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Sample records for mono-uranium nitride fuel

  1. Laboratory Directed Research and Development (LDRD) on Mono-uranium Nitride Fuel Development for SSTAR and Space Applications

    Energy Technology Data Exchange (ETDEWEB)

    Choi, J; Ebbinghaus, B; Meiers, T; Ahn, J

    2006-02-09

    The US National Energy Policy of 2001 advocated the development of advanced fuel and fuel cycle technologies that are cleaner, more efficient, less waste-intensive, and more proliferation resistant. The need for advanced fuel development is emphasized in on-going DOE-supported programs, e.g., Global Nuclear Energy Initiative (GNEI), Advanced Fuel Cycle Initiative (AFCI), and GEN-IV Technology Development. The Directorates of Energy & Environment (E&E) and Chemistry & Material Sciences (C&MS) at Lawrence Livermore National Laboratory (LLNL) are interested in advanced fuel research and manufacturing using its multi-disciplinary capability and facilities to support a design concept of a small, secure, transportable, and autonomous reactor (SSTAR). The E&E and C&MS Directorates co-sponsored this Laboratory Directed Research & Development (LDRD) Project on Mono-Uranium Nitride Fuel Development for SSTAR and Space Applications. In fact, three out of the six GEN-IV reactor concepts consider using the nitride-based fuel, as shown in Table 1. SSTAR is a liquid-metal cooled, fast reactor. It uses nitride fuel in a sealed reactor vessel that could be shipped to the user and returned to the supplier having never been opened in its long operating lifetime. This sealed reactor concept envisions no fuel refueling nor on-site storage of spent fuel, and as a result, can greatly enhance proliferation resistance. However, the requirement for a sealed, long-life core imposes great challenges to research and development of the nitride fuel and its cladding. Cladding is an important interface between the fuel and coolant and a barrier to prevent fission gas release during normal and accidental conditions. In fabricating the nitride fuel rods and assemblies, the cladding material should be selected based on its the coolant-side corrosion properties, the chemical/physical interaction with the nitride fuel, as well as their thermal and neutronic properties. The US NASA space reactor, the

  2. Nitride Fuel Development at the INL

    Energy Technology Data Exchange (ETDEWEB)

    W.E. Windes

    2007-06-01

    A new method for fabricating nitride-based fuels for nuclear applications is under development at the Idaho National Laboratory (INL). A primary objective of this research is the development of a process that could be operated as an automated or semi-automated technique reducing costs, worker doses, and eventually improving the final product form. To achieve these goals the fabrication process utilizes a new cryo-forming technique to produce microspheres formed from sub-micron oxide powder to improve material handling issues, yield rapid kinetics for conversion to nitrides, and reduced material impurity levels within the nitride compounds. The microspheres are converted to a nitride form within a high temperature particle fluidizing bed using a carbothermic process that utilizes a hydrocarbon – hydrogen - nitrogen gas mixture. A new monitor and control system using differential pressure changes in the fluidizing gas allows for real-time monitoring and control of the spouted bed reactor during conversion. This monitor and control system can provide real-time data that is used to control the gas flow rates, temperatures, and gas composition to optimize the fluidization of the particle bed. The small size (0.5 µm) of the oxide powders in the microspheres dramatically increases the kinetics of the conversion process yielding reduced process times and temperatures. Initial studies using surrogate ZrO2 powder have yielded conversion efficiencies of 90 -95 % nitride formation with only small levels of oxide and carbide contaminants present. Further studies are being conducted to determine optimal gas mixture ratios, process time, and temperature range for providing complete conversion to a nitride form.

  3. Alkaline fuel cell with nitride membrane

    Science.gov (United States)

    Sun, Shen-Huei; Pilaski, Moritz; Wartmann, Jens; Letzkus, Florian; Funke, Benedikt; Dura, Georg; Heinzel, Angelika

    2017-06-01

    The aim of this work is to fabricate patterned nitride membranes with Si-MEMS-technology as a platform to build up new membrane-electrode-assemblies (MEA) for alkaline fuel cell applications. Two 6-inch wafer processes based on chemical vapor deposition (CVD) were developed for the fabrication of separated nitride membranes with a nitride thickness up to 1 μm. The mechanical stability of the perforated nitride membrane has been adjusted in both processes either by embedding of subsequent ion implantation step or by optimizing the deposition process parameters. A nearly 100% yield of separated membranes of each deposition process was achieved with layer thickness from 150 nm to 1 μm and micro-channel pattern width of 1μm at a pitch of 3 μm. The process for membrane coating with electrolyte materials could be verified to build up MEA. Uniform membrane coating with channel filling was achieved after the optimization of speed controlled dip-coating method and the selection of dimethylsulfoxide (DMSO) as electrolyte solvent. Finally, silver as conductive material was defined for printing a conductive layer onto the MEA by Ink-Technology. With the established IR-thermography setup, characterizations of MEAs in terms of catalytic conversion were performed successfully. The results of this work show promise for build up a platform on wafer-level for high throughput experiments.

  4. Oxidation Protection of Uranium Nitride Fuel using Liquid Phase Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Paul A. Lessing

    2012-03-01

    Two methods are proposed to increase the oxidation resistance of uranium nitride (UN) nuclear fuel. These paths are: (1) Addition of USi{sub x} (e.g. U3Si2) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with various compounds (followed by densification via Spark Plasma Sintering or Liquid Phase Sintering) that will greatly increase oxidation resistance. The advantages (high thermal conductivity, very high melting point, and high density) of nitride fuel have long been recognized. The sodium cooled BR-10 reactor in Russia operated for 18 years on uranium nitride fuel (UN was used as the driver fuel for two core loads). However, the potential advantages (large power up-grade, increased cycle lengths, possible high burn-ups) as a Light Water Reactor (LWR) fuel are offset by uranium nitride's extremely low oxidation resistance (UN powders oxidize in air and UN pellets decompose in hot water). Innovative research is proposed to solve this problem and thereby provide an accident tolerant LWR fuel that would resist water leaks and high temperature steam oxidation/spalling during an accident. It is proposed that we investigate two methods to increase the oxidation resistance of UN: (1) Addition of USi{sub x} (e.g. U{sub 3}Si{sub 2}) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with compounds (followed by densification via Spark Plasma Sintering) that will greatly increase oxidation resistance.

  5. Dissolution performance of plutonium nitride based fuel materials

    Energy Technology Data Exchange (ETDEWEB)

    Aneheim, E.; Hedberg, M. [Nuclear Chemistry, Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivaegen 4, Gothenburg, SE41296 (Sweden)

    2016-07-01

    Nitride fuels have been regarded as one viable fuel option for Generation IV reactors due to their positive features compared to oxides. To be able to close the fuel cycle and follow the Generation IV concept, nitrides must, however, demonstrate their ability to be reprocessed. This means that the dissolution performance of actinide based nitrides has to be thoroughly investigated and assessed. As the zirconium stabilized nitrides show even better potential as fuel material than does the pure actinide containing nitrides, investigations on the dissolution behavior of both PuN and (Pu,Zr)N has been undertaken. If possible it is desirable to perform the fuel dissolutions using nitric acid. This, as most reprocessing strategies using solvent-solvent extraction are based on a nitride containing aqueous matrix. (Pu,Zr)N/C microspheres were produced using internal gelation. The spheres dissolution performance was investigated using nitric acid with and without additions of HF and Ag(II). In addition PuN fuel pellets were produced from powder and their dissolution performance were also assessed in a nitric acid based setting. It appears that both PuN and (Pu,Zr)N/C fuel material can be completely dissolved in nitric acid of high concentration with the use of catalytic amounts of HF. The amount of HF added strongly affects dissolution kinetics of (Pu, Zr)N and the presence of HF affects the 2 solutes differently, possibly due to inhomogeneity o the initial material. Large additions of Ag(II) can also be used to facilitate the dissolution of (Pu,Zr)N in nitric acid. PuN can be dissolved by pure nitric acid of high concentration at room temperature while (Pu, Zr)N is unaffected under similar conditions. At elevated temperature (reflux), (Pu,Zr)N can, however, also be dissolved by concentrated pure nitric acid.

  6. Fabrication of nitride fuels for transmutation of minor actinides

    Science.gov (United States)

    Minato, Kazuo; Akabori, Mitsuo; Takano, Masahide; Arai, Yasuo; Nakajima, Kunihisa; Itoh, Akinori; Ogawa, Toru

    2003-07-01

    At the Japan Atomic Energy Research Institute, the concept of the transmutation of minor actinides (MA: Np, Am and Cm) with accelerator-driven systems is being studied. The MA nitride fuel has been chosen as a candidate because of the possible mutual solubility among the actinide mononitrides and excellent thermal properties besides supporting hard neutron spectrum. MA nitrides of NpN, (Np, Pu)N, (Np, U)N, AmN, (Am, Y)N, (Am, Zr)N and (Cm, Pu)N were prepared from the oxides by the carbothermic reduction method. The prepared MA nitrides were examined by X-ray diffraction and the contents of impurities of oxygen and carbon were measured. The fabrication conditions for MA nitrides were improved so as to reduce the impurity contents. For an irradiation test of U-free nitride fuels, pellets of (Pu, Zr)N and PuN + TiN were prepared and a He-bonded fuel pin was fabricated. The irradiation test started in May 2002 and will go on for two years in the Japan Materials Testing Reactor.

  7. The prospect of uranium nitride (UN) and mixed nitride fuel (UN-PuN) for pressurized water reactor

    Science.gov (United States)

    Syarifah, Ratna Dewi; Suud, Zaki

    2015-09-01

    Design study of small Pressurized Water Reactors (PWRs) core loaded with uranium nitride fuel (UN) and mixed nitride fuel (UN-PuN), Pa-231 as burnable poison, and Americium has been performed. Pa-231 known as actinide material, have large capture cross section and can be converted into fissile material that can be utilized to reduce excess reactivity. Americium is one of minor actinides with long half life. The objective of adding americium is to decrease nuclear spent fuel in the world. The neutronic analysis results show that mixed nitride fuel have k-inf greater than uranium nitride fuel. It is caused by the addition of Pu-239 in mixed nitride fuel. In fuel fraction analysis, for uranium nitride fuel, the optimum volume fractions are 45% fuel fraction, 10% cladding and 45% moderator. In case of UN-PuN fuel, the optimum volume fractions are 30% fuel fraction, 10% cladding and 60% coolant/ moderator. The addition of Pa-231 as burnable poison for UN fuel, enrichment U-235 5%, with Pa-231 1.6% has k-inf more than one and excess reactivity of 14.45%. And for mixed nitride fuel, the lowest value of reactivity swing is when enrichment (U-235+Pu) 8% with Pa-231 0.4%, the excess reactivity value 13,76%. The fuel pin analyze for the addition of Americium, the excess reactivity value is lower than before, because Americium absorb the neutron. For UN fuel, enrichment U-235 8%, Pa-231 1.6% and Am 0.5%, the excess reactivity is 4.86%. And for mixed nitride fuel, when enrichment (U-235+Pu) 13%, Pa-231 0.4% and Am 0.1%, the excess reactivity is 11.94%. For core configuration, it is better to use heterogeneous than homogeneous core configuration, because the radial power distribution is better.

  8. Imitators of plutonium and americium in a mixed uranium- plutonium nitride fuel

    Science.gov (United States)

    Nikitin, S. N.; Shornikov, D. P.; Tarasov, B. A.; Baranov, V. G.; Burlakova, M. A.

    2016-04-01

    Uranium nitride and mix uranium nitride (U-Pu)N is most popular nuclear fuel for Russian Fast Breeder Reactor. The works in hot cells associated with the radiation exposure of personnel and methodological difficulties. To know the main physical-chemical properties of uranium-plutonium nitride it necessary research to hot cells. In this paper, based on an assessment of physicochemical and thermodynamic properties of selected simulators Pu and Am. Analogues of Pu is are Ce and Y, and analogues Am - Dy. The technique of obtaining a model nitride fuel based on lanthanides nitrides and UN. Hydrogenation-dehydrogenation- nitration method of derived powders nitrides uranium, cerium, yttrium and dysprosium, held their mixing, pressing and sintering, the samples obtained model nitride fuel with plutonium and americium imitation. According to the results of structural studies have shown that all the samples are solid solution nitrides rare earth (REE) elements in UN.

  9. ON feasibility of using nitride and metallic fuel in the MBIR reactor core

    Directory of Open Access Journals (Sweden)

    V.A. Eliseev

    2016-09-01

    Studies on the MBIR reactor, involving advanced dense fuel types, have shown that nitride fuel does not make it possible to achieve the required neutron flux value, while metallic fuel provides for the required neutron flux (practically the same as MOX fuel and a high dpa rate but requires modified temperature conditions of irradiation. The specific neutronic properties of these fuel types, as compared to the standard MOX fuel, have also been identified.

  10. Anti corrosion layer for stainless steel in molten carbonate fuel cell - comprises phase vapour deposition of titanium nitride, aluminium nitride or chromium nitride layer then oxidising layer in molten carbonate electrolyte

    DEFF Research Database (Denmark)

    2000-01-01

    Forming an anticorrosion protective layer on a stainless steel surface used in a molten carbonate fuel cell (MCFC) - comprises the phase vapour deposition (PVD) of a layer comprising at least one of titanium nitride, aluminium nitride or chromium nitride and then forming a protective layer in situ...

  11. Iron-based alloy and nitridation treatment for PEM fuel cell bipolar plates

    Science.gov (United States)

    Brady, Michael P [Oak Ridge, TN; Yang, Bing [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN

    2010-11-09

    A corrosion resistant electrically conductive component that can be used as a bipolar plate in a PEM fuel cell application is composed of an alloy substrate which has 10-30 wt. % Cr, 0.5 to 7 wt. % V, and base metal being Fe, and a continuous surface layer of chromium nitride and vanadium nitride essentially free of base metal. A oxide layer of chromium vanadium oxide can be disposed between the alloy substrate and the continuous surface nitride layer. A method to prepare the corrosion resistant electrically conductive component involves a two-step nitridization sequence by exposing the alloy to a oxygen containing gas at an elevated temperature, and subsequently exposing the alloy to an oxygen free nitrogen containing gas at an elevated temperature to yield a component where a continuous chromium nitride layer free of iron has formed at the surface.

  12. Copper nitride nanocubes: size-controlled synthesis and application as cathode catalyst in alkaline fuel cells.

    Science.gov (United States)

    Wu, Haibin; Chen, Wei

    2011-10-05

    Copper nitride nanocubes are synthesized in a facile one-phase process. The crystal size could be tuned easily by using different primary amines as capping agents. Such Pt-free nanocrystals exhibit electrocatalytic activity toward oxygen reduction and appear to be promising cathodic electrocatalysts in alkaline fuel cells.

  13. Mechanistic approach for nitride fuel evolution and fission product release under irradiation

    Science.gov (United States)

    Dolgodvorov, A. P.; Ozrin, V. D.

    2017-01-01

    A model for describing uranium-plutonium mixed nitride fuel pellet burning was developed. Except fission products generating, the model includes impurities of oxygen and carbon. Nitrogen behaviour in nitride fuel was analysed and the nitrogen chemical potential in solid solution with uranium-plutonium nitride was constructed. The chemical program module was tested with the help of thermodynamic equilibrium phase distribution calculation. Results were compared with analogous data in literature, quite good agreement was achieved, especially for uranium sesquinitride, metallic species and some oxides. Calculation of a process of nitride fuel burning was also conducted. Used mechanistic approaches for fission product evolution give the opportunity to find fission gas release fractions and also volumes of intergranular secondary phases. Calculations present that the most massive secondary phases are the oxide and metallic phases. Oxide phase contain approximately 1 % wt of substance over all time of burning with slightly increasing of content. Metallic phase has considerable rising of mass and by the last stage of burning it contains about 0.6 % wt of substance. Intermetallic phase has less increasing rate than metallic phase and include from 0.1 to 0.2 % wt over all time of burning. The highest element fractions of released gaseous fission products correspond to caesium and iodide.

  14. Boron coating on boron nitride coated nuclear fuels by chemical vapor deposition

    Science.gov (United States)

    Durmazuçar, Hasan H.; Gündüz, Güngör

    2000-12-01

    Uranium dioxide-only and uranium dioxide-gadolinium oxide (5% and 10%) ceramic nuclear fuel pellets which were already coated with boron nitride were coated with thin boron layer by chemical vapor deposition to increase the burn-up efficiency of the fuel during reactor operation. Coating was accomplished from the reaction of boron trichloride with hydrogen at 1250 K in a tube furnace, and then sintering at 1400 and 1525 K. The deposited boron was identified by infrared spectrum. The morphology of the coating was studied by using scanning electron microscope. The plate, grainy and string (fiber)-like boron structures were observed.

  15. Pre-oxidized and nitrided stainless steel alloy foil for proton exchange membrane fuel cell bipolar plates. Part 2: Single-cell fuel cell evaluation of stamped plates

    Science.gov (United States)

    Toops, Todd J.; Brady, Michael P.; Tortorelli, Peter F.; Pihl, Josh A.; Estevez, Francisco; Connors, Daniel; Garzon, Fernando; Rockward, Tommy; Gervasio, Don; Mylan, William; Kosaraju, Sree Harsha

    Thermal (gas) nitridation of stainless steel alloys can yield low interfacial contact resistance (ICR), electrically conductive and corrosion-resistant nitride containing surface layers (Cr 2N, CrN, TiN, V 2N, VN, etc.) of interest for fuel cells, batteries, and sensors. This paper presents results of proton exchange membrane (PEM) single-cell fuel cell studies of stamped and pre-oxidized/nitrided developmental Fe-20Cr-4V weight percent (wt.%) and commercial type 2205 stainless steel alloy foils. The single-cell fuel cell behavior of the stamped and pre-oxidized/nitrided material was compared to as-stamped (no surface treatment) 904L, 2205, and Fe-20Cr-4V stainless steel alloy foils and machined graphite of similar flow field design. The best fuel cell behavior among the alloys was exhibited by the pre-oxidized/nitrided Fe-20Cr-4V, which exhibited ∼5-20% better peak power output than untreated Fe-20Cr-4V, 2205, and 904L metal stampings. Durability was assessed for pre-oxidized/nitrided Fe-20Cr-4V, 904L metal, and graphite plates by 1000+ h of cyclic single-cell fuel cell testing. All three materials showed good durability with no significant degradation in cell power output. Post-test analysis indicated no metal ion contamination of the membrane electrode assemblies (MEAs) occurred with the pre-oxidized and nitrided Fe-20Cr-4V or graphite plates, and only a minor amount of contamination with the 904L plates.

  16. Breeding performance of carbide and nitride fuels in 2000 MWe LMFBRs: a preliminary report. Part I. Assumptions, constraints and methodology

    Energy Technology Data Exchange (ETDEWEB)

    Barthold, W P

    1976-09-01

    The assumptions, constraints, and methodology used in the design and analysis of 2000 MWe LMFBRs using carbide and nitride fuel are presented. The assumptions used in the nuclear, thermal and mechanical designs are discussed together with geometry constraints, operational constraints, performance constraints, constraints coming from fabrication consideration and fuel bundle-duct interaction constraints. The basic calculational flow for system design studies is described, and the computer codes used in the analyses are briefly reviewed.

  17. Uranium nitride as LWR TRISO fuel: Thermodynamic modeling of U-C-N

    Science.gov (United States)

    Besmann, Theodore M.; Shin, Dongwon; Lindemer, Terrence B.

    2012-08-01

    TRISO coated particle fuel is envisioned as a next generation replacement for current urania pellet fuel in LWR applications. To obtain adequate fissile loading the kernel of the TRISO particle will likely need to be UN instead of UO2. In support of the necessary development effort for this new fuel system, an assessment of phase regions of interest in the U-C-N system was undertaken as the fuel will be prepared by the carbothermic reduction of the oxide followed by nitriding, will be in equilibrium with carbon within the TRISO particle, and will react with minor actinides and fission products. The phase equilibria and thermochemistry of the U-C-N system is reviewed, including nitrogen pressure measurements above various phase fields. Measurements were used to confirm an ideal solution model of UN and UC adequately represents the UC1-xNx phase. Agreement with the data was significantly improved by effectively adjusting the Gibbs free energy of UN by +12 kJ/mol. This also required adjustment of the value for the sesquinitride by +17 kJ/mol to obtain agreement with phase equilibria. The resultant model together with reported values for other phases in the system was used to generate isothermal sections of the U-C-N phase diagram. Nitrogen partial pressures were also computed for regions of interest.

  18. Hydrogen storage performance of functionalized hexagonal boron nitride for fuel cell applications

    Science.gov (United States)

    Muthu, R. Naresh; Rajashabala, S.; Kannan, R.

    2017-05-01

    Developing light weight, safe, efficient and compact hydrogen storage medium are still the major concerns for the blooming of hydrogen based energy economy. In the present article, activated hexagonal boron nitride (ABN) and ABN functionalized with lithium borohydride (ABN-LiBH4) nanocomposite based hydrogen storage medium are synthesized. where a facile solvent-assistant technique was adopted for the preparation of ABN-LiBH4 nanocomposite. The prepared hydrogen storage medium was subjected to various characterization techniques such as XRD, FTIR, SEM, EDX, CHNS - elemental analysis and TGA. Sievert's-like hydrogenation setup has been utilized for hydrogenation studies. It is noticed that the ABN-LiBH4 nanocomposite exhibits an attractive high gravimetric density of 1.67 wt% at 100 °C than pristine ABN. Moreover the stored hydrogen is released in the temperature range of 115 - 150 °C and possesses an average binding energy of 0.31 eV. These results indicate that the prepared ABN-LiBH4 nanocomposite paves a way to potential solid state hydrogen storage medium towards fuel cell technology as per the targets set by US Department of Energy (DOE).

  19. Studies on plutonium-zirconium co-precipitation and carbothermal reduction in the internal gelation process for nitride fuel preparation

    Science.gov (United States)

    Hedberg, Marcus; Ekberg, Christian

    2016-10-01

    Sol-gel based techniques are one way to lower the handling of highly radioactive powders when producing transuranium-containing fuel. In this work inert matrix (Zr0.6,Pu0.4)N fuel has been produced by internal gelation followed by carbothermal reduction. No co-gelation was observed during internal gelation and a two phase material could be detected by scanning electron microscopy in the nitrided microspheres. Sintering has been performed in both Ar and N2. X-ray diffraction revealed that sintering in N2 produced a solid solution, while sintering in Ar did not. The final metal composition in the microspheres was determined by ICP-MS to be about 41% Pu and 59% Zr. Vegard's law was applied to estimate the nitride purity in the solid solution pellet to be Zr0.6Pu0.4N0.87C0.13 making the final material more of a carbonitride than a pure nitride.

  20. Surface composition effect of nitriding Ni-free stainless steel as bipolar plate of polymer electrolyte fuel cell

    Science.gov (United States)

    Yu, Yang; Shironita, Sayoko; Nakatsuyama, Kunio; Souma, Kenichi; Umeda, Minoru

    2016-12-01

    In order to increase the corrosion resistance of low cost Ni-free SUS445 stainless steel as the bipolar plate of a polymer electrolyte fuel cell, a nitriding surface treatment experiment was carried out in a nitrogen atmosphere under vacuum conditions, while an Ar atmosphere was used for comparison. The electrochemical performance, microstructure, surface chemical composition and morphology of the sample before and after the electrochemical measurements were investigated using linear sweep voltammetry (LSV), X-ray diffraction (XRD), glow discharge optical emission spectroscopy (GDS) and laser scanning microscopy (LSM) measurements. The results confirmed that the nitriding heat treatment not only increased the corrosion resistance, but also improved the surface conductivity of the Ni-free SUS445 stainless steel. In contrast, the corrosion resistance of the SUS445 stainless steel decreased after heat treatment in an Ar atmosphere. These results could be explained by the different surface compositions between these samples.

  1. Pre-oxidized and nitrided stainless steel alloy foil for proton exchange membrane fuel cell bipolar plates: Part 1. Corrosion, interfacial contact resistance, and surface structure

    Science.gov (United States)

    Brady, M. P.; Wang, H.; Turner, J. A.; Meyer, H. M.; More, K. L.; Tortorelli, P. F.; McCarthy, B. D.

    Thermal (gas) nitridation of stainless steel alloys can yield low interfacial contact resistance (ICR), electrically conductive and corrosion-resistant nitride containing surface layers (Cr 2N, CrN, TiN, V 2N, VN, etc.) of interest for fuel cells, batteries, and sensors. This paper presents results of scale-up studies to determine the feasibility of extending the nitridation approach to thin 0.1 mm stainless steel alloy foils for proton exchange membrane fuel cell (PEMFC) bipolar plates. Developmental Fe-20Cr-4V alloy and type 2205 stainless steel foils were treated by pre-oxidation and nitridation to form low-ICR, corrosion-resistant surfaces. As-treated Fe-20Cr-4V foil exhibited target (low) ICR values, whereas 2205 foil suffered from run-to-run variation in ICR values, ranging up to 2× the target value. Pre-oxidized and nitrided surface structure examination revealed surface-through-layer-thickness V-nitride particles for the treated Fe-20Cr-4V, but near continuous chromia for treated 2205 stainless steel, which was linked to the variation in ICR values. Promising corrosion resistance was observed under simulated aggressive PEMFC anode- and cathode-side bipolar plate conditions for both materials, although ICR values were observed to increase. The implications of these findings for stamped bipolar plate foils are discussed.

  2. Alternative Liquid Fuel Effects on Cooled Silicon Nitride Marine Gas Turbine Airfoils

    Energy Technology Data Exchange (ETDEWEB)

    Holowczak, J.

    2002-03-01

    With prior support from the Office of Naval Research, DARPA, and U.S. Department of Energy, United Technologies is developing and engine environment testing what we believe to be the first internally cooled silicon nitride ceramic turbine vane in the United States. The vanes are being developed for the FT8, an aeroderivative stationary/marine gas turbine. The current effort resulted in further manufacturing and development and prototyping by two U.S. based gas turbine grade silicon nitride component manufacturers, preliminary development of both alumina, and YTRIA based environmental barrier coatings (EBC's) and testing or ceramic vanes with an EBC coating.

  3. Testing of uranium nitride fuel in T-111 cladding at 1200 K cladding temperature

    Science.gov (United States)

    Rohal, R. G.; Tambling, T. N.; Smith, R. L.

    1973-01-01

    Two groups of six fuel pins each were assembled, encapsulated, and irradiated in the Plum Brook Reactor. The fuel pins employed uranium mononitride (UN) in a tantalum alloy clad. The first group of fuel pins was irradiated for 1500 hours to a maximum burnup of 0.7-atom-percent uranium. The second group of fuel pins was irradiated for about 3000 hours to a maximum burnup of 1.0-atom-percent uranium. The average clad surface temperature during irradiation of both groups of fuel pins was approximately 1200 K. The postirradiation examination revealed the following: no clad failures or fuel swelling occurred; less than 1 percent of the fission gases escaped from the fuel; and the clad of the first group of fuel pins experienced clad embrittlement whereas the second group, which had modified assembly and fabrication procedures to minimize contamination, had a ductile clad after irradiation.

  4. Investigation of titanium nitride as catalyst support material and development of durable electrocatalysts for proton exchange membrane fuel cells

    Science.gov (United States)

    Avasarala, Bharat K.

    The impending energy and climatic crisis makes it imperative for human society to seek non-fossil based alternative sources for our energy needs. Although many alternative energy technologies are currently being developed, fuel cell technology provides energy solutions, which satisfy a wide range of applications. But the current fuel cell technology is far from its target of large scale commercialization mainly because of its high cost and poor durability. Considerable work has been done in reducing the cost but its durability still needs significant improvement. Of the various materials in a PEM fuel cell, the degradation of electrocatalyst affects its durability the most, leading to performance loss. Carbon black (C) support corrosion plays a significant role in the electrocatalyst degradation and its severe affects due to potential cycling has been identified through my research. Through my resaerch, I introduce titanium nitride nanoparticles (TiN NP) as alternative catalyst supports replacing carbon black. TiN NP has higher electrical conductivity and corrosion resistance compared to that of C. The physical and electrochemical properties of TiN NP were studied and the Pt/TiN electrocatalyst was synthesized using polyol process. Upon optimizing using DOE, for desired catalyst particle size and activity, Pt/TiN is shown to have higher catalytic performance than conventional Pt/C. TiN NP are significantly influenced by the electrochemical conditions and show 'active' or 'passive' nature depending on the temperature and acidic concentration; and a temperature dependence model is proposed to understand the active/passive nature of TiN NP. A one-to-one comparison between TiN NP and C electrodes under similar electrochemical conditions show a superior performance of TiN NP as a catalyst support. The durability of the Pt/TiN electrocatalyst is also tested and it agrees well with the proposed model of active/passive nature of the TiN NP. Through theoretical calculation

  5. Chemical forms of solid fission products in the irradiated uranium—plutonium mixed nitride fuel

    Science.gov (United States)

    Arai, Yasuo; Maeda, Atsushi; Shiozawa, Ken-ichi; Ohmichi, Toshihiko

    1994-06-01

    Chemical forms of solid fission products in the irradiated (U, Pu)N fuel were estimated by both thermodynamic equilibrium calculation and electron microprobe analysis on burnup simulated samples prepared by carbothermic reduction. Besides the MX type matrix phase dissolving zirconium, niobium, yttrium and rare earth elements, the existence of two kinds of inclusion was recognized. One is URu 3 type intermetallic compound constituted by uranium and platinum group elements. The other is an alloy containing molybdenum as a principal constituent. Furthermore, the swelling rate due to solid fission products precipitation was evaluated to be about 0.5% per %FIMA.

  6. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells.

    Science.gov (United States)

    Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

    2014-09-22

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm(2)) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

  7. Thermally Nitrided Stainless Steels for Polymer Electrolyte Membrane Fuel Cell Bipolar Plates: Part 2: Beneficial Modification of Passive Layer on AISI446

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Heli [National Renewable Energy Laboratory (NREL); Brady, Michael P [ORNL; More, Karren Leslie [ORNL; Meyer III, Harry M [ORNL; Turner, John [National Renewable Energy Laboratory (NREL)

    2004-01-01

    Thermal nitridation of AISI446 mod-1 superferritic stainless steel for 24 h at 1100 C resulted in an adherent, inward growing surface layer based on (Cr, Fe){sub 2}N{sub 1-x} (x = 0--0.5). The layer was not continuous, and although it resulted in low interfacial contact resistance (ICR) and good corrosion resistance under simulated polymer electrolyte membrane fuel cell (PEMFC) cathodic conditions; poor corrosion resistance was observed under simulated anodic conditions. Nitridation for 2 h at 1100 C resulted in little nitrogen uptake and a tinted surface. Analysis by SEM, XPS, and AES suggested a complex heterogeneous modification of the native passive oxide film by nitrogen rather than the desired microns-thick exclusive Cr-rich nitride layer. Surprisingly, this modification resulted in both good corrosion resistance under simulated cathodic and anodic conditions and low ICR, well over an order of magnitude lower than the untreated alloy. Further, little increase in ICR was observed under passivating polarization conditions. The potential of this phenomenon for PEMFC bipolar plates is discussed.

  8. Effect of sintering conditions on the microstructure and mechanical properties of ZrN as a surrogate for actinide nitride fuels

    Science.gov (United States)

    Wheeler, K.; Peralta, P.; Parra, M.; McClellan, K.; Dunwoody, J.; Egeland, G.

    2007-07-01

    Pellets of sintered ZrN were studied to optimize the mechanical properties and microstructures needed in nitride fuel pellets, using ZrN as a surrogate for actinide nitrides and as potential component in low fertile and inert matrix fuels. Samples were prepared via sintering in either Ar or N2 (with and without 6% H2) and at 1300 °C or 1600 °C. A significant difference in the hardness was measured ranging from 1000 (Kg/mm2) in samples sintered at 1600 °C in argon to 100 (Kg/mm2) in samples sintered at 1300 °C in nitrogen. Samples with 6% hydrogen added to the sintering environment experienced a decrease in hardness, as well as an increase in intergranular cracking as compared to samples sintered without hydrogen, suggesting hydrogen embrittlement. Grain size was more uniform in samples sintered in pure Ar as compared to Ar-H2, while the latter had a larger fraction of high angle grain boundaries than the former. Cracking around indents had a clear tendency to follow high angle boundaries, which were found to be intrinsically weak in ZrN.

  9. The prospect of uranium nitride (UN-PuN) fuel for 25- 100MWe gas cooled fast reactor long life without refuelling

    Science.gov (United States)

    Syarifah, R. D.; Su'ud, Z.; Basar, K.; Irwanto, D.

    2016-11-01

    The prospect of uranium nitride (UN-PuN) fuel for 25-100MWe Gas Cooled Fast Reactor has been done. This research use helium coolant which has low neutron moderation, chemical inert and single phase. This study use natural uranium and plutonium. Plutonium taken from spent fuel of LWR (Light Water Reactor). So, it can reduced spent fuel in the world. The calculation use SRAC2006 and JENDL 4.0 for the data libraries. First, we calculate PIJ for fuel pin cell calculation and CITATION for core calculation. The reflector radial-axial width is 50 cm. The variation of fuel fraction is 40% until 65%, cladding 10%, and moderator 25% up to 50%. The variation of the power is 75-300 MWth (25-100 MWe). The calculation of survey parameter has been done. The variation of percentage plutonium is 7% up to 13%. We have optimum k-eff value in percentage of plutonium 11%. The high powers cause k-eff value high too. Second, the core configuration divided by three variation fuel (F1, F2, and F3). F1 is located in the central core, F2 middle core and F3 outer core. The variation percentage Plutonium for fuel F1:F2:F3 = 8%:10%:12%. The increasing power level make the burn up level increase. All case can reach burn up time plus than 20 years. The thermal powers increase cause the peak power density increase. The power 150 MWth, 225 MWth, and 300 MWth have excess reactivity (%Ak/k) less than 2%.

  10. An investigation of the typical corrosion parameters used to test polymer electrolyte fuel cell bipolar plate coatings, with titanium nitride coated stainless steel as a case study

    Science.gov (United States)

    Orsi, A.; Kongstein, O. E.; Hamilton, P. J.; Oedegaard, A.; Svenum, I. H.; Cooke, K.

    2015-07-01

    Stainless steel bipolar plates (BPP) for polymer electrolyte membrane fuel cells (PEMFCs) have good manufacturability, durability and low costs, but inadequate corrosion resistance and elevated interfacial contact resistance (ICR) in the fuel cell environment. Thin film coatings of titanium nitride (TiN) of 1 μm in thickness, were deposited by means of physical vapour deposition (PVD) process on to stainless steel (SS) 316L substrates and were evaluated, in a series of tests, for their level of corrosion protection and ICR. In the ex-situ corrosion tests, variables such as applied potential, experimental duration and pH of the sulphate electrolyte at 80 °C were altered. The ICR values were found to increase after exposure to greater applied potentials and electrolytes of a higher pH. In terms of experimental duration, the ICR increased most rapidly at the beginning of each experiment. It was also found that the oxidation of TiN was accelerated after exposure to electrolytes of a higher pH. When coated BPPs were incorporated into an accelerated fuel cell test, the degradation of the fuel cell cathode resembled the plates that were tested at the highest anodic potential (1.4 VSHE).

  11. Design Study of 200MWth Gas Cooled Fast Reactor with Nitride (UN-PuN Fuel Long Life without Refueling

    Directory of Open Access Journals (Sweden)

    Syarifah Ratna Dewi

    2016-01-01

    Full Text Available Design study of 200 MWth Gas Cooled Fast Reactor with UN-PuN fuel long life without refueling has been done. GFR is one type reactor in Generation IV reactor system. It uses helium coolant and fast neutron spectrum. Helium is chemical inert, single phase and low neutron moderation. In this study the calculations are performed by using SRAC code with PIJ calculation for the fuel pin cell calculation and CITATION calculation for core calculation. The data libraries use JENDL 3.2. The variation fuel fractions are 50% until 60%. The diameter active core is 150 cm and the height active core is 100 cm. The reflector radial-axial width is 50 cm. The variation of the powers are 100 MWth up to 500 MWth. The high power causes the high k-eff value. The optimum design is reached when the power is 200 MWth, variation percentage Plutonium for fuel F1:F2:F3=9%:11%:13%. The comparation of fuel:cladding:coolant fraction = 55%:10%:35%. The cooling down time of Plutonium is nine months. The optimum k-eff value is 1.0142 with excess reactivity value 1.403%. The decay of Plutonium decrease k-eff value in the beginning of burn up.

  12. Nano-nitride cathode catalysts of Ti, Ta, and Nb for polymer electrolyte fuel cells: Temperature-programmed desorption investigation of molecularly adsorbed oxygen at low temperature

    KAUST Repository

    Ohnishi, Ryohji

    2013-01-10

    TiN, NbN, TaN, and Ta3N5 nanoparticles synthesized using mesoporous graphitic (mpg)-C3N4 templates were investigated for the oxygen reduction reaction (ORR) as cathode catalysts for polymer electrolyte fuel cells. The temperature-programmed desorption (TPD) of molecularly adsorbed O2 at 120-170 K from these nanoparticles was examined, and the resulting amount and temperature of desorption were key factors determining the ORR activity. The size-dependent TiN nanoparticles (5-8 and 100 nm) were then examined. With decreasing particle size, the density of molecularly adsorbed O2 per unit of surface area increased, indicating that a decrease in particle size increases the number of active sites. It is hard to determine the electrochemical active surface area for nonmetal electrocatalysts (such as oxides or nitrides), because of the absence of proton adsorption/desorption peaks in the voltammograms. In this study, O2-TPD for molecularly adsorbed O2 at low temperature demonstrated that the amount and strength of adsorbed O2 were key factors determining the ORR activity. The properties of molecularly adsorbed O2 on cathode catalysts are discussed against the ORR activity. © 2012 American Chemical Society.

  13. Thermally Nitrided Stainless Steels for Polymer Electrolyte Membrane Fuel Cell Bipolar Plates: Part 1 Model Ni-50Cr and Austenitic 349TM alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Heli [National Renewable Energy Laboratory (NREL); Brady, Michael P [ORNL; Turner, John [National Renewable Energy Laboratory (NREL)

    2004-01-01

    Thermal nitridation of a model Ni-50Cr alloy at 1100 C for 2 h in pure nitrogen resulted in the formation of a continuous, protective CrN/Cr{sub 2}N surface layer with a low interfacial contact resistance. Application of similar nitridation parameters to an austenitic stainless steel, 349{sup TM}, however, resulted in a discontinuous mixture of discrete CrN, Cr{sub 2}N and (Cr,Fe){sub 2}N{sub 1-x} (x = 0--0.5) phase surface particles overlying an exposed {gamma} austenite-based matrix, rather than a continuous nitride surface layer. The interfacial contact resistance of the 349{sup TM} was reduced significantly by the nitridation treatment. However, in the simulated PEMFC environments (1 M H{sub 2}SO{sub 4} + 2 ppm F{sup -} solutions at 70 C sparged with either hydrogen or air), very high corrosion currents were observed under both anodic and cathodic conditions. This poor behavior was linked to the lack of continuity of the Cr-rich nitride surface formed on 349{sup TM} Issues regarding achieving continuous, protective Cr-nitride surface layers on stainless steel alloys are discussed.

  14. Review of actinide nitride properties with focus on safety aspects

    Energy Technology Data Exchange (ETDEWEB)

    Albiol, Thierry [CEA Cadarache, St Paul Lez Durance Cedex (France); Arai, Yasuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2001-12-01

    This report provides a review of the potential advantages of using actinide nitrides as fuels and/or targets for nuclear waste transmutation. Then a summary of available properties of actinide nitrides is given. Results from irradiation experiments are reviewed and safety relevant aspects of nitride fuels are discussed, including design basis accidents (transients) and severe (core disruptive) accidents. Anyway, as rather few safety studies are currently available and as many basic physical data are still missing for some actinide nitrides, complementary studies are proposed. (author)

  15. Crystalline boron nitride aerogels

    Science.gov (United States)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  16. Crystalline boron nitride aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  17. Boron nitride composites

    Energy Technology Data Exchange (ETDEWEB)

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2017-02-21

    According to one embodiment, a composite product includes: a matrix material including hexagonal boron nitride and one or more borate binders; and a plurality of cubic boron nitride particles dispersed in the matrix material. According to another embodiment, a composite product includes: a matrix material including hexagonal boron nitride and amorphous boron nitride; and a plurality of cubic boron nitride particles dispersed in the matrix material.

  18. Plasma nitriding of steels

    CERN Document Server

    Aghajani, Hossein

    2017-01-01

    This book focuses on the effect of plasma nitriding on the properties of steels. Parameters of different grades of steels are considered, such as structural and constructional steels, stainless steels and tools steels. The reader will find within the text an introduction to nitriding treatment, the basis of plasma and its roll in nitriding. The authors also address the advantages and disadvantages of plasma nitriding in comparison with other nitriding methods. .

  19. An intensified π-hole in beryllium-doped boron nitride meshes: its determinant role in CO2 conversion into hydrocarbon fuels.

    Science.gov (United States)

    Azofra, Luis Miguel; MacFarlane, Douglas R; Sun, Chenghua

    2016-02-28

    DFT investigations on beryllium-doped boron nitride meshes or sheets (BNs) predict the existence of a very reactive kind of novel material capable of spontaneously reducing the first hydrogenation step in the CO2 conversion mechanism. This impressive behaviour appears as a result of the very deep π-hole generated by the beryllium moieties, and also determines its selectivity towards the production of CH4.

  20. Synthesis of Uranium nitride powders using metal uranium powders

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jae Ho; Kim, Dong Joo; Oh, Jang Soo; Rhee, Young Woo; Kim, Jong Hun; Kim, Keon Sik [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-10-15

    Uranium nitride (UN) is a potential fuel material for advanced nuclear reactors because of their high fuel density, high thermal conductivity, high melting temperature, and considerable breeding capability in LWRs. Uranium nitride powders can be fabricated by a carbothermic reduction of the oxide powders, or the nitriding of metal uranium. The carbothermic reduction has an advantage in the production of fine powders. However it has many drawbacks such as an inevitable engagement of impurities, process burden, and difficulties in reusing of expensive N{sup 15} gas. Manufacturing concerns issued in the carbothermic reduction process can be solved by changing the starting materials from oxide powder to metals. However, in nitriding process of metal, it is difficult to obtain fine nitride powders because metal uranium is usually fabricated in the form of bulk ingots. In this study, a simple reaction method was tested to fabricate uranium nitride powders directly from uranium metal powders. We fabricated uranium metal spherical powder and flake using a centrifugal atomization method. The nitride powders were obtained by thermal treating those metal particles under nitrogen containing gas. We investigated the phase and morphology evolutions of powders during the nitriding process. A phase analysis of nitride powders was also a part of the present work.

  1. Innovative boron nitride-doped propellants

    Directory of Open Access Journals (Sweden)

    Thelma Manning

    2016-04-01

    Full Text Available The U.S. military has a need for more powerful propellants with balanced/stoichiometric amounts of fuel and oxidants. However, balanced and more powerful propellants lead to accelerated gun barrel erosion and markedly shortened useful barrel life. Boron nitride (BN is an interesting potential additive for propellants that could reduce gun wear effects in advanced propellants (US patent pending 2015-026P. Hexagonal boron nitride is a good lubricant that can provide wear resistance and lower flame temperatures for gun barrels. Further, boron can dope steel, which drastically improves its strength and wear resistance, and can block the formation of softer carbides. A scalable synthesis method for producing boron nitride nano-particles that can be readily dispersed into propellants has been developed. Even dispersion of the nano-particles in a double-base propellant has been demonstrated using a solvent-based processing approach. Stability of a composite propellant with the BN additive was verified. In this paper, results from propellant testing of boron nitride nano-composite propellants are presented, including closed bomb and wear and erosion testing. Detailed characterization of the erosion tester substrates before and after firing was obtained by electron microscopy, inductively coupled plasma and x-ray photoelectron spectroscopy. This promising boron nitride additive shows the ability to improve gun wear and erosion resistance without any destabilizing effects to the propellant. Potential applications could include less erosive propellants in propellant ammunition for large, medium and small diameter fire arms.

  2. Innovative boron nitride-doped propellants

    Institute of Scientific and Technical Information of China (English)

    Thelma MANNING; Henry GRAU; Paul MATTER; Michael BEACHY; Christopher HOLT; Samuel SOPOK; Richard FIELD; Kenneth KLINGAMAN; Michael FAIR; John BOLOGNINI; Robin CROWNOVER; Carlton P. ADAM; Viral PANCHAL; Eugene ROZUMOV

    2016-01-01

    The U.S. military has a need for more powerful propellants with balanced/stoichiometric amounts of fuel and oxidants. However, balanced and more powerful propellants lead to accelerated gun barrel erosion and markedly shortened useful barrel life. Boron nitride (BN) is an interesting potential additive for propellants that could reduce gun wear effects in advanced propellants (US patent pending 2015-026P). Hexagonal boron nitride is a good lubricant that can provide wear resistance and lower flame temperatures for gun barrels. Further, boron can dope steel, which drastically improves its strength and wear resistance, and can block the formation of softer carbides. A scalable synthesis method for producing boron nitride nano-particles that can be readily dispersed into propellants has been developed. Even dispersion of the nano-particles in a double-base propellant has been demonstrated using a solvent-based processing approach. Stability of a composite propellant with the BN additive was verified. In this paper, results from propellant testing of boron nitride nano-composite propellants are presented, including closed bomb and wear and erosion testing. Detailed characterization of the erosion tester substrates before and after firing was obtained by electron microscopy, inductively coupled plasma and x-ray photoelectron spectroscopy. This promising boron nitride additive shows the ability to improve gun wear and erosion resistance without any destabilizing effects to the propellant. Potential applications could include less erosive propellants in propellant ammunition for large, medium and small diameter fire arms.

  3. Methods of forming boron nitride

    Science.gov (United States)

    Trowbridge, Tammy L; Wertsching, Alan K; Pinhero, Patrick J; Crandall, David L

    2015-03-03

    A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boron nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.

  4. Methods of forming boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Trowbridge, Tammy L; Wertsching, Alan K; Pinhero, Patrick J; Crandall, David L

    2015-03-03

    A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boron nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.

  5. Gallium nitride optoelectronic devices

    Science.gov (United States)

    Chu, T. L.; Chu, S. S.

    1972-01-01

    The growth of bulk gallium nitride crystals was achieved by the ammonolysis of gallium monochloride. Gallium nitride single crystals up to 2.5 x 0.5 cm in size were produced. The crystals are suitable as substrates for the epitaxial growth of gallium nitride. The epitaxial growth of gallium nitride on sapphire substrates with main faces of (0001) and (1T02) orientations was achieved by the ammonolysis of gallium monochloride in a gas flow system. The grown layers had electron concentrations in the range of 1 to 3 x 10 to the 19th power/cu cm and Hall mobilities in the range of 50 to 100 sq cm/v/sec at room temperature.

  6. Advanced fuels for thermal spectrum reactors

    OpenAIRE

    Zakova, Jitka

    2012-01-01

    The advanced fuels investigated in this thesis comprise fuels non− conventional in their design/form (TRISO), their composition (high content of plutonium and minor actinides) or their use in a reactor type, in which they have not been used before (e.g. nitride fuel in BWR). These fuels come with a promise of improved characteristics such as safe, high temperature operation, spent fuel transmutation or fuel cycle extension, for which reasons their potentialis worth assessment and investigatio...

  7. Boron Nitride Nanotubes

    Science.gov (United States)

    Smith, Michael W. (Inventor); Jordan, Kevin (Inventor); Park, Cheol (Inventor)

    2012-01-01

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  8. Boron nitride composites

    Science.gov (United States)

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2016-02-16

    According to one embodiment, a composite product includes hexagonal boron nitride (hBN), and a plurality of cubic boron nitride (cBN) particles, wherein the plurality of cBN particles are dispersed in a matrix of the hBN. According to another embodiment, a composite product includes a plurality of cBN particles, and one or more borate-containing binders.

  9. Boron nitride composites

    Energy Technology Data Exchange (ETDEWEB)

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2016-02-16

    According to one embodiment, a composite product includes hexagonal boron nitride (hBN), and a plurality of cubic boron nitride (cBN) particles, wherein the plurality of cBN particles are dispersed in a matrix of the hBN. According to another embodiment, a composite product includes a plurality of cBN particles, and one or more borate-containing binders.

  10. Nitrogen Availability Of Nitriding Atmosphere In Controlled Gas Nitriding Processes

    Directory of Open Access Journals (Sweden)

    Michalski J.

    2015-06-01

    Full Text Available Parameters which characterize the nitriding atmosphere in the gas nitriding process of steel are: the nitriding potential KN, ammonia dissociation rate α and nitrogen availabilitymN2. The article discusses the possibilities of utilization of the nitriding atmosphere’s nitrogen availability in the design of gas nitriding processes of alloyed steels in atmospheres derived from raw ammonia, raw ammonia diluted with pre-dissociated ammonia, with nitrogen, as well as with both nitrogen and pre-dissociated ammonia. The nitriding processes were accomplished in four series. The parameters selected in the particular processes were: process temperature (T, time (t, value of nitriding potential (KN, corresponding to known dissociation rate of the ammonia which dissociates during the nitriding process (α. Variable parameters were: nitrogen availability (mN2, composition of the ingoing atmosphere and flow rate of the ingoing atmosphere (FIn.

  11. Metal Nitrides for Plasmonic Applications

    DEFF Research Database (Denmark)

    Naik, Gururaj V.; Schroeder, Jeremy; Guler, Urcan;

    2012-01-01

    Metal nitrides as alternatives to metals such as gold could offer many advantages when used as plasmonic material. We show that transition metal nitrides can replace metals providing equally good optical performance for many plasmonic applications.......Metal nitrides as alternatives to metals such as gold could offer many advantages when used as plasmonic material. We show that transition metal nitrides can replace metals providing equally good optical performance for many plasmonic applications....

  12. Nitride quantum light sources

    Science.gov (United States)

    Zhu, T.; Oliver, R. A.

    2016-02-01

    Prototype nitride quantum light sources, particularly single-photon emitters, have been successfully demonstrated, despite the challenges inherent in this complex materials system. The large band offsets available between different nitride alloys have allowed device operation at easily accessible temperatures. A wide range of approaches has been explored: not only self-assembled quantum dot growth but also lithographic methods for site-controlled nanostructure formation. All these approaches face common challenges, particularly strong background signals which contaminate the single-photon stream and excessive spectral diffusion of the quantum dot emission wavelength. If these challenges can be successfully overcome, then ongoing rapid progress in the conventional III-V semiconductors provides a roadmap for future progress in the nitrides.

  13. Synthesis and Optimization of the Sintering Kinetics of Actinide Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Drryl P. Butt; Brian Jaques

    2009-03-31

    Research conducted for this NERI project has advanced the understanding and feasibility of nitride nuclear fuel processing. In order to perform this research, necessary laboratory infrastructure was developed; including basic facilities and experimental equipment. Notable accomplishments from this project include: the synthesis of uranium, dysprosium, and cerium nitrides using a novel, low-cost mechanical method at room temperature; the synthesis of phase pure UN, DyN, and CeN using thermal methods; and the sintering of UN and (Ux, Dy1-x)N (0.7 ≤ X ≤ 1) pellets from phase pure powder that was synthesized in the Advanced Materials Laboratory at Boise State University.

  14. Transition Metal Nitrides for Electrocatalytic Energy Conversion: Opportunities and Challenges.

    Science.gov (United States)

    Xie, Junfeng; Xie, Yi

    2016-03-07

    Electrocatalytic energy conversion has been considered as one of the most efficient and promising pathways for realizing energy storage and energy utilization in modern society. To improve electrocatalytic reactions, specific catalysts are needed to lower the overpotential. In the search for efficient alternatives to noble metal catalysts, transition metal nitrides have attracted considerable interest due to their high catalytic activity and unique electronic structure. Over the past few decades, numerous nitride-based catalysts have been explored with respect to their ability to drive various electrocatalytic reactions, such as the hydrogen evolution reaction and the oxygen evolution reaction to achieve water splitting and the oxygen reduction reaction coupled with the methanol oxidation reaction to construct fuel cells or rechargeable Li-O2 batteries. This Minireview provides a brief overview of recent progress on electrocatalysts based on transition metal nitrides, and outlines the current challenges and future opportunities.

  15. Analysis of plasma nitrided steels

    Science.gov (United States)

    Salik, J.; Ferrante, J.; Honecy, F.; Hoffman, R., Jr.

    1987-01-01

    The analysis of plasma nitrided steels can be divided to two main categories - structural and chemical. Structural analysis can provide information not only on the hardening mechanisms but also on the fundamental processes involved. Chemical analysis can be used to study the kinetics for the nitriding process and its mechanisms. In this paper preliminary results obtained by several techniques of both categories are presented and the applicability of those techniques to the analysis of plasma-nitrided steels is discussed.

  16. Fatigue modelling for gas nitriding

    Directory of Open Access Journals (Sweden)

    H. Weil

    2016-10-01

    Full Text Available The present study aims to develop an algorithm able to predict the fatigue lifetime of nitrided steels. Linear multi-axial fatigue criteria are used to take into account the gradients of mechanical properties provided by the nitriding process. Simulations on rotating bending fatigue specimens are made in order to test the nitrided surfaces. The fatigue model is applied to the cyclic loading of a gear from a simulation using the finite element software Ansys. Results show the positive contributions of nitriding on the fatigue strength

  17. Advanced fast reactor fuels program. Second annual progress report, July 1, 1975--September 30, 1976

    Energy Technology Data Exchange (ETDEWEB)

    Baker, R.D. (comp.)

    1978-12-01

    Results of steady-state (EBR-II) irradiation testing, off-normal irradiation design and testing, fuel-cladding compatibility, and chemical stability of uranium--plutonium carbide and nitride fuels are presented.

  18. Titanium Nitride Cermets

    Science.gov (United States)

    1952-07-01

    C ermets 7 Effect of Amount of Metal on Strength of TiN-Ni-Cr....26 Cerme ts S Effect of Amount of Metal on Strength of TiN-Co-Cr....27 Cermets 9...Figures 7 and 8. Titanium Nitride-Nickel-Chromium Cerme ts From Figure 7, it can be seen that 2900OF was the better firing temperature. The 20% metal

  19. Plasmonic Titanium Nitride Nanostructures via Nitridation of Nanopatterned Titanium Dioxide

    DEFF Research Database (Denmark)

    Guler, Urcan; Zemlyanov, Dmitry; Kim, Jongbum

    2017-01-01

    Plasmonic titanium nitride nanostructures are obtained via nitridation of titanium dioxide. Nanoparticles acquired a cubic shape with sharper edges following the rock-salt crystalline structure of TiN. Lattice constant of the resulting TiN nanoparticles matched well with the tabulated data. Energ...

  20. Gallium nitride electronics

    Science.gov (United States)

    Rajan, Siddharth; Jena, Debdeep

    2013-07-01

    In the past two decades, there has been increasing research and industrial activity in the area of gallium nitride (GaN) electronics, stimulated first by the successful demonstration of GaN LEDs. While the promise of wide band gap semiconductors for power electronics was recognized many years before this by one of the contributors to this issue (J Baliga), the success in the area of LEDs acted as a catalyst. It set the field of GaN electronics in motion, and today the technology is improving the performance of several applications including RF cell phone base stations and military radar. GaN could also play a very important role in reducing worldwide energy consumption by enabling high efficiency compact power converters operating at high voltages and lower frequencies. While GaN electronics is a rapidly evolving area with active research worldwide, this special issue provides an opportunity to capture some of the great advances that have been made in the last 15 years. The issue begins with a section on epitaxy and processing, followed by an overview of high-frequency HEMTs, which have been the most commercially successful application of III-nitride electronics to date. This is followed by review and research articles on power-switching transistors, which are currently of great interest to the III-nitride community. A section of this issue is devoted to the reliability of III-nitride devices, an area that is of increasing significance as the research focus has moved from not just high performance but also production-worthiness and long-term usage of these devices. Finally, a group of papers on new and relatively less studied ideas for III-nitride electronics, such as interband tunneling, heterojunction bipolar transistors, and high-temperature electronics is included. These areas point to new areas of research and technological innovation going beyond the state of the art into the future. We hope that the breadth and quality of articles in this issue will make it

  1. Platinum nitride with fluorite structure

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Rong; Zhang, Xiao-Feng

    2005-01-31

    The mechanical stability of platinum nitride has been studied using first-principles calculations. By calculating the single-crystal elastic constants, we show that platinum nitride can be stabilized in the fluorite structure, in which the nitrogen atoms occupy all the tetrahedral interstitial sites of the metal lattice. The stability is attributed to the pseudogap effect from analysis of the electronic structure.

