Sample records for activated combustion synthesis

  1. Combustion synthesis

    Microsoft Academic Search

    Kashinath C Patil; Singanahally T Aruna; Sambandan Ekambaram

    1997-01-01

    Many innovative self-propagating high-temperature synthesis (SHS) techniques such as filtration, combustion, the centrifugal thermite process, field activated combustion, solid-state metathesis, flame synthesis and simultaneous SHS and densification have been developed for the synthesis of ‘advanced materials’. A novel gas producing self-propagating process initiated at low temperature using redox compounds and mixtures has been used for the preparation of fine particle

  2. Field-activated combustion synthesis of titanium aluminides

    Microsoft Academic Search

    R. Orrú; G. Cao; Z. A. Munir

    1999-01-01

    The feasibility of synthesizing the titanium aluminides Ti3Al and TiAl through field-activated, self-propagating combustion synthesis is demonstrated. A self-sustaining combustion wave\\u000a can be initiated only when the imposed field is above a threshold value for each of these two aluminides. At the threshold\\u000a values, wave propagation resulted in an incomplete reaction between the metals and the products, which contained several

  3. Field-activated combustion synthesis of titanium aluminides

    NASA Astrophysics Data System (ADS)

    Orrú, R.; Cao, G.; Munir, Z. A.

    1999-04-01

    The feasibility of synthesizing the titanium aluminides Ti3Al and TiAl through field-activated, self-propagating combustion synthesis is demonstrated. A self-sustaining combustion wave can be initiated only when the imposed field is above a threshold value for each of these two aluminides. At the threshold values, wave propagation resulted in an incomplete reaction between the metals and the products, which contained several phases in addition to the desired one. As the field strength was increased, the reaction approached completion and the amounts of the secondary phases decreased. At a sufficiently high field, a single-phase product was obtained in the case of Ti3Al, but, in the case of TiAl, the product contained Ti3Al as a secondary phase even with the highest imposed field. The effect of reactant compact density was investigated for the case of Ti3Al synthesis. At a fixed value of imposed field, the degree of reaction completion and the conversion to the desired phase increased as the relative density decreased. These observations are discussed in light of the role of the electric field in activating the self-propagating combustion synthesis reactions and the effect of relative density on this activation. The results show that the synthesis by self-propagating high-temperature synthesis (SHS) can be optimized by the combination of field strength and relative density.

  4. Combustion Synthesis of Nanocomposite Powders Using A Mechanically Activated Process

    Microsoft Academic Search

    Tatiana L. Talako; Andrei I. Letsko; Tatiana Ph. Grigorieva

    2010-01-01

    The authors investigated aspects of nanocomposite structure formation in Fe + Al + Fe2O3 and Fe + Al + Cr2O3 powder mixtures during combustion synthesis using precursors formed as a result of mechanochemical interaction at the stage of preliminary mechanical activation of reactive mixtures. Despite the significant difference in thermal effects, two types of reactions (aluminothermic reduction of oxides and formation of intermetallics from elements, though in the

  5. DOI: 10.1002/adem.200700076 Novel Method for Synthesis of Nano-Materials: Combustion of Active

    E-print Network

    Mukasyan, Alexander

    solution (aqueous) combustion synthesis (SCS) method.[1­3] Typically SCS involves a self-sustained reactionDOI: 10.1002/adem.200700076 Novel Method for Synthesis of Nano-Materials: Combustion of Active- and combustion synthesis. A combination of combustion and reactive solution approaches leads to so- called

  6. Solution Combustion Synthesis Impregnated Layer Combustion Synthesis is a Novel

    E-print Network

    Mukasyan, Alexander

    Solution Combustion Synthesis Impregnated Layer Combustion Synthesis is a Novel Methodology Engineering University of Notre Dame University of Notre Dame #12;Outline: Overview of combustion synthesis Reaction system Combustion front analaysis Theoretical model results Conclusions Acknowledgements #12

  7. Field-activated pressure-assisted combustion synthesis of MoSi 2

    Microsoft Academic Search

    J.-Y. Gao; W. Jiang

    2008-01-01

    The simultaneous synthesis and densification of MoSi2 starting from elemental Mo and Si was carried out through a process of field-activated pressure-assisted combustion synthesis\\u000a (FAPACS). After heating up to 922°C, the synthesis reaction occurs in the mode of thermal explosion but is ceased subsequently\\u000a due to a sudden shock. The product consists of MoSi2, residual Mo and amorphous Si with

  8. Combustion synthesis and nanomaterials

    Microsoft Academic Search

    Singanahally T. Aruna; Alexander S. Mukasyan

    2008-01-01

    The recent developments and trends in combustion science towards the synthesis of nanomaterials are discussed. Different modifications made to conventional combustion approaches for preparation of nanomaterials are critically analyzed. Special attention is paid to various applications of combustion synthesized nanosized products.

  9. Combustion wave structure during the MoSi 2 synthesis by Mechanically-Activated Self-propagating High-temperature Synthesis (MASHS): In situ time-resolved investigations

    Microsoft Academic Search

    Christophe Gras; Eric Gaffet; Frédéric Bernard

    2006-01-01

    In situ synchrotron time-resolved X-ray diffraction experiments coupled with an infrared imaging camera have been used to reveal the combustion wave structure during the production of MoSi2 by Mechanically Activated Self-propagating High-temperature Synthesis (MASHS). The fast combustion front exhibits a form described as an ‘equilibrium structure’ where the chemical reaction is the sole major driving force. In the MASHS process,

  10. Chemically-activated combustion synthesis of TiC–Ti composites

    Microsoft Academic Search

    Roberta Licheri; Roberto Orrù; Giacomo Cao

    2004-01-01

    The self-propagating high-temperature synthesis (SHS) of titanium carbide–titanium (TiC–Ti) composites from elemental powders in the presence of boosters (i.e., Teflon) is studied. Specifically, the dual role played by the polymer, i.e., as reaction promoter and as carburising agent, is investigated. The combustion temperature and velocity of the propagating front increase as the amount of booster added to the mixture is

  11. COMBUSTION SYNTHESIS OF ADVANCED MATERIALS: PRINCIPLESAND APPLICATIONS

    E-print Network

    Mukasyan, Alexander

    COMBUSTION SYNTHESIS OF ADVANCED MATERIALS: PRINCIPLESAND APPLICATIONS Arvind Varma, Alexander S. Gasless Combustion SynthesisFrom Elements B. Combustion Synthesis in Gas-Solid Systems C. Products of Thermite-vpe SHS D. Commercial Aspects IV. Theoretical Considerations A. Combustion Wave Propagation Theory

  12. Combustion Synthesis of Silicon Carbide 389 Combustion Synthesis of Silicon Carbide

    E-print Network

    Mukasyan, Alexander

    Combustion Synthesis of Silicon Carbide 389 X Combustion Synthesis of Silicon Carbide Alexander S. Mukasyan University of Notre Dame USA 1. Introduction Combustion synthesis (CS) is an effective technique by which combustion synthesis can occur: self - propagating high-temperature synthesis (SHS) and volume

  13. Time- and energy-efficient solution combustion synthesis of binary metal tungstate nanoparticles with enhanced photocatalytic activity.

    PubMed

    Thomas, Abegayl; Janáky, Csaba; Samu, Gergely F; Huda, Muhammad N; Sarker, Pranab; Liu, J Ping; van Nguyen, Vuong; Wang, Evelyn H; Schug, Kevin A; Rajeshwar, Krishnan

    2015-05-22

    In the search for stable and efficient photocatalysts beyond TiO2 , the tungsten-based oxide semiconductors silver tungstate (Ag2 WO4 ), copper tungstate (CuWO4 ), and zinc tungstate (ZnWO4 ) were prepared using solution combustion synthesis (SCS). The tungsten precursor's influence on the product was of particular relevance to this study, and the most significant effects are highlighted. Each sample's photocatalytic activity towards methyl orange degradation was studied and benchmarked against their respective commercial oxide sample obtained by solid-state ceramic synthesis. Based on the results herein, we conclude that SCS is a time- and energy-efficient method to synthesize crystalline binary tungstate nanomaterials even without additional excessive heat treatment. As many of these photocatalysts possess excellent photocatalytic activity, the discussed synthetic strategy may open sustainable materials chemistry avenues to solar energy conversion and environmental remediation. PMID:26018624

  14. Combustion synthesis method and products

    DOEpatents

    Holt, J. Birch (San Jose, CA); Kelly, Michael (West Alexandria, OH)

    1993-01-01

    Disclosed is a method of producing dense refractory products, comprising: (a) obtaining a quantity of exoergic material in powder form capable of sustaining a combustion synthesis reaction; (b) removing absorbed water vapor therefrom; (c) cold-pressing said material into a formed body; (d) plasma spraying said formed body with a molten exoergic material to form a coat thereon; and (e) igniting said exoergic coated formed body under an inert gas atmosphere and pressure to produce self-sustained combustion synthesis. Also disclosed are products produced by the method.

  15. Combustion synthesis method and products

    DOEpatents

    Holt, J.B.; Kelly, M.

    1993-03-30

    Disclosed is a method of producing dense refractory products, comprising: (a) obtaining a quantity of exoergic material in powder form capable of sustaining a combustion synthesis reaction; (b) removing absorbed water vapor therefrom; (c) cold-pressing said material into a formed body; (d) plasma spraying said formed body with a molten exoergic material to form a coat thereon; and (e) igniting said exoergic coated formed body under an inert gas atmosphere and pressure to produce self-sustained combustion synthesis. Also disclosed are products produced by the method.

  16. Combustion and plasma synthesis of high-temperature materials

    Microsoft Academic Search

    Z. A. Munir; J. B. Holt

    1990-01-01

    Various papers on combustion and plasmas synthesis of high-temperature materials are presented. Individual topics addressed include: self-propagation high-temperature synthesis, modeling and numerical computation of a nonsteady SHS process, new modes of quasi-periodic burning in combustion synthesis, combustion synthesis of intermetallic compounds, combustion synthesis of nickel aluminides, advanced ceramics via SHS, simultaneous combustion synthesis and densification of AlN, combustion synthesis of

  17. Combustion synthesis of advanced composite materials

    Microsoft Academic Search

    1993-01-01

    Self-propagating high temperature (combustion) synthesis (SHS), has been investigated as a means of producing both dense and expanded (foamed) ceramic and ceramic-metal composites, ceramic powders and whiskers. Several model exothermic combustion synthesis reactions were used to establish the importance of certain reaction parameters, e.g., stoichiometry, green density, combustion mode, particle size, etc. on the control of the synthesis reaction, product

  18. The synthesis of composites and solid solutions of {alpha}-SiC-AlN by field-activated combustion

    SciTech Connect

    Xue, H.; Munir, Z.A. [Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science] [Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science

    1996-10-15

    One approach to improve the relatively low fracture toughness of SiC is to add reinforcement phases in the form of fibers, whiskers, or particles. But the residual defects in composites sintered from mixtures of such reinforcement and matrix phases causes a reduction in the strength of these composites. Another way to improve the fracture toughness of SiC is to form SiC-AlN composites in situ. The crystal structures of SiC and AlN are very similar and a complete solid solution of SiC-AlN can be formed. However, the phase diagram of the SiC-AlN system shows the existence of a miscibility gap. A solid solution of SiC-AlN will decompose into two isostructural 2H phases by annealing at temperature below about 2,100 C. SiC-AlN composites with two separate phases in a modulated structure have shown much improved fracture toughness. The possibility of synthesizing composites or solid solutions of SiC and AlN by self-propagating high-temperature synthesis (SHS) is an attractive energy-saving alternative. However, while the calculated adiabatic combustion temperatures (T{sub a}) of several possible synthesis routes are high, no self-propagating combustion reaction can be initiated. In previous studies it was demonstrated that the application of an electrical field activates SHS processes, and thus the formation of SiC-AlN composites as a solid solution may be possible under the influence of an electric field.

  19. Combustion synthesis continuous flow reactor

    DOEpatents

    Maupin, G.D.; Chick, L.A.; Kurosky, R.P.

    1998-01-06

    The present invention is a reactor for combustion synthesis of inorganic powders. The reactor includes a reaction vessel having a length and a first end and a second end. The reaction vessel further has a solution inlet and a carrier gas inlet. The reactor further has a heater for heating both the solution and the carrier gas. In a preferred embodiment, the reaction vessel is heated and the solution is in contact with the heated reaction vessel. It is further preferred that the reaction vessel be cylindrical and that the carrier gas is introduced tangentially into the reaction vessel so that the solution flows helically along the interior wall of the reaction vessel. As the solution evaporates and combustion produces inorganic material powder, the carrier gas entrains the powder and carries it out of the reactor. 10 figs.

  20. Combustion synthesis continuous flow reactor

    DOEpatents

    Maupin, Gary D. (Richland, WA); Chick, Lawrence A. (West Richland, WA); Kurosky, Randal P. (Maple Valley, WA)

    1998-01-01

    The present invention is a reactor for combustion synthesis of inorganic powders. The reactor includes a reaction vessel having a length and a first end and a second end. The reaction vessel further has a solution inlet and a carrier gas inlet. The reactor further has a heater for heating both the solution and the carrier gas. In a preferred embodiment, the reaction vessel is heated and the solution is in contact with the heated reaction vessel. It is further preferred that the reaction vessel be cylindrical and that the carrier gas is introduced tangentially into the reaction vessel so that the solution flows helically along the interior wall of the reaction vessel. As the solution evaporates and combustion produces inorganic material powder, the carrier gas entrains the powder and carries it out of the reactor.

  1. Combustion Synthesis of Magnesium Aluminate

    NASA Astrophysics Data System (ADS)

    Kale, M. A.; Joshi, C. P.; Moharil, S. V.

    2011-10-01

    In the system MgO-Al2O3, three compounds MgAl2O4, MgAl6O10 (also expressed as- Mg0.4Al2.4O4) and MgAl26O40 are well known. Importance of the first two is well established. Magnesium aluminate (MgAl2O4) spinel is a technologically important material due to its interesting thermal properties. The MgAl2O4 ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl2O4 is due to various applications such as humidity-sensing and PEM fuel cells, TL/OSL dosimetry of the ionizing radiations, white light source. Interest in the MgAl6O10 has aroused due to possible use as a substrate for GaN growth. Attempt was made to synthesize these compounds by the combustion synthesis using metal nitrates as oxidizer and urea as a fuel. Compounds MgAl2O4 and MgAl6O10 were formed in a single step, while MgAl26O40 was not formed by this procedure. Activation of MgAl6O10 by rare earth ions like Ce3+, Eu3+ and Tb3+ and ns2 ion Pb2+ could be achieved. Excitation bands for MgAl6O10 are at slightly shorter wavelengths compared to those reported for MgAl2O4.

  2. Combustion Synthesis of Aluminoborate Glass Matrices

    Microsoft Academic Search

    H. C. Yi; J. Y. Guigne; L. A. Whalen; J. J. Moore

    2000-01-01

    Combustion synthesis or self-propagating high-temperature synthesis (SHS) has been used for the first time to produce glass–ceramic materials. The materials produced by the technique have a glassy matrix (aluminoborate glass) and crystalline TiB2 particles, of about 0.5 µm. The combustion characteristics and microstructures of the synthesized materials are presented.

  3. Combustion synthesis of advanced composite materials

    SciTech Connect

    Moore, J.J. (Colorado School of Mines, Golden (United States))

    1993-01-01

    Self-propagating high temperature (combustion) synthesis (SHS), has been investigated as a means of producing both dense and expanded (foamed) ceramic and ceramic-metal composites, ceramic powders and whiskers. Several model exothermic combustion synthesis reactions were used to establish the importance of certain reaction parameters, e.g., stoichiometry, green density, combustion mode, particle size, etc. on the control of the synthesis reaction, product morphology and properties. The use of an in situ liquid infiltration technique and the effect of varying the reactants and their stoichiometry to provide a range of reactant and product species i.e., solids, liquids and gases, with varying physical properties e.g., volatility and thermal conductivity, on the microstructure and morphology of synthesized composite materials is discussed. Conducting the combustion synthesis reaction in a reactive gas environment to take advantage of the synergistic effects of combustion synthesis and vapor phase transport is also examined. 10 refs.

  4. Combustion synthesis of advanced composite materials

    NASA Technical Reports Server (NTRS)

    Moore, John J.

    1993-01-01

    Self-propagating high temperature (combustion) synthesis (SHS), has been investigated as a means of producing both dense and expanded (foamed) ceramic and ceramic-metal composites, ceramic powders and whiskers. Several model exothermic combustion synthesis reactions were used to establish the importance of certain reaction parameters, e.g., stoichiometry, green density, combustion mode, particle size, etc. on the control of the synthesis reaction, product morphology and properties. The use of an in situ liquid infiltration technique and the effect of varying the reactants and their stoichiometry to provide a range of reactant and product species i.e., solids, liquids and gases, with varying physical properties e.g., volatility and thermal conductivity, on the microstructure and morphology of synthesized composite materials is discussed. Conducting the combustion synthesis reaction in a reactive gas environment to take advantage of the synergistic effects of combustion synthesis and vapor phase transport is also examined.

  5. Combustion and plasma synthesis of high-temperature materials

    SciTech Connect

    Munir, Z.A.; Holt, J.B. (California, University, Davis (United States) Lawrence Livermore National Laboratory, Livermore, CA (United States))

    1990-01-01

    Various papers on combustion and plasmas synthesis of high-temperature materials are presented. Individual topics addressed include: self-propagation high-temperature synthesis, modeling and numerical computation of a nonsteady SHS process, new modes of quasi-periodic burning in combustion synthesis, combustion synthesis of intermetallic compounds, combustion synthesis of nickel aluminides, advanced ceramics via SHS, simultaneous combustion synthesis and densification of AlN, combustion synthesis of oxide-carbide composites. Also discussed are: combustion synthesis in the Ti-C-Ni-Al systems, combustion synthesis dynamics modeling, shock-induced reaction synthesis-assisted processing of ceramics, shock consolidation of combustion-synthesized ceramics, thermal plasma synthesis ceramic powders and coatings, formation of refractory aerosol particles, silica particle formation using the counterflow diffusion flame burner, synthesis of Si, SiC, and Si3N4 powders under high number density conditions.

  6. Cost effective combustion synthesis of silicon nitride

    SciTech Connect

    Chen Yixiang [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Li Jiangtao [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100080 (China)], E-mail: ljt0012@vip.sina.com; Du Jisheng [Liaoning Jiayi Metals and Minerals Co. Ltd., Dalian 116001 (China)

    2008-06-03

    The feasibility of mechanical activation (MA)-assisted combustion synthesis (CS) of Si{sub 3}N{sub 4} was demonstrated by using Si/NH{sub 4}Cl as reactants under a nitrogen pressure of 2 MPa. MA treatment significantly enhances the reactivity of Si powders, which effectively promotes the nitridation of silicon. The NH{sub 4}Cl had the same effect as Si{sub 3}N{sub 4} diluent in preventing extensive melting of Si within the combustion wave zone. Full nitridation of Si was achieved at diluent levels as low as 5 wt%. Si{sub 3}N{sub 4} powders with {alpha}-phase contents of up to 90.6 wt% were obtained. The temperature gradient induced by heat release through radiation was responsible for discrepancies in the phase composition and morphologies of the as-synthesized product at different locations.

  7. Combustion synthesis of complex oxides

    NASA Astrophysics Data System (ADS)

    Ming, Qimin

    Advanced ceramic materials have numerous applications in electronic engineering, chemical engineering, and semiconductor industry. The synthesis of these materials at an economical cost is the bottleneck in the application of these materials. Self-propagating High-temperature Synthesis (SHS) is a new technique for producing these materials for exothermic systems by a combustion wave that propagates and produces high purity products. The full potential of SHS to produce advanced materials has not yet been utilized. In this study, we used SHS to prepare two types of complex oxides: La 1-xSrxCrO3, La0.89Sr0.1 MnO3, powders, used to make interconnect and cathode of solid oxide fuel cells; and chromium- and gallium-doped La1-xSr xFeO3-delta, mixed ionic and electronic conductive powders used to manufacture ceramic membranes for oxygen separation. A thermodynamic feasibility analysis shows that the oxidation of Cr is the main source of heat generation of La1-xSrxCrO 3, which maintains a stable reaction front. Replacing part of the metallic Cr in the reaction mixture by its oxides decreases the combustion temperature and front propagating velocity and modifies the product morphology. The oxygen needed for the Cr oxidation is provided by the decomposition of CrO3 , SrO2, or NaClO4. The predicted and observed combustion temperatures are in reasonable agreement. TG/DTA analyses of La1-xSrxCrO3 indicated that SHS stability was strongly affected by the transport of oxygen between the two regions, in which oxygen was generated by the decomposition of either NaClO4 or CrO3 and that in which it was consumed by the oxidation of Cr. Partial melting at the high combustion temperature during SHS of La 1-xSrxMnO3 increased product homogeneity. The electrical conductivity at 1000°C in air of SHS-produced cathode material (of 180 O-1·cm-1) matches that of the commercial product made by other processes. However, the SHS process provides much higher productivity and decreases processing time and the consumption of the electrical power. SrFeO3-x and LaCrO3 were the main intermediates and products for SHS of chromium-doped La0.2Sr0.8FeO 3-delta. The final structure was a solid solution of Fe and Sr rich oxides and La and Cr rich oxides. Decreasing the reactant particle size increased the homogeneity of the SHS product and increased the velocity of the propagating combustion front. The SHS produced La0.2Sr 0.8Cr0.2Fe0.8O3-delta had a maximal electrical conductivity of 8.8 O-1·cm -1 at 560°C in a pure oxygen. The material, having the highest stability in reducing conditions, had a moderate oxygen permeation rate of 3.35 x 10-9 mol/s·cm2 at 980°C in an oxygen partial pressure gradient from air to 4 x 10 -5 atm. The homogeneity and particle size of the combustion product of gallium-doped La0.5Sr0.5FeO3-delta may be increased by decreasing the cooling rate of the sample, either by increasing the sample diameter or by controlling the post-combustion temperature. The perovskite oxide maintained its cubic structure at all temperatures (from 20 to 1000°C) in air. However, decomposition occurred at 860°C under a simulated synthesis gas environment (22%CH4+21%CO2+57%H2, oxygen partial pressure of about 10-21 atm). Its maximal electrical conductivity was 142 O-1·cm-1 at 580°C under oxygen pressure of 1 atm. This material is suitable for use as a membrane in synthesis gas production, since the thermal expansions in air and reducing conditions are rather close at high temperatures.

  8. Mechanism of combustion synthesis of silicon carbide

    Microsoft Academic Search

    J. Narayan; R. Raghunathan; R. Chowdhury; K. Jagannadham

    1994-01-01

    The mechanism of self-propagating high-temperature synthesis (SHS) or combustion synthesis of SiC has been investigated using pellets consisting of silicon and carbon powders. The combustion reaction was initiated by rapidly heating the pellet on a graphite strip. The reaction products were analyzed using scanning and transmission electron microscopy, x-ray diffraction, and Raman spectroscopy. The results show that it is possible

  9. Enhanced sunlight photocatalytic activity of Ag3PO4 decorated novel combustion synthesis derived TiO2 nanobelts for dye and bacterial degradation.

    PubMed

    Eswar, Neerugatti KrishnaRao; Ramamurthy, Praveen Chandrashekarapura; Madras, Giridhar

    2015-07-01

    This study demonstrates the synthesis of TiO2 nanobelts using solution combustion derived TiO2 with enhanced photocatalytic activity for dye degradation and bacterial inactivation. Hydrothermal treatment of combustion synthesized TiO2 resulted in unique partially etched TiO2 nanobelts and Ag3PO4 was decorated using the co-precipitation method. The catalyst particles were characterized using X-ray diffraction analysis, BET surface area analysis, diffuse reflectance and electron microscopy. The photocatalytic properties of the composites of Ag3PO4 with pristine combustion synthesized TiO2 and commercial TiO2 under sunlight were compared. Therefore the studies conducted proved that the novel Ag3PO4/unique combustion synthesis derived TiO2 nanobelt composites exhibited extended light absorption, better charge transfer mechanism and higher generation of hydroxyl and hole radicals. These properties resulted in enhanced photodegradation of dyes and bacteria when compared to the commercial TiO2 nanocomposite. These findings have important implications in designing new photocatalysts for water purification. PMID:26056065

  10. Combustion synthesis and quasi-isostatic densication of powder cermets

    E-print Network

    Meyers, Marc A.

    Combustion synthesis and quasi-isostatic densi®cation of powder cermets E.A. Olevskya,* , E-propagating High-temperature synthesis (also known as SHS or combustion synthesis) presents a bright potential equation parameters. The distortion undergone by the combustion synthesis products during QIP densi

  11. Mechanism of combustion synthesis of silicon carbide

    NASA Astrophysics Data System (ADS)

    Narayan, J.; Raghunathan, R.; Chowdhury, R.; Jagannadham, K.

    1994-06-01

    The mechanism of self-propagating high-temperature synthesis (SHS) or combustion synthesis of SiC has been investigated using pellets consisting of silicon and carbon powders. The combustion reaction was initiated by rapidly heating the pellet on a graphite strip. The reaction products were analyzed using scanning and transmission electron microscopy, x-ray diffraction, and Raman spectroscopy. The results show that it is possible to produce ?-SiC without any residual silicon and carbon. Occasionally, a very small number density of ?-SiC precipitates embedded in the ?-SiC matrix was observed. Based upon the microstructural features, it is proposed that the formation of SiC involves the dissolution of carbon into liquid silicon, diffusion of C into liquid silicon, and subsequent precipitation of SiC. The size of the SiC crystallites is determined by the diffusion coefficient of carbon in liquid silicon and the time available for SiC precipitation. The activation enthalpy for the SHS process is estimated to be 59±3 kcal/mol.

  12. Gravity Effects on Combustion Synthesis of Glasses

    NASA Technical Reports Server (NTRS)

    Yi, H. C.; Guigne, J. Y.; Moore, J. J.; Robinson, L. A.; Manerbino, A. R.; Schowengerdt, F. D.; Gokoglu, S. (Technical Monitor)

    2000-01-01

    The Combustion Synthesis technique has been used to produce glasses based on B2O3-Al2O3-MgO and CaO-Al2O3. The combustion characteristics of these combustion synthesis reactions using both small cylindrical pellets (SCP) and large spherical pellets (LSP) are presented. Low density pellets (approx. 35% of their theoretical density) were used, which made synthesis of low exothermic combustion reactions possible. Microstructural analysis of reacted samples was carried out to identify the glass-forming compositions. The effects of gravity on the glass formation were studied aboard the KC-135 using SCP samples. Gravity seemed to have such obvious effects on the combustion characteristics that the wave velocity was lower and the Width of the combustion wave was larger under reduced gravity conditions. Samples produced under low gravity also had more enhanced vitrification than those on ground, while some systems also exhibited lower combustion temperatures. It was also found that the container significantly affects both the combustion characteristics and microstructure. Substantially more divitrification occurred at the area which was in contact with the support (container).

  13. Combustion and Plasma Synthesis of High-Temperature Materials

    NASA Astrophysics Data System (ADS)

    Munir, Z. A.; Holt, J. B.

    1997-04-01

    KEYNOTE ADDRESS. Self-Propagating High-Temperature Synthesis: Twenty Years of Search and Findings (A. Merzhanov). SOLID-STATE COMBUSTION SYNTHESIS. Recent Progress in Combustion Synthesis of High-Performance Materials in Japan (M. Koizumi & Y. Miyamoto). Modeling and Numerical Computation of a Nonsteady SHS Process (A. Bayliss & B. Matkowsky). New Models of Quasiperiodic Burning in Combustion Synthesis (S. Margolis, et al.). Modeling of SHS Operations (V. Hlavacek, et al.). Combustion Theory for Sandwiches of Alloyable Materials (R. Armstrong & M. Koszykowski). Observations on the Combustion Reaction Between Thin Foils of Ni and Al (U. Anselmi-Tamburini & Z. Munir). Combustion Synthesis of Intermetallic Compounds (Y. Kaieda, et al.). Combustion Synthesis of Nickel Aluminides (B. Rabin, et al.). Self-Propagating High-Temperature Synthesis of NiTi Intermetallics (H. Yi & J. Moore). Shock-Induced Chemical Synthesis of Intermetallic Compounds (S. Work, et al.). Advanced Ceramics Via SHS (T. DeAngelis & D. Weiss). In-Situ Formation of SiC and SiC-C Blocked Solids by Self-Combustion Synthesis (S. Ikeda, et al.). Powder Purity and Morphology Effects in Combustion-Synthesis Reactions (L. Kecskes, et al.). Simultaneous Synthesis and Densification of Ceramic Components Under Gas Pressure by SHS (Y. Miyamoto & M. Koizumi). The Use of Self-Propagating High-Temperature Synthesis of High-Density Titanium Diboride (P. Zavitsanos, et al.). Metal--Ceramic Composite Pipes Produced by a Centrifugal-Thermit Process (O. Odawara). Simultaneous Combustion Synthesis and Densification of AIN (S. Dunmead, et al.). Fabrication of a Functionally Gradient Material by Using a Self-Propagating Reaction Process (N. Sata, et al.). Combustion Synthesis of Oxide-Carbide Composites (L. Wang, et al.). Heterogeneous Reaction Mechanisms in the Si-C System Under Conditions of Solid Combustion (R. Pampuch, et al.). Experimental Modeling of Particle-Particle Interactions During SHS of TiB2 -Al2O3 (K. Logan, et al.). Combustion Synthesis in the Ti-C-Ni-Al System (S. Dunmead, et al.). Combustion Synthesis Dynamics Modeling (T. Kottke, et al.). Elementary Processes in SiO2-Al Thermite-Type Reactions Activated or Induced by Mechanochemical Treatment (G. Hida & I. Lin). Combustion Synthesis of Ceramic Preforms for Molten-Metal Infiltration (D. Halverson, et al.). Combustion Characteristics of Solid-Solid Systems: Experiments and Modeling (S. Kumar, et al.). Microstructure of TiB2 Sintered by the Self-Combustion Method (K. Urabe, et al..). A Laser-Ignition Study of Gasless Reactions Using Thermography (C. Chow & J. Mohler). Shock-Induced Reaction Synthesis-Assisted Processing of Ceramics (R. Ward, et al.). Summary Assessment of the Application of SPS and Related Reaction Processing to Produce Dense Ceramics (R. Rice). Shock Consolidation of Combustion-Synthesized Ceramics (A. Niiler, et al.). High-Pressure Burning Rate of Silicon in Nitrogen (M. Costantino & J. Holt). Preparation of a TiC Single Crystal by the Floating-Zone Method from a Self-Combustion Rod (S. Otani, et al.). PLASMA AND GAS-PHASE SYNTHESIS. Thermal Plasma Synthesis of Ceramic Powders and Coatings (T. Yoshida). A Theoretical Comparison of Conventional and Hybrid RF-Plasma Reactors (J. McKelliget & N. El-Kaddah). Homogeneous Nucleation and Particle Growth in Thermal Plasma Synthesis (S. Girshick & C.-P. Chiu). Formation of Refractory Aerosol Particles (R. Flagan, et al.). Ceramic-Powder Synthesis in an Aerosol Reactor (M. Alam, et al.). Silica-Particle Formation Using the Counter-Flow Diffusion Flame Burner (J. Katz, et al.). Synthesis and Properties of Low-Carbon Boron Carbides (C. Adkins, et al.). Synthesis of Si, SiC, and Si3N4 Powders Under High Number Density Conditions (J. Haggerty & J. Flint). Rapid Preparation of Titanium and Other Transition-Metal Nitride- and Carbide Powders by a Carbo-Reduction Method Using Arc-Image Heating (M. Yoshimura, et al.). Microwave Plasma Densification of Aluminum Nitride (S. Knittel & S. Risbud). Plasma Synth

  14. Perovskite membranes by aqueous combustion synthesis: synthesis and properties

    Microsoft Academic Search

    Alexander S. Mukasyan; Colleen Costello; Katherine P. Sherlock; David Lafarga; Arvind Varma

    2001-01-01

    The objective of this work is to identify optimum synthesis, compacting and sintering conditions in order to achieve a pure phase fully densified La0.8Sr0.2CrO3 (LSC) perovskite membrane. The aqueous combustion synthesis of LSC powders was investigated over a wide range of synthesis conditions by using the metal nitrates (oxidizer)–glycine (fuel) system. The powders were pressed and sintered to create dense

  15. Nanocrystalline pirochromite spinel through solution combustion synthesis

    Microsoft Academic Search

    M. J. de Andrade; M. D. Lima; R. Bonadiman; C. P. Bergmann

    2006-01-01

    The production of magnesium–chromium oxides by solution combustion synthesis was investigated using glycine and urea for the first time. Ammonium dichromate, urea\\/glycine and ammonium nitrate aqueous solutions were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and

  16. Combustion Enhancement by Active Control

    Microsoft Academic Search

    E. Haile; O. Delabroy; D. Durox; F. Lacas; S. Candel

    Active control has many potential applications in the domain of combustion. Active instability control has been successfully\\u000a demonstrated in a variety of laboratory combustors and its practical use is currently being explored. Active control methods\\u000a also appear to be suited to the optimization of combustion system operation. The external controller may be used for example\\u000a to extend the stability margin

  17. Combustion and Plasma Synthesis of High-Temperature Materials

    Microsoft Academic Search

    Z. A. Munir; J. B. Holt

    1997-01-01

    KEYNOTE ADDRESS. Self-Propagating High-Temperature Synthesis: Twenty Years of Search and Findings (A. Merzhanov). SOLID-STATE COMBUSTION SYNTHESIS. Recent Progress in Combustion Synthesis of High-Performance Materials in Japan (M. Koizumi & Y. Miyamoto). Modeling and Numerical Computation of a Nonsteady SHS Process (A. Bayliss & B. Matkowsky). New Models of Quasiperiodic Burning in Combustion Synthesis (S. Margolis, et al.). Modeling of SHS

  18. Combustion synthesis of calcium aluminates

    Microsoft Academic Search

    D. A. Fumo; M. R. Morelli; A. M. Segadães

    1996-01-01

    Commercial calcium aluminate cements for refractory use are known to contain various phases, the hydration behavior of which is interdependent and not fully understood. Hydration studies normally require that pure oxides be synthesized. Solid-state synthesis of single aluminates requires high temperatures and full conversion is not guaranteed. Moreover, it is difficult to obtain a compositionally homogeneous product with this method.

  19. Carbon combustion synthesis of nanostructured perovskites

    Microsoft Academic Search

    K. S. Martirosyan; M. Iliev; D. Luss

    2007-01-01

    A novel, economical, and energy-efficient process to produce nanostructured particles of several perovskite oxides, such as\\u000a ferroelectrics BaTiO3, SrTiO3 and LiNbO3, is described. This process, referred to as carbon combustion synthesis of oxides (CCSO) is a modified SHS process that uses\\u000a carbon as a fuel instead of a pure metal. In CCSO of nanostructured materials, the exothermic oxidation of carbon

  20. Synthesis and Characterization of CeO2 Nanoparticles via Solution Combustion Method for Photocatalytic and Antibacterial Activity Studies.

    PubMed

    Ravishankar, Thammadihalli Nanjundaiah; Ramakrishnappa, Thippeswamy; Nagaraju, Ganganagappa; Rajanaika, Hanumanaika

    2015-04-01

    CeO2 nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO2 nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450?°C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO2 having crystallite size of 35?nm. The infrared spectrum shows a strong band below 700?cm(-1) due to the Ce-O-Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302?nm. The photoluminescence spectrum shows characteristic peaks of CeO2 nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42?nm. CeO2 nanoparticles exhibit photocatalytic activity against trypan blue at pH?10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO2 nanoparticles also reduce Cr(VI) to Cr(III) and show antibacterial activity against Pseudomonas aeruginosa. PMID:25969812

  1. Synthesis and Characterization of CeO2 Nanoparticles via Solution Combustion Method for Photocatalytic and Antibacterial Activity Studies

    PubMed Central

    Ravishankar, Thammadihalli Nanjundaiah; Ramakrishnappa, Thippeswamy; Nagaraju, Ganganagappa; Rajanaika, Hanumanaika

    2015-01-01

    CeO2 nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO2 nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450?°C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO2 having crystallite size of 35?nm. The infrared spectrum shows a strong band below 700?cm?1 due to the Ce?O?Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302?nm. The photoluminescence spectrum shows characteristic peaks of CeO2 nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42?nm. CeO2 nanoparticles exhibit photocatalytic activity against trypan blue at pH?10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO2 nanoparticles also reduce CrVI to CrIII and show antibacterial activity against Pseudomonas aeruginosa. PMID:25969812

  2. Kinetics of combustion synthesis in the Ti-C and Ti-C-Ni systems

    SciTech Connect

    Dunmead, S.D.; Holt, J.B. (Lawrence Livermore National Lab., CA (USA)); Readey, D.W. (Ohio State Univ., Columbus, OH (USA)); Semier, C.E. (Semler Materials Services, Columbus, OH (US))

    1989-12-01

    The self-propagating reactions, termed self-propagating high-temperature synthesis (SHS), or more simply, combustion synthesis, have received increasing attention especially for the preparation of refractory ceramic and intermetallic compounds. The kinetics and mechanisms of combustion reactions in the Ti-C and Ti-C-Ni systems were studied. Samples were produced by igniting compacts of elemental Ti, C, and Ni powders with a tungsten heating coil under an inert argon atmosphered. Using an elementary model of the process, the apparent activation energies of these highly exothermic reactions have been determined by measuring combustion wave velocities and combustion temperatures.

  3. Novel Active Combustion Control Valve

    NASA Technical Reports Server (NTRS)

    Caspermeyer, Matt

    2014-01-01

    This project presents an innovative solution for active combustion control. Relative to the state of the art, this concept provides frequency modulation (greater than 1,000 Hz) in combination with high-amplitude modulation (in excess of 30 percent flow) and can be adapted to a large range of fuel injector sizes. Existing valves often have low flow modulation strength. To achieve higher flow modulation requires excessively large valves or too much electrical power to be practical. This active combustion control valve (ACCV) has high-frequency and -amplitude modulation, consumes low electrical power, is closely coupled with the fuel injector for modulation strength, and is practical in size and weight. By mitigating combustion instabilities at higher frequencies than have been previously achieved (approximately 1,000 Hz), this new technology enables gas turbines to run at operating points that produce lower emissions and higher performance.

  4. Combustion synthesis of titanium carbide: Theory and experiment

    Microsoft Academic Search

    J. B. Holt; Z. A. Munir

    1986-01-01

    The combustion synthesis of titanium carbide from elemental powders has been theoretically and experimentally studied as a model system for self -propagating high temperature synthesis (SHS) of refractory compounds. Calculations of the adiabatic temperature of combustion of graphite and titanium powders to form TiCx have been made to show the effects of stoichiometry, dilution and the initial temperature of the

  5. Demonstration of Active Combustion Control

    NASA Technical Reports Server (NTRS)

    Lovett, Jeffrey A.; Teerlinck, Karen A.; Cohen, Jeffrey M.

    2008-01-01

    The primary objective of this effort was to demonstrate active control of combustion instabilities in a direct-injection gas turbine combustor that accurately simulates engine operating conditions and reproduces an engine-type instability. This report documents the second phase of a two-phase effort. The first phase involved the analysis of an instability observed in a developmental aeroengine and the design of a single-nozzle test rig to replicate that phenomenon. This was successfully completed in 2001 and is documented in the Phase I report. This second phase was directed toward demonstration of active control strategies to mitigate this instability and thereby demonstrate the viability of active control for aircraft engine combustors. This involved development of high-speed actuator technology, testing and analysis of how the actuation system was integrated with the combustion system, control algorithm development, and demonstration testing in the single-nozzle test rig. A 30 percent reduction in the amplitude of the high-frequency (570 Hz) instability was achieved using actuation systems and control algorithms developed within this effort. Even larger reductions were shown with a low-frequency (270 Hz) instability. This represents a unique achievement in the development and practical demonstration of active combustion control systems for gas turbine applications.

  6. Combustion synthesis and quasi-isostatic densification of powder cermets

    Microsoft Academic Search

    E. A Olevsky; E. R Strutt; M. A Meyers

    2002-01-01

    Self-propagating High-temperature synthesis (also known as SHS or combustion synthesis) presents a bright potential for the synthesis of compounds with high degree of purity. However, for many reactions, the product is highly porous, and it must either be pulverized for subsequent densification, or densified while it is still hot and ductile. Densification has successfully been applied to a number of

  7. Combustion Synthesis of Transition Metal Carbosulfides

    NASA Astrophysics Data System (ADS)

    Wally, Pablo; Ueki, Masanori

    1998-07-01

    The combustion synthesis of ternary and quaternary carbosulfides of the transition metals was investigated to obtain high-purity materials to be tested as solid lubricants in high-temperature environments. The main carbosulfide formation mechanisms have been clarified in the case of the technologically interesting tantalum carbosulfide, enabling the preparation of reaction products with controlled purity. The formation of molten tantalum sulfide as an intermediate product was found to play a key role for obtaining a homogeneous reaction product, and the presence of excess carbon reduced the oxygen content of the carbosulfide. However, the higher the overall carbon contents, the higher is the amount of carbide impurities in the reaction products. Use of iodine or hexachlorobenzene as a catalyzer minimized the need of excess sulfur in the raw powder mixture, reduced the amount of carbide impurities, and contributed to the homogenization of the reaction products.

  8. Combustion synthesis of boride and other composites

    DOEpatents

    Halverson, Danny C. (Modesto, CA); Lum, Beverly Y. (Livermore, CA); Munir, Zuhair A. (Davis, CA)

    1989-01-01

    A self-sustaining combustion synthesis process for producing hard, tough, lightweight B.sub.4 C/TiB.sub.2 composites is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the B.sub.4 C and TiB.sub.2 reactants. For lightweight products the composition must be relatively rich in the B.sub.4 C component. B.sub.4 C-rich composites are obtained by varying the initial temperature of the reactants. The product is hard, porous material whose toughness can be enhanced by filling the pores with aluminum or other metal phases using a liquid metal infiltration process. The process can be extended to the formation of other composites having a low exothermic component.

  9. Combustion synthesis of LaFeO3 sensing nanomaterial

    NASA Astrophysics Data System (ADS)

    Zaza, F.; Pallozzi, V.; Serra, E.; Pasquali, M.

    2015-06-01

    Since industrial revolution, human activities drive towards unsustainable global economy due to the overexploitation of natural resources and the unacceptable emissions of pollution and greenhouse gases. In order to address that issue, engineering research has been focusing on gas sensors development for monitoring gas emissions and controlling the combustion process sustainability. Semiconductors metal oxides sensors are attractive technology because they require simple design and fabrication, involving high accessibility, small size and low cost. Perovskite oxides are the most promising sensing materials because sensitivity, selectivity, stability and speed-response can be modulated and optimized by changing the chemical composition. One of the most convenient synthesis process of perovskite is the citrate-nitrate auto-combustion method, in which nitrate is the oxidizing agent and citrate is the fuel and the chelating argent in the same time. Since the sensibility of perovskite oxides depends on the defective crystallographic structure and the nanomorphology, the experimental was designed in order to study the dependence of powder properties on the synthesis conditions, such as the solution acidity and the relative amount of metals, nitrates and citric acid. Crystalline structure was studied in depth for defining the effects of synthesis conditions on size, morphology and crystallographic structure of nanopowders of LaFeO3.

  10. Synthesis of AlN?SiC composites and solid solutions by field-activated self-propagating combustion

    Microsoft Academic Search

    H. Xue; Z. A. Munir

    1997-01-01

    The synthesis of AlN-SiC composites and solid solutions was achieved through the imposition of an electric field in self-propagating high-temperature reactions. Despite its highly exothermic nature, the reaction Si3N4 + 4Al + 3C = 4AlN + 3 SiC is not self-sustaining without the imposition of a threshold field (E) of 8 Vcm? 1. At higher fields, the nature of the

  11. Combustion synthesis of HfB2Al composites

    Microsoft Academic Search

    H. C. Yi; J. Y. Guigné; T. C. Woodger; J. J. Moore

    1998-01-01

    Combustion synthesis (SHS) of HfB2-Al composite materials with a wide range of HfB2-to-Al ratios corresponding to either metal (Al) or ceramic (HfB2) matrix was carried out with the emphasis on 60 and 70 vol pct Al. The effects of composition and green density of pellets on the combustion characteristics were studied. Combustion temperature, wave velocity, and reaction mode all changed

  12. Combustion synthesis of HfB 2 Al composites

    Microsoft Academic Search

    H. C. Yi; J. Y. Guigné; T. C. Woodger; J. J. Moore

    1998-01-01

    Combustion synthesis (SHS) of HfB2-Al composite materials with a wide range of HfB2-to-Al ratios corresponding to either metal (Al) or ceramic (HfB2) matrix was carried out with the emphasis on 60 and 70 vol pct Al. The effects of composition and green density of pellets\\u000a on the combustion characteristics were studied. Combustion temperature, wave velocity, and reaction mode all changed

  13. Combustion synthesis of hexagonal boron–nitride-based ceramics

    Microsoft Academic Search

    Yumin Zhang; Xiaodong He; Jiecai Han; Shanyi Du

    2001-01-01

    Pure hBN (hexagonal boron nitride) and hBN-based ceramic parts were fabricated by the combustion synthesis technique, i.e. self-propagating high-temperature synthesis (SHS). The components were manufactured by the combustion reaction of 80MPa nitrogen and the compact made by cool isostatic pressing. In the hBN-based ceramic parts, hBN powders were used as diluent and SiO2 powders as the reinforcement phase. The relative

  14. Spontaneous magnetization generated by spin, pulsating, and planar combustion synthesis

    Microsoft Academic Search

    K. S. Martirosyan; J. R. Claycomb; G. Gogoshin; R. A. Yarbrough; J. H. Miller; D. Luss

    2003-01-01

    The motion of the high temperature front during combustion synthesis of ferrite materials generates residual magnetization in cylindrical product samples. The combustion wave created a current density of up to 10 A\\/cm2, which influenced the magnetization distribution. The measured peak magnetic field intensity was up to 8 ?T. Qualitatively different magnetic field maps were generated in ferrite samples synthesized by

  15. Combustion synthesis of advanced materials: Part I. Reaction parameters

    Microsoft Academic Search

    John J. Moore; H. J. Feng

    1995-01-01

    An explanation of combustion (self propagating high temperature) synthesis (SHS) is given together with a historical perspective of the examination of such exothermic reactions. The application of thermochemical functions has been used to predict theoretically the maximum adiabatic temperature, Tad. This, combined with a knowledge of the ignition temperature, Tig, and the actual combustion temperature, Tc, has been used to

  16. Activated combustion features in the Mo-Si-C-promoter system and synthesis of MoSi{sub 2}-SiC composite powders

    SciTech Connect

    Hambartsumyan, A.A. [Laboratory of Kinetics of SHS Processes, A.B. Nalbandyan Institute of Chemical Physics, National Academy of Sciences, P. Sevak str. 5/2, Yerevan 0014 (Armenia); Khachatryan, H.L. [Department of Chemical Physics, Yerevan State University, A. Manukyan str. 1, Yerevan 0025 (Armenia)], E-mail: hayk@ichph.sci.am; Harutyunyan, A.B. [Laboratory of Kinetics of SHS Processes, A.B. Nalbandyan Institute of Chemical Physics, National Academy of Sciences, P. Sevak str. 5/2, Yerevan 0014 (Armenia); Kharatyan, S.L. [Laboratory of Kinetics of SHS Processes, A.B. Nalbandyan Institute of Chemical Physics, National Academy of Sciences, P. Sevak str. 5/2, Yerevan 0014 (Armenia); Department of Chemical Physics, Yerevan State University, A. Manukyan str. 1, Yerevan 0025 (Armenia)

    2007-12-04

    Opportunities on combustion synthesizing the MoSi{sub 2}-SiC ceramic composites in a wide range of compositions under the chemical activated mode were studied. Molybdenum, silicon powders and carbon black were used as initial reagents, and Teflon was used as an activating additive. It was established that Teflon displays a dual (kinetic and thermal) impact on the interaction between reagents. The phasic character of the combustion process evolution, being characterized by low- and high-temperature regimes, was revealed. The end-products were subjected to SEM, XRD and chemical analyses.

  17. The combustion synthesis of Ni-Ti shape memory alloys

    SciTech Connect

    Moore, J.J.; Yi, H.C. (Colorado School of Mines, Golden (USA))

    1990-08-01

    Combustion synthesis of Ni-Ti-series shape-memory alloys yields both time and energy savings over conventional production methods. The solidified combustion synthesis process products have been cold-rolled into plates which exhibit the shape-memory effect, and it was noted that shape-memory transition temperatures may be tailored over a -78 to 460 C temperature range through the substitution of a third element for Ni; this element may be Pd or Fe. Accounts are given of the experimental combustion syntheses of Ni-Ti-Fe and Ti-Ni-Pd. 24 refs.

  18. The solution combustion synthesis of nanophosphors

    SciTech Connect

    Tornga, Stephanie C [Los Alamos National Laboratory

    2009-01-01

    Nanophosphors are defined as nano-sized (1-100mn), insulating, inorganic materials that emit light under particle or electromagnetic excitation. Their unique luminescence properties provide an excellent potential for applications in radiation detection and imaging. Herein, solution combustion synthesis (SCS) is presented as a method to prepare nanophosphor powders, while X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL), photoluminescence excitation (PLE), and other techniques were used to characterize their structural and optical properties. The goal of this work is to synthesize bright, high-quality powders of nanophosphors, consolidate them into bulk materials and study their structural and optical properties using XRD, TEM, PL, and PLE. SCS is of interest because it is a robust, inexpensive, and facile technique, which yields a significant amount of a wide variety of oxide materials, in a short amount of time. Several practical nanophosphors were synthesized and investigated in this work, including simple oxides such as Y{sub 2}O{sub 3}:Bi, Y{sub 2}O{sub 3}:Tb, Y{sub 2}O{sub 3}:Eu and Gd{sub 2}O{sub 3}:Eu, complex oxides such as Gd{sub 2}SiO{sub 5}:Ce, Y{sub 2}SiO{sub 5}:Ce, Lu{sub 2}SiO{sub 5}:Ce, Zn{sub 2}SiO{sub 4}:Mn, and Y{sub 3}Al{sub 5}O{sub 12}:Ce. Results demonstrate that altering the processing parameters such as water content of the precursor solution, ignition temperature, fuel type and amount, and post-synthesis annealing can significantly improve light output, and that it is possible to optimize the luminescence output of oxyorthosilicates by reducing the amount of silica in the precursor mixture.

  19. The combustion synthesis of multilayer NiAl systems

    Microsoft Academic Search

    T. S. Dyer; Z. A. Munir; V. Ruth

    1994-01-01

    The synthesis of materials by combustion methods, including the self-propagating high-temperature synthesis (SHS) method, involves, typically, the use of powders as reactant materials. The use of particulate materials gives rise to difficulties in experimental and theoretical studies. In the former, the use of powders can result in the introduction of impurities associated with the surface films on the powders. Attempts

  20. One Step Combustion Synthesis Of YAG:Ce Phosphor For Solid State Lighting

    NASA Astrophysics Data System (ADS)

    Yadav, Pooja; Gupta, K. Vijay Kumar; Muley, Aarti; Joshi, C. P.; Moharil, S. V.

    2011-10-01

    YAG:Ce is an important phosphor having applications in various fields ranging from solid state lighting to scintillation detectors. YAG phosphors doped with activators are mainly synthesized by solid state reaction techniques that require high sintering temperatures (above 1500°C) to eliminate YAM and YAP phases. Though several soft chemical routes have been explored for synthesis of YAG, most of these methods are complex and phase pure materials are not obtained in one step, but prolonged annealing at temperatures around 1000 C or above becomes necessary. One step combustion synthesis of YAG:Ce3+ and related phosphors carried out at 500 C furnace temperature is reported here. Activation with Ce3+ could be achieved during the synthesis without taking recourse to any post-combustion thermal treatment. LEDs prepared from the combustion synthesized YAG:Ce3+, exhibited properties comparable to those produced from the commercial phosphor.

  1. Combustion synthesis of novel boron carbide

    NASA Astrophysics Data System (ADS)

    Harini, R. Saai; Manikandan, E.; Anthonysamy, S.; Chandramouli, V.; Eswaramoorthy, D.

    2013-02-01

    The solid-state boron carbide is one of the hardest materials known, ranking third behind diamond and cubic boron nitride. Boron carbide (BxCx) enriched in the 10B isotope is used as a control rod material in the nuclear industry due to its high neutron absorption cross section and other favorable physico-chemical properties. Conventional methods of preparation of boron carbide are energy intensive processes accompanied by huge loss of boron. Attempts were made at IGCAR Kalpakkam to develop energy efficient and cost effective methods to prepare boron carbide. The products of the gel combustion and microwave synthesis experiments were characterized for phase purity by XRD. The carbide formation was ascertained using finger-print spectroscopy of FTIR. Samples of pyrolized/microwave heated powder were characterized for surface morphology using SEM. The present work shows the recent advances in understanding of structural and chemical variations in boron carbide and their influence on morphology, optical and vibrational property results discussed in details.

  2. Joining NiAl using simultaneous combustion synthesis and pressure

    SciTech Connect

    Torres, R.D.; Strohaecker, T.R. (PPGEMM/UFRGS, Porto Alegre (Brazil)); Moore, J.J.; Edwards, G.R. (Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering)

    1994-02-15

    Nickel aluminide-based intermetallics are attractive in applications requiring high thermal stability, corrosion and oxidation resistance, and high-temperature mechanical properties. However, if components are to be produced using these intermetallics, efficient joining techniques need to be developed. This paper provides an initial investigation of the application of combustion (self propagating, high temperature) synthesis (SHS) as a means of joining NiAl intermetallic materials. Combustion synthesis is a technique whereby an exothermic reaction mixture is used to synthesize the required product(s). If the reaction is sufficiently exothermic, it can be self sustaining once initiated at the ignition temperature, Tig. The heat generated by the reaction results in an increase in temperature to a maximum combustion temperature, Tc, which is usually less than the calculated adiabatic temperature, Tad, on account of heat losses from the reaction. Combustion synthesis reactions can be operated in two different modes of ignition, i.e. propagating and simultaneous combustion modes. In each case, the exothermic reactant mix, typically in powder form, is pressed in the required reaction stoichiometry and at a certain green density. In reaction mixtures which are less exothermic, such as the synthesis of an intermetallic compound from its elements, e.g. reaction, the simultaneous combustion mode is often used.

