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Sample records for cubic sic 3c-sic

  1. Effects of SiC amount on phase compositions and properties of Ti3SiC2-based composites

    Institute of Scientific and Technical Information of China (English)

    蔡艳芝; 殷小玮; 尹洪峰

    2015-01-01

    The phase compositions and properties of Ti3SiC2-based composites with SiC addition of 5%−30% in mass fraction fabricated by in-situ reaction and hot pressing sintering were studied. SiC addition effectively prevented TiC synthesis but facilitated SiC synthesis. The Ti3SiC2/TiC−SiC composite had better oxidation resistance when SiC added quantity reached 20% but poorer oxidation resistance with SiC addition under 15%than Ti3SiC2/TiC composite at higher temperatures. There were more than half of the original SiC and a few Ti3SiC2 remaining in Ti3SiC2/TiC−SiC with 20% SiC addition, but all constituents in Ti3Si2/TiC composite were oxidized after 12 h in air at 1500 °C. The oxidation scale thickness of TS30, 1505.78μm, was near a half of that of T, 2715μm, at 1500 °C for 20 h. Ti3SiC2/TiC composite had a flexural strength of 474 MPa, which was surpassed by Ti3SiC2/TiC−SiC composites when SiC added amount reached 15%. The strength reached the peak of 518 MPa at 20%SiC added amount.

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. Switching Performance Evaluation of Commercial SiC Power Devices (SiC JFET and SiC MOSFET) in Relation to the Gate Driver Complexity

    DEFF Research Database (Denmark)

    Pittini, Riccardo; Zhang, Zhe; Andersen, Michael A. E.

    2013-01-01

    and JFETs. The recent introduction of SiC MOSFET has proved that it is possible to have highly performing SiC devices with a minimum gate driver complexity; this made SiC power devices even more attractive despite their device cost. This paper presents an analysis based on experimental results...... of the switching losses of various commercially available Si and SiC power devices rated at 1200 V (Si IGBTs, SiC JFETs and SiC MOSFETs). The comparison evaluates the reduction of the switching losses which is achievable with the introduction of SiC power devices; this includes analysis and considerations...

  7. Irradiation damages in Ti3SiC2

    International Nuclear Information System (INIS)

    Nappe, J.C.; Grosseau, Ph.; Guilhot, B.; Audubert, F.; Beauvy, M.

    2007-01-01

    Carbides, by their remarkable properties, are considered as possible materials (fuel cans) in reactor of generation IV. Among those studied, Ti 3 SiC 2 is particularly considered because it joins both the ceramics and metals properties. Nevertheless, its behaviour under irradiation is not known. Characterizations have been carried out on samples irradiated at 75 MeV krypton ions. They have revealed that TiO 2 (formed at the surface of Ti 3 SiC 2 ) is pulverized by the irradiation and that the crystal lattice of Ti 3 SiC 2 dilates with c. (O.M.)

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

    Indian Academy of Sciences (India)

    Administrator

    phous SiC to cubic nano-crystalline SiC films with the increase in the gas flow ratio. Raman scattering ... Auger electron spectroscopy showed that the carbon incorporation in the .... with a 514 nm Ar+ laser excitation source and the laser.

  9. 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.

  10. TiC/Ti3SiC2复合材料的制备及其性能研究%Preparation and properties of TiC/Ti3SiC2 composites

    Institute of Scientific and Technical Information of China (English)

    贾换; 尹洪峰; 袁蝴蝶; 杨祎诺

    2012-01-01

    以粉末Ti,Si,TiC和炭黑为原料,采用反应热压烧结法制备TiC/Ti3SiC2复合材料.借助XRD和SEM研究TiC含量对TiC/Ti3SiC2复合材料相组成、显微结构及力学特性的影响.结果表明:通过热压烧结可以得到致密度较高的TiC/Ti3SiC2复合材料;引入TiC可以促进Ti3SiC2的生成,当引入TiC的质量分数达30%,TiC/Ti3SiC2复合材料的弯曲强度和断裂韧性分别为406.9 MPa,3.7 MPa·m1/2;复合材料中Ti3SiC2相以穿晶断裂为主,TiC晶粒易产生拔出.%TiC/Ti3SiC2 composites were fabricated by reactive hot pressing sintering method using the mixture powder of Ti, Si, C and TiC as raw material. The effect of TiC content on phase composition, microstructure and mechanical properties of TiC/Ti3SiC2 composites was investigated by X-ray diffraction and scanning electron microscopy. The results demonstrate that dense TiC/ Ti3SiC2 composites can be obtained by hot pressing. The addition of TiC into composites can enhance the formation of TisSiC2. When the additional content of TiC reaches 30% (mass fraction) , the flexural strength and fracture toughness of TiC/Ti3SiC2 composite are 406.9 MPa and 3.7 MPa·m-2, respectively. Ti3SiC2 phase displays intergranular fracture and TiC grain pulls out from Ti3SiC2 matrix when TiC/Ti3SiC2 composite fractures.

  11. 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.

  12. Palladium transport in SiC

    International Nuclear Information System (INIS)

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

    2012-01-01

    Highlights: ► We investigate the reaction of Pd with SiC at typical HTGR operating temperatures. ► The high temperature mobility of palladium silicides within polycrystalline SiC was studied. ► Corrosion of SiC by Pd was seen in all cases. ► The preferential corrosion and penetration of Pd along grain boundaries in SiC was found. ► The penetration and transport of palladium silicides in SiC along grain boundaries was found. - Abstract: This paper reports on a transmission electron microscopy (TEM) and scanning electron microscopy (SEM) study of Pd corroded SiC. The reaction of Pd with different types of SiC at typical HTGR operating temperatures was examined. In addition the high temperature mobility of palladium silicides within polycrystalline SiC was investigated. The results indicated corrosion of the SiC by Pd in all cases studied. The corrosion leads to the formation of palladium silicides within the SiC, with the predominant phase found being Pd 2 Si. Evidence for the preferential corrosion and penetration of Pd along grain boundaries in polycrystalline SiC was found. The penetration and transport, without significant corrosion, of palladium silicides into polycrystalline SiC along grain boundaries was also observed. Implications of the findings with reference to the use of Tri Isotropic particles in HTGRs will be discussed.

  13. Palladium transport in SiC

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, E.J., E-mail: jolivier@nmmu.ac.za [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Neethling, J.H. [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer We investigate the reaction of Pd with SiC at typical HTGR operating temperatures. Black-Right-Pointing-Pointer The high temperature mobility of palladium silicides within polycrystalline SiC was studied. Black-Right-Pointing-Pointer Corrosion of SiC by Pd was seen in all cases. Black-Right-Pointing-Pointer The preferential corrosion and penetration of Pd along grain boundaries in SiC was found. Black-Right-Pointing-Pointer The penetration and transport of palladium silicides in SiC along grain boundaries was found. - Abstract: This paper reports on a transmission electron microscopy (TEM) and scanning electron microscopy (SEM) study of Pd corroded SiC. The reaction of Pd with different types of SiC at typical HTGR operating temperatures was examined. In addition the high temperature mobility of palladium silicides within polycrystalline SiC was investigated. The results indicated corrosion of the SiC by Pd in all cases studied. The corrosion leads to the formation of palladium silicides within the SiC, with the predominant phase found being Pd{sub 2}Si. Evidence for the preferential corrosion and penetration of Pd along grain boundaries in polycrystalline SiC was found. The penetration and transport, without significant corrosion, of palladium silicides into polycrystalline SiC along grain boundaries was also observed. Implications of the findings with reference to the use of Tri Isotropic particles in HTGRs will be discussed.

  14. Effect of Reactant Concentration on the Microstructure of SiC Nano wires Grown In Situ within SiC Fiber Preforms

    International Nuclear Information System (INIS)

    Kim, Weon Ju; Kang, Seok Min; Park, Ji Yeon; Ryu, Woo Seog

    2006-01-01

    Silicon carbide fiber-reinforced silicon carbide matrix (SiC f /SiC) composites are considered as advanced materials for control rods and other in-core components of high-temperature gas cooled reactors. Although the carbon fiber-reinforced carbon matrix (C f /C) composites are more mature and have advantages in cost, manufacturability and some thermomechanical properties, the SiC f /SiC composites have a clear advantage in irradiation stability, specifically a lower level of swelling and retention of mechanical properties. This offers a lifetime component for control rod application to HTGRs while the Cf/C composites would require 2-3 replacements over the reactor lifetime. In general, the chemical vapor infiltration (CVI) technique has been used most widely to produce SiC f /SiC composites. Although the technique produces a highly pure SiC matrix, it requires a long processing time and inevitably contains large interbundle pores. The present authors have recently developed 'whisker growing-assisted process,' in which one-dimensional SiC nano structures with high aspect ratios such as whiskers, nano wires and nano rods are introduced into the fiber preform before the matrix infiltration step. This novel method can produce SiC f /SiC composites with a lower porosity and an uniform distribution of pores when compared with the conventional CVI. This would be expected to increase mechanical and thermal properties of the SiC f /SiC composites. In order to take full advantage of the whisker growing strategy, however, a homogeneous growth of long whiskers is required. In this study, we applied the atmospheric pressure CVI process without metallic catalysts for the growth of SiC nano wires within stacked SiC fiber fabrics. We focused on the effect of the concentration of a reactant gas on the growth behavior and microstructures of the SiC nano wires and discussed a controlling condition for the homogenous growth of long SiC nano wires

  15. Kronig-Penney-like description for band gap variation in SiC polytypes

    NARCIS (Netherlands)

    Backes, W.H.; Nooij, de F.C.; Bobbert, P.A.; van Haeringen, W.

    1996-01-01

    A one-dimensional Kronig-Penney-like model for envelope wave functions is presented to explain the band gap variation of SiC polytypes. In this model the envelope functions obey discontinuous boundary conditions. The electronic band gaps of cubic and several hexagonal and rhombohedral SiC polytypes

  16. Stress Wave attenuation in SiC3D/Al Composite

    International Nuclear Information System (INIS)

    Yuan Chunyuan; Wang Yangwei; Li Guoju; Zhang Xu; Gao Jubin

    2013-01-01

    SiC 3D /Al composite is a kind of special composite with interpenetrating network microstructure. The attenuation properties of stress wave propagation along the SiC 3D /Al composite are studied by a Split Hopkinson Pressure Bar system and FEM simulations, and the attenuation mechanism is discussed in this paper. Results show that the attenuation rate of the stress wave in the composite is up to 1.73MPa·mm −1 . The reduction of the amplitude of waves is caused by that plenty of interfaces between SiC and Al within the composite acting with stress waves. When the incident plane wave reaches the SiC 3D /Al interface, reflection wave and transmission wave propagates in different directions along the irregular interface between SiC phase and aluminium phase due to the impedance mismatch of them, which leads to the divergence of stress wave. At the same time, some stress micro-focuses occurs in the aluminium phase for the complex wave superimposition, and some plastic deformation may take place within such micro-regions, which results in the consumption of stress wave energy. In conclusion, the stress wave attenuation is derived from divergence and consumption of stress wave.

  17. Phenomenological inelastic constitutive equations for SiC and SiC fibers under irradiation

    International Nuclear Information System (INIS)

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

    1994-01-01

    Experimental data on irradiation-induced dimensional changes and creep in β-SiC and SiC fibers is analyzed, with the objective of studying the constitutive behavior of these materials under high-temperature irradiation. The data analysis includes empirical representation of irradiation-induced dimensional changes in SiC matrix and SiC fibers as function of time and irradiation temperature. The analysis also includes formulation of simple scaling laws to extrapolate the existing data to fusion conditions on the basis of the physical mechanisms of radiation effects on crystalline solids. Inelastic constitutive equations are then developed for SCS-6 SiC fibers, Nicalon fibers and CVD SiC. The effects of applied stress, temperature, and irradiation fields on the deformation behavior of this class of materials are simultaneously represented. Numerical results are presented for the relevant creep functions under the conditions of the fusion reactor (ARIES IV) first wall. The developed equations can be used in estimating the macro mechanical properties of SiC-SiC composite systems as well as in performing time-dependent micro mechanical analysis that is relevant to slow crack growth and fiber pull-out under fusion 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. Methods for growth of relatively large step-free SiC crystal surfaces

    Science.gov (United States)

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

    2002-01-01

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

  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. Bulk Thermoelectric Materials Reinforced with SiC Whiskers

    Science.gov (United States)

    Akao, Takahiro; Fujiwara, Yuya; Tarui, Yuki; Onda, Tetsuhiko; Chen, Zhong-Chun

    2014-06-01

    SiC whiskers have been incorporated into Zn4Sb3 compound as reinforcements to overcome its extremely brittle nature. The bulk samples were prepared by either hot-extrusion or hot-pressing techniques. The obtained products containing 1 vol.% to 5 vol.% SiC whiskers were confirmed to exhibit sound appearance, high density, and fine-grained microstructure. Mechanical properties such as the hardness and fracture resistance were improved by the addition of SiC whiskers, as a result of dispersion strengthening and microstructural refinement induced by a pinning effect. Furthermore, crack deflection and/or bridging/pullout mechanisms are invoked by the whiskers. Regarding the thermoelectric properties, the Seebeck coefficient and electrical resistivity values comparable to those of the pure compound are retained over the entire range of added whisker amount. However, the thermal conductivity becomes large with increasing amount of SiC whiskers because of the much higher conductivity of SiC relative to the Zn4Sb3 matrix. This results in a remarkable degradation of the dimensionless figure of merit in the samples with addition of SiC whiskers. Therefore, the optimum amount of SiC whiskers in the Zn4Sb3 matrix should be determined by balancing the mechanical properties and thermoelectric performance.

  3. SiC Nanoparticles Toughened-SiC/MoSi2-SiC Multilayer Functionally Graded Oxidation Protective Coating for Carbon Materials at High Temperatures

    Science.gov (United States)

    Abdollahi, Alireza; Ehsani, Naser; Valefi, Zia; Khalifesoltani, Ali

    2017-05-01

    A SiC nanoparticle toughened-SiC/MoSi2-SiC functionally graded oxidation protective coating on graphite was prepared by reactive melt infiltration (RMI) at 1773 and 1873 K under argon atmosphere. The phase composition and anti-oxidation behavior of the coatings were investigated. The results show that the coating was composed of MoSi2, α-SiC and β-SiC. By the variations of Gibbs free energy (calculated by HSC Chemistry 6.0 software), it could be suggested that the SiC coating formed at low temperatures by solution-reprecipitation mechanism and at high temperatures by gas-phase reactions and solution-reprecipitation mechanisms simultaneously. SiC nanoparticles could improve the oxidation resistance of SiC/MoSi2-SiC multiphase coating. Addition of SiC nanoparticles increases toughness of the coating and prevents spreading of the oxygen diffusion channels in the coating during the oxidation test. The mass loss and oxidation rate of the SiC nanoparticle toughened-SiC/MoSi2-SiC-coated sample after 10-h oxidation at 1773 K were only 1.76% and 0.32 × 10-2 g/cm3/h, respectively.

  4. Palladium assisted silver transport in polycrystalline SiC

    Energy Technology Data Exchange (ETDEWEB)

    Neethling, J.H., E-mail: Jan.Neethling@nmmu.ac.za [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); O' Connell, J.H.; Olivier, E.J. [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa)

    2012-10-15

    The transport of silver in polycrystalline 3C-SiC and hexagonal 6H-SiC has been investigated by annealing the SiC samples in contact with a Pd-Ag compound at temperatures of 800 and 1000 Degree-Sign C and times of 24 and 67 h. The Pd was added in an attempt to improve the low wetting of SiC by Ag and further because Pd is produced in measurable concentrations in coated particles during reactor operation. Pd is also known to coalesce at the IPyC-SiC interface and to chemically attack the SiC layer. SEM, TEM and EDS were used to show that the Ag penetrates polycrystalline SiC along grain boundaries together with Pd. It is suggested that Ag transport in SiC takes place along grain boundaries in the form of moving nodules consisting of a Ag-Pd mixture. It is assumed that the nodules move along grain boundaries by dissolving the SiC at the leading edge followed by the reprecipitation of SiC at the trailing edge. Since the solubility of Cs in Ag and Pd is extremely low, it is unlikely that Cs will penetrate the SiC together with the Ag-Pd compound if present at the IPyC-SiC interface. If it is assumed that the dominant transport mechanism of Ag in intact polycrystalline SiC is indeed the Pd assisted mechanism, then the stabilization of Pd (and other metallic fission products) in the kernel could be a way of mitigating Ag release from TRISO-coated particles.

  5. Palladium assisted silver transport in polycrystalline SiC

    International Nuclear Information System (INIS)

    Neethling, J.H.; O’Connell, J.H.; Olivier, E.J.

    2012-01-01

    The transport of silver in polycrystalline 3C-SiC and hexagonal 6H-SiC has been investigated by annealing the SiC samples in contact with a Pd–Ag compound at temperatures of 800 and 1000 °C and times of 24 and 67 h. The Pd was added in an attempt to improve the low wetting of SiC by Ag and further because Pd is produced in measurable concentrations in coated particles during reactor operation. Pd is also known to coalesce at the IPyC–SiC interface and to chemically attack the SiC layer. SEM, TEM and EDS were used to show that the Ag penetrates polycrystalline SiC along grain boundaries together with Pd. It is suggested that Ag transport in SiC takes place along grain boundaries in the form of moving nodules consisting of a Ag–Pd mixture. It is assumed that the nodules move along grain boundaries by dissolving the SiC at the leading edge followed by the reprecipitation of SiC at the trailing edge. Since the solubility of Cs in Ag and Pd is extremely low, it is unlikely that Cs will penetrate the SiC together with the Ag–Pd compound if present at the IPyC–SiC interface. If it is assumed that the dominant transport mechanism of Ag in intact polycrystalline SiC is indeed the Pd assisted mechanism, then the stabilization of Pd (and other metallic fission products) in the kernel could be a way of mitigating Ag release from TRISO-coated particles.

  6. Synthesis of whiskers of SiC microwave assisted; Sintesis de whiskers de SiC asistida por microondas

    Energy Technology Data Exchange (ETDEWEB)

    Garza-Mendez, F. J.; Vanegas, A. J.; Vazquez, B. A.; Garza-Paz, J.

    2013-06-01

    We developed a new process for the synthesis of SiC whiskers assisted by microwaves; this is based on the mixture of silica xerogels and graphite powder. As energy source were used microwaves of 2.45 GHz and 1.0 kW of power RMS. On the other hand, mesoporous silica was synthesized via sol-gel, the precursors used were TEOS/H{sub 2}O and ethanol. Through analysis of the BET is determined the value of average pore size (3.0 nm) and the surface area (1090 m2/g).By mean of X-Ray diffraction it was demonstrated that the silica obtained is an amorphous solid and, the powders obtained in the microwave synthesis are {beta}-SiC. Synthesized SiC powders were observed using a SEM in secondary electron mode, it was observed that this powders consists of SiC whiskers. The effect of microwaves on the synthesis of whiskers of SiC is discussed in the present work. (Author) 19 refs.

  7. SiC for microwave power transistors

    Energy Technology Data Exchange (ETDEWEB)

    Sriram, S.; Siergiej, R.R.; Clarke, R.C.; Agarwal, A.K.; Brandt, C.D. [Northrop Grumman Sci. and Technol. Center, Pittsburgh, PA (United States)

    1997-07-16

    The advantages of SiC for high power, microwave devices are discussed. The design considerations, fabrication, and experimental results are described for SiC MESFETs and SITs. The highest reported f{sub max} for a 0.5 {mu}m MESFET using semi-insulating 4H-SiC is 42 GHz. These devices also showed a small signal gain of 5.1 dB at 20 GHz. Other 4H-SiC MESFETs have shown a power density of 3.3 W/mm at 850 MHz. The largest SiC power transistor reported is a 450 W SIT measured at 600 MHz. The power output density of this SIT is 2.5 times higher than that of comparable silicon devices. SITs have been designed to operate as high as 3.0 GHz, with a 3 cm periphery part delivering 38 W of output power. (orig.) 28 refs.

  8. Formation mechanism of SiC in C-Si system by ion irradiation

    International Nuclear Information System (INIS)

    Hishita, Shunichi; Aizawa, Takashi; Suehara, Shigeru; Haneda, Hajime

    2003-01-01

    The irradiation effects of 2 MeV He + , Ne + , and Ar + ions on the film structure of the C-Si system were investigated with RHEED and XPS. The ion dose dependence of the SiC formation was kinetically analyzed. The SiC formation at moderate temperature was achieved by 2 MeV ion irradiation when the thickness of the initial carbon films was appropriate. The evolution process of the SiC film thickness consisted of the 3 stages. The first stage was the steep increase of the SiC, and was governed by the inelastic collision. The second was the gentle increase of the SiC, and was governed by the diffusion. The last was the decrease of the SiC, and was caused by the sputtering. The formation mechanism of the SiC was discussed. (author)

  9. Photoluminescence studies of cubic phase GaN grown by molecular beam epitaxy on (001) silicon covered with SiC layer

    International Nuclear Information System (INIS)

    Godlewski, M.; Ivanov, V.Yu.; Bergman, J.P.; Monemar, B.; Barski, A.; Langer, R.

    1997-01-01

    In this work we evaluate optical properties of cubic phase GaN epilayers grown on top of (001) silicon substrate prepared by new process. Prior to the growth Si substrate was annealed at 1300-1400 o C in propane. The so-prepared substrate is covered within a thin (∼ 4 nm) SiC wafer, which allowed a successful growth of good morphological quality cubic phase GaN epilayers. The present results confirm recent suggestion on smaller ionization energies of acceptors in cubic phase GaN epilayers. (author)

  10. 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.

  11. 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.

  12. Matrix densification of SiC composites by sintering process

    International Nuclear Information System (INIS)

    Kim, Young-Wook; Jang, Doo-Hee; Eom, Jung-Hye; Chun, Yong-Seong

    2007-02-01

    The objectives of this research are to develop a process for dense SiC fiber-SiC composites with a porosity of 5% or less and to develop high-strength SiC fiber-SiC composites with a strength of 500 MPa or higher. To meet the above objectives, the following research topics were investigated ; new process development for the densification of SiC fiber-SiC composites, effect of processing parameters on densification of SiC fiber-SiC composites, effect of additive composition on matrix microstructure, effects of additive composition and content on densification of SiC fiber-SiC composites, mechanical properties of SiC fiber-SiC composites, effect of fiber coating on densification and strength of SiC fiber-SiC composites, development of new additive composition. There has been a great deal of progress in the development of technologies for the processing and densification of SiC fiber-SiC composites and in better understanding of additive-densification-mechanical property relations as results of this project. Based on the progress, dense SiC fiber-SiC composites (≥97%) and high strength SiC fiber-SiC composites (≥600 MPa) have been developed. Development of 2D SiC fiber-SiC composites with a relative density of ≥97% and a strength of ≥600 MPa can be counted as a notable achievement

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-05-16

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

  14. Pore Formation Process of Porous Ti3SiC2 Fabricated by Reactive Sintering

    Directory of Open Access Journals (Sweden)

    Huibin Zhang

    2017-02-01

    Full Text Available Porous Ti3SiC2 was fabricated with high purity, 99.4 vol %, through reactive sintering of titanium hydride (TiH2, silicon (Si and graphite (C elemental powders. The reaction procedures and the pore structure evolution during the sintering process were systematically studied by X-ray diffraction (XRD and scanning electron microscope (SEM. Our results show that the formation of Ti3SiC2 from TiH2/Si/C powders experienced the following steps: firstly, TiH2 decomposed into Ti; secondly, TiC and Ti5Si3 intermediate phases were generated; finally, Ti3SiC2 was produced through the reaction of TiC, Ti5Si3 and Si. The pores formed in the synthesis procedure of porous Ti3SiC2 ceramics are derived from the following aspects: interstitial pores left during the pressing procedure; pores formed because of the TiH2 decomposition; pores formed through the reactions between Ti and Si and Ti and C powders; and the pores produced accompanying the final phase synthesized during the high temperature sintering process.

  15. SiC Seeded Crystal Growth

    Science.gov (United States)

    Glass, R. C.; Henshall, D.; Tsvetkov, V. F.; Carter, C. H., Jr.

    1997-07-01

    The availability of relatively large (30 mm) SiC wafers has been a primary reason for the renewed high level of interest in SiC semiconductor technology. Projections that 75 mm SiC wafers will be available in 2 to 3 years have further peaked this interest. Now both 4H and 6H polytypes are available, however, the micropipe defects that occur to a varying extent in all wafers produced to date are seen by many as preventing the commercialization of many types of SiC devices, especially high current power devices. Most views on micropipe formation are based around Frank's theory of a micropipe being the hollow core of a screw dislocation with a huge Burgers vector (several times the unit cell) and with the diameter of the core having a direct relationship with the magnitude of the Burgers vector. Our results show that there are several mechanisms or combinations of these mechanisms which cause micropipes in SiC boules grown by the seeded sublimation method. Additional considerations such as polytype variations, dislocations and both impurity and diameter control add to the complexity of producing high quality wafers. Recent results at Cree Research, Inc., including wafers with micropipe densities of less than 1 cm - 2 (with 1 cm2 areas void of micropipes), indicate that micropipes will be reduced to a level that makes high current devices viable and that they may be totally eliminated in the next few years. Additionally, efforts towards larger diameter high quality substrates have led to production of 50 mm diameter 4H and 6H wafers for fabrication of LEDs and the demonstration of 75 mm wafers. Low resistivity and semi-insulating electrical properties have also been attained through improved process and impurity control. Although challenges remain, the industry continues to make significant progress towards large volume SiC-based semiconductor fabrication.

  16. Electronic Structure and Chemical Bond of Ti3SiC2 and Adding Al Element

    Institute of Scientific and Technical Information of China (English)

    MIN Xinmin; LU Ning; MEI Bingchu

    2006-01-01

    The relation among electronic structure, chemical bond and property of Ti3SiC2 and Al-doped was studied by density function and discrete variation (DFT-DVM) method. When Al element is added into Ti3SiC2, there is a less difference of ionic bond, which does not play a leading role to influent the properties. After adding Al, the covalent bond of Al and the near Ti becomes somewhat weaker, but the covalent bond of Al and the Si in the same layer is obviously stronger than that of Si and Si before adding. Therefore, in preparation of Ti3SiC2, adding a proper quantity of Al can promote the formation of Ti3SiC2. The density of state shows that there is a mixed conductor character in both of Ti3SiC2 and adding Al element. Ti3SiC2 is with more tendencies to form a semiconductor. The total density of state near Fermi lever after adding Al is larger than that before adding, so the electric conductivity may increase after adding Al.

  17. 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.

  18. Comparative study of SiC- and Si-based photovoltaic inverters

    Science.gov (United States)

    Ando, Yuji; Oku, Takeo; Yasuda, Masashi; Shirahata, Yasuhiro; Ushijima, Kazufumi; Murozono, Mikio

    2017-01-01

    This article reports comparative study of 150-300 W class photovoltaic inverters (Si inverter, SiC inverter 1, and SiC inverter 2). In these sub-kW class inverters, the ON-resistance was considered to have little influence on the efficiency. The developed SiC inverters, however, have exhibited an approximately 3% higher direct current (DC)-alternating current (AC) conversion efficiency as compared to the Si inverter. Power loss analysis indicated a reduction in the switching and reverse recovery losses of SiC metal-oxide-semiconductor field-effect transistors used for the DC-AC converter is responsible for this improvement. In the SiC inverter 2, an increase of the switching frequency up to 100 kHz achieved a state-of-the-art combination of the weight (1.25 kg) and the volume (1260 cm3) as a 150-250 W class inverter. Even though the increased switching frequency should cause the increase of the switching losses, the SiC inverter 2 exhibited an efficiency comparable to the SiC inverter 1 with a switching frequency of 20 kHz. The power loss analysis also indicated a decreased loss of the DC-DC converter built with SiC Schottky barrier diodes led to the high efficiency for its increased switching frequency. These results clearly indicated feasibility of SiC devices even for sub-kW photovoltaic inverters, which will be available for the applications where compactness and efficiency are of tremendous importance.

  19. Characterization of a n+3C/n−4H SiC heterojunction diode

    Energy Technology Data Exchange (ETDEWEB)

    Minamisawa, R. A.; Mihaila, A. [Department of Power Electronics, ABB Corporate Research Center, CH-5405 Baden-Dättwil (Switzerland); Farkas, I.; Hsu, C.-W.; Janzén, E. [Semiconductor Materials, IFM, Linköping University, SE-58183 Linköping (Sweden); Teodorescu, V. S. [National Institute of Material Physics, R-077125 Bucharest-Măgurele (Romania); Afanas' ev, V. V. [Semiconductor Physics Laboratory, KU Leuven, 3001 Leuven (Belgium); Rahimo, M. [ABB Semiconductors, Fabrikstrasse 3, CH-5600 Lenzburg (Switzerland)

    2016-04-04

    We report on the fabrication of n + 3C/n-4H SiC heterojunction diodes (HJDs) potentially promising the ultimate thermal stability of the junction. The diodes were systematically analyzed by TEM, X-ray diffraction, AFM, and secondary ion mass spectroscopy, indicating the formation of epitaxial 3C-SiC crystal on top of 4H-SiC substrate with continuous interface, low surface roughness, and up to ∼7 × 10{sup 17 }cm{sup −3} dopant impurity concentration. The conduction band off-set is about 1 V as extracted from CV measurements, while the valence bands of both SiC polytypes are aligned. The HJDs feature opening voltage of 1.65 V, consistent with the barrier height of about 1.5 eV extracted from CV measurement. We finally compare the electrical results of the n + 3C/n-4H SiC heterojunction diodes with those featuring Si and Ge doped anodes in order to evaluate current challenges involved in the fabrication of such devices.

  20. The topotactic transformation of Ti3SiC2 into a partially ordered cubic Ti(C0.67Si0.06) phase by the diffusion of Si into molten cryolite

    International Nuclear Information System (INIS)

    Barsoum, M.W.; El-Raghy, T.; Farber, L.; Amer, M.; Christini, R.; Adams

    1999-01-01

    Immersion of Ti 3 SiC 2 samples in molten cryolite at 960 C resulted in the preferential diffusion of Si atoms out of the basal planes to form a partially ordered, cubic phase with approximate chemistry Ti(C 0.67 , Si 0.06 ). The latter forms in domains, wherein the (111) planes are related by mirror planes; i.e., the loss of Si results in the de-twinning of the Ti 3 C 2 layers. Raman spectroscopy, X-ray diffraction, optical, scanning and transmission electron microscopy all indicate that the Si exists the structure topotactically, in such a way that the C atoms remain partially in their ordered position in the cubic phase

  1. Grafted SiC nanocrystals

    DEFF Research Database (Denmark)

    Saini, Isha; Sharma, Annu; Dhiman, Rajnish

    2017-01-01

    ), raman spectroscopy and X-ray diffraction (XRD) measurements. UV–Visible absorption spectroscopy was used to study optical properties such as optical energy gap (Eg), Urbach's energy (Eu), refractive index (n), real (ε1) and imaginary (ε2) parts of dielectric constant of PVA as well as PVA......Polyvinyl alcohol (PVA) grafted SiC (PVA-g-SiC)/PVA nanocomposite was synthesized by incorporating PVA grafted silicon carbide (SiC) nanocrystals inside PVA matrix. In-depth structural characterization of resulting nanocomposite was carried out using fourier transform infrared spectroscopy (FTIR...

  2. Effect of inclusion of SiC particulates on the mechanical resistance behaviour of stir-cast AA6063/SiC composites

    International Nuclear Information System (INIS)

    Balasubramanian, I.; Maheswaran, R.

    2015-01-01

    Highlights: • AA6063/SiC composites with different weight percent are stir cast. • Resistance properties against indentation, stretching force and sliding force are studied. • Increase in initiation of cleavage facets and reduces the tensile strength for 15% SiC. • Transition from micro ploughing to micro cutting wear mechanism is less due to SiC inclusion. - Abstract: This study investigates the mechanical resistance behaviour of AA6063 particulate composites with the inclusion of micron-sized silicon carbide (SiC) particles with different weight percentages in an AA6063 aluminium matrix. AA6063/SiC particulate composites containing 0, 5, 10, and 15 weight percent of SiC particles were produced by stir casting. Standard mechanical tests were conducted on the composite plates, and the mechanical resistance to indentation, tensile force and sliding force are evaluated. It has been observed that upon addition of SiC particles, the resistance against indentation is increased and the resistance against tensile force is initially increased and then decreased. Furthermore, using scanning electron microscopy (SEM), the fracture appearance of the broken specimen subjected to tensile force and morphological changes in the surface subjected to sliding force are analysed. The SEM images reveal that the addition of SiC particles in the AA6063 aluminium matrix initiates more cleavage facets. This leads to brittle fracture in the specimen subjected to tensile forces and less transition from material displacement to material removal in the specimen subjected to sliding forces

  3. The effect of SiC particle size on the properties of Cu–SiC composites

    International Nuclear Information System (INIS)

    Celebi Efe, G.; Zeytin, S.; Bindal, C.

    2012-01-01

    Graphical abstract: The relative densities of Cu–SiC composites sintered at 700 °C for 2 h are ranged from 97.3% to 91.8% for SiC with 1 μm particle size and 97.5% to 95.2% for SiC with 5 μm particle size, microhardness of composites ranged from 143 to 167 HV for SiC having 1 μm particle size and 156–182 HVN for SiC having 5 μm particle size and the electrical conductivity of composites changed between 85.9% IACS and 55.7% IACS for SiC with 1 μm particle size, 87.9% IACS and 65.2%IACS for SiC with 5 μm particle size. It was found that electrical conductivity of composites containing SiC with 5 μm particle size is better than that of Cu–SiC composites containing SiC with particle size of 1 μm. Highlights: ► In this research, the effect of SiC particle size on some properties of Cu–SiC composites were investigated. ► The mechanical properties were improved. ► The electrical properties were obtained at desirable level. -- Abstract: SiC particulate-reinforced copper composites were prepared by powder metallurgy (PM) method and conventional atmospheric sintering. Scanning electron microscope (SEM), X-ray diffraction (XRD) techniques were used to characterize the sintered composites. The effect of SiC content and particle size on the relative density, hardness and electrical conductivity of composites were investigated. The relative densities of Cu–SiC composites sintered at 700 °C for 2 h are ranged from 97.3% to 91.8% for SiC with 1 μm particle size and from 97.5% to 95.2% for SiC with 5 μm particle size. Microhardness of composites ranged from 143 to 167 HV for SiC having 1 μm particle size and from 156 to 182 HV for SiC having 5 μm particle size. The electrical conductivity of composites changed between 85.9% IACS and 55.7% IACS for SiC with 1 μm particle size, between 87.9% IACS and 65.2% IACS for SiC with 5 μm particle size.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. SiC nanoparticles as potential carriers for biologically active substances

    Science.gov (United States)

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

    2009-01-01

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

  10. 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

  11. 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.

  12. Retention and damage in 3CSiC irradiated with He and H ions

    Energy Technology Data Exchange (ETDEWEB)

    Deslandes, Alec, E-mail: alec.deslandes@csiro.au [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232 (Australia); Guenette, Mathew C. [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232 (Australia); Thomsen, Lars [Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168 (Australia); Ionescu, Mihail; Karatchevtseva, Inna; Lumpkin, Gregory R. [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232 (Australia)

    2016-02-15

    3CSiC was implanted with He and H ions using plasma immersion ion implantation (PIII). Regions of damage were created at various depths by applying a sample stage bias of 5 kV, 10 kV, 20 kV or 30 kV. Raman spectroscopy results indicate that He irradiation leads to more damage compared to H irradiation, as observed via increased disordered C and Si signals, as well as broadening of the SiC peaks. X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure spectroscopy (NEXAFS) results indicate significant change to the SiC structure and that surface oxidation has occurred following irradiation, with the degree of change varying dependent on impinging He fluence. The distributions of implanted species were measured using elastic recoil detection analysis. Despite the varying degree and depth of damage created in the SiC by the He ion irradiations, the retained H distribution was observed to not be affected by preceding He implantation.

  13. Influence of microstructure on hydrothermal corrosion of chemically vapor processed SiC composite tubes

    Science.gov (United States)

    Kim, Daejong; Lee, Ho Jung; Jang, Changheui; Lee, Hyeon-Geun; Park, Ji Yeon; Kim, Weon-Ju

    2017-08-01

    Multi-layered SiC composites consisting of monolithic SiC and a SiCf/SiC composite are one of the accident tolerant fuel cladding concepts in pressurized light water reactors. To evaluate the integrity of the SiC fuel cladding under normal operating conditions of a pressurized light water reactor, the hydrothermal corrosion behavior of multi-layered SiC composite tubes was investigated in the simulated primary water environment of a pressurized water reactor without neutron fluence. The results showed that SiC phases with good crystallinity such as Tyranno SA3 SiC fiber and monolithic SiC deposited at 1200 °C had good corrosion resistance. However, the SiC phase deposited at 1000 °C had less crystallinity and severely dissolved in water, particularly the amorphous SiC phase formed along grain boundaries. Dissolved hydrogen did not play a significant role in improving the hydrothermal corrosion resistance of the CVI-processed SiC phases containing amorphous SiC, resulting in a significant weight loss and reduction of hoop strength of the multi-layered SiC composite tubes after corrosion.

  14. 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.)

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  16. SiC Nanofibers as Long-Life Lithium-Ion Battery Anode Materials

    Directory of Open Access Journals (Sweden)

    Xuejiao Sun

    2018-05-01

    Full Text Available The development of high energy lithium-ion batteries (LIBs has spurred the designing and production of novel anode materials to substitute currently commercial using graphitic materials. Herein, twisted SiC nanofibers toward LIBs anode materials, containing 92.5 wt% cubic β-SiC and 7.5 wt% amorphous C, were successfully synthesized from resin-silica composites. The electrochemical measurements showed that the SiC-based electrode delivered a stable reversible capacity of 254.5 mAh g−1 after 250 cycles at a current density of 0.1 A g−1. It is interesting that a high discharge capacity of 540.1 mAh g−1 was achieved after 500 cycles at an even higher current density of 0.3 A g−1, which is higher than the theoretical capacity of graphite. The results imply that SiC nanomaterials are potential anode candidate for LIBs with high stability due to their high structure stability as supported with the transmission electron microscopy images.

  17. SiC Nanofibers as Long-Life Lithium-Ion Battery Anode Materials.

    Science.gov (United States)

    Sun, Xuejiao; Shao, Changzhen; Zhang, Feng; Li, Yi; Wu, Qi-Hui; Yang, Yonggang

    2018-01-01

    The development of high energy lithium-ion batteries (LIBs) has spurred the designing and production of novel anode materials to substitute currently commercial using graphitic materials. Herein, twisted SiC nanofibers toward LIBs anode materials, containing 92.5 wt% cubic β-SiC and 7.5 wt% amorphous C, were successfully synthesized from resin-silica composites. The electrochemical measurements showed that the SiC-based electrode delivered a stable reversible capacity of 254.5 mAh g -1 after 250 cycles at a current density of 0.1 A g -1 . It is interesting that a high discharge capacity of 540.1 mAh g -1 was achieved after 500 cycles at an even higher current density of 0.3 A g -1 , which is higher than the theoretical capacity of graphite. The results imply that SiC nanomaterials are potential anode candidate for LIBs with high stability due to their high structure stability as supported with the transmission electron microscopy images.

  18. 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.

  19. 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....

  20. Structural and thermal characterization of polyvinylalcohol grafted SiC nanocrystals

    DEFF Research Database (Denmark)

    Saini, Isha; Sharma, Annu; Dhiman, Rajnish

    2017-01-01

    introduced in the characteristic TO and LO mode of vibration of SiC nanocrystals after grafting procedure.XRD analysis confirmed that the grafting procedure did not alter the crystalline geometry of SiC nanocrystals. TEM and SEM images further support the FTIR and Raman spectroscopic results and confirm...... 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...... the presence of PVA layer around SiC nanocrystals. Thermal degradation behavior of PVA-g-SiC nanocrystals has been studied using TGA analysis....

  1. SiC as an oxidation-resistant refractory material. Pt. 1

    International Nuclear Information System (INIS)

    Schlichting, J.