  2. Optical characterization of gallium nitride

    NARCIS (Netherlands)

    Kirilyuk, Victoria

    2002-01-01

    Group III-nitrides have been considered a promising system for semiconductor devices since a few decades, first for blue- and UV-light emitting diodes, later also for high-frequency/high-power applications. Due to the lack of native substrates, heteroepitaxially grown III-nitride layers are usually

  3. Electrochemical nitridation of metal surfaces

    Science.gov (United States)

    Wang, Heli; Turner, John A.

    2015-06-30

    Electrochemical nitridation of metals and the produced metals are disclosed. An exemplary method of electrochemical nitridation of metals comprises providing an electrochemical solution at low temperature. The method also comprises providing a three-electrode potentiostat system. The method also comprises stabilizing the three-electrode potentiostat system at open circuit potential. The method also comprises applying a cathodic potential to a metal.

  4. Functionalized boron nitride nanotubes

    Science.gov (United States)

    Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

    2014-04-22

    A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

  5. Effects of Aqueous Vapour Consistence in Nitriding Furnace on the Quality of the Sintered Nitride

    Institute of Scientific and Technical Information of China (English)

    WANGZijiang

    1998-01-01

    If the aqueous vapour consistence is too high(>0.7%),it is very disadvantageous to the sintered products in the nitriding furnace,when silcon nitride bonded silicon carbide products are synthesized by nitridation of silicon.

  6. Fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Enomoto, Hirofumi.

    1989-05-22

    This invention aims to maintain a long-term operation with stable cell output characteristics by uniformly supplying an electrolyte from the reserver to the matrix layer over the entire matrix layer, and further to prevent the excessive wetting of the catalyst layer by smoothly absorbing the volume change of the electrolyte, caused by the repeated stop/start-up of the fuel cell, within the reserver system. For this purpose, in this invention, an electrolyte transport layer, which connects with an electrolyte reservor formed at the electrode end, is partly formed between the electrode material and the catalyst layer; a catalyst layer, which faces the electrolyte transport layer, has through-holes, which connect to the matrix, dispersely distributed. The electrolyte-transport layer is a thin sheet of a hydrophilic fibers which are non-wovens of such fibers as carbon, silicon carbide, silicon nitride or inorganic oxides. 11 figs.

  7. Surface modified stainless steels for PEM fuel cell bipolar plates

    Science.gov (United States)

    Brady, Michael P [Oak Ridge, TN; Wang, Heli [Littleton, CO; Turner, John A [Littleton, CO

    2007-07-24

    A nitridation treated stainless steel article (such as a bipolar plate for a proton exchange membrane fuel cell) having lower interfacial contact electrical resistance and better corrosion resistance than an untreated stainless steel article is disclosed. The treated stainless steel article has a surface layer including nitrogen-modified chromium-base oxide and precipitates of chromium nitride formed during nitridation wherein oxygen is present in the surface layer at a greater concentration than nitrogen. The surface layer may further include precipitates of titanium nitride and/or aluminum oxide. The surface layer in the treated article is chemically heterogeneous surface rather than a uniform or semi-uniform surface layer exclusively rich in chromium, titanium or aluminum. The precipitates of titanium nitride and/or aluminum oxide are formed by the nitriding treatment wherein titanium and/or aluminum in the stainless steel are segregated to the surface layer in forms that exhibit a low contact resistance and good corrosion resistance.

  8. Study of the Active Screen Plasma Nitriding

    Institute of Scientific and Technical Information of China (English)

    Zhao Cheng; C. X. Li; H. Dong; T. Bell

    2004-01-01

    Active screen plasma nitriding (ASPN) is a novel nitriding process, which overcomes many of the practical problems associated with the conventional DC plasma nitriding (DCPN). Experimental results showed that the metallurgical characteristics and hardening effect of 722M24 steel nitrided by ASPN at both floating potential and anodic (zero) potential were similar to those nitrided by DCPN. XRD and high-resolution SEM analysis indicated that iron nitride particles with sizes in sub-micron scale were deposited on the specimen surface in AS plasma nitriding. These indicate that the neutral iron nitride particles, which are sputtered from the active screen and transferred through plasma to specimen surface, are considered to be the dominant nitrogen carder in ASPN. The OES results show that NH could not be a critical species in plasma nitriding.

  9. Resistance of Silicon Nitride Turbine Components to Erosion and Hot Corrosion/oxidation Attack

    Science.gov (United States)

    Strangmen, Thomas E.; Fox, Dennis S.

    1994-01-01

    Silicon nitride turbine components are under intensive development by AlliedSignal to enable a new generation of higher power density auxiliary power systems. In order to be viable in the intended applications, silicon nitride turbine airfoils must be designed for survival in aggressive oxidizing combustion gas environments. Erosive and corrosive damage to ceramic airfoils from ingested sand and sea salt must be avoided. Recent engine test experience demonstrated that NT154 silicon nitride turbine vanes have exceptional resistance to sand erosion, relative to superalloys used in production engines. Similarly, NT154 silicon nitride has excellent resistance to oxidation in the temperature range of interest - up to 1400 C. Hot corrosion attack of superalloy gas turbine components is well documented. While hot corrosion from ingested sea salt will attack silicon nitride substantially less than the superalloys being replaced in initial engine applications, this degradation has the potential to limit component lives in advanced engine applications. Hot corrosion adversely affects the strength of silicon nitride in the 850 to 1300 C range. Since unacceptable reductions in strength must be rapidly identified and avoided, AlliedSignal and the NASA Lewis Research Center have pioneered the development of an environmental life prediction model for silicon nitride turbine components. Strength retention in flexure specimens following 1 to 3300 hour exposures to high temperature oxidation and hot corrosion has been measured and used to calibrate the life prediction model. Predicted component life is dependent upon engine design (stress, temperature, pressure, fuel/air ratio, gas velocity, and inlet air filtration), mission usage (fuel sulfur content, location (salt in air), and times at duty cycle power points), and material parameters. Preliminary analyses indicate that the hot corrosion resistance of NT154 silicon nitride is adequate for AlliedSignal's initial engine

  10. Synthesis of ternary metal nitride nanoparticles using mesoporous carbon nitride as reactive template.

    Science.gov (United States)

    Fischer, Anna; Müller, Jens Oliver; Antonietti, Markus; Thomas, Arne

    2008-12-23

    Mesoporous graphitic carbon nitride was used as both a nanoreactor and a reactant for the synthesis of ternary metal nitride nanoparticles. By infiltration of a mixture of two metal precursors into mesoporous carbon nitride, the pores act first as a nanoconfinement, generating amorphous mixed oxide nanoparticles. During heating and decomposition, the carbon nitride second acts as reactant or, more precisely, as a nitrogen source, which converts the preformed mixed oxide nanoparticles into the corresponding nitride (reactive templating). Using this approach, ternary metal nitride particles with diameters smaller 10 nm composed of aluminum gallium nitride (Al-Ga-N) and titanium vanadium nitride (Ti-V-N) were synthesized. Due to the confinement effect of the carbon nitride matrix, the composition of the resulting metal nitride can be easily adjusted by changing the concentration of the preceding precursor solution. Thus, ternary metal nitride nanoparticles with continuously adjustable metal composition can be produced.

  11. Boron nitride converted carbon fiber

    Science.gov (United States)

    Rousseas, Michael; Mickelson, William; Zettl, Alexander K.

    2016-04-05

    This disclosure provides systems, methods, and apparatus related to boron nitride converted carbon fiber. In one aspect, a method may include the operations of providing boron oxide and carbon fiber, heating the boron oxide to melt the boron oxide and heating the carbon fiber, mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide, and converting at least a portion of the carbon fiber to boron nitride.

  12. Hemocompatibility of titanium nitride.

    Science.gov (United States)

    Dion, I; Baquey, C; Candelon, B; Monties, J R

    1992-10-01

    The left ventricular assist device is based on the principle of the Maillard-Wenkel rotative pump. The materials which make up the pump must present particular mechanical, tribological, thermal and chemical properties. Titanium nitride (TiN) because of its surface properties and graphite because of its bulk characteristics have been chosen. The present study evaluated the in vitro hemocompatibility of TiN coating deposited by the chemical vapor deposition process. Protein adsorption, platelet retention and hemolysis tests have been carried out. In spite of some disparities, the TiN behavior towards albumin and fibrinogen is interesting, compared with the one of a reference medical grade elastomer. The platelet retention test gives similar results as those achieved with the same elastomer. The hemolysis percentage is near to zero. TiN shows interesting characteristics, as far as mechanical and tribological problems are concerned, and presents very encouraging blood tolerability properties.

  13. Study on behavior of plasma nitrided 316L in PEMFC working conditions

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Rujin [Institute of Materials and Technology, Dalian Maritime University, Linghailu No.1, Ganjingzi District, Dalian, Lianoing 116026 (China); College of Materials and Engineering, Dalian Jiaotong University, Dalian 116028 (China); Sun, Juncai [Institute of Materials and Technology, Dalian Maritime University, Linghailu No.1, Ganjingzi District, Dalian, Lianoing 116026 (China); Wang, Jianli [Department of Basic Science, Changchun University of Technology, Changchun 130012 (China)

    2008-12-15

    Stainless steel bipolar plates for the polymer electrolyte membrane fuel cell (PEMFC) offer many advantages over conventional machined graphite and graphite-composites. However, the interfacial ohmic loss between the metallic bipolar plate and membrane electrode assembly due to corrosion decreases the overall power output of PEMFC. A lower temperature (at 370 C) plasma nitriding was applied to modify the surface of stainless steel 316L bipolar plates. The results of electrochemical measurements show that corrosion resistance of the plasma nitrided 316L is improved in simulated PEMFC anode/cathode environments purged with H{sub 2}/air at 70 C. The surface conductivity of the nitrided layer is better than that of the air-formed oxide film. The interfacial contact resistance (ICR) between the passive film and carbon paper increases very little after potentiostatic polarization for 4 h, which indicates potential for good stability of this material in highly corrosive fuel cell environments. (author)

  14. Fuel flexible fuel injector

    Science.gov (United States)

    Tuthill, Richard S; Davis, Dustin W; Dai, Zhongtao

    2015-02-03

    A disclosed fuel injector provides mixing of fuel with airflow by surrounding a swirled fuel flow with first and second swirled airflows that ensures mixing prior to or upon entering the combustion chamber. Fuel tubes produce a central fuel flow along with a central airflow through a plurality of openings to generate the high velocity fuel/air mixture along the axis of the fuel injector in addition to the swirled fuel/air mixture.

  15. Quantum oscillations of nitrogen atoms in uranium nitride

    Science.gov (United States)

    Aczel, A. A.; Granroth, G. E.; MacDougall, G. J.; Buyers, W. J. L.; Abernathy, D. L.; Samolyuk, G. D.; Stocks, G. M.; Nagler, S. E.

    2012-10-01

    The vibrational excitations of crystalline solids corresponding to acoustic or optic one-phonon modes appear as sharp features in measurements such as neutron spectroscopy. In contrast, many-phonon excitations generally produce a complicated, weak and featureless response. Here we present time-of-flight neutron scattering measurements for the binary solid uranium nitride, showing well-defined, equally spaced, high-energy vibrational modes in addition to the usual phonons. The spectrum is that of a single atom, isotropic quantum harmonic oscillator and characterizes independent motions of light nitrogen atoms, each found in an octahedral cage of heavy uranium atoms. This is an unexpected and beautiful experimental realization of one of the fundamental, exactly solvable problems in quantum mechanics. There are also practical implications, as the oscillator modes must be accounted for in the design of generation IV nuclear reactors that plan to use uranium nitride as a fuel.

  16. Point defects in thorium nitride: A first-principles study

    Science.gov (United States)

    Pérez Daroca, D.; Llois, A. M.; Mosca, H. O.

    2016-11-01

    Thorium and its compounds (carbides and nitrides) are being investigated as possible materials to be used as nuclear fuels for Generation-IV reactors. As a first step in the research of these materials under irradiation, we study the formation energies and stability of point defects in thorium nitride by means of first-principles calculations within the framework of density functional theory. We focus on vacancies, interstitials, Frenkel pairs and Schottky defects. We found that N and Th vacancies have almost the same formation energy and that the most energetically favorable defects of all studied in this work are N interstitials. These kind of results for ThN, to the best authors' knowledge, have not been obtained previously, neither experimentally, nor theoretically.

  17. Leachability of nitrided ilmenite in hydrochloric acid

    CSIR Research Space (South Africa)

    Swanepoel, JJ

    2010-10-01

    Full Text Available Titanium nitride in upgraded nitrided ilmenite (bulk of iron removed) can selectively be chlorinated to produce titanium tetrachloride. Except for iron, most other components present during this low temperature (ca. 200 °C) chlorination reaction...

  18. Plasmonic titanium nitride nanostructures for perfect absorbers

    DEFF Research Database (Denmark)

    Guler, Urcan; Li, Wen-Wei; Kinsey, Nathaniel

    2013-01-01

    We propose a metamaterial based perfect absorber in the visible region, and investigate the performance of titanium nitride as an alternative plasmonic material. Numerical and experimental results reveal that titanium nitride performs better than gold as a plasmonic absorbing material...

  19. Cathodic Cage Plasma Nitriding: An Innovative Technique

    OpenAIRE

    Sousa,R.R.M.; de Araújo, F. O.; J. A. P. da Costa; Brandim,A.S.; R. A. de Brito; C. Alves

    2012-01-01

    Cylindrical samples of AISI 1020, AISI 316, and AISI 420 steels, with different heights, were simultaneously treated by a new technique of ionic nitriding, entitled cathodic cage plasma nitriding (CCPN), in order to evaluate the efficiency of this technique to produce nitrided layers with better properties compared with those obtained using conventional ionic nitriding technique. This method is able to eliminate the edge effect in the samples, promoting a better uniformity of temperature, and...

  20. Rational design of metal nitride redox materials for solar-driven ammonia synthesis

    Science.gov (United States)

    Michalsky, Ronald; Pfromm, Peter H.; Steinfeld, Aldo

    2015-01-01

    Fixed nitrogen is an essential chemical building block for plant and animal protein, which makes ammonia (NH3) a central component of synthetic fertilizer for the global production of food and biofuels. A global project on artificial photosynthesis may foster the development of production technologies for renewable NH3 fertilizer, hydrogen carrier and combustion fuel. This article presents an alternative path for the production of NH3 from nitrogen, water and solar energy. The process is based on a thermochemical redox cycle driven by concentrated solar process heat at 700–1200°C that yields NH3 via the oxidation of a metal nitride with water. The metal nitride is recycled via solar-driven reduction of the oxidized redox material with nitrogen at atmospheric pressure. We employ electronic structure theory for the rational high-throughput design of novel metal nitride redox materials and to show how transition-metal doping controls the formation and consumption of nitrogen vacancies in metal nitrides. We confirm experimentally that iron doping of manganese nitride increases the concentration of nitrogen vacancies compared with no doping. The experiments are rationalized through the average energy of the dopant d-states, a descriptor for the theory-based design of advanced metal nitride redox materials to produce sustainable solar thermochemical ammonia. PMID:26052421

  1. Rational design of metal nitride redox materials for solar-driven ammonia synthesis.

    Science.gov (United States)

    Michalsky, Ronald; Pfromm, Peter H; Steinfeld, Aldo

    2015-06-01

    Fixed nitrogen is an essential chemical building block for plant and animal protein, which makes ammonia (NH3) a central component of synthetic fertilizer for the global production of food and biofuels. A global project on artificial photosynthesis may foster the development of production technologies for renewable NH3 fertilizer, hydrogen carrier and combustion fuel. This article presents an alternative path for the production of NH3 from nitrogen, water and solar energy. The process is based on a thermochemical redox cycle driven by concentrated solar process heat at 700-1200°C that yields NH3 via the oxidation of a metal nitride with water. The metal nitride is recycled via solar-driven reduction of the oxidized redox material with nitrogen at atmospheric pressure. We employ electronic structure theory for the rational high-throughput design of novel metal nitride redox materials and to show how transition-metal doping controls the formation and consumption of nitrogen vacancies in metal nitrides. We confirm experimentally that iron doping of manganese nitride increases the concentration of nitrogen vacancies compared with no doping. The experiments are rationalized through the average energy of the dopant d-states, a descriptor for the theory-based design of advanced metal nitride redox materials to produce sustainable solar thermochemical ammonia.

  2. Theoretical Compton profile of diamond, boron nitride and carbon nitride

    Science.gov (United States)

    Aguiar, Julio C.; Quevedo, Carlos R.; Gomez, José M.; Di Rocco, Héctor O.

    2017-09-01

    In the present study, we used the generalized gradient approximation method to determine the electron wave functions and theoretical Compton profiles of the following super-hard materials: diamond, boron nitride (h-BN), and carbon nitride in its two known phases: βC3N4 and gC3N4 . In the case of diamond and h-BN, we compared our theoretical results with available experimental data. In addition, we used the Compton profile results to determine cohesive energies and found acceptable agreement with previous experiments.

  3. Ceramic processing of boron nitride insulators

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, C. S.; McCulloch, R. W.

    1977-01-01

    Fuel pin simulators (FPS) are the prime elements of several test facilities at the Oak Ridge National Laboratory (ORNL). These experimental facilities are used to conduct out-of-reactor thermal-hydraulic and mechanical interaction safety tests for both light-water and breeder reactor programs. The FPS units simulate the geometry, heat flux profiles, and operational capabilities of a reactor core element under steady-state and transient conditions. They are subjected to temperatures as high as 1600/sup 0/C (2900/sup 0/F) and power levels as high as 57.5 kW/m (17.5 kW/ft) as well as severe thermal stresses during transient tests. The insulating material in the narrow annulus between the heating coil and the FPS sheath is subjected to very rigorous conditions. Accuracy of the reactor safety test information and validity of the test data depend on the heat flux uniformity under all test conditions and on the reliable operation of all fuel pin simulators and their internal thermocouples. Boron nitride (BN), because of its high degree of chemical inertness combined with its relatively unique properties of high thermal conductivity and low electrical conductivity, is the most suitable insulating material for FPS. The important BN properties, thermal conductivity and electrical resistance, are strongly influenced by crystallite orientation and by impurities. The article describes new BN powder processing techniques, which optimize these properties.

  4. Mathematical Modelling of Nitride Layer Growth of Low Temperature Gas and Plasma Nitriding of AISI 316L

    Directory of Open Access Journals (Sweden)

    Triwiyanto A.

    2014-07-01

    Full Text Available This paper present mathematical model which developed to predict the nitrided layer thickness (case depth of gas nitrided and plasma nitrided austenitic stainless steel according to Fick’s first law for pure iron by adapting and manipulating the Hosseini’s model to fit the diffusion mechanism where nitrided structure formed by nitrided AISI 316L austenitic stainless steel. The mathematical model later tested against various actual gas nitriding and plasma nitriding experimental results with varying nitriding temperature and nitriding duration to see whether the model managed to successfully predict the nitrided layer thickness. This model predicted the coexistence of ε-Fe2-3N and γ΄-Fe4N under the present nitriding process parameters. After the validation process, it is proven that the mathematical model managed to predict the nitrided layer growth of the gas nitrided and plasma nitrided of AISI 316L SS up to high degree of accuracy.

  5. III-Nitride nanowire optoelectronics

    Science.gov (United States)

    Zhao, Songrui; Nguyen, Hieu P. T.; Kibria, Md. G.; Mi, Zetian

    2015-11-01

    Group-III nitride nanowire structures, including GaN, InN, AlN and their alloys, have been intensively studied in the past decade. Unique to this material system is that its energy bandgap can be tuned from the deep ultraviolet (~6.2 eV for AlN) to the near infrared (~0.65 eV for InN). In this article, we provide an overview on the recent progress made in III-nitride nanowire optoelectronic devices, including light emitting diodes, lasers, photodetectors, single photon sources, intraband devices, solar cells, and artificial photosynthesis. The present challenges and future prospects of III-nitride nanowire optoelectronic devices are also discussed.

  6. Boron Nitride Nanoribbons from Exfoliation of Boron Nitride Nanotubes

    Science.gov (United States)

    Hung, Ching-Cheh; Hurst, Janet; Santiago, Diana

    2017-01-01

    Two types of boron nitride nanotubes (BNNTs) were exfoliated into boron nitride nanoribbons (BNNR), which were identified using transmission electron microscopy: (1) commercial BNNTs with thin tube walls and small diameters. Tube unzipping was indicated by a large decrease of the sample's surface area and volume for pores less than 2 nm in diameter. (2) BNNTs with large diameters and thick walls synthesized at NASA Glenn Research Center. Here, tube unraveling was indicated by a large increase in external surface area and pore volume. For both, the exfoliation process was similar to the previous reported method to exfoliate commercial hexagonal boron nitride (hBN): Mixtures of BNNT, FeCl3, and NaF (or KF) were sequentially treated in 250 to 350 C nitrogen for intercalation, 500 to 750 C air for exfoliation, and finally HCl for purification. Property changes of the nanosized boron nitride throughout this process were also similar to the previously observed changes of commercial hBN during the exfoliation process: Both crystal structure (x-ray diffraction data) and chemical properties (Fourier-transform infrared spectroscopy data) of the original reactant changed after intercalation and exfoliation, but most (not all) of these changes revert back to those of the reactant once the final, purified products are obtained.

  7. Homogeneous dispersion of gallium nitride nanoparticles in a boron nitride matrix by nitridation with urea.

    Science.gov (United States)

    Kusunose, Takafumi; Sekino, Tohru; Ando, Yoichi

    2010-07-01

    A Gallium Nitride (GaN) dispersed boron nitride (BN) nanocomposite powder was synthesized by heating a mixture of gallium nitrate, boric acid, and urea in a hydrogen atmosphere. Before heat treatment, crystalline phases of urea, boric acid, and gallium nitrate were recognized, but an amorphous material was produced by heat treatment at 400 degrees C, and then was transformed into GaN and turbostratic BN (t-BN) by further heat treatment at 800 degrees C. TEM obsevations of this composite powder revealed that single nanosized GaN particles were homogeneously dispersed in a BN matrix. Homogeneous dispersion of GaN nanoparticles was thought to be attained by simultaneously nitriding gallium nitrate and boric acid to GaN and BN with urea.

  8. Investigation into nitrided spur gears

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S.; Coban, A.; Nickel, J.; Sunar, M.; Sami, M.; Abdul Aleem, B.J. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia)

    1996-12-01

    The cold forging method has been widely used in industry to produce machine parts. In general, gears are produced by shaping or hobbing. One of the shaping techniques is precision forging, which has several advantages over hobbing. In the present study, cold forging of spur gears from Ti-6Al-4V material is introduced. To improve the surface properties of the resulting gears, plasma nitriding was carried out. Nuclear reaction analysis was carried out to obtain the nitrogen concentration, while the micro-PIXE technique was used to determine the elemental distribution in the matrix after forging and nitriding processes. Scanning electron microscopy and x-ray powder diffraction were used to investigate the metallurgical changes and formation of nitride components in the surface region. Microhardness and friction tests were carried out to measure the hardness depth profile and friction coefficient at the surface. Finally, scoring failure tests were conducted to determine the rotational speed at which the gears failed. Three distinct regions were obtained in the nitride region, and at the initial stages of the scoring tests, failure in surface roughness was observed in the vicinity of the tip of the gear tooth. This occurred at a particular rotational speed and work input.

  9. Investigation into nitrided spur gears

    Science.gov (United States)

    Yilbas, B. S.; Coban, A.; Nickel, J.; Sunar, M.; Sami, M.; Aleem, B. J. Abdul

    1996-12-01

    The cold forging method has been widely used in industry to produce machine parts. In general, gears are produced by shaping or hobbing. One of the shaping techniques is precision forging, which has several advantages over hobbing. In the present study, cold forging of spur gears from Ti-6A1-4V material is introduced. To improve the surface properties of the resulting gears, plasma nitriding was carried out. Nuclear reaction analysis was carried out to obtain the nitrogen concentration, while the micro-PIXE technique was used to determine the elemental distribution in the matrix after forging and nitriding processes. Scanning electron microscopy and x-ray powder diffraction were used to investigate the metallurgical changes and formation of nitride components in the surface region. Microhardness and friction tests were carried out to measure the hardness depth profile and friction coefficient at the surface. Finally, scoring failure tests were conducted to determine the rotational speed at which the gears failed. Three distinct regions were obtained in the nitride region, and at the initial stages of the scoring tests, failure in surface roughness was observed in the vicinity of the tip of the gear tooth. This occurred at a particular rotational speed and work input.

  10. Pumped lithium loop test to evaluate advanced refractory metal alloys and simulated nuclear fuel elements

    Science.gov (United States)

    Brandenburf, G. P.; Hoffman, E. E.; Smith, J. P.

    1974-01-01

    The performance was determined of refractory metal alloys and uranium nitride fuel element specimens in flowing 1900F (1083C) lithium. The results demonstrate the suitability of the selected materials to perform satisfactorily from a chemical compatibility standpoint.

  11. The new Polish nitriding and nitriding like processes in the modern technology

    Energy Technology Data Exchange (ETDEWEB)

    Has, Z.; Kula, P. [Technical Univ. of Lodz (Poland)

    1995-12-31

    Modern technological methods for making nitrided layers and low-friction combined layers have been described. The possibilities of structures and properties forming were analyzed as well as the area and examples of application were considered. Nitrided layers are applied in high loaded frictional couples, widely. They can be formed on steel or cast iron machine parts by the classic gas nitriding process or by modern numerous nitriding technologies.

  12. Indium gallium nitride multijunction solar cell simulation using silvaco atlas

    OpenAIRE

    Garcia, Baldomero

    2007-01-01

    This thesis investigates the potential use of wurtzite Indium Gallium Nitride as photovoltaic material. Silvaco Atlas was used to simulate a quad-junction solar cell. Each of the junctions was made up of Indium Gallium Nitride. The band gap of each junction was dependent on the composition percentage of Indium Nitride and Gallium Nitride within Indium Gallium Nitride. The findings of this research show that Indium Gallium Nitride is a promising semiconductor for solar cell use. United...

  13. Phase identification of iron nitrides and iron oxy-nitrides with Mossbauer spectroscopy

    NARCIS (Netherlands)

    Borsa, DM; Boerma, DO

    2003-01-01

    The Mossbauer spectroscopy of all known Fe nitrides is the topic of this paper. Most of the data were accumulated during a study of the growth of the various Fe nitride phases using molecular beam epitaxy of Fe in the presence of a flux of atomic N, or by post-nitriding freshly grown Fe layers also

  14. Composite Reinforcement using Boron Nitride Nanotubes

    Science.gov (United States)

    2014-05-09

    Final 3. DATES COVERED (From - To) 11-Mar-2013 to 10-Mar-2014 4. TITLE AND SUBTITLE Composite Reinforcement using Boron Nitride Nanotubes...AVAILABILITY STATEMENT Approved for public release. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Boron nitride nanotubes have been proposed as a...and titanium (Ti) metal clusters with boron nitride nanotubes (BNNT). First-principles density-functional theory plus dispersion (DFT-D) calculations

  15. Analysis of plasma-nitrided steels

    Science.gov (United States)

    Salik, J.; Ferrante, J.; Honecy, F.; Hoffman, R., Jr.

    1986-01-01

    The analysis of plasma nitrided steels can be divided to two main categories - structural and chemical. Structural analysis can provide information not only on the hardening mechanisms but also on the fundamental processes involved. Chemical analysis can be used to study the kinetics for the nitriding process and its mechanisms. In this paper preliminary results obtained by several techniques of both categories are presented and the applicability of those techniques to the analysis of plasma-nitrided steels is discussed.

  16. The interaction between nitride uranium and stainless steel

    Science.gov (United States)

    Shornikov, D. P.; Nikitin, S. N.; Tarasov, B. A.; Baranov, V. G.; Yurlova, M. S.

    2016-04-01

    Uranium nitride is most popular nuclear fuel for Fast Breeder Reactor New Generation. In-pile experiments at reactor BOR-60 was shown an interaction between nitride fuel and stainless steel in the range of 8-11% burn up (HA). In order to investigate this interaction has been done diffusion tests of 200 h and has been shown that the reaction occurs in the temperature range 1000-1100 ° C. UN interacted with steel in case of high pollution oxygen (1000-2000 ppm). Also has been shown to increase interaction UN with EP-823 steel in the presence of cesium. In this case the interaction layer had a thickness about 2-3 μm. Has been shown minimal interaction with new ODS steel EP-450. The interaction layer had a thickness less then 2 μm. Did not reveal the influence of tellurium and iodine increased interaction. It was show compatibility at 1000 °C between UN and EP-450 ODS steel, chrome steel, alloying aluminium and silicium.

  17. Evaluation and silicon nitride internal combustion engine components. Final report, Phase I

    Energy Technology Data Exchange (ETDEWEB)

    Voldrich, W. [Allied-Signal Aerospace Co., Torrance, CA (United States). Garrett Ceramic Components Div.

    1992-04-01

    The feasibility of silicon nitride (Si{sub 3}N{sub 4}) use in internal combustion engines was studied by testing three different components for wear resistance and lower reciprocating mass. The information obtained from these preliminary spin rig and engine tests indicates several design changes are necessary to survive high-stress engine applications. The three silicon nitride components tested were valve spring retainers, tappet rollers, and fuel pump push rod ends. Garrett Ceramic Components` gas-pressure sinterable Si{sub 3}N{sub 4} (GS-44) was used to fabricate the above components. Components were final machined from densified blanks that had been green formed by isostatic pressing of GS-44 granules. Spin rig testing of the valve spring retainers indicated that these Si{sub 3}N{sub 4} components could survive at high RPM levels (9,500) when teamed with silicon nitride valves and lower spring tension than standard titanium components. Silicon nitride tappet rollers showed no wear on roller O.D. or I.D. surfaces, steel axles and lifters; however, due to the uncrowned design of these particular rollers the cam lobes indicated wear after spin rig testing. Fuel pump push rod ends were successful at reducing wear on the cam lobe and rod end when tested on spin rigs and in real-world race applications.

  18. AFC-1 Transmutation Fuels Post-Irradiation Hot Cell Examination 4-8 at.% - Final Report (Irradiation Experiments AFC-1B, -1F and -1Æ)

    Energy Technology Data Exchange (ETDEWEB)

    Bruce Hilton; Douglas Porter; Steven Hayes

    2006-09-01

    The AFC-1B, AFC-1F and AFC-1Æ irradiation tests are part of a series of test irradiations designed to evaluate the feasibility of the use of actinide bearing fuel forms in advanced fuel cycles for the transmutation of transuranic elements from nuclear waste. The tests were irradiated in the Idaho National Laboratory’s (INL) Advanced Test Reactor (ATR) to an intermediate burnup of 4 to 8 at% (2.7 - 6.8 x 1020 fiss/cm3). The tests contain metallic and nitride fuel forms with non-fertile (i.e., no uranium) and low-fertile (i.e., uranium bearing) compositions. Results of postirradiation hot cell examinations of AFC-1 irradiation tests are reported for eleven metallic alloy transmutation fuel rodlets and five nitride transmutation fuel rodlets. Non-destructive examinations included visual examination, dimensional inspection, gamma scan analysis, and neutron radiography. Detailed examinations, including fission gas puncture and analysis, metallography / ceramography and isotopics and burnup analyses, were performed on five metallic alloy and three nitride transmutation fuels. Fuel performance of both metallic alloy and nitride fuel forms was best correlated with fission density as a burnup metric rather than at.% depletion. The actinide bearing transmutation metallic alloy compositions exhibit irradiation performance very similar to U-xPu-10Zr fuel at equivalent fission densities. The irradiation performance of nitride transmutation fuels was comparable to limited data published on mixed nitride systems.

  19. Silicon nitride equation of state

    Science.gov (United States)

    Brown, Robert C.; Swaminathan, Pazhayannur K.

    2017-01-01

    This report presents the development of a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4).1 Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonal β-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data that have indicated a complex and slow time dependent phase change to the c-Si3N4 phase. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products; however, the need for a kinetic approach is suggested to combine with the single component solid models to simulate and further investigate the global phase coexistences.

  20. Nucleation of iron nitrides during gaseous nitriding of iron; the effect of a preoxidation treatment

    DEFF Research Database (Denmark)

    Friehling, Peter B.; Poulsen, Finn Willy; Somers, Marcel A.J.

    2001-01-01

    grains. On prolonged nitriding, immediate nucleation at the surface of iron grains becomes possible. Calculated incubation times for the nucleation of gamma'-Fe4N1-x during nitriding are generally longer than those observed experimentally in the present work. The incubation time is reduced dramatically......The nucleation of iron nitrides during gaseous nitriding has been investigated using light microscopy and X-ray diffraction. Initially, the nucleation of gamma'-Fe4N1-x on a pure iron surface starts at grain boundaries meeting the surface, from where the nitride grains grow laterally into the iron...

  1. Low temperature anodic bonding to silicon nitride

    DEFF Research Database (Denmark)

    Weichel, Steen; Reus, Roger De; Bouaidat, Salim;

    2000-01-01

    Low-temperature anodic bonding to stoichiometric silicon nitride surfaces has been performed in the temperature range from 3508C to 4008C. It is shown that the bonding is improved considerably if the nitride surfaces are either oxidized or exposed to an oxygen plasma prior to the bonding. Both bulk...

  2. Composite Reinforcement using Boron Nitride Nanotubes

    Science.gov (United States)

    2016-11-15

    ApprovedOMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for...nitride nanotubes change with the presence of atomic oxygen were also carried out. 15.  SUBJECT TERMS Nanotubes, Boron Nitride, Composites, Theoretical

  3. PECVD silicon nitride diaphragms for condenser microphones

    NARCIS (Netherlands)

    Scheeper, P.R.; Voorthuyzen, J.A.; Bergveld, P.

    1991-01-01

    The application of plasma-enhanced chemical vapour deposited (PECVD) silicon nitride as a diaphragm material for condenser microphones has been investigated. By means of adjusting the SiH4/NH3 gas-flow composition, silicon-rich silicon nitride films have been obtained with a relatively low tensile s

  4. Method of preparation of uranium nitride

    Science.gov (United States)

    Kiplinger, Jaqueline Loetsch; Thomson, Robert Kenneth James

    2013-07-09

    Method for producing terminal uranium nitride complexes comprising providing a suitable starting material comprising uranium; oxidizing the starting material with a suitable oxidant to produce one or more uranium(IV)-azide complexes; and, sufficiently irradiating the uranium(IV)-azide complexes to produce the terminal uranium nitride complexes.

  5. Thermodynamics, kinetics and process control of nitriding

    DEFF Research Database (Denmark)

    Mittemeijer, Eric J.; Somers, Marcel A. J.

    1999-01-01

    , the nitriding result is determined largely by the kinetics of the process. The nitriding kinetics have been shown to be characterised by the occurring local near-equilibria and stationary states at surfaces and interfaces, and the diffusion coefficient of nitrogen in the various phases, for which new data have...

  6. Cathodic Cage Plasma Nitriding: An Innovative Technique

    Directory of Open Access Journals (Sweden)

    R. R. M. de Sousa

    2012-01-01

    Full Text Available Cylindrical samples of AISI 1020, AISI 316, and AISI 420 steels, with different heights, were simultaneously treated by a new technique of ionic nitriding, entitled cathodic cage plasma nitriding (CCPN, in order to evaluate the efficiency of this technique to produce nitrided layers with better properties compared with those obtained using conventional ionic nitriding technique. This method is able to eliminate the edge effect in the samples, promoting a better uniformity of temperature, and consequently, a smaller variation of the thickness/height relation can be obtained. The compound layers were characterized by X-ray diffraction, optical microscopy, and microhardness test profile. The results were compared with the properties of samples obtained with the conventional nitriding, for the three steel types. It was verified that samples treated by CCPN process presented, at the same temperature, a better uniformity in the thickness and absence of the edge effect.

  7. Hard carbon nitride and method for preparing same

    Science.gov (United States)

    Haller, E.E.; Cohen, M.L.; Hansen, W.L.

    1992-05-05

    Novel crystalline [alpha](silicon nitride-like)-carbon nitride and [beta](silicon nitride-like)-carbon nitride are formed by sputtering carbon in the presence of a nitrogen atmosphere onto a single crystal germanium or silicon, respectively, substrate. 1 figure.

  8. Molten-Salt-Based Growth of Group III Nitrides

    Science.gov (United States)

    Waldrip, Karen E.; Tsao, Jeffrey Y.; Kerley, Thomas M.

    2008-10-14

    A method for growing Group III nitride materials using a molten halide salt as a solvent to solubilize the Group-III ions and nitride ions that react to form the Group III nitride material. The concentration of at least one of the nitride ion or Group III cation is determined by electrochemical generation of the ions.

  9. Solvothermal synthesis: a new route for preparing nitrides

    CERN Document Server

    Demazeau, G; Denis, A; Largeteau, A

    2002-01-01

    Solvothermal synthesis appears to be an interesting route for preparing nitrides such as gallium nitride and aluminium nitride, using ammonia as solvent. A nitriding additive is used to perform the reaction and, in the case of gallium nitride, is encapsulated by melt gallium. The syntheses are performed in the temperature range 400-800 deg. C and in the pressure range 100-200 MPa. The synthesized powders are characterized by x-ray diffraction and scanning electron microscopy. Finely divided gallium nitride GaN and aluminium nitride AlN, both with wurtzite-type structure, can be obtained by this route.

  10. Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

    Science.gov (United States)

    Yajima, S.; Omori, M.; Hayashi, J.; Kayano, H.; Hamano, M.

    1983-01-01

    A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults.

  11. Radiation Damage and Fission Product Release in Zirconium Nitride

    Energy Technology Data Exchange (ETDEWEB)

    Egeland, Gerald W. [New Mexico Inst. of Mining and Technology, Socorro, NM (United States)

    2005-08-29

    Zirconium nitride is a material of interest to the AFCI program due to some of its particular properties, such as its high melting point, strength and thermal conductivity. It is to be used as an inert matrix or diluent with a nuclear fuel based on transuranics. As such, it must sustain not only high temperatures, but also continuous irradiation from fission and decay products. This study addresses the issues of irradiation damage and fission product retention in zirconium nitride through an assessment of defects that are produced, how they react, and how predictions can be made as to the overall lifespan of the complete nuclear fuel package. Ion irradiation experiments are a standard method for producing radiation damage to a surface for observation. Cryogenic irradiations are performed to produce the maximum accumulation of defects, while elevated temperature irradiations may be used to allow defects to migrate and react to form clusters and loops. Cross-sectional transmission electron microscopy and grazing-incidence x-ray diffractometry were used in evaluating the effects that irradiation has on the crystal structure and microstructure of the material. Other techniques were employed to evaluate physical effects, such as nanoindentation and helium release measurements. Results of the irradiations showed that, at cryogenic temperatures, ZrN withstood over 200 displacements per atom without amorphization. No significant change to the lattice or microstructure was observed. At elevated temperatures, the large amount of damage showed mobility, but did not anneal significantly. Defect clustering was possibly observed, yet the size was too small to evaluate, and bubble formation was not observed. Defects, specifically nitrogen vacancies, affect the mechanical behavior of ZrN dramatically. Current and previous work on dislocations shows a distinct change in slip plane, which is evidence of the bonding characteristics. The stacking-fault energy changes dramatically with

  12. QUARTERLY PROGRESS REPORT JANUARY, FEBRUARY, MARCH, 1967 REACTOR FUELS AND MATERIALS DEVELOPMENT PROGRAMS FOR FUELS AND MATERIALS BRANCH OF USAEC DEVISION OF REACTOR DEVELOPMENT AND TECHNOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Albaugh, F. W.; Bush, S. H.; Cadwell, J. J.; de Halas, D. R.; Worlton, D. C.

    1967-06-01

    Work is reported in the areas of: fast fuels oxides and nitrides; nuclear ceramics; nuclear graphite; basic swelling studies; irradiation damage to reactor metals; ATR gas loop operation and maintenance; metallic fuels; nondestructive testing research; and fast reactor dosimetry and damage analysis.

  13. Method of synthesizing cubic system boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Yuzu, S.; Sumiya, H.; Degawa, J.

    1987-10-13

    A method is described for synthetically growing cubic system boron nitride crystals by using boron nitride sources, solvents for dissolving the boron nitride sources, and seed crystals under conditions of ultra-high pressure and high temperature for maintaining the cubic system boron nitride stable. The method comprises the following steps: preparing a synthesizing vessel having at least two chambers, arrayed in order in the synthesizing vessel so as to be heated according to a temperature gradient; placing the solvents having different eutectic temperatures in each chamber with respect to the boron nitride sources according to the temperature gradient; placing the boron nitride source in contact with a portion of each of the solvents heated at a relatively higher temperature and placing at least a seed crystal in a portion of each of the solvents heated at a relatively lower temperature; and growing at least one cubic system boron nitride crystal in each of the solvents in the chambers by heating the synthesizing vessel for establishing the temperature gradient while maintaining conditions of ultra-high pressure and high temperature.

  14. Transparent polycrystalline cubic silicon nitride

    Science.gov (United States)

    Nishiyama, Norimasa; Ishikawa, Ryo; Ohfuji, Hiroaki; Marquardt, Hauke; Kurnosov, Alexander; Taniguchi, Takashi; Kim, Byung-Nam; Yoshida, Hidehiro; Masuno, Atsunobu; Bednarcik, Jozef; Kulik, Eleonora; Ikuhara, Yuichi; Wakai, Fumihiro; Irifune, Tetsuo

    2017-01-01

    Glasses and single crystals have traditionally been used as optical windows. Recently, there has been a high demand for harder and tougher optical windows that are able to endure severe conditions. Transparent polycrystalline ceramics can fulfill this demand because of their superior mechanical properties. It is known that polycrystalline ceramics with a spinel structure in compositions of MgAl2O4 and aluminum oxynitride (γ-AlON) show high optical transparency. Here we report the synthesis of the hardest transparent spinel ceramic, i.e. polycrystalline cubic silicon nitride (c-Si3N4). This material shows an intrinsic optical transparency over a wide range of wavelengths below its band-gap energy (258 nm) and is categorized as one of the third hardest materials next to diamond and cubic boron nitride (cBN). Since the high temperature metastability of c-Si3N4 in air is superior to those of diamond and cBN, the transparent c-Si3N4 ceramic can potentially be used as a window under extremely severe conditions. PMID:28303948

  15. Friction Characteristics of Nitrided Layers on AISI 430 Ferritic Stainless Steel Obtained by Various Nitriding Processes

    Directory of Open Access Journals (Sweden)

    Hakan AYDIN

    2013-03-01

    Full Text Available The influence of plasma, gas and salt-bath nitriding techniques on the friction coefficient of AISI 430 ferritic stainless steel was studied in this paper. Samples were plasma nitrided in 80 % N2 + 20 % H2 atmosphere at 450 °C and 520 °C for 8 h at a pressure of 2 mbar, gas nitrided in NH3 and CO2 atmosphere at 570 °C for 13 h and salt-bath nitrided in a cyanide-cyanate salt-bath at 570 °C for 1.5 h. Characterisation of nitrided layers on the ferritic stainless steel was carried out by means of microstructure, microhardness, surface roughness and friction coefficient measurements. Friction characteristics of the nitrided layers on the 430 steel were investigated using a ball-on-disc friction-wear tester with a WC-Co ball as the counter-body under dry sliding conditions. Analysis of wear tracks was carried out by scanning electron microscopy. Maximum hardness and maximum case depth were achieved on the plasma nitrided sample at 520 ºC for 8 h. The plasma and salt-bath nitriding techniques significantly decreased the average surface roughness of the 430 ferritic stainless steel. The friction test results showed that the salt-bath nitrided layer had better friction-reducing ability than the other nitrided layers under dry sliding conditions. Furthermore, the friction characteristic of the plasma nitrided layer at 520 ºC was better than that of the plasma nitrided layer at 450 °C.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3819

  16. Residual Stress Induced by Nitriding and Nitrocarburizing

    DEFF Research Database (Denmark)

    Somers, Marcel A.J.

    2005-01-01

    The present chapter is devoted to the various mechanisms involved in the buildup and relief of residual stress in nitrided and nitrocarburized cases. The work presented is an overview of model studies on iron and iron-based alloys. Subdivision is made between the compound (or white) layer......, developing at the surfce and consisting of iron-based (carbo)nitrides, and the diffusion zone underneath, consisting of iron and alloying element nitrides dispersed in af ferritic matrix. Microstructural features are related directly to the origins of stress buildup and stres relief....

  17. Plasma Nitriding of Low Alloy Sintered Steels

    Institute of Scientific and Technical Information of China (English)

    Shiva Mansoorzadeh; Fakhreddin Ashrafizadeh; Xiao-Ying Li; Tom Bell

    2004-01-01

    Fe-3Cr-0.5Mo-0.3C and Fe-3Cr-1.4Mn-0.5Mo-0.367C sintered alloys were plasma nitrided at different temperatures. Characterization was performed by microhardness measurement, optical microscopy, SEM and XRD. Both materials had similar nitriding case properties. 1.4% manganese did not change the as-sintered microstructure considerably.It was observed that monophase compound layer, γ, formed with increasing temperature. Compound layer thickness increased with increasing temperature while nitriding depth increased up to a level and then decreased. Core softening was more pronounced at higher temperature owing to cementite coarsening.

  18. Residual Stress Induced by Nitriding and Nitrocarburizing

    DEFF Research Database (Denmark)

    Somers, Marcel A.J.

    2005-01-01

    The present chapter is devoted to the various mechanisms involved in the buildup and relief of residual stress in nitrided and nitrocarburized cases. The work presented is an overview of model studies on iron and iron-based alloys. Subdivision is made between the compound (or white) layer......, developing at the surfce and consisting of iron-based (carbo)nitrides, and the diffusion zone underneath, consisting of iron and alloying element nitrides dispersed in af ferritic matrix. Microstructural features are related directly to the origins of stress buildup and stres relief....

  19. Atomic Resolution Microscopy of Nitrides in Steel

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson

    2014-01-01

    MN and CrMN type nitride precipitates in 12%Cr steels have been investigated using atomic resolution microscopy. The MN type nitrides were observed to transform into CrMN both by composition and crystallography as Cr diffuses from the matrix into the MN precipitates. Thus a change from one precip...... layer between the crystalline nitride and ferrite matrix. Usually precipitates are described as having (semi) coherent or incoherent interfaces, but in this case it is more energetically favourable to create an amorphous layer instead of the incoherent interface....

  20. Synthesis of ternary nitrides by mechanochemical alloying

    DEFF Research Database (Denmark)

    Jacobsen, C.J.H.; Zhu, J.J.; Lindelov, H.;

    2002-01-01

    Ternary metal nitrides ( of general formula MxM'N-y(z)) attract considerable interest because of their special mechanical, electrical, magnetic, and catalytic properties. Usually they are prepared by ammonolysis of ternary oxides (MxM'O-y(m)) at elevated temperatures. We show that ternary...... nitrides by mechanochemical alloying of a binary transition metal nitride (MxN) with an elemental transition metal. In this way, we have been able to prepare Fe3Mo3N and Co3Mo3N by ball-milling of Mo2N with Fe and Co, respectively. The transformation sequence from the starting materials ( the binary...

  1. Plasma nitriding of AISI 52100 ball bearing steel and effect of heat treatment on nitrided layer

    Indian Academy of Sciences (India)

    Ravindra Kumar; J Alphonsa; Ram Prakash; K S Boob; J Ghanshyam; P A Rayjada; P M Raole; S Mukherjee

    2011-02-01

    In this paper an effort has been made to plasma nitride the ball bearing steel AISI 52100. The difficulty with this specific steel is that its tempering temperature (∼170–200°C) is much lower than the standard processing temperature (∼460–580°C) needed for the plasma nitriding treatment. To understand the mechanism, effect of heat treatment on the nitrided layer steel is investigated. Experiments are performed on three different types of ball bearing races i.e. annealed, quenched and quench-tempered samples. Different gas compositions and process temperatures are maintained while nitriding these samples. In the quenched and quench-tempered samples, the surface hardness has decreased after plasma nitriding process. Plasma nitriding of annealed sample with argon and nitrogen gas mixture gives higher hardness in comparison to the hydrogen–nitrogen gas mixture. It is reported that the later heat treatment of the plasma nitrided annealed sample has shown improvement in the hardness of this steel. X-ray diffraction analysis shows that the dominant phases in the plasma nitrided annealed sample are (Fe2−3N) and (Fe4N), whereas in the plasma nitrided annealed sample with later heat treatment only -Fe peak occurs.

  2. Transition Metal Carbides and Nitrides in Energy Storage and Conversion.

    Science.gov (United States)

    Zhong, Yu; Xia, Xinhui; Shi, Fan; Zhan, Jiye; Tu, Jiangping; Fan, Hong Jin

    2016-05-01

    High-performance electrode materials are the key to advances in the areas of energy conversion and storage (e.g., fuel cells and batteries). In this Review, recent progress in the synthesis and electrochemical application of transition metal carbides (TMCs) and nitrides (TMNs) for energy storage and conversion is summarized. Their electrochemical properties in Li-ion and Na-ion batteries as well as in supercapacitors, and electrocatalytic reactions (oxygen evolution and reduction reactions, and hydrogen evolution reaction) are discussed in association with their crystal structure/morphology/composition. Advantages and benefits of nanostructuring (e.g., 2D MXenes) are highlighted. Prospects of future research trends in rational design of high-performance TMCs and TMNs electrodes are provided at the end.

  3. Surface modification of titanium by plasma nitriding

    Directory of Open Access Journals (Sweden)

    Kapczinski Myriam Pereira

    2003-01-01

    Full Text Available A systematic investigation was undertaken on commercially pure titanium submitted to plasma nitriding. Thirteen different sets of operational parameters (nitriding time, sample temperature and plasma atmosphere were used. Surface analyses were performed using X-ray diffraction, nuclear reaction and scanning electron microscopy. Wear tests were done with stainless steel Gracey scaler, sonic apparatus and pin-on-disc machine. The obtained results indicate that the tribological performance can be improved for samples treated with the following conditions: nitriding time of 3 h; plasma atmosphere consisting of 80%N2+20%H2 or 20%N2+80%H2; sample temperature during nitriding of 600 or 800 degreesC.

  4. Titanium nitride nanoparticles for therapeutic applications

    DEFF Research Database (Denmark)

    Guler, Urcan; Kildishev, Alexander V.; Boltasseva, Alexandra;

    2014-01-01

    Titanium nitride nanoparticles exhibit plasmonic resonances in the biological transparency window where high absorption efficiencies can be obtained with small dimensions. Both lithographic and colloidal samples are examined from the perspective of nanoparticle thermal therapy. © 2014 OSA....

  5. Materials synthesis: Two-dimensional gallium nitride

    Science.gov (United States)

    Koratkar, Nikhil A.

    2016-11-01

    Graphene is used as a capping sheet to synthesize 2D gallium nitride by means of migration-enhanced encapsulation growth. This technique may allow the stabilization of 2D materials that are not amenable to synthesis by traditional methods.

  6. Dissolution of bulk specimens of silicon nitride

    Science.gov (United States)

    Davis, W. F.; Merkle, E. J.

    1981-01-01

    An accurate chemical characterization of silicon nitride has become important in connection with current efforts to incorporate components of this material into advanced heat engines. However, there are problems concerning a chemical analysis of bulk silicon nitride. Current analytical methods require the pulverization of bulk specimens. A pulverization procedure making use of grinding media, on the other hand, will introduce contaminants. A description is given of a dissolution procedure which overcomes these difficulties. It has been found that up to at least 0.6 g solid pieces of various samples of hot pressed and reaction bonded silicon nitride can be decomposed in a mixture of 3 mL hydrofluoric acid and 1 mL nitric acid overnight at 150 C in a Parr bomb. High-purity silicon nitride is completely soluble in nitric acid after treatment in the bomb. Following decomposition, silicon and hydrofluoric acid are volatilized and insoluble fluorides are converted to a soluble form.

  7. Reticulated porous silicon nitride-based ceramics

    OpenAIRE

    Mazzocchi, Mauro; Medri, Valentina; Guicciardi, Stefano

    2012-01-01

    The interest towards the production of porous silicon nitride originates from the unique combination of light weight, of mechanical and physical properties typical of this class of ceramics that make them attractive for many engineering applications. Although pores are generally believed to deteriorate the mechanical properties of ceramics (the strength of porous ceramics decreases exponentially with an increase of porosity), the recent literature reports that porous silicon nitride can exhib...

  8. The Nitrogen-Nitride Anode.

    Energy Technology Data Exchange (ETDEWEB)

    Delnick, Frank M.

    2014-10-01

    Nitrogen gas N 2 can be reduced to nitride N -3 in molten LiCl-KCl eutectic salt electrolyte. However, the direct oxidation of N -3 back to N 2 is kinetically slow and only occurs at high overvoltage. The overvoltage for N -3 oxidation can be eliminated by coordinating the N -3 with BN to form the dinitridoborate (BN 2 -3 ) anion which forms a 1-D conjugated linear inorganic polymer with -Li-N-B-N- repeating units. This polymer precipitates out of solution as Li 3 BN 2 which becomes a metallic conductor upon delithiation. Li 3 BN 2 is oxidized to Li + + N 2 + BN at about the N 2 /N -3 redox potential with very little overvoltage. In this report we evaluate the N 2 /N -3 redox couple as a battery anode for energy storage.

  9. Modelling of the layer evolution during nitriding processes

    Energy Technology Data Exchange (ETDEWEB)

    Figueroa, U.; Oseguera, J.; Schabes, P. [CEM, Atizapan (Mexico)

    1995-12-31

    The evolution of concomitant layers of nitrides is presented. The layer formation is experimentally achieved through two processes: Nitriding with a weakly ionized plasma and nitrogen post-discharge nitriding. The nitriding processes were performed on samples of pure iron and carbon steel. Nitriding temperatures were close but different from the eutectoid transformation point temperature. The experimental layer growth pattern is compared with a model of mass transfer, in which interface mass balance is considered. In the model the authors have considered the formation of one and two compact nitride layers. For short time of treatment, it is shown that a parabolic profile does not satisfactorily describe the layer growth.

  10. History of fast reactor fuel development

    Energy Technology Data Exchange (ETDEWEB)

    Kittel, J.H. (Argonne National Lab., IL (United States)); Frost, B.R.T. (Argonne National Lab., IL (United States)); Mustelier, J.P. (COGEMA, Velizy-Villacoublay (France)); Bagley, K.Q. (AEA Reactor Services, Risley (United Kingdom)); Crittenden, G.C. (AEA Reactor Services, Dounreay (United Kingdom)); Dievoet, J. van (Belgonucleaire, Brussels (Belgium))

    1993-09-01

    The first fast breeder eactors, constructed in the 1945-1960 time period, used metallic fuels composed of uranium, plutonium, or their alloys. They were chosen because most existing reactor operating experience had been obtained on metallic fuels and because they provided the highest breeding ratios. Difficulties in obtaining adequate dimensional stability in metallic fuel elements under conditions of high fuel burnup led in the 1960s to the virtual worldwide choice of ceramic fuels. Although ceramic fuels provide lower breeding performance, this objective is no longer an important consideration in most national programs. Mixed uranium and plutonium dioxide became the ceramic fuel that has received the widest use. The more advanced ceramic fuels, mixed uranium and plutonium carbides and nitrides, continue under development. More recently, metal fuel elements of improved design have joined ceramic fuels in achieving goal burnups of 15 to 20 percent. Low-swelling fuel cladding alloys have also been continuously developed to deal with the unexpected problem of void formation in stainless steels subjected to fast neutron irradiation, a phenomenon first observed in the 1960s. (orig.)

