WorldWideScience

Sample records for temperature gaseous nitriding

  1. 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...

  2. Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic Stainless Steel by Gaseous Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of two commercial austenitic stainless steels: AISI 304 and EN 1.4369. The materials were plastically deformed to different equivalent strains by uniaxial...... tension. Gaseous nitriding of the strained material was performed in ammonia gas at atmospheric pressure at 703 K. Microstructural characterization of the as-deformed states and the nitrided case produced included X-ray diffraction analysis, reflected light microscopy, microhardness testing. The results...

  3. Influence of plastic deformation on low temperature surface hardening of stainless steel by gaseous nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were plas...

  4. 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...

  5. Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic and Precipitation Hardening Stainless Steels by Gaseous Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...

  6. Influence of Plastic Deformation on Low-Temperature Surface Hardening of Austenitic Stainless Steel by Gaseous Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low-temperature surface hardening by gaseous nitriding of two commercial stainless steels: EN 1.4369 and AISI 304. The materials were plastically deformed to several levels of equivalent strain by conventional tens...

  7. 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

    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......, and the development of a metastable precursor for nitride formation....

  8. Low temperature gaseous surface hardening of stainless steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2011-01-01

    The present contribtion gives an overview of some of the technological aspects of low temperature thermochemical treatment of stainless steel. Examples of low temperature gaseous nitriding, carburising and nitrocarburising of stainless steel are presented and discussed. In particular......, the morphology, microstructure and characteristics of so-called expanded austenite "layers" on stainless steel are addressed....

  9. Low temperature gaseous surface hardening of stainless steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2010-01-01

    The present contribution gives an overview of some of the technological aspects of low temperature thermochemical treatment of stainless steel. Examples of low temperature gaseous nitriding, carburising and nitrocarburising of stainless steel are presented and discussed. In particular......, the morphology, microstructure and characteristics of so-called expanite “layers” on stainless steel are addressed....

  10. Effects of gaseous nitriding AISI4140 alloy steel on corrosion and hardness properties

    Science.gov (United States)

    Tamil Moli, L.; Wahab, N.; Gopinathan, M.; Karmegam, K.; Maniyarasi, M.

    2016-10-01

    Corrosion is one of the major problems in the industry especially on machinery since it weakens the structure of the machinery part and causes the mechanical failure. This will stop the production and increase the maintenance cost. In this study, the corrosion behaviour of gas nitriding on a screw press machine shaft made from AISI 4140 steel was investigated. Pitting corrosion was identified as a major cause of the shaft failure and this study was conducted to improve the corrosion resistance on the AISI 4140 alloy steel shaft by gas nitriding as a surface hardening treatment. Gas nitriding was performed with composition of 15% ammonia and 85% nitrogen at temperatures of 525 °C, 550 °C and 575 °C and with the soaking time of 30, 45 and 60 minutes, respectively. The samples were prepared as rectangular sized of 30mm x 12mm x 3mm for immersion testing. The results showed that corrosion rate of untreated samples was 77% higher compared to the nitrided samples. It was also found that hardness of the nitrided samples was higher than untreated sample. All in all, it can be concluded that gaseous nitriding can significantly improve the surface hardness and the corrosion resistance of the shaft made of AISI 4140 alloy steel, hence reduces the pitting that is the root cause of failure.

  11. On the effect of pre-oxidation on the kinetics of gaseous nitriding of iron

    DEFF Research Database (Denmark)

    Friehling, Peter B.; Somers, Marcel A.J.

    2000-01-01

    Preheating in an oxidising atmosphere is frequently used prior to gaseous nitriding. The effects of this preoxidation have been investigated and it is found that a preoxidation decrease the incubation time for the nucleation of iron nitrides. This results in a more homogeneous nucleation of iron ...

  12. Simulation of nitrogen concentration depth profiles in low temperature nitrided stainless steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Dahl, Kristian Vinter; Somers, Marcel A. J.

    2006-01-01

    A numerical model is presented, which simulates nitrogen concentration-depth profiles as obtained with low temperature gaseous nitriding of stainless steel. The evolution of the calculated nitrogen concentration-depth profiles is compared with experimental nitriding kinetics. It is shown...

  13. Experiment on the formation of boron nitride in the jet of low-temperature plasma

    Energy Technology Data Exchange (ETDEWEB)

    Pollo, I. (Politechnika Lubelska (Poland)); Aniol, S. (Politechnika Slaska, Gliwice (Poland). Katedra Chemii i Technologii Nieorganicznej)

    1981-01-01

    The paper deals with the experiments on the formation of boron nitride in the jet of nitric-argon plasma into which solid boron trioxide as well as gaseous ammonia were introduced. It was found out that the conversion process of B/sub 2/O/sub 3/ into nitride in the jet of low-temperature plasma affected by gaseous NH/sub 3/ is possible and in the conditions of our experiment did not exceed 20 per cent.

  14. 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...

  15. 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

  16. Low temperature route to uranium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Burrell, Anthony K. (Los Alamos, NM); Sattelberger, Alfred P. (Darien, IL); Yeamans, Charles (Berkeley, CA); Hartmann, Thomas (Idaho Falls, ID); Silva, G. W. Chinthaka (Las Vegas, NV); Cerefice, Gary (Henderson, NV); Czerwinski, Kenneth R. (Henderson, NV)

    2009-09-01

    A method of preparing an actinide nitride fuel for nuclear reactors is provided. The method comprises the steps of a) providing at least one actinide oxide and optionally zirconium oxide; b) mixing the oxide with a source of hydrogen fluoride for a period of time and at a temperature sufficient to convert the oxide to a fluoride salt; c) heating the fluoride salt to remove water; d) heating the fluoride salt in a nitrogen atmosphere for a period of time and at a temperature sufficient to convert the fluorides to nitrides; and e) heating the nitrides under vacuum and/or inert atmosphere for a period of time sufficient to convert the nitrides to mononitrides.

  17. Low-temperature gaseous surface hardening of stainless steel: the current status

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2009-01-01

    The present review addresses the state of the art of low-temperature gaseous surface engineering of (austenitic) stainless steel and is largely based on the authors' own work in the last 10 years. The main purpose of low temperature gaseous surface engineering of stainless steel is to develop......, the fundamental understanding acquired on homogeneous samples is applied to understand the morphology, composition, and residual stress distribution in functionally graded material, as obtained by nitriding, carburising or nitrocarburising of austenitic stainless steel. Thereafter, aspects of modelling...

  18. 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...

  19. Optimization of time–temperature schedule for nitridation of silicon ...

    Indian Academy of Sciences (India)

    compact on the basis of silicon and nitrogen reaction kinetics. J RAKSHIT and P K DAS*. Central Glass and Ceramic Research Institute, Jadavpur, Calcutta 700 032, India. MS received 27 March 2000; revised 1 June 2000. Abstract. A time–temperature schedule for formation of silicon–nitride by direct nitridation of silicon ...

  20. Effect of microstructure on the high temperature strength of nitride ...

    Indian Academy of Sciences (India)

    Unknown

    Effect of microstructure on the high temperature strength of nitride bonded silicon carbide composite. J RAKSHIT and P K DAS*. Central Glass and Ceramic Research Institute, Kolkata 700 032, India. MS received 15 March 2002; revised 3 August 2002. Abstract. Four compositions of nitride bonded SiC were fabricated with ...

  1. 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.

  2. Combustion temperature charts for industrial gaseous fuels

    Energy Technology Data Exchange (ETDEWEB)

    Matouskova, V.; Gerak, A.; Hlavacka, V.

    1975-12-01

    Researchers at Czechoslovakia's State Research Institute of Mechanical Engineering offer a method for calculating the theoretical flame temperature that includes the effect of endothermic reactions, especially the dissociation of combustion products. Charts presented for eight types of fuel gases can be used to determine the flame temperature relative to the temperature of the combustion air and to the excess-air ratio. Also considered is the relationship between these parameters and the characteristic temperature relationships for equipment using heat recovered from the flue gases to preheat incoming combustion air.

  3. Titanium nitride room-temperature ferromagnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Morozov, Iu.G., E-mail: morozov@ism.ac.ru [Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, 8 Academician Osipyan Street, Chernogolovka, Moscow Region, 142432 (Russian Federation); Belousova, O.V. [Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, 8 Academician Osipyan Street, Chernogolovka, Moscow Region, 142432 (Russian Federation); Belyakov, O.A. [Ogarev Mordovia State University, Saransk, 68 Bol' shevistskaya Street, 430005 (Russian Federation); Parkin, I.P., E-mail: i.p.parkin@ucl.ac.uk [Department of Chemistry, Materials Chemistry Research Centre, University College London, 20 Gordon Street, London, WC1H 0AJ (United Kingdom); Sathasivam, S. [Department of Chemistry, Materials Chemistry Research Centre, University College London, 20 Gordon Street, London, WC1H 0AJ (United Kingdom); Kuznetcov, M.V., E-mail: maxim1968@mail.ru [All-Russian Research Institute on Problems of Civil Defense and Emergencies of Emergency Control Ministry of Russia (EMERCOM), 7 Davidkovskaya Street, Moscow, 121352 (Russian Federation)

    2016-08-05

    Cubic and near-spherical TiN nanoparticles ranging in average size from 20 to 125 nm were prepared by levitation-jet aerosol synthesis through condensation of titanium vapor in an inert gas flow with gaseous nitrogen injection. The nanoparticles were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), BET measurements, UV–Vis, FT-IR, Raman spectroscopy, XPS, and vibrating-sample magnetometry. Room-temperature ferromagnetism with maximum magnetization up to 2.5 emu/g was recorded for the nanoparticles. The results indicate that the observed ferromagnetic ordering was related to the defect Ti–N structures on the surface of nanoparticles. This suggestion is in good correlation with the measured spectroscopical data. - Highlights: • Levitation-jet aerosol synthesis of TiN nanoparticles (NPs). • SEM, XRD, BET, UV–vis, FT-IR, Raman, XPS and magnetic characterization of the NPs. • Correlation between optical and XPS measurements data and maximum magnetization of the NPs.

  4. The elevated temperature mechanical properties of silicon nitride/boron nitride fibrous monoliths

    Science.gov (United States)

    Trice, Rodney Wayne

    A unique, all-ceramic material capable of non-brittle fracture via crack deflection has been characterized from 25sp°C through 1400sp°C. This material, called fibrous monoliths (FMs), was comprised of unidirectionally aligned 250 mum diameter cells of silicon nitride surrounded by 10 mum thick cell boundaries of boron nitride. Six weight percent yttria and two weight percent alumina were added to the silicon nitride to aid in densification. TEM experiments revealed that the sintering aids used to densify the silicon nitride cells were migrating into the boron nitride cell boundary during hot-pressing and that a fine network of micro-cracks existed between basal planes of boron nitride. Elevated temperature four point bending tests were performed on fibrous monolith ceramics from room temperature through 1400sp°C. Peak strengths of FMs averaged 510 MPa for specimens tested at room temperature through 176 MPa at 1400sp°C. Work of fractures ranged from 7300 J/msp2 to 3200 J/msp2 under the same temperature conditions. The interfacial fracture energy of boron nitride, GammasbBN, as a function of temperature has been determined using the Charalambides method. The fracture energy of boron nitride is approximately 40 J/msp2 and remained constant from 25sp°C through 950sp°C. A sharp increase in GammasbBN, to about 60 J/msp2, was observed at 1000sp°C-1050sp°C. This increase in GammasbBN was attributed to interactions of the crack tip with the cell boundary glassy phase. Subsequent measurements at 1075sp°C indicated a marked decrease in GammasbBN to near 40 J/msp2 before plateauing at 17-20 J/msp2 in the 1200sp°C-1300sp°C regime. The Mode I fracture toughness of silicon nitride was also determined using the single edge precracked beam method as a function of temperature. The He and Hutchinson model relating crack deflection at an interface to the Dundurs' parameter was applied to the current data set using the temperature dependent fracture energies of the boron

  5. 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.

  6. 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 sectio...

  7. Titanium nitride as a refractory plasmonic material for high temperature applications

    DEFF Research Database (Denmark)

    Guler, Urcan; Li, Wen-Wei; Boltasseva, Alexandra

    2014-01-01

    The use of titanium nitride as a plasmonic material for high temperature applications such as solar/thermophotovoltaics is studied numerically and experimentally. Performance of titanium nitride is compared with widely used materials in each field. © 2014 OSA....

  8. Low Temperature Gaseous Helium and very High Turbulence Experiments

    CERN Document Server

    Pietropinto, S; Castaing, B; Chabaud, B; Gagne, Y; Hébral, B; Ladam, Y; Lebrun, P; Pirotte, O; Poulain, C; Roche, P E

    2002-01-01

    Cryogenic gaseous helium gives access to extreme turbulent experimental conditions. The very high cooling helium flow rates available at CERN have been used to reach Reynolds numbers up to Re ~ 10**7 in a round jet experiment. First results are discussed.

  9. The development of gaseous detectors with solid photocathodes for low temperature applications

    CERN Document Server

    Periale, L.; Iacobaeus, C.; Francke, T.; Lund-Jensen, B.; Pavlopoulos, N.; Picchi, P.; Pietropaolo, F.

    2004-01-01

    There are several applications and fundamental research areas which require the detection of VUV light at cryogenic temperatures. For these applications we have developed and successfully tested special designs of gaseous detectors with solid photocathodes able to operate at low temperatures: sealed gaseous detectors with MgF2 windows and windowless detectors. We have experimentally demonstrated, that both primary and secondary (due to the avalanche multiplication inside liquids) scintillation lights could be recorded by photosensitive gaseous detectors. The results of this work may allow one to significantly improve the operation of some noble liquid gas TPCs.

  10. High temperature solution-nitriding and low-temperature nitriding of AISI 316: Effect on pitting potential and crevice corrosion performance

    DEFF Research Database (Denmark)

    Bottoli, Federico; Jellesen, Morten Stendahl; Christiansen, Thomas Lundin

    2018-01-01

    Stainless steels grade AISI 316 was subjected to high temperature solution nitriding and low-temperature nitriding in order to dissolve various amounts of nitrogen in the bulk (up to approx. 0.45wt%) and in a surface layer (up to approx. 13wt%), respectively. Potentiodynamic polarization tests in...... at the material surface through low-temperature nitriding resulted in a considerable improvement of the pitting potential and the crevice corrosion performance of the steels.......Stainless steels grade AISI 316 was subjected to high temperature solution nitriding and low-temperature nitriding in order to dissolve various amounts of nitrogen in the bulk (up to approx. 0.45wt%) and in a surface layer (up to approx. 13wt%), respectively. Potentiodynamic polarization tests...... in a 0.1M NaCl solution and crevice corrosion immersion tests in 3wt% FeCl3 solution were studied before and after the bulk and surface treatments.Nitrogen addition in the bulk proved to have a beneficial effect on the pitting resistance of the alloy. The formation of a zone of expanded austenite...

  11. Low temperature aluminum nitride thin films for sensory applications

    Energy Technology Data Exchange (ETDEWEB)

    Yarar, E.; Zamponi, C.; Piorra, A.; Quandt, E., E-mail: eq@tf.uni-kiel.de [Institute for Materials Science, Chair for Inorganic Functional Materials, Kiel University, D-24143 Kiel (Germany); Hrkac, V.; Kienle, L. [Institute for Materials Science, Chair for Synthesis and Real Structure, Kiel University, D-24143 Kiel (Germany)

    2016-07-15

    A low-temperature sputter deposition process for the synthesis of aluminum nitride (AlN) thin films that is attractive for applications with a limited temperature budget is presented. Influence of the reactive gas concentration, plasma treatment of the nucleation surface and film thickness on the microstructural, piezoelectric and dielectric properties of AlN is investigated. An improved crystal quality with respect to the increased film thickness was observed; where full width at half maximum (FWHM) of the AlN films decreased from 2.88 ± 0.16° down to 1.25 ± 0.07° and the effective longitudinal piezoelectric coefficient (d{sub 33,f}) increased from 2.30 ± 0.32 pm/V up to 5.57 ± 0.34 pm/V for film thicknesses in the range of 30 nm to 2 μm. Dielectric loss angle (tan δ) decreased from 0.626% ± 0.005% to 0.025% ± 0.011% for the same thickness range. The average relative permittivity (ε{sub r}) was calculated as 10.4 ± 0.05. An almost constant transversal piezoelectric coefficient (|e{sub 31,f}|) of 1.39 ± 0.01 C/m{sup 2} was measured for samples in the range of 0.5 μm to 2 μm. Transmission electron microscopy (TEM) investigations performed on thin (100 nm) and thick (1.6 μm) films revealed an (002) oriented AlN nucleation and growth starting directly from the AlN-Pt interface independent of the film thickness and exhibit comparable quality with the state-of-the-art AlN thin films sputtered at much higher substrate temperatures.

  12. Low-temperature plasma nitriding of sintered PIM 316L austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, Aecio Fernando; Scheuer, Cristiano Jose; Joanidis, Ioanis Labhardt; Cardoso, Rodrigo Perito; Mafra, Marcio; Klein, Aloisio Nelmo; Brunatto, Silvio Francisco, E-mail: brunatto@ufpr.br [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Engenharia Mecanica. Grupo de Tecnologia de Fabricacao Assistida pro Plasma e Metalurgia do Po

    2014-08-15

    This work reports experimental results on sintered PIM 316L stainless steel low-temperature plasma nitriding. The effect of treatment temperature and time on process kinetics, microstructure and surface characteristics of the nitrided samples were investigated. Nitriding was carried out at temperatures of 350, 380, 410 and 440 °C , and times of 4, 8 and 16 h, using a gas mixture composed by 60% N2 + 20% H2 + 20% Ar, at a gas flow rate of 5.00 X 10{sup 6} Nm{sup 3-1}, and a pressure of 800 Pa. The treated samples were characterized by scanning electron microscopy, X-ray diffractometry and microhardness measurements. Results indicate that low-temperature plasma nitriding is a diffusion controlled process. The calculated activation energy for nitrided layer growth was 111.4 kJmol{sup -1}. Apparently precipitation-free layers were produced in this study. It was also observed that the higher the treatment temperature and time the higher is the obtained surface hardness. Hardness up to 1343 HV{sub 0.025} was verified for samples nitrided at 440 °C. Finally, the characterization of the treated surface indicates the formation of cracks, which were observed in regions adjacent to the original pores after the treatment. (author)

  13. High temperature mechanical performance of a hot isostatically pressed silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, A.A.; Ferber, M.K.; Jenkins, M.G.; Lin, C.K.J. [and others

    1996-01-01

    Silicon nitride ceramics are an attractive material of choice for designers and manufacturers of advanced gas turbine engine components for many reasons. These materials typically have potentially high temperatures of usefulness (up to 1400{degrees}C), are chemically inert, have a relatively low specific gravity (important for inertial effects), and are good thermal conductors (i.e., resistant to thermal shock). In order for manufacturers to take advantage of these inherent properties of silicon nitride, the high-temperature mechanical performance of the material must first be characterized. The mechanical response of silicon nitride to static, dynamic, and cyclic conditions at elevated temperatures, along with reliable and representative data, is critical information that gas turbine engine designers and manufacturers require for the confident insertion of silicon nitride components into gas turbine engines. This final report describes the high-temperature mechanical characterization and analyses that were conducted on a candidate structural silicon nitride ceramic. The high-temperature strength, static fatigue (creep rupture), and dynamic and cyclic fatigue performance were characterized. The efforts put forth were part of Work Breakdown Structure Subelement 3.2.1, {open_quotes}Rotor Data Base Generation.{close_quotes} PY6 is comparable to other hot isostatically pressed (HIPed) silicon nitrides currently being considered for advanced gas turbine engine applications.

  14. Modification of Low-Alloy Steel Surface by High-Temperature Gas Nitriding Plus Tempering

    Science.gov (United States)

    Jiao, Dongling; Li, Minsong; Ding, Hongzhen; Qiu, Wanqi; Luo, Chengping

    2018-01-01

    The low-alloy steel was nitrided in a pure NH3 gas atmosphere at 640 660 °C for 2 h, i.e., high-temperature gas nitriding (HTGN), followed by tempering at 225 °C, which can produce a high property surface coating without brittle compound (white) layer. The steel was also plasma nitriding for comparison. The composition, microstructure and microhardness of the nitrided and tempered specimens were examined, and their tribological behavior investigated. The results showed that the as-gas-nitrided layer consisted of a white layer composed of FeN0.095 phase (nitrided austenite) and a diffusional zone underneath the white layer. After tempering, the white layer was decomposed to a nano-sized (α-Fe + γ'-Fe4N + retained austenite) bainitic microstructure with a high hardness of 1150HV/25 g. Wear test results showed that the wear resistance and wear coefficient yielded by the complex HTGN plus tempering were considerably higher and lower, respectively, than those produced by the conventional plasma nitriding.

  15. Structural materialization of stainless steel molds and dies by the low temperature high density plasma nitriding

    Directory of Open Access Journals (Sweden)

    Aizawa Tatsuhiko

    2015-01-01

    Full Text Available Various kinds of stainless steels have been widely utilized as a mold substrate material for injection molding and as a die for mold-stamping and direct stamping processes. Since they suffered from high temperature transients and thermal cycles in practice, they must be surface-treated by dry and wet coatings, or, by plasma nitriding. Martensitic stainless steel mold was first wet plated by the nickel phosphate (NiP, which was unstable at the high temperature stamping condition; and, was easy to crystalize or to fracture by itself. This issue of nuisance significantly lowered the productivity in fabrication of optical elements at present. In the present paper, the stainless steel mold was surface-treated by the low-temperature plasma nitriding. The nitrided layer by this surface modification had higher nitrogen solute content than 4 mass%; the maximum solid-solubility of nitrogen is usually 0.1 mass% in the equilibrium phase diagram. Owing to this solid-solution with high nitrogen concentration, the nitrided layer had high hardness of 1400 Hv within its thickness of 40 μm without any formation of nitrides after 14.4 ks plasma nitriding at 693 K. This nitrogen solid-solution treated stainless steel had thermal resistivity even at the mold-stamping conditions up to 900 K.

  16. Low temperature high density plasma nitriding of stainless steel molds for stamping of oxide glasses

    Directory of Open Access Journals (Sweden)

    Aizawa Tatsuhiko

    2016-01-01

    Full Text Available Various kinds of stainless steels have been widely utilized as a die for mold- and direct-stamping processes of optical oxide glasses. Since they suffered from high temperature transients and thermal cycles in practice, they must be surface-treated by dry and wet coatings, or, by plasma nitriding. Martensitic stainless steel mold was first wet plated by the nickel phosphate (NiP, which was unstable at the high temperature stamping condition; and, was easy to crystalize or to fracture by itself. This issue of nuisance significantly lowered the productivity in fabrication of optical oxide-glass elements. In the present paper, the stainless steel mold was surface-treated by the low-temperature plasma nitriding. The nitrided layer by this surface modification had higher nitrogen solute content than 4 mass%; the maximum solid-solubility of nitrogen is usually 0.1 mass% in the equilibrium phase diagram. Owing to this solid-solution with high nitrogen concentration, the nitrided layer had high hardness over 1400 HV within its thickness of 50 μm without any formation of nitrides after plasma nitriding at 693 K for 14.4 ks. This plasma-nitrided mold was utilized for mold-stamping of two colored oxide glass plates at 833 K; these plates were successfully deformed and joined into a single glass plate by this stamping without adhesion or galling of oxide glasses onto the nitrided mold surface.

  17. Effect of gaseous ozone for control of stored product pests at low and high temperature

    DEFF Research Database (Denmark)

    Hansen, Lise Stengård; Hansen, Peer; Vagn Jensen, Karl-Martin

    2013-01-01

    Gaseous ozone (O3) has shown potential for control of insects in stored grain. A previous laboratory study determined doses of ozone necessary to control freely exposed and internal stages of eleven stored product pest species at 20 C. In this study the impact of temperature on the effect of ozon...

  18. Thermal Cycling and High Temperature Reverse Bias Testing of Control and Irradiated Gallium Nitride Power Transistors

    Science.gov (United States)

    Patterson, Richard L.; Boomer, Kristen T.; Scheick, Leif; Lauenstein, Jean-Marie; Casey, Megan; Hammoud, Ahmad

    2014-01-01

    The power systems for use in NASA space missions must work reliably under harsh conditions including radiation, thermal cycling, and exposure to extreme temperatures. Gallium nitride semiconductors show great promise, but information pertaining to their performance is scarce. Gallium nitride N-channel enhancement-mode field effect transistors made by EPC Corporation in a 2nd generation of manufacturing were exposed to radiation followed by long-term thermal cycling and testing under high temperature reverse bias conditions in order to address their reliability for use in space missions. Result of the experimental work are presented and discussed.

  19. Dry Lubrication of High Temperature Silicon Nitride Rolling Contacts.

    Science.gov (United States)

    1980-11-01

    contamination from alumina fiber insulation surrounding the metal housing a small, metal, chimney-like arrangement was used to separate the insulation from...nitride five ball assembly revealed considerable zirconia dust on the ball surfaces and fibers from the alumina insulation surrounding the metal...Santa Ana, California 92705 "- ---- -izm_: No. of Copies Coors Porcelain Company 1 600 Ninth Street Golden, Colorado 80401 Attention: Research

  20. High-temperature sorbent method for removal of sulfur containing gases from gaseous mixtures

    Science.gov (United States)

    Young, John E.; Jalan, Vinod M.

    1984-01-01

    A copper oxide-zinc oxide mixture is used as a sorbent for removing hydrogen sulfide and other sulfur containing gases at high temperatures from a gaseous fuel mixture. This high-temperature sorbent is especially useful for preparing fuel gases for high temperature fuel cells. The copper oxide is initially reduced in a preconditioning step to elemental copper and is present in a highly dispersed state throughout the zinc oxide which serves as a support as well as adding to the sulfur sorption capacity. The spent sorbent is regenerated by high-temperature treatment with an air fuel, air steam mixture followed by hydrogen reduction to remove and recover the sulfur.

  1. High-temperature sorbent method for removal of sulfur-containing gases from gaseous mixtures

    Science.gov (United States)

    Young, J.E.; Jalan, V.M.

    1982-07-07

    A copper oxide-zinc oxide mixture is used as a sorbent for removing hydrogen sulfide and other sulfur containing gases at high temperatures from a gaseous fuel mixture. This high-temperature sorbent is especially useful for preparing fuel gases for high temperature fuel cells. The copper oxide is initially reduced in a preconditioning step to elemental copper and is present in a highly dispersed state throughout the zinc oxide which serves as a support as well as adding to the sulfur sorbtion capacity. The spent sorbent is regenerated by high-temperature treatment with an air fuel, air steam mixture followed by hydrogen reduction to remove and recover the sulfur.

  2. Silicon nitride membrane resonators at millikelvin temperatures with quality factors exceeding 10^8

    NARCIS (Netherlands)

    Yuan, M.; Cohen, M.A.; Steele, G.A.

    2015-01-01

    We study the mechanical dissipation of the fundamental mode of millimeter-sized, high quality-factor (Q) metalized silicon nitride membranes at temperatures down to 14?mK using a three-dimensional optomechanical cavity. Below 200?mK, high-Q modes of the membranes show a diverging increase of Q with

  3. Low hydrogen content silicon nitride films deposited at room temperature with a multipolar ECR plasma source

    NARCIS (Netherlands)

    Isai, I.G.; Holleman, J.; Wallinga, Hans; Woerlee, P.H.

    2004-01-01

    Silicon nitride layers with very low hydrogen content (less than 1 atomic percent) were deposited at near room temperature, from N2 and SiH4, with a multipolar electron cyclotron resonance plasma. The influences of pressure and nitrogen flow rate on physical and electrical properties were studied in

  4. Bright Room-Temperature Single-Photon Emission from Defects in Gallium Nitride.

    Science.gov (United States)

    Berhane, Amanuel M; Jeong, Kwang-Yong; Bodrog, Zoltán; Fiedler, Saskia; Schröder, Tim; Triviño, Noelia Vico; Palacios, Tomás; Gali, Adam; Toth, Milos; Englund, Dirk; Aharonovich, Igor

    2017-03-01

    Room-temperature quantum emitters in gallium nitride (GaN) are reported. The emitters originate from cubic inclusions in hexagonal lattice and exhibit narrowband luminescence in the red spectral range. The sources are found in different GaN substrates, and therefore are promising for scalable quantum technologies. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Short-term low-temperature glow discharge nitriding of 316L austenitic steel

    Directory of Open Access Journals (Sweden)

    T. Frączek

    2011-07-01

    Full Text Available The AISI 316L austenitic steel after glow discharge nitriding at temperature of T = 673 K and duration of τ=14,4 ks, for two different variants of specimen arrangement in the glow-discharge chamber was investigated. In order to assess the effectiveness of nitriding process, the surface layers profile analysis examination, surface hardness and hardness profile examination, the analysis of surface layer structures and corrosion resistance tests were performed. It has been found that application of a booster screen effects in a nitrogen diffusion depth increment into the 316L austenitic steel surface, what results in the surface layer thickness escalation.

  6. Improvement of erosion and erosion corrosion resistance of AISI420 stainless steel by low temperature plasma nitriding

    Science.gov (United States)

    Xi, Yun-tao; Liu, Dao-xin; Han, Dong

    2008-07-01

    Plasma nitriding experiments were carried out with DC-pulsed plasma in 25% N 2 + 75% H 2 atmosphere at low temperature (350 °C) and normal temperature (550 °C) for 15 h. The composition, microstructure, microhardness profiles, residual stress profiles and electrochemical impedance spectrum analyses of the nitrided samples were examined. The influence of plasma nitriding on the erosion and erosion-corrosion resistance of AISI 420 martensitic stainless steel was investigated using a jet solid particle erosion tester and a slurry erosion-corrosion tester. Results showed that the 350 °C nitriding layer was dominated by ɛ-Fe 3N and α N phase, a supersaturated nitrogen solid solution. However, nitrogen would react with Cr in the steel to form CrN precipitates directly during 550 °C nitriding, which would lead to the depletion of Cr in the solid solution phase of the nitrided layer. Both 350 and 550 °C plasma nitriding could improve the erosion resistance of AISI420 stainless steel under dry erosion, but the former showed better results. In both neutral and acid environment, while the erosion-corrosion resistance of AISI 420 was improved by means of 350 °C nitriding, it was decreased through 550 °C nitriding.

  7. The Successful Operation of Hole-type Gaseous Detectors at Cryogenic Temperatures

    CERN Document Server

    Pereiale, L.; Iacobaeus, C.; Francke, T.; Lund-Jensen, B.; Pavlopoulos, P.; Picchi, P.; Pietropaolo, F.; Tokanai, F.

    2004-01-01

    We have demonstrated that hole-type gaseous detectors, GEMs and capillary plates, can operate up to 77 K. For example, a single capillary plate can operate at gains of above 10E3 in the entire temperature interval between 300 until 77 K. The same capillary plate combined with CsI photocathodes could operate perfectly well at gains (depending on gas mixtures) of 100-1000. Obtained results may open new fields of applications for capillary plates as detectors of UV light and charge particles at cryogenic temperatures: noble liquid TPCs, WIMP detectors or LXe scintillating calorimeters and cryogenic PETs.

  8. Nitriding and Nitrocarburizing; Current Status and Future Challenges

    DEFF Research Database (Denmark)

    Somers, Marcel A. J.

    , 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......This contribution addresses the current understanding of gaseous nitriding and nitrocarburizing. Aspects of thermodynamics, kinetics and microstructure development in iron and heat treatable steel will be explained. In these materials the nitrided/ nitrocarburized case can be subdivided...

  9. Proton transfer and complex formation of angiotensin I ions with gaseous molecules at various temperature

    Energy Technology Data Exchange (ETDEWEB)

    Nonose, Shinji, E-mail: nonose@yokohama-cu.ac.jp; Yamashita, Kazuki; Sudo, Ayako; Kawashima, Minami

    2013-09-23

    Highlights: • Proton transfer from angiotensin I ions (z = 2, 3) to gaseous molecules was studied. • Temperature dependence of absolute reaction rate constants was measured. • Remarkable changes were obtained for distribution of product ions and reaction rate constants. • Proton transfer reaction was enhanced and reduced by complex formation. • Conformation changes are induced by complex formation and or by thermal collision with He. - Abstract: Proton transfer reactions of angiotensin I ions for +2 charge state, [M + 2H]{sup 2+}, to primary, secondary and aromatic amines were examined in the gas phase. Absolute reaction rate constants for proton transfer were determined from intensities of parent and product ions in the mass spectra. Temperature dependence of the reaction rate constants was measured. Remarkable change was observed for distribution of product ions and reaction rate constants. Proton transfer reaction was enhanced or reduced by complex formation of [M + 2H]{sup 2+} with gaseous molecules. The results relate to conformation changes of [M + 2H]{sup 2+} with change of temperature, which are induced by complex formation and or by thermal collision with He. Proton transfer reactions of angiotensin I ions for +3 charge state, [M + 3H]{sup 3+}, were also studied. The reaction rates did not depend on temperature so definitely.

  10. Low-Temperature Nitriding of Deformed Austenitic Stainless Steels with Various Nitrogen Contents Obtained by Prior High-Temperature Solution Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

    2016-01-01

    In the past decades, high nitrogen steels (HNS) have been regarded as substitutes for conventional austenitic stainless steels because of their superior mechanical and corrosion properties. However, the main limitation to their wider application is their expensive production process....... As an alternative, high-temperature solution nitriding has been applied to produce HNS from three commercially available stainless steel grades (AISI 304L, AISI 316, and EN 1.4369). The nitrogen content in each steel alloy is varied and its influence on the mechanical properties and the stability of the austenite...

  11. High-temperature nitridation of Nb-Ti alloys in nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Buscaglia, V.; Martinelli, A. [Nat. Res. Council, Genoa (Italy). Inst. of Phys. Chem. of Mater.; Musenich, R. [National Institute of Nuclear Physics, via Dodecaneso 33, I-16146 Genoa (Italy); Mayr, W.; Lengauer, W. [Institute for Chemical Technology of Inorganic Materials, Vienna University of Technology, Getreidemarkt 9/161, A-1060 Vienna (Austria)

    1999-02-01

    Microstructure evolution, phase composition, weight gain and layer growth kinetics of Nb-Ti alloys (10, 47, 63 and 90 at.% Ti) annealed in high-purity nitrogen atmosphere (0.3, 3 and 30 bar) were studied in the temperature range 1300-1600 C. After nitridation, the formation of an external compact nitride layer as well as extensive internal nitride precipitation was observed. The overall nitridation kinetics (weight gain) is invariably parabolic; a deviation from the initial rate law is observed at 1450 and 1600 C for the longer reaction times when the alloy core approaches nitrogen saturation and internal precipitation slows down. The parabolic rate constant is strongly affected by the Nb content in the alloy. The phases detected in the reacted samples are isostructural with those of the Nb-Ti, Nb-N and Ti-N systems. The surface nitride was {delta}-(Ti,Nb)N in any case. The morphology of the internal nitridation zone corresponds to the growth of large, oriented, nitride needles for the three alloys richer in titanium. The needles are composed of {alpha}-(Ti,Nb)(N) in the case of Ti{sub 90}Nb{sub 10} alloy and of {delta}-(Ti,Nb)N{sub 1-x} in the case of Ti{sub 63}Nb{sub 37} and Ti{sub 47}Nb{sub 53}. Such a microstructure is evidence for nucleation difficulty; coarsening of the existing particles is favoured in comparison to the formation of new precipitates. Homogeneous nucleation is hindered by the small chemical Gibbs free energy available and the elastic strain energy related to volume misfit. After initial reaction, microstructure evolution is mainly determined by the fast inward diffusion of nitrogen and the slow Nb-Ti interdiffusion in the {beta}-(Ti,Nb) alloy. Internal nitridation of Ti{sub 10}Nb{sub 90} at 1450 and 1600 C leads to the formation of fine and numerous precipitates of {beta}-(Nb,Ti){sub 2}N. (orig.) 58 refs.

  12. Correction: Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control.

    Science.gov (United States)

    Sarkar, Sujoy; Sampath, S

    2016-05-28

    Correction for 'Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control' by Sujoy Sarkar et al., Chem. Commun., 2016, 52, 6407-6410.

  13. Effect of microstructure on the high temperature strength of nitride ...

    Indian Academy of Sciences (India)

    The effect of these parameters on room temperature and high temperature strength of the composite up to 1300°C in ambient condition were studied. The high temperature flexural strength of the composite of all compositions increased at 1200 and 1300°C because of oxidation of Si3N4 phase and blunting crack front.

  14. Monitoring gaseous CO2 and ethanol above champagne glasses: flute versus coupe, and the role of temperature.

    Directory of Open Access Journals (Sweden)

    Gérard Liger-Belair

    Full Text Available In champagne tasting, gaseous CO(2 and volatile organic compounds progressively invade the headspace above glasses, thus progressively modifying the chemical space perceived by the consumer. Simultaneous quantification of gaseous CO(2 and ethanol was monitored through micro-gas chromatography (μGC, all along the first 15 minutes following pouring, depending on whether a volume of 100 mL of champagne was served into a flute or into a coupe. The concentration of gaseous CO(2 was found to be significantly higher above the flute than above the coupe. Moreover, a recently developed gaseous CO(2 visualization technique based on infrared imaging was performed, thus confirming this tendency. The influence of champagne temperature was also tested. As could have been expected, lowering the temperature of champagne was found to decrease ethanol vapor concentrations in the headspace of a glass. Nevertheless, and quite surprisingly, this temperature decrease had no impact on the level of gaseous CO(2 found above the glass. Those results were discussed on the basis of a multiparameter model which describes fluxes of gaseous CO(2 escaping the liquid phase into the form of bubbles.

  15. Monitoring gaseous CO2 and ethanol above champagne glasses: flute versus coupe, and the role of temperature.

    Science.gov (United States)

    Liger-Belair, Gérard; Bourget, Marielle; Pron, Hervé; Polidori, Guillaume; Cilindre, Clara

    2012-01-01

    In champagne tasting, gaseous CO(2) and volatile organic compounds progressively invade the headspace above glasses, thus progressively modifying the chemical space perceived by the consumer. Simultaneous quantification of gaseous CO(2) and ethanol was monitored through micro-gas chromatography (μGC), all along the first 15 minutes following pouring, depending on whether a volume of 100 mL of champagne was served into a flute or into a coupe. The concentration of gaseous CO(2) was found to be significantly higher above the flute than above the coupe. Moreover, a recently developed gaseous CO(2) visualization technique based on infrared imaging was performed, thus confirming this tendency. The influence of champagne temperature was also tested. As could have been expected, lowering the temperature of champagne was found to decrease ethanol vapor concentrations in the headspace of a glass. Nevertheless, and quite surprisingly, this temperature decrease had no impact on the level of gaseous CO(2) found above the glass. Those results were discussed on the basis of a multiparameter model which describes fluxes of gaseous CO(2) escaping the liquid phase into the form of bubbles.

  16. Low Working-Temperature Acetone Vapor Sensor Based on Zinc Nitride and Oxide Hybrid Composites.

    Science.gov (United States)

    Qu, Fengdong; Yuan, Yao; Guarecuco, Rohiverth; Yang, Minghui

    2016-06-01

    Transition-metal nitride and oxide composites are a significant class of emerging materials that have attracted great interest for their potential in combining the advantages of nitrides and oxides. Here, a novel class of gas sensing materials based on hybrid Zn3 N2 and ZnO composites is presented. The Zn3 N2 /ZnO (ZnNO) composites-based sensor exhibits selectivity and high sensitivity toward acetone vapor, and the sensitivity is dependent on the nitrogen content of the composites. The ZnNO-11.7 described herein possesses a low working temperature of 200 °C. The detection limit (0.07 ppm) is below the diabetes diagnosis threshold (1.8 ppm). In addition, the sensor shows high reproducibility and long-term stability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Pulsed laser heating of silicon-nitride capped GaAs: Optical properties at high temperature

    Science.gov (United States)

    Bhat, A.; Yao, H. D.; Compaan, A.; Horak, A.; Rys, A.

    1988-09-01

    The optical properties of silicon nitride and gallium arsenide were studied at temperatures up to and beyond the melting point of GaAs by means of laser heating. XeCl excimer and pulsed dye laser pulses, ˜10 ns in duration, were used to heat the semiconductor under nitride capping layers of varying thickness. The transient reflectivity response at 514.5 nm was used together with a multilayer interference analysis to obtain the optical constants of solid and molten GaAs and of solid Si3N4 near the 1513-K melting point of GaAs. In addition, we report the melt duration as a function of laser pulse energy for GaAs with and without capping layers.

  18. 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

  19. Low temperature sapphire nitridation: A clue to optimize GaN layers grown by molecular beam epitaxy

    Science.gov (United States)

    Widmann, F.; Feuillet, G.; Daudin, B.; Rouvière, J. L.

    1999-02-01

    The sapphire nitridation temperature is investigated as a possible parameter to improve the properties of GaN epilayers grown by molecular beam epitaxy using a radio frequency plasma source. It is found out that lowering the nitridation temperature to values as low as 200 °C allows us to drastically improve the GaN structural and optical properties. Careful examination of the interface by transmission electron microscopy reveals that, in this case, the interface between the nitridated sapphire and the AlN buffer consists of an ordered array of pure edge dislocations. In contrast, high nitridation temperatures result in a perturbed interface with the occurrence of cubic crystallites in the AlN buffer. These results, complemented by a thorough reflection high-energy electron diffraction analysis of the nitridation procedure and a secondary ion mass spectrometry investigation, are interpreted in the framework of a model whereby a higher oxygen concentration is extracted from the substrate at high nitridation temperature, leading to the formation of cubic grains with a smaller lattice parameter than the surrounding matrix and to the concomitant occurrence of defects within the buffer.

  20. Silicon nitride membrane resonators at millikelvin temperatures with quality factors exceeding 108

    Science.gov (United States)

    Yuan, Mingyun; Cohen, Martijn A.; Steele, Gary A.

    2015-12-01

    We study the mechanical dissipation of the fundamental mode of millimeter-sized, high quality-factor (Q) metalized silicon nitride membranes at temperatures down to 14 mK using a three-dimensional optomechanical cavity. Below 200 mK, high-Q modes of the membranes show a diverging increase of Q with decreasing temperature, reaching Q =1.27 ×108 at 14 mK, an order of magnitude higher than that reported before. The ultra-low dissipation makes the membranes highly attractive for the study of optomechanics in the quantum regime, as well as for other applications of optomechanics such as microwave to optical photon conversion.

  1. Structural characterization of plasma nitrided interstitial-free steel at different temperatures by SEM, XRD and Rietveld method

    Directory of Open Access Journals (Sweden)

    Ana Paula de Andrade Manfridini

    2017-01-01

    Full Text Available Plasma nitriding processes are widely used to improve surface properties of several steels and alloys. In this work, the formation of nitrides in the surface of plasma nitrided IF steels as a function of the temperature was investigated. Three cold-rolled IF steel plates were nitrided for 4 h after shot peening at three different temperatures: 450 °C, 475 °C, and 500 °C. The resultant nitrided layers were then characterized by scanning electron microscopy (SEM, X-ray diffraction (XRD, Rietveld method, and hardness measurements. Through SEM images, it was possible to visualize two main sublayers: a compound layer and a diffusion zone. Through XRD, two phases were identified in the compound layer, which were ɛ-Fe2–3N and γ′-Fe4N. The diffusion zone presented a ferritic matrix with fine precipitates, possibly α″-Fe16N2. By Rietveld, the calculated quantity of γ′-Fe4N was 68 wt.% for the sample treated at 475 °C and 58 wt.% for the one treated at 500 °C. These values were consistent with the hardness measurements. Thus, it is suggested that higher nitriding temperatures facilitate the decreasing of γ′-Fe4N and, consequently, the increasing of ɛ-Fe2–3N in the compound layer.

  2. Temperature measurementin gaseous and liquid reacting media in the case of their shock compression

    Science.gov (United States)

    Pai, V. V.; Gulevich, M. A.; Yakovlev, I. V.; Lysak, V. I.; Kuz'min, S. V.; Khaustov, S. V.

    2017-07-01

    This paper describes the results of measuring the temperatures of gaseous and liquid reacting media, which was carried out by the thermocouple method with the use of a battery (copper-Constantan-copper) of planar thermocouples, placed in the medium under study. It is shown that convective heat transfer lasting for 0.5-1.5 μs equalizes the temperatures of the "hot" thermocouple junctions and the environment. The relationship between the voltage occurring on the thermobattery during this heating and time was determined using a pulse oscilloscope. The measured maximum voltage was used to determine the temperature of the medium. A series of experiments was carried out on measuring the temperatures of water and emulsion explosive matrix, which were compressed by a shock wave, as well as the detonation products of ammonite with sodium hydrogen carbonate at various mass ratios. The estimates of heat fluxes from the detonation products to the metallic surfaces of the thermobattery contacting with them are obtained.

  3. Multi-stage pulsed laser deposition of aluminum nitride at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Duta, L. [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, 077125 Magurele (Romania); Stan, G.E. [National Institute of Materials Physics, 105 bis Atomistilor Street, 077125 Magurele (Romania); Stroescu, H.; Gartner, M.; Anastasescu, M. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Fogarassy, Zs. [Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, Konkoly Thege Miklos u. 29-33, H-1121 Budapest (Hungary); Mihailescu, N. [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, 077125 Magurele (Romania); Szekeres, A., E-mail: szekeres@issp.bas.bg [Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784 (Bulgaria); Bakalova, S. [Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784 (Bulgaria); Mihailescu, I.N., E-mail: ion.mihailescu@inflpr.ro [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, 077125 Magurele (Romania)

    2016-06-30

    Highlights: • Multi-stage pulsed laser deposition of aluminum nitride at different temperatures. • 800 °C seed film boosts the next growth of crystalline structures at lower temperature. • Two-stage deposited AlN samples exhibit randomly oriented wurtzite structures. • Band gap energy values increase with deposition temperature. • Correlation was observed between single- and multi-stage AlN films. - Abstract: We report on multi-stage pulsed laser deposition of aluminum nitride (AlN) on Si (1 0 0) wafers, at different temperatures. The first stage of deposition was carried out at 800 °C, the optimum temperature for AlN crystallization. In the second stage, the deposition was conducted at lower temperatures (room temperature, 350 °C or 450 °C), in ambient Nitrogen, at 0.1 Pa. The synthesized structures were analyzed by grazing incidence X-ray diffraction (GIXRD), transmission electron microscopy (TEM), atomic force microscopy and spectroscopic ellipsometry (SE). GIXRD measurements indicated that the two-stage deposited AlN samples exhibited a randomly oriented wurtzite structure with nanosized crystallites. The peaks were shifted to larger angles, indicative for smaller inter-planar distances. Remarkably, TEM images demonstrated that the high-temperature AlN “seed” layers (800 °C) promoted the growth of poly-crystalline AlN structures at lower deposition temperatures. When increasing the deposition temperature, the surface roughness of the samples exhibited values in the range of 0.4–2.3 nm. SE analyses showed structures which yield band gap values within the range of 4.0–5.7 eV. A correlation between the results of single- and multi-stage AlN depositions was observed.

  4. Impact of annealing temperature on the mechanical and electrical properties of sputtered aluminum nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gillinger, M.; Schneider, M.; Bittner, A.; Schmid, U. [Institute of Sensor and Actuator Systems, Vienna University of Technology, Vienna 1040 (Austria); Nicolay, P. [CTR Carinthian Tech Research AG, Villach 9524 (Austria)

    2015-02-14

    Aluminium nitride (AlN) is a promising material for challenging sensor applications such as process monitoring in harsh environments (e.g., turbine exhaust), due to its piezoelectric properties, its high temperature stability and good thermal match to silicon. Basically, the operational temperature of piezoelectric materials is limited by the increase of the leakage current as well as by enhanced diffusion effects in the material at elevated temperatures. This work focuses on the characterization of aluminum nitride thin films after post deposition annealings up to temperatures of 1000 °C in harsh environments. For this purpose, thin film samples were temperature loaded for 2 h in pure nitrogen and oxygen gas atmospheres and characterized with respect to the film stress and the leakage current behaviour. The X-ray diffraction results show that AlN thin films are chemically stable in oxygen atmospheres for 2 h at annealing temperatures of up to 900 °C. At 1000 °C, a 100 nm thick AlN layer oxidizes completely. For nitrogen, the layer is stable up to 1000 °C. The activation energy of the samples was determined from leakage current measurements at different sample temperatures, in the range between 25 and 300 °C. Up to an annealing temperature of 700 °C, the leakage current in the thin film is dominated by Poole-Frenkel behavior, while at higher annealing temperatures, a mixture of different leakage current mechanisms is observed.

  5. Size and Shape Dependence on Melting Temperature of Gallium Nitride Nanoparticles

    Directory of Open Access Journals (Sweden)

    Paneerselvam Antoniammal

    2012-01-01

    Full Text Available The study of variation of the size and shape effect on the melting property of gallium nitride nanoparticles with their spherical and cylindrical geometrical feature is theoretically explored. A numerical thermodynamical model has been devoted for the study. A comparative investigation is made between the two shapes, at the range of ~3 nm dia. The cylindrical GaN nanoparticles, whose melting point has been reported to decrease with decreasing particle radius, become larger than spherical-shaped nanoparticles. The melting temperature obtained in the present study is in line with the function of radius of curvature.

  6. Electrical properties of low pressure chemical vapor deposited silicon nitride thin films for temperatures up to 650 °C

    NARCIS (Netherlands)

    Tiggelaar, Roald M.; Groenland, A.W.; Sanders, Remco G.P.; Gardeniers, Johannes G.E.

    2009-01-01

    The results of a study on electrical conduction in low pressure chemical vapor deposited silicon nitride thin films for temperatures up to 650 °C are described. Current density versus electrical field characteristics are measured as a function of temperature for 100 and 200 nm thick stoichiometric

  7. Pressure-Volume-Temperature (PVT) Gauging of an Isothermal Cryogenic Propellant Tank Pressurized with Gaseous Helium

    Science.gov (United States)

    VanDresar, Neil T.; Zimmerli, Gregory A.

    2014-01-01

    Results are presented for pressure-volume-temperature (PVT) gauging of a liquid oxygen/liquid nitrogen tank pressurized with gaseous helium that was supplied by a high-pressure cryogenic tank simulating a cold helium supply bottle on a spacecraft. The fluid inside the test tank was kept isothermal by frequent operation of a liquid circulation pump and spray system, and the propellant tank was suspended from load cells to obtain a high-accuracy reference standard for the gauging measurements. Liquid quantity gauging errors of less than 2 percent of the tank volume were obtained when quasi-steady-state conditions existed in the propellant and helium supply tanks. Accurate gauging required careful attention to, and corrections for, second-order effects of helium solubility in the liquid propellant plus differences in the propellant/helium composition and temperature in the various plumbing lines attached to the tanks. On the basis of results from a helium solubility test, a model was developed to predict the amount of helium dissolved in the liquid as a function of cumulative pump operation time. Use of this model allowed correction of the basic PVT gauging calculations and attainment of the reported gauging accuracy. This helium solubility model is system specific, but it may be adaptable to other hardware systems.

  8. Stress Corrosion Behavior of Low-temperature Liquid-Nitrided 316 Austenitic Stainless Steel in a Sour Environment

    Science.gov (United States)

    Zhang, Xiangfeng; Wang, Jun; Fan, Hongyuan; Yan, Jing; Duan, Lian; Gu, Tan; Xian, Guang; Sun, Lan; Wang, Danqi

    2017-10-01

    Low-temperature nitridation is a widely used surface heat treatment. Low-temperature liquid nitridation was applied to 316 austenitic stainless steel and an S-phase (expanded austenite) layer was achieved on the alloy surface. The effect of the S-phase layer on corrosion resistance and stress corrosion cracking was investigated in a sour environment. When a bending stress of 164 MPa (80 pct yield stress, YS) was applied, no macroscopic corrosion cracking and pits were observed on the nitrided samples and the S-phase layer stayed intact. Although no macroscopic corrosion cracking was observed on the non-nitrided samples under 205 MPa (100 pct YS), some pits were formed on the alloy surface. This could be attributed to the high stresses and hardness, and the excellent corrosion resistance of the S-phase layer introduced by low-temperature nitridation. Supersaturated nitrogen atoms in the S-phase layer can effectively prevent the decrease in pH of the corrosive medium and accelerate the alloy repassivation kinetics. However, when the bending stress was increased to 205 and 246 MPa (100 pct YS, 120 pct YS), macroscopic cracks were observed in the presence of both tensile stress and a corrosive medium.

  9. Stress Corrosion Behavior of Low-temperature Liquid-Nitrided 316 Austenitic Stainless Steel in a Sour Environment

    Science.gov (United States)

    Zhang, Xiangfeng; Wang, Jun; Fan, Hongyuan; Yan, Jing; Duan, Lian; Gu, Tan; Xian, Guang; Sun, Lan; Wang, Danqi

    2018-01-01

    Low-temperature nitridation is a widely used surface heat treatment. Low-temperature liquid nitridation was applied to 316 austenitic stainless steel and an S-phase (expanded austenite) layer was achieved on the alloy surface. The effect of the S-phase layer on corrosion resistance and stress corrosion cracking was investigated in a sour environment. When a bending stress of 164 MPa (80 pct yield stress, YS) was applied, no macroscopic corrosion cracking and pits were observed on the nitrided samples and the S-phase layer stayed intact. Although no macroscopic corrosion cracking was observed on the non-nitrided samples under 205 MPa (100 pct YS), some pits were formed on the alloy surface. This could be attributed to the high stresses and hardness, and the excellent corrosion resistance of the S-phase layer introduced by low-temperature nitridation. Supersaturated nitrogen atoms in the S-phase layer can effectively prevent the decrease in pH of the corrosive medium and accelerate the alloy repassivation kinetics. However, when the bending stress was increased to 205 and 246 MPa (100 pct YS, 120 pct YS), macroscopic cracks were observed in the presence of both tensile stress and a corrosive medium.

  10. Native gallium adatoms discovered on atomically-smooth gallium nitride surfaces at low temperature.

    Science.gov (United States)

    Alam, Khan; Foley, Andrew; Smith, Arthur R

    2015-03-11

    In advanced compound semiconductor devices, such as in quantum dot and quantum well systems, detailed atomic configurations at the growth surfaces are vital in determining the structural and electronic properties. Therefore, it is important to investigate the surface reconstructions in order to make further technological advancements. Usually, conventional semiconductor surfaces (e.g., arsenides, phosphides, and antimonides) are highly reactive due to the existence of a high density of group V (anion) surface dangling bonds. However, in the case of nitrides, group III rich growth conditions in molecular beam epitaxy are usually preferred leading to group III (Ga)-rich surfaces. Here, we use low-temperature scanning tunneling microscopy to reveal a uniform distribution of native gallium adatoms with a density of 0.3%-0.5% of a monolayer on the clean, as-grown surface of nitrogen polar GaN(0001̅) having the centered 6 × 12 reconstruction. Unseen at room temperature, these Ga adatoms are strongly bound to the surface but move with an extremely low surface diffusion barrier and a high density saturation coverage in thermodynamic equilibrium with Ga droplets. Furthermore, the Ga adatoms reveal an intrinsic surface chirality and an asymmetric site occupation. These observations can have important impacts in the understanding of gallium nitride surfaces.