    1979-01-01

    Uses his own investigations and gives a literature survey on the oxidation and corrosion behaviour of SiC (in the form of a pure SiC powder, hot-pressed and reaction-sintered materials). The excellent stability of SiC in oxidizing atmosphere is due to the development of protective SiO 2 coatings. Any changes in these protective coatings (e.g. due to impurities with corrosive media, high porosity of SiC, etc.) lead in most cases to increased rates of oxidation and thus restrict the field of application of SiC. (orig.) [de

  2. Feasibility study on the application of carbide (ZrC, SiC) for VHTR

    Energy Technology Data Exchange (ETDEWEB)

    Park, Ji Yeon; Kim, Weon Ju; Jung, Choong Hwan; Ryu, Woo Seog; Kim, Si Hyeong; Jang, Moon Hee; Lee, Young Woo

    2006-08-15

    A feasibility study on the coating process of ZrC for the TRISO nuclear fuel and applications of SiC as high temperature materials for the core components has performed to develop the fabrication process for the advanced ZrC TRISO fuels and the high temperature structural components for VHTR, respectively. In the case of ZrC coating, studies were focused on the comparisons of the developed coating processes for screening of our technology, the evaluations of the reactions parameters for a ZrC deposition by the thermodynamic calculations and the preliminary coating experiments by the chloride process. With relate to SiC ceramics, our interesting items are as followings; an analysis of applications and specifications of the SiC components and collections of the SiC properties and establishments of data base. For these purposes, applications of SiC ceramics for the GEN-IV related components as well as the fusion reactor related ones were reviewed. Additionally, the on-going activities with related to the ZrC clad and the SiC composites discussed in the VHTR GIF-PMB, were reviewed to make the further research plans at the section 1 in chapter 3.

  3. 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.

  4. 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.

  5. High density plasma via hole etching in SiC

    International Nuclear Information System (INIS)

    Cho, H.; Lee, K.P.; Leerungnawarat, P.; Chu, S.N.G.; Ren, F.; Pearton, S.J.; Zetterling, C.-M.

    2001-01-01

    Throughwafer vias up to 100 μm deep were formed in 4H-SiC substrates by inductively coupled plasma etching with SF 6 /O 2 at a controlled rate of ∼0.6 μm min-1 and use of Al masks. Selectivities of >50 for SiC over Al were achieved. Electrical (capacitance-voltage: current-voltage) and chemical (Auger electron spectroscopy) analysis techniques showed that the etching produced only minor changes in reverse breakdown voltage, Schottky barrier height, and near surface stoichiometry of the SiC and had high selectivity over common frontside metallization. The SiC etch rate was a strong function of the incident ion energy during plasma exposure. This process is attractive for power SiC transistors intended for high current, high temperature applications and also for SiC micromachining

  6. Enhanced visible light photocatalytic H{sub 2} evolution of metal-free g-C{sub 3}N{sub 4}/SiC heterostructured photocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Biao, E-mail: wangbiao@fjirsm.ac.cn [Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); University of the Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Jingtao, E-mail: zhangjtao@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Materials Science and Engineering, Sun Yat-sen University, Guangzhou 510006 (China); Huang, Feng, E-mail: huangfeng@mail.sysu.edu.cn [Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); State Key Laboratory of Optoelectronic Materials and Technologies, School of Materials Science and Engineering, Sun Yat-sen University, Guangzhou 510006 (China)

    2017-01-01

    Highlights: • Novel g-C{sub 3}N{sub 4}/SiC composite was prepared by synthesizing g-C{sub 3}N{sub 4} on the surface of SiC. • g-C{sub 3}N{sub 4}/SiC composites exhibit much higher H{sub 2} production activity than pure g-C{sub 3}N{sub 4}. • The g-C{sub 3}N{sub 4}/SiC heterojunction mainly accounts for improved photocatalytic activity. - Abstract: g-C{sub 3}N{sub 4} has been attracting much attention for application in visible light photocatalytic water splitting due to its suitable band structure, and high thermal and chemical stability. However, the rapid recombination of photogenerated carriers has inhibited its wide use. For this reason, novel g-C{sub 3}N{sub 4}/SiC composites were prepared via in situ synthesis of g-C{sub 3}N{sub 4} on the surface of SiC, with which g-C{sub 3}N{sub 4} shows tight interaction (chemical bonding). The g-C{sub 3}N{sub 4}/SiC composites exhibit high stability in H{sub 2} production under irradiation with visible light (λ ≥ 420 nm), demonstrating a maximum of 182 μmol g{sup −1} h{sup −1}, being 3.4 times higher than that of pure g-C{sub 3}N{sub 4}. The enhanced photocatalytic H{sub 2} production ability for g-C{sub 3}N{sub 4}/SiC photocatalysts is primarily ascribed to the combined effects of enhanced separation of photogenerated carriers through efficient migration of electron and enlarged surface areas, in addition to the possible contributions of increased hydrophilicity of SiC and polymerization degree of g-C{sub 3}N{sub 4}. This study may provide new insights into the development of g-C{sub 3}N{sub 4}-based composites as stable and efficient photocatalysts for H{sub 2} production from water splitting.

  7. Stability analysis of SiO2/SiC multilayer coatings

    International Nuclear Information System (INIS)

    Fu Zhiqiang; Jean-Charles, R.

    2006-01-01

    The stability behaviours of SiC coatings and SiO 2 /SiC coatings in helium with little impurities are studied by HSC Chemistry 4.1, the software for analysis of Chemical reaction and equilibrium in multi-component complex system. It is found that in helium with a low partial pressure of oxidative impurities under different total pressure, the key influence factor controlling T cp of SiC depends is the partial pressure of oxidative impurities; T cp of SiC increases with the partial pressure of oxidative impurities. In helium with a low partial pressure of different impurities, the key influence factor of T cs of SiO 2 are both the partial pressure of impurities and the amount of impurities for l mol SiO 2 ; T cs of SiO 2 increases with the partial pressure of oxidative impurities at the same amount of the impurities for 1 mol SiO 2 while it decreases with the amount of the impurities for 1 mm SiO 2 at the same partial pressure of the impurities. The influence of other impurities on T cp of SiC in He-O 2 is studied and it is found that CO 2 , H 2 O and N-2 increase T cp of SiC in He-O 2 while H 2 , CO and CH 4 decrease T cp of SiC He-O 2 . When there exist both oxidative impurities and reductive impurities, their effect on T cs of SiO 2 can be suppressed by the other. In HTR-10 operation atmosphere, SiO 2 /SiC coatings can keep stable status at higher temperature than SiC coatings, so SiO 2 /SiC coatings is more suitable to improve the oxidation resistance of graphite in HTR-10 operation atmosphere compared with SiC coatings. (authors)

  8. Moissanite (SiC) with metal-silicide and silicon inclusions from tuff of Israel: Raman spectroscopy and electron microscope studies

    Science.gov (United States)

    Dobrzhinetskaya, Larissa; Mukhin, Pavel; Wang, Qin; Wirth, Richard; O'Bannon, Earl; Zhao, Wenxia; Eppelbaum, Lev; Sokhonchuk, Tatiana

    2018-06-01

    Here, we present studies of natural SiC that occurs in situ in tuff related to the Miocene alkaline basalt formation deposited in northern part of Israel. Raman spectroscopy, SEM and FIB-assisted TEM studies revealed that SiC is primarily hexagonal polytypes 4H-SiC and 6H-SiC, and that the 4H-SiC polytype is the predominant phase. Both SiC polytypes contain crystalline inclusions of silicon (Sio) and inclusions of metal-silicide with varying compositions (e.g. Si58V25Ti12Cr3Fe2, Si41Fe24Ti20Ni7V5Zr3, and Si43Fe40Ni17). The silicides crystal structure parameters match Si2TiV5 (Pm-3m space group, cubic), FeSi2Ti (Pbam space group, orthorhombic), and FeSi2 (Cmca space group, orthorhombic) respectively. We hypothesize that SiC was formed in a local ultra-reduced environment at respectively shallow depths (60-100 km), through a reaction of SiO2 with highly reducing fluids (H2O-CH4-H2-C2H6) arisen from the mantle "hot spot" and passing through alkaline basalt magma reservoir. SiO2 interacting with the fluids may originate from the walls of the crustal rocks surrounding this magmatic reservoir. This process led to the formation of SiC and accompanied by the reducing of metal-oxides to native metals, alloys, and silicides. The latter were trapped by SiC during its growth. Hence, interplate "hot spot" alkali basalt volcanism can now be included as a geological environment where SiC, silicon, and silicides can be found.

  9. Fabrication of SiC Composites with Synergistic Toughening of Carbon Whisker and In Situ 3C-SiC Nanowire

    Directory of Open Access Journals (Sweden)

    Zhang Yunlong

    2016-01-01

    Full Text Available The SiC composites with synergistic toughening of carbon whisker and in situ 3C-SiC nanowire have been fabricated by hot press sinter technology and annealed treatment technology. Effect of annealed time on the morphology of SiC nanowires and mechanical properties of the Cw/SiC composites was surveyed in detail. The appropriate annealed time improved mechanical properties of the Cw/SiC composites. The synergistic effect of carbon whisker and SiC nanowire can improve the fracture toughness for Cw/SiC composites. The vapor-liquid-solid growth (VLS mechanism was proposed. TEM photo showed that 3C-SiC nanowire can be obtained with preferential growth plane ({111}, which corresponded to interplanar spacing about 0.25 nm.

  10. 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.

  11. 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

  12. Homoepitaxial VPE growth of SiC active layers

    Energy Technology Data Exchange (ETDEWEB)

    Burk, A.A. Jr. [Northrop Grumman Electron. Sensors and Syst. Div., Baltimore, MD (United States); Rowland, L.B. [Northrop Grumman Sci. and Technol. Center, Pittsburgh, PA (United States)

    1997-07-01

    SiC active layers of tailored thickness and doping form the heart of all SiC electronic devices. These layers are most conveniently formed by vapor phase epitaxy (VPE). Exacting requirements are placed upon the SiC-VPE layers` material properties by both semiconductor device physics and available methods of device processing. In this paper, the current ability of the SiC-VPE process to meet these requirements is described along with continuing improvements in SiC epitaxial reactors, processes and materials. (orig.) 48 refs.

  13. Effect of TiC content on the microstructure and properties of Ti3SiC2-TiC composites in situ fabricated by spark plasma sintering

    International Nuclear Information System (INIS)

    Zhang Jianfeng; Wang Lianjun; Jiang Wan; Chen Lidong

    2008-01-01

    Spark plasma sintering technique was used to in situ fabricate high dense Ti 3 SiC 2 -TiC composites. The calculated TiC volume content from X-ray diffraction (XRD) is close to the theoretical one. It is found from fracture surface observation that TiC is about 1 μm, and Ti 3 SiC 2 is about 2-10 μm in grain size. The fracture modes consist of intergranular mainly for Ti 3 SiC 2 and transgranular fracture mainly for TiC. With the increasing of TiC volume content, Vickers hardness increases to the maximum value of 13 GPa for Ti 3 SiC 2 -40 vol.%TiC. Fracture toughness and flexural strength of the composites are also improved compared with those of monolithic Ti 3 SiC 2 except for Ti 3 SiC 2 -40 vol.%TiC composite. The main reasons for the sudden decrease of fracture toughness and flexural strength of Ti 3 SiC 2 -40 vol.%TiC composite can be attributed to the relatively lower density, some clusters of TiC in the composite and the transition of fracture mode from intergranular to transgranular. The thermal conductivities decreased with the addition of TiC. The minimum thermal conductivity is 22 W m deg. C -1 for Ti 3 SiC 2 -40 vol.%TiC composite

  14. Thermal stability of Ti3SiC2 thin films

    International Nuclear Information System (INIS)

    Emmerlich, Jens; Music, Denis; Eklund, Per; Wilhelmsson, Ola; Jansson, Ulf; Schneider, Jochen M.; Hoegberg, Hans; Hultman, Lars

    2007-01-01

    The thermal stability of Ti 3 SiC 2 (0 0 0 1) thin films is studied by in situ X-ray diffraction analysis during vacuum furnace annealing in combination with X-ray photoelectron spectroscopy, transmission electron microscopy and scanning transmission electron microscopy with energy dispersive X-ray analysis. The films are found to be stable during annealing at temperatures up to ∼1000 deg. C for 25 h. Annealing at 1100-1200 deg. C results in the rapid decomposition of Ti 3 SiC 2 by Si out-diffusion along the basal planes via domain boundaries to the free surface with subsequent evaporation. As a consequence, the material shrinks by the relaxation of the Ti 3 C 2 slabs and, it is proposed, by an in-diffusion of O into the empty Si-mirror planes. The phase transformation process is followed by the detwinning of the as-relaxed Ti 3 C 2 slabs into (1 1 1)-oriented TiC 0.67 layers, which begin recrystallizing at 1300 deg. C. Ab initio calculations are provided supporting the presented decomposition mechanisms

  15. CVD of SiC and AlN using cyclic organometallic precursors

    Science.gov (United States)

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

    1992-01-01

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

  16. Development of the fabrication process of SiC composite by polycarbosilane

    International Nuclear Information System (INIS)

    Park, Ji Yeon; Kim, Weon Ju; Kim, Jung Il; Ryu, Woo Seog

    2004-11-01

    This technical report reviewed the fabrication process of fiber reinforced ceramic composites, characteristics of the PIP process, and applications of SiC f /SiC composite to develop a silicon carbide composite by PIP method. Additionally, characteristics and thermal behaviors of a PCS+SiC powder slurry and infiltration behaviors of slurry into the SiC fabric was evaluated. The stacking behaviors of SiC fabrics infiltrated a PCS+SiC powder slurry was also investigated. Using this stacked preforms, SiC f /SiC composites were fabricated by the electron beam curing and pyrolysis process and the thermal oxidation curing and pyrolysis process, respectively. And the characteristics of both composites were compared

  17. 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.

  18. Determining the fracture resistance of advanced SiC fiber reinforced SiC matrix composites

    International Nuclear Information System (INIS)

    Nozawa, T.; Katoh, Y.; Kishimoto, H.

    2007-01-01

    Full text of publication follows: One of the perceived advantages for highly-crystalline and stoichiometric silicon carbide (SiC) and SiC composites, e.g., advanced SiC fiber reinforced chemically-vapor-infiltrated (CVI) SiC matrix composites, is the retention of fast fracture properties after neutron irradiation at high-temperatures (∼1000 deg. C) to intermediate-doses (∼15 dpa). Accordingly, it has been clarified that the maximum allowable stress (or strain) limit seems unaffected in certain irradiation conditions. Meanwhile, understanding the mechanism of crack propagation from flaws, as potential weakest link to cause composite failure, is somehow lacking, despite that determining the strength criterion based on the fracture mechanics will eventually become important considering the nature of composites' fracture. This study aims to evaluate crack propagation behaviors of advanced SiC/SiC and to provide fundamentals on fracture resistance of the composites to define the strength limit for the practical component design. For those purposes, the effects of irreversible energies related to interfacial de-bonding, fiber bridging, and microcrack forming on the fracture resistance were evaluated. Two-dimensional SiC/SiC composites were fabricated by CVI or nano-infiltration and transient-eutectic-phase (NITE ) methods. Hi-Nicalon TM Type-S or Tyranno TM -SA fibers were used as reinforcements. In-plane mode-I fracture resistance was evaluated by the single edge notched bend technique. The key finding is the continuous Load increase with the crack growth for any types of advanced composites, while many studies specified the gradual load decrease for the conventional composites once the crack initiates. This high quasi-ductility appeared due primarily to high friction (>100 MPa) at the fiber/matrix interface using rough SiC fibers. The preliminary analysis based on the linear elastic fracture mechanics, which does not consider the effects of irreversible energy

  19. 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.

  20. White light emission from fluorescent SiC with porous surface

    DEFF Research Database (Denmark)

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

    2017-01-01

    We report for the frst time a NUV light to white light conversion in a N-B co-doped 6H-SiC (fuorescent SiC) layer containing a hybrid structure. The surface of fuorescent SiC sample contains porous structures fabricated by anodic oxidation method. After passivation by 20nm thick Al2O3, the photol......We report for the frst time a NUV light to white light conversion in a N-B co-doped 6H-SiC (fuorescent SiC) layer containing a hybrid structure. The surface of fuorescent SiC sample contains porous structures fabricated by anodic oxidation method. After passivation by 20nm thick Al2O3...... 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...

  1. 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.

  2. TRISO coated fuel particles with enhanced SiC properties

    International Nuclear Information System (INIS)

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

    2009-01-01

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

  3. 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.

  4. 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....

  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 mechanis...

  6. 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.

  7. Fission-product SiC reaction in HTGR fuel

    International Nuclear Information System (INIS)

    Montgomery, F.

    1981-01-01

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

  8. Detail study of SiC MOSFET switching characteristics

    DEFF Research Database (Denmark)

    Li, Helong; Munk-Nielsen, Stig

    2014-01-01

    This paper makes detail study of the latest SiC MOSFETs switching characteristics in relation to gate driver maximum current, gate resistance, common source inductance and parasitic switching loop inductance. The switching performance of SiC MOSFETs in terms of turn on and turn off voltage...

  9. Residual stress and mechanical properties of SiC ceramic by heat treatment

    International Nuclear Information System (INIS)

    Yoon, H.K.; Kim, D.H.; Shin, B.C.

    2007-01-01

    Full text of publication follows: Silicon carbide is a compound of relatively low density, high hardness, elevated thermal stability and good thermal conductivity, resulting in good thermal shock resistance. Because of these properties, SiC materials are widely used as abrasives and refractories. In this study, SiC single and poly crystals was grown by the sublimation method using the SiC seed crystal and SiC powder as the source material. Mechanical properties of SiC single and poly crystals are carried out by using the nano-indentation method and small punch test after the heat treatment. As a result, mechanical properties of SiC poly crystal had over double than single. And SiC single and poly crystals were occurred residual stress, but residual stress was shown relaxant properties by the effect of heat treatment. (authors)

  10. 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...

  11. Fabrication of Multi-Layerd SiC Composite Tube for LWR Applications

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Daejong; Jung, Choonghwan; Kim, Weonju; Park, Jiyeon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Jongmin [Chungnam National Univ., Daejeon (Korea, Republic of)

    2013-05-15

    In this study, the chemical vapor deposition (CVD) and chemical vapor infiltration (CVI) methods were employed for the fabrication of the composite tubes. SiC ceramics and SiC-based composites have recently been studied for LWR fuel cladding applications because of good mechanical/physical properties, neutron irradiation resistance and excellent compatibility with coolant under severe accident. A multi-layered SiC composite tube as the nuclear fuel cladding is composed of the monolith SiC inner layer, SiC/SiC composite intermediate layer, and monolith SiC outer layer. Since all constituents should be highly pure, stoichiometric to achieve the good properties, it has been considered that the chemical process is a well-suited technique for the fabrication of the SiC phases.

  12. 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.

  13. Heteroepitaxy of zinc-blende SiC nano-dots on Si substrate by organometallic ion beam

    International Nuclear Information System (INIS)

    Matsumoto, T.; Kiuchi, M.; Sugimoto, S.; Goto, S.

    2006-01-01

    The self-assembled SiC nano-dots were fabricated on Si(111) substrate at low-temperatures using the organometallic ion beam deposition technique. The single precursor of methylsilicenium ions (SiCH 3 + ) with the energy of 100 eV was deposited on Si(111) substrate at 500, 550 and 600 deg. C. The characteristics of the self-assembled SiC nano-dots were analyzed by reflection high-energy electron diffraction (RHEED), Raman spectroscopy and atomic force microscope (AFM). The RHEED patterns showed that the crystal structure of the SiC nano-dots formed on Si(111) substrate was zinc-blende SiC (3C-SiC) and it was heteroepitaxy. The self-assembled SiC nano-dots were like a dome in shape, and their sizes were the length of 200-300 nm and the height of 10-15 nm. Despite the low-temperature of 500 deg. C as SiC crystallization the heteroepitaxial SiC nano-dots were fabricated on Si(111) substrate using the organometallic ion beam

  14. Research Progress on Preparation for Biomass-based SiC Ceramic

    Directory of Open Access Journals (Sweden)

    CUI He-shuai

    2017-08-01

    Full Text Available Silicon carbide (SiC ceramics prepared by the conventional process has excellent properties and wide application prospects, but the increased cost of high-temperature preparation process restricts its further development. In contrast, the abundant porous structure of biomass makes itself to be ideal replacement of SiC ceramic prepared at low temperature. This paper reviewed the structure characteristics, preparation methods, pyrolysis mechanism and influence parameters of biomass-based SiC ceramic, and eventually explored the current problems and development trends of the pretreatment of carbon source and silicon source, the pyrolysis process and the application research on the preparation for biomass-based SiC ceramic.

  15. 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

  16. Grinding Characteristics Of Directionally Aligned SiC Whisker Wheel-Comparison With Al2O3 Fiber Wheel

    Institute of Scientific and Technical Information of China (English)

    魏源迁; 山口胜美; 菊泽贤二; 洞口严; 中根正喜

    2003-01-01

    A unique SiC whisker wheel was invented,in which the whiskers were aligned normally to the grinding wheel surface.In this paper,grindabilities of the SiC whisker wheel are investigated and compared with those of other wheels of SiC grains,Al2O3 grains,as well as Al2O3 long and short fibres which were also aligned normally to the grinding wheel surface,respectively.The main research contents concern grinding characteristics of a directionally aligned SiC whisker wheel such as material-removal volume,wheel-wear rates,integrity of the ground surfaces,grinding ratios and grinding efficiency.Furthermore,grinding wheels of whiskers and fibres have a common disadvantage:they tend to load easily.The authors have proposed a simple method of loading-free grinding to overcome this propensity and investigate some related grinding characteristics under loading-free grinding conditions.

  17. 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.

  18. 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.

  19. 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.

  20. Manufacturing and characterization of porous SiC for flow channel inserts in dual-coolant blanket designs

    International Nuclear Information System (INIS)

    Bereciartu, Ainhoa; Ordas, Nerea; Garcia-Rosales, Carmen; Morono, Alejandro; Malo, Marta; Hodgson, Eric R.; Abella, Jordi; Sedano, Luis

    2011-01-01

    SiC is the primary candidate for the flow channel inserts in dual-coolant blanket concepts. Porous SiC ceramics are attractive candidates for this non-structural application, since they can satisfy the required properties through a low cost manufacturing route, compared to SiC f /SiC. This work shows first results of the manufacturing of porous SiC ceramics prepared with different amounts of Y 2 O 3 and Al 2 O 3 as sintering additives. C powders were used as pore-formers by their burnout during oxidation after sintering. Comparison of microstructure, porosity, flexural strength, thermal and electrical conductivity and corrosion under Pb-15.7Li of porous SiC without and with sintering additives is presented. The addition of 2.5 wt.% of Y 2 O 3 and Al 2 O 3 improves the mechanical properties, and reduces the thermal and electrical conductivity down to reasonable values. Preliminary corrosion tests under Pb-15.7 Li at 500 deg. C show that the absence of a dense coating on porous SiC leads to poor corrosion behavior.

  1. SYLRAMICTM SiC fibers for CMC reinforcement

    International Nuclear Information System (INIS)

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

    2000-01-01

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

  2. Synthesis of micro-sized interconnected Si-C composites

    Science.gov (United States)

    Wang, Donghai; Yi, Ran; Dai, Fang

    2016-02-23

    Embodiments provide a method of producing micro-sized Si--C composites or doped Si--C and Si alloy-C with interconnected nanoscle Si and C building blocks through converting commercially available SiO.sub.x (0

  3. Properties of SiC semiconductor detector of fast neutrons investigated using MCNPX code

    International Nuclear Information System (INIS)

    Sedlakova, K.; Sagatova, A.; Necas, V.; Zatko, B.

    2013-01-01

    The potential of silicon carbide (SiC) for use in semiconductor nuclear radiation detectors has been long recognized. The wide bandgap of SiC (3.25 eV for 4H-SiC polytype) compared to that for more conventionally used semiconductors, such as silicon (1.12 eV) and germanium (0.67 eV), makes SiC an attractive semiconductor for use in high dose rate and high ionization nuclear environments. The present work focused on the simulation of particle transport in SiC detectors of fast neutrons using statistical analysis of Monte Carlo radiation transport code MCNPX. Its possibilities in detector design and optimization are presented.(authors)

  4. 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)

  5. 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.

  6. 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.

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

    International Nuclear Information System (INIS)

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

    2013-01-01

    SiC particles are an important reinforced phase in metal matrix composites. Their effect on the microarc oxidation (MAO, also named plasma electrolytic oxidation-PEO) process of SiC p /AZ91 Mg matrix composites (MMCs) was studied and the mechanism was revealed. The corrosion resistance of MAO coating was also investigated. Voltage–time curves during MAO were recorded to study the barrier film status on the composites. Scanning electron microscopy was used to characterize the existing state of SiC particles in MAO. Energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy were used to analyze the chemical composition of the coating. Corrosion resistance of the bare and coated composites was evaluated by potentiodynamic polarization curves in 3.5% NaCl solution. Results showed that the integrality and electrical insulation properties of the barrier film on the composites were destroyed by the SiC particles. Consequently, the sparking discharge at the early stage of MAO was inhibited, and the growth efficiency of the MAO coating decreased with the increase in the volume fraction of SiC particles. SiC particles did not exist stably during MAO; they were oxidized or partially oxidized into SiO 2 before the overall sparking discharge. The transformation from semi-conductive SiC to insulating SiO 2 by oxidation restrained the current leakage at the original SiC positions and then promoted sparking discharge and coating growth. The corrosion current density of SiC p /AZ91 MMCs was reduced by two orders of magnitude after MAO treatment. However, the corrosion resistances of the coated composites were lower than that of the coated alloy.

  8. Effect of Ti and Si interlayer materials on the joining of SiC ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Yang Il; Park, Jung Hwan; Kim, Hyun Gil; Park, Dong Jun; Park, Jeong Yong; Kim, Weon Ju [LWR Fuel Technology Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-08-15

    SiC-based ceramic composites are currently being considered for use in fuel cladding tubes in light-water reactors. The joining of SiC ceramics in a hermetic seal is required for the development of ceramic-based fuel cladding tubes. In this study, SiC monoliths were diffusion bonded using a Ti foil interlayer and additional Si powder. In the joining process, a very low uniaxial pressure of ∼0.1 MPa was applied, so the process is applicable for joining thin-walled long tubes. The joining strength depended strongly on the type of SiC material. Reaction-bonded SiC (RB-SiC) showed a higher joining strength than sintered SiC because the diffusion reaction of Si was promoted in the former. The joining strength of sintered SiC was increased by the addition of Si at the Ti interlayer to play the role of the free Si in RB-SiC. The maximum joint strength obtained under torsional stress was ∼100 MPa. The joint interface consisted of TiSi{sub 2}, Ti{sub 3}SiC{sub 2}, and SiC phases formed by a diffusion reaction of Ti and Si.

  9. Detection and Analysis of Particles with Failed SiC in AGR-1 Fuel Compacts

    International Nuclear Information System (INIS)

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

    2014-01-01

    As the primary barrier to release of radioactive isotopes emitted from the fuel kernel, retention performance of the SiC layer in tristructural isotropic (TRISO) coated particles is critical to the overall safety of reactors that utilize this fuel design. Most isotopes are well-retained by intact SiC coatings, so pathways through this layer due to cracking, structural defects, or chemical attack can significantly contribute to radioisotope release. In the US TRISO fuel development effort, release of "1"3"4Cs and "1"3"7Cs are used to detect SiC failure during fuel compact irradiation and safety testing because the amount of cesium released by a compact containing one particle with failed SiC is typically ten or more times higher than that released by compacts without failed SiC. Compacts with particles that released cesium during the AGR-1 irradiation test or post-irradiation safety testing at 1600– 1800°C were identified, and individual particles with abnormally low cesium retention were sorted out with the ORNL Irradiated Microsphere Gamma Analyzer (IMGA). X-ray tomography was used for three-dimensional imaging of the internal coating structure to locate low-density pathways through the SiC layer and guide subsequent materialography by optical and scanning electron microscopy. All three cesium-releasing particles recovered from as-irradiated compacts showed a region where the inner pyrocarbon (IPyC) had cracked due to radiation-induced dimensional changes in the shrinking buffer and the exposed SiC had experienced concentrated attack by palladium; SiC failures observed in particles subjected to safety testing were related to either fabrication defects or showed extensive Pd corrosion through the SiC where it had been exposed by similar IPyC cracking. (author)

  10. Testing of porous SiC with dense coating under relevant conditions for Flow Channel Insert application

    Energy Technology Data Exchange (ETDEWEB)

    Ordás, N., E-mail: nordas@ceit.es [CEIT and Tecnun (University of Navarra), Manuel de Lardizábal 15, 20018 San Sebastián (Spain); Bereciartu, A.; García-Rosales, C. [CEIT and Tecnun (University of Navarra), Manuel de Lardizábal 15, 20018 San Sebastián (Spain); Moroño, A.; Malo, M.; Hodgson, E.R. [CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain); Abellà, J.; Colominas, S. [Institut Químic de Sarrià, University Ramon Llull, Via Augusta 390, 08017 Barcelona (Spain); Sedano, L. [CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain)

    2014-10-15

    Highlights: • Porous SiC coated by CVD with a dense coating was developed for Flow Channel Inserts (FCI) in dual-coolant blanket concept. • Porous SiC was obtained following the sacrificial template technique, using Al{sub 2}O{sub 3} and Y{sub 2}O{sub 3} as sintering additives. • Flexural strength, thermal and electrical conductivity, and microstructure of uncoated and coated porous SiC are presented. • Adhesion of coating to porous SiC and its corrosion behavior under Pb-17.5Li at 700 °C are shown. - Abstract: Thermally and electrically insulating porous SiC ceramics are attractive candidates for Flow Channel Inserts (FCI) in dual-coolant blanket concepts thanks to its relatively inexpensive manufacturing route. To prevent tritium permeation and corrosion by Pb-15.7 a dense coating has to be applied on the porous SiC. Despite not having structural function, FCI must exhibit sufficient mechanical strength to withstand strong thermal gradients and thermo-electrical stresses during operation. This work summarizes the results on the development of coated porous SiC for FCI. Porous SiC was obtained following the sacrificial template technique, using Al{sub 2}O{sub 3} and Y{sub 2}O{sub 3} as sintering additives and a carbonaceous phase as pore former. Sintering was performed in inert gas at 1850–1950 °C during 15 min to 3 h, followed by oxidation at 650 °C to eliminate the carbonaceous phase. The most promising bulk materials were coated with a ∼30 μm thick dense SiC by CVD. Results on porosity, bending tests, thermal and electrical conductivity are presented. The microstructure of the coating, its adhesion to the porous SiC and its corrosion behavior under Pb-17.5Li are also shown.

  11. SiC Composite for Fuel Structure Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yueh, Ken [Electric Power Research Inst. (EPRI), Charlotte, NC (United States)

    2017-12-22

    Extensive evaluation was performed to determine the suitability of using SiC composite as a boiling water reactor (BWR) fuel channel material. A thin walled SiC composite box, 10 cm in dimension by approximately 1.5 mm wall thickness was fabricated using chemical vapor deposition (CVD) for testing. Mechanical test results and performance evaluations indicate the material could meet BWR channel mechanical design requirement. However, large mass loss of up to 21% was measured in in-pile corrosion test under BWR-like conditions in under 3 months of irradiation. A fresh sister sample irradiated in a follow-up cycle under PWR conditions showed no measureable weight loss and thus supports the hypothesis that the oxidizing condition of the BWR-like coolant chemistry was responsible for the high corrosion rate. A thermodynamic evaluation showed SiC is not stable and the material may oxidize to form SiO2 and CO2. Silica has demonstrated stability in high temperature steam environment and form a protective oxide layer under severe accident conditions. However, it does not form a protective layer in water under normal BWR operational conditions due to its high solubility. Corrosion product stabilization by modifying the SiC CVD surface is an approach evaluated in this study to mitigate the high corrosion rate. Titanium and zirconium have been selected as stabilizing elements since both TiSiO4 and ZrSiO4 are insoluble in water. Corrosion test results in oxygenated water autoclave indicate TiSiO4 does not form a protective layer. However, zirconium doped test samples appear to form a stable continuous layer of ZrSiO4 during the corrosion process. Additional process development is needed to produce a good ZrSiC coating to verify functionality of the mitigation concept.

  12. Microwave joining of SiC

    Energy Technology Data Exchange (ETDEWEB)

    Silberglitt, R.; Ahmad, I. [FM Technologies, Inc., Fairfax, VA (United States); Black, W.M. [George Mason Univ., Fairfax, VA (United States)] [and others

    1995-05-01

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

  13. 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) ...

  14. A porous SiC ammonia sensor

    NARCIS (Netherlands)

    Connolly, E.J.; Timmer, B.H.; Pham, H.T.M.; Groeneweg, J.; Sarro, P.M.; Olthuis, Wouter; French, P.J.

    2005-01-01

    When used as the dielectric in a capacitive sensing arrangement, porous SiC has been found to be extremely sensitive to the presence of ammonia (NH3) gas. The exact sensing method is still not clear, but NH3 levels as low as 0.5 ppm could be detected. We report the fabrication and preliminary

  15. The annealing effects on irradiated SiC piezo resistive pressure sensor

    International Nuclear Information System (INIS)

    Almaz, E.; Blue, T. E.; Zhang, P.

    2009-01-01

    The effects of temperature on annealing of Silicon Carbide (SiC) piezo resistive pressure sensor which was broken after high fluence neutron irradiation, were investigated. Previously, SiC piezo resistive sensor irradiated with gamma ray and fast neutron in the Co-60 gamma-ray irradiator and Beam Port 1 (BP1) and Auxiliary Irradiation Facility (AIF) at the Ohio State University Nuclear Reactor Laboratory (OSUNRL) respectively. The Annealing temperatures were tested up to 400 C. The Pressure-Output voltage results showed recovery after annealing process on SiC piezo resistive pressure sensor. The bridge resistances of the SiC pressure sensor stayed at the same level up to 300 C. After 400 C annealing, the resistance values changed dramatically.

  16. Factors affecting the corrosion of SiC layer by fission product palladium

    International Nuclear Information System (INIS)

    Dewita, E.

    2000-01-01

    HTR is one of the advanced nuclear reactors which has inherent safety system, graphite moderated and helium gas cooled. In general, these reactors are designed with the TRISO coated particle consist of four coating layers that are porous pyrolytic carbon (PyC). inner dense PyC (IPyC), silicon carbide (SiC), and outer dense PyC (OPyC). Among the four coating layers, the SiC plays an important role beside in retaining metallic fission products, it also provides mechanical strength to fuel particle. However, results of post irradiation examination indicate that fission product palladium can react with and corrode SiC layer, This assessment is conducted to get the comprehension about resistance of SiC layer on irradiation effects, especially in order to increase the fuel bum-up. The result of this shows that the corrosion of SiC layer by fission product palladium is beside depend on the material characteristics of SiC, and also there are other factors that affect on the SiC layer corrosion. Fuel enrichment, bum-up, and irradiation time effect on the palladium flux in fuel kernel. While, the fuel density, vapour pressure of palladium (the degree depend on the irradiation temperature and kernel composition) effect on palladium migration in fuel particle. (author)

  17. InP-based photonic integrated circuit platform on SiC wafer.

    Science.gov (United States)

    Takenaka, Mitsuru; Takagi, Shinichi

    2017-11-27

    We have numerically investigated the properties of an InP-on-SiC wafer as a photonic integrated circuit (PIC) platform. By bonding a thin InP-based semiconductor on a SiC wafer, SiC can be used as waveguide cladding, a heat sink, and a support substrate simultaneously. Since the refractive index of SiC is sufficiently low, PICs can be fabricated using InP-based strip and rib waveguides with a minimum bend radius of approximately 7 μm. High-thermal-conductivity SiC underneath an InP-based waveguide core markedly improves heat dissipation, resulting in superior thermal properties of active devices such as laser diodes. The InP-on-SiC wafer has significantly smaller thermal stress than InP-on-SiO 2 /Si wafer, which prevents the thermal degradation of InP-based devices during high-temperature processes. Thus, InP on SiC provides an ideal platform for high-performance PICs.

  18. Study on porosity of ceramic SiC using small angle neutron scattering

    International Nuclear Information System (INIS)

    Li Jizhou; Yang Jilian; Kang Jian; Ye Chuntang

    1996-01-01

    The mechanical properties of functional heat-resistant ceramics SiC are significantly influenced by the concentration and dimensions of pores. Small angle neutron scattering measurements for 3 SiC samples with different densities are performed on C1-2 SANS instrument of the University of Tokyo. Two groups of the neutron data are obtained using 8 and 16 m of secondary flight path, 1 and 0.7 nm of neutron wave lengths, respectively. After deduction of background measurement and transmission correction, both neutron data are linked up with each other. The patterns of neutron data of 3 samples with Q range from 0.028∼0.5 nm -1 are almost with axial symmetry, showing that the shape of pores is almost spherical. Using Mellin transform, size distributions of pores in 3 samples are obtained. The average size (∼19 nm) of pores for hot-pressed SiC sample with higher density is smaller than the others (∼ 21 nm). It seems to be the reason why the density of hot-pressed SiC sample is higher than not hot-pressed sample

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

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  20. 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

  1. Pd/CeO2/SiC Chemical Sensors

    Science.gov (United States)

    Lu, Weijie; Collins, W. Eugene

    2005-01-01

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

  2. SiC substrate defects and III-N heteroepitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Poust, B D [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Koga, T S [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Sandhu, R [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Heying, B [Northrop Grumman Space Technology, Space and Electronics Group, Redondo Beach, CA 90278 (United States); Hsing, R [Northrop Grumman Space Technology, Space and Electronics Group, Redondo Beach, CA 90278 (United States); Wojtowicz, M [Northrop Grumman Space Technology, Space and Electronics Group, Redondo Beach, CA 90278 (United States); Khan, A [Department of Electrical Engineering, University of South Carolina, Columbia, SC (United States); Goorsky, M S [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States)

    2003-05-21

    This study addressed how defects in SiC substrates influence the crystallographic properties of AlGaN/GaN layers deposited by metallorganic vapour phase epitaxy and by molecular beam epitaxy. We employed double crystal reflection x-ray topography using symmetric (0008) and (00012) reflections with CuK{alpha} radiation ({lambda} = 1.54 A) to image dislocations, micropipes, and low angle boundaries in SiC substrates. Lattice strain near the core of a micropipe defect was estimated to be of the order of 10{sup -7}. The substrates investigated exhibited radial patterns of strain and, primarily, of tilt of the order of tens of arcsec. After deposition of the AlGaN and GaN layers, DCXRT images were generated from the substrate (0008) or (00012) and GaN epitaxial layer (0004) reflections. Full-width at half-maximum values ranging from {approx}100 to 300 arcsec were typical of the GaN reflections, while those of the 4H-SiC reflections were {approx}20-70 arcsec. Micropipes, tilt boundaries, and inclusions in the SiC were shown to produce structural defects in the GaN layers. A clear correlation between SiC substrate defects and GaN defects has been established.

  3. SiC substrate defects and III-N heteroepitaxy

    International Nuclear Information System (INIS)

    Poust, B D; Koga, T S; Sandhu, R; Heying, B; Hsing, R; Wojtowicz, M; Khan, A; Goorsky, M S

    2003-01-01

    This study addressed how defects in SiC substrates influence the crystallographic properties of AlGaN/GaN layers deposited by metallorganic vapour phase epitaxy and by molecular beam epitaxy. We employed double crystal reflection x-ray topography using symmetric (0008) and (00012) reflections with CuKα radiation (λ = 1.54 A) to image dislocations, micropipes, and low angle boundaries in SiC substrates. Lattice strain near the core of a micropipe defect was estimated to be of the order of 10 -7 . The substrates investigated exhibited radial patterns of strain and, primarily, of tilt of the order of tens of arcsec. After deposition of the AlGaN and GaN layers, DCXRT images were generated from the substrate (0008) or (00012) and GaN epitaxial layer (0004) reflections. Full-width at half-maximum values ranging from ∼100 to 300 arcsec were typical of the GaN reflections, while those of the 4H-SiC reflections were ∼20-70 arcsec. Micropipes, tilt boundaries, and inclusions in the SiC were shown to produce structural defects in the GaN layers. A clear correlation between SiC substrate defects and GaN defects has been established

  4. 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

    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 ...... the pulse duration was increased to 4 μs, where a short-circuit energy of 9.1 J was obtained. The cause of the failure is the thermal runaway leading to a drain-source short....

  5. Fabrication and characterization of SiC and ZrC composite coating on TRISO coated particle

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H. G.; Lee, S. H.; Kim, D. J.; Park, J. Y.; Kim, W. J. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    SiC coating is widely suggested as structural materials for nuclear application due to its excellent high irradiation resistance properties and high temperature mechanical properties. SiC coating on TRistructural-ISOtropic (TRISO) coated fuel particles plays an important role as a protective layer from radioactive fission gas and a mechanical structural layer. TRISO coating layer was deposited on a spherical particle by a FBCVD method. The ZrO{sub 2} spherical particles were used as a simulant kernel. TRISO coating layers consisting of a porous buffer layer, an inner PyC layer were sequentially deposited before depositing SiC or ZrC coating layer. In order investigate the phase of each composite coating layer, Raman analysis was conducted. SiC, ZrC coating and SiC/ZrC composite coating on spherical particle were successfully deposited via FBCVD method by adjusting source gas flow rate. In the SiC and ZrC composite coating, SiC phase and ZrC phase were observed by XRD and SEM analysis. In the condition of 100 sccm of ZrCl{sub 4}, 25 sccm of CH{sub 4}, and 30 sccm of MTS, only two phases of SiC and ZrC were observed and two phases are located with clean grain boundary.