  11. Electrochemical Solution Growth of Magnetic Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Monson, Todd C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pearce, Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-10-01

    Magnetic nitrides, if manufactured in bulk form, would provide designers of transformers and inductors with a new class of better performing and affordable soft magnetic materials. According to experimental results from thin films and/or theoretical calculations, magnetic nitrides would have magnetic moments well in excess of current state of the art soft magnets. Furthermore, magnetic nitrides would have higher resistivities than current transformer core materials and therefore not require the use of laminates of inactive material to limit eddy current losses. However, almost all of the magnetic nitrides have been elusive except in difficult to reproduce thin films or as inclusions in another material. Now, through its ability to reduce atmospheric nitrogen, the electrochemical solution growth (ESG) technique can bring highly sought after (and previously inaccessible) new magnetic nitrides into existence in bulk form. This method utilizes a molten salt as a solvent to solubilize metal cations and nitrogen ions produced electrochemically and form nitrogen compounds. Unlike other growth methods, the scalable ESG process can sustain high growth rates (~mm/hr) even under reasonable operating conditions (atmospheric pressure and 500 °C). Ultimately, this translates into a high throughput, low cost, manufacturing process. The ESG process has already been used successfully to grow high quality GaN. Below, the experimental results of an exploratory express LDRD project to access the viability of the ESG technique to grow magnetic nitrides will be presented.

  12. Multi-objective optimization of steel nitriding

    Directory of Open Access Journals (Sweden)

    P. Cavaliere

    2016-03-01

    Full Text Available Steel nitriding is a thermo-chemical process largely employed in the machine components production to solve mainly wear and fatigue damage in materials. The process is strongly influenced by many different variables such as steel composition, nitrogen potential (range 0.8–35, temperature (range 350–1200 °C, time (range 2–180 hours. In the present study, the influence of such parameters affecting the nitriding layers' thickness, hardness, composition and residual stress was evaluated. The aim was to streamline the process by numerical–experimental analysis allowing to define the optimal conditions for the success of the process. The optimization software that was used is modeFRONTIER (Esteco, through which was defined a set of input parameters (steel composition, nitrogen potential, nitriding time, etc. evaluated on the basis of an optimization algorithm carefully chosen for the multi-objective analysis. The mechanical and microstructural results belonging to the nitriding process, performed with different processing conditions for various steels, are presented. The data were employed to obtain the analytical equations describing nitriding behavior as a function of nitriding parameters and steel composition. The obtained model was validated through control designs and optimized by taking into account physical and processing conditions.

  13. Direct access to macroporous chromium nitride and chromium titanium nitride with inverse opal structure.

    Science.gov (United States)

    Zhao, Weitian; DiSalvo, Francis J

    2015-03-21

    We report a facile synthesis of single-phase, nanocrystalline macroporous chromium nitride and chromium titanium nitride with an inverse opal morphology. The material is characterized using XRD, SEM, HR-TEM/STEM, TGA and XPS. Interconversion of macroporous CrN to Cr2O3 and back to CrN while retaining the inverse opal morphology is also demonstrated.

  14. Junctions between a boron nitride nanotube and a boron nitride sheet.

    Science.gov (United States)

    Baowan, Duangkamon; Cox, Barry J; Hill, James M

    2008-02-20

    For future nanoelectromechanical signalling devices, it is vital to understand how to connect various nanostructures. Since boron nitride nanostructures are believed to be good electronic materials, in this paper we elucidate the classification of defect geometries for combining boron nitride structures. Specifically, we determine possible joining structures between a boron nitride nanotube and a flat sheet of hexagonal boron nitride. Firstly, we determine the appropriate defect configurations on which the tube can be connected, given that the energetically favourable rings for boron nitride structures are rings with an even number of sides. A new formula E = 6+2J relating the number of edges E and the number of joining positions J is established for each defect, and the number of possible distinct defects is related to the so-called necklace and bracelet problems of combinatorial theory. Two least squares approaches, which involve variation in bond length and variation in bond angle, are employed to determine the perpendicular connection of both zigzag and armchair boron nitride nanotubes with a boron nitride sheet. Here, three boron nitride tubes, which are (3, 3), (6, 0) and (9, 0) tubes, are joined with the sheet, and Euler's theorem is used to verify geometrically that the connected structures are sound, and their relationship with the bonded potential energy function approach is discussed. For zigzag tubes (n,0), it is proved that such connections investigated here are possible only for n divisible by 3.

  15. Structural analysis of nitride layer formed on uranium metal by glow plasma surface nitriding

    Energy Technology Data Exchange (ETDEWEB)

    Liu Kezhao, E-mail: liukz@hotmail.com [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Bin Ren [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Xiao Hong [China Academy of Engineering Physics, P.O. Box 919-71, Mianyang 621907 (China); Long Zhong [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Hong Zhanglian, E-mail: hong_zhanglian@zju.edu.cn [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Yang Hui [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Wu Sheng [China Academy of Engineering Physics, P.O. Box 919-71, Mianyang 621907 (China)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer The nitride layer was formed on uranium by glow plasma surface nitriding. Black-Right-Pointing-Pointer Four zones were observed in the nitride layer. Black-Right-Pointing-Pointer The chemical states of uranium, nitrogen, and oxygen were identified by AES. - Abstract: The nitride layer was formed on uranium metal by a glow plasma surface nitriding method. The structure and composition of the layer were investigated by X-ray diffraction and Auger electron spectroscopy. The nitride layer mainly consisted of {alpha}-phase U{sub 2}N{sub 3} nanocrystals with an average grain size about 10-20 nm. Four zones were identified in the layer, which were the oxide surface zone, the nitride mainstay zone, the oxide-existence interface zone, and the nitrogen-diffusion matrix zone. The gradual decrease of binding energies of uranium revealed the transition from oxide to nitride to metal states with the layer depth, while the chemical states of nitrogen and oxygen showed small variation.

  16. Identification of nitriding mechanisms in high purity reaction bonded silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Haggerty, J.S.

    1993-03-01

    The rapid, low-temperature nitriding results from surface effects on the Si particles beginning with loss of chemisorbed H and sequential formation of thin amorphous Si nitride layers. Rapid complete conversion to Si[sub 3]N[sub 4] during the fast reaction can be inhibited when either too few or too many nuclei form on Si particels. Optimally, [approximately] 10 Si[sub 3]N[sub 4] nuclei form per Si particles under rapid, complete nitridation conditions. Nitridation during the slow reaction period appears to progress by both continued reaction of nonpreferred Si[sub 3]N[sub 4] growth interfaces and direct nitridation of the remaining Si/vapor interfaces.

  17. Identification of nitriding mechanisms in high purity reaction bonded silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Haggerty, J.S.

    1993-03-01

    The rapid, low-temperature nitriding results from surface effects on the Si particles beginning with loss of chemisorbed H and sequential formation of thin amorphous Si nitride layers. Rapid complete conversion to Si{sub 3}N{sub 4} during the fast reaction can be inhibited when either too few or too many nuclei form on Si particels. Optimally, {approximately} 10 Si{sub 3}N{sub 4} nuclei form per Si particles under rapid, complete nitridation conditions. Nitridation during the slow reaction period appears to progress by both continued reaction of nonpreferred Si{sub 3}N{sub 4} growth interfaces and direct nitridation of the remaining Si/vapor interfaces.

  18. First-principles study of transition-metal nitrides as diffusion barriers against Al

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Zhi-Gang, E-mail: zmei@anl.gov; Yacout, Abdellatif M.; Kim, Yeon Soo; Hofman, Gerard; Stan, Marius

    2016-04-01

    Using density-functional theory based first-principles calculations we provided a comparative study of the diffusion barrier properties of TiN, ZrN, and HfN against Al for U–Mo dispersion fuel applications. We firstly examined the thermodynamic stability of these transition-metal nitrides with Al. The calculated heats of reaction show that both TiN and ZrN are thermodynamically unstable diffusion barrier materials, which might be decomposed by Al at relatively high temperatures. As a comparison, HfN is a stable diffusion barrier material for Al. To evaluate the kinetic stability of these nitride systems against Al diffusion, we investigated the diffusion mechanisms of Al in TiN, ZrN and HfN using atomic scale simulations. The effect of non-stoichiometry on the defect formation and Al migration was systematically studied.

  19. A review on the development of the advanced fuel fabrication technology

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jung Won; Lee, Yung Woo; Sohn, Dong Sung; Yang, Myung Seung; Bae, Kee Kwang; Nah, Sang Hoh; Kim, Han Soo; Kim, Bong Koo; Song, Keun Woo; Kim, See Hyung [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1995-07-01

    In this state-of art report, the development status of the advanced nuclear fuel was investigated. The current fabrication technology for coated particle fuel and non-oxide fuel such as sol-gel technology, coating technology, and carbothermic reduction reaction has also been examined. In the view point of inherent safety and efficiency in the operation of power plant, the coated particle fuel will keep going on its reputation as nuclear fuel for a high temperature gas cooled reactor, and the nitride fuel is very prospective for the next liquid metal fast breeder reactor. 43 figs., 17 tabs., 96 refs. (Author).

  20. Colloidal Plasmonic Titanium Nitride Nanoparticles: Properties and Applications

    DEFF Research Database (Denmark)

    Guler, Urcan; Suslov, Sergey; Kildishev, Alexander V.

    2015-01-01

    Optical properties of colloidal plasmonic titanium nitride nanoparticles are examined with an eye on their photothermal and photocatalytic applications via transmission electron microscopy and optical transmittance measurements. Single crystal titanium nitride cubic nanoparticles with an average...

  1. Method of manufacture of atomically thin boron nitride

    Science.gov (United States)

    Zettl, Alexander K

    2013-08-06

    The present invention provides a method of fabricating at least one single layer hexagonal boron nitride (h-BN). In an exemplary embodiment, the method includes (1) suspending at least one multilayer boron nitride across a gap of a support structure and (2) performing a reactive ion etch upon the multilayer boron nitride to produce the single layer hexagonal boron nitride suspended across the gap of the support structure. The present invention also provides a method of fabricating single layer hexagonal boron nitride. In an exemplary embodiment, the method includes (1) providing multilayer boron nitride suspended across a gap of a support structure and (2) performing a reactive ion etch upon the multilayer boron nitride to produce the single layer hexagonal boron nitride suspended across the gap of the support structure.

  2. Diffusion kinetics of nitrogen in tantalum during plasma-nitriding

    Institute of Scientific and Technical Information of China (English)

    张德元; 林勤; 曾卫军; 李放; 许兰萍; 付青峰

    2001-01-01

    The activation energies of nitrogen in tantalum on plasma nitriding conditions were calculated according to the experimental data of hardness of plasma-nitriding of tantalum vs time and temperature. The activation energy calculated is 148.873±0.390  kJ/mol. The depth increasing of nitriding layer with time follows square root relation. The nitriding process of tantalum is controlled by diffusion of nitrogen atoms in tantalum solid solution.

  3. Computational Design of Advanced Nuclear Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Savrasov, Sergey [Univ. of California, Davis, CA (United States); Kotliar, Gabriel [Rutgers Univ., Piscataway, NJ (United States); Haule, Kristjan [Rutgers Univ., Piscataway, NJ (United States)

    2014-06-03

    The objective of the project was to develop a method for theoretical understanding of nuclear fuel materials whose physical and thermophysical properties can be predicted from first principles using a novel dynamical mean field method for electronic structure calculations. We concentrated our study on uranium, plutonium, their oxides, nitrides, carbides, as well as some rare earth materials whose 4f eletrons provide a simplified framework for understanding complex behavior of the f electrons. We addressed the issues connected to the electronic structure, lattice instabilities, phonon and magnon dynamics as well as thermal conductivity. This allowed us to evaluate characteristics of advanced nuclear fuel systems using computer based simulations and avoid costly experiments.

  4. Silicon nitride ceramic having high fatigue life and high toughness

    Science.gov (United States)

    Yeckley, Russell L.

    1996-01-01

    A sintered silicon nitride ceramic comprising between about 0.6 mol % and about 3.2 mol % rare earth as rare earth oxide, and between about 85 w/o and about 95 w/o beta silicon nitride grains, wherein at least about 20% of the beta silicon nitride grains have a thickness of greater than about 1 micron.

  5. [The effect of plasma nitriding on tungsten burs].

    Science.gov (United States)

    Cicciu, D; Russo, S; Grasso, C

    1989-01-01

    The authors have experimented the nitriding's effects on some cilindrical burs carbide utilized in dentistry after disamination on the applications methodics on plasma nitriding in neurosurgery, orthopedic surgery and in odontotherapy. This reacherys point out that nitriding plasma a durings increase and cutis greater capacity establish.

  6. Nitridation of chromium powder in ammonia atmosphere

    Institute of Scientific and Technical Information of China (English)

    Ling Li; Qiang Zhen; Rong Li

    2015-01-01

    CrN powder was synthesized by nitriding Cr metal in ammonia gas flow, and its chemical reaction mechanism and nitridation process were studied. Through thermodynamic calculations, the Cr−N−O predominance diagrams were constructed for different tempera-tures. Chromium nitride formed at 700−1200°C under relatively higher nitrogen and lower oxygen partial pressures. Phases in the products were then investigated using X-ray diffraction (XRD), and the Cr2N content varied with reaction temperature and holding time. The results indicate that the Cr metal powder nitridation process can be explained by a diffusion model. Further, Cr2N formed as an intermediate product because of an incomplete reaction, which was observed by high-resolution transmission electron microscopy (HRTEM). After nitriding at 1000°C for 20 h, CrN powder with an average grain size of 63 nm was obtained, and the obtained sample was analyzed by using a scanning electron microscope (SEM).

  7. Single gallium nitride nanowire lasers.

    Science.gov (United States)

    Johnson, Justin C; Choi, Heon-Jin; Knutsen, Kelly P; Schaller, Richard D; Yang, Peidong; Saykally, Richard J

    2002-10-01

    There is much current interest in the optical properties of semiconductor nanowires, because the cylindrical geometry and strong two-dimensional confinement of electrons, holes and photons make them particularly attractive as potential building blocks for nanoscale electronics and optoelectronic devices, including lasersand nonlinear optical frequency converters. Gallium nitride (GaN) is a wide-bandgap semiconductor of much practical interest, because it is widely used in electrically pumped ultraviolet-blue light-emitting diodes, lasers and photodetectors. Recent progress in microfabrication techniques has allowed stimulated emission to be observed from a variety of GaN microstructures and films. Here we report the observation of ultraviolet-blue laser action in single monocrystalline GaN nanowires, using both near-field and far-field optical microscopy to characterize the waveguide mode structure and spectral properties of the radiation at room temperature. The optical microscope images reveal radiation patterns that correlate with axial Fabry-Perot modes (Q approximately 10(3)) observed in the laser spectrum, which result from the cylindrical cavity geometry of the monocrystalline nanowires. A redshift that is strongly dependent on pump power (45 meV microJ x cm(-2)) supports the idea that the electron-hole plasma mechanism is primarily responsible for the gain at room temperature. This study is a considerable advance towards the realization of electron-injected, nanowire-based ultraviolet-blue coherent light sources.

  8. Nonlinear conductivity in silicon nitride

    Science.gov (United States)

    Tuncer, Enis

    2017-08-01

    To better comprehend electrical silicon-package interaction in high voltage applications requires full characterization of the electrical properties of dielectric materials employed in wafer and package level design. Not only the packaging but wafer level dielectrics, i.e. passivation layers, would experience high electric fields generated by the voltage applied pads. In addition the interface between the passivation layer and a mold compound might develop space charge because of the mismatch in electrical properties of the materials. In this contribution electrical properties of a thin silicon nitride (Si3N4) dielectric is reported as a function of temperature and electric field. The measured values later analyzed using different temperature dependent exponential expressions and found that the Mott variable range hopping conduction model was successful to express the data. A full temperature/electric field dependency of conductivity is generated. It was found that the conduction in Si3N4 could be expressed like a field ionization or Fowler-Nordheim mechanism.

  9. Formation and control of stoichiometric hafnium nitride thin films by direct sputtering of hafnium nitride target

    CERN Document Server

    Gotoh, Y; Ishikawa, J; Liao, M Y

    2003-01-01

    Hafnium nitride thin films were prepared by radio-frequency sputter deposition with a hafnium nitride target. Deposition was performed with various rf powers, argon pressures, and substrate temperatures, in order to investigate the influences of these parameters on the film properties, particularly the nitrogen composition. It was found that stoichiometric hafnium nitride films were formed at an argon gas pressure of less than 2 Pa, irrespective of the other deposition parameters within the range investigated. Maintaining the nitrogen composition almost stoichiometric, orientation, stress, and electrical resistivity of the films could be controlled with deposition parameters. (author)

  10. Fracture resistance of surface-nitrided zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Feder, A.; Casellas, D.; Llanes, L.; Anglada, M. [Universidad Politecnica de Cataluna, Barcelona (Spain). Dept. of Material Science and Metallurgy

    2002-07-01

    Heat treatments have been conducted at 1650 C for 2 hours in Y-TZP stabilised with 2.5% molar of yttria in two different environments: in air and in nitrogen gas with the specimens embedded in a zirconium nitride powder bed. Relevant microstructural changes were induced by these heat treatments. It is highlighted the formation of a nitrided surface layer of about 400 {mu}m in thickness. Such layer has clear microstructural differences with respect to the bulk, and is formed by different sublayers with cubic and tetragonal phases with distinct degrees of transformability, as revealed by XRD and Raman spectroscopy. The fracture toughness and the hardness of the nitrided surface layer are higher than for the original Y-TZP. (orig.)

  11. Precipitate-Accommodated Plasma Nitriding for Aluminum Alloys

    Institute of Scientific and Technical Information of China (English)

    Patama Visittipitukul; Tatsuhiko Aizawa; Hideyuki Kuwahara

    2004-01-01

    Reliable surface treatment has been explored to improve the strength and wear resistance of aluminum alloy parts in automotives. Long duration time as well as long pre-sputtering time are required for plasma nitriding of aluminum or its alloys only with the thickness of a few micrometers. New plasma inner nitriding is proposed to realize the fast-rate nitriding of aluminum alloys. Al-6Cu alloy is employed as a targeting material in order to demonstrate the effectiveness of this plasma nitriding. Mechanism of fast-rate nitriding process is discussed with consideration of the role of Al2Cu precipitates.

  12. Low pressure growth of cubic boron nitride films

    Science.gov (United States)

    Ong, Tiong P. (Inventor); Shing, Yuh-Han (Inventor)

    1997-01-01

    A method for forming thin films of cubic boron nitride on substrates at low pressures and temperatures. A substrate is first coated with polycrystalline diamond to provide a uniform surface upon which cubic boron nitride can be deposited by chemical vapor deposition. The cubic boron nitride film is useful as a substitute for diamond coatings for a variety of applications in which diamond is not suitable. any tetragonal or hexagonal boron nitride. The cubic boron nitride produced in accordance with the preceding example is particularly well-suited for use as a coating for ultra hard tool bits and abrasives, especially those intended to use in cutting or otherwise fabricating iron.

  13. Microbial adherence to a nonprecious alloy after plasma nitriding process.

    Science.gov (United States)

    Sonugelen, Mehmet; Destan, Uhmut Iyiyapici; Lambrecht, Fatma Yurt; Oztürk, Berran; Karadeniz, Süleyman

    2006-01-01

    To investigate the microbial adherence to the surfaces of a nonprecious metal alloy after plasma nitriding. The plasma-nitriding process was performed to the surfaces of metals prepared from a nickel-chromium alloy. The microorganisms were labeled with technetium-99m. After the labeling procedure, 60 metal disks were treated with a microorganism for each use. The results revealed that the amount of adherence of all microorganisms on surfaces was changed by plasma-nitriding process; adherence decreased substantially (P plasma nitriding time were not significant (P> .05) With the plasma-nitriding process, the surface properties of nonprecious metal alloys can be changed, leading to decreased microbial adherence.

  14. Local heating with titanium nitride nanoparticles

    DEFF Research Database (Denmark)

    Guler, Urcan; Ndukaife, Justus C.; Naik, Gururaj V.;

    2013-01-01

    We investigate the feasibility of titanium nitride (TiN) nanoparticles as local heat sources in the near infrared region, focusing on biological window. Experiments and simulations provide promising results for TiN, which is known to be bio-compatible.......We investigate the feasibility of titanium nitride (TiN) nanoparticles as local heat sources in the near infrared region, focusing on biological window. Experiments and simulations provide promising results for TiN, which is known to be bio-compatible....

  15. Alkaline Capacitors Based on Nitride Nanoparticles

    Science.gov (United States)

    Aldissi, Matt

    2003-01-01

    High-energy-density alkaline electrochemical capacitors based on electrodes made of transition-metal nitride nanoparticles are undergoing development. Transition- metal nitrides (in particular, Fe3N and TiN) offer a desirable combination of high electrical conductivity and electrochemical stability in aqueous alkaline electrolytes like KOH. The high energy densities of these capacitors are attributable mainly to their high capacitance densities, which, in turn, are attributable mainly to the large specific surface areas of the electrode nanoparticles. Capacitors of this type could be useful as energy-storage components in such diverse equipment as digital communication systems, implanted medical devices, computers, portable consumer electronic devices, and electric vehicles.

  16. Boron Nitride Nanotubes for Spintronics

    Directory of Open Access Journals (Sweden)

    Kamal B. Dhungana

    2014-09-01

    Full Text Available With the end of Moore’s law in sight, researchers are in search of an alternative approach to manipulate information. Spintronics or spin-based electronics, which uses the spin state of electrons to store, process and communicate information, offers exciting opportunities to sustain the current growth in the information industry. For example, the discovery of the giant magneto resistance (GMR effect, which provides the foundation behind modern high density data storage devices, is an important success story of spintronics; GMR-based sensors have wide applications, ranging from automotive industry to biology. In recent years, with the tremendous progress in nanotechnology, spintronics has crossed the boundary of conventional, all metallic, solid state multi-layered structures to reach a new frontier, where nanostructures provide a pathway for the spin-carriers. Different materials such as organic and inorganic nanostructures are explored for possible applications in spintronics. In this short review, we focus on the boron nitride nanotube (BNNT, which has recently been explored for possible applications in spintronics. Unlike many organic materials, BNNTs offer higher thermal stability and higher resistance to oxidation. It has been reported that the metal-free fluorinated BNNT exhibits long range ferromagnetic spin ordering, which is stable at a temperature much higher than room temperature. Due to their large band gap, BNNTs are also explored as a tunnel magneto resistance device. In addition, the F-BNNT has recently been predicted as an ideal spin-filter. The purpose of this review is to highlight these recent progresses so that a concerted effort by both experimentalists and theorists can be carried out in the future to realize the true potential of BNNT-based spintronics.

  17. Boron nitride nanotubes for spintronics.

    Science.gov (United States)

    Dhungana, Kamal B; Pati, Ranjit

    2014-09-22

    With the end of Moore's law in sight, researchers are in search of an alternative approach to manipulate information. Spintronics or spin-based electronics, which uses the spin state of electrons to store, process and communicate information, offers exciting opportunities to sustain the current growth in the information industry. For example, the discovery of the giant magneto resistance (GMR) effect, which provides the foundation behind modern high density data storage devices, is an important success story of spintronics; GMR-based sensors have wide applications, ranging from automotive industry to biology. In recent years, with the tremendous progress in nanotechnology, spintronics has crossed the boundary of conventional, all metallic, solid state multi-layered structures to reach a new frontier, where nanostructures provide a pathway for the spin-carriers. Different materials such as organic and inorganic nanostructures are explored for possible applications in spintronics. In this short review, we focus on the boron nitride nanotube (BNNT), which has recently been explored for possible applications in spintronics. Unlike many organic materials, BNNTs offer higher thermal stability and higher resistance to oxidation. It has been reported that the metal-free fluorinated BNNT exhibits long range ferromagnetic spin ordering, which is stable at a temperature much higher than room temperature. Due to their large band gap, BNNTs are also explored as a tunnel magneto resistance device. In addition, the F-BNNT has recently been predicted as an ideal spin-filter. The purpose of this review is to highlight these recent progresses so that a concerted effort by both experimentalists and theorists can be carried out in the future to realize the true potential of BNNT-based spintronics.

  18. Ultrahard nanotwinned cubic boron nitride.

    Science.gov (United States)

    Tian, Yongjun; Xu, Bo; Yu, Dongli; Ma, Yanming; Wang, Yanbin; Jiang, Yingbing; Hu, Wentao; Tang, Chengchun; Gao, Yufei; Luo, Kun; Zhao, Zhisheng; Wang, Li-Min; Wen, Bin; He, Julong; Liu, Zhongyuan

    2013-01-17

    Cubic boron nitride (cBN) is a well known superhard material that has a wide range of industrial applications. Nanostructuring of cBN is an effective way to improve its hardness by virtue of the Hall-Petch effect--the tendency for hardness to increase with decreasing grain size. Polycrystalline cBN materials are often synthesized by using the martensitic transformation of a graphite-like BN precursor, in which high pressures and temperatures lead to puckering of the BN layers. Such approaches have led to synthetic polycrystalline cBN having grain sizes as small as ∼14 nm (refs 1, 2, 4, 5). Here we report the formation of cBN with a nanostructure dominated by fine twin domains of average thickness ∼3.8 nm. This nanotwinned cBN was synthesized from specially prepared BN precursor nanoparticles possessing onion-like nested structures with intrinsically puckered BN layers and numerous stacking faults. The resulting nanotwinned cBN bulk samples are optically transparent with a striking combination of physical properties: an extremely high Vickers hardness (exceeding 100 GPa, the optimal hardness of synthetic diamond), a high oxidization temperature (∼1,294 °C) and a large fracture toughness (>12 MPa m(1/2), well beyond the toughness of commercial cemented tungsten carbide, ∼10 MPa m(1/2)). We show that hardening of cBN is continuous with decreasing twin thickness down to the smallest sizes investigated, contrasting with the expected reverse Hall-Petch effect below a critical grain size or the twin thickness of ∼10-15 nm found in metals and alloys.

  19. Growth of gallium nitride and indium nitride nanowires on conductive and flexible carbon cloth substrates.

    Science.gov (United States)

    Yang, Yi; Ling, Yichuan; Wang, Gongming; Lu, Xihong; Tong, Yexiang; Li, Yat

    2013-03-07

    We report a general strategy for synthesis of gallium nitride (GaN) and indium nitride (InN) nanowires on conductive and flexible carbon cloth substrates. GaN and InN nanowires were prepared via a nanocluster-mediated growth method using a home built chemical vapor deposition (CVD) system with Ga and In metals as group III precursors and ammonia as a group V precursor. Electron microscopy studies reveal that the group III-nitride nanowires are single crystalline wurtzite structures. The morphology, density and growth mechanism of these nanowires are determined by the growth temperature. Importantly, a photoelectrode fabricated by contacting the GaN nanowires through a carbon cloth substrate shows pronounced photoactivity for photoelectrochemical water oxidation. The ability to synthesize group III-nitride nanowires on conductive and flexible substrates should open up new opportunities for nanoscale photonic, electronic and electrochemical devices.

  20. Defects in III-nitride microdisk cavities

    Science.gov (United States)

    Ren, C. X.; Puchtler, T. J.; Zhu, T.; Griffiths, J. T.; Oliver, R. A.

    2017-03-01

    Nitride microcavities offer an exceptional platform for the investigation of light–matter interactions as well as the development of devices such as high efficiency light emitting diodes (LEDs) and low-threshold nanolasers. Microdisk geometries in particular are attractive for low-threshold lasing applications due to their ability to support high finesse whispering gallery modes (WGMs) and small modal volumes. In this article we review the effect of defects on the properties of nitride microdisk cavities fabricated using photoelectrochemical etching of an InGaN sacrificial superlattice (SSL). Threading dislocations originating from either the original GaN pseudosubstrate are shown to hinder the undercutting of microdisk cavities during the photoelectric chemical etching process resulting in whiskers of unetched material on the underside of microdisks. The unetched whiskers provide a pathway for light to escape, reducing microdisk Q-factor if located in the region occupied by the WGMs. Additionally, dislocations can affect the spectral stability of quantum dot emitters, thus hindering their effective integration in microdisk cavities. Though dislocations are clearly undesirable, the limiting factor on nitride microdisk Q-factor is expected to be internal absorption, indicating that the further optimisation of nitride microdisk cavities must incorporate both the elimination of dislocations and careful tailoring of the active region emission wavelength and background doping levels.

  1. Dynamic Characterization of Silicon Nitride Cantilevers

    NARCIS (Netherlands)

    Babaei Gavan, K.

    2009-01-01

    This thesis describes a series of experiments on dynamical characterization of silicon nitride cantilevers. These devices play an important role in micro-and nanoelectromechanical systems (MEMS and NEMS). They consist of a mechanical part, a sensor or actuator, and an electronic part for readout and

  2. Local residual stress measurements on nitride layers

    NARCIS (Netherlands)

    Mansilla, C.; Ocelik, V.; De Hosson, J. Th. M.

    2015-01-01

    In this work, local stresses in different nitrided maraging steel samples of high practical interest for industrial applications were studied through the so-called micro-slit milling method using a focused ion beam. The nitrogen concentration profiles were acquired by glow discharge optical emission

  3. Nitridation of silicon by nitrogen neutral beam

    Energy Technology Data Exchange (ETDEWEB)

    Hara, Yasuhiro, E-mail: yasuhirohara2002@yahoo.co.jp [Organization for Research and Development of Innovative Science and Technology, Kansai University, Yamate-cho 3-3-35, Suita 564-8680, Osaka (Japan); Shimizu, Tomohiro; Shingubara, Shoso [Department of Mechanical Engineering, Faculty of Engineering Science, Kansai University, Yamate-cho 3-3-35, Suita 564-8680, Osaka (Japan)

    2016-02-15

    Graphical abstract: - Highlights: • Nitrided silicon was formed by nitrogen neutral beam at room temperature. • Si{sub 3}N{sub 4} layer was formed at the acceleration voltage more than 20 V. • Formed Si{sub 3}N{sub 4} layer show the effective as the passivation film in the wet etching process. - Abstract: Silicon nitridation was investigated at room temperature using a nitrogen neutral beam (NB) extracted at acceleration voltages of less than 100 V. X-ray photoelectron spectroscopy (XPS) analysis confirmed the formation of a Si{sub 3}N{sub 4} layer on a Si (1 0 0) substrate when the acceleration voltage was higher than 20 V. The XPS depth profile indicated that nitrogen diffused to a depth of 36 nm for acceleration voltages of 60 V and higher. The thickness of the silicon nitrided layer increased with the acceleration voltages from 20 V to 60 V. Cross-sectional transmission electron microscopy (TEM) analysis indicated a Si{sub 3}N{sub 4} layer thickness of 3.1 nm was obtained at an acceleration voltage of 100 V. Moreover, it was proved that the nitrided silicon layer formed by the nitrogen NB at room temperature was effective as the passivation film in the wet etching process.

  4. Gallium Nitride Crystals: Novel Supercapacitor Electrode Materials.

    Science.gov (United States)

    Wang, Shouzhi; Zhang, Lei; Sun, Changlong; Shao, Yongliang; Wu, Yongzhong; Lv, Jiaxin; Hao, Xiaopeng

    2016-05-01

    A type of single-crystal gallium nitride mesoporous membrane is fabricated and its supercapacitor properties are demonstrated for the first time. The supercapacitors exhibit high-rate capability, stable cycling life at high rates, and ultrahigh power density. This study may expand the range of crystals as high-performance electrode materials in the field of energy storage.

  5. Dynamic Characterization of Silicon Nitride Cantilevers

    NARCIS (Netherlands)

    Babaei Gavan, K.

    2009-01-01

    This thesis describes a series of experiments on dynamical characterization of silicon nitride cantilevers. These devices play an important role in micro-and nanoelectromechanical systems (MEMS and NEMS). They consist of a mechanical part, a sensor or actuator, and an electronic part for readout and

  6. Powdered Hexagonal Boron Nitride Reducing Nanoscale Wear

    Science.gov (United States)

    Chkhartishvili, L.; Matcharashvili, T.; Esiava, R.; Tsagareishvili, O.; Gabunia, D.; Margiev, B.; Gachechiladze, A.

    2013-05-01

    A morphology model is suggested for nano-powdered hexagonal boron nitride that can serve as an effective solid additive to liquid lubricants. It allows to estimate the specific surface, that is a hard-to-measure parameter, based on average size of powder particles. The model can be used also to control nanoscale wear processes.

  7. Metal surface nitriding by laser induced plasma

    Science.gov (United States)

    Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

    1996-10-01

    We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

  8. Nitriding behavior of Ni and Ni-based binary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Fonovic, Matej

    2015-01-15

    Gaseous nitriding is a prominent thermochemical surface treatment process which can improve various properties of metallic materials such as mechanical, tribological and/or corrosion properties. This process is predominantly performed by applying NH{sub 3}+H{sub 2} containing gas atmospheres serving as the nitrogen donating medium at temperatures between 673 K and 873 K (400 C and 600 C). NH{sub 3} decomposes at the surface of the metallic specimen and nitrogen diffuses into the surface adjacent region of the specimen whereas hydrogen remains in the gas atmosphere. One of the most important parameters characterizing a gaseous nitriding process is the so-called nitriding potential (r{sub N}) which determines the chemical potential of nitrogen provided by the gas phase. The nitriding potential is defined as r{sub N} = p{sub NH{sub 3}}/p{sub H{sub 2}{sup 3/2}} where p{sub NH{sub 3}} and p{sub H{sub 2}} are the partial pressures of the NH{sub 3} and H{sub 2} in the nitriding atmosphere. In contrast with nitriding of α-Fe where the nitriding potential is usually in the range between 0.01 and 1 atm{sup -1/2}, nitriding of Ni and Ni-based alloys requires employing nitriding potentials higher than 100 atm{sup -1/2} and even up to ∞ (nitriding in pure NH{sub 3} atmosphere). This behavior is compatible with decreased thermodynamic stability of the 3d-metal nitrides with increasing atomic number. Depending on the nitriding conditions (temperature, nitriding potential and treatment time), different phases are formed at the surface of the Ni-based alloys. By applying very high nitriding potential, formation of hexagonal Ni{sub 3}N at the surface of the specimen (known as external nitriding) leads to the development of a compound layer, which may improve tribological properties. Underneath the Ni{sub 3}N compound layer, two possibilities exist: (i) alloying element precipitation within the nitrided zone (known as internal nitriding) and/or (ii) development of metastable and

  9. Fossil Fuels.

    Science.gov (United States)

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with fossil fuels. Some topics covered are historic facts, development of fuels, history of oil production, current and future trends of the oil industry, refining fossil fuels, and environmental problems. Material in each unit may…

  10. Fossil Fuels.

    Science.gov (United States)

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with fossil fuels. Some topics covered are historic facts, development of fuels, history of oil production, current and future trends of the oil industry, refining fossil fuels, and environmental problems. Material in each unit may…

  11. Examination of Plasma Nitriding Microstructure with Addition of Rare Earths

    Institute of Scientific and Technical Information of China (English)

    张津

    2004-01-01

    Medium-carbon alloy steel was plasma nitrided with rare earths La,Ce and Nd into the nitriding chamber respectively.The nitriding layer microstructures with and without rare earths were compared using optical microscope,normal SEM and high resolution SEM,as well as TEM.It was found that the extent of the influence on plasma nitriding varies with different contents of rare earth.The effect of plasma nitriding is benefit from adding of Ce or Nd.The formation of hard and brittle phase Fe2-3N can be prevented and the butterfly-like structure can be improved by adding Ce or Nd.However,pure La may prevent the diffusion of nitrogen and the formation of iron nitride,and reduce the depth of diffusion layer.

  12. Liquid flow cells having graphene on nitride for microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Adiga, Vivekananda P.; Dunn, Gabriel; Zettl, Alexander K.; Alivisatos, A. Paul

    2016-09-20

    This disclosure provides systems, methods, and apparatus related to liquid flow cells for microscopy. In one aspect, a device includes a substrate having a first and a second oxide layer disposed on surfaces of the substrate. A first and a second nitride layer are disposed on the first and second oxide layers, respectively. A cavity is defined in the first oxide layer, the first nitride layer, and the substrate, with the cavity including a third nitride layer disposed on walls of the substrate and the second oxide layer that define the cavity. A channel is defined in the second oxide layer. An inlet port and an outlet port are defined in the second nitride layer and in fluid communication with the channel. A plurality of viewports is defined in the second nitride layer. A first graphene sheet is disposed on the second nitride layer covering the plurality of viewports.

  13. The Study of Plasma Nitriding of AISI304 Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    WANG Liang; JI Shi-jun; GAO Yu-zhou; SUN Jun-cai

    2004-01-01

    This paper presents results on the plasma nitriding of AISI 304 stainless steel at different temperatures in NH 3 gas. The working pressure was 100~200 Pa and the discharge voltage was 700~800V. The phase of nitrided layer formed on the surface was confirmed by X-ray diffraction. The hardness of the samples was measured by using a Vickers microhardness tester with the load of 50g. After nitriding at about 400 ℃ for two hours a nitrided layer consisting of single γN phase with thickness of 5μm was obtained. Microhardness measurements showed significant increase in the hardness from 240 HV (for untreated samples) up to 950 HV (for nitrided samples at temperature of 420℃). The phase composition, the thickness, the microstructure and the surface topography of the nitrided layer as well as its properties depend essentially on the process parameters.

  14. Wide-bandgap III-Nitride based Second Harmonic Generation

    Science.gov (United States)

    2014-10-02

    Jun-2014 Approved for Public Release; Distribution Unlimited Final Report: Wide-bandgap III - Nitride based Second Harmonic Generation The views...Report: Wide-bandgap III - Nitride based Second Harmonic Generation Report Title It was demonstrated that GaN, AlGaN and AlN lateral polar structures can...research have been socialized to the III - Nitride Optoelectronics Center of Excellence (ARL SEDD) and to the 2013 ARO Staff Research Symposium and at

  15. Dynamic Multiaxial Response of a Hot-Pressed Aluminum Nitride

    Science.gov (United States)

    2012-01-05

    Dynamic Multiaxial Response of a Hot-Pressed Aluminum Nitride by Guangli Hu, C. Q. Chen, K. T. Ramesh, and J. W. McCauley ARL-RP-0487...Laboratory Aberdeen Proving Ground, MD 21005-5066 ARL-RP-0487 June 2014 Dynamic Multiaxial Response of a Hot-Pressed Aluminum Nitride...3. DATES COVERED (From - To) January 2010–January 2013 4. TITLE AND SUBTITLE Dynamic Multiaxial Response of a Hot-Pressed Aluminum Nitride 5a

  16. Magnetism induced by electrochemical nitriding on an austenitic stainless steel

    National Research Council Canada - National Science Library

    Watanabe, Takashi; Sagara, Akio; Hishinuma, Yoshimitsu; Takayama, Sadatsugu; Tanaka, Teruya; Sano, Saburo

    2015-01-01

    .... The Nitrogen diffusion layers were predominately formed at nitrogen concentration of 23 at%. The nitriding process drastically also changed its magnetic property from non-magnetic to ferromagnetic...

  17. EXAFS investigation of low temperature nitrided stainless steel

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny

    2008-01-01

    Low temperature nitrided stainless steel AISI 316 flakes were investigated with EXAFS and X-ray diffraction analysis. The stainless steel flakes were transformed into a mixture of nitrogen expanded austenite and nitride phases. Two treatments were carried out yielding different overall nitrogen...... contents: (1) nitriding in pure NH3 and (2)nitriding in pure NH3 followed by reduction in H2. The majority of the Cr atoms in the stainless steel after treatment 1 and 2 was associated with a nitrogen–chromium bond distance comparable to that of the chemical compound CrN. The possibility of the occurrence...

  18. Comparative infrared study of silicon and germanium nitrides

    Science.gov (United States)

    Baraton, M. I.; Marchand, R.; Quintard, P.

    1986-03-01

    Silicon and germanium nitride (Si 3N 4 and Ge 3N 4) are isomorphic compounds. They have been studied in the β-phase which crystallises in the hexagonal system. The space group is P6 3/m (C 6h2). The IR transmission spectra of these two nitrides are very similar but the absorption frequencies of germanium nitride are shifted to the lower values in comparison with silicon nitride. We noted that the atomic mass effect is the only cause of this shift for the streching modes but not for the bending modes.

  19. Fuel distribution

    Energy Technology Data Exchange (ETDEWEB)

    Tison, R.R.; Baker, N.R.; Blazek, C.F.

    1979-07-01

    Distribution of fuel is considered from a supply point to the secondary conversion sites and ultimate end users. All distribution is intracity with the maximum distance between the supply point and end-use site generally considered to be 15 mi. The fuels discussed are: coal or coal-like solids, methanol, No. 2 fuel oil, No. 6 fuel oil, high-Btu gas, medium-Btu gas, and low-Btu gas. Although the fuel state, i.e., gas, liquid, etc., can have a major impact on the distribution system, the source of these fuels (e.g., naturally-occurring or coal-derived) does not. Single-source, single-termination point and single-source, multi-termination point systems for liquid, gaseous, and solid fuel distribution are considered. Transport modes and the fuels associated with each mode are: by truck - coal, methanol, No. 2 fuel oil, and No. 6 fuel oil; and by pipeline - coal, methane, No. 2 fuel oil, No. 6 oil, high-Btu gas, medium-Btu gas, and low-Btu gas. Data provided for each distribution system include component makeup and initial costs.

  20. Thermodynamics, kinetics and process control of nitriding

    DEFF Research Database (Denmark)

    Mittemeijer, Eric J.; Somers, Marcel A. J.

    1997-01-01

    As a prerequisite for the predictability of properties obtained by a nitriding treatment of iron based workpieces, the relation between the process parameters and the composition and structure of the surface layer produced must be known. At present, even the description of thermodynamic equilibrium...... of pure Fe-N phases has not been fully achieved. It is shown that taking into account the ordering of nitrogen in the epsilon and gamma' iron nitride phases leads to an improved understanding of the Fe-N phase diagram. Although consideration of thermodynamics indicates the state the system strives for...... of the International Federation for Heat Treatment and Surface Engineering held in Brighton, UK on 1-5 September 1996. (C) 1997 The Institute of Materials....

  1. Aluminum Reduction and Nitridation of Bauxite

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhikuan; ZHANG Dianwei; XU Enxia; HOU Xinmei; DONG Yanling

    2007-01-01

    The application of bauxite with low Al2O3 content has been studied in this paper and β-SiAlON has been obtained from two kinds of bauxites (Al203 content 68.08 mass% and 46.30 mass% respectively) by aluminum reduction and nitridation method.The sequence of reactions has been studied using thermal analysis (TG-DTA),X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) with EDS.Compared with carbon thermal reduction and nitridation of aluminosilicates employed presently,the reaction in the system of bauxite-Al-N2 occurs at lower temperature.β-SiAlON appears as one of the main products from 1573K and exists' stably in the range of the present experimental temperature.The microstructure of β-SiAlON obtained at 1773 K is short column with 5-10μm observed by SEM.

  2. Sheath Characteristic in ECR Plasma Nitriding

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The sheath plasma characteristics changing with the negative bias applied to the substrate during electron cyclotron resonance plasma nitriding are studied. The sheath characteristics obtained by a Langmuir single probe and an ion energy analyzer show that when the negative bias applied to the substrate is increasing, the most probable energy of ions in the sheath and the full width of half maximum of ions energy distribution increase, the thickness of the sheath also increases, whereas the saturation current of ion decreases. It has been found from the optical emission spectrum that there are strong lines of N2 and N2+. Based on our experiment results the mechanism of plasma nitriding is discussed.

  3. Boron nitride encapsulated graphene infrared emitters

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, H. R.; Zossimova, E.; Mahlmeister, N. H.; Lawton, L. M.; Luxmoore, I. J.; Nash, G. R., E-mail: g.r.nash@exeter.ac.uk [College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF (United Kingdom)

    2016-03-28

    The spatial and spectral characteristics of mid-infrared thermal emission from devices containing a large area multilayer graphene layer, encapsulated using hexagonal boron nitride, have been investigated. The devices were run continuously in air for over 1000 h, with the emission spectrum covering the absorption bands of many important gases. An approximate solution to the heat equation was used to simulate the measured emission profile across the devices yielding an estimated value of the characteristic length, which defines the exponential rise/fall of the temperature profile across the device, of 40 μm. This is much larger than values obtained in smaller exfoliated graphene devices and reflects the device geometry, and the increase in lateral heat conduction within the devices due to the multilayer graphene and boron nitride layers.

  4. Thermodynamic ground states of platinum metal nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Aberg, D; Sadigh, B; Crowhurst, J; Goncharov, A

    2007-10-09

    We have systematically studied the thermodynamic stabilities of various phases of the nitrides of the platinum metal elements using density functional theory. We show that for the nitrides of Rh, Pd, Ir and Pt two new crystal structures, in which the metal ions occupy simple tetragonal lattice sites, have lower formation enthalpies at ambient conditions than any previously proposed structures. The region of stability can extend up to 17 GPa for PtN{sub 2}. Furthermore, we show that according to calculations using the local density approximation, these new compounds are also thermodynamically stable at ambient pressure and thus may be the ground state phases for these materials. We further discuss the fact that the local density and generalized gradient approximations predict different values of the absolute formation enthalpies as well different relative stabilities between simple tetragonal and the pyrite or marcasite structures.

  5. Atomic-layer deposition of silicon nitride

    CERN Document Server

    Yokoyama, S; Ooba, K

    1999-01-01

    Atomic-layer deposition (ALD) of silicon nitride has been investigated by means of plasma ALD in which a NH sub 3 plasma is used, catalytic ALD in which NH sub 3 is dissociated by thermal catalytic reaction on a W filament, and temperature-controlled ALD in which only a thermal reaction on the substrate is employed. The NH sub 3 and the silicon source gases (SiH sub 2 Cl sub 2 or SiCl sub 4) were alternately supplied. For all these methods, the film thickness per cycle was saturated at a certain value for a wide range of deposition conditions. In the catalytic ALD, the selective deposition of silicon nitride on hydrogen-terminated Si was achieved, but, it was limited to only a thin (2SiO (evaporative).

  6. Group-III Nitride Field Emitters

    Science.gov (United States)

    Bensaoula, Abdelhak; Berishev, Igor

    2008-01-01

    Field-emission devices (cold cathodes) having low electron affinities can be fabricated through lattice-mismatched epitaxial growth of nitrides of elements from group III of the periodic table. Field emission of electrons from solid surfaces is typically utilized in vacuum microelectronic devices, including some display devices. The present field-emission devices and the method of fabricating them were developed to satisfy needs to reduce the cost of fabricating field emitters, make them compatible with established techniques for deposition of and on silicon, and enable monolithic integration of field emitters with silicon-based driving circuitry. In fabricating a device of this type, one deposits a nitride of one or more group-III elements on a substrate of (111) silicon or other suitable material. One example of a suitable deposition process is chemical vapor deposition in a reactor that contains plasma generated by use of electron cyclotron resonance. Under properly chosen growth conditions, the large mismatch between the crystal lattices of the substrate and the nitride causes strains to accumulate in the growing nitride film, such that the associated stresses cause the film to crack. The cracks lie in planes parallel to the direction of growth, so that the growing nitride film becomes divided into microscopic growing single-crystal columns. The outer ends of the fully-grown columns can serve as field-emission tips. By virtue of their chemical compositions and crystalline structures, the columns have low work functions and high electrical conductivities, both of which are desirable for field emission of electrons. From examination of transmission electron micrographs of a prototype device, the average column width was determined to be about 100 nm and the sharpness of the tips was determined to be characterized by a dimension somewhat less than 100 nm. The areal density of the columns was found to about 5 x 10(exp 9)/sq cm . about 4 to 5 orders of magnitude

  7. New nanoforms of carbon and boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Pokropivny, V V [Institute for Problems of Materials Science of National Academy of Sciences of Ukraine (Ukraine); Ivanovskii, A L [Institute of Solid State Chemistry, Urals Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation)], e-mail: Ivanovskii@ihim.uran.ru

    2008-10-31

    Data on new carbon nanostructures including those based on fullerenes, nanotubes as well monolithic diamond-like nanoparticles, nanofibres, various nanocomposites, etc., published in the last decade are generalised. The experimental and theoretical data on their atomic and electronic structures, the nature of chemical bonds and physicochemical properties are discussed. These data are compared with the results obtained in studies of nanoforms of boron nitride, an isoelectronic analogue of carbon. Potential fields of applications of the new nanostructures are considered.

  8. New nanoforms of carbon and boron nitride

    Science.gov (United States)

    Pokropivny, V. V.; Ivanovskii, A. L.

    2008-10-01

    Data on new carbon nanostructures including those based on fullerenes, nanotubes as well monolithic diamond-like nanoparticles, nanofibres, various nanocomposites, etc., published in the last decade are generalised. The experimental and theoretical data on their atomic and electronic structures, the nature of chemical bonds and physicochemical properties are discussed. These data are compared with the results obtained in studies of nanoforms of boron nitride, an isoelectronic analogue of carbon. Potential fields of applications of the new nanostructures are considered.

  9. Silicon Nitride Balls For Cryogenic Bearings

    Science.gov (United States)

    Butner, Myles F.; Ng, Lillian W.

    1990-01-01

    Resistance to wear greater than that of 440C steel. Experiments show lives of ball bearings immersed in liquid nitrogen or liquid oxygen increased significantly when 440C steel balls (running on 440C steel races) replaced by balls of silicon nitride. Developed for use at high temperatures, where lubrication poor or nonexistent. Best wear life of any bearing tested to date and ball material spalls without fracturing. Plans for future tests call for use of liquid oxygen as working fluid.

  10. Silicon Nitride Antireflection Coatings for Photovoltaic Cells

    Science.gov (United States)

    Johnson, C.; Wydeven, T.; Donohoe, K.

    1984-01-01

    Chemical-vapor deposition adapted to yield graded index of refraction. Silicon nitride deposited in layers, refractive index of which decreases with distance away from cell/coating interface. Changing index of refraction allows adjustment of spectral transmittance for wavelengths which cell is most effective at converting light to electric current. Average conversion efficiency of solar cells increased from 8.84 percent to 12.63 percent.

  11. Oxygen radical functionalization of boron nitride nanosheets

    OpenAIRE

    MAY, PETER; Coleman, Jonathan; MCGOVERN, IGNATIUS; GOUNKO, IOURI; Satti, Amro

    2012-01-01

    PUBLISHED The covalent chemical functionalization of exfoliated hexagonal boron-nitride nanosheets (BNNSs) is achieved by the solution phase oxygen radical functionalization of boron atoms in the h-BN lattice. This involves a two-step procedure to initially covalently graft alkoxy groups to boron atoms and the subsequent hydrolytic defunctionalisation of the groups to yield hydroxyl-functionalized BNNSs (OH-BNNSs). Characterization of the functionalized-BNNSs using HR-TEM, Raman, UV-Vis, F...

  12. Defects in III-Nitride Microdisk Cavities

    OpenAIRE

    Ren, C. X.; Puchtler, T. J.; Zhu, T.; Griffiths, J. T.; R. A. Oliver

    2016-01-01

    This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by the Institute of Physics. Nitride microcavities offer an exceptional platform for the investigation of light-matter interactions as well as the development of devices such as high efficiency light emitting diodes (LEDs) and low-threshold nanolasers. Microdisk geometries in particular are attractive for low-threshold lasing applications due to their ability to support high finesse whis...

  13. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    Science.gov (United States)

    Kim, Jae Woo (Inventor); Siochi, Emilie J. (Inventor); Wise, Kristopher E. (Inventor); Lin, Yi (Inventor); Connell, John (Inventor)

    2016-01-01

    A method for joining or repairing boron nitride nanotubes (BNNTs). In joining BNNTs, the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures. In repairing BNNTs, the damaged site of the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures at the damage site.

  14. Formation and Structure of Boron Nitride Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Jiang ZHANG; Zongquan LI; Jin XU

    2005-01-01

    Boron nitride (BN) nanotubes were simply synthesized by heating well-mixed boric acid, urea and iron nitrate powders at 1000℃. A small amount of BN nanowires was also obtained in the resultants. The morphological and structural characters of the BN nanostructures were studied using transmission electron microscopy. Other novel BN nanostructures, such as Y-junction nanotubes and bamboo-like nanotubes, were simultaneously observed. The growth mechanism of the BN nanotubes was discussed briefly.

  15. Wetting and infiltration of nitride bonded silicon nitride by liquid silicon

    Science.gov (United States)

    Schneider, V.; Reimann, C.; Friedrich, J.

    2016-04-01

    Nitride bonded silicon nitride (NBSN) is a promising crucible material for the repeated use in the directional solidification of multicrystalline (mc) silicon ingots for photovoltaic applications. Due to wetting and infiltration, however, silicon nitride in its initial state does not offer the desired reusability. In this work the sessile drop method is used to systematically study the wetting and infiltration behavior of NBSN after applying different oxidation procedures. It is found that the wetting of the NBSN crucible by liquid silicon can be prevented by the oxidation of the geometrical surface. The infiltration of liquid silicon into the porous crucible can be suppressed by oxygen enrichment within the volume of the NBSN, i.e. at the pore walls of the crucibles. The realized reusability of the NBSN is demonstrated by reusing a NBSN crucible six times for the directional solidification of undoped multicrystalline silicon ingots.

  16. Fusion bonding of silicon nitride surfaces

    DEFF Research Database (Denmark)

    Reck, Kasper; Østergaard, Christian; Thomsen, Erik Vilain

    2011-01-01

    While silicon nitride surfaces are widely used in many micro electrical mechanical system devices, e.g. for chemical passivation, electrical isolation or environmental protection, studies on fusion bonding of two silicon nitride surfaces (Si3N4–Si3N4 bonding) are very few and highly application...... specific. Often fusion bonding of silicon nitride surfaces to silicon or silicon dioxide to silicon surfaces is preferred, though Si3N4–Si3N4 bonding is indeed possible and practical for many devices as will be shown in this paper. We present an overview of existing knowledge on Si3N4–Si3N4 bonding and new...... results on bonding of thin and thick Si3N4 layers. The new results include high temperature bonding without any pretreatment, along with improved bonding ability achieved by thermal oxidation and chemical pretreatment. The bonded wafers include both unprocessed and processed wafers with a total silicon...

  17. Gallium nitride based logpile photonic crystals.

    Science.gov (United States)

    Subramania, Ganapathi; Li, Qiming; Lee, Yun-Ju; Figiel, Jeffrey J; Wang, George T; Fischer, Arthur J

    2011-11-09

    We demonstrate a nine-layer logpile three-dimensional photonic crystal (3DPC) composed of single crystalline gallium nitride (GaN) nanorods, ∼100 nm in size with lattice constants of 260, 280, and 300 nm with photonic band gap in the visible region. This unique GaN structure is created through a combined approach of a layer-by-layer template fabrication technique and selective metal organic chemical vapor deposition (MOCVD). These GaN 3DPC exhibit a stacking direction band gap characterized by strong optical reflectance between 380 and 500 nm. By introducing a "line-defect" cavity in the fifth (middle) layer of the 3DPC, a localized transmission mode with a quality factor of 25-30 is also observed within the photonic band gap. The realization of a group III nitride 3DPC with uniform features and a band gap at wavelengths in the visible region is an important step toward realizing complete control of the electromagnetic environment for group III nitride based optoelectronic devices.