  3. The synthesis of nickel aluminides by multilayer self-propagating combustion

    Microsoft Academic Search

    T. S. Dyer; Z. A. Munir

    1995-01-01

    The synthesis of Ni-Al intermetallic thin films by self-propagating combustion reactions was investigated for the 1:1 and\\u000a 3:1 Ni\\/Al stoichiometries. The dependence of the combustion wave velocity on the individual layer thickness was determined.\\u000a The marked decrease in velocity with layer thickness was consistent with results of modeling studies on multilayer systems.\\u000a Activation energies for the synthesis of NiAl were

  4. Sol–gel auto-combustion synthesis of samarium-doped TiO 2 nanoparticles and their photocatalytic activity under visible light irradiation

    Microsoft Academic Search

    Qi Xiao; Zhichun Si; Zhiming Yu; Guanzhou Qiu

    2007-01-01

    High photocatalytic activity of Sm3+-doped TiO2 nanocrystalline under visible light has been successfully prepared by sol–gel auto-combustion technique. The samples were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy and photoluminescence (PL) spectra. UV–vis diffuse reflectance spectra showed a slight shift to longer wavelengths and an extension of the absorption in the visible region for almost all the samarium-doped samples,

  5. New ceramic processing approaches using combustion synthesis under gas pressure

    SciTech Connect

    Miyamoto, Y. (Processing Reseach Center for High Performance Materials, Institute of Scientific and Industrial Research, Osaka Univ., Ibaraki, Osaka 567 (JP))

    1990-04-01

    Self-propagating high-temperature synthesis (SHS), or combustion synthesis, is a highly exothermic reaction accompanying formation of compounds with high formation energies. The reaction is initiated by ignition and propagated at speeds of 0.1 to 20 cm/s. Usually the reaction temperature reaches above 2100 to 3500 K. Over 300 kinds of compounds, which include many advanced ceramics and alloys are reportedly produced by this process. The authors discuss one new approach which involves the simultaneous synthesis and densification of ceramics, a process they call gas-pressure combustion sintering, and another which is the formation of nitride ceramic powders and components by nitriding combustion in pressurized nitrogen atmosphere.

  6. Combustion synthesis of ceramic-metal composite materials in microgravity

    NASA Technical Reports Server (NTRS)

    Moore, John

    1995-01-01

    Combustion synthesis, self-propagating high temperature synthesis (SHS) or reactive synthesis provides an attractive alternative to conventional methods of producing advanced materials since this technology is based on the ability of highly exothermic reactions to be self sustaining and, therefore, energetically efficient. The exothermic SHS reaction is initiated at the ignition temperature, T(sub ig), and generates heat which is manifested in a maximum or combustion temperature, T(sub c), which can exceed 3000 K . Such high combustion temperatures are capable of melting and/or volatilizing reactant and product species and, therefore, present an opportunity for producing structure and property modification and control through liquid-solid, vapor-liquid-solid, and vapor-solid transformations.

  7. Spontaneous magnetization generated by spin, pulsating, and planar combustion synthesis

    Microsoft Academic Search

    K. S. Martirosyan; J. R. Claycomb; G. Gogoshin; R. A. Yarbrough; J. H. Miller; D. Luss

    2003-01-01

    The motion of the high temperature front during combustion synthesis of ferrite materials generates residual magnetization in cylindrical product samples. The combustion wave created a current density of up to 10 A\\/cm2, which influenced the magnetization distribution. The measured peak magnetic field intensity was up to 8 muT. Qualitatively different magnetic field maps were generated in ferrite samples synthesized by

  8. Combustion Synthesis of Advanced Porous Materials in Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Zhang, X.; Moore, J. J.; Schowengerdt, F. D.; Johnson, D. P.

    1999-01-01

    Combustion synthesis, otherwise known as self-propagating high temperature synthesis (SHS), can be used to produce engineered advanced porous material implants which offer the possibility for bone ingrowth as well as a permanent structure framework for the long-term replacement of bone defects. The primary advantage of SHS is based on its rapid kinetics and favorable energetics. The structure and properties of materials produced by SHS are strongly dependent on the combustion reaction conditions. Combustion reaction conditions such as reaction stoichiometry, particle size, green density, the presence and use of diluents or inert reactants, and pre-heating of the reactants, will affect the exothermicity of the reaction. A number of conditions must be satisfied in order to obtain high porosity materials: an optimal amount of liquid, gas and solid phases must be present in the combustion front. Therefore, a balance among these phases at the combustion front must be created by the SHS reaction to successfully engineer a bone replacement material system. Microgravity testing has extended the ability to form porous products. The convective heat transfer mechanisms which operate in normal gravity, 1 g, constrain the combustion synthesis reactions. Gravity also acts to limit the porosity which may be formed as the force of gravity serves to restrict the gas expansion and the liquid movement during reaction. Infiltration of the porous product with other phases can modify both the extent of porosity and the mechanical properties.

  9. Combustion synthesis of calcium phosphate bioceramic powders A. Cu neyt Tas *,1

    E-print Network

    Tas, A. Cuneyt

    Combustion synthesis of calcium phosphate bioceramic powders A. CuÈ neyt Tas *,1 Department)2; Combustion synthesis; Hydroxyapatite 1. Introduction Calcium hydroxyapatite (HA: Ca10(PO4)6(OH)2), the major), instead of water, as the precipitation medium. Self-propagating combustion synthesis (SPCS

  10. Combustion synthesis and nanomaterials Singanahally T. Aruna a,*, Alexander S. Mukasyan b,1

    E-print Network

    Mukasyan, Alexander

    Combustion synthesis and nanomaterials Singanahally T. Aruna a,*, Alexander S. Mukasyan b,1 October 2008 Accepted 2 December 2008 Keywords: Combustion synthesis Self-propagating high-temperature synthesis Solution combustion Nanomaterials Catalysts Phosphors a b s t r a c t The recent developments

  11. DEMONSTRATION OF GAS-PHASE COMBUSTION SYNTHESIS OF NANOSIZED PARTICLES USING

    E-print Network

    Wooldridge, Margaret S.

    DEMONSTRATION OF GAS-PHASE COMBUSTION SYNTHESIS OF NANOSIZED PARTICLES USING A HYBRID BURNER) Abstract--A new approach for gas-phase combustion synthesis of nanosized particles using a novel hybrid. Introduction Gas-phase combustion synthesis is an important methodology for the production of nanosized

  12. Burning Velocities in Catalytically Assisted Self-Propagating High-Temperature Combustion Synthesis Systems

    E-print Network

    Wooldridge, Margaret S.

    Burning Velocities in Catalytically Assisted Self-Propagating High-Temperature Combustion Synthesis. © 2001 by The Combustion Institute INTRODUCTION Self-propagating high-temperature combustion synthesis of catalytically assisted self-propagating high-temperature synthesis (SHS) of the tantalum/carbon material system

  13. Spontaneous magnetization generated by spin, pulsating, and planar combustion synthesis

    NASA Astrophysics Data System (ADS)

    Martirosyan, K. S.; Claycomb, J. R.; Gogoshin, G.; Yarbrough, R. A.; Miller, J. H.; Luss, D.

    2003-06-01

    The motion of the high temperature front during combustion synthesis of ferrite materials generates residual magnetization in cylindrical product samples. The combustion wave created a current density of up to 10 A/cm2, which influenced the magnetization distribution. The measured peak magnetic field intensity was up to 8 ?T. Qualitatively different magnetic field maps were generated in ferrite samples synthesized by different combustion modes. The average magnetization vector generated by either planar or pulsating combustion was oriented at a smaller angle with respect to the pellet axis (??45°) than those generated by spin combustion (60°???80°). We estimate that an internal transient magnetic field of up to 5 mT formed in the postcombustion region when its temperature was below the Curie temperature. This explains why the Earth's field had no impact on the spontaneous magnetization field. Model calculations reproduce the qualitative features of the measured field maps.

  14. Combustion Synthesis Of Ultralow-density Nanoporous Gold Foams

    SciTech Connect

    Tappan, Bruce C [Los Alamos National Laboratory; Mueller, Alex H [Los Alamos National Laboratory; Steiner, Stephen A [Los Alamos National Laboratory; Luther, Erik P [Los Alamos National Laboratory

    2008-01-01

    A new synthetic pathway for producing nanoporous gold monoliths through combustion synthesis from Au bistetrazoJeamine complexes has been demonstrated. Applications of interest for Au nanofoams include new substrates for nanoparticle-mediated catalysis, embedded antennas, and spectroscopy. Integrated support-and-catalystin-one nanocomposites prepared through combustion synthesis of mixed AuBTA/metal oxide pellets would also be an interesting technology approach for low-cost in-line catalytic conversion media. Furthermore, we envision preparation of ultrahigh surface area gold electrodes for application in electrochemical devices through this method.

  15. New ceramic processing approaches using combustion synthesis under gas pressure

    Microsoft Academic Search

    Miyamoto

    1990-01-01

    Self-propagating high-temperature synthesis (SHS), or combustion synthesis, is a highly exothermic reaction accompanying formation of compounds with high formation energies. The reaction is initiated by ignition and propagated at speeds of 0.1 to 20 cm\\/s. Usually the reaction temperature reaches above 2100 to 3500 K. Over 300 kinds of compounds, which include many advanced ceramics and alloys are reportedly produced

  16. Combustion synthesis of ceramic matrices for immobilization of 14C

    Microsoft Academic Search

    F. Bosc-Rouessac; R. M. Marin-Ayral; A. Haidoux; N. Massoni; F. Bart

    2008-01-01

    In this study, the use of combustion synthesis for immobilization of 14C was considered. Ceramic matrices have been prepared by this method using two different devices: one non-conventional with preheating of the samples and the other conventional device where ignition was produced thanks to tungsten filament. These two devices gave rise to different mechanisms of reactions involving different amounts of

  17. Characteristics of Porous B 4 CAl 2 O 3 Composites Fabricated by the Combustion Synthesis Technique

    Microsoft Academic Search

    H. C. Yi; J. Y. Guigné; L. A. Robinson; A. R. Manerbino; J. J. Moore

    2004-01-01

    The Combustion Synthesis or Self-propagating High Temperature Synthesis (SHS) technique has been used to produce porous B4C-Al2O3 composites. The effects of the green density of the pellet on the combustion characteristics and porosity were studied. The combustion synthesis reaction was highly exothermic, generating significant vapor at the combustion front. The evolution of the vapor led to a large degree of

  18. Self-propagating combustion synthesis of intermetallic matrix composites in the ISS

    Microsoft Academic Search

    Roberto Orrù; Roberta Licheri; Antonio Mario Locci; Giacomo Cao; Jimmy De Wilde; Fabienne Lemoisson; Ludo Froyen; Inigo A. Beloki; Alexander E. Sytschev; Alexander S. Rogachev; David J. Jarvis

    2007-01-01

    Combustion Synthesis experiments have been performed on the ISS (International Space Station) during the Belgian taxi-flight\\u000a mission ODISSEA in November 2002, in the framework of the ESA-coordinated project COSMIC (Combustion Synthesis under Microgravity\\u000a Conditions). The main objective of the experiments was to investigate the general physico-chemical mechanisms of combustion\\u000a synthesis processes and the formation of products microstructure. Within the combustion

  19. Active Document Layout Synthesis

    Microsoft Academic Search

    Xiaofan Lin

    2005-01-01

    Document layout analysis has been researched for many years. However, there is little work on the reverse of document layout analysis: document layout synthesis, whose goal is to generate logically correct and aesthetically appealing layout given the text\\/image contents and the flexible layout template. This paper introduces a new automatic document layout synthesis method, which can actively pursue the optimal

  20. Self-ignition combustion synthesis of TiFe in hydrogen atmosphere

    Microsoft Academic Search

    R. Wakabayashi; S. Sasaki; I. Saita; M. Sato; H. Uesugi; T. Akiyama

    2009-01-01

    This paper describes the self-ignition combustion synthesis (SICS) of highly active titanium iron (TiFe) in a high-pressure hydrogen atmosphere without employing an activation process. In the experiments, well-mixed powders of Ti and Fe in the molar ratio of 1:1 were uniformly heated up to 1085°C, the eutectic temperature of Ti–Fe binary system, in pressurized hydrogen at 0.9MPa. The electric source

  1. Combustion synthesis of HfB2-Al composites

    NASA Astrophysics Data System (ADS)

    Yi, H. C.; Guigné, J. Y.; Woodger, T. C.; Moore, J. J.

    1998-08-01

    Combustion synthesis (SHS) of HfB2-Al composite materials with a wide range of HfB2-to-Al ratios corresponding to either metal (Al) or ceramic (HfB2) matrix was carried out with the emphasis on 60 and 70 vol pct Al. The effects of composition and green density of pellets on the combustion characteristics were studied. Combustion temperature, wave velocity, and reaction mode all changed drastically with composition and green density. The combustion mechanisms were also studied using temperature profile analysis. The combustion zone can be divided into preflame and main reaction zones, and the width of the latter was much larger than that of the former. It was also found that the combustion reaction was initiated at the melting of the aluminum and consisted of a two-step reaction sequence corresponding to the initial formation of Al3Hf and, subsequently, HfB2 compounds. The formation of Al3Hf triggered the HfB2 formation according to the following reaction mechanism: A1_3 Hf + 2B to HfB_2 + 3A1

  2. Effects of gravity on combustion synthesis of functionally graded biomaterials

    Microsoft Academic Search

    J. Moore; F. Schowengerdt; R. Ayers; M. Castillo; X. Zhang; U. Umakoshi; C. Yi; J. Guigne

    2002-01-01

    Combustion synthesis, or self-propagating, high temperature synthesis (SHS) is currently being used at the Colorado School of Mines to produce advanced materials for biomedical applications. These biomaterials include ceramic, intermetallic, and metal-matrix composites for applications ranging from structural to oxidation- and wear-resistant materials, e.g., TiC-Ti, TiC-Cr3 C2 , MoSi2 - SiC, NiAl-TiB2 , to engineered porous composites, e.g., B4 C-A

  3. Combustion synthesis of ceramic and metal-matrix composites

    NASA Technical Reports Server (NTRS)

    Moore, John J.; Feng, Heng J.; Hunter, Kevin J.; Wirth, David G.

    1993-01-01

    Combustion synthesis or self-propagating high temperature synthesis (SHS) is effected by heating a reactant mixture, to above the ignition temperature (Tig) whereupon an exothermic reaction is initiated which produces a maximum or combustion temperature, Tc. These SHS reactions are being used to produce ceramics, intermetallics, and composite materials. One of the major limitations of this process is that relatively high levels of porosity, e.g., 50 percent, remain in the product. Conducting these SHS reactions under adiabatic conditions, the maximum temperature is the adiabatic temperature, Tad, and delta H (Tad) = 0, Tad = Tc. If the reactants or products go through a phase change, the latent heat of transformation needs to be taken into account.

  4. The combustion synthesis of multilayer NiAl systems

    SciTech Connect

    Dyer, T.S.; Munir, Z.A. (Univ. of California, Davis, CA (United States)); Ruth, V. (Univ. of Oldenburg (Germany). Physics Dept.)

    1994-05-15

    The synthesis of materials by combustion methods, including the self-propagating high-temperature synthesis (SHS) method, involves, typically, the use of powders as reactant materials. The use of particulate materials gives rise to difficulties in experimental and theoretical studies. In the former, the use of powders can result in the introduction of impurities associated with the surface films on the powders. Attempts to provide a fundamental understanding of SHS reactions from model experiments suffer from the same shortcoming as well as the complex nature of the reaction interface in powder systems. In order to provide a simpler geometry for the reaction interface, experimental as well as theoretical research has examined the combustion process between thin reactant layers. Anselmi-Tamburini and Munir investigated the combustion synthesis of nickel aluminides using nickel and aluminum foils as reactants. Because of the high thermal conductivity of the foil ensembles, a self-propagating combustion reaction could not be sustained and the reactants had to be imbedded in a chemical oven. It was observed that a self-sustaining reaction between the foils (which were oriented such that the wave propagated in a parallel direction to the interfaces) does not occur until the temperature is approximately the same as the melting point of nickel. Significant interfacial reactions, however, took place ahead of the wave resulting in the formation of intermediate nickel-aluminum phases. In this paper, the authors report the results of an investigation on the combustion kinetics of relatively thin (about 200--500 nm) layers in the Ni-Al system.

  5. Gas-Phase Combustion Synthesis of Nonoxide Nanoparticles in Microgravity

    NASA Technical Reports Server (NTRS)

    Axelbaum, R. L.; Kumfer, B. M.; Sun, Z.; Chao, B. H.

    2001-01-01

    Gas-phase combustion synthesis is a promising process for creating nanoparticles for the growing nanostructure materials industry. The challenges that must be addressed are controlling particle size, preventing hard agglomerates, maintaining purity, and, if nonoxides are synthesized, protecting the particles from oxidation and/or hydrolysis during post-processing. Sodium-halide Flame Encapsulation (SFE) is a unique methodology for producing nonoxide nanoparticles that addresses these challenges. This flame synthesis process incorporates sodium and metal-halide chemistry, resulting in nanoparticles that are encapsulated in salt during the early stages of their growth in the flame. Salt encapsulation has been shown to allow control of particle size and morphology, while serving as an effective protective coating for preserving the purity of the core particles. Metals and compounds that have been produced using this technology include Al, W, Ti, TiB2, AlN, and composites of W-Ti and Al-AlN. Oxygen content in SFE synthesized nano- AlN has been measured by neutron activation analysis to be as low as 0.54wt.%, as compared to over 5wt.% for unprotected AlN of comparable size. The overall objective of this work is to study the SFE process and nano-encapsulation so that they can be used to produce novel and superior materials. SFE experiments in microgravity allow the study of flame and particle dynamics without the influence of buoyancy forces. Spherical sodium-halide flames are produced in microgravity by ejecting the halide from a spherical porous burner into a quiescent atmosphere of sodium vapor and argon. Experiments are performed in the 2.2 sec Drop Tower at the NASA-Glenn Research Center. Numerical models of the flame and particle dynamics were developed and are compared with the experimental results.

  6. Grained composite materials prepared by combustion synthesis under mechanical pressure

    DOEpatents

    Dunmead, Stephen D. (Davis, CA); Holt, Joseph B. (San Jose, CA); Kingman, Donald D. (Danville, CA); Munir, Zuhair A. (Davis, CA)

    1990-01-01

    Dense, finely grained composite materials comprising one or more ceramic phase or phase and one or more metallic and/or intermetallic phase or phases are produced by combustion synthesis. Spherical ceramic grains are homogeneously dispersed within the matrix. Methods are provided, which include the step of applying mechanical pressure during or immediately after ignition, by which the microstructures in the resulting composites can be controllably selected.

  7. Cermet materials prepared by combustion synthesis and metal infiltration

    SciTech Connect

    Holt, J.B.; Dunmead, S.D.; Halverson, D.C.; Landingham, R.L.

    1988-12-12

    Ceramic-metal composites (cermets) are made by a combination of self-propagating high temperature combustion synthesis and molten metal infiltration. Solid-gas, solid-solid and solid-liquid reactions of a powder compact produce a porous ceramic body which is infiltrated by molten metal to produce a composite body of higher density. AlN-Al and many other materials can be produced. 5 figs.

  8. Combustion synthesis of tungsten powder from sodium tungstate

    Microsoft Academic Search

    Jiang Guojian; Xu Jiayue; Zhuang Hanrui; Li Wenlan

    2011-01-01

    Tungsten powders were prepared by Self-propagating High-temperature Synthesis (SHS) method directly from hitherto unreported system: sodium tungstate (Na2WO4) and magnesium (Mg). The adiabatic temperatures of self-propagating combustion reactions with different amount of Mg in Na2WO4+Mg system were calculated. The influences of different starting conditions (molar ratios of Mg\\/Na2WO4 and relative densities of samples) on the compositions and microstructure of reaction

  9. Joining NiAl using simultaneous combustion synthesis and pressure

    Microsoft Academic Search

    R. D. Torres; T. R. Strohaecker; J. J. Moore; G. R. Edwards

    1994-01-01

    Nickel aluminide-based intermetallics are attractive in applications requiring high thermal stability, corrosion and oxidation resistance, and high-temperature mechanical properties. However, if components are to be produced using these intermetallics, efficient joining techniques need to be developed. This paper provides an initial investigation of the application of combustion (self propagating, high temperature) synthesis (SHS) as a means of joining NiAl intermetallic

  10. Cermet materials prepared by combustion synthesis and metal infiltration

    DOEpatents

    Holt, J.B.; Dunmead, S.D.; Halverson, D.C.; Landingham, R.L.

    1991-01-29

    Ceramic-metal composites (cermets) are made by a combination of self-propagating high temperature combustion synthesis and molten metal infiltration. Solid-gas, solid-solid and solid-liquid reactions of a powder compact produce a porous ceramic body which is infiltrated by molten metal to produce a composite body of higher density. AlN-Al and many other materials can be produced. 6 figures.

  11. Cermet materials prepared by combustion synthesis and metal infiltration

    DOEpatents

    Holt, Joseph B. (San Jose, CA); Dunmead, Stephen D. (Davis, CA); Halverson, Danny C. (Modesto, CA); Landingham, Richard L. (Livermore, CA)

    1991-01-01

    Ceramic-metal composites (cermets) are made by a combination of self-propagating high temperature combustion synthesis and molten metal infiltration. Solid-gas, solid-solid and solid-liquid reactions of a powder compact produce a porous ceramic body which is infiltrated by molten metal to produce a composite body of higher density. AlN-Al and many other materials can be produced.

  12. Self-ignition combustion synthesis of LaNi 5 at different hydrogen pressures

    Microsoft Academic Search

    Naoto Yasuda; Tohru Tsuchiya; Shino Sasaki; Noriyuki Okinaka; Tomohiro Akiyama

    2011-01-01

    In this paper, we describe the self-ignition combustion synthesis (SICS) of LaNi5 utilizing the hydrogenation heat of metallic calcium at different hydrogen pressures, and focus on the effect of hydrogen pressure on the ignition temperature and the initial activation of hydrogenation. In the experiments, La2O3, Ni, and Ca were dry-mixed, and then heated at 0.1, 0.5, and 1.0 MPa of hydrogen

  13. Combustion synthesis of silicon carbide assisted by a magnesium plus polytetrafluoroethylene mixture

    SciTech Connect

    Ayral, R.M. [Institut Charles Gerhardt Montpellier, PMOF-UM2-CNRS Pl. E. Bataillon, 34095 Montpellier Cedex 5 (France); Rouessac, F., E-mail: florence.rouessac@univ-montp2.fr [Institut Charles Gerhardt Montpellier, PMOF-UM2-CNRS Pl. E. Bataillon, 34095 Montpellier Cedex 5 (France); Massoni, N. [CEA, DEN, DTCD, 30207 Bagnols-sur-Ceze (France)

    2009-11-15

    In this study, the use of SiC combustion synthesis for immobilization of {sup 14}C was considered. Due to the low exothermicity of the reaction between silicon and graphite, a highly exothermic mixture (magnesium and polytetrafluoroethylene) was used both as a chemical oven and activate additive in the mixture. With this configuration the reaction between graphite and silicon was initiated and propagated on the whole sample. The self-propagating high temperature synthesis samples were characterized by using scanning electron microscopy and X-ray diffraction.

  14. Combustion Synthesis of Doped Thermoelectric Oxides

    SciTech Connect

    Selig, Jiri [Lamar University; Lin, Sidney [Lamar University; Lin, Hua-Tay [ORNL; Johnson, D Ray [ORNL

    2012-01-01

    Self-propagating high-temperature synthesis (SHS) was used to prepare silver doped calcium cobaltates (Ca1.24- xAgxCo1.62O3.86, x = 0.03 - 0.12) powders. SHS is a simple and economic process to synthesize ceramic materials with minimum energy requirements. The heat generated by the SHS reaction can sustain the propagation of the reaction front and convert reactants to desired products. The effect of doping level on thermoelectric properties was investigated in this study. Results show the substitution of calcium by silver decreases the thermal conductivity significantly. XRD and surface area measurements show synthesized powders are phase pure and have large specific surface areas.

  15. Effects of gravity on combustion synthesis of functionally graded biomaterials

    NASA Astrophysics Data System (ADS)

    Moore, J.; Schowengerdt, F.; Ayers, R.; Castillo, M.; Zhang, X.; Umakoshi, U.; Yi, C.; Guigne, J.

    Combustion synthesis, or self-propagating, high temperature synthesis (SHS) is currently being used at the Colorado School of Mines to produce advanced materials for biomedical applications. These biomaterials include ceramic, intermetallic, and metal-matrix composites for applications ranging from structural to oxidation- and wear-resistant materials, e.g., TiC-Ti, TiC-Cr3 C2 , MoSi2 - SiC, NiAl-TiB2 , to engineered porous composites, e.g., B4 C-A l2 O3 , Ti-TiBx , Ni-Ti, Ca 3 (PO4 )2 and glass- ceramic composites, e.g., CaO-SiO2 - B a O-A l2 O3 -T i B2 . The goal of the functionally graded biomaterials project is to develop new materials, graded in porosity and composition, which will combine the desirable mechanical properties of implant, e.g., NiTi, with the bone-growth enhancement properties of porous biodegradable ceramics, e.g., Ca 3 (PO4 )2 . Recent experiments on the NASA parabolic flight (KC- 135) aircraft have shown that gravity plays an important role in controlling the structure and properties of materials produced by combustion synthesis. The results of these studies, which will be presented at the conference, will provide valuable input to the design of experiments to be done in Space-DRUMSTM, a containerless materials processing facility scheduled to be placed on the International Space Station in 2003.

  16. Joining advanced materials into hybrid structures using pressurized combustion synthesis

    SciTech Connect

    Messler, R.W. Jr.; Orling, T.T. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Materials Engineering

    1994-12-31

    Demanding design requirements frequently call for the use and joining of combinations of oxide and nonoxide ceramics, intermetallics, and metals in virtually every imaginable combination in both monolithic and reinforced forms, resulting in hybrid structures. Such new, nontraditional materials and structures can be expected to require new, nontraditional joining processes. One attractive, but embryonic option, is pressurized combustion synthesis, a form of exothermic welding or brazing. Pressurized combustion synthesis or self-propagating high-temperature synthesis (SHS) joining is being systematically studied to understand the mechanism(s) of joint formation, understand the role of processing parameters, evaluate and optimize joint properties, and develop a process model for use in joint design, parameter selection, property prediction, and intelligent process control. This paper presents the results of a study on a model system of 3Ni + Al > Ni{sub 3}Al filler or intermediate between nickel-base superalloy end elements. A Gleeble thermal-mechanical simulator was used to investigate the effects of reaction temperature, hold time, applied pressure, reactant composition, and heating rate, and good insight has been gained to enable more intensive studies of process fundamentals and of techniques for producing more complex, functional gradient material (FGM) joints between dissimilar combinations of ceramics, intermetallics and metals.

  17. Combustion synthesis/quasi-isostatic pressing of TiCNiTi cermets: processing and mechanical response

    E-print Network

    Meyers, Marc A.

    Combustion synthesis/quasi-isostatic pressing of TiC­NiTi cermets: processing and mechanical and alumina particulate before initiation of the combustion reaction. The sample was ignited within the particulate and subjected to a uniaxial load immediately after passage of the combustion wave

  18. Solution combustion synthesis and characterization of nanosized bismuth ferrite

    NASA Astrophysics Data System (ADS)

    Sai Kumar, V. Sesha; Rao, K. Venkateswara; Krishnaveni, T.; Kishore Goud, A. Shiva; Reddy, P. Ranjith

    2012-06-01

    The present paper describes a simple method of nanosized BiFeO3 by the solution combustion synthesis using bismuth and iron nitrates as oxidizers and the combination fuel of citric acid and ammonium hydroxide, with fuel to oxidizer ratio (? = 1) one. The X-ray Diffraction results indicated rhombohedral phase (R3m) with JCPDS data card no: 72-2035. The ferroelectric transition of the sample at 8310C was detected by differential thermal analysis. Thermal analysis was done by Thermal gravimetric-Differential thermal analyzer and obtained results were presented in this paper.

  19. Combustion synthesis of oxide-carbide composites

    SciTech Connect

    Wang, L.L.; Munir, Z.A. (California Univ., Davis, CA (USA). Div. of Materials Science and Engineering)

    1990-02-01

    Synthesis of an oxide-carbide composite material through a self- propagating reaction process can be achieved by coupling a highly exothermic thermite reaction and a weakly exothermic carbide reaction. Two systems, one with Al and the other with Mg as the reducing agent in the presence of B{sub 2}O{sub 3} and carbon, are used as the reaction models for this investigation. Based on the experimental results, the formation Al{sub 2}O{sub 3}-B{sub 4}C and MgO-N{sub 4}C composites is proposed to involve a two-step sequential reaction mechanism. The highly exothermic thermite reaction between the reducing agent and B{sub 2}O{sub 3} occurs first, and the heat generated subsequently brings about the formation of B{sub 4}C between the liberated boron and the carbon. The exothermic reaction between Al and B{sub 2}O{sub 3} is initiated at about 850{degrees}C. In the reaction between Mg and B{sub 2}O{sub 3}, however, the interaction between Mg and B{sub 2}O{sub 3} depends on the surrounding inert gas pressure due to the high volatility of Mg. The interaction changes from one involving gaseous Mg and liquid B{sub 2}O{sub 3} to one involving liquid Mg and liquid B{sub 2}O{sub 3} as the pressure increases. In both systems, reactions between the metallic oxides (i.e. Al{sub 2}O{sub 3} or MgO) and B{sub 2}O{sub 3} compete with the thermite reaction. Although it is possible to synthesize B{sub 4}C from carbon fibers in the 6Mg+B{sub 2+}O{sub 3}+C system, the carbon fiber is only partially converted, and the carbide formed is loosely attached to the unreacted carbon core. 17 refs., 23 figs., 3 tabs.

  20. An Experimental Investigation of Gas-Phase Combustion Synthesis of SiO2 Nanoparticles Using a Multi-Element

    E-print Network

    Wooldridge, Margaret S.

    An Experimental Investigation of Gas-Phase Combustion Synthesis of SiO2 Nanoparticles Using a Multi of an experimental investigation of gas-phase combustion synthesis of silica (SiO2) particles using a multi of the MEDB in providing a controlled environment for fundamental studies of gas-phase combustion synthesis

  1. The use of an electric field as a processing parameter in the combustion synthesis of ceramics and composites

    SciTech Connect

    Munir, Z.A. [Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science

    1995-08-01

    The use of electric field to activate the process of self-propagating high-temperature (SHS) is demonstrated. Experimental observations show that for several systems, combustion synthesis is only possible with the presence of a field. Modeling studies on the synthesis of {beta}-SiC have shown the effect of field is localized in the combustion zone and that the magnitude of this effect is related to {delta}E{sup 2} where {delta} is the electric conductivity and E is the field. The modeling studies showed a linear dependence between the combustion wave velocity and the applied voltage. Experimental results show a similar relationship between velocity and voltage with a dependence on the initial relative density of the reactant compacts. Investigations on the mechanism in field-activated synthesis were also made. The results confirm a model in which the rate of heat release from the field in the combustion zone is enhanced by the presence of a molten phase, Si in the case of synthesis of silicon carbide. The effect of field on the SHS reactions was also investigated for the synthesis of composite materials. Composites of MoSi{sub 2}-SiC, MoSi{sub 2}-ZrO{sub 2}, MoSi{sub 2}-Nb and B{sub 4}C-TiB{sub 2} were formed by field-activated combustion synthesis. In the case of MoSi{sub 2}-SiC, composites with molar ratios of SiC/MoSi{sub 2}(=x) ranging from zero to one have been prepared by this method. In the absence of a field no SHS reaction is possible for x > 0. Similarly, in the case of B{sub 4}C-TiB{sub 2}, composites with B{sub 4}C/TiB{sub 2}(=y) ratios of one or larger can only be synthesized in the SHS mode in the presence of a field.

  2. Ultra-fine powders using glycine-nitrate combustion synthesis

    SciTech Connect

    Chick, L.A.; Pederson, L.R.; Bates, J.L.; Maupin, G.D.

    1991-05-01

    Fabrication of advanced, multifunctional materials frequently requires the synthesis of complex, ultra-fine powders comprised of a single phase containing several elements (multicomponent) or of several phases that are intimately mixed on a micro-scale (composite). A new combustion synthesis method, the glycine/nitrate process (GNP), is particularly useful for synthesizing ultra-fine, multicomponent oxide powders. Examples discussed include La(Sr)CrO{sub 3} and La(Sr)FeO{sub 3} perovskites and a composite of three phases, NiO, NiFe{sub 2}O{sub 4}, and Cu metal. The GNP consists of two basic steps. First, metal nitrates and a low molecular weight amino acid are dissolved in water. Second, the solution is boiled until it thickens. This viscous liquid ignites and undergoes self-sustaining combustion, producing an ash composed of the oxide product. Most refractory oxides that are composed of a combination of metals having stable nitrates should be possible to synthesize using GNP. 15 refs., 8 figs.

  3. A change in the propagation velocity during the heterogeneous micropyretic/combustion synthesis

    NASA Astrophysics Data System (ADS)

    Li, H. P.

    2006-12-01

    Micropyretic/combustion synthesis is a technique whereby a material is synthesized by the propagation of a combustion front across a powder. Heterogeneous distributions of reactants and a diluent are common during micropyretic synthesis when powders are mixed and the conventional modelling treatments thus far have only considered uniform systems. Heterogeneities in a composition are thought to result in local variations of thermophysical/chemical parameters for the reactant, such as density, heat capacity and thermal conductivity. The result is changes in combustion temperature, propagation velocity and the propagation pattern of a combustion front. This study investigates the impact of heterogeneities during micropyretic synthesis with Ni + Al. Correlations of heterogeneities in the reactants and diluent with propagation velocity and combustion temperature are also investigated. In addition, a map, considering concurrent heterogeneities in the reactants and diluent, has been generated to provide a better understanding of the effect of heterogeneities on propagation velocity during micropyretic synthesis.

  4. Active Combustion Control for Aircraft Gas Turbine Engines

    NASA Technical Reports Server (NTRS)

    DeLaat, John C.; Breisacher, Kevin J.; Saus, Joseph R.; Paxson, Daniel E.

    2000-01-01

    Lean-burning combustors are susceptible to combustion instabilities. Additionally, due to non-uniformities in the fuel-air mixing and in the combustion process, there typically exist hot areas in the combustor exit plane. These hot areas limit the operating temperature at the turbine inlet and thus constrain performance and efficiency. Finally, it is necessary to optimize the fuel-air ratio and flame temperature throughout the combustor to minimize the production of pollutants. In recent years, there has been considerable activity addressing Active Combustion Control. NASA Glenn Research Center's Active Combustion Control Technology effort aims to demonstrate active control in a realistic environment relevant to aircraft engines. Analysis and experiments are tied to aircraft gas turbine combustors. Considerable progress has been shown in demonstrating technologies for Combustion Instability Control, Pattern Factor Control, and Emissions Minimizing Control. Future plans are to advance the maturity of active combustion control technology to eventual demonstration in an engine environment.

  5. Characteristics of fluid flow in the combustion synthesis of TiC from the elements

    NASA Technical Reports Server (NTRS)

    Valone, S. M.; Behrens, R. G.

    1987-01-01

    The results of a numerical investigation of finite reservoir effects on capillary spreading at small reservoir dimensions are presently related to wave propagation phenomena in the combustion synthesis of TiC from its two elemental constituents. It is noted that gravitational forces can affect bubble coalescence by nonbuoyant means under the suitable conditions, although these conditions are expected to be rare in combustion synthesis. Finite-curved reservoirs can drive capillary flow due to surface tension and wall contact forces; these cause the wall and the metal to be completely reconfigured during combustion synthesis.

  6. Combustion synthesis of low exothermic component rich composites

    DOEpatents

    Halverson, Danny C. (Modesto, CA); Lum, Beverly Y. (Livermore, CA); Munir, Zuhair A. (Davis, CA)

    1991-01-01

    A self-sustaining combustion synthesis process for producing hard, tough, lightweight, low exothermic potential product (LEPP)/high exothermic potential product (HEPP) composites is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the LEPP and HEPP reactants. For lightweight products the composition must be relatively rich in the LEPP component. LEPP rich composites are obtained by varying the initial temperature of the reactants. The product is hard, porous material whose toughness can be enhanced by filling the pores with aluminum or other metal phases using a liquid metal infiltration process. The process can be extended to the formation of other composites having a low exothermic component.

  7. Synthesis of cobalt ferrite nanoparticles using combustion waves

    NASA Astrophysics Data System (ADS)

    de Biasi, R. S.; Figueiredo, A. B. S.; Fernandes, A. A. R.; Larica, C.

    2007-10-01

    Nanocrystalline particles of cobalt ferrite (CoFe 2O 4) were prepared by a combustion wave method, based on the Self-propagating High temperature Synthesis technique (SHS), using iron nitrate, Fe(NO 3) 3?9H 2O, cobalt nitrate, Co(NO 3) 2?6H 2O, and glycine, C 2H 5NO 2. The average particle size, determined by means of X-ray diffraction, was found to depend on the glycine-nitrate ratio and varied between 2.7 and 17 nm. By measuring at several temperatures the relative intensity of the Mössbauer spectra due to superparamagnetic particles and to ferrimagnetic particles, we determined the size distribution of the nanoparticles in one of the samples. It was found to be a log-normal distribution with a most probable diameter Dm=1.8 nm and a full width at half-height ?D=2.6 nm.

  8. Mechanical activation effect on the self-sustaining combustion reaction in the Mo–Si system

    Microsoft Academic Search

    Ch Gras; D Vrel; E Gaffet; F Bernard

    2001-01-01

    Nanostructured molybdenum disilicide (MoSi2) was synthesized using an alternative route called MASHS (mechanically activated self-propagating high-temperature synthesis). This original process combines a short duration ball milling (MA) with a self-sustaining combustion (SHS). These two steps were investigated. The microstructure evolution of the powder mixture during mechanical activation was monitored using XRD profile analysis and TEM investigations. Short duration ball milling

  9. Combustion synthesis of TiNi intermetallic compounds

    SciTech Connect

    Depiak, A.; Depiak, K.; Wierzba, I.; Karim, G.A. [Univ. of Calgary, Alberta (Canada). Dept. of Mechanical Engineering

    1996-10-01

    The technique, self-propagating high temperature synthesis (SHS) was used to produce TiNi intermetallic compounds. The reactants in the form of a compacted powder pellet were ignited in a thermal explosion mode. Microstructural observations of SHS-reacted pellets established that the combustion in air, argon or vacuum of a stoichiometric mixture of Ti and Ni powders resulted mainly in the TiNi parent phase. Some phase disparities occurred when the synthesis was carried out in air, particularly in the vicinity of the surface of the pellet. As a result of the preferential formation of TiO{sub 2} near the surface, it was observed that an intermediate product region was composed of the eutectic structure of TiNi + TiNi{sub 3}. It was observed that the ignition temperature in air was lower than that recorded for the argon and vacuum atmospheres. Through microstructural analysis it is concluded that this can be attributed to the formation of TiO{sub 2} on the surface of the pellet. This oxidation, exothermic in nature, stimulated the Ti + Ni reaction. Application is for hydrogen storage and transport applications.

  10. Gravitational Effects on Combustion Synthesis of Advanced Porous Materials

    NASA Technical Reports Server (NTRS)

    Zhang, X.; Moore, J. J.; Schowengerdt, F. D.; Thorne, K.

    2000-01-01

    Combustion Synthesis (self-Propagating high-temperature synthesis-(SHS)) of porous Ti-TiB(x), composite materials has been studied with respect to the sensitivity to the SHS reaction parameters of stoichiometry, green density, gasifying agents, ambient pressure, diluents and gravity. The main objective of this research program is to engineer the required porosity and mechanical properties into the composite materials to meet the requirements of a consumer, such as for the application of bone replacement materials. Gravity serves to restrict the gas expansion and the liquid movement during SHS reaction. As a result, gravitational forces affect the microstructure and properties of the SHS products. Reacting these SHS systems in low gravity in the KC-135 aircraft has extended the ability to form porous products. This paper will emphasize the effects of gravity (low g, 1g and 2g) on the SHS reaction process, and the microstructure and properties of the porous composite. Some of biomedical results are also discussed.

  11. Combustion diagnostic for active engine feedback control

    DOEpatents

    Green, Jr., Johney Boyd (Knoxville, TN); Daw, Charles Stuart (Knoxville, TN); Wagner, Robert Milton (Knoxville, TN)

    2007-10-02

    This invention detects the crank angle location where combustion switches from premixed to diffusion, referred to as the transition index, and uses that location to define integration limits that measure the portions of heat released during the combustion process that occur during the premixed and diffusion phases. Those integrated premixed and diffusion values are used to develop a metric referred to as the combustion index. The combustion index is defined as the integrated diffusion contribution divided by the integrated premixed contribution. As the EGR rate is increased enough to enter the low temperature combustion regime, PM emissions decrease because more of the combustion process is occurring over the premixed portion of the heat release rate profile and the diffusion portion has been significantly reduced. This information is used to detect when the engine is or is not operating in a low temperature combustion mode and provides that feedback to an engine control algorithm.

  12. Combustion based technique for synthesis and joining of refractory materials

    NASA Astrophysics Data System (ADS)

    White, Jeremiah David Edward

    Gasless combustion systems offer features that make them attractive tools for a variety of potential applications. Among them are rapid heating rates, high exothermicity, and high maximum temperatures. These characteristics were exploited to accomplish three separate concepts including the joining of refractory materials, synthesis of a pore-free composite, and the study of thermal explosion in mechanically activated powders. Honeywell Aerospace is a leading producer of carbon brakes for commercial aircraft. The manufacturing process involves chemical vapor infiltration (CVI) to form a carbon matrix around a carbon fiber preform. A major disadvantage of this approach is the time required to form a fully dense preform, which is on the order of 140 days. In addition, after the brakes are in service, they have to be discarded while there is a relatively thick amount of friction material still available. There is a profit motive for reusing these discs which are out of spec. One such example would be to perform a refurbishment by bonding a new thin C/C element onto a used "core" to produce a brake that meets performance specifications. Unfortunately, joining C/C composites is not a simple task, as carbon does not lend itself to welding, and other means (e.g. mechanical or adhesives) would not hold up to the harsh operational conditions. A novel apparatus was designed, built, and proven to join C/C using so-called reactive resistance welding (RRW). It is shown that a joint stronger than the original material can be achieved using moderate electrical current and mechanical force. Additionally, joining layers of similar thickness and microstructure were obtained with different reactive media, ranging from pellets of pressed powders (˜1-2 mm) to thin metal foils (˜25 micron). By modifying the schematic of the RRW apparatus, porous C/C was infiltrated with liquid silicon in order to form a new pore-free C/C-SiC composite. It is shown that using such a process, the silicon rapidly fills the open pore structure with only a thin layer of silicon carbide forming around the periphery of the pores. As the high-temperature treatment time is extended, carbon from the composite diffuses through this layer and reacts with the silicon subsequently crystallizing a bulk silicon carbide phase and forming an essentially pore-free composite. The utility of the apparatus was further demonstrated for the study of electrical initiation of an exothermic reactive system, Ni-Al. The effect of short-term high-energy milling on this system was investigated and it was found to significantly decrease the ignition temperature and activation energy without formation of any new phases. Scanning electron microscopy, electron dispersive x-ray spectroscopy, x-ray diffraction, infrared thermal imaging, and mechanical testing were used to study the process dynamics and properties of these materials.

  13. Microstructural transformation during combustion synthesis of MgB 2 superconductor

    Microsoft Academic Search

    Xiujuan Chen; Tiandong Xia; Mingjing Wang; Wenjun Zhao; Tianzuo Liu

    2007-01-01

    To investigate the phase transformation behaviors of combustion synthesis of MgB2, a mixture of Mg, B was used for a combustion front quenching test, and the microstructural evolution in the quenched sample was observed by scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA). The temperature–time profile of the combustion was measured, and the phase constituents of the different zones

  14. Kinetics of combustion synthesis in the TiC and TiC-Ni systems

    Microsoft Academic Search

    Stephen D. Dunmead; J. B. Holt; D. W. Readey; C. E. Semier

    1989-01-01

    The self-propagating reactions, termed self-propagating high-temperature synthesis (SHS), or more simply, combustion synthesis, have received increasing attention especially for the preparation of refractory ceramic and intermetallic compounds. The kinetics and mechanisms of combustion reactions in the Ti-C and Ti-C-Ni systems were studied. Samples were produced by igniting compacts of elemental Ti, C, and Ni powders with a tungsten heating coil

  15. Combustion Synthesis Reactions in Cold-Rolled Ni\\/Al and Ti\\/Al Multilayers

    Microsoft Academic Search

    Xiaotun Qiu; Ranran Liu; Shengmin Guo; Jesse Harris Graeter; Laszlo Kecskes; Jiaping Wang

    2009-01-01

    In this article, a cold rolling method was developed to fabricate Ni\\/Al and Ti\\/Al multilayer foils, and the combustion synthesis\\u000a reactions in the cold-rolled foils were investigated. Combustion synthesis reactions were initiated by heating one end of\\u000a the cold-rolled foil in a flame for several seconds. The Ni\\/Al foils went through three reaction stages. The first reaction\\u000a stage was a

  16. In situ combustion synthesis of dense ceramic and ceramic-metal interpenetrating phase composites

    Microsoft Academic Search

    H. J. Feng; J. J. Moore

    1995-01-01

    A model exothermic reaction is used to demonstrate the application of simultaneous combustion synthesis, conducted under a\\u000a consolidating pressure, as a one-stepin situ synthesis technique for the production of dense ceramic and ceramic-metal interpenetrating phase composites (IPC). The addition\\u000a of an excess amount of metal,e.g., Al, and\\/or a diluent,e.g., Al2O3, lowers the combustion temperature and aids in the refinement of

  17. Characteristics of the combustion synthesis of TiC and Fe-TiC composites

    Microsoft Academic Search

    A. Saidi; A. Chrysanthou; J. V. Wood; J. L. F. Kellie

    1994-01-01

    The combustion synthesis of TiC, using the thermal explosion mode, was investigated by varying some of the process parameters including the reactant particle size, the pre-compaction pressure, and the heating rate. Based on these observations, a combustion model for the reaction was developed. When iron was added to titanium and carbon black powders, the ignition temperature was dictated by the

  18. Effect of particle dispersion on the mechanism of combustion synthesis of titanium silicide

    Microsoft Academic Search

    Joanne Trambukis; Zuhair A. Munir

    1990-01-01

    The combustion synthesis (SHS) of titanium silicide (TiâSiâ) was investigated. The main combustion reaction thermal explosion occurs in the presence of a liquid phase and is usually preceded by a relatively small reaction in the solid state. The influence of Ti particle size on the dominance of each of these types of reactions was investigated. SEM observations and X-ray diffraction

  19. Temperature-enthalpy approach to the modelling of self-propagating combustion synthesis of materials

    Microsoft Academic Search

    A. K. Bhattacharya

    1992-01-01

    A new temperature-enthalpy approach has been proposed to model self-propagating combustion synthesis of advanced materials. This approach includes the effect of phase change which might take place during a combustion process. The effect of compact porosity is also modelled based on the conduction, convection and radiation in the local scale. Various parametric studies are made to analyse numerically the effects

  20. Combustion synthesis of metal-matrix composites: Part I, the Ti-TiC-Al 2O 3 system

    Microsoft Academic Search

    A. O. Kunrath; T. R. Strohaecker; J. J. Moore

    1996-01-01

    Combustion synthesis or Self-propagating High-temperature Synthesis (SHS) is a process that involves a reaction which is sufficiently exothermic to sustain itself, and, as such, provides considerable potential for the development of an affordable (low cost), energetically efficient means of producing advanced materials. In the combustion synthesis process, a mix of the reactant powders, pressed into a pellet, is heated to

  1. A Novel Combustion Synthesis Preparation of CuO/ZnO/ZrO2/Pd for Oxidative Hydrogen Production from Methanol

    E-print Network

    Mukasyan, Alexander

    A Novel Combustion Synthesis Preparation of CuO/ZnO/ZrO2/Pd for Oxidative Hydrogen Production from pre- pared via three combustion synthesis routes including volume combustion, impregnated substrate combustion, and so-called second wave impregnation combustion methods. These catalysts were characterized via

  2. Effect of synthesis temperature on the purity of product in hydriding combustion synthesis of Mg 2NiH 4

    Microsoft Academic Search

    Liquan Li; Itoko Saita; Katsushi Saito; Tomohiro Akiyama

    2002-01-01

    This paper describes the effect of synthesis temperature on hydriding combustion synthesis of Mg2NiH4 to improve the purity of product. The properties of the products were examined by means of X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The XRD patterns showed that the main phases of the products were Mg2NiH4 independently of the synthesis temperatures. However, when the samples

  3. Self-propagating high-temperature synthesis (SHS) and microwave-assisted combustion synthesis (MACS) of the thallium superconducting phases

    Microsoft Academic Search

    S. S. Bayya; R. L. Snyder

    1994-01-01

    This paper explores the speed of reaction as a parameter to minimizing thallium loss. Self-propagating high-temperature synthesis (SHS) and microwave-assisted combustion synthesis (MACS) were developed for the synthesis of Tl-2212 and Tl-2223 superconductors using Cu metal powder as a fuel. A kitchen microwave oven was used to carry out MACS reactions. The samples were reacted for few seconds and led

  4. Combustion synthesis of ZnS in microgravity

    SciTech Connect

    Goroshin, S.; Lee, J.H.S.; Frost, D.L. [McGill Univ., Montreal, Quebec (Canada). Dept. of Mechanical Engineering

    1994-12-31

    The self-heating nature of SHS (Self-propagating High-temperature Synthesis) makes it particularly suitable for microgravity processing of materials where weight and power requirements are severely restricted. The absence of convection, hydrostatic pressure, and phase separation permits the combustion front dynamics and solidification processes of SHS to be studied under controlled conditions. This paper describes recent ground-based and microgravity (NASA KC-135 parabolic flight) experiments on SHS processing of ZnS. A novel technique was used for preparing the precursor mixture of Zn + S by mixing the zinc with molten sulfur, which allows the synthesis of a high-density and high-purity product. The flame speed, quenching diameter, and temperature profile in the flame front and crystal structure of the synthesized samples have been determined. Thermocouple measurement of the temperature profile in the flame front indicates that the thermal thickness of the flame is less than 0.3 mm. The average flame speed is of the order of 7 mm/s, and slightly lower values ({approximately}4 mm/s) are observed near the quenching limit. It was found that the flame speed is not stable along the samples with diameters more than 12 mm. The quenching diameter is found to be of the order of 5 mm (in microgravity less than 4 mm). X-ray diffraction data show a wurtzite structure both in ground-based and in-flight synthesized samples, and the lattice`s parameters are most similar to the ideal ZnS wurtzite structure in the outer part of samples synthesized in microgravity. The ability to provide containerless SHS processing of molten ZnS in microgravity also has been demonstrated.

  5. A synthesis of carbon dioxide emissions from fossil-fuel combustion

    Microsoft Academic Search

    Robert Joseph Andres; Thomas A Boden; F.-M. Breon; P. Ciais; S. Davis; D Erickson; J. S. Gregg; Andrew Jacobson; Gregg Marland; J. Miller; T Oda; J. G. J. Oliver; Michael Raupach; P Rayner; K. Treanton

    2012-01-01

    This synthesis discusses the emissions of carbon dioxide from fossil-fuel combustion and cement production. While much is known about these emissions, there is still much that is unknown about the details surrounding these emissions. This synthesis explores 5 our knowledge of these emissions in terms of why there is concern about them; how they are calculated; the major global efforts

  6. Combustion synthesis and development of Ti–O–C aluminium composites

    Microsoft Academic Search

    Krzysztof Naplocha

    2011-01-01

    Aluminium matrix composite reinforced with Ti compounds was successfully fabricated by SHS combustion synthesis and squeeze casting course. Prepared samples from mixture containing Ti, C and Al2O3 fibres were heated in microwave reactor to ignite synthesis and produce porous preform for subsequent infiltrating with liquid metal. Studies showed that synthesizing temperature has been remarkably increased by applying higher magnetron power

  7. Effect of milling time on TiB2-Al2O3 composite produced by combustion synthesis

    NASA Astrophysics Data System (ADS)

    Aminikia, Behzad

    2012-09-01

    In this present research, TiB2-Al2O3 composite was fabricated by self-propagating hightemperature synthesis (SHS) of mechanically activated powders. H3BO3, TiO2 and Al as starting materials were mechanically activated for 1, 3, 6 and 9 h then pressed to form pellets. Green compacts were placed in a tube furnace with argon atmosphere, for synthesis. According to the XRD patterns showed that the TiB2-Al2O3 composite has been successfully fabricated by thermal explosion mode of combustion synthesis. Also, it was found that, 6 h is the optimum time for mechanical activation. That increasing milling time up to 9 h had no significant effect other than refining the crystallite sizes of the components specially TiB2.

  8. Combustion synthesis of a nanoceramic and its transparent properties

    NASA Astrophysics Data System (ADS)

    Luo, Junming; Li, Wen; Xu, Jilin; Deng, Liping

    2012-07-01

    La0.1Nd0.1Y1.8O3 transparent ceramics nanopowders were prepared using the combustion synthesis. To achieve such transparent ceramics, Y2O3 were used as matrix materials and La3+ and Nd3+ were used as dopants, polyethyleneglycol (PEG) as dispersants for the sintering under vacuum 10-3 Pa and 1600 °C for 6 h. The precursor and powders calcined at different temperatures were characterized using TG-DTA, XRD, BET and FESEM. The transmittance of the transparent ceramics was measured using the sub-photometer. Results showed that La3+ and Nd3+ were completely dissolved into the cubic lattice of Y2O3. The sizes of Y1.8La0.1Nd0.1O3 powders were uniform and spherical-like. The particle sizes of powders gradually increased with increasing the calcination temperature. The dispersant can effectively prevent the powders from the agglomeration, and the particle sizes of powders gradually increased with increasing citric acid. The transmittance of the Y1.8La0.1Nd0.1O3 transparent ceramics was close to its theoretical value (80%).

