GA MŠk(CZ) LM2011029 Grant - others:FUNBIO(XE) CZ.2.16/3.1.00/21568 Institutional support: RVO:68378271 Keywords : graphene * SiC * microwave Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 6.337, year: 2016

  15. Interfacial characterisation in transparent spinel matrix reinforced by SiC fibre

    Czech Academy of Sciences Publication Activity Database

    Chlup, Zdeněk; Dlouhý, Ivo; Gürbüz, S.; Dericioglu, A. F.; Kozák, Vladislav

    2009-01-01

    Roč. 409, - (2009), s. 252-259 ISSN 1013-9826. [Fractography of Advanced Ceramics III. Stará Lesná, 07.09.20058-10.09.2008] R&D Projects: GA ČR(CZ) GA106/06/0724; GA AV ČR IAA200410502 Institutional research plan: CEZ:AV0Z20410507 Keywords : interface * composite * transparent spinel * SiC fibre * fracture characteristics Subject RIV: JI - Composite Materials

  16. Oxidation Protective SiC Coating on Graphite for VHTR Core Support Structure

    International Nuclear Information System (INIS)

    Park, Jae-Won; Kim, Eung-Seon; Kim, Jae-Un; Windes, William E.

    2014-01-01

    The potential for reducing oxidation of the supporting graphite components during normal operation and accident conditions in the VHTR design has been studied. SiC coating on graphite has been studied taking into consideration of possible dimensional change of graphite by the neutron-irradiation. Functionally gradient (FG) SiC coating on the graphite has been performed to moderate the SiC/Graphite interface: E-beam evaporative coating from varied compositions of graphite/SiC mixture in the source crucibles was carried out with an ion beam mixing. The cylindrical graphite samples were uniformly coated by rotating and revolving the samples. Auger depth profile reveals that the ion beam mixed interface is broadened and a cross sectional EDS Si elemental mapping shows a smoothly graded Si profile. The grown film exhibited a stacked columnar structure owing to a frequent sample position change during the coating process, as observed by FE-SEM. As a result of 18 thermal cycling test of 500-1000℃, no film delamination was found on the coated layer, but film cracks were formed, suggesting a strong bonding. When samples were heated at 600°C in static air for 2 h, ~45 wt% of the graphite was burnt off, whereas for the SiC coated graphite only 5 wt %. When heated at 1000 °C in air, vigorous oxidation of graphite took place through a few paths (maybe the mars and/or the crack lines) in the film only leaving the coating layer. As the crack lines were covered with SiC by repeating the ion beam mixed coating process, the oxidation resistance was improved. (author)

  17. Scanning electron microscopy of the surfaces of ion implanted SiC

    Science.gov (United States)

    Malherbe, Johan B.; van der Berg, N. G.; Kuhudzai, R. J.; Hlatshwayo, T. T.; Thabethe, T. T.; Odutemowo, O. S.; Theron, C. C.; Friedland, E.; Botha, A. J.; Wendler, E.

    2015-07-01

    This paper gives a brief review of radiation damage caused by particle (ions and neutrons) bombardment in SiC at different temperatures, and its annealing, with an expanded discussion on the effects occurring on the surface. The surface effects were observed using SEM (scanning electron microscopy) with an in-lens detector and EBSD (electron backscatter diffraction). Two substrates were used, viz. single crystalline 6H-SiC wafers and polycrystalline SiC, where the majority of the crystallites were 3C-SiC. The surface modification of the SiC samples by 360 keV ion bombardment was studied at temperatures below (i.e. room temperature), just at (i.e. 350 °C), or above (i.e. 600 °C) the critical temperature for amorphization of SiC. For bombardment at a temperature at about the critical temperature an extra step, viz. post-bombardment annealing, was needed to ascertain the microstructure of bombarded layer. Another aspect investigated was the effect of annealing of samples with an ion bombardment-induced amorphous layer on a 6H-SiC substrate. SEM could detect that this layer started to crystalize at 900 °C. The resulting topography exhibited a dependence on the ion species. EBSD showed that the crystallites forming in the amorphized layer were 3C-SiC and not 6H-SiC as the substrate. The investigations also pointed out the behaviour of the epitaxial regrowth of the amorphous layer from the 6H-SiC interface.

  18. The electron spin resonance study of heavily nitrogen doped 6H SiC crystals

    Czech Academy of Sciences Publication Activity Database

    Savchenko, Dariia

    2015-01-01

    Roč. 117, č. 4 (2015), "045708-1"-"045708-6" ISSN 0021-8979 R&D Projects: GA ČR GP13-06697P; GA MŠk(CZ) LM2011029 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : electron spin resonance * conduction electrons * 6H SiC * insulator-metal transition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.101, year: 2015

  19. Development of Universal Controller Architecture for SiC Based Power Electronic Building Blocks

    Science.gov (United States)

    2017-10-30

    To) Final Technical Report 05/01 /2015-08/1 5/2017 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER Development of Universal Controller Architecture for...NOTES 14. ABSTRACT The objective of this project was to develop a Universal Controller Architecture suitable for SiC based Power Electronic...based devices resulting in an order of magnitude reduction of the control time scales as compared to converter systems utilizing conventional IGBT based

  20. A Highly intense DC muon source, MuSIC and muon CLFV search

    Energy Technology Data Exchange (ETDEWEB)

    Hino, Y.; Kuno, Y.; Sato, A. [Department of Physics, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Sakamoto, H. [Department of Physics, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Research Center of Nuclear Physics, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Matsumoto, Y.; Tran, N.H.; Hashim, I.H. [Department of Physics, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Fukuda, M.; Hayashida, Y. [Research Center of Nuclear Physics, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Ogitsu, T.; Yamamoto, A.; Yoshida, M. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2014-08-15

    MuSIC is a new muon facility, which provides the world's highest intense muon beam with continuous time structure at Research Center of Nuclear Physics (RCNP), Osaka University. It's intensity is designed to be 10{sup 8} muons per second with only 0.4 kW proton beam. Such a high intense muon beam is very important for searches of rare decay processes, for example search for the muon to electron conversion.

  1. Creep of SiC Hot-Pressed with Al, B, and C

    Energy Technology Data Exchange (ETDEWEB)

    Sixta, Mark Eldon [Univ. of California, Berkeley, CA (United States)

    2000-03-31

    The creep of a high strength, high toughness SiC, sintered with Al, B, and C was investigated. For elevated temperature applications, the time-dependent deformation, creep response, must be fully characterized for candidate materials. The mechanisms responsible for high temperature deformation in ABC-SiC were evaluated. The creep response was compared to materials that have glassy grain boundary phases but do not have interlocked grains. The creep mechanisms were assessed.

  2. Early implementation of SiC cladding fuel performance models in BISON

    Energy Technology Data Exchange (ETDEWEB)

    Powers, Jeffrey J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-09-18

    SiC-based ceramic matrix composites (CMCs) [5–8] are being developed and evaluated internationally as potential LWR cladding options. These development activities include interests within both the DOE-NE LWR Sustainability (LWRS) Program and the DOE-NE Advanced Fuels Campaign. The LWRS Program considers SiC ceramic matrix composites (CMCs) as offering potentially revolutionary gains as a cladding material, with possible benefits including more efficient normal operating conditions and higher safety margins under accident conditions [9]. Within the Advanced Fuels Campaign, SiC-based composites are a candidate ATF cladding material that could achieve several goals, such as reducing the rates of heat and hydrogen generation due to lower cladding oxidation rates in HT steam [10]. This work focuses on the application of SiC cladding as an ATF cladding material in PWRs, but these work efforts also support the general development and assessment of SiC as an LWR cladding material in a much broader sense.

  3. Thermal reaction of SiC films with tungsten and tungsten-rhenium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Roger, J.; Le Petitcorps, Y. [Univ Bordeaux 1, Lab Composites Thermostruct, CNRS-SAFRAN-CEA-UB1, UMR 5801, F-33600 Pessac, (France); Roger, J.; Audubert, F. [CEA Cadarache, DEN/DEC/SPUA/LTEC, F-13108 St Paul Les Durance, (France)

    2008-07-01

    Solid-state reactions between SiC films and W-xRe (x = 0, 5 and 25 at%) substrates on thermal annealing between 1673 K and 1873 K for various durations have been investigated. SiC coatings were deposited on metallic wires by hot filament chemical vapour deposition (HFCVD) from a gas mixture of tetramethyl-silane (TMS) and hydrogen at 1373 K under normal pressure. The interface zones were characterized using scanning electron and optical microscopies, X-ray diffraction and electron microprobe microanalysis. All analyses reveal that SiC reacts with substrates. Various metal silicides and carbides were formed in layered reaction and the presence of these phases was confirmed by electron probe microanalysis. The effects of rhenium on the reactivity were established by the determination of growth kinetics deducted from the thicknesses of reaction zones as a function of annealing time. It has been found that an increase in the diffusion kinetics and activation energy with the quantity of rhenium in the tungsten wire. (authors)

  4. Melting of SiC powders preplaced duplex stainless steel using TIG welding

    Science.gov (United States)

    Maleque, M. A.; Afiq, M.

    2018-01-01

    TIG torch welding technique is a conventional melting technique for the cladding of metallic materials. Duplex stainless steels (DSS) show decrease in performance under aggressive environment which may lead to unanticipated failure due to poor surface properties. In this research, surface modification is done by using TIG torch method where silicon carbide (SiC) particles are fused into DSS substrate in order to form a new intermetallic compound at the surface. The effect of particle size, feed rate of SiC preplacement, energy input and shielding gas flow rate on surface topography, microstructure, microstructure and hardness are investigated. Deepest melt pool (1.237 mm) is produced via TIG torch with highest energy input of 1080 J/mm. Observations of surface topography shows rippling marks which confirms that re-solidification process has taken place. Melt microstructure consist of dendritic and globular carbides precipitate as well as partially melted silicon carbides (SiC) particles. Micro hardness recorded at value ranging from 316 HV0.5 to 1277 HV0.5 which shows increment from base hardness of 260 HV0.5kgf. The analyzed result showed that incorporation of silicon carbide particles via TIG Torch method increase the hardness of DSS.

  5. Reduction of SiO2 to SiC Using Natural Gas

    Science.gov (United States)

    Ksiazek, Michal; Tangstad, Merete; Dalaker, Halvor; Ringdalen, Eli

    2014-09-01

    This paper presents a preliminary study of SiC production by use of natural gas for reduction of silica. Direct reduction of SiO2 by gas mixtures containing CH4, H2, and Ar was studied at temperatures between 1273 K and 1773 K (1000 °C and 1500 °C). Silica in form of particles between 1 and 3 mm and pellets with mean grain size 50 µm were exposed to the gas mixture for 6 hours. Influence of temperature and CH4H2 ratio was investigated. Higher temperature and CH4 concentration resulted in greater SiC production. Two kinds of SiC were found: one was deposited between SiO2 particles, the other one was deposited inside the SiO2 particles. Although the exact reaction mechanisms have not been determined, it is clear that gas-phase reactions play an important role in both cases. The reaction products were analyzed by Electron Probe Micro Analyzer.

  6. Hydrogen activated axial inter-conversion in SiC nanowires

    International Nuclear Information System (INIS)

    Ruemmeli, Mark H.; Adebimpe, David B.; Borowiak-Palen, Ewa; Gemming, Thomas; Ayala, Paola; Ioannides, Nicholas; Pichler, Thomas; Huczko, Andrzej; Cudzilo, Stanislaw; Knupfer, Martin; Buechner, Bernd

    2009-01-01

    A facile low pressure annealing route using NH 3 as a hydrogen source for the structural and chemical modification of SiC nanowires (SiCNWs) is presented. The developed route transforms SiCNWs into tubular SiC nanostructures while coaxial SiO 2 /SiCNWs reverse their sheath/core structure. Our findings suggest a decomposition process induced via the preferential substitution of silicon by hydrogen and via the difference in diffusion rates of available atomic species, which leads to axial structural rearrangement. In addition to these effects, the procedure improves the crystallinity of the samples. The process could be exploited as a viable route to manipulate a variety of nanostructures and films for doping and etching and structural manipulation. - Graphical abstract: SiC and SiO 2 /SiCNWs are shown to be structurally modified through a hydrogen activated replacement route which can even lead to the axial inter-conversion of species. The process could be exploited as a viable route to manipulate a variety of nanostructures and films for doping and etching and structural manipulation

  7. Technology roadmap for development of SiC sensors at plasma processes laboratory

    Directory of Open Access Journals (Sweden)

    Mariana Amorim Fraga

    2010-08-01

    Full Text Available Recognizing the need to consolidate the research and development (R&D activities in microelectronics fields in a strategic manner, the Plasma Processes Laboratory of the Technological Institute of Aeronautics (LPP-ITA has established a technology roadmap to serve as a guide for activities related to development of sensors based on silicon carbide (SiC thin films. These sensors have also potential interest to the aerospace field due to their ability to operate in harsh environment such as high temperatures and intense radiation. In the present paper, this roadmap is described and presented in four main sections: i introduction, ii what we have already done in the past, iii what we are doing in this moment, and iv our targets up to 2015. The critical technological issues were evaluated for different categories: SiC deposition techniques, SiC processing techniques for sensors fabrication and sensors characterization. This roadmap also presents a shared vision of how R&D activities in microelectronics should develop over the next five years in our laboratory.

  8. High-temperature mechanical and material design for SiC composites

    International Nuclear Information System (INIS)

    Ghoniem, N.M.

    1992-01-01

    Silicon Carbide (SiC) fiber reinforced composites (FRC's) are strong potential candidate structural and high heat flux materials for fusion reactors. During this past decade, they have been vigorously developed for use in aerospace and transportation applications. Recent fusion reactor systems studies, such as ARIES, have concluded that further development of SiC composites will result in significant safety, operational, and waste disposal advantages for fusion systems. A concise discussion of the main material and design issues related to the use of SiC FRC's as structural materials in future fusion systems is given in this paper. The status of material processing of SiC/SiC composites is first reviewed. The advantages and shortcomings of the leading processing technology, known as Chemical Vapor Infiltration are particularly highlighted. A brief outline of the design-relevant physical, mechanical, and radiation data base is then presented. SiC/SiC FRC's possess the advantage of increased apparent toughness under mechanical loading conditions. This increased toughness, however, is associated with the nucleation and propagation of small crack patterns in the structure. Design approaches and failure criteria under these conditions are discussed

  9. Self-Organized Graphene Nanoribbons on SiC(0001) Studied with Scanning Tunneling Microscopy

    Science.gov (United States)

    Torrance, David; Zhang, Baiqian; Hoang, Tien; First, Phillip

    2012-02-01

    Graphene nanoribbons grown directly on nanofacets of SiC(0001) offer an attractive union of top-down and bottom-up fabrication techniques. Nanoribbons have been shown to form on the facets of templated silicon carbide substrates,ootnotetextSprinkle et al., Nat. Nanotech. 5, 727 (2010). but also appear spontaneously along step-bunches on vicinal SiC(0001) miscut slightly towards . These self-organized graphene nanoribbons were characterized with low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) in ultra-high vacuum. Our measurements indicate that the graphene forms a continuous ``buffer layer'' across the SiC(0001) terraces during nanoribbon formation, with the zigzag edge of the buffer layer aligned parallel to the step-bunched nanofacets. Scanning tunneling microscopy/spectroscopy (STM/STS) was used to characterize the topography and electrical characteristics of the graphene nanoribbons. These measurements indicate that the graphene nanoribbons are highly-crystalline with predominantly zigzag edges.

  10. Infiltration of porous samples of SiC with Cu-Ti alloys

    International Nuclear Information System (INIS)

    Sanchez, R; Iturriza, I; Ordonez, S; Martinez, V

    2004-01-01

    The necessity of generating new materials with certain properties has led to research on a wide range of ceramic-metal systems, in order to obtain compound materials that combine the attractive properties of ceramics (hardness, rigidity, resistance to wear and corrosion and low density) with the characteristic toughness and ductility of metals. An attractive system is that formed by silicon carbide and copper-based alloys. The copper at 1373 K does not wet the SiC, presenting a wet angle of 140 o and generating a weak union. Additions of Ti to the Cu have been shown to improve the wettability and characteristics of the union. This work studies the infiltration of samples of SiC that contain about 35% porosity. These samples were pre-sinterized at 1650 o C and later infiltrated, at 1400 o C, with Cu-Ti alloys containing 1% to 3% in weight of Ti. An important factor in this process is the decomposition of the SiC resulting from a reaction with the Cu, producing precipitation of C which then reacts with the Ti to form TiC and increase the concentration of Si in the Cu-based alloy (CW)

  11. Effect of Residual Gas Composition on Epitaxial Growth of Graphene on SiC

    Science.gov (United States)

    Kunc, J.; Rejhon, M.; Belas, E.; Dědič, V.; Moravec, P.; Franc, J.

    2017-10-01

    In recent years, graphene growth optimization has been one of the key routes towards large-scale, high-quality graphene production. We measure in situ residual gas content during epitaxial-graphene growth on silicon carbide (SiC) to find detrimental factors of epitaxial-graphene growth. The growth conditions in high vacuum, in argon, purified argon, and the flow of argon are compared. The grown epitaxial graphene is studied by Raman-scattering mapping. We determine mechanical strain, number of graphene layers and the graphene quality. The surface topography is measured by atomic force microscopy. Charge density and carrier mobility are studied by Hall-effect measurements in van der Pauw configuration. We identify the major role of the chemical reaction of carbon and residual water. The rate of the reaction is lowered when purified argon is used. We also show that, according to time-varying gas content, it is preferable to grow graphene at higher temperatures and shorter times. Other sources of growth environment contamination are also discussed. The reaction of residual gas and SiC is discussed as one of the factors decreasing the lateral size of SiC atomically flat terraces and leading to their irregular shape. The importance of purified argon and its sufficient flow rate is concluded to be important for high-quality graphene growth as it reduces the rate of undesired chemical reactions and provides a more stable and defined growth ambient.

  12. Epitaxial Graphene on SiC: A Review of Growth and Characterization

    Directory of Open Access Journals (Sweden)

    Gholam Reza Yazdi

    2016-05-01

    Full Text Available This review is devoted to one of the most promising two-dimensional (2D materials, graphene. Graphene can be prepared by different methods and the one discussed here is fabricated by the thermal decomposition of SiC. The aim of the paper is to overview the fabrication aspects, growth mechanisms, and structural and electronic properties of graphene on SiC and the means of their assessment. Starting from historical aspects, it is shown that the most optimal conditions resulting in a large area of one ML graphene comprise high temperature and argon ambience, which allow better controllability and reproducibility of the graphene quality. Elemental intercalation as a means to overcome the problem of substrate influence on graphene carrier mobility has been described. The most common characterization techniques used are low-energy electron microscopy (LEEM, angle-resolved photoelectron spectroscopy (ARPES, Raman spectroscopy, atomic force microscopy (AFM in different modes, Hall measurements, etc. The main results point to the applicability of graphene on SiC in quantum metrology, and the understanding of new physics and growth phenomena of 2D materials and devices.