  11. Nitride precipitation during high temperature corrosion of ductile cast irons in synthetic exhaust gases

    Science.gov (United States)

    Tholence, F.; Norell, M.

    2005-02-01

    Internal nitrides form in two ductile cast irons (SiMo and Ni-Resist) intended for exhaust systems in vehicles. Samples oxidised at 650 1050 °C for 50 h in modified synthetic exhaust gases were analysed by using AES and FEG-SEM. No nitrides formed in absence of NOx. In dry petrol gas coarse nitrides (Ni-Resist in both dry and normal petrol whereas no nitrides were observed in Ni-Resist exposed to diesel gases.

  12. Temperature-controlled colossal magnetoresistance and perfect spin Seebeck effect in hybrid graphene/boron nitride nanoribbons.

    Science.gov (United States)

    Zhu, Lin; Li, Ruimin; Yao, Kailun

    2017-02-01

    Thermal spin transport properties of graphene and hexagonal boron nitride nanoribbon heterojunctions have been investigated using density functional theory calculations combined with the Keldysh nonequilibrium Green's function approach. The results showed that the perfect spin Seebeck effect and analogy negative differential thermoelectric resistance occurred in the device under a temperature difference without a gate or bias voltage. An intriguing thermally induced colossal magnetoresistance without gate regulation was also observed, which can be switched between a positive and negative value with temperature control. It was also found that the unit number of zigzag graphene nanoribbons and boron nitride nanoribbons can tune the electronic band structure and the energy gap of the heterostructure, and then modulate the thermal spin transport properties. The results suggest that graphene and hexagonal boron nitride nanoribbon heterostructures may have potential applications in graphene-based nanodevices.

  13. Remote Measurement of Pollution - A 40-Year Langley Retrospective. Part 1; Temperature and Gaseous Species

    Science.gov (United States)

    Remsberg, Ellis E.

    2011-01-01

    The National Aeronautics and Space Administration (NASA) phased down its Apollo Moon Program after 1970 in favor of a partly reusable Space Shuttle vehicle that could be used to construct and supply a manned, Earth-orbiting Space Station. Applications programs were emphasized in response to the growing public concern about Earth's finite natural resources and the degradation of its environment. Shortly thereafter, a workshop was convened in Norfolk, Virginia, on Remote Measurement of Pollution (or RMOP), and its findings are in a NASA Special Publication (NASA SP-285). The three primary workshop panels and their chairmen were focused on trace gas species (Will Kellogg), atmospheric particulates or aerosols (Verner Suomi), and water pollution (Gifford Ewing). Many of the workshop participants were specialists in the techniques that might be employed for the regional to global-scale, remote measurements from an Earth-orbiting satellite. The findings and recommendations of the RMOP Report represent the genesis of and a blueprint for the satellite, atmospheric sensing programs within NASA for nearly two decades. This paper is a brief, 40-year retrospective of those instrument developments that were an outgrowth of the RMOP activity. Its focus is on satellite measurement capabilities for temperature and gaseous species that were demonstrated by atmospheric technologists at the Langley Research Center. Limb absorption by solar occultation, limb infrared radiometry, and gas filter correlation radiometry techniques provided significant science data, so they are emphasized in this review.

  14. Photodynamics of quantum emitters in hexagonal boron nitride revealed by low-temperature spectroscopy

    Science.gov (United States)

    Sontheimer, Bernd; Braun, Merle; Nikolay, Niko; Sadzak, Nikola; Aharonovich, Igor; Benson, Oliver

    2017-09-01

    Quantum emitters in hexagonal boron nitride (hBN) have recently emerged as promising bright single photon sources. In this Rapid Communication we investigate in detail their optical properties at cryogenic temperatures. In particular, we perform temperature-resolved photoluminescence studies and measure photon coherence times from the hBN emitters. The obtained value of 81 (1 )ps translates to a width of ˜6.5 GHz which is higher than the Fourier transform limited value of ˜32 MHz . To account for the photodynamics of the emitter, we perform ultrafast spectral diffusion measurements that partially account for the coherence times. Our results provide important insight into the relaxation processes in quantum emitters in hBN which is mandatory to evaluate their applicability for quantum information processing.

  15. A kinetic study of gaseous potassium capture by coal minerals in a high temperature fixed-bed reactor

    DEFF Research Database (Denmark)

    Zheng, Yuanjing; Jensen, Peter Arendt; Jensen, Anker Degn

    2008-01-01

    The reactions between gaseous potassium chloride and coal minerals were investigated in a lab-scale high temperature fixed-bed reactor using single sorbent pellets. The applied coal minerals included kaolin, mullite, silica, alumina, bituminous coal ash, and lignite coal ash that were formed...... when heated at temperatures above 450°C. The amounts of potassium captured by metakaolin pellet decreases with increasing reaction temperature in the range of 900-1300°C and increases again with further increasing the temperature up to 1500°C. There is no reaction of pre-made mullite with KCl...

  16. High-Temperature Dielectric Properties of Aluminum Nitride Ceramic for Wireless Passive Sensing Applications.

    Science.gov (United States)

    Liu, Jun; Yuan, Yukun; Ren, Zhong; Tan, Qiulin; Xiong, Jijun

    2015-09-08

    The accurate characterization of the temperature-dependent permittivity of aluminum nitride (AlN) ceramic is quite critical to the application of wireless passive sensors for harsh environments. Since the change of the temperature-dependent permittivity will vary the ceramic-based capacitance, which can be converted into the change of the resonant frequency, an LC resonator, based on AlN ceramic, is prepared by the thick film technology. The dielectric properties of AlN ceramic are measured by the wireless coupling method, and discussed within the temperature range of 12 °C (room temperature) to 600 °C. The results show that the extracted relative permittivity of ceramic at room temperature is 2.3% higher than the nominal value of 9, and increases from 9.21 to 10.79, and the quality factor Q is decreased from 29.77 at room temperature to 3.61 at 600 °C within the temperature range.

  17. Multi-stage pulsed laser deposition of aluminum nitride at different temperatures

    Science.gov (United States)

    Duta, L.; Stan, G. E.; Stroescu, H.; Gartner, M.; Anastasescu, M.; Fogarassy, Zs.; Mihailescu, N.; Szekeres, A.; Bakalova, S.; Mihailescu, I. N.

    2016-06-01

    We report on multi-stage pulsed laser deposition of aluminum nitride (AlN) on Si (1 0 0) wafers, at different temperatures. The first stage of deposition was carried out at 800 °C, the optimum temperature for AlN crystallization. In the second stage, the deposition was conducted at lower temperatures (room temperature, 350 °C or 450 °C), in ambient Nitrogen, at 0.1 Pa. The synthesized structures were analyzed by grazing incidence X-ray diffraction (GIXRD), transmission electron microscopy (TEM), atomic force microscopy and spectroscopic ellipsometry (SE). GIXRD measurements indicated that the two-stage deposited AlN samples exhibited a randomly oriented wurtzite structure with nanosized crystallites. The peaks were shifted to larger angles, indicative for smaller inter-planar distances. Remarkably, TEM images demonstrated that the high-temperature AlN "seed" layers (800 °C) promoted the growth of poly-crystalline AlN structures at lower deposition temperatures. When increasing the deposition temperature, the surface roughness of the samples exhibited values in the range of 0.4-2.3 nm. SE analyses showed structures which yield band gap values within the range of 4.0-5.7 eV. A correlation between the results of single- and multi-stage AlN depositions was observed.

  18. Predicting Microstructure Development During HighTemperature Nitriding of Martensitic Stainless SteelsUsing Thermodynamic Modeling

    Directory of Open Access Journals (Sweden)

    Tschiptschin André Paulo

    2002-01-01

    Full Text Available Thermodynamic calculations of the Fe-Cr-N System in the region of the Gas Phase Equilibria have been compared with experimental results of maximum nitrogen absorption during nitriding of two Martensitic Stainless Steels (a 6 mm thick sheet of AISI 410S steel and green powder compacts of AISI 434L steel under N2 atmospheres. The calculations have been performed combining the Fe-Cr-N System description contained in the SGTE Solid Solution Database and the gas phase for the N System contained in the SGTE Substances Database. Results show a rather good agreement for total nitrogen absorption in the steel and nitrogen solubility in austenite in the range of temperatures between 1273 K and 1473 K and in the range of pressures between 0.1 and 0.36 MPa. Calculations show that an appropriate choice of heat treatment parameters can lead to optimal nitrogen absorption in the alloy. It was observed in the calculations that an increased pressure stabilizes CrN at expenses of Cr2N - type nitrides.

  19. 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.

  20. Aspects of the practical application of titanium alloys after low temperature nitriding glow discharge in hydrogen- free -gas media

    Energy Technology Data Exchange (ETDEWEB)

    Mashovets, N.S., E-mail: mashovets@rambler.ru [Khmelnickiy National University (Ukraine); Pastukh, I.M., E-mail: pastim@mail.ru [Khmelnickiy National University (Ukraine); Voloshko, S.M. [Khmelnickiy National University (Ukraine); National Technical University of Ukraine “Kyiv Polytechnic Institute” (Ukraine)

    2017-01-15

    Highlights: • Surface modification of titanium alloys were carried out by low-temperature nitriding in a glow discharge in hydrogen-free environment. • Research into the phase composition was performed by X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). • The above material shows the promise of the technology of low-temperature hydrogen-nitriding by glow discharge. This greatly expands the range of practical applications of titanium alloys. - Abstract: X-ray diffraction analysis, X-ray photoelectron spectroscopy, and Electron Auger-spectroscopy investigation of phase transformation on the surface of the VT8 titanium alloy after a low temperature hydrogen-free nitriding in a glow discharge. Operational characteristics of titanium alloys defined physical-mechanical characteristics of the surface and their phase composition, which depend on the process parameters of nitriding. Surface modification of titanium alloys were carried out by low-temperature nitriding in a glow discharge in hydrogen-free environment. The main advantage of this method lies in the absence of hydrogen embrittlement and complete environmental safety process. Application of the glow discharge can not only speed up the process by the order of the diffusion surface saturation with nitrogen, but also significantly alters the kinetics of the process and quality of the nitrided layer, in particular its physio-mechanical properties and phase composition. For research purposes, the standards from an α + β alloy Ti-Al6-Cr2-Mo2,5 (VT8) were used. Research into the phase composition was performed by X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Stratified analysis by AES was conducted by etching the surface of the samples’ argon ion beam with diameters of 1.5 mm with an energy of 3000 eV and a current density of 400 mA/cm{sup 2}. The above material shows the promise of the technology of low-temperature

  1. High temperature transducer using aluminum nitride single crystal for laser ultrasound detection

    Science.gov (United States)

    Kim, Taeyang; Kim, Jinwook; Jiang, Xiaoning

    2017-04-01

    In this work, a new ultrasound nondestructive testing (NDT) method based on laser-generated Lamb wave detection was proposed for high temperature (HT) NDT. Lamb waves were introduced to a stainless steel plate by the Nd:YAG pulsed laser at one point and detected by aluminum nitride (AlN) transducer at a distant position. The fundamental symmetric (S0) and antisymmetric (A0) mode Lamb waves were successfully propagated in the thin stainless steel plate. The time-of- flight (TOF) of the S0 and A0 mode waves proportionally increased with the distance (D) between the laser source and the sensor, and almost no attenuation of the amplitude was observed. For the HT NDT experiment, AlN single crystal was adopted as the ultrasonic sensor material due to its high thermal resistance of the dielectric and piezoelectric constants at the elevated temperature up to 800 °C. The combination of non-contact, portable laser source as a Lamb wave generator and temperature-robust NDT sensor made of AIN has shown its great capability to detect the Lamb waves at elevated temperatures.

  2. High Temperature Annealing Studies on the Piezoelectric Properties of Thin Aluminum Nitride Films

    Energy Technology Data Exchange (ETDEWEB)

    R. Farrell; V. R. Pagan; A. Kabulski; Sridhar Kuchibhatl; J. Harman; K. R. Kasarla; L. E. Rodak; P. Famouri; J. Peter Hensel; D. Korakakis

    2008-05-01

    A Rapid Thermal Annealing (RTA) system was used to anneal sputtered and MOVPE grown Aluminum Nitride (AlN) thin films at temperatures up to 1000°C in ambient and controlled environments. According to Energy Dispersive X-Ray Analysis (EDAX), the films annealed in an ambient environment rapidly oxidize after five minutes at 1000°C. Below 1000°C the films oxidized linearly as a function of annealing temperature which is consistent with what has been reported in literature [1]. Laser Doppler Vibrometry (LDV) was used to measure the piezoelectric coefficient, d33, of these films. Films annealed in an ambient environment had a weak piezoelectric response indicating that oxidation on the surface of the film reduces the value of d33. A high temperature furnace has been built that is capable of taking in-situ measurements of the piezoelectric response of AlN films. In-situ d33 measurements are recorded up to 300°C for both sputtered and MOVPE-grown AlN thin films. The measured piezoelectric response appears to increase with temperature up to 300°C possibly due to stress in the film.

  3. High Temperature Annealing Studies on the Piezoelectric Properties of Thin Aluminum Nitride Films

    Energy Technology Data Exchange (ETDEWEB)

    Farrell, R.; Pagan, V.R.; Kabulski, A.; Kuchibhatla, S.; Harman, J.; Kasarla, K.R.; Rodak, L.E.; Hensel, J.P.; Famouri, P.; Korakakis, D.

    2008-01-01

    A Rapid Thermal Annealing (RTA) system was used to anneal sputtered and MOVPE-grown Aluminum Nitride (AlN) thin films at temperatures up to 1000°C in ambient and controlled environments. According to Energy Dispersive X-Ray Analysis (EDAX), the films annealed in an ambient environment rapidly oxidize after five minutes at 1000°C. Below 1000°C the films oxidized linearly as a function of annealing temperature which is consistent with what has been reported in literature [1]. Laser Doppler Vibrometry (LDV) was used to measure the piezoelectric coefficient, d33, of these films. Films annealed in an ambient environment had a weak piezoelectric response indicating that oxidation on the surface of the film reduces the value of d33. A high temperature furnace has been built that is capable of taking in-situ measurements of the piezoelectric response of AlN films. In-situ d33 measurements are recorded up to 300°C for both sputtered and MOVPE-grown AlN thin films. The measured piezoelectric response appears to increase with temperature up to 300°C possibly due to stress in the film.

  4. Effect of Stress and Temperature on the Optical Properties of Silicon Nitride Membranes at 1,550 nm

    Directory of Open Access Journals (Sweden)

    Mark Fletcher

    2018-01-01

    Full Text Available Future gravitational-wave detectors operated at cryogenic temperatures are expected to be limited by thermal noise of the highly reflective mirror coatings. Silicon nitride is an interesting material for such coatings as it shows very low mechanical loss, a property related to low thermal noise, which is known to further decrease under stress. Low optical absorption is also required to maintain the low mirror temperature. Here, we investigate the effect of stress on the optical properties at 1,550 nm of silicon nitride membranes attached to a silicon frame. Our approach includes the measurement of the thermal expansion coefficient and the thermal conductivity of the membranes. The membrane and frame temperatures are varied, and translated into a change in stress using finite element modeling. The resulting product of the optical absorption and thermo-optic coefficient (dn/dT is measured using photothermal common-path interferometry.

  5. Temperature-dependent frictional properties of ultra-thin boron nitride nanosheets

    Science.gov (United States)

    Qu, Wenyang; Chen, Xiaoming; Ke, Changhong

    2017-04-01

    We investigate the temperature-dependent frictional properties of mono- and few-layer hexagonal boron nitride nanosheets (BNNSs) by using atomic force microscopy (AFM). The measurements reveal that a modest increase in sample temperature results in a substantial decrease of the frictional force between a silicon AFM tip and a BNNS, and the frictional force change is modulated by the scan velocity of the AFM tip and the number of layers in the BNNS. The activation energy of the contact rupture for the examined BNNSs is found to be around 0.35 eV, which is substantially higher than the reported values for graphene. The observed high activation energy for the BNNS is ascribed to its electronically and topographically corrugated surface, which originates from the polarized nature of B-N bonds and the size difference of B and N atoms. The findings are useful to better understand the physical properties of hexagonal BNNS materials and in the pursuit of their applications, such as substrate materials in nano electronic devices.

  6. Mechanical, Corrosion and Biological Properties of Room-Temperature Sputtered Aluminum Nitride Films with Dissimilar Nanostructure.

    Science.gov (United States)

    Besleaga, Cristina; Dumitru, Viorel; Trinca, Liliana Marinela; Popa, Adrian-Claudiu; Negrila, Constantin-Catalin; Kołodziejczyk, Łukasz; Luculescu, Catalin-Romeo; Ionescu, Gabriela-Cristina; Ripeanu, Razvan-George; Vladescu, Alina; Stan, George E

    2017-11-17

    Aluminum Nitride (AlN) has been long time being regarded as highly interesting material for developing sensing applications (including biosensors and implantable sensors). AlN, due to its appealing electronic properties, is envisaged lately to serve as a multi-functional biosensing platform. Although generally exploited for its intrinsic piezoelectricity, its surface morphology and mechanical performance (elastic modulus, hardness, wear, scratch and tensile resistance to delamination, adherence to the substrate), corrosion resistance and cytocompatibility are also essential features for high performance sustainable biosensor devices. However, information about AlN suitability for such applications is rather scarce or at best scattered and incomplete. Here, we aim to deliver a comprehensive evaluation of the morpho-structural, compositional, mechanical, electrochemical and biological properties of reactive radio-frequency magnetron sputtered AlN nanostructured thin films with various degrees of c -axis texturing, deposited at a low temperature (~50 °C) on Si (100) substrates. The inter-conditionality elicited between the base pressure level attained in the reactor chamber and crystalline quality of AlN films is highlighted. The potential suitability of nanostructured AlN (in form of thin films) for the realization of various type of sensors (with emphasis on bio-sensors) is thoroughly probed, thus unveiling its advantages and limitations, as well as suggesting paths to safely exploit the remarkable prospects of this type of materials.

  7. Mechanical, Corrosion and Biological Properties of Room-Temperature Sputtered Aluminum Nitride Films with Dissimilar Nanostructure

    Directory of Open Access Journals (Sweden)

    Cristina Besleaga

    2017-11-01

    Full Text Available Aluminum Nitride (AlN has been long time being regarded as highly interesting material for developing sensing applications (including biosensors and implantable sensors. AlN, due to its appealing electronic properties, is envisaged lately to serve as a multi-functional biosensing platform. Although generally exploited for its intrinsic piezoelectricity, its surface morphology and mechanical performance (elastic modulus, hardness, wear, scratch and tensile resistance to delamination, adherence to the substrate, corrosion resistance and cytocompatibility are also essential features for high performance sustainable biosensor devices. However, information about AlN suitability for such applications is rather scarce or at best scattered and incomplete. Here, we aim to deliver a comprehensive evaluation of the morpho-structural, compositional, mechanical, electrochemical and biological properties of reactive radio-frequency magnetron sputtered AlN nanostructured thin films with various degrees of c-axis texturing, deposited at a low temperature (~50 °C on Si (100 substrates. The inter-conditionality elicited between the base pressure level attained in the reactor chamber and crystalline quality of AlN films is highlighted. The potential suitability of nanostructured AlN (in form of thin films for the realization of various type of sensors (with emphasis on bio-sensors is thoroughly probed, thus unveiling its advantages and limitations, as well as suggesting paths to safely exploit the remarkable prospects of this type of materials.

  8. Preparation and properties of hexagonal boron nitride fibers used as high temperature membrane filter

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Xinmei, E-mail: houxinmei@ustb.edu.cn; Yu, Ziyou; Li, Yang; Chou, Kuo-Chih

    2014-01-01

    Graphical abstract: - Highlights: • h-BN fibers were successfully fabricated using H{sub 3}BO{sub 3} and C{sub 3}H{sub 6}N{sub 6} as raw materials. • The obtained BN fibers were polycrystalline and uniform in morphology. • It exhibited good oxidation resistance and low thermal expansion coefficient. - Abstract: Hexagonal boron nitride fibers were synthesized via polymeric precursor method using boric acid (H{sub 3}BO{sub 3}) and melamine (C{sub 3}H{sub 6}N{sub 6}) as raw materials. The precursor fibers were synthesized by water bath and BN fibers were prepared from the precursor at 1873 K for 3 h in flowing nitrogen atmosphere. The crystalline phase and microstructures of BN fibers were examined by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy. The results showed that h-BN fibers with uniform morphology were successfully fabricated. The well-synthesized BN fibers were polycrystalline with 0.4–1.5 μm in diameter and 200–500 μm in length. The as-prepared samples exhibited good oxidation resistance and low thermal expansion coefficient at high temperature.

  9. Room temperature single photon source using fiber-integrated hexagonal boron nitride

    Science.gov (United States)

    Vogl, Tobias; Lu, Yuerui; Lam, Ping Koy

    2017-07-01

    Single photons are a key resource for quantum optics and optical quantum information processing. The integration of scalable room temperature quantum emitters into photonic circuits remains to be a technical challenge. Here we utilize a defect center in hexagonal boron nitride (hBN) attached by Van der Waals force onto a multimode fiber as a single photon source. We perform an optical characterization of the source in terms of spectrum, state lifetime, power saturation and photostability. A special feature of our source is that it allows for easy switching between fiber-coupled and free space single photon generation modes. In order to prove the quantum nature of the emission we measure the second-order correlation function {{g}(2)}≤ft(τ \\right) . For both fiber-coupled and free space emission, the {{g}(2)}≤ft(τ \\right) dips below 0.5 indicating operation in the single photon regime. The results so far demonstrate the feasibility of 2D material single photon sources for scalable photonic quantum information processing.

  10. Spintronics: Towards room temperature ferromagnetic devices via manganese and rare earth doped gallium nitride

    Science.gov (United States)

    Luen, Melvyn Oliver

    Spintronics is a multidisciplinary field aimed at the active manipulation of spin degrees of freedom in solid-state systems. The goal being the understanding of the interaction between the particle spin and its solid-state environment, and the making of useful devices based on the acquired knowledge. If Moore's law is to continue, then we need to find alternatives to conventional microelectronics. Where conventional electronic devices rely on manipulating charge to produce desired functions, spintronic devices would manipulate both the charge flow and electron spin within that flow. This would add an extra degree of freedom to microelectronics and usher in the era of truly nanoelectronic devices. Research aimed at a whole new generation of electronic devices is underway by introducing electron spin as a new or additional physical variable, and semiconductor devices that exploit this new freedom will operate faster and more efficiently than conventional microelectronic devices and offer new functionality that promises to revolutionize the electronics industry. Long recognized as the material of choice for next-generation solid-state lighting, gallium nitride (GaN) also has proven uses in the field of high power, high frequency field-effect transistors (FETs). But its promise as a material system for spintronic applications may be its ultimate legacy. In this dissertation, the growth of gallium-manganese-nitride (GaMnN) compound semiconductor alloy was investigated through the use of an in-house built metal-organic chemical vapor deposition (MOCVD) reactor. Building on previous investigations of ferromagnetic mechanisms in GaMnN, where ferromagnetism was shown to be carrier mediated, a above room temperature ferromagnetic GaMnN i-p-n diode structure was conceived. This device proved to be the first of its kind in the world, where ferromagnetic properties are controlled via proximity of the mediating holes, upon voltage bias of adjacent structure layers

  11. Solid Lubricated Silicon Nitride Bearings at High Speed and Temperature - Phase 1

    Science.gov (United States)

    1982-02-01

    Hybrid Bearing Design Evaluated by 12 SHABERTH Computer Program Table 2 SHABERTH Computer Program Output 13 for 7205 Bearing Containing Silicon Nitride...conditions using an SKF SHABERTH computer program modified for solid lubrication and the elastic properties of the silicon nitride rolling elements. As can...8217.NG CAG i ’L - SKF TECHNOLOGY SERVICES SKF INDUSTRIES, INC 4 14ImIpL AT82D002 Table 1 - Hybrid Bearing Design Evaluated by SHABERTH Computer

  12. Biocompatibility studies of low temperature nitrided and collagen-I coated AISI 316L austenitic stainless steel.

    Science.gov (United States)

    Martinesi, M; Stio, M; Treves, C; Borgioli, F

    2013-06-01

    The biocompatibility of austenitic stainless steels can be improved by means of surface engineering techniques. In the present research it was investigated if low temperature nitrided AISI 316L austenitic stainless steel may be a suitable substrate for bioactive protein coating consisting of collagen-I. The biocompatibility of surface modified alloy was studied using as experimental model endothelial cells (human umbilical vein endothelial cells) in culture. Low temperature nitriding produces modified surface layers consisting mainly of S phase, the supersaturated interstitial solid solution of nitrogen in the austenite lattice, which allows to enhance surface microhardness and corrosion resistance in PBS solution. The nitriding treatment seems to promote the coating with collagen-I, without chemical coupling agents, in respect of the untreated alloy. For biocompatibility studies, proliferation, lactate dehydrogenase levels and secretion of two metalloproteinases (MMP-2 and MMP-9) were determined. Experimental results suggest that the collagen protection may be favourable for endothelial cell proliferation and for the control of MMP-2 release.

  13. Modelling the evolution of composition-and stress-depth profiles in austenitic stainless steels during low-temperature nitriding

    DEFF Research Database (Denmark)

    Jespersen, Freja Nygaard; Hattel, Jesper Henri; Somers, Marcel A. J.

    2016-01-01

    . In the present paper solid mechanics was combined with thermodynamics and diffusion kinetics to simulate the evolution of composition-depth and stress-depth profiles resulting from nitriding. The model takes into account a composition-dependent diffusion coefficient of nitrogen in expanded austenite, short range...... that accompanies the dissolution of high nitrogen contents in expanded austenite. An intriguing phenomenon during low-temperature nitriding is that the residual stresses evoked by dissolution of nitrogen in the solid state, affect the thermodynamics and the diffusion kinetics of nitrogen dissolution...... ordering (trapping) of nitrogen atoms by chromium atoms, and the effect of composition-induced stress on surface concentration and diffusive flux. The effect of plasticity and concentration-dependence of the yield stress was also included....

  14. Design, microstructure, and high-temperature behavior of silicon nitride sintered with rate-earth oxides

    Energy Technology Data Exchange (ETDEWEB)

    Ciniculk, M.K. (California Univ., Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering)

    1991-08-01

    The processing-microstructure-property relations of silicon nitride ceramics sintered with rare-earth oxide additives have been investigated with the aim of improving their high-temperature behavior. The additions of the oxides of Y, Sm, Gd, Dy, Er, or Yb were compositionally controlled to tailor the intergranular phase. The resulting microstructure consisted of {beta}-Si{sub 3}N{sub 4} grains and a crystalline secondary phase of RE{sub 2}Si{sub 2}O{sub 7}, with a thin residual amorphous phase present at grain boundaries. The lanthanide oxides were found to be as effective as Y{sub 2}O{sub 3} in densifying Si{sub 3}N{sub 4}, resulting in identical microstructures. The crystallization behavior of all six disilicates was similar, characterized by a limited nucleation and rapid growth mechanism resulting in large single crystals. Complete crystallization of the intergranular phase was obtained with the exception of a residual amorphous, observed at interfaces and believed to be rich in impurities, the cause of incomplete devitrification. The low resistance to oxidation of these materials was attributed to the minimization of amorphous phases via devitrification to disilicates, compatible with SiO{sub 2}, the oxidation product of Si{sub 3}N{sub 4}. The strength retention of these materials at 1300{degrees}C was found to be between 80% and 91% of room-temperature strength, due to crystallization of the secondary phase and a residual but refractory amorphous grain-boundary phase. The creep behavior was found to be strongly dependent on residual amorphous phase viscosity as well as on the oxidation behavior, as evidenced by the nonsteady-state creep rates of all materials. 122 refs., 51 figs., 12 tabs.

  15. Efficient visible-light photocatalytic oxidation of gaseous NO with graphitic carbon nitride (g-C3N4) activated by the alkaline hydrothermal treatment and mechanism analysis.

    Science.gov (United States)

    Nie, Haoyu; Ou, Man; Zhong, Qin; Zhang, Shule; Yu, Lemeng

    2015-12-30

    In this paper, an enhanced visible-light photocatalytic oxidation (PCO) of NO (∼ 400 ppm) in the presence of the graphitic carbon nitride (g-C3N4) treated by the alkaline hydrothermal treatment is evaluated. Various g-C3N4 samples were treated in different concentrations of NaOH solutions and the sample treated in 0.12 mol L(-1) of NaOH solution possesses the largest BET specific surface area as well as the optimal ability of the PCO of NO. UV-vis diffuse reflection spectra (DRS) and photoluminescence (PL) spectra were also conducted, and the highly improved photocatalytic performance is ascribed to the large specific surface area and high pore volume, which provides more adsorption and active sites, the wide visible-light adsorption edge and the narrow band gap, which is favorable for visible-light activation, as well as the decreased recombination rate of photo-generated electrons and holes, which could contribute to the production of active species. Fluorescence spectra and a trapping experiment were conducted to further the mechanism analysis of the PCO of NO, illustrating that superoxide radicals (O2(-)) play the dominant role among active species in the PCO of NO. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Thermodynamic Analysis about Nucleation and Growth of Cubic Boron Nitride Crystals in the hBN-Li3N System under High Pressure and High Temperature

    Directory of Open Access Journals (Sweden)

    Xiao-Fei Guo

    2015-02-01

    Full Text Available The nucleation of cubic boron nitride (cBN single crystals synthesized with lithium nitride (Li3N as a catalyst under high pressure and high temperature (HPHT was analyzed. Many nanometer-sized cubic boron nitride nuclei formed in the near surface layer, as detected by high resolution transmission electron microscopy. Based on the experiment results, the transformation kinetics is described by a nucleation and growth process in the thermodynamic stability region of cBN. A theoretical description is developed based on the heterogeneous nucleation and layer growth mechanism, and the relevant parameters are estimated and discussed. The critical crystal radius, r*, increases with the temperature under constant pressure; the change with temperature more pronounced at lower pressure (such as 4.5 GPa. The crystal growth velocity increased with the temperature, and it is parabolic with temperature under certain pressure. These results are consistent with experimental data.

  17. Growth of niobium nitrides by nitrogen-niobium reaction at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Musenich, R. (Istituto Nazionale di Fisica Nucleare, via Dodecaneso 33, I-16141 Genoa (Italy)); Fabbricatore, P. (Istituto Nazionale di Fisica Nucleare, via Dodecaneso 33, I-16141 Genoa (Italy)); Gemme, G. (Istituto Nazionale di Fisica Nucleare, via Dodecaneso 33, I-16141 Genoa (Italy)); Parodi, R. (Istituto Nazionale di Fisica Nucleare, via Dodecaneso 33, I-16141 Genoa (Italy)); Viviani, M. (Istituto Nazionale di Fisica Nucleare, via Dodecaneso 33, I-16141 Genoa (Italy)); Zhang, B. (Istituto Nazionale di Fisica Nucleare, via Dodecaneso 33, I-16141 Genoa (Italy)); Buscaglia, V. (Istituto di Chimica Fisica Applicata dei Materiali, Consiglio Nazionale delle Ricerche, via De Marini 6, I-16149 Genoa (Italy)); Bottino, C. (Istituto di Chimica Fisica Applicata dei Materiali, Consiglio Nazionale delle Ricerche, via De Marini 6, I-16149 Genoa (Italy))

    1994-07-01

    The reaction between nitrogen and bulk niobium under high purity conditions was studied in the range 1100-1900 C at 150 kPa. Two different nitride layers are formed: an inner [beta] phase (Nb[sub 2]N) and an outer [delta] phase (NbN). The latter undergoes a transformation to [gamma]-NbN and [epsilon]-NbN during cooling down. Nitrogen dissolves in the niobium core forming [alpha] solid solution. Both the weight gain and the thickness of the nitride layers follow the parabolic rate law, indicating that the reaction is mainly dominated by diffusional transport through the nitrides. Two parabolic kinetic stages are observed, the first before [alpha] phase saturation and the second after saturation. Data analysis based on a multiphase, moving boundary diffusion model allows the calculation of the effective nitrogen diffusion coefficients, yielding the expressions D[sub [beta

  18. submitter Superconducting instrumentation for high Reynolds turbulence experiments with low temperature gaseous helium

    CERN Document Server

    Pietropinto, S; Baudet, C; Castaing, B; Chabaud, B; Gagne, Y; Hébral, B; Ladam, Y; Lebrun, P; Pirotte, O; Roche, P

    2003-01-01

    Turbulence is of common experience and of high interest for industrial applications, despite its physical grounds is still not understood. Cryogenic gaseous helium gives access to extremely high Reynolds numbers (Re). We describe an instrumentation hosted in CERN, which provides a 6 kW @ 4.5 K helium refrigerator directly connected to the experiment. The flow is a round jet; the flow rates range from 20 g/s up to 260 g/s at 4.8 K and about 1.2 bar, giving access to the highest controlled Re flow ever developed. The experimental challenge lies in the range of scales which have to be investigated: from the smallest viscous scale η, typically 1 μm at Re=107 to the largest L∼10 cm. The corresponding frequencies: f=v/η can be as large as 1 MHz. The development of an original micrometric superconducting anemometer using a hot spot and its characteristics will be discussed together with its operation and the perspectives associated with superconducting anemometry.

  19. Role of interface roughness scattering, temperature, and structural parameters on the performance characteristics of III-nitride quantum cascade detectors

    Science.gov (United States)

    Saha, S.; Kumar, J.

    2017-02-01

    A III-nitride quantum cascade detector (QCD) for the fiber optic communication wavelength (˜1.5 μm) has been designed, and the effect of intersubband scattering processes such as longitudinal-optical phonon scattering, ionized impurity scattering, and more importantly interface roughness scattering on responsivity performance has been analyzed. Carrier transport in the detector is modeled using a simplified rate equation approach. It is observed that inclusion of interface roughness scattering in the carrier transport model significantly enhances the responsivity performance of the detector. The effects of roughness conditions for instance mean roughness height and correlation length on responsivity have been examined. The responsivity of the designed detector drops by 2.16 mA/W at 400 K compared to its low temperature value at 50 K and the detection wavelength change with temperature is insignificant, which are very helpful for the stable detection of the radiation for a wide range of operating temperatures and show the thermal stability of III-nitride QCDs. The effects of active well widths, extractor barrier widths, and extractor well widths have been further investigated. A higher responsivity performance is observed for narrower barrier widths. It is noticed that change in the active well width significantly modifies the responsivity of the detector and the wavelength gets red shifted for larger active well widths.

  20. ABOUT TEMPERATURE FIELDS AND CONDITIONS OF GASEOUS CONDENSATION OF NEBULAES IN THE PLANETARY VORTEX

    Directory of Open Access Journals (Sweden)

    L. V. Klyuchinskaya

    2014-01-01

    Full Text Available New exact solution of the spherically-axissymmetric Eiler's equations, called as plan­etary vortex, is applied to the problem of formation in planetary nebula germs of planets due to the condensation of gases in the areas of vortex instability which calls the rings of planetary vortex. It is shown that the vortex perturbations causes changes in preassure and temperature at which the gases of nebula condense themselves, forming the germs of the planets.

  1. Effect of ripples on the finite temperature elastic properties of hexagonal boron nitride using strain-fluctuation method

    Science.gov (United States)

    Thomas, Siby; Ajith, K. M.; Valsakumar, M. C.

    2017-11-01

    This work intents to put forth the results of a classical molecular dynamics study to investigate the temperature dependent elastic constants of monolayer hexagonal boron nitride (h-BN) between 100 and 1000 K for the first time using strain fluctuation method. The temperature dependence of out-of-plane fluctuations (ripples) is quantified and is explained using continuum theory of membranes. At low temperatures, negative in-plane thermal expansion is observed and at high temperatures, a transition to positive thermal expansion has been observed due to the presence of thermally excited ripples. The decrease of Young's modulus, bulk modulus, shear modulus and Poisson's ratio with increase in temperature has been analyzed. The thermal rippling in h-BN leads to strong anharmonic behaviour that causes large deviation from the isotropic elasticity. A detailed study shows that the strong thermal rippling in large systems is also responsible for the softening of elastic constants in h-BN. From the determined values of elastic constants and elastic moduli, it has been elucidated that 2D h-BN sheets meet the Born's mechanical stability criterion in the investigated temperature range. The variation of longitudinal and shear velocities with temperature is also calculated from the computed values of elastic constants and elastic moduli.

  2. Flame Shapes of Fuel Droplet Could in High Temperature Gaseous Environment under Micro-gravity

    Science.gov (United States)

    Enomoto, Hiroshi; Nagata, Hitoshi; Segawa, Daisuke; Kadota, Toshikazu

    In order to investigate the spray combustion mechanism, a new methodology (Fine Wire Sustaining method) was established. Fine wires of 14µm in diameter were used to sustain the droplets. Any arrangement of the droplets could be performed with this method. In this study, 33 fuel droplets arranged in symmetrically were subjected to the quiescent high temperature air in an electric furnace. The temperature of the environment air was about 1000K. Fuel was n-eicosane and the mean droplet diameter was 0.58mm. The standard deviation of the droplet diameter was 0.02mm. A high-speed video camera of 250ftp was provided to observe the auto-ignition and flames of fuel droplet clouds. The experiments were done at atmospheric pressure using the JAMIC drop shaft that provides 10 seconds of effective period of time for the micro-gravity. As the results, the time histories of the diameter of the particle flames had maximum and that of the diameter of the group flame had the minimum.

  3. Design, fabrication and characterization of a low-temperature co-fired ceramic gaseous bi-propellant microthruster

    Science.gov (United States)

    Wu, Ming-Hsun; Lin, Po-Shen

    2010-08-01

    A gaseous bi-propellant chemical microthruster was developed using low-temperature co-fired ceramic (LTCC) tapes. A sapphire window and silver spark ignition electrodes were successfully co-fired in the LTCC microthruster. Thrust outputs between 0.2 mN and 1.97 mN could be achieved from the 9.9 mm3 thrust chamber by hot-gas operation using ethylene-argon/oxygen mixtures. A non-premixed combustion scheme was utilized by applying an inlet configuration with offset opposing fuel and oxidizer ports. The inlet port design was able to facilitate the generation of swirling flow. Fuel/oxidant mixing could be enhanced in the thrust chamber with the swirling streams according to the cold-flow multi-species 3D computational fluid dynamics (CFD) analysis. Flame chemiluminescence measurements through the transparent observation window were performed to characterize the flame structure in the miniature combustion chamber. The flame zone was found to coincide with the stoichiometric plane predicted by the CFD simulations. Thrust measurements were accomplished by measuring the impingement force of the exhaust jet on a precision balance. The disturbance introduced by the tubing and wiring on the continuous flow microthruster could therefore be eliminated. Thrust was linearly proportional to the total mass flow rate of the inlet. The chemical energy input of the microthruster was approximately 37 W for the maximal measured thrust of 1.97 mN.

  4. Bright Room-Temperature Single Photon Emission from Defects in Gallium Nitride

    CERN Document Server

    Berhane, Amanuel M; Bodrog, Zoltán; Fiedler, Saskia; Schröder, Tim; Triviño, Noelia Vico; Palacios, Tomás; Gali, Adam; Toth, Milos; Englund, Dirk; Aharonovich, Igor

    2016-01-01

    Single photon emitters play a central role in many photonic quantum technologies. A promising class of single photon emitters consists of atomic color centers in wide-bandgap crystals, such as diamond silicon carbide and hexagonal boron nitride. However, it is currently not possible to grow these materials as sub-micron thick films on low-refractive index substrates, which is necessary for mature photonic integrated circuit technologies. Hence, there is great interest in identifying quantum emitters in technologically mature semiconductors that are compatible with suitable heteroepitaxies. Here, we demonstrate robust single photon emitters based on defects in gallium nitride (GaN), the most established and well understood semiconductor that can emit light over the entire visible spectrum. We show that the emitters have excellent photophysical properties including a brightness in excess of 500x10^3 counts/s. We further show that the emitters can be found in a variety of GaN wafers, thus offering reliable and s...

  5. Erosion–corrosion and corrosion properties of DLC coated low temperature Erosion–corrosion and corrosion properties of DLC coated low temperature

    DEFF Research Database (Denmark)

    Jellesen, Morten Stendahl; Christiansen, Thomas; Hilbert, Lisbeth Rischel

    2009-01-01

    of AISI 316 as substrate for DLC coatings are investigated. Corrosion and erosion–corrosion measurements were carried out on low temperature nitrided stainless steel AISI 316 and on low temperature nitrided stainless steel AISI 316 with a top layer of DLC. The combination of DLC and low temperature...... nitriding dramatically reduces the amount of erosion–corrosion of stainless steel under impingement of particles in a corrosive medium.......Lowtemperature nitriding of stainless steel leads to the formation of a surface zone of so-called expanded austenite, i.e. by dissolution of large amounts of nitrogen in solid solution. In the present work the possibility of using nitrogen expanded austenite “layers” obtained by gaseous nitriding...

  6. 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...

  7. Quality improvement of ZnO thin layers overgrown on Si(100 substrates at room temperature by nitridation pretreatment

    Directory of Open Access Journals (Sweden)

    Peng Wang

    2012-06-01

    Full Text Available To improve the quality of ZnO thin film overgrown on Si(100 substrate at RT (room temperature, the Si(100 surface was pretreated with different methods. The influence of interface on the overgrown ZnO layers was investigated by atomic force microscopy, photoluminescence and X-ray diffraction. We found that the nitridation pretreatment could significantly improve the quality of RT ZnO thin film through two-fold effects: one was to buffer the big lattice mismatch and ease the stress resulted from heterojunction growth; the other was to balance the interface charge, block the symmetric inheritance from the cubic Si (100 substrate and thus restrain the formation of zincblende phase.

  8. The thermal power of aluminum nitride at temperatures between 1350 and 1650 deg C in argon and nitrogen atmospheres. Ph.D. Thesis - Rhine-Westphalia High School at Aachen

    Science.gov (United States)

    Fischer, W. A.; Schuh, B.

    1978-01-01

    The test apparatus for measuring the thermal voltage of aluminum nitride for temperature differences of up to + or - 60 C between 1350 and 1650 C is described. The thermal power and its homogeneous proportion are determined and the heat transfer of the migration ions resulting from the homogeneous thermal power is calculated. The conduction mechanism in aluminum nitride is discussed.

  9. Optimization of the ASPN Process to Bright Nitriding of Woodworking Tools Using the Taguchi Approach

    Science.gov (United States)

    Walkowicz, J.; Staśkiewicz, J.; Szafirowicz, K.; Jakrzewski, D.; Grzesiak, G.; Stępniak, M.

    2013-02-01

    The subject of the research is optimization of the parameters of the Active Screen Plasma Nitriding (ASPN) process of high speed steel planing knives used in woodworking. The Taguchi approach was applied for development of the plan of experiments and elaboration of obtained experimental results. The optimized ASPN parameters were: process duration, composition and pressure of the gaseous atmosphere, the substrate BIAS voltage and the substrate temperature. The results of the optimization procedure were verified by the tools' behavior in the sharpening operation performed in normal industrial conditions. The ASPN technology proved to be extremely suitable for nitriding the woodworking planing tools, which because of their specific geometry, in particular extremely sharp wedge angles, could not be successfully nitrided using conventional direct current plasma nitriding method. The carried out research proved that the values of fracture toughness coefficient K Ic are in correlation with maximum spalling depths of the cutting edge measured after sharpening, and therefore may be used as a measure of the nitrided planing knives quality. Based on this criterion the optimum parameters of the ASPN process for nitriding high speed planing knives were determined.

  10. High-temperature soft magnetic properties of antiperovskite nitrides ZnNFe3 and AlNFe3

    Science.gov (United States)

    Fu, Yankun; Lin, Shuai; Wang, Bosen

    2015-03-01

    We report the synthesis, crystal structure, magnetic and electrical/thermal transport properties of antiperovskite nitrides ZnNFe3 and AlNFe3. Both compounds display ferromagnetic (FM) ground state and transform into the paramagnetic phase at 762 K and 770 K, respectively. At FM phase, for ZnNFe3 and AlNFe3, the saturated magnetizations at 5 K are 163 and 188 emu/g, which is the largest value among all the antiperovskite compounds; the minimal coercive forces (HC) are as low as 18.6 and 16.3 Oe; the low HC is almost constant covering a broad temperature range of 5-650 K. These characteristics indicate that both ZnNFe3 and AlNFe3 may be promising candidates of high-temperature soft magnetic material. In addition, electrons are dominant carriers owing to the negative Seebeck coefficient, the Fermi-liquid behavior is well presented via the investigation of low-temperature electrical transport, and the lattice thermal conductivity estimated by Wiedemann-Franz law is the main part of total thermal conductivity at high temperatures for both ZnNFe3 and AlNFe3.

  11. Highly Coordinated Iron and Cobalt Nitrides Synthesized at High Pressures and High Temperatures.

    Science.gov (United States)

    Niwa, Ken; Terabe, Toshiki; Kato, Daiki; Takayama, Shin; Kato, Masahiko; Soda, Kazuo; Hasegawa, Masashi

    2017-06-05

    Highly coordinated iron and cobalt nitrides were successfully synthesized via direct chemical reaction between a transition metal and molecular nitrogen at pressures above approximately 30 GPa using a laser-heated diamond anvil cell. The synthesized novel transition metal nitrides were found to crystallize into the NiAs-type or marcasite-type structure. NiAs-type FeN could be quenched at ambient pressure, although it was gradually converted to the ZnS-type structure after the pressure was released. On the other hand, CoN was recovered with ZnS-type structure through a phase transition from NiAs-type structure at approximately a few gigapascals during decompression. Marcasite-type CoN2 was also synthesized at pressures above approximately 30 GPa. High-pressure in situ X-ray diffraction measurement showed that the zero-pressure bulk modulus of marcasite-type CoN2 is 216(18) GPa, which is comparable to that of RhN2. This indicates that the interatomic distance of the N-N dimer in marcasite-type CoN2 is short because of weak orbital interaction between cobalt and nitrogen atoms, as in RhN2. Surprisingly, a first-principles electronic band calculation suggests that the NiAs-type FeN and CoN and marcasite-type CoN2 exhibit metallic characteristics with magnetic moments of 3.4, 0.6, and 1.2 μB, respectively. The ferromagnetic NiAs-type structure originates from the anisotropic arrangement of transition atoms stacked along the c axis.

  12. Gaseous Matter

    CERN Document Server

    Angelo, Joseph A

    2011-01-01

    aseous Matter focuses on the many important discoveries that led to the scientific interpretation of matter in the gaseous state. This new, full-color resource describes the basic characteristics and properties of several important gases, including air, hydrogen, helium, oxygen, and nitrogen. The nature and scope of the science of fluids is discussed in great detail, highlighting the most important scientific principles upon which the field is based. Chapters include:. Gaseous Matter An Initial Perspective. Physical Characteristics of Gases. The Rise of the Science of Gases. Kinetic Theory of

  13. Trends in long-term gaseous mercury observations in the Arctic and effects of temperature and other atmospheric conditions

    Directory of Open Access Journals (Sweden)

    A. S. Cole

    2010-05-01

    Full Text Available Gaseous elemental mercury (GEM measurements at Alert, Canada, from 1995 to 2007 were analyzed for statistical time trends and for correlations with meteorological and climate data. A significant decreasing trend in annual GEM concentration is reported at Alert, with an estimated slope of −0.0086 ng m−3 yr−1 (−0.6% yr−1 over this 13-year period. It is shown that there has been a shift in the month of minimum mean GEM concentration from May to April due to a change in the timing of springtime atmospheric mercury depletion events (AMDEs. These AMDEs are found to decrease with increasing local temperature within each month, both at Alert and at Amderma, Russia. These results support the temperature dependence suggested by previous experimental results and theoretical kinetic calculations on both bromine generation and mercury oxidation and highlight the potential for changes in Arctic mercury chemistry with climate. A correlation between total monthly AMDEs at Alert and the Polar/Eurasian Teleconnection Index was observed only in March, perhaps due to higher GEM inputs in early spring in those years with a weak polar vortex. A correlation of AMDEs at Alert with wind direction supports the origin of mercury depletion events over the Arctic Ocean, in agreement with a previous trajectory study of ozone depletion events. Interannual variability in total monthly depletion event frequency at Alert does not appear to correlate significantly with total or first-year northern hemispheric sea ice area or with other major teleconnection patterns. Nor do AMDEs at either Alert or Amderma correlate with local wind speed, as might be expected if depletion events are sustained by stable, low-turbulence atmospheric conditions. The data presented here – both the change in timing of depletion events and their relationship with temperature – can be used as additional constraints to improve the ability of models to predict

  14. 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.

  15. Surface passivation of p-type Ge substrate with high-quality GeNx layer formed by electron-cyclotron-resonance plasma nitridation at low temperature

    Science.gov (United States)

    Fukuda, Yukio; Okamoto, Hiroshi; Iwasaki, Takuro; Otani, Yohei; Ono, Toshiro

    2011-09-01

    We have investigated the effects of the formation temperature and postmetallization annealing (PMA) on the interface properties of GeNx/p-Ge fabricated by the plasma nitridation of Ge substrates using an electron-cyclotron-resonance-generated nitrogen plasma. The nitridation temperature is found to be a critical parameter in improving the finally obtained GeNx/Ge interface properties. The GeNx/Ge formed at room temperature and treated by PMA at 400 °C exhibits the best interface properties with an interface trap density of 1 × 1011 cm-2 eV-1. The GeNx/Ge interface is unpinned and the Fermi level at the Ge surface can move from the valence band edge to the conduction band edge.

  16. Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control.

    Science.gov (United States)

    Sarkar, Sujoy; Sampath, S

    2016-05-11

    A ternary, ionically conducting, deep eutectic solvent based on acetamide, urea and gallium nitrate is reported for the electrodeposition of gallium nitride/gallium indium nitride under ambient conditions; blue and white light emitting photoluminescent deposits are obtained under potential control.

  17. Empirical potential influence and effect of temperature on the mechanical properties of pristine and defective hexagonal boron nitride

    Science.gov (United States)

    Thomas, Siby; Ajith, K. M.; Valsakumar, M. C.

    2017-06-01

    The major objective of this work is to present results of a classical molecular dynamics study to investigate the effect of changing the cut-off distance in the empirical potential on the stress-strain relation and also the temperature dependent Young’s modulus of pristine and defective hexagonal boron nitride. As the temperature increases, the computed Young’s modulus shows a significant decrease along both the armchair and zigzag directions. The computed Young’s modulus shows a trend in keeping with the structural anisotropy of h-BN. The variation of Young’s modulus with system size is elucidated. The observed mechanical strength of h-BN is significantly affected by the vacancy and Stone-Wales type defects. The computed room temperature Young’s modulus of pristine h-BN is 755 GPa and 769 GPa respectively along the armchair and zigzag directions. The decrease of Young’s modulus with increase in temperature has been analyzed and the results show that the system with zigzag edge shows a higher value of Young’s modulus in comparison to that with armchair edge. As the temperature increases, the computed stiffness decreases and the system with zigzag edge possesses a higher value of stiffness as compared to the armchair counterpart and this behaviour is consistent with the variation of Young’s modulus. The defect analysis shows that presence of vacancy type defects leads to a higher Young’s modulus, in the studied range with different percentage of defect concentration, in comparison with Stone-Wales defect. The variations in the peak position of the computed radial distribution function reveals the changes in the structural features of systems with zigzag and armchair edges in the presence of applied stress.

  18. High-temperature soft magnetic properties of antiperovskite nitrides ZnNFe{sub 3} and AlNFe{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Yankun [College of Science, Shangdong University of Science and Technolog, Qingdao 266510 (China); Lin, Shuai, E-mail: linshuai17@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Wang, Bosen, E-mail: bswang@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2015-03-15

    We report the synthesis, crystal structure, magnetic and electrical/thermal transport properties of antiperovskite nitrides ZnNFe{sub 3} and AlNFe{sub 3}. Both compounds display ferromagnetic (FM) ground state and transform into the paramagnetic phase at 762 K and 770 K, respectively. At FM phase, for ZnNFe{sub 3} and AlNFe{sub 3}, the saturated magnetizations at 5 K are 163 and 188 emu/g, which is the largest value among all the antiperovskite compounds; the minimal coercive forces (H{sub C}) are as low as 18.6 and 16.3 Oe; the low H{sub C} is almost constant covering a broad temperature range of 5–650 K. These characteristics indicate that both ZnNFe{sub 3} and AlNFe{sub 3} may be promising candidates of high-temperature soft magnetic material. In addition, electrons are dominant carriers owing to the negative Seebeck coefficient, the Fermi-liquid behavior is well presented via the investigation of low-temperature electrical transport, and the lattice thermal conductivity estimated by Wiedemann–Franz law is the main part of total thermal conductivity at high temperatures for both ZnNFe{sub 3} and AlNFe{sub 3}. - Highlights: • A two-step synthetic method for high quality ZnNFe{sub 3} and AlNFe{sub 3} was demonstrated. • High Curie temperature and saturated magnetization but low coercive fields are observed. • The specific heat and electrical/thermal transport properties are investigated.

  19. 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.

  20. Effects of Nano-Aluminum Nitride on the Performance of an Ultrahigh-Temperature Inorganic Phosphate Adhesive Cured at Room Temperature

    Directory of Open Access Journals (Sweden)

    Chengkun Ma

    2017-11-01

    Full Text Available Based on the optimal proportion of resin and curing agent, an ultrahigh-temperature inorganic phosphate adhesive was prepared with aluminum dihydric phosphate, aluminium oxide ( α -Al2O3, etc. and cured at room temperature (RT. Then, nano-aluminum nitride (nano-AlN, nano-Cupric oxide (nano-CuO, and nano-titanium oxide (nano-TiO2 were added into the adhesive. Differential scanning calorimetry was conducted using the inorganic phosphate adhesive to analyze the phosphate reactions during heat treatment, and it was found that 15 wt % nano-AlN could clearly decrease the curing temperature. Scanning electron microscopy was used to observe the microphenomenon of the modified adhesive at ultrahigh-temperature. The differential thermal analysis of the inorganic phosphate adhesive showed that the weight loss was approximately 6.5 wt % when the mass ratio of resin to curing agent was 1:1.5. An X-ray diffraction analysis of the adhesive with 10% nano-AlN showed that the phase structure changed from AlPO4(11-0500 to the more stable AlPO4(10-0423 structure after heat treatment. The shear strength of the adhesive containing 10% nano-AlN reached 7.3 MPa at RT due to the addition of nano-AlN, which promoted the formation of phosphate and increased the Al3+.

  1. Effects of Nano-Aluminum Nitride on the Performance of an Ultrahigh-Temperature Inorganic Phosphate Adhesive Cured at Room Temperature.