  9. An investigation of the ignition manner effects on combustion synthesis

    Microsoft Academic Search

    Hung-Pin Li

    2003-01-01

    The multi-point ignition of combustion synthesizing NiAl compound created by computational means has been analyzed in this article. Since the combustion reaction of Ni and Al is a low exothermic reaction, it has been found that the combustion front hardly propagates in order to complete the reaction. In this study, the reaction is subsequently ignited at different points or it

  10. Technology Awareness Workshop on Active Combustion Control (ACC) in Propulsion Systems: JANNAF Combustion Subcommittee Workshop

    NASA Technical Reports Server (NTRS)

    Fry, Ronald S. (Editor); Gannaway, Mary T. (Editor)

    1997-01-01

    A JANNAF Combustion Subcommittee Technology Awareness Seminar on Active Combustion Control (ACC) in Propulsion Systems' was held 12 November 1997 at the NASA Lewis Research Center (LeRC), Cleveland, Ohio. The objectives of the seminar were: 1) Define the need and potential of ACC to meet future requirements for gas turbines and ramjets; 2) Explain general principles of ACC and discuss recent successes to suppress combustion instabilities, increase combustion efficiency, reduce emission, and extend flammability limits; 3) Identify R&D barriers/needs for practical implementation of ACC; 4) Explore potential for improving coordination of future R&D activities funded by various government agencies. Over 40 individuals representing senior management from over 20 industry and government organizations participated. This document summarizes the presentations and findings of this seminar.

  11. Combustion synthesis of molybdenum silicides and borosilicides for ultrahigh-temperature structural applications

    NASA Astrophysics Data System (ADS)

    Alam, Mohammad Shafiul

    Molybdenum silicides and borosilicides are promising structural materials for gas-turbine power plants. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at high temperatures. For example, molybdenum disilicide (MoSi2) has excellent oxidation resistance and poor mechanical properties, while Mo-rich silicides such as Mo5Si3 (called T 1) have much better mechanical properties but poor oxidation resistance. One approach is based on the fabrication of MoSi2-T 1 composites that combine high oxidation resistance of MoSi2 and good mechanical properties of T1. Another approach involves the addition of boron to Mo-rich silicides for improving their oxidation resistance through the formation of a borosilicate surface layer. In particular, Mo 5SiB2 (called T2) phase is considered as an attractive material. In the thesis, MoSi2-T1 composites and materials based on T2 phase are obtained by mechanically activated SHS. Use of SHS compaction (quasi-isostatic pressing) significantly improves oxidation resistance of the obtained MoSi2-T1 composites. Combustion of Mo-Si-B mixtures for the formation of T2 phase becomes possible if the composition is designed for the addition of more exothermic reactions leading to the formation of molybdenum boride. These mixtures exhibit spin combustion, the characteristics of which are in good agreement with the spin combustion theory. Oxidation resistance of the obtained Mo-Si-B materials is independent on the concentration of Mo phase in the products so that the materials with a higher Mo content are preferable because of better mechanical properties. Also, T2 phase has been obtained by the chemical oven combustion synthesis technique.

  12. Using Combustion Synthesis to Reinforce Berms and Other Regolith Structures

    NASA Technical Reports Server (NTRS)

    Rodriquez, Gary

    2013-01-01

    The Moonraker Excavator and other tools under development for use on the Moon, Mars, and asteroids will be employed to construct a number of civil engineering projects and to mine the soil. Mounds of loose soil will be subject to the local transport mechanisms plus artificial mechanisms such as blast effects from landers and erosion from surface vehicles. Some of these structures will require some permanence, with a minimum of maintenance and upkeep. Combustion Synthesis (CS) is a family of processes and techniques whereby chemistry is used to transform materials, often creating flame in a hard vacuum. CS can be used to stabilize civil engineering works such as berms, habitat shielding, ramps, pads, roadways, and the like. The method is to unroll thin sheets of CS fabric between layers of regolith and then fire the fabric, creating a continuous sheet of crusty material to be interposed among layers of loose regolith. The combination of low-energy processes, ISRU (in situ resource utilization) excavator, and CS fabrics, seems compelling as a general method for establishing structures of some permanence and utility, especially in the role of robotic missions as precursors to manned exploration and settlement. In robotic precursory missions, excavator/ mobility ensembles mine the Lunar surface, erect constructions of soil, and dispense sheets of CS fabrics that are covered with layers of soil, fired, and then again covered with layers of soil, iterating until the desired dimensions and forms are achieved. At the base of each berm, for example, is a shallow trench lined with CS fabric, fired and filled, mounded, and then covered and fired, iteratively to provide a footing against lateral shear. A larger trench is host to a habitat module, backfilled, covered with fabric, covered with soil, and fired. Covering the applied CS fabric with layers of soil before firing allows the resulting matrix to incorporate soil both above and below the fabric ply into the fused layer, developing a very irregular surface which, like sandpaper, can provide an anchor for loose soil. CS fabrics employ a coarse fiberglass weave that persists as reinforcement for the fired material. The fiberglass softens at a temperature that exceeds the combustion temperature by factors of two to three, and withstands the installation process. This type of structure should be more resistant to rocket blast effects from Lunar landers.

  13. Elemental analysis of combustion products by neutron activation

    SciTech Connect

    Heft, R.E.; Koszykowski, R.F.

    1980-01-01

    This paper gives a brief description of the neutron activation analysis method, which is being used to determine the elemental profile of combustion products from coal-fired power plants, oil shale retorting, and underground coal gasification. (DLC)

  14. The Effects of Gravity on Combustion and Structure Formation During Synthesis of Advanced Materials

    NASA Technical Reports Server (NTRS)

    Varma, A.; Pelekh, A.; Mukasyan, A.

    1999-01-01

    Combustion in a variety of heterogeneous systems, leading to the synthesis of advanced materials, is characterized by high temperatures (2000-3500 K) and heating rates (up to 10(exp 6) K/s) at and ahead of the reaction front. These high temperatures generate liquids and gases which are subject to gravity-driven flow. The removal of such gravitational effects is likely to provide increased control of the reaction front, with a consequent improvement in control of the microstructure of the synthesized products. Thus, microgravity experiments can lead to major advances in the understanding of fundamental aspects of combustion and structure formation under the extreme conditions of the combustion synthesis wave. In addition, the specific features of microgravity environment allow one to produce unique materials, which cannot be obtained under terrestrial conditions. The general goals of the current research are: 1) to improve the understanding of fundamental phenomena taking place during combustion of heterogeneous systems, 2) to use low-gravity experiments for insight into the physics and chemistry of materials synthesis processes, and 3) based on the obtained knowledge, to optimize processing conditions for synthesis of advanced materials with desired microstructures and properties. This research follows logically from the results of investigations we have conducted in the framework of our previous grant on gravity influence on combustion synthesis (CS) of gasless systems. Prior work, by others and by us, has clearly demonstrated that gravity plays an important role during combustion synthesis of materials. The immediate tasks for the future are to quantitatively identify the nature of observed effects, and to create accurate local kinetic models of the processes, which can lead to a control of the microstructure and properties of the synthesized materials. In summary, this is the value of the proposed research. Based on our prior work, we focus on the fundamental aspects of combustion and structure formation under the unique condition of microgravity.

  15. Gas-Phase Combustion Synthesis of Aluminum Nitride Powder

    NASA Technical Reports Server (NTRS)

    Axelbaum, R. L.; Lottes, C. R.; Huertas, J. I.; Rosen, L. J.

    1996-01-01

    Due to its combined properties of high electrical resistivity and high thermal conductivity aluminum nitride (AlN) is a highly desirable material for electronics applications. Methods are being sought for synthesis of unagglomerated, nanometer-sized powders of this material, prepared in such a way that they can be consolidated into solid compacts having minimal oxygen content. A procedure for synthesizing these powders through gas-phase combustion is described. This novel approach involves reacting AlCl3, NH3, and Na vapors. Equilibrium thermodynamic calculations show that 100% yields can be obtained for these reactants with the products being AlN, NaCl, and H2. The NaCl by-product is used to coat the AlN particles in situ. The coating allows for control of AlN agglomeration and protects the powders from hydrolysis during post-flame handling. On the basis of thermodynamic and kinetic considerations, two different approaches were employed to produce the powder, in co-flow diffusion flame configurations. In the first approach, the three reactants were supplied in separate streams. In the second, the AlCl3 and NH3 were premixed with HCl and then reacted with Na vapor. X-ray diffraction (XRD) spectra of as-produced powders show only NaCl for the first case and NaCl and AlN for the second. After annealing at 775 C tinder dynamic vacuum, the salt was removed and XRD spectra of powders from both approaches show only AlN. Aluminum metal was also produced in the co-flow flame by reacting AlCl3 with Na. XRD spectra of as-produced powders show the products to be only NaCl and elemental aluminum.

  16. Synthesis, structure, and scintillation of Ce-doped gadolinium oxyorthosilicate nanoparticles prepared by solution combustion synthesis

    NASA Astrophysics Data System (ADS)

    Jacobsohn, L. G.; Tornga, S. C.; Blair, M. W.; Bennett, B. L.; Muenchausen, R. E.; Wang, R.; Crozier, P. A.; Cooke, D. W.

    2011-10-01

    The synthesis of Ce-doped Gd oxyorthosilicate nanoparticles using the solution combustion synthesis (SCS) method was investigated as a function of the amount of SiO2 in the precursor mixture. The SCS product consists of mixtures of Ce-doped Gd2SiO5, Gd4.67(SiO4)3O, and Gd2O3, whose relative concentrations depend on the amount of SiO2 in the precursor mixture; the synthesis of GSO:Ce was obtained with a reduction by 30% of the SiO2 content. Accordingly, this is the brightest material produced, with a photoluminescence signal that is comparable to that obtained from the bulk sample. Thermoluminescence (TL) results showed a considerably lower concentration of trapping defects in the nanoparticles than in the bulk sample. A previous study [E. G. Yukihara, L. G. Jacobsohn, M. W. Blair, B. L. Bennett, S. C. Tornga, and R. E. Muenchausen, J. Lumin. 130, 2309-2316 (2010)] reporting a comparison between photoluminescence and scintillation measurements, coupled to the TL characterization, suggests that surfaces play a major role in decreasing the scintillation efficiency of the nanoparticles. These results show that it is possible to prepare relatively bright scintillator powders using the SCS method.

  17. The numerical simulation of the heterogeneous composition effect on the combustion synthesis of TiB 2 compound

    Microsoft Academic Search

    H. P. Li

    2003-01-01

    Heterogeneous distributions of reactants and diluent are usually found during powder preparation for combustion synthesis. The occurrence of the composition heterogeneity is thought to result in local variations of the thermophysical\\/chemical reactant parameters, such as density, heat capacity, and thermal conductivity; thus change combustion temperature, propagation velocity, and propagation pattern of combustion front. This study aims to address the composition

  18. Combustion synthesis of advanced materials. [using in-situ infiltration technique

    NASA Technical Reports Server (NTRS)

    Moore, J. J.; Feng, H. J.; Perkins, N.; Readey, D. W.

    1992-01-01

    The combustion synthesis of ceramic-metal composites using an in-situ liquid infiltration technique is described. The effect of varying the reactants and their stoichiometry to provide a range of reactant and product species i.e. solids, liquids and gases, with varying physical properties e.g. thermal conductivity, on the microstructure and morphology of synthesized products is also described. Alternatively, conducting the combustion synthesis reaction in a reactive gas environment is also discussed, in which advantages can be gained from the synergistic effects of combustion synthesis and vapor phase transport. In each case, the effect of the presence or absence of gravity (density) driven fluid flow and vapor transport is discussed as is the potential for producing new and perhaps unique materials by conducting these SHS reactions under microgravity conditions.

  19. Combustion synthesis of metal-matrix composites. Part 2: The Ti-TiâAl{sub y}-AlâOâ system

    Microsoft Academic Search

    A. O. Kunrath; T. R. Strohaecker; J. J. Moore

    1996-01-01

    The production of high performance materials (ceramics, intermetallics and composites) by combustion synthesis is receiving considerable attention since the process offers certain advantages with respect to simplicity and a relatively low energy requirement. The methods by which combustion synthesis (or SHS) can be used to produce metal matrix composites were outlined in an earlier paper. The use of excess liquid

  20. Characteristics of self-propagating reaction in TiN combustion synthesis

    Microsoft Academic Search

    Hiroshi Kudo; Osamu Odawara

    1989-01-01

    The characteristics of the combustion synthesis of TiN are investigated through a self-propagating reaction of titanium powder compacts of specific packing density (40% to 60% theoretical one) in the presence of flowing nitrogen gas (0.01 m3 min-1) under atmospheric pressure. It was found that the propagating velocity of the combustion wave became slower with increasing packing density. The conversion ratio

  1. The effect of gravity on the combustion synthesis of metal-ceramic composites

    Microsoft Academic Search

    H. C. Yi; J. Y. Guigné; T. C. Woodger; J. J. Moore

    1998-01-01

    The effects of gravity on the combustion characteristics and microstructure of metal-ceramic composites (HfB2\\/Al and Ni3Ti\\/TiB2 systems) were studied under both normal and low gravity conditions. Under normal gravity conditions, pellets were ignited in three orientations relative to the gravity vector. Low gravity combustion synthesis (SHS) was carried out on a DC-9 aircraft at the NASA-Lewis Research Center. It was

  2. Fabrication of porous NiTi shape memory alloy for hard tissue implants by combustion synthesis

    Microsoft Academic Search

    C. L. Chu; C. Y. Chung; P. H. Lin; S. D. Wang

    2004-01-01

    Porous NiTi shape memory alloy (SMA) with ideal pore characteristics and high strength for hard tissue implants has been fabricated by combustion synthesis in this paper. Microstructure and mechanical properties of the product were studied by optical microscope, scanning electron microscope (SEM), X-ray diffraction (XRD) and compression test respectively. The experimental results show the combustion temperature of Ni+Ti reactant system

  3. The effect of gravity on the combustion synthesis of metal-ceramic composites

    Microsoft Academic Search

    H. C. Yi; J. Y. Guigné; T. C. Woodger; J. J. Moore

    1998-01-01

    The effects of gravity on the combustion characteristics and microstructure of metal-ceramic composites (HfB2\\/Al and Ni3Ti\\/TiB2 systems) were studied under both normal and low gravity conditions. Under normal gravity conditions, pellets were ignited\\u000a in three orientations relative to the gravity vector. Low gravity combustion synthesis (SHS) was carried out on a DC-9 aircraft\\u000a at the NASA-Lewis Research Center. It was

  4. Combustion synthesis of Ni 3Al intermetallic compound in self-propagating mode

    Microsoft Academic Search

    C. L. Yeh; W. Y. Sung

    2004-01-01

    The production of Ni3Al intermetallic compound from elemental powder compacts was conducted by self-propagating high-temperature synthesis (SHS) in this study. Effects of initial sample density, preheating temperature, and particle size of the reactants on the combustion characteristics, as well as on the composition and morphology of final products were studied. Experimental observation indicated that the combustion process was preceded by

  5. Combustion synthesis of multiphase powders in the Si?C?N system

    Microsoft Academic Search

    Dariusz Kata; Jerzy Lis; R. Pampuch

    1997-01-01

    The authors present the results of investigations on combustion synthesis (SHS) in the Si?C?N system in order to prepare composite Si3N4?SiC powders. A new approach by a realisation of self-sustaining combustion in the Si?C?N system without an inert dilution is reported. This makes possible the preparation of a full range of carbide-nitride composite powders, including pure SiC and Si3N4 powders.

  6. Preparation of CoTi intermetallics by self-propagating combustion synthesis

    Microsoft Academic Search

    C. L. Yeh; C. C. Yeh

    2005-01-01

    The production of B2-type cobalt titanide (CoTi) from elemental powder compacts was conducted by self-propagating high-temperature synthesis (SHS) in this study. Effects of the initial sample density, particle size of the reactants, and initial sample temperature on the combustion characteristics, as well as on the composition of final products were studied. Unlike most of the intermetallic reactions, the combustion of

  7. Synthesis of niobium carbonitride by self-propagating combustion of Nb–C system in nitrogen

    Microsoft Academic Search

    C. L. Yeh; Y. D. Chen

    2005-01-01

    An experimental investigation on the preparation of niobium carbonitrides by self-propagating high-temperature synthesis (SHS) was conducted using compacted samples of niobium and carbon powders ignited in gaseous nitrogen. Effects of the carbon content, nitrogen pressure, and NbN addition on the combustion behavior and the degree of conversion were studied. Due to the nature of reaction in the combustion front, steady

  8. Microstructural transformation during combustion synthesis of MgB 2 superconductor

    NASA Astrophysics Data System (ADS)

    Chen, Xiujuan; Xia, Tiandong; Wang, Mingjing; Zhao, Wenjun; Liu, Tianzuo

    2007-04-01

    To investigate the phase transformation behaviors of combustion synthesis of MgB 2, a mixture of Mg, B was used for a combustion front quenching test, and the microstructural evolution in the quenched sample was observed by scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA). The temperature-time profile of the combustion was measured, and the phase constituents of the different zones of the quenched sample were inspected by X-ray diffraction (XRD). Based on these experimental results, the transformation behaviors in the SHS-synthesized superconductor MgB 2 was analyzed, and a solid phase diffusion and dissolution-precipitation mechanism was proposed.

  9. Combustion process for synthesis of carbon nanomaterials from liquid hydrocarbon

    DOEpatents

    Diener, Michael D.; Alford, J. Michael; Nabity, James; Hitch, Bradley D.

    2007-01-02

    The present invention provides a combustion apparatus for the production of carbon nanomaterials including fullerenes and fullerenic soot. Most generally the combustion apparatus comprises one or more inlets for introducing an oxygen-containing gas and a hydrocarbon fuel gas in the combustion system such that a flame can be established from the mixed gases, a droplet delivery apparatus for introducing droplets of a liquid hydrocarbon feedstock into the flame, and a collector apparatus for collecting condensable products containing carbon nanomaterials that are generated in the combustion system. The combustion system optionally has a reaction zone downstream of the flame. If this reaction zone is present the hydrocarbon feedstock can be introduced into the flame, the reaction zone or both.

  10. Self-propagating high-temperature synthesis (SHS) and microwave-assisted combustion synthesis (MACS) of the thallium superconducting phases

    NASA Astrophysics Data System (ADS)

    Bayya, S. S.; Snyder, R. L.

    1994-05-01

    This paper explores the speed of reaction as a parameter to minimizing thallium loss. Self-propagating high-temperature synthesis (SHS) and microwave-assisted combustion synthesis (MACS) were developed for the synthesis of Tl-2212 and Tl-2223 superconductors using Cu metal powder as a fuel. A kitchen microwave oven was used to carry out MACS reactions. The samples were reacted for few seconds and led to the formation of the superconducting phases. Further explorations and modifications in the processing could lead to the formation of single phases by MACS.

  11. Lean Premixed Combustion/Active Control

    SciTech Connect

    D. J. Seery

    2000-02-01

    An experimental comparison between two contrasting fuel-air swirlers for industrial gas turbine applications was undertaken at the United Technologies Research Center. The first, termed an Aerodynamic nozzle, relied on the prevailing aerodynamic forces to stabilize the downstream combustion zone. The second configuration relied on a conventional bluff plate for combustion stability and was hence named a Bluff-Body nozzle. Performance mapping over the power curve revealed the acoustic superiority of the Bluff-Body nozzle. Two dimensional Rayleigh indices calculated from CCD images identified larger acoustic driving zones associated with the Aerodynamic nozzle relative to its bluff counterpart. The Bluff-Body's success is due to increased flame stabilization (superior anchoring ability) which reduced flame motion and thermal/acoustic coupling.

  12. Nanocrystalline Cr 2O 3 and amorphous CrO 3 produced by solution combustion synthesis

    Microsoft Academic Search

    M. D. Lima; R. Bonadimann; M. J. de Andrade; J. C. Toniolo; C. P. Bergmann

    2006-01-01

    The synthesis of chromium oxides by solution combustion synthesis was investigated. Ammonium dichromate, glycine, urea and ammonium nitrate dissolved in aqueous solution were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and the fuel\\/oxidant ratio. Amorphous CrO3

  13. Simultaneous combustion synthesis (thermal explosion mode) and extrusion of nickel aluminides

    Microsoft Academic Search

    K. Morsi; S. O. Moussa; James J. Wall

    2005-01-01

    Combustion synthesis (CS) is a low-energy processing approach for a wide range of materials (e.g. ceramics, intermetallics and composites), whereby reactants are ignited to spontaneously transform to products in an exothermic reaction. The process can be subdivided into two modes of ignition. The first is termed self-propagating high temperature synthesis (SHS) in which a reactant compact is typically ignited at

  14. Particle in cell simulation of combustion synthesis of TiC nanoparticles

    Microsoft Academic Search

    G. Zuccaro; Giovanni Lapenta; G. Maizza

    2004-01-01

    A coupled continuum-discrete numerical model is presented to study the synthesis of TiC nanosized aggregates during a self-propagating combustion synthesis (SHS) process. The overall model describes the transient of the basic mechanisms gov- erning the SHS process in a two-dimensional micrometer size geometry system. At each time step, the continuum (micrometer scale) model computes the current tem- perature field according

  15. Self-propagating high-temperature (combustion) synthesis (SHS) of powder-compacted materials

    Microsoft Academic Search

    H. C. Yi; J. J. Moore

    1990-01-01

    Self-propagating high-temperature synthesis (SHS) of powder compacts is a novel processing technique currently being developed as a route for the production of engineering ceramics and other advanced materials. The process, which is also referred to as combustion synthesis, provides energy- and cost-saving advantages over the more conventional processing routes for these materials. At the same time, the rapid heating and

  16. Development of copper matrix composite reinforced with FeAl particles produced by combustion synthesis

    Microsoft Academic Search

    S. Azem; M. Nechiche; K. Taibi

    2011-01-01

    This work focuses on the synthesis of FeAl intermetallic compound by combustion synthesis (SHS process) and its inclusion as dispersoids in a copper matrix to develop a metal matrix composite (MMC) by sintering. In the first step, FeAl compound was produced by the sintering of Fe–50at.%Al at 1100°C. Then, after grinding and mixing with copper powder, it was sintered in

  17. Combustion synthesis of a complex composite based on MoSi[sub 2

    Microsoft Academic Search

    J. Subrahmanyam; R. Mohan Rao; K. Somaraju

    1994-01-01

    Self-propagating High-temperature Synthesis (SHS), also known as combustion synthesis, is gaining importance as a technique for producing powders and near net shape components of metals, intermetallics, ceramics and their composites. The agglomeration of reinforcement particles and their non-uniform distribution, which are often attributed to the poor strength of MoSi[sub 2] composites can be avoided in this process. SHS is capable

  18. Combustion synthesis of (Mo 1 ? x Cr x )Si 2 ( x = 0.00–0.30) alloys in SHS mode

    Microsoft Academic Search

    Peizhong Feng; Weisheng Liu; Akhtar Farid; Jie Wu; Jinan Niu; Xiaohong Wang; Yinghuai Qiang

    Combustion synthesis was adopted to successfully synthesize molybdenum–silicon–chromium (Mo?Si?Cr) alloys by the mode of self-propagating high-temperature synthesis (SHS). The experimental study of combustion synthesis of Mo?Si?Cr alloys was conducted on elemental powder compacts. Powder compacts with nominal compositions including MoSi2, (Mo0.95Cr0.05)Si2, (Mo0.90Cr0.10)Si2, (Mo0.85Cr0.15)Si2, (Mo0.80Cr0.20)Si2, (Mo0.75Cr0.25)Si2 and (Mo0.70Cr0.30)Si2 were employed in combustion synthesis experiments. The combustion mode, combustion temperature, flame-front propagation

  19. Low-reactive circulating fluidized bed combustion (CFBC) fly ashes as source material for geopolymer synthesis

    Microsoft Academic Search

    Hui Xu; Qin Li; Lifeng Shen; Mengqun Zhang; Jianping Zhai

    2010-01-01

    In this contribution, low-reactive circulating fluidized bed combustion (CFBC) fly ashes (CFAs) have firstly been utilized as a source material for geopolymer synthesis. An alkali fusion process was employed to promote the dissolution of Si and Al species from the CFAs, and thus to enhance the reactivity of the ashes. A high-reactive metakaolin (MK) was also used to consume the

  20. Synthesis and sintering of nanocrystalline hydroxyapatite powders by citric acid sol–gel combustion method

    Microsoft Academic Search

    Yingchao Han; Shipu Li; Xinyu Wang; Xiaoming Chen

    2004-01-01

    The citric acid sol–gel combustion method has been used for the synthesis of nanocrystalline hydroxyapatite (HAP) powder from calcium nitrate, diammonium hydrogen phosphate and citric acid. The phase composition of HAP powder was characterized by X-ray powder diffraction analysis (XRD). The morphology of HAP powder was observed by transmission electron microscope (TEM). The HAP powder has been sintered into microporous

  1. DEXTROSE-TEMPLATED MICROWAVE-ASSISTED COMBUSTION SYNTHESIS OF SPONGY METAL OXIDES

    EPA Science Inventory

    Microwave-assisted combustion synthesis of porous nanocrystalline titania and carbon coated titania is reported using dextrose as template and the product was compared with the one obtained using conventional heating furnace. Out of three compositions viz., 1:1, 1:3, and 1:5 (met...

  2. Effect of heating rate on the combustion synthesis of Ti-Al intermetallic compounds

    Microsoft Academic Search

    H. C. Yi; A. Petric; J. J. Moore

    1992-01-01

    Titanium aluminide compounds were synthesized by the thermal explosion mode of self-propagating high-temperature synthesis (SHS). The effects of heating rate on the combustion characteristics and the microstructures of the products were studied. It was found that the low density of the reacted sample was due to the outgassing of water vapour and other gases, which were released by dissociation of

  3. Electrical properties of Ni\\/YSZ cermets obtained through combustion synthesis

    Microsoft Academic Search

    U Anselmi-Tamburini; G Chiodelli; M Arimondi; F Maglia; G Spinolo; Z. A Munir

    1998-01-01

    The synthesis of Ni\\/YSZ cermet with controlled microstructural characteristics presents a lot of interest for many solid-state electrochemical applications. These materials are generally obtained by reducing poorly sintered mixtures of YSZ with nickel oxide by hydrogen. We recently proposed an alternative route based on a thermite reaction performed in a combustion regime. This method makes it possible, in one step,

  4. A study of combustion synthesis reaction in the Ti + C\\/Ti + Al system

    Microsoft Academic Search

    Chyi-Ching Hwang; Shyan-Lung Chung

    2004-01-01

    Combustion synthesis (SHS) of the Ti + C\\/Ti + Al system was investigated by using titanium, graphite and aluminum powders as reactants. These powders were thoroughly mixed and pressed into cylindrical compacts, and heated in an argon atmosphere. The effects of the reactant composition and the heating rate were studied. The phase identification and morphology observation of the products were

  5. Self-propagating combustion synthesis and plasma spraying deposition of TiC–Fe powders

    Microsoft Academic Search

    Roberta Licheri; Roberto Orrù; Giacomo Cao; Angelo Crippa; Reinhard Scholz

    2003-01-01

    The synthesis of titanium carbide\\/iron composite from elemental powders by means of self-propagating reactions to be subsequently employed for plasma spray deposition is investigated. The combustion temperature and velocity of propagating front are found to decrease as the amount of iron in the starting mixture increased. In addition, the maximum value of the iron content in the initial mixture allowable

  6. Effect of particle dispersion on the mechanism of combustion synthesis of titanium silicide

    SciTech Connect

    Trambukis, J.; Munir, Z.A. (California Univ., Davis, CA (USA). Div. of Materials Science and Engineering)

    1990-05-01

    The combustion synthesis (SHS) of titanium silicide (Ti{sub 5}Si{sub 3}) was investigated. The main combustion reaction thermal explosion occurs in the presence of a liquid phase and is usually preceded by a relatively small reaction in the solid state. The influence of Ti particle size on the dominance of each of these types of reactions was investigated. SEM observations and X-ray diffraction analyses indicate that the combustion synthesis of Ti{sub 5}Si{sub 3} proceeds according to the following sequence: TiSi{sub 2} {yields} TiSi {yields} Ti{sub 5}Si{sub 4} {yields} Ti{sub 5}Si{sub 3}.

  7. The Effect of Gravity on the Combustion Synthesis of Porous Ceramics and Metal Matrix Composites

    NASA Technical Reports Server (NTRS)

    Moore, J. J.; Woodger, T. C.; Wolanski, T.; Yi, H. C.; Guigne, J. Y.

    1997-01-01

    Combustion synthesis (self propagating, high temperature synthesis-SHS) is a novel technique that is capable of producing many advanced materials. The ignition temperature (Tig) of such combustion synthesis reactions is often coincident with that of the lowest melting point reactant. The resultant liquid metal wets and spreads around the other solid reactant particles of higher melting points, thereby improving the reactant contact and kinetics, followed by formation of the required compounds. This ignition initiates a combustion propagating wave whose narrow reaction front rapidly travels through the reactants. Since this process is highly exothermic, the heat released by combustion often melts the reactant particles ahead of the combustion front and ignites the adjacent reactant layer, resulting in a self-sustaining reaction. Whenever a fluid phase (liquid or gas) is generated by the reaction system, gravity-driven phenomena can occur. Such phenomena include convective flows of fluid by conventional or unstable convection and settling of the higher density phases. A combustion process is often associated with various kinds of fluid flow. For instance, if the SHS reaction is carried out under inert or reactive gas atmospheres, or a volatile, e.g., B2O3, is deliberately introduced as a reactant, convective flows of the gas will occur due to a temperature gradient existing in the atmosphere when a combustion wave is initiated. The increased gas flow will produce a porous (or expanded) SHS product. Owing to the highly exothermic nature of many SHS reactions, liquid phase(s) can also form before, at, or after the combustion front. The huge temperature gradient at the combustion front can induce convective flows (conventional or unstable) of the liquid phase. Each of these types of convective fluid flow can change the combustion behavior of the synthesizing reaction, and, therefore, the resultant product microstructure. In addition, when two or more phases of different density are produced at or ahead of the propagating combustion front settling of the higher density phase will occur resulting in a non-uniform product microstructure and properties.

  8. Combustion synthesis of advanced ceramic and ceramic-metal composites. Ph.D. Thesis

    SciTech Connect

    Feng, H.

    1994-01-01

    The combustion synthesis of ceramic-metal composites using an in-situ liquid infiltration technique is described and used to produce various ceramic and ceramic-metal composites. The structure and properties of the synthesized composites are strongly dependent upon the reaction parameters of the combustion reaction, and the effect of varying the reactants and their stoichiometry to provide a range of reactant and product species i.e. solids, liquids and gases, with varying physical properties, e.g., thermal conductivity, on the microstructure and morphology of synthesized products is discussed with reference to this effect on the fundamental thermochemistry of these exothermic reactions, and different mechanisms are proposed to explain the results. A model exothermic reaction is used to demonstrate the application of simultaneous combustion synthesis, conducted under a consolidating pressure, as an affordable (low cost), in-situ synthesis technique for the production of dense, interpenetrating phase ceramic and ceramic-metal composites. The effects of the important process parameters, e. g., reaction stoichiometry and diluents, green density, pressure and temperature, on microstructure and mechanical properties of these high performance composites are discussed. An examination and critical application of the important processing parameters in combustion synthesis reactions have been used to produce a model ceramic-metal-intermetallic functionally graded material (FGM). Although the FGM produced is, essentially, a model system, the investigation has demonstrated how the combustion synthesis reaction and processing parameters can be controlled to produce a dense FGM composite with a required microstructure in a simple one-step, affordable process.

  9. Synthesis of Diopside by Solution Combustion Process Using Glycine Fuel

    NASA Astrophysics Data System (ADS)

    Sherikar, Baburao N.; Umarji, A. M.

    Nano ceramic Diopside (CaMgSi2O6) powders are synthesized by Solution Combustion Process(SCS) using Calcium nitrate, Magnesium nitrate as oxidizer and glycine as fuel, fumed silica as silica source. Ammonium nitrate (AN) is used as extra oxidizer. Effect of AN on Diopside phase formation is investigated. The adiabatic flame temperatures are calculated theoretically for varying amount of AN according to thermodynamic concept and correlated with the observed flame temperatures. A “Multi channel thermocouple setup connected to computer interfaced Keithley multi voltmeter 2700” is used to monitor the thermal events during the process. An interpretation based on maximum combustion temperature and the amount of gases produced during reaction for various AN compositions has been proposed for the nature of combustion and its correlation with the characteristics of as synthesized powder. These powders are characterized by XRD, SEM showing that the powders are composed of polycrystalline oxides with crystallite size of 58nm to 74nm.

  10. Combustion synthesis of fine-particle metal aluminates

    Microsoft Academic Search

    J. J. Kingsley; K. Suresh; K. C. Patil

    1990-01-01

    Fine-particle metal aluminates, MAl2O4 where M=Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu and Zn as well as 3CaO · Al2O3 (C3A), CaAl12O19 (CA6) and MgCeAl11O19 have been prepared by the combustion of mixtures of the respective metal nitrates (oxidizers) and urea or carbohydrazide (fuels) at 500 or 350‡ C, respectively, over a time of 5 min. The solid combustion

  11. Combustion synthesis of TiAl-matrix composites in the Ti-Al-BN system

    SciTech Connect

    Mabuchi, H.; Tsuda, H.; Nakayama, Y. (Univ. of Osaka Prefecture, Osaka (Japan). Dept. of Metallurgy and Materials Science)

    1995-01-15

    The intermetallic compound TiAl has attracted much attention for its potential use as a structural high-temperature material. However, its use has been limited because of its negligible low-temperature ductility and fracture toughness and low high-temperature strength and creep. To improve these properties, recently this compound has been made as a composite material containing a secondary phase such as boride, carbide, nitride, or oxide. Recently, combustion synthesis or self-propagating, high-temperature synthesis (SHS) using powder compacts has been developed to produce intermetallics or ceramics. It is also possible to form intermetallic-intermetallic, intermetallic-ceramic, or ceramic-ceramic composites from combustion reactions between corresponding elemental constituents. It has the advantage of an in-situ forming technique compared with conventional artificial composite production approaches. In the previous studies using elemental powders, combustion reaction was carried out to form intermetallic-ceramic composites in the Ti-Al-C, or Ti-Al-N system. The compacts of Ti and Al powders with carbon powder or in gaseous nitrogen reacted exothermically, and formed a mixture product which had a fine distribution of the Ti[sub 2]AlC or Ti[sub 2]AlN particles in the matrix TiAl with a small amount of Ti[sub 3]Al. The processing technique, therefore, is of interest as a combustion reaction synthesis to make in-situ intermetallic-based composite materials. In the present work, to investigate the effect of BN addition on the reaction of Ti And Al powder mixtures, combustion synthesis of TiAl-matrix composites has been performed for the Ti-Al-BN system.

  12. Thermodynamic analysis for the combustion synthesis of SiC-B{sub 4}C composites

    SciTech Connect

    Singh, M. [NYMA, Inc., Cleveland, OH (United States). Lewis Research Center Group] [NYMA, Inc., Cleveland, OH (United States). Lewis Research Center Group

    1996-03-15

    A significant amount of attention has been focused recently on the development of new structural materials for aerospace, nuclear, armor and energy related applications. These materials should have high melting points, low density, good strength and toughness, and good oxidation and thermal shock resistance. Schwetz et al. have indicated that SiC-B{sub 4}C composite materials would have a combination of desirable mechanical and thermal properties. These include the strength, oxidation and thermal shock resistance of silicon carbide combined with the low density, hardness and wear resistance of boron carbide. Self-propagating high-temperature synthesis (SHS) or combustion synthesis (CS) has been used to produce a variety of refractory borides, carbides, nitrides, and silicides containing ceramics and composite materials. The underlying basis for this synthesis is the ability of highly exothermic reactions to sustain themselves in the form of a reaction or combustion wave. The rate of combustion wave propagation can be very rapid ({approximately}25 cm/s) and can reach temperatures as high as 5,000 K. In the CS process, reactions with extremely large thermal gradients ({approximately}10{sup 5} K/cm) can be obtained under adiabatic conditions. There are two basic modes of reaction used in combustion synthesis. One spreads mainly by propagation of combustion waves through the reactants which are heated at one end by thermal or laser energy and the reaction self-propagates. Another approach involves the heating of the entire specimen to a temperature at which the reaction becomes spontaneous and takes place simultaneously in the whole specimen.

  13. New combustion synthesis technique for the production of (InxGa1-x)2O3 powders: Hydrazine/metal nitrate method

    E-print Network

    McKittrick, Joanna

    New combustion synthesis technique for the production of (InxGa1-x)2O3 powders: Hydrazine. The combustion reaction occurred when heating the precursors between 150 and 200 °C in a closed vessel filled by a more typical combustion synthesis reaction between nitrates and a carbonaceous fuel at a higher

  14. Synthesis and characterization of actinide metal compounds formed by combustion

    SciTech Connect

    Behrens, R.G.; King, M.A.

    1985-01-01

    This paper briefly describes the results of attempts to synthesize arsenides, phosphides, and antimonides of uranium and thorium using Self-Propagating High-Temperature Synthesis (SHS) techniques. This paper first summarizes the chemistry and thermodynamics of these chemical systems, describes SHS synthesis techniques, and then describes the results of the syntheses using data from powder x-ray diffraction, metallographic, and electron microprobe analyses.

  15. Apparatus and method for gas turbine active combustion control system

    NASA Technical Reports Server (NTRS)

    Umeh, Chukwueloka (Inventor); Kammer, Leonardo C. (Inventor); Shah, Minesh (Inventor); Fortin, Jeffrey B. (Inventor); Knobloch, Aaron (Inventor); Myers, William J. (Inventor); Mancini, Alfred Albert (Inventor)

    2011-01-01

    An Active Combustion Control System and method provides for monitoring combustor pressure and modulating fuel to a gas turbine combustor to prevent combustion dynamics and/or flame extinguishments. The system includes an actuator, wherein the actuator periodically injects pulsed fuel into the combustor. The apparatus also includes a sensor connected to the combustion chamber down stream from an inlet, where the sensor generates a signal detecting the pressure oscillations in the combustor. The apparatus controls the actuator in response to the sensor. The apparatus prompts the actuator to periodically inject pulsed fuel into the combustor at a predetermined sympathetic frequency and magnitude, thereby controlling the amplitude of the pressure oscillations in the combustor by modulating the natural oscillations.

  16. Combustion synthesis of TiB2-Al2O3-Al composite materials

    NASA Technical Reports Server (NTRS)

    Feng, H. J.; Moore, J. J.; Wirth, D. G.

    1991-01-01

    The oxide-aluminum exothermic reduction reaction is presently used in the combustion-synthesis of ceramic/metal composites. An excess of Al is used in the reacting materials, which rapidly generate enough heat to exceed Al's melting point. The molten Al thus evolved is allowed to infiltrate the porous ceramic matrix as the exothermic reaction proceeds; this feature of the process turns the disadvantage of high porosity levels in combustion-synthesized materials into an advantage. Attention is given to the system obtained with 3TiO2 + 3B2O3 + (10-x)Al starting materials.

  17. Combustion synthesis of a complex composite based on MoSi[sub 2

    SciTech Connect

    Subrahmanyam, J.; Mohan Rao, R.; Somaraju, K. (Defense Metallurgical Research Lab., Hyderabad (India). Combustion Synthesis Group)

    1994-11-15

    Self-propagating High-temperature Synthesis (SHS), also known as combustion synthesis, is gaining importance as a technique for producing powders and near net shape components of metals, intermetallics, ceramics and their composites. The agglomeration of reinforcement particles and their non-uniform distribution, which are often attributed to the poor strength of MoSi[sub 2] composites can be avoided in this process. SHS is capable of producing composites with a homogeneous distribution of fine reinforcements in a single step. MoSi[sub 2] has been produced by SHS earlier. The authors have reported the combustion synthesis of MoSi[sub 2]-SiC composites and MoSi[sub 2]-WSi[sub 2] alloys. In this paper, combustion synthesis of a complex composite, namely (Mo,W)Si[sub 2]-SiC, starting from elemental powders by the thermal explosion mode is reported. In the thermal explosion mode of SHS, a volumetric reaction occurs in the reactant compact when it is rapidly heated to the ignition temperature.

  18. Combustion synthesis of titania nanoparticles in a premixed methane flame

    Microsoft Academic Search

    Hsiao-Kang Ma; Hsiung-An Yang

    2010-01-01

    Previous studies have shown that titanium tetra-isopropoxide (TTIP) can be a substitute in the production of non-poisonous and inexpensive nanostructured titania (TiO2) particles. This study discusses the combustion characteristics of synthesized titania obtained while adding TTIP into the premixed methane\\/air flames. As the TTIP concentration increased, a bright yellow flame brush, representing a region of titania nanoparticles production, appeared on

  19. A New Combustion Synthesis Method for GaN:Eu3+ and Ga2O3 :Eu3+

    E-print Network

    McKittrick, Joanna

    A New Combustion Synthesis Method for GaN:Eu3+ and Ga2O3 :Eu3+ Luminescent Powders G. A. Hirata1 between the precursors. The preparation of Eu-doped Ga2O3 powders was achieved using a new combustion)3 and Ga(NO3)3 as the precursors and hydrazine as (non-carbonaceous) fuel. A spontaneous combustion

  20. Preparation of MoB and MoB–MoSi 2 composites by combustion synthesis in SHS mode

    Microsoft Academic Search

    C. L. Yeh; W. S. Hsu

    2007-01-01

    Combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) was carried out in the Mo–B and Mo–B–Si systems for the preparation of molybdenum boride MoB and the composite of MoB–MoSi2 from elemental powder compacts. Under a preheating temperature above 150°C, the reaction of Mo with boron in the sample compact of Mo:B=1:1 is characterized by a planar combustion front

  1. Lightweight Mg-based composites with thermodynamically stable interfaces by in-situ combustion synthesis

    NASA Astrophysics Data System (ADS)

    Jo, Ilguk

    Lightweight Mg-based composites have been produced by in-situ combustion synthesis of the Al-Ti-C reaction system. The characteristics of the in-situ composites were investigated in terms of phase evolution and interfacial stability using various analysis techniques. The structural analysis results showed that full conversion of the Al-Ti-C reactants into spherical TiC reinforcements with sizes around 1mum was achieved by the combustion reaction. In-situ formed TiC had less oxygen and higher Al contents at the interface than ex-situ formed TiC; these clean interfaces with an Al layer on the reinforcements were shown to yield interfacial stability. For these reasons, the in-situ composites exhibited higher theoretical densities and also good mechanical properties compared with ex-situ produced composites. The interfacial characteristics of molten Mg with the Al-Ti-C reactants and the commercial TiC+Al substrates were evaluated using an infiltration technique under an argon atmosphere. Infiltration length increased with time at temperature, yielding activation energies (Ea) for each system. The value of Ea for the Al-Ti-C system (307.31kJ/mol) is lower than that for the other system (350.84kJ/mol); the high Ea value indicates that the infiltration is not a simple viscosity-controlled phenomenon but involves a chemical reaction. Formation of the Al3Ti phase was observed from the crystal structural analysis of the infiltrated area; thus, existence of reaction promoting the wetting of Mg. The phase evolution, reaction mechanism and kinetics of the Al-Ti-C reaction were studied using DSC and HT-XRD. It was confirmed that, along with the melting of Al, there was formation of Al3Ti by reaction between Al and Ti. A detailed structural analysis indicates that, the reaction mechanism involves melting of Al followed by formation and growth of Al 3Ti, which then contacts the graphite powder and initiates the combustion reaction. The effect of important process parameters, such as the Al content and the reactant sizes, on the microstructure of the resulting in-situ composites is discussed. Feasibility and castability of the composites were investigated by high pressure die casting the composite preforms into automotive parts and durability tests were conducted on the cast parts.

  2. Materials Science and Engineering A311 (2001) 8399 Combustion synthesis/densification of an Al2O3 TiB2 composite

    E-print Network

    Meyers, Marc A.

    2001-01-01

    Materials Science and Engineering A311 (2001) 83­99 Combustion synthesis/densification of an Al2O3 synthesis; Densification; Constitutive models www.elsevier.com/locate/msea 1. Introduction Combustion synthesis, also known as SHS, was pio- neered by Merzhanov and co-workers [1­4] and is being intensely

  3. Some Further Studies in Combustion Synthesis of the YBa2Cu307–x Superconductor

    Microsoft Academic Search

    JEAN-PASCAL LEBRAT; ARVIND VARMA

    1993-01-01

    The combustion synthesis of the YBa2Cu3Oz–x ceramic superconductor was achieved from CuBaO2 and Y2O3 mixtures, using both self-propagating high-temperature synthesis (SHS) and thermal explosion modes. Particular attention was paid to establishing the mechanism of formation of the YBa2Cu3O3–2 product. Previous studies included effects of BaO2 and Cu particle sizes, along with quenching of reacting pellets. It was shown that the

  4. Combustion synthesis and mechanical properties of dense NiTi-TiC intermetallic-ceramic composites

    Microsoft Academic Search

    Douglas E. Burkes; Guglielmo Gottoli; John J. Moore; Hu Chun Yi

    2006-01-01

    Combustion synthesis (SHS) coupled with a quasi-isostatic densification step was employed to produce dense NiTi-TiC composites.\\u000a The synthesis and characterization of five composites are presented, including ceramic-intermetallic (?50 pct ceramic) composites\\u000a and intermetallic-ceramic (?50 pct intermetallic) composites. Particle size, X-ray diffraction (XRD), and scanning electron\\u000a microscopy (SEM) analysis was conducted to characterize the microstructure of the composites. Refractory TiC and

  5. Ultrasound assisted combustion synthesis of TiC in Al-Ti-C system.

    PubMed

    Liu, Zhiwei; Rakita, Milan; Xu, Wilson; Wang, Xiaoming; Han, Qingyou

    2015-11-01

    This research investigated the effects of high-intensity ultrasound on the combustion synthesis of TiC particles in Al-Ti-C system. The process involved that high-intensity ultrasound was applied on the surface of a compacted Al-Ti-C pellet directly through a Nb probe during the thermal explosion reaction. By comparing with the sample without ultrasonic treatment, it was found that the thermal explosion reaction for synthesizing TiC phase could take place thoroughly in the ultrasonically treated sample. During the process of synthesizing TiC phase, the dissolution of solid graphite particles into the Al-Ti melt, as well as the nucleation and growth of TiC particles could be promoted effectively due to the effects of ultrasound, leading to an enhancement of the formation of TiC particles. Ultrasound assisted combustion synthesis as a simple and effective approach was proposed for synthesizing materials in this research. PMID:25937509

  6. The effect of an electric field on self-sustaining combustion synthesis: Part I. modeling studies

    NASA Astrophysics Data System (ADS)

    Feng, A.; Munir, Z. A.

    1995-05-01

    An analysis of the effect of an electric field on self-propagating high-temperature synthesis (SHS) reactions is presented. Using the synthesis of SiC as a model, the analysis showed that the imposition of a field results in a highly localized distribution of the current density. It was shown that the current is primarily restricted to the region just ahead of the combustion zone. Thus, in addition to the chemical heat release, this zone also includes heat release from an electric source, a value equivalent to ?E2 where ? is the conductivity and E is the field. From the dependence of the degree of conversion to the product on the applied voltage, it is shown that the velocity of the combustion wave is linearly proportional to the field.

  7. The Effect of Gravity on the Combustion Synthesis of Porous Biomaterials

    NASA Technical Reports Server (NTRS)

    Castillo, M.; Zhang, X.; Moore, J. J.; Schowengerdt, F. D.; Ayers, R. A.

    2003-01-01

    Production of highly porous composite materials by traditional materials processing is limited by difficult processing techniques. This work investigates the use of self propagating high temperature (combustion) synthesis (SHS) to create porous tricalcium phosphate (Ca3(PO4)2), TiB-Ti, and NiTi in low and microgravity. Combustion synthesis provides the ability to use set processing parameters to engineer the required porous structure suitable for bone repair or replacement. The processing parameters include green density, particle size, gasifying agents, composition, and gravity. The advantage of the TiB-Ti system is the high level of porosity achieved together with a modulus that can be controlled by both composition (TiB-Ti) and porosity. At the same time, NiTi exhibits shape memory properties. SHS of biomaterials allows the engineering of required porosity coupled with resorbtion properties and specific mechanical properties into the composite materials to allow for a better biomaterial.

  8. In situ combustion synthesis of dense ceramic and ceramic-metal interpenetrating phase composites

    SciTech Connect

    Feng, H.J.; Moore, J.J. [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering

    1995-04-01

    A model exothermic reaction is used to demonstrate the application of simultaneous combustion synthesis, conducted under a consolidating pressure, as a one-step in situ synthesis technique for the production of dense ceramic and ceramic-metal interpenetrating phase composites (IPC). The addition of an excess amount of metal, e.g., Al, and/or a diluent, e.g., Al{sub 2}O{sub 3}, lowers the combustion temperature and aids in the refinement of the microstructure, facilitating an increase in compressive strength and elastic modulus. The effects of the important process parameters, e.g., reaction stoichiometry and diluents, green density, pressure, and temperature, on micro-structure and properties of these high-performance composites are discussed.

  9. An investigation of the synthesis of nickel aluminides through gasless combustion

    Microsoft Academic Search

    K. A. Philpot; Z. A. Munir; J. B. Holt

    1987-01-01

    The formation of nickel aluminidms by the thermal explosion mode of gasless combustion synthesis was investigated for Ni-Al powders ranging in composition from 5 to 3O at% Al. Compound formation was found to take place sequentially starting with the most aluminium-rich and ending with AlNi3 as the predominant compound in the product. Compounds formed through both solid- and liquid-sate reactions,

  10. A combustion synthesis method to obtain alternative cermet materials for SOFC anodes

    Microsoft Academic Search

    A Ringuedé; J. A Labrincha; J. R Frade

    2001-01-01

    Homogeneous mixtures of nanocrystalline powders of Ni–YSZ, (Ni,Co)–YSZ, (Ni,Fe)–YSZ, and (Ni,Cu)–YSZ were obtained by combustion synthesis from mixtures of molten nitrates and urea. Electrolyte\\/anode bilayers were then prepared by pressing a cermet layer onto a previously pressed yttria-stabilised zirconia (YSZ) electrolyte layer, at room temperatures, and then co-firing; this yields a porous cermet anode, and a dense YSZ layer with

  11. Influence of double promotion on HDS catalysts prepared by urea-matrix combustion synthesis

    Microsoft Academic Search

    Sergio L. González-Cortés; Tian-Cun Xiao; Tsung-Wu Lin; Malcolm L. H. Green

    2006-01-01

    The stringent environmental regulations in the US, Japan and Europe are requiring significant improvement in the quality of transportation fuels. A new strategy based on urea-matrix combustion method for the synthesis of alumina-supported molybdate-based mixed oxides (i.e., bimetallic and trimetallic oxides) has been applied. This permits to control the alumina–mixed oxide interaction and therefore the HDS catalytic behaviour. The oxidic

  12. Combustion synthesis of fine AlN powder and its reaction control

    Microsoft Academic Search

    T. Sakurai; O. Yamada; Y. Miyamoto

    2006-01-01

    Aluminum nitride powder produced by the combustion synthesis (SHS) usually contains coarse particles because of its high reaction temperature. These particles make it difficult to achieve sintering. To improve sinterability, the reaction temperature was controlled by adding hydrogen gas up to 20vol.% to the reactant gas (nitrogen), and NH4F up to 1.5mass% to the reactant mixture. The reaction temperature was

  13. A comparative study on combustion synthesis of Nb–Si compounds

    Microsoft Academic Search

    C. L. Yeh; W. H. Chen

    2006-01-01

    A comparative study on the preparation of niobium silicides (such as Nb3Si, Nb5Si3, and NbSi2) in the Nb–Si system was conducted by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of different stoichiometries. Effects of the sample green density, preheating temperature, and starting stoichiometry on combustion characteristics, as well as on product composition were studied. Test specimens with five different

  14. Combustion synthesis of Ni 3Al by SHS with boron additions

    Microsoft Academic Search

    C. L. Yeh; W. Y. Sung

    2005-01-01

    The preparation of Ni3Al intermetallic compound from elemental powder compacts with the addition of boron was conducted by self-propagating high-temperature synthesis (SHS) in this study. Effects of the boron content, preheating temperature, and particle size of the reactants on the combustion characteristics, as well as on the composition and morphology of final products were studied. Experimental observation indicates that the

  15. Combustion synthesis of Ni3Al and Ni3Al-matrix composites

    Microsoft Academic Search

    J. P. Lebrat; A. Varma; A. E. Miller

    1992-01-01

    The self-propagating mode of combustion synthesis (SHS) of Ni3Al starting from compacts of stoichiometrically mixed Ni and Al powders readily forms fully reacted structures with about 3 to 5 pct porosity, if green density of the compacts is greater than about 75 pct of theoretical. SHS-produced Ni3Al matrix composites with up to 2 wt pct A12O3 whiskers also have relatively

  16. A comparative study on combustion synthesis of Ta–Si compounds

    Microsoft Academic Search

    C. L. Yeh; H. J. Wang

    2007-01-01

    A comparative study on the preparation of tantalum silicides (including TaSi2, Ta5Si3, Ta2Si, and Ta3Si) in the Ta–Si system was conducted by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of corresponding stoichiometries. For the powder compacts of Ta:Si=5:3 and 2:1, upon ignition a planar combustion front traversing the entire sample was easily achieved even without prior heating. In contrast,

  17. Effects of TiC addition on combustion synthesis of NiAl in SHS mode

    Microsoft Academic Search

    C. L. Yeh; S. H. Su; H. Y. Chang

    2005-01-01

    The preparation of NiAl intermetallic compound with the addition of TiC particles was conducted by self-propagating high-temperature synthesis (SHS) from elemental powder compacts in this study. Effects of initial sample density, preheating temperature, particle size of the reactants, and TiC content on the combustion characteristics, as well as on the composition and morphology of final products were studied. Experimental observations

  18. Combustion synthesis of Ni 3 Al and Ni 3 Al-matrix composites

    Microsoft Academic Search

    J. P. Lebrat; A. Varma; A. E. Miller

    1992-01-01

    The self-propagating mode of combustion synthesis (SHS) of Ni3Al starting from compacts of stoichiometrically mixed Ni and Al powders readily forms fully reacted structures with about\\u000a 3 to 5 pct porosity, if green density of the compacts is greater than about 75 pct of theoretical. SHS-produced Ni3Al matrix composites with up to 2 wt pct A12O3 whiskers also have relatively

  19. Combustion synthesis of advanced materials: Part II. Classification, applications and modelling

    Microsoft Academic Search

    John J. Moore; H. J. Feng

    1995-01-01

    Combustion (self propagating high temperature) synthesis (SHS) reactions have been classified into (i) simple reaction systems in which no other processing step, other than the SHS reaction, is considered; (ii) SHS reactions which involve simultaneous and\\/or subsequent densification process(es); (iii) SHS reactions coupled with vapor transport systems and those which synthesize specific products such as functionally-graded materials (FGM), thin films

  20. A comparative study on combustion synthesis of Nb–B compounds

    Microsoft Academic Search

    C. L. Yeh; W. H. Chen

    2006-01-01

    A comparative study on the preparation of specific niobium borides (including Nb3B2, NbB, Nb5B6, Nb3B4, and NbB2) in the Nb–B system was experimentally conducted by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of their corresponding stoichiometries. Effects of the sample green density, preheating temperature, and starting stoichiometry on combustion characteristics, as well as on product composition were studied. Experimental

  1. Combustion Synthesis of Ca3(PO4)2 Net-Shape Surgical Implants

    NASA Technical Reports Server (NTRS)

    Ayers, Reed A.; Castillo, Martin; Gottoli, Guglielmo; Moore, John J.; Simske, Steven J.