  13. The morphology of ceramic phases in B xC -SiC -Si infiltrated composites

    Science.gov (United States)

    Hayun, S.; Frage, N.; Dariel, M. P.

    2006-09-01

    The present communication is concerned with the effect of the carbon source on the morphology of reaction bonded boron carbide (B 4C). Molten silicon reacts strongly and rapidly with free carbon to form large, faceted, regular polygon-shaped SiC particles, usually embedded in residual silicon pools. In the absence of free carbon, the formation of SiC relies on carbon that originates from within the boron carbide particles. Examination of the reaction bonded boron carbide revealed a core-rim microstructure consisting of boron carbide particles surrounded by secondary boron carbide containing some dissolved silicon. This microstructure is generated as the outcome of a dissolution-precipitation process. In the course of the infiltration process molten Si dissolves some boron carbide until its saturation with B and C. Subsequently, precipitation of secondary boron carbide enriched with boron and silicon takes place. In parallel, elongated, strongly twinned, faceted SiC particles are generated by rapid growth along preferred crystallographic directions. This sequence of events is supported by X-ray diffraction and microcompositional analysis and well accounted for by the thermodynamic analysis of the ternary B-C-Si system.

  14. Neutron diffraction multiphase analysis on functional heat-resistant ceramics SiC

    International Nuclear Information System (INIS)

    Li Jizhou; Yang Jilian; Kang Jian; Ye Chuntang; Cui Hongtao

    1995-01-01

    Functional heat-resistant ceramics silicon carbide SiC is a highly feasible material for high temperature engineering applications. The SiC investigated is sintered into powder sample by using industrial SiC as semifinished materials. The neutron diffraction is performed on the powder neutron diffractometer at 15 MW heavy water research reactor of the China Institute of Atomic Energy. The least-squares crystal structure and profile refinements are undertaken with the multiphase Rietveld analysis program Fullprof, which was from ILL, Grenoble, France. The results fitted for neutron data show that besides the main phase of 2H (space group of P6 3 mc), there are 4H(C6mc), 6H(C6mc) and α-SiO 2 (Fd3m) of residual impurity. The abundance of 4 phases are 2H(73.1+-2.0)%, 4H(12.8+-1.7)%, 6H(14.0+-1.1)% and α-SiO 2 <0.1%. The result shows that neutron powder diffraction is becoming more and more powerful on materials science, while the new multiphase Rietveld profile program is used. The neutron diffraction analysis can be used not only to determine the structure of materials and but also to obtain the abundance of mixture phases

  15. Numerical simulation of armor capability of AI2O3 and SiC armor tiles

    Science.gov (United States)

    Rashid, T.; Aleem, M. A.; Akbar, S.; Rauf, A.; Shuaib, M.

    2016-08-01

    Alumina and Silicon Carbide armor plates have been tested numerically against 7.62x51 (mm x mm) armor piercing (AP) projectiles. A 2-D problem with axial symmetry has been designedand the simulations were carried out using commercial software ANSYS AUTODYN. Experiments were modeled for Alumina (99.5%), Alumina (99.7%) and SiC with a range of tile thicknesses (5, 10, 15 and 20 mm). The projectile was chosen as 7.62 x 51AP bullet (initial velocity 810 m/sec)with two different core materials Steel 4340 and WC, however, casing material was copper for both cores. SiC showed better defense against AP bullet as compared to Al2O3. The residual velocity and momentum of the bullet were found to decrease with increasing tile thickness. SiC tiles with thickness 15mm and 20 mm successfully sustained penetration against steel 4340 and WC core bullets, respectively. However none of the Alumina targets succeeded in stopping the bullet.

  16. High power RF performance test of an improved SiC load

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, W.H.; Kim, S.H.; Park, Y.J. [Pohang Accelerator Lab., Pohang Inst. of Sceince and Technology, Pohang (KR)] [and others

    1998-11-01

    Two prototypes of SiC loads sustaining a maximum peak power of 50 MW were fabricated by Nihon Koshuha Co. in Japan. The PAL conducted the high power RF performance tests of SiC loads to verify the operation characteristics for the application to the PLS Linac. The in-situ facility for the K 12 module was used for the test, which consists of a modulator and klystron system, waveguide network, vacuum and cooling system, and RF analyzing equipment. As the test results, no breakdown appeared up to 50 MW peak power of 1 {mu}s pulse width at a repetition rate of 50 Hz. However, as the peak power increased above 20 MW at 4 {mu}s with 10 Hz, the breakdown phenomena has been observed. Analysing the test results with the current operation power level of PLS Linac, it is confirmed that the SiC loads well satisfy the criteria of the PLS Linac operation. (author)

  17. Construction Progress of the S-IC Test Stand and Block House

    Science.gov (United States)

    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 February 4, 1963, gives an impressive look at the Block House looking directly through the ever-growing four towers of the S-IC Test Stand.

  18. Construction Progress of the S-IC Test Stand-Completed Block House

    Science.gov (United States)

    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 February 25, 1963, gives a close up look at the completed Block House. The side shown faces the S-IC Test Stand.

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

    Science.gov (United States)

    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. Again to the east, just south of the Block House, was a newly constructed Pump House. Its function was to provide water to the stand to prevent melting damage during testing. The water was sprayed through

  20. Construction Progress of the S-IC Test Stand Flame Deflector

    Science.gov (United States)

    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

  1. ELECTRON DIFFRACTION STUDY OF GRAPHENE LAYERS STRUCTURE ON CONDUCTIVE AND SEMI-INSULATING 6H-SIC (0001 SUBSTRATES

    Directory of Open Access Journals (Sweden)

    I. S. Kotousova

    2015-03-01

    Full Text Available Subject of study. Findings for the surface structure of conductive and semi-insulating substrates 6H-SiC(0001 and epitaxial graphene layers grown on them are presented. Materials and methods. We used two types of silicon carbide substrates of 6H polytype as a substrate: conductive (with resistivity less than 103 Ohm·cm, and semi-insulating (with resistivity greater than 105 Ohm·cm. Synthesis of graphene layers on substrates was carried out by thermal decomposition of SiC surface at the temperature of 1350ºC for 20 minutes in a vacuum sublimation epitaxy setup. Registration of high-energy electron diffraction (RHEED patterns for reflection was carried out using two devices: electronograph EMR-102 at an accelerating voltage of 75 kV and electron diffractometer, built into the unit MBE Compact 21T (Riber France, at an accelerating voltage of 30 kV. Main results. The oriented growth of graphene is observed on the conductive substrate. Both oriented and disordered kinds of graphene grow on the semi-insulating substrate due to the partially formation of the polycrystalline component in the multilayered graphene film which in turn is caused by the lower perfection structure of the semi-insulating substrate surface as compared to the conductive one. Practical significance. Proposed findings will help to understand the quality dependence of the grown graphene film on the structure of the used silicon carbide substrate.

  2. Finite dipole model for extreme near-field thermal radiation between a tip and planar SiC substrate

    Science.gov (United States)

    Jarzembski, Amun; Park, Keunhan

    2017-04-01

    Recent experimental studies have measured the infrared (IR) spectrum of tip-scattered near-field thermal radiation for a SiC substrate and observed up to a 50cm-1 redshift of the surface phonon polariton (SPhP) resonance peak [1,2]. However, the observed spectral redshift cannot be explained by the conventional near-field thermal radiation model based on the point dipole approximation. In the present work, a heated tip is modeled as randomly fluctuating point charges (or fluctuating finite dipoles) aligned along the primary axis of a prolate spheroid, and quasistatic tip-substrate charge interactions are considered to formulate the effective polarizability and self-interaction Green's function. The finite dipole model (FDM), combined with fluctuational electrodynamics, allows the computation of tip-plane thermal radiation in the extreme near-field (i.e., H / R ≲ 1 , where H is the tip-substrate gap distance and R is the tip radius), which cannot be calculated with the point dipole approximation. The FDM provides the underlying physics on the spectral redshift of tip-scattered near-field thermal radiation as observed in experiments. In addition, the SPhP peak in the near-field thermal radiation spectrum may split into two peaks as the gap distance decreases into the extreme near-field regime. This observation suggests that scattering-type spectroscopic measurements may not convey the full spectral features of tip-plane extreme near-field thermal radiation.

  3. Impacts of gate bias and its variation on gamma-ray irradiation resistance of SiC MOSFETs

    Energy Technology Data Exchange (ETDEWEB)

    Murata, Koichi; Mitomo, Satoshi; Matsuda, Takuma; Yokoseki, Takashi [Saitama University, Sakuraku (Japan); National Institutes for Quantum and Radiological Science and Technology (QST), Takasaki (Japan); Makino, Takahiro; Onoda, Shinobu; Takeyama, Akinori; Ohshima, Takeshi [National Institutes for Quantum and Radiological Science and Technology (QST), Takasaki (Japan); Okubo, Shuichi; Tanaka, Yuki; Kandori, Mikio; Yoshie, Toru [Sanken Electric Co., Ltd., Niiza, Saitama (Japan); Hijikata, Yasuto [Saitama University, Sakuraku (Japan)

    2017-04-15

    Gamma-ray irradiation into vertical type n-channel hexagonal (4H)-silicon carbide (SiC) metal-oxide-semiconductor field effect transistors (MOSFETs) was performed under various gate biases. The threshold voltage for the MOSFETs irradiated with a constant positive gate bias showed a large negative shift, and the shift slightly recovered above 100 kGy. For MOSFETs with non- and a negative constant biases, no significant change in threshold voltage, V{sub th}, was observed up to 400 kGy. By changing the gate bias from positive bias to either negative or non-bias, the V{sub th} significantly recovered from the large negative voltage shift induced by 50 kGy irradiation with positive gate bias after only 10 kGy irradiation with either negative or zero bias. It indicates that the positive charges generated in the gate oxide near the oxide-SiC interface due to irradiation were removed or recombined instantly by the irradiation under zero or negative biases. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Construction Progress of S-IC Test Stand Complex-Aerial

    Science.gov (United States)

    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. The F-1 Engine test stand was built north of the massive S-IC test stand. The F-1 test stand is a vertical engine firing test stand, 239 feet in elevation and 4,600 square feet in area at the base, and

  5. In Situ Growth of Core-Sheath Heterostructural SiC Nanowire Arrays on Carbon Fibers and Enhanced Electromagnetic Wave Absorption Performance.

    Science.gov (United States)

    Yan, Liwen; Hong, Changqing; Sun, Boqian; Zhao, Guangdong; Cheng, Yehong; Dong, Shun; Zhang, Dongyang; Zhang, Xinghong

    2017-02-22

    Large-scale core-sheath heterostructural SiC nanowires were facilely grown on the surface of carbon fibers using a one-step chemical vapor infiltration process. The as-synthesized SiC nanowires consist of single crystalline SiC cores with a diameter of ∼30 nm and polycrystalline SiC sheaths with an average thickness of ∼60 nm. The formation mechanisms of core-sheath heterostructural SiC nanowires (SiC nws ) were discussed in detail. The SiC nws -CF shows strong electromagnetic (EM) wave absorption performance with a maximum reflection loss value of -45.98 dB at 4.4 GHz. Moreover, being coated with conductive polymer polypyrrole (PPy) by a simple chemical polymerization method, the SiC nws -CF/PPy nanocomposites exhibited superior EM absorption abilities with maximum RL value of -50.19 dB at 14.2 GHz and the effective bandwidth of 6.2 GHz. The SiC nws -CF/PPy nanocomposites in this study are very promising as absorber materials with strong electromagnetic wave absorption performance.

  6. Influence of CO annealing in metal-oxide-semiconductor capacitors with SiO2 films thermally grown on Si and on SiC

    Science.gov (United States)

    Pitthan, E.; dos Reis, R.; Corrêa, S. A.; Schmeisser, D.; Boudinov, H. I.; Stedile, F. C.

    2016-01-01

    Understanding the influence of SiC reaction with CO, a by-product of SiC thermal oxidation, is a key point to elucidate the origin of electrical defects in SiC metal-oxide-semiconductor (MOS) devices. In this work, the effects on electrical, structural, and chemical properties of SiO2/Si and SiO2/SiC structures submitted to CO annealing were investigated. It was observed that long annealing times resulted in the incorporation of carbon from CO in the Si substrate, followed by deterioration of the SiO2/Si interface, and its crystallization as SiC. Besides, this incorporated carbon remained in the Si surface (previous SiO2/Si region) after removal of the silicon dioxide film by HF etching. In the SiC case, an even more defective surface region was observed due to the CO interaction. All MOS capacitors formed using both semiconductor materials presented higher leakage current and generation of positive effective charge after CO annealings. Such results suggest that the negative fixed charge, typically observed in SiO2/SiC structures, is not originated from the interaction of the CO by-product, formed during SiC oxidation, with the SiO2/SiC interfacial region.

  7. Enhanced tribological behavior of anodic films containing SiC and PTFE nanoparticles on Ti6Al4V alloy

    International Nuclear Information System (INIS)

    Li, Songmei; Zhu, Mengqi; Liu, Jianhua; Yu, Mei; Wu, Liang; Zhang, Jindan; Liang, Hongxing

    2014-01-01

    Highlights: • An environmental friendly sodium tartrate (C 4 O 6 H 4 Na 2 ) electrolyte is used. • SiC and PTFE nanoparticles reduce friction coefficient of composite films. • SiC and PTFE nanoparticles demonstrate a favorable synergistic effect on improving tribological properties of composite films. • Lubricating mechanisms of SiC and PTFE nanoparticles are discussed. - Abstract: Anodic films containing SiC and polytetrafluoroethylene (PTFE) nanoparticles were successfully fabricated on Ti6Al4V alloy by using anodic oxidation method in an environmental friendly electrolyte. The morphology, structure and composition of the films were studied with the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results showed that the film contained a layered structure and have a surface full of petaloid bulges, which was totally different from the common anodic oxide film of the porous kind. The tribological properties of the films were investigated with dry friction tests in terms of the friction coefficient, wear rate and the morphology of worn surfaces. The results indicated that the SiC/PTFE composite film exhibited much better anti-wear and anti-friction performances than that of the SiC composite film, the PTFE composite film and the ordinary film without nanoparticles. The SiC/PTFE composite film has friction coefficient of 0.1 and wear rate of 20.133 mg/m, which was decreased respectively by 80% and 44.5% compared with that of the ordinary film. The lubricating mechanisms of the composite film containing SiC and PTFE nanoparticles were discussed. PTFE nanoparticles could lead to the formation of lubricating layer while SiC nanoparticles inside the lubricating layer turned sliding friction to rolling friction

  8. Ru Schottky barrier contacts to n- and p-type 6H-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Samiji, M.E.; Wyk, E. van; Wu, L.; Leitch, A.W.R. [Port Elizabeth Univ. (South Africa). Dept. of Physics; Venter, A. [Vista Univ., Port Elizabeth (South Africa). Dept. of Physics

    2001-07-01

    We have investigated the formation of ruthenium Schottky contacts on both n- and p-type 6H-SiC wafers. It is found that Ru forms good quality rectifying contacts, with barrier heights of 0.67 eV and 1.06 eV for n-type and p-type SiC, respectively and ideality factors in the range 1.4 - 1.6. Annealing experiments indicated that the Ru Schottky contacts remained stable up to 450 C, above which a general deterioration in the quality of the contacts (as indicated by an increase in the measured idealities as well as an increase in the reverse bias leakage currents) was observed. It is also shown that the Ru Schottky contact to p-type SiC provides an excellent means through which to introduce hydrogen into the SiC using a hydrogen plasma. (orig.)

  9. Tensile Stress Rupture Behavior of a Woven Ceramic Matrix Composite in Humid Environments at Intermediate Temperature

    National Research Council Canada - National Science Library

    LaRochelle, Kevin J

    2005-01-01

    Stress rupture tests on the Sylramic(TM) fiber with an in-situ layer of boron nitride, boron nitride interphase, and SiC matrix ceramic matrix composite were performed at 550 degrees C and 750 degrees C with 0.0, 0.2...

  10. Electrical properties of N-polar AlGaN/GaN high electron mobility transistors grown on SiC by metalorganic chemical vapor deposition

    Science.gov (United States)

    Brown, David F.; Chu, Rongming; Keller, Stacia; DenBaars, Steven P.; Mishra, Umesh K.

    2009-04-01

    N-polar high electron mobility transistors (HEMTs) were fabricated from GaN/AlGaN/GaN heterostructures grown on n-type vicinal C-face SiC substrates by metalorganic chemical vapor deposition. The heterostructures had a sheet charge density and mobility of 6.6×1012 cm-2 and 1370 cm2 V-1 s-1, respectively. HEMTs with a gate length of 0.7 μm had a peak transconductance of 135 mS/mm, a peak drain current of 0.65 A/mm, and a three-terminal breakdown voltage greater than 150 V. At a drain bias of 20 V, the current-gain and power-gain cutoff frequencies with the pad capacitances de-embedded were 17 and 33 GHz, respectively.

  11. Step-edge-induced resistance anisotropy in quasi-free-standing bilayer chemical vapor deposition graphene on SiC

    Energy Technology Data Exchange (ETDEWEB)

    Ciuk, Tymoteusz [Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland); Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland); Cakmakyapan, Semih; Ozbay, Ekmel [Department of Electrical and Electronics Engineering, Department of Physics, Nanotechnology Research Center, Bilkent University, 06800 Bilkent, Ankara (Turkey); Caban, Piotr; Grodecki, Kacper; Pasternak, Iwona; Strupinski, Wlodek, E-mail: wlodek.strupinski@itme.edu.pl [Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland); Krajewska, Aleksandra [Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland); Institute of Optoelectronics, Military University of Technology, Gen. S. Kaliskiego 2, 00-908 Warsaw (Poland); Szmidt, Jan [Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland)

    2014-09-28

    The transport properties of quasi-free-standing (QFS) bilayer graphene on SiC depend on a range of scattering mechanisms. Most of them are isotropic in nature. However, the SiC substrate morphology marked by a distinctive pattern of the terraces gives rise to an anisotropy in graphene's sheet resistance, which may be considered an additional scattering mechanism. At a technological level, the growth-preceding in situ etching of the SiC surface promotes step bunching which results in macro steps ~10 nm in height. In this report, we study the qualitative and quantitative effects of SiC steps edges on the resistance of epitaxial graphene grown by chemical vapor deposition. We experimentally determine the value of step edge resistivity in hydrogen-intercalated QFS-bilayer graphene to be ~190 Ωμm for step height hS = 10 nm and provide proof that it cannot originate from mechanical deformation of graphene but is likely to arise from lowered carrier concentration in the step area. Our results are confronted with the previously reported values of the step edge resistivity in monolayer graphene over SiC atomic steps. In our analysis, we focus on large-scale, statistical properties to foster the scalable technology of industrial graphene for electronics and sensor applications.