  6. SiC fibre by chemical vapour deposition on tungsten filament

    Indian Academy of Sciences (India)

    Unknown

    SiC fibre by chemical vapour deposition on tungsten filament ... CMCs), in defence and industrial applications. SiC has attractive ... porosity along with chemical purity. This is lacking .... reactor. Since mercury is very toxic it should be removed.

  7. 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...... 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...... based catalysts (BASF & HISPEC). These promising results signal a new era of SiC based catalysts for fuel cell applications....

  8. Recent progress of ultrahigh voltage SiC devices for particle accelerator

    International Nuclear Information System (INIS)

    Fukuda, Kenji; Tsuji, Takashi; Shiomi, Hiromu; Mizushima, Tomonori; Yonezawa, Yoshiyuki; Kondo, Chikara; Otake, Yuji

    2016-01-01

    Silicon carbide (SiC) is the promising material for next power electronics technology used in the field such as HEV, EV, and railway, electric power infrastructure. SiC enables power devices with low loss to easily operate in an ultrahigh-voltage region because of the high breakdown electric field of SiC. In this paper, we report static and dynamic electric performances of 3300 V class SiC SBDs, IE-MOSFETs, >10 kV PiN diodes and IE-IGBTs. Especially, the electrical characteristics of IE-IGBT with the blocking voltage of 16.5 kV indicate the sufficient ability to convert the thyratron in high power RF system of an accelerator. (author)

  9. 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

  10. A microstructure study of C + SiC coating materials for first wall of fusion reactor

    International Nuclear Information System (INIS)

    Pan Ying; Gao Dihua; Lu Huaichang; Yao Yiming

    1995-03-01

    By means of OM, SEM, XRD, WDS and EDAX, a microstructure study has been made of: (1) the dependence of microstructure and crystal structure of C + SiC coating and content and distribution of SiC in it on technological process, the coating was deposited on graphite substrate by chemical vapour deposition (CVD) with C 3 H 6 , CH 3 SiCl 3 and Ar mixture gases; (2) the influence of chemical sputtering by hydrogen ions and thermal shock by electron beams with high energy on microstructure and performance of the coating. The results show that the C + SiC coating deposited at 1600 degree C has good adherence and is resistant to damage from chemical sputtering by hydrogen ions and resistant to thermal shock by electron beams. (9 refs., 16 figs., 1 tab.)

  11. Defects induced by helium implantation in SiC

    International Nuclear Information System (INIS)

    Oliviero, E.; Barbot, J.F.; Declemy, A.; Beaufort, M.F.; Oliviero, E.

    2008-01-01

    SiC is one of the considered materials for nuclear fuel conditioning and for the fabrication of some core structures in future nuclear generation reactors. For the development of this advance technology, a fundamental research on this material is of prime importance. In particular, the implantation/irradiation effects have to be understood and controlled. It is with this aim that the structural alterations induced by implantation/irradiation in SiC are studied by different experimental techniques as transmission electron microscopy, helium desorption, X-ray diffraction and Rutherford backscattering spectrometry. In this work, the different types of defects induced by helium implantation in SiC, point or primary defects (obtained at low energy (∼100 eV) until spread defects (obtained at higher energy (until ∼2 MeV)) are exposed. The amorphization/recrystallization and swelling phenomena are presented too. (O.M.)

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

    Energy Technology Data Exchange (ETDEWEB)

    Hunn, John D., E-mail: hunnjd@ornl.gov [Oak Ridge National Laboratory (ORNL), P.O. Box 2008, Oak Ridge, TN 37831-6093 (United States); Baldwin, Charles A.; Gerczak, Tyler J.; Montgomery, Fred C.; Morris, Robert N.; Silva, Chinthaka M. [Oak Ridge National Laboratory (ORNL), P.O. Box 2008, Oak Ridge, TN 37831-6093 (United States); Demkowicz, Paul A.; Harp, Jason M.; Ploger, Scott A. [Idaho National Laboratory (INL), P.O. Box 1625, Idaho Falls, ID 83415-6188 (United States)

    2016-09-15

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

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

    Indian Academy of Sciences (India)

    Unknown

    SiC based materials so derived can be used in structural applications and in designing high temperature filters and catalyst supports. Keywords. Biomimetic synthesis; carbonaceous biopreform; biomorphic Si–SiC ceramic composites; porous cellular SiC ceramics. 1. Introduction. In recent years, there has been tremendous ...

  14. 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

  15. Photoluminescence enhancement in porous SiC passivated by atomic layer deposited Al2O3 films

    DEFF Research Database (Denmark)

    Lu, Weifang; Iwasa, Yoshimi; Ou, Yiyu

    2016-01-01

    Porous SiC co-doped with B and N was passivated by atomic layer deposited (ALD) Al2O3 films to enhance the photoluminescence. After optimizing the deposition conditions, as high as 14.9 times photoluminescence enhancement has been achieved.......Porous SiC co-doped with B and N was passivated by atomic layer deposited (ALD) Al2O3 films to enhance the photoluminescence. After optimizing the deposition conditions, as high as 14.9 times photoluminescence enhancement has been achieved....

  16. X-ray micro computed tomography characterization of cellular SiC foams for their applications in chemical engineering

    Energy Technology Data Exchange (ETDEWEB)

    Ou, Xiaoxia [School of Chemical Engineering and Analytical Science, The University of Manchester, M13 9PL (United Kingdom); Zhang, Xun; Lowe, Tristan [Henry Moseley X-ray Imaging Facility, Materials Science Centre, School of Materials, The University of Manchester, M13 9PL (United Kingdom); Blanc, Remi [FEI, 3 Impasse Rudolf Diesel, BP 50227, 33708 Mérignac (France); Rad, Mansoureh Norouzi [School of Chemical Engineering and Analytical Science, The University of Manchester, M13 9PL (United Kingdom); Wang, Ying [Henry Moseley X-ray Imaging Facility, Materials Science Centre, School of Materials, The University of Manchester, M13 9PL (United Kingdom); Batail, Nelly; Pham, Charlotte [SICAT SARL, 20 Place des Halles, 67000 Strasbourg (France); Shokri, Nima; Garforth, Arthur A. [School of Chemical Engineering and Analytical Science, The University of Manchester, M13 9PL (United Kingdom); Withers, Philip J. [Henry Moseley X-ray Imaging Facility, Materials Science Centre, School of Materials, The University of Manchester, M13 9PL (United Kingdom); Fan, Xiaolei, E-mail: xiaolei.fan@manchester.ac.uk [School of Chemical Engineering and Analytical Science, The University of Manchester, M13 9PL (United Kingdom)

    2017-01-15

    Open-cell SiC foams clearly are promising materials for continuous-flow chemical applications such as heterogeneous catalysis and distillation. X-ray micro computed tomography characterization of cellular β-SiC foams at a spatial voxel size of 13.6{sup 3} μm{sup 3} and the interpretation of morphological properties of SiC open-cell foams with implications to their transport properties are presented. Static liquid hold-up in SiC foams was investigated through in-situ draining experiments for the first time using the μ-CT technique providing thorough 3D information about the amount and distribution of liquid hold-up inside the foam. This will enable better modeling and design of structured reactors based on SiC foams in the future. In order to see more practical uses, μ-CT data of cellular foams must be exploited to optimize the design of the morphology of foams for a specific application. - Highlights: •Characterization of SiC foams using novel X-ray micro computed tomography. •Interpretation of structural properties of SiC foams regarding to their transport properties. •Static liquid hold-up analysis of SiC foams through in-situ draining experiments.

  17. 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

    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...... 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...... resistance and loop inductances. With total switching energy of 340.24 μJ, the SiC MOSFET has more than six times lower switching losses than a regular Si IGBT. Implementing the SiC switches in a 3 kW T-Type inverter topology, efficiency improvements of 0.8 % are achieved and maximum efficiency of 97...

  18. Elaboration of silicon carbides nano particles (SiC): from the powder synthesis to the sintered ceramic

    International Nuclear Information System (INIS)

    Reau, A.

    2008-01-01

    Materials for the reactor cores of the fourth generation will need materials supporting high temperatures with fast neutrons flux. SiC 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 f /SiC composite development and to study the influence of the fabrication parameters. (A.L.B.)

  19. Nanocrystalline SiC film thermistors for cryogenic applications

    Science.gov (United States)

    Mitin, V. F.; Kholevchuk, V. V.; Semenov, A. V.; Kozlovskii, A. A.; Boltovets, N. S.; Krivutsa, V. A.; Slepova, A. S.; Novitskii, S. V.

    2018-02-01

    We developed a heat-sensitive material based on nanocrystalline SiC films obtained by direct deposition of carbon and silicon ions onto sapphire substrates. These SiC films can be used for resistance thermometers operating in the 2 K-300 K temperature range. Having high heat sensitivity, they are relatively low sensitive to the magnetic field. The designs of the sensors are presented together with a discussion of their thermometric characteristics and sensitivity to magnetic fields.

  20. A comparative study of low energy radiation responses of SiC, TiC and ZrC

    International Nuclear Information System (INIS)

    Jiang, M.; Xiao, H.Y.; Zhang, H.B.; Peng, S.M.; Xu, C.H.; Liu, Z.J.; Zu, X.T.

    2016-01-01

    In this study, an ab initio molecular dynamics method is employed to compare the responses of SiC, TiC and ZrC to low energy irradiation. It reveals that C displacements are dominant in the cascade events of the three carbides. The associated defects in SiC are mainly Frenkel pairs and antisite defects, whereas damage end states in TiC and ZrC generally consist of Frenkel pairs and very few antisite defects are created. It is proposed that the susceptibility to antisite formation in SiC contributes to its crystalline-to-amorphous transformation under irradiation that is observed experimentally. The stronger radiation tolerance of TiC and ZrC than SiC can be originated from their different electronic structures, i.e., the C> and C> bonds are a mixture of covalent, metallic, and ionic character, whereas the C> bond is mainly covalent. The presented results provide underlying mechanisms for defect generation in SiC, TiC and ZrC, and advance the fundamental understanding of the radiation resistances of carbide materials.

  1. 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 15......R polytypes. It is found that pyrolytic graphite results in enhanced texturing of the nucleating gas species. Reducing the pressure leads to growth of the crystallites until a closed polycrystalline SiC layer containing voids with a rough surface is developed. Bulk growth was conducted at 35 mbar Ar...

  2. Synergetic Effect of Graphene and MWCNTs on Microstructure and Mechanical Properties of Cu/Ti3SiC2/C Nanocomposites

    Science.gov (United States)

    Jiang, Xiaosong; Song, Tingfeng; Shao, Zhenyi; Liu, Wanxia; Zhu, Degui; Zhu, Minhao

    2017-11-01

    Multi-walled carbon nanotubes (MWCNTs) and graphenes have been taken for novel reinforcements due to their unique structure and performance. However, MWCNTs or graphenes reinforced copper matrix composites could not catch up with ideal value due to reinforcement dispersion in metal matrix, wettability to metal matrix, and composite material interface. Taking advantage of the superior properties of one-dimensional MWCNTs and two-dimensional graphenes, complementary performance and structure are constructed to create a high contact area between MWCNTs and graphenes to the Cu matrix. Mechanical alloying, hot pressing, and hot isostatic pressing techniques are used to fabricate Cu matrix self-lubricating nanocomposites. Effects of MWCNTs and graphenes on mechanical properties and microstructures of Cu/Ti3SiC2/C nanocomposites are studied. The fracture and strengthening mechanisms of Cu/Ti3SiC2/C nanocomposites are explored on the basis of structure and composition of Cu/Ti3SiC2/C nanocomposites with formation and function of interface.

  3. Growth and characterization of high-purity SiC single crystals

    Science.gov (United States)

    Augustine, G.; Balakrishna, V.; Brandt, C. D.

    2000-04-01

    High-purity SiC single crystals with diameter up to 50 mm have been grown by the physical vapor transport method. Finite element analysis was used for thermal modeling of the crystal growth cavity in order to reduce stress in the grown crystal. Crystals are grown in high-purity growth ambient using purified graphite furniture and high-purity SiC sublimation sources. Undoped crystals up to 50 mm in diameter with micropipe density less than 100 cm -2 have been grown using this method. These undoped crystals exhibit resistivities in the 10 3 Ω cm range and are p-type due to the presence of residual acceptor impurities, mainly boron. Semi-insulating SiC material is obtained by doping the crystal with vanadium. Vanadium has a deep donor level located near the middle of the band gap, which compensates the residual acceptor resulting in semi-insulating behavior.

  4. Passivation of hexagonal SiC surfaces by hydrogen termination

    International Nuclear Information System (INIS)

    Seyller, Thomas

    2004-01-01

    Surface hydrogenation is a well established technique in silicon technology. It is easily accomplished by wet-chemical procedures and results in clean and unreconstructed surfaces, which are extremely low in charged surface states and stable against oxidation in air, thus constituting an ideal surface preparation. As a consequence, methods for hydrogenation have been sought for preparing silicon carbide (SiC) surfaces with similar well defined properties. It was soon recognized, however, that due to different surface chemistry new ground had to be broken in order to find a method leading to the desired monatomic hydrogen saturation. In this paper the results of H passivation of SiC surfaces by high-temperature hydrogen annealing will be discussed, thereby placing emphasis on chemical, structural and electronic properties of the resulting surfaces. In addition to their unique properties, hydrogenated hexagonal SiC {0001} surfaces offer the interesting possibility of gaining insight into the formation of silicon- and carbon-rich reconstructions as well. This is due to the fact that to date hydrogenation is the only method providing oxygen-free surfaces with a C to Si ratio of 1:1. Last but not least, the electronic properties of hydrogen-free SiC {0001} surfaces will be alluded to. SiC {0001} surfaces are the only known semiconductor surfaces that can be prepared in their unreconstructed (1 x 1) state with one dangling bond per unit cell by photon induced hydrogen desorption. These surfaces give indications of a Mott-Hubbard surface band structure

  5. 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.

  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. 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_2O_3 and Y_2O_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.

  8. 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).

  9. 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).

  10. Aqueous suspensions of {alpha}Al{sub 2}O{sub 3}/SiC mixed systems

    Energy Technology Data Exchange (ETDEWEB)

    Pagnoux, C.; Baklouti, S.; Chartier, T.; Baumard, J.F. [ENSCI, Limoges (France). LMCTS

    1997-12-31

    The preparation of aqueous {alpha}-Al{sub 2}O{sub 3}, {alpha}-SiO{sub 2} and {alpha}-SiC suspensions with polyelectrolytes, respectively the NH{sub 4}{sup +} salt of polymethacrylic acid (PMA-NH{sub 4}{sup +}) and acidic form polyethylene imine (PEI-H{sup +}) is investigated. It is based on the adsorption of these polyelectrolytes which in turn depends mainly on the nature of the polyelectrolyte, and the charge density which develops on the powder surface in water. Good dispersion and stability of dispersions are then obtained through electrostatic and steric stabilization. As an application, the preparation of an Al{sub 2}O{sub 3}-SiC aqueous mixed slurry was investigated as a preliminary step for processing of Al{sub 2}O{sub 3}/SiC nanocomposites. (orig.) 2 refs.

  11. 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

  12. 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.

  13. 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)

  14. Failure probabilities of SiC clad fuel during a LOCA in public acceptable simple SMR (PASS)

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Youho, E-mail: euo@kaist.ac.kr; Kim, Ho Sik, E-mail: hskim25@kaist.ac.kr; NO, Hee Cheon, E-mail: hcno@kaist.ac.kr

    2015-10-15

    Highlights: • Graceful operating conditions of SMRs markedly lower SiC cladding stress. • Steady-state fracture probabilities of SiC cladding is below 10{sup −7} in SMRs. • PASS demonstrates fuel coolability (T < 1300 °C) with sole radiation in LOCA. • SiC cladding failure probabilities of PASS are ∼10{sup −2} in LOCA. • Cold gas gap pressure controls SiC cladding tensile stress level in LOCA. - Abstract: Structural integrity of SiC clad fuels in reference Small Modular Reactors (SMRs) (NuScale, SMART, IRIS) and a commercial pressurized water reactor (PWR) are assessed with a multi-layered SiC cladding structural analysis code. Featured with low fuel pin power and temperature, SMRs demonstrate markedly reduced incore-residence fracture probabilities below ∼10{sup −7}, compared to those of commercial PWRs ∼10{sup −6}–10{sup −1}. This demonstrates that SMRs can serve as a near-term deployment fit to SiC cladding with a sound management of its statistical brittle fracture. We proposed a novel SMR named Public Acceptable Simple SMR (PASS), which is featured with 14 × 14 assemblies of SiC clad fuels arranged in a square ring layout. PASS aims to rely on radiative cooling of fuel rods during a loss of coolant accident (LOCA) by fully leveraging high temperature tolerance of SiC cladding. An overarching assessment of SiC clad fuel performance in PASS was conducted with a combined methodology—(1) FRAPCON-SiC for steady-state performance analysis of PASS fuel rods, (2) computational fluid dynamics code FLUENT for radiative cooling rate of fuel rods during a LOCA, and (3) multi-layered SiC cladding structural analysis code with previously developed SiC recession correlations under steam environments for both steady-state and LOCA. The results show that PASS simultaneously maintains desirable fuel cooling rate with the sole radiation and sound structural integrity of fuel rods for over 36 days of a LOCA without water supply. The stress level of

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, E.J., E-mail: jolivier@nmmu.ac.za [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Neethling, J.H. [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2013-01-15

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

  17. 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_2O_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_2O_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 are

  18. 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

  19. 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.

  20. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. 10kV SiC MOSFET split output power module

    DEFF Research Database (Denmark)

    Beczkowski, Szymon; Li, Helong; Uhrenfeldt, Christian

    2015-01-01

    The poor body diode performance of the first generation of 10kV SiC MOSFETs and the parasitic turn-on phenomenon limit the performance of SiC based converters. Both these problems can potentially be mitigated using a split output topology. In this paper we present a comparison between a classical...

  3. Liquid phase sintered SiC ceramics from starting materials of different grade Cerâmicas à base de SiC sinterizadas via fase líquida a partir de matérias-primas de diferentes purezas

    Directory of Open Access Journals (Sweden)

    V. A. Izhevskyi

    2004-09-01

    Full Text Available Possibility of high performance ceramics manufactured from commercial SiC powder of technical grade has been shown. Sintering behavior and microstructure formation under conditions of liquid phase sintering (LPS with oxynitride sintering aids (AlN-Y2O3 of three SiC-based compositions have been investigated. Two of the compositions were based on Alcoa 1000 SiC powder of technical grade, and the third one, which was used as a reference, was based on H.C. Starck UF-15 fine grade commercial powder. Milling process used for Alcoa 1000 SiC powder granulometry improvement has been investigated in detail, while chemical treatment of milled SiC powders has been used for pick-up impurities removal. Dilatometric experiments showed that SiC powder of technical grade after appropriate treatment exhibits sinterability comparable with the fine grade SiC. Microstructural investigations performed on sintered samples showed that the final microstructure of the Alcoa 1000 SiC based materials was practically identical with the H.C. Starck SiC based reference ones. Preliminary investigations of hardness and fracture toughness were carried out revealing excellent results for the materials produced from cheaper, nationally produced starting powder.Neste trabalho é apresentada a possibilidade de obtenção de cerâmicas de SiC de alto desempenho a partir de matéria-prima comercial de grau técnico. Foi realizado o estudo de sinterização via fase líquida e desenvolvimento microestrutural de três composições à base de SiC tendo como aditivos de sinterização AlN e Y2O3 . Duas destas composições são à base de SiC-1000 da Alcoa, grau técnico, e a terceira, utilizada como referência, à base do UF-15 da H.C. Starck - Alemanha, pó comercial de granulometria fina. O processo de moagem do pó SiC-1000 da Alcoa foi acompanhado por medidas de distribuição granulométrica e posterior ataque químico, para remoção de impurezas. Os pós de grau técnico, ap

  4. Interfacial reaction between SiC and aluminium due to extrusion and heat treatment process

    International Nuclear Information System (INIS)

    Junaidah Jai; Fauzi Ismail; Samsiah Sulaiman; Patthi Hussain, Azmi Idris; Yoichi Murakoshi

    1999-01-01

    Chemical interaction between aluminium (Al) and silicon carbide (SiC) produces aluminium carbide (Al 4 C 3 ) which presents potential problems in the production and application of Al/SiC Metal Matrix Composit (MMC). The Al 4 C 3 formed can reduce material properties such as strength in the MMC. This research work investigates the interface reaction in Al 7075/SiC MMC made through hot extrusion process. Mixed Al 7075/SiC MMC powders were pressed at 300 degree C and extruded at 500 degree C, with a reduction ratio of 20:1. The extruded MMC was then heat-treated in air at various temperatures from 560 degree C, 600 degree C, 640 degree C, 700 degree C to 800 degree C in order to observe the interface reaction of the MMC materials. The heat-treated MMCs were then analyzed under the optical microscope, X-ray Diffraction (XRD) Spectroscope and Scanning Electron Microscope (SEM) with Energy Dispersive X-ray (EDAZ) attachment to observe the interface reaction within the MMCs. This investigation confirms there was interface reaction between SiC and aluminium

  5. 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.

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

    KAUST Repository

    Kahaly, M. Upadhyay; Kaloni, Thaneshwor P.; Schwingenschlö gl, Udo

    2013-01-01

    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.

  7. Tribological Behavior of Si3N4/Ti3SiC2 Contacts Lubricated by Lithium-Based Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Haizhong Wang

    2014-01-01

    Full Text Available The tribological performance of Si3N4 ball sliding against Ti3SiC2 disc lubricated by lithium-based ionic liquids (ILs was investigated using an Optimol SRV-IV oscillating reciprocating friction and wear tester at room temperature (RT and elevated temperature (100°C. Glycerol and the conventional imidazolium-based IL 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonylimide (L-F106 were used as references under the same experimental conditions. The results show that the lithium-based ILs had higher thermal stabilities than glycerol and lower costs associated with IL preparation than L-F106. The tribotest results show that the lithium-based ILs were effective in reducing the friction and wear of Si3N4/Ti3SiC2 contacts. [Li(urea]TFSI even produced better tribological properties than glycerol and L-F106 both at RT and 100°C. The SEM/EDS and XPS results reveal that the excellent tribological endurance of Si3N4/Ti3SiC2 contacts lubricated by lithium-based ILs was mainly attributed to the formation of surface protective films composed of various tribochemical products.

  8. A comparative study of the mechanical and thermal properties of defective ZrC, TiC and SiC.

    Science.gov (United States)

    Jiang, M; Zheng, J W; Xiao, H Y; Liu, Z J; Zu, X T

    2017-08-24

    ZrC and TiC have been proposed to be alternatives to SiC as fuel-cladding and structural materials in nuclear reactors due to their strong radiation tolerance and high thermal conductivity at high temperatures. To unravel how the presence of defects affects the thermo-physical properties under irradiation, first-principles calculations based on density function theory were carried out to investigate the mechanical and thermal properties of defective ZrC, TiC and SiC. As compared with the defective SiC, the ZrC and TiC always exhibit larger bulk modulus, smaller changes in the Young's and shear moduli, as well as better ductility. The total thermal conductivity of ZrC and TiC are much larger than that of SiC, implying that under radiation environment the ZrC and TiC will exhibit superior heat conduction ability than the SiC. One disadvantage for ZrC and TiC is that their Debye temperatures are generally lower than that of SiC. These results suggest that further improving the Debye temperature of ZrC and TiC will be more beneficial for their applications as fuel-cladding and structural materials in nuclear reactors.

  9. Electroplating chromium on CVD SiC and SiCf-SiC advanced cladding via PyC compatibility coating

    Science.gov (United States)

    Ang, Caen; Kemery, Craig; Katoh, Yutai

    2018-05-01

    Electroplating Cr on SiC using a pyrolytic carbon (PyC) bond coat is demonstrated as an innovative concept for coating of advanced fuel cladding. The quantification of coating stress, SEM morphology, XRD phase analysis, and debonding test of the coating on CVD SiC and SiCf-SiC is shown. The residual tensile stress (by ASTM B975) of electroplated Cr is > 1 GPa prior to stress relaxation by microcracking. The stress can remove the PyC/Cr layer from SiC. Surface etching of ∼20 μm and roughening to Ra > 2 μm (by SEM observation) was necessary for successful adhesion. The debonding strength (by ASTM D4541) of the coating on SiC slightly improved from 3.6 ± 1.4 MPa to 5.9 ± 0.8 MPa after surface etching or machining. However, this improvement is limited due to the absence of an interphase, and integrated CVI processing may be required for further advancement.

  10. Joining of pressureless-sintered SiC to stainless steel using Ag-Cu alloy and insert-metals

    International Nuclear Information System (INIS)

    Yano, Toyohiko; Takada, Naohiro; Iseki, Takayoshi

    1987-01-01

    Brazing of pressureless-sintered SiC to stainless steel using Ag-28 wt% Cu alloy was studied. In SiC plate joined to stainless steel rod (6 mm in diameter) using an Ag-Cu alloy powder containing 1.5 wt% Ti, the bond strength increased with decreasing brazing temperature and holding time. When the increased size of stainless steel plate (10 x 10 x 4 mm), joining was unsuccessful by the method mentioned above and even with Ti insert-metal. However, simultaneous use of Ti and Mo as insert-metal gave a good bonding in the order SiC/Ti/Mo/stainless steel, because of relaxation of residual stress due to thermal expansion mismatch. The shear strength was 30 - 50 MPa. A thin layer, probably Ti 3 SiC 2 , was observed at the interface between SiC and brazing filler immediately after melting. But with increasing both temperature and time, Ti 5 Si 3 (C) and TiC x were formed if Ti was continuously provided from the brazing filler. Since the interface of Ti 3 SiC 2 and either Ti 5 Si 3 (C) or TiC x seemed to be brittle, the formation of Ti 5 Si 3 (C) and TiC x decreased the bond strength. At lower temperature and short time, a high bond strength is expected when Ti was inserted in contact with SiC. (author)

  11. Biomorphous SiC ceramics prepared from cork oak as precursor

    Science.gov (United States)

    Yukhymchuk, V. O.; Kiselov, V. S.; Valakh, M. Ya.; Tryus, M. P.; Skoryk, M. A.; Rozhin, A. G.; Kulinich, S. A.; Belyaev, A. E.

    2016-04-01

    Porous ceramic materials of SiC were synthesized from carbon matrices obtained via pyrolysis of natural cork as precursor. We propose a method for the fabrication of complex-shaped porous ceramic hardware consisting of separate parts prepared from natural cork. It is demonstrated that the thickness of the carbon-matrix walls can be increased through their impregnation with Bakelite phenolic glue solution followed by pyrolysis. This decreases the material's porosity and can be used as a way to modify its mechanical and thermal characteristics. Both the carbon matrices (resulted from the pyrolysis step) and the resultant SiC ceramics are shown to be pseudomorphous to the structure of initial cork. Depending on the synthesis temperature, 3C-SiC, 6H-SiC, or a mixture of these polytypes, could be obtained. By varying the mass ratio of initial carbon and silicon components, stoichiometric SiC or SiC:C:Si, SiC:C, and SiC:Si ceramics could be produced. The structure, as well as chemical and phase composition of the prepared materials were studied by means of Raman spectroscopy and scanning electron microscopy.

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

    International Nuclear Information System (INIS)

    Qian Junmin; Wang Jiping; Jin Zhihao

    2004-01-01

    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 β-SiC with traces of α-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

  13. 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.

  14. 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

  15. 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

  16. Morphological and electronic properties of epitaxial graphene on SiC

    International Nuclear Information System (INIS)

    Yakimova, R.; Iakimov, T.; Yazdi, G.R.; Bouhafs, C.; Eriksson, J.; Zakharov, A.; Boosalis, A.; Schubert, M.; Darakchieva, V.

    2014-01-01

    We report on the structural and electronic properties of graphene grown on SiC by high-temperature sublimation. We have studied thickness uniformity of graphene grown on 4H–SiC (0 0 0 1), 6H–SiC (0 0 0 1), and 3C–SiC (1 1 1) substrates and investigated in detail graphene surface morphology and electronic properties. Differences in the thickness uniformity of the graphene layers on different SiC polytypes is related mainly to the minimization of the terrace surface energy during the step bunching process. It is also shown that a lower substrate surface roughness results in more uniform step bunching and consequently better quality of the grown graphene. We have compared the three SiC polytypes with a clear conclusion in favor of 3C–SiC. Localized lateral variations in the Fermi energy of graphene are mapped by scanning Kelvin probe microscopy. It is found that the overall single-layer graphene coverage depends strongly on the surface terrace width, where a more homogeneous coverage is favored by wider terraces. It is observed that the step distance is a dominating, factor in determining the unintentional doping of graphene from the SiC substrate. Microfocal spectroscopic ellipsometry mapping of the electronic properties and thickness of epitaxial graphene on 3C–SiC (1 1 1) is also reported. Growth of one monolayer graphene is demonstrated on both Si- and C-polarity of the 3C–SiC substrates and it is shown that large area homogeneous single monolayer graphene can be achieved on the Si-face substrates. Correlations between the number of graphene monolayers on one hand and the main transition associated with an exciton enhanced van Hove singularity at ∼4.5 eV and the free-charge carrier scattering time, on the other are established. It is shown that the interface structure on the Si- and C-polarity of the 3C–SiC (1 1 1) differs and has a determining role for the thickness and electronic properties homogeneity of the epitaxial graphene.

  17. 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

  18. Analysis on the sequence of formation of Ti{sub 3}SiC{sub 2} and Ti{sub 3}SiC{sub 2}/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Radhakrishnan, R.; Bhaduri, S.B. [Idaho Univ., Moscow, ID (United States). Dept. of Mining and Metallurgy; Henager, C.H. Jr. [Pacific Northwest Lab., Richland, WA (United States)

    1995-05-01

    Ti{sub 3}SiC{sub 2}, a compound in the ternary Ti-Si-C system, is reported to be ductile. This paper reports the sequence of formation of Ti{sub 3}SiC{sub 2} and Ti{sub 3}SiC{sub 2}/SiC composites involving either combustion synthesis or by displacement reaction, respectively. Onset of exothermic reaction temperatures were determined using Differential Thermal Analysis (DTA). Phases present after the exothermic temperatures were analyzed by X-Ray diffraction. Based on these observations, a route to formation of Ti{sub 3}SiC{sub 2} and Ti{sub 3}SiC{sub 2}/SiC composites is proposed for the two`s thesis methods.

  19. Manufacturing and characterization of porous SiC for flow channel inserts in dual-coolant blanket designs

    Energy Technology Data Exchange (ETDEWEB)

    Bereciartu, Ainhoa [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 San Sebastian (Spain); Ordas, Nerea, E-mail: nordas@ceit.es [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 San Sebastian (Spain); Garcia-Rosales, Carmen [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 San Sebastian (Spain); Morono, Alejandro; Malo, Marta; Hodgson, Eric R. [CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain); Abella, Jordi [Institut Quimic de Sarria, University Ramon Llull, Via Augusta 390, 08017 Barcelona (Spain); Sedano, Luis [CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain)

    2011-10-15

    SiC is the primary candidate for the flow channel inserts in dual-coolant blanket concepts. Porous SiC ceramics are attractive candidates for this non-structural application, since they can satisfy the required properties through a low cost manufacturing route, compared to SiC{sub f}/SiC. This work shows first results of the manufacturing of porous SiC ceramics prepared with different amounts of Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} as sintering additives. C powders were used as pore-formers by their burnout during oxidation after sintering. Comparison of microstructure, porosity, flexural strength, thermal and electrical conductivity and corrosion under Pb-15.7Li of porous SiC without and with sintering additives is presented. The addition of 2.5 wt.% of Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} improves the mechanical properties, and reduces the thermal and electrical conductivity down to reasonable values. Preliminary corrosion tests under Pb-15.7 Li at 500 deg. C show that the absence of a dense coating on porous SiC leads to poor corrosion behavior.

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

    Energy Technology Data Exchange (ETDEWEB)

    Morse, K. [Colorado School of Mines, Golden, CO (United States); Balooch, M.; Hamza, A.V.; Belak, J. [Lawrence Livermore National Lab., CA (United States)

    1994-12-01

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

  1. 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

  2. SiC nanofibers grown by high power microwave plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Honda, Shin-ichi; Baek, Yang-Gyu; Ikuno, Takashi; Kohara, Hidekazu; Katayama, Mitsuhiro; Oura, Kenjiro; Hirao, Takashi

    2003-01-01

    Silicon carbide (SiC) nanofibers have been synthesized on Si substrates covered by Ni thin films using high power microwave chemical vapor deposition (CVD). Characterization using transmission electron microscopy (TEM) combined with electron energy-dispersive X-ray spectroscopy (EDX) revealed that the resultant fibrous nanostructures were assigned to β-SiC with high crystallinity. The formation of SiC nanofibers can be explained by the vapor liquid solid (VLS) mechanism in which precipitation of SiC occurs from the supersaturated Ni nanoparticle containing Si and C

  3. Tailoring of SiC nanoprecipitates formed in Si

    Energy Technology Data Exchange (ETDEWEB)

    Velisa, G., E-mail: gihan.velisa@cea.fr [CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 077125 Magurele (Romania); Trocellier, P. [CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); Thomé, L. [Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, UMR8609, Bât. 108, 91405 Orsay (France); Vaubaillon, S. [CEA, INSTN, UEPTN, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); Miro, S.; Serruys, Y.; Bordas, É. [CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); Meslin, E. [CEA, DEN, Service de Recherches de Métallurgie Physique, F-91191 Gif-sur-Yvette (France); Mylonas, S. [Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, UMR8609, Bât. 108, 91405 Orsay (France); Coulon, P.E. [Ecole Polytechnique, Laboratoire des Solides Irradiés, CEA/DSM/IRAMIS-CNRS, 91128 Palaiseau Cedex (France); Leprêtre, F.; Pilz, A.; Beck, L. [CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France)

    2013-07-15

    The SiC synthesis through single-beam of C{sup +}, and simultaneous-dual-beam of C{sup +} and Si{sup +} ion implantations into a Si substrate heated at 550 °C has been studied by means of three complementary analytical techniques: nuclear reaction analysis (NRA), Raman, and transmission electron microscopy (TEM). It is shown that a broad distribution of SiC nanoprecipitates is directly formed after simultaneous-dual-beam (520-keV C{sup +} and 890-keV Si{sup +}) and single-beam (520-keV C{sup +}) ion implantations. Their shape appear as spherical (average size ∼4–5 nm) and they are in epitaxial relationship with the silicon matrix.

  4. Oxygen isotopic exchange occurring during dry thermal oxidation of 6H SiC

    Energy Technology Data Exchange (ETDEWEB)

    Vickridge, I.C. E-mail: vickridge@gps.jussieu.fr; Tromson, D.; Trimaille, I.; Ganem, J.-J.; Szilagyi, E.; Battistig, G

    2002-05-01

    SiC is a large band gap semiconductor, promising for high power and high frequency devices. The thermal oxide is SiO{sub 2} however the growth rates of thermal oxide on SiC are substantially slower than on Si, and different along the polar directions (<0 0 0 1-bar> and <0 0 0 1> in the hexagonal polytypes). Thorough understanding of the oxide growth mechanisms may give us new insights into the nature of the SiO{sub 2}/SiC interface, crucial for device applications. We have determined growth kinetics for ultra-dry thermal oxidation of 6H SiC at 1100 deg. C for pressures from 3 to 200 mbar. At 3 mbar, the lowest pressure studied, the oxide growth rates along the two polar directions are virtually the same. At higher pressures growth is faster on the carbon-terminated (0 0 0 1-bar) face. After consecutive oxidations at 1100 deg. C and 100 mbar in {sup 18}O{sub 2} and {sup 16}O{sub 2} gases, {sup 18}O depth profiles show significant isotopic exchange and oxygen movement within the oxide during oxidation.

  5. Joining of SiC ceramics and SiC/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Rabin, B.H. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

    1996-08-01

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

  6. Synthesis of nanostructured SiC using the pulsed laser deposition technique

    International Nuclear Information System (INIS)

    Zhang, H.X.; Feng, P.X.; Makarov, V.; Weiner, B.R.; Morell, G.

    2009-01-01

    We report the new results on the direct synthesis of nanostructured silicon carbide (SiC) materials using the pulsed laser deposition technique. Scanning electron microscopy images revealed that SiC nanoholes, nanosprouts, nanowires, and nanoneedles were obtained. The crystallographic structure, chemical composition, and bond structure of the nanoscale SiC materials were investigated using X-ray diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman scattering spectroscopy. The transverse optical mode and longitudinal optical mode in Raman spectra were found to become sharper as the substrate temperature was increased, while the material structure evolved from amorphous to crystalline

  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. 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.

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

    KAUST Repository

    Chen, Shanliang; Ying, Pengzhan; Wang, Lin; Wei, Guodong; Gao, Fengmei; Zheng, Jinju; Shang, Minhui; Yang, Zuobao; Yang, Weiyou; Wu, Tao

    2015-01-01

    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.

  10. Dynamic study of the thermal stability of impure Ti 3SiC 2 in argon and air by neutron diffraction

    Science.gov (United States)

    Oo, Z.; Low, I. M.; O'Connor, B. H.

    2006-11-01

    The dynamic thermal stability and topotactic phase transition of impure Ti 3SiC 2 in air and argon have been investigated by neutron diffraction (ND). In the presence of a low oxygen partial pressure as in argon, Ti 3SiC 2 underwent a surface dissociation and TiC and/or Ti 5Si 3C were detected at 1200 °C. In contrast, oxide layers of rutile (TiO 2), TiO and cristobalite (SiO 2) were detected at ∼1000, 1250 and 1300 °C respectively when exposed to an oxygen-rich environment. Near-surface depth profiling of Ti 3SiC 2 oxidized in air at 1200 °C by secondary ion mass spectroscopy (SIMS) has revealed a distinct gradation in phase composition at the interface of homogeneous rutile and heterogeneous cristobalite-rutile layers.

  11. Dynamic study of the thermal stability of impure Ti3SiC2 in argon and air by neutron diffraction

    International Nuclear Information System (INIS)

    Oo, Z.; Low, I.M; O'Connor, B.H.

    2006-01-01

    The dynamic thermal stability and topotactic phase transition of impure Ti 3 SiC 2 in air and argon have been investigated by neutron diffraction (ND). In the presence of a low oxygen partial pressure as in argon, Ti 3 SiC 2 underwent a surface dissociation and TiC and/or Ti 5 Si 3 C were detected at 1200 deg. C. In contrast, oxide layers of rutile (TiO 2 ), TiO and cristobalite (SiO 2 ) were detected at ∼1000, 1250 and 1300 deg. C respectively when exposed to an oxygen-rich environment. Near-surface depth profiling of Ti 3 SiC 2 oxidized in air at 1200 deg. C by secondary ion mass spectroscopy (SIMS) has revealed a distinct gradation in phase composition at the interface of homogeneous rutile and heterogeneous cristobalite-rutile layers

  12. 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)

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

    International Nuclear Information System (INIS)

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

    2012-01-01

    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 SF 6 -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. (paper)

  14. Structural and electrical characterization of ion beam synthesized and n-doped SiC layers

    Energy Technology Data Exchange (ETDEWEB)

    Serre, C.; Perez-Rodriguez, A.; Romano-Rodriguez, A.; Morante, J.R. [Barcelona Univ. (Spain). Dept. Electronica; Panknin, D.; Koegler, R.; Skorupa, W. [Forschungszentrum Rossendorf, Dresden (Germany); Esteve, J.; Acero, M.C. [CSIC, Bellaterra (Spain). Centre Nacional de Microelectronica

    2001-07-01

    This work reports preliminary data on the ion beam synthesis of n-doped SiC layers. For this, two approaches have been studied: (i) doping by ion implantation (with N{sup +}) of ion beam synthesized SiC layers and (ii) ion beam synthesis of SiC in previously doped (with P) Si wafers. In the first case, the electrical data show a p-type overcompensation of the SiC layer in the range of temperatures between -50 C and 125 C. The structural (XRD) and in-depth (SIMS, Spreading Resistance) analysis of the samples suggest this overcompensation to be induced by p-type active defects related to the N{sup +} ion implantation damage, and therefore the need for further optimization their thermal processing. In contrast, the P-doped SiC layers always show n-type doping. This is also accompanied by a higher structural quality, being the spectral features of the layers similar to those from the not doped material. Electrical activation of P in the SiC lattice is about one order of magnitude lower than in Si. These data constitute, to our knowledge, the first results reported on the doping of ion beam synthesized SiC layers. (orig.)

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

    OpenAIRE

    CAO Da-li; ZHOU Jing-yi; JIN Yong-ming

    2007-01-01

    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 phas...