    2006-01-01

    Self-propagating high-temperature combustion synthesis (SHS) is the basis of a method of making components of porous tricalcium phosphate [Ca3(PO4)2] and related compounds in net sizes and shapes for use as surgical implants that are compatible with bone. The SHS method offers advantages over prior methods of manufacturing Ca3(PO4)2-based surgical implants.

  2. Effect of preheating on synthesis of tantalum nitride by self-propagating combustion

    Microsoft Academic Search

    C. L. Yeh; E. W. Liu; Y. C. Chang

    2004-01-01

    An experimental investigation of self-propagating high-temperature synthesis (SHS) of tantalum nitride (TaN) was conducted with tantalum compacts in nitrogen of 0.27–1.82MPa. Effects of sample density, nitrogen pressure, and preheating temperature on the flame-front propagation velocity, combustion temperature, degree of conversion, and product composition were studied. Results showed that the SHS process of the tantalum\\/nitrogen reaction was characterized by the steady

  3. Synthesis of molybdenum silicides by the self-propagating combustion method

    Microsoft Academic Search

    S. Zhang; Z. A. Munir

    1991-01-01

    The synthesis of the silicides of molybdenum (Mo3Si, Mo5Si3, and MoSi2) by the self-propagating combustion method is investigated. Only the reactants corresponding to the last phase can be reacted in a self-sustaining mode without preheating. The product of such a reaction is single-phase MoSi2. Although reactant mixtures corresponding to the other two silicides can react in a self-sustaining mode with

  4. Synthesis And Characterization Of Zinc Oxide Nanoparticles Prepared Via Precipitation And Self-Combustion Methods

    Microsoft Academic Search

    Noorhana Yahya; Shikh Mohd. Shahrul Nizan Shikh Zahari; Anita Ramli; Noraini Muti Mohamad; Poppy Puspitasari; Nur Liyana Che Zul

    2009-01-01

    Zinc oxide is an important chemical substance that is widely used in the production of various industrial products. However, to produce nano particle ZnO remains a challenge. This paper describes the synthesis of zinc oxide nanoparticles via precipitation and self-combustion methods. By precipitation method, the dissolved zinc nitrate solution is drop wisely into aqueous sodium hydroxide, NaOH as precipitating agent.

  5. Synthesis of NiTi intermetallics by self-propagating combustion

    Microsoft Academic Search

    C. L Yeh; W. Y Sung

    2004-01-01

    The production of NiTi intermetallic compounds from elemental powder compacts was conducted by self-propagating high-temperature synthesis (SHS) in this study. Effects of initial sample density, preheating temperature, and Ni particle size on the combustion characteristics, as well as on the final composition and morphology of products were studied. For the samples with densities between 50 and 60% theoretical maximum density

  6. Experimental studies on self-propagating combustion synthesis of niobium nitride

    Microsoft Academic Search

    C. L Yeh; H. C Chuang

    2004-01-01

    An experimental investigation of self-propagating high-temperature synthesis (SHS) of niobium nitride (NbN) was conducted with niobium compacts in gaseous nitrogen. A detailed characterization of the flame propagation mode was performed in this study. Effects of sample density, nitrogen pressure, and diluent content on the degree of conversion, flame-front velocity, and combustion temperature were studied. It was found that the self-sustained

  7. Self-ignition combustion synthesis of LaNi 5 utilizing hydrogenation heat of metallic calcium

    Microsoft Academic Search

    Naoto Yasuda; Shino Sasaki; Noriyuki Okinaka; Tomohiro Akiyama

    2010-01-01

    This paper describes self-ignition combustion synthesis (SICS) of LaNi5 in a pressurized hydrogen atmosphere using metallic calcium as both the reducing agent and the heat source. In this study, the effects of hydrogen on the ignition temperature and the hydrogenation properties of the products were mainly examined. In the experiments, La2O3, Ni, and Ca were dry-mixed in the molar ratio

  8. Highly aluminium doped barium and strontium ferrite nanoparticles prepared by citrate auto-combustion synthesis

    Microsoft Academic Search

    Neil J.. Shirtcliffe; Simon Thompson; Eoin S. O’Keefe; Steve Appleton; Carole C.. Perry

    2007-01-01

    Aluminium doped barium and strontium hexaferrite nanoparticles BaAlxFe(12?x)O19 and SrAlxFe(12?x)O19 were synthesised via a sol–gel route using citric acid to complex the ions followed by an auto-combustion reaction. This method shows promise for the synthesis of complex ferrite powders with small particle size. It was found that around half of the iron could be substituted for aluminium in the barium

  9. Self-propagating high-temperature synthesis for compound thermoelectrics and new criterion for combustion processing

    PubMed Central

    Su, Xianli; Fu, Fan; Yan, Yonggao; Zheng, Gang; Liang, Tao; Zhang, Qiang; Cheng, Xin; Yang, Dongwang; Chi, Hang; Tang, Xinfeng; Zhang, Qingjie; Uher, Ctirad

    2014-01-01

    The existing methods of synthesis of thermoelectric (TE) materials remain constrained to multi-step processes that are time and energy intensive. Here we demonstrate that essentially all compound thermoelectrics can be synthesized in a single-phase form at a minimal cost and on the timescale of seconds using a combustion process called self-propagating high-temperature synthesis. We illustrate this method on Cu2Se and summarize key reaction parameters for other materials. We propose a new empirically based criterion for sustainability of the combustion reaction, where the adiabatic temperature that represents the maximum temperature to which the reacting compact is raised as the combustion wave passes through, must be high enough to melt the lower melting point component. Our work opens a new avenue for ultra-fast, low-cost, large-scale production of TE materials, and provides new insights into combustion process, which greatly broaden the scope of materials that can be successfully synthesized by this technique. PMID:25223333

  10. 40 CFR 62.15310 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...keep for municipal waste combustion units that use activated...PLANS FOR DESIGNATED FACILITIES AND POLLUTANTS Federal...Small Municipal Waste Combustion Units Constructed on... For municipal waste combustion units that use activated...hour) during all stack tests for...

  11. 40 CFR 62.15310 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...keep for municipal waste combustion units that use activated...PLANS FOR DESIGNATED FACILITIES AND POLLUTANTS Federal...Small Municipal Waste Combustion Units Constructed on... For municipal waste combustion units that use activated...hour) during all stack tests for...

  12. 40 CFR 62.15310 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...keep for municipal waste combustion units that use activated...PLANS FOR DESIGNATED FACILITIES AND POLLUTANTS Federal...Small Municipal Waste Combustion Units Constructed on... For municipal waste combustion units that use activated...hour) during all stack tests for...

  13. 40 CFR 62.15310 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...keep for municipal waste combustion units that use activated...PLANS FOR DESIGNATED FACILITIES AND POLLUTANTS Federal...Small Municipal Waste Combustion Units Constructed on... For municipal waste combustion units that use activated...hour) during all stack tests for...

  14. 40 CFR 62.15310 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...keep for municipal waste combustion units that use activated...PLANS FOR DESIGNATED FACILITIES AND POLLUTANTS Federal...Small Municipal Waste Combustion Units Constructed on... For municipal waste combustion units that use activated...hour) during all stack tests for...

  15. 40 CFR 60.1855 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...records must I keep for municipal waste combustion units that use activated carbon? ...Compliance Times for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

  16. 40 CFR 60.1855 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...records must I keep for municipal waste combustion units that use activated carbon? ...Compliance Times for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

  17. 40 CFR 60.1370 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...records must I keep for municipal waste combustion units that use activated carbon? ...Performance for Small Municipal Waste Combustion Units for Which Construction is Commenced...records must I keep for municipal waste combustion units that use activated carbon?...

  18. 40 CFR 60.1855 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...records must I keep for municipal waste combustion units that use activated carbon? ...Compliance Times for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

  19. 40 CFR 60.1370 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...records must I keep for municipal waste combustion units that use activated carbon? ...Performance for Small Municipal Waste Combustion Units for Which Construction is Commenced...records must I keep for municipal waste combustion units that use activated carbon?...

  20. 40 CFR 60.1855 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...records must I keep for municipal waste combustion units that use activated carbon? ...Compliance Times for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

  1. 40 CFR 60.1370 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...records must I keep for municipal waste combustion units that use activated carbon? ...Performance for Small Municipal Waste Combustion Units for Which Construction is Commenced...records must I keep for municipal waste combustion units that use activated carbon?...

  2. 40 CFR 60.1855 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...records must I keep for municipal waste combustion units that use activated carbon? ...Compliance Times for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

  3. 40 CFR 60.1370 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...records must I keep for municipal waste combustion units that use activated carbon? ...Performance for Small Municipal Waste Combustion Units for Which Construction is Commenced...records must I keep for municipal waste combustion units that use activated carbon?...

  4. 40 CFR 60.1370 - What records must I keep for municipal waste combustion units that use activated carbon?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...records must I keep for municipal waste combustion units that use activated carbon? ...Performance for Small Municipal Waste Combustion Units for Which Construction is Commenced...records must I keep for municipal waste combustion units that use activated carbon?...

  5. Combustion Synthesis of Glass (B 2 O 3 Al 2 O 3 -MgO)Ceramic (TiB 2 ) Composites

    Microsoft Academic Search

    H. C. Yi; J. Y. Guigne; J. J. Moore; A. R. Manerbino; L. A. Robinson; F. D. Schowengerdt

    2002-01-01

    The combustion synthesis, or self-propagating high temperature synthesis (SHS), technique has been used to produce glass ceramic composites that have a glass matrix based on B2O3-MgO-Al2O3and a crystalline ceramic phase of TiB2. Conditions for producing glassy materials by the SHS technique are discussed and the thermodynamics of these combustion reactions are analyzed. The combustion characteristics, i.e., ignition energy, combustion temperature,

  6. Combustion synthesis and structure formation in a model Cr-CrO3 self-propagating high-temperature synthesis system

    Microsoft Academic Search

    V. I YUKHVID; S. V MAKLAKOV; P. V ZHIRKOV; V. A GORSHKOV; N. I TIMOKHIN; A. Y DOVZHENKO

    1997-01-01

    The combustion synthesis (self-propagating high-temperature synthesis, SHS) of a model Cr-CrO3 system is studied both experimentally\\u000a and theoretically. The system is chemically simple, i.e. it is composed of only two elements, and convenient for combustion\\u000a and phase formation studies. A new combustion model for a “metal-metal oxide” system and a mathematical model of phase and\\u000a structure formation are developed. A

  7. Combustion synthesis of metal carbides: Part I. Model development

    Microsoft Academic Search

    A. M. Locci; A. Cincotti; F. Delogu; R. Orrù; G. Cao

    2005-01-01

    The definition of a rigorous theoretical framework for the appropriate physico-chemical description of self-propagating high-temperature synthesis (SHS) processes represents the main goal of this work which is presented in two sequential articles. In this article, a novel mathematical model to simulate SHS processes is proposed. By adopting a heterogeneous approach for the description of mass transfer phenomena, the model is

  8. Modeling the kinetics of non-isothermal heterogeneous interaction during combustion synthesis of advanced micro- and nanocrystalline materials

    Microsoft Academic Search

    Boris B. Khina

    2008-01-01

    The combustion synthesis (CS), or self-propagating high-temperature synthesis (SHS) is a cost and energy efficient route for producing a wide range of refractory compounds (carbides, silicides, intermetallics) and advanced micro- and nanocrystalline materials. However, despite 40 years of extensive studies and industrial applications, intricate phase formation mechanisms that operate during CS are still not well understood. This hinders the development

  9. Effect of pH on the production of dispersed Bi 4Ge 3O 12 nanoparticles by combustion synthesis

    Microsoft Academic Search

    Fabiane Alexsandra Andrade de Jesus; Ronaldo Santos Silva; Antonio Carlos Hernandes; Zélia Soares Macedo

    2009-01-01

    This paper reports the production of bismuth germanate ceramic scintillator (Bi4Ge3O12) by combustion synthesis (SHS) method, focusing on the influence of the synthesis parameters on the crystalline phases and agglomeration of the nanoparticles. The synthesis and sintering conditions were investigated through thermal analysis, X-ray diffraction as function of temperature, dilatometry and scanning electron microscopy. Well-dispersed Bi4Ge3O12 powder was accomplished by

  10. Effect of combustion condition on cytotoxic and inflammatory activity of residential wood combustion particles

    NASA Astrophysics Data System (ADS)

    Jalava, Pasi I.; Salonen, Raimo O.; Nuutinen, Kati; Pennanen, Arto S.; Happo, Mikko S.; Tissari, Jarkko; Frey, Anna; Hillamo, Risto; Jokiniemi, Jorma; Hirvonen, Maija-Riitta

    2010-05-01

    Residential heating is an important local source of fine particles and may cause significant exposure and health effects in populations. We investigated the cytotoxic and inflammatory activity of particulate emissions from normal (NC) and smouldering (SC) combustion in one masonry heater. The PM 1-0.2 and PM 0.2 samples were collected from the dilution tunnel with a high-volume cascade impactor (HVCI). Mouse RAW 264.7 macrophages were exposed to the PM-samples for 24 h. Inflammatory mediators, (IL-6, TNF? and MIP-2), and cytotoxicity (MTT-test), were measured. Furthermore, apoptosis and cell cycle of macrophages were analyzed. The HVCI particulate samples were characterized for ions, elements and PAH compounds. Assays of elemental and organic carbon were conducted from parallel low volume samples. All the samples displayed mostly dose-dependent inflammatory and cytotoxic activity. SC samples were more potent than NC samples at inducing cytotoxicity and MIP-2 production, while the order of potency was reversed in TNF? production. SC-PM 1-0.2 sample was a significantly more potent inducer of apoptosis than the respective NC sample. After adjustment for the relative toxicity with emission factor (mg MJ -1), the SC-PM emissions had clearly higher inflammatory and cytotoxic potential than the NC-PM emissions. Thus, operational practice in batch burning of wood and the resultant combustion condition clearly affect the toxic potential of particulate emissions.

  11. Combustion

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    The process whereby a substance is combined with oxygen with the production of heat. Burning is a familiar example of this process. The energy required to propel chemical rockets is provided by the combustion of fuel with an oxidant at very high temperatures. A common oxidant is liquid oxygen (often denoted by LOX). Others include hydrogen peroxide and nitrogen tetroxide....

  12. The effect of gravity on the combustion synthesis of metal-ceramic composites

    NASA Astrophysics Data System (ADS)

    Yi, H. C.; Guigné, J. Y.; Woodger, T. C.; Moore, J. J.

    1998-08-01

    The effects of gravity on the combustion characteristics and microstructure of metal-ceramic composites (HfB2/Al and Ni3Ti/TiB2 systems) were studied under both normal and low gravity conditions. Under normal gravity conditions, pellets were ignited in three orientations relative to the gravity vector. Low gravity combustion synthesis (SHS) was carried out on a DC-9 aircraft at the NASA-Lewis Research Center. It was found that under normal gravity conditions, both the combustion temperature and wave velocity were highest when the pellet was ignited from the bottom orientation; i.e., the wave propagation direction was directly opposed to the gravitational force. The SHS of 70 vol pct Al (in the Al-HfB2 system) was changed from unstable, slow, and incomplete when ignited from the top to unstable, faster, and complete combustion when ignited from the bottom. The hydrostatic force (height × density × gravity) in the liquid aluminum was thought to be the cause of formation of aluminum nodules at the surface of the pellet. The aluminum nodules that were observed on the surface of the pellet when reacted under normal gravity were totally absent for reactions conducted under low gravity. Buoyancy of the TiB2 particles and sedimentation of the Ni3Ti phase were observed for the Ni3Ti/TiB2 system. The possibility of liquid convective flow at the combustion front was also discussed. Under low gravity conditions, both the combustion temperature and wave velocity were lower than those under normal gravity. The distribution of the ceramic phase, i.e., TiB2 or HfB2, in the intermetallic (Ni3Ti) or reactive (Al) matrix was more uniform.

  13. Combustion

    NASA Technical Reports Server (NTRS)

    Bulzan, Dan

    2007-01-01

    An overview of the emissions related research being conducted as part of the Fundamental Aeronautics Subsonics Fixed Wing Project is presented. The overview includes project metrics, milestones, and descriptions of major research areas. The overview also includes information on some of the emissions research being conducted under NASA Research Announcements. Objective: Development of comprehensive detailed and reduced kinetic mechanisms of jet fuels for chemically-reacting flow modeling. Scientific Challenges: 1) Developing experimental facilities capable of handling higher hydrocarbons and providing benchmark combustion data. 2) Determining and understanding ignition and combustion characteristics, such as laminar flame speeds, extinction stretch rates, and autoignition delays, of jet fuels and hydrocarbons relevant to jet surrogates. 3) Developing comprehensive kinetic models for jet fuels.

  14. Combustion Synthesis Reactions in Cold-Rolled Ni/Al and Ti/Al Multilayers

    NASA Astrophysics Data System (ADS)

    Qiu, Xiaotun; Liu, Ranran; Guo, Shengmin; Graeter, Jesse Harris; Kecskes, Laszlo; Wang, Jiaping

    2009-07-01

    In this article, a cold rolling method was developed to fabricate Ni/Al and Ti/Al multilayer foils, and the combustion synthesis reactions in the cold-rolled foils were investigated. Combustion synthesis reactions were initiated by heating one end of the cold-rolled foil in a flame for several seconds. The Ni/Al foils went through three reaction stages. The first reaction stage was a displacement of reaction zone with Al3Ni as the reaction product. During the second stage, the part of the foil in the flame underwent thermal explosion. In the last stage, the heat released by thermal explosion triggered a self-propagating high-temperature synthesis (SHS) reaction across the foil that resulted in the formation of AlNi. In contrast, the Ti/Al foils experienced only two reaction stages. First, a displacement of the reaction zone propagated across the foil with formation of Al3Ti at the Ti/Al interface. Then a thermal explosion reaction occurred in the part of foil that was heated in the flame, resulting in many different phases in the reacted foil.

  15. Synthesis, droplet combustion, and sooting characteristics of biodiesel produced from waste vegetable oils

    SciTech Connect

    Li, T. X.; Zhu, D. L.; Akafuah, N.; Saito, K.; Law, C. K.

    2011-01-01

    In light of the potential of fatty acid methyl ester (FAME, i.e. biodiesel) as a renewable energy source, an innovative acid catalyzed process was developed for the synthesis of biodiesel from waste vegetable oils. The synthesized biodiesels were analytically characterized for their major components, molar fraction and molecular weight of each component, the average molecular weight, and the heat of combustion. Their droplet combustion characteristics in terms of the burning rate, flame size, and sooting tendency were subsequently determined in a high-temperature, freely-falling droplet apparatus. Results show that the biodiesel droplet has higher burning rate, and that biodiesel in general has a lower propensity to soot because its molecular oxygen content promotes the oxidation of the soot precursors.

  16. Synthesis of the Nanocrystalline Nickel Ferrite by a Novel Mechano Sol-Gel Auto-Combustion Method

    NASA Astrophysics Data System (ADS)

    Shahmirzaei, M.; Seyyed Ebrahimi, S. A.; Dehghan, R.

    In this work, a novel method of mechano sol-gel auto-combustion has been developed for production of single phase nickel ferrite nanocrystalline powder, consisting of a sol-gel auto-combustion synthesis followed by a high energy milling process before calcination. Sol-gel auto-combustion was carried out using a gel including citric acid as a reductant and metal nitrates as oxidants. This gel exhibited a self-propagating behavior after ignition in air. The effects of the intermediate high energy milling on the physical properties of the final product after calcination were investigated. The results showed that with a high energy milling of the sol-gel auto-combusted powders with a ball-to-powder mass ratio of 20 for 20 h, the temperature of calcination for synthesis of the single phase ferrite reduced from 1000°C to 700°C and the size of the ferrite crystallites decreased from 72 nm to 15 nm.

  17. Combustion synthesis: a new route for repair of gas turbine components—principles and metallurgical structure in the NiAl\\/RBD61\\/superalloy junction

    Microsoft Academic Search

    C Pascal; R. M Marin-Ayral; J. C Tédenac; C Merlet

    2003-01-01

    A new technique for repairing turbine blade materials based on combustion synthesis is described in this article. This process uses a local internal generation of heat provided by the NiAl combustion synthesis in order to rebuild damaged turbine components. In this study, a nickel base braze was inserted between a substrate of nickel base superalloy and a powders compact (Ni+Al).

  18. Combustion synthesis of heterogeneous calcium phosphate bioceramics from calcium oxide and phosphate precursors

    Microsoft Academic Search

    R. Ayers; N. Hannigan; N. Vollmer; C. Unuvar

    2011-01-01

    The solid-state reaction of combustion synthesis has been demonstrated to be capable of rapidly producing materials for biomedical\\u000a applications. Reactant powders of CaO and P2O5 were pressed into cylinders and reacted by heating a tungsten filament in either an argon, CO2 or N2 atmosphere. Reaction systems examined were: (1) 3CaO + P2O5 ? Ca3(PO4)2 (TCP) and (2) 4CaO + P2O5

  19. Combustion synthesis of MoSi{sub 2}-SiC composites

    SciTech Connect

    Subrahmanyam, J.; Rao, R.M. [Defence Metallurgical Research Lab., Hyderabad (India). Combustion Synthesis Group

    1995-02-01

    MoSi{sub 2}, SiC, and MoSi{sub 2}-SiC composites were prepared by the thermal explosion mode of self-propagating, high-temperature synthesis (SHS), from elemental powders Mo, Si, and carbon. The products were characterized using chemical analysis, X-ray diffraction, and scanning electron microscopy. The morphology of MoSi{sub 2} in the product points out that it is in the molten state at the combustion temperature. SiC in the composite shows a very fine particle morphology. These results are supported by the earlier thermochemical calculation carried out on this system.

  20. Self-ignition combustion synthesis of TiFe 1? x Ni x in hydrogen atmosphere

    Microsoft Academic Search

    Ryuta Wakabayashi; Naohito Yasuda; Sino Sasaki; Noriyuki Okinaka; Tomohiro Akiyama

    2009-01-01

    This paper describes the self-ignition combustion synthesis (SICS) of the hydrogen storage alloy TiFe1?xNix (x=0, 0.5, 0.1, 0.2, and 0.4) in a hydrogen atmosphere and the hydrogenation properties of the obtained products, in which well mixed powder of Ti, Fe, and Ni was uniformly heated to the eutectic temperature of the Ti–Fe system (1358K) for self-ignition. TiFe1?xNix was successfully obtained

  1. Self-ignition combustion synthesis of oxygen-doped TiFe

    Microsoft Academic Search

    R. Wakabayashi; S. Sasaki; T. Akiyama

    2009-01-01

    This paper describes the Self-Ignition Combustion Synthesis (SICS) of the hydrogen storage alloy Ti1.15FeOx (x=0, 0.024, and 0.050) in a hydrogen atmosphere and the obtained product's hydrogenation properties. Ti, Fe, and ?-Fe2O3 powders were mixed to produce Ti1.15FeOx and uniformly heated to the eutectic temperature 1358K for self-ignition, which occurred after the hydrogenation and decomposition of Ti. The X-ray diffraction

  2. Eu 3+ doped rare earth orthoborates, RBO 3 (R = Y, La and Gd), obtained by combustion synthesis

    Microsoft Academic Search

    Mika Tukia; Jorma Hölsä; Mika Lastusaari; Janne Niittykoski

    2005-01-01

    Vaterite type YBO3 and GdBO3 and aragonite type LaBO3 were prepared by the combustion. Combustion synthesis is a straightforward method to produce nanocrystalline powders requiring only a simple apparatus. The reaction was carried out by heating a mixture of rare earth nitrates, orthoboric acid and an organic fuel. For each RBO3, the ratios of starting materials were varied to obtain

  3. Eu3+ doped rare earth orthoborates, RBO3 (R = Y, La and Gd), obtained by combustion synthesis

    Microsoft Academic Search

    Mika Tukia; Jorma Hölsä; Mika Lastusaari; Janne Niittykoski

    2005-01-01

    Vaterite type YBO3 and GdBO3 and aragonite type LaBO3 were prepared by the combustion. Combustion synthesis is a straightforward method to produce nanocrystalline powders requiring only a simple apparatus. The reaction was carried out by heating a mixture of rare earth nitrates, orthoboric acid and an organic fuel. For each RBO3, the ratios of starting materials were varied to obtain

  4. Synthesis of SiC w\\/MoSi 2 powder by the “chemical oven” self-propagating combustion method

    Microsoft Academic Search

    Jianguang Xu; Baolin Zhang; Guojian Jiang; Wenlan Li; Hanrui Zhuang

    2006-01-01

    SiC whisker reinforced MoSi2 composite powder has been successfully synthesized by “chemical oven” combustion synthesis method. The mixtures of Si and Ti were ignited as chemical oven. XRD result shows that the combustion product is mainly composed of MoSi2 and SiC phases. SEM photo and EDS result show that SiC whisker is formed during this process.

  5. Formation of titanium silicides Ti 5Si 3 and TiSi 2 by self-propagating combustion synthesis

    Microsoft Academic Search

    C. L. Yeh; W. H. Chen; C. C. Hsu

    2007-01-01

    Preparation of titanium silicides Ti5Si3 and TiSi2 from elemental powder compacts of their corresponding stoichiometries was conducted by self-propagating high-temperature synthesis (SHS) in this study. Effects of the sample green density, preheating temperature, and starting stoichiometry on combustion characteristics, as well as on product composition were studied. Experimental evidence indicated that a self-sustained combustion front was established upon ignition and

  6. The effect of an electric field on self-sustaining combustion synthesis: Part II. field-assisted synthesis of ?-SiC

    Microsoft Academic Search

    A. Feng; Z. A. Munir

    1995-01-01

    Self-sustaining combustion synthesis of ?-SiC is shown to be possible in the presence of an electric field. Above a threshold\\u000a field of ?6.8 V ? cm?1, a combustion wave resulting from the reaction between silicon and graphite powders can be self-sustaining. A linear relationship\\u000a between the applied field and the measured wave velocity is observed, in qualitative agreement with the

  7. Combustion synthesis and effects of processing parameters on physical properties of {alpha}-alumina

    SciTech Connect

    Collins, M.V.; Hirschfeld, D.A.; Shea, L.E.

    2000-01-04

    Fine particle porous {alpha}-alumina has been prepared by a wet chemical method of combustion synthesis using an aqueous precursor containing aluminum nitrate (oxidizer) and carbohydrazide, an organic fuel as starting materials. The aluminum nitrate and carbohydrazide were reacted exothermically at 400--600 C. The synthesis of {alpha}-alumina ({alpha}-Al{sub 2}O{sub 3}) was used as a model for understanding the effects of processing parameters on physical properties such as surface area, average pore size, and residual carbon content. The porous powders were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface area analysis and elemental analysis. The decomposition of the starting materials was investigated using differential thermal and thermogravimetric analyses (DTA/TGA). It has been shown that the furnace temperature, fuel/oxidizer ratio, and precursor water content can be tailored to produce powders with different physical properties.

  8. Combustion synthesis and structural analysis of nanocrystalline nickel ferrite at low temperature regime

    NASA Astrophysics Data System (ADS)

    Shanmugavel, T.; Raj, S. Gokul; Rajarajan, G.; Kumar, G. Ramesh; Boopathi, G.

    2015-06-01

    Combustion synthesis of single phase Nickel ferrite was successfully achieved at low temperature regime. The obtained powders were calcinated to increase the crystallinity and their characterization change due to calcinations is investigated in detail. Citric acid used as a chelating agent for the synthesis of nickel ferrite. Pure single phase nickel ferrites were found at this low temperature. The average crystalline sizes were measured by using powder XRD measurements. Surface morphology was investigated through Transmission Electron Microscope (TEM). Particle size calculated in XRD is compared with TEM results. Magnetic behaviour of the samples is analyzed by using Vibrating Sample Magnetometer (VSM). Saturation magnetization, coercivity and retentivity are measured and their results are discussed in detail.

  9. Synthesis and anticancer activity of epipolythiodiketopiperazine alkaloids

    E-print Network

    Boyer, Nicolas

    The epipolythiodiketopiperazine (ETP) alkaloids are a highly complex class of natural products with potent anticancer activity. Herein, we report the application of a flexible and scalable synthesis, allowing the construction ...

  10. Effects of TiC and Al 4C 3 addition on combustion synthesis of Ti 2AlC

    Microsoft Academic Search

    C. L. Yeh; Y. G. Shen

    2009-01-01

    Preparation of the ternary carbide Ti2AlC was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) from the elemental powder compacts of Ti:Al:C=2:1:1, TiC-containing samples with TiC of 6.67–14.3mol%, and Al4C3-containing samples with Al4C3 of 1.96–10mol%. Effects of TiC and Al4C3 addition were studied on combustion characteristics and the degree of phase conversion. Due to the growth

  11. Combustion synthesis of Ti 3AlC 2 from Ti\\/Al\\/C\\/TiC powder compacts

    Microsoft Academic Search

    C. L. Yeh; Y. G. Shen

    2008-01-01

    Preparation of the ternary carbide Ti3AlC2 was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) from both the elemental powder compacts of Ti:Al:C=3:1:2 and the TiC-containing samples compressed from the powder mixtures of Ti\\/Al\\/C\\/TiC with TiC content ranging from 4.35 to 26.3mol%. The effect of TiC addition was studied on combustion characteristics and the degree of

  12. Combustion Synthesis of Yttrium BARIUM(2) COPPER(3) OXYGEN(6+X) Superconductor.

    NASA Astrophysics Data System (ADS)

    Lin, Sy-Chyi

    YBa_2Cu_3 O_{rm 6 + x} was produced from copper, barium peroxide, and yttrium oxide by Self-propagating High-temperature Synthesis (SHS) and thermal explosion methods. The SHS process was conducted in two modes: a horizontal combustion and a vertical combustion. The influence of copper particle size on the stability of the reaction front was studied. In contrast to previous studies, a stable reaction front could be maintained even when relatively large copper particles (smaller than 325 mesh) were used. In the horizontal SHS process, large diameter pellets (larger than 22 mm in diameter) enabled stable combustion at room temperature. Elevated ambient temperatures (400 {~} 500^circ C) were needed to stabilize the combustion front movement in small diameter pellets. The product had an average concentration of 84 wt% YBa_2Cu _3O_{rm 6 + x}. In the vertical SHS process, with the aid of a booster, the combustion front moved more rapidly and smoothly than that in the horizontal SHS process and gave a product concentration of about 90 wt% YBa _2Cu_3O_ {rm 6 + x}. High quality product (above 95 wt% YBa_2Cu_3 O_{rm 6 + x}) may be obtained by sintering/calcining the SHS product in an oxygen atmosphere. Three different sintering/calcining processes were studied and the required temperature and the time for each process were determined. The temperature at the center of the pellet in a vertical SHS was measured by thermocouples. The pellet temperature rise is a two step process. The first temperature rise is caused by the oxidation of the copper and the second is caused by the reaction between yttrium oxide and barium cuprate. A reaction mechanism is proposed to explain this behavior. A thermal explosion process was conducted in a continuous rotary kiln. In this mode a pellet was introduced suddenly into a heated rotary kiln causing it to be combusted. After the combustion, the pellet was sintered at 900 to 980 ^circC and a product containing about 95 wt% YBa_2Cu_3 O_{rm 6 + x} was obtained. The impacts of the thermal explosion temperature and the sintering conditions on the product quality were studied. The best temperature was found to be 800 ^circC and 100 minutes was sufficient for the pellet to reach equilibrium.

  13. Combustion of Na 2B 4O 7 + Mg + C to synthesis B 4C powders

    NASA Astrophysics Data System (ADS)

    Guojian, Jiang; Jiayue, Xu; Hanrui, Zhuang; Wenlan, Li

    2009-09-01

    Boron carbide powder was fabricated by combustion synthesis (CS) method directly from mixed powders of borax (Na 2B 4O 7), magnesium (Mg) and carbon. The adiabatic temperature of the combustion reaction of Na 2B 4O 7 + 6 Mg + C was calculated. The control of the reactions was achieved by selecting reactant composition, relative density of powder compact and gas pressure in CS reactor. The effects of these different influential factors on the composition and morphologies of combustion products were investigated. The results show that, it is advantageous for more Mg/Na 2B 4O 7 than stoichiometric ratio in Na 2B 4O 7 + Mg + C system and high atmosphere pressure in the CS reactor to increase the conversion degree of reactants to end product. The final product with the minimal impurities' content could be fabricated at appropriate relative density of powder compact. At last, boron carbide without impurities could be obtained after the acid enrichment and distilled water washing.

  14. Glycerol-assisted solution combustion synthesis of improved LiMn2O4

    NASA Astrophysics Data System (ADS)

    Liu, Guiyang; Xin, Kong; Zhang, Lili; Wang, Baosen; He, Ying

    2013-08-01

    Spinel LiMn2O4 has been synthesized by a glycerol-assisted combustion synthesis method. The phase composition and morphologies of the compound were ascertained by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrochemical characterization was performed by using CR2032 coin-type cell. XRD analysis indicates that single phase spinel LiMn2O4 with good crystallinity has been obtained as a result of 5 h treatment at 600 °C. SEM investigation indicates that the average particle size of the sample is 200 nm. The initial discharge specific capacity of the LiMn2O4 is 123 mAh/g at a current density of 30 mA/g. When the current density increased to 300 mA/g, the LiMn2O4 offered a discharge specific capacity of 86 mAh/g. Compared with the LiMn2O4 prepared by a conventional solution combustion synthesis method at the same temperature, the prepared LiMn2O4 possesses higher purity, better crystallinity and more uniformly dispersed particles. Moreover, the initial discharge specific capacity, rate capability and cycling performance of the prepared LiMn2O4 are significantly improved.

  15. Combustion synthesis of Ni3Al and Ni3Al-matrix composites

    NASA Astrophysics Data System (ADS)

    Lebrat, J. P.; Varma, A.; Miller, A. E.

    1992-01-01

    The self-propagating mode of combustion synthesis (SHS) of Ni3Al starting from compacts of stoichiometrically mixed Ni and Al powders readily forms fully reacted structures with about 3 to 5 pct porosity, if green density of the compacts is greater than about 75 pct of theoretical. SHS-produced Ni3Al matrix composites with up to 2 wt pct A12O3 whiskers also have relatively low porosity levels. Porosity increases rapidly with lower green densities, higher Al2O3, or SiC whisker contents, and the degree of reaction completeness diminishes. The SiC whiskers undergo reaction with the matrix, while Al2O3 whiskers are nonreactive. All of these observations correlate well with temperature measurements made during the course of the reaction. The SHS mode can be achieved with agglomerated particle size ratio D Al/ D Ni ? 1, larger than the limit established from studies of the thermal explosion mode of combustion synthesis D Al/ D Ni ? 0.3.

  16. MINIMIZATION OF TOXIC COMBUSTION BYPRODUCTS: REVIEW OF CURRENT ACTIVITIES

    EPA Science Inventory

    In general, toxic combustion byproducts (TCBS) are the unwanted residues remaining in flue gases, combustion ashes, and wastewaters from the operation of an incineration or combustion facility. f a combustor is not well designed and operated, it may emit too high a level of TCBS....

  17. Influence of high gas pressure on combustion synthesis of the solid–solid reaction of NiAl compound

    Microsoft Academic Search

    R. M. Marin-Ayral; M. C. Dumez; J. C. Tédenac

    2000-01-01

    We show the advantage of using high gas pressure in the improvement of combustion synthesis conditions for NiAl compound synthesis. Experiments on high pressure of argon between 10 and 500 MPa showed that the exothermicity of Ni–Al reactions was considerably reduced, with a complete reaction giving NiAl compound. Thermodynamic and kinetic studies were carried out. The results indicate that pressure

  18. Effects of calcium nitride and calcium carbonate gasifying agents on the porosity of Ni 3 Ti–TiC composites produced by combustion synthesis

    Microsoft Academic Search

    Douglas E. Burkes; Jack Milwid; Guglielmo Gottoli; John J. Moore

    2006-01-01

    Combustion synthesis or Self-propagating High Temperature Synthesis (SHS) has been used to produce highly porous materials\\u000a intended for biomedical applications. Two novel gasifying agents, calcium nitride and calcium carbonate, were employed to\\u000a increase product porosity and pore size during the combustion synthesis reaction for two SHS chemical compositions. A greater\\u000a increase in apparent porosity of the products was gained using

  19. Combustion characteristics and influential factors of isooctane active-thermal atmosphere combustion assisted by two-stage reaction of n-heptane

    SciTech Connect

    Lu, Xingcai; Ji, Libin; Ma, Junjun; Zhou, Xiaoxin; Huang, Zhen [Key Lab. for Power Machinery and Engineering of MOE, Shanghai Jiao Tong University, 200240 Shanghai (China)

    2011-02-15

    This paper presents an experimental study on the isooctane active-thermal atmosphere combustion (ATAC) which is assisted by two-stage reaction of n-heptane. The active-thermal atmosphere is created by low- and high-temperature reactions of n-heptane which is injected at intake port, and isooctane is directly injected into combustion chamber near the top dead center. The effects of isooctane injection timing, active-thermal atmosphere intensity, overall equivalence ratio, and premixed ratio on combustion characteristics and emissions are investigated. The experimental results reveal that, the isooctane ignition and combustion can be classified to thermal atmosphere combustion, active atmosphere combustion, and active-thermal atmosphere combustion respectively according to the extent of n-heptane oxidation as well as effects of isooctane quenching and charge cooling. n-Heptane equivalence ratio, isooctane equivalence ratio and isooctane delivery advance angle are major control parameters. In one combustion cycle, the isooctane ignited and burned after those of n-heptane, and then this combustion phenomenon can also be named as dual-fuel sequential combustion (DFSC). The ignition timing of the overall combustion event is mainly determined by n-heptane equivalence ratio and can be controlled in flexibility by simultaneously adjusting isooctane equivalence ratio. The isooctane ignition regime, overall thermal efficiency, and NO{sub x} emissions show strong sensitivity to the fuel delivery advance angle between 20 CA BTDC and 25 CA BTDC. (author)

  20. Hydrothermal Synthesis of Lanthanide Stannates Pyrochlore Nanocrystals for Catalytic Combustion of Soot Particulates

    PubMed Central

    2015-01-01

    Nanocrystalline La2Sn2O7 and La2Sn1.8Co0.2O7 with a phase-pure pyrochlore structure were synthesized by a hydrothermal method, and their catalytic activity was investigated for soot combustion. The as-synthesized catalysts presented relatively larger surface area, and pore volume, which was benefit to the gas molecule diffusion in the reaction. A uniform spherical structure with particle size of 200–500?nm was found in SEM. The samples via hydrothermal route are more active for catalytic soot combustion, ascribing to the spherical morphology, high surface area and improved oxygen mobility. After Co, the reducibility was improved and surface oxygen vacancy was produced, resulting in the enhanced activity and selectivity to CO2 formation.

  1. DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

    SciTech Connect

    Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

    2003-09-30

    The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, the principal objective of this work was to characterize and utilize the unburned carbon in fly ash for the production of activated carbons. The unburned carbon samples were collected from different combustion systems, including pulverized utility boilers, a utility cyclone, a stoker, and a fluidized bed combustor. LOI (loss-on-ignition), proximate, ultimate, and petrographic analyses were conducted, and the surface areas of the samples were characterized by N2 adsorption isotherms at 77K. The LOIs of the unburned carbon samples varied between 21.79-84.52%. The proximate analyses showed that all the samples had very low moisture contents (0.17 to 3.39 wt %), while the volatile matter contents varied between 0.45 to 24.82 wt%. The elemental analyses show that all the unburned carbon samples consist mainly of carbon with very little hydrogen, nitrogen, sulfur and oxygen In addition, the potential use of unburned carbon as precursor for activated carbon (AC) was investigated. Activated carbons with specific surface area up to 1075m{sup 2}/g were produced from the unburned carbon. The porosity of the resultant activated carbons was related to the properties of the unburned carbon feedstock and the activation conditions used. It was found that not all the unburned carbon samples are equally suited for activation, and furthermore, their potential as activated carbons precursors could be inferred from their physical and chemical properties. The developed porosity of the activated carbon was a function of the oxygen content, porosity and H/C ratio of the parent unburned carbon feedstock. It was observed that extended activation times and high activation temperatures increased the porosity of the produced activated carbon at the expense of the solid yield. The development of activated carbon from unburned carbon in fly ash has been proven to be a success by this study in terms of the higher surface areas of the resultant activated carbons, which are comparable with commercial activated carbons. However, unburned carbon samples obtained from coal-fired power plants as by-product have high ash content, which is unwanted for the production of activated carbons. Therefore, the separation of unburned carbon from the fly ash is expected to be beneficial for the utilization of unburned carbon to produce activated carbons with low ash content.

  2. Combustion synthesis of metal-matrix composites: Part III, the Al-Tic-Al 2O 3 system

    Microsoft Academic Search

    A. O. Kunrath; T. R. Strohaecker; J. J. Moore

    1996-01-01

    The principle of combustion synthesis to produce metal matrix composites has been outlined in earlier papers. Applying pressure either during or immediately after the reaction is completed is the most commonly used method to achieve high densification of the synthesized products. Some advanced ceramics (TiC and TiBâ) have been reported to achieve up to 95% of theoretical density using this

  3. Historical perspective and contribution of US researchers into the field of self-propagating high-temperature synthesis (SHS)\\/combustion synthesis (CS): Personal reflections

    Microsoft Academic Search

    J. W. McCauley; J. A. Puszynski

    2008-01-01

    In 1967, Merzhanov, Skhiro, and Borovinskaya published the first comprehensive paper describing self-sustaining character of reactions in a condensed phase, which could be utilized for synthesis of many ceramic and intermetallic materials [1]. In this paper, the authors demonstrated the principle of the so called “solid flame” using reactions between transition metals and boron, carbon or nitrogen. The world-wide combustion

  4. Effect Of Gravity On Porous Tricalcium Phosphate And Nonstoichiometric Titanium Carbide Produced Via Combustion Synthesis

    NASA Technical Reports Server (NTRS)

    Castillo, M.; Moore, J. J.; Schowengerdt, F. D.; Ayers, R. A.

    2003-01-01

    Novel processing techniques, such as self-propagating high temperature synthesis (SHS), have the capability to rapidly produce advanced porous materials that are difficult to fabricate by other methods. This processing technique is also capable of near net shape synthesis, while variable gravity allows the manipulation of the structure and composition of the material. The creation of porous tricalcium phosphate (TCP) is advantageous in the biomaterials field, since it is both a biocompatible material and an osteoconductive material. Porous tricalcium phosphate produced via SHS is an excellent candidate for bone scaffold material in the bone regeneration process. The porosity allows for great vascularization and ingrowth of tissue. Titanium Carbide is a nonstoichiometric biocompatible material that can be incorporated into a TiC-Ti composite system using combustion synthesis. The TiC-Ti composite exhibits a wide range of mechanical and chemical properties. Both of these material systems (TCP and TiC-Ti) can be used to advantage in designing novel bone replacement materials. Gravity plays an important role in both the pore structure and the chemical uniformity of these composite systems and offers considerable potential in advanced bone engineering.

  5. Validation of model based active control of combustion instability

    SciTech Connect

    Fleifil, M.; Ghoneim, Z.; Ghoniem, A.F.

    1998-07-01

    The demand for efficient, company and clean combustion systems have spurred research into the fundamental mechanisms governing their performance and means of interactively changing their performance characteristics. Thermoacoustic instability which is frequently observed in combustion systems with high power density, when burning close to the lean flammability limit, or using exhaust gas recirculation to meet more stringent emissions regulations, etc. Its occurrence and/or means to mitigate them passively lead to performance degradation such as reduced combustion efficiency, high local heat transfer rates, increase in the mixture equivalence ratio or system failure due to structural damage. This paper reports on their study of the origin of thermoacoustic instability, its dependence on system parameters and the means of actively controlling it. The authors have developed an analytical model of thermoacoustic instability in premixed combustors. The model combines a heat release dynamics model constructed using the kinematics of a premixed flame stabilized behind a perforated plate with the linearized conservation equations governing the system acoustics. This formulation allows model based controller design. In order to test the performance of the analytical model, a numerical solution of the partial differential equations governing the system has been carried out using the principle of harmonic separation and focusing on the dominant unstable mode. This leads to a system of ODEs governing the thermofluid variables. Analytical predictions of the frequency and growth ate of the unstable mode are shown to be in good agreement with the numerical simulations as well s with those obtained using experimental identification techniques when applied to a laboratory combustor. The authors use these results to confirm the validity of the assumptions used in formulating the analytical model. A controller based on the minimization of a cost function using the LQR technique has been designed using the analytical model and implemented on a bench top laboratory combustor. The authors show that the controller is capable of suppressing the pressure oscillations in the combustor with a settling time much shorter than what had been attained before and without exciting secondary peaks.

  6. Optical filtering and luminescence property of some molybdates prepared by combustion synthesis

    NASA Astrophysics Data System (ADS)

    Yadav, P. J.; Joshi, C. P.; Moharil, S. V.

    2014-10-01

    As an important class of lanthanide inorganic compounds, rare earth ions doped molybdates have gained much attention due to their attractive luminescence and structural properties, supporting various promising applications as phosphor materials in the fields such as white light-emitting diodes, optical fibers, biolabel, lasers, and so on. The molybdate family has promising trivalent cation conducting properties and most of the optical properties result from electron transitions of the 4f shell, which are greatly affected by the composition and structures of rare-earth compounds. In this paper we report the molybdate CaMoO4:Eu3+ for red SSL and Bi1.4Y0.6MoO6, Y6MoO12 for optical filtering, prepared by one step combustion synthesis.

  7. Development and characterization of Mn2+-doped MgO nanoparticles by solution combustion synthesis

    NASA Astrophysics Data System (ADS)

    Basha, Md. Hussain; Gopal, N. O.; Rao, J. L.; Nagabhushana, H.; Nagabhushana, B. M.; Chakradhar, R. P. S.

    2015-06-01

    Mn doped MgO Nanoparticles have been prepared by Solution Combustion Synthesis. The synthesized sample is characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Electron Paramagnetic Resonance (EPR). The prepared MgO:Mn (1 mol%) nano crystals appear to be of simple cubic crystalline phase with lattice parameters a = 4.218(2) Å and cell volume = 74.98 (7) Å3. SEM micrograph of powders show highly porous, many agglomerates with irregular morphology, large voids, cracks and pores. EPR spectrum of the sample at room temperature exhibit an isotropic sextet hyperfine pattern, centered at g=1.99, characteristic if Mn2+ ions with S=I=5/2.The observed g value and the hyperfine value reveal the ionic bonding between Mn2+ and its surroundings.

  8. Red-emitting AlN:Mn2+ phosphors prepared by combustion synthesis

    NASA Astrophysics Data System (ADS)

    Shi, Zhongqi; Zou, Yongyong; Jing, Ruifeng; Zhang, Kuo; Qiao, Guanjun; Wang, Hongjie

    2015-12-01

    Red-emitting Mn2+-doped AlN(AlN:Mn2+) phosphors were successfully prepared by a highly effective combustion synthesis method. The phase purity, morphology, element-composition and luminescence properties of the synthesized phosphors were investigated. X-ray diffraction (XRD) results show that the Mn2+-doped into the AlN host did not induce a second phase and distort the structure significantly. Scanning electron microscopy (SEM) images display that the phosphors have an irregular shape with a particle size in the range of 1-5 ?m. X-ray photoelectron spectroscopy (XPS) spectrum indicates that Mn ions are divalent state. The synthesized AlN:Mn2+ phosphors exhibit a strong red emission centered at 600 nm, which is ascribe to the 4T1(4G)-6A1(6S) transition of Mn2+ under ultraviolet excitation. The emission intensity reaches its maximum when Mn2+-doped concentration is 3 mol%.

  9. Different toxic mechanisms are activated by emission PM depending on combustion efficiency

    NASA Astrophysics Data System (ADS)

    Uski, O.; Jalava, P. I.; Happo, M. S.; Leskinen, J.; Sippula, O.; Tissari, J.; Mäki-Paakkanen, J.; Jokiniemi, J.; Hirvonen, M.-R.

    2014-06-01

    Ambient air levels of fine particulate matter (PM ? 2.5 ?m) are associated with mortality and morbidity. In addition to traffic, large quantities of fine and ultrafine particles (UFPs ? 100 nm) are emitted by residential wood combustion. Polycyclic aromatic hydrocarbon (PAH) and soot-rich emissions from small scale heating appliances have been linked with a plethora of toxicological effects. Recently, new technology appliances have been introduced into use although there are several uncertainties related to the toxicological properties of those emissions. In this study, PM1 (PM ? 1 ?m) emissions from three different biomass combustion situations were compared. PM samples were produced in a novel adjustable biomass combustion reactor to avoid the problems encountered if one uses different appliances to generate the desired combustion conditions. The combustion conditions represented efficient, intermediate and smoldering situations. The concentration related effects of the particles (15, 50,150 and 300 ?g ml-1) were investigated in a RAW264.7 macrophage cell line after 24 h' exposure. We analyzed cellular metabolic activity, cell cycle, and indicators of genotoxicty, oxidative stress and proinflammatory responses. Interestingly, the particles collected from smoldering and intermediate combustion conditions decreased cellular metabolic activity less than those from efficient combustion (10-fold difference). However, the samples from intermediate and smoldering combustion evoked greater DNA damage in the comet assay (2.5-fold difference). In contrast, only the particulate samples from efficient combustion triggered G2-cell cycle arrest and oxidative stress in the macrophages. These results indicate that ash rich PM emissions from appliances with almost complete combustion may still exert health impacts. However, particulate emissions from efficient combustion were small when compared to the two other situations. Thus, even with their faults and the obvious need for development, consumers should be encouraged to purchase efficient combustion devices in order to reduce exposure to PM induced adverse health effects.

  10. Method and apparatus for active control of combustion rate through modulation of heat transfer from the combustion chamber wall

    DOEpatents

    Roberts, Jr., Charles E.; Chadwell, Christopher J.

    2004-09-21

    The flame propagation rate resulting from a combustion event in the combustion chamber of an internal combustion engine is controlled by modulation of the heat transfer from the combustion flame to the combustion chamber walls. In one embodiment, heat transfer from the combustion flame to the combustion chamber walls is mechanically modulated by a movable member that is inserted into, or withdrawn from, the combustion chamber thereby changing the shape of the combustion chamber and the combustion chamber wall surface area. In another embodiment, heat transfer from the combustion flame to the combustion chamber walls is modulated by cooling the surface of a portion of the combustion chamber wall that is in close proximity to the area of the combustion chamber where flame speed control is desired.

  11. Particle in cell simulation of combustion synthesis of TiC nanoparticles

    NASA Astrophysics Data System (ADS)

    Zuccaro, G.; Lapenta, G.; Maizza, G.

    2004-09-01

    A coupled continuum-discrete numerical model is presented to study the synthesis of TiC nanosized aggregates during a self-propagating combustion synthesis (SHS) process. The overall model describes the transient of the basic mechanisms governing the SHS process in a two-dimensional micrometer size system. At each time step, the continuum (micrometer scale) model computes the current temperature field according to the prescribed boundary conditions. The continuum system is discretized with a desired number of uniform computational cells. Each cell contains a convenient number of computational particles which represent the actual particles mixture. The particle-in-cell (discrete) model maps the temperature field from the (continuum) cells to the particles. Depending on the temperature reached by the cell, the titanium particles may undergo a solid-liquid transformation. If the distance between the carbon particle and the liquid titanium particles is within a certain tolerance they react and a TiC particle is formed in the cell. Accordingly, the molecular dynamic method updates the location of all particles in the cell and the amount of transformation heat accounted by the cell is entered into the source term of the (continuum) heat conduction equation. The new temperature distribution progresses depending on the cells which undergo the chemical reaction. As a demonstration of the effectiveness of the overall model some examples are shown.

  12. Study of wear of combustion engines by means of thin layer activation using accelerated charged particles

    NASA Astrophysics Data System (ADS)

    Stan-Sion, C.; Plostinaru, D.; Ivanov, E. A.; Catana, M.