  18. Control of Defects in Aluminum Gallium Nitride ((Al)GaN) Films on Grown Aluminum Nitride (AlN) Substrates

    Science.gov (United States)

    2013-02-01

    like HEMTs . A nanolayer of AlGaN over GaN provides extra 2DEG charge density because of the piezoelectric effect of the AlGaN layer. The higher...Control of Defects in Aluminum Gallium Nitride ((Al) GaN ) Films on Grown Aluminum Nitride (AlN) Substrates by Iskander G. Batyrev, Chi-Chin Wu...Aluminum Gallium Nitride ((Al) GaN ) Films on Grown Aluminum Nitride (AlN) Substrates Iskander G. Batyrev and N. Scott Weingarten Weapons and

  19. Development of compound layer of iron (carbo)nitrides during nitriding of steel

    DEFF Research Database (Denmark)

    Ratajski, J.; Tacikowski, J.; Somers, Marcel A.J.

    2003-01-01

    The composition and phase constitution of a compound layer developing during gaseous nitriding was investigated at 853 K for three commercial steels (AISI 120, 4340 and 1090) and Armco iron. The compound layers were characterised by light optical microscopy, X-ray diffraction and electron probe...... microanalysis. The formation of the compound layer occurs along two distinct sequences: alpha-gamma prime-epsilon and/or alpha(theta)-epsilon2-gamma prime-epsilon1. The preferred sequence depends mainly on the chemical composition of steel and on the nitriding potential....

  20. Development of compound layer of iron (carbo)nitrides during nitriding of steel

    DEFF Research Database (Denmark)

    Ratajski, J.; Tacikowski, J.; Somers, Marcel A.J.

    2003-01-01

    The composition and phase constitution of a compound layer developing during gaseous nitriding was investigated at 853 K for three commercial steels (AISI 120, 4340 and 1090) and Armco iron. The compound layers were characterised by light optical microscopy, X-ray diffraction and electron probe...... microanalysis. The formation of the compound layer occurs along two distinct sequences: alpha-gamma prime-epsilon and/or alpha(theta)-epsilon2-gamma prime-epsilon1. The preferred sequence depends mainly on the chemical composition of steel and on the nitriding potential....

  1. UN TRISO Compaction in SiC for FCM Fuel Irradiations

    Energy Technology Data Exchange (ETDEWEB)

    Terrani, Kurt A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Trammell, Michael P. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kiggans, James O. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Jolly, Brian C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Skitt, Darren J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-11-01

    The U.S. Department of Energy Office of Nuclear Energy (DOE-NE) Advanced Fuels Campaign (AFC) is conducting research and development to elevate the technology readiness level of Fully Ceramic Microencapsulated (FCM) fuels, a candidate nuclear fuel with potentially enhanced accident tolerance due to very high fission product retention. One of the early activities in FY17 was to demonstrate production of FCM pellets with uranium nitride TRISO particles. This was carried out in preparation of the larger pellet production campaign in support of the upcoming irradiation testing of this fuel form at INL’s Advanced Test Reactor.

  2. Enhancement of the oxygen reduction on nitride stabilized pt-M (M=Fe, Co, and Ni) core–shell nanoparticle electrocatalysts

    KAUST Repository

    Kuttiyiel, Kurian A.

    2015-04-01

    Given the harsh operating conditions in hydrogen/oxygen fuel cells, the stability of catalysts is one of the critical questions affecting their commercialization. We describe a distinct class of oxygen reduction (ORR) core–shell electrocatalysts comprised of nitride metal cores enclosed by thin Pt shells that is easily synthesized. The synthesis is reproducible and amenable to scale up. Our theoretical analysis and the experimental data indicate that metal nitride nanoparticle cores could significantly enhance the ORR activity as well as the durability of the core–shell catalysts as a consequence of combined geometrical, electronic and segregation effects on the Pt shells. In addition to its fuel cells application, this class of catalysts holds promise to significantly contribute in resolving the problem of platinum scarcity and furthermore indicates the guidelines for future research and development.

  3. Fuel Cells

    DEFF Research Database (Denmark)

    Smith, Anders; Pedersen, Allan Schrøder

    2014-01-01

    Fuel cells have been the subject of intense research and development efforts for the past decades. Even so, the technology has not had its commercial breakthrough yet. This entry gives an overview of the technological challenges and status of fuel cells and discusses the most promising applications...... of the different types of fuel cells. Finally, their role in a future energy supply with a large share of fluctuating sustainable power sources, e.g., solar or wind, is surveyed....

  4. Phase diagrams and synthesis of cubic boron nitride

    CERN Document Server

    Turkevich, V Z

    2002-01-01

    On the basis of phase equilibria, the lowest temperatures, T sub m sub i sub n , above which at high pressures cubic boron nitride crystallization from melt solution is allowable in terms of thermodynamics have been found for a number of systems that include boron nitride.

  5. Vertical III-nitride thin-film power diode

    Energy Technology Data Exchange (ETDEWEB)

    Wierer, Jr., Jonathan; Fischer, Arthur J.; Allerman, Andrew A.

    2017-03-14

    A vertical III-nitride thin-film power diode can hold off high voltages (kV's) when operated under reverse bias. The III-nitride device layers can be grown on a wider bandgap template layer and growth substrate, which can be removed by laser lift-off of the epitaxial device layers grown thereon.

  6. Low temperature gaseous nitriding and carburising of stainless steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A.J.

    2005-01-01

    The response of various austenitic and duplex stainless steel grades to low temperature gaseous nitriding and carburising was investigated. Gaseous nitriding was performed in ammonia/hydrogen mixtures at temperatures ,723 K; gaseous carburising was carried out in carbon monoxide/hydrogen mixtures...

  7. Progress in preparation, properties and application of boron nitride nanomaterials

    Science.gov (United States)

    Wang, Youjun; Han, Jiaqi; Li, Yanjiao; Chen, Hao

    2017-08-01

    Boron nitride nanomaterials have attracted much and more interest in scientific research workers because of their excellent physical and chemical properties. They have become an important research hotspot in today's materials field. In this paper, boron nitride nanoparticles, "fullerenes", nanotubes, nanoribbons and Nano sheets were reviewed in terms of preparation methods, properties and potential applications.

  8. Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

    Science.gov (United States)

    Lowden, Richard A.

    1994-01-01

    A process for chemical vapor deposition of crystalline silicon nitride which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide.

  9. Modeling the kinetics of the nitriding and nitrocarburizing of iron

    DEFF Research Database (Denmark)

    Somers, Marcel A. J.; Mittemeijer, Eric J.

    1998-01-01

    The growth kinetics of the iron-nitride compound layer during nitriding and nitrocarburizing of pure iron has been investigated for various temperatures and various combinations of imposed nitrogen and carbon activities. The results indicate that no local equilibrium occurs at the gas/solid inter...

  10. Nitrogen ion irradiation of Au(110) : formation of gold nitride

    NARCIS (Netherlands)

    Šiller, L.; Hunt, M.R.C.; Brown, J.W.; Coquel, J-M.; Rudolf, P.

    2002-01-01

    Often metal nitrides posses unique properties for applications, such as great hardness, high melting points, chemical stability, novel electrical and magnetic properties. One route to the formation of metal nitride films is through ion irradiation of metal surfaces. In this report, the results of ir

  11. Vertical III-nitride thin-film power diode

    Science.gov (United States)

    Wierer, Jr., Jonathan; Fischer, Arthur J.; Allerman, Andrew A.

    2017-03-14

    A vertical III-nitride thin-film power diode can hold off high voltages (kV's) when operated under reverse bias. The III-nitride device layers can be grown on a wider bandgap template layer and growth substrate, which can be removed by laser lift-off of the epitaxial device layers grown thereon.

  12. Continuous and discontinuous precipitation in Fe-1 at.%Cr-1 at.%Mo alloy upon nitriding; crystal structure and composition of ternary nitrides

    Science.gov (United States)

    Steiner, Tobias; Ramudu Meka, Sai; Rheingans, Bastian; Bischoff, Ewald; Waldenmaier, Thomas; Yeli, Guma; Martin, Tomas L.; Bagot, Paul A. J.; Moody, Michael P.; Mittemeijer, Eric J.

    2016-05-01

    The internal nitriding response of a ternary Fe-1 at.%Cr-1 at.%Mo alloy, which serves as a model alloy for many CrMo-based steels, was investigated. The nitrides developing upon nitriding were characterised by X-ray diffraction, scanning electron microscopy, electron probe microanalysis, transmission electron microscopy and atom probe tomography. The developed nitrides were shown to be (metastable) ternary mixed nitrides, which exhibit complex morphological, compositional and structural transformations as a function of nitriding time. Analogous to nitrided binary Fe-Cr and Fe-Mo alloys, in ternary Fe-Cr-Mo alloys initially continuous precipitation of fine, coherent, cubic, NaCl-type nitride platelets, here with the composition (Cr½,Mo½)N¾, occurs, with the broad faces of the platelets parallel to the {1 0 0}α-Fe lattice planes. These nitrides undergo a discontinuous precipitation reaction upon prolonged nitriding leading to the development of lamellae of a novel, hexagonal CrMoN2 nitride along {1 1 0}α-Fe lattice planes, and of spherical cubic, NaCl-type (Cr,Mo)Nx nitride particles within the ferrite lamellae. The observed structural and compositional changes of the ternary nitrides have been attributed to the thermodynamic and kinetic constraints for the internal precipitation of (misfitting) nitrides in the ferrite matrix.

  13. Low Temperature Gaseous Nitriding of a Stainless Steel Containing Strong Nitride Formers

    DEFF Research Database (Denmark)

    Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Somers, Marcel A. J.

    Low temperature thermochemical surface hardening of the precipitation hardening austenitic stainless steel A286 in solution treated state was investigated. A286 contains, besides high amounts of Cr, also substantial amounts of strong nitride formers as Ti, Al and V. It is shown that simultaneous ...

  14. Epitaxial aluminum nitride tunnel barriers grown by nitridation with a plasma source

    NARCIS (Netherlands)

    Zijlstra, T.; Lodewijk, C.F.J.; Vercruyssen, N.; Tichelaar, F.D.; Loudkov, D.N.; Klapwijk, T.M.

    2007-01-01

    High critical current-density (10 to 420 kA/cm2) superconductor-insulator-superconductor tunnel junctions with aluminum nitride barriers have been realized using a remote nitrogen plasma from an inductively coupled plasma source operated in a pressure range of 10−3–10−1 mbar. We find a much better r

  15. Effect of plasma nitriding and titanium nitride coating on the corrosion resistance of titanium.

    Science.gov (United States)

    Wang, Xianli; Bai, Shizhu; Li, Fang; Li, Dongmei; Zhang, Jing; Tian, Min; Zhang, Qian; Tong, Yu; Zhang, Zichuan; Wang, Guowei; Guo, Tianwen; Ma, Chufan

    2016-09-01

    The passive film on the surface of titanium can be destroyed by immersion in a fluoridated acidic medium. Coating with titanium nitride (TiN) may improve the corrosion resistance of titanium. The purpose of this in vitro study was to investigate the effect of duplex treatment with plasma nitriding and TiN coating on the corrosion resistance of cast titanium. Cast titanium was treated with plasma nitriding and TiN coating. The corrosion resistance of the duplex-treated titanium in fluoride-containing artificial saliva was then investigated through electrochemical and immersion tests. The corroded surface was characterized by scanning electron microscopy (SEM) with energy-dispersive spectroscopy surface scan analysis. The data were analyzed using ANOVA (α=.05) RESULTS: Duplex treatment generated a dense and uniform TiN film with a thickness of 4.5 μm. Compared with untreated titanium, the duplex-treated titanium displayed higher corrosion potential (Ecorr) values (Pplasma nitriding and TiN coating significantly improved the corrosion resistance of cast titanium in a fluoride-containing environment. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  16. Gaseous Nitriding Process of Surface Nanocrystallized (SNCed) Steel

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The behavior of gaseous nitriding on the surface nanocrystallized (SNCed) steel was investigated. The mild steel discs were SNCed on one side by using the method of ultrasonic shot peening. The opposite side of the discs maintained the original coarse-grained condition. The gaseous nitriding was subsequently carried out at three different temperatures:460, 500 and 560℃. The compound layer growth and diffusion behavior were then studied. It was revealed that SNC pretreatment greatly enhances both diffusion coefficient D and surface reaction rate. As a result, nitriding time could be reduced to the half. It was also found that the growth of compound layer with nitriding time conformed with parabolic relationship from the start of nitriding process in the SNCed samples.

  17. Local Heating with Lithographically Fabricated Plasmonic Titanium Nitride Nanoparticles

    DEFF Research Database (Denmark)

    Guler, Urcan; Ndukaife, Justus C.; Naik, Gururaj V.;

    2013-01-01

    Titanium nitride is considered a promising alternative plasmonic material and is known to exhibit localized surface plasmon resonances within the near-infrared biological transparency window. Here, local heating efficiencies of disk-shaped nanoparticles made of titanium nitride and gold are compa......Titanium nitride is considered a promising alternative plasmonic material and is known to exhibit localized surface plasmon resonances within the near-infrared biological transparency window. Here, local heating efficiencies of disk-shaped nanoparticles made of titanium nitride and gold...... are compared in the visible and near-infrared regions numerically and experimentally with samples fabricated using e-beam lithography. Results show that plasmonic titanium nitride nanodisks are efficient local heat sources and outperform gold nanodisks in the biological transparency window, dispensing the need...... for complex particle geometries....

  18. Facile Solid-State Synthesis Route to Metal Nitride Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    Yinxiao DU; Ming LEI; Hui YANG

    2008-01-01

    By a facile and efficient solid-state reaction route using an organic reagent cyanamide (CN2H2) as a precursor with another one being metal oxides, we successfully synthesized seven technologically important metal nitrides including cubic VN, CrN, NbN, hexagonal GaN, AIN, BN, and WN at moderate temperatures. The experimental results show that cyanamide (CN2H2) is a powerfully reducing and nitridizing reagent and the metal oxides are completely converted into the corresponding nitride nanoparticles at lower temperatures than that reported in the conventional methods. It is found that CN2H2 can exhibit some interesting condensation processes, and the final products, highly active carbon nitride species, play a crucial role in the reducing and nitridizing processes.

  19. Additive Manufacturing of Dense Hexagonal Boron Nitride Objects

    Energy Technology Data Exchange (ETDEWEB)

    Marquez Rossy, Andres E [ORNL; Armstrong, Beth L [ORNL; Elliott, Amy M [ORNL; Lara-Curzio, Edgar [ORNL

    2017-05-12

    The feasibility of manufacturing hexagonal boron nitride objects via additive manufacturing techniques was investigated. It was demonstrated that it is possible to hot-extrude thermoplastic filaments containing uniformly distributed boron nitride particles with a volume concentration as high as 60% and that these thermoplastic filaments can be used as feedstock for 3D-printing objects using a fused deposition system. Objects 3D-printed by fused deposition were subsequently sintered at high temperature to obtain dense ceramic products. In a parallel study the behavior of hexagonal boron nitride in aqueous solutions was investigated. It was shown that the addition of a cationic dispersant to an azeotrope enabled the formulation of slurries with a volume concentration of boron nitride as high as 33%. Although these slurries exhibited complex rheological behavior, the results from this study are encouraging and provide a pathway for manufacturing hexagonal boron nitride objects via robocasting.

  20. Design of nitride semiconductors for solar energy conversion

    Energy Technology Data Exchange (ETDEWEB)

    Zakutayev, Andriy

    2016-01-01

    Nitride semiconductors are a promising class of materials for solar energy conversion applications, such as photovoltaic and photoelectrochemical cells. Nitrides can have better solar absorption and electrical transport properties than the more widely studied oxides, as well as the potential for better scalability than other pnictides or chalcogenides. In addition, nitrides are also relatively unexplored compared to other chemistries, so they provide a great opportunity for new materials discovery. This paper reviews the recent advances in the design of novel semiconducting nitrides for solar energy conversion technologies. Both binary and multinary nitrides are discussed, with a range of metal chemistries (Cu3N, ZnSnN2, Sn3N4, etc.) and crystal structures (delafossite, perovskite, spinel, etc.), including a brief overview of wurtzite III-N materials and devices. The current scientific challenges and promising future directions in the field are also highlighted.

  1. Safety Assessment of Boron Nitride as Used in Cosmetics.

    Science.gov (United States)

    Fiume, Monice M; Bergfeld, Wilma F; Belsito, Donald V; Hill, Ronald A; Klaassen, Curtis D; Liebler, Daniel C; Marks, James G; Shank, Ronald C; Slaga, Thomas J; Snyder, Paul W; Andersen, F Alan

    2015-01-01

    The Cosmetic Ingredient Review Expert Panel (Panel) assessed the safety of boron nitride which functions in cosmetics as a slip modifier (ie, it has a lubricating effect). Boron nitride is an inorganic compound with a crystalline form that can be hexagonal, spherical, or cubic; the hexagonal form is presumed to be used in cosmetics. The highest reported concentration of use of boron nitride is 25% in eye shadow formulations. Although boron nitride nanotubes are produced, boron nitride is not listed as a nanomaterial used in cosmetic formulations. The Panel reviewed available chemistry, animal data, and clinical data and concluded that this ingredient is safe in the present practices of use and concentration in cosmetic formulations.

  2. Requirements to the procedure and stages of innovative fuel development

    Science.gov (United States)

    Troyanov, V.; Zabudko, L.; Grachyov, A.; Zhdanova, O.

    2016-04-01

    According to the accepted current understanding under the nuclear fuel we will consider the assembled active zone unit (Fuel assembly) with its structural elements, fuel rods, pellet column, structural materials of fuel rods and fuel assemblies. The licensing process includes justification of safe application of the proposed modifications, including design-basis and experimental justification of the modified items under normal operating conditions and in violation of normal conditions, including accidents as well. Besides the justification of modified units itself, it is required to show the influence of modifications on the performance and safety of the other Reactor Unit’ and Nuclear Plant’ elements (e.g. burst can detection system, transportation and processing operations during fuel handling), as well as to justify the new standards of fuel storage etc. Finally, the modified fuel should comply with the applicable regulations, which often becomes a very difficult task, if only because those regulations, such as the NP-082-07, are not covered modification issues. Making amendments into regulations can be considered as the only solution, but the process is complicated and requires deep grounds for amendments. Some aspects of licensing new nuclear fuel are considered the example of mixed nitride uranium -plutonium fuel application for the BREST reactor unit.

  3. Burn-up characteristics of ADS system utilizing the fuel composition from MOX PWRs spent fuel

    Energy Technology Data Exchange (ETDEWEB)

    Marsodi E-mail: marsodi@batan.go.id; Lasman, K.A.S.; Nishihara, K. E-mail: nishi@omega.tokai.jaeri.go.jp; Osugi, T.; Tsujimoto, K.; Marsongkohadi; Su' ud, Z. E-mail: szaki@fi.itb.ac.id

    2002-12-01

    Burn-up characteristics of accelerator-driven system, ADS has been evaluated utilizing the fuel composition from MOX PWRs spent fuel. The system consists of a high intensity proton beam accelerator, spallation target, and sub-critical reactor core. The liquid lead-bismuth, Pb-Bi, as spallation target, was put in the center of the core region. The general approach was conducted throughout the nitride fuel that allows the utilities to choose the strategy for destroying or minimizing the most dangerous high level wastes in a fast neutron spectrum. The fuel introduced surrounding the target region was the same with the composition of MOX from 33 GWd/t PWRs spent-fuel with 5 year cooling and has been compared with the fuel composition from 45 and 60 GWd/t PWRs spent-fuel with the same cooling time. The basic characteristics of the system such as burn-up reactivity swing, power density, neutron fluxes distribution, and nuclides densities were obtained from the results of the neutronics and burn-up analyses using ATRAS computer code of the Japan Atomic Energy research Institute, JAERI.

  4. Ion nitriding; Proceedings of the International Conference, Cleveland, OH, Sept. 15-17, 1986

    Science.gov (United States)

    Spalvins, T. (Editor)

    1987-01-01

    The present conference discusses plasma-assisted surface coating/modification processes, the applications to date of ion nitriding, the effects of nitrogen on metal surfaces, ion nitriding mechanisms in Cr, Al and Cr + Al-containing 1040 steel, ion nitriding of Al and its alloys, life enhancement for forging dies, novel anode plasma nitriding developments, and a comparative study of the pulsed and dc ion-nitriding behavior in specimens with blind holes. Also discussed are the influence of heating method on ion nitriding, surface hardening of marage steels by ion nitriding without core hardness reduction, plasma nitriding of nodular cast iron sput gears, NbN composites for superconductors, the carburization of tungsten in a glow discharge methane plasma, economic considerations concerning plasma nitriding, and the corrosion properties obtained by ion nitriding.

  5. Method for exfoliation of hexagonal boron nitride

    Science.gov (United States)

    Lin, Yi (Inventor); Connell, John W. (Inventor)

    2012-01-01

    A new method is disclosed for the exfoliation of hexagonal boron nitride into mono- and few-layered nanosheets (or nanoplatelets, nanomesh, nanoribbons). The method does not necessarily require high temperature or vacuum, but uses commercially available h-BN powders (or those derived from these materials, bulk crystals) and only requires wet chemical processing. The method is facile, cost efficient, and scalable. The resultant exfoliated h-BN is dispersible in an organic solvent or water thus amenable for solution processing for unique microelectronic or composite applications.

  6. Fe nanowire encapsulated in boron nitride nanotubes

    Science.gov (United States)

    Koi, Naruhiro; Oku, Takeo; Nishijima, Masahiko

    2005-11-01

    Boron nitride (BN) nanotubes, nanohorns, nanocoils were synthesized by annealing Fe 4N and B powders at 1000 °C for 1 h in nitrogen gas atmosphere. Especially, Fe-filled BN nanotubes were produced, and investigated by high-resolution electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, electron diffraction and energy dispersive X-ray spectroscopy, which indicates that the [110] of Fe is parallel to the BN nanotube axis. Formation mechanism of Fe-filled BN nanotube was speculated based on these results.

  7. Silicon nitride film for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    El amrani, A.; Menous, I.; Mahiou, L.; Touati, A.; Lefgoum, A. [Silicon Technology Unit. 2, Boulevard Frantz Fanon, BP 140 Alger-7 Merveilles, 16200 Algiers (Algeria); Tadjine, R. [Advanced Technologies Development Centre, Cite 20 Aout 1656, Baba hassen, Algiers (Algeria)

    2008-10-15

    In this work, our aim was to determine the deposition parameters leading to optimal optical properties of Silicon nitride (SiN) film for photovoltaic application. The deposition was performed in an industrial pulsed direct-PECVD using a gas mixture of NH{sub 3}/SiH{sub 4}. After defining the optimum deposition parameters, we have chemically evaluated the film quality in BOE solution. Plasma removal of the optimized SiN films from multicrystalline 4-in solar cells allows highlighting and estimating the emitter passivation and ARC effects on the solar cell electrical performance. (author)

  8. Studies of Organometallic Precursors to Aluminum Nitride

    Science.gov (United States)

    1986-05-09

    adduct undergoes thermal decomposition to a series of intermediate R33Al +NH + R3Al :N~H- + -++ AiN + 3R1I (where at CH3, CAH, C09g, etc.) The...which the initially formed Lewis acid/base adduct undergoes thermal decomposition to a series of Intermediate altylaluminum-amide and -imide species...SIOPPLEM.ENTARY NOTATION to be publ ished in Mats. Res. Soc. Syinp. Proc. (19F86) -IL RU SBR _ Aluminum nitride, organomnetallic precutsors,imcl C7Se1

  9. Magnesium doping of boron nitride nanotubes

    Science.gov (United States)

    Legg, Robert; Jordan, Kevin

    2015-06-16

    A method to fabricate boron nitride nanotubes incorporating magnesium diboride in their structure. In a first embodiment, magnesium wire is introduced into a reaction feed bundle during a BNNT fabrication process. In a second embodiment, magnesium in powder form is mixed into a nitrogen gas flow during the BNNT fabrication process. MgB.sub.2 yarn may be used for superconducting applications and, in that capacity, has considerably less susceptibility to stress and has considerably better thermal conductivity than these conventional materials when compared to both conventional low and high temperature superconducting materials.

  10. Nitride Semiconductors Handbook on Materials and Devices

    CERN Document Server

    Ruterana, Pierre; Neugebauer, Jörg

    2003-01-01

    Semiconductor components based on silicon have been used in a wide range of applications for some time now. These elemental semiconductors are now well researched and technologically well developed. In the meantime the focus has switched to a new group of materials: ceramic semiconductors based on nitrides are currently the subject of research due to their optical and electronic characteristics. They open up new industrial possibilities in the field of photosensors, as light sources or as electronic components. This collection of review articles provides a systematic and in-depth overview of t

  11. Hard and low friction nitride coatings and methods for forming the same

    Science.gov (United States)

    Erdemir, Ali; Urgen, Mustafa; Cakir, Ali Fuat; Eryilmaz, Osman Levent; Kazmanli, Kursat; Keles, Ozgul

    2007-05-01

    An improved coating material possessing super-hard and low friction properties and a method for forming the same. The improved coating material includes the use of a noble metal or soft metal homogeneously distributed within a hard nitride material. The addition of small amounts of such metals into nitrides such as molybdenum nitride, titanium nitride, and chromium nitride results in as much as increasing of the hardness of the material as well as decreasing the friction coefficient and increasing the oxidation resistance.

  12. Ammonia Decomposition over Bimetallic Nitrides Supported on γ-Al2O3

    Institute of Scientific and Technical Information of China (English)

    Chun Shan LU; Xiao Nian LI; Yi Feng ZHU; Hua Zhang LIU; Chun Hui ZHOU

    2004-01-01

    A series of monometallic nitrides and bimetallic nitrides were prepared by temperature-programmed reaction with NH3. The effects of Co, Ni and Fe additives and the synergic action between Fe, Co, Ni and Mo on the ammonia decomposition activity were investigated. TPR-MS, XRD were also carried out to obtain better insight into the structure of the bimetallic nitride. The results of ammonia decomposition activity show that bimetallic nitrides are more active than monometallic nitrides or bimetallic oxides.

  13. Aluminum Nitride Micro-Channels Grown via Metal Organic Vapor Phase Epitaxy for MEMs Applications

    Energy Technology Data Exchange (ETDEWEB)

    Rodak, L.E.; Kuchibhatla, S.; Famouri, P.; Ting, L.; Korakakis, D.

    2008-01-01

    Aluminum nitride (AlN) is a promising material for a number of applications due to its temperature and chemical stability. Furthermore, AlN maintains its piezoelectric properties at higher temperatures than more commonly used materials, such as Lead Zirconate Titanate (PZT) [1, 2], making AlN attractive for high temperature micro and nanoelectromechanical (MEMs and NEMs) applications including, but not limited to, high temperature sensors and actuators, micro-channels for fuel cell applications, and micromechanical resonators. This work presents a novel AlN micro-channel fabrication technique using Metal Organic Vapor Phase Epitaxy (MOVPE). AlN easily nucleates on dielectric surfaces due to the large sticking coefficient and short diffusion length of the aluminum species resulting in a high quality polycrystalline growth on typical mask materials, such as silicon dioxide and silicon nitride [3,4]. The fabrication process introduced involves partially masking a substrate with a silicon dioxide striped pattern and then growing AlN via MOVPE simultaneously on the dielectric mask and exposed substrate. A buffered oxide etch is then used to remove the underlying silicon dioxide and leave a free standing AlN micro-channel. The width of the channel has been varied from 5 ìm to 110 ìm and the height of the air gap from 130 nm to 800 nm indicating the stability of the structure. Furthermore, this versatile process has been performed on (111) silicon, c-plane sapphire, and gallium nitride epilayers on sapphire substrates. Reflection High Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), and Raman measurements have been taken on channels grown on each substrate and indicate that the substrate is influencing the growth of the AlN micro-channels on the SiO2 sacrificial layer.

  14. Microstructure and Properties of Plasma Source Nitrided AISI 316 Austenitic Stainless Steel

    Science.gov (United States)

    Li, G. Y.; Lei, M. K.

    2016-11-01

    Plasma source nitriding is a relatively new nitriding technology which can overcome those inherent shortcomings associated with conventional direct current plasma nitriding technology such as the arcing surface damage, the edging effect and the hollow cathode effect. There is considerable study on the properties of nitrided samples for laboratorial scale plasma source nitriding system; however, little information has been reported on the industrial-scale plasma source nitriding system. In this work, AISI 316 austenitic stainless steel samples were nitrided by an industrial-scale plasma source nitriding system at various nitriding temperatures (350, 400, 450 and 500 °C) with a floating potential. A high-nitrogen face-centered-cubic phase (γN) formed on the surface of nitrided sample surface. As the nitriding temperature was increased, the γN phase layer thickness increased, varying from 1.5 μm for the lowest nitriding temperature of 350 °C, to 30 μm for the highest nitriding temperature of 500 °C. The maximum Vickers microhardness of the γN phase layer with a peak nitrogen concentration of 20 at.% is about HV 0.1 N 15.1 GPa at the nitriding temperature of 450 °C. The wear and corrosion experimental results demonstrated that the γN phase was formed on the surface of AISI 316 austenitic stainless steel by plasma source nitriding, which exhibits not only high wear resistance, but also good pitting corrosion resistance.

  15. Investigation of surface properties of high temperature nitrided titanium alloys

    Directory of Open Access Journals (Sweden)

    E. Koyuncu

    2009-12-01

    Full Text Available Purpose: The purpose of paper is to investigate surface properties of high temperature nitrided titanium alloys.Design/methodology/approach: In this study, surface modification of Ti6Al4V titanium alloy was made at various temperatures by plasma nitriding process. Plasma nitriding treatment was performed in 80% N2-20% H2 gas mixture, for treatment times of 2-15 h at the temperatures of 700-1000°C. Surface properties of plasma nitrided Ti6Al4V alloy were examined by metallographic inspection, X-Ray diffraction and Vickers hardness.Findings: Two layers were determined by optic inspection on the samples that were called the compound and diffusion layers. Compound layer contain TiN and Ti2N nitrides, XRD results support in this formations. Maximum hardness was obtained at 10h treatment time and 1000°C treatment temperature. Micro hardness tests showed that hardness properties of the nitrided samples depend on treatment time and temperature.Practical implications: Titanium and its alloys have very attractive properties for many industries. But using of titanium and its alloys is of very low in mechanical engineering applications because of poor tribological properties.Originality/value: The nitriding of titanium alloy surfaces using plasma processes has already reached the industrial application stage in the biomedical field.

  16. Thermodynamic Routes to Novel Metastable Nitrogen-Rich Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Holder, Aaron M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Arca, Elisabetta [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zakutayev, Andriy A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Lany, Stephan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sun, Wenhao [Lawrence Berkeley National Laboratory; Massachusetts Institute of Technology; Orvananos, Bernardo [Massachusetts Institute of Technology; Ceder, Gerbrand [Lawrence Berkeley National Laboratory; Massachusetts Institute of Technology; University of California, Berkeley

    2017-07-17

    Compared to oxides, the nitrides are relatively unexplored, making them a promising chemical space for novel materials discovery. Of particular interest are nitrogen-rich nitrides, which often possess useful semiconducting properties for electronic and optoelectronic applications. However, such nitrogen-rich compounds are generally metastable, and the lack of a guiding theory for their synthesis has limited their exploration. Here, we review the remarkable metastability of observed nitrides, and examine the thermodynamics of how reactive nitrogen precursors can stabilize metastable nitrogen-rich compositions during materials synthesis. We map these thermodynamic strategies onto a predictive computational search, training a data-mined ionic substitution algorithm specifically for nitride discovery, which we combine with grand-canonical DFT-SCAN phase stability calculations to compute stabilizing nitrogen chemical potentials. We identify several new nitrogen-rich binary nitrides for experimental investigation, notably the transition metal nitrides Mn3N4, Cr3N4, V3N4, and Nb3N5, the main group nitride SbN, and the pernitrides FeN2, CrN2, and Cu2N2. By formulating rational thermodynamic routes to metastable compounds, we expand the search space for functional technological materials beyond equilibrium phases and compositions.

  17. Characterization of plasma nitrided layers produced on sintered iron

    Directory of Open Access Journals (Sweden)

    Marcos Alves Fontes

    2014-07-01

    Full Text Available Plasma nitriding is a thermo-physical-chemical treatment process, which promotes surface hardening, caused by interstitial diffusion of atomic nitrogen into metallic alloys. In this work, this process was employed in the surface modification of a sintered ferrous alloy. Scanning electron microscopy (SEM, X-ray diffraction (XRD analyses, and wear and microhardness tests were performed on the samples submitted to ferrox treatment and plasma nitriding carried out under different conditions of time and temperature. The results showed that the nitride layer thickness is higher for all nitrided samples than for ferrox treated samples, and this layer thickness increases with nitriding time and temperature, and temperature is a more significant variable. The XRD analysis showed that the nitrided layer, for all samples, near the surface consists in a mixture of γ′-Fe4N and ɛ-Fe3N phases. Both wear resistance and microhardness increase with nitriding time and temperature, and temperature influences both the characteristics the most.

  18. Fuel cells:

    DEFF Research Database (Denmark)

    Sørensen, Bent

    2013-01-01

    A brief overview of the progress in fuel cell applications and basic technology development is presented, as a backdrop for discussing readiness for penetration into the marketplace as a solution to problems of depletion, safety, climate or environmental impact from currently used fossil and nucl......A brief overview of the progress in fuel cell applications and basic technology development is presented, as a backdrop for discussing readiness for penetration into the marketplace as a solution to problems of depletion, safety, climate or environmental impact from currently used fossil...... and nuclear fuel-based energy technologies....

  19. Preparation and Instability of Nanocrystalline Cuprous Nitride.

    Science.gov (United States)

    Reichert, Malinda D; White, Miles A; Thompson, Michelle J; Miller, Gordon J; Vela, Javier

    2015-07-06

    Low-dimensional cuprous nitride (Cu3N) was synthesized by nitridation (ammonolysis) of cuprous oxide (Cu2O) nanocrystals using either ammonia (NH3) or urea (H2NCONH2) as the nitrogen source. The resulting nanocrystalline Cu3N spontaneously decomposes to nanocrystalline CuO in the presence of both water and oxygen from air at room temperature. Ammonia was produced in 60% chemical yield during Cu3N decomposition, as measured using the colorimetric indophenol method. Because Cu3N decomposition requires H2O and produces substoichiometric amounts of NH3, we conclude that this reaction proceeds through a complex stoichiometry that involves the concomitant release of both N2 and NH3. This is a thermodynamically unfavorable outcome, strongly indicating that H2O (and thus NH3 production) facilitate the kinetics of the reaction by lowering the energy barrier for Cu3N decomposition. The three different Cu2O, Cu3N, and CuO nanocrystalline phases were characterized by a combination of optical absorption, powder X-ray diffraction, transmission electron microscopy, and electronic density of states obtained from electronic structure calculations on the bulk solids. The relative ease of interconversion between these interesting and inexpensive materials bears possible implications for catalytic and optoelectronic applications.

  20. Cubic III-nitrides: potential photonic materials

    Science.gov (United States)

    Onabe, K.; Sanorpim, S.; Kato, H.; Kakuda, M.; Nakamura, T.; Nakamura, K.; Kuboya, S.; Katayama, R.

    2011-01-01

    The growth and characterization of some cubic III-nitride films on suitable cubic substrates have been done, namely, c- GaN on GaAs by MOVPE, c-GaN and c-AlGaN on MgO by RF-MBE, and c-InN and c-InGaN (In-rich) on YSZ by RFMBE. This series of study has been much focused on the cubic-phase purity as dependent on the respective growth conditions and resulting electrical and optical properties. For c-GaN and c-InN films, a cubic-phase purity higher than 95% is attained in spite of the metastable nature of the cubic III-nitrides. However, for c-AlGaN and c-InGaN films, the cubic-phase purity is rapidly degraded with significant incorporation of the hexagonal phase through stacking faults on cubic {111} faces which may be exposed on the roughened growing or substrate surface. It has been shown that the electron mobilities in c-GaN and c-AlGaN films are much related to phase purity.

  1. Structure refinement for tantalum nitrides nanocrystals with various morphologies

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lianyun [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 30 Xue Yuan Road, Haidian District, Beijing 100083 (China); School of Science, Beijing Jiaotong University, 3 Shang Yuan Cun, Haidian District, Beijing 100044 (China); Huang, Kai; Hou, Jungang [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 30 Xue Yuan Road, Haidian District, Beijing 100083 (China); Zhu, Hongmin, E-mail: hzhu@metall.ustb.edu.cn [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 30 Xue Yuan Road, Haidian District, Beijing 100083 (China)

    2012-07-15

    Graphical abstract: Tantalum nitrides nanocrystals with various phases and morphologies for the first time have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. Highlights: ► The spherical TaN, cuboidal TaN{sub 0.83} and TaN{sub 0.5} nanocrystals have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. ► The crystal structures of different tantalum nitrides were determined by Rietveld refinement on the X-ray diffraction data and the examinations of electron microcopies. ► The specific surface area of the tantalum nitrides powders was around 10 m{sup 2} g{sup −1}. ► Tantalum nitrides powders could be suitable for capacitor with high specific capacitance. -- Abstract: Tantalum nitrides (TaN{sub x}) nanocrystals with different phase and morphology have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. The crystal structures of tantalum nitrides were determined by Rietveld refinement based on the X-ray diffraction data. The morphologies of various tantalum nitrides nanocrystals in high quality were analyzed through the electron microcopies examinations. The spherical TaN nanoparticles, cuboidal TaN{sub 0.83} and TaN{sub 0.5} nanocrystals have been selectively prepared at different annealing temperatures. In addition, the specific surface areas of the tantalum nitrides nanocrystals measured by BET method were around 9.87–11.64 m{sup 2} g{sup −1}, indicating that such nano-sized tantalum nitrides could be suitable for capacitor with high specific capacitance.

  2. Production of LEU Fully Ceramic Microencapsulated Fuel for Irradiation Testing

    Energy Technology Data Exchange (ETDEWEB)

    Terrani, Kurt A [ORNL; Kiggans Jr, James O [ORNL; McMurray, Jake W [ORNL; Jolly, Brian C [ORNL; Hunt, Rodney Dale [ORNL; Trammell, Michael P [ORNL; Snead, Lance Lewis [ORNL

    2016-01-01

    Fully Ceramic Microencapsulated (FCM) fuel consists of tristructural isotropic (TRISO) fuel particles embedded inside a SiC matrix. This fuel inherently possesses multiple barriers to fission product release, namely the various coating layers in the TRISO fuel particle as well as the dense SiC matrix that hosts these particles. This coupled with the excellent oxidation resistance of the SiC matrix and the SiC coating layer in the TRISO particle designate this concept as an accident tolerant fuel (ATF). The FCM fuel takes advantage of uranium nitride kernels instead of oxide or oxide-carbide kernels used in high temperature gas reactors to enhance heavy metal loading in the highly moderated LWRs. Production of these kernels with appropriate density, coating layer development to produce UN TRISO particles, and consolidation of these particles inside a SiC matrix have been codified thanks to significant R&D supported by US DOE Fuel Cycle R&D program. Also, surrogate FCM pellets (pellets with zirconia instead of uranium-bearing kernels) have been neutron irradiated and the stability of the matrix and coating layer under LWR irradiation conditions have been established. Currently the focus is on production of LEU (7.3% U-235 enrichment) FCM pellets to be utilized for irradiation testing. The irradiation is planned at INL s Advanced Test Reactor (ATR). This is a critical step in development of this fuel concept to establish the ability of this fuel to retain fission products under prototypical irradiation conditions.

  3. Application Of Active Screen Method For Ion Nitriding Efficiency Improvement

    Directory of Open Access Journals (Sweden)

    Ogórek M.

    2015-06-01

    Full Text Available Paper presents the research of austenitic steel AISI 304 after ion nitriding at 400°C and at t =4h, for the two different variants of samples distribution in the working plasma reactive chamber tube. In order to assess the effectiveness of ion nitriding variants emission spectroscopy – GDOES, surface hardness tests, microstructure research (LM of nitrided layers were made. It has been found that the use of active screens increases the surface layer thickness and depth of nitrogen diffusion into austenitic steel 304.

  4. High efficiency III-nitride light-emitting diodes

    Science.gov (United States)

    Crawford, Mary; Koleske, Daniel; Cho, Jaehee; Zhu, Di; Noemaun, Ahmed; Schubert, Martin F; Schubert, E. Fred

    2013-05-28

    Tailored doping of barrier layers enables balancing of the radiative recombination among the multiple-quantum-wells in III-Nitride light-emitting diodes. This tailored doping enables more symmetric carrier transport and uniform carrier distribution which help to reduce electron leakage and thus reduce the efficiency droop in high-power III-Nitride LEDs. Mitigation of the efficiency droop in III-Nitride LEDs may enable the pervasive market penetration of solid-state-lighting technologies in high-power lighting and illumination.

  5. Preparation of Ultra-fine Aluminum Nitride in Thermal Plasma

    Institute of Scientific and Technical Information of China (English)

    漆继红; 罗义文; 印永祥; 代晓雁

    2002-01-01

    Ultra-fine aluminum nitride has been synthesized by the evaporation of aluminum powder at atmospheric-pressure nitrogen plasma in a hot-wall reactor. The average size of aluminum nitride particle is 0.11μm measured by scanning electric mirror (SEM), and the purity is at least over 90% evaluated by X-Ray diffraction (XRD). The conversion of Al powder to aluminum nitride is strongly depended on the injection of NH3. Typical experimental parameters such as the feed rate of raw material, the flow rate of ammonia and the position of injecting aluminum powder into the reactor are given.

  6. Conductive and robust nitride buffer layers on biaxially textured substrates

    Science.gov (United States)

    Sankar, Sambasivan [Chicago, IL; Goyal, Amit [Knoxville, TN; Barnett, Scott A [Evanston, IL; Kim, Ilwon [Skokie, IL; Kroeger, Donald M [Knoxville, TN

    2009-03-31

    The present invention relates to epitaxial, electrically conducting and mechanically robust, cubic nitride buffer layers deposited epitaxially on biaxially textured substrates such as metals and alloys. The invention comprises of a biaxially textured substrate with epitaxial layers of nitrides. The invention also discloses a method to form such epitaxial layers using a high rate deposition method as well as without the use of forming gases. The invention further comprises epitaxial layers of oxides on the biaxially textured nitride layer. In some embodiments the article further comprises electromagnetic devices which may have superconducting properties.

  7. Microstructure of Spark Plasma-Sintered Silicon Nitride Ceramics

    Science.gov (United States)

    Lukianova, O. A.; Novikov, V. Yu.; Parkhomenko, A. A.; Sirota, V. V.; Krasilnikov, V. V.

    2017-04-01

    The microstructure and phase composition of the high-content Al2O3-Y2O3-doped spark plasma-sintered silicon nitride were investigated. Fully dense silicon nitride ceramics with a typical α-Si3N4 equiaxed structure with average grain size from 200 to 530 nm, high elastic modulus of 288 GPa, and high hardness of 2038 HV were spark plasma sintered (SPSed) at 1550 °C. Silicon nitride with elongated β-Si3N4 grains, higher hardness of 1800 HV, density of 3.25 g/cm3, and Young's modulus 300 GPa SPSed at 1650 °C was also reviewed.

  8. Fuel cells

    Directory of Open Access Journals (Sweden)

    D. N. Srivastava

    1962-05-01

    Full Text Available The current state of development of fuel cells as potential power sources is reviewed. Applications in special fields with particular reference to military requirements are pointed out.

  9. Future Fuels

    Science.gov (United States)

    2006-04-01

    Storage Devices, Fuel Management, Gasification, Fischer-Tropsch, Syngas , Hubberts’s Peak UNCLAS UNCLAS UNCLAS UU 80 Dr. Sujata Millick (703) 696...prices ever higher, and perhaps lead to intermittent fuel shortages as production fluctuates. Clearly, this competition for resources also provides oil...producers multiple options for selling their products, and raises the possibility that the US could face shortages resulting from shifts in

  10. Preparation of carbon-nitride bulk samples in the presence of seed carbon-nitride films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J. I. [Korea University of Technology and Education, Chonan (Korea, Republic of); Zorov, N. B. [Moscow State University, Moscow (Russian Federation)

    2004-05-15

    A procedure was developed for preparing bulk carbon-nitride crystals from polymeric alpha-C{sub 3}N{sub 4.2} at high pressure and high temperature in the presence of seeds of crystalline carbon-nitride films prepared by using a high-voltage discharge plasma combined with pulsed laser ablation of a graphite target. The samples were evaluated by using X-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, Auger electron spectroscopy (AES), secondary-ion mass spectrometry (SIMS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Notably, XPS studies of the film composition before and after thermobaric treatments demonstrated that the nitrogen composition in the alpha-C{sub 3}N{sub 4.2} material, which initially contained more than 58 % nitrogen, decreased during the annealing process and reached a common, stable composition of approx 45 %. The thermobaric experiments were performed at 10 - 77 kbar and 350 - 1200 .deg. C.

  11. High Temperature Oxidation of Boron Nitride. Part 1; Monolithic Boron Nitride

    Science.gov (United States)

    Jacobson, Nathan; Farmer, Serene; Moore, Arthur; Sayir, Haluk

    1997-01-01

    High temperature oxidation of monolithic boron nitride (BN) is examined. Hot pressed BN and both low and high density CVD BN were studied. It is shown that oxidation rates are quite sensitive to microstructural factors such as orientation, porosity, and degree of crystallinity. In addition small amounts of water vapor lead to volatilization of the B2O3 oxide as H(x)B(y)O(z). For these reasons, very different oxidation kinetics were observed for each type of BN.

  12. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate

    Science.gov (United States)

    Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

    2014-12-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

  13. Gallium Nitride, Indium Nitride, and Heterostructure Development Using The MEAglow Growth System

    Science.gov (United States)

    Binsted, Peter W.

    This thesis presents an in depth study of semiconductor development using a new process termed Migration Enhanced Afterglow (MEAglow). The MEAglow growth reactor is housed in the Lakehead University Semiconductor Research Lab. Thin films of gallium nitride and indium nitride are produced as well as heterostructures comprised of these two films and their ternary alloy InGaN. MEAglow is a form of plasma enhanced chemical vapour deposition (PECVD) employing migration enhanced epitaxy (MEE). The heterostructure is being developed for a novel field effect transistor (FET) based on the tunnelling of charge carriers which alter the channel conductivity. The configuration of this unique III-Nitride device should allow the FET to function as normally off in either n-type or p-type operation. Due to the difficulties in growing low temperature GaN, test devices of this abstract design were not previously possible. Further details on the device operation and growth parameters are included. Samples produced by the research reactor were characterised through x-ray diffraction (XRD), ultraviolet-near infrared-visible spectroscopy (UV-Vis-NIR), Auger spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Film growth is accomplished by an improved form of pulsed delivery Plasma Enhanced Chemical Vapour Deposition (PECVD). The reactor features a scalable hollow cathode type plasma source. Data obtained through characterisation is subjected to theoretical treatment which explains much not previously understood behaviour of the GaN films. Many challenges in III-Nitride film growth have been overcome during this research project. A method of developing structures consisting of InN and GaN within the same system has been proven.

  14. Microstructure and Hardness of High Temperature Gas Nitrided AISI 420 Martensitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    Ibrahim Nor Nurulhuda Md.

    2014-07-01

    Full Text Available This study examined the microstructure and hardness of as-received and nitrided AISI 420 martensitic stainless steels. High temperature gas nitriding was employed to treat the steels at 1200°C for one hour and four hours using nitrogen gas, followed by furnace cooled. Chromium nitride and iron nitride were formed and concentrated at the outmost surface area of the steels since this region contained the highest concentration of nitrogen. The grain size enlarged at the interior region of the nitrided steels due to nitriding at temperature above the recrystallization temperature of the steel and followed by slow cooling. The nitrided steels produced higher surface hardness compared to as-received steel due to the presence of nitrogen and the precipitation of nitrides. Harder steel was produced when nitriding at four hours compared to one hour since more nitrogen permeated into the steel.

  15. Plasma nitriding monitoring reactor: A model reactor for studying plasma nitriding processes using an active screen

    Energy Technology Data Exchange (ETDEWEB)

    Hamann, S., E-mail: hamann@inp-greifswald.de; Röpcke, J. [INP-Greifswald, Felix-Hausdorff-Str. 2, 17489 Greifswald (Germany); Börner, K.; Burlacov, I.; Spies, H.-J. [TU Bergakademie Freiberg, Institute of Materials Engineering, Gustav-Zeuner-Str. 5, 09599 Freiberg (Germany); Strämke, M.; Strämke, S. [ELTRO GmbH, Arnold-Sommerfeld-Ring 3, 52499 Baesweiler (Germany)

    2015-12-15

    A laboratory scale plasma nitriding monitoring reactor (PLANIMOR) has been designed to study the basics of active screen plasma nitriding (ASPN) processes. PLANIMOR consists of a tube reactor vessel, made of borosilicate glass, enabling optical emission spectroscopy (OES) and infrared absorption spectroscopy. The linear setup of the electrode system of the reactor has the advantages to apply the diagnostic approaches on each part of the plasma process, separately. Furthermore, possible changes of the electrical field and of the heat generation, as they could appear in down-scaled cylindrical ASPN reactors, are avoided. PLANIMOR has been used for the nitriding of steel samples, achieving similar results as in an industrial scale ASPN reactor. A compact spectrometer using an external cavity quantum cascade laser combined with an optical multi-pass cell has been applied for the detection of molecular reaction products. This allowed the determination of the concentrations of four stable molecular species (CH{sub 4}, C{sub 2}H{sub 2}, HCN, and NH{sub 3}). With the help of OES, the rotational temperature of the screen plasma could be determined.

  16. EDITORIAL: Non-polar and semipolar nitride semiconductors Non-polar and semipolar nitride semiconductors

    Science.gov (United States)

    Han, Jung; Kneissl, Michael

    2012-02-01

    Throughout the history of group-III-nitride materials and devices, scientific breakthroughs and technological advances have gone hand-in-hand. In the late 1980s and early 1990s, the discovery of the nucleation of smooth (0001) GaN films on c-plane sapphire and the activation of p-dopants in GaN led very quickly to the realization of high-brightness blue and green LEDs, followed by the first demonstration of GaN-based violet laser diodes in the mid 1990s. Today, blue InGaN LEDs boast record external quantum efficiencies exceeding 80% and the emission wavelength of the InGaN-based laser diode has been pushed into the green spectral range. Although these tremenduous advances have already spurred multi-billion dollar industries, there are still a number of scientific questions and technological issues that are unanswered. One key challenge is related to the polar nature of the III-nitride wurtzite crystal. Until a decade ago all research activities had almost exclusively concentrated on (0001)-oriented polar GaN layers and heterostructures. Although the device characteristics seem excellent, the strong polarization fields at GaN heterointerfaces can lead to a significant deterioration of the device performance. Triggered by the first demonstration non-polar GaN quantum wells grown on LiAlO2 by Waltereit and colleagues in 2000, impressive advances in the area of non-polar and semipolar nitride semiconductors and devices have been achieved. Today, a large variety of heterostructures free of polarization fields and exhibiting exceptional electronic and optical properties have been demonstrated, and the fundamental understanding of polar, semipolar and non-polar nitrides has made significant leaps forward. The contributions in this Semiconductor Science and Technology special issue on non-polar and semipolar nitride semiconductors provide an impressive and up-to-date cross-section of all areas of research and device physics in this field. The articles cover a wide range of

  17. Plasma nitriding monitoring reactor: A model reactor for studying plasma nitriding processes using an active screen

    Science.gov (United States)

    Hamann, S.; Börner, K.; Burlacov, I.; Spies, H.-J.; Strämke, M.; Strämke, S.; Röpcke, J.

    2015-12-01

    A laboratory scale plasma nitriding monitoring reactor (PLANIMOR) has been designed to study the basics of active screen plasma nitriding (ASPN) processes. PLANIMOR consists of a tube reactor vessel, made of borosilicate glass, enabling optical emission spectroscopy (OES) and infrared absorption spectroscopy. The linear setup of the electrode system of the reactor has the advantages to apply the diagnostic approaches on each part of the plasma process, separately. Furthermore, possible changes of the electrical field and of the heat generation, as they could appear in down-scaled cylindrical ASPN reactors, are avoided. PLANIMOR has been used for the nitriding of steel samples, achieving similar results as in an industrial scale ASPN reactor. A compact spectrometer using an external cavity quantum cascade laser combined with an optical multi-pass cell has been applied for the detection of molecular reaction products. This allowed the determination of the concentrations of four stable molecular species (CH4, C2H2, HCN, and NH3). With the help of OES, the rotational temperature of the screen plasma could be determined.

  18. Plasma nitriding monitoring reactor: A model reactor for studying plasma nitriding processes using an active screen.

    Science.gov (United States)

    Hamann, S; Börner, K; Burlacov, I; Spies, H-J; Strämke, M; Strämke, S; Röpcke, J

    2015-12-01

    A laboratory scale plasma nitriding monitoring reactor (PLANIMOR) has been designed to study the basics of active screen plasma nitriding (ASPN) processes. PLANIMOR consists of a tube reactor vessel, made of borosilicate glass, enabling optical emission spectroscopy (OES) and infrared absorption spectroscopy. The linear setup of the electrode system of the reactor has the advantages to apply the diagnostic approaches on each part of the plasma process, separately. Furthermore, possible changes of the electrical field and of the heat generation, as they could appear in down-scaled cylindrical ASPN reactors, are avoided. PLANIMOR has been used for the nitriding of steel samples, achieving similar results as in an industrial scale ASPN reactor. A compact spectrometer using an external cavity quantum cascade laser combined with an optical multi-pass cell has been applied for the detection of molecular reaction products. This allowed the determination of the concentrations of four stable molecular species (CH4, C2H2, HCN, and NH3). With the help of OES, the rotational temperature of the screen plasma could be determined.

  19. Pt Monolayer Shell on Nitrided Alloy Core—A Path to Highly Stable Oxygen Reduction Catalyst

    Directory of Open Access Journals (Sweden)

    Jue Hu

    2015-07-01

    Full Text Available The inadequate activity and stability of Pt as a cathode catalyst under the severe operation conditions are the critical problems facing the application of the proton exchange membrane fuel cell (PEMFC. Here we report on a novel route to synthesize highly active and stable oxygen reduction catalysts by depositing Pt monolayer on a nitrided alloy core. The prepared PtMLPdNiN/C catalyst retains 89% of the initial electrochemical surface area after 50,000 cycles between potentials 0.6 and 1.0 V. By correlating electron energy-loss spectroscopy and X-ray absorption spectroscopy analyses with electrochemical measurements, we found that the significant improvement of stability of the PtMLPdNiN/C catalyst is caused by nitrogen doping while reducing the total precious metal loading.

  20. Production of Low Enriched Uranium Nitride Kernels for TRISO Particle Irradiation Testing

    Energy Technology Data Exchange (ETDEWEB)

    McMurray, J. W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Silva, C. M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Helmreich, G. W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gerczak, T. J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Dyer, J. A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Collins, J. L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hunt, R. D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lindemer, T. B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Terrani, K. A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-06-01

    A large batch of UN microspheres to be used as kernels for TRISO particle fuel was produced using carbothermic reduction and nitriding of a sol-gel feedstock bearing tailored amounts of low-enriched uranium (LEU) oxide and carbon. The process parameters, established in a previous study, produced phasepure NaCl structure UN with dissolved C on the N sublattice. The composition, calculated by refinement of the lattice parameter from X-ray diffraction, was determined to be UC0.27N0.73. The final accepted product weighed 197.4 g. The microspheres had an average diameter of 797±1.35 μm and a composite mean theoretical density of 89.9±0.5% for a solid solution of UC and UN with the same atomic ratio; both values are reported with their corresponding calculated standard error.

  1. Heuristic Analysis Model of Nitrided Layers' Formation Consisting of the Image Processing and Analysis and Elements of Artificial Intelligence

    National Research Council Canada - National Science Library

    Tomasz Wójcicki; Michal Nowicki

    2016-01-01

    .... The objectives of the analyses of the materials for gas nitriding technology are described. The methods of the preparation of nitrided layers, the steps of the process and the construction and operation of devices for gas nitriding are given...