  16. Effect of SiC whisker addition on the microstructures and mechanical properties of Ti(C, N)-based cermets

    International Nuclear Information System (INIS)

    Wu, Peng; Zheng, Yong; Zhao, Yongle; Yu, Haizhou

    2011-01-01

    Ti(C, N)-based cermets with addition of SiC whisker (SiC w ) were prepared by vacuum sintering. The microstructures of the prepared cermets were investigated by using X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Mechanical properties such as transverse rupture strength (TRS), fracture toughness (K IC ) and hardness (HRA) were also measured. It was found that the grain size of the cermets was affected by the SiC whisker addition. The cermets with 1.0 wt.% SiC whisker addition exhibited the smallest grain size. The porosities of the cermets increased with increasing SiC whisker additions. The addition of the SiC whisker had no influence on the phase constituents of the cermets. Compared with the cermets with no whisker addition, the highest TRS and fracture toughness for cermets with 1.0 wt.% SiC whisker addition increased by about 24% and 29%, respectively. The strengthening mechanisms were attributed to finer grain size, homogeneous microstructure and moderate thickness of rim phase. The toughening mechanisms were characterized by crack deflection, whisker bridging and whisker pulling-out.

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

    DEFF Research Database (Denmark)

    Ou, Yiyu; Aijaz, Imran; Ou, Haiyan

    2012-01-01

    White light-emitting diodes (LEDs) consisting of a nitride-based blue LED chip and phosphor are very promising candidates for the general lighting applications as energy-saving sources. Recently, donor-acceptor doped fluorescent SiC has been proven as a highly efficient wavelength converter...... 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...... gold layer turns into discontinuous nano-islands. The average size of the islands is dependent on the annealing condition which could be well controlled. By using the reactive-ion etching, pseudo-periodic moth-eye structures would be obtained using the gold nano-islands as a mask layer. Reactive...

  18. The development of SiC whisker fabrication technology for nuclear applications

    International Nuclear Information System (INIS)

    Kang, Thae Khapp; Kuk, Il Hiun; Lee, Jae Chun; Rhee, Chang Kyu; Lee, Ho Jin; Park, Soon Dong

    1990-02-01

    Important process factors of carbothermic process for the growth of SiC whiskers were investigated. The crystalline form of silicon dioxide, amount of carbon addition, graphite, silicon, catalysts, additive and reaction temperature were chosen as the main factors. Morphology of the resultant products was grouped into 3 different types; whisker,noodle and power types. The addition of catalyst affected in most the formation of SiC whiskers. Effects of catalyst and additive additions and reaction atmospheres on the morphology anf growth of SiC whiskers were investigated, silicon monoxide power and carbon monoxide gas were used as the raw materials. The addition of an iron containing catalyst resulted in a very long thread-like growth of the whiskers, while that of sodium chloride helical curlings. Addition of hydrogen to the non-oxidizing atmosphere enhanced the whisker formations. Crystallization of amorphous silicon monoxide raw powder was investigated at high temperatures up to 1500 deg C in Ar atmosphere using graphite crucible. Up to 900 deg C no crystallization occurred, while at 1100 - 1300 deg C silicon formation, and at 1500 deg C silicon dioxide and silicon carbide formations were detected. A slight weight loss began 1300 deg C, and the weight loss became about 33 % at 1500 deg C. After the formation reaction of SiC whiskers, the reaction products were leached by hydrofluoric acids. The optimum concentration of the hydrofluoric acid was 2 %. (author)

  19. 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.

  20. Microstructure of SiC ceramics fabricated by pyrolysis of electron beam irradiated polycarbomethylsilane containing precursors

    International Nuclear Information System (INIS)

    Xu Yunshu; Tanaka, Shigeru

    2003-01-01

    A modified gel-casting method was developed to form the ceramics precursor matrix by using polycarbomehylsilane (PCMS) and SiC powder. The polymer precursor was mixed with SiC powder in toluene, and then the slurry samples were cast into designed shapes. The pre-ceramic samples were then irradiated by 2.0 MeV electron beam generated by a Cockcroft-Walton type accelerator in He gas flow to about 15 MGy. The cured samples were pyrolyzed and sintered into SiC ceramics at 1300degC in Ar gas. The modified gel-casting method leaves almost no internal stress in the pre-ceramic samples, and the electron beam curing not only diminished the amount of pyrolysis gaseous products but also enhanced the interface binding of the polymer converted SiC and the grains of SiC powder. Optical microscope, AFM and SEM detected no visible internal or surface cracks in the final SiC ceramics matrix. A maximum value of 122 MPa of flexural strength of the final SiC ceramics was achieved. (author)

  1. Creep behavior for advanced polycrystalline SiC fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States); Kohyama, Akira [Kyoto Univ. (Japan)] [and others

    1997-04-01

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

  2. De interactie van SiC met Fe, Ni en hun legeringen

    NARCIS (Netherlands)

    Schiepers, R.C.J.

    1991-01-01

    De interactie tussen SiC en metalen gebaseerd op Fe en Ni is bestudeerd in het temperatuurtraject 700-1035°C door middel van vaste-stof-diffusiekoppels. In de koppels van SiC met Fe, Ni en hun legeringen treden hevige reakties op, die de vorming van een goede verbinding verhinderen. Door het grate

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

    KAUST Repository

    Cheng, Yingchun; Schwingenschlö gl, Udo

    2010-01-01

    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

  4. Electrical measurement of radiation effect in SiC

    Energy Technology Data Exchange (ETDEWEB)

    Kanazawa, Satoshi; Kamiya, Koji; Kanno, Ikuo [Kyoto Univ. (Japan). Faculty of Engineering] [and others

    1996-04-01

    For aiming to limited resources and environmental conservations on the Earth, development of controlling element workable under high temperature environment was investigated so as to establish a high grade and optimum controlling system. In order to observe changes of electrical properties before and after irradiation and after annealing, and to investigate changes of carrier concentration and movability after irradiating neutron from reactor and accelerator for the SiC single crystal wafer, elucidation on neutron irradiation effect of SiC as well as finding an optimum method on nuclear conversion injection were investigated. For this reason, SiC surface was purified by its etching and was treated thermally at 1000degC for about 30 min. under argon gas atmosphere after vacuum depositing nickel on it. And then, it was irradiated neutron using Kyoto University reactor (LTL), Linac and University of Tokyo reactor (YAYOI) to measure changes of resistivity using van der Pauw. As a result, it was found that LTL irradiation data was under investigation of measuring method, that in Linac no meaning change was observed because of low irradiation, and that only YAYOI data showed increase of resistivity. (G.K.)

  5. Fundamentals of Passive Oxidation In SiC and Si3N4

    Science.gov (United States)

    Thomas-Ogbuji, Linus U.

    1998-01-01

    The very slow oxidation kinetics of silicon carbide and silicon nitride, which derive from their adherent and passivating oxide films, has been explored at length in a broad series of studies utilizing thermogravimetric analysis, electron and optical micrography, energy dispersive spectrometry, x-ray diffractometry, micro-analytical depth profiling, etc. Some interesting microstructural phenomena accompanying the process of oxidation in the two materials will be presented. In Si3N4 the oxide is stratified, with an SiO2 topscale (which is relatively impervious to O2)underlain by a coherent subscale of silicon oxynitride which is even less permeable to O2- Such "defence in depth" endows Si3N4 with what is perhaps the highest oxidation resistance of any material, and results in a unique set of oxidation processes. In SiC the oxidation reactions are much simpler, yet new issues still emerge; for instance, studies involving controlled devitrification of the amorphous silica scale confirmed that the oxidation rate of SiC drops by more than an order of magnitude when the oxide scale fully crystallizes.

  6. Characterisation of 10 kV 10 A SiC MOSFET

    DEFF Research Database (Denmark)

    Eni, Emanuel-Petre; Incau, Bogdan Ioan; Munk-Nielsen, Stig

    2015-01-01

    The objective of this paper is to characterize and evaluate the static and dynamic performances of 10 kV 10 A 4H-SIC MOSFETs at high temperatures. The results show good electrical performances of the SiC MOSFETs for high temperature operations. The double-pulse test results showed interesting...

  7. 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.

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

    International Nuclear Information System (INIS)

    Chen Libao; Xie Xiaohua; Wang Baofeng; Wang Ke; Xie Jingying

    2006-01-01

    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 -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

  9. Effect of Carbon Concentration on the Sputtering of Carbon-Rich SiC Bombarded by Helium Ions

    Directory of Open Access Journals (Sweden)

    Xinghao Liang

    2018-02-01

    Full Text Available Silicon carbide (SiC is considered as an important material for nuclear engineering due to its excellent properties. Changing the carbon content in SiC can regulate and control its elastic and thermodynamic properties, but a simulation study of the effect of carbon content on the sputtering (caused by the helium ions of SiC is still lacking. In this work, we used the Monte-Carlo and molecular dynamics simulation methods to study the effects of carbon concentration, incidence energy, incident angle, and target temperature on the sputtering yield of SiC. The results show that the incident ions’ energy and angle have a significant effect on sputtering yield of SiC when the carbon concentration in SiC is around 62 at %, while the target temperature has a little effect on the sputtering yield of SiC. Our work might provide theoretical support for the experimental research and engineering application of carbon fiber-reinforced SiC that be used as the plasma-facing material in tokamak fusion reactors.

  10. 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.)

  11. Sintering of SiC ceramics, via liquid phase, with Al{sub 2}O{sub 3}-Yb{sub 2}O{sub 3} additives; Sinterizacao de ceramicas de SiC, via fase liquida, com aditivos de Al{sub 2}O{sub 3}-Yb{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Atilio, I.; Oliveira, M.R.; Garcia, G.C.R.; Ribeiro, S., E-mail: isabelaatilio@hotmail.com [Universidade de Sao Paulo (USP/EEL), Lorena, SP (Brazil). Escola de Engenharia. Dept. de Engenharia de Materiais

    2012-07-01

    The objective of this work was to study the sintering of SiC, through liquid phase, using the additive system Al{sub 2}O{sub 3} and Yb{sub 2}O{sub 3} for the first time. The samples were sintered at temperatures of 1900, 1950 and 2000 deg C for 60 minutes. The melting point of the system was determined according to DIN 51730. It has been found the ability of wetting of SiC in the system. The densification results were: 86,36% at 1900 deg C, 88,25% at 1950 deg C and 82,09% at 2000 deg C. The average linear shrinkage was approximately 17%. There was a conversion of β-SiC in α-SiC at all temperatures and sintering phase formation Yb{sub 3}Al{sub 5}O{sub 12}. The melting temperature was 1850 deg C for de system, consistent with the value in the phase diagram, and the wetting angle of 20 deg. The system (Yb{sub 2}O{sub 3}-Al{sub 2}O{sub 3}) is promising to make liquid phase sintering of SiC, for presenting a good result of wettability. (author)

  12. Using of the Modern Semiconductor Devices Based on the SiC

    Directory of Open Access Journals (Sweden)

    Pavel Drabek

    2008-01-01

    Full Text Available This paper deals with possibility of application of the semiconductor devices based on the SiC (Silicon Carbide inthe power electronics. Basic synopsis of SiC based materials problems are presented, appreciation of their properties incomparison with current using power semiconductor devices ((IGBT, MOSFET, CoolFET transistors.

  13. Fabrication and Mechanical Properties of SiCw(p/SiC-Si Composites by Liquid Si Infiltration using Pyrolysed Rice Husks and SiC Powders as Precursors

    Directory of Open Access Journals (Sweden)

    Dan Zhu

    2014-03-01

    Full Text Available Dense silicon carbide (SiC matrix composites with SiC whiskers and particles as reinforcement were prepared by infiltrating molten Si at 1550 °C into porous preforms composed of pyrolysed rice husks (RHs and extra added SiC powder in different ratios. The Vickers hardness of the composites showed an increase from 18.6 to 21.3 GPa when the amount of SiC added in the preforms was 20% (w/w, and then decreased to 17.3 GPa with the increase of SiC added in the preforms up to 80% (w/w. The values of flexural strength of the composites initially decreased when 20% (w/w SiC was added in the preform and then increased to 587 MPa when the SiC concentration reached 80% (w/w. The refinement of SiC particle sizes and the improvement of the microstructure in particle distribution of the composites due to the addition of external SiC played an effective role in improving the mechanical properties of the composites.

  14. 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

  15. Modulating the Surface State of SiC to Control Carrier Transport in Graphene/SiC.

    Science.gov (United States)

    Jia, Yuping; Sun, Xiaojuan; Shi, Zhiming; Jiang, Ke; Liu, Henan; Ben, Jianwei; Li, Dabing

    2018-05-28

    Silicon carbide (SiC) with epitaxial graphene (EG/SiC) shows a great potential in the applications of electronic and photoelectric devices. The performance of devices is primarily dependent on the interfacial heterojunction between graphene and SiC. Here, the band structure of the EG/SiC heterojunction is experimentally investigated by Kelvin probe force microscopy. The dependence of the barrier height at the EG/SiC heterojunction to the initial surface state of SiC is revealed. Both the barrier height and band bending tendency of the heterojunction can be modulated by controlling the surface state of SiC, leading to the tuned carrier transport behavior at the EG/SiC interface. The barrier height at the EG/SiC(000-1) interface is almost ten times that of the EG/SiC(0001) interface. As a result, the amount of carrier transport at the EG/SiC(000-1) interface is about ten times that of the EG/SiC(0001) interface. These results offer insights into the carrier transport behavior at the EG/SiC heterojunction by controlling the initial surface state of SiC, and this strategy can be extended in all devices with graphene as the top layer. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. 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

  17. Enhanced thermoelectric properties of nano SiC dispersed Bi2Sr2Co2Oy Ceramics

    Science.gov (United States)

    Hu, Qiujun; Wang, Kunlun; Zhang, Yingjiu; Li, Xinjian; Song, Hongzhang

    2018-04-01

    The thermoelectric properties of Bi2Sr2Co2Oy + x wt% nano SiC (x = 0.00, 0.025, 0.05, 0.1, 0.2, and 0.3) prepared by the solid-state reaction method were investigated from 300 K to 923 K. The resistivity can be reduced effectively by adding a small amount of SiC nano particles, which is attributed to the increase of the carrier concentration. At the same time, the Seebeck coefficients can be improved effectively due to the energy filtering effect that low energy carriers are strongly dispersed at the interface between the SiC nano particles and the matrix. The decrease of thermal conductivity is due to the increase of the scattering ability of the phonons by the SiC nanoparticles distributed at the boundary of the matrix. As a result, the Bi2Sr2Co2Oy + x wt% SiC composites exhibit better thermoelectric properties. The maximum ZT value 0.24 is obtained when x = 0.05 at 923 K. Compared with the sample without SiC nano particles, the ZT value is increased by about 59.7%.

  18. The development of SiC whisker fabrication technology for nuclear applications

    International Nuclear Information System (INIS)

    Kang, Thae Khapp; Kuk, Il Hiun; Kim, Chang Kyu; Lee, Jae Chun; Lee, Ho Jin; Park, Soon Dong; Im, Gyeong Soo

    1991-02-01

    Some important experiments for whisker growth reactions, fabrication processes, and experiments for fabricarion of whisker reinforced composites have been performed. In order to investigate growth reaction of SiC whiskers, a conventional carbothermic reaction was tested. Based on the results of carbothermic process, a new process called silicothermic reaction was planned and some basic experiments were performed. Reaction characteristics of silicon monoxide, core material for SiC whisker growth in both of the reactions were investigated for basic data. Additionally, a hydrofluoric acid leaching process was tested for developing SiC whisker recovery process, and powder metallurgy process and melt sqeeze process were tried to develop aluminum-SiC whisker composites. (Author)

  19. 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.

  20. Feasibility study of a SiC sandwich neutron spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jian, E-mail: caepwujian@163.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, Sichuan Province (China); Lei, Jiarong, E-mail: jiarong_lei@163.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, Sichuan Province (China); Jiang, Yong; Chen, Yu; Rong, Ru; Zou, Dehui; Fan, Xiaoqiang [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, Sichuan Province (China); Chen, Gang; Li, Li; Bai, Song [Nanjing Electronic Devices Institute, Nanjing 210016 (China)

    2013-04-21

    Semiconductor sandwich neutron spectrometers are suitable for in-pile measurements of fast reactor spectra thanks to their compact and relatively simple design. We have assembled and tested a sandwich neutron spectrometer based on 4H-silicon carbide (4H-SiC) Schottky diodes. The SiC diodes detect neutrons via neutron-induced charged particles (tritons and alpha particles) produced by {sup 6}Li(n,α){sup 3}H reaction. {sup 6}LiF neutron converter layers are deposited on the front surface of Schottky diodes by magnetron sputtering. The responses of SiC diodes to charged particles were investigated with an {sup 241}Am alpha source. A sandwich neutron spectrometer was assembled with two SiC Schottky diodes selected based on the charged-particle-response experimental results. The low-energy neutron response of the sandwich spectrometer was measured in the neutron field of the Chinese Fast Burst Reactor-II (CFBR-II). Spectra of alpha particles and tritons from {sup 6}Li(n,α){sup 3}H reaction were obtained with two well-resolved peaks. The energy resolution of the sum spectrum was 8.8%. The primary experimental results confirmed the 4H-SiC sandwich neutron spectrometer's feasibility. -- Highlights: ► Sandwich neutron spectrometer employing 4H-SiC as a detecting material has been developed for the first time. ► {sup 6}LiF neutron converter has been deposited on the surface of 4H-SiC Schottky diode. ► Preliminary testing results obtained with the 4H-SiC sandwich neutron spectrometer are presented.

  1. 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.

  2. 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.

  3. Microstructure and microhardness characterization of Cr{sub 3}C{sub 2}-SiC coatings produced by the plasma transferred arc method

    Energy Technology Data Exchange (ETDEWEB)

    Islak, Serkan [Kastamonu Univ. (Turkey). Cide Rifat Ilgaz Vocational High School; Eski, Oezkan [Kastamonu Univ. (Turkey). Kastamonu Vocational High School; Buytoz, Soner [Firat Univ., Elazig (Turkey). Dept. of Metallurgy and Materials Engineering; Karagoez, Muzaffer [Bartin Univ. (Turkey). Dept. of Metallurgical and Materials Engineering; Stokes, Joseph [Dublin City Univ. (Ireland). School of Mechanical and Manufacturing Engineering

    2012-07-01

    The purpose of this work was to investigate the coatings made of Cr{sub 3}C{sub 2} and SiC powder manufactured on AISI 304 stainless steel applied by the plasma transferred arc (PTA) welding process. SiC content in the produced coated layer was varied between 0-100 wt. % and the effect of SiC concentration on the microstructure and hardness of the coating was measured experimentally. SEM analyses revealed that the composite coatings had a homogeneous, nonporous, and crack-free microstructure. Dendrites and interdendrite eutectics formed on the coating layer, subject to the temperature gradient and the solidification ratio. There was a significant increase in the hardness of coating layers with the effect of the {gamma}-(Fe,Ni), Cr{sub 7}C{sub 3}, Cr{sub 23}C{sub 6}, Fe{sub 5}C{sub 2}, Cr{sub 3}Si, CrSi{sub 2}, Fe{sub 0.64}Ni{sub 0.36}, CFe{sub 15.1}, C-(Fe,Cr)-Si phases formed in the microstructure. In comparison to the substrate, the microhardness of the coatings produced by PTA were 2.5-3.5 times harder. (orig.)

  4. 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

    This paper proposes a new method for the investigation of the short-circuit safe operation area (SCSOA) of state-of-the-art SiC MOSFET power modules rated at 1.2 kV based on the variations in SiC MOSFET electrical parameters (e.g., short-circuit current and gate–source voltage). According...... to the experimental results, two different failure mechanisms have been identified, both reducing the short-circuit capability of SiC power modules with respect to discrete SiC devices. Based on such failure mechanisms, two short-circuit safety criteria have been formulated: 1) the short-circuit...

  5. 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

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

    International Nuclear Information System (INIS)

    Szlufarska, Izabela; Voyles, Paul; Sridharan, Kumar; Katoh, Yutai

    2016-01-01

    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

  7. 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.

  8. Evaluation of liquid-phase sintering SiC using as additive the system Al2O3/DyO3

    International Nuclear Information System (INIS)

    Oliveira, M.R.; Atilio, I.; Garcia, G.C.R.; Ribeiro, S.

    2012-01-01

    The objective of this work was to study the liquid-phase sintering SiC with additives that has not been studied yet, Al 2 O 3 /Dy 2 O 3 , with 10% in volume. The powders were mixed, dried, and pressed in uniaxial and isostatic pressing. It was studied the melting temperature of the additives and bars were sintered at temperatures of 1900, 1950 e 2000 deg C, with averaged linear shrinkage of 17%, phase transformations of β-SiC into α-SiC and formation of Dy 3 Al 5 O 12 at all temperatures. The results showed that for further densification, the temperature of 1950 deg C is enough for a higher densification, with a low wetting angle, transformations of SiC and formation of Dy 3 Al 5 O 12 . (author)

  9. Corrosion and wear behavior of functionally graded Al2024/SiC composites produced by hot pressing and consolidation

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, Fatih; Canakci, Aykut, E-mail: aykut@ktu.edu.tr; Varol, Temel; Ozkaya, Serdar

    2015-09-25

    Highlights: • Functionally graded Al2024/SiC composites were produced by hot pressing. • Effect of the number of graded layers was investigated on the corrosion behavior. • Functionally graded composites has the most corrosion resistant than composites. • Wear mechanisms of Al2024/SiC composites were explained. - Abstract: Functionally graded Al2024/SiC composites (FGMs) with varying percentage of SiC (30–60%) were produced by hot pressing and consolidation method. The effects of SiC content and number of layers of Al2024/SiC FGMs on the corrosion and wear behaviors were investigated. The microstructures of these composites were characterized by a scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). The corrosion performances of composites were evaluated by potentiodynamic polarization scans in 3.5% NaCl solution. Corrosion experiments shows that corrosion rate (1109 mpy) of two layered FGMs which containing 50 wt.% SiC were much higher than Al2024 matrix (2569 mpy) and Al2024/50 wt.% SiC composite (2201 mpy). Mechanical properties of these composites were evaluated by microhardness measurements and ball-on-disk wear tests. As the applied load change from 15 to 20 N, the wear rates of the Al2024 increased significantly and wear mechanism transformed from mild to severe wear regime. It has been shown that Al2024/40 wt.% SiC composite has lower wear rate where adhesive and abrasive wear mechanisms play a major role.

  10. 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.

  11. Structural Analysis of Polyhedral Oligomeric Silsesquioxane Coated SiC Nanoparticles and Their Applications in Thermoset Polymers

    International Nuclear Information System (INIS)

    Reza-E-Rabby, M.; Jeelani, Sh.; Rangari, V. K.

    2015-01-01

    The SiC nanoparticles (NPs) were sonochemically coated with Octa Isobutyl (OI) polyhedral oligomeric silsesquioxane (POSS) to create a compatible interface between particle and thermoset polymer. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) techniques were used to analyze the structure of OI-POSS coated SiC nanoparticles. These results revealed the formation of a covalent bonding between SiC and OI-POSS. The transmission electron microscopy (TEM) analysis of OI-POSS coated SiC nanoparticles has also shown the indication of attachment between these two nanoparticles. The OI-POSS coated SiC nanoparticles were further reinforced into a thermoset resin system in order to evaluate mechanical and thermal properties of nano composites. The flexural strength, modulus, and glass transition temperature were found to be enhanced while SiC and OI-POSS coated SiC were infused into epoxy system compared to those properties of neat epoxy resin

  12. Structural Analysis of Polyhedral Oligomeric Silsesquioxane Coated SiC Nanoparticles and Their Applications in Thermoset Polymers

    Directory of Open Access Journals (Sweden)

    Md. Reza-E-Rabby

    2015-01-01

    Full Text Available The SiC nanoparticles (NPs were sonochemically coated with OctaIsobutyl (OI polyhedral oligomeric silsesquioxane (POSS to create a compatible interface between particle and thermoset polymer. X-ray photoelectron spectroscopy (XPS, Fourier transform infrared spectroscopy (FTIR, and X-ray diffraction (XRD techniques were used to analyze the structure of OI-POSS coated SiC nanoparticles. These results revealed the formation of a covalent bonding between SiC and OI-POSS. The transmission electron microscopy (TEM analysis of OI-POSS coated SiC nanoparticles has also shown the indication of attachment between these two nanoparticles. The OI-POSS coated SiC nanoparticles were further reinforced into a thermoset resin system in order to evaluate mechanical and thermal properties of nanocomposites. The flexural strength, modulus, and glass transition temperature were found to be enhanced while SiC and OI-POSS coated SiC were infused into epoxy system compared to those properties of neat epoxy resin.

  13. Mechanical Properties and Elastic Constants Due to Damage Accumulation and Amorphization in SiC

    International Nuclear Information System (INIS)

    Gao, Fei; Weber, William J.

    2004-01-01

    Damage accumulation due to cascade overlap, which was simulated previously, has been used to study the changes of elastic constants, bulk and elastic moduli as a function of dose. These mechanical properties generally decrease with increasing dose, and the rapid decrease at low-dose level indicates that point defects and small clusters play an important role in the changes of elastic constants rather than topological disorder. The internal strain relaxation has no effect on the elastic constants, C11 and C12, in perfect SiC, but it has a significant influence on all elastic constants calculated in damaged SiC. The elastic constants in the cascade-amorphized (CA) SiC decrease about 19%, 29% and 46% for C11, C12 and C44, respectively. The bulk modulus decrease 23% and the elastic modulus decreases 29%, which is consistent with experimental measurements. The stability of both the perfect SiC and CA-SiC under hydrostatic tension has been also investigated. All mechanical properties in the CA-SiC exhibit behavior similar to that in perfect SiC, but the critical stress at which the CA-SiC becomes structurally unstable is one order of magnitude smaller than that for perfect SiC

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

    Science.gov (United States)

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

    2006-10-01

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

  15. Features of film growth during plasma anodizing of Al 2024/SiC metal matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Xue Wenbin [Key Laboratory for Radiation Beam Technology and Materials Modification, Institute of Low Energy Nuclear Physics, Beijing Normal University, Beijing 100875 (China)]. E-mail: xuewb@bnu.edu.cn

    2006-07-15

    Plasma anodizing is a novel promising process to fabricate corrosion-resistant protective films on metal matrix composites. The corrosion-resistant films were prepared by plasma anodizing on SiC reinforced aluminum matrix composite. The morphology and microstructure of films were analyzed by scanning electron microscopy. Specifically, the morphology of residual SiC reinforcement particles in the film was observed. It is found that the most SiC reinforcement particles have been molten to become silicon oxide, but a few tiny SiC particles still remain in the film close to the composite/film interface. This interface is irregular due to the hindering effect of SiC particles on the film growth. Morphology and distribution of residual SiC particles in film provide direct evidence to identify the local melt occurs in the interior of plasma anodizing film even near the composite/film interface. A model of film growth by plasma anodizing on metal matrix composites was proposed.

  16. Features of film growth during plasma anodizing of Al 2024/SiC metal matrix composite

    International Nuclear Information System (INIS)

    Xue Wenbin

    2006-01-01

    Plasma anodizing is a novel promising process to fabricate corrosion-resistant protective films on metal matrix composites. The corrosion-resistant films were prepared by plasma anodizing on SiC reinforced aluminum matrix composite. The morphology and microstructure of films were analyzed by scanning electron microscopy. Specifically, the morphology of residual SiC reinforcement particles in the film was observed. It is found that the most SiC reinforcement particles have been molten to become silicon oxide, but a few tiny SiC particles still remain in the film close to the composite/film interface. This interface is irregular due to the hindering effect of SiC particles on the film growth. Morphology and distribution of residual SiC particles in film provide direct evidence to identify the local melt occurs in the interior of plasma anodizing film even near the composite/film interface. A model of film growth by plasma anodizing on metal matrix composites was proposed

  17. Effect of SiC Content on Microstructure and Wear Resistance of Laser Cladding SiC/Ni60A Composite Coating

    Directory of Open Access Journals (Sweden)

    ZHAO Long-zhi

    2017-03-01

    Full Text Available The SiC reinforced Ni60A alloy laser cladding coating on the 45 steel substrate was fabricated with the LDM2500-60 semiconductor laser equipment. The effect of SiC content on microstructure, dilution rate, wear resistance, friction coefficient and microhardness was investigated systematically.The results show that with the increase of SiC content, the microstructure of upper coating is refined obviously, the dilution rate, wear resistance, friction coefficient and microhardness increase firstly and then decrease;when the mass fraction of SiC is 20%, the wear resistance of the cladding coating is the best one, in which the wear loss of coating is only 0.0012g and is 1/36.3 of the matrix;the minimum friction coefficient is 0.464, the friction process is the most stable;the highest microhardness of the cladding coating is 1039.9HV0.2, which is 3.5 times of the substrate;but when the mass fraction of SiC is 25%, the microhardness and wear resistance of coating decrease.

  18. Structural stabilities and electronic properties of fully hydrogenated SiC sheet

    International Nuclear Information System (INIS)

    Wang, Xin-Quan; Wang, Jian-Tao

    2011-01-01

    The intriguing structural and electronic properties of fully hydrogenated SiC honeycomb sheet are studied by means of ab initio calculations. Based on structure optimization and phonon dispersion analysis, we find that both chair-like and boat-like configurations are dynamically stable, and the chair-like conformer is energetically more favored with an energy gain of 0.03 eV per C atom relative to the boat-like one. The chair-like and boat-like conformers are revealed to be nonmagnetic semiconductors with direct band gaps of 3.84 and 4.29 eV, respectively, both larger than 2.55 eV of pristine SiC sheet. The charge density distributions show that the bondings are characterized with covalency for both chair-like and boat-like conformers. -- Highlights: → Structural and electronic properties of fully hydrogenated SiC sheet are studied. → Both chair-like and boat-like configurations are dynamically stable. → While the chair-like conformer is energetically more favored. → The chair-like and boat-like conformers are nonmagnetic semiconductors. → The bondings are characterized with covalency.

  19. 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.

  20. 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 composite (MMC) is formed. The MMC layer has excellent hardness and wear resistance compared to the base alloy [9-13]. Man et al. [14] used a high power continuous wave Nd:YAG laser to alloy aluminium AA 6061 with preplaced NiTi (54 wt% Ni & 46 wt...Al, Ti3Al, SiC, Al and Si phases. The hardness increased from 75HV to 650HV due to the formation of the TiC particles and TiAl and Ti3Al intermetallics. Su and Lei [9] laser cladded Al-12wt%Si with a powder containing SiC and Al-12wt%Si in a 3...

  1. Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process

    Science.gov (United States)

    Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

    2017-11-01

    The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

  2. Ohmic Contacts to P-Type SiC

    National Research Council Canada - National Science Library

    Crofton, John

    2000-01-01

    Alloys of aluminum (Al) have previously been used as ohmic contacts to p-type SiC, however the characteristics and performance of these contacts is drastically affected by the type and composition of the Al alloy...

  3. High efficiency three-phase power factor correction rectifier using SiC switches

    DEFF Research Database (Denmark)

    Kouchaki, Alireza; Nymand, Morten

    2017-01-01

    This paper presents designing procedure of a high efficiency 5 kW silicon-carbide (SiC) based threephase power factor correction (PFC). SiC switches present low capacitive switching loss compared to the alternative Si switches. Therefore, the switching frequency can be increased and hence the siz...

  4. The rheological properties of shear thickening fluid reinforced with SiC nanowires

    Directory of Open Access Journals (Sweden)

    Jianhao Ge

    Full Text Available The rheological properties of shear thickening fluid (STF reinforced with SiC nanowires were investigated in this paper. Pure STF consists of 56 vol% silica nano-particles and polyethylene glycol 400 (PEG 400 solvent was fabricated; and a specific amount of SiC nanowires were dispersed into this pure STF, and then the volume fraction of PEG400 was adjusted to maintain the volume fraction of solid phase in the STF at a constant of 56%. The results showed there was almost 30% increase in the initial and shear thickening viscosity of the STF reinforced with SiC nanowires compared to the pure STF. Combining with the hydrodynamic cluster theory, the effect of the mechanism of SiC nanowire on the viscosity of STF was discussed, and based on the experimental results, an analytical model of viscosity was used to describe the rheological properties of STF, which agreed with the experimental results. Keywords: Shear thickening fluid (STF, Nanowire, Rheology, Viscosity, Analytical model

  5. Control of the graphene growth rate on capped SiC surface under strong Si confinement

    International Nuclear Information System (INIS)

    Çelebi, C.; Yanık, C.; Demirkol, A.G.; Kaya, İsmet İ.

    2013-01-01

    Highlights: ► Graphene is grown on capped SiC surface with well defined cavity size. ► Graphene growth rate linearly increases with the cavity height. ► Graphene uniformity is reduced with thickness. - Abstract: The effect of the degree of Si confinement on the thickness and morphology of UHV grown epitaxial graphene on (0 0 0 −1) SiC is investigated by using atomic force microscopy and Raman spectroscopy measurements. Prior to the graphene growth process, the C-face surface of a SiC substrate is capped by another SiC comprising three cavities on its Si-rich surface with depths varying from 0.5 to 2 microns. The Si atoms, thermally decomposed from the sample surface during high temperature annealing of the SiC cap /SiC sample stack, are separately trapped inside these individual cavities at the sample/cap interface. Our analyses show that the growth rate linearly increases with the cavity height. It was also found that stronger Si confinement yields more uniform graphene layers.

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

    Energy Technology Data Exchange (ETDEWEB)

    Halverson, H.; Curtin, W.A. [Virginia Polytechnic Institute and State Univ., Blacksburg, VA (United States)

    1996-08-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-08-01

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

  8. 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.

  9. 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

  10. 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.

  11. Graphene synthesis on SiC: Reduced graphitization temperature by C-cluster and Ar-ion implantation

    International Nuclear Information System (INIS)

    Zhang, R.; Li, H.; Zhang, Z.D.; Wang, Z.S.; Zhou, S.Y.; Wang, Z.; Li, T.C.; Liu, J.R.; Fu, D.J.

    2015-01-01

    Thermal decomposition of SiC is a promising method for high quality production of wafer-scale graphene layers, when the high decomposition temperature of SiC is substantially reduced. The high decomposition temperature of SiC around 1400 °C is a technical obstacle. In this work, we report on graphene synthesis on 6H–SiC with reduced graphitization temperature via ion implantation. When energetic Ar, C 1 and C 6 -cluster ions implanted into 6H–SiC substrates, some of the Si–C bonds have been broken due to the electronic and nuclear collisions. Owing to the radiation damage induced bond breaking and the implanted C atoms as an additional C source the graphitization temperature was reduced by up to 200 °C

  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...

  13. 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

  14. Pressureless sintering of dense Si3N4 and Si3N4/SiC composites with nitrate additives

    International Nuclear Information System (INIS)

    Kim, J.Y.; Iseki, Takayoshi; Yano, Toyohiko

    1996-01-01

    The effect of aluminum and yttrium nitrate additives on the densification of monolithic Si 3 N 4 and a Si 3 N 4 /SiC composite by pressureless sintering was compared with that of oxide additives. The surfaces of Si 3 N 4 particles milled with aluminum and yttrium nitrates, which were added as methanol solutions, were coated with a different layer containing Al and Y from that of Si 3 N 4 particles milled with oxide additives. Monolithic Si 3 N 4 could be sintered to 94% of theoretical density (TD) at 1,500 C with nitrate additives. The sintering temperature was about 100 C lower than the case with oxide additives. After pressureless sintering at 1,750 C for 2 h in N 2 , the bulk density of a Si 3 N 4 /20 wt% SiC composite reached 95% TD with nitrate additives

  15. Effects of AlN on the densification and mechanical properties of pressureless-sintered SiC ceramics

    Directory of Open Access Journals (Sweden)

    Qisong Li

    2016-02-01

    Full Text Available In the present work, SiC ceramics was fabricated with AlN using B4C and C as sintering aids by a solid-state pressureless-sintered method. The effects of AlN contents on the densification, mechanical properties, phase compositions, and microstructure evolutions of as-obtained SiC ceramics were thoroughly investigated. AlN was found to promote further densification of the SiC ceramics due to its evaporation over 1800 °C, transportation, and solidification in the pores resulted from SiC grain coarsening. The highest relative density of 99.65% was achieved for SiC sample with 15.0 wt% AlN by the pressureless-sintered method at 2130 °C for 1 h in Ar atmosphere. Furthermore, the fracture mechanism for SiC ceramics containing AlN tended to transfer from single transgranular fracture mode to both transgranular fracture and intergranular fracture modes when the sample with 30.0 wt% AlN sintered at 1900 °C for 1 h in Ar. Also, SiC ceramics with 30.0 wt% AlN exhibited the highest fracture toughness of 5.23 MPa m1/2 when sintered at 1900 °C.

  16. In-situ synchrotron x-ray study of MgB2 formation when doped by SiC

    Science.gov (United States)

    Abrahamsen, A. B.; Grivel, J.-C.; Andersen, N. H.; Herrmann, M.; Häßler, W.; Birajdar, B.; Eibl, O.; Saksl, K.

    2008-02-01

    We have studied the evolution of the reaction xMg + 2B + ySiC → zMg1-p(B1-qCq)2 + yMg2Si in samples of 1, 2, 5 and 10 wt% SiC doping. We found a coincident formation of MgB2 and Mg2Si, whereas the crystalline part of the SiC nano particles is not reacting at all. Evidence for incorporation of carbon into the MgB2 phase was established from the decrease of the a-axis lattice parameter upon increasing SiC doping. An estimate of the MgB2 lower limit grain size was found to decrease from L100 = 795 Å and L002 = 337 Å at 1 wt% SiC to L100 = 227 Å and L002= 60 Å at 10 wt% SiC. Thus superconductivity might be suppressed at 10 wt% SiC doping due to the grain size approaching the coherence length.

  17. Application of SiC masses as tube liners in municipal incinerators. Anwendung von SiC-Massen fuer Rohrverkleidungen in kommunalen Muellverbrennungsanlagen

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, In Soo.

    1993-09-02

    Phosphate-bonded SiC masses with different additives were investigated. The reference mass was a SiC mass consisting of 90% by mass of SiC and 10% by mass of Al[sub 2]O[sub 3]. The reactive alumina ([alpha]-Al[sub 2]O[sub 3]) served as reaction partner for the aluminium phosphate binder. The physical and thermomechanical properties as well as the corrosion resistance of the developed SiC masses were investigated, and the reactions of the additives with the aluminium phosphate binder were investigated. The best combination of properties required of a refractory liner for waste incinerators was found in masses with Si[sub 3]N[sub 4] additives. These masses have optimal physical and thermomechanical properties and a high resistance to the corrosive gases and alkaline slags produced in modern incinerators. (orig./EF)

  18. Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process.

    Science.gov (United States)

    Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

    2017-11-25

    The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

  19. 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)

  20. Structural, thermal, dielectric spectroscopic and AC impedance properties of SiC nanoparticles doped PVK/PVC blend

    Science.gov (United States)

    Alghunaim, Naziha Suliman

    2018-06-01

    Nanocomposite films based on poly (N-vinylcarbazole)/polyvinylchloride (PVK/PVC) blend doped with different concentrations of Silicon Carbide (SiC) nanoparticles have been prepared. The X-ray diffraction, Ultra violet-visible spectroscopy, thermogravimetric analysis and electrical spectroscopic has been used to characterize these nanocomposites. The X-ray analysis confirms the semi-crystalline nature of the films. The intensity of the main X-ray peak is decreased due to the interaction between the PVK/PVC and SiC. The main SiC peaks are absent due to complete dissolution of SiC in polymeric matrices. The UV-Vis spectra indicated that the band gap optical energy is affected by adding SiC nanoparticles because the charges transfer complexes between PVK/PVC with amount of SiC. The thermal stability is improved and the estimated values of ε‧ and ε″ are increased with increasing for SiC content due to the free charge carriers which in turn increase the ionic conductivity of the doped samples. The plots of tan δ with frequency are studied. A single peak from the plot between tan δ and Log (f) is appeared and shifted towards the higher frequency confirmed the presence of relaxing dipoles moment.

  1. In-situ synthesis of SiC particles by the structural evolution of TiCx in Al–Si melt

    International Nuclear Information System (INIS)

    Nie, Jinfeng; Li, Dakui; Wang, Enzhao; Liu, Xiangfa

    2014-01-01

    Highlights: • A facile method to in-situ synthesize SiC was developed utilizing the structural evolution of TiC x in Al–Si melt. • The SiC particles have the size range from 2.5 to 7.5 μm and a block-like morphology. • The SiC particles and (SiC + TiB 2 ) hybrid-particles reinforced Al–18Si composite were prepared. • The wear resistance effect of SiC on the based alloy was investigated. - Abstract: A facile method has been developed to in-situ synthesize SiC particles utilizing the structural instability and evolution of TiC x in Al–Si melt. It is considered that the synthesis of SiC particles occurs via the gradual reaction between TiC x and Si atoms, whilst Si content plays the crucial role in this approach. If the Si content in the melt is above 30%, TiC x directly reacts with Si and Al to form SiC, but the needle-like TiAl x Si y phase formed simultaneously will do harm to the mechanical properties of the composites. Thus, it is proposed to add B element in the melt to transform the TiAl x Si y into TiB 2 particles. Therefore, the SiC and (SiC + TiB 2 ) hybrid-particles reinforced Al–18Si composites were successfully prepared using the method. In the composites, the SiC particles have the size range from 2.5 to 7.5 μm and a block-like morphology. Furthermore, the mechanical properties of base alloy, including the wear resistance and macro-hardness, have been obviously improved by the in-situ SiC particles. Besides, the relevant underlying mechanisms are also discussed

  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. 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.