    1994-08-01

    The improvement of running-in programs for internal combustion engines by using the thin layer activation technique is presented. The wear was measured as function of time, simultaneously for cylinder walls and piston rings.

  13. Combustion synthesis of ceramic-metal composite materials - The TiC-Al2O3-Al system

    NASA Technical Reports Server (NTRS)

    Feng, H. J.; Moore, John J.; Wirth, D. G.

    1992-01-01

    Combustion synthesis was applied for producing ceramic-metal composites with reduced levels of porosity, by allowing an excess amount of liquid metal, generated by the exothermic reaction during synthesis, to infiltrate the pores. It is shown that this method, when applied to TiC-Al2O3 system, led to a decreased level of porosity in the resulting TiC-Al2O3-Al product, as compared with that of TiC-Al2O3 system. This in situ procedure is more efficient than the two-stage conventional processes (i.e., sintering followed by liquid metal infiltration), although there are limitations with respect to total penetration of the liquid metal and maintaining a stable propagation of the combustion reaction.

  14. Microstructure and kinetics of a functionally graded NiTi–TiC x composite produced by combustion synthesis

    Microsoft Academic Search

    Douglas E. Burkes; John J. Moore

    2007-01-01

    Production of a NiTi–TiCx functionally graded material (FGM) composite is possible through use of a combustion synthesis (CS) reaction employing the propagating mode (SHS). The NiTi–TiCx FGM combines the well-known and understood superelastic and shape memory capabilities of NiTi with the high hardness, wear and corrosion resistance of TiCx. The material layers were observed as functionally graded both in composition

  15. Production of Ni3Ti-TiC x intermetallic-ceramic composites employing combustion synthesis reactions

    Microsoft Academic Search

    Douglas E. Burkes; Guglielmo Gottoli; John J. Moore; Hu Chun Yi

    2006-01-01

    Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi-TiC (stoichiometric) or Ni3Ti-TiC x (nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be synthesized. The stoichiometry of TiC x , for

  16. Combustion Synthesis of PrBa 2 Cu 3 O 7?? and YBa 2 Cu 3 O 7?? cuprate materials

    Microsoft Academic Search

    N. Sehab; A. Harat; A. Benaldjia; A. Amara; M. Guerioune; G. Fillion; D. Vrel; P. Langlois

    2009-01-01

    PrBaCuO and YBaCuO cuprate materials were prepared from cooper, barium peroxide, and yttrium\\/praseodymium oxide by SHS and\\u000a standard solid-state synthesis. SHS reactions were carried out using relatively large cooper particles (< 63 im) to obtain\\u000a small product samples (13 mm in diameter). High ambient temperature was used to stabilize a combustion front in the ignited\\u000a pellets. Explored was the effect

  17. Sucrose combustion synthesis of La x Sr (1? x )MnO 3 ( x ? 0.2) powders

    Microsoft Academic Search

    K. Prabhakaran; Jorly Joseph; N. M. Gokhale; S. C. Sharma; Ramji Lal

    2005-01-01

    An energy efficient combustion synthesis has been used for the preparation of nanocrystalline LSM powder of composition La1?xSrxMnO3 (x < 0.2) using sucrose as a polymerisable fuel. Nitrate salt of La3+ and Sr2+ and acetate of Mn2+ were dissolved in water along with sucrose and concentrated by heating in to the form of a viscous resin which is then transformed

  18. Preparation of niobium borides NbB and NbB 2 by self-propagating combustion synthesis

    Microsoft Academic Search

    C. L. Yeh; W. H. Chen

    2006-01-01

    Preparation of niobium borides NbB and NbB2 was conducted by self-propagating high-temperature synthesis (SHS) from elemental powder compacts in this study. Effects of the sample green density, preheating temperature and starting stoichiometry on combustion characteristics, as well as on the composition of final products were studied. Experimental evidence indicates the self-sustained reaction zone propagating along a spiral trajectory for the

  19. Synthesis and Antibacterial Activities of Yanglingmycin Analogues.

    PubMed

    Li, Long-Bo; Dan, Wen-Jia; Tan, Fang-Fang; Cui, Li-Hui; Yuan, Zhi-Peng; Wu, Wen-Jun; Zhang, Ji-Wen

    2014-10-30

    The synthesis of Yanglingmycin and its enantiomer, along with eighteen Yanglingmycin analogues is reported. The structures were confirmed mainly by analyses of NMR spectral data. Antibacterial activity assays showed that Yanglingmycin and some of its analogues exhibited significant antibacterial activities against two important agricultural pathogenic bacteria, Ralstonia solanacearum and Pseudomonas syringae pv. actinidiae, with MIC values ranging from 3.91 to 15.62 ?g/mL. The antibacterial activities exhibited by Yanglingmycin and its analogues are promising, suggesting potential in the development of compounds for novel bactericides. PMID:25355464

  20. Synthesis and antibacterial activities of Yanglingmycin analogues.

    PubMed

    Li, Long-Bo; Dan, Wen-Jia; Tan, Fang-Fang; Cui, Li-Hui; Yuan, Zhi-Peng; Wu, Wen-Jun; Zhang, Ji-Wen

    2015-01-01

    The synthesis of Yanglingmycin and its enantiomer, along with eighteen Yanglingmycin analogues is reported. The structures were confirmed mainly by analyses of NMR spectral data. Antibacterial activity assays showed that Yanglingmycin and some of its analogues exhibited significant antibacterial activities against two important agricultural pathogenic bacteria, Ralstonia solanacearum and Pseudomonas syringae pv. actinidiae, with minimum inhibitory concentration (MIC) values ranging from 3.91 to 15.62?µg/mL. The antibacterial activities exhibited by Yanglingmycin and its analogues are promising, suggesting potential in the development of compounds for novel bactericides. PMID:25743192

  1. Combustion synthesis/quasi-isostatic pressing of TiC0.7NiTi cermets: microstructure and transformation characteristics

    E-print Network

    Meyers, Marc A.

    Combustion synthesis/quasi-isostatic pressing of TiC0.7­NiTi cermets: microstructure Abstract TiC0.7­NiTi cermets were produced by com- bustion synthesis followed by quasi-isostatic consolidation while the reaction products were still hot and ductile. The TiC0.7­NiTi cermets were characterized

  2. Structural and spectroscopic analyses of europium doped yttrium oxyfluoride powders prepared by combustion synthesis

    SciTech Connect

    Rakov, Nikifor [PG-Ciência dos Materiais, Universidade Federal do Vale do São Francisco, 48902-300 Juazeiro, BA (Brazil)] [PG-Ciência dos Materiais, Universidade Federal do Vale do São Francisco, 48902-300 Juazeiro, BA (Brazil); Guimarães, R. B.; Maciel, Glauco S. [Instituto de Física, Universidade Federal Fluminense, 24210-346 Niterói, RJ (Brazil)] [Instituto de Física, Universidade Federal Fluminense, 24210-346 Niterói, RJ (Brazil); Lozano B, W. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil)] [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil)

    2013-07-28

    A facile widely spread technique employed to produce low-cost high-yield oxide powders, combustion synthesis, was used to prepare yttrium oxyfluoride crystalline ceramic powders. The structure of the powders was analyzed by X-ray powder diffraction and Rietveld refinement. Samples heat treated at 700 °C had a predominance of vernier orthorhombic Y{sub 6}O{sub 5}F{sub 8} phase, while samples heat treated at 800 °C crystallized in stoichiometric rhombohedral YOF phase. The samples were doped with luminescent europium trivalent ions (Eu{sup 3+}) in different concentrations (1–15 wt.%) and Judd-Ofelt theory was used to probe the distortion from the inversion symmetry of the local crystal field and the degree of covalency between the rare-earth ion and the surrounding ligands. The luminescence lifetime was measured and the luminescence quantum efficiency (LQE) was estimated. We observed that Eu{sup 3+}:Y{sub 6}O{sub 5}F{sub 8} samples presented higher LQE in spite of the larger local crystal field anisotropy found for Eu{sup 3+}:YOF samples.

  3. Field-assisted combustion synthesis of MoSi[sub 2]-SiC composites

    SciTech Connect

    Gedevanishvili, S.; Munir, Z.A. (Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science)

    1994-09-15

    No investigation on the use of self-propagating high-temperature synthesis (SHS) to prepare MoSi[sub 2]/SiC composites has been reported. Reactions to synthesize such composites from elemental powders are not strongly energetic and thus cannot become self-sustaining without the pre-heating of the reactants. The adiabatic combustion temperature of MoSi[sub 2] is 1,900 K, which is at the empirically defined boundary between the occurrence and absence of SHS reactions. Since the adiabatic temperature of SiC is 1,800 K, that of the composite MoSi[sub 2] + x SiC is less than 1,900 K for any value of x. Through the application of an electric field, the authors have recently been successful in forming a variety of materials which are difficult or impossible to prepare by SHS. They report here the results of the first demonstration of the use of SHS to prepare MoSi[sub 2] + x SiC composites for 0 [le] x [le] 1.0.

  4. Auto-combustion synthesis and characterization of Mg doped CuAlO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Agrawal, Shraddha; Parveen, Azra; Naqvi, A. H.

    2015-06-01

    The synthesis of pure and Mg doped Copper aluminumoxide CuAlO2nanoparticles, a promising p-type TCO (transparent conducting oxide) have been done bysol gel auto combustion method using NaOH as a fuel, calcinated at 600°C. The structural properties were examined by XRD and SEM techniques. The optical absorption spectra of CuAlO2 sample recorded by UV-VIS spectrophotometer in the range of 200 to 800 nm have been presented. The crystallite size was determined by powder X-ray diffraction technique. The electrical behavior of pure and Mg doped CuAlO2 has been studied over a wide range of frequencies by using complex impedance spectroscopy.The variation of a.c. conductivity has been studied as function of frequency and temperature. The data taken together conclude that doping causes decreases in the ac conductivity of the nanoparticles as compared with the pure nanoparticles. Mg doping affects the optical properties and band gap.

  5. Highly aluminium doped barium and strontium ferrite nanoparticles prepared by citrate auto-combustion synthesis

    SciTech Connect

    Shirtcliffe, Neil J. [Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8NS (United Kingdom)]. E-mail: neil.shirtcliffe@ntu.ac.uk; Thompson, Simon [Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8NS (United Kingdom); O'Keefe, Eoin S. [QinetiQ, Farnborough, Hampshire (United Kingdom); Appleton, Steve [QinetiQ, Farnborough, Hampshire (United Kingdom); Perry, Carole C. [Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8NS (United Kingdom)]. E-mail: carole.perry@ntu.ac.uk

    2007-02-15

    Aluminium doped barium and strontium hexaferrite nanoparticles BaAl {sub x}Fe{sub (12-x)}O{sub 19} and SrAl {sub x}Fe{sub (12-x)}O{sub 19} were synthesised via a sol-gel route using citric acid to complex the ions followed by an auto-combustion reaction. This method shows promise for the synthesis of complex ferrite powders with small particle size. It was found that around half of the iron could be substituted for aluminium in the barium ferrite with structure retention, whereas strontium aluminium ferrites could be produced with any aluminium content including total substitution of the iron. All synthesised materials consisted of particles smaller than 1 {mu}m, which is the size of a single magnetic domain, and various doping levels were achieved with the final elemental composition being within the bounds of experimental error. The materials show structural and morphological changes as they move from iron to aluminium ferrites. Such materials may be promising for imaging applications.

  6. DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

    Microsoft Academic Search

    Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

    2001-01-01

    The implementation of increasingly stringent Clean Air Act Regulations by the coal utility industry has resulted in an increase in the concentration of unburned carbon in coal combustion fly ash. In 1999, around 6 million tons of unburned carbon were disposed in the US, due to the present lack of efficient routes for its utilization. However, unburned carbon is a

  7. Optimization of the low temperature combustion synthesis of Er3+ doped lead-natrium-yttrium-fluoride phosphor

    NASA Astrophysics Data System (ADS)

    Lu, Liping; Zhang, Xiyan

    2014-12-01

    The low-temperature combustion synthesis (LCS) method is the most popular method for the synthesis of ultrafine oxides and compound oxides. A kind of Er-Y-Pb-Na quaternary fluoride sensitive to 1.55 ?m was synthesized by the LCS method and the synthesis conditions were optimized with orthogonal experiments. Intense upconversion emissions at 522 nm, 541.4 nm and 654.7 nm corresponding to the 2H11/2, 4S3/2 and 4F9/2 transitions to the 4I15/2 ground state were observed when excited by CW laser radiation at 1.55 ?m. The effect of the carbamide amount on the phase formation and the luminescence intensity was analyzed. The product is of uniform particle size of ca. 40 nm, which is very outstanding for its reutilization in the infrared detection field.

  8. Influence of thermal conditions on the combustion synthesis of Si{sub 2}N{sub 2}O phase

    SciTech Connect

    Pradeilles, N. [Laboratoire de Physicochimie de la Matiere Condensee, LPMC UMR 5617, Universite Montpellier II cc003, Place Eugene Bataillon 34095 Montpellier Cedex 5 (France); Record, M.C. [Laboratoire TECSEN, UMR 6122, cc251, UPCAM Aix-Marseille III, Avenue de l'escadrille Normandie Niemen 13397 Marseille Cedex 20 (France); Marin-Ayral, R.M. [Laboratoire de Physicochimie de la Matiere Condensee, LPMC UMR 5617, Universite Montpellier II cc003, Place Eugene Bataillon 34095 Montpellier Cedex 5 (France)], E-mail: ayral@lpmc.univ-montp2.fr; Linde, A.V.; Studenikin, I.A.; Grachev, V.V. [Institute of Structural Macrokinetics and Materials Science (ISMAN), Chernogolovka, Moscow Region 142432 (Russian Federation)

    2008-02-05

    This work is a contribution to the study of Si{sub 2}N{sub 2}O synthesis via Self-Propagating High-temperature Synthesis (SHS). The elaboration of Si{sub 2}N{sub 2}O was carried out using two kinds of experimental equipments and differences both in reaction temperatures and in products compositions were evidenced. In order to determine the reaction mechanisms, several compositions and thermal conditions of the reactant mixture were studied. Considering our results, two kinds of reaction mechanisms for the combustion synthesis of Si{sub 2}N{sub 2}O could be suggested. Furthermore, the results previously reported in the literature have been explained in the light of this work. The SHS samples were characterized by X-ray diffraction and scanning electron microscopy (SEM) analysis. Their quantitative compositions were determined by Rietveld refinement.

  9. DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

    Microsoft Academic Search

    Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

    2000-01-01

    The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly fly ash containing unburned carbon. However, the carbonaceous residue in fly ash, unburned carbon (UC), is a potential precursor for the production of adsorbent carbons, since it has gone through a

  10. DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

    Microsoft Academic Search

    Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

    2003-01-01

    The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization.

  11. DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

    Microsoft Academic Search

    Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

    2002-01-01

    The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization.

  12. Combustion synthesis of MgO nanoparticles using plant extract: Structural characterization and photoluminescence studies

    NASA Astrophysics Data System (ADS)

    Kumar, Danith; Yadav, L. S. Reddy; Lingaraju, K.; Manjunath, K.; Suresh, D.; Prasad, Daruka; Nagabhushana, H.; Sharma, S. C.; Naika, H. Raja; Chikkahanumantharayappa, Nagaraju, G.

    2015-06-01

    Magnesium oxide nanoparticles (MgO Nps) have been successfully synthesized via solution combustion method using Parthenium plant extract as fuel for the first time. Powder X-ray diffraction (PXRD) pattern reveal that product belongs to the cubic phase (Periclase). FTIR spectrum shows the band at 822 cm-1 indicates the formation of cubic periclase MgO. The optical band gap of MgO Nps estimated from UV -Vis spectrum was found to be in the range 5.40-5.45 eV. SEM images showed that, the product is agglomerated and particle in nature. Photoluminescence (PL) studies shows violet emission at 390 nm, blue emission at 470 nm and green emission at 550 nm. MgO Nps shows good photocatalytic activity for the degradation of methylene blue (MB) dye under UV/Sun light irradiation.

  13. Supported cobalt catalysts by one-pot aqueous combustion synthesis for catalytic phenol degradation.

    PubMed

    Sun, Hongqi; Liang, Hanwen; Zhou, Guanliang; Wang, Shaobin

    2013-03-15

    Cobalt oxides (Co) and Al(2)O(3)-, SiO(2)-, and TiO(2)-supported cobalt oxide catalysts were prepared by an aqueous combustion method using urea and glycine as fuels. Their catalytic performance in activation of OXONE® for phenol degradation in aqueous solution was investigated. It was found that unsupported Co oxide and supported Co oxide presented different mechanisms in activation of OXONE® for phenol degradation. The supported Co catalysts presented higher activity in activation of OXONE® for phenol degradation due to higher dispersion of Co(3)O(4) on the supports and Co(II) coordination sites. The major oxidizing radicals were identified to be SO(4)(-) by competitive radical reactions. The Co oxides synthesized from urea or glycine showed a similar activity; however, the supported Co catalysts prepared by glycine fuel exhibited better activity than those prepared by urea. For Al(2)O(3)-, SiO(2)-, and TiO(2)-supported Co catalysts, Co/TiO(2) presented a higher activity in phenol degradation compared with Co/SiO(2) and Co/Al(2)O(3). But, Co/SiO(2) showed the best stability among the catalysts. Total organic carbon could be reduced by 80%, 72%, and 45% on Co/TiO(2), Co/SiO(2), and Co/Al(2)O(3), respectively, at 30 ppm phenol. Phenol degradation was found to follow the zero-order kinetics. The causes of deactivation were investigated, and the regeneration methods were proposed. PMID:23261351

  14. Self-propagating high temperature synthesis for compound thermoelectrics and new criterion for applicability of combustion processing

    NASA Astrophysics Data System (ADS)

    Tang, Xinfeng; Su, Xianli; Uher, Ctirad; Tang's Group Team; Uher's Group Team

    2015-03-01

    Here we report compound thermoelectric materials (Bi2Te3, Bi2Se3, Cu2Se,Cu2SnSe3, half-Heusler alloys, lead chalcogenides, skutterudites, and magnesium silicides) with thermoelectric properties comparable with materials prepared by the traditional routes of synthesis can be synthesized at a minimal cost and on the time scale of seconds using the self-propagating high temperature synthesis method. Moreover, we found that the criterion often quoted in the literature as the necessary precondition for combustion synthesis, Tad >= 1800 K, is not universal and certainly not applicable to thermoelectric compound semiconductors. Instead, we offer new empirically-based criterion, Tad /Tm , L >1, i.e., the adiabatic temperature must be high enough to melt the lower melting point component, which covers all materials synthesized by self-propagating high temperature synthesis, including the high temperature refractory compounds for which the Tad >= 1800 K criterion was originally developed. Our work opens a new avenue for ultra-fast, low cost, mass production fabrication of efficient thermoelectric materials and the new criterion greatly broadens the scope of materials that can be successfully synthesized by self-propagating high temperature synthesis. We wish to acknowledge support from the National Basic Research Program of China (973 program) under Project 2013CB632502.

  15. Combustion Synthesis of Nanoparticulate LiMgxMn1-xPO4 (x=0, 0.1, 0.2) Carbon Composites

    SciTech Connect

    Doeff, Marca M; Chen, Jiajun; Conry, Thomas E.; Wang, Ruigang; Wilcox, James; Aumentado, Albert

    2009-12-14

    A combustion synthesis technique was used to prepare nanoparticulate LiMgxMn1-xPO4 (x=0, 0.1,0.2)/carbon composites. Powders consisted of carbon-coated particles about 30 nm in diameter, which were partly agglomerated into larger secondary particles. The utilization of the active materials in lithium cells depended most strongly upon the post-treatment and the Mg content, and was not influenced by the amount of carbon. Best results were achieved with a hydrothermally treated LiMg0.2Mn0.8PO4/C composite, which exhibited close to 50percent utilization of the theoretical capacity at a C/2 discharge rate.

  16. Effect of Supports on the Gold Catalyst Activity for Catalytic Combustion of CO and HCHO

    Microsoft Academic Search

    Meilin Jia; Yuenian Shen; Changyan Li; Zhaorigetu Bao; Shishan Sheng

    2005-01-01

    The deposition-precipitation method was used to prepare gold catalysts based on different supports. Their catalytic activities for combustion of carbon monoxide (CO) and formaldehyde (HCHO) were investigated. All these catalysts showed good activity for the two reactions and the Au\\/CeO2-a catalyst exhibited the highest activity for the two reactions. Furthermore, catalysts derived from the as-precipitate hydroxides exhibited higher activity than

  17. Highly Selective Synthesis of Catalytically Active Monodisperse Rhodium Nanocubes

    SciTech Connect

    Zhang, Y.; Grass, M.E.; Kuhn, J.N.; Tao, F.; Habas, S.E.; Huang, W.; Yang, P.; Somorjai, G.A.

    2009-02-21

    Synthesis of monodisperse and shape-controlled colloidal inorganic nanocrystals (NCs) is of increasing scientific interest and technological significance. Recently, shape control of Pt, Pd, Ag, Au, and Rh NCs has been obtained by tuning growth kinetics in various solution-phase approaches, including modified polyol methods, seeded growth by polyol reduction, thermolysis of organometallics, and micelle techniques. Control of reduction kinetics of the noble metal precursors and regulation of the relative growth rates of low-index planes (i.e. {l_brace}100{r_brace} and {l_brace}111{r_brace}) via selective adsorption of selected chemical species are two keys for achieving shape modification of noble metal NCs. One application for noble metal NCs of well-defined shape is in understanding how NC faceting (determines which crystallographic planes are exposed) affects catalytic performance. Rh NCs are used in many catalytic reactions, including hydrogenation, hydroformylation, hydrocarbonylation, and combustion reactions. Shape manipulation of Rh NCs may be important in understanding how faceting on the nanoscale affects catalytic properties, but such control is challenging and there are fewer reports on the shape control of Rh NCs compared to other noble metals. Xia and coworkers obtained Rh multipods exhibiting interesting surface plasmonic properties by a polyol approach. The Somorjai and Tilley groups synthesized crystalline Rh multipods, cubes, horns and cuboctahedra, via polyol seeded growth. Son and colleagues prepared catalytically active monodisperse oleylamine-capped tetrahedral Rh NCs for the hydrogenation of arenes via an organometallic route. More recently, the Somorjai group synthesized sizetunable monodisperse Rh NCs using a one-step polyol technique. In this Communication, we report the highly selective synthesis of catalytically active, monodisperse Rh nanocubes of < 10 nm by a seedless polyol method. In this approach, Br{sup -} ions from trimethyl(tetradecyl)ammonium bromide (TTAB) effectively stabilize the {l_brace}100{r_brace} faces of Rh NCs, and induce the evolution of nanocubes (Scheme 1). For a typical synthesis, 0.2 mmol RhCl{sub 3} hydrate, 1 mmol TTAB, and 4 mmol poly(vinylpyrrolidone) (PVP, Mw = 24,000), were added to 20 ml ethylene glycol at room temperature. The stock solution was heated to 80 C and purged for 20 min while stirring, producing a dark brown solution. The flask was then heated to 185 C and maintained at this temperature for 1.5 h under an Ar atmosphere. When the reaction was complete, an excess of acetone was added to the solution at room temperature to precipitate the nanocubes. The Rh nanocubes were separated by centrifugation and washed twice by precipitation/dissolution with ethanol/hexanes.

  18. Synthesis and characteristics of the C12A7-O ? nanoparticles by citric acid sol–gel combustion method

    Microsoft Academic Search

    Lu Gong; Zhou Lin; Shen Ning; Jianqiu Sun; Jing Shen; Youshifumi Torimoto; Quanxin Li

    2010-01-01

    In this study, the O?-containing nanocrystal 12CaO·7Al2O3 (C12A7-O?) was synthesized by the citric acid sol–gel combustion method. The formation of the C12A7-O? material was investigated via X-ray diffraction, thermogravimetric analysis, differential thermal analysis, electron paramagnetic resonance, field emission-scanning electron microscopy, and time of flight mass spectroscopy. The C12A7-O? material was formed at a lower synthesis temperature (900–1150°C), with a narrower

  19. Production of Ni 3 Ti-TiC x intermetallic-ceramic composites employing combustion synthesis reactions

    Microsoft Academic Search

    Douglas E. Burkes; John J. Moore; Guglielmo Gottoli; Hu Chun Yi

    2006-01-01

    Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi-TiC (stoichiometric)\\u000a or Ni3Ti-TiC\\u000a x\\u000a (nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be\\u000a synthesized. The stoichiometry of TiC\\u000a x\\u000a , for

  20. Production of Ni 3 Ti?TiC x intermetallic-ceramic composites employing combustion synthesis reactions

    Microsoft Academic Search

    Douglas E. Burkes; Guglielmo Gottoli; John J. Moore; Hu Chun Yi

    2006-01-01

    Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi?TiC (stoichiometric)\\u000a or Ni3Ti?TiC\\u000a x\\u000a (nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be\\u000a synthesized. The stoichiometry of TiC\\u000a x\\u000a , for

  1. Self-ignition combustion synthesis of TiFe 1?xMn x hydrogen storage alloy

    Microsoft Academic Search

    NaotoYasuda; Ryuta Wakabayashi; Shino Sasaki; Noriyuki Okinaka; Tomohiro Akiyama

    2009-01-01

    The paper describes the self-ignition combustion synthesis (SICS) of the hydrogen storage alloy TiFe1?xMnx (X=0, 0.1, 0.2, 0.3, and 0.5) in a hydrogen atmosphere, where the hydrogenation properties of the products are mainly examined. In the experiments, the well-mixed powders of Ti, Fe, and Mn in the molar ratio of 1:1-X:X were uniformly heated up to 1473K, and then were

  2. Observations on combustion front propagation in self-propagating high-temperature synthesis process producing refractory ceramics

    Microsoft Academic Search

    Chang-Ho Park; Tae-Sung Kang; Sang Hwan Kim

    2002-01-01

    High-temperature refractory ceramics can be produced in the combustion regime by using self-propagating, high-temperature\\u000a synthesis (SHS) processes. The numerical simulation of the SHS process in a simplified diffusion-reaction system is investigated.\\u000a The SHS process is simplified by the one- and two-dimensional pseudo-homoge-neous environment. The stiff equations of the\\u000a SHS process are solved by using finite difference methods on two-dimensional adaptive

  3. Structural, morphological and optical investigations on BaMgAl 10O 17:Eu 2+ elaborated by a microwave induced solution combustion synthesis

    Microsoft Academic Search

    Nathalie Pradal; Audrey Potdevin; Geneviève Chadeyron; Rachid Mahiou

    2011-01-01

    Blue-emitting Eu2+-doped barium magnesium aluminate (BaMgAl10O17:Eu2+) for advanced displays and lighting devices was prepared by a microwave induced solution combustion synthesis using urea as combustion fuel and nitrates as oxidizer. Purity control of as-synthesized blue phosphor particles was undertaken by modifying the fuel to oxidizer molar ratio. X-ray diffraction, scanning electron microscopy and photoluminescence were used to investigate powders crystallinity,

  4. In situ synchrotron characterization of mechanically activated self-propagating high-temperature synthesis applied in Mo–Si system

    Microsoft Academic Search

    C. H Gras; F. Charlot; E. Gaffet; F. Bernard; J. C. Niepce

    1999-01-01

    An original experiment was designed to monitor structural and thermal evolutions during the MASHS (Mechanically Activated Self-propagating High-temperature Synthesis) process in the Mo–Si system. Time-Resolved X-Ray Diffraction (TRXRD) coupled with an infrared imaging technique was performed to study, in situ, the formation of the ?-MoSi2 phase in the combustion front. Despite a temporal resolution of 50ms between two consecutive diffractograms,

  5. Solution combustion synthesis using Schiff-base aluminum complex without fuel and optical property investigations of alumina nanoparticles

    NASA Astrophysics Data System (ADS)

    Salehi, Mehdi; Arabsarhangi, Ehsan

    2015-05-01

    Synthesis of alumina nanomaterials via a solution combustion technique using Schiff base aluminum (III) complex at 820 and 950 °C for 4 h was performed successfully. The synthesis procedure was performed using the complex in the absence and presence of urea and glycine as fuel for comparison. The obtained data showed that the procedure without using fuel resulted in a better phase and morphology. To investigate the phase formation, powder X-ray diffraction technique was used. Also, SEM micrographs were used to investigate the morphology of the obtained materials. The optical properties of the obtained materials were studied by FTIR spectra. According to the PXRD data, it was found that with annealing at 950 °C, the phase formation of the obtained materials showed cubic crystal structure with cell parameter a = 3.14 Å for gamma phase. Also, by annealing at 820 °C using fuels for 4 h, the main phase was found to be in gamma.

  6. Activated carbon and tungsten oxide supported on activated carbon catalysts for toluene catalytic combustion.

    PubMed

    Alvarez-Merino, M A; Ribeiro, M F; Silva, J M; Carrasco-Marín, F; Maldonado-Hódar, F J

    2004-09-01

    We have used activated carbon (AC) prepared from almond shells as a support for tungsten oxide to develop a series of WOx/AC catalysts for the catalytic combustion of toluene. We conducted the reaction between 300 and 350 degrees C, using a flow of 500 ppm of toluene in air and space velocity (GHSV) in the range 4000-7000 h(-1). Results show that AC used as a support is an appropriate material for removing toluene from dilute streams. By decreasing the GHSV and increasing the reaction temperature AC becomes a specific catalyst for the total toluene oxidation (SCO2 = 100%), but in less favorable conditions CO appears as reaction product and toluene-derivative compounds are retained inside the pores. WOx/AC catalysts are more selective to CO2 than AC due to the strong acidity of this oxide; this behavior improves with increased metal loading and reaction temperature and contact time. The catalytic performance depends on the nonstoichiometric tungsten oxide obtained during the pretreatment. In comparison with other supports the WOx/AC catalysts present, at low reaction temperatures, higher activity and selectivity than WO, supported on SiO2, TiO2, Al2O3, or Y zeolite. This is due to the hydrophobic character of the AC surface which prevents the adsorption of water produced from toluene combustion thus avoiding the deactivation of the active centers. However, the use of WOx/AC system is always restricted by its gasification temperature (around 400 degrees C), which limits the ability to increase the conversion values by increasing reaction temperatures. PMID:15461177

  7. An investigation on formation of Nb 2AlC by combustion synthesis of Nb 2O 5–Al–Al 4C 3 powder compacts

    Microsoft Academic Search

    C. L. Yeh; C. W. Kuo

    2010-01-01

    Preparation of layered ternary carbide Nb2AlC was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) from Nb2O5–Al–Al4C3 powder compacts. Effects of the contents of Al and Al4C3 on the product composition and combustion behavior were studied by adopting two series of sample stoichiometries with Nb2O5:Al:Al4C3 varying from 3:9:1 to 3:13:1 (for supplying additional Al) and 3:9:1

  8. The feasibility of synthesis of B[sub 4]C fiber-MgO composites by combustion

    SciTech Connect

    Wang, L.L.; Munir, Z.A.; Holt, J.B. (Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science)

    1994-07-01

    A relatively large number of carbide materials have been prepared by the combustion synthesis method. Interest in these materials is motivated, in part, by their refractory nature, high hardness, and relatively low density. In this method, the typical starting reactants consist of a mixture of metal and a carbon powders. When ignited, many of these reactant systems reach combustion temperatures which are higher than the melting point of the metal but lower than melting point of carbon. These conditions give rise to expectations of control of the size and shape of the final carbide particles by the morphology of the carbon component, as observed by Mullins and Riley. In this study, the effect of carbon fiber morphology on the B[sub 4]C phase formed via the Mg-B[sub 2]O[sub 3] thermite-based reaction was investigated. The overall reaction, 6Mg + 2B[sub 2]O[sub 3] + C [yields] 6MgO + B[sub 4]C, involves two steps, the first is a reaction between Mg and B[sub 2]O[sub 3] to form MgO and B, and the second involves the formation of B[sub 4]C. The calculated adiabatic combustion temperature, assuming an initial temperature of 25 C is 2,467 C which is higher than the melting point of boron.

  9. Utilization of spent activated carbon to enhance the combustion efficiency of organic sludge derived fuel.

    PubMed

    Chen, Wei-Sheng; Lin, Chang-Wen; Chang, Fang-Chih; Lee, Wen-Jhy; Wu, Jhong-Lin

    2012-06-01

    This study examines the heating value and combustion efficiency of organic sludge derived fuel, spent activated carbon derived fuel, and derived fuel from a mixture of organic sludge and spent activated carbon. Spent activated carbon was sampled from an air pollution control device of an incinerator and characterized by XRD, XRF, TG/DTA, and SEM. The spent activated carbon was washed with deionized water and solvent (1N sulfuric acid) and then processed by the organic sludge derived fuel manufacturing process. After washing, the salt (chloride) and sulfide content could be reduced to 99% and 97%, respectively; in addition the carbon content and heating value were increased. Different ratios of spent activated carbon have been applied to the organic sludge derived fuel to reduce the NO(x) emission of the combustion. PMID:22209404

  10. Combustion synthesis of TiN–TiB 2 composites in Ti\\/BN\\/N 2 and Ti\\/BN\\/B reaction systems

    Microsoft Academic Search

    C. L. Yeh; G. S. Teng

    2006-01-01

    An experimental study on in situ formation of TiN–TiB2 composites with a wide range of compositions by self-propagating high-temperature synthesis (SHS) was conducted in two reaction systems. Combustion of sample compacts made up of titanium (Ti) and boron nitride (BN) powders was initiated under nitrogen pressure for the synthesis of composites with TiN contents of 75–87.5mol%. Experiments with reactant compacts

  11. The effect of pressure on the combustion synthesis of a functionally-graded material: TiB[sub 2]-Al[sub 2]O[sub 3]-Al ceramic-metal composite system

    SciTech Connect

    Feng, H.J.; Moore, J.J. (Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering)

    1993-10-01

    This article describes some recent research on the synthesis of functionally-graded materials (FGM) using combustion synthesis or self-propagating high-temperature synthesis (SHS). A model ceramic-metal SHS system was investigated. The effects of combustion mode, reactant stoichiometry (xAl), green density, and applied loads on the stability of the SHS reaction and density of the FGM product are described.

  12. The effect of pressure on the combustion synthesis of a functionally-graded material: TiB[sub 2]Al[sub 2]O[sub 3]Al ceramic-metal composite system

    Microsoft Academic Search

    H. J. Feng; J. J. Moore

    1993-01-01

    This article describes some recent research on the synthesis of functionally-graded materials (FGM) using combustion synthesis or self-propagating high-temperature synthesis (SHS). A model ceramic-metal SHS system was investigated. The effects of combustion mode, reactant stoichiometry (xAl), green density, and applied loads on the stability of the SHS reaction and density of the FGM product are described.

  13. Synthesis of pure molybdenum disilicide by the “chemical oven” self-propagating combustion method

    Microsoft Academic Search

    Xu Jianguang; Zhang Baolin; Li Wenlan; Zhuang Hanrui; Jiang Guojian

    2003-01-01

    A high pure molybdenum disilicide was prepared by using the “chemical oven” enhanced self-propagating combustion method. The mixtures of Si and Ti were ignited as chemical oven. Ammonium chloride was added to the mixed powders to control the propagation rate of combustion. The compostion of product was detected by X-ray diffraction (XRD) and X-fluorescence analysis. Results show the molybdenum disilicide

  14. An artificial intelligence approach to active filter synthesis

    Microsoft Academic Search

    Krzysztof Wawryn

    1992-01-01

    This paper deals with a novel active filter synthesis method using artificial intelligence (AI). The AI-based synthesis methodology uses original analog circuit representation performed by a Prolog backward-chaining inference mechanism. Circuit representation is specified as an analog circuit language to describe filter topologies, performance characteristics, and subcircuits. Synthesis is organized as a Prolog searching program based on backward-chaining strategy to

  15. Activated ribosomal RNA synthesis in regenerated rat liver upon inhibition of protein synthesis

    Microsoft Academic Search

    Emil H. Nikolov; Bistra B. Nankova; Mariana D. Dabeva

    1991-01-01

    Cycloheximide (Cyh), administered at a dose of 5 mg\\/kg body wt blocks protein synthesis in normal rat liver (NRL) and regenerating rat liver (RRL). The rate of synthesis of 45S pre-rRNA in RRL, studied after RNA labelling in vivo is activated 2.8 times. Pre-r RNA synthesis in RRL is more sensitive to the stopped translation, but never falls down to

  16. Modeling the kinetics of non-isothermal heterogeneous interaction during combustion synthesis of advanced micro- and nanocrystalline materials

    NASA Astrophysics Data System (ADS)

    Khina, Boris B.

    2008-07-01

    The combustion synthesis (CS), or self-propagating high-temperature synthesis (SHS) is a cost and energy efficient route for producing a wide range of refractory compounds (carbides, silicides, intermetallics) and advanced micro- and nanocrystalline materials. However, despite 40 years of extensive studies and industrial applications, intricate phase formation mechanisms that operate during CS are still not well understood. This hinders the development of novel materials and SHS-based technologies. An answer to the most urgent question in this area, viz. "why in CS the interaction accomplishes in a short time, ~0.1-1 s, while the traditional furnace synthesis of the same material takes several hours for the same starting composition, particle size and final temperature," can be found only through mathematical modeling. In this work, the results of mathematical modeling of the interaction kinetics in condensed systems in non-isothermal conditions typical of CS are reported. Calculations were performed using the experimental data on SHS and diffusion parameters for the product phases on the example of TiC and NiAl. The maps of phase formation mechanisms that operate during CS are constructed. The uncommon, non-equilibrium interaction pathways, which were observed experimentally and debated in literature, are confirmed theoretically ex contrario.

  17. Calcium activity and post-ischemic suppression of protein synthesis

    Microsoft Academic Search

    B. Djuricic; G. Röhn; W. Paschen; K.-A. Hossmann

    1995-01-01

    Increase in intracellular calcium concentration is a prominent feature of ischemia and has been considered a major factor in the initiation of ischemic pathology, which involves inhibition of protein synthesis. A reduction of calcium ion activity during and immediately after in vitro ischemia did not prevent inhibition of protein synthesis in hippocampae slices. When slices were overloaded with calcium by

  18. The Effect of Pressure on the Combustion Synthesis of a Functionally-Graded Material: TiB 2 Al 2 O 3 Al Ceramic Metal Composite System

    Microsoft Academic Search

    H. J. Feng; J. J. Moore

    1993-01-01

    This article describes some recent research on the synthesis of functionally-graded materials (FGM using combustion synthesis\\u000a or self- propagating high-temperature synthesis (SHS). A model ceramic-metal SHS system was investigated based on the reaction\\u000a system: 3TiO2 + 3B2O3 + (10 + x)Al = 3TiB2 + 5Al2O2 + xAl in which x was varied between 0 and 17 to achieve the required

  19. Synthesis of nano-crystalline TaC-TaB2 by microwave-assisted combustion synthesis

    NASA Astrophysics Data System (ADS)

    Aminikia, Behzad

    2013-12-01

    In present study, TaC-TaB2 nanocrystalline powder was produced by microwave synthesis. 3Ta and B4C Al as starting materials were milled for 1, 3, 6 and 9 h then pressed to form pellets. Green compacts were placed in a microwave oven with powder equal 1100W and argon atmosphere, for synthesis. The final products were studied by XRD and SEM analytical techniques. The results showed increasing of the milling time to 9 h the synthesis of desired phases (TaC and TaB2) was associated with greater success and the amount of the side products and intermediate compounds reach to minimum in the product. Also, with increasing of milling time from 1 to 9 h the required time for synthesis of samples reduces from 3 min to 35 sec. This method is an economical method for the preparation TaC-TaB2 powder with respect to energy, time and simplicity.

  20. Combustion synthesis of metal-matrix composites. Part 1: The Ti-TiC-Al{sub 2}O{sub 3} system

    SciTech Connect

    Kunrath, A.O.; Strohaecker, T.R. [UFRGS, Porto Alegre, Rio Grande do Sul (Brazil). Dept. de Metalurgia] [UFRGS, Porto Alegre, Rio Grande do Sul (Brazil). Dept. de Metalurgia; Moore, J.J. [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering] [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering

    1996-01-15

    Combustion synthesis or Self-propagating High-temperature Synthesis (SHS) is a process that involves a reaction which is sufficiently exothermic to sustain itself, and, as such, provides considerable potential for the development of an affordable (low cost), energetically efficient means of producing advanced materials. In the combustion synthesis process, a mix of the reactant powders, pressed into a pellet, is heated to the ignition temperature, Tig, when the exothermic reaction takes place, transforming reactants into products. The heat generated by the reaction raises the temperature of the products to a maximum recorded combustion temperature, Tc, which, under adiabatic conditions, would be the adiabatic temperature, Tad. However, in most combustion reactions, Tc is less than Tad, since heat losses occur from the reaction front. Materials synthesized with each of these combustion modes are typically associated with high levels of porosity, e.g., 50%, which is manifested as both macroporosity and microporosity. Previous work demonstrated that it was possible to decrease the porosity of a TiC-Al{sub 2}O{sub 3}-Ti composite by incorporating an excess liquid metal into the combustion synthesis reaction system. This reaction utilizes aluminothermic reduction of TiO{sub 2} to generate the exothermic condition, and at the same time, uses the required TiO{sub 2}/Al stoichiometry to provide the excess Ti to generate an excess Ti in a matrix of TiC and Al{sub 2}O{sub 3}, each of which are synthesized, in-situ within the overall reaction system.

  1. Synthesis of niobium aluminides using mechanically activated self-propagating high-temperature synthesis and mechanically activated annealing process

    Microsoft Academic Search

    V Gauthier; C Josse; F Bernard; E Gaffet; J. P Larpin

    1999-01-01

    The mechanically activated self-propagating high-temperature synthesis (MASHS) technique and the mechanically activated annealing process (M2AP) were used to produce NbAl3 intermetallic compound. The MASHS process results from the combination of two steps: first, a mechanical activation of the Nb+3Al powders mixture; second, a self-propagating high-temperature synthesis (SHS). The M2AP process also results from the combination of two steps: the first

  2. Active suppression of vortex-driven combustion instability using controlled liquid-fuel injection

    NASA Astrophysics Data System (ADS)

    Pang, Bin

    Combustion instabilities remain one of the most challenging problems encountered in developing propulsion and power systems. Large amplitude pressure oscillations, driven by unsteady heat release, can produce numerous detrimental effects. Most previous active control studies utilized gaseous fuels to suppress combustion instabilities. However, using liquid fuel to suppress combustion instabilities is more realistic for propulsion applications. Active instability suppression in vortex-driven combustors using a direct liquid fuel injection strategy was theoretically established and experimentally demonstrated in this dissertation work. Droplet size measurements revealed that with pulsed fuel injection management, fuel droplet size could be modulated periodically. Consequently, desired heat release fluctuation could be created. If this oscillatory heat release is coupled with the natural pressure oscillation in an out of phase manner, combustion instabilities can be suppressed. To identify proper locations of supplying additional liquid fuel for the purpose of achieving control, the natural heat release pattern in a vortex-driven combustor was characterized in this study. It was found that at high Damkohler number oscillatory heat release pattern closely followed the evolving vortex front. However, when Damkohler number became close to unity, heat release fluctuation wave no longer coincided with the coherent structures. A heat release deficit area was found near the dump plane when combustor was operated in lean premixed conditions. Active combustion instability suppression experiments were performed in a dump combustor using a controlled liquid fuel injection strategy. High-speed Schlieren results illustrated that vortex shedding plays an important role in maintaining self-sustained combustion instabilities. Complete combustion instability control requires total suppression of these large-scale coherent structures. The sound pressure level at the excited dominant frequency was reduced by more than 20 dB with controlled liquid fuel injection method. Scaling issues were also investigated in this dump combustor to test the effectiveness of using pulsed liquid fuel injection strategies to suppress instabilities at higher power output conditions. With the liquid fuel injection control method, it was possible to suppress strong instabilities with initial amplitude of +/-5 psi down to the background noise level. The stable combustor operating range was also expanded from equivalence ratio of 0.75 to beyond 0.9.

  3. The Effect of Pressure on the Combustion Synthesis of a Functionally-Graded Material: TiB2-Al2O3-Al Ceramic- Metal Composite System

    NASA Astrophysics Data System (ADS)

    Feng, H. J.; Moore, J. J.

    1993-10-01

    This article describes some recent research on the synthesis of functionally-graded materials (FGM using combustion synthesis or self- propagating high-temperature synthesis (SHS). A model ceramic-metal SHS system was investigated based on the reaction system: 3TiO2 + 3B2O3 + (10 + x)Al = 3TiB2 + 5Al2O2 + xAl in which x was varied between 0 and 17 to achieve the required composition and phase gradients in the FGM. The effects of combustion mode, reactant stoichiometry (xAl), green density, and applied loads on the stability of the SHS reaction and density of the FGM product are described.

  4. Performance Evaluation of a High Bandwidth Liquid Fuel Modulation Valve for Active Combustion Control

    NASA Technical Reports Server (NTRS)

    Saus, Joseph R.; DeLaat, John C.; Chang, Clarence T.; Vrnak, Daniel R.

    2012-01-01

    At the NASA Glenn Research Center, a characterization rig was designed and constructed for the purpose of evaluating high bandwidth liquid fuel modulation devices to determine their suitability for active combustion control research. Incorporated into the rig s design are features that approximate conditions similar to those that would be encountered by a candidate device if it were installed on an actual combustion research rig. The characterized dynamic performance measures obtained through testing in the rig are planned to be accurate indicators of expected performance in an actual combustion testing environment. To evaluate how well the characterization rig predicts fuel modulator dynamic performance, characterization rig data was compared with performance data for a fuel modulator candidate when the candidate was in operation during combustion testing. Specifically, the nominal and off-nominal performance data for a magnetostrictive-actuated proportional fuel modulation valve is described. Valve performance data were collected with the characterization rig configured to emulate two different combustion rig fuel feed systems. Fuel mass flows and pressures, fuel feed line lengths, and fuel injector orifice size was approximated in the characterization rig. Valve performance data were also collected with the valve modulating the fuel into the two combustor rigs. Comparison of the predicted and actual valve performance data show that when the valve is operated near its design condition the characterization rig can appropriately predict the installed performance of the valve. Improvements to the characterization rig and accompanying modeling activities are underway to more accurately predict performance, especially for the devices under development to modulate fuel into the much smaller fuel injectors anticipated in future lean-burning low-emissions aircraft engine combustors.

  5. Mechanistic investigation of electric field-activated self-propagating reactions: experimental and modeling studies

    Microsoft Academic Search

    R. Orrù; A. Cincotti; G. Cao; Z. A. Munir

    2001-01-01

    The mechanism of electric field-activated self-propagating reactions is investigated using the combustion front quenching technique. In particular, previously published experimental results obtained through the field-activated combustion synthesis (FACS) of ?-SiC, TaC, Ti3Al and B4C–TiB2 are re-examined and compared. Pre-combustion and combustion stages involved during synthesis wave propagation are postulated for all systems. Subsequently, modeling results aimed at simulating the process

  6. Comparative sinterability of combustion synthesized and commercial titanium carbides

    SciTech Connect

    Manley, B.W.

    1984-11-01

    The influence of various parameters on the sinterability of combustion synthesized titanium carbide was investigaged. Titanium carbide powders, prepared by the combustion synthesis process, were sintered in the temperature range 1150 to 1600/sup 0/C. Incomplete combustion and high oxygen contents were found to be the cause of reduced shrinkage during sintering of the combustion syntheized powders when compared to the shrinkage of commercial TiC. Free carbon was shown to inhibit shrinkage. The activation energy for sintering was found to depend on stoichiometry (C/Ti). With decreasing C/Ti, the rate of sintering increased. 29 references, 16 figures, 13 tables.

  7. Amplifier insensitive integrator design for active RC filter synthesis 

    E-print Network

    Bailey, Glenn Roger

    1980-01-01

    AM?LIFIER INSENSITIVE INTEGRATOR DESIGN FOR ACTIVE RC FILTER SYNTHESIS A Thesis by GLENN ROGER BAILEY Submitted to the Graduate College of Texas A&M University in partial fulfillment of the'requirement for the degree of MASTER OF SCIENCE... May 1980 Major Subject: Electrical Engineering AMPLIFIER INSENSITIVE INTEGRATOR DESIGN FOR ACTIVE RC FILTER SYNTHESIS A Thesis by GLENN ROGER BAILEY Approved as to style and content by: (Chairman of Comit ee) (Member) ( ember) (Member) (Hea...

  8. Synthesis of La{sup 3+} doped nanocrystalline ceria powder by urea-formaldehyde gel combustion route

    SciTech Connect

    Biswas, M. [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India)] [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India); Bandyopadhyay, S., E-mail: sbando@cgcri.res.in [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Nano LC synthesized by gel combustion, using urea-formaldehyde fuel for first time. Black-Right-Pointing-Pointer Largely single crystals were produced in average range of 20-30 nm. Black-Right-Pointing-Pointer La{sup 3+} doping increases cell dimension linearly. Black-Right-Pointing-Pointer La{sup 3+} doping introduces ionic point defects but does not change electronic band gap. Black-Right-Pointing-Pointer Presence of Ce{sup 3+} indicates that this synthesis route produces reactive powders. -- Abstract: Nanocrystalline ceria powders doped with various concentrations of lanthanum oxide have been prepared following gel combustion route using for the first time urea-formaldehyde as fuel. The synthesized products were characterized by XRD, FESEM, TEM, PL and UV-vis spectroscopy. Peak positions of XRD were refined and the lattice parameters were obtained by applying Cohen's method. Unit cell parameter increases with concentration of La{sup 3+} ion and the variation is consistently linear. XRD calculations showed the dependence of crystallite size on dopant concentrations at lower level. TEM observation revealed unagglomerated particles to be single crystals in the average range of 20-30 nm. Band gap of the La{sup 3+} doped ceria materials does not change with doping. Spectroscopic experiments proved the existence of Ce{sup 3+} in the formed powder.

  9. Production of Ni3Ti-TiC x intermetallic-ceramic composites employing combustion synthesis reactions

    NASA Astrophysics Data System (ADS)

    Burkes, Douglas E.; Gottoli, Guglielmo; Moore, John J.; Yi, Hu Chun

    2006-03-01

    Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi-TiC (stoichiometric) or Ni3Ti-TiC x (nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be synthesized. The stoichiometry of TiC x , for which 0.3? x?0.5, has an important controlling effect on the formation of either Ni3Ti or NiTi; i.e., formation of TiC0.7 results in a depletion of titanium and formation of Ni3Ti. This deficiency should be considered when developing the SHS reaction. This article examines the SHS conditions under which Ni3Ti-TiC x composites are produced. Ignition, combustion and microstructure characteristics of nickel, titanium, and carbon (graphite) particles were investigated as a function of initial relative density and thermophysical properties of the reactant mixture. Combination of the thermophysical properties and burning velocities controlled TiC x particle size, yielding a dependence of particle size on cooling rate. Theoretical calculations were performed and are in good agreement with the experimental data presented.

  10. Synthesis of thermostable geopolymer from circulating fluidized bed combustion (CFBC) bottom ashes

    Microsoft Academic Search

    Hui Xu; Qin Li; Lifeng Shen; Wei Wang; Jianping Zhai

    2010-01-01

    Circulating fluidized bed combustion (CFBC) bottom ashes (CBAs) are a class of calcined aluminosilicate wastes with a unique thermal history. While landfill disposal of hazardous element-containing CBAs poses serious challenge, these wastes have long been neglected as source materials for geopolymer production. In this paper, geopolymerization of ground CBAs was investigated. Reactivity of the CBAs was analyzed by respective dissolution

  11. SHS combustion characteristics of several ceramics and intermetallic compounds. [Self-propagating High-temperature Synthesis

    Microsoft Academic Search

    Atsushi Makino; C. K. Law

    1994-01-01

    Extensive comparisons have been conducted between experimental and theoretical results for the SHS combustion characteristics of a number of solid-solid systems. The heterogeneous flame propagation theory describes a premixed mode of bulk flame propagation supported by the nonpremixed reaction of dispersed nonmetal (or higher melting point metal) particles in the liquid metal, with finite-rate reaction at the particle surface and

  12. Utilization of Coal Combustion Ashes for the Synthesis of Ordinary and Special Cements

    Microsoft Academic Search

    Milena Marroccoli; Maria Lucia Pace; Antonio Telesca; Gian Lorenzo Valenti; Fabio Montagnaro

    2010-01-01

    Raw mixes containing pulverized coal fly ash (with limestone and silica sand) or fluidized bed coal combustion ash (fly and bottom, with added limestone, anodization mud, and, when necessary, flue gas desulfurization gypsum), aimed at generating ordinary Portland or calcium sulfoaluminate clinkers, respectively, were heated in a laboratory electric oven at temperatures ranging from 1150° to 1500°C and submitted to

  13. Sol-gel auto-combustion synthesis of zinc ferrite for moderate temperature desulfurization

    SciTech Connect

    Rongjun Zhang; Jiejie Huang; Jiantao Zhao; Zhiqiang Sun; Yang Wang [Chinese Academy of Sciences, Taiyuan (China). Institute of Coal Chemistry

    2007-09-15

    Zinc ferrite as a desulfurization sorbent with an average crystallite size of about 36 nm was synthesized by a sol-gel auto-combustion method. The precursor for the sorbent was a gel obtained from metal nitrates and citric acid by a sol process. The nitrate-citrate gel exhibits a self-propagating combustion behavior, and after combustion, it can transform into a nanosized spinel structured zinc ferrite directly. The prepared sorbent has a larger specific surface area and higher reactivity when compared with the sorbent achieved by a solid mixing method, and it could efficiently reduce the H{sub 2}S concentration from 6000 ppm to less than 2 ppm at a moderate temperature range. The sulfur capacity at 400{sup o}C reaches about 38.5 g of sulfur/100 g of sorbent, which corresponds to 96.4% of the theoretical value. The temperature programmed oxidation test for the sulfided sorbent shows that the most sulfur is desorbed before 500{sup o}C. XRD results confirm that the sulfided sample after exposure to a 5% O{sub 2}/N{sub 2} gas mixture at 500{sup o}C can be regenerated completely, which indicates that the regeneration temperature of the sorbent prepared by the sol-gel auto-combustion method could be greatly reduced. 40 refs., 10 figs., 2 tabs.