    Science.gov (United States)

    Ma, Chengkun; Chen, Hailong; Wang, Chao; Zhang, Jifeng; Qi, Hui; Zhou, Limin

    2017-11-03

    Based on the optimal proportion of resin and curing agent, an ultrahigh-temperature inorganic phosphate adhesive was prepared with aluminum dihydric phosphate, aluminium oxide ( α -Al₂O₃), etc. and cured at room temperature (RT). Then, nano-aluminum nitride (nano-AlN), nano-Cupric oxide (nano-CuO), and nano-titanium oxide (nano-TiO₂) were added into the adhesive. Differential scanning calorimetry was conducted using the inorganic phosphate adhesive to analyze the phosphate reactions during heat treatment, and it was found that 15 wt % nano-AlN could clearly decrease the curing temperature. Scanning electron microscopy was used to observe the microphenomenon of the modified adhesive at ultrahigh-temperature. The differential thermal analysis of the inorganic phosphate adhesive showed that the weight loss was approximately 6.5 wt % when the mass ratio of resin to curing agent was 1:1.5. An X-ray diffraction analysis of the adhesive with 10% nano-AlN showed that the phase structure changed from AlPO₄(11-0500) to the more stable AlPO₄(10-0423) structure after heat treatment. The shear strength of the adhesive containing 10% nano-AlN reached 7.3 MPa at RT due to the addition of nano-AlN, which promoted the formation of phosphate and increased the Al3+.

  2. 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.

  3. Interactions of Gaseous HNO3 and Water with Individual and Mixed Alkyl Self-Assembled Monolayers at Room Temperature

    Science.gov (United States)

    Nishino, Noriko; Hollingsworth, Scott A.; Stern, Abraham C.; Roeselová, Martina; Tobias, Douglas J.; Finlayson-Pitts, Barbara J.

    2014-01-01

    The major removal processes for gaseous nitric acid (HNO3) in the atmosphere are dry and wet deposition onto various surfaces. The surface in the boundary layer is often covered with organic films, but the interaction of gaseous HNO3 with them is not well understood. To better understand the factors controlling the uptake of gaseous nitric acid and its dissociation in organic films, studies were carried out using single component and mixtures of C8 and C18 alkyl self-assembled monolayers (SAMs) attached to a germanium (Ge) attenuated total reflectance (ATR) crystal upon which a thin layer of SiOx had been deposited. For comparison, diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) studies were also carried out using a C18 SAM attached to the native oxide layer on the surface of silicon powder. These studies show that the alkyl chain length and order/disorder of the SAMs does not significantly affect the uptake or dissociation/recombination of molecular HNO3. Thus, independent of the nature of the SAM, molecular HNO3 is observed up to 70–90 % relative humidity. After dissociation, molecular HNO3 is regenerated on all SAM surfaces when water is removed. Results of molecular dynamics simulations are consistent with experiments and show that defects and pores on the surfaces control the uptake, dissociation and recombination of molecular HNO3. Organic films on surfaces in the boundary layer will certainly be more irregular and less ordered than SAMs studied here, therefore undissociated HNO3 may be present on surfaces in the boundary layer to a greater extent than previously thought. The combination of this observation with the results of recent studies showing enhanced photolysis of nitric acid on surfaces suggests that renoxification of deposited nitric acid may need to be taken into account in atmospheric models. PMID:24352159

  4. Measurement and thermal modeling of sapphire substrate temperature at III-Nitride MOVPE conditions

    Science.gov (United States)

    Creighton, J. Randall; Coltrin, Michael E.; Figiel, Jeffrey J.

    2017-04-01

    Growth rates and alloy composition of AlGaN grown by MOVPE is often very temperature dependent due to the presence of gas-phase parasitic chemical processes. These processes make wafer temperature measurement highly important, but in fact such measurements are very difficult because of substrate transparency in the near-IR ( 900 nm) where conventional pyrometers detect radiation. The transparency problem can be solved by using a mid-IR pyrometer operating at a wavelength ( 7500 nm) where sapphire is opaque. We employ a mid-IR pyrometer to measure the sapphire wafer temperature and simultaneously a near-IR pyrometer to measure wafer pocket temperature, while varying reactor pressure in both a N2 and H2 ambient. Near 1300 °C, as the reactor pressure is lowered from 300 Torr to 10 Torr the wafer temperature drops dramatically, and the ∆T between the pocket and wafer increases from 20 °C to 250 °C. Without the mid-IR pyrometer the large wafer temperature change with pressure would not have been noted. In order to explain this behavior we have developed a quasi-2D thermal model that includes a proper accounting of the pressure-dependent thermal contact resistance, and also accounts for sapphire optical transmission. The model and experimental results demonstrate that at most growth conditions the majority of the heat is transported from the wafer pocket to the wafer via gas conduction, in the free molecular flow limit. In this limit gas conductivity is independent of gap size but first order in pressure, and can quantitatively explain results from 20 to 300 Torr. Further analysis yields a measure of the thermal accommodation coefficients; α(H2) =0.23, α(N2) =0.50, which are in the range typically measured.

  5. Low threading dislocation density aluminum nitride on silicon carbide through the use of reduced temperature interlayers

    KAUST Repository

    Foronda, Humberto M.

    2017-11-23

    In this work, reduced threading dislocation density AlN on (0 0 0 1) 6H-SiC was realized through the use of reduced temperature AlN interlayers in the metalorganic chemical vapor deposition growth. We explored the dependence of the interlayer growth temperature on the AlN crystal quality, defect density, and surface morphology. The crystal quality was characterized using omega rocking curve scans and the threading dislocation density was determined by plan view transmission electron microscopy. The growth resulted in a threading dislocation density of 7 × 108 cm−2 indicating a significant reduction in the defect density of AlN in comparison to direct growth of AlN on SiC (∼1010 cm−2). Atomic force microscopy images demonstrated a clear step-terrace morphology that is consistent with step flow growth at high temperature. Reducing the interlayer growth temperature increased the TD inclination and thus enhanced TD-TD interactions. The TDD was decreased via fusion and annihilation reactions.

  6. Low threading dislocation density aluminum nitride on silicon carbide through the use of reduced temperature interlayers

    Science.gov (United States)

    Foronda, Humberto M.; Wu, Feng; Zollner, Christian; Alif, Muhammad Esmed; Saifaddin, Burhan; Almogbel, Abdullah; Iza, Michael; Nakamura, Shuji; DenBaars, Steven P.; Speck, James S.

    2018-02-01

    In this work, reduced threading dislocation density AlN on (0 0 0 1) 6H-SiC was realized through the use of reduced temperature AlN interlayers in the metalorganic chemical vapor deposition growth. We explored the dependence of the interlayer growth temperature on the AlN crystal quality, defect density, and surface morphology. The crystal quality was characterized using omega rocking curve scans and the threading dislocation density was determined by plan view transmission electron microscopy. The growth resulted in a threading dislocation density of 7 × 108 cm-2 indicating a significant reduction in the defect density of AlN in comparison to direct growth of AlN on SiC (∼1010 cm-2). Atomic force microscopy images demonstrated a clear step-terrace morphology that is consistent with step flow growth at high temperature. Reducing the interlayer growth temperature increased the TD inclination and thus enhanced TD-TD interactions. The TDD was decreased via fusion and annihilation reactions.

  7. 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.

  8. Trap Characterization in High Field, High Temperature Stressed Gallium Nitride High Electron Mobility Transistors

    Science.gov (United States)

    2013-03-01

    to a one dimensional Poisson - Schrodinger model with the same parameters of the fabricated device. The largest dispersion occurred before threshold...of self -heating to further improve reliability. The use of sapphire and diamond as a substrate to improve thermal characteristics was investigated...This is consistent with prior work [14]. Devices tested at higher temperatures had higher drain currents. This was to be expected due to additional

  9. Hafnium nitride films for thermoreflectance transducers at high temperatures: Potential based on heating from laser absorption

    Science.gov (United States)

    Rost, Christina M.; Braun, Jeffrey; Ferri, Kevin; Backman, Lavina; Giri, Ashutosh; Opila, Elizabeth J.; Maria, Jon-Paul; Hopkins, Patrick E.

    2017-10-01

    Time domain thermoreflectance (TDTR) and frequency domain thermoreflectance (FDTR) are common pump-probe techniques that are used to measure the thermal properties of materials. At elevated temperatures, transducers used in these techniques can become limited by melting or other phase transitions. In this work, time domain thermoreflectance is used to determine the viability of HfN thin film transducers grown on SiO2 through measurements of the SiO2 thermal conductivity up to approximately 1000 K. Further, the reliability of HfN as a transducer is determined by measuring the thermal conductivities of MgO, Al2O3, and diamond at room temperature. The thermoreflectance coefficient of HfN was found to be 1.4 × 10-4 K-1 at 800 nm, one of the highest thermoreflectance coefficients measured at this standard TDTR probe wavelength. Additionally, the high absorption of HfN at 400 nm is shown to enable reliable laser heating to elevate the sample temperature during a measurement, relative to other transducers.

  10. Free-standing gallium nitride Schottky diode characteristics and stability in a high-temperature environment

    Science.gov (United States)

    O'Mahony, Donagh; Zimmerman, Walter; Steffen, Sinje; Hilgarth, Just; Maaskant, Pleun; Ginige, Ravin; Lewis, Liam; Lambert, Benoit; Corbett, Brian

    2009-12-01

    Schottky diodes have been fabricated using low-resistivity n-type free-standing GaN substrates with a reduced defect density lowly doped n-type epi-layer and an Ni/Ti/Pt/Au Schottky contact metalization. A thermionic field emission current transport mechanism was identified with a Schottky barrier height of about 0.75 eV and a diode ideality of 1.1 measured at 25 °C, both of which increase with measurement temperature up to 200 °C. The diodes were subjected to long-term testing under forward current (1.3 A cm-2) or reverse voltage (-3.5 V) biased storage at 300 °C in N2 for 466 h and were also monitored under non-biased storage conditions for up to 1000 h at 350 °C and 400 °C in N2 or at 300 °C for 1500 h in air. Except for the non-biased storage test at 400 °C, the diodes show <10% drift in ideality and barrier height during the long-term storage tests. For the 400 °C test, there is a significant increase in both barrier height and ideality over a relatively short storage period (48 h). This to be the first reported study on the long-term stability of Schottky diodes on free-standing GaN and while no catastrophic (e.g. thermal runaway) degradation of any of the diodes was observed, it is proposed that optimized thermal annealing of the Ni-based Schottky contact metalization in the temperature range 350-400 °C is necessary for stable long-term operation at high temperature.

  11. Low-Temperature Plasma-Assisted Atomic Layer Deposition of Silicon Nitride Moisture Permeation Barrier Layers.

    Science.gov (United States)

    Andringa, Anne-Marije; Perrotta, Alberto; de Peuter, Koen; Knoops, Harm C M; Kessels, Wilhelmus M M; Creatore, Mariadriana

    2015-10-14

    Encapsulation of organic (opto-)electronic devices, such as organic light-emitting diodes (OLEDs), photovoltaic cells, and field-effect transistors, is required to minimize device degradation induced by moisture and oxygen ingress. SiNx moisture permeation barriers have been fabricated using a very recently developed low-temperature plasma-assisted atomic layer deposition (ALD) approach, consisting of half-reactions of the substrate with the precursor SiH2(NH(t)Bu)2 and with N2-fed plasma. The deposited films have been characterized in terms of their refractive index and chemical composition by spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). The SiNx thin-film refractive index ranges from 1.80 to 1.90 for films deposited at 80 °C up to 200 °C, respectively, and the C, O, and H impurity levels decrease when the deposition temperature increases. The relative open porosity content of the layers has been studied by means of multisolvent ellipsometric porosimetry (EP), adopting three solvents with different kinetic diameters: water (∼0.3 nm), ethanol (∼0.4 nm), and toluene (∼0.6 nm). Irrespective of the deposition temperature, and hence the impurity content in the SiNx films, no uptake of any adsorptive has been observed, pointing to the absence of open pores larger than 0.3 nm in diameter. Instead, multilayer development has been observed, leading to type II isotherms that, according to the IUPAC classification, are characteristic of nonporous layers. The calcium test has been performed in a climate chamber at 20 °C and 50% relative humidity to determine the intrinsic water vapor transmission rate (WVTR) of SiNx barriers deposited at 120 °C. Intrinsic WVTR values in the range of 10(-6) g/m2/day indicate excellent barrier properties for ALD SiNx layers as thin as 10 nm, competing with that of state-of-the-art plasma-enhanced chemical vapor-deposited SiNx layers of a few hundred

  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

    2014-01-01

    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.

  13. Non-isothermal scavenging of highly soluble gaseous pollutants by rain in the atmosphere with non-uniform vertical concentration and temperature distributions

    Science.gov (United States)

    Elperin, Tov; Fominykh, Andrew; Krasovitov, Boris

    2014-08-01

    We suggest a non-isothermal one-dimensional model of precipitation scavenging of highly soluble gaseous pollutants in inhomogeneous atmosphere. When gradients of soluble trace gases' concentrations and temperature in the atmosphere are small, scavenging of gaseous pollutants is governed by two linear wave equations that describe propagation of a scavenging and temperature waves in one direction. If wash-down front velocity is much larger than the velocity of the temperature front, scavenging is determined by propagating scavenging front in the atmosphere with inhomogeneous temperature distribution. We solved the derived equation by the method of characteristics and determined scavenging coefficient and the rates of precipitation scavenging for wet removal of sulfur dioxide using measured initial distributions of trace gases and temperature in the atmosphere. It is shown that in the case of exponential initial distribution of soluble trace gases and linear temperature distribution in the atmosphere, scavenging coefficient in the region between the ground and the position of a scavenging front is proportional to rainfall rate, solubility parameter in the under-cloud region, adjacent to a bottom of a cloud and to the growth constant in the formula for the initial profile of a soluble trace gas in the atmosphere. The derived formula yields the same value of scavenging coefficient for sulfur dioxide scavenging by rain as field estimates presented by McMahon and Denison (Atmos Environ 13:571-585, 1979). It is demonstrated that in the case when the altitude variation of temperature in the atmosphere is determined by the environmental lapse rate, scavenging coefficient increases with height in the region between the scavenging front and the ground. In the case when altitude temperature variation in the atmosphere is determined by temperature inversion, scavenging coefficient decreases with height in a region between the scavenging front and the ground. Theoretical

  14. Gaseous Detectors

    Science.gov (United States)

    Titov, Maxim

    Since long time, the compelling scientific goals of future high-energy physics experiments were a driving factor in the development of advanced detector technologies. A true innovation in detector instrumentation concepts came in 1968, with the development of a fully parallel readout for a large array of sensing elements - the Multi-Wire Proportional Chamber (MWPC), which earned Georges Charpak a Nobel prize in physics in 1992. Since that time radiation detection and imaging with fast gaseous detectors, capable of economically covering large detection volumes with low mass budget, have been playing an important role in many fields of physics. Advances in photolithography and microprocessing techniques in the chip industry during the past decade triggered a major transition in the field of gas detectors from wire structures to Micro-Pattern Gas Detector (MPGD) concepts, revolutionizing cell-size limitations for many gas detector applications. The high radiation resistance and excellent spatial and time resolution make them an invaluable tool to confront future detector challenges at the next generation of colliders. The design of the new micro-pattern devices appears suitable for industrial production. Novel structures where MPGDs are directly coupled to the CMOS pixel readout represent an exciting field allowing timing and charge measurements as well as precise spatial information in 3D. Originally developed for the high-energy physics, MPGD applications have expanded to nuclear physics, photon detection, astroparticle and neutrino physics, neutron detection, and medical imaging.

  15. Modelling the evolution of composition-and stress-depth profiles in austenitic stainless steels during low-temperature nitriding

    DEFF Research Database (Denmark)

    Jespersen, Freja Nygaard; Hattel, Jesper Henri; Somers, Marcel A. J.

    2016-01-01

    . In the present paper solid mechanics was combined with thermodynamics and diffusion kinetics to simulate the evolution of composition-depth and stress-depth profiles resulting from nitriding. The model takes into account a composition-dependent diffusion coefficient of nitrogen in expanded austenite, short range...

  16. Very low surface recombination velocities on 2.5 {omega}cm Si wafers, obtained with low-temperature PECVD of Si-oxide and Si-nitride

    Energy Technology Data Exchange (ETDEWEB)

    Leguijt, C.; Loelgen, P. [FOM-Institute for Atomic and Molecular Physics, Amsterdam (Netherlands); Eikelboom, J.A.; Amesz, P.H.; Steeman, R.A.; Sinke, W.C. [Unit ECN Renewable Energy, Netherlands Energy Research Foundation, Petten (Netherlands); Sarro, P.M. [Delft Institute for Micro-Electronics and Submicron technology DIMES, Delft (Netherlands); Verhoef, L.A.; Michiels, P.-P. [R and S Renewable Energy Systems BV, Helmond (Netherlands); Chen, Z.H.; Rohatgi, A. [Univerisity Centre Of Excellence for Photovoltaics Research and Education, Georgia Institute of Technology, Atlanta, GA (United States)

    1993-09-01

    The first measurements are presented of very low recombination velocities (<90 cm/s) on 2.5 {omega}cm p-type silicon wafers, passivated with low-temperature PECVD (Plasma Enhanced Chemical Vapor Deposition) of Si-oxide and Si-nitride. Also n-type emitter surfaces were passivated by PECVD. A forming gas anneal turned out to be crucial in achieving low recombination velocities. No increase of the surface recombination velocity was observed after exposure of the layers to white light at 30{sup o}C and 1000 W/m{sup 2} for 500 hours. 16 refs.

  17. Thermal discharges from Paducah Gaseous Diffusion Plant outfalls: Impacts on stream temperatures and fauna of Little Bayou and Big Bayou Creeks

    Energy Technology Data Exchange (ETDEWEB)

    Roy, W.K.; Ryon, M.G.; Hinzman, R.L. [Oak Ridge National Lab., TN (United States). Computer Science and Mathematics Div.

    1996-03-01

    The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued Kentucky Pollutant Discharge Elimination System permit No. KY 0004049. This action prompted the US Department of Energy (DOE) to request a stay of certain limits contained in the permit. An AO is being negotiated between KDOW, the US Enrichment Corporation (USEC), and DOE that will require that several studies be conducted, including this stream temperature evaluation study, in an effort to establish permit limitations. All issues associated with this AO have been resolved, and the AO is currently being signed by all parties involved. The proposed effluent temperature limit is 89 F (31.7 C) as a mean monthly temperature. In the interim, temperatures are not to exceed 95 F (35 C) as a monthly mean or 100 F (37.8 C) as a daily maximum. This study includes detailed monitoring of instream temperatures, benthic macroinvertebrate communities, fish communities, and a laboratory study of thermal tolerances.

  18. Thermal Discharges from Paducah Gaseous Diffusion Plant Outfalls: Impacts on Stream Temperatures and Fauna of Little Bayou and Big Bayou Creeks

    Energy Technology Data Exchange (ETDEWEB)

    Roy, W.K.

    1999-01-01

    The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued Kentucky Pollutant Discharge Elimination System permit No. KY 0004049. This action prompted the US Department of Energy (DOE) to request a stay of certain limits contained in the permit. An AO is being negotiated between KDOW, the United States Enrichment Corporation (USEC), and DOE that will require that several studies be conducted, including this stream temperature evaluation study, in an effort to establish permit limitations. All issues associated with this AO have been resolved, and the AO is currently being signed by all parties involved. The proposed effluent temperature limit is 89 F (31.7C) as a mean monthly temperature. In the interim, temperatures are not to exceed 95 F (35 C) as a monthly mean or 100 F (37.8 C) as a daily maximum. This study includes detailed monitoring of instream temperatures, benthic macroinvertebrate communities, fish communities, and a laboratory study of thermal tolerances.

  19. Evolution of the structure and mechanical properties of a bulk-nitrided corrosion-resistant ferritic steel upon tempering in the temperature range of 400-700°C

    Science.gov (United States)

    Rogachev, S. O.; Nikulin, S. A.; Khatkevich, V. M.

    2017-08-01

    Methods of the X-ray diffraction analysis and electron microscopy were used to study changes in the structural phase state and mechanical properties of bulk-nitrided 08Kh17T steel (0.08 wt % C, 17 wt % Cr, 0.8 wt % Ti, 0.5 wt % Si, 0.8 wt % Mn, 0.025 wt % S, and 0.035 wt % P) upon tempering in the temperature range of 400-700°C. The changes in the mechanical properties of the nitrided steel upon tempering are associated with the predominance of either the solid-solution or precipitation strengthening, i.e., with the presence of martensite in the steel structure at low temperatures of tempering and the precipitation of particles of Cr2N nitrides of different dispersity upon increasing the tempering temperature. The greatest increase in the ultimate tensile strength and yield stress (1.8-2.5 times) at a satisfactory plasticity (no less than 10%) of the bulk-nitrided steel is achieved by tempering bulk-nitrided steel in a temperature range of 600-700°C.

  20. Gaseous product mixture from Fischer-Tropsch synthesis as an efficient carbon feedstock for low temperature CVD growth of carbon nanotube carpets

    Science.gov (United States)

    Almkhelfe, Haider; Carpena-Núñez, Jennifer; Back, Tyson C.; Amama, Placidus B.

    2016-07-01

    Low-temperature chemical vapor deposition (CVD) growth of carbon nanotube (CNT) carpets from Fe and Fe-Cu catalysts using a gaseous product mixture from Fischer-Tropsch synthesis (FTS-GP) as a superior carbon feedstock is demonstrated. This growth approach addresses a persistent issue of obtaining thick CNT carpets on temperature-sensitive substrates at low temperatures using a non-plasma CVD approach without catalyst pretreatment and/or preheating of the carbon feedstock. The efficiency of the process is evidenced by the highly dense, vertically aligned CNT structures from both Fe and Fe-Cu catalysts even at temperatures as low as 400 °C - a record low growth temperature for CNT carpets obtained via conventional thermal CVD. The grown CNTs exhibit a straight morphology with hollow interior and parallel graphitic planes along the tube walls. The apparent activation energies for CNT carpet growth on Fe and Fe-Cu catalysts are 0.71 and 0.54 eV, respectively. The synergistic effect of Fe and Cu show a strong dependence on the growth temperature, with Cu being more influential at temperatures higher than 450 °C. The low activation energies and long catalyst lifetimes observed are rationalized based on the unique composition of FTS-GP and Gibbs free energies for the decomposition reactions of the hydrocarbon components. The use of FTS-GP facilitates low-temperature growth of CNT carpets on traditional (alumina film) and nontraditional substrates (aluminum foil) and has the potential of enhancing CNT quality, catalyst lifetime, and scalability.Low-temperature chemical vapor deposition (CVD) growth of carbon nanotube (CNT) carpets from Fe and Fe-Cu catalysts using a gaseous product mixture from Fischer-Tropsch synthesis (FTS-GP) as a superior carbon feedstock is demonstrated. This growth approach addresses a persistent issue of obtaining thick CNT carpets on temperature-sensitive substrates at low temperatures using a non-plasma CVD approach without catalyst

  1. Nitride alloy layer formation of duplex stainless steel using nitriding process

    Science.gov (United States)

    Maleque, M. A.; Lailatul, P. H.; Fathaen, A. A.; Norinsan, K.; Haider, J.

    2018-01-01

    Duplex stainless steel (DSS) shows a good corrosion resistance as well as the mechanical properties. However, DSS performance decrease as it works under aggressive environment and at high temperature. At the mentioned environment, the DSS become susceptible to wear failure. Surface modification is the favourable technique to widen the application of duplex stainless steel and improve the wear resistance and its hardness properties. Therefore, the main aim of this work is to nitride alloy layer on the surface of duplex stainless steel by the nitriding process temperature of 400°C and 450°C at different time and ammonia composition using a horizontal tube furnace. The scanning electron microscopy and x-ray diffraction analyzer are used to analyse the morphology, composition and the nitrided alloy layer for treated DSS. The micro hardnesss Vickers tester was used to measure hardness on cross-sectional area of nitrided DSS. After nitriding, it was observed that the hardness performance increased until 1100 Hv0.5kgf compared to substrate material of 250 Hv0.5kgf. The thickness layer of nitride alloy also increased from 5μm until 100μm due to diffusion of nitrogen on the surface of DSS. The x-ray diffraction results showed that the nitride layer consists of iron nitride, expanded austenite and chromium nitride. It can be concluded that nitride alloy layer can be produced via nitriding process using tube furnace with significant improvement of microstructural and hardness properties.

  2. Comparative results of autogenous ignition temperature measurements by ASTM G 72 and pressurized scanning calorimetry in gaseous oxygen

    Science.gov (United States)

    Bryan, C. J.; Lowrie, R.

    1986-01-01

    The autogenous ignition temperature of four materials was determined by ASTM (G 72) and pressurized differential scanning calorimetry at 0.68-, 3.4-, and 6.8-MPa oxygen pressure. All four materials were found to ignite at lower temperatures in the ASTM method. The four materials evaluated in this program were Neoprene, Vespel SP-21, Fluorel E-2160, and nylon 6/6.

  3. A novel temperature-gradient Na±β-alumina solid electrolyte based SOx gas sensor without gaseous reference electrode

    DEFF Research Database (Denmark)

    Rao, N.; Bleek, C.M. Van den; Schoonman, J.

    1992-01-01

    An electrochemical SOx ps sensor with a tubular Na+-beta"-alumina solid electrolyte has been fabricated and tested under non-isothermal conditions. The temperature difference between the reference and working electrode of the sensor cell is about 100-degrees-C, which causes a serious deviation...

  4. On the effect of pre-oxidation on the nitriding kinetics

    DEFF Research Database (Denmark)

    Friehling, Peter Bernhard; Somers, Marcel A. J.

    2000-01-01

    The oxidation of ferritic surfaces prior to gaseous nitriding has been reported to lead to improved uniformity of the compound layer thickness and enhanced nitriding kinetics. The present work considers the nucleation and growth of a model compound layer on pure iron and, using previous experimen......The oxidation of ferritic surfaces prior to gaseous nitriding has been reported to lead to improved uniformity of the compound layer thickness and enhanced nitriding kinetics. The present work considers the nucleation and growth of a model compound layer on pure iron and, using previous...... experimental and theoretical work reported in the literature, puts forward two hypotheses to explain the effects of pre-oxidation on compound layer formation. It is proposed that the nucleation of iron nitrides is enhanced by the presence of an iron-oxide layer and that the growth of an iron-nitride layer...

  5. Gaseous byproducts from high-temperature thermal conversion elemental analysis of nitrogen- and sulfur-bearing compounds with considerations for δ2H and δ18O analyses.

    Science.gov (United States)

    Hunsinger, Glendon B; Tipple, Christopher A; Stern, Libby A

    2013-07-30

    High-temperature, conversion-reduction (HTC) systems convert hydrogen and oxygen in materials into H2 and CO for δ(2)H and δ(18)O measurements by isotope ratio mass spectrometry. HTC of nitrogen- and sulfur-bearing materials produces unintended byproduct gases that could affect isotope analyses by: (1) allowing isotope exchange reactions downstream of the HTC reactor, (2) creating isobaric or co-elution interferences, and (3) causing deterioration of the chromatography. This study characterizes these HTC byproducts. A HTC system (ThermoFinnigan TC/EA) was directly connected to a gas chromatograph/quadrupole mass spectrometer in scan mode (m/z 8 to 88) to identify the volatile products generated by HTC at conversion temperatures of 1350 °C and 1450 °C for a range of nitrogen- and sulfur-bearing solids [keratin powder, horse hair, caffeine, ammonium nitrate, potassium nitrate, ammonium sulfate, urea, and three nitrated organic explosives (PETN, RDX, and TNT)]. The prominent HTC byproduct gases include carbon dioxide, hydrogen cyanide, methane, acetylene, and water for all nitrogen-bearing compounds, as well as carbon disulfide, carbonyl sulfide, and hydrogen sulfide for sulfur-bearing compounds. The 1450 °C reactor temperature reduced the abundance of most byproduct gases, but increased the significant byproduct, hydrogen cyanide. Inclusion of a post-reactor chemical trap containing Ascarite II and Sicapent, in series, eliminated the majority of byproducts. This study identified numerous gaseous HTC byproducts. The potential adverse effects of these gases on isotope ratio analyses are unknown but may be mitigated by higher HTC reactor temperatures and purifying the products with a purge-and-trap system or with chemical traps. Published in 2013. This article is a U.S. Government work and is in the public domain in the USA.

  6. Chemically adjusting plasma temperature, energy, and reactivity (CAPTEAR) method using NOx and combustion for selective synthesis of Sc3N@C80 metallic nitride fullerenes.

    Science.gov (United States)

    Stevenson, Steven; Thompson, M Corey; Coumbe, H Louie; Mackey, Mary A; Coumbe, Curtis E; Phillips, J Paige

    2007-12-26

    Goals are (1) to selectively synthesize metallic nitride fullerenes (MNFs) in lieu of empty-cage fullerenes (e.g., C60, C70) without compromising MNF yield and (2) to test our hypothesis that MNFs possess a different set of optimal formation parameters than empty-cage fullerenes. In this work, we introduce a novel approach for the selective synthesis of metallic nitride fullerenes. This new method is "Chemically Adjusting Plasma Temperature, Energy, and Reactivity" (CAPTEAR). The CAPTEAR approach with copper nitrate hydrate uses NOx vapor from NOx generating solid reagents, air, and combustion to "tune" the temperature, energy, and reactivity of the plasma environment. The extent of temperature, energy, and reactive environment is stoichiometrically varied until optimal conditions for selective MNF synthesis are achieved. Analysis of soot extracts indicate that percentages of C60 and Sc3N@C80 are inversely related, whereas the percentages of C70 and higher empty-cage C2n fullerenes are largely unaffected. Hence, there may be a "competitive link" in the formation and mechanism of C60 and Sc3N@C80. Using this CAPTEAR method, purified MNFs (96% Sc3N@C80, 12 mg) have been obtained in soot extracts without a significant penalty in milligram yield when compared to control soot extracts (4% Sc3N@C80, 13 mg of Sc3N@C80). The CAPTEAR process with Cu(NO3)2.2.5H2O uses an exothermic nitrate moiety to suppress empty-cage fullerene formation, whereas Cu functions as a catalyst additive to offset the reactive plasma environment and boost the Sc3N@C80 MNF production.

  7. Cool gaseous nebulae

    CERN Document Server

    Shaver, P A; Pottasch, S R

    1979-01-01

    The electron temperatures of diffuse gaseous nebulae have long been thought to be close to 10/sup 4/K. Much lower temperatures were derived from some of the early radio continuum and recombination line work, but these were generally considered to be wrong for a variety of reasons. While there is little doubt that the bright nebulae do indeed have temperatures of approximately 8000-9000K, there are strong indications that some nebulae of lower densities have much lower temperatures, temperatures in the absence of such effects as collisional de-excitation, stimulated emission, and pressure broadening. Several of these nebulae have been found to have temperatures below 5000K and for two of them which are discussed (RCW94 and G339.1-0.2) absolute upper limits of approximately 4700 K are imposed by the line widths alone. (11 refs).

  8. Effect of strain rate on sooting limits in counterflow diffusion flames of gaseous hydrocarbon fuels: Sooting temperature index and sooting sensitivity index

    KAUST Repository

    Wang, Yu

    2014-05-01

    The effect of the strain rate on the sooting limits in counterflow diffusion flames was investigated in various gaseous hydrocarbon fuels by varying the nitrogen dilution in the fuel and oxidizer streams. The sooting limit was defined as the critical fuel and oxygen mole fraction at which soot started to appear in the elastic light scattering signal. The sooting region for normal alkane fuels at a specified strain rate, in terms of the fuel and oxygen mole fraction, expanded as the number of carbon atoms increased. The alkene fuels (ethylene, propene) tested had a higher propensity for sooting as compared with alkane fuels with the same carbon numbers (ethane, propane). Branched iso-butane had a higher propensity for sooting than did n-butane. An increase in the strain rate reduced the tendency for sooting in all the fuels tested. The sensitivity of the sooting limit to the strain rate was more pronounced for less sooting fuels. When plotted in terms of calculated flame temperature, the critical oxygen mole fraction exhibited an Arrhenius form under sooting limit conditions, which can be utilized to significantly reduce the effort required to determine sooting limits at different strain rates. We found that the limiting temperatures of soot formation flames are viable sooting metrics for quantitatively rating the sooting tendency of various fuels, based on comparisons with threshold soot index and normalized smoke point data. We also introduce a sooting temperature index and a sooting sensitivity index, two quantitative measures to describe sooting propensity and its dependence on strain rate. © 2013 The Combustion Institute.

  9. Effect of Gaseous Ozone Exposure on the Bacteria Counts and Oxidative Properties of Ground Hanwoo Beef at Refrigeration Temperature

    Science.gov (United States)

    Cho, Youngjae; Hahn, Tae-Wook

    2014-01-01

    This study was designed to elucidate the effect of ozone exposure on the bacteria counts and oxidative properties of ground Hanwoo beef contaminated with Escherichia coli O157:H7 at refrigeration temperature. Ground beef was inoculated with 7 Log CFU/g of E. coli O157:H7 isolated from domestic pigs and was then subjected to ozone exposure (10×10−6 kg O3 h−1) at 4℃ for 3 d. E. coli O157:H7, total aerobic and anaerobic bacterial growth and oxidative properties including instrumental color changes, TBARS, catalase (CAT) and glutathione peroxidase (GPx) activity were evaluated. Ozone exposure significantly prohibited (pmeat under refrigerated storage. The results of this study provide a foundation for the further application of ozone exposure by integrating an ozone generator inside a refrigerator. Further studies regarding the ozone concentrations and exposure times are needed. PMID:26761291

  10. In-Situ Study of Gaseous Reduction of Magnetite Doped with Alumina Using High-Temperature XRD Analysis

    Science.gov (United States)

    Kapelyushin, Yury; Sasaki, Yasushi; Zhang, Jianqiang; Jeong, Sunkwang; Ostrovski, Oleg

    2015-12-01

    The reduction of magnetite of technical grade and magnetite doped with 3 mass pct Al2O3 was studied in situ using high-temperature XRD (HT-XRD) analysis. Magnetite was reduced by CO-CO2 gas (80 vol pct CO) at 1023 K (750 °C). Reduction of magnetite doped with alumina occurred from the Fe3O4-FeAl2O4 solid solution which has a miscibility gap with critical temperature of 1133 K (860 °C). The degree of reduction of magnetite was derived using Rietveld refinement of the HT-XRD spectra; the compositions of the Fe3O4-FeAl2O4 solid solution and the concentrations of carbon in γ-iron were determined from the lattice constants of the solutions. The reduction of magnetite progressed topochemically with the formation of a dense iron shell. The reduction of alumina-containing magnetite started along certain lattice planes with the formation of a network-like structure. Reduction of alumina-containing magnetite was faster than that of un-doped magnetite; this difference was attributed to the formation of the network-like structure. Hercynite content in the Fe3O4-FeAl2O4 solid solution in the process of reduction of magnetite doped with 3 mass pct Al2O3 increased from 5.11 to 20 mass pct, which is close to the miscibility gap at 1023 K (750 °C). The concentration of carbon in γ-Fe (0.76 mass pct) formed in the reduced sample of magnetite doped with 3 mass pct Al2O3 was close to the equilibrium value with 80 vol pct CO to 20 vol pct CO2 gas used in the HT-XRD experiments.

  11. Enhanced photocatalytic oxidation of gaseous elemental mercury by TiO2 in a high temperature environment.

    Science.gov (United States)

    Shen, Huazhen; Ie, Iau-Ren; Yuan, Chung-Shin; Hung, Chung-Hsuang; Chen, Wei-Hsiang; Luo, Jinjing; Jen, Yi-Hsiu

    2015-05-30

    The photo-oxidation of Hg(0) in a lab-scale reactor by titanium dioxide (TiO2) coated on the surface of glass beads was investigated at high temperatures. TiO2 was calcinated at four different temperatures of 300 °C, 400 °C, 500 °C and 600 °C (noted as Ti300, Ti400, Ti500 and Ti600) and characterized for its physicochemical properties. The calcinated TiO2 coating on the glass beads was then tested to compare the photo-oxidation efficiencies of Hg(0) with an incident light of 365 nm. The results showed that the oxidation efficiencies of Hg(0) for Ti400 and Ti500 were higher than those of Ti300 and Ti600. To enhance the photo-oxidation efficiency of Hg(0), Ti400 was selected to examine the wave lengths (λ) of 254 nm, 365 nm and visible light with various influent Hg(0) concentrations. The effects of irradiation strength and the presence of oxygen on the photo-oxidation efficiency of Hg(0) were further investigated, respectively. This study revealed that the wave length (λ) of 254 nm could promote the photo-oxidation efficiency of Hg(0) at 140 and 160 °C, while increasing the influent Hg(0) concentration and could enhance the photo-oxidation rate of Hg(0). However, the influence of 5% O2 present in the flue gas for the enhancement of Hg(0) oxidation was limited. Moreover, the intensity of the incident wave length of 365 nm and visible light were demonstrated to boost the photo-oxidation efficiency of Hg(0) effectively. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Efficient visible-light photocatalytic oxidation of gaseous NO with graphitic carbon nitride (g–C{sub 3}N{sub 4}) activated by the alkaline hydrothermal treatment and mechanism analysis

    Energy Technology Data Exchange (ETDEWEB)

    Nie, Haoyu; Ou, Man [School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094 (China); Nanjing AIREP Environmental Protection Technology Co., Ltd., Nanjing, Jiangsu 210091 (China); Zhong, Qin, E-mail: zq304@mail.njust.edu.cn [School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094 (China); Nanjing AIREP Environmental Protection Technology Co., Ltd., Nanjing, Jiangsu 210091 (China); Zhang, Shule; Yu, Lemeng [School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094 (China); Nanjing AIREP Environmental Protection Technology Co., Ltd., Nanjing, Jiangsu 210091 (China)

    2015-12-30

    Highlights: • Various porous g–C{sub 3}N{sub 4} samples were obtained by the alkaline hydrothermal treatment. • 0.12CN possesses the largest BET specific surface area and pore volume. • The NO conversion in the presence of 0.12CN reaches 40.4%. • Reasons for the enhanced PCO performance with treated g–C{sub 3}N{sub 4} was analyzed. • Further mechanism of the PCO of NO relevant with active species was investigated. - Abstract: In this paper, an enhanced visible-light photocatalytic oxidation (PCO) of NO (∼400 ppm) in the presence of the graphitic carbon nitride (g–C{sub 3}N{sub 4}) treated by the alkaline hydrothermal treatment is evaluated. Various g–C{sub 3}N{sub 4} samples were treated in different concentrations of NaOH solutions and the sample treated in 0.12 mol L{sup −1} of NaOH solution possesses the largest BET specific surface area as well as the optimal ability of the PCO of NO. UV–vis diffuse reflection spectra (DRS) and photoluminescence (PL) spectra were also conducted, and the highly improved photocatalytic performance is ascribed to the large specific surface area and high pore volume, which provides more adsorption and active sites, the wide visible-light adsorption edge and the narrow band gap, which is favorable for visible-light activation, as well as the decreased recombination rate of photo-generated electrons and holes, which could contribute to the production of active species. Fluorescence spectra and a trapping experiment were conducted to further the mechanism analysis of the PCO of NO, illustrating that superoxide radicals (·O{sub 2}{sup −}) play the dominant role among active species in the PCO of NO.

  13. 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.

  14. Effect of Gaseous Ozone Exposure on the Bacteria Counts and Oxidative Properties of Ground Hanwoo Beef at Refrigeration Temperature.

    Science.gov (United States)

    Cho, Youngjae; Muhlisin; Choi, Ji Hye; Hahn, Tae-Wook; Lee, Sung Ki

    2014-01-01

    This study was designed to elucidate the effect of ozone exposure on the bacteria counts and oxidative properties of ground Hanwoo beef contaminated with Escherichia coli O157:H7 at refrigeration temperature. Ground beef was inoculated with 7 Log CFU/g of E. coli O157:H7 isolated from domestic pigs and was then subjected to ozone exposure (10×10(-6) kg O3 h(-1)) at 4℃ for 3 d. E. coli O157:H7, total aerobic and anaerobic bacterial growth and oxidative properties including instrumental color changes, TBARS, catalase (CAT) and glutathione peroxidase (GPx) activity were evaluated. Ozone exposure significantly prohibited (pOzone exposure reduced (pozone had no clear effect. Ozone exposure increased the TBARS values during 1 to 3 d of storage (pozone exposure until 2 and 3 d of storage, respectively. This study provides information about the use of ozone exposure as an antimicrobial agent for meat under refrigerated storage. The results of this study provide a foundation for the further application of ozone exposure by integrating an ozone generator inside a refrigerator. Further studies regarding the ozone concentrations and exposure times are needed.

  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. Combined Poisson and soft-particle DLVO analysis of the specific and nonspecific adhesion forces measured between L. monocytogenes grown at various temperatures and silicon nitride.

    Science.gov (United States)

    Gordesli, F Pinar; Abu-Lail, Nehal I

    2012-09-18

    Adhesion forces between pathogenic L. monocytogenes EGDe and silicon nitride (Si(3)N(4)) were measured using atomic force microscopy (AFM) under water and at room temperature for cells grown at five different temperatures (10, 20, 30, 37, and 40 °C). Adhesion forces were then decoupled into specific (hydrogen bonding) and nonspecific (electrostatic and Lifshitz-van der Waals) force components using Poisson statistical analysis. The strongest specific and nonspecific attraction forces were observed for cells grown at 30 °C, compared to those observed for cells grown at higher or lower temperatures, respectively. By combining the results of Poisson analysis with the results obtained through soft-particle Derjaguin-Landau-Verwey-Overbeek (DLVO) analysis, the contributions of the Lifshitz-van der Waals and electrostatic forces to the overall nonspecific interaction forces were determined. Our results showed that the Lifshitz-van der Waals attraction forces dominated the total nonspecific adhesion forces for all investigated thermal conditions. However, irrespective of the temperature of growth investigated, hydrogen bonding forces were always stronger than the nonspecific forces. Finally, by combining Poisson analysis with soft-particle analysis of DLVO forces, the closest separation distances where the irreversible bacterial adhesion takes place can be determined relatively easily. For all investigated thermal conditions, the closest separation distances were <1 nm.

  17. Transient, three-dimensional heat transfer model for the laser assisted machining of silicon nitride: 1. Comparison of predictions with measured surface temperature histories

    Energy Technology Data Exchange (ETDEWEB)

    Rozzi, J.C.; Pfefferkorn, F.E.; Shin, Y.C. [Purdue University, (United States). Laser Assisted Materials Processing Laboratory, School of Mechanical Engineering; Incropera, F.P. [University of Notre Dame, (United States). Aerospace and Mechanical Engineering Department

    2000-04-01

    Laser assisted machining (LAM), in which the material is locally heated by an intense laser source prior to material removal, provides an alternative machining process with the potential to yield higher material removal rates, as well as improved control of workpiece properties and geometry, for difficult-to-machine materials such as structural ceramics. To assess the feasibility of the LAM process and to obtain an improved understanding of governing physical phenomena, experiments have been performed to determine the thermal response of a rotating silicon nitride workpiece undergoing heating by a translating CO{sub 2} laser and material removal by a cutting tool. Using a focused laser pyrometer, surface temperature histories were measured to determine the effect of the rotational and translational speeds, the depth of cut, the laser-tool lead distance, and the laser beam diameter and power on thermal conditions. The measurements are in excellent agreement with predictions based on a transient, three-dimensional numerical solution of the heating and material removal processes. The temperature distribution within the unmachined workpiece is most strongly influenced by the laser power and laser-tool lead distance, as well as by the laser/tool translational velocity. A minimum allowable operating temperature in the material removal region corresponds to the YSiAlON glass transition temperature, below which tool fracture may occur. In a companion paper, the numerical model is used to further elucidate thermal conditions associated with laser assisted machining. (author)

  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. Boron nitride composites

    Science.gov (United States)

    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.

  20. Apparatus for silicon nitride precursor solids recovery

    Science.gov (United States)

    Crosbie, Gary M.; Predmesky, Ronald L.; Nicholson, John M.

    1995-04-04

    Method and apparatus are provided for collecting reaction product solids entrained in a gaseous outflow from a reaction situs, wherein the gaseous outflow includes a condensable vapor. A condensate is formed of the condensable vapor on static mixer surfaces within a static mixer heat exchanger. The entrained reaction product solids are captured in the condensate which can be collected for further processing, such as return to the reaction situs. In production of silicon imide, optionally integrated into a production process for making silicon nitride caramic, wherein reactant feed gas comprising silicon halide and substantially inert carrier gas is reacted with liquid ammonia in a reaction vessel, silicon imide reaction product solids entrained in a gaseous outflow comprising residual carrier gas and vaporized ammonia can be captured by forming a condensate of the ammonia vapor on static mixer surfaces of a static mixer heat exchanger.

  1. Method for silicon nitride precursor solids recovery

    Science.gov (United States)

    Crosbie, Gary M.; Predmesky, Ronald L.; Nicholson, John M.

    1992-12-15

    Method and apparatus are provided for collecting reaction product solids entrained in a gaseous outflow from a reaction situs, wherein the gaseous outflow includes a condensable vapor. A condensate is formed of the condensable vapor on static mixer surfaces within a static mixer heat exchanger. The entrained reaction product solids are captured in the condensate which can be collected for further processing, such as return to the reaction situs. In production of silicon imide, optionally integrated into a production process for making silicon nitride caramic, wherein reactant feed gas comprising silicon halide and substantially inert carrier gas is reacted with liquid ammonia in a reaction vessel, silicon imide reaction product solids entrained in a gaseous outflow comprising residual carrier gas and vaporized ammonia can be captured by forming a condensate of the ammonia vapor on static mixer surfaces of a static mixer heat exchanger.

  2. Gaseous fuel nuclear reactor research

    Science.gov (United States)

    Schwenk, F. C.; Thom, K.

    1975-01-01

    Gaseous-fuel nuclear reactors are described; their distinguishing feature is the use of fissile fuels in a gaseous or plasma state, thereby breaking the barrier of temperature imposed by solid-fuel elements. This property creates a reactor heat source that may be able to heat the propellant of a rocket engine to 10,000 or 20,000 K. At this temperature level, gas-core reactors would provide the breakthrough in propulsion needed to open the entire solar system to manned and unmanned spacecraft. The possibility of fuel recycling makes possible efficiencies of up to 65% and nuclear safety at reduced cost, as well as high-thrust propulsion capabilities with specific impulse up to 5000 sec.

  3. Optimized Spiral Metal-Gallium-Nitride Nanowire Cavity for Ultra-High Circular Dichroism Ultraviolet Lasing at Room Temperature.

    Science.gov (United States)

    Liao, Wei-Chun; Liao, Shu-Wei; Chen, Kuo-Ju; Hsiao, Yu-Hao; Chang, Shu-Wei; Kuo, Hao-Chung; Shih, Min-Hsiung

    2016-05-25

    Circularly polarized laser sources with small footprints and high efficiencies can possess advanced functionalities in optical communication and biophotonic integrated systems. However, the conventional lasers with additional circular-polarization converters are bulky and hardly compatible with nanophotonic circuits, and most active chiral plasmonic nanostructures nowadays exhibit broadband emission and low circular dichroism. In this work, with spirals of gallium nitride (GaN) nanowires (NWRs) covered by a metal layer, we demonstrated an ultrasmall semiconductor laser capable of emitting circularly-polarized photons. The left- and right-hand spiral metal nanowire cavities with varied periods were designed at ultraviolet wavelengths to achieve the high quality factor circular dichroism metastructures. The dissymmetry factors characterizing the degrees of circular polarizations of the left- and right-hand chiral lasers were 1.4 and -1.6 (±2 if perfectly circular polarized), respectively. The results show that the chiral cavities with only 5 spiral periods can achieve lasing signals with the high degrees of circular polarizations.

  4. Comparative Investigation on the Heat Transfer Characteristics of Gaseous CO2 and Gaseous Water Flowing Through a Single Granite Fracture

    Science.gov (United States)

    He, Yuanyuan; Bai, Bing; Li, Xiaochun

    2017-11-01

    CO2 and water are two commonly employed heat transmission fluids in several fields. Their temperature and pressure determine their phase states, thus affecting the heat transfer performance of the water/CO2. The heat transfer characteristics of gaseous CO2 and gaseous water flowing through fractured hot dry rock still need a great deal of investigation, in order to understand and evaluate the heat extraction in enhanced geothermal systems. In this work, we develop a 2D numerical model to compare the heat transfer performance of gaseous CO2 and gaseous water flowing through a single fracture aperture of 0.2 mm in a φ 50 × 50 mm cylindrical granite sample with a confining temperature of 200°C under different inlet mass flow rates. Our results indicate that: (1) the final outlet temperatures of the fluid are very close to the outer surface temperature under low inlet mass flow rate, regardless of the sample length. (2) Both the temperature of the fluid (gaseous CO2/gaseous water) and inner surface temperature rise sharply at the inlet, and the inner surface temperature is always higher than the fluid temperature. However, their temperature difference becomes increasingly small. (3) Both the overall heat transfer coefficient (OHTC) and local heat transfer coefficient (LHTC) of gaseous CO2 and gaseous water increase with increasing inlet mass flow rates. (4) Both the OHTC and LHTC of gaseous CO2 are lower than those of gaseous water under the same conditions; therefore, the heat mining performance of gaseous water is superior to gaseous CO2 under high temperature and low pressure.

  5. Template-assisted synthesis of III-nitride and metal-oxide nano-heterostructures using low-temperature atomic layer deposition for energy, sensing, and catalysis applications (Presentation Recording)

    Science.gov (United States)

    Biyikli, Necmi; Ozgit-Akgun, Cagla; Eren, Hamit; Haider, Ali; Uyar, Tamer; Kayaci, Fatma; Guler, Mustafa Ozgur; Garifullin, Ruslan; Okyay, Ali K.; Ulusoy, Gamze M.; Goldenberg, Eda

    2015-08-01

    Recent experimental research efforts on developing functional nanostructured III-nitride and metal-oxide materials via low-temperature atomic layer deposition (ALD) will be reviewed. Ultimate conformality, a unique propoerty of ALD process, is utilized to fabricate core-shell and hollow tubular nanostructures on various nano-templates including electrospun nanofibrous polymers, self-assembled peptide nanofibers, metallic nanowires, and multi-wall carbon nanotubes (MWCNTs). III-nitride and metal-oxide coatings were deposited on these nano-templates via thermal and plasma-enhanced ALD processes with thickness values ranging from a few mono-layers to 40 nm. Metal-oxide materials studied include ZnO, TiO2, HfO2, ZrO2, and Al2O3. Standard ALD growth recipes were modified so that precursor molecules have enough time to diffuse and penetrate within the layers/pores of the nano-template material. As a result, uniform and conformal coatings on high-surface area nano-templates were demonstrated. Substrate temperatures were kept below 200C and within the self-limiting ALD window, so that temperature-sensitive template materials preserved their integrity III-nitride coatings were applied to similar nano-templates via plasma-enhanced ALD (PEALD) technique. AlN, GaN, and InN thin-film coating recipes were optimized to achieve self-limiting growth with deposition temperatures as low as 100C. BN growth took place only for >350C, in which precursor decomposition occured and therefore growth proceeded in CVD regime. III-nitride core-shell and hollow tubular single and multi-layered nanostructures were fabricated. The resulting metal-oxide and III-nitride core-shell and hollow nano-tubular structures were used for photocatalysis, dye sensitized solar cell (DSSC), energy storage and chemical sensing applications. Significantly enhanced catalysis, solar efficiency, charge capacity and sensitivity performance are reported. Moreover, core-shell metal-oxide and III-nitride materials

  6. High-pressure and high-temperature synthesis of rhenium carbide using rhenium and nanoscale amorphous two-dimensional carbon nitride

    Directory of Open Access Journals (Sweden)

    Nozomu Yasui

    2015-12-01

    Full Text Available Both Re2C and Re2N are ultra incompressible and have a bulk modulus of about 400 GPa. These materials are synthesized under high pressure and high temperature. The synthesis pressures are about 10 GPa or below for Re2C and 20–30 GPa for Re2N. If the synthesis pressure of Re2N was about 10 GPa or below, a large volume high-pressure cell like a multi-anvil apparatus can be used to synthesize Re2N. To realize this, a proper solid nitrogen source is needed instead of liquid or gas nitrogen. We used a precursor of a mixture of rhenium and home-made nanoscale amorphous two-dimensional carbon nitride as a solid nitrogen source. Consequently, the synthesis reaction produced Re2C but not Re2N. We characterized the synthesized Re2C by various techniques including high-pressure x-ray diffraction (XRD. The bulk modulus B0 of the synthesized Re2C under hydrostatic conditions was estimated to be 385.7 ± 18.0 GPa. This value is a little smaller than the previous data. When the pressure medium became non-hydrostatic, the peculiar compression behaviour occurred; the rate of broadening of XRD lines increased and the compression became negligible in the range of a few GPa. The reason for this peculiar behaviour is not known.

  7. Nitrogen Gas Flow Ratio and Rapid Thermal Annealing Temperature Dependences of Sputtered Titanium Nitride Gate Work Function and Their Effect on Device Characteristics

    Science.gov (United States)

    Liu, Yongxun; Hayashida, Tetsuro; Matsukawa, Takashi; Endo, Kazuhiko; Masahara, Meishoku; O'uchi, Shinich; Sakamoto, Kunihiro; Ishii, Kenichi; Tsukada, Junichi; Ishikawa, Yuki; Yamauchi, Hiromi; Ogura, Atsushi; Suzuki, Eiichi

    2008-04-01

    A sputtered titanium nitride (TiN) metal gate has systematically been investigated, and the dependences of TiN work function (φTiN) and device performance on nitrogen gas flow ratio [RN=N2/(N2+Ar)] in sputtering and rapid thermal annealing (RTA) temperature (TR) are clarified. It is experimentally found that φTiN slightly decreases from 4.87 to 4.78 eV with increasing RN from 17 to 83%, and it markedly decreases with increasing TR. The analysis of the electrical characteristics of fabricated metal-oxide-semiconductor field-effect transistors (MOSFETs) shows that the optimal RN range is 17-50%, and a higher RN offers a lower Vth owing to the lower φTiN. The origin of φTiN decrease with increasing RN and TR is discussed. The obtained results indicate that φTiN can be controlled by sputtering and RTA conditions, and are very useful for setting the appropriate Vth for lightly doped channel devices such as a FinFET.