  2. Room temperature synthesis of biodiesel using sulfonated graphitic carbon nitride

    Science.gov (United States)

    Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature.

  3. Microcavity effects in the photoluminescence of hydrogenated amorphous silicon nitride

    Science.gov (United States)

    Serpenguzel, Ali; Aydinli, Atilla; Bek, Alpan

    1998-07-01

    Fabry-Perot microcavities are used for the alteration of photoluminescence in hydrogenated amorphous silicon nitride grown with and without ammonia. The photoluminescence is red-near-infrared for the samples grown without ammonia, and blue-green for the samples grown with ammonia. In the Fabry- Perot microcavities, the amplitude of the photoluminescence is enhanced, while its linewidth is reduced with respect to the bulk hydrogenated amorphous silicon nitride. The microcavity was realized by a metallic back mirror and a hydrogenated amorphous silicon nitride--air or a metallic front mirror. The transmittance, reflectance, and absorbance spectra were also measured and calculated. The calculated spectra agree well with the experimental spectra. The hydrogenated amorphous silicon nitride microcavity has potential for becoming a versatile silicon based optoelectronic device such as a color flat panel display, a resonant cavity enhanced light emitting diode, or a laser.

  4. Thermal Effect of Ceramic Nanofiller Aluminium Nitride on Polyethylene Properties

    Directory of Open Access Journals (Sweden)

    Omer Bin Sohail

    2012-01-01

    Full Text Available Ethylene polymerization was done to form polyethylene nano-composite with nanoaluminum nitride using zirconocene catalysts. Results show that the catalytic activity is maximum at a filler loading of 15 mg nanoaluminum nitride. Differential scanning calorimeter (DSC and X-ray diffraction (XRD results show that percentage crystallinity was also marginally higher at this amount of filler. Thermal behavior of polyethylene nanocomposites (0, 15, 30, and 45 mg was studied by DSC and thermal gravimetric analyzer (TGA. Morphology of the component with 15 mg aluminium nitride is more fibrous as compared to 0 mg aluminium nitride and higher filler loading as shown by SEM images. In order to understand combustibility behavior, tests were performed on microcalorimeter. Its results showed decrease in combustibility in polyethylene nanocomposites as the filler loading increases.

  5. Defect complexes in carbon and boron nitride nanotubes

    CSIR Research Space (South Africa)

    Mashapa, MG

    2012-05-01

    Full Text Available The effect of defect complexes on the stability, structural and electronic properties of single-walled carbon nanotubes and boron nitride nanotubes is investigated using the ab initio pseudopotential density functional method implemented...

  6. Pair distribution functions of silicon/silicon nitride interfaces

    Science.gov (United States)

    Cao, Deng; Bachlechner, Martina E.

    2006-03-01

    Using molecular dynamics simulations, we investigate different mechanical and structural properties of the silicon/silicon nitride interface. One way to characterize the structure as tensile strain is applied parallel to the interface is to calculate pair distribution functions for specific atom types. The pair distribution function gives the probability of finding a pair of atoms a distance r apart, relative to the probability expected for a completely random distribution at the same density. The pair distribution functions for bulk silicon nitride reflect the fracture of the silicon nitride film at about 8 % and the fact that the centerpiece of the silicon nitride film returns to its original structure after fracture. The pair distribution functions for interface silicon atoms reveal the formation of bonds for originally unbound atom pairs, which is indicative of the interstitial-vacancy defect that causes failure in silicon.

  7. Bond Angles in the Crystalline Silicon/Silicon Nitride Interface

    Science.gov (United States)

    Leonard, Robert H.; Bachlechner, Martina E.

    2006-03-01

    Silicon nitride deposited on a silicon substrate has major applications in both dielectric layers in microelectronics and as antireflection and passivation coatings in photovoltaic applications. Molecular dynamic simulations are performed to investigate the influence of temperature and rate of externally applied strain on the structural and mechanical properties of the silicon/silicon nitride interface. Bond-angles between various atom types in the system are used to find and understand more about the mechanisms leading to the failure of the crystal. Ideally in crystalline silicon nitride, bond angles of 109.5 occur when a silicon atom is at the vertex and 120 angles occur when a nitrogen atom is at the vertex. The comparison of the calculated angles to the ideal values give information on the mechanisms of failure in silicon/silicon nitride system.

  8. Physics of wurtzite nitrides and oxides passport to devices

    CERN Document Server

    Gil, Bernard

    2014-01-01

    This book gives a survey of the current state of the art of a special class of nitrides semiconductors, Wurtzite Nitride and Oxide Semiconductors. It includes properties, growth and applications. Research in the area of nitrides semiconductors is still booming although some basic materials sciences issues were solved already about 20 years ago. With the advent of modern technologies and the successful growth of nitride substrates, these materials currently experience a second birth. Advanced new applications like light-emitters, including UV operating LEDs, normally on and normally off high frequency operating transistors are expected. With progress in clean room technology, advanced photonic and quantum optic applications are envisioned in a close future. This area of research is fascinating for researchers and students in materials science, electrical engineering, chemistry, electronics, physics and biophysics. This book aims to be the ad-hoc instrument to this active field of research.

  9. Ellipsometric study of silicon nitride on gallium arsenide

    Science.gov (United States)

    Alterovitz, S. A.; Bu-Abbud, G. H.; Woollam, J. A.; Liu, D.; Chung, Y.; Langer, D.

    1982-01-01

    A method for optimizing the sensitivity of ellipsometric measurements for thin dielectric films on semiconductors is described in simple physical terms. The technique is demonstrated for the case of sputtered silicon nitride films on gallium arsenide.

  10. Plasma-nitriding of tantalum at relatively low temperature

    Institute of Scientific and Technical Information of China (English)

    ZHANG Deyuan; LIN Qin; ZHAO Haomin; FEI Qinyong; GENG Man

    2004-01-01

    The combined quadratic orthogonal regression method of experiment design was employed to explore the effects of process parameters of plasma nitriding of tantalum such as total pressure, temperature and original hydrogen molar fraction on the hardness, roughness and structure of nitriding surfaces. The regression equations of hardness, roughness and structure were given according to the results of regression and statistic analysis. And the diffusion activation energy of nitrogen in tantalum on plasma nitriding conditions was calculated according to the experimental data of hardness of plasma-nitriding of tantalum vs time and temperature. The diffusion activation energy calculated belongs to (155.49 + 10.51)kJ/mol (783-983 K).

  11. Room temperature synthesis of biodiesel using sulfonated graphitic carbon nitride

    Science.gov (United States)

    Baig, R. B. Nasir; Verma, Sanny; Nadagouda, Mallikarjuna N.; Varma, Rajender S.

    2016-12-01

    Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature.

  12. Osteoblastlike cell adhesion on titanium surfaces modified by plasma nitriding.

    Science.gov (United States)

    da Silva, Jose Sandro Pereira; Amico, Sandro Campos; Rodrigues, Almir Olegario Neves; Barboza, Carlos Augusto Galvao; Alves, Clodomiro; Croci, Alberto Tesconi

    2011-01-01

    The aim of this study was to evaluate the characteristics of various titanium surfaces modified by cold plasma nitriding in terms of adhesion and proliferation of rat osteoblastlike cells. Samples of grade 2 titanium were subjected to three different surface modification processes: polishing, nitriding by plasma direct current, and nitriding by cathodic cage discharge. To evaluate the effect of the surface treatment on the cellular response, the adhesion and proliferation of osteoblastlike cells (MC3T3) were quantified and the results were analyzed by Kruskal-Wallis and Friedman statistical tests. Cellular morphology was observed by scanning electron microscopy. There was more MC3T3 cell attachment on the rougher surfaces produced by cathodic cage discharge compared with polished samples (P Plasma nitriding improves titanium surface roughness and wettability, leading to osteoblastlike cell adhesion.

  13. Experimental core electron density of cubic boron nitride

    DEFF Research Database (Denmark)

    Wahlberg, Nanna; Bindzus, Niels; Bjerg, Lasse

    candidate because of its many similarities with diamond: bonding pattern in the extended network structure, hardness, and the quality of the crystallites.3 However, some degree ionic interaction is a part of the bonding in boron nitride, which is not present in diamond. By investigating the core density...... beyond multipolar modeling of the valence density. As was recently shown in a benchmark study of diamond by Bindzus et al.1 The next step is to investigate more complicated chemical bonding motives, to determine the effect of bonding on the core density. Cubic boron nitride2 lends itself as a perfect...... in boron nitride we may obtain a deeper understanding of the effect of bonding on the total density. We report here a thorough investigation of the charge density of cubic boron nitride with a detailed modelling of the inner atom charge density. By combining high resolution powder X-ray diffraction data...

  14. An approach for evaluating the integrity of fuel applied in Innovative Nuclear Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Nakae, Nobuo, E-mail: nakae-nobuo@jnes.go.jp [Center for Research into Innovative Nuclear Energy System, Tokyo Institute of Technology, 2-12-1-N1-19, Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Ozawa, Takayuki [Advanced Nuclear System Research and Development Directorate, Japan Atomic Energy Agency, 4-33, Muramatsu, Tokai-mura, Ibaraki-ken 319-1194 (Japan); Ohta, Hirokazu; Ogata, Takanari [Nuclear Technology Research Laboratory, Central Research Institute of Electric Power Industry, 2-11-1, Iwado Kita, Komae-shi, Tokyo 201-8511 (Japan); Sekimoto, Hiroshi [Center for Research into Innovative Nuclear Energy System, Tokyo Institute of Technology, 2-12-1-N1-19, Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

    2014-03-15

    One of the important issues in the study of Innovative Nuclear Energy Systems is evaluating the integrity of fuel applied in Innovative Nuclear Energy Systems. An approach for evaluating the integrity of the fuel is discussed here based on the procedure currently used in the integrity evaluation of fast reactor fuel. The fuel failure modes determining fuel life time were reviewed and fuel integrity was analyzed and compared with the failure criteria. Metal and nitride fuels with austenitic and ferritic stainless steel (SS) cladding tubes were examined in this study. For the purpose of representative irradiation behavior analyses of the fuel for Innovative Nuclear Energy Systems, the correlations of the cladding characteristics were modeled based on well-known characteristics of austenitic modified 316 SS (PNC316), ferritic–martensitic steel (PNC–FMS) and oxide dispersion strengthened steel (PNC–ODS). The analysis showed that the fuel lifetime is limited by channel fracture which is a nonductile type (brittle) failure associated with a high level of irradiation-induced swelling in the case of austenitic steel cladding. In case of ferritic steel, on the other hand, the fuel lifetime is controlled by cladding creep rupture. The lifetime evaluated here is limited to 200 GW d/t, which is lower than the target burnup value of 500 GW d/t. One of the possible measures to extend the lifetime may be reducing the fuel smeared density and ventilating fission gas in the plenum for metal fuel and by reducing the maximum cladding temperature from 650 to 600 °C for both metal and nitride fuel.

  15. Platinum group metal nitrides and carbides: synthesis, properties and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Ivanovskii, Alexander L [Institute of Solid State Chemistry, Urals Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation)

    2009-04-30

    Experimental and theoretical data on new compounds, nitrides and carbides of the platinum group 4d and 5d metals (ruthenium, rhodium, palladium, osmium, iridium, platinum), published over the past five years are summarized. The extreme mechanical properties of platinoid nitrides and carbides, i.e., their high strength and low compressibility, are noted. The prospects of further studies and the scope of application of these compounds are discussed.

  16. Apparatus for the production of boron nitride nanotubes

    Science.gov (United States)

    Smith, Michael W; Jordan, Kevin

    2014-06-17

    An apparatus for the large scale production of boron nitride nanotubes comprising; a pressure chamber containing; a continuously fed boron containing target; a source of thermal energy preferably a focused laser beam; a cooled condenser; a source of pressurized nitrogen gas; and a mechanism for extracting boron nitride nanotubes that are condensed on or in the area of the cooled condenser from the pressure chamber.

  17. Nitrogen Atom Transfer From High Valent Iron Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Michael D. [New Mexico State Univ., Las Cruces, NM (United States); Smith, Jeremy M. [Indiana Univ., Bloomington, IN (United States)

    2015-10-14

    This report describes the synthesis and reactions of high valent iron nitrides. Organonitrogen compounds such as aziridines are useful species for organic synthesis, but there are few efficient methods for their synthesis. Using iron nitrides to catalytically access these species may allow for their synthesis in an energy-and atom-efficient manner. We have developed a new ligand framework to achieve these goals as well as providing a method for inducing previously unknown reactivity.

  18. Infrared Dielectric Properties of Low-stress Silicon Nitride

    Science.gov (United States)

    Cataldo, Giuseppe; Beall, James A.; Cho, Hsiao-Mei; McAndrew, Brendan; Niemack, Michael D.; Wollack, Edward J.

    2012-01-01

    Silicon nitride thin films play an important role in the realization of sensors, filters, and high-performance circuits. Estimates of the dielectric function in the far- and mid-IR regime are derived from the observed transmittance spectra for a commonly employed low-stress silicon nitride formulation. The experimental, modeling, and numerical methods used to extract the dielectric parameters with an accuracy of approximately 4% are presented.

  19. Progress in periodically oriented III-nitride materials

    Science.gov (United States)

    Hite, Jennifer

    2016-12-01

    The ability to grow III-nitride structures with alternating c-plane orientation has garnered interest in using these materials for new application spaces, such as frequency conversion. An overview of recent progress in growing periodically oriented (PO) III-nitrides is discussed, including AlN, AlGaN, and GaN. Successes in fabricating thick PO GaN structures (>500 mm) for uses in frequency conversion are highlighted.

  20. Optical studies of cubic III-nitride structures

    OpenAIRE

    Powell, Ross E L

    2014-01-01

    The properties of cubic nitrides grown by molecular beam epitaxy (MBE) on GaAs (001) have been studied using optical and electrical techniques. The aim of these studies was the improvement of the growth techniques in order to improve the quality of grown nitrides intended for bulk substrate and optoelectronic device applications. We have also characterised hexagonal nanocolumn structures incorporating indium. Firstly, bulk films of cubic AlxGa1-xN with aluminium fractions (x) spanning the ...

  1. Four-Wave Mixing in Silicon-Rich Nitride Waveguides

    DEFF Research Database (Denmark)

    Mitrovic, Miranda; Guan, Xiaowei; Ji, Hua

    2015-01-01

    We demonstrate four-wave mixing wavelength conversion in silicon-rich nitride waveguides which are a promising alternative to silicon for nonlinear applications. The obtained conversion efficiency reaches -13.6 dB while showing no significant nonlinear loss.......We demonstrate four-wave mixing wavelength conversion in silicon-rich nitride waveguides which are a promising alternative to silicon for nonlinear applications. The obtained conversion efficiency reaches -13.6 dB while showing no significant nonlinear loss....

  2. Defect reduction in seeded aluminum nitride crystal growth

    Science.gov (United States)

    Bondokov, Robert T.; Morgan, Kenneth E.; Schowalter, Leo J.; Slack, Glen A.

    2017-06-06

    Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density .ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

  3. Corrosion behavior of tantalum and its nitride in alkali solution

    Institute of Scientific and Technical Information of China (English)

    ZHANG Deyuan; LIN Qin; FEI Qinyong; ZHAO Haomin; KANG Guangyu; GENG Man

    2003-01-01

    The corrosion behavior of tantalum and its nitrides in stirring NaOH solutions was researched by potenfiostatic method, cyclic voltammetry and XPS. The results showed that the corrosion products were composed of Ta2O5 and NaTaO3.The corrosion reaction formula of tantalum and its nitrides was written according to cyclic volt-ampere curves. The electric charge transfer coefficient and the electric charge transfer number were calculated.

  4. CRITICAL ASSESSMENT: Gallium nitride based visible light emitting diodes

    OpenAIRE

    Oliver, Rachel A.

    2016-01-01

    This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Maney Publishing. Solid state lighting based on light-emitting diodes (LEDs) is a technology with the potential to drastically reduce energy usage, made possible by the development of gallium nitride and its alloys. However, the nitride materials family exhibits high defect densities and, in the equilibrium wurtzite crystal phase, large piezo-electric and polarisation fields arising a...

  5. Synthesis and Characterization of Hexagonal Boron Nitride (h- BN) Films

    Science.gov (United States)

    2014-01-09

    Synthesis 1. Diborane- ammonia (B2H6-NH3- gases): Early results with these precursors were published in 2012. 5 Briefly, LPCVD growth of h-BN in a hot-wall...Approved for public release; distribution is unlimited. Synthesis and Characterization of Hexagonal Boron Nitride (h- BN) Films. The views, opinions and...1 ABSTRACT Number of Papers published in peer-reviewed journals: Synthesis and Characterization of Hexagonal Boron Nitride (h-BN) Films. Report Title

  6. Colloidal Plasmonic Titanium Nitride Nanoparticles: Properties and Applications

    CERN Document Server

    Guler, Urcan; Kildishev, Alexander V; Boltasseva, Alexandra; Shalaev, Vladimir M

    2014-01-01

    Optical properties of colloidal plasmonic titanium nitride nanoparticles are examined with an eye on their photothermal via transmission electron microscopy and optical transmittance measurements. Single crystal titanium nitride cubic nanoparticles with an average size of 50 nm exhibit plasmon resonance in the biological transparency window. With dimensions optimized for efficient cellular uptake, the nanoparticles demonstrate a high photothermal conversion efficiency. A self-passivating native oxide at the surface of the nanoparticles provides an additional degree of freedom for surface functionalization.

  7. Study on Titanium Nitride Film Modified for Intraocular Lens

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Objective:To study the characteristics of the intraocular lens using ion beam sputtering depositing titanium nitride thin film on the intraocular lens(IOLs).Methods:To deposite titanium nitride thin film on the top of intraocular lens by ion beam sputtering depositing.We analyzed the surface morphology of intraocular lens through SEM and AFM.We detected intraocular lens resolution through the measurement of intraocular lens.Biocompatibility of intraocular lens is preliminary evaluated in this test.Results:T...

  8. Defect reduction in seeded aluminum nitride crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Bondokov, Robert T.; Morgan, Kenneth E.; Schowalter, Leo J.; Stack, Glen A.

    2017-04-18

    Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density.ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

  9. Performance of chromium nitride based coatings under plastic processing conditions

    OpenAIRE

    Cunha, l.; Andritschky, M.; Pischow, K.; Wang, Z.(Institute of High Energy Physics, Beijing, China); Zarychta, A.; Miranda, A. S.; A.M. Cunha

    2000-01-01

    Chromium nitride based coatings were produced in the form of monolithic and multilayer coatings, by DC and RF reactive magnetron sputtering. These coatings were deposited onto stainless steel and tool steel substrates. Chromium nitride coatings have;proved to be wear and corrosion resistant. The combination of these characteristics was necessary to protect surfaces during plastic processing. In order to select the best coatings, some mechanical and tribological tests were performed. Har...

  10. Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O

    Energy Technology Data Exchange (ETDEWEB)

    Kharlamov, Alexey [Frantsevich Institute for Problems of Materials Science of NASU, Krzhyzhanovsky St. 3, 03680 Kiev (Ukraine); Bondarenko, Marina, E-mail: mebondarenko@ukr.net [Frantsevich Institute for Problems of Materials Science of NASU, Krzhyzhanovsky St. 3, 03680 Kiev (Ukraine); Kharlamova, Ganna [Taras Shevchenko National University of Kiev, Volodymyrs' ka St. 64, 01601 Kiev (Ukraine); Fomenko, Veniamin [Frantsevich Institute for Problems of Materials Science of NASU, Krzhyzhanovsky St. 3, 03680 Kiev (Ukraine)

    2016-09-15

    For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09 nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists of weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets. - Graphical abstract: XRD pattern and schematic atomic model of one layer of reduced carbon nitride, carbon nitride oxide and synthesized carbon nitride. For the first time at the reduction by hydroquinone of the water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O is obtained the reduced carbon nitride (or reduced multi-layer azagraphene). Display Omitted - Highlights: • First the reduced carbon nitride (RCN) at the reduction of the carbon nitride oxide was obtained. • Water-soluble carbon nitride oxide was reduced by hydroquinone. • The chemical bonds in a heteroatomic plane of RCN correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. • Reduced carbon nitride consists of poorly connected heteroatomic azagraphene layers.

  11. Quantum emission from hexagonal boron nitride monolayers

    Science.gov (United States)

    Tran, Toan Trong; Bray, Kerem; Ford, Michael J.; Toth, Milos; Aharonovich, Igor

    2016-01-01

    Artificial atomic systems in solids are widely considered the leading physical system for a variety of quantum technologies, including quantum communications, computing and metrology. To date, however, room-temperature quantum emitters have only been observed in wide-bandgap semiconductors such as diamond and silicon carbide, nanocrystal quantum dots, and most recently in carbon nanotubes. Single-photon emission from two-dimensional materials has been reported, but only at cryogenic temperatures. Here, we demonstrate room-temperature, polarized and ultrabright single-photon emission from a colour centre in two-dimensional hexagonal boron nitride. Density functional theory calculations indicate that vacancy-related defects are a probable source of the emission. Our results demonstrate the unprecedented potential of van der Waals crystals for large-scale nanophotonics and quantum information processing.

  12. Aluminum nitride for heatspreading in RF IC's

    Science.gov (United States)

    La Spina, L.; Iborra, E.; Schellevis, H.; Clement, M.; Olivares, J.; Nanver, L. K.

    2008-09-01

    To reduce the electrothermal instabilities in silicon-on-glass high-frequency bipolar devices, the integration of thin-film aluminum nitride as a heatspreader is studied. The AlN is deposited by reactive sputtering and this material is shown to fulfill all the requirements for actively draining heat from RF IC's, i.e., it has good process compatibility, sufficiently high thermal conductivity and good electrical isolation also at high frequencies. The residual stress and the piezoelectric character of the material, both of which can be detrimental for the present application, are minimized by a suitable choice of deposition conditions including variable biasing of the substrate in a multistep deposition cycle. Films of AlN as thick as 4 μm are successfully integrated in RF silicon-on-glass bipolar junction transistors that display a reduction of more than 70% in the value of the thermal resistance.

  13. Thermal tuners on a Silicon Nitride platform

    CERN Document Server

    Pérez, Daniel; Baños, Rocío; Doménech, José David; Sánchez, Ana M; Cirera, Josep M; Mas, Roser; Sánchez, Javier; Durán, Sara; Pardo, Emilio; Domínguez, Carlos; Pastor, Daniel; Capmany, José; Muñoz, Pascual

    2016-01-01

    In this paper, the design trade-offs for the implementation of small footprint thermal tuners on silicon nitride are presented, and explored through measurements and supporting simulations of a photonic chip based on Mach-Zehnder Interferometers. Firstly, the electrical properties of the tuners are assessed, showing a compromise between compactness and deterioration. Secondly, the different variables involved in the thermal efficiency, switching power and heater dimensions, are analysed. Finally, with focus on exploring the limits of this compact tuners with regards to on chip component density, the thermal-cross talk is also investigated. Tuners with footprint of 270x5 {\\mu}m 2 and switching power of 350 mW are reported, with thermal-cross talk, in terms of induced phase change in adjacent devices of less than one order of magnitude at distances over 20 {\\mu}m. Paths for the improvement of thermal efficiency, power consumption and resilience of the devices are also outlined

  14. Boron Nitride Nanotube: Synthesis and Applications

    Science.gov (United States)

    Tiano, Amanda L.; Park, Cheol; Lee, Joseph W.; Luong, Hoa H.; Gibbons, Luke J.; Chu, Sang-Hyon; Applin, Samantha I.; Gnoffo, Peter; Lowther, Sharon; Kim, Hyun Jung; Danehy, Paul M.; Inman, Jennifer A.; Jones, Stephen B.; Kang, Jin Ho; Sauti, Godfrey; Thibeault, Sheila A.; Yamakov, Vesselin; Wise, Kristopher E.; Su, Ji; Fay, Catharine C.

    2014-01-01

    Scientists have predicted that carbon's immediate neighbors on the periodic chart, boron and nitrogen, may also form perfect nanotubes, since the advent of carbon nanotubes (CNTs) in 1991. First proposed then synthesized by researchers at UC Berkeley in the mid 1990's, the boron nitride nanotube (BNNT) has proven very difficult to make until now. Herein we provide an update on a catalyst-free method for synthesizing highly crystalline, small diameter BNNTs with a high aspect ratio using a high power laser under a high pressure and high temperature environment first discovered jointly by NASA/NIA JSA. Progress in purification methods, dispersion studies, BNNT mat and composite formation, and modeling and diagnostics will also be presented. The white BNNTs offer extraordinary properties including neutron radiation shielding, piezoelectricity, thermal oxidative stability (> 800 C in air), mechanical strength, and toughness. The characteristics of the novel BNNTs and BNNT polymer composites and their potential applications are discussed.

  15. Oxygen radical functionalization of boron nitride nanosheets.

    Science.gov (United States)

    Sainsbury, Toby; Satti, Amro; May, Peter; Wang, Zhiming; McGovern, Ignatius; Gun'ko, Yurii K; Coleman, Jonathan

    2012-11-14

    The covalent chemical functionalization of exfoliated hexagonal boron-nitride nanosheets (BNNSs) is achieved by the solution-phase oxygen radical functionalization of boron atoms in the h-BN lattice. This involves a two-step procedure to initially covalently graft alkoxy groups to boron atoms and the subsequent hydrolytic defunctionalization of the groups to yield hydroxyl-functionalized BNNSs (OH-BNNSs). Characterization of the functionalized-BNNSs using HR-TEM, Raman, UV-vis, FTIR, NMR, and TGA was performed to investigate both the structure of the BNNSs and the covalent functionalization methodology. OH-BNNSs were used to prepare polymer nanocomposites and their mechanical properties analyzed. The influence of the functional groups grafted to the surface of the BNNSs is investigated by demonstrating the impact on mechanical properties of both noncovalent and covalent bonding at the interface between the nanofiller and polymer matrixes.

  16. Mechanical Hysteresis of Hexagonal Boron Nitride

    Institute of Scientific and Technical Information of China (English)

    ZHOU Aiguo; LI Haoran

    2011-01-01

    Hexagonal boron nitride (h-BN) is an important structural material with layered microstructure.Because of the plastic anisotropy,this material shows obvious mechanical hysteresis (nonlinear elastic deformation).There are hysteretic loops at the cyclical load-unload stress-strain curves of h-BN.Consequently,two hot-pressed h-BN cylinders with different textures were studied.The mechanical hysteresis is heavily texture-dependent.The area of hysteretic loop is linearly related with the square of loading stresslevel.Two minor loops attached on the hysteretic loops with the same extreme stresses have congruent shapes.It can be concluded that the mechanical hysteresis of h-BN can he explained by a Kink Nonlinear Elastic model developed from the study of a ternary carbide Ti3SiC2.

  17. Pure and doped boron nitride nanotubes

    Directory of Open Access Journals (Sweden)

    M. Terrones

    2007-05-01

    Full Text Available More than ten years ago, it was suggested theoretically that boron nitride (BN nanotubes could be produced. Soon after, various reports on their synthesis appeared and a new area of nanotube science was born. This review aims to cover the latest advances related to the synthesis of BN nanotubes. We show that these tubes can now be produced in larger amounts and, in particular, that the chemistry of BN tubes appears to be very important to the production of reinforced composites with insulating characteristics. From the theoretical standpoint, we also show that (BN-C heteronanotubes could have important implications for nanoelectronics. We believe that BN nanotubes (pure and doped could be used in the fabrication of novel devices in which pure carbon nanotubes do not perform very efficiently.

  18. Laser ablation of molecular carbon nitride compounds

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, D., E-mail: d.fischer@fkf.mpg.de [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Schwinghammer, K. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience (CeNS), 80799 Munich (Germany); Sondermann, C. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Lau, V.W.; Mannhart, J. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Lotsch, B.V. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience (CeNS), 80799 Munich (Germany)

    2015-09-15

    We present a method for the preparation of thin films on sapphire substrates of the carbon nitride precursors dicyandiamide (C{sub 2}N{sub 4}H{sub 4}), melamine (C{sub 3}N{sub 6}H{sub 6}), and melem (C{sub 6}N{sub 10}H{sub 6}), using the femtosecond-pulsed laser deposition technique (femto-PLD) at different temperatures. The depositions were carried out under high vacuum with a femtosecond-pulsed laser. The focused laser beam is scanned on the surface of a rotating target consisting of the pelletized compounds. The resulting polycrystalline, opaque films were characterized by X-ray powder diffraction, infrared, Raman, and X-ray photoelectron spectroscopy, photoluminescence, SEM, and MALDI-TOF mass spectrometry measurements. The crystal structures and optical/spectroscopic results of the obtained rough films largely match those of the bulk materials.

  19. Carbon nitride frameworks and dense crystalline polymorphs

    Science.gov (United States)

    Pickard, Chris J.; Salamat, Ashkan; Bojdys, Michael J.; Needs, Richard J.; McMillan, Paul F.

    2016-09-01

    We used ab initio random structure searching (AIRSS) to investigate polymorphism in C3N4 carbon nitride as a function of pressure. Our calculations reveal new framework structures, including a particularly stable chiral polymorph of space group P 43212 containing mixed s p2 and s p3 bonding, that we have produced experimentally and recovered to ambient conditions. As pressure is increased a sequence of structures with fully s p3 -bonded C atoms and three-fold-coordinated N atoms is predicted, culminating in a dense P n m a phase above 250 GPa. Beyond 650 GPa we find that C3N4 becomes unstable to decomposition into diamond and pyrite-structured CN2.

  20. Cathodoluminescence spectra of gallium nitride nanorods.

    Science.gov (United States)

    Tsai, Chia-Chang; Li, Guan-Hua; Lin, Yuan-Ting; Chang, Ching-Wen; Wadekar, Paritosh; Chen, Quark Yung-Sung; Rigutti, Lorenzo; Tchernycheva, Maria; Julien, François Henri; Tu, Li-Wei

    2011-12-14

    Gallium nitride [GaN] nanorods grown on a Si(111) substrate at 720°C via plasma-assisted molecular beam epitaxy were studied by field-emission electron microscopy and cathodoluminescence [CL]. The surface topography and optical properties of the GaN nanorod cluster and single GaN nanorod were measured and discussed. The defect-related CL spectra of GaN nanorods and their dependence on temperature were investigated. The CL spectra along the length of the individual GaN nanorod were also studied. The results reveal that the 3.2-eV peak comes from the structural defect at the interface between the GaN nanorod and Si substrate. The surface state emission of the single GaN nanorod is stronger as the diameter of the GaN nanorod becomes smaller due to an increased surface-to-volume ratio.

  1. Thickness dependent thermal conductivity of gallium nitride

    Science.gov (United States)

    Ziade, Elbara; Yang, Jia; Brummer, Gordie; Nothern, Denis; Moustakas, Theodore; Schmidt, Aaron J.

    2017-01-01

    As the size of gallium nitride (GaN) transistors is reduced in order to reach higher operating frequencies, heat dissipation becomes the critical bottleneck in device performance and longevity. Despite the importance of characterizing the physics governing the thermal transport in thin GaN films, the literature is far from conclusive. In this letter, we report measurements of thermal conductivity in a GaN film with thickness ranging from 15-1000 nm grown on 4H-SiC without a transition layer. Additionally, we measure the thermal conductivity in the GaN film when it is 1 μm-thick in the temperature range of 300 < T < 600 K and use a phonon transport model to explain the thermal conductivity in this film.

  2. Nonlinear electronic transport behavior in Indium Nitride

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Cloves G., E-mail: cloves@pucgoias.edu.br [Departamento de Fisica, Pontificia Universidade Catolica de Goias, CP 86, 74605-010 Goiania, Goias (Brazil)

    2012-11-15

    A theoretical study on the nonlinear transport of electrons and of the nonequilibrium temperature in n-doped Indium Nitride under influence of moderate to high electric fields (in this nonlinear domain) is presented. It is based on a nonlinear quantum kinetic theory which provides a description of the dissipative phenomena developing in the system. The electric current and the mobility in the steady state are obtained, and their dependence on the electric field strength and on the concentration (that is, a mobility dependent nonlinearly on field and concentration) is obtained and analyzed. -- Highlights: Black-Right-Pointing-Pointer We have reported on the topic of nonlinear transport (electron mobility) in n-doped InN. Black-Right-Pointing-Pointer The results evidence the presence of two distinctive regimes. Black-Right-Pointing-Pointer The dependence of the mobility on the electric field is manifested through of the relaxation times.

  3. Multifractal characteristics of titanium nitride thin films

    Directory of Open Access Journals (Sweden)

    Ţălu Ştefan

    2015-09-01

    Full Text Available The study presents a multi-scale microstructural characterization of three-dimensional (3-D micro-textured surface of titanium nitride (TiN thin films prepared by reactive DC magnetron sputtering in correlation with substrate temperature variation. Topographical characterization of the surfaces, obtained by atomic force microscopy (AFM analysis, was realized by an innovative multifractal method which may be applied for AFM data. The surface micromorphology demonstrates that the multifractal geometry of TiN thin films can be characterized at nanometer scale by the generalized dimensions Dq and the singularity spectrum f(α. Furthermore, to improve the 3-D surface characterization according with ISO 25178-2:2012, the most relevant 3-D surface roughness parameters were calculated. To quantify the 3-D nanostructure surface of TiN thin films a multifractal approach was developed and validated, which can be used for the characterization of topographical changes due to the substrate temperature variation.

  4. CEMS of nitride coatings in agressive environments

    Energy Technology Data Exchange (ETDEWEB)

    Hanzel, D. [University of Ljubljana, J. Stefan Institute (Slovenia); Agudelo, A.C.; Gancedo, J.R. [Instituto de Quimica-Fisica ' Rocasolano' , CSIC (Spain); Lakatos-Varsanyi, M. [Eoetvoes University, Department of Physical Chemistry (Hungary); Marco, J.F. [Instituto de Quimica-Fisica ' Rocasolano' , CSIC (Spain)

    1998-12-15

    The corrosion properties of single layered TiN and CrN films have been compared to bi-layered and multi-layered Ti/TiN films. XPS has showed that in humid SO{sub 2} atmosphere the best corrosion properties have been achieved by a multi-layered Ti/TiN coating. Cyclic voltammetry in acetate buffer has been applied to measure the porousity and corrosion resistance of coatings. The best results have been achieved by multi-layered Ti/TiN and CrN films. Conversion electron Moessbauer spectroscopy has been used to study the changes in the interface Fe/TiN during thermal treatment in UHV. It has been shown that the amount of iron nitrides in the interface increases with increasing temperature.

  5. Optical processes in dilute nitrides Semiconductors; Alloys

    CERN Document Server

    Potter, R J

    2003-01-01

    This thesis is concerned with the narrow bandgap semiconductor alloys known as dilute nitrides. The initial part of this project was concerned with characterisation of chemical beam epitaxy (CBE) grown samples so that growth techniques could be refined. Early samples show evidence of structural/compositional disorder resulting from the large miscibility gap induced by nitrogen. Non-equilibrium growth was employed to overcome this, eventually resulting in improved material. In the second part of this project, steady-state and time-resolved photoluminescence, along with photomodulated reflectance were employed to investigate the optical properties of molecular beam epitaxy (MBE) grown GalnNAs, GaNAs and InGaAs quantum wells (QWs). Low temperature results show evidence of carrier localization, which was interpreted in terms of structural/compositional fluctuations induced by the nitrogen incorporation. Poor photoluminescence efficiency and rapid decay of emission kinetics indicate the presence of strong non-radi...

  6. Gallium Nitride Schottky betavoltaic nuclear batteries

    Energy Technology Data Exchange (ETDEWEB)

    Lu Min, E-mail: mlu2006@sinano.ac.c [Su zhou Institute of Nano-technology and Nano-bionics, CAS, Su zhou 215125 (China); Zhang Guoguang [China Institute of Atomic Energy, Beijing 102413 (China); Fu Kai; Yu Guohao [Su zhou Institute of Nano-technology and Nano-bionics, CAS, Su zhou 215125 (China); Su Dan; Hu Jifeng [China Institute of Atomic Energy, Beijing 102413 (China)

    2011-04-15

    Research highlights: {yields} Gallium Nitride nuclear batteries with Ni-63 are demonstrated for the first time. {yields} Open circuit voltage of 0.1 V and conversion efficiency of 0.32% have been obtained. {yields} The limited performance is due to thin effective energy deposition layer. {yields} The output power is expected to greatly increase with growing thick GaN films. -- Abstract: Gallium Nitride (GaN) Schottky betavoltaic nuclear batteries (GNBB) are demonstrated in our work for the first time. GaN films are grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD), and then GaN Schottky diodes are fabricated by normal micro-fabrication process. Nickel with mass number of 63 ({sup 63}Ni), which emits {beta} particles, is loaded on the GaN Schottky diodes to achieve GNBB. X-ray diffraction (XRD) and photoluminescence (PL) are carried out to investigate the crystal quality for the GaN films as grown. Current-voltage (I-V) characteristics shows that the GaN Schottky diodes are not jet broken down at -200 V due to consummate fabrication processes, and the open circuit voltage of the GNBB is 0.1 V and the short circuit current density is 1.2 nA cm{sup -2}. The limited performance of the GNBB is due to thin effective energy deposition layer, which is only 206 nm to absorb very small partial energy of the {beta} particles because of the relatively high dislocation density and carrier concentration. However, the conversion efficiency of 0.32% and charge collection efficiency (CCE) of 29% for the GNBB have been obtained. Therefore, the output power of the GNBB are expected to greatly increase with growing high quality thick GaN films.

  7. Facile synthesis of efficient photocatalytic tantalum nitride nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zheng; Wang, Jiangting; Hou, Jungang; Huang, Kai; Jiao, Shuqiang [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhu, Hongmin, E-mail: hzhu@ustb.edu.cn [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2012-11-15

    Graphical abstract: Tantalum nitride nanoparticles as a visible-light-driven photocatalyst prepared by a novel homogeneously chemical reduction of tantalum pentachloride using sodium in liquid ammonia and the morphologies, visible-light photocatalytic properties and stability of tantalum nitride nanoparticles were investigated. Highlights: ► Tantalum nitride nanoparticles have been prepared by a homogeneously chemical reduction. ► The crystal structure of tantalum nitride was determined by Rietveld refinement and XRD patterns. ► The Tantalum nitride nanoparticle size was in the range of 20–50 nm. ► Much high photocatalytic activities of Ta{sub 3}N{sub 5} nanoparticles were obtained under visible-light irradiation. -- Abstract: Tantalum nitride nanoparticles, as visible-light photocatalysts were synthesized by a two-step homogeneously chemical reduction without any polymers and templates. The well-crystallized Ta{sub 3}N{sub 5} nanoparticles with a range of 20–50 nm in size have been characterized by a number of techniques, such as XRD, XPS, SEM, TEM, BET and UV–Vis spectrum. Most importantly, the Ta{sub 3}N{sub 5} nanoparticles with good stability exhibited higher photooxidation activities in the water splitting and degradation of methylene blue under visible light irradiation than bulk Ta{sub 3}N{sub 5} particles and commercial P25 TiO{sub 2}, demonstrating that Ta{sub 3}N{sub 5} nanoparticle is a promising candidate as a visible-light photocatalyst.

  8. Nanotribological response of a plasma nitrided bio-steel.

    Science.gov (United States)

    Samanta, Aniruddha; Chakraborty, Himel; Bhattacharya, Manjima; Ghosh, Jiten; Sreemany, Monjoy; Bysakh, Sandip; Rane, Ramkrishna; Joseph, Alphonsa; Jhala, Ghanshyam; Mukherjee, Subroto; Das, Mitun; Mukhopadhyay, Anoop K

    2017-01-01

    AISI 316L is a well known biocompatible, austenitic stainless steel (SS). It is thus a bio-steel. Considering its importance as a bio-prosthesis material here we report the plasma nitriding of AISI 316L (SS) followed by its microstructural and nanotribological characterization. Plasma nitriding of the SS samples was carried out in a plasma reactor with a hot wall vacuum chamber. For ease of comparison these plasma nitrided samples were termed as SSPN. The experimental results confirmed the formations of an embedded nitrided metal layer zone (ENMLZ) and an interface zone (IZ) between the ENMLZ and the unnitrided bulk metallic layer zone (BMLZ) in the SSPN sample. These ENMLZ and IZ in the SSPN sample were richer in iron nitride (FeN) chromium nitride (CrN) along with the austenite phase. The results from nanoindentation, microscratch, nanoscratch and sliding wear studies confirmed that the static contact deformation resistance, the microwear, nanowear and sliding wear resistance of the SSPN samples were much better than those of the SS samples. These results were explained in terms of structure-property correlations. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Strategic research of advanced fuel cycle technologies in JNC

    Energy Technology Data Exchange (ETDEWEB)

    Kawata, T.; Fukushima, M.; Nomura, S. [Japan Nuclear Cycle Development Institute, Tokai Works (Japan)

    2000-07-01

    Key technologies for the future nuclear fuel cycle have been proposed and are being reviewed in JNC as a part of the Feasibility Study for an Advanced Fuel Cycle, which is to achieve a more flexible energy choice to satisfy a sustainable energy security and global environmental protection. The candidate reprocessing technologies are: 1) aqueous simplified PUREX process, 2) oxide or metallic electrowinning, and 3) fluoride volatilization for oxide, metal, or nitride fuels. The fuel fabrication methods being investigated are: 1) simplified pellet process, 2) sphere/vibro-packed process for MOX/MN fuel, and 3) casting for metal fuel. These candidate technologies are currently being compared based on past experiences, technical issues to be solved, industrial applicability for future plants, feasible options for MA/LLFP separation, and nonproliferation aspects. Alter two years of the present reviewing process, selected key technologies will be developed over the next five years to evaluate industrial applicability of reprocessing and fuel manufacturing processes for the advanced fuel cycle. (authors)

  10. Solar fuels

    Energy Technology Data Exchange (ETDEWEB)

    Bolton, J.R.

    1978-11-17

    The paper is concerned with (1) the thermodynamic and kinetic limits for the photochemical conversion and storage of solar energy as it is received on the earth's surface, and (2) the evaluation of a number of possible photochemical reactions with particular emphasis on the production of solar hydrogen from water. Procedures for generating hydrogen fuel are considered. Topics examined include the general requirements for a fuel-generation reaction, the photochemical reaction, limits on the conversion of light energy to chemical energy, an estimate of chemical storage efficiency, and the water decomposition reaction.

  11. Generation and Characteristics of IV-VI transition Metal Nitride and Carbide Nanoparticles using a Reactive Mesoporous Carbon Nitride

    KAUST Repository

    Alhajri, Nawal Saad

    2016-02-22

    Interstitial nitrides and carbides of early transition metals in groups IV–VI exhibit platinum-like electronic structures, which make them promising candidates to replace noble metals in various catalytic reactions. Herein, we present the preparation and characterization of nano-sized transition metal nitries and carbides of groups IV–VI (Ti, V, Nb, Ta, Cr, Mo, and W) using mesoporous graphitic carbon nitride (mpg-C3N4), which not only provides confined spaces for restricting primary particle size but also acts as a chemical source of nitrogen and carbon. We studied the reactivity of the metals with the template under N2 flow at 1023 K while keeping the weight ratio of metal to template constant at unity. The produced nanoparticles were characterized by powder X-ray diffraction, CHN elemental analysis, nitrogen sorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. The results show that Ti, V, Nb, Ta, and Cr form nitride phases with face centered cubic structure, whereas Mo and W forme carbides with hexagonal structures. The tendency to form nitride or carbide obeys the free formation energy of the transition metal nitrides and carbides. This method offers the potential to prepare the desired size, shape and phase of transition metal nitrides and carbides that are suitable for a specific reaction, which is the chief objective of materials chemistry.

  12. Fuel Cells

    Science.gov (United States)

    Hawkins, M. D.

    1973-01-01

    Discusses the theories, construction, operation, types, and advantages of fuel cells developed by the American space programs. Indicates that the cell is an ideal small-scale power source characterized by its compactness, high efficiency, reliability, and freedom from polluting fumes. (CC)

  13. Transport fuel

    DEFF Research Database (Denmark)

    Ronsse, Frederik; Jørgensen, Henning; Schüßler, Ingmar

    2014-01-01

    Worldwide, the use of transport fuel derived from biomass increased four-fold between 2003 and 2012. Mainly based on food resources, these conventional biofuels did not achieve the expected emission savings and contributed to higher prices for food commod - ities, especially maize and oilseeds...

  14. Nitride coating enhances endothelialization on biomedical NiTi shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ion, Raluca [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Luculescu, Catalin [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, 077125 Magurele-Bucharest (Romania); Cimpean, Anisoara, E-mail: anisoara.cimpean@bio.unibuc.ro [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Marx, Philippe [AMF Company, Route de Quincy, 18120 Lury-sur-Arnon (France); Gordin, Doina-Margareta; Gloriant, Thierry [INSA Rennes, UMR CNRS 6226 ISCR, 20 Avenue des Buttes de Coësmes, 35708 Rennes Cedex 7 (France)

    2016-05-01

    Surface nitriding was demonstrated to be an effective process for improving the biocompatibility of implantable devices. In this study, we investigated the benefits of nitriding the NiTi shape memory alloy for vascular stent applications. Results from cell experiments indicated that, compared to untreated NiTi, a superficial gas nitriding treatment enhanced the adhesion of human umbilical vein endothelial cells (HUVECs), cell spreading and proliferation. This investigation provides data to demonstrate the possibility of improving the rate of endothelialization on NiTi by means of nitride coating. - Highlights: • Gas nitriding process of NiTi is competent to promote cell spreading. • Surface nitriding of NiTi is able to stimulate focal adhesion formation and cell proliferation. • Similar expression pattern of vWf and eNOS was exhibited by bare and nitrided NiTi. • Gas nitriding treatment of NiTi shows promise for better in vivo endothelialization.

  15. First principles calculations of interstitial and lamellar rhenium nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Soto, G., E-mail: gerardo@cnyn.unam.mx [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Km 107 Carretera Tijuana-Ensenada, Ensenada Baja California (Mexico); Tiznado, H.; Reyes, A.; Cruz, W. de la [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Km 107 Carretera Tijuana-Ensenada, Ensenada Baja California (Mexico)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer The possible structures of rhenium nitride as a function of composition are analyzed. Black-Right-Pointing-Pointer The alloying energy is favorable for rhenium nitride in lamellar arrangements. Black-Right-Pointing-Pointer The structures produced by magnetron sputtering are metastable variations. Black-Right-Pointing-Pointer The structures produced by high-pressure high-temperature are stable configurations. Black-Right-Pointing-Pointer The lamellar structures are a new category of interstitial dissolutions. - Abstract: We report here a systematic first principles study of two classes of variable-composition rhenium nitride: i, interstitial rhenium nitride as a solid solution and ii, rhenium nitride in lamellar structures. The compounds in class i are cubic and hexagonal close-packed rhenium phases, with nitrogen in the octahedral and tetrahedral interstices of the metal, and they are formed without changes to the structure, except for slight distortions of the unit cells. In the compounds in class ii, by contrast, the nitrogen inclusion provokes stacking faults in the parent metal structure. These faults create trigonal-prismatic sites where the nitrogen residence is energetically favored. This second class of compounds produces lamellar structures, where the nitrogen lamellas are inserted among multiple rhenium layers. The Re{sub 3}N and Re{sub 2}N phases produced recently by high-temperature and high-pressure synthesis belong to this class. The ratio of the nitrogen layers to the rhenium layers is given by the composition. While the first principle calculations point to higher stability for the lamellar structures as opposed to the interstitial phases, the experimental evidence presented here demonstrates that the interstitial classes are synthesizable by plasma methods. We conclude that rhenium nitrides possess polymorphism and that the two-dimensional lamellar structures might represent an emerging class of materials

  16. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate.

    Science.gov (United States)

    Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

    2014-01-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm(2) using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

  17. Fast Reactor Fuel Type and Reactor Safety Performance

    Energy Technology Data Exchange (ETDEWEB)

    R. Wigeland; J. Cahalan

    2009-09-01

    Fast Reactor Fuel Type and Reactor Safety Performance R. Wigeland , Idaho National Laboratory J. Cahalan, Argonne National Laboratory The sodium-cooled fast neutron reactor is currently being evaluated for the efficient transmutation of the highly-hazardous, long-lived, transuranic elements that are present in spent nuclear fuel. One of the fundamental choices that will be made is the selection of the fuel type for the fast reactor, whether oxide, metal, carbide, nitride, etc. It is likely that a decision on the fuel type will need to be made before many of the related technologies and facilities can be selected, from fuel fabrication to spent fuel reprocessing. A decision on fuel type should consider all impacts on the fast reactor system, including safety. Past work has demonstrated that the choice of fuel type may have a significant impact on the severity of consequences arising from accidents, especially for severe accidents of low probability. In this paper, the response of sodium-cooled fast reactors is discussed for both oxide and metal fuel types, highlighting the similarities and differences in reactor response and accident consequences. Any fast reactor facility must be designed to be able to successfully prevent, mitigate, or accommodate all consequences of potential events, including accidents. This is typically accomplished by using multiple barriers to the release of radiation, including the cladding on the fuel, the intact primary cooling system, and most visibly the reactor containment building. More recently, this has also included the use of ‘inherent safety’ concepts to reduce or eliminate the potential for serious damage in some cases. Past experience with oxide and metal fuel has demonstrated that both fuel types are suitable for use as fuel in a sodium-cooled fast reactor. However, safety analyses for these two fuel types have also shown that there can be substantial differences in accident consequences due to the neutronic and

  18. Effect of variation of silicon nitride passivation layer on electron irradiated aluminum gallium nitride/gallium nitride HEMT structures

    Science.gov (United States)

    Jackson, Helen C.

    Silicon nitride passivation on AlGaNGaN heterojunction devices can improve performance by reducing electron traps at the surface. This research studies the effect of displacement damage caused by 1 MeV electron irradiation as a function of the variation of passivation layer thickness and heterostructure layer variation on AlGaN/GaN HEMTs. The effects of passivation layer thickness are investigated at thicknesses of 0, 20, 50 and 120 nanometers on AlGaNGaN test structures with either an AlN nucleation layer or a GaN cap structures which are then measured before and immediately after 1.0 MeV electron irradiation at fluences of 1016 cm-2. Hall system measurements are used to observe changes in mobility, carrier concentration and conductivity as a function of Si3N4 thickness. Models are developed that relate the device structure and passivation layer under 1 MeV radiation to the observed changes to the measured photoluminescence and deep level transient spectroscopy. A software model is developed to determine the production rate of defects from primary 1 MeV electrons that can be used for other energies and materials. The presence of either a 50 or 120 nm Si 3N4 passivation layer preserves the channel current for both and appears to be optimal for radiation hardness.

  19. DFT Studies on Electronic Structures of Boro-Nitride-Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    YAN Ming; HUANG Chun-Hui

    2005-01-01

    In this paper, the configurations of Boro-Nitride-Carbon nanotubes with BNC2 composition were optimized by ROHF method. According to the density functional theory, the electronic structures of Boro-Nitride-Carbon nanotubes were calculated by DFT/ROB3LYP method. By analyzing the energy gap, density of electronic state and bonding maps of atoms, the conductive properties of Boro-Nitride-Carbon nanotubes were obtained, and compared with those of carbon nanotubes and other Boro-Nitride nanotubes.

  20. Evanescent field phase shifting in a silicon nitride waveguide using a coupled silicon slab

    DEFF Research Database (Denmark)

    Jensen, Asger Sellerup; Oxenløwe, Leif Katsuo; Green, William M. J.

    2015-01-01

    An approach for electrical modulation of low-loss silicon nitride waveguides is proposed, using a silicon nitride waveguide evanescently loaded with a thin silicon slab. The thermooptic phase-shift characteristics are investigated in a racetrack resonator configuration.......An approach for electrical modulation of low-loss silicon nitride waveguides is proposed, using a silicon nitride waveguide evanescently loaded with a thin silicon slab. The thermooptic phase-shift characteristics are investigated in a racetrack resonator configuration....

  1. Electroless plating of thin gold films directly onto silicon nitride thin films and into micropores.

    Science.gov (United States)

    Whelan, Julie C; Karawdeniya, Buddini Iroshika; Bandara, Y M Nuwan D Y; Velleco, Brian D; Masterson, Caitlin M; Dwyer, Jason R

    2014-07-23

    A method to directly electrolessly plate silicon-rich silicon nitride with thin gold films was developed and characterized. Films with thicknesses plating free-standing ultrathin silicon nitride membranes, and we successfully plated the interior walls of micropore arrays in 200 nm thick silicon nitride membranes. The method is thus amenable to coating planar, curved, and line-of-sight-obscured silicon nitride surfaces.

  2. Technical assistance for development of thermally conductive nitride filler for epoxy molding compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Ho Jin; Song, Kee Chan; Jung, In Ha

    2005-07-15

    Technical assistance was carried out to develop nitride filler for thermally conductive epoxy molding compounds. Carbothermal reduction method was used to fabricate silicon nitride powder from mixtures of silica and graphite powders. Microstructure and crystal structure were observed by using scanning electron microscopy and x-ray diffraction technique. Thermal properties of epoxy molding compounds containing silicon nitride were measured by using laser flash method. Fabrication process of silicon nitride nanowire was developed and was applied to a patent.

  3. Ab-initio study of C and O impurities in uranium nitride

    Science.gov (United States)

    Lopes, Denise Adorno; Claisse, Antoine; Olsson, Pär

    2016-09-01

    Uranium nitride (UN) has been considered a potential fuel for Generation IV (GEN-IV) nuclear reactors as well as a possible new fuel for Light Water Reactors (LWR), which would permit an extension of the fuel residence time in the reactor. Carbon and oxygen impurities play a key role in the UN microstructure, influencing important parameters such as creep, swelling, gas release under irradiation, compatibility with structural steel and coolants, and thermal stability. In this work, a systematic study of the electronic structure of UN containing C and O impurities using first-principles calculations by the Density Functional Theory (DFT) method is presented. In order to describe accurately the localized U 5f electrons, the DFT + U formalism was adopted. Moreover, to avoid convergence toward metastable states, the Occupation Matrix Control (OMC) methodology was applied. The incorporation of C and O in the N-vacancy is found to be energetically favorable. In addition, only for O, the incorporation in the interstitial position is energetically possible, showing some degree of solubility for this element in this site. The binding energies show that the pairs (Csbnd Nvac) and (Osbnd Nvac) interact much further than the other defects, which indicate the possible occurrence of vacancy drag phenomena and clustering of these impurities in grain boundaries, dislocations and free surfaces. The migration energy of an impurity by single N-vacancy show that C and O employ different paths during diffusion. Oxygen migration requires significantly lower energy than carbon. This fact is due to flexibility in the Usbnd O chemical bonds, which bend during the diffusion forming a pseudo UO2 coordination. On the other hand, C and N have a directional and inflexible chemical bond with uranium; always requiring the octahedral coordination. These findings provide detailed insight into how these impurities behave in the UN matrix, and can be of great interest for assisting the development of

  4. Performance analysis of nitride alternative plasmonic materials for localized surface plasmon applications

    DEFF Research Database (Denmark)

    Guler, U.; Naik, G. V.; Boltasseva, Alexandra

    2012-01-01

    . Titanium nitride and zirconium nitride, which were recently suggested as alternative plasmonic materials in the visible and near-infrared ranges, are compared to the performance of gold. In contrast to the results from quasistatic methods, both nitride materials are very good alternatives to the usual...