  4. 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.

  5. Synthesis of SiC nanoparticles by SHG 532 nm Nd:YAG laser ablation of silicon in ethanol

    Science.gov (United States)

    Khashan, Khawla S.; Ismail, Raid A.; Mahdi, Rana O.

    2018-06-01

    In this work, colloidal spherical nanoparticles NPs of silicon carbide SiC have been synthesized using second harmonic generation 532 nm Nd:YAG laser ablation of silicon target dipped in ethanol solution at various laser fluences (1.5-5) J/cm2. X-Ray diffraction XRD, scanning electron microscopy SEM, transmission electron microscope TEM, Fourier transformed infrared spectroscopy FT-IR, Raman spectroscopy, photoluminescence PL spectroscopy, and UV-Vis absorption were employed to examine the structural, chemical and optical properties of SiC NPs. XRD results showed that all synthesised SiC nanoparticles are crystalline in nature and have hexagonal structure with preferred orientation along (103) plane. Raman investigation showed three characteristic peaks 764,786 and 954 cm-1, which are indexing to transverse optic TO phonon mode and longitudinal optic LO phonon mode of 4H-SiC structure. The optical absorption data showed that the values of optical energy gap of SiC nanoparticles prepared at 1.5 J/cm2 was 3.6 eV and was 3.85 eV for SiC synthesised at 5 J/cm2. SEM investigations confirmed that the nanoparticles synthesised at 5 J/cm2 are agglomerated to form larger particles. TEM measurements showed that SiC particles prepared at 1.5 J/cm2 have spherical shape with average size of 25 nm, while the particles prepared at 5 J/cm2 have an average size of 55 nm.

  6. 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.

  7. 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+.

  8. Optical study on neutron irradiation effect on hexagonal SiC single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Moritami; Kimura, Itsurou; Kanazawa, Satoshi; Kanno, Ikuo; Kamiya, Koji [Kyoto Univ. (Japan); Nakata, Toshitake; Watanabe, Masanori; Nakagawa, Masuo; Atobe, Kozo

    1996-04-01

    It is well known that SiC is a higher radiation resistant semiconductor on comparison with Si and Ge. Recently, on accompanying with advancement of developing program on nuclear fission reactor on space, development of electronic element workable effectively under severe radiation environment is desired. SiC is expected as one of such elements. Therefore, because of considering importance of understanding the effect on fundamental properties of SiC electronic element under radiation environment before its development, some studies on it was executed. In this paper, according to find out induction of interesting defect center in hexagonal 4H- and 6H-SiC single crystals irradiated with reactor neutron on light absorption and SER test, outlines of these experimental results were reported. (G.K.)

  9. The influence of various dielectric parameters on the reststrahlen region of SiC

    International Nuclear Information System (INIS)

    Engelbrecht, J.A.A.; Rooyen, I.J. van

    2011-01-01

    The reststrahlen region of SiC is analysed with the goal of establishing the origin of different shapes of this band, by varying the dielectric parameters involved when simulating the reststrahlen region as obtained by infrared reflectance. -- Research highlights: → An anomalous peak observed in the reststrahlen band of SiC was investigated. → The reflection spectrum of SiC in the reststrahlen region was simulated by theoretical calculations. → The influence on the reststrahlen band of the dielectric parameters used in the simulations is discussed. → Dielectric parameters used in the simulations did not yield the anomalous peak that is observed experimentally.

  10. The influence of various dielectric parameters on the reststrahlen region of SiC

    Energy Technology Data Exchange (ETDEWEB)

    Engelbrecht, J.A.A., E-mail: Japie.Engelbrecht@nmmu.ac.z [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Rooyen, I.J. van [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); National Laser Centre, CSIR, PO Box 395, Pretoria 0001 (South Africa)

    2011-02-01

    The reststrahlen region of SiC is analysed with the goal of establishing the origin of different shapes of this band, by varying the dielectric parameters involved when simulating the reststrahlen region as obtained by infrared reflectance. -- Research highlights: {yields} An anomalous peak observed in the reststrahlen band of SiC was investigated. {yields} The reflection spectrum of SiC in the reststrahlen region was simulated by theoretical calculations. {yields} The influence on the reststrahlen band of the dielectric parameters used in the simulations is discussed. {yields} Dielectric parameters used in the simulations did not yield the anomalous peak that is observed experimentally.

  11. Development of High-Temperature, High-Power, High-Efficiency, High-Voltage Converters Using Silicon Carbide (SiC) Delivery Order 0003: SiC High Voltage Converters, N-Type Ohmic Contract Development for SiC Power Devices

    National Research Council Canada - National Science Library

    Cheng, Lin; Mazzola, Michael S

    2006-01-01

    ... ? SiC interfaces and silicide top surfaces is important for producing uniformly low contact resistances to achieve device operation at high-current levels without hot spot formation and contact degradation...

  12. Direct growth of freestanding GaN on C-face SiC by HVPE.

    Science.gov (United States)

    Tian, Yuan; Shao, Yongliang; Wu, Yongzhong; Hao, Xiaopeng; Zhang, Lei; Dai, Yuanbin; Huo, Qin

    2015-06-02

    In this work, high quality GaN crystal was successfully grown on C-face 6H-SiC by HVPE using a two steps growth process. Due to the small interaction stress between the GaN and the SiC substrate, the GaN was self-separated from the SiC substrate even with a small thickness of about 100 μm. Moreover, the SiC substrate was excellent without damage after the whole process so that it can be repeatedly used in the GaN growth. Hot phosphoric acid etching (at 240 °C for 30 min) was employed to identify the polarity of the GaN layer. According to the etching results, the obtained layer was Ga-polar GaN. High-resolution X-ray diffraction (HRXRD) and electron backscatter diffraction (EBSD) were done to characterize the quality of the freestanding GaN. The Raman measurements showed that the freestanding GaN film grown on the C-face 6H-SiC was stress-free. The optical properties of the freestanding GaN layer were determined by photoluminescence (PL) spectra.

  13. Transfer-free synthesis of graphene-like atomically thin carbon films on SiC by ion beam mixing technique

    Science.gov (United States)

    Zhang, Rui; Chen, Fenghua; Wang, Jinbin; Fu, Dejun

    2018-03-01

    Here we demonstrate the synthesis of graphene directly on SiC substrates at 900 °C using ion beam mixing technique with energetic carbon cluster ions on Ni/SiC structures. The thickness of 7-8 nm Ni films was evaporated on the SiC substrates, followed by C cluster ion bombarding. Carbon cluster ions C4 were bombarded at 16 keV with the dosage of 4 × 1016 atoms/cm2. After thermal annealing process Ni silicides were formed, whereas C atoms either from the decomposition of the SiC substrates or the implanted contributes to the graphene synthesis by segregating and precipitating process. The limited solubility of carbon atoms in silicides, involving SiC, Ni2Si, Ni5Si2, Ni3Si, resulted in diffusion and precipitation of carbon atoms to form graphene on top of Ni and the interface of Ni/SiC. The ion beam mixing technique provides an attractive production method of a transfer-free graphene growth on SiC and be compatible with current device fabrication.

  14. 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.

  15. 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....

  16. 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

  17. 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.

  18. 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.

  19. Atomistic aspects of ductile responses of cubic silicon carbide during nanometric cutting.

    Science.gov (United States)

    Goel, Saurav; Luo, Xichun; Reuben, Robert L; Rashid, Waleed Bin

    2011-11-11

    Cubic silicon carbide (SiC) is an extremely hard and brittle material having unique blend of material properties which makes it suitable candidate for microelectromechanical systems and nanoelectromechanical systems applications. Although, SiC can be machined in ductile regime at nanoscale through single-point diamond turning process, the root cause of the ductile response of SiC has not been understood yet which impedes significant exploitation of this ceramic material. In this paper, molecular dynamics simulation has been carried out to investigate the atomistic aspects of ductile response of SiC during nanometric cutting process. Simulation results show that cubic SiC undergoes sp3-sp2 order-disorder transition resulting in the formation of SiC-graphene-like substance with a growth rate dependent on the cutting conditions. The disorder transition of SiC causes the ductile response during its nanometric cutting operations. It was further found out that the continuous abrasive action between the diamond tool and SiC causes simultaneous sp3-sp2 order-disorder transition of diamond tool which results in graphitization of diamond and consequent tool wear.

  20. Light and Strong Hierarchical Porous SiC Foam for Efficient Electromagnetic Interference Shielding and Thermal Insulation at Elevated Temperatures.

    Science.gov (United States)

    Liang, Caiyun; Wang, Zhenfeng; Wu, Lina; Zhang, Xiaochen; Wang, Huan; Wang, Zhijiang

    2017-09-06

    A novel light but strong SiC foam with hierarchical porous architecture was fabricated by using dough as raw material via carbonization followed by carbothermal reduction with silicon source. A significant synergistic effect is achieved by embedding meso- and nanopores in a microsized porous skeleton, which endows the SiC foam with high-performance electromagnetic interference (EMI) shielding, thermal insulation, and mechanical properties. The microsized skeleton withstands high stress. The meso- and nanosized pores enhance multiple reflection of the incident electromagnetic waves and elongate the path of heat transfer. For the hierarchical porous SiC foam with 72.8% porosity, EMI shielding can be higher than 20 dB, and specific EMI effectiveness exceeds 24.8 dB·cm 3 ·g -1 at a frequency of 11 GHz at 25-600 °C, which is 3 times higher than that of dense SiC ceramic. The thermal conductivity reaches as low as 0.02 W·m -1 ·K -1 , which is comparable to that of aerogel. The compressive strength is as high as 9.8 MPa. Given the chemical and high-temperature stability of SiC, the fabricated SiC foam is a promising candidate for modern aircraft and automobile applications.

  1. 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

  2. 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%.

  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. Super-hydrophobic surfaces of SiO₂-coated SiC nanowires: fabrication, mechanism and ultraviolet-durable super-hydrophobicity.

    Science.gov (United States)

    Zhao, Jian; Li, Zhenjiang; Zhang, Meng; Meng, Alan

    2015-04-15

    The interest in highly water-repellent surfaces of SiO2-coated SiC nanowires has grown in recent years due to the desire for self-cleaning and anticorrosive surfaces. It is imperative that a simple chemical treatment with fluoroalkylsilane (FAS, CF3(CF2)7CH2CH2Si(OC2H5)3) in ethanol solution at room temperature resulted in super-hydrophobic surfaces of SiO2-coated SiC nanowires. The static water contact angle of SiO2-coated SiC nanowires surfaces was changed from 0° to 153° and the morphology, microstructure and crystal phase of the products were almost no transformation before and after super-hydrophobic treatment. Moreover, a mechanism was expounded reasonably, which could elucidate the reasons for their super-hydrophobic behavior. It is important that the super-hydrophobic surfaces of SiO2-coated SiC nanowires possessed ultraviolet-durable (UV-durable) super-hydrophobicity. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. 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)].

  6. 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 purpose of this work is to propose a novel electro-thermal co-simulation approach for the new generation of SiC MOSFETs, by development of a PSpice-based compact and physical SiC MOSFET model including temperature dependency of several parameters and a Simulink-based thermal network. The PSpice...... 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...

  7. Compósitos SiCf /SiC utilizados em sistemas de proteção térmica SiCf /SiC composites for thermal protection systems

    Directory of Open Access Journals (Sweden)

    M. Florian

    2005-09-01

    Full Text Available Compósitos de carbeto de silício (SiC reforçado com fibras de carbeto de silício (SiCf são materiais candidatos em potencial para utilização em sistemas de proteção térmica em altas temperaturas devido principalmente à boa condutividade térmica na direção da fibra e muito baixa condutividade térmica na direção transversal à fibra, alta dureza, estabilidade térmica e à corrosão por oxidação. O compósito SiCf/SiC possui uma matriz de SiC reforçada com fibras contínuas policristalinas de SiC e é obtido por reações de conversão em altas temperaturas e atmosfera controlada, utilizando o compósito carbono/carbono como precursor. O processo de Reação Química em Vapor (CVR foi utilizado para a fabricação de compósitos SiCf/SiC com alta pureza na fase de SiC-beta. O compósito precursor de carbono/carbono foi fabricado com fibra de carbono não estabilizada e matriz carbonosa derivada da resina fenólica na forma de carbono isotrópico. O compósito convertido exibiu uma densidade de 1,75 g/cm³, com 40% de porosidade aberta e resistência à flexão de 80 MPa medida por ensaio flexão em 4 pontos. A área especifica medida pela técnica de BET é dependente da temperatura de conversão e das condições inicias do precursor de carbono, podendo chegar a 18 m²/g.Composites based on silicon carbide are potential candidate materials for thermal protection systems mainly due to its good thermal conductivity in fiber direction and very low transversal thermal conductivity, high hardness, corrosion and thermal resistance. SiCf/SiC composite presents a SiC matrix reinforced with SiC polycrystalline continuous fibers. The composite was obtained by conversion reactions at high temperature and controlled atmosphere from a carbon/carbon composite precursor. The CVR process was used to fabricate SiC /SiC composite with crystalline high-purity beta-SiC from a carbon-carbon precursor fabricated with non-stabilized carbon fiber and

  8. 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.

  9. 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.

  10. Atomic scale study of the chemistry of oxygen, hydrogen and water at SiC surfaces

    International Nuclear Information System (INIS)

    Amy, Fabrice

    2007-01-01

    Understanding the achievable degree of homogeneity and the effect of surface structure on semiconductor surface chemistry is both academically challenging and of great practical interest to enable fabrication of future generations of devices. In that respect, silicon terminated SiC surfaces such as the cubic 3C-SiC(1 0 0) 3 x 2 and the hexagonal 6H-SiC(0 0 0 1) 3 x 3 are of special interest since they give a unique opportunity to investigate the role of surface morphology on oxygen or hydrogen incorporation into the surface. In contrast to silicon, the subsurface structure plays a major role in the reactivity, leading to unexpected consequences such as the initial oxidation starting several atomic planes below the top surface or the surface metallization by atomic hydrogen. (review article)

  11. 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.

  12. 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).

  13. Mechanical performance of SiC three-layer cladding in PWRs

    Energy Technology Data Exchange (ETDEWEB)

    Angelici Avincola, Valentina, E-mail: valentina.avincola@kit.edu [Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Guenoun, Pierre, E-mail: pguenoun@mit.edu [Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 (United States); Shirvan, Koroush, E-mail: kshirvan@mit.edu [Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 (United States)

    2016-12-15

    Highlights: • FEA calculations of the stress distribution in SiC three-layer cladding. • Simulation of SiC mechanical performance under operation and accident conditions. • Failure probability analysis of SiC in steady-state and accident conditions. - Abstract: The silicon carbide cladding concept is currently under investigation with regard to increasing the accident tolerance and economic performance of light-water reactor fuels. In this work, the stress fields in the multi-layered silicon carbide cladding for LWR fuels are calculated using the commercial finite element analysis software ADINA. The material properties under irradiation are implemented as a function of temperature. The cladding is studied under operating and accident conditions, specifically for the loss-of-coolant accident (LOCA). During the LOCA, the blowdown and the reflood phases are modeled, including the quench waterfront. The calculated stresses along the cladding thickness show a high sensitivity to the assumptions regarding material properties. The resulting stresses are compared with experimental data and the probability of failure is calculated considering a Weibull model.

  14. Amorphization and the effect of implanted ions in SiC

    International Nuclear Information System (INIS)

    Snead, L.L.; Zinkle, S.J.

    1994-01-01

    The effects of implanted ion chemistry and displacement damage on the amorphization threshold dose of SiC were studied using cross-section transmission electron microscopy. Room temperature as well as 200 and 400 C irradiations were carried out with 3.6 MeV Fe, 1.8 MeV Cl, 1 MeV He or 0.56 MeV Si ions. The room temperature amorphization threshold dose in irradiated regions well separated from the implanted ions was found to range from 0.3 to 0.5 dpa for the four different ion species. The threshold dose for amorphization in the He, Si and Fe ion-implanted regions was also ∼0.3 to 0.5 dpa. On the other hand, the amorphization threshold in the Cl-implanted region was only about 0.1 dpa. The volume change associated with amorphization was ∼17%. No evidence for amorphization was obtained in specimens irradiated at 200 or 400 C. An understanding of the microstructural evolution of SiC under irradiation is critical to the application of these materials in fusion energy systems

  15. Mechanical Properties of SiC, Al2O3 Reinforced Aluminium 6061-T6 Hybrid Matrix Composite

    Science.gov (United States)

    Murugan, S. Senthil; Jegan, V.; Velmurugan, M.

    2018-04-01

    This paper contains the investigation of tensile, compression and impact characterization of SiC, Al2O3 reinforced Aluminium 6061-T6 matrix hybrid composite. Hybrid matrix composite fabrication was done by stir casting method. An attempt has been made by keeping Al2O3 percentage (7%) constant and increasing SiC percentage (10, 15, and 20%). After fabricating, the samples were prepared and tested to find out the various mechanical properties like tensile, compressive, and impact strength of the developed composites of different weight % of silicon carbide and Alumina in Aluminium alloy. The main objective of the study is to compare the values obtained and choose the best composition of the hybrid matrix composite from the mechanical properties point of view.

  16. 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.

  17. 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.

  18. Nanocatalytic growth of Si nanowires from Ni silicate coated SiC nanoparticles on Si solar cell.

    Science.gov (United States)

    Parida, Bhaskar; Choi, Jaeho; Ji, Hyung Yong; Park, Seungil; Lim, Gyoungho; Kim, Keunjoo

    2013-09-01

    We investigated the nanocatalytic growth of Si nanowires on the microtextured surface of crystalline Si solar cell. 3C-SiC nanoparticles have been used as the base for formation of Ni silicate layer in a catalytic reaction with the Si melt under H2 atmosphere at an annealing temperature of 1100 degrees C. The 10-nm thick Ni film was deposited after the SiC nanoparticles were coated on the microtextured surface of the Si solar cell by electron-beam evaporation. SiC nanoparticles form a eutectic alloy surface of Ni silicate and provide the base for Si supersaturation as well as the Ni-Si alloy layer on Si substrate surface. This bottom reaction mode for the solid-liquid-solid growth mechanism using a SiC nanoparticle base provides more stable growth of nanowires than the top reaction mode growth mechanism in the absence of SiC nanoparticles. Thermally excited Ni nanoparticle forms the eutectic alloy and provides collectively excited electrons at the alloy surface, which reduces the activation energy of the nanocatalytic reaction for formation of nanowires.

  19. 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.

  20. SIC POVMs and Clifford groups in prime dimensions

    International Nuclear Information System (INIS)

    Zhu Huangjun

    2010-01-01

    We show that in prime dimensions not equal to 3, each group covariant symmetric informationally complete positive operator valued measure (SIC POVM) is covariant with respect to a unique Heisenberg-Weyl (HW) group. Moreover, the symmetry group of the SIC POVM is a subgroup of the Clifford group. Hence, two SIC POVMs covariant with respect to the HW group are unitarily or antiunitarily equivalent if and only if they are on the same orbit of the extended Clifford group. In dimension 3, each group covariant SIC POVM may be covariant with respect to three or nine HW groups, and the symmetry group of the SIC POVM is a subgroup of at least one of the Clifford groups of these HW groups, respectively. There may exist two or three orbits of equivalent SIC POVMs for each group covariant SIC POVM, depending on the order of its symmetry group. We then establish a complete equivalence relation among group covariant SIC POVMs in dimension 3, and classify inequivalent ones according to the geometric phases associated with fiducial vectors. Finally, we uncover additional SIC POVMs by regrouping of the fiducial vectors from different SIC POVMs which may or may not be on the same orbit of the extended Clifford group.

  1. The origin of a peak in the reststrahlen region of SiC

    International Nuclear Information System (INIS)

    Engelbrecht, J.A.A.; Rooyen, I.J. van; Henry, A.; Janzén, E.; Olivier, E.J.

    2012-01-01

    A peak in the reststrahlen region of SiC is analyzed in order to establish the origin of this peak. The peak can be associated with a thin damaged layer on the SiC wafers, and a relation is found between surface roughness and the height of this peak, by modeling the damaged layer as an additional layer when simulating the reflectivity from the wafers.

  2. The origin of a peak in the reststrahlen region of SiC

    Energy Technology Data Exchange (ETDEWEB)

    Engelbrecht, J.A.A., E-mail: Japie.Engelbrecht@nmmu.ac.za [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Rooyen, I.J. van [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Henry, A.; Janzen, E. [Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden); Olivier, E.J. [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa)

    2012-05-15

    A peak in the reststrahlen region of SiC is analyzed in order to establish the origin of this peak. The peak can be associated with a thin damaged layer on the SiC wafers, and a relation is found between surface roughness and the height of this peak, by modeling the damaged layer as an additional layer when simulating the reflectivity from the wafers.

  3. Study on extrusion process of SiC ceramic matrix

    Science.gov (United States)

    Dai, Xiao-Yuan; Shen, Fan; Ji, Jia-You; Wang, Shu-Ling; Xu, Man

    2017-11-01

    In this thesis, the extrusion process of SiC ceramic matrix has been systematically studied.The effect of different cellulose content on the flexural strength and pore size distribution of SiC matrix was discussed.Reselts show that with the increase of cellulose content, the flexural strength decreased.The pore size distribution in the sample was 1um-4um, and the 1um-2um concentration was more concentrated. It is found that the cellulose content has little effect on the pore size distribution.When the cellulose content is 7%, the flexural strength of the sample is 40.9Mpa. At this time, the mechanical properties of the sample are the strongest.

  4. Contribution of x-ray topography and high-resolution diffraction to the study of defects in SiC

    International Nuclear Information System (INIS)

    Dudley, Michael; Huang Xianrong; Vetter, William M

    2003-01-01

    A short review is presented of the various synchrotron white beam x-ray topography (SWBXT) imaging techniques developed for characterization of silicon carbide (SiC) crystals and thin films. These techniques, including back-reflection topography, reticulography, transmission topography, and a set of section topography techniques, are demonstrated to be particularly powerful for imaging hollow-core screw dislocations (micropipes) and closed-core threading screw dislocations, as well as other defects, in SiC. The geometrical diffraction mechanism commonly underlying these imaging processes is emphasized for understanding the nature and origins of these defects. Also introduced is the application of SWBXT combined with high-resolution x-ray diffraction techniques to complete characterization of 3C/4H or 3C/6H SiC heterostructures, including polytype identification, 3C variant mapping, and accurate lattice mismatch measurements

  5. Creep behavior for advanced polycrystalline SiC fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States); Kohyama, Akira [Kyoto Univ. (Japan)] [and others

    1997-08-01

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

  6. Creep behavior for advanced polycrystalline SiC fibers

    International Nuclear Information System (INIS)

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

    1997-01-01

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

  7. Síntese de Al2O3/SiC em forno de microondas: estudo de parâmetros do processo Synthesis of Al2O3/SiC in microwave oven: study of the processing parameters

    Directory of Open Access Journals (Sweden)

    T. P. Deksnys

    2005-12-01

    Full Text Available Estudos demonstram a eficiência do método de moagem prévia do aluminossilicato precursor para a síntese da fase Al2O3/SiC por meio da reação de redução carbotérmica em forno de microondas. No presente trabalho, além da moagem do precursor, outros parâmetros de reação foram estudados, como tempo de reação, potência da radiação emitida e fluxo de gás. As reações foram realizadas em forno de microondas semi-industrial, com adaptação para inserção de gás inerte. Dois tipos de reatores foram avaliados: um reator cilíndrico, termicamente isolado, e um reator tubular de leito fixo, nos quais foram colocados os precursores peletizados. Existe uma relação direta entre a saturação da atmosfera de reação com a cinética de redução carbotérmica do aluminossilicato. Esse comportamento, aliado a elevadas potências de emissão, favorecem a formação da fase Al2O3/SiC em períodos de tempo reduzidos.Results presented elsewhere have confirmed the feasibility of the previous milling process of the starting materials for the synthesis of Al2O3/SiC by the microwave-assisted carbothermal reduction. In the present work, parameters such as precursor milling, reaction time, microwave's power level and gas flow have been investigated. Reactions were carried out in a semi-industrial microwave oven (Cober Inc., USA, which allowed the inert gas insertion. Two reactions arrangement were developed to perform the synthesis: a cylindrical reactor, thermally insulated and a pipe fluidized bed reactor. Into both reactors, the precursor was applied in a palletized form to react. There is a direct relation between the reaction atmosphere saturation and the kinetics of the carbothermal reduction. This behavior, in addiction to high power levels of microwave radiation (>1.5 KW, favors the formation of Al2O3/SiC in a short time.

  8. 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.

  9. 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.)

  10. Interlaminar shear strength of SiC matrix composites reinforced by continuous fibers at 900 °C in air

    International Nuclear Information System (INIS)

    Zhang, Chengyu; Gou, Jianjie; Qiao, Shengru; Wang, Xuanwei; Zhang, Jun

    2014-01-01

    Highlights: • The application of SiC fiber could improve ILSS of the SiC matrix composites. • The orientation of the warp fibers plays a critical role in determining ILSS of 2.5D-C/SiC. • The failure mechanisms of 2D composites involve matrix cracking, and interfacial debonding. - Abstract: To reveal the shear properties of SiC matrix composites, interlaminar shear strength (ILSS) of three kinds of silicon carbide matrix composites was investigated by compression of the double notched shear specimen (DNS) at 900 °C in air. The investigated composites included a woven plain carbon fiber reinforced silicon carbide composite (2D-C/SiC), a two-and-a-half-dimensional carbon fiber-reinforced silicon carbide composite (2.5D-C/SiC) and a woven plain silicon carbon fiber reinforced silicon carbide composite (2D-SiC/SiC). A scanning electron microscope was employed to observe the microstructure and fracture morphologies. It can be found that the fiber type and reinforcement architecture have significant impacts on the ILSS of the SiC matrix composites. Great anisotropy of ILSS can be found for 2.5D-C/SiC because of the different fracture resistance of the warp fibers. Larger ILSS can be obtained when the specimens was loaded along the weft direction. In addition, the SiC fibers could enhance the ILSS, compared with carbon fibers. The improvement is attributed to the higher oxidation resistance of SiC fibers and the similar thermal expansion coefficients between the matrix and the fibers

  11. 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.

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

    Science.gov (United States)

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

    2011-01-01

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

  13. Enhanced performance of nano-sized SiC reinforced Al metal matrix nanocomposites synthesized through microwave sintering and hot extrusion techniques

    Directory of Open Access Journals (Sweden)

    M. Penchal Reddy

    2017-10-01

    Full Text Available In the present study, nano-sized SiC (0, 0.3, 0.5, 1.0 and 1.5 vol% reinforced aluminum (Al metal matrix composites were fabricated by microwave sintering and hot extrusion techniques. The structural (XRD, SEM, mechanical (nanoindentation, compression, tensile and thermal properties (co-efficient of thermal expansion-CTE of the developed Al-SiC nanocomposites were studied. The SEM/EDS mapping images show a homogeneous distribution of SiC nanoparticles into the Al matrix. A significant increase in the strength (compressive and tensile of the Al-SiC nanocomposites with the addition of SiC content is observed. However, it is noticed that the ductility of Al-SiC nanocomposites decreases with increasing volume fraction of SiC. The thermal analysis indicates that CTE of Al-SiC nanocomposites decreases with the progressive addition of hard SiC nanoparticles. Overall, hot extruded Al 1.5 vol% SiC nanocomposites exhibited the best mechanical and thermal performance as compared to the other developed Al-SiC nanocomposites. Keywords: Al-SiC nanocomposites, Microwave sintering, Hot extrusion, Mechanical properties, Thermal expansion

  14. 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)

  15. Residual Stress Measurement of SiC tile/Al7075 Hybrid Composites by Neutron Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong Bok; Lee, Jun Ho; Hong, Soon Hyung; Ryu, Ho Jin [KAIST, Daejeon (Korea, Republic of); Lee, Sang Bok; Lee, Sang Kwan [Korea Institute of Materials Science, Changwon (Korea, Republic of); Muslihd, M. Rifai [Center for Advanced Materials Science and Technology, Tangerang (India)

    2016-05-15

    In this research, SiC which has low density, high compressive strength, and high elastic modulus was used to fabricate the armor plate. In addition, Al which has low density and high toughness was used for a metal matrix of the composites. If two materials are combined, the composite can be effective materials for light weight armor applications. However, the existence of a large difference in coefficients of thermal expansion (CTE) between SiC and Al matrix, SiC/Al composites can have residual stresses while cooled in the fabrication process. Previous research reported that residual stresses in the composites or microstructures have an effect on the fatigue life and their mechanical properties. Some researchers reported about the residual stresses in the SiCp/Al metal matrix composites by numerical simulation systems, X-ray diffraction, and destructive methods. In order to analyze the residual stress of SiC/Al composites, the neutron diffraction as the non-destructive method was performed in this research. The 50 vol.% SiC{sub p}/Al7075 composites and SiC tile inserted 50 vol.% SiC{sub p}/Al7075 hybrid composites were measured to analyze the residual stress of Al (111) and SiC (111). Both samples had the tensile residual stresses in the Al (111) and the compressive residual stresses in the SiC (111) due to the difference in CTE.

  16. Investigation on the Short Circuit Safe Operation Area of SiC MOSFET Power Modules

    DEFF Research Database (Denmark)

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

    2016-01-01

    This paper gives a better insight of the short circuit capability of state-of-the-art SiC MOSFET power modules rated at 1.2 kV by highlighting the physical limits under different operating conditions. Two different failure mechanisms have been identified, both reducing the short-circuit capability...... of SiC power modules in respect to discrete SiC devices. Based on such failure mechanisms, two short circuit criteria (i.e., short circuit current-based criterion and gate voltage-based criterion) are proposed in order to ensure their robustness under short-circuit conditions. A Safe Operation Area (SOA...

  17. 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

  18. Development of SiC Neutron Detector Assembly to Measure the Neutron Flux of the Reactor Core

    Energy Technology Data Exchange (ETDEWEB)

    Park, Se Hwan; Park, June Sic; Shin, Hee Sung; Kim, Ho Dong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Yong Kyun [Hanyang University, Seoul (Korea, Republic of)

    2012-05-15

    At present, the conventional detector to measure the neutron at harsh environment is a Self Powered Neutron Detector (SPND). Rhodium(Rh)-103 is in the SPND. When neutron is incident on the Rhodium, the neutron capture reaction occurs, and the Rh-103 is converted to Rh-104. The Rh-104 is decayed to Pd-104 by {beta}-decay, and electrons are generated as the decay products. Because of the half life of Rh-104, approximately 5 minutes are required for the SPND output to reach the equilibrium condition. Therefore the on-line monitoring of the nuclear reactor state is limited if the neutron flux in the reactor core is monitored with the SPND. Silicon carbide (SiC) has the possibility to be developed as neutron detector at harsh environment, because the SiC can be operative at high temperature and high neutron flux conditions. Previously, the basic operation properties of the SiC detector were studied. Also, the radiation response of the SiC detector was studied at high neutron and gamma dose rate. The measurement results for an ex-core neutron flux monitor or a neutron flux monitor of the spent fuel were published. The SiC detector was also developed as neutron detector to measure the fissile material with active interrogation method. However, the studies about the development of SiC detector are still limited. In the present work, the radiation damage effect of the SiC detector was studied. The detector structure was determined based on the study, and a neutron detector assembly was made with the SiC detectors. The neutron and gamma-ray response of the detector assembly is presented in this paper. The detector assembly was positioned in the HANARO research reactor core, the performance test was done. The preliminary results are also included in this paper

  19. Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

    Energy Technology Data Exchange (ETDEWEB)

    Yu Shengwang, E-mail: bkdysw@yahoo.cn; Fan Pengwei; Tang Weizhong; Li Xiaojing; Hu Haolin; Hei Hongjun; Zhang Sikai; Lu Fanxiu

    2011-11-01

    SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH{sub 3}){sub 4}) diluted in H{sub 2} as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co{sub 2}Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.

  20. Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

    International Nuclear Information System (INIS)

    Yu Shengwang; Fan Pengwei; Tang Weizhong; Li Xiaojing; Hu Haolin; Hei Hongjun; Zhang Sikai; Lu Fanxiu

    2011-01-01

    SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH 3 ) 4 ) diluted in H 2 as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co 2 Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.

  1. Influence of extrusion parameters on sic distribution and properties of AA6061/SiC composites produced by kobo method

    Energy Technology Data Exchange (ETDEWEB)

    WoĨniak, Jarosáaw; Kostecki, Marek; Broniszewski, Kamil; Olszyna, Andrzej [Faculty of Material Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Bochniak, Wáodzimierz [Faculty of Non-Ferrous Metals, AGH University of Science and Technology, Cracow (Poland)

    2013-07-01

    The influence of extrusion parameters on reinforcements distribution and properties of AA6061+x% vol. SiC p (x=0; 2.5; 5; 7.5; 10) composites was discussed in this paper The averages size of AA6061 and SiC particles were 10.6 μ m and 0.42 μ m, respectively. The composites were consolidated via powder metallurgy processing (without the sintering) and extruded by KoBo method. The microstructure was examined on each steps of production. High values of density for all produced composites were achieved. Additionally, hardness and Young’s modulus were investigated. The best reinforcement distribution and mechanical properties were obtained for composites extruded with the highest extrusion ratio. Key words: aluminum alloy, extrusion, aged hardening, metal matrix composites, microstructure.

  2. The corrosion behavior of CVI SiC matrix in SiC{sub f}/SiC composites under molten fluoride salt environment

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongda [Structural Ceramics and Composites Engineering Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); School of Graduate, University of Chinese Academy of Sciences, Beijing 100049 (China); Feng, Qian [Analysis and Testing Center, Donghua University, Shanghai 201600 (China); Wang, Zhen, E-mail: jeff@mail.sic.ac.cn [Structural Ceramics and Composites Engineering Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhou, Haijun; Kan, Yanmei; Hu, Jianbao [Structural Ceramics and Composites Engineering Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Dong, Shaoming, E-mail: smdong@mail.sic.ac.cn [Structural Ceramics and Composites Engineering Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2017-04-15

    High temperature corrosion behavior and microstructural evolution of designed chemical-vapor-infiltrated SiC matrix in SiC fiber reinforced SiC ceramic matrix composites in 46.5LiF-11.5NaF-42.0KF (mol. %) eutectic salt at 800 °C for various corrosion time was studied. Worse damage was observed as extending the exposure time, with the mass loss ratio increasing from 0.716 wt. % for 50 h to 5.914 wt. % for 500 h. The mass loss rate showed a trend of first decrease and then increase with the extended corrosion exposure. Compared with the near-stoichiometric SiC matrix layers, the O-contained boundaries between deposited matrix layers and the designed Si-rich SiC matrix layers were much less corrosion resistant and preferentially corroded. Liner relationship between the mass loss ratio and the corrosion time obtained from 50 h to 300 h indicated that the corrosion action was reaction-control process. Further corrosion would lead to matrix layer exfoliation and higher mass loss ratio.

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

    KAUST Repository

    Cheng, Yingchun; Zhu, Zhiyong; Schwingenschlö gl, Udo

    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.

  4. Molecular dynamics simulation of damage cascade creation in SiC composites containing SiC/graphite interface

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, Joseph; Chen, Di; Wang, Jing; Shao, Lin, E-mail: lshao@tamu.edu

    2013-07-15

    Silicon carbide composites have been investigated for their use as structural materials for advanced nuclear reactor designs. Although the composites have significantly enhanced mechanical properties and structure integrity, there is little known about the behavior of defects in the presence of a graphite-silicon carbide interface. In this study, molecular dynamics simulations have been used to model defect creation and clustering in a composite containing a SiC/graphite interface. Evolution of displacements as a function of time were studied and compared to bulk SiC. The results show that the first a few SiC atomic layers closest to the interface are easily damaged. However, beyond these first few atomic layers the system appears to be unaffected by the SiC interface.

  5. Characteristics of Fabricated SiC Neutron Detectors for Neutron Flux Monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han Soo; Ha, Jang Ho; Park, Se Hwan; Lee, Kyu Hong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Cheol Ho [Hanyang University, Seoul (Korea, Republic of)

    2011-05-15

    An SPND (Self-powered Neutron Detector) is commonly used for neutron detection in NPP (Nuclear Power Plant) by virtue of un-reactivity for gamma-rays. But it has a drawback, which is that it cannot detect neutrons in real time due to beta emissions (about > 48 s) after reactions between neutrons and {sup 103}Rh in an SPND. And Generation IV reactors such as MSR (Molten-salt reactor), SFR (Sodium-cooled fast reactor), and GFR (Gas-cooled fast reactor) are designed to compact size and integration type. For GEN IV reactor, neutron monitor also must be compact-sized to apply such reactor easily and much more reliable. The wide band-gap semiconductors such as SiC, AlN, and diamond make them an attractive alternative in applications in harsh environments by virtue of the lower operating voltage, faster charge-collection times compared with gas-filled detectors, and compact size.1) In this study, two PIN-type SiC semiconductor neutron detectors, which are for fast neutron detection by elastic and inelastic scattering SiC atoms and for thermal neutron detection by charged particle emissions of 6LiF reaction, were designed and fabricated for NPP-related applications. Preliminary tests such as I-V and alpha response were performed and neutron responses at ENF in HANARO research reactor were also addressed. The application feasibility of the fabricated SiC neutron detector as an in-core neutron monitor was discussed

  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. UV laser drilling of SiC for semiconductor device fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Krueger, Olaf; Schoene, Gerd; Wernicke, Tim; John, Wilfred; Wuerfl, Joachim; Traenkle, Guenther [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

    2007-04-15

    Pulsed UV laser processing is used to drill micro holes in silicon carbide (SiC) wafers supporting AlGaN/GaN transistor structures. Direct laser ablation using nanosecond pulses has been proven to provide an efficient way to create through and blind holes in 400 {mu}m thick SiC. When drilling through, openings in the front pads are formed, while blind holes stop {approx}40 {mu}m before the backside and were advanced to the electrical contact pad by subsequent plasma etching without an additional mask. Low induction connections (vias) between the transistor's source pads and the ground on the backside were formed by metallization of the holes. Micro vias having aspect ratios of 5-6 have been processed in 400 {mu}m SiC. The process flow from wafer layout to laser drilling is available including an automated beam alignment that allows a positioning accuracy of {+-}1 {mu}m with respect to existing patterns on the wafer. As proven by electrical dc and rf measurements the laser-assisted via technologies have successfully been implemented into fabrication of AlGaN/GaN high-power transistors.

  8. 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.

  9. 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.

  10. Cold spraying SiC/Al metal matrix composites: effects of SiC contents and heat treatment on microstructure, thermophysical and flexural properties

    Science.gov (United States)

    Gyansah, L.; Tariq, N. H.; Tang, J. R.; Qiu, X.; Feng, B.; Huang, J.; Du, H.; Wang, J. Q.; Xiong, T. Y.

    2018-02-01

    In this paper, cold spray was used as an additive manufacturing method to fabricate 5 mm thick SiC/Al metal matrix composites with various SiC contents. The effects of SiC contents and heat treatment on the microstructure, thermophysical and flexural properties were investigated. Additionally, the composites were characterized for retention of SiC particulates, splat size, surface roughness and the progressive understanding of strengthening, toughening and cracking mechanisms. Mechanical properties were investigated via three-point bending test, thermophysical analysis, and hardness test. In the as-sprayed state, flexural strength increased from 95.3 MPa to 133.5 MPa, an appreciation of 40% as the SiC contents increased, and the main toughening and strengthening mechanisms were zigzag crack propagation and high retention of SiC particulates respectively. In the heat treatment conditions, flexural strength appreciated significantly compared to the as-sprayed condition and this was as a result of coarsening of pure Al splat. Crack branching, crack deflection and interface delamination were considered as the main toughening mechanisms at the heat treatment conditions. Experimental results were consistent with the measured CTE, hardness, porosity and flexural modulus.