  8. Plasma etch characteristics of aluminum nitride mask layers grown by low-temperature plasma enhanced atomic layer deposition in SF{sub 6} based plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Perros, Alexander; Bosund, Markus; Sajavaara, Timo; Laitinen, Mikko; Sainiemi, Lauri; Huhtio, Teppo; Lipsanen, Harri [Department of Micro- and Nanosciences, Aalto University School of Electrical Engineering, P.O. Box 13500, FI-00076 Aalto (Finland); Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014, Jyvaeskylae,Finland (Finland); Department of Micro and Nanosciences, School of Electrical Engineering, Aalto University, P.O. Box 13500, FI-00076, Aalto (Finland)

    2012-01-15

    The plasma etch characteristics of aluminum nitride (AlN) deposited by low-temperature, 200 deg. C, plasma enhanced atomic layer deposition (PEALD) was investigated for reactive ion etch (RIE) and inductively coupled plasma-reactive ion etch (ICP-RIE) systems using various mixtures of SF{sub 6} and O{sub 2} under different etch conditions. During RIE, the film exhibits good mask properties with etch rates below 10r nm/min. For ICP-RIE processes, the film exhibits exceptionally low etch rates in the subnanometer region with lower platen power. The AlN film's removal occurred through physical mechanisms; consequently, rf power and chamber pressure were the most significant parameters in PEALD AlN film removal because the film was inert to the SF{sub x}{sup +} and O{sup +} chemistries. The etch experiments showed the film to be a resilient masking material. This makes it an attractive candidate for use as an etch mask in demanding SF{sub 6} based plasma etch applications, such as through-wafer etching, or when oxide films are not suitable.

  9. Nitriding of Co–Cr–Mo alloy in nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Ning, E-mail: ningtang@imr.tohoku.ac.jp; Li, Yunping, E-mail: lyping@imr.tohoku.ac.jp; Koizumi, Yuichiro; Chiba, Akihiko, E-mail: a.chiba@imr.tohoku.ac.jp

    2014-06-01

    Using the results of a thermodynamic analysis, a Co–Cr–Mo alloy was successfully nitrided in nitrogen at temperatures of 1073–1473 K. The near-surface microstructure of the treated Co–Cr–Mo alloy was characterized using X-ray diffraction, field-emission scanning electron microscopy, electron probe micro-analyzer, and transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy. The results indicated that the highest nitriding efficiency was achieved at the treatment temperature of 1273 K, with the size and coverage of the nitride particles on sample's surface increasing with an increase in the treatment duration. After nitriding at 1273 K for 2 h, numerous nitride particles, consisting of an outer Cr{sub 2}N layer and an inner π phase layer, were formed on top of the nitrogen-containing γ phase, and some π phase also precipitated in the alloy matrix at the sub-surface level. - Highlights: • A Co–Cr–Mo alloy was successfully nitrided in nitrogen at 1073–1473 K. • The highest nitriding efficiency of the Co–Cr–Mo alloy was achieved at 1273 K. • Numerous nitride particles formed on sample's surface during nitriding at 1273 K. • The nitride particles consist of an outer Cr{sub 2}N layer and an inner π phase layer.

  10. 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.

  11. 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.

  12. Measurement of Transient Tool Internal Temperature Fields by Novel Micro Thin Film Sensors Embedded in Polycrystalline Cubic Boron Nitride Cutting Inserts

    Science.gov (United States)

    Werschmoeller, Dirk

    Monitoring and control of thermomechanical phenomena in tooling are imperative for advancing fundamental understanding, enhancing reliability, and improving workpiece quality in material removal processes. Polycrystalline cubic boron nitride (PCBN) tools are being used heavily in numerous machining processes, e.g., machining of hardened low carbon steel and superalloys. These processes are very sensitive to variations in local cutting conditions at, or close to, the tool-workpiece interface, but lack a thorough understanding of fundamental transient thermo-mechanical phenomena present. As a result, abrupt catastrophic tool failures and degraded machined surfaces frequently occur. Existing sensors are not suitable for process control and monitoring, as they are either destructively embedded and/or do not possess the necessary spatial and temporal resolution to provide relevant data during machining. This research presents a novel approach for obtaining thermomechanical data from the close vicinity (i.e., 10s of micrometers) of the tool-workpiece interface. Arrays of micro thin film thermocouples with junction size 5 x 5 mum were fabricated by standard microfabrication methods and have been successfully embedded into PCBN using diffusion bonding. Electron microscopy and X-ray spectroscopy were employed to examine material interactions at the bonding interface and to determine optimal bonding parameters. Static and dynamic sensor performances have been characterized. The sensors exhibit excellent linearity up to 1300 °C, fast rise time of 150 ns, and possess good sensitivity. The inserts instrumented with embedded thin film C-type thermocouples were successfully applied to measure internal tool temperatures as close as 70 mum to the cutting edge while machining aluminum and hardened steel workpieces at industrially relevant cutting parameters. Acquired temperature data follow theoretical trends very well. Correlations between temperature and cutting parameters have

  13. Crystalline boron nitride aerogels

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-12-12

    This disclosure provides methods and materials related to boron nitride aerogels. For example, one aspect relates to a method for making an aerogel comprising boron nitride, comprising: (a) providing boron oxide and an aerogel comprising carbon; (b) heating the boron oxide to melt the boron oxide and heating the aerogel; (c) mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide; and (d) converting at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride. Another aspect relates to a method for making an aerogel comprising boron nitride, comprising heating boron oxide and an aerogel comprising carbon under flow of a nitrogen-containing gas, wherein boron oxide vapor and the nitrogen-containing gas convert at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride.

  14. P-type gallium nitride

    Science.gov (United States)

    Rubin, M.; Newman, N.; Fu, T.; Ross, J.; Chan, J.

    1997-08-12

    Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5{times}10{sup 11} /cm{sup 3} and hole mobilities of about 500 cm{sup 2} /V-sec, measured at 250 K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al. 9 figs.

  15. Surface modification of AISI 304 austenitic stainless steel by plasma nitriding

    Science.gov (United States)

    Liang, Wang

    2003-04-01

    Plasma nitriding of austenitic stainless steel samples has been carried out using pulse dc glow discharge plasma of NH 3 gas at substrate temperature ranging from 350 to 520 °C. A nitriding time of only 4 h has been found to produce a compact surface nitride layer composed of γN' phase with a thickness of around 7-12 μm as processing temperature remained between 420 and 450 °C. The thickness of γN phase was found to be very thin only about 2 μm after plasma nitriding at temperature below 400 °C. Microhardness measurements showed significant increase in the hardness from 240 HV (for untreated samples) up to 1700 HV (for nitrided samples at temperature of 460 °C). For nitriding at higher temperature, i.e. above 460 °C, the chromium nitrides precipitated in the nitrided layer and caused austenite phase transform into ferrite phase or iron nitrides ( γ' or ɛ). The consequent result of chromium nitride precipitation is the reduction of corrosion resistance of nitrided layer. Compressive residual stresses existed in the nitrided layer due to nitrogen diffusion into austenitic stainless steel.

  16. 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)

  17. Low-temperature nitriding of VA-group metal powders (V,Nb,Ta) in flowing NH3 gas under heating with concentrated solar beam at PSA

    OpenAIRE

    Fernandes, J. C.; Oliveira, F. A. Costa; Rosa, Luís Guerra; Rodríguez, José; Canadas, Inmaculada; Magalhães, Teresa; Shohoji, Nobumitsu

    2015-01-01

    Over the last two decades, we have been using concentrated solar beam as the reaction heat source for synthesizing carbides and nitrides of d-group transition elements in view of usage of ecological renewable energy source in place of conventional heat sources using electricity or gas. In recent works [1,2] nitriding of VIa-group metals (Cr, Mo, W) and Fe in stream of NH3 gas with suppressed extent of dissociation (uncracked NH3) was attempted under heating with concentrated solar beam. It wa...

  18. On-line gaseous formaldehyde detection by a microfluidic analytical method based on simultaneous uptake and derivatization in a temperature controlled annular flow.

    Science.gov (United States)

    Guglielmino, Maud; Bernhardt, Pierre; Trocquet, Claire; Serra, Christophe A; Le Calvé, Stéphane

    2017-09-01

    This paper is focused on the improvement of a microfluidic analytical method for the detection of low airborne formaldehyde concentrations, based on only two distinct steps permitting to reduce the response time and to improve the compactness of the device. First, gaseous formaldehyde is trapped into an acetylacetone solution at 65°C through an annular liquid/gas flow and reacts immediately to form 3,5-Diacetyl-1,4-dihydrolutidine which is then quantified by colorimetry using a liquid core waveguide (LCW). To obtain an annular flow, 3 different hydrophilic silica capillaries of 320, 450 and 530µm ID were tested and the corresponding phase diagrams were obtained in the ranges of liquid and gas flows of 5-35µLmin(-1) and 5-35mLmin(-1) respectively. Finally, the analytical performances were determined using the lowest flow values of 5µLmin(-1) and 5NmLmin(-1), ensuring an annular flow and increasing the microdevice autonomy. If the uptake yield of gaseous formaldehyde into the solution was close to 100%, only the 530µm ID capillary permits to obtain a reaction time long enough for a full conversion of formaldehyde into 3,5-Diacetyl-1,4-dihydrolutidine. With a LCW pathlength of 5cm, the microdevice response was perfectly linear in the range 0-154µgm(-3) with a detection limit of 1.8µgm(-3). Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Position Sensitive Gaseous Photomultipliers

    CERN Document Server

    Martinengo, P; Peskov, V

    2010-01-01

    Advances in the technologies associated with position sensitive gaseous detectors especially featuring CsI as reflective photoconverters will be reviewed. These photodetectors represent the most effective solution for what concerns cost and performance in the case of large area Cherenkov imaging applications in relatively low rate (or low occupancy) high energy physics and astrophysics experiments. Moreover, they are the only choice when the Cherenkov detector is embedded in a magnetic field. Recently proposed single photon MPGDs (Micropattern Gaseous Detectors) will be also discussed in view of the successful efforts so far made to extend their sensitivity to visible light. With some modifications, photosensitive gaseous detectors can also be used in the imaging of X-rays and particles.

  20. 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...

  1. Pack nitriding of aluminium using cassava waste | Shitta | Journal of ...

    African Journals Online (AJOL)

    Pack Nitriding is a process analogous to pack carbonizing. In this work, cassava leaves were employed as a source of nitrogen. Upon heating, slow decomposition of the compound provides Nitrogen, the Nitrogen was allowed to interact with aluminium metal surfaces, which were packed nitrided at temperature of 350°c.

  2. Nitriding of super alloys for enhancing physical properties

    Science.gov (United States)

    Purohit, A.

    1984-06-25

    The invention teaches the improvement of certain super alloys by exposing the alloy to an atmosphere of elemental nitrogen at elevated temperatures in excess of 750/sup 0/C but less than 1150/sup 0/C for an extended duration, viz., by nitriding the surface of the alloy, to establish barrier nitrides of the order of 25 to 100 micrometers thickness. These barrier

  3. 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...... nitride and the transition metal) to the ternary nitride was followed by Mossbauer spectroscopy (for Fe3Mo3N) and by X-ray powder diffraction ( for both Fe3Mo3N and Co3Mo3N). Usually, the preparation of a given ternary nitride by ammonolysis of a ternary oxide is dependent on the availability of an oxide...

  4. The sensitivity of the electron transport within bulk zinc-blende gallium nitride to variations in the crystal temperature, the doping concentration, and the non-parabolicity coefficient associated with the lowest energy conduction band valley

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqua, Poppy; O' Leary, Stephen K., E-mail: stephen.oleary@ubc.ca [School of Engineering, The University of British Columbia, 3333 University Way, Kelowna, British Columbia V1V 1V7 (Canada)

    2016-09-07

    Within the framework of a semi-classical three-valley Monte Carlo simulation approach, we analyze the steady-state and transient electron transport that occurs within bulk zinc-blende gallium nitride. In particular, we examine how the steady-state and transient electron transport that occurs within this material changes in response to variations in the crystal temperature, the doping concentration, and the non-parabolicity coefficient associated with the lowest energy conduction band valley. These results are then contrasted with those corresponding to a number of other compound semiconductors of interest.

  5. Effect of nanoparticle (Pd, Pd/Pt, Ni deposition on high temperature hydrogenation of Ti-V alloys in gaseous flow containing CO

    Directory of Open Access Journals (Sweden)

    S. Suwarno

    2017-02-01

    Full Text Available The hydrogenation properties of Ti-V hydrides coated with nanoparticles have been studied in gaseous mixtures of argon and hydrogen with and without additions of 1% CO. Nanoparticles of Pd, Ni, and co-deposited Pd/Pt with particle sizes of ~30–60 nm were formed by electroless deposition on the hydride surfaces. The alloy resistance to CO could be significantly improved by particle deposition. Large amounts of hydrogen were absorbed in a CO-containing gas when Ni and Pd/Pt deposition had been applied, while pure Pd deposition had no positive effect. Ni was found to have a stronger effect than those of Pd/Pt and Pd, possibly because of the size effect of Ni nanoparticles.

  6. Forced convection of ammonia. 2. part.: gaseous ammonia - very high wall temperatures (1000 to 3000 K); Convection forcee de l'ammoniac. 2. partie: ammoniac gazeux - cas de tres hautes temperatures de paroi (1000 a 3000{sup 0} K)

    Energy Technology Data Exchange (ETDEWEB)

    Perroud, P.; Rebiere, J.; Strittmatter, R. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    Heat transfer coefficients and pressure drop of gaseous ammonia in forced convection are experimentally determined. The fluid flows (mass flow rate 0.6 to 2.4 g/s) in a long tungsten tube (d{sub i} = 2.8 mm, d{sub e} = 5.1 mm, L = 700 mm) electrically heated. The temperature of the wall reaches 3000 deg. K and the fluid 2500 deg. K; maximum heat flux 530 w/cm{sup 2}. Ammonia is completely dissociated and the power necessary for dissociation reaches 30 per cent of the total power exchanged. Inlet pressure varies between 6 and 16 bars and the maximum pressure drop in the tube reaches 15 bars. Two regimes of dissociation have been shown: catalytic and homogeneous and the variation of dissociation along the length of the tube is studied. The measured heat transfer coefficients may be about 10 times these calculated by the means of classical formulae. A correlation of experimental results using enthalpy as a driving force for heat transmission is presented. Pressure drops may be calculated by the means of a classical friction factor. (authors) [French] On determine experimentalement les coefficients d'echange thermique et les pertes de charge de l'ammoniac gazeux en convection forcee. Le fluide circule avec un debit en masse compris entre 0.6 et 2.4 g/s (G = 10 a 40 g/cm{sup 2}.s) dans un tube long en tungstene (d{sub i} = 2.8 mm, d{sub e} = 5.1 mm, L = 700 mm), chauffe electriquement. La temperature de paroi atteint 3000 deg. K, celle du fluide 2500 deg. K et le flux de chaleur maximal est de 530 W/cm{sup 2}. L'ammoniac se dissocie completement, la puissance correspondant a la dissociation atteint 30 pour cent de la puissance totale echangee. La pression d'entree varie entre 6 et 16 bars et la chute de pression maximale dans le canal est de 15 bars. On distingue deux regimes de dissociation, catalytique et homogene, et on etudie la variation du taux de dissociation en fonction de la longueur du tube. Les coefficients d'echange thermique mesures

  7. Gaseous wire detectors

    Energy Technology Data Exchange (ETDEWEB)

    Va' vra, J.

    1997-08-01

    This article represents a series of three lectures describing topics needed to understand the design of typical gaseous wire detectors used in large high energy physics experiments; including the electrostatic design, drift of electrons in the electric and magnetic field, the avalanche, signal creation, limits on the position accuracy as well as some problems one encounters in practical operations.

  8. 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....

  9. Thermal Improvement and Stability of Si3N4/GeNx/p- and n-Ge Structures Prepared by Electron-Cyclotron-Resonance Plasma Nitridation and Sputtering at Room Temperature

    Science.gov (United States)

    Fukuda, Yukio; Okamoto, Hiroshi; Iwasaki, Takuro; Izumi, Kohei; Otani, Yohei; Ishizaki, Hiroki; Ono, Toshiro

    2012-09-01

    This paper reports on the thermal improvement of Si3N4/GeNx/Ge structures. After the Si3N4 (5 nm)/GeNx (2 nm) stacks were prepared on Ge substrates by electron-cyclotron-resonance plasma nitridation and sputtering at room temperature, they were thermally annealed in atmospheric N2 + 10% H2 ambient at temperatures from 400 to 600 °C. It was demonstrated that the electronic properties of the GeNx/Ge interfaces were thermally improved at temperatures of up to 500 °C with a minimum interface trap density (Dit) of ˜1×1011 cm-2 eV-1 near the Ge midgap, whereas the interface properties were slightly degraded after annealing at 600 °C with a minimum Dit value of ˜4×1011 cm-2 eV-1.

  10. 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.

  11. 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.

  12. 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.

  13. Comment on "High-temperature soft magnetic properties of antiperovskite nitrides ZnNFe3 and AlNFe3" by Yankun Fu, Shuai Lin, and Bosen Wang, J. Magn. Magn. Mater. 378 (2015) 54-58

    Science.gov (United States)

    Scholz, T.; Leineweber, A.; Dronskowski, R.

    2016-10-01

    The authors of the aforementioned manuscript have recently claimed the synthesis of the ternary nitrides ZnNFe3 (=ZnFe3N) and AlNFe3 (=AlFe3N), ordered substituted variants of the binary phase γ'-Fe4N [1]. While soft ferromagnets of such kind are presently attracting lots of attention, their history dates back for more than half a century. In particular, Al-substituted γ'-Fe4N has already been mentioned in 1961 [2], and the existence of AlFe3N has also been claimed in 2009 [3] from a two-step ammonolysis reaction combining a high-temperature sintering step and a low-temperature nitriding reaction [4]. Nonetheless, one of us had to withdraw the latter claim after finding out, by means of scanning-electron microscopy and elemental mapping, that all samples of "AlFe3N" consisted of an intimate solid mixture of γ'-Fe4N and amorphous Al2O3[5]. From what follows, we have strong reasons to believe that the authors of Ref. [1] overlooked our findings [5] and also did not synthesize ZnFe3N and AlFe3N.

  14. Gaseous fuel reactor research

    Science.gov (United States)

    Thom, K.; Schneider, R. T.

    1977-01-01

    The paper reviews studies dealing with the concept of a gaseous fuel reactor and describes the structure and plans of the current NASA research program of experiments on uranium hexafluoride systems and uranium plasma systems. Results of research into the basic properties of uranium plasmas and fissioning gases are reported. The nuclear pumped laser is described, and the main results of experiments with these devices are summarized.

  15. Hybrid gaseous photomultipliers

    CERN Document Server

    Rodionov, I; Peskov, Vladimir; Sokolova, T

    2002-01-01

    We have developed a hybrid gaseous photomultiplier. It consists of two planar parts: a sealed chamber with a semitransparent bi-alkali or SbCs photocathode (the 'scintillation chamber') and a position-sensitive gaseous detector with a CsI photocathode flushed with a gas at 1 atm (the 'readout detector'). This device was developed according to two different designs. In the first design the scintillation chamber operates with pure Xe at 1 atm pressure. Electrons created from the photocathode by visible light move through the capillary plate (which acts as a light attenuator) and produce a weak very ultra-violet (VUV) scintillation light in the gap between the capillary plate and the collecting mesh. This VUV light is detected by the readout gaseous detector. In the second design, the sealed scintillation chamber was operated in vacuum. The photoelectrons extracted from the photocathode hit the scintillator emitting VUV light. The VUV light was detected with the readout detector. A practical quantum efficiency o...

  16. Heterogeneous Reaction gaseous chlorine nitrate and solid sodium chloride

    Science.gov (United States)

    Timonen, Raimo S.; Chu, Liang T.; Leu, Ming-Taun

    1994-01-01

    The heterogeneous reaction of gaseous chlorine nitrate and solid sodium chloride was investigated over a temperature range of 220 - 300 K in a flow-tube reactor interfaced with a differentially pumped quadrupole mass spectrometer.

  17. Silicon nitride layers obtained by ECR PECVD

    NARCIS (Netherlands)

    Isai, I.G.; Holleman, J.; Woerlee, P.H.; Wallinga, Hans

    2002-01-01

    It has been found that good quality silicon nitride films can be deposited at room temperature, with an alternate electron cyclotron resonance (ECR) plasma source, called multipolar ECR. The effects of several deposition conditions on physical and electrical properties were studied in order to

  18. 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.

  19. Cathodic cage nitriding of samples with different dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, R.R.M. de [Centro Federal de Educacao Tecnologica do Piaui, Department of Mechanical, Teresina, PI (Brazil); Araujo, F.O. de [Universidade Federal Rural do Semi-Arido, Mossoro, RN (Brazil); Ribeiro, K.J.B.; Mendes, M.W.D. [Labplasma, Departamento de Fisica-UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil); Costa, J.A.P. da [Departamento de Fisica-UFC, Fortaleza, CE (Brazil); Alves, C. [Labplasma, Departamento de Fisica-UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil)], E-mail: alvesjr@pesquisador.cnpq.br

    2007-09-15

    A series of AISI 1020 steel cylindrical samples with different heights were simultaneously nitrided in cathodic cage plasma nitriding. In this technique, the samples are placed under a floating potential inside a cage in which the cathodic potential is applied. A systematic study of the nitriding temperature variation effects was carried out in order to evaluate the efficiency of such a technique over the uniformity of the formed layers. The samples were characterized by optical microscopy, X-ray diffraction and microhardness measurement. The results were compared with those ones obtained in the ionic nitriding, and was verified that the samples nitrided by this conventional technique presents less uniformity than the ones treated through this new technique.

  20. 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.

  1. 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.

  2. 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.

  3. Intrinsic ferromagnetism in hexagonal boron nitride nanosheets.

    Science.gov (United States)

    Si, M S; Gao, Daqiang; Yang, Dezheng; Peng, Yong; Zhang, Z Y; Xue, Desheng; Liu, Yushen; Deng, Xiaohui; Zhang, G P

    2014-05-28

    Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized π states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstrate such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.

  4. Influence of the surface temperature of packaging specimens on the inactivation of Bacillus spores by means of gaseous H(2) O(2).

    Science.gov (United States)

    Pruss, K; Stirtzel, S; Kulozik, U

    2012-03-01

    To determine the influence of condensation as a function of the surface temperature of aseptic packaging, on the inactivation of Bacillus spores [Bacillus subtilis (DSM 347), B. subtilis SA22, Bacillus atrophaeus] having different surface properties by means of vaporized H(2) O(2). The packaging specimens inoculated with Bacillus spores were tempered and subsequently exposed to H(2) O(2) -vapour. During the exposure, surface temperature curves were measured and the spore survival was determined. Results showed that decreasing the initial surface temperature of the packaging specimens had a positive effect on the sporicidal activity of H(2) O(2) -vapour, where the effect was less pronounced for less hydrophilic spores. The surfaces of spores were characterized by means of the water contact angle. For starting surface temperatures below the dew point temperature of the sterilant gas, the condensation of highly concentrated liquid H(2) O(2) on the packaging surface accelerates the killing of the spores, while the inferior wettability of more hydrophobic spores compared to more hydrophilic ones diminishes the effect. Regarding industrial packaging sterilization, a mixed microflora has to be inactivated. Promoting the condensation of H(2) O(2) improves in general the killing of different species of spores, however, at various degrees depending on the wettability of spores. © 2011 Technische Universität München. Journal of Applied Microbiology © 2011 The Society for Applied Microbiology.

  5. Gaseous fuel injection system

    Energy Technology Data Exchange (ETDEWEB)

    Lynch, W.M.

    1997-12-18

    A fuel injection method and apparatus, suitable for use with an internal combustion engine operated on LPG, has a reservoir for LPG with an outlet connected via a pump and a non-return valve to a heating chamber which is preferably heated by hot air or hot water, and then via a gas pressure regulator to an injector. The apparatus operates such that LPG is pumped by the pump through the non-return valve to the heating chamber where the LPG is heated to allow gaseous LPG to be transmitted to the injector once a predetermined pressure set on the regulator has been reached, whereupon the injector injects the LPG into the crankcase, transfer ports, carburettor or cylinders of the internal combustion engine. The internal combustion engine may be a two-stroke engine, and lubricant may be injected into the engine along with the gaseous LPG using lubricant injection means that are arranged to adjust the amount of lubricant in accordance with engine speed, preferably by drawing the lubricant into the fuel flow by use of the venturi effect.(author) figs.

  6. Correlation and prediction of gaseous diffusion coefficients.

    Science.gov (United States)

    Marrero, T. R.; Mason, E. A.

    1973-01-01

    A new correlation method for binary gaseous diffusion coefficients from very low temperatures to 10,000 K is proposed based on an extended principle of corresponding states, and having greater range and accuracy than previous correlations. There are two correlation parameters that are related to other physical quantities and that are predictable in the absence of diffusion measurements. Quantum effects and composition dependence are included, but high-pressure effects are not. The results are directly applicable to multicomponent mixtures.

  7. 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....

  8. Gossip: Gaseous pixels

    Science.gov (United States)

    Koffeman, E. N.

    2007-12-01

    Several years ago a revolutionary miniature TPC was developed using a pixel chip with a Micromegas foil spanned over it. To overcome the mechanical stability problems and improve the positioning accuracy while spanning a foil on top of a small readout chip a process has been developed in which a Micromegas-like grid is applied on a CMOS wafer in a post-processing step. This aluminum grid is supported on insulating pillars that are created by etching after the grid has been made. The energy resolution (measured on the absorption of the X-rays from a 55Fe source) was remarkably good. Several geometries have since been tested and we now believe that a Gas On Slimmed Silicon Pixel chip' (Gossip) may be realized. The drift region of such a gaseous pixel detector would be reduced to a millimeter. Such a detector is potentially very radiation hard (SLHC vertexing) but aging and sparking must be eliminated.

  9. Gossip: Gaseous pixels

    Energy Technology Data Exchange (ETDEWEB)

    Koffeman, E.N. [Nikhef, Kruislaan 409, 1098 SJ Amsterdam (Netherlands)], E-mail: d77@nikhef.nl

    2007-12-01

    Several years ago a revolutionary miniature TPC was developed using a pixel chip with a Micromegas foil spanned over it. To overcome the mechanical stability problems and improve the positioning accuracy while spanning a foil on top of a small readout chip a process has been developed in which a Micromegas-like grid is applied on a CMOS wafer in a post-processing step. This aluminum grid is supported on insulating pillars that are created by etching after the grid has been made. The energy resolution (measured on the absorption of the X-rays from a {sup 55}Fe source) was remarkably good. Several geometries have since been tested and we now believe that a Gas On Slimmed Silicon Pixel chip' (Gossip) may be realized. The drift region of such a gaseous pixel detector would be reduced to a millimeter. Such a detector is potentially very radiation hard (SLHC vertexing) but aging and sparking must be eliminated.

  10. GASEOUS DISCHARGE DEVICE

    Science.gov (United States)

    Gow, J.D.

    1961-01-10

    An extremely compact two-terminal gaseous discharge device is described that is capable of producing neutrons in copious quantities, relatively high energy ions, intense x rays, and the like. Principal novelty resides in the provision of a crossed electric-magnetic field region in the discharge envelope that traps electrons and accelerates them to very high energies to provide an intense ionizing medium adjacent the anode of the device for ionizing gas therein with extremely high efficiency. In addition, the crossed-field trapping region holds the electrons close to the anode whereby the acceleration of ions to the cathode is not materially effected by the electron sheath and the ions assume substantially the full energy of the anodecathode potential drop. (auth)

  11. Synthesis of tantalum carbide and nitride nanoparticles using a reactive mesoporous template for electrochemical hydrogen evolution

    KAUST Repository

    Alhajri, Nawal Saad

    2013-01-01

    Tantalum carbide and nitride nanocrystals were prepared through the reaction of a tantalum precursor with mesoporous graphitic (mpg)-C 3N4. The effects of the reaction temperature, the ratio of the Ta precursor to the reactive template (mpg-C3N4), and the selection of the carrier gas (Ar, N2 and NH3) on the resultant crystal phases and structures were investigated. The produced samples were characterized using powder X-ray diffraction (XRD), CHN elemental analyses, thermogravimetric analyses (TGA), nitrogen sorption, a temperature-programmed reaction with mass spectroscopy (MS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results indicate that the different tantalum phases with cubic structure, TaN, Ta2CN, and TaC, can be formed under a flow of nitrogen when formed at different temperatures. The Ta3N5 phase with a Ta5+ oxidation state was solely obtained at 1023 K under a flow of ammonia, which gasified the C 3N4 template and was confirmed by detecting the decomposed gaseous products via MS. Significantly, the formation of TaC, Ta2CN, and TaN can be controlled by altering the weight ratio of the C 3N4 template relative to the Ta precursor at 1573 K under a flow of nitrogen. The high C3N4/Ta precursor ratio generally resulted in high carbide content rather than a nitride one, consistent with the role of mpg-C3N4 as a carbon source. Electrochemical measurements revealed that the synthesized nanomaterials were consistently able to produce hydrogen under acidic conditions (pH 1). The obtained Tafel slope indicates that the rate-determining step is the Volmer discharge step, which is consistent with adsorbed hydrogen being weakly bound to the surface during electrocatalysis. © 2013 The Royal Society of Chemistry.

  12. Oligocyclic fatigue of the thermo chemically nitrided Ti6AI4V alloys; Fatiga oligociclicade la aleacion Ti6AI4V niturrada termoquimicamente

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, D.; Manero, J. M.; Gil, F. J.; Planell, J. A.

    2001-07-01

    The use of titanium and its alloys in applications with the presence of friction is limited due to low hardness and reduced tribological properties. Some surface treatments are available in order to correct these problems, like the thermal surface treatment by means of nitrogen gaseous diffusion at high temperature. Nitrogen enters into the materials by diffusion, creating a surface layers of increased hardness. Oligocyclic fatigue behaviour in air of Ti6Al4V alloy has been studied. Results show a reduction of oligocyclic fatigue loads up to 10% compared to the not-treated materials. Studies suggest it is not related to the titanium nitride surface layer, but to microstructural changes caused by the high temperature treatment. (Author) 7 refs.

  13. Active metal brazing of various metals on nitride ceramics

    OpenAIRE

    Pönicke, A.; Rost, A.; Schilm, J.; Michaelis, A.

    2013-01-01

    The development of new materials for thermoelectric generators (TEG) with higher operating temperatures requires improved metallised substrates. Commonly used alumina substrates with copper metallisation show low thermal conductivity and low stability against thermal cycles. Aluminum nitride (AlN) and silicon nitride (Si3N4) are very attractive alternative substrate materials due to their high thermal conductivity, electrical resistivity and mechanical strength. However, it is important to re...

  14. Heat treatment of nitrided layer formed on X37CrMoV5-1 hot working tool steel

    Science.gov (United States)

    Ciski, A.; Wach, P.; Tacikowski, J.; Babul, T.; Šuchmann, P.

    2017-02-01

    The paper presents the technology consisting of combination of the nitriding process with subsequent austenitizing at temperature above eutectoid temperature of the Fe-C system and further rapid cooling. Such treatment will cause formation of the martensite in the area of the primarily nitrided layer and the additional precipitation hardening by tempering of heat treated steel. The article shows that the heat treatment process of nitrided layer formed on X37CrMoV5-1 steel leads to strengthening of surface layer, the substrate and the core of nitrided part. Heat treatment of nitrided steel with the tempering in inert (nitrogen) or active (ammonia) atmosphere can increase the thickness of the layer formed by short-term nitriding process. After the nitriding process of X37CrMoV5-1 steel the nitrided layer had a thickness of about 160 μm, while a subsurface layer of iron nitrides had a thickness of 7 μm. After subsequent quenching and tempering processes, the nitrided layer undergoes additional diffusion and its thickness is increased to about 220 μm (inert atmosphere) or 280 μm (active atmosphere). If the tempering process is carried out in an inert atmosphere, the primarily formed layer of iron nitrides disappears. Tempering in an active atmosphere leads to forming of white layer with a thickness of 7 μm. Basic properties of nitrided layers formed in such way, like the hardness and the wear resistance, are presented.

  15. Titanium Matrix Composite Ti/TiN Produced by Diode Laser Gas Nitriding

    Directory of Open Access Journals (Sweden)

    Aleksander Lisiecki

    2015-01-01

    Full Text Available A high power direct diode laser, emitting in the range of near infrared radiation at wavelength 808–940 nm, was applied to produce a titanium matrix composite on a surface layer of titanium alloy Ti6Al4V by laser surface gas nitriding. The nitrided surface layers were produced as single stringer beads at different heat inputs, different scanning speeds, and different powers of laser beam. The influence of laser nitriding parameters on the quality, shape, and morphology of the surface layers was investigated. It was found that the nitrided surface layers consist of titanium nitride precipitations mainly in the form of dendrites embedded in the titanium alloy matrix. The titanium nitrides are produced as a result of the reaction between molten Ti and gaseous nitrogen. Solidification and subsequent growth of the TiN dendrites takes place to a large extent at the interface of the molten Ti and the nitrogen gas atmosphere. The direction of TiN dendrites growth is perpendicular to the surface of molten Ti. The roughness of the surface layers depends strongly on the heat input of laser nitriding and can be precisely controlled. In spite of high microhardness up to 2400 HV0.2, the surface layers are crack free.

  16. Occurrence of gaseous and particulate polycyclic aromatic hydrocarbons in the urban atmosphere: study of sources and ambient temperature effect on the gas/particle concentration and distribution

    Energy Technology Data Exchange (ETDEWEB)

    Tsapakis, Manolis [Environmental Chemical Processes Laboratory (ECPL), Department of Chemistry, University of Crete, EL-71409 Heraklion (Greece); Stephanou, Euripides G. [Environmental Chemical Processes Laboratory (ECPL), Department of Chemistry, University of Crete, EL-71409 Heraklion (Greece)]. E-mail: stephanou@chemistry.uoc.gr

    2005-01-01

    The presence of polycyclic aromatic hydrocarbons (PAHs) in an urban region (Heraklion, Greece) and processes that govern their atmospheric fate were studied from November 2000 until February 2002. Sixteen samples were collected, by using an artifact-free sampling device, on a monthly basis and the concentration of PAHs in gas and particulate phase was determined. The most abundant members (gas + particles) were phenanthrene (20.0 {+-} 7.0 ng m{sup -3}), fluoranthene (6.5 {+-} 1.7 ng m{sup -3}), pyrene (6.6 {+-} 2.4 ng m{sup -3}), and chrysene (3.1 {+-} 1.5 ng m{sup -3}). Total concentration (gas + particulate) of PAH ranged from 44.3 to 129.2 ng m{sup -3}, with a mean concentration of 79.3 ng m{sup -3}. Total concentration of PAHs in gas phase ranged from 31.4 to 84.7 ng m{sup -3} with non-observable seasonal variation. Conversely, maximum PAH concentrations in the particulate phase occurred during winter months. Particulate concentration varied from 11.4 to 44.9 ng m{sup -3}, with an average of 25.2 ng m{sup -3}. PAH distribution between gas and particulate phase was in agreement with the sub-cooled vapor pressure. Shift in gas/particle distribution due to difference in ambient temperature elucidated to some extent the seasonal variation of the concentration of PAHs in particles. - Capsule: Ambient PAH partitioning between gas and particle phases vary between compounds and with environmental conditions.

  17. A novel hohlraum with ultrathin depleted-uranium-nitride coating layer for low hard x-ray emission and high radiation temperature

    CERN Document Server

    Guo, Liang; Xing, Peifeng; Li, Sanwei; Yi, Taimin; Kuang, Longyu; Li, Zhichao; Li, Renguo; Wu, Zheqing; Jing, Longfei; Zhang, Wenhai; Zhan, Xiayu; Yang, Dong; Jiang, Bobi; Yang, Jiamin; Liu, Shenye; Jiang, Shaoen; Li, Yongsheng; Liu, Jie; Huo, Wenyi; Lan, Ke

    2014-01-01

    An ultra-thin layer of uranium nitrides (UN) has been coated on the inner surface of the depleted uranium hohlraum (DUH), which has been proved by our experiment can prevent the oxidization of Uranium (U) effectively. Comparative experiments between the novel depleted uranium hohlraum and pure golden (Au) hohlraum are implemented on Shenguang III prototype laser facility. Under the laser intensity of 6*10^14 W/cm2, we observe that, the hard x-ray (> 1.8 keV) fraction of this uranium hohlraum decreases by 61% and the peak intensity of total x-ray flux (0.1 keV ~ 5 keV) increases by 5%. Two dimensional radiation hydrodynamic code LARED are exploited to interpret the above observations. Our result for the first time indicates the advantage of the UN-coated DUH in generating the uniform x-ray field with a quasi Planckian spectrum and thus has important implications in optimizing the ignition hohlraum design.

  18. 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.

  19. 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

  20. Gibbs free energy of reactions involving SiC, Si3N4, H2, and H2O as a function of temperature and pressure

    Science.gov (United States)

    Isham, M. A.

    1992-01-01

    Silicon carbide and silicon nitride are considered for application as structural materials and coating in advanced propulsion systems including nuclear thermal. Three-dimensional Gibbs free energy were constructed for reactions involving these materials in H2 and H2/H2O. Free energy plots are functions of temperature and pressure. Calculations used the definition of Gibbs free energy where the spontaneity of reactions is calculated as a function of temperature and pressure. Silicon carbide decomposes to Si and CH4 in pure H2 and forms a SiO2 scale in a wet atmosphere. Silicon nitride remains stable under all conditions. There was no apparent difference in reaction thermodynamics between ideal and Van der Waals treatment of gaseous species.

  1. Plasma nitriding of AISI 52100 ball bearing steel and effect of heat ...

    Indian Academy of Sciences (India)

    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 ...

  2. The efficiency of ion nitriding of austenitic stainless steel 304 using the “active screen”

    OpenAIRE

    M. Ogórek; Z. Skuza; T. Frączek

    2015-01-01

    The study examined layers were formed on the outer surface of austenitic stainless steel 304 under glow discharge conditions in the low-temperature and short-term ion nitriding. The outer layers analyzed in the work produced in parallel in the classical process of cathode and a novel method of “active screen”, intensifying the process of nitriding.

  3. The efficiency of ion nitriding of austenitic stainless steel 304 using the “active screen”

    Directory of Open Access Journals (Sweden)

    M. Ogórek

    2015-01-01

    Full Text Available The study examined layers were formed on the outer surface of austenitic stainless steel 304 under glow discharge conditions in the low-temperature and short-term ion nitriding. The outer layers analyzed in the work produced in parallel in the classical process of cathode and a novel method of “active screen”, intensifying the process of nitriding.

  4. Low noise high-Tc superconducting bolometers on silicon nitride membranes for far-infrared detection

    NARCIS (Netherlands)

    de Nivelle, M.J.M.E.; De Nivelle, M.J.M.E.; Bruijn, M.P.; de Vries, R.; Wijnbergen, J.J.; de Korte, P.A.J.; Sanchez, Stefan; Elwenspoek, Michael Curt; Heidenblut, T.; Schwierzi, B.; Michalke, W.; Steinbeiss, E.

    1997-01-01

    High-Tc GdBa2Cu3O7 – delta superconductor bolometers with operation temperatures near 89 K, large receiving areas of 0.95 mm2 and very high detectivity have been made. The bolometers are supported by 0.62 µm thick silicon nitride membranes. A specially developed silicon-on-nitride layer was used to

  5. Pretreatment Influence on Titanium Surface Properties After Gas Nitriding

    Science.gov (United States)

    Pohrelyuk, I. M.; Lavrys, S. M.; Sakharuk, O. M.; Stasyshyn, I. V.; Penkovyi, O. V.

    2017-10-01

    Influence of an initial mechanical treatment (grinding, polishing) on geometry and physical-mechanical parameters of a commercially pure titanium (Grade 2) surface after thermodiffusive saturation by nitrogen was studied. Microstructure analysis has shown that mechanism of formation and growth of a nitride film depends on the initial mechanical treatment. Nitriding under temperature of 750 °C does not influence practically the quality of ground surfaces and decreases it on one class for polished one. For higher saturation temperatures, surface quality has little dependence from the initial treatment. The best set of geometry and physical-mechanical characteristics belongs to the surface, which was initially polished and nitrided subsequently under 750 °C temperature, which provides its high wear resistance.

  6. Hard superconducting nitrides

    Science.gov (United States)

    Chen, Xiao-Jia; Struzhkin, Viktor V.; Wu, Zhigang; Somayazulu, Maddury; Qian, Jiang; Kung, Simon; Christensen, Axel Nørlund; Zhao, Yusheng; Cohen, Ronald E.; Mao, Ho-kwang; Hemley, Russell J.

    2005-01-01

    Detailed study of the equation of state, elasticity, and hardness of selected superconducting transition-metal nitrides reveals interesting correlations among their physical properties. Both the bulk modulus and Vickers hardness are found to decrease with increasing zero-pressure volume in NbN, HfN, and ZrN. The computed elastic constants from first principles satisfy c11 > c12 > c44 for NbN, but c11 > c44 > c12 for HfN and ZrN, which are in good agreement with the neutron scattering data. The cubic δ-NbN superconducting phase possesses a bulk modulus of 348 GPa, comparable to that of cubic boron nitride, and a Vickers hardness of 20 GPa, which is close to sapphire. Theoretical calculations for NbN show that all elastic moduli increase monotonically with increasing pressure. These results suggest technological applications of such materials in extreme environments. PMID:15728352

  7. Electrical anharmonicity and dampings contributions to Cl-H → stretching band in gaseous (CH3)2O…HCl complex: Quantum dynamic study and prediction of the temperature effects

    Science.gov (United States)

    Rekik, Najeh; Alshammari, Majid F.

    2017-06-01

    In a previous work (Rekik et al., 2017), we demonstrated the ability of a simple anharmonic model of the dipole moment function of the X-H stretching band to explain a set of spectroscopic features of hydrogen bonding formation. Within the context of this model, we have shown that the origins of the broadening of the X - H → stretching band is attributed to large terms in the expansion of the autocorrelation functions due to the electrical anharmonicity. However, the question remained as to the ability of this model to treat the more complex situation in which we take into account the relaxation mechanisms that look at the effect of the surroundings and thereby gives rise to signatures of the medium to the X - H → stretching band lineshapes. Thus, in the present study, we investigated this situation by envisaging that the direct relaxation mechanism is due to the coupling between the fluctuating local electric field and the dipole moment of the complex as rationalized by Rosh and Ratner and the indirect damping resulting from the interaction of the X - H → stretch with its environment via the H-bond bridge mode. Theoretical experiments show that mixing of all these effects results in a speard and complicated structure. Using an ensemble of physically sound parameters as input into this approach, we have captured the main features in the experimental Cl - H → band in gaseous (CH3)2O…HCl complex and shown that the direct relaxation entrains a broadening of the spectra and is capable of qualitatively capturing the main features in the experimental spectra and quantitatively capturing the characteristic time scale of the vibrational dynamics of the Cl - H → stretching band. Furthermore, due to the decent agreement obtained between the theoretical and experimental line shapes at 226 K, the evolution of the IR spectra with the varaiation of temperature is proposed. The findings gained herein underscore the utility of combining simultaneously the effects of

  8. 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).

  9. 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.

  10. Investigations on the Role of N2:(N2 + CH4) Ratio on the Growth of Hydrophobic Nanostructured Hydrogenated Carbon Nitride Thin Films by Plasma Enhanced Chemical Vapor Deposition at Low Temperature

    Science.gov (United States)

    Khanis, Noor Hamizah; Ritikos, Richard; Ahmad Kamal, Shafarina Azlinda; Abdul Rahman, Saadah

    2017-01-01

    Nanostructured hydrogenated carbon nitride (CNx:H) thin films were synthesized on a crystal silicon substrate at low deposition temperature by radio-frequency plasma-enhanced chemical vapor deposition (PECVD). Methane and nitrogen were the precursor gases used in this deposition process. The effects of N2 to the total gas flow rate ratio on the formation of CNx:H nanostructures were investigated. Field-emission scanning electron microscopy (FESEM), Auger electron spectroscopy (AES), Raman scattering, and Fourier transform of infrared spectroscopies (FTIR) were used to characterize the films. The atomic nitrogen to carbon ratio and sp2 bonds in the film structure showed a strong influence on its growth rate, and its overall structure is strongly influenced by even small changes in the N2:(N2 + CH4) ratio. The formation of fibrous CNx:H nanorod structures occurs at ratios of 0.7 and 0.75, which also shows improved surface hydrophobic characteristic. Analysis showed that significant presence of isonitrile bonds in a more ordered film structure were important criteria contributing to the formation of vertically-aligned nanorods. The hydrophobicity of the CNx:H surface improved with the enhancement in the vertical alignment and uniformity in the distribution of the fibrous nanorod structures. PMID:28772460

  11. 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...

  12. In situ gas analysis during the growth of hexagonal boron nitride from ammonia borane

    Science.gov (United States)

    Wood, Grace E.; Laker, Zachary P. L.; Marsden, Alexander J.; Bell, Gavin R.; Wilson, Neil R.

    2017-11-01

    Ammonia borane (NH3 :BH3 ) is commonly used as a stoichiometric source of nitrogen and boron for the growth of hexagonal boron nitride (h-BN) by chemical vapour deposition (CVD). We use in situ gas analysis by mass spectrometry to investigate the active chemical components that evolve when an ammonia borane source is heated, and study how these components change after flowing through the CVD growth furnace. This also gives insight into the catalytic effect of copper substrates used for CVD growth of h-BN. We find that in vacuum, even at 40 °C, gaseous amino borane and polyaminoborane fragments are evolved from the solid source; as the temperature of the ammonia borane source increases, the amount of all components increases but proportionally more of the higher mass components are present. Gas phase reactions change the gas composition after flowing through the CVD growth furnace, depending on the temperature of the growth furnace, with increased dehydrogenation at higher furnace temperatures. Further reactions are catalysed by the copper substrate, with decomposition of the higher mass components evident at furnace temperatures > 900 °C. Direct comparison with CVD h-BN growth suggests that the lower mass components produced by lower ammonia borane source temperatures are preferred for larger island sizes and that furnace temperatures higher than 900 °C are required in order to initiate the catalytic effects of the copper substrate. In situ gas analysis thus gives new insight into the CVD growth of h-BN, and similar methodology could be used to optimise and understand the growth of other two dimensional materials.

  13. 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.

  14. 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

  15. gaseous fuel production by anaerobic fungal degradation of banana ...

    African Journals Online (AJOL)

    JANICO

    Production and Collection of Gaseous Fuel. The prepared slurry was placed in a Vuchner filter flask (as reactor). The reactor was made airtight using plastic stopper and the outlet of the reactor was connected to a balloon using PVC tube. The degradation temperature was maintained at 330C using water bath within which ...

  16. Fusion bonding of silicon nitride surfaces

    DEFF Research Database (Denmark)

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

    2011-01-01

    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......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...

  17. 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.

  18. Molybdenum Oxide Nitrides of the Mo2(O,N,□)5 Type: On the Way to Mo2O5.

    Science.gov (United States)

    Weber, Dominik; Huber, Manop; Gorelik, Tatiana E; Abakumov, Artem M; Becker, Nils; Niehaus, Oliver; Schwickert, Christian; Culver, Sean P; Boysen, Hans; Senyshyn, Anatoliy; Pöttgen, Rainer; Dronskowski, Richard; Ressler, Thorsten; Kolb, Ute; Lerch, Martin

    2017-08-07

    Blue-colored molybdenum oxide nitrides of the Mo2(O,N,□)5 type were synthesized by direct nitridation of commercially available molybdenum trioxide with a mixture of gaseous ammonia and oxygen. Chemical composition, crystal structure, and stability of the obtained and hitherto unknown compounds are studied extensively. The average oxidation state of +5 for molybdenum is proven by Mo K near-edge X-ray absorption spectroscopy; the magnetic behavior is in agreement with compounds exhibiting MoVO6 units. The new materials are stable up to ∼773 K in an inert gas atmosphere. At higher temperatures, decomposition is observed. X-ray and neutron powder diffraction, electron diffraction, and high-resolution transmission electron microscopy reveal the structure to be related to VNb9O24.9-type phases, however, with severe disorder hampering full structure determination. Still, the results demonstrate the possibility of a future synthesis of the potential binary oxide Mo2O5. On the basis of these findings, a tentative suggestion on the crystal structure of the potential compound Mo2O5, backed by electronic-structure and phonon calculations from first principles, is given.

  19. Low energy consumption method for separating gaseous mixtures and in particular for medium purity oxygen production

    Science.gov (United States)

    Jujasz, Albert J.; Burkhart, James A.; Greenberg, Ralph

    1988-01-01

    A method for the separation of gaseous mixtures such as air and for producing medium purity oxygen, comprising compressing the gaseous mixture in a first compressor to about 3.9-4.1 atmospheres pressure, passing said compressed gaseous mixture in heat exchange relationship with sub-ambient temperature gaseous nitrogen, dividing the cooled, pressurized gaseous mixture into first and second streams, introducing the first stream into the high pressure chamber of a double rectification column, separating the gaseous mixture in the rectification column into a liquid oxygen-enriched stream and a gaseous nitrogen stream and supplying the gaseous nitrogen stream for cooling the compressed gaseous mixture, removing the liquid oxygen-enriched stream from the low pressure chamber of the rectification column and pumping the liquid, oxygen-enriched steam to a predetermined pressure, cooling the second stream, condensing the cooled second stream and evaporating the oxygen-enriched stream in an evaporator-condenser, delivering the condensed second stream to the high pressure chamber of the rectification column, and heating the oxygen-enriched stream and blending the oxygen-enriched stream with a compressed blend-air stream to the desired oxygen concentration.

  20. 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.

  1. Synthesis of boron nitride from boron containing poly (vinyl alcohol ...

    Indian Academy of Sciences (India)

    A ceramic precursor, prepared by condensation reaction from poly(vinyl alcohol) (PVA) and boric acid (H3BO3) in 1:1, 2:1 and 4:1 molar ratios, was synthesized as low temperature synthesis route for boron nitride ceramic. Samples were pyrolyzed at 850°C in nitrogen atmosphere followed by characterization using Fourier ...

  2. Enhanced thermoelectric properties in boron nitride quantum-dot

    Directory of Open Access Journals (Sweden)

    Changning Pan

    Full Text Available We have investigated the ballistic thermoelectric properties in boron nitride quantum dots by using the nonequilibrium Green’s function approach and the Landauer transport theory. The result shows that the phonon transport is substantially suppressed by the interface in the quantum dots. The resonant tunneling effect of electron leads to the fluctuations of the electronic conductance. It enhances significantly the Seebeck coefficient. Combined with the low thermal conductance of phonon, the high thermoelectric figure of merit ZT ∼0.78 can be obtained at room temperature T = 300 K and ZT ∼0.95 at low temperature T = 100 K. It is much higher than that of graphene quantum dots with the same geometry parameters, which is ZT ∼0.29 at room temperature T = 300 K and ZT ∼0.48 at low temperature T = 100 K. The underlying mechanism is that the boron nitride quantum dots possess higher thermopower and lower phonon thermal conductance than the graphene quantum dots. Thus the results indicate that the thermoelectric properties of boron nitride can be significantly enhanced by the quantum dot and are better than those of graphene. Keywords: Thermoelectric properties, Boron nitride quantum dot, Electron transport, Phonon transport

  3. Spin transport in fully hexagonal boron nitride encapsulated graphene

    NARCIS (Netherlands)

    Gurram, M.; Omar, S.; Zihlmann, S.; Makk, P.; Schoenenberger, C.; van Wees, B. J.

    2016-01-01

    We study fully hexagonal boron nitride (hBN) encapsulated graphene spin valve devices at room temperature. The device consists of a graphene channel encapsulated between two crystalline hBN flakes: thick-hBN flake as a bottom gate dielectric substrate which masks the charge impurities from SiO2/Si

  4. 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.

  5. Neutron diffraction and gravimetric study of the iron nitriding reaction under ammonia decomposition conditions.

    Science.gov (United States)

    Wood, Thomas J; Makepeace, Joshua W; David, William I F

    2017-10-18

    Ammonia decomposition over iron catalysts is known to be affected by whether the iron exists in elemental form or as a nitride. In situ neutron diffraction studies with simultaneous gravimetric analysis were performed on the nitriding and denitriding reactions of iron under ammonia decomposition conditions. The gravimetric analysis agrees well with the Rietveld analysis of the neutron diffraction data, both of which confirm that the form of the iron catalyst is strongly dependent on ammonia decomposition conditions. Use of ammonia with natural isotopic abundance as the nitriding agent means that the incoherent neutron scattering of any hydrogen within the gases present is able to be correlated to how much ammonia had decomposed. This novel analysis reveals that the nitriding of the iron occurred at exactly the same temperature as ammonia decomposition started. The iron nitriding and denitriding reactions are shown to be related to steps that take place during ammonia decomposition and the optimum conditions for ammonia decomposition over iron catalysts are discussed.

  6. Impurity-induced disorder in III-nitride materials and devices

    Science.gov (United States)

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

    2014-11-25

    A method for impurity-induced disordering in III-nitride materials comprises growing a III-nitride heterostructure at a growth temperature and doping the heterostructure layers with a dopant during or after the growth of the heterostructure and post-growth annealing of the heterostructure. The post-growth annealing temperature can be sufficiently high to induce disorder of the heterostructure layer interfaces.

  7. On the photon annealing of silicon-implanted gallium-nitride layers

    Energy Technology Data Exchange (ETDEWEB)

    Seleznev, B. I., E-mail: Boris.Seleznev@novsu.ru [Novgorod State University (Russian Federation); Moskalev, G. Ya. [OKB-Planeta, Inc. (Russian Federation); Fedorov, D. G. [Novgorod State University (Russian Federation)

    2016-06-15

    The conditions for the formation of ion-doped layers in gallium nitride upon the incorporation of silicon ions followed by photon annealing in the presence of silicon dioxide and nitride coatings are analyzed. The conditions of the formation of ion-doped layers with a high degree of impurity activation are established. The temperature dependences of the surface concentration and mobility of charge carriers in ion-doped GaN layers annealed at different temperatures are studied.

  8. 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.

  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. 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.

  11. Kinetic modelling of chlorination of nitrided ilmenite using MATLAB

    Energy Technology Data Exchange (ETDEWEB)

    Ramakrishnan, Sivakumar, E-mail: srsivakumar@usm.my; Kwok, Teong Chen, E-mail: ctck@live.com; Hamid, Sheikh Abdul Rezan Sheikh Abdul, E-mail: rezanshk@gmail.com [School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300, Nibong Tebal, Penang (Malaysia)

    2016-07-19

    In the present study, chlorination of nitride ilmenite using 2{sup k} factorial design was investigated. The reduction experiments were carried out in a temperature range of 400°C to 500°C, chlorination duration from 1 hour to 3 hours and using different type of carbon reactant. Phases of raw materials and reduced samples were analyzed by X-ray diffraction (XRD). Ilmenite was reduced to TiO{sub x}C{sub y}N{sub z} through carbothermal and nitridation for further chlorination into titanium tetrachloride. The Design of Experiment analysis suggested that the types of carbon reactant contribute most influence to the extent of chlorination of nitride ilmenite. The extent of chlorination was highest at 500°C with 3 hours chlorination time and carbon nanotube as carbon reactant.

  12. 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.

  13. 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.