  5. UN{sub 2−x} layer formed on uranium metal by glow plasma nitriding

    Energy Technology Data Exchange (ETDEWEB)

    Long, Zhong [China Academy of Engineering Physics, P.O. Box 919-71, Mianyang 621907 (China); Hu, Yin [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Chen, Lin [China Academy of Engineering Physics, P.O. Box 919-71, Mianyang 621907 (China); Luo, Lizhu [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Liu, Kezhao, E-mail: liukz@hotmail.com [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Lai, Xinchun, E-mail: lai319@yahoo.com [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China)

    2015-01-25

    Highlights: • We used a very simple method to prepare nitride layer on uranium metal surface. • This modified layer is nitrogen-rich nitride, which should be written as UN{sub 2−x}. • TEM images show the nitride layer is composed of nano-sized grains. • XPS analysis indicates there is uranium with abnormal low valence in the nitride. - Abstract: Glow plasma nitriding is a simple and economical surface treatment method, and this technology was used to prepare nitride layer on the surface of uranium metal with thickness of several microns. The composition and structure of the nitride layer were analyzed by AES and XRD, indicating that this modified layer is nitrogen-rich uranium nitride, which should be written as UN{sub 2−x}. TEM images show the nitride layer is composed of nano-sized grains, with compact structure. And XPS analysis indicates there is uranium with abnormal low valence existing in the nitride. After the treated uranium storage in air for a long time, oxygen just entered the surface several nanometers, showing the nitride layer has excellent oxidation resistance. The mechanism of nitride layer formation and low valence uranium appearance is discussed.

  6. Corrosion behaviour of the 42CrMo4 Steel Nitrided by Plasma

    Directory of Open Access Journals (Sweden)

    Okba Belahssen

    2014-01-01

    Full Text Available This paper presents corrosion behaviour of alloy 42CrMo4 steel nitrided by plasma. Different samples were tested: untreated and plasma nitrided samples. The corrosion behaviour was evaluated by electrochemical techniques (potentiodynamic curves and electrochemical impedance spectroscopy. The corrosion tests were carried out in acid chloride solution 1M. The best corrosion protection was observed for samples nitrided.

  7. Turbostratic boron nitride coated on high-surface area metal oxide templates

    DEFF Research Database (Denmark)

    Klitgaard, Søren Kegnæs; Egeblad, Kresten; Brorson, M.

    2007-01-01

    Boron nitride coatings on high-surface area MgAl2O4 and Al2O3 have been synthesized and characterized by transmission electron microscopy and by X-ray powder diffraction. The metal oxide templates were coated with boron nitride using a simple nitridation in a flow of ammonia starting from ammonium...

  8. Imaging Gallium Nitride High Electron Mobility Transistors to Identify Point Defects

    Science.gov (United States)

    2014-03-01

    REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE IMAGING GALLIUM NITRIDE HIGH ELECTRON MOBILITY TRANSISTORS TO IDENTIFY...Identification of these trends will assist in the improvement of gallium nitride HEMT fabrication processes leading to the development of more...reliable devices. 14. SUBJECT TERMS Electron microscopy, Gallium Nitride (GaN), high electron mobility transistor (HEMT

  9. Corrosion behaviour of the 42CrMo4 Steel Nitrided by Plasma

    OpenAIRE

    Okba Belahssen; Abdelouahed Chala; Said Benramache

    2014-01-01

    This paper presents corrosion behaviour of alloy 42CrMo4 steel nitrided by plasma. Different samples were tested: untreated and plasma nitrided samples. The corrosion behaviour was evaluated by electrochemical techniques (potentiodynamic curves and electrochemical impedance spectroscopy). The corrosion tests were carried out in acid chloride solution 1M. The best corrosion protection was observed for samples nitrided.

  10. Effective Duration of Gas Nitriding Process on AISI 316L for the Formation of a Desired Thickness of Surface Nitrided Layer

    Directory of Open Access Journals (Sweden)

    Mahmoud Hassan R. S.

    2014-07-01

    Full Text Available High temperature gas nitriding performed on AISI 316L at the temperature of 1200°C. The microstructure of treated AISI 316L samples were observed to identify the formation of the microstructure of nitrided surface layer. The grain size of austenite tends to be enlarged when the nitriding time increases, but the austenite single phase structure is maintained even after the long-time solution nitriding. Using microhardness testing, the hardness values drop to the center of the samples. The increase in surface hardness is due to the high nitrogen concentration at or near the surface. At 245HV, the graph of the effective duration of nitriding process was plotted to achieve the maximum depth of nitrogen diffuse under the surface. Using Sigma Plot software best fit lines of the experimental result found and plotted to find out effective duration of nitriding equation as Y=1.9491(1-0.7947x, where Y is the thickness of nitrided layer below the surface and X is duration of nitriding process. Based on this equation, the duration of gas nitriding process can be estimated to produce desired thickness of nitrided layer.

  11. Functional carbon nitride materials — design strategies for electrochemical devices

    Science.gov (United States)

    Kessler, Fabian K.; Zheng, Yun; Schwarz, Dana; Merschjann, Christoph; Schnick, Wolfgang; Wang, Xinchen; Bojdys, Michael J.

    2017-06-01

    In the past decade, research in the field of artificial photosynthesis has shifted from simple, inorganic semiconductors to more abundant, polymeric materials. For example, polymeric carbon nitrides have emerged as promising materials for metal-free semiconductors and metal-free photocatalysts. Polymeric carbon nitride (melon) and related carbon nitride materials are desirable alternatives to industrially used catalysts because they are easily synthesized from abundant and inexpensive starting materials. Furthermore, these materials are chemically benign because they do not contain heavy metal ions, thereby facilitating handling and disposal. In this Review, we discuss the building blocks of carbon nitride materials and examine how strategies in synthesis, templating and post-processing translate from the molecular level to macroscopic properties, such as optical and electronic bandgap. Applications of carbon nitride materials in bulk heterojunctions, laser-patterned memory devices and energy storage devices indicate that photocatalytic overall water splitting on an industrial scale may be realized in the near future and reveal a new avenue of 'post-silicon electronics'.

  12. Two-dimensional gallium nitride realized via graphene encapsulation

    Science.gov (United States)

    Al Balushi, Zakaria Y.; Wang, Ke; Ghosh, Ram Krishna; Vilá, Rafael A.; Eichfeld, Sarah M.; Caldwell, Joshua D.; Qin, Xiaoye; Lin, Yu-Chuan; Desario, Paul A.; Stone, Greg; Subramanian, Shruti; Paul, Dennis F.; Wallace, Robert M.; Datta, Suman; Redwing, Joan M.; Robinson, Joshua A.

    2016-11-01

    The spectrum of two-dimensional (2D) and layered materials `beyond graphene’ offers a remarkable platform to study new phenomena in condensed matter physics. Among these materials, layered hexagonal boron nitride (hBN), with its wide bandgap energy (~5.0-6.0 eV), has clearly established that 2D nitrides are key to advancing 2D devices. A gap, however, remains between the theoretical prediction of 2D nitrides `beyond hBN’ and experimental realization of such structures. Here we demonstrate the synthesis of 2D gallium nitride (GaN) via a migration-enhanced encapsulated growth (MEEG) technique utilizing epitaxial graphene. We theoretically predict and experimentally validate that the atomic structure of 2D GaN grown via MEEG is notably different from reported theory. Moreover, we establish that graphene plays a critical role in stabilizing the direct-bandgap (nearly 5.0 eV), 2D buckled structure. Our results provide a foundation for discovery and stabilization of 2D nitrides that are difficult to prepare via traditional synthesis.

  13. Surface properties of nitrided layer on AISI 316L austenitic stainless steel produced by high temperature plasma nitriding in short time

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yang, E-mail: metalytu@163.com [Department of Materials Science and Engineering, Yantai University, Qingquan Road 32, Yantai 264005 (China); Wang, Zhuo [Department of Materials Science and Engineering, Yantai University, Qingquan Road 32, Yantai 264005 (China); Wang, Liang [Department of Materials Science and Engineering, Dalian Maritime University, Linghai Road 1, Dalian 116026 (China)

    2014-04-01

    Graphical abstract: - Highlights: • The 8 μm nitrided layer was produced on the surface of AISI 316L stainless steel by plasma nitrided at high temperatures (540 °C) within 1 h. • The nitrided layer consisted of nitrogen expanded austenite and possibly a small amount of free-CrN and iron nitrides. • It could critically reduce processing time compared with low temperature nitriding. • High temperature plasma nitriding could improve pitting corrosion resistance of the substrate in 3.5% NaCl solution. - Abstract: It has generally been believed that the formation of the S phase or expanded austenite γ{sub N} with enough thickness depends on the temperature (lower than 480 °C) and duration of the process. In this work, we attempt to produce nitrogen expanded austenite layer at high temperature in short time. Nitriding of AISI 316L austenitic stainless steel was carried out at high temperatures (>520 °C) for times ranging from 5 to 120 min. The microstructures, chemical composition, the thickness and the morphology of the nitrided layer, as well as its surface hardness, were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, optical microscopy, scanning electron microscopy, and microhardness tester. The corrosion properties of the untreated and nitrided samples were evaluated using anodic polarization tests in 3.5% NaCl solution. The results confirmed that nitrided layer was shown to consist of γ{sub N} and a small amount of free-CrN and iron nitrides. High temperature plasma nitriding not only increased the surface hardness but also improved the corrosion resistance of the austenitic stainless steel, and it can critically reduce processing time compared with low temperature nitriding.

  14. Fluorescent lighting with aluminum nitride phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Cherepy, Nerine J.; Payne, Stephen A.; Seeley, Zachary M.; Srivastava, Alok M.

    2016-05-10

    A fluorescent lamp includes a glass envelope; at least two electrodes connected to the glass envelope; mercury vapor and an inert gas within the glass envelope; and a phosphor within the glass envelope, wherein the phosphor blend includes aluminum nitride. The phosphor may be a wurtzite (hexagonal) crystalline structure Al.sub.(1-x)M.sub.xN phosphor, where M may be drawn from beryllium, magnesium, calcium, strontium, barium, zinc, scandium, yttrium, lanthanum, cerium, praseodymium, europium, gadolinium, terbium, ytterbium, bismuth, manganese, silicon, germanium, tin, boron, or gallium is synthesized to include dopants to control its luminescence under ultraviolet excitation. The disclosed Al.sub.(1-x)M.sub.xN:Mn phosphor provides bright orange-red emission, comparable in efficiency and spectrum to that of the standard orange-red phosphor used in fluorescent lighting, Y.sub.2O.sub.3:Eu. Furthermore, it offers excellent lumen maintenance in a fluorescent lamp, and does not utilize "critical rare earths," minimizing sensitivity to fluctuating market prices for the rare earth elements.

  15. Porous Boron Nitride with Tunable Pore Size.

    Science.gov (United States)

    Dai, Jun; Wu, Xiaojun; Yang, Jinlong; Zeng, Xiao Cheng

    2014-01-16

    On the basis of a global structural search and first-principles calculations, we predict two types of porous boron-nitride (BN) networks that can be built up with zigzag BN nanoribbons (BNNRs). The BNNRs are either directly connected with puckered B (N) atoms at the edge (type I) or connected with sp(3)-bonded BN chains (type II). Besides mechanical stability, these materials are predicted to be thermally stable at 1000 K. The porous BN materials entail large surface areas, ranging from 2800 to 4800 m(2)/g. In particular, type-II BN material with relatively large pores is highly favorable for hydrogen storage because the computed hydrogen adsorption energy (-0.18 eV) is very close to the optimal adsorption energy (-0.15 eV) suggested for reversible hydrogen storage at room temperature. Moreover, the type-II materials are semiconductors with width-dependent direct bandgaps, rendering the type-II BN materials promising not only for hydrogen storage but also for optoelectronic and photonic applications.

  16. Nonlinear Refractory Plasmonics with Titanium Nitride Nanoantennas.

    Science.gov (United States)

    Gui, Lili; Bagheri, Shahin; Strohfeldt, Nikolai; Hentschel, Mario; Zgrabik, Christine M; Metzger, Bernd; Linnenbank, Heiko; Hu, Evelyn L; Giessen, Harald

    2016-09-14

    Titanium nitride (TiN) is a novel refractory plasmonic material which can sustain high temperatures and exhibits large optical nonlinearities, potentially opening the door for high-power nonlinear plasmonic applications. We fabricate TiN nanoantenna arrays with plasmonic resonances tunable in the range of about 950-1050 nm by changing the antenna length. We present second-harmonic (SH) spectroscopy of TiN nanoantenna arrays, which is analyzed using a nonlinear oscillator model with a wavelength-dependent second-order response from the material itself. Furthermore, characterization of the robustness upon strong laser illumination confirms that the TiN antennas are able to endure laser irradiation with high peak intensity up to 15 GW/cm(2) without changing their optical properties and their physical appearance. They outperform gold antennas by one order of magnitude regarding laser power sustainability. Thus, TiN nanoantennas could serve as promising candidates for high-power/high-temperature applications such as coherent nonlinear converters and local heat sources on the nanoscale.

  17. Fully CMOS-compatible titanium nitride nanoantennas

    Energy Technology Data Exchange (ETDEWEB)

    Briggs, Justin A., E-mail: jabriggs@stanford.edu [Department of Applied Physics, Stanford University, 348 Via Pueblo Mall, Stanford, California 94305 (United States); Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, California 94305 (United States); Naik, Gururaj V.; Baum, Brian K.; Dionne, Jennifer A. [Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, California 94305 (United States); Petach, Trevor A.; Goldhaber-Gordon, David [Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, California 94305 (United States)

    2016-02-01

    CMOS-compatible fabrication of plasmonic materials and devices will accelerate the development of integrated nanophotonics for information processing applications. Using low-temperature plasma-enhanced atomic layer deposition (PEALD), we develop a recipe for fully CMOS-compatible titanium nitride (TiN) that is plasmonic in the visible and near infrared. Films are grown on silicon, silicon dioxide, and epitaxially on magnesium oxide substrates. By optimizing the plasma exposure per growth cycle during PEALD, carbon and oxygen contamination are reduced, lowering undesirable loss. We use electron beam lithography to pattern TiN nanopillars with varying diameters on silicon in large-area arrays. In the first reported single-particle measurements on plasmonic TiN, we demonstrate size-tunable darkfield scattering spectroscopy in the visible and near infrared regimes. The optical properties of this CMOS-compatible material, combined with its high melting temperature and mechanical durability, comprise a step towards fully CMOS-integrated nanophotonic information processing.

  18. Hexagonal boron-nitride nanomesh magnets

    Science.gov (United States)

    Ohata, C.; Tagami, R.; Nakanishi, Y.; Iwaki, R.; Nomura, K.; Haruyama, J.

    2016-09-01

    The formation of magnetic and spintronic devices using two-dimensional (2D) atom-thin layers has attracted attention. Ferromagnetisms (FMs) arising from zigzag-type atomic structure of edges of 2D atom-thin materials have been experimentally observed in graphene nanoribbons, hydrogen (H)-terminated graphene nanomeshes (NMs), and few-layer oxygen (O)-terminated black phosphorus NMs. Herein, we report room-temperature edge FM in few-layer hexagonal boron-nitride (hBN) NMs. O-terminated hBNNMs annealed at 500 °C show the largest FM, while it completely disappears in H-terminated hBNNMs. When hBNNMs are annealed at other temperatures, amplitude of the FM significantly decreases. These are highly in contrast to the case of graphene NMs but similar to the cases of black phosphorus NM and suggest that the hybridization of the O atoms with B(N) dangling bonds of zigzag pore edges, formed at the 500 °C annealing, strongly contribute to this edge FM. Room-temperature FM realizable only by exposing hBNNMs into air opens the way for high-efficiency 2D flexible magnetic and spintronic devices without the use of rare magnetic elements.

  19. Alumimun nitride piezoelectric NEMS resonators and switches

    Science.gov (United States)

    Piazza, G.

    2010-04-01

    A major challenge associated with the demonstration of high frequency and fast NanoElectroMechanical Systems (NEMS) components is the ability to efficiently transduce the nanomechanical device. This work presents noteworthy opportunities associated with the scaling of piezoelectric aluminum nitride (AlN) films from the micro to the nano realm and their application to the making of efficient NEMS resonators and switches that can be directly interfaced with conventional electronics. Experimental data showing NEMS AlN resonators (250 nm thick with lateral features as small as 300 nm) vibrating at record-high frequencies approaching 10 GHz with Qs close to 500 are presented. These NEMS resonators could be employed as sensors to tag analyte concentrations that reach the part per trillion levels or for frequency synthesis and filtering in ultra-compact microwave transceivers. 100 nm thick AlN films have been used to fabricate NEMS actuators for mechanical computing applications. Experimental data confirming that bimorph nanopiezo- actuators have the same piezoelectric properties of microscale counterparts and can be adopted for the implementation of mechanical logic elements are presented.

  20. Fully CMOS-compatible titanium nitride nanoantennas

    Science.gov (United States)

    Briggs, Justin A.; Naik, Gururaj V.; Petach, Trevor A.; Baum, Brian K.; Goldhaber-Gordon, David; Dionne, Jennifer A.

    2016-02-01

    CMOS-compatible fabrication of plasmonic materials and devices will accelerate the development of integrated nanophotonics for information processing applications. Using low-temperature plasma-enhanced atomic layer deposition (PEALD), we develop a recipe for fully CMOS-compatible titanium nitride (TiN) that is plasmonic in the visible and near infrared. Films are grown on silicon, silicon dioxide, and epitaxially on magnesium oxide substrates. By optimizing the plasma exposure per growth cycle during PEALD, carbon and oxygen contamination are reduced, lowering undesirable loss. We use electron beam lithography to pattern TiN nanopillars with varying diameters on silicon in large-area arrays. In the first reported single-particle measurements on plasmonic TiN, we demonstrate size-tunable darkfield scattering spectroscopy in the visible and near infrared regimes. The optical properties of this CMOS-compatible material, combined with its high melting temperature and mechanical durability, comprise a step towards fully CMOS-integrated nanophotonic information processing.

  1. Hyperbolic phonon polaritons in hexagonal boron nitride

    Science.gov (United States)

    Dai, Siyuan

    2015-03-01

    Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. While hyperbolic responses are normally achieved with metamaterials, hexagonal boron nitride (hBN) naturally possesses this property due to the anisotropic phonons in the mid-infrared. Using scattering-type scanning near-field optical microscopy, we studied polaritonic phenomena in hBN. We performed infrared nano-imaging of highly confined and low-loss hyperbolic phonon polaritons in hBN. The polariton wavelength was shown to be governed by the hBN thickness according to a linear law persisting down to few atomic layers [Science, 343, 1125-1129 (2014)]. Additionally, we carried out the modification of hyperbolic response in heterostructures comprised of a mononlayer graphene deposited on hBN. Electrostatic gating of the top graphene layer allows for the modification of wavelength and intensity of hyperbolic phonon polaritons in bulk hBN. The physics of the modification originates from the plasmon-phonon coupling in the hyperbolic medium. Furthermore, we demonstrated the ``hyperlens'' for subdiffractional imaging and focusing using a slab of hBN.

  2. Preparation of graphitic carbon nitride by electrodeposition

    Institute of Scientific and Technical Information of China (English)

    LI Chao; CAO Chuanbao; ZHU Hesun

    2003-01-01

    The CNx thin film was deposited on Si(100) substrate from a saturated acetone solution of cyanuric trichloride and melamine (cyanuric trichloride/melamine=1︰1.5) at room temperature. X-ray diffraction (XRD) results showed that the diffraction peaks in the pattern coincided well with those of graphite-like carbon nitride calculated in the literature. The lattice constants (a=4.79 A, c=6.90 A) for g-C3N4 matched with those of ab initio calculations (a=4.74 A, c=6.72 A) quite well. X-ray photoelectron spectroscopy (XPS) measurements indicated that the elements in the deposited films were mostly of C and N (N/C=0.75), and N (400.00 eV) bonded with C (287.72 eV) in the form of six-member C3N3 ring. The peaks at 800 cm-1, 1310 cm-1 and 1610 cm-1 in the Fourier transform infrared (FTIR) spectrum indicated that triazine ring existed in the product. These results demonstrated that crystalline g-C3N4 was obtained in the CNx film.

  3. Polymeric photocatalysts based on graphitic carbon nitride.

    Science.gov (United States)

    Cao, Shaowen; Low, Jingxiang; Yu, Jiaguo; Jaroniec, Mietek

    2015-04-01

    Semiconductor-based photocatalysis is considered to be an attractive way for solving the worldwide energy shortage and environmental pollution issues. Since the pioneering work in 2009 on graphitic carbon nitride (g-C3N4) for visible-light photocatalytic water splitting, g-C3N4 -based photocatalysis has become a very hot research topic. This review summarizes the recent progress regarding the design and preparation of g-C3N4 -based photocatalysts, including the fabrication and nanostructure design of pristine g-C3N4 , bandgap engineering through atomic-level doping and molecular-level modification, and the preparation of g-C3N4 -based semiconductor composites. Also, the photo-catalytic applications of g-C3N4 -based photocatalysts in the fields of water splitting, CO2 reduction, pollutant degradation, organic syntheses, and bacterial disinfection are reviewed, with emphasis on photocatalysis promoted by carbon materials, non-noble-metal cocatalysts, and Z-scheme heterojunctions. Finally, the concluding remarks are presented and some perspectives regarding the future development of g-C3N4 -based photocatalysts are highlighted.

  4. Boron Nitride Nanostructures: Fabrication, Functionalization and Applications.

    Science.gov (United States)

    Yin, Jun; Li, Jidong; Hang, Yang; Yu, Jin; Tai, Guoan; Li, Xuemei; Zhang, Zhuhua; Guo, Wanlin

    2016-06-01

    Boron nitride (BN) structures are featured by their excellent thermal and chemical stability and unique electronic and optical properties. However, the lack of controlled synthesis of quality samples and the electrically insulating property largely prevent realizing the full potential of BN nanostructures. A comprehensive overview of the current status of the synthesis of two-dimensional hexagonal BN sheets, three dimensional porous hexagonal BN materials and BN-involved heterostructures is provided, highlighting the advantages of different synthetic methods. In addition, structural characterization, functionalizations and prospective applications of hexagonal BN sheets are intensively discussed. One-dimensional BN nanoribbons and nanotubes are then discussed in terms of structure, fabrication and functionality. In particular, the existing routes in pursuit of tunable electronic and magnetic properties in various BN structures are surveyed, calling upon synergetic experimental and theoretical efforts to address the challenges for pioneering the applications of BN into functional devices. Finally, the progress in BN superstructures and novel B/N nanostructures is also briefly introduced.

  5. Nanoscale optical properties of indium gallium nitride/gallium nitride nanodisk-in-rod heterostructures.

    Science.gov (United States)

    Zhou, Xiang; Lu, Ming-Yen; Lu, Yu-Jung; Jones, Eric J; Gwo, Shangjr; Gradečak, Silvija

    2015-03-24

    III-nitride based nanorods and nanowires offer great potential for optoelectronic applications such as light emitting diodes or nanolasers. We report nanoscale optical studies of InGaN/GaN nanodisk-in-rod heterostructures to quantify uniformity of light emission on the ensemble level, as well as the emission characteristics from individual InGaN nanodisks. Despite the high overall luminescence efficiency, spectral and intensity inhomogeneities were observed and directly correlated to the compositional variations among nanodisks and to the presence of structural defect, respectively. Observed light quenching is correlated to type I1 stacking faults in InGaN nanodisks, and the mechanisms for stacking fault induced nonradiative recombinations are discussed in the context of band structure around stacking faults and Fermi level pinning at nanorod surfaces. Our results highlight the importance of controlling III-nitride nanostructure growths to further reduce defect formation and ensure compositional homogeneity for optoelectronic devices with high efficiencies and desirable spectrum response.

  6. Fuel control system for dual fuel engines

    Energy Technology Data Exchange (ETDEWEB)

    Helmich, M.J.; Ryan, W.P.; Marvin, D.H.

    1987-11-24

    A fuel governing system for an engine adapted for operation on a first fuel and a second fuel is described comprising: a first fuel governing system including a spontaneous motion metering means; and a second fuel governing system, the second fuel governing system further comprising: means for providing a first signal indicative of position of the first fuel metering means, which signal approximates total load on the engine, means for providing a second signal of the selected percentage of first fuel relative to total load, means for controlling flow of the second fuel to the engine, which flow causes reflective displacement of the first fuel metering means, means for determining the difference between the first signal and the second signal, which difference is indicative of distance the first fuel metering means must be moved to attain the selected percentage of first fuel relative to total load, and means for causing operation of the means for controlling flow of the second fuel to the engine to cause displacement of the first fuel metering means equal to the distance the first fuel metering means must be moved to attain the selected percentage of first fuel relative to total load.

  7. A Stability Study of Ni/Yttria-Stabilized Zirconia Anode for Direct Ammonia Solid Oxide Fuel Cells.

    Science.gov (United States)

    Yang, Jun; Molouk, Ahmed Fathi Salem; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Eguchi, Koichi

    2015-12-30

    In recent years, solid oxide fuel cells fueled with ammonia have been attracting intensive attention. In this work, ammonia fuel was supplied to the Ni/yttria-stabilized zirconia (YSZ) cermet anode at 600 and 700 °C, and the change of electrochemical performance and microstructure under the open-circuit state was studied in detail. The influence of ammonia exposure on the microstructure of Ni was also investigated by using Ni/YSZ powder and Ni film deposited on a YSZ disk. The obtained results demonstrated that Ni in the cermet anode was partially nitrided under an ammonia atmosphere, which considerably roughened the Ni surface. Moreover, the destruction of the anode support layer was confirmed for the anode-supported cell upon the temperature cycling test between 600 and 700 °C because of the nitriding phenomenon of Ni, resulting in severe performance degradation.

  8. Hexagonal boron nitride nanoparticles decorated halloysite clay nanotubes as a potential hydrogen storage medium

    Energy Technology Data Exchange (ETDEWEB)

    Muthu, R. Naresh, E-mail: rnaresh7708@gmail.com; Rajashabala, S. [School of Physics, Madurai Kamaraj University, Madurai-625021, Tamil Nadu (India); Kannan, R. [Department of Physics, University College of Engineering, Anna University, Dindigul-624622 (India); Department of Materials Science and Engineering, Cornell University, Ithaca 14850, New York (United States)

    2016-05-23

    The light weight and compact hydrogen storage materials is still prerequisite for the carbon free hydrogen fuel cell technology. In this work, the hydrogen storage performance of acid treated halloysite clay nanotubes (A-HNTs) and hexagonal boron nitride (h-BN) nanoparticles decorated acid treated halloysite nanoclay composite (A-HNT-h-BN) are demonstrated, where facile ultrasonic technique is adopted for the synthesis of A-HNT-h-BN nanoclay composite. Hydrogen storage studies were carried out using Sieverts-like hydrogenation setup. The A-HNTs and A-HNT-h-BN nanoclay composite were analyzed by XRD, FTIR, HRTEM, EDX, CHNS-elemental analysis and TGA. The A-HNT-h-BN nanoclay composite shows superior storage capacity of 2.19 wt% at 50 °C compared to the A-HNTs (0.58 wt%). A 100% desorption of stored hydrogen is noted in the temperature range of 138–175 °C. The average binding energy of hydrogen was found to be 0.34 eV for the prepared A-HNT-h-BN nanoclay composite. The excellent storage capability of A-HNT-h-BN nanoclay composite towards hydrogen at ambient temperature may find bright perspective in hydrogen fuel cell technology in near future.

  9. Hexagonal boron nitride nanoparticles decorated halloysite clay nanotubes as a potential hydrogen storage medium

    Science.gov (United States)

    Muthu, R. Naresh; Rajashabala, S.; Kannan, R.

    2016-05-01

    The light weight and compact hydrogen storage materials is still prerequisite for the carbon free hydrogen fuel cell technology. In this work, the hydrogen storage performance of acid treated halloysite clay nanotubes (A-HNTs) and hexagonal boron nitride (h-BN) nanoparticles decorated acid treated halloysite nanoclay composite (A-HNT-h-BN) are demonstrated, where facile ultrasonic technique is adopted for the synthesis of A-HNT-h-BN nanoclay composite. Hydrogen storage studies were carried out using Sieverts-like hydrogenation setup. The A-HNTs and A-HNT-h-BN nanoclay composite were analyzed by XRD, FTIR, HRTEM, EDX, CHNS-elemental analysis and TGA. The A-HNT-h-BN nanoclay composite shows superior storage capacity of 2.19 wt% at 50 °C compared to the A-HNTs (0.58 wt%). A 100% desorption of stored hydrogen is noted in the temperature range of 138-175 °C. The average binding energy of hydrogen was found to be 0.34 eV for the prepared A-HNT-h-BN nanoclay composite. The excellent storage capability of A-HNT-h-BN nanoclay composite towards hydrogen at ambient temperature may find bright perspective in hydrogen fuel cell technology in near future.

  10. Structure and properties of nitrided surface layer produced on NiTi shape memory alloy by low temperature plasma nitriding

    Energy Technology Data Exchange (ETDEWEB)

    Czarnowska, Elżbieta [Children' s Memorial Health Institute, Pathology Department, Al. Dzieci Polskich 20, 04-730 Warsaw (Poland); Borowski, Tomasz [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland); Sowińska, Agnieszka [Children' s Memorial Health Institute, Pathology Department, Al. Dzieci Polskich 20, 04-730 Warsaw (Poland); Lelątko, Józef [Silesia University, Faculty of Computer Science and Materials Science, 75 Pułku Piechoty 1A, 41-500 Chorzów (Poland); Oleksiak, Justyna; Kamiński, Janusz; Tarnowski, Michał [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland); Wierzchoń, Tadeusz, E-mail: twierz@inmat.pw.edu.pl [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland)

    2015-04-15

    Highlights: • Low temperature plasma nitriding process of NiTi shape memory alloy is presented. • The possibility of treatment details of sophisticated shape. • TiN surface layer has diffusive character. • TiN surface layer increases corrosion resistance of NiTi alloy. • Produced TiN layer modify the biological properties of NiTi alloy. - Abstract: NiTi shape memory alloys are used for bone and cardiological implants. However, on account of the metallosis effect, i.e. the release of the alloy elements into surrounding tissues, they are subjected to various surface treatment processes in order to improve their corrosion resistance and biocompatibility without influencing the required shape memory properties. In this paper, the microstructure, topography and morphology of TiN surface layer on NiTi alloy, and corrosion resistance, both before and after nitriding in low-temperature plasma at 290 °C, are presented. Examinations with the use of the potentiodynamic and electrochemical impedance spectroscopy methods were carried out and show an increase of corrosion resistance in Ringer's solution after glow-discharge nitriding. This surface titanium nitride layer also improved the adhesion of platelets and the proliferation of osteoblasts, which was investigated in in vitro experiments with human cells. Experimental data revealed that nitriding NiTi shape memory alloy under low-temperature plasma improves its properties for bone implant applications.

  11. Elastic properties of indium nitrides grown on sapphire substrates determined by nano-indentation: In comparison with other nitrides

    Directory of Open Access Journals (Sweden)

    Ichiro Yonenaga

    2015-07-01

    Full Text Available The hardness of wurtzite indium nitride (α-InN films of 0.5 to 4 μm in thickness was measured by the nano-indentation method at room temperature. After investigation of crystalline quality by x-ray diffraction, the hardness and Young’s modulus were determined to be 8.8 ± 0.4 and 184 ± 5 GPa, respectively, for the In (0001- and N ( 000 1 ̄ -growth faces of InN films. The bulk and shear moduli were then derived to be 99 ± 3 and 77 ± 2 GPa, respectively. The Poisson’s ratio was evaluated to be 0.17 ± 0.03. The results were examined comprehensively in comparison with previously reported data of InN as well as those of other nitrides of aluminum nitride and gallium nitride. The underlying physical process determining the moduli and hardness was examined in terms of atomic bonding and dislocation energy of the nitrides and wurtzite zinc oxide.

  12. Preliminary Investigation of Candidate Materials for Use in Accident Resistant Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Jason M. Harp; Paul A. Lessing; Blair H. Park; Jakeob Maupin

    2013-09-01

    As part of a Collaborative Research and Development Agreement (CRADA) with industry, Idaho National Laboratory (INL) is investigating several options for accident resistant uranium compounds including silicides, and nitrides for use in future light water reactor (LWR) fuels. This work is part of a larger effort to create accident tolerant fuel forms where changes to the fuel pellets, cladding, and cladding treatment are considered. The goal fuel form should have a resistance to water corrosion comparable to UO2, have an equal to or larger thermal conductivity than uranium dioxide, a melting temperature that allows the material to stay solid under power reactor conditions, and a uranium loading that maintains or improves current LWR power densities. During the course of this research, fuel fabricated at INL will be characterized, irradiated at the INL Advanced Test Reactor, and examined after irradiation at INL facilities to help inform industrial partners on candidate technologies.

  13. Low-Temperature Nitriding by Means of SMAT

    Institute of Scientific and Technical Information of China (English)

    W.P. Tong; H.W. Zhang; N.R. Tao; Z.B. Wang; J. Lu; K. Lu

    2004-01-01

    The microstructure in the surface layer of iron and steel samples can be refined at the nanometer scale by means of a surface mechanical attrition treatment (SMAT) that generates repetitive severe plastic deformation to the surface layer.The subsequent nitriding kinetics of the as-treated samples with the nanostructured surface layer is greatly enhanced so that the nitriding temperatures can be reduce to 300 ~ 400 ℃ regions. This enhanced processing method demonstrates both the technological significance of nanomaterials in advancing the traditional processing techniques, and provides a new approach for selective surface reactions in solids. This article reviews the present state of the art in this field. The microstructure and properties of SMAT samples nitrided will be summarized. Further considerations of the development and applications of this new technique will also be presented.

  14. Nanoparticle plasmonics: going practical with transition metal nitrides

    Directory of Open Access Journals (Sweden)

    Urcan Guler

    2015-05-01

    Full Text Available Promising designs and experimental realizations of devices with unusual properties in the field of plasmonics have attracted a great deal of attention over the past few decades. However, the high expectations for realized technology products have not been met so far. The main complication is the absence of robust, high performance, low cost plasmonic materials that can be easily integrated into already established technologies such as microelectronics. This review provides a brief discussion on alternative plasmonic materials for localized surface plasmon applications and focuses on transition metal nitrides, in particular, titanium nitride, which has recently been shown to be a high performance refractory plasmonic material that could replace and even outperform gold in various plasmonic devices. As a material compatible with biological environments and the semiconductor industry, titanium nitride possesses superior properties compared to noble metals such as high temperature durability, chemical stability, corrosion resistance, low cost and mechanical hardness.

  15. Nitridation in Photon-Assisted Process Using Argon Excimer Lamp

    Science.gov (United States)

    Toshikawa, Kiyohiko; Amari, Kouichi; Ishimura, Sou; Katto, Masahito; Yokotani, Atsushi; Kurosawa, Kou

    2006-05-01

    We attempted silicon nitridation that continuously deposits silicon with monosilane (SiH4) and nitrides the silicon with ammonia (NH3) at a low temperature using a vacuum ultraviolet excimer lamp. We used an argon excimer lamp (λ=126 nm, h ν=9.8 eV) so that SiH4 and NH3 can absorb photons and dissociate. Nitrogen exists only near the film surface at a low temperature, and its concentration increases at a high temperature. This photon-assisted process is very feasible for the nitridation of semiconductor devices and flat panel displays in the near future, because it is a low-temperature and low-damage process.

  16. Electronic Biosensors Based on III-Nitride Semiconductors

    Science.gov (United States)

    Kirste, Ronny; Rohrbaugh, Nathaniel; Bryan, Isaac; Bryan, Zachary; Collazo, Ramon; Ivanisevic, Albena

    2015-07-01

    We review recent advances of AlGaN/GaN high-electron-mobility transistor (HEMT)-based electronic biosensors. We discuss properties and fabrication of III-nitride-based biosensors. Because of their superior biocompatibility and aqueous stability, GaN-based devices are ready to be implemented as next-generation biosensors. We review surface properties, cleaning, and passivation as well as different pathways toward functionalization, and critically analyze III-nitride-based biosensors demonstrated in the literature, including those detecting DNA, bacteria, cancer antibodies, and toxins. We also discuss the high potential of these biosensors for monitoring living cardiac, fibroblast, and nerve cells. Finally, we report on current developments of covalent chemical functionalization of III-nitride devices. Our review concludes with a short outlook on future challenges and projected implementation directions of GaN-based HEMT biosensors.

  17. Thermally grown thin nitride films as a gate dielectric

    CERN Document Server

    Shin, H C; Hwang, T K; Lee, K R

    1998-01-01

    High-quality very thin films ( <=6 nm) of silicon nitride were thermally grown in ammonia atmosphere with an IR (Infrared) gold image furnace. As-grown nitride film was analyzed using AES(Auger Emission Spectroscopy). Using MIS (Metal-Insulator-Semiconductor) devices, the growth rate was calculated using CV (Capacitance-Voltage) measurements and various electrical characteristics were obtained using CV, IV (Current-Voltage), trapping, time-dependent breakdown, high-field stress, constant current injection stress and dielectric breakdown techniques. These characteristics showed that very thin thermal silicon nitride films can be used as gate dielectrics for future highly scaled-down ULSI (Ultra Large Scale Integrated) devices, especially for EEPROM (Electrically Erasable and Programmable ROM)'s.

  18. Electronic Biosensors Based on III-Nitride Semiconductors.

    Science.gov (United States)

    Kirste, Ronny; Rohrbaugh, Nathaniel; Bryan, Isaac; Bryan, Zachary; Collazo, Ramon; Ivanisevic, Albena

    2015-01-01

    We review recent advances of AlGaN/GaN high-electron-mobility transistor (HEMT)-based electronic biosensors. We discuss properties and fabrication of III-nitride-based biosensors. Because of their superior biocompatibility and aqueous stability, GaN-based devices are ready to be implemented as next-generation biosensors. We review surface properties, cleaning, and passivation as well as different pathways toward functionalization, and critically analyze III-nitride-based biosensors demonstrated in the literature, including those detecting DNA, bacteria, cancer antibodies, and toxins. We also discuss the high potential of these biosensors for monitoring living cardiac, fibroblast, and nerve cells. Finally, we report on current developments of covalent chemical functionalization of III-nitride devices. Our review concludes with a short outlook on future challenges and projected implementation directions of GaN-based HEMT biosensors.

  19. Effect of oxygen plasma on nanomechanical silicon nitride resonators

    Science.gov (United States)

    Luhmann, Niklas; Jachimowicz, Artur; Schalko, Johannes; Sadeghi, Pedram; Sauer, Markus; Foelske-Schmitz, Annette; Schmid, Silvan

    2017-08-01

    Precise control of tensile stress and intrinsic damping is crucial for the optimal design of nanomechanical systems for sensor applications and quantum optomechanics in particular. In this letter, we study the influence of oxygen plasma on the tensile stress and intrinsic damping of nanomechanical silicon nitride resonators. Oxygen plasma treatments are common steps in micro and nanofabrication. We show that oxygen plasma for only a few minutes oxidizes the silicon nitride surface, creating several nanometer thick silicon dioxide layers with a compressive stress of 1.30(16) GPa. Such oxide layers can cause a reduction in the effective tensile stress of a 50 nm thick stoichiometric silicon nitride membrane by almost 50%. Additionally, intrinsic damping linearly increases with the silicon dioxide film thickness. An oxide layer of 1.5 nm grown in just 10 s in a 50 W oxygen plasma almost doubled the intrinsic damping. The oxide surface layer can be efficiently removed in buffered hydrofluoric acid.

  20. Active Control of Nitride Plasmonic Dispersion in the Far Infrared.

    Energy Technology Data Exchange (ETDEWEB)

    Shaner, Eric A.; Dyer, Gregory Conrad; Seng, William Francis; Bethke, Donald Thomas; Grine, Albert Dario,; Baca, Albert G.; Allerman, Andrew A.

    2014-11-01

    We investigate plasmonic structures in nitride-based materials for far-infrared (IR) applications. The two dimensional electron gas (2DEG) in the GaN/AlGaN material system, much like metal- dielectric structures, is a patternable plasmonic medium. However, it also permits for direct tunability via an applied voltage. While there have been proof-of-principle demonstrations of plasma excitations in nitride 2DEGs, exploration of the potential of this material system has thus far been limited. We recently demonstrated coherent phenomena such as the formation of plasmonic crystals, strong coupling of tunable crystal defects to a plasmonic crystal, and electromagnetically induced transparency in GaAs/AlGaAs 2DEGs at sub-THz frequencies. In this project, we explore whether these effects can be realized in nitride 2DEG materials above 1 THz and at temperatures exceeding 77 K.

  1. Cobalt phosphate-modified barium-doped tantalum nitride nanorod photoanode with 1.5% solar energy conversion efficiency

    KAUST Repository

    Li, Yanbo

    2013-10-03

    Spurred by the decreased availability of fossil fuels and global warming, the idea of converting solar energy into clean fuels has been widely recognized. Hydrogen produced by photoelectrochemical water splitting using sunlight could provide a carbon dioxide lean fuel as an alternative to fossil fuels. A major challenge in photoelectrochemical water splitting is to develop an efficient photoanode that can stably oxidize water into oxygen. Here we report an efficient and stable photoanode that couples an active barium-doped tantalum nitride nanostructure with a stable cobalt phosphate co-catalyst. The effect of barium doping on the photoelectrochemical activity of the photoanode is investigated. The photoanode yields a maximum solar energy conversion efficiency of 1.5%, which is more than three times higher than that of state-of-the-art single-photon photoanodes. Further, stoichiometric oxygen and hydrogen are stably produced on the photoanode and the counter electrode with Faraday efficiency of almost unity for 100 min. © 2013 Macmillan Publishers Limited. All rights reserved.

  2. Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C3N4)O

    Science.gov (United States)

    Kharlamov, Alexey; Bondarenko, Marina; Kharlamova, Ganna; Fomenko, Veniamin

    2016-09-01

    For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C3N4)O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09 nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C3N4. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists of weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets.

  3. Hardness evaluation, stoichiometry and grain size of titanium nitride films obtained with plasma nitriding on Ti-6Al-4V samples

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcellos, Marcos Antonio Zen; Lima, Saulo Cordeiro; Hinrichs, Ruth [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre (Brazil)

    2010-07-01

    Titanium nitride films were formed on the surface of Ti-6Al-4V discs by plasma nitriding (glow discharge) in different N{sub 2}:H{sub 2} atmospheres at several substrate temperatures. In this study the influence of the process parameters on dynamic micro-hardness were investigated. Grain sizes of the nitride films, determined with X Ray Diffraction, were related to the nitriding parameters. TiNx stoichiometry was determined with Nuclear Reaction Analysis and showed a correlation to substrate temperature during the nitriding process. Micro-hardness measurements were taken on the nitrided surfaces. Grain sizes increased for a particular gas composition of 60%N{sub 2}+40%H{sub 2} where hardness was lowest. (author)

  4. Compressive creep of silicon nitride with additives; Fluencia por compressao de nitreto de silicio aditivado

    Energy Technology Data Exchange (ETDEWEB)

    Shibuya, Newton Hissao; Cavalcanti, Celso Berilo Cidade; Piorino Neto, Francisco; Silva, Vitor Alexandre da; Silva, Cosme Roberto Moreira da [Centro Tecnico Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil). Inst. de Aeronautica e Espaco

    1995-12-31

    Manufacturing of engine and turbine components made of silicon nitride based ceramics requires knowledge of thermochemical properties such as resistance to compressive creep. In order to characterize this property a compressive creep apparatus was assembled at AMR/IAE/CTA, able to work at 1450 deg C in a continuous mode. Test pieces were prepared from mixtures of silicon nitride with rare earth carbonate and aluminium nitride. These test pieces were pressureless sintered at 1750 deg C for 30 minutes under nitrogen atmosphere. Experiments showed that rare earth carbonate and aluminium nitride are suitable additives for silicon nitride. (author) 1 fig., 2 tabs.

  5. Effect of Plasma Nitriding Parameters on the Wear Resistance of Alloy Inconel 718

    Science.gov (United States)

    Kovací, Halim; Ghahramanzadeh ASL, Hojjat; Albayrak, Çigdem; Alsaran, Akgün; Çelik, Ayhan

    2016-11-01

    The effect of the temperature and duration of plasma nitriding on the microstructure and friction and wear parameters of Inconel 718 nickel alloy is investigated. The process of plasma nitriding is conducted in a nitrogen-hydrogen gaseous mixture at a temperature of 400, 500 and 600°C for 1 and 4 h. The modulus of elasticity of the nitrided layer, the micro- and nanohardness, the surface roughness, the friction factor and the wear resistance of the alloy are determined prior to and after the nitriding. The optimum nitriding regime providing the best tribological characteristics is determined.

  6. Neutron detection using boron gallium nitride semiconductor material

    OpenAIRE

    Katsuhiro Atsumi; Yoku Inoue; Hidenori Mimura; Toru Aoki; Takayuki Nakano

    2014-01-01

    In this study, we developed a new neutron-detection device using a boron gallium nitride (BGaN) semiconductor in which the B atom acts as a neutron converter. BGaN and gallium nitride (GaN) samples were grown by metal organic vapor phase epitaxy, and their radiation detection properties were evaluated. GaN exhibited good sensitivity to α-rays but poor sensitivity to γ-rays. Moreover, we confirmed that electrons were generated in the depletion layer under neutron irradiation. This resulted in ...

  7. Lateral electrochemical etching of III-nitride materials for microfabrication

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jung

    2017-02-28

    Conductivity-selective lateral etching of III-nitride materials is described. Methods and structures for making vertical cavity surface emitting lasers with distributed Bragg reflectors via electrochemical etching are described. Layer-selective, lateral electrochemical etching of multi-layer stacks is employed to form semiconductor/air DBR structures adjacent active multiple quantum well regions of the lasers. The electrochemical etching techniques are suitable for high-volume production of lasers and other III-nitride devices, such as lasers, HEMT transistors, power transistors, MEMs structures, and LEDs.

  8. New amorphous interface for precipitate nitrides in steel

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Kadkhodazadeh, Shima; Grumsen, Flemming Bjerg

    2014-01-01

    to be enveloped in an amorphous shell a few nm thick, thus leaving them without any coherency with the matrix. The amorphous nature of the shells could be ascertained with high resolution microscopy and dark field techniques. When extracted from the ferrite matrix the amorphous shells were observed to crystallize...... during electron beam exposure. The amorphous shells were observed around Ta- and Nb-based nitrides, which are considered to have a high interfacial energy with the ferrite matrix. They were not observed around V-based nitrides which have a Baker–Nutting relationship with low-misfit to the matrix....

  9. Inter-layer potential for hexagonal boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Leven, Itai; Hod, Oded, E-mail: odedhod@tau.ac.il [Department of Chemical Physics, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978 (Israel); Azuri, Ido; Kronik, Leeor [Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100 (Israel)

    2014-03-14

    A new interlayer force-field for layered hexagonal boron nitride (h-BN) based structures is presented. The force-field contains three terms representing the interlayer attraction due to dispersive interactions, repulsion due to anisotropic overlaps of electron clouds, and monopolar electrostatic interactions. With appropriate parameterization, the potential is able to simultaneously capture well the binding and lateral sliding energies of planar h-BN based dimer systems as well as the interlayer telescoping and rotation of double walled boron-nitride nanotubes of different crystallographic orientations. The new potential thus allows for the accurate and efficient modeling and simulation of large-scale h-BN based layered structures.

  10. Structure, Mechanics and Synthesis of Nanoscale Carbon and Boron Nitride

    Science.gov (United States)

    Rinaldo, Steven G.

    This thesis is divided into two parts. In Part I, we examine the properties of thin sheets of carbon and boron nitride. We begin with an introduction to the theory of elastic sheets, where the stretching and bending modes are considered in detail. The coupling between stretching and bending modes is thought to play a crucial role in the thermodynamic stability of atomically-thin 2D sheets such as graphene. In Chapter 2, we begin by looking at the fabrication of suspended, atomically thin sheets of graphene. We then study their mechanical resonances which are read via an optical transduction technique. The frequency of the resonators was found to depend on their temperature, as was their quality factor. We conclude by offering some interpretations of the data in terms of the stretching and bending modes of graphene. In Chapter 3, we look briefly at the fabrication of thin sheets of carbon and boron nitride nanotubes. We examine the structure of the sheets using transmission and scanning electron microscopy (TEM and SEM, respectively). We then show a technique by which one can make sheets suspended over a trench with adjustable supports. Finally, DC measurements of the resistivity of the sheets in the temperature range 600 -- 1400 C are presented. In Chapter 4, we study the folding of few-layer graphene oxide, graphene and boron nitride into 3D aerogel monoliths. The properties of graphene oxide are first considered, after which the structure of graphene and boron nitride aerogels is examined using TEM and SEM. Some models for their structure are proposed. In Part II, we look at synthesis techniques for boron nitride (BN). In Chapter 5, we study the conversion of carbon structures of boron nitride via the application of carbothermal reduction of boron oxide followed by nitridation. We apply the conversion to a wide variety of morphologies, including aerogels, carbon fibers and nanotubes, and highly oriented pyrolytic graphite. In the latter chapters, we look at the

  11. Size effects in band gap bowing in nitride semiconducting alloys

    DEFF Research Database (Denmark)

    Gorczyca, I.; Suski, T.; Christensen, Niels Egede

    2011-01-01

    Chemical and size contributions to the band gap bowing of nitride semiconducting alloys (InxGa1-xN, InxAl1-xN, and AlxGa1-xN) are analyzed. It is shown that the band gap deformation potentials of the binary constituents determine the gap bowing in the ternary alloys. The particularly large gap bo...... bowing in In-containing nitride alloys can be explained by specific properties of InN, which do not follow trends observed in several other binaries....

  12. Wear monitoring of protective nitride coatings using image processing

    DEFF Research Database (Denmark)

    Rasmussen, Inge Lise; Guibert, M.; Belin, M.

    2010-01-01

    A double-layer model system, consisting of a thin layer of tribological titanium aluminum nitride (TiAlN) on 17 top of titanium nitride (TiN), was deposited on polished 100Cr6 steel substrates. The TiAlN top-coatings 18 were exposed to abrasive wear by a reciprocating wear process in a linear tribo...... processing by color detection is a potential technique for early 25 warning or determination of residual thickness of tribological tool coatings prior to complete wear....

  13. Communication: Water on hexagonal boron nitride from diffusion Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Al-Hamdani, Yasmine S.; Ma, Ming; Michaelides, Angelos, E-mail: angelos.michaelides@ucl.ac.uk [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Alfè, Dario [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT (United Kingdom); Lilienfeld, O. Anatole von [Institute of Physical Chemistry and National Center for Computational Design and Discovery of Novel Materials, Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel (Switzerland); Argonne Leadership Computing Facility, Argonne National Laboratories, 9700 S. Cass Avenue Argonne, Lemont, Illinois 60439 (United States)

    2015-05-14

    Despite a recent flurry of experimental and simulation studies, an accurate estimate of the interaction strength of water molecules with hexagonal boron nitride is lacking. Here, we report quantum Monte Carlo results for the adsorption of a water monomer on a periodic hexagonal boron nitride sheet, which yield a water monomer interaction energy of −84 ± 5 meV. We use the results to evaluate the performance of several widely used density functional theory (DFT) exchange correlation functionals and find that they all deviate substantially. Differences in interaction energies between different adsorption sites are however better reproduced by DFT.

  14. NOVEL SALTS OF GRAPHITE AND A BORON NITRIDE SALT

    Energy Technology Data Exchange (ETDEWEB)

    Bartlett, Neil; Biagioni, R.N.; McQuillan, B.W.; Robertson, A.S.; Thompson, A.C

    1977-12-01

    Graphite is oxidized by O{sub 2}{sup +} AsF{sub 6}{sup -} and by OsF{sub 6} to give first-stage graphite salts C{sub 8}{sup +} MF{sub 6}{sup -} and S{sub 2}O{sub 6}F{sub 2} oxidizes both graphite and boron nitride to yield the salts C{sub 12}{sup +} SO{sub 3}F{sup -} and (BN){sub 4}{sup +} SO{sub 3}F{sup -}, the latter being the first example of a first-stage boron nitride salt.

  15. Colloidal Plasmonic Titanium Nitride Nanoparticles: Properties and Applications

    Directory of Open Access Journals (Sweden)

    Guler Urcan

    2015-01-01

    Full Text Available Optical properties of colloidal plasmonic titanium nitride nanoparticles are examined with an eye on their photothermal and photocatalytic applications via transmission electron microscopy and optical transmittance measurements. Single crystal titanium nitride cubic nanoparticles with an average size of 50 nm, which was found to be the optimum size for cellular uptake with gold nanoparticles [1], exhibit plasmon resonance in the biological transparency window and demonstrate a high absorption efficiency. A self-passivating native oxide at the surface of the nanoparticles provides an additional degree of freedom for surface functionalization. The titanium oxide shell surrounding the plasmonic core can create new opportunities for photocatalytic applications.

  16. Designing of TJ VCSEL based on nitride materials

    Science.gov (United States)

    Sarzała, R. P.; Pijanowski, K.; Gebski, M.; Marciniak, M.; Nakwaski, W.

    2016-12-01

    Different structures of nitride Vertical-Cavity Surface-Emitting Lasers (VCSELs) have been developed in recent years. However there is still many problems with such constructions, especially with electrical and optical confinement, current injection and construction and fabrication of mirrors. In this paper we present novel approach to nitride VCSEL designing. We investigated structure with tunnel junction (TJ) and top and bottom dielectric distributed Bragg reflectors (DBRs). Using our three-dimensional self-consistent model we investigated thermal and electrical properties of such laser. We also proposed replacing bottom DBR by monolithic high contrast grating mirror (MHCG) and presented optical properties of VCSEL with such mirrors.

  17. Inter-layer potential for hexagonal boron nitride

    Science.gov (United States)

    Leven, Itai; Azuri, Ido; Kronik, Leeor; Hod, Oded

    2014-03-01

    A new interlayer force-field for layered hexagonal boron nitride (h-BN) based structures is presented. The force-field contains three terms representing the interlayer attraction due to dispersive interactions, repulsion due to anisotropic overlaps of electron clouds, and monopolar electrostatic interactions. With appropriate parameterization, the potential is able to simultaneously capture well the binding and lateral sliding energies of planar h-BN based dimer systems as well as the interlayer telescoping and rotation of double walled boron-nitride nanotubes of different crystallographic orientations. The new potential thus allows for the accurate and efficient modeling and simulation of large-scale h-BN based layered structures.

  18. Nitriding and Nitrocarburizing; Current Status and Future Challenges

    DEFF Research Database (Denmark)

    Somers, Marcel A. J.

    in a compound layer consisting of iron (carbo-)nitrides and a diffusion zone, consisting of a dispersion of alloying element nitrides in ferrite. The compound layer provides beneficial tribological and corrosion performance, while the diffusion zone is responsible for improved fatigue performance. Furthermore......, aspects of low temperature surface hardening of stainless steels in a gaseous environment will be addressed. Here, the developed case consists of expanded austenite and/or expanded martensite, which essentially is a super saturated solid solution of nitrogen/carbon in austenite/martensite. The current...

  19. Thermal Aspects of Using Alternative Nuclear Fuels in Supercritical Water-Cooled Reactors

    Science.gov (United States)

    Grande, Lisa Christine

    A SuperCritical Water-cooled Nuclear Reactor (SCWR) is a Generation IV concept currently being developed worldwide. Unique to this reactor type is the use of light-water coolant above its critical point. The current research presents a thermal-hydraulic analysis of a single fuel channel within a Pressure Tube (PT)-type SCWR with a single-reheat cycle. Since this reactor is in its early design phase many fuel-channel components are being investigated in various combinations. Analysis inputs are: steam cycle, Axial Heat Flux Profile (AHFP), fuel-bundle geometry, and thermophysical properties of reactor coolant, fuel sheath and fuel. Uniform and non-uniform AHFPs for average channel power were applied to a variety of alternative fuels (mixed oxide, thorium dioxide, uranium dicarbide, uranium nitride and uranium carbide) enclosed in an Inconel-600 43-element bundle. The results depict bulk-fluid, outer-sheath and fuel-centreline temperature profiles together with the Heat Transfer Coefficient (HTC) profiles along the heated length of fuel channel. The objective is to identify the best options in terms of fuel, sheath material and AHFPS in which the outer-sheath and fuel-centreline temperatures will be below the accepted temperature limits of 850°C and 1850°C respectively. The 43-element Inconel-600 fuel bundle is suitable for SCWR use as the sheath-temperature design limit of 850°C was maintained for all analyzed cases at average channel power. Thoria, UC2, UN and UC fuels for all AHFPs are acceptable since the maximum fuel-centreline temperature does not exceed the industry accepted limit of 1850°C. Conversely, the fuel-centreline temperature limit was exceeded for MOX at all AHFPs, and UO2 for both cosine and downstream-skewed cosine AHFPs. Therefore, fuel-bundle modifications are required for UO2 and MOX to be feasible nuclear fuels for SCWRs.