  11. 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)

  12. Nanocrystalline SiC and Ti3SiC2 Alloys for Reactor Materials: Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Henager, Charles H. [pnnl; Alvine, Kyle J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Roosendaal, Timothy J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shin, Yongsoon [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nguyen, Ba Nghiep; Borlaug, Brennan A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jiang, Weilin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Arreguin, Shelly A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-01-15

    A new dual-phase nanocomposite of Ti₃SiC₂/SiC is being synthesized using preceramic polymers, ceramic powders, and carbon nanotubes (CNTs) designed to be suitable for advanced nuclear reactors and perhaps as fuel cladding. The material is being designed to have superior fracture toughness compared to SiC, adequate thermal conductivity, and higher density than SiC/SiC composites. This annual report summarizes the progress towards this goal and reports progress in understanding certain aspects of the material behavior but some shortcomings in achieving full density or in achieving adequate incorporation of CNTs. The measured thermal conductivity is adequate and falls into an expected range based on SiC and Ti₃SiC₂. Part of this study makes an initial assessment for Ti₃SiC₂ as a barrier to fission product transport. Ion implantation was used to introduce fission product surrogates (Ag and Cs) and a noble metal (Au) in Ti₃SiC₂, SiC, and a synthesized at PNNL. The experimental results indicate that the implanted Ag in SiC is immobile up to the highest temperature (1273 K) applied in this study; in contrast, significant out-diffusion of both Ag and Au in MAX phase Ti₃SiC₂ occurs during ion implantation at 873 K. Cs in Ti₃SiC₂ is found to diffuse during post-irradiation annealing at 973 K, and noticeable Cs release from the sample is observed. This study may suggest caution in using Ti₃SiC₂ as a fuel cladding material for advanced nuclear reactors operating at very high temperatures. Progress is reported in thermal conductivity modeling of SiC-based materials that is relevant to this research, as is progress in modeling the effects of CNTs on fracture strength of SiC-based materials.

  13. Brazing of AlN to SiC by a Pr silicide: Physicochemical aspects

    Energy Technology Data Exchange (ETDEWEB)

    Koltsov, A. [SIMAP - UMR CNRS 5266, INP Grenoble-UJF, Domaine Universitaire, BP 75, 1130 rue de la Piscine, 38402 Saint Martin d' Heres, Cedex (France)], E-mail: alexey.koltsov@arcelor.com; Hodaj, F.; Eustathopoulos, N. [SIMAP - UMR CNRS 5266, INP Grenoble-UJF, Domaine Universitaire, BP 75, 1130 rue de la Piscine, 38402 Saint Martin d' Heres, Cedex (France)

    2008-11-15

    In view of their very different thermomechanical properties, joining of metals to ceramics by brazing is usually performed by means of one or more interlayers. In a recent investigation AlN was chosen as interlayer material for brazing SiC to a superalloy. The aim of the present study is to determine an alloy with a high melting point (close to 1200 deg. C) enabling brazing of AlN to SiC. Two types of experiments are performed with a Si-17 at.% Pr eutectic alloy (T{sub m} = 1212 deg. C): sessile drop experiments to determine wetting and brazing of AlN and SiC plates to determine gap filling. Experiments are carried out in high vacuum to promote deoxidation. Interfacial reactivity, joint microstructure and type of failure occurring during cooling are examined by optical and scanning electron microscopy.

  14. Brazing of AlN to SiC by a Pr silicide: Physicochemical aspects

    International Nuclear Information System (INIS)

    Koltsov, A.; Hodaj, F.; Eustathopoulos, N.

    2008-01-01

    In view of their very different thermomechanical properties, joining of metals to ceramics by brazing is usually performed by means of one or more interlayers. In a recent investigation AlN was chosen as interlayer material for brazing SiC to a superalloy. The aim of the present study is to determine an alloy with a high melting point (close to 1200 deg. C) enabling brazing of AlN to SiC. Two types of experiments are performed with a Si-17 at.% Pr eutectic alloy (T m = 1212 deg. C): sessile drop experiments to determine wetting and brazing of AlN and SiC plates to determine gap filling. Experiments are carried out in high vacuum to promote deoxidation. Interfacial reactivity, joint microstructure and type of failure occurring during cooling are examined by optical and scanning electron microscopy

  15. Effect of LaB6 on the thermal shock property of MoSi2-SiC coating for carbon/carbon composites

    International Nuclear Information System (INIS)

    Li Ting; Li Hejun; Shi Xiaohong

    2013-01-01

    Highlights: ► LaB 6 -MoSi 2 -SiC and MoSi 2 -SiC multi-composition coatings were coated on C/C composites by pack cementation. ► The microstructure and thermal shock resistance of both coatings were investigated. ► The addition of LaB 6 can increase the compactness, flexural strength and fracture toughness of the MoSi 2 -SiC coating simultaneously. ► Both coatings bond well with the substrates before and after thermal cycling oxidation between 1773 K and room temperature. ► The LaB 6 -MoSi 2 -SiC coated C/C shows better thermal shock resistance than the MoSi 2 -SiC coated C/C. - Abstract: LaB 6 -MoSi 2 -SiC and MoSi 2 -SiC coatings were prepared on the surface of carbon/carbon composites by pack cementation method. The crystal structures of the coatings were measured by X-ray diffraction. The morphologies and element distributions were also analyzed by scanning electron microscopy and energy dispersive spectroscopy, respectively. The effect of LaB 6 on the microstructure and thermal shock resistance of MoSi 2 -SiC coating was investigated. The results indicated that the LaB 6 -MoSi 2 -SiC coating possessed a denser structure and superior thermal shock resistance. After 25 times of thermal cycling oxidation between 1773 K and room temperature, the weight losses of the LaB 6 -MoSi 2 -SiC and MoSi 2 -SiC coated samples were 0.627% and 2.019%, respectively.

  16. Mechanical properties and electrical conductivity of Cu-Cr and Cu-Cr-4% SiC nanocomposites for thermo-electric applications

    International Nuclear Information System (INIS)

    Mula, Suhrit; Sahani, Pankajini; Pratihar, S.K.; Mal, Siddhartha; Koch, Carl C.

    2011-01-01

    Highlights: → Ball-milled Cu-Cr and Cu-Cr-SiC nanopowders successfully consolidated by microwave sintering. → Addition of nanosize SiC in Cu-Cr leads to enhanced sintered density, wear and hardness. → A good combination of wear resistance, hardness and electrical conductivity resulted in Cu 94 Cr 6 -4% SiC. → Microwave suscepting SiC particles played a pivotal role in good densification retaining matrix grains 99 Cr 1 , Cu 94 Cr 6 , Cu 99 Cr 1 -4 wt.% SiC and Cu 94 Cr 6 -4 wt.% SiC (average particle size ∼30 nm). The 50 h ball-milled samples were uniaxially pressed, and then pellets were sintered at 800 deg. C, 900 deg. C and 1000 deg. C for a constant soaking period of 30 min by microwave sintering technique. Microstructural characterization was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Sintered compacts resulted a highly densified compacts (∼95% relative density) while retaining ultra-fine grains (100-200 nm) in the matrix. The mechanical properties, namely, hardness and wear resistance, and electrical conductivity of the sintered specimens were also evaluated. The best combination of mechanical properties (e.g. hardness ∼2.4 GPa) and electrical conductivity (60.3% of IACS) were obtained for Cu 94 Cr 6 -4 wt.% SiC sintered at 900 deg. C. This is possibly due to presence of ultra-fine grains in the bulk samples, good densification and proper bonding between particles. The results were analyzed in the light of interactions of microwaves between metallic matrix and microwave susceptive SiC particulates.

  17. 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.

  18. 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.

  19. Effect of re-melting on particle distribution and interface formation in SiC reinforced 2124Al matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Durbadal, E-mail: durbadal73@yahoo.co.in [MEF Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Viswanathan, Srinath [Dept of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL (United States)

    2013-12-15

    The interface between metal matrix and ceramic reinforcement particles plays an important role in improving properties of the metal matrix composites. Hence, it is important to find out the interface structure of composite after re-melting. In the present investigation, the 2124Al matrix with 10 wt.% SiC particle reinforced composite was re-melted at 800 °C and 900 °C for 10 min followed by pouring into a permanent mould. The microstructures reveal that the SiC particles are distributed throughout the Al-matrix. The volume fraction of SiC particles varies from top to bottom of the composite plate and the difference increases with the decrease of re-melting temperature. The interfacial structure of re-melted 2124Al–10 wt.%SiC composite was investigated using scanning electron microscopy, an electron probe micro-analyzer, a scanning transmission electron detector fitted with scanning electron microscopy and an X-ray energy dispersive spectrometer. It is found that a thick layer of reaction product is formed at the interface of composite after re-melting. The experimental results show that the reaction products at the interface are associated with high concentration of Cu, Mg, Si and C. At re-melting temperature, liquid Al reacts with SiC to form Al{sub 4}C{sub 3} and Al–Si eutectic phase or elemental Si at the interface. High concentration of Si at the interface indicates that SiC is dissociated during re-melting. The X-ray energy dispersive spectrometer analyses confirm that Mg- and Cu-enrich phases are formed at the interface region. The Mg is segregated at the interface region and formed MgAl{sub 2}O{sub 4} in the presence of oxygen. The several elements identified at the interface region indicate that different types of interfaces are formed in between Al matrix and SiC particles. The Al–Si eutectic phase is formed around SiC particles during re-melting which restricts the SiC dissolution. - Highlights: • Re-melted composite shows homogeneous particle

  20. 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

  1. Large-scale synthesis of monodisperse SiC nanoparticles with adjustable size, stoichiometric ratio and properties by fluidized bed chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Rongzheng; Liu, Malin, E-mail: liumalin@tsinghua.edu.cn; Chang, Jiaxing [Tsinghua University, Institute of Nuclear and New Energy Technology, Collaborative Innovation Center of Advanced Nuclear Energy Technology (China)

    2017-02-15

    A facile fluidized bed chemical vapor deposition method was proposed for the synthesis of monodisperse SiC nanoparticles by using the single precursor of hexamethyldisilane (HMDS). SiC nanoparticles with average particle size from 10 to 200 nm were obtained by controlling the temperature and the gas ratio. An experimental chemical vapor deposition phase diagram of SiC in the HMDS-Ar-H{sub 2} system was obtained and three regions of SiC-Si, SiC and SiC-C can be distinguished. The BET surface area and the photoluminescence properties of the SiC nanoparticles can be adjusted by changing the nanoparticle size. For the SiC nanospheres with free carbon, a novel hierarchical structure with 5 ~ 8 nm SiC nanoparticles embedded into the graphite matrix was obtained. The advantages of fluidized bed technology for the preparation of SiC nanoparticles were proposed based on the features of homogenous reaction zone, narrow temperature distribution, ultra-short reactant residence time and mass production.

  2. Large-scale synthesis of monodisperse SiC nanoparticles with adjustable size, stoichiometric ratio and properties by fluidized bed chemical vapor deposition

    International Nuclear Information System (INIS)

    Liu, Rongzheng; Liu, Malin; Chang, Jiaxing

    2017-01-01

    A facile fluidized bed chemical vapor deposition method was proposed for the synthesis of monodisperse SiC nanoparticles by using the single precursor of hexamethyldisilane (HMDS). SiC nanoparticles with average particle size from 10 to 200 nm were obtained by controlling the temperature and the gas ratio. An experimental chemical vapor deposition phase diagram of SiC in the HMDS-Ar-H_2 system was obtained and three regions of SiC-Si, SiC and SiC-C can be distinguished. The BET surface area and the photoluminescence properties of the SiC nanoparticles can be adjusted by changing the nanoparticle size. For the SiC nanospheres with free carbon, a novel hierarchical structure with 5 ~ 8 nm SiC nanoparticles embedded into the graphite matrix was obtained. The advantages of fluidized bed technology for the preparation of SiC nanoparticles were proposed based on the features of homogenous reaction zone, narrow temperature distribution, ultra-short reactant residence time and mass production.

  3. Joining technology—A challenge for the use of SiC components in HTRs

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, M., E-mail: marion.herrmann@tu-dresden.de; Meisel, P.; Lippmann, W.; Hurtado, A.

    2016-09-15

    The availability of suitable joining technologies is paramount to the further advancement of ceramic components and their use in HTRs. Among other joining technologies, a modified brazing technology using a laser beam for heating the components to be joined has been developed at TU Dresden. The laser-induced heating behavior of the ceramic material is determined by the interactions between the material and the laser beam. This was shown in two different silicon carbide materials (SSiC and SiC{sub f}-reinforced ceramic material) using a diode laser with wavelengths 808 nm and 940 nm. The laser-based technique was illustrated by three different examples: sealing of monolithic SiC with a pin configuration for fuel claddings, sealing of SiC heat pipes with a length of 1 m, and demonstration of the transferability of the laser technique to fiber-reinforced components by means of a SiC{sub f}/SiCN material. Because the covalent bonding of SiC does not allow conventional welding, much research has been devoted to developing alternative filler systems. Glass or glass–ceramic fillers enable the tailoring of properties such as CTE and viscosity. Glasses are thermally stable up to their glass transition temperatures. It was shown that the crystallization of the yttrium aluminosilicate glass composition of the present work allows it to be used at 1050 °C without any significant changes occurring in braze tightness. For the SiC heat pipes with sodium as the working fluid, a sodium-resistant metal braze consisting of Ni–Ti–Si was formed. The long-term resistance of this filler to sodium at 800 °C was proven. The results demonstrate the possibility of using the laser-based joining technique for the joining of different SiC materials as well as for different brazing materials.

  4. SiC detectors to monitor ionizing radiations emitted from nuclear events and plasmas

    Science.gov (United States)

    Torrisi, L.; Cannavò, A.

    2016-09-01

    Silicon Carbide (SiC) semiconductor detectors are increasingly employed in Nuclear Physics for their advantages with respect to traditional silicon (Si). Such detectors show an energy resolution, charge mobility, response velocity and detection efficiency similar to Si detectors. However, the higher band gap (3.26 eV), the lower leakage current (∼10 pA) maintained also at room temperature, the higher radiation hardness and the higher density with respect to Si represent some indisputable advantages characterizing such detectors. The devices can be employed at high temperatures, at high absorbed doses and in the case of high visible light intensities, for example, in plasma, for limited exposition times without damage. Generally SiC Schottky diodes are employed in reverse polarization with an active region depth of the order of 100 µm, purity below 1014 cm-3 and an active area lower than 1 cm2. Measurements in the regime of proportionality with the radiation energy released in the active region and measurements in time-of-flight configuration are employed for nuclear emission events produced at both low and high fluences. Alpha spectra demonstrated an energy resolution of about 1.3% at 5.8 MeV. Radiation emission from laser-generated plasma can be monitored in terms of detected photons, electrons and ions, using the laser pulse as a start signal and the radiation detection as a stop signal, enabling to measure the ion velocity by knowing the target-detector flight distance. SiC spectra acquired in the Messina University laboratories using radioactive ion sources and at the PALS laboratory facility in Prague (Czech Republic) are presented. A preliminary study of the use of SiC detectors, embedded in a water equivalent polymer, as a dosimeter is presented and discussed.

  5. Enhanced defects recombination in ion irradiated SiC

    International Nuclear Information System (INIS)

    Izzo, G.; Litrico, G.; Grassia, F.; Calcagno, L.; Foti, G.

    2010-01-01

    Point defects induced in SiC by ion irradiation show a recombination at temperatures as low as 320 K and this process is enhanced after running current density ranging from 80 to 120 A/cm 2 . Ion irradiation induces in SiC the formation of different defect levels and low-temperature annealing changes their concentration. Some levels (S 0 , S x and S 2 ) show a recombination and simultaneously a new level (S 1 ) is formed. An enhanced recombination of defects is besides observed after running current in the diode at room temperature. The carriers introduction reduces the S 2 trap concentration, while the remaining levels are not modified. The recombination is negligible up to a current density of 50 A/cm 2 and increases at higher current density. The enhanced recombination of the S 2 trap occurs at 300 K, which otherwise requires a 400 K annealing temperature. The process can be related to the electron-hole recombination at the associated defect.

  6. EBSD characterization of the growth mechanism of SiC synthesized via direct microwave heating

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jigang, E-mail: wangjigang@seu.edu.cn [Jiangsu Key Laboratory of Advanced Metallic Materials, School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Xizang Key Laboratory of Optical Information Processing and Visualization Technology, School of Information Engineering, Xizang Minzu University, Xianyang 712082 (China); Huang, Shan; Liu, Song; Qing, Zhou [Jiangsu Key Laboratory of Advanced Metallic Materials, School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China)

    2016-04-15

    Well-crystallized 3C-silicon carbide (SiC) grains/nanowires have been synthesized rapidly and conveniently via direct microwave heating, simply using silicon dioxide powders and artificial graphite as raw materials. The comprehensive characterizations have been employed to investigate the micro-structure of the obtained 3C-SiC products. Results indicated that, different from the classic screw dislocation growth mechanism, the 3C-SiC grains/nanowires synthesized via high-energy vacuum microwave irradiation were achieved through the two-dimension nucleation and laminar growth mechanism. Especially, the electron backscattered diffraction (EBSD) was employed to characterize the crystal planes of the as-grown SiC products. The calculated Euler angles suggested that the fastest-growing crystal planes (211) were overlapped gradually. Through the formation of the (421) transformation plane, (211) finally evolved to (220) which existed as the side face of SiC grains. The most stable crystal planes (111) became the regular hexagonal planes in the end, which could be explained by the Bravais rule. The characterization results of EBSD provided important experimental information for the evolution of crystal planes. - Graphical abstract: The formation of 3C-SiC prepared via direct microwave heating follows the mechanism of two-dimension nucleation and laminar growth. - Highlights: • 3C−SiC grains/nanowires were obtained via direct microwave heating. • 3C−SiC followed the mechanism of two-dimension nucleation and laminar growth. • In-situ EBSD analysis provided the experimental evidences of the growth.

  7. Growth of boron doped hydrogenated nanocrystalline cubic silicon carbide (3C-SiC) films by Hot Wire-CVD

    Energy Technology Data Exchange (ETDEWEB)

    Pawbake, Amit [School of Energy Studies, Savitribai Phule Pune University, Pune 411 007 (India); Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Mayabadi, Azam; Waykar, Ravindra; Kulkarni, Rupali; Jadhavar, Ashok [School of Energy Studies, Savitribai Phule Pune University, Pune 411 007 (India); Waman, Vaishali [Modern College of Arts, Science and Commerce, Shivajinagar, Pune 411 005 (India); Parmar, Jayesh [Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Bhattacharyya, Somnath [Department of Metallurgical and Materials Engineering, IIT Madras, Chennai 600 036 (India); Ma, Yuan‐Ron [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China); Devan, Rupesh; Pathan, Habib [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Jadkar, Sandesh, E-mail: sandesh@physics.unipune.ac.in [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India)

    2016-04-15

    Highlights: • Boron doped nc-3C-SiC films prepared by HW-CVD using SiH{sub 4}/CH{sub 4}/B{sub 2}H{sub 6}. • 3C-Si-C films have preferred orientation in (1 1 1) direction. • Introduction of boron into SiC matrix retard the crystallanity in the film structure. • Film large number of SiC nanocrystallites embedded in the a-Si matrix. • Band gap values, E{sub Tauc} and E{sub 04} (E{sub 04} > E{sub Tauc}) decreases with increase in B{sub 2}H{sub 6} flow rate. - Abstract: Boron doped nanocrystalline cubic silicon carbide (3C-SiC) films have been prepared by HW-CVD using silane (SiH{sub 4})/methane (CH{sub 4})/diborane (B{sub 2}H{sub 6}) gas mixture. The influence of boron doping on structural, optical, morphological and electrical properties have been investigated. The formation of 3C-SiC films have been confirmed by low angle XRD, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) spectroscopy and high resolution-transmission electron microscopy (HR-TEM) analysis whereas effective boron doping in nc-3C-SiC have been confirmed by conductivity, charge carrier activation energy, and Hall measurements. Raman spectroscopy and HR-TEM analysis revealed that introduction of boron into the SiC matrix retards the crystallanity in the film structure. The field emission scanning electron microscopy (FE-SEM) and non contact atomic force microscopy (NC-AFM) results signify that 3C-SiC film contain well resolved, large number of silicon carbide (SiC) nanocrystallites embedded in the a-Si matrix having rms surface roughness ∼1.64 nm. Hydrogen content in doped films are found smaller than that of un-doped films. Optical band gap values, E{sub Tauc} and E{sub 04} decreases with increase in B{sub 2}H{sub 6} flow rate.

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

    Science.gov (United States)

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

    2016-09-01

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

  9. Performance evaluation of a high power DC-DC boost converter for PV applications using SiC power devices

    Science.gov (United States)

    Almasoudi, Fahad M.; Alatawi, Khaled S.; Matin, Mohammad

    2016-09-01

    The development of Wide band gap (WBG) power devices has been attracted by many commercial companies to be available in the market because of their enormous advantages over the traditional Si power devices. An example of WBG material is SiC, which offers a number of advantages over Si material. For example, SiC has the ability of blocking higher voltages, reducing switching and conduction losses and supports high switching frequency. Consequently, SiC power devices have become the affordable choice for high frequency and power application. The goal of this paper is to study the performance of 4.5 kW, 200 kHz, 600V DC-DC boost converter operating in continuous conduction mode (CCM) for PV applications. The switching behavior and turn on and turn off losses of different switching power devices such as SiC MOSFET, SiC normally ON JFET and Si MOSFET are investigated and analyzed. Moreover, a detailed comparison is provided to show the overall efficiency of the DC-DC boost converter with different switching power devices. It is found that the efficiency of SiC power switching devices are higher than the efficiency of Si-based switching devices due to low switching and conduction losses when operating at high frequencies. According to the result, the performance of SiC switching power devices dominate the conventional Si power devices in terms of low losses, high efficiency and high power density. Accordingly, SiC power switching devices are more appropriate for PV applications where a converter of smaller size with high efficiency, and cost effective is required.

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

    Science.gov (United States)

    2017-10-30

    SiC Based Power Electronic Building Blocks Award Number Title of Research 30 October 2017 SUBMITTED BY D R. HERBERT L. G INN, Pl DEPT. OF...Naval Research , Philadelphia PA, Aug. 2017. • Ginn, H.L. Bakos J., "Development of Universal Controller Architecture for SiC Based Power Electronic...Controller Implementation for MMC Converters", Workshop on Control Architectures for Modular Power Conversion Systems, Office of Naval Research , Arlington VA

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

    Indian Academy of Sciences (India)

    Utilizing thermoelectric technology to aerodynamic heat harvesting on the ... in terms of the computational fluid dynamics and the thermal conduction theory. ... It is shown that doping elements with good ... ous SiC materials, yet few experimental studies have been ... polymer-derived consolidated SiC-based ceramics, which.

  12. 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.)

  13. 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...... with SiC MOSFETs is not so clear-cut. This paper now explores this issue by presenting a detailed comparison of the use of Si and SiC devices for a three-level T-Type inverter operating in grid-tie applications. The study uses datasheet values, switching loss measurements and calibrated heat sink thermal...... 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....

  14. Structure of tris(trimethylsilylcyclopentadienyl)uranium(III), [(CH3)3SiC5H43U

    International Nuclear Information System (INIS)

    Brennan, J.; Andersen, R.A.; Zalkin, A.

    1986-02-01

    Crystals of [(CH 3 ) 3 SiC 5 H 4 ] 3 U are orthorhombic, Pbca, with a = 22.630(8), b = 29.177(10) and c = 8.428(3) A at 23 0 C. For Z = 8 the calculated density is 1.551 g/cm 3 . The structure was refined by full-matrix least-squares to a conventional R factor of 0.041 [2251 data, F 2 > 2 sigma(F 2 )]. The uranium atom is bonded to the three cyclopentadienyl rings in a pentahapto fashion and is in the plane of the ring centroids. The U to ring distances are 2.54, 2.47 and 2.51 A, and the average U-C distance is 2.78 +- 0.04 A. 7 refs., 1 fig., 3 tabs

  15. 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...... by an optimization process to facilitate the extraction of the model’s parameters in a more automated way relying on a small number of experimental waveforms. Through extensive experimental work, it is shown that the model accurately predicts both static and dynamic performances. The series connection of two Si......C power modules has been investigated through the validation of the static and dynamic conditions. Thanks to the developed model, a better understanding of the challenges introduced by uneven voltage balance sharing among series connected devices is possible....

  16. CaO-Al2O3 glass-ceramic as a joining material for SiC based components: A microstructural study of the effect of Si-ion irradiation

    Science.gov (United States)

    Casalegno, Valentina; Kondo, Sosuke; Hinoki, Tatsuya; Salvo, Milena; Czyrska-Filemonowicz, Aleksandra; Moskalewicz, Tomasz; Katoh, Yutai; Ferraris, Monica

    2018-04-01

    The aim of this work was to investigate and discuss the microstructure and interface reaction of a calcia-alumina based glass-ceramic (CA) with SiC. CA has been used for several years as a glass-ceramic for pressure-less joining of SiC based components. In the present work, the crystalline phases in the CA glass-ceramic and at the CA/SiC interface were investigated and the absence of any detectable amorphous phase was assessed. In order to provide a better understanding of the effect of irradiation on the joining material and on the joints, Si ion irradiation was performed both on bulk CA and CA joined SiC. CA glass-ceramic and CA joined SiC were both irradiated with 5.1 MeV Si2+ ions to 3.3 × 1020 ions/m2 at temperatures of 400 and 800 °C at DuET facility, Kyoto University. This corresponds to a damage level of 5 dpa for SiC averaged over the damage range. This paper presents the results of a microstructural analysis of the irradiated samples as well as an evaluation of the dimensional stability of the CA glass-ceramic and its irradiation temperature and/or damage dependence.

  17. 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

  18. Estudo da viabilidade de obtenção de cerâmicas de SiC por infiltração espontânea de misturas eutéticas de Y2O3-AlN, Y2O3-Al2O3, R2O3-AlN Study of the viability to produce SiC ceramics by Y2O3-AlN, Y2O3-Al2O3, R2O3-AlN spontaneous infiltration

    Directory of Open Access Journals (Sweden)

    G. C. R. Garcia

    2008-06-01

    Full Text Available As cerâmicas de carbeto de silício, SiC, apresentam excelentes propriedades quando obtidas por infiltração de determinados líquidos. Na infiltração o tempo de contato entre o líquido e o SiC a temperaturas elevadas é muito curto, diminuindo a probabilidade de formação dos produtos gasosos que interferem negativamente na resistência da peça final, como ocorre na sinterização via fase líquida. O objetivo deste trabalho é mostrar uma correlação entre molhabilidade e capacidade de infiltração de alguns aditivos em compactos de SiC. Foram preparados compactos de SiC por prensagem isostática a frio e posterior pré-sinterização via fase sólida. Nesses compactos foram infiltradas misturas de Y2O3-AlN, Y2O3-Al2O3, R2O3-AlN, nas composições eutéticas, 10 ºC acima da temperatura de fusão das respectivas misturas por 4, 8 e 12 min. Após infiltração, as amostras foram analisadas quanto à densidade aparente e real, fases cristalinas, microestrutura e grau de infiltração, sendo que as amostras infiltradas com Y2O3-AlN apresentaram melhores resultados.Silicon carbide ceramics, SiC, obtained by liquid infiltration have shown excellent properties. In infiltration process the contact time of the liquid with SiC at elevated temperature is short, decreasing the probability to form gaseous products that contribute negatively in the final product properties. This phenomenon occurs during SiC liquid phase sintering. The purpose of the present study was to investigate the correlation between wettability and infiltration tendency of some additives in SiC compacts. SiC compacts were prepared by cold isostatic pressing followed by solid phase pre-sintering. Into the compacts were introduced Y2O3-AlN, Y2O3-Al2O3, R2O3-AlN liquids with eutectic compositions at a temperature 10 ºC higher than the melting point of each mixture for 4, 8 and 12 min. Before infiltration, the samples were analyzed by determining densities, crystalline phases

  19. 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.

  20. Effect of high temperature annealing on the microstructure of SCS-6 SiC fibers

    Science.gov (United States)

    Ning, X. J.; Pirouz, P.; Bhatt, R. T.

    1992-01-01

    The effect of annealing the SCS-6 SiC fiber for one hour at 2000 C in an argon atmosphere is reported. The SiC grains in the fiber coarsen appreciably and the intergranular carbon films segregate to the grain junctions. It would appear that grain growth in the outer part of the fiber is primarily responsible for the loss in fiber strength and improvement in fiber creep resistance.

  1. Halogenation of SiC for band-gap engineering and excitonic functionalization

    Science.gov (United States)

    Drissi, L. B.; Ramadan, F. Z.; Lounis, S.

    2017-11-01

    The optical excitation spectra and excitonic resonances are investigated in systematically functionalized SiC with Fluorine and/or Chlorine utilizing density functional theory in combination with many-body perturbation theory. The latter is required for a realistic description of the energy band-gaps as well as for the theoretical realization of excitons. Structural, electronic and optical properties are scrutinized and show the high stability of the predicted two-dimensional materials. Their realization in laboratory is thus possible. Large band-gaps of the order of 4 eV are found in the so-called GW approximation, with the occurrence of bright excitons, optically active in the four investigated materials. Their binding energies vary from 0.9 eV to 1.75 eV depending on the decoration choice and in one case, a dark exciton is foreseen to exist in the fully chlorinated SiC. The wide variety of opto-electronic properties suggest halogenated SiC as interesting materials with potential not only for solar cell applications, anti-reflection coatings or high-reflective systems but also for a possible realization of excitonic Bose-Einstein condensation.

  2. Experimental studies on the transport of silver and cesium fission products in SiC

    International Nuclear Information System (INIS)

    Gerczak, Tyler; Tan, Lizhen; Allen, Todd

    2009-01-01

    To understand the release of Ag and Cs in SiC we have designed an integrated experimental and modeling program to understand the potential role of microstructure on fission product transport. We have encapsulated SiC/Ag and SiC/Cs diffusion couples in a molybdenum canister to ensure contact between the two diffusion couple elements and no Ag or Cs loss to the surrounding environment. The diffusion couples are exposed to temperatures spanning 800 to 1500degC for up to 1000 hrs to simulate normal and the onset of accident conditions. The relationship between the microstructure and diffusion will be understood by employing a variety of techniques such as scanning electron microscopy (SEM), electron backscattered detection (EBSD), energy dispersive spectroscopy (EDS), Rutherford backscattering (RBS), and Raman spectroscopy to characterize morphology, grain boundary character distribution, chemical composition, and crystalline structure. In addition computer modeling is also being used to investigate the diffusion of silver through SiC, but will not be discussed in this paper. A multi-scale approach based on ab initio techniques, molecular dynamics, and continuum rate equations is being pursued to establish relationships between complex microstructures and diffusion rates. Initial work has begun on transport through bulk SiC and on building realistic models of grain boundaries in SiC. (author)

  3. 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

  4. 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....

  5. 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

  6. 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

  7. THERMAL CONDUCTIVITY OF SIC AND C FIBERS

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-09-01

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

  8. Wear behavior of A356/M{sub 7}C{sub 3} and A356/SiC particulate metal matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Turhan, H. [Univ. of Firat, Dept. of Metallurgy, Elazig (Turkey); Yilmaz, O. [Univ. of Firat, Dept. of Metallurgical Engineering, Elazig (Turkey)

    2002-06-01

    The stability of M{sub 7}C{sub 3} carbides as reinforcement for A356 materials for tribological applications has been investigated. For this purpose, A356/M{sub 7}C{sub 3}, A356/SiC and A356/M{sub 7}C{sub 3}/SiC composites were prepared by powder metallurgy and tested at room temperature against SAE 4620 steel ring and AISI 304 stainless steel counterfaces under loads of 10 - 150 N. For comparison, also unreinforced A356 specimens were processed and tested under the same conditions. The tribological behavior was evaluated by microstructural examination of the wear-effected zones and by weight loss measurements of the specimens and counterfaces. The wear behavior of A356/M{sub 7}C{sub 3} composite gave an excellent result as function of the applied load because the M{sub 7}C{sub 3} particles act as load-bearing elements due to their excellent bonding to the Al matrix, and their interfaces withtood the wear stresses even at the highest applied load. Moreover, the M{sub 7}C{sub 3} particles limited the incorporation of wear debris into the Al matrix and reduced the wear damage occasioned to the steel counterfaces compared to that of A356 Al alloy. (orig.)

  9. 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.

  10. 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.

  11. 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...

  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. 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.

  15. Trapping Effects in GaN and SiC Microwave FETs

    National Research Council Canada - National Science Library

    Binari, Steven C; Klein, P. B; Kazior, Thomas E

    2002-01-01

    ...). This is particularly true for the wide bandgap devices. In this paper, we review the various trapping phenomena observed in SiC- and GaN-based FETs that contribute to compromised power performance...

  16. 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.

  17. 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

  18. Effect of nitrogen on the electrochemical performance of core–shell structured Si/C nanocomposites as anode materials for Li-ion batteries

    International Nuclear Information System (INIS)

    Tao, Hua-Chao; Huang, Mian; Fan, Li-Zhen; Qu, Xuanhui

    2013-01-01

    Highlights: ► N-containing core–shell structured Si/C nanocomposites are prepared via two steps. ► The N-containing Si/C nanocomposites exhibit high capacity and excellent cycling stability. ► The appropriate nitrogen has a beneficial effect on the electrochemical performance. -- Abstract: Core–shell structured Si/C nanocomposites with different nitrogen contents are prepared by in situ polymerization of aniline in the suspension of silicon nanoparticles followed by carbonization of Si/polyaniline (PANI) nanocomposites at different temperatures. The nitrogen contents of Si/C nanocomposites decrease gradually with increasing carbonization temperatures. The effect of nitrogen contents on the electrochemical performance of Si/C nanocomposites as anode materials for lithium ion batteries is investigated. It is found that the Si/C nanocomposites with 4.75 wt.% nitrogen exhibit the high specific capacity of 795 mAh g −1 after 50 cycles at a current density of 100 mA g −1 and excellent cycling stability. The appropriate nitrogen in Si/C nanocomposites plays a beneficial role in the improvement of electrochemical performance. The nitrogen in Si/C nanocomposites increases the reversible capacity, which may be due to the formation of vacancies and dangling bonds around the nitrogen sites

  19. 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.)

  20. 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.)

  1. Vacuum brazing of high volume fraction SiC particles reinforced aluminum matrix composites

    Science.gov (United States)

    Cheng, Dongfeng; Niu, Jitai; Gao, Zeng; Wang, Peng

    2015-03-01

    This experiment chooses A356 aluminum matrix composites containing 55% SiC particle reinforcing phase as the parent metal and Al-Si-Cu-Zn-Ni alloy metal as the filler metal. The brazing process is carried out in vacuum brazing furnace at the temperature of 550°C and 560°C for 3 min, respectively. The interfacial microstructures and fracture surfaces are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy spectrum analysis (EDS). The result shows that adequacy of element diffusion are superior when brazing at 560°C, because of higher activity and liquidity. Dislocations and twins are observed at the interface between filler and composite due to the different expansion coefficient of the aluminum alloy matrix and SiC particles. The fracture analysis shows that the brittle fracture mainly located at interface of filler and composites.

  2. Enhanced oxidation resistance of SiC coating on Graphite by crack healing at the elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jae-Won; Kim, Eung-Seon; Kim, Jae-Un; Kim, Yoo-Taek [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Windes, William E. [Idaho National Laboratory, Idaho (United States)

    2015-10-15

    An oxidation protective SiC coating on the graphite components could assist in slowing the oxidation down. However, the irradiation induced dimensional changes in the graphite (shrinkage followed by swelling) can occur, while the SiC CVD coating has been reported to swell even at a low dose neutron irradiation. In this work, functionally gradient electron beam evaporative coating with an ion beam processing was firstly conducted and then SiC coating on the FG coating to the desired thickness is followed. For the crack healing, both the repeated EB-PVD and CVD were performed. Oxidation and thermal cycling tests of the coated specimens were performed and reflected in the process development. In this work, efforts have been paid to heal the cracks in the SiC coated layer on graphite with both EB-PVD and CVD. CVD seems to be more appropriate coating method for crack healing probably due to its excellent crack-line filling capability for high density and high aspect ratio.

  3. The Development of a Hybrid-Type Radiation Detector with SiC for a Reactor Robot

    International Nuclear Information System (INIS)

    Lee, Nam Ho; Cho, Jai Wan; Kim, Seung Ho

    2005-01-01

    For a robot working in a harsh environment such as a nuclear reactor environment or a space environment, requirements of on-board radiation detectors are not the same as those for environments around human. SiC devices with the wide band-gap are less dependent on temperature than Si counterparts and the can be the better candidate for the high radiation environment. With this background, radiation performance of a commercial SiC detector in a Co-60 gamma-ray environment has been evaluated. In addition to the SiC detector, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) detector has been incorporated as a backup. With this MOSFET sensor the dosimeter can keep its radiation exposure history even with loss of power. It is not only a redundant feature but also a diverse feature. The dosimetry module can be attached to mobile robot for high radiation environment was developed. This module has both SiC diode and pMOSFET mentioned above. The monitoring program which receives the radiation information from them and gives out the alarm signal when the difference of the two values from them is over the preset level was constructed. Because both the SiC pulse-type detector and the MOSFET dosimeter are small and light weight, they can be easily accommodated on a small printcircuit board for a tight space on a robot arm or for a small spacecraft

  4. Orthorhombic Intermediate State in the Zinc Blende to Rocksalt Transformation Path of SiC at High Pressure

    International Nuclear Information System (INIS)

    Catti, Michele

    2001-01-01

    The mechanism of the B3/B1 phase transition of SiC has been investigated by periodic LCAO-DFT least-enthalpy calculations. A new transformation pathway, based on a Pmm2 orthorhombic intermediate state with two SiC units per cell, is found to be energetically favored over the traditional R3m mechanism. The computed activation enthalpy is 0.75eV/SiC unit at the predicted transition pressure of 92GPa (B3LYP functional). Activation enthalpy and activation volume vs pressure are analyzed to characterize the kinetic aspects of the transformation

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

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Xixi; Wang, Xianlong; Zheng, Xiaohong, E-mail: xhzheng@theory.issp.ac.cn; Zeng, Zhi [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Hao, Hua [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2016-06-06

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

  6. Rotated domain network in graphene on cubic-SiC(001)

    International Nuclear Information System (INIS)

    Chaika, Alexander N; Aristov, Victor Y; Molodtsova, Olga V; Zakharov, Alexei A; Marchenko, Dmitry; Sánchez-Barriga, Jaime; Varykhalov, Andrei; Babenkov, Sergey V; Portail, Marc; Zielinski, Marcin; Murphy, Barry E; Krasnikov, Sergey A; Lübben, Olaf; Shvets, Igor V

    2014-01-01

    The atomic structure of the cubic-SiC(001) surface during ultra-high vacuum graphene synthesis has been studied using scanning tunneling microscopy (STM) and low-energy electron diffraction. Atomically resolved STM studies prove the synthesis of a uniform, millimeter-scale graphene overlayer consisting of nanodomains rotated by ±13.5° relative to the 〈110〉-directed boundaries. The preferential directions of the domain boundaries coincide with the directions of carbon atomic chains on the SiC(001)-c(2 × 2) reconstruction, fabricated prior to graphene synthesis. The presented data show the correlation between the atomic structures of the SiC(001)-c(2 × 2) surface and the graphene/SiC(001) rotated domain network and pave the way for optimizing large-area graphene synthesis on low-cost cubic-SiC(001)/Si(001) wafers. (paper)

  7. 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.

  8. Advances in SiC materials and devices: an industrial point of view

    Energy Technology Data Exchange (ETDEWEB)

    Siergiej, R.R.; Clarke, R.C.; Sriram, S.; Agarwal, A.K.; Bojko, R.J.; Morse, A.W.; Balakrishna, V.; MacMillan, M.F.; Brandt, C.D. [Northrop Grumman ESSS Sci. and Technol. Center, Pittsburgh, PA (United States); Burk, A.A. Jr. [Northrop Grumman ESSS Adv. Technol. Lab. Baltimore, MD (United States)

    1999-07-30

    Silicon carbide (SiC) is an emerging semiconductor that has proven itself especially well-suited to high temperature power switching and high-frequency power generation. In this paper we examine recent advances in materials development and device performance. In boule growth we have focused on increasing boule diameter and reducing defect counts. Two conductivity types have been developed (1) semi-insulating for MESFETs, and (2) highly conducting boules for SITs and power switches. Very uniform planetary multi-wafer epitaxial layer growth on these wafers is described, in which specular epitaxial layers have been obtained with growth rates of 3-5{mu}m h{sup -1} exhibiting unintentional n-type doping of {proportional_to}1 x 10{sup 15} cm{sup -3}, and room temperature Hall mobilities of {proportional_to}1000 cm{sup 2} V{sup -1} s{sup -1}. Controlled n-type doping between {proportional_to}5 x 10{sup 15} cm{sup -3} and >1 x 10{sup 19} cm{sup -3} has also been demonstrated using nitrogen doping. SiC finds application in high temperature power switching devices and microwave power transistors. MOS turn-off thyristors (MTO{sup TM}) are being investigated as power switches because they offer ease of turn-off, 500 C operation and reduced cooling requirements. In the fabrication of high-power, high-frequency transistors at UHF, L-, S-, and X-bands SiC has been found superior to both silicon and GaAs. For example, a 4H-SiC UHF television module has demonstrated good signal fidelity at the 2000 W PEP level, S-band transistor packages have shown 300 W peak power for radar applications, and 6 W power output has been obtained at X-band. (orig.)