  12. Long-Term Reliability of a Hard-Switched Boost Power Processing Unit Utilizing SiC Power MOSFETs

    Science.gov (United States)

    Ikpe, Stanley A.; Lauenstein, Jean-Marie; Carr, Gregory A.; Hunter, Don; Ludwig, Lawrence L.; Wood, William; Iannello, Christopher J.; Del Castillo, Linda Y.; Fitzpatrick, Fred D.; Mojarradi, Mohammad M.; hide

    2016-01-01

    Silicon carbide (SiC) power devices have demonstrated many performance advantages over their silicon (Si) counterparts. As the inherent material limitations of Si devices are being swiftly realized, wide-band-gap (WBG) materials such as SiC have become increasingly attractive for high power applications. In particular, SiC power metal oxide semiconductor field effect transistors' (MOSFETs) high breakdown field tolerance, superior thermal conductivity and low-resistivity drift regions make these devices an excellent candidate for power dense, low loss, high frequency switching applications in extreme environment conditions. In this paper, a novel power processing unit (PPU) architecture is proposed utilizing commercially available 4H-SiC power MOSFETs from CREE Inc. A multiphase straight boost converter topology is implemented to supply up to 10 kilowatts full-scale. High Temperature Gate Bias (HTGB) and High Temperature Reverse Bias (HTRB) characterization is performed to evaluate the long-term reliability of both the gate oxide and the body diode of the SiC components. Finally, susceptibility of the CREE SiC MOSFETs to damaging effects from heavy-ion radiation representative of the on-orbit galactic cosmic ray environment are explored. The results provide the baseline performance metrics of operation as well as demonstrate the feasibility of a hard-switched PPU in harsh environments.

  13. Effect of Copper Coated SiC Reinforcements on Microstructure, Mechanical Properties and Wear of Aluminium Composites

    Science.gov (United States)

    Kori, P. S.; Vanarotti, Mohan; Angadi, B. M.; Nagathan, V. V.; Auradi, V.; Sakri, M. I.

    2017-08-01

    Experimental investigations are carried out to study the influence of copper coated Silicon carbide (SiC) reinforcements in Aluminum (Al) based Al-SiC composites. Wear behavior and mechanical Properties like, ultimate tensile strength (UTS) and hardness are studied in the present work. Experimental results clearly revealed that, an addition of SiC particles (5, 10 and 15 Wt %) has lead in the improvement of hardness and ultimate tensile strength. Al-SiC composites containing the Copper coated SiC reinforcements showed better improvement in mechanical properties compared to uncoated ones. Characterization of Al-SiC composites are carried out using optical photomicrography and SEM analysis. Wear tests are carried out to study the effects of composition and normal pressure using Pin-On Disc wear testing machine. Results suggested that, wear rate decreases with increasing SiC composition, further an improvement in wear resistance is observed with copper coated SiC reinforcements in the Al-SiC metal matrix composites (MMC’s).

  14. Dimensional stability and anisotropy of SiC and SiC-based composites in transition swelling regime

    Science.gov (United States)

    Katoh, Yutai; Koyanagi, Takaaki; McDuffee, Joel L.; Snead, Lance L.; Yueh, Ken

    2018-02-01

    Swelling, or volumetric expansion, is an inevitable consequence of the atomic displacement damage in crystalline silicon carbide (SiC) caused by energetic neutron irradiation. Because of its steep temperature and dose dependence, understanding swelling is essential for designing SiC-based components for nuclear applications. In this study, swelling behaviors of monolithic CVD SiC and nuclear grade SiC fiber - SiC matrix (SiC/SiC) composites were accurately determined, supported by the irradiation temperature determination for individual samples, following neutron irradiation within the lower transition swelling temperature regime. Slightly anisotropic swelling behaviors were found for the SiC/SiC samples and attributed primarily to the combined effects of the pre-existing microcracking, fiber architecture, and specimen dimension. A semi-empirical model of SiC swelling was calibrated and presented. Finally, implications of the refined model to selected swelling-related issues for SiC-based nuclar reactor components are discussed.

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

    Science.gov (United States)

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

    2013-02-01

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

  16. Study of defects in radiation tolerant semiconductor SiC

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Hisayoshi; Kawasuso, Atsuo; Ohshima, Takeshi; Yoshikawa, Masahito; Nashiyama, Isamu [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; Okumura, Hajime; Yoshida, Sadafumi

    1997-03-01

    Electron spin resonance (ESR) was used to study defects introduced in n-type 6H-SiC by 3 MeV electron irradiation. Two ESR signals labeled A and B related to radiation induced defects were observed. An ESR signal B can be explained by a fine interaction with an effective spin S=1. The g and D tensors of the signal B were found to be axially symmetric along the c-axis. The principal values of the g were obtained to be g parallel = 2.003 and g perpendicular = 2.008, and the absolute value of the D was 3.96x10{sup -2} cm{sup -1} at 100 K for this signal. It was also found that the value |D| decreased with increasing temperature. Isochronal annealing showed that the A and B centers have annealing stages of {approx_equal}200degC and {approx_equal}800degC, respectively. Tentative structural models are discussed for these ESR centers. (author)

  17. Mechanical Behaviour and Morphology of A356/SiC Nanocomposites Using Stir Casting

    Science.gov (United States)

    Tanwir Alam, Md.; Arif, Sajjad; Husain Ansari, Akhter

    2017-08-01

    In this research an attempt has been made to explore the experimental investigation of A356/SiC nanocomposites using two step stir casting process. A356 alloy ingot was selected for the matrix and the reinforcement (aluminium fine powder (99.9%) plus nano size SiC mechanically forged by using ball mill at 100 rpm for duration of 10 hours). Ball milling process enhances the wettability of the particles. Reinforcement was varied from 1% to 5% with a step of 1% by weight. The stirring process was carried out at 500±50 rpm with stirring duration 10 minutes in two steps. The melt composites were poured at 680±20° C into the die to fabricate the composites. In this process of fabrication, less oxides/segregations were depicted. Tensile strengths of fabricated composites were evaluated by using UTM and toughness was calculated from area under stress-strain curve. To identify the involvement and presence of the nanoreinforcement into the matrix alloy (A356), fractured surfaces of the fabricated nanocomposites were examined using SEM and EDX. Tensile test results have shown the fracture mechanism and enhanced mechanical properties with the addition of forged nanoreinforcements. Yield tensile strength (YTS) and ultimate tensile strength (UTS) of A356 parent alloy found as 212.76 MPa and 219.90 MPa respectively. The improvement of 41% in YTS and 45% in UTS in case of A356/SiC nanocomposites were investigated. Decrease in % elongation and toughness with increase in forged nanoreinforcement were predicted. Proper distribution of reinforcement was attributed by SEM micrographs. EDX spectrum disclosed the presence of the constituents in the parent alloy (A356) and stir cast nanocomposites.

  18. Electrical Parasitics and Thermal Modeling for Optimized Layout Design of High Power SiC Modules

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Blaabjerg, Frede; Dutta, Atanu

    2016-01-01

    and parasitic inductance models of SiC power modules. These models can replace the models by Finite Element Methods (FEM) to predict temperatures and electrical parasitics of power modules with much faster speed and acceptable errors and will be used for study of real operation of power modules. As a case study......, the presented models are verified by a conventional and an optimized power module layout. The optimized layout is designed based on the reduction of stray inductance and temperature in a P-cell and N-cell half-bridge module. The presented models are verified by FEM simulations and also experiment....

  19. Mission-profile-based stress analysis of bond-wires in SiC power modules

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Iannuzzo, Francesco; Blaabjerg, Frede

    2016-01-01

    This paper proposes a novel mission-profile-based reliability analysis approach for stress on bond wires in Silicon Carbide (SiC) MOSFET power modules using statistics and thermo-mechanical FEM analysis. In the proposed approach, both the operational and environmental thermal stresses are taken...... and the mechanical stress on bond wires is consequently extracted by finite-element simulations. In the final step, the considered mission profile is translated in a stress sequence to be used for Rainflow counting calculation and lifetime estimation....

  20. Evolution of the internal friction in SIC particle reinforced 8090 Al-Li metal matrix composite

    International Nuclear Information System (INIS)

    Gutierrez-Urrutia, I.; Gallego, I.; No, M. L.; San Juan, J. M.

    2001-01-01

    The present study has been undertaken to investigate the mechanisms of thermal stress relief at the range of temperatures below room temperature for the metal matrix composite Al-Li 8090/SiC. For this aim the experimental technique of internal friction has been used which has been showed up very effective. Several thermal cycles from 453 K to 100 K were used in order to measures the internal friction as well as the elastic modules of the material concluding that thermal stresses are relaxed by microplastic deformation around the reinforcements. It has been also related the variation in the elastic modules with the different levels of precipitation. (Author) 18 refs

  1. Mechanism of Si intercalation in defective graphene on SiC

    KAUST Repository

    Kaloni, Thaneshwor P.

    2012-10-01

    Previously reported experimental findings on Si-intercalated graphene on SiC(0001) seem to indicate the possibility of an intercalation process based on the migration of the intercalant through atomic defects in the graphene sheet. We employ density functional theory to show that such a process is in fact feasible and obtain insight into its details. By means of total energy and nudged elastic band calculations we are able to establish the mechanism on an atomic level and to determine the driving forces involved in the different steps of the intercalation process through atomic defects.

  2. Influence of neutron irradiation on etching of SiC in KOH

    Science.gov (United States)

    Mokhov, E. N.; Kazarova, O. P.; Soltamov, V. A.; Nagalyuk, S. S.

    2017-07-01

    The effect of reactor neutron irradiation on the etch rate of SiC in potassium hydroxide has been studied. In the case of high irradiation doses (1019-1021 cm-2), the etch rate of silicon carbide has been shown to drastically rise, especially in the [0001]Si direction. This considerably mitigates the orientation anisotropy of polar face etching. After high-temperature annealing (up to 1200-1400°C), a higher etch rate of irradiated crystals persists. The results have been explained by the high concentration of radiation-induced (partially clustered) defects they contain.

  3. Electronic states density and solution volume of hydrogen solution in SiC alloys

    International Nuclear Information System (INIS)

    Gervasoni, J.L.; Furnari, J.C.

    2012-01-01

    The new reactor concepts are characterized by higher efficiency, better utilization of nuclear fuel and nuclear waste minimization. This approach means that this will be to enter a new and deep structural analysis of materials with a tensile strength significantly higher than those currently used radiation. To achieve high performance parameters, continuous research and testing of new materials will be needed. In this paper we concentrate on the analysis of SiC alloys, because due to their unique properties, this alloy can be used in high temperature conditions, where the silicon, semiconductor material of choice does not work (author)

  4. Formation of SiC nanoparticles in an atmospheric microwave plasma

    Directory of Open Access Journals (Sweden)

    Martin Vennekamp

    2011-10-01

    Full Text Available We describe the formation of SiC nanopowder using an atmospheric argon microwave plasma with tetramethylsilane (TMS as precursor. The impact of several process conditions on the particle size of the product is experimentally investigated. Particles with sizes ranging from 7 nm to about 20 nm according to BET and XRD measurements are produced. The dependency of the particle size on the process parameters is evaluated statistically and explained with growth-rate equations derived from the theory of Ostwald ripening. The results show that the particle size is mainly influenced by the concentration of the precursor material in the plasma.

  5. Key technology for (V)HTR: laser beam joining of SiC

    International Nuclear Information System (INIS)

    Knorr, J.; Lippmann, W.; Reinecke, A.M.; Wolf, R.; Rasper, R.; Kerber, A.; Wolter, A.

    2005-01-01

    Laser beam joining has numerous advantages over other methods presently known. After having been developed successful for brazing silicon carbide for high temperature applications, this technology is now also available for silicon nitride. Thus the field of application of SiC and Si 3 N 4 which are very interesting materials for the nuclear sector is considerably extended thanks to this new technology. Ceramic encapsulation of fuel and absorber increases the margins for operation at very high temperatures. Additionally, without ceramic encapsulation of the main core components, it will be difficult to continue claiming non-catastrophic behaviour for the (V)HTR. (orig.)

  6. Technique for measuring irradiation creep in polycrystalline SiC fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Hamilton, M.L.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

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

  7. Psychometric properties of the spanish language version of the stress in children questionnaire (SiC

    Directory of Open Access Journals (Sweden)

    Alejandra Caqueo-Urízar

    2014-03-01

    Full Text Available This study describes an analysis of the psychometric properties of a Spanish language version of the Stress in Children (SiC questionnaire. A group of Chilean school children was evaluated. The results show a tested version of the mentioned questionnaire which consists of 16 items distributed across two factors (emotional well-being and sources of distress. Internal consistency indices (Cronbach's alpha-coefficients were high. It is concluded there are appropriate psychometric properties for the Stress in Children questionnaire for this group of Chilean children. It is, therefore, a brief and easy to understand instrument of child assessment.

  8. Construction and characterization of spherical Si solar cells combined with SiC electric power inverter

    Science.gov (United States)

    Oku, Takeo; Matsumoto, Taisuke; Hiramatsu, Kouichi; Yasuda, Masashi; Shimono, Akio; Takeda, Yoshikazu; Murozono, Mikio

    2015-02-01

    Spherical silicon (Si) photovoltaic solar cell systems combined with an electric power inverter using silicon carbide (SiC) field-effect transistor (FET) were constructed and characterized, which were compared with an ordinary Si-based converter. The SiC-FET devices were introduced in the direct current-alternating current (DC-AC) converter, which was connected with the solar panels. The spherical Si solar cells were used as the power sources, and the spherical Si panels are lighter and more flexible compared with the ordinary flat Si solar panels. Conversion efficiencies of the spherical Si solar cells were improved by using the SiC-FET.

  9. The structure of carbon in chemically vapor deposited SiC monofilaments

    Science.gov (United States)

    Ning, X. J.; Pirouz, P.; Lagerlof, K. P. D.; Dicarlo, J.

    1990-01-01

    Electron diffraction and high resolution TEM have been used to study the microstructures of C-rich regions in CVD SCS-6 SiC fibers. The reciprocal lattice of such structures, and their diffraction patterns, have been ascertained on the basis of geometrical considerations. While the C microstructures in the substrate filament and the outer coating layers of the fabric are consistent with different distributions of Oberlin's (1989) 'basic structural units', the microstructure of the inner substrate coating is consistent with turbostratic C.

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

    Science.gov (United States)

    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. In this photo taken February 4, 1963, the Block House exterior is complete.

  11. Construction Progress of the S-IC Test Stand Water Valve

    Science.gov (United States)

    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 photograph, a construction worker demonstrates the size of the massive water valve that was used in the testing cooling

  12. Construction Progress of the S-IC Pump House Water Tanks

    Science.gov (United States)

    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. This close up photograph, taken September 5, 1963, shows the ground level frame work for the Pump House and its massive

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

    Science.gov (United States)

    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. This photograph, taken September 25, 1963, depicts the construction progress of the Pump House and massive round water

  14. Donor-acceptor-pair emission characterization in N-B doped fluorescent SiC

    DEFF Research Database (Denmark)

    Ou, Yiyu; Jokubavicius, Valdas; Kamiyama, Satoshi

    2011-01-01

    In the present work, we investigated donor-acceptor-pair emission in N-B doped fluorescent 6H-SiC, by means of photoluminescence, Raman spectroscopy, and angle-resolved photoluminescence. The photoluminescence results were interpreted by using a band diagram with Fermi-Dirac statistics. It is shown...... intensity in a large emission angle range was achieved from angle-resolved photoluminescence. The results indicate N-B doped fluorescent SiC as a good wavelength converter in white LEDs applications....

  15. 5.8kV SiC PiN Diode for Switching of High-Efficiency Inductive Pulsed Plasma Thruster Circuits

    Science.gov (United States)

    Toftul, Alexandra; Polzin, Kurt A.; Hudgins, Jerry L.

    2014-01-01

    Inductive Pulsed Plasma Thruster (IPPT) pulse circuits, such as those needed to operate the Pulsed Inductive Thruster (PIT), are required to quickly switch capacitor banks operating at a period of µs while conducting current at levels on the order of at least 10 kA. [1,2] For all iterations of the PIT to date, spark gaps have been used to discharge the capacitor bank through an inductive coil. Recent availability of fast, high-power solid state switching devices makes it possible to consider the use of semiconductor switches in modern IPPTs. In addition, novel pre-ionization schemes have led to a reduction in discharge energy per pulse for electric thrusters of this type, relaxing the switching requirements for these thrusters. [3,4] Solid state switches offer the advantage of greater controllability and reliability, as well as decreased drive circuit dimensions and mass relative to spark gap switches. The use of solid state devices such as Integrated Gate Bipolar Transistors (IGBTs), Gate Turn-off Thyristors (GTOs) and Silicon-Controlled Rectifiers (SCRs) often involves the use of power diodes. These semiconductor devices may be connected antiparallel to the switch for protection from reverse current, or used to reduce power loss in a circuit by clamping off current ringing. In each case, higher circuit efficiency may be achieved by using a diode that is able to transition, or 'switch,' from the forward conducting state ('on' state) to the reverse blocking state ('off' state) in the shortest amount of time, thereby minimizing current ringing and switching losses. Silicon Carbide (SiC) PiN diodes offer significant advantages to conventional fast-switching Silicon (Si) diodes for high power and fast switching applications. A wider band gap results in a breakdown voltage 10 times that of Si, so that a SiC device may have a thinner drift region for a given blocking voltage. [5] This leads to smaller, lighter devices for high voltage applications, as well as reduced

  16. Investigation of Embedded Si/C System Exposed to a Hybrid Reaction of Centrifugal-Assisted Thermite Method.

    Directory of Open Access Journals (Sweden)

    Reza Mahmoodian

    Full Text Available A novel method is proposed to study the behavior and phase formation of a Si+C compacted pellet under centrifugal acceleration in a hybrid reaction. Si+C as elemental mixture in the form of a pellet is embedded in a centrifugal tube. The pellet assembly and tube are exposed to the sudden thermal energy of a thermite reaction resulted in a hybrid reaction. The hybrid reaction of thermite and Si+C produced unique phases. X-ray diffraction pattern (XRD as well as microstructural and elemental analyses are then investigated. XRD pattern showed formation of materials with possible electronic and magnetic properties. The cooling rate and the molten particle viscosity mathematical model of the process are meant to assist in understanding the physical and chemical phenomena took place during and after reaction. The results analysis revealed that up to 85% of materials converted into secondary products as ceramics-matrix composite.