  14. Design and Operation of the Synthesis Gas Generator System for Reformed Propane and Glycerin Combustion

    E-print Network

    Pickett, Derek

    2013-12-31

    Due to an increased interest in sustainable energy, biodiesel has become much more widely used in the last several years. Glycerin, one major waste component in biodiesel production, can be converted into a hydrogen rich synthesis gas to be used...

  15. Influence of thermal conditions on the combustion synthesis of Si 2N 2O phase

    Microsoft Academic Search

    N. Pradeilles; M. C. Record; R. M. Marin-Ayral; A. V. Linde; I. A. Studenikin; V. V. Grachev

    2008-01-01

    This work is a contribution to the study of Si2N2O synthesis via Self-Propagating High-temperature Synthesis (SHS).The elaboration of Si2N2O was carried out using two kinds of experimental equipments and differences both in reaction temperatures and in products compositions were evidenced.In order to determine the reaction mechanisms, several compositions and thermal conditions of the reactant mixture were studied.Considering our results, two

  16. The effect of an electric field on self-sustaining combustion synthesis: Part I. modeling studies

    Microsoft Academic Search

    A. Feng; Z. A. Munir

    1995-01-01

    An analysis of the effect of an electric field on self-propagating high-temperature synthesis (SHS) reactions is presented.\\u000a Using the synthesis of SiC as a model, the analysis showed that the imposition of a field results in a highly localized distribution\\u000a of the current density. It was shown that the current is primarily restricted to the region just ahead of the

  17. In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion

    PubMed Central

    Wang, Han; Chen, Chunlin; Zhang, Yexin; Peng, Lixia; Ma, Song; Yang, Teng; Guo, Huaihong; Zhang, Zhidong; Su, Dang Sheng; Zhang, Jian

    2015-01-01

    Combustion catalysts have been extensively explored to reduce the emission of hydrocarbons that are capable of triggering photochemical smog and greenhouse effect. Palladium as the most active material is widely applied in exhaust catalytic converter and combustion units, but its high capital cost stimulates the tremendous research on non-noble metal candidates. Here we fabricate highly defective cobalt oxide nanocrystals via a controllable oxidation of carbon-encapsulated cobalt nanoparticles. Strain gradients induced in the nanoconfined carbon shell result in the formation of a large number of active sites featuring a considerable catalytic activity for the combustion of a variety of hydrocarbons (methane, propane and substituted benzenes). For methane combustion, the catalyst displays a unique activity being comparable or even superior to the palladium ones. PMID:26074206

  18. In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion.

    PubMed

    Wang, Han; Chen, Chunlin; Zhang, Yexin; Peng, Lixia; Ma, Song; Yang, Teng; Guo, Huaihong; Zhang, Zhidong; Su, Dang Sheng; Zhang, Jian

    2015-01-01

    Combustion catalysts have been extensively explored to reduce the emission of hydrocarbons that are capable of triggering photochemical smog and greenhouse effect. Palladium as the most active material is widely applied in exhaust catalytic converter and combustion units, but its high capital cost stimulates the tremendous research on non-noble metal candidates. Here we fabricate highly defective cobalt oxide nanocrystals via a controllable oxidation of carbon-encapsulated cobalt nanoparticles. Strain gradients induced in the nanoconfined carbon shell result in the formation of a large number of active sites featuring a considerable catalytic activity for the combustion of a variety of hydrocarbons (methane, propane and substituted benzenes). For methane combustion, the catalyst displays a unique activity being comparable or even superior to the palladium ones. PMID:26074206

  19. Effects of TiC and TiN addition on combustion synthesis of Ti 2AlC 0.5N 0.5 solid solutions

    Microsoft Academic Search

    C. L. Yeh; C. W. Kuo; F. S. Wu

    2010-01-01

    Preparation of the solid solution Ti2AlC0.5N0.5 was investigated by self-propagating high-temperature synthesis (SHS) from TiC- and TiN-diluted powder compacts. For the TiC-added samples, combustion reaction was conducted in gaseous nitrogen of 0.45–1.82MPa. The increase of nitrogen pressure augments the combustion temperature and thus accelerates the reaction front. However, the phase composition of the synthesized product is not affected by the

  20. Coal combustion science

    SciTech Connect

    Hardesty, D.R. (ed.); Baxter, L.L.; Fletcher, T.H.; Mitchell, R.E.

    1990-11-01

    The objective of this activity is to support the Office of Fossil Energy in executing research on coal combustion science. This activity consists of basic research on coal combustion that supports both the Pittsburgh Energy Technology Center (PETC) Direct Utilization Advanced Research and Technology Development Program, and the International Energy Agency (IEA) Coal Combustion Science Project. Specific tasks include: coal devolatilization, coal char combustion, and fate of mineral matter during coal combustion. 91 refs., 40 figs., 9 tabs.

  1. Synthesis and Characterization of Nanosized Dy-Doped of Ceria Developed by Microwave Assisted Combustion Route

    Microsoft Academic Search

    S. A. Acharya; K. Singh; S. S. Bhoga

    2010-01-01

    Nanosized Ce1-xDyxO2-x\\/2 (DDC, x = 0.05—0.25 mol%) were synthesized by combustion routes induced by microwaves (MS) and compared with the same composition prepared by conventional (CS) method. The conventional and microwave sintering routes were also used to consolidate the pellets. The samples were characterized by X-ray diffractometry (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and AC impedance spectroscopy.

  2. Selective self-propagating combustion synthesis of hexagonal and orthorhombic nanocrystalline yttrium iron oxide

    Microsoft Academic Search

    Ling Wu; Jimmy C. Yu; Lizhi Zhang; Xinchen Wang; Siukong Li

    2004-01-01

    Macroporous nanocrystalline YFeO3 was prepared by a self-propagating combustion method using yttrium nitrate and iron nitrate as precursors and glycine as a fuel. The phase structure of the product can be selectively controlled to be hexagonal or orthorhombic by simply adjusting the ratio of glycine to nitrate. The samples were characterized by X-ray diffraction (XRD) analysis, N2 adsorption, micro-Raman spectroscopy,

  3. Synthesis and luminescence of europium doped yttria nanophosphors via a sucrose-templated combustion method

    Microsoft Academic Search

    Lingling Xu; Bo Wei; Zhiguo Zhang; Zhe Lü; Hong Gao; Yungang Zhang

    2006-01-01

    Nanocrystalline Y2O3:Eu phosphors have been successfully synthesized by a novel combustion method using sucrose as a chelating agent and fuel. The sucrose hydrolysation and complexing mechanisms are discussed. X-ray diffraction analysis showed that the cubic phase can be formed at a low temperature of 400 °C, and transmission electron microscopy observations revealed that the phosphor particles were 30-50 nm annealed

  4. Synthesis of YAG powder by the modified sol–gel combustion method

    Microsoft Academic Search

    Lin Yang; Tiecheng Lu; Hui Xu; Nian Wei

    2009-01-01

    Yttrium aluminum garnet (YAG) precursor was prepared by sol–gel combustion method using ethanol as solvent. Nano-sized YAG powders were obtained by precalcining the precursor at 500°C, and then calcining at different temperatures. The phase formation and characteristics of YAG powders were investigated by means of XRD, TG\\/DSC and TEM. Pure crystalline YAG phase was obtained at 800°C, without any intermediate

  5. Facile synthesis of nanocrystalline zinc ferrite via a self-propagating combustion method

    Microsoft Academic Search

    Hun Xue; Zhaohui Li; Xuxu Wang; Xianzhi Fu

    2007-01-01

    Macroporous nanocrystalline zinc ferrite with single spinel-phase was prepared by a facile self-propagating combustion method using zinc nitrate, iron nitrate and glycine. The as-prepared ZnFe2O4 were characterized by X-ray diffraction (XRD) analysis, N2 adsorption, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy dispersive X-ray spectrum (EDS). The magnetic properties of the prepared

  6. Metal Sulfide Synthesis by Self-Propagating Combustion of Sulfur-Containing Complexes

    Microsoft Academic Search

    R. K. Tukhtaev; V. V. Boldyrev; A. I. Gavrilov; S. V. Larionov; L. I. Myachina; Z. A. Savel'eva

    2002-01-01

    Coordination compounds of thiourea with cadmium(II), zinc(II), bismuth(III), and indium(III) nitrates were synthesized. The self-sustained combustion of these complexes, as well as that of thiosemicarbazide coordination compounds of nickel(II), cobalt(II), iron(II), copper(II), lead(II), and zinc(II) nitrates, was studied in an inert atmosphere. All these compounds burn to yield metal sulfides. The particle size and morphology of the product depend on

  7. Combustion synthesis of high porosity SiC foam with nanosized grains

    Microsoft Academic Search

    J. F. Qiu; J. T. Li; K. L. Smirnov

    2010-01-01

    High porosity silicon carbide (SiC) foam with nanosized grains was synthesized by a newly developed process involving two steps: (i) preparation of Si\\/C foam by gel-casting technique and (ii) fabrication of SiC foam by combustion Si\\/C foam in nitrogen atmosphere. The as-synthesized SiC foam with a high porosity in the range 70–90% exhibited an attractive strength up to 1.6MPa. SEM

  8. New Synthesis of Ferrite–Silica Nanocomposites by a Sol–Gel Auto-Combustion

    Microsoft Academic Search

    C. Cannas; A. Musinu; D. Peddis; G. Piccaluga

    2004-01-01

    A sol–gel autocombustion method was used to synthesize nanometric metal-oxide powders, and was extended for the first time to prepare ferrite–silica nanocomposites. The gels obtained by mixing suitable amounts of citric acid, metal nitrates, ammonia (pure phases) and tetraethylortosilicate (nanocomposites) were converted directly to ferrite (either ?-Fe2O3 or CoFe2O4) or ferrite–silica composites through a rapid autocombustion reaction. The combustion involves

  9. Synthesis of La and Nb doped PZT powder by the gel-combustion method

    NASA Astrophysics Data System (ADS)

    Cernea, M.; Montanari, G.; Galassi, C.; Costa, A. L.

    2006-03-01

    Lanthanum and niobium doped PZT with composition (Pb0.93La0.07)[(Zr0.60Ti0.40)]0.9825Nb0.0175O3 (PZTLN) was prepared by the gel-combustion method. A precursor sol was obtained from lead nitrate, zirconyl nitrate, lanthanum oxide, peroxo-citrato-niobium and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate/nitrate (CA/NO3- = 1.3, 0.36 and 0.09) were used to prepare very fine powders of PZTLN. The gels resulting from these sols were transformed into powders by an auto-combustion process at <=400 °C. The powders consisted of rhombohedral PZT (PbZr0.60Ti0.40O3), pyrochlore (Pb2Ti2O6) and lead carbonate (Pb2O·CO3) phases. The pure rhombohedral phase is found in PZTLN pellets sintered at 1100 °C for all citrate/nitrate ratios. Titanium and niobium precursors were modified with peroxo radicals. During the gel-combustion reaction, the temperature of the gel increases, leading to lead evaporation. The loss of lead as well as the particle size increases as the CA/NO3- ratio decreases. The smallest grained powder (about 50 nm) was obtained with the ratio CA/NO3- equal to 0.09.

  10. Use of combustion and thermal explosion for the synthesis of intermetallic compounds and their alloys

    Microsoft Academic Search

    V. I. Itin; A. D. Bratchikov; L. N. Postnikova

    1980-01-01

    Methods of utilizing the heat evolving during reactions between components for the synthesis of intermetallic compounds and their alloys may vary depending on the character of the exothermic processes occurring in the metal powder mixtures employed. During the initiation of a reaction in some local volume of a substance heat is liberated in the reaction zone. This raises the temperature

  11. A new approach to the modeling of SHS reactions: Combustion synthesis of transition metal aluminides

    Microsoft Academic Search

    Silvia Gennari; Umberto Anselmi Tamburini; Filippo Maglia; Giorgio Spinolo; Zuhair A. Munir

    2006-01-01

    A recently developed numerical simulation of self-propagating high-temperature synthesis (SHS) using an approach based on microscopic reaction mechanisms and utilizing appropriate physical parameters is applied to the SHS of a fairly large group of transition metal aluminides. The model was utilized to analyze temperature profiles and wave instability and the results were interpreted in terms of chemical and thermal effects.

  12. Synthesis, droplet combustion, and sooting characteristics of biodiesel produced from waste vegetable oils

    Microsoft Academic Search

    T. X. Li; D. L. Zhu; N. K. Akafuah; K. Saito; C. K. Law

    2011-01-01

    In light of the potential of fatty acid methyl ester (FAME, i.e. biodiesel) as a renewable energy source, an innovative acid catalyzed process was developed for the synthesis of biodiesel from waste vegetable oils. The synthesized biodiesels were analytically characterized for their major components, molar fraction and molecular weight of each component, the average molecular weight, and the heat of

  13. Activation of catalysts for synthesizing methanol from synthesis gas

    DOEpatents

    Blum, David B. (108 Tall Oaks Dr., Wayne, NJ 07470); Gelbein, Abraham P. (45 Headley Rd., Morristown, NJ 07960)

    1985-01-01

    A method for activating a methanol synthesis catalyst is disclosed. In this method, the catalyst is slurried in an inert liquid and is activated by a reducing gas stream. The activation step occurs in-situ. That is, it is conducted in the same reactor as is the subsequent step of synthesizing methanol from a methanol gas stream catalyzed by the activated catalyst still dispersed in a slurry.

  14. Motion Analysis by Synthesis: Automatically Annotating Activities in Video

    E-print Network

    Ramanan, Deva

    1 Motion Analysis by Synthesis: Automatically Annotating Activities in Video Deva Ramanan, Member An important vision problem is to automatically describe what people are doing a sequence of video system that labels the activities of multiple people in a video sequence. The system decouples the choice

  15. Synthesis of La and Nb doped PZT powder by the gel-combustion method

    Microsoft Academic Search

    M. Cernea; G. Montanari; C. Galassi; A. L. Costa

    2006-01-01

    Lanthanum and niobium doped PZT with composition (Pb0.93La0.07)[(Zr0.60Ti0.40)]0.9825Nb0.0175O3 (PZTLN) was prepared by the gel-combustion method. A precursor sol was obtained from lead nitrate, zirconyl nitrate, lanthanum oxide, peroxo-citrato-niobium and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate\\/nitrate (CA\\/NO3- = 1.3, 0.36 and 0.09) were used to prepare very fine powders of PZTLN. The gels

  16. Synthesis of terbium doped calcium phosphate nanocrystalline powders by citric acid sol–gel combustion method

    Microsoft Academic Search

    Yingchao Han; Xinyu Wang; Shipu Li; Xionghua Ma

    2009-01-01

    Terbium doped calcium phosphate (Tb-doped CaP) nanocrystalline powders were synthesized by the citric acid sol–gel combustion\\u000a method. The phase composition, morphology and luminescent property of Tb-doped CaP nanocrystalline powders were characterized\\u000a by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, fluorescence spectrophotometer\\u000a and fluorescence microscopy. At 700 °C, Tb-doped CaP nanocrystalline powders are composed of HAP (main phase) and ?-TCP

  17. Development and characterization of MgO:Nd,Li synthesized by solution combustion synthesis for 2D optically stimulated luminescence dosimetry

    Microsoft Academic Search

    L. C. Oliveira; E. D. Milliken; E. G. Yukihara

    The objective of this work is to investigate MgO:Nd,Li synthesized by solution combustion synthesis (SCS) as an optically stimulated luminescence (OSL) material for 2D dosimetry. We characterized the thermoluminescence (TL), OSL, radioluminescence (RL), OSL emission spectrum, and OSL luminescence lifetime of MgO:Nd,Li. We also carried out a preliminary investigation on the OSL signal stability. The results indicates that MgO:Nd,Li has

  18. Elaboration of platinum-modified NiAl coatings by combustion synthesis: Simultaneous repairing and coating of Ni-based superalloys

    Microsoft Academic Search

    M. C. Record; H. De Jouvancourt; R. M. Marin-Ayral

    2007-01-01

    The “SHS build-up process” under high gas pressure was previously reported in literature by the authors in order to repair\\u000a damaged turbine blades. In this process, a brazing foil is inserted between a substrate of Ni-based superalloy and a reactant\\u000a compact made of the 50 at % Ni-50 at % Al mixture. The heat released during the combustion synthesis of

  19. Growth of Continuous Diamond Film by Hot Filament C VD Technique on SiC\\/TiC Pellets, Synthesized Using Combustion Synthesis

    Microsoft Academic Search

    R. Raghunathan; R. Chowdhury; W. Fan; K. Jagannadham; J. Narayan

    1995-01-01

    ?-SiC\\/TiC composites were synthesized using the process of self propagating-high temperature combustion synthesis (SHS). The heat released during the exothermic reaction between the metal and the carbon powder results in the melting of silicon and the titanium into which the carbon diffuses and then (3-SiC and TiC precipitates out from the supersaturated solution. The composite was characterized using X-ray diffraction

  20. Simultaneous synthesis and densification of TiB\\/ ?-Ti(N) composite material by self-propagating combustion under nitrogen pressure

    Microsoft Academic Search

    S. Nakane; O. Yamada; Y. Miyamoto; M. Yoshinaka; K. Hirota; O. Yamaguchi

    1999-01-01

    Simultaneous synthesis and densification of TiB\\/?-Ti(N) composites from Ti (70mol%)\\/ B (30mol%) powder compacts are achieved by self-propagating combustion under a nitrogen pressure of 5MPa. Dense composite materials (97.5% of theoretical) exhibit excellent mechanical properties, in which their fracture toughness and bending strength are 7.8MPam1\\/2 and 640MPa, respectively. Rodlike TiB grains greatly enhance the mechanical properties.

  1. Near-infrared quantum cutting in Ce3+, Er3+, and Yb3+ doped yttrium silicate powders prepared by combustion synthesis

    NASA Astrophysics Data System (ADS)

    Rakov, Nikifor; Maciel, Glauco S.

    2011-10-01

    Yttrium silicate (YS) powders doped with Ce3+, Er3+, and Yb3+ were prepared by combustion synthesis. The material was investigated for use as energy downconverters to reduce thermalization losses in crystalline Si solar cells. The powders were excited by UV light (355 nm), and near-infrared emission around 1 ?m was observed corresponding to a quantum cutting (QC) effect. The QC process occurs via cooperative energy transfer from Ce3+ (sensitizer) to Yb3+ (activator) in Ce3+:Yb3+ co-doped YS powders. QC was also observed in Er3+:Yb3+ co-doped YS powder via sequential energy transfer. The idea of synergy by use of Ce3+:Er3+:Yb3+ triply doped system to enhance the QC efficiency was investigated. We observed that the QC performance of Ce3+:Er3+:Yb3+ triply doped YS powder is not superior to that of Ce3+:Yb3+ co-doped YS powder due to near-infrared luminescence quenching induced by energy back-transfer from Yb3+ to Er3+.

  2. Formation of Ti 3AlC 2\\/Al 2O 3 and Ti 2AlC\\/Al 2O 3 composites by combustion synthesis in Ti–Al–C–TiO 2 systems

    Microsoft Academic Search

    C. L. Yeh; C. W. Kuo; Y. C. Chu

    2010-01-01

    Preparation of Ti3AlC2\\/Al2O3 and Ti2AlC\\/Al2O3 in situ composites was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS). The SHS process incorporates the thermite reaction of Al with TiO2 into solid state combustion of the Ti–Al–C system. The extent of thermite reaction involved in the SHS process was studied on the product composition and combustion behavior. It

  3. Combustion synthesis and engineering of nanoparticles for electronic, structural and superconductor applications

    SciTech Connect

    Stangle, G.C.; Amarakoon, V.R.W.; Schulze, W.A.

    1993-05-28

    Fully dense, nanocrystalline ceramic articles were prepared by the new nanofabrication process. The process consists of two steps: synthesis of ceramic nanoparticles and fabrication of dense, nanocrystalline ceramic parts. The synthesis step produced 10-nanometer-diameter crystallites, and is capable of being scaled up to kilogram/hour production rates. The fabrication step produced dense parts at significantly reduced sintering temperatures and times -- representing a factor of 10--100 reduction in process energy requirements. The process was demonstrated by producing ultrafine-grained yttria-stabilized ZrO[sub 2], an important material with a variety of energy-related applications (solid electrolytes, oxygen sensors, electrode materials, thermal barrier coatings, etc.). Results from this period clearly illustrate the capabilities of this energy-efficient and directly commercializable process for producing dense, nanocrystalline, multicomponent oxide ceramics.

  4. Burning velocities in catalytically assisted self-propagating high-temperature combustion synthesis systems

    Microsoft Academic Search

    T. KIM; M. S. WOOLDRIDGE

    2001-01-01

    The current work presents an experimental study of catalytically assisted self-propagating high-temperature synthesis (SHS) of the tantalum\\/carbon material system. The effects of controlled amounts of two gas-phase transport agents (carbon dioxide and vaporized iodine) were examined. The gas-phase transport agents resulted in burning velocities 2 to 4 times faster than burning velocities observed in comparable catalytically assisted and unassisted Ta\\/C

  5. Synthesis of cobalt ferrite (CoFe2O4) nanoparticles using combustion, coprecipitation, and precipitation methods: A comparison study of size, structural, and magnetic properties

    NASA Astrophysics Data System (ADS)

    Houshiar, Mahboubeh; Zebhi, Fatemeh; Razi, Zahra Jafari; Alidoust, Ali; Askari, Zohreh

    2014-12-01

    In this work the cobalt ferrite (CoFe2O4) nanoparticles are synthesized using three different methods; combustion, coprecipitation, and precipitation. Size, structural, and magnetic properties were determined and compared using X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). XRD data analysis showed an average size of 69.5 nm for combustion, 49.5 nm for coprecipitation, and 34.7 nm for precipitation samples which concorded with SEM images. XRD data further revealed a reverse cubic spinel structure with the space group Fd-3m in all three samples. VSM data of samples showed a saturation point in the magnetic field of less than 15 kOe. Magnetization saturation (Ms) was 56.7 emu/g for combustion synthestized samples, 55.8 emu/g for coprecipitation samples, and 47.2 emu/g for precipitation samples. Coercivity (Hc) was 2002 Oe for combustion synthestized samples, 850 Oe for coprecipitation samples, and 233 Oe for precipitation samples. These results show that various methods of nanoparticle synthesis can lead to different particle sizes and magnetic properties. Hc and Ms are greatest in the combustion method and least in precipitation method.

  6. The Synthesis and Antimicrobial Activity of Heterocyclic Derivatives of Totarol

    PubMed Central

    2012-01-01

    The synthesis and antimicrobial activity of heterocyclic analogues of the diterpenoid totarol are described. An advanced synthetic intermediate with a ketone on the A-ring is used to attach fused heterocycles, and a carbon-to-nitrogen atom replacement is made on the B-ring by de novo synthesis. A-ring analogues with an indole attached exhibit, for the first time, enhanced antimicrobial activity relative to the parent natural product. Preliminary experiments demonstrate that the indole analogues do not target the bacterial cell division protein FtsZ as had been hypothesized for totarol. PMID:23119123

  7. The Synthesis and Antimicrobial Activity of Heterocyclic Derivatives of Totarol.

    PubMed

    Kim, Michelle B; O'Brien, Terrence E; Moore, Jared T; Anderson, David E; Foss, Marie H; Weibel, Doug-Las B; Ames, James B; Shaw, Jared T

    2012-08-28

    The synthesis and antimicrobial activity heterocyclic analogs of the diterpenoid totarol are described. An advanced synthetic intermediate with a ketone on the A-ring is used to attach fused heterocycles and a carbon-to-nitrogen atom replacement is made on the B-ring by de novo synthesis. A-ring analogs with an indole attached exhibit, for the first time, enhanced antimicrobial activity relative to the parent natural product. Preliminary experiments demonstrate that the indole analogs do not target the bacterial cell division protein FtsZ as had been hypothesized for totarol. PMID:23119123

  8. Novel combustion method to prepare octahedral NiO nanoparticles and its photocatalytic activity

    SciTech Connect

    Jegatha Christy, A.; Umadevi, M., E-mail: ums10@yahoo.com

    2013-10-15

    Graphical abstract: - Highlights: • NiO nanoparticles were synthesized by solution combustion method. • Prepared NiO nanoparticles are fcc structure. • Synthesized NiO nanoparticles are octahedral shape. • Shows good photocatalytic activity. - Abstract: Nickel oxide nanoparticles (NiO NPs) were synthesized by solution combustion method using glycine and citric acid as fuels. The X-ray diffraction (XRD) result confirms the face centered cubic (fcc) structure of NiO. The octahedral shape of NiO NPs was confirmed by field emission scanning electron microscope (FESEM) and high resolution transmission electron microscopy (HRTEM). It is possible to suggest that the organic fuel (citric acid/glycine) is responsible for the formation of the octahedral shape due to the easier complex formation. Photocatalytic activity of NiO NPs also evaluated and found that the prepared NiO NPs have high photocatalytic degradation. In the present study, the crystalline nature and shape of the NiO nanoparticles plays a vital role in determining the photocatalytic activity.

  9. SHS combustion characteristics of several ceramics and intermetallic compounds. [Self-propagating High-temperature Synthesis

    SciTech Connect

    Makino, Atsushi (Shizuoka Univ., Hamamatsu (Japan). Dept. of Energy and Mechanical Engineering); Law, C.K. (Princeton Univ., NJ (United States). Dept. of Mechanical and Aerospace Engineering)

    1994-03-01

    Extensive comparisons have been conducted between experimental and theoretical results for the SHS combustion characteristics of a number of solid-solid systems. The heterogeneous flame propagation theory describes a premixed mode of bulk flame propagation supported by the nonpremixed reaction of dispersed nonmetal (or higher melting point metal) particles in the liquid metal, with finite-rate reaction at the particle surface and temperature-sensitive Arrhenius-type condensed-phase mass diffusivity. Systems examined are those of borides (TiB[sub 2], ZrB[sub 2], and HfB[sub 2]) and intermetallic compounds (NiAl, TiCo, and TiNi). By using a consistent set of physico-chemical parameters for these systems, satisfactorily quantitative agreement is demonstrated for the effects of mixture ratio, degree of dilution, and particle size on the burning velocity. Experimental flammability limits are also predicted by the theory.

  10. USE OF COMBUSTION SYNTHESIS IN PREPARING CERAMIC-MATRIX AND METAL-MATRIX COMPOSITE POWDERS

    SciTech Connect

    Weil, K. Scott; Hardy, John S.

    2005-03-01

    A standard combustion-based approach typically used to synthesize nanosize oxide powders has been modified to prepare composite oxide-metal powders for subsequent densification via sintering or hot-pressing into ceramic- or metal-matrix composites. Copper and cerium nitrate salts were dissolved in the appropriate ratio in water and combined with glycine, then heated to cause autoignition. The ratio of glycine-to-total nitrate concentration was found to have the largest effect on the composition, agglomerate size, crystallite size, and dispersivity of phases in the powder product. After consolidation and sintering under reducing conditions, the resulting composite compact consists of a well-dispersed mixture of sub-micron size reinforcement particles in a fine-grained matrix.

  11. EPR investigation on synthesis of Lithium zinc vanadate using sol-gel-combustion route and its optical properties

    NASA Astrophysics Data System (ADS)

    Pathak, Nimai; Gupta, Santosh K.; Prince, Angelina; Kadam, R. M.; Natarajan, V.

    2014-01-01

    The present work describes the synthesis of Lithium zinc vanadate (LiZnVO4) nanophosphor prepared by sol-gel-combustion method and its optical properties. The prepared sample was characterized by X-ray diffraction, SEM, electron paramagnetic resonance and photoluminescence spectroscopy. X-ray diffraction study showed the formation of pure LiZnVO4 at 600 °C with distorted phenacite structure. SEM investigation revealed that the phosphor powder has spherical morphology with particle size of about 100-200 nm. EPR study showed the change of coordination sphere around vanadium from axially distorted octahedral symmetry to tetrahedral geometry along with the change in oxidation state of vanadium ion from +4 to +5. The emission spectrum showed a broad emission at 543 nm with ?ex = 375 nm. The decay time obtained on mono-exponential fitting was 8.3 ?s. The colour coordinates of the system were evaluated using CIE index diagram to be 0.31 and 0.41, which suggest that the prepared material is a potential green emitting phosphor. A bright green colour emission was also observed directly from this phosphor upon excitation with an UV source.

  12. Thermochemical evaluation of combustion synthesis of MoSi[sub 2]-SiC composites

    SciTech Connect

    Jandhyala, S. (Defence Metallurgical Research Lab., Hyderabad (India). Combustion Synthesis Group)

    1993-01-01

    Thermochemical calculations were carried out for the self-propagating high-temperature synthesis (SHS) of SiC-particulate-reinforced MoSi[sub 2] composites. These composites can be prepared using the elemental powders of Mo, Si, and C by SHS. Adiabatic temperatures were calculated at different initial temperatures for the reactions forming MoSi[sub 2], SiC, and their composites. Amounts of liquid phase of MoSi[sub 2] formed at various temperatures and mole ratios were computed.

  13. Preparation of molybdenum borides by combustion synthesis involving solid-phase displacement reactions

    Microsoft Academic Search

    C. L. Yeh; W. S. Hsu

    2008-01-01

    Preparation of molybdenum borides of five different phases in the Mo–B binary system (including Mo2B, MoB, MoB2, Mo2B5, and MoB4) was performed by self-propagating high-temperature synthesis (SHS) with two kinds of the reactant samples. When elemental powder compacts with an exact stoichiometry corresponding to the boride phase were employed, self-sustaining reaction was only achieved in the sample with Mo:B=1:1 and

  14. Assisted self-sustaining combustion reaction in the Fe–Si system: Mechanical and chemical activation

    Microsoft Academic Search

    Ch. Gras; N. Zink; F. Bernard; E. Gaffet

    2007-01-01

    This work presents original investigations carried out to improve the activated self-propagating high-temperature synthesis (SHS) process in the Fe–Si system: different ignition modes are tested (volume heating as opposed to a local ignition source), and the use of additive is considered in order to enhance the SHS type reactivity in the Fe–Si system. When 20wt.% of KNO3 is added to

  15. ChemTeacher: Combustion

    NSDL National Science Digital Library

    2011-01-01

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Combustion page includes resources for teaching students about the chemistry behind combustion.

  16. Synthesis of Surface-Active Quaternary Amino Polyfluorosiloxanes

    E-print Network

    Chaudhury, Manoj K.

    , on further reaction with various amines followed by quaternization, gave quaternary amino polyfluorosiloxanes prepared by quaternization of fluorocarbon amines using alkyl halide. Quaternary fluorocarbon7 (CF3)2CF(CF2Synthesis of Surface-Active Quaternary Amino Polyfluorosiloxanes ASHISH VAIDYA, MANOJ CHAUDHURY

  17. Synthesis of (-)-arctigenin derivatives and their anticancer activity.

    PubMed

    Gui-Rong, Chen; Li-Ping, Cai; De-Qiang, Dou; Ting-Guo, Kang; Hong-Fu, Li; Fu-Rui, Li; Ning, Jiang

    2012-01-01

    The natural dibenzylbutyrolactone type lignanolide (-)-arctigenin, which was prepared from fructus arctii, showed obvious anticancer activity. The synthesis of four new (-)-arctigenin derivatives and their anticancer bioactivities were examined. The structures of the four new synthetic derivatives were elucidated. PMID:21867457

  18. Adrenoceptor-activated Nitric Oxide Synthesis in Salivary Acinar Cells

    Microsoft Academic Search

    D. K. Looms; S. Dissing; K. Tritsaris; A. M. Pedersen; B. Nauntofte

    2000-01-01

    We investigated the cellular regulation of nitric oxide synthase (NOS) activity in isolated acinar cells from rat parotid and human labial salivary glands, using the newly developed fluorescent nitric oxide (NO) indicator, DAF-2. We found that sympathetic stimulation with norepinephrine (NE) caused a strong increase in NO synthesis that was not seen after parasympathetic stimulation with acetylcholine. In rat parotid

  19. Combustion synthesis of metal-matrix composites. Part 2: The Ti-Ti{sub x}Al{sub y}-Al{sub 2}O{sub 3} system

    SciTech Connect

    Kunrath, A.O.; Strohaecker, T.R. [UFRGS, Porto Alegre, Rio Grande do Sul (Brazil). Dept. de Metalurgia] [UFRGS, Porto Alegre, Rio Grande do Sul (Brazil). Dept. de Metalurgia; Moore, J.J. [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering] [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering

    1996-01-15

    The production of high performance materials (ceramics, intermetallics and composites) by combustion synthesis is receiving considerable attention since the process offers certain advantages with respect to simplicity and a relatively low energy requirement. The methods by which combustion synthesis (or SHS) can be used to produce metal matrix composites were outlined in an earlier paper. The use of excess liquid metal in the combustion synthesis reaction has already been successfully employed to achieve low porosity products. This metallic phase may be generated by an in-situ reduction of a metal oxide or by adding an excess of some metal to the reactants. Coupling a simultaneous consolidation (pressing) process with the SHS reaction has been found to produce dense bodies. This work discussed in this paper is concerned with the synthesis of a metallic/intermetallic matrix composite reaction system which can be represented by equation. With this reaction, high volume fractions of metallic/intermetallic phases can be produced. The metal-matrix produced by this reaction is predominantly a mixture of Ti{sub 3}Al + Ti as indicated in the appropriate area of the Ti-Al phase diagram. Increasing x increases the volume fraction of Ti. TiAl was observed in only one of the four different stoichiometries studied, i.e., x = 1, as detected by XRD. Using this reaction, there is a constant amount of excess Al and a variable excess of Ti. These stoichiometries produce composites with varying Ti-Al ratios that allow the matrix composition of the composite to be varied along the concentration axis of the Ti-Al phase diagram.

  20. Solution-combustion synthesis and photoluminescence properties of YBO3:Tb3+ phosphor powders

    NASA Astrophysics Data System (ADS)

    Onani, Martin O.; Okil, Joseph O.; Dejene, Francis B.

    2014-04-01

    YBO3:Tb3+ nanocrystalline phosphors were successfully deposited by a solution-combustion method, using rare-earth nitrates, urea and boric acid as starting materials. The crystal structure, morphology, chemical composition and photoluminescence properties of the films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The results of SEM and XRD revealed that the powders were composed of spherical YBO3:Tb3+ nanocrystals with average grain size of between 50 and 100 nm. The electron diffraction spectroscopy (EDS) confirmed the presence of the Y, B, O, and C. The XRD measurements revealed YBO3:Tb3+ (JCPDS:83-1205) structure when annealed at 1000 °C for 2 h. The YBO3:Tb3+ powders exhibited emissions at 490, 545 and 585 nm, which were assigned to the 5D4-7F6, 5D4-7F5 and 5D4-7F4 transitions of Tb3+, respectively. Among them, the green emission at 545 nm (5D4-7F5) was dominant.

  1. Synthesis, structure and electromagnetic properties of Mn-Zn ferrite by sol-gel combustion technique

    NASA Astrophysics Data System (ADS)

    Wang, Wenjie; Zang, Chongguang; Jiao, Qingjie

    2014-01-01

    The electromagnetic absorbing behaviors of a thin coating fabricated by mixing Mn-Zn ferrite with epoxy resin (EP) were studied. The spinel ferrites Mn1-xZnxFe2O4 (x=0.2, 0.5 and 0.8) were synthesized with citrate acid as complex agent by sol-gel combustion method. The microstructure and surface morphology of Mn-Zn ferrite powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The complex permittivity and complex permeability of the fabricated ferrite/EP composites were investigated in terms of their contributions to the absorbing properties in the low frequency (10 MHz to 1 GHz). The microwave absorption of the prepared ferrite/EP composites could be tailored by matching the dielectric loss and magnetic loss and by controlling the doped metal ratio. The composites with the ferrite composition x=0.2 are found to show higher reflection loss compared with the composites with other compositions. It is proposed that the prepared composites can potentially be applied in electromagnetic microwave absorbing field.

  2. EGCG assisted green synthesis of ZnO nanopowders: Photodegradative, antimicrobial and antioxidant activities.

    PubMed

    Suresh, D; Udayabhanu; Nethravathi, P C; Lingaraju, K; Rajanaika, H; Sharma, S C; Nagabhushana, H

    2014-11-01

    Zinc oxide nanopowders were synthesized by solution combustion method using Epigallocatechin gallate (EGCG) a tea catechin as fuel. The structure and morphology of the product was characterized by Powder X-ray Diffraction, Scanning Electron Microscopy, photoluminescence and UV-Visible spectroscopy. The nanopowders (Nps) were subjected to photocatalytic and biological activities such as antimicrobial and antioxidant studies. PXRD patterns demonstrate that the formed product belongs to hexagonal wurtzite system. SEM images show that the particles are agglomerated to form sponge like structure and the average crystallite sizes were found to be ?10-20nm. PL spectra exhibit broad and strong peak at 590nm due to the Zn-vacancies, and O-vacancies. The prepared ZnO Nps exhibit excellent photocatalytic activity for the photodegradation of malachite green (MG) and methylene blue (MB) indicating that the ZnO NPs are potential photocatalytic semiconductor materials. ZnO NPs exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus using the agar well diffusion method. Furthermore, the ZnO nano powders show good antioxidant activity by potentially scavenging DPPH radicals. The study successfully demonstrates synthesis of ZnO NPs by simple ecofriendly route employing EGCG as fuel that exhibit superior photodegradative, antibacterial and antioxidant activities. PMID:25459708

  3. Effect of KCl, NaCl and CaCl{sub 2} mixture on volume combustion synthesis of TiB{sub 2} nanoparticles

    SciTech Connect

    Nekahi, Atiye [Mining and Metallurgical Engineering Department, Amirkabir University of Technology, 424 Hafez Ave., Tehran 15875-4413 (Iran, Islamic Republic of)] [Mining and Metallurgical Engineering Department, Amirkabir University of Technology, 424 Hafez Ave., Tehran 15875-4413 (Iran, Islamic Republic of); Firoozi, Sadegh, E-mail: s.firoozi@aut.ac.ir [Mining and Metallurgical Engineering Department, Amirkabir University of Technology, 424 Hafez Ave., Tehran 15875-4413 (Iran, Islamic Republic of)] [Mining and Metallurgical Engineering Department, Amirkabir University of Technology, 424 Hafez Ave., Tehran 15875-4413 (Iran, Islamic Republic of)

    2011-09-15

    Highlights: {yields} A low melting diluent lowers the ignition temperature in combustion synthesis. {yields} Deagglomerated synthesized products are formed as the result of diluent addition. {yields} Addition of 45% salt mixture resulted in formation of 70 nm TiB{sub 2} nanoparticles. {yields} Thermodynamically unstable Mg{sub 2}TiO{sub 4} and Mg{sub 3}B{sub 2}O{sub 6} by-products were formed. {yields} Small change in particle size was observed with addition of salt mixture. -- Abstract: Preparation of titanium diboride (TiB{sub 2}) nanoparticles was carried out by volume combustion synthesis. TiO{sub 2}, B{sub 2}O{sub 3} and elemental Mg were mixed with 0-60% salt mixture of KCl, NaCl and CaCl{sub 2} with increment of 15% as a low melting temperature diluent. Compressed samples were synthesized in a tubular furnace at a constant heating rate under argon atmosphere. Thermal analysis of the process showed that the addition of the low melting temperature salts mixture led to a significant decrease in ignition and combustion temperatures. Synthesized samples were then leached by nitric and hydrochloric acids to remove impurities. The samples were examined by XRD, SEM and DLS analysis. The results showed the formation of fine deagglomerated particles with the addition of the salts mixture. The results revealed that 45% salts mixture had the smallest average particle size of about 90 nm.

  4. In vitro immunotoxic and genotoxic activities of particles emitted from two different small-scale wood combustion appliances

    NASA Astrophysics Data System (ADS)

    Tapanainen, Maija; Jalava, Pasi I.; Mäki-Paakkanen, Jorma; Hakulinen, Pasi; Happo, Mikko S.; Lamberg, Heikki; Ruusunen, Jarno; Tissari, Jarkko; Nuutinen, Kati; Yli-Pirilä, Pasi; Hillamo, Risto; Salonen, Raimo O.; Jokiniemi, Jorma; Hirvonen, Maija-Riitta

    2011-12-01

    Residential wood combustion appliances emit large quantities of fine particles which are suspected to cause a substantial health burden worldwide. Wood combustion particles contain several potential health-damaging metals and carbon compounds such as polycyclic aromatic hydrocarbons (PAH), which may determine the toxic properties of the emitted particles. The aim of the present study was to characterize in vitro immunotoxicological and chemical properties of PM 1 ( Dp ? 1 ?m) emitted from a pellet boiler and a conventional masonry heater. Mouse RAW264.7 macrophages were exposed for 24 h to different doses of the emission particles. Cytotoxicity, production of the proinflammatory cytokine TNF-? and the chemokine MIP-2, apoptosis and phases of the cell cycle as well as genotoxic activity were measured after the exposure. The type of wood combustion appliance had a significant effect on emissions and chemical composition of the particles. All the studied PM 1 samples induced cytotoxic, genotoxic and inflammatory responses in a dose-dependent manner. The particles emitted from the conventional masonry heater were 3-fold more potent inducers of programmed cell death and DNA damage than those emitted from the pellet boiler. Furthermore, the particulate samples that induced extensive DNA damage contained also large amounts of PAH compounds. Instead, significant differences between the studied appliances were not detected in measurements of inflammatory mediators, although the chemical composition of the combustion particles differed considerably from each other. In conclusion, the present results show that appliances representing different combustion technology have remarkable effects on physicochemical and associated toxicological and properties of wood combustion particles. The present data indicate that the particles emitted from incomplete combustion are toxicologically more potent than those emitted from more complete combustion processes.

  5. Optimal cooperative control synthesis of active displays

    NASA Technical Reports Server (NTRS)

    Gary, Sanjay; Schmidt, David K.

    1987-01-01

    A technique is developed that is intended to provide a systematic approach to synthesizing display augmentation for optimal manual control in complex, closed-loop tasks. A cooperative control synthesis technique, previously developed to design pilot-optimal control augmentation for the plant, is extended to incorporate the simultaneous design of performance enhancing displays. The technique utilizes an optimal control model of the man in the loop. It is applied to the design of a quickening control law for a display and a simple K/(s squared) plant, and then to an F-15 type aircraft in a multichannel task. Utilizing the closed-loop modeling and analysis procedures, the results from the display design algorithm are evaluated and an analytical validation is performed. Experimental validation is recommended for future efforts.

  6. Active Control of High Frequency Combustion Instability in Aircraft Gas-Turbine Engines

    NASA Technical Reports Server (NTRS)

    Corrigan, Bob (Technical Monitor); DeLaat, John C.; Chang, Clarence T.

    2003-01-01

    Active control of high-frequency (greater than 500 Hz) combustion instability has been demonstrated in the NASA single-nozzle combustor rig at United Technologies Research Center. The combustor rig emulates an actual engine instability and has many of the complexities of a real engine combustor (i.e. actual fuel nozzle and swirler, dilution cooling, etc.) In order to demonstrate control, a high-frequency fuel valve capable of modulating the fuel flow at up to 1kHz was developed. Characterization of the fuel delivery system was accomplished in a custom dynamic flow rig developed for that purpose. Two instability control methods, one model-based and one based on adaptive phase-shifting, were developed and evaluated against reduced order models and a Sectored-1-dimensional model of the combustor rig. Open-loop fuel modulation testing in the rig demonstrated sufficient fuel modulation authority to proceed with closed-loop testing. During closed-loop testing, both control methods were able to identify the instability from the background noise and were shown to reduce the pressure oscillations at the instability frequency by 30%. This is the first known successful demonstration of high-frequency combustion instability suppression in a realistic aero-engine environment. Future plans are to carry these technologies forward to demonstration on an advanced low-emission combustor.

  7. Synthesis and biological activities of new halophenols.

    PubMed

    Zheng, FeiLang; Ban, ShuRong; Feng, XiuE; Zhao, ChengXiao; Du, GuanHua; Li, QingShan

    2013-03-01

    A series of new halophenols were synthesized, and their structures were established on the basis of 1H, 13C NMR and mass spectral data. All of the prepared compounds were screened for their in vitro protein tyrosine kinase (PTK) and vascular smooth muscle cell (VSMC) proliferation inhibitory activity. Twelve halophenols showed significant PTK inhibitory activity, most of them exhibited stronger activities than that of genistein, a positive reference compound. Several halophenols also displayed moderate VSMC proliferation inhibitory activity, compound 8c showed higher activity than that of tetrandrine, a positive reference compound. The preliminary structure-activity relationships of these compounds were investigated and discussed. The results provided a foundation for the action mechanism study and further structure optimization of the halophenols. PMID:22946534

  8. Total Synthesis and Antimicrobial Activity of Chlorocatechelin A.

    PubMed

    Kishimoto, Shinji; Nishimura, Shinichi; Hatano, Masaki; Igarashi, Masayuki; Kakeya, Hideaki

    2015-06-19

    Chlorocatechelin A (1) is a structurally unique microbial siderophore containing two units of 4-chloro-2,3-dihydroxybenzoic acid (CDB) and a characteristic acylguanidine structure. Purification from the microbe culture is not an easy task due to the lability of the acylguanidine and its chelating nature. Here we report the first convergent total synthesis and antimicrobial activity of chlorocatechelin A (1). The bis-acylated arginine was constructed using a Schotten-Baumann reaction whereas the CDB component was synthesized from o-vanillin (8). Condensation with an ornithine derivative synthesized from 1-benzyl d-glutamate was followed by deprotection in basic and neutral conditions to complete the total synthesis. We examined the antimicrobial activity of chlorocatechelin A (1) and found that this siderophore was active against desferrioxamine B (DFB)-sensitive microbes including the fish pathogen Pasteurella piscicida. PMID:26018853

  9. Microwave induced combustion synthesis of ceramic and ceramic-metal composites

    SciTech Connect

    Yiin, T.; Barmatz, M. [California Institute of Technology, Pasadena, CA (United States); Feng, H.; Moore, J. [Colorado School of Mines, Golden, CO (United States)

    1995-12-31

    Microwaves were used to induce self-propagating high temperature synthesis (SHS) in the reaction 3TiO{sub 2}+3C+(4+x)Al {yields} 3TiC+2Al{sub 2}O{sub 3}+xAl. The SHS process was studied for x = 0 and 4, using slow and fast heating rates and with and without the application of uniaxial pressure. Less than 50 watts was required to internally ignite the samples using a TE{sub 102} microwave cavity mode. Uniaxial stresses in the range of 200-1400 psi were continuously applied along the vertical axis of some of the processed samples as the SHS reactions were initiated. SEM photomicrographs clearly indicate differences in the formation of whiskers and other microstructural features in the products obtained from microwave and conventional hot wire techniques. The x = 0 samples processed with fast and slow microwave heating rates reached higher densities than the conventionally processed samples.

  10. Synthesis and activity of proteasome inhibitors.

    PubMed

    Dunn, Derek; Iqbal, Mohamed; Chatterjee, Sankar

    2014-02-01

    Among its various catalytic activities, "chymotrypsin-like" activity of proteasome, a large multicatalytic proteinase complex has emerged as the focus of drug discovery efforts in cancer therapy. Herein, we report results from our investigation on a series of peptidomimetic inhibitors. PMID:23339427

  11. Modelling of flame temperature of solution combustion synthesis of nanocrystalline calcium hydroxyapatite material and its parametric optimization

    Microsoft Academic Search

    Samir K. Ghosh; Sukhomay Pal; Sujit K. Roy; Surjya K. Pal; Debabrata Basu

    2010-01-01

    Hydroxyapatite (HAp), an important bio-ceramic was successfully synthesized by combustion in the aqueous system containing\\u000a calcium nitrate-di-ammonium hydrogen orthophosphate-urea. The combustion flame temperature of solution combustion reaction\\u000a depends on various process parameters, and it plays a significant role in the phase formation, phase stability and physical\\u000a characteristics of calcium hydroxyapatite powder. In this work, an attempt has been made to

  12. Synthesis and antitumor activity of tetrandrine derivatives.

    PubMed

    Wu, Chun-Zhen; Lai, Long; Hu, Xiao; Lei, Rong-Rong; Yang, Yi-Fang

    2013-09-01

    Tetrandrine possesses antitumor activity, however, only a few studies on its structure modification were reported. To improve the antitumor activity of tetrandrine, 20 new tetrandrine derivatives were designed and synthesized by Sonogashira and Suzuki reactions. Their antitumor activities were evaluated against three tumor cell lines including A549, HepG2, and BGC-823 by methyl thiazolyl tetrazolium assay with taxol as a positive control. The results showed that compounds 2c and 2g were highly potent against BGC-823 cell line, and compounds 1i and 1k showed particular activity against HepG2 cells. These results demonstrated that compounds 1i, 1k, 2c, and 2g were promising leads for further investigation. PMID:23944846

  13. Synthesis and biological activities of 8-arylflavones

    Microsoft Academic Search

    Tran Thanh Dao; Soo Bae Kim; Kwan-Seog Sin; Sanghee Kim; Hyun Pyo Kim

    2004-01-01

    A number of 8-arylflavones have been synthesized as congeners of wogonin and evaluated for their inhibitory activities of\\u000a PGE2 production. 8-Arylflavones were obtained from commercially available chrysin via two different synthetic pathways. Most 8-arylflavones\\u000a exhibited much reduced inhibitory activities against COX-2 catalyzed PGE2 production compared to that of wogonin. Functional group replacement at the 8-position of wogonin from methoxy to

  14. Interaction of pulsating and spinning waves in condensed phase combustion

    SciTech Connect

    Booty, M.R.; Margolis, S.B.; Matkowsky, B.J.

    1986-10-01

    The authors employ a nonlinear stability analysis in the neighborhood of a multiple bifurcation point to describe the interaction of pulsating and spinning modes of condensed phase combustion. Such phenomena occur in the synthesis of refractory materials. In particular, they consider the propagation of combustion waves in a long thermally insulated cylindrical sample and show that steady, planar combustion is stable for a modified activation energy/melting parameter less than a critical value. Above this critical value primary bifurcation states, corresponding to time-periodic pulsating and spinning modes of combustion, emanate from the steadily propagating solution. By varying the sample radius, the authors split a multiple bifurcation point to obtain bifurcation diagrams which exhibit secondary, tertiary, and quarternary branching to various types of quasi-periodic combustion waves.

  15. Decomposition synthesis approach to design of RF and microwave active circuits

    Microsoft Academic Search

    L. I. Babak

    2001-01-01

    The paper presents a new decomposition synthesis method for designing linear and nonlinear active high-frequency circuits. This method allows the synthesis of passive correction (matching, compensation, feedback, etc.) networks from circuit performance specifications, with a circuit block diagram given. The method forms the basis of unified synthesis procedure for a wide range of RF and microwave active semiconductor circuits. Statements

  16. COMBUSTION SYNTHESIS AND CHARACTERIZATION OF NANOCRYSTALLINE ALKALINE EARTH ALUMINATE Sr4Al14O25:RE(RE = Eu, Dy, Sm)

    NASA Astrophysics Data System (ADS)

    Hedaoo, V. P.; Bhatkar, V. B.; Omanwar, S. K.

    2013-08-01

    Nanoscale phosphors have superior performance characteristics than the bulk phosphors. This paper explains the synthesis and characterization like XRD, FTIR, SEM and photoluminescence properties of nanocrystalline Sr4Al14O25 doped with rare earth elements like europium, dysprosium and samarium by combustion method. XRD showed the nanoscale crystalline nature of as-prepared samples. SEM confirmed size of the particle less than 100 nm. Photoluminescent emission spectra showed strong orange red emission at 593 nm for Sr4Al14O25:Sm3+. The green emission of Eu2+ was observed at around 490 nm for Sr4Al14O25:Eu2+.