  14. Nano boron nitride flatland.

    Science.gov (United States)

    Pakdel, Amir; Bando, Yoshio; Golberg, Dmitri

    2014-02-07

    Recent years have witnessed many breakthroughs in research on two-dimensional (2D) nanomaterials, among which is hexagonal boron nitride (h-BN), a layered material with a regular network of BN hexagons. This review provides an insight into the marvellous nano BN flatland, beginning with a concise introduction to BN and its low-dimensional nanostructures, followed by an overview of the past and current state of research on 2D BN nanostructures. A comprehensive review of the structural characteristics and synthetic routes of BN monolayers, multilayers, nanomeshes, nanowaves, nanoflakes, nanosheets and nanoribbons is presented. In addition, electronic, optical, thermal, mechanical, magnetic, piezoelectric, catalytic, ecological, biological and wetting properties, applications and research perspectives for these novel 2D nanomaterials are discussed.

  15. Nitride stabilized core/shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kuttiyiel, Kurian Abraham; Sasaki, Kotaro; Adzic, Radoslav R.

    2018-01-30

    Nitride stabilized metal nanoparticles and methods for their manufacture are disclosed. In one embodiment the metal nanoparticles have a continuous and nonporous noble metal shell with a nitride-stabilized non-noble metal core. The nitride-stabilized core provides a stabilizing effect under high oxidizing conditions suppressing the noble metal dissolution during potential cycling. The nitride stabilized nanoparticles may be fabricated by a process in which a core is coated with a shell layer that encapsulates the entire core. Introduction of nitrogen into the core by annealing produces metal nitride(s) that are less susceptible to dissolution during potential cycling under high oxidizing conditions.

  16. Room-temperature CW operation of a nitride-based vertical-cavity surface-emitting laser using thick GaInN quantum wells

    Science.gov (United States)

    Furuta, Takashi; Matsui, Kenjo; Horikawa, Kosuke; Ikeyama, Kazuki; Kozuka, Yugo; Yoshida, Shotaro; Akagi, Takanobu; Takeuchi, Tetsuya; Kamiyama, Satoshi; Iwaya, Motoaki; Akasaki, Isamu

    2016-05-01

    We demonstrated a room-temperature (RT) continuous-wave (CW) operation of a GaN-based vertical-cavity surface-emitting laser (VCSEL) using a thick GaInN quantum well (QW) active region and an AlInN/GaN distributed Bragg reflector. We first investigated the following two characteristics of a 6 nm GaInN 5 QWs active region in light-emitting diode (LED) structures. The light output power at a high current density (∼10 kA/cm2) from the 6 nm GaInN 5 QWs was the same or even higher than that from standard 3 nm 5 QWs. In addition, we found that hole injection into the farthest QW from a p-layer was sufficient. We then demonstrated a GaN-based VCSEL with the 6 nm 5 QWs, resulting in the optical confinement factor of 3.5%. The threshold current density under CW operation at RT was 7.5 kA/cm2 with a narrow (0.4 nm) emission spectrum of 413.5 nm peak wavelength.

  17. β-Molybdenum nitride: synthesis mechanism and catalytic response in the gas phase hydrogenation of p-chloronitrobenzene

    NARCIS (Netherlands)

    Cárdenas-Lizana, F.; Gómez-Quero, S.; Perret, N.; Kiwi-Minsker, L.; Keane, M.A.

    2011-01-01

    A temperature programmed treatment of MoO3 in flowing N2 + H2 has been employed to prepare β-phase molybdenum nitride (β-Mo2N) which has been used to promote, for the first time, the catalytic hydrogenation of p-chloronitrobenzene. The reduction/nitridation synthesis steps have been monitored in

  18. 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.

  19. Gaseous Electron Multiplier (GEM) Detectors

    Science.gov (United States)

    Gnanvo, Kondo

    2017-09-01

    Gaseous detectors have played a pivotal role as tracking devices in the field of particle physics experiments for the last fifty years. Recent advances in photolithography and micro processing techniques have enabled the transition from Multi Wire Proportional Chambers (MWPCs) and Drift Chambers to a new family of gaseous detectors refer to as Micro Pattern Gaseous Detectors (MPGDs). MPGDs combine the basic gas amplification principle with micro-structure printed circuits to provide detectors with excellent spatial and time resolution, high rate capability, low material budget and high radiation tolerance. Gas Electron Multiplier (GEMs) is a well-established MPGD technology invented by F. Sauli at CERN in 1997 and deployed various high energy physics (HEP) and nuclear NP experiment for tracking systems of current and future NP experiments. GEM detector combines an exceptional high rate capability (1 MHz / mm2) and robustness against harsh radiation environment with excellent position and timing resolution performances. Recent breakthroughs over the past decade have allowed the possibility for large area GEMs, making them cost effective and high-performance detector candidates to play pivotal role in current and future particle physics experiments. After a brief introduction of the basic principle of GEM technology, I will give a brief overview of the GEM detectors used in particle physics experiments over the past decades and especially in the NP community at Thomas Jefferson National Laboratory (JLab) and Brookhaven National Laboratory (BNL). I will follow by a review of state of the art of the new GEM development for the next generation of colliders such as Electron Ion Collider (EIC) or High Luminosity LHC and future Nuclear Physics experiments. I will conclude with a presentation of the CERN-based RD51 collaboration established in 2008 and its major achievements regarding technological developments and applications of MPGDs.

  20. 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.

  1. 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...

  2. Silicon Nitride Bearings for Total Joint Arthroplasty

    National Research Council Canada - National Science Library

    McEntire, Bryan; Lakshminarayanan, Ramaswamy; Ray, Darin; Clarke, Ian; Puppulin, Leonardo; Pezzotti, Giuseppe

    2016-01-01

      The articulation performance of silicon nitride against conventional and highly cross-linked polyethylene, as well as for self-mated silicon nitride bearings, was examined in a series of standard hip simulation studies...

  3. Use of high-thermal conductive aluminum nitride based ceramics in vacuum UHF electronic devices

    Directory of Open Access Journals (Sweden)

    Chasnyk V. I.

    2013-06-01

    Full Text Available Analysis of properties and characteristics of the alumina, beryllium oxide and aluminum nitride based ceramic materials used in UHF electronic devices has been made. It was shown that the complex of parameters including structural and functional characteristics of the high-thermal conductive aluminum nitride ceramics prevail over all types of alumina ceramics and is not lower than the same characteristics of the beryllium oxide ceramics especially at the temperatures higher than 450 °C. The examples of the prevailing use of the aluminum nitride ceramics inside vacuum UHF-region devices: TWT’s and klystrons.

  4. Hydrogen and Gaseous Fuel Safety and Toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Lee C. Cadwallader; J. Sephen Herring

    2007-06-01

    Non-traditional motor fuels are receiving increased attention and use. This paper examines the safety of three alternative gaseous fuels plus gasoline and the advantages and disadvantages of each. The gaseous fuels are hydrogen, methane (natural gas), and propane. Qualitatively, the overall risks of the four fuels should be close. Gasoline is the most toxic. For small leaks, hydrogen has the highest ignition probability and the gaseous fuels have the highest risk of a burning jet or cloud.

  5. 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).

  6. Plasma nitriding of CA-6NM steel: effect of H2 + N2 gas mixtures in nitride layer formation for low N2 contents at 500 ºC

    Directory of Open Access Journals (Sweden)

    Angela Nardelli Allenstein

    2010-12-01

    Full Text Available This work aims to characterize the phases, thickness, hardness and hardness profiles of the nitride layers formed on the CA-6NM martensitic stainless steel which was plasma nitrided in gas mixtures containing different nitrogen amounts. Nitriding was performed at 500 ºC temperature, and 532 Pa (4 Torr pressure, for gas mixtures of 5% N2 + 95% H2, 10% N2 + 90% H2, and 20% N2 + 80% H2, and 2 hours nitriding time. A 6 hours nitriding time condition for gas mixture of 5% N2 + 95% H2 was also studied. Nitrided samples results were compared with non-nitrided condition. Thickness and microstructure of the nitrided layers were characterized by optical microscopy (OM, using Villela and Nital etchants, and the phases were identified by X-ray diffraction. Hardness profiles and hardness measured on surface steel were determined using Vickers hardness and nanoindentation tester, respectively. It was verified that nitrided layer produced in CA-6NM martensitc stainless steel is constituted of compound layer, being that formation of the diffusion zone was not observed for the studied conditions. The higher the nitrogen amounts in gas mixture the higher is the thickness of the nitrided layer and the probability to form different nitride phases, in the case γ'-Fe4N, ε-Fe2-3N and CrN phases. Intrinsic hardness of the nitrided layers produced in the CA-6NM stainless steel is about 12-14 GPa (~1200-1400 HV.

  7. 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. Energy-filtered...... TEM images and XPS results showed that oxygen was replaced by nitrogen. In contrast to nanoscale processing challenges of refractory TiN, well-understood material synthesis of TiO2 provides an attractive route to large-scale fabrication of refractory plasmonic materials with complex designs...

  8. Improved silicon nitride for advanced heat engines

    Science.gov (United States)

    Yeh, Harry C.; Fang, Ho T.

    1991-01-01

    The results of a four year program to improve the strength and reliability of injection-molded silicon nitride are summarized. Statistically designed processing experiments were performed to identify and optimize critical processing parameters and compositions. Process improvements were monitored by strength testing at room and elevated temperatures, and microstructural characterization by optical, scanning electron microscopes, and scanning transmission electron microscope. Processing modifications resulted in a 20 percent strength and 72 percent Weibull slope improvement of the baseline material. Additional sintering aids screening and optimization experiments succeeded in developing a new composition (GN-10) capable of 581.2 MPa at 1399 C. A SiC whisker toughened composite using this material as a matrix achieved a room temperature toughness of 6.9 MPa m(exp .5) by the Chevron notched bar technique. Exploratory experiments were conducted on injection molding of turbocharger rotors.

  9. A boron nitride nanotube peapod thermal rectifier

    Energy Technology Data Exchange (ETDEWEB)

    Loh, G. C., E-mail: jgloh@mtu.edu [Department of Physics, Michigan Technological University, Houghton, Michigan 49931 (United States); Institute of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632 (Singapore); Baillargeat, D. [CNRS-International-NTU-Thales Research Alliance (CINTRA), 50 Nanyang Drive, Singapore 637553 (Singapore)

    2014-06-28

    The precise guidance of heat from one specific location to another is paramount in many industrial and commercial applications, including thermal management and thermoelectric generation. One of the cardinal requirements is a preferential conduction of thermal energy, also known as thermal rectification, in the materials. This study introduces a novel nanomaterial for rectifying heat—the boron nitride nanotube peapod thermal rectifier. Classical non-equilibrium molecular dynamics simulations are performed on this nanomaterial, and interestingly, the strength of the rectification phenomenon is dissimilar at different operating temperatures. This is due to the contingence of the thermal flux on the conductance at the localized region around the scatterer, which varies with temperature. The rectification performance of the peapod rectifier is inherently dependent on its asymmetry. Last but not least, the favourable rectifying direction in the nanomaterial is established.

  10. 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.

  11. 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.

  12. Study of total ionization by {alpha} particles, in pure gases and gaseous mixtures containing metastable atoms, as a function of temperature; Etude de l'ionisation totale par les paricules {alpha}, dans les gaz purs et les melanges gazeux contenant des atomes metastables, en fonction de la temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bristeau, P. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    Experiments have been carried out on the total ionization by alpha particles, in pure gases and gaseous mixtures containing metastable atoms, as a function of temperature. Using a different experimental method, the results for the mean ionization energy at 300 K given by Jesse in 1953 have been confirmed to within 1 per cent. It is established that in pure gases the mean energy W required to form a pair of ions remains constant as the temperature varies from 77 to 300 K. It is shown that there is a temperature effect for W in binary gas mixtures of the type A-B containing meta-stable atoms A{sup *} and an 'impurity' B. A systematic study is made of the change {delta}W in W as a function of the temperature and of the B 'impurity' concentration in the mixtures Ne - Ar, Ne - Kr, Ne - H{sub 2}, Ne - N{sub 2}, Ne - CH{sub 4} and He - Ar. Experiments have been carried out on a ternary gas mixture of the type A - B - C, where C is a second ionizable 'impurity' added to the binary mixture A - B; they show the existence of excited atoms B{sup *} formed from the 'impurity' B. Finally, it is shown that the amount of metastable atoms formed in a pure gas must be very close to the number N{sub 0} of ion pairs, and that there must exist a correlation between the number N{sub 0} of ion pairs and the number {approx_equal} N{sub 0} of metastable atoms created in the pure rare gases. (author) [French] On realise des experiences sur l'ionisation totale par les particules alpha, dans les gaz purs et les melanges gazeux contenant des atomes metastables, en fonction de la temperature. Avec une methode experimentale differente, on retrouve a mieux que 1 pour cent pres les valeurs de l'energie moyenne d'ionisation que JESSE a obtenues en 1953 et a 300 K. On etablit que dans les gaz purs, l'energie moyenne W pour creer une paire d'ions demeure constante, quand la temperature varie entre 77 et 300 K. On met en evidence un

  13. Gaseous emissions from waste combustion.

    Science.gov (United States)

    Werther, Joachim

    2007-06-18

    An overview is given on methods and technologies for limiting the gaseous emissions from waste combustion. With the guideline 2000/76/EC recent European legislation has set stringent limits not only for the mono-combustion of waste in specialized incineration plants but also for co-combustion in coal-fired power plants. With increased awareness of environmental issues and stepwise decrease of emission limits and inclusion of more and more substances into the network of regulations a multitude of emission abatement methods and technologies have been developed over the last decades. The result is the state-of-the-art waste incinerator with a number of specialized process steps for the individual components in the flue gas. The present work highlights some new developments which can be summarized under the common goal of reducing the costs of flue gas treatment by applying systems which combine the treatment of several noxious substances in one reactor or by taking new, simpler routes instead of the previously used complicated ones or - in the case of flue gas desulphurisation - by reducing the amount of limestone consumption. Cost reduction is also the driving force for new processes of conditioning of nonhomogenous waste before combustion. Pyrolysis or gasification is used for chemical conditioning whereas physical conditioning means comminution, classification and sorting processes. Conditioning yields a fuel which can be used in power plants either as a co-fuel or a mono-fuel and which will burn there under much better controlled conditions and therefore with less emissions than the nonhomogeneous waste in a conventional waste incinerator. Also for cost reasons, co-combustion of wastes in coal-fired power stations is strongly pressing into the market. Recent investigations reveal that the co-firing of waste can also have beneficial effects on the operating behavior of the boiler and on the gaseous emissions.

  14. 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.

  15. Copper atoms embedded in hexagonal boron nitride as potential catalysts for CO oxidation: A first-principles investigation

    KAUST Repository

    Liu, Xin

    2014-01-01

    We addressed the electronic structure of Cu atoms embedded in hexagonal boron nitride (h-BN) and their catalytic role in CO oxidation by first-principles-based calculations. We showed that Cu atoms prefer to bind directly with the localized defects on h-BN, which act as strong trapping sites for Cu atoms and inhibit their clustering. The strong binding of Cu atoms at boron vacancy also up-shifts the energy level of Cu-d states to the Fermi level and promotes the formation of peroxide-like intermediate. CO oxidation over Cu atoms embedded in h-BN would proceed through the Langmuir-Hinshelwood mechanism with the formation of a peroxide-like complex by reaction of coadsorbed CO and O2, with the dissociation of which the a CO2 molecule and an adsorbed O atom are formed. Then, the embedded Cu atom is regenerated by the reaction of another gaseous CO with the remnant O atom. The calculated energy barriers for the formation and dissociation of peroxide complex and regeneration of embedded Cu atoms are as low as 0.26, 0.11 and 0.03 eV, respectively, indicating the potential high catalytic performance of Cu atoms embedded in h-BN for low temperature CO oxidation. © the Partner Organisations 2014.

  16. 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.

  17. 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.

  18. 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.

  19. Parameter Optimization of Nitriding Process Using Chemical Kinetics

    Science.gov (United States)

    Özdemir, İ. Bedii; Akar, Firat; Lippmann, Nils

    2016-12-01

    Using the dynamics of chemical kinetics, an investigation to search for an optimum condition for a gas nitriding process is performed over the solution space spanned by the initial temperature and gas composition of the furnace. For a two-component furnace atmosphere, the results are presented in temporal variations of gas concentrations and the nitrogen coverage on the surface. It seems that the exploitation of the nitriding kinetics can provide important feedback for setting the model-based control algorithms. The present work shows that when the nitrogen gas concentration is not allowed to exceed 6 pct, the Nad coverage can attain maximum values as high as 0.97. The time evolution of the Nad coverage also reveals that, as long as the temperature is above the value where nitrogen poisoning of the surface due to the low-temperature adsorption of excess nitrogen occurs, the initial ammonia content in the furnace atmosphere is much more important in the nitriding process than is the initial temperature.

  20. Effect of SPD surface layer on plasma nitriding of Ti–6Al–4V alloy

    Energy Technology Data Exchange (ETDEWEB)

    Farokhzadeh, K.; Qian, J.; Edrisy, A., E-mail: edrisy@uwindsor.ca

    2014-01-01

    A severe plastic deformation (SPD) surface layer was introduced by shot peening to enhance the nitriding kinetics in low-temperature (600 °C) plasma nitriding of Ti–6Al–4V alloy. The effect of this pretreatment on the nitrided microstructures and phase compositions was investigated by analytical microscopy techniques e.g. scanning and transmission electron microscopy (SEM, TEM) and X-ray diffraction (XRD) analysis. Microstructural investigations revealed the formation of a compound layer consisting of a 0.6 µm thick nanocrystalline TiN layer followed by a 0.5 µm thick layer of Ti{sub 2}N with a larger grain size (0.1–0.5 µm). The development of TiN nanograins was attributed to accelerated nitriding kinetics due to the increased preferential nucleation sites in the SPD layer. Furthermore, the thickness of nitrogen diffusion zone (DZ) increased by 50% in the pretreated plasma nitrided alloy when compared with that of the untreated one. This is likely promoted by an increase in density of subsurface microstructural defects, such as twins and grain boundaries. The sliding behaviour and interfacial adhesion of the nitrided surfaces were evaluated by micro-scratch tests within a load range of 1–20 N. Compared with untreated-plasma-nitrided alloy, the pretreated nitrided surfaces exhibited a higher load bearing capacity and better interfacial bonding. They exhibited no chipping or spallation, even after multiple sliding passes at the highest applied load of 20 N in contrary to the untreated plasma nitrided surfaces.

  1. Silicon nitride microwave photonic circuits

    NARCIS (Netherlands)

    Roeloffzen, C.G.H.; Zhuang, L.; Taddei, Caterina; Taddei, Caterina; Leinse, Arne; Heideman, Rene; van Dijk, Paulus W.L.; Oldenbeuving, Ruud; Marpaung, D.A.I.; Burla, M.; Buria, Maurizio; Boller, Klaus J.

    2013-01-01

    We present an overview of several microwave photonic processing functionalities based on combinations of Mach-Zehnder and ring resonator filters using the high index contrast silicon nitride (TriPleXTM) waveguide technology. All functionalities are built using the same basic building blocks, namely

  2. Waste conversion into high-value ceramics: Carbothermal nitridation synthesis of titanium nitride nanoparticles using automotive shredder waste.

    Science.gov (United States)

    Mayyas, Mohannad; Pahlevani, Farshid; Maroufi, Samane; Liu, Zhao; Sahajwalla, Veena

    2017-03-01

    Environmental concern about automotive shredder residue (ASR) has increased in recent years due to its harmful content of heavy metals. Although several approaches of ASR management have been suggested, these approaches remain commercially unproven. This study presents an alternative approach for ASR management where advanced materials can be generated as a by-product. In this approach, titanium nitride (TiN) has been thermally synthesized by nitriding pressed mixture of automotive shredder residue (ASR) and titanium oxide (TiO 2 ). Interactions between TiO 2 and ASR at non-isothermal conditions were primarily investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry. Results indicated that TiO 2 influences and catalyses degradation reactions of ASR, and the temperature, at which reduction starts, was determined around 980 °C. The interaction between TiO 2 and ASR at isothermal conditions in the temperature range between 1200 and 1550 °C was also studied. The pressed mixture of both materials resulted in titanium nitride (TiN) ceramic at all given temperatures. Formation kinetics were extracted using several models for product layer diffusion-controlled solid-solid and solid-fluid reactions. The effect of reactants ratio and temperature on the degree of conversion and morphology was investigated. The effect of reactants ratio was found to have considerable effect on the morphology of the resulting material, while temperature had a lesser impact. Several unique structures of TiN (porous nanostructured, polycrystalline, micro-spherical and nano-sized structures) were obtained by simply tuning the ratio of TiO 2 to ASR, and a product with appreciable TiN content of around 85% was achieved after only one hour nitridation at 1550 °C. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Transition-Metal Nitride Core@Noble-Metal Shell Nanoparticles as Highly CO Tolerant Catalysts.

    Science.gov (United States)

    Garg, Aaron; Milina, Maria; Ball, Madelyn; Zanchet, Daniela; Hunt, Sean T; Dumesic, James A; Román-Leshkov, Yuriy

    2017-07-17

    Core-shell architectures offer an effective way to tune and enhance the properties of noble-metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core-shell carbide material (Pt/TiWC). X-ray photoelectron spectroscopy revealed significant core-level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d-states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO. The ability to control shell coverage and vary the heterometallic composition of the shell and nitride core opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Corrosion Behavior of Active Screen Plasma Nitrided 38CrMoAl Steel under Marine Environment

    Science.gov (United States)

    Yang, Li; He, Yongyong; Mao, JunYuan; Zhang, Lei

    2017-10-01

    The 38CrMoAl steels were nitrided at different temperatures for 7 h using active screen plasma discharge. The analysis showed that the thick compound layer composed of ε-Fe2–3N and γ‧-Fe4N was formed on the surface. The corrosion behavior was evaluated by measuring the anodic polarization curves in natural sea water (similar 3.5% NaCl solution), and observation of corroded surface were conducted. The electromechanical measurements indicated that the corrosion potential of the nitrided specimens shifted to a nobler value compared to that of untreated specimens. Passive regions were also observed in the polarization curves for all the nitrided specimens. These results indicate that active screen plasma nitriding can enhance the corrosion resistance of the 38CrMoAl steel under marine environment.

  5. Single photon emitters in boron nitride: More than a supplementary material

    Science.gov (United States)

    Koperski, M.; Nogajewski, K.; Potemski, M.

    2018-03-01

    We present comprehensive optical studies of recently discovered single photon sources in boron nitride, which appear in form of narrow lines emitting centres. Here, we aim to compactly characterise their basic optical properties, including the demonstration of several novel findings, in order to inspire discussion about their origin and utility. Initial inspection reveals the presence of narrow emission lines in boron nitride powder and exfoliated flakes of hexagonal boron nitride deposited on Si/SiO2 substrates. Generally rather stable, the boron nitride emitters constitute a good quality visible light source. However, as briefly discussed, certain specimens reveal a peculiar type of blinking effects, which are likely related to existence of meta-stable electronic states. More advanced characterisation of representative stable emitting centres uncovers a strong dependence of the emission intensity on the energy and polarisation of excitation. On this basis, we speculate that rather strict excitation selectivity is an important factor determining the character of the emission spectra, which allows the observation of single and well-isolated emitters. Finally, we investigate the properties of the emitting centres in varying external conditions. Quite surprisingly, it is found that the application of a magnetic field introduces no change in the emission spectra of boron nitride emitters. Further analysis of the impact of temperature on the emission spectra and the features seen in second-order correlation functions is used to provide an assessment of the potential functionality of boron nitride emitters as single photon sources capable of room temperature operation.

  6. An Annotated Bibliography on Silicon Nitride for Structural Applications

    Science.gov (United States)

    1977-03-01

    microscopy. The major oxidation product is cristobalite which forms around internal pores (Stage I) and eventually as a dense surface layer (Stage II...specimen is not cooled through the cristobalite inversion temperature at ~250 C. 21. Engel, W., Gugel, E., and Thuemmler, F., "Fluage du niture de...the reaction. 35. Grieveson, P., Jack, K. H., and Wild, S., "The Crystal Structures of Alpha and Beta Silicon and Germanium Nitrides", Special

  7. Refractory plasmonics with titanium nitride: broadband metamaterial absorber.

    Science.gov (United States)

    Li, Wei; Guler, Urcan; Kinsey, Nathaniel; Naik, Gururaj V; Boltasseva, Alexandra; Guan, Jianguo; Shalaev, Vladimir M; Kildishev, Alexander V

    2014-12-17

    A high-temperature stable broadband plasmonic absorber is designed, fabricated, and optically characterized. A broadband absorber with an average high absorption of 95% and a total thickness of 240 nm is fabricated, using a refractory plasmonic material, titanium nitride. This absorber integrates both the plasmonic resonances and the dielectric-like loss. It opens a path for the interesting applications such as solar thermophotovoltaics and optical circuits. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Supramolecular intermediates in the synthesis of polymeric carbon nitride from melamine cyanurate

    Energy Technology Data Exchange (ETDEWEB)

    Dante, Roberto C., E-mail: rcdante@yahoo.com [Facultad de Mecánica, Escuela Politécnica Nacional (EPN), Ladrón de Guevara E11-253, Quito (Ecuador); Sánchez-Arévalo, Francisco M. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, Apdo. Postal 70-360, Cd. Universitaria, Mexico D.F. 04510 (Mexico); Chamorro-Posada, Pedro [Dpto. de Teoría de la Señal y Comunicaciones e IT, Universidad de Valladolid, ETSI Telecomunicación, Paseo Belén 15, 47011 Valladolid (Spain); Vázquez-Cabo, José [Dpto. de Teoría de la Señal y Comunicaciones, Universidad de Vigo, ETSI Telecomunicación, Lagoas Marcosende s/n, Vigo (Spain); Huerta, Lazaro [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, Apdo. Postal 70-360, Cd. Universitaria, Mexico D.F. 04510 (Mexico); Lartundo-Rojas, Luis [Centro de Nanociencias y Micro y Nanotecnologías—IPN, Luis Enrique Erro s/n, U. Prof. Adolfo López Mateos, 07738 Ciudad de Mexico, Distrito Federal (Mexico); Santoyo-Salazar, Jaime [Departamento de Física, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, CINVESTAV-IPN, Apdo. Postal 14-740, Mexico D.F. 07360 (Mexico); and others

    2015-03-15

    The adduct of melamine and cyanuric acid (MCA) was used in past research to produce polymeric carbon nitride and precursors. The reaction yield was considerably incremented by the addition of sulfuric acid. The polymeric carbon nitride formation occurs around 450 °C at temperatures above the sublimation of the adduct components, which occurs around 400 °C. In this report the effect of sulfuric acid on MCA was investigated. It was found that the MCA rosette supramolecular channel structures behave as a solid solvent able to host small molecules, such as sulfuric acid, inside these channels and interact with them. Therefore, the sulfuric acid effect was found to be close to that of a solute that causes a temperature increment of the “solvent sublimation” enough to allowing the formation of polymeric carbon nitride to occur. Sulfate ions are presumably hosted in the rosette channels of MCA as shown by simulations. - Graphical abstract: The blend of melamine cyanurate and sulfuric acid behaves like a solution so that melamine cyanurate decomposition is shifted to temperatures high enough to react and form polymeric carbon nitride. - Highlights: • The adduct of melamine and cyanuric acid behaves as a solid solvent. • The blend of sulfuric acid and melamine cyanurate behaves like a solution. • Melamine cyanurate decomposition is shifted to higher temperatures by sulfuric acid. • The formation of polymeric carbon nitride occurs for these higher temperatures.

  9. 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...

  10. 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.

  11. 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.

  12. 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; hide

    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.

  13. 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.

  14. Gaseous Nitrogen Orifice Mass Flow Calculator

    Science.gov (United States)

    Ritrivi, Charles

    2013-01-01

    The Gaseous Nitrogen (GN2) Orifice Mass Flow Calculator was used to determine Space Shuttle Orbiter Water Spray Boiler (WSB) GN2 high-pressure tank source depletion rates for various leak scenarios, and the ability of the GN2 consumables to support cooling of Auxiliary Power Unit (APU) lubrication during entry. The data was used to support flight rationale concerning loss of an orbiter APU/hydraulic system and mission work-arounds. The GN2 mass flow-rate calculator standardizes a method for rapid assessment of GN2 mass flow through various orifice sizes for various discharge coefficients, delta pressures, and temperatures. The calculator utilizes a 0.9-lb (0.4 kg) GN2 source regulated to 40 psia (.276 kPa). These parameters correspond to the Space Shuttle WSB GN2 Source and Water Tank Bellows, but can be changed in the spreadsheet to accommodate any system parameters. The calculator can be used to analyze a leak source, leak rate, gas consumables depletion time, and puncture diameter that simulates the measured GN2 system pressure drop.

  15. Zinc nitride thin films: basic properties and applications

    Science.gov (United States)

    Redondo-Cubero, A.; Gómez-Castaño, M.; García Núñez, C.; Domínguez, M.; Vázquez, L.; Pau, J. L.

    2017-02-01

    Zinc nitride films can be deposited by radio frequency magnetron sputtering using a Zn target at substrate temperatures lower than 250°C. This low deposition temperature makes the material compatible with flexible substrates. The asgrown layers present a black color, polycrystalline structures, large conductivities, and large visible light absorption. Different studies have reported about the severe oxidation of the layers in ambient conditions. Different compositional, structural and optical characterization techniques have shown that the films turn into ZnO polycrystalline layers, showing visible transparency and semi-insulating properties after total transformation. The oxidation rate is fairly constant as a function of time and depends on environmental parameters such as relative humidity or temperature. Taking advantage of those properties, potential applications of zinc nitride films in environmental sensing have been studied in the recent years. This work reviews the state-of-the-art of the zinc nitride technology and the development of several devices such as humidity indicators, thin film (photo)transistors and sweat monitoring sensors.

  16. Alternative gaseous fuels safety assessment

    Energy Technology Data Exchange (ETDEWEB)

    Krupka, M.C.; Laquer, H.L.; Peaslee, A.T.

    1983-12-01

    Public acceptance of alternative transportation fuels in the United States is contingent not only upon the requisite technical, environmental, and economic factors but also upon demonstration through adequate assessment, testing, and operational experience that the intrinsic risk is either equivalent to or less than that associated with energy carriers presently in common use. In support of work sponsored by the Office of Vehicle and Engine R and D of the Department of Energy, a relative safety assessment of alternative gaseous and reference liquid fuels utilized for light automotive transportation in the public sector was completed. The specific fuels considered were compressed natural gas (CNG); liquefied natural gas (LNG); liquefied petroleum gas (LPG); and the liquid fuels, gasoline and diesel. The assessment methodology describes and develops the relative hazards of these fuels from an integrated generic physicochemical property and accident scenario point of view. A technique involving a method of eliciting expert judgment combined with a comparative scoring methodology was applied in establishing fuel relative safety rankings.

  17. 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...

  18. Physical Chemistry of Energetic Nitrides.

    Science.gov (United States)

    1987-05-28

    ZIP Cod.) 10. SOURCE OP PUNOING NOS. PROGRAM PROJECT TASK WORK UNIT Boiling AFB DC 203320 NONONO 11. TITLE (include Security CIaa~feieoi 611(J2F 0...streams of gaseous CINCO and BrNCO were prepared by using the method outlined by Frost and co-workers. 2 7 In brief, streams of C1 2 or Br 2 heavily...the isocyanates as found 27 by Frost , et. al. 2. Photochemistry of ClNCO The UV-VUV absorption spectrum recorded for gaseous CINCO is shown in Figure

  19. Soft magnetism in nitrided Fe93Ni4Cr3 and Fe94Ni4T2 cold-rolled alloys

    NARCIS (Netherlands)

    Craus, CB; Chezan, AR; Chechenin, NG; Boerma, DO; Niesen, L

    The magnetic properties in relation with the structure of nitrided cold-rolled Fe93Ni4Cr3 and Fe94Ni4Ti2 were studied. Various low-temperature nitriding treatments were applied in order to obtain soft magnetic materials. We show that the magnetic anisotropy depends sensitively on the nitrogen

  20. 7th International Symposium on Gaseous Dielectrics

    CERN Document Server

    James, David

    1994-01-01

    The Seventh International Symposium on Gaseous Dielectrics was held in Knoxville, Tennessee, U. S. A. , on April 24-28, 1994. The symposium continued the interdisciplinary character and comprehensive approach of the preceding six symposia. Gaseous DielecIries VII is a detailed record of the symposium proceedings. It covers recent advances and developments in a wide range of basic, applied and industrial areas of gaseous dielectrics. It is hoped that Gaseous DielecIries VII will aid future research and development in, and encourage wider industrial use of, gaseous dielectrics. The Organizing Committee of the Seventh International Symposium on Gaseous Dielectrics consisted of G. Addis (U. S. A. ), L. G. Christophorou (U. S. A. ), F. Y. Chu (Canada), A. H. Cookson (U. S. A. ), O. Farish (U. K. ), I. Gallimberti (Italy) , A. Garscadden (U. S. A. ), D. R. James (U. S. A. ), E. Marode (France), T. Nitta (Japan), W. Pfeiffer (Germany), Y. Qiu (China), I. Sauers (U. S. A. ), R. J. Van Brunt (U. S. A. ), and W. Zaengl...

  1. Theoretical investigation of chemical and physical properties of gaseous fuels

    Energy Technology Data Exchange (ETDEWEB)

    Hermann, Fredrik

    1999-12-01

    This thesis is discussing the chemical and physical properties of different gaseous fuels. A mapping of about seventy gaseous fuels resulted in eleven type gases, these gases have mainly five components (inerts, H{sub 2}, CO, CH{sub 4} and higher order of hydrocarbons) of different quantities. Calculations of heating value and Wobbe number have been done. Dew point temperatures have been estimated by using three different programs. Flammability limits, laminar flame speed and auto ignition temperatures have been calculated by using a kinetic and chemical program developed by Mauss. Flammability limits have been compared with Le Chatelier's law and measurements. Problems related to combustion such as flash back, lift off and instability are closely connected with flame speed and flow patterns. These problems are discussed in terms of laminar flame speed and Reynolds' number. The main results of this study were: Auto ignition temperature for gas mixtures behavior is very complex and unpredictable. In general small quantities of hydrogen decrease the temperature of auto ignition. The calculations of flammability limits by the kinetic and chemical software showed good agreement to measurements. Low Btu gases requires large flow area in order to avoid large pressure drop.

  2. 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.

  3. 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.

  4. Comment on “High-temperature soft magnetic properties of antiperovskite nitrides ZnNFe{sub 3} and AlNFe{sub 3}” by Yankun Fu, Shuai Lin, and Bosen Wang, J. Magn. Magn. Mater. 378 (2015) 54–58

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, T. [Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, Landoltweg 1, RWTH Aachen University, D-52056 Aachen (Germany); Leineweber, A. [Institute of Materials Science, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 5, D-09599 Freiberg (Germany); Dronskowski, R., E-mail: drons@HAL9000.ac.rwth-aachen.de [Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, Landoltweg 1, RWTH Aachen University, D-52056 Aachen (Germany)

    2016-10-15

    The authors of the aforementioned manuscript have recently claimed the synthesis of the ternary nitrides ZnNFe{sub 3} (=ZnFe{sub 3}N) and AlNFe{sub 3} (=AlFe{sub 3}N), ordered substituted variants of the binary phase γ‘-Fe{sub 4}N [1]. While soft ferromagnets of such kind are presently attracting lots of attention, their history dates back for more than half a century. In particular, Al-substituted γ‘-Fe{sub 4}N has already been mentioned in 1961 [2], and the existence of AlFe{sub 3}N has also been claimed in 2009 [3] from a two-step ammonolysis reaction combining a high-temperature sintering step and a low-temperature nitriding reaction [4]. Nonetheless, one of us had to withdraw the latter claim after finding out, by means of scanning-electron microscopy and elemental mapping, that all samples of “AlFe{sub 3}N” consisted of an intimate solid mixture of γ‘-Fe{sub 4}N and amorphous Al{sub 2}O{sub 3}[5]. From what follows, we have strong reasons to believe that the authors of Ref. [1] overlooked our findings [5] and also did not synthesize ZnFe{sub 3}N and AlFe{sub 3}N. - Highlights: • The synthesis of ZnFe{sub 3}N and AlFe{sub 3}N is questioned. • The diffraction data of ZnFe{sub 3}N and AlFe{sub 3}N resemble those of Fe{sub 4}N. • The magnetic data of ZnFe{sub 3}N and AlFe{sub 3}N are compatible with those of Fe{sub 4}N. • There is no physical evidence for the existence of ZnFe{sub 3}N and AlFe{sub 3}N.

  5. Formation of graphitic carbon nitride and boron carbon nitride film on sapphire substrate

    Science.gov (United States)

    Kosaka, Maito; Urakami, Noriyuki; Hashimoto, Yoshio

    2018-02-01

    As a novel production method of boron carbon nitride (BCN) films, in this paper, we present the incorporation of B into graphitic carbon nitride (g-C3N4). First, we investigated the formation of g-C3N4 films via chemical vapor deposition (CVD) using melamine powder as the precursor. The formation of g-C3N4 films on a c-plane sapphire substrate was confirmed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy measurements. The deposition temperature of g-C3N4 films was found to be suitable between 550 and 600 °C since the degradation and desorption of hexagonal C–N bonds should be suppressed. As for BCN films, we prepared BCN films via two-zone extended CVD using ammonia borane as the B precursor. Several XPS signals from B, C, and N core levels were detected from B-incorporated g-C3N4 films. While the N composition was almost constant, the marked tendencies for increasing B composition and decreasing C composition were achieved with the increase in the B incorporation, indicating the incorporation of B atoms by the substitution for C atoms. Optical absorptions were shifted to the high-energy side by B incorporation, which indicates the successful formation of BCN films using melamine and ammonia borane powders as precursors.

  6. Physical and Tribological Properties of Nitrided AISI 316 Stainless Steel Balls

    Directory of Open Access Journals (Sweden)

    Yang Shicai

    2016-01-01

    Full Text Available AISI 316 austenitic stainless steel balls (diameters 5.0 and 12.0 mm, typical hardness 250 HV0.3 and flat samples (20×20×2.0 mm were nitrided by a pulsed glow discharge Ar/N2 plasma. Hardness of the ball surfaces was analysed using Vickers indentation. Thermal stability of the nitrided balls (diameter 12.0 mm was studied using a furnace to heat them in air for 8 hours at temperatures up to 700.0°C and then, after cooling to room temperature, the surface hardness of the heated balls was re-measured. Scanning electron microscopy and X-ray diffraction were used to study the microstructures, composition and phase formation of the nitrided sublayers. Unlubricated pin-on-disc wear testing was used to evaluate the wear resistance of nitrided stainless steel balls (5.0 mm diameter and the results were compared with similar testing on hardened Cr-Steel balls (5 mm diameter with hardness of about 650 HV0.3. All the test results indicated that the nitrided AISI 316 austenitic stainless steel balls have advantages over the hardened Cr-Steel balls in terms of retaining high hardness after heat treatment and high resistance to sliding wear at room temperature under higher counterpart stress. These properties are expected to be beneficial for wide range of bearing applications.

  7. Effect of Plasma Nitriding Process Conditions on Corrosion Resistance of 440B Martensitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    Łępicka Magdalena

    2014-09-01

    Full Text Available Martensitic stainless steels are used in a large number of various industrial applications, e.g. molds for plastic injections and glass moldings, automotive components, cutting tools, surgical and dental instruments. The improvement of their tribological and corrosion properties is a problem of high interest especially in medical applications, where patient safety becomes a priority. The paper covers findings from plasma nitrided AISI 440B (PN-EN or DIN X90CrMoV18 stainless steel corrosion resistance studies. Conventionally heat treated and plasma nitrided in N2:H2 reaction gas mixture (50:50, 65:35 and 80:20, respectively in two different temperature ranges (380 or 450°C specimens groups were examined. Microscopic observations and electrochemical corrosion tests were performed using a variety of analytical techniques. As obtained findings show, plasma nitriding of AISI 440B stainless steel, regardless of the process temperature, results in reduction of corrosion current density. Nevertheless, applying thermo-chemical process which requires exceeding temperature of about 400°C is not recommended due to increased risk of steel sensitization to intergranular and stress corrosion. According to the results, material ion nitrided in 450°C underwent leaching corrosion processes, which led to significant disproportion in chemical composition of the corroded and corrosion-free areas. The authors suggest further research into corrosion process of plasma nitrided materials and its degradation products.

  8. Effects of crystallinity and chemical variation on apparent band-gap shift in polycrystalline indium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Chen, P.P.-T., E-mail: patrick.chen@mq.edu.a [Department of Physics and Astronomy, Faculty of Science, Macquarie University, Sydney, NSW 2109 (Australia); Downes, J.E.; Fernandes, A.J.; Butcher, K.S.A.; Wintrebert-Fouquet, M. [Department of Physics and Astronomy, Faculty of Science, Macquarie University, Sydney, NSW 2109 (Australia); Wuhrer, R.; Phillips, M.R. [Microstructural Analysis Unit, Faculty of Science, University of Technology, Sydney, Broadway, NSW 2007 (Australia)

    2011-01-03

    The nature of the apparent band-gap shift in polycrystalline indium nitride thin-films, grown by remote-plasma-enhanced chemical vapour deposition at 535 {+-} 10 {sup o}C, has been investigated separately in relation to growth temperature dependent crystallinity and chemical variation. Substrates of sapphire and gallium nitride on sapphire were used to study the effect of a stress-reduced template on indium nitride crystallite quality and apparent band-gap. To mimic surface growth temperature variations two glass substrates of differing thickness and thermal conductivity were intentionally used for the same growth conditions. The samples were characterised using optical transmission, scanning electron microscope, X-ray diffraction, and high-resolution X-ray photoelectron spectroscopy. The results indicate that the apparent band-gap shift in polycrystalline narrow band-gap indium nitride thin-films is not primarily determined by the quality of indium nitride crystallites but rather it is associated with growth temperature dependent chemical variations in the films.

  9. Electrical and thermal conductivities of the graphene, boron nitride and silicon boron honeycomb monolayers

    Science.gov (United States)

    Mousavi, Hamze; Khodadadi, Jabbar; Moradi Kurdestany, Jamshid; Yarmohammadi, Zahra

    2016-11-01

    Density of states, electrical and thermal conductivities of electrons in graphene, boron nitride and silicon boron single sheets are studied within the tight-binding Hamiltonian model and Green's function formalism, based on the linear response theory. The results show that while boron nitride keeps significantly the lowest amounts overall with an interval of zero value in low temperatures, due to its insulating nature, graphene exhibits the most electrical and thermal conductivities, slightly higher than silicon boron except for low temperature region where the latter surpasses, owing to its metallic character. This work might make ideas for creating new electronic devices based on honeycomb nanostructures.

  10. Characterization of nitride hole lateral transport in a charge trap flash memory by using a random telegraph signal method

    Science.gov (United States)

    Liu, Yu-Heng; Jiang, Cheng-Min; Lin, Hsiao-Yi; Wang, Tahui; Tsai, Wen-Jer; Lu, Tao-Cheng; Chen, Kuang-Chao; Lu, Chih-Yuan

    2017-07-01

    We use a random telegraph signal method to investigate nitride trapped hole lateral transport in a charge trap flash memory. The concept of this method is to utilize an interface oxide trap and its associated random telegraph signal as an internal probe to detect a local channel potential change resulting from nitride charge lateral movement. We apply different voltages to the drain of a memory cell and vary a bake temperature in retention to study the electric field and temperature dependence of hole lateral movement in a nitride. Thermal energy absorption by trapped holes in lateral transport is characterized. Mechanisms of hole lateral transport in retention are investigated. From the measured and modeled results, we find that thermally assisted trap-to-band tunneling is a major trapped hole emission mechanism in nitride hole lateral transport.

  11. High Kinetic Energy Penetrator Shielding and High Wear Resistance Materials Fabricated with Boron Nitride Nanotubes (BNNTS) and BNNT Polymer Composites

    Science.gov (United States)

    Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Lowther, Sharon E. (Inventor); Bryant, Robert George (Inventor)

    2015-01-01

    Boron nitride nanotubes (BNNTs), boron nitride nanoparticles (BNNPs), carbon nanotubes (CNTs), graphites, or combinations, are incorporated into matrices of polymer, ceramic or metals. Fibers, yarns, and woven or nonwoven mats of BNNTs are used as toughening layers in penetration resistant materials to maximize energy absorption and/or high hardness layers to rebound or deform penetrators. They can be also used as reinforcing inclusions combining with other polymer matrices to create composite layers like typical reinforcing fibers such as Kevlar.RTM., Spectra.RTM., ceramics and metals. Enhanced wear resistance and usage time are achieved by adding boron nitride nanomaterials, increasing hardness and toughness. Such materials can be used in high temperature environments since the oxidation temperature of BNNTs exceeds 800.degree. C. in air. Boron nitride based composites are useful as strong structural materials for anti-micrometeorite layers for spacecraft and space suits, ultra strong tethers, protective gear, vehicles, helmets, shields and safety suits/helmets for industry.

  12. Synthesis and superconducting properties of niobium nitride nanowires and nanoribbons.

    Energy Technology Data Exchange (ETDEWEB)

    Patel, U.; Avci, S.; Xiao, Z. L.; Hua, J.; Yu, S. H.; Ito, Y.; Divan, R.; Ocola, L. E.; Zheng, C.; Claus, H.; Hiller, J.; Welp, U.; Miller, D. J.; Kwok, W. K.; Northern Illinois Univ.

    2007-10-15

    Superconducting niobium nitride wires and ribbons with transverse dimensions down to tens of nanometers were synthesized by annealing NbSe{sub 3} nanostructure precursors in flowing ammonia gas at temperatures up to 1000 C. Their critical temperatures increase with increasing annealing temperatures and reach 9-11.2 K when sintered at 950 C or above. X-ray diffraction analyses identified Nb{sub 4}N{sub 5} and Nb{sub 5}N{sub 6} phases, dominating at annealing temperatures below and above 950 C, respectively. Transport measurements show magnetoresistance oscillations at temperatures near the superconducting transition due to vortex-row confinement effects and voltage jumps in current-voltage characteristics at low temperatures attributed to hot-spot behavior.

  13. Synthesis and superconducting properties of niobium nitride nanowires and nanoribbons

    Science.gov (United States)

    Patel, U.; Avci, S.; Xiao, Z. L.; Hua, J.; Yu, S. H.; Ito, Y.; Divan, R.; Ocola, L. E.; Zheng, C.; Claus, H.; Hiller, J.; Welp, U.; Miller, D. J.; Kwok, W. K.

    2007-10-01

    Superconducting niobium nitride wires and ribbons with transverse dimensions down to tens of nanometers were synthesized by annealing NbSe3 nanostructure precursors in flowing ammonia gas at temperatures up to 1000°C. Their critical temperatures increase with increasing annealing temperatures and reach 9-11.2K when sintered at 950°C or above. X-ray diffraction analyses identified Nb4N5 and Nb5N6 phases, dominating at annealing temperatures below and above 950°C, respectively. Transport measurements show magnetoresistance oscillations at temperatures near the superconducting transition due to vortex-row confinement effects and voltage jumps in current-voltage characteristics at low temperatures attributed to hot-spot behavior.

  14. Tunable Nitride Josephson Junctions.

    Energy Technology Data Exchange (ETDEWEB)

    Missert, Nancy A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Henry, Michael David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lewis, Rupert M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Howell, Stephen W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wolfley, Steven L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brunke, Lyle Brent [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wolak, Matthaeus [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-12-01

    We have developed an ambient temperature, SiO2/Si wafer - scale process for Josephson junctions based on Nb electrodes and Ta x N barriers with tunable electronic properties. The films are fabricated by magnetron sputtering. The electronic properties of the TaxN barriers are controlled by adjusting the nitrogen flow during sputtering. This technology offers a scalable alternative to the more traditional junctions based on AlOx barriers for low - power, high - performance computing.

  15. 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...

  16. PECVD silicon nitride diaphragms for condenser microphones

    NARCIS (Netherlands)

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

    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

  17. Pulsed laser deposition of thin refractory metal nitride films

    Science.gov (United States)

    Fernandez, Manuel; Bereznai, M.; Caricato, A. P.; D'Anna, Emilia; Juhasz, A.; Leggieri, Gilberto; Luches, Armando; Majni, Guiseppe; Martino, Maurizio; Mengucci, Paolo; Nagy, P. M.; Nanai, Laszlo; Toth, Zsolt

    2003-11-01

    We report on the deposition of thin transition metal nitride (TMN) films by ablating Mo, Ta, V and W targets in low-pressure (1, 10 and 100 Pa) nitrogen atmosphere by KrF excimer laser pulses, and on their characterization. The targets were foils of high purity (99.8%). 3" Si(111) wafers wre used as substrates. Film characteristics (composition, crystalline structure, hardness) were studied as a function of N2 pressure, KrF laser fluence (4.5-19 J/cm2), substrate temperature (20-750°C) and target to substrate distance (30-70 mm). Rutherford backscattering spectrometery (RBS) was used to calculate thickness of the films and identification of the composition. TMN films ar formed already at low N2 ambient pressures (1 Pa) and laser fluences (6 J/cm2) on substrates at room temperature. XRD investigations show that films deposited at elevated temperatures are mostly polycrystalline. While Mo, W and Ta nitrides show respectively a γ-Mo2N, β-W2N and δ-TaN phase in almost any deposition condition, vanadium nitride shows a prevalent phase of δ-VN at N2 pressures of 1-10 Pa, while at higher pressures (100 Pa) and at relatively high laser fluences (16-19 J/cm2) the dominant phase is β-V2N. Generally the crystallinity of the films improves by increasing the substrate temperature. Well-crystallinzed films are obtained on substrates heated at 500°C. Surface morphology, microhardness and electrical resistivity of the films are discussed as a function of both the nitrogen pressure and substrate temperature.

  18. Patterning of magnetic structures on austenitic stainless steel by local ion beam nitriding

    Energy Technology Data Exchange (ETDEWEB)

    Menendez, E. [Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain)], E-mail: enric.menendez@uab.es; Martinavicius, A.; Liedke, M.O.; Abrasonis, G.; Fassbender, J. [Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden (Germany); Sommerlatte, J. [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Germany); Nielsch, K. [Institut fuer Angewandte Physik, Universitaet Hamburg, Jungiusstrasse 11, D-20355 Hamburg (Germany); Surinach, S.; Baro, M.D. [Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Nogues, J. [Institucio Catalana de Recerca i Estudis Avancats (ICREA) and Institut Catala de Nanotecnologia, Edifici CM7, Campus Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Sort, J. [Institucio Catalana de Recerca i Estudis Avancats (ICREA) and Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain)

    2008-10-15

    Periodic arrays of ferromagnetic structures with micrometer and submicrometer lateral sizes have been prepared at the surface of a paramagnetic austenitic stainless steel by means of ion beam nitriding through different types of shadow masks (such as transmission electron microscopy grids or self-assembled porous alumina membranes). This method takes advantage of the formation of the ferromagnetic supersaturated nitrogen solid solution {gamma}{sub N} phase (i.e., expanded austenite) upon nitriding at moderate temperatures. The local character of the induced ferromagnetism is confirmed by magneto-optical Kerr effect measurements together with magnetic force microscopy imaging. Furthermore, the influence of the nitriding temperature and time on the induced ferromagnetic and structural properties has been analyzed.

  19. Electrical and thermal conductivities of the graphene, boron nitride and silicon boron honeycomb monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Mousavi, Hamze, E-mail: hamze.mousavi@gmail.com [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of); Khodadadi, Jabbar [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of); Moradi Kurdestany, Jamshid [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65201 (United States); Yarmohammadi, Zahra [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of)

    2016-11-25

    Density of states, electrical and thermal conductivities of electrons in graphene, boron nitride and silicon boron single sheets are studied within the tight-binding Hamiltonian model and Green's function formalism, based on the linear response theory. The results show that while boron nitride keeps significantly the lowest amounts overall with an interval of zero value in low temperatures, due to its insulating nature, graphene exhibits the most electrical and thermal conductivities, slightly higher than silicon boron except for low temperature region where the latter surpasses, owing to its metallic character. This work might make ideas for creating new electronic devices based on honeycomb nanostructures. - Highlights: • Electronic properties of graphene, silicon boron, and boron nitride planes are compared. • Tight-binding Hamiltonian model and Green's function formalism are implemented. • This work might make ideas for creating new electronic devices based on honeycomb nanostructures.

  20. Annealing and deposition effects of the chemical composition of silicon rich nitride

    DEFF Research Database (Denmark)

    Andersen, Karin Nordström; Svendsen, Winnie Edith; Stimpel-Lindner, T.

    2005-01-01

    Silicon-rich nitride, deposited by LPCVD, is a low stress amorphous material with a high refractive index. After deposition the silicon-rich nitride thin film is annealed at temperatures above 1100 oC to break N-H bonds, which have absorption peaks in the wavelength band important for optical...... telecommunication. However, silicon clustering appears in the thin films when annealing above 1150 oC. Clustering is undesirable in waveguide materials because the localized variations of the refractive index associated with the clusters lead to Raleigh scattering, which can cause significant propagation loss...... in optical waveguides. This means that the annealing temperature must be high enough to break the N-H bonds, but no so high as to produce clusters. Therefore, the process window for an annealing step lies between 1100 and 1150 oC. The chemical composition of amorphous silicon-rich nitride has been...

  1. Effect of nitridation on the MOVPE growth of InN on c-, r- and a-plane sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Solopow, Sergej; Dinh, Duc; Pristovsek, Markus; Kneissl, Michael [TU Berlin, Institute of Solid State Physics, Hardenbergstr. 36, 10623 Berlin (Germany)

    2011-07-01

    Growth of high quality InN is still challenging because of a narrow growth window and lack of suitable substrates. We report on the growth of InN on different oriented sapphire substrates, i.e. a-plane (11 anti 20), c-plane (0001), m-plane (10 anti 10) and r-plane (10 anti 12) using metalorganic vapor phase epitaxy (MOVPE). To grow InN directly on the sapphire substrate, a nitridation process is used to improve crystallinity and optical properties. We have grown InN layers after nitridation for 2min at different temperatures from 500 C to 1050 C. We found that the nitridation temperature strongly affects the morphology as well as the orientation of InN layers. Atomic force microscopic (AFM) measurements on the grown samples showed smoother surfaces at higher nitridation temperatures. c-oriented InN was grown on c-plane sapphire with in-plane relationship of [10 anti 10] parallel [11 anti 20]{sub Sapphire}. On the a-plane sapphire we obtained c-oriented InN with in-plane relationship of [1 anti 100]{sub InN} parallel [0001]{sub Sapphire} and [11 anti 20]{sub InN} parallel [1 anti 100]{sub Sapphire} at nitridation temperature higher than 900 C and additional in-plane relationship by temperatures below 900 C. We have grown also a-oriented InN on r-plane sapphire at nitridation temperature higher than 800 {sup circle} C. At nitridation temperatures below 800 C this orientation disappears.

  2. Gaseous insulators for high voltage electrical equipment

    Science.gov (United States)

    Christophorou, Loucas G.; James, David R.; Pace, Marshall O.; Pai, Robert Y.