  20. The Role of Carbides in Formation of Surface Layer on Steel X153CrMoV12 Due to Low-Pressure Nitriding (Vacuum Nitriding)

    Science.gov (United States)

    Januszewicz, B.; Wołowiec, E.; Kula, P.

    2015-05-01

    The mechanism of formation of surface layer on steel X153CrMoV12 in the process of vacuum nitriding (low-pressure nitriding) in a universal vacuum furnace in an atmosphere of dissociated ammonia at a pressure of 30 × 102 Pa (30 mbar) is studied by the methods of light microscopy and measurement of microhardness. The chemical composition of the nitrided layers is determined.

  1. ZeroFlow - new, environmentally friendly method of controlled gas nitriding used for selected car parts

    Science.gov (United States)

    Kowalska, J.; Małdziński, L.

    2016-09-01

    This article presents new method of controlled gas nitriding called ZeroFlow, which is used for nitriding of selected car parts, such as crankshafts, camshafts, piston rings, poppet valve springs and discs, piston pins or nozzles for unit injectors. This article will discuss the essence of controlled gas nitriding process, with an emphasis on the influence of process parameters on results of nitriding process. This information are the basis to understand the issue of the kinetics of nitrided layer growth, and as it follows - for its practical application in designing, regulation and control of nitriding processes using simulation models (simulator of the kinetics of nitrided layer growth). This article will also present the simulator of the kinetics of nitrided layer growth, which supports nitriding using ZeroFlow method - through the use of simulator layers are obtained in the shortest possible time, which is connected with the lowest energy consumption; therefore, nitriding process using ZeroFlow method and simulator of the kinetics of nitrided layer growth is both economical and environmentally friendly.

  2. Global nuclear energy partnership fuels transient testing at the Sandia National Laboratories nuclear facilities : planning and facility infrastructure options.

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, John E.; Wright, Steven Alan; Tikare, Veena; MacLean, Heather J. (Idaho National Laboratory, Idaho Falls, ID); Parma, Edward J., Jr.; Peters, Curtis D.; Vernon, Milton E.; Pickard, Paul S.

    2007-10-01

    The Global Nuclear Energy Partnership fuels development program is currently developing metallic, oxide, and nitride fuel forms as candidate fuels for an Advanced Burner Reactor. The Advance Burner Reactor is being designed to fission actinides efficiently, thereby reducing the long-term storage requirements for spent fuel repositories. Small fuel samples are being fabricated and evaluated with different transuranic loadings and with extensive burnup using the Advanced Test Reactor. During the next several years, numerous fuel samples will be fabricated, evaluated, and tested, with the eventual goal of developing a transmuter fuel database that supports the down selection to the most suitable fuel type. To provide a comparative database of safety margins for the range of potential transmuter fuels, this report describes a plan to conduct a set of early transient tests in the Annular Core Research Reactor at Sandia National Laboratories. The Annular Core Research Reactor is uniquely qualified to perform these types of tests because of its wide range of operating capabilities and large dry central cavity which extents through the center of the core. The goal of the fuels testing program is to demonstrate that the design and fabrication processes are of sufficient quality that the fuel will not fail at its design limit--up to a specified burnup, power density, and operating temperature. Transient testing is required to determine the fuel pin failure thresholds and to demonstrate that adequate fuel failure margins exist during the postulated design basis accidents.

  3. Synthesis and electrochemical characterization of TixTayAlzN1-δOγ for fuel cell catalyst supports

    Science.gov (United States)

    Wakabayashi, Ryo H.; Abruña, Héctor D.; DiSalvo, Francis J.

    2017-02-01

    Quinary TixTayAlzN1-δOγ of various compositions have been prepared by a co-precipitation method followed by ammonolysis. The nitride samples were examined as potential catalyst supports in polymer electrolyte membrane fuel cells. The nitride products crystallized in the rock salt (NaCl) structure over a wide range of compositions. The addition of Ta and Al was highly beneficial towards improving the chemical and electrochemical stability of TiN, without a significant loss of electrical conductivity. Platinum particles were successfully deposited on the (oxy)nitride samples, and the composite samples at some compositions were found to be comparable to Pt/carbon in their stability and catalytic activity even without optimizing the Pt deposition and dispersion processes.

  4. The Structure and Properties of Pulsed dc Sputtered Nanocrystalline NbN Coatings for Proton Exchange Membrane Fuel Cell.

    Science.gov (United States)

    Chun, Sung-Yong

    2016-02-01

    Niobium nitride coatings for the surface modified proton exchange membrane fuel cells with various pulse parameters have been prepared using dc (direct current) and asymmetric-bipolar pulsed dc magnetron sputtering. The pulse frequency and the duty cycle were varied from 5 to 50 kHz and 50 to 95%, respectively. The deposition rate, grain size and resistivity of pulsed dc sputtered films were decreased when the pulse frequency increased, while the nano hardness of niobium nitride films increased. We present in detail coatings (e.g., deposition rate, grain size, prefer-orientation, resistivity and hardness). Our studies show that niobium nitride coatings with superior properties can be prepared using asymmetric-bipolar pulsed dc sputtering.

  5. Elastic Properties of Several Silicon Nitride Films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X.; Metcalf, T. H.; Wang, Q.; Photiadis, D. M.

    2007-01-01

    We have measured the internal friction (Q{sup -1}) of amorphous silicon nitride (a-SiN{sub x}) films prepared by a variety of methods, including low-pressure chemical-vapor deposition (LPCVD), plasma-enhanced chemical-vapor deposition (PECVD), and hot-wire chemical-vapor deposition (HWCVD) from 0.5 K to room temperature. The measurements are made by depositing the films onto extremely high-Q silicon double paddle oscillator substrates with a resonant frequency of {approx}5500 Hz. We find the elastic properties of these a-SiN{sub x} films resemble those of amorphous silicon (a-Si) films, demonstrating considerable variation which depends on the film growth methods and post deposition annealing. The internal friction for most of the films shows a broad temperature-independent plateau below 30 K, characteristic of amorphous solids. The values of Q{sup -1}, however, vary from film to film in this plateau region by more than one order of magnitude. This has been observed in tetrehedrally covalent-bonded amorphous thin films, like a-Si, a-Ge, and a-C. The PECVD films have the highest Q{sup -1} just like a normal amorphous solid, while LPCVD films have an internal friction more than one order of magnitude lower. All the films show a reduction of Q{sup -1} after annealing at 800 C, even for the LPCVD films which were prepared at 850 C. This can be viewed as a reduction of structural disorder.

  6. Graphitic carbon nitride based nanocomposites: a review.

    Science.gov (United States)

    Zhao, Zaiwang; Sun, Yanjuan; Dong, Fan

    2015-01-07

    Graphitic carbon nitride (g-C(3)N(4)), as an intriguing earth-abundant visible light photocatalyst, possesses a unique two-dimensional structure, excellent chemical stability and tunable electronic structure. Pure g-C(3)N(4) suffers from rapid recombination of photo-generated electron-hole pairs resulting in low photocatalytic activity. Because of the unique electronic structure, the g-C(3)N(4) could act as an eminent candidate for coupling with various functional materials to enhance the performance. According to the discrepancies in the photocatalytic mechanism and process, six primary systems of g-C(3)N(4)-based nanocomposites can be classified and summarized: namely, the g-C(3)N(4) based metal-free heterojunction, the g-C(3)N(4)/single metal oxide (metal sulfide) heterojunction, g-C(3)N(4)/composite oxide, the g-C(3)N(4)/halide heterojunction, g-C(3)N(4)/noble metal heterostructures, and the g-C(3)N(4) based complex system. Apart from the depiction of the fabrication methods, heterojunction structure and multifunctional application of the g-C(3)N(4)-based nanocomposites, we emphasize and elaborate on the underlying mechanisms in the photocatalytic activity enhancement of g-C(3)N(4)-based nanocomposites. The unique functions of the p-n junction (semiconductor/semiconductor heterostructures), the Schottky junction (metal/semiconductor heterostructures), the surface plasmon resonance (SPR) effect, photosensitization, superconductivity, etc. are utilized in the photocatalytic processes. Furthermore, the enhanced performance of g-C(3)N(4)-based nanocomposites has been widely employed in environmental and energetic applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation, carbon dioxide reduction, disinfection, and supercapacitors. This critical review ends with a summary and some perspectives on the challenges and new directions in exploring g-C(3)N(4)-based advanced nanomaterials.

  7. Aviation fuels outlook

    Science.gov (United States)

    Momenthy, A. M.

    1980-01-01

    Options for satisfying the future demand for commercial jet fuels are analyzed. It is concluded that the most effective means to this end are to attract more refiners to the jet fuel market and encourage development of processes to convert oil shale and coal to transportation fuels. Furthermore, changing the U.S. refineries fuel specification would not significantly alter jet fuel availability.

  8. Fuel processors for fuel cell APU applications

    Science.gov (United States)

    Aicher, T.; Lenz, B.; Gschnell, F.; Groos, U.; Federici, F.; Caprile, L.; Parodi, L.

    The conversion of liquid hydrocarbons to a hydrogen rich product gas is a central process step in fuel processors for auxiliary power units (APUs) for vehicles of all kinds. The selection of the reforming process depends on the fuel and the type of the fuel cell. For vehicle power trains, liquid hydrocarbons like gasoline, kerosene, and diesel are utilized and, therefore, they will also be the fuel for the respective APU systems. The fuel cells commonly envisioned for mobile APU applications are molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), and proton exchange membrane fuel cells (PEMFC). Since high-temperature fuel cells, e.g. MCFCs or SOFCs, can be supplied with a feed gas that contains carbon monoxide (CO) their fuel processor does not require reactors for CO reduction and removal. For PEMFCs on the other hand, CO concentrations in the feed gas must not exceed 50 ppm, better 20 ppm, which requires additional reactors downstream of the reforming reactor. This paper gives an overview of the current state of the fuel processor development for APU applications and APU system developments. Furthermore, it will present the latest developments at Fraunhofer ISE regarding fuel processors for high-temperature fuel cell APU systems on board of ships and aircrafts.

  9. GSPEL - Fuel Cell Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Fuel Cell Lab (FCL)Provides testing for technology readiness of fuel cell systems The FCL investigates, tests and verifies the performance of fuel-cell systems...

  10. GSPEL - Fuel Cell Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Fuel Cell Lab (FCL) Provides testing for technology readiness of fuel cell systems The FCL investigates, tests and verifies the performance of fuel-cell systems...

  11. Fuel cells: A survey

    Science.gov (United States)

    Crowe, B. J.

    1973-01-01

    A survey of fuel cell technology and applications is presented. The operating principles, performance capabilities, and limitations of fuel cells are discussed. Diagrams of fuel cell construction and operating characteristics are provided. Photographs of typical installations are included.

  12. Bone tissue response to plasma-nitrided titanium implant surfaces

    Directory of Open Access Journals (Sweden)

    Emanuela Prado FERRAZ

    2015-02-01

    Full Text Available A current goal of dental implant research is the development of titanium (Ti surfaces to improve osseointegration. Plasma nitriding treatments generate surfaces that favor osteoblast differentiation, a key event to the process of osteogenesis. Based on this, it is possible to hypothesize that plasma-nitrided Ti implants may positively impact osseointegration. Objective The aim of this study was to evaluate the in vivo bone response to Ti surfaces modified by plasma-nitriding treatments. Material and Methods Surface treatments consisted of 20% N2 and 80% H2, 450°C and 1.5 mbar during 1 h for planar and 3 h for hollow cathode. Untreated surface was used as control. Ten implants of each surface were placed into rabbit tibiae and 6 weeks post-implantation they were harvested for histological and histomorphometric analyses. Results Bone formation was observed in contact with all implants without statistically significant differences among the evaluated surfaces in terms of bone-to-implant contact, bone area between threads, and bone area within the mirror area. Conclusion Our results indicate that plasma nitriding treatments generate Ti implants that induce similar bone response to the untreated ones. Thus, as these treatments improve the physico-chemical properties of Ti without affecting its biocompatibility, they could be combined with modifications that favor bone formation in order to develop new implant surfaces.

  13. Bond length variation in hydronitride molecules and nitride crystals

    Science.gov (United States)

    Buterakos, L. A.; Gibbs, G. V.; Boisen, M. B.

    1992-08-01

    Bond lengths calculated for the coordination polyhedra in hydronitride molecules match average values observed for XN bonds involving main group X-cations in nitride crystals to within ˜0.04 Å. As suggested for oxide and sulfide molecules and crystals, the forces that determine the average bond lengths recorded for coordinated polyhedra in hydronitride molecules and nitride crystals appear to be governed in large part by the atoms that comprise the polyhedra and those that induce local charge balance. The forces exerted on the coordinated polyhedra by other parts of the structure seem to play a small if not an insignificant role in governing bond length variations. Bonded radii for the nitride ion obtained from theoretical electron density maps calculated for the molecules increase linearly with bond length as observed for nitride crystals with the rock salt structure. Promolecule radii calculated for the molecules correlate with bonded and ionic radii, indicating that the electron density distributions in hydronitride molecules possess a significant atomic component, despite bond type.

  14. Compositional analysis of silicon oxide/silicon nitride thin films

    Directory of Open Access Journals (Sweden)

    Meziani Samir

    2016-06-01

    Full Text Available Hydrogen, amorphous silicon nitride (SiNx:H abbreviated SiNx films were grown on multicrystalline silicon (mc-Si substrate by plasma enhanced chemical vapour deposition (PECVD in parallel configuration using NH3/SiH4 gas mixtures. The mc-Si wafers were taken from the same column of Si cast ingot. After the deposition process, the layers were oxidized (thermal oxidation in dry oxygen ambient environment at 950 °C to get oxide/nitride (ON structure. Secondary ion mass spectroscopy (SIMS, Rutherford backscattering spectroscopy (RBS, Auger electron spectroscopy (AES and energy dispersive X-ray analysis (EDX were employed for analyzing quantitatively the chemical composition and stoichiometry in the oxide-nitride stacked films. The effect of annealing temperature on the chemical composition of ON structure has been investigated. Some species, O, N, Si were redistributed in this structure during the thermal oxidation of SiNx. Indeed, oxygen diffused to the nitride layer into Si2O2N during dry oxidation.

  15. Thermionic field emission in gold nitride Schottky nanodiodes

    Science.gov (United States)

    Spyropoulos-Antonakakis, N.; Sarantopoulou, E.; Kollia, Z.; Samardžija, Z.; Kobe, S.; Cefalas, A. C.

    2012-11-01

    We report on the thermionic field emission and charge transport properties of gold nitride nanodomains grown by pulsed laser deposition with a molecular fluorine laser at 157 nm. The nanodomains are sandwiched between the metallic tip of a conductive atomic force microscope and a thin gold layer forming thus a metal-semiconductor-metal junction. Although the limited existing data in the literature indicate that gold nitride was synthesized previously with low efficiency, poor stability, and metallic character; in this work, it is shown that gold nitride nanodomains exhibit semiconducting behavior and the metal-semiconductor-metal contact can be modeled with the back-to-back Schottky barrier model. From the experimental I-V curves, the main charge carrier transport process is found to be thermionic field emission via electron tunneling. The rectifying, near symmetric and asymmetric current response of nanocontacts is related to the effective contact area of the gold nitride nanodomains with the metals. A lower limit for the majority charge carriers concentration at the boundaries of nanodomains is also established using the full depletion approximation, as nanodomains with thickness as low as 6 nm were found to be conductive. Current rectification and charge memory effects are also observed in "quite small" conductive nanodomains (6-10 nm) due to stored charges. Indeed, charges near the surface are identified as inversion domains in the phase shift mapping performed with electrostatic force microscopy and are attributed to charge trapping at the boundaries of the nanodomains.

  16. Methods for improved growth of group III nitride buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Melnik, Yurity; Chen, Lu; Kojiri, Hidehiro

    2014-07-15

    Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphology of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).

  17. Spatial Inhomogeneity of Luminescence in III-Nitride Compounds

    Directory of Open Access Journals (Sweden)

    Gintautas TAMULAITIS

    2011-11-01

    Full Text Available The band gap of III-nitride semiconductors cover a wide range from 0.77 eV (band gap of InN to 6.2 eV (AlN. Thus, light-emitting diodes emitting from infrared to deep into ultraviolet can be fabricated using ternary III-nitrides InGaN, AlGaN, and AlInN with appropriate composition. However, growing the compounds with any desirable composition often encounters substantial difficulties due to phase separation, structural quality of the epilayers, impurities and extended defects, etc. The spatial inhomogeneity of emission properties in III-nitride epilayers and quantum well structures provides an informative insight into carrier migration, localization, and recombination and is important for development of light-emitting devices. In this paper, we introduce the techniques for luminescence study with spatial resolution (microphotoluminescence, confocal microscopy, scanning near field optical microscopy and cathodoluminescence, discuss material properties leading to emission inhomogeneity and review results on spatial distribution of photoluminescence and cathodoluminescence in InGaN and AlGaN, which are the most important ternary III-nitride compounds for application in light-emitting devices.http://dx.doi.org/10.5755/j01.ms.17.4.768

  18. BORON NITRIDE CAPACITORS FOR ADVANCED POWER ELECTRONIC DEVICES

    Energy Technology Data Exchange (ETDEWEB)

    N. Badi; D. Starikov; C. Boney; A. Bensaoula; D. Johnstone

    2010-11-01

    This project fabricates long-life boron nitride/boron oxynitride thin film -based capacitors for advanced SiC power electronics with a broad operating temperature range using a physical vapor deposition (PVD) technique. The use of vapor deposition provides for precise control and quality material formation.

  19. Synthesis of hexagonal boron nitride graphene-like few layers

    Science.gov (United States)

    Yuan, S.; Toury, B.; Journet, C.; Brioude, A.

    2014-06-01

    Self-standing highly crystallized hexagonal boron nitride (h-BN) mono-, bi- and few-layers have been obtained for the first time via the Polymer Derived Ceramics (PDCs) route by adding lithium nitride (Li3N) micropowders to liquid-state polyborazylene (PBN). Incorporation of Li3N as a crystallization promoter allows the onset of crystallization of h-BN at a lower temperature (1200 °C) than under classical conditions (1800 °C). The hexagonal structure was confirmed by both electron and X-ray diffraction.Self-standing highly crystallized hexagonal boron nitride (h-BN) mono-, bi- and few-layers have been obtained for the first time via the Polymer Derived Ceramics (PDCs) route by adding lithium nitride (Li3N) micropowders to liquid-state polyborazylene (PBN). Incorporation of Li3N as a crystallization promoter allows the onset of crystallization of h-BN at a lower temperature (1200 °C) than under classical conditions (1800 °C). The hexagonal structure was confirmed by both electron and X-ray diffraction. Electronic supplementary information (ESI) available: See DOI: 10.1039/c4nr01017e

  20. Methods for improved growth of group III nitride buffer layers

    Science.gov (United States)

    Melnik, Yurity; Chen, Lu; Kojiri, Hidehiro

    2014-07-15

    Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphology of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).

  1. Preparation of Crystallized Carbon Nitride Based on Microwave Plasma CVD

    National Research Council Canada - National Science Library

    Masatoshi INOUE; Yukihiro SAKAMOTO; Matsufumi TAKAYA

    2010-01-01

    ... on. To obtain this material, generally CH4 is used as a carbon source. Therefore, to make clear the effects of the reaction gas on the preparation of carbon nitride, we tried to use C2H4 as a carbon source instead of CH4...

  2. Crystallographic phases and magnetic properties of iron nitride films

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guo-Ke [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China); Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China); Liu, Yan; Zhao, Rui-Bin [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China); Shen, Jun-Jie [Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China); Wang, Shang; Shan, Pu-Jia; Zhen, Cong-Mian [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China); Hou, Deng-Lu, E-mail: houdenglu@mail.hebtu.edu.cn [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China)

    2015-08-31

    Iron nitride films, including single phase films of α-FeN (expanded bcc Fe), γ′-Fe{sub 4}N, ε-Fe{sub 3−x}N (0 ≤ x ≤ 1), and γ″-FeN, were sputtered onto AlN buffered glass substrates. It was found possible to control the phases in the films merely by changing the nitrogen partial pressure during deposition. The magnetization decreased with increased nitrogen concentration and dropped to zero when the N:Fe ratio was above 0.5. The experimental results, along with spin polarized band calculations, have been used to discuss and analyze the magnetic properties of iron nitrides. It has been demonstrated that in addition to influencing the lattice constant of the various iron nitrides, the nearest N atoms have a significant influence on the exchange splitting of the Fe atoms. Due to the hybridization of Fe-3d and N-2p states, the magnetic moment of Fe atoms decreases with an increase in the number of nearest neighbor nitrogen atoms. - Highlights: • Single phase γ′-Fe{sub 4}N, ε-Fe{sub 3−x}N, and γ″-FeN films were obtained using dc sputtering. • The phases in iron nitride films can be controlled by the nitrogen partial pressure. • The nearest N neighbors have a significant influence on the exchange splitting of Fe.

  3. Microstructural Characterization of Low Temperature Gas Nitrided Martensitic Stainless Steel

    DEFF Research Database (Denmark)

    Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Somers, Marcel A. J.

    2015-01-01

    The present work presents microstructural investigations of the surface zone of low temperature gas nitrided precipitation hardening martensitic stainless steel AISI 630. Grazing incidence X-ray diffraction was applied to investigate the present phases after successive removal of very thin sections...

  4. Vacancy complexes in carbon and boron nitride nanotubes

    CSIR Research Space (South Africa)

    Mashapa, MG

    2012-10-01

    Full Text Available The effect of divacancies on the stability, structural and electronic properties of carbon and boron nitride nanotubes is studied using the ab initio density functional method. VBBN is more stable in the boron-rich and less stable in the nitrogen...

  5. Hexagonal Boron Nitride Self-Launches Hyperbolic Phonon Polaritons

    NARCIS (Netherlands)

    Gilburd, Leonid; Kim, Kris S.; Ho, Kevin; Trajanoski, Daniel; Maiti, Aniket; Halverson, Duncan; de Beer, Sissi; Walker, Gilbert C.

    2017-01-01

    Hexagonal boron nitride (hBN) is a 2D material that supports traveling waves composed of material vibrations and light, and is attractive for nanoscale optical devices that function in the infrared. However, the only current method of launching these traveling waves requires the use of a metal

  6. Stress in and texture of PVD deposited metal nitride films

    NARCIS (Netherlands)

    Machunze, R.

    2010-01-01

    Thin metal nitride films deposited by Physical Vapor Deposition (PVD) are used amongst many other applications as wear protective coatings in tool industry or as diffusion barriers in integrated circuit technology. Typically these films exhibit a residual in-plane stress when deposited onto rigid su

  7. Advances and directions of ion nitriding/carburizing

    Science.gov (United States)

    Spalvins, Talivaldis

    1989-01-01

    Ion nitriding and carburizing are plasma activated thermodynamic processes for the production of case hardened surface layers not only for ferrous materials, but also for an increasing number of nonferrous metals. When the treatment variables are properly controlled, the use of nitrogenous or carbonaceous glow discharge medium offers great flexibility in tailoring surface/near-surface properties independently of the bulk properties. The ion nitriding process has reached a high level of maturity and has gained wide industrial acceptance, while the more recently introduced ion carburizing process is rapidly gaining industrial acceptance. The current status of plasma mass transfer mechanisms into the surface regarding the formation of compound and diffusion layers in ion nitriding and carbon build-up ion carburizing is reviewed. In addition, the recent developments in design and construction of advanced equipment for obtaining optimized and controlled case/core properties is summarized. Also, new developments and trends such as duplex plasma treatments and alternatives to dc diode nitriding are highlighted.

  8. Atomistic models of hydrogenated amorphous silicon nitride from first principles

    NARCIS (Netherlands)

    Jarolimek, K.; Groot, R.A. de; Wijs, G.A. de; Zeman, M.

    2010-01-01

    We present a theoretical study of hydrogenated amorphous silicon nitride (a-SiNx:H), with equal concentrations of Si and N atoms (x=1), for two considerably different densities (2.0 and 3.0 g/cm3). Densities and hydrogen concentration were chosen according to experimental data. Using

  9. Heterostructures for Increased Quantum Efficiency in Nitride LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Robert F. [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2010-09-30

    Task 1. Development of an advanced LED simulator useful for the design of efficient nitride-based devices. Simulator will contain graphical interface software that can be used to specify the device structure, the material parameters, the operating conditions and the desired output results. Task 2. Theoretical and experimental investigations regarding the influence on the microstructure, defect concentration, mechanical stress and strain and IQE of controlled changes in the chemistry and process route of deposition of the buffer layer underlying the active region of nitride-based blue- and greenemitting LEDs. Task 3. Theoretical and experimental investigations regarding the influence on the physical properties including polarization and IQE of controlled changes in the geometry, chemistry, defect density, and microstructure of components in the active region of nitride-based blue- and green-emitting LEDs. Task 4. Theoretical and experimental investigations regarding the influence on IQE of novel heterostructure designs to funnel carriers into the active region for enhanced recombination efficiency and elimination of diffusion beyond this region. Task 5. Theoretical and experimental investigations regarding the influence of enhanced p-type doping on the chemical, electrical, and microstructural characteristics of the acceptor-doped layers, the hole injection levels at Ohmic contacts, the specific contact resistivity and the IQE of nitride-based blue- and green-emitting LEDs. Development and optical and electrical characterization of reflective Ohmic contacts to n- and p-type GaN films.

  10. III-nitride grown on freestanding GaN nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yongjin; Zhu, Hongbo [Institute of Communication Technology, Nanjing University of Posts and Telecommunications, Nanjing, Jiang-Su 210003 (China); Hu, Fangren; Hane, Kazuhiro [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan)

    2012-03-15

    We report here the epitaxial growth of III-nitride on the freestanding GaN nanostructures by molecular beam epitaxy growth. Various GaN nanostructures are defined by electron beam lithography and realized on GaN-on-silicon substrate by fast atom beam etching. Silicon substrate beneath GaN nanostructures is removed from the backside to form the freestanding GaN slab, and the epitaxial growth of III-nitride by MBE is performed on the prepared GaN template. The selective growth takes place with the assistance of GaN nanostructures and generates hexagonal III-nitride pyramids. Thin epitaxial structures, depending on the shape and the size of GaN nanostructure, can produce the promising optical performance. This work opens the way to combine silicon micromachining with the epitaxial growth of III-nitride by MBE on GaN-on-silicon substrate for further integrated optics (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Proportional control valves integrated in silicon nitride surface channel technology

    NARCIS (Netherlands)

    Groen, Maarten S.; Groenesteijn, Jarno; Meutstege, Esken; Brookhuis, Robert A.; Brouwer, Dannis M.; Lötters, Joost C.; Wiegerink, Remco J.

    2015-01-01

    We have designed and realized two types of proportional microcontrol valves in a silicon nitride surface channel technology process. This enables on-die integration of flow controllers with other surface channel devices, such as pressure sensors or thermal or Coriolis-based (mass) flow sensors, to o

  12. Low temperature silicon nitride waveguides for multilayer platforms

    Science.gov (United States)

    Domínguez Bucio, T.; Tarazona, A.; Khokhar, A. Z.; Mashanovich, G. Z.; Gardes, F. Y.

    2016-05-01

    Several 3D multilayer silicon photonics platforms have been proposed to provide densely integrated structures for complex integrated circuits. Amongst these platforms, great interest has been given to the inclusion of silicon nitride layers to achieve low propagation losses due to their capacity of providing tight optical confinement with low scattering losses in a wide spectral range. However, none of the proposed platforms have demonstrated the integration of active devices. The problem is that typically low loss silicon nitride layers have been fabricated with LPCVD which involves high processing temperatures (<1000 ºC) that affect metallisation and doping processes that are sensitive to temperatures above 400ºC. As a result, we have investigated ammonia-free PECVD and HWCVD processes to obtain high quality silicon nitride films with reduced hydrogen content at low temperatures. Several deposition recipes were defined through a design of experiments methodology in which different combinations of deposition parameters were tested to optimise the quality and the losses of the deposited layers. The physical, chemical and optical properties of the deposited materials were characterised using different techniques including ellipsometry, SEM, FTIR, AFM and the waveguide loss cut-back method. Silicon nitride layers with hydrogen content between 10-20%, losses below 10dB/cm and high material quality were obtained with the ammonia-free recipe. Similarly, it was demonstrated that HWCVD has the potential to fabricate waveguides with low losses due to its capacity of yielding hydrogen contents <10% and roughness <1.5nm.

  13. Gallium Nitride MMICs for mm-Wave Power Operation

    NARCIS (Netherlands)

    Quay, R.; Maroldt, S.; Haupt, C.; Heijningen, M. van; Tessmann, A.

    2009-01-01

    In this paper a Gallium Nitride MMIC technology for high-power amplifiers between 27 GHz and 101 GHz based on 150 nm- and 100 nm-gate technologies is presented. The GaN HEMT MMICs are designed using coplanar waveguide transmission-line-technology on 3-inch semi-insulating SiC substrates. The measure

  14. Tailor-made functionalization of silicon nitride surfaces

    NARCIS (Netherlands)

    Arafat, A.; Schroën, C.G.P.H.; Smet, de L.C.P.M.; Sudhölter, E.J.R.; Zuilhof, H.

    2004-01-01

    This communication presents the first functionalization of a hydrogen-terminated silicon-rich silicon nitride (Si3Nx) surface with a well-defined, covalently attached organic monolayer. Properties of the resulting monolayers are monitored by measurement of the static water contact angle, X-ray photo

  15. Development of high-thermal-conductivity silicon nitride ceramics

    Directory of Open Access Journals (Sweden)

    You Zhou

    2015-09-01

    Full Text Available Silicon nitride (Si3N4 with high thermal conductivity has emerged as one of the most promising substrate materials for the next-generation power devices. This paper gives an overview on recent developments in preparing high-thermal-conductivity Si3N4 by a sintering of reaction-bonded silicon nitride (SRBSN method. Due to the reduction of lattice oxygen content, the SRBSN ceramics could attain substantially higher thermal conductivities than the Si3N4 ceramics prepared by the conventional gas-pressure sintering of silicon nitride (SSN method. Thermal conductivity could further be improved through increasing the β/α phase ratio during nitridation and enhancing grain growth during post-sintering. Studies on fracture resistance behaviors of the SRBSN ceramics revealed that they possessed high fracture toughness and exhibited obvious R-curve behaviors. Using the SRBSN method, a Si3N4 with a record-high thermal conductivity of 177 Wm−1K−1 and a fracture toughness of 11.2 MPa m1/2 was developed. Studies on the influences of two typical metallic impurity elements, Fe and Al, on thermal conductivities of the SRBSN ceramics revealed that the tolerable content limits for the two impurities were different. While 1 wt% of impurity Fe hardly degraded thermal conductivity, only 0.01 wt% of Al caused large decrease in thermal conductivity.

  16. Dispersion engineering silicon nitride waveguides for broadband nonlinear frequency conversion

    NARCIS (Netherlands)

    Epping, J.P.

    2015-01-01

    In this thesis, we investigated nonlinear frequency conversion of optical wavelengths using integrated silicon nitride (Si3N4) waveguides. Two nonlinear conversion schemes were considered: seeded four-wave mixing and supercontinuum generation. The first—seeded four-wave mixing—is investigated by a n

  17. Continuous Fiber Ceramic Composite (CFCC) Program: Gaseous Nitridation

    Energy Technology Data Exchange (ETDEWEB)

    R. Suplinskas G. DiBona; W. Grant

    2001-10-29

    Textron has developed a mature process for the fabrication of continuous fiber ceramic composite (CFCC) tubes for application in the aluminum processing and casting industry. The major milestones in this project are System Composition; Matrix Formulation; Preform Fabrication; Nitridation; Material Characterization; Component Evaluation

  18. Bone tissue response to plasma-nitrided titanium implant surfaces.

    Science.gov (United States)

    Ferraz, Emanuela Prado; Sverzut, Alexander Tadeu; Freitas, Gileade Pereira; Sá, Juliana Carvalho; Alves, Clodomiro; Beloti, Marcio Mateus; Rosa, Adalberto Luiz

    2015-01-01

    A current goal of dental implant research is the development of titanium (Ti) surfaces to improve osseointegration. Plasma nitriding treatments generate surfaces that favor osteoblast differentiation, a key event to the process of osteogenesis. Based on this, it is possible to hypothesize that plasma-nitrided Ti implants may positively impact osseointegration. Objective The aim of this study was to evaluate the in vivo bone response to Ti surfaces modified by plasma-nitriding treatments. Material and Methods Surface treatments consisted of 20% N2 and 80% H2, 450°C and 1.5 mbar during 1 h for planar and 3 h for hollow cathode. Untreated surface was used as control. Ten implants of each surface were placed into rabbit tibiae and 6 weeks post-implantation they were harvested for histological and histomorphometric analyses. Results Bone formation was observed in contact with all implants without statistically significant differences among the evaluated surfaces in terms of bone-to-implant contact, bone area between threads, and bone area within the mirror area. Conclusion Our results indicate that plasma nitriding treatments generate Ti implants that induce similar bone response to the untreated ones. Thus, as these treatments improve the physico-chemical properties of Ti without affecting its biocompatibility, they could be combined with modifications that favor bone formation in order to develop new implant surfaces.

  19. Nitride RCLEDs grown by MBE for POF applications

    Energy Technology Data Exchange (ETDEWEB)

    Calle, F.; Naranjo, F.B.; Fernandez, S.; Sanchez-Garcia, M.A.; Calleja, E.; Munoz, E. [ISOM and Departamento de Ingenieria Electronica, ETSI de Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain)

    2002-08-16

    Data links by means of plastic optical fibres (POF) demand efficient light emitting diodes (LEDs) at 510 nm, the most promising candidate being nitride-based resonant-cavity LEDs (RCLEDs). These devices include InGaN/GaN multiple-quantum-well (MQW) structures, and GaN/AlGaN distributed Bragg reflectors. Molecular beam epitaxy (MBE) offers some advantages for the fabrication of nitride RCLEDs, like high In incorporation in the active region, and control of the interface quality in the mirror. The main steps in the development of nitride-based RCLEDs using radio-frequency plasma-assisted MBE are addressed, with emphasis in a) p-type doping of GaN by MBE; b) the optimisation of growth, the design and characterisation of AlGaN/GaN stacks for a reflector in the micro-cavity; and c) the growth of InGaN layers, InGaN/GaN MQWs, and conventional InGaN LEDs, which are studied by structural, electrical and optical techniques. The design and fabrication of nitride RCLEDs, which satisfy spectral and thermal specifications for POF applications, are finally described. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  20. Future aviation fuels overview

    Science.gov (United States)

    Reck, G. M.

    1980-01-01

    The outlook for aviation fuels through the turn of the century is briefly discussed and the general objectives of the NASA Lewis Alternative Aviation Fuels Research Project are outlined. The NASA program involves the evaluation of potential characteristics of future jet aircraft fuels, the determination of the effects of those fuels on engine and fuel system components, and the development of a component technology to use those fuels.

  1. Catalytic Fuel Conversion Facility

    Data.gov (United States)

    Federal Laboratory Consortium — This facility enables unique catalysis research related to power and energy applications using military jet fuels and alternative fuels. It is equipped with research...

  2. MEMS Aluminum Nitride Technology for Inertial Sensors

    Science.gov (United States)

    Vigevani, Gabriele

    2011-12-01

    The design and fabrication of MEMS Inertial Sensors (both accelerometers and gyroscopes) made of Aluminum Nitride (AlN) is described in this dissertation. The goal of this work is to design and fabricate inertial sensors based on c-axis oriented AlN polycrystalline thin films. AlN is a post-CMOS compatible piezoelectric material widely used for acoustic resonators, such Bulk Acoustic Wave (BAW) and Lamb Wave Resonators (LWR). In this work we develop the design techniques necessary to obtain inertial sensors with AlN thin film technology. Being able to use AlN as structural material for both acoustic wave resonator and sensing elements is key to achieve the three level integration of RF-MEMS components, sensing elements and CMOS in the same chip. Using AlN as integration platform is particularly suitable for large consumer emerging markets where production costs are the major factor that determine a product success. In order to achieve a platform integration, the first part of this work focuses on the fabrication process: starting from the fabrication technology used for LWR devices, this work shows that by slightly modifying some of the fabrication steps it is possible to obtain MEMS accelerometers and gyroscopes with the same structural layers used for LWR. In the second part of this work, an extensive analysis, performed with analytical and Finite Element Models (FEM), is developed for beam and ring based structures. These models are of great importance as they provide tools to understand the physics of lateral piezoelectric beam actuation and the major limitations of this technology. Based on the models developed for beam based resonators, we propose two designs for Double Ended Tuning Fork (DETF) based accelerometers. In the last part of the dissertation, we show the experimental results and the measurements performed on actual devices. As this work shows analytically and experimentally, there are some fundamental constraints that limit the ultimate sensitivity

  3. New applications advisable for gallium nitride

    Directory of Open Access Journals (Sweden)

    S.J. Pearton

    2002-06-01

    The explosive increase of interest in the AlGaInN family of materials in recent years has been fueled by the application of blue/green/UV light-emitting diodes (LEDs in full-color displays, traffic lights, automotive lighting, and general room lighting (using so-called white LEDs1. In addition, blue/green laser diodes can be used in high storage-capacity digital versatile disk (DVD systems2. AlGaN-based photodetectors are also useful for solar-blind UV detection and have applications as flame sensors for control of gas turbines or detection of missiles.

  4. Nitridation of Nb surface by nanosecond and femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Farha, Ashraf Hassan [Department of Electrical and Computer Engineering and the Applied Research Center, Old Dominion University, Norfolk, VA 23529 (United States); Department of Physics, Faculty of Science, Ain Shams University, Cairo 11566 (Egypt); Ozkendir, Osman Murat [Tarsus Technology Faculty, Mersin University, Tarsus 33480 (Turkey); Koroglu, Ulas; Ufuktepe, Yüksel [Department of Physics, Cukurova University, Adana 01330 (Turkey); Elsayed-Ali, Hani E., E-mail: helsayed@odu.edu [Department of Electrical and Computer Engineering and the Applied Research Center, Old Dominion University, Norfolk, VA 23529 (United States)

    2015-01-05

    Highlights: • Laser nitridation of niobium is performed with nanosecond and femtosecond pulses. • Formation of NbN{sub x} with mixed α, β and δ phases was observed. • For femtosecond laser processed samples, laser induced ripple patterns oriented parallel to the beam polarization were formed. • X-ray absorption near edge structure show formation of Nb{sub 2}O{sub 5} on the surface of the samples. - Abstract: Niobium nitride samples were prepared by laser nitridation in a reactive nitrogen gas environment at room temperature using a Q-switched Nd:YAG nanosecond laser and a Ti:sapphire femtosecond laser. The effects of laser fluence on the formed phase, surface morphology, and electronic properties of the NbN{sub x} were investigated. The samples were prepared at different nanosecond laser fluences up to 5.0 ± 0.8 J/cm{sup 2} at fixed nitrogen pressure of ∼2.7 × 10{sup 4} Pa formed NbN{sub x} with mainly the cubic δ-NbN phase. Femtosecond laser nitrided samples were prepared using laser fluences up to 1.3 ± 0.3 mJ/cm{sup 2} at ∼4.0 × 10{sup 4} Pa nitrogen pressure. Laser induced ripple patterns oriented parallel to the beam polarization were formed with spacing that increases with the laser fluence. To achieve a laser-nitrided surface with desired crystal orientation the laser fulence is an important parameter that needs to be properly adjusted.

  5. RF-sputtered silicon and hafnium nitrides - Properties and adhesion to 440C stainless steel

    Science.gov (United States)

    Grill, A.; Aron, P. R.

    1983-01-01

    Silicon nitride and hafnium nitride coatings were deposited by reactive RF sputtering on oxidized and unoxidized 440C stainless steel substrates. Sputtering was done in mixtures of argon and nitrogen gases from pressed powder silicon nitride and from hafnium metal targets. Depositions were at two background pressures, 8 and 20 mtorr, and at two different fractions (f) of nitrogen in argon, 0.25 and 0.60, for hafnium nitride and at f = 0.25 for silicon nitride. The coatings and the interface between the coating and substrates were investigated by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis and Auger electron spectroscopy. A Knoop microhardness of 1650 + or 100 kg/sq mm was measured for hafnium nitride and 3900 + or 500 kg/sq mm for silicon nitride. The friction coefficients between a 440C rider and the coatings were measured under lubricated conditions. Scratch test results demonstrate that the adhesion of hafnium nitride to both oxidized and unoxidized 440C is superior to that of silicon nitride. Oxidized 440C is found to have increased adhesion, to both nitrides, over that of unoxidized 440C.

  6. RF-sputtered silicon and hafnium nitrides - Properties and adhesion to 440C stainless steel

    Science.gov (United States)

    Grill, A.; Aron, P. R.

    1983-01-01

    Silicon nitride and hafnium nitride coatings were deposited by reactive RF sputtering on oxidized and unoxidized 440C stainless steel substrates. Sputtering was done in mixtures of argon and nitrogen gases from pressed powder silicon nitride and from hafnium metal targets. Depositions were at two background pressures, 8 and 20 mtorr, and at two different fractions (f) of nitrogen in argon, 0.25 and 0.60, for hafnium nitride and at f = 0.25 for silicon nitride. The coatings and the interface between the coating and substrates were investigated by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis and Auger electron spectroscopy. A Knoop microhardness of 1650 + or 100 kg/sq mm was measured for hafnium nitride and 3900 + or 500 kg/sq mm for silicon nitride. The friction coefficients between a 440C rider and the coatings were measured under lubricated conditions. Scratch test results demonstrate that the adhesion of hafnium nitride to both oxidized and unoxidized 440C is superior to that of silicon nitride. Oxidized 440C is found to have increased adhesion, to both nitrides, over that of unoxidized 440C.

  7. Wear and isothermal oxidation kinetics of nitrided TiAl based alloys

    Institute of Scientific and Technical Information of China (English)

    赵斌; 吴建生; 孙坚

    2002-01-01

    Gas nitridation of TiAl based alloys in an ammonia atmosphere was c arried out. The evaluation of the surface wear resistance was performed to compare with those of the non-nitrided alloys. It is concluded that high temperature nitridation raised wear resistance of TiAl based alloys markedly. The tribol ogical behaviors of the nitrided alloys were also discussed. The oxidation kinetics of the nitrided TiAl based alloys were investigated at 800~1000 ℃ in hot air. It is concluded that nitridation is detrimental to the oxidation resistance of TiAl based alloys under the present conditions. The nitrided alloys exhibit increased oxidizing rate with the prolongation of nitridation time at 800 ℃. However, alloys nitrided at 940 ℃ for 50 hdisplay a sign of better oxidat ion resistance than the other nitrided alloys at more severe oxidizing conditions. The parabolic rate law is considered as the basis of the data processing and interpretation of the mass gainvs time data. As a comparison with it, attempts were made to fit the data with the power law. The oxidation kinetic parameter kn, kp and n were measured and the trends were discussed.

  8. Synthesis of graphitic carbon nitride by reaction of melamine and uric acid

    Energy Technology Data Exchange (ETDEWEB)

    Dante, Roberto C., E-mail: rcdante@yahoo.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Martin-Ramos, Pablo, E-mail: pablomartinramos@gmail.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Correa-Guimaraes, Adriana, E-mail: acg@iaf.uva.es [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Martin-Gil, Jesus, E-mail: jesusmartingil@gmail.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain)

    2011-11-01

    Highlights: {yields} Graphitic carbon nitrides by CVD of melamine and uric acid on alumina. {yields} The building blocks of carbon nitrides are heptazine nuclei. {yields} Composite particles with alumina core and carbon nitride coating. - Abstract: Graphitic carbon nitrides were synthesized starting from melamine and uric acid. Uric acid was chosen because it thermally decomposes, and reacts with melamine by condensation at temperatures in the range of 400-600 deg. C. The reagents were mixed with alumina and subsequently the samples were treated in an oven under nitrogen flux. Alumina favored the deposition of the graphitic carbon nitrides layers on the exposed surface. This method can be assimilated to an in situ chemical vapor deposition (CVD). Infrared (IR) spectra, as well as X-ray diffraction (XRD) patterns, are in accordance with the formation of a graphitic carbon nitride with a structure based on heptazine blocks. These carbon nitrides exhibit poor crystallinity and a nanometric texture, as shown by transmission electron microscopy (TEM) analysis. The thermal degradation of the graphitic carbon nitride occurs through cyano group formation, and involves the bridging tertiary nitrogen and the bonded carbon, which belongs to the heptazine ring, causing the ring opening and the consequent network destruction as inferred by connecting the IR and X-ray photoelectron spectroscopy (XPS) results. This seems to be an easy and promising route to synthesize graphitic carbon nitrides. Our final material is a composite made of an alumina core covered by carbon nitride layers.

  9. Plasma nitriding of a precipitation hardening stainless steel to improve erosion and corrosion resistance

    Energy Technology Data Exchange (ETDEWEB)

    Cabo, Amado, E-mail: cabo@ionar.com.ar [IONAR S.A., Buenos Aires (Argentina); Bruhl, Sonia P.; Vaca, Laura S.; Charadia, Raul Charadia, E-mail: sonia@frcu.utn.erdu.ar, E-mail: vacal@frcu.utn.edu.ar, E-mail: charadia@frcu.urn.edu.ar, E-mail: dalibone@frcu.utn.edu.ar [Surface Engineering Group (GIS), Universidad Tecnologica Nacional, Facultad Regional Concepcion del Uruguay (Argentina)

    2010-07-01

    Precipitation hardening stainless steels are used as structural materials in the aircraft and the chemical industry because of their good combination of mechanical and corrosion properties. The aim of this work is to analyze the structural changes produced by plasma nitriding in the near surface of Thyroplast PH X Supra®, a PH stainless steel from ThyssenKrupp, and to study the effect of nitriding parameters in wear and corrosion resistance. Samples were first aged and then nitriding was carried out in an industrial facility at two temperatures, with two different nitrogen partial pressures in the gas mixture. After nitriding, samples were cut, polished, mounted in resin and etched with Vilella reagent to reveal the nitrided case. Nitrided structure was also analyzed with XRD. Erosion/Corrosion was tested against sea water and sand flux, and corrosion in a salt spray fog (ASTM B117). All nitrided samples presented high hardness. Samples nitrided at 390 deg C with different nitrogen partial pressure showed similar erosion resistance against water and sand flux. The erosion resistance of the nitrided samples at 500 deg C was the highest and XRD revealed nitrides. Corrosion resistance, on the contrary, was diminished; the samples suffered of general corrosion during the salt spray fog test. (author)

  10. Porous graphitic carbon nitride synthesized via direct polymerization of urea for efficient sunlight-driven photocatalytic hydrogen production.

    Science.gov (United States)

    Zhang, Yuewei; Liu, Jinghai; Wu, Guan; Chen, Wei

    2012-09-07

    Energy captured directly from sunlight provides an attractive approach towards fulfilling the need for green energy resources on the terawatt scale with minimal environmental impact. Collecting and storing solar energy into fuel through photocatalyzed water splitting to generate hydrogen in a cost-effective way is desirable. To achieve this goal, low cost and environmentally benign urea was used to synthesize the metal-free photocatalyst graphitic carbon nitride (g-C₃N₄). A porous structure is achieved via one-step polymerization of the single precursor. The porous structure with increased BET surface area and pore volume shows a much higher hydrogen production rate under simulated sunlight irradiation than thiourea-derived and dicyanamide-derived g-C₃N₄. The presence of an oxygen atom is presumed to play a key role in adjusting the textural properties. Further improvement of the photocatalytic function can be expected with after-treatment due to its rich chemistry in functionalization.

  11. The function-led design of Z-scheme photocatalytic systems based on hollow carbon nitride semiconductors.

    Science.gov (United States)

    Zheng, Dandan; Pang, Chenyang; Wang, Xinchen

    2015-12-21

    A ternary photocatalyst has been successfully constructed through the integration of Au, CdS and hollow carbon nitride nanospheres (HCNS), where Au nanoparticles were designed to shuttle interparticle transfer of charge carriers between CdS and HCNS photosensitizers to establish two-photon (Z-scheme) photocatalytic tandem systems for solar fuel production. The solid-state CdS-Au-HCNS Z-scheme nanocomposites were efficient for H2 evolution (with a quantum yield of 8.7% at 420 nm) and CO2 reduction catalysis with visible light irradiation. This work further proves the feasibility of employing hollow conjugated polymer photocatalysts in the function-led design of artificial Z-type photosynthetic machinery on soft material interfaces.

  12. Constituted oxides/nitrides on nitriding 304, 430 and 17-4 PH stainless steel in salt baths over the temperature range 723 to 923 K

    Science.gov (United States)

    Shih, Teng-Shih; Huang, Yung-Sen; Chen, Chi-Fan

    2011-10-01

    The progressively developed oxides and nitrides that form on nitriding 304, 430 and 17-4 PH stainless steel are analysed by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) in this study. The experimental results show that the Cr contents and matrix structures (ferrite, austenite and martensite) play an important role in forming FeCr 2O 4, Cr 2O 3 and Fe 2O 3 oxides as well as nitrides. After a short immersion time, oxides of Cr 2O 3 and FeCr 2O 4 form in nitride films on 304 stainless steel samples. Fe 2O 3 oxide will subsequently form following an increasing immersion time. For the 430 stainless steel, Cr 2O 3 predominately forms after a short dipping time which hinders the growth of the nitride layer. As a result, this sample had the thinnest nitride film of the three for a given immersion time. After the formation of oxides, both CrN and Cr 2N were detected near the surface of the nitride films of three samples while Cr 2N phases formed in the deeper zone. The greatest amount of Fe 2O 3 oxide among the three samples was obtained on the nitriding 17-4 PH stainless steel which also had a high intensity count of N 1s.

  13. Microstructural characterization of an AISI-SAE 4140 steel without nitridation and nitrided; Caracterizacion microestructural de un acero AISI-SAE 4140 sin nitrurar y nitrurado

    Energy Technology Data Exchange (ETDEWEB)

    Medina F, A.; Naquid G, C. [Gerencia de Ciencia de Materiales, Depto. de Sintesis y Caracterizacion de Materiales, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    2000-07-01

    It was micro structurally characterized an AISI-SAE 4140 steel before and after of nitridation through the nitridation process by plasma post-unloading microwaves through Optical microscopy (OM), Scanning electron microscopy (SEM) by means of secondary electrons and retrodispersed, X-ray diffraction (XRD), Energy dispersion spectra (EDS) and mapping of elements. (Author)

  14. Carbon Nanotube/Boron Nitride Nanocomposite as a Significant Bifunctional Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions.

    Science.gov (United States)

    Patil, Indrajit M; Lokanathan, Moorthi; Ganesan, Balakrishnan; Swami, Anita; Kakade, Bhalchandra

    2017-01-12

    It is an immense challenge to develop bifunctional electrocatalysts for oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) in low temperature fuel cells and rechargeable metal-air batteries. Herein, a simple and cost-effective approach is developed to prepare novel materials based on carbon nanotubes (CNTs) and a hexagonal boron nitride (h-BN) nanocomposite (CNT/BN) through a one-step hydrothermal method. The structural analysis and morphology study confirms the formation of a homogeneous composite and merging of few exfoliated graphene layers of CNTs on the graphitic planes of h-BN, respectively. Moreover, the electrochemical study implies that CNT/BN nanocomposite shows a significantly higher ORR activity with a single step 4-electron transfer pathway and an improved onset potential of +0.86 V versus RHE and a current density of 5.78 mA cm(-2) in alkaline conditions. Interestingly, it exhibits appreciably better catalytic activity towards OER at low overpotential (η=0.38 V) under similar conditions. Moreover, this bifunctional catalyst shows substantially higher stability than a commercial Pt/C catalyst even after 5000 cycles. Additionally, this composite catalyst does not show any methanol oxidation reactions that nullify the issues due to fuel cross-over effects in direct methanol fuel cell applications.

  15. Study on the selection of nuclear fuel type for a hybrid power extration reactor

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, D. H.; Park, W. S. [KAERI, Taejon (Korea, Republic of)

    1999-05-01

    In order to solve the problem related to long-lived radioactive nuclides in spent fuel, development of a subcritical transmutation reactor concept is emerging. One of the important issues for the design of the reactor may be the selection of a suitable nuclear fuel type. This study presents a logical decision model for this issue using an analytic hierachy process (AHP). Hierarchy is a representation of a system to study the functional relations of its components and its impact on the entire system. The study shows first how to construct hierachy representing their relations and then measure the individual element's impact to the entire system for a quantitative decision making. Current four fuel types; metal, oxide, molten salt, and nitride, were selected and analyzed based on several characteristics with respect to overall comparison. Based on the decision model, the study concludes that the metal fuel type is the best choice for the transmutation reactor.

  16. Modeling and Analysis of FCM UN TRISO Fuel Using the PARFUME Code

    Energy Technology Data Exchange (ETDEWEB)

    Blaise Collin

    2013-09-01

    The PARFUME (PARticle Fuel ModEl) modeling code was used to assess the overall fuel performance of uranium nitride (UN) tri-structural isotropic (TRISO) ceramic fuel in the frame of the design and development of Fully Ceramic Matrix (FCM) fuel. A specific modeling of a TRISO particle with UN kernel was developed with PARFUME, and its behavior was assessed in irradiation conditions typical of a Light Water Reactor (LWR). The calculations were used to access the dimensional changes of the fuel particle layers and kernel, including the formation of an internal gap. The survivability of the UN TRISO particle was estimated depending on the strain behavior of the constituent materials at high fast fluence and burn-up. For nominal cases, internal gas pressure and representative thermal profiles across the kernel and layers were determined along with stress levels in the pyrolytic carbon (PyC) and silicon carbide (SiC) layers. These parameters were then used to evaluate fuel particle failure probabilities. Results of the study show that the survivability of UN TRISO fuel under LWR irradiation conditions might only be guaranteed if the kernel and PyC swelling rates are limited at high fast fluence and burn-up. These material properties are unknown at the irradiation levels expected to be reached by UN TRISO fuel in LWRs. Therefore, more effort is needed to determine them and positively conclude on the applicability of FCM fuel to LWRs.

  17. HTGR fuel and fuel cycle technology

    Energy Technology Data Exchange (ETDEWEB)

    Lotts, A.L.; Coobs, J.H.

    1976-08-01

    The status of fuel and fuel cycle technology for high-temperature gas-cooled reactors (HTGRs) is reviewed. The all-ceramic core of the HTGRs permits high temperatures compared with other reactors. Core outlet temperatures of 740/sup 0/C are now available for the steam cycle. For advanced HTGRs such as are required for direct-cycle power generation and for high-temperature process heat, coolant temperatures as high as 1000/sup 0/C may be expected. The paper discusses the variations of HTGR fuel designs that meet the performance requirements and the requirements of the isotopes to be used in the fuel cycle. Also discussed are the fuel cycle possibilities, which include the low-enrichment cycle, the Th-/sup 233/U cycle, and plutonium utilization in either cycle. The status of fuel and fuel cycle development is summarized.

  18. Fuel development for gas-cooled fast reactors

    Science.gov (United States)

    Meyer, M. K.; Fielding, R.; Gan, J.