  17. Analysis of dynamic characteristics of SiC Schottky barrier diodes at high switching frequency based on junction capacitance

    Science.gov (United States)

    Maeda, Ryosuke; Okuda, Takafumi; Hikihara, Takashi

    2018-04-01

    In this paper, we focus on relationships between dynamic characteristics and device structures of SiC Schottky barrier diodes (SBDs) to investigate their switching capabilities. A device model based on junction capacitance and thermionic emission theory is proposed. To measure the dynamic characteristics of SiC SBD, a high-frequency (10 MHz) and high-voltage (200 Vpp) wave generator is fabricated. By comparing simulated results with experimental results, it is found that the proposed model can represent the dynamic characteristics at 10 MHz and 200 °C, and the simple device model based on junction capacitance and thermionic emission theory well describes the switching behaviors of SiC SBDs at full operational temperature. The proposed device model is beneficial for designing high-power converters, at both wide temperature and wide frequency ranges.

  18. Estudio de la reactividad entre aleaciones de aluminio y partículas de SiC

    Directory of Open Access Journals (Sweden)

    Ureña, A.

    2000-04-01

    Full Text Available The SiC reinforcement particles react with the molten aluminium to form Al4C3 that is brittle and sensitive to the the humidity. This reaction degrades the properties of the SiC reinforced aluminium matrix composites. The extend of the reaction in the Al/SiC interface depends on the fabrication parameters such as the temperature, residence time, atmosphere and chemical composition of the aluminium matrix and the reinforcement. Systematic studies on the reactivity between the SiC particles and molten aluminium alloys have been performed, analysing the effect of the presence of a SiO2 layer, which was formed by oxidation on the ceramic particles before their incorporation into the melt, as a protective barrier for preventing the attack of the SiC. As well, the effect of the metal matrix composition on the interfacial reactivity has been studied employing different aluminium alloys: AA1070 (99,7% Al, A-319.0 (Al-6Si-3Cu and A-332.0 (Al-11Si-1,5Cu. The composites were prepared by mixture of SiC particles (30 % vol. %, cold pressure and fusion at 900 ºC, varying the residence time in the furnace, which simulated a cast fabrication process. The results are compared with those obtained for a metal matrix composite (AA2014/SiC/13p.

    Las partículas de refuerzo de SiC reaccionan con el aluminio fundido y forman Al4C3 que es frágil y sensible al contacto con la humedad, lo que degrada las propiedades de los materiales compuestos constituidos por ambos componentes. La reacción en la intercara Al/SiC depende de varios parámetros de fabricación como temperatura, tiempo de residencia, atmósfera y composición química, tanto de la matriz de aluminio como del refuerzo de SiC. Se han realizado estudios sistemáticos de reactividad entre partículas de SiC y aluminio fundido, analizando el efecto que tiene la formación de una capa de SiO2 por oxidación de las partículas cerámicas, antes de su incorporación en el fundido, como barrera protectora

  19. Deposition of low stress, high transmittance SiC as an x-ray mask membrane using ECR plasma CVD

    CERN Document Server

    Lee, S Y; Lim, S T; Ahn, J H

    1998-01-01

    SiC for x-ray mask membrane is deposited by Electron Cyclotron Resonance plasma Chemical Vapor Deposition from SiH sub 4 /CH sub 4 Ar mixtures. Stoichiometric SiC is deposited at SiH sub 4 /CH sub 4 ratio of 0.4, deposition temperature of 600.deg.C and microwave power of 500 W with +- 5% thickness uniformity, As-deposited film has compressive residual stress, very smooth surface (31 A rms) and high optical transmittance of 90% at 633 nm wavelength. The microstructure of this film consists of the nanocrystalline particle (100 A approx 200A) embedded in amorphous matrix. Residual stress can be turned to tensile stress via Rapid Thermal Annealing in N sub 2 atmosphere, while suppressing structural change during annealing, As a result, smooth (37 A rms) SiC film with moderate tensile stress and high optical transmittance (85% at 633 nm wavelength) is obtained.

  20. Chemical vapor deposition of SiC on C-C composites as plasma facing materials for fusion application

    International Nuclear Information System (INIS)

    Kim, W. J.; Lee, M. Y.; Park, J. Y.; Hong, G. W.; Kim, J. I.; Choi, D. J.

    2000-01-01

    Because of the low activation and excellent mechanical properties at elevated temperatures, carbon-fiber reinforced carbon(C-C) composites have received much attention for plasma facing materials for fusion reactor and high-temperature structural applications such as aircrafts and space vehicles. These proposed applications have been frustrated by the lack of resistance to hydrogen erosion and oxidation on exposure to ambient oxidizing conditions at high temperature. Although Silicon Carbide (SiC) has shown excellent properties as an effective erosion-and oxidation-protection coating, many cracks are developed during fabrication and thermal cycles in use due to the Coefficients of Thermal Expansion(CTE) mismatch between SiC and C-C composite. In this study, we adopted a pyrolitic carbon as an interlayer between SiC and C-C substrate in order to minimize the CTE mismatch. The oxidation-protection performance of this composite was investigated as well

  1. Studies on the Codeposition of SiC Nanopowder with Nickel, Cobalt, and Co-Ni Alloys

    Directory of Open Access Journals (Sweden)

    Ewa Rudnik

    2014-01-01

    Full Text Available Electrodeposition of SiC nanopowder (approximately 120 nm with nickel, cobalt, and Co-Ni alloy matrix was studied. It was found that particles suspended in the bath affect slightly the reduction of metallic ions. Incorporation of the ceramic particles was governed mainly by the morphology of the matrix surface, while no strict correlation between the amount of cobalt ions adsorbed on the powder and the SiC content in the composites was found. Microhardness of nickel deposits was 585±5 HV, while for cobalt-rich coatings (84–95 wt.% Co the values were in the range of 260–290 HV, independently of the SiC content in the coatings. Fine-grained nickel deposits were characterized by good corrosion resistance, while cobalt and Co-Ni alloys showed high corrosion current densities.

  2. Oxygen reduction and methanol oxidation behaviour of SiC based Pt nanocatalysts for proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Dhiman, Rajnish; Stamatin, Serban Nicolae; Andersen, Shuang Ma

    2013-01-01

    with the present carbon based substrates. We have recently examined suitably sized silicon carbide (SiC) particles as catalyst supports for fuel cells based on the stable chemical and mechanical properties of this material. In the present study, we have continued our work with studies of the oxygen reduction...... and methanol oxidation reactions of SiC supported catalysts and measured them against commercially available carbon based catalysts. The deconvolution of the hydrogen desorption signals in CV cycles shows a higher contribution of Pt (110) & Pt (111) peaks compared to Pt (100) for SiC based supports than...... for carbon based commercial catalyst, when HClO4 is used as electrolyte. The Pt (110) & Pt (111) facets are shown to have higher electrochemical activities than Pt (100) facets. To the best of our knowledge, methanol oxidation studies and the comparison of peak deconvolutions of the H desorption region in CV...

  3. Effect of SiC Nanowhisker on the Microstructure and Mechanical Properties of WC-Ni Cemented Carbide Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Xiaoyong Ren

    2014-01-01

    Full Text Available Ultrafine tungsten carbide-nickel (WC-Ni cemented carbides with varied fractions of silicon carbide (SiC nanowhisker (0–3.75 wt.% were fabricated by spark plasma sintering at 1350°C under a uniaxial pressure of 50 MPa with the assistance of vanadium carbide (VC and tantalum carbide (TaC as WC grain growth inhibitors. The effects of SiC nanowhisker on the microstructure and mechanical properties of the as-prepared WC-Ni cemented carbides were investigated. X-ray diffraction analysis revealed that during spark plasma sintering (SPS Ni may react with the applied SiC nanowhisker, forming Ni2Si and graphite. Scanning electron microscopy examination indicated that, with the addition of SiC nanowhisker, the average WC grain size decreased from 400 to 350 nm. However, with the additional fractions of SiC nanowhisker, more and more Si-rich aggregates appeared. With the increase in the added fraction of SiC nanowhisker, the Vickers hardness of the samples initially increased and then decreased, reaching its maximum of about 24.9 GPa when 0.75 wt.% SiC nanowhisker was added. However, the flexural strength of the sample gradually decreased with increasing addition fraction of SiC nanowhisker.

  4. Processing, Microstructure, and Mechanical Properties of Si3N4/SiC Nanocomposites from Precursor Derived Ceramics

    Science.gov (United States)

    Strong, Kevin Thomas, Jr.

    Polymer-derived ceramics (PDCs) provides a unique processing route to create Si3N4/SiC composites. Silazane precursor polyureasilazane (Ceraset PURS20) produce's an amorphous SiCN ceramic at temperatures of ~800 -- 1200 °C and crystallizes to a Si3N4/SiC nanocomposite at temperatures >1500 °C. A novel processing technique was developed where crosslinked polymers were heat-treated in a reactive NH3 atmosphere to control the stoichiometry of the pyrolyzed SiCN ceramic. Using this technique processing parameters were established to produce SiCN powders that resulted in nanocomposites with approximately 0, 5, 10, 20 and 30 vol. % SiC. Lu2O3 was added to these powders as a sintering aid and were densified using Hot Pressing and Field Assisted Sintering. The sintered nanocomposites resulted in microstructures with multiple-length scales. These length-scales included Si3N4 (0.1 -- 5 microm), SiC (10 -- 100 nm) and the intergranular grain boundary phase (<1 nm). Using a combination of SEM and TEM it was possible to quantify some of these microstructural features such as the size and location of the SiC. Hardness and fracture toughness testing was conducted to compared the room temperature mechanical properties of these resultant microstructures. This research was intended to develop robust processing approaches that can be used to control the nanostructures of Si3N4/SiC composites with significant structural features at multiple length scales. The control of their features and the investigation of their affect on the properties of composites can be used to simulate the affect of the structure on properties. These models can then be used to design optimal microstructures for specific applications.

  5. Enhancing the oxidation resistance of graphite by applying an SiC coat with crack healing at an elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jae-Won, E-mail: pjw@kaeri.re.kr [Korea Atomic Energy Research Institute, 1045 Daedeok-Daero, Yuseong-Gu, Daejeon-City (Korea, Republic of); Kim, Eung-Seon; Kim, Jae-Un [Korea Atomic Energy Research Institute, 1045 Daedeok-Daero, Yuseong-Gu, Daejeon-City (Korea, Republic of); Kim, Yootaek [Dept. of Materials Engineering, Kyonggi Universtiy, Suwon (Korea, Republic of); Windes, William E. [Idaho National Laboratory, Idaho Falls, ID 83415 (United States)

    2016-08-15

    Highlights: • Ion beam mixed SiC coating was performed on the graphite for the enhanced adhesion. • The SiC coated was cracked at the elevated temperature, confirming the strong bonding, and then was vigorously oxidized leaving only the SiC layer. • For crack healing, CVD crack healing increased by ∼4 times in 20% weight reduction in air at 900 °C as compared to PVD crack healing. - Abstract: The potential of reducing the oxidation of the supporting graphite components during normal and/or accident conditions in the Very High Temperature Reactor (VHTR) design has been studied. In this work efforts have been made to slow the oxidation process of the graphite with a thin SiC coating (∼ 10 μm). Upon heating at ≥ 1173 K in air, the spallations and cracks were formed in the dense columnar structured SiC coating layer grown on the graphite with a functionally gradient electron beam physical vapor deposition (EB-PVD. In accordance with the formations of these defects, the sample was vigorously oxidized, leaving only the SiC coating layer. Then, efforts were made to heal the surface defects using additional EB-PVD with ion beam bombardment and chemical vapor deposition (CVD). The EB-PVD did not effectively heal the cracks. But, the CVD was more appropriate for crack healing, likely due to its excellent crack line filling capability with a high density and high aspect ratio. It took ∼ 34 min for the 20% weight loss of the CVD crack healed sample in the oxidation test with annealing at 1173 K, while it took ∼ 8 min for the EB-PVD coated sample, which means it took ∼4 times longer at 1173 K for the same weight reduction in this experimental set-up.

  6. Enhancing the oxidation resistance of graphite by applying an SiC coat with crack healing at an elevated temperature

    International Nuclear Information System (INIS)

    Park, Jae-Won; Kim, Eung-Seon; Kim, Jae-Un; Kim, Yootaek; Windes, William E.

    2016-01-01

    Highlights: • Ion beam mixed SiC coating was performed on the graphite for the enhanced adhesion. • The SiC coated was cracked at the elevated temperature, confirming the strong bonding, and then was vigorously oxidized leaving only the SiC layer. • For crack healing, CVD crack healing increased by ∼4 times in 20% weight reduction in air at 900 °C as compared to PVD crack healing. - Abstract: The potential of reducing the oxidation of the supporting graphite components during normal and/or accident conditions in the Very High Temperature Reactor (VHTR) design has been studied. In this work efforts have been made to slow the oxidation process of the graphite with a thin SiC coating (∼ 10 μm). Upon heating at ≥ 1173 K in air, the spallations and cracks were formed in the dense columnar structured SiC coating layer grown on the graphite with a functionally gradient electron beam physical vapor deposition (EB-PVD. In accordance with the formations of these defects, the sample was vigorously oxidized, leaving only the SiC coating layer. Then, efforts were made to heal the surface defects using additional EB-PVD with ion beam bombardment and chemical vapor deposition (CVD). The EB-PVD did not effectively heal the cracks. But, the CVD was more appropriate for crack healing, likely due to its excellent crack line filling capability with a high density and high aspect ratio. It took ∼ 34 min for the 20% weight loss of the CVD crack healed sample in the oxidation test with annealing at 1173 K, while it took ∼ 8 min for the EB-PVD coated sample, which means it took ∼4 times longer at 1173 K for the same weight reduction in this experimental set-up.

  7. Stability and electronic properties of SiC nanowire adsorbed on MoS{sub 2} monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Munish, E-mail: munishsharmahpu@live.com; Pooja,; Ahluwalia, P. K. [Department of Physics, Himachal Pradesh University, Shimla, H. P., 171005 (India); Kumar, Ashok [Department of Physics, Panjab University, Chandigarh, 160014 (India)

    2015-06-24

    Structural stability and electronic properties of silicon carbide (SiC) nano-wire on MoS{sub 2} 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.

  8. SiC JFET Cascode Loss Dependency on the MOSFET Output Capacitance and Performance Comparison with Trench IGBTs

    DEFF Research Database (Denmark)

    Pittini, Riccardo; Zhang, Zhe; Andersen, Michael A. E.

    2013-01-01

    In power electronics there is a general trend to increase converters efficiencies and power densities; for this reason new power semiconductors based on materials such as Silicon Carbide (SiC) and Gallium Nitride (GaN) are becoming more popular. This is especially valid for renewable energies...... output capacitance on the switching performance of the SiC Cascode connection in terms of switching energy loss, dV/dt and dI/dt stresses. The Cascode connection switching performances are compared with the switching performance latest Trench IGBTs. The analysis is based on a set of several laboratory...

  9. High-Speed Gate Driver Using GaN HEMTs for 20-MHz Hard Switching of SiC MOSFETs

    OpenAIRE

    Okuda, Takafumi; Hikihara, Takashi

    2017-01-01

    In this paper, we investigated a gate driver using a GaN HEMT push-pull configuration for the high-frequency hard switching of a SiC power MOSFET. Low on-resistance and low input capacitance of GaN HEMTs are suitable for a high-frequency gate driver from the logic level, and robustness of SiC MOSFET with high avalanche capability is suitable for a valve transistor in power converters. Our proposed gate driver consists of digital isolators, complementary Si MOSFETs, and GaN HEMTs. The GaN HEMT...

  10. Associations of Pd, U and Ag in the SiC layer of neutron-irradiated TRISO fuel

    Energy Technology Data Exchange (ETDEWEB)

    Lillo, T.M., E-mail: thomas.lillo@inl.gov [Materials Science & Engineering Department, Idaho National Laboratory, Idaho Falls, ID 83415-2211 (United States); Rooyen, I.J. van [Fuel Performance and Design Department, Idaho National Laboratory, Idaho Falls, ID 83415-6188 (United States)

    2015-05-15

    Highlights: • Fission products in the SiC layer of a neutron-irradiated TRISO particle were analyzed. • Pd, Ag and U found in grain boundary, matrix and triple junction precipitates. • U never found alone or with Ag, only associated with Pd. • Not all boundaries and triple junctions had fission products. • Grain boundary crystallographic parameters likely a factor in migration behavior. - Abstract: Knowledge of the associations and composition of fission products in the neutron irradiated SiC layer of high-temperature gas reactor TRISO fuel is important to the understanding of various aspects of fuel performance that presently are not well understood. Recently, advanced characterization techniques have been used to examine fuel particles from the Idaho National Laboratory’s AGR-1 experiment. Nano-sized Ag and Pd precipitates were previously identified in grain boundaries and triple points in the SiC layer of irradiated TRISO nuclear fuel. Continuation of this initial research is reported in this paper and consists of the characterization of a relatively large number of nano-sized precipitates in three areas of the SiC layer of a single irradiated TRISO nuclear fuel particle using standardless EDS analysis on focused ion beam-prepared transmission electron microscopy samples. Composition and distribution analyses of these precipitates, which were located on grain boundaries, triple junctions and intragranular precipitates, revealed low levels, generally <10 atomic %, of palladium, silver and/or uranium with palladium being the most common element found. Palladium by itself, or associated with either silver or uranium, was found throughout the SiC layer. A small number of precipitates on grain boundaries and triple junctions were found to contain only silver or silver in association with palladium while uranium was always associated with palladium but never found by itself or in association with silver. Intergranular precipitates containing uranium were

  11. The role of interfacial microstructure in the mechanical properties of SiC whisker reinforced Si3N4

    International Nuclear Information System (INIS)

    Swan, A.H.; Dunlop, G.L.

    1991-01-01

    SiC whisker reinforced Si 3 N 4 can be produced using a number of different methods. These include hot pressing (HP), hot isostatic pressing (HIP), reaction bonding (RB), nitrided pressureless sintering (NPS) and various combinations of these methods. This paper is concerned with the microstructure of SiC whisker reinforced Si 3 N 4 materials fabricated by both nitrided pressureless sintering and hot pressing. Attention has been given to the microstructure of as-sintered materials, crack paths within the microstructure and also microstructural changes that occur during high temperature deformation

  12. Comparison of the Contact stress and friction behavior of SiC and ZrO2 materials

    International Nuclear Information System (INIS)

    Lindberg, L.J.; Richerson, D.W.

    1985-01-01

    Studies were performed to further elucidate the friction and contact- stress characteristics of structural ceramic materials. New data for fully stabilized and partially stabilized zirconia ceramics are compared with prior test results for sintered SiC. The comparison provides further evidence that the high temperature friction characteristics of sinstered SiC are strongly influenced by the presence of a viscous surface layer. The results also show that a ceramic material with lower coefficient of friction and higher fracture toughness has increased resistance to strength-reducing surface damage due to contact stress

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

    Science.gov (United States)

    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.