    1979-01-01

    Gaseous insulators comprise compounds having high attachment cross sections for electrons having energies in the 0-1.3 electron volt range. Multi-component gaseous insulators comprise compounds and mixtures having overall high electron attachment cross sections in the 0-1.3 electron volt range and moderating gases having high cross sections for inelastic interactions with electrons of energies 1-4 electron volts. Suitable electron attachment components include hexafluorobutyne, perfluorobutene-2, perfluorocyclobutane, perfluorodimethylcyclobutane, perfluorocyclohexene, perfluoromethylcyclohexane, hexafluorobutadiene, perfluoroheptene-1 and hexafluoroazomethane. Suitable moderating gases include N.sub.2, CO, CO.sub.2 and H.sub.2. The gaseous insulating mixture can also contain SF.sub.6, perfluoropropane and perfluorobenzene.

  3. Magnetovolume effects in manganese nitrides with antiperovskite structure

    Science.gov (United States)

    Takenaka, Koshi; Ichigo, Masayoshi; Hamada, Taisuke; Ozawa, Atsushi; Shibayama, Takashi; Inagaki, Tetsuya; Asano, Kazuko

    2014-02-01

    Magnetostructural correlations in antiperovskite manganese nitrides were investigated systematically for stoichiometric and solid solution Mn3Cu1-xAxN (A = Co, Ni, Zn, Ga, Ge, Rh, Pd, Ag, In, Sn or Sb). This class of nitrides is attracting great attention because of their giant negative thermal expansion, which is achieved by doping Ge or Sn into the A site as a relaxant of the sharp volume contraction on heating (spontaneous volume magnetostriction ωs) because of the magnetovolume effects. The physical background of large ωs and mechanism of how the volume contraction becomes gradual with temperature are central concerns for the physics and applications of these nitrides. An entire dataset of thermal expansion, crystal structure and magnetization demonstrates that the cubic triangular antiferromagnetic state is crucial for large ωs. The intimate relationship between ωs and the magnetic structure is discussed in terms of geometrical frustration related to the Mn6N octahedron and magnetic stress concept. The results presented herein also show that ωs depends on the number of d electrons in the A atom, suggesting the important role of the d orbitals of the A atom. Not all the dopants in the A site, but the elements that disturb the cubic triangular antiferromagnetic state, are effective in broadening the volume change. This fact suggests that instability neighboring the phase boundary is related to the broadening. The relation between the gradual volume change and the local structure anomaly is suggested by recent microprobe studies.

  4. III-nitride semiconductors and their modern devices

    CERN Document Server

    2013-01-01

    This book is dedicated to GaN and its alloys AlGaInN (III-V nitrides), semiconductors with intrinsic properties well suited for visible and UV light emission and electronic devices working at high temperature, high frequency, and harsh environments. There has been a rapid growth in the industrial activity relating to GaN, with GaN now ranking at the second position (after Si) among all semiconductors. This is mainly thanks to LEDs, but also to the emergence of lasers and high power and high frequency electronics. GaN-related research activities are also diversifying, ranging from advanced optical sources and single electron devices to physical, chemical, and biological sensors, optical detectors, and energy converters. All recent developments of nitrides and of their technology are gathered here in a single volume, with chapters written by world leaders in the field. This third book of the series edited by B. Gil is complementary to the preceding two, and is expected to offer a modern vision of nitrides and...

  5. III-nitride semiconductors for intersubband optoelectronics: a review

    Science.gov (United States)

    Beeler, M.; Trichas, E.; Monroy, E.

    2013-07-01

    III-nitride nanostructures have recently emerged as promising materials for new intersubband (ISB) devices in a wide variety of applications. These ISB technologies rely on infrared optical transitions between quantum-confined electronic states in the conduction band of GaN/Al(Ga)N nanostructures, namely quantum wells or quantum dots. The large conduction band offset (about 1.8 eV for GaN/AlN) and sub-picosecond ISB relaxation of III-nitrides render them appealing materials for ultrafast photonic devices in near-infrared telecommunication networks. Furthermore, the large energy of GaN longitudinal-optical phonons (92 meV) opens prospects for high-temperature THz quantum cascade lasers and ISB devices covering the 5-10 THz band, inaccessible to As-based technologies due to phonon absorption. In this paper, we describe the basic features of ISB transitions in III-nitride quantum wells and quantum dots, in terms of theoretical calculations, material growth, spectroscopy, resonant transport phenomena, and device implementation. The latest results in the fabrication of control-by-design devices such as all-optical switches, electro-optical modulators, photodetectors, and lasers are also presented.

  6. Magnetovolume effects in manganese nitrides with antiperovskite structure.

    Science.gov (United States)

    Takenaka, Koshi; Ichigo, Masayoshi; Hamada, Taisuke; Ozawa, Atsushi; Shibayama, Takashi; Inagaki, Tetsuya; Asano, Kazuko

    2014-02-01

    Magnetostructural correlations in antiperovskite manganese nitrides were investigated systematically for stoichiometric and solid solution Mn3Cu1-x A x N (A = Co, Ni, Zn, Ga, Ge, Rh, Pd, Ag, In, Sn or Sb). This class of nitrides is attracting great attention because of their giant negative thermal expansion, which is achieved by doping Ge or Sn into the A site as a relaxant of the sharp volume contraction on heating (spontaneous volume magnetostriction ωs) because of the magnetovolume effects. The physical background of large ωs and mechanism of how the volume contraction becomes gradual with temperature are central concerns for the physics and applications of these nitrides. An entire dataset of thermal expansion, crystal structure and magnetization demonstrates that the cubic triangular antiferromagnetic state is crucial for large ωs. The intimate relationship between ωs and the magnetic structure is discussed in terms of geometrical frustration related to the Mn6N octahedron and magnetic stress concept. The results presented herein also show that ωs depends on the number of d electrons in the A atom, suggesting the important role of the d orbitals of the A atom. Not all the dopants in the A site, but the elements that disturb the cubic triangular antiferromagnetic state, are effective in broadening the volume change. This fact suggests that instability neighboring the phase boundary is related to the broadening. The relation between the gradual volume change and the local structure anomaly is suggested by recent microprobe studies.

  7. Ferromagnetic Josephson junctions with niobium nitride

    Science.gov (United States)

    Yamashita, Taro; Makise, Kazumasa; Kawakami, Akira; Terai, Hirotaka

    Recently, novel physics and device applications in hybrid structures of superconductor (SC) and ferromagnet (FM), e.g., spin injection into SC, long-range Josephson effect, cryogenic memory, have been studied actively. Among various interesting phenomena in SC/FM structures, a π state (π junction) emerged in ferromagnetic Josephson junctions (SC/FM/SC) is attractive as a superconducting phase shifter for superconducting devices. In the present work, we developed the ferromagnetic Josephson junction in order to realize a quiet superconducting flux qubit with a π junction. Contrary to conventional flux qubits, the qubit with a π junction can be operated without an external magnetic field which is a noise source, and thus good coherence characteristics is expected. As a superconducting material, we adopted niobium nitride (NbN) with high superconducting critical temperature of 16 K, which can be grown epitaxially on a magnesium oxide substrate. Regarding the ferromagnetic material we used copper nickel (CuNi), and fabricated the NbN/CuNi/NbN junctions and then evaluated the dependences of the Josephson critical current on the temperature, thickness and so on. This research was supported by JST, PRESTO.

  8. Gaseous Electronics Tables, Atoms, and Molecules

    CERN Document Server

    Raju, Gorur Govinda

    2011-01-01

    With the constant emergence of new research and application possibilities, gaseous electronics is more important than ever in disciplines including engineering (electrical, power, mechanical, electronics, and environmental), physics, and electronics. The first resource of its kind, Gaseous Electronics: Tables, Atoms, and Molecules fulfills the author's vision of a stand-alone reference to condense 100 years of research on electron-neutral collision data into one easily searchable volume. It presents most--if not all--of the properly classified experimental results that scientists, researchers,

  9. Positron annihilation in boron nitride

    Directory of Open Access Journals (Sweden)

    N.Amrane

    2006-01-01

    Full Text Available Electron and positron charge densities are calculated as a function of position in the unit cell for boron nitride. Wave functions are derived from pseudopotential band structure calculations and the independent particle approximation (IPM, respectively, for electrons and positrons. It is observed that the positron density is maximum in the open interstices and is excluded not only from ion cores but also to a considerable degree from valence bonds. Electron-positron momentum densities are calculated for (001,110 planes. The results are used in order to analyse the positron effects in BN.

  10. III-Nitride Based Optoelectronics

    Science.gov (United States)

    2010-01-01

    the screening effect induced by the current flow and a self - consistent Poisson - Schrodinger calculation with time dependency would be needed to account...Section 4 "InGaN Quantum Dots for Green Emission", the growth and optical properties of self -assembled InGaN quantum dots (QDs) on GaN templates are...are compared in Figure 25. QW and QD structures consist of 3 MQW (3 nm InGaN / 7 nm 23 Ill-Nitride Based Optoelectronics Northwestern University

  11. A simple thermal decomposition-nitridation route to nanocrystalline boron nitride (BN) from a single N and B source precursor

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Hong; Chen Youjian [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma Jianhua, E-mail: mjh820@ustc.edu [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Nanomaterials and Chemistry Key Laboratory, Advanced Materials Research Center of Wenzhou, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Tong Hanxuan; Yang Jiang; Ni Danwei; Hu Huiming; Zheng Fangqing [Oujiang College, Wenzhou University, Wenzhou, Zhejiang 325027 (China)

    2011-06-09

    Graphical abstract: Display Omitted Highlights: > Nanocrystalline BN was synthesized via a thermal decomposition-nitridation route. > B and N sources come from a single cheap safe precursor NH{sub 4}HB{sub 4}O{sub 7}.3H{sub 2}O. > The reaction could be carried out in an autoclave at 650 deg. C for 8 h. > X-ray powder diffraction patterns indicate that the product is hexagonal BN. > The product has good thermal stability and oxidation resistance below 900 deg. C. - Abstract: Nanocrystalline boron nitride (BN) was synthesized via a simple thermal decomposition-nitridation route by the reaction of hydrated ammonium tetraborate (NH{sub 4}HB{sub 4}O{sub 7}.3H{sub 2}O) and metallic magnesium powders in an autoclave at 650 deg. C. The crystal phase, morphology, grain size, and chemical composition of the as-prepared products were characterized in detail by X-ray powder diffraction (XRD), energy dispersion spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The products were also studied by FT-IR and the thermogravimetric analysis (TGA). Results revealed that the as-synthesized nanocrystalline were h-BN, and they had diameters within 100 nm. They had good thermal stability and oxidation resistance in high temperature.

  12. Chlorination Kinetics of Titanium Nitride for Production of Titanium Tetrachloride from Nitrided Ilmenite

    Science.gov (United States)

    Ahmadi, Eltefat; Rezan, Sheikh Abdul; Baharun, Norlia; Ramakrishnan, Sivakumar; Fauzi, Ahmad; Zhang, Guangqing

    2017-10-01

    The kinetics of chlorination of titanium nitride (TiN) was investigated in the temperature range of 523 K to 673 K (250 °C to 400 °C). The results showed that the extent of chlorination slightly increased with increasing temperature and decreasing particle size of titanium nitride at constant flow rate of N2-Cl2 gas mixture. At 523 K (250 °C), the extent of chlorination was 85.6 pct in 60 minutes whereas at 673 K (400 °C), it was 97.7 pct investigated by weight loss measurement and confirmed by ICP analyses. The experimental results indicated that a shrinking unreacted core model with mixed-control mechanism governed the chlorination rate. It was observed that the surface chemical reaction of chlorine gas on the surface of TiN particles was rate controlling in the initial stage and, during later stage, internal (pore) diffusion through the intermediate product layer was rate controlling step. Overall the process follows the mixed-control model incorporating both chemical reaction and internal diffusion control. The activation energy for the chlorination of TiN was found to be about 10.97 kJ mol-1. In processing TiCl4 from TiN and TiO0.02C0.13N0.85, the solids involved in the chlorination process were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectrometer (EDX). The SEM/EDX results demonstrated the consumption of TiN particles with extent of chlorination that showed shrinking core behavior.

  13. Gaseous carburising of self-passivating Fe–Cr-Ni alloys in acetylene-hydrogen mixtures

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Hummelshøj, Thomas Strabo; Somers, Marcel A. J.

    2011-01-01

    Gaseous carburising of self-passivating Fe–Cr–Ni alloys in acetylene–hydrogen was investigated for temperatures up to 823 K. Acetylene–hydrogen gas mixtures allow both the activation of the surface and the subsequent carburising at a high and adjustable carburising potential. For relatively low...

  14. Gaseous mercury fluxes from forest soils in response to forest harvesting intensity: A field manipulation experiment

    Science.gov (United States)

    M. Mazur; C.P.J. Mitchell; C.S. Eckley; S.L. Eggert; R.K. Kolka; S.D. Sebestyen; E.B. Swain

    2014-01-01

    Forest harvesting leads to changes in soil moisture, temperature and incident solar radiation, all strong environmental drivers of soil-air mercury (Hg) fluxes. Whether different forest harvesting practices significantly alter Hg fluxes from forest soils is unknown.We conducted a field-scale experiment in a northern Minnesota deciduous forest wherein gaseous Hg...

  15. The speed law for highly radiative flames in a gaseous mixture with large activation energy

    NARCIS (Netherlands)

    van den Berg, G.J.B.; Brauner, C.-M.; Hulshof, J.; Lunardi, A.

    2005-01-01

    We study a thermodiffusive combustion model for premixed flames propagating in reactive gaseous mixtures which contain inert dust. As observed by Joulin, radiative transfer of heat may significantly enhance the flame temperature and its propagation speed. The Joulin effect is at its most pronounced

  16. Technological aspects of gaseous pixel detectors fabrication

    NARCIS (Netherlands)

    Blanco Carballo, V.M.; Salm, Cora; Smits, Sander M.; Schmitz, Jurriaan; Melai, J.; Chefdeville, M.A.; van der Graaf, H.

    2007-01-01

    Integrated gaseous pixel detectors consisting of a metal punctured foil suspended in the order of 50μm over a pixel readout chip by means by SU-8 insulating pillars have been fabricated. SU-8 is used as sacrificial layer but metallization over uncrosslinked SU-8 presents adhesion and stress

  17. Synthesis, thermal stability, and photocatalytic activity of nanocrystalline gallium nitride via the reaction of Ga{sub 2}O{sub 3} and NH{sub 4}Cl at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hong; Chen, Youjian; Fu, Li [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma, Jianhua, E-mail: mjh820@ustc.ed [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Nanomaterials and Chemistry Key Laboratory, Advanced Materials Research Center of Wenzhou, Wenzhou University, Wenzhou, Zhejiang 325027 (China)

    2010-06-11

    Nanocrystalline gallium nitride (GaN) was prepared via one simple route by the reaction of metallic magnesium powders with gallium sesquioxide (Ga{sub 2}O{sub 3}) and ammonium chloride (NH{sub 4}Cl) in an autoclave at 650 {sup o}C. X-ray powder diffraction (XRD) pattern indicated that the product was hexagonal GaN, and the cell constant was (a = 3.18962 A, c = 5.18674 A). Scanning electron microscopy (SEM) images showed that the sample consisted of particles with an average size of about 30 nm in diameter. Raman spectroscopy study showed a frequency shift towards lower side due to the polycrystalline nature of the synthesized GaN. The hexagonal GaN powder exhibited good photocatalytic activity in degradation of Rhodamine-B (RhB) under 300 W mercury lamp light irradiation. The product was also studied by the thermogravimetric analysis (TGA). It had good thermal stability and oxidation resistance below 750 {sup o}C in air.

  18. Experimental and theoretical evaluation of the laser-assisted machining of silicon nitride

    Science.gov (United States)

    Rozzi, Jay Christopher

    This study focused on the experimental and theoretical evaluation of the laser assisted machining (LAM) of silicon nitride ceramics. A laser assisted machining facility was constructed whose main components consist of a COsb2 laser and a CNC lathe. Surface temperature histories were first measured and compared to a transient, three-dimensional numerical simulation for a rotating silicon nitride workpiece heated by a translating laser for ranges of the workpiece rotational and laser-translation speeds, as well as the laser beam diameter and power. Excellent agreement was obtained between the experimental and predicted temperature histories. Laser assisted machining experiments on silicon nitride ceramic workpieces were completed for a wide range of operating conditions. Data for cutting forces and surface temperature histories illustrated that the lower bound for the avoidance of cutting tool and/or workpiece fracture for LAM is defined by the YSiAlON glass transition temperature (920-970sp°C). As temperatures near the cutting tool increase to values above the glass transition temperature range, the glassy phase softened, facilitating plastic deformation and, correspondingly, the production of semi-continuous or continuous chips. The silicon nitride machined workpiece surface roughness (Rsb{a}=0.39\\ mum) for LAM at the nominal operating condition was nearly equivalent to a value associated with the grinding of silicon nitride using a diamond wheel (Rsb{a}=0.2\\ mum). By examining the machined surfaces and chips, it was shown that LAM does not produce detectable sub-surface cracking or significant silicon nitride microstructure alteration, respectively. A transient, three-dimensional numerical heat transfer model of laser assisted machining was constructed, which includes a preheat phase and material removal, with the associated changes in the workplace geometry. Excellent agreement was obtained between the measured and predicted temperature histories. The strong

  19. Optical and Micro-Structural Characterization of MBE Grown Indium Gallium Nitride Polar Quantum Dots

    KAUST Repository

    El Afandy, Rami

    2011-07-07

    Gallium nitride and related materials have ushered in scientific and technological breakthrough for lighting, mass data storage and high power electronic applications. These III-nitride materials have found their niche in blue light emitting diodes and blue laser diodes. Despite the current development, there are still technological problems that still impede the performance of such devices. Three-dimensional nanostructures are proposed to improve the electrical and thermal properties of III-nitride optical devices. This thesis consolidates the characterization results and unveils the unique physical properties of polar indium gallium nitride quantum dots grown by molecular beam epitaxy technique. In this thesis, a theoretical overview of the physical, structural and optical properties of polar III-nitrides quantum dots will be presented. Particular emphasis will be given to properties that distinguish truncated-pyramidal III-nitride quantum dots from other III-V semiconductor based quantum dots. The optical properties of indium gallium nitride quantum dots are mainly dominated by large polarization fields, as well as quantum confinement effects. Hence, the experimental investigations for such quantum dots require performing bandgap calculations taking into account the internal strain fields, polarization fields and confinement effects. The experiments conducted in this investigation involved the transmission electron microscopy and x-ray diffraction as well as photoluminescence spectroscopy. The analysis of the temperature dependence and excitation power dependence of the PL spectra sheds light on the carrier dynamics within the quantum dots, and its underlying wetting layer. A further analysis shows that indium gallium nitride quantum dots through three-dimensional confinements are able to prevent the electronic carriers from getting thermalized into defects which grants III-nitrides quantum dot based light emitting diodes superior thermally induced optical

  20. 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, develo......, 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....

  1. Hydrochloric acid aerosol and gaseous hydrogen chloride partitioning in a cloud contaminated by solid rocket exhaust

    Science.gov (United States)

    Sebacher, D. I.; Bendura, R. J.; Wornom, D. E.

    1980-01-01

    Partitioning of hydrogen chloride between hydrochloric acid aerosol and gaseous HCl in the lower atmosphere was experimentally investigated in a solid rocket exhaust cloud diluted with humid ambient air. Airborne measurements were obtained of gaseous HCl, total HCl, relative humidity and temperature to evaluate the conditions under which aerosol formation occurs in the troposphere in the presence of hygroscopic HCl vapor. Equilibrium predictions of HCl aerosol formation accurately predict the measured HCl partitioning over a range of total HCl concentrations from 0.6 to 16 ppm.

  2. A transfer technique for high mobility graphene devices on commercially available hexagonal boron nitride

    NARCIS (Netherlands)

    Zomer, P. J.; Dash, S. P.; Tombros, N.; van Wees, B. J.

    2011-01-01

    We present electronic transport measurements of single and bilayer graphene on commercially available hexagonal boron nitride. We extract mobilities as high as 125 000 cm(2) V-1 s(-1) at room temperature and 275 000 cm(2) V-1 s(-1) at 4.2 K. The excellent quality is supported by the early

  3. Silicon-doped boron nitride coated fibers in silicon melt infiltrated composites

    Science.gov (United States)

    Corman, Gregory Scot; Luthra, Krishan Lal

    1999-01-01

    A fiber-reinforced silicon--silicon carbide matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is produced. The invention also provides a method for protecting the reinforcing fibers in the silicon--silicon carbide matrix composites by coating the fibers with a silicon-doped boron nitride coating.

  4. Effect of cooling rate on properties of plasma nitrided AISI 1010 steel

    OpenAIRE

    ALVES Jr, Clodomiro; Lima, José de Anchieta; HAJEK, VACLAV; Cunha, João Batista Marimon; Santos,Carlos Alberto

    2007-01-01

    In this work, AISI 1010 steel samples were plasma nitrided into 20% N 2 100 Pa and 400 Pa for N 2 and H 2 , respectively), temperatures of 500 and 580 °C, during 2 h. Three different procedures for cooling were accomplished after nitriding. In the first procedure the cooling occurred naturally, that is, the sample was kept on substrate holder. In the second one the sample was pulled off and cooling in a cold surface. Finally, in the third cooling process the sample was...

  5. Investigation of Microstructure and Corrosion Propagation Behaviour of Nitrided Martensitic Stainless Steel Plates

    Directory of Open Access Journals (Sweden)

    Abidin Kamal Ariff Zainal

    2014-07-01

    Full Text Available Martensitic stainless steels are commonly used for fabricating components. For many applications, an increase in surface hardness and wear resistance can be beneficial to improve performance and extend service life. However, the improvement in hardness of martensitic steels is usually accompanied by a reduction in corrosion strength. The objective of this study is to investigate the effects of nitriding on AISI 420 martensitic stainless steel, in terms of microstructure and corrosion propagation behavior. The results indicate that the microstructure and phase composition as well as corrosion resistance were influenced by nitriding temperatures.

  6. Fabrication of translucent boron nitride dispersed polycrystalline silicon nitride ceramics

    Science.gov (United States)

    Joshi, B.; Fu, Z.; Niihara, K.; Lee, S. W.

    2011-03-01

    Optical transparency was achieved at infrared region and overall translucent silicon nitride was fabricated using hot press sintering (HPS). The increase in h-BN content decreased the optical transparency. Microstructral observations shows that the optical, mechanical and tribological properties of BN dispersed polycrystalline Si3N4 ceramics were affected by the density, α:β-phase ratio and content of h-BN in sintered ceramics. The hot pressed samples were prepared from the mixture of α-Si3N4, AlN, MgO and h-BN at 1850°C. The composite contained from 0.25 to 2 mass % BN powder with sintering aids (9% AlN + 3% MgO). Maximum transmittance of 57% was achieved for 0.25 mass % BN doped Si3N4 ceramics. Fracture toughness was increased and wear volume and friction coefficient were decreased with increase in BN content.

  7. Solid–gaseous phase transformation of elemental contaminants during the gasification of biomass

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Ying; Ameh, Abiba [Centre for Bioenergy & Resource Management, School of Energy, Environment & Agrifood, Cranfield University, Cranfield MK43 0AL (United Kingdom); Lei, Mei [Centre for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101 (China); Duan, Lunbo [Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096 (China); Longhurst, Philip, E-mail: P.J.Longhurst@cranfield.ac.uk [Centre for Bioenergy & Resource Management, School of Energy, Environment & Agrifood, Cranfield University, Cranfield MK43 0AL (United Kingdom)

    2016-09-01

    Disposal of plant biomass removed from heavy metal contaminated land via gasification achieves significant volume reduction and can recover energy. However, these biomass often contain high concentrations of heavy metals leading to hot-corrosion of gasification facilities and toxic gaseous emissions. Therefore, it is of significant interest to gain a further understanding of the solid–gas phase transition of metal(loid)s during gasification. Detailed elemental analyses (C, H, O, N and key metal/metalloid elements) were performed on five plant species collected from a contaminated site. Using multi-phase equilibria modelling software (MTDATA), the analytical data allows modelling of the solid/gas transformation of metal(loid)s during gasification. Thermodynamic modelling based on chemical equilibrium calculations was carried out in this study to predict the fate of metal(loid) elements during typical gasification conditions and to show how these are influenced by metal(loid) composition in the biomass and operational conditions. As, Cd, Zn and Pb tend to transform to their gaseous forms at relatively low temperatures (< 1000 °C). Ni, Cu, Mn and Co converts to gaseous forms within the typical gasification temperature range of 1000–1200 °C. Whereas Cr, Al, Fe and Mg remain in solid phase at higher temperatures (> 1200 °C). Simulation of pressurised gasification conditions shows that higher pressures increase the temperature at which solid-to-gaseous phase transformations takes place. - Highlights: • Disposal of plants removed from metal contaminated land raises environmental concerns • Plant samples collected from a contaminated site are shown to contain heavy metals. • Gasification is suitable for plant disposal and its emission is modelled by MTDATA. • As, Cd, Zn and Pb are found in gaseous emissions at a low process temperature. • High pressure gasification can reduce heavy metal elements in process emission.

  8. Adsorption of diazinon and hinosan molecules on the iron-doped boron nitride nanotubes surface in gas phase and aqueous solution: A computational study

    Energy Technology Data Exchange (ETDEWEB)

    Farmanzadeh, Davood, E-mail: d.farmanzad@umz.ac.ir; Rezainejad, Hamid

    2016-02-28

    Graphical abstract: - Highlights: • Fe doping on boron nitride nanotubes increases their chemical reactivity. • The vdW interactions have a remarkable contribution of total adsorption energies. • FeNBNNTs is better adsorbent for adsorbing mentioned OPs especially hinosan. • Results can be helpful for planning an efficient nanofilter to remove OP pollutants. - Abstract: In this study, the geometric structures and electronic properties of two widely used organophosphorus pesticides, diazinon and hinosan, boron nitride nanotubes (BNNTs) and Fe doped boron nitride nanotubes (FeBNNTs) as adsorbents of these pesticides are studied by density functional theory calculation as well as dispersion correction by Grimme method. The results show that Fe doping in boron nitride nanotubes structures increases the potency of nanotubes to adsorb mentioned pesticides, especially when Fe atom located instead of N atom. Comparing the adsorption energies of diazinon on FeBNNTs with ones for hinosan demonstrate that the adsorption of hinosan is energetically more favorable by FeBNNTs. Assessment of adsorption energies in aqueous solution confirmed significant decrease in their values compared to ones in gaseous phase. However, the adsorption of diazinon and hinosan on both BNNTs and FeBNNTs are exothermic. So, BNNTs and FeBNNTs may be promising candidates as appropriate adsorbents for adsorbing diazinon and hinosan. Also, the results of calculations have revealed that van der Waals interaction energies are remarkably large in adsorption of diazinon and hinosan on all boron nitride nanotubes.

  9. Erection of duct-like graphitic carbon nitride with enhanced photocatalytic activity for ACB photodegradation

    Science.gov (United States)

    Muhmood, Tahir; Xia, Mingzhu; Lei, Wu; Wang, Fengyun

    2018-02-01

    Novel duct graphitic carbon nitride (DCN) was successfully prepared using the temperature control method in a quartz tube furnace from commercially available melamine and evaluated against the photo-degradation of latent organic pollutants, acarbose (ACB). These prepared materials were characterized by UV–Vis spectroscopy, Fourier transform infrared spectra, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The characterization results indicated that the synthesized material was in the form of a duct-like structure and has greater adsorption capacity and photocatalytic ability as compared to traditionally synthesized graphitic carbon nitride materials. The DCN split theACB completely into many intermediates, which were depicted in the HPLC-MS spectrum for knowing the acarbose photo-degrdation pathway. The duct-like morphology of graphitic carbon nitride has improved properties, such as increasing the surface area and decelerating the e ‑/h + recombination, which increase the light absorbance ability with enhanced photoactivity.

  10. Simple method for cleaning gallium nitride (0001)

    Science.gov (United States)

    Machuca, Francisco; Liu, Zhi; Sun, Yun; Pianetta, P.; Spicer, W. E.; Pease, R. F. W.

    2002-09-01

    Achieving clean surfaces is a major and challenging requirement for the study of surfaces and surface reactions. We describe the use of synchrotron radiation (SR) to probe the electronic structure of the gallium nitride (GaN) (0001) surface that has undergone wet chemical cleaning sequences followed by heating. By using SR in the range of 200-1000 eV the core levels of Ga, N, O, and C are monitored. Immersion in a 4:1 solution of sulfuric acid (51%) to hydrogen peroxide (30%) followed by a 700 degC (200 degC below decomposition temperature) vacuum anneal (less-than-or-equal10-10 Torr) results in a reduction of carbon and oxygen coverage to a few percent of a monolayer. This suggests a weakly bound oxide of carbon being chemisorbed to the GaN surface after the sulfuric acid/hydrogen peroxide treatment and it is removed by the heating. copyright 2002 American Vacuum Society.

  11. Influence of surface nano/ultrafine structure formed via pre-deep rolling process on the plasma nitriding characteristics of the AISI 316L stainless steel

    Science.gov (United States)

    Tadi, A. Jafari; Hosseini, S. R.; Semiromi, M. Naderi

    2017-08-01

    Influence of deep rolling prior to plasma nitriding on microstructure and hardness of the AISI 316L stainless steel was investigated in this paper. Deep rolling using `ball-point' tool was conducted on the 316L stainless steel bar at multiple passes. Then, plasma nitriding was performed on the as-received and deep-rolled kinds at 450 °C temperature for 5 h. Structural characterisation was done using optical microscope, field emission scanning electron microscope, feritscope, X-ray diffractometer, and glow discharge optical emission spectroscope as well as hardness measurement by a Vickers micro-hardness tester at 0.1 kgf. An ultrafine structure and a nitrogen-rich layer were, respectively, formed on the rolled and nitrided surfaces. Surface hardness was increased from 210 up to 450, 670 and 1050 HV0.1 after the rolling, nitriding, and rolling-nitriding processes, respectively. Thickness of the nitrided layer was increased from 12 to 20 µm and diffusion depth of nitrogen from 12 to 25 µm via conducting the deep rolling before the nitriding process. The rolling-nitriding process was resulted in rising of nitrogen concentration by a factor of about 3 at near-surface regions.

  12. Mesoporous Vanadium Nitride Synthesized by Chemical Routes

    National Research Council Canada - National Science Library

    Mishra, Pragnya P; Theerthagiri, J; Panda, Rabi N

    2014-01-01

    Nanocrystalline vanadium nitride (VN) materials are synthesized by two different routes, namely, the urea route and the ammonia route, using various V2O5 precursors obtained by citric acid–based sol–gel method...

  13. Thermodynamics, kinetics and process control of nitriding

    DEFF Research Database (Denmark)

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

    1999-01-01

    As a prerequisite for 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 iron-nitrogen phases has not been achieved fully. It has been shown that taking into account ordering of nitrogen in the epsilon and gamma' iron-nitride phases, leads to an improved understanding of the Fe-N phase diagram. Although thermodynamics indicate the state the system strives for......, 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...

  14. 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....

  15. Excimer laser reactive deposition of vanadium nitride thin films

    Science.gov (United States)

    D'Anna, E.; Di Cristoforo, A.; Fernández, M.; Leggieri, G.; Luches, A.; Majni, G.; Mengucci, P.; Nanai, L.

    2002-01-01

    We report on the deposition of thin vanadium nitride films by ablating vanadium targets in low-pressure N 2 atmosphere, and on their characterization. The targets were vanadium foils (purity 99.8%). 3 in. Si(1 1 1) wafers were used as substrates. Film characteristics (composition and crystalline structure) were studied as a function of N 2 pressure (0.5-200 Pa), KrF laser fluence (4.5-19 J/cm 2), substrate temperature (20-750 °C) and target-to-substrate distance (30-70 mm). Vanadium nitride is already formed at low N 2 ambient pressures (1 Pa) and laser fluences (6 J/cm 2) on substrates at room temperature. At the N 2 pressures of 1-10 Pa, the prevalent phase is VN. At higher pressures (100 Pa) and at relatively high laser fluences (16-19 J/cm 2), the dominant phase is V 2N. The crystallinity of the films improves by increasing the substrate temperature. Well-crystallized films are obtained on substrates heated at 500 °C.

  16. Thermal behaviour of chromium nitride/titanium–titanium carbonitride multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Angerer, P., E-mail: paul.angerer@mcl.at [Materials Center Leoben Forschung GmbH, 8700 Leoben (Austria); Lackner, J.M. [JOANNEUM RESEARCH Forschungsgesellschaft mbH, Institute for Surface Technologies and Photonics, Functional Surfaces, 8712 Niklasdorf (Austria); Wiessner, M.; Maier, G.A. [Materials Center Leoben Forschung GmbH, 8700 Leoben (Austria); Major, L. [Institute of Metallurgy and Materials Science Polish Academy of Sciences, 25 Reymonta Street, 30-059 Krakow (Poland)

    2014-07-01

    Chromium nitride/titanium–titanium carbonitride multilayers composed of a 40 nm Cr interface followed by a 4.4 μm thick Cr{sub 2}N layer, a 150 nm thick Ti layer, and a 1 μm thick TiC{sub x}N{sub y} top layer were deposited on silicon wafers by magnetron sputtering. The structural changes and the phase content changes of these multilayer samples were studied by means of high-temperature in-situ X-ray diffraction experiments at temperatures up to 550 °C. The lattice constants of the Cr phase as well as the Ti phase display an aberrant expansion behaviour during these experiments which is influenced by the defect structure, a nitrogen incorporation, and residual stress in the layers. The results were compared with structural data obtained by ex-situ transmission electron microscopy investigations of pristine and heated material, revealing phase separation and strong diffusion phenomena. - Highlights: • Magnetron sputtering of chromium nitride/titanium–titanium carbonitride layers • High temperature in-situ observations of structural changes up to 550 °C performed • Formation of crystalline TiN,TiC{sub x}N{sub y}, Cr{sub 2}N, and metallic Cr phases observed • Aberrant variations of the cell parameters of the Ti metal phase were found.

  17. Evidence of nanodomes in carbon nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, S.; Laugier, M.T. [Material and Surface Science Institute (MSSI) and Department of Physics, University of Limerick, Limerick (Ireland)

    2004-01-01

    This article reports the synthesis of hard and conductive carbon nitride thin films with evidence of formation of nanodomes over a range of substrate temperature from 50 C to 550 C. The size of the nanodomes increases from 40-80 nm at room temperature to 200-400 nm at high temperature (550 C). Electrical characterization shows that these films have conductive behaviour with a resistivity depending on the size of the nanodomes. Resistivity values of 19 m{omega}cm were found for nanodomes of size 40-80 nm falling to 6 m{omega}cm for nanodomes of size 200-400 nm. Nanoindentation results show that the hardness and Young's modulus of these films are in the range from 9-22 GPa and 100-168 GPa respectively and these values decrease as the size of the nanodomes increases. GXRD results confirm that a crystalline graphitic carbon nitride structure has formed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Gaseous material capacity of open plasma jet in plasma spray-physical vapor deposition process

    Science.gov (United States)

    Liu, Mei-Jun; Zhang, Meng; Zhang, Qiang; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

    2018-01-01

    Plasma spray-physical vapor deposition (PS-PVD) process, emerging as a highly efficient hybrid approach, is based on two powerful technologies of both plasma spray and physical vapor deposition. The maximum production rate is affected by the material feed rate apparently, but it is determined by the material vapor capacity of transporting plasma actually and essentially. In order to realize high production rate, the gaseous material capacity of plasma jet must be fundamentally understood. In this study, the thermal characteristics of plasma were measured by optical emission spectrometry. The results show that the open plasma jet is in the local thermal equilibrium due to a typical electron number density from 2.1 × 1015 to 3.1 × 1015 cm-3. In this condition, the temperature of gaseous zirconia can be equal to the plasma temperature. A model was developed to obtain the vapor pressure of gaseous ZrO2 molecules as a two dimensional map of jet axis and radial position corresponding to different average plasma temperatures. The overall gaseous material capacity of open plasma jet, take zirconia for example, was further established. This approach on evaluating material capacity in plasma jet would shed light on the process optimization towards both depositing columnar coating and a high production rate of PS-PVD.

  19. Chemical vapor deposition of amorphous tungsten nitride for applications in ultra-large scale interconnect technologies

    Science.gov (United States)

    Kelsey, Jean E.

    Increasing demands on computer chip technology require exploration of novel materials and deposition techniques. The driving need to reduce device dimensions without increasing device delay time has forced a move towards copper interconnects. Copper interconnects require an encapsulating barrier layer to prevent diffusion into the dielectric layer, as well as a passivation layer to protect against oxidation. One potential material for the barrier layer is tungsten nitride (WNx). Tungsten nitride is expected to perform well as a barrier because of its refractory nature and excellent thermal, chemical, and mechanical properties. In addition, it can be deposited in amorphous form. Amorphous materials have no grain boundaries, thereby making grain boundary diffusion, a fast path diffusion mechanism, impossible. In this work, a chemical vapor deposition (CVD) process was developed for the deposition of tungsten nitride. CVD was selected because it has the potential to deposit highly conformal film. High conformality is critical in a barrier layer in order to ensure viable coverage at the bottom and sides of device structures without sacrificing critical space that would be better used by the copper metal. In this manner, the total resistivity of the interconnect is minimized. The CVD WNx process was systematically optimized for film conformality, resistivity and growth rate. This was achieved by thoroughly examining film nucleation and growth characteristics, and analyzing resulting film properties. Adhesion of copper to the CVD films was qualified using stud pull tests, while X-ray diffraction was implemented to determine crystallization temperature of the amorphous phase. Additionally, diffusion barrier properties of the CVD tungsten nitride were assessed using sputter deposited copper, and compared to those of sputter deposited tungsten nitride. Thermally activated barrier failure was studied as a function of barrier thickness using Rutherford backscattering

  20. Large-scale characterization of silicon nitride-based evanescent couplers at 532nm wavelength

    Science.gov (United States)

    Claes, Tom; Jansen, Roelof; Neutens, Pieter; Du Bois, Bert; Helin, Philippe; Severi, Simone; Van Dorpe, Pol; Deshpande, Paru; Rottenberg, Xavier

    2014-05-01

    Recently, the photonics community has a renewed attention for silicon nitride.1-3 When deposited at temperatures below 650K with plasma-enhanced chemical vapor deposition (PECVD),4 it enables photonic circuits fabricated on-top of standard complementary metaloxidesemiconductor (CMOS) electronics. Silicon nitride is moreover transparent to wavelengths that are visible to the human eye and detectable with available silicon detectors, thus offering a photonics platform for a range of applications that is not accessible with the popular silicon-on-insulator platform. However, first-time-right design of large-scale circuits for demanding specifications requires reliable models of the basic photonic building blocks, like evanescent couplers (Figure 1), components that couple power between multiple waveguides. While these models typically exist for the silicon-on-insulator platform, they still lack maturity for the emerging silicon nitride platform. Therefore, we meticulously studied silicon nitride-based evanescent couplers fabricated in our 200mm-wafer facility. We produced the structures in a silicon nitride film deposited with low-temperature PECVD, and patterned it using optical lithography at a wavelength of 193nm and reactive ion etching. We measured the performance of as much as 250 different designs at 532nm wavelength, a central wavelength in the visible range for which laser sources are widespread. For each design, we measured the progressive transmission of up-to 10 cascaded identical couplers (Figure 2(a)), yielding very accurate figures for the coupling factor (Figure 2(b)). This paper presents the trends extracted from this vast data set (Figure 3), and elaborates on the impact of the couplers bend radius and gap on its coupling factors (Figure 4 and Figure 5). We think that the large- scale characterization of evanescent couplers presented in this paper, in excellent agreement with the simulated performance of the devices, forms the basis for a component

  1. Internal nitridation of nickel-base alloys; Innere Nitrierung von Nickelbasis-Legierungen

    Energy Technology Data Exchange (ETDEWEB)

    Krupp, U.; Christ, H.J. [Siegen Univ. (Gesamthochschule) (Germany). Inst. fuer Werkstofftechnik

    1998-12-31

    The chromuim concentration is the crucial variable in nitridation processes in nickel-base alloys. Extensive nitridation experiments with various specimen alloys of the system Ni-Cr-Al-Ti have shown that the Cr itself starts to form nitrides as from elevated initial concentrations of about 10 to 20 weight%, (depending on temperature), but that lower concentrations have an earlier effect in that they induce a considerable increase in the N-solubility of the nickel-base alloys. This causes an accelerated nitridation attack on the alloying elements Ti and Al. Apart from experimental detection and analysis, the phenomenon of internal nitridation could be described as well by means of a mathematical model calculating the diffusion with the finite-differences method and determining the precipitation thermodynamics by way of integrated equilibrium calculations. (orig./CB) [Deutsch] Im Verlauf der Hochtemperaturkorrosion von Nickelbasis-Superlegierungen kann durch beanspruchungsbedingte Schaedigungen der Oxiddeckschicht ein Verlust der Schutzwirkung erfolgen und als Konsequenz Stickstoff aus der Atmosphaere in den Werkstoff eindringen. Der eindiffundierende Stickstoff bildet vor allem mit den Legierungselementen Al, Cr und Ti Nitridausscheidungen, die zu einer relativ rasch fortschreitenden Schaedigung fuehren koennen. Eine bedeutende Rolle bei diesen Nitrierungsprozessen in Nickelbasislegierungen spielt die Cr-Konzentration in der Legierung. So ergaben umfangreiche Nitrierungsexperimente an verschiedenen Modellegierungen des Systems Ni-Cr-Al-Ti, dass Cr zwar selbst erst ab Ausgangskonzentrationen von ca. 10-20 Gew.% (abhaengig von der Temperatur) Nitride bildet, allerdings bereits bei geringen Konzentrationen die N-Loeslichkeit von Nickelbasis-Legierungen entscheidend erhoeht. Dies hat zur Folge, dass es zu einem beschleunigten Nitrierungsangriff auf die Legierungselemente Ti und Al kommt. Neben den experimentellen Untersuchungen konnte das Phaenomen der inneren

  2. Integration of Electrodeposited Ni-Fe in MEMS with Low-Temperature Deposition and Etch Processes

    National Research Council Canada - National Science Library

    Giuseppe Schiavone; Jeremy Murray; Richard Perry; Andrew R Mount; Marc P Y Desmulliez; Anthony J Walton

    2017-01-01

    .... In addition, a low temperature deposition and surface micromachining process is presented in which silicon dioxide and silicon nitride are used, respectively, as sacrificial material and structural dielectric...

  3. 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.

  4. 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.

  5. Basic processes and trends in gaseous detectors

    CERN Multimedia

    1999-01-01

    Almost a century after the invention of the proportional counter, a large research effort is still devoted to better understand the basic properties of gaseous detectors, and to improve their performances and reliability, particularly in view of use at the high radiation levels expected at LHC. In the first part of the lectures, after a brief introduction on underlying physical phenomena, I will review modern sophisticated computational tools, as well as some classic "back of the envelope" analytical methods, available today for estimating the general performances of gaseous detectors. In the second part, I will analyze in more detail problems specific to the use of detectors at high rates (space charge, discharges, aging), and describe the recent development of powerful and perhaps more reliable devices, particularly in the field of position-sensitive micro-pattern detectors.

  6. Trends and new developments in gaseous detectors

    CERN Document Server

    AUTHOR|(CDS)2069485

    2004-01-01

    Almost one century ago the method of particle detection with gaseous detectors was invented. Since then they have been exploited successfully in many experiments using a wide variety of different applications. The development is still going on today. The underlying working principles are today well understood and with the help of modern simulation techniques, new configurations can be easily examined and optimized before a first experimental test. Traditional wire chamber ensembles demonstrate that they are still up to date and are well prepared to meet also the challenges of LHC. Applications will be discussed using TPCs in high multiplicity environments with standard Multi-Wire Proportional Chamber (MWPC) as readout as well as drift tubes in a muon spectrometer for a Large Hadron Collider (LHC) experiment. Triggered by the evolving printed circuit technology, a new generation of gaseous detectors with very high position resolution and rate capability has emerged. Two representatives (MICROMEGAS, GEM) have p...

  7. Software digitizer for high granular gaseous detector

    CERN Document Server

    Haddad, Y; Boudry, V

    2014-01-01

    A sampling calorimeter using gaseous sensor layers with digital readout [1] is near perfect for ``Particle Flow Algorithm'' [2,3] approach, since it is homogeneous over large surfaces, robust, cost efficient, easily segmentable to any readout pad dimension and size and almost insensitive to neutrons. Monte-Carlo (MC) programs such as GEANT4 [4] simulate with high precision the energy deposited by particles. The sensor and electronic response associated to a pad are calculated in a separate ``digitization'' process. We develop a general method for simulating the pad response using the spatial information from a simulation done at high granularity. The digitization method proposed here has been applied to gaseous detectors including Glass Resistive Plate Chambers (GRPC) and MicroMegas, and validated on test beam data. Experimental observable such as pad multiplicity and mean number of hits at different thresholds have been reproduced with high precision.

  8. Low-threshold indium gallium nitride quantum dot microcavity lasers

    Science.gov (United States)

    Woolf, Alexander J.

    Gallium nitride (GaN) microcavities with embedded optical emitters have long been sought after as visible light sources as well as platforms for cavity quantum electrodynamics (cavity QED) experiments. Specifically, materials containing indium gallium nitride (InGaN) quantum dots (QDs) offer an outstanding platform to study light matter interactions and realize practical devices, such as on-chip light emitting diodes and nanolasers. Inherent advantages of nitride-based microcavities include low surface recombination velocities, enhanced room-temperature performance (due to their high exciton binding energy, as high as 67 meV for InGaN QDs), and emission wavelengths in the blue region of the visible spectrum. In spite of these advantages, several challenges must be overcome in order to capitalize on the potential of this material system. Such diffculties include the processing of GaN into high-quality devices due to the chemical inertness of the material, low material quality as a result of strain-induced defects, reduced carrier recombination effciencies due to internal fields, and a lack of characterization of the InGaN QDs themselves due to the diffculty of their growth and therefore lack of development relative to other semiconductor QDs. In this thesis we seek to understand and address such issues by investigating the interaction of light coupled to InGaN QDs via a GaN microcavity resonator. Such coupling led us to the demonstration of the first InGaN QD microcavity laser, whose performance offers insights into the properties and current limitations of the nitride materials and their emitters. This work is organized into three main sections. Part I outlines the key advantages and challenges regarding indium gallium nitride (InGaN) emitters embedded within gallium nitride (GaN) optical microcavities. Previous work is also discussed which establishes context for the work presented here. Part II includes the fundamentals related to laser operation, including the

  9. Treatment of nitridation by microwave post discharge plasma in an AISI 4140 steel; Tratamiento de nitruracion por plasma post-descarga micro-ondas en un acero AISI 4140

    Energy Technology Data Exchange (ETDEWEB)

    Medina F, A. [Instituto Tecnologico de Morelia, Morelia e Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico); Rodriguez L, V.; Zamora R, L. [ININ, Mexico D.F. (Mexico); Oseguera P, J

    1998-07-01

    The objective of this work is to determine through X-ray diffraction, microhardness measurement and scanning electron microscopy those main operation parameters of the microwave post discharge treatment (temperature of treatment, gas mixture and permanence time) nitriding an AISI 4140 steel and to characterize the compact layer of nitrides formed during the treatment. (Author)

  10. National Gas Survey. Synthesized gaseous hydrocarbon fuels

    Energy Technology Data Exchange (ETDEWEB)

    None

    1978-06-01

    The supply-Technical Advisory Task Force-Synthesized Gaseous Hydrocarbon Fuels considered coal, hydrocarbon liquids, oil shales, tar sands, and bioconvertible materials as potential feedstocks for gaseous fuels. Current status of process technology for each feedstock was reviewed, economic evaluations including sensitivity analysis were made, and constraints for establishment of a synthesized gaseous hydrocarbon fuels industry considered. Process technology is presently available to manufacture gaseous hydrocarbon fuels from each of the feedstocks. In 1975 there were eleven liquid feedstock SNG plants in the United States having a capacity of 1.1 billion SCFD. There can be no contribution of SNG before 1982 from plants using feedstocks other than liquids because there are no plants in operation or under construction as of 1977. Costs for SNG are higher than current regulated prices for U.S. natural gas. Because of large reserves, coal is a prime feedstock candidate although there are major constraints in the area of coal leases, mining and water permits, and others. Commercial technology is available and several new gasification processes are under development. Oil shale is also a feedstock in large supply and commercial process technology is available. There are siting and permit constraints, and water availability may limit the ultimate size of an oil shale processing industry. Under projected conditions, bioconvertible materials are not expected to support the production of large quantities of pipeline quality gas during the next decade. Production of low or medium Btu gas from municipal solid wastes can be expected to be developed in urban areas in conjunction with savings in disposal costs. In the economic evaluations presented, the most significant factor for liquid feedstock plants is the anticipated cost of feedstock and fuel. The economic viability of plants using other feedstocks is primarily dependent upon capital requirements.

  11. Biaxial Compressive Strain Engineering in Graphene/Boron Nitride Heterostructures

    Science.gov (United States)

    Pan, Wei; Xiao, Jianliang; Zhu, Junwei; Yu, Chenxi; Zhang, Gang; Ni, Zhenhua; Watanabe, K.; Taniguchi, T.; Shi, Yi; Wang, Xinran

    2012-11-01

    Strain engineered graphene has been predicted to show many interesting physics and device applications. Here we study biaxial compressive strain in graphene/hexagonal boron nitride heterostructures after thermal cycling to high temperatures likely due to their thermal expansion coefficient mismatch. The appearance of sub-micron self-supporting bubbles indicates that the strain is spatially inhomogeneous. Finite element modeling suggests that the strain is concentrated on the edges with regular nano-scale wrinkles, which could be a playground for strain engineering in graphene. Raman spectroscopy and mapping is employed to quantitatively probe the magnitude and distribution of strain. From the temperature-dependent shifts of Raman G and 2D peaks, we estimate the TEC of graphene from room temperature to above 1000K for the first time.

  12. Alternative gaseous-fuels safety assessment

    Energy Technology Data Exchange (ETDEWEB)

    Krupka, M.C.; Peaslee, A.T. Jr.; Laquer, H.L.

    1983-01-01

    A relative safety assessment of alternative gaseous and reference liquid fuels utilized for light automotive transportation in the public sector was completed. The specific fuels considered were compressed natural gas (CNG), liquefied natural gas (LNG), liquefied petroleum gas (LPG), and the liquid fuels, gasoline and diesel. The assessment methodology describes and develops the relative hazards of these fuels from an integrated generic physicochemical property and accident scenario point of view. A technique involving a method of eliciting expert judgment combined with a comparative scoring methodology was applied in establishing fuel relative safety rankings. Limitations of this type of assessment are discussed. Selected accident scenarios included fuel leakage in both residential and public garages; fueling line rupture at a refueling station in the presence of user vehicles or delivery vehicles; and vehicle collisions under rural, urban, and vehicular tunnel conditions. Overall, the results obtained demonstrate dependency upon the specific application or scenario. Gaseous fuels have increased relative risks in certain situations and are relatively safe in others. The results suggest that alternative gaseous fuels are not disqualified for public usage. The assessment also provides rationale for the development of selected safe handling criteria and recommendations.

  13. Large spin accumulation and crystallographic dependence of spin transport in single crystal gallium nitride nanowires

    Science.gov (United States)

    Park, Tae-Eon; Park, Youn Ho; Lee, Jong-Min; Kim, Sung Wook; Park, Hee Gyum; Min, Byoung-Chul; Kim, Hyung-Jun; Koo, Hyun Cheol; Choi, Heon-Jin; Han, Suk Hee; Johnson, Mark; Chang, Joonyeon

    2017-06-01

    Semiconductor spintronics is an alternative to conventional electronics that offers devices with high performance, low power and multiple functionality. Although a large number of devices with mesoscopic dimensions have been successfully demonstrated at low temperatures for decades, room-temperature operation still needs to go further. Here we study spin injection in single-crystal gallium nitride nanowires and report robust spin accumulation at room temperature with enhanced spin injection polarization of 9%. A large Overhauser coupling between the electron spin accumulation and the lattice nuclei is observed. Finally, our single-crystal gallium nitride samples have a trigonal cross-section defined by the (001), () and () planes. Using the Hanle effect, we show that the spin accumulation is significantly different for injection across the (001) and () (or ()) planes. This provides a technique for increasing room temperature spin injection in mesoscopic systems.

  14. Research of influence of gas nitriding duration on formation of diffusion layer of steel 20Kh2N4A

    Directory of Open Access Journals (Sweden)

    Kateryna O. Kostyk

    2015-06-01

    Full Text Available The research of the gas nitriding process, which allows to obtain a high surface quality of steel parts and has a wide application in mass production, is relevant. Aim of the research is to study the influence of gas nitriding modes on the structure and properties of alloy steel. The research material in this work is steel 20Kh2N4A. Nitriding of the samples is carried out in a shaft furnace at the temperature of 510…530 °C during 35, 40, 46 and 48 h. It is found that the alloy steel 20Kh2N4A preliminary heat treatment before nitriding provides the hardness of products core to 279...321 HV due to the formation of perlite-sorta structure with carbides of alloying elements. The results show that increasing the duration of nitriding from 35 to 48 hours at 510…530 °С increases the depth of nitrided layer from 0,35 to 0,55 mm with surface hardness up to 648 MPa at the maximum depth of the layer. The results of this research can be used in industry and research works.

  15. Effect of gas nitriding on CO2 corrosion for 35CrMo steel after surface nanocrystallization.

    Science.gov (United States)

    Wang, Bingying; Zhou, Shengnan; Wang, Jingjing; Zhao, Bin

    2014-10-01

    This paper studies the influence of ultrasonic surface rolling procession (USRP) and gas nitriding on CO2 corrosion for 35CrMo steel. The microstructure of the nanocrystallized surface caused by USRP and the nitrided layer were studied by means of HRTEM and optical microscope, respectively. High temperature high pressure autoclave was adopted to study the CO2 corrosion behavior of 35CrMo steel. The characteristics of CO2 corrosion scales on 35CrMo steel were investigated by the SEM, EDS and XRD techniques. The experimental results show that after USRP about 250 μm rheological layer forms on the metal surface, and the average grain size is 25 nm. USRP thicken the nitrided layer, 10 hours' gas nitriding at 550 degrees C lower the corrosion rate while the combine of gas nitriding and USRP enhances the corrosion resistance furthest; and the surface nanocrystallization increases the content of Cr and changes the corrosion product film from FeCO3 to FeCO3 and Cr2O3, and from loose crystal structure to amorphous flocculent structure. The corrosion resistance of 35CrMo has been improved significantly by USRP and gas nitriding.

  16. Kinetics and thermodynamics of Si(111) surface nitridation in ammonia

    Science.gov (United States)

    Mansurov, Vladimir G.; Malin, Timur V.; Galitsyn, Yurij G.; Shklyaev, Alexander A.; Zhuravlev, Konstantin S.