  9. 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 ...

  10. Electronic-structure origin of the anisotropic thermopower of nanolaminated Ti3SiC2 determined by polarized x-ray spectroscopy and Seebeck measurements

    DEFF Research Database (Denmark)

    Magnuson, Martin; Mattesini, Maurizio; Van Nong, Ngo

    2012-01-01

    Nanolaminated materials exhibit characteristic magnetic, mechanical, and thermoelectric properties, with large contemporary scientific and technological interest. Here we report on the anisotropic Seebeck coefficient in nanolaminated Ti3SiC2 single-crystal thin films and trace the origin to aniso......Nanolaminated materials exhibit characteristic magnetic, mechanical, and thermoelectric properties, with large contemporary scientific and technological interest. Here we report on the anisotropic Seebeck coefficient in nanolaminated Ti3SiC2 single-crystal thin films and trace the origin...... value of 4–6 μV/K. Employing a combination of polarized angle-dependent x-ray spectroscopy and density functional theory we directly show electronic structure anisotropy in inherently nanolaminated Ti3SiC2 single-crystal thin films as a model system. The density of Ti 3d and C 2p states at the Fermi...... level in the basal ab plane is about 40% higher than along the c axis. The Seebeck coefficient is related to electron and hole-like bands close to the Fermi level, but in contrast to ground state density functional theory modeling, the electronic structure is also influenced by phonons that need...

  11. Effects of UV light intensity on electrochemical wet etching of SiC for the fabrication of suspended graphene

    Science.gov (United States)

    O, Ryong-Sok; Takamura, Makoto; Furukawa, Kazuaki; Nagase, Masao; Hibino, Hiroki

    2015-03-01

    We report on the effects of UV light intensity on the photo assisted electrochemical wet etching of SiC(0001) underneath an epitaxially grown graphene for the fabrication of suspended structures. The maximum etching rate of SiC(0001) was 2.5 µm/h under UV light irradiation in 1 wt % KOH at a constant current of 0.5 mA/cm2. The successful formation of suspended structures depended on the etching rate of SiC. In the Raman spectra of the suspended structures, we did not observe a significant increase in the intensity of the D peak, which originates from defects in graphene sheets. This is most likely explained by the high quality of the single-crystalline graphene epitaxially grown on SiC.

  12. Wear behavior of AA 5083/SiC nano-particle metal matrix composite: Statistical analysis

    Science.gov (United States)

    Hussain Idrisi, Amir; Ismail Mourad, Abdel-Hamid; Thekkuden, Dinu Thomas; Christy, John Victor

    2018-03-01

    This paper reports study on statistical analysis of the wear characteristics of AA5083/SiC nanocomposite. The aluminum matrix composites with different wt % (0%, 1% and 2%) of SiC nanoparticles were fabricated by using stir casting route. The developed composites were used in the manufacturing of spur gears on which the study was conducted. A specially designed test rig was used in testing the wear performance of the gears. The wear was investigated under different conditions of applied load (10N, 20N, and 30N) and operation time (30 mins, 60 mins, 90 mins, and 120mins). The analysis carried out at room temperature under constant speed of 1450 rpm. The wear parameters were optimized by using Taguchi’s method. During this statistical approach, L27 Orthogonal array was selected for the analysis of output. Furthermore, analysis of variance (ANOVA) was used to investigate the influence of applied load, operation time and SiC wt. % on wear behaviour. The wear resistance was analyzed by selecting “smaller is better” characteristics as the objective of the model. From this research, it is observed that experiment time and SiC wt % have the most significant effect on the wear performance followed by the applied load.

  13. Preparation of SiC thin films by ion beam technology and PECVD

    International Nuclear Information System (INIS)

    Chen Changqing; Ren Congxin; Yang Lixin; Yan Jinlong; Zheng Zhihong; Zhou Zuyao; Chen Ping; Liu Xianghuai; Chen Xueliang

    1998-01-01

    The formation of β-SiC buried layers in p-type Si by ion beam methods is reported and a comparison of the results obtained under different experimental conditions is made. The preparation of amorphous SiC thin films by IBED is presented and the enhanced deposition of Xe + is found superior to that of Ar + . The work of synthesizing hydrogenated amorphous SiC films by RIBS and RIBAD is described with a discussion on the dependence of some physical parameters on the partial pressure ratio pCH 4 /pAr. Finally given is a brief introduction to a high quality α-SiC:H film which is prepared by PECVD and can exhibit green luminescence at room temperature

  14. Effect Of SiC Particles On Sinterability Of Al-Zn-Mg-Cu P/M Alloy

    Directory of Open Access Journals (Sweden)

    Rudianto H.

    2015-06-01

    Full Text Available Premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder was analyzed as matrix in this research. Gas atomized powder Al-9Si with 20% volume fraction of SiC particles was used as reinforcement and added into the alloy with varied concentration. Mix powders were compacted by dual action press with compaction pressure of 700 MPa. High volume fraction of SiC particles gave lower green density due to resistance of SiC particles to plastic deformation during compaction process and resulted voids between particles and this might reduce sinterability of this mix powder. Sintering was carried out under ultra high purity nitrogen gas from 565°-580°C for 1 hour. High content of premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder gave better sintering density and reached up to 98% relative. Void between particles, oxide layer on aluminum powder and lower wettability between matrix and reinforcement particles lead to uncompleted liquid phase sintering, and resulted on lower sintering density and mechanical properties on powder with high content of SiC particles. Mix powder with wt90% of Alumix 431D and wt10% of Al-9Si-vf20SiC powder gave higher tensile strength compare to another mix powder for 270 MPa. From chemical compositions, sintering precipitates might form after sintering such as MgZn2, CuAl2 and Mg2Si. X-ray diffraction, DSC-TGA, and SEM were used to characterize these materials.

  15. Optimization of KOH etching parameters for quantitative defect recognition in n- and p-type doped SiC

    Science.gov (United States)

    Sakwe, S. A.; Müller, R.; Wellmann, P. J.

    2006-04-01

    We have developed a KOH-based defect etching procedure for silicon carbide (SiC), which comprises in situ temperature measurement and control of melt composition. As benefit for the first time reproducible etching conditions were established (calibration plot, etching rate versus temperature and time); the etching procedure is time independent, i.e. no altering in KOH melt composition takes place, and absolute melt temperature values can be set. The paper describes this advanced KOH etching furnace, including the development of a new temperature sensor resistant to molten KOH. We present updated, absolute KOH etching parameters of n-type SiC and new absolute KOH etching parameters for low and highly p-type doped SiC, which are used for quantitative defect analysis. As best defect etching recipes we found T=530 °C/5 min (activation energy: 16.4 kcal/mol) and T=500 °C/5 min (activation energy: 13.5 kcal/mol) for n-type and p-type SiC, respectively.

  16. 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 ...

  17. SIC Industriemonitor najaar 2003

    NARCIS (Netherlands)

    Brouwer, N.; de Nooij, M.; Pomp, M.

    2003-01-01

    In juni 2000 publiceerde de Stichting voor Economisch Onderzoek (SEO) van de Universiteit van Amsterdam in opdracht van Stichting voor Industriebeleid en Communicatie (SIC) een ontwerp voor een SIC industriemonitor met een voorstel voor de inhoud en de structuur van een dergelijke monitor. Op dat

  18. Mechanism of Si intercalation in defective graphene on SiC

    KAUST Repository

    Kaloni, Thaneshwor P.; Cheng, Yingchun; Schwingenschlö gl, Udo; Upadhyay Kahaly, M.

    2012-01-01

    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

  19. Rapid degradation of azo dye Direct Black BN by magnetic MgFe{sub 2}O{sub 4}-SiC under microwave radiation

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Jia; Yang, Shaogui, E-mail: yangsg@nju.edu.cn; Li, Na; Meng, Lingjun; Wang, Fei; He, Huan; Sun, Cheng

    2016-08-30

    Highlights: • MgFe{sub 2}O{sub 4}-SiC was first successfully synthesized. • MgFe{sub 2}O{sub 4}-SiC attained the maximum absorbing value of 13.32 dB at 2.57 GHz, which reached extremely high RL value at low frequency range. • Fast decolorization and high TOC removal of azo dye Direct Black BN with complicated structure could occur with MgFe{sub 2}O{sub 4}-SiC under MW radiation. • MgFe{sub 2}O{sub 4}-SiC had better MW absorbing property and higher MW catalytic activity than MnFe{sub 2}O{sub 4}-SiC under the same condition. • MgFe{sub 2}O{sub 4}-SiC was of practical use in the wastewater treatment. - Abstract: A novel microwave (MW) catalyst, MgFe{sub 2}O{sub 4} loaded on SiC (MgFe{sub 2}O{sub 4}-SiC), was successfully synthesized by sol-gel method, and pure MgFe{sub 2}O{sub 4} was used as reference. The MgFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4}-SiC catalysts were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), N{sub 2} adsorption analyzer (BET specific surface area), X-ray photoelectron spectroscopy (XPS). The electromagnetic parameters of the prepared catalysts were measured by vector network analyzer. The reflection loss (RL) based on the electromagnetic parameters calculated in Matlab showed MgFe{sub 2}O{sub 4}-SiC attained the maximum absorbing value of 13.32 dB at 2.57 GHz, which reached extremely high RL value at low frequency range, revealing the excellent MW absorption property of MgFe{sub 2}O{sub 4}-SiC. MW-induced degradation of Direct Black BN (DB BN) over as-synthesized MgFe{sub 2}O{sub 4}-SiC indicated that degradation efficiency of DB BN (20 mg L{sup −1}) in 5 min reached 96.5%, the corresponding TOC removal was 65%, and the toxicity of DB BN after degradation by MgFe{sub 2}O{sub 4}-SiC obviously decreased. The good stability and applicability of MgFe{sub 2}O{sub 4}-SiC on the degradation process were also discovered. Moreover, the ionic chromatogram during degradation

  20. 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.

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

    OpenAIRE

    Pinzón, Cristian; de Paz Santana, Yanira; Bajo Pérez, Javier; Abraham, Ajith P.; Corchado Rodríguez, Juan M.

    2009-01-01

    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 k...

  2. 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.

  3. Rare-earth element doped Si3N4/SiC micro/nano-composites-RT and HT mechanical properties

    Czech Academy of Sciences Publication Activity Database

    Lojanová, Š.; Tatarko, P.; Chlup, Zdeněk; Hnatko, M.; Dusza, J.; Lenčéš, Z.; Šajgalík, P.

    2010-01-01

    Roč. 30, č. 9 (2010), s. 1931-1944 ISSN 0955-2219 Institutional research plan: CEZ:AV0Z20410507 Keywords : Si3N4 * SiC * Nano-composites * Fracture toughness * Hardness * Strength * Creep Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.574, year: 2010

  4. 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

  5. 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.

  6. Microstructure and fracture in SiC whisker reinforced 2124 aluminum composite

    Science.gov (United States)

    Nieh, T. G.; Raninen, R. A.; Chellman, D. J.

    1985-01-01

    The microstructures of extruded and hot-rolled 2124 Al-15 percent (by weight) SiC whisker composites have been investigated, experimentally. Among the specific factors studied were: the strength of the whisker-matrix interfaces; (2) the presence of oxides; (3) the presence of defective whiskers; (4) and the presence of distribution of intermetallic compounds, impurities in the SiC(w) powder, and microstructural inhomogeneities. Modifications in the microstructure of the SiC/AL composites due to hot rolling and extrusion are illustrated in a series of microphotographs. It was found that hot rolling along the axis of extrusion was associated with some types of whisker damage, while the whiskers still retain their original orientation. Hot-rolling perpendicular to the axis of extrusion, however, tended to rotate the whiskers and produced a nearly isotropic material. Whisker free zones were virtually eliminated or reduced in size by hot rolling. In situ Auger fractography of the composite showed that the interfacial bonding between the SiC and the Al matrix was good and that Al2O2 had no significant influence on the fracture mechanics of the composite.

  7. 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...

  8. Microstructural evolution and mechanical properties of Ti3SiC2-TiC composites

    International Nuclear Information System (INIS)

    Tian, WuBian; Sun, ZhengMing; Hashimoto, Hitoshi; Du, YuLei

    2010-01-01

    Ti 3 SiC 2 -TiC composites were fabricated by pulse discharge sintering technique using three different sets of powder mixtures, i.e. Ti/Si/TiC (TC30), Ti/Si/C/TiC (SI30) and Ti/Si/C (TSC30). Based on X-ray diffraction (XRD) analysis and microstructural observations, starting powder reactants were found to have little effect on phase content but strong influence on the microstructure in terms of phase distribution. The phase distribution mainly relies on the heat released from reaction and the liquid phase content formed during sintering. The mechanical properties of the fabricated dense samples demonstrate that more homogeneous phase distribution, available by choosing the starting reactants of SI30, results in higher flexural strength, whereas the Vickers hardness is almost independent of the microstructure. The enhanced flexural strength in sample SI30 sintered at 1400 o C is mainly attributed to the homogeneous TiC distribution in the microstructure.

  9. Reflood Heat Transfer in SiC and Graphene Oxide Coated Tube

    International Nuclear Information System (INIS)

    Kim, Kyung Mo; Lee, Seung Won; Bang, In Cheol

    2013-01-01

    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

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

    Science.gov (United States)

    Rodolfo, Jacques

    2017-11-01

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

  11. Influence of surface oxidation on the radiative properties of ZrB{sub 2}-SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ning, E-mail: lncaep@163.com [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, 621900 (China); Xing, Pifeng; Li, Cui [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, 621900 (China); Wang, Peng [School of Material Science and Engineering, Shandong University of Technology, Zibo 255049 (China); Jin, Xinxin [College of Materials Science and Engineering, Harbin University of Science and Technology, Harbin 150040 (China); Zhang, Xinghong [Science and Technology on Advanced Composites in Special Environments Laboratory, Harbin Institute of Technology, Harbin 150001 (China)

    2017-07-01

    Highlights: • Surface component affected radiative properties of ZrB{sub 2}-SiC composites significantly. • Emissivity in long-wave range gradually increased with the thickness of oxide scale. • The surface temperature had a little effect on radiative properties of composites. • Influence of surface roughness on emissivity could be negligible. • Covering the surface with glass is a method for improving radiative properties. - Abstract: The spectral emissivities of ZrB{sub 2}-20 vol.% SiC composites with various surface components of ZrB{sub 2}/SiC (ZS1), silica-rich glass (ZS2) and porous zirconia (ZS3) were measured using infrared spectrometer in the wavelength range from 2.5 to 25.0 μm. The relationship between surface oxidation (associated with surface component, thickness of oxide scale, testing temperature as well as roughness) and the radiative properties of ZrB{sub 2}-SiC composites were investigated systematically. Surface component affected the radiative properties of composites significantly. The total emissivity of ZS1 varied from 0.22 to 0.81 accompanied with surface oxidation in the temperature range 300–900 °C. The emissivity of ZS2 was about 1.5 times as that of ZS3 under the same testing conditions. The oxide scale on specimen surface enhanced the radiative properties especially in terms of short-wave range, and the emissivity in the long-wave range gradually increased with the thickness of oxide scale within a certain range. The influence of testing temperature and surface roughness was also investigated. The testing temperature had a little effect on radiative properties, whereas effect of surface roughness could be negligible.

  12. Change of I-V characteristics of SiC diodes upon reactor irradiation; Modification des caracteristiques I-V de jonctions p-n au SiC du fait d'une irradiation dans un reacteur; Izmeneniya kharakteristik I-V vyrashchennogo v SiC perekhoda tipa p-n posle oblucheniya ego v reaktore; Modificaciones que sufren por irradiacion en un reactor las caracteristicas I-V de uniones p-n en SiC

    Energy Technology Data Exchange (ETDEWEB)

    Heerschap, M; De Coninck, R [Solid State Physics Dept., SCK-CEN, Mol (Belgium)

    1962-04-15

    In search for semiconductors, which can be used in high-flux reactors in order to measure flux distributions, we irradiated SiC p-n junctions in the Belgium BR-1 reactor. Two types of SiC-diodes of different origin have been irradiated. These junctions are grown in the Lely-furnace. The change in forward and reverse characteristics have been measured during and after irradiation up to temperatures of 150{sup o}C, while measurements up to a temperature of 500{sup o}C are in progress. It has been found that one type resists BR-1 neutrons up to an integrated flux of 10{sup 15} n/cm{sup 2}, while the other resists irradiation up to a flux of 10{sup 17} n/cm{sup 2}. The changes in characteristics are given as well as the result of some annealing experiments. (author) [French] En recherchant des semi-conducteurs pouvant servir a mesurer les distributions de flux dans les reacteurs a haut flux de neutrons, les auteurs ont irradie des jonctions p-n au SiC dans le reacteur belge BR-1. Deux types de diodes a SiC d'origines differentes ont ete ainsi irradies. Les jonctions en question sont preparees par etirage dans le four Lely. Les auteurs ont mesure les modifications subies par les caracteristiques I-V apres et pendant l'irradiation a des temperatures allant jusqu'a 150{sup o}C; ils poursuivent leurs mesures dans la gamme des temperatures allant de 150{sup o}C a 500{sup o}C. Us ont constate que l'un des types de diode a SiC resiste aux neutrons du reacteur BR-1 jusqu'a 10{sup 15} n/cm{sup 2}, tandis que l'autre type resiste a l'irradiation jusqu'a 10{sup 17} n/cm{sup 2}. Les auteurs indiquent les modifications subies par les caracteristiques, ainsi que le resultat de certaines experiences de recuit. (author) [Spanish] Los autores estan tratando de encontrar semiconductores con los que sea posible medir distribuciones de flujo en reactores de flujo elevado, y con este fin irradiaron uniones p-n del SiC en el reactor BR-1 de Belgica. Irradiaron dos tipos de diodos de SiC de

  13. 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

  14. 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.

  15. 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 within...... 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....

  16. 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...

  17. 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...

  18. 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

    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...... 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...... cyclic studies are here reported for the first time for SiC based catalysts. The reaction kinetics for the oxygen reduction and for methanol oxidation with Pt/SiC are observed to be similar to the carbon based catalysts. The SiC based catalyst shows a higher specific surface activity than BASF (Pt...

  19. Taking SiC Power Devices to the Final Frontier: Addressing Challenges of the Space Radiation Environment

    Science.gov (United States)

    Lauenstein, Jean-Marie; Casey, Megan

    2017-01-01

    Silicon carbide power device technology has the potential to enable a new generation of aerospace power systems that demand high efficiency, rapid switching, and reduced mass and volume in order to expand space-based capabilities. For this potential to be realized, SiC devices must be capable of withstanding the harsh space radiation environment. Commercial SiC components exhibit high tolerance to total ionizing dose but to date, have not performed well under exposure to heavy ion radiation representative of the on-orbit galactic cosmic rays. Insertion of SiC power device technology into space applications to achieve breakthrough performance gains will require intentional development of components hardened to the effects of these highly-energetic heavy ions. This work presents heavy-ion test data obtained by the authors over the past several years for discrete SiC power MOSFETs, JFETs, and diodes in order to increase the body of knowledge and understanding that will facilitate hardening of this technology to space radiation effects. Specifically, heavy-ion irradiation data taken under different bias, temperature, and ion beam conditions is presented for devices from different manufacturers, and the emerging patterns discussed.

  20. Early stages of sliding wear behaviour of Al2O3 and SiC reinforced aluminium

    International Nuclear Information System (INIS)

    Bonollo, F.; Ceschini, L.; Garagnani, G.L.; Palombarini, G.; Tangerini, I.; Zambon, A.

    1993-01-01

    Al matrix composites reinforced by 10 vol.% Al 2 O 3 and SiC particles were subjected to dry sliding tests against steel using a slider-on-cylinder tribometer. Damage mechanisms were 'micro-machining' of the steel carried out by ceramic particles, plastic deformation and oxidation of the metal matrix, as well as abrasion. The results were discussed on the basis of the third-body wear model. (orig.)

  1. Improving breakdown voltage and self-heating effect for SiC LDMOS with double L-shaped buried oxide layers

    Science.gov (United States)

    Bao, Meng-tian; Wang, Ying

    2017-02-01

    In this paper, a SiC LDMOS with double L-shaped buried oxide layers (DL-SiC LDMOS) is investigated and simulated. The DL-SiC LDMOS consists of two L-shaped buried oxide layers and two SiC windows. Using 2-D numerical simulation software, Atlas, Silvaco TCAD, the breakdown voltage, and the self-heating effect are discussed. The double-L shaped buried oxide layers and SiC windows in the active area can introduce an additional electric field peak and make the electric field distribution more uniform in the drift region. In addition, the SiC windows, which connect the active area to the substrate, can facilitate heat dissipation and reduce the maximum lattice temperature of the device. Compared with the BODS structure, the DL-SiC LDMOS and BODS structures have the same device parameters, except of the buried oxide layers. The simulation results of DL-SiC LDMOS exhibits outstanding characteristics including an increase of the breakdown voltage by 32.6% to 1220 V, and a low maximum lattice temperature (535 K) at room temperature.

  2. Development and Characterization of Carbon Nanotubes (CNTs) and Silicon Carbide (SiC) Reinforced Al-based Nanocomposites

    Science.gov (United States)

    Gujba, Kachalla Abdullahi

    increase in internal strains were observed as milling progressed with increase in wt.% reinforcement due to the severe plastic deformation. Al/SiC and Al/CNTs were successfully consolidated by the SPS at sintering temperatures of 400, 450 and 500°C with SiC at 5, 12 and 20wt% and 0.5wt%CNT milled for 20hrs and 3 hrs respectively. It was obtained that sintering temperature of 500°C was the most suitable as the densification achieved for SiC reinforced sample was above 98% and 100% for unreinforced sample. The hardness increased with increasing SiC content from 0, 5 to 12 wt% i.e 68, 82, 85 respectively. At 20%wt of SiC a slight decrease in the hardness was observed i.e. 70 which might be attributed to high wt.% SiC, a similar trend was observed for the other alloy studied. For CNT reinforced samples, the hardness and densification increased significantly and 100% densification was obtained at 500ºC, a hardness value from 68 to 82 was achieved from 0 to 0.5wt%CNT with a similar trend to the other alloy of interest. Conclusively, sintering of both alloys at 500ºC and above is the most suitable, the use of SiCp and CNTs as reinforcements improved the hardness, 12wt% SiC showed better hardness values than 20wt% SiC at all three temperatures and the Al alloy containing higher Si in its alloying elements showed better hardness values using the same reinforcement and sintering parameters.

  3. 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.

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

    International Nuclear Information System (INIS)

    Morse, M.; Wu, P.; Choi, S.; Kim, T.H.; Brown, A.S.; Losurdo, M.; Bruno, G.

    2006-01-01

    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

  5. 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.

  6. Effect of heat treatment on microstructure and interface of SiC particle reinforced 2124 Al matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Durbadal, E-mail: durbadal73@yahoo.co.in [MEF Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Viswanathan, Srinath [Dept of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL (United States)

    2013-11-15

    The microstructure and interface between metal matrix and ceramic reinforcement of a composite play an important role in improving its properties. In the present investigation, the interface and intermetallic compound present in the samples were characterized to understand structural stability at an elevated temperature. Aluminum based 2124 alloy with 10 wt.% silicon carbide (SiC) particle reinforced composite was prepared through vortex method and the solid ingot was deformed by hot rolling for better particle distribution. Heat treatment of the composite was carried out at 575 °C with varying holding time from 1 to 48 h followed by water quenching. In this study, the microstructure and interface of the SiC particle reinforced Al based composites have been studied using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), electron probe micro-analyzer (EPMA) associated with wavelength dispersive spectroscopy (WDS) and transmission electron microscopy (TEM) to identify the precipitate and intermetallic phases that are formed during heat treatment. The SiC particles are uniformly distributed in the aluminum matrix. The microstructure analyses of Al–SiC composite after heat treatment reveal that a wide range of dispersed phases are formed at grain boundary and surrounding the SiC particles. The energy dispersive X-ray spectroscopy and wavelength dispersive spectroscopy analyses confirm that finely dispersed phases are CuAl{sub 2} and CuMgAl{sub 2} intermetallic and large spherical phases are Fe{sub 2}SiAl{sub 8} or Al{sub 15}(Fe,Mn){sub 3}Si. It is also observed that a continuous layer enriched with Cu and Mg of thickness 50–80 nm is formed at the interface in between Al and SiC particles. EDS analysis also confirms that Cu and Mg are segregated at the interface of the composite while no carbide is identified at the interface. - Highlights: • The composite was successfully heat treated at 575°C for 1

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

    International Nuclear Information System (INIS)

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

    2008-01-01

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

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  9. Residual stress analysis in carbon fiber-reinforced SiC ceramics

    International Nuclear Information System (INIS)

    Broda, M.

    1998-01-01

    Systematic residual stress analyses are reported, carried out in long-fiber reinforced SiC ceramics. The laminated C fiber /SiC matrix specimens used were prepared by polymer pyrolysis, and the structural component specimens used are industrial products. Various diffraction methods have been applied for non-destructive evaluation of residual stress fields, so as to completely detect the residual stresses and their distribution in the specimens. The residual stress fields at the surface (μm) have been measured using characteristic X-radiation and applying the sin 2 ψ method as well as the scatter vector method. For residual stress field analysis in the mass volume (cm), neutron diffraction has been applied. The stress fields in the fiber layers (approx. 250μm) have been measured as a function of their location within the laminated composite by using an energy-dispersive method and synchrotron radiation. By means of the systematic, process-accompanying residual stress and phase analyses, conclusions can be drawn as to possible approaches for optimization of fabrication parameters. (orig./CB) [de

  10. Report on the Fracture Analysis of HfB(sub 2)-SiC and ZrB(sub 2)-SiC Composites; TOPICAL

    International Nuclear Information System (INIS)

    MECHOLSKY, JR. JOHN J.

    2001-01-01

    Hafnium diboride-silicon carbide (HS) and zirconium diboride-silicon carbide (ZS) composites are potential materials for high temperature, thermal shock applications such as for components on re-entry vehicles. In order to establish material constants necessary for evaluation of in situ fracture, bars fractured in four-point flexure were examined using fractographic principles. The fracture toughness was determined from measurements of the critical crack sizes and the strength values and the crack branching constants were established to use in forensic fractography for future in-flight tests. The fracture toughnesses range from about 13 MPam(sup 1/2) at room temperature to about 6 MPam(sup 1/2) at 1400 C for ZrB(sub 2)-Sic composites and from about 13 MPam(sup 1/2) at room temperature to about 4 MPam(sup 1/2) at 1400 C for HfB(sub 2)-SiC composites. Thus, the toughnesses of either the HS or ZS composites have the potential for use in thermal shock applications. Processing and manufacturing defects limited the strength of the test bars. However, examination of the microstructure on the fracture surfaces shows that the processing of these composites can be improved. There is potential for high toughness composites with high strength to be used in thermal shock conditions if the processing and handling are controlled

  11. Computer simulation of range and damage distributions of He ions in SiC

    International Nuclear Information System (INIS)

    Miyagawa, Yoshiko; Ato, Yasuro; Miyagawa, Soji

    1984-01-01

    The experimental projected ranges of various heavy ions in an amorphous Si target in the energy region where the nuclear stopping dominates are compared with calculations using the computer simulation program SASAMAL with the Lenz-Jensen, Moliere, Thomas-Fermi and Kalbitzer-Oetzmann (KO) screening parameters. In most cases. the best agreement was obtained with the KO screening parameters. The projected range distributions of He ions implanted in an SiC target were calculated using SASAMAL with KO screening parameters. The agreement between the SASAMAL(KO) results and our experimental data was satisfactory when the electronic stopping parameter k=1.3 k sub(NS) was used. The energy and the depth distributions of the primary knock-on atoms and the depth distributions of the recoil energy density with various values of the displacement energy Esub(d) were also calculated using SASAMAL(KO) for He ions in SiC. (author)

  12. Crystal growth and characterization of fluorescent SiC

    DEFF Research Database (Denmark)

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

    -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...

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

    Energy Technology Data Exchange (ETDEWEB)

    Savchenko, D., E-mail: dariyasavchenko@gmail.com [Institute of Physics of the Czech Academy of Sciences, Prague 182 21 (Czech Republic); National Technical University of Ukraine “Kyiv Polytechnic Institute,” Kyiv 03056 (Ukraine); Shanina, B.; Kalabukhova, E. [V.E. Lashkaryov Institute of Semiconductor Physics, NASU, Kyiv 03028 (Ukraine); Pöppl, A. [Institute of Experimental Physics II, Leipzig University, Leipzig D-04103 (Germany); Lančok, J. [Institute of Physics of the Czech Academy of Sciences, Prague 182 21 (Czech Republic); Mokhov, E. [A.F. Ioffe Physical Technical Institute, RAS, St. Petersburg 194021 (Russian Federation); Saint-Petersburg National Research University of Information Technologies, Mechanics and Optics, St. Petersburg 19710 (Russian Federation)

    2016-04-07

    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 10{sup 17 }cm{sup −3} at T = 10–40 K. The donor electrons of the N donors substituting quasi-cubic “k1” and “k2” sites (N{sub k1,k2}) in both types of the samples revealed the similar temperature dependence of the spin-lattice relaxation rate (T{sub 1}{sup −1}), which was described by the direct one-phonon and two-phonon processes induced by the acoustic phonons proportional to T and to T{sup 9}, respectively. The character of the temperature dependence of the T{sub 1}{sup −1} for the donor electrons of N substituting hexagonal (“h”) site (N{sub h}) 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 (T{sub m}{sup −1}) with the temperature increase for the N{sub h} donors in both types of the samples, as well as for the N{sub k1,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 T{sub m} for the N{sub k1,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 N{sub h} and N{sub k1,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.

  14. Recovery behavior of high purity cubic SiC polycrystals by post-irradiation annealing up to 1673 K after low temperature neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Idris, Mohd Idzat, E-mail: idzat.i.aa@m.titech.ac.jp [Department of Nuclear Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550 Japan (Japan); The National University of Malaysia, School of Applied Physics, Faculty of Science and Technology, 43600 Bangi Selangor (Malaysia); Yamazaki, Saishun; Yoshida, Katsumi; Yano, Toyohiko [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550 Japan (Japan)

    2015-10-15

    Two kinds of high purity cubic (β) SiC polycrystals, PureBeta-SiC and CVD-SiC, were irradiated in the BR2 reactor (Belgium) up to a fluence of 2.0–2.5 × 10{sup 24} (E > 0.1 MeV) at 333–363 K. Changes in macroscopic lengths were examined by post-irradiation thermal annealing using a precision dilatometer up to 1673 K with a step-heating method. The specimen was held at each temperature step for 6 h and the change in length of the specimen was recorded during each isothermal annealing step from 373 K to 1673 K with 50 K increments. The recovery curves were analyzed with the first order model, and rate constants at each annealing step were obtained. Recovery of defects, induced by neutron irradiation in high purity β-SiC, has four stages of different activation energies. At 373–573 K, the activation energy of PureBeta-SiC and CVD-SiC was in the range of 0.17–0.24 eV and 0.12–0.14 eV; 0.002–0.04 eV and 0.006–0.04 eV at 723–923 K; 0.20–0.27 eV and 0.26–0.31 eV at 923–1223 K; and 1.37–1.38 eV and 1.26–1.29 eV at 1323–1523 K, respectively. Below ∼1223 K the recombination occurred possibly for closely positioned C and Si Frenkel pairs, and no long range migration is deemed essential. Nearly three-fourths of recovery, induced by neutron irradiation, occur by this mechanism. In addition, at 1323–1523 K, recombination of slightly separated C Frenkel pairs and more long-range migration of Si interstitials may have occurred for PureBeta-SiC and CVD-SiC specimens. Migration of both vacancies may be restricted up to ∼1523 K. Comparing to hexagonal α-SiC, high purity β-SiC recovered more quickly in the lower annealing temperature range of less than 873 K, in particular less than 573 K. - Highlights: • Two kinds of high purity cubic (β) SiC polycrystals were irradiated. • Macroscopic lengths were examined by post-irradiation thermal annealing. • The recovery curves were analyzed with first order model.

  15. 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.

  16. Single-source-precursor Synthesis and High-temperature Behavior of SiC Ceramics Containing Boron

    Science.gov (United States)

    Gui, Miaomiao; Fang, Yunhui; Yu, Zhaoju

    2014-12-01

    In this paper, a hyperbranched polyborocarbosilane (HPBCS) was prepared by a one-pot synthesis with Cl2Si(CH3)CH2Cl, Cl3SiCH2Cl and BCl3 as the starting materials. The obtained HPBCS was characterized by GPC, FT-IR and NMR, and was confirmed to have hyperbranched structures. The thermal property of the resulting HPBCS was investigated by TGA. The ceramic yield of the HPBCS is about 84% and that of the counterpart hyperbranched hydridopolycarbosilane is only 45%, indicating that the introduction of boron into the preceramic polymer significantly improved the ceramic yield. With the polymer-derived ceramic route, the final ceramics were annealed at 1800 °C in argon atmosphere for 2 h in order to characterize the microstructure and to evaluate the high-temperature behavior. The final ceramic microstructure was studied by XRD and SEM, indicating that the introduction of boron dramatically inhibits SiC crystallization. The boron-containing SiC ceramic shows excellent high-temperature behavior against decomposition and crystallization at 1800 °C.

  17. Trace element determination in presolar SiC grains by synchrotron x-ray fluorescence: Commencement of a coordinated multimethod study

    International Nuclear Information System (INIS)

    Knight, K.B.; Sutton, S.R.; Newville, M.; Davis, A.M.; Dauphas, N.; Lewis, R.S.; Amari, S.; Steele, I.M.; Savina, M.R.; Pellin, M.J.

    2008-01-01

    We determined trace element compositions of individual ∼1-3 ?m presolar SiC grains from 6 KJG grains and 26 additionally cleaned KJG grains from the Murchison CM chondrite using nondestructive synchrotron X-ray fluorescence (SXRF). Presolar SiC grains are robust remnants of stellar matter ejected from stars. They survived processing in the early solar system and retain the nucleosynthetic fingerprints of their stellar progenitors. As such, they represent unique physical probes of the interiors of stars. Presolar SiC grains are commonly analyzed by mass spectrometric techniques that determine isotopic compositions and, to some degree, elemental concentrations. These techniques, however, are destructive, and can be subject to matrix effects. Elemental composition data on presolar grains remain scarce and affected by contamination and analytical artifacts. In addition, contamination has plagued isotopic characterization of some elements such as Mo and Ba. We determined trace element compositions of individual ∼1-3 (micro)m presolar SiC grains from the Murchison CM chondrite using nondestructive synchrotron X-ray fluorescence (SXRF). Samples included the KJG fraction, and a second KJG fraction that underwent additional cleaning. As every cleaning step results in some grain loss, one goal of this study was to justify additional cleaning of grains. Six KJG grains and 26 additionally cleaned KJG grains were analyzed, with location and identities of individual grains noted for future correlated isotopic study.

  18. 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.

  19. Enhanced cycle stability of micro-sized Si/C anode material with low carbon content fabricated via spray drying and in situ carbonization

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dingsheng; Gao, Mingxia, E-mail: gaomx@zju.edu.cn; Pan, Hongge; Liu, Yongfeng; Wang, Junhua; Li, Shouquan; Ge, Hongwei

    2014-08-01

    Highlights: • Micro-sized Si/C composites were fabricated via. spray drying and carbonization. • Multi-morphology carbon was formed in the Si/C composites. • Si/C composite with 5.6 wt.% C provides significant improved cycling stability. • Multi-morphology carbon plays effective role in improving the electrochemical property. • The method provides potential for mass production of superior Si-based anode materials. - Abstract: Micro-sized Si/C composites with in situ introduced carbon of multi-morphology were fabricated via spray drying a suspension of commercial micro-sized Si and citric acid followed by a carbonization. Different ratios of Si to citric acid were used to optimize the composition and structure of the composites and thus the electrochemical performance. Carbon flakes including crooked and flat ones were well dispersed in between the Si particles, forming Si/C composites. Floc-like carbon layers and carbon fragments were also found to cover partially the Si particles. The Si/C composite with a low carbon content of 5.6 wt.% provides an initial reversible capacity of 2700 mA h/g and a capacity of 1860 mA h/g after 60 cycles at a current density of 100 mA/g as anode material for lithium-ion batteries (LIBs), which are much higher than those of pristine Si and the Si/C composites with higher carbon content. The mechanism of the enhancement of electrochemical performance of the micro-sized Si/C composite is discussed. The fabrication method and the structure design of the composites offer valuable potential in developing adaptable Si-based anode materials for industrial applications.

  20. Ion-beam synthesis and photoluminescence of SiC nanocrystals assisted by MeV-heavy-ion-beam annealing

    International Nuclear Information System (INIS)

    Khamsuwan, J.; Intarasiri, S.; Kirkby, K.; Chu, P.K.; Singkarat, S.; Yu, L.D.

    2012-01-01

    This work explored a novel way to synthesize silicon carbide (SiC) nanocrystals for photoluminescence. Carbon ions at 90 keV were implanted in single crystalline silicon wafers at elevated temperature, followed by irradiation using xenon ion beams at an energy of 4 MeV with two low fluences of 5 × 10 13 and 1 × 10 14 ions/cm 2 at elevated temperatures for annealing. X-ray diffraction, Raman scattering, infrared spectroscopy and transmission electron microscopy were used to characterize the formation of nanocrystalline SiC. Photoluminescence was measured from the samples. The results demonstrated that MeV-heavy-ion-beam annealing could indeed induce crystallization of SiC nanocrystals and enhance emission of photoluminescence with violet bands dominance due to the quantum confinement effect.

  1. Synthesis and characterization of porous crystalline SiC thin films prepared by radio frequency reactive magnetron sputtering technique

    Energy Technology Data Exchange (ETDEWEB)

    Qamar, Afzaal, E-mail: afzaalqamar@gmail.com [Department of Physics and Applied Mathematics, PIEAS, Nilore, Islamabad, Punjab 42600 (Pakistan); Mahmood, Arshad [National Institute of Laser and Optronics, Nilore, Islamabad (Pakistan); Sarwar, Tuba; Ahmed, Nadeem [Department of Physics and Applied Mathematics, PIEAS, Nilore, Islamabad, Punjab 42600 (Pakistan)

    2011-05-15

    Hexagonal SiC thin films have been deposited using radio frequency reactive magnetron sputtering technique by varying the substrate temperature and other deposition conditions. Prior to deposition surface modification of the substrate Si(1 0 0) played an important role in deposition of the hexagonal SiC structure. The effect of substrate temperature during deposition on structure, composition and surface morphology of the SiC films has been analyzed using atomic force microscopy, Fourier transform infrared spectroscopy and spectroscopic ellipsometry. X-ray diffraction in conventional {theta}-2{theta} mode and omega scan mode revealed that the deposited films were crystalline having 8H-SiC structure and crystallinity improved with increase of deposition temperature. The bonding order and Si-C composition within the films showed improvement with the increase of deposition temperature. The surface of thin films grew in the shape of globes and columns depending upon deposition temperature. The optical properties also showed improvement with increase of deposition temperature and the results obtained by ellipsometry reinforced the results of other techniques.

  2. Bond formation in hafnium atom implantation into SiC induced by high-energy electron irradiation

    International Nuclear Information System (INIS)

    Yasuda, H.; Mori, H.; Sakata, T.; Naka, M.; Fujita, H.

    1992-01-01

    Bilayer films of Hf (target atoms)/α-SiC (substrate) were irradiated with 2 MeV electrons in an ultra-high voltage electron microscope (UHVEM), with the electron beam incident on the hafnium layer. As a result of the irradiation, hafnium atoms were implanted into the SiC substrate. Changes in the microstructure and valence electronic states associated with the implantation were studied by a combination of UHVEM and Auger valence electron spectroscopy. The implantation process is summarized as follows. (1) Irradiation with 2 MeV electrons first induces a crystalline-to-amorphous transition in α-SiC. (2) Hafnium atoms which have been knocked-off from the hafnium layer by collision with the 2 MeV electrons are implanted into the resultant amorphous SiC. (3) The implanted hafnium atoms make preferential bonding to carbon atoms. (4) With continued irradiation, the hafnium atoms repeat the displacement along the beam direction and the subsequent bonding with the dangling hybrids of carbon and silicon. The repetition of the displacement and subsequent bonding lead to the deep implantation of hafnium atoms into the SiC substrate. It is concluded that implantation successfully occurs when the bond strength between a constituent atom of a substrate and an injected atom is stronger than that between constituent atoms of a substrate. (Author)

  3. Fission products silver, palladium, and cadmium identification in neutron-irradiated SiC TRISO particles using a Cs-Corrected HRTEM

    Energy Technology Data Exchange (ETDEWEB)

    Rooyen, I.J. van, E-mail: isabella.vanrooyen@inl.gov [Fuel Design and Development Department, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID, 83415-6188 (United States); Olivier, E.J.; Neethling, J.H. [Centre for High Resolution Electron Microscopy, Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2016-08-01

    Electron microscopy investigations of selected coated particles from the first advanced gas reactor experiment at Idaho National Laboratory provided important information on fission product distribution and chemical composition in the silicon-carbide (SiC) layer. Silver precipitates were nano-sized, and therefore high-resolution transmission electron microscopy (HRTEM) was used to provide more information at the atomic level. Based on gamma-ray analysis, this particle which was irradiated to an average burnup of 19.38% fissions per initial metal atom, may have released as much as 10% of its available Ag-110 m inventory during irradiation. The HRTEM investigation focused on silver, palladium, and cadmium due to interest in silver transport mechanisms and possible correlation with palladium and silver previously found. Palladium, silver, and cadmium were found to co-exist in some of the SiC grain boundaries and triple junctions. This study confirmed palladium both at inter and intragranular sites. Phosphor was identified in SiC grain boundaries and triple points. - Highlights: • First high resolution electron microscopy fission product nano-structural locations of irradiated TRISO coated particles. • Pd observed inside SiC grains in proximity to planar defects e.g. stacking faults. • Ag co-exists with Pd and Cd only may suggest a Pd-assisted transport mechanism. • First finding of neutron transmutation product P, in SiC layer of TRISO coated particles. No direct link to Ag transport. • No significant Pd corrosion of SiC observed even at this high resolution images.