  14. Determination of SiC ceramic foams microstructure properties by X-rays microtomography

    International Nuclear Information System (INIS)

    Nagata, Rodrigo; Appoloni, Carlos Roberto; Fernandes, Jaquiel Salvi

    2009-01-01

    Silicon carbide ceramic foams (SiC) can operate at high temperatures, which allow them to be used as heat exchangers, liquid metal filters, composite of rocket nozzles, etc. For many of these applications it is very important to know the foams' porosity. In this work the porosity of SiC ceramic foams was determined by X-rays microtomography, a powerful non-destructive technique that allows the analysis of the sample's internal structure. The samples have pore densities of 30, 45, 60, 80 and 100 pores per inch (ppi). The spatial resolution obtained was 24.8 μm. The cross sections' reconstruction was performed with a cone beam filtered backprojection algorithm. In the analyses, micropores were observed in the foam's lattice wire of the 30 ppi and 45 ppi samples. Micropores were present in few cross sections of 60 ppi sample too, but it was not found in the 80 ppi and 100 ppi samples. The total porosities obtained were Φ = (88.8 ± 4.3) %, Φ = (85.2 ± 1.4) %, Φ = (82.3 ± 1.8) %, Φ (79.9 ± 1.3) % and Φ = (80.4 ± 1.5) %, for the 30, 45, 60, 80 and 100 ppi samples, respectively. (author)

  15. Microstructure and Properties of Spark Plasma Sintered Aluminum Containing 1 wt.% SiC Nanoparticles

    Directory of Open Access Journals (Sweden)

    Ismaila Kayode Aliyu

    2015-01-01

    Full Text Available The low hardness and strength of aluminum, which limits its use in many industrial applications, could be increased through the addition of nanoparticles. However, the appropriate processing method and parameters should be carefully selected in order to achieve the desired improvement in properties. In this work, aluminum was reinforced with low weight fraction (1 wt.% of SiC nanoparticles and consolidated through spark plasma sintering. The effect of processing parameters on the densification, microstructure, and properties of the processed material was investigated. Field Emission Scanning Electron Microscope (FE-SEM equipped with Energy Dispersive X-ray Spectroscopy (EDS facility was used to characterize the microstructure and analyze the reinforcement’s distribution in sintered samples. Phases present were characterized through X-ray diffraction (XRD. A densimeter and a digital microhardness tester were used to measure the density and hardness, respectively. Compressive tests were performed using universal testing machine. A fully dense Al-1 wt.% SiC sample was obtained. Analysis of density and hardness values showed that the influence of applied pressure was more pronounced than heating rate while the influence of sintering temperature was more significant than sintering time. Within the range of parameters used, the highest values of the characterized properties were obtained at a sintering temperature of 600 °C, sintering time of 10 min, pressure of 50 MPa, and heating rate of 200 °C/min.

  16. First-principles study of point-defect production in Si and SiC

    International Nuclear Information System (INIS)

    Windl, W.; Lenosky, T.J.; Kress, J.D.; Voter, A.F.

    1998-03-01

    The authors have calculated the displacement-threshold energy E(d) for point-defect production in Si and SiC using empirical potentials, tight-binding, and first-principles methods. They show that -- depending on the knock-on direction -- 64-atom simulation cells can be sufficient to allow a nearly finite-size-effect-free calculation, thus making the use of first-principles methods possible. They use molecular dynamics (MD) techniques and propose the use of a sudden approximation which agrees reasonably well with the MD results for selected directions and which allows estimates of Ed without employing an MD simulation and the use of computationally demanding first-principles methods. Comparing the results with experiment, the authors find the full self-consistent first-principles method in conjunction with the sudden approximation to be a reliable and easy method to predict E d . Furthermore, they have examined the temperature dependence of E d for C in SiC and found it to be negligible

  17. Role of SiC substrate surface on local tarnishing of deposited silver mirror stacks

    Science.gov (United States)

    Limam, Emna; Maurice, Vincent; Seyeux, Antoine; Zanna, Sandrine; Klein, Lorena H.; Chauveau, Grégory; Grèzes-Besset, Catherine; Savin De Larclause, Isabelle; Marcus, Philippe

    2018-04-01

    The role of the SiC substrate surface on the resistance to the local initiation of tarnishing of thin-layered silver stacks for demanding space mirror applications was studied by combined surface and interface analysis on model stack samples deposited by cathodic magnetron sputtering and submitted to accelerated aging in gaseous H2S. It is shown that suppressing the surface pores resulting from the bulk SiC material production process by surface pretreatment eliminates the high aspect ratio surface sites that are imperfectly protected by the SiO2 overcoat after the deposition of silver. The formation of channels connecting the silver layer to its environment through the failing protection layer at the surface pores and locally enabling H2S entry and Ag2S growth as columns until emergence at the stack surface is suppressed, which markedly delays tarnishing initiation and thereby preserves the optical performance. The results revealed that residual tarnishing initiation proceeds by a mechanism essentially identical in nature but involving different pathways short circuiting the protection layer and enabling H2S ingress until the silver layer. These permeation pathways are suggested to be of microstructural origin and could correspond to the incompletely coalesced intergranular boundaries of the SiO2 layer.

  18. Reflood Heat Transfer in SiC and Graphene Oxide Coated Tube

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung Mo; Lee, Seung Won; Bang, In Cheol [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

    2013-10-15

    The reflood tests have been performed flowing water into bare tube and nanoparticles coated tube at constant flow rate (3 cm/s). The quenching curves have been obtained at atmospheric pressure. Finally, Scanning Electron Microscopy (SEM) images are acquired and contact angles are measured in order to observe the surface structures and wettability effect on cooling performance. The quenching time decreases and quenching velocity increases as the coating time of nanoparticles on the tube increases, because the nanoparticles deposited on the tube destabilize and rupture the vapor film early in the effect of increased Leidenfrost point temperature. The SiC nanoparticles coated tubes have better quenching performance than GO nanoparticles coated tubes. The SEM images and contact angle observations proved the enhanced wettability and rough surface due to deposition of SiC nanoparticles. And the wettability of GO nanoparticles coated tubes shows the increase at 600 s coating. But, the wettability decreases on GO nanoparticles tube coated for 900 s despite the enhanced quenching performance. Thus, the porous structure affects to the better cooling performance in case of GO nanoparticles coated tubes.

  19. Characterization of rare-earth doped Si 3 N4 /SiC micro/nanocomposites

    Directory of Open Access Journals (Sweden)

    Peter Tatarko

    2010-03-01

    Full Text Available Influence of various rare-earth oxide additives (La2O3, Nd2O3, Sm2O3, Y2O3, Yb2O3 and Lu2O3 on the mechanical properties of hot-pressed silicon nitride and silicon nitride/silicon carbide micro/nano-composites has been investigated. The bimodal character of microstructures was observed in all studied materials where elongated β-Si3N4 grains were embedded in the matrix of much finer Si3N4 grains. The fracture toughness values increased with decreasing ionic radius of rare-earth elements. The fracture toughness of composites was always lower than that of monoliths due to their finer Si3N4/SiC microstructures. Similarly, the hardness and bending strength values increased with decreasing ionic radius of rare-earth elements either in monoliths or composites. On the other hand, the positive influence of finer microstructure of the composites on strength was not observed due to the present defects in the form of SiC clusters and non-reacted carbon zones. Wear resistance at room temperature also increased with decreasing ionic radius of rare-earth element. Significantly improved creep resistance was observed in case either of composite materials or materials with smaller radius of RE3+.

  20. Structural consequences of hydrogen intercalation of epitaxial graphene on SiC(0001)

    Energy Technology Data Exchange (ETDEWEB)

    Emery, Jonathan D., E-mail: jdemery@anl.gov, E-mail: bedzyk@northwestern.edu; Johns, James E.; McBriarty, Martin E.; Hersam, Mark C. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Wheeler, Virginia H.; Kurt Gaskill, D. [U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Detlefs, Blanka [ESRF—The European Synchrotron, CS 40220, 71, Avenue des Martyrs, 38043 Grenoble (France); Bedzyk, Michael J., E-mail: jdemery@anl.gov, E-mail: bedzyk@northwestern.edu [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States)

    2014-10-20

    The intercalation of various atomic species, such as hydrogen, to the interface between epitaxial graphene (EG) and its SiC substrate is known to significantly influence the electronic properties of the graphene overlayers. Here, we use high-resolution X-ray reflectivity to investigate the structural consequences of the hydrogen intercalation process used in the formation of quasi-free-standing (QFS) EG/SiC(0001). We confirm that the interfacial layer is converted to a layer structurally indistinguishable from that of the overlying graphene layers. This newly formed graphene layer becomes decoupled from the SiC substrate and, along with the other graphene layers within the film, is vertically displaced by ∼2.1 Å. The number of total carbon layers is conserved during the process, and we observe no other structural changes such as interlayer intercalation or expansion of the graphene d-spacing. These results clarify the under-determined structure of hydrogen intercalated QFS-EG/SiC(0001) and provide a precise model to inform further fundamental and practical understanding of the system.

  1. Assessment of intrinsic small signal parameters of submicron SiC MESFETs

    Science.gov (United States)

    Riaz, Mohammad; Ahmed, Muhammad Mansoor; Rafique, Umair; Ahmed, Umer Farooq

    2018-01-01

    In this paper, a technique has been developed to estimate intrinsic small signal parameters of submicron SiC MESFETs, designed for high power microwave applications. In the developed technique, small signal parameters are extracted by involving drain-to-source current, Ids instead of Schottky barrier depletion layer expression. It has been demonstrated that in SiC MESFETs, the depletion layer gets modified due to intense transverse electric field and/or self-heating effects, which are conventionally not taken into account. Thus, assessment of AC small signal parameters by employing depletion layer expression loses its accuracy for devices meant for high power applications. A set of expressions for AC small signal elements has been developed using Ids and its dependence on device biasing has been discussed. The validity of the proposed technique has been demonstrated using experimental data. Dr. Ahmed research interests are in Microelectronics, Microwave and RF Engineering and he has supervised numerous MS and PhD research projects. He authored over 100 research papers in the field of microelectronics. Dr. Ahmed is a fellow of the Institution of Engineering and Technology (IET), UK.; a Chartered Engineer (CEng) from the UK Engineering Council and holds the title of European Engineer (Eur Ing) from the European Federation of National Engineering Association (FEANI), Brussels. He is a life member of PEC (Pak); EDS & MTTS (USA). article>

  2. The SiC hardware of the Sentinel-2 multi spectral instrument

    Science.gov (United States)

    Bougoin, Michel; Lavenac, Jérôme

    2017-11-01

    The Sentinel-2 mission is a major part of the GMES (Global Monitoring for Environment and Security) program which has been set up by the European Union, on a joint initiative with the European Space Agency. A pair of identical satellites will observe the earth from a sun-synchronous orbit at 786 km altitude. Astrium is the prime contractor of the satellites and their payload. The MultiSpectral Instrument features a "all-SiC" TMA (Three Mirror Anastygmat) telescope. MSI will provide optical images in 13 spectral bands, in the visible and also the near infra-red range, with a 10 to 60 m resolution and a 290 km wide swath. The Boostec® SiC material is used mainly for its high specific stiffness (Youngs modulus / density) and its high thermal stability (thermal conductivity / coefficient of thermal expansion) which allow to reduce the distortions induced by thermo-elastic stresses. Its high mechanical properties as well as the relevant technology enable to make not only the mirrors but also the structure which holds them and the elements of the focal plane (including some detectors packaging). Due to the required large size, accuracy and shape complexity, developing and manufacturing some of these SiC parts required innovative manufacturing approach. It is reviewed in the present paper.

  3. Mechanical and corrosion performance of SiC multilayer containing porous layers

    Energy Technology Data Exchange (ETDEWEB)

    Vega Bolivar, C M; Biamino, S; Pavese, M; Fino, P; Badini, C [Department of Materials Science and Chemical Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Haehner, P, E-mail: claudia.vegabolivar@polito.it [JRC-Institute for Energy European Commission NL-1755 ZG Petten (Netherlands)

    2011-10-29

    Presently, one of the most interesting approaches to the generation of H{sub 2} is based on sulphur-based cycles, that however require structural components able to work in a corrosive environment at high temperature. Silicon carbide (SiC) is one of the most promising materials for this application, and to increase its limited toughness multilayered structures can be envisaged, since crack deviation and delamination increase energy adsorption during fracture. In this work tape casting and pressureless sintering were used to produce SiC samples consisting in alternating dense and porous layers, the porosity being realised by the insertion of pore forming agents during the preparation of the green ceramic. The mechanical properties of these materials were studied both at room temperature and at 1550 deg. C. The effect of corrosion at 850 deg. C by a mixture of H{sub 2}O, O{sub 2} and SO{sub 2} was studied by comparing microstructure and mechanical behaviour before and after long-term (1000 h) corrosion treatments. Corrosion resistance was very good, and flexural strength was strongly increased due to a combined effect of crack tip blunting and compressive residual stress formation. Concerning the architecture instead, the insertion of porous layers brings to a reduction of flexural strength, while Young's modulus remains almost constant.

  4. EFFECT OF THE Si POWDER ADDITIONS ON THE PROPERTIES OF SiC COMPOSITES

    Directory of Open Access Journals (Sweden)

    GUOGANG XU

    2012-09-01

    Full Text Available By means of transient plastic phase process, the SiC silicon carbide kiln furniture materials were produced through adding Si powder to SiC materials. At the condition of the same additions of SiO2 powder, the effect of the Si powder additions on properties of silicon carbide materials after sintered at 1450°C for 3 h in air atmosphere was studied by means of SEM and other analysis methods. The results showed that silicon powder contributes to both sintering by liquid state and plastic phase combination to improve the strength of samples. When the Si powder additions is lower than 3.5 %, the density and strength of samples increase and porosity decrease with increasing Si powder additions. However when the Si powder additions is higher than 3.5 %, the density and strength of samples decrease and porosity increase with increasing Si powder additions. With increasing of Si additions, the residual strength of sample after thermal shocked increased and linear change rate decreased, and get to boundary value when Si additions is 4.5 %. The results also indicated that at the same sintering temperature, the sample with 3.5 % silicon powder has maximum strength.

  5. Amorphous SiC layers for electrically conductive Rugate filters in silicon based solar cells

    Science.gov (United States)

    Janz, S.; Peters, M.; Künle, M.; Gradmann, R.; Suwito, D.

    2010-05-01

    The subject of this work is the development of an electrically conductive Rugate filter for photovoltaic applications. We think that the optical as well as the electrical performance of the filter can be adapted especially to the requirements of crystalline Si thin-film and amorphous/crystalline silicon tandem solar cells. We have deposited amorphous hydrogenated Silicon Carbide layers (a-SixC1-x:H) with the precursor gases methane (CH4), silane (SiH4) and diborane (B2H6) applying Plasma Enhanced Chemical Vapour Deposition (PECVD). Through changing just the precursor flows a floating refractive index n from 1.9 to 3.5 (at 633 nm) could be achieved quite accurately. Different complex layer stacks (up to 200 layers) with a sinusoidal refractive index variation normal to the incident light were deposited in just 80 min on 100x100 mm2. Transmission measurements show good agreement between simulation and experiment which proofs our ability to control the deposition process, the good knowledge of the optical behaviour of the different SiC single layers and the advanced stage of our simulation model. The doped single layers show lateral conductivities which were extremely dependent on the Si/C ratio.

  6. Radiometric flight results from the HyperSpectral Imager for Climate Science (HySICS)

    Science.gov (United States)

    Kopp, Greg; Smith, Paul; Belting, Chris; Castleman, Zach; Drake, Ginger; Espejo, Joey; Heuerman, Karl; Lanzi, James; Stuchlik, David

    2017-04-01

    Long-term monitoring of the Earth-reflected solar spectrum is necessary for discerning and attributing changes in climate. High radiometric accuracy enables such monitoring over decadal timescales with non-overlapping instruments, and high precision enables trend detection on shorter timescales. The HyperSpectral Imager for Climate Science (HySICS) is a visible and near-infrared spatial/spectral imaging spectrometer intended to ultimately achieve ˜ 0.2 % radiometric accuracies of Earth scenes from space, providing an order-of-magnitude improvement over existing space-based imagers. On-orbit calibrations from measurements of spectral solar irradiances acquired by direct views of the Sun enable radiometric calibrations with superior long-term stability than is currently possible with any manmade spaceflight light source or detector. Solar and lunar observations enable in-flight focal-plane array (FPA) flat-fielding and other instrument calibrations. The HySICS has demonstrated this solar cross-calibration technique for future spaceflight instrumentation via two high-altitude balloon flights. The second of these two flights acquired high-radiometric-accuracy measurements of the ground, clouds, the Earth's limb, and the Moon. Those results and the details of the uncertainty analyses of those flight data are described.

  7. Properties of amorphous SiC coatings deposited on WC-Co substrates

    Directory of Open Access Journals (Sweden)

    A.K. Costa

    2003-01-01

    Full Text Available In this work, silicon carbide films were deposited onto tungsten carbide from a sintered SiC target on a r.f. magnetron sputtering system. Based on previous results about the influence of r.f. power and argon pressure upon the properties of films deposited on silicon substrates, suitable conditions were chosen to produce high quality films on WC-Co pieces. Deposition parameters were chosen in order to obtain high deposition rates (about 30 nm/min at 400 W rf power and acceptable residual stresses (1.5 GPa. Argon pressure affects the energy of particles so that films with higher hardness (30 GPa were obtained at low pressures (0.05 Pa. Wear rates of the coated pieces against a chromium steel ball in a diamond suspension medium were found to be about half of the uncoated ones. Hardness and wear resistance measurements were done also in thermally annealed (200-800 °C samples revealing the effectiveness of SiC coatings to protect tool material against severe mechanical degradation resulting of high temperature (above 500 °C oxidation.

  8. Synthesis of graphene on SiC substrate via Ni-silicidation reactions

    International Nuclear Information System (INIS)

    Macháč, P.; Fidler, T.; Cichoň, S.; Mišková, L.

    2012-01-01

    In this work, the features of graphene layers are studied with the aim of preparing the thinnest layers possible. The graphene layers were prepared by the annealing of Ni/SiC structures. The main advantage of this process is a relatively low temperature compared with the method of graphene epitaxial growth on SiC and short annealing times compared with the chemical vapor deposition method. We prepared graphene layers from several Ni/SiC structures in which the Ni layer thickness ranged from 1 to 200 nm. The parameters of the annealing process (temperature, rate of temperature increase, annealing time) were modified during the experiments. The formed graphene layers were analyzed by means of Raman spectroscopy. From the spectra, the basic parameters of graphene, such as the number of carbon layers and crystallinity, were determined. The annealing of the Ni(200 nm)/SiC structure at 1080 °C for 10 s, produced graphene in the form of 3–4 carbon monolayers. The value was verified by X-ray Photoelectron Spectroscopy (XPS). Good agreement was achieved in the results obtained using Raman spectroscopy and XPS. - Highlights: ► Low temperature preparation of graphene by the annealing of Ni/SiC structures. ► Raman spectroscopy used for the analyzing of graphene layers. ► Optimal structure Ni(200)/SiC annealed at 1080 °C for 10 s. ► Graphene prepared in the form of 3–4 carbon monolayers.