    2016-05-01

    Kinetics and thermodynamics of Si(111) surface nitridation under an ammonia flux at different substrate temperatures are investigated by reflection high-energy electron diffraction. Two different stages of the nitridation process were revealed. The initial stage is the fast (within few seconds) formation of ordered two-dimensional SiN phase, occuring due to the topmost active surface Si atom (Sisurf) interaction with ammonia molecules. It is followed by the late stage consisting in the slow (within few minutes) amorphous Si3N4 phase formation as a result of the interaction of Si atoms in the lattice site (Siinc) with chemisorbed ammonia molecules. It was found that the ordered SiN phase formation rate decreases, as the temperature increases. The kinetic model of the initial stage was developed, in which the ordered SiN phase formation is the two-dimensional phase transition in the lattice gas with SiN cells. The enthalpy of the active surface Si atom generation on the clean Si(111) surface was estimated to be about 1.5 eV. In contrast, the amorphous Si3N4 phase formation is the normal (thermally activated) chemical process with the first-order kinetics, whose activation energy and pre-exponential factor are 2.4 eV and 108 1/s, respectively.

  17. Intrinsic half-metallicity in fractal carbon nitride honeycomb lattices.

    Science.gov (United States)

    Wang, Aizhu; Zhao, Mingwen

    2015-09-14

    Fractals are natural phenomena that exhibit a repeating pattern "exactly the same at every scale or nearly the same at different scales". Defect-free molecular fractals were assembled successfully in a recent work [Shang et al., Nature Chem., 2015, 7, 389-393]. Here, we adopted the feature of a repeating pattern in searching two-dimensional (2D) materials with intrinsic half-metallicity and high stability that are desirable for spintronics applications. Using first-principles calculations, we demonstrate that the electronic properties of fractal frameworks of carbon nitrides have stable ferromagnetism accompanied by half-metallicity, which are highly dependent on the fractal structure. The ferromagnetism increases gradually with the increase of fractal order. The Curie temperature of these metal-free systems estimated from Monte Carlo simulations is considerably higher than room temperature. The stable ferromagnetism, intrinsic half-metallicity, and fractal characteristics of spin distribution in the carbon nitride frameworks open an avenue for the design of metal-free magnetic materials with exotic properties.

  18. Amber light-emitting diode comprising a group III-nitride nanowire active region

    Science.gov (United States)

    Wang, George T.; Li, Qiming; Wierer, Jr., Jonathan J.; Koleske, Daniel

    2014-07-22

    A temperature stable (color and efficiency) III-nitride based amber (585 nm) light-emitting diode is based on a novel hybrid nanowire-planar structure. The arrays of GaN nanowires enable radial InGaN/GaN quantum well LED structures with high indium content and high material quality. The high efficiency and temperature stable direct yellow and red phosphor-free emitters enable high efficiency white LEDs based on the RGYB color-mixing approach.

  19. Quantitative Thermochemical Measurements in High-Pressure Gaseous Combustion

    Science.gov (United States)

    Kojima, Jun J.; Fischer, David G.

    2012-01-01

    We present our strategic experiment and thermochemical analyses on combustion flow using a subframe burst gating (SBG) Raman spectroscopy. This unconventional laser diagnostic technique has promising ability to enhance accuracy of the quantitative scalar measurements in a point-wise single-shot fashion. In the presentation, we briefly describe an experimental methodology that generates transferable calibration standard for the routine implementation of the diagnostics in hydrocarbon flames. The diagnostic technology was applied to simultaneous measurements of temperature and chemical species in a swirl-stabilized turbulent flame with gaseous methane fuel at elevated pressure (17 atm). Statistical analyses of the space-/time-resolved thermochemical data provide insights into the nature of the mixing process and it impact on the subsequent combustion process in the model combustor.

  20. 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.

  1. 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 ...

  2. Fabrication of translucent boron nitride dispersed polycrystalline silicon nitride ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, B [Department of Metallurgy and Material Engineering, Sunmoon University (Korea, Republic of); Fu, Z [State Key Lab of Advanced Technology for Material Synthesis and Processing, Wuhan University of Technology (China); Niihara, K [Nagaoka University of Technology, Nagaoka (Japan); Lee, S W, E-mail: joshibhupen@gmail.com [Department of Environment Engineering, Sunmoon University, Asan (Korea, Republic of)

    2011-03-15

    Optical transparency was achieved at infrared region and overall translucent silicon nitride was fabricated using hot press sintering (HPS). The increase in h-BN content decreased the optical transparency. Microstructral observations shows that the optical, mechanical and tribological properties of BN dispersed polycrystalline Si{sub 3}N{sub 4} ceramics were affected by the density, {alpha}:{beta}-phase ratio and content of h-BN in sintered ceramics. The hot pressed samples were prepared from the mixture of {alpha}-Si{sub 3}N{sub 4}, AlN, MgO and h-BN at 1850 deg. C. The composite contained from 0.25 to 2 mass % BN powder with sintering aids (9% AlN + 3% MgO). Maximum transmittance of 57% was achieved for 0.25 mass % BN doped Si{sub 3}N{sub 4} ceramics. Fracture toughness was increased and wear volume and friction coefficient were decreased with increase in BN content.

  3. 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.

  4. Sulfur-Doped Carbon Nitride Polymers for Photocatalytic Degradation of Organic Pollutant and Reduction of Cr(VI).

    Science.gov (United States)

    Zheng, Yun; Yu, Zihao; Lin, Feng; Guo, Fangsong; Alamry, Khalid A; Taib, Layla A; Asiri, Abdullah M; Wang, Xinchen

    2017-04-01

    As a promising conjugated polymer, binary carbon nitride has attracted extensive attention as a metal-free and visible-light-responsive photocatalyst in the area of photon-involving purification of water and air. Herein, we report sulfur-doped polymeric carbon nitride microrods that are synthesized through thermal polymerization based on trithiocyanuric acid and melamine (TM) supramolecular aggregates. By tuning the polymerization temperature, a series of sulfur-doped carbon nitride microrods are prepared. The degradation of Rhodamine B (RhB) and the reduction of hexavalent chromium Cr(VI) are selected as probe reactions to evaluate the photocatalytic activities. Results show that increasing pyrolysis temperature leads to a large specific surface area, strong visible-light absorption, and accelerated electron-hole separation. Compared to bulk carbon nitride, the highly porous sulfur-doped carbon nitride microrods fabricated at 650 °C exhibit remarkably higher photocatalytic activity for degradation of RhB and reduction of Cr(VI). This work highlights the importance of self-assembly approach and temperature-control strategy in the synthesis of photoactive materials for environmental remediation.

  5. Compositional and stable carbon isotopic fractionation during non-autocatalytic thermochemical sulfate reduction by gaseous hydrocarbons

    Science.gov (United States)

    Xia, Xinyu; Ellis, Geoffrey S.; Ma, Qisheng; Tang, Yongchun

    2014-01-01

    The possibility of autocatalysis during thermochemical sulfate reduction (TSR) by gaseous hydrocarbons was investigated by examination of previously reported laboratory and field data. This reaction was found to be a kinetically controlled non-autocatalytic process, and the apparent lack of autocatalysis is thought to be due to the absence of the required intermediate species. Kinetic parameters for chemical and carbon isotopic fractionations of gaseous hydrocarbons affected by TSR were calculated and found to be consistent with experimentally derived values for TSR involving long-chain hydrocarbons. Model predictions based on these kinetic values indicate that TSR by gaseous hydrocarbon requires high-temperature conditions. The oxidation of C2–5 hydrocarbons by sulfate reduction is accompanied by carbon isotopic fractionation with the residual C2–5 hydrocarbons becoming more enriched in 13C. Kinetic parameters were calculated for the stable carbon isotopic fractionation of gaseous hydrocarbons that have experienced TSR. Model predictions based on these kinetics indicate that it may be difficult to distinguish the effects of TSR from those of thermal maturation at lower levels of hydrocarbon oxidation; however, unusually heavy δ13C2+ values (>−10‰) can be diagnostic of high levels of conversion (>50%). Stoichiometric and stable carbon isotopic data show that methane is stable under the investigated reaction conditions and is likely a product of TSR by other gaseous hydrocarbons rather than a significant reactant. These results indicate that the overall TSR reaction mechanism for oxidation of organic substrates containing long-chain hydrocarbons involves three distinct phases as follows: (1) an initial slow and non-autocatalytic stage characterized by the reduction of reactive sulfate by long-chain saturated hydrocarbons; (2) a second autocatalytic reaction phase dominated by reactions involving reduced sulfur species and partially oxidized hydrocarbons; (3

  6. Formation of oriented nitrides by N{sup +} ion implantation in iron single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Costa, A.R.G. [CFMC, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); IST/IPFN, Universidade de Lisboa, Campus Tecnológico e Nuclear, E.N.10, 2686-953 Sacavém (Portugal); Silva, R.C. da [IST/IPFN, Universidade de Lisboa, Campus Tecnológico e Nuclear, E.N.10, 2686-953 Sacavém (Portugal); Ferreira, L.P. [CFMC, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Dep. Física, Fac. Ciências e Tecnologia, Universidade de Coimbra, 3004-516 Coimbra (Portugal); Carvalho, M.D. [CCMM/Dep. Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Silva, C. [CFMC, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Dep. Física, Fac. Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Franco, N. [IST/IPFN, Universidade de Lisboa, Campus Tecnológico e Nuclear, E.N.10, 2686-953 Sacavém (Portugal); Godinho, M. [CFMC, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Dep. Física, Fac. Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); and others

    2014-01-15

    Iron single crystals were implanted with nitrogen at room temperature, with a fluence of 5×10{sup 17} cm{sup −2} and 50 keV energy, to produce iron nitride phases and characterize the influence of the crystal orientation. The stability and evolution of the nitride phases and diffusion of implanted nitrogen were studied as a function of successive annealing treatments at 250 °C in vacuum. The composition, structure and magnetic properties were characterized using RBS/channeling, X-Ray Diffraction, Magnetic Force Microscopy, Magneto-optical Kerr Effect and Conversion Electron Mössbauer Spectroscopy. In the as-implanted state the formation of Fe{sub 2}N phase was clearly identified in all single crystals. This phase is not stable at 250 °C and annealing at this temperature promotes the formation of ε-Fe{sub 3}N, or γ′-Fe{sub 4}N, depending on the orientation of the substrate. - Highlights: • Oriented magnetic iron nitrides were obtained by nitrogen implantation into iron single crystals. • The stable magnetic nitride phase at 250 °C depends on the orientation of the host single crystal, being γ'-Fe{sub 4}N or ε-Fe{sub 3}N. • The easy magnetization axis was found to lay in the (100) plane for cubic γ'-Fe{sub 4}N and out of (100) plane for hexagonal ε-Fe{sub 3}N.

  7. Steady-state fuel behavior modeling of nitride fuels in FRAPCON-EP

    Science.gov (United States)

    Feng, Bo; Karahan, Aydın; Kazimi, Mujid S.

    2012-08-01

    Fuel material properties and mechanistic fission gas models in FRAPCON-EP were updated to model the steady-state behavior of high-porosity nitride fuel operating at temperatures below half of the melting point. The fuel thermal conductivity and fuel thermal expansion models were updated with correlations for UN and (U,Pu)N fuels. Hot-pressing of the as-fabricated porosity was modeled as a function of the hydrostatic pressure and creep rate. The solid fission product swelling was assumed to increase linearly with burnup. Fission gas swelling constitutive models were updated to appropriately capture the intragranular gas bubble evolution in nitride fuel. Intergranular gas swelling was neglected due to the assumed high porosity of the fuel. The fission gas release behavior was modeled by fitting the fission gas diffusion coefficient in UN to FRAPCON's default fission gas release model. This fitted gas diffusion coefficient reflects the effects of porosity, burnup, operating temperature, fission rate, and bubble sink strength. Fission gas release and fuel swelling benchmarks against irradiation data were performed. The updated code was applied to UN fuel in typical PWR geometry and operating conditions, with an extended cycle length of 24 months. The results show that swelling of the nitride fuel up to 60 MWd/kg burnup did not lead to excessive straining of the cladding. Furthermore, this study showed that a porous (>15% porosity) nitride fuel pellet could achieve a much higher margin to failure from the cladding collapse and grid-to-rod fretting.

  8. Group III-nitride thin films grown using MBE and bismuth

    Science.gov (United States)

    Kisielowski, Christian K.; Rubin, Michael

    2000-01-01

    The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

  9. Microstructure and corrosion resistance of nitrogen-rich surface layers on AISI 304 stainless steel by rapid nitriding in a hollow cathode discharge

    Science.gov (United States)

    Li, Yang; He, Yongyong; Zhang, Shangzhou; Wang, Wei; Zhu, Yijie

    2018-01-01

    Nitriding treatments have been successfully applied to austenitic stainless steels to improve their hardness and tribological properties. However, at temperatures above 450 °C, conventional plasma nitriding processes decrease the corrosion resistance due to the formation of CrN phases within the modified layer. In this work, AISI 304 austenitic stainless steels were efficiently treated by rapid plasma nitriding at a high temperature of 530 °C in a hollow cathode discharge. The enhanced ionization obtained in the hollow cathode configuration provided a high current density and, consequently, a high temperature could be attained in a short time. The nitrided layers were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results indicated that the dual-layer structure of the nitrided layer consists of a high-N face-centered cubic structure with a free CrN precipitate outer (top) layer and a nitrogen-expanded austenite S-phase bottom layer. The rapid nitriding-assisted hollow cathode discharge technique permits the use of high temperatures, as high as 530 °C, without promoting degradation in the corrosion resistance of stainless steel.

  10. Magnetovolume effects in manganese nitrides with antiperovskite structure

    Directory of Open Access Journals (Sweden)

    Koshi Takenaka

    2014-01-01

    Full Text Available Magnetostructural correlations in antiperovskite manganese nitrides were investigated systematically for stoichiometric and solid solution Mn3Cu1−xAxN (A = Co, Ni, Zn, Ga, Ge, Rh, Pd, Ag, In, Sn or Sb. This class of nitrides is attracting great attention because of their giant negative thermal expansion, which is achieved by doping Ge or Sn into the A site as a relaxant of the sharp volume contraction on heating (spontaneous volume magnetostriction ωs because of the magnetovolume effects. The physical background of large ωs and mechanism of how the volume contraction becomes gradual with temperature are central concerns for the physics and applications of these nitrides. An entire dataset of thermal expansion, crystal structure and magnetization demonstrates that the cubic triangular antiferromagnetic state is crucial for large ωs. The intimate relationship between ωs and the magnetic structure is discussed in terms of geometrical frustration related to the Mn6N octahedron and magnetic stress concept. The results presented herein also show that ωs depends on the number of d electrons in the A atom, suggesting the important role of the d orbitals of the A atom. Not all the dopants in the A site, but the elements that disturb the cubic triangular antiferromagnetic state, are effective in broadening the volume change. This fact suggests that instability neighboring the phase boundary is related to the broadening. The relation between the gradual volume change and the local structure anomaly is suggested by recent microprobe studies.

  11. Nanostructured silicon nitride from wheat and rice husks

    Energy Technology Data Exchange (ETDEWEB)

    Qadri, S. B.; Rath, B. B.; Gorzkowski, E. P.; Wollmershauser, J. A.; Feng, C. R. [Materials Science and Component Technology Directorate, Naval Research Laboratory, Washington, D.C. 20375 (United States)

    2016-04-07

    Nanoparticles, submicron-diameter tubes, and rods of Si{sub 3}N{sub 4} were synthesized from the thermal treatment of wheat and rice husks at temperatures at and above 1300 °C in a nitrogen atmosphere. The whole pattern Rietveld analysis of the observed diffraction data from treatments at 1300 °C showed the formation of only hexagonal α-phase of Si{sub 3}N{sub 4} with an R-factor of 1%, whereas samples treated at 1400 °C and above showed both α- and β-phases with an R-factor of 2%. Transmission electron microscopy showed the presence of tubes, rods, and nanoparticles of Si{sub 3}N{sub 4}. In a two-step process, where pure SiC was produced first from rice or wheat husk in an argon atmosphere and subsequently treated in a nitrogen atmosphere at 1450 °C, a nanostructured composite material having α- and β-phases of Si{sub 3}N{sub 4} combined with cubic phase of SiC was formed. The thermodynamics of the formation of silicon nitride is discussed in terms of the solid state reaction between organic matter (silica content), which is inherently present in the wheat and rice husks, with the nitrogen from the furnace atmosphere. Nanostructures of silicon nitride formed by a single direct reaction or their composites with SiC formed in a two-step process of agricultural byproducts provide an uncomplicated sustainable synthesis route for silicon nitride used in mechanical, biotechnology, and electro-optic nanotechnology applications.

  12. 77 FR 51825 - Ferrovanadium and Nitrided Vanadium From Russia

    Science.gov (United States)

    2012-08-27

    ... COMMISSION Ferrovanadium and Nitrided Vanadium From Russia Determination On the basis of the record \\1... antidumping duty order on ferrovanadium and nitrided vanadium from Russia would not be likely to lead to... contained in USITC Publication 4345 (August 2012), entitled Ferrovanadium and Nitrided Vanadium from Russia...

  13. Anticorrosion nitrided layers on unalloyed and alloyed steels

    Science.gov (United States)

    Wach, P.; Michalski, J.; Burdyński, K.; Ciski, A.

    2017-02-01

    In the paper, nitrided layers on unalloyed and alloyed steels and their corrosion properties are presented. Nitrided layers in the controlled gas nitriding process on C10 and 42CrMo4 steels were formed. Two types of nitrided layers are presented: with nitride iron layers above and below 15 µm. Nitrided layer with nitride layer above 15 µm has good corrosion resistance, but after nitriding of machine parts were subsequently oxidised and impregnated. In the second type of nitrided layer, the surface layers of iron nitrides had a thickness of 3.0 to 11.0 µm. Nitrided layers with a surface layer of iron nitrides with the γ’ (Fe4N) structure were formed on unalloyed steel and investigated. The so-formed layers were subject to basic metallographic, X-ray diffraction and corrosion resistance studies carried out by electrochemical methods and in a neutral salt spray chamber. It was found that the layers consisting only of γ’ phase had a good corrosion resistance. Necessary requirements for achieving an enhanced resistance comprise their complete tightness and thickness not lower than 9.0 µm. Thinner layers had good electrochemical properties but did not exhibit corrosion resistance in the salt spray chamber.

  14. Dynamic response of multiwall boron nitride nanotubes subjected to ...

    Indian Academy of Sciences (India)

    Dynamic behaviours of multiwall boron nitride nanotubes (MWBNNTs) with finite length were studied by employing continuum ... Multiwall boron nitride nanotube; dynamic response; impact; wave propagation. 1. Introduction. Boron nitride .... eV nm6 26 and R0 = 0.344 nm27 in equation (11) yields η = 0.262 GPa nm−1.

  15. Plasma nitridation optimazation for sub-15 A gate dielectrics

    NARCIS (Netherlands)

    Cubaynes, F.N; Cubaynes, F.N.; Schmitz, Jurriaan; van der Marel, C.; Snijders, J.H.M.; Veloso, A.; Rothschild, A.; Olsen, C.; Date, L.

    2003-01-01

    The work investigates the impact of plasma nitridation process parameters upon the physical properties and upon the electrical performance of sub-15 A plasma nitrided gate dielectrics. The nitrogen distribution and chemical bonding of ultra-thin plasma nitrided films have been investigated using

  16. Microstructure characterization of fluidized bed nitrided Fe–Si and ...

    Indian Academy of Sciences (India)

    Unknown

    gations on the nitrided samples were carried out by optical and SEM microscopic observations, X-ray diffraction and Mössbauer spectroscopy. Both the compound and diffusion layers were investigated. Keywords. Fe–Si; Fe–Si–Al foils; thermochemical nitriding treatment; fluidized-bed; structure; nitriding mechanism. 1.

  17. Composite boron nitride neutron detectors

    Science.gov (United States)

    Roth, M.; Mojaev, E.; Khakhan, O.; Fleider, A.; Dul`kin, E.; Schieber, M.

    2014-09-01

    Single phase polycrystalline hexagonal boron nitride (BN) or mixed with boron carbide (BxC) embedded in an insulating polymeric matrix acting as a binder and forming a composite material as well as pure submicron size polycrystalline BN has been tested as a thermal neutron converter in a multilayer thermal neutron detector design. Metal sheet electrodes were covered with 20-50 μm thick layers of composite materials and assembled in a multi-layer sandwich configuration. High voltage was applied to the metal electrodes to create an interspacing electric field. The spacing volume could be filled with air, nitrogen or argon. Thermal neutrons were captured in converter layers due to the presence of the 10B isotope. The resulting nuclear reaction produced α-particles and 7Li ions which ionized the gas in the spacing volume. Electron-ion pairs were collected by the field to create an electrical signal proportional to the intensity of the neutron source. The detection efficiency of the multilayer neutron detectors is found to increase with the number of active converter layers. Pixel structures of such neutron detectors necessary for imaging applications and incorporation of internal moderator materials for field measurements of fast neutron flux intensities are discussed as well.

  18. Filling boron nitride nanotubes with metals

    Science.gov (United States)

    Golberg, D.; Xu, F.-F.; Bando, Y.

    The authors' endeavors over the last few years with respect to boron nitride (BN) nanotube metal filling are reviewed. Mo clusters of 1-2 nm in size and FeNi Invar alloy (Fe 60 at.% Ni 40 at.%) or Co nanorods of 20-70 nm in diameter were embedded into BN nanotube channels via a newly developed two-stage process, in which multi-walled C nanotubes served as templates for the BN multi-walled nanotube synthesis. During cluster filling, low-surface-tension and melting-point Mo oxide first filled a C nanotube through the open tube ends, followed by fragmentation of this filling into discrete clusters via O2 outflow and C-->BN conversion within tubular shells at high temperature. During nanorod filling, C nanotubes containing FeNi or Co nanoparticles at the tube tips were first synthesized by plasma-assisted chemical vapor deposition on FeNi Invar alloy or Co substrates, respectively, and, then, the nanomaterial was heated to the melting points of the corresponding metals in a flow of B2O3 and N2 gases. During this second stage, simultaneous filling of nanotubes with a FeNi or Co melt through capillarity and chemical modification of C tubular shells to form BN nanotubes occurred. The synthesized nanocomposites were analyzed by scanning and high-resolution transmission electron microscopy, electron diffraction, electron-energy-loss spectroscopy and energy-dispersive X-ray spectroscopy. The nanostructures are presumed to function as `nanocables' having conducting metallic cores (FeNi, Co, Mo) and insulating nanotubular shields (BN) with the additional benefit of excellent environmental stability.

  19. Thermal insulation for high temperature microwave sintering operations and method thereof

    Science.gov (United States)

    Holcombe, Cressie E.; Dykes, Norman L.; Morrow, Marvin S.

    1995-01-01

    Superior microwave transparent thermal insulations for high temperature microwave sintering operations were prepared. One embodiment of the thermal insulation comprises granules of boron nitride coated with a very thin layer of glassy carbon made by preparing a glassy carbon precursor and blending it with boron nitride powder to form a mixture. The blended mixture is granulated to form a grit which is dried and heated to form the granules of boron nitride coated with a glassy carbon. Alternatively, grains of glassy carbon are coated with boron nitride by blending a mixture of a slurry comprising boron nitride, boric acid binder, and methyl alcohol with glassy carbon grains to form a blended mixture. The blended mixture is dried to form grains of glassy carbon coated with boron nitride. In addition, a physical mixture of boron nitride powder and glassy carbon grains has also been shown to be an excellent thermal insulation material for microwave processing and sintering.

  20. Method of preparing thermal insulation for high temperature microwave sintering operations

    Science.gov (United States)

    Holcombe, Cressie E.; Dykes, Norman L.; Morrow, Marvin S.

    1996-01-01

    Superior microwave transparent thermal insulations for high temperature microwave sintering operations were prepared. One embodiment of the thermal insulation comprises granules of boron nitride coated with a very thin layer of glassy carbon made by preparing a glassy carbon precursor and blending it with boron nitride powder to form a mixture. The blended mixture is granulated to form a grit which is dried and heated to form the granules of boron nitride coated with a glassy carbon. Alternatively, grains of glassy carbon are coated with boron nitride by blending a mixture of a slurry comprising boron nitride, boric acid binder, and methyl alcohol with glassy carbon grains to form a blended mixture. The blended mixture is dried to form grains of glassy carbon coated with boron nitride. In addition, a physical mixture of boron nitride powder and glassy carbon grains has also been shown to be an excellent thermal insulation material for microwave processing and sintering.

  1. Progress in GEM-based gaseous photomultipliers

    CERN Document Server

    Chechik, R; Breskin, Amos; Buzulutskov, A F; Guedes, G P; Mörmann, D; Singh, B K

    2003-01-01

    We discuss recent progress in gaseous photomultipliers (GPMTs) comprising UV-to-visible spectral range photocathodes (PCs) coupled to multiple Gas Electron Multipliers (GEM). The PCs may be either semitransparent or reflective ones directly deposited on the first-GEM surface. These detectors provide high gain, even in noble gases, are sensitive to single photons, have nanosecond time resolution, and offer good localization. The operation of CsI-based GPMTs in CF sub 4 opens new applications in Cherenkov detectors, where both the radiator and the photosensor operate in the same gas. The latest results on sealed visible-light detectors, combining bialkali PCs and Kapton-made GEMs are presented.

  2. Electrostatic Precipitation in Nearly Pure Gaseous Nitrogen

    Science.gov (United States)

    Buhler, Charles; Calle, Carlos; Clements, Sid; Cox, Bobby; Ritz, Mindy

    2008-01-01

    Electrostatic precipitation was performed in a nearly pure gaseous nitrogen system as a possible remedy for black dust contaminant from high pressure 6000 psi lines at the NASA Kennedy Space Center. The results of a prototype electrostatic precipitator that was built and tested using nitrogen gas at standard atmospheric pressures is presented. High voltage pulsed waveforms are generated using a rotating spark gap system at 30 Hz. A unique dust delivery system utilizing the Venturi effect was devised that supplies a given amount of dust per unit time for testing purposes.

  3. Some gaseous pollutants in Nakorn Sri Thammarat.

    Science.gov (United States)

    Kanatharana, P; Pahina, W

    1991-10-01

    Three gaseous pollutants, carbon monoxide, nitrogen dioxide, and sulfur dioxide were studied in the Nakorn Sri Thammarat Province area (Thailand) during March-August 1987. Air samples were taken from 12 stations covering four districts, i.e., Tungsong, Pakpanang, Muang, and Kanoum. Five stations are located in areas of light traffic conditions and low human population and seven are in densely populated areas with heavy traffic conditions.In this study the concentrations of pollutants found were in the range of non-detectable-0.7 ppm for carbon monoxide, 0.6-7.4 pphm for nitrogen dioxide, and non-detectable-7.4 pphm for sulfur dioxide.

  4. Contact resistance and adhesion characteristics of oxidized tantalum nitride mirors

    Energy Technology Data Exchange (ETDEWEB)

    Kramer, D.K.

    1975-11-01

    Oxidation of tantalum nitride resistor films used in hybrid microcircuits is an unavoidable phenomenon known to affect interfacial properties between resistor and conductor layers. At room temperature, oxide thickness increases with time at an unknown rate; therefore, a three-day limitation between Ta/sub 2/N and Cr/Au conductor deposition is presently specified for hybrid microcircuits. The effects of Ta/sub 2/N aging on resistor-conductor contact resistance and conductor bondability were evaluated. Accelerated aging produced oxide layers of various thicknesses which were then correlated to contact resistance. Analytical data and calculations indicate that a 25 percent increase in contact resistance would occur by exposing the Ta/sub 2/N to air for approximately three years at room temperature and pressure prior to metallization. However, little or no change in bondability would be expected.

  5. Phonon wave interference in graphene and boron nitride superlattice

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xue-Kun; Zhou, Wu-Xing; Tang, Li-Ming; Chen, Ke-Qiu, E-mail: keqiuchen@hnu.edu.cn [Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082 (China); Xie, Zhong-Xiang [Department of Mathematics and Physics, Hunan Institute of Technology, Hengyang 421002 (China)

    2016-07-11

    The thermal transport properties of the graphene and boron nitride superlattice (CBNSL) are investigated via nonequilibrium molecular dynamics simulations. The simulation results show that a minimum lattice thermal conductivity can be achieved by changing the period length of the superlattice. Additionally, it is found that the period length at the minimum shifts to lower values at higher temperatures, and that the depth of the minimum increases with decreasing temperature. In particular, at 200 K, the thermal conductivities of CBNSLs with certain specific period lengths are nearly equal to the corresponding values at 300 K. A detailed analysis of the phonon spectra shows that this anomalous thermal conductivity behavior is a result of strong phonon wave interference. These observations indicate a promising strategy for manipulation of thermal transport in superlattices.

  6. Structure and Thermal Stability of Copper Nitride Thin Films

    Directory of Open Access Journals (Sweden)

    Guangan Zhang

    2013-01-01

    Full Text Available Copper nitride (Cu3N thin films were deposited on glass via DC reactive magnetron sputtering at various N2 flow rates and partial pressures with 150°C substrate temperature. X-ray diffraction and scanning electron microscopy were used to characterize the microstructure and morphology. The results show that the films are composed of Cu3N crystallites with anti-ReO3 structure. The microstructure and morphology of the Cu3N film strongly depend on the N2 flow rate and partial pressure. The cross-sectional micrograph of the film shows typical columnar, compact structure. The thermal stabilities of the films were investigated using vacuum annealing under different temperature. The results show that the introducing of argon in the sputtering process decreases the thermal stability of the films.

  7. Optically-pumped dilute nitride spin-VCSEL.

    Science.gov (United States)

    Schires, Kevin; Al Seyab, Rihab; Hurtado, Antonio; Korpijärvi, Ville-Markus; Guina, Mircea; Henning, Ian D; Adams, Michael J

    2012-02-13

    We report the first room temperature optical spin-injection of a dilute nitride 1300 nm vertical-cavity surface-emitting laser (VCSEL) under continuous-wave optical pumping. We also present a novel experimental protocol for the investigation of optical spin-injection with a fiber setup. The experimental results indicate that the VCSEL polarization can be controlled by the pump polarization, and the measured behavior is in excellent agreement with theoretical predictions using the spin flip model. The ability to control the polarization of a long-wavelength VCSEL at room temperature emitting at the wavelength of 1.3 µm opens up a new exciting research avenue for novel uses in disparate fields of technology ranging from spintronics to optical telecommunication networks.

  8. Molecular dynamics simulation of deformation twin in rocksalt vanadium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Tao [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Peng, Xianghe, E-mail: xhpeng@cqu.edu.cn [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044 (China); Zhao, Yinbo [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Li, Tengfei [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Li, Qibin [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Wang, Zhongchang, E-mail: zcwang@wpi-aimr.tohoku.ac.jp [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2016-08-05

    We perform molecular dynamics simulation of nano-indentation with a cylindrical indenter to investigate the formation mechanism of deformation twin in vanadium nitride (VN) with a rocksalt structure. We find that the deformation twins occur during the loading stage, and subsequently conduct a systematic analysis of nucleation, propagation and thickening of a deformation twin. We find that the nucleation of a partial dislocation and its propagation to form a stacking fault are premise of deformation twin formation. The sequential nucleation and propagation of partial dislocation on adjacent parallel {111} planes are found to cause the thickening of the deformation twin. Moreover, the deformation twins can exist in VN at room temperature. - Highlights: • MD simulations of indentation are performed to study the deformation twin in VN. • The deformation twins can occur in VN during the loading stage. • The nucleation, propagation and thickening of a deformation twin are analyzed. • The deformation twins can exist in VN at room temperature.

  9. Solid-gaseous phase transformation of elemental contaminants during the gasification of biomass.

    Science.gov (United States)

    Jiang, Ying; Ameh, Abiba; Lei, Mei; Duan, Lunbo; Longhurst, Philip

    2016-09-01

    Disposal of plant biomass removed from heavy metal contaminated land via gasification achieves significant volume reduction and can recover energy. However, these biomass often contain high concentrations of heavy metals leading to hot-corrosion of gasification facilities and toxic gaseous emissions. Therefore, it is of significant interest to gain a further understanding of the solid-gas phase transition of metal(loid)s during gasification. Detailed elemental analyses (C, H, O, N and key metal/metalloid elements) were performed on five plant species collected from a contaminated site. Using multi-phase equilibria modelling software (MTDATA), the analytical data allows modelling of the solid/gas transformation of metal(loid)s during gasification. Thermodynamic modelling based on chemical equilibrium calculations was carried out in this study to predict the fate of metal(loid) elements during typical gasification conditions and to show how these are influenced by metal(loid) composition in the biomass and operational conditions. As, Cd, Zn and Pb tend to transform to their gaseous forms at relatively low temperatures (gasification temperature range of 1000-1200°C. Whereas Cr, Al, Fe and Mg remain in solid phase at higher temperatures (>1200°C). Simulation of pressurised gasification conditions shows that higher pressures increase the temperature at which solid-to-gaseous phase transformations takes place. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  10. Microstructure and micro-Raman studies of nitridation and structure transition of gallium oxide nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ning, J.Q. [Department of Physics and HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Xu, S.J., E-mail: sjxu@hku.hk [Department of Physics and HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Wang, P.W.; Song, Y.P.; Yu, D.P. [Electronic Microscopy Laboratory and State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, Hong Kong (China); Shan, Y.Y.; Lee, S.T. [Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong (China); Yang, H. [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123, Hong Kong (China)

    2012-11-15

    Here we present a detailed study on nitridation and structure transition in monoclinic gallium oxide ({beta}-Ga{sub 2}O{sub 3}) nanowires grown on Si substrates with chemical vapor phase epitaxy. The nanowires were systematically nitridated at different temperatures. Their morphologies and microstructures were precisely characterized using field-emission scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and confocal micro-Raman spectroscopy. It is found that heat treatment of Ga{sub 2}O{sub 3} nanowires in the gas of ammonia results in rich substructures including the Ga{sub 2}O{sub 3} phase, the crystalline GaN phase, and other meta structures. The identification of these structures helps to understand some interesting phenomena observed in nanostructures, such as the microstructural origin of the unknown Raman lines in GaN nanowires. - Highlights: Black-Right-Pointing-Pointer Nitridation and structure transition of Ga{sub 2}O{sub 3} significantly depend on temperature. Black-Right-Pointing-Pointer G-N bonds form at lower temperatures but the Ga{sub 2}O{sub 3} lattice is still dominant. Black-Right-Pointing-Pointer Amorphous GaN coexists with crystalline Ga{sub 2}O{sub 3} at higher temperatures. Black-Right-Pointing-Pointer Crystalline GaN with distinct morphology is obtained at much higher temperatures.

  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. Thermodynamics, kinetics and process control of nitriding

    DEFF Research Database (Denmark)

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

    1997-01-01

    , the nitriding result is determined largely by kinetics. Nitriding kinetics are shown to be characterised by local near equilibria and stationary states at surfaces and interfaces, and the diffusion coefficient of nitrogen in the various phases, for which new data are presented. The necessary background......, The Netherlands; Professor Mittemeijer is now also at the Max Planck Institute for Metals Research, Seestrasse 92, D-70174 Stuttgart, Germany and Professor Somers is now in the Division of Metallurgy, Technical University of Denmark, Bldg 204, DK 2800, Lyngby, Denmark. Contribution to the 10th Congress...

  13. Conducting metal oxide and metal nitride nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    DiSalvo, Jr., Francis J.; Subban, Chinmayee V.

    2017-12-26

    Conducting metal oxide and nitride nanoparticles that can be used in fuel cell applications. The metal oxide nanoparticles are comprised of for example, titanium, niobium, tantalum, tungsten and combinations thereof. The metal nitride nanoparticles are comprised of, for example, titanium, niobium, tantalum, tungsten, zirconium, and combinations thereof. The nanoparticles can be sintered to provide conducting porous agglomerates of the nanoparticles which can be used as a catalyst support in fuel cell applications. Further, platinum nanoparticles, for example, can be deposited on the agglomerates to provide a material that can be used as both an anode and a cathode catalyst support in a fuel cell.

  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. Studies on Tribological Behavior of Aluminum Nitride-Coated Steel

    Science.gov (United States)

    Ionescu, G. C.; Nae, I.; Ripeanu, R. G.; Dinita, A.; Stan, G.

    2017-02-01

    The new opportunities introduced by the large development of the IoT (internet of things) are increasing the demand for sensors to be located as close as possible to the supervised process. The Aluminum Nitride (AIN) is one of the most promising materials for sensors due to its piezoelectric, excellent mechanical properties, chemical inertness and high melting point. Due to these material properties, the AlN sensors are suitable to operate in high temperature and harsh environment conditions and therefore are very promising to be employed in industrial applications. In this article are presented the studies conducted on several Aluminum Nitride-Coated Steel structures with the goal of producing sensors embedded in the ball bearings, bearings and other mobile parts of machine tools. The experiments were conducted on simple coatings structures without lubricating materials and the obtained results are promising, demonstrating that, with some limitations the AIN could be used in such applications. This paper was accepted for publication in Proceedings after double peer reviewing process but was not presented at the Conference ROTRIB’16

  16. Innovative Monitoring of Atmospheric Gaseous Hydrogen Fluoride

    Directory of Open Access Journals (Sweden)

    Stefano Dugheri

    2016-01-01

    Full Text Available Hydrogen fluoride (HF is a basic raw material for a wide variety of industrial products, with a worldwide production capacity of more than three million metric tonnes. A novel method for determining particulate fluoride and gaseous hydrogen fluoride in air is presented herewith. Air was sampled using miniaturised 13 mm Swinnex two-stage filter holders in a medium-flow pumping system and through the absorption of particulate fluoride and HF vapours on cellulose ester filters uncoated or impregnated with sodium carbonate. Furthermore, filter desorption from the holders and the extraction of the pentafluorobenzyl ester derivative based on solid-phase microextraction were performed using an innovative robotic system installed on an xyz autosampler on-line with gas chromatography (GC/mass spectrometry (MS. After generating atmospheres of a known concentration of gaseous HF, we evaluated the agreement between the results of our sampling method and those of the conventional preassembled 37 mm cassette (±8.10%; correlation coefficient: 0.90. In addition, precision (relative standard deviation for n=10, 4.3%, sensitivity (0.2 μg/filter, and linearity (2.0–4000 μg/filter; correlation coefficient: 0.9913 were also evaluated. This procedure combines the efficiency of GC/MS systems with the high throughput (96 samples/day and the quantitative accuracy of pentafluorobenzyl bromide on-sample derivatisation.

  17. Position-sensitive gaseous photomultipliers research and applications

    CERN Document Server

    Francke, Tom; Peskov, Vladimir

    2016-01-01

    Gaseous photomultipliers are defined as gas-filled devices capable of recording single ultraviolet (UV) and visible photons with high position resolution. Used in a variety of research areas, these detectors can be paired with computers to treat and store imaging information of UV-light. Position-Sensitive Gaseous Photomultipliers: Research and Applications explores the advancement of gaseous detectors as applied for single photon detection. Emphasizing emerging perspectives and new ways to apply gaseous detectors across research fields, this research-based publication is an essential reference source for engineers, physicists, graduate-level students, and researchers.

  18. Multishock comparison of dense gaseous H2 + He mixtures up to 30 GPa.

    Science.gov (United States)

    Gu, Y J; Chen, Q F; Cai, L C; Chen, Z Y; Zheng, J; Jing, F Q

    2009-05-14

    Time-resolved spectral radiation histories of the gaseous H(2) + He mixtures under shock loadings were measured by using a six-wavelength channel pyrometer. The initial gaseous mixtures had a mole component of H(2):He = 1:1.21, which were shocked from room temperature and initial pressure of 20 MPa to a pressure range of 1-30 GPa and temperature range of 3000-7000 K by means of a two-stage light-gas gun. Multishock reverberations between the base-plate and sapphire window can be observed up to the fifth-shock compressions. The experimental data are in good agreement with self-consistent fluid variational theory calculations in which the dissociation process of hydrogen molecules and various interactions among atomic and molecular species are taken into account.

  19. Four Terminal Gallium Nitride MOSFETs

    Science.gov (United States)

    Veety, Matthew Thomas

    All reported gallium nitride (GaN) transistors to date have been three-terminal devices with source, drain, and gate electrodes. In the case of GaN MOSFETs, this leaves the bulk of the device at a floating potential which can impact device threshold voltage. In more traditional silicon-based MOSFET fabrication a bulk contact can be made on the back side of the silicon wafer. For GaN grown on sapphire substrates, however, this is not possible and an alternate, front-side bulk contact must be investigated. GaN is a III-V, wide band gap semiconductor that as promising material parameters for use in high frequency and high power applications. Possible applications are in the 1 to 10 GHz frequency band and power inverters for next generation grid solid state transformers and inverters. GaN has seen significant academic and commercial research for use in Heterojunction Field Effect Transistors (HFETs). These devices however are depletion-mode, meaning the device is considered "on" at zero gate bias. A MOSFET structure allows for enhancement mode operation, which is normally off. This mode is preferrable in high power applications as the device has lower off-state power consumption and is easier to implement in circuits. Proper surface passivation of seminconductor surface interface states is an important processing step for any device. Preliminary research on surface treatments using GaN wet etches and depletion-mode GaN devices utilizing this process are discussed. Devices pretreated with potassium pursulfate prior to gate dielectric deposition show significant device improvements. This process can be applied to any current GaN FET. Enhancement-mode GaN MOSFETs were fabricated on magnesium doped p-type Wurtzite gallium nitride grown by Metal Organic Chemical Vapor Deposition (MOCVD) on c-plane sapphire substrates. Devices utilized ion implant source and drain which was activated under NH3 overpressure in MOCVD. Also, devices were fabricated with a SiO2 gate dielectric

  20. Work Function Characterization of Potassium-Intercalated, Boron Nitride Doped Graphitic Petals

    Directory of Open Access Journals (Sweden)

    Patrick T. McCarthy

    2017-07-01

    Full Text Available This paper reports on characterization techniques for electron emission from potassium-intercalated boron nitride-modified graphitic petals (GPs. Carbon-based materials offer potentially good performance in electron emission applications owing to high thermal stability and a wide range of nanostructures that increase emission current via field enhancement. Furthermore, potassium adsorption and intercalation of carbon-based nanoscale emitters decreases work functions from approximately 4.6 eV to as low as 2.0 eV. In this study, boron nitride modifications of GPs were performed. Hexagonal boron nitride is a planar structure akin to graphene and has demonstrated useful chemical and electrical properties when embedded in graphitic layers. Photoemission induced by simulated solar excitation was employed to characterize the emitter electron energy distributions, and changes in the electron emission characteristics with respect to temperature identified annealing temperature limits. After several heating cycles, a single stable emission peak with work function of 2.8 eV was present for the intercalated GP sample up to 1,000 K. Up to 600 K, the potassium-intercalated boron nitride modified sample exhibited improved retention of potassium in the form of multiple emission peaks (1.8, 2.5, and 3.3 eV resulting in a large net electron emission relative to the unmodified graphitic sample. However, upon further heating to 1,000 K, the unmodified GP sample demonstrated better stability and higher emission current than the boron nitride modified sample. Both samples deintercalated above 1,000 K.

  1. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells

    Science.gov (United States)

    2014-01-01

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li+Cl–), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li+Cl– catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA. PMID:24748912

  2. Two-Dimensional Modeling of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistor

    National Research Council Canada - National Science Library

    Holmes, Kenneth

    2002-01-01

    Gallium Nitride (GaN) High Electron Mobility Transistors (HEMT's) are microwave power devices that have the performance characteristics to improve the capabilities of current and future Navy radar and communication systems...

  3. Study of the high power laser-metal interactions in the gaseous atmospheres

    Science.gov (United States)

    Lugomer, Stjepan; Bitelli, G.; Stipancic, M.; Jovic, F.

    1994-08-01

    The tantalum and titanium plates were treated by pulsed, high power CO2 laser in the pressurized atmospheres of N2 and O2. Studies performed by the optical microscopy, microhardness measurements, and the auger electron spectroscopy revealed: (1) topographic modification of the surface caused by the temperature field; (2) metal hardening, caused by the laser shock; and (3) alloying/cladding, caused by the chemical reaction between the metal surface and the gaseous atmosphere.

  4. Effect of Hypergravity Stress on Gaseous Exchange and Survival of Young and Old Guinea Pigs

    Science.gov (United States)

    Muradian, Kh. K.; Timchenko, A. N.

    Hypergravity tolerance decreases in aging Guinea pigs, the range being lower than in other studied species of laboratory mammals - mice, hamsters, and rats. Moreover, for the gaseous exchange rate and body temperature, the decline during the stress is not characteristic for Guinea pigs of both age groups, in contrast to other species. In general, hypergravity tolerance of Guinea pigs could be more appropriate experimental models.

  5. Plasmonic spectral tunability of conductive ternary nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Kassavetis, S.; Patsalas, P., E-mail: ppats@physics.auth.gr [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Bellas, D. V.; Lidorikis, E. [Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina (Greece); Abadias, G. [Institut Pprime, Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS-ENSMA, 86962 Chasseneuil-Futuroscope (France)

    2016-06-27

    Conductive binary transition metal nitrides, such as TiN and ZrN, have emerged as a category of promising alternative plasmonic materials. In this work, we show that ternary transition metal nitrides such as Ti{sub x}Ta{sub 1−x}N, Ti{sub x}Zr{sub 1−x}N, Ti{sub x}Al{sub 1−x}N, and Zr{sub x}Ta{sub 1−x}N share the important plasmonic features with their binary counterparts, while having the additional asset of the exceptional spectral tunability in the entire visible (400–700 nm) and UVA (315–400 nm) spectral ranges depending on their net valence electrons. In particular, we demonstrate that such ternary nitrides can exhibit maximum field enhancement factors comparable with gold in the aforementioned broadband range. We also critically evaluate the structural features that affect the quality factor of the plasmon resonance and we provide rules of thumb for the selection and growth of materials for nitride plasmonics.

  6. 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

  7. Producing Silicon Carbide/Silicon Nitride Fibers

    Science.gov (United States)

    1986-01-01

    Manufacturing process makes CxSiyNz fibers. Precursor fibers spun from extruding machine charged with polycarbosilazane resin. When pyrolyzed, resin converted to cross-linked mixture of silicon carbide and silicon nitride, still in fiber form. CxSiyNz fibers promising substitutes for carbon fibers in high-strength, low-weight composites where high electrical conductivity unwanted.

  8. Gallium nitride junction field-effect transistor

    Science.gov (United States)

    Zolper, John C.; Shul, Randy J.

    1999-01-01

    An all-ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorous co-implantation, in selected III-V semiconductor materials.

  9. 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.

  10. 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

  11. 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.

  12. Slip casting and nitridation of silicon powder

    Science.gov (United States)

    Seiko, Y.

    1985-01-01

    Powdered Silicon was slip-cast with a CaSO4 x 0.5H2O mold and nitrided in a N atm. containing 0 or 5 vol. % H at 1000 to 1420 deg. To remove the castings, the modeling faces were coated successively with an aq. salt soap and powdered cellulose containing Na alginate, and thus prevented the sticking problem.

  13. CuNNi3: a new nitride superconductor with antiperovskite structure

    Science.gov (United States)

    He, Bing; Dong, Cheng; Yang, Lihong; Chen, Xiaochao; Ge, Linhui; Mu, Libin; Shi, Youguo

    2013-12-01

    We have successfully synthesized a new Ni-based antiperovskite nitride, CuNNi3, which exhibits superconductivity with a transition temperature Tc of 3.2 K. This compound is the second nitride superconductor in the Ni-based antiperovskites. We report the synthesis and physical properties of CuNNi3, characterized via x-ray diffraction, magnetization, resistivity, and heat capacity measurements. The temperature dependence of the specific heat is consistent with an isotropic s-wave gap (Δ0 = 0.42 meV). The estimated electron-phonon coupling strength (λep = 0.53) suggests that the superconductivity in CuNNi3 is induced by electron-phonon coupling, and the gap ratio (2Δ0/kBTc) of 3.05 indicates that it is a weak coupling superconductor. Furthermore, the relatively high Ginzburg-Landau parameter (κ = 24.6) signifies that CuNNi3 is a type II superconductor.

  14. Hydrogen separation by nanocrystalline titanium nitride membranes with high hydride ion conductivity

    Science.gov (United States)

    Kura, Chiharu; Kunisada, Yuji; Tsuji, Etsushi; Zhu, Chunyu; Habazaki, Hiroki; Nagata, Shinji; Müller, Michael P.; De Souza, Roger A.; Aoki, Yoshitaka

    2017-10-01

    The production of pure hydrogen for use in energy applications and related industries often relies on the permeation of hydrogen through palladium-based membranes. However, the scarcity of Pd reserves necessitates the development of affordable alternatives with high hydrogen permeability. Here we report room-temperature hydrogen permeability of titanium nitrides (widely used as tough and inert coating materials) enabled by mixed hydride ion-electron conductivity. Combined spectroscopic, permeability and microgravimetric measurements reveal that nanocrystalline TiNx membranes feature enhanced grain-boundary diffusion of hydride anions associated with interfacial Ti cations on nanograins. Since the corresponding activation energies are very low (kJ mol-1), these membranes yield a considerably higher room-temperature hydrogen flux than Pd membranes of equivalent thickness. Overall, the current study establishes general guidelines for developing hydride ion transport membranes based on a simple transition metal nitride for hydrogen purification, membrane reactors and other applications.

  15. Nano Indentation Inspection of the Mechanical Properties of Gold Nitride Thin Films

    Directory of Open Access Journals (Sweden)

    Armen Verdyan

    2007-10-01

    Full Text Available The morphology and the local mechanical properties of gold nitride thin films were studied by atomic force microscope (AFM. Gold nitride films were deposited for the first time on silicon substrate without any buffer layer at room temperature by reactive pulsed laser ablation deposition (RPLD. The films were fabricated on (100 Si wafers by RPLD technique in which KrF excimer laser was used to ablate a gold target in N2 atmosphere (0.1 GPa-100 Pa and ambient temperature. Scanning electron microscopy (SEM and atomic force microscopy inspections showed that the films were flat plane with rms roughness in the range of 35.1 nm-3.6 nm, depending on the deposition pressure. Rutherford backscattering spectrometry (RBS and energy dispersion spectroscopy (EDS used to detect the nitrogen concentration in the films, have revealed a composition close to Au3N. The film

  16. Comparison of the ultrafast hot electron dynamics of titanium nitride and gold for plasmonic applications

    Science.gov (United States)

    Doiron, Brock; Li, Yi; Mihai, Andrei P.; Cohen, Lesley F.; Petrov, Peter K.; Alford, Neil M.; Oulton, Rupert F.; Maier, Stefan A.

    2017-08-01

    With similar optical properties to gold and high thermal stability, titanium nitride continues to prove itself as a promising plasmonic material for high-temperature applications in the visible and near-infrared. In this work, we use transient pump probe differential reflection measurements to compare the electron energy decay channels in titanium nitride and gold thin films. Using an extended two temperature model to incorporate the photoexcited electrons, it is possible to separate the electron-electron and electron-phonon scattering contributions immediately following the arrival of the pump pulse. This model allows for incredibly accurate determination of the internal electronic properties using only optical measurements. As the electronic properties are key in hot electron applications, we show that titanium nitide has substantially longer electron thermalization and electron-phonon scattering times. With this, we were also able to resolve electron thermal conduction in the film using purely optical measurements.

  17. Electrical behavior of multi-walled carbon nanotube network embedded in amorphous silicon nitride

    Directory of Open Access Journals (Sweden)

    Buiculescu Raluca

    2011-01-01

    Full Text Available Abstract The electrical behavior of multi-walled carbon nanotube network embedded in amorphous silicon nitride is studied by measuring the voltage and temperature dependences of the current. The microstructure of the network is investigated by cross-sectional transmission electron microscopy. The multi-walled carbon nanotube network has an uniform spatial extension in the silicon nitride matrix. The current-voltage and resistance-temperature characteristics are both linear, proving the metallic behavior of the network. The I-V curves present oscillations that are further analyzed by computing the conductance-voltage characteristics. The conductance presents minima and maxima that appear at the same voltage for both bias polarities, at both 20 and 298 K, and that are not periodic. These oscillations are interpreted as due to percolation processes. The voltage percolation thresholds are identified with the conductance minima.

  18. Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Bikramjeet; Singh, Paviter; Kumar, Akshay, E-mail: akshaykumar.tiet@gmail.com [Advanced Functional Materials lab, Department of Nanotechnology, Sri Guru Granth Sahib World University, Fatehgarh Sahib-140406 Punjab (India); Kumar, Manjeet [Department of Materials Engineering, Defense Institute of Advanced Technology (DU), Pune 411025 (India); Thakur, Anup [Material Science Research Lab, Department of basic and Applied Sciences, Punjabi University Patiala 147002 (India)

    2015-05-15

    Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H{sub 3}BO{sub 3}). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications as well boron neutron capture therapy (BNCT)

  19. NASA Research on the Hydrodynamics of the Gaseous Vortex Reactor

    Science.gov (United States)

    Ragsdale, Robert G.

    1960-01-01

    The experimental and analytical results to date of a study of a two-component gaseous vortex system are presented in this paper. Analytical expressions for tangential velocity and static-pressure profiles in a turbulent vortex show good agreement with experimental data. Airflow rates from 0.075 to 0.14 pound per second and corresponding tangential velocities from 160 to 440 feet per second are correlated by turbulent Reynolds numbers from 1.95 to 2.4. An analysis of an air-bromine gas mixture in a turbulent vortex indicates that a boundary value of bromine-to-air radial velocity ratio (u(2)/u(1)) of 0.999 gives essentially no bromine buildup, while a value of 0.833 results in considerable separation. For a constant value of (u(2)/u(1))(0) the bromine buildup increases as (1) the tangential velocity increases, (2) the air-to-bromine weight-flow ratio decreases, (3) the airflow rate decreases, (4) the temperature decreases, and (5) the turbulence decreases. Analytical temperature, pressure, and tangential-velocity profiles are also presented. Preliminary experimental results indicate that the flow of an air-bromine mixture through a vortex field results in a bromine density increase to a maximum value; followed by a decrease; the air density exhibits a uniform decrease from the outer vortex radius to the exhaust-nozzle radius.

  20. Scanning proximal microscopy study of the thin layers of silicon carbide-aluminum nitride solid solution manufactured by fast sublimation epitaxy

    Directory of Open Access Journals (Sweden)

    Tománek P.

    2013-05-01

    Full Text Available The objective of the study is a growth of SiC/(SiC1−x(AlNx structures by fast sublimation epitaxy of the polycrystalline source of (SiC1−x(AlNx and their characterisation by proximal scanning electron microscopy and atomic force microscopy. For that purpose optimal conditions of sublimation process have been defined. Manufactured structures could be used as substrates for wide-band-gap semiconductor devices on the basis of nitrides, including gallium nitride, aluminum nitride and their alloys, as well as for the production of transistors with high mobility of electrons and also for creation of blue and ultraviolet light emitters (light-emitted diodes and laser diodes. The result of analysis shows that increasing of the growth temperature up to 2300 K allows carry out sublimation epitaxy of thin layers of aluminum nitride and its solid solution.