    2007-09-01

    The Generation IV Gas-cooled Fast Reactor (GFR) concept is proposed to combine the advantages of high-temperature gas-cooled reactors (such as efficient direct conversion with a gas turbine and the potential for application of high-temperature process heat), with the sustainability advantages that are possible with a fast-spectrum reactor. The latter include the ability to fission all transuranics and the potential for breeding. The GFR is part of a consistent set of gas-cooled reactors that includes a medium-term Pebble Bed Modular Reactor (PBMR)-like concept, or concepts based on the Gas Turbine Modular Helium Reactor (GT-MHR), and specialized concepts such as the Very High-Temperature Reactor (VHTR), as well as actinide burning concepts [A Technology Roadmap for Generation IV Nuclear Energy Systems, US DOE Nuclear Energy Research Advisory Committee and the Generation IV International Forum, December 2002]. To achieve the necessary high power density and the ability to retain fission gas at high temperature, the primary fuel concept proposed for testing in the United States is dispersion coated fuel particles in a ceramic matrix. Alternative fuel concepts considered in the US and internationally include coated particle beds, ceramic clad fuel pins, and novel ceramic 'honeycomb' structures. Both mixed carbide and mixed nitride-based solid solutions are considered as fuel phases.

  19. Microscopic investigation of pitting corrosion in plasma nitrided austenitic stainless steel; Mikroskopische Untersuchung von Lochkorrosion an plasmanitriertem austenitischem rostfreiem Stahl

    Energy Technology Data Exchange (ETDEWEB)

    Escalada, Lisandro; Simison, Silvia N. [Univ. of Mar del Plata (Argentina). Faculty of Engineering; Bruehl, Sonia P. [National Univ. of Technology, Concepcion del Uruguay (Argentina). Surface Engineering Group

    2014-10-01

    UNS 31603 austenitic stainless steel was nitrided using different techniques, and pitting corrosion resistance was analysed in a chloride solution. All nitriding techniques, LEII, PI. and convectional DC nitriding produced a nitrided layer called S phase which is corrosion resistant. Pits morphology and layer structure was investigated using optical and electronic microscopy, SEM-FIB, EDS, and a 3D reconstruction of a pit was assessed using FIB tomography. It was concluded that pits are initiated in MnS inclusions and a channel was generated passing through the nitrided layer, connecting the steel with the electrolyte. Base alloy dissolution was observed beneath the nitrided layer.

  20. Preparation and characterization of boron nitride/carbon fiber composite with high specific surface area

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yan; Fan, Mingwen [Wuhan Univ. (China). Key Laboratory for Oral Biomedical Engineering; Yuan, Songdong; Xiong, Kun; Hu, Kunpeng; Luo, Yi [Hubei Univ. of Technology, Wuhan (China). School of Chemistry and Chemical Engineering; Li, Dong [Hubei Univ. of Technology, Wuhan (China). School of Chemistry and Chemical Engineering; Oxford Univ. (United Kingdom). Chemistry Research Lab.

    2014-06-15

    Boron nitride can be used as a good catalyst carrier because of its high thermal conductivity and chemical stability. However, a high specific surface area of boron nitride is still desirable. In this work, a carbon fiber composite coated with boron nitride villous nano-film was prepared, and was also characterized by means of scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis. The results indicated that the carbon fibers were covered by uniform villous boron nitride films whose thickness was about 150 - 200 nm. The specific surface area of the boron nitride/carbon fiber composite material was 96 m{sup 2} g{sup -1}, which was markedly improved compared with conventional boron nitride materials. (orig.)

  1. Effect of Nitridation on Morphology, Structural Properties and Stress of A1N Films

    Institute of Scientific and Technical Information of China (English)

    HU Wei-Guo; JIAO Chun-Mei; WEI Hong-Yuan; ZHANG Pan-Feng; KANG Wing-Ting; ZHANG Ri-Qing; LIU Xiang-Lin

    2008-01-01

    @@ We investigate effects of nitridation on A1N morphology, structural properties and stress.It is found that 3 min nitridation can prominently improve A1N crystal structure, and slightly smooth the surface morphology.However, 10min nitridation degrades out-of-plane crystal structure and surface morphology instead.Additionally, 3-min nitridation introduces more tensile stress (1.5 GPa) in A1N films, which can be attributed to the weaker islands 2D coalescent.Nitridation for 10 rain can introduce more defects, or even forms polycrystallinity interlayer, which relaxes the stress.Thus, the stress in A1N with 10 min nitridation decreases to -0.2 GPa compressive stress.

  2. Validity of "sputtering and re-condensation" model in active screen cage plasma nitriding process

    Science.gov (United States)

    Saeed, A.; Khan, A. W.; Jan, F.; Abrar, M.; Khalid, M.; Zakaullah, M.

    2013-05-01

    The validity of "sputtering and re-condensation" model in active screen plasma nitriding for nitrogen mass transfer mechanism is investigated. The dominant species including NH, Fe-I, N2+, N-I and N2 along with Hα and Hβ lines are observed in the optical emission spectroscopy (OES) analysis. Active screen cage and dc plasma nitriding of AISI 316 stainless steel as function of treatment time is also investigated. The structure and phases composition of the nitrided layer is studied by X-ray diffraction (XRD). Surface morphology is studied by scanning electron microscopy (SEM) and hardness profile is obtained by Vicker's microhardness tester. Increasing trend in microhardness is observed in both cases but the increase in active screen plasma nitriding is about 3 times greater than that achieved by dc plasma nitriding. On the basis of metallurgical and OES observations the use of "sputtering and re-condensation" model in active screen plasma nitriding is tested.

  3. NITROGEN POTENTIAL DURING ION NITRIDING PROCESS IN GLOW-DISCHARGE PLASMA

    Directory of Open Access Journals (Sweden)

    A. A. Kozlov

    2015-01-01

    Full Text Available The paper considers problems on regulation of phase composition of a nitrided layer during gas and ion nitriding process in a glow-discharge. It has been established that  available models for control of nitrided layer structure with the help of nitriding index (nitrogen potential can not be applied for nitriding process in the glow-discharge. Principal difference of the ion nitriding from the gas one is in the fact that chemically active nitrogen is formed in the discharge zone (cathode layer and its mass-transfer is carried out in the form of an active particle flow (ions, atoms, molecules which directed to the metal surface.Interrelation of chemical discharge activity with such characteristics of nitriding steel as nitrogen solubility in  α-solid solution and  coefficient diffusion during ion nitriding in low-discharge plasma. It has been shown that regulation of the nitride layer structure during ion nitriding is reached due to changes in nitrogen flow density in plasma. While supporting the flow at the level of nitrogen solubility in  one phase or another (α, γ′  it is possible to obtain the nitrided layer consisting only of α-solid solution or γ′-nitride layer and diffusion sub-layer. Moreover a specific range of nitrogen flow density values exists for every steel grade where it is possible to ensure a limiting nitrogen concentration in α-solid solution and the γ′-layer characterized by low diffusion  mobility is not formed on the surface.

  4. Cathodic cage nitriding of AISI 409 ferritic stainless steel with the addition of CH4

    Directory of Open Access Journals (Sweden)

    Rômulo Ribeiro Magalhães de Sousa

    2012-04-01

    Full Text Available AISI 409 ferritic stainless steel samples were nitrided using the cathodic cage plasma nitriding technique (CCPN, with the addition of methane to reduce chromium precipitation, increase hardness and wear resistance and reduce the presence of nitrides when compared to plasma carbonitriding. Microhardness profiles and X-Ray analysis confirm the formation of a very hard layer containing mainly ε-Fe3N and expanded ferrite phases.

  5. Fabrication and Optical Recombination in III-Nitride Microstructures and Devices

    Science.gov (United States)

    2003-10-01

    Fabrication and optical investigations of III-nitride microstructures Our group has pioneered the fabrication of micro - and nano -size photonic... pumped individual III-nitride micro -size LEDs and micro -LED arrays and observed enhanced quantum efficiencies. The micro -size LEDs were fabricated...quality III-nitride QWs, heterostructures, microstructures, and micro -devices and to study their optical and optoeletronic properties. By optimizing

  6. Effect of nitride chemical passivation of the surface of GaAs photodiodes on their characteristics

    Science.gov (United States)

    Kontrosh, E. V.; Lebedeva, N. M.; Kalinovskiy, V. S.; Soldatenkov, F. Yu; Ulin, V. P.

    2016-11-01

    Characteristics of GaAs photodiodes have been studied before and after the chemical nitridation of their surface in hydrazine sulfide solutions, which leads to substitution of surface As atoms with N atoms to give a GaN monolayer. The resulting nitride coatings hinder the oxidation of GaAs in air and provide a decrease in the density of surface states involved in recombination processes. The device characteristics improved by nitridation are preserved during a long time.

  7. High K Oxide Insulated Gate Group III Nitride-Based FETs

    Science.gov (United States)

    2014-03-21

    the physical and electrical properties of high-k dielectric oxides on gallium nitride were explored. The efficacies of several cleaning procedures...surface roughening. Parameters examined included the oxide composition (AI203, Ti02, and Ga203), the gallium nitride crystallographic orientation (c...and m-plane), and its crystal polarity (Ga- anc N-polar). 15. SUBJECT TERMS Gallium nitride , oxides, atomic layer deposition, capitance-voltage

  8. Research on Abrasives in the Chemical Mechanical Polishing Process for Silicon Nitride Balls

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Silicon nitride (Si 3N 4) has been the main material for balls in ceramic ball bearings, for its lower density, high strength, high hardness, fine thermal stability and anticorrosive, and is widely used in various fields, such as high speed and high temperature areojet engines, precision machine tools and chemical engineer machines. Silicon nitride ceramics is a kind of brittle and hard material that is difficult to machining. In the traditional finishing process of silicon nitride balls, balls are lapped...

  9. Low-Pt loaded on a vanadium nitride/graphitic carbon composite as an efficient electrocatalyst for the oxygen reduction reaction.

    Science.gov (United States)

    Yin, Jie; Wang, Lei; Tian, Chungui; Tan, Taixing; Mu, Guang; Zhao, Lu; Fu, Honggang

    2013-10-04

    The high cost of platinum electrocatalysts for the oxygen reduction reaction (ORR) has hindered the commercialization of fuel cells. An effective support can reduce the usage of Pt and improve the reactivity of Pt through synergistic effects. Herein, the vanadium nitride/graphitic carbon (VN/GC) nanocomposites, which act as an enhanced carrier of Pt nanoparticles (NPs) towards ORR, have been synthesized for the first time. In the synthesis, the VN/GC composite could be obtained by introducing VO3 (-) and [Fe(CN)6 ](4-) ions into the polyacrylic weak-acid anion-exchanged resin (PWAR) through an in-situ anion-exchanged route, followed by carbonization and a subsequent nitridation process. After loading only 10 % Pt NPs, the resulting Pt-VN/GC catalyst demonstrates a more positive onset potential (1.01 V), higher mass activity (137.2 mA mg(-1) ), and better cyclic stability (99 % electrochemical active surface area (ECSA) retention after 2000 cycles) towards ORR than the commercial 20 % Pt/C. Importantly, the Pt-VN/GC catalyst mainly exhibits a 4 e(-) -transfer mechanism and a low yield of peroxide species, suggesting its potential application as a low-cost and highly efficient ORR catalyst in fuel cells.

  10. Elasticity and inelasticity of silicon nitride/boron nitride fibrous monoliths.

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, B. I.; Burenkov, Yu. A.; Kardashev, B. K.; Singh, D.; Goretta, K. C.; de Arellano-Lopez, A. R.; Energy Technology; Russian Academy of Sciences; Univer. de Sevilla

    2001-01-01

    A study is reported on the effect of temperature and elastic vibration amplitude on Young's modulus E and internal friction in Si{sub 3}N{sub 4} and BN ceramic samples and Si{sub 3}N{sub 4}/BN monoliths obtained by hot pressing of BN-coated Si{sub 3}N{sub 4} fibers. The fibers were arranged along, across, or both along and across the specimen axis. The E measurements were carried out under thermal cycling within the 20-600 C range. It was found that high-modulus silicon-nitride specimens possess a high thermal stability; the E(T) dependences obtained under heating and cooling coincide well with one another. The low-modulus BN ceramic exhibits a considerable hysteresis, thus indicating evolution of the defect structure under the action of thermoelastic (internal) stresses. Monoliths demonstrate a qualitatively similar behavior (with hysteresis). This behavior of the elastic modulus is possible under microplastic deformation initiated by internal stresses. The presence of microplastic shear in all the materials studied is supported by the character of the amplitude dependences of internal friction and the Young's modulus. The experimental data obtained are discussed in terms of a model in which the temperature dependences of the elastic modulus and their features are accounted for by both microplastic deformation and nonlinear lattice-atom vibrations, which depend on internal stresses.

  11. Photocurrent generation in carbon nitride and carbon nitride/conjugated polymer composites.

    Science.gov (United States)

    Byers, Joshua C; Billon, Florence; Debiemme-Chouvy, Catherine; Deslouis, Claude; Pailleret, Alain; Semenikhin, Oleg A

    2012-09-26

    The semiconductor and photovoltaic properties of carbon nitride (CNx) thin films prepared using a reactive magnetron cathodic sputtering technique were investigated both individually and as composites with an organic conjugated polymer, poly(2,2'-bithiophene) (PBT). The CNx films showed an increasing thickness as the deposition power and/or nitrogen content in the gas mixture increase. At low nitrogen content and low deposition power (25-50 W), the film structure was dominated by the abundance of the graphitic sp(2) regions, whereas at higher nitrogen contents and magnetron power CNx films started to demonstrate semiconductor properties, as evidenced by the occurrence of photoconductivity and the development of a space charge region. However, CNx films alone did not show any reproducible photovoltaic properties. The situation changed, however, when CNx was deposited onto conjugated PBT substrates. In this configuration, CNx was found to function as an acceptor material improving the photocurrent generation both in solution and in solid state photovoltaic devices, with the external quantum efficiencies reaching 1% at high nitrogen contents. The occurrence of the donor-acceptor charge transfer was further evidenced by suppression of the n-doping of the PBT polymer by CNx. Nanoscale atomic force microscopy (AFM) and current-sensing AFM data suggested that CNx may form a bulk heterojunction with PBT.

  12. Evaluation of plasma nitriding efficiency of titanium alloys for medical applications

    Directory of Open Access Journals (Sweden)

    T. Frączek

    2009-04-01

    Full Text Available The surface layers obtained on selected titanium alloys, used in medicine, by the nitriding under glow discharge condition were investigated. The results concern of: α- titanium alloy Grade 2 and α + β alloys Grade 5 and Grade 5 ELI nitrided in temperature below 873 K. The nitriding experiments were performed in a current glow-discharge furnace JON-600 with assisting of unconventional methods. After nitriding surface layers were characterised by surface microhardness measurements, chemical depth profiles, microhardness depth profiles and wear resistance tests.

  13. Nitriding of high speed steel by bipolar PBII for improvement in adhesion strength of DLC films

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Junho, E-mail: choi@mech.t.u-tokyo.ac.jp [University of Tokyo, Tokyo (Japan); Soejima, Koji; Kato, Takahisa [University of Tokyo, Tokyo (Japan); Kawaguchi, Masahiro [Tokyo Metropolitan Industrial Technology Research Institute (TIRI), Tokyo (Japan); Lee, Wonsik [Korea Institute of Industrial Technology (KITECH), Incheon (Korea, Republic of)

    2012-02-01

    In the present study, bipolar plasma based ion implantation and deposition (bipolar PBII) was used for plasma nitriding of high speed steel (SKH2), and the effects of the treatment parameters (positive pulse voltage, negative pulse voltage, treatment pressure, treatment time, and precursor gases) on the nitriding process were investigated. The hardness, roughness, and depth of nitride layer were also measured. The adhesion strength of diamond-like carbon (DLC) films coated on the nitride substrate was evaluated by carrying out Rockwell indentation and microscratch tests. Nitriding by bipolar PBII was achieved in the combining of two effects: nitrogen ion implantation by applying a high negative pulse voltage and thermal diffusion of nitrogen atoms under the application of a high positive pulse voltage. However, a very high voltage negative pulse caused surface roughening of the nitride layer. Application of a high positive pulse voltage during nitriding was found to be effective in promoting the thermal diffusion of the implanted nitrogen atoms. Effective nitriding could be achieved under the following conditions: high positive pulse voltage, low negative pulse voltage, high nitrogen gas pressure, and addition of hydrogen to the precursor gas. The adhesion strength of the DLC films on the SKH2 substrate was well improved after nitriding.

  14. Scanning tunneling microscopy of initial nitridation processes on oxidized Si(100) surface with radical nitrogen

    CERN Document Server

    Takahashi, R; Ikeda, H; Sakashita, M; Sakai, A; Yasuda, Y; Nakatsuka, O; Zaima, S

    2003-01-01

    We have investigated the initial nitridation processes on oxidized Si(100) with radical nitrogen at a substrate temperature of 850degC using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). It is found that the thin oxide layer suppresses the changes of original Si step structures during nitridation, and this effect critically depends on the growth conditions of the oxide layer. Comparison of the nitride island morphology to the case of the clean surface suggests that the migration of the precursor during nitridation is suppressed by the oxygen in the layer. (author)

  15. Structural, electronic, mechanical and magnetic properties of rare earth nitrides REN (RE= Pm, Eu and Yb)

    Energy Technology Data Exchange (ETDEWEB)

    Murugan, A. [Department of physics, N.M.S.S.V.N college, Madurai, Tamilnadu 625019 (India); Rajeswarapalanichamy, R., E-mail: rrpalanichamy@gmail.com [Department of physics, N.M.S.S.V.N college, Madurai, Tamilnadu 625019 (India); Santhosh, M. [Department of physics, N.M.S.S.V.N college, Madurai, Tamilnadu 625019 (India); Iyakutti, K. [Department of physics and Nanotechnology, SRM University, Chennai, Tamilnadu 603203. India. (India)

    2015-07-01

    The structural, electronic and mechanical properties of rare earth nitrides REN (RE=Pm, Eu and Yb) are investigated in NaCl and CsCl, and zinc blende structures using first principles calculations based on density functional theory. The calculated lattice parameters are in good agreement with the available results. Among the considered structures, these nitrides are most stable in NaCl structure. A pressure induced structural phase transition from NaCl to CsCl phase is observed in all these nitrides. The electronic structure reveals that these rare earth nitrides are half metallic at normal pressure. These nitrides are found to be covalent and ionic in the stable phase. The computed elastic constants indicate that these nitrides are mechanically stable and elastically anisotropic. Our results confirm that these nitrides are ferromagnetic in nature. A ferromagnetic to non-magnetic phase transition is observed at the pressures of 21.5 GPa and 46.1 GPa in PmN and YbN respectively. - Highlights: • Rare earth nitrides PmN, EuN and YbN are found to be ferromagnetic in nature. • Electronic, structural, elastic and mechanical properties of rare earth nitrides are investigated. • A pressure induced structural phase transition is predicted under high pressure. • Electronic structure reveals that these materials exhibit half-metallic behavior. • Computed elastic moduli obey the mechanical stability condition.

  16. Preparation of high-pressure phase boron nitride films by physical vapor deposition

    CERN Document Server

    Zhu, P W; Zhao, Y N; Li, D M; Liu, H W; Zou Guang Tian

    2002-01-01

    The high-pressure phases boron nitride films together with cubic, wurtzic, and explosive high-pressure phases, were successfully deposited on the metal alloy substrates by tuned substrate radio frequency magnetron sputtering. The percentage of cubic boron nitride phase in the film was about 50% as calculated by Fourier transform infrared measurements. Infrared peak position of cubic boron nitride at 1006.3 cm sup - sup 1 , which is close to the stressless state, indicates that the film has very low internal stress. Transition electron microscope micrograph shows that pure cubic boron nitride phase exits on the surface of the film. The growth mechanism of the BN films was also discussed.

  17. Tribology of nitriding layer, TiN coatings and their complex on AISI D2 steel

    Institute of Scientific and Technical Information of China (English)

    WANG Ke-sheng; ZHANG De-yuan; DONG Ding-fu

    2004-01-01

    The sliding wear and impact wear resistances of D2 steel with nitriding layer, PVD titanium nitride coating and their duplex treatment were investigated. The experimental results suggest that the duplex treatment has the best sliding and impact wear resistances under experimental conditions. And the wear resistance of PVD titanium nitride is better than that of nitriding. The impact wear resistance and wear mechanism of all three surface layers remain unchanged under impact load of 0.2 J or 1 J. All samples end with the same symptom of flaking.

  18. Method and apparatus for use of III-nitride wide bandgap semiconductors in optical communications

    Energy Technology Data Exchange (ETDEWEB)

    Hui, Rongqing (Lenexa, KS); Jiang,Hong-Xing (Manhattan, KS); Lin, Jing-Yu (Manhattan, KS)

    2008-03-18

    The present disclosure relates to the use of III-nitride wide bandgap semiconductor materials for optical communications. In one embodiment, an optical device includes an optical waveguide device fabricated using a III-nitride semiconductor material. The III-nitride semiconductor material provides for an electrically controllable refractive index. The optical waveguide device provides for high speed optical communications in an infrared wavelength region. In one embodiment, an optical amplifier is provided using optical coatings at the facet ends of a waveguide formed of erbium-doped III-nitride semiconductor materials.

  19. The influence of nitride thickness variations on the switching speed of MNOS memory transistors

    DEFF Research Database (Denmark)

    Bruun, Erik

    1978-01-01

    The influence of nitride thickness variations on the switching speed of MNOS memory transistors is examined. The switching time constant is calculated as a function of the nitride thickness using a model of modified Fowler-Nordheim injection. The calculated characteristics compare well with measu......The influence of nitride thickness variations on the switching speed of MNOS memory transistors is examined. The switching time constant is calculated as a function of the nitride thickness using a model of modified Fowler-Nordheim injection. The calculated characteristics compare well...

  20. Mesoporous carbon nitride-tungsten oxide composites for enhanced photocatalytic hydrogen evolution.

    Science.gov (United States)

    Kailasam, Kamalakannan; Fischer, Anna; Zhang, Guigang; Zhang, Jinshui; Schwarze, Michael; Schröder, Marc; Wang, Xinchen; Schomäcker, Reinhard; Thomas, Arne

    2015-04-24

    Composites of mesoporous polymeric carbon nitride and tungsten(VI) oxide show very high photocatalytic activity for the evolution of hydrogen from water under visible light and in the presence of sacrificial electron donors. Already addition of very small amounts of WO3 yields up to a twofold increase in the efficiency when compared to bulk carbon nitrides and their composites and more notably even to the best reported mesoporous carbon nitride-based photocatalytic materials. The higher activity can be attributed to the high surface area and synergetic effect of the carbon nitrides and the WO3 resulting in improved charge separation through a photocatalytic solid-state Z-scheme mechanism.

  1. Ab-initio study of C and O impurities in uranium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Denise Adorno; Claisse, Antoine; Olsson, Pär, E-mail: polsson@kth.se

    2016-09-15

    Uranium nitride (UN) has been considered a potential fuel for Generation IV (GEN-IV) nuclear reactors as well as a possible new fuel for Light Water Reactors (LWR), which would permit an extension of the fuel residence time in the reactor. Carbon and oxygen impurities play a key role in the UN microstructure, influencing important parameters such as creep, swelling, gas release under irradiation, compatibility with structural steel and coolants, and thermal stability. In this work, a systematic study of the electronic structure of UN containing C and O impurities using first-principles calculations by the Density Functional Theory (DFT) method is presented. In order to describe accurately the localized U 5f electrons, the DFT + U formalism was adopted. Moreover, to avoid convergence toward metastable states, the Occupation Matrix Control (OMC) methodology was applied. The incorporation of C and O in the N-vacancy is found to be energetically favorable. In addition, only for O, the incorporation in the interstitial position is energetically possible, showing some degree of solubility for this element in this site. The binding energies show that the pairs (C−N{sub vac}) and (O−N{sub vac}) interact much further than the other defects, which indicate the possible occurrence of vacancy drag phenomena and clustering of these impurities in grain boundaries, dislocations and free surfaces. The migration energy of an impurity by single N-vacancy show that C and O employ different paths during diffusion. Oxygen migration requires significantly lower energy than carbon. This fact is due to flexibility in the U−O chemical bonds, which bend during the diffusion forming a pseudo UO{sub 2} coordination. On the other hand, C and N have a directional and inflexible chemical bond with uranium; always requiring the octahedral coordination. These findings provide detailed insight into how these impurities behave in the UN matrix, and can be of great interest for assisting the

  2. Reactive Mechanical Alloying Synthesis of Nanocrystalline Cubic Zirconium Nitride

    Institute of Scientific and Technical Information of China (English)

    QIU Li-Xia; YAO Bin; DING Zhan-Hui; ZHAO Xu-Dong; JI Hong; DU Xiao-Bo; JIA Xiao-Peng; ZHENG Wei-Tao

    2008-01-01

    Zirconium nitride powders with rock salt structure (γ-ZrNx) are prepared by mechanical milling of a mixture of Zirconium and hexagonal boron nitride (h-BN) powders.The products are analysed by x-ray diffraction (XRD),scanning electron microscopy (SEM),and Raman spectroscopy (RS).The formation mechanism of γ-ZrNx by ball milling technique is investigated in detail.N atoms diffuse from amorphous BN (a-BN) into Zr to form Zr(N) solid solution alloy,then the Zr(N) solid solution alloy decomposes into γ-ZrNx.No ZrB2 is observed in the as-milled samples or the samples annealed at 1050℃ for 2 h.

  3. Preparation and dielectric properties of porous silicon nitride ceramics

    Institute of Scientific and Technical Information of China (English)

    LI Jun-qi; LUO Fa; ZHU Dong-mei; ZHOU Wan-cheng

    2006-01-01

    Porous silicon nitride ceramics with difference volume fractions of porosity from 34.1% to 59.2% were produced by adding different amount of the pore-forming agent into initial silicon nitride powder. The microwave dielectric property of these ceramics at a frequency of 9.36 GHz was studied. The crystalline phases of the samples were determined by X-ray diffraction analysis. The influence of porosity on the dielectric properties was evaluated. The results show that α-Si3N4 crystalline phase exists in all the samples while the main crystalline phase of the samples is β-Si3N4,indicating that the a/b transformation happens during the preparation of samples and the transformation is incomplete. There is a dense matrix containing large pores and cavities with needle-shaped and flaky β-Si3N4 grains distributing. The dielectric constant of the ceramics reduces with the increase of porosity.

  4. Neutron detection using boron gallium nitride semiconductor material

    Energy Technology Data Exchange (ETDEWEB)

    Atsumi, Katsuhiro [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561 (Japan); Inoue, Yoku; Nakano, Takayuki, E-mail: ttnakan@ipc.shizuoka.ac.jp [Department of Electrical and Materials Science, Graduate School of Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561 (Japan); Mimura, Hidenori; Aoki, Toru [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8011 (Japan)

    2014-03-01

    In this study, we developed a new neutron-detection device using a boron gallium nitride (BGaN) semiconductor in which the B atom acts as a neutron converter. BGaN and gallium nitride (GaN) samples were grown by metal organic vapor phase epitaxy, and their radiation detection properties were evaluated. GaN exhibited good sensitivity to α-rays but poor sensitivity to γ-rays. Moreover, we confirmed that electrons were generated in the depletion layer under neutron irradiation. This resulted in a neutron-detection signal after α-rays were generated by the capture of neutrons by the B atoms. These results prove that BGaN is useful as a neutron-detecting semiconductor material.

  5. Optical stability of silicon nitride MIS inversion layer solar cells

    Science.gov (United States)

    Jaeger, K.; Hezel, R.

    1985-09-01

    For MIS inversion layer solar cells with silicon nitride as an AR coating, accelerated optical stress tests were performed. Degradation of the cell characteristics occurred which was found to be caused by photons with energies equal to or greater than 3.7 eV (wavelength of 335 nm or less). Generation of interface states at the silicon-insulator interface by UV light is shown to be the mechanism responsible. The original cell data could be completely restored by heat treatment (activation energy 0.5 eV) and partially by illumination with short-wavelength light. As the most striking result, however, it is demonstrated that the UV light-induced instability can be drastically improved by incorporation of cesium ions into the silicon nitride layer. An interpretation is given for this effect.

  6. Subsurface Aluminum Nitride Formation in Iron-Aluminum Alloys

    Science.gov (United States)

    Bott, June H.

    Transformation-induced plasticity (TRIP) steels containing higher amounts of aluminum than conventional steels are ideal for structural automotive parts due to their mechanical properties. However, the aluminum tends to react with any processing environment at high temperatures and therefore presents significant challenges during manufacturing. One such challenge occurs during secondary cooling, reheating, and hot-rolling and is caused by a reaction with nitrogen-rich atmospheres wherein subsurface aluminum nitride forms in addition to internal and external oxides. The nitrides are detrimental to mechanical properties and cause surface cracks. It is important to understand how these nitrides and oxides form and their consequences for the quality of steel products. This study looks at model iron-aluminum (up to 8 wt.% aluminum) alloys and uses confocal laser scanning microscopy, x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectrometry, and transmission electron microscopy to study the effect of various conditions on the growth and development of these precipitates in a subsurface oxygen-depleted region. By using model alloys and controlling the experimental atmosphere, this study is able to understand some of the more fundamental materials science behind aluminum nitride formation in aluminum-rich iron alloys and the relationship between internal nitride and oxide precipitation and external oxide scale morphology and composition. The iron-aluminum alloys were heated in N2 atmospheres containing oxygen impurities. It was found that nitrides formed when bulk aluminum content was below 8 wt.% when oxygen was sufficiently depleted due to the internal oxidation. In the samples containing 1 wt.% aluminum, the depth of the internal oxide and nitride zones were in agreement with a diffusion-based model. Increasing aluminum content to 3 and 5 wt% had the effects of modifying the surface-oxide scale composition and increasing its continuity

  7. Caracterisation of Titanium Nitride Layers Deposited by Reactive Plasma Spraying

    Science.gov (United States)

    Roşu, Radu Alexandru; Şerban, Viorel-Aurel; Bucur, Alexandra Ioana; Popescu, Mihaela; Uţu, Dragoş

    2011-01-01

    Forming and cutting tools are subjected to the intense wear solicitations. Usually, they are either subject to superficial heat treatments or are covered with various materials with high mechanical properties. In recent years, thermal spraying is used increasingly in engineering area because of the large range of materials that can be used for the coatings. Titanium nitride is a ceramic material with high hardness which is used to cover the cutting tools increasing their lifetime. The paper presents the results obtained after deposition of titanium nitride layers by reactive plasma spraying (RPS). As deposition material was used titanium powder and as substratum was used titanium alloy (Ti6Al4V). Macroscopic and microscopic (scanning electron microscopy) images of the deposited layers and the X ray diffraction of the coatings are presented. Demonstration program with layers deposited with thickness between 68,5 and 81,4 μm has been achieved and presented.

  8. III-nitride based light emitting diodes and applications

    CERN Document Server

    Han, Jung; Amano, Hiroshi; Morkoç, Hadis

    2017-01-01

    The revised edition of this important book presents updated and expanded coverage of light emitting diodes (LEDs) based on heteroepitaxial GaN on Si substrates, and includes new chapters on tunnel junction LEDs, green/yellow LEDs, and ultraviolet LEDs. Over the last two decades, significant progress has been made in the growth, doping and processing technologies of III-nitride based semiconductors, leading to considerable expectations for nitride semiconductors across a wide range of applications. LEDs are already used in traffic signals, signage lighting, and automotive applications, with the ultimate goal of the global replacement of traditional incandescent and fluorescent lamps, thus reducing energy consumption and cutting down on carbon-dioxide emission. However, some critical issues must be addressed to allow the further improvements required for the large-scale realization of solid-state lighting, and this book aims to provide the readers with details of some contemporary issues on which the performanc...

  9. Magnetism induced by electrochemical nitriding on an austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    Takashi Watanabe

    2015-04-01

    Full Text Available The surface of a Fe-Ni-Cr Alloy (SUS316L plate was electrochemically nitrided in molten LiF-KF salt including Li3N at 873K. The crystal structure changed from fcc structure to bct structure with nitrogen introduction. The Nitrogen diffusion layers were predominately formed at nitrogen concentration of 23 at%. The nitriding process drastically also changed its magnetic property from non-magnetic to ferromagnetic. The magnetic field of 20 kOe saturated the magnetic moment with its magnetization of 81 emu/g at 10K. The anisotropic magnetization is ascertained. Based on CrN formation and Cr extraction from the original Fe-Ni-Cr system, the induced ferromagnetism was discussed.

  10. Formation and characterization of DNA microarrays at silicon nitride substrates.

    Science.gov (United States)

    Manning, Mary; Redmond, Gareth

    2005-01-01

    A versatile method for direct, covalent attachment of DNA microarrays at silicon nitride layers, previously deposited by chemical vapor deposition at silicon wafer substrates, is reported. Each microarray fabrication process step, from silicon nitride substrate deposition, surface cleaning, amino-silanation, and attachment of a homobifunctional cross-linking molecule to covalent immobilization of probe oligonucleotides, is defined, characterized, and optimized to yield consistent probe microarray quality, homogeneity, and probe-target hybridization performance. The developed microarray fabrication methodology provides excellent (high signal-to-background ratio) and reproducible responsivity to target oligonucleotide hybridization with a rugged chemical stability that permits exposure of arrays to stringent pre- and posthybridization wash conditions through many sustained cycles of reuse. Overall, the achieved performance features compare very favorably with those of more mature glass based microarrays. It is proposed that this DNA microarray fabrication strategy has the potential to provide a viable route toward the successful realization of future integrated DNA biochips.

  11. Potential applications of boron nitride nanotubes as drug delivery systems.

    Science.gov (United States)

    Ciofani, Gianni

    2010-08-01

    In recent years, there has been an explosion of research in the 'bio-nano' field, with the discovery and introduction of ever more fascinating materials for applications as drug delivery systems, sensors, transducers, and so on. The author's group, for the first time in the literature, proposed boron nitride nanotubes as a valid alternative to carbon nanotubes and other kinds of inorganic materials, because of their improved chemical properties that theoretically guarantee better stability and compatibility in a biological context. In this paper, the bio-applications of boron nitride nanotubes that have emerged in the literature are summarized, with special attention given to their exploitation as safe drug delivery and targeting carriers. Finally, the possibility of combining their physical and chemical properties is approached, highlighting the features that render these innovative nanovectors unique and exceptional candidates for many bio-applications.

  12. Theoretical treatment of nitriding and nitrocarburizing of iron

    Science.gov (United States)

    Du, Hong; Ågren, John

    1996-04-01

    Mathematical models are developed for both nitriding and nitrocarburizing of iron taking into account the diffusion of N or C and N through various phases and the thermodynamic properties of the ternary Fe-C-N system. Analytical solutions are obtained for the ɛ/γ' bilayer growth of the compound layer assuming constant diffusion coefficients, and the results are compared with those obtained from numerical simulations taking into account the concentration-dependent diffusivities. No significant difference was found between these two methods for nitriding of iron. For nitrocarburizing of iron, it was found that the off-diagonal diffusivities of the ɛ and γ' phases must be taken into account in the analytical solution in order to obtain reasonable results. In addition, it is shown that the phase constitution of the compound layer produced during nitrocarburizing of iron can be predicted by the numerical simulation.

  13. Silicon Nitride: A Synthetic Mineral for Vertebrate Biology

    Science.gov (United States)

    Pezzotti, Giuseppe; McEntire, Bryan J.; Bock, Ryan; Boffelli, Marco; Zhu, Wenliang; Vitale, Eleonora; Puppulin, Leonardo; Adachi, Tetsuya; Yamamoto, Toshiro; Kanamura, Narisato; Bal, B. Sonny

    2016-08-01

    The remarkable stoichiometric flexibility of hydroxyapatite (HAp) enables the formation of a variety of charged structural sites at the material’s surface which facilitates bone remodeling due to binding of biomolecule moieties in zwitterionic fashion. In this paper, we report for the first time that an optimized biomedical grade silicon nitride (Si3N4) demonstrated cell adhesion and improved osteoconductivity comparable to highly defective, non-stoichiometric natural hydroxyapatite. Si3N4’s zwitterionic-like behavior is a function of the dualism between positive and negative charged off-stoichiometric sites (i.e., N-vacancies versus silanols groups, respectively). Lattice defects at the biomaterial’s surface greatly promote interaction with positively- and negatively-charged functional groups in biomolecules, and result in the biologically effective characteristics of silicon nitride. These findings are anticipated to be a starting point for further discoveries of therapeutic bone-graft substitute materials.

  14. Silicon Nitride Waveguides for Plasmon Optical Trapping and Sensing Applications

    CERN Document Server

    Zhao, Qiancheng; Huang, Yuewang; Capolino, Filippo; Boyraz, Ozdal

    2015-01-01

    We demonstrate a silicon nitride trench waveguide deposited with bowtie antennas for plasmonic enhanced optical trapping. The sub-micron silicon nitride trench waveguides were fabricated with conventional optical lithography in a low cost manner. The waveguides embrace not only low propagation loss and high nonlinearity, but also the inborn merits of combining micro-fluidic channel and waveguide together. Analyte contained in the trapezoidal trench channel can interact with the evanescent field from the waveguide beneath. The evanescent field can be further enhanced by plasmonic nanostructures. With the help of gold nano bowtie antennas, the studied waveguide shows outstanding trapping capability on 10 nm polystyrene nanoparticles. We show that the bowtie antennas can lead to 60-fold enhancement of electric field in the antenna gap. The optical trapping force on a nanoparticle is boosted by three orders of magnitude. A strong tendency shows the nanoparticle is likely to move to the high field strength region,...

  15. Synthesis of boron nitride nanotubes from unprocessed colemanite

    Directory of Open Access Journals (Sweden)

    Saban Kalay

    2013-12-01

    Full Text Available Colemanite (Ca2B6O11·5H2O is a natural and new precursor material for the synthesis of boron nitride nanotubes (BNNTs. BNNTs have been synthesized from unprocessed colemanite for the first time. The reaction parameters such as time, catalyst type, catalyst amount and temperature were optimized. It was found that the BNNT formation follows the base growth mechanism, which was initiated with a complex of boron nitride (BN and iron atoms. The obtained BNNTs were characterized by using SEM, TEM, and spectroscopic techniques such as UV–vis, Raman, FTIR and XRD. The BNNTs were randomly oriented and multi-walled with an outer diameter of 10–30 nm and a wall thickness of 5 nm. This novel BNNT synthesis method can be used to obtain high yield, low cost and pure BNNTs.

  16. Molecular beam epitaxy for high-efficiency nitride optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Heffernan, J.; Kauer, M.; Windle, J.; Hooper, S.E.; Bousquet, V.; Zellweger, C.; Barnes, J.M. [Sharp Laboratories of Europe, Edmund Halley Road, Oxford Science Park, Oxford OX4 4GB (United Kingdom)

    2006-06-15

    We review the significant progress made in the development of nitride laser diodes by molecular beam epitaxy (MBE). We report on our recent result of room temperature continuous-wave operation of InGaN quantum well laser diodes grown by MBE. Ridge waveguide lasers fabricated on freestanding GaN substrates have a continuous-wave threshold current of 125 mA, corresponding to a threshold current density of 5.7 kA cm{sup -2}. The lasers have a threshold voltage of 8.6 V and a lifetime of several minutes. We outline the further technical challenges associated with demonstrating lifetimes of several thousand hours and present an assessment of the potential of MBE as a growth method for commercial quality nitride optoelectronic devices. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Valence electronic structure of tantalum carbide and nitride

    Institute of Scientific and Technical Information of China (English)

    FAN; ChangZeng

    2007-01-01

    The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent, metallic and ionic characters. For a quantitative analysis of the relative strength of these components, their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN, which coincides to that deduced from the first-principles method.……

  18. Valence electronic structure of tantalum carbide and nitride

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent, metallic and ionic characters. For a quantitative analysis of the relative strength of these components, their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN, which coincides to that deduced from the first-principles method.

  19. Preferential orientation in metal nitride deposited by the UBM system

    Directory of Open Access Journals (Sweden)

    Jhon Jairo Olaya

    2010-05-01

    Full Text Available This work was aimed at studying the influence of ion bombardment on the preferred orientation (OP of transition metal nitrides (TMN produced by the reactive sputtering technique with a variable unbalanced magnetron through permanent magnets. Tita- nium nitride (TiN coatings were thus studied by varying two parameters: ion-atom ratio on the substrate (Ji/Ja and nitrogen flux. Deposition conditions were as follows: 7 mTorr working pressure, ~ 380ºC substrate temperature, 2 and 8.5 sccm nitrogen flux and 245-265 discharge power. The results showed that preferred orientation (111 and the crystalline behaviour of the produced coatings depended more on nitrogen flux than on ion bombardment. Similarly, micro-hardness measured on films deposited on steel AISI-M2 substrates increased from 1600 to 2000 HV0.025 when nitrogen flux was increased.

  20. Ultra-low threshold gallium nitride photonic crystal nanobeam laser

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Nan, E-mail: nanniu@fas.harvard.edu; Woolf, Alexander; Wang, Danqing; Hu, Evelyn L. [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States); Zhu, Tongtong; Oliver, Rachel A. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Quan, Qimin [Rowland Institute at Harvard University, Cambridge, Massachusetts 02142 (United States)

    2015-06-08

    We report exceptionally low thresholds (9.1 μJ/cm{sup 2}) for room temperature lasing at ∼450 nm in optically pumped Gallium Nitride (GaN) nanobeam cavity structures. The nanobeam cavity geometry provides high theoretical Q (>100 000) with small modal volume, leading to a high spontaneous emission factor, β = 0.94. The active layer materials are Indium Gallium Nitride (InGaN) fragmented quantum wells (fQWs), a critical factor in achieving the low thresholds, which are an order-of-magnitude lower than obtainable with continuous QW active layers. We suggest that the extra confinement of photo-generated carriers for fQWs (compared to QWs) is responsible for the excellent performance.

  1. Amorphous carbon buffer layers for separating free gallium nitride films

    Science.gov (United States)

    Altakhov, A. S.; Gorbunov, R. I.; Kasharina, L. A.; Latyshev, F. E.; Tarala, V. A.; Shreter, Yu. G.

    2016-11-01

    The possibility of using amorphous diamond-like carbon (DLC) films for self-separation of gallium nitride (GaN) layers grown by hydride vapor-phase epitaxy has been analyzed. DLC films have been synthesized by plasma-enhanced chemical vapor deposition under low pressure on sapphire (Al2O3) substrates with a (0001) crystallographic orientation. The samples have been studied by the methods of Raman scattering and X-ray diffraction analysis. It is shown that thin DLC films affect only slightly the processes of nucleation and growth of gallium nitride films. Notably, the strength of the "GaN film-Al2O3" substrate interface decreases, which facilitates separation of the GaN layers.

  2. Double Sided Si(Ge)/Sapphire/III-Nitride Hybrid Structure

    Science.gov (United States)

    Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor)

    2016-01-01

    One aspect of the present invention is a double sided hybrid crystal structure including a trigonal Sapphire wafer containing a (0001) C-plane and having front and rear sides. The Sapphire wafer is substantially transparent to light in the visible and infrared spectra, and also provides insulation with respect to electromagnetic radio frequency noise. A layer of crystalline Si material having a cubic diamond structure aligned with the cubic direction on the (0001) C-plane and strained as rhombohedron to thereby enable continuous integration of a selected (SiGe) device onto the rear side of the Sapphire wafer. The double sided hybrid crystal structure further includes an integrated III-Nitride crystalline layer on the front side of the Sapphire wafer that enables continuous integration of a selected III-Nitride device on the front side of the Sapphire wafer.

  3. Neutron induced degradation in nitrided pyrogenic field oxide MOS capacitors

    CERN Document Server

    Vaidya, S J; Shaikh, A M; Chandorkar, A N

    2002-01-01

    Neutron induced oxide charge trapping and generation of interface states in MOS capacitors with pyrogenic and nitrided pyrogenic field oxides have been studied. In order to assess the damage due to neutrons alone, it is necessary to account for the damage produced by the accompanying gamma rays from neutron radiation. This is done by measuring the intensity of gamma radiation accompanying neutrons at different neutron fluences at the irradiation position. MOS capacitor structures were subjected to neutron radiation in a swimming pool type of reactor. Other samples from the same batch were then subjected to an equivalent dose of gamma radiation from a Co sup 6 sup 0 source. The difference in the damage observed was used to characterize the damage caused by neutrons. It is observed that neutrons, though uncharged, are capable of causing ionization damage. This damage is found to be significant when the radiation is performed under biased conditions. Nitridation in different ambients is found to improve the radi...

  4. Hardness and thermal stability of cubic silicon nitride

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Kragh, Flemming; Frost, D. J.

    2001-01-01

    The hardness and thermal stability of cubic spinel silicon nitride (c-Si3N4), synthesized under high-pressure and high-temperature conditions, have been studied by microindentation measurements, and x-ray powder diffraction and scanning electron microscopy, respectively The phase at ambient...... temperature has an average hardness of 35.31 GPa, slightly larger than SiO2 stishovite, which is often referred to as the third hardest material after diamond and cubic boron nitride. The cubic phase is stable up to 1673 K in air. At 1873 K, alpha -and beta -Si3N4 phases are observed, indicating a phase...... transformation sequence of c-to-alpha -to-beta -Si3N4 phases....

  5. Nitridation of silicon /111/ - Auger and LEED results

    Science.gov (United States)

    Delord, J. F.; Schrott, A. G.; Fain, S. C., Jr.

    1980-01-01

    Clean silicon (111) (7x7) surfaces at up to 1050 C have been reacted with nitrogen ions and neutrals produced by a low energy ion gun. The LEED patterns observed are similar to those previously reported for reaction of silicon (111) (7x7) with NH3. The nitrogen KLL peak exhibits no shift or change in shape with nitride growth. At the same time the magnitude of the elemental silicon LVV peak at 92 eV decreases progressively as a new peak at 84 eV increases. The position of both peaks appears to be independent of the degree of nitridation. Since the Auger spectra are free of oxygen and other impurities, these features can be attributed only to silicon, nitrogen, and their reaction products. Characteristic features of the Auger spectra are related to LEED observations and to the growth of microcrystals of Si3N4.

  6. Neutron detection using boron gallium nitride semiconductor material

    Directory of Open Access Journals (Sweden)

    Katsuhiro Atsumi

    2014-03-01

    Full Text Available In this study, we developed a new neutron-detection device using a boron gallium nitride (BGaN semiconductor in which the B atom acts as a neutron converter. BGaN and gallium nitride (GaN samples were grown by metal organic vapor phase epitaxy, and their radiation detection properties were evaluated. GaN exhibited good sensitivity to α-rays but poor sensitivity to γ-rays. Moreover, we confirmed that electrons were generated in the depletion layer under neutron irradiation. This resulted in a neutron-detection signal after α-rays were generated by the capture of neutrons by the B atoms. These results prove that BGaN is useful as a neutron-detecting semiconductor material.

  7. Sensitivity study for accident tolerant fuels: Property comparisons and behavior simulations in a simplified PWR to enable ATF development and design

    Energy Technology Data Exchange (ETDEWEB)

    Spencer, Kristina Yancey, E-mail: kristina.yancey@gmail.com; Sudderth, Laura; Brito, Ryan A.; Evans, Jordan A.; Hart, Clifford S.; Hu, Anbang; Jati, Andi; Stern, Karyn; McDeavitt, Sean M., E-mail: mcdeavitt@tamu.edu

    2016-12-01

    Highlights: • This study compared four accident tolerant fuels against uranium dioxide. • Material property correlations were developed to evaluate fuel performance. • The fuels’ neutronic and thermal hydraulic behaviors were studied in the AP1000. • No fuel type performed better in all areas, but each has strengths and weaknesses. • More research is needed to build a complete model of the fuel performances. - Abstract: Since the events at the Fukushima-Daiichi nuclear power plant, there has been increased interest in developing fuels to better withstand accidents for current light water reactors. Four accident tolerant fuel candidates are uranium oxide with beryllium oxide additives, uranium oxide with silicon carbide matrix additives, uranium nitride, and uranium nitride with uranium silicide composite. The first two candidates represent near-term high performance uranium oxide with high thermal conductivity and neutron transparency, and the second two represent mid-term high-density fuels with highly beneficial thermal properties. This study seeks to understand the benefits and drawbacks of each option in place of uranium dioxide. To assess the material properties for each of the fuel types, an extensive literature review was performed for material property data. Correlations were then made to evaluate the properties during reactor operation. Neutronics and thermal hydraulics studies were also completed to determine the impact of the use of each candidate in an AP1000 reactor. In most cases, the candidate fuels performed more desirably than uranium dioxide, but no fuel type performed better in all aspects. Much more research needs to be performed to build a complete model of the fuel performances, primarily experimental data for uranium silicide. Each of the fuels studied has its own benefits and drawbacks, and the comparisons discussed in this report can be used to aid in determining the most appropriate fuel depending on the desired specifications.

  8. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

    NARCIS (Netherlands)

    Du, S.; Lin, K.; Malladi, S.R.K.; Lu, Y.; Sun, S.; Xu, Q.; Steinberger-Wilckens, R.; Dong, H.

    2014-01-01

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support

  9. Numerical Simulation of Ballistic Impact of Layered Aluminum Nitride Ceramic

    Science.gov (United States)

    2015-09-01

    configuration simulated in this work duplicates that examined in experiments of Yadav and Ravichandran.1 As shown in Fig. 1a, a WHA (tungsten heavy alloy... WHA ) 157 c aJohnson GR, Holmquist TJ, Beissel SR. Response of aluminum nitride (including a phase change) to large strains, high strain rates, and...results cannot be isolated in the present set of simulations, but possibilities include the following: the WHA material may be weaker than that

  10. Urbach's tail in III-nitrides under an electric field

    OpenAIRE

    Rodrigues, CG; Vasconcellos, AR; Luzzi, R.; Freire, VN

    2001-01-01

    We consider electron-hole recombination in wide-gap strong-polar semiconductors of the III-nitride family under high electric fields. The calculated low-energy side of the luminescense spectrum displays the so-called Urbach's tail, which is characterized as resulting from the presence of sidebands in the form of replicas of the main band, corresponding to recombination with accompanying emission of one, two, etc., LO phonons. The influence of the nonequilibrium macroscopic state of hot carrie...

  11. Synthesis of boron nitride nanotubes and their applications

    OpenAIRE

    Saban Kalay; Zehra Yilmaz; Ozlem Sen; Melis Emanet; Emine Kazanc; Mustafa Çulha

    2015-01-01

    Boron nitride nanotubes (BNNTs) have been increasingly investigated for use in a wide range of applications due to their unique physicochemical properties including high hydrophobicity, heat and electrical insulation, resistance to oxidation, and hydrogen storage capacity. They are also valued for their possible medical and biomedical applications including drug delivery, use in biomaterials, and neutron capture therapy. In this review, BNNT synthesis methods and the surface modification stra...

  12. Charge carrier transport properties in layer structured hexagonal boron nitride

    Directory of Open Access Journals (Sweden)

    T. C. Doan

    2014-10-01

    Full Text Available Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV, hexagonal boron nitride (hBN has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K. The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of μ ∝ (T/T0−α with α = 3.02, satisfying the two-dimensional (2D carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ħω = 192 meV (or 1546 cm-1, which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

  13. Development of compound layer during nitriding and nitrocarburising

    DEFF Research Database (Denmark)

    Somers, Marcel A. J.

    2010-01-01

    The development of the compound layer during gaseous nitriding and nitrocarburising of Fe-based material is described. The first nucleation of the compound layer at the surface depends on the competition between dissociation of ammonia and the removal nitrogen from the surface by solid state...... diffusion and desorption or the competition with a carburising reaction. During layer growth surface reactions as well as solid state diffusion and phase transformations determine the layer growth kinetics....

  14. Sintering of nano crystalline silicon carbide doping with aluminium nitride

    Indian Academy of Sciences (India)

    M S Datta; A K Bandyopadhyay; B Chaudhuri

    2002-04-01

    Sinterable silicon carbide powders were prepared by attrition milling and chemical processing of an acheson type -SiC. Pressureless sintering of these powders was achieved by addition of aluminium nitride together with carbon. Nearly 99% sintered density was obtained. The mechanism of sintering was studied by scanning electron microscopy and transmission electron microscopy. This study shows that the mechanism is a solid sintering process.

  15. Method for forming monolayer graphene-boron nitride heterostructures

    Science.gov (United States)

    Sutter, Peter Werner; Sutter, Eli Anguelova

    2016-08-09

    A method for fabricating monolayer graphene-boron nitride heterostructures in a single atomically thin membrane that limits intermixing at boundaries between graphene and h-BN, so as to achieve atomically sharp interfaces between these materials. In one embodiment, the method comprises exposing a ruthenium substrate to ethylene, exposing the ruthenium substrate to oxygen after exposure to ethylene and exposing the ruthenium substrate to borazine after exposure to oxygen.

  16. Electronic structure of spontaneously strained graphene on hexagonal Boron Nitride

    OpenAIRE

    San-Jose, Pablo; Gutiérrez, Ángel; Sturla, Mauricio; Guinea, Francisco

    2014-01-01

    Hexagonal Boron Nitride substrates have been shown to dramatically improve the electric properties of graphene. Recently, it has been observed that when the two honeycomb crystals are close to perfect alignment, strong lattice distortions develop in graphene due to the moir\\'e adhesion landscape. Simultaneously a gap opens at the Dirac point. Here we derive a simple low energy model for graphene carriers close to alignment with the substrate, taking into account spontaneous strains at equilib...

  17. Nanoporous Carbon Nitride: A High Efficient Filter for Seawater Desalination

    OpenAIRE

    Weifeng LI; Yang, Yanmei; Zhou, Hongcai; Zhang, Xiaoming; Zhao, Mingwen

    2015-01-01

    The low efficiency of commercially-used reverse osmosis (RO) membranes has been the main obstacle in seawater desalination application. Here, we report the auspicious performance, through molecular dynamics simulations, of a seawater desalination filter based on the recently-synthesized graphene-like carbon nitride (g-C2N) [Nat. Commun., 2015, 6, 6486]. Taking advantage of the inherent nanopores and excellent mechanical properties of g-C2N filter, highly efficient seawater desalination can be...

  18. GaN Substrates for III-Nitride Devices

    OpenAIRE

    2010-01-01

    Despite the rapid commercialization of III-nitride semiconductor devices for applications in visible and ultraviolet optoelectronics and in high-power and high-frequency electronics, their full potential is limited by two primary obstacles: i) a high defect density and biaxial strain due to the heteroepitaxial growth on foreign substrates, which result in lower performance and shortened device lifetime, and ii) a strong built-in electric field due to spontaneous and piezoelectric polarization...

  19. Integrated silicon and silicon nitride photonic circuits on flexible substrates.

    Science.gov (United States)

    Chen, Yu; Li, Mo

    2014-06-15

    Flexible integrated photonic devices based on crystalline materials on plastic substrates have a promising potential in many unconventional applications. In this Letter, we demonstrate a fully integrated photonic system including ring resonators and grating couplers, based on both crystalline silicon and silicon nitride, on flexible plastic substrate by using the stamping-transfer method. A high yield has been achieved by a simple, yet reliable transfer method without significant performance degradation.

  20. Phonon spectrum of single-walled boron nitride nanotubes

    Institute of Scientific and Technical Information of China (English)

    Xiao Yang; Yan Xiao-Hong; Cao Jue-Xian; Mao Yu-Liang; Xiang Jun

    2004-01-01

    Based on a force constant model, we investigated the phonon spectrum and then specific heat of single-walled boron nitride nanotubes. The results show that the frequencies of Raman and infrared active modes decrease with increasing diameter in the low frequency, which is consistent with the results calculated by density functional theory.The fitting formulae for diameter and chirality dependence of specific heat at 300K are given.