  4. First principles calculations of optical properties of the armchair SiC ...

    Indian Academy of Sciences (India)

    Dao-Bang Lu

    2018-02-13

    Feb 13, 2018 ... 1College of Mechanical and Electronic Engineering, Nanyang Normal University ... properties of the O-, F- and H-terminated SiC nanoribbons with armchair ..... 300. 600. 900. 1200. 1500. 0. 5. 10 15 20 25 30. 0. 300. 600. 900.

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

    DEFF Research Database (Denmark)

    Wei, Yi; Fadil, Ahmed; Ou, Haiyan

    2017-01-01

    ) of the emissions of the donor-acceptor pairs of the SiC substrate. Roomtemperature measurements of photoluminescence (PL), transmittance and time-resolved photoluminescence (TRPL) were applied to characterize the LSP resonances. Through the finitedifference time-domain (FDTD) simulation of the LSP resonance...

  6. 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.

  7. Si/C and H coadsorption at 4H-SiC{0001} surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wachowicz, E., E-mail: elwira@ifd.uni.wroc.pl [Institute of Experimental Physics, University of Wrocław, Plac M. Borna 9, PL-50-204 Wrocław (Poland); Interdisciplinary Centre for Mathematical and Computational Modelling, University of Warsaw, Pawińskiego 5a, PL-02-106 Warsaw (Poland)

    2016-06-15

    Highlights: • Si on C-terminated and C on Si-terminated surface adsorb in the H{sub 3} hollow site. • The preferred adsorption site is in contrary to the stacking order of bulk crystal. • The presence of hydrogen increases the adsorption energy of Si/C. • Hydrogen weakens the bonds between the adsorbed Si or C and the surface. • Carbon adsorbs on top of the surface carbon on the C-terminated surface. • With both C and H on Si-terminated surface the surface state vanishes. - Abstract: Density functional theory (DFT) study of adsorption of 0.25 monolayer of either Si or C on 4H-SiC{0001} surfaces is presented. The adsorption in high-symmetry sites on both Si- and C-terminated surfaces was examined and the influence of the preadsorbed 0.25 ML of hydrogen on the Si/C adsorption was considered. It was found out that for Si on C-terminated surface and C on Si-terminated the most favourable is threefolded adsorption site on both clean and H-precovered surface. This is contrary to the bulk crystal stacking order which would require adsorption on top of the topmost surface atom. In those cases, the presence of hydrogen weakens the bonding of the adsorbate. Carbon on the C-terminated surface, only binds on-top of the surface atom. The C−C bond-length is almost the same for the clean surface and for one with H and equals to ∼1.33 Å which is shorter by ∼0.2 than in diamond. The analysis of the electronic structure changes under adsorption is also presented.

  8. The Effect of SiC Polytypes on the Heat Distribution Efficiency of a Phase Change Memory.

    Science.gov (United States)

    Aziz, M. S.; Mohammed, Z.; Alip, R. I.

    2018-03-01

    The amorphous to crystalline transition of germanium-antimony-tellurium (GST) using three types of silicon carbide’s structure as a heating element was investigated. Simulation was done using COMSOL Multiphysic 5.0 software with separate heater structure. Silicon carbide (SiC) has three types of structure; 3C-SiC, 4H-SiC and 6H-SiC. These structures have a different thermal conductivity. The temperature of GST and phase transition of GST can be obtained from the simulation. The temperature of GST when using 3C-SiC, 4H-SiC and 6H-SiC are 467K, 466K and 460K, respectively. The phase transition of GST from amorphous to crystalline state for three type of SiC’s structure can be determined in this simulation. Based on the result, the thermal conductivity of SiC can affecting the temperature of GST and changed of phase change memory (PCM).

  9. Changes in work function due to NO2 adsorption on monolayer and bilayer epitaxial graphene on SiC(0001)

    Science.gov (United States)

    Caffrey, Nuala M.; Armiento, Rickard; Yakimova, Rositsa; Abrikosov, Igor A.

    2016-11-01

    The electronic properties of monolayer graphene grown epitaxially on SiC(0001) are known to be highly sensitive to the presence of NO2 molecules. The presence of small areas of bilayer graphene, on the other hand, considerably reduces the overall sensitivity of the surface. We investigate how NO2 molecules interact with monolayer and bilayer graphene, both free-standing and on a SiC(0001) substrate. We show that it is necessary to explicitly include the effect of the substrate in order to reproduce the experimental results. When monolayer graphene is present on SiC, there is a large charge transfer from the interface between the buffer layer and the SiC substrate to the molecule. As a result, the surface work function increases by 0.9 eV after molecular adsorption. A graphene bilayer is more effective at screening this interfacial charge, and so the charge transfer and change in work function after NO2 adsorption is much smaller.

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

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Gang [Institute for Advanced Materials, Devices and Nanotechnology, Rutgers University, Piscataway, New Jersey 08854 (United States); Xu, Can; Feldman, Leonard C. [Institute for Advanced Materials, Devices and Nanotechnology, Rutgers University, Piscataway, New Jersey 08854 (United States); Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Yakshinskiy, Boris; Wielunski, Leszek; Gustafsson, Torgny [Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Bloch, Joseph [Institute for Advanced Materials, Devices and Nanotechnology, Rutgers University, Piscataway, New Jersey 08854 (United States); NRCN, Beer-Sheva 84190 (Israel); Dhar, Sarit [Department of Physics, Auburn University, Auburn, Alabama 36849 (United States)

    2014-11-10

    We combine nuclear reaction analysis and electrical measurements to study the effect of water exposure (D{sub 2}O) on the n-type 4H-SiC carbon face (0001{sup ¯}) 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 D{sub 2}O exposure is proportional to the total D amount at the interface.

  11. Residual stress in thick low-pressure chemical-vapor deposited polycrystalline SiC coatings on Si substrates

    Science.gov (United States)

    Choi, D.; Shinavski, R. J.; Steffier, W. S.; Spearing, S. M.

    2005-04-01

    Residual stress in thick coatings of polycrystalline chemical-vapor deposited SiC on Si substrates is a key variable that must be controlled if SiC is to be used in microelectromechanical systems. Studies have been conducted to characterize the residual stress level as a function of deposition temperature, Si wafer and SiC coating thickness, and the ratios of methyltrichlorosilane to hydrogen and hydrogen chloride. Wafer curvature was used to monitor residual stress in combination with a laminated plate analysis. Compressive intrinsic (growth) stresses were measured with magnitudes in the range of 200-300MPa; however, these can be balanced with the tensile stress due to the thermal-expansion mismatch to leave near-zero stress at room temperature. The magnitude of the compressive intrinsic stress is consistent with previously reported values of surface stress in combination with the competition between grain-boundary energy and elastic strain energy.

  12. Hydrogen intercalation of single and multiple layer graphene synthesized on Si-terminated SiC(0001) surface

    International Nuclear Information System (INIS)

    Sołtys, Jakub; Piechota, Jacek; Ptasinska, Maria; Krukowski, Stanisław

    2014-01-01

    Ab initio density functional theory simulations were used to investigate the influence of hydrogen intercalation on the electronic properties of single and multiple graphene layers deposited on the SiC(0001) surface (Si-face). It is shown that single carbon layer, known as a buffer layer, covalently bound to the SiC substrate, is liberated after hydrogen intercalation, showing characteristic Dirac cones in the band structure. This is in agreement with the results of angle resolved photoelectron spectroscopy measurements of hydrogen intercalation of SiC-graphene samples. In contrast to that hydrogen intercalation has limited impact on the multiple sheet graphene, deposited on Si-terminated SiC surface. The covalently bound buffer layer is liberated attaining its graphene like structure and dispersion relation typical for multilayer graphene. Nevertheless, before and after intercalation, the four layer graphene preserved the following dispersion relations in the vicinity of K point: linear for (AAAA) stacking, direct parabolic for Bernal (ABAB) stacking and “wizard hat” parabolic for rhombohedral (ABCA) stacking

  13. 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...

  14. A critical review of growth of low-dimensional carbon nanostructures on SiC (0 0 0 1): impact of growth environment

    International Nuclear Information System (INIS)

    Lu Weijie; Boeckl, John J; Mitchel, William C

    2010-01-01

    Graphene and carbon nanotube (CNT) structures have promise for many electronic device applications and both have been grown on SiC through the decomposition of the substrate. It is well known that both graphene and aligned CNTs are grown under similar conditions with overlapping temperature and pressure ranges, but a fundamental understanding of the two types of growths is actively being researched. Moreover, various technical challenges need to be overcome to achieve improvement in the electronic and structural quality of these carbon-based nanostructures on SiC. Specifically, an understanding and control of the SiC surface graphitization process and interface structure needs to be established. In this review, we focus on graphene growth on SiC (0 0 0 1) (Si-face) as a model system in comparison with aligned CNT growth on SiC. The experimental growth aspects for graphene growth, including vacuum and ambient growth environments, and growth temperature are summarized, then proposed decomposition and growth mechanisms are discussed. Both thermal and chemical decomposition processes are presented and special emphasis is given to the role of growth process variations between laboratories. The chemical reactions driving the graphitization process and ultimately the carbon nanostructure growth on SiC are discussed. It is suggested that the composition of the residual gases in the growth environment is a critical parameter and that gas composition at the growth temperature should be monitored.

  15. 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

  16. 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...

  17. 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.

  18. Multilayer oxidation resistant coating for SiC coated carbon/carbon composites at high temperature

    International Nuclear Information System (INIS)

    Li Hejun; Jiao Gengsheng; Li Kezhi; Wang Chuang

    2008-01-01

    To prevent carbon/carbon (C/C) composites from oxidation, a multilayer coating based on molybdenum disilicide and titanium disilicide was formed using a two-step pack cementation technique in argon atmosphere. XRD and SEM analysis showed that the internal coating was a bond SiC layer that acts as a buffer layer, and that the external multilayer coating formed in the two-step pack cementation was composed of two MoSi 2 -TiSi 2 -SiC layers. This coating, which is characterized by excellent thermal shock resistance, could effectively protect the composites from exposure to an oxidizing atmosphere at 1773 K for 79 h. The oxidation of the coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating

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

    Science.gov (United States)

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

    2000-01-01

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

  20. 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)

  1. 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.

  2. 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.

  3. The 13C-pocket structure in AGB models: constraints from zirconium isotope abundances in single mainstream SiC grains

    International Nuclear Information System (INIS)

    Liu, Nan; Davis, Andrew M.; Pellin, Michael J.; Gallino, Roberto; Bisterzo, Sara; Savina, Michael R.

    2014-01-01

    We present postprocess asymptotic giant branch (AGB) nucleosynthesis models with different 13 C-pocket internal structures to better explain zirconium isotope measurements in mainstream presolar SiC grains by Nicolussi et al. and Barzyk et al. We show that higher-than-solar 92 Zr/ 94 Zr ratios can be predicted by adopting a 13 C-pocket with a flat 13 C profile, instead of the previous decreasing-with-depth 13 C profile. The improved agreement between grain data for zirconium isotopes and AGB models provides additional support for a recent proposal of a flat 13 C profile based on barium isotopes in mainstream SiC grains by Liu et al.

  4. Effects of ultrasonic vibration on microstructure and mechanical properties of nano-sized SiC particles reinforced Al-5Cu composites.

    Science.gov (United States)

    Li, Jianyu; Lü, Shulin; Wu, Shusen; Gao, Qi

    2018-04-01

    Ultrasonic vibration (UV) treatment has been successfully applied to improve the particles distribution of nano-sized SiC particles (SiC p ) reinforced Al-5Cu alloy matrix composites which were prepared by combined processes of dry high energy ball milling and squeeze casting. When UV treatment is applied, the distribution of nano-sized SiC p has been greatly improved. After UV for 1 min, large particles aggregates are broken up into small aggregates due to effects of cavitation and the acoustic streaming. After UV for 5 min, all the particles aggregates are dispersed and the particles are uniformly distributed in the composites. Compared with the Al-5Cu matrix alloy, the ultimate tensile strength, yield strength and elongation of the 1 wt% nano-sized SiC p /Al-5Cu composites treated by UV for 5 min are 270 MPa, 173 MPa and 13.3%, which are increased by 7.6%, 6.8% and 29%, respectively. The improvements of mechanical properties after UV are attributed to the uniform distribution of nano particles, grain refinement of aluminum matrix alloy and reduction of porosity in the composites. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Exploring the effects of SiC reinforcement incorporation on mechanical properties of friction stir welded 7075 aluminum alloy: Fatigue life, impact energy, tensile strength

    International Nuclear Information System (INIS)

    Bahrami, Mohsen; Helmi, Nader; Dehghani, Kamran; Givi, Mohammad Kazem Besharati

    2014-01-01

    In the current research, the role of SiC nano-particles in improving the mechanical properties of friction stir welded (FSWed) 7075 aluminum alloy is investigated. To this end, friction stir welding (FSW) was conducted at 1250 rpm and 40 mm/min. The experiment carried out with and without incorporating SiC nano-particles along the joint line. Cross-sectional microstructures of the joints were characterized employing optical and scanning electron microscopy (SEM). Results achieved through X-ray diffraction (XRD) confirmed the presence of SiC powders. Moreover, it was discovered that the volume fraction of the reinforcement particles was 20%. Along with an excellent bonding between SiC nano-particles and aluminum matrix, SEM photograph demonstrated a good dispersion of SiC reinforcements. Atomic force microscopy (AFM) results were also in tight agreement with the recent SEM microstructure. Thanks to the presence of SiC nano-particles, tensile strength, percent elongation, fatigue life, and toughness of the joint improved tremendously. The fracture morphologies were in good agreement with corresponding ductility results

  6. Exploring the effects of SiC reinforcement incorporation on mechanical properties of friction stir welded 7075 aluminum alloy: Fatigue life, impact energy, tensile strength

    Energy Technology Data Exchange (ETDEWEB)

    Bahrami, Mohsen, E-mail: Mohsen.bahrami@aut.ac.ir [Faculty of Mining and Metallurgical Engineering, Amirkabir University of Technology (AUT), Hafez Avenue, Tehran (Iran, Islamic Republic of); Helmi, Nader [Faculty of Mining and Metallurgical Engineering, Amirkabir University of Technology (AUT), Hafez Avenue, Tehran (Iran, Islamic Republic of); Dehghani, Kamran [Faculty of Mining and Metallurgical Engineering, Amirkabir University of Technology (AUT), Hafez Avenue, Tehran (Iran, Islamic Republic of); Centre of Excellence in Smart Structures and Dynamical Systems (Iran, Islamic Republic of); Givi, Mohammad Kazem Besharati [Department of Mechanical Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2014-02-10

    In the current research, the role of SiC nano-particles in improving the mechanical properties of friction stir welded (FSWed) 7075 aluminum alloy is investigated. To this end, friction stir welding (FSW) was conducted at 1250 rpm and 40 mm/min. The experiment carried out with and without incorporating SiC nano-particles along the joint line. Cross-sectional microstructures of the joints were characterized employing optical and scanning electron microscopy (SEM). Results achieved through X-ray diffraction (XRD) confirmed the presence of SiC powders. Moreover, it was discovered that the volume fraction of the reinforcement particles was 20%. Along with an excellent bonding between SiC nano-particles and aluminum matrix, SEM photograph demonstrated a good dispersion of SiC reinforcements. Atomic force microscopy (AFM) results were also in tight agreement with the recent SEM microstructure. Thanks to the presence of SiC nano-particles, tensile strength, percent elongation, fatigue life, and toughness of the joint improved tremendously. The fracture morphologies were in good agreement with corresponding ductility results.

  7. Process-property relationships of SiC chemical vapor deposition in the Si/H/C/O system

    International Nuclear Information System (INIS)

    Richardson, C.; Takoudis, C.G.

    1999-01-01

    The thermal, chemical, and physical properties of SiC make it an attractive material for a wide range of applications from wear resistant coatings on tools to high temperature microelectronics operations. A comprehensive thermodynamic analysis has been performed for the Si/H/C/O system from which a priori process-property relationships of the chemical vapor deposition (CVD) of silicon carbide (SiC) are obtained. The parameter space for pure silicon carbide growth is reported for five orders of magnitude of the system water vapor level (1 ppb--100 ppm), four orders of magnitude of system pressure (0.1--760 Torr), and two orders of magnitude of C/Si feed ratio (0.25--20) and H 2 /Si feed ratio (50--10,000). Lower growth temperatures for pure SiC are predicted in clean systems with low system water vapor levels, at stoichiometric to near carbon excess conditions (C/Si ≅ 1 to C/Si > 1), at high carrier gas flow rates (large H 2 /Si feed ratios), and at low operating pressures. Because relative C/Si and H 2 /Si feed ratios have been considered, the predictions in this study are applicable to both multiple and single precursor systems. Further, these results are valid for the CVD of α-SiC as well as β-SiC. Experimental data reported on the growth of α-SiC and β-SiC are found to be in satisfactory agreement with the theoretical predictions, for numerous systems that include multiple and single source, silicon and carbon, species

  8. 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.

  9. Promising SiC support for Pd catalyst in selective hydrogenation of acetylene to ethylene

    Science.gov (United States)

    Guo, Zhanglong; Liu, Yuefeng; Liu, Yan; Chu, Wei

    2018-06-01

    In this study, SiC supported Pd nanoparticles were found to be an efficient catalyst in acetylene selective hydrogenation reaction. The ethylene selectivity can be about 20% higher than that on Pd/TiO2 catalyst at the same acetylene conversion at 90%. Moreover, Pd/SiC catalyst showed a stable catalytic life at 65 °C with 80% ethylene selectivity. With the detailed characterization using temperature-programmed reduction (H2-TPR), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption analysis, CO-chemisorption and thermo-gravimetric analysis (TGA), it was found that SiC owns a lower surface area (22.9 m2/g) and a broad distribution of meso-/macro-porosity (from 5 to 65 nm), which enhanced the mass transfer during the chemical process at high reaction rate and decreased the residence time of ethylene on catalyst surface. Importantly, SiC support has the high thermal conductivity, which favored the rapid temperature homogenization through the catalyst bed and inhabited the over-hydrogenation of acetylene. The surface electronic density of Pd on Pd/SiC catalyst was higher than that on Pd/TiO2, which could promote desorption of ethylene from surface of the catalyst. TGA results confirmed a much less coke deposition on Pd/SiC catalyst.

  10. The measurement of Ksub(IC) in single crystal SiC using the indentation method

    International Nuclear Information System (INIS)

    Henshall, J.L.; Brookes, C.A.

    1985-01-01

    The present work has concentrated on investigating the underlying fracture toughness behaviour of SiC single crystals. This material was chosen because of the commercial importance of the various polycrystalline forms of SiC and the relative ready availability of reasonably sized single crystals. This study has examined the feasibility of using the indentation technique to determine Ksub(IC) in SiC single crystals. This requires much more less complex experimentation and also affords the possibility of being able to use this method to study the orientation dependence of Ksub(IC) in a similar manner to that used to investigate anisotropy in indentation hardness behaviour. A single crystal of 6H-SiC was used for all the hardness and conventional Ksub(IC) results reported here. The particular polytype and orientation were determined using the Laue X-ray method. All the measurements were made under ambient conditions. Three-point bend tests, with a 6 mm span on single edge notched beams, SENB, orientated such that the plane of the notch was brace 112-bar0 brace and the crack propagation direction were used for the conventional Ksub(IC) tests. The hardness indentations were all made on one particular SENB test piece after it had been fractured. The results are discussed. (author)

  11. Estudio de la Citotoxicidad de Cerámicas Biomórficas de SiC Recubiertas con Vidrio Bioactivo

    Directory of Open Access Journals (Sweden)

    Borrajo, J. P.

    2006-04-01

    Full Text Available In the past years there was a need to develop new tough bioactive materials capable to resist high loads when implanted in the body, that led to the production of bioactive coatings on metallic substrates. A new approach, which consists of biomorphic silicon carbide (SiC coated with bioactive glass by Pulsed Laser Deposition (PLD, was recently presented. This new material joins the high mechanical strength, lightness and porosity of biomorphic SiC and the bioactive properties of PLD glass films. In this work, a multiple evaluation of this new material is presented starting from the biomorphic SiC morphology and porosity, following with the bioactivity in simulated body fluid of the coatings, and ending with a deep in vitro study with MG-63 cells. The citotoxicity of the SiC coated and uncoated and the cell proliferation and attachment were studied.

    La necesidad de desarrollar nuevos implantes basados en materiales bioactivos que sean capaces de soportar grandes cargas mecánicas ha llevado a la producción de sustratos metálicos recubiertos con cerámicas bioactivas. Recientemente se ha propuesto un dispositivo alternativo que consiste en un sustrato de carburo de silicio (SiC biomórfico recubierto con vidrio bioactivo, mediante la técnica de Depósito por Láser Pulsado (PLD, y que dispone de la resistencia mecánica adecuada, además de gran ligereza y una porosidad intrínseca muy favorable de cara a la implantación. En este trabajo se presenta un estudio interdisciplinar de este nuevo material centrado en la morfología y porosidad de sustratos de SiC provenientes de diferentes maderas, la bioactividad de los recubrimientos producidos por PLD y en la evaluación in vitro con células de osteosarcoma MG-63 con la que se ha determinado la citotoxicidad de estos materiales y se ha estudiado la influencia de los mismos en la adhesión y la proliferación celular.

  12. 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.

  13. Pós de Al2O3/SiC obtidos a partir de reação de redução carbotérmica Al2O3/SiC powders from carbothermal reduction reaction

    Directory of Open Access Journals (Sweden)

    F. M. Spiandorello

    1999-12-01

    Full Text Available Neste trabalho foram utilizadas matérias-primas naturais para a obtenção de pós Al2O3/SiC através da redução carbotérmica das mesmas por um agente rico em carbono. Os aluminossilicatos estudados foram caulim, cianita e ilita-moscovita, sendo que os mesmos foram reduzidos ou por negro de fumo ou por grafite. Os pós resultantes da reação foram caracterizados por microscopia eletrônica de varredura e transmissão, difração de raios X e picnometria de hélio. Durante a reação, as diferenças existentes tanto na estrutura das matérias-primas quanto na composição química produziram pós com morfologia diversa. Foram encontradas estruturas como grandes aglomerados esféricos, whiskers, partículas e aglomerados fibrosos.In this work natural raw materials were used to obtain Al2O3/SiC powders by carbothermal reduction. The aluminosilicates studied were kaolin, kyanite and illite-muscovite and the reductor agents were carbon black or graphite. The reaction powders were characterized by transmission and scanning electron microscopy, X-ray diffraction and helium picnometry. During the reaction, the differences among the raw materials structures as well as into the chemical composition produced powders with several morphologies. Big spherical agglomerates, whiskers, particles and fibrous clusters were found.

  14. Reliability Assessment of SiC Power MOSFETs From The End User's Perspective

    DEFF Research Database (Denmark)

    Karaventzas, Vasilios Dimitris; Nawaz, Muhammad; Iannuzzo, Francesco

    2016-01-01

    The reliability of commercial Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) is investigated, and comparative assessment is performed under various test environments. The MOSFETs are tested both regarding the electrical properties of the dies and the packaging...

  15. 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.

  16. Interracial Structure and Formation Mechanism of Ultrasonic-assisted Brazed Joint of SiC Ceramics with Al-12Si Filler Metals in Air

    Institute of Scientific and Technical Information of China (English)

    Xiaoguang Chen; Ruishan Xie; Zhiwei Lai; Lei Liu; Jiuchun Yan; Guisheng Zou

    2017-01-01

    Ultrasonic-assisted brazing of SiC ceramics was performed by filling with an Al--12Si alloy at a low temperature of 620 ℃ in air.The interfacial characteristics and formation mechanism were investigated.The joint shear strength reached 84-94 MPa using the ultrasonic time of 2-16 s.The fracture morphology showed that the fracture path initiated and propagated in the joint alloy.The thin film of amorphous SiO2 that formed on the SiC surface was non-uniformly decomposed and diffused into the liquid Al-12Si alloy under the cavitation erosion effect of ultrasound.Abnormal isolated blocks of Al2SiO5 compounds formed at the interface between Al--12Si and a thicker SiO2 layer formed during the thermal oxidation treatment of the SiC ceramic.The SiO2 layer on the SiC ceramic did not hinder or impair the wetting and bonding process,and a stronger bond could form between Al-12Si and SiO2 or SiC in ultrasonicassisted brazing.

  17. Reinforcement of 2124 Al alloy with low micron SiC and nano Al2O3 via solid-state forming

    CSIR Research Space (South Africa)

    Gxowa, Z

    2015-07-01

    Full Text Available A powder metallurgical process was used to fabricate Metal Matrix Composites (MMCs). A 2124 aluminium alloy was reinforced with 5 and 10 vol. % of Al2O3 (40-70nm) to form Metal Matrix Nano Composites (MMNCs) as well as 10 and 15 vol. % of SiC (1...

  18. 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

  19. 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.

  20. 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

  1. Effect of cutting temperature on hardness of SiC and diamond in the nano-cutting process of monocrystalline silicon

    Science.gov (United States)

    Wang, Jiachun; Li, Yuntao; Liu, Xiaoxuan; Lv, Maoqiang

    2016-10-01

    In the process of cutting silicon by natural diamond tools, groove wear happens on the flank face of cutting tool frequently.Scholars believe that one of the wear reasons is mechanical scratching effect by hard particles like SiC. To reveal the mechanical scratching mechanism, it is essential to study changes in the mechanical properties of hard particles and diamond, especially the effect of cutting temperature on hardness of diamond and hard particles. Molecular dynamics (MD) model that contact-zone temperature between tool and workpiece was calculated by dividing zone while nano-cutting monocrystalline silicon was established, cutting temperature values in different regions were computed as the simulation was carried out.On this basis, the models of molecular dynamics simulation of SiC and diamond were established separately with setting the initial temperature to room temperature. The laws of length change of C-C bond and Si-C bond varing with increase of simulation temperature were studied. And drawing on predecessors' research on theoretical calculation of hardness of covalent crystals and the relationship between crystal valence electron density and bond length, the curves that the hardness of diamond and SiC varing with bond length were obtained. The effect of temperature on the hardness was calculated. Results show that, local cutting temperature can reach 1300K.The rise in cutting temperature leaded to a decrease in the diamond local atomic clusters hardness,SiC local atomic clusters hardness increased. As the cutting temperature was more than 1100K,diamond began to soften, the local clusters hardness was less than that of SiC.

  2. The characteristics of photo-CVD SiO{sub 2} and its application on SiC MIS UV photodetectors

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.H.; Chang, C.S.; Chang, S.J.; Su, Y.K.; Chiou, Y.Z.; Liu, S.H.; Huang, B.R

    2003-07-15

    SiO{sub 2} layers were deposited onto SiC by photo-chemical vapor deposition (photo-CVD) using deuterium (D{sub 2}) lamp as the excitation source. For the photo-SiO{sub 2} deposited 500 deg. C, interface state density (D{sub it}) was estimated to be 5.66x10{sup 11} cm{sup -2} eV{sup -1}. With an applied electric field of 4 MV cm{sup -1}, it was found that the leakage current was only 3.15x10{sup -8} A cm{sup -2} for the photo-CVD SiO{sub 2} layer prepared at 500 deg. C. It was also found that photo-SiO{sub 2} could effectively suppress dark current of SiC-based photodetectors (PDs). It was found that we could reduce dark current of SiC-based PDs by about three orders of magnitude by the insertion of a 5 nm-thick photo-CVD SiO{sub 2} film in between Indium-tin-oxide (ITO) contact and the underneath SiC. Photocurrent to dark current ratio of ITO/SiO{sub 2}/SiC MIS PDs was also found to be much larger than that of conventional ITO/SiC Schottky barrier PDs.

  3. 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.

  4. 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

  5. Si/C composite lithium-ion battery anodes synthesized using silicon nanoparticles from porous silicon

    International Nuclear Information System (INIS)

    Park, Jung-Bae; Lee, Kwan-Hee; Jeon, Young-Jun; Lim, Sung-Hwan; Lee, Sung-Man

    2014-01-01

    The synthesis of Si nanoparticles by ultrasonication processing of porous Si powder and a novel method for preparing a high-capacity Si/C composite using this technique is reported. The porous Si powder is prepared by selectively etching the silicide phase of a Ti 24 Si 76 alloy consisting of Si and silicide phases. The particle size of the nanocrystalline Si is determined by the crystallite size of the Si and silicide phases in the alloy powder. Ultrasonication of the porous Si obtained from the mechanically alloyed Ti 24 Si 76 alloy generates nanocrystalline Si particles of size about 5 nm. Growth of the Si and silicide phases in the alloy is induced by annealing of the mechanically alloyed sample, with a consequent increase in the size of the Si particles obtained after ultrasonication. Application of the ultrasonication process to the fabrication of Si/C composite anode materials generates nanometer-scale Si particles in situ that are distributed in the matrix. Analysis of the phases obtained and evaluation of the distribution of the nanometer-scale Si particles in the composites via XRD/TEM measurements show that the nanometer-scale Si particles are effectively synthesized and uniformly distributed in the carbon matrix, leading to enhanced electrochemical performance of the Si/C composites

  6. Scanning and transmission electron microscopy study of the microstructural changes occurring in aluminium matrix composites reinforced with SiC particles during casting and welding: interface reactions

    Science.gov (United States)

    Urena; Gomez De Salazar JM; Gil; Escalera; Baldonedo

    1999-11-01

    Processing of aluminium matrix composites (AMCs), especially those constituted by a reactive system such as Al-SiC, presents great difficulties which limit their potential applications. The interface reactivity between SiC and molten Al generates an aluminium carbide which degrades the composite properties. Scanning and transmission electron microscopes equipped with energy-dispersive X-ray spectroscopes are essential tools for determining the structure and chemistry of the Al-SiC interfaces in AMCs and changes occurring during casting and arc welding. In the present work, an aluminium-copper alloy (AA2014) reinforced with three different percentages of SiC particles was subjected to controlled remelting tests, at temperatures in the range 750-900 degrees C for 10 and 30 min. Arc welding tests using a tungsten intert gas with power inputs in the range 850-2000 W were also carried out. The results of these studies showed that during remelting there is preferential SiC particle consumption with formation of Al4C3 by interface reaction between the solid SiC particle and the molten aluminium matrix. The formation of Al4C3 by the same mechanism has also been detected in molten pools of arc welded composites. However, in this case there was formation of an almost continuous layer of Al4C3, which protects the particle against further consumption, and formation of aciculate aluminium carbide on the top weld. Both are formed by fusion and dissolution of the SiC in molten aluminium followed by reaction and precipitation of the Al4C3 during cooling.

  7. Distribution of the grain limit character in SiC and its effect on the diffusion of fission products in the TRISO fuel particles; Distribucion del caracter de limite de grano en SiC y su efecto sobre la difusion de los productos de fision en las particulas de combustible TRISO

    Energy Technology Data Exchange (ETDEWEB)

    Cancino T, F.; Lopez H, E., E-mail: Eddie.lopez@cinvestav.edu.mx [IPN, Centro de Investigacion y de Estudios Avanzados, Unidad Saltillo, Av. Industria Metalurgica 1062, Zona Industrial, 25900 Ramos Arizpe, Coahuila (Mexico)

    2017-09-15

    At present is accepted that silver diffuses through silicium carbide (SiC) by diffusion in grain boundaries, although little is known about the characteristics of grain boundaries in SiC, and how these change depending on the type of sample. In this work, was observed that there are small but important differences between the SiC in the tri-structural isotropic (TRISO) particles and that of the monoliths, which could explain some of the differences observed in experiments on diffusion in the literature. Five different types (coatings and monoliths) of SiC produced by chemical vapor deposition (CVD) were characterized by electron backscatter diffraction (EBSD). In all the samples the SiC was mainly composed of high-angle grain boundaries (∼ 65%), with a small fraction of grain boundaries of low-angle (about 15%) and 20% of the coincidence site lattice (CSL). The morphology of the monoliths is constituted by large grains, surrounded by smaller grains; in the particles of the TRISO fuel, both columnar and equi axial grains were observed, with a more uniform distribution over the surface of the coating. (Author)

  8. Demonstration of SiC Pressure Sensors at 750 C

    Science.gov (United States)

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

    2014-01-01

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

  9. 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...

  10. Influence wt.% of SiC and borax on the mechanical properties of AlSi-Mg-TiB-SiC composite by the method of semi solid stir casting

    Science.gov (United States)

    Bhiftime, E. I.; Guterres, Natalino F. D. S.; Haryono, M. B.; Sulardjaka, Nugroho, Sri

    2017-04-01

    SiC particle reinforced metal matrix composites (MMCs) with solid semi stir casting method is becoming popular in recent application (automotive, aerospace). Stirring the semi solid condition is proven to enhance the bond between matrix and reinforcement. The purpose of this study is to investigate the effect of the SiC wt.% and the addition of borax on mechanical properties of composite AlSi-Mg-TiB-SiC and AlSi-Mg-TiB-SiC/Borax. Specimens was tested focusing on the density, porosity, tensile test, impact test microstructure and SEM. AlSi is used as a matrix reinforced by SiC with percentage variations (10, 15, 20 wt.%). Giving wt.% Borax which is the ratio of 1: 4 between wt.% SiC. The addition of 1.5% of TiB gives grain refinement. The use of semi-solid stir casting method is able to increase the absorption of SiC particles into a matrix AlSi evenly. The improved composite presented here can be used as a guideline to make a new composite.

  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. A TEM quantitative evaluation of strengthening in an Mg-RE alloy reinforced with SiC

    International Nuclear Information System (INIS)

    Cabibbo, Marcello; Spigarelli, Stefano

    2011-01-01

    Magnesium alloys containing rare earth elements are known to have high specific strength, good creep and corrosion resistance up to 523 K. The addition of SiC ceramic particles strengthens the metal matrix composite resulting in better wear and creep resistance while maintaining good machinability. The role of the reinforcement particles in enhancing strength can be quantitatively evaluated using transmission electron microscopy (TEM). This paper presents a quantitative evaluation of the different strengthening contributions, determined through TEM inspections, in an SiC Mg-RE composite alloy containing yttrium, neodymium, gadolinium and dysprosium. Compression tests at temperatures ranging between 290 and 573 K were carried out. The microstructure strengthening mechanism was studied for all the compression conditions. Strengthening was compared to the mechanical results and the way the different contributions were combined is also discussed and justified. - Research Highlights: → TEM yield strengthening terms evaluation on a Mg-RE SiC alloy. → The evaluation has been extended to different compression temperature conditions. → Linear and Quadratic sum has been proposed and validated. → Hall-Petch was found to be the most prominent strengthening contributions.

  13. 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

    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...... measurements and data post-processing in order to properly characterize the devices and quantify whether the SiC JFET Cascode connection can provide good performances with a simple MOSFET gate driver....

  14. Effect of clustering on the mechanical properties of SiC particulate-reinforced aluminum alloy 2024 metal matrix composites

    International Nuclear Information System (INIS)

    Hong, Soon-Jik; Kim, Hong-Moule; Huh, Dae; Suryanarayana, C.; Chun, Byong Sun

    2003-01-01

    Al 2024-SiC metal matrix composite (MMC) powders produced by centrifugal atomization were hot extruded to investigate the effect of clustering on their mechanical properties. Fracture toughness and tension tests were conducted on specimens reinforced with different volume fractions of SiC. A model was proposed to suggest that the strength of the MMCs could be estimated from the load transfer model approach that takes into consideration the extent of clustering. This model has been successful in predicting the experimentally observed strength and fracture toughness values of the Al 2024-SiC MMCs. On the basis of experimental observations, it is suggested that the strength of particulate-reinforced MMCs may be calculated from the relation: σ y =σ m V m +σ r (V r -V c )-σ r V c , where σ and V represent the yield strength and volume fraction, respectively, and the subscripts m, r, and c represent the matrix, reinforcement, and clusters, respectively

  15. 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

  16. 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

  17. 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.

  18. Distribution of the grain limit character in SiC and its effect on the diffusion of fission products in the TRISO fuel particles

    International Nuclear Information System (INIS)

    Cancino T, F.; Lopez H, E.

    2017-09-01

    At present is accepted that silver diffuses through silicium carbide (SiC) by diffusion in grain boundaries, although little is known about the characteristics of grain boundaries in SiC, and how these change depending on the type of sample. In this work, was observed that there are small but important differences between the SiC in the tri-structural isotropic (TRISO) particles and that of the monoliths, which could explain some of the differences observed in experiments on diffusion in the literature. Five different types (coatings and monoliths) of SiC produced by chemical vapor deposition (CVD) were characterized by electron backscatter diffraction (EBSD). In all the samples the SiC was mainly composed of high-angle grain boundaries (∼ 65%), with a small fraction of grain boundaries of low-angle (about 15%) and 20% of the coincidence site lattice (CSL). The morphology of the monoliths is constituted by large grains, surrounded by smaller grains; in the particles of the TRISO fuel, both columnar and equi axial grains were observed, with a more uniform distribution over the surface of the coating. (Author)

  19. Effect of re-oxidation annealing process on the SiO2/SiC interface characteristics

    International Nuclear Information System (INIS)

    Yan Hongli; Jia Renxu; Tang Xiaoyan; Song Qingwen; Zhang Yuming

    2014-01-01

    The effect of the different re-oxidation annealing (ROA) processes on the SiO 2 /SiC interface characteristics has been investigated. With different annealing processes, the flat band voltage, effective dielectric charge density and interface trap density are obtained from the capacitance—voltage curves. It is found that the lowest interface trap density is obtained by the wet-oxidation annealing process at 1050 °C for 30 min, while a large number of effective dielectric charges are generated. The components at the SiO 2 /SiC interface are analyzed by X-ray photoelectron spectroscopy (XPS) testing. It is found that the effective dielectric charges are generated due to the existence of the C and H atoms in the wet-oxidation annealing process. (semiconductor technology)

  20. Several loadings and stresses of first wall of SiC with metal liner on conceptual design of moving ring reactor 'KARIN-1'

    International Nuclear Information System (INIS)

    Nishikawa, Masahiro; Tachibana, Eizaburo; Watanabe, Kenji; Fujiie, Yoichi.

    1983-01-01

    On conceptual design of moving ring reactor ''KARIN-I'' (Output: 1850 MWe), the first wall of SiC with metal liner is considered by reason that SiC ceramics has specific features of excellent radiation damage resistance in fast neutron spectra and a very low residual radioactivity, and that the thin metal liner has good compatibility with liquid lithium and good vaccum-tight, however, a extent electromagnetic interaction. The electromagnetic force applied on the metal liner and several pressure losses of liquid lithum flow are estimated, and these forces correspond to the fluid mechanical loading on SiC first wall. Thermal loading by neutron flux is calculated on the first wall to obtain temperature distributions along the flow direction and toward the wall thickness. At the outlet of the burning section, the surface temperature of SiC rises to the value of 825 0 C on plasma side and on the metal liner, it rises to the value of 540 0 C. Finally, the stress analysis is performed. The thermal stress is about one order larger than the stress induced by the fluid mechanical loading. At the inlet of the burning section, the average tensile stress of 22.4kg/mm 2 is induced on the outer side of SiC wall, and on the inner side, the average compressive stress of -26.1kg/mm 2 is induced. At the outlet of the burning section, the tensile stress is found to oscillate between 25.5kg/mm 2 and 27.3kg/mm 2 on the outer side of SiC wall by frequency of 1 Hz, and on the inner side, the compressive stress also oscillates between -21.6kg/mm 2 and -29.0kg/mm 2 by the same frequency. These stresses are within the value of fracture stress, (72.5kg/mm 2 ). Difficult residual problems on the first wall are also discussed. (author)