  17. Synthesis and characterization of nanocrystalline LiNi 0.5Co 0.5VO 4 powders by citric acid assisted sol–gel combustion process

    Microsoft Academic Search

    S. Vivekanandhan; M. Venkateswarlu; N. Satyanarayana

    2008-01-01

    Nanocrystalline LiNi0.5Co0.5VO4 powders were synthesized by sol–gel combustion process with metal nitrates, as the source of metal ions and citric acid, as a chelating agent. The effect of citric acid amount on the synthesis of nanocrystalline LiNi0.5Co0.5VO4 powders was investigated through TG\\/DTA, FTIR, XRD and SEM analysis. Thermal behavior of the dried gels was studied by TG\\/DTA thermograms. Structural coordination

  18. An experimental investigation on combustion synthesis of transition metal silicides V 5Si 3, Nb 5Si 3, and Ta 5Si 3

    Microsoft Academic Search

    C. L. Yeh; W. H. Chen

    2007-01-01

    Preparation of transition metal silicides V5Si3, Nb5Si3, and Ta5Si3 was conducted by self-propagating high-temperature synthesis (SHS) from elemental powder compacts at their stoichiometries. The propagation mode of self-sustaining reactions, flame-front velocity, combustion temperature, and phase composition of end products were extensively studied. For the reactant compacts from the mixtures of V:Si=5:3 and Ta:Si=5:3, a planar flame front propagating in a

  19. Formation of Ti 2AlC 0.5N 0.5 solid solutions by combustion synthesis of Al 4C 3-containing samples in nitrogen

    Microsoft Academic Search

    C. L. Yeh; C. W. Kuo; F. S. Wu

    2010-01-01

    Preparation of the solid solution Ti2AlC0.5N0.5 from the powder compacts composed of Ti, Al4C3, and Al or AlN was investigated by self-propagating high-temperature synthesis (SHS) under gaseous nitrogen. The molar proportion of three reactant powders was formulated as Ti:Al4C3:Al (or AlN)=2:1\\/6:1\\/3. For both types of the samples, the increase of nitrogen pressure from 0.45 to 1.82MPa augments the combustion temperature

  20. A study on the heat-treatments of nanocrystalline nickel substituted BaW hexaferrite produced by low combustion synthesis method

    Microsoft Academic Search

    Rahul Sharma; Ramesh Chandra Agarwala; Vijaya Agarwala

    2007-01-01

    The novel low temperature combustion synthesis (LCS) method for the preparation of nanocrystalline W-type BaW hexaferrite i.e. BaNi2Fe16O27 has been carried out by citrate precursor using the sol-to-gel (S–G) followed by gel-to-nanocrystalline (G–N) conversion. Decomposition behaviors and the phases associated therein are investigated by means of thermal analysis (DTA\\/DTG\\/TG) and XRD, respectively. Atomic absorption spectroscopy (AAS) has been used to

  1. Active Combustion Control for Aircraft Gas-Turbine Engines-Experimental Results for an Advanced, Low-Emissions Combustor Prototype

    NASA Technical Reports Server (NTRS)

    DeLaat, John C.; Kopasakis, George; Saus, Joseph R.; Chang, Clarence T.; Wey, Changlie

    2012-01-01

    Lean combustion concepts for aircraft engine combustors are prone to combustion instabilities. Mitigation of instabilities is an enabling technology for these low-emissions combustors. NASA Glenn Research Center s prior activity has demonstrated active control to suppress a high-frequency combustion instability in a combustor rig designed to emulate an actual aircraft engine instability experience with a conventional, rich-front-end combustor. The current effort is developing further understanding of the problem specifically as applied to future lean-burning, very low-emissions combustors. A prototype advanced, low-emissions aircraft engine combustor with a combustion instability has been identified and previous work has characterized the dynamic behavior of that combustor prototype. The combustor exhibits thermoacoustic instabilities that are related to increasing fuel flow and that potentially prevent full-power operation. A simplified, non-linear oscillator model and a more physics-based sectored 1-D dynamic model have been developed to capture the combustor prototype s instability behavior. Utilizing these models, the NASA Adaptive Sliding Phasor Average Control (ASPAC) instability control method has been updated for the low-emissions combustor prototype. Active combustion instability suppression using the ASPAC control method has been demonstrated experimentally with this combustor prototype in a NASA combustion test cell operating at engine pressures, temperatures, and flows. A high-frequency fuel valve was utilized to perturb the combustor fuel flow. Successful instability suppression was shown using a dynamic pressure sensor in the combustor for controller feedback. Instability control was also shown with a pressure feedback sensor in the lower temperature region upstream of the combustor. It was also demonstrated that the controller can prevent the instability from occurring while combustor operation was transitioning from a stable, low-power condition to a normally unstable high-power condition, thus enabling the high-power condition.

  2. Combustion of dried animal dung as biofuel results in the generation of highly redox active fine particulates

    Microsoft Academic Search

    Ian S Mudway; Sean T Duggan; Chandra Venkataraman; Gazala Habib; Frank J Kelly; Jonathan Grigg

    2005-01-01

    BACKGROUND: The burning of biomass in the developing world for heating and cooking results in high indoor particle concentrations. Long-term exposure to airborne particulate matter (PM) has been associated with increased rates of acute respiratory infections, chronic obstructive lung disease and cancer. In this study we determined the oxidative activity of combustion particles derived from the biomass fuel dung cake

  3. Presence of estrogenic activity from emission of fossil fuel combustion as detected by a recombinant yeast bioassay

    NASA Astrophysics Data System (ADS)

    Wang, Jingxian; Wu, Wenzhong; Henkelmann, Bernhard; You, Li; Kettrup, Antonius; Schramm, Karl-Werner

    Estrogenic activities of emission samples generated by fossil fuel combustion were investigated with human estrogen receptor (ER) recombinant yeast bioassay. The results showed that there were weak but clear estrogenic activities in combustion emissions of fossil fuels including coal, petroleum, and diesel. The estrogenic relative potency (RP) of fossil fuel combustion was the highest in petroleum-fired car, followed by coal-fired stove, diesel-fired agrimotor, coal-fired electric power station. On the other hand, the estrogenic relative inductive efficiency (RIE) was the highest in coal-fired stove and coal-fired electric power station, followed by petroleum-fired car and diesel-fired agrimotor. The estrogenic activities in the sub-fractions from chromatographic separation of emitted materials were also determined. The results indicated that different chemical fractions in these complex systems have different estrogenic potencies. The GC/MS analysis of the emission showed that there were many aromatic carbonyls, big molecular alcohol, PAHs and derivatives, and substituted phenolic compounds and derivatives which have been reported as environmental estrogens. The existence of estrogenic substances in fossil fuel combustion demands further investigation of their potential adverse effects on human and on the ecosystem. The magnitude of pollution due to global usage of fossil fuels makes it imperative to understand the issue of fossil fuel-derived endocrine activities and the associated health risks, particularly the aggregated risks stemmed from exposure to toxicants of multiple sources.

  4. Impact of oxy-fuel combustion gases on mercury retention in activated carbons from a macroalgae waste: effect of water.

    PubMed

    Lopez-Anton, M A; Ferrera-Lorenzo, N; Fuente, E; Díaz-Somoano, M; Suarez-Ruíz, I; Martínez-Tarazona, M R; Ruiz, B

    2015-04-01

    The aim of this study is to understand the different sorption behaviors of mercury species on activated carbons in the oxy-fuel combustion of coal and the effect of high quantities of water vapor on the retention process. The work evaluates the interactions between the mercury species and a series of activated carbons prepared from a macroalgae waste (algae meal) from the agar-agar industry in oxy-combustion atmospheres, focussing on the role that the high concentration of water in the flue gases plays in mercury retention. Two novel aspects are considered in this work (i) the impact of oxy-combustion gases on the retention of mercury by activated carbons and (ii) the performance of activated carbons prepared from biomass algae wastes for this application. The results obtained at laboratory scale indicate that the effect of the chemical and textural characteristics of the activated carbons on mercury capture is not as important as that of reactive gases, such as the SOx and water vapor present in the flue gas. Mercury retention was found to be much lower in the oxy-combustion atmosphere than in the O2+N2 (12.6% O2) atmosphere. However, the oxidation of elemental mercury (Hg0) to form oxidized mercury (Hg2+) amounted to 60%, resulting in an enhancement of mercury retention in the flue gas desulfurization units and a reduction in the amalgamation of Hg0 in the CO2 compression unit. This result is of considerable importance for the development of technologies based on activated carbon sorbents for mercury control in oxy-combustion processes. PMID:25585865

  5. Synthesis and Activity of Biomimetic Biofilm Disruptors

    PubMed Central

    2013-01-01

    Biofilms are often associated with human bacterial infections, and the natural tolerance of biofilms to antibiotics challenges treatment. Compounds with antibiofilm activity could become useful adjuncts to antibiotic therapy. We used norspermidine, a natural trigger for biofilm disassembly in the developmental cycle of Bacillus subtilis, to develop guanidine and biguanide compounds with up to 20-fold increased potency in preventing biofilm formation and breaking down existing biofilms. These compounds also were active against pathogenic Staphylococcus aureus. An integrated approach involving structure–activity relationships, protonation constants, and crystal structure data on a focused synthetic library revealed that precise spacing of positively charged groups and the total charge at physiological pH distinguish potent biofilm inhibitors. PMID:23406351

  6. Effects of using Al 4C 3 as a reactant on formation of Ti 3AlC 2 by combustion synthesis in SHS mode

    Microsoft Academic Search

    C. L. Yeh; Y. G. Shen

    2009-01-01

    Preparation of the ternary carbide Ti3AlC2 was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) from both the elemental powder compacts of Ti:Al:C=3:1:2 and the Al4C3-containing samples compressed from the powder mixtures of Ti\\/Al\\/C\\/Al4C3 with Al4C3 content ranging from 1.85 to 5.56mol%. The reactant compact with 5.56mol% Al4C3 represents a composition of 3Ti+1.25C+0.25Al4C3, within which Al4C3

  7. Circadian telomerase activity and DNA synthesis for timing peptide administration

    Microsoft Academic Search

    Yi Qu; Zhengrong Wang; Xiang Huang; Chaomin Wan; Chun-lei Yang; Bailin Liu; Germaine Cornelissen; Franz Halberg

    2003-01-01

    DNA synthesis and telomerase activity were assessed in nude mice transplanted with hepatic carcinoma. Hepatic cancer cells (SMMC-7721) were implanted into both flanks of each of 14 BALB\\/C mice synchronized in 12h of light alternating with 12h of darkness (LD12:12) for 4 weeks. At 7 timepoints, tumor samples were collected for measurement of cellular DNA content by flow cytometry and

  8. Specific features of the behavior of synthetic diamond in a self-propagating high-temperature synthesis (SHS) combustion wave

    Microsoft Academic Search

    K. L. Padyukov; E. A. Levashov; I. P. Borovinskaya; A. G. Kost

    1992-01-01

    The behavior of synthetic diamond powder in an SHS combustion wave is considered by using the model Ti-B-diamond system as an example. The results presented show that the diamond can retain its properties when exposed to the extreme thermal conditions realized in an SHS combustion wave.

  9. Specific features of the behavior of synthetic diamond in a self-propagating high-temperature synthesis (SHS) combustion wave

    NASA Astrophysics Data System (ADS)

    Padyukov, K. L.; Levashov, E. A.; Borovinskaya, I. P.; Kost, A. G.

    1992-11-01

    The behavior of synthetic diamond powder in an SHS combustion wave is considered by using the model Ti-B-diamond system as an example. The results presented show that the diamond can retain its properties when exposed to the extreme thermal conditions realized in an SHS combustion wave.

  10. Effects of Al and Al 4C 3 contents on combustion synthesis of Cr 2AlC from Cr 2O 3–Al–Al 4C 3 powder compacts

    Microsoft Academic Search

    C. L. Yeh; C. W. Kuo

    2011-01-01

    Preparation of the ternary carbide Cr2AlC was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) from the Cr2O3–Al–Al4C3 powder compact. Effects of the contents of Al and Al4C3 on the product composition and combustion behavior were studied by formulating the reactant mixture with a stoichiometric proportion of Cr2O3:Al:Al4C3=3:5x:y, where x and y varied from 1.0 to

  11. Direct synthesis of La 9.33Si 6O 26 ultrafine powder via sol–gel self-combustion method

    Microsoft Academic Search

    Changan Tian; Junliang Liu; Jun Cai; Yanwei Zeng

    2008-01-01

    Single phase La9.33Si6O26 ultrafine powder, as a kind of highly activated precursor to prepare medium-to-low temperature electrolyte for solid oxide fuel cells (SOFCs), has been successfully synthesized via a non-aqueous sol–gel and self-combustion approach from the starting materials: lanthanum nitrate (La(NO3)3·6H2O), citric acid, ethylene glycol (EG), tetraethyl orthosilicate (TEOS) and ammonium nitrate. The details of gel's self-combustion were investigated by

  12. Synthesis and biological activity of 8-arylergolines.

    PubMed

    Bach, N J; Kornfeld, E C; Dorman, D E

    1977-08-01

    9,10-Didehydro-6-methyl-8beta-arylergolines 2, in which the carboxyl group of lysergic acid and isolysergic acid is replaced by various aryl groups, were prepared in two steps by alkylation of aromatic substrates with the tetracyclic allylic alcohol 3, followed by aromatization with MnO2. The new ergolines 2 have modest prolactin-inhibiting and rat antimuricidal activities and possess significant alpha-blocking and antiserotonin properties. PMID:561190

  13. Synthesis and antimalarial activity of febrifugine derivatives.

    PubMed

    Takeuchi, Y; Koike, M; Azuma, K; Nishioka, H; Abe, H; Kim, H S; Wataya, Y; Harayama, T

    2001-06-01

    The regioisomers (2a,b) of the piperidine ring of febrifugine (1a) and isofebrifugine (1b) were synthesized from 4-allyl-3-piperidone (5). Reduction of 5 afforded a mixture of the trans and cis alcohols (6a,b) without diastereoselectivity; this result differentiated it from the reduction of 2-allyl-3-piperidone (14). The antimalarial activity of 2a,b and related compounds was tested. PMID:11411524

  14. Activation and de novo synthesis of hydrogenase in Chlamydomonas

    SciTech Connect

    Roessler, P.G.; Lien, S.

    1984-12-01

    Two distinct processes are involved in the formation of active hydrogenase during anaerobic adaptation of Chlamydomonas reinhardtii cells. In the first 30 minutes of anaerobiosis, nearly all of the hydrogenase activity can be attributed to activation of constituitive polypeptide precursor, based on the insensitivity of the process to treatment with cycloheximide (15 micrograms per milliliter). This concentration of cycloheximide inhibits protein synthesis by greater than 98%. After the initial activation period, de novo protein synthesis plays a critical role in the adaptation process since cycloheximide inhibits the expression of hydrogenase in maximally adapted cells by 70%. Chloramphenicol (500 micrograms per milliliter) has a much lesser effect on the adaptation process. Incubation of cell-free extracts under anaerobic conditions in the presence of dithionite, dithiothreitol, NADH, NADP, ferredoxin, ATP, Mg/sup 2 +/, Ca/sup 2 +/, and iron does not lead to active hydrogenase formation. Furthermore, in vivo reactivation of oxygen-inactivated hydrogenase does not appear to take place. The adaptation process is very sensitive to the availability of iron. Iron-deficient cultures lose the ability to form active hydrogenase before growth, photosynthesis, and respiration are significantly affected. Preincubation of iron-deficient cells with iron 2 hours prior to the adaptation period fully restores the capacity of the cells to synthesize functional hydrogenase.

  15. Synthesis of protopanaxadiol derivatives and evaluation of their anticancer activities

    PubMed Central

    Du, Guang-Jian; Dai, Qing; Williams, Stainley; Wang, Chong-Zhi; Yuan, Chun-Su

    2010-01-01

    Protopanaxadiol (PPD), an aglycon of ginseng saponins, has shown anticancer activity in previous studies. Here we report the semi-synthesis of 9 PPD derivatives with acetyl substitutions. Subsequently, the antiproliferative effects of these 9 analogs on different human cancer cell lines were investigated. Compounds 1 and 3 showed more significant and more potent antiproliferative activity compared to PPD and other derivatives. A flow cytometric assay indicated that Compounds 1 and 3 arrested cell cycle progression in the G1 phase and significantly induced apoptosis of cancer cells. PMID:20926945

  16. Solution combustion synthesis of CeO{sub 2}-CeAlO{sub 3} nano-composites by mixture-of-fuels approach

    SciTech Connect

    Aruna, S.T. [Surface Engineering Division, National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560017 (India); Kini, N.S. [Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India)], E-mail: nagesh.kini@gmail.com; Rajam, K.S. [Surface Engineering Division, National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560017 (India)

    2009-04-02

    Nano-composites of CeO{sub 2}-CeAlO{sub 3} are synthesised by solution combustion method employing (a) urea and (b) a mixture of urea and glycine as fuels with corresponding metal nitrates. The as-prepared powders are all nano-sized (5-30 nm) and the same is confirmed by broadening of the X-ray diffraction peaks and transmission electron microscopy. A starting composition of Ce:Al in the atomic ratio 4:6 gives rise to different phases depending on the fuel being used for combustion. When urea alone is used as fuel, nano-crystalline CeO{sub 2} phase is formed with Al{sub 2}O{sub 3} being in the amorphous state. When the mixture of fuels is used, a mixture of nano-sized CeO{sub 2} and CeAlO{sub 3} phases is obtained. However, upon sintering at 1400 deg. C in air, the stable phases CeO{sub 2} and {alpha}-Al{sub 2}O{sub 3} are formed in both the cases. Combustion synthesis using mixture-of-fuels is proposed to be a route to stabilise low oxidation compounds such as CeAlO{sub 3}.

  17. The combustion synthesis of the ferroelectric material, BaTiO{sub 3}, studied by time-resolved X-ray diffraction

    SciTech Connect

    Larson, E.M. [College of Science and Allied Health, Grand Canyon University, Phoenix, Arizona 85017 (United States); Wong, J.; Holt, J.B.; Waide, P.A.; Rupp, B. [Lawrence Livermore National Laboratory, University of California, PO Box 808, Livermore, California 94551 (United States)

    1999-06-01

    The combustion synthesis of the common ferroelectric material, BaTiO{sub 3}, was developed using the stoichiometry: BaO{sub 2}+0.2thinspTi+0.8thinspTiO{sub 2}{r_arrow}BaTiO{sub 3}+0.3thinspO{sub 2}. An adiabatic temperature, T{sub ad}, of the reaction was calculated from known thermodynamic data to be 1917thinsp{degree}C. Real time chemical changes in the formation of BaTiO{sub 3} during the reaction have been monitored using time-resolved X-ray diffraction with synchrotron radiation as the X-ray source. A time resolution of 250 ms was achieved. The combustion synthesis of BaTiO{sub 3} was followed by observing the intensities of reactant and product Bragg diffraction peaks in order to qualitatively identify the phases present. Because BaTiO{sub 3} forms initially as a cubic phase, X-ray diffraction of the product was monitored for a period of 20 min after the reaction to observe the phase transformation to the tetragonal form. This transformation is evident in these post-reaction scans as the cubic 110 and 220 peaks are split to the tetragonal 101/110 and 202/220 ones, respectively. {copyright} {ital 1999 International Centre for Diffraction Data.}

  18. Combustion synthesis of metal-matrix composites. Part 3: The Al-TiC-Al{sub 2}O{sub 3} system

    SciTech Connect

    Kunrath, A.O.; Strohaecker, T.R. [UFRGS, Porto Alegre, Rio Grande do Sul (Brazil). Dept. de Metalurgia] [UFRGS, Porto Alegre, Rio Grande do Sul (Brazil). Dept. de Metalurgia; Moore, J.J. [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering] [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering

    1996-01-15

    The principle of combustion synthesis to produce metal matrix composites has been outlined in earlier papers. Applying pressure either during or immediately after the reaction is completed is the most commonly used method to achieve high densification of the synthesized products. Some advanced ceramics (TiC and TiB{sub 2}) have been reported to achieve up to 95% of theoretical density using this technique. The current research is a continuation of the work on the TiC-Al{sub 2}O{sub 3}-Al system, in which an excess amount of liquid aluminum is generated by the exothermic reaction and infiltrates the pores of the ceramic matrix improving the densification of the product. The current research is aimed at synthesizing high volume fractions, i.e., > 50%, metal matrix composites using the SHS reaction. The stability of this reaction is inversely proportional to the excess amount of the metal phase added to the reactants, i.e. xAl. The excess Al acts as a diluent, taking heat from the reaction front, and making it difficult to ignite and/or sustain the reaction in pellets with stoichiometries of high volume fractions of metal. For this reason, the simultaneous combustion (thermal explosion) mode was chosen to perform the synthesis reaction and in which the whole pellet is heated to the ignition temperature.

  19. Synthesis, structural investigation and magnetic properties of Zn2+ substituted cobalt ferrite nanoparticles prepared by the sol-gel auto-combustion technique

    NASA Astrophysics Data System (ADS)

    Raut, A. V.; Barkule, R. S.; Shengule, D. R.; Jadhav, K. M.

    2014-05-01

    Structural morphology and magnetic properties of the Co1-xZnxFe2O4 (0.0?x?1.0) spinel ferrite system synthesized by the sol-gel auto-combustion technique using nitrates of respective metal ions have been studied. The ratio of metal nitrates to citric acid was taken at 1:3. The as prepared powder of cobalt zinc ferrite was sintered at 600 °C for 12 h after TG/DTA thermal studies. Compositional stoichiometry was confirmed by energy dispersive analysis of the X-ray (EDAX) technique. Single phase cubic spinel structure of Co-Zn nanoparticles was confirmed by XRD data. The average crystallite size (t), lattice constant (a) and other structural parameters of zinc substituted cobalt ferrite nanoparticles were calculated from XRD followed by SEM and FTIR. It is observed that the sol-gel auto-combustion technique has many advantages for the synthesis of technologically applicable Co-Zn ferrite nanoparticles. The present investigation clearly shows the effect of the synthesis method and possible relation between magnetic properties and microstructure of the prepared samples. Increase in nonmagnetic Zn2+ content in cobalt ferrite nanoparticles is followed by decrease in nB, Ms and other magnetic parameters. Squareness ratio for the Co-ferrite was 1.096 at room temperature.

  20. Combustion devices technology team - An overview and status of STME-related activities

    Microsoft Academic Search

    P. K. Tucker; Margie Croteau-Gillespie

    1992-01-01

    The Consortium for CFD applications in propulsion technology has been formed at NASA\\/Marshall Space Flight Center. The combustion devices technology team is one of the three teams that constitute the Consortium. While generally aiming to advance combustion devices technology for rocket propulsion, the team's efforts for the last 1 and 1\\/2 years have been focused on issues relating to the

  1. Synthesis and antifungal activities of miltefosine analogs

    PubMed Central

    Ravu, Ranga Rao; Chen, Ying-Lien; Jacob, Melissa R.; Pan, Xuewen; Agarwal, Ameeta K.; Khan, Shabana I.; Heitman, Joseph; Clark, Alice M.; Li, Xing-Cong

    2013-01-01

    Miltefosine is an alkylphosphocholine that shows broad-spectrum in vitro antifungal activities and limited in vivo efficacy in mouse models of cryptococcosis. To further explore the potential of this class of compounds for the treatment of systemic mycoses, nine analogs (3a–3i) were synthesized by modifying the choline structural moiety and the alkyl chain length of miltefosine. In vitro testing of these compounds against the opportunistic fungal pathogens Candida albicans, Candida glabrata, Candida krusei, Aspergillus fumigatus, and Cryptococcus neoformans revealed that N-benzyl-N,N-dimethyl-2-{[(hexadecyloxy)hydroxyphosphinyl]oxy}ethanaminium inner salt (3a), N,N-dimethyl-N-(4-nitrobenzyl)-2-{[(hexadecyloxy)hydroxyphosphinyl]oxy}ethanaminium inner salt (3d), and N-(4-methoxybenzyl)-N,N-dimethyl-2-{[(hexadecyloxy)hydroxyphosphinyl]oxy}ethanaminium inner salt (3e) exhibited minimum inhibitory concentrations (MIC) of 2.5–5.0 ?g/mL against all tested pathogens, when compared to miltefosine with MICs of 2.5–3.3 ?g/mL. Compound 3a showed low in vitro cytotoxicity against three mammalian cell lines similar to miltefosine. In vivo testing of 3a and miltefosine against C. albicans in a mouse model of systemic infection did not demonstrate efficacy. The results of this study indicate that further investigation will be required to determine the potential usefulness of the alkylphosphocholines in the treatment of invasive fungal infections. PMID:23891181

  2. Synthesis and antifungal activity of novel streptochlorin analogues.

    PubMed

    Zhang, Ming-Zhi; Chen, Qiong; Xie, Cai-Hong; Mulholland, Nick; Turner, Sarah; Irwin, Dianne; Gu, Yu-Cheng; Yang, Guang-Fu; Clough, John

    2015-03-01

    Streptochlorin, first isolated as a new antibiotic in 1988 from the lipophilic extracts of the mycelium of a Streptomyces sp, is an indole natural products with a variety of biological activities. Based on the methods developed for the synthesis of pimprinine in our laboratory, we have synthesized a series of indole-modified streptochlorin analogues and measured their activities against seven phytopathogenic fungi. Some of the analogues displayed good activity in the primary assays, and the seven compounds 10b, 10c, 11e, 13e, 21, 22c and 22e (shown in Figure 1) were identified as the most promising candidates for further study. Structural optimization is still ongoing with the aim of discovering synthetic analogues with improved antifungal activity. PMID:25633493

  3. SYNTHESIS AND BIOLOGICAL ACTIVITY OF NITRO-SUBSTITUTED CYCLOPENTA-FUSED PAH

    EPA Science Inventory

    PAH containing a peripherally fused cyclopenta ring are genotoxically active in Salmonella and mammalian cells and have been identified in combustion emissions. Since the cyclopenta ring is predicted to be susceptible to electrophilic attack, nitrosubstituted cyclopenta-fused PAH...

  4. Dense Layered Molybdenum DisilicideSilicon Carbide Functionally Graded Composites Formed by Field-Activated Synthesis

    E-print Network

    Paulino, Glaucio H.

    formed from elemental powders in one step, using the field-activated pressure-assisted combustion method, in which heat or mass transfer causes the formation of a gradient.2 A common and relatively simple

  5. Low temperature synthesis of ultrafine Pb(Zr,Ti)O3 powder by sol-gel combustion

    Microsoft Academic Search

    J. Schaefer; W. Sigmund; S. Roy; F. Aldinger

    1997-01-01

    Lead zirconate titanate powders are derived from a novel aqueous-based citrate-nitrate\\/oxynitrate sol-gel combustion process. Aqueous solutions of metal nitrates or oxynitrates are transformed into gels with citric acid under heating. The received gels undergo a self-propagating combustion reaction on heating to 180°C and subsequently yield voluminous ashes. These ashes form single phase perovskite Pb(Zr{sub 0.53}Ti{sub 0.47})O powder with a specific

  6. Experimental and numerical investigations of jet active control for combustion applications

    NASA Astrophysics Data System (ADS)

    Faivre, Vincent; Poinsot, Thierry

    2004-08-01

    Controlling the mixing of a gas (usually fuel) issuing from a tube into surrounding air is a basic problem in multiple combustion systems. The purpose of the present work is to develop an actuator device to control the mixing enhancement of an axisymmetric non-reactive jet. The actuators consist of four small jets feeding the primary jet flow. These four jets are oriented to add an azimuthal component to the velocity field. The influence of the jets' deflection and position along the main jet duct is discussed. Schlieren photographs and planar laser-induced fluorescence measurements are used to compare the efficiency of the three configurations of interest. The effect of 'control-to-main' mass flow rates' ratio is quantified through hot wire anemometry results. Large eddy simulations (LES) of both forced and unforced configurations are also performed. The objectives of the numerical part of this work are to understand the actuator effect and to validate LES as a tool to study active control. This paper was presented at the Third International Symposium on Turbulence and Shear Flow Phenomena (Sendai, Japan, 24-27 June 2003).

  7. Efficient discovery of bioactive scaffolds by activity-directed synthesis.

    PubMed

    Karageorgis, George; Warriner, Stuart; Nelson, Adam

    2014-10-01

    The structures and biological activities of natural products have often provided inspiration in drug discovery. The functional benefits of natural products to the host organism steers the evolution of their biosynthetic pathways. Here, we describe a discovery approach--which we term activity-directed synthesis--in which reactions with alternative outcomes are steered towards functional products. Arrays of catalysed reactions of ?-diazo amides, whose outcome was critically dependent on the specific conditions used, were performed. The products were assayed at increasingly low concentration, with the results informing the design of a subsequent reaction array. Finally, promising reactions were scaled up and, after purification, submicromolar ligands based on two scaffolds with no previous annotated activity against the androgen receptor were discovered. The approach enables the discovery, in tandem, of both bioactive small molecules and associated synthetic routes, analogous to the evolution of biosynthetic pathways to yield natural products. PMID:25242481

  8. Synthesis and Antimicrobial Activity of Silver-Doped Hydroxyapatite Nanoparticles

    PubMed Central

    Ciobanu, Carmen Steluta; Iconaru, Simona Liliana; Chifiriuc, Mariana Carmen; Costescu, Adrian; Le Coustumer, Philippe; Predoi, Daniela

    2013-01-01

    The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications. The aim of this study was the evaluation of Ca10?xAgx(PO4)6(OH)2 nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures. PMID:23509801

  9. Antifungal activity of silver nanoparticles obtained by green synthesis.

    PubMed

    Mallmann, Eduardo José J; Cunha, Francisco Afrânio; Castro, Bruno N M F; Maciel, Auberson Martins; Menezes, Everardo Albuquerque; Fechine, Pierre Basílio Almeida

    2015-01-01

    Silver nanoparticles (AgNPs) are metal structures at the nanoscale. AgNPs have exhibited antimicrobial activities against fungi and bacteria; however synthesis of AgNPs can generate toxic waste during the reaction process. Accordingly, new routes using non-toxic compounds have been researched. The proposal of the present study was to synthesize AgNPs using ribose as a reducing agent and sodium dodecyl sulfate (SDS) as a stabilizer. The antifungal activity of these particles against C. albicans and C. tropicalis was also evaluated. Stable nanoparticles 12.5 ± 4.9 nm (mean ± SD) in size were obtained, which showed high activity against Candida spp. and could represent an alternative for fungal infection treatment. PMID:25923897

  10. Synthesis, characterization and antiproliferative activity of ?-aryl-?-iodo-?-lactones

    NASA Astrophysics Data System (ADS)

    Wzorek, Alicja; Gawdzik, Barbara; G?adkowski, Witold; Urbaniak, Mariusz; Bara?ska, Anita; Mali?ska, Maura; Wo?niak, Krzysztof; Kempi?ska, Katarzyna; Wietrzyk, Joanna

    2013-09-01

    A convenient pathway for the synthesis of new of ?-aryl-?-iodo-?-lactones is described. The synthetic route led to both cis and trans isomers which were separated by column chromatography or crystallization. The structures of synthesized compounds were confirmed by spectroscopic methods: IR, NMR and HR-MS. For lactones with naphthyl ring (6e and 7e) the crystal structures were also obtained. The lactones were screened for biological evaluation against cancer line HL-60 (human promyelocytic leukemia). The tests showed that the presence of substituent at the benzene ring does not significantly affect the antiproliferative activity of the compound.

  11. Effect of additives on the WGS activity of combustion synthesized CuO\\/CeO 2 catalysts

    Microsoft Academic Search

    T. Tabakova; V. Idakiev; J. Papavasiliou; G. Avgouropoulos; T. Ioannides

    2007-01-01

    This paper presents a study on the role of additives (samaria, lanthana, zirconia, and zinc oxide) to ceria as a support of copper catalysts for low-temperature WGSR. A single-step urea-combustion procedure was used for preparation of highly active catalysts. The results revealed the beneficial role of Sm2O3 and ZnO doping in increasing BET surface area and total pore volume of

  12. Effect of nitrogen-containing impurities on the activity of perovskitic catalysts for the catalytic combustion of methane.

    PubMed

    Buchneva, Olga; Gallo, Alessandro; Rossetti, Ilenia

    2012-11-01

    LaMnO(3), either pure or doped with 10 mol % Sr, has been prepared by flame pyrolysis in nanostructured form. Such catalysts have been tested for the catalytic flameless combustion of methane, achieving very high catalytic activity. The resistance toward poisoning by some model N-containing impurities has been checked in order to assess the possibility of operating the flameless catalytic combustion with biogas, possibly contaminated by S- or N-based compounds. This would be a significant improvement from the environmental point of view because the application of catalytic combustion to gas turbines would couple improved energy conversion efficiency and negligible noxious emissions, while the use of biogas would open the way to energy production from a renewable source by means of very efficient technologies. A different behavior has been observed for the two catalysts; namely, the undoped sample was more or less heavily poisoned, whereas the Sr-doped sample showed slightly increasing activity upon dosage of N-containing compounds. A possible reaction mechanism has been suggested, based on the initial oxidation of the organic backbone, with the formation of NO. The latter may adsorb more or less strongly depending on the availability of surface oxygen vacancies (i.e., depending on doping). Decomposition of NO may leave additional activated oxygen species on the surface, available for low-temperature methane oxidation and so improving the catalytic performance. PMID:23039114

  13. Synthesis of nano-sized amorphous boron powders through active dilution self-propagating high-temperature synthesis method

    SciTech Connect

    Wang, Jilin [The State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Gu, Yunle [School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan 430073 (China); Li, Zili [The State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Wang, Weimin, E-mail: wangwm@hotmail.com [The State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Fu, Zhengyi [The State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

    2013-06-01

    Graphical abstract: Nano-sized amorphous boron powders were synthesized by active dilution self-propagating high-temperature synthesis (SHS) method. The effects of endothermic reaction rate, the possible chemical reaction mechanism and active dilution model for synthesis of the product were also discussed. Highlights: ? Nano-sized amorphous boron powders were synthesized by active dilution self-propagating high-temperature synthesis method. ? The morphology, particle size and purity of the samples could be effectively controlled via changing the endothermic rate. ? The diluter KBH{sub 4} played an important role in active dilution synthesis of amorphous nano-sized boron powders. ? The active dilution method could be further popularized and become a common approach to prepare various inorganic materials. - Abstract: Nano-sized amorphous boron powders were synthesized by active dilution self-propagating high-temperature synthesis (SHS) method at temperatures ranging from 700 °C to 850 °C in a SHS furnace using Mg, B{sub 2}O{sub 3} and KBH{sub 4} as raw materials. Samples were characterized by X-ray powder diffraction (XRD), Laser particle size analyzer, Fourier transform infrared spectra (FTIR), X-ray energy dispersive spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission TEM (HRTEM). The boron powders demonstrated an average particle size of 50 nm with a purity of 95.64 wt.%. The diluter KBH{sub 4} played an important role in the active dilution synthesis of amorphous nano-sized boron powders. The effects of endothermic reaction rate, the possible chemical reaction mechanism and active dilution model for synthesis of the product were also discussed.

  14. Advanced Combustion

    SciTech Connect

    Holcomb, Gordon R. [NETL

    2013-03-11

    The activity reported in this presentation is to provide the mechanical and physical property information needed to allow rational design, development and/or choice of alloys, manufacturing approaches, and environmental exposure and component life models to enable oxy-fuel combustion boilers to operate at Ultra-Supercritical (up to 650{degrees}C & between 22-30 MPa) and/or Advanced Ultra-Supercritical conditions (760{degrees}C & 35 MPa).

  15. Synthesis, characteristics and antimicrobial activity of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Janaki, A. Chinnammal; Sailatha, E.; Gunasekaran, S.

    2015-06-01

    The utilization of various plant resources for the bio synthesis of metallic nano particles is called green technology and it does not utilize any harmful protocols. Present study focuses on the green synthesis of ZnO nano particles by Zinc Carbonate and utilizing the bio-components of powder extract of dry ginger rhizome (Zingiber officinale). The ZnO nano crystallites of average size range of 23-26 nm have been synthesized by rapid, simple and eco friendly method. Zinc oxide nano particles were characterized by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX). FTIR spectra confirmed the adsorption of surfactant molecules at the surface of ZnO nanoparticles and the presence of ZnO bonding. Antimicrobial activity of ZnO nano particles was done by well diffusion method against pathogenic organisms like Klebsiella pneumonia, Staphylococcus aureus and Candida albicans and Penicillium notatum. It is observed that the ZnO synthesized in the process has the efficient antimicrobial activity.

  16. Synthesis, characteristics and antimicrobial activity of ZnO nanoparticles.

    PubMed

    Janaki, A Chinnammal; Sailatha, E; Gunasekaran, S

    2015-06-01

    The utilization of various plant resources for the bio synthesis of metallic nano particles is called green technology and it does not utilize any harmful protocols. Present study focuses on the green synthesis of ZnO nano particles by Zinc Carbonate and utilizing the bio-components of powder extract of dry ginger rhizome (Zingiber officinale). The ZnO nano crystallites of average size range of 23-26 nm have been synthesized by rapid, simple and eco friendly method. Zinc oxide nano particles were characterized by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX). FTIR spectra confirmed the adsorption of surfactant molecules at the surface of ZnO nanoparticles and the presence of ZnO bonding. Antimicrobial activity of ZnO nano particles was done by well diffusion method against pathogenic organisms like Klebsiella pneumonia, Staphylococcus aureus and Candida albicans and Penicillium notatum. It is observed that the ZnO synthesized in the process has the efficient antimicrobial activity. PMID:25748589

  17. Thermally sprayed wire-mesh catalysts for the purification of flue gases from small-scale combustion of bio-fuel Catalyst preparation and activity studies

    Microsoft Academic Search

    A. F. Ahlström-Silversand; C. U. Ingemar Odenbrand

    1997-01-01

    Catalytically active wire meshes were used to combust different pollutants present in flue gases from bio-fuel combustion, e.g. CO, propylene, terpenes and tar. Alumina was spray-deposited onto wire meshes of Kanthal AF (8–20 Tayler mesh) with a plasma spray equipment. The specific surface area of the ceramic layer was increased through wash coating, in-situ precipitation or sol-treatment. The catalytically active

  18. Synthesis of nanocrystalline NiCuZn ferrite powders by sol–gel auto-combustion method

    Microsoft Academic Search

    Zhenxing Yue; J. Zhou; Longtu Li; Hongguo Zhang; Zhilun Gui

    2000-01-01

    A nitrate–citrate gel was prepared from metal nitrates and citric acid by sol–gel process, in order to synthesize Ni0.25Cu0.25Zn0.50Fe2O4 ferrite. The thermal decomposition process was investigated by DTA-TG, IR and XRD techniques. The results revealed that the nitrate–citrate gel exhibits self-propagating combustion behavior. After combustion, the gel directly transformed into single-phase, nano-sized NiCuZn ferrite particles with spinel crystal structure. The

  19. Glycosphingolipid synthesis inhibition limits osteoclast activation and myeloma bone disease.

    PubMed

    Ersek, Adel; Xu, Ke; Antonopoulos, Aristotelis; Butters, Terry D; Santo, Ana Espirito; Vattakuzhi, Youridies; Williams, Lynn M; Goudevenou, Katerina; Danks, Lynett; Freidin, Andrew; Spanoudakis, Emmanouil; Parry, Simon; Papaioannou, Maria; Hatjiharissi, Evdoxia; Chaidos, Aristeidis; Alonzi, Dominic S; Twigg, Gabriele; Hu, Ming; Dwek, Raymond A; Haslam, Stuart M; Roberts, Irene; Dell, Anne; Rahemtulla, Amin; Horwood, Nicole J; Karadimitris, Anastasios

    2015-06-01

    Glycosphingolipids (GSLs) are essential constituents of cell membranes and lipid rafts and can modulate signal transduction events. The contribution of GSLs in osteoclast (OC) activation and osteolytic bone diseases in malignancies such as the plasma cell dyscrasia multiple myeloma (MM) is not known. Here, we tested the hypothesis that pathological activation of OCs in MM requires de novo GSL synthesis and is further enhanced by myeloma cell-derived GSLs. Glucosylceramide synthase (GCS) inhibitors, including the clinically approved agent N-butyl-deoxynojirimycin (NB-DNJ), prevented OC development and activation by disrupting RANKL-induced localization of TRAF6 and c-SRC into lipid rafts and preventing nuclear accumulation of transcriptional activator NFATc1. GM3 was the prevailing GSL produced by patient-derived myeloma cells and MM cell lines, and exogenous addition of GM3 synergistically enhanced the ability of the pro-osteoclastogenic factors RANKL and insulin-like growth factor 1 (IGF-1) to induce osteoclastogenesis in precursors. In WT mice, administration of GM3 increased OC numbers and activity, an effect that was reversed by treatment with NB-DNJ. In a murine MM model, treatment with NB-DNJ markedly improved osteolytic bone disease symptoms. Together, these data demonstrate that both tumor-derived and de novo synthesized GSLs influence osteoclastogenesis and suggest that NB-DNJ may reduce pathological OC activation and bone destruction associated with MM. PMID:25915583

  20. Synthesis and antibacterial activity of novel C12 ethyl ketolides.

    PubMed

    Burger, Matthew T; Hiebert, Christy; Seid, Mehran; Chu, Daniel T; Barker, Lynn; Langhorne, Mike; Shawar, Ribhi; Kidney, Jolene; Desai, Manoj C; Plattner, Jacob J

    2006-08-15

    A novel series of C(12) ethyl erythromycin derivatives have been discovered which exhibit in vitro and in vivo potency against key respiratory pathogens, including those resistant to erythromycin. The C(12) modification involves replacing the natural C(12) methyl group in the erythromycin core with an ethyl group via chemical synthesis. From the C(12) ethyl macrolide core, a series of C(12) ethyl ketolides were prepared and tested for antibacterial activity against a panel of relevant clinical isolates. Several compounds were found to be potent against macrolide-sensitive and -resistant bacteria, whether resistance was due to ribosome methylation (erm) or efflux (mef). In particular, the C(12) ethyl ketolides 4k,4s,4q,4m, and 4t showed a similar antimicrobial spectrum and comparable activity to the commercial ketolide telithromycin. The in vivo efficacy of several C(12) ethyl ketolides was demonstrated in a mouse infection model with Streptococcus pneumoniae as pathogen. PMID:16697203

  1. Synthesis and antibacterial activity of of silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Maliszewska, I.; Sadowski, Z.

    2009-01-01

    Silver nanoparticles have been known to have inhibitory and bactericidal effects but the antimicrobial mechanism have not been clearly revealed. Here, we report on the synthesis of metallic nanoparticles of silver using wild strains of Penicillium isolated from environment. Kinetics of the formation of nanosilver was monitored using the UV-Vis. TEM micrographs showed the formation of silver nanoparticles in the range 10-100 nm. Obtained Ag nanoparticles were evaluated for their antimicrobial activity against the gram-positive and gram-negative bacteria. As results, Bacillus cereus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were effectively inhibited. Nanosilver is a promising candidate for development of future antibacterial therapies because of its wide spectrum of activity.

  2. The combination of the polymeric solution - sol - gel process and combustion synthesis to manufacture BiPbSrCaCuO powder

    NASA Astrophysics Data System (ADS)

    Mao, Chuanbin; Zhou, Lian; Wu, Xiaozu; Sun, Xiangyun

    1996-11-01

    The polymeric solution - sol - gel (SSG) process has been greatly improved by combination of the high homogeneity of SSG and the high efficiency of combustion synthesis to manufacture BiPbSrCaCuO powder with high homogeneity, ultrafine particles and low carbon content for fabrication of high-0953-2048/9/11/012/img8 silver-sheathed bismuth-based 2223 superconducting tape. The improved SSG, termed solution - sol - gel - SHS (SSGS), is realized by ignition of homogeneous wet gel derived from polymeric SSG. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infared spectroscopy (FTIR) are used to optimize the SSG process and investigate the mechanism of the SSG transition.

  3. Combustion synthesis and luminescent properties of a blue-green emitting phosphor: (Ba1.95, Eu0.05)ZnSi2O7:B3+

    NASA Astrophysics Data System (ADS)

    Yao, Shan-Shan; Li, Yuan-Yuan; Xue, Li-Hong; You, Yan; Yan, You-Wei

    2009-12-01

    A blue-green emitting phosphor (Ba1.95, Eu0.05)ZnSi2O7: B{/x 3+} was prepared by combustion synthesis and an efficient blue-green emission under near-ultraviolet was observed. The luminescence, crystallinity and particle sizes were investigated by using luminescence spectrometry, X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The emission spectrum shows a single band centered at 503 nm, which corresponds to the 4 f 65 d 1 ?4 f 7 transition of Eu2+. The excitation spectrum is a broad band extending from 260 to 465 nm, which matches the emission of ultraviolet light-emitting diodes. The optical absorption spectra of the (Ba1.95, Eu0.05)ZnSi2O7: B{/0.06 3+} exhibited band-gap energies of 3.9 eV. The results showed that boric acid was effective in improving the luminescence intensity of (Ba1.95, Eu0.05)ZnSi2O7, and the optimum molar ratio of boric acid to zinc nitrate was about 0.06. The phosphor (Ba1.95, Eu0.05)ZnSi2O7: B{0.06/3+} synthesized by combustion method showed 1.5 times improved emission intensity compared with that of the Ba1.95ZnSi2O7: Eu{0.05/2+} phosphor under ? ex = 353 nm.

  4. Microwave-induced combustion synthesis of Ce 1? x Sm x O 2? x\\/2 powder and its characterization

    Microsoft Academic Search

    Dong Yong Chung; Eil Hee Lee

    2004-01-01

    Samarium-doped ceria powders for solid electrolyte ceramics were synthesized by a microwave-induced heating combustion process. Cerium nitrate and samarium nitrate were used as the starting materials and various organic compounds, such as citric acid, alanine and glycine as the fuels. The decomposition of gels was investigated by simultaneous thermogravimetry analysis (TGA) and differential thermal analysis (DTA) experiments. The produced ashes

  5. Study of wear between piston ring and cylinder housing of an internal combustion engine by thin layer activation technique

    NASA Astrophysics Data System (ADS)

    Chowdhury, D. P.; Chaudhuri, Jayanta; Raju, V. S.; Das, S. K.; Bhattacharjee, B. B.; Gangadharan, S.

    1989-07-01

    The wear analysis of a compression ring and cylinder housing of an Internal Combustion Engine by thin layer activation (TLA) with 40 MeV ?-particles from the Variable Energy Cyclotron at Calcutta is reported. The calibration curves have been obtained for Fe and Ni using stacked foil activation technique for determining the absolute wear in these machine parts. It has been possible to determine the pattern of wear on the points along the surface of machine components. The minimum detectable depth in this wear study has been estimated at 0.11 ± 0.04 ?m.

  6. Lightweight, Actively Cooled Ceramic Matrix Composite Thrustcells Successfully Tested in Rocket Combustion Lab

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.; Elam, Sandra K.; Effinger, Michael R.

    2002-01-01

    In a joint effort between the NASA Glenn Research Center and the NASA Marshall Space Flight Center, regeneratively cooled ceramic matrix composite (CMC) thrustcells were developed and successfully tested in Glenn's Rocket Combustion Lab. Cooled CMC's offer the potential for substantial weight savings over more traditional metallic parts. Two CMC concepts were investigated. In the first of these concepts, an innovative processing approach utilized by Hyper-Therm, Inc., allowed woven CMC coolant containment tubes to be incorporated into the complex thruster design. In this unique design, the coolant passages had varying cross-sectional shapes but maintained a constant cross-sectional area along the length of the thruster. These thrusters were silicon carbide matrix composites reinforced with silicon carbide fibers. The second concept, which was supplied by Ceramic Composites, Inc., utilized copper cooling coils surrounding a carbon-fiber-reinforced carbon matrix composite. In this design, a protective gradient coating was applied to the inner thruster wall. Ceramic Composites, Inc.'s, method of incorporating the coating into the fiber and matrix eliminated the spallation problem often observed with thermal barrier coatings during hotfire testing. The focus of the testing effort was on screening the CMC material's capabilities as well as evaluating the performance of the thermal barrier or fiber-matrix interfacial coatings. Both concepts were hot-fire tested in gaseous O2/H2 environments. The test matrix included oxygen-to-fuel ratios ranging from 1.5 to 7 with chamber pressures to 400 psi. Steady-state internal wall temperatures in excess of 4300 F were measured in situ for successful 30-sec test runs. Photograph of actively cooled composite thrustcell fabricated by Hyper-Therm is shown. The thrustcell is a silicon-carbide-fiber-reinforced silicon carbide matrix composite with woven cooling channels. The matrix is formed via chemical vapor infiltration. Photograph of hot-fire test of an actively cooled carbon-fiber-reinforced carbon matrix composite thrustcell is also shown. This composite thrustcell, which was fabricated by CCI, Inc., was wound with copper cooling coils to contain the water coolant. The tests were run with oxygen fuel ratios up to seven with chamber pressures of 200 psia.

  7. Nonanolides of natural origin: structure, synthesis, and biological activity.

    PubMed

    Sun, P; Lu, S; Ree, T V; Krohn, K; Li, L; Zhang, W

    2012-01-01

    Naturally occurring nonanolides (synonym decanolides) are a large family of secondary metabolites with an interesting 10- membered macrolide subunit. Metabolites of the nonanolide family have been found to have various biological activities, including cytotoxic, phytotoxic, antimalarial, antifungal, antibacterial, and antimicrofilament activities. An early review of the chemistry and bioactivity of nonanolides was presented in 1996, covering the literature published between 1975 and 1995. During the past decades, the broad spectrum of bioactivity and the intriguing structure of the medium-sized ring in nonanolide analogues have continuously drawn the attention of biologists and natural product and synthetic chemists, resulting in a great number of publications. This review summarizes in whole the recent progress in the field of the nonanolides of natural origin, aiming to give the readers a brief view of the compounds, concerning their natural occurrence, structural elucidation, biological activities, total synthesis, and structure-activity relationships. The article covers the literature published in the period from the beginning of 1996 to July 2011. PMID:22612710

  8. Series feedback integrated active microstrip antenna synthesis and characterisation

    NASA Astrophysics Data System (ADS)

    Fusco, V. F.

    1992-01-01

    A methodology for the optimal design of a FET based integrated active microstrip antennas is demonstrated; the electrical characteristics of the antenna are also discussed. The antenna consists of a rectangular microstrip patch peripherally loaded with a single GaAs MESFET. The microstrip patch acts as both the radiating element and the optimal FET drain load impedance required for oscillator synthesis. The active patch element operates as a series feedback oscillator and the microstrip patch is resonated in its fundamental mode. An NEC 71084 packaged FET is used as the active device in the patch element which itself is constructed on RT-Duroid 5880 material. The element has a free running frequency of 9.625 GHz (at 3 V) and exhibits excellent electrical characteristics. Experimental results are presented for the frequency pushing characteristics of the element which are nearly linear. The active element is capable of producing an output power level of 8 mW with 10 percent efficiency at 2.3 V, and has an external Q factor of 32.

  9. Synthesis, characterization and performance of single-component CO2-binding organic liquids (CO2BOL) for post combustion CO2 capture

    SciTech Connect

    Koech, Phillip K.; Heldebrant, David J.; Rainbolt, James E.; Zheng, Feng; Smurthwaite, Tricia D.

    2010-03-31

    Carbon dioxide (CO2) emission to the atmosphere will increase significantly with the shift to coal powered plants for energy generation. This increase in CO2 emission will contribute to climate change. There is need to capture and sequester large amounts of CO2 emitted from these coal power plants in order to mitigate the environmental effects. Here we report the synthesis, characterization and system performance of multiple third generation CO2 binding organic liquids (CO2BOLs) as a solvent system for post combustion gas capture. Alkanolguanidines and alkanolamidines are single component CO2BOLs that reversibly bind CO2 chemically as liquid zwitterionic amidinium / guanidinium alkylcarbonates. Three different alkanolguanidines and alkanolamidines were synthesized and studied for CO2 capacity and binding energetics. Solvent performance of these three CO2BOLs was evaluated by batch-wise CO2 uptake and release over multiple cycles. Synthesis of CO2BOLs, characterization, CO2 uptake, selectivity towards CO2 as well as solvent tolerance to water will be discussed.

  10. Sol–gel auto combustion synthesis of CoFe{sub 2}O{sub 4}/1-methyl-2-pyrrolidone nanocomposite with ethylene glycol: Its magnetic characterization

    SciTech Connect

    Topkaya, R., E-mail: rtopkaya@gyte.edu.tr [Department of Physics, Gebze Institute of Technology, 41400 Gebze, Kocaeli (Turkey); Kurtan, U. [Department of Chemistry, Fatih University, 34500 B.Çekmece, Istanbul (Turkey); Junejo, Y. [Department of Chemistry, Fatih University, 34500 B.Çekmece, Istanbul (Turkey); National Center of Excellence in Analytical Chemistry, University of Sindh, 76080 Jamshoro (Pakistan); Baykal, A. [Department of Chemistry, Fatih University, 34500 B.Çekmece, Istanbul (Turkey)

    2013-09-01

    Graphical abstract: - Highlights: • CoFe{sub 2}O{sub 4} was generated by sol–gel autocombustion using 1-methyl-2-pyrrolidone and ethylene glycol. • The presence of spin-disordered surface layer on magnetic core was established. • A linear dependence of the coercivity on temperature was fitted to Kneller's law. - Abstract: Magnetic nanoparticles were generated by sol–gel auto combustion synthesis of metal salts in the presence of 1-methyl-2-pyrrolidone, a functional solvent and ethylene glycol as usual solvent. The average crystallite size was obtained by using line profile fitting as 11 ± 5 nm. The saturation magnetization value decreases with usage of the ethylene glycol in synthesis. The observed exchange bias effect further confirms the existence of the magnetically ordered core surrounded by spin-disordered surface layer and the ethylene glycol. Square-root temperature dependence of coercivity can be fitted to Kneller's law in the temperature range of 10–400 K. The reduced remanent magnetization values lower than the theoretical value of 0.5 for non-interacting single domain particles indicate the CoFe{sub 2}O{sub 4}-1-methyl-2-pyrrolidone nanocomposite to have uniaxial anisotropy instead of the expected cubic anisotropy according to the Stoner–Wohlfarth model.

  11. Comparative investigation on chemical looping combustion of coal-derived synthesis gas containing H2S over supported NiO oxygen carriers

    SciTech Connect

    Ksepko, E.; Siriwardane, R.; Tian, H.; Simonyi, T.; Sciazko, M.

    2010-01-01

    Chemical looping combustion (CLC) of simulated coal-derived synthesis gas was conducted with NiO oxygen carriers supported on SiO2, ZrO2, TiO2, and sepiolite. The effect of H2S on the performance of these samples for the CLC process was also evaluated. Five-cycle thermogravimetric analysis (TGA) tests at 800 #1;C indicated that all oxygen carriers had a stable performance at 800 #1;C, except NiO/SiO2. Full reduction/oxidation reactions of the oxygen carrier were obtained during the five-cycle test. It was found that support had a significant effect on reaction performance of NiO both in reduction and oxidation rates. The reduction reaction was significantly faster than the oxidation reaction for all oxygen carriers, while the oxidation reaction is fairly slow due to oxygen diffusion on NiO layers. The reaction profile was greatly affected by the presence of H2S, but there was no effect on the capacity due to the presence of H2S in synthesis gas. The presence of H2S decreased reduction reaction rates significantly, but oxidation rates of reduced samples increased. X-ray diffraction (XRD) data of the oxidized samples after a five-cycle test showed stable crystalline phases without any formation of sulfides or sulfites/sulfates. Increase in reaction temperature to 900 #1;C had a positive effect on the performance.