  9. Understanding the Mechanism of SiC Plasma-Enhanced Chemical Vapor Deposition (PECVD) and Developing Routes toward SiC Atomic Layer Deposition (ALD) with Density Functional Theory.

    Science.gov (United States)

    Filatova, Ekaterina A; Hausmann, Dennis; Elliott, Simon D

    2018-04-17

    Understanding the mechanism of SiC chemical vapor deposition (CVD) is an important step in investigating the routes toward future atomic layer deposition (ALD) of SiC. The energetics of various silicon and carbon precursors reacting with bare and H-terminated 3C-SiC (011) are analyzed using ab initio density functional theory (DFT). Bare SiC is found to be reactive to silicon and carbon precursors, while H-terminated SiC is found to be not reactive with these precursors at 0 K. Furthermore, the reaction pathways of silane plasma fragments SiH 3 and SiH 2 are calculated along with the energetics for the methane plasma fragments CH 3 and CH 2 . SiH 3 and SiH 2 fragments follow different mechanisms toward Si growth, of which the SiH 3 mechanism is found to be more thermodynamically favorable. Moreover, both of the fragments were found to show selectivity toward the Si-H bond and not C-H bond of the surface. On the basis of this, a selective Si deposition process is suggested for silicon versus carbon-doped silicon oxide surfaces.

  10. Underlay of low-rate machine-type D2D links on downlink cellular links

    DEFF Research Database (Denmark)

    Pratas, Nuno K.; Popovski, Petar

    2014-01-01

    Wireless cellular networks feature two emerging technological trends: direct Device-to-Device (D2D) communications and Machine-Type Communications (MTC). MTC devices (MTDs) pose new challenges to the cellular network, such as low transmission power and massive access that can lead to overload...... connection allows underlay operation with Successive Interference Cancellation (SIC) during the cellular downlink transmissions. We consider different ways to use SIC and investigate the trade-off between, on one hand, the achieved rate for the downlink cellular users and, on the other hand, the outage...... probability for the MTC link. The results show that SIC is an important enabler of low-power underlay D2D transmission for low-rate machine-type traffic; however, it may incur a significant rate penalty for the cellular users when trying to meet the outage requirements of the MTC link....

  11. Modeling thermal and irradiation-induced swelling effects on the integrity of Ti 3 SiC 2 /SiC joints

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.

    2017-11-01

    Previously, results for CVD-SiC joints created using solid state displacement reactions to form a dual-phase SiC/MAX phase irradiated at 800°C and 5 dpa indicated some extent of cracking in the joint and along the CVD-SiC/joint interface. This paper elucidates the origin of cracking by thermomechanical modeling combined with irradiation-induced swelling effects using a continuum damage approach with support of micromechanical modeling. Three irradiation temperatures (400°C, 500°C and 800°C) are considered assuming experimental irradiation doses in a range leading to saturation swelling in SiC. The analyses indicate that a SiC/MAX joint heated to 400°C fails during irradiation-induced swelling at this temperature while it experiences some damage after being heated to 500°C and irradiated at the same temperature. However, it fails during cooling from 500°C to room temperature. The joint experiences minor damage when heated to and irradiated at 800°C but does not fail after cooling. The prediction agrees with the experimental findings available for this case.

  12. Durability and Design Issues of Thermal/environmental Barrier Coatings on Sic/sic Ceramic Matrix Composites Under 1650 C Test Conditions

    Science.gov (United States)

    Zhu, Dong-Ming; Choi, Sung R.; Ghosn, Louis J.; Miller, Robert A.

    2004-01-01

    Ceramic thermal/environmental barrier coatings for SiC-based ceramics will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. However, the coating durability remains a major concern with the ever-increasing temperature requirements. Currently, advanced T/EBC systems, which typically include a high temperature capable zirconia- (or hahia-) based oxide top coat (thermal barrier) on a less temperature capable mullite/barium-strontium-aluminosilicate (BSAS)/Si inner coat (environmental barrier), are being developed and tested for higher temperature capability Sic combustor applications. In this paper, durability of several thermal/environmental barrier coating systems on SiC/SiC ceramic matrix composites was investigated under laser simulated engine thermal gradient cyclic, and 1650 C (3000 F) test conditions. The coating cracking and delamination processes were monitored and evaluated. The effects of temperature gradients and coating configurations on the ceramic coating crack initiation and propagation were analyzed using finite element analysis (FEA) models based on the observed failure mechanisms, in conjunction with mechanical testing results. The environmental effects on the coating durability will be discussed. The coating design approach will also be presented.

  13. Ge-intercalated graphene: The origin of the p-type to n-type transition

    KAUST Repository

    Kaloni, Thaneshwor P.

    2012-09-01

    Recently huge interest has been focussed on Ge-intercalated graphene. In order to address the effect of Ge on the electronic structure, we study Ge-intercalated free-standing C 6 and C 8 bilayer graphene, bulk C 6Ge and C 8Ge, as well as Ge-intercalated graphene on a SiC(0001) substrate, by density functional theory. In the presence of SiC(0001), there are three ways to obtain n-type graphene: i) intercalation between C layers; ii) intercalation at the interface to the substrate in combination with Ge deposition on the surface; and iii) cluster intercalation. All other configurations under study result in p-type states irrespective of the Ge coverage. We explain the origin of the different doping states and establish the conditions under which a transition occurs. © Copyright EPLA, 2012.

  14. Photoluminescence Enhancement in Nanotextured Fluorescent SiC Passivated by Atomic Layer Deposited Al2O3 Films

    DEFF Research Database (Denmark)

    Lu, Weifang; Ou, Yiyu; Jokubavicius, Valdas

    2016-01-01

    The influence of thickness of atomic layer deposited Al2O3 films on nano-textured fluorescent 6H-SiC passivation is investigated. The passivation effect on the light emission has been characterized by photoluminescence and time-resolved photoluminescence at room temperature. The results show...... as passivation in fluorescent SiC based white LEDs applications....

  15. Wear behaviour of A356 aluminium alloy reinforced with micron and nano size SiC particles

    CSIR Research Space (South Africa)

    Camagu, ST

    2013-07-01

    Full Text Available A method for producing metal matrix composites MMC was successfully implemented for mixing nano and low micron (“Hybrid”) sized SiC reinforcing particles in an aluminium alloy matrix. Due to the improved specific modulus and strength, MMC...

  16. Circuit mismatch and current coupling effect influence on paralleling SiC MOSFETs in multichip power modules

    DEFF Research Database (Denmark)

    Li, Helong; Beczkowski, Szymon; Munk-Nielsen, Stig

    2015-01-01

    This paper reveals that there are circuit mismatches and a current coupling effect in the direct bonded copper (DBC) layout of a silicon carbide (SiC) MOSFET multichip power module. According to the modelling and the mathematic analysis of the DBC layout, the mismatch of the common source stray...

  17. Status of silicon carbide (SiC) as a wide-bandgap semiconductor for high-temperature applications: A review

    Science.gov (United States)

    Casady, J. B.; Johnson, R. W.

    1996-10-01

    Silicon carbide (SiC), a material long known with potential for high-temperature, high-power, high-frequency, and radiation hardened applications, has emerged as the most mature of the wide-bandgap (2.0 eV ≲ Eg ≲ 7.0 eV) semiconductors since the release of commercial 6HSiC bulk substrates in 1991 and 4HSiC substrates in 1994. Following a brief introduction to SiC material properties, the status of SiC in terms of bulk crystal growth, unit device fabrication processes, device performance, circuits and sensors is discussed. Emphasis is placed upon demonstrated high-temperature applications, such as power transistors and rectifiers, turbine engine combustion monitoring, temperature sensors, analog and digital circuitry, flame detectors, and accelerometers. While individual device performances have been impressive (e.g. 4HSiC MESFETs with fmax of 42 GHz and over 2.8 W mm -1 power density; 4HSiC static induction transistors with 225 W power output at 600 MHz, 47% power added efficiency (PAE), and 200 V forward blocking voltage), material defects in SiC, in particular micropipe defects, remain the primary impediment to wide-spread application in commercial markets. Micropipe defect densities have been reduced from near the 1000 cm -2 order of magnitude in 1992 to 3.5 cm -2 at the research level in 1995.

  18. Corrosion resistant coatings for SiC and Si{sub 3}N{sub 4} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Thierry; Shaokai Yang; J.J. Brown

    1998-09-01

    It is the goal of this program to (1) develop coatings for SiC and Si{sub 3}N{sub 4} that will enhance their performance as heat exchangers under coal combustion conditions and (2) to conduct an in-depth evaluation of the cause and severity of ceramic heat exchanger deterioration and failure under coal combustion conditions.

  19. Heteroepitaxial growth of SiC films by carbonization of polyimide Langmuir-Blodgett films on Si

    Directory of Open Access Journals (Sweden)

    Goloudina S.I.

    2017-01-01

    Full Text Available High quality single crystal SiC films were prepared by carbonization of polyimide Langmuir-Blodgett films on Si substrate. The films formed after annealing of the polyimide films at 1000°C, 1100°C, 1200°C were studied by Fourier transform-infrared (FTIR spectroscopy, X-ray diffraction (XRD, Raman spectroscopy, transmission electon microscopy (TEM, transmission electron diffraction (TED, and scanning electron microscopy (SEM. XRD study and HRTEM cross-section revealed that the crystalline SiC film begins to grow on Si (111 substrate at 1000°C. According to the HRTEM cross-section image five planes in 3C-SiC (111 film are aligned with four Si(111 planes at the SiC/Si interface. It was shown the SiC films (35 nm grown on Si(111 at 1200°C have mainly cubic 3C-SiC structure with a little presence of hexagonal polytypes. Only 3C-SiC films (30 nm were formed on Si (100 substrate at the same temperature. It was shown the SiC films (30-35 nm are able to cover the voids in Si substrate with size up to 10 μm.

  20. Fast neutron detection at near-core location of a research reactor with a SiC detector

    Science.gov (United States)

    Wang, Lei; Jarrell, Josh; Xue, Sha; Tan, Chuting; Blue, Thomas; Cao, Lei R.

    2018-04-01

    The measurable charged-particle produced from the fast neutron interactions with the Si and C nucleuses can make a wide bandgap silicon carbide (SiC) sensor intrinsically sensitive to neutrons. The 4H-SiC Schottky detectors have been fabricated and tested at up to 500 °C, presenting only a slightly degraded energy resolution. The response spectrum of the SiC detectors were also obtained by exposing the detectors to external neutron beam irradiation and at a near-core location where gamma-ray field is intense. The fast neutron flux of these two locations are ∼ 4 . 8 × 104cm-2 ṡs-1 and ∼ 2 . 2 × 107cm-2 ṡs-1, respectively. At the external beam location, a Si detector was irradiated side-by-side with SiC detector to disjoin the neutron response from Si atoms. The contribution of gamma ray, neutron scattering, and charged-particles producing reactions in the SiC was discussed. The fast neutron detection efficiencies were determined to be 6 . 43 × 10-4 for the external fast neutron beam irradiation and 6 . 13 × 10-6 for the near-core fast neutron irradiation.

  1. Reaction mechanisms at 4H-SiC/SiO2 interface during wet SiC oxidation

    Science.gov (United States)

    Akiyama, Toru; Hori, Shinsuke; Nakamura, Kohji; Ito, Tomonori; Kageshima, Hiroyuki; Uematsu, Masashi; Shiraishi, Kenji

    2018-04-01

    The reaction processes at the interface between SiC with 4H structure (4H-SiC) and SiO2 during wet oxidation are investigated by electronic structure calculations within the density functional theory. Our calculations for 4H-SiC/SiO2 interfaces with various orientations demonstrate characteristic features of the reaction depending on the crystal orientation of SiC: On the Si-face, the H2O molecule is stable in SiO2 and hardly reacts with the SiC substrate, while the O atom of H2O can form Si-O bonds at the C-face interface. Two OH groups are found to be at least necessary for forming new Si-O bonds at the Si-face interface, indicating that the oxidation rate on the Si-face is very low compared with that on the C-face. On the other hand, both the H2O molecule and the OH group are incorporated into the C-face interface, and the energy barrier for OH is similar to that for H2O. By comparing the calculated energy barriers for these reactants with the activation energies of oxide growth rate, we suggest the orientation-dependent rate-limiting processes during wet SiC oxidation.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    Amorphous WO x films were prepared on the SiC crystal by using two different methods, namely, reactive pulsed laser deposition (RPLD) and reactive deposition by ion sputtering (RDIS). After deposition, the WO x films were annealed in an air. The RISD film possessed a m-WO 3 structure and consisted of closely packed microcrystals. Localized swelling of the films and micro-hills growth did not destroy dense crystal packing. RPLD film had layered β-WO 3 structure with relatively smooth surface. Smoothness of the films were destroyed by localized swelling and the micro-openings formation was observed. Comparative study of m-WO 3 /SiC, Pt/m-WO 3 /SiC, and P-WO 3 /SiC samples shows that structural characteristics of the WO 3 films strongly influence on the voltage/current response as well as on the rate of current growth during H 2 detection at elevated temperatures. (paper)

  3. PENGARUH PEMBELAJARAN TEAM ASSISTED INDIVIDUALIZATION (TAI BERBANTUAN MEDIA SMART AND INTERESTING CARD (SIC TERHADAP HASIL BELAJAR SISWA

    Directory of Open Access Journals (Sweden)

    Kun Khuriya Pratiwi

    2015-11-01

    Full Text Available This experiment aimed to determine the influence of student’s learning outcomes of Senior High School (SHS in Parakan through the application of TAI (Team Assisted Individualization assisted of SIC (Smart and Interesting Card media on the subject of redox reaction. The population in this experiment were X grade students Senior High School (SHS in Parakan of the school year 2011/2012. Determination of the sample used cluster random sampling system that obtained two classes where X-3 as an experimental group that was treated by using TAI method assisted by SIC media and X-4 as a control group that was treated conventional methods. The research data was obtained by the method of documentation, testing, questionnaire and observation. The final analysis methods are normalization test, the similarity of two varians test, difference of two average test, gain test, biserial correlation, determination coefficient and analysis of questionnaire and observation sheet. The results showed that experiment class better than the control class. The results of study obtained results of the experimental group had an average 76,78 and a control group had an average of 67,82. TAI method assisted by SIC media give contribution to the learning outcome as 30%.Key words: TAI learning, SIC media 

  4. The impact of SiC substrate treatment on the heteroepitaxial growth of GaN by plasma assisted MBE

    Energy Technology Data Exchange (ETDEWEB)

    Brown, A.S.; Kim, T.H.; Choi, S.; Morse, M.; Wu, P. [Department of Electrical and Computer Engineering, Duke University, Durham, NC 27709 (United States); Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G. [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, and INSTM via Orabona 4 -70126, Bari (Italy)

    2005-11-01

    We report on the impact of the preparation of the Si-face 4H-SiC(0001){sub Si} substrate using a Ga flash-off process on the epitaxial growth of GaN by plasma-assisted molecular beam epitaxy. The nucleation, as well as the resultant structural and morphological properties of GaN grown directly on 4H-SiC(0001){sub Si} are strongly influenced by the chemical and morphological modifications of the SiC surface induced by the Ga flash-off process. Herein we describe the impact of the specific concentration of Ga incident on the surface (quantified in terms of monolayer (ML) coverage): of 0.5 ML, 1ML and 2ML. The residual oxygen at the SiC surface, unintentional SiC nitridation and the formation of cubic GaN grains during the initial nucleation stage, are all reduced when a 2 ML Ga flash is used. All of the above factors result in structural improvement of the GaN epitaxial layers. The correlation between the SiC surface modification, the initial nucleation stage, and the GaN epitaxial layer structural quality has been articulated using x-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy and spectroscopic ellipsometry data. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. A High Frequency (HF) Inductive Power Transfer Circuit for High Temperature Applications Using SiC Schottky Diodes

    Science.gov (United States)

    Jordan, Jennifer L.; Ponchak, George E.; Spry, David J.; Neudeck, Philip G.

    2018-01-01

    Wireless sensors placed in high temperature environments, such as aircraft engines, are desirable to reduce the mass and complexity of routing wires. While communication with the sensors is straight forward, providing power wirelessly is still a challenge. This paper introduces an inductive wireless power transfer circuit incorporating SiC Schottky diodes and its operation from room temperature (25 C) to 500 C.

  6. A Manufacturing Cost and Supply Chain Analysis of SiC Power Electronics Applicable to Medium-Voltage Motor Drives

    Energy Technology Data Exchange (ETDEWEB)

    Horowitz, Kelsey [National Renewable Energy Lab. (NREL), Golden, CO (United States); Remo, Timothy [National Renewable Energy Lab. (NREL), Golden, CO (United States); Reese, Samantha [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2017-03-24

    Wide bandgap (WBG) semiconductor devices are increasingly being considered for use in certain power electronics applications, where they can improve efficiency, performance, footprint, and, potentially, total system cost compared to systems using traditional silicon (Si) devices. Silicon carbide (SiC) devices in particular -- which are currently more mature than other WBG devices -- are poised for growth in the coming years. Today, the manufacturing of SiC wafers is concentrated in the United States, and chip production is split roughly equally between the United States, Japan, and Europe. Established contract manufacturers located throughout Asia typically carry out manufacturing of WBG power modules. We seek to understand how global manufacturing of SiC components may evolve over time by illustrating the regional cost drivers along the supply chain and providing an overview of other factors that influence where manufacturing is sited. We conduct this analysis for a particular case study where SiC devices are used in a medium-voltage motor drive.

  7. 11.72 sq cm SiC Wafer-scale Interconnected 64 kA PiN Diode

    Science.gov (United States)

    2012-01-30

    breakdown voltage yield of 83% was achieved. The diodes selected demonstrate sharp onsets of breakdown voltage as illustrated in Fig. 3. Diodes...645-648, pp. 1017-1020, 2010. [2] D. Peters, W. Bartsch , B. Thomas, and R. Sommer, ―6.5 kV SiC PiN Diodes with Improved Forward Characteristics

  8. Surface passivation of nano-textured fluorescent SiC by atomic layer deposited TiO2

    DEFF Research Database (Denmark)

    Lu, Weifang; Ou, Yiyu; Jokubavicius, Valdas

    2016-01-01

    Nano-textured surfaces have played a key role in optoelectronic materials to enhance the light extraction efficiency. In this work, morphology and optical properties of nano-textured SiC covered with atomic layer deposited (ALD) TiO2 were investigated. In order to obtain a high quality surface...