  1. Processing development for ceramic structural components: the influence of a presintering of silicon on the final properties of reaction bonded silicon nitride. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    1982-03-01

    The influence of a presintering of silicon on the final properties of reaction bonded silicon nitride has been studied using scanning electron and optical microscopy, x-ray diffraction analysis, 4 pt. bend test, and mecury intrusion porosimetry. It has been shown that presintering at 1050/sup 0/C will not affect the final nitrided properties. At 1200/sup 0/C, the oxide layer is removed, promoting the formation of B-phase silicon nitride. Presintering at 1200/sup 0/C also results in compact weight loss due to the volatilization of silicon, and the formation of large pores which severely reduce nitrided strength. The development of the structure of sintered silicon compacts appears to involve a temperature gradient, with greater sintering observed near the surface.

  2. The Importance Of Surface Topography For The Biological Properties Of Nitrided Diffusion Layers Produced On Ti6Al4V Titanium Alloy

    Directory of Open Access Journals (Sweden)

    Wierzchoń T.

    2015-09-01

    Full Text Available Diffusion nitrided layers produced on titanium and its alloys are widely studied in terms of their application for cardiac and bone implants. The influence of the structure, the phase composition, topography and surface morphology on their biological properties is being investigated. The article presents the results of a study of the topography (nanotopography of the surface of TiN+Ti2N+αTi(N nitrided layers produced in low-temperature plasma on Ti6Al4V titanium alloy and their influence on the adhesion of blood platelets and their aggregates. The TEM microstructure of the produced layers have been examined and it was demonstrated that the interaction between platelets and the surface of the titanium implants subjected to glow-discharge nitriding can be shaped via modification of the roughness parameters of the external layer of the TiN titanium nitride nanocrystalline zone.

  3. Distribution of nitrogen and defects in SiO(x)N(y)/Si structures formed by the thermal nitridation of SiO2/Si

    Science.gov (United States)

    Vasquez, R. P.; Madhukar, A.; Grunthaner, F. J.; Naiman, M. L.

    1986-01-01

    Previously reported nitrogen distributions in SiO2 films on Si which have been thermally nitrided at 1000 C have been explained by a kinetic model of the nitridation process which rests upon the effects of interfacial strain. A critical test of this kinetic model is the validity of the predictions regarding nitrogen distributions obtained at other nitridation temperatures. In this work, nitrogen distributions determined via X-ray photoelectron spectroscopy are reported for samples nitrided at 800 and 1150 C, and are shown to be consistent with the kinetic model. In addition, the intensity of a fluorine marker is found to correlate with the nitrogen distribution, and is postulated to be related to kinetically generated defects in the dielectric film, consistent with the strain-dependent energy of formation of defects proposed recently to explain electrical data.

  4. Simulating Isotope Enrichment by Gaseous Diffusion

    Science.gov (United States)

    Reed, Cameron

    2015-04-01

    A desktop-computer simulation of isotope enrichment by gaseous diffusion has been developed. The simulation incorporates two non-interacting point-mass species whose members pass through a cascade of cells containing porous membranes and retain constant speeds as they reflect off the walls of the cells and the spaces between holes in the membranes. A particular feature is periodic forward recycling of enriched material to cells further along the cascade along with simultaneous return of depleted material to preceding cells. The number of particles, the mass ratio, the initial fractional abundance of the lighter species, and the time between recycling operations can be chosen by the user. The simulation is simple enough to be understood on the basis of two-dimensional kinematics, and demonstrates that the fractional abundance of the lighter-isotope species increases along the cascade. The logic of the simulation will be described and results of some typical runs will be presented and discussed.

  5. Gaseous Viscous Peeling of Linearly Elastic Substrates

    Science.gov (United States)

    Elbaz, Shai; Jacob, Hila; Gat, Amir

    2017-11-01

    We study pressure-driven propagation of gas into a micron-scale gap between two linearly elastic substrates. Applying the lubrication approximation, the governing nonlinear evolution equation describes the interaction between elasticity and viscosity, as well as weak rarefaction and low-Mach-number compressibility, characteristic to gaseous microflows. Several physical limits allow simplification of the evolution equation and enable solution by self-similarity. During the peeling process the flow-field transitions between the different limits and the respective approximate solutions. The sequence of limits occurring during the propagation dynamics can be related to the thickness of the prewetting layer of the configuration at rest, yielding an approximate description of the entire peeling dynamics. The results are validated by numerical solutions of the evolution equation. Israel Science Foundation 818/13.

  6. Background reduction of a spherical gaseous detector

    Energy Technology Data Exchange (ETDEWEB)

    Fard, Ali Dastgheibi [Laboratoire Souterrain de Modane, France ali.dastgheibi-fard@lsm.in2p3.fr (France); Loaiza, Pia; Piquemal, Fabrice [Laboratoire Souterrain de Modane (France); Giomataris, Ioannis; Gray, David; Gros, Michel; Magnier, Patrick; Navick, Xavier-François [CEA Saclay - IRFU/SEDI - 91191 Gif sur Yvette (France); Savvidis, Ilias [Aristotle University of Thessaloniki (Greece)

    2015-08-17

    The Spherical gaseous detector (or Spherical Proportional Counter, SPC) is a novel type of detector. It consists of a large spherical volume filled with gas, using a single detection readout channel. The detector allows 100 % detection efficiency. SEDINE is a low background version of SPC installed at the Laboratoire Souterrain de Modane (LSM) underground laboratory (4800 m.w.e) looking for rare events at very low energy threshold, below 100 eV. This work presents the details on the chemical cleaning to reduce internal {sup 210}Pb surface contamination on the copper vessel and the external radon reduction achieved via circulation of pure air inside anti-radon tent. It will be also show the radon measurement of pure gases (Ar, N, Ne, etc) which are used in the underground laboratory for the low background experiments.

  7. Allis Prize Lecture: Gaseous Electronics Physics Inside

    Science.gov (United States)

    Garscadden, Alan

    2002-10-01

    I was fortunate to enjoy the advice of K. G. Emeleus during my graduate studies and for many years afterwards. He introduced me to the papers of Will Allis and later I was privileged to correspond with Professor Allis. At this time I had moved from the Queens university environment to work at a large Air Force base. There I have worked with a lot of smart people, including several who also come to the GEC each year to be refreshed and calibrated. A personal overview is presented on a few of the many roles that atomic, molecular and optical physics, including gaseous electronics, play in programs of the Air Force Research Laboratory and subsequently on AF systems and operations. While there have been misses, overall there have been many successes with impacts that provide more effective systems, as recent experiences have demonstrated. Some example studies, involving primarily electron collision physics, successful and unsuccessful in being chosen for application, are discussed.

  8. Test Beam Measurements on Picosec Gaseous Detector.

    CERN Document Server

    Sohl, Lukas

    2017-01-01

    In the Picosec project micro pattern gaseous detectors with a time resolution of some ten picoseconds are developed. The detectors are based on Micromegas detectors. With a cherenkov window and a photocathode the time jitter from different position of the primary ionization clusters can be substituted. This reports describes the beam setup and measurements of different Picosec prototypes. A time resolution of under 30 ps has been measured during the test beam. This report gives an overview of my work as a Summer Student. I set up and operated a triple-GEM tracker and a trigger system for the beam. During the beam I measured different prototypes of Picosec detectors and analysed the data.

  9. TEM study of indium and gallium nitride nanocrystals in silica gasses obtained by the sol-gel method.

    Science.gov (United States)

    Krajczyk, L; Jabłoński, J M; Nyk, M; Strek, W; Misiewicz, J

    2006-09-01

    GaN and InN nanocrystals in silica glasses prepared by the sol-gel method were studied by transmission electron microscopy techniques. Morphology, structure and phase composition of silica gel containing Ga or In as function of the calcination and nitridation temperature were investigated.

  10. Precision tracking with a single gaseous pixel detector

    NARCIS (Netherlands)

    Tsigaridas, S.; van Bakel, N.; Bilevych, Y.; Gromov, V.; Hartjes, F.; Hessey, N.P.; de Jong, P.; Kluit, R.

    2015-01-01

    The importance of micro-pattern gaseous detectors has grown over the past few years after successful usage in a large number of applications in physics experiments and medicine. We develop gaseous pixel detectors using micromegas-based amplification structures on top of CMOS pixel readout chips.

  11. Removing gaseous NH3 using biochar as an adsorbent

    Science.gov (United States)

    Ammonia is a major fugitive gas emitted from livestock operations and fertilization production. This study tested the potential of various biochars in removing gaseous ammonia via adsorption processes. Gaseous ammonia adsorption capacities of various biochars made from two different feedstocks (wood...

  12. 49 CFR 538.8 - Gallon Equivalents for Gaseous Fuels.

    Science.gov (United States)

    2010-10-01

    ... VEHICLES § 538.8 Gallon Equivalents for Gaseous Fuels. The gallon equivalent of gaseous fuels, for purposes... Natural Gas 0.823 Liquefied Natural Gas 0.823 Liquefied Petroleum Gas (Grade HD-5)* 0.726 Hydrogen 0.259...

  13. Anomalous Insulator-Metal Transition in Boron Nitride-Graphene Hybrid Atomic Layers

    Science.gov (United States)

    2012-08-13

    hexagonal boron nitride (h-BNC) constitute a new kind of disordered 2D electronic system. Magnetoelectric transport measurements performed at low...Magnetoelectric transport measurements performed at low temperature in vapor phase synthesized h-BNC atomic layers show a clear and anomalous transition from...Tallahassee, Florida 32310, USA 3Nano-Bio Spectroscopy Group and ETSF Scientific Development Centre, Departamento de Fı́sica de Materiales , Centro de Fı́sica

  14. Selective three-phase hydrogenation of aromatic nitro-compounds over β-molybdenum nitride

    NARCIS (Netherlands)

    Cárdenas-Lizana, F.; Lamey, D.; Gómez-Quero, S.; Perret, N.; Kiwi-Minsker, L.; Keane, M.A.

    2011-01-01

    A tetragonal molybdenum nitride (β-Mo2N) has been prepared by temperature programmed treatment of MoO3 in flowing N-2 + H-2 and for the first time shown to catalyze the liquid phase selective hydrogenation (T = 423 K; P-H2 = 11 bar) of a series of para-substituted (-H, -OH, -O-CH3, -CH3, -Cl, -I and

  15. 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.

  16. Thermal and corrosion properties of silicon nitride for copper die casting components

    OpenAIRE

    Khader, I.; Renz, A.; Kailer, A.; Haas, D.

    2013-01-01

    Due to the high melting temperature of copper and copper alloys, conventional die-steel components used in pressure die casting these materials exhibit short service lifetimes and undergo thermal fatigue. Thermal and corrosion properties of silicon nitride were studied to assess the material's applicability in substituting conventional die-steels in casting copper and copper alloys. In this study, experiments were conducted to test the thermal shock resistance and corrosion behaviour of a com...

  17. The Effects of Thermal Cycling on Gallium Nitride and Silicon Carbide Semiconductor Devices for Aerospace Use

    Science.gov (United States)

    Patterson, Richard L.; Hammoud, Ahmad

    2012-01-01

    Electronics designed for use in NASA space missions are required to work efficiently and reliably under harsh environment conditions. These Include radiation, extreme temperatures, thermal cycling, to name a few. Preliminary data obtained on new Gallium Nitride and Silicon Carbide power devices under exposure to radiation followed by long term thermal cycling are presented. This work was done in collaboration with GSFC and JPL in support of the NASA Electronic Parts and Packaging (NEPP) Program

  18. Methods for reformation of gaseous hydrocarbons using electrical discharge

    KAUST Repository

    Cha, Min Suk

    2017-02-16

    Methods for the reformation of gaseous hydrocarbons are provided. The methods can include forming a bubble containing the gaseous hydrocarbon in a liquid. The bubble can be generated to pass in a gap between a pair of electrodes, whereby an electrical discharge is generated in the bubble at the gap between the electrodes. The electrodes can be a metal or metal alloy with a high melting point so they can sustain high voltages of up to about 200 kilovolts. The gaseous hydrocarbon can be combined with an additive gas such as molecular oxygen or carbon dioxide. The reformation of the gaseous hydrocarbon can produce mixtures containing one or more of H2, CO, H2O, CO2, and a lower hydrocarbon such as ethane or ethylene. The reformation of the gaseous hydrocarbon can produce low amounts of CO2 and H2O, e.g. about 15 mol-% or less.

  19. Numerical modeling and experimental investigation of laser-assisted machining of silicon nitride ceramics

    Science.gov (United States)

    Shen, Xinwei

    Laser-assisted machining (LAM) is a promising non-conventional machining technique for advanced ceramics. However, the fundamental machining mechanism which governs the LAM process is not well understood so far. Hence, the main objective of this study is to explore the machining mechanism and provide guidance for future LAM operations. In this study, laser-assisted milling (LAMill) of silicon nitride ceramics is focused. Experimental experience reveals that workpiece temperature in LAM of silicon nitride ceramics determines the surface quality of the machined workpiece. Thus, in order to know the thermal features of the workpiece in LAM, the laser-silicon nitride interaction mechanism is investigated via heating experiments. The trends of temperature affected by the key parameters (laser power, laser beam diameter, feed rate, and preheat time) are obtained through a parametric study. Experimental results show that high operating temperature leads to low cutting force, good surface finish, small edge chipping, and low residual stress. The temperature range for brittle-to-ductile transition should be avoided due to the rapid increase of fracture toughness. In order to know the temperature distribution at the cutting zone in the workpiece, a transient three-dimensional thermal model is developed using finite element analysis (FEA) and validated through experiments. Heat generation associated with machining is considered and demonstrated to have little impact on LAM. The model indicates that laser power is one critical parameter for successful operation of LAM. Feed and cutting speed can indirectly affect the operating temperatures. Furthermore, a machining model is established with the distinct element method (or discrete element method, DEM) to simulate the dynamic process of LAM. In the microstructural modeling of a beta-type silicon nitride ceramic, clusters are used to simulate the rod-like grains of the silicon nitride ceramic and parallel bonds act as the

  20. Modeling of a UV laser beam—silicon nitride interaction

    Science.gov (United States)

    Dgheim, J. A.

    2016-11-01

    A numerical model is developed to study heat and radiation transfers during the interaction between a UV laser beam and silicon nitride. The laser beam has temporal Gaussian or Gate shapes of a wavelength of 247 nm, with pulse duration of 27 ns. The mathematical model is based on the heat equation coupled to Lambert-Beer relationship by taking into account the conduction, convection and radiation phenomena. The resulting equations are schemed by the finite element method. Comparison with the literature shows qualitative and quantitative agreements. The investigated parameters are the temperature, the timing of the melting process and the melting phase thickness. The effects of the laser fluences, ranging from 500 to 16 000 J.m-2, the Gaussian and Gate shapes on the heat transfer, and the melting phenomenon are studied.

  1. High-pressure direct synthesis of aluminium nitride

    CERN Document Server

    Bockowski, M; Grzegory, I; Krukowski, S; Wróblewski, M; Porowski, S

    2002-01-01

    We report the results of direct synthesis of aluminium nitride (AlN) under high nitrogen pressure up to 1 GPa and temperatures up to 2000 K. At pressure from 10 to 650 MPa we observe the combustion synthesis of AlN. As the result of the combustion process one can obtain the AlN sintered powder or AlN/Al metal matrix composites. For N sub 2 pressure higher than 650 MPa the crystal growth of AlN from the solution of atomic nitrogen in aluminium is possible. Both needle-like and bulk AlN single crystals, up to 1 cm and 1 mm, respectively, have been obtained.

  2. The atomic and electronic structure of amorphous silicon nitride

    CERN Document Server

    Alvarez, F

    2002-01-01

    Using a novel approach to the ab initio generation of random networks we constructed two nearly stoichiometric samples of amorphous silicon nitride with the same content x= 1.29. The two 64-atom periodically-continued cubic diamond-like cells contain 28 silicons and 36 nitrogens randomly substituted, and were amorphized with a 6 f s time step by heating them to just below their melting temperature with a Harris-functional based, molecular dynamics code in the LDA approximation. The averaged total radial distribution function (RDF) obtained is compared with some existing Tersoff-like potential simulations and with experiment; ours agree with experiment. All the partial radial features are calculated and the composition of the second peak also agrees with experiment. The electronic structure is calculated and the optical gaps obtained using both a HOMO-LUMO approach and the Tauc-like procedure developed recently that gives reasonable gaps. (Author)

  3. Thermal and electrical properties of silicon nitride substrates

    Directory of Open Access Journals (Sweden)

    H. S. Dow

    2017-09-01

    Full Text Available This work presents the results of studies on the thermal and electrical properties of sintered silicon nitride to investigate the effects of non-oxide additives. With regard to electrical transport properties, a high electrical resistivity of 1014 ∼ 1015 Ωcm at 323 K was observed with Si3N4 substrates. Typical electrical resistivity and thermal conductivity values of the Si3N4 substrates were 1015 Ωcm and 90 W/mK at room temperature, respectively. Based on the results of XPS measurement, it is suggested that the addition of Nb significantly improved oxygen gettering by the phases of Nb2O5. Based on the analysis of the thermal conductivity of Si3N4 substrates, it appears that the interaction between oxygen and Nb in Si3N4, enhanced the thermal conduction rate of Si3N4.

  4. Modeling and simulation of bulk gallium nitride power semiconductor devices

    Directory of Open Access Journals (Sweden)

    G. Sabui

    2016-05-01

    Full Text Available Bulk gallium nitride (GaN power semiconductor devices are gaining significant interest in recent years, creating the need for technology computer aided design (TCAD simulation to accurately model and optimize these devices. This paper comprehensively reviews and compares different GaN physical models and model parameters in the literature, and discusses the appropriate selection of these models and parameters for TCAD simulation. 2-D drift-diffusion semi-classical simulation is carried out for 2.6 kV and 3.7 kV bulk GaN vertical PN diodes. The simulated forward current-voltage and reverse breakdown characteristics are in good agreement with the measurement data even over a wide temperature range.

  5. Germanium nitride and oxynitride films for surface passivation of Ge radiation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Maggioni, G., E-mail: maggioni@lnl.infn.it [Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); Laboratori Nazionali di Legnaro, Istituto Nazionale di Fisica Nucleare, Viale dell’Universita’2, I-35020 Legnaro, Padova (Italy); Carturan, S. [Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); Laboratori Nazionali di Legnaro, Istituto Nazionale di Fisica Nucleare, Viale dell’Universita’2, I-35020 Legnaro, Padova (Italy); Fiorese, L. [Laboratori Nazionali di Legnaro, Istituto Nazionale di Fisica Nucleare, Viale dell’Universita’2, I-35020 Legnaro, Padova (Italy); Dipartimento di Ingegneria dei Materiali e delle Tecnologie Industriali, Università di Trento, Via Mesiano 77, I-38050 Povo, Trento (Italy); Pinto, N.; Caproli, F. [Scuola di Scienze e Tecnologie, Sezione di Fisica, Università di Camerino, Via Madonna delle Carceri 9, Camerino (Italy); INFN, Sezione di Perugia, Perugia (Italy); Napoli, D.R. [Laboratori Nazionali di Legnaro, Istituto Nazionale di Fisica Nucleare, Viale dell’Universita’2, I-35020 Legnaro, Padova (Italy); Giarola, M.; Mariotto, G. [Dipartimento di Informatica—Università di Verona, Strada le Grazie 15, I-37134 Verona (Italy)

    2017-01-30

    Highlights: • A surface passivation method for HPGe radiation detectors is proposed. • Highly insulating GeNx- and GeOxNy-based layers are deposited at room temperature. • Deposition parameters affect composition and electrical properties of the layers. • The improved performance of a GeNx-coated HPGe diode is assessed. - Abstract: This work reports a detailed investigation of the properties of germanium nitride and oxynitride films to be applied as passivation layers to Ge radiation detectors. All the samples were deposited at room temperature by reactive RF magnetron sputtering. A strong correlation was found between the deposition parameters, such as deposition rate, substrate bias and atmosphere composition, and the oxygen and nitrogen content in the film matrix. We found that all the films were very poorly crystallized, consisting of very small Ge nitride and oxynitride nanocrystallites, and electrically insulating, with the resistivity changing from three to six orders of magnitude as a function of temperature. A preliminary test of these films as passivation layers was successfully performed by depositing a germanium nitride film on the intrinsic surface of a high-purity germanium (HPGe) diode and measuring the improved performance, in terms of leakage current, with respect to a reference passivated diode. All these interesting results allow us to envisage the application of this coating technology to the surface passivation of germanium-based radiation detectors.

  6. Computational and experimental study of copper–gold nitride formation

    Energy Technology Data Exchange (ETDEWEB)

    Ponce-Cázares, I., E-mail: iponce@cnyn.unam.mx [Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Carretera Tijuana-Ensenada No. 3918, A. Postal 360, 22860 Ensenada, B.C. (Mexico); Soto, G., E-mail: gerardo@cnyn.unam.mx [Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana-Ensenada, C.P. 22860 Ensenada, B.C. (Mexico); Moreno-Armenta, Ma. Guadalupe, E-mail: moreno@cnyn.unam.mx [Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana-Ensenada, C.P. 22860 Ensenada, B.C. (Mexico); De la Cruz, W., E-mail: wencel@cnyn.unam.mx [Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana-Ensenada, C.P. 22860 Ensenada, B.C. (Mexico)

    2015-08-25

    Highlights: • The new Cu{sub 3}Au-nitride compound was successfully grown by the sputtering method. • This material is Cu{sub 3}Au{sub 0.5}N with cubic system (Pm3m space group), where the gold randomly occupies half of the 1a Wyckoff sites. • The material was a pseudo-gap conductor with conductance as good as a heavily-doped semiconductor at room temperature. - Abstract: This work investigates the formation of a Cu{sub 3}Au-nitride alloy using experimental and computational methods. For this purpose, we prepared a custom-made Cu–Au target and then hit it with argon ions in the presence of molecular nitrogen that produced a film on Corning glass. This film was analyzed using spectroscopic and diffraction techniques. The four-point-probe method and Tauc plots were applied to determine the electrical and optical properties of this thin film. Using first principle calculations a structural model was constructed that validated our observations. The crystalline system that we used was cubic (Pm3m space group) with half the sites filled with Au randomly. The composition was close to Cu{sub 3}Au{sub 0.5}N. In agreement with the electrical measurements and calculations, the Cu{sub 3}Au{sub 0.5}N band structure was highly affected by the Au incorporation since the electrical resistance and carrier density were in the 10{sup −3} Ω cm and 10{sup 22} cm{sup −3} ranges, respectively, and the optical gap decreased 0.61 eV with respect to the Cu{sub 3}N. The material was a pseudo-gap conductor with conductance as good as a heavily-doped semiconductor at room temperature; this should give it great potential for use in the optoelectronics industry.

  7. Ultrasensitive string-based temperature sensors

    DEFF Research Database (Denmark)

    Larsen, Tom; Schmid, Silvan; Gronberg, L.

    2011-01-01

    Resonant strings are a promising concept for ultra sensitive temperature detection. We present an analytical model for the sensitivity with which we optimize the temperature response of resonant strings by varying geometry and material. The temperature sensitivity of silicon nitride and aluminum ...

  8. Investigation of gaseous propellant combustion and associated injector/chamber design guidelines

    Science.gov (United States)

    Calhoon, D. F.; Ito, J. I.; Kors, D. L.

    1973-01-01

    Injector design criteria are provided for gaseous hydrogen-gaseous oxygen propellants. Design equations and procedures are presented which will allow an injector-chamber designer to a priori estimate of the performance, compatibility and stability characteristics of prototype injectors. The effects of chamber length, element geometry, thrust per element, mixture ratio, impingement angle, and element spacing were evaluated for four element concepts and their derivatives. The data from this series of tests were reduced to a single valued mixing function that describes the mixing potential of the various elements. Performance, heat transfer and stability data were generated for various mixture ratios, propellant temperatures, chamber pressures, contraction ratios, and chamber lengths. Applications of the models resulted in the design of procedures, whereby the performance and chamber heat flux can be calculated directly, and the injector stability estimated in conjunction with existing models.

  9. Plasma-assisted atomic layer epitaxial growth of aluminum nitride studied with real time grazing angle small angle x-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Virginia R.; Nepal, Neeraj; Johnson, Scooter D.; Robinson, Zachary R.; Nath, Anindya; Kozen, Alexander C.; Qadri, Syed B.; DeMasi, Alexander; Hite, Jennifer K.; Ludwig, Karl F.; Eddy, Charles R.

    2017-05-01

    Wide bandgap semiconducting nitrides have found wide-spread application as light emitting and laser diodes and are under investigation for further application in optoelectronics, photovoltaics, and efficient power switching technologies. Alloys of the binary semiconductors allow adjustments of the band gap, an important semiconductor material characteristic, which is 6.2 eV for aluminum nitride (AlN), 3.4 eV for gallium nitride, and 0.7 eV for (InN). Currently, the highest quality III-nitride films are deposited by metalorganic chemical vapor deposition and molecular beam epitaxy. Temperatures of 900 °C and higher are required to deposit high quality AlN. Research into depositing III-nitrides with atomic layer epitaxy (ALEp) is ongoing because it is a fabrication friendly technique allowing lower growth temperatures. Because it is a relatively new technique, there is insufficient understanding of the ALEp growth mechanism which will be essential to development of the process. Here, grazing incidence small angle x-ray scattering is employed to observe the evolving behavior of the surface morphology during growth of AlN by ALEp at temperatures from 360 to 480 °C. Increased temperatures of AlN resulted in lower impurities and relatively fewer features with short range correlations.

  10. Low-loss binder for hot pressing boron nitride

    Science.gov (United States)

    Maya, Leon

    1991-01-01

    Borazine derivatives used as low-loss binders and precursors for making ceramic boron nitride structures. The derivative forms the same composition as the boron nitride starting material, thereby filling the voids with the same boron nitride material upon forming and hot pressing. The derivatives have a further advantage of being low in carbon thus resulting in less volatile byproduct that can result in bubble formation during pressing.

  11. Nitriding using cathodic cage technique of martensitic stainless steel AISI 420 with addition of CH4

    National Research Council Canada - National Science Library

    De Sousa, R.R.M; De Araújo, F.O; Da Costa, J.A.P; De Sousa, R.S; Alves JR, C

    2008-01-01

    AISI 420 martensitic stainless steel samples were nitrided by cathodic cage technique with addition of methane in the atmosphere aiming to reduce chromium nitride precipitation, to increase hardness...

  12. 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)

  13. Local residual stress measurements on nitride layers

    Energy Technology Data Exchange (ETDEWEB)

    Mansilla, C.; Ocelík, V.; De Hosson, J.Th.M., E-mail: j.t.m.de.hosson@rug.nl

    2015-06-11

    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 spectroscopy. The residual stress state was measured on the surface and also in cross-section, i.e. examining effects of the nitrogen concentration gradient. It is shown that an enhanced lateral resolution can be achieved when a novel multiple fitting approach is employed. The results presented show an overall agreement with stress profiles obtained by X-ray diffraction. Finite Element Modeling is used to explain the apparent discrepancies. A clear correlation between the residual stress and nitriding profiles has been found and the applicability of this method is shown in particular when stress gradients are present.

  14. Growth of graphene films from non-gaseous carbon sources

    Science.gov (United States)

    Tour, James; Sun, Zhengzong; Yan, Zheng; Ruan, Gedeng; Peng, Zhiwei

    2015-08-04

    In various embodiments, the present disclosure provides methods of forming graphene films by: (1) depositing a non-gaseous carbon source onto a catalyst surface; (2) exposing the non-gaseous carbon source to at least one gas with a flow rate; and (3) initiating the conversion of the non-gaseous carbon source to the graphene film, where the thickness of the graphene film is controllable by the gas flow rate. Additional embodiments of the present disclosure pertain to graphene films made in accordance with the methods of the present disclosure.

  15. Study of reactions between uranium-plutonium mixed oxide and uranium nitride and between uranium oxide and uranium nitride; Etude des reactions entre l`oxyde mixte d`uranium-plutonium et le nitrure d`uranium et entre l`oxyde d`uranium et le nitrure d`uranium

    Energy Technology Data Exchange (ETDEWEB)

    Lecraz, C.

    1993-06-11

    A new type of combustible elements which is a mixture of uranium nitride and uranium-plutonium oxide could be used for Quick Neutrons Reactors. Three different studies have been made on the one hand on the reactions between uranium nitride (UN) and uranium-plutonium mixed oxide (U,Pu)O{sub 2}, on the other hand on these between UN and uranium oxide UO{sub 2}. They show a sizeable reaction between nitride and oxide for the studied temperatures range (1573 K to 1973 K). This reaction forms a oxynitride compound, MO{sub x} N{sub y} with M=U or M=(U,Pu), whose crystalline structure is similar to oxide`s. Solubility of nitride in both oxides is studied, as the reaction kinetics. (TEC). 32 refs., 48 figs., 22 tabs.

  16. Tensile properties of ADI material in water and gaseous environments

    Energy Technology Data Exchange (ETDEWEB)

    Rajnovic, Dragan, E-mail: draganr@uns.ac.rs [Faculty of Technical Sciences, University of Novi Sad, Trg D. Obradovića 6, 21000 Novi Sad (Serbia); Balos, Sebastian; Sidjanin, Leposava [Faculty of Technical Sciences, University of Novi Sad, Trg D. Obradovića 6, 21000 Novi Sad (Serbia); Eric Cekic, Olivera [Innovation Centre, Faculty of Mechanical Engineering, University of Belgrade, Kraljice Marije 16, 11120 Belgrade (Serbia); Grbovic Novakovic, Jasmina [Vinca Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11000 Belgrade (Serbia)

    2015-03-15

    Austempered ductile iron (ADI) is an advanced type of heat treated ductile iron, having comparable mechanical properties as forged steels. However, it was found that in contact with water the mechanical properties of austempered ductile irons decrease, especially their ductility. Despite considerable scientific attention, the cause of this phenomenon remains unclear. Some authors suggested that hydrogen or small atom chemisorption causes the weakening of the surface atomic bonds. To get additional reliable data of that phenomenon, in this paper, two different types of austempered ductile irons were tensile tested in various environments, such as: argon, helium, hydrogen gas and water. It was found that only the hydrogen gas and water gave a statistically significant decrease in mechanical properties, i.e. cause embrittlement. Furthermore, the fracture surface analysis revealed that the morphology of the embrittled zone near the specimen surface shares similarities to the fatigue micro-containing striation-like lines, which indicates that the morphology of the brittle zone may be caused by cyclic local-chemisorption, micro-embrittlement and local-fracture. - Highlights: • In contact with water and other liquids the ADI suddenly exhibits embrittlement. • The embrittlement is more pronounced in water than in the gaseous hydrogen. • The hydrogen chemisorption into ADI surface causes the formation of a brittle zone. • The ADI austempered at lower temperatures (300 °C) is more resistant to embrittlement.

  17. Modelling structure and properties of amorphous silicon boron nitride ceramics

    Directory of Open Access Journals (Sweden)

    Johann Christian Schön

    2011-06-01

    Full Text Available Silicon boron nitride is the parent compound of a new class of high-temperature stable amorphous ceramics constituted of silicon, boron, nitrogen, and carbon, featuring a set of properties that is without precedent, and represents a prototypical random network based on chemical bonds of predominantly covalent character. In contrast to many other amorphous materials of technological interest, a-Si3B3N7 is not produced via glass formation, i.e. by quenching from a melt, the reason being that the binary components, BN and Si3N4, melt incongruently under standard conditions. Neither has it been possible to employ sintering of μm-size powders consisting of binary nitrides BN and Si3N4. Instead, one employs the so-called sol-gel route starting from single component precursors such as TADB ((SiCl3NH(BCl2. In order to determine the atomic structure of this material, it has proven necessary to simulate the actual synthesis route.Many of the exciting properties of these ceramics are closely connected to the details of their amorphous structure. To clarify this structure, it is necessary to employ not only experimental probes on many length scales (X-ray, neutron- and electron scattering; complex NMR experiments; IR- and Raman scattering, but also theoretical approaches. These address the actual synthesis route to a-Si3B3N7, the structural properties, the elastic and vibrational properties, aging and coarsening behaviour, thermal conductivity and the metastable phase diagram both for a-Si3B3N7 and possible silicon boron nitride phases with compositions different from Si3N4: BN = 1 : 3. Here, we present a short comprehensive overview over the insights gained using molecular dynamics and Monte Carlo simulations to explore the energy landscape of a-Si3B3N7, model the actual synthesis route and compute static and transport properties of a-Si3BN7.

  18. GEM - A novel gaseous particle detector

    CERN Document Server

    Meinschad, T

    2005-01-01

    The work carried out within the framework of this Ph.D. deals with the construction of gaseous prototype detectors using Gas Electron Multiplier electrodes for the amplification of charges released by ionizing particles. The Gas Electron Multiplier (GEM) is a thin metal-clad polymer foil, etched with a high density of narrow holes, typically 50-100mm-2. On the application of a potential difference between the conductive top and bottom sides each hole acts as independent proportional counter. This new fast device permits to reach large amplification factors at high rates with a strong photon and ion-mediated feedback suppression due to the avalanche confinement in the GEM-holes. Here, in particular studies have been performed, which should prove, that the GEM-technology is applicable for an efficient measurement of single Cherenkov photons. These UV-photons can be detected in different ways. An elegant solution to develop large area RICH-detectors is to evaporate a pad-segmented readout-cathode of a multi-wire...

  19. Vortex breakdown in gaseous swirling jets

    Science.gov (United States)

    Sanchez, Antonio L.; Carpio, Jaime; Williams, Forman A.

    2017-11-01

    Numerical integrations of the axisymmetric Navier-Stokes equations are employed to describe the structure of low-Mach-number gaseous swirling jets with jet-to-ambient density ratios ρj /ρa of order unity. The integrations consider moderately large values of the Reynolds number on the order of a few hundred and values of the swirl ratio S of order unity. Slender jets are found to exist for values of S below a critical value of order unity, at which vortex breakdown occurs. As in the case of constant density jets (Billant, Chomaz, and Huerre, JFM 1998), two different types of axisymmetric vortex breakdown are identified, namely, a bubble state and a cone configuration. The critical values of S characterizing the existence of the different solutions are determined as a function of ρj /ρa . Additional computations based on the quasicylindrical approximation are employed to describe slender subcritical jets. The results indicate that the breakdown of the quasicylindrical approximation provides an accurate prediction for the transition from the slender solution to the bubble state, whereas a prediction for the transition to the cone state can be obtained by consideration of the structure of the flow at small distances from the jet exit. This work was supported by the US AFOSR Grant No. FA9550-16-1-0443.

  20. First gaseous boronization during pulsed discharge cleaning

    Energy Technology Data Exchange (ETDEWEB)

    Ko, J., E-mail: jinseok@nfri.re.kr [Department of Physics, University of Wisconsin, Madison, WI (United States); Den Hartog, D.J.; Goetz, J.A.; Weix, P.J.; Limbach, S.T. [Department of Physics, University of Wisconsin, Madison, WI (United States)

    2013-01-15

    The first successful gaseous boronization during a pulsed discharge is reported. Sublimation of o-carborane (C{sub 2}B{sub 10}H{sub 12}) combined with pulsed discharge plasmas with a repetition rate of 1 Hz is used to produce a hard boron-containing coating for reversed field pinch (RFP) plasmas in the Madison Symmetric Torus. X-ray photoelectron spectroscopy with Ar ion beam etching for silicon coupons installed at the plasma boundary shows about 60% boron concentration in the deposited layer. Both profilometer and scanning electron microscope analyses of the silicon coupons imply a strong toroidally non-uniform deposition depending on the location of the o-carborane injection. The layer thickness ranges from 50 to 300 nm. Ellipsometry calibrated with the profilometer results yields a refractive index of 2.2-2.3 for the films. The high refractive index implies that the coating is hard and has a well-ordered morphology. A reduction in wall recycling has consistently been observed after all boronization sessions. Comparison of the X-ray spectra in standard RFP plasmas before and after boronization indicates a slight decrease in the effective ionic charge.

  1. Action-FRET of a Gaseous Protein.

    Science.gov (United States)

    Daly, Steven; Knight, Geoffrey; Halim, Mohamed Abdul; Kulesza, Alexander; Choi, Chang Min; Chirot, Fabien; MacAleese, Luke; Antoine, Rodolphe; Dugourd, Philippe

    2017-01-01

    Mass spectrometry is an extremely powerful technique for analysis of biological molecules, in particular proteins. One aspect that has been contentious is how much native solution-phase structure is preserved upon transposition to the gas phase by soft ionization methods such as electrospray ionization. To address this question-and thus further develop mass spectrometry as a tool for structural biology-structure-sensitive techniques must be developed to probe the gas-phase conformations of proteins. Here, we report Förster resonance energy transfer (FRET) measurements on a ubiquitin mutant using specific photofragmentation as a reporter of the FRET efficiency. The FRET data is interpreted in the context of circular dichroism, molecular dynamics simulation, and ion mobility data. Both the dependence of the FRET efficiency on the charge state-where a systematic decrease is observed-and on methanol concentration are considered. In the latter case, a decrease in FRET efficiency with methanol concentration is taken as evidence that the conformational ensemble of gaseous protein cations retains a memory of the solution phase conformational ensemble upon electrospray ionization. Graphical Abstract ᅟ.

  2. Automated sampling and control of gaseous simulations

    KAUST Repository

    Huang, Ruoguan

    2013-05-04

    In this work, we describe a method that automates the sampling and control of gaseous fluid simulations. Several recent approaches have provided techniques for artists to generate high-resolution simulations based on a low-resolution simulation. However, often in applications the overall flow in the low-resolution simulation that an animator observes and intends to preserve is composed of even lower frequencies than the low resolution itself. In such cases, attempting to match the low-resolution simulation precisely is unnecessarily restrictive. We propose a new sampling technique to efficiently capture the overall flow of a fluid simulation, at the scale of user\\'s choice, in such a way that the sampled information is sufficient to represent what is virtually perceived and no more. Thus, by applying control based on the sampled data, we ensure that in the resulting high-resolution simulation, the overall flow is matched to the low-resolution simulation and the fine details on the high resolution are preserved. The samples we obtain have both spatial and temporal continuity that allows smooth keyframe matching and direct manipulation of visible elements such as smoke density through temporal blending of samples. We demonstrate that a user can easily configure a simulation with our system to achieve desired results. © 2013 Springer-Verlag Berlin Heidelberg.

  3. 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.

  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. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. 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.

  6. New Tunneling Features in Polar III-Nitride Resonant Tunneling Diodes

    Directory of Open Access Journals (Sweden)

    Jimy Encomendero

    2017-10-01

    Full Text Available For the past two decades, repeatable resonant tunneling transport of electrons in III-nitride double barrier heterostructures has remained elusive at room temperature. In this work we theoretically and experimentally study III-nitride double-barrier resonant tunneling diodes (RTDs, the quantum transport characteristics of which exhibit new features that are unexplainable using existing semiconductor theory. The repeatable and robust resonant transport in our devices enables us to track the origin of these features to the broken inversion symmetry in the uniaxial crystal structure, which generates built-in spontaneous and piezoelectric polarization fields. Resonant tunneling transport enabled by the ground state as well as by the first excited state is demonstrated for the first time over a wide temperature window in planar III-nitride RTDs. An analytical transport model for polar resonant tunneling heterostructures is introduced for the first time, showing a good quantitative agreement with experimental data. From this model we realize that tunneling transport is an extremely sensitive measure of the built-in polarization fields. Since such electric fields play a crucial role in the design of electronic and photonic devices, but are difficult to measure, our work provides a completely new method to accurately determine their magnitude for the entire class of polar heterostructures.

  7. Tensile creep performance of a developmental in-situ reinforced silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, A.A.; Kirkland, T.P.; Lin, H.T.; Ferber, M.K. [Oak Ridge National Lab., TN (United States); Li, C.W.; Goldacker, J.A. [Allied-Signal, Inc., Morristown, NJ (United States)

    1997-02-01

    The evaluation was done between 1300 and 1425 C in ambient air. Minimum creep rate was evaluated vs tensile stress and temperature, and measured tensile creep performances of two different specimen geometries (buttonhead and dogbone - machined from same billet) were compared. This Si nitride exhibited comparable or better creep resistance than other Si nitrides described in the literature. Measured creep response of the material and lifetime were observed to be geometry dependent; the smaller cross-sectioned dogbone samples exhibited faster creep rates and shorter lives, presumably due to faster oxidation-induced damage in this geometry. The tensile creep rates and lifetimes were found to be well represented by the Monkman- Grant relation between 1350 and 1425 C, with some evidence suggesting stratification of the data for the 1300 C tests and a change in dominant failure mode between 1300 and 1350 C. Lastly, values of the temperature-compensated stress exponent and activation energy for tensile creep were found to decrease by 80 and 75% in compression, respectively, illustrating anisotropic creep behavior in this Si nitride.

  8. New Tunneling Features in Polar III-Nitride Resonant Tunneling Diodes

    Science.gov (United States)

    Encomendero, Jimy; Faria, Faiza Afroz; Islam, S. M.; Protasenko, Vladimir; Rouvimov, Sergei; Sensale-Rodriguez, Berardi; Fay, Patrick; Jena, Debdeep; Xing, Huili Grace

    2017-10-01

    For the past two decades, repeatable resonant tunneling transport of electrons in III-nitride double barrier heterostructures has remained elusive at room temperature. In this work we theoretically and experimentally study III-nitride double-barrier resonant tunneling diodes (RTDs), the quantum transport characteristics of which exhibit new features that are unexplainable using existing semiconductor theory. The repeatable and robust resonant transport in our devices enables us to track the origin of these features to the broken inversion symmetry in the uniaxial crystal structure, which generates built-in spontaneous and piezoelectric polarization fields. Resonant tunneling transport enabled by the ground state as well as by the first excited state is demonstrated for the first time over a wide temperature window in planar III-nitride RTDs. An analytical transport model for polar resonant tunneling heterostructures is introduced for the first time, showing a good quantitative agreement with experimental data. From this model we realize that tunneling transport is an extremely sensitive measure of the built-in polarization fields. Since such electric fields play a crucial role in the design of electronic and photonic devices, but are difficult to measure, our work provides a completely new method to accurately determine their magnitude for the entire class of polar heterostructures.

  9. A new gaseous and combustible form of water

    Energy Technology Data Exchange (ETDEWEB)

    Santilli, Ruggero Maria [Institute for Basic Research, P.O. Box 1577, Palm Harbor, FL 34682 (United States)

    2006-08-15

    In this paper we present, apparently for the first time, various measurements on a mixture of hydrogen and oxygen called HHO gas produced via a new electrolyzer (international patents pending by Hydrogen Technologies Applications, Inc. of Clearwater, Florida), which mixture is distinctly different than the Brown and other known gases. The measurements herein reported suggest the existence in the HHO gas of stable clusters composed of H and O atoms, their dimers H-O, and their molecules H{sub 2}, O{sub 2} and H{sub 2}O whose bond cannot entirely be of valence type. Numerous anomalous experimental measurements on the HHO gas are reported in this paper for the first time. To reach their preliminary, yet plausible interpretation, we introduce the working hypothesis that the clusters constituting the HHO gas constitute another realization of a recently discovered new chemical species called for certain technical reasons magnecules as well as to distinguish them from the conventional 'molecules' [Santilli RM. Foundations of hadronic chemistry with applications to new clean energies and fuels. Boston, Dordrecht, London: Kluwer Academic Publisher; 2001]. It is indicated that the creation of the gaseous and combustible HHO from distilled water at atmospheric temperature and pressure occurs via a process structurally different than evaporation or separation, thus suggesting the existence of a new form of water, apparently introduced in this paper for the first time, with the structure (HxH)-O where 'x' represents the new magnecular bond and '-' the conventional molecular bond. The transition from the conventional H-O-H species to the new (HxH)-O species is predicted by a change of the electric polarization of water caused by the electrolyzer. When H-O-H is liquid, the new species (HxH)-O can only be gaseous, thus explaining the transition of state without evaporation or separation energy. Finally, the new species (HxH)-O is predicted to be

  10. Tungsten nitride coatings obtained by HiPIMS as plasma facing materials for fusion applications

    Science.gov (United States)

    Tiron, Vasile; Velicu, Ioana-Laura; Porosnicu, Corneliu; Burducea, Ion; Dinca, Paul; Malinský, Petr

    2017-09-01

    In this work, tungsten nitride coatings with nitrogen content in the range of 19-50 at% were prepared by reactive multi-pulse high power impulse magnetron sputtering as a function of the argon and nitrogen mixture and further exposed to a deuterium plasma jet. The elemental composition, morphological properties and physical structure of the samples were investigated by Rutherford backscattering spectrometry, atomic force microscopy and X-ray diffraction. Deuterium implantation was performed using a deuterium plasma jet and its retention in nitrogen containing tungsten films was investigated using thermal desorption spectrometry. Deuterium retention and release behaviour strongly depend on the nitrogen content in the coatings and the films microstructure. All nitride coatings have a polycrystalline structure and retain a lower deuterium level than the pure tungsten sample. Nitrogen content in the films acts as a diffusion barrier for deuterium and leads to a higher desorption temperature, therefore to a higher binding energy.

  11. Plasma-enhanced growth, composition, and refractive index of silicon oxy-nitride films

    DEFF Research Database (Denmark)

    Mattsson, Kent Erik

    1995-01-01

    -product. A model, that combine the chemical net reaction and the stoichiometric rules, is found to agree with measured deposition rates for given material compositions. Effects of annealing in a nitrogen atmosphere has been investigated for the 400 °C– 1100 °C temperature range. It is observed that PECVD oxy....... This relation suggest that the refractive index of oxy-nitride with a low nitrogen concentration is determined by the material density. It is suggested that the relative oxygen concentration in the gas flow is the major deposition characterization parameter, and that water vapor is the predominant reaction by...... nitrogen concentrations between 2 and 10 at. %. A simple atomic valence model is found to describe both the measured atomic concentrations and published material compositions for silicon oxy-nitride produced by PECVD. A relation between the Si–N bond concentration and the refractive index is found...

  12. Thermal transport in boron nitride nanotorus—towards a nanoscopic thermal shield

    Energy Technology Data Exchange (ETDEWEB)

    Loh, G. C., E-mail: jgloh@mtu.edu [Institute of High Performance Computing, 1 Fusionopolis Way, 16-16 Connexis, Singapore 138632 (Singapore); Department of Physics, Michigan Technological University, Houghton, Michigan 49931 (United States); Baillargeat, D. [CNRS-International-NTU-Thales Research Alliance (CINTRA), 50 Nanyang Drive, Singapore 637553 (Singapore)

    2013-11-14

    Nanotori, or nanorings, are topological variants of nanotubes and are conceived to have different properties from their tubular form. In this study, the toroidal arrangement of boron nitride is introduced. Using classical molecular dynamics simulations, the thermal behaviour (thermal conductivity and thermal stability) of the boron nitride nanotorus and its relationship with the structural characteristics are investigated. Its circumferential thermal rectification strength displays a linear dependence on the bending coefficient of the nanostructure. Surface kinks are relatively inconsequential on its circumferential mode of conduction, as compared to its axial sense. The circumferential conductivity in the diffusive regime is calculated to be approximately 10 W/m K, while the axial conductivity is more than tenfold of this value. All nanotori with different toroidal characters show excellent thermal stability at extremely high temperatures approaching 3400 K. With consideration to its favourable properties, a thermal shield made up of a parallel row of nanotori is proposed as a nanoscale thermal insulation device.

  13. Shock Syntheses of Novel Nitrides and Biomolecules

    Science.gov (United States)

    Sekine, Toshimori

    2013-06-01

    High-pressure spinel nitride of Si3N4 was discovered more than 10 years ago. Since then there have been many studies on the spinel nitrides and related materials including oxynitrides. We have developed shock synthesis method to investigate their structural, mechanical, chemical, physical, and optical properties. At the same time we tried to synthesize carbon nitrides from the organic substances. And later we extended to shock synthesis of ammonia through the Haber-Bosch reaction under shock in order to apply geochemical subjects related to the origin of life. The simplest amino acid of glycine, as well as animes (up to propylamine) and carboxylic acids (up to pentanoic acid), has been synthesized successfully in aqueous solutions through meteoritic impact reactions. Recently we are trying to make more complex biomolecules for implications of biomolecule formation for the origin of life through meteorite impacts on early Earth's ocean. These results of shock syntheses may imply significant contributions to materials science and Earth and planetary sciences. This research is collaborated with National Institute for Materials Science and Tohoku University.

  14. 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.

  15. Application-oriented nitride substrates: The key to long-wavelength nitride lasers beyond 500 nm

    Science.gov (United States)

    Sharma, T. K.; Towe, E.

    2010-01-01

    We present results based on quantum mechanical estimates of the longest emission wavelength for nitride laser diodes grown on c-plane GaN/sapphire substrates. The results indicate that the absence of polarization-induced electric fields in nonpolar/semipolar GaN substrates does not necessarily guarantee that nitride lasers will operate at the longest possible wavelength for a given set of parameters. Our calculations suggest that the limit on the longest possible wavelength of nitride lasers is constrained by the lattice mismatch rather than by the strength of the polarization-induced electric field. Although it may be possible to develop lasers that approach the green portion of the electromagnetic spectrum (˜520 nm) by growing the structures on nonpolar/semipolar GaN substrates, the development of red and near-infrared nitride lasers appears extremely difficult by merely growing the structures on any crystallographic orientation of the GaN substrate. We suggest that efficient lasers emitting at the green, red, and near-infrared wavelengths can be developed by growing the laser structures on a proposed application-oriented nitride substrate (AONS) that is lattice-matched to the epilayers grown on it. The AONSs are bulk InxGa1-xN ternary substrates with Indium compositions chosen to lattice-match the epilayers to be grown on them. The concept of the AONS can be extended deep into the infrared region by increasing the Indium mole fraction of the quantum well layers in the active region of the laser and by choosing the AONS that best matches the specific wavelength desired. We believe it would be possible, by using this concept, to make nitride lasers at the fiber-optic communication windows at 1.3 and 1.55 μm, thus eliminating the need to use the hazardous arsenides/phosphides materials currently used to make the communications lasers.

  16. Improvement of wear resistance for C45 steel using plasma nitriding, nitrocarburizing and nitriding/ manganese phosphating duplex treatment

    Science.gov (United States)

    Doan, T. V.; Kusmič, D.; Pospíchal, M.; Dobrocký, D.

    2017-02-01

    This article focuses on effect of plasma nitriding, nitrocarburizing and nitriding/manganese phosphating duplex treatments to wear resistance of C45 steel substrate. The wear test “ball on disc” was conducted to evaluate the coefficient of friction and wear rate using the BRUKER UMT-3 tribometer. The analysis results indicated that nitrocarburizing obtained the best wear resistance; the worst wear resistance was plasma nitriding. Manganese phosphating coating enabled to reduce the coefficient of friction enhanced wear resistance nitrided layer. The used surface treatments also improve non-equal wear of tempered surface over the sliding track.

  17. The effect of deposition parameters on the boron nitride films grown on Si(100) by PLD with nanosecond pulses

    Science.gov (United States)

    Luculescu, C. R.; Sato, Shunichi; Fenic, Constantin G.

    2004-10-01

    The effects of several deposition parameters on the quality of deposited boron nitride (BN) films by pulsed laser deposition (PLD) with short laser pulses are studied. The laser fluence, nitrogen background pressure, Si(100) substrate temperature and laser wavelength were varied in order to find the maximum content of the cubic phase in our BN films. We found that laser fluence and wavelength are affecting strongly the structure of BN films while background pressure and substrate temperature are affecting slightly the film morphology.

  18. Stress reduction of cubic boron nitride films by oxygen addition

    Energy Technology Data Exchange (ETDEWEB)

    Ye, J. [Forschungszentrum Karlsruhe, IMF I, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)], E-mail: Jian.Ye@imf.fzk.de; Ulrich, S.; Ziebert, C.; Stueber, M. [Forschungszentrum Karlsruhe, IMF I, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)

    2008-12-01

    Cubic boron nitride (c-BN) films with significantly reduced residual stresses were successfully grown onto silicon substrates by means of controlled oxygen addition into the films. The deposition was based on radio-frequency magnetron sputtering of a hexagonal boron nitride (h-BN) target, and was accomplished in a reactive mode using gas mixtures of argon, nitrogen, and oxygen at 0.3 Pa pressure, 400 deg. C growth temperature, and - 250 V substrate bias. Results of systematic investigations are shown in this article with respect to the critical influences of oxygen concentration during deposition upon the stress, cubic phase fraction, as well as nanohardness of the deposited films. Under the specified growth conditions, the formation of c-BN was generally completely hindered for oxygen concentrations above 1.5 vol.% in the gas mixture. At concentrations below approximately 1 vol.%, the added oxygen exhibits however marginal influences on the c-BN fraction, but on the other side a strong impact on the stress of the deposited films. Cubic-phase dominated films (containing 70-80 vol.% c-BN) with their compressive stress three times reduced were thus produced through careful control of oxygen fraction in the gas mixture, showing an excellent nanohardness of almost 60 GPa. For such films, a post-deposition thermal treatment at 900 deg. C led to an additional drastic stress reduction resulting in a final residual stress that is almost 10 times lower than that of as-deposited c-BN films without intentional oxygen addition.

  19. Gaseous Helium Reclamation at Rocket Test Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The ability to restore large amounts of vented gaseous helium (GHe) at rocket test sites preserves the GHe and reduces operating cost. The used GHe is vented into...

  20. Elastocaloric effect on the piezoelectric potential of boron nitride nanotubes

    Science.gov (United States)

    Zhang, Jin

    2017-10-01

    In this paper, molecular dynamics (MD) simulations and analytical calculations are performed to study the influence of the elastocaloric effect (ECE) on the piezoelectric potential of hexagonal boron nitride (BN) nanotubes. To take into account the ECE in the simulations and calculations, the adiabatic condition is required. To reach this goal, the heat transfer between the BN nanotubes and their environment is excluded in the present study. In MD simulations, we find a large ECE in BN nanotubes, which will make the temperature of the BN nanotubes greatly change after external loads are applied on them. Moreover, the piezoelectric and dielectric properties of BN nanotubes calculated from MD simulations are found to be strongly dependent on the temperature. The temperature-dependent piezoelectric and dielectric properties together with the ECE are thus considered in the analytical calculations of the piezoelectric potential of BN nanotubes. The obtained analytical results reveal that the large ECE in BN nanotubes will make the piezoelectric potential of BN nanotubes strongly depend on the loading path of external loads. Specifically, stretching a BN nanotube is found to be more efficient than compressing the nanotube to generate the piezoelectric potential. These results are expected to significantly expand the knowledge of the electromechanical behaviours of piezoelectric nanomaterials and provide important guidelines for the optimum design of piezotronics nanodevices.