  12. Synthesis and biological activities of novel dexibuprofen tetraacetylriboflavin conjugates.

    PubMed

    Banekovich, Christian; Ott, Ingo; Koch, Thao; Matuszczak, Barbara; Gust, Ronald

    2007-02-01

    A series of novel dexibuprofen derivatives covalently linked via alkylene spacers of variable length to tetraacetylated riboflavin have been developed. The target compounds became accessible by reaction of the chloromethyl ester of dexibuprofen with tetraacetylriboflavin (compound 7) or by synthesis of the appropriate N3-(omega-iodoalkyl)-2',3',4',5'-Tetraacetylriboflavin followed by treatment with dexibuprofen (derivatives 8-11), respectively. Biological screening revealed that the target compounds exhibit antiproliferative effects on MCF-7 breast cancer and HT-29 colon carcinoma cells with IC50 values in the range of 8-15 microM. Enzymatic studies on human platelets indicated significant COX-1 inhibitory activities of the target compounds. PMID:17110105

  13. Synthesis and structural activity relationship study of antitubercular carboxamides.

    PubMed

    Ugwu, D I; Ezema, B E; Eze, F U; Ugwuja, D I

    2014-01-01

    The unusual structure and chemical composition of the mycobacterial cell wall, the tedious duration of therapy, and resistance developed by the microorganism have made the recurrence of the disease multidrug resistance and extensive or extreme drug resistance. The prevalence of tuberculosis in synergy with HIV/AIDS epidemic augments the risk of developing the disease by 100-fold. The need to synthesize new drugs that will shorten the total duration of effective treatment and/or significantly reduce the dosage taken under DOTS supervision, improve on the treatment of multidrug-resistant tuberculosis which defies the treatment with isoniazid and rifampicin, and provide effective treatment for latent TB infections which is essential for eliminating tuberculosis prompted this review. In this review, we considered the synthesis and structure activity relationship study of carboxamide derivatives with antitubercular potential. PMID:25610646

  14. Combustion devices technology team - An overview and status of STME-related activities

    NASA Astrophysics Data System (ADS)

    Tucker, P. K.; Croteau-Gillespie, Margie

    1992-07-01

    The Consortium for CFD applications in propulsion technology has been formed at NASA/Marshall Space Flight Center. The combustion devices technology team is one of the three teams that constitute the Consortium. While generally aiming to advance combustion devices technology for rocket propulsion, the team's efforts for the last 1 and 1/2 years have been focused on issues relating to the Space Transportation Main Engine (STME) nozzle. The nozzle design uses hydrogen-rich turbine exhaust to cool the wall in a film/dump scheme. This method of cooling presents challenges and associated risks for the nozzle designers and the engine/vehicle integrators. Within the nozzle itself, a key concern is the ability to effectively and efficiently film cool the wall. From the National Launch System vehicle base standpoint, there are concerns with dumping combustible gases at the nozzle exit and their potential adverse effects on the base thermal environment. The Combustion Team has developed and is implementing plans to use validated CFD tools to aid in risk mitigation for both areas.

  15. A status of the activities of the NASA. Marshall Space Flight Center Combustion Devices Technology Team

    Microsoft Academic Search

    Kevin Tucker

    1992-01-01

    The Consortium for Computational Fluid Dynamics (CFD) Applications in Propulsion Technology was established to focus on computational fluid dynamics applications in propulsion. Specific areas of effort include developing the CFD technology required to address rocket propulsion issues, validating the technology, and applying the validated technology to design problems. The Combustion Devices Technology Team was formed to implement the above objectives

  16. Energy efficiency analyses of active flow aftertreatment systems for lean burn internal combustion engines

    Microsoft Academic Search

    Ming Zheng; Graham T. Reader

    2004-01-01

    The use of three way catalytic converters in stoichiometric burn reciprocating internal combustion engine systems has proved to be an effective and efficient method for reducing the level of criteria pollutants. However, such passive systems have not been as successful in emission amelioration when combined with lean burn engines. This is because of the thermochemical nature of the exhaust gases

  17. Facile Synthesis of Lead-Free Piezoelectric Sodium Niobate (NaNbO3) Powders via the Solution Combustion Method

    Microsoft Academic Search

    Nopsiri Chaiyo; Anucha Ruangphanit; Banjong Boonchom; Naratip Vittayakorn

    2011-01-01

    Nanocrystalline perovskite sodium niobate, NaNbO3 (NN), was prepared by means of the glycine-nitrate combustion process (GNP). This was achieved by using sodium nitrate and niobium pentoxide as starting materials. The X-ray diffraction technique (XRD) was used to investigate the phase formation and purity of synthesized powder. The morphology of the powder obtained was characterized using a scanning electron microscope (SEM).

  18. The role of microstructure refinement on the impact ignition and combustion behavior of mechanically activated Ni/Al reactive composites

    NASA Astrophysics Data System (ADS)

    Mason, B. A.; Groven, L. J.; Son, S. F.

    2013-09-01

    Metal-based reactive composites have great potential as energetic materials due to their high energy densities and potential uses as structural energetic materials and enhanced blast materials however these materials can be difficult to ignite with typical particle size ranges. Recent work has shown that mechanical activation of reactive powders increases their ignition sensitivity, yet it is not fully understood how the role of microstructure refinement due to the duration of mechanical activation will influence the impact ignition and combustion behavior of these materials. In this work, impact ignition and combustion behavior of compacted mechanically activated Ni/Al reactive powder were studied using a modified Asay shear impact experiment where properties such as the impact ignition threshold, ignition delay time, and combustion velocity were identified as a function of milling time. It was found that the mechanical impact ignition threshold decreases from an impact energy of greater than 500 J to an impact energy of ˜50 J as the dry milling time increases. The largest jump in sensitivity was between the dry milling times of 25% of critical reaction milling time (tcr) (4.25 min) and 50% tcr (8.5 min) corresponding to the time at which nanolaminate structures begin to form during the mechanical activation process. Differential scanning calorimetry analysis indicates that this jump in the sensitivity to thermal and mechanical impact is dictated by the formation of nanolaminate structures, which reduce the temperature needed to begin the dissolution of nickel into aluminum. It was shown that a milling time of 50%-75% tcr may be near optimal when taking into account both the increased ignition sensitivity of mechanical activated Ni/Al and potential loss in reaction energy for longer milling times. Ignition delays due to the formation of hotspots ranged from 1.2 to 6.5 ms and were observed to be in the same range for all milling times considered less than tcr. Combustion velocities ranged from 20-23 cm/s for thermally ignited samples and from 25-31 cm/s for impacted samples at an impact energy of 200-250 J.

  19. Double ignitions of Ni?Al combustion reactions

    Microsoft Academic Search

    2003-01-01

    Double ignitions of Ni?Al combustion reactions have been numerically studied in this research. Due to the lower exothermic heat of the metallic reactions, the propagation of Ni?Al combustion front during combustion synthesis is found to extinguish half way for some reactions. To allow the combustion front to propagate completely, the reaction is always ignited again during the experimental demonstration. In

  20. Synthesis, characterization and antimicrobial activity of some novel benzimidazole derivatives

    PubMed Central

    Krishnanjaneyulu, Immadisetty Sri; Saravanan, Govindaraj; Vamsi, Janga; Supriya, Pamidipamula; Bhavana, Jarugula Udaya; Sunil Kumar, Mittineni Venkata

    2014-01-01

    A series of novel N-((1H-benzoimidazol-1-yl) methyl)-4-(1-phenyl-5-substituted-4, 5-dihydro-1-benzoimidazol-1-yl) methyl)-4-(1-phenyl-5-substituted-4, 5-dihydro-1H-pyrazol-3-yl) benzenamine were synthesized by treating various 1-(4-((1H-benzoimidazol-1-yl) methylamino) phenyl)-3-substitutedprop-2-en-1-one with phenyl hydrazine in the presence of sodium acetate through a simple ring closure reaction. The starting material, 1-(4-((1H-benzoimidazol-1-yl) methylamino) phenyl)-3-substitutedprop-2-en-1-one,-benzoimidazol-1-yl) methylamino) phenyl)-3-substitutedprop-2-en-1-one, was synthesized from o-phenylenediamine by a multistep synthesis. All the synthesized compounds were characterized by spectroscopic means and elemental analyses. The title compounds were investigated for in vitro antibacterial and antifungal properties against some human pathogenic microorganisms by employing the agar streak dilution method using Ciprofloxacin and Ketoconazole as standard drugs. All title compounds showed activity against the entire strains of microorganism. Structural activity relationship studies reveal that compounds possessing an electron-withdrawing group display better activity than the compounds containing electron-donating groups, whereas the unsubstituted derivatives display moderate activity. Based on the results obtained, N-((1H-benzoimidazol-1-yl) methyl)-4-(1-phenyl-5-(4-(trifluoromethyl) phenyl)-4,5-dihydro-1H-pyrazol-3-yl) benzenamine 5i was found to be very active compared with the rest of the compounds and standard drugs that were subjected to antimicrobial assay. PMID:24696814

  1. Catalytic asymmetric synthesis of 4-nitropyrazolidines: an access to optically active 1,2,3-triamines.

    PubMed

    Lykke, Lennart; Carlsen, Bjørn Dreiø; Rambo, Raoní Scheibler; Jørgensen, Karl Anker

    2014-08-13

    The first catalytic enantio- and diastereoselective synthesis of 4-nitropyrazolidines is presented. Asymmetric hydrogen-bonding activation of nitro-olefins facilitated the 1,3-dipolar cycloaddition with hydrazones, affording optically active 4-nitropyrazolidines containing three continuous stereogenic centers as a single diastereomer in up to 99% ee. Furthermore, it is demonstrated that the optically active 4-nitropyrazolidines can be applied as precursors for the synthesis of highly interesting 1,2,3-triamines. PMID:25072940

  2. Proceedings of the Combustion Institute, Volume 29, 2002/pp. 26352643 DEMONSTRATION OF TEMPERATURE AND OH MOLE FRACTION

    E-print Network

    Wooldridge, Margaret S.

    fractions in combustion synthesis flames. Introduction Gas-phase combustion synthesis (GPCS) of nano/hydrogen/oxygen/argon flames, verifying the applicability of the diagnostic approach to combustion synthesis systems- structured materials is a powerful synthesis method, capable of generating high-purity materials [1

  3. A status of the activities of the NASA. Marshall Space Flight Center Combustion Devices Technology Team

    NASA Technical Reports Server (NTRS)

    Tucker, Kevin

    1992-01-01

    The Consortium for Computational Fluid Dynamics (CFD) Applications in Propulsion Technology was established to focus on computational fluid dynamics applications in propulsion. Specific areas of effort include developing the CFD technology required to address rocket propulsion issues, validating the technology, and applying the validated technology to design problems. The Combustion Devices Technology Team was formed to implement the above objectives in the broad area of combustion driven flows. In an effort to bring CFD to bear in the design environment, the team has focused its efforts on the Space Transportation Main Engine nozzle. The main emphasis has been on the film cooling scheme used to cool the nozzle wall. Benchmark problems have been chosen to validate CFD film cooling capabilities. CFD simulations of the subscale nozzle have been made. Also, CFD predictions of the base flow resulting from this type of nozzle have been made. The status of these calculations is presented along with future plans. Information is given in viewgraph form.

  4. A status of the activities of the NASA. Marshall Space Flight Center Combustion Devices Technology Team

    NASA Astrophysics Data System (ADS)

    Tucker, Kevin

    1992-07-01

    The Consortium for Computational Fluid Dynamics (CFD) Applications in Propulsion Technology was established to focus on computational fluid dynamics applications in propulsion. Specific areas of effort include developing the CFD technology required to address rocket propulsion issues, validating the technology, and applying the validated technology to design problems. The Combustion Devices Technology Team was formed to implement the above objectives in the broad area of combustion driven flows. In an effort to bring CFD to bear in the design environment, the team has focused its efforts on the Space Transportation Main Engine nozzle. The main emphasis has been on the film cooling scheme used to cool the nozzle wall. Benchmark problems have been chosen to validate CFD film cooling capabilities. CFD simulations of the subscale nozzle have been made. Also, CFD predictions of the base flow resulting from this type of nozzle have been made. The status of these calculations is presented along with future plans. Information is given in viewgraph form.

  5. Synthesis of novel bisindolylmethane Schiff bases and their antibacterial activity.

    PubMed

    Imran, Syahrul; Taha, Muhammad; Ismail, Nor Hadiani; Khan, Khalid Mohammed; Naz, Farzana; Hussain, Memona; Tauseef, Saima

    2014-01-01

    In an effort to develop new antibacterial drugs, some novel bisindolylmethane derivatives containing Schiff base moieties were prepared and screened for their antibacterial activity. The synthesis of the bisindolylmethane Schiff base derivatives 3-26 was carried out in three steps. First, the nitro group of 3,3'-((4-nitrophenyl)-methylene)bis(1H-indole) (1) was reduced to give the amino substituted bisindolylmethane 2 without affecting the unsaturation of the bisindolylmethane moiety using nickel boride in situ generated. Reduction of compound 1 using various catalysts showed that combination of sodium borohydride and nickel acetate provides the highest yield for compound 2. Bisindolylmethane Schiff base derivatives were synthesized by coupling various benzaldehydes with amino substituted bisindolylmethane 2. All synthesized compounds were characterized by various spectroscopic methods. The bisindolylmethane Schiff base derivatives were evaluated against selected Gram-positive and Gram-negative bacterial strains. Derivatives having halogen and nitro substituent display weak to moderate antibacterial activity against Salmonella typhi, S. paratyphi A and S. paratyphi B. PMID:25102118

  6. Synthesis and analgesic activities of endomorphin-2 and its analogues.

    PubMed

    Shi, Zhi-Hao; Wei, Yun-Yang; Wang, Chuan-Jin; Yu, Li

    2007-03-01

    Endomorphin-2 (1; H-Tyr-Pro-Phe-Phe-NH2; EM2) and its novel cyclic asparagine (cycloAsn) analogues, H-Tyr-cAsn(CHPh)-Phe-Phe-NH2 (2) and H-Tyr-cAsn(CHMe2)-Phe-Phe-NH2 (3), were synthesized via liquid-phase synthesis. The structures of the products and intermediates were characterized by IR, 1H-NMR, MS, and HR-MS analyses. The antinociceptive activity of EM2 and its cyclic asparagine analogues were assessed in AcOH-induced abdominal constriction tests in mice with i.p. injection. The results show that the antinociceptive activities of EM2 and its cyclic asparagine analogue 2 were higher than those of aspirine and meperidine. Analogue 2 was observed to be a stronger analgesic with dose-dependence than EM2. The test mice did not show any tendency to be addicted while administrated of analogue 2 repeatedly and regularly. PMID:17372948

  7. Synthesis of high thermal conductivity nano-scale aluminum nitride by a new carbothermal reduction method from combustion precursor

    NASA Astrophysics Data System (ADS)

    Kuang, JiaCai; Zhang, ChangRui; Zhou, XinGui; Wang, SiQing

    2003-09-01

    AlN nano-scale powder was obtained through a new carbothermal reduction from combustion precursor at 1500°C for 2 h in graphite furnace. The resultant product was a white solid powder, characterized by XRD, TEM, SAD and FIIR spectra. The results indicated that the product consisted of wurtzite AlN with an average size of about 80 nm. Through presureless and free-additive sintering at 1850°C for 6 h, it showed that AlN nano-scale powders possess excellent sintering property, whose thermal conductivity was measured to be 120 W/m K. High thermal conductivity mechanism was proposed.

  8. Combustion synthesis of CaSc 2O 4:Ce 3+ nano-phosphors in a closed system

    Microsoft Academic Search

    Wen-Fang Peng; Shao-Yu Zou; Guan-Xi Liu; Quan-Lan Xiao; Rui Zhang; Li-Juan Xie; Li-Wei Cao; Jian-Xin Meng; Ying-Liang Liu

    2011-01-01

    The CaSc2O4:Ce3+ nano-phosphors were successfully prepared by a single-step combustion method at an ignition temperature as low as 200°C in a closed autoclave using glycine as a fuel and PEG4000 as a dispersant. The samples were characterized by X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscope (TEM). The results revealed that CaSc2O4:Ce3+ nano-phosphors can

  9. Triggered instabilities in rocket motors and active combustion control for an incinerator afterburner

    NASA Astrophysics Data System (ADS)

    Wicker, Josef M.

    1999-11-01

    Two branches of research are conducted in this thesis. The first deals with nonlinear combustion response as a mechanism for triggering combustion instabilities in solid rocket motors. A nonlinear wave equation is developed to study a wide class of combustion response functions to second-order in fluctuation amplitude. Conditions for triggering are derived from analysis of limit cycles, and regions of triggering are found in parametric space. Introduction of linear cross-coupling and quadratic self-coupling among the acoustic modes appears to be how the nonlinear combustion response produces triggering to a stable limit cycle. Regions of initial conditions corresponding to stable pulses were found, suggesting that stability depends on initial phase angle and harmonic content, as well as the composite amplitude, of the pulse. Also, dependence of nonlinear stability upon system parameters is considered. The second part of this thesis presents research for a controller to improve the emissions of an incinerator afterburner. The developed controller was experimentally tested at the Naval Air Warfare Center (NAWC), on a 50kW-scale model of an afterburner for Naval shipboard incinerator applications. Acoustic forcing of the combustor's reacting shear layer is used to control the formation of coherent vortical structures, within which favorable fuel-air mixing and efficient combustion can occur. Laser-based measurements of CO emissions are used as the performance indicator for the combustor. The controller algorithm is based on the downhill simplex method and adjusts the shear layer forcing parameters in order to minimize the CO emissions. The downhill simplex method was analyzed with respect to its behavior in the face of time-variation of the plant and noise in the sensor signal, and was modified to account for these difficulties. The control system has experimentally demonstrated the ability (1) to find optimal control action for single- and multi-variable control, (2) to maintain optimal control for time-varying operating states, and (3) to automatically adjust auxiliary fuel in response to changing stoichiometry of the incoming waste pyrolysis gas. Also presented but not tested in the experiments are an expert-type model-guidance feature to aid convergence of the controller to optimum control, and methodology for maintaining flammability.

  10. Synthesis of highly ordered 30 nm NiFe2O4 particles by the microwave-combustion method

    NASA Astrophysics Data System (ADS)

    Mahmoud, M. H.; Elshahawy, A. M.; Makhlouf, Salah A.; Hamdeh, H. H.

    2014-11-01

    NiFe2O4 of 30 nm average size was synthesized by microwave combustion and subsequent solid state reaction at 1273 K. The materials were characterized by X-ray diffraction, TEM, vibrating sample magnetometery and Mössbauer spectroscopy. The microwave combustion produced materials were comprised chemically of ferrites and a smaller amount of hematite. The NiFe2O4 particles have the cubic spinel structure with crystallites of sizes less than 10 nm, and were found to have low magnetization, and essentially no hysteresis loop; characteristics of superparamagnetism. Upon annealing at temperatures 973 K and below, crystallite growth was accompanied by increase in both coercive field and magnetization. The coercive field was a maximum for the sample annealed at 973 K. On the other hand, crystallite growth at higher annealing temperatures yielded mainly ferrites and improvement in soft magnetic properties. Mössbauer and magnetization measurements indicate that the fine NiFe2O4 particles produced at the annealing temperature of 1273 K are in good chemical and magnetic order, excluding the spins arrangement at the surface of the particles which show spin glass-like behavior.

  11. Optical properties and dye-sensitized solar cell applications of ZnO nanostructures prepared by microwave combustion synthesis.

    PubMed

    Manikandan, A; Vijaya, J Judith; Ragupathi, C; Kennedy, L John

    2014-03-01

    In the present study, ZnO nanoparticles (ZNPs) and nanoflakes (ZNFs) were prepared by conventional combustion method and microwave combustion method, respectively. The structural phase and morphology were investigated by using X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM) and high resolution transmission electron microscopy (HR-TEM). The crystallite size was calculated using Scherrer formula, and it lies in the range of 20-21 nm for ZNFs and 23-28 nm for ZNPs. The elemental analysis was investigated by energy dispersive X-ray analysis (EDX). Also, absorbance and emission spectra were measured by using diffuse reflectance (DRS) and photoluminescence (PL) studies. The band gap was measured using Kubelka-Munk model and it shows 3.47 eV for ZNFs and 3.26 eV for ZNPs. A fill factor (FF) of 0.57, short-circuit current (J(sc)) of 8.02 mA/cm2, open-circuit voltage (V(oc)) of 0.70 V and an overall light to electricity conversion efficiency (eta) of 1.62% were obtained from the dye-sensitized solar cell (DSSCs) based on ZNFs. PMID:24745267

  12. Synthesis of Li2TiO3 by sol-gel combustion method and its gel-casting formation

    NASA Astrophysics Data System (ADS)

    Hong, Ming; Zhang, Yingchun; Mi, Yingying; Jiang, Yuanyuan; Xiang, Maoqiao

    2014-12-01

    Lithium metatitanate (Li2TiO3) has been recognized as a candidate of ceramic tritium breeder materials for its excellent performance. In this paper, Li2TiO3 powder was synthetized by a modified sol-gel combustion process, and the ratio of fuel to oxidizer was optimized. DTA-TG analysis indicated that an intense exothermic reaction occurred at 539 K, which led to the formation of a voluminous white powder. No additional annealing process was required, as pure crystalline ?-Li2TiO3 was directly obtained from the combustion reaction. The powder had nano-scale structure and large specific surface area of 9.6 m2/g. Li2TiO3 pebbles with desired size and shape were prepared by gel-casting technique using the as-prepared powder. The pebbles reached a high density (81-86% T.D) after sintered at a relatively low temperature (?1373 K) for 2 h. The sintering pebbles had a smooth surface, homogeneous microstructure and small grain size.

  13. Comparison of ?13C and 14C activities of CO 2 samples combusted in closed-tube and elemental-analyzer systems

    NASA Astrophysics Data System (ADS)

    Minami, Masayo; Goto, Akiko S.; Omori, Takayuki; Ohta, Tomoko; Nakamura, Toshio

    2010-04-01

    For combustion of organic samples, a closed tube-combustion (CTC) method is generally used, but this method requires much time and labor. The AMS facility at the Center for Chronological Research, Nagoya University, has established a CO 2 production and purification system using an elemental analyzer (EA) connected to cryogenic traps. This system enables faster combustion and CO 2 purification of samples than does the conventional CTC method. We compared measured carbon yields, ?13C values and 14C activities between EA and CTC samples of carbon standards of various sample quantities. This newly developed EA system had low background 14C activity due to sample preparation; the background activity was similar to that observed for the CTC method. The EA system also showed high precision and accuracy for ?13C and 14C measurements. The EA sample data obtained from conventional quantities (>1 mg carbon) of standards showed good agreement with the results obtained by the CTC method and with the consensus values, though background contamination was detected for samples containing <0.5 mg carbon. Oxalic acid standards containing <0.5 mg carbon that were analyzed by the CTC method tended to have widely varying values of carbon yield, ?13C and 14C activity, suggesting that the CO 2 produced by combustion might have been prone to adsorption to an inner wall of the combustion tube, to CuO or to both, and that the CO 2 produced in the CTC method might have decomposed.

  14. Synthesis, characterization and optical properties of Mn2+ activated Y3Al5O12 phosphor

    NASA Astrophysics Data System (ADS)

    Selot, Anupam; Dhoble, S. J.; Aynyas, Mahendra; Bhatt, Sanjay

    2013-06-01

    The synthesis and characterization of Y3Al5O12 phosphor with varying concentration of Mn2+ ion prepared by combustion technique is reported in this paper. The two photoluminescence (PL) emission peak exhibit 389nm and 412nm blue region, on 354nm excitation. It is found that the concentration quenching is occurred when Mn2+ ion at lowest concentration 0.05mol% of Mn2+ ion, which shift to broad band around 412 and 428 nm. These results are supported by corresponding X-ray diffraction measurements which exhibit crystalline nature. The results suggest the possibility of utilizing as a phosphor in white lighting devices.

  15. Ignition and reaction mechanism of Co–Al and Nb–Al intermetallic compounds prepared by combustion synthesis

    Microsoft Academic Search

    C. Milanese; F. Maglia; A. Tacca; U. Anselmi-Tamburini; C. Zanotti; P. Giuliani

    2006-01-01

    The ignition and propagation mechanism of the self-propagating high-temperature synthesis of several cobalt and niobium aluminides was investigated. Two propagation mechanisms were identified depending on the stoichiometry of the starting mixture. Al-rich compositions propagate through a dissolution–precipitation mechanism while Al-poor mixtures require solid state diffusion. The ignition temperatures were measured by means of microthermocouples in quasi-adiabatic conditions through experiments carried

  16. The Synthesis of Active Metabolites and Analogues of Vitamin D3

    NASA Astrophysics Data System (ADS)

    Yakhimovich, R. I.

    1980-04-01

    The literature date on the synthesis of the active metabolites and analogues of vitamin D3 (cholecalciferol), which play an important role in regulating the homeostatis of calcium in the organism, are reviewed. The bibliography includes 150 references.

  17. Third millenium ideal gas and condensed phase thermochemical database for combustion (with update from active thermochemical tables).

    SciTech Connect

    Burcat, A.; Ruscic, B.; Chemistry; Technion - Israel Inst. of Tech.

    2005-07-29

    The thermochemical database of species involved in combustion processes is and has been available for free use for over 25 years. It was first published in print in 1984, approximately 8 years after it was first assembled, and contained 215 species at the time. This is the 7th printed edition and most likely will be the last one in print in the present format, which involves substantial manual labor. The database currently contains more than 1300 species, specifically organic molecules and radicals, but also inorganic species connected to combustion and air pollution. Since 1991 this database is freely available on the internet, at the Technion-IIT ftp server, and it is continuously expanded and corrected. The database is mirrored daily at an official mirror site, and at random at about a dozen unofficial mirror and 'finger' sites. The present edition contains numerous corrections and many recalculations of data of provisory type by the G3//B3LYP method, a high-accuracy composite ab initio calculation. About 300 species are newly calculated and are not yet published elsewhere. In anticipation of the full coupling, which is under development, the database started incorporating the available (as yet unpublished) values from Active Thermochemical Tables. The electronic version now also contains an XML file of the main database to allow transfer to other formats and ease finding specific information of interest. The database is used by scientists, educators, engineers and students at all levels, dealing primarily with combustion and air pollution, jet engines, rocket propulsion, fireworks, but also by researchers involved in upper atmosphere kinetics, astrophysics, abrasion metallurgy, etc. This introductory article contains explanations of the database and the means to use it, its sources, ways of calculation, and assessments of the accuracy of data.

  18. Chemically Adjusting Plasma Temperature, Energy and Reactivity (CAPTEAR) Method Using NOx and Combustion for Selective Synthesis of Sc3N@C80 Metallic Nitride Fullerenes

    PubMed Central

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

    2008-01-01

    Goals are (1) to selectively synthesize 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 (MNFs). 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 Sc3N@C80). The CAPTEAR process with Cu(NO3)2·2.5 H2O 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. PMID:18052069

  19. Synthesis and antibacterial activity of novel C12 vinyl ketolides.

    PubMed

    Burger, Matthew T; Lin, Xiaodong; Chu, Daniel T; Hiebert, Christy; Rico, Alice C; Seid, Mehran; Carroll, Georgia L; Barker, Lynn; Huh, Kay; Langhorne, Mike; Shawar, Ribhi; Kidney, Jolene; Young, Kelly; Anderson, Scott; Desai, Manoj C; Plattner, Jacob J

    2006-03-01

    A novel series of C12 vinyl erythromycin derivatives have been discovered which exhibit in vitro and in vivo potency against key respiratory pathogens. The C12 modification involves replacing the natural C12 methyl group in the erythromycin core with a vinyl group via chemical synthesis. From the C12 vinyl macrolide core, a series of C12 vinyl ketolides was prepared. Several compounds were found to be potent against macrolide-sensitive and -resistant bacteria. The C12 vinyl ketolides 6j and 6k showed a similar antimicrobial spectrum and comparable activity to the commercial ketolide telithromycin. However, the pharmacokinetic profiles of C12 vinyl ketolides 6j and 6k in rats differ from that of telithromycin by having higher lung-to-plasma ratios, larger volumes of distribution, and longer half-lives. These pharmacokinetic differences have a pharmacodynamic effect as both 6j and 6k exhibited better in vivo efficacy than telithromycin in rat lung infection models against Streptococcus pneumoniae and Haemophilus influenzae. PMID:16509588

  20. Control of the activity and synthesis of aspartate transcarbamylase in Aerobacter aerogenes 

    E-print Network

    Deutsch, Walter Andrew

    1971-01-01

    CONTROL OF THE ACTIVITY AND SYNTHESIS OF ASPARTATE TRANSCARBAMYLASE IN AEBOBACTER AEB0GENES A Thesis by Walter Andrew Deutsch Submitted to the Graduate College of Texas A&M University in partial fulfillsmnt of the requirements for the degree... of MASTER OF SCIENCE December, l97l - Ma)or Sub)ect: Genetics CONTROL OF THE ACTIVITY AND SYNTHESIS OF ASPARTATE TRANSCARBAMYLASE IN AEROBAGTER AEBOGENES A Thesis by Walter Andrew Deutsch Approved as to style and content by: (Chairman of Committee...

  1. One-step solution-combustion synthesis of complex spinel titanate flake particles with enhanced lithium-storage properties

    NASA Astrophysics Data System (ADS)

    Li, Xue; Xiao, Qian; Liu, Bo; Lin, Huangchang; Zhao, Jinbao

    2015-01-01

    In this work, we report the formation of porous Li2MTi3O8 (M = Zn, Co) flakes (hereafter referred to as f-Li2MTi3O8) via a facile one-step solution-combustion in less than 10 min. As anodes for rechargeable lithium-ion batteries, the synthesized f-Li2MTi3O8 exhibits high reversible charge-discharge capacity, great cycling stability and high rate performance. These results can be attributed to the intrinsic characteristics of spinel Li2MTi3O8 flakes, in which a porous framework could provide a diffusion space for lithium ion insertion into and extraction from the anode material, resulting in excellent cycle performance, even cycling at high rate of 2000 mA g-1.

  2. Low-temperature metal-oxide thin-film transistors formed by directly photopatternable and combustible solution synthesis.

    PubMed

    Rim, You Seung; Lim, Hyun Soo; Kim, Hyun Jae

    2013-05-01

    We investigated the formation of ultraviolet (UV)-assisted directly patternable solution-processed oxide semiconductor films and successfully fabricated thin-film transistors (TFTs) based on these films. An InGaZnO (IGZO) solution that was modified chemically with benzoylacetone (BzAc), whose chelate rings decomposed via a ?-?* transition as result of UV irradiation, was used for the direct patterning. A TFT was fabricated using the directly patterned IGZO film, and it had better electrical characteristics than those of conventional photoresist (PR)-patterned TFTs. In addition, the nitric acid (HNO3) and acetylacetone (AcAc) modified In2O3 (NAc-In2O3) solution exhibited both strong UV absorption and high exothermic reaction. This method not only resulted in the formation of a low-energy path because of the combustion of the chemically modified metal-oxide solution but also allowed for photoreaction-induced direct patterning at low temperatures. PMID:23534400

  3. Activation of AMP-activated protein kinase inhibits protein synthesis associated with hypertrophy in the cardiac myocyte.

    PubMed

    Chan, Anita Y M; Soltys, Carrie-Lynn M; Young, Martin E; Proud, Christopher G; Dyck, Jason R B

    2004-07-30

    A necessary mediator of cardiac myocyte enlargement is protein synthesis, which is controlled at the levels of both translation initiation and elongation. Eukaryotic elongation factor-2 (eEF2) mediates the translocation step of peptide-chain elongation and is inhibited through phosphorylation by eEF2 kinase. In addition, p70S6 kinase can regulate protein synthesis by phosphorylating eEF2 kinase or via phosphorylation of ribosomal protein S6. We have recently shown that eEF2 kinase is also controlled by phosphorylation by AMP-activated protein kinase (AMPK), a key regulator of cellular energy homeostasis. Moreover, the mammalian target of rapamycin has also been shown to be inhibited, indirectly, by AMPK, thus leading to the inhibition of p70S6 kinase. Although AMPK activation has been shown to modulate protein synthesis, it is unknown whether AMPK could also be a regulator of cardiac hypertrophic growth. Therefore, we investigated the role of AMPK activation in regulating protein synthesis during both phenylephrine- and Akt-induced cardiac hypertrophy. Metformin and 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside were used to activate AMPK in neonatal rat cardiac myocytes. Activation of AMPK significantly decreased protein synthesis induced by phenylephrine treatment or by expression of constitutively active Akt. Activation of AMPK also resulted in decreased p70S6 kinase phosphorylation and increased phosphorylation of eEF2, suggesting that inhibition of protein synthesis involves the eEF2 kinase/eEF2 axis and/or the p70S6 kinase pathway. Together, our data suggest that the inhibition of protein synthesis by pharmacological activation of AMPK may be a key regulatory mechanism by which hypertrophic growth can be controlled. PMID:15159410

  4. Eigensystem synthesis for active flutter suppression on an oblique-wing aircraft

    NASA Technical Reports Server (NTRS)

    Alag, G. S.; Burken, J. J.; Gilyard, G. B.

    1986-01-01

    The application of the eigensystem synthesis technique to place the closed-loop eigenvalues and shape the closed-loop eigenvectors has not been practical for active flutter suppression, primarily because of the availability of only one control surface (aileron) for flutter suppression. The oblique-wing aircraft, because of its configuration, provides two independent surfaces (left and right ailerons), making the application of eigensystem synthesis practical. This paper presents the application of eigensystem synthesis using output feedback for the design of an active flutter suppression system for an oblique-wing aircraft. The results obtained are compared with those obtained by linear quadratic Gaussian techniques.

  5. Synthesis and antibacterial activity evaluation of two androgen derivatives.

    PubMed

    Lauro, Figueroa-Valverde; Francisco, Díaz-Cedillo; Elodia, García-Cervera; Eduardo, Pool-Gómez; Maria, López-Ramos; Marcela, Rosas-Nexticapa; Lenin, Hau-Heredia; Bety, Sarabia-Alcocer

    2015-01-01

    In this study two androgen derivatives were synthesized using several strategies; the first stage an aza-steroid derivative (3) was developed by the reaction of a testosterone derivative (1) with thiourea (2) in presence of hydrogen chloride. The second step, involves the synthesis of an amino-steroid derivative (4) by the reaction of 1 with 2 using boric acid as catalyst. The third stage was achieved by the preparation of an aminoaza-androgen derivative (6) by the reaction of 3 with ethylenediamine using boric acid as catalyst. In addition, the compound 6 was made reacting with dihydrotestosterone to form a new androgen derivative (7) in presence of boric acid. The following step was achieved by the reaction of 7 with chloroacetyl chloride to synthesize an azetidinone-androgen derivative (8) using triethylamine as catalyst. Additionally, a thiourea-androgen derivative (9) was synthetized by the reaction of 4 with dihydrotestosterone using boric acid as catalyst. Finally, the compound 9 was made reacting with chloroacetyl chloride in presence of triethylamine to synthesize a new azetidinone-androgen derivative (10). On the other hand, antibacterial activity of compounds synthesized was evaluated on Gram negative (Escherichia coli and Vibrio cholerae) and Gram positive (Staphylococos aureus) bacteria. The results indicate that only the compound 3 and 8 decrease the growth bacterial of E. coli and V. cholerae. Nevertheless, growth bacterial of S. aureus was not inhibited by these compounds. These data indicate that antibacterial activity exerted by the compounds 3 and 8 depend of their structure chemical in comparison with the controls and other androgen derivatives that are involved in this study. PMID:25448363

  6. Importance of activity data for improving the residential wood combustion emission inventory at regional level

    NASA Astrophysics Data System (ADS)

    Pastorello, Cinzia; Caserini, Stefano; Galante, Silvia; Dilara, Panagiota; Galletti, Fabio

    2011-06-01

    The contribution of residential wood combustion (RWC) to emission inventory at local level was estimated using a bottom-up approach for the Lombardy Region of North Italy. A survey, based on the CATI (Computer Assisted Telephone Interviewing) method, has been undertaken through 18,000 interviews. The interviews had the objective to characterize the RWC use in this region, in term of both total and municipal wood consumption. Details on the type of appliances used in RWC were also gathered. The results of the survey were then statistically analyzed in order to allow an estimate of RWC with high spatial resolution (i.e., at municipal level) in relation to the size and altitude of the territory. The work provides new evidence of the importance of wood combustion as a key source for PM and NMVOC emissions at local level, and thus highlights the importance of technological improvements and new policies aimed at emission reduction in this sector. Considering the great differences in average PM emission factors between low efficiency appliances (fireplaces, old stoves) and high efficiency ones (new stoves, pellet burners), this work emphasizes the importance of obtaining more detailed information on the types of wood appliances used for arriving at a reliable PM emission inventory for RWC.

  7. A facile gel-combustion route for fine particle synthesis of spinel ferrichromite: X-ray and Mössbauer study on effect of Mg and Ni content

    SciTech Connect

    Vader, V.T., E-mail: vtv_chem@rediffmail.com [Walchand College of Arts and Science, Solapur 413 006 (India); Achary, S.N. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Meena, S.S. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2014-02-01

    Highlights: • A novel and facile synthesis route. • Transformation of system from random to inverse spinel. • Appearance of superparamagnetism phase. - Abstract: A novel nitrate–citrate gel combustion route was used to prepare fine particle of a series Mg{sub 1?x}Ni{sub x}FeCrO{sub 4} (0.0 ? x ? 1.0) and its structural properties were investigated. The in situ oxidizing environment provided by the nitrate ions in the gel increases the rate of oxidation and lowers the decomposition temperature of component. All the samples after sintering were characterized at room temperature by X-ray diffraction (XRD) method and Mössbauer spectroscopy techniques. The X-ray and Mössbauer studies confirmed the single phase cubic spinel structure with all Fe ions in 3+ charge state. XRD and Mössbauer studies revealed that the samples of x = 0.0, and 0.2 are random spinel and show rather broad lines, while x = 0.4–1.0 are inverse spinel.

  8. Sol-gel auto-combustion synthesis, structural and enhanced magnetic properties of Ni2+ substituted nanocrystalline Mg-Zn spinel ferrite

    NASA Astrophysics Data System (ADS)

    Bobade, D. H.; Rathod, S. M.; Mane, Maheshkumar L.

    2012-09-01

    Nanocrystalline arrays of Ni2+ substituted Mg-Zn spinel ferrite having a generic formula Mg0.7-xNixZn0.3Fe2O4 (x=0.0, 0.2, 0.4 and 0.6) were successfully synthesized by sol-gel auto-combustion technique. The fuel used in the synthesis process was citric acid and the metal nitrate-to-citric acid ratio was taken as 1:3. The phase, crystal structure and morphology of Mg-Ni-Zn ferrites were investigated by X-ray diffraction, scanning electron microscopy, and Fourier transformer infrared spectroscopy techniques. The lattice constant, crystallite size, porosity and cation distribution were determined from the X-ray diffraction data method. The FTIR spectroscopy is used to deduce the structural investigation and redistribution of cations between octahedral and tetrahedral sites of Mg-Ni-Zn spinel structured material. Morphological investigation suggests the formation of grain growth as the Ni2+ content x increases. The saturation magnetization and magneton number were determined from hysteresis loop technique. The saturation magnetization increases with increasing Ni2+ concentration ‘x’ in Mg-Zn ferrite.

  9. Spray combustion

    SciTech Connect

    Chigier, N. [Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Mechanical Engineering

    1995-12-31

    A survey is presented of the most recent developments in the field of spray combustion. Topics discussed are: physical processes of atomization; drop clusters; droplet arrays and streams; ideal sprays; cloud combustion; theoretical models of spray diffusion flames; spray diagnostic techniques; measurement of drop temperature; and spray combustion measurements. 67 refs.

  10. Simulating Combustion

    Microsoft Academic Search

    G. Merker; C. Schwarz; G. Stiesch; F. Otto

    2006-01-01

    The content spans from simple thermodynamics of the combustion engine to complex models for the description of the air\\/fuel mixture, ignition, combustion and pollutant formation considering the engine periphery of petrol and diesel engines. Thus the emphasis of the book is on the simulation models and how they are applicable for the development of modern combustion engines. Computers can be

  11. Combustion synthesis and engineering nanoparticles for electronic, structural and superconductor applications. Final report, May 31, 1992--May 30, 1996

    SciTech Connect

    Stangle, G.C.; Schulze, W.A.; Amarakoon, V.R.W.

    1996-05-30

    Dense, nanocrystalline ceramic articles of doped ZrO{sub 2} (for use in solid electrolytes, oxygen sensors, electrode materials, thermal barrier coatings, etc.), BaTiO{sub 3} (for capacitor applications), and YBa{sub 2}Cu{sub 3}O{sub 7-x} (a high-temperature superconductor with uses, e.g., in magnetic flux trapping and high-speed capacitor applications) were prepared by the new nanofabrication process that has been developed in this research program. The process consists of two steps: synthesis of ceramic nanoparticles, and fabrication of dense ceramic articles that possess nanocrystalline features. The synthesis step is capable of producing 10-nanometer-diameter crystallites of doped ZrO{sub 2}, and of being scaled up to kilogram/hour production rates. The fabrication step produced dense, ultrafine-grained articles at significantly reduced sintering temperatures and times--representing a factor of 10-100 reduction in process energy requirements. The process has thus been shown to be technically feasible, while a preliminary engineering cost analysis of a pilot plant-scale version of the process indicates that it is both a cost- and an energy-efficient method of producing nanoparticles and nanocrystalline ceramics from those nanoparticles. One U.S. patent for this process has been allowed, and an additional five (continuation-in-part) applications have been filed. Technology transfer efforts have begun, through ongoing discussions with representatives from three manufacturing concerns.

  12. Progress in Studies on Rutaecarpine. II.-Synthesis and Structure-Biological Activity Relationships.

    PubMed

    Son, Jong-Keun; Chang, Hyeun Wook; Jahng, Yurngdong

    2015-01-01

    Rutaecarpine is a pentacyclic indolopyridoquinazolinone alkaloid found in Evodia rutaecarpa and other related herbs. It has a variety of intriguing biological properties, which continue to attract the academic and industrial interest. Studies on rutaecarpine have included isolation from new natural sources, development of new synthetic methods for its total synthesis, the discovery of new biological activities, metabolism, toxicology, and establishment of analytical methods for determining rutaecarpine content. The present review focuses on the synthesis, biological activities, and structure-activity relationships of rutaecarpine derivatives, with respect to their antiplatelet, vasodilatory, cytotoxic, and anticholinesterase activities. PMID:26111170

  13. Combustion synthesis of blue-emitting submicron CaAl4O7:Eu2+, Dy3+ persistence phosphor.

    PubMed

    Yerpude, A N; Dhoble, S J

    2012-01-01

    Long persistence phosphor CaAl4O7:Eu(2+), Dy(3+) were prepared by a combustion method. The phosphors were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), decay time measurement techniques and photoluminescence spectra (PL). The CaAl4O7:Eu(2+), Dy(3+) phosphor showed a broad blue emission, peaking at 445?nm when excited at 341?nm. Such a blue emission can be attributed to the intrinsic 4f???5d transitions of Eu(2+) in the host lattices. The lifetime decay curve of the Dy(3+) co-doped CaAl4O7:Eu(2+) phosphor contains a fast decay component and another slow decay one. Surface morphology also has been studied by SEM. The calculated CIE colour chromaticity coordinates was (0.227, 043). We have also discussed a possible long-persistent mechanism of CaAl4O7:Eu(2+), Dy(3+) phosphor. All the results indicate that this phosphor has promising potential for practical applications in the field of long-lasting phosphors for the purposes of sign boards and defence. PMID:22162513

  14. Synthesis of nanocrystalline magnesium titanate by an auto-igniting combustion technique and its structural, spectroscopic and dielectric properties

    SciTech Connect

    Suresh, M.K. [Electronic Materials Research Laboratory, DST-FIST Sponsored Postgraduate and Research Department of Physics, Mar Ivanios College, Nalanchira, Thiruvananthapuram 695015, Kerala (India)] [Electronic Materials Research Laboratory, DST-FIST Sponsored Postgraduate and Research Department of Physics, Mar Ivanios College, Nalanchira, Thiruvananthapuram 695015, Kerala (India); Thomas, J.K., E-mail: jkthomasemrl@yahoo.com [Electronic Materials Research Laboratory, DST-FIST Sponsored Postgraduate and Research Department of Physics, Mar Ivanios College, Nalanchira, Thiruvananthapuram 695015, Kerala (India); Sreemoolanadhan, H. [Vikram Sarabai Space Centre, Indian Space Research Organization, Department of Space, Thiruvananthapuram (India)] [Vikram Sarabai Space Centre, Indian Space Research Organization, Department of Space, Thiruvananthapuram (India); George, C.N. [Department of Physics, Bishop Moore College, Mavelikkara (India)] [Department of Physics, Bishop Moore College, Mavelikkara (India); John, Annamma; Solomon, Sam [Dielectric Materials Research Laboratory, Department of Physics, St. John's College, Anchal 691306, Kerala (India)] [Dielectric Materials Research Laboratory, Department of Physics, St. John's College, Anchal 691306, Kerala (India); Wariar, P.R.S. [Department of Physics, University College, Thiruvananthapuram, Kerala (India)] [Department of Physics, University College, Thiruvananthapuram, Kerala (India); Koshy, J. [Electronic Materials Research Laboratory, DST-FIST Sponsored Postgraduate and Research Department of Physics, Mar Ivanios College, Nalanchira, Thiruvananthapuram 695015, Kerala (India)] [Electronic Materials Research Laboratory, DST-FIST Sponsored Postgraduate and Research Department of Physics, Mar Ivanios College, Nalanchira, Thiruvananthapuram 695015, Kerala (India)

    2010-07-15

    Nanocrystalline magnesium titanate was synthesized through an auto-ignited combustion method. The phase purity of the powder was examined using X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy and Raman spectroscopy. The transmission electron microscopy study showed that the particle size of the as-prepared powder was in between 20 and 40 nm. The nanopowder could be sintered to 98% of the theoretical density at 1200 {sup o}C for 3 h. The microstructure of the sintered surface was examined using scanning electron microscopy. The dielectric constant ({epsilon}{sub r}) of 16.7 and loss factor (tan {delta}) of the order of 10{sup -4} were obtained at 5 MHz when measured using LCR meter. The quality factor (Q{sub u} x f) 73,700 and temperature coefficient of resonant frequency ({tau}{sub f}) -44.3 ppm/{sup o}C, at 6.5 GHz are the best reported values for sintered pellets obtained from phase pure nanocrystalline MgTiO{sub 3} powder.

  15. Laccase Catalyzed Synthesis of Iodinated Phenolic Compounds with Antifungal Activity

    PubMed Central

    Ihssen, Julian; Schubert, Mark; Thöny-Meyer, Linda; Richter, Michael

    2014-01-01

    Iodine is a well known antimicrobial compound. Laccase, an oxidoreductase which couples the one electron oxidation of diverse phenolic and non-phenolic substrates to the reduction of oxygen to water, is capable of oxidizing unreactive iodide to reactive iodine. We have shown previously that laccase-iodide treatment of spruce wood results in a wash-out resistant antimicrobial surface. In this study, we investigated whether phenolic compounds such as vanillin, which resembles sub-structures of softwood lignin, can be directly iodinated by reacting with laccase and iodide, resulting in compounds with antifungal activity. HPLC-MS analysis showed that vanillin was converted to iodovanillin by laccase catalysis at an excess of potassium iodide. No conversion of vanillin occurred in the absence of enzyme. The addition of redox mediators in catalytic concentrations increased the rate of iodide oxidation ten-fold and the yield of iodovanillin by 50%. Iodinated phenolic products were also detected when o-vanillin, ethyl vanillin, acetovanillone and methyl vanillate were incubated with laccase and iodide. At an increased educt concentration of 0.1 M an almost one to one molar ratio of iodide to vanillin could be used without compromising conversion rate, and the insoluble iodovanillin product could be recovered by simple centrifugation. The novel enzymatic synthesis procedure fulfills key criteria of green chemistry. Biocatalytically produced iodovanillin and iodo-ethyl vanillin had significant growth inhibitory effects on several wood degrading fungal species. For Trametes versicolor, a species causing white rot of wood, almost complete growth inhibition and a partial biocidal effect was observed on agar plates. Enzymatic tests indicated that the iodinated compounds acted as enzyme responsive, antimicrobial materials. PMID:24594755

  16. Laccase catalyzed synthesis of iodinated phenolic compounds with antifungal activity.

    PubMed

    Ihssen, Julian; Schubert, Mark; Thöny-Meyer, Linda; Richter, Michael

    2014-01-01

    Iodine is a well known antimicrobial compound. Laccase, an oxidoreductase which couples the one electron oxidation of diverse phenolic and non-phenolic substrates to the reduction of oxygen to water, is capable of oxidizing unreactive iodide to reactive iodine. We have shown previously that laccase-iodide treatment of spruce wood results in a wash-out resistant antimicrobial surface. In this study, we investigated whether phenolic compounds such as vanillin, which resembles sub-structures of softwood lignin, can be directly iodinated by reacting with laccase and iodide, resulting in compounds with antifungal activity. HPLC-MS analysis showed that vanillin was converted to iodovanillin by laccase catalysis at an excess of potassium iodide. No conversion of vanillin occurred in the absence of enzyme. The addition of redox mediators in catalytic concentrations increased the rate of iodide oxidation ten-fold and the yield of iodovanillin by 50%. Iodinated phenolic products were also detected when o-vanillin, ethyl vanillin, acetovanillone and methyl vanillate were incubated with laccase and iodide. At an increased educt concentration of 0.1 M an almost one to one molar ratio of iodide to vanillin could be used without compromising conversion rate, and the insoluble iodovanillin product could be recovered by simple centrifugation. The novel enzymatic synthesis procedure fulfills key criteria of green chemistry. Biocatalytically produced iodovanillin and iodo-ethyl vanillin had significant growth inhibitory effects on several wood degrading fungal species. For Trametes versicolor, a species causing white rot of wood, almost complete growth inhibition and a partial biocidal effect was observed on agar plates. Enzymatic tests indicated that the iodinated compounds acted as enzyme responsive, antimicrobial materials. PMID:24594755

  17. Production of TiB{sub 2}-TiN composites by combustion synthesis and their properties

    SciTech Connect

    Tomoshige, Ryuichi; Murayama, Akio; Matsushita, Toru [Kumamoto Inst. of Tech. (Japan). Dept. of Industrial Chemistry

    1997-03-01

    The self-propagating high-temperature synthesis (SHS) process has been applied to formation of composites consisting of TiB{sub 2} and TiN ceramics synthesized simultaneously. Ti, B, and BN powders were used as raw materials. the SHS reaction was initiated by a tungsten heating coil. XRD experiments confirmed that the reaction was complete, and that only TiB{sub 2} and TiN phases were detected. Microstructural observations revealed that both TiN and TiB{sub 2} crystal grains had small sizes of less than 1 {micro}m in the composites with high TiN content. Inhibition of grain growth can be attributed to the pinning effect of TiN grains. Excellent corrosion resistance was obtained for HCl reagent.

  18. Influence of thermal conductivity on steady state propagation speed in combustion synthesis of Mo + 2Si green compacts

    SciTech Connect

    Azad, G.S.; Huque, Z.; Cui, T.

    1998-07-01

    Thermal conductivities of Mo + 2Si powder mixture compacts are experimentally investigated and the results are presented in this paper. These compacts are used in self-propagating high temperature synthesis (SHS) of refractory, ceramic, and composite materials. Thermal conductivity values of these compacts are important for accurate modeling of the SHS process. Results show that, thermal conductivities of the compacts increased for an increase in initial density, but decreased with an increase of Mo/2Si mixture ratios. The experimental results also show the dependency trend of thermal conductivity on particle size of the constituents. A numerical model was also developed to predict the steady state propagation speed along a vertical cylindrical compact employing Kanury kinetic model. An important dimensionless parameter, the Damkohler number was introduced. The effects of the variation of thermal conductivity on propagation speed due to the changes in initial density and composition mixture ratio are also presented.

  19. Observation of intermetallic Ni{sub 3}Ti whiskers during combustion synthesis reactions in the Ni-Ti-C system

    SciTech Connect

    Chrysanthou, A.; Kassim, K.H. [Univ. of Nottingham (United Kingdom). Dept. of Materials Engineering and Materials Design] [Univ. of Nottingham (United Kingdom). Dept. of Materials Engineering and Materials Design

    1995-10-01

    The term self-propagating high-temperature synthesis (SHS) describes a process reaction where, once ignited, the reactants spontaneously transform into products due to the exothermic nature of the reaction. The work which is reported here was part of a program of research studying the potential of the SHS process for the production of metal-matrix composites for wear-resistant applications based on TiC in a nickel matrix. Self-propagating reactions between titanium and carbon black, generating 30--90% TiC by weight in Ni, were studied. Although SHS reactions for this particular system have been studied by other researchers, the observation of whisker growth while using this technique has not previously been reported.

  20. Measurement of Microbial Activity and Growth in the Ocean by Rates of Stable Ribonucleic Acid Synthesis

    PubMed Central

    Karl, David M.

    1979-01-01

    A relatively simple and extremely sensitive technique for measuring rates of stable ribonucleic acid (RNA) synthesis was devised and applied to bacterial cultures and seawater samples. The procedure is based upon the uptake and incorporation of exogenous radiolabeled adenine into cellular RNA. To calculate absolute rates of synthesis, measurements of the specific radioactivity of the intracellular adenosine 5?-triphosphate pools (precursor to RNA) and of the total amount of radioactivity incorporated into stable cellular RNA per unit time are required. Since the rate of RNA synthesis is positively correlated with growth rate, measurements of RNA synthesis should be extremely useful for estimating and comparing the productivities of microbial assemblages in nature. Adenosine 5?-triphosphate, adenylate energy charge, and rates of stable RNA synthesis have been measured at a station located in the Columbian Basin of the Caribbean Sea. A subsurface peak in RNA synthesis (and therefore growth) was located within the dissolved oxygen minimum zone (450 m), suggesting in situ microbiological utilization of dissolved molecular oxygen. Calculations of the specific rates of RNA synthesis (i.e., RNA synthesis per unit of biomass) revealed that the middepth maximum corresponded to the highest specific rate of growth (420 pmol of adenine incorporated into RNA·day?1) of all depths sampled, including the euphotic zone. The existence of an intermediate depth zone of active microbial growth may be an important site for nutrient regeneration and may serve as a source of reduced carbon for mesopelagic and deep sea environments. PMID:16345461