  9. Associations of Pd, U and Ag in the SiC layer of neutron-irradiated TRISO fuel

    Energy Technology Data Exchange (ETDEWEB)

    Lillo, Thomas [Idaho National Lab. (INL), Idaho Falls, ID (United States); Rooyen, Isabella Van [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-05-01

    Knowledge of the associations and composition of fission products in the neutron irradiated SiC layer of high-temperature gas reactor TRISO fuel is important to the understanding of various aspects of fuel performance that presently are not well understood. Recently, advanced characterization techniques have been used to examine fuel particles from the Idaho National Laboratory’s AGR-1 experiment. Nano-sized Ag and Pd precipitates were previously identified in grain boundaries and triple points in the SiC layer of irradiated TRISO nuclear fuel. Continuation of this initial research is reported in this paper and consists of the characterization of a relatively large number of nano-sized precipitates in three areas of the SiC layer of a single irradiated TRISO nuclear fuel particle using standardless EDS analysis on focused ion beam-prepared transmission electron microscopy samples. Composition and distribution analyses of these precipitates, which were located on grain boundaries, triple junctions and intragranular precipitates, revealed low levels, generally <10 atomic %, of palladium, silver and/or uranium with palladium being the most common element found. Palladium by itself, or associated with either silver or uranium, was found throughout the SiC layer. A small number of precipitates on grain boundaries and triple junctions were found to contain only silver or silver in association with palladium while uranium was always associated with palladium but never found by itself or in association with silver. Intergranular precipitates containing uranium were found to have migrated ~23 μm along a radial direction through the 35 μm thick SiC coating during the AGR-1 experiment while silver-containing intergranular precipitates were found at depths up to ~24 μm in the SiC layer. Also, Pd-rich, nano-precipitates (~10 nm in diameter), without evidence for the presence of either Ag or U, were revealed in intragranular regions throughout the SiC layer. Because not all

  10. Propiedades mecánicas de SiC biomórfico poroso

    Directory of Open Access Journals (Sweden)

    López Robledo, M. J.

    2005-10-01

    Full Text Available Biomorphic SiC (bioSiC materials fabricated by silicon infiltration of chescoal preforms have been studied. As a result of this process, a porous SiC ceramics with remnant silicon partially filling pores is obtained. This remnant silicon can considerably alter the mechanical properties of the bioSiC but it can be effectively removed by reaction with a mixture of HF and HNO3 producing a clean pororus bioSiC. In this work the comparison of the mechanical properties of bioSiC from preforms of beech, eucalyptus and pine, with and without remanent silicon is studied. High temperature mechanical properties were studied from deformation tests in compression at constant strain rate. Microstructural characterization of the samples, before and after the mechanical tests, was performed by scanning electron microscopy (SEM.

    Se han estudiado carburos de silicio biomórficos (bioSiC fabricados mediante infiltración reactiva de silicio líquido en una preforma de carbón de origen vegetal. Se obtiene así una cerámica porosa de SiC con silicio remanente en sus poros. Este silicio puede alterar considerablemente las propiedades mecánicas de los bioSiC. Este trabajo preliminar se centra en el estudio de las propiedades mecánicas de los bioSiC fabricados a partir de preformas de haya, eucalipto y pino, tras reacción con una disolución de HF y HNO3 que elimina ostensiblemente el silicio residual. Las propiedades mecánicas a altas temperaturas fueron estudiadas a partir de ensayos de compresión a velocidad de deformación constante. La caracterización microestructural del material resultante, antes y después de los ensayos mecánicos, fue realizada mediante Microscopía Electrónica de Barrido (MEB.

  11. Erosion behaviour of physically vapour-deposited and chemically vapour-deposited SiC films coated on molybdenum during oxygenated argon beam thinning

    International Nuclear Information System (INIS)

    Shikama, T.; Kitajima, M.; Fukutomi, M.; Okada, M.

    1984-01-01

    The erosion behaviour during bombardment with a 5 keV argon beam at room temperature was studied for silicon carbide (SiC) films of thickness of about 10 μm coated on molybdenum by physical vapour deposition (PVD) and chemical vapour deposition (CVD). The PVD SiC (plasma-assisted ion plating) exhibited a greater thinning rate than the CVD SiC film. Electron probe X-ray microanalysis revealed that the chemical composition of PVD SiC was changed to a composition enriched in silicon by the bombardment, and there was a notable change in its surface morphology. The CVD SiC retained its initial chemical composition with only a small change in its surface morphology. Auger electron spectroscopy indicated that silicon oxide was formed on the surface of PVD SiC by the bombardment. The greater thinning rate and easier change in chemical composition in PVD SiC could be attributed to its readier chemical reaction with oxygen due to its more non-uniform structure and weaker chemical bonding. Oxygen was present as one of the impurities in the argon beam. (Auth.)

  12. New criteria for sepsis-induced coagulopathy (SIC) following the revised sepsis definition: a retrospective analysis of a nationwide survey.

    Science.gov (United States)

    Iba, Toshiaki; Nisio, Marcello Di; Levy, Jerrold H; Kitamura, Naoya; Thachil, Jecko

    2017-09-27

    Recent clinical studies have shown that anticoagulant therapy might be effective only in specific at-risk subgroups of patients with sepsis and coagulation dysfunction. The definition of sepsis was recently modified, and as such, old scoring systems may no longer be appropriate for the diagnosis of sepsis-associated coagulopathy. The aim of this study was to evaluate prognostic factors in patients diagnosed with sepsis and coagulopathy according to the new sepsis definition and assess their accuracy in comparison with existing models. Retrospective analysis of the nationwide survey for recombinant human soluble thrombomodulin. General emergency and critical care centres in secondary and tertiary care hospitals. We evaluated the prognostic value of the newly proposed diagnostic criteria for sepsis-induced coagulopathy (SIC). A total of 1498 Japanese patients with sepsis and coagulopathy complications who were treated with recombinant thrombomodulin were analysed in this study. The platelet count, prothrombin time (PT) ratio, fibrinogen/fibrin degradation products, systemic inflammatory response syndrome score and Sequential Organ Failure Assessment (SOFA) score obtained just before the start of treatment were examined in relation to the 28-day mortality rate. The platelet count, PT ratio and total SOFA were independent predictors of a fatal outcome in a logistic regression model. A SIC score was defined using the three above-mentioned variables with a positivity threshold of 4 points or more. The SIC score predicted higher 28-day mortality rate compared with the current Japanese Association for Acute Medicine-disseminated intravascular coagulation score (38.4%vs34.7%). The SIC score is based on readily available parameters, is easy to calculate and has a high predictive value for 28-day mortality. Future studies are warranted to evaluate whether the SIC score may guide the decision to initiate anticoagulant therapy. © Article author(s) (or their employer(s) unless

  13. The nanostructure and microstructure of SiC surface layers deposited by MWCVD and ECRCVD

    Science.gov (United States)

    Dul, K.; Jonas, S.; Handke, B.

    2017-12-01

    Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) have been used to investigate ex-situ the surface topography of SiC layers deposited on Si(100) by Microwave Chemical Vapour Deposition (MWCVD) -S1,S2 layers and Electron Cyclotron Resonance Chemical Vapor Deposition (ECRCVD) - layers S3,S4, using silane, methane, and hydrogen. The effects of sample temperature and gas flow on the nanostructure and microstructure have been investigated. The nanostructure was described by three-dimensional surface roughness analysis based on digital image processing, which gives a tool to quantify different aspects of surface features. A total of 13 different numerical parameters used to describe the surface topography were used. The scanning electron image (SEM) of the microstructure of layers S1, S2, and S4 was similar, however, layer S3 was completely different; appearing like grains. Nonetheless, it can be seen that no grain boundary structure is present in the AFM images.

  14. Microstructure of nitrides grown on inclined c-plane sapphire and SiC substrate

    International Nuclear Information System (INIS)

    Imura, M.; Honshio, A.; Miyake, Y.; Nakano, K.; Tsuchiya, N.; Tsuda, M.; Okadome, Y.; Balakrishnan, K.; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I.

    2006-01-01

    High-quality (112-bar 0) GaN layers with atomically flat surface have been grown on a precisely offset-angle-controlled (11-bar 02) sapphire substrate by metal-organic vapor phase epitaxy (MOVPE). Insertion of AlGaN layer between underlying AlN layer and GaN was found to improve crystalline quality of upper GaN layer. In addition, a combination of high growth condition followed and epitaxial lateral overgrowth has been employed for the growth of GaN and this helped in reducing the dislocation density in the resultant layers. GaN and AlN were grown on (303-bar 8) SiC substrates by MOVPE and sublimation methods, respectively. The crystal orientation of GaN and AlN could be just aligned to that of the substrate. Microstructure analysis of the layers was also carried out by transmission electron microscopy

  15. Experimental Studies on SiC and Rice Husk Ash Reinforced Al Alloy Composite

    Directory of Open Access Journals (Sweden)

    Shivaprakash Y. M.

    2018-01-01

    Full Text Available In this research work Aluminium alloy with Cu (4.5% as the major alloying element is used as the matrix in which SiC and Rice Husk Ash (RHA are dispersed to develop a hybrid composite. The dispersion is done by the motorized stir casting arrangement. The composite is fabricated by varying the proportions of the reinforcements in the base alloy. The composite specimens were tested for density changes, hardness and the wear. The microstructure images showed a uniform dispersion of the reinforcements in the matrix and this resulted in higher strength to weight ratio. The increase in strength of the composite is probably attributed to the increase in the dislocation density. Also, the abrasive wear resistance of the produced composite is found to be superior as compared to the matrix alloy because of the hard-ceramic particles in the reinforcements.

  16. Effect of van der Waals interactions on the stability of SiC polytypes

    Energy Technology Data Exchange (ETDEWEB)

    Kawanishi, Sakiko, E-mail: s-kawa@tagen.tohoku.ac.jp; Mizoguchi, Teruyasu [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2016-05-07

    Density functional theory calculations with a correction of the long-range dispersion force, namely, the van der Waals (vdW) force, are performed for SiC polytypes. The lattice parameters are in good agreement with those obtained from the experiments. Furthermore, the stability of the polytypes in the experiments, which show 3C-SiC as the most stable, is reproduced by the present calculations. The effects of the vdW force on the electronic structure and the stability of polytypes are discussed. We observe that the vdW interaction is more sensitive to the cubic site than the hexagonal site. Thus, the influence of the vdW force increases with decreasing the hexagonality of the polytype, which results in the confirmation that the most stable polytype is 3C-SiC.

  17. A prescriptive intergenerational-tension ageism scale: succession, identity, and consumption (SIC).

    Science.gov (United States)

    North, Michael S; Fiske, Susan T

    2013-09-01

    We introduce a novel ageism scale, focusing on prescriptive beliefs concerning potential intergenerational tensions: active, envied resource succession, symbolic identity avoidance, and passive, shared-resource consumption (SIC). Four studies (2,010 total participants) were used to develop the scale. Exploratory factor analysis formed an initial 20-item, 3-factor solution (Study 1). The scale converges appropriately with other prejudice measures and diverges from other social control measures (Study 2). It diverges from antiyouth ageism (Study 3). The Study 4 experiment yielded both predictive and divergent validity apropos another ageism measure. Structural equation modeling confirmed model fit across all studies. Per an intergenerational-tension focus, younger people consistently scored the highest. As generational equity issues intensify, the scale provides a contemporary tool for current and future ageism research.

  18. SiC heat pump converters with support for voltage unbalance in distribution grids

    DEFF Research Database (Denmark)

    Trintis, Ionut; Douglass, Philip; Maheshwari, Ramkrishan

    2015-01-01

    in the transition to smart grids, and heat pumps are to be the first promising smart loads. They can be used for load shedding but also for unbalance compensation purposes. When they are equipped with a back to back compressor drive and a proper control strategy, grid support can be provided to reduce the negative......This paper studies the impact of involving the demand side of the LV grid into the grid conditioning process. Heat pumps are distribution loads with a substation capacity increase in the last years, with expectancy of growth in the coming years. Controlling the loads is the first step...... sequence component in the voltage at the installation point. Two control strategies are proposed and investigated experimentally on a SiC heat pump converter prototype....

  19. Design of a low parasitic inductance SiC power module with double-sided cooling

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Fei [The University of Tennessee, Knoxville; Liang, Zhenxian [Cree Inc.; Wang, Fei [ORNL; Wang, Zhiqiang [ORNL

    2017-03-01

    In this paper, a low-parasitic inductance SiC power module with double-sided cooling is designed and compared with a baseline double-sided cooled module. With the unique 3D layout utilizing vertical interconnection, the power loop inductance is effectively reduced without sacrificing the thermal performance. Both simulations and experiments are carried out to validate the design. Q3D simulation results show a power loop inductance of 1.63 nH, verified by the experiment, indicating more than 60% reduction of power loop inductance compared with the baseline module. With 0Ω external gate resistance turn-off at 600V, the voltage overshoot is less than 9% of the bus voltage at a load of 44.6A.

  20. Acousto-electric transport in MgO/ZnO-covered graphene on SiC

    Science.gov (United States)

    Liou, Y.-T.; Hernández-Mínguez, A.; Herfort, J.; Lopes, J. M. J.; Tahraoui, A.; Santos, P. V.

    2017-11-01

    We investigate the acousto-electric transport induced by surface acoustic waves (SAWs) in epitaxial graphene (EG) coated by a MgO/ZnO film. The deposition of a thin MgO layer protects the EG during the sputtering of a piezoelectric ZnO film for the efficient generation of SAWs. We demonstrate by Raman and electric measurements that the coating does not harm the EG structural and electronic properties. We report the generation of two SAW modes with frequencies around 2 GHz. For both modes, we measure acousto-electric currents in EG devices placed in the SAW propagation path. The currents increase linearly with the SAW power, reaching values up to almost two orders of magnitude higher than in previous reports for acousto-electric transport in EG on SiC. Our results agree with the predictions from the classical relaxation model of the interaction between SAWs and a two dimensional electron gas.

  1. Crack growth in glass matrix composite reinforced by long SiC fibres

    Czech Academy of Sciences Publication Activity Database

    Kotoul, M.; Vysloužil, T.; Boccaccini, A. R.; Dlouhý, Ivo

    2008-01-01

    Roč. 49, č. 2 (2008), s. 158-170 ISSN 0167-8442 R&D Projects: GA ČR(CZ) GA101/05/0320; GA ČR(CZ) GA106/05/0495; GA ČR(CZ) GA106/06/0724 Institutional research plan: CEZ:AV0Z20410507 Keywords : brittle matrix composites * SiC fibres * Chevron-notch specimen * crack bridging * R-curve modelling * Weight functions Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.011, year: 2008 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V55-4R8MDGM-1&_user=625109&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000031719&_version=1&_urlVersion=0&_userid=625109&md5=a4cd27b71f0d9e50e49f28aa2e8a71ff

  2. Graphene etching on SiC grains as a path to interstellar polycyclic aromatic hydrocarbons formation.

    Science.gov (United States)

    Merino, P; Švec, M; Martinez, J I; Jelinek, P; Lacovig, P; Dalmiglio, M; Lizzit, S; Soukiassian, P; Cernicharo, J; Martin-Gago, J A

    2014-01-01

    Polycyclic aromatic hydrocarbons as well as other organic molecules appear among the most abundant observed species in interstellar space and are key molecules to understanding the prebiotic roots of life. However, their existence and abundance in space remain a puzzle. Here we present a new top-down route to form polycyclic aromatic hydrocarbons in large quantities in space. We show that aromatic species can be efficiently formed on the graphitized surface of the abundant silicon carbide stardust on exposure to atomic hydrogen under pressure and temperature conditions analogous to those of the interstellar medium. To this aim, we mimic the circumstellar environment using ultra-high vacuum chambers and investigate the SiC surface by in situ advanced characterization techniques combined with first-principles molecular dynamics calculations. These results suggest that top-down routes are crucial to astrochemistry to explain the abundance of organic species and to uncover the origin of unidentified infrared emission features from advanced observations.

  3. Generation of periodic structures on SiC upon laser plasma XUV/NIR radiations

    Czech Academy of Sciences Publication Activity Database

    Gemini, L.; Margarone, Daniele; Trusso, S.; Juha, Libor; Limpouch, Jiří; Mocek, Tomáš; Ossi, P.M.

    2013-01-01

    Roč. 31, č. 3 (2013), s. 547-550 ISSN 0263-0346 R&D Projects: GA MŠk ED1.1.00/02.0061; GA MŠk EE.2.3.20.0087; GA MŠk ED2.1.00/01.0027 Grant - others:ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061; OP VK 2 LaserGen(XE) CZ.1.07/2.3.00/20.0087; HILASE(XE) CZ.1.05/2.1.00/01.0027 Institutional support: RVO:68378271 Keywords : generation of periodic structures * laser plasma irradiation of SiC * LDPE plasma formation by ultra-short pulse laser * XUV/NIR dual action Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.701, year: 2013

  4. A study on the reaction between SiC and Pd, (2)

    International Nuclear Information System (INIS)

    Namba, Takashi; Minato, Kazuo; Yamawaki, Michio; Fukuda, Kousaku.

    1989-01-01

    An out of pile experiment was performed on the corrosion of the SiC layer by fission product Pd in the Triso-coated fuel particles of high temperature gas-cooled reactor. In order to clarify the corrosion mechanism, influence of Pd activity on the corrosion was studied. Seven Au-Pd alloys with different Pd contents were prepared and simulated TRISO-coated particles were heated in the powder of the alloys at 1473 and 1573K. The Pd-SiC reaction zones were observed and analyzed by XMA. From the experimental results, the reaction rate was found to be dependent on Pd activity. The dependence of the reaction rate on temperature and time was also discussed. (author)

  5. SiC materials: a semiconductor family for the next century

    Science.gov (United States)

    Camassel, Jean; Contreras, Sylvie; Robert, Jean-Louis

    2000-03-01

    The current status of SiC semiconductor materials is reviewed, with emphasize on forthcoming applications. In a first part one focuses on the most important physical properties. Then, power device and micro-opto-electronic applications, using both 4H and 6H-SiC, are presented. Technological problems which have to be solved in order to realize simple planar device are considered. Emphasize is set on the French and European efforts, and on the USA and Japan's ones. In a second part, one deals with advanced high temperature industrial sensor applications. Interest for cubic 3C-SiC eposited on Silicon On Insulator (SOI) is demonstrated and results of comparative examinations of different 3CSiC/SOI materials are briefly given.

  6. CALIBRATING THE JOHNSON-HOLMQUIST CERAMIC MODEL FOR SIC USING CTH

    International Nuclear Information System (INIS)

    Cazamias, J. U.; Bilyk, S. R.

    2009-01-01

    The Johnson-Holmquist ceramic material model has been calibrated and successfully applied to numerically simulate ballistic events using the Lagrangian code EPIC. While the majority of the constants are ''physics'' based, two of the constants for the failed material response are calibrated using ballistic experiments conducted on a confined cylindrical ceramic target. The maximum strength of the failed ceramic is calibrated by matching the penetration velocity. The second refers to the equivalent plastic strain at failure under constant pressure and is calibrated using the dwell time. Use of these two constants in the CTH Eulerian hydrocode does not predict the ballistic response. This difference may be due to the phenomenological nature of the model and the different numerical schemes used by the codes. This paper determines the aforementioned material constants for SiC suitable for simulating ballistic events using CTH.

  7. Optical beam induced current measurements: principles and applications to SiC device characterization

    Energy Technology Data Exchange (ETDEWEB)

    Raynaud, Christophe; Nguyen, Duy-Minh; Dheilly, Nicolas; Tournier, Dominique; Brosselard, Pierre; Lazar, Mihai; Planson, Dominique [Ampere Laboratory UMR CNRS, INSA de Lyon, Villeurbanne (France)

    2009-10-15

    This paper deals with the characterization of SiC devices by optical beam induced currents (OBIC). OBIC is a technique that measures a photocurrent in response to a fine UV laser beam that is scanned laterally over the surface of the device. In this way a number of important material and device parameters can be derived. We concentrate here on three aspects, the field profile in reverse biased diodes with particular emphasis on field terminating issues at the device edges under high reverse voltages; the minority carrier lifetimes in 6H-SiC; and the determination of ionization coefficients for electrons and holes in 6H-SiC. The latter are important material parameters for the modelling of high power devices and determine their break-through voltage. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Structural and electronic properties of Si nanocrystals embedded in amorphous SiC matrix

    International Nuclear Information System (INIS)

    Song Chao; Rui Yunjun; Wang Quanbiao; Xu Jun; Li Wei; Chen Kunji; Zuo Yuhua; Wang Qiming

    2011-01-01

    Research highlights: → Amorphous silicon carbide thin films were annealed at 900 deg. C and 1000 deg. C to form Si nanocrystals embedded in amorphous SiC matrix. The average size of Si nanocrystals is around 7-9 nm. For the sample annealed at 1000 o C, the crystallinity can be reached to 70%. → As increasing the annealing temperature, the dark conductivity is increased accompanying with the increase of crystallinity of the film. The dark conductivity reaches to 1.2 x 10 -6 S cm -1 for the sample annealed at 1000 o C, which is 4 orders of magnitude higher than that of as-deposited film. → The possible transport mechanism was proposed and discussed. The temperature-dependent conductivity results reveal that the carrier transport process is dominated by the thermally activated transport process. - Abstract: Si-rich hydrogenated amorphous silicon carbide thin films were prepared by plasma-enhanced chemical vapor deposition technique. As-deposited films were subsequently annealed at 900 deg. C and 1000 deg. C to form Si nanocrystals embedded in amorphous SiC matrix. Raman spectra demonstrate the formation of Si nanocrystals with size around 7-9 nm. For the sample annealed at 1000 o C, the crystallinity can be reached to 70%. As increasing the annealing temperature, the dark conductivity is increased accompanying with the increase of crystallinity of the film. The dark conductivity reaches to 1.2 x 10 -6 S cm -1 for the sample annealed at 1000 deg. C, which is 4 orders of magnitude higher than that of as-deposited film. It is found that the carrier transport process is dominated by the thermally activated transport process according to the temperature-dependent conductivity results.

  9. Original Ge-induced phenomena on various SiC(0 0 0 1) reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Ait-Mansour, K [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Dentel, D [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Kubler, L [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Diani, M [LSGM, Departement de Physique, Faculte des Sciences et Techniques, Tanger BP 416 (Morocco); Derivaz, M [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Bischoff, J L [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France)

    2007-10-21

    Using complementary surface analysis techniques, we study the Ge growth on distinct SiC(0 0 0 1) reconstructions and elucidate complex mechanisms occurring by thermal activation. Two Si-rich reconstructions (3 x 3) and ({radical}3 x {radical}3)R30{sup 0}({radical}3), and one C-rich, (6{radical}3 x 6{radical}3)R30{sup 0}(6{radical}3), are concerned, on which Ge is found to grow in Stranski-Krastanov and Volmer-Weber modes, respectively. The best Ge-wetting layer is favoured on the {radical}3 (less Si-rich) because closest to a perfect truncated SiC(0 0 0 1) termination. At sufficiently high temperature, the Ge-wetting layer is organized in the form of a (4 x 4)Ge reconstruction for which we propose a first atomic model that is based on the 3 x 3 structure. Annealing Ge on the (3 x 3) and 6{radical}3 surfaces provokes spectacular successive 2D/3D and unusual 3D/2D transitions not only of Ge but also of Si and C, respectively, coming from the surface initial richness. In both cases, a phase separation is observed either in the 2D or 3D structures, which is unexpected for the Ge/Si binary system and somewhat usual for the Ge/C one. In the case of Ge on 6{radical}3, a special 2D heterostructure graphite/Ge/SiC is achieved at the atomic level. This acts as a Schottky barrier and then can be promising for future possible applications. (review article)

  10. Effects of SiC nanoparticles orally administered in a rat model: Biodistribution, toxicity and elemental composition changes in feces and organs

    Energy Technology Data Exchange (ETDEWEB)

    Lozano, Omar, E-mail: omar.lozanogarcia@fundp.ac.be [Namur Nanosafety Center (NNC), NAmur Research Institute for LIfe Sciences (NARILIS), University of Namur - FUNDP, Rue de Bruxelles 61, B-5000 Namur (Belgium); Research Centre for the Physics of Matter and Radiation (PMR-LARN), University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Laloy, Julie; Alpan, Lütfiye [Namur Nanosafety Center (NNC), NAmur Research Institute for LIfe Sciences (NARILIS), University of Namur - FUNDP, Rue de Bruxelles 61, B-5000 Namur (Belgium); Department of Pharmacy, NAMEDIC, Namur Thrombosis and Hemostasis Center (NTHC), University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Mejia, Jorge [Namur Nanosafety Center (NNC), NAmur Research Institute for LIfe Sciences (NARILIS), University of Namur - FUNDP, Rue de Bruxelles 61, B-5000 Namur (Belgium); Research Centre for the Physics of Matter and Radiation (PMR-LARN), University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Rolin, Stéphanie [Namur Nanosafety Center (NNC), NAmur Research Institute for LIfe Sciences (NARILIS), University of Namur - FUNDP, Rue de Bruxelles 61, B-5000 Namur (Belgium); Department of Pharmacy, NAMEDIC, Namur Thrombosis and Hemostasis Center (NTHC), University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Toussaint, Olivier [Namur Nanosafety Center (NNC), NAmur Research Institute for LIfe Sciences (NARILIS), University of Namur - FUNDP, Rue de Bruxelles 61, B-5000 Namur (Belgium); Laboratory of Biochemistry and Cellular Biology (URBC), University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Dogné, Jean-Michel [Namur Nanosafety Center (NNC), NAmur Research Institute for LIfe Sciences (NARILIS), University of Namur - FUNDP, Rue de Bruxelles 61, B-5000 Namur (Belgium); Department of Pharmacy, NAMEDIC, Namur Thrombosis and Hemostasis Center (NTHC), University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); and others

    2012-10-15

    Background: Silicon carbide (SiC) presents noteworthy properties as a material such as high hardness, thermal stability, and photoluminescent properties as a nanocrystal. However, there are very few studies in regard to the toxicological potential of SiC NPs. Objectives: To study the toxicity and biodistribution of silicon carbide (SiC) nanoparticles in an in vivo rat model after acute (24 h) and subacute (28 days) oral administrations. The acute doses were 0.5, 5, 50, 300 and 600 mg·kg{sup −1}, while the subacute doses were 0.5 and 50 mg·kg{sup −1}. Results: SiC biodistribution and elemental composition of feces and organs (liver, kidneys, and spleen) have been studied by Particle-Induced X-ray Emission (PIXE). SiC and other elements in feces excretion increased by the end of the subacute assessment. SiC did not accumulate in organs but some elemental composition modifications were observed after the acute assessment. Histopathological sections from organs (stomach, intestines, liver, and kidneys) indicate the absence of damage at all applied doses, in both assessments. A decrease in the concentration of urea in blood was found in the 50 mg·kg{sup −1} group from the subacute assessment. No alterations in the urine parameters (sodium, potassium, osmolarity) were found. Conclusion: This is the first study that assesses the toxicity, biodistribution, and composition changes in feces and organs of SiC nanoparticles in an in vivo rat model. SiC was excreted mostly in feces and low traces were retrieved in urine, indicating that SiC can cross the intestinal barrier. No sign of toxicity was however found after oral administration. -- Highlights: ► SiC nanoparticles were orally administered to rats in acute and subacute doses. ► SiC was found in low traces in urine. It is mostly excreted in feces within 5 days. ► SiC excretion rate, feces and organ elemental composition change with time. ► No morphological alteration were found on GI tract, liver, kidneys

  11. Short-circuit ruggedness assessment of a 1.2 kV/180 A SiC MOSFET power module

    DEFF Research Database (Denmark)

    Ionita, Claudiu; Nawaz, Muhammad; Ilves, Kalle

    2017-01-01

    While investigations on short-circuit ruggedness of discrete SiC MOSFET are widely encountered in the scientific literature, there is not so much research dealing with the operational robustness of high power SiC MOSFET modules. In this paper, the short-circuit (SC) ruggedness under hard switching...... fault (HSF) of a commercial 1.2 kV/180 A SiC MOSFET power module in half-bridge configuration will be presented. The test conditions, such as DC-link voltage (VDC), gate resistance (Rg) and gate-source supply voltage (VGS) are varied systematically to investigate the effect of these parameters...

  12. Growth of Hexagonal Columnar Nanograin Structured SiC Thin Films on Silicon Substrates with Graphene–Graphitic Carbon Nanoflakes Templates from Solid Carbon Sources

    Science.gov (United States)

    Liu, Xingfang; Sun, Guosheng; Liu, Bin; Yan, Guoguo; Guan, Min; Zhang, Yang; Zhang, Feng; Chen, Yu; Dong, Lin; Zheng, Liu; Liu, Shengbei; Tian, Lixin; Wang, Lei; Zhao, Wanshun; Zeng, Yiping

    2013-01-01

    We report a new method for growing hexagonal columnar nanograin structured silicon carbide (SiC) thin films on silicon substrates by using graphene–graphitic carbon nanoflakes (GGNs) templates from solid carbon sources. The growth was carried out in a conventional low pressure chemical vapor deposition system (LPCVD). The GGNs are small plates with lateral sizes of around 100 nm and overlap each other, and are made up of nanosized multilayer graphene and graphitic carbon matrix (GCM). Long and straight SiC nanograins with hexagonal shapes, and with lateral sizes of around 200–400 nm are synthesized on the GGNs, which form compact SiC thin films. PMID:28809227

  13. Wear-triggered self-healing behavior on the surface of nanocrystalline nickel aluminum bronze/Ti3SiC2 composites

    Science.gov (United States)

    Zhai, Wenzheng; Lu, Wenlong; Zhang, Po; Wang, Jian; Liu, Xiaojun; Zhou, Liping

    2018-04-01

    Self-healing can protect materials from diverse damages, but is intrinsically difficult in metals. This paper demonstrates a potential method through a simultaneous decomposition and oxidation of Ti3SiC2 to achieve healing of stress cracking on the surface of nickel aluminum bronze (NAB)/Ti3SiC2 nanocrystalline composites during fretting wear. At the finest nanocrystalline materials, a crack recovery would be attained at 76.5%. The repetitive fretting wear leads to a modest amount of 'flowability' of Ti3SiC2 toward the crack, facilitating crack recovery. Along with the wear-triggered self-healing, the NAB/Ti3SiC2 shows an improved tribological performance with the stable decreased friction torque due to the formation of lubrication TiO2 oxide.

  14. Effect of high temperature annealing on the grain size of CVD-grown SiC and experimental PBMR TRISO coated particles

    CSIR Research Space (South Africa)

    Mokoduwe, SM

    2010-10-01

    Full Text Available Recent research and development activities of the PBMR Fuel Characterization and Optimization Programme focused on the high temperature characteristics of the PBMR fuel and more specifically on the SiC layer. PBMR fuel consists of Tri...

  15. Integrated SiC Super Junction Transistor-Diode Devices for High-Power Motor Control ModulesOoperating at 500 C, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Monolithic Integrated SiC Super Junction Transistor-JBS diode (MIDSJT) devices are used to construct 500oC capable motor control power modules for direct integration...

  16. A possibility of enhancing Jc in MgB2 film grown on metallic hastelloy tape with the use of SiC buffer layer

    International Nuclear Information System (INIS)

    Putri, W. B. K.; Kang, B.; Ranot, M.; Lee, J. H.; Kang, W. N.

    2014-01-01

    We have grown MgB 2 on SiC buffer layer by using metallic Hastelloy tape as the substrate. Hastelloy tape was chosen for its potential practical applications, mainly in the power cable industry. SiC buffer layers were deposited on Hastelloy tapes at 400, 500, and 600 degrees C by using a pulsed laser deposition method, and then by using a hybrid physical-chemical vapor deposition technique, MgB 2 films were grown on the three different SiC buffer layers. An enhancement of critical current density values were noticed in the MgB 2 films on SiC/Hastelloy deposited at 500 and 600 degrees C. From the surface analysis, smaller and denser grains of MgB 2 tapes are likely to cause this enhancement. This result infers that the addition of SiC buffer layers may contribute to the improvement of superconducting properties of MgB 2 tapes.

  17. Effect of turning parameters on surface roughness of A356/5% SiC composite produced by electromagnetic stir casting

    Energy Technology Data Exchange (ETDEWEB)

    Dwivedi, S. P.; Kumar, Sudhir; Kumar, Ajay [Noida Institute of Engineering Technology, U.P (India)

    2012-12-15

    In the present investigation, A356 alloy 5 wt% SiC composite is fabricated by electromagnetic stir casting process. An attempt has been made to investigate the effect of CNC lathe process parameters like cutting speed, depth of cut, and feed rate on surface roughness during machining of A356 alloy 5 wt% SiC particulate metal-matrix composites in dry condition. Response surface methodology (Box Behnken Method) is chosen to design the experiments. The results reveal that cutting speed increases surface roughness decreases, whereas depth of cut and feed increase surface roughness increase. Optimum values of speed (190 m/min), feed (0.14 mm/rev) and depth of cut (0.20 mm) during turning of A356 alloy 5 wt% SiC composites to minimize the surface roughness (3.15>m) have been find out. The mechanical properties of A356 alloy 5 wt% SiC were also analyzed.

  18. Characterization and formation of NV centers in 3 C , 4 H , and 6 H SiC: An ab initio study

    Science.gov (United States)

    Csóré, A.; von Bardeleben, H. J.; Cantin, J. L.; Gali, A.

    2017-08-01

    Fluorescent paramagnetic defects in solids have become attractive systems for quantum information processing in recent years. One of the leading contenders is the negatively charged nitrogen-vacancy (NV) defect in diamond with visible emission, but an alternative solution in a technologically mature host is an immediate quest for many applications in this field. It has been recently found that various polytypes of silicon carbide (SiC), that are standard semiconductors with wafer scale technology, can host a NV defect that could be an alternative qubit candidate with emission in the near infrared region. However, there is much less known about this defect than its counterpart in diamond. The inequivalent sites within a polytype and the polytype variations offer a family of NV defects. However, there is an insufficient knowledge on the magneto-optical properties of these configurations. Here we carry out density functional theory calculations, in order to characterize the numerous forms of NV defects in the most common polytypes of SiC including 3 C , 4 H , and 6 H , and we also provide new experimental data in 4 H SiC. Our calculations mediate the identification of individual NV qubits in SiC polytypes. In addition, we discuss the formation of NV defects in SiC, providing detailed ionization energies of NV defects in SiC, which reveals the critical optical excitation energies for ionizing these qubits in SiC. Our calculations unravel the challenges to produce NV defects in SiC with a desirable spin bath.

  19. Evaluations of thermal shock resistance and fracture toughness of SiC as a gas turbine blade at high temperatures. Gas turbine yo SiC yokuzai no koon ni okeru tainetsu shogekisei no hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Sato, S.; Kurumada, A.; Kudo, Y.; Chikahata, H.; Shibano, M.; Miyata, H. (Ibaraki Univ., Ibaraki (Japan). Faculty of Engineering Hitachi Ltd., Tokyo (Japan))

    1989-12-20

    This paper shows the results of the experiments on the thermal shock resistance and the thermal shock fracture toughness of ceramic blade used for high quality high temperature gas turbines. Using disk specimens of alpha SiC blade, the thermal shock resistance and the thermal shock fracture toughness are determined by means of Joule {prime} s heating at a central area of disk specimens at 1000 {degree} C (4.3 sec.) and at 1200 {degree} C, 1300 {degree} C, and 1600 {degree} C (4.5 sec.) . Both of the thermal shock resistance and fracture toughness decreases as the temperature increases until 1300 {degree} C, and then increases from 1300 to 1600 {degree} C. Both show maximum values at 1600 {degree} C. The writers consider that this is due to the stress release by the increase of ductility at high temperature. The experiments were also performed for SC-101 which is used for semiconductor base as reference material. The thermal shock resistance and fracture toughness of SC-101 at 1200 {degree} C is three times and 1.4 times larger respectively than SiC. The writers considered that it is caused by the high thermal conductivity three times larger than alpha SiC. 11 refs., 12 figs.

  20. Accurate evaluation of fast threshold voltage shift for SiC MOS devices under various gate bias stress conditions

    Science.gov (United States)

    Sometani, Mitsuru; Okamoto, Mitsuo; Hatakeyama, Tetsuo; Iwahashi, Yohei; Hayashi, Mariko; Okamoto, Dai; Yano, Hiroshi; Harada, Shinsuke; Yonezawa, Yoshiyuki; Okumura, Hajime

    2018-04-01

    We investigated methods of measuring the threshold voltage (V th) shift of 4H-silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) under positive DC, negative DC, and AC gate bias stresses. A fast measurement method for V th shift under both positive and negative DC stresses revealed the existence of an extremely large V th shift in the short-stress-time region. We then examined the effect of fast V th shifts on drain current (I d) changes within a pulse under AC operation. The fast V th shifts were suppressed by nitridation. However, the I d change within one pulse occurred even in commercially available SiC MOSFETs. The correlation between I d changes within one pulse and V th shifts measured by a conventional method is weak. Thus, a fast and in situ measurement method is indispensable for the accurate evaluation of I d changes under AC operation.